温度和应变率对拉伸载荷下记忆合金本构关系的影响

用于高温Split Hopkinson Bar(SHB)试验的新型快速加热电炉，可在1min左右将试件加热至500度，最高可加热至1000度，且金属材料和非金属材料均可加热，在20－800度和0．00208－350s^-1范围内研究了温度和变率对拉伸载荷下铁基形状记忆合金本构关系的影响，结果表明，随着应变率提高，材料强度提高，延伸率降低，材料强度，延伸率及应变率敏感性随温度升高而降低。     

智能扩展的展望

过去十年里,我们学到的有夫人类智能活动的知识比以往任何时期都更多。这种新知识导致了目前在人工智能计算机程序设计和执行方面的突破。研究的主攻方向是推理判断领域,目的是创造出“专家”知识库系统来扩展人类知识的应用。把一项重要的技术转变为人工地运用智能特性、算法语言、试探法和原函数的计算机程序和计算机系统结构,对于我们来说还刚刚起步。到目前为止,只能由人脑借助于“专家系统”的创建才能完成。     

未来的计算机的体系结构

自从1981年10月在东京的国际会议上日本发表第五代计算机规划以来,在计算机科学界渐渐承认冯·诺依曼式计算机的地位将变得愈来愈不重要。计算从顺序而集中转向并行而分布,此时大量的系统必须在一起工作,这将要求有新一代的通用计算机。     

海洋天气船

地球上,陆地的面积占地球表面积的三分之一弱,海洋面积占三分之二强。在陆地的平原和高山上建立天气站已有悠久的历史,而且站点为数众多,为人类探索天气规律,战胜自然灾害起了重要作用。在浩瀚无垠的海洋上建立天气站,较之陆地(无辶)为困难,但是取得的气象资料对海运、民用航空和其他社会目的具有重大的实用价值,所以欧美国家在它们来往必经的北大西洋上建立海洋天气站已经有三十多年的历史了。 1947年7月,英国改装了一艘轻巡洋舰,在北大西洋上建立世界第一艘专门性天气船,次年2月英国又使三艘同样的船只加入这一行列。这些船只在北大西洋上从事连续性的水面和高空气象观测和海洋水文记录,为横越大西洋的英国飞机和船只的     

复杂机械系统的优化设计

本书首先用数学模型来描述复杂的机械系统，然后，将机械系统的优化设计归结为在互相制约的性能中合理地协调众多的设计变量，最后达到优化设计的目的，书中给出一些地面车辆中的优化问题实例来说明理论的应用。     

乘超级电梯上太空

上天揽月,再出发到火星,只要乘上超级电梯。这电梯怎么建?安在哪儿?动力从哪里来?……现在开始研究,没准未来太空梯最牛的设计师就是你!     

Microstructural evaluation and nanohardness of an AlCoCuCrFeNiTi high-entropy alloy

An AlCoCuCrFeNiTi high-entropy alloy(HEA) was prepared by mechanical alloying and sintering to study the effect of Ti addition to the widely studied AlCoCuCrFeNi system. The structural and microstructural characteristics were investigated by X-ray diffraction(XRD), scanning electron microscopy(SEM), and transmission electron microscopy(TEM). The formation of four micrometric phases was detected: a Cu-rich phase with a face-centered cubic(fcc) structure, a body-centered cubic(bcc) solid solution with Cu-rich plate-like precipitates(fcc), an ordered bcc phase, and a tetragonal structure. The XRD patterns corroborate the presence of a mixture of bcc-, fcc-, and tetragonal-structured phases. The Vickers hardness of the alloy under study was more than twice that of the AlCoCuCrFeNi alloy. Nanoindentation tests were performed to evaluate the mechanical response of the individual phases to elucidate the relationship between chemical composition, crystal structure, and mechanical performance of the multiphase microstructure of the AlCoCuCrFeNiTi HEA.     

Effect of high anodic polarization on the passive layer properties of superduplex stainless steel friction stir welds at different chloride electrolyte pH values and temperatures

The conditions used for friction stir welding of duplex stainless steels determine the resulting mechanical and corrosion performance of the material.This study investigates the corrosion resistance of UNS S32750 and S32760 superduplex stainless steels(SDSSs)joined by friction stir welding,employing cyclic polarization,Mott–Schottky,and microscopy techniques for analysis.The microscopy images indicated the presence of a deleterious intermetallic phase after electrolytic etching of S32760,as well as decreased corrosion resistance.The presence of molybdenum in the steels promoted better passive behavior at low pH.The Mott–Schottky curves revealed p-n heterojunction behavior of the passive oxide.Images acquired after the polarization test by scanning electron microscopy showed higher passivation propensity with increases of temperature and pH.