El Crucero de Santa Maria, Mexico
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Ramirez M.,National Autonomous University of Mexico | Nava-Gomez G.G.,CIMAV | Nava-Gomez G.G.,Technological Institute of Ciudad Juarez | Sabina F.J.,National Autonomous University of Mexico | And 4 more authors.
International Journal of Engineering Science | Year: 2012

Recently an enhancement of certain mechanical properties of composites have been shown to be attained by the introduction of auxetic phases (materials with negative Poisson's value) such as indentation resistance, fracture toughness and improved energy absorption. Here one aim is to use well-known closed-form formulas for the effective stiffness and engineering constants of a periodic composite where the repetitive cell is a laminate of n elastic isotropic constituents. The formulas are given as a function of the elastic stiffnesses or in terms of the engineering constants of the constituents and their volume fraction. Effective mechanical properties are independent of the order in which the laminas are taken. In order to confirm the theoretical formulas and show them reliable, comparisons with two independent numerical calculations using finite element are given. They are excellent. For a bilaminate the conditions by which Young's moduli are enhanced are given. Also we provide expressions for auxetic and enhancement windows. The stiffness constants exhibit certain characteristics associated with auxetics such as the negativity of non-diagonal components of the stiffness tensor. It is shown that the laminas combination of positive-positive materials may be produce enhancement of Young's moduli as some auxetic-auxetic ones. The relative indentation compliance of a circular punch upon transversely isotropic medium is calculated using Fabrikant's formulas. Two different indentations are considered. In one the indenter and the bilaminate are in frictionless contact and in the other they are bonded. The indentation attains the asymptotic limits of Boussinesq or Mossakovskii-Spence when the auxetic phase is very thin compared with the width of the non-auxetic phase and in the opposite case. The results given here may be of interest in practical applications using composites with auxetic constituents when the microstructure is small compared with the dimensions of the laminate. © 2012 Elsevier Ltd. All rights reserved.


Mendez Gonzalez L.C.,Autonomous University of Ciudad Juárez | Rodriguez Borbon M.I.,Autonomous University of Ciudad Juárez | Valles-Rosales D.J.,New Mexico State University | Del Valle A.,New Mexico State University | Rodriguez A.,Technological Institute of Ciudad Juarez
Quality and Reliability Engineering International | Year: 2015

Present reliability models, which estimate the lifetime of electronic devices, work under the assumption that the voltage level must be constant when an Accelerated Life Testing is performed. Nevertheless, in a real operational environment, electronic devices are subjected to electrical variations present in the power lines; that means the voltage has a time-varying behavior, which breaks the assumption of reliability models. Thus, in this paper, a reliability model is presented, which describes the lifetime of electronic devices under time-varying voltage via a parametric function. The model is based on the Cumulative Damage Model with random failure rate and the modified Inverse Power Law. In order to estimate the parameters of the proposed model, the maximum likelihood method was employed. A case study based on the time-varying voltage induced by electrical harmonics when Alternate Current/Direct Current (AC/DC) transformer is connected to the power line is presented in this paper. © 2015 John Wiley & Sons, Ltd.


Olvera H.A.,University of Texas at El Paso | Lopez M.,University of Texas at El Paso | Guerrero V.,University of Texas at El Paso | Garcia H.,Technological Institute of Ciudad Juarez | Li W.-W.,University of Texas at El Paso
Journal of Exposure Science and Environmental Epidemiology | Year: 2013

Exposure to diesel-emitted particles has been linked to increased cancer risk and cardiopulmonary diseases. Because of their size (<100 nm), exposure to ultrafine particles (UFPs) emitted from heavy-duty diesel vehicles (HDDV) might result in greater health risks than those associated with larger particles. Seasonal UFP levels at the International Bridge of the Americas, which connects the US and Mexico and has high HDDV traffic demands, were characterized. Hourly average UFP concentrations ranged between 1.7 × 10 3 /cc and 2.9 × 10 5 /cc with a mean of 3.5 × 10 4 /cc. Wind speeds <2 m s -1 and temperatures <15 °C were associated with particle number concentrations above normal conditions. The presence of HDDV had the strongest impact on local UFP levels. Varying particle size distributions were associated with south- and northbound HDDV traffic. Peak exposure occurred on weekday afternoons. Although in winter, high exposure episodes were also observed in the morning. Particle number concentrations were estimated to reach background levels at 400 m away from traffic. The populations exposed to UFP above background levels include law enforcement officers, street vendors, private commuters, and commercial vehicle drivers as well as neighbors on both sides of the border, including a church and several schools. © 2013 Nature America, Inc. All rights reserved.


Al-Qudah O.,University of Texas at El Paso | Woocay A.,Technological Institute of Ciudad Juarez | Woocay A.,University of Texas at El Paso | Walton J.,University of Texas at El Paso
Applied Geochemistry | Year: 2011

In this study, the hydrogeochemical program PHREEQC was used to determine the chemical speciation and mineral saturation indices (SIs) of groundwater in the vicinity of the proposed high-level nuclear waste repository at Yucca Mountain, Nevada (USA). In turn, these data were used to interpret the origin and recharge mode of groundwater, to elucidate the mechanisms of flow and transport, and to determine potential sources of groundwater contamination. PHREEQC was run to determine aqueous dissolved species and minerals that would be in equilibrium with the study area's groundwater. Selected major ions, associated SI, F- and Ca/Na ion exchange were then examined using the multivariate statistical methods of principal component factor analysis and k-means cluster analysis. Analysis of dissolved ion concentrations, SIs, and Ca/Na ion exchange allows simultaneous consideration of arithmetic (raw concentrations) and logarithmic (SI, ion exchange) variables that describe the hydrochemical system and, therefore, can provide further insight into the system's behavior. The analysis indicates that the dominant processes and reactions responsible for the hydrochemical evolution in the system are (1) evaporative concentration prior to infiltration, (2) carbonate equilibrium, (3) silicate weathering reactions, (4) limited mixing with saline water, (5) dissolution/precipitation of calcite, dolomite and fluorite, and (6) ion exchange. Principal component factor analysis and k-means cluster analysis of factor scores allow the reduction of dimensions describing the system and the identification of hydrogeochemical facies and the processes that defined and govern their evolution. Statistical analysis results indicate that the northern, west face and southern Yucca Mountain groundwater is fresh water with low concentrations of Ca2+, Mg2+, Cl-, Ca2+/(Na+)2, and CaF2. The Fortymile Wash groundwater is dilute. The carbonate signature is shown in the Ash Meadows and Death Valley waters with high fluorite SI. Finally, the Crater Flat, Stripped Hills, and Skeleton Hills are dominated by Ca/Na ion exchange, Mg and Ca. The hydrochemical and statistical analyses showed three main groundwater signatures or hydrochemical processes indicating groundwater evolution, potential flowpaths, and recharge areas. The flowpaths are the trace of the Amargosa River, the trace of Fortymile Wash, and its convergence with the Amargosa River. This appears to represent not just a groundwater flow path, but traces of surface runoff infiltration as well. © 2011 Elsevier Ltd.


Flores-Garcia S.,Autonomous University of Ciudad Juárez | Alfaro-Avena L.L.,Autonomous University of Ciudad Juárez | Chavez-Pierce J.E.,Autonomous University of Ciudad Juárez | Luna-Gonzalez J.,Autonomous University of Ciudad Juárez | Gonzalez-Quezada M.D.,Technological Institute of Ciudad Juarez
American Journal of Physics | Year: 2010

Many students enrolled in introductory mechanics courses have difficulties with understanding the concept of static equilibrium. Some of these difficulties are related to the concept of force in the context of tension in massless strings. We identify three kinds of misconceptions: Students' beliefs that the angle of the string and proximity to the object are related to the tension. Students also use incorrect compensation arguments to reason about situations where both the angle and proximity change simultaneously. These difficulties were identified during investigations conducted in laboratory and lecture sessions at three universities in the United States and Mexico. © 2010 American Association of Physics Teachers.


de La Riva Rodriguez J.,Technological Institute of Ciudad Juarez | Estrada E.I.,Technological Institute of Ciudad Juarez | Reyes Martinez R.M.,Technological Institute of Ciudad Juarez | Prieto A.W.,Technological Institute of Ciudad Juarez
Advances in Intelligent Systems and Computing | Year: 2016

The present research’s main purpose is to analyze and develop a table of energy expenditure (EE), for the eight principal operational jobs of the automotive harnesses industry. These are: cable cutting, pressing, manual assembly, assembly on board, taping operation, electrical testing, quality inspection and material handling. Sample size consisted of 65 workers performing similar activities from three industries. Energy expenditure in the jobs studied varies from 2.21 kcal/min ±0.965 standard deviation to 4.24 kcal/min ±1.058 standard deviation. For each job their kcal/min were calculated and a model was constructed that could be used to determinate the energy consumption for those works. © Springer International Publishing Switzerland 2016.


Carrillo-Gutierrez T.,Autonomous University of Baja California | Martinez R.M.R.,Technological Institute of Ciudad Juarez | de La Riva Rodriguez J.,Technological Institute of Ciudad Juarez | Sanchez-Leal J.,Technological Institute of Ciudad Juarez
Advances in Intelligent Systems and Computing | Year: 2016

This document presents a study of human factors that influence human errors from the perspective of cognitive ergonomics. The purpose of the research is to determine the root of human errors from the perspective of the human factors that affect the quality of the product. The study of took place in the context of the Maquiladora Industry. The scientific methodology used is located in Cognitive anthropology, through the application of the theory of the Cultural consensus. The methodological approach of the study corresponds to the mixed methods. The design of the study was cross-sectional, descriptive and analytical. The population studied was that of multifunctional operators, existing in the company’s two modalities: those in manufacturing support and those in quality inspection support. With this research, it is possible to move closer to a classification of the causes root of human errors that affect the product quality in the industry maquiladora in Tijuana, Mexico. With this knowledge it is possible to propose preventive actions in Maquiladora improvement projects. © Springer International Publishing Switzerland 2016.


Soto K.C.A.,Autonomous University of Baja California | Rivera H.H.,Technological Institute of Ciudad Juarez | de La Riva Rodriguez J.,Technological Institute of Ciudad Juarez | Martinez R.M.R.,Technological Institute of Ciudad Juarez
Advances in Intelligent Systems and Computing | Year: 2016

Due to the scarcity of natural resources, the high competitiveness between companies and the need to create new business opportunities, some manufacturers are becoming interested in activities that involve more complexity than conventional manufacturing of its products. This is the case of companies being the original manufacturers of a product, engaged in reverse logistics to recover it at the end of its useful life and apply remanufacturing. The main objective of this research is to identify how human factors influence the activities of planning and production control, specifically in the remanufacturing process. However, it is interesting to note that it is not possible to establish a fair comparison between the conventional manufacturing process and remanufacturing in this regard. Remanufacturing is a process with greater uncertainty, so that establishing relationships with influential human factors allows: first, to make a more realistic approach to the situation in the company; second, determine the manner in which the staff makes decisions about the process and; third, develop a strategy allowing the company to improve its key performance indicators. Remanufacturing, is a relatively new process, the papers found with this approach are scarce. So conducting exploratory, descriptive and explanatory research was considered. To start this research, a study was conducted including employees of seven companies in the auto parts remanufacturing industry. In the first place, semi-structured interviews were applied; thereby the basic information to design the survey was obtained, which prior to its implementation was validated. After collecting the data, a confirmatory factor analysis was developed. Subsequently, we proceeded with the design and implementation of a SEM (Structural Equations Modelling). This allowed proposing a theoretical model to interpret the information provided by employees in the implementation phase of interviews and surveys. The model is convincing in demonstrating that the activities of planning and production control in remanufacturing are strongly affected by the human factor and has a significant impact on its key performance indicators. © Springer International Publishing Switzerland 2016.


Walton J.,University of Texas at El Paso | Woocay A.,Technological Institute of Ciudad Juarez
Journal of Green Building | Year: 2013

Hydraulic fracturing occurs when high pressure fluids primarily consisting of water and sand are pumped at high pressure into subsurface formations, typically shale that contains natural gas and/or oil. The high pressure fluid causes the rock to fracture. The new fractures increase the surface area of the shale and better interconnect previously existing fractures, allowing more natural gas and/or oil to be pumped from the formation. Modern hydraulic fracturing, referred to as "fracking," is an evolving technology that largely began after 2000 and has significantly increased natural gas production in the United States in the past five years with corresponding decreases in natural gas prices. The revolution in hydraulic fracturing has been made possible by technological advancements in directional drilling. In the past, wells were drilled vertically and sometimes passed only briefly into the producing formation. Shale is a sedimentary rock that is initially formed underwater as a horizontal layer containing compacted mud that is cemented into rock. Intact shale has a low permeability, making fluid movement slow except along natural or artificial fractures in the rock. In the case of the Marcellus Shale in Pennsylvania, the shale is approximately 100 to 250 feet thick. The Barnett Shale in Central Texas is between 100 and 500 ft, averaging about 300 ft; Eagle Ford Shale in South Texas is very variable with an average of about 250 ft; Fayetteville Shale in Arkansas is between 60-575 ft, average of about 200 ft; Haynesville Shale in Northwest Louisiana averages about 250 ft. Tectonic activity may later deform the initially horizontal layer into different angles and shapes, but the fundamental problem remains of how to most efficiently extract fluids from relatively thin and deep rock layers that have low permeability. Directional drilling allows a well to be oriented in a vertical direction until the shale layer is approached and then turned in to the approximately horizontal direction needed to follow along the shale layer (Figure 1). The wells can be turned in any compass direction, allowing multiple wells from a single pad to reach areas of several square miles in the producing shale location, thus significantly reducing their surface footprint and disturbance when compared to vertical drilling. Wells have been drilled more than a mile deep and a mile in horizontal reach. Furthermore, the Marcellus Shale is underlain by the thicker Utica Shale, making it likely that the same pads may years later be used to drill wells into the Utica Shale as well when gas prices rise sufficiently to make deeper drilling cost effective. Information on the extents of the Marcellus and Utica Shale formations is available in USGS reports listed in their Energy Resources Program (USGS, 2013) and at the website geology.com (Geology.com, 2013). The second key to increased access to energy resources is hydraulic fracturing. Shales naturally have a low permeability, meaning removal of resources is slow and inefficient. High pressure fluids containing proppants (e.g., sand), biocides, friction reducers, corrosion inhibitors, iron control, scale inhibitors, surfactants, and acids are injected into the wells to cause fracturing of the shale. The proppants move into the newly created fractures and expanded natural fractures and then prop the fractures open when the fluids are removed. The injected fluid is primarily (~99.5%) sand and water and the additive mixtures change by location, company, and as the technology evolves. Much of the injected water is later extracted from the well during production, along with formation waters. The exact spacing of pads, number of wells per pad, orientation of wells drilled from each pad, and well distance in the horizontal and vertical directions, depends upon surface access, drilling rights, formation properties, and economics. Leasing is an issue. Leases typically expire after a fixed period of time (typically about 5 years) if there is no drilling activity. Companies can drill but choose not to hydraulically fracture or produce from the well prior to lease expiration in order to lock up the resources until the economics of production improve. Hydraulic fracturing has revolutionized the energy field, causing the United States to switch from a need to import natural gas to a situation where export of natural gas is being considered. Energy independence, low energy costs, and economic development are clear positives that have been advanced by the revolution in hydraulic fracturing. This paper will summarize some of the environmental impacts associated with fracking. The order of subjects is approximately from the most obvious and certain to more subtle impacts.


Al-Qudah O.M.,University of Texas at El Paso | Woocay A.,Technological Institute of Ciudad Juarez | Walton J.C.,University of Texas at El Paso
Hydrological Processes | Year: 2015

Stormwater along ephemeral arroyos and areal infiltration in nearby boreholes were studied in the Amargosa Desert Region of Southern Nevada, USA. Chemical composition of ephemeral stream runoff was measured at elevations below where areal infiltration generally occurs in arid environments using lysimeters designed for this study. Borehole cuttings from several wells were evaluated in terms of chloride migration. Analysis of the borehole data indicates that net areal infiltration has been insignificant for the past 10000+years. This is associated with an environment where chloride and other soluble salts accumulate in shallow sediments and potentially in runoff waters. Measured storm events during the 4-year study period were small and localized but sufficient to produce surface runoff, at least near the lysimeters. Composition of storm runoff captured by the lysimeters was found to be a combination of the water chemistry types found in precipitation and from leaching tests of near-surface sediments. All major cations and bicarbonate increased relative to chloride when precipitation interacted with sediments to form ephemeral stream runoff. The changes were consistent with calculated saturation indices. Despite the long-term accumulation of chloride in soils and deep sediments caused by complete evapotranspiration of infiltrating precipitation, runoff waters were characterized by low chloride and total dissolved solids. This study presents a limitation of the chloride mass-balance method, as chloride and water migration were disassociated from each other in the study area. © 2014 John Wiley & Sons, Ltd.

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