6,287 research outputs found
An algebraic criterion for the onset of chaos in nonlinear dynamic systems
The correspondence between iterated integrals and a noncommutative algebra is used to recast the given dynamical system from the time domain to the Laplace-Borel transform domain. It is then shown that the following algebraic criterion has to be satisfied for the outset of chaos: the limit (as tau approaches infinity and x sub 0 approaches infinity) of ((sigma(k=0) (tau sup k) / (k* x sub 0 sup k)) G II G = 0, where G is the generating power series of the trajectories, the symbol II is the shuffle product (le melange) of the noncommutative algebra, x sub 0 is a noncommutative variable, and tau is the correlation parameter. In the given equation, symbolic forms for both G and II can be obtained by use of one of the currently available symbolic languages such as PLI, REDUCE, and MACSYMA. Hence, the criterion is a computer-algebraic one
Bifurcations in unsteady aerodynamics
Nonlinear algebraic functional expansions are used to create a form for the unsteady aerodynamic response that is consistent with solutions of the time dependent Navier-Stokes equations. An enumeration of means of invalidating Frechet differentiability of the aerodynamic response, one of which is aerodynamic bifurcation, is proposed as a way of classifying steady and unsteady aerodynamic phenomena that are important in flight dynamics applications. Accomodating bifurcation phenomena involving time dependent equilibrium states within a mathematical model of the aerodynamic response raises an issue of memory effects that becomes more important with each successive bifurcation
A SIMULATION MODEL FOR PREDICTING AND ANALYZING MANPOWER REQUIREMENTS
Labor and Human Capital,
One-degree-of-freedom motion induced by modeled vortex shedding
The motion of an elastically supported cylinder forced by a nonlinear, quasi-static, aerodynamic model with the unusual feature of a motion-dependent forcing frequency was studied. Numerical solutions for the motion and the Lyapunov exponents are presented for three forcing amplitudes and two frequencies (1.0 and 1.1 times the Strouhal frequency). Initially, positive Lyapunov exponents occur and the motion can appear chaotic. After thousands of characteristic times, the motion changes to a motion (verified analytically) that is periodic and damped. This periodic, damped motion was not observed experimentally, thus raising questions concerning the modeling
Sliding Performance of PEI Composites Under Dry Atmospheric Conditions
In this work, the dry sliding wear behavior of PEI+15%PTFE and PEI+20%GFR polymer composites
rubbing against PPS+40%SGFR, BMC+15%LGFR and stainless steel were investigated using a pin–on–
disc arrangement. Test conditions were 20 to 60N loads and at 0.5 m/s sliding speeds. It was observed that,
the specific wear rate showed very little sensitivity to the varying load. For all material combinations used
in this investigation, the coefficient of friction decreases linearly with the increase in load. The specific
wear rate decreases with the increase in applied load for polymer-polymer combinations but increases or
shows no change with the increase in load value for polymer- steel disc combinations. Finally it is concluded
that the wear resistance of 15% PTFE filled PEI composite is higher than that of 20% glass fibre reinforced
poly-ether-imide polymer composite against different polymer and steel counter-faces.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3526
Solution of Massless Spin One Wave Equation in Robertson-Walker Space-time
We generalize the quantum spinor wave equation for photon into the curved
space-time and discuss the solutions of this equation in Robertson-Walker
space-time and compare them with the solution of the Maxwell equations in the
same space-time.Comment: 16 Pages, Latex, no figures, An expanded version of paper published
in International Journal of Modern Physics A, 17 (2002) 113
Restoration of error-diffused images using projection onto convex sets
Cataloged from PDF version of article.In this paper, a novel inverse halftoning method is
proposed to restore a continuous tone image from a given half-tone
image. A set theoretic formulation is used where three sets are defined
using the prior information about the problem. A new spacedomain
projection is introduced assuming the halftoning is performed
using error diffusion, and the error diffusion filter kernel is
known. The space-domain, frequency-domain, and space-scale domain
projections are used alternately to obtain a feasible solution
for the inverse halftoning problem which does not have a unique
solution
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