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Articles 2431 - 2460 of 2904

Full-Text Articles in Engineering

The Application Of Discrete-Event Simulation For Demining Strategy Evaluation, Hui-Chiao Jen May 2008

The Application Of Discrete-Event Simulation For Demining Strategy Evaluation, Hui-Chiao Jen

Industrial, Manufacturing, and Systems Engineering Dissertations - Archive

Teams of mobile autonomous robots have been proposed for the detection and clearing of landmines. Several competing strategies for automated mine detection have been proposed. This paper will discuss the development of a tool that will support the quantitative analysis of various automated mine detection approaches used in Humanitarian Demining and Military Mine Field Breaching. The approaches used to model mine detection in a scout, breaching, and Humanitarian Demining scenario using a discrete-event simulation analysis tool are discussed. The model assumes that each UGV is autonomous rather than being directly controlled by a centralized command and control system. The algorithm …


Passivation Of Si (100) Surface And Fabrication Of Doping-Free Mosfet, Muhammad Yusuf Ali May 2008

Passivation Of Si (100) Surface And Fabrication Of Doping-Free Mosfet, Muhammad Yusuf Ali

Electrical Engineering Dissertations - Archive

Chalcogen atoms have been successfully used for the passivation of GaAs(100) as well as Ge(100) and Si(100) substrates. Unlike GaAs(100) and Ge(100), the native oxide(SiO2) of Si(100) substrate is not soluble in ammonium sulfide solution ((NH4)2Sx) or water, which is a major problem to passivate Si(100) surface in a solution. In this work, a wet chemical process has been developed in which a compatible etchant ammonium hydroxide (NH4OH) is added with a passivating solution ((NH4)2S). Because of the compatibility of the etchant with the passivating solution, native oxide on Si(100) surface is removed in-situ to expose a fresh and clean …


Mitigation Of Vibration In A Permanent Magnet Synchronous Machine Using Field Reconstruction, Umamaheshwar Krishnamurthy May 2008

Mitigation Of Vibration In A Permanent Magnet Synchronous Machine Using Field Reconstruction, Umamaheshwar Krishnamurthy

Electrical Engineering Dissertations - Archive

Permanent magnet synchronous machines (PMSM) are widely used due to their unique characteristics including high efficiency, high power density, simple construction, simple maintenance, and relative ease of control. With increasing need for automation, survivable and fault tolerant motor drives are highly in demand in many sectors of industry. Advancement in the area of modern power electronics has allowed researchers a great deal of flexibility in implementing complex control routines. While considerable of focus has been placed on improving schemes of control, not much effort has been put improvements in the performance of electric drives. It is also important to note …


Methodology For Reverse Supply Chain Design In Consumer Electronics Industry, Santhanam Rajagopalan May 2008

Methodology For Reverse Supply Chain Design In Consumer Electronics Industry, Santhanam Rajagopalan

Industrial, Manufacturing, and Systems Engineering Dissertations - Archive

Reverse Logistics (RL), the art and science of moving goods typically from the end consumer towards the upstream end of supply chains, has been the subject of many strategic meetings in organizations today. This is attributed mainly due to the tighter federal environmental legislations on product returns and a hugely untapped potential that has been often overlooked by the managers. Traditionally, enterprises spend most of the improvement initiatives in optimizing its forward supply chain (FSC) performance that aims to delight the end consumer. However, it is not a panacea by itself in the process of continuously satisfying the end customer. …


Determining The Flow Characteristics Of A Perfusion Device For Donor Heart Transport, Michael Louis Cobert May 2008

Determining The Flow Characteristics Of A Perfusion Device For Donor Heart Transport, Michael Louis Cobert

Bioengineering Theses - Archive

Current technology has limits organ transport for transplantation to static storage, thereby reducing the reasonable distance of travel. Continuous machine perfusion has been proposed as a viable alternative to improving function and outcome. A series of studies with such a device have been developed to elucidate the method by which optimal results can be achieved. Adult mongrel dog hearts were established in a device that provided continuous perfusion of oxygenated fluid and enabled precise control of flow rate, oxygenation, and fluid temperature. The first series of experiments sought to determine an optimal flow rate for tissue perfusion at one of …


Fabrication Of Fept Ferromagnetic Nanoparticles, Kevin Eugene Elkins Apr 2008

Fabrication Of Fept Ferromagnetic Nanoparticles, Kevin Eugene Elkins

Material Science and Engineering Dissertations - Archive

Fabrication of chemically disordered FePt particles ranging from 2 - 9 nm with a precision of 1 nm has been achieved through modification of key process variables including surfactant concentration, heating rates and the type of iron precursor. In addition, the shape evolution of the FePt nanoparticles during particle growth can be manipulated to give cubic or rod geometries through changes to the surfactant injection sequence and solvent system. The primary method for synthesis of the disordered FePt nanoparticles is the polyol reduction reported by Fievet et al., which has been modified and used extensively for synthesis of diff ering …


Flight Data Analysis And Simulation Of Wind Effects During Aerial Refueling, Timothy Allen Lewis Apr 2008

Flight Data Analysis And Simulation Of Wind Effects During Aerial Refueling, Timothy Allen Lewis

Mechanical and Aerospace Engineering Theses - Archive

This thesis presents an analysis of data obtained in an automated aerial refueling test flight conducted with a KC-135 as the tanker and a Learjet 25 as the surrogate receiver UAV. The purpose is to identify the wind induced by the tanker wake and its effect on the receiver aircraft. From the available flight data, a direct computation of the winds experienced by the tanker and receiver is carried out. The mean variation of the receiver wind is compared with the tanker wind when the receiver is at the observation and contact positions. This results in the identification of the …


Impact Of Lateral Swell Pressure On Retaining Structure Design Using Expansive Cohesive Backfill, Mark G. Thomas Apr 2008

Impact Of Lateral Swell Pressure On Retaining Structure Design Using Expansive Cohesive Backfill, Mark G. Thomas

Civil Engineering Theses - Archive

Since cohesive soils are difficult to drain once becoming saturated, in order to reduce lateral earth pressures exerted by saturated cohesive soils on retaining structures, retaining wall designs most always specify use of drainable granular backfill. However, costs for the importation of granular backfill materials continues to increase due to depletion of these materials in certain areas, and to the ever-increasing costs for material transportation, largely related to increased labor and fuel prices. These factors, together with the costs of removing replaced cohesive materials, and coupled with resource and environmental conservation concerns, are driving efforts to develop reasonable and prudent …


Closed-Form Development Of A Family Of Higher Order Tetrahedral Elements Through The Fourth Order, Sara Elizabeth Mccaslin Apr 2008

Closed-Form Development Of A Family Of Higher Order Tetrahedral Elements Through The Fourth Order, Sara Elizabeth Mccaslin

Mechanical and Aerospace Engineering Dissertations - Archive

This research is concerned with the development and implementation of a family of tetrahedral elements through the fourth order. The straight-sided tetrahedral elements are developed in closed-form. This work investigates the efficiency of closed-form implementation of stiffness matrices and error estimators compared to numerical implementation. An additional objective is the compaction of closed-form source-code files which require as little storage space as possible, a more pronounced requirement at high p-levels. For the straight-sided elements through p-level 4, the stiffness matrix, equivalent nodal load vectors, and error estimators (based on nodal averaging) are developed using closed-form equations obtained through the use …


Non-Linear Finite Element Dynamic Analysis Of Tapered Hollow Steel Poles For Passive Base Isolation, Tri Le Apr 2008

Non-Linear Finite Element Dynamic Analysis Of Tapered Hollow Steel Poles For Passive Base Isolation, Tri Le

Civil Engineering Dissertations - Archive

Long tapered poles are commonly used to support Closed Circuit Television (CCTV) Cameras for security and traffic monitoring. Images received from CCTV are normally distorted depending on the wind induced vibration characteristics of the forcing function. To reduce image distortion, three approaches are integrated to optimize the process, which are: (1) development of equations for pole's frequency of vibration in terms of its geometric variables; (2) development of a mechanical damping device to isolate the pole's vibration from that of the camera; and (3) development of an electrical image processing device for image corrections. The identification of a pole's natural …


Dynamic Properties Of Compacted Soils Using Resonant Column With Self-Contained Bender Elements, Roshnara Mohammad Apr 2008

Dynamic Properties Of Compacted Soils Using Resonant Column With Self-Contained Bender Elements, Roshnara Mohammad

Civil Engineering Theses - Archive

A comprehensive series of resonant column and bender elements tests were simultaneously performed in the developed RC/BE apparatus. RC/BE tests were conducted on compacted specimens of poorly graded sand (SP) and high plasticity clay (CH) prepared at different moisture contents (17.7, 22.1, 25.5, 30.2% by weight for clay, and 5, 10, 15, 20% by weight for sand) and under different confining pressures (0, 2.5, 5.0, and 10.0 psi, or 0, 17.2, 34.4, 69.0 kPa) in order to assess the influence of key environmental factors, such as compaction induced suction and confining pressure, on small-strain stiffness properties of unsaturated soils, such …


Practical Evaluation And Analysis Of Passive Uhf Rfid Tags, Ananyaa Gautham Apr 2008

Practical Evaluation And Analysis Of Passive Uhf Rfid Tags, Ananyaa Gautham

Electrical Engineering Theses - Archive

In this thesis, we have identified the important parameters that impact the performance of passive UHF RFID tags and developed a testing methodology to evaluate and characterize tags. We have also developed the theory to validate the empirical data and analysis. The high performance, low cost and increased storage capacity of the RFID tags has led to the economic adoption of this technology by many industries. Choosing the right tag for the right application might be quite a task with the number of commercially available tags today. It is very important to test the tags and analyze the results to …


Web Based Integrated Multiple Function Customer Demand And Budget Management System, Supun Tiptipakorn Apr 2008

Web Based Integrated Multiple Function Customer Demand And Budget Management System, Supun Tiptipakorn

Electrical Engineering Dissertations - Archive

Traditionally, most end-use residential consumers receive flat rate monthly electricity bills based on load profiling rate calculations from different utilities' consumer classes. Those flat rates do not relate and reflect the true and time-varying costs of electricity supply during actual time of consumptions. Without acknowledging the cost differences, consumers do not have any incentive to adjust their load consumption patterns, and inefficiencies of resource allocations can result. Cheaper-cost off-peak load users can end up paying to offset those expensive peak load users. Additionally, peak load users may still consume their loads without any awareness that their power networks may have …


Analysis And Optimization Of A Crashworthy Helicopter Seat, Nauman A. L Mhaskar Mar 2008

Analysis And Optimization Of A Crashworthy Helicopter Seat, Nauman A. L Mhaskar

Mechanical and Aerospace Engineering Theses - Archive

The objective of a crashworthy seat is to improve the survivability of occupants (cockpit and cabin) in helicopter crashes. All modern helicopter seats are equipped with an energy absorber to reduce lumbar spine load during crash landing. The main objective of this research is to carry out the structural analysis and optimization of a helicopter crashworthy troop seat assembly using finite element methods. The transient dynamic nonlinear finite element analysis helps in identifying whether the seat structure will survive in a crash landing situation, and optimization helps in reducing the weight of the crashworthy seat. The seat is analyzed using …


Improving The Bit Error Rate Performance Of Gsm System Using A Independent Component Analysis Based Non-Linear Filter, Kumarabhijeet Singh Mar 2008

Improving The Bit Error Rate Performance Of Gsm System Using A Independent Component Analysis Based Non-Linear Filter, Kumarabhijeet Singh

Electrical Engineering Theses - Archive

Presently, call drop out is considered a major problem in wireless communication. A large percentage of call drops take place due to network congestion, handover failure and high bit error rate.Our main objective is to reduce call drops due to high bit error rate using a newly proposed signal processing block (SPB) at the receiver section of a mobile handset. The SPB helps improve the performance of the wireless system, particularly Global Systems for Mobile (GSM) by providing a coding gain over the existing system. In this work, we carried out a simulation of the physical layer of a GSM …


Performance Evaluation Of Greedy Heuristic For Sip Analyzer In H.264/Svc, Jaydeep Vijay Inamdar Mar 2008

Performance Evaluation Of Greedy Heuristic For Sip Analyzer In H.264/Svc, Jaydeep Vijay Inamdar

Electrical Engineering Theses - Archive

The latest scalable video coding standard, H.264/SVC uses many components of H.264/AVC standard to maintain backward compatibility and also has proposed many tools to support scalable video coding with increased coding efficiency. SIP Analyzer is one such tool incorporated in JSVM (Joint Scalable Video Model) software which is the reference software for the SVC project. SIP Analyzer implements Selective Interlayer Prediction strategy to encode the bitstream so as to improve coding performance in scenarios where multiple adaptation is not needed without losing much if the same bitstream is used in scenario where multiple adaptation is needed. Core of this algorithm …


Fast Algorithms For Mdct And Low Delay Filterbanks Used In Audio Coding, Ravi Kiran Chivukula Mar 2008

Fast Algorithms For Mdct And Low Delay Filterbanks Used In Audio Coding, Ravi Kiran Chivukula

Electrical Engineering Theses - Archive

Modern audio and speech coding systems use filterbank and transform coding techniques to decorrelate the input signal. Cosine-modulated, perfect reconstruction, pseudo-QMF filterbanks are most commonly used for this purpose. In this thesis, we present three propositions. First, a fast algorithm for modified discrete cosine transform (MDCT) for transform lengths of the form 5× 2m and 15× 2m is presented. This algorithm is based on mapping the MDCT to DCT-II via DCT-IV and using the involutory property of the DCT-IV matrix. This leads to a reduction in the number of multiplications and constant memory requirement. The algorithm also uses very efficient …


On Reducing Call Drop Outs By Improving Bit Error Rate Performance In A Gsm Mobile Communications System, Sudeep Sharma Mar 2008

On Reducing Call Drop Outs By Improving Bit Error Rate Performance In A Gsm Mobile Communications System, Sudeep Sharma

Electrical Engineering Theses - Archive

Call Drop Out is one of the most annoying problems in Mobile Communications. It is one of the most important Quality of Service (QoS) indicators for a mobile carrier. Over the years, many strategies have been proposed to solve the problem of call drop out. But the problem is still prevalent. One of the important reasons for call drop outs is high Bit Error Rate (BER). In general, many existing wireless systems set a threshold BER before a call is dropped. In this work, our intent is to reduce the call drop out due to high BER. Towards that end, …


Simulation Analysis Of Orthogonal Frequency Division Multiplexing Systems With Diversity Reception, Sai Sravan Bharadwaj Karri Feb 2008

Simulation Analysis Of Orthogonal Frequency Division Multiplexing Systems With Diversity Reception, Sai Sravan Bharadwaj Karri

Electrical Engineering Theses - Archive

With the rapid increase in the utility of voice and data services, there is a demand for higher data rates and reliability in wireless communications. A wireless communication channel is prone to degrading effects such as multi-path fading, ISI etc. Orthogonal Frequency Division Multiplexing (OFDM), a candidate for the 4^{th} generation wireless systems, mitigates these effects and supports higher data rates.The performance analysis of a complex system like OFDM,is a challenging task where analytical methods become cumbersome to be used. Simulation based approaches provide a fair estimate of the performance in such cases. In this thesis, the performance of an …


Phase Iv Development Of A Short-Radius Guardrail For Intersecting Roadways, Karla A. Polivka, Cody S. Stolle, Robert W. Bielenberg, Ronald K. Faller, Dean L. Sicking, John R. Rohde, John D. Reid Feb 2008

Phase Iv Development Of A Short-Radius Guardrail For Intersecting Roadways, Karla A. Polivka, Cody S. Stolle, Robert W. Bielenberg, Ronald K. Faller, Dean L. Sicking, John R. Rohde, John D. Reid

Nebraska Department of Transportation: Research Reports

No abstract provided.


Semi-Analytical Complex Variable Based Stochastic Finite Element Method, Weiya Jin Jan 2008

Semi-Analytical Complex Variable Based Stochastic Finite Element Method, Weiya Jin

Mechanical and Aerospace Engineering Dissertations - Archive

The stochastic finite element method (SFEM) is an approach that allows an analyst to define material, load, and geometry parameters as random variables to represent uncertainty in an engineering problem. The method is then used to estimate the probability of exceeding specified performance thresholds. A necessary ingredient for this analysis is consistent, accurate and efficient algorithms for computing finite element response sensitivities. In this work, the semi-analytical complex variable method (SACVM) is introduced as a method for computing accurate response sensitivities of stochastic models. The SACVM incorporates the complex variable method (CVM) with the semi-analytical method (SAM). It takes advantage …


Corrosion Behavior Of Zn-Ni Coatings Deposited By Electrolytic Plasma Processing, Giancarlo Rios Jan 2008

Corrosion Behavior Of Zn-Ni Coatings Deposited By Electrolytic Plasma Processing, Giancarlo Rios

Material Science and Engineering Theses - Archive

In the current research project, three groups of Zn-Ni coatings of various Ni contents were deposited on comercial carbon steel by electrolytic plasma processing (EPP), a novel surface modification technique. The coating characteristics were studied along with their corrosion behavior in order to determine their potential as electroplated Cd coating replacements. The latter electroplated coatings are currently used in aerospace applications but are toxic and hazardous to humans and the environment. Coating surfaces and cross sections were analyzed by scanning electron microscopy (SEM) while compositional analysis was conducted by energy-dispersive spectroscopy (EDS). Phase structure analysis was carried out by x-ray …


Fabrication And Characterization Of Cobalt-Diamond-Like-Carbon (Co-Dlc) Nanocomposites, Gunjan Shebe Jan 2008

Fabrication And Characterization Of Cobalt-Diamond-Like-Carbon (Co-Dlc) Nanocomposites, Gunjan Shebe

Material Science and Engineering Theses - Archive

In recent years, synthesis of magnetic nanocomposites has been receiving significant attention. These nanocomposites offer opportunities to develop active nanomaterials with various applications like magnetic data storage and biomedical applications. They can be designed to provide excellent magnetic properties. However, high saturation magnetization materials, such as Co are not biocompatible. Thus, designing nanocomposites with magnetic phase embedded in biocompatible protective shells is of immense interest. In this study, Co-DLC nanocomposites were synthesized using a hybrid CVD/PVD technique and different combination of processing parameters were used to vary the concentration of Co in the nanocomposites. X-ray photoelectron spectroscopy showed, that with …


Effects Of Edge Distance, Hole Size Ratio And Hole Spacing On Peak Stresses Of Composite Laminate With Multiple Holes, Manishkumar Kheradiya Jan 2008

Effects Of Edge Distance, Hole Size Ratio And Hole Spacing On Peak Stresses Of Composite Laminate With Multiple Holes, Manishkumar Kheradiya

Mechanical and Aerospace Engineering Theses - Archive

Unlike isotropic material, the stress distribution of laminate with a hole varies with its size, its material properties and fiber orientations of each layer. Moreover, presence of a hole in the neighborhood of another hole may also affect their stress distribution, too. The major objective of this study is to determine stress distribution of finite width laminated composite having multiple holes. The effect of stress concentration due to presence of holes in each angle ply of laminated composite is a focus of this study. Three dimensional finite element models are developed to determine the stress distribution in laminate using commercial …


Characterization And Cooling Capacity Enhancement Of A Porous Ceramic Wick Based Coldplate, Mauricio Adrian Salinas Jan 2008

Characterization And Cooling Capacity Enhancement Of A Porous Ceramic Wick Based Coldplate, Mauricio Adrian Salinas

Mechanical and Aerospace Engineering Dissertations - Archive

Current passive cooling methods of aerospace and military, high heat-flux electronics include the use of thermal planes made of exotic metal alloys, which have been designed, at a great expense, to have high thermal conductivity and low density (i.e. light weight). Also, phase change modules composed of a metal matrix saturated with a solid phase change material are being employed for systems requiring a transient cooling scheme such as expendable weapons. This method requires the heat to be transferred from the source location, through the metal matrix (typically a porous aluminum foam), to the available phase change material. Preliminary empirical …


Thermal Design Optimization Of Internally Cooled Turbine Blades, James Daniel Ruiz Jan 2008

Thermal Design Optimization Of Internally Cooled Turbine Blades, James Daniel Ruiz

Mechanical and Aerospace Engineering Theses - Archive

This paper outlines the use of Computational Fluid Dynamics (CFD) and Genetic Algorithm (GA) Optimization to enhance the design of a 3-dimensional internally cooled turbine blade. The optimization code utilizes principles of Genetic Algorithms to optimize (i.e. minimize) the integrated heat flux through the turbine blade. The optimization is accomplished by adjusting the size and position (within pre-determined constraints) of cooling passages internal to the turbine blade. Starting with an aerodynamically optimized airfoil shape, cooling passage designs are generated by the optimization process and coupled with boundary and airfoil domains. The analysis becomes a Conjugate Heat Transfer (CHT) problem analyzing …


Development Of Spectral And Wavelet Time-Of-Flight Methods For Propagating Shock And Detonation Waves, Alfredo Albert Ortiz Jan 2008

Development Of Spectral And Wavelet Time-Of-Flight Methods For Propagating Shock And Detonation Waves, Alfredo Albert Ortiz

Mechanical and Aerospace Engineering Theses - Archive

An accurate time delay estimate for a propagating disturbance, including an estimate of its uncertainty, is important in many areas of science. Several techniques were developed for determining the propagation time of a shock and detonation wave. The speed of the propagating wave was then determined by the time delay estimates provided for the best techniques. The techniques used ranged from the commonly used time-of-flight method to a nonstationary cross-spectral density phase method that provided a statistical estimation of the propagation time. The time delay results for a shock tube experiment showed that most of the methods had difficulties in …


Thermal Analysis Of Pulse Detonation Engines, Raghu Raman Ghandikota Jan 2008

Thermal Analysis Of Pulse Detonation Engines, Raghu Raman Ghandikota

Mechanical and Aerospace Engineering Theses - Archive

The pulse detonation engine (PDE) is a compact system that can be modeled thermodynamically by the Humphrey cycle and is capable of high efficiency. The rapid heat release for stochiometric fuel/oxidizer ratios results in developing high temperatures. The high temperatures produced during its operation can cause the engine to fail. Thus, operating this engine for a longer duration would become dubious if the temperatures are not dissipated from it. The current research aims to perform a preliminary thermal analysis. This analysis consists of two steps. The first step is to determine the heat dissipated from the engine using the unsteady …


Effect Of Pullout And Torsional Strength Of Composites With Co-Molded Thread Inserts, Dan L. Reller Jan 2008

Effect Of Pullout And Torsional Strength Of Composites With Co-Molded Thread Inserts, Dan L. Reller

Mechanical and Aerospace Engineering Theses - Archive

Rotorcraft transmission housings and drive system components are typically made from cast metals due to their highly complex geometries. Utilizing composite materials offers potential to reduce weigh and manufacturing cost while increasing corrosive resistance and extending part life. Traditional compression molded composites have not been utilized in aerospace because they typically experience low fiber volume fraction. Currently there are numerous materials which offer opportunities for composites in drive system housing applications and also offer the ability to co-mold details to reduce post mold operations. One of the issues associated with composite structures is the ability to fasten them to one …


Electromagnetic Flow Control: A Review And Experimental Development And Testing Of A Compact Actuator, Eric Braun Jan 2008

Electromagnetic Flow Control: A Review And Experimental Development And Testing Of A Compact Actuator, Eric Braun

Mechanical and Aerospace Engineering Theses - Archive

This thesis is divided into two sections which both relate to the field of magnetohydrodynamics and particularly electromagnetic flow control (EMFC). The first section contains a review of recent research in EMFC. The second section presents the experimental results of a compact EMFC actuator designed for use at low speeds where the flow conductivity is raised by conductive seed particle injection.Fifty years ago, publications began to discuss the possibilities of using EMFC to improve aerodynamic performance. This led to an era of research that focused on coupling the fundamentals of magnetohydrodynamics (MHD) with propulsion, control, and power generation systems. Unfortunately, …