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。     

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。     

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。     

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。     

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。     

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。     

等离子体中弹丸消融的探讨

本文采用弹丸消融的双区域模型,对弹丸消融过程进行了数值求解。分析Parks的模型,发现其定标律不适合于高温度、低密度的等离子体中弹丸的消融。估计了热电子能量分布函数对消融率的影响。     

Self-organization of five species in a cyclic competition game

Cyclic competition game models, particularly the “rock–paper–scissors” model, play important roles in exploring the problem of multi-species coexistence in spatially ecological systems. We propose an extended “rock–paper–scissors” game to model cyclic interactions among five species, and find that two of the five can coexistent when biodiversity disappears, which is different from the “rock–paper–scissors” game. As the number of fingers is five, we named the new model the “fingers” game, where the thumb, forefinger, middle finger, ring finger, and little finger cyclically dominate their subsequent species and are dominated by their former species. We investigate the “fingers” model in two ways: direct simulations and nonlinear partial differential equations. An important finding is that the number of species in a cyclic competition game has an influence on the emergence of biodiversity. To be specific, the “rock–paper–scissors” model is in favor of maintaining biodiversity in comparison with the “fingers” model when the variables (population size, reproduction rate, selection rate, and migration rate) are the same. It is also shown that the mobility and reproduction rate can promote or jeopardize biodiversity.     

Experimental study on downstep in Chinese intonation

Downstep in pitch contour of Chinese Putonghua is examined using subtly designed sentences by controlling tone combinations. The results show both automatic and nonautomatic downstep phenomena exist in Chinese. In non-automatic downstep, low tones compress downwards the pitch range of the following syllables. and the main influence of downstep is on topline. Low tone not only lower the topline behind it, but also raise the high tones before it, the effects are compatible with each other. In automatic downstep, the topline of pitch contour in intonational phrase is presented as a linear downtrend, but it differs among speakers due to the effect of personal stress practice. In comparison with downstep phenomenon in other tone or non-tone languages, the downstep ratio in Chinese is not constant, and the domain of downstep is not limited within the adjacent tones.     

Contrastive analysis on tone between Putonghua and Taiwan Mandarin

The differences of the pitch and duration of Chinese syllables between Putonghua （PTH） and Taiwan Mandarin （TM） were studied. The speech materials to be used are not only isolated syllables, but also sentences. The results reveal that： For the isolated syllables, T1 and T2 in TM are influenced by Minnan dialect, therefore their pitch are lower than those in PTH. T3 is fall-rise in PTH, while it is fall in TM. Moreover, the syllable duration sequence for different tone is T3〉T2〉T1〉T4 in PTH, while it is T1〉T2〉T3〉T4 in TM. For the syllables in sentences, T2 is mid-rise in PTH, while it is mid-level in TM. And the T3 is longer than T4 but shorter than T1 or T2 in PTH, while it is the shortest in TM. Furthermore the effects of prosodic phrase boundary on duration for different tones are almost the same in PTH, but the lengthening part of T1 or T2 is longer than that of T3 or T4 in TM.     

Abelian-Higgs phase of SU(2) QCD and glueball energy

It is shown that SU(2) QCD admits an dual Abelian-Higgs phase, with a Higgs vacuum of a type-Ⅱ superconductor. This is done by using a connection decomposition for the gluon field and the random-direction approximation. Using a bag picture with soft wall, we presented a calculational procedure for the glueball energy based on the recent proof for wall-vortices [Nucl. Phys. B 741(2006)1].     

Signal generation in an isotropic medium in scanning electron acoustic microscope

Based on the research in Ref. [5][Materials Science and Engineering, 1989; A122： 57 63], an improved model of heat source is set up, the different modes of Lamb wave in an isotropic sample generated by a chopped electron beam at frequency f are obtained with integral transform and normal function expansion method, and the output signal of PZT coupled at the back surface of the sample is found out. The generation mechanism of SEAM （Scanning Electron Acoustic Microscopy） signal is discussed. It shows that the SEAM is a near field imaging technique with high spatial resolution and its best lateral spatial resolution is about 2√2α （α is the radius of the focused electron beam）. Some of experimental results of SEAM images are presented in the paper and it shows that the spatial resolution of SEAM is better than 0.5 μm and smaller than the thermal diffusion length of the sample. Therefore the character of near field imaging in SEAM is also proved experimentally.     

High efficiency filtering using two-dimensional photonic crystal coupled cavity structures

Transmission spectra of coupled cavity structures (CCSs) in two-dimensional (2D) photonic crystals (PCs) are investigated using a coupled mode theory, and an optical filter based on CCS is proposed. The performance of the filter is investigated using finite-difference time-domain (FDTD) method, and the results show that within a very short coupling distance of about 3λ, where λ is the wavelength of signal in vacuum, the incident signals with different frequencies are separated into different channels with a contrast ratio of 20 dB. The advantages of this kind of filter are small size and easily tunable operation frequencies.     

Real-time restoration of rotational blurred image using gradient-loading

The key to the restoration of rotational motion blurred image is how to restore the image under a low cost and to correct the irreversibility of the degradation function matrix.Based on the special qualities of degradation function matrix and precise deduction in space-domain, we present a new approach using gradient-loading for restoration of rotational blurred image.By easily adding a gradient operator, the irreversibility of the original matrix is corrected and can be applied for inverse filtering then.Gradientloading is the optimized approach which combines the advantages of both the approaches using constrained least square filtering and traditional diagonal-loading.Compared with the approach using least square filtering, its peak signal-to-noise ratio (PSNR) is improved from 3.18 to 6.46dB, while the computing time is reduced to 1/2-1/3.Experimental results demonstrate the effectiveness, noise-resistibility, robustness, and low complexity of this approach, which make it more suitable for real-time environment.     

All-Optical Logic Device Using Bent Nonlinear Tapered Y-Junction Waveguide Structure

We propose an all-optical logic device made of a bent tapered Y-junction waveguide with a Kerr-type nonlinear interface. It could provide an AND gate, OR gate, and exclusive-OR (XOR) gate. We could obtain different transmission results by adjusting the bending angle. The numerical simulation results show that the device functions as AND, OR, and XOR gates.     

Real-time, continuous-wave terahertz imaging by a pyroelectric camera

Real-time, continuous-wave terahertz (THz) imaging is demonstrated. A 1.89-THz optically-pumped farinfrared laser is used as the illumination source, and a 124 × 124 element room-temperature pyroelectric camera is adopted as the detector. With this setup, THz images through various wrapping materials are shown. The results show that this imaging system has the potential applications in real-time mail and security inspection.