地球同步卫星BSR硅太阳电池阵输出功率衰减规律分析

长期受粒子辐照、紫外辐照等因素的影响,地球同步卫星的太阳电池阵输出功率会出现较为明显的衰减。这里选取某地球同步卫星使用的背表面反射(BSR)硅太阳电池阵为研究对象,采用光强因子和温度因子修正太阳电池阵的输出功率,使用局部加权回归散点平滑法(LOWESS)分析了其在设计寿命期间的输出功率衰减规律;同时基于LOWESS建立了预测模型,用于硅太阳电池阵超寿运行期间的功率预测。实测数据表明:本文构建的预测模型可以满足超寿地球同步卫星在轨管理使用需求。     

非静止轨道通信卫星星座间同频干扰概率分析

随着全球非静止轨道（non-geostationary orbit,NGSO）通信星座系统的大规模部署及应用,使用相同频率的星座系统之间存在着相互干扰的风险。NGSO系统间同频干扰概率的有效评估方法及合理评价指标是评估干扰风险及设计规避策略的基础,通过分析星座构型与地面站可视空域内卫星出现概率分布特性的关系,利用地面站接收端干扰噪声比保护阈值,建立了概率评估参数指标,并以OneWeb系统、O3b系统以及SpaceX系统为例,分析了全球范围地面站不同NGSO系统间发生有害干扰的概率分布特性。当系统间卫星出现概率分布趋同,会使有害干扰概率增加;反之,不同NGSO系统卫星在可视空域出现概率分布的较大差异会有效降低有害干扰概率。     

Application in prestiction friction compensation for angular velocity loop of inertially stabilized platforms

To overcome the influence of the nonlinear friction on the gimbaled servo-system of an inertial stabilized platforms(ISPs) with DC motor direct-drive, the methods of modeling and compensation of the nonlinear friction are proposed. Firstly, the inapplicability of LuGre model when trying to interpret the backward angular displacement in the prestiction regime is observed experimentally and the reason is deduced theoretically. Then, based on the dynamic model of direct-drive ISPs, a modified LuGre model is proposed to describe the characteristic of the friction in the prestiction regime. Furthermore, the state switch condition of the three friction regimes including presliding, gross sliding and prestiction is presented. Finally, a composite compensation controller including a nonlinear friction observer and a feedforward compensator based on the novel LuGre model is designed to restrain the nonlinear friction and to improve the control precision. Experimental results indicate that compared with those of the conventional proportion–integration–differentiation(PID) control method and the PID plus LuGre model-based friction compensation method, the dwell-time has decreased from 0.2 s to almost 0 s, the position error decreased to 86.7%and the peak-to-peak value of position error decreased to 80% after the novel compensation controller is added. It concludes that the composite compensation controller can greatly improve the control precision of the dynamic sealed ISPs.     

A nonlinear background removal method for seismo-ionospheric anomaly analysis under a complex solar activity scenario: A case study of the M9.0 Tohoku earthquake

A precise determination of ionospheric total electron content (TEC) anomaly variations that are likely associated with large earthquakes as observed by global positioning system (GPS) requires the elimination of the ionospheric effect from irregular solar electromagnetic radiation. In particular, revealing the seismo-ionospheric anomalies when earthquakes occurred during periods of high solar activity is of utmost importance. To overcome this constraint, a multiresolution time series processing technique based on wavelet transform applicable to global ionosphere map (GIM) TEC data was used to remove the nonlinear effect from solar radiation for the earthquake that struck Tohoku, Japan, on 11 March, 2011. As a result, it was found that the extracted TEC have a good correlation with the measured solar extreme ultraviolet flux in 26–34 nm (EUV_26–34) and the 10.7 cm solar radio flux (F_10.7). After removing the influence of solar radiation origin in GIM TEC, the analysis results show that the TEC around the forthcoming epicenter and its conjugate were significantly enhanced in the afternoon period of 8 March 2011, 3 days before the earthquake. The spatial distributions of the TEC anomalous and extreme enhancements indicate that the earthquake preparation process had brought with a TEC anomaly area of size approximately 1650 and 5700 km in the latitudinal and longitudinal directions, respectively.     

月面高温下推力器可靠性试验

嫦娥五号着陆上升组合体落月后将经历月昼强红外辐射环境，由于推力器喷管导热影响，使推进剂管路与电磁阀面临高温环境，推进系统存在管路内氧化剂汽化和推力器性能下降甚至无法正常工作的问题，影响上升器月面起飞正常姿态控制。为了研究高温下推力器的工作性能，进行了高温下氟塑料阀芯与氧化剂相容性调研，提出了电磁阀和推力器可靠性增长及可靠性验证试验方法，分析了温度与电磁阀阀芯行程的关系，获取了高温环境下推力器的稳态及脉冲工作性能，在小子样条件下评估了推力器可靠性置信下限及月面起飞上升推进系统可靠度，通过月面高温排气及月面起飞上升姿态控制对研究结果进行了航天器在轨飞行验证，圆满完成了上升器月面起飞上升任务。所提出的研究方法及思路具有很好的工程适用性。     

童话之城——哥本哈根

哥本哈根位于波罗的海和北海之间的厄勒海峡西岸,集聚着充满童话气质的古堡与皇宫、乡村与庄园。不论是沉淀了古老历史的还是延续着皇族传奇的各类建筑,都鳞次栉比地坐落在这里。哥本哈根融合了古典与现代的艺术气息,阿肯艺术中心、路易斯安娜博物馆、国家博物馆、丹麦国家美术馆等众多艺术博物馆各领风骚。富有皇族气质的哥本哈根,贯穿着全年度的各种主题节庆,令狂欢从夏季一直延续到冬季。最著名的莫过于哥本哈根国际爵士音乐节,在每年7月将持续整整10天,着实是不容错过的年度盛会!     

The Evolving Sigmoid: Evidence for Magnetic Flux Ropes in the Corona Before, During, and After CMES

It is generally accepted that the energy that drives coronal mass ejections (CMEs) is magnetic in origin. Sheared and twisted coronal fields can store free magnetic energy which ultimately is released in the CME. We explore the possibility of the specific magnetic configuration of a magnetic flux rope of field lines that twist about an axial field line. The flux rope model predicts coronal observables, including heating along forward or inverse S-shaped, or sigmoid, topological surfaces. Therefore, studying the observed evolution of such sigmoids prior to, during, and after the CME gives us crucial insight into the physics of coronal storage and release of magnetic energy. In particular, we consider (1) soft-X-ray sigmoids, both transient and persistent; (2) The formation of a current sheet and cusp-shaped post-flare loops below the CME; (3) Reappearance of sigmoids after CMEs; (4) Partially erupting filaments; (5) Magnetic cloud observations of filament material.     

中层大气受迫Rossby波包的非线性相互作用：Ⅱ.数值计算

本文对中层大气受迫Ｒｏｓｓｂｙ波包的非线性三波相互作用问题作了进一步的数值分析，结果表明，三个波包随时间演化达到的平衡态与文献［１］的理论结果完全一致，而且仅当系统中只有中等波长波包不受外源强迫时，系统运动有可能出现两个稳定平衡态，在一定外源强度范围内，平衡态会产生尖点突变，平衡态随外源的变化有滞后分岔的特征，系统运动最终达到的平衡态不仅与外源强度的变化方式有关，而且依赖于初始状态。     

浮动零点法及其在声表面波（SAW）传感器中的应用

温度是影响传感器精度的重要因素。本文介绍了一种新的温度误差校正方法，即浮动零点法。该方法以差动原理和浮动坐标为基础，是实现温度校正较为理想的方法。     

Linux路由实现机制分析

通过对Linux2.4.20版内核路由模块代码的分析和研究,详尽地阐述了Linux路由机制的实现思想和技术特点,对于更好地使用Linux的路由功能和在Linux路由上进行二次开发都具有实际的指导意义。