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Articles 153571 - 153600 of 192950
Full-Text Articles in Engineering
Stress-State Adaptation Of Human Femur Increases Its Effective Fracture Toughness, Y. N. Yeni, Timothy L. Norman
Stress-State Adaptation Of Human Femur Increases Its Effective Fracture Toughness, Y. N. Yeni, Timothy L. Norman
Engineering and Computer Science Faculty Publications
No abstract provided.
Improving Voltage Stability By Reactive Power Reserve Management, Feng Dong, Badrul H. Chowdhury, Mariesa Crow, Levent Acar
Improving Voltage Stability By Reactive Power Reserve Management, Feng Dong, Badrul H. Chowdhury, Mariesa Crow, Levent Acar
Electrical and Computer Engineering Faculty Research & Creative Works
The amount of reactive reserves at generating stations is a measure of the degree of voltage stability. With this perspective, an optimized reactive reserve management scheme based on the optimal power flow is proposed. Detailed models of generator limiters, such as those for armature and field current limiting must be considered in order to utilize the maximum reactive power capability of generators, so as to meet reactive power demands during voltage emergencies. Participation factors for each generator in the management scheme are predetermined based on the voltage-var (V-Q) curve methodology. The Bender's decomposition methodology is applied to the reactive reserve …
Pulse Regulation Control Technique For Integrated High-Quality Rectifier-Regulators, Mehdi Ferdowsi, Ali Emadi
Pulse Regulation Control Technique For Integrated High-Quality Rectifier-Regulators, Mehdi Ferdowsi, Ali Emadi
Electrical and Computer Engineering Faculty Research & Creative Works
The pulse regulation control scheme is presented and applied to the boost integrated flyback rectifier/energy storage dc/dc (BIFRED) converter as the most popular member of the integrated high-quality rectifier-regulators (IHQRR). In contrast to the conventional control techniques, the principal idea of pulse regulation is to regulate the output voltage using a series of high- and low-power pulses generated by the current of the input inductor, which is operating in discontinuous conduction mode (DCM). Analysis of the BIFRED converter operating in DCM is presented. Fundamentals of pulse regulation as well as its stability analysis and the estimation of the output voltage …
The Matrix Pencil For Power System Modal Extraction, A. Singh, Mariesa Crow
The Matrix Pencil For Power System Modal Extraction, A. Singh, Mariesa Crow
Electrical and Computer Engineering Faculty Research & Creative Works
This work introduces the matrix pencil modal extraction method through the use of several illustrative examples. This method is used to estimate the eigenvalues of reduced-order models of large nonlinear systems based on their dynamic responses.
Fabrication Of Hollow Waveguides With Sacrificial Aluminum Cores, John P. Barber, Donald B. Conkey, Jeffrey Ryan Lee, Neal B. Hubbard, Larry L. Howell, Aaron R. Hawkins, Gongliang Yin, Holger Schmidt
Fabrication Of Hollow Waveguides With Sacrificial Aluminum Cores, John P. Barber, Donald B. Conkey, Jeffrey Ryan Lee, Neal B. Hubbard, Larry L. Howell, Aaron R. Hawkins, Gongliang Yin, Holger Schmidt
Faculty Publications
We have developed a process to fabricate dielectric waveguide structures with long hollow cores formed by etching a sacrificial core material. The process is compatible with other planar silicon fabrication techniques. Using aluminum as the sacrificial material, we have investigated fabrication limits and design parameters that determine mechanical integrity of the waveguides. Internal pressure due to the production of gaseous compounds during the core removal process was identified as the yield-limiting factor. A mechanical model based on finite element analysis and confirmed by experiment, predicts ultimate pressures sustainable by these structures. Waveguides less than 10 m wide with 2- m-thick …
A Graph-Based Model For Component-Based Software Development, Sahra Sedigh, Arif Ghafoor
A Graph-Based Model For Component-Based Software Development, Sahra Sedigh, Arif Ghafoor
Electrical and Computer Engineering Faculty Research & Creative Works
Software metrics can be used to objectively quantify the quality of software components and systems, alleviating quality and risk concerns and raising assurance in component-based systems. In this paper, we present a graph-based model for component-based software development. We assume that a number of components have been characterized in terms of non-functional metrics of importance to the software system being developed, and that the interfaces connecting various components have been similarly characterized. The emphasis of this work is on cost and quality of the system under development, and reaching an acceptable compromise between the two.
Reinforcement Learning-Based Output Feedback Control Of Nonlinear Systems With Input Constraints, Pingan He, Jagannathan Sarangapani
Reinforcement Learning-Based Output Feedback Control Of Nonlinear Systems With Input Constraints, Pingan He, Jagannathan Sarangapani
Electrical and Computer Engineering Faculty Research & Creative Works
A novel neural network (NN) -based output feedback controller with magnitude constraints is designed to deliver a desired tracking performance for a class of multi-input-multi-output (MIMO) discrete-time strict feedback nonlinear systems. Reinforcement learning in discrete time is proposed for the output feedback controller, which uses three NN: 1) a NN observer to estimate the system states with the input-output data; 2) a critic NN to approximate certain strategic utility function; and 3) an action NN to minimize both the strategic utility function and the unknown dynamics estimation errors. The magnitude constraints are manifested as saturation nonlinearities in the output feedback …
High-Anisotropy Nanocluster Films For High-Density Perpendicular Recording, David J. Sellmyer, Minglang Yan, Yinfan Xu, Ralph Skomski
High-Anisotropy Nanocluster Films For High-Density Perpendicular Recording, David J. Sellmyer, Minglang Yan, Yinfan Xu, Ralph Skomski
Materials Research Science and Engineering Center: Faculty Publications
This paper reports results on the synthesis and magnetic properties of L10:X nanocomposite films, where L10 = FePt, CoPt, and X = C, Ag, etc. Two fabrication methods are discussed: nonepitaxial growth of oriented perpendicular media, and monodispersed nanoparticle-assembled films grown with a gas-aggregation source. The magnetic properties are controllable through variations in the nanocluster properties and nanostructure. The films show promise for development as recording media at extremely high areal densities.
Evaluation Of Alternate Cable Anchor Designs And Three-Cable Guardrail Adjacent To Steep Slope, Ryan M. Nelson, Dean L. Sicking, Ronald K. Faller, John D. Reid, John R. Rohde, Karla A. Polivka, Jason A. Hascall
Evaluation Of Alternate Cable Anchor Designs And Three-Cable Guardrail Adjacent To Steep Slope, Ryan M. Nelson, Dean L. Sicking, Ronald K. Faller, John D. Reid, John R. Rohde, Karla A. Polivka, Jason A. Hascall
Nebraska Department of Transportation: Research Reports
No abstract provided.
Using Neural Networks To Identify The Effect Of Construction Factors On The Cost Of Reinforced Concrete Elements, Ahmed Aly El-Sotouhy
Using Neural Networks To Identify The Effect Of Construction Factors On The Cost Of Reinforced Concrete Elements, Ahmed Aly El-Sotouhy
Archived Theses and Dissertations
No abstract provided.
Modelling And Validation Of A Propellant Mixer For Controller Design, Hanz Richter, Enrique Barbieri, Fernando Figueroa Nasa Stennis Space Center
Modelling And Validation Of A Propellant Mixer For Controller Design, Hanz Richter, Enrique Barbieri, Fernando Figueroa Nasa Stennis Space Center
Mechanical Engineering Faculty Publications
A mixing chamber used in rocket engine testing at the NASA Stennis Space Center is modelled by a system of two nonlinear ordinary differential equations. The mixer is used to condition the thermodynamic properties of cryogenic liquid propellant by controlled injection of the same substance in the gaseous phase. The three inputs of the mixer are the positions of the valves regulating the liquid and gas flows at the inlets, and the position of the exit valve regulating the flow of conditioned propellant. Mixer operation during a test requires the regulation of its internal pressure, exit mass flow, and exit …
Microwave Backscatter Modeling Of Erg Surfaces In The Sahara Desert, David G. Long, Haroon Stephen
Microwave Backscatter Modeling Of Erg Surfaces In The Sahara Desert, David G. Long, Haroon Stephen
Faculty Publications
The Sahara desert includes large expanses of sand dunes called ergs. These dunes are formed and constantly reshaped by prevailing winds. Previous study shows that Saharan ergs exhibit significant radar backscatter (σ˚) modulation with azimuth angle (∅). We use σ˚ measurements observed at various incidence angles and ∅ from the NASA Scatterometer (NSCAT), the SeaWinds scatterometer, the ERS scatterometer (ESCAT), and the Tropical Rainfall Measuring Mission's Precipitation Radar to model the σ˚ response from sand dunes. Observations reveal a characteristic relationship between the backscatter modulation and the dune type, i.e., the number and orientation of the dune slopes. Sand dunes …
Observation And Characterization Of Radar Backscatter Over Greenland, David G. Long, Ivan S. Ashcraft
Observation And Characterization Of Radar Backscatter Over Greenland, David G. Long, Ivan S. Ashcraft
Faculty Publications
Characterization of the microwave signature of the Greenland snow surface enables delineation of the different snow facies and is a tool for tracking the effects of climate change. A new empirical observation model is introduced that uses a limited number of parameters to characterize the snow surface based on the dependence of radar backscatter on incidence angle, azimuth angle, spatial gradient, and temporal rate of change. The individual model parameters are discussed in depth with examples using data from the NASA Scatterometer (NSCAT) and from the C-band European Remote Sensing (ERS) satellite Advanced Microwave Instrument in scatterometer mode. The contribution …
Fracture Toughness Of Human Femoral Neck Cortical Bone Is Reduced With Age And With Increased Osteon Eccentricity, Y. N. Yeni, Timothy L. Norman
Fracture Toughness Of Human Femoral Neck Cortical Bone Is Reduced With Age And With Increased Osteon Eccentricity, Y. N. Yeni, Timothy L. Norman
Engineering and Computer Science Faculty Presentations
No abstract provided.
Catalytic Wet Air Oxidation Of Phenol In Concurrent Downflow And Upflow Packed-Bed Reactors Over Pillared Clay Catalyst, Jing Guo, Muthanna H. Al-Dahhan
Catalytic Wet Air Oxidation Of Phenol In Concurrent Downflow And Upflow Packed-Bed Reactors Over Pillared Clay Catalyst, Jing Guo, Muthanna H. Al-Dahhan
Chemical and Biochemical Engineering Faculty Research & Creative Works
An Experimental Study is Presented for Comparing the Behavior of a Packed Bed Reactor in the Catalytic Liquid-Phase Oxidation of Aqueous Phenol with Two Modes of Operation, Downflow and Upflow. the Operating Parameters Investigated Included Temperature, Reactor Pressure, Gas Flowrate, Liquid Hourly Space Velocity and Feed Concentration. Because of the Completely Wetted Catalyst, the Upflow Reactor Generally Performs Better for High Pressures and Low Feed Concentrations When the Liquid Reactant Limitation Controls the Rate. the Interaction between the Reactor Hydrodynamics, Mass Transfer, and Reaction Kinetics is Discussed. for Both Operation Modes, Complete Phenol Removal and Significant Total Organic Carbon (TOC) …
A Virtual Environment For Remote Testing Of Complex Systems, Loredana Cristaldi, Alessandro Ferrero, Antonello Monti, Ferdinanda Ponci, William Mckay, Roger A. Dougal
A Virtual Environment For Remote Testing Of Complex Systems, Loredana Cristaldi, Alessandro Ferrero, Antonello Monti, Ferdinanda Ponci, William Mckay, Roger A. Dougal
Faculty Publications
Complex systems, realized by integration of several components or subsystems, pose specific problems to simulation environments. It is, in fact, desirable to simulate the complex system altogether, and not component by component, since the operation of the single part depends on the surrounding system and an early verification can prevent damages and save time for modifications. The availability of detailed and validated models of the single parts is therefore critical. This task may be difficult to achieve. In fact, in industrial applications, where a system can be a mix of different devices produced by different manufacturers, the physical device may …
Working Postures Of Dentists And Dental Hygienists, Richard W. Marklin, Kevin Cherney
Working Postures Of Dentists And Dental Hygienists, Richard W. Marklin, Kevin Cherney
Mechanical Engineering Faculty Research and Publications
A joint study was conducted by a manufacturer of dental stools in the Midwest of the United
States and Marquette University to measure the occupational postures of dentists and dental hygienists. The postures of 10 dentists and 10 dental hygienists were assessed using work sampling and video techniques. Postura! data of the neck, shoulders and lower back were recorded from video and categorized into 30-degree intervals: O (neutral posture of respective joint), 30, 60 and 90 degrees. Each subject's postures were observed while they were treating patients during a four-hour period, during which 100 observations of postures were recorded at …
Turbo Space-Time Coding For Mimo Systems : Designs And Analyses, Hangjun Chen
Turbo Space-Time Coding For Mimo Systems : Designs And Analyses, Hangjun Chen
Dissertations
Multiple input multiple output (MIMO) systems can provide high diversity, high data rate or a mix of both, for wireless communications. This dissertation combines both modes and suggests analyses and techniques that advance the state of the art of MIMO systems. Specifically, this dissertation studies turbo space-time coding schemes for MIMO systems.
Before the designs of turbo space-time codes are presented, a fundamental tool to analyze and design turbo coding schemes, the extrinsic information transfer (EXIT) chart method, is extended from the binary/nonbinary code case to coded modulation case. This extension prepares the convergence analysis for turbo space-time code.
Turbo …
Experimental Technique For Studying High-Temperature Phase Equilibria In Reactive Molten Metal Based Systems, Alexandre Ermoline
Experimental Technique For Studying High-Temperature Phase Equilibria In Reactive Molten Metal Based Systems, Alexandre Ermoline
Dissertations
The general objective of this work is to develop an experimental technique for studying the high-temperature phase compositions and phase equilibria in molten metal-based binary and ternary systems, such as Zr-O-N, B-N-O, Al-O, and others. A specific material system of Zr-O-N was selected for studying and testing this technique.
The information about the high-temperature phase equilibria in reactive metal-based systems is scarce and their studying is difficult because of chemical reactions occurring between samples and essentially any container materials, and causing contamination of the system.
Containerless microgravity experiments for studying equilibria in molten metal-gas systems were designed to be conducted …
Congestion Control In Resilient Packet Ring Networks, Alharbi Fahd
Congestion Control In Resilient Packet Ring Networks, Alharbi Fahd
Dissertations
The Resilient Packet Ring (RPR) is a new metro technology; RPR shares SONET's ability in providing fast recovery from link and node failures as well as inherits the cost and simplicity of Ethernet. RPR, like SONET/SDH, is a ring based architecture consisting of two optical rotating rings (uni-directional). In RPR, packets are removed from the ring at the destination so that different segments of the ring can be used at the same time for different flows; as a result, the spatial reuse feature is achieved. Enabling the spatial reuse feature introduces the challenge of guaranteeing fairness among the nodes sharing …
Behavior Of Structural Concrete Members Strengthened By Composite Fabrics, Jian Chen
Behavior Of Structural Concrete Members Strengthened By Composite Fabrics, Jian Chen
Dissertations
The new technique of using Fiber Reinforced Polymer (FRP) materials to repair and strengthen various concrete members is becoming more and more popular in structural retrofitting field. Among all the confining materials, Carbon Fiber Reinforced Polymer (CFRP) fabric jackets are identified as an effective way to enhance the strength and ductility of concrete members due to its superior mechanical properties. This study investigates the detailed structural behavior of confined concrete members using CFRP fabric jackets by both analytical and experimental approaches.
A series of CFRP wrapped concrete cylinder tests were conducted to study the compressive stress-strain behavior for CFRP confined …
Detection Of Network Anomalies And Novel Attacks In The Internet Via Statistical Network Traffic Separation And Normality Prediction, Jun Jiang
Dissertations
With the advent and the explosive growth of the global Internet and the electronic commerce environment, adaptive/automatic network and service anomaly detection is fast gaining critical research and practical importance. If the next generation of network technology is to operate beyond the levels of current networks, it will require a set of well-designed tools for its management that will provide the capability of dynamically and reliably identifying network anomalies. Early detection of network anomalies and performance degradations is a key to rapid fault recovery and robust networking, and has been receiving increasing attention lately.
In this dissertation we present a …
The Feasibility Of Micromachined Dynamic Resonant Beam Coriolis True Mass Flow Meter, Sang Hwui Lee
The Feasibility Of Micromachined Dynamic Resonant Beam Coriolis True Mass Flow Meter, Sang Hwui Lee
Dissertations
The technological advances of micro-electro-mechanical systems (MEMS) in the past two decades have been remarkable for innovations in microfluidic systems as well as automotive applications such as pressure sensors and accelerometers. MEMS flow sensing has emerged as a field of interest in microfluidics, with a variety of sensing methods being miniaturized, such as thermal anemometry, ultrasonic sensing and flow measurement based on the Coriolis effect. Coriolis sensing is particularly attractive since, unlike most other methods which provide volumetric flow information, Coriolis sensing is capable of providing a direct, true mass flow measurement. Because of this advantage, Coriolis flow sensing has …
Corrosion Studies On Alpha Tantalum And Beta Tantalum Coated Steel, Sung Min Maeng
Corrosion Studies On Alpha Tantalum And Beta Tantalum Coated Steel, Sung Min Maeng
Dissertations
Tantalum coating by sputtering, one form of physical vapor deposition (PVD), has been investigated as a replacement for chromium coatings on gun bores to protect them from erosion and corrosion due to its high ductility and high corrosion resistance in aggressive environments. When deposited as a film on steel substrates by sputtering, either α-Ta, β-Ta, or a mixture of both phases have been observed under varying deposition conditions. To evaluate corrosion behavior of Ta coatings, electrochemical impedance spectroscopy and potentiodynamic polarization were conducted as a function of coating thickness. The coating porosity was observed to decrease with increasing coating thickness …
Image Data Hiding, Zhicheng Ni
Image Data Hiding, Zhicheng Ni
Dissertations
Image data hiding represents a class of processes used to embed data into cover images.
Robustness is one of the basic requirements for image data hiding. In the first part of this dissertation, 2D and 3D interleaving techniques associated with error-correction-code (ECC) are proposed to significantly improve the robustness of hidden data against burst errors.
In most cases, the cover image cannot be inverted back to the original image after the hidden data are retrieved. In this dissertation, one novel reversible (lossless) data hiding technique is then introduced. This technique is based on the histogram modification, which can embed a …
Bus Arrival Time Prediction Using Stochastic Time Series And Markov Chains, Rajat Rajbhandari
Bus Arrival Time Prediction Using Stochastic Time Series And Markov Chains, Rajat Rajbhandari
Dissertations
Public transit agencies rely on disseminating accurate and reliable information to transit users to achieve higher service quality and attract more users. With the development of new technologies, the concept of providing users with reliable information about bus arrival times at bus stops has become increasingly attractive. Due to the fact that bus operation parameters and variables are highly stochastic, modeling prediction of bus travel and arrival times has become one of the many challenging tasks.
Stochastic time series and delay propagation models to predict bus arrival times using historical information were developed. Markov models were developed to predict propagation …
Uniaxial And Triaxial Behavior Of High Strength Concrete With And Without Steel Fibers, Xiaobin Lu
Uniaxial And Triaxial Behavior Of High Strength Concrete With And Without Steel Fibers, Xiaobin Lu
Dissertations
This study first presents an extensive experimental research program on the true uniaxial and triaxial compression behavior for both high strength concrete (HSC) and steel fiber reinforced high strength concrete (SFHSC). The experimental study mainly focuses on the octahedral shear stress strain relationship of those two types of concrete, which is adopted as the basis to develop a new incremental constitutive model. Emphasis is also put on the investigation of the variation of tangent Poisson's ratio under not only uniaxial but also triaxial stress conditions. The effect of cyclic loading on this parameter is also addressed.
According to this research, …
Computational Studies Of Viscoelastic Multiphase Flows, Shriram B. Pillapakkam
Computational Studies Of Viscoelastic Multiphase Flows, Shriram B. Pillapakkam
Dissertations
A finite element code based on the level set method is developed for performing two and three dimensional direct numerical simulations (DNS) of viscoelastic two-phase flow problems. The Oldroyd-B constitutive equation is used to model the viscoelastic liquid. The code is used to study transient and steady state shapes of Newtonian and viscoelastic drops in simple shear and buoyancy driven flows. The roles of the governing dimensionless parameters: Capillary number (Ca), Deborah Number (De) and the polymer concentration parameter c, in determining deformation of drops and bubbles, are also analyzed.
The numerical code permits us to vary Ca, De and …
Development And Application Of Fractionation Procedure For Drinking Water Organic Matters, Yong Pu
Development And Application Of Fractionation Procedure For Drinking Water Organic Matters, Yong Pu
Dissertations
USEPA mandates a control of disinfection by-products (DBPs) in finished drinking water and recommends reduction of natural organic matters (NOM), DBP precursors, to achieve this regulatory goal. Studies relating NOM with DBP include fractionation of water samples, characterization of collected organic fractions, fractions' formation potential tests, and jar or similar tests to remove NOM. This study discussed a current resin fractionation procedure on principle, procedure, and its efficiency when applied to water samples of low NOM (< 5mgIL). The primary objective of this research is to develop a fractionation procedure intended for water of low NOM by carefully applying mass balance concept through each fraction's fractionation and a selection of stable ion exchange resins. A new protocol was presented with triple columns of XAD-8 adsorption resin, one column of AG-MP-50 cationic resin, and another column of WA 10 weak anionic resin in sequence. This protocol was experimented and confirmed for its efficiency (±10% loss of mass) with samples from Canal Road (CR) and Raritan Millstone (RM) surface water treatment plants (WTPs) in central New Jersey. The second objective of this study is to develop a statistical model with a potential of online delineation of organic fractions of NOM. The resulting model based on samples of Passaic Valley Water Commission (PVWC) WTP in northern New Jersey was applied to predict organic fractions of samples from CR and RM plants. Paired T-test (paired t ratio 1.15 < t critical 2.02) indicated a good correlation between the predicted and actual fraction concentration. Finally, samples of Middlesex Water Company (MWC) were fractionated and Trihalomethane formation potential tests (THMFP) on collected fraction showed hydrophilic matters possessed a higher potential to produce TTHM in finished water than hydrophobic matter. Jar tests indicated while coagulation was effective in removing hydrophobic matter, it may not be optimum for removal of hydrophilic matter.
This study developed an accurate fractionation procedure for low NOM waters. It provided a better understanding of organic matter transformation at different treatment …