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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.
11

Assimetrias interlaterais na coordenação interarticular de movimentos manuais circulares cíclicos / Interlateral asymmetries in interjoint coordination on cyclic circular manual movements

Pereira, Carla Ferro 30 March 2011 (has links)
A dominância lateral para controle motor tem sido proposta ser devida a uma capacidade superior em lidar com a dinâmica do movimento com o hemisfério/lado corporal dominante. A partir desta hipótese, é esperado que o braço dominante apresente tanto trajetórias mais precisas quanto modos de coordenação mais estáveis. Além disso, tal assimetria motora deveria ser mais evidente em movimentos mais rápidos. No presente estudo foi avaliada a assimetria interlateral de desempenho na coordenação interarticular/ intramembro em movimentos realizados em diferentes frequências. Foi analisada a coordenação interarticular entre o ombro e o cotovelo do mesmo braço em uma tarefa de realizar movimentos circulares com as mãos, comparando o desempenho entre os braços dominante e não-dominante. O estudo foi realizado com 16 adultos jovens, que realizaram a tarefa em cinco frequências de movimento, variando de 40% a 100% da frequência individual máxima. Movimentos angulares das articulações foram analisados através de marcadores refletivos fixados no ombro, cotovelo e punho de ambos os braços. Os marcadores foram rastreados automaticamente por meio de um sistema optoeletrônico, com frequência de aquisição de 240 Hz, e análise em 3D. Os resultados demonstraram que o desempenho com o braço não-dominante apresentou as seguintes diferenças em comparação com o braço dominante: trajetória da mão e amplitudes angulares mais variáveis, maior participação do cotovelo, coordenação em modo antifase (braço dominante: relação de fase de aproximadamente 120º) e maior variabilidade de modo de coordenação. De forma geral, as assimetrias interlaterais foram acentuadas em frequências de movimento mais altas. Estes resultados indicam que a vantagem de desempenho com o braço dominante é devida a um modo de coordenação mais consistente e efetivo em realizar a trajetória desejada / Lateral dominance for motor control has been proposed to be due to a superior capacity to deal with motion dynamics with the dominant cerebral hemisphere/body side. From this conjecture, it is expected the dominant arm to present both an increased capacity to perform more accurate trajectories and a more stable interjoint coordination. Moreover, such motor asymmetry should be more evident in fast movements. We assessed interjoint coordination between the shoulder and the elbow on a circle drawing task, comparing performance between the dominant and the non-dominant arm. The study was conducted with 16 young adults, who performed the task on five movement frequencies, ranging from 40% to 100% of the individual maximum. Angular motion of the joints was recorded through reflective markers attached at the shoulder, elbow and wrist of both arms. Markers were tracked automatically by using an optoelectronic system, with data sampling frequency set at 240 Hz, and 3D analysis. The results showed that performance with the non-dominant arm had the following differences in comparison with the dominant arm: more variable hand trajectory and joint amplitudes, interjoint coordination in antifase (dominant arm: phase relation of approximately 120º) and increased variability in the coordination mode. Overall, interlateral asymmetries were amplified in higher movement frequencies. These results indicate that the advantage of the dominant arm resides in a more stable and effective mode of coordination in performing the desired trajectory
12

Análise do comportamento estrutural de sistemas de drenagem viária constituídos por tubos plásticos flexíveis envolvidos com areia. / Structural behavior analysis of draining road systems.

Schmitz, Cristiane Salerno 13 December 2002 (has links)
Este trabalho objetivou o conhecimento do comportamento estrutural de um sistema solo-tubo plástico flexível de paredes estruturadas frente a cargas permanentes sobre a tubulação e carregamentos móveis, como os provenientes de tráfego de veículos. Para o estudo, foram construídas valas em verdadeira grandeza na Área de Pesquisas e Testes de Pavimentos DAER-RS/UFRGS em Porto Alegre, RS, onde se dispõe de um equipamento simulador de tráfego, utilizado para aplicação de cargas estáticas e cíclicas na superfície dos sistemas solo-tubo. As variáveis independentes controladas são o grau de compactação do material que envolve o tubo e altura do mesmo material sobre o tubo. As variáveis medidas são a deflexão do tubo sob carregamento do simulador e o deslocamento permanente causado pela carga de solo sobre o tubo. O controle de compactação do material de envolvimento do tubo foi realizado com três equipamentos diferentes e os resultados foram comparados. Os resultados de deflexão e deslocamento pemanente foram utilizados para cálculo dos valores de módulo de reação E' do maerial de envolvimento do tubo e foram comparados com os encontrados na literatura. Constatou-se o comportamento elástico dos tubos sob carregamento repetido, e no caso em que o tubo é instalado muito próximo da superfície, as deflexões no sistema são de tal magnitude que chegam a ser prejudiciais ao pavimento construído sobre a vala. Ficou comprovada a importância da cuidadosa compactação do material de envolvimento do tubo para o bom desempenho estrutural do sistema solo-tubo flexível. / This work aimed at the knowledge of the structural behavior of a ribbed flexible plastic buried pipe system undergoing permanent loads on the piping and mobile loads, as the ones deriving from the traffic of vehicles. For this study, full scale ditches were built at the DAER-RS/UFRGS Pavement Research and Test Area in Porto Alegre, RS, where there is a equipment for simulating traffic, used for applying both static and cyclic loads on the ditch surface. The controled independent variables are the involving material density and the height of this material on the pipe. The variables measured are the pipe deflection under simulator load and the permanent displacement caused by the soil load on the pipe. The compaction control of involving material was carried out with three different types of equipment and results were compared. The results for pemanent deflection and displacement were used to calculate the Modulus of Soil Reaction (E') values of the involving material and these were compared to the ones found in the literature. The pipe elastic behavior under repeated load was observed, and where the pipe is installed too close to the surface, the system deflections are of such magnitude that they affect the pavement built over the ditch. The careful compaction of the involving material proved to be of paramount importance to a good structural performance of the flexible buried pipe system.
13

Modeling Relationships between Cycles in Psychology: Potential Limitations of Sinusoidal and Mass-Spring Models

January 2019 (has links)
abstract: With improvements in technology, intensive longitudinal studies that permit the investigation of daily and weekly cycles in behavior have increased exponentially over the past few decades. Traditionally, when data have been collected on two variables over time, multivariate time series approaches that remove trends, cycles, and serial dependency have been used. These analyses permit the study of the relationship between random shocks (perturbations) in the presumed causal series and changes in the outcome series, but do not permit the study of the relationships between cycles. Liu and West (2016) proposed a multilevel approach that permitted the study of potential between subject relationships between features of the cycles in two series (e.g., amplitude). However, I show that the application of the Liu and West approach is restricted to a small set of features and types of relationships between the series. Several authors (e.g., Boker & Graham, 1998) proposed a connected mass-spring model that appears to permit modeling of more general cyclic relationships. I showed that the undamped connected mass-spring model is also limited and may be unidentified. To test the severity of the restrictions of the motion trajectories producible by the undamped connected mass-spring model I mathematically derived their connection to the force equations of the undamped connected mass-spring system. The mathematical solution describes the domain of the trajectory pairs that are producible by the undamped connected mass-spring model. The set of producible trajectory pairs is highly restricted, and this restriction sets major limitations on the application of the connected mass-spring model to psychological data. I used a simulation to demonstrate that even if a pair of psychological time-varying variables behaved exactly like two masses in an undamped connected mass-spring system, the connected mass-spring model would not yield adequate parameter estimates. My simulation probed the performance of the connected mass-spring model as a function of several aspects of data quality including number of subjects, series length, sampling rate relative to the cycle, and measurement error in the data. The findings can be extended to damped and nonlinear connected mass-spring systems. / Dissertation/Thesis / Masters Thesis Psychology 2019
14

[en] ESTIMATING AND FORECASTING IN VAR MODELS WHITH SHORT-RUN AND LONG-RUN RESTRICTIONS: A MONTE CARLO STUDY / [pt] ESTIMAÇÃO E PREVISÃO EM MODELOS VAR COM RESTRIÇÕES DE CURTO E LONGO PRAZO: UM ESTUDO MONTE CARLO

CARLOS ENRIQUE CARRASCO GUTIERREZ 29 March 2007 (has links)
[pt] Neste trabalho estuda-se, por meio de simulação Monte- Carlo, a importância de duas restrições para a estimação e a previsão do Modelo Vetorial Autoregressivo - VAR, quais sejam: cointegração e características cíclicas comuns, relativas ao longo-prazo e ao curto-prazo, respectivamente. Cabe observar que as restrições cíclicas comuns de curto- prazo consideradas neste trabalho estão na forma fraca (Weak Form - WF), como definido por Hecq, Palma e Urbain (2006). Esta tese tem dois objetivos. O primeiro trata da investigação do desempenho de duas classes de critérios de informação para a seleção dos parâmetros do modelo. O primeiro critério, denotado por IC(p), refere-se ao critério tradicional, enquanto o segundo, denotado por IC (p, s), refere-se ao critério de seleção alternativo como proposto por Vahid e Issler (2002). Quanto aos segundo objetivo, a investigação avalia o desempenho da previsão de três modelos: i) modelo que considera as restrições de cointegração e do tipo WF; ii) modelo que apenas considera as restrições de cointegração e iii) modelo sem restrições. Os resultados indicam que o critério de informação alternativo, IC(p, s), apresenta desempenho superior ao modelo escolhido pelos critérios convencionais IC(p). Em relação ao desempenho da previsão, o modelo que considera as restrições de cointegração e do tipo WF apresenta desempenho predicativo superior. / [en] This paper investigates the importance of two restrictions included in the estimation and the forecasting of the Vectorial Autoregressive - VAR model using simulation Monte- Carlo. Those are the cointegration and the common cyclical characteristics restrictions related to the long run and the short run, respectively. The short run common cyclical restrictions considered in this work are in the Weak Form - WF, as defined by Hecq, Palm and Urbain (2006). This thesis has two main objectives. The first goal deals with performance of two classes of information criteria for the selection of the parameters in the model. The first criterion, denoted by IC(p) refers to the traditional technique, while the second one, denoted by IC(p,s) refers to the alternative selection criterion as proposed by Vahid and Issler (2002). On the concern of the second objective, it evaluates the forecasting accuracy of three models: i) model that considers the cointegration and WF restrictions; ii) model that just considers the cointegration restrictions and iii) model without any restrictions. On balance, the results indicate that the alternative information criterion, IC(p, s), has a better performance than the chosen model using the conventional criteria IC (p). In terms of the forecasting accuracy, the model which considers the cointegration and WF restrictions presents superior predicative performance.
15

Cyclical Fluctuation and Industry Dynamics in Taiwan High-Technology Industries

Lin, Shu-Hung 12 July 2007 (has links)
In markets with cyclical fluctuations, firms may have different dynamic decision rules facing upturns and downturns of industry cycles. This paper extends the dynamic factor demand model to consider industry cycles. Because investment behavior could be endogenous uncertainty involved on industry dynamics, the current industry dynamic models with state-of-the-art would not appropriately interpret industry dynamics. In order to solve the uncertain problem, we utilize the idea of transfer probability in Markov switching model to catch the industry cyclical behavior. Explicitly incorporating the Markov regime switching mechanism based on Nelson and Kim (2000), this paper measures the firm¡¦s dynamic adjustments when facing upturns and downturns of industry cycles. The empirical work is based on firm level data of Taiwan high-technology industries. The empirical results show that the expansionary strategy in labor and capital usage may not have positive impacts on output when considering uncertainty that may be casued by business cycles. To have correct prediction in cyclical fluctuation becomes important task for high-technology firms. However, the positive contribution of exogenous technology to output growth is so significant. This proves why every industry tries to impel technology in recent years. The industry dynamic model integrated with cyclical fluctuation and demand uncertainty allows us to examine how sharp changes in financial factors might affect investment behavior, technological nature and adjustment effects for industries in facing demand and investment shocks.
16

The governing cycle and the dynamics of new majority formation

Nichols, Curtis William 02 April 2013 (has links)
In this dissertation I advance a new, regime style, governing cycle theory to account for the constitutional origins and political dynamics of new majority formation. It is these periodic attempts to reorder politics and overcome conditions of entropy that I argue best account for the broad contours of American political development. Using a historical institutional approach, I argue that the U.S. Constitution’s durable separation of powers design interacts with America’s two party system to unintentionally structure political conflict in ways that makes it almost impossible for anyone to address the inevitable build up of entropy in the political system. Recurrently, this challenges partisan leaders to renew politics via the formation of a new governing majority. Partisan leaders accomplish this goal by completing three tasks: 1) shifting the main axis of partisan conflict; 2) assembling a new majority coalition that allows for effective control of federal governing institutions; and, 3) locking-in partisan priorities and advantage through institutionalization of a new governing regime. Through case study analysis, I demonstrate that the dynamics of new governing majority formation can play out in either a straightforward or a protracted manner depending on whether or not partisan leaders initially succeed or fail to accomplish these tasks. This leads to new interpretations of the crucial “System of 1896” and “Reagan Revolution” cases, which allows me to argue for the superiority of my new cyclical theory and to conclude that the governing cycle contains the American polity’s best opportunity to reorder and revitalize itself. / text
17

Cikliškai lenkiamų srieginių jungčių deformavimas ir stiprumas / Deformation and Strength af a Cyclically Bent Threaded Connection

Juchnevičius, Žilvinas 06 February 2012 (has links)
Disertacijoje, taikant apkrovų pasiskirstymo sriegio vijose modeliavimą, nagrinėjamos lenkiamų srieginių jungčių mažaciklio stiprumo problemos. Mo-dernesnės daugiaciklio ir mažaciklio ilgaamžiškumo skaičiavimo metodikos detaliai kiekybiškai įvertina ašinės apkrovos pasiskirstymą vijose, kuris leidžia detaliau ir tiksliau įvertinti konstrukcijos ypatumų įtaką. Disertacijoje siekiama ir cikliškai lenkiamoms srieginėms jungtims sukurti apkrovos pasiskirstymo sriegyje skaičiavimo metodą ir pritaikyti jį ciklinio stiprumo skaičiavimui Sudaryta lenkiamos srieginės jungties elementų poslinkių darnos lygtis įga-lino sukurti trijų ruožų ir daugiaruožį lenkimo apkrovos pasiskirstymo jung¬tyje modelius ir įdiegti juos į norminio mažaciklio ilgaamžiškumo skaičiavimo gran-dinę. Pirmame skyriuje pateikta literatūros šaltinių analizė. Jame apžvelgiama sunkiai apkrautų srieginių jungčių taikymo sritis ir apkrovimo sąlygos, apžvel¬giami ir analizuojami atlikti tyrimai, susiję su srieginių jungčių cikliniu stipru-mu. Antrame skyriuje pateikti sriegio vijų poros deformavimo savybių eksperi¬mentinio tyrimo rezultatai ir anksčiau literatūroje neminėtų nukraunamos ir pa-kartotinai apkraunamos vijų poros savybių analizė. Trečiame skyriuje pateikta srieginės jungties elementų deformavimo sche¬ma, poslinkių darnos diferencialinės lygtys, diferencialinių lygčių analitiniai sprendiniai ir lenkiamos srieginės jungties modeliai – trijų ruožų ir daugiaruožis tamprieji modeliai lenkimo apkrovos... [toliau žr. visą tekstą] / Industry equipment such as pressure vessels, mining equipment, heat exchang-ers, steam generators and other structures are provided with bolted closures for the purpose of in-service inspection and maintenance of internal components. Threaded connections often experience variable cyclic loads due to temperature, inner pressure and variation in the deformation of connection fittings. Often, studs and screws are not only affected by an axial load, but also by bending moments. More sophisticated high-cycle and low-cycle durability calculation meth-odologies have been already developed for threaded connections experiencing cyclic axial loads, and in these methodologies the distribution of axial load among turns is assessed quantitatively. The quantitative data of load distribu-tion in the thread enables a more accurate assessment of the influence of the constructional design particularities (connection length, material, nut and turn’s form) and the deformation stages of the connection element. These durability calculation methodologies are not applied for threaded connections that are cyclically bent, as the analytical models that are suitable for practical application in the load distribution of the turns have not been cre-ated for bent threaded connections. In this field, no models have been created to be calculated by the BE method. As the threaded connection is a complex node consisting of deformed el-ements, the load distribution among turns is influenced by the... [to full text]
18

Evolution of Reproduction and Stress Tolerance in Brachionid Rotifers

Smith, Hilary April 08 1900 (has links)
Stress can be a driving force for new evolutionary changes leading to local adaptation, or may be responded to with pre-existing, ancestral tolerance mechanisms. Using brachionid rotifers (microzooplankton) as a study system, I demonstrate roles of both conserved physiological mechanisms (heat shock protein induction) and rapid evolution of traits in response to ecologically relevant stressors such as temperature and hydroperiod. Rapid evolution of higher levels of sex and dormancy in cultures mimicking temporary waters represents an eco-evolutionary dynamic, with trait evolution feeding back into effects on ecology (i.e., reduced population growth). I also reveal that prolonged culture in a benign laboratory environment leads to evolution of increased lifespan and fecundity, perhaps due to reduction of extrinsic mortality factors. Potential mechanisms (e.g., hormonal signals) are suggested that may control evolvability of facets of the stress response. Due to prior studies suggesting a role of progesterone signaling in rotifer sex and dormancy, the membrane associated progesterone receptor is assayed as a candidate gene that could show positive selection indicating rapid divergence. Despite some sequence variation that may contribute to functional differences among species, results indicate this hormone receptor is under purifying selection. Detailed analyses of multiple stress responses and their evolution as performed here will be imperative to understanding current patterns of local adaptation and trait-environment correlations. Such research also is key to predicting persistence of species upon introduction to novel habitats and exposure to new stressors (e.g., warming due to climate change). Perhaps one of the most intriguing results of this dissertation is the rapid, adaptive change in levels of sex and dormancy in a metazoan through new mutations or re-arrangements of the genetic material. This suggests species may be able to rapidly evolve tolerance of new stressors, even if standing genetic variation does not currently encompass the suite of alleles necessary for survival.
19

Beliefs about Change and Predicted Future Health Status

January 2012 (has links)
abstract: Beliefs about change reflect how we understand phenomena and what kind of predictions we make for the future. Cyclical beliefs about change state that events are in a constant flux, and change is inevitable. Linear beliefs about change state that events happen in a non-fluctuating pattern and change is not commonplace. Cultural differences in beliefs about change have been documented across various domains, but research has yet to investigate how these differences may affect health status predictions. The present study addresses this gap by inducing different beliefs about change in a European-American college sample. Health status predictions were measured in terms of predicted likelihood of exposure to the flu virus, of contraction of the flu, and of receiving a flu vaccine. Most differences were observed among those who have a recent history of suffering from the flu. Among them, cyclical thinkers tended to rate their likelihood for exposure and contraction to be higher than linear thinkers. However, linear thinkers indicated that they were more likely to receive a flu vaccine. The different patterns suggest the possibility that cyclical beliefs may activate concepts related to cautionary behaviors or pessimistic biases, while linear beliefs may activate concepts related to taking action and exercising control over the environment. Future studies should examine the interplay between beliefs about change and the nature of the predicted outcome. / Dissertation/Thesis / M.A. Psychology 2012
20

Análise do comportamento estrutural de sistemas de drenagem viária constituídos por tubos plásticos flexíveis envolvidos com areia. / Structural behavior analysis of draining road systems.

Cristiane Salerno Schmitz 13 December 2002 (has links)
Este trabalho objetivou o conhecimento do comportamento estrutural de um sistema solo-tubo plástico flexível de paredes estruturadas frente a cargas permanentes sobre a tubulação e carregamentos móveis, como os provenientes de tráfego de veículos. Para o estudo, foram construídas valas em verdadeira grandeza na Área de Pesquisas e Testes de Pavimentos DAER-RS/UFRGS em Porto Alegre, RS, onde se dispõe de um equipamento simulador de tráfego, utilizado para aplicação de cargas estáticas e cíclicas na superfície dos sistemas solo-tubo. As variáveis independentes controladas são o grau de compactação do material que envolve o tubo e altura do mesmo material sobre o tubo. As variáveis medidas são a deflexão do tubo sob carregamento do simulador e o deslocamento permanente causado pela carga de solo sobre o tubo. O controle de compactação do material de envolvimento do tubo foi realizado com três equipamentos diferentes e os resultados foram comparados. Os resultados de deflexão e deslocamento pemanente foram utilizados para cálculo dos valores de módulo de reação E' do maerial de envolvimento do tubo e foram comparados com os encontrados na literatura. Constatou-se o comportamento elástico dos tubos sob carregamento repetido, e no caso em que o tubo é instalado muito próximo da superfície, as deflexões no sistema são de tal magnitude que chegam a ser prejudiciais ao pavimento construído sobre a vala. Ficou comprovada a importância da cuidadosa compactação do material de envolvimento do tubo para o bom desempenho estrutural do sistema solo-tubo flexível. / This work aimed at the knowledge of the structural behavior of a ribbed flexible plastic buried pipe system undergoing permanent loads on the piping and mobile loads, as the ones deriving from the traffic of vehicles. For this study, full scale ditches were built at the DAER-RS/UFRGS Pavement Research and Test Area in Porto Alegre, RS, where there is a equipment for simulating traffic, used for applying both static and cyclic loads on the ditch surface. The controled independent variables are the involving material density and the height of this material on the pipe. The variables measured are the pipe deflection under simulator load and the permanent displacement caused by the soil load on the pipe. The compaction control of involving material was carried out with three different types of equipment and results were compared. The results for pemanent deflection and displacement were used to calculate the Modulus of Soil Reaction (E') values of the involving material and these were compared to the ones found in the literature. The pipe elastic behavior under repeated load was observed, and where the pipe is installed too close to the surface, the system deflections are of such magnitude that they affect the pavement built over the ditch. The careful compaction of the involving material proved to be of paramount importance to a good structural performance of the flexible buried pipe system.

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