首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 93 毫秒
1.
无论从外观上还是飞行原理上看,直升机与普通飞机都有着极大的差别。普通飞机是通过调节各部位机翼和尾翼的状态使飞机周围的气压形成压强从而进行飞行活动的,直升机由于没有机翼与尾翼,因此气动力是由主旋翼尾旋翼生成,从而来完成机身的上升、前进、悬停以及方向的控制。本文接下来将对直升机自动飞行原理以及操作系统进行一个简单的分析,首先对直升机的垂直起飞要求进行概述从而使自动飞行原理得以探索研究,其次讲述了直升机旋翼的工作原理以及操作。  相似文献   

2.
颤振是一种高度危险的自激运动,飞机在飞行包线内不允许出现颤振。针对轻型飞机机翼的颤振问题,采用侧壁支撑的方式将全尺寸机翼通过钢架固定在风洞侧壁,用弹簧组模拟副翼的弹性支持条件,并在翼根加装了半机身整流罩,在机翼外侧加装了防护绳,利用8米×6米风洞进行了颤振测试。结果表明,在飞机飞行速度范围内,机翼未出现颤振现象。试验结果为飞机颤振评估提供了依据。  相似文献   

3.
弹射模型滑翔机一般由机翼、机身、水平尾翼和垂直尾翼四部分组成(图1),它没有动力装置,而是利用拉长的橡筋所产生的弹力将模型弹入空中的。材料适合做模型的木材种类很多,应当因地制宜。一般机翼和尾翼(特别是尾翼)用重量轻的木材制做;机身别需用靱性较好的木材制作。选择木材时,应选用干燥的直纹木料。如条件允许,用桐木做机翼和尾翼,松木做机身更好。其它如:椴木、木棉木等都是做机翼机  相似文献   

4.
正全球最大太阳能飞机"阳光动力"2号近日完成首次环球飞行,全程达3.5万千米。飞机翼展长72米,机翼上的约1.7万块太阳能电池为飞机提供全部动力,可昼夜飞行,有两名驾驶员。"太阳神"号无人驾驶太阳能飞机重量比小型汽车还要轻,但活动机翼全面伸展时却达7 5米,机身上有14个螺旋桨。2001年在夏威夷的一次试飞中达到了2.28万米高度,但在2003年的一次飞行中遏湍流解体。  相似文献   

5.
正坐飞机时看看窗外就会发现,多数飞机的机翼上都有一根根"小尾巴"。这些"小尾巴"是放电刷,用来释放飞机机体上的静电,防止静电对飞机通信系统造成干扰。飞机在高速飞行时,由于空气和其他杂质的摩擦,机身会产生静电正电荷,它们均匀分布在机身表面。大气层也是一个电磁场,在电磁场的作用下,这些电荷会集中  相似文献   

6.
机翼是飞机飞行必不可少的组成部分,了解其在飞行过程中周围流场的状态对设计者在设计机翼结构时起到非常关键的作用。利用ANSYS-CFX软件建立飞机机翼有限元模型,通过建模和设置边界条件分别对机翼低音速,超音速和临界音速三个约束条件下机翼的状态进行分析,得到相应的数据及云图。分析结果得出在飞机飞行过程中,机翼周围的流速与压力大小成反比,并且机翼最前端所受的压力最大,同时由压力云图可以得出,飞机在接近音速条件下其周围所受的压力最大,在飞机突破音障之后,机翼周围的压力反而减小。同时由仿真结果得到一些重要数据,为高空飞行时机翼的设计和改进提供了数据依据。  相似文献   

7.
构型 民用飞机机身下部整流罩结构一般位于机身中下部,主要作用是在满足主起落架收放功能的前提下,在主起落架与机身之间、机翼与机身之间调整气流、减小空气阻力,保证机身的气动外形要求;此外,其将主起结构、系统设备及管路封闭起来,防止雨水、冰雹和跑道碎石进入后造成腐蚀、堵塞或损坏.  相似文献   

8.
《科学中国人》2023,(2):70-71
<正>数字情感交互概念车为实现电动化、数字化、循环永续的未来,国外汽车公司发布了一款数字情感交互概念车,以数字方式完成了三者的融合。在设计者看来,未来的车内数字化功能将远远超出当下我们接触的语音控制和驾驶辅助系统,会变得更加智能、更有共情能力,而数字情感交互概念车或将成为人们生活中的可靠伙伴。飞行汽车这是一款具备垂直起飞和降落性能的电动车,采用增程式驱动,可在空中行驶402千米。它具备可折叠的机翼,机翼折叠时,机身与一辆运动型多用途汽车的大小差不多,并拥有足够的内部空间,可以舒适地搭乘4名乘客。图中为此车原型机,预计2026年将实现量产。  相似文献   

9.
最近,日本政府综合了建筑业和流体研究学会在5年前就开始研究及实验的一项设想,提出利用地下隧道,以时速600公里的地下飞机往来于各大都市之间。根据设想,地下飞机的机身全长50米,高4米,宽2.4米,呈流线型;机身前后都设有机翼,机翼为长方  相似文献   

10.
正采用三种CFD计算方法对直升机的机身模型进行了计算,得到了三组机身气动特性数据,并用风洞试验结果和CFD计算结果进行飞行品质计算,包括配平、稳定性、操纵性,分析机身气动特性对直升机飞行品质的影响。在直升机设计涉及的学科中,机身的气动设计是基础也是重要的一环,直接影响整个直升机的飞行性能和飞行品质,对直升机飞行安全、飞行效率与经济性等都具有决定性的影响。鉴于空气动力学问题本身的复杂性和求解难度,直升机机身气动设计主要是依赖于风洞试验并结合设计人员的工程经验,风洞试验一直都是提供机身气动力数据以及指导直升机设计的主要手段,但是风洞试验花费时间长,经济代价高,  相似文献   

11.
This study examined how students who had no prior experience with videoconferencing would react to the use of videoconferencing as an instructional medium. Students enrolled in seven different courses completed a questionnaire at the beginning of the semester and again at the end of the semester. Students at the origination and remote sites did not differ in their reactions toward videoconferencing but there was a significant difference for gender. Women reacted less favorably to videoconferencing. Compared to the beginning of the semester, students reported significantly less positive attitudes toward taking a course through videoconferencing at the end of the semester. There were no significant differences in students' attitudes toward videoconferencing across courses at the beginning of the semester but there were significant differences across the courses at the end of the semester. The results suggest the need for better preparation for both students and instructors.  相似文献   

12.
Ajoint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology and his co-workers from Norway, US and Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells, suggesting that China's projected climate warming could decrease the pest's numbers. The study was published in Proceedings of theNational Academy of Sciences on 17 September, 2007.  相似文献   

13.
A computer-mediated group is a complex entity whose members exchange many types of information via multiple means of communication in pursuit of goals specific to their environment. Over time, they coordinate technical features of media with locally enacted use to achieve a viable working arrangement. To explore this complex interaction, a case study is presented of the social networks of interactions and media use among members of a class of computer-supported distance learners. Results show how group structures associated with project teams dominated who communicated with whom, about what, and via which media over the term, and how media came to occupy their own communication niches: Webboard for diffuse class-wide communication; Internet Relay Chat more to named others but still for general communication across the class; and e-mail primarily for intrateam communication. Face-to-face interaction, occurring only during a short on-campus session, appears to have had a catalytic effect on social and emotional exchanges. Results suggest the need to structure exchanges to balance class-wide sharing of ideas with subgroup interactions that facilitate project completion, and to provide media that support these two modes of interaction.  相似文献   

14.
Electronic data interchange (EDI) provides means for interorganizational communication, creates network externalities, requires an advanced information technology (IT) infrastructure, and relies on standards. In the diffusion of such innovations, institutional involvement is imperative. Such institutions contain governmental agencies, national and global standardization organizations, local government, and nonprofit private organizations like industry associations. The last type of organizations we call intermediating institutions. They intermediate or coordinate ("inscribe") the activities of a group of would-be adopters. Unfortunately, little is known of how these organizations shape the EDI diffusion trajectory. In this article we examine one specific type of intermediating organizations?industry associations?and how they advanced the EDI diffusion process in the grocery sectors of Hong Kong, Denmark and Finland. We identify six institutional measures, placed into a matrix formed by the mode of involvement (influence vs. regulation) and the type of diffusion force (supply push vs. demand pull), that can be mobilized to further the EDI diffusion. Industry associations were found to be active users of all these measures to varying degrees. Their role was critical especially in knowledge building, knowledge deployment, and standard setting. Furthermore, institutional involvement varied due to policy and cultural contingencies and power dependencies.  相似文献   

15.
The increasing prospects of digital piracy has prompted the perceived need by electronic publishers to adopt technical systems of protection, and governments to reform their copyright laws. This article is a preliminary study of the management of intellectual property by electronic publishers, defined as those involved in the production of online databases, and CD-ROMs. It focuses on three main issues: (1) how electronic publishers view the increasing threat of piracy; (2) the methods of protection employed to protect intellectual property in digital format; and (3) the importance of technological protection of intellectual property in electronic publications. The analysis is based on a sample of 23 UK electronic publishers. The interviews revealed an interesting assortment of protection methods and did not show that technological protection was a preferred way. Instead, the means of protection, in addition to copyright law, comprised niche markets, pricing, trust, bad publicity, and nontechnical and technical means.  相似文献   

16.
Long-standing conflict between domain name registrants and trademark holders prompted the Internet Corporation for Assigned Names and Numbers (ICANN) to create a global, mandatory arbitration procedure known as the Uniform Dispute Resolution Policy (UDRP). The UDRP has been used in 2166 cases involving 3938 domain names as of 1 November 2000. The policy gives the initiator of a complaint, generally a trademark holder, the right to choose which ICANN-accredited dispute resolution service provider (RSP) will handle the case. During the preparation of the UDRP,some feared that complainant selection would lead to "forum shopping" that might bias the results. This article performs a statistical assessment of the forum-shopping thesis and finds support for it. There are statistically significant differences in the various RSPs' propensity to take away names from defendants; there are also major differences in the number of cases brought to each RSP. RSPs who take away names have the larger share of cases. The study examines other variables that might explain differences in market share, such as price, the plaintiff's nationality, or the time taken to decide a case. It finds that nationality and time also are correlated with market share. The study concludes that shopping for a favorable outcome is an important factor in the UDRP.  相似文献   

17.
Prof. Raymond C.K. Chen, a neuropsychologist with the CAS Institute of Psychology, has made novel progress in his studies of schizophrenia. His work has been reported by a recent issue of Behavioural Neurology.  相似文献   

18.
<正>In Xishuangbanna,one of China’s most biodiverse regions,landscape has changed dramatically during the past three decades due to the conversion of tropical rainforest to rubber plantations.In steep areas,terraces are often constructed before planting rubber trees,which causes two important changes in the soil:the destabilization of soil in the bench terraces and the increased vulnerability of unvegetated riser faces to erosion.Few studies have documented the nature and intensity of erosion on bench terraces.Prof.LIU Wenjie and his colleagues from the Xishuangbanna Tropical Botanical Garden(XTBG)conducted a study in Menglun County(21°5′39″N,101°15′55″E),Xishuangbanna to evaluate the influence  相似文献   

19.
<正>Chinese scientists plan to apply Earth Observation technologies to protect the critically endangered wild camels(Camelus ferus).With the help of remote sensing,satellite positioning,geographical information system and wireless sensors networks,they will be able to access the distribution and population of the wild camels and protect their habitats.The project will be carried out by the International Research Center for Wild Camel Conservation,which was jointly established earlier this year by the Institute of Remote Sensing and Digital Earth(RADI)of the Chinese  相似文献   

20.
<正>The Paul Gerson Unna Research Group on Dermatogenomics was founded in October 2012 at the Partner Institute for Computational Biology.The ultimate goal of the group is to understand the biology of skin and skin appendages.  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