激光脉冲编码抗有源干扰效果研究

激光脉冲编码是激光制导武器的抗干扰措施之一。角度欺骗式干扰和高重频干扰是目前半主动激光制导武器的主要有源干扰来源。为研究不同激光脉冲编码方式对激光半主动制导武器抗这两种干扰性能的影响,本文针对敌方激光告警机的识别算法与我方导引头的解码过程,提出自相关函数与归一化互相关函数评价方法,并对目前主要编码方式进行仿真,仿真结果表明:激光脉冲编码的抗角度欺骗式干扰能力受编码序列周期性与脉冲间隔随机性的影响；抗高重频激光干扰能力受编码序列脉冲间隔随机性的影响；LFSR状态码的抗角度欺骗式干扰与抗高重频干扰效果均优于其他编码方式。     

Model validation and model structure determination

This paper gives a tutorial overview of basic approaches for model validation and model structure determination.Work partially supported by the Swedish Research Council for Engineering Sciences under contract 98-654.     

微机械谐振器的快速测试方法

为了缩短微机械谐振器的测量时间,提高测量效率.提出了一种针对压阻检测的微谐振器的频率特性测试新方法,该方法利用欧姆鉴相器,积分器和微处理器实现对微弱信号的有效检测.欧姆鉴相器以检测电阻为鉴相器,利用欧姆定律实现参考信号和被测信号的乘法鉴相运算;通过积分器实现对鉴相结果的积分运算,抑制干扰和噪声;微处理器用于对积分数据的...     

k-NN classification of handwritten characters via accelerated GAT correlation

This paper addresses the problem of reinforcing the ability of the k-NN classification of handwritten characters via distortion-tolerant template matching techniques with a limited quantity of data. We compare three kinds of matching techniques: the conventional simple correlation, the tangent distance, and the global affine transformation (GAT) correlation. Although the k-NN classification method is straightforward and powerful, it consumes a lot of time. Therefore, to reduce the computational cost of matching in k-NN classification, we propose accelerating the GAT correlation method by reformulating its computational model and adopting efficient lookup tables. Recognition experiments performed on the IPTP CDROM1B handwritten numerical database show that the matching techniques of the simple correlation, the tangent distance, and the accelerated GAT correlation achieved recognition rates of 97.07%, 97.50%, and 98.70%, respectively. The computation time ratios of the tangent distance and the accelerated GAT correlation to the simple correlation are 26.3 and 36.5 to 1.0, respectively.     

基于互相关定位法的干涉仪分析与仿真

首次提出用时域互相关法处理Sagnac/Mach-Zehnder分布式光纤传感系统的干涉输出信号, 对扰动进行检测和定位。首先对Sagnac/Mach-Zehnder分布式光纤传感系统进行了扰动检测和定位的理论分析, 推导出扰动引起的干涉输出信号的表达式, 利用Bessel函数展开, 确定了该系统的两路干涉输出满足时域互相关的特性。在此基础上进一步分析了两路干涉信号的表达式, 提出基频定位法和微分定位法两种时域互相关方法处理干涉信号, 确定扰动位置。对两种扰动定位方法进行了Matlab仿真, 并通过实验在多个扰动位置多次验证了两种方法的正确性。     

Global Avalanche Characteristics of Boolean Functions by Concatenation

In order to measure the correlation propeties of two Boolean functions,the global avalanche characteristics of Boolean functions constructed by concatenation are discussed,i.e.,f_1‖f_2and f_1‖f_2‖f_3‖f_4.Firstly,for the function f = f_1‖f_2,the cross-correlation function of f_1,f_2 in the special condition are studied.In this case,f,f_1,f_2 must be in desired form.By computing their sum-of-squares indicators,the crosscorrelation function between f_1,f_2 is obtained.Secondly,for the function g = f_1‖f_2‖f_3‖f_4,by analyzing the relation among their auto-correlation functions,their sum-of-squares indicators are investigated.Based on them,the sum-of-squares indicators of functions obtained by Canteaut et al.are investigated.The results show that the correlation property of g is good when the correlation properties of Boolean functions f_1,f_2,f_3,f_4 are good.     

Micro-motion feature analysis and parameter estimation methods for moving ship

Micro-motion parameter estimation is an important way to improve ability of radar to detect the ship target. Focusing on the difficulty and speed problems existing in the current parameter estimation method of a complex moving ship, based on the analytical result of the echo's time-frequency features, a novel method to estimate the micro-motion period by calculating the backward shift cross-correlation coefficients of the echo's sparse time-frequency matrix is proposed in this paper. Firstly, the backward shift cross-correlation coefficients of the echo's sparse time-frequency matrix are calculated using the FFT (fast Fourier transform) algorithm. The peaks positions of the cross-correlation coefficients matrix are then detected. Finally, the period can be figured out quickly. Compared with the general method, the proposed method can estimate the micro-motion period accurately and quickly. A computer simulation is given to illustrate the effectiveness of the proposed method.     

基于相关算法的电磁流量计抗噪性能研究

针对电磁流量计在低速测量时,信号被噪声淹没不能准确测量的问题,引入了相关检测算法.本文介绍了相关检测算法进行流量测量的基本原理,通过在电磁流量计测量中引入相关检测算法,滤掉了噪声干扰,提高了信号的信噪比,使电磁流量计在低速或者在低信噪比的情况下测量时,性能有较大改善,精度可达0.5%左右.在低流速时能够稳定的显示数据.     

基于截面含气率的气／液两相流相关速度测量

基于双截面电阻层析成像技术进行气／液两相流的相关速度测试研究,分析了相关速度测量原理,提出了基于截面含气率的相关测速方法。通过插值增加上游、下游双截面含气率的采样数据,利用独立开发的软件系统具有的数据存储与回放功能对基于截面含气率的相关测速方法进行评定实验。实验结果表明：该方法测速精度较高,且稳定可靠。     

Characterization of laser hardened steels by laser induced ultrasonic surface waves

Ultrasonic surface waves are suitable for the characterization of surface hardened materials. This is shown on laser hardened turbine blades. The martensitic microstructure within the surface layer of surface hardened steels has a lower surface wave propagation velocity than the annealed or normalized substrate material. Because the propagation velocity depends on the ratio of layer thickness to wavelengthd/, its measurement allows the determination of the hardening depth. If the surface wave frequency is high enough, the surface wave propagates mainly within the hardened layer. A correlation of the surface wave velocity to the surface hardness has been found. Because the variation of the surface velocity in hardened steels is small, a high measurement accuracy is necessary to obtain the interesting hardening parameters with sufficient certainty. Therefore, a measuring arrangement has been developed where laser pulses, guided by optical fibers to the surface hardened structure, generate simultaneously surface wave pulses at two different positions. The two ultrasonic pulses are received by a piezoelectric transducer. The surface wave velocity is obtained from the time delay between these pulses which is determined by the cross-correlation method. To evaluate simultaneously surface waves with different penetration depths from the same signal acquisition, digital filtering has been used in connection with the cross-correlation.