同轴监测激光深熔焊熔池小孔的特征分析

为了研究激光焊接工艺参量以及焊接材料对熔池、小孔形貌的影响,搭建了激光焊接同轴监测系统,对比研究了有无辅助光源和不同工艺条件下、采用中心波长分别为532nm和808nm窄带滤光片同轴监测的熔池、小孔图像特征。结果表明,采用808nm激光辅助光源照明和808nm窄带滤光片,可清晰地拍摄到熔池、小孔以及穿透孔特征图像;相同的工艺条件下,熔池变化小,小孔动态波动且波动幅度小,穿透孔的时变动态特征较小孔则明显不同;熔池宽度随激光功率的增加而增大,随焊接速率增大而减小;不同材料激光焊接的熔池、小孔和穿透孔的同轴监测验证了本监测系统的稳定性。该研究对激光焊接质量实时监控有理论指导意义。     

激光深熔焊熔池及小孔的检测

激光深熔焊熔池-小孔包含丰富的反映熔深的信息.本文建立了基于视觉的熔池-小孔同轴检测系统,拍摄了不同焊接速度下熔池-小孔的清晰的图像,分析了熔池宽度、小孔直径随焊接速度的变化规律研究发现,小孔直径随焊接速度的增大先增加后减小,熔池宽度随焊接速度的增大而减小.     

大功率Nd:YAG激光深熔焊接过程中同轴辐射光的采集

同轴信息监测是一种直接对熔池和小孔进行监测的方法。本文介绍了激光深熔焊接过程中 ,同轴信号的采集原理和光路设计 ,利用同轴信息采集光路的激光焊接镜头采集了大功率Nd :YAG激光焊接过程中辐射的同轴光信号。对Q2 35钢激光深熔焊接过程中 ,从焊接熔池和等离子体中辐射的同轴光谱曲线是以连续谱为背景谱 ,当焊接参数的变化时 ,同轴辐射光的相对光强发生变化 ,而其与波长的对应关系没有变化。在激光深熔点焊过程中同时采集了同轴和水平辐射的光强信息 ,对比发现二者具有不同的峰值波长 ,并且在 5 5 0nm～ 5 80nm的波段内 ,二者的相对强度对比明显     

CO2激光-MIG复合对接焊熔透工艺

在有坡口间隙对接焊时，焊缝根部成形状态是衡量复合焊搭桥质量及其适应能力的重要指标。因此研究了CO2激光惰性气体金属弧焊(MIG)复合焊接3 mm厚不锈钢板时激光功率、电弧电流、激光-电弧距离、焊接速度、坡口间隙等工艺参数对根部熔宽的影响，并通过CCD摄像机对焊接过程中的等离子体进行了观察。研究表明，随着焊接参数的变化，CO2激光-MIG复合焊存在四种熔透状态，对某一间隙范围，选择合适的激光功率、电弧电流、激光电弧距离与焊接速度可以获得“适度熔透”的良好根部成形。激光功率、电弧电流过小，速度过大则会产生“未熔透”或“不稳定熔透”，反之则“过熔透”。间隙较大时，激光功率对熔透的影响较小。另外还研究了不同激光电弧距离对等离子体形态及其对熔透的影响。     

激光-MIG复合焊背面熔宽的检测

对接焊中,背面熔宽最直接地反映了熔透状态.为获取CO2激光-MIG复合焊背面熔宽的信息,本文采用视觉传感器获得了熔池背面清晰的图像,并运用图像增强及边界追踪的算法提取了熔池边缘,通过多帧图像取平均值的方法确定了输出熔池宽度的最佳位置,从而成功确定了熔池的背面宽度.     

激光焊接熔透过程同轴光信号检测

高功率激光焊接过程中，熔透是保证焊缝质量的前提。实现焊接熔透控制首先要提取出焊接熔透过程中的特征信号。本文针对激光焊接过程中的等离子体光信号检测，设计了同轴光信号检测传感器。在平板、斜板以及阶梯板焊接实验中，得出了不同熔透状态下，同轴光信号的变化规律。     

融合时序信息的激光焊接熔透状态识别方法

熔池/匙孔区域包含丰富的激光焊接质量信息,基于该区域对熔透状态进行准确识别对于激光焊接的在线控制至关重要。针对熔池区域存在蒸汽和飞溅等干扰且相邻的熔透状态之间特征区分度低带来的模式识别困难的问题,提出了一种融合时序信息的激光焊接熔透状态识别方法。所提方法以熔池/匙孔图像序列作为底层输入,首先通过两个卷积层和两个池化层提取熔池/匙孔图像的空域特征;其次通过双向长短时记忆神经网络提取熔池/匙孔图像的时域特征;最后将时空特征输入全连接网络进行特征降维并用SOFTMAX函数进行分类。所提方法建立了从熔池/匙孔图像到熔透类型的端到端的识别模型。试验结果表明,所提方法在测试集上的识别准确率达99.26%,对单幅图像的识别时间为9.43 ms,可满足在线监测的需求。进一步的对比试验表明所提方法对学习率和优化器的变化具有鲁棒性。     

激光焊接熔池的实时检测与分析

激光精密焊接技术在焊点的精确定位以及焊接缺陷的实时检测方面还存在一些有待解决的问题。激光焊接过程会产生大量的等离子体, 严重影响机器视觉系统的成像质量。试验证明, 通过给机器视觉系统添加同轴辅助照明光源可实时获得清晰的熔池图像。在理想状态下, 激光焊接的熔池形状应为圆形, 根据这一特点设计了速度较快且准确度高的矩阵法进行熔池边缘的快速检测。利用圆拟合的方法在获得熔池中心坐标和半径的同时, 还可进行边缘缺陷的实时检测。     

基于多传感器融合的激光焊接熔透状态的识别

为实现对激光焊接过程中常出现的不同熔透状态的实时辨识,使用多种传感器采集焊接过程中的可听声、蓝紫光和红外辐射信号,并提取了反映熔透状态的6个信号特征。基于特征级的多传感器信息融合技术,采用模拟退火算法对信号特征进行组合优化和关联融合,确定了反映融合规则的“特征融合系数”,并以BP网络为框架构建识别熔透状态的模式分类器。研究结果表明,通过样本训练和信号特征优化组合,所构建的模式分类器对“过熔透”、“完全熔透”、“不稳定熔透”和“未熔透”等四种熔透状态的辨识准确率达到88%以上。从而提供了一种有效的激光焊接质量在线检测方法。     

激光熔覆成形中熔池表面温度场的检测与研究

针对激光熔覆成形中熔池表面温度场难以测量的问题,搭建了彩色CCD同轴测温系统。通过优化实验参数,该测温平台可获得清晰、稳定的熔池表面图像,对所拍图像进行处理和计算,可以得到熔池表面的温度场。为了验证得到的温度场是否准确,搭建了红外测温系统,通过对熔池表面不同区域进行测温,得到了与CCD测量结果基本吻合的熔池表面温度分布。两种不同的测温方式得到一致的温度场,说明此测温平台是实用、可靠的,为通过实时检测熔池表面温度进而控制熔覆成形系统打下基础。     

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.     

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.     

Teleportation of an arbitrary unknown N-qubit entangled state under the controlling of M controllers

A new quantum protocol to teleport an arbitrary unknown N-qubit entangled state from a sender to a fixed receiver under M controllers(M < N) is proposed. The quantum resources required are M non-maximally entangled Greenberger-Home-Zeilinger (GHZ) state and N-M non-maximally entangled Einstein-Podolsky-Rosen (EPR) pairs. The sender performs N generalized Bell-state measurements on the 2N particles. Controllers take M single-particle measurement along x-axis, and the receiver needs to introduce one auxiliary two-level particle to extract quantum information probabilistically with the fidelity unit if controllers cooperate with it.     

Diode-end-pumped Nd:YVO4/LBO lasers with 4.2W continuous-wave output at 457 nm

A continuous-wave (CW) 457 nm blue laser operating at the power of 4.2 W is demonstrated by using a fiber coupled laser diode module pumped Nd: YVO4 and using LBO as the intra-cavity SHG crystal With the optimization of laser cavity and crystal parameters, the laser operates at a very high efficiency. When the pumping power is about 31 W, the output at 457nm reaches 4.2 W, and the optical to optical conversion efficiency is about 13.5% accordingly. The stability of the out putpower is better than 1.2% for 8 h continuously working.     

Critical Stage Rule-Based Real Time Dispatch（RTD）System in Highly-Mixed-Products （HMP） FAB

An improving utilization and efficiency of critical equipments in semiconductor wafer fabrication facilities are concerned. Semiconductor manufacturing FAB is one of the most complicated and cost sensitive environments. A good dispatching tool will make big difference in equipment utilization and FAB output as a whole. The equipment in this paper is In-Line DUV Scanner. There are many factors impacting utilization and output on this equipment group. In HMP environment one of the issues is changing of reticule in this area and idle counts due to load unbalance between equipments. Here we'll introduce a rule-based RTD system which aiming at decreasing the number of recipe change and idle counts among a group of scanner equipment in a high-mixed-products FAB.