3D nonlinear wave heating of coronal loops

The heating of solar coronal loops by the resonant absorption or phase-mixing of incident wave energy is investigated in the framework of 3D nonlinear magnetohydrodynamics (MHD) by means of numerical simulations.     

Thermal cyclotron radiation from a hot coronal loop with helical magnetic field

The spectral and polarization properties of thermal cyclotron radio emission from a hot coronal loop with a current along the axis are computed. The magnetic field is supposed to have a component along the loop axis as well as a poloidal part due to the current, both components being of comparable magnitude. In this specific configuration a helical magnetic field is present with a remarkable minimum of its absolute value along the loop axis and a maximum at its periphery. The presence of one or two maxima of magnetic field value along the line of sight results in increasing optical thickness of the gyroresonance layers at appropriate frequencies in the microwave band and, therefore, in enhanced radio emission at those harmonics which are optically thin (for example,s=4). These cannot be observed in models with the commonly employed magnetic field configuration (longitudinal along the loop axis).We show that the frequency spectrum of thermal cyclotron radiation from a hot coronal loop with a helical magnetic field differs from that of the standards-component source (with smooth frequency characteristics and polarization corresponding toe-mode) in that plenty of fine structures (line-like features and cut-offs) are present and theo-mode is prevalent in some frequency intervals. The enhanced radio emission at high harmonics and the complicated form of frequency spectrum in the model considered imply that some microwave sources, which are poorly explained in traditional models of solar active regions, may be associated with helical magnetic fields in hot coronal loops. Computations allow one to indicate spectral and polarizational peculiarities of local sources testifying to the presence of a helical magnetic field.     

宽带LFM信号的线性度测量

介绍了一种采用微波延迟线鉴相的方法对宽带LFM信号的线性度进行测量的装置。在该装置中,使用光纤、电缆实现微波延时,在小波变换的基础上采用相位建模以提高瞬时频率的测频准确度,根据线性调频信号的调频形式建立数学模型,得出了线性度的数学表达式。     

无人机高速DS/FH混合扩频通信系统关键模块设计

针对UAV(Unmanned Aerial Vehicle,无人机)测控链路高抗干扰需求,给出了实现跳频速率20 000次/s的扩跳混合无人机测控数据链系统实现方案.系统采用跳频频率并行捕获模式.跳频源设计采用直接频率合成、DDS(Direct Digital Synthesis,直接数字频率合成)和PLL (Phase-Locked Loop,锁相环)相结合的混合频率合成技术.利用相位响应滤波器,通过正交调制技术完成MSK(Minimum Shift Keying,最小频移键控)、GMSK (GaussianMinimum Shift Keying,高斯最小频移键控)调制.通过推导得出2 bit差分解调输出与载波频率选择有关,且为四分之数据率的整数倍关系.然后通过实例分析给出了跳频频率间隔选取方法,即跳频间隔应当将临近跳频的主瓣分开,同时跳频载波频率应当设在其他跳频频谱的零点处.最后总结了高速扩跳频系统参数设计一般步骤.     

光纤环及其骨架材料膨胀系数测量方法研究与实现

介绍了一种光纤环及其骨架膨胀系数的简易测量方法,并组建了测量系统。利用铝材和不锈钢,对系统的可行性进行了验证,同时用该系统测量了光纤环及不同骨架的膨胀系数,并对实验数据进行了分析研究,实验结果表明：该系统能够为找出与光纤环相匹配的骨架材料提供技术支撑,具有一定的实用和推广应用价值。     

双三角翼俯仰振荡运动的流场特性数值模拟

 建立了适用于双三角翼大迎角非定常分离流场模拟的数值方法,研究双三角翼俯仰振荡时的动态流场特性,给出动态流场结构和气动力性能随迎角的变化规律,重点考察了减缩频率、转轴位置、平均迎角和振幅等参数对动态流场迟滞效应和气动力曲线迟滞环的影响。研究结果表明:俯仰振荡到相同大迎角时上仰和下俯的流场存在明显差异;减缩频率对气动力迟滞效应的影响相对大于转轴位置;平均迎角的变化导致双三角翼背风区流场结构呈现不同流态,而振幅的大小决定这些流态的数目,事实上俯仰运动时如果跨越的流态数目越多则流场结构的动态响应滞后现象就越显著。通过数值分析,有利于提高对双三角翼在俯仰振荡运动条件下的非定常特性和流场滞后效应等非线性现象的认识。     

基于仲裁环的光纤通道性能分析

随着航空电子系统的发展,光纤通道技术正在逐渐取代传统的总线型通信网络。仲裁环作为一种经济的光纤通道拓扑结构,目前得到了较广泛的研究。本文利用OPNET modeler建立了光纤通道仲裁环及其节点状态机模型,并通过仿真对基于仲裁环的光纤通道性能进行了分析,为深入研究光纤通道奠定了理论基础。     

测速雷达信标测量数据复原新方法

给出了一种测速雷达信标测量多普勒频率复原的新方法,此方法与目标运动的初始轨道参数无关。与已有方法相比较,新方法解决了已有数据复原方法对初始轨道参数的依赖性,理论上消除了初始轨道参数精度对数据复原精度的影响。通过与已有方法计算结果的比对分析表明,新方法能够满足数据处理精度要求,具有较好的适用性,是实现信标测量数据复原的有效途径。     

某型飞机空中受油管自动开锁故障分析

针对某型飞机空中受油管在收上位置钢珠锁自动开锁故障,对空中受油管液压收放系统、电路控制系统、收上位置钢珠锁工作原理进行分析,比对钢珠锁开锁压力理论计算和收放系统回油压力测试试验结果,找出空中受油管收上位置钢珠锁自动开锁原因,提出改进建议。     

“T”型尾翼飞机的深失速特性研究

应用时间历程法讨论了“Ｔ”型尾翼飞机的深失速开环特性，分析了气动力矩特性和升降舵操纵规律对深失速改出特性的影响。建立了深失速闭环特性计算数学模型，分析了驾驶员数学模型参数变化对深失速特性的影响。研究结果表明，气动力矩特性，升降舵操纵规律和驾驶员模型参数的变化对“Ｔ”型尾翼飞机的深失速改出特性有显著的影响。