共查询到20条相似文献,搜索用时 93 毫秒
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郑泽尧 《西安航空技术高等专科学校学报》1988,(2)
小小风筝人人会做,但要放高飞稳却非易事,因为简单的风筝中蕴藏着复杂的科学道理,即使是风筝里手,亦未必深知其中奥妙。本文试图用简单的空气动力理论和普通的力学分析方法,介绍风筝的飞行原理和放飞技巧,供广大风筝爱好者分析研究。 飞机是现代科学技术的结晶,而风筝却是飞机的前身。世界第一架飞机就是从风筝试验中诞生的。图一莱特兄弟正在进行风筝试验,探索飞机的飞行原理和操纵特性。风筝和飞机的受力特点几乎相同。 相似文献
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1 引言 风筝在中国已有两千余年的历史,中世纪时传到了西方。后来,西方国家利用风筝飞行的原理发明了滑翔机。1903年12月17日,美国的莱特兄弟发明了“飞行者”1号实验飞行器——飞机。风筝、滑翔机和飞机都是重于空气的飞行器,必须借助于空气的相对运动才能升空。风筝靠拉线产生的风力飞上天,飞机则必须靠强大的动力装置的牵引才能飞行。动力装置或发动机对于飞机实在太重要了。正如在世界上颇负盛名的前苏联空气动力学家弗·谢·佩什诺夫所说:“飞机发展过程中的每一新成就首先是由新型发动机决定的,发动机是飞行必不可少的动力源。”世界百年航空史证明,正是动力装置的发展才促进了飞机的发展。 相似文献
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ARetrospectionoftheHistoryoftheCommercialAircraft在北京航空馆里,一张张图片,一份份解说词,让我们跨越时空,展现了一幅人类航空事业的绚丽画卷──从发明和创造风筝、火箭、孔明灯、竹错蜒、热气球等飞行器械,到飞机的问世:从以木材和蒙布为主的双翼机到喷气式超音速飞机,这种富有创造性的科学技术的发展,体现了人类的聪明才智和永无止境的探索精神。诚然,飞机的发展尚不到一个世纪,可在这即将结束的ZO世纪里,几乎每个Ic年都有有代表性的新的运输机推出。一、运输机发展的历史19O3年莱特兄弟第一架可操纵的动力飞机问世,… 相似文献
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《中国民用航空》2004,(5)
国办要求加强民航飞行安全管理The State Council Office Demanded to Strengthen Flight Safety Management国务院办公厅5月中旬发出通知:要求各地区、各相关部门联手严厉打击危害民航净空安全的违法违规行为,为民航飞机提供良好的机场净空环境,确保民航飞行安全。近年来,民航无线电陆空通信频率多次受到不明电台的非法干扰,特别是今年3月12日至4月12日接连发生8起,干扰事件明显增多,严重危及民航飞行安全。外,一些单位、个人在机场附近施放气球、风筝、燃烧秸秆等,对飞机安全起降也构成严重威胁。为确保民航飞行安全,经国务院同意,国… 相似文献
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如何推动我国战略性新兴产业发展是一个热点问题。技术创新是战略性新兴产业发展的重要支撑,然而只有将技术创新与商业模式结合起来,才能真正实现产业化发展。针对产业层面的商业模式设计,提出了技术创新、市场创新、价值网络和赢利模式四个构成要素,并基于商业模式的价值创造、价值传递和价值实现的逻辑过程,而对四个要素的逻辑关系进行了说明。 相似文献
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Jonathan Arons 《Space Science Reviews》1979,24(4):437-510
Some current topics in the theory of pulsar magnetospheres and their emission are reviewed. The mode of plasma supply and its consequences for structure of planetary and stellar magnetospheres is discussed. In the pulsar case, the plasma is supplied by electrical forces, in contrast to all other known examples. The resulting theories of particle acceleration along polar field lines are then reviewed, and the total energization of the charge separated plasma is summarized, when pair creation is absent. The effects of pair creation are reviewed using models of the resulting steady and unsteady flows, when the polar zones of the pulsar emit either electrons or ions. The application of these theories of acceleration and plasma supply to pulsars is discussed, with particular attention paid to the total amount of electron-positron plasma created and its momentum distribution. Qualitative agreement is shown between the spatial structure of the relativistically outflowing plasma described in one version of these models and the morphology of pulsar wave forms. Various aspects of radiation emission and transport are summarized, based on the polar current flow model with pair creation, and the phenomenon of marching subpulses is discussed. The corotation beaming and the relativistically expanding current sheet models for pulsar emission are also discussed briefly, and the paper concludes with a brief discussion of the relation between the theories of polar flow with pair plasma and the problem of the energization of the Crab Nebula.Proceedings of the NASA/JPL Workshop on the Physics of Planetary and Astrophysical Magnetospheres. 相似文献
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王德全 《郑州航空工业管理学院学报(管理科学版)》2006,24(3):99-103
我国券商所遭遇的窘境是券商角色严重错位所致,过度膨胀的自营业务和理财业务导致券商资金“饥渴”。要摆脱所遭遇的窘境,应恢复券商从事产品创造和产品销售的本来面目,弱化资金博弈模型的买方业务,从资本和风险的角度综合安排融资结构和数量。正确处理做大与做强的关系,证券业的兼并重组如果不能体现优势互补、取长补短,并进行有效的资源整合和团队文化的融合,形成1+1〉2的效应,将难以达到预期效果。所以,不但要关注数量和规模指标,更要关注质量和效率指标;不仅要注重短期的盈利能力,更要注重风险防范和风险控制能力。制定符合企业自身资源优势的个性化竞争战略规划,通过业务创新改善盈利模式并构筑其核心竞争力,这才是券商摆脱目前困境的关键所在。 相似文献
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The Intelligent Synthesis Environment (ISE) being developed by NASA, UVA, and JPL for significantly enhancing the rapid creation of innovative affordable products and missions is described. ISE uses a synergistic combination of leading-edge technologies, including high-performance computing, high-capacity communications and networking, virtual product development, knowledge-based engineering, computational intelligence, human-computer interaction, and product information management. The environment will link scientists, design teams, manufacturers, suppliers, and consultants who participate in the mission synthesis, as well as in the creation and operation of the aerospace system. It will radically advance the process by which complex science missions are synthesized, and high-tech engineering systems are designed, manufactured, and operated. The evolution of engineering design is described along with the shortcomings of current product development techniques. The need for ISE to create high-science payoff missions and aerospace systems at affordable costs is discussed. The five major components critical to ISE and some of their sub-elements are described: namely, human-ISE interaction; infrastructure for distributed collaboration; rapid synthesis and simulation tools; intelligent life-cycle system integration; and cultural change in the creative process. Related government and industry programs are outlined and future impact of ISE on complex missions and aerospace systems is discussed. 相似文献
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A. N. Markushin V. K. Merkushin V. M. Byshin A. V. Baklanov 《Russian Aeronautics (Iz VUZ)》2009,52(3):361-364
The results of experimental studies carried out for creation and development of an annular combustion chamber with reduced
NO
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emission for a full-scale gas turbine plant are presented. 相似文献
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文章从企业内在价值出发,推导出企业价值创造的三个重要驱动因素和条件;通过驱动因素、敏感性和可行性以及SWOT分析,构建平衡记分卡财务、顾客、内部经营和学习与成长4个方面的绩效指标。使其成为一种有效的价值管理工具。 相似文献
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化学气相渗透制备氧化硅基复合材料 总被引:10,自引:0,他引:10
以正硅酸乙酯为氧化硅先驱体,以 Nextel4 80纤维三维编织体作为沉积载体,采用化学气相渗透的方法制备了 Nextel4 80 /氧化硅复合材料。研究了正硅酸乙酯温度和沉积温度对沉积速率和渗透效果的影响,分析了沉积过程中产生瓶颈效应和固相粉末的原因以及沉积产物的相和复合材料的显微结构。结果表明 :1沉积速率随正硅酸乙酯温度和沉积温度的升高而显著升高;2瓶颈效应是由于正硅酸乙酯浓度过高,导致沉积速率过快引起的;3固相粉末是因为沉积温度过高,正硅酸乙酯分子或分解的过渡产物在到达沉积区域前已经完全分解引起的;4正硅酸乙酯为先驱体的化学气相沉积产物为无定型氧化硅;5化学气相沉积获得的无定型氧化硅基体与纤维有较佳的热匹配。 相似文献
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