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Full-Text Articles in Engineering

A General Code To Simulate The Effect Of Indirect Lightning On Overhead Lines Using Emtp-Type Programs, Hasan Jun 2016

A General Code To Simulate The Effect Of Indirect Lightning On Overhead Lines Using Emtp-Type Programs, Hasan

Master's Theses

In this thesis, a general code is obtained to allow the simulation of the transient response of transmission lines excited by a nearby lightning stroke using EMTP–type programs, namely PSCAD and ATP.

Initially, the frequency domain modeling of single phase and multiconductor transmission lines is described and assessed by means of several application examples. As a second stage, the transmission line model is used to implement an illuminated transmission line model (line excited by an electromagnetic field excitation) using Taylor’s formulation. Then, a general code is developed in MATLAB to obtain the response of a field excited line ...


Microwave Nondestructive Evaluation Of Aircraft Radomes, David Bennett Johnson Jan 2008

Microwave Nondestructive Evaluation Of Aircraft Radomes, David Bennett Johnson

Retrospective Theses and Dissertations

As the aviation industry continues to experience increased demand on maintenance turn-around time with decreased budgets, the airlines in particular seek advances in cost and efficiency for inspection technology. Such improvements not only increase aviation safety, but also lead to significant cost savings and avoidances. One particular inspection need is that of aircraft radomes, often found as the nosecone such as that seen in Figure 1.1, housing the plane's weather radar. This structure, fabricated out of low-loss/permittivity composite materials (such as fiberglass), must appear as "electrically transparent" as possible to the radar. Like a window to the ...


An Examination Of Single Link Failure In An Optical Network With Full Grooming, David Lastine Jan 2007

An Examination Of Single Link Failure In An Optical Network With Full Grooming, David Lastine

Retrospective Theses and Dissertations

This thesis considers a survivable optical network with link-based protection that can survive one fault, has links each with a fixed total bidirectional capacity, and full grooming at each node. An upper bound on the total primary capacity the network can provide is derived from conditions that are necessary but not sufficient to guarantee restoration. An ILP formulation is developed and presented that achieves this bound when possible for a given topology, and tends to spread out backup capacity by insisting on using small cycles to form backup routes. The blocking probability of connections in a network thus protected is ...


Assessing Placement Of Controllers And Nonlinear Behavior Of Electrical Power System Using Normal Form Information , Shu Liu Jan 2006

Assessing Placement Of Controllers And Nonlinear Behavior Of Electrical Power System Using Normal Form Information , Shu Liu

Retrospective Theses and Dissertations

In this dissertation, normal form (NF) theory is used to characterize and quantify nonlinear modal interaction near critical equilibria. The research focus is on the analysis of second-order modal interaction and the study of nonlinear aspects of system behavior of interest to the design and location of system controllers;A systematic approach to derive second-order NF representations in the neighborhood of equilibrium points is presented. Nonlinear interaction measures based on this model are then obtained to assess the extent and distribution of nonlinearity in the system. Finally, analytical criteria are developed to predict the existence of nonlinear modal interactions that ...


Transmission System Reconfiguration For Corrective Control , Wei Shao Jan 2006

Transmission System Reconfiguration For Corrective Control , Wei Shao

Retrospective Theses and Dissertations

When a power system is in the alert state, a severe contingency may bring the system into the emergency state, resulting in overloads, voltage violations, cascading failures, or even loss of stability, and force system operators to take appropriate corrective control actions. It is widely known that transmission system reconfiguration (TSR), including transmission line switching, bus-bar switching, shunt element switching, transformer tap changing, and FACTS control, may change the states of the power systems, and consequently, affect the distribution of power flows, transmission losses, short circuit currents, voltage profiles as well as the transient stability of power systems. Under the ...


Condition-Based Hazard Rate Estimation And Optimal Maintenance Scheduling For Electrical Transmission System , Jiang Yong Jan 2006

Condition-Based Hazard Rate Estimation And Optimal Maintenance Scheduling For Electrical Transmission System , Jiang Yong

Retrospective Theses and Dissertations

The effectiveness of expending maintenance resources can vary dramatically depending on the target and timing of the maintenance activities. The objective of the work to develop a method of allocating economic resources and scheduling maintenance tasks among bulk transmission system equipment, so as to optimize the effect of maintenance with respect to the mitigation of component failure consequences. Techniques including condition-based failure rate estimation of electric transmission system components, analysis of failure consequences in power system, probabilistic modeling and risk assessment, and optimization are integrated in the work. Hidden Markov model is a good tool to estimate instantaneous status for ...


An Integrated Placement And Routing Approach , Min Pan Jan 2006

An Integrated Placement And Routing Approach , Min Pan

Retrospective Theses and Dissertations

As the feature size continues scaling down, interconnects become the major contributor of signal delay. Since interconnects are mainly determined by placement and routing, these two stages play key roles to achieve high performance. Historically, they are divided into two separate stages to make the problem tractable. Therefore, the routing information is not available during the placement process. Net models such as HPWL, are employed to approximate the routing to simplify the placement problem. However, the good placement in terms of these objectives may not be routable at all in the routing stage because different objectives are optimized in placement ...


Security Enhancement In Passive Optical Networks Through Wavelength Hopping And Sequences Cycling Technique , Walid Suleiman Shawbaki Jan 2006

Security Enhancement In Passive Optical Networks Through Wavelength Hopping And Sequences Cycling Technique , Walid Suleiman Shawbaki

Retrospective Theses and Dissertations

Growth in the telecommunication industry continues to expand with requirements evolving around increased bandwidth and security. Advances in networking technologies have introduced low cost optical components that has made passive optical networks (PON) the choice for providing huge bandwidth to end users. PON are covered by established standards such as IEEE 802.3ah and ITU-T G.983.1/984.1, with star topology of broadcast and select (B&S) on shared fiber links that poses security vulnerability in terms of confidentiality and privacy;Research and reports in the literature focus around increasing cardinality via coding schemes that lack in addressing security, which was left for implementation in application layers via cryptography. This dissertation presents an ...


Spatial Signal Processing In Wireless Sensor Networks , Benhong Zhang Jan 2006

Spatial Signal Processing In Wireless Sensor Networks , Benhong Zhang

Retrospective Theses and Dissertations

Wireless sensor networks (WSNs) are gaining attention in recent years. Considering the potential low cost of a single sensor-processor unit in the near future, it is envisioned that there will be large-scale deployments of sensor networks for various applications: environmental, medical, inventory control, energy management, structural health monitoring, etc. A WSN comprises of a large number of nodes that individually have limited energy and computational power; however, by cooperating with each other, they can jointly perform tasks that are difficult to handle by traditional centralized sensing systems;In this dissertation, spatial and spatio-temporal signal processing methods are developed for WSNs ...


Yield And Performance Enhancement Of Analog And Mixed Signal Circuits , Yu Lin Jan 2006

Yield And Performance Enhancement Of Analog And Mixed Signal Circuits , Yu Lin

Retrospective Theses and Dissertations

Parametric yield models for widely used area allocation schemes in ratio-critical analog circuits are developed in this dissertation. It is shown that some of the most widely used area allocation schemes are suboptimal and that significant improvements in parametric yield can be achieved with less intuitive area allocation approaches such as the optimal and near-optimal area allocation methods introduced in this work. Simulations and experimental results are presented which show quantitatively what improvements in yield can be achieved with improved area allocation strategies for resistive feedback amplifiers and R-2R DACs;A strategy to optimize the power consumption in a class ...


Nanocrystalline Silicon Thin Film Transistors , Durga Prasanna Panda Jan 2006

Nanocrystalline Silicon Thin Film Transistors , Durga Prasanna Panda

Retrospective Theses and Dissertations

Flexible, large area circuits represent a new form of electronics which have led to rapidly rising and promising applications in displays, sensors, medical devices and other areas. The most important challenge in realizing these macroelectronic systems is fabricating the required thin film transistors on plastic substrates with a low thermal budget. Here most TFTs are fabricated using amorphous silicon (a-Si) as the active channel layer and amorphous silicon nitride as the gate dielectric layer. Low device mobility and electrical instability are the main disadvantages of a-Si TFT. Laser annealed polycrystalline silicon TFTs offer much better device performance and stability, and ...


Damping Controller Design For Facts Devices In Power Systems Using Novel Control Techniques , Qian Liu Jan 2006

Damping Controller Design For Facts Devices In Power Systems Using Novel Control Techniques , Qian Liu

Retrospective Theses and Dissertations

Power systems are under increasing stress as deregulation introduces several new economic objectives for operation. Since power systems are being operated close to their limits, weak connections, unexpected events, hidden failures in protection system, human errors, and a host of other factors may cause a system to lose stability and even lead to catastrophic failure. Therefore, the need for improved system damping in a wider operating range is gaining more attention. Among the available damping control methods, each approach has advantages and disadvantages in different systems. The effectiveness of damping control depends on the devices chosen, the system modal feature ...


Uniform Resource Visualization , Kukjin Lee Jan 2006

Uniform Resource Visualization , Kukjin Lee

Retrospective Theses and Dissertations

Computing environments continue to increase in scale, heterogeneity, and hierarchy, with resource usage varying dynamically during program execution. Computational and data grids and distributed collaboration environments are examples. To understand performance and gain insights into developing applications that efficiently use system resources, performance visualization has proven useful. Performance visualization tools, however, often are specific to a particular resource at a certain level of the system, possibly with fixed views. Thus, they limit a user's ability to observe a performance problem associated with multiple resources across system levels and platforms. To address this limitation, information integration is necessary. In this ...


Power System Dynamic Security Analysis Via Decoupled Time Domain Simulation And Trajectory Optimization , Dan Yang Jan 2006

Power System Dynamic Security Analysis Via Decoupled Time Domain Simulation And Trajectory Optimization , Dan Yang

Retrospective Theses and Dissertations

Electric power systems are subject to disturbances in the operation, and may encounter system failures such as power outages and blackouts due to disturbances. Power system security analysis plays an important role in improving the survivability to disturbances. This dissertation proposes advanced computational and optimization techniques that can be applied to mitigate instabilities in power systems subject to disturbances. The research work has been integrated into a general framework for power system dynamic security analysis. The proposed methods cover strategies for both power system instability assessment and control, and provide a fast simulation algorithm and coordinated optimization techniques to improve ...


A 2.4ghz Fast-Switching Integer-N Frequency Synthesizer , Sreenath Thoka Jan 2006

A 2.4ghz Fast-Switching Integer-N Frequency Synthesizer , Sreenath Thoka

Retrospective Theses and Dissertations

The adaptive bandwidth technique is commonly used to implement fast switching in low-spurious frequency synthesizers. In this technique the high loop bandwidth used during the switching mode has to be restored once switching is complete. The process of restoring the bandwidth adds to the total switching time because of the glitches on the VCO control voltage arising from the perturbation caused in the loop. Often in applications demanding ultra fast switching times and tight error tolerances, the additional settling time due to these secondary glitches can be a significant fraction of the total switching time. In this thesis, a more ...


Tradeoffs And Limitations In Networked Control Systems , Prashanth Srinivasa Padmasola Jan 2006

Tradeoffs And Limitations In Networked Control Systems , Prashanth Srinivasa Padmasola

Retrospective Theses and Dissertations

Control and communication have been increasingly studied together in the recent past. The 'Satellite - Ground Controller' is a classic example of a remote control problem. Another closely related topic of study is control over an unreliable communication network and its applications seem to grow continuously. Networked Control Systems (NCS) is a rapidly growing research topic and examples of practical significance include multiple vehicle coordination, air-traffic control, and Micro-Electro-Mechanical Systems (MEMS). The work presented consists of two problems (1) The Remote control problem and (2) The Networked control problem. The remote control problem we address is the feedback stabilization of a ...


Transient Force Atomic Force Microscopy: Systems Approaches To Emerging Applications , Deepak Ranjan Sahoo Jan 2006

Transient Force Atomic Force Microscopy: Systems Approaches To Emerging Applications , Deepak Ranjan Sahoo

Retrospective Theses and Dissertations

In existing dynamic mode operation of Atomic Force Microscopes (AFMs) steady-state signals like amplitude and phase are used for detection and imaging of material. Due to the high quality factor of the cantilever probe the corresponding methods are inherently slow. In this dissertation, a novel methodology for fast interrogation of material that exploits the transient part of the cantilever motion is developed. This method effectively addresses the perceived fundamental limitation on bandwidth due to high quality factors. It is particularly suited for the detection of small time scale tip-sample interactions. Analysis and experiments show that the method results in significant ...


Fundamental Limits In Gaussian Channels With Feedback: Confluence Of Communication, Estimation, And Control , Jialing Liu Jan 2006

Fundamental Limits In Gaussian Channels With Feedback: Confluence Of Communication, Estimation, And Control , Jialing Liu

Retrospective Theses and Dissertations

The emerging study of integrating information theory and control systems theory has attracted tremendous attention, mainly motivated by the problems of control under communication constraints, feedback information theory, and networked systems. An often overlooked element is the estimation aspect; however, estimation cannot be studied isolatedly in those problems. Therefore, it is natural to investigate systems from the perspective of unifying communication, estimation, and control;This thesis is the first work to advocate such a perspective. To make Matters concrete, we focus on communication systems over Gaussian channels with feedback. For some of these channels, their fundamental limits for communication have ...


Transient Eddy Current Response Due To A Subsurface Crack In A Conductive Plate , Fangwei Fu Jan 2006

Transient Eddy Current Response Due To A Subsurface Crack In A Conductive Plate , Fangwei Fu

Retrospective Theses and Dissertations

Eddy current nondestructive evaluation (NDE) is usually carried out by exciting a time harmonic field using an inductive probe. However, a viable alternative is to use transient eddy current NDE in which a current pulse in a driver coil produces a transient field in a conductor that decays at a rate dependent on the conductivity and the permeability of the material and the coil configuration. By using transient eddy current, it is possible to estimate the properties of the conductive medium and to locate and size potential flaws from the measured probe response. The fundamental study described in this dissertation ...


The Virtual Storm: An Exploratory Virtual Environment Of A Supercell Tornadic Thunderstorm For Meteorological Education , Galen William Faidley Jan 2006

The Virtual Storm: An Exploratory Virtual Environment Of A Supercell Tornadic Thunderstorm For Meteorological Education , Galen William Faidley

Retrospective Theses and Dissertations

The driving motivation behind the Virtual Storm is to provide students with a hands-on means to learning about severe weather. Hands-on experiences are considered an important teaching method. The Virtual Storm addresses the lack of hands-on experience in severe weather education through the use of computer graphics and virtual reality technology.;Formal user studies were used to determine the effectiveness of the Virtual Storm as a teaching tool. The study results did not show a measurable benefit of using the Virtual Storm. However, the user tests may not have captured the true value of the Virtual Storm since they focused ...


Explicit Characterization Of Bandgap References , Xin Dai Jan 2006

Explicit Characterization Of Bandgap References , Xin Dai

Retrospective Theses and Dissertations

Stable and precision voltage references are an integral part of many analog and mixed-signal integrated circuits. Bandgap references have been widely used for precision on-chip voltage sources in both bipolar and CMOS processes. Conspicuously absent in the literature are explicit relationships between the output voltage and temperature of bandgap references. Temperature characteristics of bipolar junction transistors (BJT's) are developed to explicitly characterize the I-V relationship of BJT's. Based on this characterization, an explicit relationship for the output voltage of a popular bandgap reference structure is developed. Within the context of this explicit relationship, temperature stability properties of references ...


Isecube: A Portable Iseage , Ryan Roger Rathje Jan 2006

Isecube: A Portable Iseage , Ryan Roger Rathje

Retrospective Theses and Dissertations

As the Internets' potential continues to grow in functionality and services, malicious activity becomes more prevalent. Professionals and researchers are working hard to create and implement secure systems, but this can require extensive tools and training to arising situations.;ISECUBE has been developed to be used in conjunction with Iowa State University's Internet Scale Event and Attack Generation Environment (ISEAGE) to act as a self sustaining portable environment as well as an extension of its functionality and services. ISECUBE is a transportable device that provides different realistic environments. These environments were designed with the classroom, research collaboration, and corporate ...


Economic Efficiencies Of The Energy Flows From The Primary Resource Suppliers To The Electric Load Centers , Ana Margarida Quelhas Alves De Freitas Jan 2006

Economic Efficiencies Of The Energy Flows From The Primary Resource Suppliers To The Electric Load Centers , Ana Margarida Quelhas Alves De Freitas

Retrospective Theses and Dissertations

The economic efficiency of the electric energy system depends not only on the performance of the electric generation and transmission subsystems, but also on the ability to produce and transport the various forms of primary energy, particularly coal and natural gas. However, electric power systems have traditionally been developed and operated without a conscious awareness of the energy system-wide implications, namely the consideration of the integrated dynamics with the fuel markets and infrastructures. This has been partly due to the difficulty of formulating models capable of analyzing the large-scale, complex, time-dependent, and highly interconnected behavior of the integrated energy system ...


Mimo Communication Systems: Receiver Design And Diversity-Multiplexing Tradeoff Analysis , Wei Mo Jan 2006

Mimo Communication Systems: Receiver Design And Diversity-Multiplexing Tradeoff Analysis , Wei Mo

Retrospective Theses and Dissertations

After a few decades' evolution of wireless communication systems, to ensure reliable high-speed communication over unreliable wireless channels is still one of the major challenges facing researchers and engineers. The use of multiple antennas at transmitter and receiver, known as multiple-input multiple-output (MIMO) communications, is one promising technology delivering desired wireless services. The main goal of this thesis is to study two important issues in wireless MIMO communication systems: receiver design for coded MIMO systems, and diversity-multiplexing tradeoff analysis in general fading channels;In the first part of this thesis, we decompose the receiver design problem into two sub-problems: MIMO ...


Diversity Receiver Design And Channel Statistic Estimation In Fading Channels , Jinghua Jin Jan 2006

Diversity Receiver Design And Channel Statistic Estimation In Fading Channels , Jinghua Jin

Retrospective Theses and Dissertations

The main goal of this thesis is to provide an in-depth study of two important techniques that are effective in improving the performance, data rate, or bandwidth-efficiency in wireless communication systems. The two techniques are, first, diversity combining equipped with quadrature amplitude modulation (QAM), and second, the estimation of fading channel statistical properties;To effectively combat the adverse effect of fading and to improve the error rate performance in wireless communications, one of the major approaches is to employ diversity combining techniques. In the first part of this thesis, we focus on the equal gain combining (EGC) and hybrid-selection equal ...


Sampled Charge Reuse For Power Reduction In Switched Capacitor Data Converters , Saqib Qayyum Malik Jan 2006

Sampled Charge Reuse For Power Reduction In Switched Capacitor Data Converters , Saqib Qayyum Malik

Retrospective Theses and Dissertations

Advances in semiconductor fabrication have enabled the shrinking of digital systems dramatically over the years. Although digital circuitry benefits tremendously from the constant shrinking of the device sizes, the benefits for analog circuits are not quite so dramatic. Low power is of critical importance in all mobile devices. Any reduction in power in the embedded analog-to-digital converters (ADCs) in such devices can help prolong the battery life. A technique is proposed that can be used to reduce power dissipation in ADCs that use switched-capacitor gain stages. It is shown for a pipeline ADC that the signal charge stored across the ...


Improving The Stability Of Amorphous Silicon Solar Cells By Chemical Annealing , Nanlin Wang Jan 2006

Improving The Stability Of Amorphous Silicon Solar Cells By Chemical Annealing , Nanlin Wang

Retrospective Theses and Dissertations

Amorphous silicon solar cells have been extensively studied. However, it is found that the properties of a-Si:H solar cells degrade upon light illumination, and this limits their application. Recently, it has been shown that this instability is correlated with the presence of SiH2 bonds, and a technique, namely chemical annealing, was suggested to improve the stability of a-Si:H. Although a number of results have been reported, no chemical annealed devices with good quality were reported;In this work, chemical annealing technique was studied to improve the stability of a-Si:H solar cells. It is found that when the ...


Distributed Real-Time Operating System (Drtos) Modeling In Specc , Ziyu Zhang Jan 2006

Distributed Real-Time Operating System (Drtos) Modeling In Specc , Ziyu Zhang

Retrospective Theses and Dissertations

System level design of an embedded computing system involves a multi-step process to refine the system from an abstract specification to an actual implementation by defining and modeling the system at various levels of abstraction. System level design supports evaluating and optimizing the system early in design exploration.;Embedded computing systems may consist of multiple processing elements, memories, I/O devices, sensors, and actors. The selection of processing elements includes instruction-set processors and custom hardware units, such as application specific integrated circuit (ASIC) and field programmable gate array (FPGA). Real-time operating systems (RTOS) have been used in embedded systems as ...


On-Line Computation Of System Operating Limits With Respect To Thermal Constraints , Abdul Kader Abou-Ardate Jan 2006

On-Line Computation Of System Operating Limits With Respect To Thermal Constraints , Abdul Kader Abou-Ardate

Retrospective Theses and Dissertations

The purpose of security assessment is to verify the security of the current state of the system and find the secure regions within which the system can operate. In operations, a secure system involves respecting all operating criteria at pre- and post- contingency conditions. Operating limits include thermal, voltage and angle limits as well as all forms of stability. This thesis presents a computationally efficient and extremely fast method of computing real-time thermal security operating limits (SOLs) for any line imposed by reliability criteria for NERC's class B (i.e., N-1) contingencies. The method makes use of linear sensitivity ...


Growth And Properties Of Nanocrystalline Ge And Ge[Subscript 1-X]C[Subscript X] Films And Photovoltaic Devices , Xuejun Niu Jan 2005

Growth And Properties Of Nanocrystalline Ge And Ge[Subscript 1-X]C[Subscript X] Films And Photovoltaic Devices , Xuejun Niu

Retrospective Theses and Dissertations

Germanium, with its almost direct gap band structure, is an attractive material for photovoltaic applications. Carbon is added to the germanium lattice to increase the band gap. Since germanium and carbon are not soluble in equilibrium, only a metastable process can be used for growth.;In this research, we used a remote, low pressure electron cyclotron resonance plasma enhanced chemical vapor deposition system (ECR-PECVD) to deposit nanocrystalline Ge and Ge1-xCx films. Nanocrystalline germanium:H films were grown on glass and stainless steel substrates from a mixture of germane and hydrogen. X-ray diffraction spectra revealed a predominant <220> orientation in the films ...