925 resultados para Permanent dipoles
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This paper presents the optimal design of a surface mounted permanent-magnet (PM) Brushless direct-current (BLDC) motor meant for spacecraft applications. The spacecraft applications requires the choice of a motor with high torque density, minimum cogging torque, better positional stability and high torque to inertia ratio. Performance of two types of machine configurations viz Slotted PMBLDC and Slotless PMBLDC with Halbach array are compared with the help of analytical and finite element (FE) methods. It is found that unlike a Slotted PMBLDC motor, the Slotless type with Halbach array develops zero cogging torque without reduction in the developed torque. Moreover, the machine being coreless provides high torque to inertia ratio and zero magnetic stiction
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La obra se presenta en edición bilingue español/inglés .- Incluye una sección de apéndices en la que aparecen tablas y gráficos que recogen datos estadísticos sobre la experiencia didáctica, así como información general sobre la UE
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Many approaches to force control have assumed the ability to command torques accurately. Concurrently, much research has been devoted to developing accurate torque actuation schemes. Often, torque sensors have been utilized to close a feedback loop around output torque. In this paper, the torque control of a brushless motor is investigated through: the design, construction, and utilization of a joint torque sensor for feedback control; and the development and implementation of techniques for phase current based feedforeward torque control. It is concluded that simply closing a torque loop is no longer necessarily the best alternative since reasonably accurate current based torque control is achievable.
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A fundamental question in visual neuroscience is how to represent image structure. The most common representational schemes rely on differential operators that compare adjacent image regions. While well-suited to encoding local relationships, such operators have significant drawbacks. Specifically, each filter's span is confounded with the size of its sub-fields, making it difficult to compare small regions across large distances. We find that such long-distance comparisons are more tolerant to common image transformations than purely local ones, suggesting they may provide a useful vocabulary for image encoding. . We introduce the "Dissociated Dipole," or "Sticks" operator, for encoding non-local image relationships. This operator de-couples filter span from sub-field size, enabling parametric movement between edge and region-based representation modes. We report on the perceptual plausibility of the operator, and the computational advantages of non-local encoding. Our results suggest that non-local encoding may be an effective scheme for representing image structure.
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Increasingly used in online auctions, buyout prices allow bidders to instantly purchase the item listed. We distinguish two types: a temporary buyout option disappears if a bid above the reserve price is made; a permanent one remains throughout the auction or until it is exercised. In a model featuring time-sensitive bidders with uniform valuations and Poisson arrivals but endogenous bidding times, we focus on finding temporary and permanent buyout prices maximizing the seller's discounted revenue, and examine the relative benefit of using each type of option in various environments. We characterize equilibrium bidder strategies in both cases and then solve the problem of maximizing seller's utility by simulation. Our numerical experiments suggest that buyout options may significantly increase a seller’s revenue. Additionally, while a temporary buyout option promotes early bidding, a permanent option gives an incentive to the bidders to bid late, thus leading to concentrated bids near the end of the auction.
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Describe la incertidumbre en que el trabajo de los docentes se ve inmerso, debido a los continuos cambios de gobierno, los cuales afectan al quehacer educativo a través de la creación de leyes. En medio del debate permanente los docentes se sienten huérfanos, solos, ante unas necesidades en las aulas que son difíciles de dar respuesta debido a la falta de formación, de habilidades y sobretodo de apoyo externo, de la sociedad y de la família.
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Resumen tomado del autor. Contiene tablas varias: de resultado, encuesta y gu??a de entrevista
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Se estudia la delicada situaci??n de las escuelas rurales y la gran importancia de la actuaci??n de los docentes que trabajan en ellas. Se analiza el perfil que tendr??a que tener el profesional que trabaja en estos centros y para ello se indica c??mo deber??an ser la formaci??n inicial y permanente espec??ficas del maestro rural, temas olvidados en los actuales planes de estudio de magisterio.
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Resumen tomado de la propia revista
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Se analiza, como paso previo a la conceptualización de qué es la formación del profesorado, la definición de la tarea docente. En segundo lugar, se aborda la diferente naturaleza de la formación del profesorado para las etapas de educación infantil, primaria y secundaria, los caminos para obtener dicha formación, los sistemas de aprendizaje y, más concretamente los movimientos de renovación pedagógica. La curiosidad, la innovación, la investigación y el aprendizaje son el motor de las actividades de formación que se desarrollan en estos movimientos, a menudo por delante de los procesos institucionales.