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Reyes-Malanche J.A.,San Luis Potosi Institute of Scientific Research and Technology | Vazquez N.,Technological Institute of Celaya | Leyva-Ramos J.,San Luis Potosi Institute of Scientific Research and Technology
IET Power Electronics | Year: 2015

Low voltage and high current are typical requirements for the input source of the new family of microprocessors; therefore there is the need to develop new topologies and control strategies that can meet such requirements. A narrow duty ratio has limited the application of the conventional buck converter for wider step-down DC-DC conversion. An interesting option is to consider the quadratic buck converter; however, there is still the problem to obtain a wider step-down conversion. In this study, a switched-capacitor quadratic buck converter is proposed such that a wider conversion ratio is obtained for lower-output voltages. The converter consists of a quadratic buck converter with an array of capacitors and diodes, also referred as a voltage multiplier. To illustrate the behaviour of the proposed converter, experimental results are shown for a conversion from 36 to 1.5 V and an output power of 30 W. The efficiency of the proposed converter can be effectively increased when soft-switching and synchronous rectification are implemented. © The Institution of Engineering and Technology 2015. Source


Flores-Hernandez C.G.,Autonomous University of Mexico State | Flores-Hernandez C.G.,National Autonomous University of Mexico | Colin-Cruz A.,Autonomous University of Mexico State | Velasco-Santos C.,Technological Institute of Queretaro | And 7 more authors.
Polymers | Year: 2014

The performance as reinforcement of a fibrillar protein such as feather keratin fiber over a biopolymeric matrix composed of polysaccharides was evaluated in this paper. Three different kinds of keratin reinforcement were used: short and long biofibers and rachis particles. These were added separately at 5, 10, 15 and 20 wt% to the chitosan-starch matrix and the composites were processed by a casting/solvent evaporation method. The morphological characteristics, mechanical and thermal properties of the matrix and composites were studied by scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry and dynamic mechanical analysis. The thermal results indicated that the addition of keratin enhanced the thermal stability of the composites compared to pure matrix. This was corroborated with dynamic mechanical analysis as the results revealed that the storage modulus of the composites increased with respect to the pure matrix. The morphology, evaluated by scanning electron microscopy, indicated a uniform dispersion of keratin in the chitosan-starch matrix as a result of good compatibility between these biopolymers, also corroborated by FTIR. These results demonstrate that chicken feathers can be useful to obtain novel keratin reinforcements and develop new green composites providing better properties, than the original biopolymer matrix. © 2014 by the authors. Source


Lomas-Soria C.,University of Queretaro | Ramos-Gomez M.,University of Queretaro | Guevara-Olvera L.,Technological Institute of Celaya | Guevara-Gonzalez R.,University of Queretaro | And 3 more authors.
International Journal of Molecular Sciences | Year: 2011

Diabetic nephropathy (DN) is a major complication of diabetes and is caused by an imbalance in the expression of certain genes that activate or inhibit vital cellular functions of kidney. Despite several recent advances, the pathogenesis of DN remains far from clear, suggesting the need to carry out studies identifying molecular aspects, such as gene expression, that could play a key role in the development of DN. There are several techniques to analyze transcriptome in living organisms. In this study, the suppression subtractive hybridization (SSH) method was used to generate up- and down-regulated subtracted cDNA libraries in the kidney of streptozotocin (STZ)-induced diabetic rats. Northern-blot analysis was used to confirm differential expression ratios from the obtained SSH clones to identify genes related to DN. 400 unique SSH clones were randomly chosen from the two subtraction libraries (200 of each) and verified as differentially expressed. According to blast screening and functional annotation, 20.2% and 20.9% of genes were related to metabolism proteins, 9% and 3.6% to transporters and channels, 16% and 6.3% to transcription factors, 19% and 17.2% to hypothetical proteins, and finally 24.1 and 17.2% to unknown genes, from the down- and up-regulated libraries, respectively. The down- and up-regulated cDNA libraries differentially expressed in the kidney of STZ diabetic rats have been successfully constructed and some identified genes could be highly important in DN. © 2011 by the authors; licensee MDPI, Basel, Switzerland. Source


Vazquez N.,Technological Institute of Celaya | Cervantes I.,Applied Mathematics
Proceedings of the 6th Andean Region International Conference, Andescon 2012 | Year: 2012

Paralleling converters is normally employed to increase power capacity in different applications, such as autonomous micro grid systems and unininterruptible power supplies. These systems share the current between the different converters, but it must be in an equalized manner, no matter different type of loads or conditions. This paper propose an alternative to operate parallel inverters, the proposal is able to reconfigure its operation by itself under connection or disconnection of inverter modules, and the system keeps uniformly shared the current between the power units. Selected control strategy is sliding mode control due to its robustness under large uncertain variations. Operation and experimental results are shown. © 2012 IEEE. Source


Flores I.,National Autonomous University of Mexico | Mota M.M.,University of Amsterdam | Hernandez S.,Technological Institute of Celaya
27th European Modeling and Simulation Symposium, EMSS 2015 | Year: 2015

The urban transport infrastructure is one of the most important problems for the cities, and involves many aspects that concern to citizens, governments and the economical growth of the countries. The objective of this paper is to show how this issue has been studied in recent years, with emphasis in the use of simulation and optimization at the whole planning process. We also consider the important key topics as sustainability, costs and risks, mobility and environment impact. Some study cases are shown in order to clarify the concepts presented. Source

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