Browsing by Subject "Approximation"
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Item Open Access Batch scheduling to minimize the weighted number of tardy jobs(Pergamon Press, 2007) Erel, E.; Ghosh, J. B.In this paper, we address a single-machine scheduling problem with due dates and batch setup times to minimize the weighted number of tardy jobs. We give a pseudo-polynomial dynamic program and a fully-polynomial approximation scheme for the case where the due dates are uniform within a family.Item Open Access Decoherence in open quantum systems : a realistic approach(2006) Savran, KerimDecoherence mechanisms of opcu quantum systems ın intcraction with an enviromental bath is investigated using the master equation formalism. Widely used two-level approximation is questioned.Item Open Access Energy transfer rate in Coulomb coupled quantum wires(American Institute of Physics, 1997) Tanatar, BilalWe study the energy transfer rate for electrons in two parallel quantum wires due to interwire Coulomb interactions. The energy transfer rate between the wires (similar to the Coulomb drag effect in which momentum transfer rate is measured) is calculated as a function of temperature for several wire separation distances. We employ the full wave vector and frequency dependent random-phase approximation at finite temperature to describe the effective interwire Coulomb interaction. We find that the energy transfer rate at intermediate temperatures (i.e., T similar to 0.3E(F)) is dominated by the collective modes (plasmons) of ale system. Nonlinear effects on the energy transfer rate is also explored. (C) 1997 American Institute of Physics.Item Open Access Overdetermined systems of linear equations(Springer, 2009) Pınar, Mustafa Ç.; Floudas, C. A.; Pardalos, P. M.Item Open Access Plasmon-LO-phonon coupling effects on the drag rate in double quantum-well systems(Elsevier, 1997) Güven, Kaan; Tanatar, BilalWe study the Coulomb drag rate for electrons in a double-quantum-well structure taking into account the electron-optical phonon interactions. The full wave vector and frequency dependent random-phase approximation (RPA) at finite temperature is employed to describe the effective interlayer Coulomb interaction. The electron-electron and electron-optical phonon couplings are treated on an equal footing. The electron-phonon mediated interaction contribution is investigated for different layer separations and layer densities. We find that the drag rate at high temperatures (i.e., T greater than or equal to 0.3 E-F) is dominated by the coupled plasmon-phonon of the system. Including the local-field effects in an approximate way we estimate the importance of intralayer correlations to be significant. (C) 1997 Elsevier Science Ltd.Item Open Access The Smoluchowski-Kramers limit of stochastic differential equations with arbitrary state-dependent friction(Springer, 2015) Hottovy, S.; McDaniel, A.; Wehr, J.; Volpe, G.We study a class of systems of stochastic differential equations describing diffusive phenomena. The Smoluchowski-Kramers approximation is used to describe their dynamics in the small mass limit. Our systems have arbitrary state-dependent friction and noise coefficients. We identify the limiting equation and, in particular, the additional drift term that appears in the limit is expressed in terms of the solution to a Lyapunov matrix equation. The proof uses a theory of convergence of stochastic integrals developed by Kurtz and Protter. The result is sufficiently general to include systems driven by both white and Ornstein-Uhlenbeck colored noises. We discuss applications of the main theorem to several physical phenomena, including the experimental study of Brownian motion in a diffusion gradient.