散乱点云自适应滤波算法

提出一种散乱点云自适应滤波算法,该算法采用改进的R*-树组织散乱点云的拓扑近邻关系,基于该结构快速准确获取局部型面参考数据,自适应调节二维高斯分布的数字特征计算滤波权值,计算局部型面参考数据对原始型面数据的影响因子,以此作为权值计算各点滤波后的坐标,采用加权平均方法实现散乱点云的自适应滤波.实验证明该算法可有效提高点云的滤波效率,在保留原始型面特征的基础上,减小点云的随机误差,提高光顺性.     

Ka频段低轨遥感卫星可变编码调制应用效能研究

分辨率的不断提高对低轨遥感卫星的星地数据传输能力提升提出了迫切需求,导致X频段星地数传通道压力急剧增加,而Ka频段可用带宽是X频段的4倍,理论上可大幅提升传输能力。当前低轨遥感卫星的星地数据传输通常采用固定编码调制（CCM）和可变编码调制（VCM）,均未利用地面站仰角增大时大气衰减减小所带来的信道条件改善,对链路资源造成浪费。针对此问题,对指定地面站和链路可用度,综合考虑自由空间损耗和大气衰减随接收仰角增加而同时减小的特性,提出基于DVB S2标准的Ka频段星上VCM系统实现方案,给出传输效能评估标准,并对降雨特性不同的喀什站、北京站、三亚站CCM,VCM的Ka频段传输效能进行了对比仿真分析,以寻找出适合不同站点的星地数传方案。仿真结果表明：干旱少雨的喀什站更适合采用CCM,且链路可用度高达99.82%;雨量中等的北京站可根据用户使用需求灵活选择CCM或VCM;而降雨丰富的三亚站更适合采用VCM,不仅可将传输效能提升8.37%,还可将链路可用度提升11.23%。     

25t级氢氧膨胀循环发动机推力室氧腔流动仿真

为提高25 t级氢氧膨胀循环发动机推力室氧喷嘴出口流量均匀性,采用CFD方法对氧腔内流场进行了三维稳态数值仿真研究,分析了造成出口流量分布不均的原因,并据此设计了4种改进结构的氧腔,对每种结构进行了细节优化。通过数值仿真得到了不同方案氧腔内的流场分布以及喷嘴出口流量分布,对比分析了均流板和液氧入口结构对出口流量均匀性的...     

Orbital steady motions of a system of two bodies with an elastic connection

Steady motions of a pair of mass points connected by a rigid rod were studied by Abrarova and Karapetyan [1], the motions of a pair of mass points connected by an elastic spring were considered by Burov and Stepanov [2]. The present article is devoted to the existence, stability and bifurcation of the steady motions for a system composed of two bodies connected by an elastic torsional spring. Each of these bodies is a massless bar with mass points at the ends. One supposes that these bars are elastically connected and the system moves in the plane of the orbit of its mass centre. The trivial steady motions are studied (the principal axes of inertia of the system are directed as the radius-vector of the centre of inertia and as the tangent to the orbit). The non-trivial steady motions (the principal axes of inertia of the system are not directed as the radius vector or as the tangent to the orbit and the bars are not orthogonal each other) are also studied. We expose the complete study of the stability and of the bifurcation diagrams.     

2A14铝合金返修焊技术

根据2A14铝合金的冶金特点，针对对接接头和锁底焊缝的不同要求，提出了相应的采用缺陷槽的补焊工艺。分析了焊接位置、补焊层数及两面补焊、预热和缓冷、补焊的收／起弧及长度、电源选择、环境控制、补焊顺序和方向，以及装配等因素的影响。由不同运载贮箱补焊的结果可知，该工艺措施有效，补焊质量较好，提高了补焊的一次合格率。     

A comparison of ionosonde measured foF2 and IRI-2016 predictions over China

A comparison of the ionospheric F-region critical frequency (foF2) between ionosonde measurements and IRI-2016 predictions is studied over China during the period from January 2008 to October 2016. Four stations are selected, and the latitude coverage starts at 49.4°N and ends at 23.2°N with a sequential latitude interval of about 10°, the corresponding geomagnetic latitudes are from 39.5°N to 13.2°N. The results show that the variability of the observed foF2 versus latitudes, seasons, local time and levels of solar activity could be well reproduced by IRI-2016. However, the daily lowest value of foF2 from the IRI-2016 prediction occurs earlier than that from the ionosonde. Around the sunrise, the IRI-2016 prediction shows a very sharp rise and grows much faster than the observed foF2 in every month. The foF2 difference between the two options (URSI and CCIR) in IRI-2016 increases as the F10.7 index decreases. During 2008–2009, the annual average deviations of URSI and CCIR range from ?5% to ?10% and from 5% to ?5%, respectively. Generally, the CCIR performs better than URSI during postsunset under low solar activity or in Equatorial Ionization Anomaly (EIA) region over China, while it shows no large difference in performance with URSI in other locations or for other time.     

民航华北空管局设备管理综合数据库系统的建设

本文通过对华北空管局设备管理现状和信息化技术的深入研究探讨，详细阐述了构建华北空管局设备管理综合数据库系统的关键技术和框架结构。     

XPDM型露点仪在医用氧气分析中的应用

介绍了XPDM型露点仪的工作原理、仪器结构、技术指标、操作方法等.     

基于局域网的智能家庭网关

为了实现小区的智能化管理，以提高小区管理人员的工作效率和管理水平及小区居民的生活质量，提出了一种基于嵌入式网关的智能家庭网关，采用智能家庭网关并结合以太网技术而构建的小区智能管理系统，实现了对小区家庭的防火、防盗、煤气泄漏、紧急求助报警，水电气三表远程自动抄收，家电远程控制等功能。是真正意义上的网络化、智能化的家庭控制系统。     

Short-term forecasting regional model to predict M(3000)F2 over the European sector: Comparisons with the IRI model during moderate,disturbed, and very disturbed geomagnetic conditions

The hourly measurements of M(3000)F2 (M(3000)F2_meas) and the hourly quiet-time values of M(3000)F2 (M(3000)F2_QT) relative to the ionospheric observatories of Poitiers, Lannion, Dourbes, Slough, Rome, Juliusruh, Kaliningrad, Uppsala, Lyckesele, Sodankyla, and Kiruna as well as the hourly time-weighted accumulation series derived from the geomagnetic planetary index ap (ap(τ)), were considered during the period January 1957–December 2003 and used for the development of 11 short-term forecasting local models (STFLM) of M(3000)F2.