A. Van Brecht - Academia.edu (original) (raw)

Papers by A. Van Brecht

EU rules for the welfare of pigs define 40 lx for a minimum period of eight hours per day as the ... more EU rules for the welfare of pigs define 40 lx for a minimum period of eight hours per day as the minimum standards of light intensity in swine buildings. The aim of this study was to verify if the 40 lx light intensity level requested by EU rules was achieved in naturally vs. artificially illuminated areas of a pig house and to investigate light intensity distribution within the building and the pens. For this purpose, light intensity was continuously monitored in two compartments of a piggery at the height of 1.50 m along the central corridor, according to standard inspections adopted in pig farms. As a second step, light intensity was measured in a three dimensional grid at 5 heights (0 to 1.5 m) in six different positions in the pens to investigate light distribution at the heights of animals and humans. The light intensity level required by EU rules was reached 93\ub15.65% (9:00 am to 5:00 pm) in the artificially illuminated areas. In pens illuminated only by natural light and without dunging areas, the 40 lx level was never reached, while in pens with dunging areas the 40 lx were reached 83\ub11.83% (9:00 am to 5:00 pm). Analysis of the 3D distribution of light intensity revealed that the light level remained very low (15 lx) inside the pen

Transactions of the ASAE, 2005

It is known that there can be a significant temperature difference between the position of the cl... more It is known that there can be a significant temperature difference between the position of the climate controller sensor (room temperature) and the animal−occupied zone (AOZ) in a pig room. This study explores the advantages of using AOZ temperature in climate control. The objectives were: (1) to evaluate a current climate control system in a practical room with ground channel ventilation for weaned piglets by comparing AOZ and room temperature, and (2) to determine advantages of control of the heating system based on AOZ temperature by a model−based predictive (MBP) controller. Comparison of AOZ and room temperature showed that during the first 10 days of the two experimental batches, AOZ temperature was lower and showed greater fluctuations than room temperature, most likely due to the switching of the heating system (on/off). Animals close to the sensor could disturb the AOZ measurement. This was not the case during colder nights, when animals moved away from the sensor and the measured AOZ temperature was a good indicator of the air temperature around the animals. The data for those periods were suitable for use in this climate control study, but when applying the system in practice the disturbing effect needs to be prevented by better protection of the AOZ sensor. For the second objective, the course of the AOZ temperature was modeled based on data for five nights when the heating switched on and off several times (goodness of fit R t 2 = 0.77). One of the models was integrated in a simulated MBP controller that uses the model to predict future AOZ temperature; the controller switches the heating system on before the AOZ gets too cold and off before it gets too warm. The simulated AOZ temperature was more stable during an 11 h cold period; the standard deviation was reduced from 0.44°C to 0.18°C.

International Conference: Postharvest Unlimited, 2003

... ITEM METADATA RECORD. Title: CFD model validation for a ventilated installation. Authors:Zeri... more ... ITEM METADATA RECORD. Title: CFD model validation for a ventilated installation. Authors:Zerihun Desta, Tadiwos Van Brecht, A Meyers, Johan Baelmans, Tine Berckmans, Daniël. Issue Date: Feb-2003. Host Document: SHS Acta Horticulturae vol:599 pages:405-411. ...

Transactions of the ASAE, 2002

In relation to the percentage of chicks that hatch out of eggs in an incubator, the maintenance o... more In relation to the percentage of chicks that hatch out of eggs in an incubator, the maintenance of the optimum incubation temperature (37.2_C to 37.8_C) is a critical factor. The temperature of the embryo depends on three factors: (1) the air temperature of the incubator, (2) the exchange of heat between the egg and its micro-environment, and (3) the time-variable heat production of the embryo. In commercial incubators, the transport of heat between the egg and its environment is mainly the result of convection. The objective of this research is to quantify the gradients of the eggshell temperature and to quantify the heat transport between the eggshell and the surrounding air. The airflow pattern plays an important role in the spatio-temporal gradients of eggshells. Although the setpoint of the air temperature was 37.7_C, the spatio-temporal eggshell temperatures at day 17 varied between 36.51_C and 37.98_C. Despite these large eggshell temperature spatio-temporal gradients, 222 chicks hatched from the 300 incubated eggs. The fertility of the eggs was 78%. Using the eggshell surface temperatures, the mean convection coefficient at the beginning and at the end of the incubation process was determined.

Transactions of the ASAE, 2004

In a ventilated space, the incoming air jet and the resulting airflow pattern play key roles in t... more In a ventilated space, the incoming air jet and the resulting airflow pattern play key roles in the removal and distribution of heat, moisture, harmful gases, and particles from or around living organisms (man, animal, and plant). In this research, an optical flow algorithm was used to visualize and quantify the two−dimensional velocity components of a visualized air jet in a ventilated room. The airflow is visualized by adding smoke particles to the air. The results of the optical flow algorithm are in agreement with experimental measurements, and the algorithm is a low−cost alternative technique to measure the two−dimensional velocity components. This technique might be used to quantify the airflow pattern by image analysis. The maximum absolute error of the mean air speed calculated by the optical flow algorithm compared to the measured mean air speed distribution is 0.0162 m/s, which is a relative error of 16%.

Transactions of the ASABE, 2009

Light intensity in swine buildings is regulated by European rules that define minimum standards f... more Light intensity in swine buildings is regulated by European rules that define minimum standards for the welfare of pigs. This directive requires that "pigs must be kept in light with an intensity of at least 40 lux for a minimum period of eight hours per day" from 9:00 a.m. to 5:00 p.m. The objective of this study was to verify if the 40 lux light intensity level, as requested by EU rules for pig welfare, was achieved in a naturally versus artificially illuminated pig house under field conditions and to investigate the influence of the building structure on light intensity distribution within the building and the pens. Light intensity was monitored in an experimental swine facility comprising two different animal compartments in northern Italy. During the four-month trial, light intensity was recorded continuously at a frequency of 1 min using sensors located 1.50 m above the floor along the central corridor. As a second step, light intensity was measured in a three-dimensional grid at 0, 20, 75, 100, and 150 cm above the floor in six different positions within each pen to investigate how light was distributed in the pens at the heights of animals and humans. The results showed that, in the artificially illuminated areas, the light intensity required by EU rules for pig welfare was met a mean of 93% (89% in pens without dunging areas and 97% in pens with dunging areas) of the time between 9:00 a.m. and 5:00 p.m. In the areas illuminated only by natural light, the required light intensity level was achieved a mean of 41.5% of the time; in pens without dunging areas, the required light intensity level was never reached, while pens with dunging areas were illuminated at 40 lux 83% of the time. In general, based on EU rules, natural lighting was insufficient compared to artificial lighting in pens with no openings other than windows. Wider windows, positioned closer to the floor, could improve the lighting of the pen, avoiding the use of artificial light. Analysis of the 3-D distribution of light intensity, performed under clear sky conditions, revealed that light intensity at 150Ăcm height, as compared with lower heights, depends mostly on natural light coming from inlets and from the openings connecting the pens with the dunging areas. Nevertheless, even at this height, the light level remained very low (15 lux) and was totally insufficient for inspection of animals by the veterinarian or the farmer. For an identical light source, the 3-D distribution of light intensity in the compartment and in a pen depends on the type of pig building, the position of the pen in the building, and the presence of openings to the outside. The 3-D gradient of light intensity, or the variation of light intensity, measured in a single pen reached 3.98 lux m-1 , while the gradient in a compartment reached 4.45 lux m-1 , showing a non-homogeneous light distribution in the building.

Transactions of the ASABE, 2006

In addition to production, physiology, and health, behavior is an important issue with respect to... more In addition to production, physiology, and health, behavior is an important issue with respect to animal welfare when evaluating novel housing systems. Behavioral characteristics are usually evaluated by audiovisual observation done by a human observer present on the scene. This method is time consuming, expensive, subjective, and prone to human error. Automated objective surveillance, by means of inexpensive cameras and image-processing techniques, has the ability to generate data that provide an objective measure of behavior, without disturbing the animals. The specific purpose of this study was to develop a fully automatic on-line image-processing technique to quantify the behavior of a single laying hen as opposed to the current human visual observation. The image-processing system is based on the principle that the classification of behavior can be translated into classification of time series of different postures of the hen. The hen's postures can be recognized in the camera image. The classification of the hen's behavior is performed by dynamic analysis of a set of measurable parameters, which are calculated from the images using image-processing techniques. The parameters were chosen based on their computational demands and analysis of their discriminative power regarding the different types of a specific behavior. A first implementation of the system allowed us to identify three different types of individual behavior (standing, walking, and scratching). The objective of further investigation will be the classification of up to 15 different types of behavior, such as pecking, eating, drinking, wing stretching, etc.

Transactions of the ASABE, 2010

During the final phase of incubation, continuous recording and analysis of embryo sounds allow es... more During the final phase of incubation, continuous recording and analysis of embryo sounds allow estimations about the percentage of hatched chickens. The objective of this study was to predict the time at which all eggs in an industrial incubator had passed the stage of internal pipping (IP100%). Chicken vocalization starts around day 19 when lung respiration commences. The amount of chicken vocalization increases during the hatching process, resulting in an increase of sound energy in the frequency range of 2500 to 3300 Hz. Using a standard microphone mounted inside the incubator, continuous sound recordings were processed to monitor the sound intensity during the hatching process. The method discussed in this article was assessed in an industrial-scale hatch setter (19,200 eggs) and repeated five times. The results show that the sound intensity signal results in a specific pattern that holds information about the stage of hatching. It was shown for five trials that the time at which automatic IP100% detection occurred was within ±3 h of the manually observed time for IP100%. The results imply that real-time sound recording and analysis during incubation allow prediction of the hatch outcome in industrial incubators. Such an acoustic monitoring system might provide industrial users with valuable information for hatch management.

SPIE Proceedings, 1999

In a ventilated space, the incoming air jet and the resulting air flow pattern play key roles in ... more In a ventilated space, the incoming air jet and the resulting air flow pattern play key roles in the removal or supply of heat, moisture, and harmful gases from or to living organisms (man, animal, plant). In this research, two low cost image processing methods (boundary peeling and optical flow) were developed to quantify the 2-D trajectory and the deflection angle of an air jet in a ventilated room. The image processing algorithms were applied to a wide range of air jets in a laboratory test room. Based on the deflection angle of the air jet trajectory from the initial path, a distinction could be made between falling, instable or horizontal air jets.

International Journal of Vehicle Design, 2004

A data-based mechanistic (DBM) approach was used to model the spatio-temporal temperature distrib... more A data-based mechanistic (DBM) approach was used to model the spatio-temporal temperature distribution in the imperfectly mixed fluid in a car. The first phase of DBM involves the identification of a mathematical model from experimental data. A second order model proves to deliver a sufficiently good description of the temperature dynamics of the system (R 2 = 0.985). Furthermore, the physical interpretation of this second order model provides a useful variable. The physical meaning of one of the model parameters is what is called the local volumetric concentration of fresh air flow inside the car. It thus becomes possible to quantify the local air freshness in a complex geometric space as the interior of a car, only using simple temperature measurements. This technique could become a valuable tool in evaluating the performance of for instance climate controllers in interior spaces.

International Journal of Control, 2005

An on-line mathematical approach was used to model the 3-D spatio-temporal temperature distributi... more An on-line mathematical approach was used to model the 3-D spatio-temporal temperature distribution in an imperfectly mixed forced ventilated room. A second-order model proved to be a sufficiently good description of the temperature dynamics (R-2 = 0.929) of the system for control ...

Indoor Air, 2004

The present paper outlines a modeling approach, which has been developed to model the internal dy... more The present paper outlines a modeling approach, which has been developed to model the internal dynamics of heat and moisture transfer in an imperfectly mixed ventilated airspace. The modeling approach, which combines the classical heat and moisture balance differential equations with the use of experimental time-series data, provides a physically meaningful description of the process and is very useful for model-based control purposes. The paper illustrates how the modeling approach has been applied to a ventilated laboratory test room with internal heat and moisture production. The results are evaluated and some valuable suggestions for future research are forwarded.

Ergonomics, 2007

The performance of climate control systems in vehicles becomes more and more important, especiall... more The performance of climate control systems in vehicles becomes more and more important, especially against the background of the important relationship between compartment climate and driver mental condition and, thus, traffic safety. The performance of two different types of climate control systems, an un-air-conditioned heating/cooling device (VW) and an air-conditioning climate control unit (BMW), is compared using modern and practical evaluation techniques quantifying both the dynamic 3-D temperature distribution and the local air refreshment rate. Both systems suffer from considerable temperature gradients: temperature gradients in the U-AC (VW) car up to 8-9 degrees C are encountered, while the AC (BMW) delivers clear improvement resulting in temperature gradients of 5-6 degrees C. The experiments clearly demonstrate the effect of the presence of even a single passenger on the thermal regime, increasing the existing thermal discrepancies in the compartment with 15% independent of ventilation rate. Furthermore, in terms of air refreshment rates in the vehicle compartment, an air-conditioning unit halves the air refreshment time at all positions in the vehicle cabin, delivering a significant improvement in terms of human comfort. Similarly, extra air inlets in the back compartment of a car deliver progress in terms of cabin refreshment rate (93 s down to 50 s).

Energy and Buildings, 2004

This paper outlines a methodology for the reduction of a complex computational fluid dynamics (CF... more This paper outlines a methodology for the reduction of a complex computational fluid dynamics (CFD) model using data-based mechanistic (DBM) modelling technique. For this study a full scale, adiabatic walled ventilated installation was used. Primarily, a CFD model that is three dimensional, transient and turbulent was proposed and solved by a commercial package CFX 4.3 in order to obtain informative data that will be used to build a DBM model. At the inlet a step rise in temperature was applied and the ventilation rate is kept steady. Turbulence is modelled by the widely used standard k-model. Temperature responses at 36 monitoring positions inside the installation were extracted out of the simulation. In the second stage of the work, for the same ventilation system, a DBM model was formulated from an energy balance equation. The simplified refined instrumental variable (SRIV) algorithm is employed as model parameter identification tool. The obtained highly accurate model parameters for all monitoring positions demonstrate the possibility of reducing complex CFD models using identification technique.

Energy and Buildings, 2005

In this paper a data based mechanistic (DBM) model is proposed using a simplified heat balance fo... more In this paper a data based mechanistic (DBM) model is proposed using a simplified heat balance formulation for modelling the temperature distribution inside a full scale ventilated room. The model has a number of parameters which are physically meaningful and determined using time temperature data obtained from experiments for several inlet air flow rates. At the inlet a step input in air temperature is applied and temperature responses at 36 sensor locations were recorded. For all ventilation rates used, the parameters of the model are extracted using statistical identification technique. Later, model based predictive control (MBPC) algorithm is developed to control temperature profiles on pre-selected sensor locations. The developed DBM model is compact in structure and found to capture the temperature distribution with high accuracy. The MBPC, which is distinguished by explicit use of process models, is robust for disturbance and noise effects. Besides it has high tracking capability of the reference trajectory.

Proceedings of the …, 2003

... ITEM METADATA RECORD. Title: Reduction of complex CFD model using data based model approach. ... more ... ITEM METADATA RECORD. Title: Reduction of complex CFD model using data based model approach. Authors: Zerihun Desta, Tadiwos Van Brecht, A Meyers, Johan Baelmans, Tine Berckmans, Daniël. Issue Date: Oct-2003. ...

Proceedings of the …, 2004

... ITEM METADATA RECORD. Title: Numerical analysis of the local mean age of air and the local re... more ... ITEM METADATA RECORD. Title: Numerical analysis of the local mean age of air and the local refreshment frequency for forced ventilation system. Authors: Zerihun Desta, Tadiwos × Van Brecht, A Meyers, Johan Baelmans, Tine Berckmans, Daniël. Issue Date: 2004. ...