上海一座多联曲线高架桥的分析

本文对上海一座具有悬臂铰节点的多联曲线连续箱形梁桥的可行性方案提出了两种比较实用的分析方法。第一种分析方法系基于曲线薄壁梁的翘曲扭转理论的解析法,第二种为考虑翘曲作用的曲线格子梁理论的刚度法。所得分析结果基本吻合,它表明两种方法的可靠性。两者比较,后者节省机时,应用简捷而且不受支座条件和断面变化的限制,具有更大的适应性和灵活性。本文系国家自然科学基金资助研究项目“大城市高架桥理论分析的研究”的内容。有关的计算机程序现已扩充应用于其它形式的曲线桥梁分析。     

匹配最大根小于2的图的匹配等价类

本文刻画了匹配最大根小于2的图及其补图的匹配等价图类。     

On the cusum of squares test for variance change in nonstationary and nonparametric time series models

In this paper we consider the problem of testing for a variance change in nonstationary and nonparametric time series models. The models under consideration are the unstable AR(q) model and the fixed design nonparametric regression model with a strong mixing error process. In order to perform a test, we employ the cusum of squares test introduced by Inclán and Tiao (1994,J. Amer. Statist. Assoc.,89, 913–923). It is shown that the limiting distribution of the test statistic is the sup of a standard Brownian bridge as seen in iid random samples. Simulation results are provided for illustration.     

ADI方法在液桥Marangoni对流控制的数值模拟中的应用

我们采用一种ADI方法用于Marangoni对流控制的计算模拟.本文着重在数值上考察了这种应用.结果表明,这种ADI方法的应用是成功和有效的.     

Periodic solutions of a nonlinear suspension bridge equation with damping and nonconstant load

The paper is concerned with the existence of periodic solutions for the Lazer-McKenna suspension bridge equation with damping and nonconstant load. By using the Lyapunov-Schmidt reduction methods, the author discuss the relationship between the sign-changing solutions and the source terms. The result answers partly the open problem in Lazer and McKenna (SIAM Rev. 32 (1990) 537-578).     

Numerical and theoretical evaluations of AC losses for single and infinite numbers of superconductor strips with direct and alternating transport currents in external AC magnetic field

AC losses in a superconductor strip are numerically evaluated by means of a finite element method formulated with a current vector potential. The expressions of AC losses in an infinite slab that corresponds to a simple model of infinitely stacked strips are also derived theoretically. It is assumed that the voltage-current characteristics of the superconductors are represented by Bean’s critical state model. The typical operation pattern of a Superconducting Magnetic Energy Storage (SMES) coil with direct and alternating transport currents in an external AC magnetic field is taken into account as the electromagnetic environment for both the single strip and the infinite slab. By using the obtained results of AC losses, the influences of the transport currents on the total losses are discussed quantitatively.     

铁电体电源起爆金属桥箔的数值计算分析

 为探讨铁电体电源对金属桥箔的起爆作用,对冲击波作用下PZT95/5铁电体对铜桥箔的放电过程进行了数值计算。通过引入金属桥箔电阻非线性变化的FIRESET模型,考虑回路电感及回路电阻,计算了负载为铜桥箔时的铁电体的电响应。讨论了铁电体并联数量、回路电感对桥箔爆炸特性的影响。计算结果表明：当并联排列的铁电体电极面积达到0.006 m²以上时,在桥箔上可产生高于100 GA/m²的电流密度,能够有效起爆桥箔。而回路中存在适当的电感将有利于铁电体电源起爆桥箔。计算方法和结果能够为起爆金属桥箔的铁电体电源设计提供理论根据。     

Reduced dielectric loss and leakage current in CaCu3Ti4O12/SiO2/CaCu3Ti4O12 multilayered films

The CaCu₃Ti₄O₁₂/SiO₂/CaCu₃Ti₄O₁₂ (CCTO/SiO₂/CCTO) multilayered films were prepared on Pt/Ti/SiO₂/Si substrates by pulsed laser deposition method. It has been demonstrated that the dielectric loss and the leakage current density were significantly reduced with the increase of the SiO₂ layer thickness, accompanied with a decrease of the dielectric constant. The CCTO film with a 20 nm SiO₂ layer showed a dielectric loss of 0.065 at 100 kHz and the leakage current density of 6×10⁻⁷ A/cm² at 100 kV/cm, which were much lower than those of the single layer CCTO films. The improvement of the electric properties is ascribed to two reasons: one is the improved crystallinity; the other is the reduced free carriers in the multilayered films.     

LCR分流电路下压电声子晶体智能材料的带隙

将带有LCR分流电路的压电陶瓷片对贴在铝和环氧树脂组成的声子晶体结构中.使智能材料的机械振动与压电陶瓷的压电效应耦合起来,推导出机械振动在压电陶瓷片上的等效附加应力;使LCR分流电路中的电磁振荡效应和声子晶体的能带特性有机结合,计算了在分流电路作用下智能材料扭转和弯曲振动的带隙特性,研究了电阻、电感、电容元件的改变对压电声子晶体智能材料带隙的影响.研究结果表明:在合理尺寸下,随着分流电路中电阻值的增大,带隙的频率范围变宽,但衰减幅值有所降低;电感和电容值的增大都可以使带隙向低频移动,带隙的衰减幅值随着电感值的增大而升高,但随着电容值的增大而降低.从而给压电声子晶体智能材料减震降噪的控制提供了一种新思路.     

AC operation and runaway electron behaviour in HT-7 tokamak

Operation of HT-7 tokamak in a multicycle alternating square wave plasma current regime is reported. A set of AC operation experiments, including LHW heating to enhance plasma ionization during the current transition and current sustainment, is described. The behaviour of runaway electrons is analysed by four HXR detectors tangentially viewing the plasma in the equatorial plane, within energy ranges 0.3--1.2~MeV and 0.3--7~MeV, separately. High energy runaway electrons (\sim MeV) are found to circulate predominantly in the opposite direction to the plasma current, while the number of low energy runaway electrons (\sim tens to hundreds of keV) circulating along the plasma current is comparable to that in the direction opposite to the plasma current. AC operation with lower hybrid current drive (LHCD) is observed to have an additional benefit of suppressing the runaway electrons if the drop of the loop voltage is large enough.