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Radiophysics and Quantum Electronics - It is demonstrated that Maxwell’s equations permit the existence of invisible spherical objects made of materials with isotropic electromagnetic... 相似文献
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基于SPH方法的瞬态粘弹性流体的数值模拟 总被引:1,自引:1,他引:1
运用SPH(Smoothed Particle Hydrodynamics)方法模拟基于Oldroyd-B模型的平面突然起动Couette流,通过数值解与解析解的比较,验证SPH方法模拟瞬态粘弹性流动的准确性;且对基于Oldroyd-B模型的方腔驱动流进行SPH模拟.采用一种新的固壁边界处理方法,有效地防止了粒子穿透,提高数值计算的准确性.用数值算例验证SPH方法对粘弹性流体模拟的有效性和稳定性. 相似文献
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Technical Physics - Electrodynamic characteristics of the L-and C-range horn antennas made of carbon-composite materials with graphene-containing binding substance are studied. The main attention... 相似文献
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Numerical Study on Left-Handed Materials Made of Ferrite and Metallic Wires 总被引:1,自引:0,他引:1
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Due to coupling effect, we show that it is difficult to realize the left-handed material by placing metallic wires directly into a ferrite matrix. However by introducing an insulating material round the metallic wires to decouple the direct interaction between the metallic wire and ferrite matrix, we have proposed two microstructures, which are shown by numerical simulation to have negative refractive indexes. The influence of microstructure on the transmission property is also examined. 相似文献
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Baoqing Zeng Ning Liu Zhonghai Yang 《International Journal of Infrared and Millimeter Waves》2004,25(11):1621-1631
Vacuum microelectronic triode performance, based upon a unit cell with a nanotube field emitter, gate, and anode, was evaluated via computer simulation. Electron emission was calculated from the modified Fowler-Nordheim equation. The dependence of emitted current, upon geometrical factors, e.g., nanotube radius, nanotube height, and gate's hole radius, is shown. The device design parameters of trans-conductance, and cutoff frequency have been calculated, which show that this structure can be used as a microwave and millimeter wave amplifier. Electron current flux is shown for time-dependent 1–Thz sinusoidal variation frequency input. 相似文献
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Technical Physics - A novel method of studying mass transfer processes in porous media has been considered. The method allows one to carry out operation monitoring of the diffusivity in thin... 相似文献
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根据初级像差理论广泛研究了由左手性介质构造的平板透镜系统的赛德尔像差特性.由初级像差加和定理推导了适合于这种系统的赛德尔和数公式,并指出了寻找消赛德尔像差的平板透镜系统的方法.作为两个特例,分别讨论了消赛德尔像差的左手性介质单透镜和双胶合透镜系统. 相似文献
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通过Keggin结构稀土硅钨杂多配合物K13[Ln(SiW11O39)2] (其中Ln=La,Ce,Pr,Nd,Sm,简写为Ln(SiW11)2)与碘化(E)-N-甲基-4-(2-(4-二甲氨基苯基)乙烯基)吡啶(C16H19N2I,AI)反应,制备了一系列含轻稀土元素的硅钨杂多配合物与半菁衍生物的复合材料。应用元素分析和TG-DTA确定配合物的组成为(C16H19N2)10K3[Ln(SiW11O39)2]。利用红外光谱、紫外-可见光谱和荧光光谱研究了上述复合材料的光学性质及复合材料中无机组分与有机组分间的相互作用。 相似文献
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Russian Physics Journal - The determination of the elastic wave propagation velocity using ultrasonic methods for a calculation of the elastic constants imposes constraints on the geometry of... 相似文献
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设计了一种左手材料复合双棱镜,由两块各向同性左手材料棱镜与夹在其间的、其界面与光轴成一定的角度的单轴各向异性左手材料平板构成.研究了发生在其内部界面上的古斯-汉森位移.分析了发生折射的条件和古斯-汉森位移的符号.研究发现,反射波与透射波有相同的古斯-汉森位移,透射波的古斯-汉森位移随着薄层厚度的增加而振荡,整体上呈增加趋势;在透射共振点,透射波的古斯-汉森位移达到极大值,且极大值可达入射波波长的数十倍;发现入射角和光轴与界面的角度对透射波的古斯-汉森位移有很大影响.最后简单地探讨了这种双棱镜的潜在应用. 相似文献
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左手介质椭圆光波导基模传播特性 总被引:1,自引:0,他引:1
在椭圆柱坐标系中,采用分离变量方法,得出了左手介质椭圆光波导本征方程的近似解,通过数值计算,分析了椭圆波导偏心率、左手介质的电容率、磁导率对椭圆光波导基模传播特性的影响,并将左介质光波导与右手介质光波导基模特性进行对比,得出左手介质光波导的基模特性与右手介质光波导基模特性差别不大的结论. 相似文献
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能量选择系统是医用质子回旋加速器放疗系统中极其重要的部件,主要用来调节质子束能量,使得从加速器出来的质子束能量满足临床治疗计划的要求。能量选择系统的核心部件是降能器,目前降能器大多采用石墨作为降能材料。近些年提出用铍或者碳化硼替代石墨作为降能器材料的设想,以期望提高质子束流的传输效率。利用蒙特卡罗软件TOPAS模拟200 MeV质子在石墨、铍和碳化硼三种不同材料多楔形结构降能器中的输运过程,统计了穿过降能器后质子以及产生的次级中子的能量通量,并计算了质子束流在穿过不同降能器后的能量分散,据此得到了三种材料降能器厚度与质子能量之间的关系曲线,同时也分析了不同降能器对质子束传输效率的影响以及次级中子产额的情况。通过对比发现,三种材料降能器对束流的能量发散效果相当,而使用铍或者碳化硼都能提高束流传输效率,尤其铍降能器的性能较优。但铍和碳化硼与质子相互作用会产生更多的次级中子,因此在实际应用时需要更多地考虑次级中子对设备的辐射防护。Energy selection system (ESS) is an important component for medical proton cyclotron system. It has been widely used to modulate the proton energy in accordance with treatment requirements. ESS consists of the energy degrader which was mostly made of graphite. Recent years, to improve the transmission efficiency of the proton beams, beryllium and boron carbide have been proposed to substitute the graphite. In this work, the Monte Carlo code, TOPAS, was used to simulate the transport process of 200 MeV proton beams traversing the multi-wedge energy degrader made of graphite, beryllium and boron carbide, respectively. Energy fluxes of the protons and secondary neutrons after degrader, as well as the energy dispersion of the degraded proton beams, were calculated. It is found that the energy dissipation effect is nearly identical for all three kinds of degrader material, but using the beryllium or even boron carbide can improve the proton transmission efficiency. However, more secondary neutrons would be produced when proton beams interact with the beryllium and boron carbide, suggesting the need of additional consideration for radiation shielding to devices. 相似文献
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The scattering diagram of a stock index results in a complex network structure, which can be used to analyze the viscoelastic properties of the index. The change along x- or y-direction of the diagram corresponds to purely elastic (or spring like) movement whereas the diagonal change at an angle of 45° corresponds to purely viscous (or dashpot like) movement. The viscous component pushes the price from its current value to any other value, while the elastic component acts like a restoring force. Four indices, namely, DJI, S&P-500, NASDAQ-100, and NASDAQ-composite were studied for the period of 2001-2009. NASDAQ-composite displayed very high elasticity while NASDAQ-100 displayed the highest fluidity in the time period considered. The fluidity of DJI and S&P-500 came out to be close to each other, and they are almost the same in the second half of the period. 相似文献
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