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SSRN 2024年

作者： Yang, Pan Wang, Hui Wu, Xiaomeng Xiao, Shupei Zheng, Xuan You, Yan Zhang, Shaojun Wu, Ye State Key Joint Laboratory of Environment Simulation and Pollution Control School of Environment Tsinghua University Beijing100084 China State Environmental Protection Key Laboratory of Sources and Control of Air Pollution Complex Beijing100084 China College of Chemistry and Environmental Engineering Shenzhen University Guangdong Shenzhen518060 China National Observation and Research Station of Coastal Ecological Environments in Macao Macao Environmental Research Institute Macau University of Science and Technology 999078 China

Assessing the emissions of heavy-duty diesel trucks (HDDTs) is crucial for managing air quality in megacities, especially concerning nitrogen oxides (NOX) and black carbon (BC). This study employed mobile plume chasing to monitor the real-world emissions of over 7,778 HDDTs in Shenzhen. The findings indicate that the real-world NOX emission factors (EF) of China IV trucks did not differ significantly from those of China III, whereas China V and VI vehicles demonstrated fleet-averaged reductions of 27% and 85%, respectively. For China V, a significant decrease in the NOX EF for HDDTs registered after 2017 was attributed to the installation of advanced aftertreatment systems, including diesel oxidation catalysts (DOC) and Diesel Particle Filters (DPF), along with selective catalytic reduction (SCR). These technologies led to an average reduction of 42% in NOX and 61% in BC emissions. Seasonal variations were pronounced, with winter (~20°C) NOX EF 40% higher than summer (~35°C) levels. Conversely, BC EF decreased by 26% in winter, indicating significant impacts of ambient temperature on emissions. Spatial analysis revealed that the average NOX EF of HDDTs on east freeways was 1.4 times higher than that on urban expressways, influenced by variations in the proportion of vehicle types segmented by usage. These findings offer a comprehensive perspective on HDDTs emissions, highlighting the importance of large-scale emission monitoring through plume chasing for precise and effective control of real-world HDDTs emissions. © 2024, The Authors. All rights reserved.

关键词： Nitrogen oxides

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Directly visualization of excitonic wavefunction in 2D semiconductors by angle resolved photoemission spectroscopy

Directly visualization of excitonic wavefunction in 2D semic...

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Conference on Lasers and Electro-Optics (CLEO)

作者： Michael K. L. Man Julien Madéo Chakradhar Sahoo Kaichen Xie Marshall Campbell Vivek Pareek Arka Karmakar E Laine Wong Abdullah Al-Mahboob Nicholas S. Chan David R. Bacon Xing Zhu Mohamed Abdelrasoul Xiaoquin Li Tony F. Heinz Felipe H. da Jornada Ting Cao Keshav M. Dani Femtosecond Spectroscopy Unit Okinawa Institute of Science and Technology Okinawa Japan School of Physics University of Hyderabad Hyderabad Telangana India University of Washington Seattle WA USA Center for Complex Quantum System The University of Texas at Austin Austin TX USA Stanford University Stanford CA USA SLAC National Accelerator Laboratory Menlo Park CA USA

Using time- and angle-resolved photoemission spectroscopy on a microscopic sample of a 2D semiconductor, we visualized directly the excitonic wavefunction in real- and momentums-pace.

ISBN: (纸本)9781943580910

Using time- and angle-resolved photoemission spectroscopy on a microscopic sample of a 2D semiconductor, we visualized directly the excitonic wavefunction in real- and momentums-pace.

关键词： Visualization Spectroscopy Semiconductor lasers Microscopy Lasers and electrooptics Laser excitation Photoelectricity

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Distributed cooperative guidance for maneuvering targets with directed conmunication topologies

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Hangkong Xuebao/Acta Aeronautica et Astronautica Sinica 2020年 41卷

作者： Dong, Xiaofei Ren, Zhang Chi, Qingxi Li, Qingdong School of Automation Science and Electrical Engineering Beihang University Beijing100083 China Science and Technology on Complex System Control and Intelligent Agent Cooperation Laboratory Beijing100074 China Science and Technology on Aircraft Control Laboratory Beihang University Beijing100083 China Beijing Advanced Innovation Center for Big Data and Brain Computing Beihang University Beijing100083 China

This paper studies the distributed cooperative guidance for maneuvering targets with directed communication topologies. First, a guidance system model is established based on the geometric relationship between the aircraft and the target, in which the nonlinear problem is solved by feedback linearization. In this design, the unknown maneuver of the target is observed by the extended state observer, and the estimation of the unknown maneuver of the target is applied to the design of the guidance law. In this process, the influence of the target maneuvering on the time-to-go is eliminated by means of direct compensation. Then, the designed guidance law is brought into the guidance model, transforming the problem of cooperative guidance into the problem of consensus. Next, the necessary and sufficient conditions for the convergence of the designed cooperative guidance law are obtained by conducting the pole analysis. Finally, the designed cooperative guidance law and the method of the parameter selection are analyzed by adopting the simulation analysis. © 2020, Beihang University Aerospace Knowledge Press. All right reserved.

关键词： State estimation

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Decision Tree Pruning Method Using Delayed Sampling

Decision Tree Pruning Method Using Delayed Sampling

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International Conference on Information Technologies (InfoTech)

作者： Sergei Alexandrovich Mitrofanov Eugene Stanislavovich Semenkin Department of System Analysis and Operations Research Institute of Informatics and Telecommunications Reshetnev Siberian State University of Science and Technology Krasnoyarsk Russian Federation Scientific and Educational Center "Artificial Intelligence Technologies" Bauman Moscow State Technical University Moscow Russian Federation Laboratory "Hybrid Methods of Modeling and Optimization in Complex Systems" Siberian Federal University Krasnoyarsk Russian Federation

ISBN: (数字)9798350365689

ISBN: (纸本)9798350365696

Algorithms based on decision trees have been around for quite some time, however, they are still one of the most popular because of their efficiency and the interpretability of their results. One of the main problems of decision trees is their high tendency to overfit. There are various ways to solve this problem, but this paper proposes a new method based on tree pruning using delayed sampling. The tree is trained using the Separation Measure and Differential Evolution algorithms. The proposed approach improves the standard method and is compared with it. The proposed approach demonstrates higher efficiency than the standard algorithm, and also improves the interpretability of the resulting trees.

关键词： Visualization Machine learning algorithms Accuracy Measurement uncertainty Machine learning Sampling methods Decision trees Stakeholders Information technology Standards

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Role of elasto-inertial turbulence in viscoelastic drag-reducing turbulence

arXiv

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arXiv 2021年

作者： Zhang, Wenhua Zhang, Hongna Li, Yuke Yu, Bo Li, Fengchen Key Laboratory of Efficient Utilization of Low and Medium Grade Energy MOE School of Mechanical Engineering Tianjin University Tianjin300350 China Sino-French Institute of Nuclear Engineering and Technology Sun Yat-sen University Zhuhai519082 China Department of Physics of Complex System Weizmann Institute of Science Rehovot7610001 Israel School of Mechanical Engineering Beijing Institute of Petrochemical Technology Beijing102617 China

Two kinds of nonlinearities coexist in viscoelastic fluid flows, i.e., inertia and elasticity, which can engender different types of chaotic states including IT, DRT, ET and EIT. The state of MDR, the ultimate state of DRT induced by adding polymers to Newtonian IT, is recently regarded as EIT. This letter quantitatively demonstrates the role of IT and EIT in DRT via the contributions of RSS and the nonlinear part of ESS to flow drag. The nature of DRT is re-examined in a wide range of flow conditions covering a series of flow regimes from the onset of DR to MDR. We argue that EIT related dynamics appears in DRT long before settling to MDR regime and competitively coexists with IT in both spatial and temporal domain at moderate and high Re. More specifically, at low DR condition, EIT firstly emerges close to the channel walls. With the increase of elasticity, low-drag EIT gradually replaces high-drag IT from channel walls to center, resulting in a drastic decrease of flow drag comparing with IT. When EIT dynamics dominates the whole channel, MDR phenomenon is formed. Our findings provide evidences that DRT phenomenon is the result of IT and EIT interaction. Copyright © 2021, The Authors. All rights reserved.

关键词： Turbulence

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Contaction of Atoms for Outstanding Dielectric Characteristics in Kx-Passivated Polymer Dielectrics

SSRN

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SSRN 2022年

作者： Li, Xiao-Fen Wang, Tian-Yu Liu, Bai-Xin Liu, Jian-Bo Zhang, Gui-Xin Wang, Zhong Lin School of Materials Science and Engineering Tsinghua University Beijing100084 China State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing100084 China CAS Center for Excellence in Nanoscience Beijing Institute of Nanoenergy and Nanosystems Chinese Academy of Sciences Beijing100083 China School of Nanoscience and Technology University of Chinese Academy of Sciences Beijing100049 China School of Material Science and Engineering Georgia Institute of Technology AtlantaGA30332 United States

High dielectric characteristics polymer dielectrics are crucial for high-power, high-integration, and high-energy storage density electrical devices and film capacitors. However, polymer dielectrics accumulate much charge during operation, causing local electric field distortion and flashover or breakdown. The deep-level defect state (electron/hole accumulation center) is a fundamental factor affecting dielectric strength. Unfortunately, related research, especially on passivating deep-level defects in polymer dielectrics, is minimal. In this paper, based on experiments and first-principles calculations, it is found that KX (X=F, Cl, Br, I) effectively passivates deep-level defect states in polymer dielectrics. Further analysis of the physical passivation mechanism reveals that the deep-level defect cation passivation principle is the cation dipole effect on polymers. The principle of anion passivation of deep-level defects by suspending anions and cations is the key to producing more stable C covalent bonds. This stable covalent bond transfers the local charge from the C with the lone electron pair that originally contains the hanging bond. Therefore, some transfer occurs and the anion implements effective passivation. This paper addresses the design of high-performance polymer dielectrics, providing a reference for experimental and theoretical analyses. © 2022, The Authors. All rights reserved.

关键词： Passivation

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Wide-Area Damping Control Enhanced by Non-Invasive Data Verification Against False Data Injection Attacks

SSRN

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SSRN 2024年

作者： Sun, Zhenglong Long, Hao Li, Zewei Gao, Bo Wei, Xiaoqiang Belikov, Juri Levron, Yoash Department of Electrical Engineering Key Laboratory of Modern Power System Simulation and Control & Renewable Energy State Grid Jiashan County Power Supply Company Jiaxing China State Grid Heilongjiang Electric Power Company Limited Heilongjiang China The Andrew and Erna Viterbi Faculty of Electrical Engineering Technion Israel Institute of Technology Haifa Israel Department of Software Science Tallinn University of Technology Tallinn Estonia Northeast Electric Power University China

The increasing interconnectivity of power systems and the integration of renewable energy sources into the grid have exacerbated the low-frequency oscillation problem, which directly impacts the stability of the power grid. The performance of wide-area damping control (WADC), which is an effective oscillation suppression technique , is susceptible to false data injection attacks (FDIA). This study proposes a non-intrusive data verification method using an adaptive variational autoencoder (AVAE) combined with a deep convolutional neural network (DCNN) to enhance WADC’s resistance to FDIA. The method integrates data dimensionality reduction of AVAE and reconstruction capabilities with DCNN’s feature extraction advantages. Itemploys adaptive thresholds to dynamically track grid data fluctuations, accurately distinguishing between normal and abnormal measurements and improving attack detection and performance discrimination. In addition, the study proposes an intelligent repair process based on latent representations for anomalous data in the repair module, using hierarchical clustering and Gaussian mixture models post-Bayesian inference to repair data. AVAE then reconstructs the repaired data, mitigating attack impacts. simulations on IEEE 39-Bus, 68-Bus, and 118-bus systems demonstrate that this method effectively detects network attacks and restores manipulated signals with minimal reconstruction errors, thus ensuring grid stability and reliability. © 2024, The Authors. All rights reserved.

关键词： Convolutional neural networks

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Based on the Scenario Set Generation technology, the Shared Energy Storage Site Selection and Capacity Determination Problem Considering the Grid Constraints

Based on the Scenario Set Generation Technology, the Shared ...

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Power science and technology (ICPST), IEEE International Conference on

作者： Xiaobiao Fu Jinyu Guo Baoju Li Cuiping Li Yao Wang Junhui Li Guanqun Zhang Xingxu Zhu Dispatching and Control Center State Grid Jilin Electric Power Co. Ltd Chang Chun China Key Laboratory of Modern Power System Simulation and Control & Renewable Energy Technology Ministry of Education(Northeast Electric Power University) Ji Lin China Power Science Research Institute State Grid Jilin Electric Power Co. Ltd Chang Chun China

ISBN: (数字)9798350349030

ISBN: (纸本)9798350349047

This paper addresses the shared energy storage siting and sizing problem, considering grid constraints based on scenario generation techniques. In the context of high penetration of renewable energy, the power system faces practical challenges such as increased uncertainty and scarcity of flexible resources. To tackle these issues, a two-layer optimization model is proposed in this study. It utilizes scenario generation techniques to obtain possible scenarios for renewable energy and load outputs, and incorporates grid constraints for economic dispatch. Through iterative optimization, an optimal shared energy storage siting and sizing solution that meets the requirements of the power grid is obtained. Additionally, the paper discusses the impact on the accommodation capacity of renewable energy and proposes countermeasures in system economic dispatch. However, there are still limitations in uncertainty estimation, energy storage planning, and investment cost calculations in this paper. Furthermore, further enhancement is needed in terms of quantification theories supporting the economic evaluation of shared energy storage siting and sizing. Overall, this research aims to provide an optimization approach for the shared energy storage siting and sizing problem, incorporating scenario generation techniques and grid constraints, to promote stable operation and economic development of power systems with high penetration of renewable energy.

关键词： Renewable energy sources Uncertainty Costs Optimization models Robustness Planning Scenario generation

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Approaching the Fundamental Limit of Orbital-Angular-Momentum Multiplexing Through a Hologram Metasurface

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Physical Review Applied 2021年第6期16卷 064042-064042页

作者： Shuai S.A. Yuan Jie Wu Menglin L.N. Chen Zhihao Lan Liang Zhang Sheng Sun Zhixiang Huang Xiaoming Chen Shilie Zheng Li Jun Jiang Xianmin Zhang Wei E.I. Sha College of Information Science and Electronic Engineering Zhejiang University Hangzhou 310027 China Department of Education of Anhui Province Ministry of Education and the Key Laboratory of Electromagnetic Environmental Sensing Anhui University Hefei 230039 China Department of Electrical and Electronic Engineering The University of Hong Kong Hong Kong Department of Electronic and Electrical Engineering University College London Torrington Place London WC1E 7JE United Kingdom Anhui Province Key Laboratory of Simulation and Design for Electronic Information System Hefei Normal University Hefei 230601 China School of Electronic Science and Engineering University of Electronic Science and Technology of China Chengdu 611731 China School of Information and Communications Engineering Xi’an Jiaotong University Xi’an 710049 China

Establishing and approaching the fundamental limit of orbital-angular-momentum (OAM) multiplexing are necessary and increasingly urgent for current multiple-input multiple-output research. In this work, we elaborate the fundamental limit in terms of independent scattering channels (or the degrees of freedom of scattered fields) through angular-spectral analysis, in conjunction with a rigorous Green’s function method. The scattering-channel limit is universal for arbitrary spatial-mode multiplexing, which is launched by a planar electromagnetic device, such as antenna, metasurface, etc., with a predefined physical size. As a proof of concept, we demonstrate both theoretically and experimentally the limit by a phase-only metasurface hologram that transforms orthogonal OAM modes to plane-wave modes scattered at critically separated angular-spectral regions. Particularly, a minimax optimization algorithm is applied to suppress angular-spectrum aliasing, achieving good performances in both full-wave simulation and experimental measurement at microwave frequencies. This work offers a theoretical upper bound and corresponding approach route for engineering designs of OAM multiplexing.

关键词： Angular momentum of light Polarization of light Spatial profiles of optical beams Devices Metamaterials Surfaces Holography Light scattering

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Robust Imagined Speech Production from Electrocorticography with Adaptive Frequency Enhancement

Robust Imagined Speech Production from Electrocorticography ...

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International Joint Conference on Neural Networks (IJCNN)

作者： Xu Xu Chong Fu Junxin Chen Gwanggil Jeon David Camacho School of Computer Science and Engineering Northeastern University Shenyang China School of Software Dalian University of Technology Dalian China Key Laboratory of Intelligent Computing in Medical Image Ministry of Education Northeastern University Shenyang China Engineering Research Center of Security Technology of Complex Network System Ministry of Education Shenyang China College of Information Technology Incheon National University Incheon Korea Department of Computer Systems Engineering Universidad Politécnica de Madrid Madrid Spain

ISBN: (数字)9798350359312

ISBN: (纸本)9798350359329

Imagined speech production with electrocorticography (ECoG) plays a crucial role in brain-computer interface system. A challenging issue is the great variation underlying the frequency bands of the ECoG signals’ encode information, which makes current methods difficult to generate imagined speech with stable quality among different persons. To this end, we propose a robust model to generate high-quality imagined speech from ECoG. A frequency enhancement branch is first designed to adaptively modulate the frequency information, whose product is fed into the following multi-scale channel attention module for robust feature extraction and fusion. By incorporating both the mel-spectrum and audio as training constraints, a multi-constraint decoder branch is finally constructed for imagined speech production. The performance of our model is evaluated on a high-quality dateset, i.e, Single Word Production Dutch-iBIDS. It yields Pearson correlation scores that are all above 0.8, and the standard deviationsare are all below 0.2 in different volunteers. Experimental results demonstrate that our model is effective and robust for ECoG based imagined speech production, and has advantages over peer methods.

关键词： Training Adaptation models Frequency modulation Correlation Neuroscience Production Speech enhancement

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