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1.
螺旋波在不同的物理、化学和生物系统中普遍存在.周期外场,比如极化电场,尤其是具有旋转对称性的圆极化电场可对螺旋波动力学产生重要影响.本文综述了极化电场对可激发介质中螺旋波的控制,包括共振漂移、同步、手征对称性破缺、多臂螺旋波的稳定、次激发介质中的螺旋波、三维回卷波湍流态的控制、心脏组织中螺旋波的去钉扎、心脏组织中螺旋波湍流态的控制等.  相似文献   

2.
Evolution of spiral wave generated from the excitable media within the Barkley model is investigated. The external gradient electric field modulated by the logistic map is imposed on the media (along x- and y-axis). Drift and break up of spiral wave are observed when the amplitude of the electric field is modulated by the chaotic signal from the logistic map, and the whole system could become homogeneous finally and the relevant results are compared when the gradient electric field is modulated by the Lorenz or Rossler chaotic signal.  相似文献   

3.
马军  应和平  李延龙 《中国物理》2007,16(4):955-961
In this paper, an intermittent local electric shock scheme is proposed to suppress stable spiral waves in the Barkley model by a weak electric shock (about 0.4 to 0.7) imposed on a random selected n × n grids (n =1 - 5, compared with the original 256×256 lattice) and monitored synchronically the evolutions of the activator on the grids as the sampled signal of the activator steps out a given threshold (i.e., the electric shock works on the n ~ n grids if the activator u ≤ 0.4 or u ≥ 0.8). The numerical simulations show that a breakup of spiral is observed in the media state evolution to finally obtain homogeneous states if the electric shock with appropriate intensity is imposed.  相似文献   

4.
螺旋线型微秒级高压长脉冲产生器数值模拟   总被引:1,自引:1,他引:0       下载免费PDF全文
 探索了采用CST软件和PSpice软件进行加速器场分布数值模拟的方法,利用该方法可方便地获取设备内部动态场分布图及动态电压变化规律。针对螺旋线型μs级高压长脉冲产生器系统建立了数值模拟模型,给出了详细的模拟步骤及结果。分析表明,利用场分布模拟方法获取的电压变化规律与电路模拟方法获取的结果是一致的。基于CST模拟方法,可以给出螺旋线及主开关等电气结构的瞬态电场分布,场强增强点主要出现在螺旋带的外沿及金属电极连接处,在介质支撑内部也有较高的场强分布。  相似文献   

5.
荧光光谱法研究低频脉冲电场对胰岛素分子的作用   总被引:2,自引:0,他引:2  
胰岛素作为一种胞间信号分子,对于生命信息的传递起着极为重要的作用。探讨低频脉冲电场对胰岛素分子的作用,对于从细胞信号系统的角度来解释生物电磁效应有着十分重要的意义。在实验中,对照组和场暴露组之间荧光峰值强度的差别表明了低频脉冲电场改变了胰岛素分子的构象,低频脉冲电场可能通过破坏胰岛素分子氢键和重新形成某些氢键来改变它的构象。本文结果表明胞间信号分子也是低频电磁场作用的一个重要靶体。  相似文献   

6.
马军  易鸣  李炳伟  李延龙 《中国物理 B》2008,17(7):2438-2445
In this paper, the evolution of the pattern transition induced by the vortical electric field (VEF) is investigated. Firstly, a scheme is suggested to generate the VEF by changing the spatial magnetic field. Secondly, the VEF is imposed on the whole medium, and the evolutions of the spiral wave and the spatiotemporal chaos are investigated by using the numerical simulation. The result confirms that the drift and the breakup of the spiral wave and the new net-like pattern are observed when different polarized fields are imposed on the whole medium respectively. Finally, the pattern transition induced by the polarized field is discussed theoretically.  相似文献   

7.
Complete analysis of the properties of breathers in spiral multiferroic structures in the sine-Gordon model has been presented. The methods of the excitation and detection of the breathers in the external electric and magnetic fields have been discussed.  相似文献   

8.
We present a precise measurement of a weak radio frequency electric field with a frequency of ■3 GHz employing a resonant atomic probe that is constituted with a Rydberg cascade three-level atom, including a cesium ground state |6S(1/2)〉,an excited state |6P(3/2)〉, and Rydberg state |nD(5/2)〉. Two radio frequency(RF) electric fields, noted as local and signal fields, couple the nearby Rydberg transition. The two-photon resonant Rydberg electromagnetically induced transparency(Rydberg-EIT) is employed to directly read out the weak signal field having hundreds of k Hz difference between the local and signal fields that is encoded in the resonant microwave-dressed Rydberg atoms. The minimum detectable signal fields of ESmin= 1.36 ± 0.04 mV/m for 2.18 GHz coupling |68D(5/2)〉→ |69P(3/2)〉 transition and 1.33 ± 0.02 mV/m for 1.32 GHz coupling |80D(5/2)〉→ |81P(3/2)〉 transition are obtained, respectively. The bandwidth dependence is also investigated by varying the signal field frequency and corresponding -3 dB bandwidth of 3 MHz is attained. This method can be employed to perform a rapid and precise measurement of the weak electric field, which is important for the atom-based microwave metrology.  相似文献   

9.
A new electrostatic field measurement method: The coherent-notch field mill   总被引:1,自引:0,他引:1  
Conventional electric field mill designs are not able to measure quasi-static atmospheric electric fields in the vicinity of high-voltage power systems. The electric fields generated by such power systems produce severe perturbations to the quasi-static background electric field. Filtering of these perturbations by the field mill circuitry seems to be easy because of their periodically alternating character. However, the operation of a field mill involves an effective signal filtering method, as presented in this paper. Because field mill operation gives rise to amplitude modulation of the incident electric field under measurement, a new technique based on coherent demodulation and notch filtering is proposed. Simulation and experimental results validate the excellent performance of the proposed method for measuring sudden step functions in electric field in presence of a severely perturbed ambient.  相似文献   

10.
热疗用环形平面换能器声场特性的研究   总被引:5,自引:0,他引:5       下载免费PDF全文
钱盛友 《应用声学》2003,22(3):11-16
引入负声源,导出了环形平面换能器声场的简洁表示式,计算了单个圆环、多个同心圆环同时激励及环阵相控聚焦声源产生的声场,分析了环的宽度、环数及聚焦点位置等因素对声场特征的影响。提出根据各阵元在声场中某点产生的声压的相位来确定各阵元电激励信号的延时,此方法较根据各阵元到该点的平均声程确定各阵元电激励信号的延时,能更难确地在该点实现聚焦。  相似文献   

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