检索结果-南通市图书馆

New evidence for lack of CMB power on large scales

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3期53卷 567-570页

作者： LIU Hao1 & LI TiPei1,2.3 1 Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, beijing 100049, china 2.{2. of Physics & Center for Astrophysics, tsinghua university, beijing 100084, china 3 {2. of engineering Physics & Center for Astrophysics, tsinghua university, beijing 100084, china 1. Key Laboratory of Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 China2. Department of Physics & Center for Astrophysics Tsinghua University Beijing 100084 China3. Department of Engineering Physics & Center for Astrophysics Tsinghua University Beijing 100084 China

A digitalized temperature map is recovered from the first light sky survey image published by the Planck team, from which an angular power spectrum of the cosmic microwave background (CMB) is derived. The amplitudes of the low multipoles (low-l) measured from the preliminary Planck power spectrum are significantly lower than those reported by the WMAP team. Possible systematical effects are far from enough to explain the observed low-l differences.

关键词： cosmology cosmic microwave background data analysis

A user-space file system for on-demand legacy desktop software

在线全文

学校读者我要写书评

暂无评论

Science china(Information Sciences) 2011年第6期54卷 1142-1150页

作者： ZHANG YouHui 1,2., SU GeLin 1,2.& ZHENG WeiMin 1,2.1 department of Computer Science and Technology, tsinghua university,{2., china 2.tsinghua National Laboratory for Information Science and Technology, tsinghua university,{2., china 1. department of Computer Science and Technology Tsinghua University Beijing 100084 China2. Tsinghua National Laboratory for Information Science and Technology Tsinghua University Beijing 100084 China

Some user-level virtualization technologies have been used to convert legacy software (like the existing Windows desktop applications) into the on-demand software without any modification. To give the client a friendly and compatible method to access on-demand legacy software across the Internet, this paper presents a clientend file system for this usage case. It is a Windows user-space file system based on the cloud storage (where the on-demand software is stored), which converts the local file system accesses into remote visits. Quite a few optimizations are adopted and adjusted to suit the file-access-pattern of on-demand software, including the local cache, metadata/data/software prefetch and content-addressable storage (CAS), to decrease the number of remote visits and/or to overlap IO (input/output) operations with software execution. Detailed access-pattern analyses are also presented. This file system has been implemented and tests show that it is practical for much daily-used software-a local cache of limited size can provide up to 80% hit ratio and the corresponding overhead of running-time is about 37%. Owing to this method, on any compatible and networked computer, a user can use his/her personalized software conveniently although it does not exist on the local host.

关键词： on-demand software software as a service user-space file system cloud storage

Truncation error calculation based on Richardson extrapolation for variable-step collaborative simulation

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) 2011年第6期54卷 1238-1250页

作者： ZHANG HeMing 1 , LIANG SiLu 2., SONG ShiJi 1 & WANG HongWei 3 1 department of Automation, TNList, tsinghua university,{2., china 2.Computer and Information Management Center, tsinghua university{2., china 3 engineering Design Centre, engineering department, Cambridge university, Cambridge CB2.1PZ, UK 1. department of Automation TNList Tsinghua University Beijing 100084 China2. Computer and Information Management Center Tsinghua University Beijing 100084 China3. Engineering Design Centre Engineering Department Cambridge University Cambridge CB2 1PZ UK

Collaborative simulation is an effective approach to performing simulation analysis for complex systems by integrating models developed for different engineering disciplines. Collaborative simulation issues include the modeling of coupled multidisciplinary systems, and the simulation running time integration of these models that are solved parallelly. Estimation of the local truncation error of coupling models is the key to solve multidisciplinary collaborative simulation problem, which is actually used to restrict the simulation step. This paper presents a variable-step method based on Richardson extrapolation for calculating the local truncation error to solve collaborative simulation problem of multidisciplinary coupling models. Formulas for estimating the local truncation error are derived through theoretical analysis by using integration methods and interpolation technologies, respectively. The simulation experiments are illustrated to validate the accuracy and efficiency of proposed collaborative simulation algorithm in comparison with the usual combinative algorithm.

关键词： multidisciplinary systems collaborative simulation variable-step algorithm error estimation

Measurement and simulation of the two-phase velocity correlation in sudden-expansion gas-particle flows

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 Mechanica Sinica 2011年第4期27卷 494-501页

作者： Li-Xing Zhou.Yang Liu.Yi Xu department of engineering Mechanics,{2. university,100084 beijing,china Marine engineering College,Dalian Maritime university,11602. Dalian,china department of engineering Mechanics Tsinghua University Beijing China Marine engineering College Dalian Maritime University Dalian China

In this paper the present authors measured the gas-particle two-phase velocity correlation in sudden expansion gas-particle flows with a phase Doppler particle anemometer （PDPA） and simulated the system behavior by using both a Reynolds-averaged Navier-Stokes （RANS） model and a large-eddy simulation （LES）. The results of the measurements yield the axial and radial time-averaged velocities as well as the fluctuation velocities of gas and three particle-size groups （30μm, 50μm, and 95μm） and the gasparticle velocity correlation for 30μm and 50μm particles. From the measurements, theoretical analysis, and simulation, it is found that the two-phase velocity correlation of sudden-expansion flows, like that of jet flows, is less than the gas and particle Reynolds stresses. What distinguishes the two-phase velocity correlations of sudden-expansion flow from those of jet and channel flows is the absence of a clear relationship between the two-phase velocity correlation and particle size in sudden-expansion flows. The measurements, theoretical analysis, and numerical simulation all lead to the above-stated conclusions. Quantitatively, the results of the LES are better than those of the RANS model.

关键词： PDPA measurement - Simulation Two-phasevelocity correlation Sudden expansion gas-particle flows

Multi-dimensional project management models for mega-construction companies and their applications

在线全文

学校读者我要写书评

暂无评论

Science china(Technological Sciences) 2011年第S1期54卷 118-124页

作者： LIN ZhengHang 1,2.QIANG MaoShan 1,2.TANG WenZhe 1,2.FAN QiXiang 3 &LIU Qiang 4 1 Institute of Project Management and Construction Technology,tsinghua university,{2. 100084,china 2.State Key Laboratory of Hydraulic and engineering,tsinghua university,{2. 100084,china 3 china Three Gorges Corporation,Yichang 443002.china 4 School of Software,tsinghua university,{2. 100084,china 1. Institute of Project Management and Construction Technology Tsinghua University Beijing 100084 China2. State Key Laboratory of Hydraulic and Engineering Tsinghua University Beijing 100084 China3. China Three Gorges Corporation Yichang 443002 China4. School of Software Tsinghua University Beijing 100084 China

china is undertaking an increasing number of mega-infrastructure projects along with its rapid economic *** participants in these projects,understand how to adapt the proper and efficient management strategies is *** this paper,we propose three distinct models for companies under various background and management requirements,based on sophisticated data analysis and model ***,we successfully committed these models with hydropower development projects and achieved a great progress in enhancing management efficiency.

关键词： project management models mega-construction companies applications hydropower development companies

An introduction to tsinghua Cloud

在线全文

学校读者我要写书评

暂无评论

Science china(Information Sciences) 2010年第7期53卷 1481-1486页

作者： ZHENG WeiMin1,2.1department of Computer Science and Technology, tsinghua university,{2., china 2.4} National Laboratory for Information Science and Technology,{2., china 1. department of Computer Science and Technology Tsinghua University Beijing 100084 China2. Tsinghua National Laboratory for Information Science and Technology Beijing 100084 China

Cloud computing has become a trend that draws attention from both academia and industry all over the world. This paper unveils details of tsinghua Cloud, a comprehensive solution for cloud computing developed by Tsing... 详细信息

关键词： cloud computing distributed file system virtual computing environment data sharing

Implementation of a multiple round quantum dense coding using nuclear magnetic resonance

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(Physics,Mechanics & Astronomy) 2005年第6期48卷 706-715页

作者： ZHANG Jingfu1, XIE Jingyi2. WANG Chuan1, DENG Zhiwei3, LU Zhiheng4, & LONG Guilu1,5 1. Key Laboratory For Quantum Information and Measurements of MOE, department of Physics, tsinghua university,{2.,china 2. department of Materials Science and engineering, beijing Normal university, beijing 100875, china 3. Testing and Analytical Center, beijing Normal university, beijing 100875,china 4. department of Physics, beijing Normal university, beijing 100875, china 5. Key Laboratory For atomic and Molecular Nanosciences, tsinghua university,{2.,china 1. Key Laboratory For Quantum Information and Measurements of MOE Department of Physics Tsinghua University 100084 Beijing China 2. department of Materials science and engineering Beijing Normal University 100875 Beijing China 3. Testing and Analytical Center Beijing Normal University 100875 Beijing China 4. department of Physics Beijing Normal University 100875 Beijing China 5. Key Laboratory For Atomic and Molecular Nanosciences Tsinghua University 100084 Beijing China

A multiple round quantum dense coding scheme based on the quantum phase estimation algorithm is proposed and implemented in a three qubit nuclear magnetic resonance (NMR) quantum computer. Using an m + 1 qubit system, Bob can transmit one of 2.+1 messages to Alice, through manipulating only one qubit and exchanging it between Alice and Bob for m rounds. The information capacity is enhanced to m + 1 bits as compared to m bits in a classical scheme. The scheme has been demonstrated in NMR system, and the experimental results show a good agreement between theory and experiment.

关键词： quantum dense coding, multiple round, nuclear magnetic resorance

INFLUENCES OF ACID POST-TREATMENT ON THE MORPHOLOGY OF SOAP-FREE P(MMA-EA-MAA)PARTICLES PREPARED BY SEEDED EMULSION POLYMERIZATION

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2005年第5期23卷 479-485页

作者： Kai Kang Cheng-you Kan Yi Du De-shan Liu department of Chemical engineering,School of Materials Science and engineering,tsinghua university,beijing 100084,china tsinghua Univ Dept Chem Engn Sch Mat Sci & Engn Beijing 100084 Peoples R China

Soap-free poly（methyl methacrylate-ethyl acrylate-methacrylic acid） latex particles with narrow size distribution were synthesized by seeded emulsion polymerization, and the porous particles were created by a stepwise alkali/acid treatment method. Effects of acid treatment conditions on the particle morphology were investigated. Results show that one to three pores were formed inside most of particles after post-treatment. At pH 7.0, when the treatment temperature was lower than 70℃, the size of particles and the volume of pores remained almost unchanged, and these two values increased significantly when the temperature was higher than 70℃. Both the particle size and the pore volume decreased with the increase of initial pH value and treatment time in the acid treatment. As the pH was below 4.0 and the treatment time was longer than 180 min, the particles shrunk in size.

关键词： Soap-free emulsion polymerization Particle morphology Porous structure Acid treatment Methyl methacrylate based copolymer.

Cilia and ciliopathies:From Chlamydomonas and beyond

在线全文

学校读者我要写书评

暂无评论

Science china(Life Sciences) 2008年第6期51卷 479-486页

作者： PAN JunMin department of Biological Sciences and Biotechnology, tsinghua university,{2., china 1. department of Biological Sciences and Biotechnology Tsinghua University Beijing 100084 China

The biological function of motile cilia/flagella has long been recognized. The non-motile primary cilium, once regarded as a vestigial organelle, however, has been found recently to play unexpected roles in mammalian physiology and development. Defects in cilia have profound impact on human health. Diseases related to cilia, collectively called ciliopathies include male infertility, primary cilia dyskinesia, renal cyst formation, blindness, polydactyly, obesity, hypertension, and even mental retardation. Our current understanding of cilia and ciliopathies has been fueled by basic research employing various model organisms including Chlamydomonas, a unicellular green alga. This review article provides a general introduction to the cell biology of cilia and an overview of various cilia-related diseases.

关键词： Chlamydomonas cilia flagellla human disease ciliopathy