检索结果-南通市图书馆

Selective electrochemical production of hydrogen peroxide at zigzag edges of exfoliated molybdenum telluride nanoflakes

在线全文

学校读者我要写书评

暂无评论

national Science Review 2020年第8期7卷 1360-1366页

作者： xuan Zhao Yu Wang Yunli Da Xinxia Wang Tingting Wang Mingquan.xu Xiaoyun he Wu Zhou Yafei Li Jonathan n.Coleman Yanguang Li Institute of Functional nano and Soft Materials (FUnSOM) Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices Soochow University College of Chemistry and Materials Science Nanjing Normal University College of Material Science and Opto-Electronic Technology University of Chinese Academy of Sciences School of Physical Sciences and CAS Key Laboratory of Vacuum Sciences University of Chinese Academy of Sciences School of Physics CRANN and AMBER Centers Trinity College Dublin

The two-electron reduction of molecular oxygen represents an effective strategy to enable the green, mild and on-demand synthesis of hydrogen peroxide. Its practical viability, however, hinges on the development of advanced electrocatalysts, preferably composed of non-precious elements, to selectively expedite this reaction, particularly in acidic medium. Our study here introduces 2H-MoTe;for the first time as the efficient non-precious-metal-based electrocatalyst for the electrochemical production of hydrogen peroxide in acids. We show that exfoliated 2H-MoTe;nanoflakes have high activity(onset overpotential ～140 mV and large mass activity of 27 A g;at 0.4 V versus reversible hydrogen electrode), great selectivity（H;O;percentage up to 93%） and decent stability in 0.5 M H;SO;. Theoretical simulations evidence that the high activity and selectivity of 2H-MoTe;arise from the proper binding energies of HOO;and O;at its zigzag edges that jointly favor the two-electron reduction instead of the four-electron reduction of molecular oxygen.

关键词： hydrogen peroxide production non-precious-metal-based electrocatalyst molybdenum telluride liquid phase exfoliation zigzag edges

Structure Characterization of Fluorosilicone Oils

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

China Petroleum Processing & Petrochemical Technology 2011年第4期13卷 53-57页

作者： Yang Jiedan Yang he xu Jing Li Hangquan Beijing University of Chemical Technology Beijing 100029 SInOPEC Research Institute of Petroleum Processing Beijing 100083

Fluorosilicone oil is polysiloxane with alkyl side chains containing fluorine, and because of its excellent thermal oxidation stability, cold flow property and cryogenic property, it can be widely used as a high temperature lubricant in the field of military aerospace industry. Two kinds of fluorosilicone oils, FSiO-a and FSiO-b, were synthesized by different pro- cessing means. FTICR MS was used to collect the information on composition and structure of the two polymers, respec- tively. The test results show that the two fluorosilicone oils have different contents of fluorine-containing chain segments (m/ n value), the maximum distribution of m/n value of FSiO-a oil ranges from 0.22 to 0.25, and that of FSiO-b oil ranges from 0.4 to 0.67. Difference in synthesis techniques makes this discrepancy and affects the quality and thermal stability of the fluoro- silicone oils.

关键词： fluorosilicone oil molecular structure lubricity antioxidant

Exploratory study of betavoltaic battery using ZnO as the energy converting material

在线全文

学校读者我要写书评

暂无评论

nuclear Science and Techniques 2019年第4期30卷 62-69页

作者： Xiao-Yi Li Jing-Bin Lu Yu-Min Liu xu xu Rui he Ren-Zhou Zheng College of Physics Jilin University

Third-generation-semiconductor zinc oxide is utilized as an energy converting material in a betavoltaic battery, where 0.06 Ci^(63) ni and 8 Ci^(147) Pm are used as the beta sources. Based on a Monte Carlo simulation, the full scales of the devices are derived as 17 and 118 lm,respectively, for both sources. The influences of semiconductor doping concentrations on the electrical properties of the devices are analyzed. For a typical doping concentration n_A= 10^(17) cm^(-3), n_D= 10^(16) cm^(-3), the conversion efficiencies are 7.177% and 1.658%, respectively, using63 ni and147 Pm sources. The calculation results of energy deposition in materials for the two sources show that the doping concentrations drop to 1 × 10^(13)–5×10^(14) cm^(-3) and 1 × 10^(12)–5×10^(13), and accordingly, the energy conversion efficiencies rise to 14.212% and 18.359%, respectively.

关键词： Radioisotope Beta voltaic effect Zinc oxide nuclear battery Monte Carlo simulation

Use of ^(15)n stable isotope to quantify nitrogen transfer between mycorrhizal plants

在线全文

学校读者我要写书评

暂无评论

Journal of Plant Ecology 2009年第3期2卷 107-118页

作者： Xinhua he Minggang xu Guo Yu Qiu Jianbin Zhou School of Life Sciences Yunnan Normal UniversityKunmingYunnan 650092China School of Plant Biology(M084) University of Western AustraliaCrawleyWestern Australia 6009Australia Institute of Agricultural Resources and Regional Planning Chinese Academy of Agricultural SciencesBeijing 100081China Key Laboratory for Environmental and Urban Sciences Shenzhen Graduate SchoolPeking UniversityShenzhen 518055China State Key Laboratory of Earth Surface Processes and Resource Ecology Beijing Normal UniversityBeijing 100875China College of Resource and Environmental Sciences Northwest A&F UniversityYanglingShaanxi 712100China

Aims Mycorrhizas(fungal roots)play vital roles in plant nutrient acquisition,performance and productivity in terrestrial *** mycorrhizas(AM)and ectomycorrhizas(EM)are mostly important since soil nutrients,including nH+4,nO3 and phosphorus,are translocated from mycorrhizal fungi to *** species,genera and even families of plants could be interconnected by mycorrhizal mycelia to form common mycorrhizal networks(CMns).The function of CMns is to provide pathways for movement or transfer of nutrients from one plant to *** the past four decades,both ^(15)n external labeling or enrichment(usually expressed as atom%)and ^(15)n naturally occurring abundance(d^(15)n,&)techniques have been employed to trace the direction and magnitude of n transfer between plants,with their own advantages and *** Findings The heavier stable isotope ^(15)n is discriminated against 14n during biochemical,biogeochemical and physiological processes,due to a greater atomic *** general,non-n2-fixing plants had greater d^(15)n values than n2-fixing(;0&)*** d^(15)n often varied by 5 to 10&in the order:non-mycorrhizas/AMs>EMs>ericoid *** in d^(15)n(&)or ^(15)n(atom%)values could thus provide n transfer information between plants.A range of between 0 to 80%of one-way n transfer had been observed from n2-fixing mycorrhizal to non-n2-fixing mycorrhizal plants,but generally less than or around 10%in the reverse ***-to-plant n transfer may provide practical implications for plant performance in n-limited *** that n translocation or cycling is crucial,and the potential benefits of n transfer are great in both agricultural and natural ecosystems,more research is warranted on either oneway or two-way n transfers mediated by CMns with different species and under field conditions.

关键词： ^(15)n enrichment ^(15)n natural abundance(^(15)n) ^(15)n stable isotope common mycorrhizal networks(CMns) nitrogen transfer

A 4H–SiC betavoltaic battery based on a ^(63)ni source

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

nuclear Science and Techniques 2018年第11期29卷 295-303页

作者： Yu-Min Liu Jing-Bin Lu Xiao-Yi Li xu xu Rui he Hui-Dong Wang College of Physics Jilin University

A 4H–SiC–^(63)ni p–n-junction-based betavoltaic battery is investigated. The Monte Carlo method is used to simulate the self-absorption effect of the ^(63)ni source, the backscattering process, and the transport of beta particles in 4H–SiC material. The main factors that affect the energy conversion efficiencies of the cell are analyzed. Based on the simulation results, it can be calculated that, when the thickness of the ^(63)ni source increases from 2 ×10^(-3) to10 lm, the theoretical maximum device conversion efficiency increases from 16.77 to 23:51% and the total conversion efficiency decreases from 16.73 to 1:48%.Furthermore, a feasible design with a maximum output power density of 0:36 μW=cm^2 and an optimal device conversion efficiency of 23:5% is obtained.

关键词： 4H–SiC–63ni betavoltaic battery p–n junction Energy conversion efficiency

Diversifying Top-κRoutes with Spatial Constraints

在线全文

学校读者我要写书评

暂无评论

Journal of Computer Science & Technology 2019年第4期34卷 818-838页

作者： Hong-Fei xu Yu Gu Jian-Zhong Qi Jia-Yuan he Ge Yu College of Computer Science and Engineering Northeastern UniversityShenyang 110169China Department of Computing and Information Systems The University of MelbourneMelbourneVIC 3010Australia

Trip recommendation has become increasingly popular with the rapid growth of check-in data in location-based social *** existing studies focused only on the popularity of *** this paper,we consider further the usability of trip recommendation results through spatial *** thereby formulate a new type of queries named spatial diversified top-κroutes(SDκR)*** type of queries finds k trip routes with the highest popularity,each of which starts at a given starting point,consumes travel time within a given time budget,and passes through points of interest(POIs)of given *** two trip routes returned are diversified to a certain degree defined by the spatial distance between the two *** show that the SDkR problem is *** propose two precise algorithms to solve the *** first algorithm starts with identifying all candidate routes that satisfy the query constraints,and then searches for theκ-route combination with the highest *** second algorithm identifies the candidate routes and builds up the optimalκ-route combination progressively at the same ***,we propose an approximate algorithm to obtain even higher query efficiency with precision *** demonstrate the effectiveness and efficiency of the proposed algorithms on real *** experimental results show that our algorithms find popular routes with diversified POI *** approximate algorithm saves up to 90%of query time compared with the baseline algorithms.

关键词： trip recommendation spatial diversity route search check-in data

Selective Insertion in Copolymerization of Ethylene and Styrene Catalyzed by Half-Titanocene System Bearing Ketimide Ligand： A Theoretical Study

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Chemistry 2017年第11期35卷 1731-1738页

作者： Xiaowei xu Gaohong he ning-ning Wei Ce Hao Yu Pan State Key Laboratory of Fine Chemicals School of Petroleum and Chemical Engineering Dalian University of Technology Panjin Liaoning 124221 China School of Life Science and Medicine Dalian University of Technology Panjin Liaoning 124221 China

The copolymerization of ethylene and styrene can be efficiently carried out by using Cp＊TiCl2（n=CtBu2）/ MAO （Cp＊=η5-C5Me5） system, yielding the poly（ethylene-co-styrene）s with isolated styrene units. In order to in- vestigate the reasons for formation of the structure, the mechanism of copolymerization, especially the selective in- sertion of ethylene and styrene, is studied in detail by density functional theory （DFT） method. At the initiation stage, insertion of ethylene is kinetically more favorable than insertion of styrene, and insertion of styrene kinet- ically and thermodynamically prefers 2,1-insertion. That is different from the conventional half-titanocene system, in which the 1,2-insertion is favorable. At chain propagation stage, the computational results suggest that the con- tinuous insertion of styrene is hard to occur at room temperature due to the high free energy barriers （28.90 and 35.04 kcal/mol for 1,2-insertion, and 29.15 and 34.00 kcal/mol for 2,1-insertion） and thermodynamically unfavora- ble factors in two different conditions. That is mainly attributed to the steric hindrance between the coming styrene and chain-end styrene or ketimide ligand. The computational results are in good agreement with the experimental data.

关键词： polymerization mechanism density functional theory (DFT) half-tianocene copolymerization selec-tive insertion

Palladium installed copper-organic framework for C–C coupling reactions

维普期刊数据库评论

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 Chemistry 2025年

作者： Yu-Mei Wang Mei-Xia Tao Kai-Ming Mo xu Chen Shu-Hua Zhong Elena S Shubina Guo-Hong ning Dan Li College of Chemistry and Materials Science Guangdong Provincial Key Laboratory of Supramolecular Coordination ChemistryJinan University A.n.nesmeyanov Institute of Organoelement Compounds Russian Academy of Sciences

The formation of C–C bonds is a crucial aspect of organic synthesis. Synthesists' long-term objective is to identify novel catalysts to optimize reaction systems based on traditional transition metal catalysis. This study explores the synthesis and catalytic potential of palladium-installed covalent metal-organic frameworks(CMOFs) based on copper cyclic trinuclear units(Cu-CTUs). By incorporating palladium ions into the imine-based framework JnM-7 through a straightforward immersion method, we achieved a notable enhancement in catalytic activity for critical C–C coupling reactions, including C–H arylation and Sonogashira cross-coupling. The resulting JnM-7-Pd demonstrated remarkable stability and recyclability, maintaining its efficiency over at least three cycles without any decline in efficiency.

关键词：

Performance analysis of ARQ schemes with code combining over nakagami-m fading channel

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

The Journal of China Universities of Posts and Telecommunications 2009年第5期16卷 14-19页

作者： xu Wen-bo nIU Kai LIn Jia-ru he Zhi-qiang School of Information and Telecommunication Engineering Beijing University of Posts and Telecommunications Beijing 100876 China

This article investigates the performance of hybrid automatic repeat request （HARQ） with code combining over the ideally interleaved nakagami-m fading channel. Two retransmission protocols with coherent equal gain code combining are adopted, where the entire frame and several selected portions of the frame are repeated in protocols I and II, respectively. Protocol II could be viewed as a generalization of the recently proposed reliability-based HARQ. To facilitate performance analysis, an approximation of the product of two independent nakagami-m distributed random variables is first developed. Then the approximate analysis is utilized to obtain exact frame error probability （FEP） for protocol I, and the upper bound of the FEP for protocol II. Furthermore, the throughput performance of both two protocols is presented. Simulation results show the reliability of the theoretical analysis, where protocol II outperforms protocol I in the throughput performance due to the reduced amount of transmitted information.

关键词： code combining HARQ nakagami-m fading performance analysis