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。     

Optimization of beamforming and path planning for UAV-assisted wireless relay networks

Recently, unmanned aerial vehicles （UAVs） acting as relay platforms have attracted considerable attention due to the advantages of extending coverage and improving connectivity for long-range communications. Specifically, in the scenario where the access point （AP） is mobile, a UAV needs to find an efficient path to guarantee the connectivity of the relay link. Motivated by this fact, this paper proposes an optimal design for beamforming （BF） and UAV path planning. First of all, we study a dual-hop amplify-and-forward （AF） wireless relay network, in which a UAV is used as relay between a mobile AP and a fixed base station （BS）. In the network, both of the AP and the BS are equipped with multiple antennas, whereas the UAV has a single antenna. Then, we obtain the output signal~to-noise ratio （SNR） of the dual-hop relay network. Based on the criterion of maximizing the output SNR, we develop an optimal design to obtain the solution of the optimal BF weight vector and the UAV heading angle. Next, we derive the closed-form outage probability （OP） expression to investigate the performance of the dual-hop relay network conveniently. Finally, computer simulations show that the proposed approach can obtain nearly optimal flying path and OP performance, indicating the effectiveness of the proposed algorithm. Furthermore, we find that increasing the antenna number at the BS or the maximal heading angle can significantly improve the performance of the considered relay network.     

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.     

大膨胀比跨声速涡轮流动结构及损失的数值研究

为了揭示跨声速大膨胀比涡轮损失的主要特点和两种不同尾缘冷却方式对损失的影响,以典型大膨胀比跨声速涡轮和跨声速叶栅为研究对象开展了数值研究。研究发现大膨胀比跨声速涡轮的主要损失是叶型损失,占到总损失的65%左右,尾缘激波损失是叶型损失的主要来源。尾缘全劈缝冷气入射通过提高尾缘基压区基压来减少尾缘膨胀波对气流的加速程度,从而降低最高马赫数和激波损失,尾缘压力面劈缝冷气入射通过改变叶片尾缘压力面激波波系结构,使原来的一道激波变成两道或者两道以上的弱激波,从而减少激波损失。两种尾缘冷气方式都有利于降低大膨胀比跨声速涡轮激波损失,但压力面劈缝冷气入射方式效果更为明显。     

一种用于液晶曝光中的激光检测系统

介绍了一种非接触式激光检测系统，可用于检测液晶曝光中液晶模板与基板之间的间隙，给出了该种系统的测量原理、硬件系统、信号处理方法、测量结果、分辨力和误差分析，并指出了这种测量系统的应用。     

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.     

积木式方法与试验金字塔的历史沿革与发展趋势

采用积木式方法构建试验金字塔是目前已经被广泛接受的用来完成大型飞机结构强度验证的基本手段。本文概述了积木式方法和试验金字塔的发展历程和趋势，介绍了不同型号的美军机在研制过程中所建立的强度验证试验金字塔的统计结果，并且从试验层级、对象、目的和类型等四个方面比较了试验内容的数量与经费占比，由此来说明基础层级试验验证工作在强度验证试验金字塔中重要性和经济性。通过对虚拟试验在强度验证工作中的发展趋势、应用和限制的介绍，为顺利完成相关的全尺寸部件和整机的强度验证提供可靠的保障手段。     

Filament Thread-like Structures and Their?Small-amplitude Oscillations

Thanks to gradually improving observational capabilities, both from space and ground-based observatories, it is now generally accepted that thin threads (width ??200 km) constitute the building blocks of solar filaments and prominences. At ultra-small scales, high quality image sequences show a non-static picture of filaments and reveal that their oscillatory behavior is an important dynamic feature of these structures. Filament seismology sheds light on the internal magnetic structures of filaments and their interactions with surrounding solar regions. Understanding the overall magnetic topology of solar filaments and prominences including their small-scale thread-like structures is essential in interpretation and understanding of their oscillations. For this reason we aim here to present an update of the dynamic and spatial structures of prominences and filaments as inferred from high resolution observations in the past decennia. Some constraints in high resolution observations are addressed. Our review focuses mainly on the observational aspects and aims to summarize recent oscillation studies of individual filament threads and groups of threads. Finally, some theoretical interpretations of oscillations of filament threads and the inferred physical conditions of filament plasma are also discussed.     

Energy Release and Particle Acceleration in Flares: Summary and Future Prospects

RHESSI measurements relevant to the fundamental processes of energy release and particle acceleration in flares are summarized. RHESSI??s precise measurements of hard X-ray continuum spectra enable model-independent deconvolution to obtain the parent electron spectrum. Taking into account the effects of albedo, these show that the low energy cut-off to the electron power-law spectrum is typically ?tens of keV, confirming that the accelerated electrons contain a large fraction of the energy released in flares. RHESSI has detected a high coronal hard X-ray source that is filled with accelerated electrons whose energy density is comparable to the magnetic-field energy density. This suggests an efficient conversion of energy, previously stored in the magnetic field, into the bulk acceleration of electrons. A new, collisionless (Hall) magnetic reconnection process has been identified through theory and simulations, and directly observed in space and in the laboratory; it should occur in the solar corona as well, with a reconnection rate fast enough for the energy release in flares. The reconnection process could result in the formation of multiple elongated magnetic islands, that then collapse to bulk-accelerate the electrons, rapidly enough to produce the observed hard X-ray emissions. RHESSI??s pioneering ??-ray line imaging of energetic ions, revealing footpoints straddling a flare loop arcade, has provided strong evidence that ion acceleration is also related to magnetic reconnection. Flare particle acceleration is shown to have a close relationship to impulsive Solar Energetic Particle (SEP) events observed in the interplanetary medium, and also to both fast coronal mass ejections and gradual SEP events. New instrumentation to provide the high sensitivity and wide dynamic range hard X-ray and ??-ray measurements, plus energetic neutral atom (ENA) imaging of SEPs above ??2 R_??, will enable the next great leap forward in understanding particle acceleration and energy release is large solar eruptions??solar flares and associated fast coronal mass ejections (CMEs).