基于代理模型的气动外形优化

探讨了一种将CAD软件、CFD商用软件与代理模型相结合的飞机气动外形优化方法。重点介绍建立气动分析代理模型的过程,这一过程包括确定设计变量及其取值范围、生成试验设计点、建立参数化几何模型、CFD数值计算、提取气动特性和构造代理模型。通过一个简单的机翼气动外形优化算例验证了这种方法的可行性和有效性。     

What is wrong with space system cost models? A survey and assessment of cost estimating approaches

Despite several decades of research and refinement in cost estimating tools and practices, the final cost of US space programs continues to exceed initial cost estimates by an average of more than 45%. Thus, program cost models not only exhibit error, they are seriously biased. A structured review surveyed techniques, approaches, models and conceptual tools related to space program cost estimating, to understand cost in complex space systems. Analysis shows problems of cost estimating result from the growing complexity of space programs, failures in managing growth, and mission failures. Although there is greater expectation for the models to accurately predict program costs, the current models used for seeking funding for large space programs are inadequate due to (1) inability to predict future, (2) lack of insight, and (3) process replaces judgment in decision making.     

热防护用发汗冷却技术的研究进展（I）——冷却方式分类、发汗冷却材料及其基本理论模型

综述了国内外航天热防护用冷却技术的分类、发汗冷却材料研究现状以及发汗冷却技术理论模型的研究进展。比较分析了发汗冷却技术与其他冷却技术的优缺点，并对发汗冷却技术的理论模型作了初步的探讨。     

人体手端点到点运动的优化轨迹生成与控制

考虑肢体肌肉的生理特征和肌肉收缩的动力学行为,利用肌肉等长收缩的最小功准则研究了人体手端点到点运动的优化轨迹生成与控制问题.讨论了肌肉收缩的动力学特性,建立水平面内上肢运动的动力学模型,提出将肌肉等长收缩的最小功准则作为优化的目标函数,运用最优化理论将手端点到点的运动问题转化为最优控制问题,设计了求解手端运动优化轨迹的迭代算法,得到了手端运动的控制规律和优化轨迹.算例仿真表明该方法对手端运动优化轨迹的预测是有效的.     

CFE方法在导弹发射动力学建模中的应用

在传统的发射动力学微分方程基础上,添加了CFE(Constraint Force Equation)方法中的约束方程和自由度方程,建立了基于CFE方法的导弹发射动力学模型.以倾斜发射导弹系统为研究对象,定义了1个二自由度约束节点来描述导弹与发射架间的约束关系,通过建模计算得到了发射过程的约束力和约束力矩,最后利用软件ADAMS(Automatic Dynamic Analysis of Mechanical Systems)对该算例进行了计算,取得了一致的结果,从而验证了该方法在导弹发射动力学建模中应用的有效性,扩大了该方法的应用范围.     

Influence of time variable geopotential models on precise orbits of altimetry satellites,global and regional mean sea level trends

During the last decade a significant progress has been reached in the investigation of the gravity field of the Earth. Besides static, also time variable geopotential models have been recently created. In this paper we investigate the impact of the recent time variable geopotential models on altimetry satellite orbits and such altimetry products based on these orbits, as global and regional mean sea level trends. We show that the modeling of time variable gravity improves the orbit solutions, at least for the GRACE period where time variable gravity is sufficiently accurately observed by this mission. Our analysis includes six geopotential models jointly developed by GFZ German Research Centre for Geosciences and Space Geodesy Research Group (CNES/GRGS) Toulouse: the stationary model EIGEN-GL04S, a stationary version of EIGEN-6S (EIGEN-6S_stat), a corrected version of EIGEN-6S and three enhanced versions of EIGEN-6S called EIGEN-6S2, EIGEN-6S2A and EIGEN-6S2B. By “stationary” we mean “containing periodic parameters such as annual and semi-annual variations, but no secular (drift) terms”. We computed precise orbits for the radar altimetry satellites ERS-1, ERS-2, TOPEX/Poseidon, and Envisat over 20 years between 1991 and 2011. The orbit, single-mission and multi-mission altimetry crossover analyses show that the time variable models EIGEN-6S_corrected, EIGEN-6S2 and its two precursors EIGEN-6S2A/B perform notably better than the stationary models for the GRACE period from 2003 onwards. Thus, using EIGEN-6S2 and EIGEN-6S2A/B we have got 3.6% smaller root mean square fits of satellite laser ranging observations for Envisat, as when using EIGEN-GL04S. However, for the pre-GRACE period 1991–2003, the stationary geopotential models EIGEN-GL04S and EIGEN-6S_stat as well as EIGEN-6S2 having no drift terms for degree 3–50 at this time interval perform superior compared to EIGEN-6S_correct and EIGEN-6S2A/B which contain drifts for this period. We found, that the time variable geopotential models have a low (0.1–0.2 mm/yr) impact on our results for the global mean sea level trend. However, we found strong East/West differences up to 3 mm/yr in the regional mean sea level trends when using orbits of all four satellites based on time variable and stationary geopotential models. We show that these differences are related to the relative drifts of the centers-of-origin between the orbit solutions based on the time variable and stationary geopotential models. From the results of our detailed study, we conclude that the final version of the time variable gravity field model EIGEN-6S2 performs best for the four satellites tested. This model provides the most reliable and mission-consistent sea level estimates for the whole time period from 1992 to 2010. This model is of maximum spherical harmonic degree and order 260 and contains time series for drifts as well as annual and semiannual variations of the spherical harmonic coefficients for degree 2–50.     

可复用的需求建模方法

提出了一种特征驱动的可复用需求建模方法(RRM,Reusable RequirementMethod),此方法定义了一个可复用的需求建模过程(RRMP,Reusable Requirement Modeling Process),在领域工程和应用工程两个层面上都提出了相对完整的需求建模方法并将两个阶段有机地融合在一起.将主要研究方向着眼于领域模型的正确建立、合理剪裁和对象化过程,从而得到针对于具体应用的需求模型.在RRMP的过程指导下还将设计一个需求定制与应用开发平台(RAP,Requirement customing Application developing Platform).RAP平台立足于需求获取阶段,以用户易理解的图形化方式灵活直观地与用户进行需求交互,根据用户定制的需求自动生成具体应用的标准需求开发文档和开发过程中所产生的统一建模语言(UML,Unified Modeling Language),并最终开发出用户所需的领域内特定应用的原型系统.RAP平台主要包含3个部分:图形化需求定制工具,需求开发文档生成工具和目标应用开发工具.     

基于受油能力的加油机效能分析

受油能力逐渐成为加油机设计的必备能力。然而现有的加油机效能分析方法没有考虑受油能力因素的影响。为了分析受油能力对加油机效能的影响,首先,通过对历史上典型加油机远程部署战例的分析,研究受油能力对加油机作战效能的影响。其次,对加油机机队加受油过程进行详细分析,并在此基础上建立基于受油能力的加油机机队能力模型。通过对单机种加油机机队的加油能力模型和基于受油能力的加油机机队加油能力模型进行分析,分析加油机具有受油能力对加油机机队加油效能的重大影响,从而为加油机设计提供参考。     

Evaluation of Turbulence Models in Predicting Hypersonic and Subsonic Base Flows Using Grid Adaptation Techniques

The flows behind the base of a generic rocket, at both hypersonic and subsonic flow conditions, are numerically studied. The main concerns are addressed to the evaluation of turbulence models and the using of grid adaptation techniques. The investiga- tion focuses on two configurations, related to hypersonic and subsonic experiments. The applicability tests of different turbulence models are conducted on the level of two-equation models calculating the steady state solution of the Reynolds-averaged Navier-Stokes(RANS) equations. All used models, the original Wilcox k-ω, the Menter shear-stress transport (SST) and the explicit algebraic Reynolds stress model(EARSM) formulation, predict an asymmetric base flow in both cases caused by the support of the models. A comparison with preliminary experimental results indicates a preference for the SST and EARSM results over the results from the older k-ω model. Sensitivity studies show no significant influence of the grid topology or the location of the laminar to turbulent transition on the base flow field, but a strong influence of even small angles of attack is reported from the related experiments.