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排序方式: 共有183条查询结果,搜索用时 15 毫秒
61.
Anton T. Kearsley Giles A. Graham Mark J. Burchell Michael J. Cole Zu Rong Dai Nicholas Teslich John P. Bradley Richard Chater Penelope A. Wozniakiewicz John Spratt Gary Jones 《Meteoritics & planetary science》2007,42(2):191-210
Abstract— The known encounter velocity (6.1 kms?1) and particle incidence angle (perpendicular) between the Stardust spacecraft and the dust emanating from the nucleus of comet Wild‐2 fall within a range that allows simulation in laboratory light‐gas gun (LGG) experiments designed to validate analytical methods for the interpretation of dust impacts on the aluminum foil components of the Stardust collector. Buckshot of a wide size, shape, and density range of mineral, glass, polymer, and metal grains, have been fired to impact perpendicularly on samples of Stardust Al 1100 foil, tightly wrapped onto aluminum alloy plate as an analogue of foil on the spacecraft collector. We have not yet been able to produce laboratory impacts by projectiles with weak and porous aggregate structure, as may occur in some cometary dust grains. In this report we present information on crater gross morphology and its dependence on particle size and density, the pre‐existing major‐ and trace‐element composition of the foil, geometrical issues for energy dispersive X‐ray analysis of the impact residues in scanning electron microscopes, and the modification of dust chemical composition during creation of impact craters as revealed by analytical transmission electron microscopy. Together, these observations help to underpin the interpretation of size, density, and composition for particles impacted on the Stardust aluminum foils. 相似文献
62.
多模态医学图象的SVD-ICP配准方法 总被引:4,自引:0,他引:4
多模态医学图象的配准在医学诊断和治疗计划中起着重要的作用。本文提出一种基于轮廓特征的迭代最近点(SVD-ICP)的配准方法。这种方法结合了SVD最优化解析方法和迭代搜索的优点来解决图象轮廓点的匹配问题,适用于不同模态医学图象之间的配准。我们关于CT-MRI和PET-MRI二维图象的配准实验证明了该方法的有效性。 相似文献
63.
64.
柄海鞘Styela clava中的甾醇化合物的分离和鉴定 总被引:2,自引:0,他引:2
应用GC-MS技术从青岛海域产柄海鞘Styela
clava中分离鉴定出5种甾醇化合物,分别是(22Z)-26,27-二降-麦角甾-5,22-二烯-3β-醇(1),胆甾-5,22-二稀-3β-醇(2),胆甾醇(3),胆甾烷醇(4),(22E)-麦角甾-5,22-二烯-3β-醇(5)。 相似文献
65.
66.
以西秀区2000、2010和2020年乡村聚落斑块为基础数据,运用乡村位序-规模法则、聚落规模等级模型等方法,分析西秀区乡村聚落等级规模分布特征及演变规律,并分析屯堡聚落在该过程的发展变化。结果显示:1)乡村聚落总规模、聚落数量总体上呈增长趋势,3个时段屯堡聚落面积占乡村聚落总面积的比例超过20%;2)西秀区乡村聚落规模分布符合乡村位序-规模法则,拟合优度在0.90以上,负指数分布特征突出,并表现出“首位聚落”和“垂尾”分布特征,2000—2010年乡村聚落规模趋于集中分布,2010—2020年趋于均衡;3)不同等级乡村聚落空间分布位置相对稳定,数量上呈低等级向高等级演变;4)屯堡聚落规模稳定增长,是高位序、高规模等级聚落的重要组成部分,但少部分屯堡聚落位序出现倒退现象。未来应科学规划乡村聚落用地布局,形成合理的乡村聚落等级规模结构,保护屯堡文化,打造区域特色聚落。 相似文献
67.
Jun-Liang Zhao Li Chen Zhong-Liang Zu Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai 《中国天文和天体物理学报》2006,6(3):287-296
Absolute proper motions and radial velocities of 202 open clusters in the solar neighborhood, which can be used as tracers of the Galactic disk, are used to investigate the kinematics of the Galaxy in the solar vicinity, including the mean heliocentric velocity components (u_1,u_2,u_3) of the open cluster system, the characteristic velocity dispersions (σ_1,σ_2,σ_3), Oort constants (A, B) and the large-scale radial motion parameters (C,D) of the Galaxy. The results derived from the observational data of proper motions and radial velocities of a subgroup of 117 thin disk young open clusters by means of a maximum likelihood algorithm are: (u_1,u2,u3) = (-16.1±1.0, -7.9±1.4,-10.4±1.5) kms~(-1), (σ_1,σ_2,σ_3) = (17.0 ±0.7,12.2±0.9,8.0±1.3) kms~(-1),(A,B) = (14.8±1.0,-13.0±2.7) kms~(-1) kpc~(-1) ,and(C,D) = (1.5±0.7,-1.2±1.5) kms~(-1) kpc~(-1) . A discussion on the results and comparisons with what was obtained by other authors is given. 相似文献
68.
The marine environmental forecast plays an increasingly important role in economic growth and infrastructure development, and touches upon many fields and aspects, including marine security, energy resources development and protection, ocean shipping and fisheries. Global Ocean Data Assimilation Experiment (GODAE) OceanView supports the national research groups providing them with coordination and technical support among the partners. Forecasting centers develop and establish global operational ocean forecast systems. The global operational ocean forecasting system uses the ocean dynamic numerical model as the dynamic framework, and the near real-time high-quality observation input field is integrated into the model by data assimilation to realize the future environmental forecasts of the marine conditions covering the multi-time scale. The products are routinely validated with observations in order to assess their quality. This paper briefly introduced and reviewed the development process and current situation of the global ocean forecasting system covered by GODAE OceanView, and outlined the future development of global ocean forecasting. 相似文献
69.
Evolution of an anticyclonic eddy southwest of Taiwan 总被引:8,自引:1,他引:7
Tingting Zu Dongxiao Wang Changxiang Yan Igor Belkin Wei Zhuang Ju Chen 《Ocean Dynamics》2013,63(5):519-531
Satellite images of sea-surface temperature, surface chlorophyll a concentration, and sea-level anomaly, together with ocean reanalysis data of Asia and Indian–Pacific Ocean (AIPOcean1.0), are utilized to study the three-dimensional characteristics and evolution of an anticyclonic warm eddy adjacent to the southwest coast of Taiwan during October and November 2006. Originated from the Kuroshio intrusion in the Luzon Strait, but unlike previously found westward moving anticyclonic eddies (AE) in the northeastern South China Sea, this AE was so close to the Taiwan coast and stayed where it was formed for over 1 month until it dissipated. Energy analysis is utilized to study the evolution process of the AE, and it shows that the barotropic instability (BTI) and baroclinic instability introduced by the Kuroshio intrusion flow appear to be the main energy sources for the AE. Periodical enhancement/relaxation of local northeasterly monsoon and its associated negative wind stress curl modify the current patterns in this region, reinforce the intraseasonal variability of the Kuroshio intrusion flow, and act together with Kuroshio to form the AE. Eddies detected from AIPOcean1.0 data also show that AEs are most likely to be generated southwest of Taiwan during the transition period of summer monsoon to winter monsoon, and generally, the BTI of Kuroshio intrusion contributes more than the direct wind stress work to the increase of the eddy kinetic energy for the generation and growth of the AEs. 相似文献
70.
长期的露天开采严重破坏了矿山地理地质环境,产生了地质灾害隐患。在介绍矿区地理地质背景的基础上,系统地描述该矿区土地、植被、地形和地貌被破坏的情况,分析崩塌、滑坡和泥石流地质灾害隐患。为改善生态环境,打造全国知名旅游景区,提出全面停止矿山开采,并进行分期治理。先期重点清除存在隐患的废石堆,然后清除边坡破碎危岩体,并辅以绿化措施。 相似文献