We theoretically study steady-state nonequilibrium properties of various open electronic systems subject to time-independent external bias. A charge current is established across each system by its coupling to two external particle reservoirs maintained at different chemical potentials. We discuss the impact of intra-reservoir electron correlations on transport, and examine how reservoir-generated dissipation and nonequilibrium-induced decoherence influence these systems. The effect of intra-lead electron interactions on transport is investigated in the context of a phonon-coupled single molecule transistor driven by Luttinger-liquid source and drain leads. The semi-classical master equation approach is used to compute current and noise characteristics of the device for various interaction strengths in the leads. The results suggest the possibility of tuning the Fano factor of the device using intra-lead electron interactions. The Keldysh path integral formalism is used to theoretically formulate models that describe the remaining open nonequilibrium systems. We consider voltage-induced electron-phonon scattering and electron mass enhancement due to phonons in a model metallic system. The possibility of adjusting the acoustic phonon velocity and the Thomas-Fermi screening length with external voltage is discussed. The effects of dissipation is investigated in an open BCS superconducting graphene, where the dissipation-induced rearrangement of its ground state from the BCS superconductor to the Fermi liquid is examined. The results theoretically infer prospects for a voltage-tuned metal-to-BCS quantum phase transition in graphene. Lastly, we develop a theory of nonequilibrium quantum criticality in open itinerant Ising and Heisenberg magnets. Both departures from equilibrium at conventional quantum critical points and the physics of phase transitions induced by the nonequilibrium drive are analyzed.

This thesis studies the mechanics which can be associated with asphalt concrete compaction and develops continuum models in a general thermo-mechanical setting which can be used in future work to corroborate experimental compaction experiment results. Modeling asphalt concrete compaction, and also the ability to thereby predict response of mixes, is of great importance to the pavement industry. Asphalt concrete exhibits nonlinear response even at small strains and the response of asphalt concrete to different types of loading is quite different. The properties of asphalt concrete are highly influenced by the type and amount of the aggregates and the asphalt used. The internal structure of asphalt concrete continues to evolve during the loading process. This is due to the influence of different kinds of activities at the micro-structure level and to the interactions with the environment. The properties of asphalt concrete depend on its internal structure. Hence, we need to take into account the evolution of the internal structure in modeling the response of asphalt concrete. A theoretical model has been developed using the notion of multiple natural configurations to study a variety of non-linear dissipative responses of real materials. By specifying the forms for the stored energy and the rate of dissipation function of the material, a specific model was developed using this framework to model asphalt compaction. A compressible model is developed by choosing appropriate forms of stored energy and rate of dissipation function. Finally, a parametric study of the model is presented for a simple compression deformation. It is anticipated that the present work will aid in the development of better constitutive equations which in turn will accurately model asphalt compaction both in laboratory and in field. Distinct numerical approaches have been used to demonstrate the applicability of the theoretical framework to model material response of asphalt.

Reproduction de : Thèse de doctorat : Acoustique : Le Mans : 2006. / Titre provenant de l'écran-titre. Bibliogr. p. 113-114.

Includes bibliographical references (p. 207-216).

Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, June 2003. / Thesis advisor(s): Young Shin, Ilbae Ham. Includes bibliographical references (p. 63). Also available online.

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Στην παρούσα διατριβή παρουσιάζονται μεθοδολογίες σχεδιασμού που επιτρέπουν την μείωση την κατανάλωση ενέργειας σε υλοποιήσεις ασύρματων εφαρμογών πολυμέσων. Οι προτεινόμενες μεθοδολογίες βελτιστοποιούν την διαχείριση της μνήμης, η κατανάλωσης της οποίας είναι η κυρίαρχη συνιστώσα της συνολικής κατανάλωσης ισχύος στις εφαρμογές πολυμέσων. Επιπλέον, η διατριβή πραγματεύεται τεχνικές για χαμηλής κατανάλωσης διαμερισμό, ο οποίος είναι απαραίτητος για την εκτέλεση σε πραγματικό χρόνο των υψηλής υπολογιστικής πολυπλοκότητας εφαρμογών πολυμέσων. Στόχο της παρούσας διατριβής αποτελεί και η βελτιστοποίηση, όσον αφορά την κατανάλωση ισχύος, των κυκλωμάτων ασύρματης μετάδοσης των πολυμέσων. Στο πλαίσιο αυτό η διατριβή ασχολείται με τεχνικές διαχείρισης ισχύος, και προτείνει υλοποιήσεις που χρησιμοποιούν τις τεχνικές αυτές. Οι μεθοδολογίες και τεχνικές λαμβάνουν υπόψη και την επιφάνεια ολοκλήρωσης και ταχύτητα εκτέλεσης. Τα ισοζύγια (trade-offs) αναγνωρίζονται, και όπου αυτά υπάρχουν προτείνονται μέθοδοι για την αποδοτική τους επίλυση. / In this Ph.D. dissertation, design methodologies that enable energy minimization of wireless multimedia application realizations are presented. The proposed methodologies mainly optimize the management of the memory subsystem, which role is dominant as far as energy dissipation of multimedia application is concerned. Furthermore, techniques for the low-power partitioning, which is required for the real-time implementation of the highly computational complex multimedia applications, are proposed. Apart from the multimedia processing itself the dissertation, also focuses on the transmition of the multimedia content. To this end, power management techniques applicable for the design of wireless receivers are proposed. The proposed techniques are employed for the design of real-life implementation of low and medium rate receivers. Apart from energy minimization The proposed methodologies and techniques take into account constraints regarding the integration area as well as the processing time. The involved trade-offs are identified, and methods for their efficient exploration are proposed

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High order accurate finite difference methods for hyperbolic and parabolic initial boundary value problems (IBVPs) are considered. Particular focus is on time dependent wave propagating problems in complex domains. Typical applications are acoustic and electromagnetic wave propagation and fluid dynamics. To solve such problems efficiently a strictly stable, high order accurate method is required. Our recipe to obtain such schemes is to: i) Approximate the (first and second) derivatives of the IBVPs with central finite difference operators, that satisfy a summation by parts (SBP) formula. ii) Use specific procedures for implementation of boundary conditions, that preserve the SBP property. iii) Add artificial dissipation. iv) Employ a multi block structure. Stable schemes for weakly nonlinear IBVPs require artificial dissipation to absorb the energy of the unresolved modes. This led to the construction of accurate and efficient artificial dissipation operators of SBP type, that preserve the energy and error estimate of the original problem. To solve problems on complex geometries, the computational domain is broken up into a number of smooth and structured meshes, in a multi block fashion. A stable and high order accurate approximation is obtained by discretizing each subdomain using SBP operators and using the Simultaneous Approximation Term (SAT) procedure for both the (external) boundary and the (internal) interface conditions. Steady and transient aerodynamic calculations around an airfoil were performed, where the first derivative SBP operators and the new artificial dissipation operators were combined to construct high order accurate upwind schemes. The computations showed that for time dependent problems and fine structures, high order methods are necessary to accurately compute the solution, on reasonably fine grids. The construction of high order accurate SBP operators for the second derivative is one of the considerations in this thesis. It was shown that the second derivative operators could be closed with two order less accuracy at the boundaries and still yield design order of accuracy, if an energy estimate could be obtained.