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基于自一致性的磁共振并行成像高效重构算法 被引量:2
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作者 段继忠 张立毅 +1 位作者 刘昱 孙云山 《天津大学学报(自然科学与工程技术版)》 EI CAS CSCD 北大核心 2014年第5期414-419,共6页
磁共振并行成像技术能够显著地减少成像时间,然而高质量的图像重构比较困难.为了提高重构图像的质量,基于自一致性的SPIRiT框架,提出了一种高效的重构算法.该算法针对一个含有数据一致性、校准一致性和联合稀疏性正则项的复杂优化问题,... 磁共振并行成像技术能够显著地减少成像时间,然而高质量的图像重构比较困难.为了提高重构图像的质量,基于自一致性的SPIRiT框架,提出了一种高效的重构算法.该算法针对一个含有数据一致性、校准一致性和联合稀疏性正则项的复杂优化问题,首先将该问题简化成一般性最优化问题;再使用算子分离算法将其分解成一个梯度计算问题和一个可通过软阈值法求解的去噪问题;最后,再使用加速方案对算法进行加速.实验结果表明,当加速因子为8时,采用所提出的新算法的重构图像比采用POCS算法的重构图像的SNR提高约2.4,dB,且重构时间也节约了约30%.对于要求高质量重构图像的场合,所提出的算法能够满足需求. 展开更多
关键词 图像重构 磁共振成像 并行成像 自一致性 算子分裂 压缩感知
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基于SIDWT和迭代自一致性的快速并行成像重建方法
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作者 段继忠 钱青青 《上海交通大学学报》 EI CAS CSCD 北大核心 2023年第5期582-592,共11页
为提高并行磁共振成像的重建速度,基于平移不变离散小波变换(SIDWT)和迭代自一致性并行成像重建(SPIRiT)模型,提出一种高效的重建方法fSIDWT-SPIRiT.该方法针对含有数据一致项、校正一致项和L1范数正则项的复杂优化问题,首先将数据一致... 为提高并行磁共振成像的重建速度,基于平移不变离散小波变换(SIDWT)和迭代自一致性并行成像重建(SPIRiT)模型,提出一种高效的重建方法fSIDWT-SPIRiT.该方法针对含有数据一致项、校正一致项和L1范数正则项的复杂优化问题,首先将数据一致项和校正一致项进行合并处理,之后利用快速投影迭代软阈值算法进行求解以实现快速并行磁共振成像重建.最后,在不同人体器官的数据集上进行测试.仿真实验结果表明:与其他方法相比,该方法能够在保证图像重建质量的同时,具有更快的收敛速度. 展开更多
关键词 并行磁共振成像 迭代自一致性并行成像重建模型 图像重建 快速投影迭代软阈值算法 平移不变离散小波变换
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The Modified Magnetohydrodynamical Equations
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作者 EvangelosChaliasos 《Communications in Theoretical Physics》 SCIE CAS CSCD 2003年第1X期101-102,共2页
After finding the really self-consistent electromagnetic equations for a plasma, we proceed in a similar fashion to find how the magnetohydrodynamical equations have to be modified accordingly. Substantially this is d... After finding the really self-consistent electromagnetic equations for a plasma, we proceed in a similar fashion to find how the magnetohydrodynamical equations have to be modified accordingly. Substantially this is done by replacing the "Lorentz" force equation by the correct (in our case) force equation. Formally we have to use the vector potential instead of the magnetic field intensity. The appearance of the formulae presented is the one of classical vector analysis. We thus find a set of eight equations in eight unknowns, as previously known concerning the traditional MHD equations. 展开更多
关键词 电气力学 等离子体 磁流体力学方程 自一致性 一维流体近似
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Construction of Coherence Identity in Sports: The Case of the "Grand Raid" Running Race in Nature of Reunion Island
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作者 Pascal Duret Muriel Augustini 《Sociology Study》 2011年第2期115-120,共6页
Sportsmen who engage in sports in open natural settings are not always coherent in their behaviors towards environment; in fact, they seldom are. From survey made on a sport event the "Grand Raid 2010", a foot race ... Sportsmen who engage in sports in open natural settings are not always coherent in their behaviors towards environment; in fact, they seldom are. From survey made on a sport event the "Grand Raid 2010", a foot race in mountains of Reunion Island, the authors discover that these sportsmen are not the good activists fighting for a green planet that they imagine they are. The authors try to explain the disparity between the perception that they have of themselves and the reality of their practices. 展开更多
关键词 NATURE SPORTS environmentalist IDENTITY COHERENCE
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Bose Description of Pauli Spin Operators and Related Coherent States
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作者 JIANGNian-Quan FANHong-Yi LUHai-Liang 《Communications in Theoretical Physics》 SCIE CAS CSCD 2005年第1期17-21,共5页
Using both the fermionic-kike and the bosonic-like properties of the Paulispin operators σ_+, σ_-, and σ_z we discuss the derivation of Bose description of the Pauli spinoperators originally proposed by Shigefumi N... Using both the fermionic-kike and the bosonic-like properties of the Paulispin operators σ_+, σ_-, and σ_z we discuss the derivation of Bose description of the Pauli spinoperators originally proposed by Shigefumi Naka, and deduce another new bosonic representation ofPauli operators. The related coherent states, which are nonlinear coherent state and coherent spinstates for two spins, respectively, are constructed. 展开更多
关键词 bose description of pauli spin operators nonlinear coherent state coherentspin state
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On Identical Problems of Natural Convection in Enclosures and Applications of the Identity Character 被引量:3
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作者 Yang, M. Tao, W.Q. +1 位作者 Wang, Q.W. Lui, S.S. 《Journal of Thermal Science》 SCIE EI CAS CSCD 1993年第2期116-125,共10页
In this paper, a concept of 'identical problems' of natural convection in enclosures is presented. A pair of problems of natural convection in enclosures is said to be identical if they look different in appea... In this paper, a concept of 'identical problems' of natural convection in enclosures is presented. A pair of problems of natural convection in enclosures is said to be identical if they look different in appearance but with appropriate selection of coordinates and appropriate definition of dimensionless variables for each problem, they will have identical geometric configurations and identical dimensionless governing equations and related boundary conditions. The identical characteristics of a pair of problems of natural convection in enclosures with an internal isolated island are demonstrated via dimensionless mathematical formulation and flow visualization results. Numerical computations are performed and the predicted streamlines agree with the flow visualization results. A number of other possible pairs of identical problems are also presented. Applications of the identical character are provided and assumptions under which the identical problems may exist are discussed. 展开更多
关键词 natural convection enclosure flow identical problems
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Finite-time adaptive consensus of a class of multi-agent systems 被引量:17
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作者 LIU KeXin WU LuLu +1 位作者 Lü JinHu ZHU HengHui 《Science China(Technological Sciences)》 SCIE EI CAS CSCD 2016年第1期22-32,共11页
Multi-agent systems(MASs) are ubiquitous in natural and artificial systems. This paper aims to establish the finite-time adaptive consensus criterion for a class of MASs with nonlinear dynamics. Traditionally, the fin... Multi-agent systems(MASs) are ubiquitous in natural and artificial systems. This paper aims to establish the finite-time adaptive consensus criterion for a class of MASs with nonlinear dynamics. Traditionally, the finite-time consensus criterion is often established based on the prior information on Lipschitz constants and the eigenvalues of Laplacian matrix. However, it is difficult to acquire the above prior information for most real-world engineering systems. To overcome the above difficulty, this paper develops the finite-time consensus criteria for a class of MASs with nonlinear dynamics via adaptive technique. In detail, we design the finite-time distributed node-based and edge-based adaptive consensus protocols for a class of MASs with fixed and switching topologies. Numerical simulations are also given to validate the proposed finite-time adaptive consensus criterion. 展开更多
关键词 Multi-agent systems adaptive control finite-time consensus switching topology
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Integrated adaptive dynamic surface car-following control for nonholonomic autonomous electric vehicles 被引量:4
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作者 GUO JingHua LUO YuGong LI KeQiang 《Science China(Technological Sciences)》 SCIE EI CAS CSCD 2017年第8期1221-1230,共10页
In this paper,the car-following control problem of nonholonomic autonomous electric vehicles in the curved highway is studied.Owing to the fact that the nonholonomic autonomous electric vehicles have the features of s... In this paper,the car-following control problem of nonholonomic autonomous electric vehicles in the curved highway is studied.Owing to the fact that the nonholonomic autonomous electric vehicles have the features of strong coupling,parametric uncertainties,nonlinearities and external disturbances,a novel integrated adaptive car-following control system is constructed to supervise the longitudinal and lateral motions of vehicles.Firstly,an adaptive fuzzy dynamic surface car-following control strategy is presented to determine a vector of total forces and torque of autonomous electric vehicles,which can guarantee the uniform ultimate boundedness of close-loop control signals.Then,an optimal tire forces distribution law is proposed to dynamically allocate the desired coupled tire longitudinal and lateral forces in real-time.Finally,simulation results illustrate the effectiveness and robustness of the proposed car-following control approach. 展开更多
关键词 autonomous electric vehicles car following adaptive dynamic surface control strong coupling integrated control
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