Time filter

Source Type

Xaman J.,CENIDET | Esquivel-Ramon J.,Campeche Institute of Technology | Chavez Y.,CENIDET | Hernandez-Perez I.,CENIDET
Mechanics and Industry | Year: 2017

In this paper the design of a cut bar system to determine the thermal conductivity of conductive solid materials is presented. The system works under the comparative method, therefore two reference samples with known thermal conductivity are needed. The thermal design consisted on defining the physical configuration of the thermal system, materials to use and their dimensions, in order to evaluate their thermal performance by varying these parameters to calculate the maximum percentage design error. Given that the thermal design was parametric, the finite volume method was used to solve the heat conduction equation in the cut bar system, which allowed us to vary the different parameters that make up the thermal system such as length and diameter of the bars, insulation thickness, type of reference material, etc. The numerical code developed was verified with one analytical solution. It was found that, the thermal design of a cut bar instrument to determine the thermal conductivity of solid materials within the interval 0.58 ≤ λ ≤ 429 W.m-1.K-1 shows a maximum design error of 3.77% associated to the length of the sample material. The results in this paper allow one to kwon the error by design which can be taken into account as a source of uncertainty when determining the thermal conductivity of solid materials. © 2016 AFM, EDP Sciences.


Sosa M.,Autonomous University of Campeche | Perez-Lopez T.,Autonomous University of Campeche | Reyes J.,Autonomous University of Campeche | Corvo F.,Autonomous University of Campeche | And 3 more authors.
International Journal of Electrochemical Science | Year: 2011

Chloride ion, present in marine breeze and seawater is considered the main external agent to damage reinforced concrete in marine environments. It affects the passivity of steel film and provokes the initiation of corrosion. This study analyzes the changes in concrete contour and interface steel-concrete on samples exposed to continuous immersed seawater, alternated wet in seawater/dry at atmosphere and continuous weathering at atmosphere. The next elements: chloride, calcium, iron, oxygen and magnesium were determinate by using SEM/EDX analysis. Immersed concrete specimens show high amount of chloride at the steel-concrete interface, followed by those exposes to alternated wet-dry cycles, while atmospheric samples practically do not present this ion. Similar sequence of chloride concentration was obtained for the contour of specimens. The noticeable presence of high quantity of magnesium at contour evidence the formation of particular compounds such as brucite and dolomite in those samples exposed to total immersion and alternated wet-dry alternated cycles. Monitoring of electrochemical impedance spectroscopy, shows passivity for steel embedded bars for concrete samples exposed to atmosphere, activity to immersed specimens and transition passive-active for wet-dry cycles. The effect of the exposure conditions on concrete degradation in marine environment is presented. © 2011 by ESG.


Perez-Pacheco E.,Campeche Institute of Technology
Annual Technical Conference - ANTEC, Conference Proceedings | Year: 2014

Nowadays geotextiles play a significant part in coastal protection and erosion prevention design and maintenance techniques. The growth in their use worldwide as geotubes for recovering damaged coastal due to its easiness of manipulation and excellent mechanical properties has been extraordinary. The focus of this paper is on better understanding of the importance of the textile architecture/geometry and the mechanical properties when applied as geotubes for sand recovery. The paper provides an overview of the current erosion in the Yucatan coast and the solutions shoreline protection as well as the effect of geotextile architecture on mechanical behavior.


Moo-Huchin V.M.,Campeche Institute of Technology | Estrada-Mota I.,Campeche Institute of Technology | Estrada-Leon R.,Campeche Institute of Technology | Cuevas-Glory L.,Technological Institute of Mérida | And 4 more authors.
Food Chemistry | Year: 2014

The aim to the study was to determine the physicochemical composition, bioactive compounds and antioxidant activity of fruits from Yucatan, Mexico such as star apple, cashew, mombin, mamey sapote, white sapote, sugar apple, sapodilla, dragon fruit, nance, ilama, custard apple, mamoncillo and black sapote. The physicochemical characteristics were different between fruits and were good sources of bioactive compounds. The edible part with the highest values of antioxidant activity were mamoncillo, star apple, mombin, cashew, white sapote, ilama, custard apple, sugar apple, and nance. Total soluble phenols content showed a correlation with antioxidant activity by ABTS (R = 0.52, P ≤ 0.05) and DPPH (R = 0.43, P ≤ 0.05). A high correlation was obtained between the two assays (ABTS and DPPH) used to measure antioxidant activity in the tropical fruit species under study (R = 0.82, P ≤ 0.05). The results show promising perspectives for the exploitation and use of tropical fruits studied with significant levels of nutrients and antioxidant activity. © 2013 Elsevier Ltd. All rights reserved.


Moo-Huchin V.M.,Campeche Institute of Technology | Moo-Huchin M.I.,Technological University of Mexico | Estrada-Leon R.J.,Campeche Institute of Technology | Cuevas-Glory L.,Technological Institute of Mérida | And 4 more authors.
Food Chemistry | Year: 2015

The aim of this study was to determine the antioxidant compounds, antioxidant activity and content of individual phenolic compounds of freeze-dried peel from three tropical fruits grown in Yucatan, México: purple star apple (Chrysophyllum cainito L.), yellow cashew and red cashew (Anacardium occidentale). The freeze-dried peels were good source of antioxidant compounds. ABTS and DPPH values in the peel from each fruit were 3050.95-3322.31 μM Trolox/100 g dry weight (DW) or 890.19-970.01 mg of vitamin C/100 g DW, and 1579.04-1680.90 μM Trolox/100 g DW or 340.18-362.18 mg of vitamin C/100 g DW, respectively. Six phenolic compounds were identified in the peel from the tropical fruits studied: ferulic, caffeic, sinapic, gallic, ellagic and myricetin. This study demonstrated that freeze-dried peels from purple star apple, yellow cashew and red cashew, could serve as potential sources of antioxidants for use in food and pharmaceutical industries. © 2014 Elsevier Ltd. All rights reserved.


Vargas-Caamal A.,Research Center Estudios Avanzados | Cabellos J.L.,Research Center Estudios Avanzados | Ortiz-Chi F.,Campeche Institute of Technology | Rzepa H.S.,Imperial College London | And 2 more authors.
Chemistry - A European Journal | Year: 2016

The potential energy surfaces of the HCl(H2O)n (n is the number of water molecules) clusters are systematically explored using density functional theory and high-level ab initio computations. On the basis of electronic energies, the number of water molecules needed for HCl dissociation is four as reported by some experimental groups. However, this number is five owing to the inclusion of entropic factors. Wiberg bond indices are calculated and analyzed, and the results provide a quadratic correlation and classification of clusters according to the nondissociated, partially dissociated, and fully dissociated character of the H-Cl bond. Our computations show that if temperature is not controlled during the experiment, the values obtained for the dipole moment (or for any measurable property) are susceptible to change, providing a different picture of the number of water molecules needed for HCl dissociation in a nanoscopic droplet. Acid dissociation: High-level ab initio and DFT computations show that four water molecules are needed for HCl dissociation, but this number increases to five if entropic factors are considered (see figure). The temperature affects the dipole moments obtained, giving a different picture of the number of water molecules needed for HCl dissociation in a nanoscopic droplet. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Moo-Huchin V.M.,Campeche Institute of Technology | Cabrera-Sierra M.J.,Research Center Cientifica Of Yucatan | Estrada-Leon R.J.,Campeche Institute of Technology | Rios-Soberanis C.R.,Research Center Cientifica Of Yucatan | And 5 more authors.
Food Hydrocolloids | Year: 2015

Starch sources with different physicochemical properties are demanded by new applications that require specific properties. Ramon starch was characterized by X-ray diffraction, thermogravimetric analysis, fourier transform infrared spectroscopy (FTIR) analysis and rheology, and compared to corn starch. Ramon starch exhibited a C-type X-ray diffraction pattern. According to thermogravimetric analysis, degradation of corn and Ramon starches occurred in the temperature range between 292 and 369°C, which coincides with the degradation of other starches studied. Pasting properties varied among the corn and Ramon starches. Ramon and corn starches were characterized as viscoelastic systems with G' ≥ G'', during the stages of heating-cooling kinetics. These results support the potential use of Ramon starch as a thickening and gelling agent in food, an excipient in pharmaceutical solid forms, and as biodegradable polymers for food packaging. © 2014 Elsevier Ltd.


Perez-Pacheco E.,Campeche Institute of Technology | Moo-Huchin V.M.,Campeche Institute of Technology | Estrada-Leon R.J.,Campeche Institute of Technology | Ortiz-Fernandez A.,Campeche Institute of Technology | And 3 more authors.
Carbohydrate Polymers | Year: 2014

In this paper, the Ramon starch was isolated and its chemical composition and physical and microscopic characteristics were determined. Corn starch was used as reference. In general, the proximal composition was similar between starches studied. Ramon starch granules were oval-spherical and rounded with sizes between 6.5 and 15 μm. Starch purity was high (92.57%) with amylose content of 25.36%. The gelatinization temperature was 83.05 C and transition enthalpy was 21.423 J/g. At 90 C, solubility was 20.42%, swelling power 17.64 g water/g starch and water absorption capacity was 13 g water/g starch. The pH, clarity and color (Hue angle) of Ramon starch were higher to those reported for corn starch. The results achieved suggest that Ramon starch has potential for application in food systems requiring high processing temperatures and it is also a promising option for use in the manufacture of biodegradable materials. © 2013 Elsevier Ltd. All rights reserved.


Perez-Pacheco E.,Campeche Institute of Technology | Cauich-Cupul J.I.,Research Center Cientifica Of Yucatan | Valadez-Gonzalez A.,Research Center Cientifica Of Yucatan | Herrera-Franco P.J.,Research Center Cientifica Of Yucatan
Journal of Materials Science | Year: 2013

A carbon fiber/epoxy unidirectional laminated composite was exposed to a humid environment and the effect of moisture absorption on the mechanical properties and failure modes was investigated. The composites were exposed to three humidity conditions, namely, 25, 55, and 95 % at a constant temperature of 25 C. The carbon fiber-epoxy laminated composites for two different carbon fiber surface treatments were used. The results showed that the mechanical properties differ considerably for each fiber surface treatment. The application of a coupling agent enhanced the fiber-matrix adhesion and reduced dependence of the properties on humidity. The damage mechanism observed at micromechanical level was correlated to acoustic emission signals from both laminated composites. The untreated carbon fiber failure mode was attributed to fiber-matrix interfacial failure and for the silane-treated carbon fiber reinforced epoxy laminate attributed to matrix yielding followed by fiber failure with no signs of fiber-matrix interface failure for moisture contents up to 1.89 %. © 2012 Springer Science+Business Media New York.


Estrada-Leon R.J.,Campeche Institute of Technology | Magana-Monforte J.G.,Autonomous University of Yucatán | Segura-Correa J.C.,Autonomous University of Yucatán
Tropical Animal Health and Production | Year: 2014

The genetic parameters for Brahman cattle under the tropical conditions of Mexico are scarce. Therefore, heritabilities, additive direct and maternal correlations, and genetic correlations for birth weight (BW) and 205 days adjusted weaning weight (WW205) were estimated in four Brahman cattle herds in Yucatan, Mexico. Parameters were estimated fitting a bivariate animal model, with 4,531 animals in the relationship matrix, of which 2,905 had BW and 2,264 had WW205. The number of sires and dams identified for both traits were 122 and 962, respectively. Direct heritability estimates for BW and WW205 were 0.41 ± 0.09 and 0.43 ± 0.09, and maternal heritabilities were 0.15 ± 0.07 and 0.38 ± 0.08, respectively. Genetic correlations between direct additive and maternal genetic effects for BW and WW205 were -0.41 ± 0.22 and -0.50 ± 0.15, respectively. The direct genetic, maternal, and phenotypic correlations between BW and WW205 were 0.77 ± 0.09, 0.61 ± 0.18, and 0.35, respectively. The moderate to high genetic parameter estimates suggest that genetic improvement by selection is possible for those traits. The maternal effects and their correlation with direct effects should be taken into account to reduce bias in genetic evaluations. © 2014 Springer Science+Business Media Dordrecht.

Loading Campeche Institute of Technology collaborators
Loading Campeche Institute of Technology collaborators