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QoS-awared replica placement techniques in data grid applications

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Science china(Information Sciences) 2010年第8期53卷 1487-1496页

作者： XIAO Nong, FU Wei & LU XiCheng school of computer, national university of defense technology, changsha 410073, china 1. school of computer National University of Defense Technology Changsha 410073 China

Quality of service is one of the most important factors for successful grid applications. However, individual QoS constraint (IQC) and QoS-awared replica placement have not yet been well addressed in the existing data grid. Existing QoS-awared replica placement algorithms neither can support multiple QoS attributes, nor have good scalability. In this paper, a three-phrase QoS-awared replica placement algorithm based on matrix, namely TP-GABMAC, is presented to solve these problems. Furthermore, a replica ring mechanism is introduced to maintain replica consistency and manage update conflicting. Experiments and analysis demonstrate that the proposed algorithms are not only stable and scalable, but also work well under different network topologies, access patterns and workloads.

关键词： grid data grid QoS-awared replica placement replica ring

A logistic regression model for Semantic Web service matchmaking

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Science china(Information Sciences) 2012年第7期55卷 1715-1720页

作者： WEI DengPing 1 ,WANG Ting 1 & WANG Ji 2 1 school of computer,national university of defense technology,changsha 410073,china 2 national Laboratory for Parallel and Distributed Processing,changsha 410073,china 1. school of computer National University of Defense Technology Changsha 410073 China2. National Laboratory for Parallel and Distributed Processing Changsha 410073 China

Semantic Web service matchmaking,as one of the most challenging problems in Semantic Web services (SWS),aims to filter and rank a set of services with respect to a service query by using a certain matching *** this paper,we propose a logistic regression based method to aggregate several matching strategies instead of a fixed integration (e.g.,the weighted sum) for SWS *** logistic regression model is trained on training data derived from binary relevance assessments of existing test collections,and then used to predict the probability of relevance between a new pair of query and service according to their matching values obtained from various matching *** are then ranked according to the probabilities of relevance with respect to each *** method is evaluated on two main test collections,SAWSDL-TC2 and Jena Geography Dataset(JGD).Experimental results show that the logistic regression model can effectively predict the relevance between a query and a service,and hence can improve the effectiveness of service matchmaking.

关键词： Semantic Web service matchmaking logistic regression

Opitimization of tunneling carbon nanotube-FETs based on stair-case doping strategy

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Science china(Information Sciences) 2010年第12期53卷 2696-2704页

作者： ZHOU HaiLiang ,JIANG Jiang,ZHANG MinXuan & FANG Liang school of computer,national university of defense technology,changsha 410073,china 1. school of computer National University of Defense Technology Changsha 410073 China

Due to the fact that either holes or electrons can band-to-band-tunnel(BTBT) through channelsource/drain contacts,tunneling carbon nanotube field effect transistors(T-CNFETs) suffer from ambipolar transporting *** suppress such ambipolar conductance,a novel device design based on stair-case doping strategy of drain region is proposed first in this *** dependences of available ON-OFF current ratio,practical ON-OFF current ratio with certain gate bias range and the average sub-threshold swing on the doping level of drain region are *** results show that such device design can not only increase the ON-OFF current ratio largely but also result in a clear decrease of sub-threshold *** the same time,however,such stair-case doping strategy would broaden the depletion region and result in an increase of device area *** attention should be paid to the choice of doping level of drain region to make a proper tradeoff between power,speed and area in application.

关键词： tunneling carbon nanotube-FETs ambipolar conductance band-to-band-tunneling stair-case doping

Survey of DHT topology construction techniques in virtual computing environments

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Science china(Information Sciences) 2011年第11期54卷 2221-2235页

作者： ZHANG YiMing 1,2,LU XiCheng 1,2 & LI DongSheng 1,21 national Laboratory for Parallel and Distributed Processing (PDL),changsha 410073,china 2 school of computer,national university of defense technology,changsha 410073,china 1. national Laboratory for Parallel and Distributed Processing (PDL) Changsha 410073 China2. School of Computer National University of Defense Technology Changsha 410073 China

The Internet-based virtual computing environment (iVCE) is a novel network computing *** characteristics of growth,autonomy,and diversity of Internet resources present great challenges to resource sharing in *** DHT overlay (DHT for short) technique has various advantages such as high scalability,low latency,and desirable availability,and is thus an important approach to realizing efficient resource *** construction is a key technique for structured overlays that realizes basic overlay functions including dynamic maintenance and message *** this paper,we first introduce the traditional techniques of DHT topology construction,focusing mainly on dynamic maintenance and message routing of typical DHTs,DHT indexing techniques for complex queries,and DHT grouping techniques for matching domain *** then present recent advances in DHT topology construction techniques in iVCE taking advantage of the characteristics of Internet ***,we discuss the future of DHT topology construction techniques.

关键词： virtual computing environments DHT overlays topology construction distributed indexing flexible routing

Parallel Algorithm in Surface Wave Waveform Inversion

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Wuhan university Journal of Natural Sciences 2001年第Z1期6卷 574-578页

作者： Cao Xiao lin, Song Jun qiang school of computer Science, national university of defense technology, changsha 410073, china school of computer Science National University of Defense Technology Changsha China

In Surface wave waveform inversion, we want to reconstruct 3D shear wave velocity structure, which calculation beyond the capability of the powerful present day personal computer or even workstation. So we designed a high paralleled algorithm and carried out the inversion on Parallel computer based on the partitioned waveform inversion (PWI). It partitions the large scale optimization problem into a number of independent small scale problems and reduces the computational effort by several orders of magnitude. We adopted surface waveform inversion with a equal block(2 o×2 o) discretization.

关键词： surface wave waveform inversion parallel algorithm partitioned waveform inversion

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Towards estimating expected sizes of probabilistic skylines

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Science china(Information Sciences) 2011年第12期54卷 2574-2584页

作者： YANG YongTao & WANG YiJie national Key Laboratory for Parallel and Distributed Processing, school of computer, national university of defense technology, changsha 410073, china 1. national Key Laboratory for Parallel and Distributed Processing School of Computer National University of Defense Technology Changsha 410073 China

We consider the maximal vector problem on uncertain data, which has been recently posed by the study on processing skyline queries over a probabilistic data stream in the database context. Let D n be a set of n points in a d-dimensional space and q (0 < q 1) be a probability threshold; each point in D n has a probability to occur. Our problem is concerned with how to estimate the expected size of the probabilistic skyline, which consists of all the points that are not dominated by any other point in D n with a probability not less than q. We prove that the upper bound of the expected size is O(min{n, (- ln q)(ln n) d-1 }) under the assumptions that the value distribution on each dimension is independent and the values of the points along each dimension are distinct. The main idea of our proof is to find a recurrence about the expected size and solve it. Our results reveal the relationship between the probability threshold q and the expected size of the probabilistic skyline, and show that the upper bound is poly-logarithmic when q is not extremely small.

关键词： probabilistic skyline probabilistic data streams expected size

SPECTRAL-DIFFERENCE METHOD FOR TWO-DIMENSIONAL COMPRESSIBLE FLUID FLOW

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Journal of Computational Mathematics 1998年第1期16卷 15-26页

作者： Yue-shan Xiong (Department of computer, national university of defense technology, changsha, china) 国防科技大学计算机系湖南长沙

We develop a combined Fourier spectral-finite difference method for solving 2-dimensional, semi-periodic compressible fluid how problem. The error estimation, as well as the convergence rate, is presented.

关键词： spectral-difference method compressible fluid flow error estimation

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A new satellite to satellite tracking algorithm from Doppler-shifted frequency measurements

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Progress in Natural Science:Materials International 2007年第10期17卷 1226-1234页

作者： Li Qiang, Guo Fucheng and Zhou Yiyu(school of Electronic Science & Engineering, national university of defense technology, changsha 410073, china) school of Electronic Science & Engineering National University of Defense Technology Changsha 410073 China

A new satellite to satellite tracking (SST) algorithm from Doppler-shifted frequency measurements is proposed. The estimation principle is demonstrated and the mathematic model of SST is established. The state estimation methods for a user (the cooperative case) and target satellites (the non-cooperative case) are presented based on particle swarm optimization (PSO). The Cramer-Rao lower bounds (CRLB) are deduced as well. Performance of the new algorithm is validated through computer simulations, which proved that the proposed method is effective in terms of the estimation quality compared with CRLB and superior in accuracy to the Bearings-Only (BO) method in almost all simulation cases except for the case that an enough long tracking arc-length is obtained for a user satellite.

关键词： satellite to satellite tracking (SST) Doppler-shifted frequency (DSF) Space Surveillance Network (SSN) particle swarm optimization (PSO).

A type of M2 -transmitter N2 -receiver MIMO radar array and 3D imaging theory

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Science china(Information Sciences) 2011年第10期54卷 2147-2157页

作者： ZHU YuTao & SU Yi school of Electronic Science and Engineering,national university of defense technology,changsha 410073,china 1. school of Electronic Science and Engineering National University of Defense Technology Changsha 410073 China

With two-dimensional synthetic apertures,a wideband radar array can realize 3D imaging of air targets,but this needs large numbers of antenna ***,when the transmitting frequency is very high,the interval of array elements makes it hard to fit the available space,which makes the imaging resolution *** paper proposes a type of M 2 -transmitter N 2 -receiver multiple-input multiple-output (MIMO) radar,which is equivalent to a rectangular radar array with (M N) 2 T/R antenna elements based on phase center approximation theory,and which can realize the 3D imaging of air *** 3D imaging theory and MIMO inverse synthetic aperture radar (MIMO-ISAR) 3D imaging theory are also proposed in this paper,and two simulations are given to show their validity.

关键词： MIMO radar array phase center approximation 3D imaging ISAR