Nanoengineering of Flux Pinning Sites in High－Tc Superconductors

Volume pinning forces were determined for a variety of bulk high-Tc superconductors of the 123-type from magnetization measurements. By means of scaling of the pinning forces, the acting pinning mechanisms in various temperature ranges were identified. The Nd-based superconductors and some YBCO crystals exhibited a dominating pinning of the δTc-type (i.e., small, superconducting pinning sites). In contrast to this, the addition of insulating 211 particles provided pinning of the δl-type; providing effective pinning in the entire temperature range acting as a “background” pinning mechanism for the peak effect. Due to the small coherence lengths of the high-Tc compounds, effective pinning sites are defects or particles of nanometer size relative to ε^3. Integral magnetic measurements of the magnetization as a function of temperature in large applied magnetic fields (up to 7 T) revealed that practically all high-Tccompounds were spatially inhomogeneous, which could becaused by oxygen deficiency (YBCO), solid solutions of Nd/Ba (NdBCO and other light rare earth compounds), intergrowths (Bi-based superconductors), and doping by pair-breaking dopants like Zn, Pr. This implies that the superconducting sample consists of stronger and weaker superconducting areas, coupled together. In large applied fields, this coupling gets broken and the magnetization versus temperature curves revealed more than one superconducting transition. In contrast, irradiation experiments by neutrons, protons,and heavy-ions enabled the artificial introduction of very effective pinning sites into the high-Tc superconductors, thus creating a large variety of different observations using magnetic data. From all these observations, we construct a pinning diagram for bulk high-Tc superconductors explaining many featuresobserved in high-Tc samples.     

用矿物锁住二氧化碳

这是一种常见的矿物，它可以消除燃烧气体中的二氧化碳，但在其自然状态下这种功效却是极其缓慢的。现在美国宾夕法尼亚州立大学的一个研究小组正在改变蛇纹岩，以使其在几小时内便可将矿物燃料燃烧产生的二氧化碳吸收掉，而不再要很长的时间。     

苏联解体锁住世界最大碳存储

1991年,苏联正式解体为若干个独立的国家,随之而来的工业崩溃减少了俄罗斯产生的温室气体排放量——帮助其很容易地就达到了《京都议定书》的气候目标。     

粗规律与它的单向安全

利用函数单向S-粗集(function one direction singular rough sets),给出粗规律的概念,粗规律是被w(x)-,w(x)-构成的规律对{w(x)-,w(x)-};因为函数单向S-粗集的属性集{α-,α-}发生变化,粗规律{w(x)-,w(x)-}也发生变化.利用椭圆曲线,给出粗规律锁住概念,提出粗规律锁住定理,并给出应用.     

麦特卡尔夫定律及其存在的问题

分析了麦特卡尔夫定律(Metcalfe'sLaw)对正的网络外部性(Externalities)的依赖性及其对网络价值估计的局限性,指出了该法则的缺陷,并给出了相应的结论.     

一种简单有效通用的厚、薄板壳元

提出一种简单有效的四边形平板壳元，它由基于Ｍｉｎｄｌｉｎ板理论的平板弯曲元与带有平面内转动的平面膜单元组成。单元中每个结点有六个自由度，易于模拟复杂的壳面连接和易于与别的带有转动自由度的单元相容，此种板壳元能顺利通过弯曲，膜小片检验，无剪切和膜“锁住”及多余零能模式，计算方法简便，适用范围广，且计算精度十分理想，具有广泛的应用前景。     

锁住雨水的绿色实践

始建于19世纪中期,遍及汉堡全城的地下管网,是欧洲大陆首个现代化排水系统,也是欧洲以及美国大城市效仿的样本。然而,近年来,当一些城市为防涝大建"地下宫殿"之时,汉堡却开始为它的"地下血脉"减负。汉堡水务局提出一个耳目一新的观点:下水道并不是越宽越好,因为下水道不是解决排水问题的全部答案。近年来,汉堡着力研究雨水的就地处理,利用绿地"锁住"雨水,实现天然的"自然