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Papers by Daniel Espinoza

KnE Engineering, 2018

Se cuantificaron, analizaron y compararon propiedades físicas de tres diluyentes (Shellsol, Orfom... more Se cuantificaron, analizaron y compararon propiedades físicas de tres diluyentes (Shellsol, Orfom y Escaid) utilizados en extracción por solvente de cobre y una solución sintética de lixiviación de minerales de cobre (PLS) con una concentración representativa de hierro y cobre. Las propiedades analizadas fueron densidad, viscosidad y tensión Interfacial, además se evaluó el efecto del porcentaje de extractante (porcentaje de extractante presente en la fase organica expresada en volumen/volumen) (% v/v) en la fase organica sobre la densidad y la viscosidad. Las concentraciones de cobre y hierro en el PLS fueron de 4,5 [g/L] y 5,0 [g/L] respecivamente. Las temperaturas utilizadas fueron 25, 35 y 45 °C. Los resultados obtenidos muestran que la temperatura produce un efecto similar sobre la densidad de los diluyentes y PLS, obteniéndose una tendencia semejante en las curvas con leves variaciones; por su parte el efecto de la temperatura sobre la viscosidad presenta las mayores diferenc...

Origen del conocimiento científico en Nuevo León. Innovaciones prehistóricas

Numerical simulations of high-speed, high-altitude flow over re-entry objects have been carried o... more Numerical simulations of high-speed, high-altitude flow over re-entry objects have been carried out for a variety of flow conditions corresponding to test cases proposed for the 1st Spacecraft Demise Workshop. In the continuum regime, conventional computational fluid dynamics (CFD) has been employed to characterise the aerothermodynamic loads acting on the bodies and to predict the shock structures in the surrounding flow fields. In the upper atmosphere, transition-continuum regime the direct simulation Monte Carlo (DSMC) approach has been applied using the quantum-kinetic (Q-K) chemistry model to account for the dissociation of nitrogen. Both CFD and DSMC approaches have been applied within the framework of the open-source CFD toolbox OpenFOAM.

Discrete Applied Mathematics, 2015

We consider the problem of separating maximally violated inequalities for the precedence constrai... more We consider the problem of separating maximally violated inequalities for the precedence constrained knapsack problem. Though we consider maximally violated constraints in general, special emphasis is placed on induced cover inequalities and induced clique inequalities. Our contributions include a new partial characterization of maximally violated inequalities, a new safe shrinking technique, and new insights on strengthening and lifting. This work follows on the work of Boyd (1993), Park and Park (1997), van de .

Lecture Notes in Computer Science, 2005

introduced the domino-parity inequalities for the symmetric traveling salesman problem and showed... more introduced the domino-parity inequalities for the symmetric traveling salesman problem and showed that if the support graph of an LP solution is planar, then the separation problem can be solved in polynomial time. We generalize domino-parity inequalities to multi-handled configurations, introducing a superclass of bipartition and star inequalities. Also, we generalize Letchford's algorithm, proving that for a fixed integer k, one can separate a superclass of k-handled clique-tree inequalities satisfying certain connectivity characteristics with respect to the planar support graph. We describe an implementation of Letchford's algorithm including pruning methods to restrict the search for dominoes, a parallelization of the main domino-building step, heuristics to obtain planar-support graphs, a safe-shrinking routine, a randomwalk heuristic to extract additional violated constraints, and a tightening procedure to allow us to modify existing inequalities as the LP solution changes. We report computational results showing the strength of the new routines, including the optimal solution of the TSPLIB instance pla33810.

Evaluation of Analog vs. ASIC Input/Filter Stage for Multimodal Biopotential Wearable Sensor Data Acquisition

2012 IEEE Ninth Electronics, Robotics and Automotive Mechanics Conference, 2012

ABSTRACT The current trends in wearable sensor technology suggest that, in the next decade or so,... more ABSTRACT The current trends in wearable sensor technology suggest that, in the next decade or so, garments will commonly include some form of biometric/biopotential measurement system and will be of great value for gathering ambulatory metadata for remote diagnosis. In parallel, the introduction of new powerful mixed-signal devices will enhance the possibility of garments including cost-effective biopotential measurements, over the classical analog signal conditioning configurations. This paper presents the use of a recently introduced ASIC device (ADS1298) for measuring ECG, EEG and EMG data, towards developing a multimodal biopotential measurement system. Two programmable analog filter configurations are tested for comparison. The results show that adjusting the analog filters to accommodate different biopotentials is an unfeasible task in comparison with the ASIC device, which proved useful for measuring common biopotentials: ECG, EMG and EEG, and thus is more suitable for wearable sensor applications.

PLoS ONE, 2011

Environmental factors, such as the macronutrient composition of the diet, can have a profound imp... more Environmental factors, such as the macronutrient composition of the diet, can have a profound impact on risk of diabetes and metabolic syndrome. In the present study we demonstrate how a single, simple dietary factor-leucine-can modify insulin resistance by acting on multiple tissues and at multiple levels of metabolism. Mice were placed on a normal or high fat diet (HFD). Dietary leucine was doubled by addition to the drinking water. mRNA, protein and complete metabolomic profiles were assessed in the major insulin sensitive tissues and serum, and correlated with changes in glucose homeostasis and insulin signaling. After 8 weeks on HFD, mice developed obesity, fatty liver, inflammatory changes in adipose tissue and insulin resistance at the level of IRS-1 phosphorylation, as well as alterations in metabolomic profile of amino acid metabolites, TCA cycle intermediates, glucose and cholesterol metabolites, and fatty acids in liver, muscle, fat and serum. Doubling dietary leucine reversed many of the metabolite abnormalities and caused a marked improvement in glucose tolerance and insulin signaling without altering food intake or weight gain. Increased dietary leucine was also associated with a decrease in hepatic steatosis and a decrease in inflammation in adipose tissue. These changes occurred despite an increase in insulin-stimulated phosphorylation of p70S6 kinase indicating enhanced activation of mTOR, a phenomenon normally associated with insulin resistance. These data indicate that modest changes in a single environmental/nutrient factor can modify multiple metabolic and signaling pathways and modify HFD induced metabolic syndrome by acting at a systemic level on multiple tissues. These data also suggest that increasing dietary leucine may provide an adjunct in the management of obesity-related insulin resistance.

Operations Research Letters, 2007

The use of floating-point calculations limits the accuracy of solutions obtained by standard LP s... more The use of floating-point calculations limits the accuracy of solutions obtained by standard LP software. We present a simplex-based algorithm that returns exact rational solutions, taking advantage of the speed of floating-point calculations and attempting to minimize the operations performed in rational arithmetic. Extensive computational results are presented.

Is the digitization of laparoscopic movement using accessible alternative technologies possible?

Minimally Invasive Therapy & Allied Technologies, 2011

It is widely documented that laparoscopic surgeons require training, and an objective evaluation ... more It is widely documented that laparoscopic surgeons require training, and an objective evaluation of the training that they receive. The most advanced evaluation systems integrate the digitization of the movement of laparoscopic tools. A great number of these systems, however, do not permit the use of real tools and their high cost limits their academic impact. Likewise, it is documented that new and accessible systems need to be developed. The aim of this article is to explore the possibility of digitizing the movement of laparoscopic tools in a three-dimensional workspace, using accessible alternative technology. Our proposal uses a commercial Wii video game control in conjunction with a program for determining kinematic variables during the execution of a recognition task.

Journal of Hand Surgery (European Volume), 2010