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Numerical Investigation on Characteristics of Supercritical CO_(2)Heat Transfer in Vertical Circular Tubes with Circumferentially Half-Side Heating

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Journal of Thermal Science 2024年第5期33卷 1744-1756页

作者： zhang yan zhang Xinyi yan Chenshuai WU Wenhua GAO Erman School of Energy and Power Engineering Northeast Electric Power UniversityJilin 132012China

The design of heat exchangers in the advanced supercritical power conversion system cannot be separated from the study of heat transfer ***-side heating mode is often encountered for solar receiver and supercritical ***,the characteristics of supercritical CO_(2)(sCO_(2))convection heat transfer in vertical tubes with circumferentially half-side heating was numerically investigated through the SST k-ωturbulent model which matches well with the experimental ***,heat transfer between sCO_(2)upflow and downflow was *** to film boiling heat transfer at subcritical pressure,numerical results were processed according to the supercritical pseudo-phase transition hypothesis,with liquid-like phase in the tube core region and vapor-like film in the region near the heated tube *** structure of two layers was demarcated by pseudo-critical temperature T_(pc).Therefore,sCO_(2)heat transfer was assessed according to double thermal resistances caused by vapor-like film near the wall and core liquid-like *** findings suggest that wall temperature for upflow is higher than that for downflow,which is attributed to larger thermal resistance in the fluid domain for upflow than that for *** difference guarantees the excellent heat transfer performance for downflow than *** is also further concluded that the formation of vapor-like film near the wall due to pseudo-phase transition plays a key role in dominating wall temperature and inducing heat transfer deterioration in half-side heating *** present contribution is significant to the design of supercritical heat exchanger under half-side heating mode.

关键词： supercritical CO_(2) pseudo-phase transition half-side heating thermal resistance flow direction

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Geochronological and geochemical constraints on the petrogenesis and geodynamic process of Hemler,Vlinder,and Il'ichev seamount lavas in NW Pacific

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Science China Earth Sciences 2024年第6期67卷 1856-1871页

作者： Xun WEI yan zhang Xuefa SHI Hui zhang Key Laboratory of Marine Geology and Metallogeny First Institute of OceanographyMinistry of Natural ResourcesQingdao 266061China Laboratory for Marine Geology Qingdao Marine Science and Technology CenterQingdao 266237China Shandong Key Laboratory of Deep Sea Mineral Resources Development(Preparatory) Qingdao 266061China

Oceanic intraplate volcanoes with linear age progressions are usually accepted to be derived from melting of an upwelling mantle *** seamount groups in NW Pacific,however,show complex age-distance relationships that are difficult to explain using the classic“mantle plume hypothesis”,and thus their origins are *** this study,we present ^(40)Ar-^(39)Ar age,geochemical,and Sr-Nd-Pb-Hf isotopic data of lavas from Hemler,Vlinder,and Il’ichev seamounts in NW Pacific,to elucidate their petrogenesis and geodynamic *** lavas from Hemler,Vlinder,and Il’ichev seamounts are classified as alkali basalt,basanite/nephelinite,and *** with Mg O>8 wt.%exhibit high contents of CaO,FeO^(T),and TiO_(2),similar to the composition of melts formed from reaction between carbonated eclogite-derived melts and fertile *** lavas have elevated Zr/Hf ratios(40.6-45.2)and negative Zr and Hf anomalies,indicating the presence of a carbonate component in the mantle *** are enriched in incompatible trace elements and have enriched mantle 1(EM1)-like SrNd-Pb-Hf isotopic *** isotopic compositions of Vlinder,Il’ichev basanite,and Hemler lavas in this study are similar to the Rarotonga *** occurring at the same seamount,the Il’ichev alkali basalts display more depleted SrNd-Hf isotopic compositions compared to Il’ichev *** to plate tectonic reconstruction results,the ages of Hemler(100.1 Ma),Vlinder pre-(100.2 Ma)and post-shield(87.5 Ma),and Il’ichev(56.4 Ma)lavas clearly deviate from the Macdonald,Arago,Rarotonga,and Samoa hotspot tracks,indicating that they cannot directly originate from mantle *** propose that in the mid-Cretaceous,when the Pacific plate passed over Rarotonga hotspot,melting of Rarotonga plume formed the Vlinder(main-shield stage),Pako,and Ioah *** Rarotonga(and possibly Samoa)plume materials would have been dispersed into the surrounding asthenosphere by mantle conve

关键词： Mantle plume Magellan seamount trail Carbonated mantle component Hotspot Lithosphere extension

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A novel graph oversampling framework for node classification in class-imbalanced graphs

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Science China(Information Sciences) 2024年第6期67卷 214-229页

作者： Riting XIA Chunxu zhang yan zhang Xueyan LIU Bo yanG Key Laboratory of Symbolic Computation and Knowledge Engineering of Ministry of Education Jilin University College of Artificial Intelligence Jilin University College of Computer Science and Technology Jilin University College of Communication Engineering Jilin University

Graph neural network(GNN) is a promising method to analyze graphs. Most existing GNNs adopt the class-balanced assumption, which cannot deal with class-imbalanced graphs well. The oversampling technique is effective in alleviating class-imbalanced problems. However, most graph oversampling methods generate synthetic minority nodes and their edges after applying GNNs. They ignore the problem that the representations of the original and synthetic minority nodes are dominated by majority nodes caused by aggregating neighbor information through GNN before oversampling. In this paper, we propose a novel graph oversampling framework, termed distribution alignment-based oversampling for node classification in classimbalanced graphs(named Graph-DAO). Our framework generates synthetic minority nodes before GNN to avoid the dominance of majority nodes caused by message passing in GNNs. Additionally, we introduce a distribution alignment method based on the sum-product network to learn more information about minority nodes. To our best knowledge, it is the first to use the sum-product network to solve the class-imbalanced problem in node classification. A large number of experiments on four real datasets show that our method achieves the optimal results on the node classification task for class-imbalanced graphs.

关键词： graph neural network class-imbalanced graphs sum-product network oversampling node classification

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Effects of formal credit on pastoral household expense: Evidence from the Qinghai-Xizang Plateau of China

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Journal of Integrative Agriculture 2024年第5期23卷 1774-1785页

作者： yan zhang Yi Huang Fan zhang Zeng Tang State Key Laboratory of Herbage Improvement and Grassland Agro-ecosystems College of Pastoral Agriculture Science and TechnologyLanzhou UniversityLanzhou 730020China

Formal credit is critical in agricultural production,allowing more expenditure and productive input,thereby improving farmers'*** pastoral China,formal financial institutions are gradually ***,a limited understanding remains of how formal credit affects herders'household *** on a survey of 544 herders from the Qinghai-Xizang Plateau of China,this study adopted the propensity score matching approach to identify the effect of formal credit on herders'total household expenses,daily expenses,and productive *** results found that average age,grassland mortgage,and other variables significantly affected herders'participation in formal *** credit could significantly improve household expenses,especially productive expenses.A heterogeneity analysis showed that formal credit had a greater impact on the household total expense for those at higher levels of wealth;however,it significantly affected the productive expense of herders at lower wealth ***,the mediating effect indicated that formal credit could affect herders'household income,thus influencing their household ***,this study suggests that policies should improve herders'accessibility to formal credit.

关键词： formal credit herders expense Qinghai-Xizang Plateau

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Carbon Emission Effects Driven by Evolution of Chinese Dietary Structure from 1987 to 2020

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Chinese Geographical Science 2024年第1期34卷 181-194页

作者： ZHU Yuanyuan zhang yan ZHU Xiaohua Key Laboratory of Geographic Process Analysis&Simulation Hubei Province Central China Normal UniversityWuhan430079China Institute of Geographic Sciences and Natural Resources Research Chinese Academy of SciencesBeijing100101China

Exploring carbon emission effects based on the evolution of residents’ dietary structure to achieve the carbon neutrality goal and mitigate climate change is an important *** study took China as the research object(data excluding Hong Kong,Macao and Taiwan) and used the carbon emission coefficient method to quantitatively measure the food carbon emissions from 1987–2020,then analyzed the carbon emission effects under the evolution of dietary *** results showed that during the study period,the Chinese dietary structure gradually changed to a high-carbon consumption *** dietary structure of urban residents developed to a balanced one,while that of rural residents developed to a high-quality *** the study period,the per capita food carbon emissions and total food consumption of Chinese showed an increasing *** per capita food carbon emissions of residents in urban and rural showed an overall upward *** total food carbon emissions in urban increased significantly,while that in rural increased first and then *** influence of beef and mutton on carbon emissions is the highest in dietary *** with the balanced dietary pattern,the food carbon emissions of Chinese residents had not yet reached the peak,but were evolving to a high-carbon consumption pattern.

关键词： dietary structure structural evolution carbon emission effects carbon neutrality China

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Kinetic model of vibration screening for granular materials based on biological neural network

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Particuology 2024年第5期88卷 98-106页

作者： Zhan Zhao yan zhang Fang Qin Mingzhi Jin School of Agricultural Engineering Jiangsu UniversityZhenjiang212013China Shandong Academy of Agricultural Machinery Sciences Ji'nan250100China

The kinetic model is the theoretical basis for optimizing the structure and operation performance of vibration screening *** this paper,a biological neurodynamic equation and neural connections were established according to the motion and interaction properties of the material under vibration *** material feeding to the screen and the material passing through apertures were considered as excitatory and inhibitory inputs,respectively,and the generated stable neural activity landscape was used to describe the material distribution on the 2D screen *** dynamic process of material vibration screening was simulated using discrete element method(DEM).By comparing the similarity between the material distribution established using biological neural network(BNN)and that obtained using DEM simulation,the optimum coefficients of BNN model under a certain screening parameter were determined,that is,one relationship between the BNN model coefficients and the screening operation parameters was *** screening parameters were randomly selected,and the corresponding relationships were established as a ***,with straw/grain ratio,aperture diameter,inclination angle,vibration strength in normal and tangential directions as inputs,five independent adaptive neuro-fuzzy inference systems(ANFIS)were established to predict the optimum BNN model coefficients,*** training results indicated that ANFIS models had good stability and *** flexibility and adaptability of the proposed BNN method was demonstrated by modeling material distribution under complex feeding conditions such as multiple regions and non-uniform rate.

关键词： Kinetic model Material distribution Vibration screening Biological neural network DEM simulation Adaptive neuro-fuzzy inference systems

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An effective strategy of constructing multi-metallic oxides of ZnO/ CoNiO_(2)/CoO/C microflowers for improved supercapacitive performance

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Chinese Journal of Chemical Engineering 2024年第3期67卷 1-8页

作者： Wei Guo yan zhang Xiaxin Lei Shuang Wang College of Physics Taiyuan University of TechnologyJinzhong 030600China College of Environmental Science and Engineering Taiyuan University of TechnologyJinzhong 030600China Shanxi Key Laboratory of Gas Energy Efficient and Clean Utilization Taiyuan University of TechnologyTaiyuan 030024China

In this work,a new ZnO/CoNiO_(2)/CoO/C metal oxides composite is prepared by cost-effective hydrothermal method coupled with annealing process under N_(2) ***,the oxidation-defect annealing environment is conducive to both morphology and component of the composite,which flower-like ZnO/CoNiO_(2)/CoO/C is *** from good chemical stability of ZnO,high energy capacity of CoNiO_(2) and CoO and good conductivity of C,the as-prepared sample shows promising electrochemical behavior,including the specific capacity of 1435 C·g^(-1) at 1 A·g^(-1),capacity retention of 87.3%at 20 A·g^(-1),and cycling stability of 90.5%for 3000 cycles at 5 A·g^(-1),***,the prepared ZnO/CoNiO_(2)/CoO/C/NF//AC aqueous hybrid supercapacitors device delivers the best specific energy of 55.9 W·h·kg^(-1) at 850 W·kg^(-1).The results reflect that the as-prepared ZnO/CoNiO_(2)/CoO/C microflowers are considered as high performance electrode materials for supercapacitor,and the strategy mentioned in this paper is benefit to prepare mixed metal oxides composite for energy conversion and storage.

关键词： Composites Electrochemistry Hydrothermal Transition metal oxides Structural control Supercapacitors

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Investigation of formaldehyde sources and its relative emission intensity in shipping channel environment

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Journal of Environmental Sciences 2024年第8期142卷 142-154页

作者： Jiaqi Liu Shanshan Wang yan zhang Yuhao yan Jian Zhu Sanbao zhang Tianyu Wang Yibing Tan Bin Zhou Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention(LAP3) Department of Environmental Science and EngineeringFudan UniversityShanghai 200433China Institute of Eco-Chongming(IEC) No.20 Cuiniao RoadShanghai 202162China Institute of Atmospheric Sciences Fudan UniversityShanghai 200433China National Observations and Research Station for Wetland Ecosystems of the yangtze Estuary Fudan UniversityShanghai 200438China Institute of Digitalized Sustainable Transformation Big Data InstituteFudan UniversityShanghai 200433China

Formaldehyde(HCHO)is considered one of the most abundant gas-phase carbonyl compounds in the atmosphere,which can be directly emitted through transportation ***-Path Differential Optical Absorption Spectroscopy(LP-DOAS)was used to observe HCHO in the river channel of Wusong Wharf in Shanghai,China for the whole year of *** to the impact of ship activity,the annual average HCHO level in the channel is about2.5 times higher than that in the nearby campus *** explain the sources of HCHO under different meteorological conditions,the tracer-pair of CO and O_(x)(NO_(2)+O_(3))was used on the clustered air *** results of the source appointment show that primary,secondary and background account for 24.14%(3.34±1.19 ppbv),44.78%(6.20±2.04ppbv)and 31.09%(4.31±2.33 ppbv)of the HCHO in the channel when the air masses were from the mixed direction of the city and channel,*** performing background station subtraction at times of high primary HCHO values and resolving the plume peaks,directly emitted HCHO/NO_(2)in the channel environment and plume were determined to be mainly distributed between 0.2 and *** cargo ships with higher sailing speeds or main engine powers tend to have higher HCHO/NO_(2)*** the knowledge of NO_(2)(or NO_(x))emission levels from ships,this study may provide data support for the establishment of HCHO emission factors.

关键词： HCHO LP-DOAS Channel environment Ship emissions

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Modulating redox transition kinetics by anion regulation in Ni-Fe-X(X=O,S,Se,N,and P)electrocatalyst for efficient water oxidation

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Nano Research 2024年第6期17卷 4720-4728页

作者： Liting Wei Kaini zhang Rui Zhao Lei zhang yan zhang Suyi yang Jinzhan Su International Research Center for Renewable Energy&State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an 710049China Department of Applied Chemistry Yuncheng UniversityYuncheng 044000China

NiFe-based electrocatalysts will experience dynamical surface reconstruction during oxygen evolution reaction(OER)process,and the derived metal(oxy)hydroxide hybrids on the surface have been considered as the actual active species for *** efforts have been dedicated to understanding the surface reconstruction,but there is rare research on recognizing the origin of improved performance derived from anion species of ***,the OER electrocatalytic characteristics were tuned with different anions in NiFe-based catalyst,using NiFe-based oxides/nitride/sulfide/selenides/phosphides(NiFeX,X=O,N,S,Se,and P)as the model *** combination of X-ray photoelectronic spectroscopy,electrochemical tests,operando spectroscopic characterizations,and density functional theory(DFT)calculations,reveals that anion with lower electronegativity in NiFe-based catalyst leads to higher conductivity and delayed valence transition of Ni sites,as well as optimized adsorption behavior towards oxygen intermediates,contributing to enhanced OER ***,NiFeP electrocatalyst demonstrates an ultralow overpotential of 265 mV at 20 mA·cm−2 for OER,as well as long-term *** work not only offers further insights into the effect of anionic electronegativity on the intrinsic OER electrocatalytic properties of NiFe-based electrocatalyst but also provides guide to design efficient non-noble metal-based electrocatalysts for water oxidation.

关键词： oxygen evolution reaction(OER) anion species electronegativity valence transition

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Large porewater exchange reshapes saltmarsh carbon and greenhouse gas budgets on local and global scales

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Science China Earth Sciences 2024年第7期67卷 2195-2209页

作者： Xiaogang CHEN Isaac RSANTOS Lucheng ZHAN Yu yan YAU yan zhang Ling LI Key Laboratory of Coastal Environment and Resources of Zhejiang Province School of EngineeringWestlake UniversityHangzhou 310024China Department of Marine Sciences University of GothenburgGothenburg 41319Sweden College of Water Conservancy and Hydropower Engineering Hohai UniversityNanjing 210024China

Saltmarshes are carbon-rich ecosystems that play a role in climate regulation by efficiently sequestrating atmospheric CO_(2).Climate change is a major threat to saltmarshes and will impact saltmarsh carbon ***,porewater-derived carbon outwelling emerges as a crucial pathway for carbon sequestration,but it has been largely overlooked in ***,we assessed the drivers of dissolved carbon exports and greenhouse gas emissions in a saltmarsh and placed those observations into a global *** our study site,porewater exchange(PEX)was the major process controlling dissolved carbon and greenhouse gas *** our results with 33 other studies in saltmarshes worldwide,porewater-derived carbon fluxes were equivalent to~48% of average global saltmarsh primary productivity and 2.2 times greater than global organic carbon ***,our local observations and global upscaling demonstrate the major role played by PEX in saltmarsh carbon *** part of dissolved inorganic carbon returns to the atmosphere as CO_(2),the remaining bicarbonate fraction is stored in the ocean over long time *** findings strengthen global blue carbon assessments and build arguments for the use of saltmarshes as nature-based solutions for global climate change.

关键词： Coastal carbon Global carbon budget Carbon neutrality Nature-based solutions Coastal wetlands Submarine groundwater discharge

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