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Perez-Sarinana B.Y.,National Autonomous University of Mexico | De Leon-Rodriguez A.,San Luis Potosí Institute of Scientific Research and Technology | Saldana-Trinidad S.,Chiapas Polytechnic University | Joseph S.P.,National Autonomous University of Mexico
BioResources | Year: 2015

A response surface methodology with 2k full factorial design was applied to obtain optimum conditions for bioethanol production using coffee mucilage (CM) as the substrate and Saccharomyces cerevisiae NRRL Y-2034 as the inoculum. CM is an agro-industrial residue mainly composed of simple sugars; the product yield and productivity process were analyzed with respect to the fermentation, pH, temperature, and the initial sugar concentration. Employing the following predicted optimum operational conditions attained the highest bioethanol production: pH 5.1, temperature 32 °C, and initial sugar concentration 61.8 g/L. The estimated bioethanol production was 15.02 g/L, and the experimental production was 16.29 g/L ± 0.39 g/L, with a bioethanol yield of 0.27 g/L and a productivity process of 0.34 g/Lh. Glycerol was the predominant byproduct of the fermentative metabolism of S. cerevisiae. The response surface methodology was successfully employed to optimize CM fermentation. In the fermentative processes with yeast, optimizing the conditions of the culture medium is needed to fully exploit the potential of the strains and maximize the production of bioethanol.

Castro-Villarreal P.,Autonomous University of Chiapas | Ruiz-Sanchez R.,Chiapas Polytechnic University
Physical Review B - Condensed Matter and Materials Physics | Year: 2017

The general covariance of the Dirac equation is exploited in order to explore the curvature effects appearing in the electronic properties of graphene. Two physical situations are then considered: the weak curvature regime, with R<1/L2, and the strong curvature regime, with 1/L2 R<1/d2, where R is the scalar curvature, L is a typical size of a sample of graphene, and d is a typical size of a local domain where the curvature is pronounced. In the first scenario, we found that the curvature transforms the conical nature of the dispersion relation due to a shift in the momentum space of the Dirac cone. In the second scenario, the curvature in the local domain affects the charge carriers in such a manner that bound states emerge; these states are declared to be pseudo-Landau states because of the analogy with the well known Landau problem; here the curvature emulates the role of the magnetic field. Seeking more tangible curvature effects we calculate, e.g., the electronic internal energy of graphene in the small curvature regime and give an expression for the ground state energy in the strong curvature regime. © 2017 American Physical Society.

PubMed | Technological University of Mexico, Chiapas Polytechnic University and Colegio de Mexico
Type: Journal Article | Journal: Revista Argentina de microbiologia | Year: 2015

The tons of organic waste that are annually generated by agro-industry, can be used as raw material for methane production. For this reason, it is important to previously perform biodegradability tests to organic wastes for their full scale methanization. This paper addresses biodegradability, methane production and the behavior of populations of eubacteria and archaeabacteria during anaerobic digestion of banana, mango and papaya agroindustrial wastes. Mango and banana wastes had higher organic matter content than papaya in terms of their volatile solids and total solid rate (94 and 75% respectively). After 63 days of treatment, the highest methane production was observed in banana waste anaerobic digestion: 63.89ml CH4/per gram of chemical oxygen demand of the waste. In the PCR-DGGE molecular analysis, different genomic footprints with oligonucleotides for eubacteria and archeobacteria were found. Biochemical methane potential results proved that banana wastes have the best potential to be used as raw material for methane production. The result of a PCR- DGGE analysis using specific oligonucleotides enabled to identify the behavior of populations of eubacteria and archaeabacteria present during the anaerobic digestion of agroindustrial wastes throughout the process.

Sevilla-Camacho P.Y.,Chiapas Polytechnic University | Sevilla-Camacho P.Y.,Autonomous University of Queretaro | Robles-Ocampo J.B.,Chiapas Polytechnic University | Robles-Ocampo J.B.,Autonomous University of Queretaro | And 2 more authors.
Measurement: Journal of the International Measurement Confederation | Year: 2015

We present a reconfigurable system to detect and indicate online and in real time, the cutting tool conditions in high-speed face milling. It consists of a data acquisition system (DAS) and a hardware signal processing (HSP) unit. The DAS acquires and digitalizes the cutting vibration signals generated from machining tests performed under different tool conditions and cutting parameters. The HSP unit processes the digitalized vibration signals using reconfigurable IIR band-pass digital filter and statistical techniques, designed and implemented into a single field-programmable gate array (FPGA) and coefficients read-only memories. The system operation is divided into learning and monitoring modes. The tool condition is indicated by an alarm signal, one LED indicator, and a message shown on four-digit seven-segment displays. In all experiments, the system correctly detected the tool condition. The proposed system is fast, compact, reliable, and economical, and no modification of the machine-tool structure is required. © 2014 Elsevier Ltd. All rights reserved.

Ibanez G.,University of Arts and Science of Chiapas | Lopez A.,Chiapas Polytechnic University | Cuevas S.,National Autonomous University of Mexico
International Communications in Heat and Mass Transfer | Year: 2012

The influence of the geometrical and physical parameters on entropy generation for a viscous flow between infinite parallel walls of finite thickness is studied by solving the momentum and energy conservation equations. The conjugate heat transfer problem in the fluid and solid walls is solved analytically using thermal boundary conditions of the third kind at the outer surfaces of the walls and continuity of temperature and heat flux across the fluid-wall interfaces. Analytic solutions for the velocity and temperature fields in the fluid and walls are used to calculate the local and global entropy generation rate. Conditions under which this quantity is minimized are determined for certain suitable combination of geometrical and physical parameters of the system. Special attention has been given to the effect of the wall thickness on the entropy generation rate. It is found that the global entropy generation reaches a minimum for specific values of the wall thickness ratio, when the other parameters are fixed. © 2012 Elsevier Ltd.

Muniz J.,Chiapas Polytechnic University | Sansores E.,National Autonomous University of Mexico | Castillo R.,Chiapas Polytechnic University
Theoretical Chemistry Accounts | Year: 2013

The prediction of the series of [Au3X3M2] compounds (with X = H, F, Cl, Br, I and M = Li, Na, K, Rb, Cs) has been carried out by ab initio and DFT calculations. The systems are chemically stable due to their high chemical hardness. An unusual Au-Au attraction was found on each of the compounds along the series, addressing a strong metalophilic interaction of the aurophilic type. A strong aromatic character on the center of the [Au3X3]2-ring was also detected in the compounds under study, enhancing the stability of the species. The mechanism behind the bonding of the systems is mainly ruled by an electrostatic interaction among the 2 M+ cations and the [Au3X3]2-monolayer sheet in accordance with CDA and Ziegler analysis; only a slight orbital contribution yielded by back-donation from the alkaline metals to the [Au3X3]2-monolayer sheet is involved. It was shown that the [Au3Cl3M2] group has the highest Fukui indexes, indicating that a catalytic reaction may rise from an electrophilic attack centered at the Au atoms or a nucleophilic attack on the alkaline-earth metals. The latter was tested with the most stable system of this group, namely [Au3Cl3Li2], allowing it to interact with a CO molecule; the optimized [Au3Cl3Li2] [CO] system represents a bound state that highlights the reactive properties of the species. An extended-M-S-M-S-M- (with S representing the [Au3X3]2-system) linear chain model was also predicted at DFT level. Considering its spatial representation of the frontier molecular orbitals, it was found that a possible electronic transfer along the chain may take place via the triggering of an electron, suggesting the existence of a nanowire. © Springer-Verlag Berlin Heidelberg 2013.

Muniz J.,Chiapas Polytechnic University | Sansores E.,National Autonomous University of Mexico | Olea A.,Chiapas Polytechnic University | Valenzuela E.,Chiapas Polytechnic University
International Journal of Quantum Chemistry | Year: 2013

An ab initio, systematic study on the aromaticity involving the group of metalated extended porphyrins, termed meso-hexakis(pentafluorophenyl)- substituted[26]hexaphyrin( (HP), was performed for the first time. The aromatic behavior of the system shifted to antiaromatic in the [28]HP analogue, due to the presence of hydrogen atoms that break the orbital symmetry. The absorption bands observed in the experiment were assigned to an intraligand charge transfer, where the intrametallic character is also important. The excited states reveal the absorption of visible light and the possibility of electronic transfer to different systems. We propose a system such as single-walled carbon nanohorns (SWCNHs), due to their special electronic properties, and predict a novel nanohybrid material. The evidence of electronic communication between both species is presented in this work. The HP aromaticity and the spatial configuration of the interaction with SWCNHs are also related to the strength of electronic transfer among the systems, making the HP metalated antiaromatic species and their corresponding nanohybrids potential candidates to be used as building blocks in photovoltaic cell materials. © 2012 Wiley Periodicals, Inc.

Mendoza-Perez A.F.,Chiapas Polytechnic University | Hernandez-Lerma O.,CINVESTAV
Mathematical Methods of Operations Research | Year: 2010

This paper deals with discrete-time Markov control processes in Borel spaces, with unbounded rewards. The criterion to be optimized is a long-run samplepath (or pathwise) average reward subject to constraints on a long-run pathwise average cost. To study this pathwise problem, we give conditions for the existence of optimal policies for the problem with "expected" constraints. Moreover, we show that the expected case can be solved by means of a parametric family of optimality equations. These results are then extended to the problem with pathwise constraints. © 2010 Springer-Verlag.

Gonzalez-Mendoza M.,Monterrey Institute of Technology | Ibarra Orozco R.E.,Chiapas Polytechnic University | Garcia Gamboa A.L.,Monterrey Institute of Technology | Hernandez-Gress N.,Monterrey Institute of Technology | And 2 more authors.
Expert Systems with Applications | Year: 2014

This work presents a comparative analysis of specific, rather than general, mathematical programming implementation techniques of the quadratic optimization problem (QP) based on Support Vector Machines (SVM) learning process. Considering the Karush-Kuhn-Tucker (KKT) optimality conditions, we present a strategy of implementation of the SVM-QP following three classical approaches: (i) active set, also divided in primal and dual spaces, methods, (ii) interior point methods and (iii) linearization strategies. We also present the general extension to treat large-scale applications consisting in a general decomposition of the QP problem into smaller ones, conserving the exact solution approach. In the same manner, we propose a set of heuristics to take into account for a better than a random selection process for the initialization of the decomposition strategy. We compare the performances of the optimization strategies using some well-known benchmark databases. © 2013 Elsevier Ltd. All rights reserved.

Sevilla-Camacho P.Y.,Chiapas Polytechnic University | Robles-Ocampo J.B.,Chiapas Polytechnic University | Muniz-Soria J.,Chiapas Polytechnic University | Lee-Orantes F.,Chiapas Polytechnic University
International Journal of Advanced Manufacturing Technology | Year: 2015

This paper presents a monitoring method for on-line detection and indication of the occurrence of a cutting tool failure during high-speed face milling. The method consists of processing of the vibration signal using a reconfigurable infinite impulse response (IIR) bandpass digital filter and statistical techniques. The healthy tool threshold and the filter passband are adjusted and configured based on the cutting parameters that were set up during the machining process. For this process, sets of filter coefficients are pre-calculated for a number of defined insert passing frequencies ranges. The method is verified on-line during machining tests that are carried out at different tool failure levels and using various cutting parameters. In all experimental tests, the method allows the tool condition to be detected and indicated correctly. The proposed method is therefore shown to be simple, fast, computationally efficient, and reliable for the detection and indication of the presence of several types of tool failures for various cutting parameters, and the use of this method does not require any modification of the machine tool structure. © 2015 Springer-Verlag London

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