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The impact of the atmospheric turbulence-development tendency on new particle formation: a common finding on three continents

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National Science Review 2021年第3期8卷 140-150页

作者： Hao Wu Zhanqing Li Hanqing Li Kun Luo Yuying Wang Peng Yan Fei Hu Fang Zhang Yele Sun Dongjie Shang Chunsheng Liang Dongmei Zhang Jing Wei Tong Wu Xiaoai Jin Xinxin Fan Maureen Cribb Marc L.Fischer Markku Kulmala Tuukka Pet?j? State Key Laboratory of Remote Sensing Science College of Global Change and Earth System ScienceBeijing Normal University ESSIC and Department of Atmospheric Science University of MarylandCollege Park State Key Laboratory of Clean Energy Utilization Zhejiang University School of Atmospheric Physics Nanjing University of Information Science and Technology Meteorological Observation Center China Meteorological Administration State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry Institute of Atmospheric Physics Chinese Academy of Sciences State Key Joint Laboratory of Environmental Simulation and Pollution Control College of Environmental Sciences and Engineering Peking University State Key Joint Laboratory of Environment Simulation and Pollution Control School of Environment Tsinghua University Lawrence Berkeley National Laboratory Institute for Atmospheric and Earth System Research/Physics Faculty of ScienceUniversity of Helsinki Aerosol and Haze Laboratory Beijing Advanced Innovation Center for Soft Matter Science and Engineering Beijing University of Chemical Technology Joint International Research Laboratory of Atmospheric and Earth System Sciences School of Atmospheric Sciences Nanjing University

A new mechanism of new particle formation(NPF) is investigated using comprehensive measurements of aerosol physicochemical quantities and meteorological variables made in three continents,including Beijing,China;the Southern Great Plains site in the USA;and SMEAR Ⅱ Station in Hyytiala,Finland.D espite the considerably different emissions of chemical species among the sites,a common relationship was found between the characteristics of NPF and the stability *** stability parameter(ζ=Z/L,where Z is the height above ground and L is the Monin-Obukhov length) is found to play an important role;it drops significantly before NPF as the atmosphere becomes more unstable,which may serve as an indicator of nucleation *** the atmosphere becomes unstable,the NPF duration is closely related to the tendency for turbulence development,which influences the evolution of the condensation ***,the unstable atmosphere may dilute pre-existing particles,effectively reducing the condensation sink,especially at coarse mode to foster *** new mechanism is confirmed by model simulations using a molecular dynamic model that mimics the impact of turbulence development on nucleation by inducing and intensifying homogeneous nucleation events.

关键词： new particle formation turbulence development molecular dynamic

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Capacitor Voltage Balancing Strategy Based on Zero-Sequence Voltage Injection for Half-Wave Commutated Modular Multilevel Converter

Capacitor Voltage Balancing Strategy Based on Zero-Sequence ...

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International Conference on Power Electronics and Motion control (IPEMC)

作者： Nan Fu Bao Liu Yunfei Xu Sitong Zhu Kui Wang Yongdong Li Department of Electrical Engineering State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China State Key Laboratory of Advanced Power Transmission Technology State Grid Smart Grid Research Institute Co. Ltd Changping Beijing China Electric Power Research Institute of State Grid Liaoning Electric Power Co. Ltd. Shenyang China

ISBN: (数字)9798350351330

ISBN: (纸本)9798350351347

Half-wave commutated modular multilevel converter (HWC-MMC) is suitable for high-voltage large-capacity AC-AC conversion, and an appropriate capacitor voltage balancing strategy is essential. This paper analyzes the condition of capacitor voltage balancing and proposes a capacitor voltage balancing strategy based on optimal zero-sequence voltage injection using the model predictive control. Finally, the simulation is carried out to verify the proposed strategy.

关键词： Multilevel converters Voltage fluctuations Capacitors High-voltage techniques Power system harmonics Power electronics Steady-state

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Antagonism between ambient ozone increase and urbanization-oriented population migration on Chinese cardiopulmonary mortality

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The Innovation 2023年第6期4卷 48-58页

作者： Haitong Zhe Sun Junchao Zhao Xiang Liu Minghao Qiu Huizhong Shen Serge Guillas Chiara Giorio Zosia Staniaszek Pei Yu Michelle W.L.Wan Man Mei Chim Kim Robin van Daalen Yilin Li Zhenze Liu Mingtao Xia Shengxian Ke Haifan Zhao Haikun Wang Kebin He Huan Liu Yuming Guo Alexander T.Archibald lYusuf Hamied Department of Chemistry University of CambridgeCambridge CB21EWUK Department of Earth Sciences University of CambridgeCambridge CB23EQUK Department of Environmental Health and Engineering Johns Hopkins Bloomberg School of Public HealthBaltimoreMD 21205USA State Key Joint Laboratory of ESPC State Environmental Protection Key Laboratory of Sources and Control of Air Pollution ComplexSchool of EnvironmentTsinghua UniversityBejing 100084China School of Atmospheric Sciences Nanjing UniversityNanjing 210023China Department of Earth System Science Stanford UniversityStanfordCA 94305USA School of Environmental Science and Engineering Southern University of Science and TechnologyShenzhen 518p55China Department of Statistical Science University College LondonLondon WC1E 6BTUK The Alan Turing Institute London NW12DBUK School of Public Heath and Preventive Medicine Monash UniversityMelboumeVIC 3004Australia British Heart Foundation Cardiovascular Epidemiology Unit Department of Public Health and Primary CareUniversity of CambridgeCambridge CB18RNUK Heart and Lung Research Institute University of CambridgeCambridge CB20BDUK Baroelona Supercomputing Center Department of Earth Sciences08034 BarcelonaSpain School of Environmental Science and Engineering Nanjing University of Information Science and TechnologyNanjing 210044China Department of Mathematics University of CaliformiaLos AngelesLos AngelesCA 90095USA State Key Laboratory of New Ceramics and Fine Processing KeyLaboratory of Advanced Materials of Ministry of EducationSchool of Materials Science and EngineeringTsinghua UniversityBeijing 100084China Department of Engineering University of CambridgeCambridge CB21PZUK National Centre for Atmospheric Science Cambridge CB21EWUK

Everincreasing ambient ozone(O3)pollution in China has been exacerbating cardiopulmonary premature ***,the urban-rural exposure inequity has seldom been ***,we assess populationcale 03 exposure and mortality burdens between 1990 and 2019 based on integrated pollution tracking and epidemiological *** find Chinese population have been suffering from climbing 03 exposure by 4.3±2.8 ppb per decade as a result of rapid urbanization and growing prosperity of socioeconomic *** residents are broadly exposed to 9.8±4.1 ppb higher ambient O3 than the adjacent urban citizens,and thus urbaniza-tion-oriented migration compromises the exposure-associated mortality on total *** excess premature deaths attributable to longterm 03 exposure,373,500(95%uncertainty interval[U]:240,600-510,900)in 2019,is underestimated in previous studies due to ignorance of cardiovascular *** 03 pollution policy should focus more on rural population who are facing an aggravating threat of mortality risks to ameliorate environmental health injustice.

关键词： ambient urban urbanization

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Estimating the value of a statistical life in China: A contingent valuation study in six representative cities

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Chinese Journal of Population,Resources and Environment 2023年第4期21卷 269-278页

作者： Chaoji Cao Xinke Song Wenjia Cai Yichao Li Jianhui Cong Xueying Yu Mengzhao Gao Can Wang Ministry of Education Key Laboratory for Earth System Modeling Department of Earth System ScienceTsinghua UniversityBeijing100084China Center for Healthy Cities Institute for China Sustainable UrbanizationTsinghua UniversityBeijing100084China Tsinghua Urban Institute Tsinghua UniversityBeijing100084China State Key Joint Laboratory of Environment Simulation and Pollution Control School of EnvironmentTsinghua UniversityBeijing100084China Center for Statistical Science Tsinghua UniversityBeijing100084China Department of Industrial Engineering Tsinghua UniversityBeijing100084China School of Economics and Management Shanxi UniversityTaiyuan030000China School of Economics and Management Beihang UniversityBeijing100191China Beijing Advanced Innovation Center for Big Data-based Precision Medicine Beihang UniversityBeijing100191China Key Laboratory of Big Data-Based Precision Medicine(Beihang University) Ministry of Industry and Information TechnologyBeijing100191China

The value of a statistical life(VSL)is a crucial tool for monetizing health *** explore the VSL in China,this study examines people’s willingness to pay(WTP)to reduce death risk from air pollution in six representative cities in China based on face-to-face contingent valuation interviews(n=3936)from March 7,2019 to September 30,*** results reveal that the WTP varied from CNY 455 to 763 in 2019(USD 66-111),corresponding to a VSL range of CNY 3.79-6.36 million(USD 549395-921940).The VSL in China in 2019 is estimated to be CNY 4.76 million(USD 689659).The statistics indicate that monthly expenditure levels,environmental concerns,risk attitudes,and assumed market acceptance,which have seldom been dis‐cussed in previous studies,significantly impact WTP and *** findings will serve as a reference for ana‐lyzing mortality risk reduction benefits in future research and for policymaking.

关键词： Air pollution Contingent valuation method Willingness to pay Value of a statistical life China

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MRI-guided robot intervention—current state-of-the-art and new challenges

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Med-X 2023年第1期1卷 1-41页

作者： Huang, Shaoping Lou, Chuqian Zhou, Ying He, Zhao Jin, Xuejun Feng, Yuan Gao, Anzhu Yang, Guang-Zhong Institute of Medical Robotics and School of Biomedical Engineering Shanghai Jiao Tong University Shanghai China National Engineering Research Center of Advanced Magnetic Resonance Technologies for Diagnosis and Therapy (NERC-AMRT) Shanghai Jiao Tong University Shanghai China Materials and Technology Center of Robotics Empa Dübendorf Switzerland State Key Lab of Metal Matrix Composites and School of Materials Science and Engineering Shanghai Jiao Tong University Shanghai China Institute of Medical Robotics and Department of Automation Shanghai Jiao Tong University Shanghai China The Key Laboratory of System Control and Information Processing Ministry of Education Shanghai China

Magnetic Resonance Imaging (MRI) is now a widely used modality for providing multimodal, high-quality soft tissue contrast images with good spatiotemporal resolution but without subjecting patients to ionizing radiation. In addition to its diagnostic potential, its future theranostic value lies in its ability to provide MRI-guided robot intervention with combined structural and functional mapping, as well as integrated instrument localization, target recognition, and in situ, in vivo monitoring of the therapeutic efficacy. Areas of current applications include neurosurgery, breast biopsy, cardiovascular intervention, prostate biopsy and radiotherapy. Emerging applications in targeted drug delivery and MRI-guided chemoembolization are also being pursued. Whilst promising progress has been made in recent years, there are still significant basic science research and engineering challenges. This paper provides a comprehensive review of the current state-of-the-art in MRI-guided robot intervention and allied technologies in actuation, sensing, new materials, interventional instruments, and interactive/real-time MRI. Potential future research directions and new clinical developments are also discussed.

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Design of wavelength division multiplexing devices based on tunable edge states of valley photonic crystals

arXiv

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arXiv 2022年

作者： Han, YuHui Fei, HongMing Lin, Han Zhang, MingDa Liu, Xin Wang, XiaoRong Cao, BinZhao Yang, YiBiao Xiao, LianTuan Department of Physics and Optoelectronics Taiyuan University of Technology Taiyuan030024 China Key Laboratory of Advanced Transducers and Intelligent Control System Ministry of Education Taiyuan University of Technology Taiyuan030024 China Centre for Translational Atomaterials Faculty of Science Engineering and Technology Swinburne University of Technology HawthornVIC3122 Australia

Wavelength division multiplexing (WDM) devices are key elements of Photonic integrated circuits (PICs). Conventional WDM devices based on silicon waveguides and photonic crystals have limited transmittance due to high loss introduced by the strong backward scattering from defects. In addition, it is challenging to reduce the footprint of those devices. Here we theoretically demonstrate a WDM device in the telecommunication range based on all-dielectric silicon topological valley photonic crystal (VPC) structures. We tune its effective refractive index by tuning the physical parameters of the lattice in the silicon substrate, which can continuously tune the working wavelength range of the topological edge states, which allows designing WDM devices with different channels. The WDM device has two channels (1470 nm-1523 nm and 1548 nm-1609 nm), with contrast ratios of 22.4 dB and 24.9 dB, respectively. The principle of manipulating the working bandwidth of the topological edge states can be generally applied in designing different integratable photonic devices, thus it will find broad applications. Copyright © 2022, The Authors. All rights reserved.

关键词： Photonic devices

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Liquid Metal Manifold Microchannel Heat Sink for Ultra-High Heat Flux Cooling

SSRN

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SSRN 2024年

作者： Zhang, Mingkuan Gao, Qi Zhao, Zhiyuan Guo, Luna Li, Xuan Zhang, Chao Zhang, Xudong Rao, Wei Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control School of Mechanical Engineering Tianjin University of Technology Tianjin300384 China National Demonstration Center for Experimental Mechanical and Electrical Engineering Education Tianjin University of Technology China School of mechanical engineering Tianjin University of Commerce Tianjin300134 China Institute of Refrigeration and Cryogenics Shanghai Jiao Tong University Shanghai200240 China Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Department of Engineering Mechanics Tsinghua University Beijing Beijing100084 China CAS Key Laboratory of Cryogenics Technical Institute of Physics and Chemistry Chinese Academy of Sciences China Beijing Key Lab of CryoBiomedical Engineering and Key Lab of Cryogenics Beijing100190 China

The reduction in transistor dimensions and advancements in chip integration have led to a dramatic increase in the heat flux of chip. advanced heat dissipation technology has become the pivotal in ensuring the normal operation of chips and fully utilizing chip performance. Room temperature liquid metal convection cooling technology has demonstrated its efficacy as a viable approach for addressing high heat flux heat dissipation. However, the smaller specific heat capacity of liquid metal leads to a large temperature rise, imposing a constraint on the progression of liquid metal cooling technology. To overcome this drawback, this paper proposed a liquid metal manifold channel structure designed to convert the continuous long-range flow into a segmented short-range flow. The good matching between liquid metal and manifold structures is adequately demonstrated through a comparison with alternative coolant and channel structure. The simulation results demonstrate the effectiveness of liquid metal manifold channel cooling in dealing with a heat flux of 1000 W/cm², ensuring that the maximum temperature of the chip remains below 351.7 K. Moreover, the convective heat transfer coefficient even reaches 106 W/(m2·K), which is ten times larger than that of water conventional microchannel heat sink. The orthogonal experiments were conducted to analyze how the structural parameters affect the dissipation performance, including the height of the microchannel, ratio of manifold length to fin length, length of fin in manifold, width of channel, and ratio of fin with to channel width. It concluded that the height of the microchannel has been identified as the most critical factor. This manifold structure mitigates the inherent limitation of the lower specific heat capacity of liquid metal, paving the way for effective thermal management of electronic devices subjected to ultra-high heat flux. © 2024, The Authors. All rights reserved.

关键词： Heat flux

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Hierarchical Learning for IRS-Assisted MEC systems with Rate-Splitting Multiple Access

arXiv

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arXiv 2024年

作者： Wu, Yinyu Zhang, Xuhui Ren, Jinke Shen, Yanyan Yang, Bo Wang, Shuqiang Guan, Xinping Niyato, Dusit The Shenzhen Institute of Advanced Technology Chinese Academy of Sciences Guangdong518055 China The University of Chinese Academy of Sciences Beijing100049 China The Shenzhen Future Network of Intelligence Institute The School of Science and Engineering The Guangdong Provincial Key Laboratory of Future Networks of Intelligence The Chinese University of Hong Kong Guangdong Shenzhen518172 China Shenzhen University of Advanced Technology Guangdong518055 China The Department of Automation The Key Laboratory of System Control and Information Processing Ministry of Education Shanghai Jiao Tong University Shanghai200240 China The College of Computing and Data Science Nanyang Technological University Singapore639798 Singapore

Intelligent reflecting surface (IRS)-assisted mobile edge computing (MEC) systems have shown notable improvements in efficiency, such as reduced latency, higher data rates, and better energy efficiency. However, the resource competition among users will lead to uneven allocation, increased latency, and lower throughput. Fortunately, the rate-splitting multiple access (RSMA) technique has emerged as a promising solution for managing interference and optimizing resource allocation in MEC systems. This paper studies an IRS-assisted MEC system with RSMA, aiming to jointly optimize the passive beamforming of the IRS, the active beamforming of the base station, the task offloading allocation, the transmit power of users, the ratios of public and private information allocation, and the decoding order of the RSMA to minimize the average delay from a novel uplink transmission perspective. Since the formulated problem is non-convex and the optimization variables are highly coupled, we propose a hierarchical deep reinforcement learning-based algorithm to optimize both continuous and discrete variables of the problem. Additionally, to better extract channel features, we design a novel network architecture within the policy and evaluation networks of the proposed algorithm, combining convolutional neural networks and densely connected convolutional network for feature extraction. Simulation results indicate that the proposed algorithm not only exhibits excellent convergence performance but also outperforms various benchmarks. Copyright © 2024, The Authors. All rights reserved.

关键词： Deep reinforcement learning

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Towards Energy-Efficiency: Integrating MATD3 Reinforcement Learning Method for Computational Offloading in RIS-Aided UAV-MEC Environments

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IEEE Internet of Things Journal 2025年

作者： Wu, Liangshun Zhang, Cong Zhang, Bin Du, Jianbo Qu, Junsuo Key Laboratory of Embedded System and Service Computing Tongji University Ministry of Education Shanghai201804 China Shanghai Key Laboratory of Trustworthy Computing East China Normal University Shanghai201210 China School of Electronic Information and Electrical Engineering Shanghai Jiao Tong University Shanghai200240 China Xi'an Key Laboratory of Advanced Control and Intelligent Process School of Automation Xi'an University of Posts & Telecommunications Xi'an710061 China Xinjiang University of Political Science and Law Tumushuke832003 China School of Remote Sensing and Information Engineering Wuhan University Wuhan430079 China Department of Computer City University of Hong Kong 999077 Hong Kong School of Communications and Information Engineering Xi'an University of Posts & Telecommunications Xi'an710061 China

With the proliferation of IoT devices, there is an escalating demand for enhanced computing and communication capabilities. Mobile Edge Computing (MEC) addresses this need by relocating computing resources to the network edge, thereby delivering swifter and more efficient services. This paper introduces a computation offloading and energy consumption optimization framework that leverages Reconfigurable Intelligent Surfaces (RIS), Unmanned Aerial Vehicles (UAVs), and MEC. The scheme aims to maximize energy efficiency through the optimization of task allocation, RIS phase shifts, and UAV trajectories. By employing the Multi-Agent Twin Delayed Deep Deterministic Policy Gradient (MATD3) reinforcement learning algorithm, the paper further refines UAV trajectories and RIS configurations. The simulation results indicate that the proposed method surpasses the traditional Concave-Convex Procedure (CCCP) algorithm in both UAV trajectory control and RIS configuration, demonstrating quicker convergence and enhanced stability. The method proves to be adaptable to diverse environments and tasks, showcasing notable benefits in RIS-assisted interference suppression, particularly with large RIS, thereby enhancing UAV data reception rates. Additionally, MATD3 exhibits faster and smoother convergence for extended task durations and smaller RIS scenarios. Simulation results reveal that UAVs tend to move closer to RIS, with energy efficiency falling as IoT tasks increase, affirming the proposed algorithm's high energy efficiency and effectiveness. © 2025 IEEE.

关键词： Unmanned aerial vehicles (UAV)

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Selection for Schottky Barrier Diodes with Various On-Resistance in Full-SiC Voltage Source Converters

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IEEE Transactions on Industry Applications 2025年

作者： Chen, Yuzhi Li, Chi Liu, Jianwei Wu, Yifan Liu, Zicheng Zheng, Zedong Tsinghua University State Key Laboratory of Power System Operation and Control Department of Electrical Engineering Beijing100084 China Huazhong University of Science and Technology State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic Engineering Wuhan430074 China

In Silicon Carbide based voltage source converters (VSCs), pairing Schottky barrier diodes (SBDs) presents trade-offs. While SBDs reduce the freewheeling loss and mitigate the adverse effects of bipolar conduction, their junction capacitance also contributes to increased switching loss. This paper proposes a systematic selection strategy for SBDs aimed at enhancing converter efficiency, using on-resistance as the design variable. A three-phase VSC with 1.2 kV MOSFETs and four sets of 1.2 kV SBDs is demonstrated as the case study. The static and switching characteristics for MOSFET/SBD pair are measured and analyzed over a wide temperature range. VSC efficiency is evaluated in both inverter and rectifier modes under different operating conditions. It appears that VSC using SBDs with 126% of the MOSFETs' resistance exhibits an overall superior performance. A 4 kW full-SiC VSC prototype is developed to validate the proposed selection strategy. Compared to other SBDs, using the recommended selection enhances VSC efficiency by up to 2% (± 0.5%) under light loads while maintaining high performance under medium and heavy loads. Compared to freewheeling by the body diode, using the recommended selection enhances VSC efficiency by an average of 0.4% (± 0.1%) across nearly the entire load range. © 1972-2012 IEEE.

关键词： Schottky barrier diodes

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