Garcia J.C.,University of Huelva |
Zamudio M.A.M.,University of Huelva |
Perez A.,University of Huelva |
De Alva H.E.,Technological Institute of Ciudad Madero |
Lopez F.,University of Huelva
Journal of Chemical Technology and Biotechnology | Year: 2011
BACKGROUND: A central composite experimental design and multiple regression were used to model the production of pulp and paper sheets from a Paulownia fortunei × tormentosa × elongata trihybrid clone. Also, the same experiments were carried out with the solid phase after autohydrolysis of the raw material. RESULTS: The results were compared with those obtained from the solid phase remaining after autohydrolysis of the raw material with a view to optimizing the use of hemicelluloses and cellulose by fractionation. Pulp and paper sheets from the trihybrid clone surpass those from other Paulownia species such as P. fortunei and P. elongata in physical properties such as tensile index (11.6-49.1 Nm g-1), burst index (0.23-2.41 MPa m2 kg-1), tear index (0.71-3.03 mN m2 g-1) and intrinsic viscosity (427-958 cm3 g-1). CONCLUSIONS: The solid phase obtained by autohydrolysis of the Paulownia trihybrid provides pulp and paper sheets comparable in strength-related properties with those of pulp directly produced from the raw material, but using substantially milder operating conditions and with the added advantage that the autohydrolysis treatment provides highly valorizable liquor. © 2011 Society of Chemical Industry.
Mar-Hernandez E.,Technological Institute of Ciudad Madero |
Gonzalez-Escobar M.,CICESE |
International Geology Review | Year: 2012
Tiburon Basin is characterized by a thick sedimentary fill that records the evolution of one of the rift segments of the East Pacific Rise. Its structure corresponds to an echelon pull-apart basin bounded by two dextral-oblique faults. Unlike basins in the southern Gulf of California that are underlain by oceanic crust, rift basins in the northern Gulf of California contain sedimentary thickness (up to 6 km) that masks the structure of the crust. To study the architecture of the Tiburon Basin, two-dimensional, multichannel seismic reflection data collected by Petróleos Mexicanos (PEMEX) in the early 1980s were used. The data base is a grid of lines, 5-20 km apart, with 6s of record in 48 channels. Additional seismic data of the Ulloa 99 project were also interpreted. Our results indicate that the general structural pattern of the Tiburon Basin is controlled by two dextral-oblique faults: De Mar and Tiburon. De Mar lies to the east and ends in elevated basement transferring the stress to the Desemboque fault. The latter borders the incoming basement from the Sonora and Tiburon faults to the west, ending to the north in an antiform. Four structural domains are recognized: (1) the northern Tiburon domain is a high basement that divides the Delfin Basin to the northeast and exhibits extensional folds with their axes parallel to the basement and its flanks; (2) the Libertad domain is a sheared basement high along the margin of Sonora and forms the right step of the Tepoca Basin to the north; (3) the Tiburon central domain defines a broad sag cut by a dense NE-striking pattern of normal faults with opposed dips in the depocentre and abruptly ends to the west against the Tiburon fault; and (4) the southern Tiburon domain forms a basement ramp offshore Isla Tiburon and is controlled by a pattern of NNE-striking normal faults on the south that likely connect at an oblique angle (60) to the De Mar fault. We propose a rhombochasm basin model with more than 6s of sedimentary record in the depocentre, in which the basement is not recorded. The NW-trending faults in the Libertad domain possibly continue towards the Sonora coastal plain. The principal NW-trending dextral faults and the secondary NNE-striking pattern of normal faults cut the shallow strata of this domain. © 2012 Taylor & Francis.
Brachetti-Sibaja S.B.,Technological Institute of Ciudad Madero |
Brachetti-Sibaja S.B.,Altamira |
Dominguez-Crespo M.A.,Altamira |
Torres-Huerta A.M.,Altamira |
And 2 more authors.
Journal of the Electrochemical Society | Year: 2012
Rare earth conversion films were obtained on the AA6061 aluminum alloy by the immersion method varying several experimental conditions such as rare earth (RE) concentration, bath temperature and immersion time. Formation dynamics of RE coatings and the effect of bath conditions on their structure, morphology, topography and corrosion resistance properties were investigated for the protection of this substrate immersed in an aqueous solution of NaCl. X-ray diffraction and scanning electron microscopy results revealed that the increment of the RE concentration caused some small cracks around the aluminum alloy intermetallic phase, whereas bath temperature and immersion time stimulated the conversion of the rare earths to more stable compounds, La 2O 3 and CeO 2. During electrochemical evaluation, the CeCCs displayed a steady state potential at times longer than 250 min; as for LaCCs, longer time intervals were required to reach a stable potential. After covering with rare earth conversion films, the anticorrosive properties of the aluminum alloy were evidently improved. This enhancement is presumably due to the improved barrier properties of the anticorrosion product layer. Additional active corrosion protection was originated from the inhibiting action of the lanthanide ions trapped either as oxides or hydroxides in this surface layer. © 2011 The Electrochemical Society.
Angeles M.E.,National Autonomous University of Mexico |
Angeles M.E.,Technological Institute of Ciudad Madero |
Rodriguez F.,National Autonomous University of Mexico |
Magana C.,National Autonomous University of Mexico
Pigment and Resin Technology | Year: 2012
Purpose - When coatings are applied to industrial equipment, they have to be able to stand the heat produced by solar energy and/or by different conditions on the process. Therefore, the purpose of this paper is to study the effect of temperature on the protective properties of coatings since this parameter degrades the polymer structure. In addition, the temperature effects on dry coating can also be specified. Design/methodology/approach - In order to know the behaviour of an organic coating at different temperatures, a drying aging cycle was performed by heating on substrate steel and free-of-substrate films during ten uninterrupted days at three and different temperatures: 65, 85 and 100°C. At the end of this period, the aged films were analyzed by means of electrochemical impedance spectroscopy (EIS) measurements, thermal analysis (DSC and TGA), Fourier transform infrared spectroscopy (FTIR), and scanning electronic microscopy (SEM). Findings - The most critical temperature for the aging was 85°C and "over-cured" phenomenon were observed on the aged films which were reported by EIS, thermal and IR analyses. Practical Implications - These aging conditions were tested on a very strong and rigid resin containing a barrier pigment. Thus, it can also be applied to other plastic coatings, such as vinyl or alkyd ones, by modifying the temperatures according to glass transition temperature (T g), as well as the ageing time depending on the hardness and resistance of such coatings and, of course, the protective effect of the pigment. In addition, another aggressive electrolyte, such as synthetic sea water, chloride, sulphide media, as well as inhibitors or ecological pigments could be used in order to predict its behaviour in different corrosive media. Originality/value - The value of this work is on the specific temperatures used for the aging method applied to a rigid resin which revealed the overcured phenomena and the behaviour of the pigment; so if it is applied to a more plastic and flexible coating, it may reveal other phenomena and promote other kind of degradation, maybe even more aggressive ones. © Emerald Group Publishing Limited.
Rosas-Caro J.C.,Technological Institute of Ciudad Madero |
Mancilla-David F.,University of Colorado at Denver |
Ramirez-Arredondo J.M.,CINVESTAV |
Bakir A.M.,University of Colorado at Denver
IET Power Electronics | Year: 2012
This study presents a topology for a pulse width modulated (PWM) three-phase voltage regulator that uses only two driving switches, providing high reliability and making the switching stage simpler and cheaper compared with other available configurations. The proposed topology is suitable for voltage regulation on the distribution power system. It is able to regulate the steady-state voltage and to reject voltage variations such as flicker or sags caused by large motors start. In addition, the compensator features a topology free of energy storage elements. The PWM control is based on dc signals, asynchronous from the grid, simpler than the control used for traditional voltage source converters - it does not require a phase-locked loop, and does not involve trigonometric calculations. As a result of this, the controller can be achieved with an analogue controller or a low-cost microcontroller. The proof of concept is performed with a 220 V three-phase voltage regulator, which is simulated and prototyped in the laboratory. © The Institution of Engineering and Technology 2012.