检索结果-南通市图书馆

Laplacian smoothing transform for face recognition

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

science china(Information sciences) 2010年第12期53卷 2415-2428页

作者： GU SuiCheng, TAN Ying & HE XinGui Key Laboratory of Machine Perception (MOE) Department of Machine Intelligence, school of electronics engineering and computer science peking university, beijing 100871, china Key Laboratory of Machine Perception (MOE) Department of Machine Intelligence School of Electronics Engineering and Computer Science peking university

In this paper, we investigate how to extract the lowest frequency features from an image. A novel Laplacian smoothing transform (LST) is proposed to transform an image into a sequence, by which low frequency features of an image can be easily extracted for a discriminant learning method for face recognition. Generally, the LST is able to be an efficient dimensionality reduction method for face recognition problems. Extensive experimental results show that the LST method performs better than other pre-processing methods, such as discrete cosine transform (DCT), principal component analysis (PCA) and discrete wavelet transform (DWT), on ORL, Yale and PIE face databases. Under the leave one out strategy, the best performance on the ORL and Yale face databases is 99.75% and 99.4%; however, in this paper, we improve both to 100% with a fast linear feature extraction method for the first time.

关键词： Laplacian smoothing transform (LST) face recognition principal component analysis (PCA) discrete cosine transform (DCT) discrete wavelet transform (DWT) linear discriminant analysis (LDA)

A SQP optimization method for shimming a permanent MRI magnet

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Progress in Natural science:Materials International 2009年第10期19卷 1439-1443页

作者： Zhe Jina,Xing Tangb,Bin Menga,Donglin Zu b,Weimin Wanga,a Institute of Quantum electronics,school of electronics engineering and computer science,peking university,beijing 100871,china b Institute of Heavy Ion Physics,beijing Key Laboratory of Medical Physics and engineering,school of Physics,peking university,beijing 100871,china Institute of Quantum electronics School of Electronics Engineering and Computer Science Peking University Beijing 100871 China Institute of Heavy Ion Physics Beijing Key Laboratory of Medical Physics and Engineering School of Physics Peking University Beijing 100871 China

Based on the sequential quadratic programming(SQP) method,a new approach is presented in this paper to gain a uniform magnetic field for a permanent MRI magnet with biplanar ***,the adopted shimming piece is modeled as a magnetic dipole moment to calculate its effect on the background field over the imaging region of ***,the SQP method is utilized to determine the ideal solution for the shimming ***,the ideal solution is discrete,and the quantization error control technique is used for special *** new method helps to reduce the inhomogeneity from 1234.5 ppm to 21.4 ppm over a 36 cm diameter spherical volume(DSV),within hours in practical shimming work.

关键词： Magnetic resonance imaging(MRI) Field shimming Sequential quadratic programming(SQP) Permanent MRI magnet

Behavioural equivalences of a probabilistic pi-calculus

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

science china(Information sciences) 2012年第9期55卷 2031-2043页

作者： CHEN WeiEn,CAO YongZhi & WANG HanPin Key Laboratory of High Confidence Software Technologies,Ministry of Education of china,Institute of Software,school of electronics engineering and computer science,peking university,beijing 100871,china Key Laboratory of High Confidence Software Technologies Ministry of Education of China Institute of Software School of Electronics Engineering and Computer Science Peking University Beijing China

Although different kinds of probabilistic π-calculus have been introduced and found their place in quantitative verification and evaluation,their behavioural equivalences still lack a deep *** propose a simple probabilistic extension of the π-calculus,π p,which is inspired by Herescu and Palamidessi’s probabilistic asynchronous π-*** early semantics of our π p is *** generalise several classic behavioural equivalences to probabilistic versions,obtaining the probabilistic(strong) barbed equivalence and probabilistic bisimulation for π *** we prove that the coincidence between the barbed equivalence and bisimilarity in the π-calculus is preserved in the probabilistic setting.

关键词： probabilistic pi-calculus behavioural equivalence probabilistic bisimulation probabilistic barbed bisimulation

A new simulated annealing method of designing NMR biplanar shim coils

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Progress in Natural science:Materials International 2006年第7期16卷 747-752页

作者： QI Feng, TANG Xin, WANG Weimin, SHEN Yifei, LIU Shaopo and JIANG Zhongde ( Key Laboratory for Quantum Information and Measurements of Ministry of Education, school of electronics engineering & computer science, peking university, beijing 100871, china Institute of Heavy Ion Physics, and beijing Key Laboratory of Medical Physics and engineering, Physical school, peking university, beijing 100871, china) peking Univ Sch Elect Engn & Comp Sci Minist Educ Key Lab Quantum Informat & Measurements Beijing 100871 Peoples R China peking Univ Sch Phys Beijing Key Lab Med Phys & Engn Beijing 100871 Peoples R China peking Univ Inst Heavy Ion Phys Beijing 100871 Peoples R China

A new SA (simulated annealing) method is presented for the design of longitudinal shim coils for NMR (nuclear magnetic resonance) equipment. First, AGL (adaptive Gauss-Lobatto) quadrature used by the traditional SA method is analyzed. Two kinds of complete elliptic integrals are introduced to integrate the spatial magnetic field, which increases the computing speed by 13. 3 times. Then, the system energy calculation is extended to the field of the z-axis. The results illustrate that the coil-set efficiency designed by the new SA method is 15 % higher than that of the traditional one, and the field inhomogeneity is reduced from 1.20 % to 0.49 % . Finally, a prototype of coil assembly for NMR rock-core analyzer is built, and the experimental results are in good agreement with the theoretically calculated results.

关键词： NMR shim coil design simulated-annealing method complete elliptic integral.

Predicting Polymerase Ⅱ Core Promoters by Cooperating Transcription Factor Binding Sites in Eukaryotic Genes

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Acta Biochimica et Biophysica Sinica 2004年第4期36卷 250-258页

作者： Xiao-Tu MA, Min-Ping QIAN*, and Hai-Xu TANG1 school of Mathematical sciences, peking university and Center for Theoretical Biology, peking university, beijing 100871, china 1Department of computer science and engineering, university of California, San Diego, La Jolla CA 92093-0114, USA school of Mathematical sciences Peking University and Center for Theoretical Biology Peking UniversityBeijing 100871 China Department of computer science and engineering University of CaliforniaSan Diego La Jolla CA 92093-0114 USA

Several discriminate functions for predicting core promoters that based on the potential cooperation between transcription factor binding sites (TFBSs) are discussed. It is demonstrated that the promoter predicting accuracy is improved when the cooperation among TFBSs is taken into consideration. The core promoter region of a newly discovered gene CKLFSF1 is predicted to locate more than 1.5 kb far away from the 5' end of the transcript and in the last intron of its upstream gene, which is experimentally confirmed later. The core promoters of 3402 human RefSeq sequences, obtained by extending the mRNAs in human genome sequences, are predicted by our algorithm, and there are about 60% of the predicted core promoters locating within the ± 500 bp region relative to the annotated transcription start site.

关键词： promoter transcription factor binding site transcription start site gene finding

Distributed GIS oriented generalized image pyramid and its practice

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

science china(Technological sciences) 2010年第S1期53卷 99-104页

作者： XIA YuBin,PANG PeiYu & WENG JingNong school of computer science and engineering,Beihang university,beijing 100191,china school of computer science and engineering Beihang University Beijing China

Gaussian pyramid framework (GPF) and Laplacian pyramid framework (LPF) are the two main frameworks used for transmission and structure of spatial image and geometric *** is the main approach for progressive transmission of spatial image *** paper discusses the issues in structure,transmission and storage efficiency of spatial data in the current spatially distributed visualization *** in the paper a novel approach is introduced to structure and store spatial data based on the *** new approach builds (spatial) index for transformed frequency data within different ranges based on splitting high-frequency and low-frequency data by biorthogonal *** approach decreases the storage consumption and network data traffic for transmission while enables the progressive transmission of spatial image.

关键词： redundancy spatial index progressive transmission generalized pyramid structure Laplacian pyramid framework

维普期刊数据库

Performance Modeling and Approximate Analysis of Multiserver Multiqueue Systems with Poisson and Self-similar Arrivals

在线全文

学校读者我要写书评

暂无评论

Journal of university of science and Technology beijing 2001年第2期8卷 145-151页

作者： Zhiguang Shan, Chuang Lin, Yang Yang, Yan Wang (Information engineering school, university of science and Technology beijing, beijing 100083, china) (Department of computer science and Technology, Tsinghua university, beijing 100084, china) Information engineering school University of Science and Technology Beijing 100083 China

The problem of state space explosion is still ran outstanding challenge in Markovian performance analysis for multiserver multiqueue (MSMQ) systems. The system behavior of a MSMQ system is described using stochastic high-level Petri net (SHLPN) models, and an approximate performance analysis technique is proposed based on decomposition and refinement methods as well as iteration technique. A real MSMQ system, Web-server cluster, is investigated. The performance of an integrated scheme of request dispatching and scheduling is analyzed with both Poisson and self-similar request arrivals. The study shows that the approximate analysis technique significantly reduces the complexity of the model solution and is also efficient for accuracy of numerical results.

关键词： multiserver multiqueue (MSMQ) system Web-server cluster performance analysis stochastic high-level Petri net (SHLPN) request dispatching request scheduling

维普期刊数据库

The (⊿+2,2)-incidence coloring of outerplanar graphs

在线全文

学校读者我要写书评

暂无评论

Progress in Natural science:Materials International 2008年第5期18卷 575-578页

作者： Shudong Wanga,b,c, Jin Xu a,b, Fangfang Mac, Chunxiang Xua,b a Institute of Software, school of Electronic engineering and computer science, peking university, beijing 100871, china b Key Laboratory of High Con dence Software Technologies, Ministry of Education, beijing 100871, china c College of Information science and engineering, Shandong university of science and Technology, Qingdao 266510, china Institute of Software School of Electronic Engineering and Computer Science Peking University Beijing 100871 China Key Laboratory of High Confidence Software Technologies Ministry of Education Beijing 100871 China College of Information science and engineering Shandong University of Science and Technology Qingdao 266510 China

An incidence coloring of graph G is a coloring of its incidences in which neighborly incidences are assigned di erent colors. In this paper, the incidence coloring of outerplanar graphs is discussed using the techniques of exchanging colors and the double inductions from the aspect of con guration property. Results show that there exists a (D + 2,2)-incidence coloring in every outerplanar graph, where D is the maximum degree of outerplanar graph.

关键词： Incidence coloring Incidence chromatic number Outerplanar graph

Relaying Selection with Network-coded Cooperative Protocols in Aeronautical Communications

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2010年第1期23卷 75-83页

作者： Du Bing,Zhang Jun school of electronics and Information engineering,beijing university of Aeronautics and Astronautics,beijing 100191,china school of electronics and Information engineering Beijing University of Aeronautics and Astronautics Beijing 100191 China

In this article, we exploit the idea of network-coded cooperative protocol in aeronautical communications which combines different source nodes＇ information at the relay and joint decoding at the destination. Recently, the network coding in cooperative communications has been categorized into two mainstreams, bit-level and signal-level combinations, which are both discussed in the article. And to be exclusively,multiple access relay channel（MARC） is adopted. The mutual information expressions of both above-cited network-coded protocols are deduced, which prove that without proper selected relays to perform network coding, the spatial diversity of the proposed protocol cannot be obtained. This then leads to search for the selection and grouping algorithms. An adjacency matrix is defined to describe the connectivity of the nodes in one radio contact disk, so that, the selection and grouping of algorithm is equivalent to constructing this adjacency matrix to minimize the system outage probability evaluated in term of the mutual information. Besides, a network-coded cooperative protocol requires the acyclic network, of which the construction is to avoid loop-4 in the matrix. The article ends with simulations to demonstrate the viability of the proposed algorithms.

关键词： communication network coding outage probability mutual information bit-level signal-level

维普期刊数据库