舰船磁性磁场分解教学模式分析

舰船磁性磁场分解是舰船物理场等领域教学的重点和难点.本文提出并分析了先进行磁性分解后进行磁场分解的教学模式.在磁性分解阶段,舰船磁性按照舰船坐标系分解为3个分量,每个分量包括感应和固定2个部分,共6种磁性.在磁场分解阶段,每种磁性在舰船坐标系下产生3个磁场分量,共分解为18个磁场分量.所提出的教学模式条理清晰,逻辑性强...     

基于点电源的船舶静态电场深度换算方法研究

为了对船舶静电场进行反演,提出了基于点电源的静电场深度换算方法. 利用泰勒展开式的收敛半径对场源的个数和位置进行了准确计算,建立了空气-海水-海床三层模型中等效场源系统的线性方程组,通过对线性方程组的求解达到计算等效点源强度和船舶等效电偶极矩的目的. 最后,利用Beasy软件计算的船舶电场信号作为仿真数据对所提方法的有效性进行了检验,结果表明:该算法计算量小,精度较高,能够实现对任意场点的电场进行换算.     

罗兰-C脉冲水下传播特性高精度预测理论算法研究

对罗兰-C脉冲水下传播特性预测模型算法进行推导研究,综合考虑了信号先沿陆海表面、再由空气入水传播时的路径损耗、相位延迟、色散效应及空气海水界面两侧场量的约束条件.分析了0~10m不同海水深度罗兰-C电场幅度与相位的变化,并与无畸变的标准场信号进行比较.结果显示:随着入水深度增加,色散效应导致脉冲前沿展宽,跟踪点相位超前.该结果去除了由参比场量近似引入的误差,精度更高.     

离子波纹场纵向电场分量对离子波纹激光的影响

通过非线性数值模拟，研究了离子波纹激光（ＩＲＬ）中离子波纹场的纵向电场分量对束－波互作用的影响。结果表明，离子波纹场的纵向分量对ＩＲＬ的工作状况具有较大的影响。其中互作用长度的选择是非常重要的     

基于深度学习的可见光图像舰船目标检测与识别

为探究深度卷积神经网络在舰船检测与识别中的应用,研究了基于深度学习方法的可见光图像舰船目标检测与识别,总结了适用的可见光图像舰船数据集与针对舰船目标的网络优化方法.研究表明,迁移学习、先验框改进、特征优化等方法均能提升舰船检测与识别的准确率.未来应结合多源特征的融合,对轻量化舰船识别、细粒度舰船分类等方向进行研究.     

空中三维电场传感器及其标定方法研究

空中电场是以三维矢量形式存在的,以往用于空中电场探测的电场传感器主要实现矢量电场的一个或两个分量的探测.介绍了一种新型的空中三维电场传感器,可实现空中矢量电场的三维检测,并对该三维电场传感器的标定方法进行了仿真分析,设计出该传感器的专用标定装置.测试数据表明该传感器的输出与外部电场呈良好的线性关系,与理论分析一致,证明了该电场传感器结构设计和标定方法的合理性.     

封闭介质盒中三维隐藏金属目标的散射仿真和图像重构

基于点目标散射原理,通过计算封闭介质中隐藏目标的全方位电磁散射,进行成像重构.宽带频率步进雷达从不同水平方位发送平面电磁波探测隐藏目标,获取隐藏目标各水平方位向后向散射电场.通过二维样条插值得到二维均匀采样的散射电场,将重采样数据进行二维快速Fourier变换得到二维重构图像.采用体面混合积分方程的矩量法计算复杂结构金属目标与介质盒环境的后向散射电场.通过有、无隐藏目标时的多方位后向散射电场的差值场实现目标重构成像.由封闭介质盒中隐藏3个金属球和1把金属手枪,分别进行重构成像,以说明该方法的有效性.     

地-电离层中水平激发极低频场的勒让德展开算法

地-电离层空腔中水平激励极低频(Extremely Low Frequency,ELF)场强可表示为勒让德函数及其导数的级数和,利用勒让德函数迭代公式,提出了极低频水平偶极子在地电离层空腔中激励场的计算新算法.将该方法近区场的计算结果与半空间水平偶极子激励场计算结果对比,远场区结果与Bannister(dir.+ind.)公式计算结果对比,验证了新算法的正确性和精度.将本算法应用至几Hz以下,可获得特殊规律：远区电场、磁场水平分量与方位角无关,电场水平分量方向与偶极矩方向平行,磁场水平分量方向与之垂直.     

玻恩近似下的无相位检测电磁成像方法

提出玻恩近似下用无相位检测数据重建复目标的方法.由电场积分方程推导散射场的实部和虚部之间的关系;在玻恩近似下基于散射场实部虚部关系,利用优化算法由无相位电磁检测数据反演目标散射场的实部和虚部;最后利用标准玻恩反演法对目标进行成像.数值实验显示该方法能有效地对弱散射目标成像.     

一种光纤传感器温度与应变同时解调的方法

文章分析了一种利用外差检测所得微波信号的电场振幅和频率来计算后向布里渊散射光功率及频移的方法.该方法通过对功率较强的微波信号进行数值拟合,利用得到的直流分量和交流分量计算出后向散射光功率、频移及其随温度、应变变化的系数矩阵.数值结果表明,温度、应变的解调精度分别为1℃、100 με,但也受到一定采样频率的限制.     

层流介质中曲面螺旋桨旋转对腐蚀静电场的影响

为了研究实际海水环境下螺旋桨转速及海水流速对舰船腐蚀静电场的影响,提出了一种层流介质条件下腐蚀静电场的求解方法.结合流体力学及电化学相关理论,建立层流状态下的曲面螺旋桨旋转模型,利用动量积分法和电化学方法分别求解层流介质下曲面桨叶表面的边界层厚度和极限腐蚀电流密度,基于该电流密度建立电偶极子模型对腐蚀静电场进行求解,并通过实验验证结论的正确性.结果表明：层流状态下,静电场的幅值大小随着螺旋桨转速及介质流速的增加而增加,在流速及转速较小时,理论数据与实验数据拟合程度较好.     

基于电流线等效的潜艇磁场估算与仿真

根据潜艇水下腐蚀相关电磁信号的产生机理,该文提出可采用由电偶极子首尾相接而成的电流线对其进行模拟。分别采用边界元建模及电流线建模方法对潜艇模型的水下静态电场进行计算,对比分析结果表明,将电流线作为对潜艇水下腐蚀相关静态电磁信号进行估算的数学模型是可行的。在此基础上,结合分层导电媒质中水平直流电偶极子的磁场表达式,对潜艇腐蚀相关静态磁场在全空间中的分布特征进行了仿真分析。结果表明,空气中潜艇腐蚀相关静态磁场近场量值可测,分布特征明显,可用于航空探潜;海水中潜艇腐蚀相关静态磁场远场按距离的平方反比衰减,可用于消磁潜艇的远程探测。分析所得典型结论为进一步的应用研究奠定了基础。     

静电场对强激光场中氢原子产生高次谐波的影响

利用分裂算符方法数值求解了真实氢原子在强激光场和静电场作用下的含时薛定谔方程,研究了静电场对强激光场中氢原子产生高次谐波的影响.研究表明,静电场加入后,奇次谐波的强度有所降低,并且谐波谱中出现偶次谐波和双平台结构.利用小波变换,观察了高次谐波在不同时刻的发射情况.借助于半经典理论,解释了在静电场作用下高次谐波发生变化的机制.     

Comparison of interpolation and extrapolation methods with a method using multiresolution wavelet transform in dosimetric experiments

International and national organizations have recommended limits for the protection of mobile phone users and standards are going to be established to certify the compliance of mobile phone with these limits. To ensure this conformity, numerical and experimental dosimetric analyses are essential to evaluate the electric field in the user’s head. The use of interpolation and extrapolation is then necessary to evaluate the electric fields components which cannot be measured. In this paper, an interpolation/extrapolation method using wavelets is presented. This method is applied to one, two, and three-dimensional sampled data from dosimetric experiments and compared with other interpolation/extrapolation techniques.     

Monte Carlo simulation of THz maser based on optical phonon transittime resonance in GaN

The linear and nonlinear analysis of microwave power amplification and generation in the terahertz (THz) frequency range is carried out by the Monte Carlo method in bulk wurtzite GaN. It is shown that a dynamic negative differential mobility persists up to 80 K due to the transit-time resonance associated with optical phonons. The generation frequency depends almost linearly on the static electric field strength and can be tuned in the wide frequency range from 0.2 to 3 THz when the electric field varies from 1 up to 12 kV/cm. The optimum amplitude of the microwave electric field generated by bulk GaN is found to be of the order of the static electric field thus leading to a significant maximum efficiency of about 1 to 1.5% for microwave power generation in the THz frequency range     

平板电容器边缘电场特性探究

平板电容器是＂电磁场与电磁波＂课程中静态场部分的重点分析对象。一般根据平板电容器的均匀电荷分布,求解平板电容器的电位和电场分布。本文考虑实际平板导体上电荷分布的不均匀性,利用逼近的方法,从分析导体的电荷密度出发,得出电荷分布的边缘效应,从而确定平板电容器边缘附近的电位和电场分布。仿真结果表明此逼近方法切实可行,具有一定...     

A data complementary method for thunderstorm point charge localization based on atmospheric electric field apparatus array group

Data loss or distortion causes adverse effects on the accuracy and stability of the thunderstorm point charge localization. To solve this problem, we propose a data complementary method based on the atmospheric electric field apparatus array group. The electric field component measurement model of the atmospheric electric field apparatus is established, and the orientation parameters of the thunderstorm point charge are defined. Based on the mirror method, the thunderstorm point charge coordinates are obtained by using the potential distribution formulas. To test the validity of the basic algorithm, the electric field component measurement error and the localization accuracy are studied. Besides the azimuth angle and the elevation angle, the localization parameters also include the distance from the apparatus to the thunderstorm cloud. Based on a primary electric field apparatus, we establish the array group of apparatuses. Based on this, the data measured by each apparatus is complementarily processed to regain the thunderstorm point charge position. The results show that, compared with the radar map data, this method can accurately reflect the location of the thunderstorm point charge, and has a better localization effect. Additionally, several observation results during thunderstorm weather have been presented.     

有限差分法在静态电磁场计算中的应用

介绍了采用有限差分法求解特殊边界条件下二维静态电场问题,并将电磁场数值方法的思想体现在处理过程中。对场域中的电势、电位进行了具体的分析和计算,给出了用C语言进行编程计算得到场量数据的流程图,最后利用MATLAB强大的绘图功能对结果进行可视化。由文章研究问题所得图形结果可以清晰的看出静电场中的电势线及电场线的分布,同时也验证了电场线与等电位线相互垂直,以及电势在媒质分界面连续的经典理论。     

A numerical solution to full-vector electromagnetic scattering bythree-dimensional nonlinear bounded dielectrics

This paper deals with electromagnetic scattering by nonlinear dielectric objects. In particular, a numerical approach is developed that is aimed at determining the distributions of the electromagnetic field vector inside a three-dimensional nonlinear, inhomogeneous, isotropic scatterer illuminated by a time-periodic incident electric field vector. An integral-equation formulation for the full-vector scattering problem is considered, and the nonlinear effect is taken into account by introducing equivalent sources and a Fourier-series representation. A system of integral equations (for each harmonic vector component and for the static term) is obtained that includes the internal electric field distribution as the unknown. After discretization, the solution is reduced to solving an algebraic system of nonlinear equations. Some preliminary numerical results are reported concerning scatterers that exhibit a specific (quadratic) dependence of the dielectric permittivity on the total electric field. The harmonic components of the scattered electric field outside the objects are also computed