1,368,812 research outputs found
Aplicação de técnicas de controle robusto baseadas em LMI'S para sistemas elétricos de potência /
No full textDissertação (Mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico.Este trabalho apresenta um método de projeto robusto decontroladores de Sistemas de Potência via Inequações Matriciais Lineares (LMI's), de modo a fornecer maior amortecimento para as oscilações eletromecânicas do sistema. Com o projeto robusto do controlador, a estabilidade do sistema deve ser assegurada na presença de incertezas no mesmo, onde estas incertezas foram consideradas neste trabalho como sendo do tipo Linear Convexa. Duas abordagens utilizandoLMI's foram consideradas, sendo a primeira um problema de factibilidade e a segunda um problema de dedesempenho H2. Em ambas as abordagens resolve-se um problema convexo de otimização. O sistema é representado na forma algébrico-diferencial. O controlador utiliza a estrutura comumente empregada na indústria com realimentação desaídas. A viabilidade destas abordagens bem como suas limitações foram avaliadas através de testes em um sistema máquina x barra infinita e um sistema multimáquinas. Simulações dos sistemas não-lineares foram utilizadas para comprovar os resultados
The parameterization and the analysis of small groups by means of the Response Dependence of Subjects Model (RDSM)
No full textCristante and Robusto (1999) introduced a model devised for the parameterization of small groups in the social sciences (RDSM – response dependence of subjects model). The model belongs to the family of Rasch models (Andrich, 1982, 1985). In this contribution a validation study is conducted in order to verify the empirical applicability of the model. The RDSM is applied to a set of data in market research; the participants are 200 mobile telephone consumers. The main results are as follows: (a) Twenty four small subgroups of participants are
obtained, where each one is well defined by means of a unit parameter and a location parameter on a latent trait. In this way the RDSM allows an appropriate grouping of the sample considered. (b) Low familiarity of consumers with mobile telephone technology correlates with a stereotyped representation of the attributes of telephone devices. (c) From a quantitative point of view, the results confirm the applicability of the RDSM within the data considered
MÉTODO ROBUSTO DE TRES PASOS PARA LA DEMODULACIÓN DE FASE ÓPTICA USANDO UN FILTRO DE CUADRATURA ROBUSTO
No full text"En este trabajo presentamos un método de tres pasos robusto al error de desentonamiento y al ruido blanco, que tiene como finalidad extraer la fase óptica. El método esta basado en un filtro de cuadratura que es obtenido mediante la minimización de una función de costo. Debido a que el método de interferometría de corrimiento de fase (acrónimo en ingles PSI), de tres pasos, es muy sensibles a los errores de desentonamiento y al ruido, el cual provoca que la fase óptica extraída sea incorrecta. Por esta razón proponemos un método robusto que calcula la fase correctamente cuando existen este tipo de errores.
El método de tres pasos robusto puede entenderse como un problema inverso donde a partir de una señal G dada nosotros queremos encontrar un campo complejo F. El desempeño de nuestro método es evaluado mediante la comparación de su desviación estándar con la desviación del método tradicional PSI de tres pasos. Mediante los resultados obtenidos comprobamos que nuestro método recupera la fase óptica con un error menor que con respecto al método tradicional PSI.
Recovering a probabilistic knowledge structure by constraining its parameter space
No full textIn the Basic Local Independence Model (BLIM) of Doignon and Falmagne (Knowledge Spaces, Springer, Berlin, 1999), the probabilistic relationship between the latent knowledge states and the observ- able response patterns is established by the introduction of a pair of parameters for each of the problems: a lucky guess probability and a careless error probability. In estimating the parameters of the BLIM with an empirical data set, it is desirable that such probabilities remain reasonably small. A special case of the BLIM is proposed where the parameter space of such probabilities is constrained. A simulation study shows that the constrained BLIM is more effective than the unconstrained one, in recovering a probabilistic knowledge structure
Presentación - País raquítico, país robusto : la cartografía del poblamiento y despoblamiento de los municipios colombianos
No full textEl despoblamiento es un fenómeno que avanza de manera tácita afectando hoy por hoy a cerca de la mitad de los municipios del país. Otra porción significativa de estos, casi una tercera parte, se encuentra en riesgo de despoblamiento y, por tanto, sobre una porción cada vez más pequeña de municipios recae la responsabilidad de la acogida al crecimiento de la población. El país raquítico es ese conjunto de municipios que padecen el despoblamiento y que contrasta con el país robusto que acoge sistemáticamente a más residentes. El desequilibrio es la regla en la ocupación del territorio colombiano y tiende a acentuarse ante la omisión estatal para intervenir a fin de contrarrestar sus externalidades negativas. Esta obra se ocupa de llamar la atención societal sobre la cuestión poblacional en Colombia, acudiendo al balance certero de los demógrafos, a las explicaciones sociodemográficas y a las propuestas de política de los economistas espaciales.Depopulation is a phenomenon that is advancing tacitly and currently affects nearly half of the country's municipalities. Another significant portion of these, almost a third, is at risk of depopulation and, therefore, an increasingly smaller portion of the municipalities is responsible for the population growth. The rickety country is that set of municipalities suffering from depopulation and which contrasts with the robust country that systematically welcomes more residents. The imbalance is the rule in the occupation of the Colombian territory and tends to be accentuated by the State's failure to intervene in order to counteract its negative externalities. This work is concerned with drawing societal attention to the population issue in Colombia, drawing on the accurate assessment of demographers, sociodemographic explanations and policy proposals of spatial economists.Primera edició
Il modello Many Facet Rasch Measurement per il benchmarking
No full textThe Many Facer Rasch Measurement model (Linacre, 1989) is a Rasch model which allows us to estimate parameters not only for person's "ability" in a item and the item "difficulty", but also for other aspects (facets) that are believed to be relevant to the research goals. Because of its peculia~ities,this model is especially indicated for benchmarking. It combines the properties of every Rasch model with the flexibility of use and the ease in considering different dimensions which share the same latent trait. In this article, the model features in relation to benchmarking are discussed, and benchmarking is ap-
plied to hospitals and departments as regards patients' satisfaction
Accelerated life testing in mechanical design
No full textThe introduction of new products on the market is a time-consuming process, which typically includes both design and testing phases. Often, the experimental validation phase significantly affects the overall process time. Indeed, in many industrial sectors, the product development procedure is based on trial and error methodologies. Intermediate validation tests are performed on full-scale physical prototypes and, based on their outcome, the design is updated (in the case of a negative result) or validated (if the result is positive). The efficiency of this method in terms of time-resources is notoriously sub-optimal.
To improve the efficiency of this process it is, for example, possible to exploit accelerated test methodologies, which consist in subjecting the product to test conditions that exceed its actual working conditions. In this way, a reduction in the number of cycles necessary to bring the component to final failure can be achieved, with obvious beneficial effects on the efficiency of the process. Another way to accelerate the test is to switch from testing the top-level assembly to performing tests on subassemblies or individual components.
It is however mandatory, to ensure that the results obtained with these test methods are useful for the design, to take appropriate precautions. For example, it is essential to preserve the original failure mode of the component. To do this, it is necessary, among other things, to know the relationship between the boundary conditions of the entire assembly and the stresses of the individual components. In the present paper, the methodology described above is illustrated with reference to its application to locking industry components (demonstrator).
Several experimental tests have been carried out, in order to characterize the fatigue life and wear resistance of the materials involved in the construction of the demonstrator.
Numerical FEM models were also developed to determine the stresses of the sub-assemblies and components of the demonstrator during the test phase.
Combining the experimental results with the numerical ones, it was possible to develop an analytical model. Such model allows estimating the endurance of the demonstrator when subjected to accelerated tests. The model has shown a good correlation with experimental results.
The principles underlying this procedure can be applied, without any loss in terms of generality, to many sectors of the industry
A latent class model approach for the assessment of interpersonal relations within a small set of persons
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