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Articles 3001 - 3030 of 6329
Full-Text Articles in Engineering
Structural Characterization Of Multimetallic Nanoparticles, Vineetha Mukundan
Structural Characterization Of Multimetallic Nanoparticles, Vineetha Mukundan
Open Access Dissertations
Bimetallic and trimetallic alloy nanoparticles have enhanced catalytic activities due to their unique structural properties. Using in situ time-resolved synchrotron based x-ray diffraction, we investigated the structural properties of nanoscale catalysts undergoing various heat treatments. Thermal treatment brings about changes in particle size, morphology, dispersion of metals on support, alloying, surface electronic properties, etc. First, the mechanisms of coalescence and grain growth in PtNiCo nanoparticles supported on planar silica on silicon were examined in detail in the temperature range 400-900°C. The sintering process in PtNiCo nanoparticles was found to be accompanied by lattice contraction and L10chemical ordering. …
Acrolein As A Novel Therapeutic Target For Spinal Cord Injury Induced Neuropathic Pain, Jonghyuck Park
Acrolein As A Novel Therapeutic Target For Spinal Cord Injury Induced Neuropathic Pain, Jonghyuck Park
Open Access Dissertations
Despite years of research, post-spinal cord injury (SCI) chronic neuropathic pain remains refractory to treatment and drastically impairs quality of life for SCI victims beyond paralysis. Although inflammation and free radicals contribute to neuropathic pain in SCI, the mechanism is not completely clear. We have recently demonstrated that acrolein, a product and catalyst of lipid peroxidation, induces a vicious cycle of oxidative stress, amplifying its effects and perpetuating oxidative stress and inflammation. In the current study, we have confirmed that acrolein is elevated significantly at least two weeks post-SCI which coincides with the emergence of hyperalgesia (mechanical, cold and thermal). …
Advanced Iii-V / Si Nano-Scale Transistors And Contacts: Modeling And Analysis, Seung Hyun Park
Advanced Iii-V / Si Nano-Scale Transistors And Contacts: Modeling And Analysis, Seung Hyun Park
Open Access Dissertations
The exponential miniaturization of Si CMOS technology has been a key to the electronics revolution. However, the continuous downscaling of the gate length becomes the biggest challenge to maintain higher speed, lower power, and better electrostatic integrity for each following generation. Hence, novel devices and better channel materials than Si are considered to improve the metal-oxide-semiconductor field-effect transistors (MOSFETs) device performance. III-V compound semiconductors and multi-gate structures are being considered as promising candidates in the next CMOS technology. III-V and Si nano-scale transistors in different architectures are investigated (1) to compare the performance between InGaAs of III-V compound semiconductors and …
Structure-Functionality Relationship Of Collagen Scaffolds For Tissue Engineering, Seungman Park
Structure-Functionality Relationship Of Collagen Scaffolds For Tissue Engineering, Seungman Park
Open Access Dissertations
Tissue engineering is a promising technology that enables scientists to create artificial organs or replace damaged tissues using animal cells and other components. For successful tissue regeneration, many factors should be taken into account, however, three components are most crucial: cell, scaffold, and soluble factor(s). In order to check the functionality after regeneration of desired tissues, various approaches have been attempted, depending on the physical, biological, and chemical properties of the tissues. Recently, the importance of the extracellular matrix (ECM) microstructure is being considered to be important in this regard. The ECM is closely associated with various functional properties of …
Effects Of Flow Orientation On Condensation In Tubes, Il Chung Park
Effects Of Flow Orientation On Condensation In Tubes, Il Chung Park
Open Access Dissertations
This study explores the interfacial and heat transfer characteristics of annular condensation of FC-72 in vertical downflow, vertical upflow and horizontal flow as well as the effects of channel orientation on flow condensation. Two separate condensation test modules are employed, one for high-speed video imaging of the film interface and the second for heat transfer measurements. Condensation in both test modules is achieved by rejecting the heat to a counterflow of cooling water. The heat transfer measurements are obtained along the inner wall of an 11.89-mm i.d. and 1,259.84-mm long stainless steel tube. ^ For vertical downflow, the film at …
Development Of A Static Bioactive Stent Prototype And Dynamic Aneurysm-On-A-Chip(Tm) Model For The Treatment Of Aneurysms, Lisa M. Reece
Development Of A Static Bioactive Stent Prototype And Dynamic Aneurysm-On-A-Chip(Tm) Model For The Treatment Of Aneurysms, Lisa M. Reece
Open Access Dissertations
Aneurysms are pockets of blood that collect outside blood vessel walls forming dilatations and leaving arterial walls very prone to rupture. Current treatments include: (1) clipping, and (2) coil embolization, including stent-assisted coiling. While these procedures can be effective, it would be advantageous to design a biologically active stent, modified with magnetic stent coatings, allowing cells to be manipulated to heal the arterial lining. Further, velocity, pressure, and wall shear stresses aid in the disease development of aneurysmal growth, but the shear force mechanisms effecting wound closure is elusive. Due to these factors, there is a definite need to cultivate …
Non-Intrusive Two-Phase Flow Regime Identification And Transport Characterization In Microchannels Subject To Uniform And Non-Uniform Heat Input, Susan N. Ritchey
Non-Intrusive Two-Phase Flow Regime Identification And Transport Characterization In Microchannels Subject To Uniform And Non-Uniform Heat Input, Susan N. Ritchey
Open Access Dissertations
Direct integration of compact microchannel heat sinks is an attractive thermal management solution for the dissipation of high heat fluxes, specifically under boiling conditions that provide high rates of heat transfer at a uniform heat sink temperature. Under two-phase flow conditions, the heat transfer and pressure drop are a function of the local flow regime. Development of sensors that detect local void fraction and flow regimes may enable better understanding of the fundamental flow phenomena. ^ The void fraction in air-water two-phase adiabatic flow in a microchannel is measured in this work using a custom-designed impedance-based sensor with electrodes on …
Power-Efficient High-Speed Interface Circuit Techniques, Elkim Felipe Roa Fuentes
Power-Efficient High-Speed Interface Circuit Techniques, Elkim Felipe Roa Fuentes
Open Access Dissertations
Inter- and intra-chip connections have become the new challenge to enable the scaling of computing systems, ranging from mobile devices to high-end servers. Demand for aggregate I/O bandwidth has been driven by applications including high-speed ethernet, backplane micro-servers, memory, graphics, chip-to-chip and network onchip. I/O circuitry is becoming the major power consumer in SoC processors and memories as the increasing bandwidth demands larger per-pin data rate or larger I/O pin count per component. The aggregate I/O bandwidth has approximately doubled every three to four years across a diverse range of standards in different applications. However, in order to keep pace …
A New Passive Surface Water Flux Meter For Simultaneous Measurement Of Contaminant And Water Fluxes In Streams And Rivers, Stephen A. Sassman
A New Passive Surface Water Flux Meter For Simultaneous Measurement Of Contaminant And Water Fluxes In Streams And Rivers, Stephen A. Sassman
Open Access Dissertations
A passive surface water flux meter (PSFM) for measurement of contaminant concentration/flux in rivers and streams is described and tested. The novel PSFM design was developed for portability and ease of adaptability for a variety of contaminant classes. Although previous designs have been evaluated under constant flow conditions, the PSFM has never been used for measurement of pesticides or hormones and this is the first time that it has been tested under transient flow. Discharge through the PSFM is assessed by measuring miscible displacement of alcohol tracers from granular activated carbon (GAC). The tracer retardation factors (R) measured by miscible …
Silica Nanoparticles As Vehicles For Therapy Delivery In Neurological Injury, Desiree Schenk
Silica Nanoparticles As Vehicles For Therapy Delivery In Neurological Injury, Desiree Schenk
Open Access Dissertations
Acrolein, a very reactive aldehyde, is a culprit in the biochemical cascade after primary, mechanical spinal cord injury (SCI), which leads to the destruction of tissue initially unharmed, referred to as "secondary injury". Additionally, in models of multiple sclerosis (MS) and some clinical research, acrolein levels are significantly increased. This aldehyde overwhelms the natural anti-oxidant system, reacts freely with proteins, and releases during lipid peroxidation (LPO), effectively regenerating its self. Due to its ability to make more copies of itself in the presence of tissue via lipid peroxidation, researchers believe that acrolein plays a role in the increased destruction of …
Predicting Lubrication Performance Between The Slipper And Swashplate In Axial Piston Hydraulic Machines, Andrew T. Schenk
Predicting Lubrication Performance Between The Slipper And Swashplate In Axial Piston Hydraulic Machines, Andrew T. Schenk
Open Access Dissertations
Engineering of the sliding interfaces within swashplate type axial piston machines represents the most complex and difficult part of the design process. The sliding interfaces are subject to significant normal loads which must be supported while simultaneously preventing component wear to ensure long lasting operation. Proper lubrication design is essential to separate the solid bodies from each other, but the complexity of the physics involved makes this a difficult problem. This work focuses on lubrication and the resulting energy losses at the sliding interface between the slipper and swashplate. ^ To better understand the slipper lubrication performance, a numerical model …
Theory Of Topological Insulators And Its Applications, Parijat Sengupta
Theory Of Topological Insulators And Its Applications, Parijat Sengupta
Open Access Dissertations
An important pursuit in semiconductor physics is to discover new materials to sustain the continuous progress and improvements in the current electronic devices. Traditionally, three material types are in use: 1) Metals 2) Semiconductors 3) Insulators. All the three material types are classified according to the energy gap between conduction and valence bands derived from band theory of solids. Recent theoretical predictions and confirmed by experimental observations have provided evidence that there exists materials which behave as insulators in the bulk but possess gapless conducting states on the surface. These new class of materials are called topological insulators (TI). In …
Acquisition, Retention And Transfer Of Heavy Equipment Operator Skills Through Simulator Training, Chung Yin So
Acquisition, Retention And Transfer Of Heavy Equipment Operator Skills Through Simulator Training, Chung Yin So
Open Access Dissertations
Initiatives and collaborations among heavy construction equipment manufacturing companies and training technology firms to develop and employ simulators for varied training purposes are becoming commonplace. However, human factors research on simulator training for operators of construction equipment is still sparse. For simulator training to be effective, it is necessary to understand how skills are learned using the simulator, how those skills are transferred to other tasks, devices, and real scenarios, and how well skills are retained after simulator training. ^ This research is on skill development, specifically as it applies to operator training for two specific types of heavy construction …
Structure And Activity Relationships Of Bimetallic Catalysts For Aqueous Phase Reforming And The Water-Gas Shift Reaction, Fred Gerald Sollberger
Structure And Activity Relationships Of Bimetallic Catalysts For Aqueous Phase Reforming And The Water-Gas Shift Reaction, Fred Gerald Sollberger
Open Access Dissertations
As the existing deposits of petroleum and non-renewable energy resources are exhausted, become more difficult to extract, and remain in politically unstable regions of the world, the search for long term alternatives for fuels and chemicals from renewable sources such as biomass continues. One promising process for the production of renewable hydrogen to use in conversion of biomass to fuels and chemicals is aqueous phase reforming (APR) of cellulose-derived carbohydrates. In the first study Pt/MWCNT catalysts have been promoted by addition of transition metal promoters Cu, Ni, Co, Fe, Mn, Mo, W, and Re in Pt:M 1:1 atomic ratios to …
Understanding Preferred Leg Stiffness And Layered Control Strategies For Locomotion, Zhuohua H. Shen
Understanding Preferred Leg Stiffness And Layered Control Strategies For Locomotion, Zhuohua H. Shen
Open Access Dissertations
Despite advancement in the field of robotics, current legged robots still cannot achieve the kind of locomotion stability animals and humans have. In order to develop legged robots with greater stability, we need to better understand general locomotion dynamics and control principles. Here we demonstrate that a mathematical modeling approach could greatly enable the discovery and understanding of general locomotion principles. ^ It is found that animal leg stiffness when scaled by its weight and leg length falls in a narrow region between 7 and 27. Rarely in biology does such a universal preference exist. It is not known completely …
Shape From Inconsistent Silhouette: Reconstruction Of Objects In The Presence Of Segmentation And Camera Calibration Error, Amy Tabb
Open Access Dissertations
Silhouettes are useful features to reconstruct the object shape when the object is textureless or the shape classes of objects are unknown. In this dissertation, we explore the problem of reconstructing the shape of challenging objects from silhouettes under real-world conditions such as the presence of silhouette and camera calibration error. This problem is called the Shape from Inconsistent Silhouettes problem. A psuedo-Boolean cost function is formalized for this problem, which penalizes differences between the reconstruction images and the silhouette images, and the Shape from Inconsistent Silhouette problem is cast as a psuedo-Boolean minimization problem. We propose a memory and …
Digital Provenance - Models, Systems, And Applications, Salmin Sultana
Digital Provenance - Models, Systems, And Applications, Salmin Sultana
Open Access Dissertations
Data provenance refers to the history of creation and manipulation of a data object and is being widely used in various application domains including scientific experiments, grid computing, file and storage system, streaming data etc. However, existing provenance systems operate at a single layer of abstraction (workflow/process/OS) at which they record and store provenance whereas the provenance captured from different layers provide the highest benefit when integrated through a unified provenance framework. To build such a framework, a comprehensive provenance model able to represent the provenance of data objects with various semantics and granularity is the first step. In this …
Optical Spectroscopy And Langmuir Probe Diagnostics Of Microwave Plasma In Synthesis Of Graphene-Based Nanomaterials, Alfredo D. Tuesta
Optical Spectroscopy And Langmuir Probe Diagnostics Of Microwave Plasma In Synthesis Of Graphene-Based Nanomaterials, Alfredo D. Tuesta
Open Access Dissertations
Along with the revolutionary discovery and development of carbon nanostructures, such as carbon nanotubes and graphitic sheets, has arrived the potential for their application in the fields of medicine, bioscience and engineering due to their exceptional structural, thermal and electrical properties. As roll-to-roll plasma deposition systems begin to provide means for large scale production of these nanodevices, a detailed understanding of the environment responsible for their synthesis is imperative in order to more accurately design and control the growth of carbon nanodevices. To date, the understanding of the chemistry and kinetics that govern the synthesis of carbon nanodevices is only …
Algebraic Level Sets For Cad/Cae Integration And Moving Boundary Problems, Kritika Upreti
Algebraic Level Sets For Cad/Cae Integration And Moving Boundary Problems, Kritika Upreti
Open Access Dissertations
Boundary representation (B-rep) of CAD models obtained from solid modeling kernels are commonly used in design, and analysis applications outside the CAD systems. Boolean operations between interacting B-rep CAD models as well as analysis of such multi-body systems are fundamental operations on B-rep geometries in CAD/CAE applications. However, the boundary representation of B-rep solids is, in general, not a suitable representation for analysis operations which lead to CAD/CAE integration challenges due to the need for conversion from B-rep to volumetric approximations. The major challenges include intermediate mesh generation step, capturing CAD features and associated behavior exactly and recurring point containment …
Computing With Spintronics: Circuits And Architectures, Rangharajan Venkatesan
Computing With Spintronics: Circuits And Architectures, Rangharajan Venkatesan
Open Access Dissertations
This thesis makes the following contributions towards the design of computing platforms with spintronic devices. 1) It explores the use of spintronic memories in the design of a domain-specific processor for an emerging class of data-intensive applications, namely recognition, mining and synthesis (RMS). Two different spintronic memory technologies — Domain Wall Memory (DWM) and STT-MRAM — are utilized to realize the different levels in the memory hierarchy of the domain-specific processor, based on their respective access characteristics. Architectural tradeoffs created by the use of spintronic memories are analyzed. The proposed design achieves 1.5X-4X improvements in energy-delay product compared to a …
Control Of Morphology Al-Fe-Si Phase In Al-Si-Cu Hypoeutectic Alloy, Meng Wang
Control Of Morphology Al-Fe-Si Phase In Al-Si-Cu Hypoeutectic Alloy, Meng Wang
Open Access Dissertations
Aluminum-Silicon (Al-Si) alloys are one of the most versatile aluminum alloys. Iron is considered one of the most harmful elements in Al-Si diecasting alloy because its presence leads to the precipitation of many AlFeSi intermetallic phases and unacceptable mechanical properties, such as reduction in ductility. Thus controlling the fraction and morphology of AlFeSi phase, especially the β-AlFeSi phase is an important way to improve the ductility of Al-Si die casting alloys. ^ In this dissertation, thermodynamics calculation of AlFeSi phase formation and fraction change during solidification process were conducted using Thermo-Calc software. A series of experiments, including adjusting cooling rates, …
Design And Analysis Of Solar Cells By Coupled Electrical - Optical Simulation, Xufeng Wang
Design And Analysis Of Solar Cells By Coupled Electrical - Optical Simulation, Xufeng Wang
Open Access Dissertations
Careful electrical design and optical design are both crucial for achieving high-efficiency solar cells. It is common to link these two aspects serially; the optical design is first done to minimize reflection and maximize light trapping, and then the resulting optical generation rate is input to the electrical simulation. For very high efficiency solar cells that approach the Shockley-Queisser limit, however, electrical and optical transports are tightly coupled in both directions. Photons generated by radiative recombination can be reabsorbed to create additional electron-hole pairs (so-called photon recycling), which decreases losses. A variety of novel photon management schemes are currently being …
Estimating Toner Usage With Laser Electrophotographic Printers, And Object Map Generation From Raster Input Image, Lu Wang
Open Access Dissertations
Accurate estimation of toner usage is an area of on-going importance for laser, electrophotographic (EP) printers. In Part 1, we propose a new two-stage approach in which we first predict on a pixel-by-pixel basis, the absorptance from printed and scanned pages. We then form a weighted sum of these pixel values to predict overall toner usage on the printed page. The weights are chosen by least-squares regression to toner usage measured with a set of printed test pages. Our two-stage predictor significantly outperforms existing methods that are based on a simple pixel counting strategy in terms of both accuracy and …
Role Of Group Ii Metabotropic Glutamate Receptor Subtype 2 (Mglur2) In Appetitive And Consummatory Aspects Of Ethanol Reinforcement, Kyle Allyson Windisch
Role Of Group Ii Metabotropic Glutamate Receptor Subtype 2 (Mglur2) In Appetitive And Consummatory Aspects Of Ethanol Reinforcement, Kyle Allyson Windisch
Open Access Dissertations
Background: Group II metabotropic glutamate receptors (mGluR2/3) are predominately presynaptically located Gi/o coupled receptors that are highly expressed in the cortex, nucleus accumbens, amygdala, and hippocampus. Previous studies suggest that group II mGluRs are involved in regulating ethanol (EtOH) consumption and seeking following extinction (Backstrom and Hyytia, 2005; Kufahl, et al., 2011). The sipper tube model, which allows for procedural separation of seeking and consumption, was used to further clarify the role of mGluR2/3 in EtOH-seeking and consumption. The non-selective group II mGluR agonist LY379268 (LY37) and selective mGluR2 positive allosteric modulator (PAM) BINA were used to determine the …
Measurement Of Combustion Response To Transverse Modes At High Pressure, Matthew Kenneth Wierman
Measurement Of Combustion Response To Transverse Modes At High Pressure, Matthew Kenneth Wierman
Open Access Dissertations
A two dimensional transverse combustor capable of producing and modulating an unstable flowfield was tested at Purdue. The combustor used an array of coaxial ox-centered shear injector elements. The oxidizer posts were able to be discretely changed in length between tests to investigate different post resonance conditions. A single Study element was placed in the middle of the driven unsteady flowfield so its response could be measured using pressure measurement and high speed imagery. This approach was supported by past testing of the longitudinal Continuously Variable Resonance Combustor and past transverse chambers. Mean flow rates and pressures were fixed across …
Current Steering And Electrode Spanning With Partial Tripolar Stimulation Mode In Cochlear Implants, Ching-Chih Wu
Current Steering And Electrode Spanning With Partial Tripolar Stimulation Mode In Cochlear Implants, Ching-Chih Wu
Open Access Dissertations
Cochlear implants (CIs) partially restore hearing sensation to profoundly deaf people by electrically stimulating the surviving auditory neurons. However, CI users perform poorly in challenging listening tasks such as speech recognition in noise and Cochlear implants (CIs) partially restore hearing sensation to profoundly deaf people by electrically stimulating the surviving auditory neurons. However, CI users perform poorly in challenging listening tasks such as speech recognition in noise and music perception, possibly due to the small number of implanted electrodes and the large current spread of electric stimulation. Although current spread may be reduced using partial tripolar (pTP) stimulation mode, the …
Model-Based Powertrain Design And Control System Development For The Ideal All-Wheel Drive Electric Vehicle, Haotian Wu
Model-Based Powertrain Design And Control System Development For The Ideal All-Wheel Drive Electric Vehicle, Haotian Wu
Open Access Dissertations
The transfer case based all-wheel drive electric vehicle (TCAWDEV) and dual-axle AWDEV have been investigated to balance concerns about energy consumption, drivability and stability of vehicles. However, the mentioned powertrain architectures have the torque windup issue or the wheel skidding issue. The torque windup is an inherent issue of mechanical linked all-wheel drive systems. The hydraulic motor-based or the electric motor-based ideal all-wheel drive powertrain can provide feasible solutions to the mentioned issues. An ideal AWDEV (IAWDEV) powertrain architecture and its control schemes were proposed by this research; the architecture has four independent driving motors in powertrain. The IAWDEV gives …
Crossflow Instability And Transition On A Circular Cone At Angle Of Attack In A Mach-6 Quiet Tunnel, Christopher A. C Ward
Crossflow Instability And Transition On A Circular Cone At Angle Of Attack In A Mach-6 Quiet Tunnel, Christopher A. C Ward
Open Access Dissertations
To investigate the effect of roughness on the stationary crossflow vortices, roughness elements 2 inches from the nosetip were created in a Torlon insert section of a 7-deg half-angle cone at 6-deg angle of attack in the Boeing/AFOSR Mach-6 Quiet Tunnel. Roughness elements with depths and diameters on the order of 500 microns were found to have a significant effect on the generation of the stationary vortices and the location of crossflow-induced transition under quiet flow. Crossflow-induced transition was measured under fully quiet flow. The controlled roughness elements also appeared to dominate the generation of the vortices, overwhelming the effect …
Coal Gasification For Fuel Synthesis: Multiphysics Modeling And New Concepts, Jian Xu
Coal Gasification For Fuel Synthesis: Multiphysics Modeling And New Concepts, Jian Xu
Open Access Dissertations
Fuel synthesis through gasification of carbonaceous materials (e.g. coal and biomass) has the potential to provide a solution to the increasing demand for energy and liquid transportation fuels. To theoretically understand the complex physical and chemical processes in a gasifier and to identify the most influential parameters for syngas production, we first developed a multi-physics and multi-scale model to simulate the gasification processes in a well-stirred reactor. This model is the first of its kind and considers detailed gas-phase chemistry, particle-phase reactions, moisture drying, devolatilization, porous structure evolution, convective and radiative heat transfer, as well as full coupling between the …
Effects Of Web Reinforcement Discontinuities On The Seismic Response Of Structural Walls, Ying Wang
Effects Of Web Reinforcement Discontinuities On The Seismic Response Of Structural Walls, Ying Wang
Open Access Dissertations
Field evidence was interpreted to suggest that discontinuities in the longitudinal web reinforcement caused severe damage in structural walls during strong ground motion. To test this hypothesis, six small-scale reinforced concrete structural walls were tested under lateral displacement reversals. Test variables included the presence of web longitudinal reinforcement discontinuities and number of loading cycles. The test results indicated that unit tensile strains in longitudinal reinforcing bars in boundary elements were approximately 50% higher in structural walls with web longitudinal reinforcement cutoffs relative to walls without reinforcement cutoffs. Higher unit tensile strains caused an increase in permanent strain accumulation, increasing the …