关于大系统周期解的存在性

本文应用Liapunov函数方法,研究了复合大系统dx/(dt)=P(t)A(t)x的稳定性,在此基础上,给出了周期大系统dx/dt=P(t)A(t)x+f(x)存在平稳振荡的充分条件,并且给出了非线性周期复合大系统dx/dt=P(t)A(t)x+g(t,x)的解的有界性和周期解的存在性的充分条件,改进了文[3～6]的有关结果。     

大型循环流化床锅炉燃烧系统数学模拟

数学模型是研究和发展大型循环流化床锅炉的重要方法.在浙江大学提出的适用于中小型循环流化床锅炉的整体数学模型的基础上,建立了适用于大型循环流化床锅炉的数学模型.模型采用了基于环-核结构的流体动力学模型,并考虑了宽筛分燃料颗粒所经历的破碎、燃烧等过程.模拟了国内一台300MWe循环流化床锅炉,模拟计算结果与锅炉的运行测量值...     

Low-Temperature Fast Production of Carbon and Acetic Acid Dual-Promoted Pd/C Catalysts

The Pd/C catalysts are widely used in synthesis of fine chemicals in industry, but their production suffers from a complicated two-step process involving impregnation and reduction, and requires large amounts of solvents and reductant, which would lead to a series of issues such as time consumption, resource waste and environmental pollution. Herein, ultra-small Pd nanoparticles uniformly anchored on carbon nanotubes (Pd/CNTs) were synthesized by using a one-pot and low-temperature reduction strategy. The present process/technology is very sensitive to and controlled by the supports and solvents, and the carbon support and acetic acid synergistically play crucial and decisive roles in the fast production of Pd/C catalysts. Also, the used solvents can be recycled and reutilized, which meets the requirements of sustainable chemistry and green economy. When the as-obtained Pd/CNTs catalyst was used to catalyze the oxidation of benzyl alcohol to benzaldehyde, it achieved a conversion efficiency as high as 99.3 % and a high selectivity up to >99.9 %. The simple, scalable and environmentally friendly strategy can be extended to anchor Pd nanoparticles on various carbon substrates, which sheds a new light on the synthesis of Pd/C catalysts.     

多层快速多极子算法中的两步插值技术

多层快速多极子算法(MLFMA)在快速多极子算法(FMM)的基础上按多层聚集、层间转移和多层扩散的思路以达到优化矩阵向量积的运算的目的,其中多层聚集和多层扩散过程,随着层数递增,角谱积分采样点数逐层递增,为了快速计算角谱积分,需要采用插值技术和反插值技术以提高计算效率.应用两步插值技术替代传统的单步插值技术,大幅提高了多层快速多极子层间插值反插值操作的计算效率,对于应用普通个人计算机求解特大电大尺寸问题,具有重要意义.     

非结构化网格下大范围波浪的折绕射计算

从含流缓坡方程出发,推导出光程函数方程。采用基于非结构化网格下的有限体积法对光程函数方程和波作用守恒方程进行数值离散和联合求解,从而构建了一个考虑绕射的计算近岸大范围波浪传播过程的数值模型。模型的空间步长不再受制于波长的限制,同时非结构化网格可以很好地拟合复杂岸线变形。模型分别通过了施奈尔定律、直立防波堤后的波浪绕射和圆形浅滩上的波浪变形验证,结果表明,该数值模式能有效模拟复杂边界条件和大范围水域下近岸波浪的传播过程中的折射和绕射等变形。     

大型结构变形实时摄像测量方法

本文对实时测量大型结构静力变形实验中如何应用摄像测量方法展开研究。针对实时摄像测量的两个主要难题研究解决方法,即图像特征点自动提取和多像机图像特征点自动对应。通过在待测结构表面粘贴LED发光灯或使用激光光栅投影做为合作标志点,提出NNLOG(normalnized negative laplacian of gaussian)算子用于图像上合作标志点的实时提取与跟踪;根据多摄像机约束关系,构造对极几何约束代价函数,解决多像机图像特征点之间的对应问题。设计实现了精度实验,表明位移测量误差小于1mm,相对误差小于1%,基于本文方法实现的测量系统已应用于某型飞机静力变形实验。     

High-efficiency improved symmetric successive over-relaxation preconditioned conjugate gradient method for solving large-scale finite element linear equations

Fast solving large-scale linear equations in the finite element analysis is a classical subject in computational mechanics. It is a key technique in computer aided engineering （CAE） and computer aided manufacturing （CAM）. This paper presents a high-efficiency improved symmetric successive over-relaxation （ISSOR） preconditioned conjugate gradient （PCG） method, which maintains lelism consistent with the original form. Ideally, the by 50% as compared with the original algorithm. the convergence and inherent paralcomputation can It is suitable for be reduced nearly high-performance computing with its inherent basic high-efficiency operations. By comparing with the numerical results, it is shown that the proposed method has the best performance.     

The Analysis of Network Scale and Reliability in Ring-and-Tree-Based Metro-Access Network with LAN Service

In this article, a (ring-and-tree)-based metro-access network architecture is proposed. By using some conventional optical components, the network can realize passivity in both a remote node and optical network unit (ONU). By employing ring-and-tree topology, the network cannot only provide protection for feeder fibers, but also realize large-scale access. By connecting the ONUs into a ring, the network cannot only carry out mutual protections between ONUs, but also support LAN-service transmission. The analysis of system performance demonstrates the effectiveness of the architecture.     

On the influences of key modelling constants of large eddy simulations for large-scale compartment fires predictions

An in-house large eddy simulation (LES) based fire field model has been developed for large-scale compartment fire simulations. The model incorporates four major components, including subgrid-scale turbulence, combustion, soot and radiation models which are fully coupled. It is designed to simulate the temporal and fluid dynamical effects of turbulent reaction flow for non-premixed diffusion flame. Parametric studies were performed based on a large-scale fire experiment carried out in a 39-m long test hall facility. Several turbulent Prandtl and Schmidt numbers ranging from 0.2 to 0.5, and Smagorinsky constants ranging from 0.18 to 0.23 were investigated. It was found that the temperature and flow field predictions were most accurate with turbulent Prandtl and Schmidt numbers of 0.3, respectively, and a Smagorinsky constant of 0.2 applied. In addition, by utilising a set of numerically verified key modelling parameters, the smoke filling process was successfully captured by the present LES model.