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Carbon-based materials with combined functions of thermal management and electromagnetic protection: Preparation, mechanisms, properties, and applications

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Nano Research 2024年第3期17卷 883-903页

作者： Junwei yue Yiyu Feng Mengmeng qin Wei Feng School of Materials Science and Engineering and tianjin Key Laboratory of Composite and Functional Materials Tianjin UniversityTianjin 300350China

The proliferation of high-power,highly informationized,and highly integrated electronic devices and weapons equipment has given rise to increasingly conspicuous issues about electromagnetic(EM)pollution and thermal *** issues,in turn,impose constraints on the performance of such equipment and jeopardize personnel *** materials,owing to their diverse and modifiable structures,offer adjustable thermal and electric conductivity,rendering them highly promising for applications in fields such as thermal management and EM protection which have garnered extensive research and *** pursuit of integrated device and equipment development has elevated the demand for multifunctional materials,prompting significant research into carbon-based composite materials that include both thermal management and EM protection ***,there are no relevant reviews on this topic at ***,this work consolidates research findings from recent years on carbon matrix composites exhibiting dual attributes of thermal management and EM *** attributes include thermally conductive electromagnetic interference(EMI)shielding materials,thermally insulating EMI shielding materials,thermally conductive EM wave(EMW)absorbing materials,and thermally insulating EMW absorbing *** paper elucidates the fundamental principles underpinning thermal conduction,thermal insulation,EMW absorbing,and EMI ***,it engages in discussions surrounding areas of contention,design strategies,and the functional properties of various material ***,the paper concludes by presenting the challenges encountered and potential research strategies about composites endowed with both thermal management and EM protection functionalities,while also envisaging the development of novel multifunctional EM protection materials.

关键词： carbon-based composites electromagnetic interference shielding microwave absorption thermal conduction thermal insulation

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Enhanced bright green luminescence from GdOF:Ho^(3+) up-conversion phosphor via Yb^(3+) doping

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Journal of Rare Earths 2024年第2期42卷 263-269,I0002页

作者： Linjun qin yue Guo Jing Xu Lixi Wang Qitu Zhang College of Materials Science and Engineering Nanjing Tech UniversityNanjing211816China

In this paper,a series of GdOF-based green phosphors doped with Ho^(3+) and Yb^(3+) ions was prepared by a simple co-precipitation *** crystal structure s and optical prope rties were investigated in *** intensity of the emission of GdOF:Yb^(3+),Ho^(3+) phosphors is enhanced by the effective energy transfer from Yb^(3+) to Ho^(3+),and the optimal luminescence is achieved with the Ho^(3+)doping amount of 0.1 mol%as well as Yb^(3+) doping amount of 5 mol%.Tunable UC emission of samples is achieved by adjusting the doping concentration of Ho^(3+) or Yb^(3+).The purity of the green UC emission is further improved by enhancing the excitation pumping *** addition,logarithmic functions of green,red and nearinfrared radiation intensities were calculated versus logarithmic function of pump power for further study.A possible UC luminescence mechanism between Yb^(3+) and Ho^(3+) is discussed based on powerdependent UC luminescence spectrum and decay *** results suggest that GdOF:Yb^(3+),Ho^(3+)phosphors with bright and high-purity green UC emission have potential applications in the fields of bioimaging,display and illumination.

关键词： Up-conversion GdOF Lanthanide ions Rare earths

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Associative Tasks Computing Offloading Scheme in Internet of Medical Things with Deep Reinforcement Learning

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China Communications 2024年第4期21卷 38-52页

作者： Jiang Fan qin Junwei Liu Lei tian Hui School of Communications and Information Engineering Xi’an University of Posts and TelecommunicationsXi’an 710121China State Key Laboratory of Networking and Switching Technology Beijing University of Posts and TelecommunicationsBeijing 100876China

The Internet of Medical Things(Io MT) is regarded as a critical technology for intelligent healthcare in the foreseeable 6G era. Nevertheless, due to the limited computing power capability of edge devices and task-related coupling relationships, Io MT faces unprecedented challenges. Considering the associative connections among tasks, this paper proposes a computing offloading policy for multiple-user devices(UDs) considering device-to-device(D2D) communication and a multi-access edge computing(MEC)technique under the scenario of Io MT. Specifically,to minimize the total delay and energy consumption concerning the requirement of Io MT, we first analyze and model the detailed local execution, MEC execution, D2D execution, and associated tasks offloading exchange model. Consequently, the associated tasks’ offloading scheme of multi-UDs is formulated as a mixed-integer nonconvex optimization problem. Considering the advantages of deep reinforcement learning(DRL) in processing tasks related to coupling relationships, a Double DQN based associative tasks computing offloading(DDATO) algorithm is then proposed to obtain the optimal solution, which can make the best offloading decision under the condition that tasks of UDs are associative. Furthermore, to reduce the complexity of the DDATO algorithm, the cacheaided procedure is intentionally introduced before the data training process. This avoids redundant offloading and computing procedures concerning tasks that previously have already been cached by other UDs. In addition, we use a dynamic ε-greedy strategy in the action selection section of the algorithm, thus preventing the algorithm from falling into a locally optimal solution. Simulation results demonstrate that compared with other existing methods for associative task models concerning different structures in the Io MT network, the proposed algorithm can lower the total cost more effectively and efficiently while also providing a tradeoff between delay and energy co

关键词： associative tasks cache-aided procedure double deep Q-network Internet of Medical Things(IoMT) multi-access edge computing(MEC)

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The engineering of circular causality for specialization and design of complex systems:cad2CAS and casCAD2

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Frontiers of Information Technology & Electronic Engineering 2024年第2期25卷 323-332页

作者： Xiaolong LIANG Rui qin Juanjuan LI Fei-yue WANG Faculty of Innovation Engineering Macao University of Science and TechnologyMacao999078China State Key Laboratory of Multimodal Artificial Intelligence Systems Chinese Academy of SciencesBeijing100190China The State Key Laboratory for Management and Control of Complex Systems Chinese Academy of SciencesBeijing100190China

The emergence of decentralized autonomous organizations and operations(DAOs),equipped with innovative mechanisms,enables new possibilities for transforming traditional social collaborative *** are the underlying drive... 详细信息

关键词： complexity. circular equipped

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Numerical Study on Reduction in Aerodynamic Drag and Noise of High-Speed Pantograph

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Computer Modeling in Engineering & Sciences 2024年第5期139卷 2155-2173页

作者： Deng qin Xing Du tian Li Jiye Zhang State Key Laboratory of Rail Transit Vehicle System Southwest Jiaotong UniversityChengdu610031China School of Electrical Engineering Southwest Jiaotong UniversityChengdu610031China

Reducing the aerodynamic drag and noise levels of high-speed pantographs is important for promoting environmentally friendly,energy efficient and rapid advances in train *** computational fluid dynamics theory and the K-FWH acoustic equation,a numerical simulation is conducted to investigate the aerodynamic characteristics of high-speed pantographs.A component optimization method is proposed as a possible solution to the problemof aerodynamic drag and noise in high-speed *** results of the study indicate that the panhead,base and insulator are the main contributors to aerodynamic drag and noise in high-speed ***,a gradual optimization process is implemented to improve the most significant components that cause aerodynamic drag and *** optimizing the cross-sectional shape of the strips and insulators,the drag and noise caused by airflow separation and vortex shedding can be *** aerodynamic drag of insulator with circular cross section and strips with rectangular cross section is the *** insulators and optimizing the chamfer angle and height of the windward surface of the strips can improve the aerodynamic performance of the *** addition,the streamlined fairing attached to the base can eliminate the complex flow and shield the radiated *** contrast to the original pantograph design,the improved pantograph shows a 21.1%reduction in aerodynamic drag and a 1.65 dBA reduction in aerodynamic noise.

关键词： High-speed pantograph aerodynamic drag aerodynamic noise reduction optimizing

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Point Cloud Classification Using Content-Based Transformer via Clustering in Feature Space

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IEEE/CAA Journal of Automatica Sinica 2024年第1期11卷 231-239页

作者： Yahui Liu Bin tian Yisheng Lv Lingxi Li Fei-yue Wang the State Key Laboratory for Management and Control of Complex Systems Institute of AutomationChinese Academy of SciencesBeijing 100190 the School of Artificial Intelligence University of Chinese Academy of SciencesBeijing 100190 IEEE the Transportation and Autonomous Systems Institute(TASI)and the Department of Electrical and Computer Engineering Purdue School of Engineering and TechnologyIndiana University-Purdue University Indianapolis(IUPUI)Indianapolis 46202 USA

Recently, there have been some attempts of Transformer in 3D point cloud classification. In order to reduce computations, most existing methods focus on local spatial attention,but ignore their content and fail to establish relationships between distant but relevant points. To overcome the limitation of local spatial attention, we propose a point content-based Transformer architecture, called PointConT for short. It exploits the locality of points in the feature space(content-based), which clusters the sampled points with similar features into the same class and computes the self-attention within each class, thus enabling an effective trade-off between capturing long-range dependencies and computational complexity. We further introduce an inception feature aggregator for point cloud classification, which uses parallel structures to aggregate high-frequency and low-frequency information in each branch separately. Extensive experiments show that our PointConT model achieves a remarkable performance on point cloud shape classification. Especially, our method exhibits 90.3% Top-1 accuracy on the hardest setting of ScanObjectN N. Source code of this paper is available at https://***/yahuiliu99/PointC onT.

关键词： Content-based Transformer deep learning feature aggregator local attention point cloud classification

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Effect of streamlined nose length on aerodynamic performance of high-speed train with a speed of 400 km/h

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2024年第7期25卷 525-540页

作者： Nianxun LI tian LI Zhiyuan DAI Deng qin Jiye ZHANG State Key Laboratory of Rail Transit Vehicle System Southwest Jiaotong UniversityChengdu 610031China

The streamlined nose length(SNL)plays a crucial role in determining the aerodynamic performance of high-speed *** appropriate SNL can not only effectively reduce the magnitude of aerodynamic drag and lift forces,but also improve the performance of the high-speed train in tunnel passing and crosswind *** this study,a numerical simulation of the aerodynamic performance of high-speed trains at a speed of 400 km/h,with varying SNLs,is conducted using the k-ωshear stress transport(SST)turbulence *** different SNLs include 6.0,7.0,8.0,9.0,9.8,12.0,15.0,and 18.0 *** order to validate the accuracy of the numerical simulation,its results are compared with wind tunnel test data obtained from the *** simulation is carried out using compressible and incompressible gases to determine the effect of gas compressibility on *** impact of SNL on the aerodynamic performance of the trains is analyzed in terms of aerodynamic forces,velocity,and pressure *** comparison to the original train,the train with a 6.0 m SNL experienced a 10.8%increase in overall aerodynamic ***,the lift forces on the head and tail cars increased by 35.7%and 75.5%,*** the other hand,the train with an 18.0 m SNL exhibited a 16.5%decrease in aerodynamic ***,the lift forces on the head and tail cars decreased by 21.9%and 49.7%,*** aerodynamic drag force of the entire train varies linearly with the SNL,while the aerodynamic lift of the tail car follows a quadratic function in relation to the SNL.

关键词： Streamlined nose length(SNL) High-speed train Aerodynamic performance Numerical simulation Flow structures

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A scalable one-pot strategy for the development of polymer electrolytes adaptable to room-temperature high-voltage lithium batteries

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Chinese Chemical Letters 2024年第3期35卷 461-467页

作者： yue Guo Xinxin Qu Zhen Li Ruiyuan tian Xiaokong Liu State Key Laboratory of Supramolecular Structure and Materials College of ChemistryJilin UniversityChangchun 130012China Key Laboratory of Physics and Technology for Advanced Batteries(Ministry of Education) College of PhysicsJilin UniversityChangchun 130012China

Poly(ethylene oxide)(PEO)polymer electrolytes(PEs)have been commercially applied in LiFePO_(4)||Li solid-state lithium batteries(SSLBs).However,it remains challenging to develop PEO-based PEs applicable to the high-voltage SSLBs with higher energy density,owing to the poor electrochemical stability of ***,we report a scalable strategy for fabricating PEO-based PEs with high-voltage compatibility,by exploiting a new mechanism to stabilize the cathode-electrolyte interface in the highvoltage *** protocol only involves a one-pot synthesis procedure to covalently crosslink the PEO chains,in the presence of high-content lithium bis(trifluoromethylsulphonyl)imide(LiTFSI)salts and N,N-dimethylformamide(DMF).LiTFSI-DMF supramolecular aggregates are formed and firmly embedded in the polymer network,endowing the PE with high room-temperature ionic *** dissociated and highly concentrated TFSI^-anions can enter the Helmholtz layer close to the high-voltage cathode,leading to the formation of a thin and homogeneous cathode electrolyte interface(CEI),mainly composed of LiF,on the *** CEI with high electrochemical stability can effectively stabilize the cathode-electrolyte interface,enabling long-term stable cycling of the high-voltage LiCoO_(2)||Li and nickelrich NCM_(622)||Li batteries at room *** simplicity and scalability of the strategy makes the reported PEO-based PE potentially applicable in high-voltage SSLBs in practice.

关键词： Lithium batteries Polymer electrolytes Poly(ethylene oxide) Energy density High-voltage cathodes

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Anthropogenic Influence on Decadal Changes in Concurrent Hot and Dry Events over China around the Mid-1990s

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Advances in Atmospheric Sciences 2024年第2期41卷 233-246页

作者： qin SU Buwen DONG Fangxing tian Nicholas P.KLINGAMAN Yunnan Key Laboratory of Meteorological Disasters and Climate Resources in the Great Mekong Subregion Yunnan UniversityKunming 650500China Department of Atmospheric Sciences Yunnan UniversityKunming 650500China National Centre for Atmospheric Science Department of MeteorologyUniversity of ReadingReadingRG66BBUK Geofysisk Institut University of BergenBergen 5007Norway Citadel Investment Group Moor House120 London WallLondonRG66BBUK

The frequency and duration of observed concurrent hot and dry events(HDEs) over China during the growing season(April–September) exhibit significant decadal changes across the mid-1990s. These changes are characterized by increases in HDE frequency and duration over most of China, with relatively large increases over southeastern China(SEC), northern China(NC), and northeastern China(NEC). The frequency of HDEs averaged over China in the present day(PD,1994–2011) is double that in the early period(EP, 1964–81);the duration of HDEs increases by 60%. Climate experiments with the Met Office Unified Model(MetUM-GOML2) are used to estimate the contributions of anthropogenic forcing to HDE decadal changes over China. Anthropogenic forcing changes can explain 60%–70% of the observed decadal changes,suggesting an important anthropogenic influence on HDE changes over China across the mid-1990s. Single-forcing experiments indicate that the increase in greenhouse gas(GHG) concentrations dominates the simulated decadal changes,increasing the frequency and duration of HDEs throughout China. The change in anthropogenic aerosol(AA) emissions significantly decreases the frequency and duration of HDEs over SEC and NC, but the magnitude of the decrease is much smaller than the increase induced by GHGs. The changes in HDEs in response to anthropogenic forcing are mainly due to the response of climatological mean surface air temperatures. The contributions from changes in variability and changes in climatological mean soil moisture and evapotranspiration are relatively small. The physical processes associated with the response of HDEs to GHG and AA changes are also revealed.

关键词： concurrent hot and dry events decadal variation greenhouse gases aerosol emissions

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Climatic drivers of the Canadian wildfire episode in 2023

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Atmospheric and Oceanic Science Letters 2024年第4期17卷 23-28页

作者： Yihan Hu Xu yue Chenguang tian Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control Collaborative Innovation Center of Atmospheric Environment and Equipment TechnologySchool of Environmental Science and EngineeringNanjing University of Information Science&Technology(NUIST)NanjingChina

2023年5月加拿大发生极端野火事件并持续4个月时间.野火污染物排放对当地和下风向的空气质量造成了严重影响.本文对驱动此次野火事件的气象因子和相关大尺度环流进行了探究.研究表明,此次极端野火排放的二氧化碳相较往年同期增长了0.37G... 详细信息

2023年5月加拿大发生极端野火事件并持续4个月时间.野火污染物排放对当地和下风向的空气质量造成了严重影响.本文对驱动此次野火事件的气象因子和相关大尺度环流进行了探究.研究表明,此次极端野火排放的二氧化碳相较往年同期增长了0.37Gt (527.1%).受罗斯贝波频散影响,同期加拿大中西部区域出现持续的位势高度正异常,促进气流下沉并引发局地高温,中西部区域5-6月最高温平均上升8.11℃,部分区域甚至超过10℃,导致野火排放的显著增长.受有利地形和泛北极地区快速增暖的影响,预期未来加拿大中西部发生极端野火的概率可能会显著上升.

关键词：野火气候变化遥相关极端天气碳排放

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