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Articles 2911 - 2940 of 3180

Full-Text Articles in Engineering

Polymer-Based Rf Mems Devices, Jianqun Wang Aug 2007

Polymer-Based Rf Mems Devices, Jianqun Wang

Electrical Engineering Dissertations - Archive

The radio frequency micro-electro-mechanical system (RF MEMS) technology is rapidly transitioning from the research stage to commercial applications. Reducing material and fabrication costs, realizing IC compatibility, and improving the RF performance have been main focal points of many recent works. In this dissertation, we target at developing a RF MEMS methodology which realizes CMOS compatibility, cost effectiveness and high performance at the same time. The current RF MEMS devices are mostly constructed on quartz and III-V compound materials to achieve low RF losses. These approaches proved to have excellent RF performance. However these materials are expensive and unable to be …

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Model Reference Adaptive Control Using Stacked Identifiers, Weider Chung Aug 2007

Model Reference Adaptive Control Using Stacked Identifiers, Weider Chung

Electrical Engineering Dissertations - Archive

Model reference adaptive control is a major design method for controlling plants with uncertain parameters. The primary objective of this dissertation is to develop a new design approach for the model reference adaptive control of a single-input single-output linear time-invariant plant. The proposed method, called the "Model reference adaptive control using stacked identifiers," uses a stacked identifier structure that is new to the field of adaptive control. The goal is to make the output of the plant asymptotically track the output of the first identifier, and then driving the output of the first identifier to track that of the second …

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1/F Noise In Hafnium Based High-K Gate Dielectric Mosfets And A Review Of Modeling, Siva Prasad Devireddy Aug 2007

1/F Noise In Hafnium Based High-K Gate Dielectric Mosfets And A Review Of Modeling, Siva Prasad Devireddy

Electrical Engineering Dissertations - Archive

For next generation MOSFETs, the constant field scaling rule dictates a reduction in the gate oxide thickness among other parameters. Consequently, gate leakage current becomes a serious issue with very thin SiO2 that is conventionally used as gate dielectric since it is the native oxide for Si substrate. This has driven an industry wide search for suitable alternate 'high-k' gate dielectric that has a high value of relative permittivity compared to SiO2 thereby presenting a physically thicker barrier for tunneling carriers while providing a high gate capacitance. Consequently, it is essential to study the properties of these novel materials and …

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Sequences Of Near-Optimal Feedforward Neural Networks, Pramod Lakshmi Narasimha Aug 2007

Sequences Of Near-Optimal Feedforward Neural Networks, Pramod Lakshmi Narasimha

Electrical Engineering Dissertations - Archive

In order to facilitate complexity optimization in feedforward networks, several integrated growing and pruning algorithms are developed. First, a growing scheme is reviewed which iteratively adds new hidden units to full-trained networks. Then, a non-heuristic one-pass pruning technique is reviewed, which utilizes orthogonal least squares. Based upon pruning, a one-pass approach is developed for producing the validation error versus network size curve. Then, a combined approach is devised in which grown networks are pruned. As a result, the hidden units are ordered according to their usefulness, and less useful units are eliminated. In several examples, it is shown that networks …

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Optimization Of Coupling From A Sub-Wavelength Metal Nanoaperture To A Gaussian Mode, Muthiah Annamalai Aug 2007

Optimization Of Coupling From A Sub-Wavelength Metal Nanoaperture To A Gaussian Mode, Muthiah Annamalai

Electrical Engineering Theses - Archive

We model the surface resonance effects in a 1D-array of corrugations on a metal-dielectric film with a sub-wavelength nanoaperture, following the earlier work by Moreno et-al [Moreno:2003]. We are interested in computing the coupling of the highly-directional light field emerging from the metal nanoaperture to the lowest-order Gaussian mode. We follow the approach by Vasilyev [Vasilyev:2005], to compute the coupling to a fundamental Gaussian mode. We have developed an optimization routine to compute the field emission patterns from a metal nanoaperture, resonant wavelength and transmission coupling to fundamental Gaussian mode for various geometrical parameters of the metal nanoastructure. We optimize …

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A Robust Cooperative Localization System For A Heterogeneous Team Of Small Unmanned Ground Vehicles, Veera Jawahar Vibeeshanan Aug 2007

A Robust Cooperative Localization System For A Heterogeneous Team Of Small Unmanned Ground Vehicles, Veera Jawahar Vibeeshanan

Industrial, Manufacturing, and Systems Engineering Dissertations - Archive

This dissertation presents an organic approach to the cooperative localization problem by sequentially solving the problems of sensor calibration, multi-sensor fusion filtering, and cooperative localization. Successful navigation of unmanned ground vehicles requires accurate localization. Localization refers to the determination of the pose (position and orientation) of an unmanned ground vehicle with respect to a local or a global frame of reference. Cooperative localization is suited to multi-vehicle systems where vehicles with better accuracy in localization can assist those with poor accuracy through communication and relative pose sensing. A parametric modeling approach is presented for sensor calibration. Designed experiments are conducted …

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Integrated Nurse Staffing And Assignment Under Uncertainty, Prattana Punnakitikashem Aug 2007

Integrated Nurse Staffing And Assignment Under Uncertainty, Prattana Punnakitikashem

Industrial, Manufacturing, and Systems Engineering Dissertations - Archive

One of the major problems in the United States health care system is a shortage of nurses. Baby boomers and an increasing elderly population are the main reasons for a rapidly growing demand for nurses. Besides the decline in enrollments in registered nurse degree programs, many nurses have suffered from work burnout. High workloads and undesirable schedules are two major issues that cause nurses' job dissatisfaction. As a result, nurses plan to leave their jobs causing low retention and low entering rates. One consequence of the shortage is that excessive workload on nurses decreases the quality of patient care. Many …

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A Data-Integrated Simulation-Based Optimization Approach For Nurse-Patient Assignment, Duraikannan Sundaramoorthi Aug 2007

A Data-Integrated Simulation-Based Optimization Approach For Nurse-Patient Assignment, Duraikannan Sundaramoorthi

Industrial, Manufacturing, and Systems Engineering Dissertations - Archive

This research develops a novel data-integrated simulation to evaluate nurse-patient assignments (SIMNA) based on a real data set provided by Baylor Regional Medical Center (Baylor) in Grapevine, Texas. Tree-based models and kernel density estimation were utilized to extract important knowledge from the data for the simulation. Classification and Regression Tree models, data mining tools for prediction and classification, were used to develop five tree structures: (a) four classification trees, from which transition probabilities for nurse movements are determined; and (b) a regression tree, from which the amount of time a nurse spends in a location is predicted based on factors …

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Capacity Estimation Of Two-Sided Type C Weaves On Freeway, Phong Thanh Vo Jul 2007

Capacity Estimation Of Two-Sided Type C Weaves On Freeway, Phong Thanh Vo

Civil Engineering Dissertations - Archive

A weaving section is a common design on major highway facilities that has been an interest to researchers for years. Weaving areas are characterized by frequent lane changes, which significantly reduce the capacity of the freeway system. The 2000 Highway Capacity Manual (HCM) defined weaving capacity as "any combination of flows that causes the density to reach the LOS E/F boundary condition of 43 pcpmpl for freeways" based on configuration, number of lanes in the weaving section, free-flow speed, length of the weave, and volume ratio (VR). However, no research has been focused on the two-sided type C weaves, which …

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Development Of Quality-Aware Video Systems And Nmr Spectrum Registration, Basavaraj Hiremath Jul 2007

Development Of Quality-Aware Video Systems And Nmr Spectrum Registration, Basavaraj Hiremath

Electrical Engineering Theses - Archive

The work introduces a novel concept of Quality-Aware Video (QAV) System and demonstrates its successful implementation. During the course, it develops algorithms for reduced reference video quality assessment and for data hiding. The idea here is to extract quality defining features of the video sequence and embed them in the original video without causing any perceptual changes to obtain QAV. Such a QAV can then be exposed to distortions and adverse attacks that affect the perceptual quality of the video. At the receiving end, the algorithm extracts the quality features of the distorted video, decode the original video quality features, …

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Modeling Isotropic Organs Using Beam Models For The Haptic Simulation Of Blunt Dissections Of Bile Duct, Vishal Dalmiya Jul 2007

Modeling Isotropic Organs Using Beam Models For The Haptic Simulation Of Blunt Dissections Of Bile Duct, Vishal Dalmiya

Electrical Engineering Theses - Archive

Haptic modeling of organs using existing approaches is still not realistic and/or real time. We propose and develop the mathematical foundation of a new approach to modeling organs using beams. Beams are well known entities in Civil and Structural engineering. We develop their mathematical properties in the context of organ characteristics. The real time advantage arises from the fact that a single beam implementation eliminates hundreds, if not thousands of mass springs from the traditional mass spring models and, thousands of polygons from the finite element method (FEM). Even more importantly, our derivation works for both large and small deflections. …

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Detection And Opportunistic Spectrum Access In Sensor Networks, Hung Dinh Ly Jul 2007

Detection And Opportunistic Spectrum Access In Sensor Networks, Hung Dinh Ly

Electrical Engineering Theses - Archive

This thesis examines target detection problems in Radar Sensor Networks (RSN) and opportunistic spectrum access problem in Cognitive Sensor Networks (CSN). First, studies on the Space-Time Adaptive Processing (STAP) and radar waveform design are provided. Investigation into the target detection performance gain of RSN when STAP and radar waveform design are combined in RSN is then performed. Studies in this thesis show that detection performance of RSN using our proposal is superior to that of a single radar system using STAP only. To further studies on target detection, the multi-target detection problem in RSN is also examined. Signal, interference, and …

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Dynamic Chracteristics And Stability Analysis Of Muncipal Solid Waste In Bioreactor Landfills, Mohamed Adil Haque Jul 2007

Dynamic Chracteristics And Stability Analysis Of Muncipal Solid Waste In Bioreactor Landfills, Mohamed Adil Haque

Civil Engineering Dissertations - Archive

Bioreactor landfills are operated to enhance refuse decomposition, gas production, and waste stabilization. The major aspect of bioreactor landfill operation is the recirculation of generated leachate back through the refuse mass. Due to the accelerated decomposition and settlement of solid waste, bioreactor landfills are gaining popularity as an alternative to the conventional landfill designed under Subtitle D regulations. However, recirculation of leachate or addition of water to accelerate the waste decomposition changes the biodegradation and geotechnical characteristics of waste mass. Our understanding of changes in engineering characteristics of solid waste with accelerated decomposition is limited. There is a need to …

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Wireless Sensor Network Lifetime Analysis And Energy Efficient Techniques, Haining Shu Jul 2007

Wireless Sensor Network Lifetime Analysis And Energy Efficient Techniques, Haining Shu

Electrical Engineering Dissertations - Archive

Wireless microsensor networks is one of the most important technologies for the 21st century. In distributed sensor networks energy-aware techniques are used to reduce energy consumption. Various sensor network applications have taken energy efficiency into consideration. This thesis report focuses on a new approach based on fuzzy logic systems to analyze the lifetime of a wireless sensor network. It demonstrates that a type-2 fuzzy membership function (MF), i.e., a Gaussian MF with uncertain standard deviation (std) is most appropriate to model a single node lifetime in wireless sensor networks. This research studies two basic sensor placement schemes: square-grid and hex-grid. …

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Power Control And Multi-Target Identification In Cognitive Wireless Networks, Hong-Sam Thi Le Jul 2007

Power Control And Multi-Target Identification In Cognitive Wireless Networks, Hong-Sam Thi Le

Electrical Engineering Theses - Archive

Recent research results have shown that cognitive wireless networks (CWN) have the potential to alleviate spectrum scarcity problem resulting from current policies for radio resource allocation management and dramatically improve the overall performance of communication systems. Unlike conventional wireless networks, which lack the flexibility and adaptation in their operations, CWNs exploit cognitive radio technology which provides cognitive wireless devices with the ability to sense the situation, adapt to the environment and take appropriate actions correspondingly. There have been many challenges in building a fully functional CWN. New developments and approaches need to be proposed to allow radio users to share …

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Synthesis And Characterization Of Polythiophene Derivatives, Xin Chen May 2007

Synthesis And Characterization Of Polythiophene Derivatives, Xin Chen

Material Science and Engineering Dissertations - Archive

In Chapter 1, the history of conducting polymers, especially polythiophene and its derivatives, was briefly reviewed. Different approaches of structural modifications to afford small bandgap polythiophene derivatives were discussed. The emergence of metal-containing polymers (metallopolymers) as functional materials has attracted tremendous attention around the world. Introducing metals into thiophene-based oligomers and polymers, whether the backbone or the side chain of the p-conjugated framework, the electronic, optical, or magnetic properties of the material are expected to by significantly affected by metals through various mechanisms. Synthesis methods to prepare poly(thienylene vinylene) were also briefly reviewed in this chapter. In Chapter 2, the …

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Autonomous And Cooperative Multi-Uav Guidance In Adversarial Environment, Ugur Zengin May 2007

Autonomous And Cooperative Multi-Uav Guidance In Adversarial Environment, Ugur Zengin

Mechanical and Aerospace Engineering Dissertations - Archive

The research presented in this dissertation is aimed at developing rule-based autonomous and cooperative guidance strategies for UAVs to perform missions such as path planning, target tracking and rendezvous while reducing their risk/threat exposure level, and avoiding threats and/or obstacles by utilizing measurement information provided by sensors. First, a mathematical formulation is developed to represent the area of operation that contains various types of threats, obstacles, restricted areas, in a single framework. Once constructed, there will be no need to distinguish between adversaries as the framework already contains the information on what needs to be avoided and the level of …

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Design, Analysis And Development Of A Morphable Wing Structure For Unmanned Aerial Vehicle Performance Augmentation, Abhijit Hiraman Supekar May 2007

Design, Analysis And Development Of A Morphable Wing Structure For Unmanned Aerial Vehicle Performance Augmentation, Abhijit Hiraman Supekar

Mechanical and Aerospace Engineering Theses - Archive

In this research, we propose mechanisms to continuously morph a wing from a lower aspect ratio to a higher and to further extremities of a gull and an inverted-gull configuration. The mechanism comprises of a linear actuator for the extension of the wing and the servo motors to obtain the gull and inverted gull configurations. The initial design and preliminary finite element representation using 3D-beams and plates in ANSYS Classic were the benchmarks to proceed for the detailed structural analysis of the complete wing in ANSYS Workbench. An elliptical pressure distribution at the quarter cord is assumed for the linear …

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Design And Implementation Of A Feedback Linearizing Controller And Kalman Filter For A Magnetic Levitation System, John Andrew Henley May 2007

Design And Implementation Of A Feedback Linearizing Controller And Kalman Filter For A Magnetic Levitation System, John Andrew Henley

Mechanical and Aerospace Engineering Theses - Archive

The principal investigation undertaken in this research is the development and subsequent implementation of a feedback linearizing nonlinear controller and extended Kalman filter for a laboratory-based Magnetic Levitation (Maglev) device. The Maglev hardware is both highly nonlinear and open-loop unstable in its dynamic response. The control and estimation scheme proposed in this work is first validated using an increasingly sophisticated level of simulations. The control and estimation algorithm had the sensor noise identified using hardware data. Then, the plant noise covariance is tuned using both on-line and off-line hardware data. Additionally, the output of the nonlinear controller is then mapped …

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Experimental Study Of Laminated Composite Tubes Under Bending, Puneet Saggar May 2007

Experimental Study Of Laminated Composite Tubes Under Bending, Puneet Saggar

Material Science and Engineering Theses - Archive

Bending stiffness of laminated composite tubes was determined experimentally using four-point bending test. The experimental results were compared with the results obtained by the laminated plate and smear property approaches. The results indicate that experimental values are closer to prediction of the laminated plate approach compared to smear property approach. Effects of tube radius and stacking sequence and fiber orientation of the walled thickness laminate on bending stiffness and strength of composite tubes were studied. Fracture analysis was conducted to investigate the failure process of the tube. Both techniques of x-ray radiography and optical microscopy were used in this study. …

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A Generic Stability And Control Tool For Flight Vehicle Conceptual Design: Aeromech Software Development, Gary John Coleman May 2007

A Generic Stability And Control Tool For Flight Vehicle Conceptual Design: Aeromech Software Development, Gary John Coleman

Mechanical and Aerospace Engineering Theses - Archive

During the conceptual design (CD) phase, various solution concepts must, and should, be explored to select the best flight vehicle size and configuration in order to meet the mission requirements. As the aerospace industry advances novel aerospace flight vehicle configurations promising larger operational performance and overall efficiency, demanding integrated flight vehicles like the flying wing configuration (FWC) or blending wing body (BWB) are under investigation. Some of these novel configurations rely on novel control effectors (CE) and complex flight control systems in order to obtain the desired performance objectives. Clearly, stability and control plays an important roll in the design …

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Experimental Studies To Address Strengths Of Limestone Cores, Sulfate Heave Problems In Limestone Cores And Tunnel Lining, Vivekananda Chikyala May 2007

Experimental Studies To Address Strengths Of Limestone Cores, Sulfate Heave Problems In Limestone Cores And Tunnel Lining, Vivekananda Chikyala

Civil Engineering Theses - Archive

Sulfate induced heave is a common scenario in tunnels located on sedimentary rocks containing Pyrites. Pyrite oxidation produces Gypsum which is a major source of natural sulfates. DART NC -1B tunnel is located in Dallas, north Texas. Dallas is located on sedimentary rocks with high Pyrite content and has a history of sulfate induced heave problems in several projects. In spring 2005 & 2006, the shotcrete liner in DART NC-1B tunnel showed cracking associated with water leaks. Considering the local geology and the history of the tunnel, researchers at The University of Texas at Arlington (UTA) suspected probable occurrence of …

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Performance Studies On Rigid Pavement Sections Built On Stabilized Sulfate Soils, Deepti Vasudev May 2007

Performance Studies On Rigid Pavement Sections Built On Stabilized Sulfate Soils, Deepti Vasudev

Civil Engineering Theses - Archive

Soils of Southeast Arlington are highly expansive and rich in sulfates. They undergo sulfate induced heaving when traditional calcium based stabilizers are used for soil stabilization (Puppala et al. 1998). Traditional stabilizers do not provide effective solution since they are known to induce heaving, termed in the literature as sulfate induced heaving (Hunter, 1988). Both swelling and softening of these soils rich in sulfates induce considerable damage to overlying pavement infrastructure. Typically, high sulfate soils treated with calcium based stabilizers form ettringite mineral. Ettringite undergoes heaving when hydrated (Hunter, 1988; Puppala et al. 2001). Since this sulfate-induced heave is caused …

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Tissue And Vascular Oxygenation Dynamics Determined By Optical Approaches And Mri, Mengna Xia May 2007

Tissue And Vascular Oxygenation Dynamics Determined By Optical Approaches And Mri, Mengna Xia

Bioengineering Dissertations - Archive

Tumor oxygenation is a crucial factor to determine the efficiency of non-surgery therapy, such as radiotherapy and chemotherapy. Therefore, various approaches have been applied to tumor in order to improve the tumor oxygen level. Breathing oxygenrich gas with normobaric or hyperbaric pressure has been demonstrated to overcome hypoxia, but with marginal success. Therefore, the outcome would be improved greatly, if the responsive tumors were identified a priori. Two non-invasive techniques were applied to monitor tumor oxygenation dynamics simultaneously when rats were exposed to hyperoxic gas intervention. 19F MRI provides tumor tissue oxygen tension (pO2) images, while Near Infrared Spectroscopy (NIRS) …

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Effects Of A Debonding Flaw Size And Location On The Flexural Performance Of Cfrp Retrofitted Steel Sections, Sharad C. Choudhary May 2007

Effects Of A Debonding Flaw Size And Location On The Flexural Performance Of Cfrp Retrofitted Steel Sections, Sharad C. Choudhary

Civil Engineering Theses - Archive

In US there are several thousand steel bridges at present. Out of them many bridges are at various level of advance deteriorations due to many years of service life and environmental factors. These bridges cannot be fully replaced so retrofitting is the best choice .Earlier steel plates were used. With introduction of FRP in 1960.It is replacing the steel plates as they are lighter in weight and can be made stronger than steel. While installation of these FRP some kinds of Flaws are encountered. The variation of strength of carbon fiber reinforced laminate used for structural repair or strengthening containing …

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Wireless Sensor Network Testbed: Measurement And Analysis, Rahul Pramod Sawant May 2007

Wireless Sensor Network Testbed: Measurement And Analysis, Rahul Pramod Sawant

Electrical Engineering Theses - Archive

Energy conservation is critical in Wireless Sensor Networks. Replacing or recharging batteries is not an option for sensors deployed in hostile environments. Generally communication electronics in the sensor utilizes most energy. This thesis studies the effect of changing the transmission power and baud rate on transmission distance. Using Shannon channel capacity formula and Log - Distance Path Loss Model, transmission distance is shown to be related to transmit power and baud rate. Extensive empirical readings are taken to confirm the above relation. The path loss exponent got as a result of data fitting is within the acceptable range for wireless …

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Electromagnetically Actuated Devices For Optical Coherence Tomography Applications, Hans P. Hu May 2007

Electromagnetically Actuated Devices For Optical Coherence Tomography Applications, Hans P. Hu

Electrical Engineering Dissertations - Archive

A fast optical scanning device has always been desired for numerous applications such as biomedical imaging, optical communications, and variety of sensing and actuating applications. This dissertation presents a new scanning device operated using external magnetic field with low cost, high function versatility, low field strength, and low power consumption. The design architecture of this device shows its potential for in vivo application with an advantage that addresses the concern of safety. Materials properties are examined using alternating gradient magnetometer(AGM) to verify its performance. Pressure and temperature invariant fabrication processes are implemented to make this device without complicated equipments. The …

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Discrete-Time Control Algorithms And Adaptive Intelligent Systems Designs, Asma Azmi Al-Tamimi May 2007

Discrete-Time Control Algorithms And Adaptive Intelligent Systems Designs, Asma Azmi Al-Tamimi

Electrical Engineering Dissertations - Archive

In this work, approximate dynamic programming (ADP) designs based on adaptive critic structures are developed to solve the discrete-time optimal control problems in which the state and action spaces are continuous. This work considers linear discrete-time systems as well as nonlinear discrete-time systems that are affine in the input. This research resulted in forward-in-time reinforcement learning algorithms that converge to the solution of the Generalized Algebraic Riccati Equation (GARE) for linear systems. For the nonlinear case, a forward-in-time reinforcement learning algorithm is presented that converges to the solution of the associated Hamilton-Jacobi Bellman equation (HJB). The results in the linear …

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Performance Analysis Of Dpsk Systems With Mimo Employing Egc Over Wireless Fading Channels, Iyad Al Falujah May 2007

Performance Analysis Of Dpsk Systems With Mimo Employing Egc Over Wireless Fading Channels, Iyad Al Falujah

Electrical Engineering Dissertations - Archive

The proliferation of digital wireless communication services has increased the congestion of the available radio spectrum. In addition to that, wireless communications are encountered by multipath channel fading. To alleviate the scarcity of the radio spectrum and multipath channel fading, attention in this dissertation is placed on differentially coherent phase shift keying (DPSK) systems with equal gain combining (EGC) diversity reception. DPSK systems are capable of achieving high spectral efficiency with adequate performance over wireless fading channels. Several wireless communication systems have adopted DPSK such as the time division multiple access (TDMA) version of the North American Digital Cellular (NADC) …

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Investigation Of Information Processing And Cognitive Performance Capacities With Different Instrumentation Configurations, Saju John Mathew May 2007

Investigation Of Information Processing And Cognitive Performance Capacities With Different Instrumentation Configurations, Saju John Mathew

Bioengineering Theses - Archive

The focus of this thesis is the investigation of two new performance capacity tests related to a concept known as "situational awareness": 1) Visual Motor Multitask Performance Capacity (VMMPC) and 2) Visual Auditory Information Processing Dexterity (VAIPD). These represent major components of human information processing and are therefore important in situations ranging from driving and other activities of daily living to occupational and sport tasks. These tests have been recently designed and implemented on a laboratory-based instrument called the BEP I. In the present project, they are implemented on a different, more portable platform that is under development and known …

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