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�����ܲٚ����쳣�����£��Ž������� 《核聚变与等离子体物理》2018,38(2):221-227
介绍了质子治疗加速器输运部二极磁铁电流源的技术要求、主电路拓扑。该电源要求输出电流精度为25ppm,纹波小于25ppm。电源输出电流纹波由低频纹波和高频纹波组成。对电源输出电流纹波的形成机理进行了详细的理论分析和数学计算。得出了基于冲量控制原理的脉冲宽度调制(PWM)电流跟踪控制技术可以有效消除输入低频纹波对输出电流的影响。同时也对输出电流高频纹波采用两种方法进行了定量的数学分析,并得出量化的结论和计算公式。借助AnsoftSimplorer电路仿真软件构建模型,验证了纹波规律结论及计算公式的准确性,并且提出了相应的纹波抑制策略。 相似文献
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Y. DengG.P. Zhao L. ChenH.W. Zhang X.L. Zhou 《Journal of magnetism and magnetic materials》2011,323(5):535-538
The reduced exchange coupling has been incorporated in our micromagnetic calculations for the hysteresis loops of Nd2Fe14B/α-Fe and Sm40Fe60/Ni80Fe20 multilayers. Analysis shows that nucleation and pinning fields are sensitive to the value of the interface coupling constant Ji when the soft layer thickness Ls is small. Hysteresis loops have been obtained for a trilayer system with a soft α-Fe sandwiched between two Nd2Fe14B layers for different values of Ls and Ji. As Ji decreases, nucleation field decreases while the pinning field increases. In the meantime, the squareness of the loops is deteriorated, which results in smaller energy product. For thick soft layer the coercivity mechanism transforms from pinning to nucleation as the interface coupling decreases, and vice versa. The above calculations have been extended to a Sm40Fe60/Ni80Fe20 bilayer and compared with available experimental data. The theoretical loop is consistent with the experimental one when the value of Ji is taken as 10% of the bulk one, demonstrating that the interface coupling in the experiment is far away from perfect coupling. 相似文献
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Quanliang CaoXiaotao Han Liang Li 《Journal of magnetism and magnetic materials》2011,323(15):1919-1924
Deep magnetic capture and clinical application are the current trends for magnetic targeted drug delivery system. More promising and possible strategies are needed to overcome the current limitations and further improve the magnetic targeting technique. Recent advances in the development of targeting magnet system show promise in progressing this technology from the laboratory to the clinic. Starting from well-known basic concepts, current limitations of magnetic targeted drug delivery system are analyzed. Meanwhile, the design concepts and evaluations of some effective improvements in magnet system are discussed and reviewed with reference to (i) reasonable design of magnet system; (ii) control modes of magnet system used to generate dynamical magnetic fields; and (iii) magnetic field driving types. 相似文献
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通过理论分析结合计算机仿真试验剖析了磁共振成像(MRI)中梯度场线性对图像质量影响的原理,在梯度场线性有缺陷的情况下,用实例和计算机模拟直观的展示了重建图像和模拟结果. 结合研发实践发现,在永磁微小口径、低场强用于鼠类等小动物成像情况下,对梯度场线性度的要求远高于文献中提出的指标. 依靠软件改进,图像没有本质的提高,尝试补偿技术耗时费力效果也不理想. 说明了对永磁微小口径成像仪研发线性度更好的梯度线圈是提高图像质量的关键技术之一. 揭示了在理想条件下普适的理论原理,在不同的实践条件下有不同的趋近理想条件要求. 将具有独立知识产权的高线性梯度线圈安装在自行研制的仪器上得到了较好的图像. 相似文献
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García-Naranjo JC Mastikhin IV Colpitts BG Balcom BJ 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2010,207(2):337-344
Unilateral magnetic resonance (UMR) has become, in different research areas, a powerful tool to interrogate samples of arbitrary size. Numerous designs have been suggested in the literature to produce the desired magnetic field distributions, including designs which feature constant magnetic field gradients suitable for diffusion and profiling experiments. This work presents a new approach which features extended constant magnetic field gradients with a three magnet array. Constant gradients of more than 3cm extent can be achieved in a very simple, compact and safe design. Diffusion measurements from different positions over the magnet are presented in addition to practical applications for reservoir core plug characterization. The idea of a solenoid as a probe for specific measurements in UMR is introduced. Simple profiling experiments are also presented. 相似文献
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随着超导技术和制冷技术的相互促进和共同发展 ,制冷机直接冷却的超导磁体系统已从概念设计走向实际应用。电流源保护控制系统是超导磁体系统的重要组成部分 ,其主要作用是为超导磁体系统提供稳定电流并实现可靠的保护控制。文中首先分析了制冷机冷却型超导磁体系统用电流源的工作过程及其特殊的控制和保护要求 ,然后设计了一个以单片机为核心的自动保护控制系统。 相似文献
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Dr. Xin-Da Huang Xiu-Fang Ma Prof. Dr. Li-Min Zheng 《Angewandte Chemie (International ed. in English)》2023,62(15):e202300088
Photo-responsive lanthanide-based single-molecule magnets (SMM) hold great promise for future switching and memory devices. Herein, we report a dysprosium phosphonate [DyIII(SCN)2(NO3)(depma)2(4-hpy)2] ( 1Dy ), which features a supramolecular framework containing layers of hydrogen-bonding network and pillars of π–π interacted anthracene units. The photocycloaddition reaction of anthracene pairs led to a rapid and reversible single-crystal-to-single-crystal (SC–SC) structural transition to form the 1D coordination polymer [DyIII(SCN)2(NO3)(depma2)(4-hpy)2]n ( 2Dy ), accompanied by photoswitchable SMM properties with the reduction of effective energy barrier by half and the narrowing of the butterfly-like hysteresis loop. The diluted sample showed a photo-induced switch of the blocking temperature (TB) from 3.8 K for 1Dy@Y to 2.6 K for 2Dy@Y . This work may inspire the construction of lanthanide-based molecular materials with targeted photo-responsive magnetic properties. 相似文献
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EAST���弰��������ϵͳ��� 总被引:1,自引:1,他引:0
EAST运行中的温度改变会导致磁体及冷屏产生形变和位移。为了测量此位移的变化,利用一个延长臂,把位移转移到较易测量的位置,然后采用直滑式电位器把位移变化转换成电压变化并测量出其值,最终转换成位移的变化值。该测量系统解决了EAST装置中磁体和冷屏位移测量的难题。 相似文献