德国成型设备应用国产化珠粒的研究

为了提高消失模铸件的质量,某公司从德国引进先进的消失模预发泡机和泡沫成型机,该机器需要与之相匹配的珠粒材料及制作工艺。通过消失模白模珠粒材料国产化,即消失模白模珠粒(共聚物)材料配方及材料预发泡、成型等工艺性能的优化,进行发泡参数的微调、优化与控制,使其成功应用于进口预发泡设备。     

The Numerical Simulation of the Broadband Spiral Antenna Design Based on Hybrid Backed-Cavity

In the paper, the hybrid backed-cavity with EBG (Electromagnetic Band-Gap) structure and PEC (Perfect Electronic Conductor) is proposed for Archimedean spiral antenna, which can make the spiral antenna work over the 10:1 bandwidth, without the loss introduced by absorbing materials. Based on the AMC characteristic (Artificial Magnetic Conductor), the EBG is placed in the outer region of backed-cavity to improve the blind spot gain in the low frequency. The PEC at the center of the structure is used to obtain high gain at high frequency. The better antenna performances are achieved in the low profile spiral antenna. A typical spiral antenna with hybrid backed cavity is numerically studied. The novel spiral antenna design with hybrid backed cavity is validated by simulated results.     

Segregation Behaviour and Microstructure of Alloy 718VADER Ingot

The segregation behaviour and miclostructure of an alloy 718 VADER ingot in comparison with a VAR ingot were studied. The results show that one serious problem of the alloy 718 VADER ingot is dealing with radial chemistry gradients (especially macro-segregation in Nb). The main factor of Nb gradient forming is the flow of Nb rich fluid through passages among the cellular structures driven by centrifugal force from the rotating mold, Detailed structure and micro-segregation studies on ingots impress us that the VADER process does not show the advantage on the improvement of micro-segregation especially in Nb. The cellular structure produced by the VADER process is no more effective in reducjng Nb micro-segregation during homogenization treatment than the dendritic structure by the VAR process. Experimental results lead us to believe that the VADER process is unsuitable to manufacture alloy 718.     

薄层钝化纳米铝粒子研究

采用蒸发冷凝方法制备纳米铝粉,由于其表面具有很高的活性,对所制备的纳米铝粒子进行了表面钝化.采用小角X射线散射测定纳米铝粉粒度,SEM、TEM、HRTEM、XRD、ED等方法分析钝化纳米铝的形貌、化学组成和结构.结果表明,所制备的钝化纳米铝的平均粒度为80nm,ED分析有Al和Al2O3的衍射斑点但,Al2O3的含量较少,与XRD的分析结果一致,HRTEM可见在Al颗粒的表面形成了厚度小于5nm的均匀氧化膜.     

Wavelength-division multiplexed thin-film filters used in tilted incident angles of light

The properties of wavelength-division multiplexed (WDM) narrowband filters used in tilted collimated light are described. The wavelength shift for s polarization in a low-index-spacer filter is larger than that for p polarization when the filter is tilted, but it is smaller in a high-index-spacer filter. Therefore the passbands of the tilted filter can be centered at the same wavelength for two polarization modes by use of high- and low-index materials, as appropriate, as spacers or by selection of a moderate-index material instead of a spacer. With such spacers, WDM filters used for incident angles of 20 degrees or even greater are constructed. Experimental results agree with the computed ones.     

基于双椭圆平面热源模型的FeCrNiMo 激光熔覆热力耦合数值分析

针对煤矿液压支架和海洋平台立柱的表面防护与修复的工程需求, 采用 FeCrNiMo 马氏体不锈钢粉末在 27SiMn 结构钢基体表面进行激光熔覆, 以改善基体表面的耐磨、 耐蚀综合性能。 本文旨在研究激光能量密度对 FeCrNiMo 熔覆层的截面特征及其开裂倾向的影响, 采用热力耦合有限元模拟方法, 基于双椭圆平面热源模型, 计算分析了 FeCrNiMo 不锈钢粉在 27SiMn 钢基板表面的激光熔覆过程中, 在不同的激光输入能量密度条件下, 熔覆层的温度场和应力场的演变过程。 并采用相同工艺参数进行激光熔覆实验, 通过稀释率（熔覆层横截面中, 母材熔化的面积与整个熔覆层横截面积的百分比） 和熔宽情况的对比, 以验证模拟结果的可靠性。 进而研究激光 能量密度对熔覆层稀释率、 熔宽及其开裂倾向的影响规律。 熔覆层的稀释率、 熔宽均随输入能量密度的增加而增 大, 当输入功率达到 3000W, 熔覆速度 6mm/s 时可获得较理想的稀释率和熔宽。 而熔覆层边缘的应力随输入能 量密度的增加而增大, 其开裂倾向增大; 而熔覆层中心线附近的应力随功率增大而有所降低。 在激光熔覆过程中 提高输入能量虽有利于增大熔宽, 提高熔覆效率, 但是同时增加了熔覆层的稀释率及其边缘开裂倾向。     

时变路网下带混合时间窗的车辆路径问题

针对时变路网下带混合时间窗的车辆路径问题,综合考虑多中心联合配送、混合时间窗、车辆行驶速度连续变化及车辆行驶速度、载重量对油耗的影响,以车辆派遣成本、油耗成本及时间窗惩罚成本之和最小为目标建立优化模型,并设计自适应遗传-大邻域搜索算法对其进行求解。该算法采用自适应交叉、变异以加快种群寻优速度,并引入时差插入法改进交叉算子和变异算子,嵌入移除算子和插入算子对可行解进行摧毁和重建以增加种群的多样性。通过多组算例验证算法的有效性,并分析了混合时间窗客户的比例变化及车辆行驶速度变化对车辆调度方案的影响,结果表明自适应遗传-大邻域搜索算法较基本算法有着更好的求解性能。该研究成果可丰富车辆路径问题的相关研究,为物流企业优化决策配送方案提供理论依据。     

WiMAX关键技术研究

WiMAX可用于提供建设成本低、兼容程度高、互操作性强的BWA解决方案。WiMAX宽带接入技术可以弥补传统基于有线的宽带接入技术的盲区,并且更加简便、经济。在有线接入方式难以覆盖的地方．WiMAX完全可以替代有线。文章主要分析了正交频分复用（OFDM）、正交频分多址（OFDMA）、混合自动请求重传（HARQ）、自适应调制编码（AMC）、自适应天线系统（AAS）和多输入多输出（MIMO）的工作原理和优缺点,并对这些技术在WiMAX中的应用进行了简要介绍。     

A High Gain and Broadband C-Band Aperture-Coupled Patch Antenna

A aperture-coupled patch antenna is designed with parasitic elements connecting to the rectangle ring on the bottom of antenna substrate through metal vias, which lead the current induced by patch radiator to the top surface of antenna substrate. Therefore, the effective radiation is enhanced and higher gain is achieved. The bandwidth is broadened simultaneously due to the structure of aperture-coupled patch antenna with parasitic elements. Compared to the conventional aperture-coupled patch antenna, the antenna gain increases averagely 2 dB due to the novel structure. Compared to patch antenna of electromagnetic band-gap, the dimensions of novel patch antenna greatly decreases, which can be used as element in the array antenna. Two kinds manufactured antenna are both measured in an anechoic chamber. The good agreements between numerical simulation and experimental prototype have been obtained.     

一种基于载波相位时间差分的惯性/卫星组合方法

传统的惯性/卫星紧耦合组合导航系统使用卫星伪距/伪距率作为量测,卫星伪距率一般可以提供厘米/秒级精度的速度信息;而载波相位时间差分观测量可以达到毫米级精度且无需参考接收机。本文分析了载波相位时间差分的原理,并将其应用到惯性/卫星组合导航系统中;在滤波器的设计中使用状态延迟滤波法处理载波相位时间差分观测量,使惯性/卫星组合导航系统达到了较高的速度精度。