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1.
王超  王秋良 《低温物理学报》2005,27(Z1):989-994
遗传算法是一种行之有效的优化算法,具有很强的自适应性、鲁棒性和全局搜索能力,但其亦存在着未成熟收敛及进化缓慢等问题.为提高遗传算法的寻优性能并考虑到磁体工程实际问题,本文对遗传算法作了改进,并与局部优化算法序列二次规划算法相结合形成一种优势互补的混合算法,并将其应用于3.2T传导冷却Bi系高温超导磁体的优化设计中,取得了良好效果.  相似文献   

2.
遗传算法具有很强的自适应性、鲁棒性和全局搜索能力,但其局部搜索能力相对较弱,计算后期易出现进化缓慢、过早收敛等问题,蚁群算法是近几年迅速发展起来的一种新的全局优化算法,具有正反馈机制,但是计算初期由于信息素差别小,初始收敛速度较慢.本文将这两种优化方法结合起来,充分发挥各自的优势,形成了遗传-蚁群混合算法,并选用测试函数对算法的优化性能作了对比计算,最后以高温超导匀场磁体为实际应用目标,以绕制磁体所用超导带长度为目标函数对磁体结构进行优化设计,优化方案比原始方案节省7.32%的超导带材用量.  相似文献   

3.
冯忠奎  胡格丽  许莹  朱光  周峰  戴银明  王秋良 《物理学报》2013,62(23):230701-230701
本文发展了开放式自屏蔽全身成像高场超导磁共振成像(MRI)磁体的优化设计方法,使设计出来的磁体仅有4 对超导线圈. 这种开放结构的超导MRI磁体优化设计方法集成了线性规划算法和遗传算法. 通过迭代线性规划算法可以在考虑成像区域(DSV)磁感应强度约束、磁场不均匀度约束、5 Gs线范围约束、线圈区域最大磁场值约束和最大环向应力约束的条件下,获得用线量最少的线圈初始形状和位置,同时可以得到每个线圈的层数和每层匝数;通过遗传算法可以提高DSV区域的磁场不均匀度,以达到高质量成像的要求. 这种集成的优化设计方法既可以灵活有效的设计开放式MRI磁体,也可以设计传统的圆柱形MRI磁体,本文通过一个1.2 T的开放式MRI磁体的设计清楚的展示了这种优化方法. 关键词: 线性规划算法 遗传算法 自屏蔽 开放式超导MRI磁体  相似文献   

4.
磁体结构的好坏将直接关系到磁体的制造成本以及磁体能否正常运行.在磁体结构的优化设计中,选定磁体的体积为目标函数,在满足磁体储能,符合超导材料的B~J特性,尽量减小漏磁等条件下,使目标函数达到最小.文章选定新一带超导涂层导体Ⅵ瑚为SMES线圈的制造材料,分析了Y系带材的材料特性,并采用大型有限元仿真软件ANSYS和磁体优化中常用的算法-模拟退火算法(simulated annealing)对SMES线圈进行优化仿真分析.得出最优的磁体结构.  相似文献   

5.
螺管线圈具有结构简单,材料利用率高等优点,是一种应用较为广泛的磁体结构.但单螺管线圈也具有漏磁较大,均匀度不高的缺点.针对螺管线圈的基本特征,包括磁场强度、磁场分布、磁体的内半径、磁体的漏磁等,本文利用数值计算的方法对高温超导螺管磁体结构进行了优化.在结构优化过程中,文中采用全局搜索能力较强的遗传算法和局部搜索能力较强的非线性规划算法相结合的非线性遗传算法进行优化,使超导磁体在满足一定约束条件的情况下达到最少的超导带材用量,以节约磁体的制造成本.同时比较分析了结构优化前后超导磁体的DSV(diameter spherical volume)区域的均匀度和杂散场分布.  相似文献   

6.
单边磁共振成像(MRI)系统由于其良好的开放性引起了越来越多的关注,这种系统的成像样品区位于磁体外侧,其形状为薄片形,其磁体结构设计是一个全新的问题. 本文基于鞍点理论,探索这种单边磁体在其外侧产生均匀样品区的可行性,通过对几种单边磁体结构磁场特性的研究,指出适当设计的永磁磁体能够在磁体外侧产生鞍点. 最后给出一种符合成像要求的单边永磁MRI磁体结构. 单边MRI磁体结构的可行性分析及磁体结构的成功设计,为开展完全开放式磁共振成像装置的研究打下了坚实的基础.  相似文献   

7.
基于遗传算法和分布式计算的气动优化设计   总被引:3,自引:1,他引:2  
詹浩  白俊强  段卓毅  华俊 《计算物理》2004,21(4):359-362
采用求解NS方程作为气动优化设计的CFD分析方法,为了提高基于遗传算法的气动优化设计的效率,发展了一种基于分布式并行计算的混合遗传算法,并应用该方法进行了气动优化设计.设计实践表明,该方法是可行的,且由于采用了混合遗传算法和分布式并行计算而提高了优化的质量和效率.  相似文献   

8.
本文提出一种基于0-1整数线性规划的自屏蔽磁共振成像(MRI)超导磁体设计方法.在磁体线圈可行载流区内按照所用线材尺寸划分网格,同时综合考虑线材内最大磁感应强度、成像区磁场均匀度、漏场范围等设计要求,以超导线材使用量最小为目标函数,采用0—1整数线性规划算法得到磁体线圈的初始导线集中区块分布;然后通过合理的调整限制各分离导线区块截面尺寸及其中心位置,得到最终易于实际加工和绕制的矩形磁体线圈结构.并根据不同的约束要求,该方法也适用于其他结构超导磁体的优化设计.文中最后给出一个设计实例.  相似文献   

9.
本文针对使用YBCO带材的螺线管型SMES,使用Ansoft Maxwell建立了其电磁模型.考虑到YBCO带材临界电流的各向异性,利用Ansoft Maxwell场计算器建立了与线材呈40°角的最大磁场强度的函数.实现了YBCO磁体临界电流、实际运行电流及实际储能容量的快速准确的计算.变换了磁体形状变量空间,并利用参数化计算缩小搜索范围,以缩短优化算法的收敛时间.基于以上工作,结合Ansoft Maxwell提供的遗传算法优化工具,实现了对100KJ螺线管型超导磁体的设计,并对优化计算结果进行了分析.  相似文献   

10.
磁共振成像(MRI)中的磁体系统是MRI整体装置的主体,而主磁体作为磁体系统的核心,为整个磁体系统提供基础磁场。其磁场位型、均匀性直接关系到磁体系统其它组件的设计以及最终的性能。文中提出一种利用ANSYS中的概率设计——Monte Carlo进行主磁体优化的设计方法,使得中心场区的磁场偏差从几千ppm降低到120 ppm左右。达到设计的目的.  相似文献   

11.
Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.  相似文献   

12.
A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.  相似文献   

13.
A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.  相似文献   

14.
The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.  相似文献   

15.
Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·104 Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.  相似文献   

16.
17.
A transient suppression method for piezoelectric ceramic transducer is presented. By adding some special pedestal pulses to the original transmitted signal, the transient effects in the output of the transducer can be just precisely transmission by use of a narrowband transducer. canceled, thereby achieving the broadband The experimental results show that the transient responses of the sinusoid pulses and coded signals are suppressed successfully and the acoustic waveforms radiated into the surrounding water are improved significantly.  相似文献   

18.
We experimentally demonstrate amplitude squeezed soliton utilizing intensity-dependent self-phase modulation in an asymmetric Sagnac interferometer.The system.whose components are connected via ferrule connector/physical connection(FC/PC)fiber connectors,constitutes all-fiber configuration to generate squeezed soliton.Soliton amplitude reduction measured by homodyne detection is near 4.0 dB below the shot-noise level.Optimal squeezing fields in both simple and compact all-fiber configuration are obtained.  相似文献   

19.
The(2 1)-dimensional nonlinear Schr(o)dinger(NLS)equation with spatially inhomogeneous nonlinearities is investigated,which describes propagation of light in(2 1)-dimensional nonlinear optical media with inhomogeneous nonlinearities.New types of optical modes and nonlinear effects in optical media are presented numerically.The results reveal that the regular split of beam can be obtained in (2 1)-dimensional nonlinear optical media with inhomogeneous nonlinearities,by adjusting the guiding parameter.Furthermore,the stability of beam regular split is discussed numerically,and the results reveal that the beam regular split is stable to the finite initial perturbations.  相似文献   

20.
In the real-world application of face recognition system, owing to the difficulties of collecting samples or storage space of systems, only one sample image per person is stored in the system, which is so-called one sample per person problem. Moreover, pose and illumination have impact on recognition performance. We propose a novel pose and illumination robust algorithm for face recognition with a single training image per person to solve the above limitations. Experimental results show that the proposed algorithm is an efficient and practical approach for face recognition.  相似文献   

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