A general technique for the generation of canonical channel models and demonstrate the application of the technique to time-frequency and time-scale integral kernel operators is developed. As an example, the derivatio...
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A general technique for the generation of canonical channel models and demonstrate the application of the technique to time-frequency and time-scale integral kernel operators is developed. As an example, the derivation of Sayeed/Aazhang's time-frequency canonical channel characterization that forms the basis for the time-frequency RAKE receiver is shown. Then, a canonical time-scale channel model for wideband communication is developed.
This paper designs space-time codes for standard PSK and QAM signal constellations that have flexible rate, diversity and require no constellation expansion. Central to this construction are binary partitions of the P...
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This paper designs space-time codes for standard PSK and QAM signal constellations that have flexible rate, diversity and require no constellation expansion. Central to this construction are binary partitions of the PSK and QAM constellations that appear in codes designed for the Gaussian channel. The space-time codes presented here are designed by separately specifying the different levels of the binary partition in the space-time array. The individual levels are addressed by either the binary symmetric matrices associated with codewords in a Kerdock code or other families of binary matrices. Binary properties of these sets are sufficient to verify the diversity property of the codewords in the complex domain. Larger sets of binary symmetric matrices (such as the set used in Delsarte-Goethals codes) are used to trade diversity protection for increased rate.
In this paper a synchronization controller for differential mobile robots is proposed. The synchronization goal is to control the angular position of each wheel to a desired trajectory and at the same time the differe...
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In this paper a synchronization controller for differential mobile robots is proposed. The synchronization goal is to control the angular position of each wheel to a desired trajectory and at the same time the differential (or synchronization) error between the angular position of the two wheels. In this way it is ensured that the mobile robot follows the desired path trajectory with the proper orientation. The controller is based on a computed torque architecture and a set of observers to estimate the angular velocity of the wheels. So that the controller only requires angular position measurements of the wheels.
The article discusses the partial solution to image deblurring. In this problem, the best way to choose the regularization parameter is by eye. Some nonlinear reconstruction algorithms that reduce the problem are also...
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The article discusses the partial solution to image deblurring. In this problem, the best way to choose the regularization parameter is by eye. Some nonlinear reconstruction algorithms that reduce the problem are also discussed. In many applications, one must choose the regularization parameter by automatic methods rather than by eye.
We present a new formulation of the incompressible Navier-Stokes equation in terms of an auxiliary field that differs from the velocity by a gauge transformation. The gauge freedom allows us to assign simple and speci...
We study a fluid jet descending through stratified surroundings at low Reynolds number in Hele-Shaw flow. The jet buckles and overturns inside a conduit of entrained fluid which supports smooth or unstable traveling w...
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We study a fluid jet descending through stratified surroundings at low Reynolds number in Hele-Shaw flow. The jet buckles and overturns inside a conduit of entrained fluid which supports smooth or unstable traveling waves. A model of the recirculating flow within the conduit shows that buckling and waves arise from Kelvin-Helmholtz instabilities and quantitatively accounts for the main experimental observations. Beyond the onset of the instability, a damped, forced Burgers’ equation obtained from corrections to Darcy’s law for small Reynolds number governs the interface dynamics and supports singularities corresponding to the observed jet overturning and unstable waves.
In this paper we present a controller that solves the problem of position coordination of two (or more) robotic systems, under a master-slave scheme, in the case when only position measurements are available. The cont...
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A controller that solves the problem of position synchronization of two (or more) robot systems, under a cooperative scheme, in the case when only position measurements are available, is presented. The synchronization...
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A controller that solves the problem of position synchronization of two (or more) robot systems, under a cooperative scheme, in the case when only position measurements are available, is presented. The synchronization controller consists of a feedback control law and a set of nonlinear observers. It is shown that the controller yields semi-global exponential convergence of the synchronization closed loop errors. Experimental results show, despite obvious model uncertainties, a good agreement with the predicted convergence.
When a macroscopic metallic wire is subject to tensile stress, it necks down smoothly as it elongates. We show that nanowires with radii comparable to the Fermi wavelength display remarkably different behavior. Using ...
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When a macroscopic metallic wire is subject to tensile stress, it necks down smoothly as it elongates. We show that nanowires with radii comparable to the Fermi wavelength display remarkably different behavior. Using concepts from fluid dynamics, a partial differential equation for nanowire shape evolution is derived from a semiclassical energy functional that includes electron-shell effects. A rich dynamics involving movement and interaction of kinks connecting locally stable radii is found, and a new class of universal equilibrium shapes is predicted.
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