We are involved in the design and control of a 1-dimensional positioning mechanism for a range of 50 /spl mu/m and an accuracy of 30 pm. Only piezoelectric actuators can be used to manage such small displacements. How...
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ISBN:
(纸本)0780341872
We are involved in the design and control of a 1-dimensional positioning mechanism for a range of 50 /spl mu/m and an accuracy of 30 pm. Only piezoelectric actuators can be used to manage such small displacements. However, these actuators show hysteretic behavior and lengthening saturation. The extremely small displacements are measured by means of capacitive sensors. In order to design a controller a model of the positioning mechanism and the actuators is developed. Contrary to the existing literature, in our model the hysteresis is described by a differential equation. The mechanical characteristics of the design, and therefore also of the model, are chosen such that they are practically realizable and advantageous for controller design. The final nonlinear fifth order state space model is believed to be suitable for a nonlinear control technique like feedback linearization.
Summary form only given. In recent years, much attention has been given to wavelength-division multiplexed (WDM) systems due to their ability to maximize lightwave communications. In practice, the combined effects of ...
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ISBN:
(纸本)1557524432
Summary form only given. In recent years, much attention has been given to wavelength-division multiplexed (WDM) systems due to their ability to maximize lightwave communications. In practice, the combined effects of linear dispersion and nonlinear self phase modulation impose severe limitations on the long-haul performance of non-return-to-zero (NRZ) systems. The aim of this presentation is to provide an analytic description of the nonlinear pulse evolution in a NRZ communications system under a dispersion-management scheme.
Infinite, recursive versions of NP optimization problems are defined. For example, MAX CLIQUE becomes the question of whether a recursive graph contains an infinite clique. The work was motivated by trying to understa...
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Infinite, recursive versions of NP optimization problems are defined. For example, MAX CLIQUE becomes the question of whether a recursive graph contains an infinite clique. The work was motivated by trying to understand what makes some NP problems highly undecidable in the infinite case, while others remain on low levels of the arithmetical hierarchy. Two results are proved; one enables using knowledge about the infinite case to yield implications to the finite case, and the other enables implications in the other direction. Taken together, the two results provide a method for proving (finitary) problems to be outside the syntactic class MAX NP, hence outside MAX SNP too. The technique is illustrated with many examples.< >
The topics discussed here are network models of object recognition; a comput.tional theory of recognition; psychophysical support for a view-interpolation model: and an open issue, features of recognition. The authors...
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The topics discussed here are network models of object recognition; a comput.tional theory of recognition; psychophysical support for a view-interpolation model: and an open issue, features of recognition. The authors survey a successful replication of central characteristics of performance in 3-D object recognition by a comput.tional model based on interpolation among a number of stored views of each object. Network models of 3-D object recognition based on interpolation among specific stored views behave in several respects similarly to human observers in a number of recognition tasks. Even closer replication of human performance in recognition should be expected, once the issue of the features used to represent object views is resolved.< >
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