基于FPGA的超声波无损检测信号处理研究

针对超声波无损检测中检测信号存在噪声干扰这一问题,采用了将乘加运算转化为查找表的并行分布式算法,在FPGA上实现了一个16阶FIR低通滤波器.通过QuartusⅡ进行硬件仿真,仿真结果表明设计的FIR滤波器滤波效果良好,且运行速度较快.     

数字式超声波无损检测和成像处理系统

论文介绍了一种数字式超声波无损检测和成像处理系统.分析了这一检测系统与传统超声波检测系统的不同点;阐述了系统的工作原理及关键技术部件.     

基于C.Maclaurin展式的圆弧绘制算法

在分析和研究各类圆弧绘制算法的基础上,根据C.Maclaurin展开武构造了一个圆弧绘制算法.解决了圆弧绘制算法中的效率与精度之间的矛盾,是一个高效率、高精度的弧绘制算法.     

激光超声波无损检测技术

多年来，工业超声波无损检测技术是应用一个耦会介质由压电换能器将产生的超声信号耦合到测试样品表面并得到回波，通过传感器对这些返回信号的强度、频率和时限的测量而获取测试样品的内部缺陷参数。而采用激光耦会超声波检测，无需耦会介质，也不需要精确地控制表面和换能器之间的角度（因为测试样品的表面可起换能器的作用），可以进行小于10μm空间分辨率的更快速和远距离非接触（无损）超声波检测，且操作简便，较之传统的工业超声波无损检测方法，激光检测技术更具有优越性。一束聚焦的激光脉冲能量引入到材料表面引起温度上升并使材…     

任意波形编辑软件中手动任意绘制功能的设计

虚拟仪器技术在计算机测量与检测领域中有着广阔的应用.它将传统仪器由硬件实现的数据分析处理与显示功能,改由强大的计算机完成.针对当前任意波形发生器的手动任意绘制功能的广泛需求,提出利用虚拟仪器技术开发该软件系统的方法,并给出了基于LabWindows/CVI软件平台设计手动任意绘制波形功能软件的具体实现.通过实际的的测试和评估,该软件运行良好,证明设计方法完全可行.     

超声波检测等离子弧焊焊接铜与不锈钢对接接头残余应力研究

基于超声波检测对等离子弧焊接铜与不锈钢对接接头的残余应力进行研究。本文针对等离子弧焊铜与不锈钢对接接头在传统检测过程中容易出现漏探及错探的问题,运用超声波进行无损检测,从造成焊接缺陷的起因及形态,到定位、定性及定量方法的合理选用进行了全面深入的探讨。提出了针对此类异种金属的焊接接头适合于现场操作的方法,验证了此类检测方法的合理性。     

相移迁移法在激光超声合成孔径聚焦技术中的应用

通过分析脉冲源激光辐照于工件表面激发的多模式、宽带超声体波信号并结合合成孔径聚焦技术(SAFT),实现了对工件内部微小缺陷的检测、定位和成像。首先基于有限元仿真模拟了激光激发超声波在含缺陷样品中的传播过程,编写了基于相移迁移法(PSM)的SAFT成像算法,然后在实验中使用激光在含缺陷样品表面激发超声波,使用激光测振仪探测超声波,并基于已有算法和探测结果对样品内缺陷进行了检测和定位,以验证算法的正确性。有限元仿真以及实验结果均表明,将激光超声技术与频域SAFT-PSM结合,能够有效地对微小缺陷进行检测和定位,且其图像重构速度快于时域SAFT,可为激光超声无损检测提供更快速的实时技术方案。     

飞秒激光超声时域分析用于无损检测研究

为了进一步探究飞秒激光诱导超声波在无损检测领域中的应用,本文提出了一种基于飞秒激光的超声时域分析方法,实现了对物质的无损检测。该方法首先将飞秒激光聚焦到被测物体表面激发出超声脉冲,然后通过采集超声脉冲的时域信号来对被测物体的内部结构进行可视化无损检测。为了验证方法的有效性,我们进行了以下两个实验:首先,我们对水泥样品进行了扫描并分析得到了其中的孔洞的位置;此外,我们还对未知内部结构的金属镜筒进行了扫描,检测出了其中透镜组的位置。理论分析和实验结果均证明了实验方法的有效性,与传统的超声无损检测技术相比,基于飞秒激光的超声时域分析方法能够简单快速地实现无损检测,具有良好的应用前景。     

基于灰度控制的任意端点直线反走样算法研究

针对使用灰度控制算法不能准确绘制端点不在像素中心点的直线的问题,结合Wu算法,提出了一种基于灰度控制的任意端点直线反走样算法。介绍了Wu算法思想和灰度控制反走样算法,对两种算法进行数学分析,提出灰度控制不能解决的问题及问题产生的后果。结合Wu算法提出了新的基于灰度控制的算法,新算法减少了距离计算和灰度转换的计算,同时解决了任意端点直线的反走样问题。对新算法的效率和反走样效果进行仿真计算。仿真结果表明,新算法比Wu算法效率更高,绘制直线所用时间平均减少33.91%;新算法比灰度控制算法绘制直线更准确,特别是在直线移动的过程中,有较好的动态显示效果。本文提出的新算法,效率较高,显示效果较好,具有很高的应用价值。     

局部放电超声波定位智能算法的研究

电力变压器其绝缘状况对于电力系统的可靠性运行有重大影响.在现场运行中,局部放电是导致电力变压器绝缘劣化的重要原因之一,超声波检测是电气设备局部放电检测、空间定位中重要的非电测法,其定位的准确与否直接影响电气设备故障诊断和快速判断.本文针对传统算法易陷入局部最优、定位误差大的问题,提出了线性策略粒子群的智能优化算法,仿真结果验证了该算法具有全局最优,现场监测结果也证明了其算法的准确性和有效性.     

素域Fp上的安全椭圆曲线的选取及基点快速算法的研究

文中介绍了安全椭圆曲线的设计要求和传统的安全椭圆曲线生成算法;这里的创新之处在于:采用逆向思维方式,首次提出准基点理论,改进了传统的安全椭圆曲线生成算法,改进后的算法使得安全椭圆曲线和基点的生成同时完成,是目前最快的理想椭圆曲线密码体系参数生成算法。     

Efficient modal analysis of arbitrarily shaped waveguides composed of linear, circular, and elliptical arcs using the BI-RME method

This paper deals with the accurate and efficient modal analysis of arbitrarily shaped waveguides whose cross section is defined by a combination of straight, circular, and/or elliptical arcs. A novel technique for considering the presence of circular and/or elliptical segments within the frame of the well-known boundary integral-resonant mode expansion (BI-RME) method is proposed. This new extended BI-RME method will allow a more accurate solution of a wider number of hollow conducting waveguides with arbitrary profiles, which are usually present in most modern passive waveguide components. To show the advantages of this new extended technique, the modal chart of canonical (circular and elliptical) waveguides, as well as of irises with great practical interest (i.e., cross-shaped irises with rounded corners) has been first successfully solved. Next, a computer-aided-design software package based on such a novel modal analysis tool has first been validated with the accurate analysis of a referenced complex dual-mode filter, and then applied to the complete design of a novel twist component for K-band application based on circular and elliptical waveguides. A prototype of this novel device has been manufactured and measured for verification purposes.     

Generalized concatenation of encoded tamed frequency modulation

A novel construction for encoded tamed frequency modulation (TFM) is introduced which is based on the principles of generalized concatenation. The inner TFM is partitioned into nested subsystems which increases the free Euclidean distances. In order to obtain a large distance among the nested TFM subsystems, the scrambler matrices have to be computed which transfer the original TFM into the equivalent TFM with better partitioning properties. Then outer convolutional codes with different error-correcting capabilities are used to protect the partitioning. The new concatenated and generalized concatenated constructions were simulated in an additive white Gaussian noise channel. A multistep decoding algorithm based on soft-output demodulation was used. We present various simulation results which show a significant coding gain in comparison with the best known trellis codes having the same trellis state complexity     

Real-time elliptical head contour detection under arbitrary pose and wide distance range

In this paper, we propose a real time elliptical head contour detection method based on quadrant arcs, which is efficient and robust to arbitrary head pose and wide distance range. First, the moving object area is detected according to background model which is built on three color channels. Then, all the valid elliptical arcs are extracted out from connected edges, and classified into four kinds of quadrant arc sets according to their gradient information. Finally, the arcs lying in different sets are combined to fit out the elliptical head contour based on the least square method. Experimental results confirm the robustness and the accuracy of this method under arbitrary head pose and wider distance range, as well as the real time property, strong robustness to long or short hair and with or without hat.     

适合CBTC系统无线信道加密算法

分析了现有地铁CBTC无线信道安全问题,针对其加密算法RC4的缺陷,提出了一种新的基于Montgomery型曲线ECC快速加密算法.与一般形式的传统的Montgomery型椭圆曲线密码相比,该算法可部分恢复y坐标的值数,具有更高的安全性.该算法与传统椭圆曲线密码相比,具有更快的计算速度并能有效地抵御时间攻击和能量攻击,从而证明了利用ECC密码体制来代替RC4密码体制的可行性.算法对提高椭圆曲线密码的在CBTC等无线通信系统的实现效率有一定意义.     

基于遗传算法的排产优化方法

针对单件小批量生产车间的优化排产问题,采用遗传算法进行研究,设计了一种分组编码方案,提出了可处理零部件间装配关系的适应度函数算法。介绍了遗传算法在车间优化排产中的实现方法及结果,重点讨论了编码方案及适应度函数设计。基于此算法,开发了生产作业计划排产软件,可完成顺排产与倒排产的自动排产,实现工艺排产的智能化。     

System reliability estimation using simulation combined with network reductions

This paper proposes a dynamic Monte Carlo sampling method, called the conditional minimal cut set (COMICS) algorithm, where all arcs are not simulated at each trial and all minimal cut sets need not be given in advance. The proposed algorithm repeats simulating a minimal cut set composed of the arcs which originate from the (new) source node and reducing the network on the basis of the states of simulated arcs until the s-t connectedness is confirmed. We develop the importance sampling estimator, the total hazard estimator and the hazard importance sampling estimator which are all based on the proposed algorithm, and compare the performance of these simulation estimators. It is found that these estimators can significantly reduce the variance of the raw simulation estimator and the usual importance sampling estimator.     

优化扩域上椭圆曲线标量乘的一个新算法

提出了一种优化扩域上椭圆曲线标量乘的新算法.算法基于Frobenius映射和二进制串的逻辑操作.文中对这个算法给出了细致精确的分析,而且在此基础上对新算法作了进一步改进.最后从理论分析和实际仿真两个方面就新算法和传统算法进行了比较.指出新算法执行时间比传统的φ-adic算法要少20%到40%.     

Elliptic cylinder geometry for distinguishability analysis in impedance tomography

Electrical impedance tomography (EIT) is a technique that computes the cross-sectional impedance distribution within the body by using current and voltage measurements made on the body surface. It has been reported that the image reconstruction is distorted considerably when the boundary shape is considered to be more elliptical than circular as a more realistic shape for the measurement boundary. This paper describes an alternative framework for determining the distinguishability region with a finite measurement precision for different conductivity distributions in a body modeled by elliptic cylinder geometry. The distinguishable regions are compared in terms of modeling error for predefined inhomogeneities with elliptical and circular approaches for a noncircular measurement boundary at the body surface. Since most objects investigated by EIT are noncircular in shape, the analytical solution for the forward problem for the elliptical cross section approach is shown to be useful in order to reach a better assessment of the distinguishability region defined in a noncircular boundary. This paper is concentrated on centered elliptic inhomogeneity in the elliptical boundary and an analytic solution for this type of forward problem. The distinguishability performance of elliptical cross section with cosine injected current patterns is examined for different parameters of elliptical geometry.     

一种基于LM算法的激光足印中心提取方法

足印探测法是星载激光测高仪真实性校验的常用方法,而激光足印的中心提取是足印探测法的关键技术之一。针对受到大气湍流的影响的激光足印信号,提出一种基于Levenberg-Marquard(LM)算法的激光足印中心提取方法,以椭圆高斯函数为目标函数模型,通过椭圆高斯特征参数更新和迭代,以目标函数与观察值的残差作为判据,从而实现对特定参数即激光足印中心的提取。采用前40项泽尼克多项式模拟大气湍流作为激光足印在大气传输过程中的噪声,利用仿真数据对算法的提取精度和稳定性进行验证,实验结果表明,本文算法比传统的中心定位方法有着更高的定位精度并且相对稳定,假设激光足印探测器的布设间距为4 m,本文算法比其他传统算法的提取精度至少优于0.5 m。