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近年来,人工自旋冰(Artificial spin ice,ASI)因具有潜在的应用价值以及理论研究价值而倍受关注,成为磁学领域的研究热点之一。以往的研究集中在Square和Kagome两种晶格结构,由于能量势垒和阻挫的大量存在,实验上难以通过退磁等方法达到其内部相互作用决定的能量基态。本文基于Kagome晶格结构提出了一种新的人工自旋冰结构,并基于蒙特卡罗模拟了三种不同的退磁方法对体系能量的影响。结果表明,退磁过程中旋转磁场方向可更有效地降低体系能量,并诱导多种磁结构的出现。 相似文献
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PeneloPET是一种基于PENELOPE的PET专用蒙特卡罗仿真工具.文章介绍了PeneloPET 的主要特点及使用PeneloPET进行PET仿真的一般过程,并以GE Healthcare的双环型eXplore Vista microPET为原型验证了PeneloPET仿真的有效性.仿真结果显示,PeneloPE... 相似文献
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The single beam dose profiles of Leksell Gamma Unit are simulated and the rsults are compared with the experimental results of ELEKTA.The effect of diameter of cylinder souce on the dose profile is also studied and the yielded results show that there are not much difference of the dose profiles between a point source and cylinder source when diameter is less than 1mm. 相似文献
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中子大气传输特性的Monte Carlo 模拟 总被引:2,自引:2,他引:0
用Monte Carlo方法计算了中子通过大气传输到不同高度轨道探测器的中子注量和能谱。研究结果表明:到达不同轨道的中子的能谱结构相同.因此中子能谱的基本结构在大气传输过程中保持不变;在保持能谱基本结构不变的前提下.随中子的传输.其低能中子份额在缓慢增大,高能中子份额在缓慢减小;大气中的中子注量超过了自由空间中相应的中子注量;能谱及注量的研究结果同时证明了中子的大气传输主要受散射机制而不是吸收机制所控制。 相似文献
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低真空中SPIG性能的蒙特卡罗模拟研究 总被引:1,自引:1,他引:0
应用蒙特卡罗技术对低真空中六极离子导向器的性能进行了计算机模拟研究。模拟计算跟踪每个离子的轨迹直至它逃离感兴趣的区域或达到终点。离子在低真空六极射频电场中受到来自电场和剩余气体两方面的作用力,这两个力对离子的运动影响在模拟中分开计算。前者用龙格-库塔方法求解运动微分方程,后者体现为离子与气体分子之间的两体撞,RS模型和MSW模型用于计算碰撞过程。 相似文献
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Jing ZHANG 《等离子体科学和技术》2022,24(2):25401
In this study, we computationally examined the dynamics of dielectric barrier discharge in hydrogen sulfide. The simulations were performed with a 1d3v particle-in-cell/Monte Carlo collision model in which a parallel-plate electrode geometry with dielectrics was used. Particle recombination process is represented in the model. The discharge mode was found to be initially Townsend discharge developing from the cathode to the anode, and at the peak of the current, a more stable glow discharge develops from the anode to the cathode. A higher applied voltage results in sufficient secondary electrons to trigger a second current peak, and then the current amplitude increases. As the frequency is increased, it leads to the advance of the phase and an increase in the amplitude of the current peak. A higher dielectric permittivity also makes the discharge occur earlier and more violently in the gap. 相似文献
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用计算机模拟的方法获得正电子在半导体材料的迁移率,讨论了正电子有效质量,杂质浓度和温度对正电子迁移率的影响。 相似文献
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本文介绍多元分层动态靶溅射的快速Monte Carla模拟程序的计算过程、程序框图以及应用实例。本程序采用二体碰撞近似描述原子间的散射过程,所用作用势为Molière近似的Thomas-Fermi势。在相同计算精度下,该程序的计算时间约为原程序的一半。该程序可用于计算几百eVkeV离子轰击多元无定型靶的溅射产额,给出溅射能谱、角分布及深度来源分布等计算结果。 相似文献
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Yoshiko Miyagawa Soji Miyagawa 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2002,190(1-4):256-260
In the surface analysis methods such as X-ray photoelectron spectroscopy, Auger electron spectroscopy, or secondary-ion mass spectroscopy, sputtering processes are used for depth profiling. However, ion beam bombardment changes the surface composition and the surface structure, which deteriorates the accuracy of the surface analysis and the depth resolution. We studied the preferential sputtering in some materials consisting of two components with different mass ratio by using the dynamic Monte Carlo simulation. Dose dependence of the depth profile of composition is presented. By Ar sputtering, the surface compositions of Au0.25Cu0.75, Au0.67Al0.33, and Ni0.5Cu0.5 alloys changed to Au0.28Cu0.72, Au0.76Al0.24, and Ni0.67Cu0.33, respectively. These results agreed with the experimental data. In order to compare the effect of mass ratio on the preferential sputtering, B–C, Si–C, and W–C systems were investigated. In B–C system, preferential sputtering by 1 and 3 keV Ar ion was negligible. In W–C system, a significant preferential sputtering occurred. In Si–C system, carbon was enriched in the outermost surface layer at a fluence lower than 3×1016 ions/cm2. At higher fluence, the partiality in concentration recovers because of the balance between the enrichment and the preferential sputtering. 相似文献
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The electron swarm parameters of SF6/N2 are calculated in the present study using an improved Monte Carlo collision simulation method (MCS). And some improved sampling techniques are also adopted. The simulation results show that the improved simulation method can provide more accurate results. 相似文献
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爆炸物检测中的模拟计算 总被引:1,自引:1,他引:0
为优化基于伴随α粒子技术的爆炸物检测系统中的γ探测器和数据分析软件,利用蒙特卡罗程序EGSnrc对γ探测器的探测效率和能量响应分别进行了模拟。NaI(Tl)、BGO等几种无机闪烁体γ探测器探测效率的模拟计算结果为探测器的优化选择提供依据;对碳、氧单质元素、硝酸氨、模拟炸药样品在14MeV中子作用下的特征γ射线,在Φ5″×8″NaI(Tl)探测器的能量响应模拟计算结果进行了分析,并与实验测量能量响应进行了比较。结果表明,模拟方法可靠,应用该方法可对其他的单质材料来进行响应计算以建立响应函数数据库。 相似文献
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康普顿背散射成像的蒙特卡罗模拟 总被引:5,自引:0,他引:5
康普顿背散射成像是利用康普顿效应判断被照射物体内部结构的方法,广泛应用于工业和医学诊断领域。介绍应用MCNP程序模拟康普顿背散城像的问题,计算了250keV电子轰击钨靶产生的X射线潜为源的X射线检测碳和铁的康普顿背散射光子角分布,得到这两种物质的不同散射特性。 相似文献
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伽玛刀体模剂量分布的Monte Carlo模拟 总被引:1,自引:1,他引:0
运用Monte Carlo方法模拟了伽玛刀Leksell gamma unit在体模中的吸收剂量的分布,计算结果与实验结果基本相符。 相似文献
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矿石品位仪主要利用电子对湮灭效应测量较高原子序数金属的含量多少,影响矿石品位仪测量效果和精度的因素有很多。本文主要利用蒙特卡罗模拟方法分析伽玛探测器安装位置对矿石品位仪测量效果的影响,并比较了Ra-226和Co-60两种伽玛放射源应用到矿石品位仪的测量效果差异。 相似文献
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运用蒙特卡罗方法计算出特殊形状钚材料近距离的中子的能谱、空间分布,避免了用仪器近距离测量的精度受仪器体积影响较大的不足。同时利用注量-剂量转换因子算出近距离中子剂量,为工作人员的安全提供参考。 相似文献
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Raffaele Bencardino Josef Uher 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2010,268(5):513-518
An approach is described for efficiently modelling delayed activation analysis experiments, where radioactivity is induced in a sample through irradiation with neutrons or gamma-rays and subsequently measured by a separate detection system. The continuous single-history method is used, in which a single computer code tracks both the initial irradiation quantum and the decay products of any induced radioactive nuclei in a single event using Monte Carlo methods. Key aspects of the approach include the forcing of both the irradiation and decay processes to improve efficiency and the ability to simulate complex radioactive decays producing multiple, coincident decay products. The method has been implemented in the general-purpose EGSnrc code. A comparison with experimental results for the photoactivation of a gold foil is presented. 相似文献
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