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  • Thesis

  • Authors: Emami, Ahmad (2006)

  • Security is a serious concern in wireless networks. In order to eliminate the vulnerabilities in previous Standards, the IEEE 802.11i Standard is designed to provide security enhancements in MAC layer. The authentication process consists of several components, including an 802.1X authentication phase using TLS over EAP, a 4-Way Handshake to establish a fresh session key, and an optional Group Key Handshake for group communications. The objective of this work is to analyze IEEE 802.11i with respect to data confidentiality, integrity, mutual authentication, and availability. Under our threat model, 802.111 appears to provide effective data confidentiality and integrity when CCMP is used. 802.111 may also provide satisfactory mutual authentication and key management, although there ar...

  • Thesis

  • Authors: Beyaz, Ahmet (2006)

  • We introduce the notion of super vertex operator algebra with enhanced conformal structure, which is a refinement of the notion of super vertex operator algebra, and we present applications of this notion to three sporadic simple groups: the largest sporadic group of Conway, the sporadic group of Suzuki, and the sporadic group of Rudvalis. For the Conway group we construct what may be considered a natural super-analogue of the Moonshine Module, where the role of the Virasoro algebra is now played by the N = 1 Virasoro superalgebra, and we find that the full group of automorphisms is Conway's largest sporadic group. We also verify a uniqueness result for this object, which is directly analogous to that conjectured to hold for the Moonshine Module. Replacing the N = 1 Virasoro super...

  • Thesis

  • Authors: Fleckenstein, Anne E. (2006)

  • Multiple drug resistance is quickly becoming an obstacle to the treatment of disease. Bacteria, parasitic protazoa, yeast and mammalian cancer cells develop mutations that render them resistant to a wide variety of structurally and chemically different compounds. In the yeast Saccharomyces cerevisiae, one of the main mechanisms causing drug resistance is the loss of function of ABC transporters that are responsible for effluxing the drug from the cell. The main ABC transporter responsible for efflux of many different drugs is Pdr5p. However, earlier work (Fleckenstein 1999; Shallom and Golin, 1996) shows that this is not the only pathway mediating resistance to these drugs. The global regulator Sin4p and the transcription factor YRRI operate in a PDR5-independent pathway to ...

  • Thesis

  • Authors: Liu, Tongyin (2006)

  • In this dissertation, probabilistic constrained stochastic programming problems are con¬sidered with discrete random variables on the r.h.s. in the stochastic constraints. In Chapter 2 and 3, it is assumed that the random vector has multivariate Poisson, bino¬mial or geometric distribution. We prove a general theorem that implies that in each of the above cases the c.d.f. majorizes the product of the univariate marginal c.d.f's and then use the latter one in the probabilistic constraints. The new problem is solved in two steps: (1) first we replace the c.d.f's in the probabilistic constraint by smooth logconcave functions and solve the continuous problem; (2) search for the optimal so¬lution for the case of the discrete random variables. In Chapter 4, numerical examples are presente...

  • Thesis

  • Authors: Azer, Karim (2006)

  • In this thesis, we present a one-dimensional model for blood flow in arteries, without assuming an a priori shape for the velocity profile across an artery. We combine the one-dimensional equations for conservation of mass and momentum with the Womersley model for the velocity profile in an iterative way. The pressure gradient of the one-dimensional model drives the Womersley equations, and the velocity profiles calculated then feed back into both the friction and nonlinear parts of the one-dimensional model. Besides enabling us to evaluate the friction correctly and also use the velocity profile to correct the nonlinear terms, the velocity profiles play a central role in the calculation of the effective diffusion coefficient, and convection coefficient, in the theory of Taylor diff...

  • Thesis

  • Authors: Zhong, Jie (2006)

  • Many types of auctions are discussed in the literature such as single item auctions, sequential auctions, and combinatorial auctions. Proxy bidding has proven useful in solving iterative auction problems in many real-world auction formats. In this dissertation, I propose a new type of iterative auction called the Simple Combinatorial Proxy Auction. A popular method for solving the iterative proxy auction problems is simulating the incremental bidding decisions of the agents. However, this approach has some disadvantages. In this dissertation, I present a new approach called the Price Trajectory Algorithm to solve iterative auction problems. This approach computes the agents’ allocation of their attention across the bundles only at “inflection points” – the points at which agents ch...

  • Thesis

  • Authors: Huỳnh, Thanh Công.;  Advisor: Lee, Jong Tai (2009)

  • Hydrogen-fueled engines with external mixture formation have potentially high thermal efficiency because of a more homogeneous inlet mixture. In addition, the structure of such engines is relatively simple. The practical use of hydrogen can be visible in the short term. The occurrence of backfire at high engine load conditions, however, is an important problem. Because of this, the method of attaining both high efficiency and high power without backfire in a hydrogen-fueled engine is the most important key. The backfire phenomena of hydrogen-air mixtures in the intake system are often a result of backflow of a pre-ignited fast flame from combustion chamber during the valve overlap period. When the valve overlap period is short enough, backfire may not occur even under high load ope...

  • Thesis

  • Authors: Gamber, Emily (2006)

  • We give a classification of cellular automata in arbitrary dimensions and on arbitrary subshift spaces from the point of view of symbolic and topological dynamics. A cellular automaton is a continuous, shift-commuting map on a subshift space; these objects were first investigated from a purely mathematical point of view by Hedlund in 1969. In the 1980’s, Wolfram categorized one-dimensional cellular automata based on features of their asymptotic behavior which could be seen on a computer screen. Gilman’s work in 1987 and 1988 was the first attempt to mathematically formalize these characterizations of Wolfram’s, using notions of equicontinuity, expansiveness, and measure-theoretic analogs of each. We introduce a topological classification of cellular automata in dimensions two and hi...

  • Thesis

  • Authors: Tam, Mary C. (2006)

  • Coupled cluster (CC) and density functional theory (DFT) are highly regarded as robust quantum chemical methods for accurately predicting a wide variety of properties, such as molecular structures, thermochemical data, vibrational spectra, etc., but there has been little focus on the theoretical prediction of optical rotation. This property, also referred to as circular birefringence, is inherent to all chiral molecules and occurs because such samples exhibit di erent refractive indices for left- and right- circularly polarized light. This thesis focuses on the theoretical prediction of this chiroptic property using CC and DFT quantum chemical models. Several small chiral systems have been studied, including (S)-methyloxirane, (R)-epichlorohydrin, (R)-methylthiirane, and the conform...

  • Thesis

  • Authors: Mehmood, Faisal (2006)

  • Ab initio electronic structure calculations based on density functional theory with the generalized gradient approximation and ultrasoft pseudopotentials have been applied to understand the effect of the local environment on the characteristics of chemisorption of selected atoms and molecules on low and high Miller index surfaces of transition metals. In some calculations the full-potential linearized augmented plane wave method was employed for a more accurate description of electronic struc¬ture. On a set of low and high Miller index surfaces of Cu with coordination ranging from 6 to 9 we find a decrease in CO adsorption energy with an increase in the local coordination. This general trend is found to be in qualitative agreement with experiment. The largest binding energy of CO i...