航空发动机涡轮盘低循环疲劳寿命研究

结合某型涡轴发动机一级涡轮盘低循环疲劳寿命研究的工程实践,阐述了对涡轮盘低循环疲劳寿命研究的一般过程和方法,提出了涡轮盘低循环疲劳寿命试验的加载程序和方法,对开展同类型的涡轮盘疲劳寿命研究具有借鉴作用。     

几种紧凑回热面传热和流动的实验和数值研究

运用计算流体动力学方法,建立单元控制体模型,对回热器主要型面(不锈钢锯齿型面、CC型一次表面)的传热及流动特性进行了数值模拟,并与实验结果进行对比,结果表明,数值结果与实验结果吻合的较好.在此基础上,研究了CC型面结构参数等对传热流动性能的影响,并且通过j/f的大小比较了不同结构参数下CC型面以及不锈钢锯齿型面的表面性能,为回热器的优化设计提供依据.      

Petri网在制造系统建模与仿真中的应用

依据面向对象的Petri网的理论,给出了制造系统的建模过程,最后将统一建模语言(UML)融入到制造系统的建模与仿真中,通过实例进一步阐明了Petri网在制造系统建模与仿真中是如何应用的。     

降低热变形的卫星有效载荷安装结构优化设计

在整星有限元热变形分析基础上,以有效载荷安装结构热变形最小为目标,对安装结构依次进行拓扑优化及设计敏度分析和尺寸优化。结果表明：通过优化设计,在显著降低该结构热变形的同时大幅减小其质量;拓扑优化给出结构基本构型,尺寸优化进一步细化结构设计方案,二者结合能有效改进结构设计。     

飞行器控制的伪线性系统方法——第二部分：方法与展望

针对第一部分提出的六类典型飞行器控制问题的共性伪线性系统模型，介绍了二阶伪线性系统的直接参数化设计方法：通过设计伪线性状态反馈控制律，可使闭环系统化为一个具有指定特征结构的二阶线性定常系统，并提供了控制系统设计中的所有自由度。另外，还以希望的闭环向量结构要求、闭环系统的干扰抑制要求和最小闭环特征值灵敏度要求为例，展示了通过综合优化设计自由度来实现控制系统的多目标设计思想。最后展望了伪线性系统理论的发展前景。     

Land use/land cover classification using time series Landsat 8 images in a heavily urbanized area

It is of great significance to timely, accurately, and effectively monitor land use/cover in city regions for the reasonable development and utilization of urban land resources. The remotely sensed dynamic monitoring of Land use/land cover (LULC) in rapidly developing city regions has increasingly depended on remote-sensing data at high temporal and spatial resolutions. However, due to the influence of revisiting periods and weather, it is difficult to acquire enough time-series images with high quality at both high temporal and spatial resolution from the same sensor. In this paper we used the temporal-spatial fusion model ESTARFM (Enhanced Spatial and Temporal Adaptive Reflectance Fusion Model) to blend Landsat8 and MODIS data and obtain time-series Landsat8 images. Then, land cover information is extracted using an object-based classification method. In this study, the proposed method is validated by a case study of the Changsha City. The results show that the overall accuracy and Kappa coefficient were 94.38% and 0.88, respectively, and the user/producer accuracies of vegetation types were all over 85%. Our approach provides an accurate and efficient technical method for the effective extraction of land use/cover information in the highly heterogeneous regions.     

地球同步轨道卫星混合推进转移轨道特性分析

以地球同步轨道卫星转移轨道设计为背景，针对全化学推进燃料消耗大和全电推进转移时间长的问题，开展了化学 电混合推进转移轨道优化设计与特性分析。首先，讨论了轨道倾角和近地点幅角变化对混合推进转移轨道的影响。研究表明，在混合推进优化设计中需要将轨道倾角作为优化变量之一。然后，以近地点半径、远地点半径、轨道倾角为优化变量生成搜索网格，得到过渡轨道集。针对每条过渡轨道，构建化学推进转移段和电推进转移段。其中化学推进段采用单圈兰伯特转移解算，电推进段采用混合法优化。最后，以燃料消耗和转移时间为指标，在搜索域内开展解算分析，研究了混合推进轨道在整个搜索域内的变化趋势。该方法可以提供具有不同燃料消耗和转移时间的混合推进转移解集，拓宽了解空间，可供轨道设计人员根据任务约束灵活选用。     

Mission planning optimization of video satellite for ground multi-object staring imaging

This study investigates the emergency scheduling problem of ground multi-object staring imaging for a single video satellite. In the proposed mission scenario, the ground objects require a specified duration of staring imaging by the video satellite. The planning horizon is not long, i.e., it is usually shorter than one orbit period. A binary decision variable and the imaging order are used as the design variables, and the total observation revenue combined with the influence of the total attitude maneuvering time is regarded as the optimization objective. Based on the constraints of the observation time windows, satellite attitude adjustment time, and satellite maneuverability, a constraint satisfaction mission planning model is established for ground object staring imaging by a single video satellite. Further, a modified ant colony optimization algorithm with tabu lists (Tabu-ACO) is designed to solve this problem. The proposed algorithm can fully exploit the intelligence and local search ability of ACO. Based on full consideration of the mission characteristics, the design of the tabu lists can reduce the search range of ACO and improve the algorithm efficiency significantly. The simulation results show that the proposed algorithm outperforms the conventional algorithm in terms of optimization performance, and it can obtain satisfactory scheduling results for the mission planning problem.     

Inter-satellite calibration of FengYun 3 medium energy electron fluxes with POES electron measurements

We perform an L-shell dependent inter-satellite calibration of FengYun 3 medium energy electron measurements with POES measurements based on rough orbital conjunctions within 5?min?×?0.1?L?×?0.5 MLT. By comparing electron flux data between the U.S. Polar Orbiting Environmental Satellites (POES) and Chinese sun-synchronous satellites including FY-3B and FY-3C for a whole year of 2014, we attempt to remove less reliable data and evaluate systematic uncertainties associated with the FY-3B and FY-3C datasets, expecting to quantify the inter-satellite calibration factors for the 150–350?keV energy channel at L?=?2–7. Compared to the POES data, the FY-3B and FY-3C data generally exhibit a similar trend of electron flux variations but more or less underestimate them within a factor of 5 for the medium electron energy 150–350?keV channel. Good consistency in the flux conjunctions after the inter-calibration procedures gives us certain confidence to generalize our method to calibrate electron flux measurements from various satellite instruments.     

飞行器控制的伪线性系统方法——第一部分：综述与问题

首先将非线性控制方法归纳成三类：基于李雅普诺夫泛函的设计方法、基于最优控制思想的设计方法和以线性为主导的设计方法，并对此三类方法进行了简略的综述。然后进一步在此类划分的框架下概述了飞行器控制的非线性方法，并引入了伪线性系统的概念。最后介绍了卫星姿态与轨道控制、飞行器制导与控制中的六类典型飞行器控制问题的二阶伪线性系统描述。