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2009

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Articles 2911 - 2940 of 4158

Full-Text Articles in Engineering

Study Of Film Cooling Effectiveness: Conical, Trenched And Asymmetrical Shaped Holes, Humberto Zuniga Jan 2009

Study Of Film Cooling Effectiveness: Conical, Trenched And Asymmetrical Shaped Holes, Humberto Zuniga

Electronic Theses and Dissertations

Film cooling is a technique whereby air from the compressor stage of a gas turbine engine is diverted for cooling purposes to parts, such as the turbine stage, that operate at very high temperatures. Cooling arrangements include impingement jets, finned, ribbed and turbulated channels, and rows of film cooling holes, all of which over the years have become progressively more complex. This costly, but necessary complexity is a result of the industry's push to run engines at increasingly higher turbine inlet temperatures. Higher temperatures mean higher efficiency, but they also mean that the turbine first stage operates hundreds of degrees …

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Unified Large And Small Signal State-Space Based Modeling And Symbolic Simulation For Pwm Converters, Ehab Shoubaki Jan 2009

Unified Large And Small Signal State-Space Based Modeling And Symbolic Simulation For Pwm Converters, Ehab Shoubaki

Electronic Theses and Dissertations

In this Dissertation, which concentrates on discrete modeling for control purposes of DC/DC converters and simulation through symbolic techniques. A Unified Discrete State-Space Model for power converters in CCM is presented. Two main approaches to arriving at the discrete model are used. The first approach involves an impulse function approximation of the duty cycle modulation of the converter switches, and this approach results in a small signal discrete model. The Second approach is direct and does not involve any approximation of the modulation, this approach yields both a large signal nonlinear discrete model and a linear small signal model. Harmonic …

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Delay Modeling And Long-Range Predictive Control Of Czochralski Growth Process, Dhaval Shah Jan 2009

Delay Modeling And Long-Range Predictive Control Of Czochralski Growth Process, Dhaval Shah

Electronic Theses and Dissertations

This work presents the Czochralski growth dynamics as time-varying delay based model, applied to the growth of La3Ga5.5Ta0.5O14 (LGT) piezoelectric crystals. The growth of high-quality large-diameter oxides by Czochralski technique requires the theoretical understanding and optimization of all relevant process parameters, growth conditions, and melts chemistry. Presently, proportional-integral- derivative (PID) type controllers are widely accepted for constant-diameter crystal growth by Czochralski. Such control systems, however, do not account for aspects such as the transportation delay of the heat from crucible wall to the crystal solidification front, heat radiated from the crucible wall above the melt surface, and varying melt level. …

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Pulse Frequency Modulation Zcs Flyback Converter In Inverter Applications, Feng Tian Jan 2009

Pulse Frequency Modulation Zcs Flyback Converter In Inverter Applications, Feng Tian

Electronic Theses and Dissertations

Renewable energy source plays an important role in energy co-generation and distribution. A traditional solar-based inverter system has two stages cascaded, which has simpler controller but low efficiency. A new solar-based single-stage grid-connected inverter system can achieve higher efficiency by reducing the power semiconductor switching loss and output stable and synchronizing sinusoid current into the utility grid. In Chapter 1, the characteristic I-V and P-V curve of PV array has been illustrated. Based on prediction of the PV power capacity installed on the grid-connected and off-grid, the trends of grid-tied inverter for DG system have been analyzed. In Chapter 2, …

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Connectionless Approach: A Localized Scheme To Mobile Ad Hoc Networks, Yao Ho Jan 2009

Connectionless Approach: A Localized Scheme To Mobile Ad Hoc Networks, Yao Ho

Electronic Theses and Dissertations

According to a Gartner Group (www.gartner.com) report in September 2008, the worldwide telecommunications market is on pace to reach $2 trillion in 2008. Gartner predicts that by 2012, the ratio of mobile to fixed connections will exceed 4-to-1. The North American mobile data market grew to 141.1 million connections in 2007, with a compound annual growth rate of 41.7 percent. It is believed that a large portion will be ad hoc and multi-hop connections, which will open many opportunities for Mobile Ad hoc NETwork (MANET) applications and Wireless Mesh Network (WMN) applications. A MANET is a self-organizing multi-hop wireless network …

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Learning Techniques For Information Retrieval And Mining In High-Dimensional Databases, Hao Cheng Jan 2009

Learning Techniques For Information Retrieval And Mining In High-Dimensional Databases, Hao Cheng

Electronic Theses and Dissertations

The main focus of my research is to design effective learning techniques for information retrieval and mining in high-dimensional databases. There are two main aspects in the retrieval and mining research: accuracy and efficiency. The accuracy problem is how to return results which can better match the ground truth, and the efficiency problem is how to evaluate users' requests and execute learning algorithms as fast as possible. However, these problems are non-trivial because of the complexity of the high-level semantic concepts, the heterogeneous natures of the feature space, the high dimensionality of data representations and the size of the databases. …

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Reduced Visibility Related Crashes In Florida: Crash Characteristics, Spatial Analysis And Injury Severity, Al-Ahad Ekram Jan 2009

Reduced Visibility Related Crashes In Florida: Crash Characteristics, Spatial Analysis And Injury Severity, Al-Ahad Ekram

Electronic Theses and Dissertations

Roadway crashes related to vision obstruction due to fog/smoke (FS) conditions constitute a challenge for traffic engineers. Previous research efforts mostly concentrated on the snow and rain related crashes. Statistics show that Florida is among the top three states in terms of crashes due to vision obstruction by FS. This research culminated in a comprehensive study of fog and smoke related crashes in the state of Florida. The analysis took into account the crashes that occurred between 2003 and 2007 on Florida state roads. Spatial analysis and injury severity analysis have been conducted and significant results have been identified. The …

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The Calibration, Validation, And Comparison Of Vissim Simulations Using The Two-Fluid Model, Jeremy Crowe Jan 2009

The Calibration, Validation, And Comparison Of Vissim Simulations Using The Two-Fluid Model, Jeremy Crowe

Electronic Theses and Dissertations

The microscopic traffic simulation program VISSIM is a powerful tool that has been used by transportation engineers and urban planners around the world. A VISSIM simulation is meant to depict the performance of the physical road network through the use of modeling tools and behavioral parameters. The process which gets the model to the point of matching real world conditions is called calibration and requires a means of relating the real world to the simulated world. The topic of this thesis discusses a new means of calibration using the two-fluid model. The two-fluid model is a macroscopic modeling technique which …

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Work Zone Effects On Performance Of A Toll Plaza, Jingyu Liu Jan 2009

Work Zone Effects On Performance Of A Toll Plaza, Jingyu Liu

Electronic Theses and Dissertations

No-lane closure workzone is typical during the construction of open road tolling lanes of a toll plaza. The influence of no-lane closure on toll plazas' performance is unknown because very few studies have been conducted to address this topic. The open road tolling (ORT) has become the new trend of operating an efficient toll plaza. So, the upgrading of a toll plaza from gated E-pass to open road E-pass has become common. The better the toll plaza authority knows about the influence of this construction and congestion effects, the better it can serve the costumers. This project mainly deals with …

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A Gis Safety Study And A County-Level Spatial Analysis Of Crashes In The State Of Florida, Ali Darwiche Jan 2009

A Gis Safety Study And A County-Level Spatial Analysis Of Crashes In The State Of Florida, Ali Darwiche

Electronic Theses and Dissertations

The research conducted in this thesis consists of a Geographic Information Systems (GIS) based safety study and a spatial analysis of vehicle crashes in the State of Florida. The GIS safety study is comprised of a County and Roadway Level GIS analysis of multilane corridors. The spatial analysis investigated the use of county-level vehicle crash models, taking spatial effects into account. The GIS safety study examines the locations of high trends of severe crashes (includes incapacitating and fatal crashes) on multilane corridors in the State of Florida at two levels, county level and roadway level. The GIS tool, which is …

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Flow Visualization In Microfluidic Expansion And Mixing, Ehsan Yakhshi-Tafti Jan 2009

Flow Visualization In Microfluidic Expansion And Mixing, Ehsan Yakhshi-Tafti

Electronic Theses and Dissertations

Micro particle image velocimetry (microPIV) is a non-intrusive tool for visualizing flow in micron-scale conduits. Using this investigative instrument, two experimental studies were performed to understand flow behaviors in microfluidic channels - a sudden expansion step flow and laminar velocity profile variation in diffusion driven mixing. First, flow in a backward facing step feature (1:5 expansion ratio) in a microchannel was taken as the subject of microPIV flow visualization. The onset and development of a recirculation flow was studied as a function of flow rate. This flow pattern was further used to investigate two major parameters affecting microPIV measurements; the …

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Study Of The Hydrodynamics Of Droplet Impingement On A Dry Surface Using Lattice Boltzmann Method, Xin Gu Jan 2009

Study Of The Hydrodynamics Of Droplet Impingement On A Dry Surface Using Lattice Boltzmann Method, Xin Gu

Electronic Theses and Dissertations

In this work, a two-phase lattice Boltzmann method (LBM) approach is implemented to investigate the hydrodynamic behavior of a single droplet impingement on a dry surface. LBM is a recently developed powerful technique to compute a wide range of fluid flow problems, especially in applications involving interfacial dynamics and complex geometries. Instead of solving the non-linear Navier-Stokes equations, which are complicated partial differential equations, LBM solves a set of discretized linear equations, which are easy to implement and parallelize. The fundamental idea of LBM is to recover the macroscopic properties of the fluid which obeys Navier-Stokes equations, by using simplified …

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Characterization Of A Hydrogen-Based Synthetic Fuel In A Shock Tube, Troy Flaherty Jan 2009

Characterization Of A Hydrogen-Based Synthetic Fuel In A Shock Tube, Troy Flaherty

Electronic Theses and Dissertations

Shock-tube experiments were performed with syngas mixtures near atmospheric pressure with varying equivalence ratios behind reflected shock waves. Pressure and hydroxyl radical (OH*) emission traces were recorded and used to calculate ignition delay time for a single mixture at equivalence ratios of [phi ]=0.4, 0.7, 1.0, and 2.0 over a range of temperatures from 913-1803 K. The syngas mixture was tested at full concentration as well as with 98% dilution in Argon. The full concentration mixtures were used to compare ignition delay time measurements with the theoretical calculations obtained through the use of chemical kinetics modeling using the Davis et …

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Efficiency Improvement Techniques For High Voltage Capacitor Charging Methods, Michael Islas Jan 2009

Efficiency Improvement Techniques For High Voltage Capacitor Charging Methods, Michael Islas

Electronic Theses and Dissertations

The goal of this thesis is to design and fabricate a DC-to-DC converter for use in high-voltage capacitor charging applications. The primary objectives include increasing the efficiency and reducing the cost of traditional methods used for this application. Traditional methods were not designed specifically for high-voltage capacitor charging and were thus very primitive and exhibited lower efficiency. Prior methods made use of a high voltage power supply and a current limiting resistor or control scheme. The power supply would often only operate efficiently at a single voltage value and would thus function poorly over a range used in charging a …

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Design And Modeling Of Radiation Hardened Lateral Power Mosfets, Matthew Landowski Jan 2009

Design And Modeling Of Radiation Hardened Lateral Power Mosfets, Matthew Landowski

Electronic Theses and Dissertations

Galactic-cosmic-rays (GCR) exist in space from unknown origins. A cosmic ray is a very high energy electron, proton, or heavy ion. As a GCR transverses a power semiconductor device, electron-hole-pairs (ehps) are generated along the ion track. Effects from this are referred to as single-event-effects (SEEs). A subset of a SEE is single-event burnout (SEB) which occurs when the parasitic bipolar junction transistor is triggered leading to thermal runaway. The failure mechanism is a complicated mix of photo-generated current, avalanche generated current, and activation of the inherent parasitic bipolar transistor. Current space-borne power systems lack the utility and advantages of …

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Simulation Of Brightness Temperatures For The Microwave Radiometer On The Aquarius/Sac-D Mission., Salman Khan Jan 2009

Simulation Of Brightness Temperatures For The Microwave Radiometer On The Aquarius/Sac-D Mission., Salman Khan

Electronic Theses and Dissertations

Microwave radiometers are highly sensitive receivers capable of measuring low levels of natural blackbody microwave emissions. Remote sensing by satellite microwave radiometers flying on low-earth, polar orbiting, satellites can infer a variety of terrestrial and atmospheric geophysical parameters for scientific and operational applications, such as weather and climate prediction. The objective of this thesis is to provide realistic simulated ocean brightness temperatures for the 3-channel Microwave Radiometer (MWR), which will be launched in May 2010 on the joint NASA/CONAE Aquarius/SAC-D Mission. These data will be used for pre-launch geophysical retrieval algorithms development and validation testing. Analyses are performed to evaluate …

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Characterization Of An Inline Row Impingement Channel For Turbine Blade Cooling Applications, Mark Ricklick Jan 2009

Characterization Of An Inline Row Impingement Channel For Turbine Blade Cooling Applications, Mark Ricklick

Electronic Theses and Dissertations

Gas turbines have become an intricate part of today's society. Besides powering practically all 200,000+ passenger aircraft in use today, they are also a predominate form of power generation when coupled with a generator. The fact that they are highly efficient, and capable of large power to weight ratios, makes gas turbines an ideal solution for many power requirement issues faced today. Designers have even been able to develop small, micro-turbines capable of producing efficient portable power. Part of the turbine's success is the fact that their efficiency levels have continuously risen since their introduction in the early 1800's. Along …

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The Integrated User Experience Evaluation Model: A Systematic Approach To Integrating User Experience Data Sources, Roberto Champney Jan 2009

The Integrated User Experience Evaluation Model: A Systematic Approach To Integrating User Experience Data Sources, Roberto Champney

Electronic Theses and Dissertations

Evaluating the user experience (UX) associated with product interaction is a challenge for current human-systems developers. This is largely due to a lack of theoretical guidance for directing how best to assess the UX and a paucity of tools to support such evaluation. This dissertation provided a framework and tools for guiding and supporting evaluation of the user experience. This doctoral research involved reviewing the literature on UX, using this knowledge to build first build a theoretical model of the UX construct and later develop a theoretical model to for the evaluation of UX in order to aid evaluators – …

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The Future Scenario Of Creating A Digital Sme Community In The Irish Construction Industry, Alan V. Hore, Roger West, Alan Redmond Jan 2009

The Future Scenario Of Creating A Digital Sme Community In The Irish Construction Industry, Alan V. Hore, Roger West, Alan Redmond

Conference papers

The problems associated with the Construction Industry not being able to manage and com-municate electronically product and project data between collaborating firms and within individual companies is compounded by the large number of small companies that have not adopted advanced Information Com-munication Technology (ICT). The typical nature of the service provided in construction, being an on-site and often highly customised service are generally identified as the reason for the low ICT uptake. The majority of Irish companies in the construction sector are Small to Medium sized Enterprises (SMEs). As eBusiness opens up the Irish economy to international competition Irish SMEs …

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A Flexible Web Based Learning Tool For Construction And Surveying Students Using Building Information Modelling And Laser Scanning, Maurice Murphy, Garrett Keenaghan, Eugene Mcgovern, Sara Pavia Jan 2009

A Flexible Web Based Learning Tool For Construction And Surveying Students Using Building Information Modelling And Laser Scanning, Maurice Murphy, Garrett Keenaghan, Eugene Mcgovern, Sara Pavia

Conference papers

Teaching and training construction and surveying students using computer simulations of buildings although recently developed is not new. In the case of this project a novel aspect is introduced through applying advanced recording and building modelling techniques developed in the Faculty of the Built Environment in the Technological University of Dublin. In summary this learning software uses parametric objects representing intelligent building components which are brought together virtually by the student to create or form an entire building. The library of parametric objects contain the real world geometry, texture and specification of building parts allowing the student to virtually analyse …

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Object Detection And Texture Classification With Applications To The Diagnosis Of Skin Cancer, Jonathan Blackledge, D. A. Dubovitskiy Jan 2009

Object Detection And Texture Classification With Applications To The Diagnosis Of Skin Cancer, Jonathan Blackledge, D. A. Dubovitskiy

Books/Book chapters

We present an approach to object detection and recognition in a digital image using a classification method that is based on the application of a set of features that include fractal parameters such as the Lacunarity and Fractal Dimension. The principal issues associated with object recognition are presented and a self-learning procedure for designing a decision making engine using fuzzy logic and membership function theory considered. The methods discussed, and the ‘system’ developed, have a range of applications in ‘machine vision’ and in this publication, we focus on the development and implementation of a skin cancer screening system that can …

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An Evolutionary Perspective On Engineering Design, William Grimson, Mike Murphy Jan 2009

An Evolutionary Perspective On Engineering Design, William Grimson, Mike Murphy

Books/Book chapters

No abstract provided.

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Liberal Studies In Engineering And Technology, William Grimson, Michael Dyrenfurth, Mike Murphy Jan 2009

Liberal Studies In Engineering And Technology, William Grimson, Michael Dyrenfurth, Mike Murphy

Books/Book chapters

No abstract provided.

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Uniarab: An Universal Machine Translator System For Arabic Based On Role And Reference Grammar, Brian Nolan, Yasser Salem Jan 2009

Uniarab: An Universal Machine Translator System For Arabic Based On Role And Reference Grammar, Brian Nolan, Yasser Salem

Conference Papers

This paper presents a machine translation system (Hutchins 2003) called UniArab (Salem, Hensman and Nolan 2008). It is a proof-of-concept system supporting the fundamental aspects of Arabic, such as the parts of speech, agreement and tenses. UniArab is based on the linking algorithm of RRG (syntax to semantics and vice versa). UniArab takes MSA Arabic as input in the native orthography, parses the sentence(s) into a logical meta-representation based on the fully expanded RRG logical structures and, using this, generates perfectly grammatical English output with full agreement and morphological resolution. UniArab utilizes an XML-based implementation of elements of the Role …

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Renewable Energy Resources And Technologies Applicable To Ireland, Fergal O'Rourke, Fergal Boyle, Anthony Reynolds Jan 2009

Renewable Energy Resources And Technologies Applicable To Ireland, Fergal O'Rourke, Fergal Boyle, Anthony Reynolds

Articles

The energy consumed in Ireland is primarily achieved by the combustion of fossil fuels. Ireland’s only indigenous fossil fuel is peat; all other fossil fuels are imported. As well as fossil fuels continually becoming more expensive, their use as an energy source also has a negative impact on the environment. Ireland’s energy consumption can be separated into 3 divisions; transportation, electricity generation and heat energy. Ireland however has a vast range of high quality renewable energy resources. Ireland has set a target of 33% of its electricity will be generated from renewable sources by 2020[1]. The use of biomass, wind …

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Managing Livestock Manure To Protect Environmental Quality, Brian L. Benham, Richard B. Ferguson, Christopher G. Henry, Michael A. Reynolds, Charles A. Shapiro, James P. Stack, Charles S. Wortmann Jan 2009

Managing Livestock Manure To Protect Environmental Quality, Brian L. Benham, Richard B. Ferguson, Christopher G. Henry, Michael A. Reynolds, Charles A. Shapiro, James P. Stack, Charles S. Wortmann

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Proper utilization of livestock manure is a major environmental concern. Livestock manure has typically been considered a ‘waste product’ of livestock production. A more accurate name for this material is a ‘recycled resource’ from the production of livestock. By managing livestock manure, the producer has a second chance to utilize the nutrients that have already been paid for but not fully utilized by the animal. Collecting, containing, and properly spreading livestock manure will incur additional costs for the producer. However, these costs can be offset or justified by the producer in terms of the yield enhancement and nutrient credits that …

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Integrated Capture And Spectroscopic Detection Of Viruses, Crystal A. Vargas, Allison A. Wilhelm, Jeremy Williams, Pierre Lucas, Kelly A. Reynolds, Mark R. Riley Jan 2009

Integrated Capture And Spectroscopic Detection Of Viruses, Crystal A. Vargas, Allison A. Wilhelm, Jeremy Williams, Pierre Lucas, Kelly A. Reynolds, Mark R. Riley

Department of Agricultural and Biological Systems Engineering: Faculty Publications

The goal of this work is to develop an online monitoring scheme for detection of viruses in flowing drinking water. The approach applies an electrodeposition process that is similar to the use of charged membrane filters previously employed for collection of viruses from aqueous samples. In the present approach, charged materials are driven onto a robust optical sensing element which has high transparency to infrared light. A spectroscopic measurement is performed using the evanescent wave that penetrates no more than 1 m from the surface of an infrared optical element in an attenuated total reflectance measurement scheme. The infrared measurement …

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Investigation Of River Eutrophication As Part Of A Low Dissolved Oxygen Tmdl Implementation, Gary M. Litton, W. T. Stringfellow, J. Herr, M. Brunell, S. Borglin Jan 2009

Investigation Of River Eutrophication As Part Of A Low Dissolved Oxygen Tmdl Implementation, Gary M. Litton, W. T. Stringfellow, J. Herr, M. Brunell, S. Borglin

All Faculty Articles - School of Engineering and Computer Science

In the United States, environmentally impaired rivers are subject to regulation under total maximum daily load (TMDL) regulations that specify watershed wide water quality standards. In California, the setting of TMDL standards is accompanied by the development of scientific and management plans directed at achieving specific water quality objectives. The San Joaquin River (SJR) in the Central Valley of California now has a TMDL for dissolved oxygen (DO). Low DO conditions in the SJR are caused in part by excessive phytoplankton growth (eutrophication) in the shallow, upstream portion of the river that create oxygen demand in the deeper estuary. This …

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Response Sensitivity Of Highway Bridges To Random Multi-Component Earthquake Excitation, Kyle Cronin Jan 2009

Response Sensitivity Of Highway Bridges To Random Multi-Component Earthquake Excitation, Kyle Cronin

Electronic Theses and Dissertations

Highway bridges provide a critical lifeline during extreme seismic events and must maintain serviceability under a large range of earthquake intensities. Consequently, the advent of more computational power has allowed more advanced analysis approaches for predicting performance and vulnerability of highway bridges under these seismic loads. In traditional two-dimensional finite element analyses, it has been demonstrated that the incidence angle of the ground motion can play a significant role in structural response. As three-dimensional nonlinear time history analyses are used more frequently in practice, ground motions are still usually applied along a single bridge axis. It is unknown how three …

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Spin-Orbit Splittings In Si/Sige Quantum Wells: From Ideal Si Membranes To Realistic Hterostructures, M. Prada, G. Klimeck, R. Joynt Jan 2009

Spin-Orbit Splittings In Si/Sige Quantum Wells: From Ideal Si Membranes To Realistic Hterostructures, M. Prada, G. Klimeck, R. Joynt

Birck and NCN Publications

We present a calculation of the wavevector-dependent subband level splitting from spin-orbit coupling in Si/SiGe quantum wells. We first use the effective-mass approach, where the splittings are parameterized by separating contributions from the Rashba and Dresselhaus terms. We then determine the inversion asymmetry parameters by fitting tight-binding numerical results obtained using the quantitative nanoelectronic modeling tool, NEMO-3D. We describe the relevant coefficients as a function of applied electric field and well width in our numerical simulations. Symmetry arguments can also predict the behavior, and an extensive analysis is also presented in this work. Using vast computational resources, we treat alloy …

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