非守恒型粘性流方程的展开方法和数值模拟

在曲线坐标系中，给出了非守恒粘性流矢量方程一种新的展开方法，应用此展开方法使方程的展开式得到简化。对扩压管和二维平面叶栅进行了数值计算，计算结果表明，所给出的新展开式具有实用价值。     

对电磁场能流矢量的另一种表达式

电磁场能流矢量的另一种表达式是从玻印亭矢量中舍弃△×（φＨ）项而得到的。能流矢量的这种新形式与我们通常的直觉相符。而且它能得出一个加速电荷的拉莫尔（Ｌａｒｍｏｒ）辐射公式。     

结构振动声强法研究及应用

振动声强技术通过绘制功率流矢量图和流线图来分析结构噪声源及能量传播路径,可以清晰体现振动声能的分布和传播。对振动和噪声控制具有重要的理论意义和应用前景。本文总结了振动声强试验和理论计算技术的发展,并推导了受迫振动板中声强分量与振动能量的数学关系;最后对振动声强法在复杂结构振动功率流控制和结构损伤识别中的应用进行了展望。     

离心压气机叶尖间隙泄漏流动数值研究

采用离心压气机计算机辅助设计系统,设计了一个离心压气机叶轮,对这一叶轮在不同叶尖间隙下内部流场进行了数值计算。给出了不同弦长截面二次流矢量、二次流流以及机匣壁面极限流线等计算结果。结果表明叶尖间隙的大小与泄漏流动的强度密切相关。分流叶片的泄漏流动随着叶尖间隙的增大而增强。通道涡与合适的叶尖间隙所形成的泄漏涡相互作用可以削弱泄漏强度,改善流动。     

基于热质理论的广义热弹性动力学模型

具有微尺度传热特征的超常传热过程中,热流矢与温度梯度之间存在延迟效应,且热流的运动受到空间效应的影响.基于热质概念的普适导热定律,结合Clausius不等式和Helmholtz自由能公式,构建了计及热流矢和温度对时间和空间惯性效应的广义热弹性动力学模型,推导了各向同性材料超常传热行为的热弹性控制方程组.通过与已有广义热弹性动力学模型进行对比分析可得,当热流密度不大的条件下,热流矢与温度对空间的惯性效应可忽略时,基于热质概念的广义热弹性模型可分别退化为L-S,G-L和G-N的模型;对于尺度微观、稳态导热条件时,热流矢与温度对空间的惯性效应不可忽略,此时导热系数将受到热质运动惯性效应的影响,利用所建模型可揭示稳态导热时呈现的非傅里叶现象,并可避免基于已有广义模型得到的导热系数随结构特征尺寸变化的非物理现象.     

噪声源非均匀分布海洋环境噪声水平声能流理论分析

研究水平非均匀分布噪声源所产生的各向异性海洋环境噪声场声能流。提出一种混合型非均匀分布噪声源模型,理论分析并数值计算了此模型情况下的环境噪声场水平声能流。结果表明:非均匀分布噪声源引起的海洋环境噪声场具有显著非零平均水平声能流;不同接收点的水平声能流明显不同;其幅度和方向取决于各个局部海域不等强度声源产生的合成噪声声能流矢量和。研究了两接收点间噪声的声压和振速水平分量、振速水平分量归一化相关系数随两接收点间距的关系,各量之间表现出较强相关性,为分析水下矢量声场目标探测技术性能提供理论依据。      

细导线密绕螺线管的磁场

利用圆电流矢势和磁场的叠加原理，导出了细导线密绕螺线管磁场的级数表达式。     

准洛伦兹变换与平面电磁波方程——多普勒效应

根据光速不变性和相对性原理,导出一对共轭变换．通过“比例中值定理”完成电磁场的洛伦兹变换．阐述了动系中平面电磁波方程和能流矢量共轭变换的形式．应用“相位不变性”原理讨论了多普勒效应光频的共轭变换,并借助于中值定理完成光频的洛伦兹变换．最后,引入爱因斯坦阐明的极隧射线实验来检验光频共轭变换及其推论的正确与否．     

流矢图的单帧两次曝光记录

利用电视ＰＡＬ制式的隔行扫描原理,把摄像机拍摄的一幅图象拆分为前后两场,经过最小误差示踪粒子匹配方法的力象处理,获得了较好的瞬时流矢图。     

动态背景下基于光流场分析的运动目标检测算法

针对现有动态背景下运动目标检测算法的不足,提出一种基于光流场分析的运动目标检测算法.首先根据前背景在光流梯度幅值和光流矢量方向上的差异确定目标的大致边界,然后通过点在多边形内部原理获得边界内部的稀疏像素点,最后以超像素为节点,利用混合高斯模型拟合的表观信息和超像素的时空邻域关系构建马尔可夫随机场模型的能量函数,并通过使目标函数能量最小化得到最终的运动目标检测结果.该算法不需要任何先验假设,能够同时处理动态背景和静态背景两种情况.多组实验结果表明,本文算法在检测的准确性和处理速度上均优于现有算法.     

低杂波驱动的共振电子径向能量输运

在低杂波驱动电流的托卡马克中,可出现波驱动的共振电子径向能流,由定向能流和传导型能流两部分组成,其效应可能与碰撞效应可比,从而改变了驱动电流的基本图象。 关键词：     

Interaction of magnetostatic waves with current carriers in stratified structures

The interaction of magnetostatic waves with charge carriers in ferrite-semiconductor and ferrite-electron flux structures is reviewed. The basic equations needed to calculate the interaction effects in these structures are provided. Attention is turned to the possibility of amplifying fast magnetostatic waves in bodies of revolution by means of circular electron drift over the body surface. The possibility is discussed of amplifying magnetostatic waves in a ferrite film by an electron flux band. The interaction of magnetoelastic waves with electrons in ferrite-semiconductor structures is considered. A method of calculating the static EMF (electromotive force), induced by traveling MSW (magnetostatic waves) in a ferrite-semiconductor structure, is discussed. Attention is turned to circular currents, flowing in the semiconductor, which can vary substantially the longitudinal EMF and lead to generation of a transverse EMF in the structure. We discuss experimental studies on detection of interaction of magnetostatic waves with charge carriers, suggesting the possibility of wave amplification in ferrite-semiconductor and ferrite-electron flux structures, and exploring EMF induction mechanisms in the regime of traveling waves and ferromagnetic resonance.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 5–29, January, 1989.     

Observations of slow electron holes at a magnetic reconnection site

We report in situ observations of high-frequency electrostatic waves in the vicinity of a reconnection site in the Earth's magnetotail. Two different types of waves are observed inside an ion-scale magnetic flux rope embedded in a reconnecting current sheet. Electron holes (weak double layers) produced by the Buneman instability are observed in the density minimum in the center of the flux rope. Higher frequency broadband electrostatic waves with frequencies extending up to f(pe) are driven by the electron beam and are observed in the denser part of the rope. Our observations demonstrate multiscale coupling during the reconnection: Electron-scale physics is induced by the dynamics of an ion-scale flux rope embedded in a yet larger-scale magnetic reconnection process.     

Plasma jet braking: energy dissipation and nonadiabatic electrons

We report in situ observations by the Cluster spacecraft of wave-particle interactions in a magnetic flux pileup region created by a magnetic reconnection outflow jet in Earth's magnetotail. Two distinct regions of wave activity are identified: lower-hybrid drift waves at the front edge and whistler-mode waves inside the pileup region. The whistler-mode waves are locally generated by the electron temperature anisotropy, and provide evidence for ongoing betatron energization caused by magnetic flux pileup. The whistler-mode waves cause fast pitch-angle scattering of electrons and isotropization of the electron distribution, thus making the flow braking process nonadiabatic. The waves strongly affect the electron dynamics and thus play an important role in the energy conversion chain during plasma jet braking.     

Weak magnetohydrodynamic turbulence of a magnetized plasma

A weak turbulence of the magnetohydrodynamic waves in a strongly magnetized plasma was studied in the case when the plasma pressure is small as compared to the magnetic field pressure. In this case, the principal nonlinear mechanism is the resonance scattering of fast magnetoacoustic and Alfvén waves on slow magnetoacoustic waves. Since the former waves are high-frequency (HF) with respect to the latter, the total number of HF waves in the system is conserved (adiabatic invariant). In the weak turbulence regime, this integral of motion generates a Kolmogorov spectrum with a constant flux of the number of HF waves toward the longwave region. The shortwave region features a Kolmogorov spectrum with a constant energy flux. An exact angular dependence of the turbulence spectra is determined for the wave propagation angles close to the average magnetic field direction.     

Konenkov’s waves in anisotropic layered plates

Rayleigh-type flexural waves localized near the edge of a thin anisotropic layered plate are investigated. The following effects are revealed: a wave attenuation with oscillations, a change of sign of the energy flux for certain types of anisotropy, and the appearance of stationary waves.     

Interference of copropagating and counterpropagating surface waves

In the case of propagation of copropagating and counterpropagating surface waves along the interface of two media, the existence of a substantial difference in the spatial distribution of the energy flux components associated with the interference of active and reactive components of the field was established. The interference flux of the counterpropagating waves that is connected with the reactive components is undamped along the direction of propagation of the waves.     

On the energy flux of stationary electromagnetic waves in anisotropic dissipative media with spatial dispersion

The special features of the propagation of electromagnetic wave in gyrotropic medium with dispersion and resonant dissipation (specifically, in a magnetoactive plasma) are studied. Even though the anti-Hermitian components of the permittivity tensor are substantial in magnitude, weakly damped waves can exist in such media. However, the well-known phenomenological expression for the energy flux of waves in a medium with spatial dispersion is inapplicable for them. A theory extending this expression to the case studied is developed. The modified expression for the energy flux is used to construct the Hamiltonian for the ray optics of such media.     

Propagation of plane waves through the interface between media with dislocations

The laws of propagation of plane waves in homogeneous media with dislocations in the presence of an interface are considered using the equations of the defect field theory. The reflection coefficients and the refractive indices of displacement waves and the waves of a defect field, which is characterized by a dislocation density tensor and a dislocation flux density tensor, are determined. The dependences of these quantities on the parameters of the adjacent media are analyzed.     

Dispersive nature of high mach number collisionless plasma shocks: Poynting flux of oblique whistler waves

Whistler wave trains are observed in the foot region of high Mach number quasiperpendicular shocks. The waves are oblique with respect to the ambient magnetic field as well as the shock normal. The Poynting flux of the waves is directed upstream in the shock normal frame starting from the ramp of the shock. This suggests that the waves are an integral part of the shock structure with the dispersive shock as the source of the waves. These observations lead to the conclusion that the shock ramp structure of supercritical high Mach number shocks is formed as a balance of dispersion and nonlinearity.