检索结果-南通市图书馆

Terahertz radiation sources based on free electron lasers and their applications

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({2. sciences) 2012年第1期55卷 1-15页

作者： TAN Ping1,HUANG Jiang2.LIU KaiFeng2.XIONG YongQian2.FAN MingWu1,2.1Department of Electronic and information engineering,Huazhong University of {2. and Technology,Wuhan 43.074,china 2.ollege of Electrical and Electronic engineering,State Key Laboratory of Advanced Electromagnetic engineering and Technology,Huazhong University of {2. and Technology,Wuhan 43.074,china 1. Department of Electronic and information engineering Huazhong University of Science and Technology Wuhan 430074 China2. College of Electrical and Electronic Engineering State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan 430074 China

The tunability,high power and flexible picoseconds-pulse time structure of terahertz(THz)radiation make the THz free-electron laser(FEL)a very attractive THz source of coherent *** paper focuses on the development and perspectives of THz radiation sources based on the *** principles of the low gain THz FEL oscillator,the SASE THz FEL amplifier and the supperradiant THz FEL are reviewed briefly,and the key technologies of THz FEL,such as injector,accelerator,undulator and optical cavity,are discussed,*** current status of and future prospects for THz radiation sources based on the FEL are emphasized in this *** research and development have shown bright future in free-electron laser(FEL)THz radiation *** potential applications can be carried out in the field of imaging,material research,biology medicine,communication,diagnostics and many others.

关键词： terahertz source terahertz applications free electron laser

A novel method for evaluating and improving the 1H-MRSI glioma data quality

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Progress in Natural science:Materials International 2005年第8期15卷 765-768页

作者： YUAN Kehong 1,2. LU Hongyu2. BAO Shanglian2., CHEN Qiansheng1, LI Shaowu3.and DUAN Chaijie2.1. Key Laboratory of Pure and Applied Mathematics, School of Mathematical sciences, Beijing 100871, {2. 2. The Research Center for Tumor Diagnosis and Therapeutical Physics & the Beijing Key Laboratory of Medical Physics and engineering, Peking University, Beijing 100871, {2. 3. The Tian Tan Hospital, Beijing 100050, {2.) Key Laboratory of Pure and Applied Mathematics School of Mathematical Sciences Beijing 100871 China. The Research Center for Tumor Diagnosis and Therapeutical Physics & the Beijing Key Laboratory of Medical Physics and engineering Peking University Beijing 100871 China. The Tian Tan Hospital Beijing 100050 China

Metabolic information obtained by proton magnetic resonance spectroscopic imaging (1H-MRSI) has been approved to be a powerful tool to identify either benign or malignant glioma, as well as to confirm the tumor level. However, 1H-MRSI data are affected by various factors, such as the thermal noise, eddy currents, susceptibility artifacts, and rigid body motion. To get accurate quantitative metabolic information, the key problem is to assess the 1H-MRSI data quality. In this paper, we introduce a new evaluating system to filter the data, and a new method, called wavelet denoising method, to improve the data quality under the evaluating system. Experimental results on 1H-MRSI glioma data demonstrate that preprocessing is prerequisite and the proposed algorithm with evaluating system is effective.

关键词： 1H-MRSI evaluating system glioma data quality wavelet denoising

Comparison of the influence factors on NDVI for CCD camera and WFI imager on CBERS-02

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(Technological sciences) 2005年第S2期48卷 100-115页

作者： YU Tao1,3. LI Xiaoying1,2.3. ZHANG Yong1,2.3. ZHAO Feng1,2.3. GU Xingfa1,3.4, ZHU Li1,2.3. WANG Pengxin5 & MIN Xiangjun6 1. State Key Laboratory of Remote Sensing science Institute of Remote Sensing Application, CAS, Bei- jing 100101, china 2. Graduate University of Chinese Academy of sciences, Beijing 10003., china 3. The Center for National Spaceborne Demonstration, Beijing 100101, china 4. Institut National de la Recherche Agronomique, Climat Sol Environnement, 84914 Avignon, France 5. College of information and Electrical engineering, china Agricultural University, Beijing 100083. china 6. china Center for Resource Satellite Data and Application, Beijing 10083., china 1. State Key Laboratory of Remote Sensing science Institute of Remote Sensing Application CAS 100101 Beijing China 2. The Center for National Spaceborne Demonstration 100101 Beijing China 3. Graduate University of Chinese Academy of sciences 100039 Beijing China 4. Institut National de la Recherche Agronomique Climat Sol Environnent 84914 Avignon France 5. College of information and Electrical engineering China Agricultural University 100083 Beijing China 6. china Center for Resource Satellite Data and Application 100830 Beijing China

CCD and WFI are payloads in the visible light and near infrared bands on CBERS satellites and they have not been applied widely, especially WFI. This article mainly probes into the potential of these two sensors’ application in the vegetation monitoring and analyses the influences of radiometric calibration, atmosphere conditions and sun-observing geometry, etc. on NDVI obtained from these two sensors respectively. In addition it analyses the effect of the spectral response difference of red and near infrared spectral bands in CCD and WFI sensors on NDVI. Results indicate that radiometric calibration is the most important factor on NDVI, which cannot be applied to vegetation monitoring without radiometric calibration. Results also demonstrate that near surface NDVI is different greatly from that of TOA which change with atmosphere conditions. The study shows that NDVI is also affected by the non-lambertian character of surface and the change of the atmospheric path with the observing geometry. And NDVI of WFI is higher than that of CCD. They are very different because of their spectral difference, but they have a good linear relevant relationship.

关键词： CCD WFI NDVI LAI.

维普期刊数据库

A new method for adaptive color image filtering

在线全文

学校读者我要写书评

暂无评论

Chinese science Bulletin 2000年第13期45卷 1230-1235页

作者： JIANG Gangyi, YU Mei & YU Bokang1. Department, of information & Electronic engineering, Hang/hou University of Commerce, Hangzhou 3.003., {2. 2. Department, of Electronic engineering, Hangzhou institute of Electronics engineering, Hangzhou 3.003., {2. 3. State Key Laboratory on Machine Perception, Peking University, Beijing 100871, {2. Correspondence should be addressed to Yu Mei Department of information & Electronic engineering Hangzhou University of Commerce Hangzhou China State Key Laboratory on Machine Perception Peking University Beijing China Department of Electronic engineering Hangzhou Institute of Electronics Engineering Hangzhou China

An adaptive color image filter (ACIF) is proposed in this note. Through analyzing noise corruption of color image, efficient locally adaptive filters are chosen for image enhancement. The proposed adaptive color image filter combines advantages of both nonlinear vector filters and linear filters, it attenuates noise and preserves edges and details very well. Experimental results show that the proposed filter performs better than vector median filter, directional-distance filter, directional-magnitude vector filter, adaptive nearest-neighbor filter, and α-trimmed mean filter.

关键词： color image noise analysis locally adaptive filters adaptive color image filter (ACIF).

维普期刊数据库

Black-box testing based on colorful taint analysis

在线全文

学校读者我要写书评

暂无评论

science china({2. sciences) 2012年第1期55卷 171-183页

作者： CHEN Kai1,2.3.FENG DengGuo1,SU PuRui1&ZHANG YingJun1,2.3.1State Key Laboratory of information Security,Institute of Software,Chinese Academy of {3.,Beijing 100190,{2. 2.tate Key Laboratory of information Security,Graduate University of Chinese Academy of {3.s,Beijing 100049,{2. 3.ational engineering Research Center of information Security,Beijing 100190,{2. 1. State Key Laboratory of information Security Institute of Software Chinese Academy of Science Beijing 100190 China2. State Key Laboratory of Information Security Graduate University of Chinese Academy of Sciences Beijing 100049 China3. National Engineering Research Center of Information Security Beijing 100190 China

Software vulnerability detection is one of the most important methods for guaranteeing software *** main classes of methods can detect vulnerabilities in binary files:white-box testing and black-box *** former needs to construct and solve path constraints to detect *** has two main drawbacks:path exploding and complexity of *** latter often aimlessly exhausts various inputs to test binary *** paper combines both testing methods to detect vulnerabilities in binary *** analyzing the input elements that aect check condition corresponding to a certain check point,we can generate one class of inputs that get to the check point to increase fuzzing *** analyzing the relationship between guard conditions and check condition,the redundant check points are *** taint analysis method(CTAM)is proposed to compute guard conditions,which is more ecient than traditional taint analysis method(TTAM).We implemented a prototype and made several experiments on *** results showed that our method could increase the eciency of black-box testing.

关键词： software testing vulnerability detection dynamic testing black-box testing colorful taint analysis

RST transforms resistant image watermarking based on centroid and sector-shaped partition

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({2. sciences) 2012年第3期55卷 650-662页

作者： ZHAO Yao1,2., NI RongRong1,2. & ZHU ZhenFeng1,2. 1Institute of {3. science, Beijing Jiaotong University, Beijing 100044, {2. 2.eijing Key Laboratory of Advanced {3. science and Network Technology, Beijing 100044, {2. 1. Institute of information science Beijing Jiaotong University Beijing 100044 China2. Beijing Key Laboratory of Advanced Information Science and Network Technology Beijing 100044 China

A novel digital watermarking scheme featuring centroid-based sectoring is proposed in this paper. To get higher robustness against geometric attacks, such as rotation, scaling, and translation (RST), a delicate synchronization mechanism was developed and incorporated into the proposed approach. During the process of watermark embedding, the original image was partitioned into sectors based on the image centroid. Synchronization information as well as the message bits is then embedded into these sectors. With the help of the centroid-based sectoring and synchronization information, the proposed approach is capable of restoring the correct sectoring even if it has experienced severe geometric distortion. This attribute ensures the correct recovery of embedded watermarks and contributes to the robustness of the proposed scheme. A series of experiments have been conducted to verify the feasibility and effectiveness of the proposed approach. Experimental results show that the proposed scheme possesses good robustness against RST attacks and considerable robustness against other common image processing attacks.

关键词： digital watermarking geometrical transform attacks RST transforms

Rule Generation Based on Dominance Matrices and Functions

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Transactions of Tianjin University 2004年第1期10卷 54-58页

作者：安利平陈增强袁祉仝凌云 College of International Business Nankai UniversityTianjin 300071ChinaCollege of Information Technical Science Nankai UniversityTianjin 300071 China College of information Technical science Nankai University

Rough set theory has proved to be a useful tool for rule induction. But, the theory based on indiscernibility relation or similarity relation cannot induce rules from decision tables with criteria. Greco et al have proposed a new rough set approach based on dominance relation to handle the problems. The concept of dominance matrix is put forward and the dominance function is constructed to compute the minimal decision rules which are more general and applicable than the ones induced by the classical rough set theory. In addition, the methodology of simplification is presented to eliminate the redundancy in the rule set.

关键词： Decision tables Mathematical techniques

维普期刊数据库

A fast stereoscopic video coding algorithm based on JMVM

在线全文

学校读者我要写书评

暂无评论

science china({2. sciences) 2011年第6期54卷 1218-1226页

作者： DENG ZhiPin 1,2., JIA KeBin 1 , CHAN YuiLam 2., FU ChangHong 2.& SIU WanChi 2.1 Department of Electronic information & Control engineering, Beijing University of Technology, Beijing 10012., {2. 2.Department of Electronic information engineering, Hong Kong Polytechnic University, Hong Kong, {2. 1. Department of Electronic information & Control engineering Beijing University of Technology Beijing 100124 China2. Department of Electronic Information Engineering Hong Kong Polytechnic University Hong Kong China

In order to exploit the intra-view and inter-view dependencies in stereo video coding, a fast joint motion and disparity estimation algorithm is proposed in this paper. An efficient search strategy based on the motion-disparity constraint is developed, in which both the motion and disparity vectors can be obtained simultaneously with low complexity. Moreover, a credible initial predictive vector set is designed with the aid of the temporal and spatial neighboring blocks so that the coding efficiency can be further enhanced. The experimental results demonstrate that the proposed algorithm can reduce more than 96% coding time compared with the JMVM full search with a negligible quality drop.

关键词： H.2.4 stereoscopic video coding disparity estimation motion estimation

SQUARE attack on block ciphers with low algebraic degree

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({2. sciences) 2010年第10期53卷 1988-1995页

作者： SUN Bing 1 , LI RuiLin 1 , QU LongJiang 1,3.& LI Chao 1,2.3.1 science College of National University of Defense Technology, Changsha 410073. china 2.State Key Laboratory of {2. Security, Graduate University of Chinese Academy of sciences, Beijing 100049, china 3.National Mobile Communications Research Laboratory, southeast University, Nanjing 2.0096, china 1. science College of National University of Defense Technology Changsha 410073 China3. National Mobile Communications Research Laboratory Southeast University Nanjing 210096 China2. State Key Laboratory of Information Security Graduate University of Chinese Academy of Sciences Beijing 100049 China

By using an algebraic method, the mathematical foundation of SQUARE attack is studied in this paper. We point out that a SQUARE distinguisher exists if and only if the degree of the polynomial function between n-bit input which is active and n-bit output which is balanced is 2.n-2. And the algebraic method can also be used to determine the property of a balanced set after passed through a nonlinear S-box, by which in some cases we can find a SQUARE distinguisher with more rounds. The validity of SQUARE attack and the influence of the choice of S-box are also studied. If the round function of a Feistel cipher has a low algebraic degree, a SQUARE attack cannot recover the right keys in some special cases. However, SQUARE attack on SPN ciphers always holds. The relations among SQUARE attack and some other cryptanalytic method are studied, showing that if a cipher is breakable by SQUARE attack, then it is also breakable by the interpolation attack.

关键词： SQUARE attack interpolation attack integral attack block cipher