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Fluorescent carbon dots synthesized in solid phase and air for application in LEDs

Nano Research 2024年第9期17卷 8495-8503页

作者： Wei-Jie zheng Zhao-Nan Sun Yi-ming Wang huan-ming Xiong Department of Chemistry and Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials Fudan UniversityShanghai 200438China

Carbon dots(CDs)have been widely adopted as optical materials because of their excellent luminescent ***,most of the reported synthetic methods are conducted in solvents,especially hydrothermal/solvothermal reactions,leading to intractable problems such as toxic and flammable solvents,complex and inseparable by-products,and dangerously high pressures and ***-phase synthesis of CDs in air is an effective solution to overcome the above issues,but solid reactions always result in uncontrolled growth and agglomeration of *** this study,some inorganic salts are selected as catalysts for synthesizing CDs in solid states and air,which also play as dispersants to hinder CDs *** the meantime,some aromatic derivatives containing hydroxyl and amino groups are chosen as carbon sources,ground with the optimized catalyst,and then heated together in *** production yields are affected by the reaction time and reactant ratio,while the graphitization degrees of the CDs are determined by the reaction *** IG/ID value of their Raman spectra increases from 0.59 to 0.85,and the particle size decreases from 2.5 to 1.4 nm when the synthesis temperature is increased from 200 to 280℃.The as-prepared CDs show emission peaks ranging from 366 to 606 nm,with the photoluminescence(PL)quantum yield up to 53%.Their emission color variation mainly results from different carbon sources,which can be ascribed to the differences in the element composition,functional groups,and graphitic nitrogen content of these *** dispersing CDs of different concentrations into polyvinyl alcohol(PVA)and combining them with blue LEDs,cold,standard,and warm white light emitting devices(WLEDs)are prepared,with a color rendering index(CRI)up to *** the as-prepared CDs have antioxidant ability at high temperature,the as-prepared WLEDs have long lifespans,remaining the effective white luminescence after 72 h continuous work.

关键词： carbon dot solid-phase synthesis white LED photoluminescence inorganic salt catalysis

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Numerical investigation on dynamic response of the screen mesh in vibrating screening through DEM-FEM co-simulation

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Particuology 2024年第4期87卷 205-217页

作者： huan Zhang Xiao zheng Weimin Jing Key Laboratory of MetallurgicalEquipment and Control Technology Ministry of EducationWuhan University of Science and TechnologyWuhan430081 China Hubei Key Laboratory of Mechanical Transmssion and Manufacturing Engineering Wuhan University of Science and TechnologyWuhan430081China College of Mechanical and Vehicle Engineering Chongqing UniversityChongqing400044China

Dynamic response of the screen mesh is of great significance in the optimum vibrating screen *** this paper,based on the DEM-FEM co-simulation method,the effect of screening parameters on the dynamic response of the screen mesh is explored and the mechanism is revealed on the particle ***,a virtual experiment on a linear vibrating screen was carried out to analyze the screening pa-rameters'effect with both impact load and sustained stress inflicted on the screen ***,the time-domain evolution regularity of the screen mesh LVA(Local Vibration Amplitude)under different particle plugging conditions was investigated based on the ***,the influence of screening parameters on LVA and its distribution was *** results show that the screening parameters can greatly affect the screen mesh LVA and its distribution by changing the movement of the granular material and the particle penetration probability,which provides an important basis for the optimal design of the screen mesh and its supporting structure.

关键词： Vibrating screen Dynamic response DEM-FEM Screening parameters Local vibration amplitude

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Selective N-Methylation of N-Methylaniline with CO_(2) and H_(2) over Cu/In_(2)O_(3) Catalyst

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Chinese Journal of Chemistry 2024年第3期42卷 276-282页

作者： huan zheng Bo Qian Lin He State Key Laboratory for Oxo Synthesis and Selective Oxidation Lanzhou Institute of Chemical PhysicsChinese Academy of SciencesLanzhouGansu730000 China University of Chinese Academy of Sciences Beijing100049 China

N-Methylation of amines with CO_(2) and H2 is a potential approach for CO_(2) utilization because N-methylated amines can be used as solvents and organic intermediates. In_(2)O_(3)-supported Cu (Cu/In_(2)O_(3)) acts as an effective heterogeneous catalyst for N-methylation reaction of N-methylaniline (MA) with CO_(2) and H_(2),showing higher N,N-dimethylaniline (DMA) selectivity than other supported Cu catalysts. On one hand,the dispersion of Cu can be improved by the defective In_(2)O_(3) support. On the other hand,In_(2)O_(3) support is active in the dissociative adsorption of CO_(2) through C—O bond breaking. In addition,the H_(2) dissociation ability of In_(2)O_(3) can also be enhanced by Cu. The combination of Cu and In_(2)O_(3) is effective in the activation of CO_(2),the adsorption of intermediate N-methylformanilide (MFA),the hydrogenation of MFA to DMA and the prohibition of C—N bond cleavage side reactions,thereby enhancing the reaction rate of MA conversion and the selectivity to DMA.

关键词： N-Methylation CO_(2) Cu/In_(2)O_(3) Supported catalysts Heterogeneous catalysis

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An improved analysis method for assessing the nuclear-heating impact on the stability of toroidal field magnets in fusion reactors

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Nuclear Science and Techniques 2024年第6期35卷 163-176页

作者： Yu-Dong Lu Jin-Xing zheng Xu-Feng Liu huan Wu Jian Ge Kun Xu ming Li Hai-Yang Liu Lei Zhu Fei Liu Institute of Plasma Physics Hefei Institutes of Physical ScienceChinese Academy of SciencesHefei 230031China University of Science and Technology of China Hefei 230026China

The superconducting magnet system of a fusion reactor plays a vital role in plasma confinement,a process that can be dis-rupted by various operational factors.A critical parameter for evaluating the temperature margin of superconducting magnets during normal operation is the nuclear heating caused by D-T *** study investigates the impact of nuclear heat-ing on a superconducting magnet system by employing an improved analysis method that combines neutronics and thermal *** the magnet system,toroidal field(TF)magnets are positioned closest to the plasma and bear the highest nuclear-heat load,making them prime candidates for evaluating the influence of nuclear heating on *** enhance the modeling accuracy and facilitate design modifications,a parametric TF model that incorporates heterogeneity is established to expedite the optimization design process and enhance the accuracy of the computations.A comparative analysis with a homogeneous TF model reveals that the heterogeneous model improves accuracy by over 12%.Considering factors such as heat load,magnetic-field strength,and cooling conditions,the cooling circuit facing the most severe conditions is selected to calculate the temperature of the *** selection streamlines the workload associated with thermal-hydraulic *** approach enables a more efficient and precise evaluation of the temperature margin of TF ***,it offers insights that can guide the optimization of both the structure and cooling strategy of superconducting magnet systems.

关键词： Superconducting magnet Nuclear heating Neutronics Thermal hydraulics

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Applications of mercury stable isotopes for tracing volcanism in the geologic record

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Science China Earth Sciences 2024年第5期67卷 1436-1458页

作者： Qing GONG ming-Xing LING Wang zheng State Key Laboratory of Nuclear Resources and Environment East China University of TechnologyNanchang 330013China School of Earth System Science Institute of Surface-Earth System ScienceTianjin UniversityTianjin 300072China

Mercury(Hg)enrichments in ancient sediments have been used as a proxy of volcanism,especially large igneous province(LIP)***,considering the existence of other potential Hg sources besides volcanoes and the diverse factors(e.g.,organic matters,clay minerals,sulfide minerals and Fe oxides)that can affect Hg sequestration,there are considerable uncertainties to simply regard sedimentary Hg anomalies as signatures of volcanic *** stable isotopes,a promising tool for tracing the origins and transformations of Hg,have been increasingly used for determining the causes of Hg spikes and understanding the geochemical behavior of Hg in the geologic *** date,lots of researches have applied Hg concentrations and Hg isotopes to identify LIP volcanisms linking with significant geological events such as mass extinctions,ocean anoxic events and other environmental perturbations that mainly occurred in the ***,the results in previous studies clearly show that not all Hg enrichments are derived from volcanic inputs,which emphasize the need for more caution in using Hg as a fingerprint of *** a better understanding of Hg isotopes in the future,there will be important implications for Hg isotopes to reconstruct volcanic activities in the rock records and their impacts on biological evolution.

关键词： Mercury stable isotopes Large igneous province Mass extinction event Ocean anoxic event

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MnO-pillared graphene blocks enabling the ultrastable and ultrafast aqueous zinc ion batteries

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Science China Chemistry 2024年第9期67卷 2930-2940页

作者： zheng Liu Zhipeng Qiu Zhiyuan Li Tong Wei Zhuangjun Fan huan Pang School of Chemistry and Chemical Engineering Yangzhou UniversityYangzhou 225002China School of Materials Science and Engineering China University of PetroleumQingdao 266580China

Due to the low cost,high theoretical capacity,and environmental friendliness,manganese-based cathodes are regarded as promising alternatives for aqueous zinc ion batteries(AZIBs).However,the practicality of the zinc-manganese system is faced with great challenges,such as the inevitable structural collapse of the cathode and controversial energy storage ***,we propose a novel concept of spatial deposition mechanism through the addition of MnSO_(4) additives in the Mn O-pillared graphene blocks(G-MnO).The covalent interface between MnO nanoparticles and multilayered graphene nanosheets can construct an in-built micro-electric field,which is beneficial for consecutive electron transfer(in both horizontal and vertical directions).On this basis,the surficial activity of MnO confined in the interlayered nano-space is greatly enhanced and provides enough spatial deposition and subsequent reaction site for MnSO_(4) additives,thus firstly extending the surficial controlled process to stereoscopic space,effectively improving the electrochemical performance of ***,the assembled Zn//G-Mn O battery exhibits an excellent rate capability of 281.5 mAhg^(-1)at 0.1 A g^(-1)and 106 mAhg^(-1)at 20 Ag^(-1),and impressive cycling stability(93 mAhg^(-1)remaining after 5,000 cycles).This finding may provide a new opportunity for the rational design of surficial controlled energy storage and conversion devices.

关键词： zinc-ion battery manganese monoxide laminated constructure ultrahigh rate performance graphene

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Spatiotemporal Prediction of Urban Traffics Based on Deep GNN

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Computers, Materials & Continua 2024年第1期78卷 265-282页

作者： ming Luo Huili Dou Ning zheng School of Computer Science Hangzhou Dianzi UniversityHangzhou310018China Zhejiang Institute of Communications Hangzhou310012China School of Cyberspace Security Hangzhou Dianzi UniversityHangzhou310018China

Traffic prediction already plays a significant role in applications like traffic planning and urban management,but it is still difficult to capture the highly non-linear and complicated spatiotemporal correlations of traffic *** well as to fulfil both long-termand short-termprediction objectives,a better representation of the temporal dependency and global spatial correlation of traffic data is *** order to do this,the Spatiotemporal Graph Neural Network(S-GNN)is proposed in this research as amethod for traffic *** S-GNN simultaneously accepts various traffic data as inputs and investigates the non-linear correlations between the *** terms of modelling,the road network is initially represented as a spatiotemporal directed graph,with the features of the samples at the time step being captured by a convolution *** order to assign varying attention weights to various adjacent area nodes of the target node,the adjacent areas information of nodes in the road network is then aggregated using a graph *** data is output using a fully connected layer at the *** findings show that S-GNN can improve short-and long-term traffic prediction accuracy to a greater extent;in comparison to the control model,the RMSE of S-GNN is reduced by about 0.571 to 9.288 and the MAE(Mean Absolute Error)by about 0.314 to *** experimental results on two real datasets,Pe MSD7(M)and PEMS-BAY,also support this claim.

关键词： Urban traffic traffic temporal correlation GNN prediction

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A Novel Analysis Approach of Uniform Persistence for an Epidemic Model with Quarantine and Standard Incidence Rate

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Acta Mathematicae Applicatae Sinica 2024年第3期40卷 695-707页

作者： Song-bai GUO Yu-ling XUE Xi-liang LI Zuo-huan zheng School of Science Beijing University of Civil Engineering and ArchitectureBeijing 102616China School of Mathematics and Statistics Hainan Normal UniversityHaikou 571158China Academy of Mathematics and Systems Science Chinese Academy of SciencesBeijing 100190China School of Mathematics and Information Science Shandong Technology and Business UniversityYantai 264005China School of Mathematical Sciences University of Chinese Academy of SciencesBeijing 100049China

Inspired by the transmission characteristics of the coronavirus disease 2019(COVID-19),an epidemic model with quarantine and standard incidence rate is first developed,then a novel analysis approach is proposed for finding the ultimate lower bound of the number of infected individuals,which means that the epidemic is uniformly persistent if the control reproduction number R_(c)>*** approach can be applied to the related biomat hem at ical models,and some existing works can be improved by using *** addition,the infection-free equilibrium V^(0)of the model is locally asymptotically stable(LAS)if R_(c)1.

关键词： uniform persistence epidemic model control reproduction number quarantine standard incidence rate

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Reliability-BasedModel for Incomplete Preventive ReplacementMaintenance of Photovoltaic Power Systems

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Energy Engineering 2024年第1期121卷 125-144页

作者： Wei Chen ming Li Tingting Pei Cunyu Sun huan Lei School of Electrical Engineering and Information Engineering Lanzhou University of TechnologyLanzhou730050China

At present,the operation and maintenance of photovoltaic power generation systems mainly comprise regular maintenance,breakdown maintenance,and condition-based maintenance,which is very likely to lead to over-or under-repair of ***,a preventive maintenance and replacement strategy for PV power generation systems based on reliability as a constraint is ***,a hybrid failure function with a decreasing service age factor and an increasing failure rate factor is introduced to describe the deterioration of PV power generation equipment,and the equipment is replaced when its reliability drops to the replacement threshold in the last ***,based on the reliability as a constraint,the average maintenance cost and availability of the equipment are considered,and the non-periodic incomplete maintenance model of the PV power generation system is established to obtain the optimal number of repairs,each maintenance cycle and the replacement cycle of the PV power generation system ***,the inverter of a PV power plant is used as a research *** model in this paper is compared and analyzed with the equal cycle maintenance model without considering reliability and the maintenance model without considering the equipment replacement threshold,Through model comparison,when the optimal maintenance strategy is(0.80,4),the average maintenance cost of this paper’s model are decreased by 20.3%and 5.54%and the availability is increased by 0.2395% and 0.0337%,respectively,compared with the equal-cycle maintenance model without considering the reliability constraint and the maintenance model without considering the equipment replacement ***,this maintenance model can ensure the high reliability of PV plant operation while increasing the equipment availability to improve the system economy.

关键词： Reliability photovoltaic power system average maintenance cost availability incomplete preventive maintenance hybrid failure rate

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Scaling laws governing the elastic properties of 3D graphenes

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Science China(Technological Sciences) 2024年第6期67卷 1748-1756页

作者： LI ming LU Guo YU HaoDong LI MengLei zheng FaWei Centre for Quantum Physics Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement(MOE)School of PhysicsBeijing Institute of TechnologyBeijing100081China Beijing Key Lab of Nanophotonics&Ultrafine Optoelectronic Systems School of PhysicsBeijing Institute of TechnologyBeijing100081China Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijing100088China Department of Physics Capital Normal UniversityBeijing100048China

In this study,we comprehensively investigated the scaling law for elastic properties of three-dimensional honeycomb-like graphenes(3D graphenes)using hybrid neural network potential-based molecular dynamics simulations and theoretical *** elastic constants were obtained as functions of honeycomb hole size,denoted by the graphene wall length *** five independent elastic constants in the large-L limit are proportional to L^(-1).The associated coefficients are combinations of elastic constants of two-dimensional ***-order terms including L^(-2)and L^(-3)emerge for finite L *** have three origins,the distorted areas close to the joint lines of 3D graphenes,the variation in solid angles between graphene plates,and the bending distortion of graphene ***,the chirality becomes essential with decreasing L because the joint line structures are different between the armchair and zigzag-type 3D *** findings provide insights into the elastic properties of graphene-based superstructures and can be used for further studies on graphene-based materials.

关键词： scaling law neural network elastic properties 3D graphene

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