Simulation and Analysis of Crashworthiness of Fuel Tank for Helicopters

Crashworthiness requirement of fuel tanks is one of the important requirements in helicopter designs. The relations among the protection frame, textile layer and rubber layer of the fuel tank are introduced. Two appropriate FE models are established, one is for an uncovered helicopter fuel tank without protection frame, and the other is for fuel tank with protection frame. The dynamic responses of the two types of fuel tanks impinging on the ground with velocities of 17.3 m/s are numerically simulated for the purpose of analyzing energy-absorbing capabilities of the textile layer and protection frame. The feasibility of the current crashworthiness design of the fuel tank is examined though comparing the dynamic response behaviors of the two fuel tanks.     

Experimental Study on Effects of Fuel Injection on Scramjet Combustor Performance

In order to investigate the effects of fuel injection distribution on the scramjet combustor performance, there are conducted three sets of test on a hydrocarbon fueled direct-connect scramjet test facility. The results of Test A, whose fuel injection is carried out with injectors located on the top-wall and the bottom-wall, show that the fuel injection with an appropriate close-front and centralized distribution would be of much help to optimize combustor performances. The results of Test B, whose fuel injection is performed at the optimal injection locations found in Test A, with a given equivalence ratio and different injection proportions for each injector, show that this injection mode is of little benefit to improve combustor performances. The results of Test C with a circumferential fuel injection distribution displaies the possibility of ameliorating combustor performance. By analyzing the effects of injection location parameters on combustor performances on the base of the data of Test C, it is clear that the injector location has strong coupled influences on combus- tor performances. In addition, an inner-force synthesis specific impulse is used to reduce the errors caused by the disturbance of fuel supply and working state of air heater while assessing combustor performances.     

Flight Flutter Modal Parameters Identification with Atmospheric Turbulence Excitation Based on Wavelet Transformation

针对基于大气紊流激励的飞机颤振试验数据具有信噪比低以及测量数据以加速度响应形式给出等特点,将小波变换与随机减量法相结合对飞机颤振模态参数进行识别,首先利用随机减量法获得结构在非零初始加速度条件下的自由衰减响应,然后对该自由衰减响应进行Morlet连续小波变换,为使变换简单,本文采用了Parseval定理和留数定理,利用Morlet的带通滤波特性,通过搜索小波变换系数在不同的尺度区域内的极大值,再根据小波变换系数的极大值、相角与固有振动频率及阻尼系数间的关系,即可识别出各模态参数。并对利用小波变换识别颤振模态参数时,实现模态解耦应满足的条件进行了分析研究。通过仿真和飞机颤振试验数据分析,验证了该识别方法不仅简单、有效和可行,而且具有较强的抗噪性。     

基于数字孪生技术的准确度检测平台开发及应用

面向飞机结构件高精密和智能化准确度检测的需求,采用数字孪生方法及关键技术,以Unity 3D作为平台开发环境,通过搭建数字化模型,结合传感技术和物联网技术,开发了基于数字孪生技术的飞机结构件准确度检测平台,即DT-MEAS数字孪生平台.为数字孪生技术在航空制造业的应用提供了新的模式与方法.     

众眼看宇宙

惊奇土卫二 原本籍籍无名的土卫二（Enceladus）,由于美国航宇局“卡西尼”号探测器的最新发现,一跃而成为除地球之外的太阳系另一大主角。2008年3月,“卡西尼”发回的数据暗示,这颗卫星南极的冰盖之下,可能拥有一大片液态水构成的海洋。地下水透过冰裂缝喷涌而出,形成了壮观的“喷泉”——同时喷出的,还有生命必需的有机化合物。     

我国自主研发的火星探测器模型公开亮相

3月8日,“十一五”国家重大科技成就展在北京开幕。在这次展览中,我国自主研发的火星探测器模型首次与公众见面。有关负责人透露,该探测器将于2018年奔赴火星,执行我国第一次自主火星探测任务。     

诀别太空 解甲归田——记“发现”号航天飞机最后一次太空任务

好事多磨 ＂是时候了,它们已经工作了很长的时间,创造了神话般的成就。我们会期待着它们带着荣光退役,然后下一代飞船的时代开启。＂ 迈克尔·巴勒特这样评价航天飞机,他是本次＂发现＂号航天飞机任务的队员之一。     

“阿波罗”技术大“变脸”

<正>当今时代的"太空竞赛"虽然在某种程度上具有浓厚的政治与军事背景,但从客观上却大大地促进了人类的科技进步,改善了人类的生活环境,就像核武器的发明被转化为核电技术一样,由此得到的高新技术和产品迅速转     

高科技装备成就“惊天一跳”

2012年10月14日,现年43岁的奥地利跳伞高手菲利克斯·鲍姆加特纳（Felix Baumgarmer）搭乘热气球搭载的吊舱进入12．8万英尺（约合3．9万米）的高空后。纵身跃下,用血肉之躯突破音速,最终历时4分22秒平安降落到美国新墨西哥州的指定地点,打破了高空跳伞的高度和速度纪录,从而成功创造历史。而这一创举恰好也是对驾驶X-1试验飞机的美国上尉查尔斯·耶格尔在65年前的10月14日成为世界上第一个速度突破音速的人的最好纪念。     

“你这个+NP”在语篇中的情感语义类型及成因

"你这个+NP"常被用来执行汉语交际中的情感表达功能。论文对"你这个+NP"在语篇中的情感语义类型及其成因进行了分析,总结出"你这个+NP"主要表达两种情感语义:消极语义和积极语义,其丰富的情感语义是由话语的"主观性"和"预设"造成的。