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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
381

Alocação ótima de reguladores de tensão em sistemas de distribuição de energia elétrica radiais usando uma formulação linear inteira mista. -

Alves, Raiane Piacente. January 2012 (has links)
Orientador: Marcos Julio Rider Flores / Banca: Rubén Augusto Romero Lázaro / Banca: Carlos Alberto Castro Júnior / Resumo: O presente trabalho apresenta o desenvolvimento de uma formulação linear inteira mista (equivalente à formulação não linear inteira mista) para resolver o problema de alocação de reguladores de tensão ao longo dos alimentadores primários de sistemas de distribuição de energia elétrica radiais, com o objetivo de melhorar o perfil da magnitude de tensão, reduzir as perdas de potência ativa da rede e a minimização dos custos de instalação dos equipamen-tos. Na formulação proposta, o cálculo do ponto de operação em regime permanente de um sistema de distribuição radial é modelado matematicamente usando expressões lineares. O uso de um modelo de programação linear inteira mista garante a convergência para a solução óti-ma usando ferramentas de otimização clássica existentes. Os sistemas testes de 70-, 136-, 202- e 400-nós são utilizados para mostrar a precisão do modelo matemático, assim como também a eficiência da técnica de solução proposta para resolver o problema de alocação de reguladores de tensão em um sistema de distribuição radial / Abstract: This work shows the development of a mixed integer linear formulation to solve the voltage regulators allocation problem in radial electrical distribution systems, with the goal of improving the voltage magnitude profile, reducing the active power losses and mini-mizing the investment cost. In the proposed formulation, the steady-state operation point of the radial distribution system is modeled through linear expressions. The use of a mixed-integer linear formulation guarantees convergence to optimality using existing optimization software. The 70-, 136-, 202- and 400-node test systems are used in order to show the accura-cy of the mathematical model as well as the efficiency of the proposed solution technique to solve the allocation problem of voltage regulators in a radial distribution system / Mestre
382

A parametric level set method for the design of distributed piezoelectric modal sensors

Hoffmann, Sandra 04 May 2016 (has links) (PDF)
Distributed modal filters based on piezoelectric polymer have especially become popular in the field of active vibration control to reduce the problem of spillover. While distributed modal filters for one-dimensional structures can be found analytically based on the orthogonality between the mode shapes, the design for two-dimensional structures is not straightforward. It requires a continuous gain variation in two dimensions, which is not realizable from the current manufacturing point of view. In this thesis, a structural optimization problem is considered to approximate distributed modal sensors for two-dimensional plate structures, where the thickness is constant but the polarization can switch between positive and negative. The problem is solved through an explicit parametric level set method. In this framework, the boundary of a domain is represented implicitly by the zero isoline of a level set function. This allows simultaneous shape and topology changes. The level set function is approximated by a linear combination of Gaussian radial basis functions. As a result, the structural optimization problem can be directly posed in terms of the parameters of the approximation. This allows to apply standard optimization methods and bypasses the numerical drawbacks, such as reinitialization, velocity extension and regularization, which are associated with the numerical solution of the Hamilton-Jacobi equation in conventional methods.Since the level set method based on the shape derivative formally only allows shape but not topology transformation, the optimization problem is firstly tackled with a derivative-free optimization algorithm. It is shown that the approach is able to find approximate modal sensor designs with only few design variables. However, this approach becomes unsuitable as soon as the number of optimization variables is growing. Therefore, a sensitivity-based optimization approach is being applied, based on the parametric shape derivative which is with respect to the parameters of the radial basis functions. Although the shape derivatives does not exist at points where the topology changes, it is demonstrated that an optimization routine based on a SQP solver is able to perform topological changes during the optimization and finds optimal designs even from poor initial designs. In order to include the sensors' distribution as design variable, the parametric level set approach is extended to multiple level sets. It turns out that, despite the increased design space, optimal solutions always converge to full-material polarization designs. Numerical examples are provided for a simply supported as well as a cantilever square plate. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished
383

Propuesta de un boletín informativo radiofónico en la programación de una emisora de cobertura regional en Lambayeque, año 2011

Sánchez Larios, Lucía del Rosario January 2013 (has links)
El presente trabajo de investigación expone las características, estilo y producción de los boletines informativos como una de las especies informativas radiofónicas, usándolas en su contexto periodístico y en las diversas programaciones radiales de una emisora. Aquí, las noticias son el eje fundamental para mantener informada a la población. El objetivo general de la investigación es proponer el proyecto del programa piloto de un boletín informativo radiofónico para mejorar la producción de boletines que se transmitirán en la programación de una radio de cobertura regional en Lambayeque. Entre sus objetivos específicos, está el hacer un diagnóstico previo de la posible audiencia del proyecto del programa piloto, elaborar una propuesta del proyecto del programa piloto de boletines informativos radiofónicos en base a opinión a especialistas y una muestra seleccionada, y ofrecer un trabajo de investigación que pueda servir de modelo para la producción de boletines informativos radiofónicos. Por último, se explica en forma detallada la naturaleza, objetivos, público objetivo, horario, estructura, frecuencia, contenido y finalidad de la propuesta aplicada en la investigación. Esta investigación es de tipo cualitativa propositiva.
384

Transplant-Induced Working Memory Deficits in Hippocampectomized Rats

Woodruff, Michael L., Baisden, Ronald H., Cannon, Richard L. 01 January 1993 (has links)
This experiment determined the effects of transplantation of fetal hippocampus on the ability of male rats with hippocampal lesions to acquire versions of a radial arm maze that depended on either extramaze cues or intramaze cues for solution. Rats receiving transplants took significantly more trials than control rats to emit three consecutive errorless trials in the extramaze cue (spatial) variation of the maze. Rats with just hippocampal lesions never differed from any other group. No differences in this measure were found for the intramaze cue condition. Rats receiving transplants made more repeat entries into reinforced arms in both versions of the maze than control rats and more reentries into neverbaited arms in the spatial maze. Rats with hippocampal lesions failed to differ from any other group on this measure in the spatial maze, but were different from normal rats in the intramaze cue maze. These data suggest that in some tasks transplants of fetal tissue lead to greater behavioral impairment than lesions alone.
385

Deficits in Spatial Learning and Memory in Adult Mice Following Acute, Low or Moderate Levels of Prenatal Ethanol Exposure During Gastrulation or Neurulation

Schambra, Uta B., Lewis, C. Nicole, Harrison, Theresa A. 01 July 2017 (has links)
Debate continues on the merits of strictly limiting alcohol consumption during all of pregnancy, and whether “safe” consumption levels and/or times exist. Only a relatively few experimental studies have been conducted that limit the timing of exposure to specific events during development and the exposure level to one that might model sporadic, incidental drinking during pregnancy. In the present study, the effects of two acute gavage exposures to low and moderate levels of ethanol (peak blood ethanol concentrations (BEC) of 104 and 177 mg/dl, respectively) either during gastrulation on gestational day (GD) 7 (at GD7:0 h and GD7:4 h) or during neurulation on GD8 (at GD8:6 h and GD8:10 h) on the spatial learning and memory abilities of adult mice in the radial arm maze (RAM) were examined. Mice were selected from a prenatal ethanol exposure (PAE) cohort that had been tested as neonates for their sensorimotor development (Schambra et al., 2015) and as juveniles and young adults for open field activity levels and emotionality (Schambra et al., 2016). Mice exposed on either of the two gestational days to acute, low or moderate levels of ethanol were deficient in overall performance in the RAM in adulthood. Importantly, mice in ethanol exposed groups took longer to reach criterion in the RAM, and many mice in these groups failed to do so after 48 trials when testing was terminated. Exposure to a low level of ethanol on either GD7 or GD8, or a moderate level on GD7, resulted in significant impairment in spatial reference (long-term) memory, while only mice exposed on GD7 to the low level of ethanol were significantly impaired in spatial working (short-term) memory. Mice exposed to the low ethanol level on either day had significantly shorter response latencies, which may reflect impairment of processes related to response inhibition or executive attention in these mice. For all measures, distributions of individual scores revealed a relatively small subset of mice in each PAE group who scored well outside the range of the control group, which skewed the population distributions to varying degrees in the direction of worse performance for the PAE groups. Overall the data suggest that after acute, low level ethanol exposure early in gestation, the likelihood that an individual mouse embryo experienced measureable ill-effects due to the exposure was rather low, but in a few of the embryos, damage occurred that resulted in significant deficits in later performance. The overall characteristics of our cohort of PAE mice, including delayed sensorimotor development, mild hypoactivity and increased emotionality, as shown in previous studies, together with deficits in spatial learning and memory as shown here, resemble those in a subset of human Fetal Alcohol Spectrum Disorder (FASD) diagnoses, specifically ADHD-Inattentive type (ADHD-I) and/or Sluggish Cognitive Tempo (SCT). Although possible correspondences between mechanisms underlying PAE-induced deficits in mice and those operating in humans remain undefined, further study with this mouse PAE model may ultimately help advance understanding of the causes of these conditions in affected children. This study highlights the possibility of risk associated with low to moderate sporadic alcohol consumption during the first month of human pregnancy.
386

Análisis de las temáticas desarrolladas por las radios comunitarias y educativas: Radio Cutivalú y Radio Vino

Ballena Castillo, Maria de Jesus January 2019 (has links)
El presente trabajo de investigación tuvo como objetivo principal analizar las temáticas desarrolladas por las radios comunitarias y educativas: radio Cutivalú y radio Vino; y como objetivos específicos los siguientes: describir las características de las radios comunitarias y educativas: radio Cutivalú y radio Vino, identificar las temáticas que se desarrollan en radio Cutivalú y radio Vino, y señalar los aportes de las temáticas en el desarrollo de las comunidades en las que están establecidas radio Cutivalú y radio Vino. La metodología que se utilizó en la investigación fue cualitativa, con un enfoque hermenéutico, y los instrumentos aplicados fueron entrevistas a los habitantes de Piura y Jayanca, lugares donde se ubican las radios materia de estudio, para conocer los aportes que estas generan en ellos. El trabajo concluyó que, el aporte principal de radio Cutivalú y radio Vino, con la información que transmiten a la población, es la transmisión de valores y la concientización de los ciudadanos en temas de política, salud y educación, principalmente, y una reflexión dirigida a que estos se conviertan en agentes activos de la transformación de su entorno social.
387

Rotational Structure of Extremely Floppy van der Waals Complexes: Adiabatic Separation of Angular and Radial Motion

Ward, P. Daniel 01 May 2000 (has links)
The adiabatic or Born-Oppenheimer approximation is often used in molecular calculations to simplify the solution to the Schrodinger equation. The basis of the approximation is the large difference in the relative motions of the nuclei and electrons in the molecule-the electrons are able to respond almost instantly to the movements of the nuclei. Thus, the nuclei may be regarded as being fixed in a certain position and the Schrodinger equation can then be solved using the potential obtained by solving the electronic problem at fixed nuclear configuration. A similar argument can be used to decouple the angular and radial motions of many van der Waals complexes because, like nuclei in molecules, the radial motions in many van der Waals complexes are strongly localized. Fixing the radial separation between the atoms and molecules in the complex to a particular value results in a Schrodinger equation that is much simpler to solve because it is only dependent on angles. van der Waals complexes containing helium atoms, however, present a dilemma because the extremely weak interactions present also lead to large amplitude radial as well as angular motions. Because the basis of the adiabatic approximation is a large difference in time scale between the angular and radial motions, the validity of the adiabatic approximation for helium complexes is uncertain. In this thesis, the adiabatic separation of angular and radial motion is shown to be accurate for extremely floppy complexes of helium by demonstrating its use on the van der Waals molecule He-HCN. A major application of this method is expected to be the quick calculation of approximate wave functions for Diffusion Monte Carlo studies of the rotation of impurity molecules inside ultra-cold droplets of helium. The method presented here is significantly faster than other methods (e.g., Variational Monte Carlo) that have been used to calculate approximate wave functions for Diffusion Monte Carlo.
388

Global summation of radial frequency patterns and the effect of sudden onset glare on shape discrimination

Ekure, Edgar 12 June 2014 (has links)
ABSTRACT Global summation of radial frequency patterns and the effect of sudden onset glare on shape discrimination The purpose of this study was to provide evidence of global pooling around the circumference of the Radial frequency (RF) pattern, and to study the effect of sudden onset glare on shape discrimination. The RF stimuli were generated by the amplitude modulation of the radius of a circle which deforms them from circularity, while the cross sectional luminance profile was the fourth derivative of Gaussians (D4). The amplitude of the stimuli determines how distinct the pattern is and thus measures the degree of sensitivity while the radial frequency determines the number of lobes the pattern has. In the first part of the study, whole RF patterns (RF3 to RF16) and open component fractions (0.125, 0.25, 0.5, 0.75), which are incomplete sectors of the whole, were tested against their respective reference unmodulated patterns. Subjects were tasked with discriminating minute deviations from their reference patterns. In the second part of the study, high contrast (20 X detection threshold) RF3 and RF4 contours and equivalent low contrast (5 X detection threshold) RF3 and RF4 contours were used as stimuli. Shape discrimination threshold for the high contrast target was determined with and without sudden onset glare. The result of the first part of the study showed that threshold decreased significantly as larger component RF patterns were tested (p < 0.05). The decrease could not be accounted for by the probabilistic sampling of local filters (probability summation). The result of the second part of the study showed that shape discrimination threshold increased with sudden onset glare. The increase was even more pronounced with lower mean luminance and when smaller fractions of the contours were tested. Shape discrimination threshold was significantly higher with high contrast contours in the presence of glare than equivalent low contrast contours, indicating that the veiling luminance model alone could not account for a decrease in visual performance in this shape discrimination task.
389

Morfología del periodismo radial y su relación con el desarrollo cultural de Pasco

Charry Aysanoa, Pedro Amílcar January 2009 (has links)
Morfología del periodismo radial y su relación con el desarrollo cultural de Pasco, es un estudio que se desarrolla en el afán de identificar los espacios y sus contenidos, en cuanto a los programas denominados informativos o noticieros de la radio en la ciudad Cerro de Pasco. La masificación de estos programas es un indicador que la actividad preferente de los egresados de comunicación de los centros superiores de la ciudad, es la producción de programas periodísticos en la radio, mientras que la televisión y la prensa tienen muy poca demanda. Es una investigación descriptiva correlacional desde el punto de vista del método cuantitativo. Aquí se establece una relación entre la variable X: forma de hacer periodismo radial, con la variable Y: desarrollo de la cultura en la población de Pasco, para cuyo efecto se hizo un trabajo de campo, habiendo recogido datos en una muestra de 413 sujetos elegidos probabilísticamente con un intervalo de confianza del 95% y un margen de error del 0,5%. Las unidades identificadas de la muestra, han sido oyentes de los informativos radiales de esta ciudad, a quienes se les suministró una encuesta de opinión. Desde el punto de vista del método cualitativo, el estudio presenta el análisis de contenido de 3 de los informativos radiales más escuchados de las emisoras locales y el contenido y un análisis intencional selectivo de uno de ellos, que tiene arraigo popular en esta ciudad. / Tesis
390

Dřevěná konstrukce planetária / Timber structure of the planetarium

Patková, Aneta January 2012 (has links)
The subject matter of this theses is a static design and appraisal of a structure of the planetarium roof. It is a cupola over the circular plan and consists of two radial arched ribs. This theses contains two varieties of its structure.

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