关于角度量列为基本量的探讨

在SI国际单位制中,平面角是导出量,平面角的单位“弧度”是辅助单位。但是,平面角既不能由长度基本单位导出,又不能溯源至长度基本单位,因此不能确立导出关系。平面角应用广泛,作用重要,具有独特的性能,符合基本量的要求,因此提出：平面角,简称“角度”,是基本量;平面角的单位“度、（角）分、（角）秒”,是基本单位,以供探讨。     

Highly reliable relative navigation for multi-UAV formation flight in urban environments

Formation flight of multiple Unmanned Aerial Vehicles (UAVs) is expected to bring significant benefits to a wide range of applications. Accurate and reliable relative position information is a prerequisite to safely maintain a fairly close distance between UAVs and to achieve inner-system collision avoidance. However, Global Navigation Satellite System (GNSS) measurements are vulnerable to erroneous signals in urban canyons, which could potentially lead to catastrophic consequences. Accordingly, on the basis of performing relative positioning with double differenced pseudoranges, this paper develops an integrity monitoring framework to improve navigation integrity (a measure of reliability) in urban environments. On the one hand, this framework includes a fault detection and exclusion scheme to protect against measurement faults. To accommodate urban scenarios, spatial dependence in the faults are taken into consideration by this scheme. On the other hand, relative protection level is rigorously derived to describe the probabilistic error bound of the navigation output. This indicator can be used to evaluate collision risk and to warn collision danger in real time. The proposed algorithms are validated by both simulations and flight experiments. Simulation results quantitatively reveal the sensitivity of navigation performance to receiver configurations and environmental conditions. And experimental results suggest high efficiency and effectiveness of the new integrity monitoring framework.     

近距平行跑道容量评估与优化

本文系统地归纳了各种制约近距平行跑道运行容量的因素,并对比单跑道容量评估方法,针对不同运行模式提出了容量评估思路。同时结合实际工作中可能遇到的运行方式提出具体的调整适用方法,为近距跑道的优化使用提出建议。     

Estimation of precipitable water vapour from GPS measurements in Argentina: Validation and qualitative analysis of results

This paper presents PWV estimates from GPS data computed at four continuously operated GPS stations in Argentina established at Buenos Aires, Córdoba, Rosario and Salta over a 1 year period (2006–2007). The objective is to analyze the behaviour of the GPS PWV estimation using mean tropospheric temperature (_Tm$T_m$) values from the Bevis model, Sapucci model and obtained by a numerical integration of variables provided by the operational analysis of the National Centre of Environmental Prediction (NCEP). The results are validated using PWV values from nearest radio soundings. Moreover, a comparison between PWV values determined from microwave sensors deployed on the NOAA-18 satellite and PWV from GPS observations is also presented.     

Snow-covered lake ice in GPS multipath reception – Theory and measurement

Speculary reflected signals from the ground can significantly affect the performance of Global Positioning System receivers. For this type of multipath condition, the received powers are primarily the sum of the speculary reflected and direct signals. These reflected signals can provide useful information about the land-surface composition. In this paper, we discuss the special case of a snow-covered frozen lake, with incident energy at 1.57542 GHz with right-hand circularly polarization at elevation angles between 2° and 40°. The relative received powers are computed and measured for various thicknesses of lake ice. The received powers for both theory and measurement have the same behavior throughout a range of elevation angles. The potential for inferring lake ice thickness is explored for a snow-covered lake ice case study.     

固液混合火箭发动机仿真与优化设计

建立了固液混合火箭发动机的仿真模型和相应的单目标和多目标优化模型,编制了系统仿真程序;采用差分进化算法针对不同的优化目标对发动机的参数进行优化;针对挤压式系统建立了质量模型,在优化过程中考虑了主要部件结构质量对发动机性能的影响;针对固液发动机常用的侧面燃烧药柱编制了内弹道计算程序。以药柱几何参数、氧化剂流量、燃烧室平均工作压强和喷管扩张比等参数为设计变量,对发动机平均比冲、总质量、关机时飞行速度和密度比冲等性能参数进行优化,在Pareto分析的基础上选择了氧化剂流量、燃烧室平均工作压强和喷管扩张比对发动机性能的影响作了深入研究;最后对某型固液发动机进行了优化分析。     

构建民用航空产品研制工程技术体系的探讨

从商用航空产品市场客户特性决定了商用航空产品产业链向下游延伸的事实出发,说明商用航空产品研制的工程技术体系不应该简单借用军用产品研制的经验,而要从全产业链的工程技术活动出发,创建适合自身需求的新的工程技术体系,特别是在数字化时代,对产品数据包和产品研制数据流动要有新的认识,以求更科学有效地涵盖产品全寿命期,以包括设计、制造和服务三大技术分体系在内的产品工程技术体系运作来替代传统意识下的仅以设计为内涵的产品研制技术体系运作,保障商用航空产品研制的成功。     

SSPS太阳能收集系统研究现状及发展趋势

为研究太阳能收集系统在未来空间太阳能电站(SSPS)中的发展和应用,对比和分析国内外典型系统设计方案的结构特点、光收集特性及优、缺点,展望空间太阳能电站太阳能收集系统的发展趋势,并提出对新材料、新结构、新技术、新理论和新方法的发展和应用需求。     

人造毛皮机微电脑控制器的设计与实现

本文介绍一种新型的人造毛皮机微电脑控制系统，文中详细介绍控制系统的组成，工作原理及软件设计，该控制系统采用微电脑技术和步进电机技术帝现了对各梳理头喂毛量的精确控制，以确保毛皮的均匀性和质量，同时系统还具备各种自停报警功能的统计功能。     

车载设备的振动响应

本文用力阻抗法推导出车载设备在受车内动力设备或地面振动干扰时的振动响应公式。