水下管道超声导波检测实验研究

扭转模态导波T(0,1)对液体载荷不敏感,其用于水下管道检测是一种具有潜在吸引力的导波模态。基于T(0,1)导波,研制了一套可用于水下管道检测的新型换能器阵列,并在实验室环境中进行了系列检测实验。换能器采用厚度剪切型压电陶瓷作为敏感元件。卡具装置采用模块化设计,模块间通过销轴连接。这种设计使换能器阵列具有一定的柔性,并可方便拆卸各模块以满足不同直径管道对于换能器数量的要求。实验结果表明,换能器阵列能在水下管道中高效激励和接收T(0,1)模态导波。模拟损伤回波信号到达时间和幅度较好地反映了损伤的轴向位置及大小。换能器阵列具有安装简单,使用灵活的特点,为水下管道超声导波检测提供了有效手段。     

基于PZT传感器的管道扭转模态激励效果研究

导波激励模态单一性与衰减特性是导波激励效果的重要指标。采用PZT传感器,在建立基于PZT-5材料传感器并置于管道一端均匀对称分布的导波激励系统的基础上,以模态单一性与降低衰减特性为目标,研究了在低频段内模态特性以及传感器对T(0,1)模态的影响,得出了激励T(0,1)模态的最优激励方案。     

小口径管扭转模态导波在线检测

采用扭转模态导波T(0,1)开展了小口径管在线检测研究。考虑管线服役环境及其结构特征,研制了一种适用于小口径管线在线检测的新型传感器阵列。传感器采用剪切型压陶瓷晶片作为敏感元件,具有柔性、轻质的特点。实验表明,环向布置的传感器阵列能够在管线中高效激励T(0,1)模态导波;通过提取回波信号中的各模态导波信息,实验系统能有效辨识管线中缺陷的状态变化;对于含有支撑结构的小口径管,比较并分析管线中导波散射信号及特征结构处回波信号的变化有助于辨识支撑结构附近区域损伤的产生及扩展。     

旋转反射镜式超声传感器的研究

针对小管道在役检测的特点，对旋转反射镜式传感器结构的不漏检条件进行了详细分析，并对单焦距超声传感器用于小管道在役检测时的相对误差进行了讨论；在超声检测分析的基础上，对旋转反射镜式传感器进行了结构设计，它由超声传感器、平面反射镜、旋转机构、微型电机和连接器等部件组成；小管道液浸超声检测室内试验表明，在适当的采样率和系统增益情况下，反射镜式超声传感器可用于小管道的在役检测。     

超声导波管道诊断仪系统主机的实现

本系统主机主要有三个功能:首先,产生一脉冲激励源,其中心频率、周期数、幅值、重复频率等参数均可设置以适用于超声导波信号特征,并进行信号处理、功率放大,从而驱动负载产生超声导波,以实现对被检测管道的激励;其次,实现对传感器输出的信号调理、数据采集、数据保存及数据传输;最后,实现其它辅助功能。本文详细阐述了超声导波脉冲激励源及多通道高速数据采集的实现。     

基于压电超声导波的管道缺陷检测数值模拟

建立了压电材料与管道结构的超声与机械多物理场耦合有限元数值分析模型,采用ANSYS数值分析软件,在认识管道中导波频散特性的基础上,对利用压电陶瓷(PZT)激发的纵向导波进行数值模拟,探究压电超声用于管道损伤识别的机理。在管道模型的自由端周向分布16个PZT激励器激发入射导波,运用与之相距50mm处的PZT接收检测信号,对不同尺寸的单裂纹管道模型进行了数值模拟。结果表明,运用纵向导波检测能准确识别出管道缺陷的存在,且回波的幅值与缺陷尺寸有明显的正相关性,对接收信号时程进行分析可较准确地定位缺陷位置。     

基于模态分离算法的管道焊缝缺陷周向定位研究

针对管道焊缝质量的检测问题,研究了一种基于超声导波的管道环焊缝缺陷周向定位方法,可快速确定管道焊缝中的缺陷周向位置。该方法基于超声导波模态分离算法,分离出焊缝回波信号中的对称、非对称模态,提取对称、非对称模态峰值,并利用非对称模态与焊缝中非对称缺陷的对应关系,确定缺陷所在周向位置。通过试验验证了该方法的正确性,并总结出可检测缺陷的范围。     

基于超声导波波谱法管道缺陷检测仿真研究

针对超声导波检测难以准确判定管道缺陷的问题,通过分析超声导波遇管道缺陷后其回波的传播,提出了以波谱法来定位和定量管道缺陷。采用ANSYS软件仿真了T(0, 1)模态超声导波在带缺陷管道中的传播,得到检测的幅值波谱图,发现波谱图中缺陷处的颜色总是最先变化;通过分析所有节点同一时间坐标信号的幅值,发现相对最大缺陷信号幅值,幅值衰减在1/10内的节点数与缺陷的周向尺寸之间存在确定的系数关系。     

基于导波能量差的管道缺陷周向定位实验研究

针对超声导波检测需通过对回波信号进行分析而得到管道健康信息,而无法反映缺陷的周向位置信息的问题。文中采用超声导波方法对管道缺陷周向定位进行了研究,分析了超声导波在管道中遇缺陷后的能量分布,以及周向定位的原理。根据F(1,3)模态导波周向波数只有一个的特性,提出了象限能量差定位缺陷方法,并对该方法进行了实验研究,结果表明,方法可以准确地判定出缺陷所在周向位置。     

油气管道高速漏磁检测系统中传感器研究和设计

为了提高漏磁检测的精度,文章研制了一种用于油气管道漏磁检测系统中的电磁感应式传感器,该传感器安置在二维高速漏磁检测装置中,实现对油气管道缺陷信号的实时检测,获得管道的缺陷信号.介绍了传感器的结构,带磁汇聚装置的磁化系统装置;设计实验与普通的霍尔传感器的检测精度进行分析比较.试验结果表明该传感器在高速管道漏磁检测中能够检测到微小缺陷,比霍尔传感器有更高的灵敏度.     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.     

A rigorous proof of MIMO channel capacity’s increase with antenna number

It is well known that adding more antennas at the transmitter or at the receiver may offer larger channel capacity in the multiple-input multiple-output（MIMO） communication systems. In this letter, a simple proof is presented for the fact that the channel capacity increases with an increase in the number of receiving antennas. The proof is based on the famous capacity formula of Foschini and Gans with matrix theory.