高精度可连续调节宽带猝发信号发生器设计

本文设计了一种使用纯硬件的设计方法，实现低失真率，频率精度高，且产生连续可调的猝发信号。使用模拟乘法器调幅和模拟开关关断实现矩形窗、汉宁窗、海明窗等不同的加窗形式。另外猝发信号发生器采用了以单片机为核心的嵌入式控制系统，方便地上位机对信号发生器控制。通过串口通信上位机（个人计算机）可以在线修改信号发生器的猝发时间间隔，猝发脉冲宽度，以及信号频率。该信号发生器最高频率达1.8MHz，可以广泛应用于超声导波，电磁超声检测，以及激光脉冲控制等。     

机械裂纹无损检测方法综述

针对机械裂纹扩展以及检测的问题,对常用的裂纹无损检测方法进行了叙述,具体介绍了磁粉检测和渗透检测技术的发展现状。对近年来新兴的激光超声检测技术、电磁超声检测技术、超声红外热成像检测技术、脉冲涡流及涡流阵列检测技术的特点、作用原理进行了详细的说明,对比了相对传统检测技术的优势,对各新型无损检测技术的发展方向进行了总结分析。研究结果表明:未来新型裂纹无损检测方法的发展趋势将由人工向智能化、全自动化、图像化检测发展,复合模式检测在新技术中的应用愈加广泛,检测仪器设备的发展以降低能耗和提高信噪比为主,新型裂纹无损检测技术在特殊工程领域的应用将更加专业化。     

脉冲涡流无损检测技术应用研究

脉冲涡流与传统涡流不同，脉冲涡流通过测量磁场最大值出现的时间来确定缺陷的位置。对脉冲涡流的检测原理进行了分析，设计了脉冲波形发生器和垂直磁场检测电路，并通过试验对此方法进行了验证。     

空心圆柱体中的周向超声导波

通过理论分析及数值计算研究空心圆柱体中周向导波的传播及频散特性,确定影响空心圆柱体中周向导波传播与频散的几何形状因素;对比不同形状空心圆柱体同相应板的导波频散特性,找出其中的关系;其结果是：在低频段,利用第2个周向导波模态作为薄壁空心圆柱体纵向缺陷无损检测较适合。     

Theory of fully developed mixed convection including flow reversal: A nonlinear Boussinesq approximation approach

In this article, an exact solution is obtained to investigate the role of nonlinear Boussinesq approximation on mixed convection flow in a vertical channel subject to asymmetric wall heating. The nonlinear density variation with temperature (NDT) in the buoyancy term is introduced to the momentum equation and solved exactly by direct integration. During the course of graphical and numerical computations, results show that the role of NDT is to increase fluid velocity as well as skin‐friction while it reduces the rate of heat transfer. In addition, reverse flow formation at the walls is increased due to the inclusion of NDT (nonlinear Boussinesq approximation).     

涡流检测缺陷模糊认识的新方法

针对无损检测中缺陷特征及危害程度具有某种模糊性的现象，提出用模糊逻辑来完成缺陷识别的思想。为满足在线识别自然缺陷的要求，提出了一种新的模糊聚类方法，并给出了在涡流检测中的应用结果。     

多晶氟化镁(MgF2)导弹整流罩内散射颗粒定量无损检测方法研究

将ＣＣＤ摄像技术与计算机数字图像处理技术用于散射颗粒的定量检测，设计制造了配套设备－ＳＧ－９５型散射颗粒定量检测系统，首次实现了多晶ＭｇＦ２导弹整流罩散射颗粒的工程定量检测与自动计数，检测精度优于１０μｍ。     

Matrix factorization methods: Application to thermal NDT/E

A typical problem in thermal nondestructive testing/evaluation (TNDT/E) is that of unsupervised feature extraction from the experimental data. Matrix factorization methods (MFMs) are mathematical techniques well suited for this task. In this paper we present the application of three MFMs: principal component analysis (PCA), non-negative matrix factorization (NMF), and archetypal analysis (AA). To better understand the peculiarities of each method the results are first compared on simulated data. It will be shown that the shape of the data set strongly affects the performance. A good understanding of the actual shape of the thermal NDT data is required to properly choose the most suitable MFM, as it is shown in the application to experimental data.     

Novel SFS-NDT in the field of defect detection

NDT plays a crucial role in everyday life and is necessary to assure safety and reliability. NDT applied to surface detection as far as possible should be a non-contacting technique operating easily with low inspection costs and a high accuracy, human beings as inspectors as well as the environment should not be harmed. A novel NDT based on Shape From Shading (SFS) is introduced in this paper. SFS is a prospecting 3D recovery method because it recovers 3D shape of work piece only from one image. We firstly use SFS in the field of 3D surface defect detection, which is an effective way to guarantee the product quality. Compared with other defect detection method, this SFS method only needs CCD, optical system, image-collection card and computer. It has the merits such as low cost, easy operation, non-contact, non-destructive, no harming to people, and it is 3D overall shape detection. SFS-NDT has been used in the online defect detection measurement of TianJin SanHuan new material Ltd in Chinese Academy of Science. The 3D shape recovery method and application in the field of defect detection are presented. The precision of 3D recovery is analyzed.     

无损检测技术在雷达波吸收材料研究中的应用

采用ＮＤＴ方法中涡流检测技术研制出吸波涂层专用测厚仪。这种涡流测厚方法适用于涂敷在铝合金基材上的铁磁性吸波涂层，测量简便、准确，对涂层无损坏，解决了在大型工件上施工时吸波涂层厚度的控制问题。