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Simulation study of phase retrieval for hard X-ray in-line phase contrast imaging

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Science china(Physics,Mechanics & Astronomy) 2005年第4期48卷 450-458页

作者： YU Bin1,2, PENG Xiang1,2, TIAN Jindong1, NIU Hanben1, DIAO Luhong3 & LI Hua3 1. key laboratory of Optoelectronic Devices and Systems of Ministry of Education, Institute of Optoelec- tronics, Shenzhen University, Shenzhen 518060, china 2. state key laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072,china 3. key laboratory of Intelligent information Processing, Institute of Computing Technology, Chinese Academy of Sciences, beijing 100080,china 1. key laboratory of Optoelectronic Devices and Systems of Ministry of Education Institute of Optoelectronics Shenzhen University 518060 Shenzhen China 2. state key laboratory of Precision Measuring Technology and Instruments Tianjin University 300072 Tianjin China 3. key laboratory of Intelligent information Processing Institute of Computing Technology Chinese Academy of Sciences 100080 Beijing China

Two algorithms for the phase retrieval of hard X-ray in-line phase contrast imaging are presented. One is referred to as Iterative Angular Spectrum Algorithm (IASA) and the other is a hybrid algorithm that combines IASA with TIE (transport of intensity equation). The calculations of the algorithms are based on free space propagation of the angular spectrum. The new approaches are demonstrated with numerical simulations. Comparisons with other phase retrieval algorithms are also performed. It is shown that the phase retrieval method combining the IASA and TIE is a promising technique for the application of hard X-ray phase contrast imaging.

关键词： X-ray optics, phase contrast imaging, phase retrieval, angular spectrum, hard X-ray.

A Group-Oriented (t,n) Threshold Signature Scheme with Traceable Signers

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Wuhan University Journal of Natural Sciences 2008年第6期13卷 680-684页

作者： TAN Zuowen1,2 1. School of information Technology, Jiangxi University of Finance and Economics, Nanchang 330013, Jiangxi, china 2. state key laboratory of information security/Institute of Software, Chinese Academy of Sciences, beijing 100190, china School of information Technology Jiangxi University of Finance and Economics Nanchang 330013 Jiangxi China state key laboratory of information security/Institute of Software Chinese Academy of Sciences Beijing 100190 China

A group-oriented （t, n） threshold signature scheme employs the cryptographic techniques of secret share, allows any subset of t players out of n players to sign message on behalf of the group and disallows the creation of a valid signature if fewer than t players take part in the signature protocol. In this paper, we proposed a new group-oriented （t, n） threshold signature schemes with traceable signers based on Schnorr signature. The proposed scheme is proved traceable, robust and unforgeable against the ＂static＂ adversary with the discrete logarithm assumption in the random oracle model and existence of broadcast channel. The proofs of the strongest security （existential unforgeability against adaptively chosen message attacks under the discrete logarithm assumption） are provided in the random oracle model.

关键词： threshold signature random oracle model robustness

A heuristic path-estimating algorithm for large-scale real-time traffic information calculating

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Science china(Technological Sciences) 2008年第S1期51卷 165-174页

作者： L WeiFeng1,ZHU TongYu1,WU DongDong2,DAI Hong3 & HUANG Jian1 1 state key laboratory for Software Development Environment,Beihang University,beijing 100083,china 2 beijing Transportation information Center,beijing 100055,china 3 College of Arts & Science,beijing Union University,beijing 100083,china 1. state key laboratory for Software Development Environment Beihang University Beijing 100083 China 2. beijing Transportation information Center Beijing 100055 China 3. College of Arts & Science Beijing Union University Beijing 100083 China

As the original Global Position System (GPS) data in Floating Car Data have the accuracy problem,this paper proposes a heuristic path-estimating algorithm for large-scale real-time traffic information calculating. It uses the heuristic search method,imports the restriction with geometric operation,and makes comparison between the vectors composed of the vehicular GPS points and the special road network model to search the set of vehicular traveling route candidates. Finally,it chooses the most optimal one according to weight. Experimental results indicate that the algorithm has considerable efficiency in accuracy (over 92.7%) and com-putational speed (max 8000 GPS records per second) when handling the GPS tracking data whose sampling rate is larger than 1 min even under complex road network conditions.

关键词： path-estimating floating car data (FCD) road network vector GPS

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

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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, beijing 100084, china 2. key laboratory for Atomic and Molecular NanoSciences, Tsinghua University, beijing 100084, 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.

A computational trust model for access control in P2P

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Science china(information Sciences) 2010年第5期53卷 896-910页

作者： LANG Bo state key laboratory of Software Development Environment, Beihang University, beijing 100191, china 1. state key laboratory of Software Development Environment Beihang University Beijing 100191 China

Trust brings a new method for building scalable and fine-grained access control mechanism in P2P systems. The quantificational expression of trust and the calculation of trust in a trust network are the basis of trust degree based access control. In this paper, the properties of trust is analyzed by referring to the fruits from social science; the semantics of trust in the context of access control is described, and a trust degree based access control model named TDBAC is introduced. Basing on the properties and semantics of trust, a computational trust model which includes a multilevel comprehensive evaluation method for expressing direct trust and calculators for computing recommended trust is put forward. To compute trust in a trust network, an algorithm that transforms a trust network to a computable expression is given. The algorithm simplifies the computation process and is also flexible.

关键词： trust management access control trust degree based access control computational trust model trust graph expression

Level Set interface treatment and its application in Euler method

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Science china(Physics,Mechanics & Astronomy) 2010年第2期53卷 227-236页

作者： WU KaiTeng1,2,HAO Li3,WANG Cheng4 & ZHANG Li1,2 1 Numerical Simulation Sichuan Higher School key laboratory,Neijiang Normal University,Neijiang 641112,china 2 College of Mathematics and information Science,Neijiang Normal University,Neijiang 641112,china 3 College of Science,beijing University of Civil Engineering and Architecture,beijing 10004.,china 4 state key laboratory of Explosion Science and Technology,beijing Institute of Technology,beijing 100081,china 1. Numerical Simulation Sichuan Higher School key laboratory Neijiang Normal University Neijiang 641112 China2. College of Mathematics and Information Science Neijiang Normal University Neijiang 641112 China3. College of Science Beijing University of Civil Engineering and Architecture Beijing 100044 China4. State Key Laboratory of Explosion Science and Technology Beijing Institute of Technology Beijing 100081 China

Level Set interface treatment method is introduced into Euler method,which is employed for interface treatment method for multi-materials. Combined with the ghost fluid method,the moving interface is tracked. Fifth-order WENO spatial discretization and third-order TVD Runge-Kutta time discretization methods are used. Shock-wave action on bubble,implosion and velocity field Shock effect bubbles; implosion and velocity field are simulated by means of LS-MMIC3D programmed by C++. Nu-merical results show that the Level Set interface treatment method is effective and feasible for multi-material interface treatment in comparison with the WENO method.

关键词： Euler method Level Set method shock-wave action on bubble implosion numerical simulation

Fuzzy tracking control design for hypersonic vehicles via T-S model

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Science china(information Sciences) 2011年第3期54卷 521-528页

作者： GAO DaoXiang 1 & SUN ZengQi 2 1 School of Technology, beijing Forestry University, beijing 100083, china 2 state key laboratory of Intelligent Technology and System, Department of Computer Science and Technology, Tsinghua University, beijing 100084, china 1. School of Technology Beijing Forestry University Beijing 100083 China2. State Key Laboratory of Intelligent Technology and System Department of Computer Science and Technology Tsinghua University Beijing 100084 China

The main focus of this paper is on designing a T-S fuzzy controller for the hypersonic vehicle. The longitudinal dynamics of the vehicle are studied using time-scale decomposition to reduce the complexity of T-S modeling. The dynamic inversion with PI control technique is applied for the slow dynamics to derive the flight path angle command and throttle setting by taking the pilot altitude and velocity command as its inputs. The T-S fuzzy controller is designed for the fast dynamics to derive the elevator deflection to track the flight path angle command. The discrepancy between the T-S model and real vehicle model is considered by using sliding mode control for the system stability. Simulation results are included to show the effectiveness of the controller.

关键词： fuzzy control T-S model sliding mode control hypersonic vehicle

Multiparty quantum secret sharing of classical and quantum messages

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Progress in Natural Science:Materials International 2007年第1期17卷 26-31页

作者： CHEN Pan, DENG Fuguo and LONG Guilu ( key laboratory for Quantum information and Measurements, and Department of Physics, Tsinghua University, beijing 100084, china key laboratory of Beam Technology and Material Modification, MOE, Institute of Low Energy Nuclear Physics, and Department of Material Science and Engineering, beijing Normal University, beijing 100875, china beijing Radiation Center, beijing 100875, china key laboratory for Atomic and Molecular Nano-Sciences, Tsinghua University, beijing 100084, china) [a]key laboratory for Quantum information and Measurements and Department of Physics Tsinghua University Beijing China [b]key laboratory of Beam Technology and Material Modification MOE Institute of Low Energy Nuclear Physics and Department of Material Science and Engineering Beijing Normal University Beijing China [c]beijing Radiation Center Beijing China [d]key laboratory for Atomic and Molecular Nano-Sciences Tsinghua University Beijing China

A scheme for multiparty quantum secret sharing of classical and quantum messages is proposed by using entanglement swapping. This scheme can distribute not only the classical information but also the quantum informati... 详细信息

关键词： quantum secret sharing classical message quantum message EPR pair.

Image-based modeling of inhomogeneous single-scattering participating media

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Science china(information Sciences) 2010年第6期53卷 1141-1150页

作者： HU Yong 1 , QI Yue 1 & TONG Xin 2 1 state key laboratory of Virtual Reality Technology and Systems, Beihang University, beijing 100191, china 2 Microsoft Research Asia, beijing 100080, china 1. state key laboratory of Virtual Reality Technology and Systems Beihang University Beijing 100191 China2. Microsoft Research Asia Beijing 100080 China

We propose a method to reconstruct inhomogeneous single-scattering participating media, which could preserve fine high-frequency details of density *** data and the ratio of absorption coefficient to scattering coefficient are used to describe the spatial-varying density distribution and optical properties of certain participating media, and a function between the above parameters and captured pixel values is *** the problem of how to find solutions to these parameters is formulated into a nonlinear numerical optimization *** order to reduce large time overheads and numerical instability brought by simultaneously solving large numbers of voxels, we propose an initialization algorithm for enabling the assigned density values to satisfy the regularity of brightness distribution in captured images approximately as well as a progressive refinement algorithm for multi-resolution volumetric ***, we propose a parallel multi-voxel gradient computation algorithm of utilizing hardware acceleration to reduce time overheads in gradient computation for large numbers of *** results indicate that our method is well suited for reconstructing thin smoke, retaining high-frequency details from images captured from multiple viewpoints.

关键词： single-scattering participating media smoke modeling volumetric modeling image based modeling