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Probing interactions at two-dimensional heterointerfaces by boron nitride-wrapped tip

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Nano Research 2021年第3期14卷 692-698页

作者： Baowen Li xiaofei liu Wanlin Guo Key Laboratory for Intelligent Nano Materials and Devices of the Ministry of Education State Key Laboratory of Mechanics and Control of Mechanical StructuresNanjing University of Aeronautics and AstronauticsNanjing210016China

Non-covalent interactions are important for two-dimensional heterointerfaces but challenged to be accurately determined,especially when the dielectric hexagonal boron nitride(BN)is ***,we present a comprehensive quantitative investigation on the interactions at the interfaces of BN-BN,BN-molybdenum disulfide,and BN-graphite using a BN-wrapped atomic force microscope tip and first-principle *** critical adhesion forces at BN-molybdenum disulfide and BN-graphite interfaces are measured to be 1.107±0.062 and 0.999±0.053 times that at BN-BN interface,respectively,while increase to 1.195±0.076 and 1.085±0.075 *** exposure of the tip to radiation in scanning electron microscopy,with data repeatability higher than 86%.The result with non-radiated tip agrees with the van der Waals interactions predicted by the state-of-the-art density functional theory-based vdW2D method,whereas the effect of radiation comes from the introduced charges in the tip,indicating the crucial roles of both dispersion and electrostatic interactions in construction,manipulation and device application of two-dimensional heterostructures.

关键词： graphene molybdenum disulfide(MoS_(2)) boron nitride(BN) van der Waals force force-displacement curve

A primal-dual approximation algorithm for the k-prize-collecting minimum vertex cover problem with submodular penalties

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Frontiers of Computer Science 2023年第3期17卷 125-132页

作者： xiaofei liu Weidong LI Jinhua YANG School of Information Science and Engineering Yunnan UniversityKunming 650500China School of Mathematics and Statistics Yunnan UniversityKunming 650500China Dianchi College of Yunnan University Kunming 650228China

In this paper,we consider the-prize-collecting minimum vertex cover problem with submodular penalties,which generalizes the well-known minimum vertex cover problem,minimum partial vertex cover problem and minimum vertex cover problem with submodular *** are given a cost graph and an *** problem determines a vertex set such that covers at least *** objective is to minimize the total cost of the vertices in plus the penalty of the uncovered edge set,where the penalty is determined by a submodular *** design a two-phase combinatorial algorithm based on the guessing technique and the primal-dual framework to address the *** the submodular penalty cost function is normalized and nondecreasing,the proposed algorithm has an approximation factor *** the submodular penalty cost function is linear,the approximation factor of the proposed algorithm is reduced to,which is the best factor if the unique game conjecture holds.

关键词： vertex cover k-prize-collecting primal-dual approximation algorithm

Physics-informed neural network approach for heat generation rate estimation of lithium-ion battery under various driving conditions

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Journal of Energy Chemistry 2023年第3期78卷 1-12,I0001页

作者： Hui Pang Longxing Wu Jiahao liu xiaofei liu Kai liu School of Mechanical and Precision Instrument Engineering Xi’an University of TechnologyXi’an 710048ShaanxiChina

Accurate insight into the heat generation rate(HGR) of lithium-ion batteries(LIBs) is one of key issues for battery management systems to formulate thermal safety warning strategies in *** this reason,this paper proposes a novel physics-informed neural network(PINN) approach for HGR estimation of LIBs under various driving ***,a single particle model with thermodynamics(SPMT) is first constructed for extracting the critical physical knowledge related with battery ***,the surface concentrations of positive and negative electrodes in battery SPMT model are integrated into the bidirectional long short-term memory(BiLSTM) networks as physical *** combined with other feature variables,a novel PINN approach to achieve HGR estimation of LIBs with higher accuracy is ***,some critical hyperparameters of BiLSTM used in PINN approach are determined through Bayesian optimization algorithm(BOA) and the results of BOA-based BiLSTM are compared with other traditional BiLSTM/LSTM ***,combined with the HGR data generated from the validated virtual battery,it is proved that the proposed approach can well predict the battery HGR under the dynamic stress test(DST) and worldwide light vehicles test procedure(WLTP),the mean absolute error under DST is 0.542 kW/m^(3),and the root mean square error under WLTP is1.428 kW/m^(3)at 25℃.Lastly,the investigation results of this paper also show a new perspective in the application of the PINN approach in battery HGR estimation.

关键词： Lithium-ion batteries Physics-informed neural network Bidirectional long-term memory Heat generation rate estimation Electrochemical model

Analysis of diffusion behavior of harmful emissions from trackless rubber-wheel diesel vehicles in underground coal mines

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International Journal of Mining Science and Technology 2022年第6期32卷 1285-1299页

作者： Yun Hua Wen Nie Qiang liu xiaofei liu Chengyi liu Weiwei Zhou Fengning Yu College of Safety and Environmental Engineering Shandong University of Science and TechnologyQingdao 266590China State Key Laboratory of Mining Disaster Prevention and Control Co-founded by Shandong Province and the Ministry of Science and Technology Shandong University of Science and TechnologyQingdao 266590China

To define the diffusion behavior of harmful exhaust substances from diesel vehicles and support safety risk assessments of underground coal mines,we performed a multi-species coupling calculation of the emission and diffusion of harmful substances from a trackless rubber-wheel diesel vehicle.A computational fluid dynamics(CFD)model of the diffusion of harmful emissions was hence established and *** the perspective of risk analysis,the diffusion behavior and distribution of hazardous substances emitted by the diesel vehicle were studied under 4 different conditions;moreover,we identified areas characterized by hazardous levels of *** the vehicle idled upwind in the roadway,high-risk areas formed behind and to the right of the vehicle:particularly high concentrations of pollutants were measured near the rear floor of the vehicle and within 5 m behind the *** the vehicle idled downwind,high-risk areas formed in front of it:particularly high concentrations of pollutants were measured near the floor and within 5 m from the front of the *** the above cases,the driver would not breathe highly polluted air and would be relatively *** the vehicle idled into the chamber,however,high-risk areas formed on both sides of the vehicle and near the upper *** entry of the vehicle caused a greater increase in the concentration of pollutants in the chamber and in the driver’s breathing zone compared with reverse entry.

关键词： Diesel vehicle Harmful emissions Diffusion behavior CFD model Underground coal mine

Simulation of Gas Oil Hydrotreater Heat Exchange Tube and Crystallization Prediction of NH_(4)Cl by Thermodynamic Equilibrium

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China Petroleum Processing & Petrochemical Technology 2023年第2期25卷 142-154页

作者： Jin Haozhe liu Xinyu liu xiaofei Gu Youjie Li Xiaojun Fu Dexiao Institute of Flow-Induced Corrosion Zhejiang Sci-Tech UniversityHangzhou 310018 Key Laboratory of Fluid Transmission Technology of Zhejiang Province Zhejiang Sci-Tech UniversityHangzhou 310018 Institute of Flow-Induced Corrosion and Intelligent Prevention and Control Changzhou UniversityChangzhou 213164

The hydrotreater system heat exchanger is one of the main pieces of heat exchange equipment in petrochemical *** recent years,oil resources have shown a deterioration trend of high sulfur and high acid content,with corrosion risk being prominent in oil *** the multi-medium flow corrosion risk of the hydrotreater heat exchanger pipeline in a petrochemical enterprise as the research object,based on the parameter characteristics of corrosive NH_(3) and HCl media under a high-temperature and high-pressure environment,the ammonium salt crystallization and deposition mechanism under multi-phase flow is *** thermodynamic equilibrium curve is modified based on the thermodynamic principle and fugacity coefficient variation,and the prediction model of ammonium chloride crystallization in hydrotreater heat exchanger under high temperature and high pressure is constructed according to the *** study uses the mixture model,the flow-thermal coupling method,and the discrete phase model method to carry out the numerical simulation of multiphase flow and the numerical prediction of particle distribution characteristics in the heat exchanger pipeline of the hydrotreater heat exchange equipment,so as to realize the quantitative prediction of the particle crystallization deposition distribution in the *** results show that with the decrease of temperature,the crystallization occurs first on both sides of the center of the tube bundle,and more crystallization occurs in the lower half of the U-shaped tube,which may seriously lead to problems such as pipe blockage and under-deposit corrosion.

关键词： hydrotreating processing process modeling thermodynamic equilibrium ammonium salt crystallization numerical simulation and prediction

Facile Fabrication and Optical Properties of Nanostructural PbSe Films

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Chemical Research in Chinese Universities 2014年第6期30卷 987-990页

作者： liu Meng QI xiaofei WU Xionggang ZHANG Hengning Xi 'an Modern Chemistry Research Institute Xi 'an 710065 P. R. China

PbSe films with different nanostructures, such as nanoparticles, nanohollows and hierarchical structures, can be synthesized by adjusting the current density and the reaction temperature via a convenient and efficient electrochemical route in the absence of hard template and surfactant. The calculated band gaps of the prepared PbSe nanoparticles and nanohollows were about 0.32 and 0.43 eV, respectively. This suggests that quantum size effect in nanohollows greatly influences their band gap. This preparation method possesses remarkable advantages, such as low cost, high efficiency and easy preparation, which are very suitable for preparing nanomaterials.

关键词： Thin film PbSe Electrodeposition Nanostructural material Optical property

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水库下采煤安全性评价分析

煤炭技术 2025年第1期44卷 135-139页

作者：裴书锋魏福泽刘晓飞华北水利水电大学地球科学与工程学院郑州450046 华北水利水电大学地质灾害防控研究所郑州450046 郑州煤炭工业(集团)有限责任公司郑州450007

为了分析水库下采煤对水库及地表的影响,以某煤矿32采区为例,采用理论计算、数值模拟相结合的研究方法,分析了煤层开采后上覆岩层破坏形成的导水裂缝带高度,采用概率积分法和数值模拟得到了某煤矿地表水库地表最大下沉值和水平变形值。... 详细信息

为了分析水库下采煤对水库及地表的影响,以某煤矿32采区为例,采用理论计算、数值模拟相结合的研究方法,分析了煤层开采后上覆岩层破坏形成的导水裂缝带高度,采用概率积分法和数值模拟得到了某煤矿地表水库地表最大下沉值和水平变形值。结果表明:导水裂缝带最大标高距底部的高差均大于250 m,导水裂缝带不会影响到水库安全,地表水平变形最大值远小于规定允许变形值,在地表水库下进行煤炭开采是安全的。通过32采区工作面的安全开采,验证了分析方法与结果的合理性。

关键词：水库下采煤导水裂缝带地表沉降数值模拟

Ammonium Salt Deposition Characteristics in an Air Cooler System Based on the Coupling of Fluid Flow and Heat Transfer Simulation

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China Petroleum Processing & Petrochemical Technology 2019年第4期21卷 94-102页

作者： Jin Haozhe Zhou Junfeng liu Wenwen liu xiaofei Ou Guofu The Institute of Flow-Induced Corrosion Zhejiang Sci-Tech UniversityHangzhou 310018 The Insititute of Flow-Induced Corrosion and Intelligent Precaution and Control Changzhou UniversityChangzhou 213016

The ammonium salt corrosion is a typical failure mode for the hydrogenation reaction effluent air cooler(REAC) system. In order to investigate the corrosion characteristics in the REAC system, numerical simulations were performed by using the mixture model, the heating transfer model, and the particles tracking model. The results show that the differences between the temperature and the velocity at each cross section of the first-row and second-row tubes are small. The inertia of the particles plays an important role in the particle’s deposition, and the smaller particles distribute more uniformly in the air cooler. However, for larger particles, they prefer falling from the inner side of the vertical elbow, and preferentially depositing at the inlet header and pipes before saturation. In the heat exchanger tubes, the particle deposition number is larger in the second-row tubes than that in the first-row tubes, and the high-risk tubes mainly concentrate on the middle and right side of the air cooler. The kinetic parameters of the particles are in accordance with the blocking-prone position in many real operating conditions.

关键词： hydrogenation air cooler multiphase flow ammonium salt corrosion particles drifting

SPATIOTEMPORAL VARIATION OF WATER QUALITY AND ALGAL BIOMASS IN ERHAI LAKE AND ITS ENVIRONMENTAL MANAGEMENT IMPLICATIONS

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Frontiers of Agricultural Science and Engineering 2023年第4期10卷 566-578页

作者： xiaofei liu Yue WU Zhaokui NI Shengrui WANG Guangdong-Hong Kong Joint Laboratory for Water Security Center of Water ResearchBeijing Normal University at ZhuhaiZhuhai519087China Engineering Research Center of Ministry of Education on Groundwater Pollution Control and Remediation College of Water SciencesBeijing Normal UniversityBeijing 100875China National Engineering Laboratory for Lake Pollution Control and Ecological Restoration Chinese Research Academy of Environmental SciencesBeijing 100012China Yunnan Key Laboratory of Pollution Process and Management of Plateau Lake Watershed Kunming 650034China

Elucidating the spatiotemporal pattern of water quality and algal biomass is crucial for accurately tracing pollution sources and reducing the risk of algal blooms in lake *** study analyzed the spatiotemporal variability of water quality and algal biomass in Erhai Lake from 1994 to 2021 using water quality index(WQi),Mann-Kendall test and Sen's slope combined *** potential causes of water quality deterioration and algal biomass dynamics were also *** results showed that the historical changes in the water environment of Erhai Lake mainly had three stages:satisfactory(1994-2001),deteriorating(2002-2010)and improving(2011-2021).The changes in water quality and algal biomass were primarily affected by total nitrogen,total phosphorus and chemical oxygen demand in different *** water environment of Erhai Lake is currently improving significantly,starting in the southern area that is furthest from the sources of agricultural pollution,especially in summer and *** is attributed to the implementation of control measures resulting in lower pollutant loads at particular times and ***,it is necessary to continue to promote standardized livestock farming,to strengthen rural wastewater collection and to investigate measures such as the interruption of the endogenous cycle.

关键词： dating pollution starting