自紧身管疲劳寿命的可靠性分析

基于概率断裂力学理论和Monte Carlo模拟方法，给出了自紧身管疲劳寿命的可靠性分析方法．自紧残余应力采用了符合身管材料具有强化和包辛格效应性能推导的公式计算，身管工作的应力强度因子通过权函数方法得到．实例分析结果表明，对数正态分布为身管疲劳寿命的最佳分布，同时给出了各种置信度和可靠度下的身管疲劳寿命．另外，还分析了初始裂纹尺寸和材料的断裂韧性对身管疲劳寿命的影响．该研究对保证身管的安全，避免灾难性事故的发生具有重要意义．     

A Field Monte Carlo Formulation for Calculating the Probability Density Function of a Single Scalar in a Turbulent Flow

The probability density function (PDF) formulation of one scalar field undergoing diffusion, turbulent convection and chemical reaction is restated in terms of stochastic fields. These fields are smooth in space as they have a length scale similar to that of the PDF. Their evolution is described by a set of stochastic partial differential equations, which are solved using a finite volume scheme with a stochastic source term. The application of this methodology to a particular flow is shown first for a linear source term, with exact analytical solution for the mean and standard deviation, and then for a nonlinear reaction.     

进气道实验中动态数据采集及处理方法研究

本文介绍了进气道实验中动态数据采集及处理方法，研究了滤波器截止频率以及进气道不同流量对动态畸变指数的影响，对在干扰状态下得到的数据以传统方法、统计方法、误差方法进行了分析及处理，并对所得到的实时数据进行了频谱分析。     

Molecular Architecture Manipulation in Free Radical Copolymerization: An Advanced Monte Carlo Approach to Screening Copolymer Chains with Various Comonomer Sequence Arrangements

A Kinetic Monte Carlo (KMC) simulation approach has been adopted in this study to capture evolutionary events in the course of free radical copolymerization, through which batch and starved‐feed semibatch processes are compared. The implementation of the KMC code deve­loped in this work: (i) enables satisfactory control of the molecular weight of the copolymer by tracking the profiles of concentrations of macroradicals, monomers, and polymer as well as degree of polymerization, polydispersity, and chain length distribution; (ii) captures the bivariate distribution of chain length and copolymer composition; (iii) comprehensively tracks and analyzes detailed information on the molecular architecture of the growing chains, thus distinguishing between sequence length and polydispersity of chains produced in batch and starved‐feed semibatch operations; (iv) makes possible the screening of products, based on such details as the number and weight fractions of products having different comonomer units located at various positions along the copolymer chains. The aforementioned characteristics are achieved by stochastic calculations through code developed in‐house. This KMC simulator becomes a very useful tool for the development of tailored copolymers through free radical polymerization, with blocks separated with single units of a different type.

     

Topological Effect on the Structure of Self‐Assembled Aggregates from Amphiphilic Macromolecules in Solution

The self‐assembled morphologies of cyclic amphiphiles, which are composed of a long hydrophobic block and a short hydrophilic block, in selective solutions are studied by using a simulated annealing method. The morphological dependence of the aggregates on solvent quality is investigated. The topology effects are studied by comparing results from linear counterparts of the amphiphiles. It is observed that, in addition to spherical micelles, cylindrical micelles, disklike micelles, vesicles, and large compound micelles, muticompartment vesicles with several fluidic cores can be formed by the cyclic systems. The morphologies are regulated by the interaction parameter ε_AS between the hydrophobic block and solvents. Furthermore, it is revealed that the differences of characteristics of the self‐assembled aggregates originate from the difference in architectural constraint. The wide region of forming multicompartment vesicles suggests that cyclic amphiphilic macromolecules could be a suitable candidate for applications to deliver multiple functional components by compartmentalizing different components in different confined space of vesicles.     

使用压缩感知的遥感图像振荡畸变几何校正方法

卫星平台振动和反射镜震颤会引起遥感图像中的振荡畸变。这类畸变难以通过常用的几何校正方法消除。对此,提出了一种使用压缩感知的几何校正方法。该方法基于有理函数模型(RFM)进行几何校正。在校正过程中,利用初始的RFM计算出地面控制点(GCPs)在图像中的投影坐标与实际成像坐标之间的偏差(称为投影偏差),以地面控制点处的投影偏差作为采样值,使用压缩感知技术重构出所有像元处的投影偏差,并据此对RFM进行像方补偿;利用经过补偿的RFM进行遥感图像纠正。通过补偿,消除了振荡畸变引起的RFM模型误差,进而提高校正性能。利用实测数据验证了该方法的有效性,并通过仿真数据分析了地标点的数量与分布对该几何校正方法性能的影响。