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An introduction to Tsinghua Cloud

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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, Beijing 100084, China 2.singhua {2. laboratory for information science and technology, Beijing 100084, China Department of Computer science and technology Tsinghua University Beijing China Tsinghua national laboratory for {2. science and technology Beijing 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

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

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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, Beijing 100084, China 2.Tsinghua {2. laboratory for information science and technology, Tsinghua University, Beijing 100084, China Department of Computer science and technology Tsinghua University Beijing China Tsinghua national laboratory for {2. science and technology Tsinghua University Beijing 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

Polynomial analysis of canopy spectra and biochemical component content inversion

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science China Earth sciences 2005年第10期48卷 1780-1791页

作者： YAN Chunyan1, LIU Qiang1, NIU Zheng1, WANG Jihua2. HUANG Wenjiang2.& LIU Liangyun 2.1. State Key laboratory of Remote Sensing science, Jointly Sponsored by the Institute of Remote Sensing Applications of Chinese Academy of sciences and Beijing Normal University, Beijing 100101, China 2. national Engineering Research Center for information technology in Agriculture, Beijing 100089, China Jointly Sponsored by the Institute of Remote Sensing Applications of Chinese Academy of sciences and Beijing Normal University national Engineering Research Center for information {2. in Agriculture

A polynomial expression model was developed in this paper to describe directional canopy spectra, and the decomposition of the polynomial expression was used as a tool for re-trieving biochemical component content from canopy multi-angle spectra. First, the basic formula of the polynomial expression was introduced and the physical meaning of its terms and coeffi-cients was discussed. Based on this analysis, a complete polynomial expression model and its decomposition method were given. By decomposing the canopy spectra simulated with SAILH model, it shows that the polynomial expression can not only fit well the canopy spectra, but also show the contribution of every order scattering to the whole reflectance. Taking the first scattering coefficients a10 and a01 for example, the test results show that the polynomial coefficients reflect very well the hot spot phenomenon and the effects of viewing angles, LAI and leaf inclination angle on canopy spectra. By coupling the polynomial expression with leaf model PROSPECT, a canopy biochemical component content inversion model was given. In the simulated test, the canopy multi-angle spectra were simulated by two different models, SAILH and 4-SCALE re-spectively, then the biochemical component content was retrieved by inverting the coupled polynomial expression + PROSPECT model. Results of the simulated test are promising, and when applying the algorithm to measured corn canopy multi-angle spectra, we also get relatively accurate chlorophyll content. It shows that the polynomial analysis provides a new method to get biochemical component content independent of any specific canopy model.

关键词： polynomial expression, canopy spectra, decomposition, biochemical component content, inversion.

Progress of Solid Electrolytes and the Electrochemical Sensors

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Journal of Materials science & technology 1997年第3期13卷 173-178页

作者： Yanruo HONG(national lab. on Solid Electrolytes and Metallurgical Testing Techniques, University of {2. and technology Beijing,Beijing 100083, China) national lab. on Solid Electrolytes and Metallurgical Testing Techniques University of Science and Technology Beijing Beijing 100083 China

Four types of solid state electrochemical sensors and their general principles are introduced in the paper. The novel type-IV sensors developed in the last few years are emphasized to study hereafter. The ways to design new electrochemical sensors and the directions to develop new solid electrolytes for new electrochemical sensors are also discussed.

关键词： Li Ba Progress of Solid Electrolytes and the Electrochemical Sensors Wang

Corslet: A shared storage system keeping your data private

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science China(information sciences) 2011年第6期54卷 1119-1128页

作者： XUE Wei 1,2., SHU JiWu 1,2., LIU Yang 1 & XUE Mao 1 1 Department of Computer science and technology, Tsinghua University, Beijing 100084, China 2.Tsinghua {2. laboratory for information science and technology, Tsinghua University, Department of Computer science and technology Tsinghua University Beijing China Tsinghua national laboratory for {2. science and technology Tsinghua University Beijing China

With the exponential growth of digital data, it is becoming more and more popular to store data in shared distributed storage systems inside the same organization. In such shared distributed storage systems, an ordinary user usually does not have the control permission over the whole system, and thus cannot secure data storage or data sharing of his own files. To solve this issue, this paper proposes a new system architecture to secure file storing and sharing efficiently over untrusted shared storage and network environments. Based on this architecture, this paper designs and implements a stackable secure storage system called Corslet. Corslet can run directly on deployed underlying storage systems without modification, while bringing end-to-end confidentiality and integrity as well as efficient access control for user data. For individual users, Corslet is easy to use, and does not require users to maintain or manage any keys on their client machines locally. The Bonnie++ and IOzone benchmark results show that the throughput of Corslet over NFS can achieve more than 90% of native NFS throughput in most tests, proving that Corslet can provide enhanced security for user data while maintaining acceptable performance.

关键词： storage security access control key management shared file system

Calibration based universal JPEG steganalysis

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science in China(Series F) 2009年第2期52卷 260-268页

作者： HUANG FangJun1,2.& HUANG JiWu1,2.1 School of information science and {2.,Sun Yat-Sen University,Guangzhou 5102.5,China 2.Guangdong Key lab. of information Security {2.,Sun Yat-Sen University,Guangzhou 5102.5,China School of information science and {2. Sun Yat-Sen University Guangzhou China Guangdong Key lab. of information Security {2. Sun Yat-Sen University Guangzhou China

For steganalysis of JPEG images, features derived in the embedding domain appear to achieve a preferable performance. However, with the existing JPEG steganography, the minor changes due to the hidden secret data are not easy to be explored directly from the quantized block DCT （BDCT） coefficients in that the energy of the carrier image is much larger than that of the hidden signal. In this paper, we present an improved calibration-based universal JPEG steganalysis, where the microscopic and macroscopic calibrations are combined to calibrate the local and global distribution of the quantized BDCT coefficients of the test image. All features in our method are generated from the difference signal be- tween the quantized BDCT coefficients of the test image and its corresponding microscopic calibrated image, or calculated as the difference between the signal extracted from test image and its corresponding macroscopic calibrated image. The extracted features will be more effective for our classification. Moreover, through using the Markov empirical transition matrices, both magnitude and sign dependencies along row scanning and column scanning patterns existed in intra-block and inter-block quantized BDCT coefficients are employed in our method. Experimental results demonstrate that our proposed scheme outperforms the best effective JPEG steganalyzers having been presented.

关键词： JPEG steganography steganalysis microscopic calibration macroscopic calibration

Influence of magnetic current on the ground state entanglement in an isotropic transverse XY chain

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Progress in Natural science:Materials International 2007年第10期17卷 1147-1151页

作者： Liu Dan1,2., Zhang Yong3 and Long Guilu1,2.1. Key laboratory for Atomic and Molecular Nanosciences, and Department of Physics, Tsinghua University, Beijing 100084, China 2. Center of Quantum {2. science and technology, Tsinghua national laboratory for {2. science and technology, Beijing 100084, China 3. Institute of Physics, School of sciences, Beijing University of Posts and Telecommunications, Beijing 100876, China) Key laboratory for Atomic and Molecular Nanosciences Department of Physics Tsinghua University Beijing 100084 China Center of Quantum information science and {2. Tsinghua National Laboratory for Information Science and Technology Beijing 100084 China Institute of Physics School of Sciences Beijing University of Posts and Telecommunications Beijing 100876 China

We study the ground state entanglement in a three-qubit XY chain under the influence of a magnetization current. It is found that the ground state changes from a W state to a disentangled state as the magnetic field varies. When the Lagrange multiplier λ>3, namely under a strong magnetic current, the ground state holds onto a W state for a large range of the magnetic field strength. A phase transition to the magnetization-current phase occurs under a certain condition.

关键词： Heisenberg-XY chain magnetic-current phase transition.

Steganalysis of stochastic modulation steganography

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science in China(Series F) 2006年第3期49卷 273-285页

作者： HE Junhui1,2.& HUANG Jiwu1,2.1. School of information science and {2., Sun Yat-sen University, Guangzhou 5102.5, China 2. Guangdong Province Key laboratory of information Security, Guangzhou 5102.5, China School of information science and {2. Sun Yat-sen University Guangzhou China Guangdong Province Key laboratory of information Security Guangzhou China

Stochastic modulation steganography embeds secret message within the cover image by adding stego-noise with a specific probabilistic distribution. No method is known to be applicable to the estimation of stochastic modulation steganography. By analyzing the distributions of the horizontal pixel difference of images before and after stochastic modulation embedding, we present a new steganalytic approach to accurately estimate the length of secret message in stochastic modulation steganography. The pro- posed method first establishes a model describing the statistical relationship among the differences of the cover image, stego-image and stego-noise. In the case of stegoimage-only steganalysis, rough estimate of the distributional parameters of the cover image＇s pixel difference is obtained with the use of the provided stego-image. And grid search and Chi-square goodness of fit test are exploited to estimate the length of the secret message embedded with stochastic modulation steganography. The experimental results demonstrate that our new approach is effective for steganalyzing stochastic modulation steganography and accurately estimating the length of the secret message.

关键词： information hiding steganography steganalysis stochastic modulation statistical distribution models of difference.

A new heuristic algorithm for the circular packing problem with equilibrium constraints

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science China(information sciences) 2011年第8期54卷 1572-1584页

作者： LIU JingFa 1,2.LI Gang 3 & GENG HuanTong 1 1 School of Computer and Software,Nanjing University of information science & {2.,Nanjing 2.0044,China 2.Network information Center,Nanjing University of information science & {2., Nanjing 2.0044,China 3 School of Mathematics and Physics,Nanjing University of information science & {2.,Nanjing 2.0044,China School of Computer and Software Nanjing University of Information Science & Technology Nanjing China Network information Center Nanjing University of Information Science & Technology Nanjing China School of Mathematics and Physics Nanjing University of Information Science & Technology Nanjing China

The circular packing problem with equilibrium constraints is an optimization problem about simplified satellite module layout design.A heuristic algorithm based on tabu search is put forward for solving this *** algorithm begins from a random initial configuration and applies the gradient method with an adaptive step length to search for the minimum energy *** jump out of the local minima and avoid the search doing repeated work,the algorithm adopts the strategy of tabu *** the process of tabu search,we improve the traditional neighboring solutions,tabu objects and the acceptance criteria of the current solution *** test two sets of benchmarks consisting of 11 representative instances from the current *** numerical results show that the proposed algorithm breaks the records in seven out of 11 instances,and obtains the optimal solutions for the other four instances.

关键词： equilibrium constraints packing problem heuristic algorithm tabu search layout optimization