Escobar B.,Technological Institute of Cancun |
Barbosa R.,University of Quintana Roo |
Miki Yoshida M.,CIMAV |
Verde Gomez Y.,Technological Institute of Cancun
Journal of Power Sources | Year: 2013
Pt colloidal nanoparticles were synthesized by simultaneous chemical reduction of metallic salts in presence of poly (N-vinyl-2-pyrrolidone) as protecting agent. The uniform and highly ordered Pt colloidal nanoparticles were associated to well dispersed particles ranging in particle size distribution around 4.5 ± 1.9 nm. The nanoparticles were deposited onto multiwalled carbon nanotubes (MWCNT). MWCNT were synthesized by chemical vapor deposition (CVD) method. Before the metal impregnation, the MWCNT were treated with HNO3 in reflux. Prepared Pt catalyst were characterized by various physical and electrochemical techniques, that is, X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Raman spectroscopy and cyclic voltammetry (CV). Raman spectroscopy reveals changes intensity ratio IG′/IG in the samples, after the cleaning process and Pt loading, indicating changes in the crystallinity of the materials. HRTEM showed Pt particles between 6.1 ± 0.9 nm and 6.5 ± 1.5 nm are well dispersed along the carbon nanotubes. XRD patterns show characteristics peaks corresponding to graphite and metallic Pt. The electrochemical properties of the MWCNT supported Pt nanoparticles were investigated by analyzing the response of the nanostructured catalyst for cyclic voltammetry and compared with a commercial material. © 2013 Elsevier B.V. All rights reserved.
De Leon-Aldaco S.E.,National Center for Research and Development of Technology |
Calleja H.,National Center for Research and Development of Technology |
Chan F.,University of Quintana Roo |
Jimenez-Grajales H.R.,Electric Research Institute of Mexico
IEEE Transactions on Power Electronics | Year: 2013
This paper presents the reliability analysis of a push-pull converter intended for connection to a 125-W photovoltaic (PV) panel. Four prototypes of the converter were built and tested, using transistors with different ratings. Failure rates were calculated using theMIL HDBK 217 and the IEC TR 62380 procedures. In the latter case, the predictionwas performed taking into account an annual mission profile obtained from the intended installation site, in an area with desert climate temperatures. Failure rate results obtained withMIL HDBK 217 show small differences among the converters, the best performance obtained from the prototype with the lowest on-resistance. Results obtained with IEC TR 62380 indicate that thermal cycles have a significant effect in reliability performance, and should be considered carefully, because PV systems often see large temperature variations.With both procedures, the failure rate contributions from magnetic devices were higher than expected. © 2013 IEEE.
Chan F.,University of Quintana Roo |
IEEE Transactions on Industrial Electronics | Year: 2011
This paper presents the reliability estimation of the power stages in three grid-connected photovoltaic systems. The circuits analyzed are an integrated topology, a two-stage configuration, and a three-stage one, all commutating in the hard-switching mode. The reliability-related parameters, such as the failure rate, are calculated following the procedure outlined in MIL-HDBK 217. A comparison between the topologies is performed, and both the components and the stress factor with the highest contribution to the failure rate are identified. The methods to calculate junction temperature variations are included. © 2006 IEEE.
Gutierrez-Aguirre M.A.,University of Quintana Roo |
Cervantes-Martinez A.,University of Quintana Roo
Journal of Natural History | Year: 2013
In Mexico the knowledge of the freshwater copepod fauna is largely incomplete; after a field expedition to survey the Calanoida and Cyclopoida richness in Chiapas (southeastern Mexico), three species increase the full inventory in the country (of around 86 species). In this manuscript the first record of the genus Metacyclops in Mexico and a new record of Acanthocyclops einslei are reported. In addition, a full description of specimens of a new species assignable to the genus Mastigodiaptomus (M. suarezmoralesi sp. nov.) is presented. This research provides a full morphological description of adult males and females of the new species as well as comments on the morphology of Aglaodiaptomus clavipes. The new records were compared with previous taxonomic reports. Detailed analysis and illustration of the copepod morphology have been performed with the aid of camera lucida, light microscopy and scanning electron microscopy. Most of the species recorded show Neotropical affinity. http://www.zoobank.org/urn:lsid:zoobank.org:pub:4E3C5C42-F73E-4D91-A85F-E5794B146734. © 2013 Copyright Taylor and Francis Group, LLC.
Delgado-Blas V.H.,University of Quintana Roo
Helgoland Marine Research | Year: 2014
Available type material of Prionospio heterobranchia Moore, 1907, P. (Prionospio) texana Hartman, 1951, P. spongicola Wesenberg-Lund, 1958 and P. (P.) newportensis Reish, 1959, as well as newly collected material from the Southern Gulf of Mexico and Chetumal Bay in the Caribbean Sea, was examined. Several important differences were found between P. heterobranchia, P. (Prionospio) texana, P. spongicola and P. (P.) newportensis, and as a result, these three species are removed from synonymy with P. heterobranchia Moore, 1907, and redescribed and reinstated as valid species. In addition, three new species were identified and described: P. caribensis sp. nov., P. rosariae sp. nov. and P. jamaicensis sp. nov. A key to all species of Prionospio with five pairs of branchiae is provided. © 2013 Springer-Verlag Berlin Heidelberg and AWI.
Delgado-Blas V.H.,University of Quintana Roo |
Salazar-Silva P.,Colegio de Mexico
Zootaxa | Year: 2011
The aim of this study was to provide a revised taxonomic catalogue of Spionidae species recorded from the Grand Caribbean. The names included were compiled from the checklists of Salazar-Vallejo (1996) and Perkins and Savage (1975). Names were revised and updated based on recent revisions. For each species, the original name is included together with current and previous names under which it has been recorded; all with associated citations. The type locality of each species, museum or institution where the type materials are deposited, and comments on systematics and geographic distributions are also included. The catalogue lists 66 species in 24 genera and at the end a list of species with questionable distribution in the Grand Caribbean is included. © 2011 . Magnolia Press.
Mejia-Ortiz L.M.,University of Quintana Roo |
Lopez-Mejia M.,University of Quintana Roo
Crustaceana | Year: 2011
In the Papaloapan River two freshwater prawns with abbreviated development have been recorded: Macrobrachium villalobosi (a stygobitic species) and Macrobrachium totonacum (an epigeal species). In this paper we describe four new species from this genus, and the distribution of these six species along the river basin. M. oaxacae nov. sp. occurs in the River La Junta, and together with M. cosolapaense nov. sp. is geographically close to the stygobitic species and M. totonacum, but differs from these in the following aspects: pigmentation, the number of rostral spines, and the relative proportions of the articles of the second pereiopod, of appendix masculina and appendix interna, and the number of spines on the appendix masculina. Macrobrachium mazatecum nov. sp. lives in two streams in Veracruz: the first close to Tierra Blanca Veracruz and the second on the Zapotal Veracruz near Mpio. Lerdo de Tejada. This species was also recorded in two springs near Valle Nacional Oaxaca, and differs from M. oaxacae nov. sp. and M. cosolapaense nov. sp. in the number of rostral spines, and the relative proportions on the articles of second pereiopod, of appendix masculina and appendix interna, and of the spines on the appendix masculina. Finally, Macrobrachium jacatepecense nov. sp. occurs only in a spring near Jacatepec, Oaxaca. This species differs from the other species in the relative proportions of the articles of the second pereiopod: however, it is very close to Macrobrachium oaxacae nov. sp. in the number of rostral spines, but based on the geographical distribution of both species and other features, it is clearly a different species. In this Papaloapan River basin, the distribution of this complex of species is very limited, because the various populations live in very restricted areas associated with springs or small streams, and without direct interconnections. All these new species are comparable with the epigeal Macrobrachium species in the southeast of Mexico that have abbreviated larval development. © 2011 Koninklijke Brill NV, Leiden.
Aguilar J.O.,Research Center Cientifica Of Yucatan |
Aguilar J.O.,University of Quintana Roo |
Bautista-Quijano J.R.,Research Center Cientifica Of Yucatan |
Aviles F.,Research Center Cientifica Of Yucatan
Express Polymer Letters | Year: 2010
Electrical conductivity of 150-200 μm thick polysulfone films loaded with 0.05-0.75% w/w multiwall carbon nanotubes was systematically investigated for two types of dispersion states, uniformly dispersed and agglomerated at the micro-scale. The percolation threshold was found at 0.11% and 0.068% w/w for the uniformly dispersed and agglomerated films, respectively. Overall, the conductivity of the films with agglomerated nanotubes was higher than that of the uniformly dispersed ones, with marked differences of 2 to 4 orders of magnitude for carbon nanotubes loadings in the upper vicinity of the percolation threshold (0.1-0.3% w/w). The increased conductivity of the agglomerated state is explained by the increased nanotube-to-nanotube contact after the percolating network has formed, which facilitates electron transfer. © BME-PT.
Atoche A.C.,Autonomous University of Yucatán |
Castillo J.V.,University of Quintana Roo
Sensors | Year: 2012
A high-speed dual super-systolic core for reconstructive signal processing (SP) operations consists of a double parallel systolic array (SA) machine in which each processing element of the array is also conceptualized as another SA in a bit-level fashion. In this study, we addressed the design of a high-speed dual super-systolic array (SSA) core for the enhancement/reconstruction of remote sensing (RS) imaging of radar/synthetic aperture radar (SAR) sensor systems. The selected reconstructive SP algorithms are efficiently transformed in their parallel representation and then, they are mapped into an efficient high performance embedded computing (HPEC) architecture in reconfigurable Xilinx field programmable gate array (FPGA) platforms. As an implementation test case, the proposed approach was aggregated in a HW/SW co-design scheme in order to solve the nonlinear ill-posed inverse problem of nonparametric estimation of the power spatial spectrum pattern (SSP) from a remotely sensed scene. We show how such dual SSA core, drastically reduces the computational load of complex RS regularization techniques achieving the required real-time operational mode. © 2012 by the authors.
Delgado-Blas V.H.,University of Quintana Roo
Zootaxa | Year: 2015
Six species of Prionospio are described from the Southern Gulf of Mexico and the Caribbean Sea. Five of these species, P austella sp. nov., P. crassumbranchiata sp. nov., P. jonatani sp. nov., P oligopinnulata sp. nov., and P. rotunda sp. nov. are new to science whereas Prionospio cristata Foster, 1971 has been previously described from the Grand Caribbean region. P. austella sp. nov. has a prostomium with a small medial peak on the anterior margin, low dorsal folds on chaetigers 6-11, rounded and subtriangular neuropodial lamellae on chaetigers 1 and 3, respectively, and all hooks lack a secondary hood. P. crassumbranchiata sp. nov. has a laterally separate peristomium partially fused dorsally with chaetiger 1, digiti-form pinnules on the lateral and posterior faces of the first pair of branchiae and rectangular neuropodial lamellae on chaetigers 2-5. Prionospio jonatani sp. nov. has a narrow prostomium, subtriangular notopodial lamellae on chaetigers 6-21, notopodial prechaetal lamellae slightly basally fused with the notopodial postchaetal lamellae and square neuropodial lamellae on chaetiger 3. P. oligopinnulata sp. nov. has a square-shaped prostomium, high dorsal crests on chaetigers 7-8, low dorsal folds on chaetigers 9-14, subtriangular neuropodial lamellae on chaetigers 2-3, and branchial pairs 2 and 3 are triangular. P rotunda sp. nov. has an anteriorly rounded prostomium, trapezoid neuropodial lamellae on chaetiger 3, high dorsal crests on chaetiger 7, and branchial pairs 2 and 3 are cirriform. A key is provided for all the species known from the Grand Caribbean region in the "steentrupi-group" with four branchial pairs. Copyright © 2015 Magnolia Press.