大型石油储罐用钢板拉力分层原因分析

通过金相显微镜和扫描电镜等分析测试手段,对大型石油储罐用钢出现的拉力分层现象进行了研究分析。研究发现,拉力分层主要出现在带状组织区域,钢板心部的带状组织是导致拉力分层的直接原因;铸坯中Mn的显微偏析是储罐用钢带状组织产生的内因。     

Design of gas‐phase synthesis of core‐shell particles by computational fluid–aerosol dynamics

Core‐shell particles preserve the bulk properties (e.g., magnetic and optical) of the core while its surface is modified by a shell material. Continuous aerosol coating of core TiO₂ nanoparticles with nanothin silicon dioxide shells by jet injection of hexamethyldisiloxane precursor vapor downstream of titania particle formation is elucidated by combining computational fluid and aerosol dynamics. The effect of inlet coating vapor concentration and mixing intensity on product shell thickness distribution is presented. Rapid mixing of the core aerosol with the shell precursor vapor facilitates efficient synthesis of hermetically coated core‐shell nanoparticles. The predicted extent of hermetic coating shells is compared with the measured photocatalytic oxidation of isopropanol by such particles as hermetic SiO₂ shells prevent the photocatalytic activity of titania. Finally, the performance of a simpler, plug‐flow coating model is assessed by comparisons with the present detailed computational fluid dynamics (CFD) model in terms of coating efficiency and silica average shell thickness and texture. © 2011 American Institute of Chemical Engineers AIChE J, 2011     

热浸镀锌带钢表面条纹状缺陷产生原因分析

在生产热浸镀锌带钢时，带钢表面经常出现漏镀、黑点等各种缺陷，条纹状缺陷也是其中一种。采用扫描电镜和能谱仪对连续热浸镀锌带钢的镀层表面条纹状缺陷进行了测试与分析。研究表明，该条纹状缺陷位置处基板内存在裂缝，导致基板内表层出现了分层，裂缝内同时存在基板的氧化铁皮、氧化圆点和镀锌层，表面镀层较薄，该缺陷应为连铸板坯表面存在纵裂纹以及后续热轧轧制所致。镀锌板表面出现该缺陷后，不仅影响板面外观，而且在冲压成形过程中易发生镀层剥落和起皮而导致工件报废。     

多波束测深中声速剖面的分层EOF自适应重构

在海水性质变化剧烈地区利用重构声速剖面进行多波束测深时,传统的经验正交函数(Empirical Orthogonal Functions,EOF)方法在阶次选取时未顾及声速浅水的复杂性和深水的平稳性的特点。针对传统EOF方法存在计算量大、精度低等问题,给出了一种声速剖面EOF重构中分层阶次的确定方法。根据常梯度声线跟踪计算深度,在满足0.25%倍水深限差的要求下,统计有效波束比,采用自适应方法确定出合理的阶次。实验结果表明,该方法相较于传统EOF重构声速剖面测深的阶次选取方法,降低了运算量,提高了精度。     

Cross‐layer error recovery in wireless access networks: The ARQ proxy approach

Wireless networks are being increasingly employed to provide mobile access to network services. In most existing standards, reliable transmission on the wireless medium is achieved through the introduction of ARQ schemes at MAC layer, a strategy which is also employed by TCP for reliable end‐to‐end data delivery. The paper proposes an approach to overcome the performance degradation deriving from the duplicate ARQ strategies implemented at the transport and MAC layers by introducing a cross‐layer solution to reduce un‐necessary transmissions on the wireless medium. Furthermore, the paper describes how the proposed scheme, called ARQ Proxy, can be deployed in three different wireless technologies (3G Long‐Term Evolution, Wi‐Fi, and WiMAX) and provides extensive validation of the achievable improvement through simulations. Copyright © 2011 John Wiley & Sons, Ltd.     

Quo vadis thermal spraying?

This paper is devoted to thermal spraying and presents the state of our current knowledge, as well as the following research or development needs: spraying heat sources, i.e., flame, high-velocity oxifuel flame (HVOF), detonation gun (D-Gun), and plasma torches; particle heat and momentum transfer (measurements and modeling), process on-line control, powder morphologies, and injection within the hot jet and reactions with environment; coating formation, i.e., particle flattening and solidification, splat layering, residual stresses, coating microstructure, and properties; and reliability and reproducibility of coatings.     

基于分层模式的软件体系结构在日立ERP系统开发中的应用

本文首先介绍了分层模式的软件体系结构理论,并分析其在软件开发中的作用和地位,然后将该体系结构应用于日立ERP帐务系统项目的开发中.把软件系统结构定为界面层、业务处理层和数据层,进而设计、编程和测试,有效地降低了软件开发过程的复杂度,提高了系统的开发效率和可靠性.     

壳聚糖/聚乙烯醇改善纸基材料的水蒸气和氧气阻隔性能研究

研究了壳聚糖和聚乙烯醇在改善纸基材料水蒸气(极性气体)和氧气(非极性气体)阻隔性能上的应用效果,探讨了壳聚糖/聚乙烯醇不同质量比和不同复合方式(共混和分层)对纸基材料水蒸气和氧气阻隔性能、机械性能和涂层稳定性的影响。结果表明,随着壳聚糖和聚乙烯醇质量比的降低,纸基材料的水蒸气阻隔性能逐渐增强,同时氧气阻隔性能逐渐降低;壳聚糖/聚乙烯醇分层涂布纸的水蒸气和氧气透过量均低于壳聚糖/聚乙烯醇共混涂布纸。当壳聚糖和聚乙烯醇的质量比为1∶1时,壳聚糖/聚乙烯醇分层涂布纸的水蒸气透过量和氧气透过量分别为9.36 g/(m~2·d)和31.93cm~3/(m~2·d);与纯壳聚糖涂布纸相比,水蒸气透过量降低了约92%,与壳聚糖/聚乙烯醇共混涂布纸相比,水蒸气透过量降低了约68%,氧气透过量降低了约67%。     

基于多信息体素空间划分的高效自由曲面分层算法

随着多自由度增材制造技术的发展,直接基于曲面的分层处理和路径规划方法被广泛研究。针对目前曲面分层算法通用性不强、效率低下等问题,提出基于多信息体素空间划分的高效鲁棒的自由曲面分层算法。通过将三角面片表面体素化,快速筛选出相交三角面片,算法时间复杂度由传统算法的平方复杂度降低为线性复杂度,解决了以往曲面分层算法难以处理大尺寸复杂模型的问题。根据三角网格邻接边的拓扑连续性避免同一轮廓环交点在不同求交条件下的重复计算,解决交点重复求交过程因为浮点数计算误差导致的点扩散问题,获取正确曲面轮廓交线环。最后对交线环内部的曲面进行三角剖分,获取曲面内部信息,得到曲面分层结果。测试了不同模型的圆柱面、球面、自由曲面等类型的曲面分层处理以及算法运行时间,验证了本算法的高效性和正确性。在6轴KUKA机器人和2轴变位机组合装备上对螺旋桨模型进行加工试验,证明了本算法的实用性。     

DT冷冻靶分层技术进展

为了实现ICF点火,制备均匀的高密度DT燃料靶,克服DT燃料自身重力对靶内DT燃料分布不均匀的影响,使用β自分层、IR增强及等离子体增强分层技术是当今国外常见的技术手段。较详细地介绍了β自分层、IR增强及等离子体增强分层技术的基本原理、影响分层质量的主要因素及难点、分层装置的简单结构示意图。