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University of Texas at El Paso

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Articles 271 - 279 of 279

Full-Text Articles in Civil and Environmental Engineering

Transition Metal Catalysts For Hydrodesulfurization Reactions Applied To Petroleum Industry, Brenda Torres Jan 2009

Transition Metal Catalysts For Hydrodesulfurization Reactions Applied To Petroleum Industry, Brenda Torres

Open Access Theses & Dissertations

Catalysis plays a fundamental role in petroleum refining and basic petrochemical industries creating new routes in the development of industrial processes. Moreover, catalysis has become indispensable to the solution of environmental pollution problems and therefore on public health. World wide concerns for preservation of the environment has motivated the development of "Green" catalyst based technologies, to achieve a better utilization of petroleum resources and demands for cleaner transportation fuels. These environmental concerns have led to increasingly drastic regulations on sulfur, nitrogen and aromatics content in fuels. Sulfur content in the motor and diesel fuels is continuously reduced by regulations to …

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Screening The Phytoremediation Potential Of Native Plants Growing On Mine Tailings In Arizona, Usa, Md Nazmul Haque Jan 2008

Screening The Phytoremediation Potential Of Native Plants Growing On Mine Tailings In Arizona, Usa, Md Nazmul Haque

Open Access Theses & Dissertations

Mining companies have been playing an important role for the utilization of the Earth's natural resources for the prosperity of human society. However, the mining of resources has generated solid wastes called tailings that have become a serious environmental threat worldwide. Technologies such as soil caping have been used to remediate the problem. Nevertheless, the remediation of mine tailings using conventional technologies is costly and environmentally unpleasant. Since the last few decades, a plant based technology known as phytoremediation has appeared as a promising alternative. Several plant species have demonstrated to have phytoremediation capabilities; though, best results have been obtained …

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Quantifying Anisotropy In Asphalt Concrete Pavements Using An Ultrasonic Method, Monica C. Jurado Jan 2008

Quantifying Anisotropy In Asphalt Concrete Pavements Using An Ultrasonic Method, Monica C. Jurado

Open Access Theses & Dissertations

Asphalt concrete is a bonded granular material whose internal structure is anisotropic. Such anisotropy is due to anisotropic particles and void's structure, particle distribution and orientation, and restrain and force pattern used during compaction. Even with this knowledge asphalt concrete design is made considering asphalt concrete as an isotropic material. The biggest difference between an isotropic and anisotropic material is that, an isotropic material is characterized by two independent constants and an anisotropic material could be characterized by up to 81 constants. An extensive research to characterize and quantify anisotropy is only available for some composite materials. Based on the …

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Expert System Design Guide For Lower Classification Roads Over High Pi Clays, Yaqi Wanyan Jan 2008

Expert System Design Guide For Lower Classification Roads Over High Pi Clays, Yaqi Wanyan

Open Access Theses & Dissertations

This research was focused on low-volume roads over expansive clayey soils in Texas. In spite of the redundant pavement designs recommended and widely used in Texas for roads in high PI clay areas, these pavements often fail prematurely. This failure occurs primarily because of the highly variable properties of the clayey subgrade throughout the year due to moisture fluctuations. The problematic nature of high PI clays, despite the fact that volumetric changes such as heaving are sometime considered in the design, is of concern since they contribute to roughness and longitudinal shrinkage cracking of the road, and as such the …

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Analysis Of Number And Mass Concentration Of Coarse And Fine, Nancy Garcia Jan 2008

Analysis Of Number And Mass Concentration Of Coarse And Fine, Nancy Garcia

Open Access Theses & Dissertations

There is currently much concern over particles suspended in the ambient air, their effects on people and the environment throughout the world. The suspended particles can cause adverse health effects, reduce visibility and over the course of time wear buildings. Primary air quality concerns are of particles, their effects and their key characteristics. Particle number concentration (NC) of traffic emissions is an important element of the study, specifically heavy duty diesel engine emissions. Particle number concentration is the number of particles of a specific size in a unit of air; in this study they are measured by the number of …

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Guidelines For Using Local Material For Roadway Base And Subbase, Biraj Gautam Jan 2008

Guidelines For Using Local Material For Roadway Base And Subbase, Biraj Gautam

Open Access Theses & Dissertations

Flexible base materials that meet TxDOT specifications are getting more difficult to purchase in many TxDOT Districts. As a result, higher quality materials have to be hauled long distances, sometimes from other States. This act would significantly increase the costs associated with the construction of roads and subsequent maintenance and rehabilitation of them. Lower quality (i.e., out-of-specification) materials are normally available. If through appropriate modifications of the materials (adjusting the gradation or/and stabilization) or structural design (specifying thicker layers of base and/or hot mix) the use of the local materials can be permitted, the construction can be accelerated and significant …

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Allocating Emergency Response Vehicles To Cover Critical Infrastructures, Hao Lei Jan 2008

Allocating Emergency Response Vehicles To Cover Critical Infrastructures, Hao Lei

Open Access Theses & Dissertations

Optimal deployment of limited emergency response service units in a metropolitan area is of interests to public agencies. The limited emergency units not only have to respond to the demand for service by residents and businesses, but also cover Critical Infrastructures (CIs). This Thesis formulates an improved optimization model to allocate different types of Emergency Response Service (ERS) units among their candidate base stations. The allocation of units must ensure maximum coverage to CIs, subject to the capacities of the base stations, service standard in terms of time to reach the CIs, and the availability of the ERS units (when …

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Quality Evaluation Of Portland Cement Concrete At Early Age With Free-Free Resonant Column, Gilberto Wenglas Jan 2008

Quality Evaluation Of Portland Cement Concrete At Early Age With Free-Free Resonant Column, Gilberto Wenglas

Open Access Theses & Dissertations

At early age, the behavior and mechanical properties of portland cement concrete changes rapidly with time due to hydration. The hydration process consists of a series of chemical reactions that accelerate nonlinearly with the rise in temperature. The hydration process consists of three stages: the dormant period, the setting time, and the hardening time. Timely opening of roads and resumption of constructions depend of the knowledge of these stages. The initial and final setting times are arbitrarily determined by a standard test (ASTM C 403). Although the setting time has been studied for many decades, the new technologies allow making …

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Uplift Capacity Of Rigid Pile In Clay Under Inclined Load, Godwin Ikechukwu Ubanyionwu May 1985

Uplift Capacity Of Rigid Pile In Clay Under Inclined Load, Godwin Ikechukwu Ubanyionwu

Open Access Theses & Dissertations

This thesis investigates the uplift capacity of rigid vertical piles embedded in saturated or near-saturated clayey soils subjected to inclined uplifting loads. Pile foundations are widely used in civil engineering applications requiring resistance to both axial and lateral forces, including transmission tower foundations, foundations on expansive soils, and mat foundations in areas subject to rising groundwater tables. While considerable research had addressed compressive load bearing capacity and lateral resistance of piles, experimental data on pile behavior under inclined uplift loading remained scarce at the time of this study. The present study was undertaken to conduct a systematic series of laboratory …

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