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931.
932.
On the interpretation of the forbidden spots observed in the electron diffraction patterns of flat Au triangular nanoparticles 总被引:1,自引:0,他引:1
In many cases nanostructures present forbidden spots in their electron diffraction patterns when they are observed by transmission electron microscopy (TEM). To interpret their TEM and high resolution transmission electron microscopy (HRTEM) images properly, an understanding of the origin of these spots is necessary. In this work we comment on the origin of the forbidden spots observed in the [111] and [112] electron diffraction patterns of flat gold triangular nanoparticles. The forbidden spots were successfully indexed as corresponding to the first laue Zone (FOLZ) and the HRTEM images presented a contrast produced by the interference of the zero-order Laue zone (ZOLZ) and FOLZ spots. We discuss the use of the forbidden spots in the study of the structure of nanoparticles and show that they are related to the shape and incompleteness of layers in the very thin particles. 相似文献
933.
Slips and falls and associated outdoor injuries are prevalent in cold climates. The objectives of this field investigation were to describe the consequences of slips and falls on ice and snow and the associated injuries, to assess the risks of various icy and snowy surfaces, to identify design needs of footwear, and to ascertain preventive measure preferences of outdoor workers. The organizations investigated were a newspaper delivery service, a military regiment, mining and construction industries. The results showed that fall events occur most frequently on ice covered with snow. This is due to the difficulty of perceiving hidden risks in order to adjust gait strategies. The professional footwear provided does not provide enough protection against slips and falls. Slip resistant properties are ranked as one of the top requirements by the users. Their most preferred preventive measures are footwear with anti-slip properties and the application of anti-slip materials, such as sand or salt. 相似文献
934.
A new delay system approach to network-based control 总被引:5,自引:0,他引:5
This paper presents a new delay system approach to network-based control. This approach is based on a new time-delay model proposed recently, which contains multiple successive delay components in the state. Firstly, new results on stability and H∞ performance are proposed for systems with two successive delay components, by exploiting a new Lyapunov-Krasovskii functional and by making use of novel techniques for time-delay systems. An illustrative example is provided to show the advantage of these results. The second part of this paper utilizes the new model to investigate the problem of network-based control, which has emerged as a topic of significant interest in the control community. A sampled-data networked control system with simultaneous consideration of network induced delays, data packet dropouts and measurement quantization is modeled as a nonlinear time-delay system with two successive delay components in the state and, the problem of network-based H∞ control is solved accordingly. Illustrative examples are provided to show the advantage and applicability of the developed results for network-based controller design. 相似文献
935.
化工精馏高效节能技术开发及应用 总被引:5,自引:2,他引:3
高效节能精馏流程通过优化构造流程结构,合理利用精馏塔顶蒸汽的冷凝潜热,可以大幅度降低精馏过程的能耗.本文系统研究各种节能型精馏流程,重点分析3种热泵精馏、4种多效精馏和4种热偶精馏的流程特点,建立节能型精馏流程优化模拟及分析系统,将模拟优化计算的结果与普通精馏流程对比.结果表明,热泵精馏节能率可达80%以上,多效精馏40%以上,热偶精馏20%以上,为工业化应用提供设计依据和友好的平台. 相似文献
936.
基于层次B样条的自由形状特征重用 总被引:1,自引:0,他引:1
借助层次B样条技术提出了一种自由形状特征的重用算法.首先利用低通滤波和泊松方程对源曲面上特征区域进行基面与细节特征的分离操作,求得基面与特征之间的偏移矢量场;然后利用平面参数化将偏移矢量场应用到目标曲面上完成特征重构;最后借助层次B样条技术优化重用结果.实验结果表明,该算法能够有效地完成自由形状特征的重用. 相似文献
937.
为了得到光顺的多项式插值曲面,首先把空间散乱数据点划分为三角形网格,在每个给定数据点处构造C^1连续的分片二次多项式曲面片,针对各数据点的邻接点个数不同,分别利用弯折能量和拉伸能量建立目标函数,极小化目标函数确定插值曲面的未知量,在保持原有的形状特征的同时构造光顺的分片插值曲面,最后用实例说明了文中方法的有效性. 相似文献
938.
939.
某旋翼试验台振动信号的采集与预处理系统 总被引:1,自引:0,他引:1
介绍了某直升机旋翼试验台的振动数据采集和预处理系统的设计和组成.其中信号采集系统分为两大部分:一部分根据同步脉冲测量旋翼转速、周期;另一部分由同步脉冲信号控制A/D转换器实现定点触发采集数据.信号预处理包括原始信号的降噪和整周期重采样.对比研究了时域平均和小波分解技术的降噪能力,结果表明该系统简捷有效. 相似文献
940.