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Acta Mechanica Sinica 2015年第4期31卷 494-499页

作者： Manrui Ren Ze Liu quan-shui zheng Jefferson Zhe Liu Department of Engineering Mechanics and Center for Nano and Micro Mechanics Tsinghua University Department of Mechanical and Aerospace Engineering Monash University

Mechanical exfoliation is a widely used method to isolate high quality graphene layers from bulk graphite. In our recent experiments, some ordered microstructures, consisting of a periodic alternation of kinks and stripes, were observed in thin graphite flakes that were mechanically peeled from highly oriented pyrolytic graphite. In this paper, a theoretical model is presented to attribute the formation of such ordered structures to the alternation of two mechanical processes during the exfoliation：（1） peeling of a graphite flake and （2） mechanical buckling of the flake being sub- jected to bending. In this model, the width of the stripes L is determined by thickness h of the flakes, surface energy Y, and critical buckling strain ecr. Using some appropriate values of y and ecr that are within the ranges determined by other inde- pendent experiments and simulations, the predicted relations between the stripe width and the flake thickness agree reason- ably well with our experimental measurements. Conversely, measuring the L-h relations of the periodic microstructures in thin graphite flakes could help determine the critical mechan- ical buckling strain εcr and the interface energy γ.

关键词： HOPG Mechanical exfoliation Periodic microstructures Kinking Mechanical buckling

Molecular transformation of dissolved organic matter in refinery wastewaters: Characterized by FT-ICR MS coupled with electrospray ionization and atmospheric pressure photoionization

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Petroleum Science 2023年第1期20卷 590-599页

作者： Chen He Wei-ming Chen Chun-Mao Chen quan Shi State Key Laboratory of Heavy Oil Processing Beijing Key Laboratory of Oil and Gas Pollution ControlChina University of PetroleumBeijing 102249China Faculty of Geosciences and Environmental Engineering Southwest Jiaotong UniversityChengduSichuan 611756China

Dissolved organic matter(DOM)in refinery wastewater is an extremely complex mixture of various organic *** mass spectrometry,it is impossible to characterize all of the DOM molecules with only one ionization *** this study,negative-ion,electrospray ionization(ESI),positive-ion ESI,and positive-ion atmospheric pressure photoionization(APPI)were coupled with Fourier transform ion cyclotron resonance mass spectrometry(FT-ICR MS)to analyze the molecular composition of DOM in a refinery wastewater stream during the treatment *** were obvious differences in the heteroatom composition,number of DOM constituents,and chemical properties in refinery wastewater under the three ionization *** CHO and CHOS compounds detected by(+)ESI,basic CHN and CHON compounds detected by(þ)ESI,and hydrocarbons detected by(+)APPI were analyzed to determine the molecular transformations that occurred during *** an anaerobic biological treatment process,acidic CHO and CHOS compounds with a high oxygen content were preferentially removed,and acidic CHO and CHOS compounds with a low oxygen content were *** an aerobic biological process,acidic CHO and CHOS compounds with a low oxygen content were preferentially removed,and acidic CHO and CHOS compounds with a high oxygen content were *** whole biological treatment process has a poor removal efficiency for CHN and CHON compounds,and *** activated carbon(AC)adsorption process removed different heteroatom compounds mainly with a low oxygen content for acidic and basic *** transformation mechanism of CHO and CHOS compounds in the biological treatment process was analyzed by the Kendrick mass defect(KMD)theory and a mass difference network *** the anaerobic process,large amounts of oxygenated CHO and CHOS compounds were degraded by decarboxylation,deoxydation,demethoxylation,and dehydration reactions,and converted to lower oxygen content *** the aerobic

关键词： Refinery wastewater DOM Molecular transformation ESI APPI FT-ICR MS

Numerical simulation of axial liquid film cooling in rocket combustor

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航空动力学报 2013年第2期28卷 459-465页

作者： YANG Wei SUN Bing zheng Li-ming School of Astronautics Beijing University of Aeronautics and Astronautics

Numerical simulation has been done for liquid film cooling in liquid rocket *** species of axial Navier-Stokes equations have been solved for liquid-film / hot-gas flow field,and k-εequations have been used for compressible turbulent *** results of the model agree well with the results of software *** results show that :(1) Liquid film can decrease the wall heat flux and temperature effectively,and the cold border area formed by the film covers the whole combustor and nozzle wall.(2) The turbulent viscosity is higher than the physical viscosity,and its biggest value is in the border area of the convergent area in *** effect of turbulent flow on the whole simulation field can not be ignored.(3) The mass fraction of kerosene at the film inlet is 1,but it decreases along the nozzle wall and achieves its lowest value at the ***,the mass fraction of kerosene near the wall is the biggest at any axial location.

关键词： liquid rocket engine liquid film cooling heat flux numerical simulation turbulent flow

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

A chemo-mechanical model for fully-coupled lithiation reaction and stress generation in viscoplastic lithiated silicon

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Science China(Technological Sciences) 2019年第8期62卷 1365-1374页

作者： BUREBI Yi ming JIA zheng QU ShaoXing Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province Center for X-MechanicsDepartment of Engineering MechanicsZhejiang University

Development of stresses in silicon(Si) anodes of lithium-ion batteries is strongly affected by its mechanical properties. Recent experiments reveal that the mechanical behavior of lithiated silicon is viscoplastic, thereby indicating that lithiation-induced mechanical stresses are dependent on the lithiation reaction rate. Experimental evidence also accumulates that the rate of lithiation reaction is conversely affected by the magnitude of mechanical stresses. These experimental observations demonstrate that lithiation reaction and stress generation in silicon anodes are fully coupled. In this work, we formulate a chemo-mechanical model considering the two-way coupling between lithiation reaction and viscoplastic deformation in silicon nanoparticle *** on the model, the position of the lithiation interface, the interface velocity, and the lithiation-induced stresses can be solved simultaneously via numerical methods. The predicted interface velocity is in line with experimental measurements reported in the literature. We demonstrate that the lithiation-induced stress field depends on the lithiation reaction through two parameters:the migration velocity and the position of the lithiation interface. We identify a stress-mitigation mechanism in viscoplastic silicon anodes: the stress-regulated lithiation reaction at the interface serves as a "brake" to reduce the interface velocity and mitigate the lithiation-induced stresses, protecting the Si nanoparticle anode from being subjected to excessive mechanical stresses.

关键词： lithium-ion battery lithiation-induced stress stress-regulated lithiation viscoplasticity

Hydrodynamic Performance of An Integrated System of Breakwater and A Multi-Chamber OWC Wave Energy Converter

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China Ocean Engineering 2024年第4期38卷 543-556页

作者： NING De-zhi ZHANG Xiang-yu WANG Rong-quan ZHAO ming State Key Laboratory of Coastal and Offshore Engineering Dalian University of TechnologyDalian 116024China Dalian Key Laboratory of Offshore Renewable Energy Dalian University of TechnologyDalian 116024China School of Computing Engineering and MathematicsUniversity of Western SydneyPenrith NSW 2751Australia

A multi-chamber oscillating water column wave energy converter(OWC-WEC)integrated to a breakwater is *** hydrodynamic characteristics of the device are analyzed using an analytical model based on the linear potential flow theory.A pneumatic model is employed to investigate the relationship between the air mass flux in the chamber and the turbine *** effects of chamber width,wall draft and wall thickness on the hydrodynamic performance of a dual-chamber OWC-WEC are *** results demonstrate that the device,with a smaller front wall draft and a wider rear chamber exhibits a broader effective frequency *** device with a chamber-width-ratio of 1:3 performs better in terms of power ***,results from the analysis of a triplechamber OWC-WEC demonstrate that reducing the front chamber width and increasing the rearward chamber width can improve the total performance of the *** the number of chambers from 1 to 2 or 3 can widen the effective frequency bandwidth.

关键词： oscillating water column power extraction efficiency potential flow theory wave energy converter multi-chamber

Influence of propagation direction on operation performance of rotating detonation combustor with turbine guide vane

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Defence Technology（防务技术） 2021年第5期17卷 1617-1624页

作者： Wan-li Wei Yu-wen Wu Chun-sheng Weng quan zheng National Key Laboratory of Transient Physics Nanjing University of Science and TechnologyNanjing210094China

Due to the pressure gain combustion characteristics,the rotating detonation combustor(RDC)can enhance thermodynamic cycle ***,the performance of gas-turbine engine can be further improved with this combustion *** the present study,the RDC operation performance with a turbine guide vane(TGV)is experimentally *** and air are used as propellants while hydrogen and air mass flow rate are about 16.1 g/s and 500 g/s and the equivalence ratio is about 1.0.A pre-detonator is used to ignite the ***-frequency dynamic pressure transducers and silicon pressure sensors are employed to measure pressure oscillations and static pressure in the combustion *** experimental results show that the steady propagation of rotating detonation wave(RDW)is observed in the combustion chamber and the mean propagation velocity is above 1650 m/s,reaching over 84%of theoretical Chapman-Jouguet detonation *** and counterclockwise propagation directions of RDW are *** clockwise propagation direction,the static pressure is about 15%higher in the combustor compared with counterclockwise propagation direction,but the RDW dominant frequency is *** the oblique shock wave propagates across the TGV,the pressure oscillations reduces *** addition,as the detonation products flow through the TGV,the static pressure drops up to 32%and 43%for clockwise and counterclockwise propagation process respectively.

关键词： Rotating detonation combustor Propagation direction Turbine guide vane Operation performance

Feasibility of measuring moisture content of green sand by a low frequency multiprobe detector based on dielectric characteristics

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China Foundry 2023年第3期20卷 197-206页

作者： De-quan Shi Gui-li Gao ming Sun Ya-xin Huang School of Materials and Chemistry University of Shanghai for Science and TechnologyShanghai 200093China School of Mechanical and Energy Engineering Shanghai Technical Institute of Electronics and InformationShanghai 201411China School of Materials Science&Chemical Engineering Harbin University of Science and TechnologyHarbin 150040China

Green sand is a mixture of silica sand,bentonite,water and coal powder,and other *** content is an important index to characterize the properties of green *** on the dielectric characteristics of green sand and transmission line theory,a method for rapidly measuring the moisture content of green sand by means of a low frequency multiprobe detector was proposed.A system was constructed,where six detectors with different arrangements and probes were *** experimental results showed that the voltage difference of transmission line increases with the increasing frequency before 29 MHz while decreases after 35 MHz.A voltage difference platform occurs in the range of 29-35 MHz,which is suitable for measuring the moisture content due to its insensitivity to *** electric field intensity gradually decreases with the increase of the probe depth,and the intensity of central probe is always greater than that of the edge *** the distance of the probe away from the sand sample surface is 80 mm,the electric field intensity of the edge probe is found to be very *** optimal excitation frequency for measuring the moisture content of green sand is 29-33 *** optimal detector is the one with one center probe and three edge probes,and their lengths are 80 mm and 60 mm,*** distance between the center and edge probes is 25 mm,and the diameter of probes is 5 *** the voltage difference of transmission line,bentonite content,coal powder content and compactability as parameters of the input layer,and the moisture content as a parameter of the output layer,a three-layer BP artificial neural network model for predicting the moisture content of green sand was constructed according to the experimental results at 33 *** prediction error of the model is not higher than 3.3% when the moisture content of green sand is within the range of 3wt.%-7wt.%.

关键词： green sand dielectric property moisture content multiprobe detector BP artificial neural network model

Modelling and numerical simulation of isothermal oxidation of an individual magnetite pellet based on computational fluid dynamics

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Journal of Iron and Steel Research International 2021年第7期28卷 799-808页

作者： Zhou Pu Feng Zhou Yue Sun ming Zhang Bo-quan Li Department of Instrumentation Science and Technology Jiangsu UniversityZhenjiang 212013JiangsuChina

A mathematical model based on the computational fluid dynamics method,heat and mass transfer in porous media and the unreacted shrinking core model for the oxidation reaction of an individual magnetite pellet during preheating was *** commercial software COMSOL Multiphysics was used to simulate the change in the oxidation degree of the pellet at different temperatures and oxygen concentrations,and the simulated results were compared with the exper-imental *** model considered the influence of the exothermic heat of the reaction,and the enthalpy change was added to calculate the heat released by the *** results show that the oxidation rate on the surface of the pellet is much faster than that of the inside of the *** and oxygen concentration have great influence on the pellet oxidation ***,the exothermic calculation results show that there is a non-isothermal phenomenon inside the pellet,which leads to an increase in temperature inside the single *** the preheating condition of 873-1273 K(20%oxygen content),the heat released by the pellet oxidation reaction in a chain grate is 7.8×10^(6)-10.8×10^(6) kJ/h,which is very large and needs to be considered in the magnetite pellet oxidation modelling.

关键词： Magnetite pellet Oxidation Numerical simulation Unreacted shrinking core model Computational fluid dynamics

Randomized controlled trial on the efficacy and safety of autologous serum eye drops in dry eye syndrome

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World Journal of Clinical Cases 2023年第28期11卷 6774-6781页

作者： Na zheng Si-quan Zhu Department of Ophthalmology Chengdu University of Traditional Chinese MedicineChengdu 610032Sichuan ProvinceChina Department of Ophthalmology Beijing Anzhen Hospital Affiliated to China Medical UniversityBeijing 100029China

BACKGROUND Autologous serum eye drops(ASEDs),a novel treatment derived from blood serum,have emerged as a groundbreaking solution for managing dry eye syndrome(DES).These drops have shown significant promise in relieving the distressing symptoms of *** study aimed to evaluate the safety and effectiveness of ASEDs compared to traditional treatments,which often prove inadequate or result in unwanted side effects,particularly in individuals with moderate-to-severe *** To evaluate whether ASEDs are safer and more effective than conventional artificial tears in the treatment of moderate-to-severe *** This multi-centered randomized controlled trial included 240 patients with moderate-to-severe DES from three ophthalmology clinics in *** were randomly assigned to receive either ASEDs or artificial tears for 12 *** primary outcome was the change in the ocular surface disease index(OSDI)score,with secondary outcomes including tear break-up time(TBUT),Schirmer I test,corneal fluorescein staining(CFS),and conjunctival impression cytology(CIC).Statistics analysis was performed using an analysis of covariance with adjustments made for baseline *** Our findings revealed that both ASEDs and artificial tears significantly improved the OSDI score,TBUT,Schirmer I test,CFS,and CIC from baseline to week *** ASEDs group showed significantly greater improvement in all these measures than the artificial tears group(all P values<0.05).The average difference in the OSDI score between the two cohorts was-10.3(95%confidence interval:-13.6 to-7.0),indicating a substantial improvement in the ASEDs *** occurrence of adverse events was comparable between cohorts,with no reports of severe adverse *** ASEDs are more effective and safer than artificial tears for mitigating symptoms of moderate-to-severe *** could be an alternative/supplementary therapy for patients with DES less responsive to traditional treatments.

关键词： Autologous serum eye drops Dry eye syndrome Safety Effectiveness Alternative therapy Conventional artificial tears