Dynamic modeling and analysis of single-stage boost inverters under normal and abnormal conditions

Inverters play key roles in connecting sustainable energy (SE) sources to the local loads and the ac grid. Although there has been a rapid expansion in the use of renewable sources in recent years, fundamental research, on the design of inverters that are specialized for use in these systems, is still needed. Recent advances in power electronics have led to proposing new topologies and switching patterns for single-stage power conversion, which are appropriate for SE sources and energy storage devices. The current source inverter (CSI) topology, along with a newly proposed switching pattern, is capable of converting the low dc voltage to the line ac in only one stage. Simple implementation and high reliability, together with the potential advantages of higher efficiency and lower cost, turns the so-called, single-stage boost inverter (SSBI), into a viable competitor to the existing SE-based power conversion technologies.^ The dynamic model is one of the most essential requirements for performance analysis and control design of any engineering system. Thus, in order to have satisfactory operation, it is necessary to derive a dynamic model for the SSBI system. However, because of the switching behavior and nonlinear elements involved, analysis of the SSBI is a complicated task.^ This research applies the state-space averaging technique to the SSBI to develop the state-space-averaged model of the SSBI under stand-alone and grid-connected modes of operation. Then, a small-signal model is derived by means of the perturbation and linearization method. An experimental hardware set-up, including a laboratory-scaled prototype SSBI, is built and the validity of the obtained models is verified through simulation and experiments. Finally, an eigenvalue sensitivity analysis is performed to investigate the stability and dynamic behavior of the SSBI system over a typical range of operation. ^

Human Capital Decisions and Employee Satisfaction at Selected Hotels in India

Understanding the role of human capital is one of the key considerations in delivering and sustaining competitiveness. Managing employees in the hospitality industry is particularly a challenging task as the industry is considered to be labor intensive. High turnover and increasing employee demands are among the problems that are identified as threats to maintaining a strong competitive position. Successful hotels attempt to retain their best employees in an effort to adapt to changing environments and increased competition. Effective hotel human resource systems can produce positive outcomes, through effective employee retention strategies that focus on work force motivation, attitudes and perception. The positive implementation of these strategies can influence and create employee satisfaction. This study aims to focus on the relationship between the mediating variables of motivation, attitudes, perception and their effect on employee satisfaction. These findings are based upon an extensive survey carried out between April 2009 and June 2009 in the small mountainous state of Uttarakhand, located within the Indian sub-continent. Although the area of study is confined to the Kumaon region of Uttarakhand, the authors contend that the findings and implications can be applied to other remote developing tourist destinations in other regions.

With the highest ideals: The Florida State Normal College at DeFuniak Springs, 1887--1905

The urgent need for teachers led the Florida legislature in 1887 to establish the Florida State Normal College at DeFuniak Springs. The college closed in 1905 with passage of the Buckman Act, which mandated a complete reorganization of state-supported higher education and ended coeducation for white students. This small college, open for eighteen years, was uniquely situated in time and place to examine larger questions in American educational history as well as contribute to the history of higher education in Florida, which developed differently than in other states.^ This historical case study used archival sources to examine this institution, and contribute to the history of the origins of Florida's system of higher education. Key questions guiding the research were the nature of the students, fundamental aspects of school life, the impact of the school on the students, and the role of the school in the development of higher education in Florida. Original sources included the Catalogs, Register and Minutes of the school. The census of 1900 was used to develop information on the backgrounds of the students. Findings were: DeFuniak Springs was chosen for the school because of the Florida Chautauqua; the school was coeducational and had few rules but the internalized social codes of the students resulted in almost no difficulties with discipline; the students, a majority of whom were women, were from middle-class southern families; the college compared favorably in faculty, facilities and curriculum to institutions elsewhere; although few students graduated, alumni played a key role in shaping Florida's common schools; and, the Buckman Act entirely changed the nature of higher education in Florida.^ Implications were: The coeducational nature of the college a hundred years ago significantly changes the picture of Florida's higher education; the school was small, but its influence far outlasted the institution; and, the school struggled with issues which continue to trouble modern educators such as finances, the legislature, student retention, underpreparedness, and the proper structuring of a curriculum, which indicates the persistence of these issues. ^

Comparative reproductive biology of two Florida pawpaws Asimina reticulata Chapman and Asimina tetramera Small

I investigated the phenology and breeding systems of two Florida endemic pawpaws, Asimina reticulata, widespread in peninsular Florida, and A. tetramera, a federally endangered species limited to two counties on the Atlantic Coastal Ridge. The purpose of this study was to determine if differences contribute to the rarity of Asimina tetramera compared with A. reticulata. The study was conducted in sand pine scrub sites with the largest populations of A. tetramera in the two counties. Flowering seasons differ for the two species. Both species are hermaphroditic and strongly protogynous. Pollination experiments show that neither species is autogamous and the primary breeding mechanism is outcrossing, although low levels of geitonogamous pollination occur in mature scrub habitats. High levels of inbreeding depression were noted in both species at both sites but inbreeding depression was relaxed the first year post-fire. Fruit set in mature habitats may be pollinator limited. ^ I studied insects associated with the flowers in sand pine scrub habitat in southeastern Florida from 1994–1996. The most commonly represented orders were Coleoptera (25 spp.), Lepidoptera. (3 spp.) and Hymenoptera. (3 spp.). All Coleoptera. were flower visitors; one species, Euphoria sepulchralis (Fabricius)(Scarabeaidae), visited flowers of the two Asimina species at both sites. Eurytides marcellus (Cramer) (Lepidoptera: Papilionidae) eggs and larvae were observed on both species of Asimina during each year of the study. ^ Resource management techniques were applied to a mature sand pine scrub community in Jonathan Dickinson State Park in southeastern Florida for the management of Asimina tetramera. Manipulations conducted in 1996 included combinations of fire and mechanical treatments. I measured effects of these treatments on flowering and fruit set on A. tetramera and found cutting and burning was most effective in increasing flowering, followed by burning. Mechanical cutting and mulching had no significant effect. ^

Signal processing of physiological signals for automated assessment of stress in computer users

The need to provide computers with the ability to distinguish the affective state of their users is a major requirement for the practical implementation of affective computing concepts. This dissertation proposes the application of signal processing methods on physiological signals to extract from them features that can be processed by learning pattern recognition systems to provide cues about a person's affective state. In particular, combining physiological information sensed from a user's left hand in a non-invasive way with the pupil diameter information from an eye-tracking system may provide a computer with an awareness of its user's affective responses in the course of human-computer interactions. In this study an integrated hardware-software setup was developed to achieve automatic assessment of the affective status of a computer user. A computer-based "Paced Stroop Test" was designed as a stimulus to elicit emotional stress in the subject during the experiment. Four signals: the Galvanic Skin Response (GSR), the Blood Volume Pulse (BVP), the Skin Temperature (ST) and the Pupil Diameter (PD), were monitored and analyzed to differentiate affective states in the user. Several signal processing techniques were applied on the collected signals to extract their most relevant features. These features were analyzed with learning classification systems, to accomplish the affective state identification. Three learning algorithms: Naïve Bayes, Decision Tree and Support Vector Machine were applied to this identification process and their levels of classification accuracy were compared. The results achieved indicate that the physiological signals monitored do, in fact, have a strong correlation with the changes in the emotional states of the experimental subjects. These results also revealed that the inclusion of pupil diameter information significantly improved the performance of the emotion recognition system. ^

Social and environmental regulation of signal plasticity and signal reliability in the electric fish Brachyhypopomus gauderio

The balance between the costs and benefits of conspicuous signals ensures that the expression of those signals is related to the quality of the bearer. Plastic signals could enable males to maximize conspicuous traits to impress mates and competitors, but reduce the expression of those traits to minimize signaling costs, potentially compromising the information conveyed by the signals. ^ I investigated the effect of signal enhancement on the information coded by the biphasic electric signal pulse of the gymnotiform fish Brachyhypopomus gauderio. Increases in population density drive males to enhance the amplitude of their signals. I found that signal amplitude enhancement improves the information about the signaler's size. Furthermore, I found that the elongation of the signal's second phase conveys information about androgen levels in both sexes, gonad size in males and estrogen levels in females. Androgens link the duration of the signal's second phase to other androgen-mediated traits making the signal an honest indicator of reproductive state and aggressive motivation. ^ Signal amplitude enhancement facilitates the assessment of the signaler's resource holding potential, important for male-male interactions, while signal duration provides information about aggressive motivation to same-sex competitors and reproductive state to the opposite sex. Moreover, I found that female signals also change in accordance to the social environment. Females also increase the amplitude of their signal when population density increases and elongate the duration of their signal's second phase when the sex ratio becomes female-biased. Indicating that some degree of sexual selection operates in females. ^ I studied whether male B. gauderio use signal plasticity to reduce the cost of reproductive signaling when energy is limited. Surprisingly, I found that food limitation promotes the investment in reproduction manifested as signal enhancement and elevated androgen levels. The short lifespan and single breeding season of B. gauderio diminishes the advantage of energy savings and gives priority to sustaining reproduction. I conclude that the electric signal of B. gauderio provides reliable information about the signaler, the quality of this information is reinforced rather than degraded with signal enhancement.^

Experimental deuteron momentum distributions with reduced final state interactions

This dissertation presents a study of the D( e, e′p)n reaction carried out at the Thomas Jefferson National Accelerator Facility (Jefferson Lab) for a set of fixed values of four-momentum transfer Q 2 = 2.1 and 0.8 (GeV/c)2 and for missing momenta pm ranging from pm = 0.03 to pm = 0.65 GeV/c. The analysis resulted in the determination of absolute D(e,e′ p)n cross sections as a function of the recoiling neutron momentum and it's scattering angle with respect to the momentum transfer [vector] q. The angular distribution was compared to various modern theoretical predictions that also included final state interactions. The data confirmed the theoretical prediction of a strong anisotropy of final state interaction contributions at Q2 of 2.1 (GeV/c)2 while at the lower Q2 value, the anisotropy was much less pronounced. At Q2 of 0.8 (GeV/c)2, theories show a large disagreement with the experimental results. The experimental momentum distribution of the bound proton inside the deuteron has been determined for the first time at a set of fixed neutron recoil angles. The momentum distribution is directly related to the ground state wave function of the deuteron in momentum space. The high momentum part of this wave function plays a crucial role in understanding the short-range part of the nucleon-nucleon force. At Q2 = 2.1 (GeV/c)2, the momentum distribution determined at small neutron recoil angles is much less affected by FSI compared to a recoil angle of 75°. In contrast, at Q2 = 0.8 (GeV/c)2 there seems to be no region with reduced FSI for larger missing momenta. Besides the statistical errors, systematic errors of about 5–6 % were included in the final results in order to account for normalization uncertainties and uncertainties in the determi- nation of kinematic veriables. The measurements were carried out using an electron beam energy of 2.8 and 4.7 GeV with beam currents between 10 to 100 &mgr; A. The scattered electrons and the ejected protons originated from a 15cm long liquid deuterium target, and were detected in conicidence with the two high resolution spectrometers of Hall A at Jefferson Lab.^

Digital signal processing implementation for near real-time wavelet transformation system for binary images

Communication has become an essential function in our civilization. With the increasing demand for communication channels, it is now necessary to find ways to optimize the use of their bandwidth. One way to achieve this is by transforming the information before it is transmitted. This transformation can be performed by several techniques. One of the newest of these techniques is the use of wavelets. Wavelet transformation refers to the act of breaking down a signal into components called details and trends by using small waveforms that have a zero average in the time domain. After this transformation the data can be compressed by discarding the details, transmitting the trends. In the receiving end, the trends are used to reconstruct the image. In this work, the wavelet used for the transformation of an image will be selected from a library of available bases. The accuracy of the reconstruction, after the details are discarded, is dependent on the wavelets chosen from the wavelet basis library. The system developed in this thesis takes a 2-D image and decomposes it using a wavelet bank. A digital signal processor is used to achieve near real-time performance in this transformation task. A contribution of this thesis project is the development of DSP-based test bed for the future development of new real-time wavelet transformation algorithms.