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21.
Over the past fifteen years, major U.S. initiatives for the development of new launch vehicles have been remarkably unsuccessful. The list is long: NLI, SLI, and X-33, not to mention several cancelled programs aimed at high speed airplanes (NASP, HSCT) which would share some similar technological problems.The economic aspects of these programs are equally as important to their success as are the technical aspects. In fact, by largely ignoring economic realities in the decisions to undertake these programs and in subsequent management decisions, space agencies (and their commercial partners) have inadvertently contributed to the eventual demise of these efforts.The transportation revolution that was envisaged by the promises of these programs has never occurred. Access to space is still very expensive; reliability of launch vehicles has remained constant over the years; and market demand has been relatively low, volatile and slow to develop. The changing international context of the industry (launching overcapacity, etc.) has also worked against the investment in new vehicles in the U.S. Today, unless there are unforeseen technical breakthroughs, orbital space access is likely to continue as it has been with high costs and market stagnation.Space exploration will require significant launching capabilities. The details of the future needs are not yet well defined. But, the question of the launch costs, the overall demand for vehicles, and the size and type of role that NASA will play in the overall launch market is likely to influence the industry. This paper will emphasize the lessons learned from the economic and management perspective from past launch programs, analyze the issues behind the demand for launches, and project the challenges that NASA will face as only one new customer in a very complex market situation. It will be important for NASA to make launch vehicle decisions based as much on economic considerations as it does on solving new technical challenges.  相似文献   
22.
Henry R. Hertzfeld   《Space Policy》2007,23(4):210-220
Economic and commercial spacepower is about market dominance and control. The USA is still the largest investor in space in the world and the technological and commercial leader in many areas but its leadership is being challenged. When other nations have similar capabilities, control becomes a problem, assuming, as is the case with space, that control is also a critical issue in security. Moreover, exerting spacepower may be inconsistent with expanded commercial developments in space, raising investment risks and creating incentives for foreign competitors. To the extent that global market opportunity is denied by restrictive commercial policies, spacepower from a purely international economic competitive perspective is diminished. Though it is encouraging that the US commercial space policies have been in Presidential Documents over the past 20 years, they have been unintentionally undermined to a large extent by other policies, with security almost always trumping commerce. This paper examines the way globalization and commercial space developments have changed the nature of spacepower and suggests that the USA's reactions to these changes have not thus far served it well.  相似文献   
23.
In this paper we discuss a simple temperature-driven segmentation technique that can be used for autonomous terminal guidance of anti-tank munitions. A ratio between two images from different IR bands is taken to form an emissivity independent image that is a function of temperature only. Size and temperature discrimination can then be used to find hot spots of interest. Candidate targets are segmented from the image about the points of interest using an.algorithm that finds all regions in multi-region objects and does not require a priori intensity information. Size and gross shape features are used to determine if the segmented objects are to be classified as targets. The key to this approach is the initial hot spot extraction. The temperature dependent ratio image allows quick and confident screening of the entire field of view, so that only the regions of interest require further processing. The described techniques effectively found tanks in the presence of common battlefield clutter when used with synthetic IR imagery provided by Georgia Tech Research Institute. The simplicity, effectiveness and potential speed of this technique make it ideal for autonomous guidance of expendable anti-tank weapons, especially where only low resolution IR imagery is available.  相似文献   
24.
The New Horizons instrument named Ralph is a visible/near infrared multi-spectral imager and a short wavelength infrared spectral imager. It is one of the core instruments on New Horizons, NASA’s first mission to the Pluto/Charon system and the Kuiper Belt. Ralph combines panchromatic and color imaging capabilities with SWIR imaging spectroscopy. Its primary purpose is to map the surface geology and composition of these objects, but it will also be used for atmospheric studies and to map the surface temperature. It is a compact, low-mass (10.5 kg) power efficient (7.1 W peak), and robust instrument with good sensitivity and excellent imaging characteristics. Other than a door opened once in flight, it has no moving parts. These characteristics and its high degree of redundancy make Ralph ideally suited to this long-duration flyby reconnaissance mission.  相似文献   
25.
<正>在航空公司新的库存模式中,零备件需求预测软件、物流管理专家、零部件分销商、制造商将扮演着越来越重要的角色。在过去,航空公司为了保障航班的正常运营,会贮存大量的库存件。而现在,在激烈的市场竞争和高成本压力下,航空公司逐渐开始改变原有库存模式,寻求可靠的备件配送方式,以尽量缩短其周转时间。可靠的备件配送方式要求必须在正确的时间将正确的备件运送至正确的地  相似文献   
26.
Attempts to rebuild US commercial launch capabilities through stimulating private industry will be constrained by the fact that free-market competition does not really exist in the space industry. As the worldwide supply of launch vehicles grows, the policy now offered by the US government is only likely to fragment the US space launch vehicle industry. The author argues in favour of a proposal to establish a quasi-governmental corporation for space launches which would both safeguard the interests of government and commercial users and ensure that business acumen was applied.  相似文献   
27.
The combination of the large effective area and the very low internal background of the ROSAT Position Sensitive Proportional Counter provides an extremely sensitive instrument for the study of diffuse X-ray sources. In this paper we review new results on the X-ray structure of nearby clusters as measured with ROSAT. Substructure is a common feature in these objects. Such structure provides evidence that clusters have formed relatively recently through mergers of relatively large subunits. This behavior is predicted by hierarchical formation theories in a dense universe.  相似文献   
28.
<正>机体制造商对于新一代飞机供应链所做的策略调整已经影响到售后服务市场的格局。在此调整的过程中航空产业链中的各方都面临着巨大的挑战,制造商通过业务集成加大对售后服务市场的掌控,但管理其庞大的内部业务远比想象中更困难,维修企业则面临更加激烈的市场竞争。在新一代波音787和空客A350飞机的研制过程中,波音公司和空客公司开始将更多地设计和制造工作转移给系统或部件供应商,这一转变同样也映射到了售后服务市场,影响到售后服务市场的格局,其中独立维修企业的感触最深。在售后服务市场中,负责集成和总  相似文献   
29.
Logistical constraints during long-duration space expeditions will limit the ability of Earth-based mission control personnel to manage their astronaut crews and will thus increase the prevalence of autonomous operations. Despite this inevitability, little research exists regarding crew performance and psychosocial adaptation under such autonomous conditions. To this end, a newly-initiated study on crew management systems was conducted to assess crew performance effectiveness under rigid schedule-based management of crew activities by Mission Control versus more flexible, autonomous management of activities by the crews themselves. Nine volunteers formed three long-term crews and were extensively trained in a simulated planetary geological exploration task over the course of several months. Each crew then embarked on two separate 3–4 h missions in a counterbalanced sequence: Scheduled, in which the crews were directed by Mission Control according to a strict topographic and temporal region-searching sequence, and Autonomous, in which the well-trained crews received equivalent baseline support from Mission Control but were free to explore the planetary surface as they saw fit. Under the autonomous missions, performance in all three crews improved (more high-valued geologic samples were retrieved), subjective self-reports of negative emotional states decreased, unstructured debriefing logs contained fewer references to negative emotions and greater use of socially-referent language, and salivary cortisol output across the missions was attenuated. The present study provides evidence that crew autonomy may improve performance and help sustain if not enhance psychosocial adaptation and biobehavioral health. These controlled experimental data contribute to an emerging empirical database on crew autonomy which the international astronautics community may build upon for future research and ultimately draw upon when designing and managing missions.  相似文献   
30.
A wealth of satellite data has provided information on weather and climate phenomena for the past 40 years. Within this period, however, the heavy human and economic costs of natural disasters have increased considerably. Using hurricanes, droughts, floods and earthquakes which occurred in the USA as examples, this article describes how Earth science can be applied to such situations to predict or mitigate their effects. The economic value of providing such information is discussed, as are the issues that can affect how successful its provision will be.  相似文献   
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