两种高空核爆电磁脉冲电缆耦合效应的比较

 有关高空核爆电磁脉冲(HEMP)的标准，我国推荐的1976 HEMP和IEC推荐的1996 HEMP的早期波形是不同的。针对两种HEMP标准，采用传输线方程计算了不同长度电缆受HEMP影响的情况，结果表明电缆的1976 HEMP早期耦合效应较1996 HEMP早期耦合效应要严重的多。     

Advances in melt-processed HTS applications at politecnico di torino

Summary This paper deals with a comparison of chemical, physical and mechanical characterisation of YBCO samples obtained with Temporary-Liquid-Densification Melt Growth (TLDMG). Ba₂YCu₃O_7-x +50% excess BaY₂CuO₅ pellets were prepared from different Ba-Y-Cu-O system phases, suitable to produce during the heat treatment temporary liquids at temperatures lower than 1000°C. A mechanical characterisation was performed in zero-field-cooling and field-cooling condition, showing hysteretic behaviour and creep of the levitation force. Measurements of magnetic hysteresis cycles in low fields and a.c. susceptibility were also performed. Some mechanical applications (high-speed electric motor and flywheel energy accumulator) were built and tested. The work now proceeds on two new industrial applications of melt-processed HTSC materials. Paper presented at the “VII Congresso SATT? Torino, 4–7 October 1994.     

Radiation-induced dielectric loss in hydrocarbon polymers

The dielectric loss of several cables insulated with hydrocarbon polymers has been measured over the frequency range of 10^?3–10⁴ Hz at 50° after being subjected to neutron doeses of up to 65 Mrad. The loss data show that a new loss process appears upon irradiation and that the frequencies associated with this loss are not those that are characteristic of those found for the unirradiated polymaric relaxations, ruling out main-chain motions. This loss seems to be related to dose and is probably due to local dipoles that are formed by the irradiation. It is also shown that the dominant behavior is not due to simple ionic conductivity. © 1993 John Wiley & Sons, Inc.     

一种基于传输线方程的埋地电缆电磁脉冲耦合时域分析方法

 埋地电缆和其它金属长导体对核电磁脉冲的耦合分析对于确定合理的工程防护措施具有重要意义。采用Agrawal模型和时域有限差分算法对线缆耦合问题进行了分析，针对该模型中需要计算土壤阻抗与电流项卷积、土壤导纳与电压项卷积的问题，提出了一种土壤阻抗特性的线性拟合处理方法，可避免复杂的卷积计算。介绍了该方法的基本原理和试用结果。这一模型拟合法适用于确定无时域解析表达式的传输线模型参数，与传输线模型的时域有限差分方法相结合，可用于分析非均匀场作用下传输线的耦合。     

水电站蜗壳垫层平面铺设范围的确定原则

目前工程界对如何合理确定水电站蜗壳垫层平面铺设范围尚无统一认识.本文采用三维有限元方法,从座环位移变形、座环抗剪性能、机墩结构位移变形、流道结构承受的扭转力比例四个方面讨论了垫层平面铺设范围的确定原则.研究结果表明,若蜗壳结构问题的主要矛盾是座环和机墩位移变形过大,则平面上垫层末端宜设置在蜗壳135°～180°断面之间;但从改善座环抗剪性能和流道结构受力条件的角度来讲,垫层末端宜设置在蜗壳0°～90°断面之间或270°断面之后.考虑到座环抗剪性能和流道结构受力条件可以通过局部的工程措施予以改善,因此应该优先考虑座环和机墩结构的不均匀变形问题,据此确定蜗壳垫层平面铺设范围.     

电磁耦合实验平台系统线缆束的电磁拓扑分析

复杂线缆束系统的电磁耦合分析,随着电磁环境的日趋复杂化,显得越来越困难。而高功率电磁辐射技术的发展,对具有复杂电缆束网络和电子设备的系统,带来了严重的电磁威胁。这从电磁攻击与电磁防护两方面,对复杂线缆束的电磁耦合分析,都提出了更加迫切的需求。由于复杂线缆束网络所涉及的几何空间的边界条件十分复杂,所以很难用时域有限差分(FDTD)或频域有限差分(FDFD)方法求解复杂线缆束网络系统的电磁耦合问题。我们在基于传输线理论,采用拓扑学中将空间按照拓扑结构进行分解的思想,建立了线缆束网络电磁耦合的拓扑模型,得出了计算复杂线缆束网络系统终端耦合电压与电流的计算方法,并给出了仿真计算实例用以验证电磁拓扑法处理线缆网络电磁耦合效应的有效性。     

Nonlinear stochastic analysis of subharmonic response of a shallow cable

The paper deals with the subharmonic response of a shallow cable due to time variations of the chord length of the equilibrium suspension, caused by time varying support point motions. Initially, the capability of a simple nonlinear two-degree-of-freedom model for the prediction of chaotic and stochastic subharmonic response is demonstrated upon comparison with a more involved model based on a spatial finite difference discretization of the full nonlinear partial differential equations of the cable. Since the stochastic response quantities are obtained by Monte Carlo simulation, which is extremely time-consuming for the finite difference model, most of the results are next based on the reduced model. Under harmonical varying support point motions the stable subharmonic motion consists of a harmonically varying component in the equilibrium plane and a large subharmonic out-of-plane component, producing a trajectory at the mid-point of shape as an infinity sign. However, when the harmonical variation of the chordwise elongation is replaced by a narrow-banded Gaussian excitation with the same standard deviation and a centre frequency equal to the circular frequency of the harmonic excitation, the slowly varying phase of the excitation implies that the phase difference between the in-plane and out-of-plane displacement components is not locked at a fixed value. In turn this implies that the trajectory of the displacement components is slowly rotating around the chord line. Hence, a large subharmonic response component is also present in the static equilibrium plane. Further, the time variation of the envelope process of the narrow-banded chordwise elongation process tends to enhance chaotic behaviour of the subharmonic response, which is detectable via extreme sensitivity on the initial conditions, or via the sign of a numerical calculated Lyapunov exponent. These effects have been further investigated based on periodic varying chord elongations with the same frequency and standard deviation as the harmonic excitation, for which the amplitude varies in a well-defined way between two levels within each period. Depending on the relative magnitude of the high and low amplitude phase and their relative duration the onset of chaotic vibrations has been verified.     

多跨连续长索在支座处存在滑移的非线性静力分析

提出了一种考虑悬索结构在中支座存在滑移时的非线性计算方法，推导出关于索元无应力长度发生变化时的滑移刚度公式，并进行了实例计算。计算结果表明，本文的方法正确，计算精度满足实际工程要求，并能使计算工作且大大减少，可供悬索结构设计、施工时参考。     

基于生存分析模型的游客停留天数影响因素分析——以大连滨海旅游为例

游客的停留天数是影响旅游经济发展的一个重要因素。但是,由于停留天数变量特有的统计属性和复杂性,如数据删失和非负性,使得经济研究领域很少有学者系统地的研究这一问题。本文通过使用计量经济学的参数化生存分析模型分析游客停留天数的决定因素,这对旅游需求研究是一个很好的创新。在研究过程中,为了揭示影响游客停留天数的主要因素,本文考虑了多个关于游客的社会-人口统计特征等变量。结果显示,重复旅行的游客和距离较远的游客会停留较长的天数。因此,未来研究需要进一步分析具有这些特征的游客群体以及他们的经济状况和旅游活动特征等情况。游客的收入水平和年龄也对停留天数具有显著的影响。此外,游客受教育程度越高,停留天数越少。最后,本文分别分析了这些结果对旅游管理决策的含义。     

考虑非稳态风荷载斜拉索风雨激振响应分析

为研究自然风荷载对斜拉桥拉索风雨激振的影响,将数值模拟的非稳态风荷载作用到拉索振动微分方程中,对拉索振动响应进行了详细分析。首先,针对水线初始位置,使用最小二乘法拟合得到水线初始位置方程;接着,采用四阶Runge-Kutta法求解拉索振动响应。通过比较在非稳态风和稳态平均风作用下的拉索响应,发现在非稳态风荷载下拉索最大振幅的变化趋势并没有发生较大改变,皆是随着风速的增大先增大后减小;但拉索的整个振动过程发生了变化,伴随着节拍改变,其最大振幅也出现在不同振动周期内。此外,从风速-振幅曲线知,对频率为1 Hz,2 Hz和3 Hz的拉索,在一定风速范围内,考虑非稳态风荷载的拉索振幅反而更大,而且此时的风速范围也更大。