检索结果-南通市图书馆

Mobility of rhenium and selenium during chemical weathering and their implication for petrogenic organic carbon oxidation

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China Earth Sciences 2024年第3期67卷 740-750页

作者： Yuhong ZHANG Jin WANG Yuanxin QU Chao Zhu Zhangdong JIN State Key Laboratory of Loess and Quaternary Geology Institute of Earth EnvironmentChinese Academy of SciencesXi'an 710061China University of Chinese Academy of Sciences Beijing 100049China Xi'an Institute for Innovative Earth Environment Research Xi'an 710061China Institute of Global Environmental Change Xi'an Jiaotong UniversityXi'an 710049China

The oxidative weathering of petrogenic organic carbon(OC_(petro)) is an important source of carbon dioxide(CO_(2)) into the atmosphere on geological timescales and significantly influences the carbon cycle and global climate change. However, at present, a robust proxy to assess OC_(petro)oxidation is lacking. Riverine rhenium(Re) has emerged as a potential proxy to trace OC_(petro)oxidation, but little is known about Re sources and its relationship with OC_(petro)oxidation. To better understand the robustness of this proxy, we analyzed a shale weathering profile from the early Cambrian Shuijingtuo Formation in Chengkou County, Chongqing City, to address the mobility of Re and selenium(Se) and their relationship with the oxidation of OC_(petro)by analyses of the elemental variation and sequential extraction. The results showed that the chemical index of alteration(CIA)increases from the fresh bedrock to the weathered sections, indicating enhanced weathering intensity. Based on the sequential extraction and mass transfer coefficients(τ), Re and Se mainly exist in the organic phase of shale and are paired lost with OC_(petro) during weathering, with no obvious correlation with sulfide minerals. Furthermore, the different proportions of Re and Se loss with OC_(petro) loss can be attributed to their different geochemical behaviors during weathering. Our study supports Re as a robust proxy to trace OC_(petro) oxidation, whereas Se is the potential one. In the future, combined studies on various sedimentary rock profiles with catchment basins are needed to determine the sources of riverine Re and Se and their relationships with OC_(petro) oxidation.

关键词： Rhenium and selenium Shale Mobility OC_(petro) Chemical weathering

Post-spin crossing dynamics determine the regioselectivity in open-shell singlet biradical recombination

在线全文

学校读者我要写书评

暂无评论

Organic Chemistry Frontiers 2022年第4期9卷 995-1003页

作者： Min zhu chao Zheng State Key Laboratory of Organometallic Chemistry Shanghai Institute of Organic ChemistryChinese Academy of Sciences345 Lingling LuShanghai 200032China School of Physical Science and Technology ShanghaiTech University100 Haike RoadShanghai 201210China

Radical recombination is among the fastest reactions in organic chemistry.Achieving high levels of selectivity in this type of reaction is rather challenging.In a recent report on visible-light-induced dearo-mative cycloaddition of pyrrole-tethered vinylcyclopropanes,extraordinary regioselectivity was observed during the intramolecular open-shell singlet biradical recombination step.

关键词： singlet radical regioselectivity

Numerical investigations on gas-solid flow in circulating fluidized bed risers using a new cluster-based drag model

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Particuology 2022年第4期20卷 9-23页

作者： Zeneng Sun chao Zhang Jesse zhu Department of Chemical and Biochemical Engineering.The University of Western Ontario LondonOntarioN6A 3K7Canada Department of Mechanical and Materials Engineering The University of Western OntarioLondonOntarioN6A 3K7Canada

A cluster-based drag model is proposed for the gas-solid circulating fluidized bed(CFB)riser by including the cluster information collected from image processing and wavelet analysis into the calculation of system drag.The performance of the proposed drag model is compared with some commonly used drag models.A good agreement with the experimental data is achieved by the proposed cluster-based drag model.Error analysis of the proposed cluster-based drag model based on the local distributions of solids holdup and particle velocity is conducted.The clustering phenomenon in the low-density and high-density CFB risers and the effect of the cluster size on the simulation accuracy are also numerically studied by the proposed drag model.

关键词： Drag model Clustering effect Gas-solid flow structures Circulating fluidized bed

The soil Microbial Carbon Pump as a new concept for terrestrial carbon sequestration

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China Earth Sciences 2021年第4期64卷 545-558页

作者： chao LIANG Xuefeng zhu Institute of Applied Ecology Chinese Academy of SciencesShenyang 110016China

Soil is a huge terrestrial carbon pool, which has higher carbon storage than the sum of atmospheric and terrestrial vegetation carbon. Small fluctuations in soil carbon pool can affect regional carbon flux and global climate change. As soil organic carbon plays key roles in soil carbon storage and sequestration, studying its composition, sources and stability mechanism is a key to deeply understand the functions of terrestrial ecosystem and how it will respond to climate changes. The recently-proposed concept of soil Microbial Carbon Pump(MCP) emphasizes the importance of soil microbial anabolism and its contributions to soil carbon formation and stabilization, which can be applied for elucidating the source, formation and sequestration of soil organic carbon. This article elaborates MCP-mediated soil carbon sequestration mechanism and its influencing factors, as well as representative scientific questions we may explore with the soil MCP conceptual framework.

关键词： Soil Microbial Carbon Pump Entombing Effect Carbon cycling Soil microorganisms Soil organic carbon Microbial residues Amino sugars Soil fauna

Expedient Trifluoromethylacylation of Styrenes Enabled by Photoredox Catalysis

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemistry 2022年第1期40卷 59-64页

作者： Lu Wang Heng Zhang Chuan zhu chao Feng Technical Institute of Fluorochemistry(TIF) Institute of Advanced Synthesis(IAS)School of Chemistry and Molecular EngineeringNanjing Tech University30 South Puzhu RoadNanjingJiangsu 211816China

Herein,we disclosed a photoredox enabled protocol for trifluoromethylacylation of styrenes through a radical-carboanion cascade and subsequent oxidation.With a broad range of aldehydes and inexpensive Langlois reagent as acyl and CF3 precursor,respectively,the alkene motif could be readily converted into β-trifluoromethyl ketones in moderate to good yields and with excellent regioselectivity.Besides CF3,di-,mono-and non-fluorinated C-radicals were revealed amenable in this reaction,providing good opportunity for the construction of structurally diverse ketones of interest in pharmaceutical research.Additionally,the utility of this protocol was further demonstrated by successful extension to trifluoromethylarylation and-alkylation by employing arylcyanide or acrylates in place of carbonyls.

关键词： Trifluoromethylacylation Alkenes Photocatalysis CF_(3)radical Radical-polar crossover

Investigation on bonding interfaces of an SA508 steel billet manufactured by additive forging

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research(International) 2022年第12期29卷 2016-2023页

作者： Xin-jin Zhang Tian-sheng Wang Zhi-Chao Zhu Lin zhu State Key Laboratory of Metastable Materials Science and Technology Yanshan UniversityQinhuangdao 066004HebeiChina China First Heavy Industries Co. Ltd.Qiqihaer 161042HeilongjiangChina

An experimental steel billet of SA508 reactor pressure vessel material was manufactured by the additive forging method,and microstructure and mechanical properties of the hot-compression bonding interface were systematically investigated.The result indicated that oxidation levels of bonding interfaces were well controlled using vacuum electron beam welding.It was easy to discriminate interfaces from base materials during the optical microstructure observation,since interfaces were characterized by grain or phase boundaries in a straight line.Test results of uniaxial tensile experiments(at 20 and 350°C)and Charpy V-notched impact tests(at 0 and 20°C)showed that fracture behaviour of all those samples appeared at the base material,and bonding interfaces showed advantage of strength and toughness at the forge bonding state.

关键词： Reactor pressure vessel Additive forging Interfacial microstructure Mechanical property

Overview of composition and technique process study on 2:17-type Sm-Co high-temperature permanent magnet

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Rare Metals 2021年第4期40卷 790-798页

作者： chao Wang Ming-Gang zhu Division of Functional Materials Central Iron and Steel Research InstituteBeijing 100081China

Sm-Co permanent magnets are widely used in aerospace equipments,tubes,sensors and hybrid electric vehicles due to their excellent magnetic properties at both room and high temperatures.Compared to that of Nd-Fe-B magnets,the capability of reliably operating at temperatures up to 500℃ is the biggest preponderance of Sm-Co permanent magnets.However,the reliable high-temperature magnetic properties are susceptible to composition and technique processes.So,appropriate composition and matched technique processes are prerequisites for good high-temperature magnetic properties.This review mainly emphasizes the influences of Sm,Fe,Cu and Zr contents and technique processes on development of high-temperature performance and discusses the controversial hightemperature coercivity mechanism of 2:17-type high-temperature Sm-Co magnets.

关键词： 2-type Sm-Co magnet High temperature Coercivity temperature coefficient Coercivity mechanism

Selective C-C bonds formation,N-alkylation and benzo[d]imidazoles synthesis by a recyclable zinc composite

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2022年第1期33卷 266-270页

作者： Guanxin zhu Zheng-chao Duan Haiyan zhu Dongdong Ye Dawei Wang The Key Laboratory of Synthetic and Biological Colloids Ministry of EducationSchool of Chemical and Material EngineeringJiangnan UniversityWuxi 214122China State Key Laboratory of Pulp and Paper Engineering South China University of TechnologyGuangzhou 510640China School of Chemical and Environmental Engineering Hubei Minzu UniversityEnshi 445000China

Earth abundant metals are much less expensive,promising,valuable metals and could be served as catalysts for the borrowing hydrogen reaction,dehydrogenation and heterocycles synthesis,instead of noble metals.The uniformly dispersed zinc composites were designed,synthesized and carefully characterized by means of XPS,EDS,TEM and XRD.The resulting zinc composite showed good catalytic activity for the N-alkylation of amines with amines,ketones with alcohols in water under base-free conditions,while unsaturated carbonyl compounds could also be synthesized by tuning the reaction conditions.Importantly,it was the first time to realize the synthesis of 2-aryl-1H-benzo[d]imidazole derivatives by using this zinc composite under green conditions.Meanwhile,this zinc catalyst could be easily recovered and reused for at least five times.

关键词： Unsymmetrical Zinc Borrowing hydrogen Recyclability Selective

Effects of Pilot Fuel Ratio on Combustion Process:Flow Field Structure and Pollutant Emissions

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 2023年第6期32卷 2321-2335页

作者： ZONG chao JI Chenzhen CHENG Jiaying zhu Tong Postdoctoral Station of Mechanical Engineering Tongji UniversityShanghai201804China School of Mechanical Engineering Tongji UniversityShanghai201804China

As the only controllable means of a micro gas turbine(MGT)combustor during unit operation,pilot fuel ratio(PFR)is the key to achieving stable combustion and low pollutant emission.This paper discusses the influence of PFR on the inner flow field structure and pollutant emissions.The steady-state three-dimensional RANS method with a 40-step reduced methane-air kinetics mechanism is used to study the reaction flow field and species field with PFR of 9.0%,12.7%,15.2%and 17.6%.Results show that,with the decrease in PFR,the axial velocity and temperature near the central axis of the combustion chamber show a tendency to decrease.A similar separation phenomenon occurred in the core pyrolysis reaction zone(measured by HCO)and oxidation zone(measured by OH),which is more conducive to promoting the oxidation of CO.The quantitative effect of the pilot flame on nitrogen oxides(NO_(x))was separated by using inert gas instead of nitrogen in combustion air.It was found that the NOx produced by the pilot flame under the operation condition with a PFR of 9.0%was 3.2×10^(−6),accounting for 17.4%of the total NOx emission,which was twice that of PFR.

关键词： micro gas turbine pilot fuel ratio flow field structure carbon monoxide nitrogen oxide