星载定向链路多目标优化设计

提出一种针对星载定向链路的多目标优化设计方法。定向链路的优化设计过程是一个多目标优化的过程,要求定向链路在质量、功耗等条件的约束下,尽量满足飞行任务对其功能的需要。文中首先建立定向链路各分目标函数的数学模型,然后根据卫星任务的需求为各分目标函数分配权重,最后通过统一目标法将各分目标函数组成一个统一目标函数,并对统一目标函数进行优化,进而实现对定向链路的优化设计。     

机载情报侦察数据链中的空地链路建模与仿真

针对机载情报侦察链中空地通信链路的特点,建立了统一的信道模型。模型包括大尺度衰落模型和基于三径信道模型的小尺度衰落模型。在给出了信道衰落模型的具体仿真方法后,分析了飞机飞行距离、工作频率及径向飞行速度等参数对信道特性产生的影响,为进行链路预算和解决多径干扰提供理论上的依据和参考。结果表明：不管信息传输速率多大,由于多径的影响在飞机飞行过程中频率选择性衰落都是不可避免的,但信息传输速率越高,衰落越严重;多普勒频移并不直接影响信道特性,但多径信道下的多普勒频移通过引起多普勒扩展而使信道具有了时变性。     

可变编码调制在遥感卫星中的应用效能研究

随着遥感卫星观测数据量的日益增加，卫星数据传输能力已成为制约遥感卫星使用效能的瓶颈因素。为充分利用近地遥感卫星数据传输的链路资源，采用可变编码调制（VCM）技术，通过对星地数传信道条件的动态评估，在保证链路传输误码率和链路余量的前提下，自适应地进行当前信道条件下的最优编码调制方式切换，充分利用系统链路余量，提高卫星星地数据传输效能。利用该方法，对VCM数传链路效能进行仿真分析，与相同符号速率的固定编码调制（CCM）体制相比，VCM传输效能平均提升42.1%，可为遥感卫星的数传通道设计提供借鉴。     

Empirical model of cosmic ray spectrum in energy interval 1 MeV–100 GeV during 11-year solar cycle

The galactic cosmic rays (GCR) are the main ionization source at altitude of ∼3–35 km in the atmosphere. For high latitude anomalous cosmic ray (ACR) component has also a significant influence on the atmospheric ionization. We propose an empirical model for differential spectra D(E) of galactic and anomalous cosmic rays in energy interval 1 MeV–100 GeV during solar cycle. In the model data are used which cover three solar cycles: 20, 22 and 23. The LEAP87, IMAX92, CAPRICE94, AMS98 and BESS experimental spectra for protons and alpha particles are fitted to the proposed empirical model. The modulated GCR differential spectra are compared with force-field approximation to the one-dimensional transport equation and with solutions of two-dimensional cosmic ray transport equation. For experimental spectra, the calculation of the model parameters is performed by Levenberg–Marquardt algorithm, applied to the special case of least squares. Algorithm that combines the rapid local convergence of Newton–Raphson method with globally convergent method for non-linear systems of equations is applied for theoretically obtained differential spectra. The described programmes are realized in algorithmic language C++. The proposed model gives practical possibility for investigation of experimental data from measurements of galactic cosmic rays and their anomalous component.     

结构响应主动控制系统设计与试验验证

振动控制是直升机设计的关键技术之一。本文首先介绍了如何进行结构响应主动控制(ACSR)系统的设计,然后详细说明了为此开发的ACSR系统的框架和软硬件基本组成,最后通过ACSR系统装直11进行地面试验和飞行试验,验证了该系统的可行性和抑制振动的有效性。     

一起新材料应用引起的航空机轮故障分析

TC11钛合金在首次应用于某型飞机机轮刹车壳体时,由于对TC11的特性掌握不透,设计考虑不周,造成了使用过程中刹车壳体卡台断裂的故障。通过分析故障原因,制订了改进措施,经试验试飞验证,改进措施有效,为TC11在航空机轮上的推广应用积累了经验。     

Specific features of the high-speed plasma stream cycles

The high-speed plasma streams in the solar wind are investigated during the solar cycles nos. 20–22 (1964–1996), separately on the two types of streams according to their solar origin: the HSPS produced by coronal holes (co-rotating) and the flare-generated, in keeping with the classification made in different catalogues. The analysis is performed taking into account the following high-speed stream parameters: the durations (in days), the maximum velocities, the velocity gradients and, the importance of the streams. The time variation of these parameters and the high-speed plasma streams occurrence rate show an 11-year periodicity with some differences between the solar cycles considered. A detailed analysis of the high-speed stream 11-year cycles is made by comparison with the “standard” cycles of the sunspot relative number (Wolf number). The different behaviour of the high-speed stream parameters between even and odd solar cycles could be due to the 22-year solar magnetic cycle. The increased activity of the high-speed plasma streams on the descendant phases of the cycles, regardless of their solar sources, proves the existence of some special local conditions of the solar plasma and the magnetic field on a large scale that allow the ejection of the high energy plasma streams. This fact has led us to the analysis the stream parameters during the different phases of the solar cycles (minimum, ascendant, maximum and, descendant) as well as during the polar magnetic field reversal intervals. The differences between the phases considered are pointed out. The solar cycles 20 and 22 reveal very similar dynamics of the flare-generated and also co-rotating stream parameters during the maximum, descendant and reversal intervals. This fact could be due to their position in a Hale Cycle (the first component of the 22-year solar magnetic cycle). The 21st solar cycle dominance of all co-rotating stream parameters against the 20th and 22nd solar cycle ones, during almost all phases, could be due to the same structure of a Hale Cycle – solar cycle 21 is the second component in a 22-year SC. During the reversal intervals, all high-speed stream parameters have comparable values with the ones of the maximum phases of the cycles even if this interval contains a small part of the descendant branch (solar cycles 20 and 22).     

基于CCSDS Proximity-1协议的动态变帧长策略研究

为提高邻近航天器之间的通信效率,研究了Proximity-1协议与传统链路层协议的最大区别——"通信互动"功能。对航天器之间通信过程中的动态变帧长策略进行了分析,给出了不同信道环境下的最佳帧长取值,并通过实时选择最佳帧长实现了动态变帧长策略方案。利用仿真手段验证了动态变帧长策略对通信效率的改善性能。仿真结果表明,吞吐量效率最多可提高80%,证明文章提出的动态变帧长策略能在很大程度上提高通信效率。     

ACARS原理分析

本文着重分析了 ACARS 工作原理,论证了调制体制的优越性,对微机控制下链信息发射的软件流程进行了模拟设计。     

全球疫情下的中国内地航空网络对外连通性

新冠肺炎疫情给世界航空网络的连通性造成重大影响，网络的通达程度明显降低。为了研究中国内地的航空网络对外连通性在疫情影响下的变化，提出对外连通效率这一评价指标，并根据国内外疫情爆发不同阶段的特点采用不同的链路删除规则进行分析。研究结果表明：在疫情爆发前期，因许多国家对中国内地旅客采取入境限制措施，中国内地的航空网络对外连通效率与疫情前相比下降率最大达到39.8%，同等情形下，禁止入境措施对中国内地的对外连通性影响比停飞直航大将近一个数量级，而这两种限制措施造成的影响在不同国家间的横向差异性也巨大。此外，一些与中国内地不存在直航的国家如果采取限制入境措施，也会对中国内地的对外连通性产生很大影响。在疫情爆发中后期，全球的航线连接缩减并未对中国内地的航空对外连通性产生明显影响，中国国际航线间的连通替代关系大大提升了航空网络在此类极端情形下的鲁棒性。