声光信号融合的外弹道参数测量方法研究

分析了弹丸激波马赫角在超声速飞行物体研究中的意义,指出现代靶场测试中针对激波马赫角的测试手段的不足。给出了一种全新的激波马赫角、弹丸速度以及弹丸飞行距离的测量方法。通过分析激波声学压电传感器接收到激波的时间,以及高速目标探测器接收到超音速飞行弹丸遮光时间,结合两种探测器的位置空间信息,构建了一种基于声光双信号的外弹道参数测试系统的数学模型。建立仿真模型分析,基于声光双信号的弹丸马赫角的误差低于0.6%。实验结果表明,对于超音速飞行的弹丸,基于声光信号探测系统检测弹道参数测量系统具有较高的测量精度。为后续的多信号探测外弹道参数奠定了基础。     

风速对声点阵立靶系统建模及算法的影响研究

室外靶场中点阵声学立靶应用时风对报靶精度有较大影响。使用几何方法推导了激波到达时间、矢量风速、弹丸速度和入射角、着靶位置之间的模型方程,然后将激波到达时间显式表述。该显式表达式可简化非线性最小二乘法求解并加速了收敛性,可同时求得弹丸着靶位置以及速度、入射角,可适用于不同的传感器阵列样式。通过仿真给出了风速对报靶精度影响的误差图。     

不同电极结构下双通道大气压He等离子体射流数值研究

采用二维轴对称流体模型对单电极结构（不锈钢针管）和双电极结构（不锈钢针管-高压环形电极）下同轴双通道进气的大气压氦气等离子体射流进行了对比研究。研究表明:相比于单电极结构,双电极结构下射流的传播速度明显降低,介质管内尤为严重。同时双电极结构下射流的空间结构也发生了显著变化。在单电极结构下,随射流发展由环形中空结构转变为实心圆盘结构;而在双电极结构下则呈现出实心圆盘结构至环形中空结构再至实心圆盘结构的演化过程,改善了射流空间分布的均匀性。此外,还研究了双电极结构下高压环形电极厚度对射流的影响。研究表明,随环形电极厚度的增加,射流的传播速度进一步降低,射流通道径向收缩,同时环形中空结构的射流内径减小,进而改善了射流径向分布的均匀性。     

弹丸激波在激光光幕靶测量中的影响分析

分析了弹丸在飞越激光光幕靶时弹丸激波对激光传播的影响。针对难于实际测量由激波形成的空气折射率分布问题,应用弹丸超音速绕流场的数值计算结果和折射定律,借助SolidWorks软件分析了激波内折射率为常数的情况下光线穿过激波时的折射和出射轨迹,并用模拟实验验证了其正确性。讨论了激波对激光光幕靶测量的影响,为光幕靶的设计与应用提供了依据。     

基于改进型六幕光幕靶的弹道测量技术研究

现有的六幕光幕靶测量系统实现了近距离弹丸速度、姿态以及着靶坐标的测量,而在实际工程应用中需要计算的是弹丸整个飞行过程中的速度、姿态以及远距离的落点坐标。针对现有系统工程部署中的不足,提出了双交叉结构的六幕光幕靶的设计原理。利用双交叉结构的六幕光幕靶的测量结果以及外弹道计算原理,通过四阶龙格-库塔方程建立了弹道测量模型,实现了弹丸飞行全过程的弹道测量和计算。通过使用弹道系数1.0的标准弹丸进行仿真实验和分析,计算出其射程和射高分别可以达到16 269m和3 672m,证明了其与实际的弹丸运动曲线相吻合,能够实际应用于工程部署。     

用高速摄影机拍摄气体爆轰波反应区

人们很早就注意到可燃气体混合物中火焰在一定的条件下可以达到很高的传播速度。这种现象称之为爆轰。根据ZND模型,气体爆轰实际上是带有化学反应区的激波。它的结构是激波后方紧跟一个化学反应区,两者构成了爆轰波波阵面。爆轰波的特点是1)传播速度高,一般为2000m/S左右。2)伴随有发光现象。根据ZND模型,可燃气体的化学反应在反应区中进行,因而反应区具有一定的宽度。 人们对爆轰波作了大量的研究,但由于波阵面的传播速度太快,限制了对波阵面结构诸如阵面形状,反应区宽度等的研究。     

双三角阵声靶测试系统研究

声靶容易构成较大的测试靶面,常用在大口径弹药的立靶密集度测试中。为了消除声波在空气中传播速度变化对声靶测试精度的影响,采用双三角阵声阵列模型使测量公式中不再引入声波速度。为了使测试系统紧凑、可靠,整个测试系统由双三角阵列、多通道数据采集仪、计算机系统构成。对测试系统进行了实弹射击实验,在2 m×2 m靶面内,弹着点测量误差为±10 mm。     

基于舰载光电跟踪仪的舰炮对海射击报靶方法

针对大中口径舰炮对海射击训练时,缺少设备测量相对靶船中心的弹丸落点散布精度,提出了一种利用舰载光电跟踪仪交汇测量方法。以靶船型值为基准,利用靶船型值在屏幕上的像素尺寸,求出相对光电跟踪仪电视中心的弹着点线及偏置角,将两艘舰艇光电跟踪仪分别测量出的两条弹着点线相交,即可求出相对于靶船中心的脱靶量。给出了交会测量弹着水柱的数学模型,对测量精度进行了分析,计算结果表明脱靶量误差小于3m。     

PELE弹丸壳体的损伤断裂模型

结合横向效应增强型侵彻体(PELE)侵彻金属靶板的数值模拟结果和实验结果,将PELE弹丸壳体膨胀断裂过程分为加速膨胀和匀速膨胀两个阶段。在封加波提出的损伤度模型的基础上,推导得到PELE弹丸壳体的损伤断裂方程;并通过PELE壳体断裂实例计算了PELE弹丸壳体膨胀断裂过程的参数,分析了弹丸着靶速度与壳体断裂之间的关系,为PELE弹丸设计提供了理论指导。     

高温等离子体中固体弹丸消融过程的研究

本文求得了弹丸消融过程的自洽解析解。结果表明:Parks的弹丸消融理论需要修正;弹丸消融速率由消融物云和表面蒸发层共同控制;入射电子通过消融物云时慢化效应并不显著;消融物离开弹丸表面时一般呈部分电离态;聚变堆条件下,弹丸表面可能会出现激波。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.     

Fiber Modal Index Measurements Based on Fiber Gratings

A novel method based on fiber gratings for measuring the effective indices of fiber modes is proposed. The effective index difference between the core mode and a cladding mode was obtained by analyzing the interference fringe of a pair of cascaded long-period fiber gratings. In order to extract the core mode index from the measured index difference, an index matching oil immersion method is proposed. By analyzing the interaction between the cladding mode and the oil applied on the cladding surface, the mode order and the effective index of the involved cladding mode might be calculated. Experimental results about the interference fringe shifts induced by the oil index and the oil-applied length are also presented.     

Optical Pulse Compression Schemes That Use Nonlinear Bragg Gratings

Nonlinear optical pulse compression of picosecond pulses typically requires long lengths of optical fiber and multiple components. Periodic structures, such as fiber Bragg gratings, are highly dispersive at wavelengths outside of the photonic bandgap. This implies that such gratings can be used as very short all-fiber compressors. In this paper a number of such compression schemes are reviewed involving uniform and nonuniform fiber Bragg gratings, relying on both soliton and nonsoliton compression principles. Experimental results supporting the corresponding underlying theory are also presented. Finally, an extension of one of the compression schemes is shown, which allows the generation of adjustable high-repetition rate soliton trains.