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sharifnassab--arsalan
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On the possibility of network scheduling with polynomial complexity and delay
, Article IEEE/ACM Transactions on Networking ; 2017 ; 10636692 (ISSN) ; Golestani, S. J ; Sharif University of Technology
2017
Abstract
Considering the collection of all networks with independent set interference model, Shah, Tse, and Tsitsiklis showed that there exist scheduling algorithms with polynomial complexity and delay, only if the maximum independent set problem can be solved in polynomial time (equivalently, P=NP). In this paper, we extend this result to arbitrary collections of networks and present a clear-cut criterion for the existence of polynomial complexity and delay scheduling algorithms relative to a given collection of networks with arbitrary interference models, not confined to independent set interference or SINR models, and not necessarily encompassing all network topologies. This amounts to the...
Scheduling in Communication Networks: Inherent Limitations and Analytical Tools
, Ph.D. Dissertation Sharif University of Technology ; Golestani, Jamaloddin (Supervisor)
Abstract
Scheduling algorithms are responsible for allocation of various types of resources, interference management, and choosing the times and paths through which messages are to be delivered in a communication network. We consider certain fundamental problems in network scheduling. Any scheduling algorithm, to be practical, must have tractable computational complexity and tolerable delay. In the first part of the thesis, we address the following question: “for a given class of networks, does there exist a scheduling algorithm that performs polynomially many computations (in terms of the network dimensions), while keeping the expected delay of the network polynomially bounded (again in terms of the...
Sensitivity to cumulative perturbations for a class of piecewise constant hybrid systems
, Article IEEE Transactions on Automatic Control ; Volume 65, Issue 3 , 2020 , Pages 1057-1072 ; Tsitsiklis, J. N ; Jamaloddin Golestani, S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2020
Abstract
We consider a class of continuous-Time hybrid dynamical systems that correspond to subgradient flows of a piecewise linear and convex potential function with finitely many pieces, and which includes the fluid-level dynamics of the Max-Weight scheduling policy as a special case. We study the effect of an external disturbance/perturbation on the state trajectory, and establish that the magnitude of this effect can be bounded by a constant multiple of the integral of the perturbation. © 1963-2012 IEEE
Fluctuation bounds for the max-weight policy with applications to state space collapse
, Article Stochastic Systems ; Volume 10, Issue 3 , 2020 , Pages 223-250 ; Tsitsiklis, J. N ; Jamaloddin Golestani, S ; Sharif University of Technology
INFORMS Inst.for Operations Res.and the Management Sciences
2020
Abstract
We consider a multihop switched network operating under a max-weight scheduling policy and show that the distance between the queue length process and a fluid solution remains bounded by a constant multiple of the deviation of the cumulative arrival process from its average. We then exploit this result to prove matching upper and lower bounds for the time scale over which additive state space collapse (SSC) takes place. This implies, as two special cases, an additive SSC result in diffusion scaling under nonMarkovian arrivals and, for the case of independent and identically distributed arrivals, an additive SSC result over an exponential time scale. © 2020 The Author(s)
Optimal Multicriteria Design of HTS Transformer and Construction of a Laboratory Scale Sample
, Ph.D. Dissertation Sharif University of Technology ; Vakilian, Mehdi (Supervisor) ; Fardmanesh, Mehdi (Co-Supervisor) ; Hekmati, Arsalan (Co-Supervisor)
Abstract
Employing high-temperature superconducting (HTS) tapes, instead of copper or aluminum wires for winding in a superconducting transformer, results in a series of significant advantages; such as: smaller volume, lighter weight, higher efficieny, greatly extended overload capability, better voltage regulation, lower life cycle cost, fault current limiting capability, lower environmental pollution and lower risk potential against fire hazards.In this thesis, optimal design of flux diverter using genetic algorithm for axial short circuit force reduction in HTS transformers has been performed. Then, multilayered flux diverters have been proposed for reduction of weight and losses. The impact of...