8,533 research outputs found

    Statistics Of The Burst Model At Super-critical Phase

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    We investigate the statistics of a model of type-I X-ray burst [Phys. Rev. E, {\bf 51}, 3045 (1995)] in its super-critical phase. The time evolution of the burnable clusters, places where fire can pass through, is studied using simple statistical arguments. We offer a simple picture for the time evolution of the percentage of space covered by burnable clusters. A relation between the time-average and the peak percentage of space covered by burnable clusters is also derived.Comment: 11 Pages in Revtex 3.0. Two figures available by sending request to [email protected]

    Multiple-input multiple-output visible light communication receivers for high data-rate mobile applications

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    Visible light communication (VLC) is an emerging form of optical wireless communication that transmits data by modulating light in the visible spectrum. To meet the growing demand for wireless communication capacity from mobile devices, we investigate multiple-input multiple-output (MIMO) VLC to achieve multiplexing capacity gains and to allow multiple users to simultaneously transmit without disrupting each other. Previous approaches to receive VLC signals have either been unable to simultaneously receive multiple independent signals from multiple transmitters, unable to adapt to moving transmitters and receivers, or unable to sample the received signals fast enough for high-speed VLC. In this dissertation, we develop and evaluate two novel approaches to receive high-speed MIMO VLC signals from mobile transmitters that can be practically scaled to support additional transmitters. The first approach, Token-Based Pixel Selection (TBPS) exploits the redundancy and sparsity of high-resolution transmitter images in imaging VLC receivers to greatly increase the rate at which complementary metal-oxide semiconductor (CMOS) active pixel sensor (APS) image sensors can sample VLC signals though improved signal routing to enable such high-resolution image sensors to capture high-speed VLC signals. We further model the CMOS APS pixel as a linear shift-invariant system, investigate how it scales to support additional transmitters and higher resolutions, and investigate how noise can affect its performance. The second approach, a spatial light modulator (SLM)-based VLC receiver, uses an SLM to dynamically control the resulting wireless channel matrix to enable relatively few photodetectors to reliably receive from multiple transmitters despite their movements. As part of our analysis, we develop a MIMO VLC channel capacity model that accounts for the non-negativity and peak-power constraints of VLC systems to evaluate the performance of the SLM VLC receiver and to facilitate the optimization of the channel matrix through the SLM

    Combining a fuzzy optimal model with a genetic algorithm to solve multi-objective rainfall–runoff model calibration

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    Title on pre-published version: Combining a fuzzy optimal model with a genetic algorithm to solve multiobjective rainfall-runoff model calibrationAuthor name used in this publication: C. T. ChengAuthor name used in this publication: C. P. OuAuthor name used in this publication: K. W. Chau2002-2003 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe

    No Superluminal Signaling Implies Unconditionally Secure Bit Commitment

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    Bit commitment (BC) is an important cryptographic primitive for an agent to convince a mutually mistrustful party that she has already made a binding choice of 0 or 1 but only to reveal her choice at a later time. Ideally, a BC protocol should be simple, reliable, easy to implement using existing technologies, and most importantly unconditionally secure in the sense that its security is based on an information-theoretic proof rather than computational complexity assumption or the existence of a trustworthy arbitrator. Here we report such a provably secure scheme involving only one-way classical communications whose unconditional security is based on no superluminal signaling (NSS). Our scheme is inspired by the earlier works by Kent, who proposed two impractical relativistic protocols whose unconditional securities are yet to be established as well as several provably unconditionally secure protocols which rely on both quantum mechanics and NSS. Our scheme is conceptually simple and shows for the first time that quantum communication is not needed to achieve unconditional security for BC. Moreover, with purely classical communications, our scheme is practical and easy to implement with existing telecom technologies. This completes the cycle of study of unconditionally secure bit commitment based on known physical laws.Comment: This paper has been withdrawn by the authors due to a crucial oversight on an earlier work by A. Ken

    Dual-mode operation of DC-excited memory motors under flux regulation

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    The concept of memory is due to the fact that the magnetization level of permanent magnets (PMs) in the motor can be easily regulated by a temporary dc current pulse and then be memorized automatically. By incorporating this concept into the hybrid-field doubly salient PM (DSPM) motor, the resulting dc-excited memory motor can offer effective and efficient air-gap flux control. The purpose of this paper is to newly propose and implement dual-mode operation for the dc-excited memory motor. Namely, by regulating the magnetization level of the PMs, the motor can operate either under the DSPM mode or under the switched reluctance mode while maintaining similar operating performances. Both simulation and experimentation are used to verify the validity of the proposed dual-mode operation. © 2011 IEEE.published_or_final_versio

    Flood control management system for reservoirs

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    Author name used in this publication: Chun-Tian ChengAuthor name used in this publication: K. W. Chau2003-2004 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe
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