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Gas kinetic algorithm for flows in Poiseuille-like microchannels using Boltzmann model equation

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science china(Physics,Mechanics & Astronomy) 2005年第4期48卷 496-512页

作者： LI Zhihui1,2, ZHAng Hanxin1 & FU Song2 ⒈ national laboratory for CFD, Hypervelocity Aerodynamics Institute,china Aerodynamics Research and Development Center,Mianyang 621000,china 2.Department of Engineering Mechanics,tsinghua University,beij.ng 100084,china 1. national laboratory for CFD Hypervelocity Aerodynamics Institute China Aerodynamics Research and Development Center 621000 Mianyang China 2. Department of Engineering Mechanics Tsinghua University 100084 Beijing China

The gas-kinetic unified algorithm using Boltzmann model equation have been extended and developed to solve the micro-scale gas flows in Poiseuille-like micro-channels from Micro-Electro-Mechanical Systems (MEMS). The numerical modeling of the gas kinetic boundary conditions suitable for micro-scale gas flows is presented. To test the present method, the classical Couette flows with various Knudsen numbers, the gas flows from short microchannels like plane Poiseuille and the pressure-driven gas flows in two-dimensional short microchannels have been simulated and compared with the approximate solutions of the Boltzmann equation, the related DSMC results, the modified N-S solutions with slip-flow boundary theory, the gas-kinetic BGK-Burnett solutions and the experimental data. The comparisons show that the present gas-kinetic numerical algorithm using the mesoscopic Boltzmann simplified velocity distribution function equation can effectively simulate and reveal the gas flows in microchannels. The numerical experience indicates that this method may be a powerful tool in the numerical simulation of micro-scale gas flows from MEMS.

关键词： Boltzmann model equation, discrete velocity ordinate method, finite-difference scheme, Couette flow, Poiseuille flow, gas flow in short-microchannel.

A Novel Red-eye Removal Approach in Digital Color Photos

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A Novel Red-eye Removal Approach in Digital Color Photos

Study on simulation and experiment of array micro Faraday cup ion detector for FAIMS

The 2010 IEEE International Conference on Progress in Informatics and Computing

作者： Yanfang Wang and Bo Han tsinghua national laboratory for information science and technology(TNList) Department of Automation tsinghua University beij.ng 100084 china

＜正＞Red-eye artifact is induced by the light reflected off retinal capillaries when photos are taken under weak light using *** automatic method is proposed to remove red-eye artifacts in digital images in this ***,a face detector based on histograms of oriented gradients（HOG） features and Real Adaboost algorithm is employed to select faces,and eyeboxes which contain one eye in each of them are obtained from the detected ***,a mask which records candidates for red-eye is calculated by two segmentation criteria computing over each ***,the candidate mask is processed by morphological filters and several heuristic exclusive principles to locate the target red-eye *** last,the red-eye defect is compensated by an adaptive correction *** proposed method is efficient and effective when tested on real images taken by different digital cameras.

关键词： face detection image segmentation red-eye detection and correction

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science china(Technological sciences) 2010年第12期53卷 3225-3231页

作者： TAng Fei, WAng XiaoHao, ZHAng Liang & YAN ZiLin State Key laboratory of Precision Measurement technology and Instruments, Department of Precision Instruments and Mechanology, tsinghua University, beij.ng 100084, china 1. State Key laboratory of Precision Measurement technology and Instruments Department of Precision Instruments and Mechanology Tsinghua University Beijing 100084 China

An array micro Faraday cup ion detector for FAIMS (High-field Asymmetric Waveform Ion Mobility Spectrometry) was introduced, with which the size of the FAIMS system was reduced. With simple structure, good stability, low noise, large measurements range, this detector can work under the condition of atmospheric pressure. The array micro Faraday cup was composed of gate electrode, sensitive electrode and shielding electrode. The sensitive electrode was made of tens of crossing silicon columns with diameter of 200 μm. It was fabricated through typical MEMS technology, which was compatible completely with plane FAIMS. It was shown from FLUENT simulation result that the resistance to gas motion was low and the flow field distribution was helpful for full absorption of the ion in this array design. Through electricity simulation, the method to reduce interference on the detection signal of the micro Faraday cup was given out. Connecting with KEITHLEY 237 ampere meter, the noise level of the array micro Faraday cup was lower than 0.5 pA. The output signal of the acetone sample measured by experiment was about 210 pA. Through contrast experiment, the design parameter of the micro Faraday cup was obtained primarily. This array micro Faraday cup can meet the requirements of the FAIMS system.

关键词： FAIMS MEMS Faraday cup ion detector low current

Secure network coding in the presence of eavesdroppers

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science china(information sciences) 2010年第3期53卷 648-658页

作者： LUO MingXing1,2,3, YAng YiXian1,2,3, WAng LiCheng1,2,3 & NIU XinXin1,2,3 1information Security Center, State Key laboratory of Networking and Switching technology, beij.ng University of Posts and Telecommunications, beij.ng 100876, china 2Key laboratory of Network and information Attack and Defence technology of MOE, beij.ng University of Posts and Telecommunications, beij.ng 100876, china 3national Engineering laboratory for Disaster Backup and Recovery, beij.ng University of Posts and Telecommunications, beij.ng 100876, china 1. information Security Center State Key Laboratory of Networking and Switching Technology Beijing University of Posts and Telecommunications Beijing 100876 China2. Key Laboratory of Network and Information Attack and Defence Technology of MOE Beijing University of Posts and Telecommunications Beijing 100876 China3. National Engineering Laboratory for Disaster Backup and Recovery Beijing University of Posts and Telecommunications Beijing 100876 China

Our concern, in the paper, is to construct information-theoretic secure network coding in the presence of eavesdroppers. Based on the generalized attack model and all-or-nothing transformation, the security of network coding in the generalized combination network can be characterized by the network capacity and the min-cut bound of wiretapping set from the source. Furthermore, it can be extended to any directed acyclic networks with single source. Compared with the traditional results, we construct information-theoretic secure network coding without additional encryptions and giving up any capacity.

关键词： all-or-nothing transformation secure network coding eavesdropping

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Lp shape deformation

science china(information sciences) 2012年第5期55卷 983-993页

作者： GAO Lin1,ZHAng GuoXin 1 & LAI YuKun 2 1 Department of Computer science and technology,tsinghua University,beij.ng 100084,china 2 School of Computer science and Informatics,Cardiff University,Wales CF24 3AA,UK 1. Department of Computer science and technology Tsinghua University Beijing 100084 China2. School of Computer Science and Informatics Cardiff University Wales CF24 3AA UK

Shape deformation is a fundamental tool in geometric *** methods consider preserving local details by minimizing some energy functional measuring local distortions in the L 2 *** strategy distributes distortions quite uniformly to all the vertices and penalizes ***,there is no unique answer for a natural deformation as it depends on the nature of the *** by recent sparse signal reconstruction work with non L 2 norm,we introduce general L p norms to shape deformation;the positive parameter p provides the user with a flexible control over the distribution of unavoidable *** with the traditional L 2 norm,using smaller p,distortions tend to be distributed to a sparse set of vertices,typically in feature regions,thus making most areas less distorted and structures better *** the other hand,using larger p tends to distribute distortions more evenly across the whole *** flexibility is often desirable as it mimics objects made up with different *** specifying varying p over the shape,more flexible control can be *** demonstrate the effectiveness of the proposed algorithm with various examples.

关键词： shape deformation Lp norm geometric modeling

Contourlet HMT model with directional feature

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science china(information sciences) 2012年第7期55卷 1563-1578页

作者： WAng XiangHai 1,2,3 ,CHEN MingYing 1 ,SOng ChuanMing 1,2 ,XU MengChun 1 & FAng LingLing 3 1 College of Computer and information technology,Liaoning Normal University,Dalian 116029,china 2 State Key laboratory for Novel Software technology,Nanjing University,Nanjing 210093,china 3 Provincial Key laboratory for Computer information Processing technology,Soochow University,Suzhou 215006,china 1. College of Computer and information technology Liaoning Normal University Dalian 116029 China2. State Key Laboratory for Novel Software Technology Nanjing University Nanjing 210093 China3. Provincial Key Laboratory for Computer Information Processing Technology Soochow University Suzhou 215006 China

According to Shanno's information theory,the directional feature of texture is defined as the value of directional variable when an image signal attains a singularity of random *** terms of this definition,we calculate the texture's directional features using Tamura's method and study the directional probability distribution of Contourlet *** we find that the directional features tend to be conveyed across parent and child *** on this conclusion,we establish a novel probability distribution model of hidden direction variables under the condition of hidden state variable's distribution,named Contourlet HMT model with directional *** structure and training method of the model are presented as ***,an unsupervised context-based image segmentation algorithm is proposed on the basis of the proposed *** effectiveness is verified via extensive experiments carried out on several synthesized images and remote sensing images.

关键词： directional feature Contourlet HMT Contourlet HMT with directional feature unsupervised texture segmentation

Sufficient and necessary conditions for Lyapunov stability of Lorenz system and their application

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science china(information sciences) 2010年第8期53卷 1574-1583页

作者： LUO Qi 1 , LIAO XiaoXin 2 & ZEng ZhiGang 2 1 College of information and Control, Nanjing University of information science and technology, Nanjing 210044, china 2 Department of Control science and Engineering, Huazhong University of science and technology, Image Processing and Intelligent Control Key laboratory of Education Ministry of china, Wuhan 430074, china 1. College of information and Control Nanjing University of Information Science and Technology Nanjing 210044 China2. Department of Control Science and Engineering Huazhong University of Science and Technology Image Processing and Intelligent Control Key Laboratory of Education Ministry of China Wuhan 430074 China

The sufficient and necessary conditions for Lyapunov stability of the zero equilibrium point of Lorenz system are discussed, and some brief criteria are presented for globally exponential stability, globally asymptotical stability and instability. Furthermore, the behavior of the non-zero equilibrium point of Lorenz system is also investigated, and several sufficient and necessary conditions are provided for locally exponential stability and instability. The established theorems in this paper develop and extend the existing achievements on Lyapunov stability of Lorenz system. In conclusion, by applying the obtained results, some less conservative feedback-control laws are derived to guarantee the globally exponential stability of the chaos control of Chen system, Lu¨ system, Yang-Chen system and Yu-Xia Li system.

关键词： Lorenz system Lyapunov stability sufficient and necessary condition bifurcation values globally exponential synchronization

Estimation of LISS(local input-to-state stability) properties for nonlinear systems

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science china(Technological sciences) 2010年第4期53卷 909-917页

作者： WU ShengYu,MEI ShengWei & ZHAng XueMin State Key laboratory of Power Systems,Department of Electrical Engineering,tsinghua University,beij.ng 100084,china 1. State Key laboratory of Power Systems Department of Electrical Engineering Tsinghua University Beijing 100084 China

Compared with input-to-state stability(ISS) in global version,the concept of local input-to-state stability(LISS) is more relevant and meaningful in *** key of assessing LISS properties lies in investigating three main ingredients,the local region of initial states,the local region of external inputs and the asymptotic *** is the objective of this paper to propose a numerical algorithm for estimating LISS properties on the theoretical foundation of quadratic form LISS-Lyapunov *** developments of linear matrix inequality(LMI) methods,this algorithm is effective and powerful.A typical power electronics based system with common DC bus is served as a demonstration for quantitative results.

关键词： locally input-to-state stability LISS-Lyapunov function linear matrix inequality

The Second Law of Thermodynamics in a Quantum Heat Engine Model

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Communications in Theoretical Physics 2006年第3期45卷 417-420页

作者： ZHAng Ting CAI Li-Feng CHEN Ping-Xing LI Cheng-Zu Department of Applied Physics,national University of Defence technology,Changsha 410073,chinaCHEN Ping-Xing Key laboratory of Quantum information,University of science and technology of china,Hefei 230026,china Department of Applied Physics National University of Defence Technology Key laboratory of Quantum information University of Science and Technology of China

The second law of thermodynamics has been proven by many facts in classical *** there any newproperty of it in quantum world?In this paper,we calculate the change of entropy in ***’s model for quantumheat engine(QHE)and prove the broad validity of the second law of *** is shown that the entropy ofthe quantum heat engine neither decreases in a whole cycle,nor decreases in either stage of the *** second lawof thermodynamics still holds in this QHE ***,although the modified quantum heat engine is capable ofextracting more work,its efficiency does not improve at *** is neither beyond the efficiency of ***’s initialmodel,nor greater than the reversible Carnot efficiency.

关键词： second law of thermodynamics entropy quantum heat engine