Noncommutative Geometry and D-Branes

We apply noncommutative geometry to a system of N parallel D-branes, which is interpreted as a quantum space. The Dirac operator defining the quantum differential calculus is identified to be the supercharge for strings connecting D-branes. As a result of the calculus, Connes' Yang-Mills action functional on the quantum space reproduces the dimensionally reduced U(N) super Yang-Mills action as the low energy effective action for D-brane dynamics. Several features that may look ad hoc in a noncommutative geometric construction are shown to have very natural physical or geometric origin in the D-brane picture in superstring theory.Comment: 16 pages, Latex, typos corrected and minor modification mad

An aerodynamic analysis of a novel small wind turbine based on impulse turbine principles

This document is the Accepted Manuscript of the following article: Pei Ying, Yong Kang Chen, and Yi Geng Xu, ‘An aerodynamic analysis of a novel small wind turbine based on impulse turbine principles’, Renewable Energy, Vol. 75: 37-43, March 2015, DOI: https://doi.org/10.1016/j.renene.2014.09.035, made available under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License CC BY NC-ND 4.0 http://creativecommons.org/licenses/by-nc-nd/4.0/The paper presents both a numerical and an experimental approach to study the air flow characteristics of a novel small wind turbine and to predict its performance. The turbine model was generated based on impulse turbine principles in order to be employed in an omni-flow wind energy system in urban areas. The results have shown that the maximum flow velocity behind the stator can be increased by 20% because of a nozzle cascade from the stator geometry. It was also observed that a wind turbine with a 0.3 m rotor diameter achieved the maximum power coefficient of 0.17 at the tip speed ratio of 0.6 under the wind velocity of 8.2 m/s. It was also found that the power coefficient was linked to the hub-to-tip ratio and reached its maximum value when the hub-to-tip ratio was 0.45. It is evident that this new wind turbine has the potential for low working noise and good starting feature compared with a conventional horizontal axis wind turbine.Peer reviewedFinal Accepted Versio

Non-Archimedean meromorphic solutions of functional equations

In this paper, we discuss meromorphic solutions of functional equations over non-Archimedean fields, and prove analogues of the Clunie lemma, Malmquist-type theorem and Mokhon'ko theorem

Noncommutative Gauge Theories in Matrix Theory

We present a general framework for Matrix theory compactified on a quotient space R^n/G, with G a discrete group of Euclidean motions in R^n. The general solution to the quotient conditions gives a gauge theory on a noncommutative space. We characterize the resulting noncommutative gauge theory in terms of the twisted group algebra of G associated with a projective regular representation. Also we show how to extend our treatments to incorporate orientifolds.Comment: 11 pages, Latex, discussions on orientifolds adde

Convergence of martingale solution to slow-fast systems with jumps modulated by Markovian switching

This paper investigates the convergence of martingale solutions to slow-fast systems with jumps modulated by Markovian switching on weakly irreducible class. The key point here is to deals with slow-fast systems and two-time-scale Markovian switching simultaneously, while averaging on the slow component requires two invariant measures respectively due to the coexistence of the fast component and Markovian switching. We first investigate the slow-fast systems modulated by Markovian chains with single weakly irreducible class, and the existence and uniqueness of the solution will be proved. Then weak convergence is presented based on tightness and the exponential ergodicity of the fast component with the martingale method, where the appropriate perturbed test functions plays a decisive role in processing. Finally we extend results to the case of the multiple irreducible class

Brane Creation in M(atrix) Theory

We discuss, in the context of M(atrix) theory, the creation of a membrane suspendend between two longitudinal five-branes when they cross each other. It is shown that the membrane creation is closely related to the degrees of freedom in the off-diagonal blocks which are related via dualities to the chiral fermionic zero mode on a 0-8 string. In the dual system of a D0-brane and a D8-brane in type \IIA theory the half-integral charges associated with the ``half''-strings are found to be connected to the well-known fermion-number fractionalization in the presence of a fermionic zero mode. At sufficiently short distances, the effective potential between the two five-branes is dominated by the zero mode contribution to the vacuum energy.Comment: 14 pages, Latex. A new paragraph on p.10 and acknowledgement added. v3: The version for publication: minor revisions and typos correcte

CEG 702-01: Advanced Computer Networks

This course provides an in-depth examination of the fundamental concepts and principles in communications and computer networks. Topics include: queuing analysis, ATM, frame relay, performance analysis of routings, and flow and congestion controls