汽车发动机罩外板A级曲面的逆向设计与分析

基于点云的汽车车身外覆盖件曲面逆向设计一直是困扰车身开发人员的技术难题,解决这一问题对于缩短车身开发时间有重要的意义.概述汽车A级曲面的理论和方法,探讨制定了逆向设计流程.以某车型汽车发动机罩外板A级曲面的设计为例,阐述设计方案、轮廓线提取和曲面生成等关键技术,解决了设计中出现的问题.     

汽车轻量化之白车身减重

白车身减重作为汽车轻量化设计过程中的重要环节之一,是在保证车身刚度、NVH、碰撞安全、强度耐久等重要车身性能指标的前提下,对车身重量与成本进行的最优化设计过程。通过一款车型减重实例,介绍了几种有效的白车身减重方法。     

基于分形特征的钢水连续测温传感器损伤诊断

提出了一种利用截面轮廓线分形维数,对钢水连续测温传感器的损伤进行诊断的方法.首先提取出经过使用的钢水连续测温传感器截面轮廓.采用最小二乘法拟合出该轮廓线的基准圆,将传感器截面轮廓线映射到以基准圆圆周方向和径向方向为横、纵坐标的二维平面坐标系上.采用盒计数方法计算出轮廓线的分形维数,并以Chi2法对分形维度进行离散化.结果表明:钢水连续测温传感器表面具有自相似特征;传感器表面形貌不同时,轮廓线的分形维数有明显差异;随着热震破坏在传感器损毁中重要性的增加,传感器截面轮廓线分形维数增加.当轮廓线的分形维数在1.00至1.07时,传感器的损毁为侵蚀损毁;当轮廓线分形维数在1.10至2.00时,损毁为热震损毁.采用该方法,判断出传感器寿命较短时损毁的主要原因为侵蚀.     

基于遗传算法与仿真的偏置碰撞安全结构改进研究

针对某款在中国新车评价体系偏置碰撞试验中存在较大安全问题的国产车型,通过分析该车偏置碰撞形式下结构的设计缺陷,将试验设计、响应面模型、遗传算法相结合对车身前部安全性关键部件的厚度进行优化,通过改进对车身变形起关键作用部件的结构特征,实现汽车前舱刚度的匹配,使整体结构合理变形。仿真结果表明,在兼顾正碰安全性与车身轻量化的前提下,优化设计与结构改进有效地提高了该车型的40%偏置碰撞安全性。     

基于可制造性约束的车身变截面梁关联优化设计

在车身主断面设计过程中,变截面梁的设计一直存在较多问题,其形状设计受到结构性能和可制造性因素的多重约束。文中对车身变截面梁的设计问题进行了研究,通过构造基于工程约束的形状优化关联设计变量,建立了车身薄壁结构的多截面关联优化设计算法,实现了考虑可制造性约束的变截面梁优化设计方法,还可支持多种材料设计。同时提出了适合工程优化的最优解选择评分公式,实现了最优解的自动选取。该方法既可以应用于正向设计过程中车身主断面的变截面梁轮廓线的确定,也可对现有梁的结构性能的改进优化,实现制造成本降低和车身轻量化设计。文中给出具体的变截面梁关联优化算法,并通过某车型B柱截面优化实例验证了该算法的有效性。     

模块化平台的模块划分及共享模块筛选方法

为实现概念设计阶段在汽车模块化平台下对汽车白车身结构进行的模块化设计,提出一套划分模块并从中筛选出共享模块和非共享模块的方法。首先,在保证车身性能的同时考虑车身制造成本和装配成本,提出一种改进的图分解算法,进而能够定义出车身装配结构的最佳划分方式,并依此进行车身结构模块的划分;以该划分方式为基础,根据结构发生改动时所涉及到模具的成本和制造的复杂程度进行优先级排序,定义并筛选出其中的核心共享模块、参数化设计模块和柔性调整模块;在施加平台级约束后,平台下某车型的性能和单独优化该车性能的差值应控制在一定范围内,可根据该差值是否满足要求动态调整三种模块的筛选结果。算例以某三款车型的白车身底板为对象进行了划分和筛选,结果证明了该方法的有效性。     

白车身焊装线柔性定位单元的设计与应用

柔性定位单元是白车身焊装线柔性定位的关键设备,多台柔性定位单元可组成一个白车身定位系统。通过设计柔性定位单元以及将之应用于白车身底板焊装线、柔性总拼系统等的白车身柔性定位,能实现白车身焊装的多车型混流共线生产,大幅提升汽车白车身制造的柔性程度和生产效率。     

基于主断面控制要点在车身设计中的应用研究

车身断面设计是汽车设计过程中的一项核心技术,其设计质量的优劣直接影响整车的品质。主要介绍了车身断面设计的定义、性能参数和控制要点,并给出了某款车型车身主断面位置图。针对焊接边的接合宽度、零部件的间隙和段差、包边尺寸和密封件压缩量的要求,阐述了断面控制要点在车身设计中的应用。     

压铸模具分型线的自动确定方法研究

提出了一种自动确定模具分型线的方法,该方法首先离散铸件的实体造型的边线和面,并把离散点投影到主平面上,然后采用改进后的AIpha Shapes算法计算主平面上离散点的外轮廓线;再根据脱模方向,通过外轮廓点向铸件做射线,求得射线与铸件边线的交点,并连接交点得到铸件上的轮廓线;最后通过优化评价这些轮廓线得到分型线.实例结果显示,该方法具有较好的实用性和较高的效率.     

先进CAD技术在汽车车身设计中的应用

采用先进的可视化设计CAD造型软件，完成了整体车身426个内、外覆盖件及骨架类零件的造型；基于新车身开发的继承性特点，采用参数化设计的方法，可快速实现基本车型向新开发车型的转变，从而大大提高了设计效率。     

低温密封酸溶——高分辨电感耦合等离子体质谱法测定地质样品中50个微量元素的评价

The method based on the determination of trace elements in geological samples by sector high resolution inductively coupled plasma mass spectrometry with mixed acid digestion procedure has been evaluated. The evaluation show that the results of 29 elements including Li, Cr, Co, Ni, Cu, Zn, Ga, Rb, Y, Cs, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, W, Tl, Bi, Th and U are satisfactory; V, Sr, Nb, Mo, In, Sb, Ba and Pb are acceptable; Sc, Cd, Hf, Ti, Mn, Fe, Ge and Sn have of large deviations, Be, Ta, Zr, As and Se are worse.     

微波消解-电感耦合等离子体质谱法测定食品中18种元素

建立了食品中钠、镁、铝、钾、钙、钒、铬、锰、铁、镍、铜、锌、砷、硒、镉、锡、汞、铅的电感耦合等离子体质谱（ICP–MS）测定方法。样品经过微波消解,在线加入内标校正基体效应,通过修正方程校正质量数干扰,各元素校正曲线的相关系数均大于0.9995。对多种国家生物标准物质进行验证,测定值与标准值相符,相对标准偏差RSD（n=6）小于8.71%,加标回收率为71.8%～109.5%。     

The structure and function of auditory chordotonal organs in insects

Insects are capable of detecting a broad range of acoustic signals transmitted through air, water, or solids. Auditory sensory organs are morphologically diverse with respect to their body location, accessory structures, and number of sensilla, but remarkably uniform in that most are innervated by chordotonal organs. Chordotonal organs are structurally complex Type I mechanoreceptors that are distributed throughout the insect body and function to detect a wide range of mechanical stimuli, from gross motor movements to air-borne sounds. At present, little is known about how chordotonal organs in general function to convert mechanical stimuli to nerve impulses, and our limited understanding of this process represents one of the major challenges to the study of insect auditory systems today. This report reviews the literature on chordotonal organs innervating insect ears, with the broad intention of uncovering some common structural specializations of peripheral auditory systems, and identifying new avenues for research. A general overview of chordotonal organ ultrastructure is presented, followed by a summary of the current theories on mechanical coupling and transduction in monodynal, mononematic, Type 1 scolopidia, which characteristically innervate insect ears. Auditory organs of different insect taxa are reviewed, focusing primarily on tympanal organs, and with some consideration to Johnston's and subgenual organs. It is widely accepted that insect hearing organs evolved from pre-existing proprioceptive chordotonal organs. In addition to certain non-neural adaptations for hearing, such as tracheal expansion and cuticular thinning, the chordotonal organs themselves may have intrinsic specializations for sound reception and transduction, and these are discussed. In the future, an integrated approach, using traditional anatomical and physiological techniques in combination with new methodologies in immunohistochemistry, genetics, and biophysics, will assist in refining hypotheses on how chordotonal organs function, and, ultimately, lead to new insights into the peripheral mechanisms underlying hearing in insects.     

微波消解-电感耦合等离子体质谱法同时测定茶叶中42种元素

建立了电感耦合等离子体质谱法（IcP—Ms）标准模式和优化的碰撞池模式（CCT）结合同时测定茶叶中Li、Be、Mg、Al、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Ga、As、Se、Sr、Mo、Ag、Cd、Sn、Sb、Cs、Ba、Tl、Pb、Bi和16种稀土元素共42种元素的方法。样品经过微波消解,以Ge、In、Re为内标消除基体干扰,通过碰撞池技术消除多原子质谱干扰测定上述元素。对于所测元素校准曲线的相关系数均大于0．9990,回收率范围为90％-110％,相对标准偏差为0．22％-3．97％,大部分元素检出限均小于0．5μg·kg^-1。该方法简便、省时、准确、灵敏度高,适用于实际样品的检测。     

һ�ֹ���������������Ǽ����о�

?????????????????????????????????????????????????????????????10.6eV?????????????????????????????????????????屻????????漴???????岶?????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????м??????????????????????????????????????л????????ж??????????????????й????г??????     

Huge clusters of embryonic stem cells in human embryos: A morphologic study

Background: Nothing is known about huge clusters (HC) of embryonic stem cells (ESC) in human fetal organs (HFO). Aim: To know the status of HC‐ESC in HFO. Methods: Morphology and immunohistochemistry (IHC) in 32 HFO of 7–40 gestational weeks (GW). Results: HC‐ESC were seen in many HFO including central nervous system, spinal cords, spine, soft tissue, bone, skin, thyroid, lung, liver, pancreas, gall bladder, extrahepatic bile duct, adrenal, kidney, bladder, foregut, midgut, hindgut, female and male genital organs, and neurons. HC‐ESC's were composed of two populations depending on constituting cells. One were large cells with ample acidophilic cytoplasms with vesicular nuclei and nucleoli. The other were small cells with scant cytoplasm with hyperchromatic nuclei without nucleoli, resembling lymphocytes. The HC‐ESC were frequently showed neuronal differentiation. HC‐ESC were positive for NCAM, synaptophysin, NSE, chromogranin, PDGFRA, AFP, ErbB2, bcl‐2, KIT, MET. They were negative for CD45, CD3, CD20, EMA, CEA, CA19‐9, cytokeratin (CK) 7, CK8, CK18, CK19, MUC1, MUC2, MUC5AC, and MUC6. The mean Ki‐67 labeling index (LI) was 13% ± 7%. HC‐ESC showed a little glycogen but lacked mucins. These HC‐ESC were seen in 7–25 GW, and they were rarely seen in 26–40 GW. Conclusions: The morphology, IHC, and ontogeny of HC‐ESC were described. Microsc. Res. Tech. 77:825–831, 2014. © 2014 Wiley Periodicals, Inc.     

Epibiotic microorganisms on copepods and other marine crustaceans

Although the occurrence of microbial (algal, protozoan, bacterial, and fungal) epibionts on marine crustaceans and other invertebrates has been documented repeatedly, the ecological context and significance of these relationships generally are not well understood. Recently, several studies have examined the population and community ecology of algal and protozoan epibionts on freshwater crustaceans. Even so, the study of microbial epibionts in aquatic environments is still in its infancy. In this review, we summarize associations of microalgae, protozoans, and bacteria with marine crustaceans, especially copepods. We note differences and commonalities across epibiont taxa, consider host-epibiont cycling of nutrients, generate hypotheses relevant to the ecology of the host and the epibiont, and suggest future research opportunities. Microsc. Res. Tech. 37:116–135, 1997. © 1997 Wiley-Liss, Inc.     

Assessment of PM-EDM cycle factors influence on machining responses and surface properties of biomaterials: A comprehensive review

Powder mixed-electro discharge machining (PM-EDM) is recently evolving machining technique which can simultaneously remove and modify the machined surface through thermo-electrical process. It is a modified form of EDM in which the conductive powder elements are added in the dielectric liquid to enhance machined surface characteristics and machining responses. The commonly used biomaterials such as 316L stainless steel, Ti-based alloy, Ni–Ti, Mg alloy, and Co–Mo–Cr alloy have excellent mechanical characteristics while the biofunction of these materials are not in satisfactory level. Due to higher hardness, brittleness, and heat resistant natures of the biomaterials, it is very challenging to machine them with conventional machining. Both the system efficiency and modified surface properties depend on the associated electrical and non-electrical factors of PM-EDM cycle. This review focuses on the influence of process factors such as current, pulse duration, tool-polarity, duty cycle, potential voltage, types of liquid, and added powder concentration on performance outputs including material removal and tool wear rate, coating thickness, coarseness, microhardness, coating adhesion bonding, biocompatibility, and resistant to corrosion. This study also discusses influence of various powders on machining and modified surface characteristics of biomaterials. The future research scopes and challenges of PM-EDM process are included in this study thoroughly.     

A review of ultrafine particles as antiwear additives and friction modifiers in lubricating oils

This paper gives an overview of developments in the use of ultrafine particles in lubricating oils to reduce wear and friction. Work on several types of particles, such as graphite, MoS₂, PTFE, BN, fullerene, and Cu, as well as more novel and unusual particles used as lubricant additives, is reviewed. The paper summarises the results of a number of workers in this field. The tribological mechanism by which ultrafine particles operate is considered, and some conclusions, including possible future directions for research, are drawn.     

碳纤维山地自行车架生产工艺的发展现状与发展趋势

碳纤维自行车架具有质量轻、强度高、刚度好、抗振性强等优点,是竞技山地车架发展的趋势。目前,碳纤维山地自行车架的生产多以RTM工艺为基础,国内外在设计和生产方面进行了大量创新,研究出诸如OCLV、IsoTruss、IsoGrid和ExoGrid以及ALMA、OIZ和Arantix等专利技术和产品,也暴露出了一些问题。未来几年,碳纤维山地自行车架的生产工艺在吸收、引进各种先进技术的同时,将有望进一步提高整体性能和降低生产成本。