非线性耦合Ginzburg-Landau方程组的整体吸引子

为研究系数与时间有关的一维非线性耦合Ginzburg-Landau方程组在周期边界条件下整体吸引子的存在性,采用经典的Galerkin逼近方法,得到了方程组在周期边界条件下整体解的存在性及唯一性,再利用能量方法,证明了整体吸引子的存在性.     

UPML吸收边界条件统一建模与优化方法

单轴各向异性介质完全匹配层(UPML)是时域有限差分方法(FDTD)的一种理想的吸收边界条件,但多个子区域的迭代运算增加了UPML实现的难度和耗用资源.通过寻找UPML区域中介质属性的变化规律,提出实现UPML吸收边界条件的统一建模方法,并在此基础上提出两种精简辅助变量占用空间的优化算法——六区域分割方法和压缩变量方法.计算结果表明,统一建模方法只需三次循环即可完成三个方向所有介质参数及迭代系数的初始化;六区域分割方法虽然节省了大量无用存储空间,但速度最慢;压缩变量方法不仅节省存储空间、方便编程实现,而且提高了仿真速度.     

复合吸水颗粒深部液流转向剂注入性研究

由于吸水网络与控制网络的互穿结构,复合吸水材料颗粒具有吸水膨胀速度可控、吸水后强度高的特点。通过填砂管模型、变径管模型研究了复合吸水颗粒深部液流转向剂的注入特性、吸水后在孔喉中的运移情况。实验结果表明：在粒径小于孔喉尺寸的前提下,未吸水膨胀前颗粒可以顺利注入;吸水后即使颗粒直径大于孔喉直径也可以通过拉伸变形顺利通过,通过后立即恢复原状。注入过程中填砂管渗透率降低,颗粒膨胀后渗透率进一步降低,颗粒膨胀后在驱替压力足够大的情况下依然可以在填砂管微孔中运移。     

Effects of Temperature on Enantiomerization Energy and Distribution of Isomers in the Chiral Cu13 Cluster

In this study, we report the lowest energy structure of bare Cu₁₃ nanoclusters as a pair of enantiomers at room temperature. Moreover, we compute the enantiomerization energy for the interconversion from minus to plus structures in the chiral putative global minimum for temperatures ranging from 20 to 1300 K. Additionally, employing nanothermodynamics, we compute the probabilities of occurrence for each particular isomer as a function of temperature. To achieve that, we explore the free energy surface of the Cu₁₃ cluster, employing a genetic algorithm coupled with density functional theory. Moreover, we discuss the energetic ordering of isomers computed with various density functionals. Based on the computed thermal population, our results show that the chiral putative global minimum strongly dominates at room temperature.     

一类检错编码方案

提出了一类检错编码方案,给出了它的计算方法,求出了它检查出各类错误的概率。特别地,从这类检错编码方案,可以推导出《中华人民共和国国家标准：数据处理——校验码系统》和《International Standard ISO 7064》中的各个校验码系统。     

冲击波条件下横卧钢管变形简化数值模拟方法研究

为研究横卧钢管吸能特性,我们对其在冲击波条件下变形、吸能特性进行了试验研究。根据试验结果,利用折线模型对钢管变形过程进行了简化,提出了横卧钢管变形简化数值模拟方法,并根据试验结果确定了简化模型参数与钢管几何尺寸、荷载之间的关系,进而确定了简化模型的相关参数。简化计算结果与试验结果吻合较好,表明该简化方法是合理的。其研究成果可以为模卧钢管吸能层的工程设计提供有益的参考。     

压力阀的独立阻尼减振调压技术研究

液压溢流阀等定值压力阀主要靠弹簧进行压力调节。以锥阀芯溢流阀为例,阀芯开启时不易稳定,需要对锥角、弹簧刚度和进口容积腔等参数进行良好的匹配。并且,稳定性容易受系统工况特性的影响。针对压力阀低阻尼的特性,提出了一种新的减振调压技术,利用独立阻尼系统和弹簧的共同减振提高阀芯的稳定性。与现有的阀芯稳定性改进技术不同,独立阻尼减振调压技术不增加元件本身的压力损失,对加工精度的要求较低。通过与普通锥阀的特性对比,分析了独立阻尼减振调压结构的工作原理和工作特性,并对影响该结构性能的主要参数进行了仿真计算。结果表明:独立阻尼减振调压结构具有较好的动态稳定性,腔室容积等参数影响其工作特性。     

Discrete non‐local absorbing boundary condition for exterior problems governed by Helmholtz equation

The finite element method is employed to approximate the solutions of the Helmholtz equation for water wave radiation and scattering in an unbounded domain. A discrete, non‐local and non‐reflecting boundary condition is specified at an artificial external boundary by the DNL method, yielding an equivalent problem that is solved in a bounded domain. This procedure formulates a boundary value problem in a bounded region by imposing a relation in the discrete medium between the nodal values at the two last layers. For plane geometry, this relation can be found by straightforward eigenvalue decomposition. For circular geometry, the plane condition is applied at the external layer and this condition is condensed through a structured annular region, resulting in a condition at an inner radius. Exterior problems with a bounded internal physical obstacle are considered. It is well‐known that these kind of problems are well‐posed, and have a unique solution. Numerical studies based on standard Galerkin methodology examine the dependence of the DNL condition with respect to the circular annular region width. The DNL condition is compared with local boundary conditions of several orders. Numerical examples confirm the important improvement in accuracy obtained by the DNL method over standard conditions. Copyright © 1999 John Wiley & Sons, Ltd.     

一种吸波材料涂层厚度的在线测量方法

该文提出了一种用微波魔T桥式电路来现场测量吸波材料涂层厚度的方法.该方法具有设备简单、操作方便、适合于无损测量等优点.实验证明该方案可行.     

Cahn-Hilliard-Navier-Stokes方程的长时间行为

【目的】Cahn-Hilliard-Navier-Stokes方程是由不可压缩的Navier-Stokes方程和高阶各项异性Cahn-Hilliard方程耦合而成,具有广泛应用和重要作用。【方法】通过能量估计得到方程的解半群存在有界吸收集和一致紧性。【结果】利用吸引子存在性定理验证了整体吸引子的存在性。【结论】研究了该方程在相对浓度满足Neumann边界条件下的长时间行为。