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Articles 2161 - 2190 of 2584

Full-Text Articles in Engineering

Nucleation And Growth Behavior Of Tellurite-Based Glasses Suitable For Mid-Infrared Applications, Jonathan Massera Dec 2009

Nucleation And Growth Behavior Of Tellurite-Based Glasses Suitable For Mid-Infrared Applications, Jonathan Massera

All Dissertations

Optical fibers transmitting in the 2-5 μm mid-infrared (MIR) spectral region are highly desirable for a variety of military and civilian applications including super-continuum generation, infrared countermeasures (IRCM), and MIR laser sources. These new applications in the mid-infrared require novel optical materials that transmit in this window and can be fabricated into fiber. As tellurite glasses are known to have good transparency in the (NIR) region, tellurite-based glasses are the material of choice for this study due to their high linear and nonlinear refractive index, their low glass transition temperature and the ability to form them into optical fiber.
This …

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A Scanpath Comparison Of The Salient Features Of Weather Among General Aviation Pilots Based On Training And Experience, Michael Sawyer Dec 2009

A Scanpath Comparison Of The Salient Features Of Weather Among General Aviation Pilots Based On Training And Experience, Michael Sawyer

All Dissertations

Over the last 20 years the number of annual accidents in general aviation has seen a steady decline. The annual number of fatal accidents, however, has remained relatively stable. Adverse weather is consistently cited as a leading cause of fatal accidents in general aviation; weather accidents have a fatality rate nearly four times that of other general aviation accidents. Reviews of accident data reveal that often these accidents occur when inexperienced pilots who are certified only for visual flight rules flight continue into adverse weather. The Situation Assessment Hypothesis suggests these accidents occur when pilots fail to accurately recognize weather …

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Production And Characterization Of Novel Shaped Fibers For Fluid Sorption And Transport, Lisa Fuller Dec 2009

Production And Characterization Of Novel Shaped Fibers For Fluid Sorption And Transport, Lisa Fuller

All Dissertations

This work investigated the production and characterization of novel shaped fibers for fluid adsorption and transport. Shaped fibers such as Y, H, and octolobal, as well as conventional round fibers, were extruded using a research melt extruder. The fibers were extruded from 18 melt flow index (MFI) polypropylene (PP) and blends of 18 MFI PP and 400 MFI PP. Hydrophilic spin finish Bozzetto Favorol SF2 was applied to the surface of extruded fibers and hydrophilic polyester additive LB-100 was included in the blend of some H fibers to increase the hydrophilicity of the fiber surface. The geometric shape retention of …

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Synthesis And Spectroscopic Characterization Of Nanostructured Thermoelectric Materials, Jason Reppert Dec 2009

Synthesis And Spectroscopic Characterization Of Nanostructured Thermoelectric Materials, Jason Reppert

All Dissertations

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 study, it has been shown that Bi nanowires with small enough diameters (~10 nm), prepared via the pulsed laser vaporization method, undergo …

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Inter-Tube Bonding And Defects In Carbon Nanotubes And The Impact On The Transport Properties And Micro-Morphology, Keqin Yang Dec 2009

Inter-Tube Bonding And Defects In Carbon Nanotubes And The Impact On The Transport Properties And Micro-Morphology, Keqin Yang

All Dissertations

The transport properties of the carbon nanotubes (CNTs) are affected by the tube-tube interaction and the defects presented in the system. Inter-tube bonding, formed during spark plasma sintering (SPS) process, lowers the electrical/thermal resistivity at the tube-tube junctions and also causes new scattering mechanisms such as strong electron-phonon coupling (EPC) at low temperature. More evidences have been found by changing the SPS temperature and doping the CNTs to support the electron-phonon coupling is Kohn anomaly (KA) in as-SPSed CNTs. The phonon drag, appearing in thermoelectric power (TEP) of the as-SPSed CNTs at low temperature, can be explained in the framework …

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Covalent Immobilization Of L1 Neural Cell Adhesion Molecule To Acrylated Tetronicâ® Hydrogels For Neural Regeneration, Rebecca Cribb Dec 2009

Covalent Immobilization Of L1 Neural Cell Adhesion Molecule To Acrylated Tetronicâ® Hydrogels For Neural Regeneration, Rebecca Cribb

All Dissertations

Spinal cord injuries cost the United States $20 billion per year, with an existing patient population of 256,000 growing by an estimated 12,000 each year. Current clinical therapies for spinal cord injury are limited to spinal immobilization and realignment via traction, surgery, administration of methylprednisolone sodium succinate (MPSS) within eight hours post-injury, and rehabilitation exercises. While these therapies are important and may minimize damage and restore limited function, there is a dire clinical need for treatments to address the growing population of chronically-injured patients.
Varying degrees of axonal regeneration and functional recovery following spinal cord injury have been achieved in …

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Real-Time Vehicle Parameter Estimation And Adaptive Stability Control, John Limroth Dec 2009

Real-Time Vehicle Parameter Estimation And Adaptive Stability Control, John Limroth

All Dissertations

This dissertation presents a novel Electronic Stability Control (ESC) strategy that is capable of adapting to changing vehicle mass, tire condition and road surface conditions. The benefits of ESC are well understood with regard to assisting drivers to maintain vehicle control during extreme handling maneuvers or when extreme road conditions such as ice are encountered. However state of the art ESC strategies rely on known and invariable vehicle parameters such as vehicle mass, yaw moment of inertia and tire cornering stiffness coefficients. Such vehicle parameters may change over time, especially in the case of heavy trucks which encounter widely varying …

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Evaluation Of Fluid Diodes As Pulmonary Heart Valve Replacements, Tiffany Camp Dec 2009

Evaluation Of Fluid Diodes As Pulmonary Heart Valve Replacements, Tiffany Camp

All Dissertations

Children born with congenital heart disease often times suffer from severe chronic pulmonary insufficiency. Palliative treatments for this condition may come early on in the life of the patient; however, if it becomes severe enough, a pulmonary valve replacement may be required. There currently is not a permanent option for a replacements valve. Therefore, a need exists to develop a permanent solution. Knowing that the right heart circulation is more tolerant of moderate levels of regurgitation (0 - 35%) and pressure gradient (0 - 30 mmHg), this study investigates the hypothesis that a fluid diode, a motionless valve that offers …

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Dynamics Of Ultrasonic Consolidation, James Gibert Dec 2009

Dynamics Of Ultrasonic Consolidation, James Gibert

All Dissertations

Ultrasonic consolidation (UC) is a solid state rapid manufacturing process derived from ultrasonic welding of thin metal foils coupled with contour milling to achieve functional accurate components. The bonding of metal is accomplished by the local application of high frequency vibration energy under pressure producing a metallurgical bond without melting the base material. Its unique nature allows the design and fabrication of structural panels for satellites, production of injection molding tools, functionally graded structures, metal-matrix composites, embedded sensors, armor, and fiber embedded adaptive structures. It is commonly theorized that interfacial motion and friction at the bonding interface play a prominent …

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Creation Of Bioactive Surfaces To Modulate Cell Behavior Using Surface Initiated Photoiniferter-Mediated Graft Photopolymerization, Nihar Shah Dec 2009

Creation Of Bioactive Surfaces To Modulate Cell Behavior Using Surface Initiated Photoiniferter-Mediated Graft Photopolymerization, Nihar Shah

All Dissertations

Biomaterials widely used in biomedical applications still face biocompatibility issues arising from non-specific protein adsorption on the foreign surface, and the consequent undesired cell response. Emerging evidence suggests that imparting specific bioactivity to the biomaterial's surface to elicit favorable response from cells, (like osseointegration of joint implants and endothelialization of stents) can yield much better biocompatibility results when combined with passive prevention of protein adsorption. In more complex diseases like spinal cord injury and cardiomyopathy, specific biomolecules are required to elicit desired cell responses for successful regeneration. However, for success of such biomolecule based strategies, the effects of various parameters …

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Volumetric Flank Wear Characterization For Titanium Milling Insert Tools, Uli Burger, Mathew Kuttolamadom, April Bryan, Laine Mears, Thomas Kurfess Oct 2009

Volumetric Flank Wear Characterization For Titanium Milling Insert Tools, Uli Burger, Mathew Kuttolamadom, April Bryan, Laine Mears, Thomas Kurfess

Publications

Machining wear models are useful for the prediction of tool life and the estimation of machining productivity. Existing wear models relate the cutting parameters of feed, speed, and depth of cut to tool wear. The tool wear is often reported as changes in flank width or crater depth. However, these one-dimensional wear measurements do not fully characterize the tool condition when tools wear by other types of wear such as notching, chipping, and adhesion. This is especially true when machining difficult-to-machine materials such as titanium. This paper proposes another approach for characterizing tool wear. It is based on taking measurements …

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Electrodeposition Of Nanocrystalline Ni-Based Alloys, Hanseung Park Aug 2009

Electrodeposition Of Nanocrystalline Ni-Based Alloys, Hanseung Park

All Theses

Nanocrystalline materials can often process superior properties, but they are generally unstable against grain growth. Addition of a dopant can stabilize nanocrystalline alloys by decreasing the excess grain boundary energy as the thermodynamic driving force for grain growth and reducing grain boundary mobility via a kinetic effect of solute drag. In this thesis study, eight Ni-based alloys (Ni-W, Ni-P, Ni-Mo, Ni-Cu, Ni-B, Ni-Mg, Ni-Zn and Ni-Co) and pure Ni were made using an electrodeposition method. It is concluded that the use of different dopant can drastically affect the deposition mechanism as well as the morphology of resultant films. Ni-W and …

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Colloidal Electroluminescence: Novel Routes To Controlled Emission Of Organic Light Emitting Diode Devices, Christopher Huebner Aug 2009

Colloidal Electroluminescence: Novel Routes To Controlled Emission Of Organic Light Emitting Diode Devices, Christopher Huebner

All Dissertations

In recent years the importance of the organic light emitting diode (OLED) has grown immensely, and the past two decades have seen ongoing and exhaustive research in organic routes to solid state lighting,
wherein electricity is directly converted into emitted light through an excited state relaxation mechanism. The benefits of incorporating polymeric and small molecule materials into solid state lighting devices include high efficiences, low production costs, amenability to large-scale production and devices, reduced environmental impact and low energy consumption. Herein are presented novel routes to materials engineering and preparation, device fabrication and emission tailoring through the abilility to form …

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Effects Of Meeting Spaces On The Performance Of A Concept Selection Task By Engineering Design Teams, Necmettin Ozkan Aug 2009

Effects Of Meeting Spaces On The Performance Of A Concept Selection Task By Engineering Design Teams, Necmettin Ozkan

All Theses

Given the increasing importance of collaboration and the resulting use of virtual tools, this research investigates the performance of engineering design teams using a concept selection task in three meeting spaces, face-to-face, 2D online and 3D virtual. Cisco's WebEx and Sun Microsystems' Wonderland were used as the 2D online meeting space and the 3D virtual environment, respectively. Twenty-four two-person design teams were formed and randomly assigned to the meeting spaces. Eight teams performed a cell-phone concept selection task in each meeting space. Four dependent variables were measured: task completion time, team satisfaction, self-evaluated quality and expert-evaluated quality. Following data collection, …

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The Effect Of Bio-Based Materials On Quality And Shelf Life Of Celery, Chike Ifezue Aug 2009

The Effect Of Bio-Based Materials On Quality And Shelf Life Of Celery, Chike Ifezue

All Theses

Bio-based materials have garnered increasing interest as food packaging
materials because they are derived from renewable resources such
as corn starch, cellulose and sugar beet. These materials do have the disadvantage
of having
poor mechanical performance compared to non-bio based materials and their
effect on quality and shelf life of some produce is unknown.
This research studied the effect of three bio-based materials on quality
and self life of celery. Materials consist of biopolymer films and LDPE
film. The variable materials were: Polylactic Acid (PLA), a versatile
biodegradable aliphatic polyester derived from 100% renewable resources,
Ecoflex, a biodegradable aliphatic-aromatic copolyester, …

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Estimation Of Maximum Achievable End-To-End Throughput In Ieee 802.11 Based Wireless Mesh Networks, Gayatri Venkatesh Aug 2009

Estimation Of Maximum Achievable End-To-End Throughput In Ieee 802.11 Based Wireless Mesh Networks, Gayatri Venkatesh

All Theses

Wireless mesh networks can be quickly deployed in various situations to provide temporary to permanent wireless network coverage. To assess the feasibility and reliability of a given end-to-end communication need, it is essential for communication end points to accurately estimate their achievable end-to-end throughput. Several capacity, end-to-end throughput, and available bandwidth estimation techniques have been studied in the past for wired and wireless networks. The contention among wireless nodes arising due to the IEEE 802.11 medium access control protocol's channel access mechanism renders the estimation of such network attributes challenging in multi-hop networks. This thesis evaluates Adhoc Probe, one state-of-the-art …

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Characterization And Enhancement Of Sensing Properties Of Piezoelectric Materials With Applications To Vibration Suppression, Siddharth Aphale Aug 2009

Characterization And Enhancement Of Sensing Properties Of Piezoelectric Materials With Applications To Vibration Suppression, Siddharth Aphale

All Theses

This thesis undertakes the study of piezoelectric properties of polymer-based fabric and film sensors. An enhancement in piezoelectric properties of such sensors, as noted through earlier work, is observed with increasing weight ratios of nanomaterials dispersed in the polymer matrix. A comprehensive mathematical model using cantilever beams is developed to analyze this enhancement both qualitatively and quantitatively. An experimental setup is also developed to implement the proposed real time signal processing necessary to collect required data towards the characterization. In order to distinguish piezoelectric materials from other materials, study of the frequency response of developed fabric sensors to periodic chirp …

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On The Modeling Of Energy Harvesters And Analysis Of Their Response Under Time-Varying Frequency Excitations, Thiago Seuaciuc-Osorio Aug 2009

On The Modeling Of Energy Harvesters And Analysis Of Their Response Under Time-Varying Frequency Excitations, Thiago Seuaciuc-Osorio

All Theses

Energy harvesting is a process by which otherwise wasted ambient energy can be captured and transformed into a useful form. Historical examples of this concept include windmills, sailing ships, and waterwheels. Modern technologies and current energy needs have brought this same concept to a smaller scale wherein small wireless devices with minute energy consumption can be operated autonomously. Today, many critical electronic devices, such as health-monitoring sensors, pace makers, spinal stimulators, electric pain relievers, etc. require minimal amounts of power to function, which permits utilizing energy from their environment to power them. By exploiting the ability of active materials and …

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Hierarchical Bayesian Cortical Models: Analysis And Acceleration On Multicore Architectures, Pavan Yalamanchili Aug 2009

Hierarchical Bayesian Cortical Models: Analysis And Acceleration On Multicore Architectures, Pavan Yalamanchili

All Theses

There is a significant interest in the research community to develop large scale,
high performance implementations of neuromorphic models. These have the potential to
provide significantly stronger information processing capabilities than current computing
algorithms. This thesis examines the parallelization of two recent biologically inspired
hierarchical Bayesian cortical models onto recent multicore architectures. These models
have been developed recently based on new insights from neuroscience and have several
advantages over traditional neural networks. In particular, they need far fewer network
nodes to simulate a large scale cortical model than traditional neural networks, making
them computationally more efficient. This is the first …

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Motion Segmentation From Clustering Of Sparse Point Features Using Spatially Constrained Mixture Models, Shrinivas Pundlik Aug 2009

Motion Segmentation From Clustering Of Sparse Point Features Using Spatially Constrained Mixture Models, Shrinivas Pundlik

All Dissertations

Motion is one of the strongest cues available for segmentation. While motion segmentation finds wide ranging applications in object detection, tracking, surveillance, robotics, image and video compression, scene reconstruction, video editing, and so on, it faces various challenges such as accurate motion recovery from noisy data, varying complexity of the models required to describe the computed image motion, the dynamic nature of the scene that may include a large number of independently moving objects undergoing occlusions, and the need to make high-level decisions while dealing with long image sequences. Keeping the sparse point features as the pivotal point, this thesis …

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Use Of Orthogonal Arrays For Efficient Evaluation Of Geometric Designs For Reducing Vibration Of A Non-Pneumatic Wheel During High-Speed Rolling, William Rutherford Aug 2009

Use Of Orthogonal Arrays For Efficient Evaluation Of Geometric Designs For Reducing Vibration Of A Non-Pneumatic Wheel During High-Speed Rolling, William Rutherford

All Theses

During high speed rolling of a non-pneumatic wheel, vibration may be produced by the interaction of collapsible spokes with a shear deformable ring as they enter the contact region, buckle and then snap back into a state of tension. In the present work, a 2D planar finite element model with geometric nonlinearity and explicit time-stepping is used to simulate rolling of the non-pneumatic wheel. Vibration characteristics are measured from the FFT frequency spectrum of the time-signals of perpendicular distance of marker nodes from the virtual plane of the spoke, thickness change in the ring between spokes, and ground reaction forces. …

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Development Of A Rigid Ring Tire Model And Comparison Among Various Tire Models For Ride Comfort Simulations, Norm Frey Aug 2009

Development Of A Rigid Ring Tire Model And Comparison Among Various Tire Models For Ride Comfort Simulations, Norm Frey

All Theses

One vehicle subassembly that is of great importance to automobile manufacturers for tuning final vehicle performance is the pneumatic tire. Pneumatic tires present themselves as unique tuning tools as they 1) are the sole link between the roadway surface and the integrated vehicle suspension, chassis and steering systems, and 2) provide a wide range of tunability over many vehicle performances, including handling (steering feel as well as chassis dynamics), traction (braking, driving, and cornering), and ride comfort (roadway isolation). Therefore the vehicle manufacturing industry continues to research and refine various aspects of tire modeling to improve up-front integrated tire/vehicle CAE/CAD …

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Implementation Of Genetic Algorithms In Fpga-Based Reconfigurable Computing Systems, Nahid Alam Aug 2009

Implementation Of Genetic Algorithms In Fpga-Based Reconfigurable Computing Systems, Nahid Alam

All Theses

Genetic Algorithms (GAs) are used to solve many optimization problems in science and engineering. GA is a heuristics approach which relies largely on random numbers to determine the approximate solution of an optimization problem. We use the Mersenne Twister Algorithm (MTA) to generate a non-overlapping sequence of random numbers with a period of 219937-1. The random numbers are generated from a state vector that consists of 624 elements. Our work on state vector generation and the GA implementation targets the solution of a flow-line scheduling problem where the flow-lines have jobs to process and the goal is to find a …

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Synthesis Of Optimal Usage Of Available Aggregates In Highway Construction And Maintenance, Benjamin Skidmore Aug 2009

Synthesis Of Optimal Usage Of Available Aggregates In Highway Construction And Maintenance, Benjamin Skidmore

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The optimization of the available aggregates for highway construction and maintenance is vital both from an economic and environmental perspective. By not optimizing the aggregate supply project costs escalate as a simple response to supply and demand, and just as important the fact that aggregate is a natural resource and a limited one, it is crucial that is used as efficiently as possible. This paper examines specifically the use of aggregates by the South Carolina Department of Transportation, but can easily be adapted to any state. Through DOT and quarry surveys and an examination of aggregate gradation specifications it was …

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Acceleration Of Spiking Neural Networks On Multicore Architectures, Rommel Jalasutram Aug 2009

Acceleration Of Spiking Neural Networks On Multicore Architectures, Rommel Jalasutram

All Theses

The human cortex is the seat of learning and cognition. Biological scale
implementations of cortical models have the potential to provide significantly more
power problem solving capabilities than traditional computing algorithms. The large
scale implementation and design of these models has attracted significant attention
recently. High performance implementations of the models are needed to enable such
large scale designs. This thesis examines the acceleration of the spiking neural network
class of cortical models on several modern multicore processors. These include the
Izhikevich, Wilson, Morris-Lecar, and Hodgkin-Huxley models. The architectures
examined are the STI Cell, Sun UltraSPARC T2+, and Intel Xeon …

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A Dual Input Bidirectional Power Converter For Charging And Discharging A Phev Battery, Daniel Fain Aug 2009

A Dual Input Bidirectional Power Converter For Charging And Discharging A Phev Battery, Daniel Fain

All Theses

This thesis looks at a new design for a dual input bidirectional power converter (DIBPC) for charging and discharging a PHEV battery. The design incorporates a power factor correcting rectifier aimed at optimizing the battery charging efficiency from either a 120 VAC or 240 VAC source or discharging the battery to a usable AC voltage at 120 VAC. For simplicity and cost-effectiveness, the DIBPC is constructed using a standard IGBT 6-pack intended for motor control. The DIBPC is designed specifically to provide efficient operation with 120 VAC and 240 VAC inputs while achieving a very low THDI. The DIBPC also …

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Accuracy And Multi-Core Performance Of Machine Learning Algorithms For Handwritten Character Recognition, Sumod Mohan Aug 2009

Accuracy And Multi-Core Performance Of Machine Learning Algorithms For Handwritten Character Recognition, Sumod Mohan

All Theses

There have been considerable developments in the quest for intelligent machines since the beginning of the cybernetics revolution and the advent of computers. In the last two decades with the onset of the internet the developments have been extensive. This quest for building intelligent machines have led into research on the working of human brain, which has in turn led to the development of pattern recognition models which take inspiration in their structure and performance from biological neural networks. Research in creating intelligent systems poses two main problems. The first one is to develop algorithms which can generalize and predict …

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Survey Of Concurrent Engineering Environments And The Application Of Best Practices Towards The Development Of A Multiple Industry, Multiple Domain Environment, Jonathan Osborn Aug 2009

Survey Of Concurrent Engineering Environments And The Application Of Best Practices Towards The Development Of A Multiple Industry, Multiple Domain Environment, Jonathan Osborn

All Theses

This thesis investigates the best practices of fifteen existing Concurrent Engineering Environments (CEE). A CEE is defined as any environment, from physical to virtual, designed to facilitate concurrent engineering with multiple domain experts real time. All existing environments surveyed have been focused on the aerospace industry showing significant reductions in design time and cost. I have identified hardware, software, and peopleware as three major classifications as well as sixteen subcategories with which to compare the different CEEs. The success in reducing time and cost of designs seen in the aerospace industry with the introduction of CEEs can and should be …

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The Characterization, Isolation, And Fractionation Of Natural Organic Matter From Three Surface Waters, Olivia Orr Aug 2009

The Characterization, Isolation, And Fractionation Of Natural Organic Matter From Three Surface Waters, Olivia Orr

All Theses

The main objective of this study was to gain insight to the principles of isolation of natural organic matter (NOM) using reverse osmosis (RO) and subsequent fractionation using resin adsorption chromatography (RAC). Specifically, this study evaluated the RO and RAC methods for NOM characterization from three surface waters with varying physiochemical characteristics. Efficiency of RO was assessed by closing mass balances for dissolve organic carbon (DOC). Mass balances were also closed for dissolved nitrogen (DN), bromide (Br-), nitrate (NO3-), total calcium (Ca), total potassium (K), total manganese (Mn), total iron (Fe), total magnesium (Mg), total aluminum (Al), total copper (Cu), …

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Hydraulic Modeling To Inform Stream Maintenance Practices In South Carolina, Kelly Owens Aug 2009

Hydraulic Modeling To Inform Stream Maintenance Practices In South Carolina, Kelly Owens

All Theses

The Crabtree Canal located in Horry County, SC is the main conveyor of stormwater in a watershed that has undergone considerable urbanization in the last few decades. Evidence of bank instability and inchannel erosion is widely seen in the Crabtree Canal system. Principal sediment inputs are landscape sources and in-channel sources. A study was initiated to provide a working management tool to determine hydrodynamic conditions on the watershed driven by a hypothetical storm event and alternative channel configurations. The management tool comprised of a one-dimensional HEC-RAS model of the Crabtree Canal and was developed to aid the Horry County stormwater …

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