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Articles 2221 - 2250 of 2584

Full-Text Articles in Engineering

Design Of A Multi-Echelon Global Supply Chain Network With Microsoftå¨ Excel Premium Solver Plataform, Wilder Ferreira May 2009

Design Of A Multi-Echelon Global Supply Chain Network With Microsoftå¨ Excel Premium Solver Plataform, Wilder Ferreira

All Theses

I designed a global supply chain distribution model of one single product, with the objective of minimizing the costs of transportation, handling materials, duties and tariffs, production, and fixed infrastructure. The distribution network has a combination of manufacturing facilities (fixed and to-be-determined), warehouses (to-be-determined), distribution centers (to-be-determined), and customer zones at fixed locations. This network design is similar to the mathematical mixed-integer linear model from Tsiakis, Shah and Pantelides (2001). This model has been implemented in Microsoft Excel, using the Standard Simplex method from Frontline, Inc. This model optimizes the number of facilities worldwide (multi-echelon) along with the flow of …

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Development Of A Nonlinear Ride Quality Model To Aid In Tweelå© Parameter Selection, Marc Paradiso May 2009

Development Of A Nonlinear Ride Quality Model To Aid In Tweelå© Parameter Selection, Marc Paradiso

All Theses

The ride comfort of a vehicle is very important to both automotive and tire manufacturers. Unfortunately the ride comfort provided by the tire has an inverse relationship with the handling ability of the vehicle. Michelin has sought to decouple ride comfort and handling capability by developing a non-pneumatic tire they have dubbed the TWEEL©. To better understand what effects fitting a TWEEL with specific characteristics would have on the ride comfort of a vehicle a computer simulation was developed to study the effects of TWEEL stiffness and deflection on ride comfort.
The vehicle model used in the simulation is a …

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Effect Of Molecular Weight Reduction By Gamma Irradiation On The Antimicrobial Activity Of Chitosan, Ebuel Sirmats May 2009

Effect Of Molecular Weight Reduction By Gamma Irradiation On The Antimicrobial Activity Of Chitosan, Ebuel Sirmats

All Theses

The antimicrobial effectiveness of lower molecular weight (LMW) chitosan solutions was tested against Listeria innocua inoculated on TSA and MOX agar plates by the direct droplet method. The chitosan solutions were prepared by dissolving chitosan in 1% (v/v) acetic acid at concentrations ranging from 0.5 to 2.0% and irradiating with Co60 gamma rays ranging from 1 to 20 kGy. MW measurements of chitosan were determined by using HPSEC-MALLS-RI. The MW of chitosan varied from 114.8 kDa to 17.4 kDa and decreased with increasing irradiation dosages. Plate counts on TSA agar from shaker flask assays showed no significant differences among chitosan …

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Taxonomy Of Physical Prototypes: Structure And Validation, Ashwin Michaelraj May 2009

Taxonomy Of Physical Prototypes: Structure And Validation, Ashwin Michaelraj

All Theses

This thesis introduces a taxonomy of physical prototypes, and validates the proposed taxonomy by five different approaches. The proposed taxonomy is validated by, (i) checking the orthogonality of individual elements of the taxonomy, (ii) benchmarking the taxonomy with existing classifications of prototypes, (iii) demonstrating its utility by applying it to classify different prototypes, (iv) building a prototype database containing 35 different prototypes, and (v) consistency evaluation of the prototype database using a description logic based software called ProtŽgŽ.
The results indicate that the proposed taxonomy is capable of distinguishing prototypes with greater accuracy when compared to existing classifications. The orthogonality …

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The Effect Of Hydrostatic Pressure On Bladder Smooth Muscle Cell Function, Margaret Drumm May 2009

The Effect Of Hydrostatic Pressure On Bladder Smooth Muscle Cell Function, Margaret Drumm

All Theses

Previous research has demonstrated that bladder smooth muscle cells (BSMC) respond to various forms of mechanical stimuli, including stretch and hydrostatic pressure, by increases of cell proliferation, activation of intracellular signaling pathways, and alteration of contractile and synthetic marker protein expression. These cellular/molecular level changes are all indicative of a BSMC phenotypic shift that can negatively impact the bladder function at the tissue and organ level. The objective of the present study is to test a hypothesis that bladder SMCs shift their phenotype from contractile to synthetic in response to elevated hydrostatic pressure. Rat bladder SMC cultures were exposed to …

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Growth And Modeling Of Freshwater Algae As A Function Of Media Inorganic Carbon Content, Mary Watson May 2009

Growth And Modeling Of Freshwater Algae As A Function Of Media Inorganic Carbon Content, Mary Watson

All Theses

In response to global climate change, the Department of Energy (DOE) has specified advanced biological processes, such as cultivation of algal biomass in alkaline ponds, as part of a carbon management plan. The goal of this thesis was to investigate use of a mixed freshwater algal culture for biological carbon mitigation. Extensive review of carbonate dynamics, laboratory investigations to characterize algal growth, and development of a dynamic algal growth model were completed.
The presented literature review summarizes carbonate equilibria and kinetics needed for development of carbon mitigation technologies, especially in freshwaters. Reaction mechanisms, equilibrium relationships, kinetic rate constants, and kinetic …

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Investigation Of Training Algorithms For Hidden Markov Models Applied To Automatic Speech Recognition, Eric Fang May 2009

Investigation Of Training Algorithms For Hidden Markov Models Applied To Automatic Speech Recognition, Eric Fang

All Theses

The work presented in this thesis focuses on simulating a speech recognizer which is trained by different people with different speaking styles and investigates how sensitive the training and recognition processes are to the variations in the training data. There are four main parts to this work. The first involves an experiment of weighting methods for training with multiple observation sequences. The second involves the testing of different initial parameters. The third part includes the first experiment involving training with multiple observation sequences. The model's sensitivity to variations in training data was evaluated by comparing the cases of different values …

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An Evaluation Of Function-Based Representations And Information Archival In Engineering Design, Benjamin Caldwell May 2009

An Evaluation Of Function-Based Representations And Information Archival In Engineering Design, Benjamin Caldwell

All Theses

Recent research in function-based design includes the development of a vocabulary of functions, the Functional Basis, and a repository of products and their functions. Many design tools are being developed around this vocabulary and repository to support conceptual design. The usefulness of these tools, however, is dependent on the quality of the vocabulary and the information contained in the repository. In this research, both the vocabulary and the repository are empirically evaluated to understand their strengths and limitations. A statistical analysis is performed on function models in the repository to determine the frequency of usage of Functional Basis terms. It …

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A Pulsatile Bioreactor For Conditioning Tissue Engineered Heart Valves, Leslie Sierad May 2009

A Pulsatile Bioreactor For Conditioning Tissue Engineered Heart Valves, Leslie Sierad

All Theses

Tissue engineered constructs with autologous adult stem cells capable of self-repair and growth are highly desired replacements for diseased heart valves. However, the current approaches have inadequate mechanical properties to withstand in vivo implantation. Therefore, our group hypothesized that an in vitro environment of physiological intra-cardiac pressures and flow will stimulate stem cells to differentiate and remodel valvular scaffold constructs before implantation.
The group developed a pneumatic-driven conditioning system (Aim I) consisting of a three-chambered heart valve bioreactor, a pressurized compliance tank, a reservoir tank, one-way valves, pressure-retaining valves, and pressure transducers. The system can be sterilized using conventional autoclaving …

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The Effect Of Bond Strength Of Flexible Laminates On Puncture Resistance, Rijosh Cheruvathur May 2009

The Effect Of Bond Strength Of Flexible Laminates On Puncture Resistance, Rijosh Cheruvathur

All Theses

This work was aimed at understanding whether the bond strength of laminates will affect the puncture resistance of the laminate. Even though a strongly bonded adhesive layer in between two webs will considerably improve the mechanical properties of the laminate compared to that of the individual materials, there is a general belief in the packaging industry that having a lower bond strength helps to improve the bending or, in other words, the flexibility of the laminate thereby increases the tear and puncture resistance.
Laminations of aluminum foil and polyethylene terephthalate (PET) were used as a model system to determine the …

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Experimental Study Of The Three-Stream Scalar Mixing In A Turbulent Coaxial Jet, Matthew Dinger May 2009

Experimental Study Of The Three-Stream Scalar Mixing In A Turbulent Coaxial Jet, Matthew Dinger

All Theses

In the present study we investigate three-stream scalar mixing in a turbulent coaxial jet. In
this flow the center jet and the annulus, consisting of acetone-doped air and ethylene respectively, are
mixed with the co-flow air. A unique aspect of this study compared to previous studies of three-scalar
mixing is that two of the scalars (the center jet and air) are separated from the third (annulus);
therefore, this flow better approximates the mixing process in a nonpremixed turbulent reactive
flow. Planar laser-indiced fluorescence and Rayleigh scattering are employed to measure the mass
fractions of the acetone-doped air and ethylene, respectively. …

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Wide Operating Range For A Circular Waveguide Probe In Spherical Near-Field Measurements, Xiong Wang May 2009

Wide Operating Range For A Circular Waveguide Probe In Spherical Near-Field Measurements, Xiong Wang

All Theses

This thesis discusses spherical near-field measurements implemented by a circular waveguide probe which has much shorter length and wider operating range than those proposed similar circular probes. A brief introduction of spherical near-field measurement techniques is provided first. We also introduce the well-known conclusion that utilizing first-order probes simplifies the measurements and associated near-field to far-field transformation. Accordingly, a relatively short circular waveguide probe antenna is designed and fabricated. Detailed fields of this probe are analyzed to demonstrate that it is still a first-order probe even though the length is short. Furthermore, it radiates only first-order fields over a wide …

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Fast Generation Of Receiver-Based Statistics In Frequency Hop Radios Without Decoder Simulation, Michael Masse May 2009

Fast Generation Of Receiver-Based Statistics In Frequency Hop Radios Without Decoder Simulation, Michael Masse

All Theses

Receiver-based statistics can contain useful information about the quality a wireless channel. We examine methods of generating receiver statistics without real-time simulation of the receiver and the decoder, particularly during a network-level simulation. Attention is restricted to a receiver employing binary orthogonal signaling, noncoherent demodulation, and a soft-decision decoder in a frequency-hop network. Data is gathered from off-line simulations of channel, demodulation, and decoding processes, using a family of turbo product codes. Study and analysis of the data are used to characterize the behavior of the receiver statistics and determine on-line methods of generating the statistics in network-level simulations. To …

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Development, Parameterization And Validation Of Dynamic Material Models For Soil And Transparent Armor Glass, Bhaskar Pandurangan May 2009

Development, Parameterization And Validation Of Dynamic Material Models For Soil And Transparent Armor Glass, Bhaskar Pandurangan

All Dissertations

Despite the signing of several mine ban treaties in the 1990's, it is widely recognized that there is a landmine crisis. The following are some of the main aspects of this crisis: (a) Millions of unexploded landmines remain deployed all over the world; (b) Thousands of civilians are killed or maimed every year by unintended detonations of the mines; (c) The cost of medical treatment of landmine injuries runs into the millions; (d) the ability of the international community to provide the humanitarian relief in terms of medical services, safe drinking water and food, etc., is greatly hampered by landmine …

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Surface And Bulk Modification Of Poly(Lactic Acid), Rahul Rasal May 2009

Surface And Bulk Modification Of Poly(Lactic Acid), Rahul Rasal

All Dissertations

The major drawbacks of PLA are its poor toughness and lack of readily reactable groups. Unfortunately, typical methods of PLA toughening are associated with significant modulus and/or ultimate tensile strength (UTS) loss. The main objective of this research was to toughen PLA, with minimal modulus and/or UTS loss, and introduce reactive groups into the PLA matrix in one step. Initially, this objective was divided into two separate parts: PLA surface modification followed by toughening.
PLA film was solvent cast from chloroform solution and was surface modified using a sequential two-step photografting approach. Benzophenone was photografted onto the film surface in …

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Adsorption-Induced Changes In Enzyme Bioactivity Correlated With Adsorbed Protein Orientation And Conformation, Kenan Fears May 2009

Adsorption-Induced Changes In Enzyme Bioactivity Correlated With Adsorbed Protein Orientation And Conformation, Kenan Fears

All Dissertations

Systems using immobilized enzymes are attractive for a wide range of industrial and medical applications because they allow for fabrication of stable, reusable substrates with a highly specific functionality. The performance of these systems is greatly influenced by the orientation and conformation of the immobilized enzymes. To investigate these relationships, we have developed and applied methods to quantitatively assess the secondary structure of adsorbed enzyme layers on planar surfaces using circular dichroism (CD) spectropolarimetry and evaluate their bioactivity using colorimetric assays. When combined with knowledge of an enzyme's native structure, these methods provide a means to correlate changes in enzyme …

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Development Of The Integrated Censored Robust-Tolerance Engineering Design Systems Via Improved Response Surface Modeling, Abdul-Baasit Shaibu May 2009

Development Of The Integrated Censored Robust-Tolerance Engineering Design Systems Via Improved Response Surface Modeling, Abdul-Baasit Shaibu

All Dissertations

In this dissertation, we intend to integrate censoring into robust-tolerance engineering using improved dual response surface modeling. This is perhaps the first attempt in the quality control literature. In the literature, response surface models have largely been restricted to second order (or quadratic) models and robust-tolerance designs have been restricted to situations involving complete observations. We intend to show that higher order response surface models can be more powerful in terms of prediction ability, and are therefore more reliable than the preferred quadratic models in the general context of robust design. We will also consider formulating robust and tolerance designs …

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Foundations Of Design Method Development, Sudhakar Teegavarapu May 2009

Foundations Of Design Method Development, Sudhakar Teegavarapu

All Dissertations

A systematic procedure for developing design methods, tools, and/or processes, referred to as meta-method, is proposed. It is hypothesized that design methods developed without following a systematic procedure are not effective and thus are not widely accepted by industry and academia likewise. The systematic framework provided by the meta-method will ensure 1) faster development of design methods, 2) enable tracking of requirements throughout the development process, 3) facilitate efficient exploration and selection of alternatives, 4) document the development process for future reuse, 5) help in testing and validation of design methods, and 6) bridge gap between multiple disciplines by forming …

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Development Of A Methodology For Evaluating And Anticipating Improvised Explosive Device Threat Activity Using A Fault Tree Based Process, Benjamin Bennett May 2009

Development Of A Methodology For Evaluating And Anticipating Improvised Explosive Device Threat Activity Using A Fault Tree Based Process, Benjamin Bennett

All Dissertations

This document is a redacted version of the original dissertation titled 'Development of a Methodology for Evaluating and Anticipating Improvised Explosive Device Threat Activity Using a Fault Tree Based Process.' To allow for publication, information was removed which was considered sensitive in nature or which could be used by those who employ the Improvised Explosive Device, to negate any advantage gained by this research. The complete un-redacted dissertation is available (with proper vetting) to those whishing to further develop the concepts outlined in this document. Those interested in obtaining access to the complete document should contact the Joint IED Defeat …

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Microcantilever-Based Force Sensing, Control And Imaging, Reza Saeidpourazar May 2009

Microcantilever-Based Force Sensing, Control And Imaging, Reza Saeidpourazar

All Dissertations

This dissertation presents a distributed-parameters base modeling framework for microcantilever (MC)-based force sensing and control with applications to nanomanipulation and imaging. Due to the widespread applications of MCs in nanoscale force sensing or atomic force microscopy with nano-Newton to pico-Newton force measurement requirements, precise modeling of the involved MCs is essential. Along this line, a distributed-parameters modeling framework is proposed which is followed by a modified robust controller with perturbation estimation to target the problem of delay in nanoscale imaging and manipulation. It is shown that the proposed nonlinear model-based controller can stabilize such nanomanipulation process in a very short …

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Simulation And Behavior Of Corrosion Deteriorated Reinforced Concrete Members, M. A. Shayanfar, Amir Safiey Apr 2009

Simulation And Behavior Of Corrosion Deteriorated Reinforced Concrete Members, M. A. Shayanfar, Amir Safiey

Publications

Several reinforced concrete (RC) infrastructures are now crumbling from corrosion of steel bars in concrete. The paper presents the recent advancements in analytical simulation of corrosion aftereffects on behavior of RC members. The model juxtaposes the experimental findings with analytical relationships. The implementation of the model into a nonlinear finite element formulation as well as the experimental and analytical backgrounds are discussed. The abilities of the resulted program have been studied by modeling some experimental specimens showing a reasonable agreement between the analytical and experimental findings.

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Synthesis And Characterization Of Polymer Brushes For Controlled Adsorption Of Proteins, Olha Hoy Dec 2008

Synthesis And Characterization Of Polymer Brushes For Controlled Adsorption Of Proteins, Olha Hoy

All Dissertations

Performance of biomedical devices to a large extent depends on the interactions between the device surface and the biological liquids/protein molecules. To achieve controllable interactions between the device and biomolecules and still retain the required mechanical strength on the whole, modification of the surface is often done.
In the present study surface properties were modified through a polymer brush approach. After the modification, surfaces gain tunability toward protein adsorption. Mixed polymer brushes consisting of protein repelling and protein attractive components were used, with a 'grafting to' method employed for the synthesis of polymer layers. First, poly(ethylene glycol), the protein repelling …

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The Development Of Hyaluronic Acid Biomaterials For Vascular Tissue Engineering, Samir Ibrahim Dec 2008

The Development Of Hyaluronic Acid Biomaterials For Vascular Tissue Engineering, Samir Ibrahim

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Current vascular implant materials poorly interact with medial smooth muscle cells (SMCs) allowing the permanent loss of vascular elastin, eliminated by trauma or disease, a crucial element in maintaining the natural biomechanics of the blood vessel and overall vascular homeostasis. In addition, these materials insufficiently recruit vascular endothelial cells (ECs) to form a normally functional, confluent endothelium that acts as the interface between the blood and vascular tissue and regulates numerous vital vascular processes. As a result, the restenosis, or re-occlusion, rate within these devices has remained fairly high stimulating the investigation of numerous new materials capable of providing the …

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Hydraulic Actuated Automotive Cooling Systems - Nonlinear Control And Test, John Wagner, M H. Salah, P M. Frick, D M. Dawson Dec 2008

Hydraulic Actuated Automotive Cooling Systems - Nonlinear Control And Test, John Wagner, M H. Salah, P M. Frick, D M. Dawson

Publications

The replacement of traditional automotive mechanical cooling system components with computer controlled servo-motor driven actuators can improve temperature tracking and reduce parasitic losses. The integration of hydraulic actuators in the engine cooling circuit offers greater power density in a smaller package space when compared with electric actuators. In this paper, a comprehensive nonlinear backstepping robust control technique is developed to regulate the engine coolant temperature by controlling a hydraulic coolant pump and radiator fan. An experimental test bench has been assembled to investigate the hydraulic automotive thermal system performance. Representative numerical and experimental results are presented and discussed. Overall, the …

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Independent Torque Distribution Management Systems For Vehicle Stability Control, Indrasen Karogal Dec 2008

Independent Torque Distribution Management Systems For Vehicle Stability Control, Indrasen Karogal

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Vehicle Dynamics Control (VDC) systems, also called Electronic Stability Control (ESC) systems, are active on-board safety systems intended to stabilize the dynamics of vehicle lateral motion. In so doing, these systems reduce the possibility of the driver's loss of control of the vehicle in some critical or aggressive maneuvers. One approach to vehicle dynamics control is the use of appropriate drive torque distribution to the wheels of the vehicle. This thesis focuses on particular torque distribution management systems suitable for vehicles with independently driven wheels.
In conducting this study, a non-linear seven degree-of-freedom vehicle model incorporating a non-linear tire model …

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Nonlinear Finite Element Analysis Of Tweel Geometric Parameter Modifications On Spoke Dynamics During High Speed Rolling, Maya Ramachandran Dec 2008

Nonlinear Finite Element Analysis Of Tweel Geometric Parameter Modifications On Spoke Dynamics During High Speed Rolling, Maya Ramachandran

All Theses

The acoustic signature and noise produced by non-pnuematic wheels such as the Michelin TWEELTM is a critical design criteria for automotive and other mobility applications. The TWEELTM structure consists of three basic parts: (1) a circular deformable 'shear beam', (2) collapsible spokes and (3) a rigid hub. During high speed rolling the TWEELTM produces acoustic noise which is hypothesized to be due to resonant vibration of the TWEELTM spokes as they enter the contact region, buckle and then snap back into a state of tension. In order to identify and help understand the causes of acoustic noise for a rolling …

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Modeling, Analysis And Control Of Flexible Solid-State Hysteretic Actuators, Kushan Vora Dec 2008

Modeling, Analysis And Control Of Flexible Solid-State Hysteretic Actuators, Kushan Vora

All Theses

A distributed parameters modeling and control framework for flexible solid-state hysteretic actuator is presented in this work. For the simplicity of analysis, the actuator dynamic behavior is decoupled and treated separately from the hysteresis nonlinearity. To include the effects of widely-used flexural mechanisms, a mass-spring-damper boundary condition is considered for system. Moreover, the effect of electromechanical actuation is included as a concentrate force at the boundary. The problem is then divided into two parts: first part deals with free motion analysis of system in order to obtain eigenvalues and eigenfunctions using the expansion theorem and a standard eigenvalue problem procedure. …

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Investigation Of The Merging Of Two Axisymmetric Turbulent Jets, Jeffrey Smith Dec 2008

Investigation Of The Merging Of Two Axisymmetric Turbulent Jets, Jeffrey Smith

All Theses

A study was done to determine the converging distance of two axisymmetric turbulent jets and to compare the experimental results with the Reichardt hypothesis. This experiment consisted of measuring the velocity profiles of the two jets and manipulating the momentum ratio between the jets. Through testing, it was determined that the Reichardt hypothesis while efficient, over predicts the converging distance of the jets by up to 25% in some cases.
An Acoustic Doppler Velocimeter (ADV) was used to take measurements across the path of the jets and monitored the velocity and the turbulent kinetic energy. After observing the velocity profiles, …

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An Investigation On Spot-Weld Modeling Complexity For Crash Simulation, Srinivasan Vimalanathan Dec 2008

An Investigation On Spot-Weld Modeling Complexity For Crash Simulation, Srinivasan Vimalanathan

All Theses

In order to design car body structures which are safe during crash, modern automotive manufacturers perform both full-scale experimental crash tests and computer simulation of vehicle crash events using commercially available Finite Element Analysis (FEA) packages such as ABAQUS or LS-DYNA. Use of crash simulations significantly reduces the number of real time crash experiments needed and reduces the time required for design changes. However, in order to capture accurately crash behavior during high-speed impact, a large amount of detailed FEA modeling features such as number and types of elements, mesh element size, number of components, different types of connectors, material …

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Synthesis And Characterization Of Macromolecular Layers Grafted To Polymer Surfaces, Oleksandr Burtovyy Dec 2008

Synthesis And Characterization Of Macromolecular Layers Grafted To Polymer Surfaces, Oleksandr Burtovyy

All Dissertations

The composition and behavior of surfaces and interfaces play a pivotal role in dictating the overall efficiency of the majority of polymeric materials and devices. Surface properties of the materials can be altered using surface modification techniques. It is necessary to highlight that successful methods of surface modification should affect only the upper layer of the polymer material without changing bulk properties. The processes must introduce new functionalities to the surface, optimize surface roughness, lubrication, hydrophobicity, hydrophilicity, adhesion, conductivity, and/or biocompatibility.
Research presented in this dissertation is dedicated to the synthesis, characterization, and application of thin macromolecular layers anchored to …

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