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Temporal and spatial evolution of global major grain trade patterns

Journal of Integrative Agriculture 2024年第3期23卷 1075-1086页

作者： Ziqi Yin Jiaxuan Hu Jing Zhang Xiangyang Zhou Lingling Li Jianzhai Wu Agricultural Information institute Chinese Academy of Agricultural SciencesBeijing 100081China institute of Scientific and technical Information of China Beijing 100038China Zibo Agricultural Science Research institute Zibo 255000China Zibo institute for Digital Agriculture and Rural Research Zibo 255000China

The complex and volatile international landscape has significantly impacted global grain supply security. This study uses a complex network analysis model to examine the evolution and trends of the global major grain trade from 1990 to 2020, focusing on network topology, centrality ranking, and community structure. There are three major findings. First, the global major grain trade network has expanded in scale, with a growing emphasis on diversification and balance. During the study period, the United States, Canada, China, and Brazil were the core nodes of the network. Grain-exporting countries were mainly situated in Asia, the Americas, and Europe, and importing countries in Asia, Africa, and Europe. Second, a significant increase in the number of high centrality countries with high export capacity occurred, benefiting from natural advantages such as fertile land and favorable climates. Third, the main global grain trade network is divided into four communities, with the Americas-Europe community being the largest and most widespread. The formation of the community pattern was influenced by geographic proximity, driven by the core exporting countries. Therefore, the world needs to enhance the existing trade model, promote the multi-polarization of the grain trade network, and establish a global vision for the future community. Countries and regions should participate actively in global grain trade security governance and institutional reform, expand trade links with other countries, and optimize import and export policies to reduce trade risks.

关键词： grain trade pattern evolution complex network

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Method for passivation of propellant residues in orbital stage tank of launch vehicle

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Chinese Journal of Aeronautics 2024年第1期37卷 64-76页

作者： Valeriy TRUSHLYAKOV Ivan LESNYAK Alexey PANICHKIN Department of Aviation and Rocket Building Omsk State Technical UniversityOmsk 644050Russia Sobolev institute of Mathematics of the Siberian Branch of Russian Academy of Sciences Novosibirsk 630090Russia

The problem of removing unused liquid propellant residues from the tanks of spent spacecraft and orbital stages of Launch Vehicles(LV)leads to their explosion and the formation of space debris in *** provide a solution to this problem,a method for removing liquid propellant residues from the LV tanks after the mission completion is *** method is based on the gasification of liquid propellant residues in the tanks under acoustic-vacuum exposure and the discharge of the gasification products into the surrounding outer *** investigations were carried out on a Ground-based Experimental Installation(GEI)to determine the coefficient of heat transfer from the surface of an acoustic radiator to a *** obtained coefficient was then used to calculate the energy costs for the gasification of *** estimates are given on the example of the tank with kerosene residues from a spent second stage of the LV“Soyuz-2.1 v”.The optimal discharge rate at which kerosene does not freeze is 0.14 m^(3)/***,the acoustic exposure leads to an increase in the mass of evaporated kerosene over a given time by96.1%,and the energy costs are 1756.7 kJ(approximately 50% of the remaining electrical energy).

关键词： Propellant Weightlessness Liquid evaporation Heat and mass transfer Acoustics Vacuum Vapor bubbles

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Enhanced superelasticity and reversible elastocaloric effect in nano-grained NiTi alloys with low stress hysteresis

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Chinese Physics B 2024年第5期33卷 557-562页

作者：周敏王维苏浩健胡忠军李来风 Key Laboratory of Cryogenic Science and Technology Technical Institute of Physics and ChemistryChinese Academy of SciencesBeijing 100190China Songshan Lake Materials Laboratory Dongguan 523808China

Solid-state cooling technologies have been considered as potential alternatives for vapor compression cooling *** search for refrigeration materials displaying a unique combination of pronounced caloric effect,low hysteresis,and high reversibility on phase transformation was very active in recent ***,we achieved increase in the elastocaloric reversibility and decrease in the friction dissipation of martensite transformations in the superelastic nano-grained NiTi alloys obtained by cold rolling and annealing treatment,with very low stress hysteresis(6.3 MPa)under a large applied strain(5%).Large adiabatic temperature changes(△T_(max)=16.3 K atε=5%)and moderate COP_(mater)values(maximum COP_(mater)=11.8 atε=2%)were *** present nano-grained NiTi alloys exhibited great potential for applications as a highly efficient elastocaloric material.

关键词： elastocaloric effect stress hysteresis superelasticity NiTi alloy

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Fault diagnosis of a marine power-generation diesel engine based on the Gramian angular field and a convolutional neural network

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2024年第6期25卷 470-482页

作者： Congyue LI Yihuai HU Jiawei JIANG Dexin CUI Merchant Marine College Shanghai Maritime UniversityShanghai 201306China School of Mechanical and Energy Engineering Shanghai Technical Institute of Electronics&InformationShanghai 201411China

Marine power-generation diesel engines operate in harsh *** vibration signals are highly complex and the feature information exhibits a non-linear *** is difficult to extract effective feature information from the network model,resulting in low fault-diagnosis *** address this problem,we propose a fault-diagnosis method that combines the Gramian angular field(GAF)with a convolutional neural network(CNN).Firstly,the vibration signals are transformed into 2D images by taking advantage of the GAF,which preserves the temporal *** raw signals can be mapped to 2D image features such as texture and *** integrate the feature information,the images of the Gramian angular summation field(GASF)and Gramian angular difference field(GADF)are fused by the weighted average fusion ***,the channel attention mechanism and temporal attention mechanism are introduced in the CNN model to optimize the CNN learning *** the concept of residuals in the attention mechanism improves the feasibility of ***,the weighted average fused images are fed into the CNN for feature extraction and fault *** validity of the proposed method is verified by experiments with abnormal valve *** average diagnostic accuracy is 98.40%.When−20 dB≤signal-to-noise ratio(SNR)≤20 dB,the diagnostic accuracy of the proposed method is higher than 94.00%.The proposed method has superior diagnostic ***,it has a certain anti-noise capability and variable-load adaptive capability.

关键词： Multi-attention mechanisms(MAM) Convolutional neural network(CNN) Gramian angular field(GAF) Image fusion Marine power-generation diesel engine Fault diagnosis

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Thermal Performance of a 4 K High-Frequency Pulse Tube Cryocooler with Different Working Fluids

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Journal of Thermal Science 2024年第4期33卷 1468-1479页

作者： GAO Zhaozhao YANG Biao FAN Xiaoyu CHEN Liubiao WANG Junjie Key Laboratory of Cryogenic Science and Technology Technical Institute of Physics and ChemistryChinese Academy of SciencesBeijing100190China University of Chinese Academy of Sciences Beijing100049China

The high-frequency pulse tube cryocooler(HPTC)represents a promising miniature cryocooling technology due to its compact structure and the absence of low-temperature moving ***,limited to the non-ideal gas effect of4He,the HPTC is hard to obtain high cooling performance in the liquid helium temperature range.3He as the working fluid can effectively improve the cooling performance of the HPTC,but the high cost hinders its wide *** consideration of both cooling performance and cost-effectiveness,this paper explores the feasibility of utilizing^(3)He-^(4)He mixtures as the working fluid for ***,the experimental results of a developed HPTC based4He are *** a total power consumption of 575 W,the lowest temperature of 3.26 K was *** the measured cooling power at 4.2 K was 20.8 *** the theoretical utmost efficiency of the cryocooler was calculated in terms of the thermophysical properties of the working fluids,using ^(3)He-^(4)He mixtures with different compositions as the working *** whole machine modeling of the HPTC was further carried out,and the influence of the working fluids with different components on the structural parameters such as double-inlet and inertance tube,and operating parameters such as pressure and frequency were *** calculated results show that the cooling power is expected to be increased to36 mW and 53 mW if the equimolar ^(3)He-^(4)He mixture and pure ^(3)He are used,respectively.

关键词： high-frequency pulse tube cryocooler ^(3)He-^(4)He mixture liquid helium temperature thermally coupled

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Highly efficient tunable photodetector with a bipolar response in van der Waals heterojunctions

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Science China(Technological Sciences) 2024年第2期67卷 639-646页

作者： SHI ChaoFan ZHANG Shi XIAO KeNing ZHANG LiBo HAN Li ZHU YuLin TANG WeiWei LIU ChangLong LI GuanHai CHEN XiaoShuang College of Physics and Optoelectronic Engineering Hangzhou Institute for Advanced StudyUniversity of Chinese Academy of Sciences Hangzhou310024China State Key Laboratory of Infrared Physics Shanghai Institute of Technical PhysicsChinese Academy of SciencesShanghai 200083China

The heterojunction integration of two-dimensional(2D)materials via van der Waals(vdW)forces,unencumbered by lattice and processing constraints,constitutes an efficacious approach to enhance the overall optoelectronic performance of photodetectors,due to an assortment of distinctive light-matter ***,vdW heterojunction photodetectors based on transition metal dichalcogenides(TMDs)face an inevitable trade-off between low dark currents and high responsivity,curtailing the application potential of myriad novel optoelectronic components in sensing,spectral,and communication *** this study,we present the successful actualization of a highly sensitive,self-powered,and gate-tunable bipolar response *** mechanisms underlying photocurrent generation were scrutinized via bias-,power-,and position-dependent mapping photoresponse measurements,identifying the photovoltaic effect,which is attributable to the Schottky junction’s built-in electric field,as the predominant *** prototype Au-WS2-graphene photodetector exhibits a remarkable light on/off ratio of 1.2×10^(6),a specific detectivity of 6.12×10^(11)cm H^(z1/2)W^(-1)with 20μs response time at 638 *** wide gate-tunable responsivity provides an adjustability scope,ranging from 0.9 to 3.1 A W^(-1).Notably,the device demonstrates an exceptional linear photocurrent response,with a linear dynamic range(LDR)value approximating 130 dB,which significantly surpasses that of other photodetectors based on TMDs.

关键词： WS2/graphene van der Waals heterojunction gate-tunable bipolar response

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Comprehensive insights into recent innovations:Magnesium-inclusive high-entropy alloys

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Journal of Magnesium and Alloys 2024年第4期12卷 1311-1345页

作者： Andrii Babenko Ehsan Ghasali Saleem Raza Kahila Baghchesaraee Ye Cheng Asif Hayat Peng Liu Shuaifei Zhao Yasin Orooji Shandong Vocational and technical University of International Studies Rizhao 276826China Zhejiang Normal University Jinhua 321004China Geelong Institute for Frontier MaterialsDeakin UniversityVIC 3216Australia

This review focuses on thermodynamic and physical parameters,synthesis methods,and reported phases of Magnesium(Mg)containing high-entropy alloys(HEAs).Statistical data of publications concerning Mg-containing HEAs were collected and *** on the chemical elements included in Mg-containing HEAs,their theoretical end experimental densities,thermodynamic parameters,physical parameters,fabricated techniques and reported phases were also collected and *** the basis of this information,a new classification for HEAs was *** is also shown that the existing thermodynamic parameters cannot accurately predict the formation of a single phase solid solution for Mg-containing *** physical parameters of Mg-containing HEAs are within a wide range,and most of the synthesized Mg-containing HEAs have a complex multiphase structure.

关键词： Magnesium High-entropy alloys Classification Thermodynamic parameters Physical parameters

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Absence of BCS–BEC crossover in FeSe0.45Te0.55 superconductor

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Chinese Physics B 2024年第7期33卷 89-96页

作者：贾俊杰谷亚东殷超辉束英杰陈逸雯史聚民张杏陈浩苗泰民任晓琳梁波朱文培蔡能张丰丰张申金杨峰王志敏彭钦军许祖彦毛寒青刘国东任治安赵林周兴江 National Laboratory for Superconductivity Beijing National Laboratory for Condensed Matter PhysicsInstitute of Physics Chinese Academy of Sciences University of Chinese Academy of Sciences technical institute of Physics and Chemistry Chinese Academy of Sciences Songshan Lake Materials Laboratory

In iron-based superconductor Fe（Se,Te）, a flat band-like feature near the Fermi level was observed around the Brillouin zone center in the superconducting state. It is under debate whether this is the evidence on the presence of the BCS–BEC[Bardeen–Cooper–Schrieffer（BCS）, Bose–Einstein condensation（BEC）] crossover in the superconductor. High-resolution laser-based angle-resolved photoemission measurements are carried out on high quality single crystals of FeSe0.45Te0.55superconductor to address the issue. By employing different polarization geometries, we have resolved and isolated the dyz band and the topological surface band, making it possible to study their superconducting behaviors separately. The dyz band alone does not form a flat band-like feature in the superconducting state and the measured dispersion can be well described by the BCS picture. We find that the flat band-like feature is formed from the combination of the dyz band and the topological surface state band in the superconducting state. These results reveal the origin of the flat band-like feature and rule out the presence of BCS-BEC crossover in Fe（Se,Te） superconductor.

关键词： FeSe_(0.45)Te_(0.55) ARPES electronic structure superconducting gap BCS-BEC crossover

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Heat Transfer Enhancement of the Absorber Tube in a Parabolic Trough Solar Collector through the Insertion of Novel Cylindrical Turbulators

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Fluid Dynamics & Materials Processing 2024年第6期20卷 1279-1297页

作者： Yasser Jebbar Fadhil Fluiful Wisam Khudhayer Department of Electrical Techniques Al-Mussaib Technical InstituteAl-Furat Al-Awsat Technical UniversityBabilIraq Department of Physics Collage of ScienceUniversity of KerbalaKarbalaIraq Department of Energy Engineering Collage of Engineering/Al-MusayabUniversity of BabylonBabilIraq

This study includes an experimental and numerical analysis of the performances of a parabolic trough collector(PTC)with and without cylindrical *** PTC is designed with dimensions of 2.00 m in length and 1.00 m in *** related reflector is made of lined sheets of aluminum,and the tubes are made of stainless steel used for the absorption of *** have an outer diameter of 0.051 m and a wall thickness of 0.002 ***,used as a heat transfer fluid(HTF),flows through the absorber tube at a mass flow rate of 0.7 kg/*** dimensions of cylindrical turbulators are 0.04 m in length and 0.047 m in *** are performed using the ANSYS Fluent 2020 R2 *** PTC performance is evaluated by comparing the experimental and numerical outcomes,namely,the outlet temperature,useful heat,and thermal efficiency for a modified tube(MT)(tube with novel cylindrical turbulators)and a plain tube(PT)(tube without novel cylindrical turbulators).According to the results,the experimental outlet temperatures recorded 63.2°C and 50.5°C for the MT and PT,*** heat gain reaches 1137.5 Win the MT and 685.8 Win the *** to the PT collector,the PTC exhibited a(1.64 times)higher efficiency.

关键词： Parabolic trough collector turbulators absorber tube ANSYS thermal efficiency

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Magnesium oxide(MgO)nanoadsorbents in wastewater treatment:A comprehensive review

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Journal of Magnesium and Alloys 2024年第5期12卷 1709-1773页

作者： H.C.S.Perera V.Gurunanthanan Anoop Singh M.M.M.G.P.G.Mantilaka G.Das Sandeep Arya Department of Physics Khalifa UniversityAbu Dhabi12788United Arab Emirates Postgraduate institute of Science University of PeradeniyaPeradeniyaSri Lanka Department of Humanities and Sciences Guru Nanak Institutions Technical CampusIbrahimpatnamHyderabad501506India Centre for Global Health Research Saveetha Medical College and HospitalsSaveetha Institute of Medical and Technical SciencesChennai602105Tamil NaduIndia Department of Physics University of JammuJammu and Kashmir180006India

Wastewater contamination by heavy metals and synthetic dyes presents a significant environmental challenge,necessitating effective and sustainable separation *** review article provides a detailed examination of magnesium oxide(MgO)nanoparticles as an innovative nanoadsorbent for wastewater treatment,with a specific focus on heavy metal and dye *** review comprehensively explores various aspects of MgO nanoparticles,including their structural characteristics and synthesis *** article delves into the morphology and crystallographic arrangement of MgO nanoparticles,offering insights into their structural *** the complexity of adsorption processes,the review identifies and analyzes parameters influencing the adsorption efficiency of MgO nanoparticles,such as temperature,pH,contact time,initial concentration,and co-existing *** interplay between these parameters and the adsorption capability of MgO nanoparticles emphasizes the importance of optimizing operational ***,the review assesses various synthesis methods for MgO nanoparticles,including sol-gel,hydrothermal,precipitation,green synthesis,solvothermal,and template-assisted *** discusses the advantages,limitations,and resulting nanoparticle characteristics of each method,enabling readers to grasp the implications of synthesis processes on adsorption *** comprehensive review consolidates current insights into the effectiveness of MgO nanoparticles as a potent nanoadsorbent for removing heavy metals and dyes from wastewater covering a wide spectrum of aspects related to MgO ***,there is a need to investigate the use of MgO in the treatment of actual wastewater or river water,in order to leverage its cost-effectiveness and high efficiency for practical water treatment applications in real-time.

关键词： MgO nanoparticles Nanoadsorbent Wastewater treatment Heavy metals Dye separation Adsorption Synthesis methods

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