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Micro segment analysis of supercritical methane thermal-hydraulic performance and pseudo-boiling in a PCHE straight channel

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PETROLEUM SCIENCE 2024年第2期21卷 1275-1289页

作者： cai, Wei-hua Northeast Elect Power Univ Lab Thermofluid Sci & Nucl Engn Jilin 132000 Jilin Peoples R China Northeast Elect Power Univ Sch Energy & Power Engn Jilin 132000 Jilin Peoples R China

The printed circuit heat exchanger (PCHE) is receiving wide attention as a new kind of compact heat exchanger and is considered as a promising vaporizer in the LNG process. In this paper, a PCHE straight channel in the length of 500 mm is established, with a semicircular cross section in a diameter of 1.2 mm. Numerical simulation is employed to investigate the flow and heat transfer performance of supercritical methane in the channel. The pseudo -boiling theory is adopted and the liquid -like, two -phase -like, and vapor -like regimes are divided for supercritical methane to analyze the heat transfer and flow features. The results are presented in micro segment to show the local convective heat transfer coefficient and pressure drop. It shows that the convective heat transfer coefficient in segments along the channel has a significant peak feature near the pseudo -critical point and a heat transfer deterioration when the average fluid temperature in the segment is higher than the pseudo -critical point. The reason is explained with the generation of vapor -like film near the channel wall that the peak feature related to a nucleateboiling -like state and heat transfer deterioration related to a film -boiling -like state. The effects of parameters, including mass flow rate, pressure, and wall heat flux on flow and heat transfer were analyzed. In calculating of the averaged heat transfer coefficient of the whole channel, the traditional method shows significant deviation and the micro segment weighted average method is adopted. The pressure drop can mainly be affected by the mass flux and pressure and little affected by the wall heat flux. The peak of the convective heat transfer coefficient can only form at high mass flux, low wall heat flux, and near critical pressure, in which condition the nucleate -boiling -like state is easier to appear. Moreover, heat transfer deterioration will always appear, since the supercritical flow will finally develop into a filmboiling -like state. So heat transfer deterioration shou

关键词： Printed circuit heat exchanger Vaporization Supercritical methane Pseudo -boiling Micro segment analysis CIRCUIT HEAT-EXCHANGER INTERMEDIATE FLUID VAPORIZER OPTIMIZATION FLOW CO2 DESIGN CROSS CYCLE LINE

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Total Coloring of Planar Graphs without Chordal 7-cycles

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Acta Mathematica Sinica,English Series 2015年第12期31卷 1951-1962页

作者： hua CAI School of Mathematics Shandong University Department of Mathematics Changji University

A k-total-coloring of a graph G is a coloring of vertices and edges of G using k colors such that no two adjacent or incident elements receive the same color.In this paper,it is proved that if G is a planar graph with... 详细信息

关键词： Planar graph total coloring chordal 7-cycle

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Long-term agricultural contamination shaped diversity response of sediment microbiome

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Journal of Environmental Sciences 2021年第1期33卷 90-99页

作者： Lei Zhang Ziyin Wang hua CAI Wenxuan Lu Jing Li School of Civil Engineering and Architecture Chuzhou UniversityChuzhou 239000China Nanjing Institute of Geography and Limnology Chinese Academy of SciencesNanjing 210008China Fisheries Research Institute Anhui Academy of Agricultural SciencesHefei 230036China

The pollution caused by agricultural production poses a threat to the ecological integrity of river ecosystems,altering the structure and function of river ecosystems.Differences in microbial community structure provide useful information about the impact of agricultural pollution on the biological integrity of ecosystems,but generally convey little information regarding ecosystem functions.In this study,using Illumina MiSeq sequencing technology based on the 16 S rRNA gene,river sediment samples associated with four different types of agricultural pollution were comprehensively analyzed.The results show that the total organic carbon(TOC)content was highest at the YZS site(animal husbandry sewage)among the assayed sites,but the species richness and uniformity were lowest at this site,which may have been caused by the high nutrient source of the sewage.Furthermore,in the three YZS samples affected by the long-term discharge of aquaculture tail-water,the unique genus Dechloromonas and the genus Candidatus-Competitor were observed,which are strongly correlated with phosphorus conversion.The formation of network modules may correspond to the coexistence of functional bacteria accustomed to multiple niche combinations under different agricultural pollution conditions in river sediments.According to the PICRUSt functional prediction,the bacterial community in the agricultural polluted river sediment primarily harbored 46 subfunctions,exhibiting richness of functions.Overall,our results provide a more comprehensive understanding of the structure and ecological processes associated with the aggregation of bacterial communities,which is beneficial for the management of river environments.

关键词： Agricultural pollution Bacterial community Illumina miseq sequencing Co-occurrence patterns Functional prediction

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The Substantive Entity and Conceptual Ontology of the Object of Social Science Research and the Future of Anthropology

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Social Sciences in China 2022年第3期43卷 146-161页

作者： cai hua 李光辉(译) Institute of Anthropology Peking University 不详

In this dialogue,cai hua and Maurice Godelier ask whether there has been a change in the research entity.This question concerns the representation of the“world of the other”and its impact on the intellectual world since the advent of postmodernism.cai hua states that when he was an overseas student in France in the 1980s,he could not see any traces of colonization.The postmodern movement is simply a kind of emotional catharsis and cannot be called“scientific research”in a rigorous sense.As a scientist,if your position is neutral,you cannot see the other in a dichotomous way;the other is simply what you research,and you arenot part of the other.

关键词： substantive entity conceptual ontology anthropology

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Strengthening-toughening methods and mechanisms of Mg-Li alloy:a review

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Rare Metals 2022年第4期41卷 1176-1188页

作者： Xiang Peng Wen-cai Liu Guo-hua Wu National Engineering Research Center of Light Alloy Net Forming and State Key Laboratory of Metal Matrix Composite School of Materials Science and EngineeringShanghai Jiao Tong UniversityShanghai 200240China

Magnesium-lithium(Mg-Li) alloy,as the lightest metal structure material,has unparalleled market prospects in aerospace,weapons and equipment,electronic technology,transportation,and many other fields.However,it is hard to balance the superlight and high strength of Mg-Li alloy,and the inferior high-temperature strength and poor high-temperature stability limit the wide application of Mg-Li alloy.At present,the main methods to improve the mechanical properties of Mg-Li alloy are alloying,grain refinement,and compound strengthening.The domestic and overseas research progress in the strengthening and toughening methods and mechanisms of Mg-Li alloy are reviewed,and the future development of the high strength and high toughness Mg-Li alloy is prospected.

关键词： Mg-Li alloy Solution strengthening Precipitation strengthening Grain reflnement strengthening Compound strengthening

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On Total Colorings of Some Special 1-planar Graphs

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Acta Mathematicae Applicatae Sinica 2017年第3期33卷 607-618页

作者： Lin SUN Jian-liang WU hua CAI Department of Mathematics Changji University School of Mathematics Shandong University

A graph is 1-planar if it can be drawn on the plane so that each edge is crossed by at most one other edge. In this paper, we verify the total coloring conjecture for every 1-planar graph G if either △（G） ≥9 and g（G）≥ 4, or △（G） ≥ 7 and g（G）≥5, where △（G） is the maximum degree of G and g（G） is the girth of G.

关键词： 1-planar graph total coloring discharging method girth r-minimal graph

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Electrochemical borylation of nitroarenes

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Science China Chemistry 2023年第2期66卷 534-539页

作者： Linlin Du Binfeng Zhang Shuohan Ji Hu cai hua Zhang Key Laboratory of Catalysis and Energy Materials Chemistry of Ministry of Education&Hubei Key Laboratory of Catalysis and Materials Science School of Chemistry and Materials ScienceSouth-Central Minzu UniversityWuhan430074China School of Chemistry and Chemical Engineering Nanchang UniversityNanchang330031China

A simple electrochemically mediated method for the conversion of nitroarenes to aryl boronic esters is presented.Electrochemical borylation of a diverse range of nitroarenes,including the late-stage borylation of bioactive molecules,is furnished at room temperature under simple conditions,thereby demonstrating the broad utility and functional-group tolerance of this protocol.This transformation provides a convenient and practical access to aryl boronic esters from widely available nitroarenes,which would significantly streamline the synthetic process of diverse functionalized arenes.

关键词： electrochemistry borylation nitroarenes arylboronic esters organic synthesis

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A Totally(Δ+1)-colorable 1-planar Graph with Girth at Least Five

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Acta Mathematica Sinica,English Series 2016年第11期32卷 1337-1349页

作者： Lin SUN Jian Liang WU hua CAI School of Mathematics Shandong University Ji'nan 250100 P. R. China Department of Mathematics Changji University Changji 831100 P. R. China

A graph is 1-planar if it can be drawn on the plane so that each edge is crossed by at most one other edge. In this paper, we prove that every 1-planar graph G with maximum degree △（G）〉 12 and girth at least five... 详细信息

关键词： 1-planar graph total coloring discharging method girth

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Strange quark star and the parameter space of the quasi-particle model

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Communications in Theoretical Physics 2021年第10期73卷 125-131页

作者： Wen-hua CAI Qing-Wu Wang College of physics Sichuan UniversityChengdu 610064China

The properties of strange quark stars are studied within the quasi-particle model. Taking into account chemical equilibrium and charge neutrality, the equation of state(EOS) of(2+ 1)-flavor quark matter is obtained. We illustrate the parameter spaces with constraints from two aspects: one is based on the astronomical results of PSR J0740+ 6620 and GW 170 817,and the other is based on the constraints proposed from the theoretical study of a compact star that the EOS must ensure the tidal deformability Λ_(1.4)=190_(-120)^(+390) and support a maximum mass above 1.97M⊙. It is found that neither type of constraints can restrict the parameter space of the quasi-particle model in a reliable region and thus we conclude that the low mass compact star cannot be a strange quark star.

关键词： strange quark compact star tidal deformability quasi-particle model neutron star

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One-step Synthesis and Photocatalytic Degradation Performance of Sulfur-doped Porous g-C_(3)N_(4)Nanosheets

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China Petroleum Processing & Petrochemical Technology 2022年第1期24卷 81-89页

作者： Liu Yuan Zhao hua Li Huipeng cai Tianfeng School of Petrochemical Engineering Liaoning Petrochemical UniversityLiaoning 113001

In this study,the sulfur-doped porous g-C_(3)N_(4) nanosheets(CN-T-U 1.75)were synthesized successfully by onestep calcination utilizing urea and thiourea as precursors.Under visible light irradiation,CN-T-U 1.75 showed remarkable photocatalytic activity for Rhodamine B(RhB)degradation with a kinetic reaction rate constant of 0.01838 min^(-1).The characterization analysis indicated that CN-T-U 1.75 had a higher specific surface area and the doping altered the energy band structure.This work offers a new viewpoint on modifying the band structure of a photocatalyst using a doping strategy,as well as new insights into the generation routes of active species involved in the photocatalytic process.

关键词： sulfur-doped g-C3N4 nanosheets photocatalysis degradation

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