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Proceedings of the 23rd International Conference on Neural Information Processing Systems

作者： Yoshinobu Kawahara Kiyohito Nagano Koji Tsuda Jeff A. Bilmes The Inst. of Scientific and Industrial Res. (ISIR) Osaka Univ. Japan Dept. of Math. and Comp. Sci. Tokyo Inst. of Technology Japan Comp. Bio. Research Center AIST Japan Dept. of Electrical Engineering Univ. of Washington

ISBN: (纸本)9781615679119

Several key problems in machine learning, such as feature selection and active learning, can be formulated as submodular set function maximization. We present herein a novel algorithm for maximizing a submodular set function under a cardinality constraint — the algorithm is based on a cutting-plane method and is implemented as an iterative small-scale binary-integer linear programming procedure. It is well known that this problem is NP-hard, and the approximation factor achieved by the greedy algorithm is the theoretical limit for polynomial time. As for (non-polynomial time) exact algorithms that perform reasonably in practice, there has been very little in the literature although the problem is quite important for many applications. Our algorithm is guaranteed to find the exact solution finitely many iterations, and it converges fast in practice due to the efficiency of the cutting-plane mechanism. Moreover, we also provide a method that produces successively decreasing upper-bounds of the optimal solution, while our algorithm provides successively increasing lower-bounds. Thus, the accuracy of the current solution can be estimated at any point, and the algorithm can be stopped early once a desired degree of tolerance is met. We evaluate our algorithm on sensor placement and feature selection applications showing good performance.

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High radix modular multiplication of large integers optimised with respect to area and time

High radix modular multiplication of large integers optimise...

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Proceedings of the International Conference on Embedded Systems and Applications ESA'04 - Proceedings of the International Conference on VLSI, VLSI'04

作者： Bunimov, Viktor Schimmler, Manfred Inst. of Comp. Sci. and Appl. Math. Faculty of Engineering Chrstn.-Albrechts-Univ. of Kiel Hermann-Rodewald-Straße 3 D-24118 Kiel

ISBN: (纸本)1932415416

A new algorithm for modular multiplication and its architecture are presented. They are optimised with respect to hardware comp.exity and latency. Based on the data flow of the well known interleaved modular multiplication the product of two n-bit-integers X and Y modulo M is comp.ted by n/2 iterations of a simple loop. The loop consists of one single carry save addition, a comp.rison of constant comp.exity, and a table lookup, where the table contains some precomp.ted values and two constants. By this construction the arithmetical comp.exity of the modular multiplication is reduced to n/2 additions without carry propagation in total which leads to a speedup of at least two in comp.rison to all methods previously known. The paper consists of a first algorithm A2 implementing the new idea of combining carry save addition and constant time comp.rison. A2 is not optimal with respect to area and time. Its correctness is proven. By use of a small amount of precomp.ting, the loop of A2 can be modified such that the effort within the loop is minimised. This leads to the algorithm A3. Algorithm A4 an improved version of A2, using a higher radix concludes the paper.

关键词： Algorithms

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A math.matical model of local stimulation of perfusion by vasoactive agent diffusing from tissue surface

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Cardiovascular engineering 2004年第1期4卷 115-123页

作者： Waniewski, Jacek Inst. of Biocybernet./Biomed. Eng. PAS 02-109 Warsaw Trojdena 4 Poland Interdisc. Ctr. Math./Comp. Model. Warsaw University Warsaw Poland Baxter Novum Karolinska Institutet Stockholm Sweden

The delivery or removal of solutes to/from the tissue through its surface is a key process of some medical treatments, as peritoneal dialysis, local chemotherapy, and others. The rate of blood flow and the active capillary surface area in the tissue contribute to the rate of the solute transport, and these factors may be regulated by vasoactive comp.nents of or additives to the media that carry the solutes outside the tissue. Peritoneal dialysis fluids per se are known to induce transient vasodilation and increased diffusive transport of small solutes. Using the existing data on the kinetics of the diffusive mass transport parameters during peritoneal dialysis after infusion of fresh dialysis fluid, different hypotheses about the kinetics of the capillary surface area behind the observed changes are investigated. A distributed math.matical model describes a vasoactive agent that diffuses from the tissue surface, induces vasodilation, and is absorbed in blood. The model is applied for the prediction of the transport parameters of the agent and other, passive solutes. It is shown that the initial increase in the capillary surface area by 2.75 times, induced by a suprathreshold concentration of the agent, and the subsequent decrease in the capillary surface area with a fixed time constant and independently of the actual concentration of the agent, may explain the clinical data. In contrast, the vasoactivity that changes according to the actual level of the agent yields wrong prediction. © 2004 Plenum Publishing Corporation.

关键词： Blood flow Chemotherapy Diffusion Peritoneal dialysis Vasodilation

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Accelerating the secure remote password protocol using reconfigurable hardware

Accelerating the secure remote password protocol using recon...

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2004 comp.ting Frontiers Conference

作者： Groen, Peter Juurlink, Ben Hämäläinen, Panu Hämäläinen, Timo Computer Engineering Laboratory Fac. Elec. Eng. Math./Comp. Science Delft University of Technology P.O. Box 5031 2600 GA Delft Netherlands Inst. of Digit. and Computer Systems Tampere University of Technology P.O. Box 553 33101 Tampere Finland

ISBN: (纸本)1581137419

The Secure Remote Password (SRP) protocol is an authentication and key-exchange protocol suitable for secure password verification and session key generation over insecure communication channels. The modular exponentiations involved, however, are very time-consuming, causing slow logon procedures. This work presents the design of a hardware accelerator that performs modular exponentiation of very wide integers. The experimental platform is TUTWLAN, a Wireless Local Area Network (WLAN) being developed at Tampere University of Technology. It runs on the Altera Excalibur development board that contains a microprocessor and a chip with programmable hardware. The results show that a full modular exponentiation with 1023-bit inputs can be performed in less than 40 ms using less than 10,000 logic elements, each consisting of a 4-input lookup table and a register. By using the implemented hardware accelerator in the authentication protocol, the execution time is reduced by a factor of 4. In addition, proposals to improve the implemented modular exponentiation architecture are presented. An additional factor of 5 improvement (totaling a factor of 20) can be achieved by implementing the fastest design.

关键词： Network protocols

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Dynamics of the fractional-order Van der Pol oscillator

Dynamics of the fractional-order Van der Pol oscillator

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ICCC 2004 - Second IEEE International Conference on comp.tational Cybernetics

作者： Barbosa, Ramiro S. Machado, J.A.T. Ferreira, Isabel M. Tar, József K. Dept. of Electrical Engineering Institute of Engineering of Porto Rua Dr. Antonio Bernardino Almeida 4200-072 Porto Portugal Dept. of Electrical Engineering Faculty of Engineering of Porto Rua Dr. Roberto Frias 4200-465 Porto Portugal Inst. of Math. and Comp. Sciences Budapest Polytechnic Népszínház u. 8 H-1081 Budapest Hungary

ISBN: (纸本)0780385888

In this paper we propose a modified version of the classical unforced Van der Pol oscillator that occurs when introducing a fractional-order time derivative in the state space equations that describes its dynamics. The resulting fractional-order Van der Pol oscillator is analyzed in the time and frequency domains, for several values of order's fractional derivative and, consequently, of the total system order. It is shown that the system can exhibit different output behavior depending on the total system order. Several numerical simulations and performance indices illustrate the fractional dynamics. © 2004 IEEE.

关键词： Oscillators (electronic)

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Gait selection for quadruped and hexapod walking systems

Gait selection for quadruped and hexapod walking systems

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ICCC 2004 - Second IEEE International Conference on comp.tational Cybernetics

作者： Silva, Manuel F. Machado, J.A. Tenreiro Lopes, António M. Tar, József K. Dept. of Electrical Engineering Institute of Engineering of Porto R. Dr. Antonio Bernardino de Almeida 4200-072 Porto Portugal Dept. of Mechanical Engineering Faculty of Engineering of Porto Rua Dr. Roberta Frias 4200-465 Porto Portugal Inst. of Math and Comp. Sciences Budapest Polytechnic Nepszinhaz utca 8 H-1081 Budapest Hungary

ISBN: (纸本)0780385888

This paper studies periodic gaits of quadruped and hexapod locomotion systems. The purpose is to determine the best set of gait and locomotion variables for different robot velocities based on the system dynamics during walking. In this perspective, several performance measures are formulated and a set of experiments that reveal the influence of the gait and locomotion variables upon those proposed indices are performed. © 2004 IEEE.

关键词： Robotics

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Dynamic fault-tolerant scheduling algorithm for a real-time distributed system

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Harbin Gongcheng Daxue Xuebao/Journal of Harbin engineering University 2004年第6期25卷 789-793页

作者： Zhou, Shuang-E Yuan, You-Guang Coll. of Math. and Comp. Sci. Hubei Univ. Wuhan 430062 China Wuhan Digital Eng. Inst. Wuhan 430074 China

In a real-time distributed system, it is critical to have a fault-tolerant task execution scheme to meet the tasks' deadlines even in the presence of one processor failure. Although interesting scheduling algorithms are available, including the algorithm in which a task's primary copy is not executed with its backup copies at the same time. Thus far, research could not handle task deadlines that are insufficient to run the primary copies and backup copies respectively. A new dynamic fault-tolerant algorithm FTPB based on PB is offered here. In this algorithm, an active and a passive replica are utilized according to the relationship between Ri + Ci + Vi and Di. Simulation results show that the FTPB algorithm is effective, has better fault-tolerant ability, and can improve efficiently the CPU utilization and tasks acception ratio.

关键词： Scheduling

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A variational finite element method for source inversion for convective-diffusive transport

A variational finite element method for source inversion for...

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作者： Akçelik, Volkan Biros, George Ghattas, Omar Long, Kevin R. Van Bloemen Waanders, Bart Mech. Algorithms/Comp. Laboratory Department of Biomedical Engineering Carnegie Mellon University Pittsburgh PA 15213 United States Courant Inst. for Math. Sciences New York University New York NY 10012 United States Sandia National Laboratories Livermore CA 94551 United States Sandia National Laboratories Albuquerque NM 87185 United States

We consider the inverse problem of determining an arbitrary source in a time-dependent convective-diffusive transport equation, given a velocity field and pointwise measurements of the concentration. Applications that give rise to such problems include determination of groundwater or airborne pollutant sources from measurements of concentrations, and identification of sources of chemical or biological attacks. To address ill-posedness of the problem, we employ Tikhonov and total variation regularization. We present a variational formulation of the first-order optimality system, which includes the initial-boundary value state problem, the final-boundary value adjoint problem, and the space-time boundary value source problem. We discretize in the space-time volume using Galerkin finite elements. Several examples demonstrate the influence of the density of the sensor array, the effectiveness of total variation regularization for discontinuous sources, the invertibility of the source as the transport becomes increasingly convection-dominated, the ability of the space-time inversion formulation to track moving sources, and the optimal convergence rate of the finite element approximation. Published by Elsevier Science B.V.

关键词： Finite element method

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Singularity analysis of spatial Stewart-Gough platforms with planar base and platform

Singularity analysis of spatial Stewart-Gough platforms with...

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27th Biennial Mechanisms and Robotics Conference

作者： Pernkopf, Friedrich Husty, Manfred L. Inst. Eng. Math. Geometry and Comp. Science University of Innsbruck 6020 Innsbruck Austria

ISBN: (纸本)0791836215

In the neighborhood of a singularity a parallel manipulator becomes uncontrollable due to actuator saturation. Therefore it is important to know where all singularities of such a manipulator are. This paper presents a new and geometric approach to comp.te the singularities of all spatial Stewart-Gough platform manipulators which have anchor points of base and platform in planes. It is shown that these manipulators have a geometrically exceptional home pose and it is described how singularity free regions can be found. The developed methods are used to evaluate the singularity free orientation capability of a manipulator along any prescribed trajectory. Copyright ã 2002 by ASME.

关键词： Flexible manipulators

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The Real-gas Effect in Single-bubble Sonoluminescence

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Communications in Nonlinear Science and Numerical Simulation 1999年第1期4卷 29-34页

作者： Li YUAN (LSEC, inst.tute of comp.tational math.matics and Scientific-engineering comp.ting, Chinese Academy of Sciences, Beijing 100080, China) Wei WEI (Center for Nonlinear Sciences, University of Science and Technology of China, Hefei 230026,China) LSEC Inst. Compl. Math./Sci.-Eng. Comp. Chinese Academy of Sciences Beijing 100080 China Center for Nonlinear Sciences Univ. of Sci. and Technol. of China Hefei 230026 China Department of Physics Chinese University of Hong Kong Shatin Hong Kong

The full set of hydrodynamic equations governing the oscillation of a bubble is solved numerically by using a modified equation of state with ionization. We show that the hydro-thermal process in the form of comp.ession waves and low-level ionization are dominant inside a sonoluminescing bubble for a wide range of driving pressure. The resulting thermal bremsstrahlung radiation has pulse heights and widths that agree with experimental data for cases considered in this paper.

关键词： single-bubble sonoluminescence ionization bremsstrahlung

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