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Articles 1861 - 1890 of 2584

Full-Text Articles in Engineering

Injection Molding Of Micro-Features, Manjesh Dubey Aug 2011

Injection Molding Of Micro-Features, Manjesh Dubey

All Theses

A method for creating regular arrays of surface features in the 10µm to 200µm range over large areas in metallic materials enables the use of treated surfaces on injection molds. This surface control is used for manufacturing products with controllable optical, tribological, heat transfer, and surface tension properties. However, the flow, filling, and solidification behavior of molten polymer at the micro scale is not well understood.
Therefore, the purpose of this study is to understand the formation of micro-structure on a polymer surface and derive a range of robust solutions for injection molding of these micro-featured surfaces. This study uses …


Retrofit Solutions For Sealed Pervious Concrete Pavements, Gregory Bunting Aug 2011

Retrofit Solutions For Sealed Pervious Concrete Pavements, Gregory Bunting

All Theses

The goal of this research was to design, implement, and evaluate several retrofit solutions for sealed pervious concrete. Properly functioning pervious concrete pavements allow water to drain through the structure, eliminating the need for traditional drainage infrastructure. A recent study of South Carolina porous pavements (Putman 2010) revealed that some pervious concrete pavements are not properly draining, either because of sealing at the surface. Sealed pavements are generally a result of construction processes, and sealed pavements cannot be fixed with sediment removal techniques such as vacuuming and pressure washing. This study investigates a technique to increase infiltration of sealed pervious …


Evaluation Of Warm Mix Open Graded Friction Course Mixtures, James Wurst Aug 2011

Evaluation Of Warm Mix Open Graded Friction Course Mixtures, James Wurst

All Theses

The goal of this study was to evaluate EvothermTM (a chemical package) and foaming (a water-injection method) warm mix asphalt (WMA) technologies to determine their effectiveness in producing high quality open graded friction course (OGFC) mixes. Specifically, this study focused on the effect of the removal of stabilizing additives (fibers and polymers) on the optimum binder content and performance of WMA OGFC mixtures. By focusing on additive removal, this study attempted to evaluate practical production concerns and the possible benefits of WMA technologies combined with OGFC.
The EvothermTM WMA and foaming WMA mixes were compared to traditional HMA OGFC by …


Predicting The Thermal Performance For The Multi-Objective Vehicle Underhood Packing Optimization Problem, Ravi Teja Katragadda Aug 2011

Predicting The Thermal Performance For The Multi-Objective Vehicle Underhood Packing Optimization Problem, Ravi Teja Katragadda

All Theses

The ever increasing demands towards improvement in vehicle performance and passenger comfort have led the automotive manufacturers to further enhance the design in the early stages of the vehicle development process. Though, these design changes enhance the overall vehicle performance to an extent, the placement of these components under the car hood also plays a vital role in increasing the vehicle performance. The study of the placement of these components in an automobile underhood forms a 3-Dimensional packaging problem. In the past, a study on the automobile underhood packaging problem was conducted and a multi objective optimization routine with three …


Friction Stir Welding (Fsw) Process Modeling And Fsw Joint Design For Blast Survivable Structures, Anand Hariharan Aug 2011

Friction Stir Welding (Fsw) Process Modeling And Fsw Joint Design For Blast Survivable Structures, Anand Hariharan

All Theses

In order to satisfy the need for better ballistic performance against lethal threats, new grades of Titanium (e.g. Ti-6Al-4V) and Aluminum (e.g. AA5083) alloys are being employed in the design of blast survivable structures. These better performing alloys are not readily amenable to conventional welding process or result in inferior welds when joined using conventional welding process. On the other hand, Friction Stir Welding (FSW), a relatively new welding process, has been found to be successful in producing good quality welds in these alloys. FSW also offers better weld performance in comparison with the conventional welding process. But the methodology …


Investigation Of The Effect Of Aggregate Gradation On Open Graded Friction Course Mixtures, Talat Mansour Aug 2011

Investigation Of The Effect Of Aggregate Gradation On Open Graded Friction Course Mixtures, Talat Mansour

All Theses

An open graded friction course (OGFC) is a type of porous pavement that has been used to improve safety, mainly in wet conditions. However, this mix also has exhibited poor durability and strength which limits its use in some pavement applications. This research investigated the effect of aggregate gradation on the performance of OGFCs. Ten OGFC gradations which are used by twenty different states were compared. One asphalt binder was used throughout the research (PG76-22) and hydrated lime and cellulose fibers were also added to all of the mixes.
Several tests, using various standardized testing procedures, were used in this …


Sediment Based Turbidity Analyses For Representative South Carolina Soils, Katherine Resler Aug 2011

Sediment Based Turbidity Analyses For Representative South Carolina Soils, Katherine Resler

All Theses

Construction activities have been recognized to have significant impacts on the environment. Excess sediment from construction sites is frequently deposited into nearby surface waters, negatively altering the chemical, physical and biological properties of the water body. This environmental concern has led to strict laws concerning erosion and sediment control, such as imposing permit conditions that limit the concentration of suspended solids that can be present in effluent water from construction sites. However, sediment concentration measurements are not routinely used to detect and correct short-term problems or permit violations because laboratory analysis of sediment concentrations is time-consuming and costly. Nevertheless, timely, …


Effect Of Accelerated Aging On Mechanical Properties And Structure Of Nano-Scale Composite Systems, David Economy Aug 2011

Effect Of Accelerated Aging On Mechanical Properties And Structure Of Nano-Scale Composite Systems, David Economy

All Theses

Nano-scale composites are being investigated by academic, industrial, and national laboratories for potential applications such as wear resistant coatings and high strength foils. These structures are of interest due to their as-fabricated mechanical properties, such as high strength for nanolaminates. However, there have only been limited studies of the long-term mechanical stability. A greater understanding of how these systems might respond to sustained use is needed before these systems transition from research laboratories into widespread application. It is the objective of this thesis to clarify the link between accelerated aging using elevated temperatures over time and mechanical properties of two …


Analytical Solutions Using High Order Composite Laminate Theory For Honeycomb Sandwich Plates With Viscoelastic Frequency Dependent Damping, Nan Shan Aug 2011

Analytical Solutions Using High Order Composite Laminate Theory For Honeycomb Sandwich Plates With Viscoelastic Frequency Dependent Damping, Nan Shan

All Theses

Analytical methods allow parametric changes in geometric and material properties of a honeycomb sandwich plate for studies of stiffness, mass, and damping characteristics with low computational cost. However, studies based on analytical methods are still limited with frequency independent damping models. Specifically, previous analytical models have not consider the frequency dependent damping for viscoelastic honeycomb core sandwich composites, while some work has been done on studying the honeycomb sandwich plate using finite element method, which can be computationally expensive for multiple parameter studies. Therefore, in this work, the honeycomb sandwich plate is studied analytically based on the cellular material theory, …


Extracting Depth Information From Stereo Vision System, Using A Correlation And A Feature Based Methods, Mahmoud Abdelhamid Aug 2011

Extracting Depth Information From Stereo Vision System, Using A Correlation And A Feature Based Methods, Mahmoud Abdelhamid

All Theses

This thesis presents a new method to extract depth information from stereo-vision acquisitions using a feature and a correlation based approaches. The main implementation of the proposed method is in the area of Autonomous Pick & Place, using a robotic manipulator. Current vision-guided robotics are still based on a priori training and teaching steps, and still suffer from long response time.
The study uses a stereo triangulation setup where two Charged Coupled Devices CCDs are arranged to acquire the scene from two different perspectives. The study discusses the details of two methods to calculate the depth; firstly a correlation matching …


Viscoelastic Damping Of Hexagonal Honeycomb Sandwich Panels, Nikhil Seera Aug 2011

Viscoelastic Damping Of Hexagonal Honeycomb Sandwich Panels, Nikhil Seera

All Theses

Composite sandwich structures with a viscoelastic core material constrained between thin stiff face sheets are an effective means of damping in engineering applications. Damping introduces energy dissipation which helps control vibration amplitudes. Conventional Hexagonal honeycombs are often referred to as regular honeycombs and are defined by cellular geometry with effective positive Poisson's ratio. Regular honeycombs are commonly used for the cores of sandwich plates because of their low density and high stiffness properties. Honeycombs with negative in-plane Poisson's ratio are known as Auxetic honeycombs and offer enhancement of mechanical properties such as impact absorption, damage resistance, when compared to regular …


Behavior Of The Next-D Beam Shear Key: A Finite Element Approach, Armando Flores Aug 2011

Behavior Of The Next-D Beam Shear Key: A Finite Element Approach, Armando Flores

All Theses

State Departments of Transportation have been using adjacent precast bridges for many years. A vital component of this type of bridges is the connection between the members, which is typically done with a grouted shear key. Shear keys have changed through time to adapt to the requirements of bridge design. An assessment of the Northeast Extreme Tee with integral deck (NEXT-D) was performed for the SCDOT as a development possibility for short span bridges. This research focuses on the finite element analysis study of the NEXT-D's specific shear key configuration.
A review of shear key configurations used by different DOTs …


Electrokinetic Transport And Manipulation Of Particles In Curved Microchannels, Junjie Zhu Aug 2011

Electrokinetic Transport And Manipulation Of Particles In Curved Microchannels, Junjie Zhu

All Dissertations

The investigation of electrokinetic particle transport in confined microchannels has practical significances in a variety of applications ranging from traditional gel electrophoresis to electrokinetic microfluidics-based lab-on-a-chip devices. To date, however, studies on particle electrokinetics have been limited to primarily theoretical or numerical analyses in straight microchannels of simple geometries. Very little work has been done on electrokinetic particle motions in real microchannels which usually consist of one or multiple turns. This thesis is dedicated to the fundamental and applied studies of electrokinetic transport and manipulation of particles in various curved microchannels using a combined experimental, theoretical, and numerical method.
First, …


Contaminant Mass Transfer During Boiling In Fractured Geologic Media, Fei Chen Aug 2011

Contaminant Mass Transfer During Boiling In Fractured Geologic Media, Fei Chen

All Dissertations

Remediation of fractured geologic media contaminated with chlorinated volatile organic compounds that diffuse into the matrix is challenging using isothermal methods. Due to the low permeability of the matrix material and uncertainty of fracture networks, it is difficult to flush the system with any type of fluid or deliver remediation agents into the matrix. However, thermal methods have some promises. When the matrix is heated above water boiling temperature, depressurization in the fractures may trigger water boiling in the matrix, which, as a result, generates a large volumetric steam flow toward adjacent fractures, stripping the adsorbed or dissolved volatile contaminants …


Effects On Hydrogen Adsorption And Activation On Platinum In A Fuel Cell Catalyst, Jack Zhang Aug 2011

Effects On Hydrogen Adsorption And Activation On Platinum In A Fuel Cell Catalyst, Jack Zhang

All Dissertations

Proton exchange membrane fuel cells are a highly efficient source of power generation that is needed to sustain the energy demands of today's more environmentally conscience society. However, the presence of impurities in the hydrogen fuel stream, such as CO, H2S, and NH3 from the steam reforming/partial oxidation of hydrocarbons/methanol, can severely poison the Pt electrocatalyst present in the fuel cell electrode causing degradation in the fuel cell performance. To counter these poisoning effects, fuel cell manufacturers are forced to use higher Pt loadings, which dramatically increases material costs and prevents the successful commercialization of the technology. …


The Effects Of Weather Recognition Training On General Aviation Pilot Situation Assessment And Tactical Decision Making When Confronted With Adverse Weather Conditions, Chansik Kim Aug 2011

The Effects Of Weather Recognition Training On General Aviation Pilot Situation Assessment And Tactical Decision Making When Confronted With Adverse Weather Conditions, Chansik Kim

All Dissertations

Previous general aviation (GA) accident studies showed that decision errors were more associated with fatal GA accidents than other kinds of human errors, and weather related accidents, especially continued visual flight rules (VFR) flight into instrument meteorological conditions (IMC), remained the major cause of fatal GA accidents. Thus, finding the underlying causes of GA pilots' decision errors and continued VFR flight into adverse weather conditions are needed to reduce weather related GA accidents as well as fatal GA accidents.
Causal factors and hypotheses of weather related GA accidents show that knowledge, experience, motivation, and weather information frequently have been referred …


Multi-Length Scale Modeling Of The High-Pressure, Large-Strain, High-Strain-Rate Response Of Soda-Lime Glass, William Bell Aug 2011

Multi-Length Scale Modeling Of The High-Pressure, Large-Strain, High-Strain-Rate Response Of Soda-Lime Glass, William Bell

All Dissertations

Development of new transparent armor systems is essential for the protection of the current and future US armed forces, especially in light of the recent military operations The Operation Iraqi Freedom in Iraq and The Operation Enduring Freedom in Afghanistan. These conflicts have introduced a new military theater without a well-defined battle front and new types of threats (e.g. improvised explosive devices, IEDs). Development and modeling of new transparent armor systems for use in numerous applications from vehicle windows to face shields is a current area of thrust aimed at addressing the shortcomings of existing systems in order to better …


An Experimental And Computational Study Of Windborne Debris In Severe Storms, Arash Karimpour Aug 2011

An Experimental And Computational Study Of Windborne Debris In Severe Storms, Arash Karimpour

All Dissertations

Abstract
This research focuses on an experimental and theoretical investigation of windborne debris emanating from loose gravel on built-up roofs. During severe storms, windborne debris can cause considerable physical harm and property damage. One of the major sources of flying debris in large commercial areas is loose gravel on built-up roofs. Such loose gravel can be responsible loss of life and significant property damage. Despite the high risk of windborne debris, their flight mechanics are poorly understood. To better understand windborne debris flight, a series of experiments were conducted in the Clemson University Boundary Layer Wind Tunnel. These experiments were …


Low-Resolution Vision For Autonomous Mobile Robots, Vidya Nariyambut Murali Aug 2011

Low-Resolution Vision For Autonomous Mobile Robots, Vidya Nariyambut Murali

All Dissertations

The goal of this research is to develop algorithms using low-resolution images to perceive and understand a typical indoor environment and thereby enable a mobile robot to autonomously navigate such an environment. We present techniques for three problems: autonomous exploration, corridor classification, and minimalistic geometric representation of an indoor environment for navigation.
First, we present a technique for mobile robot exploration in unknown indoor environments using only a single forward-facing camera. Rather than processing all the data, the method intermittently examines only small 32X24 downsampled grayscale images. We show that for the task of indoor exploration the visual information is …


Modeling Of Strain Effect On Thermal And Electrical Transport Properties Of Si/Ge Nanocomposites And Its Applications, Yaoyao Xu Aug 2011

Modeling Of Strain Effect On Thermal And Electrical Transport Properties Of Si/Ge Nanocomposites And Its Applications, Yaoyao Xu

All Dissertations

Nanocomposites are composite materials which incorporate nanosized particles, platelets or fibers. The addition of nanosized phases into the bulk matrix can lead to significantly different material properties compared to their macrocomposite counterparts. Due to their extraordinary properties, nanocomposites promise new applications in many fields such as ultra-high strength and ultra-light automotive parts, non-linear optics, biomedical applications, sensors and actuators, and thermoelectric devices. The design and fabrication of nanocomposite structures, devices and systems can be accelerated by developing accurate and efficient computational tools that can describe the properties and behavior of the nanocomposites. However, the development of such tools is challenging …


Development Of Reduced Complexity Models For Electromagnetic Modeling, Changyi Su Aug 2011

Development Of Reduced Complexity Models For Electromagnetic Modeling, Changyi Su

All Dissertations

The current and field distributions of various structures can be calculated using full-wave numerical modeling codes. However, this approach is limited by the complex models and extensive computational resources required to analyze the details of each structure. In addition, brute-force modeling of the entire geometry provides relatively little physical insight into the electromagnetic interference (EMI) source mechanisms. Alternatively an effective equivalent model can be obtained by eliminating sources and structures that do not contribute significantly to the radiated emissions and focusing on the features that could possibly be significant sources of EMI. Equivalent models are generally much simpler than model-everything …


An Investigation Of The Effects Of Surfactant Monolayers On Natural Convection Heat Transfer And Evaporative Mass Transfer, Steven Bower Aug 2011

An Investigation Of The Effects Of Surfactant Monolayers On Natural Convection Heat Transfer And Evaporative Mass Transfer, Steven Bower

All Dissertations

Laboratory experiments are presented that reveal the effects of surfactant monolayers on natural convection heat transfer and evaporation from bodies of water; more specifically, the situation is studied where the bulk temperature of the water is greater than the temperature of the air so that evaporative convection occurs. Four sets of experiments were performed in a laboratory environment on insulated tanks of different widths and depths for the following surface conditions: 1) clean surface, 2) oleyl alcohol covered surface, 3) stearic acid covered surface, and 4) stearyl alcohol covered surface. An infrared (IR) camera was used to verify the existence …


Computational-Analysis Assisted Introduction Of Friction Stir Welding Into Development Of Light-Weight High-Survivability Military Vehicles, Guruprasad Arakere Aug 2011

Computational-Analysis Assisted Introduction Of Friction Stir Welding Into Development Of Light-Weight High-Survivability Military Vehicles, Guruprasad Arakere

All Dissertations

High strength aluminum alloys with superior blast/ballistic resistance against armor piercing (AP) threats and with high vehicle light-weighing potential are being increasingly used as military-vehicle armor. Due to the complex structure of these vehicles, they are commonly constructed through joining (mainly welding) of the individual components. Unfortunately, these alloys are not very amenable to conventional fusion based welding technologies (e.g. Gas Metal Arc Welding (GMAW)) and in-order to obtain high-quality welds, solid-state joining technologies such as Friction Stir Welding (FSW) have to be employed. However, since FSW is a relatively new and fairly complex joining technology, its introduction into advanced …


The Effects Of Fundamental Mixture Parameters On Hot-Mix Asphalt Performance Properties, Wenbin Zhao Aug 2011

The Effects Of Fundamental Mixture Parameters On Hot-Mix Asphalt Performance Properties, Wenbin Zhao

All Dissertations

Asphalt pavements are composed of three components: aggregate, asphalt binder, and air. In the process of plant production and on-site construction, the construction quality can vary in the three component and the variability can further affect a pavement's future performance.. This research identifies aggregate gradation, binder content, and air voids content as the fundamental parameters. Understanding the fundamental parameters' influence on the HMA mixture's performance properties can provide valuable information on how to improve the current quality insurance practice. The objective of this study is to conduct well-controlled experiments to investigate how mix gradation, air voids and small range binder …


Social Sustainability Considerations During Planning And Design: A Framework Of Processes For Construction Projects, Rodolfo Valdes Vasquez Aug 2011

Social Sustainability Considerations During Planning And Design: A Framework Of Processes For Construction Projects, Rodolfo Valdes Vasquez

All Dissertations

With increased awareness of issues such as global resource shortages and climate change, sustainability efforts are becoming more common in the construction industry. While these efforts often consider economic and environmental factors, a truly sustainable construction project also needs to include such social considerations as its impact on the surrounding community and the safety, health, and education of the workforce. For the construction industry, social sustainability requires integrating processes for improving safety, health and well-being over the project life cycle. However, an empirical and comprehensive framework defining these social sustainability processes in construction projects has yet to be clearly delineated. …


Metaheuristics For Hub Location Models, Ornurai Sangsawang Aug 2011

Metaheuristics For Hub Location Models, Ornurai Sangsawang

All Dissertations

In this research, we propose metaheuristics for solving two p-hub median problems.. The first p-hub median problem, which is NP-hard, is the uncapacitated single p-hub median problem (USApHMP). In this problem, metaheuristics such as genetic algorithms, simulated annealing and tabu search, are applied in different types of representations. Caching is also
applied to speed up computational time of the algorithms. The results clearly demonstrate that tabu search with a permutation solution representation, augmented with caching is the highest performing method, both in terms of solution quality and computational time among these algorithms for the USApHMP. We also investigate the performance …


Anticipating U.S. Population-Level Health And Economic Impacts Using Discrete-Event Simulation To Guide Health Policy Decisions, Odette Reifsnider Aug 2011

Anticipating U.S. Population-Level Health And Economic Impacts Using Discrete-Event Simulation To Guide Health Policy Decisions, Odette Reifsnider

All Dissertations

This dissertation presents two applications of discrete-event simulation (DES) to represent clinical processes: (1) a model to quantify the risk of the maternal obese and diabetic intrauterine environment influence on progression to adult obesity and diabetes, and (2) a model to evaluate health and economic outcomes of different smoking cessation strategies. The first application considers the public health impact of the diabetic and obese intrauterine environment's effect on the prevalence of diabetes and obesity across subsequent generations. We first develop a preliminary DES model to investigate and characterize the epidemiology of diabetes during pregnancy and birth outcomes related to maternal …


Improving Quality Of Service In Ems Systems By Reducing Disparities Between Service Zones, Sunarin Chanta Aug 2011

Improving Quality Of Service In Ems Systems By Reducing Disparities Between Service Zones, Sunarin Chanta

All Dissertations

Emergency medical service (EMS) systems respond to emergency or urgent calls so as to provide immediate care, such as pre-hospital care and/or transportation, to hospitals. Care must be provided in a timely manner; in fact quality of service is usually directly associated with response time. To reduce the response time, the number and location of vehicles within the service area are important variables. However with limited capacity, increasing the number of vehicles is often an infeasible alternative. Therefore, a critical design goal is to decide at which facilities stations should be located in order to serve as much demand as …


Thermoelectric Properties Of Nickel And Titanium Co-Intercalated Titanium Diselenide, Timothy Holgate Aug 2011

Thermoelectric Properties Of Nickel And Titanium Co-Intercalated Titanium Diselenide, Timothy Holgate

All Dissertations

Thermoelectric materials are involved in the direct conversion between thermal and electrical energy. They may be used to generate power from a thermal gradient or to pump heat in or out of a system when driven with DC power. Much of the recent advances in thermoelectric research have been in materials whose thermoelectric efficiency has been optimized at temperatures above room temperature where power generation is the main application.
The question that I seek to answer in this dissertation is to use our standard experimental techniques in order to assess the possibility of a class of transition metal dichalcogenides bases …


Investigation Into The Role Of Airfield Pavement Deicer In Concrete Pavement Deterioration, David Wingard Aug 2011

Investigation Into The Role Of Airfield Pavement Deicer In Concrete Pavement Deterioration, David Wingard

All Dissertations

Premature deterioration of concrete due to materials-related distresses has been observed with increased frequency in airfield pavements across the United States in the past two decades. The use of a new breed of deicing chemicals based on alkali-acetates and alkali-formates, starting in the early 1990s, has been suspected to be one of the significant reasons for the increase in the observed deterioration. Previous laboratory-based studies have found that the early-age deterioration in concrete is associated with exposure to deicers causing acceleration of the Alkali Silica Reaction (ASR) deterioration mechanism and consequent failure. However, no systematic forensic studies on the impact …