一种基于IFS的二维真彩分形变形方法

提出了一种由迭代函数系统(IFS)所描述的二维真彩分形变形的新方法。首先建立二维真彩IFS分形模型,然后通过仿射变换的对应、规范化、匹配及插值实现了变形过程。实验结果表明:分形吸引子形状颜色过渡自然,这为分形的生成与动画提供了新的有效途径。     

线电荷在双层圆柱形介质中的电势

采用多重镜像方法导出了线电荷在双层圆柱形介质中的电势，由此得出表面复盖有介质薄膜的导体圆柱外的电势及三层平面介质像电荷的大小与位置。     

Freeze–thaw damage and chemical change of a portland cement concrete in the presence of diluted deicers

The present study experimentally investigates the effect of different diluted deicers on concrete deterioration. Laboratory simulations of environmental freeze/thaw cycling were first conducted on Portland cement concrete specimens in the presence of various deicers (NaCl, K-formate, NaCl-based deicer, K-acetate-based deicer, Na-acetate/Na-formate blend deicer, CMA deicer, or MgCl₂ liquid deicer); and SEM/EDX measurements were then conducted for the concrete samples. Under the experimental conditions in this study, the CMA solid deicer and the MgCl₂ liquid deicer were benign to the concrete durability, whereas K-formate and the Na-acetate/Na-formate blend deicer showed moderate amount of weight loss and noticeable deterioration of the concrete. NaCl, the NaCl-based deicer, and the K-acetate-based deicer were the most deleterious to the concrete. In addition to exacerbating physical distresses, each investigated chemical or diluted deicer chemically reacted with some of the cement hydrates and formed new products in the pores and cracks. Such physiochemical changes of the cement paste induced by the deicers pose various levels of risks for the concrete durability.     

平衡式光接收模块的性能分析

模拟通信要求高的载噪比低失真 ,平衡式光接收模块既可对信号进行放大 ,又可改善非线性失真 ,本文研究了其工作原理 ,详细分析了平衡式光接收模块的性能     

落地式拱形体育场看台挑篷结构CFD分析

以某后端开口的落地式拱形体育场看台挑篷为背景.采用计算流体力学(CFD)软件Fluent得到该结构的风压力、风压系数分布以及结构附近的流场分布.对风压和流场分布进行r详细的描述和讨论,发现这种挑篷形式与一般悬挑式体育场看台挑篷类似,最不利工况为风从前缘正面吹来对屋盖造成的强大上吸力.在实际设计中挑篷体埠!系数可分别取为...     

Dynamic modeling and simulation of electrodynamic tether system in stationkeeping phase

Dynamics is one of the fundamentally important aspects of all space tether research. This paper derives the dynamic equations of electrodynamic tether system (EDT) in stationkeeping phase using Newton’s laws. This paper further analyzes the tether system motion rules under electrodynamic drag, gravity induced force, and tether tension. Numerical simulation of electrodynamic tether system in station-keeping phase is calculated using an approach that combines the central difference method, fourth-order Runge-Kutta method, and predictor-corrector method, among others. The simulation results show that the motion of electrodynamic tether in stationkeeping phase not only contains librations caused by the motion of endmass, but also contains vertical and longitudinal vibrations of tether. If the motion of endmass is ignored, it is much similar to the vibration of cable with two immovable pinned-supports, in which the mid-span has the largest amplitude of vibration. Based on this, the main satellite and the endmass at both ends of tether can be treated as immovable pinned-supports when the tether vibration and tension of electrodynamic tether system in impermanency are investigated.     

直升机载战场侦察雷达空时自适应处理实用方法研究

针对直升机平台的特点,本文研究了直升机载战场侦察雷达杂波抑制与平台运动补偿的可能有效途径,主要包括传统的DPCA方法、-ADPCA方法、-STAP方法、随机抽取单元辅助通道-STAP方法和扩展的-STAP方法。理论分析与计算机仿真表明,扩展的-STAP方法更适合于多种非理想情况(如:阵元幅相误差、载机偏航、航速误差等)和电子战环境,具有更强的杂波与干扰抑制能力和更强的误差鲁棒性,而且,该方法既可用于相控阵雷达,又可用于连续型天线系统,是直升机载战场侦察雷达有效地实现杂波抑制与平台运动补偿的可取方案。     

氨基离子液体/CO_2高温高效吸收式制冷循环研究

本文选用高热稳定性的氨基功能型离子液体3-丙胺基-三丁基鏻甘氨酸盐([aP_(4443)][Gly])水溶液为吸收剂与CO_2组成新型吸收式制冷循环工质对。根据已测定的CO_2在[aP_(4443)][Gly]水溶液中的溶解度,拟合并外延得到300～510 K、1～10 MPa条件下[aP_(4443)][Gly]水溶液中CO_2的溶解度。测定了285～365 K温度范围内不同浓度[aP_(4443)][Gly]水溶液的质量定压热容,计算得到[aP_(4443)][Gly]水溶液的焓。用两种方法分析了[aP_(4443)][Gly]水溶液对CO_2的吸收焓,得到[aP_(4443)][Gly]水溶液/CO_2体系焓。根据以上数据分析计算[aP_(4443)][Gly]水溶液/CO_2单效吸收式制冷性能系数。结果表明:[aP_(4443)][Gly]水溶液/CO_2工质对可以在较高温度环境下工作,在发生温度为393.15 K,蒸发温度为278.15 K,冷却温度为303.15 K时,制冷性能系数可达0.87;在更高的发生温度下,制冷性能系数可达0.91,说明[aP_(4443)][Gly]水溶液/CO_2工质对具有成为新型吸收式制冷工质对的巨大潜力。     

Mo丝网上双层Ir/W高温抗氧化涂层的制备与表征

为改善溅射依涂层与钼基体之间的结合力,在钼基体与依涂层之间制备了钨粘结层,并成功在钼丝网上制备了双层的铱/钨涂层。研究表明,钨粘结层的制备能有效改善铱涂层与钼基体之间的结合力,从而有效抑制铱涂层的剥落。对于制备态的样品,W粘结层与铱涂层以及钼基体之间未出现明显的互扩散。X射线衍射结果表明,溅射铱涂层为多晶结构且呈(111)择优取向生长。根据Movchan-Demchishin模型,所制备的双层铱/钨涂层的显微结构与“1区”结构类似,该结构表明所制备的涂层横向结合力弱,在拉应力状态下易发生开裂。     

Survivability-oriented optimal node density for randomly deployed wireless sensor networks

The survivability is usually critical for wireless sensor networks,which are often deployed in the unattended harsh environment.Lots of technical schemes to improve the survivability depend on the redundant resources of the sensor networks.The amount of resources is usually determined by the node density during the deployment phase.For the random deployment and random node failures,the quantitative relation between the survivability and the node density is studied.Based on the conditional survivability,the node density to meet the required survivability level is presented.Finally,the survivability for unpredictable failures and the optimal node density to maximize the price–performance ratio are also discussed.