With the increased attention on high efficiency and energy savings, power electronic energy conversion equipment is increasingly incorporated in all levels of the power system. The drawback of such equipment is the generation of nonsinusoidal currents in the power distribution network due to the nonlinear operation. Harmonic currents may distort the line voltages and lead to several unwanted effects including equipment overheating, system failure, interference with communication systems, etc. In response to these concerns, this research presents an active filter for the cancellation of harmonic line current distortion. The active filter used in this research is connected in parallel with the nonlinear load and is designed for a three-phase three-wire industrial power system. The filter consists of a voltage source inverter connected through a coupling inductor to the terminals of the ac-source. The inverter is controlled via a space vector-pulse width modulation (SVPWM) algorithm that is generated using a digital signal processor (DSP). In order to reduce the distortion resulting from the switching nature of the active filter inverter, a switching ripple filter is connected in parallel. The control algorithm of the active filter is based on the rotating reference frame theory. For each harmonic which is to be cancelled, a corresponding synchronous reference frame is generated to extract the harmonic phase and magnitude. With this information, each harmonic current component can be separately controlled and the proposed algorithm can therefore compensate for hardware effects such as measuring delays and component transfer functions. For the extraction of the harmonic components, a finite impulse response filter is used in order to quickly react to changing load currents. An adapting algorithm is implemented to compensate for slowly varying system parameters. Simulations under varying load and transient conditions are performed. The results show nearly perfect cancellation performance for the proposed active filter control algorithm. / Graduation date: 2001

Researchers and practitioners continue to be concerned about the magnitude, extent, and effects of response distortion when self-report personality measures are used in high-stakes testing. One method for mitigating response distortion that has not received much empirical attention is profile matching. Profile matching assesses the fit between test-takers’ predictor profiles and a standard profile which represents an ideal or high performing employee’s profile. Since profile matching assesses fit, it can capture nonlinear effects. Furthermore, high predictor scores are not necessarily associated with higher criterion scores. Test–takers who distort their responses by choosing inaccurately extreme response options may improve their chances of being hired if a linear model is used, but this approach is unlikely to be effective if a profile matching strategy is used as long as the standard profile is unknown to the test-takers. As such, the primary objective of the present study was to examine the extent to which profile matching may alleviate concerns about response distortion. A secondary objective was to examine characteristics of the standard profile that are associated with the efficacy of this approach. The present study compared the effects of response distortion on personality test scores, and their criterion-related validity in predicting tenure, based on a linear composite and a profile fit score. The present study used data from 996 applicants who completed a personality test in a high-stakes testing context. Missing data were imputed for a subset of applicants who did not complete two response distortion scales. As such, the results provided an initial proof-of-concept of the effectiveness of profile matching as a personnel decision-making strategy using a blend of real and simulated data. The results suggest that profile fit scores are less related to response distortion and display higher criterion-related validity than linear composite scores. However, the difference in criterion-related validity could not be attributed to response distortion. The results further suggest that the amount of scatter in the standard profile is negatively associated with the profile fit score’s susceptibility to response distortion and positively related to criterion-related validity.

Operational Transconductance Amplifiers (OTAs) with high linearity and wide input range characteristics have become a focus of interest for analog continuous-time circuits. In this research, we intend to develop a low distortion, wide swing CMOS OTA. The supply voltage is 5V. Simulation results show that the OTA is linear, tunable and wide swing. The transconductance can be tuned from 23£gA/V to 37£gA/V. When a 3VPP input signal with 1MHz is applied, THD of the OTA is 51dB. The OTA is used to realize a 1-MHz 7th-order Butterworth lowpass filter. When a 1VPP input signal with 100KHz is applied, THD of the lowpass filter is 50dB. All the circuits are designed based on the UMC 0.5£gm 2p2m CMOS process technology.

Due to advanced in computer technology¡Avideo data are becoming available in the daily life. The method of managing Multi-media video database is more and more important¡Aand traditional database management for text documents is not suitable for video database; therefore, efficient video database must equip video summary. Video summarization contains a number of key-frame and the key-frame is a simple yet effective form of summarizing a video sequence and the video summarization help user browses rapidly and effectively find out video that the user wants to find. Video summarization except extraction of key-frame has another important key, the number of key-frame. When storage and network bandwidth are limited, the number of key-frame must conform to the limit condition and as far as possible find the representative key-frame. Video summarization is important topic for managing Multi-media video. The number of key-frame in video summarization is related to distortion between video summarization and original video sequence. The number of key-frame is more, the distortion between video summarization and original video sequence is smaller. This paper emphasizes key-frame extraction and the rate of key-frame. First the user inputs the number of key-frame and then extracts the key-frame that has smallest distortion between original video sequence in key-frame number limit situation. In order to understand the entire video structure¡Athe Normalized the graph cuts(NCuts) group method is carried out to cluster similar video paragraph. The resulting clusters form a direction temporal graph and a shortest path algorithm is proposed to find main structure of video. The performance of the proposed method is demonstrated by experiments on a collection of videos from Open Vide Project. We provided a meaningful comparison between results of the proposed summarization with Open Vide storyboard and the PME based approach.

Although fine granularity scalability (FGS) video coding based on matching pursuits and bit-plane coding have been proven to have better coding efficiency than discrete-cosine-transform-based FGS at low bit rates, it might not be the most efficient method in terms of rate-distortion optimization (RDO). We propose a rate-distortion optimization FGS video coding by dividing a frame into blocks to generate block-based embedded bit-streams and reorganize the bit-streams into several quality layers according to the rate-distortion slopes. The comparison between FGS matching pursuit video coding and RDO-FGS matching pursuit video coding is shown in the experimental results.

Section to section alignment is a preliminary step to the creation of three dimensional reconstructions from serial section electron micrographs. Typically, the micrograph of one section is aligned to its neighbors by analyzing a set of fiducial points to calculate an appropriate polynomial transform. This transform is then used to map all of the pixels of the micrograph into alignment. Such transforms are usually linear or piecewise linear in order to limit the accumulation of small errors, which may occur with the use of higher–order approximations. Linear alignment is unable to correct common higher order geometric distortions, such as lens distortion in the case of TEM, and scan distortion in the case of transmission-mode SEM. Here, we attempt to show that standard calibration replicas may be used to calculate a high order distortion model despite the irregularities that are often present in them. We show that SEM scan distortion has much less of an effect than TEM lens distortion; however, the effect of TEM distortion on prior geometric measurements made over three-dimensional reconstructions of dendrites, axons, and synapses and their subcellular compartments is negligible. / text

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 105-107). Also available via the Internet.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Orientador: José Carlos Rossi / Banca: Antonio Carlos Delaiba / Banca: Carlos Alberto Canesin / Resumo: Este trabalho tem por objetivo a proposição de um estudo de caso realizado em uma planta industrial, cuja linha de produção se concentra na área da metalurgia. O principal enfoque foi direcionado na avaliação e nos efeitos causados pelas correntes distorcidas, geradas por cargas não lineares, nos barramentos e alimentadores da industria. Com o objetivo de avaliar o impacto das cargas elétricas, com características não lineares, as instalada e a serem instaladas no sistema elétrico da industria. Foi realizada também uma avaliação geral da planta da indústria através da análise das faturas de energia elétrica buscando identificar nos principais indicadores, os desvios no sistema elétrico da planta. Entre estes, podemos destacar a demanda, o consumo, os reativos excedentes e outros. Todos os procedimentos desenvolvidos neste trabalho foram direcionados no sentido de se usar racionalmente a energia elétrica e controlar o seu desperdício. / Abstract: This work aims to study a case carried out in an industrial plant, whose production line is concentrated on the metallurgy field. The main objective was addressed in the evaluation and in the effects caused by the distortion of the currents, due to nonlinear loads connected at the industry busbar and feeders. With the objective of evaluating the impact of the electric loads, with non- linear characteristics, or installed in the industry electric system. It was also accomplished a general evaluation of the industry plant by analyzing the electric power invoices looking for identifying, in the main quality power indicators, the deviations in the electric plant system. Among these, we can mention the demand, the consumption, the exceeding reactives and others. All the procedures developed in this work were addressed aiming to use the electric power rationally and to control its waste. / Mestre

Measurements of the turbulent flow field through a highly staggered cascade propulsor configuration in the Virginia Tech cascade wind tunnel have been taken. Predictions of the same flow using Rapid Distortion Theory (RDT) were performed. Measurements and predictions were compared. The comparison was oriented to check the aptness of RDT in describing this kind of flow. Since this study represents the initial steps of a major project, the RDT model was kept simple. The non-penetration condition (blade blocking effect) was not modeled and the viscous effects were roughly accounted for. This work reveals the capabilities of RDT in predicting the development of turbulence convected through a highly staggered cascade propulsor configuration formed by non-symmetrical airfoils. This present study was possible thank to the support from the Office of Naval Research, in particular Candace Wark and Pat Purtell, under grant number NAG 00014-99-1-0230. / Master of Science