直线加速Kinnersley黑洞中Dirac粒子的热辐射

在直线加速Kinnersley时空中,将相互耦合的Dirac方程化为二阶方程,采用新的乌龟坐标变换,在视界面附近消除二阶方程中的耦合化成了标准波动方程,得到辐射温度函数和Hawking热辐射谱. 关键词： 黑洞 Dirac方程 乌龟坐标变换 Hawking辐射     

各向同性光波导受到各向同性微扰时的严格矢量耦合模理论

从Maxwell方程出发，推导出各向同性光波导受到各向同性微扰时严格的非正交矢量耦合模理论，在耦合系数的表达式中发现不包含Wei-Ping Huang 的准矢量耦合模理论中的偏振耦合项，但在推导过程中曾出现过偏振耦合项.最后认为这是由于偏振耦合项是二阶小量，而弱导近似忽略了与之相等的二阶小量耦合项.因此,严格的矢量耦合模理论不存在该项而准矢量耦合模理论可把偏振耦合项作为修正项.     

撕裂模环效应耦合的数值模拟

应用三点中心差分格式示解了在端点有二阶可去奇点和在有理面上具有一阶不可去奇点的撕裂模方程，并提出了近似等价网格的构造方法，在不同的安全因子分布下，对具有环效应耦合撕裂模方程进行了数值模拟，得到相应的判断稳定性的连接参量，耦合强度参数，增长因子等物理量。通过这些数值结果可以得出，环效应在线性阶段对撕裂模的影响得很小的。     

重新初始化的LS方法跟踪二维可压缩多介质流界面运动

 用非耦合求解方法计算Level Set函数方程与流体力学方程组，应用重新初始化的Level Set函数确保距离函数性质，流体力学方程组采用二阶精度多介质流波传播差分格式计算，重新初始化方程采用五阶WENO格式计算。并给出了二维可压缩多介质流界面运动的计算结果。     

双源耦合注入准二阶孤子及其通信应用

基于光纤中孤子传输的支配方程，借助分裂步长Ｆｏｕｒｉｅｒ变换法，提出了双源耦合注入准二阶孤子并数值模拟了准二阶孤子与一阶孤子的相互作用，提出并初步论证了基于二阶孤子的三进制光纤孤子通信设想，它能够使中继距离进一步扩大同时，又使信息量增加ｌｏｇ２Ｍ＝ｌｏｇ２ ３＝１．６并可降低对光源高功率注入的要求。     

一类带限定变换的二阶耦合线性微分方程组的解析解

用函数和方程变换将二阶耦合线性微分方程组转化为一阶非线性类椭圆方程，并给出了一次和二次限定变换下方程组的Jacobi椭圆函数解析解，所得结果修正了文献中超导特例的近似解，进一步肯定了超导边界层电场的存在性. 关键词： 微分方程 Jacobi椭圆函数 解析解 超导     

偏振模色散对非线性光纤环镜微波光子开关的影响及其补偿

建立了考虑PMD在内的NOLM微波光子开关光波传输方程，给出了基于耦合非线性薛定谔方程的分步傅里叶法，三维庞加莱球理论和琼斯传输矩阵法的数值分析模型.仿真获得在光子开关中微波直接强度调制光载波的传输过程，以及在不同调制带宽下一阶和二阶PMD对光波信号和NOLM功率传输函数的影响.指出PMD造成NOLM开关性能钝化和消光比严重恶化，并引起信号信噪比下降和旁瓣泄漏.当调制带宽大于40GHz时,二阶PMD的影响比一阶PMD更加严重.最后讨论了NOLM中的PMD补偿问题.     

周期性极化铌酸锂波导全光开关特性分析

从理论方面研究了基于和频与差频级联二阶非线性效应的周期性极化铌酸锂波导全光开关的特性,给出了耦合模方程在满足相位匹配条件下小信号近似的解析表达式.用数值方法求解耦合模方程,讨论了相位失配情况下输出的信号光功率与控制光功率的关系.分析了全光开关器件的极化反转光栅周期、晶体温度、控制光波长等参量的容差特性与相互作用长度和晶体温度的关系 关键词： 级联二阶非线性 光开关 准相位匹配 周期性极化铌酸锂     

一种水平变化波导中声传播问题的耦合模态法

针对介质参数及海底边界水平变化波导中的声传播问题,本文基于多模态导纳法提出一种能量守恒且便于数值稳定求解的耦合模态方法.将声压表示为一组正交完备的本地本征函数之和,对声压满足的Helmholtz方程在本地本征函数上作投影,推导出关于声压模态系数的二阶耦合模态方程组.耦合矩阵直观描述水平变化因素对模态耦合的贡献.为避免直接求解二阶耦合模态方程组可能遇到的数值发散问题,将其重构为两个耦合的一阶演化方程组,引入导纳矩阵并使用Magnus数值积分方法获得稳定的声场解.利用该耦合模态方法数值计算水平变化波导中的声场,并与COMSOL参考解比较,结果表明该耦合模态理论能够精确求解水平变化波导中的点源及分布源传播问题.     

BBO晶体中飞秒脉冲的二次和三次谐波振荡产生

同时考察了群速色散失配、最低阶群速色散和二阶群速色散。研究了在ＢＢＯ晶体中飞秒激光脉冲的谐产生，计算了ＢＢＯ晶体的作为波长函数的晶体的最低阶和二谐群速色散，借助求解改进的耦合波方程的数值计算，得到了飞秒脉冲的二次及三次谐波辐射，分析了最低工阶及二阶ＧＶＤ对于基波脉冲和谐波脉的影响，最后考虑了三次谐波产生中群速失配的补偿。     

辐射换热的输运模拟研究

本文从辐时与传输的基本原理出发，引进辐射推动力及流热参数的概念，建立了一般情况下辐射传热的二阶微分方程的数学模型。该方程具有传输方程的特点，使得辐射传热的处理在方法上与导热、流动问题相一致。     

基于图像的飞行器红外辐射特性测量

通过将目标在一定波段内的红外辐射等效为红外成像系统前一定距离下黑体在对应波段内的红外辐射,建立了等效辐射方程。根据黑体辐射定标实验数据,利用非线性回归方法确定了在不同的积分时间条件下红外凝视成像系统输出红外图像的灰度值与在一定距离下的黑体温度之间的定量关系,建立了辐射定标方程。在Visual C++6.0平台下,在对红外目标图像进行SUSAN滤波等预处理后,分析了已知目标距离的红外图像的灰度均值。首先根据辐射定标方程计算出目标等效为黑体的温度,然后利用等效辐射方程反推目标的红外辐射强度,以达到根据跟踪的红外图像确定红外目标辐射特性的目的。此项研究不仅可以为目标识别提供目标分类、识别和辨认所必需的光谱数据库,而且还可以为红外预警提供重要的参考数据。     

Generation of tunable electromagnetic radiation by a dust ripple in dusty plasmas

It is shown that a pre-existing dust ripple in a dusty plasma may excite tunable electromagnetic radiation. For our purposes, we use the Maxwell equation and the electron equation of motion to derive a Mathieu equation in the presence of a spatially oscillating dust ripple. The Mathieu equation admits instability of an electromagnetic wave. Criteria under which instability occurs are presented. Explicit expression for the electromagnetic radiation frequency and the growth rate are obtained. The possible relevance of our investigation to nonthermal electromagnetic radiation sources from laboratory and cosmic dusty plasmas is considered.     

Inverse Problems of the Near-Field Radiothermometry

It is shown that the one-dimensional problem of near-field microwave radiometry in the case of a smoothly inhomogeneous medium can be reduced to an integral equation similar to the well-known solution of the radiation transfer equation. The kernel of this integral equation depends on only one parameter determined experimentally. This makes it possible to determine the subsurface temperature profiles by using a set of near-field antennas of arbitrary design for which the sounding-depth range is overlapped by the effective depth of formation of the radiation received by these antennas. In the case of near-field measurements, the previously obtained joint solution of the radiation transfer equation and the thermal diffusion equation can also be modified and applied for monitoring the subsurface temperature profile using the temporal dependence of the received signal.     

Time-dependent radiative transfer with automatic flux limiting

We discuss a simple method for solving the time-dependent transfer problem. This scheme is automatically flux-limited and affords physical insight into how flux limitation occurs. We then develop a second-order, time-dependent radiation energy equation that is similar in form to the diffusion limit radiation energy equation. This time-dependent energy equation approaches physically reasonable equations in optically thick and thin regions. Computational aspects of solving this energy equation are discussed.     

自由电子激光辐射场的经典理论分析

以经典电动力学分析自由电子激光辐射场,讨论辐射场的一般特性,并利用麦克斯韦方程组、波动方程、电子连续性方程以及相对论电子运动的洛伦兹力方程和能量方程一起系统地建立了自由电子激光辐射场的自洽解方法. 关键词：     

Theory of transfer with delay for trapping of nonstationary acoustic radiation in a resonant randomly inhomogeneous medium

The propagation of a quasimonochromatic wave packet of acoustic radiation in a discrete randomly-inhomogeneous medium under the condition that the carrier frequency of the packet is close to the resonance frequency of Mie scattering by an isolated scatterer is studied. The two-frequency Bethe-Salpeter equation in the form of an exact kinetic equation that takes account of the accumulation of the acoustic energy of the radiation inside the scatterers is taken as the initial equation. This kinetic equation is simplified by using the model of resonant point scatterers, the approximation of low scatterer density, and the Fraunhofer approximation in the theory of multiple scattering of waves. This leads to a new transport equation for nonstationary radiation with three Lorentzian delay kernels. In contrast to the well-known Sobolev radiative transfer equation with one Lorentzian delay kernel, the new transfer equation takes account of the accumulation of radiation energy inside the scatterers and is consistent with the Poynting theorem for nonstationary acoustic radiation. The transfer equation obtained with three Lorentzian delay kernels is used to study the Compton-Milne effect—trapping of a pulse of acoustic radiation diffusely reflected from a semi-infinite resonant randomly-inhomogeneous medium, when the pulse can spend most of its propagation time in the medium being “trapped” inside the scatterers. This specific albedo problem for the transfer equation obtained is solved by applying a generalized nonstationary invariance principle. As a result, the function describing the scattering of a diffusely reflected pulse can be expressed in terms of a generalized nonstationary Chandrasekhar H-function, satisfying a nonlinear integral equation. Simple analytical asymptotic expressions are found for the scattering function for the leading and trailing edges of a diffusely reflected δ-pulse as functions of time, the reflection angle, the mean scattering time of the radiation, the elementary delay time, and the parameter describing the accumulation of radiation energy inside the scatterers. These asymptotic expressions demonstrate quantitatively the retardation of the growth of the leading edge and the retardation of the decay of the trailing edge of a diffusely reflected δ-pulse when the conventional radiative transfer regime goes over to a regime of radiation trapping in a resonant randomly-inhomogeneous medium. Zh. éksp. Teor. Fiz. 113, 432–444 (February 1998)     

同步辐射的相对论推导

根据加速带电粒子在与其瞬时对静止的参考系中的辐射公式,通过场的相对论变换,直接导出同步辐射粒子的辐射公式。     

开口/封闭薄壳体声辐射和散射的统一边界积分方程解法

推导了在二维和三维空间下开口和封闭薄壳体在任意阻抗边界条件下声辐射和散射的统一边界积分方程.相对于以前的求解方法,该方程求解声辐射和散射问题具有相同的影响矩阵,能够同时求解薄壳体气动和振动噪声的辐射和散射现象,以及分析壳体声阻抗对声波传播的影响.推导的方程可以应用于叶轮机械、管道等噪声和消声器消声性能的预测等方面.在此方程基础上,可以进一步考虑运动边界和运动介质对声辐射和散射的影响. 关键词： 薄壳体 声阻抗 积分方程 边界元方法