淬火／回火热处理对TiAl基合金晶粒细化的影响

研究了淬火/回火热处理中淬火温度和回火时间对Ti-48Al-2Cr-0.5Mo合金晶粒细化的影响。研究表明:一定的淬火/回火热处理能将大小约为1000μm的铸态组织细化成为18～30μm的均匀双态组织;TiAl基合金的细化效果严重依赖淬火阶段的加热温度,温度升高,得到的块状组织较细,羽毛状组织体积分数减少,在两相区回火时,高温淬火组织的回火组织较细,而时间的延长,晶粒长大,但不明显。     

基础隔震体系地震反应特征与方案优选

隔震建筑采用水平剪切型模型,隔震体系为橡胶垫、滑移和并联基础隔震系统,隔震层模型采用双线性滞回模型。研究了在不同隔震层屈服剪力和隔震周期时,不同隔震系统对结构地震反应的影响。研究表明,对于规则型隔震结构,经合理设计的并联隔震结构兼具橡胶垫和滑移隔震体系的优点,为优选方案。以一实际工程为例,分析了竖向不规则隔震结构的地震反应特点。研究表明,对竖向不规则结构,橡胶垫隔震体系为优选方案。     

流动诱导空腔振荡及其声激励抑制的实验研究

实验研究了矩形空腔在外部高速气流作用下诱导的空腔内流支振荡问题，以及从空腔前缘加入纯音声激励以抑制空腔内流动振荡技术。实验发现，在一定的气流速度和空腔几何尺寸下，空腔内流动会出现强烈的自持振荡。采用前缘声激励，在某些声激励频率和适当强度下，通过控制腔口前缘剪切层的初期发展，可使原来处于振荡状态下空腔内的脉动压力级峰值降低１４ｄＢ以上，线性总声压级降低５ｄＢ。     

SCR技术制备A2017半固态材料及其触变性能的研究

单辊搅拌技术 (SCRShearing/CoolingRollProcess)技术制备的A2 0 17半固态材料比常规铸造坯组织优良 ;SCR技术制备的A2 0 17半固态材料在 5 30～ 5 70℃范围内 ,可以进行触变成形 ;半固态成形平均屈服强度比热加工时的屈服强度低 10MPa ;A2 0 17半固态材料触变过程分为四个阶段 ,稳定触变阶段A2 0 17半固态材料的触变性能稳定 ,半固态加工时容许的最大加工变形范围为 6 4 %～ 72 %。     

基于粗集的调度Agent知识库建模研究

首先通过相识集、招标集、投标集和中标者的概念，描述了车间调度系统中的调度Agent与资源Agent间任务分配的招投标关系；运用粗集理论，基于任务的属性和资源Agent完全任务的成本、质量、负荷和时间等属性构造决策表；在分析了决策表的特征基础上，生成调度规则集，即调度知识库；最后给出车间调度Agent的调度过程算法。     

基于电力综合集成的多绕组双流发电机技术分析

为解决采用传统发电机的移动电站输出电源种类单一,而采用多台发电机又会造成底盘过载影响机动性的问题,文章基于电力综合集成技术,分析研究实现发电机的双流发电的关键技术,突破发电机多绕组发电及励磁解耦等难题,减小了电机体积、降低了电机重量,有利于移动电站的多功能化与小型化设计。     

Integration of lessons from recent research for “Earth to Mars” life support systems

Development of reliable and robust strategies for long-term life support for planetary exploration must be built from real-time experimentation to verify and improve system components. Also critical is incorporating a range of viable options to handle potential short-term life system imbalances. This paper revisits some of the conceptual framework for a Mars base prototype which has been developed by the authors along with others previously advanced (“Mars on Earth^®”) in the light of three years of experimentation in the Laboratory Biosphere, further investigation of system alternatives and the advent of other innovative engineering and agri-ecosystem approaches. Several experiments with candidate space agriculture crops have demonstrated the higher productivity possible with elevated light levels and improved environmental controls. For example, crops of sweet potatoes exceeded original Mars base prototype projections by an average of 46% (53% for best crop) ultradwarf (Apogee) wheat by 9% (23% for best crop), pinto bean by 13% (31% for best crop). These production levels, although they may be increased with further optimization of lighting regimes, environmental parameters, crop density etc. offer evidence that a soil-based system can be as productive as the hydroponic systems which have dominated space life support scenarios and research. But soil also offers distinct advantages: the capability to be created on the Moon or Mars using in situ space resources, reduces long-term reliance on consumables and imported resources, and more readily recycling and incorporating crew and crop waste products. In addition, a living soil contains a complex microbial ecosystem which helps prevent the buildup of trace gases or compounds, and thus assist with air and water purification. The atmospheric dynamics of these crops were studied in the Laboratory Biosphere adding to the database necessary for managing the mixed stands of crops essential for supplying a nutritionally adequate diet in space. This paper explores some of the challenges of small bioregenerative life support: air-sealing and facility architecture/design, balance of short-term variations of carbon dioxide and oxygen through staggered plantings, options for additional atmospheric buffers and sinks, lighting/energy efficiency engineering, crop and waste product recycling approaches, and human factor considerations in the design and operation of a Mars base. An “Earth to Mars” project, forging the ability to live sustainably in space (as on Earth) requires continued research and testing of these components and integrated subsystems; and developing a step-by-step learning process.     

超声速条件下多体干扰与分离试验研究

采用根据国外公开文献设计的类CAV模型,在0．6m×0．6m 跨/超声速风洞中开展了多体干扰与分离网格测力试验研究,初步获得了典型多体飞行器分离过程中的气动特性变化规律。试验结果表明,载荷模型气动特性受分离位置变化影响非常明显。载荷模型沿轴向分离时,气动力（矩）逐步接近自由流中气动力（矩）值,载荷模型法向位置改变会引发其气动力（矩）值发生更为剧烈的变化。引发这种现象的原因有两个：一是尾迹和头激波的发展改变了不同轴向位置处载荷模型的表面流态,从而影响了其气动特性;二是母机模型底部流动具有明显的非对称膨胀特征,不同法向位置处流速大小和方向差异明显,导致载荷模型气动特性随法向位置变化更为剧烈。     

Injection of 40-kHz-modulated electron beam from the satellite: II. Excitation of electrostatic and whistler waves

Beam-plasma interaction effects are studied during the active space experiment with electron and Xe-ion beam injections in an ionospheric plasma. Permanent 40-kHz-modulated electron beam injection occurs simultaneously with a xenon-ion beam injected by the Hall-type plasma thruster operating in a square-pulse mode (100/50 s for a job/pause duration). The unusual behavior of the background charged particle fluxes and wave activity stimulated during the beam-plasma interaction have been registered by the scientific instruments onboard Intercosmos-25 station (IK-25) and Magion-3 subsatellite. The longitudinal and electromagnetic wave instabilities and their mutual relationship are considered in order to explain the observed effects. The excitation of electrostatic waves by the electron injection has been considered for different resonance conditions near the linear stability boundary. Beam-driven electromagnetic instability is responsible for the backward-propagating whistler waves excited via cyclotron resonance. Competition of these two beam instabilities is one of the subjects of the present study.     

超精密设备的简谐激励主动消振

某些超精密设备可以简化成一个简单的二自由度振动系统,上质量块起到消振作用,当对下质量块施加简谐激振时,设备主体振动被削弱,若上下质量块重量比选择适当,则设备主体振动可完全消除。