在高频负荷下钛合金及耐热合金持久强度的研究

1.引言 新型优质材料的制造及其在工艺上的应用与金属疲劳强度问题的研究,关系极为密切。这一问题对于现代航空发动机构造的发展具有特别重要的意义。因为,这种发动机的零件是在高温和高频振动负荷的情况之下工作的。在喷气发动机中,负荷最大的零件     

Short-wave infrared reflectance investigation of sites of paleobiological interest: applications for Mars exploration

Rover missions to the rocky bodies of the Solar System and especially to Mars require lightweight, portable instruments that use minimal power, require no sample preparation, and provide suitably diagnostic mineralogical information to an Earth-based exploration team. Short-wave infrared (SWIR) spectroscopic instruments such as the Portable Infrared Mineral Analyser (PIMA, Integrated Spectronics Pty Ltd., Baulkham Hills, NSW, Australia) fulfill all these requirements. We describe an investigation of a possible Mars analogue site using a PIMA instrument. A survey was carried out on the Strelley Pool Chert, an outcrop of stromatolitic, silicified Archean carbonate and clastic succession in the Pilbara Craton, interpreted as being modified by hydrothermal processes. The results of this study demonstrate the capability of SWIR techniques to add significantly to the geological interpretation of such hydrothermally altered outcrops. Minerals identified include dolomite, white micas such as illite-muscovite, and chlorite. In addition, the detection of pyrophyllite in a bleached and altered unit directly beneath the succession suggests acidic, sulfur-rich hydrothermal activity may have interacted with the silicified sediments of the Strelley Pool Chert.     

Small step or giant leap? Human locomotion on Mars

Human locomotion on Mars will be considerably different from on Earth. Optimum walking speeds will be approximately 30% lower and transitioning from a walk to a run will occur at a speed 25% slower. Peak vertical forces will be reduced by as much as 50%, and although ground contact time will remain constant with locomotion in 1 g, stride length and stride time will increase. During running on Mars airborne time will increase by approximately 80% in comparison to running on the Earth. On Mars, half as much energy will be required to travel the equivalent distance on Earth and it will be 65% more economical to run rather than to walk. Crews will, therefore, find themselves using a loping gait--a running-like action, with a slight upper body lean and an extended aerial phase, an unfamiliar gait in terrestrial locomotion.     

用于飞机健康监控的传感器技术不断升级

得益于数据处理和存储技术的进步，从飞机上获取的数据量呈爆发式增长，可对飞机实施预测性维修的机会也越来越多。其中，不断进步的传感器技术是支撑飞机健康监控技术发展的关键因素。     

基于自联想网络的发动机传感器解析余度技术

本文提出了一种基于自联想神经网络的传感器解析余度技术。在这种网络中,冗余传感器的信息被压缩、重组进入网络的第一部分,网络的第二部分将压缩信息恢复出来。基于数据融合原理,若一个传感器发生故障,其它传感器仍可提供足够的信息代替发生故障的传感器。理论分析和用于涡轴发动机的仿真结果表明,这种特殊结构的自联想网络具有良好的过滤噪声和故障信号的作用,特别适合于用作不易建模的复杂对象的传感器信号重构     

THE STUDY OF AIRPORTTERRAIN EFFECTS ON AUTOLAND FOR ANY AIRPLANE

<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)).     

21世纪士兵的新装备——微型无人飞行器

由于高能量储备和微型精确飞行控制技术的突破性进展,一种供士兵用的比鸟还小的微型侦察无人机已被列入美国国防研制计划     

钝尾物体底部压力计算

 提出了一种简便可靠的计算钝尾物体表面压力分布及底部压力的方法。将钝尾物体绕流流场分为无粘区、边界层区和分离区。无粘区和边界层区分别用位流理论和边界层理论计算。分离区由根据尾流函数等建立的替代模型模拟。利用奇点法解出整个模型的压力分布。计算釆用迭代法进行。对Vanwagenen模型和鲁尔大学模型进行了计算,结果表明该方法是成功的。     

冷轧无间隙原子钢中的微带生成机理

分析了冷轧体心立方金属中微带的形成原因.基于塑性变形理论,运用Taylor模型和Bishop＆Hill最大功原理,计算了变形体心立方晶体中滑移系上的切应变分布.计算结果表明,冷轧时当晶粒的轧向平行于晶粒的某些特定取向时,大量的局部切应变将集中产生在一个滑移面上并在此形成微带.这一高度局域性的切应变是形成剪切带的原因.此时,剪切带与轧制方向之间夹角为30°.另外,微带呈片状是双交滑移的结果,透射电子显微镜观察到的剪切带所在晶粒的取向和所在滑移面证实了这一微带的形成机制.     

评定运载火箭成本的TRANSCOST模型及其应用

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.