检索结果-内蒙古大学图书馆

IEEE Symposium on Nuclear science (NSS/MIC)

作者： Arman Rahmim Jing Tang M. R. Ay F. M. Bengel Department of Radiology and the Department of Electrical and Computer Engineering Johns Hopkins University Baltimore MD USA Division of Imaging Physics and System Analysis Philips Healthcare Cleveland OH USA Research Center of Science and Technology Department of Medical Physics and Biomedical Engineering Tehran University of Medical Sciences Tehran Iran Department of Radiology Johns Hopkins University Baltimore MD USA

Routine clinical myocardial perfusion (MP) PET imaging involves the use of cardiac gating only. Nonetheless, respiratory motion of the heart can considerably degrade the quality of MP images and the quantitative accuracy of myocardial uptake estimates. We first performed a quantitative evaluation of the degrading contributions of cardiac (C) and respiratory (R) motion, as well as non-motion factors of Rb-82 positron range, photon non-collinearity, crystal scattering and penetration. For a normal human simulated phantom, we showed that the combination of all above factors resulted in -48% underestimation of myocardial activity, while corrections for all non-motion factors resulted in 21%, 36% and 41% underestimated myocardial activities in the presence of C, R and C&R motion. This means that compensation for respiratory motion must be considered as critical towards achieving overall motion compensation and/or resolution modeling. To achieve respiratory motion compensation, we used translation motion vectors to first match respiratory-only gated images to the end-expiration reference frame. Next, for each cardiac gate, a 4D EM reconstruction algorithm was applied to the R-gated data within that cardiac phase. Three techniques were compared involving reconstructions of (a) a single R-gate only, and all R-gates (b) without and (c) with respiratory motion correction (MC). Using simulated PET data, quantitative comparisons of noise vs. bias trace-off curves indicated notable improvements for the proposed 4D respiratory MC method. Using CHO analysis as applied to the task of perfusion defect detection, ROC analysis of the three methods resulted in AUC values of 0.610±0.039, 0.645±0.038 and 0.821±0.029. The CLABROC statistical test revealed that the proposed MC technique significantly outperformed the other two methods in the task of defect detection.

关键词： Positron emission tomography Logic gates Image reconstruction Myocardium Computed tomography Heart

来源：评论

学校读者我要写书评

暂无评论

Research of geometric computing and its theory

引用

Shanghai Jiaotong Daxue Xuebao/Journal of Shanghai Jiaotong University 2010年第3期44卷 407-412页

作者： He, Yuan-Jun Department of Computer Science and Engineering MOE-Microsoft Key Laboratory for Intelligent Computing and Intelligent System Shanghai Jiaotong University Shanghai 200240 China

A new geometric computing theory was proposed. On the definition level of geometric elements, using the Cartesian coordinates ideology as reference, 2D and 3D ″geometric algebra elements″ (or ″geometric elements″ for short, which could construct an upper-level element in the solving sequence) were constructed by geometry algebraization methods. On the processing level of geometries, geometric problems were solved with geometry methods, by which a geometric element solving sequence could be constructed. Directional property was introduced into geometries in this theory and geometries were represented in a unified format. They help to simplify the processing of finding the geometric element solving sequence for a geometry problem. The paper also tried to theoretically find out an integrated solution for geometry ambiguity issues, and established a unified, standardized geometry computing architecture. The Leibniz's mind-to process geometric objects with geometric language-was implemented in an indirect way!

关键词： Geometry

来源：评论

学校读者我要写书评

暂无评论

Monte Carlo analysis of a low power domino gate under parameter fluctuation

引用

Journal of Semiconductors 2009年第12期30卷 113-117页

作者：汪金辉吴武臣宫娜侯立刚彭晓宏高大明 VLSI and System Laboratory Beijing University of Technology Department of Computer Science and Engineering State University of New York at Buffalo

Using the multiple-parameter Monte Carlo method, the effectiveness of the dual threshold voltage technique （DTV） in low power domino logic design is analyzed. Simulation results indicate that under significant temperature and process fluctuations, DTV is still highly effective in reducing the total leakage and active power consumption for domino gates with speed loss. Also, regarding power and delay characteristics, different structure domino gates with DTV have different robustness against temperature and process fluctuation.

关键词： domino gate temperature and process fluctuation effectiveness

来源：评论

学校读者我要写书评

暂无评论

Optimal Control of Affine Nonlinear Continuous-time systems Using an Online Hamilton-Jacobi-Isaacs Formulation

Optimal Control of Affine Nonlinear Continuous-time Systems ...

引用

2010 49th IEEE Conference on Decision and Control

作者： T. Dierks S. Jagannathan DRS Sustainment System Inc. 201 Evans Lane St. Louis MO 63121 Department of Electrical and Computer Engineering Missouri University of Science and Technology 301 W. 16th St. Rolla MO 65409

ISBN: (纸本)9781424477456

Solving the Hamilton-Jacobi-Isaacs (HJI) equation, commonly used in H_(infinity) optimal control, is often referred to as a two-player differential game where one player tries to minimize the cost function while the other tries to maximize it. In this paper, the HJI equation is formulated online and forward-in-time using a novel single online approximator (SOLA)-based scheme to achieve optimal regulation and tracking control of affine nonlinear continuous-time systems. The SOLA-based adaptive approach is designed to learn the infinite horizon HJI equation, the corresponding optimal control input, and the worst case disturbance. A novel parameter tuning algorithm is derived which not only achieves the optimal cost function, control input, and the disturbance, but also ensures the system states remain bounded during the online learning. Lyapunov methods are used to show that all signals are uniformly ultimately bounded (UUB) while ensuring the approximated signals approach their optimal values with small bounded error. In the absence of OLA reconstruction errors, asymptotic convergence to the optimal signals is demonstrated, and simulation results illustrate the effectiveness of the approach.

关键词： Optimal control Cost functions Continuous time systems Affine In-law Lyapunov methods signals control input tracking control Bounded disturbance trees (mathematics)

来源：评论

学校读者我要写书评

暂无评论

Four-level superradiant laser with full atomic cooperativity

引用

Physical Review A 2010年第5期81卷 053809-053809页

作者： Deshui Yu Jingbiao Chen Department of Applied Physics Graduate School of Engineering The University of Tokyo Bunkyo-ku Tokyo 113-8656 Japan Institute of Quantum Electronics and State Key Laboratory of Advanced Optical Communication System & Network School of Electronics Engineering & Computer Science Peking University Beijing 100871 People's Republic of China State Key Laboratory of Precision Spectroscopy East China Normal University Shanghai 200062 People's Republic of China

We investigate a four-level superradiant laser whose intensity is proportional to N2 and whose linewidth scales as 1/N2. In the absence of spontaneous emissions, we derive the stationary solutions of the atomic full cooperativity, analyze their stabilities, and find the corresponding irreducible representation based on group U(4). We also investigate the spectra of the phase and amplitude fluctuations of the fields inside and outside the cavity and find that the amplitude fluctuations of the output fields cannot be squeezed in the low-frequency limit, which is completely different from the three-level superradiant laser system. Finally, we consider the stationary solutions corresponding to the partial cooperativity due to the symmetry breaking of U(4) induced by the atomic spontaneous emissions.

关键词： Spontaneous emission

来源：评论

学校读者我要写书评

暂无评论

New features of Easy Java Simulations for 3D Modeling

引用

IFAC Proceedings Volumes 2010年第24期42卷 250-255页

作者： Carlos A. Jara Francisco Esquembre Francisco A. Candelas Fernando Torres Sebastián Dormido Department of Physics System Engineering and Signal Theory University of Alicante Alicante Spain (e-mail:{carlos.jara francisco.candelas fernando.torres}@ua.es) Department of Mathematics University of Murcia Murcia Spain (e-mail: fem@um.es) Department of Computer Science and Automatic Control UNED University Madrid Spain (e-mail: sdormido@dia.uned.es)

This paper presents a new interface framework which has been added to Easy Java Simualtions' environment in order to improve its graphical features for 3D modeling. These new 3D capabilities provide users a set of new view elements which can be used to develop models with a high degree of reality. In this way, Easy Java Simulations becomes a powerful tool to easily and quickly create 3D realistic simulations.

关键词： computer simulation modeling programming environment software tool virtual reality

来源：评论

学校读者我要写书评

暂无评论

Movement Persuit Control of an Offshore Automated Platform via a RAM-based Neural Network

Movement Persuit Control of an Offshore Automated Platform v...

引用

International Conference on Control, Automation, Robotics and Vision

作者： Horacio L. Franca Joao Carlos P. da Silva Omar Lengerke Max S. Dutra Massimo De Gregorio Felipe M. G. Franca Computer Science Department Mathematics Institute Universidade Federal do Rio de Janeiro Rio de Janeiro Brazil Mechanical Engineering Program COPPE Universidade Federal do Rio de Janeiro Rio de Janeiro Brazil Istituto di Cibernetica "Eduardo Caianiello" Consiglio Nazionale delle Ricerche (CNR) Naples Italy System Engineering and Computer Science Program COPPE Universidade Federal do Rio de Janeiro Rio de Janeiro Brazil

ISBN: (纸本)9781424478149

The reproduction of the movements of a ship by automated platforms, without the use of sensors providing exact data related to the numeric variables involved, is a non-trivial matter. The creation of an artificial vision system that can follow the cadence of said ship, in six axes of freedom, is the goal of this research. Considering that a real time response is a requisite in this case, it was decided to adopt a Boolean artificial neural network system that could identify and follow arbitrary interest points that could define, as a group, a model of the movement of an observed vessel. This paper describes the development of a prototype based on the Boolean perceptron model WiSARD (Wilkie, Stonham and Aleksander's Recognition Device), that is being implemented in the C programming language on a desktop computer using a regular webcam as input.

关键词： Stewart platform weightless neural networks WiSARD

来源：评论

学校读者我要写书评

暂无评论

Robustify a job-shop schedule according to the payload of the machine

Robustify a job-shop schedule according to the payload of th...

引用

International Conference on Services systems and Services Management, ICSSSM

作者： Zhiyang You Zhigang Sun Xibin Zhao Daxin Zang Department of Computer Science and Technology Tsinghua University Beijing China School of Software Tsinghua University Beijing China Key Laboratory of Information System Security Ministry of Education School of Software Tsinghua University Beijing China Software Engineering Institute Beijing Aeronautics and Astronautics University Beijing China

Robust scheduling is an effective way to solve job-shop scheduling problem (JSP) under a dynamic and stochastic environment with uncertainties, which may lead to numerous schedule disruptions. Maintaining the optimization obtained, the robust schedule is more stable in execution. The vast majority of the researches on robust scheduling concentrate on the development of the robustness and stabilization with an optimization target that minimizes makespan. However, other optimization targets are needed in reality, and in this paper, we introduce another optimization target that maximizes the payload of the machine, which can reflect the capacity of machine. This work applies a two-step way to achieve a robust schedule. A baseline schedule in the deterministic environment is generated first, which pursues standard optimization criterions, and then the temporal buffers are inserted into the baseline schedule which make the schedule absorb some level of unexpected disruption without rescheduling. According to the payload of each machine which should be close to the maximum at any time in execution, we can get each size of the temporal buffers inserted into the different operations. An extensive experiment is used to show the relative performance of the proposed robust schedule. It is shown that the schedule is robust and stable under the stochastic disturbance coupling with minimal makespan tardiness and symmetry payload.

关键词： Robustness Payloads Job shop scheduling Uncertainty Processor scheduling Dynamic scheduling Stochastic processes Switches computer science Space technology

来源：评论

学校读者我要写书评

暂无评论

Relevance feedback of content-based image retrieval using support vector machine

Relevance feedback of content-based image retrieval using su...

引用

2009 5th IEEE GCC Conference and Exhibition, GCC 2009

作者： Selamat, Ali Lim, Pei-Geok Department of Software Engineering Faculty of Computer Science and Information System Malaysia

ISBN: (纸本)9781424438853

The rapid growth of computer technologies and the advent of the World Wide Web have increased the amount and the complexity of multimedia information. A content-based image retrieval (CBIR) system has been developed as an efficient image retrieval tool, whereby the user can provide their query to the system to allow it to retrieve the user's desired image from the image database. However, the traditional relevance feedback of CBIR has some limitations that will decrease the performance of the CBIR system, such as the imbalance of training-set problem, classification problem, limited information from user problem, and insufficient training-set problem. Therefore, in this study, we proposed an enhanced relevance-feedback method to support the user query based on the representative image selection and weight ranking of the images retrieved. The support vector machine (SVM) has been used to support the learning process to reduce the semantic gap between the user and the CBIR system. From these experiments, the proposed learning method has enabled users to improve their search results based on the performance of CBIR system. In addition, the experiments also proved that by solving the imbalance training set issue, the performance of CBIR could be improved.

关键词： Support vector machines

来源：评论

学校读者我要写书评

暂无评论

An Algorithm for Role Mapping Across Multi-domains Employing RBAC

引用

电子学报(英文版) 2009年第1期18卷 37-41页

作者： WANG Xiaoqing GU Tianyang GUO Yong ZHENG Yanxing ZONG Jianjian GONG Bo Department of Computer Science and Technology Tsinghua University Beijing 100084 China Beijing Institute of System Engineering Beijing 100101 China School of Computer Science and Technology BeiHang University Beijing 108040 China

The problem of access control across multiple security domains in data sharing environment is addressed and a rule-based algorithm for role mapping across multi-domains is presented. The algorithm resolves efficiently the conflicts of cyclic inheritance and separation of duties, and the problem of regression inheritance. The algorithm takes the “Least privilege theorem” into account and prohibits accesses from illegal domains. Further more, the algorithm makes the establishment of role mapping across multi-domains more efficiently by preserving historical information of role mapping paths established successfully before, and satisfies preferably the access control requirement across dynamic multi-domains in data sharing environment. Evaluation by access instances shows the efficiency of our algorithm.

关键词：映射算法 RBAC 控制要求环境问题数据共享职责分离最小特权历史资料

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：