一类Adams型的并行混合方法

构造了一类Adams型的并行多步混合方法 ,得到了A 稳定的三步三阶方法和A(α) 稳定的四步四阶 (α =89.99°)及五步五阶 (α =84.92°)方法的具体计算公式 .数值试验表明 ,这类方法对于求解刚性常微分方程是有效的     

刚性桥面铺装层厚度的估算

本文在对目前普遍存在的桥面铺装层破损现象分析的基础上 ,归纳其中主要力学成因 ,建立了关于桥面铺装及行车道板内力分析的简化力学模型 ,并进而针对常见钢筋混凝土梁式桥刚性桥面铺装层的厚度进行了估算     

Improved multimode pushover procedure for asymmetric in plan buildings under biaxial seismic excitation—application to tall buildings

An improved version of a recently developed multimode pushover procedure for asymmetric in plan buildings under biaxial seismic excitation is presented and evaluated. The proposed methodology is quite similar to the well‐known modal pushover analysis. However, the establishment of the equivalent single‐degree‐of‐freedom systems is based on a new concept, which takes into account multidirectional seismic effects. The proposed methodology does not require independent analysis in the two orthogonal directions, and therefore, the application of simplified directional combination rules is avoided. The improvement presented here consists in definition of correction factors to be applied to the response values at the stiff side of buildings. An extensive evaluation study comprising applications to tall buildings is presented. The response parameters obtained from the proposed methodology in most cases envelope the values resulting from nonlinear dynamic analysis (NDA). Furthermore, the mean errors with regard to the NDA results are smaller than those obtained from a multimode pushover procedure comprising independent analysis along two horizontal axes and directional combination of the results. In general, the proposed methodology provides a reasonable estimation of the seismic performance of asymmetric buildings.     

淤泥土在被动状态下破坏机理的模型实验研究

目前大量的深基坑开挖工程事故主要发生在沿江及沿海饱和淤泥土地区，其关键问题在于对淤泥土的被动土压力认识不足。针对这一问题，通过大量系统的室内模拟试验，对绕刚性墙板上端转动条件下墙后土体的破坏机理进行了研究。在绕刚性墙板上端转动的被动位移形式下，墙后饱和淤泥土体滑移线产生具有渐进性质，被动状态下的发展过程分为三个阶段，即：线性段；渐进破坏段；破坏发展段。同时试验还表明，淤泥土在被动状态发展过程中，土体所承受的被动荷载大小决定于淤泥的流动性质及墙体转动位移的大小。     

浅谈劲性骨架在高墩施工中的作用

结合某高墩施工实例,就劲性骨架在施工中的作用作了论述,并对劲性骨架尺寸确定及布设、劲性骨架强度及刚度估算进行了探讨,实践证明劲性骨架在该工程中的应用取得了良好的效果。     

Low frequency noise reduction using stiff light composite panels

The experiment presented in this paper is to investigate and analyze the noise reduction at low frequency using stiff light composite panels. Since these composite panels are made of lightweight and stiff materials, this actuation strategy will enable the creation of composite panels for duct noise control without using traditional heavy structural mass. The results suggest that the mass-spring resonance absorption in the case of a comparatively stiff thick panel with a thin flexible plate is more efficient with minimum weight, when subjected to low-frequency (<500 Hz). The efficiency of the panel absorber depends on the mass of the thin flexible plate and the stiffness of the panel.     

如何选择国产大型硬塑真空挤出机

分析了我国当前大型硬塑真空挤出机的现状,从设计、制造、可靠性、维修、能耗等方面论述了选择大型硬塑真空挤出机的技术要求,认为新型砖厂必须选择大型硬塑真空挤出机。     

劲性混凝土框架施工技术

介绍了劲性混凝土框架在钢柱、钢梁周围配置钢筋,浇筑混凝土,钢构件和混凝土连成一体的施工方法,应用该方法具有承载力高、塑性好、抗震性能好、经济效益显著等优点,满足了高度和跨度大的要求。     

A study of direct and Krylov iterative sparse solver techniques to approach linear scaling of the integration of chemical kinetics with detailed combustion mechanisms

The integration of the stiff ODE systems associated with chemical kinetics is the most computationally demanding task in most practical combustion simulations. The introduction of detailed reaction mechanisms in multi-dimensional simulations is limited by unfavorable scaling of the stiff ODE solution methods with the mechanism’s size. In this paper, we compare the efficiency and the appropriateness of direct and Krylov subspace sparse iterative solvers to speed-up the integration of combustion chemistry ODEs, with focus on their incorporation into multi-dimensional CFD codes through operator splitting. A suitable preconditioner formulation was addressed by using a general-purpose incomplete LU factorization method for the chemistry Jacobians, and optimizing its parameters using ignition delay simulations for practical fuels. All the calculations were run using a same efficient framework: SpeedCHEM, a recently developed library for gas-mixture kinetics that incorporates a sparse analytical approach for the ODE system functions. The solution was integrated through direct and Krylov subspace iteration implementations with different backward differentiation formula integrators for stiff ODE systems: LSODE, VODE, DASSL. Both ignition delay calculations, involving reaction mechanisms that ranged from 29 to 7171 species, and multi-dimensional internal combustion engine simulations with the KIVA code were used as test cases. All solvers showed similar robustness, and no integration failures were observed when using ILUT-preconditioned Krylov enabled integrators. We found that both solver approaches, coupled with efficient function evaluation numerics, were capable of scaling computational time requirements approximately linearly with the number of species. This allows up to three orders of magnitude speed-ups in comparison with the traditional dense solution approach. The direct solvers outperformed Krylov subspace solvers at mechanism sizes smaller than about 1000 species, while the Krylov approach allowed more than 40% speed-up over the direct solver when using the largest reaction mechanism with 7171 species.     

深基坑开挖中的应力路径

土的力学性质取决于它的应力历史,应力状态和应力路径。为了认识和理解深基坑开挖引起的变化必须研究由于水平和垂直应力的释放而产生的有效应力变化。为此介绍和讨论了微裂硬粘土中１０ｍ深基坑附近的有效应力变化,比较了现场观测到的应力路径和室内试验得到的应力路径,发现连续墙前的有效应力路径与室内不排水伸长试验的应力路径相同;但是,那些墙后的应力路径,除应力状态接近主动破坏外,与室内对原状土不排水压缩试验得到的也不尽相同,通常假定的基坑迅速开挖中的不排水性质似乎在墙后土体中也没有保持。