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By means of a symbolic calculus for finding solutions of difference equations, we derive explicit eigenvalues, eigenvectors and inverses for tridiagonal Toeplitz matrices with four perturbed corners.2000 Mathematics subject classification: primary 15A09, 15A18; secondary 39A10.

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SUMMARYThis paper presents a high-performance LED lamp driver with an improved single-stage Flyback configuration. A constant current control method is used to regulate the lamp current and brightness. A laboratory prototype has been built and tested. With the prototype, high efficiency, high power factor, and constant lamp current can be achieved under different pieces of LED series connection.

Abstract-This paper presents a dimmable light-emitting diode (LED) driver with adaptive feedback control for low-power lighting applications. An improved pulsewidth modulation dimming technique is studied for regulating the LED current and brightness. Under universal input voltage operation, high efficiency and high power factor can be achieved by a coupled inductor singleended primary inductance converter power factor correction (PFC) converter with a simple commercial transition-mode PFC controller. The operation principles and design considerations of the studied LED driver are analyzed and discussed. A laboratory prototype is also designed and tested to verify the feasibility.Index Terms-Coupled inductor single-ended primary inductance converter power factor correction (SEPIC PFC), dimmable light-emitting diode (LED) driver, universal input voltage.

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In this paper, the existence of solutions for a system of nonlinear equations is considered. 2 n nonzero real solutions are obtained by using the critical point theory. Additionally, the Dirichlet boundary value problems of even order difference equations and partial difference equations are investigated.  2005 Elsevier Inc. All rights reserved.