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Castaneda I.E.,CIMAV | Gonzalez-Rodriguez J.G.,Autonomous University of Mexico State | Dominguez-Patino G.,Autonomous University of Mexico State | Sandoval-Jabalera R.,UACH | And 3 more authors.
International Journal of Electrochemical Science | Year: 2011

An investigation about the corrosion resistance of Ni-Al-Cu intermetallic alloys in simulated human body fluid environments has been carried out by using electrochemical techniques. Tested alloys included 50 (wt %) Ni-(20 and 25) Al-(20 and 25) Cu using the Hank's solution. For comparison, 316L type stainless steel has also been evaluated. Electrochemical techniques included potentiodynamic polarization curves, linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS), and electrochemical noise measurements, EN. Different techniques have shown that, generally speaking, Ni-Al-Cu alloys showed a lower corrosion resistance than conventional 316L type stainless steel only during a few days. Their corrosion resistance decreased as the Cu content in the alloy decreased. The alloys were susceptible to pitting type of corrosion on the γ'-(Ni, Cu)3Al Curich phases. © 2011 by ESG.


Balderrama-Castaneda S.,UACH | Lujan-Alvarez C.,UACH | Lewis D.K.,Oklahoma State University | Ortega-Gutierrez J.A.,UACH | de Jong B.H.J.,Colegio de Mexico
Madera Bosques | Year: 2011

The feasibility of converting sawmill residues in electricity through gasification was evaluated in two ejido sawmills, Rocheachi and Tatahuichi, in the Guachochi municipality of Chihuahua State. The area has a semi cold climate, with temperature and precipitation annual means of 10,6 oC and 800 mm, respectively; the tree cover is dominated by pine and pine-oak communities with Pinus arizonica and P. duranguensis being the main species used for logging. The residues flow was estimated and its chemical composition and heating value characterized. The selected technology was the fixed bed downdraft gasifier; the costs and specifications data were provided by a Chinese supplier. The main assumptions were: 1,3 kgDM/kwh, 80% plant factor, electricity output sold for street lighting at 80% of commercial price. The financial viability was evaluated through the configuration of (100, 200, 400 and 800) kw systems and three scenarios: base, optimistic and pessimistic. The effect of additional revenues from carbon credits sold at the voluntary market at 4, 5 and 6 US$/tCO2 was assessed. The internal rate of return (IRR) increased consistently with increasing the systems' capacity with the 800kw being the most economically attractive. without carbon credits, the 100 kw system showed no positive values at any scenario whereas the 800 kw system was the only one with positive IRR in all the scenarios with a range of 3% to 13%; the additional revenues from carbon credits added 2,3 and 2,9% to the low and high scenarios, respectively. In the context of the study, the systems evaluated would satisfy the additionality criteria required by the carbon market.


Mendez-Cardenas J.P.,UACh | Cevallos-Ferriz S.R.S.,National Autonomous University of Mexico | Calvillo-Canadell L.,National Autonomous University of Mexico | Rodriguez-Yam G.A.,UACh | And 2 more authors.
Review of Palaeobotany and Palynology | Year: 2014

A wood type preserved in Oligocene sediments of Coayuca de Andrade, Puebla, Mexico, is described and compared to Loxopterygium Hook. f. (Anacardiaceae). Among the characters that sustain this assignment are growth rings are marked by 2-3 rows of flattened latewood fibers. The vessel elements are circular to oval, predominantly solitary and radial multiples of 2 and 3. The perforation plates are simple, intervascular pits are alternate, oval and polygonal, with lenticular apertures, some of them are coalescent. Axial parenchyma is paratracheal scanty. Rays correspondent to the heterogeneous Kribs type IIB and one to two radial canals occur in multiseriate rays. These same characteristics are important to distinguish it from the extant species in the genus and support the recognition of a new species, Loxopterygium andradensii Méndez-Cárdenas et al. The presence of this new species in the Cenozoic of Mexico confirms the importance of Anacardiaceae in the flora and vegetation of low latitude North America, reinforcing the idea that some elements of the Neotropical flora were in North America before the Plio-Pleistocene Great Biotic exchange and that at some point it was important for the diversification of some taxa. © 2014 Elsevier B.V.


Jimenez-Rosales J.D.,National Autonomous University of Mexico | Amendola-Massiotti R.D.,National Autonomous University of Mexico | Vazquez-Hernandez I.,National Autonomous University of Mexico | Huerta-Bravo M.,National Autonomous University of Mexico | And 2 more authors.
Tropical and Subtropical Agroecosystems | Year: 2014

Animal production in mixed grazing systems is more efficient than in single-species systems. The objective of this study was to assess intake and composition of the diet of cows grazing in swards of alfalfa (Medicago sativa) with orchard ( Dactylis glomerata). 12 New-Zealand Holstein lactating cows were used and 24 pregnant Pelibuey Ewes. Grazing was rotational intensive of leaders and followers. Under a randomized design with two replicates per paddock, two treatments were evaluated mixed grazing and single grazing dairy cows. The experimental units were lots of 3 cows and the respective grazed areas. In the case of mixed grazing two lots of 12 ewes were used. The variables measured were mass of offer forage, mass of residual forage, botany, morphological and chemical composition of the diet of cows. Estimated variables for both species were forage intake and grade of use. The intake of cows was not affected by the grazing system (P>0.05). However the NDF and ADF of the forage consumed by single grazing cows were higher (P = 0.012 and 0.020); on the other hand mixed grazing cows consumed 25% more alfalfa (P =0.004). Forage intake of ewes was 32% higher in swards of 2 years (P<0.04). The cows grazing with breeding ewes as followers in swards of alfalfa-orchard was an alternative to grazing management; simultaneously improved the quality of the diet of the leaders cows and allowed feed dreeding ewes at very low cost. © 2014, Universidad Autonoma de Yucatan. All rights reserved.


Busquets J.,Norwegian University of Science and Technology | Zilic F.,UACh | Aron C.,UACh | Manzoliz R.,UACh
OCEANS 2013 MTS/IEEE Bergen: The Challenges of the Northern Dimension | Year: 2013

The coordination between a fleet of ocean automatic vehicles is an interesting area of research. The communication between an Autonomous Underwater Vehicle AUV and in-shore stations is a difficult question. Satellite communications are expensive; they provides only a limited bandwidth and the link is not always guaranteed when it is needed. High speed communications are difficult from underwater vehicles since their antennas are affected by the sea surface conditions when they are on the surface, especially when rough sea conditions are present. Using a Surface Autonomous Vehicle (SAV) in the proximity of the AUV as a coordination station between a Command Center (CC) in shore and the AUV fleet will be an advantage for reaching a good guaranteed link between shore and the individual vehicles. The constraint of avoiding costly satellite communications on AUVs leads to the consideration of using commercial inexpensive communication systems based on UMTS and WIFI protocols, together with inexpensive acoustic underwater devices for range and bearing control and basic communications. In order to be useful for the mission the previously mentioned surface vehicle faces the challenge of operating in a wide range of weather conditions. In this paper a solution is proposed by considering a dual system composed by a SAV and a fleet of AUV in tandem navigation strategy. In order to avoid vehicle damage, malfunction or lose of communication between shore and AUVs, robust and fault tolerant dual system propulsion and a multiple communication platform ASV is proposed. © 2013 IEEE.


Bonilla M.,CINVESTAV | Martinez-Garcia J.C.,CINVESTAV | Antonio C.,CCU Justo Sierra | Arteaga R.,UACh
2015 12th International Conference on Electrical Engineering, Computing Science and Automatic Control, CCE 2015 | Year: 2015

Because of its significance for the improvement of the efficiency in crop production, it is of fundamental importance to identify the plant critical periods (which characterize the sensitivity of the plant to the atmospheric elements). Since in the case of some development stages it is not possible to observe them by a simple sight, it is usual to destroy some sampling plants to get the required information. In this work, the crop growth process of the maize (Zea mays, sp) is analyzed for finding its critical phases by means of non destructive techniques. For this, at first the stem elongation process is analyzed by studying the dynamical behavior of an hypothetic unitary mass particle, concentrated in the stem appendix, traveling through an apparent potential well. And then, a Non Destructive Detection Procedure is proposed, which is based on two concatenated Recursive Constrained Least-Square Algorithm with orthogonal projections. The critical periods are predicted until 3 weeks of anticipation. © 2015 IEEE.

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