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Efficient estimation for additive hazards regression with bivariate current status data

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Science China Mathematics 2012年第4期55卷 763-774页

作者： TONG XingWei 1,,HU Tao 2 & SUN JianGuo 3,4.1 School of mathematical sciences,beijing Normal university,beijing 100875,China 2 School of mathematical sciences,Capital Normal university,beijing 10004.,China 3 School of Mathematics,Jilin university,Changchun 130012,China 4.department of Statistics,university of Missouri,Columbia,MO 65211,USA 1. School of mathematical sciences Beijing Normal University Beijing 100875 China2. School of Mathematical Sciences Capital Normal University Beijing 100048 China3. School of Mathematics Jilin University Changchun 130012 China4. Department of Statistics University of Missouri Columbia MO 65211 USA

This paper discusses efficient estimation for the additive hazards regression model when only bivariate current status data are available. Current status data occur in many fields including demographical studies and tumorigenicity experiments （Keiding, 1991; Sun, 2006） and several approaches have been proposed for the additive hazards model with univariate current status data （Linet M., 1998; Martinussen and Scheike, 2002）. For bivariate data, in addition to facing the same problems as those with univariate data, one needs to deal with the association or correlation between two related failure time variables of interest. For this, we employ the copula model and an efficient estimation procedure is developed for inference. Simulation studies are performed to evaluate the proposed estimates and suggest that the approach works well in practical situations. An illustrative example is provided.

关键词： bivariate current status data copula model counting processes efficient estimation joint survivalfunction

Dark output characteristic of γ-ray irradiated CMOS digital image sensors

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Rare Metals 2002年第1期21卷 79-84页

作者： MENG Xiangti and KANG A iguo Institute of Nuclear Energy Technology, tsinghua university, beijing 100084. China Institute of Nuclear Energy Technology Tsinghua University 北京 100084

The quality of dark output images from the CMOS (complementarymetal oxide semiconductor) black and white (B & W) digital imagesensors captured before and after γ-ray irradiation was studied. Thecharacteristic parameters of the dark output images captured atdifferent radiation dose, e.g. average brightness and itsnon-uniformity of dark out- put images, were analyzed by our testsoftware. The primary explanation for the change of the parameterswith the radi- ation dose was given.

关键词： CMOS digital image sensor gamma radiation dark output characteristic Si

Large eddy simulation of stably stratified turbulence

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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, tsinghua university, 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

PEPTIDES FORMATION FROM DIPP-HIS

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Chinese Chemical Letters 1995年第3期6卷 211-214页

作者： Yao Wu SHAO Yu Fen ZHAO (department of Chemistry,tsinghua university,beijing.{4. Tsing Hua Univ Dept Chem Beijing 100084 Peoples R China

When DIPP-HIS was incubated in water, citrate buffer. DMF and other mixed solvents. phosphoryl dipeptide, tripeptide even tetrapeptide were found. When DIPP-HIS was incubated with aspartic acid tinder the same conditi... 详细信息

关键词： PEPTIDES FORMATION FROM DIPP-HIS

A secure multi-party computation solution to intersection problems of sets and rectangles

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Progress in Natural Science:Materials International 2006年第5期16卷 538-545页

作者： LI Shundong, DAI Yiqi, WANG Daoshun and LUO Ping (department of Computer Science and Technology, beijing Normal university, beijing 100875, China department of Computer Science and Technology, tsinghua university, beijing 100084. China) [a]department of computer Science and Technology Beijing Normal University Beijing China [b]department of Computer Science and Technology Tsinghua University Beijing China

Secure multi-party computation (SMC) is a research focus in international cryptographic community. At present, there is no SMC solution to the intersection problem of sets. In this paper, we first propose a SMC solution to this problem. Applying Cantor encoding method to computational geometry problems, and based on the solution to set-intersection problem, we further propose solutions to points inclusion problem and intersection problem of rectangles and further prove their privacy-preserving property with widely accepted simulation paradigm. Compared with the known solutions, these new solutions are of less computational complexity and less communication complexity, and have obvious superiority in computational and communication complexity.

关键词： Cantor encoding secure multi-party computation set-intersection rectangle-intersection computational complexity.

Multi-swingby optimization of mission to Saturn using global optimization algorithms

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Acta Mechanica Sinica 2009年第6期25卷 839-845页

作者： Kaijian Zhu Junfeng Li Hexi Baoyin School of Aerospace, tsinghua university,100084.beijing, China School of Aerospace Tsinghua University 100084 Beijing China

Based on the trajectory design of a mission to Saturn, this paper discusses four different trajectories in various swingby cases. We assume a single impulse to be applied in each case when the spacecraft approaches a celestial body. Some optimal trajectories ofEJS, EMS, EVEJS and EVVEJS flying sequences are obtained using five global optimization algorithms： DE, PSO, DP, the hybrid algorithm PSODE and another hybrid algorithm, DPDE. DE is proved to be supe- rior to other non-hybrid algorithms in the trajectory optimi- zation problem. The hybrid algorithm of PSO and DE can improve the optimization performance of DE, which is vali- dated by the mission to Saturn with given swingby sequences. Finally, the optimization results of four different swingby sequences are compared with those of the ACT of ESA.

关键词： Swingby trajectory . Global optimization .Hybrid algorithm . Mission design

NUMERICAL SIMULATION OF DISCONTINUOUS FLOW IN CIRCULAR CONDUITS

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Journal of Hydrodynamics 1996年第3期8卷 64-74页

作者： Mao Ze-Yu (Hydraulics Group, department of hydraulic enginering, tsinghua university, beijing 100084. P. R. China) tsinghua Univ Beijing China

A numerical model based upon both the characteristic method and the equations of continuity and momentum is presented for simulating the movement of hydraulic jumps in circular cross-sectional conduits under the unsteady flow conditions. The hydraulic jump, in the numerical simulation of unsteady flow with a moving discontinuity,was treated as a moving boundary within the computational domain defined by the spacetime grid. The laboratory tests under the unsteady flow conditions were carried out to examine the applicability of the presented numerical model of the hydraulic jump movement. Complete test results for a range of Froude numbers are presented that may be used by other researchers for the verification of mathematical model. The inclusion of initial and boundary condition is investigated. A comparison of the computed and measured results shows that the agreement between them is satisfactory.

关键词： numerical simulation discontinuous flow moving boundary jump,characteristics

Computational intelligence:From mathematical point of view

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Chinese Science Bulletin 1999年第10期44卷 865-880页

作者： QIAN Minping and GONG Guangludepartment of Probability and Statistics, Peking university, beijing 100871, China department of Applied Mathematics,{4., beijing 100084. China Deportment of Probability and Statistics Peking University Beijing China department of Applied Mathematics Tsinghua University Beijing China

A simple but illustrative survey is given on various approaches of computational intelligence with their features, applications and the mathematical tools involved, among which the simulated annealing, neural networks, genetic and evolutionary programming, self-organizing learning and adapting algorithms, hidden Markov models are recommended intensively. The common mathematical features of various computational intelligence algorithms are ***, two common principles of concessive strategies implicated in many computational intelligence algorithms are discussed.

关键词： computational intelligence simulated annealing neural network genetic algorithm evolutionary program-ming self-organizing learning self-adapting algorithm hidden Markov model concession strategy.

Cloning and characterization of cotton heteromeric acetyl-CoA carboxylase genes

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Progress in Natural Science:Materials International 2007年第12期17卷 1412-1418页

作者： Qiao Zhixin and Liu Jinyuan(Laboratory of Molecular Biology and Protein Science Laboratory of the Ministry of Education, department of Biological sciences and Biotechnology, tsinghua university, beijing {4. China) Laboratory of Molecular Biology and Protein Science Laboratory of the Ministry of Education Department of Biological Sciences and Biotechnology Tsinghua University Beijing 100084 China

Heteromeric acetyl-coenzyme A (CoA) carboxylase (ACCase) catalyzes the formation of malonyl-CoA from acetyl-CoA. It plays an essential role in fatty acid synthesis in prokaryotes and most of plants. The heteromeric ACCase is composed of four subunits: biotin carboxylase (BC), biotin carboxyl carrier protein (BCCP), and α- and β-subunits of carboxyltransferase (α- and β-CT). In this study, we cloned five novel genes encoding the subunits of heteromeric ACCase (one BC, BCCP and β-CT, and two α-CTs) from cotton (Gossypium hirsutum cv. zhongmian 35) by RACE-PCR. The deduced amino acid sequence of these cDNAs shares high similarity with other reported heteromeric ACCase subunits. The phylogenetic analysis indicated that the different subunits of heteromeric ACCase were grouped in a similar pattern. Southern blot analysis revealed the milti-copy patterns of these heteromeric ACCase genes in cotton genome. Semi-quantitative RT-PCR demonstrated that heteromeric ACCase genes were constitutively expressed in all of the cotton tissues, but the transcripts accumulated at a relatively low level in roots. To our knowledge, this is the first report about characterization of the heteromeric ACCase genes in cotton.

关键词： heteromeric ACCase cotton gene cloning fatty acid synthesis.