电磁拉盖尔-高斯光束通过湍流时偏振度研究

基于相干性和偏振性统一理论,经理论推导,得出部分相干电磁拉盖尔-高斯光束在湍流中传输时偏振度的解析表达式.经数值计算,结果表明:在湍流中,当源偏振度(P0)、结构常数C2n、相干长度和光束阶数不同时,经过足够长传输距离,部分相干电磁拉盖尔-高斯光束的偏振度逐渐趋向于P0,而在自由空间中,该光束的偏振度达到其各自不同的极限值;当δx=δy时,不论在自由空间中还是在湍流中,光束的偏振度都不改变.此结论对部分相干光的大气传输在激光雷达成像以及远距离相干测量和光通信等领域有实用意义.     

湍流大气中的激光传输仿真研究

采用傅里叶变换思想,使用不同角频率正弦函数旋转叠加的方法生成不同湍流尺度的相位屏,对符合Kolmogorov谱的大气随机相位屏进行了仿真模拟,并模拟出高斯光束经过大、小尺度湍流后的传输截面及在接收面上的光场分布情况,通过分析对比,与理论结果有很好的一致性,对进一步进行激光大气湍流效应的研究具有重要意义.     

GH4169合金电子束焊接接头CTOD断裂韧度

根据GB/T2358—94标准,分别在20℃和650℃下,对GH4169合金电子束焊接接头的裂纹尖端张开位移(CTOD)进行测试。取SE(B)试样进行三点弯曲试验,然后由所得到的20℃和650℃下母材和电子束焊缝的P-V曲线来计算CTOD值,比较两个温度下的试验结果,对试验结果进行了分析讨论。     

H型钢轧机水平辊轴向移动装置结构形式

水平辊轴向移动是H型钢轧机进行辊缝调整、控制产品尺寸精度的重要方法,已广泛应用在H型钢轧机中,研究其结构及控制原理对于自主开发H型钢轧机具有重要意义。     

He气氛对大气颗粒物样品外束PIXE分析影响的初步研究

为改善北师大外束PIXE系统对Al、Si等较轻元素的探测限,在该系统探测器前加装进He装置。采用美国MicroMatter公司的标准样品,在进He量为92.0 SCCM(标况毫升每分钟)的条件下对系统进行刻度,得到GUPIXWIN软件进行定量分析用的16种元素的刻度因子,并同不进He条件下的刻度因子进行比较。在保持实验几何条件不变的情况下,研究He气量对大气颗粒物样品中Si、S、Cl等元素探测限的影响,结果表明:进He量为92.0 SCCM时,可使大气颗粒物样品中Al、Si元素的探测限较不进He气时分别降低80%和47%。     

TRIP600钢板成形汽车前纵梁冲压工艺研究

TRIP高强度钢板具有高强度、高应变率变形时的高动态吸能特性,符合现代汽车用钢材料的发展趋势。基于有限元法对TRIP600的汽车前纵梁冲压成形过程进行数值模拟,通过调整坯料外形,改善了成形质量;采用多元非线性回归模型分别拟合成形工艺参数(压边力、摩擦因数和拉深筋阻力)与破裂目标函数及回弹目标函数间的非线性关系,并基于NSGA-II多目标遗传算法,进行了成形工艺参数的优化,进一步提高了成形质量。     

移动机器人的超声波传感器发散角标定及应用

为了提高移动机器人在作业站点的定位精度,在考虑入射角的基础上,分析了发散角对超声波传感器测距的影响,建立了同时考虑发散角及入射角的超声波传感器测距函数关系表达式;提出了超声波传感器发散角的标定方法,并通过实验对发散角进行了标定;通过对比实验可以看出,所提出的关系表达式提高了超声波传感器距离测量精度。在此基础上提出了利用自动导航车(AGV)单个侧面两个超声波传感器实现移动机器人在作业站点侧向、前向及姿态3个方向的位姿定位方法,最后将该方法用于自主研发的移动机器人的定位试验,验证了该方法的正确性和有效性。     

Using a principal components analysis for developing a robust design of electron beam welding

This paper presents the application of principal components analysis for Taguchi orthogonal experiments to develop a robust electron beam welding treatment (EBWT) process with high efficiency multiple performance characteristics (MPCs). In this study, the principal components analysis (PCA) design incorporating the correlation matrix of tested trials is employed. In the first step, the MPCs are reduced to two independent components using PCA. Both components accounted for 98.8% of the total variance. The first principal component (PC), which refers to the integrated hardening capability index of the EBWT process, accounts for 70.7% of the total variation. The remaining 28.1% were contributed by the second PC, which can be interpreted as the penetration capability index. In the second step, we identify the most important PC loading vectors using PCA, and estimate the importance of the PCs. By using PCA, relationships between different MPCs can be investigated and the most important factors for the variance of the EBWT process can be identified. The experimental results show that redundant information could be eliminated by using principal components in conjunction with Taguchi’s orthogonal array experiments. This proposed approach is simple, effective, and efficient for developing a robust and high-efficiency EBWT process of high quality. In this study, the MPCs in the EBWT process are successfully optimized .     

Development of a fast atom beam gun for surface-activated bonding

Surface-activated bonding (SAB), also called room-temperature bonding, is used in three-dimensional integration technology for semiconductor devices. An Ar fast atom beam (FAB) is used for SAB. However, conventional FAB guns must be replaced after hundreds of minutes of irradiation because carbon abrasion powders are generated by Ar ions sputtering in the gun. Therefore, this study develops a novel FAB gun with improved lifetime. The proposed FAB gun applies magnetic fields to guide Ar ions to reduce sputtering in the gun and improve irradiation efficiency. The proposed FAB gun indicates the possibility of improving gun lifetime.     

Techniques trend analysis of propagating laser beam quality measurement

Different methods of measuring a propagating laser beam quality are summarized.The disadvantages in traditional way in measuring a laser beam quality is analyzed and the insufficiencies of the Shack-Hartmannin method which is commonly using wave front technique at present is pointed out.Finally,the transmission intensity equation based(TIE-based)measuring way in a laser beam quality evaluation and the corresponding advantages are discussed,which is believed to be a deve-l oping trend in laser beam evaluation.