4,568 research outputs found
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, âAn aerodynamic analysis of a novel small wind turbine based on impulse turbine principlesâ, 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
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
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