An efficient solver for the RANS equations and a one-equation turbulence model

A three-stage Runge-Kutta (RK) scheme with multigrid and an implicit preconditioner has been shown to be an effective solver for the fluid dynamic equations. Using the algebraic turbulence model of Baldwin and Lomax, this scheme has been used to solve the compressible Reynolds-averaged Navier–Stokes (RANS) equations for transonic and low-speed flows. In this paper we focus on the convergence of the RK/Implicit scheme when the effects of turbulence are represented by the one-equation model of Spalart and Allmaras. With the present scheme the RANS equations and the partial differential equation of the turbulence model are solved in a loosely coupled manner. This approach allows the convergence behavior of each system to be examined. Point symmetric Gauss-Seidel supplemented with local line relaxation is used to approximate the inverse of the implicit operator of the RANS solver. To solve the turbulence equation we consider three alternative methods: diagonally dominant alternating direction implicit (DDADI), symmetric line Gauss-Seidel (SLGS), and a two-stage RK scheme with implicit preconditioning. Computational results are presented for airfoil flows, and comparisons are made with experimental data. We demonstrate that the two-dimensional RANS equations and a transport-type equation for turbulence modeling can be efficiently solved with an indirectly coupled algorithm that uses RK/Implicit schemes.     

提高陀螺仪控制电源性能指标的研究

通过对陀螺仪控制电源的硬件和软件电路的分析,研究了提高其性能指标的软硬件的具体实施方案。CPU和产生SPWM波信号芯片SA8282配合使用,选用IPM作为功率变换器的主开关器件,采用PID数字控制器,并通过实验证明方案的可行性。实测中,测量电路精度和反应时间达到了设计要求,保护电路动作也足够灵敏。     

Internet密钥交换协议的安全性分析

Internet密钥交换(IKE)协议是IPSec协议体系中最重要的部分,对于在不安全网络上安全地进行通信具有重要的意义。文章从主模式交换协商过程的分析入手,分析比较了几种验证算法的安全强度,之后从防止中间人的攻击,复杂性,防止DOS攻击等方面指出了IKE协议的缺陷和不足,并提出了相应的改进意见。     

IKE安全机制的研究

研究了Internet密钥交换协议(IKE)安全机制的体系结构,分析了利用主模式和积极模式进行认证密钥交换创建一个ISAKMP SA的第1阶段,以及用快模式协商一个非ISAKMP SA的第2阶段,并对IKE的4种认证算法进行了比较,分析了IKE存在的安全缺陷。     

基于SA-WPSO的遥感图像校正方法

提出一种基于SA-WPSO的遥感图像校正方法。该方法利用多项式模型对图像进行初步几何校正,得到多项式校正系数后,将模拟退火(SA)思想引入粒子群优化(PSO)算法,通过改进的SA-WPSO算法优化多项式校正系数,在此基础上实现图像的几何校正。实验结果证明,与二次多项式及三次多项式校正方法相比,该方法的校正精度更高、鲁棒性更好。     

Determination of azinphos-methyl and parathion-methyl in honey by stripping voltammetry

An electrochemical method for the determination of azinphos-methyl and parathion-methyl in honey is presented. The determination is established by adsorptive stripping differential pulse voltammetry at hanging mercury working electrode.In contrast to the chromatographic methods for the determination of pesticide residues, the sample preparation of the proposed method is minimal; analytes were extracted from honey samples with a mixture of (acetone):(Britton-Robinson buffer) and then were analyzed without any additional pretreatment.The response of the analytes either individually or as a mixture was studied for a series of deposition time and molar ratio. Two quantitation protocols were compared, using either the external calibration or the standard addition method. Accuracy was tested with spiked honey samples obtaining good recovery values. The limit of detection for the honey sample (for deposition time of 10 s) was calculated 51.71 μg kg⁻¹ for MeP and 65.87 μg kg⁻¹ for AzMet.     

核电压力容器用钢SA533B的变形抗力及其数学模型

用Gleeble-3500热模拟试验机对SA533B核电压力容器用钢进行热压缩试验,研究不同热变形条件下SA533B钢的高温变形抗力,分析了变形温度、变形速率及变形量与变形抗力之间的关系,利用回归分析确立合适的变形抗力数学模型。结果表明,变形温度对变形抗力影响较大,变形速率较低时变形抗力变化较大,变形量对变形抗力的影响主要在变形初期。变形抗力数学模型为： σ=4311.322584×ε^0.098ε’ ^0.0874exp(-0.0034T+0.2813ε)     

AP1000核电站用大直径薄壁SA106B无缝钢管的研制

介绍了AP1000核电站核岛蒸汽发生器系统用大直径薄壁SA106B无缝钢管的性能特点、生产工艺及关键技术。经检验,SA106B钢管的冶金质量、化学成分、力学性能、无损检测等各项指标均满足ASME相关规范的要求,能够满足AP1000核电站核岛蒸汽发生器系统对碳钢无缝钢管的需求。     

核电厂蒸汽发生器SA213T22传热管表面氧化膜的耐蚀性

人工研制了核电厂蒸汽发生器SA213T22传热管的高温氧化膜,采用SEM、XRD、热重分析法分别对氧化膜厚度、微观形貌、成分和稳定性进行了观察和分析。结果表明:氧化膜具有均匀、完整、无孔隙、稳定性好的特点;经高温氧化及矿物油封闭处理后,SA213T22传热管的耐蚀性得到了显著提高,在不同环境中挂片31个月后,试样均未发生腐蚀,完全满足工程应用的要求。     

核电SA508-3钢焊接连续冷却转变曲线的分析

针对首次应用到核电上的SA508-3钢,在Gleeblei500D热模拟机上,采用膨胀法测定了SH-CCT曲线,获得了焊接工艺特征参数t8/5从3.75～20 000 s范围内的焊接热影响区组织变化规律.结果表明,获得全部马氏体相变的冷却时间为15 s,全部贝氏体相变的冷却时间60 8＜t8/5≤3 000 s,全部铁素体和珠光体相变的冷却时间为6000 s;当t8/5≤100 s时,焊接热影响区硬度高于350 HV,存在淬硬和裂纹敏感性;当t8/5≥20 000 B时,焊接热影响区硬度小于母材硬度,易出现软化现象.