CO2激光-TIG复合焊接气体的保护方式

保护气体组成及其保护方式是决定CO2激光-钨极氩弧焊(TIG)电弧复合焊接工艺稳定性和激光、电弧两种热源能否有效耦合并取得增强的焊接熔深的关键原因。为此,采用不同的气体保护方式在316L不锈钢板上进行了一系列CO2激光-TIG电弧复合焊接实验。结果表明,只有在合理的气体保护方式下才能取得增强的焊接结果,其中气体保护方式对激光等离子体和电弧等离子体相互作用程度的影响是决定能否有效耦合的关键因素。单独TIG焊炬保护不能保证激光和电弧的有效耦合,TIG焊炬加旁轴喷嘴的方式只能在较窄的参数范围内获得有效耦合,而TIG焊炬加同轴喷嘴的保护方式则在较宽的范围内都能保证两种热源的有效耦合。     

The fitting of depth distributions of ion implanted analytes by split student-t functions: The physical basis and a recommended procedure

The non-standardized fitting of depth distributions of ion implanted analytes in solid matrices by arbitrarily chosen functions, as practiced at present, is unsatisfactory for the communication of results and is unacceptable for certification of ion implanted reference materials. Sampling theory applied to the nuclear slowing-down process of swift ions suggests that split Student-t functions should provide the mathematical representation sought. The exact shape and mathematical form of these functions are fully described and readily communicated by the use of five parameters (mode, two shape parameters and two scale parameters). A simple and fast fitting procedure is proposed.Dedicated to Professor Günther Tölg on the occasion of his 60th birthday     

新型的嵌入式LCD显示系统低功耗技术

随着多媒体在手持移动设备中的广泛应用，包含了显示缓存，显示控制模块，显示背光电路和显示屏的LCD（Liquid Crystal Display）显示系统在系统总功耗中占据了主要地位。提出了一种在文本浏览或使用编辑器时，降低显示系统功耗来达到减低总体功耗的系统设计，它利用新的动态色深调整，缓存驻留，关闭主存的方法使得总体功耗降低了20％～30％。     

动能侵彻体垂直侵彻半无限厚混凝土靶的试验研究

分析了国内外对混凝土侵彻机理、试验和仿真的研究情况,提出了一种大长径比动能侵彻体侵彻混凝土的模拟试验方法,通过侵彻速度为300m／s～600m／s的57mm动能侵彻弹对半无限厚靶的垂直侵彻试验,得到了最大侵彻深度、着靶姿态等试验参数。由侵彻混凝土的经验公式得到的最大侵彻深度数据与试验数据基本吻合,试验数据为反深层工事的毁伤机理和数字仿真研究提供依据,同时通过毁伤效应的试验研究,为找到一条高效毁伤典型深层工事的方法提供条件。     

竖向均布荷载作用在地基内部时的土中应力公式

建筑物基础一般都是埋入地基中，且有一定深度，而目前土中应力计算所常依据的布西奈斯克解却是假定荷载地表面导出的。本文以半无限体内受竖向力作用的明德林公式为根据，通过积分而首次完整地推导出竖向矩形均布荷载作用在地基内部上的土中应力分量解析表达式，并与布氏公式进行比较，说明其应用范围，以便于工程设计人员在设计时使用。     

基于离散-连续耦合方法的隧道压力拱特性研究

隧道压力拱问题一直是隧道工程研究的关键问题,目前常用的连续介质数值模拟方法对于隧道压力拱特性的微观研究有所欠缺,而擅长微观力学研究的离散元数值模拟方法对计算机存储空间和计算时间的要求太高。基于现有离散-连续耦合思路,通过力的传递实现离散-连续模型的耦合;研究了耦合算法中的平均应力计算方法、平均应力计算区域面积及耦合程序遍历颗粒方法;基于自行开发优化的离散-连续耦合程序,模拟了隧道开挖后的围岩受力特性,研究了隧道压力拱形成机理及压力拱特性;计算了埋深分别为10 m,14 m,18 m,22 m,26 m,30 m和34 m情况下的隧道开挖产生的压力拱应力集中等效区域,揭示了隧道压力拱随着隧道埋深的变化规律。研究结果表明,自行开发优化的离散-连续耦合程序能在保证计算精度的前提下,充分发挥离散元方法在微观力学研究方面的优势;隧道开挖后,开挖面周边范围出现层状压力环,但在拱顶和仰拱底附近区域的围岩压力环的环间接触力降低,围岩承载能力急剧降低,形成压力拱;随着隧道埋深的增加,隧道压力拱应力集中等效区域减小,隧道周边围岩的压力拱承载能力越来越大;但当隧道埋深达到一定界限后,隧道压力拱高度趋于稳定。     

Linear gravity waves on Maxwell fluids of finite depth

Linear surface gravity waves on Maxwell viscoelastic fluids with finite depth are studied in this paper. A dispersion equation describing the spatial decay of the gravity wave in finite depth is derived. A dimensionless memory (time) number 0 is introduced. The dispersion equation for the pure viscous fluid will be a specific case of the dispersion equation for the viscoelastic fluid as θ=0. The complex dispersion equation is numerically solved to investigate the dispersion relation. The influences of θ and water depth on the dispersion characteristics and wave decay are discussed. It is found that the role of elasticity for the Maxwell fluid is to make the surface gravity wave on the Maxwell fluid behave more like the surface gravity wave on the inviscid fluid.     

Enhancement of photo‐conversion efficiency in Cu2ZnSn(S,Se)4 thin‐film solar cells by control of ZnS precursor‐layer thickness

CZTSSe thin‐film absorbers were grown by stacked ZnS/SnS/Cu sputtering with compound targets, and the precursors were annealed in a furnace with a Se atmosphere. We controlled the thickness of the ZnS precursor layer for the CZTSSe thin films in order to reduce the secondary phases and to improve the performance of the devices. The optimal value of the ZnS precursor thickness was determined for the CZTSSe absorbers, and this configuration showed an efficiency of up to 9.1%. In this study, we investigated the depth profiles of the samples in order to determine the presence of secondary phases in the CZTSSe thin films by Raman spectroscopy and Kelvin probe force microscopy. Cu₂SnSe₃, ZnSe, and MoSe₂ secondary phases appeared near the back contact, and the work function distribution of the CZTSSe thin‐film surface and the secondary phase distribution were different depending on the depths of the absorber layer. This phase characterization allows us to describe the effects that changes in the thickness of the ZnS precursor can have on the performance of the CZTSSe thin‐film solar cells. Although it is important to identify the phases, the effects of secondary phases and point defects are not yet fully understood, even in optimal devices. Therefore, phase identification that is based on the work function and the results obtained from the Raman spectra in terms of the depth profile are instrumental to improve the surface and interface of CZTSSe thin‐film solar cells. Copyright © 2015 John Wiley & Sons, Ltd.     

浅海动态环境下蛙人探测声呐布放深度优化技术

蛙人探测声呐的探测性能及作用距离不仅与目标海区的声速剖面和自身性能参数有关,还与其布放深度有关,其布放深度的选择对于水下目标探测具有重要意义。以射线跟踪理论为基础,建立了基于探测概率感知的声呐性能评估模型;提出了一种声呐布放深度自适应优化算法,该算法以不同准则进行两次筛选优化后可得到声呐最佳布放深度。仿真结果表明：在不同水文情况下,所提优化算法可以有效选择最优布放深度,进而提高声呐对目标的探测性能。     

Depth of almost strictly sign regular matrices

The concept of depth of an almost strictly sign regular matrix is introduced and used to simplify some algorithmic characterizations of these matrices.