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Study on tungsten sintering temperature field based on electromagnetic simulation and computational fluid dynamics

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Tungsten 2024年第2期6卷 355-366页

作者： Lu-Yan Wang Yue-Guang Yu Jian-Xin Dong Kai-Ping Du Shan-Yu Liu Cao-Bing Li University of Science and Technology beijing Beijing 100083China BGRIMM Technology Group Beijing 100160China China Iron&Steel research Institute Group Beijing 100081China

In order to study the influence of various sintering variables more intuitively and clearly,electromagnetic field analysis and computational fl uid dynamics are used to analyze the infl uence of gas flow,heating power and other process parameters on the temperature range of medium-frequency sintering in this *** results indicate that the uniformity of temperature fi eld is determined by the gas flow rate and heating *** the heating power is 50 kW,the stable temperature drops about 10 K for every 1 m^(3)·h^(−1)increase of hydrogen *** peak value of the maximum temperature diff erence on the tungsten rods gradually increases with the increase of the hydrogen flow rate,and it appears slightly *** temperature distribution of tungsten rods in furnace is similar with diff erent hydrogen flow *** the same time,the closer to the furnace wall,the higher the temperature of the tungsten *** temperature diff erence between tungsten rods mainly occurred within 1 h after the beginning of *** the heating power can improve the stable temperature,but has little eff ect on the heating *** heating power can increase the peak value of the maximum temperature diff erence on the tungsten rods,but has little eff ect on the occurrence time of the peak value of the maximum temperature diff erence on the tungsten *** the heating power will increase the temperature diff erence of a single tungsten rod,but the temperature diff erence of a single tungsten rod never exceeds 65 *** study can be used to guide the process optimization *** with numerical simulation calculation,the sintering parameters with low energy consumption and high temperature uniformity can be quickly and eff ectively found,thus improving the microstructure and properties of sintered tungsten products.

关键词： Tungsten products Sintering Hydrogen flow rate Heating power

Visible-Light-Mediated Photocatalyst-Free Hydroacylation of Azodicarboxylic Acid Derivatives with 4-Acyl-1,4-dihydropyridines

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Chinese Journal of Chemistry 2024年第11期42卷 1230-1236页

作者： Li Liu Jing Wang Xiaoying Feng Kun Xu Wei Liu Xia Peng Hongguang Du Jiajing Tan Department of Organic Chemistry College of ChemistryBeijing University of Chemical TechnologyBeijing100029 China Sinopec beijing research Institute of Chemical Industry Beijing100013 China Faculty of Environment and Life Beijing University of TechnologyBeijing100124 China

A visible-light-enabled,photocatalyst-free hydroacylation reaction of azodicarboxylic acid derivatives was *** radical conjugate addition(RCA)protocol relied on the dual role of 4-acyl-1,4-dihydropyridine(acyl-DHP)reagents that besides being as radical reservoirs,they also enabled the conversion of radical adducts to anion intermediates via ***“catalyst-oxidant-additive free”conditions,a wide range of structurally different acyl hydrazide products were readily obtained in 56%—99%*** utility of this transformation was further demonstrated by the scale-up synthesis and downstream derivatization.

关键词： Azo compounds Radicals Acylation 4-Acyl-1,4-dihydropyridine Photochemistry

Dynamic Scene Graph Generation of Point Clouds with Structural Representation Learning

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Tsinghua Science and Technology 2024年第1期29卷 232-243页

作者： Chao Qi Jianqin Yin Zhicheng Zhang Jin Tang School of Artificial Intelligence Beijing University of Posts and TelecommunicationsBeijing 100876China Standard and Metrology research Institute China Academy of Railway Sciences Corporation LimitedBeijing 100081China

Scene graphs of point clouds help to understand object-level relationships in the 3D *** graph generation methods work on 2D structured data,which cannot be used for the 3D unstructured point cloud *** point-cloud-based methods generate the scene graph with an additional graph structure that needs labor-intensive manual *** address these problems,we explore a method to convert the point clouds into structured data and generate graphs without given ***,we cluster points with similar augmented features into groups and establish their relationships,resulting in an initial structural representation of the point ***,we propose a Dynamic Graph Generation Network(DGGN)to judge the semantic labels of targets of different *** dynamically splits and merges point groups,resulting in a scene graph with high *** show that our methods outperform other baseline *** output reliable graphs describing the object-level relationships without additional manual labeled data.

关键词： scene graph generation structural representation point cloud

Investigations of the mechanical response of dummy HTPB propellant grain under ultrahigh acceleration overload conditions using onboard flight-test measurements

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Defence Technology（防务技术） 2024年第2期32卷 473-484页

作者： Yiming Zhang Ningfei Wang Weihua Ma Ran Wang Long Bai Yi Wu School of Aerospace Engineering Beijing Institute of TechnologyBeijing 100081China beijing System Design Institute of Electro-mechanic Engineering Beijing 100854China Xi'an Changfeng research Institute of Mechanism and Electricity Xi'an 710065China

In this paper,to study the mechanical responses of a solid propellant subjected to ultrahigh acceleration overload during the gun-launch process,specifically designed projectile flight tests with an onboard measurement system were *** projectiles containing dummy HTPB propellant grains were successfully recovered after the flight tests with an ultrahigh acceleration overload value of 8100 *** onboard-measured time-resolved axial displacement,contact stress and overload values were successfully obtained and *** compression tests of the dummy HTPB propellant used in the gunlaunched tests were carried out at low and intermediate strain rates to characterize the propellant's dynamic properties.A linear viscoelastic constitutive model was employed and applied in finite-element simulations of the projectile-launching *** the launch process,the dummy propellant grain exhibited large deformation due to the high acceleration overload,possibly leading to friction between the motor case and propellant *** calculated contact stress showed good agreement with the experimental results,though discrepancies in the overall displacement of the dummy propellant grain were *** dynamic mechanical response process of the dummy propellant grain was analysed in *** results can be used to estimate the structural integrity of the analysed dummy propellant grain during the gun-launch process.

关键词： Gun-launched flight test Dummy HTPB propellant Onboard measurements Utrahigh overload Mechanical response

LociScan,a tool for screening genetic marker combinations for plant variety discrimination

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The Crop Journal 2024年第2期12卷 583-593页

作者： Yang Yang Hongli Tian Hongmei Yi Zi Shi Lu Wang Yaming Fan Fengge Wang Jiuran Zhao beijing Key Laboratory of Maize DNA Fingerprinting and Molecular Breeding Maize Research InstituteBeijing Academy of Agriculture and Forestry SciencesBeijing 100097China

To reduce the cost and increase the efficiency of plant genetic marker fingerprinting for variety discrimination,it is desirable to identify the optimal marker *** describe a marker combination screening model based on the genetic algorithm(GA)and implemented in a software tool,Loci ***-based variety discrimination power provided the largest optimization space among multiple fitness *** GA parameters,an increase in population size and generation number enlarged optimization depth but also calculation *** algorithm afforded the same optimization depth as GA but vastly increased calculation *** comparison with two other software tools,Loci Scan accommodated missing data,reduced calculation time,and offered more fitness *** large datasets,the sample size of training data exerted the strongest influence on calculation time,whereas the marker size of training data showed no effect,and target marker number had limited effect on analysis speed.

关键词： Plant variety discrimination Genetic marker combination Variety discrimination power Genetic algorithm

Design parameter optimization method for a prestressed steel structure driven by multi-factor coupling

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Frontiers of Structural and Civil Engineering 2024年第7期18卷 1066-1083页

作者： Guo-Liang SHI Zhan-Sheng LIU De-Chun LU Qing-Wen ZHANG Majid DEZHKAM Ze-Qiang WANG Faculty of Architecture Civil and Transportation EngineeringBeijing University of TechnologyBeijing 100124China The Key Laboratory of Urban Security and Disaster Engineering of the Ministry of Education Beijing University of TechnologyBeijing 100124China beijing Building Construction research Institute Co. Ltd.Beijing 100039China

To achieve efficient structural design,it is crucial to reduce the cost of materials while ensuring structural *** study proposes an optimization method for design parameters(DPs)in a prestressed steel structure driven by multi-factor *** accomplish this,a numerical proxy model of prestressed steel structures is established with integration of DPs and mechanical parameters(MPs).A data association-parameter analysis-optimization selection system is established.A correlation between DPs and MPs is established using a back propagation(BP)neural *** correlation provides samples for parameter analysis and optimization *** are used to characterize the safety of the *** on the safety grade analysis,the key DPs that affect the mechanical properties of the structure are obtained.A mapping function is created to match the MPs and the key *** optimal structural DPs are obtained by setting structural materials as the optimization objective and safety energy as the constraint *** theoretical model is applied to an 80-m-span gymnasium and verified with a scale test physical *** MPs obtained using the proposed method are in good agreement with the experimental *** with the traditional design method,the design cycle can be shortened by more than 90%.Driven by the optimal selection method,a saving of more than 20% can be achieved through reduction of structural material ***,the cross-sectional dimensions of radial cables have a substantial influence on vertical *** initial tension and cross-sectional size of the upper radial cable exhibit the most pronounced impact on the stress distribution in that *** initial tension and cross-sectional size of the lower radial cable hold the greatest sway over the stress distribution in that cable.

关键词： structure design association relationship performance analysis optimum selection experimental verification

Production induced fracture closure of deep shale gas well under thermo-hydro-mechanical conditions

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Petroleum Science 2024年第3期21卷 1796-1813页

作者： Shi-Ming Wei Yang Xia Yan Jin Xu-Yang Guo Jing-Yu Zi Kai-Xuan Qiu Si-Yuan Chen College of Science China University of Petroleum(Beijing)Beijing102249China CNOOC research Institute Ltd Beijing100028China The University of Hong Kong Hong Kong999077China

Deep shale gas reservoirs have geological characteristics of high temperature,high pressure,high stress,and inferior ability to pass through *** multi-stage fractured horizontal well is the key to exploiting the deep shale gas ***,during the production process,the effectiveness of the hydraulic fracture network decreases with the closure of fractures,which accelerates the decline of shale gas *** this paper,we addressed the problems of unclear fracture closure mechanisms and low accuracy of shale gas production prediction during deep shale gas *** we established the fluid—solid—heat coupled model coupling the deformation and fluid flow among the fracture surface,proppant and the shale *** the fluid—solid—heat coupled model was applied to the fracture network,it was well solved by our numerical method named discontinuous discrete fracture *** with the conventional discrete fracture method,the discontinuous discrete fracture method can describe the three-dimensional morphology of the fracture while considering the effect of the change of fracture surface permeation coefficient on the coupled fracture—matrix flow and describing the displacement discontinuity across the *** simulations revealed that the degree of fracture closure increases as the production time proceeds,and the degree of closure of the secondary fractures is higher than that of the primary *** creep and proppant embedment both increase the degree of fracture *** reduction in fracture surface permeability due to proppant embedment reduces the rate of fluid transfer between matrix and fracture,which has often been overlooked in the ***,it significantly impacts shale gas production,with calculations showing a 24.7%cumulative three-year yield *** study is helpful to understand the mechanism of hydraulic fracture ***,it provides the theoretical guidance for maintaining the long

关键词： Shalegas Fracture closure Fluid-solid-heat coupling Discontinuous discrete fracture

Enhanced electrocatalytic CO_(2)reduction to formic acid using nanocomposites of In_(2)O_(3)@C with graphene

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Nano research 2024年第6期17卷 5031-5039页

作者： Wenxiang Li Shuo Gao Chuanruo Yang Juntao Yang Amjad Nisar Guolei Xiang Junsu Jin beijing Key Laboratory of Membrane Science and Technology Beijing University of Chemical TechnologyBeijing 100029China Nanomaterials research Group PDPINSTECHIslamabad 44000Pakistan Institute of Industrial Chemistry College of ChemistryBeijing University of Chemical TechnologyBeijing 100029China

In_(2)O_(3)is an effective electrocatalyst to convert CO_(2)to formic acid(HCOOH),but its inherent poor electrical conductivity limits the efficient charge transfer during the ***,the tendency of In_(2)O_(3)particles to agglomerate during synthesis further limits the exposure of active *** we address these issues by leveraging the template effect of graphene oxide and employing InBDC as a self-sacrificing template for the pyrolysis synthesis of In_(2)O_(3)@*** resulting In_(2)O_(3)@C/rGO-600 material features In_(2)O_(3)@C nanocubes uniformly anchored on a support of reduced graphene oxide(rGO),significantly enhancing the active sites *** conductive rGO network facilitates charge transfer during electrocatalysis,and the presence of oxygen vacancies generated during pyrolysis,combined with the strong electron-donating ability of rGO,enhances the adsorption and activation of CO_(2).In performance evaluation,In_(2)O_(3)@C/rGO-600 exhibits a remarkable HCOOH Faradaic efficiency exceeding 94.0%over a broad potential window of−0.7 to−1.0 V(*** hydrogen electrode(RHE)),with the highest value of 97.9%at−0.9 V(***)in a ***,the material demonstrates an excellent cathodic energy efficiency of 71.6%at−0.7 V(***).The study underscores the efficacy of uniformly anchoring metal oxide nanoparticles onto rGO for enhancing the electrocatalytic CO_(2)reduction performance of materials.

关键词： In_(2)O_(3)@C nanocomposite electrochemical CO_(2)reduction reduced graphene oxide oxygen vacancy

Climatic impacts induced by winter wheat irrigation over North China simulated by the nonhydrostatic RegCM4.7

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Advances in Climate Change research 2024年第2期15卷 197-210页

作者： Jia WU Zhen-Yu HAN Xue-Jie GAO Zheng-Jia LIU National Climate centre China Meteorological AdministrationBeijing 100081China Key Laboratory for Climate Studies China Meteorological AdministrationBeijing 100081China Climate Change research Center Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Nanjing University of Information Science and TechnologyNanjing 210044China Institute of Geographic Sciences and Natural Resources research Chinese Academy of SciencesBeijing 100101China

Quantification of the impact of winter wheat irrigation on the climate and the occurrence of extreme climatic events over North China is crucial for regional adaptation *** related studies mainly focused on the impact on surface processes;however,few focused on the effects of extreme events using high-resolution nonhydrostatic regional climate ***,the 9-km-resolution nonhydrostatic RegCM4.7 was coupled with a crop irrigation scheme and an updated winter wheat irrigation dataset to better simulate irrigation *** experiments were conducted with and without winter wheat irrigation to isolate the effects of *** showed that irrigation simulation reduces the model biases in temperature,precipitation,latent heat flux,soil moisture,sensitive heat flux,and top-layer soil ***,it also reduces the bias and increases the correlation with observations obtained in irrigated areas,especially in summer,indicating better representation of irrigation *** wheat irrigation tends to cause substantial cooling of the local surface maximum,minimum,and mean air temperatures(by-1.68,-0.34,and-0.79℃,respectively)over irrigated areas of North China,with the largest changes observed in relation to maximum ***,precipitation is found to increase during spring and summer,which is strongly related to water vapor transport in the lower levels of the *** analyses indicated that the number of annual mean hot days decrease(-13.9 d),whereas the number of both comfort days(+10.2 d)and rainy days(days with total precipitation greater than 1 mm:+6.6 d)increase over irrigated areas,demonstrating beneficial feedback to human perception and ***,although the heat wave risk increases(number of annual mean heat wave days:+5.8 d),the impact is limited to small areas within irrigated ***,no notable change was found in terms of heavy rainfall events and precipitation intensity

关键词： Nonhydrostatic regional climate model Irrigation effect Extreme events North China