880 resultados para theory and modeling


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We utilised methods of chaos theory that were originally used in a 1990’s study to analyse the behaviour of various Hungarian socio-economic macro indicators, both historically and their expected behaviour in the future. In this study, we present the method adapted to PC and the behaviour of the selected macro indicators. We characterize the pathways our society and economy has experienced and where they are heading to into the future by the means of these indicators. Comparing the present results of analysis with the results twenty years ago (when today’s present was the future) we came to the conclusion that most of the indicators became less chaotic, thus the socio-economic courses were getting more stable over the past two decades. We conclude that the opportunity to change them is slowly diminishing, it will be more and more difficult to renew the Hungarian socio-economic indicators, and to turn the processes to more desirable courses. Recommendations for change interventions are then provided.

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The field of chemical kinetics is an exciting and active field. The prevailing theories make a number of simplifying assumptions that do not always hold in actual cases. Another current problem concerns a development of efficient numerical algorithms for solving the master equations that arise in the description of complex reactions. The objective of the present work is to furnish a completely general and exact theory of reaction rates, in a form reminiscent of transition state theory, valid for all fluid phases and also to develop a computer program that can solve complex reactions by finding the concentrations of all participating substances as a function of time. To do so, the full quantum scattering theory is used for deriving the exact rate law, and then the resulting cumulative reaction probability is put into several equivalent forms that take into account all relativistic effects if applicable, including one that is strongly reminiscent of transition state theory, but includes corrections from scattering theory. Then two programs, one for solving complex reactions, the other for solving first order linear kinetic master equations to solve them, have been developed and tested for simple applications.

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This study investigated how students perceived their motivation in high school social studies classes in school and to determine if a correlation exists between students’ grade level, race, gender, and their motivation. The sample included 337 high school students in Broward County, Florida. To assess students’ perceptions on their motivation the academic self-regulation questionnaire was utilized. Results indicate that social studies students show high levels of external regulation, with a mean score at 22.31 on a scale of 36 points. The results show a mean score of 24 on a scale of 28 points for identified regulation among social studies students. Findings revealed that student motivation could be gauged. No statistical significance was found between high school students’ grade level, race, gender, and their motivation in social studies classes. The findings of this study have shown that students at Boyd H. Anderson High School want to learn social studies.

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This paper examines the assumptions and paradigms used to discuss diversity and equity in adult education literature using critical race theory as a lens. Five themes emerged from the critique that may initiate an innovative dialogue about the realities and subjectivities singling out racial and ethnic minorities in the USA.

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The authors’ review of literature about Bandura’s (1977) social learning theory and self-efficacy leads to implications on how this theory can positively affect prison work release programs and inmate post-release outcomes. Additionally, several causes of deviant behavior have been explained by social learning theory concepts.

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The purpose of this study was to explore the relationship between faculty perceptions, selected demographics, implementation of elements of transactional distance theory and online web-based course completion rates. This theory posits that the high transactional distance of online courses makes it difficult for students to complete these courses successfully; too often this is associated with low completion rates. Faculty members play an indispensable role in course design, whether online or face-to-face. They also influence course delivery format from design through implementation and ultimately to how students will experience the course. This study used transactional distance theory as the conceptual framework to examine the relationship between teaching and learning strategies used by faculty members to help students complete online courses. Faculty members' sex, number of years teaching online at the college, and their online course completion rates were considered. A researcher-developed survey was used to collect data from 348 faculty members who teach online at two prominent colleges in the southeastern part of United States. An exploratory factor analysis resulted in six factors related to transactional distance theory. The factors accounted for slightly over 65% of the variance of transactional distance scores as measured by the survey instrument. Results provided support for Moore's (1993) theory of transactional distance. Female faculty members scored higher in all the factors of transactional distance theory when compared to men. Faculty number of years teaching online at the college level correlated significantly with all the elements of transactional distance theory. Regression analysis was used to determine that two of the factors, instructor interface and instructor-learner interaction, accounted for 12% of the variance in student online course completion rates. In conclusion, of the six factors found, the two with the highest percentage scores were instructor interface and instructor-learner interaction. This finding, while in alignment with the literature concerning the dialogue element of transactional distance theory, brings a special interest to the importance of instructor interface as a factor. Surprisingly, based on the reviewed literature on transactional distance theory, faculty perceptions concerning learner-learner interaction was not an important factor and there was no learner-content interaction factor.

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The theories of orthogonal cultural identification and self-categorization are offered as links in examining the possible racioethnic differences in job satisfaction. It is posited that racioethnicity (Cox & Blake, 1991) is multidimensional with at least three conceptually distinct dimensions. Since there is a need for consistent terminology with respect to these distinct dimensions, the following new terms are offered to differentiate among them: "physioethnicity" refers to the physiological dimension of racioethnicity; "socioethnicity" refers to the sociocultural dimension; and "psychoethnicity" refers to the psychological dimension.^ Results showed that for the dominant group (Hispanics in this case) (1) bicultural and multicultural individuals were more satisfied with coworkers than acultural and monocultural individuals and (2) individuals with higher strength of psychoethnicity were more satisfied with coworkers, the work itself, and supervision than those with lower strength of psychoethnicity. The findings suggest racioethnic differences within the dominant group and between groups beyond race. ^

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Chromium (Cr) is a metal of particular environmental concern, owing to its toxicity and widespread occurrence in groundwater, soil, and soil solution. A combination of hydrological, geochemical, and microbiological processes governs the subsurface migration of Cr. Little effort has been devoted to examining how these biogeochemical reactions combine with hydrologic processes influence Cr migration. This study has focused on the complex problem of predicting the Cr transport in laboratory column experiments. A 1-D reactive transport model was developed and evaluated against data obtained from laboratory column experiments. ^ A series of dynamic laboratory column experiments were conducted under abiotic and biotic conditions. Cr(III) was injected into columns packed with β-MnO 2-coated sand at different initial concentrations, variable flow rates, and at two different pore water pH (3.0 and 4.0). In biotic anaerobic column experiments Cr(VI) along with lactate was injected into columns packed with quartz sand or β-MnO2-coated sand and bacteria, Shewanella alga Simidu (BrY-MT). A mathematical model was developed which included advection-dispersion equations for the movement of Cr(III), Cr(VI), dissolved oxygen, lactate, and biomass. The model included first-order rate laws governing the adsorption of each Cr species and lactate. The equations for transport and adsorption were coupled with nonlinear equations for rate-limited oxidation-reduction reactions along with dual-monod kinetic equations. Kinetic batch experiments were conducted to determine the reduction of Cr(VI) by BrY-MT in three different substrates. Results of the column experiments with Cr(III)-containing influent solutions demonstrate that β-MnO2 effectively catalyzes the oxidation of Cr(III) to Cr(VI). For a given influent concentration and pore water velocity, oxidation rates are higher, and hence effluent concentrations of Cr(VI) are greater, at pH 4 relative to pH 3. Reduction of Cr(VI) by BrY-MT was rapid (within one hour) in columns packed with quartz sand, whereas Cr(VI) reduction by BrY-MT was delayed (57 hours) in presence of β-MnO 2-coated sand. BrY-MT grown in BHIB (brain heart infusion broth) reduced maximum amount of Cr(VI) to Cr(III) followed by TSB (tryptic soy broth) and M9 (minimum media). The comparisons of data and model results from the column experiments show that the depths associated with Cr(III) oxidation and transport within sediments of shallow aquatic systems can strongly influence trends in surface water quality. The results of this study suggests that carefully performed, laboratory column experiments is a useful tool in determining the biotransformation of redox-sensitive metals even in the presence of strong oxidant, like β-MnO2. ^

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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. ^

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This paper chronicles White South African journalist Donald Woods’ life (1933-2001) as he transformed from holding racist beliefs that Blacks were “people who were there to be your servants,” to becoming one of his country’s leading anti-apartheid activists. Adult learning and development via perspective transformation theory are explored.

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A two-dimensional, 2D, finite-difference time-domain (FDTD) method is used to analyze two different models of multi-conductor transmission lines (MTL). The first model is a two-conductor MTL and the second is a threeconductor MTL. Apart from the MTL's, a three-dimensional, 3D, FDTD method is used to analyze a three-patch microstrip parasitic array. While the MTL analysis is entirely in time-domain, the microstrip parasitic array is a study of scattering parameter Sn in the frequency-domain. The results clearly indicate that FDTD is an efficient and accurate tool to model and analyze multiconductor transmission line as well as microstrip antennas and arrays.

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While analysis of the effect which education and migration have on development is neither clear cut, nor obvious, regimes such as those of Jamaica have traditionally placed great emphasis on development through education at all levels. The process of human resource development and the accumulation of human capital is intended to unlock the door to modernization. Nevertheless, our findings indicate a considerable loss of professional and skilled personnel -- the same group that embody a disproportionate amount of educational expenditure relative to the population. Insofar as planning is concerned this migration represents a negative factor. The developing country of Jamaica is unintentionally supplying the developed world with an "annual gift" of human capital which its economy cannot afford. The major issue becomes: to what extent can any government "protect" its investments by restricting movements of capital and people. The general assumption of this paper is that the question of human rights cannot be ignored especially in democracies (which Jamaica decidedly is), where movement is seen as an ingrained human right. During the 1970s and 1980s, Jamaica and the Caribbean as a whole has lost much through intellectual capital migrations. Yet brains may also die in their own environment, if deprived the ability to create their own criteria and goals. Forcing people to stay with their money and know-how may only serve to produce and economic environment overgrown with weeds of lethargy, indolence and mediocrity.

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Esta tesis trata sobre aproximaciones de espacios métricos compactos. La aproximación y reconstrucción de espacios topológicos mediante otros más sencillos es un tema antigüo en topología geométrica. La idea es construir un espacio muy sencillo lo más parecido posible al espacio original. Como es muy difícil (o incluso no tiene sentido) intentar obtener una copia homeomorfa, el objetivo será encontrar un espacio que preserve algunas propriedades topológicas (algebraicas o no) como compacidad, conexión, axiomas de separación, tipo de homotopía, grupos de homotopía y homología, etc. Los primeros candidatos como espacios sencillos con propiedades del espacio original son los poliedros. Ver el artículo [45] para los resultados principales. En el germen de esta idea, destacamos los estudios de Alexandroff en los años 20, relacionando la dimensión del compacto métrico con la dimensión de ciertos poliedros a través de aplicaciones con imágenes o preimágenes controladas (en términos de distancias). En un contexto más moderno, la idea de aproximación puede ser realizada construyendo un complejo simplicial basado en el espacio original, como el complejo de Vietoris-Rips o el complejo de Cech y comparar su realización con él. En este sentido, tenemos el clásico lema del nervio [12, 21] el cual establece que para un recubrimiento por abiertos “suficientemente bueno" del espacio (es decir, un recubrimiento con miembros e intersecciones contractibles o vacías), el nervio del recubrimiento tiene el tipo de homotopía del espacio original. El problema es encontrar estos recubrimientos (si es que existen). Para variedades Riemannianas, existen algunos resultados en este sentido, utilizando los complejos de Vietoris-Rips. Hausmann demostró [35] que la realización del complejo de Vietoris-Rips de la variedad, para valores suficientemente bajos del parámetro, tiene el tipo de homotopía de dicha variedad. En [40], Latschev demostró una conjetura establecida por Hausmann: El tipo de homotopía de la variedad se puede recuperar utilizando un conjunto finito de puntos (suficientemente denso) para el complejo de Vietoris-Rips. Los resultados de Petersen [58], comparando la distancia Gromov-Hausdorff de los compactos métricos con su tipo de homotopía, son también interesantes. Aquí, los poliedros salen a relucir en las demostraciones, no en los resultados...