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Articles 2431 - 2460 of 2512

Full-Text Articles in Engineering

Low-Complexity Iterative Detection Techniques For Slow-Frequency-Hop Spread-Spectrum Communications With Reed-Solomon Coding., Harish Ramchandran May 2007

Low-Complexity Iterative Detection Techniques For Slow-Frequency-Hop Spread-Spectrum Communications With Reed-Solomon Coding., Harish Ramchandran

All Dissertations

Slow-frequency-hop (SFH) spread-spectrum communications provide a high level of robustness in packet-radio networks for both military and commercial applications. The use of a Reed-Solomon (R-S) code has proven to be a good choice for use in a SFH system for countering the critical channel impairments of partial-band fading and partial-band interference. In particular, it is effective when reliability information of dwell intervals and individual code symbols can be obtained and errors-and-erasures decoding (EE) can be employed at the receiver.
In this dissertation, we consider high-data-rate SFH communications for which the channel in each frequency slot is frequency selective, manifesting itself …

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Models Of Semi-Systematic Visual Search, Sourav Das May 2007

Models Of Semi-Systematic Visual Search, Sourav Das

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Visual search is an important aspect of many examination and monitoring tasks. As a result, visual search performance has been the topic of many empirical investigations. These investigations have reported that individual search performance depends on subject factors such as search behavior, which has motivated the development of models of visual search that incorporate this behavior. Search behavior ranges from random to strictly systematic; variation in behavior is commonly assumed to be caused by differences in memory retrieval and search strategy. Accordingly, a mathematical model of semi-systematic search is proposed here that can account for both memory retrieval and other …

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Analytical And Intelligent Techniques For Dynamically Secure Dispatches, Aftab Alam May 2007

Analytical And Intelligent Techniques For Dynamically Secure Dispatches, Aftab Alam

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The NERC August 14th Blackout report brought out by the task force cited 'failure to ensure operation within secure limits' as one of the main reasons. Many of the numerous recommendations focused on the need for better real-time tools for operators and reliability coordinators. In the absence of such tools the operators are limited to operating in conservative secure operating regions established using offline studies. At the same time, with the fast inception of deregulation, the need to ensure a reliable and secure power system has become all the more vital. The success of a competitive market is dependent upon …

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Information Flow To Support Front End Planning, Ryan George May 2007

Information Flow To Support Front End Planning, Ryan George

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Previous research has demonstrated the value of front end planning as it impacts project performance. This dissertation summarizes the findings of a research project which examined ways to improve information flow through the front end planning process. The front end planning process was carefully diagrammed as consisting of 33 distinct information flow activities, each with its own information flow entities and interactions. Fifty-one questionnaire survey forms were analyzed to obtain data for the 33 information flow activities that included activity duration, resources expended, and other supplemental insights such as the extent of information availability. The 51 projects were then grouped …

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Domination And Decomposition In Multiobjective Programming, Alexander Engau May 2007

Domination And Decomposition In Multiobjective Programming, Alexander Engau

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During the last few decades, multiobjective programming has received much attention for both its numerous theoretical advances as well as its continued success in modeling and solving real-life decision problems in business and engineering. In extension of the traditionally adopted concept of Pareto optimality, this research investigates the more general notion of domination and establishes various theoretical results that lead to new optimization methods and support decision making.
After a preparatory discussion of some preliminaries and a review of the relevant literature, several new findings are presented that characterize the nondominated set of a general vector optimization problem for which …

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Soar Checkers - An Intelligent Checkers Playing Agent In Soar, Jithu Menon May 2007

Soar Checkers - An Intelligent Checkers Playing Agent In Soar, Jithu Menon

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The classic board game of checkers is ideally suited for research in AI game-playing programs or agents. The objective behind Soar Checkers is to investigate if it is possible to create an agent-based game playing system that would beat novices with ease and at least challenge advanced novice to intermediate-level players by designing a rules-based expert system whose knowledge base consists of nothing more than the rules of checkers, and a set of guidelines for game-play based on good strategy. Soar was chosen as the platform for building this agent because it came built-in with features that facilitate creating rules-based …

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Energy Absorption Of Sine Wave Beams Subjected To Axial Impact Loading, Robert Smith May 2007

Energy Absorption Of Sine Wave Beams Subjected To Axial Impact Loading, Robert Smith

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Energy absorbers ideally remove kinetic energy efficiently and reliably while minimizing force magnitudes felt on the moving body. Until now, energy absorber design has concentrated on thin-walled prismatic tubes and tapered tubes. Sine wave beams (SWB) have been previously investigated as energy absorbers under lateral impacting situations only. This thesis investigates the energy absorption of the SWB under axial impact. FE models simulated the energy absorbing response of the SWB. Parametric analyses were performed using the structure's thickness, the web amplitude, and the period number of the web. The SWB's performance is evaluated and then compared to the prismatic structures. …

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Extrapolation Of Time And Frequency Responses Of Resonant Antennas Using Damped Sinusoids And Orthogonal Polynomials, James Frye May 2007

Extrapolation Of Time And Frequency Responses Of Resonant Antennas Using Damped Sinusoids And Orthogonal Polynomials, James Frye

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An extrapolation technique is presented which reduces the computational demands of obtaining a wide-band electromagnetic response from a resonant antenna using traditional computational methods. It has been shown that a wide-band response can be extrapolated by fitting early-time and low-frequency data as a summation of orthogonal polynomials. However, because the polynomials provide compact time support, representation of long time responses intrinsic to resonant structures in practice proves inefficient and can lead to numerical instabilities. This thesis outlines incorporating damped sinusoids to efficiently and reliably extrapolate time and frequency responses of resonant antennas due to a wide-band source. A genetic algorithm …

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Modeling Requirements Propagation To Generate Solutions For Minimizing Mass, Thulasiram Ezhilan May 2007

Modeling Requirements Propagation To Generate Solutions For Minimizing Mass, Thulasiram Ezhilan

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This thesis investigates the issue of weight reduction in moderately complex systems by addressing how to cascade the requirements to the individual components. Though mass can be reduced using different techniques such as material substitution or structural optimization; a systematic method for allocating mass as a function of requirements is necessary to provide novel alternate solutions that enable reduction of mass of the system while satisfying the requirements and tests governing them. Such a method can be developed by exploring different aspects of achieving weight reduction through change propagation in the parameters/elements governing the system. Though efforts have been made …

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Machinability And Microstructure Stability During The Machining Of Pure Copper And Titanium Processed By Equal Channel Angular Pressing, Mason Morehead May 2007

Machinability And Microstructure Stability During The Machining Of Pure Copper And Titanium Processed By Equal Channel Angular Pressing, Mason Morehead

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For ultrafine grained materials (containing microstructures of 100-300 nm) to be manufactured and used in industry, machining research is needed to form and shape these materials into their final dimensions. Because of their high internal energy, UFG materials are known to have microstructures which are susceptible to undesirable changes at low temperatures. In this study, pure ultrafine grained copper and titanium as well as their respective coarse grained (CG) counterparts were tested for their relative machinability and microstructure stability through lathe turning. To evaluate the machinability cutting forces, tool wear, chip morphology, and surface roughness were studied using different cutting …

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A Study Of Induced Drag And Spanwise Lift Distribution For Three-Dimensional Inviscid Flow Over A Wing, Scott Monsch May 2007

A Study Of Induced Drag And Spanwise Lift Distribution For Three-Dimensional Inviscid Flow Over A Wing, Scott Monsch

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Numerical results for an untwisted, finite rectangular wing (NACA 0012, AR = 6.7) using no flap deflections are compared against theoretical lifting line predictions. The numerical approach used an Euler-based computational fluid dynamic (CFD) solver. A span-wise lift distribution was extracted from the CFD solution. The comparison between the predicted numerical and lifting-line span-wise lift distributions shows good agreement with a maximum deviation of only 2.4% over the wing span.
The induced drag was extracted from the downstream wake using a wake integral technique referred to as Trefftz plane analysis. The predictions for induced drag based on surface integration, wake …

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On The Effects Of Estimation Error And Jitter In Ultra-Wideband Communication , Greta Grizzard May 2007

On The Effects Of Estimation Error And Jitter In Ultra-Wideband Communication , Greta Grizzard

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The opening of the 3.6 - 10.1 GHz frequency spectrum below the 'noise-floor' by the FCC in 2002 has made possible the prospect of reusing this frequency spectrum through ultra-wideband (UWB) communication. In this thesis, we compare the performance of several UWB systems in the presence of estimation error and jitter. We then develop two alternative decision schemes to combat the effect of jitter in the UWB system. Numerical results show that one of the schemes provides significantly better performance in the presence of severe jitter than maximal ratio combining and minimal degradation of performance if jitter is not present. …

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Effects Of Ionizing Radiaton On Diaphyseal Cortical Bone, Neil Travis May 2007

Effects Of Ionizing Radiaton On Diaphyseal Cortical Bone, Neil Travis

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Radiation exposure is experienced in both radiotherapy and exploratory space missions. As cancer treatments improve and astronauts aim to explore beyond low earth, radiation's effects on bone must be clearly understood. Nine-week old female C57BL/6 mice were evaluated for cortical bone changes by mechanical testing, micro-computed tomography, quantitative histomorphometry, percent mineralization and micro-hardness indentation. Study one, Multi-Type study, mice received a 2 Gray (Gy) gamma, proton, iron and carbon whole body radiation dose and sacrificed 110 days post-exposure. Study two, High-Dose study, mice received a 7 Gy gamma radiation whole body dose and sacrificed 14 days post-exposure. Neither study revealed …

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Using Cross-Sectioned Multilayer Polymer Film And Surface Modification To Form Chemically Patterned Substrates , Chun Zhang May 2007

Using Cross-Sectioned Multilayer Polymer Film And Surface Modification To Form Chemically Patterned Substrates , Chun Zhang

All Dissertations

Highly layered structures are important to micro- and nanofabrication technologies for understanding and controlling surface structures through manipulation of chemical and physical interactions. The objective of this work was to develop a new approach to create micro- and nanopatterned surfaces using multilayer polymer films of commercially available and inexpensive polymers instead of inorganic substrates. As an example, linear low density polyethylene (LLDPE) and ethylene-co-acrylic acid copolymer (EAA) were used as alternating inert and reactive polymers, respectively. Thin cross-sections of the multilayer molded sheets were prepared by ultra-microtoming.
As a precursor to the multilayer work, surface modification of EAA was conducted …

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Wall And Ground Movements In A Braced Excavation In Clays And Serviceability Reliability Of Adjacent Buildings, Cheng Liang Hsiao May 2007

Wall And Ground Movements In A Braced Excavation In Clays And Serviceability Reliability Of Adjacent Buildings, Cheng Liang Hsiao

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The goal of this dissertation research is to establish an improved procedure for evaluating the excavation-induced ground settlement and building serviceability. This research covers several closely related topics. Firstly, a simplified small strain soil model developed by Hsieh et al. (2003), called the Modified Pseudo Plasticity (MPP) model, is evaluated for its capability and performance in the prediction of the excavation-induced ground deformation behavior using Finite Element Method (FEM). Secondly, for the development of the envisioned empirical models for estimating the excavation-induced wall and ground responses, a database of excavation case histories are compiled. To complement the database of excavation …

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Dynamic Measurements Of Lubrication Film Thickness Of Uhmwpe Contacts For Total Joint Replacements, Andrew Clark May 2007

Dynamic Measurements Of Lubrication Film Thickness Of Uhmwpe Contacts For Total Joint Replacements, Andrew Clark

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A new contact sensing technology previously developed in the Biotribology Laboratory at Clemson University was further studied, evaluated, and characterized to extend its use to the measurement of lubricating film thickness. First, the laboratory's force-controlled knee joint simulator was used while dynamic contact pressure measurements under both dry and lubricated conditions were made using the sensor technology employed in two different artificial knee implant geometries. Each implant was machined by the manufacturer from custom blocks of ultra high molecular weight polyethylene (UHMWPE) containing a grid of discrete sensing regions. The difference between the dry and lubricated contact areas measured at …

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A Lean Modeling Protocol For Evaluating Green Project Delivery, Leidy E. Klotz, Michael Horman, Mark Bodenschatz Apr 2007

A Lean Modeling Protocol For Evaluating Green Project Delivery, Leidy E. Klotz, Michael Horman, Mark Bodenschatz

Publications

The first vital step to leaning an operation is to model or map the processes used to deliver value in that operation. This allows the requisite understanding of where waste and non value-adding activity exists, and provides the foundation for improvement. Current protocols for modeling operations present the basic tenets for lean mapping, but tend to be based in manufacturing language, and are not easily adapted to capital facilities projects. “Green” or “sustainable” capital projects delivered using current project delivery systems seem to be laden with hidden waste. These projects tend to be more challenging to deliver due increased levels …

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Real-Time System Identification For Impact-Based Part Positioning, Laine Mears, Jeannie Falcon Mar 2007

Real-Time System Identification For Impact-Based Part Positioning, Laine Mears, Jeannie Falcon

Publications

Simplified part positioning in manufacturing has been achieved using pushing or tapping actuation in place of more complex pick-and-place systems. However, positioning by impact introduces a new source of uncertainty: interfacial frictional effects of sliding, which can result in an uncontrollable and often poorlypredictable actuation distance. The described work provides a friction-based dynamic model of the sliding distance after impact that is used to predict static friction characteristics. A prototype system is simulated and validation data used to improve the model. A control algorithm is also described, tested and validated over a range of actuated masses.

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Study Of Structure Development During Melt Spinning Of Isotactic Polypropylene Fibers Using Raman Spectroscopy And Wide Angle X-Ray Diffraction Simultaneously , Dushyanth Pandana Jan 2007

Study Of Structure Development During Melt Spinning Of Isotactic Polypropylene Fibers Using Raman Spectroscopy And Wide Angle X-Ray Diffraction Simultaneously , Dushyanth Pandana

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ABSTRACT
Isotactic polypropylene (iPP) fibers have a wide variety of applications. Specific end-use applications require specific properties, which are dependent on the polymer morphology produced during processing. Therefore, the final properties of a material are dependent on the processing parameters. iPP fibers are produced mainly by melt spinning. The important processing parameters in the melt spinning process include, the extrusion temperatures, the throughput and shear rates, the rate of cooling, and the feed and draw roll take-up velocities. An understanding of how the morphology develops along the spinline, and the effect of processing parameters on the morphology is crucial in …

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Comparative Study Of Haptic And Visual Feedback For Kinesthetic Training Tasks, Ravikiran Singapogu Jan 2007

Comparative Study Of Haptic And Visual Feedback For Kinesthetic Training Tasks, Ravikiran Singapogu

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Haptics is the sense of simulating and applying the sense of human touch. Application of touch sensations is done with haptic interface devices. The past few years has seen the development of several haptic interface devices with a wide variety of technologies used in their design. This thesis introduces haptic technologies and includes a survey of haptic interface devices and technologies. An improvement in simulating and applying touch sensation when using the Quanser Haptic Wand with proSense is suggested in this work using a novel five degree-of-freedom algorithm. This approach uses two additional torques to enhance the three degree-of-freedom of …

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Synthesis And Photocatalysis Study Of Brookite Phase Titanium Dioxide Nanoparticles, Radhika Bhave Jan 2007

Synthesis And Photocatalysis Study Of Brookite Phase Titanium Dioxide Nanoparticles, Radhika Bhave

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Titanium dioxide is used in variety of applications like photocatalysis, self-cleaning coatings, fog proof glass and water purifier. A lot of research is being done in synthesis and applications of TiO2. Titanium dioxide or TiO2 mainly exists in three phases namely anatase, brookite and rutile. Current studies relate to synthesis of brookite phase TiO2 nanoparticles by ambient condition sol (ACS) process and characterization of these particles for phase purity, morphology and surface area analysis. The photoactivity of these particles was investigated and absorption in the visible light region was detected. This implies brookite to have good potential to be used …

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Application Of Classical Versus Bayesian Statistical Methods To On-Line Radiological Monitoring, Amy Attardo Jan 2007

Application Of Classical Versus Bayesian Statistical Methods To On-Line Radiological Monitoring, Amy Attardo

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The on-line monitoring for illicit radioactive material with a minimum number of false detections is a critical need for homeland security. The primary objectives of this work were to apply both Bayesian and classical statistical process control chart techniques to the on-line monitoring of radiological data and to then compare the Type I and Type II error incidence rates. Two versions of the cumulative sum (CUSUM) and Shiryayev-Roberts (S-R) procedures known as total reset and alarm reset methods were developed. The best method in terms of Type I errors was the S-R total reset method. In terms of Type II …

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Dynamic Networking Of Exemplars: Towards A Mechanical Design Visual Programming Language, Shashidhar Putti Jan 2007

Dynamic Networking Of Exemplars: Towards A Mechanical Design Visual Programming Language, Shashidhar Putti

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Developing mechanical engineering design automation applications using current day textual programming languages like C, C++ requires extensive programming skills. However, learning to program in these environments can be time consuming and often frustrating to mechanical engineers due to the use of complex textual constructs and syntax to represent an algorithm in a linear fashion. Further, these programming languages offer a poor visualization of the data and the data flow due to their textual nature. The use of graphical objects for programming makes visualization easier and also eliminates the need for linear representation of algorithms. This thesis initiates the development of …

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Impulsive-Actuation Part Positioning Through Constrained Energy Balance Planning, Laine Mears, Thomas R. Kurfess Jan 2007

Impulsive-Actuation Part Positioning Through Constrained Energy Balance Planning, Laine Mears, Thomas R. Kurfess

Publications

Impulsive actuation has been researched in the past two decades as an inexpensive alternative to multi-degree-of-freedom precision positioning systems. The position of a sliding workpiece can be controlled by a 2-degree-offreedom actuation system through simple pushing path planning. However, the final part position as a result of the last touch of the actuator is subject to uncertainty in the friction model used for actuation planning, particularly the free-sliding distance undergone by the workpiece after losing contact with the actuator. This paper first reviews an impact planning method, then augments it using a restitutionbased model that results in an explicit actuator …

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Elastic Degradable Polyurethanes For Biomedical Applications, Changhong Zhang Dec 2006

Elastic Degradable Polyurethanes For Biomedical Applications, Changhong Zhang

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Several series of polyurethanes were synthesized with linear or crosslinked structures by using different synthesis routes. Two studies are mentioned: (1) the synthesis of degradable polyurethanes with linear structure and the investigation of the elasticity and cytophilicity of the materials as function of the chain extender, and (2) the synthesis and the investigation of the biocompatibility, degradation, hydrophilicity and mechanical properties of the polyurethane-based hydrogels with crosslinked structure.

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Effect Of South Caroline Belt Law On Safety Belt Use, Sourabh Patki Dec 2006

Effect Of South Caroline Belt Law On Safety Belt Use, Sourabh Patki

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A number of factors and accessories help save lives and prevent injuries to road users, yet safety belts have become synonymous with automobile safety today, unlike any accessory before or since their introduction in automobiles. However, the scientific advances in automobile safety, followed by the acceptance of the necessity for safety in automobiles by both the manufacturers and the population, finally leading to the introduction of safety features and their incorporation within the laws occurred over a much longer span, continuing even today. Today's Safety movement aims at increasing safety belt using an awareness campaigns, accompanied by enforcement. Safety belt …

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Influence Of Socio-Economic And Demographic Factors On Crashes In Rural South Carolina At Sub-County Level, Sunil Jakhadi Dec 2006

Influence Of Socio-Economic And Demographic Factors On Crashes In Rural South Carolina At Sub-County Level, Sunil Jakhadi

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State of South Carolina ranks high in the fatality rates. The state is a predominately a rural state with more percentage of rural roads. This research focuses on the statistical variation of crash rates between the county and block-group, especially rural once to the state. Also, it focuses on the possibility of various socio-economic and demographic characters influence on the high crash rates particularly in rural South Carolina.
Crash database for the year 2004 was acquired from South Carolina Department of Transportation and was processed by the research team at Clemson University. This processed database was imported into GIS. Spatial …

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Validation Of An Inertial Sensor System For Quantifying Knee Function, Aaron Koslin Dec 2006

Validation Of An Inertial Sensor System For Quantifying Knee Function, Aaron Koslin

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Gait analysis has become a useful tool for clinicians in evaluating the progression of pathologies through functional analysis. The high cost and dedicated laboratories associated with the traditional camera-based motion analysis systems present the need for an alternative system. Direct measurement of kinetic parameters using inertial sensors (gyroscopes and accelerometers), in place of indirect calculations from position data obtained using cameras, has been shown effective in resolving important gait parameters.
In order to directly compare gait parameters obtained using inertial sensors and a camera system, data was simultaneously collected from both systems for seven test subjects during normal gait. Three …

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Life Cycle Cost Analysis Of Pavements: State-Of-The-Practice, Zeynep Guven Dec 2006

Life Cycle Cost Analysis Of Pavements: State-Of-The-Practice, Zeynep Guven

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Life Cycle Cost Analysis (LCCA) is performed by transportation agencies in the design phase of transportation projects in order to be able to implement more economical strategies, to support decision processes in pavement type selection (flexible or rigid) and also to assess the relative costs of different rehabilitation options within each type of pavement. However, most of the input parameters are inherently uncertain. In order to implement the LCCA process in a reliable and trustworthy manner, this uncertainty must be addressed. This thesis summarizes a through research that aims at improving the existing LCCA approach for South Carolina Department of …

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Elevated Neutral-To-Earth Voltage In Distribution Systems Including Harmonics, Jian Jiang Dec 2006

Elevated Neutral-To-Earth Voltage In Distribution Systems Including Harmonics, Jian Jiang

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The elevated neutral-to-earth voltage (NEV), and the related phenomenon called stray voltage, is analyzed in multigrounded distribution systems. Elevated NEV is typically caused by fundamental frequency currents returning to the source via the neutral conductor and earth. However, harmonic distortion is also found to contribute to elevated NEV. A multiphase harmonic load flow algorithm is developed to examine the effects of various factors on the NEV, including unsymmetrical system configuration, load unbalance and harmonic injection. To fulfill this objective, the system modeling is adapted to include the neutral conductor into the component equivalent circuit. The overhead transmission line is remodeled …

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