检索结果-南通市图书馆

Improvement of the classification accuracy in discriminating diabetic retinopathy by multifocal electroretinogram analysis

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2007年第8期17卷 913-918页

作者： Xu Jin~1 Hu Guangshu~(1**) Huang Houbin~2.(1.department of Biomedical engineering,{2. university,beijing 100084,china 2.department of Ophthalmology,General Hospital of Chinese PLA,beijing 100853,china) [a]department of Biomedical engineering Tsinghua University Beijing China [b]department of Ophthalmology General Hospital of Chinese PLA Beijing China

The multifocal electroretinogram (mfERG) is a newly developed electrophysiological *** this paper,a classifi- cation method is proposed for early diagnosis of the diabetic retinopathy using mfERG *** records were obtained from eyes of healthy individuals and patients with diabetes at different *** each mfERG record,103 local responses were *** value of each point on all the mfERG local responses was looked as one potential feature to classify the experimental *** sub- sets were selected from the feature space by comparing the inter-intra *** on the selected feature subset,Fisher's linear classi- fiers were *** the final classification decision of the record was made by voting all the classifiers' *** the method to classify all experimental subjects,very low error rates were *** crucial properties of the diabetic retinopathy classification method are also discussed.

关键词： diabetic retinopathy multifocal electroretinogram feature selection linear classifier

The numbers of periodic orbits hidden at fixed points of 2.dimensional holomorphic mappings

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 Mathematics 2010年第3期53卷 863-886页

作者： ZHANG GuangYuan department of Mathematical Sciences, tsinghua university,{2., china 1. department of Mathematical Sciences Tsinghua University Beijing 100084 China

Let △n be the ball |x| < 1 in the complex vector space C n , let f :△n→ C n be a holomorphic mapping and let M be a positive integer. Assume that the origin 0 = (0, . . . , 0) is an isolated fixed point of both f a... 详细信息

Let △n be the ball |x| 2. For a 2.× 2.matrix A that is arbitrarily given, the goal of this paper is to give a necessary and sufficient condition for A, such that O M (f, 0)≥2.for all holomorphic mappings f :△2.→ C 2.such that f(0) = 0, Df(0) = A and that the origin 0 is an isolated fixed point of f M .

关键词： complex dynamical systems periodic points fixed point indices

Large eddy simulation of stably stratified turbulence

在线全文

学校读者我要写书评

暂无评论

Science china(Physics,Mechanics & Astronomy) 2010年第1期53卷 135-146页

作者： SHEN Zhi, LI YuPeng, CUI GuiXiang & ZHANG ZhaoShun department of engineering Mechanics,{2., beijing 100084, china 1. department of engineering Mechanics Tsinghua University Beijing 100084 China

Stable stratification turbulence, as a common phenomenon in atmospheric and oceanic flows, is an important mechanism for numerical prediction of such flows. In this paper the large eddy simulation is utilized for investigating stable stratification turbulence numerically. The paper is expected to provide correct statistical results in agreement with those measured in the atmosphere or ocean. The fully developed turbulence is obtained in the stable stratification fluid by large eddy simulation with different initial velocity field and characteristic parameters, i.e. Reynolds number Re and Froude number Fr. The evolution of turbulent kinetic energy, characteristic length scales and parameters is analyzed for investigating the development of turbulence in stable stratification fluid. The three-dimensional energy spectra, horizontal and vertical energy spectrum, are compared between numerical simulation and real observation in the atmosphere and ocean in order to test the reliability of the numerical simulation. The results of numerical cases show that the large eddy simulation is capable of predicting the properties of stable stratification turbulence in consistence with real measurements at less computational cost. It has been found in this paper that the turbulence can be developed under different initial velocity conditions and the internal wave energy is dominant in the developed stable stratification turbulence. It is also found that the characteristic parameters must satisfy certain conditions in order to have correct statistical property of stable stratification turbulence in the atmosphere and ocean. The Reynolds number and Froude number are unnecessarily equal to those in atmosphere or ocean, but the Reynolds number must be large enough, say, greater than 10 2., and Froude number must be less than 0.1. The most important parameter is ReFr 2.which must be greater than 10.

关键词： stratified turbulence internal wave potential vortex large eddy simulation

Numerical simulation of air-water two-phase flow over stepped spillways

在线全文

学校读者我要写书评

暂无评论

Science china(Technological Sciences) 2006年第6期49卷 674-684页

作者： CHENG Xiangju1, CHEN Yongcan1 & LUO Lin2.1. department of Hydraulic engineering,{2., beijing 100084, china 2. State Key Laboratory of Hydraulics and Mountain River engineering, Sichuan university, Chengdu 610065, china department of Hydraulic engineering Tsinghua University Beijing 100084 China State Key Laboratory of Hydraulics Mountain River engineering Sichuan University Chengdu 610065 China

Stepped spillways for significant energy dissipation along the chute have gained interest; popularity among researchers; dam engineers. Due to the complexity of air-water two-phase flow over stepped spillways, the finite volume computational fluid dynamics module of the FLUENT software was used to simulate the main characteristics of the flow. Adopting the RNG k- turbulence model, the mixture flow model for air-water two-phase flow was used to simulate the flow field over stepped spillway with the PISO arithmetic technique. The numerical result successfully reproduced the complex flow over a stepped spillway of an experiment case, including the interaction between entrained air bubbles; cavity recirculation in the skimming flow regime, velocity distribution; the pressure profiles on the step surface as well. The result is helpful for understanding the detailed information about energy dissipation over stepped spillways.

关键词： stepped spillway, mixture model, RNG k-εmodel, air-water two-phase flow.

Mapping and overlapping based carrier frequency searching technique for rapid GNSS long PN-code acquisition

在线全文

学校读者我要写书评

暂无评论

Science china(Information Sciences) 2010年第12期53卷 2642-2652页

作者： LI Hong ,LU MingQuan & FENG ZhenMing department of Electronic engineering,{2. university,beijing 100084,china 1. department of Electronic engineering Tsinghua University Beijing 100084 China

In global navigation satellite systems(GNSS),because of the long period and high chip rate of long pseudo-noise(PN) code,the rapid acquisition is hard to *** speed up search process,in the paper,a mapping and overlapping based carrier frequency searching technique is *** mapping incoming signals of the same interval to different carrier frequency cells and overlapping together the mapped incoming signals that correspond to the same code phase,the technique reduces the number of the cells to be *** effect of the technique on detection and mean acquisition time performance is *** is shown that the technique reduces the cells to be searched and shortens mean acquisition time at the expense of degrading detection *** technique is fit to the previously published acquisition methods and is capable of improving their mean acquisition time *** and simulation results validate the analysis.

关键词： carrier frequency cells mapping overlapping acquisition performance

Measuring-basis-encrypted six-state quantum key distribution scheme

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1期16卷 84-89页

作者： CHEN Pan1, DENG Fuguo1, WANG Pingxiao1 and LONG Guilu1,2.(Key Laboratory for Quantum Information and Measurements and department of Physics, tsinghua university,{2., china 2. Key Laboratory for Atomic and Molecular NanoSciences, tsinghua university,{2., china) [a]department of Physics Tsinghua University Key Laboratory for Quantum Information and Measurements Beijing China [b]tsinghua university Key Laboratory for Atomic and Molecular NanoSciences Beijing China

A six-state quantum key distribution scheme with measuring-basis encryption technique, which is based on the six-state protocol and the MBE protocol, is proposed. In this modified six-state quantum key distribution protocol, Alice and Bob use a control key to synchronize the use of their measuring-basis so that they always use the same measuring-basis. This modified six-state quantum key distribution protocol retains the advantage of higher security and at the same time has a higher efficiency.

关键词： quantum key distribution measuring-basis encrypted six-state security.

On mean curvatures in submanifolds geometry

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 Mathematics 2008年第6期51卷 1127-1134页

作者： GE JianQuan department of Mathematical Sciences,tsinghua {2.,beijing 100084,china department of Mathematical Sciences Tsinghua University Beijing 100084 China

By using moving frame theory,first we introduce 2.-th mean curvatures and(2.+1)-th mean curvature vector fields for a *** then give an integral expression of them that characterizes them as mean values of symmetric functions of principle *** we apply it to derive directly the celebrated Weyl-Gray tube formula in terms of integrals of the 2.-th mean curvatures and some Minkowski-type integral formulas.

关键词： moving frame mean curvature tube 53A07 53C42

On fixed-points and singular values of transcendental meromorphic functions

在线全文

学校读者我要写书评

暂无评论

Science china Mathematics 2010年第3期53卷 887-894页

作者： ZHENG JianHua department of Mathematical Sciences, tsinghua university,{2., china 1. department of Mathematical Sciences Tsinghua University Beijing 100084 China

In this paper we make a further discussion of a relationship between the number of fixed-points and distribution of singular values along the round annuli centered at the origin of a transcendental meromorphic function. To attain our purpose we first establish a fundamental inequality for the modulus of derivative of a holomorphic covering mapping whose image is an annulus by virtue of the hyperbolic metric. The inequality is of independent significance. We make a simple survey on some domain constants for hyperbolic domains.

关键词： meromorphic functions fixed points singular points hyperbolic metric covering mapping

INTERFACIAL REACTIONS OF METAL FILMS WITH AlN SUBSTRATE

在线全文

学校读者我要写书评

暂无评论

中国有色金属学会会刊：英文版 1996年第2期6卷 81-85页

作者： He Xiangjun Tao Kun Fan Yudian (department of Materials Science and engineering,{2., beijing 100084) department of Materials Science and engineering Tsinghua University Beijing 100084 China

ＩＮＴＥＲＦＡＣＩＡＬＲＥＡＣＴＩＯＮＳＯＦＭＥＴＡＬＦＩＬＭＳＷＩＴＨＡｌＮＳＵＢＳＴＲＡＴＥＨｅＸｉａｎｇｊｕｎ；ＴａｏＫｕｎ；ＦａｎＹｕｄｉａｎ（ＤｅｐａｒｔｍｅｎｔｏｆＭａｔｅｒｉａｌｓＳｃｉｅｎｃｅａｎｄＥ... 详细信息

ＩＮＴＥＲＦＡＣＩＡＬＲＥＡＣＴＩＯＮＳＯＦＭＥＴＡＬＦＩＬＭＳＷＩＴＨＡｌＮＳＵＢＳＴＲＡＴＥＨｅＸｉａｎｇｊｕｎ；ＴａｏＫｕｎ；ＦａｎＹｕｄｉａｎ（ＤｅｐａｒｔｍｅｎｔｏｆＭａｔｅｒｉａｌｓＳｃｉｅｎｃｅａｎｄＥｎｇｉｎｅｅｒｉｎｇ，Ｔｓｉｎｇｈ...

关键词： thin films interfacial reactions AlN substrate