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A novel method for evaluating and improving the 1H-MRSI glioma data quality

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Progress in Natural Science:Materials International 2005年第8期15卷 765-768页

作者： YUAN Kehong 1,2. LU Hongyu2. BAO Shanglian2., CHEN Qiansheng1, LI Shaowu3 and DUAN Chaijie2.1. Key Laboratory of Pure and Applied Mathematics, school of Mathematical Sciences, beijing 100871, {2. 2. The Research Center for Tumor Diagnosis and Therapeutical physics & the beijing Key Laboratory of Medical physics and Engineering, peking University, beijing 100871, {2. 3. The Tian Tan Hospital, beijing 100050, {2.) Key Laboratory of Pure and Applied Mathematics School of Mathematical Sciences Beijing 100871 China. The Research Center for Tumor Diagnosis and Therapeutical physics & the beijing Key Laboratory of Medical physics and Engineering Peking University Beijing 100871 China. The Tian Tan Hospital Beijing 100050 China

Metabolic information obtained by proton magnetic resonance spectroscopic imaging (1H-MRSI) has been approved to be a powerful tool to identify either benign or malignant glioma, as well as to confirm the tumor level. However, 1H-MRSI data are affected by various factors, such as the thermal noise, eddy currents, susceptibility artifacts, and rigid body motion. To get accurate quantitative metabolic information, the key problem is to assess the 1H-MRSI data quality. In this paper, we introduce a new evaluating system to filter the data, and a new method, called wavelet denoising method, to improve the data quality under the evaluating system. Experimental results on 1H-MRSI glioma data demonstrate that preprocessing is prerequisite and the proposed algorithm with evaluating system is effective.

关键词： 1H-MRSI evaluating system glioma data quality wavelet denoising

Pole assignment in descriptor periodic systems

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Science china Mathematics 2005年第10期48卷 1309-1332页

作者： FAN Hung-Yuan~1 LIN Wen-Wei~1 & XU Shufang~2.1. Department of Mathematics,Tsing Hua University,Hsinchu 30043,china 2. LMAM,school of Mathematical Sciences,{2. University,beijing 100871,china 1. Department of Mathematics Tsing Hua University 30043 Hsinchu China 2. LMAM School of Mathematical Sciences Peking University 100871 Beijing China

In this paper a pole assignment problem is considered for the descriptor linear discrete-time periodic systems, which is using the periodic proportional-derivative feedback to modify a given system such that the closed loop system has a specified selfconjugate set of eigenvalues. It is shown that the complete reachability of an open loop periodic system is equivalent to the possibility of assigning an arbitrary set of the eigenvalues to the system by choosing the suitable periodic proportional-derivative feedback.A computational approach is also proposed to solve the problem, which uses the reliable numerical techniques based on the orthogonal transformations. Numerical examples are presented to illustrate the effectiveness of the proposed approach.

关键词： descriptor linear periodic system, pole assignment, proportional and derivative feedback, numerical method, periodic Schur decomposition.

BRILL-NOETHER MATRIX FOR RANK TWO VECTOR BUNDLES

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Chinese Annals of Mathematics,Series B 2002年第4期23卷 531-538页

作者： TAN XIAOJIANGschool of Mathematical Sciences, peking University, {2., china school of Mathematical Sciences Peking University Beijing 100871 China

Let X be an arbitrary smooth irreducible complex projective curve, E (?)X a rank two vector bundle generated by its sections. The author first represents ?as a triple {D1,D2.f}, where D1 , D2.are two effective divisors with d = deg(D1) + deg(D2., and f ∈ H?X, [D1] |D2. is a. collection of polynomials. E is the extension of [D2. by [D1] which is determined by f. By using / and the Brill-Noether matrix of D1+D2. the author constructs a 2. × d matrix WE whose zero space gives Im{H0(X,[D1]) (?) H0(X, [D1] |D1)}(?) Im{H?X, E) (?) H0(X,[D2.) (?) H0(X, [D2.|D2.} From this and H0(X,E) = H0(X,[D1]) (?)Im{H0(X,E) (?) H0(X, [D2.)}, it is got in particular that dimH0(X, E) = deg(E) - rank(WE) + 2.

关键词： Brill-Noether matrix Vector bundle Effective divisor

r-matrix and algebraic-geometric symplectic map

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Chinese Science Bulletin 1999年第2期44卷 114-118页

作者： QIAO ZhijunInstitute of Mathematics and school of Mathematical Sciences, peking University, {2., china Institute of Mathematics and school of Mathematical Sciences Peking University Beijing China

A new Lax matrix is introduced for the integrable symplectic map (ISM), and the non-dynamical(i. e. constant) r-matrix of ISM is obtained. Moreover, an effective approach is systematically presented to construct the explicit solution(here, the explicit solution means algebraic-geometric solution expressed by the Riemann-Theta function) of a soliton system or nonlinear evolution equation from Lax matrix, r-matrix, and the theory of nonlinearization through taking the Toda lattice as an example. The given algebraic-geometric solution of the Toda lattice is almost-periodic and includes the periodic and finite-band solution.

关键词： symplectic map r-matrix algebraic-geometric solution.

Experimental measurement of growth patterns on fossil corals:Secular variation in ancient Earth-Sun distances

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Chinese Science Bulletin 2010年第35期55卷 4010-4017页

作者： ZHANG WeiJia1,3,4,LI ZhengBin2.3 & LEI Yang1 1 Department of physics,peking University,{2.,china 2.Department of Electrical Engineering and Computer Science,peking University,{2.,china 3 State Key Laboratory of Advanced Optical Communication Systems & Networks,peking University,{2.,china 4 Committee of Yuanpei Honors Program,peking University,{2.,china Department of physics Peking University Beijing 100871 China State Key Laboratory of Advanced Optical Communication Systems & Networks Peking University Beijing 100871 China Committee of Yuanpei Honors Program Peking University Beijing 100871 China Department of Electrical Engineering and Computer Science Peking University Beijing 100871 China

In recent years,much attention has been given to the increase in the Earth-Sun distance,with the modern rate reported as 5-15 m/cy on the basis of astronomical ***,traditional methods cannot measure the ancient leaving rates,so a myriad of research attempting to provide explanations were met with unmatched *** this paper we consider that the growth patterns on fossils could reflect the ancient Earth-Sun *** mechanical analysis of both the Earth-Sun and Earth-Moon systems,these patterns confirmed an increase in the Earth-Sun *** a large number of well-preserved specimens and new technology available,both the modern and ancient leaving rates could be measured with high precision,and it was found that the Earth has been leaving the Sun over the past 0.53 billion *** Earth's semi-major axis was 146 million kilometers at the beginning of the Phanerozoic Eon,equating to 97.6% of its current *** modern leaving rates are 5-14 m/cy,whereas the ancient rates were much *** results indicate a special expansion with an average expansion coefficient of 0.57H0 and deceleration in the form of Hubble *** the basis of experimental results,the Earth's semi-major axis could be represented by a simple formula that matches fossil measurements.

关键词：地球太阳古代距离生长模式实验石珊瑚量化

OBLIQUE DERIVATIVE PROBLEMS FOR SECOND ORDER NONLINEAR MIXED EQUATIONS WITH DEGENERATE LINE

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Acta Mathematica Scientia 2008年第3期28卷 604-612页

作者：闻国椿 school of Mathematical Sciences Peking University

The present article deals with oblique derivative problems for some nonlinear mixed equations with parabolic degeneracy, which include the Tricomi problem as a special case. First, the formulation of the problems for the equations is given; next, the representation and estimates of solutions for the above problems are obtained; finally, the existence of solutions for the problems is proved by the successive iteration and the compactness principle of solutions of the problems. In this article, the author uses the complex method, namely, the complex functions in the elliptic domain and the hyperbolic complex functions in hyperbolic domain are used.

关键词： Oblique derivative problems nonlinear mixed equations parabolic degeneracy

SOME BOUNDARY VALUE PROBLEMS FOR NONLINEAR DEGENERATE ELLIPTIC EQUATIONS OF SECOND ORDER

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Acta Mathematica Scientia 2007年第3期27卷 663-672页

作者：闻国椿 school of Mathematical Sciences Peking University

The present article deals with some boundary value problems for nonlinear elliptic equations with degenerate rank 0 including the oblique derivative problem. Firstly the formulation and estimates of solutions of the oblique derivative problem are given, and then by the above estimates and the method of parameter extension, the existence of solutions of the above problem is proved. In this article, the complex analytic method is used, namely the corresponding problem for degenerate elliptic complex equations of first order is firstly discussed, afterwards the above problem for the degenerate elliptic equations of second order is solved.

关键词： Boundary value problems nonlinear elliptic equations parabolic degeneracy

A malware detection model based on a negative selection algorithm with penalty factor

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Science china(Information Sciences) 2010年第12期53卷 2461-2471页

作者： ZHANG PengTao 1,2., WANG Wei 1,2.& TAN Ying 1,2.1 Department of Machine Intelligence, school of Electronics Engineering and Computer Science, peking University, {2., china 2.Key Laboratory of Machine Perception, Ministry of Education, peking University, {2., china 1. Department of Machine Intelligence School of Electronics Engineering and Computer Science Peking University Beijing 100871 China2. Key Laboratory of Machine Perception Ministry of Education Peking University Beijing 100871 China

A malware detection model based on a negative selection algorithm with penalty factor (NSAPF) is proposed in this paper. This model extracts a malware instruction library (MIL), containing instructions that tend to appear in malware, through deep instruction analysis with respect to instruction frequency and file frequency. From the MIL, the proposed model creates a malware candidate signature library (MCSL) and a benign program malware-like signature library (BPMSL) by splitting programs orderly into various short bit strings. Depending on whether a signature matches "self", the NSAPF further divides the MCSL into two malware detection signature libraries (MDSL1 and MDSL2., and uses these as a two-dimensional reference for detecting suspicious programs. The model classifies suspicious programs as malware and benign programs by matching values of the suspicious programs with MDSL1 and MDSL2. Introduction of a penalty factor C in the negative selection algorithm enables this model to overcome the drawback of traditional negative selection algorithms in defining the harmfulness of "self" and "nonself", and focus on the harmfulness of the code, thus greatly improving the effectiveness of the model and also enabling the model to satisfy the different requirements of users in terms of true positive and false positive rates. Experimental results confirm that the proposed model achieves a better true positive rate on completely unknown malware and a better generalization ability while keeping a low false positive rate. The model can balance and adjust the true positive and false positive rates by adjusting the penalty factor C to achieve better performance.

关键词： penalty factor negative selection algorithm signature extraction artificial immune system mal- ware detection

How Fast Could a Proto-pulsar Rotate?

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Chinese Journal of Astronomy and Astrophysics 2002年第6期2卷 533-538页

作者： Ren-Xin Xu, Hong-Guang Wang and Guo-Jun QiaoDepartment of Astronomy, school of physics, peking University, {2. Department of Astronomy School of Physics Peking University Beijing 100871

According to two estimated relations between the initial period and the dynamo-generated magnetic dipole field of pulsars, we calculate the statistical distributions of pulsar initial periods. It is found that proto-pulsars are very likely to have rotation periods between 2. ms and 30 ms, and that most of the pulsars rotate initially at a period < 60 ms. Our result supports the asymmetric neutrino emission model for pulsar kick.

关键词： pulsars neutron stars magnetic fields