声场干涉结构相似度匹配的目标运动参数估计

针对水中运动声源定位问题,建立了一种基于声场干涉结构谱向量相似度匹配的目标运动参数估计方法。结合声场干涉结构水平纵向相关特性,利用目标辐射噪声LOFAR谱图中不同频率的谱值序列,基于两方位-两距离目标运动要素计算方法获取的目标距离解向量,构造声场干涉结构谱向量相似度匹配代价因子,实现目标运动参数估计。仿真数据与试验数据验证结果表明:在绘制的目标运动要素解算结果可视化分布图中可清晰呈现出目标初距、航向和速度结果。该算法实现过程简单、解算效率高,对目标方位误差有较好的鲁棒性。      

基于频谱Sevcik维数的目标运动速度估计*

在声目标无源估计应用中,目标与接收器存在相对运动时,接收的目标辐射的噪声信号存在多普勒频移。多普勒频移中包含目标的运动参数信息。针对线谱信号多普勒频移目标运动参数获取问题,提出一种基于频谱Sevcik维数的目标运动速度获取方法。首先利用Doppler-warping变换对接收信号进行重采样,然后对重采样后的频谱信号求Sevcik维数,最后通过寻找Sevcik最小值来实现速度估计。仿真证实了所提方法的有效性,在相同仿真条件下,所提方法相较于频谱求熵算法,速度搜索结果不仅具有更窄的主瓣宽度,而且可提高抗噪性5dB左右。两组实验数据的速度估计误差小于5%,证明了本文算法的有效性。     

快速正交搜索算法在水声信号处理中的应用*

信号的谱估计技术作为一种十分重要且应用广泛的信号分析处理手段,对其性能的不断提升和改进一直是水声信号处理领域研究的重点和热点。对此,该文将快速正交搜索算法应用于水声信号的谱估计中,通过隐式正交对参数进行搜索,实现对信号频率、幅度、相位的估计。仿真和实验数据处理结果表明,相较于传统的谱估计方法,该方法能稳定且准确地估计水声信号的多个参数,获得频率分辨率较高的谱估计结果。     

利用频域β-warping变换的浅海修正纯方位目标运动分析方法

针对纯方位目标运动分析方法收敛时间较长的问题,提出了一种利用频域β-warping变换的浅海修正纯方位目标运动分析方法.该方法利用频域β-warping变换从声强干涉结构中提取与目标距离成线性关系的时延,进而估计距离特征量,并利用距离特征量推导得到的目标状态向量的线性约束修正纯方位扩展卡尔曼滤波算法。数值仿真结果表明,对于浅海匀速直线运动目标,在信噪比不低于8 dB的情况下,与常规纯方位扩展卡尔曼滤波算法相比,改进算法将距离估计的收敛时间由26.5 min缩短至11.5 min.在浅海水平不变波导远场条件下,该方法可以快速稳定地估计距离特征量,并能够对目标进行可靠地跟踪定位。      

基于倒谱分析的单水听器目标运动参数估计

基于浅海射线声学多途结构,提出了一种具有高稳健性、高精度的单水听器目标运动参估计方法.针对匀速直线运动目标,综合多途时延差和运动学几何关系,构建了目标三维多途时延模型,进而获得目标运动参数与多途时延差的非线性时间映射.研究了典型水声信道的倒谱表达式,提出了利用倒谱提取多途时延差的策略.采用差分进化综合优化手段估计目标运动参数,提高了算法的稳健性.理论及仿真结果表明,倒谱的时间分辨率不受信号带宽的限制,而主要取决于信号类型和信噪比;CW信号的倒谱对多普勒不敏感;参数估计精度主要取决于时延差估计精度和参与差分进化运算的信息量,当包含有最近点信息时参数估计性能较好.水池实验结果进一步验证了方法的正确性和有效性.     

Robust passive range estimation using the waveguide invariant

The waveguide invariant principle is used to estimate the range to a broadband acoustic source in a shallow-water waveguide using a single acoustic receiver towed along a path directly toward the acoustic source. A relationship between the signal processing parameters and the ocean-acoustic environmental parameters is used to increase the effective signal-to-noise ratio without requiring detailed knowledge of the environment. Heuristics are developed to estimate the minimum source bandwidth and minimum horizontal aperture required for range estimation. A range estimation algorithm is tested on experimental and simulated data for source ranges of 500-2200 m and frequencies from 350 to 700 Hz. The algorithm is accurate to within approximately 25% for the cases tested and requires only a minimal amount of a priori environmental knowledge.     

浅海运动目标波束域波导不变量测距方法研究

波导不变量是描述海洋波导环境声信号水平距离与频率干涉结构现象的特征参量。运动目标波导不变量测距方法需要已知目标速度值,运动目标速度一般是未知的。针对这一问题,本文提出了一种利用水平线阵估计目标运动速度的浅海波导不变量测距方法。该方法通过不同时刻波束域声信号互谱分析进行声源速度估计,结合HOUGH变换提取的LOFAR图斜率和波导不变量进行运动目标测距。仿真结果表明,该方法能够有效的进行运动目标的距离估计。利用2013年7月浅海实验数据,该方法估计出了发射船的距离,并与GPS测量的距离进行对比,相对误差小于10%。      

利用信号自相关函数warping变换的浅海水下移动观测平台机动优化方法

水下移动观测平台的机动航路对纯方位目标运动分析方法的使用性能具有重要的影响。针对此问题,提出了一种利用信号自相关函数warping变换的浅海水下移动观测平台机动优化方法。该方法利用warping变换从接收信号自相关函数中提取与目标距离相关的简正波相干项的特征频率,进而估计距离特征量,再根据预估的目标初始距离范围估计目标运动态势范围。针对观测平台机动方式为匀速转弯运动的情况,以目标方位变化率为评价指标得到了观测平台在所估计的目标运动态势范围下的最优转弯角速率。在浅海Pekeris波导环境下的数值仿真结果和实验数据处理结果表明:方位变化率与纯方位扩展卡尔曼滤波算法的性能密切相关;利用warping变换可以有效地估计距离特征量;观测平台根据以方位变化率为评价指标得到的最优转弯角速率进行机动可以获得较好的目标跟踪性能,收敛时间较短,目标位置估计误差较小。      

混沌伪随机序列的谱熵复杂性分析

为了准确分析混沌伪随机序列的结构复杂性,采用谱熵算法对Logistic映射、Gaussian映射和TD-ERCS系统产生的混沌伪随机序列复杂度进行了分析.谱熵算法具有参数少、对序列长度N(惟一参数)和伪随机进制数K鲁棒性好的特点.采用窗口滑动法分析了混沌伪随机序列的复杂度演变特性,计算了离散混沌系统不同初值和不同系统参数条件下的复杂度.研究表明,谱熵算法能有效地分析混沌伪随机序列的结构复杂度;在这三个混沌系统中,TD-ERCS系统为广域高复杂度混沌系统,复杂度性能最好;不同窗口和不同初值条件下的混沌系统复杂度在较小范围内波动.为混沌序列在信息安全中的应用提供了理论和实验依据.     

基于多光谱辐射特性的高速目标识别定位系统

为了实现高速目标的快速识别及定位,采用多光谱辐射与声定位技术联用,在被动探测的状态下快速获取被测目标爆炸波的光谱特性及声特性,从而分析判断其种类、位置等重要参数信息。推导了多光谱辐射目标识别检出公式,计算了采用激波声定位方法获取光程距离的精度及合理的积分时间。实验分别采用5.56 mm北约弹、7.62 mm 56式步枪弹、12.7 mm 54式机枪弹作为被识别目标弹丸,通过丹麦B&K公司的2209脉冲声压计完成声压峰值采集,获得了三种目标弹丸的速度、距离信息。由静态傅里叶变换干涉系统与ICX387AL型CCD完成干涉条纹的采集,再将获得的光程信息代入多光谱目标识别算法中,从而通过目标的光谱特性识别弹丸的类型。实验结果显示,5.56 mm北约弹的三个特征波长位置幅值接近,966 nm位置处幅值最大;7.62 mm步枪弹在935 nm位置上幅值最大,其他两个位置上幅值相近;12.7 mm机枪弹的三个波长呈阶梯状分布。在多次测试过程中,经光谱标定、特征波长提取等方法对采集得到的三组光谱数据均可成功识别弹丸的种类并给出目标位置,满足设计要求。     

Droplet transport and coalescence kinetics in emulsions subjected to acoustic fields

A method to aid the separation of the oil phase from aqueous emulsions using a low-intensity, resonant ultrasonic field has recently been developed. The density and compressibility difference between the dispersed and continuous phases within the emulsion results in a net force on the oil drops that pushes them toward the pressure antinodes of the standing-wave field, where coalescence subsequently occurs. A trajectory model is developed to predict the relative motion of drops subjected to the acoustic field. Such trajectories are sensitive to the physical properties and relative size of interacting drops, the initial configuration of the drops, and acoustic field parameters. Model predictions are validated by comparing experimentally observed trajectories with those predicted by the model. The modeling approach is then extended to determine the temporal evolution of the size of the region surrounding a target drop cleared by coalescence as a function of physical and acoustic field parameters. These results form the basis of a population balance model that attempts to track the size-evolution of a drop population coalescing under the influence of an acoustic field.     

Articulatory-acoustic kinematics: the production of American English /s/

Due to its aerodynamic, articulatory, and acoustic complexities, the fricative /s/ is known to require high precision in its control, and to be highly resistant to coarticulation. This study documents in detail how jaw, tongue front, tongue back, lips, and the first spectral moment covary during the production of /s/, to establish how coarticulation affects this segment. Data were obtained from 24 speakers in the Wisconsin x-ray microbeam database producing /s/ in prevocalic and pre-obstruent sequences. Analysis of the data showed that certain aspects of jaw and tongue motion had specific kinematic trajectories, regardless of context, and the first spectral moment trajectory corresponded to these in some aspects. In particular contexts, variability due to jaw motion is compensated for by tongue-tip motion and bracing against the palate, to maintain an invariant articulatory-aerodynamic goal, constriction degree. The change in the first spectral moment, which rises to a peak at the midpoint of the fricative, primarily reflects the motion of the jaw. Implications of the results for theories of speech motor control and acoustic-articulatory relations are discussed.     

Monte Carlo uncertainty simulation of surface emissivity at ambient temperature obtained by dual spectral infrared radiometry

The Monte Carlo statistical method was used to estimate the uncertainty of the emissivity, obtained by dual spectral infrared radiometry, of gray surfaces at ambient temperature. A large number of simulations were carried out, by selecting a wide range of values from parameters that directly affect the resulting emissivity: the emissivity of the target surface, the background temperature of the surrounding surfaces, the maximum error of the detectors, and the width and spectral location of the bands of the detectors.In summary, the level of uncertainty grows very quickly as the background temperature approximates the target surface. In terms of the spectral characteristics of the detectors, it was found that narrow bands, far apart from each other, and short wavelength bands provide the lowest uncertainty from all simulated emissivity values.     

Study of acoustic field modulation in the regenerator by double loudspeakers method

A model to modulate acoustic field in a regenerator of a thermoacoustic system by the double loudspeakers method is presented in this paper. The equations are derived for acoustic field modulation. They represent the relations among acoustic field (complex pressure p(0), complex velocity u(0), and acoustic impedance Z(0)), driving parameters of loudspeakers (voltage amplitude and its phase difference), and operating parameters involved in a matrix H (frequency, temperature of regenerator). The range of acoustic field is adjustable and limited by the maximal driving voltages of loudspeakers according to driving parameters. The range is simulated and analyzed in the amplitude-phase and complex coordinate planes for a given or variable H. The simulated results indicate that the range has its intrinsic characteristics. The expected acoustic field in a regenerator can be obtained feasibly by the modulation.     

Radiation force on absorbing targets and power measurements of a high intensity focused ultrasound (HIFU) source

Based on the analytic expressions for the radiated field of a circular concave piston given by Hasegawa et al.,an integral for calculation of the radiation force on a plane absorbing target in a spherically focused field is derived.A general relation between acoustic power P and normal radiation force Fn is obtained under the condition of kr 1.Numerical computation is carried out by using the symbolic computation program for practically focused sources and absorbing circular targets.The results show that,for a given source,there is a range of target positions where the radiation force is independent of the target's position under the assumption that the contribution of the acoustic field behind the target to the radiation force can be neglected.The experiments are carried out and confirm that there is a range of target positions where the measured radiation force is basically independent of the target's position even at high acoustic power (up to 700 W).It is believed that when the radiation force method is used to measure the acoustic power radiated from a focused source,the size of the target must be selected in such a way that no observable sound can be found in the region behind the target.     

SiO2波导布拉格器件中声表面波及声光相互作用分析

针对SiO2光波导声光布拉格器件,计算了SiO2非对称平板波导TE模式的横向场分布;给出了SiO2/ZnO/Air层状介质结构的性能方程、运动方程和麦克斯韦方程,推导出这种层状结构的特征方程,并结合所满足的边界条件,得到了各层介质的位移及电磁场分布;计算了声表面波所引起的光学相对介质隔离率张量的变化,最后讨论了声光衍射效率和光场与声场的重叠积分、声功率、声频率、声孔径和光波导参数之间的关系。结果表明,在低频范围内光场与声表面波场重叠良好;低阶模的重叠积分始终大于高阶模重叠积分,最低阶模与声表面波相互作用最强,所需声功率最小;当声功率一定时,增加声孔径可以提高衍射效率。     

Sound source localization in an ocean waveguide

A robust algorithm for sound source localization in shallow sea based on a 2D Fourier transform of source motion interference patterns is developed. A spectrogram in time-frequency coordinates obtained after a Fourier transform contains localized areas of spectral density intensity of constructively interfering modes and a distributed area of noise spectral density. Signal spectral density is localized in an area whose linear sizes are determined by the lowest frequency and spatial scales of field variability. The peak input signal-to-noise ratio is estimated for a single receiver when robust detection is ensured and estimates of speed and initial distance to the receiver are close to the actual values. The high robustness of the algorithm is based on the coherent summation of mode amplitudes occurring at different times. Experimental results demonstrating the effectiveness of the algorithm are presented. For higher than peak signal-to-noise ratios, random estimates of the parameters are close to their statistically average values.     

基于高分辨谱估计方法的快速运动目标分析*

水下运动目标产生的声场由一系列不同模态的简正波组成,不同模态简正波具有不同的多普勒频率移动,携带了运动目标速度、频率等参数的信息。针对快速运动目标水下辐射声场的这一特点,采用高分辨谱估计Burg算法估计不同模态简正波多普勒频移,进而获得运动目标的速度、频率参数估计。数值仿真结果表明,高分辨谱估计Burg算法获得了高频率分辨率,在较短的观测时间或是阵元不足的情况下,较准确地估计了多普勒频移,获得了目标运动速度和初始频率等运动参数。     

基于大数据分析的移动对象轨迹预测方法

对移动对象的轨迹预测将在移动目标跟踪识别中具有较好的应用价值。移动对象轨迹预测的基础是移动目标运动参量的采集和估计,移动目标的运动参量信息特征规模较大,传统的单分量时间序列分析方法难以实现准确的参量估计和轨迹预测。提出一种基于大数据多传感信息融合跟踪的移动对象轨迹预测算法。首先进行移动目标对象进行轨迹跟踪的控制对象描述和约束参量分析,对轨迹预测的大规模运动参量信息进行信息融合和自正整定性控制,通过大数据分析方法实现对移动对象运动参量的准确估计和检测,由此指导移动对象轨迹的准确预测,提高预测精度。仿真结果表明,采用该算法进行移动对象的运动参量估计和轨迹预测的精度较高,自适应性能较强,稳健性较好,相关的指标性能优于传统方法。     

Motion tracking in infrared imaging for quantitative medical diagnostic applications

In medical applications, infrared (IR) thermography is used to detect and examine the thermal signature of skin abnormalities by quantitatively analyzing skin temperature in steady state conditions or its evolution over time, captured in an image sequence. However, during the image acquisition period, the involuntary movements of the patient are unavoidable, and such movements will undermine the accuracy of temperature measurement for any particular location on the skin. In this study, a tracking approach using a template-based algorithm is proposed, to follow the involuntary motion of the subject in the IR image sequence. The motion tacking will allow to associate a temperature evolution to each spatial location on the body while the body moves relative to the image frame. The affine transformation model is adopted to estimate the motion parameters of the template image. The Lucas–Kanade algorithm is applied to search for the optimized parameters of the affine transformation. A weighting mask is incorporated into the algorithm to ensure its tracking robustness. To evaluate the feasibility of the tracking approach, two sets of IR image sequences with random in-plane motion were tested in our experiments. A steady-state (no heating or cooling) IR image sequence in which the skin temperature is in equilibrium with the environment was considered first. The thermal recovery IR image sequence, acquired when the skin is recovering from 60-s cooling, was the second case analyzed. By proper selection of the template image along with template update, satisfactory tracking results were obtained for both IR image sequences. The achieved tracking accuracies are promising in terms of satisfying the demands imposed by clinical applications of IR thermography.