复杂系统的可靠性分析方法研究

本文对未来的运载器的复杂控制系统的可靠性建模、分配和预计的一般方法和程序及综合分析方法进行了讨论和研究。并简述了复杂系统的计算机辅助可靠性分析。     

用于雷达波形的无损压缩编码

讨论了用算术编码实现波形数据的无损压缩。对波形数据进行无损压缩时 ,如果把每个可能的样本值看作一个符号 ,符号表会非常庞大 ,导致算法不可行。基于这种原因 ,本文用一个符号表示一定范围内波形数据 ,而不是单个波形数据 ,然后在此基础上设计了一种编码方案。先是无损线性预测 ,去除了波形数据之间的相关性。并假定产生的差值序列具有白功率谱 ,幅度服从高斯分布 ,第二步是算术编码。最后给出了对雷达回波数据进行压缩的实验结果。     

Effects of TADs on the F region of the mid-latitude ionosphere during an intense geomagnetic storm

Based on observations of two ionosondes at Wuhan and Kokubunji, this paper presents effects of TADs on the daytime mid-latitude ionosphere during the intense geomagnetic storm on March 31, 2001. During a positive ionospheric storm, the start of the enhancement of the foF2 (F2 peak plasma frequency) at Wuhan lags that at Kokubunji by 15 min, which corresponds to the time interval of traveling atmospheric disturbances (TADs’) propagation from Kokubunji to Wuhan. Associated with the uplifting of the hmF2 (height of F2 peak) caused by TADs, it is observed by the two ionosondes that the F1 cusp becomes better developed. Therefore, during a geomagnetic storm, TADs originating from the auroral oval may have a strong influence on the shape of the electron density profile in the F1 region ionosphere at middle latitudes. It is highly likely that TADs are responsible for the evolution of the F1 cusp.     

Review and propositions for the sliding/impact wear behavior in a contact interface

A thermal-solid-liquid complex operational environment induces structural interface developing a typical coupling sliding/impact wear behavior.It results in contact damage until systems fail,which may cause significant economic losses and catastrophic consequences.The key point of solving this problem is to reveal the coupling damage mechanism of the sliding/impact behavior in typical systems and life characterization under a complicate evolving environment.This has been a hot topic in the area of mechanical reliability.The main work in this paper can be concluded as follows.Firstly,the main industries in which the\"sliding/impact behavior\"takes place have been introduced.Then,existing studies on the wear mechanism and degree analysis are presented,which includes surface morphology analysis,wear debris analysis,and wear degree measurement.Meanwhile,existing problems in theoretical modeling and experiments in current research are summarized,so as to point out a bright direction for future research on wear prediction.They include interface contact modeling,mathematic coupling mechanism modeling,wear equation establishment,and wear life characterization,which can provide some new ideas for improving the existing studies on the sliding/impact wear behavior.     

Deformation of the ionosphere structure during the space weather events on October–November 2003

We present the spatial maps of the ionosphere–plasmasphere slab thickness τ (ratio of the vertical total electron content, TEC, to the F-region peak electron density, NmF2) during the intense ionospheric storms of October–November 2003. The model-assisted technology for estimate of the upper boundary of the ionosphere, hup, from the slab thickness components in the bottomside and topside ionosphere – eliminating the plasmasphere contribution of τ – is applied at latitudes 35° to 70°N and longitudes −10° to 40°E, from the data of 20 observatories of GPS-TEC and ionosonde networks, for selected days and hours of October and November 2003. The daily–hourly values of NmF2, hmF2 and TECgps are used as the constrained parameters for the International Reference Ionosphere extended to the plasmasphere, IRI-Plas, during the ionospheric quiet days, positive and negative storm phases for estimate of τ and hup. Good correlation has been found between the slab thickness and the upper boundary of the ionosphere for the intense ionospheric storms at October–November 2003. During the negative phase of the ionospheric storm, when the ionospheric plasma density is exhausted, the nighttime upper boundary of the ionosphere is greatly uplifted towards the magnetosphere tail, while the daytime upper boundary of the ionosphere is reduced below 500 km over the Earth.     

Application of Wuhan Ionospheric Oblique Backscattering Sounding System (WIOBSS) for the investigation of midlatitude ionospheric irregularities

An upgrade of Wuhan Ionospheric Backscattering Sounding System (WIOBSS) was developed in 2015. Based on the Universal Serial Bus (USB), and a high performance FPGA, the newly designed WIOBSS has a completely digital structure, which makes it portable and flexible. Two identical WIOBSSs, which were situated at Mile (24.31°N, 103.39°E) and Puer (22.74°N, 101.05°E) respectively, were used to investigate the ionospheric irregularities. The comparisons of group distance, Doppler shift and width between Mile-Puer and Puer-Mile VHF ionospheric propagation paths indicate that the reciprocity of the irregularities is satisfied at midlatitude region. The WIOBSS is robust in the detection of ionospheric irregularities.     

DLR-F6翼身组合体数值计算

使用自行研制的混合网格亚跨超声速流场解算器程序MFlow计算了AIAA第三届阻力会议提供的DLR-F6及其带整流装置FX2B情况下的阻力。重点分析了两者的网格收敛特性、阻力极曲线以及压力分布等,并与阻力会议的各个软件的计算结果进行比较。详细分析了DLR-F6翼身结合处后缘附近网格精度对分离气泡计算的影响。计算结果表明,MFlow程序的计算精度与国外软件相近,能够为阻力计算提供比较精确的结果。     

基于SVR选择性集成的机场噪声预测模型研究

机场噪声预测对机场规划设计、航班计划制定以及机场噪声控制具有十分重要的作用。针对机场周围各个监测点上的单飞行事件进行噪声预测。由于机场噪声数据的复杂性,用单一的SVR方法对其预测往往得出局部优化结果,不能达到理想的预测效果,针对这一问题,提出一种基于SVR选择性集成的机场噪声预测方法,通过Adaboost方法对机场噪声数据进行采样训练得到多个SVR预测模型,并结合一种排序方法对预测模型进行选择集成得到最终机场噪声预测值,取得了较好的预测效果。