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The mechanism of scroll wave turbulence is investigated in excitable media with rotational anisotropy. We adopt the Barkley model with heterogeneity in the diffusion constants. Through comparative numerical studies, we demonstrate the vortex turbulence results from the rotational anisotropy's cooperation with negative filament tension or competition with positive filament tension. The presence of rotational anisotropy can enlarge the parameter region leading to negative-tension induced wave turbulence in isotropic media. 相似文献
83.
Simulation of dielectric resonator for high-Tc radio frequency superconducting quantum interference device 下载免费PDF全文
Nowadays, the high-critical-temperature radio frequency
superconducting quantum interference device (high-$T_{\rm c }$ rf
SQUID) is usually coupled to a dielectric resonator that is a
standard $10\times 10\times 1$~mm3 SrTiO$3 (STO) substrate
with a YBa2Cu$3O$_{7 - \delta }$ (YBCO) thin-film flux
focuser deposited on it. Recently, we have simulated a dielectric
resonator for the high-$T_{\rm c }$ rf SQUID by using the ANSOFT High
Frequency Structure Simulator (ANSOFT HFSS). We simulate the
resonant frequency and the quality factor of our dielectric
resonator when it is unloaded or matches a 50-$\Omega$ impedance.
The simulation results are quite close to the practical
measurements. Our study shows that ANSOFT HFSS is quite suitable for
simulating the dielectric resonator used for the high-$Tc rf
SQUID. Therefore, we think the ANSOFT HFSS can be very helpful
for investigating the characteristics of dielectric resonators for
high-$Tc rf SQUIDs. 相似文献
84.
实验研究并分析了调Q Nd:YAG 脉冲激光诱导光纤损伤特性.设计了在真空条件下全石英光纤传输1064 nm 脉冲激光实验.通过将激光注入光纤端面气压降低到10—100 Pa, 光纤端面击穿阈值提高到大气环境下的185 倍.结合光纤端面损伤形貌分析可知,光纤端面损伤主要是由于激光驻波场和烧蚀共同作用的结果,光纤端面或内部大量的缺陷降低了光纤抗激光损伤的能力.在真空条件下由于光纤端面光学击穿阈值的提高,激光诱导光纤损伤特性又表现出了另外一种损伤模式——光纤初始输入段损伤.它发生在光纤输入段附
关键词:
激光损伤
光束传输
真空
石英光纤 相似文献
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高速目标再入大气层或在临近空间飞行时,空气电离形成的等离子体鞘套和尾迹对目标的雷达散射特性会产生影响.为了研究不同模型尾迹流场及其电磁散射特性规律和相似性,以氧化铝球模型为研究对象,在弹道靶设备上开展了双尺度参数相同的条件下高速球模型尾迹流场及其电磁散射相似性实验研究.由二级轻气炮发射模型,模型直径分别为8.0、10.0、12.0、15.0 mm,速度约6 km/s,靶室压力分别为6.3,5.0,4.2,3.3 k Pa,采用阴影照相系统测量模型激波脱体距离、电子密度测量系统测量模型尾迹的电子密度分布、X波段单站雷达系统测量在视角为40?的模型及流场的雷达散射截面(RCS)分布.实验结果表明:在速度不变、双尺度参数相同的条件下,随着模型尺寸的增加,激波脱体距离逐渐增加,激波脱体距离与模型直径之比近似相同;不同模型尾迹电子密度测量曲线的趋势和数量级一致,表明不同模型的尾迹流场适用于双缩尺律;不同尺寸模型尾迹的总体RCS与分布RCS均不相同,表明不同模型尾迹的电磁散射不适用于二元缩尺律;高速球模型全目标电磁散射能量分布在模型及其绕流区域、等离子体尾迹区域;高速球模型全目标电磁散射能量在模型及绕流场区域出现1个强散射中心,在模型湍流尾迹区域出现多个散射中心;高速球模型尾迹的RCS测量信号呈现随机性分布特性,幅度脉动和频率脉动均没有周期性;随着模型尺寸的增加,模型尾迹的总体RCS增加,尾迹脉动频率的变化范围减小. 相似文献
87.
The forward and inverse problem of cardiac magnetic fields based on concentric ellipsoid torso-heart model 下载免费PDF全文
<正>This paper constructs a concentric ellipsoid torso-heart model by boundary element method and investigates the impacts of model structures on the cardiac magnetic fields generated by both equivalent primary source—a current dipole and volume currents.Then by using the simulated magnetic fields based on the torso-heart model as input,the cardiac current sources—an array of current dipoles by optimal constrained linear inverse method are constructed.Next, the current dipole array reconstruction considering boundaries are compared with that in an unbounded homogeneous medium.Furthermore,the influence of random noise on reconstruction is also considered and the reconstructing effect is judged by several reconstructing parameters. 相似文献
88.
超高速碰撞微波辐射强度测量 总被引:3,自引:0,他引:3
针对超高速碰撞物理现象研究需要,为了确认超高速碰撞过程中的电磁辐射信号能作为超高速碰撞产生的可探测物理量之一,利用研制的8 mm微波辐射计在中国空气动力研究与发展中心FD-18A超高速碰撞靶开展了超高速碰撞过程中的微波辐射强度测量初步试验研究。对试验测量方案进行了介绍,获得了弹丸超高速撞击半无限铝靶和半无限铜靶时产生的微波辐射强度测量试验结果。弹丸为直径5 mm 的LY12铝球,撞击速度1.98~4.3 km/s,撞击角为0°,结果表明:在本试验条件下,超高速碰撞产生了明显的微波辐射强度,材料的不同导致碰撞过程中产生的微波辐射强度差别较大。 相似文献
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It is widely accepted that the heart current source can be reduced into a current multipole. By adopting three linear inverse methods, the cardiac magnetic imaging is achieved in this article based on the current multipole model expanded to the first order terms. This magnetic imaging is realized in a reconstruction plane in the centre of human heart, where the current dipole array is employed to represent realistic cardiac current distribution. The current multipole as testing source generates magnetic fields in the measuring plane, serving as inputs of cardiac magnetic inverse problem. In the heart-torso model constructed by boundary element method, the current multipole magnetic field distribution is compared with that in the homogeneous infinite space, and also with the single current dipole magnetic field distribution. Then the minimum-norm least-squares (MNLS) method, the optimal weighted pseudoinverse method (OWPIM), and the optimal constrained linear inverse method (OCLIM) are selected as the algorithms for inverse computation based on current multipole model innovatively, and the imaging effects of these three inverse methods are compared. Besides, two reconstructing parameters, residual and mean residual, are also discussed, and their trends under MNLS, OWPIM and OCLIM each as a function of SNR are obtained and compared. 相似文献