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Free-surface film flow of a suspension and a related concentration instabilityTimberlake, Brian D. (Brian Davis) 01 April 2004 (has links)
Film flow of a suspension has been investigated both experimentally and theoretically. Gravity-driven free-surface inclined plane flow of a suspension of neutrally buoyant particles has been investigated using a stereoscopic particle imaging velocimetry technique. Particles have been shown to migrate away from the solid surface, and the film thickness has been shown to
decrease as the fluid moves down the inclined plane. The free surface has been characterized using a light reflection technique, which shows that surface topography is affected by the inclination angle, and the particle concentration.
This flow has been modeled based on a suspension normal stress approach. A boundary condition at the free surface has been examined, and model predictions have been compared with experimental results. The model predicts that the film thickness, relative to its initial value, will decrease with the bulk particle concentration.
The thin film flow over the inner cylinder in partially filled Couette flow of a suspension has been experimentally investigated as well as modeled. Concentration bands have been shown to form under a variety of different fill fractions, bulk particle concentrations, inclination angles, ratio of inner to outer cylinder, and rotation rates of the inner cylinder. The banding phenomena ranges from a regime where bands are small, mobile and relatively similar in concentration to the bulk, to a regime where
the concentration bands are larger, stationary, and where the space between them is completely devoid of particles.
The role of the film thickness in the band formation process has been investigated, and has led to a model for the band formation process based on a difference in the rate that fluid can drain from height fluctuations relative to the particles.
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Análise do comportamento do centro de pressão (CoP) na posição ereta quieta em situação de aclive, declive e horizontal diante da movimentação cefálica. / Analysis of the behavior of the pressure center (CoP) in the upright standing position in slope, slope and horizontal position in front of the cephalic movement.Silveira, Silvana Rocha da 29 September 2017 (has links)
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Previous issue date: 2017-09-29 / O controle postural é um requisito imprescindível para a execução das habilidades motoras durante as tarefas das atividades de vida diária, logo, há a necessidade constante de ajuste dos segmentos corporais para garantir a autonomia e independência da mobilidade humana, dentro da conjuntura da acessibilidade. Os ajustes posturais são resultantes da interação do sistema sensório–motor e da sua correlação com o meio ambiente, produzindo orientação e estabilidade postural esperada durante a execução das atividades diárias, sendo ela estática ou dinâmica. Deste modo, o objetivo do estudo foi analisar e comparar o comportamento do centro de pressão na posição ereta quieta em situação de aclive, declive e horizontal diante da movimentação cefálica, entre três grupos com faixas etárias diferentes. O estudo transversal foi composto de 28 indivíduos, de ambos os gêneros, divididos em três grupos por faixas etárias (20 a 29 anos, 30 a 59 anos e acima de 60 anos), de acordo com os critérios de inclusão. O instrumento de avaliação constituiu-se por uma plataforma de força acoplada numa rampa com 15° e em um platô horizontal. A coleta dos dados seguiu um protocolo pré-determinado, envolvendo a posição ereta quieta com olhos abertos (OA), em quatro condições cefálicas, em três situações: aclive, declive e horizontal. Os dados obtidos foram trabalhados por meio do programa Matlab® e para a análise estatística foi aplicado o programa Action Start, utilizando a análise descritiva dos dados e o Teste Anova: fator único, Teste-t: duas amostras em par para média e Teste-t: duas amostras presumindo variâncias diferentes. Os resultados do presente estudo apontaram que a oscilação do CoP na posição ereta quieta com olhos abertos, se alteram diante das condições em que o segmento cefálico encontra – se em movimento, independente das situações de aclive, declive e horizontal, principalmente nos grupos com faixa etária igual ou superior a 60 anos / Postural control is an essential requirement for the performance of motor skills during daily activities, so there is a constant need to adjust the body segments to ensure the autonomy and independence of human mobility, within the context of accessibility. Postural adjustments result from the interaction of the sensor - motor system and its correlation with the environment, producing orientation and postural stability expected during the execution of daily activities, being static or dynamic. Thus, the objective of the study was to analyze and compare the behavior of the pressure center in the standing upright position in slope, slope and horizontal situation in front of the head movement, between three groups with different age groups. The cross-sectional study consisted of 28 individuals of both genders, divided into three groups by age group (20 to 29 years, 30 to 59 years and above 60 years), according to the inclusion criteria. The evaluation instrument consisted of a force platform coupled on a ramp with 15 ° and a horizontal plateau. Data collection followed a predetermined protocol, involving the standing upright position with open eyes (OA), in four cephalic conditions, in three situations - slope, slope and horizontal. The data obtained were worked through the Matlab® program and for the statistical analysis the Action program was applied using descriptive data analysis and the Anova test: single factor, t-test: two samples in pairs for mean and t-test: Two samples assuming different variances. The results of the present study pointed out that the oscillation of the CoP in the quiet standing position with open eyes, are altered by the conditions in which the cephalic segment is in motion, independent of slope, slope and horizontal situations, Aged 60 years or over
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Caracterização da radiação solar: o caso da Cidade Universitária/USP e da Ilha do Cardoso/Cananéia / Characterization of solar radiation: the case of the USP/SP and Cardoso Island/CananeíaRosa, Daniel Jordão de Magalhães 26 August 2003 (has links)
A ética e a luta pela equidade social e melhoria da qualidade de vida das populações impulsiona a busca pela universalização do atendimento do serviço energético e pela utilização racional dos recursos renováveis existentes em cada local. Nesse sentido, o aproveitamento da energia solar apresenta-se como uma excelente alternativa, seja para disponibilizar pequenas quantidades de energia elétrica, utilizando-se de geradores fotovoltaicos, seja para o aquecimento de água ou ainda para o condicionamento ambiental de edificações. Em qualquer desses casos, são necessárias informações confiáveis sobre o recurso solar disponível. O presente trabalho se insere nesse contexto buscando, além de propor um padrão para instalação de estações solarimétricas, para o sistema de unidades utilizado e para a rotina de calibração e manutenção dos equipamentos, caracterizar a radiação solar no Estado de São Paulo, tendo como um de seus objetivos oferecer dados de irradiação solar diária média mensal, centrando a atenção na cidade de São Paulo e no Vale do Ribeira, no litoral sul do Estado de São Paulo. Esta última área, localizada no município de Cananéia, possui baixos índices de eletrificação rural e grande potencial de utilização de sistemas fotovoltaicos para suprir a demanda de residências isoladas. Como, em geral, os painéis para aproveitamento do recurso solar são instalados em uma determinada inclinação, para se dimensionar corretamente um sistema é necessário transformar os dados de irradiação solar de plano horizontal para plano inclinado. Assim, foram testados os diversos modelos presentes na literatura para o cálculo da irradiação global diária mensal em plano inclinado a partir de dados em plano horizontal. Todos esses modelos necessitam de dados de irradiação difusa, ou seja, a irradiação proveniente de toda a esfera celeste, menos diretamente do Sol, para poderem ser utilizados. Dessa maneira, o presente trabalho buscou testar os diversos modelos que calculam a irradiação difusa a partir da irradiação global e, com a verificação da inadequação desses, propõe uma nova correlação, mais apropriada para nossa realidade. / Ethics, and the struggle both for social equity and the improvement of the standard of living of populations, drive the efforts for both the universalization of energy provision and the rational utilization of existing renewable resources. Accordingly, utilizing solar energy presents itself as an excellent alternative, whether it is to make available small quantities of electric energy, utilizing photovoltaic generators, for heating water, or for environmental conditioning. Whatever the case, it is necessary to have reliable information on available solar resource. This work seeks to develop standards for implementation of solarimetric stations, for the unit system to be utilized and for the routine of calibration and maintenance of equipment. It also seeks to characterize solar radiation in the state of São Paulo, with one of its objectives being the supply of data of monthly average daily irradiation in the city of São Paulo and the Ribeira Valley (south coast of São Paulo state). The latter has low levels of rural electrification and great potential for utilizing photovoltaic systems in the supply of energy for isolated residences. As solar panels are generally installed on a sloped surface, the correct dimensioning of systems requires converting solar irradiation data from horizontal plane to tilted plane. Thus, several models presented in the literature that calculate monthly average daily irradiation on inclined plane from available data measured on horizontal plane were tested. All such models need diffuse irradiation data, that is, irradiation originating from the entire sky, except that originating directly from the sun, to be utilized. For this reason, this work sought to test several models that establish correlations for the calculation of diffuse solar irradiation from global solar irradiation. As the inadequacy of such models was verified, this proposes a new correlation that is more appropriate for the conditions of the state of São Paulo.
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Komparace učebnic fyziky pro základní školy / The comparison of physics textbooks for basic schoolsMAZANEC, Radim January 2014 (has links)
The thesis deals with the comparison of physics textbooks for primary schools. The purpose of this thesis is to determine the representation of individual sets of textbooks in primary schools in the South Bohemian Region, to develop and test custom teaching concepts revolving around thematic unit of 'Simple Machines'. This work is addressed primarily to teachers as a tool to enhance teaching effectiveness, to support the imagination and to increase interest in physics among pupils. These are the reasons why thematic unit, called Simple Machines, has been developed in form of interactive presentation, whose contribution and efficiency has been practically verified directly during physics classes in few selected primary schools. Benefits have been verified through accredited didactic tests and their evaluation and results are processed at the end of this thesis.
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Caracterização da radiação solar: o caso da Cidade Universitária/USP e da Ilha do Cardoso/Cananéia / Characterization of solar radiation: the case of the USP/SP and Cardoso Island/CananeíaDaniel Jordão de Magalhães Rosa 26 August 2003 (has links)
A ética e a luta pela equidade social e melhoria da qualidade de vida das populações impulsiona a busca pela universalização do atendimento do serviço energético e pela utilização racional dos recursos renováveis existentes em cada local. Nesse sentido, o aproveitamento da energia solar apresenta-se como uma excelente alternativa, seja para disponibilizar pequenas quantidades de energia elétrica, utilizando-se de geradores fotovoltaicos, seja para o aquecimento de água ou ainda para o condicionamento ambiental de edificações. Em qualquer desses casos, são necessárias informações confiáveis sobre o recurso solar disponível. O presente trabalho se insere nesse contexto buscando, além de propor um padrão para instalação de estações solarimétricas, para o sistema de unidades utilizado e para a rotina de calibração e manutenção dos equipamentos, caracterizar a radiação solar no Estado de São Paulo, tendo como um de seus objetivos oferecer dados de irradiação solar diária média mensal, centrando a atenção na cidade de São Paulo e no Vale do Ribeira, no litoral sul do Estado de São Paulo. Esta última área, localizada no município de Cananéia, possui baixos índices de eletrificação rural e grande potencial de utilização de sistemas fotovoltaicos para suprir a demanda de residências isoladas. Como, em geral, os painéis para aproveitamento do recurso solar são instalados em uma determinada inclinação, para se dimensionar corretamente um sistema é necessário transformar os dados de irradiação solar de plano horizontal para plano inclinado. Assim, foram testados os diversos modelos presentes na literatura para o cálculo da irradiação global diária mensal em plano inclinado a partir de dados em plano horizontal. Todos esses modelos necessitam de dados de irradiação difusa, ou seja, a irradiação proveniente de toda a esfera celeste, menos diretamente do Sol, para poderem ser utilizados. Dessa maneira, o presente trabalho buscou testar os diversos modelos que calculam a irradiação difusa a partir da irradiação global e, com a verificação da inadequação desses, propõe uma nova correlação, mais apropriada para nossa realidade. / Ethics, and the struggle both for social equity and the improvement of the standard of living of populations, drive the efforts for both the universalization of energy provision and the rational utilization of existing renewable resources. Accordingly, utilizing solar energy presents itself as an excellent alternative, whether it is to make available small quantities of electric energy, utilizing photovoltaic generators, for heating water, or for environmental conditioning. Whatever the case, it is necessary to have reliable information on available solar resource. This work seeks to develop standards for implementation of solarimetric stations, for the unit system to be utilized and for the routine of calibration and maintenance of equipment. It also seeks to characterize solar radiation in the state of São Paulo, with one of its objectives being the supply of data of monthly average daily irradiation in the city of São Paulo and the Ribeira Valley (south coast of São Paulo state). The latter has low levels of rural electrification and great potential for utilizing photovoltaic systems in the supply of energy for isolated residences. As solar panels are generally installed on a sloped surface, the correct dimensioning of systems requires converting solar irradiation data from horizontal plane to tilted plane. Thus, several models presented in the literature that calculate monthly average daily irradiation on inclined plane from available data measured on horizontal plane were tested. All such models need diffuse irradiation data, that is, irradiation originating from the entire sky, except that originating directly from the sun, to be utilized. For this reason, this work sought to test several models that establish correlations for the calculation of diffuse solar irradiation from global solar irradiation. As the inadequacy of such models was verified, this proposes a new correlation that is more appropriate for the conditions of the state of São Paulo.
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Ecoulement des milieux granulaires cohésifs soumis à des vibrationsBenedetti, Arnaud 14 December 2012 (has links)
Nous nous intéressons à l'écoulement de milieux granulaires cohésifs soumis à des vibrations horizontales en vue d'une application au remplissage des moules de presse. L'effet des vibrations est analysé pour un grain ou un milieu granulaire déposé sur un plan incliné et un milieu granulaire contenu dans une conduite verticale de section constante. Pour un grain polyédrique, trois régimes sont identifiés : stick, stick-slip et slip. Un modèle basé sur le bilan des forces appliquées à un grain a permis de préciser les limites de ces trois domaines. La vitesse des grains tend vers une asymptote lorsque l'inclinaison est inférieure à 0,7 fois l'angle de frottement entre les grains et le plan. Par ailleurs, l'inertie du grain conduit à une réduction de l'amplitude de son oscillation lorsque l'accélération augmente. La comparaison modèle-expérience permet d'estimer le coefficient de frottement. Pour un milieu granulaire de faible épaisseur, nous retrouvons les mêmes tendances. Les milieux granulaires épais sont le lieu de forts cisaillements provoquant leur étalement très rapide. En conduite verticale, une compétition s'établit entre les déplacements horizontal et vertical des particules. Selon l'inertie, les vibrations appliquées pourront conduire soit à une dilatance soit à une compaction. Cette dernière provient du déplacement de la conduite et du milieu granulaire en sens opposé pendant une partie d'une période de vibration. Si le phénomène de compaction atteint le centre de la conduite, il se forme des arches qui bloquent l'écoulement. Les observations faites à l'échelle mésoscopique permettent d'interpréter les vitesses d'écoulement mesurées à l'échelle macroscopique. / With the target to improve the feeding step during the moulding process, we study the flow of cohesive granular matter submitted to vibration. Vibration effects are first analyzed on the sliding motion of a single particle on inclined plane and also on granular matter sample deposited on an inclined plane or in a vertical funnel. For a single particle, three regimes are identified: stick, stick-slip and slip regimes. A simple model based on the movement equation of one grain allows to determinate the limits between the three regimes. The grain velocity reaches asymptote when the plane inclination is below 0.7 times the friction angle between the grain and the substrate. Otherwise, when the acceleration increases, the grain inertia leads to reduce the transverse amplitude of the grain oscillation motion. The comparison between experimental and numerical results allows to estimate a value for the friction coefficient parameter. For a granular sample, we find the same tendencies. Thick granular layers are submitted to high shear, causing a fast spreading. In vertical funnel, there is a competition between vertical and horizontal motions. Depending on granular inertia, submitted vibrations could lead to dilatancy due to the shear or lead to compaction. This compaction is due to an opposite motion direction between the sample and the funnel during one part of the period vibration. If the compaction reaches the center of the funnel, arches are formed and jammed the flow. Observations realized at mesoscopic scale allow to interpret flow velocities measured at macroscopic scale.
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Comparaisons des exigences d’équilibre dynamique lors de la négociation de l’escalier et d’un plan incliné chez les personnes en santéOiknine, Natalie 08 1900 (has links)
Inclined planes and stairs are current in the environment and represent a barrier for seniors and people with mobility problems. Slower progression, alteration in gait pattern likely explains the high rate of fall on these surfaces, but their effect on balance is not well known. Our objective was thus to compare the difficulty in maintaining dynamic stability during the ascent and descent of an inclined plane and stairs at natural and slow walking speed in healthy individuals. Ten young healthy participants ascended and descended an inclined plane and stairs, instrumented with force- platforms to record ground reaction forces. Whole-body kinematics was also recorded to determine balance difficulty using the stabilizing and destabilizing forces, center of mass velocity and step length. Analyses of variance were used to compare the effect of surface (inclined plane vs. stairs), direction (ascent vs. descent) and speed (natural vs. slow). The stabilizing force was higher on the inclined plane than on the stairs, with a higher velocity of the center of mass. Stabilizing force was higher and destabilizing force was lower during descent than ascent only in the inclined plane but destabilizing force was lower during ascent than descent on the stairs. Slower gait speed reduced balance difficulty on both surfaces. Step length was shorter in the stairs than on the inclined plane, and particularly during descent, and at slow gait speed. Balance difficulty was higher on the inclined plane than on the stairs and at natural speed than at slow speed. The effect of direction was opposite between surfaces with higher difficulty during descent of the inclined plane, but during ascent of the stairs. Further studies are necessary in older adults or individuals with balance deficits. / La présence d’un escalier ou d’un plan incliné constitue souvent un obstacle sérieux à la réalisation des habitudes de vie des personnes ayant des incapacités physiques et même chez les personnes âgées. L’objectif général de cette étude était de quantifier l’équilibre dynamique lors de la négociation (montée et descente) d’un escalier et d’un plan incliné chez des sujets en santé. Dix sujets en santé ont été recrutés pour participer à l’évaluation. Les participants ont effectué la montée et la descente du plan incliné et de l’escalier à vitesse naturelle puis à vitesse lente. L’évaluation a compris un enregistrement de la cinématique de l’ensemble du corps. L’ensemble des données ont servi à analyser la force déstabilisante, la force stabilisante, la vitesse du centre de masse et la longueur de pas. Des ANOVAs et des tests t de Student ont permis de comparer l’effet de la surface (plan incliné vs. Escalier), de la direction (montée vs. Descente) et de la vitesse (naturelle vs. lente). La force stabilisante était plus élevée sur le plan incliné qu’à l’escalier, avec une vitesse de centre de masse plus élevée. La force stabilisante était plus élevée et la force déstabilisante était plus basse durant la descente en comparaison avec la montée sur le plan incliné. Par contre, à l’escalier, la force déstabilisante était plus basse lors de la montée en comparaison avec la descente. La vitesse de marche lente a réduit la difficulté en termes d’équilibre sur les deux surfaces. Les pas étaient plus courts sur l’escalier en comparaison avec le plan incliné, particulièrement lors de la descente à vitesse naturelle. L’effet de direction était opposé entre les surfaces, avec une difficulté plus élevée durant la descente du plan incliné et durant la montée de l’escalier. Des études approfondies seront nécessaires chez les personnes âgées et les personnes ayant des déficits de la balance.
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