同无黑子耀斑相协的微波爆发机制的探讨

1980—1984年期间,我们在云南天文台9375MHz,3653MHz和2902 HHz三个波段的射电观测资料中,查到11组微波爆发与无黑子耀斑相伴随。本文研究了这些爆发与耀斑的大气层高度,射电爆发类型以及通过落进峰值流量-时间图的位置,确认出爆发机制是活动区中作麦克斯韦分布电子的热轫致辐射。     

“AP/HTPB/Al/催化剂”推进剂燃烧模拟计算方法

本文以我们在文献[1～4]中提出的“AP/HTPB/Al”推进剂燃烧模型为基础,首先讨论了催化剂作用部位与推进剂燃速、压力指数变化的关系,然后引入一个催化剂作用因子B.并以二茂铁系列催化剂为例,对模型中的几个与二茂铁催化剂作用部位相连系的反应动力学参数作“催化作用因子”校正,计算研究了四种二茂铁催化剂用量对燃速、压力指数的影响规律.计算结果与实验符合得很好,相对误差均小于±10%,证明本文提出的模拟计算方法具有较高的可靠性.     

多机并联火箭羽流流场及其底部热环境分析

For the problem that the plume flow field structure of a multi engine parallel rocket is complicated and the bottom thermal environment is extremely harsh, which may cause the failure of the engine structural components, the plume flow field and thermal environment at different altitudes are studied through numerical simulation. The result is compared with the measured results in flight which shows that when the rocket is flying at a low altitude, the plume of the engines do not interfere with each other. As the flight altitude increases, the plumes gradually expand and begin to interfere with each other, and finally there is an obvious backflow at the bottom of the rocket. The maximum heat flux at the moment of take off is basically the same as the measured value in flight. Before the backflow occurs, the heat flux mainly consists of radiant heat, the convective heat flow increases as the flight altitude grows, but it is also much smaller than the peak heat flow at takeoff. The result has certain guiding significance for the optimal design of engine structure thermal protection.     

涡桨飞机发展现状及关键气动问题

独特的动力形式赋予了涡桨飞机优越的推进效率和良好的低速机动、起降性能，使得其在军用及民用领域占有重要的地位并得以不断发展，但同时也带来了一系列需要重点关注的设计问题。本文从目前国内外涡桨飞机的发展现状和设计特点出发，提出其面临的主要气动问题。重点针对国内亟待发展的舰载类涡桨飞机起降过程中的失速和操纵问题进行深入研究，剖析了翼面附近流动的分离状态和发展趋势对于失速特性及操纵安全性的影响规律，归纳总结出需要关注的关键约束和设计原则。在此基础上，通过对一组计算实例的分析，给出了机翼空间流场变化特征和宏观气动力之间的内在联系，并深入阐述了三维增升构型与干净构型及其各站位翼剖面的设计关联性。     

论动机理论对大学英语教学的启示

学习动机是学习者在第二语言习得过程的诸多因素中最具能动性的因素,是推动大学生进行学习活动的动力,直接影响到大学生进行学习活动的积极性。二语习得中的动机理论给我们大学英语教学以重要启示,它将会成为大学英语教学成功与否的关键所在。     

Coupled Stress-Electricity Model for Electromagnetic Emission Induced by Concrete Fracture

Electromagnetic emission induced during concrete fracturing is of great significance to health monitoring of concrete structures.A coupled stress-electricity model is established by analyzing the interaction between stress and electricity during concrete fracturing.And based on this model,the electromagnetic radiation parameters are calculated.The theoretical calculation is well coincident with experimental results.This work provides theoretical support for concrete testing system.     

High temporal resolution global PWV dataset of 2005–2016 by using a neural network approach to determine the mean temperature of the atmosphere

Atmospheric water vapour plays an important role in phenomena related to the global hydrologic cycle and climate change. However, the rapid temporal–spatial variation in global tropospheric water vapour has not been well investigated due to a lack of long-term, high-temporal-resolution precipitable water vapour (PWV). Accordingly, this study generates an hourly PWV dataset for 272 ground-based International Global Navigation Satellite System (GNSS) Service (IGS) stations over the period of 2005–2016 using the zenith troposphere delay (ZTD) derived from global-scale GNSS observation. The root mean square (RMS) of the hourly ZTD obtained from the IGS tropospheric product is approximately 4 mm. A fifth-generation reanalysis dataset of the European Centre for Medium-range Weather Forecasting (ECMWF ERA5) is used to obtain hourly surface temperature (T) and pressure (P), which are first validated with GNSS synoptic station data and radiosonde data, respectively. Then, T and P are used to calculate the water vapour-weighted atmospheric mean temperature (Tm) and zenith hydrostatic delay (ZHD), respectively. T and P at the GNSS stations are obtained via an interpolation in the horizontal and vertical directions using the grid-based ERA5 reanalysis dataset. Here, Tm is calculated using a neural network model, whereas ZHD is obtained using an empirical Saastamoinen model. The RMS values of T and P at the collocated 693 radiosonde stations are 1.6 K and 3.1 hPa, respectively. Therefore, the theoretical error of PWV caused by the errors in ZTD, T and P is on the order of approximately 2.1 mm. A practical comparison experiment is performed using 97 collocated radiosonde stations and 23 GNSS stations equipped with meteorological sensors. The RMS and bias of the hourly PWV dataset are 2.87/?0.16 and 2.45/0.55 mm, respectively, when compared with radiosonde and GNSS stations equipped with meteorological sensors. Additionally, preliminary analysis of the hourly PWV dataset during the EI Niño event of 2014–2016 further indicates the capability of monitoring the daily changes in atmospheric water vapour. This finding is interesting and significant for further climate research.     

Particle swarm optimization applied to hypersonic reentry trajectories

This paper presents the novel use of the particle swarm optimization(PSO)to generate the end-to-end trajectory for hypersonic reentry vehicles in a quite simple formulation.The velocitydependent bank angle profile is developed to reduce the search space of unknown parameters based on the constrained PSO algorithm.The path constraints are enforced by setting the fitness function to be infinite on condition that the particles violate the maximum allowable values.The PSO algorithm also provides a much easier means to satisfy the terminal conditions by adding penalty terms to the fitness function.Furthermore,the approximate reentry landing footprint is fast constructed by incorporating an interpolation model into the standardized bank angle profiles.Numerical simulations demonstrate that the PSO method is a feasible and flexible tool to generate the end-to-end trajectory and landing footprint for hypersonic reentry vehicles.     

无源滤波器频率漂移的一种迭代算法

文章介绍了无源滤波器在试验过程中产生的典型幅频特性漂移曲线，并针对这些典型曲线提出了基于均方误差最小原则和牛顿迭代的频率漂移算法。     

现代喷气战斗机的发动机安装设计

发动机安装设计是飞机设计的一项重要工作,战斗机的发动机安装设计工作尤为重要且任务复杂.本文在收集整理大量文献资料的基础上,概述现代战斗机发动机的安装设汁,重点剖析了国外八个型号战斗机的发动机安装设计实例,比较各型战机的发动机安装设计异同,包括安装形式设计和安装节等结构部件的细节设计等.通过实例剖析和异同比较,有助于深入理解发动机安装设计的特点和规律,发展我国有自身特色的发动机安装设计解决方案.