Investigation of LO-Coupled Noise for a Sideband Separation Superconducting SIS Receiver

The Superconducting Superconductor-Insulator-Superconductor (SIS) receivers have become the preferred method for (sub)millimeter-wave radio astronomical observations due to the extremely low receiver noise temperature. The coupling noise of the local oscillator (LO) system is also a part of the receiver noise. In many years of astronomical observations, it is found that the LO-coupled noise cannot be completely ignored, which has a certain impact on the sensitivity of astronomical observations. The noise temperature of the superconducting SIS receiver was tested using two different kinds of signal generators as the primary signal source of the LO system. It is found that the base noise output by the signal generator can be coupled into the receiver to increase the receiver noise. By adding a narrow band filter to the output of the signal generator, the base noise of the signal generator can be filtered out, and this part noise of the receiver can be eliminated, the overall noise of the receiver is reduced, and the sensitivity of the telescope is improved.     

Forbidden transition probabilities of astrophysical interest among low-lying states of V III

Electric and magnetic multipole transitions among low-lying states of doubly ionized vanadium were computed using the multi-configuration Hartree-Fock (MCHF) method with Breit-Pauli (BP) corrections to a non-relativistic Hamiltonian. Energy levels were determined up to and including 3d ²(¹ G)4s b ² G _7/2 and computed energies were found to be in good agreement with experiment and other theories. In addition to Einstein A _ki coefficients for some E2 and M1 transitions, lifetime data and selected weighted oscillator strengths are also reported.     

弹塑性耦合条件下沥青混凝土的应力-应变关系

三轴试验的结果表明,由于应用于水利工程的沥青混凝土自身的孔隙率小,侧向作用效应十分明显,体积变形较小,且主要表现为剪胀特性,目前已有的非线性和弹塑性模型难以正确地反映复杂应力状态下的这种力学行为。考虑沥青混凝土不遵守关联流动法则和Drucker公设,其弹性系数伴随塑性变形过程而改变,建议了一个在弹塑性耦合基础上的双屈服面弹塑性模型,与室内三轴试验结果吻合良好。     

大型换流站阀厅结构地震响应弹塑性分析

利用有限元方法对带悬挂阀的阀厅结构进行地震响应弹塑性分析,研究不同场地土条件、不同地震动作用对阀厅结构以及悬吊设备地震响应的影响.研究结果表明:阀厅结构在纵向和三向地震作用下存在较明显的扭转效应;三向地震输入时,吊杆产生的拉力约为单向输入的2倍;悬吊设备竖向地震响应大于水平地震响应,大震下悬吊设备竖向加速度约为水平向的...     

非均匀流中立管涡激振动模型预测分析

文中分析了非均匀流中,张紧式海洋立管的涡激振动,采用新的加速度耦合尾流振子模型作为预测细长海洋工程柔性结构的计算工具,将预测结果中的横向位移包络线及最大幅值与实验观测值、shear7软件计算值进行了对比,可以发现模型的计算结果与实验观测结果吻合得很好.     

基于二次抛物线型强度包络线的管桩挤土效应分析

假定管桩在沉桩时的挤土过程是一个圆柱形孔扩张过程。基于具有抛物线型强度包络线和圆孔扩张理论对管桩的挤土效应进行分析研究。分析了桩周土体周围土体的弹塑性力学行为,得到应力场和位移场等的表达式,并求得其塑性区半径、孔内最终压力。其结果可以为管桩工程问题提供理论依据。     

调相白噪声背景中高稳频率源参数估计

调相白噪声背景中高稳频率源参数的估计是一个应用广泛的信号处理问题 ,给出了利用平方拟合估计频率源参数的方法 ,它是最小平方误差意义下的估计 ,并根据模拟的数据对这种方法作了验证。     

非共轴本构模型在吸力桶地基承载力

土体在剪切变形过程中产生主应力方向的旋转时,主应变率方向与主应力方向之间存在着非共轴现象,然而,传统的弹塑性本构模型并不能考虑该现象的影响。通过在传统本构模型屈服面的切线方向增加一项非共轴塑性应变率,即可实现对非共轴现象的反映。利用有限元软件ABAQUS的材料子程序接口UMAT,通过显式积分算法和自动分步方法实现了非共轴模型在有限元分析中的应用。首先,对砂土的单剪试验进行数值模拟,预测了主应力方向和主应变率方向之间的关系,所得结论与试验结果较为吻合。然后,针对吸力桶与砂质地基间的相互作用问题进行弹塑性有限元计算,分析了土体主应力方向在剪切变形过程中的旋转规律,以及桶体的端部阻力、侧壁摩擦阻力和顶部阻力在变形过程中的变化规律。最后,检验了非共轴现象对地基承载力计算结果的影响。研究结果表明,所开发的非共轴模型对非共轴现象具有良好的预测能力。     

行波作用下盾构法隧道复杂系统的弹塑性地震反应分析

本文基于盾构法隧道等效连续化计算模型,利用有限元法建立了在地震行波作用下复杂盾构法隧道系统弹塑性受力分析的模型和求解方法。通过算例验证了有限元法的适用性。对上海市穿越黄浦江的延安东路盾构法隧道复杂系统进行了地震行波作用下的反应分析,得出在地震作用下隧道内力大小、分布及其影响因素的诸多结论。     

Slope stability analysis in 3D using numerical limit analysis (NLA) and elasto-plastic analysis (EPA)

The present paper addresses the problem of factor of safety (FS) determination in 3D slope stability analysis. For that purpose, use is made of two numerical methods/techniques in three benchmark problems: numerical limit analysis (NLA) and elasto-plastic analysis (EPA). Finite elements are used in both techniques. The primary objective of the study is, by comparing the two techniques, to establish the feasibility of using NLA in the evaluation of 3D slope stability problems and to establish its practical applicability and competitiveness in relation to EPA. Because of their geometry or their boundary conditions, the problems cannot be analysed as plane strain state problems or using the 2D limit equilibrium technique. In both methods, an FS is determined for the slopes by reducing the strength parameters of the geological materials using a scalar factor, known as the strength reduction factor. From the comparison of the FSs and of the computational efforts required for the two numerical techniques, it was possible to establish NLA’s competiveness and viability for the analysis of real 3D slope stability problems when implemented in an efficient manner.