相似耦合系统的统计能量分析

根据相关或互不相关激励条件下非保守耦合系统的统计能量分析原理,建立了两个相似的SEA系统之间的能量关系,提出了由已知系统预估未知相似系统的SEA方法。通过对保守和非保守耦合情况下板-梁和板-边框两个相似耦合系统的研究,分别从理论和实验上论证了这种方法的合理性。作为方法的应用,本文研究了两个相似切削系统的切削噪声问题,研究结果表明,理论分析和实验结果有很好的一致性,该方法可以有效地用于复杂耦合系统动态问题的研究。     

轴对称体声振耦合的边界子波谱与有限元耦合方法

探讨了子波在Helmholtz积分方程及声振耦合中的应用,在建立了求解轴对称Helmholtz积分方程的子波谱方法的基础上,构造了轴对称子波谱与轴对称有限元的耦合方法,该方法可以处理轴对称问题的任意边界条件.进行了声振耦合问题的模态分析.     

非保守耦合系统的统计能量分析原理

传统的统计能量分析(SEA)理论不能解决非保守耦合系统的能量分析问题。本文在非保守耦合振子的能量分布与功率流特征的研究基础上,推导了互不相关随机激励条件下非保守耦合系统的功率平衡方程式及各有关功率项的计算式,建立了非保守耦合系统的统计能量分析理论。研究结果表明,保守耦合仅是非保守耦合的一个特例,耦合阻尼对非保守耦合系统的能量分布和功率流的特征有着显著的影响,只有在耦合阻尼远小于系统内阻尼时这种影响才可近似忽略。作为理论的一个应用实例,本文对非保守耦合板的能量问题进行了理论和实验研究。     

原子核四极振动声子的波函数

应用声子产生与湮没算符的对易性质,讨论了四极振动声子的波函数的分类问题。从而避开了许多关于群表示论的专门知识。在本文中给出了按群链U₅（?）R₅（?）SU₂（?）SU₂'分类的声子波函数的明显表达式,以及这些波函数间的一些重要关系。对于按群链U₅（?）R₅（?）R₃分类的波函数,给出了一个系统地规定其附加指标的方法,并给出了按群链U₅（?）R₅（?）R₃分类的波函数的一般表达式。在本文中还推导出了辛弱数P确定时声子总角动量的可取值与重复度的一般公式,并给出了p≤30时声子总角动量的可取值及重复度的数值表。     

用最小二乘法求无限深势阱基态能量和波函数

本文用最小二乘法求出了粒子在无限深势阱（-a〈x〈a）中运动时的基态能量和波函数，并和精确解进行了比较，相差很小．     

氩原子基态波函数和能量的解析计算

以第一性原理和变分原理为基础,给出了氩原子基态波函数的一种解析表达式,计算了基态氩原子(含类氩离子)的能量,导出了所涉及的所有积分的解析表达式.对氩原子,所得到的能量理论值与实验值的相对误差为0.22%.     

声表面波彩色电视图象中频滤波器

声表面波滤波器是一种无源器件,它具有体积小、工艺简单、重复性好、成品率高以及性能稳定可靠等优点。     

水中弹性结构声散射和声辐射机理——结构和水的声-振耦合作用

从三个方面综述水中弹性结构声散射和声辐射的机理,特别强调声-振耦合或流体负荷作用。首先从阻抗的角度讨论声-振耦合作用。对于典型问题散射和辐射声场可以用阻抗的形式表示,系统的总阻抗等于机械阻抗和辐射声阻抗之和。表面振速只依赖于总阻抗,而声辐射依赖于辐射声阻抗与总阻抗之比。总阻抗等于零给出系统的特征方程,方程的根就是声场函数的极点。其次应用共振散射和辐射理论讨论声-振耦合作用。此理论将声场表示成各种共振再辐射模态的叠加,从振动的角度揭示声-振耦合机理。已经证明,模态的再辐射效率近似正比于复频率极点的虚部。第三,应用基于Sommerfeld-Watson变换的表面弹性波理论讨论声-振耦合作用。此理论将声场表示成各种表面弹性波-环绕波的再辐射的叠加,从波动的角度揭示声-振耦合机理。也可以证明,环绕波的再辐射效率近似正比于复波数极点的虚部。     

试验制导武器的声振技术

空对空导弹的大部分寿命是由发射飞机携带着,在这期间它遭受到由飞机飞行所激发的各种振动。对于现代化性能优良的军用飞机,这种振动是十分激烈的。所有导弹,不论是从空中、海面或地面发射,在飞行中都会经受由各种源激发的振动。为了正确模拟这些条件,应该调查典型导弹中的振动源和它们传向电子设备的路程。     

A hybrid formulation for mid-frequency analysis of assembled structures

A new formulation able to predict the behaviour of structures in the mid-frequency range is presented in this paper. The mid-frequency field is a hybrid domain for which assembled structures exhibit simultaneously low- and high-frequency behaviours, depending on the material and geometrical properties of different subsystems. Thus, dealing with the mid-frequency field requires simulation methods which are able to account the differences in behaviour of different subsystems. The hybrid formulation is based on the coupling of two different formulations, the finite elements for the low-frequency behaving subparts and a probabilistic formulation, the smooth integral formulation, applied to the high-frequency subsystems. The hybrid method enables to correctly predict the deterministic response of the low-frequency parts which is not affected by randomness, and the smooth trend of the contributions of the high-frequency parts. The paper is concluded with several numerical examples computed for coupled one- and two-dimensional structures.     

Dependence of the induced loss factor on the coupling forms and coupling strengths: energy analysis

In two recent papers, the induced loss factor is determined via the modification to the loss factor in the linear impedance of a master oscillator caused by its coupling to a set of satellite oscillators. A loss factor is basically an energetic quantity and, therefore, one may inquire whether the induced loss factor may be estimated via an energy analysis (EA). An answer to this question is sought. It is shown that the linear impedance analysis and EA yields identical results for the induced loss factor in the appropriate frequency range. This frequency range spans the distribution of resonance frequencies of the satellite oscillators. In this frequency range, the identity of the results is not only in terms of gross features but also in detail. Finally, the relationship of EA to statistical energy analysis (SEA) is explored. The loss factors assigned to the satellite oscillators are cast in terms of modal overlap parameters. It is found necessary for the validation of SEA, in the light of EA, that these parameters exceed a certain threshold. In specific situations of interest the threshold values may exceed unity.     

A quantitative criterion validating coupling power proportionality in statistical energy analysis

The response of two general spring-coupled elements is investigated to develop a unifying approach to the weak coupling criterion in Statistical Energy Analysis (SEA). First, the coupled deterministic equations of motion are expressed in the bases given by the uncoupled elements’ eigenmodes. Then, an iterative solution is expressed as a succession of exchanges between elements, where uncoupled motion provides the start approximation, converging if the ‘coupling eigenvalue’ is less than unity, in which case coupling is said to be weak. This definition is related to whether response is ‘local’ or ‘global’, encompassing a number of previously defined coupling strength definitions, applying for deterministically described structures. A stochastic ensemble is defined by that its members are equal to the investigated structure but the elements have random frequencies. It is required that the coupling eigenvalue be less than unity for all members of the ensemble. This requirement generates the title subject of the article: ‘the modal interaction strength’. It is similar to the previously defined coupling strength criterion characterising the ensemble average energy flow in uni-dimensional waveguides. Finally, SEA models are formulated in terms of the uncoupled elements’ modal data.     

A mode-based approach for the mid-frequency vibration analysis of coupled long- and short-wavelength structures

A mode-based approach is described for the mid-frequency vibration analysis of a complex structure built-up from a long-wavelength source and a short-wavelength receiver. The source and the receiver respectively have low and high modal densities and modal overlaps. Each substructure is described in terms of its uncoupled, free-interface natural modes. The interface forces and displacements are decomposed in terms of a set of interface basis functions. Enforcing equilibrium and continuity conditions along the interface hence yields an analytical solution for the vibration response of the built-up structure. Expressions for the frequency response of the source and the power transmitted to the receiver are found. The correlations between the modal properties of the source and the receiver along the interface are derived. These modify the dynamic stiffness matrix of the structure. The flexible receiver is seen to add effective mass and damping to the source. The modes of the short-wavelength receiver are then described statistically in terms of a simple standing wave model. This approximation avoids the need for a modal analysis of the receiver. The results are compared with those of other methods including fuzzy structure theory. Numerical and experimental examples for beam-stiffened plate models are presented.     

双折射晶体中旋光效应的耦合波理论

与传统的旋光效应理论不同，采用三阶赝张量κ⁽²⁾_jkl描述旋光现象，并将相关的电极化强度作微扰处理，直接从Maxwell方程组出发推导出了双折射晶体中自然旋光效应的耦合波方程组并得到解析解.该解析解包含了已有的旋光效应宏观理论结果，可方便地用于描述任意偏振态的单色光波在任意点群的双折射旋光晶体中沿任意方向的传播行为.最后，以石英晶体为例,通过对出射光波的偏振态分析，研究了波矢失配对旋光效应的影响. 关键词： 耦合波理论 旋光效应 非线性光学     

高功率微波照射下半空间上方天线罩耦合特性

利用两次傅里叶变换得到半空间界面的反射波后,将直接入射波和界面反射波两个时域脉冲源通过等效原理引入到包含目标的时域有限差分(FDTD)的计算域中。计算了高功率微波入射情形下,改变入射面、极化方式时天线罩内部观察点的能流密度的变化,并总结其规律。数值算例表明,对于贴近地面的目标来讲,半空间的反射波会给目标内部带来新的能量冲击。该方法可以用于计算目标内部耦合近场及功率密度。     

高功率微波照射下半空间上方天线罩耦合特性

利用两次傅里叶变换得到半空间界面的反射波后,将直接入射波和界面反射波两个时域脉冲源通过等效原理引入到包含目标的时域有限差分（FDTD）的计算域中。计算了高功率微波入射情形下,改变入射面、极化方式时天线罩内部观察点的能流密度的变化,并总结其规律。数值算例表明,对于贴近地面的目标来讲,半空间的反射波会给目标内部带来新的能量冲击。该方法可以用于计算目标内部耦合近场及功率密度。     

大口径光学元件中频波前的检测

大口径光学元件中频波前的准确评价已成为高功率激光系统中关注的焦点,元件中频波前均方根值是重要评价指标之一。根据波前中频检测频段及波前检测设备频响特性,将波前的中频区域分为两个检测频段,分别采用干涉仪和光学轮廓仪实现了中频波前均方根值的检测。采用大口径干涉仪可实现全口径波前中频区域低频段波前的检测,通过比对大口径干涉仪和采用小口径干涉仪结合分块融合平均方法的检测结果,提出采用分块融合平均方法也可检测相应频段全口径波前均方根。采用光学轮廓仪通过离散采样的方法检测大口径元件中频区域高频段波前均方根,针对不同离散采样方式的实验结果表明：33的采样方式能满足对410 mm410 mm口径元件中频区域高频段波前均方根的检测。     

基于子空间分析的人脸识别方法研究

人脸识别技术是模式识别和机器视觉领域的一个重要研究方向,在众多人脸识别的算法中,基于子空间分析的特征提取方法以其稳定可靠的识别效果成为了人脸识别中特征提取的主流方法之一。本文对目前应用较多的子空间分析方法进行了研究,具体介绍了线性子空间分析方法：主成分分析（PCA）、线性鉴别分析（LDA）、独立主成分分析（ICA）、快速主成分分析（FastICA）等及非线性子空间分析方法：基于核的PCA （KPCA）等的基本思想及其在人脸识别中的研究进展,包括一些新的研究成果。此外,还应用orl及Yale B人脸库对几个基础的子空间方法进行了验证实验。实验结果表明,在几个子空间分析方法中,FastICA算法取得了最高的识别率。最后结合实验结果对各算法的优缺点进行了分析总结。     

Wave coupling theory of quadratic electro-optic effect and its applications

Wave coupling theory of quadratic electro-optic effect is developed by considering the third-order nonlinearity as a perturbation in lossless nonmagnetic centrosymmetric medium. A general solution of the resultant equations is given to describe the quadratic electro-optic effect for the electromagnetic wave propagating along an arbitrary direction with applied external electric field. The effect of the polarization state on electro-optic coupling is studied in paraelectric phase KLTN crystals. A novel application of wave coupling theory of quadratic effect is described, namely polarization rotator, which can rotate the polarization of the electromagnetic wave with an arbitrary angle.