二维翼型绕流的CE/SE方法

采用时空守恒元和解元CE/SE(space-time Conservation Element and Solution Element method)法,求解二维Euler方程,开展了翼型绕流的无粘数值模拟研究.用非敏感克朗数计算格式消除克朗数过小引起的数值耗散对解的污染,结合当地时间步长法,解决网格不均匀引起的当地克朗数变化跨度大的问题.对NACA0012翼型的无激波流场进行了二维数值模拟,并与AGARD算例做了对比.结果表明:CE/SE方法的计算结果与AGARD结果吻合得很好,为该数值计算方法对翼型绕流数值模拟的进一步应用奠定了基础.      

静气动弹性模型的设计和风洞试验

研究气动弹性问题的主要手段有数值计算、风洞试验和飞行试验三种,气动弹性风洞试验具有可靠性高（相比数值计算）和代价低（相比飞行试验）等优势,已成为航空航天飞行器气动弹性性能评估和校核的重要手段。以亚声速和跨声速气动弹性风洞试验技术为主,分别从静气动弹性、颤振和阵风试验三个角度,阐述了国内外在模型设计、数据采集处理、模型支撑、阵风发生装置、阵风载荷减缓等方面开展的主要研究工作,总结了气动弹性风洞试验在飞行器研制中的重要意义,并对我国未来气动弹性试验能力的发展提出几点建议。     

翼型近尾迹流动的PIV研究—动力学机制

利用在线式互相关PIV(ParticleImageVelocimetry)系统,在低速风洞中对NACA0012翼型在雷诺数2.39×105,0°和4°攻角下的近尾迹流动进行了详细测量。实验结果表明,翼型近尾迹存在有序的涡街结构,涡街在尾缘处形成后,在向下游的迁移中,会经历一个发展壮大、失稳破碎的演化过程,流动从有序走向无序。翼型的近尾迹是一种以旋涡的运动学特性和动力学机制为主导的流动现象。本文着重探讨了翼型尾缘处的涡街形成机理,尾迹内的流动机制,以及近尾迹的流动稳定性。      

中央翼后梁复合材料与金属方案对比分析

复合材料作为一种优良的航空材料,具有比强度高、比刚度大、材料力学性能可设计等优点。金属材料由于成本不高,能够满足不同设计需求而被广泛应用,同时制造加工技术成熟。以某型飞机为例,详细分析和探讨了中央翼后梁采用复合材料和金属材料2 套方案,为中央翼后梁结构设计提供支持。     

An improved approach to model ionospheric delays for single-frequency Precise Point Positioning

PPP with low-cost, single-frequency receivers has been receiving increasing interest in recent years because of its large amount of possible users. One crucial issue in single-frequency PPP is the mitigation of ionospheric delays which cannot be removed by combining observations on different frequencies. For this purpose, several approaches have been developed, such as, the approach using ionospheric model corrections with proper weight, the GRAPHIC (Group and Phase Ionosphere Calibration) approach, and the method to model ionospheric delays over a station with a low polynomial or stochastic process. From our investigation on the stochastic characteristics of the ionospheric delay over a station, it cannot be precisely represented by either a deterministic model in the form of a low-order polynomial or a stochastic process for each satellite, because of its strong irregular spatial and temporal variations. Therefore, a novel approach is developed accordingly in which the deterministic representation is further refined by a stochastic process for each satellite with an empirical model for its power density. Furthermore, ionospheric delay corrections from a constructed model using GNSS data are also included as pseudo-observations for a better solution. A large data set collected from about 200 IGS stations over one month in 2010 is processed with the new approach and several commonly adopted approaches for validation. The results show its significant improvements in terms of positioning accuracy and convergence time with a negligible extra processing time, which is also demonstrated by data collected with a low-cost, handheld, single-frequency receiver.     

Exploring for natural gas using reflectance spectra of surface soils

Reflectance spectra in the visible and near-infrared wavelengths provide a rapid and inexpensive means for determining the mineralogy of samples and obtaining information on chemical composition. Hydrocarbon microseepage theory establishes a cause-and-effect relation between oil and gas reservoirs and some special surface anomalies, which mainly include surface hydrocarbon microseepage and related alterations. Therefore, we can explore for oil, gas by determining reflectance spectra of surface anomalies. This idea has been applied to the R&D project of exploring for natural gas in Qinghai province of China using NASA EO-1 satellite with the Hyperion sensor (June 2005 to June 2006). In this project, in order to improve the accuracy of exploration targets of natural gas mapped in the field studied, an integrated practical system of exploration of oil and gas was built by the analysis of not only hyperspectral remote sensing data but also data provided from field work. In this paper, our efforts were focused on the analysis of the 799 reflectance spectra provided from the field work. In order to properly define the typical form of hydrocarbon microseepage with spectroscopy and fulfill the data analysis, it was necessary to build a spectral model. In this spectral model the most important features of hydrocarbon microseepage in the surface of our study area, i.e., diagnostic spectral macroscopic features and diagnostic spectral absorption features, were proposed and extracted, respectively. The distribution of coexisting anomalies, which results from both alteration minerals and hydrocarbons, is estimated by the diagnostic macroscopic features mainly using Spectral Angle Mapper (SAM) classifier. On the other hand, the diagnostic absorption features of two main absorption bands presented abundant local information, based on deep analysis of which, we are able to map the anomalies of alteration minerals and hydrocarbons, respectively. Additionally, a general framework of analysis and key classification algorithms applied to the Hyperion data have been introduced briefly. In our work, three exploration targets of natural gas were identified from the study area which covers 2100 km². In the three exploration targets, three wildcats have been drilled by China National Petroleum Corporation (CNPC) since July 2006, and all the three wells have been proven some industrial reserves.     

基于Pro/E骨架模型的阀体参数化设计

Pro/E软件自上而下的设计模式符合产品的设计思路,骨架模型设计是自上而下设计的方法之一。骨架模型反映了产品的总体结构和设计方案,保证产品设计合理性和装配的准确性。通过阀体骨架模型的设计,实现阀体的参数化和系列化。     

基于改进极限学习机的光谱定量建模方法

依据近红外光谱(NIR)产生原理,提出了粒子群优化极限学习机(PSO-ELM)算法,运用于小样本氨水浓度定量分析。通过优化极限学习机(ELM)隐藏节点参数,解决了极限学习机由于输入权值和隐含层偏差随机产生的建模结果具有随机性的问题,提高了预测模型的稳定性、精确度和泛化性能。经实验验证,优化后的PSO-ELM相比ELM,模型预测集均方根误差由0.01166减小至0.00322,预测集相关系数由0.9951提高至0.9979。将优化后的模型预测结果与支持向量机(SVM)、BP神经网络算法等传统方法的建模结果进行对比,优化后的PSO-ELM算法具有较高的精确度和良好的泛化性能,模型预测效果优于传统的定量回归分析算法。     

工程知识管理系统模型研究

针对工程知识管理系统模型多样化的现状,从需求、功能和应用三个方面论述了对工程知识管理系统模型的理解和认识以及需求、功能及应用模型的含义和组成。提出工程知识管理系统模型由知识需求、系统功能和知识应用构成。在工程知识管理系统模型的基础上,成功设计开发出工程知识管理系统实例,并在航天企业中形成了一定规模的应用。