San Jeronimo Ixtepec, Mexico
San Jeronimo Ixtepec, Mexico

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May-Lozano M.,Metropolitan Autonomous University | Mendoza-Escamilla V.,Metropolitan Autonomous University | Rojas-Garcia E.,Metropolitan Autonomous University | Lopez-Medina R.,Metropolitan Autonomous University | And 2 more authors.
Journal of Cleaner Production | Year: 2017

The photocatalytic and sonophotocatalytic degradation of Orange II was investigated using a synthesized catalyst with low cost materials. Iron (III) oxide-titanium (IV) oxide (1% Fe) photocatalyst was synthesized by sol-gel method and pure titanium dioxide was used as photocatalytic reference material. Their crystallographic structures were determined by X-ray diffraction. The surface area and pore diameter was studied by Brunauer–Emmett–Teller method (N2 adsorption/desorption). The samples were characterized by Scanning Electron Microscopy (SEM) with Energy Dispersive X-Ray Analysis (EDX). SEM images show the formation of particles with spherical geometry. Synergistic effects of ultrasound and photocatalysis were demonstrated. Three different ultrasonic frequencies were tested 250 kHz, 500 kHz and 1000 kHz. The best catalytic activity (higher Orange II degradation efficiency) was obtained at 500 kHz. Test results show that it is possible the total decolourisation of the Orange II dye in aqueous media by the sonophotocatalytic process using visible light, without producing hazardous by-products. The process can be considered as a potential environmentally friendly technique for organic synthetic dyes degradation. © 2017 Elsevier Ltd

Morales-Sandoval M.,Polytechnic University of Victoria | Feregrino-Uribe C.,National Institute of Astrophysics, Optics and Electronics | Cumplido R.,National Institute of Astrophysics, Optics and Electronics | Algredo-Badillo I.,Istmo University of Mexico
Proceedings of the 2011 7th Southern Conference on Programmable Logic, SPL 2011 | Year: 2011

Elliptic Curve Cryptography (ECC) is a kind of cryptography that provides the security information services using shorter keys than other known public-key crypto-algorithms without decreasing the security level. This makes ECC a good choice for implementing security services in constrained devices, like the mobile ones. However, the diversity of ECC implementation parameters recommended by international standards has led to interoperability problems among ECC implementations. This work presents the design and implementation results of a novel FPGA coprocessor for ECC than can be reconfigured at run time to support different implementation parameters and hence, different security levels. Regardless there are several related works in the literature, to our knowledge this is the first ECC coprocessor that makes use of a partial reconfigurable methodology to deal with interoperability problems in ECC. A suitable application of the proposed reconfigurable coprocessor is the security protocol IPSec, where the domain parameters for ECC-based cryptographic schemes, like digital signature or encryption, have to be negotiated and agreed upon by the communication partners at run time. © 2011 IEEE.

Algredo-Badillo I.,Istmo University of Mexico | Feregrino-Uribe C.,National Institute of Astrophysics, Optics and Electronics | Cumplido R.,National Institute of Astrophysics, Optics and Electronics | Morales-Sandoval M.,Polytechnic University of Victoria
Computers and Electrical Engineering | Year: 2010

Applications of wireless communications networks are emerging continuously. To offer a good level of security in these applications, new standards for wireless communications propose solutions based on cryptographic algorithms working on special modes of operation. This work presents a custom hardware architecture for the AES-CCM protocol (AES-CCMP) which is the basis for the security architecture of the IEEE 802.11i standard. AES-CCMP is based on the AES-CCM algorithm that performs the Advanced Encryption Standard (AES) in CTR with CBC-MAC mode (CCM mode), plus specialized data formatting modules, providing different security services through iterative and complex operations. Results of implementing the proposed architecture targeting FPGA devices are presented and discussed. A comparison against similar works shows significant improvements in terms of both throughput and efficiency. © 2010 Elsevier Ltd. All rights reserved.

Campos-Garcia M.,National Autonomous University of Mexico | Moreno-Oliva V.I.,Istmo University of Mexico | Diaz-Uribe R.,National Autonomous University of Mexico | Granados-Agustin F.,National Institute of Astrophysics, Optics and Electronics | Santiago-Alvarado A.,Technological University of Mixteca
Applied Optics | Year: 2011

A method for testing fast aspheric convex surfaces with dynamic null screens using LCDs is shown. A flat null screen is designed and displayed on an LCD monitor with drop-shaped spots in such a way that the image, which is formed by reflection on the test surface, becomes an exactly square array of circular spots if the surface is perfect. Any departure from this geometry is indicative of defects on the surface. Here the whole surface is tested at once. The position of the spots on the LCD can be changed in a dynamic way, to perform point-shifting of the image spots. The proposed procedure improves the dynamic point-shifting method. As has been shown previously, this process reduces the numerical error during the integration procedure, thereby improving the sensitivity of the test. The positioning accuracy for the screen spots is related to the LCD's spatial resolution. Results of the evaluation of a parabolic convex surface with f/# = 0.22 are shown. © 2011 Optical Society of America.

Velasco-Perez A.,University of the East of Mexico | Alvarez-Ramirez J.,Metropolitan Autonomous University | Solar-Gonzalez R.,Istmo University of Mexico
Revista Mexicana de Ingeniera Qumica | Year: 2011

This paper addresses the multiple input - single output (MISO) control problem of a simple generic model of a CSTR. The control design is based on simple models and the inversion of dead-beat filters. It is proposed a synthesis procedure of controllers based on the factorization of MISO plants that leads to a parallel control structure. The proposed controller performs a balance in the use of the control inputs via an optimization problem. Numerical simulations show the performance and comparison of the control scheme against its counterparts SISO.

Cortina-Marrero H.J.,National Autonomous University of Mexico | Martinez-Alonso C.,National Autonomous University of Mexico | Hechavarria-Difur L.,Istmo University of Mexico | Hu H.,National Autonomous University of Mexico
EPJ Applied Physics | Year: 2013

Bilayer hybrid solar cells were prepared by solution deposition of CdS thin films on conductive glass substrates (ITO), followed by spin-coating or drop-casting poly (3-hexylthiophene) (P3HT) solution on a CdS surface. After a slow drying process, the P3HT films of different thicknesses (from 100 to 725 nm) were annealed at temperatures (T1) from 110 to 190 C, called pre-metal contact annealing. Then carbon paint was collocated on top of P3HT and gold was evaporated. The whole structure was annealed for the second time, called post-metal contact annealing, at temperature (T2) between 110 and 190 C. The continuous increase of the (1 0 0) crystalline plane and the optical absorption coefficient of P3HT films with annealing temperatures indicates the improvement of molecular order inside the polymer films induced by the thermal annealing process. The better ordered P3HT films lead to lower series resistance and higher fill factor in the corresponding solar cells, suggesting the enlargement of charge carrier mobility in annealed P3HT films. On the other hand, the photovoltaic performance is also affected by T2 temperature; a low T2 improves the ohmic contact between P3HT and the metal contact to benefit the charge carrier extraction, whereas a high T2 may deteriorate that union. The same observation was obtained in CdS/P3HT solar cells with P3HT films of different thicknesses. The best energy conversion efficiency of 0.44% was obtained in CdS/P3HT cells with 305 nm thick P3HT annealed at T1 = 190 C and T2 = 110 C for 10 min each. © 2013 EDP Sciences.

Campos-Garcia M.,National Autonomous University of Mexico | Cossio-Guerrero C.,National Autonomous University of Mexico | Moreno-Oliva V.I.,Istmo University of Mexico | Huerta-Carranza O.,National Autonomous University of Mexico
Applied Optics | Year: 2015

In order to measure the shape of fast convex aspherics, such as the corneal surface of the human eye, we propose the design of a conical null-screen with a radial point distribution (spots similar to ellipses) drawn on it in such a way that its image, which is formed by reflection on the test surface, becomes an exact array of circular spots if the surface is perfect. Any departure from this geometry is indicative of defects on the evaluated surface. We present the target array design and the surface evaluation algorithm. The precision of the test is increased by performing an iterative process to calculate the surface normals, reducing the numerical errors during the integration. We show the applicability of the null-screen based topographer by testing a spherical calibration surface of 7.8 mm radius of curvature and 11 mm in diameter. Here we obtain an rms difference in sagitta between the evaluated surface and the best-fitting sphere less than 1 μm. © 2015 Optical Society of America.

Lumbreras J.A.,Istmo University of Mexico | Huirache-Acuna R.,National Autonomous University of Mexico | Rivera-Munoz E.M.,National Autonomous University of Mexico | Berhault G.,CNRS Research on Catalysis and Environment in Lyon | Alonso-Nunez G.,National Autonomous University of Mexico
Catalysis Letters | Year: 2010

Unsupported Ni/MoS2 and Ni/WS2 HDS catalysts were prepared by in situ activation of hexamethylenediammonium thiometallates promoted with Ni. The method involved an aqueous solution reaction of ammonium thiomolybdate (ATM) or ammonium thiotungstate (ATT) with Ni(NO3) 2•6H2O and hexamethylenediamine. Ni-promoted precursors were then in situ activated during the hydrodesulfurization (HDS) of dibenzothiophene (DBT) producing Ni/MoS2 and Ni/WS2 catalysts. Solids were analyzed after the in situ activation by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and for textural properties by using the BET and BJH methods. Catalysts with relatively high surface area and type IV N2 adsorption-desorption isotherms were obtained. The use of the hexamethylenediammonium precursor led to a significant nickel promotion of MoS2 and WS2 catalysts. For Ni/MoS2, the use of this carbon-containing precursor was found to be more beneficial for the final HDS catalytic activity than using the classical ammonium tetrathiomolybdate (ATM) without carbon. For Ni/WS 2, compared to tetraalkylammonium thiosalts, the lower amount of carbon in excess formed during the decomposition of the hexamethylenediammonium precursor coupled with a lower crystallization rate of WS2 favors a correct nickel accommodation on the WS2 edges. © 2009 Springer Science+Business Media, LLC.

Cano-Cruz E.M.,Istmo University of Mexico | Lopez-Orozco F.,Istmo University of Mexico
Advanced Science Letters | Year: 2015

Systems controlled through measuring physical environmental parameters, such as temperature, humidity and atmospheric pressure, are very important for the automatization of industrial processes, where advances in electronics have played a key role. This paper presents the design and development of a low-cost and efficient tool based on an SHT11 sensor to measure the temperature and humidity of the environment. The system also proposes a wireless connectivity using Bluetooth communication standard, providing a reliable, portable and low-cost tool for an industry where an environmental control is necessary to carry out critical processes. © 2015 American Scientific Publishers. All rights reserved.

Mezura-Montes E.,Laboratorio Nacional Of Informatica Avanzada Lania Ac | Miranda-Varela M.E.,Istmo University of Mexico | Del Carmen Gomez-Ramon R.,University Del Carmen
Information Sciences | Year: 2010

Motivated by the recent success of diverse approaches based on differential evolution (DE) to solve constrained numerical optimization problems, in this paper, the performance of this novel evolutionary algorithm is evaluated. Three experiments are designed to study the behavior of different DE variants on a set of benchmark problems by using different performance measures proposed in the specialized literature. The first experiment analyzes the behavior of four DE variants in 24 test functions considering dimensionality and the type of constraints of the problem. The second experiment presents a more in-depth analysis on two DE variants by varying two parameters (the scale factor F and the population size NP), which control the convergence of the algorithm. From the results obtained, a simple but competitive combination of two DE variants is proposed and compared against state-of-the-art DE-based algorithms for constrained optimization in the third experiment. The study in this paper shows (1) important information about the behavior of DE in constrained search spaces and (2) the role of this knowledge in the correct combination of variants, based on their capabilities, to generate simple but competitive approaches. © 2010 Elsevier B.V. All rights reserved.

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