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2007

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Articles 691 - 720 of 3831

Full-Text Articles in Engineering

High-Speed Data Acquisition And Fpga Detected Pulse Blanking System For Interference Mitigation In Radio Astronomy, Micah Alexander Lillrose Aug 2007

High-Speed Data Acquisition And Fpga Detected Pulse Blanking System For Interference Mitigation In Radio Astronomy, Micah Alexander Lillrose

Theses and Dissertations

Radio astronomy is the discipline dedicated to the study of celestial emissions in the radio band from a few MHz to 300 GHz. In recent years, spurious emissions from man-made devices that operate at these frequencies have made detection of astronomical signals difficult. These harmful RF transmissions are called radio frequency interference (RFI). One strategy to remove RFI is to apply spatial filtering using an array antenna. This thesis documents the development of a high-speed data acquisition system used to record data from 7- and 19-element phased array feeds. The system supports synchronous sampling over all channels and streams data …


Risk Assessment For Hazardous Materials Incident, Washington County, Tennessee: Road Transportation, Rail Transportation, And Hazardous Materials Storage., Steed Kenlee Stagnolia Aug 2007

Risk Assessment For Hazardous Materials Incident, Washington County, Tennessee: Road Transportation, Rail Transportation, And Hazardous Materials Storage., Steed Kenlee Stagnolia

Electronic Theses and Dissertations

This study was conducted to provide a quantitative risk assessment for road transportation, railway transportation, and storage of hazardous materials in Washington County, Tennessee. A roadside survey, railroad hazardous materials survey, and a chemical inventory were conducted. It revealed an estimated 267,858 HAZMAT shipments per year on primary and secondary roadways and an estimated total of 9.4 x 109 tons of HAZMAT shipped by rail per year. There are 49 facilities that store a daily average of 33,722,700 lbs of HAZMAT. The risk of a hazardous materials incident occurring in Washington County is highest for Interstate transportation. The risk for …


Where Do We Get The Next Generations Of Space Engineers & Scientists?, Robert J. Twiggs Aug 2007

Where Do We Get The Next Generations Of Space Engineers & Scientists?, Robert J. Twiggs

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs titled "Where do we get the Next Generations Of Space Engineers & Scientists?" from August 13, 2007.


The Effect Of Flame Structure On Soot Formation And Transport In Turbulent Nonpremixed Flames Using Direct Numerical Simulation, David O. Lignell, Jacqueline H. Chen, Philip J. Smith, Tianfeng Lu, Chung K. Law Aug 2007

The Effect Of Flame Structure On Soot Formation And Transport In Turbulent Nonpremixed Flames Using Direct Numerical Simulation, David O. Lignell, Jacqueline H. Chen, Philip J. Smith, Tianfeng Lu, Chung K. Law

Faculty Publications

Direct numerical simulations of a two-dimensional, nonpremixed, sooting ethylene flame are performed to examine the effects of soot–flame interactions and transport in an unsteady configuration. A 15-step, 19-species (with 10 quasi-steady species) chemical mechanism was used for gas chemistry, with a two-moment, four-step, semiempirical soot model. Flame curvature is shown to result in flames that move, relative to the fluid, either toward or away from rich soot formation regions, resulting in soot being essentially convected into or away from the flame. This relative motion of flame and soot results in a wide spread of soot in the mixture fraction coordinate. …


Asmo American Student Moon Orbiter, Robert J. Twiggs, Yvonne Clearwater Aug 2007

Asmo American Student Moon Orbiter, Robert J. Twiggs, Yvonne Clearwater

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professors Bob Twiggs and Yvonne Clearwater  titled "ASMO American Student Moon Orbiter" from August 11, 2007.


Strong Guiding Of Light In Hollow Nanowire Structures, Liang Chen, James De Leon, Xiaomin Jin Aug 2007

Strong Guiding Of Light In Hollow Nanowire Structures, Liang Chen, James De Leon, Xiaomin Jin

Electrical Engineering

We have theoretically investigated the guiding mode patterns of hollow nanowires. Two types of nanowires, round shape and hexagonal shape, are examined with different combination of outer and inner radii. Because of electric field discontinuity at hollow interfaces and evanescent modes overlap in low refractive index region, strong light guiding and confinement are achieved in both hollow wire structures.


Development And Evaluation Of An Enrichment Culture For Bioaugmentation Of The P-Area Chlorinated Ethene Plume At The Savannah River Site, Elizabeth Wood Aug 2007

Development And Evaluation Of An Enrichment Culture For Bioaugmentation Of The P-Area Chlorinated Ethene Plume At The Savannah River Site, Elizabeth Wood

All Theses

The Twin Lakes chlorinated ethene plume at the Department of Energy's
Savannah River Site (SRS) emerges in a wetland in which trichloroethene (TCE) is
completely reduced to ethene and ethane. Novel strains of Dehalococcoides have been
detected from the wetland area. The objectives of this study were 1) to develop an
enrichment culture capable of completely dechlorinating TCE and tetrachloroethene
(PCE) to ethene using samples from the wetland; 2) to evaluate the use of lactate,
emulsified vegetable oil and corn syrup as possible electron donors for biostimulation of
the P-area chlorinated ethene plume at SRS that is not undergoing natural …


Pursuit-Evasion With Acceleration, Sensing Limitation, And Electronic Counter Measures, Jing-En Pang Aug 2007

Pursuit-Evasion With Acceleration, Sensing Limitation, And Electronic Counter Measures, Jing-En Pang

All Theses

Abstract: The use of game theory to analyze the optimal behaviors of both pursuers and evaders originated with Isaac's work at the Rand Corporation in the 1950's. Although many variations of this problem have been considered, published work to date is limited to the case where both players have constant velocities. In this thesis, we extend previous work by allowing players to accelerate. Analysis of this new problem using Newton's laws imposes an additional constraint to the system, which is the relationship between players' velocities and allowed turning radius. We find that analysis of this relationship provides new insight into …


An In Vitro Evaluation Of Dbm As A Tissue Engineered Scaffold, Stephanie Arnold Aug 2007

An In Vitro Evaluation Of Dbm As A Tissue Engineered Scaffold, Stephanie Arnold

All Theses

Over 500,000 bone graft procedures are performed each year in the United States. Bone grafting involves a surgical procedure to replace missing bone. Problems can arise with donor and defect sites during and after surgery, sometimes resulting in poor clinical results. The development and optimization of bone graft substitutes via a tissue engineering approach could markedly improve bone graft surgical outcome. Demineralized bone matrix (DBM), a bone graft material, is currently used in a clinical setting but has variable success rates.
The primary objective of the research presented in this thesis was to assess the cellular activity of D1 mouse …


Laser-Assisted Synthesis And Optical Properties Of Bismuth Nanorods, Jason Reppert Aug 2007

Laser-Assisted Synthesis And Optical Properties Of Bismuth Nanorods, Jason Reppert

All Theses

Bismuth in the bulk form is a semimetal with a rhombohedral structure. It has a small band overlap between the conduction and valence bands and a highly anisotropic electron effective-mass tensor. Thermoelectric materials, in which one of the three dimensions is in the nanometer regime, exhibit unique quantum confinement properties and have generated much interest in recent years. Theoretical investigations have suggested that nanowires with diameters <10 nm will possess a figure-of-merit ZT>2. Prior to this research, it has been shown by the Dresselhaus group at MIT that Bi nanowires with small enough diameters (~50 nm), prepared via the template-method, undergo a transition from a semimetal …


Performance Of Serial, Matched-Filter Packet Acquisition Algorithms With A Preamble-Sequence Acceptance Criterion, Javier Schloemann Aug 2007

Performance Of Serial, Matched-Filter Packet Acquisition Algorithms With A Preamble-Sequence Acceptance Criterion, Javier Schloemann

All Theses

In this thesis, we consider two methods to improve the acquisition performance of a packet radio system that uses serial, matched-filter acquisition: an adaptive acquisition threshold, and an acceptance criterion for the system's preamble sequences. Each packet transmission includes a fixed-length acquisition preamble, and the preamble sequence used in packet transmissions is changed at predetermined times based on a sequence-generation algorithm. It is shown that acquisition performance depends largely on the sidelobe energy of the preamble sequence, the acquisition threshold, and the signal-to-noise ratio.
The first method uses a threshold-scaling technique to account for the variation in the signal-to-noise ratio. …


Advanced Thermal Management For Internal Combustion Engines, Thomas Mitchell Aug 2007

Advanced Thermal Management For Internal Combustion Engines, Thomas Mitchell

All Theses

The automotive cooling system has unrealized potential to improve internal combustion engine performance through enhanced coolant temperature control and reduced parasitic losses. Advanced automotive thermal management systems use controllable actuators (e.g., smart thermostat valve, variable speed water pump, and electric radiator fan) in place of conventional mechanical cooling system components to improve engine temperature tracking over most operating ranges. To optimize advanced cooling system performance, the electro-mechanical actuators must work in harmony to control engine temperature. The design and placement of cooling components should also be considered when attempting to maximize the performance.
In this research project, two distinct vehicle …


Nonlinear Modeling Of The Adsorption-Induced Surface Stress In Piezoelectrically-Driven Microcantilever Biosensors, Mana Afshari Aug 2007

Nonlinear Modeling Of The Adsorption-Induced Surface Stress In Piezoelectrically-Driven Microcantilever Biosensors, Mana Afshari

All Theses

Microcantilever-based biosensors are rapidly becoming an enabling sensing technology for a variety of label-free biological applications due to their extreme applicability, versatility and low cost. These sensors operate through the adsorption of species on the functionalized surface of microcantilevers. The adsorption of biological species induces surface stress which originates from the molecular interactions such as adhesion forces of attraction/repulsion, electrostatic forces or the surface charge redistribution of the underlying substrate. This surface stress, consequently, alters the resonance frequency of the microcantilever beam.
This study presents a general framework towards modeling resonance frequency changes induced due to the surface stress arising …


Measurement Of Poisson’S Ratio With Contact-Resonance Atomic Force Microscopy, D.C. Hurley, Joseph A. Turner Aug 2007

Measurement Of Poisson’S Ratio With Contact-Resonance Atomic Force Microscopy, D.C. Hurley, Joseph A. Turner

Nebraska Center for Materials and Nanoscience: Faculty Publications

We describe contact-resonance atomic force microscopy (AFM) methods to quantitatively measure Poisson’s ratio ν or shear modulus G at the same time as Young’s modulus E. In contact-resonance AFM, the frequencies of the cantilever’s resonant vibrations are measured while the tip is in contact with the sample. Simultaneous measurement of flexural and torsional vibrational modes enables E and ν to be determined separately. Analysis methods are presented to relate the contact-resonance frequencies to the tip-sample contact stiffness, which in turn determines the sample’s nanoscale elastic properties. Experimental results are presented for a glass specimen with fused silica used as …


A Study Of Estimation Techniques And Of Mechatronic System Design And Testing, Brett Castelloe Aug 2007

A Study Of Estimation Techniques And Of Mechatronic System Design And Testing, Brett Castelloe

All Theses

This thesis is a collection of two projects that the author worked on during his master's studies at Clemson University. The first project--adaptive camera calibration--involves the design and simulation of an estimator for the calibration parameters of a camera. The second project--basket drive wear testing--includes the design of a test plan for measuring wear on a mechatronic system.


Transmission Gate Based Dual Rail Logic For Differential Power Analysis Resistant Circuits, Srinidhi Narasimha Char Aug 2007

Transmission Gate Based Dual Rail Logic For Differential Power Analysis Resistant Circuits, Srinidhi Narasimha Char

All Theses

Cryptographic devices with hardware implementation of the algorithms are increasingly being used in various applications. As a consequence, there is an increased need for security against the attacks on the cryptographic system. Among various attack techniques, side channel attacks pose a significant threat to the hardware implementation. Power analysis attacks are a type of side channel attack where the power leakage from the underlying hardware is used to eavesdrop on the hardware operation. Wave pipelined differential and dynamic logic (WDDL) has been found to be an effective countermeasure to power analysis. This thesis studies the use of transmission gate based …


Analyzing Relationships Between Lightning And Rain In Order To Improve Estimation Accuracy Of Rain , Justin Lapp Aug 2007

Analyzing Relationships Between Lightning And Rain In Order To Improve Estimation Accuracy Of Rain , Justin Lapp

All Theses

The remote estimation of rainfall rate R is essential for the aviation industry, agriculture, and food warning. Radar, the current means of R estimation, is not available in much of the world. In addition, this measurement involves a level of inaccuracy. Using lightning to detect rain is a relatively inexpensive alternative to radar systems and can be done from existing satellites. Previous research has revealed correlations between lightning and rain, suggesting either that it is possible to estimate R using lightning, or that it is possible to use it to correct for a portion of the radar inaccuracies. These correlations …


Approaches To Mitigate The Impact Of Dissolved Organic Matter On The Adsorption Of Synthetic Organic Contaminants By Activated Carbon, Abhishek Yadav Aug 2007

Approaches To Mitigate The Impact Of Dissolved Organic Matter On The Adsorption Of Synthetic Organic Contaminants By Activated Carbon, Abhishek Yadav

All Theses

The main objective of this study was to conduct a systematic investigation of various approaches to mitigate the competition of dissolved organic matter (DOM) on the adsorption of synthetic organic contaminants (SOCs) by activated carbons. TCE and atrazine were selected as the target SOCs because they are known to adsorb in different pore size regions. TCE adsorbs in the primary micropore region (i.e., <10 ) which is inaccessible to the majority of the DOM components, while atrazine adsorbs in the secondary micropore region (i.e., 10-20 ) which is partially accessible to some DOM components. The adsorbents used in this study consisted of four activated carbons (OLC, CRC, F400He, and HD4000ST) and one activated carbon fiber (ACF: ACF10). All sorbents were basic and hydrophobic in nature and represented a set of activated carbons with gradually widening pore size distribution, from the extremely microporous carbons (ACF10 and OLC) to carbons with some amount of mesopores (CRC and F400He) and finally a predominantly mesoporous (HD4000ST) carbon.
Isotherms were performed as single solute and after preloading with a dissolved organic matter (5 mg DOC/L and 20 mg DOC/L) for both TCE and atrazine and using the five activated carbons. Single solute isotherm results showed …


Fabrication And Characterization Of Cu/4h-Sic Schottky Diodes, Ruth Solomon Aug 2007

Fabrication And Characterization Of Cu/4h-Sic Schottky Diodes, Ruth Solomon

All Theses

Copper Schottky contacts to n-type 4H Silicon Carbide with nickel ohmic contacts were fabricated. The electrical and physical characteristics of these Schottky diodes were analyzed and the results are presented. I-V measurements revealed two sets of characteristics, one indicating nearly ideal Schottky behavior and the other exhibiting regions with two barrier heights. The reason for this observed phenomenon was studied and attributed to the in-homogeneity of the Silicon Carbide surface. The I-V and C-V characteristics were used to extract the electrical parameters, which include barrier height, ideality factor, reverse saturation current density, and doping concentration. The measured barrier height was …


Development Of A Microscopic Moirž Interferometry System, Jeremy Brougher Aug 2007

Development Of A Microscopic Moirž Interferometry System, Jeremy Brougher

All Theses

The human tooth is an amazing structure that is worthy of detailed research and analysis. For over half a century, various tests have been conducted to acquire more information about the structural and material properties of dentin, enamel, and the dentin-enamel junction. Unfortunately, variations still exist in the experimental results, even in the most recently collected data. The primary focus of the majority of material property testing on human teeth has been hardness testing utilizing indentation and nanoindentation analysis. However, several limitations still exist with the indentation technique. Thus, the moirŽ fringe analysis method, specifically microscopic moirŽ interferometry, has been …


Glycosaminoglycan Stabilization Reduces Tissue Buckling In Bioprosthetic Heart Valves, Sagar Shah Aug 2007

Glycosaminoglycan Stabilization Reduces Tissue Buckling In Bioprosthetic Heart Valves, Sagar Shah

All Theses

Currently, bioprosthetic heart valves are crosslinked with glutaraldehyde to prevent tissue degradation and to reduce tissue antigenicity. Glutaraldehyde forms stable crosslinks with collagen via a Schiff base reaction of the aldehyde with an amine group of the hydroxylysine/lysine in collagen. However, within a decade of implantation, 20-30% of these bioprostheses will become dysfunctional and over 50% will fail due to degeneration within 12-15 years post-operatively.
Gylcosaminoglycans, a major constituent of valvular tissue, play an important role in maintaining a hydrated environment necessary for absorbing compressive loads, modulating shear stresses, and resisting tissue buckling. One of the disadvantages of glutaraldehyde crosslinking …


Modeling And Simulation Of A Laser Deposition Process, Frank W. Liou, Zhiqiang Fan, Heng Pan, Kevin P. Slattery, Mary Kinsella, Joseph William Newkirk, Hsin-Nan Chou Aug 2007

Modeling And Simulation Of A Laser Deposition Process, Frank W. Liou, Zhiqiang Fan, Heng Pan, Kevin P. Slattery, Mary Kinsella, Joseph William Newkirk, Hsin-Nan Chou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A laser deposition process involves the supply of metallic powders into a laser-heated spot where the powder is melted and forms a melt puddle which quickly solidifies into a bead. In order to design an effective system, the laser beam, the powder beam, and their interactions need to be fully understood. In this paper, the laser-material interaction within the melt pool is reported using a multi-scale model: A macroscopic model to model mass, heat, and momentum transfer. Experiments were also conducted to validate the simulation model.


Numerical Simulation Of The Evolution Of Solidification Microstructure In Laser Deposition, Zhiqiang Fan, Todd E. Sparks, Frank W. Liou, Anand Jambunathan, Yaxin Bao, Jianzhong Ruan, Joseph William Newkirk Aug 2007

Numerical Simulation Of The Evolution Of Solidification Microstructure In Laser Deposition, Zhiqiang Fan, Todd E. Sparks, Frank W. Liou, Anand Jambunathan, Yaxin Bao, Jianzhong Ruan, Joseph William Newkirk

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A predictive model is developed to simulate the evolution of the solidification microstructure during the laser deposition process. The microstructure model is coupled with a comprehensive macroscopic thermodynamic model. This model simulates dendritic grain structures and morphological evolution in solidification. Based on the cellular automata approach, this microstructure model takes into account the heterogeneous nucleation both within the melt pool and at the substrate/melt interface, the growth kinetics, and preferential growth directions of dendrites. Both diffusion and convection effects are included. This model enables prediction and visualization of grain structures during and after the deposition process. This model is applied …


Aqueous-Based Extrusion Fabrication Of Ceramics On Demand, Michael S. Mason, Tieshu Huang, Robert G. Landers, Ming-Chuan Leu, Greg Hilmas, Michael W. Hayes Aug 2007

Aqueous-Based Extrusion Fabrication Of Ceramics On Demand, Michael S. Mason, Tieshu Huang, Robert G. Landers, Ming-Chuan Leu, Greg Hilmas, Michael W. Hayes

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Aqueous-Based Extrusion Fabrication is an additive manufacturing technique that extrudes ceramic slurries of high solids loading layer by layer for part fabrication. The material reservoir in a previously developed system has been modified to allow for starting and stopping of extrusion process on demand. Design pros and cons are examined and a comparison between two material reservoir designs is made. Tests were conducted to determine the optimal deposition parameters for starting and stopping of the extrudate on demand. The collected test data is used to create a process model that describes the relationship between ram velocity and material extrusion rate. …


Design Of Embedded Resistance Heating Element Using Rapid Manufacturing Process, Ravi Philip, Todd E. Sparks, Frank W. Liou Aug 2007

Design Of Embedded Resistance Heating Element Using Rapid Manufacturing Process, Ravi Philip, Todd E. Sparks, Frank W. Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper discusses the design of heating element suitable for embedding in a rapid manufacturing process. A specific pattern is built using the laser deposition Process available at the University of Missouri--Rolla. A resistance heating element which is then cast into place using a castable refractory material, which acts as an electrical insulator. An application of this technology is for preheating the substrate before direct metal deposition.


Modeling And Validation Of Temperature And Concentration For Rapid Freeze Prototyping, Frances D. Bryant, Ming-Chuan Leu Aug 2007

Modeling And Validation Of Temperature And Concentration For Rapid Freeze Prototyping, Frances D. Bryant, Ming-Chuan Leu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Rapid Freeze Prototyping is a solid freeform fabrication process that uses water as the main build material in a cold environment to create three-dimensional parts. A eutectic sugar-water solution (C6H12O6 – H2O) has been used as a sacrificial material in order to create complex 3D parts with features such as overhangs. A study of the interaction of the build and support materials is presented in this paper. The temperature of both materials during deposition and subsequent cooling is modeled using a semi-empirical model and a theoretical model. A concentration model is used to …


Variable Powder Flow Rate Control In Laser Metal Deposition Processes, Lie Tang, Jianzhong Ruan, Robert G. Landers, Frank W. Liou Aug 2007

Variable Powder Flow Rate Control In Laser Metal Deposition Processes, Lie Tang, Jianzhong Ruan, Robert G. Landers, Frank W. Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper proposes a novel technique, called Variable Powder Flow Rate Control (VPFRC), for the regulation of powder flow rate in laser metal deposition processes. The idea of VPFRC is to adjust the powder flow rate to maintain a uniform powder deposition per unit length even when disturbances occur (e.g., the motion system accelerates and decelerates). Dynamic models of the powder delivery system motor and the powder transport system (i.e., five-meter pipe, powder dispenser, and cladding head) are first constructed. A general tracking controller is then designed to track variable powder flow rate references. Since the powder flow rate at …


Thermocouple Embedding For The Production Of A Substrate For Rapid Manufacturing, Rana Gunaratnam, Todd E. Sparks, Frank W. Liou Aug 2007

Thermocouple Embedding For The Production Of A Substrate For Rapid Manufacturing, Rana Gunaratnam, Todd E. Sparks, Frank W. Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper reports the results of a set of experiments testing methods to embed thermocouples during laser deposition. Various operating settings and shielding materials are explored. Temperature readings of the embedded thermocouples are compared with surface temperature readings taken by a non-contact digital pyrometer during the deposition process. Also, possibilities of using this information for system control are discussed.


Response To "Comment On 'Adhesion-Delamination Mechanics Of A Presented Rectangular Film Adhered Onto A Rigid Substrate' [J. Appl. Phys. 101, 024903 (2007)]", Kai-Tak Wan, Gang Duan Aug 2007

Response To "Comment On 'Adhesion-Delamination Mechanics Of A Presented Rectangular Film Adhered Onto A Rigid Substrate' [J. Appl. Phys. 101, 024903 (2007)]", Kai-Tak Wan, Gang Duan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

No abstract provided.


Experimental Investigation Of Effect Of Environment Temperature On Freeze-Form Extrusion Fabrication, Xiyue Zhao, Michael S. Mason, Tieshu Huang, Ming-Chuan Leu, Robert G. Landers, Greg Hilmas, Samuel J. Easley, Michael W. Hayes Aug 2007

Experimental Investigation Of Effect Of Environment Temperature On Freeze-Form Extrusion Fabrication, Xiyue Zhao, Michael S. Mason, Tieshu Huang, Ming-Chuan Leu, Robert G. Landers, Greg Hilmas, Samuel J. Easley, Michael W. Hayes

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Freeze-form Extrusion Fabrication (FEF) is an additive manufacturing technique that extrudes ceramic loaded aqueous pastes layer by layer below the paste freezing temperature for component fabrication. A computer controlled 3-D gantry system has been developed for the FEF process. The system includes a temperature control subsystem that allows for fabrication of components below the paste freezing temperature. The low temperature environment allows for larger component fabrication. Comparisons in terms of layer thickness, self-sustaining ability, and system response were performed between 0⁰C and -20⁰C for alumina sample fabrications. The minimum deposition angles without use of support material have been determined for …