一种热电势的简易表达法

当具有不同温度分布的多种导体连接在一个环路中时,按照帕尔贴电势和汤姆逊电势分析环路中的总的热电势是困难的。选择一些导体作为标准电极,就能把总的热电势分成一系列单一导体的独立热电势,用这个方法,分析工作将变得十分简单。     

Weibull分布可靠性试验与评估

本文从工程应用出发，提出了Weibull分布寿命产品，特别是大型复杂产品的可靠性试验安排与评估方法，对型号可靠性试验与评估工作具有一定的指导意义。     

转捩对超临界机翼压力分布的影响分析

介绍了风洞试验中的固定转捩形式以及使用限制，通过对某超临界机翼压力分布的试验与数值计算结果的比较，重点分析了不同位置的固定转捩对机翼压力分布的影响，并对出现的问题做了分析。     

典型隐身飞机的RCS起伏统计特性

雷达散射截面(RCS)起伏统计特性可以用来预测雷达的检测性能和评估飞机的散射特性。采用高频计算方法获取了6种典型隐身飞机在光学区8个频率点、两种极化方式、不同入射条件下的周向RCS统计数据。应用3种较新的起伏模型对统计数据进行拟合,通过对比分析各组数据的拟合效果,得出了各模型在数据拟合时存在的普遍规律:卡方(Chi-square)模型对概率密度分布曲线的峰值估计较为合理,对数正态模型容易将峰值高估,但在峰值之后卡方模型的拟合效果通常不如对数正态模型;统计数据均值的平方与方差之比越大(可达0.1~1.0),则卡方模型双自由度越大(可达1.1~1.5),拟合效果也越好,按Kolmogorov-Smirnov检验方法其误差在0.15~0.25范围内;统计数据的均值中值比越小(低至1.5~5.0),则对数正态模型拟合效果越好,误差在0.01~0.25范围内;在dB·m2单位制下,采用对数正态模型和勒让德多项式模型可以在更广的范围内更好地拟合各组数据,其拟合误差多在0.10以下。     

Analytic estimation and numerical modeling of actively cooled thermal protection systems with nickel alloys

Actively cooled thermal protection system has great influence on the engine of a hypersonic vehicle, and it is significant to obtain the thermal and stress distribution in the system. So an analytic estimation and numerical modeling are performed in this paper to investigate the behavior of an actively cooled thermal protection system. The analytic estimation is based on the electric analogy method and finite element analysis（FEA） is applied to the numerical simulation. Temperature and stress distributions are obtained for the actively cooled channel walls with three kinds of nickel alloys with or with no thermal barrier coating（TBC）. The temperature of the channel wall with coating has no obvious difference from the one with no coating, but the stress with coating on the channel wall is much smaller than that with no coating. Inconel X-750 has the best characteristics among the three Ni-based materials due to its higher thermal conductivity, lower elasticity module and greater allowable stress. Analytic estimation and numerical modeling results are compared with each other and a reasonable agreement is obtained.     

A novel method for importance measure analysis in the presence of epistemic and aleatory uncertainties

For structural systems with both epistemic and aleatory uncertainties, research on quantifying the contribution of the epistemic and aleatory uncertainties to the failure probability of the systems is conducted. Based on the method of separating epistemic and aleatory uncertainties in a variable, the core idea of the research is firstly to establish a novel deterministic transition model for auxiliary variables, distribution parameters, random variables, failure probability, then to propose the improved importance sampling(IS) to solve the transition model. Furthermore,the distribution parameters and auxiliary variables are sampled simultaneously and independently;therefore, the inefficient sampling procedure with an ‘‘inner-loop' for epistemic uncertainty and an‘‘outer-loop' for aleatory uncertainty in traditional methods is avoided. Since the proposed method combines the fast convergence of the proper estimates and searches failure samples in the interesting regions with high efficiency, the proposed method is more efficient than traditional methods for the variance-based failure probability sensitivity measures in the presence of epistemic and aleatory uncertainties. Two numerical examples and one engineering example are introduced for demonstrating the efficiency and precision of the proposed method for structural systems with both epistemic and aleatory uncertainties.     

细水雾喷嘴出口流场的数值模拟与分析

<正>随着世界环保意识的增强,哈龙灭火剂由于其会造成大气污染而被逐渐淘汰。细水雾灭火系统作为一种新的灭火替代技术,具有无环境污染、迅速高效灭火、耗水量低、水渍损失小等特点,从而引起了国际消防界的广泛重视。经过多年的发展,如今细水雾灭火系统已经在航空航天、水上船舶、日常建筑等领域得到了广泛的研究与应用。对于细水雾灭火系统而言,系统工作压力与细水雾喷嘴结构对于雾化效果有很大的影响,而喷嘴的雾化效果直     

燃烧组件时域分布参数系统动力学模型

液体火箭发动机的动态特性,特别是与燃烧组件相关的系统动力学特性,一直是理论研究和工程设计中重要的研究内容。在时域上建立了非线性分布参数燃烧组件动力学模型。将时域的频率研究范围从低频扩充到涵盖一阶纵向声学频率的中高频范围。采用了时空分离的方法对模型进行数值求解,采用ROE格式对模型进行空间离散,采用Dassl隐式变步长格...     

基于整数规划的终端区空域扇区划分研究

扇区划分是终端区空域规划的研究内容之一,划分后能覆盖不均匀的交通分布,缓解需求与容量的不平衡,从而提高空域系统的运行效率。将终端区扇区划分作为一个整数规划问题,在约束条件中考虑了间隔规则、飞行路径需求和机场跑道结构的几何约束等,根据最优解来生成终端区扇区。以某终端区算例,验证了整数规划模型的可行性。