Digital Image Correlation Using Specific Shape Function for Stress Intensity Factor Measurement

The stress intensity factor (SIF) is a critical parameter associated with the fracture behaviour of materials. In this paper, we select the displacement function around a crack tip as the shape function of the digital image correlation (DIC), which makes it possible to directly calculate the SIF by the correlation scheme. Moreover, we use a non-rectangular subset, which can reduce the influence of plastic deformation and crack width on the DIC measurement accuracy. We measured the SIF of a mode I crack in a super-hard aluminium alloy specimen to verify the performance of the proposed method. Our experimental results show that a DIC with a specific shape function can be used to accurately and efficiently calculate the SIF. Furthermore, we also present a practical application of our proposed method for determining the SIF, crack propagation angle and crack tip displacement. © 2017, Tianjin University and Springer-Verlag Berlin Heidelberg.

E.O.威尔逊与生物多样性保护

1980年,《哈佛杂志》(Harvard Magazine)的编辑邀请了7位哈佛大学教授,请他们提出未来10年全球即将面对的最大难题。其中4人提出贫穷问题,理由分别是人口过度膨胀、乡村人潮大举涌入城市,以及资本主义盛行带来的贫富差距加剧。第5位教授把焦点放在美国自身,提出福利国家和政府管控过度的议题。

海洋保护区管理与保护成效评估的方法与进展

全球物种多样性的持续下降使得生物多样性保护面临巨大挑战,海洋生物多样性的保护任务尤其艰巨。海洋保护区是保护生物多样性的有效方式之一,如何对其成效进行评估是当前研究热点。然而,目前针对海洋保护区的评估体系较少,而且评估指标多侧重于管理成效。近年来随着全球生物多样性监测网络和数据库的建立,以及多种新技术(如遥感、声呐系统、卫星追踪、基因组学等)在海洋生物多样性监测中的应用,使得从生态系统到基因水平的多层次连续监测成为可能。基于此,建议未来我国海洋保护区成效评估应在充分利用新技术方法的基础上,加强长期科学监测,建立并完善生物多样性监测数据库和信息共享机制,发展跨学科的综合保护成效评估体系,加强基于生物多样性监测的保护成效评估。

新冠肺炎时期公众对野生动物消费和贸易意愿的调查

新冠肺炎疫情的暴发,使得对野生动物的消费与贸易中的公共健康安全问题引起广泛关注。为了给相关的立法和政策制定提供参考,我们通过网络对于全国及部分海外华人发放问卷进行了调查,共收回74,040份有效问卷。根据问卷调查结果,本文对普通公众对于野生动物消费和贸易立法意愿及影响因素进行了分析。研究结果包括:(1)公众对全面取缔野味餐馆和集市、禁止消费野味、禁止野生动物及其制品的买卖以及禁止野生动物商业性活体展演的立法动议持赞成态度的比例均超过90%;(2)现有野生动物消费群体经历新冠肺炎疫情后倾向于停止消费行为;(3)曾经消费野生动物或周围有人从事野生动物相关产业的群体相比其他人群更有可能不支持全面禁止对野生动物的消费和贸易。结果表明,全国人民代表大会常务委员会禁食野生动物的决定和修改野生动物保护法的动议在受高等教育者和城镇居民中有良好的公众基础。

Three-in-one to enhance visible-light driven photocatalytic activity of BiOCl: Synergistic effect of mesocrystalline stacking superstructure, porous nanosheet and oxygen vacancy

Simultaneously integrating mesocrystalline stacking superstructures,porous nanosheets and defective oxygen vacancies(OVs)into BiOCl crystals is an available strategy to enhance the visible-light-driven photocatalytic activity.Herein,we report a facile etching agent-assisted hydrothermal approach to achieve one-pot fabrication of mesocrystalline BiOCl porous nanosheet stacking superstructures with defective OVs,which show high catalytic activities towards to the visible-light-driven degradation of organic dyes.The formation of stacking superstructure in a mesocrystalline BiOCl is responsibility for increasing the transport of charge carriers.Experimental results and theoretical calculations suggest that the presence of OVs is beneficial to tuning the energy band structure for the improvement of visible light harvesting,prolonging the lifetime and enhancing the oxidation activity of photogenerated charge carriers.Additionally,the porous morphology and thin nanosheet building block could supply abundant active sites for photocatalysis.This research might arouse in-depth investigations on the development of novel precursor-modified strategy for the synthesis of high-active BiOX(X¼Cl,Br and I)-based photocatalysts.