摘要：Photoredox catalysis has become an indispensable solution for the synthesis of small organic ***,the precise construction of single-atomic active sites not only determines the catalytic performance,but also avails the understanding of structure–activity ***,we develop a facile approach to immobilize single-atom Ni sites anchored porous covalent organic framework(COF)by use of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)trianiline and 2,6-diformylpyridine(Ni SAS/TD-COF).Ni SAS/TDCOF catalyst achieves excellent catalytic performance in visible-light-driven catalytic carbon–nitrogen cross-coupling reaction between aryl bromides and amines under mild *** reaction provides amine products in excellent yields(71%–97%)with a wide range of substrates,including aryl and heteroaryl bromides with electron-deficient,electron-rich and neutral ***,Ni SAS/TD-COF could be recovered from the reaction mixture,corresponding to the negligible loss of photoredox performance after several *** work provides a promising opportunity upon rational design of single-atomic active sites on COFs and the fundamental insight of photoredox mechanism for sustainable organic transformation.

摘要：Pyridinic N is widely regarded as the active center while pyrrolic N has low‐activity in metal‐free N‐doped carbon for electrocatalytic CO_(2) reduction reaction(CO_(2)RR)to CO,but this viewpoint remains open to *** this study,through density functional theoretical calculations,we first illustrate that the intrinsic activity of pyrrolic N is high enough for effectively catalyzing CO_(2)RR,however,due to the interplay with the neighboring pyridinic N sites,the activity of pyrrolic N is dramatically ***,experimentally,metal‐free N‐doped carbon spheres(NCS)electrocatalysts without significant pyridinic N content are prepared for CO_(2)*** pyrrolic N in NCS shows a direct‐positive correlation with the performance for CO_(2)RR,representing the active center with high *** optimum NCS could produce syngas with a wide range of CO/H_(2) ratio(0.09 to 12)in CO_(2)RR depending on the applied potential,meanwhile,the best selectivity of 71%for CO can be *** adding a small amount of pyridinic N to the optimum NCS dramatically decreases the activity for CO_(2)RR,further verifying the suppressed activity of pyrrolic N sites by the neighboring pyridinic N *** work reveals the interaction between a variety of N species in N‐doped carbon,and the potential of pyrrolic N as the new type of active site for electrocatalysts,which can improve our understanding of the electrocatalysis mechanism and be helpful for the rational design of high‐efficient electrocatalysts.

摘要：Binuclear ruthenium complexes bearing the2,2'‐bipyridine‐6,6'‐dicarboxylate(bda)ligand have been demonstrated to be highly active catalysts towards water oxidation with CeIV as an ***,the catalytic properties of ruthenium dimers have not yet been explored for visible light‐driven water ***,the photocatalytic performance of a dipyridyl propane‐bridged ruthenium dimer2was investigated in comparison with its monomeric precursor,[Ru(bda)(pic)2](1),in CH3CN/phosphate buffer mixed solvent in a three‐component system including a photosensitizer and a sacrificial electron *** results showed that the activity of each catalyst was strongly dependent on the content of CH3CN in the phosphate buffer,which not only affected the driving force for water oxidation,but also altered the kinetics of the reaction,probably through different mechanisms associated with the O–O bond *** a result,dimer2showedsignificantly higher activity than monomer1in the solvent containing a low content of CH3CN,and comparable activities were attained with a high content of CH3CN in the *** the optimal conditions,complex2achieved a turnover number of638for photocatalytic O2evolution.

摘要：A molecular [Ru(bda)]-type(bda = 2,2’-bipyridine-6,6’-dicarboxylate) water oxidation catalyst with 4-vinylpyridine as the axial ligand(Complex 1) was immobilized or co-immobilized with 1-(trifluoromethyl)-4-vinylbenzene(3 F) or styrene(St) blocking units on the surface of glassy carbon(GC) electrodes by electrochemical polymerization, in order to prepare the corresponding poly-1@GC, poly-1+P3 F@GC, and poly-1+PSt@GC functional electrodes. Kinetic measurements of the electrode surface reaction revealed that [Ru(bda)] triggers the O–O bond formation via(1) the radical coupling interaction between the two metallo-oxyl radicals(I2 M) in the homo-coupling polymer(poly-1), and(2) the water nucleophilic attack(WNA) pathway in poly-1+P3 F and poly-1+PSt copolymers. The comparison of the three electrodes revealed that the second coordination sphere of the water oxidation catalysts plays vital roles in stabilizing their reaction intermediates, tuning the O–O bond formation pathways and improving the water oxidation reaction kinetics without changing the first coordination structures.

摘要：我国是小型水果种植大国,小型水果外形类椭球状,如冬枣、桂圆、金桔、杨梅、李子、圣女果等,深受广大消费者喜爱。为解决小型水果采收过程中效率低、危险系数大、采收机具功能单一的问题,根据小型水果外形结构,设计出集采摘、枝叶分离、分级于一体的小型水果多功能采收装置。应用仿人手的梳齿采摘爪实现小型水果采摘;V形布置的橡胶对辊达到枝叶分离目的;分层布置的圆皮带实现果实分级。通过装置试验和响应面分析,确定梳齿采摘爪间距为16 mm,V形枝叶分离对辊转速为100 r/min,分级皮带转速为100 r/min,在此工作参数下,装置采摘效率高,枝叶残留率仅为2%,优于人工采摘,分级精度达到95%,果实破损率为0.2%。本装置集多功能于一体,结构简单,效率高,保障人身安全,提高小型水果采收机械化程度,为我国农业机械发展奠定基础。

摘要：随着大型集成芯片等电子设备的释热率不断升高,普通的微通道热沉(MHS)已很难满足其散热需求。自相似微通道热沉(SSHS)作为一种新的换热结构设计,与一般的微通道热沉(MHS)相比,具有更好的综合性能和应用前景,但SSHS内部依然存在一定的流量分配和换热不均等缺陷。为克服SSHS自身的缺陷,提高其工作性能,本文将原有的入口分流通道改为渐缩式设计,以缓解SSHS原型设计中流量分配不均的缺陷;同时,利用数值方法在分析各结构参数影响基础上进行优化设计。鉴于SSHS内每个换热单元结构均相同,选择了一个完整的换热单元进行模拟分析和参数优化,计算单元包含10个溢流通道、半个入口分流通道与半个出流通道。换热工质为水,单元的流量范围为0.27~0.90 kg/h,工作压力为常压,盖板热负荷为1 MW/m2,计算模型为层流模型(范围150~500)。数值分析结果表明:对于原型设计,入口分流通道末端存在较强烈的滞止效应,直接导致各溢流通道之间流量分配不均,溢流通道间的流量分配相差9.5~12.9倍,且流量分配不均直接导致换热不均,盖板外壁面的温差达到了10.8~12.1℃。通过将分流通道改为渐缩式斜坡结构,可以一定程度上消除滞止效应的影响。经过优化对比分析发现,随着斜坡角度的增加,流量分配的均匀性和换热均匀性均得到进一步提高,但同时也导致流动阻力有一定的增加。综合考虑后,确定斜坡角度为4.3°时,可在计算参数范围内使优化结构获得最佳的综合性能。虽然导致系统压降最大增加12%左右,但使流量分配从最大相差12.9倍降至仅相差2.7倍,平均换热均匀性提高了50%以上。改进和优化后的设计可为SSHS的推广应用提供参考和借鉴。

摘要：以美国10 MW熔盐实验堆(MSRE)为研究对象,设计空气冷却和水冷却2种非能动余热排出系统。通过建立相应的数学模型,采用C++语言编程,分别对系统的主要特性进行研究,并对2种系统的运行特性进行比较分析。结果表明,虽然空气冷却和水冷却均能满足系统的排热要求,并能形成稳定的自然循环,但从长期冷却性能方面看,空气冷却方案的综合性能更好。

摘要：在“碳达峰”、“碳中和”的目标背景下,绿色低碳、清洁高效成为资源开采的新要求,也对科学开采这一复杂系统问题的研究提出了新的方向。阐述了矿产资源开采理念的发展演化,综述了近年来国内外在科学开采方面的研究现状,构建了安全、高效、绿色、低碳、经济、科学管理“六位一体”的科学开采体系,丰富了科学开采的内涵和框架。从复杂科学问题的判断标准、科学开采体系的特征两方面进行推断,得出科学开采属于复杂问题,承载科学开采复杂问题的系统是复杂系统。以复杂科学的思路研究科学开采的复杂性,构建科学开采复杂系统模型,从顶层设计、中层连接和底层基础3个层次思考了实现科学开采的新途径,为实现矿产资源的科学开采提供了新的发展方向。

摘要：自相似微通道热沉(SSHS)作为一种新的换热结构设计,比一般的微通道热沉(MHS)具有更好的综合性能。前期工作通过将内部分流通道改为渐缩式斜坡结构,使内部流量分配不均受到了很大抑制。本文在此基础上,利用数值模拟方法进一步分析了微通道(溢流通道)形状对SSHS流动及传热过程的影响。计算结果表明,原设计中溢流通道内存在较大的低流速区,导致了不均匀的换热过程;将矩形截面微通道改为梯形截面,可以减小溢流通道内低速区的流通面积,从而使微通道内的流动和换热过程更加均匀;进一步对比分析发现,随着溢流通道顶部宽度mw减小,低流速区域占比进一步减小,换热均匀性有所提高;该结构优化方案对流动阻力的影响较小,流量在0.18~1.8kg/h范围内,流动阻力增加平均不超过5%,但换热均匀性平均提高15%左右。

摘要：为了提高现行船舶号灯在复杂光环境中的可识别性,更好地保障船舶夜航安全,运用色度学及半导体激光器的发光原理,设计了一种新型船舶号灯。选取长度大于等于50m的机动船的右舷灯和桅灯为实验对象,在三维实体建模软件(Lighttools)环境下建立右舷灯和桅灯的实体模型,并对这2种号灯的半导体激光器光谱区波长、光谱权重、功率、光线数量、光线追迹阈值等参数进行设置,模拟了不同接收距离处灯光的颜色属性。模拟结果表明:半导体激光号灯右舷灯颜色刺激纯度为1;半导体激光号灯中桅灯光色的色品坐标与参考白光(色品坐标为(1/3,1/3))接近,二者均符合《国际海上避碰规则》对号灯颜色属性的要求。