4 resultados para Continuous dynamic recrystallization

em Universidad de Alicante


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We address the optimization of discrete-continuous dynamic optimization problems using a disjunctive multistage modeling framework, with implicit discontinuities, which increases the problem complexity since the number of continuous phases and discrete events is not known a-priori. After setting a fixed alternative sequence of modes, we convert the infinite-dimensional continuous mixed-logic dynamic (MLDO) problem into a finite dimensional discretized GDP problem by orthogonal collocation on finite elements. We use the Logic-based Outer Approximation algorithm to fully exploit the structure of the GDP representation of the problem. This modelling framework is illustrated with an optimization problem with implicit discontinuities (diver problem).

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We present an extension of the logic outer-approximation algorithm for dealing with disjunctive discrete-continuous optimal control problems whose dynamic behavior is modeled in terms of differential-algebraic equations. Although the proposed algorithm can be applied to a wide variety of discrete-continuous optimal control problems, we are mainly interested in problems where disjunctions are also present. Disjunctions are included to take into account only certain parts of the underlying model which become relevant under some processing conditions. By doing so the numerical robustness of the optimization algorithm improves since those parts of the model that are not active are discarded leading to a reduced size problem and avoiding potential model singularities. We test the proposed algorithm using three examples of different complex dynamic behavior. In all the case studies the number of iterations and the computational effort required to obtain the optimal solutions is modest and the solutions are relatively easy to find.

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Among the factors that affect the convergence towards the European Higher Education Area, university teaching staff's motivation is fundamental, and consequently, it is crucial to empirically know what this motivation depends on. In this context, one of the most relevant changes in the teacher-student relationship is assessment. In fact, the transition from a static assessment -focused on only one temporal point (final exam)- to a dynamic assessment, will require changes in thought and action, both on the part of teachers and students. In this line, the objective of this paper is to analyze the determinants of teaching staff's predisposition to the continuous assessment method. Specifically, we consider the following explanatory dimensions: teaching method used (which measures their degree of involvement with the ongoing adaptation process), type of subject (core, compulsory and optional), and teacher's personal characteristics (professional status and gender). The empirical application carried out at the University of Alicante uses Logit Models with Random Coefficients to capture heterogeneity, and shows that "cooperative learning" is a clear-cut determinant of "continuous assessment" as well as "continuous assessment plus final examination". Also, a conspicuous result, which in turn becomes a thought-provoking finding, is that professional status is highly relevant as a teacher's engagement is closely related to prospects of stability. Consequently, the most relevant implications from the results revolve around the way academic institutions can propose and implement inducement for their teaching staff.

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Among the factors that affect the convergence towards the European Higher Education Area, university teaching staff's motivation is fundamental, and consequently, it is crucial to empirically know what this motivation depends on. In this context, one of the most relevant changes in the teacher-student relationship is assessment. In fact, the transition from a static assessment -focused on only one temporal point (final exam)- to a dynamic assessment, will require changes in thought and action, both on the part of teachers and students. In this line, the objective of this paper is to analyze the determinants of teaching staff's predisposition to the continuous assessment method. Specifically, we consider the following explanatory dimensions: teaching method used (which measures their degree of involvement with the ongoing adaptation process), type of subject (core, compulsory and optional), and teacher's personal characteristics (professional status and gender). The empirical application carried out at the University of Alicante uses Logit Models with Random Coefficients to capture heterogeneity, and shows that "cooperative learning" is a clear-cut determinant of "continuous assessment" as well as "continuous assessment plus final examination". Also, a conspicuous result, which in turn becomes a thought-provoking finding, is that professional status is highly relevant as a teacher's engagement is closely related to prospects of stability. Consequently, the most relevant implications from the results revolve around the way academic institutions can propose and implement inducement for their teaching staff.