Mechanical analysis of deepwater drilling riser system based on multibody system dynamics

A multibody system including a drilling riser system,tensioners and a floating platform is key equipment for offshore oil and gas drilling.Most of the previous studies only focus on the drilling riser system rather than the multibody system.Mechanical characteristics of the deepwater drilling riser system cannot be analyzed accurately in a simplified model.Therefore,a three-dimensional multibody analysis program is developed.The static and dynamic characteristics of the deepwater drilling riser system under different platform motions are analyzed based on the developed program.The results show that the static displacement of the riser system with tensioners is smaller than that without tensioners,which means the tensioners can suppress the deformation of the riser system.Under surge and sway motions of the platform,the dynamic displacement of the riser system with tensioners is also smaller than that without tensioners due to the tensioner suppression effect.Besides,the heave motion induces a uniform axial vibration of the riser system,while roll and pitch motions excite the riser system to vibrate laterally.Compared with the stress amplitude due to surge and sway motions,the stress amplitude of the riser system due to heave,roll and pitch motions is relatively small but cannot be neglected.

Emerging dual-atomic-site catalysts for electrocatalytic CO_(2)reduction

The electrochemical CO_(2)reduction reaction(CO_(2)RR)to yield high-value added fuels and chemicals provides a promising approach towards global carbon neutrality.Constant endeavors have been devoted to the exploration of high-efficiency catalyst with rapid reaction kinetics,low energy input,and high selectivity.In addition to the maximum metal atomic utilization and unique catalytic performance of single-atom catalyst(SAC),dual-atomic-site catalysts(DASCs)offer more sophisticated and tunable atomic structure through the modulations of another adjacent metal atom,which can bring new opportunities for CO_(2)RR as a deeper extension of SACs and have recently aroused surging interest.In this review,we highlight the recent advances on DASCs for enhancing CO_(2)RR.First,the classification,synthesis,and identification of DASCs are provided according to the geometric structure and electronic configuration of dual-atomic active sites.Then,the catalytic applications of DASCs in CO_(2)RR are categorized based on marriage-type,hetero-nuclear,and homo-nuclear dual-atomic sites.Particularly,the structure-activity relationship of DASCs in CO_(2)RR is elaborately summarized through systematically analyzing the reaction pathways and the atom structures.Finally,the opportunities and challenges are proposed for inspiring the design of future DASCs with high structural accuracy and high CO_(2)RR activity and selectivity.

基因组学技术在生物多样性保护研究中的应用

在分子生物学、细胞生物学、微生物学、遗传学等学科的推动下,生物多样性研究从仅关注宏观表型的博物学,迅速演化为涵盖生态系统、物种和遗传多样性等多个维度的综合性生命科学。组学技术,尤其是DNA测序技术的更新和发展,使获取DNA序列所需的成本大幅下降,促进了近年来其在生物多样性研究中取得的一系列令人瞩目成就。本文将从物种水平的遗传多样性和群落水平的物种多样性两个层面总结和介绍与DNA相关的组学技术在生物多样性研究中的一些创新和应用。其中,物种水平主要是总结单一个体的基因组和单物种多个体在时空多个维度上的群体遗传研究;而群落水平的物种多样性层面主要总结现有的分子鉴定技术(metabarcoding,eDNA,iDNA等),以及上述新技术在群落多样性评估、旗舰保护物种监测以及物种间相互作用关系等研究中的应用。