Current Issue : October - December Volume : 2014 Issue Number : 4 Articles : 5 Articles
Filtered renewal processes are used to forecast daily river flows. For these processes, contrary to filtered Poisson processes, the time\nbetween consecutive events is not necessarily exponentially distributed, which is more realistic. The model is applied to obtain oneand\ntwo-day-ahead forecasts of the flows of the Delaware and Hudson Rivers, both located in the United States. Better results are\nobtained than with filtered Poisson processes, which are often used to model river flows....
This paper presents a method of designing a state-observer based modified repetitive-control system that provides a given H? level\nof disturbance attenuation for a class of strictly proper linear plants. Since the time delay in a repetitive controller can be treated\nas a kind of disturbance, we convert the system design problem into a standard state-feedback H? control problem for a linear\ntime-invariant system. The Lyapunov functional and the singular-value decomposition of the output matrix are used to derive\na linear-matrix-inequality (LMI) based design algorithm for the parameters of the feedback controller and the state-observer. A\nnumerical example demonstrates the validity of the method....
We report on inversion of the Fourier transformwhen the frequency variable can be scaled in a variety of differentways that improve\nthe resolution of certain parts of the frequency domain. The corresponding inverse Fourier transform is shown to exist in the form\nof two dual scale-frequency series. Upon discretization of the continuous scale factor, this Fourier transformseries inverse becomes\na certain nonharmonic double series, a discretized scale-frequency (DSF) series. The DSF series is also demonstrated, theoretically\nand practically, to be rate-optimizablewith respect to its two free parameters,when it satisfies, as an entropy maximizer, a pertaining\nrecursive nonlinear programming problem incorporating the entropy-based uncertainty principle....
Uniform shear flow of an incompressible inviscid fluid past a two-dimensional smooth concave body is studied; a stream function\nfor resulting flow is obtained. Results for the same flow past a circular cylinder or a circular arc or a kidney-shaped body are\npresented as special cases of the main result. Also, a stream function for resulting flow around the same body is presented for an\noncoming flow which is the combination of a uniform stream and a uniform shear flow. Possible fields of applications of this study\ninclude water flows past river islands, the shapes of which deviate from circular or elliptical shape and have a concave region, or\npast circular arc-shaped river islands and air flows past concave or circular arc-shaped obstacles near the ground....
Theflow of a thin liquid film over a heated stretching surface is considered in this study. Due to a potential nonuniformtemperature\ndistribution on the stretching sheet, a temperature gradient occurs in the fluid which produces surface tension gradient at the free\nsurface of the thin film. As a result, the free surface deforms and these deformations are advected by the flow in the stretching\ndirection.This work focuses on the inverse problem of reconstructing the sheet temperature distribution and the sheet stretch rate\nfromobserved free surface variations. This work builds on the analysis of Santra and Dandapat (2009) who, based on the long-wave\nexpansion of the Navier-Stokes equations, formulate a partial differential equation which describes the evolution of the thickness\nof a film over a nonisothermal stretched surface. In this work, we show that after algebraic manipulation of a discrete form of the\ngoverning equations, it is possible to reconstruct either the unknown temperature field on the sheet and hence the resulting heat\ntransfer or the stretching rate of the underlying surface.We illustrate the proposed methodology and test its applicability on a range\nof test problems....
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