High resolution limb observations of clouds by the CRISTA-NF experiment during the SCOUT-O3 tropical aircraft campaign

The Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere – New Frontiers (CRISTA-NF) experiment on board the Russian research aircraft Geophysica measures limb emission spectra with an unprecedented vertical and horizontal resolution in the 4–15 μm wavelength region. The IR spectra measured during the SCOUT-O3 Tropical Aircraft Campaign have been analysed with respect of cloud occurrence, cloud vertical and horizontal extent, cloud spatial structures and their utilisation for trace gas retrievals. In addition indicators for ice water content and optical thickness of the clouds have been adopted. These new kinds of measurements in the upper troposphere/lower stratosphere region are especially valuable for the design and development of future space borne high resolution limb sounders.     

大型结冰风洞云雾场适航应用符合性验证

结冰风洞云雾场符合性是大型结冰风洞适航应用的基础。为验证3 m×2 m结冰风洞云雾场符合性，发展了基于SAE ARP5905的结冰风洞云雾场符合性验证方法，针对主试验段构型，开展了结冰云雾场符合性验证试验，获得了试验段内液滴尺寸和液态水含量拟合关系，考察了喷嘴水压、液滴尺寸、试验段气流速度和喷嘴数量对试验段液态水含量的影响，形成了主试验段结冰云雾控制包线。结果表明：主试验段内液滴尺寸分布具有显著的单峰分布特征，体积中值直径（MVD）模拟范围近似在10~75 μm之间；试验段中心处液态水含量随着喷嘴水压和MVD的增大而增大，同时近似与试验段气流速度成反比，与喷嘴数量成正比；增大喷嘴水压和喷嘴数量会提高试验段内云雾液态水含量空间均匀性，但是增大气流速度却会减弱试验段内云雾空间均匀性；3 m×2 m结冰风洞主试验段结冰云雾控制包线可以覆盖大部分适航条例25部附录C结冰气象条件，但对低液态水含量结冰条件的模拟仍存在局限。     

多功能大气探测激光雷达应用

激光雷达具有高的时间和空间分辨率、优越的方向性和相干性、高的探测精度和实时快速的数据获取能力，已经被广泛应用于大气探测、环境监测等领域。随着技术的发展，大气探测激光雷达由最初的单波长、单功能朝着多波长、多功能方向发展，技术更加成熟，操作更加方便。本文将介绍大气探测激光雷达的基本原理，及其在探测大气气溶胶和云、水汽、温度、污染物和大气边界层高度等方面的数据应用。最后，对多波长多功能大气探测激光雷达的数据应用发展进行了总结和展望。     

Experimental investigation of flow and distortion mitigation by mechanical vortex generators in a coupled serpentine inlet-turbofan engine system

The performance of compact, aggressive ducts in advanced propulsion systems is limited by the internal flow separation coupled with the formation of secondary counter-rotating vortices that give rise to intensive flow distortions at the duct exit. An experimental investigation was conducted to study the flow field and passive suppression of flow separation and Aerodynamic Interface Plane (AIP) distortion in a serpentine air inlet duct. Tests were performed by a turbofan engine at several Engine Operating Points (EOPs) from 56% (idle) to 100% (max). A large total pressure deficit region arose at the upper part of the AIP, which was associated with the upper surface flow separation. Using the new mechanical S-type vortex generators in two longitudinal positions (VG1 and VG2), separation and loss were diminished at the upper part of the duct and AIP. The VG2 arrangement attained the maximum reductions in distortion coefficients which were 73.72%, 60.7% and 37.8% in DC(90°), DC(60°) and ΔP_C/P metrics, respectively. In the next step of the study, some unsteady aspects of the flow field were analyzed inside the duct. The separation onset and reattachment points were determined by the standard deviation of static pressure on the upper surface. The AIP spectral distribution showed that the boundary of low pressure and high pressure recovery regions was dominated by the maximum fluctuations. Furthermore, the PSD diagram of several probes at AIP revealed the vortex shedding frequency and its higher harmonics at separation region. The energy content of distinct unsteady spectral features in the bare configuration was significantly reduced using VGs, which showed the improvement of flow at the duct exit.     

Analysis of the solar sail deformation based on the point cloud method

The deformation of the solar-sail membrane is an important factor for causing inaccuracies in the solar-sail missions. This paper describes the solar sail under deformation by using a new modelling technique based on point cloud and triangular mesh generation. Two types of deformation, stemming from wrinkling and billowing, are modelled. The changes in the solar radiation pressure force and the moment caused by deformation are calculated and compared to the ideal non-deformed case. The heliocentric spiral trajectory and the orbital angular momentum reversal trajectory are taken as examples to quantify the influence of the deformation from an orbit point of view. Additionally, point cloud simplification, based on the normal vector and bounding box, is utilized to simplify the original deformed-sail model. It involves a reasonable reduction and renewal of the points in the model considering the variation of surface curvature. The simplification and its modelling accuracy are numerically investigated as well as computational efficiency.     

Ground-Based Cloud Using Exponential Entropy/Exponential Gray Entropy and UPSO

Objective and accurate classification model or method of cloud image is a prerequisite for accurate weather monitoring and forecast. Thus safety of aircraft taking off and landing and air flight can be guaranteed. Thresholding is a kind of simple and effective method of cloud classification. It can realize automated ground-based cloud detection and cloudage observation. The existing segmentation methods based on fixed threshold and single threshold cannot achieve good segmentation effect. Thus it is difficult to obtain the accurate result of cloud detection and cloudage observation. In view of the above-mentioned problems, multi-thresholding methods of ground-based cloud based on exponential entropy/exponential gray entropy and uniform searching particle swarm optimization （UPSO） are proposed. Exponential entropy and exponential gray entropy make up for the defects of undefined value and zero value in Shannon entropy. In addition, exponential gray entropy reflects the relative uniformity of gray levels within the cloud cluster and background cluster. Cloud regions and background regions of different gray level ranges can be distinguished more precisely using the multi-thresholding strategy. In order to reduce computational complexity of original exhaustive algorithm for multi-threshold selection, the UPSO algorithm is adopted. It can find the optimal thresholds quickly and accurately. As a result, the real-time processing of segmentation of groundbased cloud image can be realized. The experimental results show that, in comparison with the existing groundbased cloud image segmentation methods and multi-thresholding method based on maximum Shannon entropy, the proposed methods can extract the boundary shape, textures and details feature of cloud more clearly. Therefore, the accuracies of cloudage detection and morphology classification for ground-based cloud are both improved.     

云计算综述

论述了云计算的起源、概念、特点,与分布式计算和网格计算的区别;介绍了云计算厂商,及各厂商采用的数据存储、数据管理、编程模式、提供的服务种类云计算存在的问题,特别是云计算安全的风险种类及防护方法。提出了云计算需解决的问题。     

一种控制微涡轮叶尖泄漏流的新技术(英文)

提出了一种逆向涡流发生器控制叶尖泄漏流的新技术,利用压力面和叶顶面的压力差将气流从压力面引入,在叶顶面逆着叶尖泄漏流方向高速射出从而控制和减小叶尖泄漏流。对某典型毫米尺度涡轮叶栅进行了有/无逆向涡流发生器流场的数值研究,分析了逆向涡流发生器对流场及叶栅性能的影响。结果表明在典型进口条件下,逆向涡流发生器使得叶尖间隙泄漏流量降低了2.8%,周向载荷升高了7.7%;与无逆向涡流器情形相比,有逆向涡流器时涡轮效率提高了约1.2%。     

基于三维点云重建的助推器位姿估计

助推器分离是运载火箭发射过程中的关键动作之一,常用的激光雷达姿态测量技术在助推器分离阶段受外界干扰严重,难以准确获得位姿。基于视觉的助推器位姿变化测量技术具有优秀的抗干扰能力,通过搭建三维点云重建网络,以图像为输入,三维点云为输出,在构建的助推器分离过程的图像 点云数据上进行了训练和测试,对测试重建的助推器点云使用主成分分析的方法完成了位姿的估算。测试结果表明,所建立的三维点云重建网络可以根据仿真图像数据,精确测量助推器分离阶段的位姿变化,在R2score指标下,对三维坐标的预测分数均在0.98以上,姿态角平均误差约为21°,预测分数则均在0.80以上。     

多序列激光阴影成像技术研究及应用

为获取超高速碰撞过程中弹丸的飞行姿态及碰撞所产生的碎片云特性,开展了多序列激光阴影成像技术研究。利用多光源空间分离、偏振分光、光束角放大和补偿滤光等技术解决了单色光带来的衍射和干涉噪声以及碰撞瞬间强烈的自发光干扰问题,并先后在碰撞靶上建立了2序列、4序列和8序列激光阴影成像系统。该系统可以获得最小间隔1μs、曝光时间10ns、像素1000万的多个不同时刻的超高速瞬态变化过程图像,并在超高速碰撞靶试验中得到应用,获得了2～7km/s 撞击速度时碎片云的多序列阴影图像,该序列图像清晰地描述了碎片云的轮廓发展变化过程。该技术以低成本的方式实现了超高速摄影机的功能,满足目前碰撞试验粒子的飞行姿态及碎片云显示需要,并可以应用于其它超高速瞬态过程测量及流场结构显示。