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311.
1998年世界许多地区出现的经济和金融动荡对近期世界民航业的旅客运输的前景罩上一层阴影。但是,多方面的发展资料显示出,在今后几年里,货运飞机的市场仍然强劲。其中最为显著的一点是,空中客车工业公司积极参与与波音和麦道的传统强项货机市场的角逐,并获得来自美国联合包裹运送公司的大笔订单。在90年代,为了满足不断增长的需求,每年全球西方制造的货运喷气飞机机队大约增加80架。在今后20年,每年该数字预计增加一倍。货运机队飞机达到1500架下页表是全球1470架西制货机队的构成情况。另外,俄罗斯/独联体的经营者还有大约600架… 相似文献
312.
Sai F. Lee 《航空学报》1993,14(12):596-602
<正> The terrain profile at several airports has caused some difficulty with autolands on the DC-10 and MD-80. Some operators have reported that the pilot had to disconnect the flight guidance system during flare and land manually. At present, the autoland guidance system is not uniquely designed to handle the variations of terrain. Since there is no accurate substitute for radio altitude(h_(rad)) the only variable left to improve is radio altitude rate (h_(rad)). 相似文献
313.
314.
首先介绍评定运载火箭的研制和发射成本的解析模型的结构,着重讨论评定使用成本的新方法,并引入众多参数来修正模型.尔后以“阿里安”4后继型为例,讨论用于未来系统分析和成本比较的模型,分析了采用10种不同方案的可贮低温燃料两级火箭的研制和发射成本.欧洲未来运载火箭系统的关键是要最佳解决有限的研制费用与期望的最低发射成本之间的矛盾.多次使用系统能使发射成本大为降低,但研制费用较大.基于实际参数的成本解析模型能为选择运载火箭方案提供重要的信息. 相似文献
315.
Magnetic Field Fluctuations in the Solar Wind, Foreshock and Magnetosheath: Cluster Data Analysis 总被引:1,自引:1,他引:0
46 magnetosheath crossing events from the two years (2001.2-2003.1) of Cluster magnetic field measurements are identified and used to investigate the characters of the magnetic field fluctuations in the regions of undisturbed solar wind, foreshock, magnetosheath. The preliminary results indicate the properties of the plasma turbulence in the magnetosheath are strongly controlled by IMF orientation with respect to the bow shock normal. The amplitude of the magnetic field magnitude and direction variations behind quasi-parallel bow shock are larger than those behind quasi-perpendicular bow shock. Almost purely compressional waves are found in quasi-perpendicular magnetosheath. 相似文献
316.
Input data of the system are two-dimensional images and one-dimensional distributions of total and polarized solar emission at 5.2 cm wavelength obtained with SSRT. Together with photoheliograms, magnetograms, Hα-filtergrams and characteristics of active regions received from other sources, they form the initial database. The first stage includes superimposing the images, identifying microwave sources with active regions, assigning NOAA numbers to the sources, and determining for each active region the heliolatitude, extent, and inclination angle of the group's axis to the equator. These data are used to calculate the boundaries of longitude zones for each active region. A next stage involves determining the brightness temperatures of microwave sources less than the polarization distribution, the degree of polarization, and microwave emission flux, as well as calculating the parameters of microwave sources. Each parameter is assigned its own value of the weight factor, and the sum of values is used to draw the conclusion about the flare occurrence probability in each active region and on the Sun in general. 相似文献
317.
低速液体射流在高速湍流气体作用下的气液同轴射流雾化流场是瞬态密集型喷雾场,高速湍流中影响和控制雾化的因素很多。针对空气雾化流场液核分布与特征进行分析,开发了模拟液核的随机浸入体模型,结合大涡模拟方法对同轴射流空气雾化喷嘴下游流场进行数值模拟。模拟结果与实验结果对比表明:随机浸入体模型可快速捕捉液核的长度和位置信息。当气液动量比M为3~10000时,能够较准确地预测液核长度,当M>10时,其预测结果远优于唯象模型;该模型能够捕捉回流区、大尺度涡等流场结构。同时,可以准确地预测喷嘴附近的液滴粒径,特别是在气流速度较大(>60m/s)时,液滴平均直径预测误差<10%。 相似文献
318.
目前航空航天领域采用的微叠层复合材料主要集中在Fe、Ni、Ti和Al的合金或金属间化合物上。这类金属的金属间化合物具有熔点高、密度低、热导率好及抗高温性能好等优点,可被用作航空飞行器或航空发动机的高温结构材料。但是这类金属间化合物具有其本征脆性,导致其室温下的断裂韧性很差,因而应用受到限制。为解决这一问题,采用特种加工技术制备出具备微叠层结构的金属/金属间化合物复合材料是理想的手段之一。 相似文献
319.
Y. Miyashita 《空间科学学报》2010,30(4):312-320
Magnetic reconnection is one of the most important, dynamic phenomena in the magnetotail in terms of magnetic field line configuration change and energy release. It is believed to occur in the distant magnetotail mainly during southward interplanetary magnetic field periods and in the near-Earth magnetotail in association with substorms. In the present paper, we discuss several important issues concerning magnetic reconnection in the magnetotail associated with substorms, such as reconnection signatures, location, timing, spatial scale, and behavior, from the macroscopic, observational point of view. 相似文献
320.
N.I. Ismail A.H. Zulkifli M.Z. Abdullah M. Hisyam Basri Norazharuddin Shah Abdullah 《中国航空学报》2013,26(5):1093-1105
Abstract Implementing the morphing technique on a micro air vehicle (MAV) wing is a very chal- lenging task, due to the MAWs wing size limitation and the complex morphing mechanism. As a result, understanding aerodynamic characteristics and flow configurations, subject to wing structure deformation of a morphing wing MAV has remained obstructed. Thus, this paper presents the investigation of structural deformation, aerodynamics performance and flow formation on a pro- posed twist morphing MAV wing design named perimeter reinforced (PR)-compliant wing. The numerical simulation of two-way fluid structure interaction (FSI) investigation consist of a quasi- static aeroelastic structural analysis coupled with 3D incompressible Reynolds-averaged Navier- Stokes and shear-stress-transport (RANS-SST) solver utilized throughout this study. Verification of numerical method on a rigid rectangular wing achieves a good correlation with available exper- imental results. A comparative aeroelastic study between PR-compliant to PR and rigid wing per- formance is organized to elucidate the morphing wing performances. Structural deformation results show that PR-compliant wing is able to alter the wing's geometric twist characteristic, which has directly influenced both the overall aerodynamic performance and flow structure behavior. Despite the superior lift performance result, PR-compliant wing also suffers from massive drag penalty, which has consequently affected the wing efficiency in general. Based on vortices investigation, the results reveal the connection between these aerodynamic performances with vortices formation on PR-comoliant wing. 相似文献