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Santiago de Querétaro, Mexico

Verde C.,Institute Ingenieria
European Control Conference, ECC 1999 - Conference Proceedings | Year: 2015

In this paper, it is proposed to estimate the robustness of a closed loop system by a error model which is obtained calculating the difference between the transfer matrix of the closed loop system with nominal and uncertain plant. For the estimation it is assumed an approximated model of the uncertainty in frequency domain. An advantage of this error model is its generality since it allows to consider additive, multiplicative or feedback uncertainty Δ. Additionally, here it is introduced a procedure based on this estimation to select the signals spectrum which must be weighted in the objective function used to synthesize linear controller. This procedure simplifies the task to weight signals in the frequency domain cost to be minimized, which could become a difficult job, specially for MIMO systems. Specifically, considering the standard H optimal control problem, the approach is validated with two design problems. © 1999 EUCA. Source


Arreola-Vargas J.,San Luis Potosi Institute of Scientific Research and Technology | Celis L.B.,San Luis Potosi Institute of Scientific Research and Technology | Buitron G.,Institute Ingenieria | Razo-Flores E.,San Luis Potosi Institute of Scientific Research and Technology | Alatriste-Mondragon F.,San Luis Potosi Institute of Scientific Research and Technology
International Journal of Hydrogen Energy | Year: 2013

Feasibility of hydrogen production from acid and enzymatic oat straw hydrolysates was evaluated in an anaerobic sequencing batch reactor at 35 °C and constant substrate concentration (5 g chemical oxygen demand/L). In a first experiment, hydrogen production was replaced by methane production. Selective pressures applied in a second experiment successfully prevented methane production. During this experiment, initial feeding with glucose/xylose, as model substrates, promoted biomass granulation. Also, the highest hydrogen molar yield (HMY, 2 mol H2/mol sugar consumed) and hydrogen production rate (HPR, 278 mL H2/L-h) were obtained with these model substrates. Gradual substitution of glucose/xylose by acid hydrolysate led to disaggregation of granules and lower HPR and HMY. When the model substrates were completely substituted by enzymatic hydrolysate, the HMY and HPR were 0.81 mol H 2/mol sugar consumed and 29.6 mL H2/L-h, respectively. Molecular analysis revealed a low bacterial diversity in the stages with high hydrogen production and vice versa. Furthermore, Clostridium pasteurianum was identified as the most abundant species in stages with a high hydrogen production. Despite that feasibility of hydrogen production from hydrolysates was demonstrated, lower performance from hydrolysates than from model substrates was obtained. Copyright © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. Source


Cerezo J.,Institute Ingenieria | Best R.,National Autonomous University of Mexico | Romero R.J.,Autonomous University of Mexico State
Applied Thermal Engineering | Year: 2011

There is a continuous research effort being carried out worldwide on the development of absorption cooling systems with the objective of increasing their performance, one important area is the search for more efficient heat exchangers and alternative working fluids that can improve the performance of NH3-H2O and H2O-LiBr that are commonly used in commercial absorption refrigeration machines. In this work the study of a plate heat exchangers used as bubble absorbers with NH3-LiNO3 and NH3-NaSCN as alternative working fluids is carried out. A mathematical model was developed in order to analyze the absorption process in a bubble absorber with NH3-H2O, NH3-LiNO 3 and NH3-NaSCN as working fluids using a plate heat exchanger at refrigeration conditions and low generator temperatures. The results show that NH3-H2O and NH3-NaSCN working fluids obtained higher absorber thermal loads and absorbed vapor mass values than NH3-LiNO3, the lower values for the latter were caused mainly by the high solution viscosity that decreases the efficiency of the absorption process. On the other hand, NH3-LiNO3 obtained the highest COP value from a single effect absorption refrigeration system simulation, however, NH3-NaSCN obtained a higher COP than NH3-H2O; therefore NH3-NaSCN seems to be a good working fluid to be tested in an absorption machine. © 2011 Elsevier Ltd. All rights reserved. Source


Pineda-Porras O.,Los Alamos National Laboratory | Ordaz M.,Institute Ingenieria
Journal of Pipeline Systems Engineering and Practice | Year: 2010

Though differential ground subsidence (DGS) impacts the seismic response of segmented buried pipelines and increases their vulnerability, there are no fragility formulations that estimate repair rates under such conditions found in the literature. Although physical models that estimate pipeline seismic damage considering other cases of permanent ground subsidence (e.g., faulting, tectonic uplift, liquefaction, and landslides) have been extensively reported, this is not the case for DGS. The refinement of the study of two important phenomena in Mexico City-the 1985 Michoacan earthquake and the sinking of the city due to ground subsidence-has contributed to the analysis of the interrelation of pipeline damage, ground motion intensity, and DGS. From the analysis of the 122 cm (48 in.) diameter pipeline network of the Mexico City water system, fragility formulations for segmented buried pipeline systems for two DGS levels are proposed. The novel parameter PGV2/PGA (composite parameter in terms of peak ground velocity (PGV) and peak ground acceleration has been used as a seismic parameter in these formulations because in previous studies it has shown better correlation to pipeline damage than PGV alone. By comparing the proposed fragility formulations, it is concluded that a change in the DGS level (from low-medium to high) could increase the pipeline repair rates (number of repairs per kilometer) by factors ranging from 1.3 to 2.0, with a higher seismic intensity corresponding to a lower factor. © 2010 ASCE. Source


Azpurua M.A.,Institute Ingenieria
Progress In Electromagnetics Research B | Year: 2012

This paper proposes a simple semi-analytical method for designing coil-systems for homogeneous magnetostatic field generation. The homogeneity of the magnetic field and the average magnitude of the magnetic flux density inside of the volume of interest are the objective functions chosen for the selection of the coil-system geometry (size and location), number of coils and the number of turns of each winding. The spatial distribution of the magnetostatic field is estimated superposing the magnetic induction numerically computed from the analytical expression of the magnetic field generated by each coil, obtained using the Biot-Savart's law and the current filament method. The homogeneous magnetic field is synthesized using an iterative algorithm based on TABU search with geometric constraints, which varies the design parameters of the windings to meet the requirements. The number of turns of each coil and gauge of wire used for the windings is adjusted automatically in order to achieve the target average magnitude of the magnetic induction under the constraints imposed by power consumption. This method was used to design a coil arrangement that can generate up to 10 mT within a volume 0.5 m×0.5 m×1 m with 99% of spatial homogeneity, with square loops of length less than or equal to 1.5 m, and with a power dissipated by Joule effect less than or equal to 1 W per coil. The synthesized magnetic field distribution was validated using Finite Element Method simulation, showing a good correspondence between the objective values and the simulated fields. This method is an alternative to design magnetic field exposure systems over large volumes such as those used in bioelectromagnetics applications. Source

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