连续小波变换应用于密集模态参数识别

用连续小波变换方法进行模态参数识别时,减小小波函数的带宽可以提高小波变换的频率分辨能力,但同时也会增大边沿效应,影响密集模态参数识别的精度。本文提出了极值位置方法,在模态耦合严重的小波脊附近,找到模态解耦最好的尺度,在此尺度上进行频率和阻尼的识别,可以获得较好的识别精度。使用Morlet小波函数,对GARTEUR飞机模型中的三阶密集模态进行识别,验证了该方法的有效性。     

Comparative analysis of four different single-frequency PPP models on positioning performance and atmosphere delay retrieval

Single-frequency precise point positioning (SF-PPP) has attracted increasing attention due to its high precision and cost effectiveness. With various strategies to handle the dominant error, i.e., ionosphere delay, the ionosphere-float (IF), ionosphere-free-half (IFH), ionosphere-corrected (IC), and ionosphere-weighted (IW) SF-PPP models are certain to possess different characteristics and performance levels. This study is dedicated to assessing and comparing the four models from model characteristics, positioning performance, and atmosphere delay retrieval. The model comparison shows that IC and IW models are full-rank while IF and IFH models have a rank deficiency of size one that will result in biased estimations, which means the better solvability of IC and IW models. The experiments are carried out based on the 7-day Global Positioning System (GPS) observations collected at 57 global Multi-GNSS Experiment (MGEX) stations and Global Ionosphere Map (GIM) products. The results indicate that the IW model can accelerate SF-PPP convergence and achieve higher positioning accuracy compared to the other three SF-PPP models, especially in kinematic mode. With convergence criteria of 0.25 m in horizontal and 0.5 m in vertical, the east/north/up convergence times of IW model are 0.5/15.0/25.0 min and 0.5/16.0/36.5 min for static and kinematic modes, respectively. The IW model is able to achieve an instantaneous positioning accuracy of 0.28/0.35/0.75 m. In addition, a real kinematic test also demonstrates the best positioning solutions of IW model. Regarding troposphere delay retrieval, the IF, IFH, and IW models obtain a comparable daily accuracy of 3.0 cm on average, while the IC model achieves the worst accuracy of 8.0 cm. For precise ionosphere delay estimation, IW model only needs an average initialization time of 34.3 min, but a longer initialization time of 51.6 min is required for IF model. The daily precision of ionosphere delay estimation for IW model can reach up to 10.8 cm. At the present accuracy of GIM products, it is suggested that the IW model should be adopted for SF-PPP first due to its superior performance in positioning and atmosphere delay retrieval.     

Assessing ecohydrological factors variations and their relationships at different spatio-temporal scales in semiarid area,northwestern China

As a typical semiarid farming-pastoral ecotone sensitive to the environmennt, the Plain of West Liaohe Basin (WLBP) is currently experiencing drastic environmental changes. To identify how environmental change affect vegetation in the WLBP, we analysed spatiotemporal variation characteristics of Ecological environment factors based on monthly and annual air temperature (T), precipitation (P) and Normalized Difference Vegetation Index (NDVI) from 1982 to 2015. And the correlations between them were investigated by correlation analysis (Simple correlation, partial correlation and complex correlation) at temporal and spatial scale. The results showed that: (1) the vegetation growth of the WLBP showed ameliorated trend, with a change rate of 0.004/yr.; (2) P was more sensitive to NDVI than T; (3) and the influence of hydrothermal changes on vegetation growth was more significant than that of the change of single climate factors at time scales; (4) the effects of anthropogenic factors on vegetation change were 75.07% (1982–1993) and 98.08% (1994–2015), respectively. At the temp-special scales, P&T and land use type change (LUCC) were the main climatic and anthropogenic factors that affect vegetation changes, respectively.     

采用MSCMG群的卫星平台敏捷机动控制地面闭环试验验证

针对新型惯性执行机构磁悬浮控制力矩陀螺(Magnetically suspended control moment gyro, MSCMG),基于金字塔构型开展卫星平台敏捷机动控制地面闭环试验研究,以验证MSCMG的姿态控制性能。首先基于MSCMG搭建卫星平台控制地面试验系统,建立数学模型;接着针对气浮台外界扰动抑制及大角度敏捷机动控制问题,基于变参数滑模控制设计姿态控制算法,采用鲁棒伪逆方法进行MSCMG群框架角速度分配;并针对MSCMG的特性对框架角速度和角加速度进行了限幅,开展闭环控制试验研究。试验结果表明,采用MSCMG进行气浮台姿态稳定控制实验,可以实现姿态稳定度优于5×10~(-4)(°)/s,且在实现30°/15 s的机动指标时,MSCMG框架角速度具有良好的跟踪性能,且磁悬浮转子在输出大力矩时仍然保持稳定悬浮,具有较强的鲁棒性。通过地面闭环试验验证了MSCMG作为姿控执行机构的优异性能,为其未来进一步应用研究奠定基础。     

雷达模拟机管制案例课件制作系统的设计

一、引言 随着民航事业的飞速发展，空中交通流量的不断增加，空中交通管制服务将面临严峻的挑战。如何在新形势下进一步提高管制员培训的质量，以更好地为确保飞行安全服务，成为了每一个管制培训工作者思考的问题。要达到这一目标，对培训设备进行不断改进以适应前进中的管制工作，是一个重要的方面。     

3D STUDIO在飞机机动飞行科目中的应用研究

简述了采用３ＤＳＴＵＤＩＯ软件后，给飞机机动飞行科目试飞结果分析带来的重要变化。并从实际应用的角度论述了３ＤＳＴＵＤＩＯ辅助提高飞机设计完善性的原因；展望了将３ＤＳＴＵＤＩＯ软件，应用于辅助完善飞机设计的前景。     

直升机－舰组合风限图计算方法研究

首先简要叙述了国外风限图的研究概况及国内现状，在分析影响安全起降的各种因素的基础上，建立了风限图模拟计算的数学模型，并针对某直升机－舰组合风限图进行了计算。计算结果表明：所建立的数学模型切合实际，计算过程正确合理，得到的风限图比较真实地反映了直升机－舰配合能力。该方法较国外主要通过试飞得到风限图的方法相比可节省人力、物力和财力，具有安全性，为风限图的研制提供了新的途径。     

投入产出理论中两种消耗系数关系的新推证

从随机过程中状态转移矩阵的概仿出发，对投入产出理论中从直接消耗系数Ａ求得完全消耗系数矩阵Ｔ，提出一种新的推证方法，证明了Ａ与Ｔ之间的数量依存关系。     

语音合成遥控指令回报系统

本文介绍了用于无人机的语音合成回报系统,代替传统的信号盘灯光显示,向地面指挥监测人员回报遥控指令接收情况。语音合成系统由基于LPC原理制成的单片语音合成处理器TMS5220组成,用Z-80 CPU实现控制。系统结构简单,通用性强,合成语音清晰、自然可懂。     

铝板中锰含量的测定

研究了在酸性介质下，氟化钠为掩蔽剂，用高碘酸钠来氧化对氨基苯磺酸，用催化动力学测定痕量锰的新方法，该方法检出下限为４×１０－８ｇ／ｍＬ，线性范围为０．０５～０．６μｇ／ｍＬ，可应用于铝板中锰含量的测定。