Morphological Structure and Chemical Composition of Cometary Nuclei and Dust

The chemical composition of comet nuclei derived from current data on interstellar dust ingredients and comet dust and coma molecules are shown to be substantially consistent with each other in both refractory and volatile components. When limited by relative cosmic abundances the water in comet nuclei is constrained to be close to 30% by mass and the refractory to volatile ratio is close to 1:1. The morphological structure of comet nuclei, as deduced from comet dust infrared continuum and spectral emission properties, is described by a fluffy (porous) aggregate of tenth micron silicate core-organic refractory mantle particle on which outer mantles of predominantly H₂O ices contain embedded carbonaceous and polycyclic aromatic hydrocarbon (PAH) type particles of size in the of 1 - 10nm range. This revised version was published online in June 2006 with corrections to the Cover Date.     

工业4.0语义下智能焊接技术发展综述

工业4.0的提出为制造业的发展注入新的活力,并引发全球制造业智能化、信息化、网络化升级.在基于信息物理系统(CPSs)智能制造的发展热潮下,智能焊接技术是当前热点问题.介绍了信息物理系统、工业产业链等相关概念,解释了基于制造业产业链的“工业4.0”的内涵.以历次工业革命为背景,阐明了焊接技术的发展脉络.通过对信息物理系统架构的分析,提出了智能焊接技术在各个层次中的关键技术,并对该领域的发展趋势进行了展望,对智能焊接更好的发展具有指导意义.     

A new modeling method of solar energetic proton events for ISO specification

Solar energetic protons degrade performance and reliability of spacecraft systems due to single-event effects, total dose effects and displacement damage in electronics components including solar cells. On designing a solar cell panel, a total fluence of solar energetic protons (SEPs) which cause solar cell damage is needed to estimate power loss of the solar cells over mission life. Nowadays a solar panel area of spacecraft is increasing as spacecraft mission life becomes longer (15–18 years). Thus an accurate SEP model is strongly required for the cost-minimum design from the aerospace industry. The SEP model, JPL-91 proposed by Feynman et al., is currently used widely for solar cell designing. However, it is known that the JPL-91 model predicts higher fluences of protons than values actually experienced in space, especially after 7 years on orbit. In addition, the model is based on several assumptions, and also needs Monte-Carlo simulations for calculating fluences. In this study, we propose a new method for modeling SEPs especially focused on solar cell degradation. The newly-proposed method is empirical, which constructs a model based directly upon proton flux measurement data taken by instruments onboard spacecraft. This method has neither assumptions nor dependence on SEP event selection, both of which are needed in JPL-91. The model fluences derived from this method show lower fluences in longer missions compared to JPL-91. This method has been proposed to ISO (International Organization for Standardization) and has been discussed for a new standard SEP model.     

一种新型电动舵机系统

介绍了一种为某型无人驾驶直升机研制的新型电动舵机系统。该系统采用了航空精密微型滚珠螺旋副和基于智能功率集成电路（ＳｍａｒｔＰｏｗｅｒＩＣ－ＳＰＩＣ）的ＰＷＭ（ＰｕｌｓｅＷｉｄｔｈＭｏｄｕｌａ－ｔｉｏｎ）伺服放大器，具有精度高、频带宽、线性度好、效率高和线位移输出方式等特点。文中详细描述了该系统的设计思想和结构特点。频响测试和机载试飞表明：这种新型的电动舵机系统具有良好的动态响应过程，完全满足无人驾驶直升机的使用要求     

反求工程中的点云数据采集

对反求工程中常用点云数据的采集方式进行了总结,对三维数据采集系统应用时所出现的累积误差过大、数据采集不便或数据缺失等问题进行了探讨,并提出了相应的解决方案。     

Fabrication of Diamond-like Carbon Films by Ion Assisted Middle Frequency Unbalanced Magnetron Sputtering

Diamond-like carbon (DLC) films are deposited by the Hall ion source assisted by the mid-frequency unbalanced magnetron sput-tering technique. The effects of the substrate voltage bias, the substrate temperature, the Hall discharging current and the argon/nitrogen ratio on the DLC film’s performance were studied. The experimental results show that the film’s surface roughness, the hardness and the Young’s modulus increase firstly and then decrease with the bias voltage incrementally increases. Also when the substrate temperature rises, the surface roughness of the film varies slightly, but its hardness and Young’s modulus firstly increase followed by a sharp decrease when the temperature surpassing 120 ℃. With the Hall discharging current incrementally rising, the hardness and Young’s modulus of the film decrease and the surface roughness of the film on 316L stainless steel firstly decreased and then remains constant.     

中国第一座桥梁风洞的研制

同济大学土木工程防灾国家实验室于1994年10月建成一座可供全桥模型试验的大型桥梁风洞，试验段14m×15m×2m（长×宽×高）。风洞的总体布局及结构安排突出地强调了非航空类风洞的特点，结构上采用砖混结构与钢结构相结合的方法，并以砖混结构为主，这就大大的缩短了建造周期，降低了成本。建成后的桥梁风洞总体造型美观并具有良好的气流品质，达到或超过了原设计中的性能指标，为我国桥梁建造业填补了空白。     

Sequential dynamic resource allocation in multi-beam satellite systems: A learning-based optimization method

Multi-beam antenna and beam hopping technologies are an effective solution for scarce satellite frequency resources. One of the primary challenges accompanying with Multi-Beam Satellites(MBS) is an efficient Dynamic Resource Allocation(DRA) strategy. This paper presents a learning-based Hybrid-Action Deep Q-Network(HADQN) algorithm to address the sequential decision-making optimization problem in DRA. By using a parameterized hybrid action space,HADQN makes it possible to schedule the beam patte...     

飞机电气化背景下的先进航空电机系统

多电/全电飞机将机载二次能源逐步统一为电能,电推进飞机进一步将电能用于飞行动力源,飞机电气化被认为是飞机机电系统与动力系统融合的重大革新,已经成为航空技术发展的重要方向。航空电机系统是支撑飞机电气化的重要基础。文中介绍了飞机电气化的基本概念和发展现状,阐述了电气化对飞机电源与用电设备的重要影响,重点论述了航空电机系统对飞机电气化发展的重要性及其面临的研究机遇与挑战。基于此,系统分析了适应飞机电气化发展需求的先进航空发电机与电动机系统,并进一步总结了支撑先进电机系统发展的关键技术,包括新型电工材料与器件、冷却技术、多物理场耦合分析方法与集成化综合设计理念。     

单自由度混合磁悬浮轴承控制系统模型的研究

介绍了单自由度永磁偏置的混合磁悬浮轴承的工作原理,提出了永磁磁通与电磁磁通叠加计算混合磁悬浮轴在的方法,给出了由这种方法导出的计算磁感应强度的理论计算公式,建立了混合磁悬浮轴承的数学模型及其控制模型,以ＰＩＤ为控制策略,导出混合磁悬浮轴承系统稳定性和动态性能的传递函数,通过理论分析和实验验证,得出了增大永磁内部磁动势可以提高轴承的承载力,稳定性,减小功放损耗的结论。