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. ^

The Basis of Support for Hugo Chávez: Measuring the Determinants of Presidential Job Approval in Venezuela

Since 1999, Venezuela has experienced a dramatic transformation of its political system with the coming to power of Hugo Chávez and his movement, known in Venezuela as Chavismo. Chávez has dismantled the previous political system and established neo-populist structures that rely on his personal appeal and the close collaboration of the armed forces. Chávez has relied heavily on significant support from the poor and those who felt economically and politically excluded by the “Punto Fijo system.” President Chávez has built an impressive record of electoral victories; winning every electoral contest except one since coming to power in 1999. He continues to receive relatively high levels of support among sectors of Venezuelan society. However, there is evidence of growing discontent with high crime rates, high levels of inflation, and significant corruption in the public administration. Using data from the AmericasBarometer surveys conducted in 2007, 2008 and 2010, this paper seeks to examine the basis of Chávez’s popular support. In general, the AmericasBarometer findings suggest that Venezuelans support for President Chávez is closely linked to the access to social programs and that as long as the government is able to fund these social programs or missions, particularly MERCAL and Barrio Adentro, it will possess an important tool to garner and sustain support for President Chávez. Our analysis, however, also indicates that evaluations of the national economic situation, more than crime or insecurity, are a key factor that could undermine support for the regime.

Employee Job Satisfaction in Major Cruise Lines

A survey of 244 crew members with six major cruise Iines indicated the most satisfaction with organization and supervision, satisfaction with working environment and ship life, and least satisfaction with rewards. The study suggests that the analysis of job satisfaction level may be used to develop organizational strategies to improve shipboard employee job satisfaction.

Role Stress, Emotional Exhaustion, and Job Satisfaction in the Hotel Industry: The Moderating Role of Supervisory Support

The purpose of this study is to investigate supervisory support as a moderator of the effects of role conflict and role ambiguity on emotional exhaustion and job satisfaction. This study also examines the moderating role of supervisory support on the relationship between emotional exhaustion and job satisfaction. Data were collected from a sample of frontline hotel employees in Northern Cyprus. The aforementioned relationships were tested based on hierarchical multiple regression analysis. The results demonstrate that supervisory support mitigates the impact of role conflict on emotional exhaustion and further reveal that supervisory support reduces the effect of emotional exhaustion on job satisfaction. There is no empirical support for the rest of the hypothesized relationships. Implications of the empirical results are discussed, and future research directions are offered.

The Food Service Industry Environment: Market Volatility Analysis

In their dialogue entitled - The Food Service Industry Environment: Market Volatility Analysis - by Alex F. De Noble, Assistant Professor of Management, San Diego State University and Michael D. Olsen, Associate Professor and Director, Division of Hotel, Restaurant & Institutional Management at Virginia Polytechnic Institute and State University, De Noble and Olson preface the discussion by saying: “Hospitality executives, as a whole, do not believe they exist in a volatile environment and spend little time or effort in assessing how current and future activity in the environment will affect their success or failure. The authors highlight potential differences that may exist between executives' perceptions and objective indicators of environmental volatility within the hospitality industry and suggest that executives change these perceptions by incorporating the assumption of a much more dynamic environment into their future strategic planning efforts. Objective, empirical evidence of the dynamic nature of the hospitality environment is presented and compared to several studies pertaining to environmental perceptions of the industry.” That weighty thesis statement presumes that hospitality executives/managers do not fully comprehend the environment in which they operate. The authors provide a contrast, which conventional wisdom would seem to support and satisfy. “Broadly speaking, the operating environment of an organization is represented by its task domain,” say the authors. “This task domain consists of such elements as a firm's customers, suppliers, competitors, and regulatory groups.” These are dynamic actors and the underpinnings of change, say the authors by way of citation. “The most difficult aspect for management in this regard tends to be the development of a proper definition of the environment of their particular firm. Being able to precisely define who the customers, competitors, suppliers, and regulatory groups are within the environment of the firm is no easy task, yet is imperative if proper planning is to occur,” De Noble and Olson further contribute to support their thesis statement. The article is bloated, and that’s not necessarily a bad thing, with tables both survey and empirically driven, to illustrate market volatility. One such table is the Bates and Eldredge outline; Table-6 in the article. “This comprehensive outline…should prove to be useful to most executives in expanding their perception of the environment of their firm,” say De Noble and Olson. “It is, however, only a suggested outline,” they advise. “…risk should be incorporated into every investment decision, especially in a volatile environment,” say the authors. De Noble and Olson close with an intriguing formula to gauge volatility in an environment.

Maximum Justifiable Investment Analysis Determines Property Valuation

Investors and developers are often faced with the task of determining the worth or value of a real estate entity that presently exists or is proposed for development. This article explains the process for determining the value of a proposed project and, subsequently, the maximum investment dollars the project can cover, while at the same time producing a reasonable return for the investor. A proposed 300-room hotel serves as the real estate entity to be analyzed.

AIDS workplace *policy adoption and implementation in local government: An analysis of departmental variation

This is an empirical study whose purpose was to examine the process of innovation adoption as an adaptive response by a public organization and its subunits existing under varying degrees of environmental uncertainty. Meshing organization innovation research and contingency theory to form a theoretical framework, an exploratory case study design was undertaken in a large, metropolitan government located in an area with the fourth highest prevalence rate of HIV/AIDS in the country. A number of environmental and organizational factors were examined for their influence upon decision making in the adoption/non-adoption as well as implementation of any number of AIDS-related policies, practices, and programs.^ The major findings of the study are as follows. For the county government itself (macro level), no AIDS-specific workplace policies have been adopted. AIDS activities (AIDS education, AIDS Task Force, AIDS Coordinator, etc.), adopted county-wide early in the epidemic, have all been abandoned. Worker infection rates, in the aggregate and throughout the epidemic have been small. As a result, absent co-worker conflict (isolated and negligible), no increase in employee health care costs, no litigation regarding discrimination, and no major impact on workforce productivity, AIDS has basically become a non-issue at the strategic core of the organization. At the departmental level, policy adoption decisions varied widely. Here the predominant issue is occupational risk, i.e., both objective as well as perceived. As expected, more AIDS-related activities (policies, practices, and programs) were found in departments with workers known to have significant risk for exposure to the AIDS virus (fire rescue, medical examiner, police, etc.). AIDS specific policies, in the form of OSHA's Bloodborn Pathogen Standard, took place primarily because they were legislatively mandated. Union participation varied widely, although not necessarily based upon worker risk. In several departments, the union was a primary factor bringing about adoption decisions. Additional factors were identified and included organizational presence of AIDS expertise, availability of slack resources, and the existence of a policy champion. Other variables, such as subunit size, centralization of decision making, and formalization were not consistent factors explaining adoption decisions. ^

Employee perceptions of workplace empowerment in relation to self -reported intent to stay on the job

As the nursing profession faces a shortage of nurses, workplace initiatives focused on retaining employees are critical to the United States healthcare industry (Sochalski, 2002). The purpose of this research was to determine whether self-reported intent to stay on the job was related to perceptions of workplace empowerment using Kanter's (1977) theory of organizational empowerment as a framework. ^ The sample consisted of 206 Florida registered nurses. Four self-report scales and a demographic questionnaire were administered by mail. The Conditions for Work Effectiveness Questionnaire (CWEQ; Chandler, 1987), Job Activity Scale (JAS; Laschinger, Kutzscher, & Sabiston, 1993), Organizational Relationships Scale (ORS; Laschinger, Sabiston, & Kutzscher, 1993) and an intent to stay instrument (Kim, Price, Mueller & Watson, 1996) were used to measure perceived access to empowerment structures, perceived formal power, perceived informal power, and intent to stay, respectively. The data were analyzed using descriptive statistics, correlational analysis, and hierarchical regression. ^ Twenty-eight percent of the variance of intent to stay was explained by perceived access to empowerment structures, perceived formal power, and perceived informal power when holding age, gender, education, overall nursing experience, and number of years on current job constant. Perceived access to empowerment structures (CWEQ total score) was the best predictor of self-reported intent to stay for this sample. Of the four components of perceived access to work empowerment structures, perceived access to opportunity and resources were the best predictors of nurses' intent to stay on the job. ^ This study was the first step in establishing the relationship between Kanter's full model and intent to remain on the job, which is a stepping stone for the development of effective retention strategies based on a workplace empowerment model. This knowledge is particularly important in today's healthcare industry where healthcare administrators and human resource development practitioners are ideally positioned to implement organizational strategies to enhance access to work empowerment structures and potentially reduce turnover and mitigate the effects of nursing shortage. ^

A theoretical analysis of eyewitness identification: Dual -process theory, signal detection theory and eyewitness confidence

Given the growing number of wrongful convictions involving faulty eyewitness evidence and the strong reliance by jurors on eyewitness testimony, researchers have sought to develop safeguards to decrease erroneous identifications. While decades of eyewitness research have led to numerous recommendations for the collection of eyewitness evidence, less is known regarding the psychological processes that govern identification responses. The purpose of the current research was to expand the theoretical knowledge of eyewitness identification decisions by exploring two separate memory theories: signal detection theory and dual-process theory. This was accomplished by examining both system and estimator variables in the context of a novel lineup recognition paradigm. Both theories were also examined in conjunction with confidence to determine whether it might add significantly to the understanding of eyewitness memory. ^ In two separate experiments, both an encoding and a retrieval-based manipulation were chosen to examine the application of theory to eyewitness identification decisions. Dual-process estimates were measured through the use of remember-know judgments (Gardiner & Richardson-Klavehn, 2000). In Experiment 1, the effects of divided attention and lineup presentation format (simultaneous vs. sequential) were examined. In Experiment 2, perceptual distance and lineup response deadline were examined. Overall, the results indicated that discrimination and remember judgments (recollection) were generally affected by variations in encoding quality and response criterion and know judgments (familiarity) were generally affected by variations in retrieval options. Specifically, as encoding quality improved, discrimination ability and judgments of recollection increased; and as the retrieval task became more difficult there was a shift toward lenient choosing and more reliance on familiarity. ^ The application of signal detection theory and dual-process theory in the current experiments produced predictable results on both system and estimator variables. These theories were also compared to measures of general confidence, calibration, and diagnosticity. The application of the additional confidence measures in conjunction with signal detection theory and dual-process theory gave a more in-depth explanation than either theory alone. Therefore, the general conclusion is that eyewitness identifications can be understood in a more complete manor by applying theory and examining confidence. Future directions and policy implications are discussed. ^

Predicting success or failure of tax -base revenue sharing attempts: A comparative analysis

To promote regional or mutual improvement, numerous interjurisdictional efforts to share tax bases have been attempted. Most of these efforts fail to be consummated. Motivations to share revenues include: narrowing fiscal disparities, enhancing regional cooperation and economic development, rationalizing land-use, and minimizing revenue losses caused by competition to attract and keep businesses. Various researchers have developed theories to aid understanding of why interjurisdictional cooperation efforts succeed or fail. Walter Rosenbaum and Gladys Kammerer studied two contemporaneous Florida local-government consolidation attempts. Boyd Messinger subsequently tested their Theory of Successful Consolidation on nine consolidation attempts. Paul Peterson's dual theories on Modern Federalism posit that all governmental levels attempt to further economic development and that politicians act in ways that either further their futures or cement job security. Actions related to the latter theory often interfere with the former. Samuel Nunn and Mark Rosentraub sought to learn how interjurisdictional cooperation evolves. Through multiple case studies they developed a model framing interjurisdictional cooperation in four dimensions. ^ This dissertation investigates the ability of the above theories to help predict success or failure of regional tax-base revenue sharing attempts. A research plan was formed that used five sequenced steps to gather data, analyze it, and conclude if hypotheses concerning the application of these theories were valid. The primary analytical tools were: multiple case studies, cross-case analysis, and pattern matching. Data was gathered from historical records, questionnaires, and interviews. ^ The results of this research indicate that Rosenbaum-Kammerer theory can be a predictor of success or failure in implementing tax-base revenue sharing if it is amended as suggested by Messinger and further modified by a recommendation in this dissertation. Peterson's Functional and Legislative theories considered together were able to predict revenue sharing proposal outcomes. Many of the indicators of interjurisdictional cooperation forwarded in the Nunn-Rosentraub model appeared in the cases studied, but the model was not a reliable forecasting instrument. ^

Network construction and graph theoretical analysis of functional language networks in pediatric epilepsy

This dissertation introduces a new approach for assessing the effects of pediatric epilepsy on the language connectome. Two novel data-driven network construction approaches are presented. These methods rely on connecting different brain regions using either extent or intensity of language related activations as identified by independent component analysis of fMRI data. An auditory description decision task (ADDT) paradigm was used to activate the language network for 29 patients and 30 controls recruited from three major pediatric hospitals. Empirical evaluations illustrated that pediatric epilepsy can cause, or is associated with, a network efficiency reduction. Patients showed a propensity to inefficiently employ the whole brain network to perform the ADDT language task; on the contrary, controls seemed to efficiently use smaller segregated network components to achieve the same task. To explain the causes of the decreased efficiency, graph theoretical analysis was carried out. The analysis revealed no substantial global network feature differences between the patient and control groups. It also showed that for both subject groups the language network exhibited small-world characteristics; however, the patient's extent of activation network showed a tendency towards more random networks. It was also shown that the intensity of activation network displayed ipsilateral hub reorganization on the local level. The left hemispheric hubs displayed greater centrality values for patients, whereas the right hemispheric hubs displayed greater centrality values for controls. This hub hemispheric disparity was not correlated with a right atypical language laterality found in six patients. Finally it was shown that a multi-level unsupervised clustering scheme based on self-organizing maps, a type of artificial neural network, and k-means was able to fairly and blindly separate the subjects into their respective patient or control groups. The clustering was initiated using the local nodal centrality measurements only. Compared to the extent of activation network, the intensity of activation network clustering demonstrated better precision. This outcome supports the assertion that the local centrality differences presented by the intensity of activation network can be associated with focal epilepsy.^

Comprehensive forensic toxicological analysis of designer drugs

New designer drugs are constantly emerging onto the illicit drug market and it is often difficult to validate and maintaincomprehensive analytical methods for accurate detection of these compounds. Generally, toxicology laboratories utilize a screening method, such as immunoassay, for the presumptive identification of drugs of abuse. When a positive result occurs, confirmatory methods, such as gas chromatography (GC) or liquid chromatography (LC) coupled with mass spectrometry (MS), are required for more sensitive and specific analyses. In recent years, the need to study the activities of these compounds in screening assays as well as to develop confirmatory techniques to detect them in biological specimens has been recognized. Severe intoxications and fatalities have been encountered with emerging designer drugs, presenting analytical challenges for detection and identification of such novel compounds. The first major task of this research was to evaluate the performance of commercially available immunoassays to determine if designer drugs were cross-reactive. The second major task was to develop and validate a confirmatory method, using LC-MS, to identify and quantify these designer drugs in biological specimens.^ Cross-reactivity towards the cathinone derivatives was found to be minimal. Several other phenethylamines demonstrated cross-reactivity at low concentrations, but results were consistent with those published by the assay manufacturer or as reported in the literature. Current immunoassay-based screening methods may not be ideal for presumptively identifying most designer drugs, including the "bath salts." For this reason, an LC-MS based confirmatory method was developed for 32 compounds, including eight cathinone derivatives, with limits of quantification in the range of 1-10 ng/mL. The method was fully validated for selectivity, matrix effects, stability, recovery, precision, and accuracy. In order to compare the screening and confirmatory techniques, several human specimens were analyzed to demonstrate the importance of using a specific analytical method, such as LC-MS, to detect designer drugs in serum as immunoassays lack cross-reactivity with the novel compounds. Overall, minimal cross-reactivity was observed, highlighting the conclusion that these presumptive screens cannot detect many of the designer drugs and that a confirmatory technique, such as the LC-MS, is required for the comprehensive forensic toxicological analysis of designer drugs.^

Acceptable vs. marginal police officers' psychological ratings : a longitudinal comparison of job performance

Archival research was conducted on the inception of preemployment psychological testing, as part of the background screening process, to select police officers for a local police department. Various issues and incidents were analyzed to help explain why this police department progressed from an abbreviated version of a psychological battery, to a much more sophisticated and comprehensive set of instruments. While doubts about psychological exams do exist, research has shown that many are valid and reliable in predicting job performance of police candidates. During a three year period, a police department hired 162 candidates (133 males and 29 females) who received "acceptable" psychological ratings and 71 candidates (58 males and 13 females) who received "marginal" psychological ratings. A document analysis consisted of variables that have been identified as job performance indicators which police psychological testing tries to predict, and "screen in" or "screen out" appropriate applicants. The areas of focus comprised the 6-month police academy, the 4-month Field Training Officer (FTO) Program, the remaining probationary period, and yearly performance up to five years of employment. Specific job performance variables were the final academy grade average, supervisors' evaluation ratings, reprimands, commendations, awards, citizen complaints, time losses, sick time usage, reassignments, promotions, and separations. A causal-comparative research design was used to determine if there were significant statistical differences in these job performance variables between police officers with "acceptable" psychological ratings and police officers with "marginal" psychological ratings. The results of multivariate analyses of variance, t-tests, and chi-square procedures as applicable, showed no significant differences between the two groups on any of the job performance variables.

A Cross-Generational Analysis of Spanish-to-English Lexico-Semantic Phenomena in Emerging Miami English

Sociolinguists have documented the substrate influence of various languages on the formation of dialects in numerous ethnic-regional setting throughout the United States. This literature shows that while phonological and grammatical influences from other languages may be instantiated as durable dialect features, lexical phenomena often fade over time as ethnolinguistic communities assimilate with contiguous dialect groups. In preliminary investigations of emerging Miami Latino English, we have observed that lexical forms based on Spanish lexical forms are not only ubiquitous among the speech of the first generation Cuban Americans but also of the second. Examples, observed in field work, casual observation, and studied formally in an experimental context include the following: “get down from the car,” which derives from the Spanish equivalent, bajar del carro instead of “get out of the car”. The translation task administered to thirty-one participants showed a variety lexical phenomena are still maintained at equal or higher frequencies.

Principal Component Analysis and Assessment of Language Network Activation Patterns in Pediatric Epilepsy

This dissertation establishes a novel data-driven method to identify language network activation patterns in pediatric epilepsy through the use of the Principal Component Analysis (PCA) on functional magnetic resonance imaging (fMRI). A total of 122 subjects’ data sets from five different hospitals were included in the study through a web-based repository site designed here at FIU. Research was conducted to evaluate different classification and clustering techniques in identifying hidden activation patterns and their associations with meaningful clinical variables. The results were assessed through agreement analysis with the conventional methods of lateralization index (LI) and visual rating. What is unique in this approach is the new mechanism designed for projecting language network patterns in the PCA-based decisional space. Synthetic activation maps were randomly generated from real data sets to uniquely establish nonlinear decision functions (NDF) which are then used to classify any new fMRI activation map into typical or atypical. The best nonlinear classifier was obtained on a 4D space with a complexity (nonlinearity) degree of 7. Based on the significant association of language dominance and intensities with the top eigenvectors of the PCA decisional space, a new algorithm was deployed to delineate primary cluster members without intensity normalization. In this case, three distinct activations patterns (groups) were identified (averaged kappa with rating 0.65, with LI 0.76) and were characterized by the regions of: 1) the left inferior frontal Gyrus (IFG) and left superior temporal gyrus (STG), considered typical for the language task; 2) the IFG, left mesial frontal lobe, right cerebellum regions, representing a variant left dominant pattern by higher activation; and 3) the right homologues of the first pattern in Broca's and Wernicke's language areas. Interestingly, group 2 was found to reflect a different language compensation mechanism than reorganization. Its high intensity activation suggests a possible remote effect on the right hemisphere focus on traditionally left-lateralized functions. In retrospect, this data-driven method provides new insights into mechanisms for brain compensation/reorganization and neural plasticity in pediatric epilepsy.