Transmission Modes of Closed Elliptic-Groove Waveguides for Millimeter Waves

In this paper, a new type of horizontal-flat and vertical-flat closed elliptic-groove guides is firstly presented. The field components and characteristic equations for some main transmission modes of the closed elliptic-groove guides are derived by with the help of the mode-matching method and Mathieu function. The variations of the cut-off wavelengths along with eccentricities, widths and lengths of the parallel plates for a number of lower order transmission modes of the closed elliptic-groove guides are also analysed in detail. The calculated results in good agreement with ones in the relevant references are of very important values in theoretical researches and actual applications of closed elliptic-groove guides for millimeter and submillimeter waves.     

烧结车间热工设备隔热层厚度计算与构造

本文就我国南方钢铁厂烧结车间热辐射强度较大的热矿槽、主排气管等热工设备的隔热计算进行了讨论并提出了计算方案。     

爆炸烧结过程及其热力学分析

研究分析了在柱面聚合激波的作用下，粉体材料的爆炸烧结过程，计算了理想的柱面收缩率和粉粒的熔化量，从热力学角度分析了粉体材料在烧结过程中的内能增加及其能量转化，并探讨和计算了预热粉体爆炸烧结有利因素。     

自行火炮重量重心测试误差评估

随着自行火炮机动性的不断提高，对自行火炮武器系统的重量重心指标要求也越来越高，通过理论建模来计算自行火炮武器系统的重量重心误差比较大，专门的称重平台的维护和使用又不方便，因此，寻找一种简易而有效的测试方法是必要的。本文从测试原理及方法入手，着重对测试结果的误差进行了分析与评估。     

有限介质绝缘电阻对C—V测量的影响

本文描述了在高频和准静态C-V测量中,二氧化硅介质层有限电阻对测量准确性的影响。特别是在准静态测量中,由于频率相当低,MOS电容值只有100pF左右,所产生的位移电流为10(-9)～10(-14)A范围,介质层有限电阻产生的漏电流对测量准确性影响很大。因此,在存在漏电流的情况下,必须从测得的数值中扣除漏电流,才能进行界面态密度的计算。     

T300/LD2热循环时产生滞后环原因及改善方法探讨

T300/LD2复合材料在热循环时产生滞后环并留下很大的残留应变。本文对T300/LD2试样在热循环时产生滞后环和残留应变的原因进行分析和探讨。实验结果表明,基体在热循环时大量的塑性变形是产生滞后环和残留应变的主要原因,并通过在界面预设不同应力和缩短热循环温度区间来研究界面应力状态和热循环温度区间跟热循环时滞后环和残留应变之间的关系。提出了改善残留应变和滞后的方法(1)尽量减少复合材料的使用环境中的温度变化,(2)根据材料的使用环境,经过各种预处理使复合材料在工作时基体处于弹性变形状态,(3)提高基体的屈服强度。     

SiCw/6061Al复合材料冲击破坏行为

本文用夏比冲击试验(Instrumented Charpy Testing)与SEM断口分析研究了SiCw/6061Al复合材料的冲击破坏行为.与SiCw是混乱分布的铸态SiCw/6061Al复合材料相比,挤压变形后材料的冲击韧性明显提高.热挤压变形改善了材料的性能.研究观察发现了分层开裂的现象.本文详细讨论了SiCw/6061Al复合材料的冲击断裂方式、比较了变形前后冲击破坏方式的差异,并分析了热挤压变形后韧性提高的原因.     

Formation of Yb α-SiAlON whiskers by heat treatment of hot-pressed bulk samples

Novel α-SiAlON whiskers with various morphologies were produced at the surface of hot-pressed bulk samples by heat treatment at an elevated temperature of 1800 °C. Other than straight whiskers with or without nodules on their heads, curved bow-like and kinked whiskers were also observed. The growth mechanisms of different whiskers were discussed in detail, and it was proposed that the VLS (vapour–liquid–solid) mechanism was the predominant growth mode responsible for the formation of a majority of whiskers. With continuous vaporization and consumption by reactions, the liquid droplet necessary for VLS would be exhausted in some cases, and at this time VS mechanism could also become active.     

燃烧合成NiAl/TiC复合材料及其微观形貌

采用燃烧合成的方法合成NiAl/TiC复相材料,采用XRD分析了合成材料的相组成,结果表明产物由TiC和NiAl相组成,没有其他的物相产生.用SEM研究了合成产物的微观形貌,SEM图像显示产物的宏观形貌为多孔结构,微观形貌观察显示TiC相颗粒呈近球状.NiAl相则包裹在TiC相的周围,形成三维网状结构,靠近TiC颗粒边缘NiAl以胞状方式生长,远离TiC颗粒的NiAl以枝晶方式长大.     

等截面梁纯弯曲振动的几何非线性分析

在讨论梁纯弯曲微幅振动时，考虑在材料力学的讨论中梁的挠度微分方程忽略项后，线性问题变为非线性问题。利用非线性理论对该非线性问题进行了讨论，得到了周期解稳定和不稳定区域的分界线方程和频率响应方程，得到忽略挠度几何非线性因素的条件。