DYNA Revista | Universidad Nacional de Colombia (original) (raw)

Issue 196 by DYNA Revista

The management of fire safety in buildings is conducted in accordance with the type of use-risk c... more The management of fire safety in buildings is conducted in accordance with the type of use-risk category (Building occupancy code). For
Building type XI “libraries and archives” and XII “industrial, workshops and warehouses", the determination of the risk category involves
the calculation of the modified fire load density, which can be done by two methods used interchangeably by the technician: deterministic
and probabilistic. This study aims to investigate variation results obtained with the calculation of the modified fire load density using two
methods and the classification of the Building occupancy code. The performed calculations referred to real buildings of type XII, with
defined and distinct materials and activities. The different results determine a variation in the risk category, which consequently, will
define the technical criteria to be applied to the Building occupancy code in the implementation for Building Fire Safety measures.

Organizations should regularly conduct an assessment of their occupational hazards in order to de... more Organizations should regularly conduct an assessment of their occupational hazards in order to design and implement preventive measures
that are necessary and sufficient to deal with the level of risk, the costs of prevention and the safety at levels considered acceptable by the
organization. Furthermore, the selection of measures to be implemented in an organization should take into account both internal and
external costs. Externalities are of great importance in terms of the costs of accidents at work; nevertheless, they are not often properly
addressed by the organizations. In this paper we describe an application of the Delphi method to understand how externalities can be
included in Occupational Safety and Health.

Risk assessment is an essential tool to support risk decisions. However, this process may not alw... more Risk assessment is an essential tool to support risk decisions. However, this process may not always be applied effectively, and this can
limit the quality of the preventative action. This is particularly critical in sectors that have a lot of micro and small companies, such as
Olive Oil Mills (OOMs). To better understand how to improve the quality of the risk assessment at OOMs, this study aims to analyze the
views of Occupational Safety and Health (OSH) practitioners on the key difficulties/limitations in this process and identify some
improvements to current practices. This analysis was based on a questionnaire that was developed and given to 13 OSH practitioners
working for OOMs. The results showed that the time available to perform the risk assessment is the major limitation. The need for a specific
tool for risk assessment in the OOM sector was identified, and the use of accident reports from the entire sector was indicated as an
alternative to the absence of data at company level.

The morbidity associated with WRMSDs leads to productivity losses (absenteeism and presenteeism) ... more The morbidity associated with WRMSDs leads to productivity losses (absenteeism and presenteeism) in healthcare organizations, which
induces a substantive impact (cost).. The present study aimed to evaluate the impact (cost) of WRMSDs for accidents involving nurses and
nurses’ aides in a small Portuguese hospital. It begins by identifying the workplace accidents (WA) that these occupational groups suffered
between 2009 and 2013, which resulted in WRMSDs. Healthcare workers answered a questionnaire with WQL-8 and SPS-6 scales to
determine the levels of presenteeism. This study adopted a human capital methodology in order to estimate the indirect costs of lost
productivity from WRMSDs. Patient transfers are a major cause of WRMSDs, with most prevalent injuries being in the lumbar region.
Between 2009 and 2013 there is a loss of productivity in this institution estimated of €222,015.98 from WA with WRMSDs that lead to
absenteeism and presenteeism (€ 189,679.87 absenteeism and € 32,158.86 presenteeism).

Analysis of accident reports has been a useful tool in occupational safety research. According to... more Analysis of accident reports has been a useful tool in occupational safety research. According to European Statistics on Accidents at Work framework
(ESAW), important variables related to the main circumstances of accidents are being gathered in Europe. The purpose of this paper is to present a method
for analysis of accident databases that are coded according to the ESAW and based on Multiple Correspondence Analysis. The method proposed considers
the implicit conceptual relationship between the exposure and accident variables in order to identify main areas for public policy intervention. This method
is presented by analyzing specific working processes using a dataset of the accidents that were reported in the Andalusian manufacturing over a ten-year
period. The method presented allowed easy identification of the main associations candidates for public intervention programs. Each could be object to
further detailed research before designing the intervention program. This method could help policy makers when identifying areas for public intervention.

The main objective of this study is to analyze the perception of Occupational Health and Safety i... more The main objective of this study is to analyze the perception of Occupational Health and Safety in small construction projects in the Brazilian
construction industry. The adopted approach is qualitative in nature and seeks to understand the character of the current practices through
interviews held with ‘actors’ who are directly involved in small-scale building sites, as well as with others who are involved in large-scale work
sites. In Brazil, there is a weakness in supervision at small construction projects. This is due to numerous factors, such as the low visibility of
these types of works and short deadlines, as well as the lack of knowledge about Occupational Health and Safety. This study reinforces and
illustrates the idea of the inherent dangers involved in the occupational health of workers in small construction projects. It also indicates that there
is a need to put greater emphasis on compliance with Occupational Health and Safety principles, which are covered by the current Brazilian
Legislation and Regulatory Standards. This should be undertaken in order to ensure that the work in small-scale building sites is more visible
and, especially, to ensure acceptable health and safety conditions for construction workers.

Nanotechnology has aroused great interest in the construction industry because new materials with... more Nanotechnology has aroused great interest in the construction industry because new materials with outstanding properties are being designed, and
the features of traditional materials can be improved. However, exposure to nanomaterials is the most recent new emerging risk in the construction
industry and the current knowledge about this topic is limited. This paper aims to identify the main aspects regarding the exposure to and use of
nanomaterials in the construction sector from a risk prevention perspective. This starting point allows authors to establish a set of recommendations
structured in order to identify how and where to act in order to manage the risk of exposure to nanomaterial on construction sites.

The prevalence of obesity is increasing throughout the workforce. Manual lifting tasks are common... more The prevalence of obesity is increasing throughout the workforce. Manual lifting tasks are common and can produce significant muscle loading.
This study compared muscular activity between obese and non-obese subjects, using surface Electromyography (EMG), during manual lifting.
Six different lifting tasks (with 5, 10 and 15 kg loads in free and constrained styles) were performed by 14 participants with different obesity
levels. EMG data normalization was based on the percentage of Maximum Contraction during each Task (MCT). Muscle Activation Times (AT)
before each task were also evaluated. The study suggests that obesity can increase MCT and delay muscle AT. These findings reinforce the need
to develop further studies focused on obesity as a risk factor for the development of musculoskeletal disorders.

Work-related musculoskeletal disorders are a common problem among office workers. The purpose of ... more Work-related musculoskeletal disorders are a common problem among office workers. The purpose of this study is to evaluate the impact
of a workplace exercise program on neck and shoulder pain and flexibility in office workers. The workstation assessment was performed
using Rapid Office Strain Assessment. Workers were assessed for pain pre- and post-implementation of the workplace exercise program
using the Nordic Questionnaire for Musculoskeletal Symptoms, and for flexibility. The program lasted 3 months and entailed twice weekly
sessions. The sample consisted of an intervention group (n = 30) and a control group (n = 8). The results suggest improvements in pain
reduction and increased flexibility. The workers had less musculoskeletal pain at the end of the evaluation. The increase in flexibility
between the evaluations was significant in the intervention group, though there were slight improvements there too.

The early Cretaceous Ciénaga Marbles that crop out in the NW foothills of the Santa Marta Massif ... more The early Cretaceous Ciénaga Marbles that crop out in the NW foothills of the Santa Marta Massif (Colombian Caribbean region) present an epigenetic
mineral assemblage (skarn-type), overprinting the metamorphic mineral assemblage previously developed along the regional metamorphic history that
affected this unit. The skarn-type mineralogy allows at least three paragenetic contexts to be distinguished, which are represented by the following
neoformed minerals: (a) garnet, forsterite, diopside, titanite, wollastonite and calcite (early anhydrous metamorphic stage), (b) actinolite, tremolite, allanite
and clinohumite (metasomatic or hydrated stage), and (c) chlorite, serpentine, sepiolite and quartz (late low temperature retrograde stage, probably due to
infiltration of descending meteoric waters). The skarn-type mineralogy is observed as alteration halos developed around porphyritic granodiorites
emplaced as sills between anisotropy planes related to metamorphic regional foliation of rock that are considered to be the causative bodies of the skarntype
mineralogy. Zircon U-Pb ages obtained from granodioritic bodies yielded an age of 55.5±0.7 Ma (Ypresian, Early Eocene). The formation of the
skarn-type mineralogy in the Ciénaga Marbles is temporarily related to the formation and emplacement of hydrated silicate masses that were generated
at the beginning of the subduction polarity change (i.e. when the Caribbean oceanic plate began to subduct beneath South American continental plate).

Iron-doped TiO2 catalysts were prepared by impregnation in order to study their photocatalytic ac... more Iron-doped TiO2 catalysts were prepared by impregnation in order to study their photocatalytic activity in the treatment of wastewater from
the textile industry. Characterization of the catalysts before and after reaction was performed using techniques including total surface area
measurement, X-Ray diffraction and elemental analysis via X-Ray fluorescence. Varying pH conditions, H2O2 concentrations and catalyst
quantities were evaluated during the photocatalytic reactions. Fe-TiO2 catalysts were shown to be highly active in the reduction of chemical
oxygen demand (% COD) and % color reduction in the water treated.

The objective of this study was to verify whether the energy content and nutritional composition ... more The objective of this study was to verify whether the energy content and nutritional composition of meals consumed at work (lunch)
correlated with the energy expenditure and nutritional status of workers from different sectors (administration and production) of different
industries. The sample consisted of 292 workers. Many anthropometric dimensions were assessed, such as physical activity energy
expenditure, and daily energy expenditure (DEE). Food intake was measured directly for five days. The study comprised an assessment of
the correlation between sectors and gender, a qualitative assessment between obesity indicators, and a principal component analysis (PCA).
Overweight workers prevailed, and DEE differed by gender and work sector (p<0.05). PCA showed that the majority of the individuals
with high energy expenditure and high energy and fats consumption levels were males.

The present article studies the influence of two pozzolanic additions, metakaolin (MK) and silica... more The present article studies the influence of two pozzolanic additions, metakaolin (MK) and silica fume (SF), and the water/binder ratio
(w/b) on the electrochemical re-alkalization (ER) of reinforced mortars as a technique to prevent reinforcement corrosion in carbonated
concrete. Mixtures with a 10% (by weight) addition as a replacement for cement at w/b ratios of 0.45 and 0.65 were prepared. Test
specimens were exposed to carbonation in a chamber under controlled conditions (1% CO2, 65%RH, and 25°C), until reaching two levels
of carbonation (50% and 100%). ER was applied for a period of 15 days using sodium carbonate as the electrolyte and a current density of
1 A/m2. From the evaluated additions, MK is highlighted, which generated a resistance increase of 53.51% relative to that of the reference
mixture and contributes to improvements of durability properties. Regarding the ER technique, the specimens with greater w/b ratios and
partial carbonation were more effective.

The surfaces of a personalized maxillofacial prosthesis were manufactured in a relatively short p... more The surfaces of a personalized maxillofacial prosthesis were manufactured in a relatively short period of time and at a moderate cost. The
surface topography was generated with a Computer-Aided Design system from the Computerized Axial Tomography of a maxillofacial
area. The design of the machining manufacturing process, its simulation and verification, were facilitated by the use of a virtual machine
tool equivalent to the real machine tool available. Finally, the manufacturing process was successfully achieved by using a conventional 3-
axis vertical machining center equipped with a fourth external rotational axis. Using a 3-axis machine tool with an additional axis is less
expensive than using a 5-axis machine. There is abundant literature on machining of free-form surfaces using a 5-axis machine tool, but
there are few precedents for the manufacturing of this kind of surface using a 4-axis machine.

This paper presents the results of an experiment carried out on 21 subjects, all of whom had an e... more This paper presents the results of an experiment carried out on 21 subjects, all of whom had an engineering background, with the aim of
determining the influence of the designer’s attitude on the design process and on the finished design. The participants were asked to solve
a range of design problems by employing different methods while their emotional response parameters were being registered by a noninvasive
neuroheadset. The recorded data was used firstly to compare the different reactions of the subjects when using different design
methods. A second analysis was carried out to determine whether the variations in the emotional parameters bore any direct relation to the
creativity of the outcomes. The results obtained indicate a relation between emotional parameters, individuals and the design method used.
However, there does not appear to be any direct association between emotional parameters and the creativity of the results.

Nanofluids are colloidal suspensions of nanometer-sized particles (metals, metallic oxides or car... more Nanofluids are colloidal suspensions of nanometer-sized particles (metals, metallic oxides or carbon nanotubes) in a base fluid (polar or
non-polar). Nanofluids have interesting properties that make them useful especially in the design of compact heat transfer equipment.
Laminar convective heat transfer of nanofluids (water, Al2O3) in a square and circular ducts has been studied numerically using the software
ANSYS/FLUENT 12.1. Results for the Nusselt number, skin coefficient friction, temperature and velocity profiles are presented for four
nanoparticle volume fractions (􀟮 = 0 − 20%) and Reynolds numbers (Re = 800, 1300 and 2000). For the studied Re numbers, Nu is
decreased by 12% and 10%, when 􀟮 is increased from 0% to 10% and from 10% to 20%, respectively. Regard to the skin friction factor,
the obtained value is increased around a 30% when 􀟮 is increased 10%.

Foods may have both solid and liquid properties, and are described as viscoelastic products. Know... more Foods may have both solid and liquid properties, and are described as viscoelastic products. Knowledge on such viscoelastic features is
very useful for quality control and/or food stability. The purpose of this work was to evaluate the effect of the application of 1-MCP on the
viscoelastic properties of minimally processed yellow pitahaya during refrigeration storage, by using a stress relaxation test. Viscoelastic
parameters were determined through Generalized Maxwell and Peleg’s rheologic models. Both rheological models proved suitable to
predict viscoelastic behavior; however, Peleg’s model better described this behavior. Samples of treated and non-treated pitahaya with 1-
MCP decreased their elastic behavior (firmness decrease) during storage. Fruit treated with 1-MCP showed a greater elastic component
than non-treated samples during storage. These two rheological models were suitable for predicting the viscoelastic behavior, however

In order to analyze the main reasons, the adoption process, outcomes and satisfaction obtained by... more In order to analyze the main reasons, the adoption process, outcomes and satisfaction obtained by the architecture firms and other actors involved
in the process of adopting the ISO 14006 eco-design standard, we developed a qualitative research using a Delphi type methodology, based on the
results of a previous multiple case study research conducted with nine architecture firms. Among the main results, it should be highlighted the
difficulties faced by architecture firms to obtain environmental information of raw materials, the poor recognition given by the client to
environmental aspects compared with costs and the limited role of government supporting eco-design adoption, increasing the level of requirements
of environmental legislation, and taking into account environmental issues in public tenders. It is also noteworthy the main stakeholders involved
in the adoption and certification process of the ISO 14006 have demonstrated a medium or medium-high level of satisfaction.

This paper presents a model for the optimal design of reinforced rectangular concrete beams for s... more This paper presents a model for the optimal design of reinforced rectangular concrete beams for singly reinforced sections. It develops an
analytical approach to the problem, based on a criterion of minimum cost and minimum weight design with a reduced number of design
variables. Representative examples are presented to illustrate the applicability of the formulation in accordance with building code
requirements for structural concrete (ACI 318S-13), including the comments on the standards. A comparison is made between the optimal
design solution and current design practice for reinforced rectangular concrete beams. The optimal solution for the design of reinforced
rectangular concrete beams shows clearly that significant savings can be made in the costs of the construction materials used – i.e.
reinforcement steel and concrete. In addition, the problem formulation can be applied using a nonlinear mathematical programming format.

This work applies a test that detects dependence between pairs of variables. The kind of dependen... more This work applies a test that detects dependence between pairs of variables. The kind of dependence is a non-linear one, and the test is
known as cross-bicorrelation, which is associated with Brooks and Hinich [1]. We study dependence periods between U.S. Standard and
Poor’s 500 (SP500), used as a benchmark, and six Latin American stock market indexes: Mexico (BMV), Brazil (BOVESPA), Chile
(IPSA), Colombia (COLCAP), Peru (IGBVL) and Argentina (MERVAL). We have found windows of nonlinear dependence and comovement
between the SP500 and the Latin American stock markets, some of which coincide with periods of crisis, leading to an
interpretation of a possible contagion or interdependence.

Data Envelopment Analysis is a non-parametrical approach for efficiency evaluation of so-called D... more Data Envelopment Analysis is a non-parametrical approach for efficiency evaluation of so-called DMUs (Decision Making Units) and takes into
account multiple inputs and outputs. For each inefficient DMU, a target is provided which is constituted by the inputs or outputs levels that are
to be attained for the inefficient DMU to become efficient. However, multiobjective models, known as MORO (Multiobjective Model for Ratio
Optimization) provide a set of targets for inefficient DMU, which provides alternatives among which the decision-maker can choose. In this
paper, we proposed an extension of the MORO models to take into account non-discretionary variables, i.e., variables that cannot be controlled.
We present a numerical example to illustrate the proposed multiobjective model. We also discuss the characteristics of this model, as well as the
advantages of offering a set of targets for the inefficient DMUs when there are non-discretionary variables in the data set.

This article presents a mathematical model for drying thin layer carrot slices (Daucus carota) us... more This article presents a mathematical model for drying thin layer carrot slices (Daucus carota) using a heat pump dryer (HPD). To select
the equation that best describes the drying curve, 10 semi-theoretical and/or empirical models were evaluated. The parameters were
determined using the Sigma-Plot® program, and their goodness of fit was compared using the correlation coefficient, R2; Chi-squared, χ2;
standard error of the estimate (SEE) and root mean square error (RMSE). Additionally, the effect of the relative moisture, sample thickness
and air velocity on the effective diffusivity of the process was evaluated using a response surface tool. Although all the models correctly
fit the experimental data, based on the statistical tests, the Wang-Singh model was selected as the best.

The problem of urban road accidents in Colombia is remarkable and has a significant magnitude. Fo... more The problem of urban road accidents in Colombia is remarkable and has a significant magnitude. For this reason, a technical study of this
important public health scourge is important. The quantitative techniques employed are usually highly aggregated and will not correctly
identify the determinant variables of the problem. This paper examines the relationship between urban road accidents and variables related
to road infrastructure, environment, traffic volumes and traffic control. Some accident-prone sections in the city of Cartagena (Colombia)
are specifically identified by the empirical Bayesian method based on GIS. A total of 69 accident-prone sections were identified in the city.
It was evident that the marginal effect on the accident rate for motorcycles is well above that for cars and buses. Empirical evidence also
showed that the sections located in commercial areas tend to have higher frequency of accidents due to the high presence of pedestrians.

The damage induced by radiation in the pyrographite is accompanied by significant plastic deforma... more The damage induced by radiation in the pyrographite is accompanied by significant plastic deformation. Microcracks arise in the
edges of the radiated areas that develop radially in the direction of the unaffected matrix. The peculiarities in the formation of the
tension state of the radiated area and adjacent unaffected areas are analyzed in order to explain the reasons behind the growth of
cracks. The analysis is carried out on graphite disks with constant thicknesses that are exposed to radiation with high-energy electrons
in an HVTEM-JEOL 1000. A differential equation for specific load conditions is obtained from the analysis of equilibrium conditions
of a disc-shaped element.

This paper details a cross-sectional, descriptive observational in vitro study of a pseudo-experi... more This paper details a cross-sectional, descriptive observational in vitro study of a pseudo-experimental nature that analyzes Electron Microscopy
(SEM) by scanning the physical behavior of enamel and dentin calcium hydroxyapatite. The purpose is to describe the separation of these two
mineralized dental tissues at the dentin-enamel junction (DEJ) when the teeth are subjected to high temperatures. This study provides scientific
evidence that may broaden the discussion on the use of separation of the dentin-enamel junction as a constant and repetitive reliable marker for
forensic use (use in forensic sciences) that can contribute to the dental identification process and documentation in a legal medical autopsy, given
a situation in which bodies or human remains have been burned, carbonizated or incinerated.

The coded aperture snapshot spectral imager (CASSI) is an optical architecture that captures spec... more The coded aperture snapshot spectral imager (CASSI) is an optical architecture that captures spectral images using compressive sensing. This system
improves the sensing speed and reduces the large amount of collected data given by conventional spectral imaging systems. In several applications,
it is necessary to analyze changes that occur between short periods of time. This paper first presents a sparsity analysis for spectral video signals, to
obtain accurate approximations and better comply compressed sensing theory. The use of the CASSI system in compressive spectral video sensing
then is proposed. The main goal of this approach is to capture the spatio-spectral information of dynamic scenes using a 2-dimensional set of
projections. This application involves the use of a digital micro-mirror device that implements the traditional coded apertures used by CASSI.
Simulations show that accurate reconstructions along the spatial, spectral and temporal axes are attained, with PSNR values of around 30 dB.

Work stress increasingly affects many workers from different countries. Conditions such as high d... more Work stress increasingly affects many workers from different countries. Conditions such as high demand, low social support and low job
control are considered predictors of increased stress. With data obtained from the V European Working Conditions Survey (EWCS) a
Bayesian network model was made. It provides information on the levels of stress in relation to model demand-control-social support
(DCS), differentiating into work situations as they are, self-employed, private and public. To deepen understanding of the interrelationships
between these variables sensitivity analysis of individual and overall were performed to check the DCS model assumptions. This model
applied in the V EWCS identified the variations and similarities between different work situations, proving that having low levels of
demand, together with control and high social support, the likelihood of stress decreases.

The objective of this study was to evaluate the efficiency of the Saraz method in order to quanti... more The objective of this study was to evaluate the efficiency of the Saraz method in order to quantify ammonia emissions generated in opened
or hybrid animal production facilities, and to determine an equation for the adjustment method. To do this, we developed beacon equipment,
with input and output gas sectors, hoods and absorbent porous material. After the collection, the amount of ammonia captured in the
environment was determined in the laboratory. Different ammonia concentrations were evaluated in addition to the different speeds of the
exhaust air. Considering the results, it can be concluded that for the situations analyzed the Saraz method is efficient, but as with other
methods, with an increase of air velocity and concentration, its efficiency decreases. An equation for the adjustment of the Saraz method
was generated to determine the concentration and the rate of ammonia emissions inside animal facilities.

Voltage sags and swells are among the power quality disturbances that represent the biggest econo... more Voltage sags and swells are among the power quality disturbances that represent the biggest economic losses for affected users. It is
therefore necessary to undertake a suitable characterization of those events to conduct studies that permit the causes and possible mitigation
techniques to be identified. This work describes the development of monitoring modules to characterize voltage sags and swells that could
be used in Electromagnetic Transients Programs - EMTP (for example the ATP – Alternative Transients Program). The implemented
module uses a novel method to characterize these disturbances. The results of the implementation show that the voltage sags and swells
are appropriately characterized; furthermore, less sampled data is required from a voltage signal with respect to the conventional RMS
voltage method. This could optimize the capture and analysis process of information in power quality monitoring.

The use of Cu and Ti in Zn alloys improves mechanical properties as solid solution and dispersoid... more The use of Cu and Ti in Zn alloys improves mechanical properties as solid solution and dispersoid particles (grain refiners) may harden the
material and reduce creep deformation. This is one of the main design problems for parts made with Zn alloys, even at room temperature.
In this work the mechanical behavior of a Zn-Cu-Ti low alloy is presented using tensile tests at different strain rates, as well as creep tests
at different loads to obtain the value of the strain rate coefficient m in samples parallel and perpendicular to the rolling direction of the Zn
strip. The microstructure of the alloy in its raw state, as well as heat treated at 250°C, is also analyzed, as the banded structure produced by
rolling influences the strengthening mechanisms that can be achieved through the treatment parameters.

$Research paper thumbnail of Non-destructive in situ analysis of garnet by combining scanning electron microscopy and X-ray diffraction techniques$

By using the X-ray powder diffraction (XRPD) micro X-rays diffraction (μXRD) and scanning electro... more By using the X-ray powder diffraction (XRPD) micro X-rays diffraction (μXRD) and scanning electron microscopy, the structural characterization
of minerals is far more reliable and accurate. The identification and elemental and compositional quantification of minerals by these non-destructive
techniques improve the quality of the results and allow a full analysis of the material. The data obtained by these techniques revealed the presence of
garnet-type spessartine, in addition to trace elements and compounds that form the overall material. The structural refinement of spessartine was
performed using the Rietveld method from data obtained by conventional diffraction and by using the MDI RIQAS analysis software. With the data
acquired by μXRD using an area detector, a shorter exposure time (compared to that required by the 0L and 1D detectors) was achieved, and there
was no need for particle size reduction of the mineral. It was also possible to identify the spessartine and other compounds in smaller concentrations
(in situ measurements). By combining scanning electron microscopy and X-ray diffraction techniques, both worked from a characterization point of
view. The examination by micro X-ray diffraction did not require physical separation of the sample. Using this information and the above advanced
analytical techniques, the identification of garnet can be undertaken much more reliably.

This paper details the design and implementation of a simultaneous dual true random numbers gener... more This paper details the design and implementation of a simultaneous dual true random numbers generator using only one laser and a digital
signal processing system with a DE0 Nano FPGA. We implemented the random generator in such a way that a vacuum optical field will
exist in our system. Taking advantage of the inherently random nature of the field, simultaneously quadrature components are measured in
order to generate a truly random voltage signal. Also, we used a dynamical system of statistical analysis to eliminate any residual component
of direct current on output voltage signal due to an (unavoidable) optical power imbalance in the optical system that was implemented.
Finally, were measured the parameters of the auto-correlation and bias probability with values of 0.00010, 0002, respectively, which means
that our system can be considered as a true random sequence generator capable of producing two sequences in an independent manner with
a bit rate of up to 25 MHz.

This paper presents a model and simulations, which was built with a System Dynamics methodology a... more This paper presents a model and simulations, which was built with a System Dynamics methodology applied to waste management in the
bioethanol supply chain in Colombia. The stages of the supply chain used were cane planting, production and the distribution process. The
residues taken into account were bagasse and vinasse. Moreover, four simulation scenarios were performed in which the values of variables
modified management strategies. The installed bioethanol production capacity was increased to observe the evolution of increased waste
generation evaluated. The initial conditions for the simulation were modified to represent a production of about 2,500,000 liters / day. This
leads to an increased generation of vinasse of over 400 million liters on average in a month and around more than 1 million tones of bagasse.
The results are used to estimate the impact of management strategies on the amount of waste generated in the production of bioethanol.

A good rheological characterization can be used as a control parameter within the industrial proc... more A good rheological characterization can be used as a control parameter within the industrial processing of kaolin. The kaolin used was
characterized by SEM, XRD, XRF and particle size. Also it was classified and separated in three sizes of fine material, which was
introduced in suspensions with three different size distributions. The analysis was based on a rheological study of the fine particles
influence, on the suspension viscosity. The results show that it is possible to modify the viscosity by altering the fines content without
changing the solid fraction of the suspension. Suspensions of kaolin with 40% content of fines tend to decrease its viscosity value.
Suspensions with quantities of fine greater than 60 %, increase the value of its viscosity. In the research are also presented the proposed
mechanisms by which the presence of fine increases or decreases the value of the viscosity of a suspension.

Finite element method simulations were implemented to understand how the strain energy is distrib... more Finite element method simulations were implemented to understand how the strain energy is distributed in a disk-like sample during a
punch shear test. Material’s Young modulus can be estimated from this test; however, there is not enough available information about the
distribution of the strain energy inside the sample during the deformation process. The proposed methodology seeks to give insight into
the deformation process. Experimental results for a cured silicon rubber sample were used to validate the simulation results. It was found
that the estimation of the Young modulus with the punch shear test depends on the ratio between the span-to-punch diameters. This
conclusion applies to the simulated results, following Timoshenko’s theory for the deformation of thin plates. Understanding how energy
is accumulated during a punch shear test is an important and useful characteristic in terms of the design of armor systems.

The main objective of the project management team is to implement the project taking into conside... more The main objective of the project management team is to implement the project taking into consideration the Budget, schedule and constraints.
In addition, project accomplishment, especially with large projects, requires the project to be correctly envisaged. Earned value (EV) management
is a valuable technique for analyzing and controlling the performance of the project and predicting the total cost before its completion. Thus,
fuzzy systems such as Adaptive Network based on the Fuzzy Inference System (ANFIS) and Parallel Structure based on the Fuzzy System
(PSFS) are used to predict the project completion time. In this paper, the plan value diagram is used to predict the earn value diagram using three
methods. These three methods are based on the PSFS and Neural Networks (NNs), which help with the implementation of the projects in
organizations. The results of these three methods decreased the prediction error of the EV diagram by up to 2%.

This paper presents a robust minutiae based method for fingerprint verification. The proposed met... more This paper presents a robust minutiae based method for fingerprint verification. The proposed method uses Delaunay Triangulation to
represent minutiae as nodes of a connected graph composed of triangles. The minimum angle over all triangulations is maximized, which
gives local stability to the constructed structures against rotation and translation variations. Geometric thresholds and minutiae data were
used to characterize the triangulations created from input and template fingerprint images. The effectiveness of the proposed method is
confirmed through calculations of false acceptance rate (FAR), false rejected rate (FRR) and equal error rate (EER) over FVC2002
databases compared to the results of other approaches.

Digital social networks have proven to be of great support for organizations that are increasingl... more Digital social networks have proven to be of great support for organizations that are increasingly using new forms of social communication
every day, seeking to improve their productivity and competitiveness. The main objective of this study is to explain how organizations,
particularly Institutions of Higher Education, can improve their competitive position through the use of digital social networks from the
perspective of relationship management and management of communications, in order to achieve better results in terms of teamwork
satisfaction, relationship marketing and educational excellence. For this objective, the application of a relational coordination model, based
on the sharing of objectives, optimal knowledge management, mutual respect and efficient communication mechanisms, is suggested.

The main objective of this research is to investigate the feasibility of using the residual powde... more The main objective of this research is to investigate the feasibility of using the residual powder obtained from organic waste to replace a
part of Portland cement during concrete production. The chemical and physical properties of the organic residual powder were first
investigated using scanning transmission electron microscopy (STEM) and energy dispersive X-ray spectroscopy (EDS). The replacement
ratios of cement have also been studied for 0%, 5%, 10%, 15%, and 20% of the residual powder by weight. Moreover, we evaluated the
compressive strength, specific gravity, water absorption, and voids content of the concrete specimens that were modified with different
concentrations of the residual powder. Results indicate that 5% residual powder concentration resulted in better physical and mechanical
properties of the modified concrete when compared with the reference concrete. At this concentration, the addition of residual powder act
as fillers in concrete, reducing the amount of voids and causing a higher density in the material.

A system for the detection and localization of roadway potholes is proposed and is aimed at colle... more A system for the detection and localization of roadway potholes is proposed and is aimed at collecting data on the roadway potholes using
the accelerometer, GPS and compass that are embedded into smartphones using the Android operating system. This system has a scalable
mobile architecture that contributes to capturing environment information using multiple devices with a large geographic coverage.

This paper describes a vehicle simulation toolbox developed under Matlab® environment, which can ... more This paper describes a vehicle simulation toolbox developed under Matlab® environment, which can be used to estimate the range of a
vehicle battery, or a fuel cell/battery hybrid system. The model is function of mechanical and physical variables that depend not only on
the vehicle but also on the ground. This toolbox can be extended to GPS tracking files by means of reading data file plug-ins. Even standard
drive cycles can be simulated. Battery and hydrogen consumption, hydrogen storage tank level, battery state of charge, power consumption
and fuel cell energy production, maximum range and maximum number of cycles for a real route can be determined. The model facilitates
the prediction of the vehicle range and the hydrogen and energy consumption. Real route simulation gives a good approximation of the
vehicle speed close to real-life services instead of using driving cycles that are quite arbitrary approximations to a real route.

Cement production is intensive in terms of energy consumption. An analysis of the resources invol... more Cement production is intensive in terms of energy consumption. An analysis of the resources involved in manufacturing clinker needs a corresponding
mass and energy balance. This balance may indicate the existence of residual heat flows that are not used. This paper summarizes the development
of a protocol for the evaluation of a cement plant rotary kiln to implement an Organic Rankine Cycle (ORC) system for cogeneration. The results
show that 19.2% of the energy preheater exhaust gas can be recovered to be used in producing 5.5 GWh/year of electricity and 23.7 GWh/year of
thermal energy in the cement plant. The electricity generated would represent annual savings of 1.18 $/t cement. The thermal energy produced in
cogeneration, equivalent to coal in the plant itself, represents cement savings of 0.51 $/t cement and emissions reductions of 8 kt CO2/year.

Alginate is a linear polymer composed of -1,4 linked mannuronic acid and its epimer, -L-guluron... more Alginate is a linear polymer composed of -1,4 linked mannuronic acid and its epimer, -L-guluronic acid, and frequently extracted from
marine algae, as from bacteria such as Azotobacter and Pseudomonas. Here, we show the impact of conventional and unconventional
carbon sources on A. vinelandii growth, alginate production, its mean molecular weight (MMW) and its viscosifying power. Starting with
20 g/L of sugars, the highest biomass concentration was obtained using deproteinized and hydrolyzed whey (6.67±0.72 g/L), and sugarcane
juice (6.68±0.45 g/L). However, the maximum alginate production was achieved using sucrose (5.11±0.37 g/L), as well the highest alginate
yield and specific productivity. Otherwise, the higher alginate MMW was obtained using sugarcane juice (1203±120 kDa), and the higher
viscosifying power was obtained using deproteinized/ hydrolyzed whey (23.8±2.6 cps L/galg). This information suggests that it is possible
to manipulate the productivity and molecular characteristics of alginates, as a function of the carbon source used. All this, together with
the knowledge of the effects of environmental conditions will allow for high yields of high added value biopolymers.

Nowadays, knowledge is a powerful tool in order to obtain benefits within organizations. This is ... more Nowadays, knowledge is a powerful tool in order to obtain benefits within organizations. This is especially true when semantic web
technologies are being adapted for the requirements of enterprises. In this regard, the Simple Knowledge Organization System (SKOS) is
an area of work developing specifications and standards to support the use of knowledge organization systems. Over recent years, SKOS
has become one of the sweet spots in the linked data (LD) ecosystems. In this paper, we propose a linked data-based approach using SKOS,
in order to manage the knowledge from supply chains. Additionally, this paper covers how SKOS can be enriched by ontologies and LD
to further improve semantic information management. This is due to the fact that the supply chain literature focuses on assets, data, and
information elements of exchange between supply chain partners, despite improved integration and collaboration requiring the development
of more complex features of know-how and knowledge.

The current pressure of global competition is demanding faster, reliable, flexible, and cheaper p... more The current pressure of global competition is demanding faster, reliable, flexible, and cheaper products. Thus, in order to keep up with customer
demands, companies need to continuously improve their manufacturing systems and develop new strategies. Supply chain management (SCM) is
currently the most important tactic for modern companies to maintain their competitiveness. Supplier selection process (SSP) plays an important role
in SCM and has been studied extensively in the past years as a tool to provide guidance and help to researchers and decision makers. Green supply
chain management (GSCM) arose due to the recent increase in environmental protection. Consequently, the correspondent green supplier selection
process (GSSP) has become more and more critical in GSCM. This paper presents a review of studies published in scientific journals during the last
five years about green criteria utilized in multi-criterion decision making (MCDM) techniques for GSSP. Furthermore, it identifies the most commonly
used MCDM techniques, in journals, universities, and academic departments where this type of research is being developed.

The effect of crosswinds on the risk of railway vehicles overturning has been a major issue ever ... more The effect of crosswinds on the risk of railway vehicles overturning has been a major issue ever since manufacturers began to produce
lighter vehicles that run at high speeds. However, ride comfort can also be influenced by crosswinds, and this effect has not been thoroughly
analyzed. This article describes the effect of crosswinds on ride comfort in high speed trains when running on curves and for several wind
velocities under a Chinese hat wind scenario, which is the scenario recommended by the standard. Simulation results show that the
combination of crosswinds and the added stiffness of the lateral bumpstop on the secondary suspension can become a significant source of
instability, leading to flange-to-flange contact and greatly jeopardizing ride comfort. Moreover, this comfort problem is an issue even when
the wheel unloading ratio is well below the standard’s limits and vehicle safety can be guaranteed.

The reutilization of waste generated by industrial processes has become a majorenvironmental obje... more The reutilization of waste generated by industrial processes has become a majorenvironmental objective in scientific and technical research.
In the construction sector, there is a broad range of techniques for the exploitation of different types of waste, which can then be used as a
replacement for raw materials. This paper presents the results of a study of vinasse, a by-product of biomass ethanol, andanalyzes its
viability as a bitumen modifier in asphalt mixes. For this purpose, four AC-16S asphalt mixes were evaluated for moisture sensitivity,
plastic deformation, stiffness, and fatigue. The mix formulas were the following: (Mix 1) 50/70 bitumen; (Mix 2) 50/70 bitumen modified
with 10% vinasse; (Mix 3) rubber bitumen; (Mix 4) rubber bitumen modified with 10% vinasse. The results of this study showed that
bitumen modified with vinasse improved the mechanical performance of the AC-16S mix and also contributed to the valorization of vinasse
waste.

This consistency assessment of highways’ geometrical design has the objective of providing safer ... more This consistency assessment of highways’ geometrical design has the objective of providing safer roads. There are two types of models for
consistency assessment: aggregated and disaggregated. The first one considers the difference between design and operating speed at the
middle point of isolated horizontal curves. The second one considers the spatial variation of the operating speed profile along the horizontal
curve. This paper compares the two types of consistency assessment models, using naturalistic speed and geometry data obtained in 34
horizontal curves of two-lane rural roads in Chile, using a 10 Hz GPS. Results obtained showed that in only 19 cases both methods are
equivalent. This equivalence occurred only when operating speed profiles have the lowest spatial variance along the curves. If the operating
speed profile has a high variance the consistency level obtained using both methods is different and the better option is combine it.

Monte Carlo simulations combined with the Heisenberg model and Metropolis algorithm were used to ... more Monte Carlo simulations combined with the Heisenberg model and Metropolis algorithm were used to study the equilibrium magnetic
properties of magnetic multi-core nanoparticles of magnetite. Three effects were considered in this simulation: the Zeeman effect, magneto
crystalline anisotropy, and dipolar interaction. Moreover, the influence of the size distribution (mean diameter and standard deviation) on
the magnetization was analyzed. As an important result, a reduction of the equilibrium magnetization caused by the dipolar interaction and
the magneto crystalline anisotropy was observed. On the other hand, the nanoparticle size increase produces an enhancement in the
equilibrium magnetization, because of the lower influence of dipolar interaction. Cooling temperature effect was also observed, presenting
a decrease in the equilibrium magnetization as the temperature was increased. The influence of the easy axis direction was studied.

A broad-range tunable all optical wavelength conversion scheme that is based on a dual driven Mac... more A broad-range tunable all optical wavelength conversion scheme that is based on a dual driven Mach-Zehnder modulator with an integrated microwave
generator to tune the channel spacing along the entire C band, is proposed. Successful signal demodulation up to 8 wavelength conversions, in steps of
50-400 GHz of 100 Gbps Nyquist QPSK channels with configurable channel spacing is reported. The proposed wavelength conversion scheme enables
flexible wavelength routing on gridless optical networks, as can be seen in the Superchannels with a BER lower than 10-13.

Due to the heterogeneity of rocks, their tensile strength is around 10% of their compressive stre... more Due to the heterogeneity of rocks, their tensile strength is around 10% of their compressive strength, which means that breakage is mainly
caused by tensile stress. The measure of tensile stress is very difficult due to rock fragility, so it has usually been measured by indirect
measurement methods , including the Brazilian test. However, recent works indicate that the tensile strength values obtained through the
Brazilian test must be increased by almost 26%.
To understand this divergence, indirect tensile tests have been monitored. The aim is to know the material deformation and load increase
by means of stepwise regression. Stress fields in slightly deformed samples are analyzed and modeled (3D finite differences) with loads
applied on flat and curved plates and different Young's modulus. Finally, the results are analyzed and compared with strength values
reported using Timoshenko theory and Hondros' approximation.

Vast sections of the planet face either a dearth of ground-based weather stations or are hampered... more Vast sections of the planet face either a dearth of ground-based weather stations or are hampered by the poor quality of those in service. In
response, researchers are forced to turn to climate field databases, as they constitute a source of reliable information for local studies.
Insofar as the Amazon region, these databases prove to be valuable given their open-access platform and the fact that this expansive region
possesses few quality stations (coupled with insufficient temporal coverage). However, before basing research on such archives, this
information should be compared against in situ station measurements. Then, the present study assesses the validity of temperature and
precipitation information furnished by University of Delaware’s database (UD-ATP) by means of a comparison with the open-access
information available from Climate Explorer project (CLIMEXP). Results show that UD-ATP database offers better precipitation data
representation, especially on Brazil, which is perhaps the effect of higher-quality and larger-quantity observed data.

This paper discusses the experimental results of a prototype slab-wall that is subjected to verti... more This paper discusses the experimental results of a prototype slab-wall that is subjected to vertical and horizontal cyclic loading. The key
aspects under discussion are: (a) the differences between the capacity resistance of a wall supported on a slab vs. a wall supported on a
fixed base, (b) the implications when shear walls are placed directly on transfer concrete slabs, and (c) the effects that these walls cause on
the slabs. The most important results presented herein are the change on lateral stiffness and resistance capacity of the load-bearing wall
supported on a slab versus the wall supported on a fixed base. Analytical finite element slab-wall models were built using ANSYS. During
the experimental test process of horizontal loading, we detected that the stiffness of the slab-wall system decreased by a third compared to
the one on the fixed base wall; a result that supported by the numerical models.

Ternary mixtures of geopolymers obtained from the alkaline activation of metakaolin (MK), boiler ... more Ternary mixtures of geopolymers obtained from the alkaline activation of metakaolin (MK), boiler slag (BS), and rice husk ash (RHA)
using a solution of potassium hydroxide were mechanically, thermally, and microstructurally characterized. The geopolymer properties
and final microstructures indicate that the addition of BS, despite containing large amounts of unburned material (16.36%), allows for
greater densification and greater homogeneity of the geopolymeric gel, which results in greater stability in strength at long curing ages.
Substitution of 30% of MK by BS results in an increase in compressive strength of up to 21% and 122% after 28 and 180 days of curing,
respectively. These results demonstrate the possibility of the construction sector using geopolymers based on MK and adding BS and RHA
to obtain cementitious materials with a lower environmental impact.

In this paper new tuning rules for Proportional Integral Derivative (PID) are presented, which ar... more In this paper new tuning rules for Proportional Integral Derivative (PID) are presented, which are based on Internal Model Control (IMC).
This set of equations minimizes the performance index, in this case, the Integral Absolute Error (IAE). Furthermore, a correlation is
proposed in order to calculate the tuning parameter of the method, where a holding oscillation response is obtained regarding changes in
the set point. This value represents a stability limit for the IMC method. The overall development is then applied to an Inverse Response
System of second order and with dead time.

This paper presents the development of a data acquisition system and the evaluation of the electr... more This paper presents the development of a data acquisition system and the evaluation of the electromagnetic phenomena associated with
power quality according to the IEEE Standard 1159-1992 and applied to the particular case of single-phase electrical power systems. The
evaluation software is implemented in the Labview® professional software using a NI 6009 USB board of the National Instrument® as
acquisition device. The hardware implementation of the sensors was shown. Also the development of the algorithm and the design of a
graphical user interface for viewing of the voltage and current waveforms, spectra, frequency and the power quality disturbances such as
sags, swells, undervoltage, overvoltage, so on. Likewise, at the end a concise analysis of costs is presented to show that the developed
system has a lower price to current solutions that are available in the market. Finally a study case was shown.

Assess one's own abilities realistically and critically is the key for a continuous adaptation to... more Assess one's own abilities realistically and critically is the key for a continuous adaptation to the changing labor market conditions. The
university system must train the future engineers to rate their own performance accurately, reducing biases as self-benevolence. This paper
analyzes, with a sample of students of Industrial Engineering, the accuracy of self-assessment in oral presentations, using a scoring rubric.
The results of several statistical tests indicate that students are good assessors of others work, but benevolent with their own work. In
addition, men evaluate themselves significantly higher than women do. Finally, self-assessment tend to compensate for others assessments,
mainly in the case of students considered worse by teachers. These results point to the need of including self-assessment activities in an
increasing number to improve students’ performance.

This paper presents an application method of a Maintenance Management Program through the impleme... more This paper presents an application method of a Maintenance Management Program through the implementation of predictive tools and the Total Productivity Maintenance (TPM) methodology as a contribution for the energy efficiency improvement in thermoelectric power plants. The results of the vibration analysis, lubricating oil condition and of the thermograph analysis are registered as diagnostic methods. The innovative advance in this paper was the application of four pillars from the TPM methodology at the control of the internal combustion engines efficiency at a thermoelectric power plant. This research has the objective to provide a more reliable maintenance process through the implementation of the measurement and control of the operating parameters of the plant resulting in a better management by reducing the stops due unforeseen problems. Some results of the methodology application were shown like: annual maintenance cost reduction due corrective maintenance, increase of the mean time between failure (MTBF) and reduction of the mean time to repair (MTTR) in all applied areas. These results reflected in a more reliable power generation without putting the facilities of the plant at risk with an annual cost reduction for the company.

A huge landslide took place at Alto Verde residential complex at the end of 2008 in the city of M... more A huge landslide took place at Alto Verde residential complex at the end of 2008 in the city of Medellin, Colombia, claiming the lives of
twelve people and destroying six houses. Landslides are characterized by large deformations in the soil mass. This study used the material
point method (MPM), a particle-based method that takes advantage of a double Lagrangian-Eulerian discretization. This approach provides
a robust framework that enables the numerical simulation of large strains, without mesh entanglement issues that are common with the
Finite Element Method. The numerical model proposed here assumes simplifications of the geotechnical, morphological and structural
buildings conditions on the site. Nevertheless, the final numerical deformed configuration described the geometric features observed in the
field successfully. The result allows applications such as the design of barriers, risk assessment or determination of a minimum safe distance
for a building from a slope susceptible to landslides.

The energy "Trilemma" seeks to develop an electricity market which simultaneously ensures environ... more The energy "Trilemma" seeks to develop an electricity market which simultaneously ensures environmental quality, security of supply,
and economic sustainability. The objective of this paper is to present the "Trilemma" energy as the latest trend in the design of energy
policy. For this, a theoretical framework is presented in sections 2 and 3, in section 4 and 5 the importance of security of supply and
economic sustainability are discussed, respectively. In section 6 the energy "trilemma" is presented, in section 7 a brief state of the art is
showed. Finally in section 8, it is approached three different electricity markets. It is concluded that the regulator has passed in recent years
from encouraging a liberalized market scheme, to promote a scheme based on intervention through policies that affect the market
competitiveness but allow achieving its environmental goals.

This paper presents the study of the ground plane effect in passband filters using metamaterial c... more This paper presents the study of the ground plane effect in passband filters using metamaterial cells in Open Split Ring Resonators (OSRR) structures on microstrip substrates. Three different configurations have been proposed, namely: by removing partially the ground plane of the OSRR cell back end, by windows design over the ground plane at the back end of each cell and by placing a full ground plane. The conducted analysis shows that the filter transmission response featuring a ground plane including windows proved to be the most flattened with the middle bandwidth of the three configurations. On the other hand, the performance of these filters is similar to a conventional filter based on three-pole microstrip technology but with a considerable reduction in size of about 60%.

This paper proposes a methodological design based on the development, creation, adaptation and im... more This paper proposes a methodological design based on the development, creation, adaptation and implementation of some analysis tools and the deployment of the risk management process content in standard ISO 31000. This allows for the design of a monitoring and quality control system of critical variables associated with equipment and operating conditions for the purpose of identifying and mitigating sources diversions product specifications. It also seeks to harmonize work philosophies with international management standards. The validation was performed by an industrial company from the city of Barranquilla. The content of this paper provides professionals and industry with a way to address and improve the capacity of any type of manufacturing process in any organization through standardized steps.

Both the Internet and communications & information technology (ICT), are making a valuable contri... more Both the Internet and communications & information technology (ICT), are making a valuable contribution to education. Remote experimentation is an example of the contribution that becomes as a solution to various problems involved with practices in situ, which are a fundamental aspect in the development of skills in engineering education. In this work, we have implemented a learning manager to experience with optoelectronic devices via internet, this tool is composed of a hardware platform comprising a set of electronic components such as light emitting diodes and optocouplers, each one with its respective signal conditioning and communication interfaces; additionally, a Web 2.0 user interface and learning management concepts and content are included. Those facilitate administration and promoting collaborative learning regarding social networks.

A sample of Colombian natural clinker was evaluated as a raw material in a laboratory-scale synth... more A sample of Colombian natural clinker was evaluated as a raw material in a laboratory-scale synthesis of zeolitic materials using two methods of alkaline fusion, followed by two aging methods, and finally hydrothermal treatment during three different periods of time. Fusion was carried out with solid and aqueous NaOH and followed by static or ultrasonic aging. The process ended with a hydrothermal reaction. Natural clinker was converted into several zeolitic materials. The characteristics of the resulting zeolitic materials and the effects of experimental variations are discussed.

The decision-making problems have attracted the attention of many researchers in a wide range of ... more The decision-making problems have attracted the attention of many researchers in a wide range of disciplines. The decision situations in which multiple individuals involved, each with their own knowledge about alternatives of the decision problem requires advanced to deal with this difficulty techniques. This work evaluates the impact of training received by a group of workers in the assessments are modeled using different kinds of information provided by different groups of experts to manage the uncertainty and subjectivity of such assessments for there to infer its relationship with the training received. Therefore, it is necessary and appropriate to establish a framework adapted to the heterogeneous nature of these criteria. Model and manage uncertainty has been successful and involves making computing processes with words hence the model 2-tuples linguistic representation is offered as a solution for their accuracy, ease of information management in complex frameworks, as to give greater interpretability of the resulting data.

Find alternative energy sources is one of the challenges that came with XXI century and this pape... more Find alternative energy sources is one of the challenges that came with XXI century and this paper makes an analysis about wave energy, which presents several advantages over fossil based energy and even other renewable energy sources. Among them are its low environmental impact and its high energy density. Wave energy is beginning to be considered as an important and promising renewable resource in many countries. The objective of this paper is to evaluate the wave energy potential at the southern coast of the Gulf of Mexico; the sea states were observed and was obtained that the available mean wave power is 55.91 W/m. In addition, this paper shows that, in the study site, the most energetic season is fall and the less energetic season is spring. This differs from the global trend, were the most energetic season is winter, and the less energetic season is spring.

The aim of this work is to evaluate the incidence rate of the previous acclimatization of biomass... more The aim of this work is to evaluate the incidence rate of the previous acclimatization of biomass and the presence of any other easily biodegradable substrates, such as sucrose. This experiment will be undertaken with sunflower oil biodegradation in a batch reactor with suspended biomass. It used a biomass concentration of 5000 mg/l in batch reactors, and in every condition the elimination of oil by means of biodegradation was achieved with levels ranging from 10 to 90 % It was noticed that sludge acclimation substantially improves biodegradation efficiency by increasing the average biodegradation from a value of 30% to 80%. When adding sucrose to an acclimatized biomass stage, biodegradation sunflower oil is reduced, from an average value of 80% to 60%.

In this paper, a study of the propagation of partial discharge pulses in the stator winding of a ... more In this paper, a study of the propagation of partial discharge pulses in the stator winding of a synchronous machine is presented. This study was performed by injecting artificial partial discharge pulses in the stator winding of a 2.4 kV/210 kVA salient-pole synchronous machine. It was found that the propagation of the partial-discharge PD signals is presented in two modes: the slow mode, in which the coil acts as a transmission line; and the fast mode, in which the pulse propagates through the overhangs. The fast mode is due to capacitive and inductive couplings in the overhangs. In the slow mode, a PD signal manifests itself at the generator terminals after a transit time that depends on the distance traveled by the pulse. A strong positive linear correlation was observed between the arrival time in the slow mode and the length traveled by the pulse in this mode. The DC ohmic resistance between the injection point and the measurement point was used to represent the distance traveled by the pulse in the slow mode. The capacitive and inductive couplings also cause a crosstalk between the phases. As a consequence, a PD signal can be measured at different phases to the origin phase. In the slow mode, the signal will suffer attenuation in amplitude due to the dispersion and the absorption of energy while it propagates in the slow mode.

The learning of classification rules is a classic problem of the automatic learning. The algorith... more The learning of classification rules is a classic problem of the automatic learning. The algorithm IRBASIR for the induction of classification rules based on similaridad relations allows to discover knowledge starting from decision systems that contain features with continuous and discrete domains. This algorithm has shown to obtain higher results than other well-known algorithms. In this article, several modifications to this algorithm based on the Fuzzy sets theory are proposed, taking into account the measure quality of similarity. The experimental results show that using the fuzzy sets theory allow to obtain higher results than the original algorithm.

This article presents a feasibility study of a new polymer-ceramic composite material applied as ... more This article presents a feasibility study of a new polymer-ceramic composite material applied as a thermal insulator on the surface of a low net volume household refrigerator. This paper describes its manufacture in a succinct manner, and a thermal and energy comparison between the factory refrigerator and the refrigerator with the composite installed. Based on the experiments, it is concluded that when using the composite, the average internal temperature of the fridge is increased by 1°C, for practical and design purposes, the refrigerator still functions below 3°C. It was also found that at stable operating conditions the energy consumption using the composite saves approximately 1.5%. Despite these slight savings, the pyro-expanded perlite composite acts as a thermal isolating material. This material may exhibit better ease of use and thermal, energetic and economic benefits, without omitting the environmental characteristics that they favor.

Landfills are engineering structures formed with a specific material, whose shear strength proper... more Landfills are engineering structures formed with a specific material, whose shear strength properties can be determined in a similar way, as it is done for a geotechnical material. This paper presents results from an experimental program carried out to obtain the strength parameters for Presidente landfill at Valle del Cauca (Colombia). The experimental program included unconsolidated undrained direct shear tests (UU) performed on laboratory reconstituted samples. Variation of the internal friction angle and cohesion, as a function of the specific weight, depth and decomposition time of the landfill was evaluated. Results were also compared to international values used for design purposes. Results showed a remarkable influence of the waste decomposition time in the shear strength. Some relationship with the depth was also found. Obtained strength parameters are within international ranges recommended for design purposes.

The present work deals with the impact crusher energy efficiency at San Andres Zeolitic Plant. Va... more The present work deals with the impact crusher energy efficiency at San Andres Zeolitic Plant. Varying the operational parameters levels (rotor velocity, hammer row number and crusher capacity) were carried up two experimental series: First series was aimed to obtain the influence of the operational parameters on the power consumed by the crusher motor; the second series evaluated the crusher specific energy consumption behavior. First series empirical model obtained describes the influence of operational parameters on power consumption. Also the relationship among specific energy consumption and crusher speed and capacity were obtained. The most efficient operational regimen corresponded to 1100 rpm of the rotor velocity, 2 hammer row numbers and 15 t/h of crusher capacity.

This work proposes a methodology to predict the elastic modulus of lightweight aggregate concrete... more This work proposes a methodology to predict the elastic modulus of lightweight aggregate concretes. To this end an analytical formula is achieved by curve fitting experimental results from 135 concrete samples made of 45 different mixes. The validation of the proposed methodology is carried out by applying the obtained analytical formula to a set of 90 concrete samples made of 30 different mixes. Comparisons with other methods applied to predicting the elastic modulus of lightweight aggregate concretes indicate that the results show good agreement and suggest that the proposed methodology could be applied in practical situations.

Nb-V complex carbide coatings were produced on AISI D2 steel substrates using the thermo-reactive... more Nb-V complex carbide coatings were produced on AISI D2 steel substrates using the thermo-reactive diffusion (TRD) process in order to improve the surface hardness and wear resistance of this tool steel. The carbide coating treatment was performed using molten borax with added ferroniobium, ferrovanadium, and aluminum at temperatures of 1223, 1293, and 1363 K for 2, 3, 4, and 5 h. The coating layers were characterized with scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS). The growth rates of the coatings were studied, and a kinetic model of the layer thickness was constructed as a function of the time and temperature treatment. The hardness and friction coefficient (COF) of the coatings was measured through nanoindentation and pin on disk test respectively. The carbide layers had a homogeneous thickness and a hardness of 37.63 GPa, which is close to values obtained in superhard materials, and the COF was in the range of 0,3 for the coated steels.

This research focusses on tribological analysis of Titanium Aluminum Nitride (TiAlN) coatings dep... more This research focusses on tribological analysis of Titanium Aluminum Nitride (TiAlN) coatings deposited by means of Triode Magnetron Sputtering, when used as a protective coating on forming tools. The analysis is carried out from the microstructural properties which directly influence the tribological behavior. It was observed that the predominant wear mechanisms on the surface are delamination and tribo-oxidation; an increase in the useful life of the tool was observed making hard coatings an excellent alternative in the metalworking industry.

This paper states an approach for the operationalization of a solution architecture model, as an ... more This paper states an approach for the operationalization of a solution architecture model, as an integral part of the development process and the applications maintenance. The proposed approach has been put into practice in a Company from the financial sector. The process of construction and implementation process of technological solution in an Enterprise takes multiple practices and management models, and it brings into play different roles and actors during its execution, from the business and technological perspective. Recently, the concept of solution architecture, has emerged as a better practice (little explored and documented) and it is being used in the execution of initiatives related with the development of technology solutions cycle, also it interacts collaboratively with other better management practices as software and enterprise architecture.

The deployment of digital TV in Uruguay is ongoing, following the ISDB-Tb standard. The channels ... more The deployment of digital TV in Uruguay is ongoing, following the ISDB-Tb standard. The channels allocation process was completed, and after the adoption of a testing protocol, the introduction of decoders and receivers began in early 2014. Testing their compliance with the standards is of paramount importance in order to foster migration towards it and to provide a platform to local developers. The government committed the School of Engineering and the Software Testing Centre to the elaboration of the testing protocol. This article reports the key aspects of this work: the analysis of the standards, the definition of a type approval protocol and the experience gained by applying the testing procedures. Its goal is to share the experience and contribute to the improvement of the digital TV adoption process, hopefully aiding to avoid some problems that were detected during this work, both in regulation and in devices compliance to the standards.

In this paper the thermal analysis of the push out test of steel – concrete channel connections a... more In this paper the thermal analysis of the push out test of steel – concrete channel connections at elevated temperatures is carried out. The study takes into account numeric results generated by the program SuperTempcalc for two alternatives: protected and unprotected beams. Temperatures are proposed to be considered in determining the reduction factors of resistance and the impact of these results in determining the strength of the connection is evaluated. Finally, a simplified method for calculating the resistance of the connection is proposed, which considers defined temperatures in the concrete by the thermal analysis and is consistent with the formulations for calculating the resistanceof channel connections at room temperature and with the current formulation for stud connections at elevated temperatures provided by international codes.

The strategic members of collaborative supply chain have been looking for actions to synchronize ... more The strategic members of collaborative supply chain have been looking for actions to synchronize their links. The purpose is to improve the customer service and fulfill the challenges of the globalized competitiveness. This trend is known as integrated supply chain and improves the companies performance as a whole. In this paper, an integration model of collaborative supply chain was developed considering the strategical, tactical and operational perspectives. To implement it, a measurement instrument was designed and validated statistically. Also a mathematical model using fuzzy logic was designed and applied among 36 small, medium and large Mexican companies to determine their integration level and propose specific actions that allow them to improve it.

Time and cost overruns in highway construction are usual in Colombia. Contractors regularly fail ... more Time and cost overruns in highway construction are usual in Colombia. Contractors regularly fail in cost estimation and construction scheduling. An analysis of important factors on time and cost overruns in highway construction in southwest Colombia is presented in this paper. Forty highway construction projects were reviewed. Data from construction documents were collected to prepare a data base for probabilistic analysis. Data collected include scheduled construction time and cost, actual construction time and cost, and unexpected events which could have affected the construction process. Data were used in a probabilistic cost and schedule risk analysis to identify critical factors in construction time and cost overruns in the region. It was found that the activities that most affect the time and cost overruns are the construction of the granular base and the asphalt layer. The most common causes of construction overruns were found to be poor cost and duration estimates, rain, and materials supply problems.

Distributed generation currently has caused an increase in the installation or renewable energy g... more Distributed generation currently has caused an increase in the installation or renewable energy generation resources near the consumption
centers and the ability to operate in the event of a failure of the interconnected system in isolation mode. However, this type of generation
and operation has not progressed significantly in Colombia due to the lack of financial mechanisms. This paper presents a model in System
Dynamics that proposes a mechanism for the promotion of distributed resources by including regulatory incentives known as Renewable
Energy Premium Tariff and incentives for providing technical support for the distribution and transmission system. Proposed mechanisms
help to promote the use of renewable energy in Colombia and further enhance the tools so that grid operators can avoid accidental
disconnection.

This paper presents a novel methodology to characterize loads using the instantaneous power tenso... more This paper presents a novel methodology to characterize loads using the instantaneous power tensor theory in three-phase three-wire or four-wire systems. Tensor theory is based on the dyadic product between voltage and current instantaneous vectors; this definition allows us to represent the phenomena of power quality produced by loads operation, through the deformation of a cube and the trajectory of one of its three-dimensional vectors. This new way of characterization could help researchers to construct better models of three-phase loads, or to achieve a better monitoring and machines diagnosis. Results are reached by implementing simulations in MATLAB® and endorsed with experimental measurements.

Voltage sags are the most common power quality disturbances in electrical facilities. It may caus... more Voltage sags are the most common power quality disturbances in electrical facilities. It may cause malfunction in sensitive equipment and process interruption. The distribution static compensator (DSTATCOM) is a device that can compensate voltage sags by injecting reactive power into distribution systems. This paper shows the influence on voltage sags characteristics by the presence of twelve-pulse DSTATCOM in the modified IEEE-13 distribution system. The analysis is performed by means of a random generation of disturbances using a MATLAB routine to identify the critical buses of the test system. Further, the DSTATCOM model taking advantage of the available elements from ATP/EMTP software is described. Simulations show that when DSTATCOM is placed directly to an affected bus it is possible to obtain a complete mitigation of the voltage sag. Finally, the relation between the reactive power injected by DSTATCOM, the type of voltage sag and the location of the affected bus is considered.

A model to improve the estimation of the power and energy from photovoltaic installations under d... more A model to improve the estimation of the power and energy from photovoltaic installations under dynamic shading conditions is proposed in this paper. The model considers the shaded profile in each photovoltaic module and the temperature profile to update the model parameters of each photovoltaic module. The impact of dynamic shades on the power production is analyzed, illustrating the large errors introduced by classical prediction approaches, which consider non-shading at all or average shading. Moreover, a procedure to model the shades profile in any environment is described and illustrated. Finally, experimental irradiance and environment temperature profiles are used to evaluate the performance of the proposed model in contrast with the classical approaches. The results illustrate that the classical approaches overestimate the power produced by the photovoltaic array, in contrast with the power produced by the proposed model.

This paper presents a methodology to estimate the effects of heating and lifetime in Low Voltage ... more This paper presents a methodology to estimate the effects of heating and lifetime in Low Voltage conductors (LV) due to the presence of stationary power quality disturbances. Conductor overheating and cable insulation accelerated aging can be caused by temporary increases in the RMS values of the voltages and currents due to stationary disturbances. Waveform distortion, unbalance and phase displacements can be considered among the stationary disturbances. For disturbances with short duration, there are no significant reductions in the insulation lifetime, but disturbances acting for long time periods will cause cumulative and detrimental effects. Currently valid models for insulation aging are employed; the expected power quality disturbance levels are extracted from power quality databases. A discussion about the effects on insulation lifetime is presented.

This paper shows the behavior of a three-phase power converter with resistive load using a quasi-... more This paper shows the behavior of a three-phase power converter with resistive load using a quasi-sliding and a chaos control techniques for output voltage regulation. Controller is designed using Zero Average Dynamic (ZAD) and Fixed Point Inducting Control (FPIC) techniques. Designs have been tested in a Rapid Control Prototyping (RCP) system based on Digital Signal Processing (DSP) for dSPACE platform. Bifurcation diagrams show the robustness of the system. Chaos detection is a signal processing method in the time domain, and has power quality phenomena detection applications. Results show that the phase voltage in the load has sinusoidal performance when it is controlled with these techniques. When delay effects are considered, experimental and numerical results match in both of stable and transition to chaos zones.

Distributed generation (DG) is an important issue for distribution networks due to the improvemen... more Distributed generation (DG) is an important issue for distribution networks due to the improvement in power losses, but the location and size of generators could be a difficult task for exact techniques. The metaheuristic techniques have become a better option to determine good solutions and in this paper the application of a bat-inspired algorithm (BA) to a problem of location and size of distributed generation in radial distribution systems is presented. A comparison between particle swarm optimization (PSO) and BA was made in the 33-node and 69-node test feeders, using as scenarios the change in active and reactive power, and the number of generators. PSO and BA found good results for small number and capacities of generators, but BA obtained better results for difficult problems and converged faster forall scenarios. The maximum active power injections to reduce power losses in the distribution networks were found for the five scenarios.

The occurrence of impact events (e.g. blackouts with vast geographic coverage) into electrical cr... more The occurrence of impact events (e.g. blackouts with vast geographic coverage) into electrical critic infrastructure systems usually require the analysis of cascade failure root causes through the conduction of structural vulnerability studies, with well-defined methodologies that may guide decision-making for the implementation of prevention actions and for operation recovery of the power system (e.g. N-1 and Nt contingency studies). This technical contribution provides some alternative techniques based upon complex networks and graph theory, which in the last few years, have been proposed as useful methodologies for analysis of physical behavior of electric power systems. Vulnerability assessment is achieved by testing their performance into random risks and deliberate attack threat scenarios. Results shown in this proposal lead to conclusions on the use of complex networks for contingency analysis by means of studies of those events that result in cascade failures and consumer disconnections.

A specialized genetic algorithm applied to the solution of the electric grid interdiction problem... more A specialized genetic algorithm applied to the solution of the electric grid interdiction problem is presented in this paper. This problem consists in the interaction of a disruptive agent who aims at maximizing damage of the power system (measured as load shed), and the system operator, who implements corrective actions to minimize system load shed. This problem, also known as “the terrorist threat problem”, is formulated in a bi-level programming structure and solved by means of a genetic algorithm. The solution identifies the most vulnerable links of the network in terms of a terrorist attack, providing signals for future reinforcement of the network or more strict surveillance of critical elements. The proposed approach has been tested on three case studies: a didactic five-bus power system, a prototype of the Colombian power system and the IEEE Reliability Test System. Results show the robustness and applicability of the proposed approach.

This paper proposes a methodology to model and analyze the security scheme required by a microgri... more This paper proposes a methodology to model and analyze the security scheme required by a microgrid that considers the participation of renewable energy sources. This security scheme is represented by an up and down spinning reserve, which allows to drive the system frequency to a steady state after the occurrence of events associated not only to forecast errors in the electricity demand (as traditional schemes do), but also to forecast errors in the power availability of the intermittent energy sources. The proposed methodology was implemented on a real microgrid that considers the interconnection of a photovoltaic generator. From this, it was concluded that the security scheme designed for the microgrid efficiently ensured the relation between generation and demand, at each study hour.

This paper presents a methodology for the relative location of voltage sags source based on volta... more This paper presents a methodology for the relative location of voltage sags source based on voltage measurements only. Network faults are the most frequent disturbances in the electrical systems and in turn are the causes that generate most voltage sags. Thus, the proposed algorithm considers only voltage sags by network faults, and a minimum of three voltage meters is required. Power quality can be evaluated automatically using the characterizing and extracting information from voltage records. The positive sequence voltages are the descriptors used to determine the relative location of the voltage sags causes, and the methodology is applied to a simulation where its effectiveness is verified. Matlab was used for validating this methodology, and voltage records of simulated voltage sags were generated in ATP-EMTP.

A methodology that is based on epidemiological analysis to assess risk factors and harmonic disto... more A methodology that is based on epidemiological analysis to assess risk factors and harmonic distortion incidence rate in a distribution network is proposed in this paper. The methodology analyzes the current harmonics emission risk at the PCC due to the connection of disturbing loads. These loads are modeled, and multiple loads connection scenarios are simulated using Monte Carlo Algorithms. From the simulation results, potential risk factors for critical harmonics indicators are identified, leading to a classification of the scenarios into groups of exposed or unexposed to risk factors. Finally, the incidence rate of harmonics is calculated for each load connection scenario and the risk of critical harmonics scenarios due to the exposure to risk factors is estimated.

The need for new generation systems has motivated the development of microgrids. This new concept... more The need for new generation systems has motivated the development of microgrids. This new concept may provide significant benefits such as losses reduction, high degree of efficiency and reliability to the transmission and distribution networks. This paper presents generalities about microgrids, including general structure and different topologies. Also an original methodology for facilitating its design and evaluation is proposed. Finally, the microgrid located at the Parque Tecnológíco de Guatiguará at the Universidad Industrial de Santander, is analyzed and an operation analysis is included for different operations stages of loads and generation, the performance of operation of storage systems, the interaction with the grid and an energy balance for all the system.

In this paper, the characteristics and definitions of NZEBs are studied. In particular, the metho... more In this paper, the characteristics and definitions of NZEBs are studied. In particular, the methods for calculating balance for each concept and methodology are analyzed in this work, taking into account the interaction of the NZEB with the energy grid, the emissions produced per energy consumption and the introduction of the primary energy concept as an indicator of balance. High-energy-efficient appliances are the main interest in this paper due to their importance and level of use in tropical regions. How these appliances can reduce energy consumption is described, as well as their impact on electrical performance being of significant benefit in Colombia. That is if they could be applied on a massive scale in projects related to Viviendas de Interés Social –VIS (social dwellings) in the long term.

Load modeling is an important task in power system stability analysis and control. Taking this in... more Load modeling is an important task in power system stability analysis and control. Taking this into account, the development of dynamic load models using a measurement-based load modeling strategy and an improved particle swarm optimization algorithm is presented in this paper. To accomplish this objective, a measurement-based parameter estimation method is used for identification of an exponential recovery load model. Measurements are obtained performing dynamic simulation of an IEEE 30-bus test system under several disturbances, and, additionally, a cross validation technique is applied for an analysis of load model generalization capability. An adequate load modeling improves the comprehension of load behavior and the capability of reproducing transient events on power systems.

The impedance-based approaches for fault location in power distribution systems determine a fault... more The impedance-based approaches for fault location in power distribution systems determine a faulted line section. Next, these require of the voltages and currents at one or both section line ends to exactly determine the fault location. It is a challenge because in most of the power distribution systems, measurements are only available at the main substation. This document presents a modeling proposal for the power distribution system and an easy implementation method to estimate the voltages and currents at the faulted line section, using the measurements at the main substation, the line, load, transformer parameters and other serial and shunt connected devices and the power system topology. The approach here proposed is tested using a fault locator based on superimposed components, where the distance estimation error is lower than 1.5% in all of the cases.

Electronic devices have a non-linear characteristic and emit harmonics into the low voltage grid.... more Electronic devices have a non-linear characteristic and emit harmonics into the low voltage grid. Different harmonic studies analyze their impact on the grids based on different types of harmonic models. The most used model is the constant current source. Measurements have shown that the harmonic currents emitted by electronic devices depend on the circuit topology and the existing supply voltage distortion. This paper quantifies the impact of supply voltage distortion on the harmonic current emission of individual devices and the summation of multiple devices. After a classification of the commonly used circuit topologies, a time-domain model is developed for each of them. Then the individual and combined impact of voltage harmonics on the harmonic current emission of the modeled devices is analyzed based on simulations. Finally the impact of voltage distortion on the summation of multiple devices is analyzed and the accuracy of constant current source models is evaluated.

In this paper the design and construction of a reduced scale model indented to be used for measur... more In this paper the design and construction of a reduced scale model indented to be used for measuring lightning induced voltages on overhead lines placed over inclined terrain is presented. The paper includes details about the voltage impulse source developed and used in obtaining fast front current surges along the reduced scale lightning channel. The experiment, although, it is only a first approximation of the phenomenon, is useful to validate exact expressions and simulation results obtained from several numerical methods. Additionally, several simulations are made by means of the FDTD method, which have the aim of showing the expected measurements of the reduced scale model.

Descendant Clock Auctions have been increasingly used in power markets. Traditional approaches ar... more Descendant Clock Auctions have been increasingly used in power markets. Traditional approaches are focused on discovering the bidders’ best response but neglecting the bidders’ adaptation. This paper presents an algorithm based on decision theory to estimate the bidders’ behavior throughout the auction. The proposed model uses portfolio concepts and historical data of spot markets to estimate a long-term contract supply curve. This model was applied to evaluate the Colombia’s Organized Market (MOR). Demand curve parameters and round size were varied to evaluate their impact over auction outputs. Results show that the demand curve has a quite small impact over bidders’ decisions and round size management is useful to avoid non-competitive bidders’ behavior. In addition, it is shown that auction’s starting prices strongly influence auction’s clearing prices. These results are extremely helpful to design market structures in power markets.

This paper presents a new method for the characterization and diagnosis of electrical disturbance... more This paper presents a new method for the characterization and diagnosis of electrical disturbances caused by fuses operation in the electrical distribution systems. A set of descriptors is proposed in order to quantify the typical features of the distortions caused by operation of expulsion and current limiting fuses. A multivariate statistical analysis is performed to select the descriptors with the best profiles qualifiers and the optimal decision thresholds are selected to classify the disturbances using machine learning algorithms. Voltage and current signals of the fuses operation are obtained from the ATP-EMTP simulation, as well as some real signals, to be all used in the validation of the new proposed algorithm, obtaining optimal performance and efficiency results. The algorithm was implemented in Matlab and the computational requirements are minimal.

Vega et al. [1] analyzed the influence of the attributes’ dependence when ranking a set of altern... more Vega et al. [1] analyzed the influence of the attributes’ dependence when ranking a set of alternatives in a multicriteria decision making problem with TOPSIS. They also proposed the use of the Mahalanobis distance to incorporate the correlations among the attributes in TOPSIS. Even in those situations for which dependence among attributes is very slight, the results obtained for the Mahalanobis distance are significantly different from those obtained with the Euclidean distance, traditionally used in TOPSIS, and also from results obtained using any other distance of the Minkowsky family. This raises serious doubts regarding the selection of the distance that should be employed in each case. To deal with the problem of the attributes’ dependence and the question of the selection of the most appropriate distance measure, this paper proposes to use a new method for synthesizing the distances to the ideal and the anti-ideal in TOPSIS. The new procedure is based on the Analytic Hierarchy Process and is able to capture the relative importance of both distances in the context given by the measure that is considered; it also provides rankings, which are closer to the distances employed in TOPSIS, regardless of the dependence among the attributes. The new technique has been applied to the illustrative example employed in Vega et al.

The vehicle routing problem under capacity constraints based on ubiquitous computing in a perspec... more The vehicle routing problem under capacity constraints based on ubiquitous computing in a perspective of deploying PSS (Product-Service Systems) configurations for urban goods transport, is addressed. It takes into account the specificities of city logistics under an emerging markets context. In this case, it involved: i) low logistical capabilities of decision makers; ii) limited availability of data; and iii) restricted access to high performance technology to compute optimal transportation routes. Therefore, the use of free download software providing inexpensive solutions (time and resources) is proposed. The paper shows the implementation of results to a software tool based on Graph Theory used to analyze and solve a CVRP (Capacitated Vehicle Routing Problem). The case of a local food delivery company located in a large city in Mexico was used. Based on small fleet vehicles with the same technical specifications and comparable load capacity.

As proposed by Michael Godet, an Structural Analysis exercise applied to achieve a representation... more As proposed by Michael Godet, an Structural Analysis exercise applied to achieve a representation of the system as close to reality as possible, and reducing its complexity to its essential macrovariables in the research on sustainable tourist called "Ruta del Oro" in Nariño Colombia, which seeks to conjugate the geologic mining patrimony with other resources existing in the field. It was discovered that the macrovariables that determine the system are the geology, the geomorphology and the climate; those on which it is possible to intervene to equilibrate it are, the water, the territorial structure, the vegetation and to a lesser extent, the soil. The dependent macrovariables are the landscape, the cultural resources and the fauna. These results were contrasted with the correspondent cartography, secondary information and fieldwork. It is concluded that the macrovariables of the investigation and the role identified each one are the adequate.

The supplier selection is a critical activity within the administration of the supply chain. It i... more The supplier selection is a critical activity within the administration of the supply chain. It is considered a complex problem given that it involves different aspects such as the alternatives to evaluate, the multiple criteria involved as well as the group of decision makers with different opinions. In this sense, the literature reports several methods to help in this difficult activity of selecting the best supplier. However, there are still some gaps in these methods; therefore, it is imperative to further develop research. Thus, the purpose of this paper is to report a hybrid method between MOORA and intuitionistic fuzzy sets for the selection of suppliers with a focus on multi-criteria and multi-group environment. The importance of decision makers, criteria and alternatives are evaluated in terms of intuitionistic fuzzy sets. Then, MOORA is used in order to determine the best supplier. An experimental case is developed in order to explain the proposed method in detail and to demonstrate its practicality and effectiveness.

In this paper we explore the multi-commodity flow formulation for the Asymmetric Traveling Salesm... more In this paper we explore the multi-commodity flow formulation for the Asymmetric Traveling Salesman Problem (ATSP) to obtain dual bounds. The procedure employed is a variant of a relax and cut procedure proposed in the literature that computes the Lagrangean multipliers associated to the subtour elimination constraints preserving the optimality of the multipliers associated to the assignment constraints. The results obtained by the computational study are encouraging and show that the proposed algorithm generated good dual bounds for the ATSP with a low execution time.

Mexico is the world’s third largest consumer of Polyethylene Terephthalate (PET), only preceded b... more Mexico is the world’s third largest consumer of Polyethylene Terephthalate (PET), only preceded by the United States and China. PET is commonly used in plastic containers such as beverage bottles and food packaging. It can be argued that the main problem regarding pollution generated by PET waste lies in the lack of appropriate solid waste management. The decision regarding facility location is the central issue in solid waste management. A mixed integer linear programming model of the capacitated facility location problem is proposed and then a genetic algorithm is designed to optimize the model. The problem is described as follows: given the quantities of PET generated in the northern region of Veracruz, Mexico, by considering five cities and each as a single generation source, a collection center has to be selected among a set of pre-identified locations in the town of Tempoal, Veracruz; in order to serve a set of demand points in the re-use market; demands are assumed to be uncertain. The aim is to minimize the system’s overall cost.

This paper addresses the short-term generation planning (STGP) through thermoelectric units. The ... more This paper addresses the short-term generation planning (STGP) through thermoelectric units. The mathematical model is presented as a Mixed Integer Non Linear Problem (MINLP). Several works on the state of art of the problem have revealed that the computational effort of this problem grows exponentially with the number of time periods and number of thermoelectric units. Therefore, we present two alternatives to solve a STGP based on Benders’ partitioning algorithm and Lagrangian relaxation in order to reduce the computational effort. The proposal is to apply primal and dual decomposition techniques, which exploit the structure of the problem to reduce solution time by decomposing the STGP into a master problem and a subproblem. For Benders’ algorithm, the master problem is a Mixed Integer Problem (MIP) and for the subproblem, it is a Non Linear Problem (NLP). For Lagrangian relaxation, the master problem and the subproblem are MINLP. The computational experiments show the performance of both decomposition techniques applied to the STGP. These techniques allow us to save computation time when compared to some high performance commercial solvers.

This work presents a model to obtain a stochastic frontier production function of a Mexican power... more This work presents a model to obtain a stochastic frontier production function of a Mexican power generation company. The stochastic frontier allows us to evaluate the technical efficiency of an energy producer according of the level of inputs. Electricity generation based on thermal generation is highly expensive due to operational inefficiency of thermal power plants. At the moment, in Mexico, technical efficiency of thermal power units has not been studied for the national electricity system. Therefore, in order to know the productivity levels of thermal generation, an empirical application of the stochastic frontier model is obtained using a panel data of thermoelectric units from the Mexican electricity system for the 2009-2013 period.

Distribution is one of the most important processes in a supply chain, given that it represents u... more Distribution is one of the most important processes in a supply chain, given that it represents up to two thirds of company logistics costs and up to 20% of the total cost of products. For that reason, it is essential to optimize the costs of distribution. A steel producer located in Monterrey distributes their products to different parts of Mexico. Currently, the distribution is carried out through empirical knowledge, underusing resources and generating unnecessary costs. The aim is to undertake the distribution process more efficiently. This paper presents an optimization model based on vehicle routing problem (VRP), for the distribution of heavy pipes taking into account the company’s own characteristics, such as: rented heterogeneous fleet, multiple shipments of products, split deliveries and open cycles (meaning that the routes may not necessarily end in the depot).

This paper presents an analysis of the effects of management commitment and organization of work ... more This paper presents an analysis of the effects of management commitment and organization of work teams in the benefits of implementing Kaizen in industrial enterprises during planning stages. To gather information, 200 questionnaires were applied to 68 companies distributed in the states of Tabasco, Sinaloa and Chihuahua in Mexico and in the province of Camagüey, Cuba. We used the methodology of least partial squares with the WarpPLS 4.0 software to develop a model of structural equations that explains such effects. The results show that when there is a high level of managerial commitment, this impacts the profits and competitiveness of companies positively. We also found that the organization of work teams has positive impacts on competitive benefits and these, in turn, on economic benefits. As a result of this study, we present the impact of certain critical success factors of Kaizen on the benefits of its implementation, which is a key factor in its sustainability over time.

Foreign trade barriers and duties have been significantly reduced by multilateral agreements and ... more Foreign trade barriers and duties have been significantly reduced by multilateral agreements and integration mechanisms among nations. Logistics costs represent a significant proportion of the final price of the items, especially of the commodities. For this reason, minimizing logistics costs is an important challenge for nations in order to enhance competiveness of foreign trade and in particular to take advantage of natural resources rents. In this article, we propose a holistic framework for estimating logistics costs, focused on determining over costs that result from inefficient procedures and a lack of adequate public policies and regulations of the public entities. These issues have not been considered in the literature, and this article fills this gap. As a case study, we present the application of the framework to estimate over costs in some natural resources logistics chains of Bolivia. A discussion of the results found is presented together with recommendations for further research.

The purpose of this work was to explore and define the sourcing services of Mexican third parties... more The purpose of this work was to explore and define the sourcing services of Mexican third parties in order to provide a better understanding of how they contribute to the attractiveness of the country as a low-cost production region. Given the exploratory nature of this research, the case study was the research method selected to collect relevant information. Two Mexican companies associated with global supply chains of different types—product-driven and buyer-driven—were selected as representative cases. Primary information was collected through in-depth personal interviews, site visits and secondary documents. The analysis of the two cases allowed the determination of the supplier governance structure and the assessment of the third parties’ contribution to the integration of local suppliers to global supply chains (GSC). In addition, the analysis contributes to the establishment of the value outsourcing services represent for international buyers as well.

The solubility of CO2 in Colombian heavy oil was calculated using the Peng-Robinson cubic equatio... more The solubility of CO2 in Colombian heavy oil was calculated using the Peng-Robinson cubic equation of state and the Lee-Kesler correlations. The crude was represented as a mixture of pseudo-components and for each one of them, the thermodynamic and critical properties were estimated. The results obtained in representing the oil with four, five and six pseudo-components show that all these representations produce similar results and therefore the use of four pseudo-components is sufficient and has a lower computational cost. Excellent results were obtained by comparing the experimental and calculated data. For this system, it is enough to have a complete characterization of the SARA analysis and to use four pseudo-components to adequately model the vapor-liquid equilibrium of CO2 -heavy oil.

Research and Development (R&D) project management style in companies can be different according w... more Research and Development (R&D) project management style in companies can be different according with their size and technological intensity. R&D Projects are characterized by high technical and economic uncertainty. And their execution carried out a learning process, although its aims were achieve the results planned. Results from a sample of 71 Spanish firms evidence that best practice in R&D project management promote the innovation in two ways. The purpose of practices is positively related to absorptive capacity of knowledge (CAC) in the organisation, and in turn, CAC affects the success of R&D projects.

Dyes and pigments are beginning to do in the country considered as a series of compounds that can... more Dyes and pigments are beginning to do in the country considered as a series of compounds that can have toxicological characteristics beyond the aesthetic aspects in wastewater. This review attempted to cluster the most effective treatments for the removal, destruction and mineralization of dyes and pigments present in wastewater depend on the physicochemical properties of the constituent molecules. The kinetics of removal of BOD, COD, "real" colour and "apparent" in effluents, in addition to operating times were studied to determine the set of physical technologies, chemical, biological and combined major and influence nowadays. Among the most relevant treatment technologies highlights the adsorption and filtration, advanced oxidation technologies (photocatalysis, ozonation, fenton / UV, electrocoagulation, etc.) and sequential biological processes (type anaerobic - aerobic). The influence of variables such as the pH, the initial concentration of dye and solubility, among others, on the kinetics of removal of specific dyes are evident.

The purpose of this paper is to present a quantitative approach to the selection of the mining ex... more The purpose of this paper is to present a quantitative approach to the selection of the mining extraction method by developing a methodological problem of discrete multicriteria decision making (MCDM), this approach seeks to support the process of planning and mine design. Select the extractive method is one of the problems of Discrete Multicriteria Decision (MCDM) where decision-makers had problems in assigning weight to each criterion. To solve this problem, this article suggests the ENTROPY method. This paper wants to handle the subjectivity inherent to this problem by using the VIKOR method, which yields results in a compromise alternative. The methodology proposed in this article applies in coal deposit located in the western side of Cerro Tasajero in Norte de Santander, Colombia

Design and ecology are critical issues in the industrial sector. Products are subject to constant... more Design and ecology are critical issues in the industrial sector. Products are subject to constant review and optimization for survival in the market, and limited by their impact on the planet. Decisions about a new product affect its life cycle, consumers, and especially the environment. In order to achieve quality solutions, eco-effectiveness must be considered, therefore, in the design of a process, its product development and associated system. An orderly methodology is essential to help towards creating products that meet both user needs and current environmental requirements, under paradigms that create environmental value. To date, the industry has developed techniques in an attempt to address these expectations under Cradle-to-Cradle (C2C), which is loosely structured around the conceptual frameworks and design techniques. The present work describes a new framework that encompasses all stages of design, and enables interaction under a set of principles developed for C2C. Under this innovative new paradigm emerges the Genomic Model of Eco-innovation and Eco-design, proposed as a methodology for designing products that meet individual and collective needs, and which enables the design of eco-friendly products, by integrating them into the framework of the ISO standards of Life Cycle Assessment (LCA), eco-design, eco-labeling, and C2C certification.

Mechanical and tribological properties of CrN coatings grown on steel substrates AISI 304 and AIS... more Mechanical and tribological properties of CrN coatings grown on steel substrates AISI 304 and AISI 4140 using the magnetron sputtering technique were analyzed. Coatings were grown at two pressures of work, 0.4 and 4.0 Pa. The films grown on AISI 304 at a pressure of work of 0.4 showed the highest hardness because they presented a larger grain size and lower roughness. For CrN synthesized at 0.4 Pa, the surface damage was lower during the tribological test. Adherence studies were also carried out, obtaining Lc1 and Lc2 for coatings produced at both pressures and on both substrates. Better adherence behavior was observed for films grown at a low pressure because these films were thicker (~890 nm).

In Weibull accelerated life test analysis (ALT) with two or more variables (X2, X3, ... Xk), we e... more In Weibull accelerated life test analysis (ALT) with two or more variables (X2, X3, ... Xk), we estimated, in joint form, the parameters of the life stress model r{X(t)} and one shape parameter β. These were then used to extrapolate the conclusions to the operational level. However, these conclusions are biased because in the experiment design (DOE) used, each combination of the variables presents its own Weibull family (βi, ηi). Thus the estimated β is not representative. On the other hand, since (βi, ηi) is determined by the variance of the logarithm of the lifetime data σt2 , the response variance σy2 and the correlation coefficient R2, which increases when variables are added to the analysis, β is always overestimated. In this paper, the problem is statistically addressed and based on the Weibull families (βi, ηi) a vector Yη is estimated and used to determine the parameters of r{X(t)}. Finally, based on the variance σy2 of each level, the variance of the operational level σop2 is estimated and used to determine the operational shape parameter βop. The efficiency of the proposed method is shown by numerical applications and by comparing its results with those of the maximum likelihood method (ML).

This study selects, in a structured manner, relevant articles with scientific recognition and sim... more This study selects, in a structured manner, relevant articles with scientific recognition and simultaneously identifies these publications’ characteristics that may scientifically enrich the proposed topic. The topic involves ergonomic costs as a criterion for evaluating and improving organizational performance in industry. This study uses Proknow-C as a theoretical instrument for intervention. The following results are obtained: a) a bibliographic portfolio of 16 items, aligned with the view adopted by researchers who served as this research’s theoretical framework; b) the Applied Ergonomics journal shows the highest number of scientific articles in the bibliographic portfolio; and c) Ergonomics, Costs, and Evaluation are the most frequent keywords. The studies selected using the methodology indicate that successful ergonomic projects result in substantially reduced production costs and associated economic and financial gain for the industry.

The quantitative scale of electronegativity, obtained by Linus Pauling, as a result of qualitativ... more The quantitative scale of electronegativity, obtained by Linus Pauling, as a result of qualitative electron affinity background, generated
multiple different and interesting proposals until today, which have proved to be the effort of ingenuity to get a universal concept of affinity,
which has resulted incomplete. Thermodynamics, specifically its thermochemical branch, has offered an explanation, which has been
accepted by The International Union of Pure and Applied Chemistry (IUPAC), as incomplete as the former. In both cases, it is thought that
the error is in regard to affinity as a property, rather than a behavior.

Salting and subsequent curing are part of the traditional processing method used in the meat and ... more Salting and subsequent curing are part of the traditional processing method used in the meat and fish industry. Different preserving
agents (sodium chloride, nitrite, nitrate, among others) are added in this process. Nowadays, more attention is paid to the amount of salts
added and the salting time employed. For this reason, it is important to know the factors governing salt penetration and the most
convenient process conditions. The transfer mechanism of the salts through the structure is an interesting aspect in meat and fish
processing technology. Mathematical models are the best way to discover the factors, which govern this process, which may represent
and explain the observed data and predict the behaviour under different conditions. The objective of this review is to describe the use of
the mathematical models to simulate meat and fish salting and the benefits derived from their use. Most of the models used to describe
the salting process are diffusional, based on Fick’s second law, although empirical ones are also used. For modelling purposes a good
description of the experimental results should be guaranteed. The complexity of the model will depend on the objective to be reached and
will be analysed in each case.

The infrastructure for hydrocarbon transportation has grown significantly to supply the needs of ... more The infrastructure for hydrocarbon transportation has grown significantly to supply the needs of a greater number of settlements; however,
due to problems in the supply networks, accidental spills or leaks can contaminate the underlying soils. This paper addresses soils
contaminated with gasoline, and it analyzes the changes that occur in a tropical residual soil after contamination. Analysis was carried out
by using specific laboratory tests to characterize the type of soil (Miniature Compacted Tropical Classification, Suction, Pinhole Test,
Collapse Potential, X-ray Diffraction, Scanning Electron Microscopy, pH determination) and by performing traditional tests (natural
humidity, specific gravity, granulometry, Atterberg limits, direct shear, etc.). These tests were conducted with samples in their natural state,
as well as contaminated samples, in order to elucidate possible variations in the mechanical characteristics of the material.

This article presents an intelligent system for container stacking based on fuzzy logic. The meth... more This article presents an intelligent system for container stacking based on fuzzy logic. The method establishes a defined criterion for
accepting or rejecting in real time an entry request to the stacking areas of the port in Valparaiso, Chile. A case study based on expert
knowledge illustrates the proposed method with real data. First, the optimum solution is determined for a problem of maximization of entries,
based on historical records from the traffic and information center of Valparaiso Port. Second, this solution is used to establish a strategy for
making “the best possible decisions.” The combination of the optimization and the fuzzy results (which consider the type of cargo, prices,
and capacity) is performed at two levels. First, the optimization results are used as feed for the fuzzy system to determinate a ratio of future
acceptances. Second, the optimization results are compared to the fuzzy system results in order to estimate a parameter to establish the
minimal percentage value for accepting a request. As a result, a proper use of the stacking area is achieved, which results in an increase of
profits and revenue management.

Anodizing of ferritic stainless steel has been used for decoration purposes to obtain a barrier e... more Anodizing of ferritic stainless steel has been used for decoration purposes to obtain a barrier effect. The most commonly used electrolyte for this
process is INCO (5M H2SO4 + 2,5M CrO3). INCO electrolyte with glycerin addition induces the formation of ordered porous structures, because
glycerin reduces the electrolyte conductivity. Ferritic stainless steel was anodized in electrolyte composed by 2M H2SO4 with glycerin addition
in different concentrations, without chromium oxide addition. It was observed that the addition of 90 v/v% glycerin promoted a reduction in the
electrolyte conductivity, which caused an increase in the anodizing potential. The glycerin addition to the electrolyte diminished the oxide
dissolution in the electrolytic solution, promoting the formation of an oxide with an ordered porous structure.

The notable increase in global consumption of plastics and their long residence time in the atmos... more The notable increase in global consumption of plastics and their long residence time in the atmosphere show the great need for
biodegradable products. In this project, we developed biodegradable polymers based on citric acid and glycerol. Their synthesis was
carried out at different conditions of constant temperature and concentration and they were synthesized using an economically viable
method. Characterization was undertaken using: Acid number, FTIR spectroscopy, refractive index, viscosity, impact analysis, tensile
test, hardness, calorimetry, the % humidity (oven method with recirculating air), and density determination, along with qualitative
evidence to corroborate their biodegradability. These elaborated polymers were mixed with medical grade PVC formulation, obtaining a
hybrid polymer, showing their mechanical properties were changed.

This work describes a methodology to evaluate the landscape residual impact of an opencast coal m... more This work describes a methodology to evaluate the landscape residual impact of an opencast coal mine in Laciana Valley (Spain),
applying a landscape impact index that evaluates: the loss of visual quality of the landscape due to the extractive activity and its visual
influence, depending on the visual absorption capacity of the environment, the degree of restoration of the upset areas, and its visibility
from the zones most frequented by the population. Final results of the evaluation show severe and moderate impacts on landscape
depending on the landscape unit. The landscape impact index is shown as a useful tool that can be applied to restoration designs,
environmental vigilance plans and recovery of areas degraded by mining activity.

This work presents a study of variance to rotation key encryption processors based on the Fourier... more This work presents a study of variance to rotation key encryption processors based on the Fourier transform. It was determined that the
key in rectangular coordinates allows a tolerance level of less than 0.2 degrees of rotation of the key in the decryption process. Thus, the
solution is to build the key in polar coordinates, by means of circular harmonics expansion; in this way, the tolerance threshold rises to
about 40 degrees of rotation of the key in the decryption process. This solution is an added value for optical encryption processors. I have
developed a computational tool for simulations and results obtained in this study.

This paper evaluates the toxicity associated with two industrial wastes used as raw material of g... more This paper evaluates the toxicity associated with two industrial wastes used as raw material of geopolymers. These wastes are fly ash
(FA) and spent catalyst catalytic cracking (FCC). The residues were characterized using techniques such as XRF, XRD, SEM and laser
granulometry. Two geopolymers systems based on FA-100% and FCC-100% were produced using SiO2/Al2O3 molar ratios of 6,0 and
2,4 and Na2O/SiO2 of 0,20 and 0,25 respectively. The technique TCLP (Toxicity Characteristic Leaching Procedure) was applied in
order to evaluate the toxicity. Cr, V, Zn, Ni, As, Ba, Sr, Pb and Cd elements were analyzed. The results indicate that concentrations
of heavy metals leachate (except V and As) are low compared with the environmental standards. The geopolymers studied are
considered effective in terms of inmobilizing contaminants.

In this work, we present a hybrid technique that combines a Genetic Algorithm with meta-heuristic... more In this work, we present a hybrid technique that combines a Genetic Algorithm with meta-heuristics to solve a problem in RENAULT
France’s production plants. The method starts with an initial solution obtained by means of a GRASP (Greedy Randomized Adaptive
Search Procedure) used as an input for a Genetic Algorithm complemented by a Simulated Annealing procedure of population
improvement. We establish a comparison point among the different techniques used in the method. Their performances are evaluated as
well as that of the entire method. The conclusion is that hybrid methods have clear advantages for the treatment of production planning
problems.

The transformations taking place in the Amazon, considered the "lungs of the planet", have specia... more The transformations taking place in the Amazon, considered the "lungs of the planet", have special significance, not only for energy
savings, but also for its environmental impact due to the reduction of greenhouse gases. Since 2010, in Manaus, the capital of Amazonas
in Brazil, many power plants are replacing fuel oil with natural gas for power generation. Because of the large natural gas reserves in the
region, this fuel has become the best choice for power plants built in this place. This paper analyzes the technical economic and
environmental impact of the substitution of fuel oil by natural gas in the analyzed power generation plant.

In this paper, symmetrical and unsymmetrical voltage sags are classified according to the severit... more In this paper, symmetrical and unsymmetrical voltage sags are classified according to the severity of the effects produced on the behavior
of induction motors, using the double-cage rotor model. The analyzed variables are: current and torque peaks, and speed loss in transient
and steady states. The severity of these effects is analyzed with 14640 voltage sags, both at the beginning of the voltage sag and when the
voltage is recovered, by changing the type, magnitude, duration, and initial-point-of-wave. Four mechanical torque loads were used for
the analysis, three with constant behavior and one with quadratic behavior. The results show the durations and initial-point-of-wave with
more severe effects for each type of voltage sag. Finally, a classification that depends on the type of voltage sag and the variable of
interest is obtained.

In the search for strategies to mitigate climate change, the promotion of renewable energy is a m... more In the search for strategies to mitigate climate change, the promotion of renewable energy is a major challenge worldwide, particularly
for developing countries such as Brazil and Colombia, which aim to diversify their power grids by using unconventional renewable
energy sources. One of the main obstacles is the development of innovative projects. Increasing oil palm cultivation in the Amazon
region for the food and biodiesel industries is producing a large volume of biomass. The present study outlines a methodology for
analysis of renewable energy projects based on identification of environmental, economic, and social sustainability criteria and indicators
(C&I) for the oil palm production chain. This methodology was then used to develop a computer simulation model in the RETScreen®
International software environment for financial viability and risk analysis.

Recent research is focusing on methods that enable effective consumption of digital content. Stud... more Recent research is focusing on methods that enable effective consumption of digital content. Students are continually exposed to streams
of digital content. An information system for learning was designed. Such a tool intends to connect learning in formal channels with the
ability to learn in informal channels. The proposed methodology built upon the application was tested through a quasi-experimental
research, implementing and evaluating its influence on how engineering students learnt in an advanced engineering course where
concepts are complex. The sample is of fifty-eight students enrolled in Computer Engineering at Universidad de Almería. Their
knowledge was evaluated using a specifically designed exam. Results suggest that the effectiveness of the methodology used and the
learning tool itself were both robust and fulfilled the hypothesis. The contrast tests Snedecor F for ANOVA two tail and two-sample Tstudent
test suggested the effectiveness of the learning tool proposed.

Washing machine manufacturers are working towards producing quieter appliances as many people con... more Washing machine manufacturers are working towards producing quieter appliances as many people consider noise emission a key factor
when buying. Although the spinning cycle is the noisiest, the amount of noise the pump makes is the cause for many users’ complaints. In an
attempt to reduce the noise emitted when a washing machine is pumping out, an experimental study was performed. First, the measurement
of the sound pressure allowed us to identify the main sources of noise as the electric motor and the vibration of the cabinet. Next, a detailed
analysis based on the measurement of the vibration of the cabinet provided information about the predominant radiating panels. It was also
inferred that the electromagnetic noise is drowned out by the structure-borne noise. Finally, several proposals to diminish the sound power
were analyzed, and a reduction of 3 dBA was achieved by decreasing the contact zone of the pump with the kick plate.

This paper presents the first systematic atmospheric corrosion assessment in Bogota. Main facts a... more This paper presents the first systematic atmospheric corrosion assessment in Bogota. Main facts about the study are related with special
characteristics of the City, such as population (more than eight million inhabitants), and altitude (2600 m over the sea level). Relative
humidity, temperature, and sulphate dioxide (SO2) concentration were measured. Simultaneously, corrosion rate of AISI-SAE 1006 plain
steel was measured throughout a year. Results show that atmospheric corrosion is between low and medium levels, C2–C3, according to
the ISO 9223 standard. Nevertheless, estimations from meteorological parameters produce lower corrosivity and, taking into account
SO2 concentrations, corrosivity in places with higher relative humidity, are higher than corrosivity measured on steel coupons. In
general, the main pollution problem is particulate matter, but higher corrosion rates were directly associated with SO2 levels. Gaps
between found results and international estimation methodologies are evident. Some relative explanations are proposed.

Singular Spectrum Analysis (SSA) is a non-parametric technique that allows the decomposition of a... more Singular Spectrum Analysis (SSA) is a non-parametric technique that allows the decomposition of a time series into signal and noise. Thus, it is a
useful technique to trend extraction, smooth and filter a time series. The effect on performance of both Box and Jenkins' and Holt-Winters
models when applied to the time series filtered by SSA is investigated in this paper. Three different methodologies are evaluated in the SSA
approach: Principal Component Analysis (PCA), Cluster Analysis and Graphical Analysis of Singular Vectors. In order to illustrate and compare
the methodologies, in this paper, we also present the main results of a computational experiment with the monthly residential consumption of
electricity in Brazil.

A diesel generator was simulated operating with palm oil as fuel and hydrogen doping the inlet ai... more A diesel generator was simulated operating with palm oil as fuel and hydrogen doping the inlet air. The objective was to investigate how
the addition of hydrogen can accelerate the end of vegetable oil combustion, and consequently improve the electrical efficiency of the
generator set up, for the same mass flow rate of fuel. The simulations were performed using AVL BOOST software and validated with
experimental data. The generator was simulated operating with 75%, 80% and 100% of the nominal load using palm oil in nature, and
hydrogen being injected at the intake manifold in parcels of 5% to a maximum of 20% in energy content by replacing the main fuel. The
simulations showed increase in electrical power, reduction in specific fuel consumption, improving the overall efficiency of the generator
set with 100% load. Good results were obtained with operation at 75% of the nominal load.

A method to extract 3D information using a white light interferometer without using PZT is presen... more A method to extract 3D information using a white light interferometer without using PZT is presented. Instead a positioning system that
uses the phase sensitivity of a target periodic is employed. The image treatment realized on the periodic target permits to calculate the
relative distance between Mirau objective and object surface. Topographic reconstructions of objects with dimensions of some tenths of
millimeters were calculated with an accuracy of approximately 28 nanometers. Theoretical analysis and experimental results are shown.

This research deals with the use of a calculus method in multi-criteria optimization. A modificat... more This research deals with the use of a calculus method in multi-criteria optimization. A modification do the algorithm of variable
integration was carried out, in order to establish a terminal criterion during the multi-objective optimization of the reactive power
compensation, in electric supply nets. It demanded the use of heuristic techniques, where the existence of high number of nodes, guided
the research towards methods able to minimize the required processing time to find a solution, without affecting the quality of the results,
and the convergence of the process, in spite of the high number of present members within the total population to be evaluated.

In this paper, we analyze in detail a Spanish historical nineteenth-century invention used for mi... more In this paper, we analyze in detail a Spanish historical nineteenth-century invention used for mineral extraction: the Emilina machine. In
particular, three-dimensional modeling is performed using software parametric (CATIA v5) of each of the elements of the set. Also, after
obtaining the 3D model, a functional analysis using techniques of Computer Aided Engineering has been performed, based on the
analysis of the von Mises stress and displacement, ensuring that the highest stress concentrations occur in the principal axis, the radii of
the pulleys, the upper cable of the main drum, the connection between the secondary shaft and the main drum and the wood support
structure, and that the highest concentration of displacements on the steering wheel of the steam machine, in the main shaft on which it is
coupled and in the pulleys.

Aluminum coatings were deposited on stainless steels AISI 304 and AISI 316 at a temperature range... more Aluminum coatings were deposited on stainless steels AISI 304 and AISI 316 at a temperature range from 560 to 600°C by CVD-FBR, using a
bed consisting of a 10% aluminum powder and 90% of bed inert (alumina) which was fluidized with Ar and an activator mixture of hydrochloric
acid with hydrogen (HCl/H2). The coating without heat treatment includes the follow species: Al13Fe4, Fe2Al5, FeAl2 and Al5FeNi for both steels.
In addition, the heat treatment causes the aluminum to diffuse into the substrate and the iron diffuse towards the surface of the coating, making
the transformation of previous existing compounds to FeAl, Fe2Al5, FeAl2, Al0.99Fe0.99Ni0.02, AlNi and Fe2AlCr. Thermodynamic simulation was
conducted with the Thermo-Calc software to obtain information of the possible composition and amount of deposited material, for selected
conditions. The specimens coated and uncoated were exposed at 750 ºC in an atmosphere where the vapor was transported to the samples using a
N2 flow of 40 ml/min plus 100% water vapor (H2O). The two uncoated substrates behaved differently, since the steel AISI 304 performed well
and gained little weight (0.49 mg/cm2), compared to the steel AISI 316 that lost too much weight (25.4 mg/cm2). Coated steels gained little
weight during thousand hours of exposure (0.26 mg/cm2) and support very well the corrosive attack compared to uncoated substrates.

The model developed tries to predict the stresses and strains of the structure of the pavement in... more The model developed tries to predict the stresses and strains of the structure of the pavement in a more real way, doing a lineal elastic
structural analysis in three dimensions with capacity to model loads of double axes, that which constitutes an advance regarding twodimensional
axisymmetrical models that only represent the state tense-deformational of the pavement under loads of simple axes. Earlier
stages of this research showed two-dimensional models under different load scenarios, league between layers and nonlinear constitutive
models, however the purpose is to move towards analysis methodology stress-strain state under standard loads. The model was
implemented in the Algor program and a comparison with the Elsym5 multilayer freeware was performed. The results warn the
existence of shear stress concentrations that can be causing major flaws that are not considered in traditional design methods which could
lead to the possibility of reassessed.

Asphaltene aggregation process was studied using molecular dynamics techniques. Four different st... more Asphaltene aggregation process was studied using molecular dynamics techniques. Four different structures were used. The first three
molecules have a continental structure, with condensed aromatic cores, while the forth has an archipelago structure, with small groups of
aromatic rings connected with saturated chains. The molecules were constructed in an atomistic framework, in which atoms are described
individually. Interaction forces were calculated at 300 K and 200 atm; Van der Waals and electrostatic interactions were evaluated
separately. For all four molecules the solubility parameter was calculated. It was found that Van der Waals interactions due to the
presence of aromatic rings and electrostatic forces caused by the presence of heteroatoms such as oxygen, nitrogen and sulfur, are equally
relevant in the aggregation of asphaltene molecules. For all molecules it was found asphaltene systems are more stable in aggregation
state than in monomeric state. For continental structures, the presence of long ramifications obstructs the formation of asphaltene
aggregates. For archipelago structures, the flexibility of the molecules enables the aggregation with other structures. The presence of
heteroatoms creates a repulsive force that hinders the aggregation process. The molecular volume and the cohesive energy are also
sensitive to the geometric configuration and the composition of the species, which affects the solubility parameter.

This article shows a retrospective analysis of energy demand and atmospheric pollution by urban t... more This article shows a retrospective analysis of energy demand and atmospheric pollution by urban transport in Aburrá Valley, where
Medellín is the main city. The study was carried out using LEAP model between 2000 and 2010, in order to generate information for
defining strategies to help reduce air pollution in Aburrá Valley. The results show that despite the rapid increase of vehicles, the energy
demand and CO2 emissions grew slowly, while criteria pollutant emissions decreased during the last decade. Also, the study shows that
during the modeled period trucks were an important source of CO, NOX, SOX and PM2.5. Motorcycles (2-cycles) were also important
contributors to VOC vehicular emissions.

The (Nb2O5) niobium pentoxide compound was synthetized by Pechini method. The followed synthesis ... more The (Nb2O5) niobium pentoxide compound was synthetized by Pechini method. The followed synthesis protocol is promising to obtain
Nb2O5 nanoparticles, in orthorhombic phase. This phase was obtained in the samples calcined at 600°C for 2 hours and the submitted at
500°C for 22 hours in gas flow. For the phase determination and crystal structure was performed XRD. The BET method was used to
obtain surface area measurements of the obtained oxide. Raman scattering was employed in order to analyze the nanostructures
vibrational spectrum and FEG-SEM in order to study the morphology of the obtain oxides.

Although mathematical modeling is a general engineering skill, problem analysis and solution desi... more Although mathematical modeling is a general engineering skill, problem analysis and solution design conventional tools in systems
engineering, such as use case diagrams, class diagrams and relational diagrams among others, are often not supported by a mathematical
model or this is not made explicit during learning. This may affect the ability of the systems engineer for interdisciplinary work, whose
participation in the requirements determination phase of the software development process can be reduced to be notified of the needs
identified by the other actors, without a critical contribution of its party. This paper presents results of research that show the favorable
effect of collaborative work mediated by information and communication technology ICT on System Dynamics mathematical modeling
skills developing by Systems Engineering students.

Integrating emerging technologies has shown to have the potential to improve access to rehabilita... more Integrating emerging technologies has shown to have the potential to improve access to rehabilitation services and the adherence for
physical therapy when they are applied into telemedicine environments. This systematic review aims to explore telerehabilitation systems
that use motion capture and video games for upper-limb rehabilitation purposes. Motion capture was focused on the information fusion
from inertial sensors and other technologies. The search was limited to 2010-2013, from which 667 papers were obtained; afterwards,
duplicate papers were removed, thus, reducing the sample to 57 papers with full text availability. Finally, only 3 of them were selected by
approaching the subject of this study. We conclude that the fusion information from inertial sensors and other motion capture
technologies appears to be a new tendency in remote monitoring of motor rehabilitation process. However, the combination of them with
active video games in physiotherapy programs is only an emerging research area with promising results.

We statistically analysed the chemical components present in waste water from mines in Galicia (N... more We statistically analysed the chemical components present in waste water from mines in Galicia (NW Spain). These elements pose a risk
to public health and the environment, most particularly in the event of a failure in the containment structure of a pond or dam.
The statistical processing of the data, which started with an analysis of the typical contaminants present in mining ponds and dams,
pointed to the potential limitations of using non-spatial models for spatially structured data.
Our results indicate the greater potential of the generalized linear spatial model over the generalized linear model for analysis of spatially
structured data. We also show how a misspecification of the model for analysing spatial data can lead to misleading conclusions, which
might lead, in turn, to poorly designed protective or corrective measures.

This paper introduces a broadband planar inverted-F antenna (PIFA) with U–Shaped capacitive feed ... more This paper introduces a broadband planar inverted-F antenna (PIFA) with U–Shaped capacitive feed technique for higher LTE band
applications. The proposed antenna is based on a simple PIFA, where the capacitive feed plate, radiating plate and ground plate is
modified into a U–Shaped such that the antenna can have wideband characteristics. With the use of the proposed feeding configuration,
the antenna shows a very wide pattern and impedance bandwidth of about 81.6% for VSWR ≤ 2.0 from 1.66 GHz to 3.95 GHz which can
cover the higher band of LTE (1.71GHz-3.8GHz), DCS 1800, DCS 1900, UCDMA, UMTS, IMT 2000, DMB, Wi-Fi, 2.4GHz, WiMAX
(2.3–2.5 GHz), WiMAX (3.4–3.5 GHz) and Bluetooth applications.

The fixation of arsenic contained in gases produced during pyrometallurgical processes by using s... more The fixation of arsenic contained in gases produced during pyrometallurgical processes by using solid ferric oxide was studied in the
range 873-1073 K under different oxygen potential and solid aggregates porosities. Arsenic fixation on solid iron oxides is described by
the pore blocking model under the studied conditions. The solid product of the reaction has a molar volume 3 times larger than the solid
reactant causing fast decreasing of the inter-granular spacing. The activation energies of arsenic fixation reaction are 34.96 and 35.46
kJ/mol for porosities of 0.88 and 0.74 respectively, and for porosity of 0.55 the activation energy was 26.88 kJ/mol. These values of
activation energy show that intra-pellets diffusion has an effect only in samples with 0.55 porosity. Minor sintering of particles was
detected. Industrial application of the concept demands a reaction system, which in is required better gas-solid contact for attaining larger
conversions.

Tropical soils are soils that exhibit physical, chemical, mineralogical and mechanical characteri... more Tropical soils are soils that exhibit physical, chemical, mineralogical and mechanical characteristics that differ from those of temperate zone soils as a result of factors such as weather, humidity and other conditions of the tropics. These characteristics and the anthropogenic contamination of the environment are the subject of the present study, which aims to analyze a soil of tropical residual origin located in the municipality of Guarne – Antioquia (Colombia). Laboratory tests, some of which are more adequate to characterize this type of soil than classical methods (miniature compacted tropical classification, suction, the pinhole test, breakdown, the collapse index, X-ray diffraction, scanning electron microscopy) are performed on samples in their natural state and samples contaminated with a soap solution to establish the differences between the geotechnical characteristics of this soil under both conditions. Subsequently, the influence of the contaminant on the soil’s properties is discussed.

This paper is aimed at studying the elastoplastic behavior of longitudinally stiffened girder web... more This paper is aimed at studying the elastoplastic behavior of longitudinally stiffened girder webs subjected to patch loading and bending.
The investigation is carried out by means of nonlinear finite element analysis to study the structural behavior of the girder components
(flanges, web and stiffener) at ultimate limit state. Initial geometrical imperfections, plastic material behavior and large deflection effects
are considered in the model. For the numerical model validation, the computer results from the simulations are compared with
experimental results taken from the literature. A parametric study was carried out in order to investigate the influence of the applied
bending moment and the relative location of the stiffener on the ultimate strength to patch loading.

This work aims at obtaining optimal configurations of trigeneration systems in order to satisfy r... more This work aims at obtaining optimal configurations of trigeneration systems in order to satisfy required demands for electricity and
thermal loads for heating and cooling, evaluating the impact of the electricity, steam and chilled water production costs. A trigeneration
system produces electricity, heat and cooling effect using electricity or heat available. Emphasis is made on systems using absorption
chillers, including one using a hybrid absorption ejecto-compression chiller, here called tetra-combined trigeneration system. The
performance evaluation of systems is carried out by the application of exergy and exergoeconomic analysis of the proposed alternatives
in order to determine exergy efficiency and exergy based costs on production of system utilities. The Genetic Algorithms method has
been chosen for optimization to show the applicability of evolutionary techniques in trigeneration plants. The optimization shows
important profits in the exergy based costs of products, by means of the exergetic efficiency maximization of the different trigeneration
systems.

The development of an analog device to wirelessly modulate and record twelve cardiac leads, PC as... more The development of an analog device to wirelessly modulate and record twelve cardiac leads, PC assisted is reported. The system, which
has been developed using low cost components, contains only one signal conditioning stage and one stage for amplitude modulation with
FM transmission/reception. Also it contains an interface to select the cardiac leads remotely, which is based in the transmission/decoding
of audible dual frequency tones. The device has been tested on a group of volunteers simultaneously using a registered trademark
electrocardiograph, to assess the performance of the new device. Furthermore, the experimental results indicate that the device is a tool
suitable to conduct studies of vector-cardiography with maximum uncertainties of 20 % in the cardiac axis orientation measurement

The production of hydrogen by anaerobic fermentation of urban organic waste from fruits and veget... more The production of hydrogen by anaerobic fermentation of urban organic waste from fruits and vegetables was studied. Ten tests were
carried out under an incomplete factorial experiment design with four factors and three levels. The factors were: acidification pH,
acidification time, operational pH, and organic load. The response variables were: maximum hydrogen content (%) and maximum
hydrogen production (L/day). The results were fitted to a quadratic polynomial model. In the case of the maximum hydrogen content, an
R2 and an R2adjusted of 0.9987 and 0.988 were obtained, respectively. For the maximum production, an R2 and an R2adjusted of 0.9815 and
0.833 were obtained, respectively. Three mathematical techniques were used to obtain the maximum values in the response variables.
Fuzzy logic showed the best fit between the experimental values and estimated values. In addition, it predicts a maximum hydrogen
content of 58.5% and a maximum production of 63.4 L/day.

The environmental impacts caused by human activity, affects all productive and commercial activit... more The environmental impacts caused by human activity, affects all productive and commercial activities that support the day to day. The
products of massive consume such as footwear drive large impacts according to the materials and processes used for their manufacture.
This paper present a literature review with the main aim to identify which are the phases and materials that cause greater environmental
impacts to the environment, focusing on leather shoes. The results demonstrate that different authors reach similar results in terms of
phases and high impact materials. The results permit change the current way of action and to focus the main efforts of research on
tanning process.

The objective of this work is the implementation of passive water trough barriers to put in pract... more The objective of this work is the implementation of passive water trough barriers to put in practice EN-14591-2:2007 standard, as well as
an update of the continuing study of passive water barriers. The viability of water barriers in typical Spanish small cross section galleries
was analyzed and full scale testing at “Barbara” experimental mine in Poland was carried out. Suggestions for proper implementation of
standards in Spain are presented.

In this paper, we focus on the practical aspects of the formulation of industrial mixtures effici... more In this paper, we focus on the practical aspects of the formulation of industrial mixtures efficiently. Proposing a working strategy that
integrates the design of experiments and the PDCA cycle, from the point of view of the experimenter, rather than from theoretical
perspective, develop to define the experimental plan, get the data and adjust a statistically significant and high practical significance
model.

This research proposal applies geostatistical techniques to discover the relationship between the... more This research proposal applies geostatistical techniques to discover the relationship between the geographic locations of different gas
stations and the operational characteristics offered by the transport network of the city of Manizales. This research is supported by basic
information gathered for more than a year using GPS equipment (more than 18 million records). The time needed to get to gas stations is
calculated as well as the spatial coverage in terms of population and area. Graphical results are obtained and these explain the time
needed to get to a particular gas station. Quantitative comparisons are made among the different types of gas stations and the sectors of
the city lacking gas stations coverage are established