首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   20篇
  免费   0篇
大气科学   4篇
地球物理   6篇
地质学   4篇
天文学   5篇
自然地理   1篇
  2014年   1篇
  2013年   2篇
  2012年   2篇
  2010年   2篇
  2005年   1篇
  2004年   1篇
  2003年   1篇
  2001年   1篇
  1998年   1篇
  1996年   1篇
  1995年   1篇
  1994年   2篇
  1992年   2篇
  1986年   1篇
  1979年   1篇
排序方式: 共有20条查询结果,搜索用时 15 毫秒
1.
Forthcoming human planetary exploration will require increased scientific return (both in real time and post-mission), longer surface stays, greater geographical coverage, longer and more frequent EVAs, and more operational complexities than during the Apollo missions. As such, there is a need to shift the nature of astronauts’ scientific capabilities to something akin to an experienced terrestrial field scientist. To achieve this aim, the authors present a case that astronaut training should include an Apollo-style curriculum based on traditional field school experiences, as well as full immersion in field science programs. Herein we propose four Learning Design Principles (LDPs) focused on optimizing astronaut learning in field science settings. The LDPs are as follows:
(1)
LDP#1: Provide multiple experiences: varied field science activities will hone astronauts’ abilities to adapt to novel scientific opportunities
(2)
LDP#2: Focus on the learner: fostering intrinsic motivation will orient astronauts towards continuous informal learning and a quest for mastery
(3)
LDP#3: Provide a relevant experience—the field site: field sites that share features with future planetary missions will increase the likelihood that astronauts will successfully transfer learning
(4)
LDP#4: Provide a social learning experience—the field science team and their activities: ensuring the field team includes members of varying levels of experience engaged in opportunities for discourse and joint problem solving will facilitate astronauts’ abilities to think and perform like a field scientist.
The proposed training program focuses on the intellectual and technical aspects of field science, as well as the cognitive manner in which field scientists experience, observe and synthesize their environment. The goal of the latter is to help astronauts develop the thought patterns and mechanics of an effective field scientist, thereby providing a broader base of experience and expertise than could be achieved from field school alone. This will enhance their ability to execute, explore and adapt as in-field situations require.  相似文献   
2.
A synthesis of pollen evidence from Etang du Pourra, a small pond in Rhodanian Provence, France, complemented by new sedimentological, mineralogical and palynological data allow a reassessment of the Lateglacial-Holocene vegetation and climatic history of the area. The Etang du Pourra succession is shown to consist of two parts; the lower part dates from the Lateglacial and the upper reveals the Holocene pollen-stratigraphic succession typical of the region. In the Lateglacial, a humid and cooler phase is recorded before the Younger Dryas conditions progressively set in. In the Holocene succession, the consequences of human modifications on the environment are clearly visible in changes in mineralogy and pollen stratigraphy.  相似文献   
3.
General circulation model experiments with surface albedo changes   总被引:1,自引:0,他引:1  
K. Laval 《Climatic change》1986,9(1-2):91-102
In 1975, Charney proposed a biogeophysical feedback mechanism to partly explain the droughts that occur in desert border areas. He showed that a perturbation of albedo (due to a natural or anthropogenic decrease of vegetation) can be unstable and lead to a variation of precipitation in the region where albedo is changed.Several numerical experiments have been achieved with general circulation models to study the sensitivity of climate to surface albedo. We compare the GLAS and LMD model results for the Sahel. For all models, rainfall decreases when albedo increases and net radiative heating of soil decreases. We show the variations of circulation simulated by the LMD model that we obtain when albedo is increased. These changes are compared to the weakening of Easterly Jet at 200 mb observed during dry years.  相似文献   
4.
Large-scale runoff routing models (RRMs) are important as a validation tool for GCMs, and to close the hydrological cycle in fully-coupled climate models. The model RiTHM was developed to simulate the discharge of large rivers from the total runoff simulated by the LMD GCM. It uses a 1024×800 grid, nested in the 64×50 grid of the LMD GCM. The runoff simulated in a GCM grid cell is uniformly distributed over the underlying cells, where a series of two reservoirs accounts for the delay related to infiltration through the unsaturated zone and aquifers. The resulting riverflow is routed assuming pure translation along the drainage network, extracted with a GIS from a 5 min DEM. The transfer time from a cell to the outlet depends on topography, and on a basin-wide parameter, the time of concentration. RiTHM was calibrated in 11 river basins, using a realistic runoff forcing (computed by the land surface model SECHIBA from reanalyzed meteorological forcing). This led to a very satisfactory reproduction of observed hydrographs. The main problems were related to hydraulic processes neglected in RiTHM (reservoirs, diversion of riverflow because of flooding or irrigation). These results helped to validate SECHIBA, except for its snow processes, shown to be too simple. With the same parameters, RiTHM was also forced with runoff from the LMD GCM. This induced an important degradation of the simulated hydrographs, regarding both volume and timing. It was largely explained by errors in precipitation, and more generally climate, in the GCM. The direct calibration of RiTHM under the GCM-runoff forcing markedly improved the timing of simulated discharge, which could be interesting for land–atmosphere–ocean coupling. This work demonstrated that the usefulness of RRMs for GCMs strongly depends on their adequate calibration.  相似文献   
5.
6.
The results of the scientific cooperation between astronomers of the Byurakan and Marseille observatories on the study of diffuse matter in the Galaxy are presented.H -emission is discovered in the direction of h and x Per. Fabry-Perot observations of three HII-regions, Sh2-152, 153, and 106, show the expansion of the diffuse matter relative to the exciting stars. In the Sh2-106 region a probable jet is found. It is shown that in star forming regions the diffuse matter takes part in expansion motions together with stars.Published in Astrofizika, Vol. 38, No. 4, pp. 559–564, October–December, 1995.  相似文献   
7.
Résumén

L’analyse séquentielle et la sédimentologie de faciès sont appliquées aux grès numidiens. Ces méthodes fournissent des données nouvelles concernant l’origine de ces dépôts. Ceux-ci présentent des associations de faciès proximales et résultent de transports sur des distances relativement courtes. On n’observe pas de dépôts distaux. Plusieurs dépo-centres sableux. vraisemblablement des éventails radiaux, de vraient être répartis tout le long d’un bassin. Ces données rendent difficile de situer ce bassin au Sud des « noyaux » kabyles, ceux-ci fournissant à cette époque un matériel terrigène déposé en discordance ou alimentant les grès micacés » périphériques; la bordure « tellienne » ne semblant pas non plus avoir pu laisser transiter des sables (transports continentaux puis marins). Il est donc logique de placer le bassin au nord des « noyaux » kabyles. Cependant, la question de l’origine continentale du matériel quart/eux n’étant pas réglée (Afrique ou continent septentrional), celte position pose le problème paléogéographique de la disposition des terres ou des deltas ayant permis le drainage continental de ces sables jusqu’aux points d’entrée sous-marine.  相似文献   
8.
The fate of inflows into lakes has been extensively studied during summer stratification but has seen relatively little focus during the weak winter stratification, with or without ice-cover. Field observations are presented of groundwater inflow into a shallow bay of a subarctic lake. Atmospheric forcing of the bay during the study period was extremely variable and coincided with spring ice-cover break-up. Two dominant wind regimes were identified; (1) weak wind-forcing (wind speed <5 m s−1 or land-fast ice-cover), and (2) strong wind-forcing (wind speed >5 m s−1 and open water). At a relatively constant temperature of ~3.3°C, the groundwater inflow was closer to the temperature of maximum density than the water in the main body of the lake, which during the observed winter stratification is ~1.2°C. During weak wind-forcing, the stratification within Silfra Bay approximated two-layers as this denser groundwater formed a negatively buoyant underflow. A calculated underflow entrainment rate of 2.8 × 10−3 agrees well with other underflow studies. During strong wind-forcing, the water column out to the mouth of the bay became weakly stratified as the underflow was entrained vertically by wind-stirring. Observed periods of mixing can be predicted to occur when turbulent kinetic energy (TKE) production by wind stirring integrated over the underflow hydraulic residence time in the bay exceeds the potential energy associated with the stratification. A decrease of ice cover, as observed in the studied subarctic lake over the last decade, will result in the underflow being more frequently exposed to the strong wind-forcing regime during winter, thereby altering the winter distribution of groundwater inflow within the lake.  相似文献   
9.
Robotic platforms are essential for future human planetary and lunar exploration as they can operate in more extreme environments with a greater endurance than human explorers. In this era of space exploration, a terrestrial analog that can be used for development of the coordination between manned and robotic vehicles will optimize the scientific return of future missions while concurrently minimizing the downtime of both human explorers and robotic platforms. This work presents the use of underwater exploratory robots - autonomous underwater vehicles (AUV), remotely operated vehicles (ROV), and manned submersibles - as analogues for mixed human-robot exploration of space. Subaqueous settings present diverse challenges for navigation, operation and recovery that require the development of an exploration model of a similar complexity as required for space exploration. To capitalize on the strengths of both robotic and human explorers this work presents lessons learnt with respect to the fields of human-robotic interface (HRI) and operator training. These are then used in the development of mission evaluation tools: (1) a task efficiency index (TEI), (2) performance metrics, and (3) exploration metrics. Although these independent evaluations were useful for specific missions, further refinement will be required to fully evaluate the strengths and capabilities of multiple platforms in a human-robotic exploration campaign in order to take advantage of unforeseen science opportunities in remote settings.  相似文献   
10.
Land-surface processes are part of the lower boundary conditions for the atmosphere. The schemes used in general circulation models (GCM) to represent this forcing are relatively simple but they play an important role in the simulation of climate. This paper compares three different land-surface schemes used in GCM. All were run with the same imposed atmospheric conditions in order to analyse the differences in the hydrological cycle. The intercomparison showed that simulated evaporation, runoff and soil moisture were different in all three cases. In order to get a better understanding of the mechanisms at work in the models, features from two of the schemes were included in the other scheme. With these modifications we were able to reduce the wide range between model results. We showed that the surface resistance and field capacity were essential parameters in determining the annual cycle of evaporation and that a representation of subgrid-scale variability of soil moisture had an important impact on runoff.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号