共轴反转直升机传动系统构型现状

共轴刚性旋翼高速直升机由共轴反转的两幅旋翼实现悬停和爬升,由尾推进桨实现高速前飞,旋翼不需要倾转,相对倾转式旋翼机可靠性更高,具有较好的发展前景.共轴反转传动系统是共轴刚性旋翼高速直升机的关键传动部件.本文分析了共轴反转传动系统构型原理;针对共轴反转输出功能需求,将共轴反转传动系统分为以圆柱齿轮为基础、以锥齿轮为基础、...     

一种基于迁移学习的遥测数据异常检测方法

为解决卫星遥测数据异常检测面临的数据不平衡且缺乏有标签样本的问题,提出一种基于一维卷积神经网络(1dCNN)迁移学习的异常检测方法.首先利用源域卫星的遥测数据对1dCNN进行预训练,使得模型的卷积层具有卫星状态特征的提取能力;然后将训练好的模型迁移到缺乏标签数据的目标域卫星中;利用目标域有标签样本对预训练模型进行微调,...     

月壤剖面锥型螺旋刃成孔钻头设计

针对月壤剖面钻进成孔探测需求,提出一种锥型螺旋刃成孔钻头,建立其钻进排屑性能的理论模型,并以此开展钻头结构参数的优化设计。在此基础上,分析螺旋刃切削姿态及其切削参数,基于直线刃平面切削理论建立锥型螺旋刃成孔钻头钻进切削负载预估模型,开展锥型螺旋刃成孔钻头模拟月壤剖面钻进负载特性试验验证。研究结果表明,相比于直线刃钻头,锥型螺旋刃成孔钻头的钻进排屑性能更优,而且钻进切削负载模型与试验结果具有较好的吻合度。研究成果对我国拟实施的月面钻取采样工程具有重要的借鉴价值。     

一种高动态卫星网络的拥塞控制算法

针对卫星网络通信路径发生改变引起往返时延突变,导致现有的拥塞控制机制中超时重传时间估计不准确,并对拥塞窗口计算产生不利影响的问题,提出一种基于链路长度的带宽估计TCPW\|BLC算法。该算法通过计算通信链路长度合理调整拥塞窗口、慢启动阈值及超时重传定时器中相关参数的增益因子,使拥塞控制算法在往返时延突变情况下仍保持较高吞吐量,适应卫星网络动态环境特性。NS2仿真结果表明,TCPW\|BLC算法相比TCPW算法在卫星网络中吞吐量性能提高了2.8%,有效降低了时延突变给拥塞控制机制造成的不利影响。     

切风模式风力发电飞行器的进展与挑战

风能是当今主流的可再生能源种类之一,目前传统风力发电机只能利用近地风能,而高空风能储量巨大且较为稳定,具有很大的开发价值及潜力。对于高空风能的利用,国际上已经制定出多种方案,部分已进行了飞行试验,而国内相关研究尚处于起步阶段。围绕高空风力发电系统(AWES)的种类和发展情况进行研究,分析了切风模式AWES的飞行原理,介绍了国外代表性的切风模式AWES项目案例,指出了切风模式AWES所包含的系留缆绳、精确控制、多功能基站以及综合优化等关键问题,为国内相关领域的后续研究提供参考。     

动压马达半球零件表面微观工艺特征对 产品设计原理的影响研究

零件加工过程的工艺因素都会给零件表面及表层带来(留下)特有的微观特征,这种微观特征与产品设计原理和零件性能特性要求的匹配性对高精度惯性产品的固有性能会产生至关重要的作用.首次在惯性仪表制造体系中引入了零件表面微观工艺特征性概念,以解决仪表精度提高和合格率问题.采用微观工艺特征分析方法思路,从产品设计技术特征(原理特征和性能特征)角度,从更微观、更微小的细节去识别、分析加工合格的零件存在的某些特征状态.初步分析了动压马达半球零件加工表面存在的两类微观特征可能导致惯性仪表生产合格率低、参数稳定性差的影响机理和特征形成的制造因素,提出了改变和完善产品制造工艺设计的思路.     

空间细胞机器人系统关键技术及其应用

针对传统空间操控装置难以适应未来大型空间设施在轨建设的问题,提出一种能够实现多层次自重构的空间细胞机器人系统,并对其概念体系以及设计理念进行了分析。介绍了空间三角桁架装配场景下的空间细胞机器人系统硬件设计。提出了空间细胞机器人系统关键技术,包括多智能体协同不确定行为规划、多层次机器人系统构型决策、多智能体协同无环境地图自主导航以及多智能体分层协同分布式控制等。最后结合空间细胞机器人系统的特点与优势,对其应用前景进行了展望。     

Solar variability and minor constituents in the lower thermosphere and in the mesosphere

Space Science Reviews - The variation in the solar irradiance related for example to the 11-year cycle leads to changes in the photodissociation and photo-ionization of the upper and middle...     

Solar maximum mission experiment: Early results of the hard X-ray imaging experiment

We have selected four widely different flares from the early period of operations of the Hard X-Ray Imaging Spectrometer (HXIS) on SMM to illustrate the characteristic imaging properties of this experiment. For the small flare of April 4, 1980, we demonstrate the instrument's capability for locating a compact source. In the weak, but extensive, flare of April 6 we show how well the instrument can display spatial structure, and also the low level of the instrument background. In the 1B flare of April 7 we are able to locate positions of the X-ray emission in the soft and hard channels, and estimate the positional variations of the emission patches. Finally, in the IN flare of April 10, which produced the strongest hard X-ray burst we have seen so far, we repeat some of the studies made for the April 7 event, and also demonstrate the capability of the HXIS instrument to study the development, with high time resolution, of individual 8″ × 8″ elements of the flare.     

Helium, Oxygen, Proton, and Electron (HOPE) Mass Spectrometer for the Radiation Belt Storm Probes Mission

The HOPE mass spectrometer of the Radiation Belt Storm Probes (RBSP) mission (renamed the Van Allen Probes) is designed to measure the in situ plasma ion and electron fluxes over 4π sr at each RBSP spacecraft within the terrestrial radiation belts. The scientific goal is to understand the underlying physical processes that govern the radiation belt structure and dynamics. Spectral measurements for both ions and electrons are acquired over 1 eV to 50 keV in 36 log-spaced steps at an energy resolution ΔE _FWHM/E≈15 %. The dominant ion species (H⁺, He⁺, and O⁺) of the magnetosphere are identified using foil-based time-of-flight (TOF) mass spectrometry with channel electron multiplier (CEM) detectors. Angular measurements are derived using five polar pixels coplanar with the spacecraft spin axis, and up to 16 azimuthal bins are acquired for each polar pixel over time as the spacecraft spins. Ion and electron measurements are acquired on alternate spacecraft spins. HOPE incorporates several new methods to minimize and monitor the background induced by penetrating particles in the harsh environment of the radiation belts. The absolute efficiencies of detection are continuously monitored, enabling precise, quantitative measurements of electron and ion fluxes and ion species abundances throughout the mission. We describe the engineering approaches for plasma measurements in the radiation belts and present summaries of HOPE measurement strategy and performance.