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2022 International Conference on Networking and Network Applications, NaNA 2022

作者： Yu, Han Zhan, Jie Libin, Jiao Han, Jun-Mei School of Physics and Electronic Science Hunan University of Science and Technology Xiangtan412001 China Science and Technology on Communication Networks Laboratory Shijiazhuang050081 China National Key Laboratory for Complex Systems Simulation Department of Systems General Design Institute of Systems Engineering Beijing100101 China

ISBN: (数字)9781665461313

ISBN: (纸本)9781665461313

IEEE 802.11 Wireless Local Area Network (WLAN) is a popular way for mobile devices to access the Internet. Operators and service providers often increase the density of wireless access points in order to provide users with better connections and user experience. As a result, WLAN users find themselves covered by multiple access points. In traditional wireless multi-hotspot networks most user terminals choose the access point with the strongest signal without considering the existing load on that access point, leading to severe congestion and load imbalance problems. This paper proposes an improved NSGA-ii-based load balancing strategy for wireless multi-hotspot networks, which determines which hotspot should be associated with each user terminal by taking into account the current access point load, the received signal strength and the throughput size of the user terminal. The simulation results show that compared with the traditional strongest signal First (SSF) strategy, the proposed load balancing strategy can improve the network throughput by more than 30%. © 2022 IEEE.

关键词： IEEE Standards

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Architecture transformation research on joint border defense systems-of-systems 2021

Architecture transformation research on joint border defense...

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2021 5th International Conference on Management Engineering, Software Engineering and Service sciences, ICMSS 2021

作者： Zhang, Mengmeng Yi, Shuanghui Lin, Menglong Chen, Honghui Science and Technology on Information Systems Engineering Laboratory China National Key Laboratory for Complex System Simulation China

ISBN: (纸本)9781450389709

Currently, with the deepening of development and open of China's border, issues of border joint defense become increasingly arduous. Traditional means of cooperation and coordination are far from being able to align requirements;information systems of different joint defense units are difficult to interconnect and interoperate;the previous results of joint defense informatization are difficult to inherit. The main reason is the lack of border joint defense information construction with a top-level design approach. Via the lens of top-level design, this paper establishes a multi-viewpoint architecture framework and transformation process, develops the as-is and to-be joint defense architecture, and finally analyzes transformation principles from the as-is architecture to to-be architecture. This paper mainly explores the architecture transformation mechanisms under the border joint defense scenario. © 2021 ACM.

关键词： Architecture

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MD-TransUNet: TransUNet with Multi-attention and Dilated Convolution for Brain Stroke Lesion Segmentation 19th

MD-TransUNet: TransUNet with Multi-attention and Dilated C...

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19th EAI International Conference on Collaborative Computing: Networking, Applications and Worksharing, CollaborateCom 2023

作者： Xu, Jie Wan, Jian Zhang, Xin School of Computer Science and Technology Hangzhou Dianzi University Zhejiang310018 China Key Laboratory of Complex Systems Modeling and Simulation Ministry of Education Ministry of Education Beijing China School of Information and Electronic Engineering Zhejiang University of Science and Technology Zhejiang China Key Laboratory of Marine Ecosystem Dynamics Second Institute of Oceanography Ministry of Natural Resources Hangzhou China

ISBN: (纸本)9783031545276

The accurate segmentation of stroke lesion regions holds immense significance in shaping treatment strategies and rehabilitation protocols. Due to the large difference in the volume of stroke lesion areas and the great similarity between lesion areas and normal tissues, most of the existing methods for lesion segmentation cannot deal with these problems well. This paper proposes a novel network named MD-TransUNet for the segmentation of stroke lesions, whose framework is based on the UNet architecture. To fully obtain deep image features, it uses ResNet50 for downsampling. MD (multi-dilated) module is employed as the skip connection to gain more receptive fields. Different receptive fields can adapt to varying volumes of lesion areas. Then, a feature extraction module with multi-level attention mechanism is designed using ConvLSTM, non-local spatial attention, and channel attention modules to suppress useless information expression in skip connections and upsampling processes while focusing more on effective spatial and channel information in features. The experiments show that our proposed network gets superior performance than benchmark methods and indicates the generalization and effectiveness of the proposed model. © ICST Institute for Computer sciences, Social Informatics and Telecommunications Engineering 2024.

关键词： Convolution

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Rapid Modeling and Model Order Reduction of Launch Vehicle Based on Digital Twin 2nd

Rapid Modeling and Model Order Reduction of Launch Vehicle B...

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2nd International Conference of Mechanical System Dynamics, ICMSD 2023

作者： Huang, Tianyou Wang, Qingtao Liu, Xiong Liu, Zhendong Wang, Qixiao School of Science Nanjing University of Science and Technology Nanjing China Institute of Launch Dynamics Nanjing University of Science and Technology Nanjing China National Key Laboratory of Complex Multibody System Dynamics Nanjing University of Science and Technology Nanjing China Shanghai Aerospace Systems Engineering Institute Shanghai China

ISBN: (纸本)9789819980475

In this paper, a dynamic analysis technique for complex launch vehicle models using digital twin technology is introduced. A parameterized model of the launch vehicle is established and simulations are conducted on a multi-physics simulation platform. The resulting analysis file is then integrated into a system-level multi-physical domain digital twin platform. To simplify the model, singular value decomposition (SVD) method is employed to reduce its complexity. Numerical comparison and error analysis are performed between the reduced model and the original model. By comparing and analyzing the reduced order models with different levels of error, the effectiveness of the digital twin approach is demonstrated. Furthermore, the reduced order model within the digital twin framework is encapsulated. This encapsulation enables the realization of comprehensive life cycle configuration management for the launch vehicle equipment. Overall, this technique offers a promising approach for analyzing and managing complex models of the context of launch vehicles. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.

关键词： Launch vehicles

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Parameterized Modelling of Stage Separation of Launch Vehicles with Modelica 2nd

Parameterized Modelling of Stage Separation of Launch Vehicl...

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2nd International Conference of Mechanical System Dynamics, ICMSD 2023

作者： Zhang, Wenfeng Cai, Xiaoshuang Liu, Zhendong Liu, Xiong Tong, Yifan Shanghai Aerospace Systems Engineering Institute Shanghai China School of Science Nanjing University of Science and Technology Nanjing China Institute of Launch Dynamics Nanjing University of Science and Technology Nanjing China National Key Laboratory of Complex Multibody System Dynamics Nanjing University of Science and Technology Nanjing China

ISBN: (纸本)9789819980475

In order to improve launching capability and performance, almost all launch vehicles in active service contain two or more stages. During the launch process, it is of vital importance to gradually reduce the weight of the launch vehicles by separating and jettisoning spent stages which have burned out its propellant. The separation process between the stages plays a crucial role in guaranteeing the safety of the launch vehicles and ensuring a successful launch. Consequently, it is essential for launch vehicle designers to well understand the stage-separation dynamics which is quite complex and affected by many system parameters. To evaluate the impact of the system parameters on the stage-separation mission, a parameterized model is established for a two-stage launch vehicle using the Modelica language along with the software MWorks. As representative parameters to evaluate, the mass-center positions of the first and second stages, both the positions and directions of the active forces, the residual thrusts, the positive thrusts, the retro thrusts, the masses and moments of inertia of the two stages, are all taken into account for dynamic analysis. The parameterized Modelica model is built by exploiting the idea of the equation-based causal modelling to numerically simulate the stage-separation process and evaluate the influence of the parameters on the system responses. simulation results based on representative case studies indicate that the separation process of the first and second stages can be well described by the Modelica model. Besides, a comparison with Adams software demonstrates the results of the Modelica model agree well with those obtained using Adams. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.

关键词： Launch vehicles

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Modeling and simulation of Stage Separation System of Launch Vehicles Based on MWorks 2nd

Modeling and Simulation of Stage Separation System of Launch...

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2nd International Conference of Mechanical System Dynamics, ICMSD 2023

作者： Pu, Jinrui Wang, Qingtao Liu, Zhendong Cai, Xiaoshuang Liu, Xiong School of Science Nanjing University of Science and Technology Nanjing China Institute of Launch Dynamics Nanjing University of Science and Technology Nanjing China National Key Laboratory of Complex Multibody System Dynamics Nanjing University of Science and Technology Nanjing China Shanghai Aerospace Systems Engineering Institute Shanghai China

ISBN: (纸本)9789819980475

The current methods for modeling, simulating, and verifying the stage separation system of a launch vehicle are limited to specific models and cannot be universally validated. Moreover, it is a time-consuming and labor-intensive task to remodel a launch vehicle with different topologies. To address this issue, this paper proposes a solution using the software MWorks. The approach involves establishing basic component models for launch vehicles, including the first stage, second stage, thrust, and explosive bolts. These component models are then utilized to create a model library for the stage separation of a launch vehicle. By employing this library, the stage separation process of a specific launch vehicle model can be simulated and analyzed to ensure the safety of the separation under harsh conditions. This methodology offers a more efficient and flexible approach to validate the stage separation system of launch vehicles. By utilizing the established model library, the need for extensive remodeling is eliminated, saving both time and effort. The simulation results provide valuable insights into the safety and effectiveness of the stage separation process. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.

关键词： Launch vehicles

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MBSE-Based Guidance System simulation of Launch Vehicle 2nd

MBSE-Based Guidance System Simulation of Launch Vehicle

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2nd International Conference of Mechanical System Dynamics, ICMSD 2023

作者： Ma, Guowei Wang, Qingtao Zhang, Wenfeng Yu, Rendong Liu, Xiong School of Science Nanjing University of Science and Technology Nanjing China Institute of Launch Dynamics Nanjing University of Science and Technology Nanjing China National Key Laboratory of Complex Multibody System Dynamics Nanjing University of Science and Technology Nanjing China Shanghai Aerospace Systems Engineering Institute Shanghai China

ISBN: (纸本)9789819980475

In the traditional development process of the launch vehicle guidance system, the system is designed repeatedly in the earlier stage and the verification of the system is conducted in the later stage. This development mode may cause some problems, such as low design efficiency and high cost. In order to improve the shortcomings of the traditional development process, in this paper the MBSE (Model Based System Engineering) method is introduced in the design phase of the launch vehicle guidance system, and the MBSE-based design model is used to carry out system verification in real time. The application of this method greatly improves the design efficiency of the launch vehicle guidance system. The MBSE-based simulation model of the launch vehicle guidance system is established, the system perturbation guidance simulation is carried out, and the result is compared with the standard design trajectory to verify the correctness of the guidance system designed based on MBSE. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.

关键词： Launch vehicles

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Lightweight design and deployment of object detection model for low-light scenes 4

Lightweight design and deployment of object detection model ...

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4th International Conference on Computer Vision, Application, and Algorithm, CVAA 2024

作者： Sun, Kangjian Huo, Ju Jiang, Xiaona Gao, Yichao Cai, Chen School of Electrical Engineering and Automation Harbin Institute of Technology Harbin China National Key Laboratory of Modeling and Simulation for Complex Systems Harbin China China FAW Corporation Limited Changchun China College of Design and Engineering National University of Singapore Singapore Signal and Communication Research Institute China Academy of Railway Sciences Beijing China

ISBN: (数字)9781510687622

ISBN: (纸本)9781510687615

Low-light scenes are common in fields such as autonomous driving, which tests the robustness of intelligent systems. This paper tests the performance of object detection in low-light scenes based on the YOLOv8n model. In order to solve the constraint of limited computing power of embedded devices, the YOLOv8n model is adjusted through model pruning and knowledge distillation. The complexity of the model is reduced through these lightweight operations. While ensuring the detection performance as much as possible, the multiply-accumulate operations (MACs) and parameters of the model decreased by about 40% and 27% respectively. The proposed model is evaluated on the Exclusively Dark (ExDARK) dataset and achieves a mean average precision (mAP) value of 0.672. In addition, the proposed model is migrated to the embedded platform NVIDIA Jetson Xavier NX. The deployment process is optimized by multi-process scheduling and multi-thread scheduling. Experiments are also conducted on real data, and the results show that the proposed model can provide a feasible solution for vision-based nighttime autonomous driving. © 2025 SPIE.

关键词： Object detection Deep learning Image processing

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General theory for designing phonon transport in alloyed/doped materials

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science China(Physics,Mechanics & Astronomy) 2024年第12期67卷 133-140页

作者： Chenhan Liu Chao Wu Wei Liu Yunshan Zhao Gang Zhang Hongmin Yang Yunfei Chen Micro-and Nano-scale Thermal Measurement and Thermal Management Laboratory Key Laboratory of Numerical Simulation for Large Complex SystemsMinistry of EducationSchool of Energy and Mechanical EngineeringNanjing Normal UniversityNanjing210023China School of Electrical and Automation Engineering Nanjing Normal UniversityNanjing210023China Phonon Engineering Research Center of Jiangsu Province Center for Quantum Transport and Thermal Energy ScienceInstitute of Physics Frontiers and Interdisciplinary SciencesSchool of Physics and TechnologyNanjing Normal UniversityNanjing210023China Agency for Science Technology and ResearchInstitute of High-Performance ComputingSingapore138632Singapore Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments School of Mechanical EngineeringSoutheast UniversityNanjing211100China

Alloying/doping is a widely used technique for improving the electrical,mechanical,and optical properties of ***,this technology induces significant distortions in the lattice structure,mass distribution,and potential field,greatly enhancing phonon ***,we introduce the concept of alloying/doping path and employ crystal symmetry,lattice deformation,and electron distribution to characterize *** on this new concept,the phonon thermal transport behavior in alloyed/doped materials can be well designed,and along different alloying/doping paths,the difference in thermal conductivity can be up to 45 *** one hand,strategic alloying/doping that combines high crystal symmetry,large lattice contraction,and the same electron distribution suppresses phonon-phonon scattering phase space,induces phonon stiffening,and bolsters electronic structure symmetry,*** synergistic effects significantly improve thermal *** the other hand,random alloying/doping has a low symmetry,leading to the typical“U”shape of alloying/doping level-dependent thermal *** theory is corroborated in three-dimensional(3D)Si,2D MoS_(2),and quasi-1D TiS_(3),affirming its efficacy and broad applicability in controlling phonon transport.

关键词： phonon transport alloyed/doped materials crystal symmetry lattice contraction electronic structure

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Characterization and prediction of tailpipe ammonia emissions from in-use China 5/6 light-duty gasoline vehicles

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Frontiers of Environmental science & Engineering 2024年第1期18卷 71-81页

作者： Lewei Zeng Fengbin Wang Shupei Xiao Xuan Zheng Xintong Li Qiyuan Xie Xiaoyang Yu Cheng Huang Qingyao Hu Yan You Ye Wu College of Chemistry and Environmental Engineering Shenzhen UniversityShenzhen 518060China State Key Laboratory of Engines Tianjin UniversityTianjin 300072China China Automotive Technology and Research Center Co.Ltd. Tianjin 300300China CATARC Automotive Test Center(Guangzhou)Co.Ltd. Guangzhou 511300China State Environmental Protection Key Laboratory of Cause and Prevention of Urban Air Pollution Complex Shanghai Academy of Environmental SciencesShanghai 200233China National Observation and Research Station of Coastal Ecological Environments in Macao Macao Environmental Research InstituteMacao University of Science and TechnologyMacao SAR 999078China School of Environment State Key Joint Laboratory of Environment Simulation and Pollution ControlTsinghua UniversityBeijing 100084China

On-road tailpipe ammonia (NH3) emissions contribute to urban secondary organic aerosol formation and have direct or indirect adverse impacts on the environment and human health. To understand the tailpipe NH3 emission characteristics, we performed comprehensive chassis dynamometer measurements of NH3 emission from two China 5 and two China 6 light-duty gasoline vehicles (LDGVs) equipped with three-way catalytic converters (TWCs). The results showed that the distance-based emission factors (EFs) were 12.72 ± 2.68 and 3.18 ± 1.37 mg/km for China 5 and China 6 LDGVs, respectively. Upgrades in emission standards were associated with a reduction in tailpipe NH3 emission. In addition, high NH3 EFs were observed during the engine warm-up period in cold-start cases owing to the intensive emissions of incomplete combustion products and suitable catalytic temperature in the TWCs. Notably, based on the instantaneous NH3 emission rate, distinct NH3–emitting events were detected under high/extra high velocity or rapid acceleration. Furthermore, NH3 emission rates correlated well with engine speed, vehicle specific power, and modified combustion efficiency, which were more easily accessible. These strong correlations were applied to reproduce NH3 emissions from China 5/6 LDGVs. The predicted NH3 EFs under different dynamometer and real-world cycles agreed well with existing measurement and prediction results, revealing that the NH3 EFs of LDGVs in urban routes were within 8.55–11.62 mg/km. The results presented here substantially contribute to improving the NH3 emission inventory for LDGVs and predicting on-road NH3 emissions in China.

关键词： NH3 instantaneous emissions Catalytic temperature Vehicle specific power Combustion efficiency Emission prediction

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