无约束优化问题的非单调自适应信赖域算法

对无约束优化问题提出一种非单调自适应信赖域算法,每次迭代充分利用当前的迭代点包含的一次导数的信息自动产生一个信赖域半径．在一定的条件下,证明了该算法的收敛性,并通过数值实验验证了该算法的有效．     

Assessment of uncertainty in the CFD simulation of the wave-induced loads on a vertical cylinder

The paper addresses different uncertainty analysis methods commonly used for uncertainty quantification in Computational Fluid Dynamics (CFD) studies and compares a constant Courant–Friedrichs–Lewy (CFL) number based approach for uncertainty estimation to the ITTC recommended grid and time-independent procedures. Four different uncertainty estimation procedures are presented and discussed. To compare their performance and better understand CFD related uncertainty quantification in wave load simulations on offshore structures, the methods are applied to a case study of the wave loads on a fixed vertical cylinder. The numerical or CFD wave tank is generated using the open-source CFD toolkit OpenFOAM. Uncertainty is assessed for the case study using four different uncertainty estimation procedures for verification and later, validation is attempted by comparing the CFD results with experiments. The study concludes that a constant CFL number based uncertainty study provides more stable results and is better suited for uncertainty estimation in CFD than the ITTC recommended individual grid and time step uncertainty study.     

大西安都市区轨道交通线网规划与优化思路分析

为探讨城市变化过程中线网规划的发展规律、变化趋势及优化方法,以大西安都市区为例,研究历次城市规划、线网规划主要技术指标特征,通过ROXY指数定量分析其变化特征并分析存在问题,结合研究对象特征提出未来线网优化思路并给出优化方案。经计算,ROXY指数在不同阶段的结果分别为161.75,16.20,-85.41,结果表明大西安都市区呈现"集中-分散"的发展趋势,需求特征日趋多样化。既有线网规划存在服务范围小、多网融合程度低、线网层次单一等问题,可通过发展多网融合、多层次多制式轨道交通来满足城市发展与交通需求的变化。     

水下航行体热尾流特性的技术融合

为得到红外探测水下航行体中全面的热尾流特性,提出一种技术融合的研究方法,即先将水下航行体排出的冷却水形成的热尾流近似为圆形断面的自由湍流热射流,在密度分层环境中,根据射流的积分方程建立热尾流特性的计算模型;再采用Runge-Kutta法进行数值仿真;最后利用含少量黑墨水的尾流流迹摄影、数字温度传感器多点测温和红外成像等技术进行融合实验研究。研究得到了热尾流浮升轨迹的发展、高度的增长、宽度的扩展、时间的增长、温度的分布和水面红外图像的变化等规律。仿真与实验结果的相符验证了研究方法的可行性。研究方法和所得结果有助于红外探测水下航行体技术的发展。     

Grid convergence study in the resistance calculation of a trimaran

As a new type of hull form, trimaran has remarkable excellent performances and has drawn more and more attention. When the viscous CFD technology now available is applied to the research of resistance performance of trimaran, the spatial discretization would usually result in the grid error and uncertainty, and thus the considerable discrepancy between the numerical results and the experimental data. In order to ascertain how much the grid would affect the calculation, the grid convergence should be studied. A mathematical trimaran was chosen as an example, with the commercial code CFX for the simulation, VOF for surface treatment, and the grid study was carried out based on two different turbulence models. It was concluded that carrying out grid study is helpful in estimating the grid error and uncertainty, and indicating the direction of improving the credibility of the numerical calculation, and, in addition to grid errors and uncertainties, the turbulence modeling errors and uncertainties contribute to the simulation errors.     

彩色多普勒血流会聚法对二尖瓣返流定量的评价

为探讨血流会聚新方法对二尖瓣返流定量诊断的临床价值 ,采用脉冲多普勒法作对照 ,研究36例二尖瓣返流患者。结果表明血流会聚法返流量与脉冲多普勒计算返流量具有良好相关性 (r=0 .81～ 0 .94 ,P <0 .0 0 0 1)。血流会聚法计算二尖瓣返流量合适的混叠极限速度为 4 8cm/ s左右。认为血流会聚法是一种准确、可靠且实用的二尖瓣返流量计算方法。     

两场有限元的误差估计问题

本文证明了两场变分问题有限元解的存在唯一性定理,并进行了相应的误差估计。在 此基础上,本文进一步给出了两场有限元几一收敛和尹一收敛的误差估计式,为发展 有关的自适应分析工作,提供了数学依据。      

Hilbert空间广义变分不等式的迭代方法

应用辅助原则技术,在部分相关强单调和非空有界闭子集条件下,提出了一个解广义变分不等式问题的预测校正算法.作为应用,给出了许多解不同类型变分不等式的新的结果.     

关于换行逆修正法

给出了求解非线性方程组Ｆ（ｘ）＝０的一种不含求逆运算的换行法。该方法保护了Ｆ‘（ｘ）的稀疏性的传递性，避免了矩阵求道，具有适用范围广，计算量少等优点。     

一维波动方程反问题的一种迭代解法及其敛速估计

对地震勘探中的一维波动方程反问题，给出了一种迭代解法，并证明了该算法的收敛性。