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Heterogeneous temporal graph powered DRL algorithm for channel allocation in Maritime IoT Systems

COMPUTER COMMUNICATIONS 2024年 213卷 260-270页

作者： Li, Zongwang Xie, Zhuochen He, Xiaohe liang, xuwen Chinese Acad Sci Innovat Acad Microsatellites 1 Xueyang Rd Shanghai 201304 Peoples R China Univ Chinese Acad Sci 1 Yanqihu East Rd Beijing 101408 Peoples R China

In actual maritime Internet of Things systems, the communication environment is characterized by its time-varying nature and the presence of highly heterogeneous network structures. Those attributes present considerable challenges in devising resource allocation strategies. Given the limited availability of frequency resources, designing a reasonable and flexible channel allocation strategy (CAS) is the primary task for meeting diverse and dynamic communication demands. In this paper, a heterogeneous temporal graph powered deep reinforcement learning algorithm is proposed to optimize the CAS to maximize the channel efficiency in a real-world maritime Internet of Things system. Specifically, we build relation-based heterogeneous edges to connect different types of terminal nodes and adopt a time encoding technology to capture the dynamic evolution of communication scenarios over time. The memory and public mailbox modules are constructed as the implementation entities of the information aggregation method based on the attention mechanism. In addition, we develop a corresponding heterogeneous temporal neural network to estimate the real-time resource requirements of target terminals, and subsequently learn the optimal CAS based on the deep reinforcement learning algorithm from the perspective of maximizing the cumulative channel efficiency. Simulation results prove that the proposed algorithm significantly outperforms the other state-of-the-art algorithms in terms of the channel efficiency and generalization ability.

关键词： Maritime IoT Heterogeneous temporal graph Deep reinforcement learning

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Intelligent Spectrum Sharing Strategy for Integrated Satellite-Maritime Heterogeneous Mobile Networks

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2024年第5期73卷 6780-6794页

作者： Wu, Ruiwen Li, Zongwang Xie, Zhuochen liang, xuwen Univ Chinese Acad Sci Beijing 100049 Peoples R China Shanghai Innovat Acad Microsatellites Shanghai 201304 Peoples R China Shanghai Engn Ctr Microsatellites Shanghai 201210 Peoples R China

Spectrum sharing is a pivotal technology for integrated satellite-maritime network to improve spectrum efficiency. However, the majority of existing spectrum sharing approaches relied on time-frequency multiplexing to circumvent or suppress interference, and often overlooked the problem of incomplete observability and interference present in heterogeneous systems. This limitation hindered overall system throughput improvements. In this article, an intelligent spectrum sharing strategy for integrated satellite-maritime heterogeneous mobile networks is firstly proposed. This strategy aims to operate co-frequency communication transmissions within the interference constraints, as derived from protocols and standards of International Telecommunication Union (ITU), to maximize the overall system throughput and spectral efficiency. Furthermore, considering the limitation that the satellite cannot fully observe channel statuses, we model the spectrum sharing process as a Partially Observable Markov Decision Process (POMDP). We employ an algorithm architecture that combines Dueling Deep Q-learning Network (DQN) and Double DQN to address this challenge, which enables satellites to efficiently evaluate the value of all channel allocation actions, thereby enhancing decision-making accuracy and algorithm convergence speed. Simulation results validate the superiority of our proposed strategy over compared methods in terms of throughput and stability.

关键词： Satellites Throughput Marine vehicles Interference Satellite broadcasting Optimization ITU Satellite-maritime heterogeneous mobile networks spectrum sharing interference constraints partially observable Markov decision process (POMDP) double dueling deep Q-learning network (DQN)

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Online analysis of iron ore slurry using PGNAA technology with artificial neural network

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NUCLEAR ENGINEERING AND TECHNOLOGY 2024年第7期56卷 2835-2841页

作者： Huang, Haolong Cai, Pingkun liang, xuwen Jia, Wenbao Nanjing Univ Aeronaut & Astronaut Dept Nucl Sci & Technol Nanjing 211106 Peoples R China Collaborat Innovat Ctr Radiat Med Jiangsu Higher E Suzhou 215000 Peoples R China

Real-time analysis of metallic mineral grade and slurry concentration is significant for improving flotation efficiency and product quality. This study proposes an online detection method of ore slurry combining the Prompt Gamma Neutron Activation Analysis (PGNAA) technology and artificial neural network (ANN), which can provide mineral information rapidly and accurately. Firstly, a PGNAA analyzer based on a D-T neutron generator and a BGO detector was used to obtain a gamma-ray spectrum dataset of ore slurry samples, which was used to construct and optimize the ANN model for adaptive analysis. The evaluation metrics calculated by leave-one-out cross-validation indicated that, compared with the weighted library least squares (WLLS) approach, ANN obtained more precise and stable results, with mean absolute percentage errors of 4.66% and 2.80% for Fe grade and slurry concentration, respectively, and the highest average standard deviation of only 0.0119. Meanwhile, the analytical errors of the samples most affected by matrix effects was reduced to 0.61 times and 0.56 times of the WLLS method, respectively.

关键词： Mineral grade Slurry concentration Online detection Prompt gamma neutron activation analysis Artificial neural network

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A novel method for satellite prediction of VDE-TER service traffic information based on multilayers bidirectional LSTM

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INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING 2024年第0期

作者： Wu, Ruiwen Li, Zongwang Xie, Zhuochen liang, xuwen Univ Chinese Acad Sci Sch Elect Elect & Commun Engn Beijing 100049 Peoples R China Chinese Acad Sci Shanghai Innovat Acad Microsatellites Shanghai Peoples R China Shanghai Engn Ctr Microsatellites Shanghai Peoples R China

Satellite prediction of very high frequency (VHF) Data Exchange (VDE)-Terrestrial (VDE-TER) ship-to-ship Self-Organized Networks (SON) service traffic information is crucial for wireless resource allocation of VHF Data Exchange System (VDES). Due to the VDE-TER, channel load observed by the satellite changes rapidly and the historical information cached on the satellite is limited;the prediction of VDE-TER service traffic is difficult. This paper proposes a multilayer bidirectional long short-term memory (LSTM) neural network model (MLB-LSTM), which controls the amount of forgetting of historical information and the amount of memory of current information through the LSTM unit, so that the model can better learn the nonlinear changes of service traffic. The bidirectional LSTM module combines forward and backward time series data, reducing the amount of data required for prediction and enhancing the prediction accuracy of the model. Numerical results show that the proposed prediction model significantly outperforms traditional methods and is able to adapt to rapidly changing VDE-TER data. This paper proposes a multilayer bidirectional long short-term memory (LSTM) neural network model (MLB-LSTM), which controls the amount of forgetting of historical information and the amount of memory of current information through the LSTM unit, so that the model can better learn the nonlinear changes of service traffic. The bidirectional LSTM module combines forward and backward time series data, reducing the amount of data required for prediction and enhancing the prediction accuracy of the model. image

关键词： bidirectional LSTM LEO satellite multidimensional time series prediction VHF data exchange system

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Microstructure, mechanical and neutron shielding properties of aluminum borate ceramics obtained from alumina and boric acid

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JOURNAL OF THE AUSTRALIAN CERAMIC SOCIETY 2024年第3期60卷 905-915页

作者： Lao, Dong Zhang, Yan Huang, Lingfeng liang, xuwen Jia, Wenbao Nanjing Univ Aeronaut & Astronaut NUAA Dept Nucl Sci & Technol Nanjing 211106 Peoples R China East China Univ Technol Engn Res Ctr Nucl Technol Applicat Minist Educ Nanchang 330013 Peoples R China Jiangsu Higher Educ Inst Collaborat Innovat Ctr Radiat Med Suzhou 215006 Peoples R China

In this study, a series of aluminum borate ceramics (ABCs) with needle-like whiskers were obtained using a low-cost, solid-state, pressureless sintering ceramic route, without any additives during the preparation process. The effects of different alumina/boric acid molar ratios and sintering temperatures on the phase composition, microstructure, mechanical properties, specific surface area, pore size distribution, and sub-cadmium neutron shielding properties of ABCs were studied using orthogonal experiments. It was observed that pure phase aluminum borate (Al18B4O33) ceramics could be obtained at 1100 degree celsius, forming a mass of needle-like whiskers. The whiskers' aspect ratio, fracture work, specific surface area, and pore size distribution of ABCs are maximized when ABCs are sintered at 1100 degree celsius with 9:6 alumina/boric acid molar ratio. In this condition, ABCs (0.5 cm) can shield 70% of sub-cadmium neutrons (E<0.4 eV). These findings demonstrate the great potential of aluminum borate ceramics for neutron shielding applications.

关键词： Aluminum borates ceramics (ABCs) Solid-state reaction synthesis Al18B4O33 whiskers Mechanical properties Sub-cadmium neutron shielding capacity

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Analog Beamforming Enabled Multicasting: Finite-Alphabet Inputs and Statistical CSI

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IEEE COMMUNICATIONS LETTERS 2024年第8期28卷 1785-1789页

作者： Wu, Yanjun Xie, Zhong Xie, Zhuochen Ouyang, Chongjun liang, xuwen Univ Chinese Acad Sci Beijing 100049 Peoples R China Chinese Acad Sci Innovat Acad Microsatellites Shanghai 201304 Peoples R China Chinese Acad Sci Key Lab Satellite Digitalizat Technol Shanghai 201210 Peoples R China Chinese Acad Sci Natl Space Sci Ctr Beijing 100190 Peoples R China Chinese Acad Sci Shanghai Engn Ctr Microsatellites Shanghai 201210 Peoples R China Univ Coll Dublin Coll Engn & Architecture Sch Elect & Elect Engn Dublin D04 V1W8 Ireland ShanghaiTech Univ Sch Informat Sci & Technol Shanghai 201210 Peoples R China

The average multicast rate (AMR) is analyzed in a multicast channel utilizing analog beamforming with finite-alphabet inputs, considering statistical channel state information (CSI). New expressions for the AMR are derived for non-cooperative and cooperative multicasting scenarios. Asymptotic analyses are conducted in the high signal-to-noise ratio regime to derive the array gain and diversity order. It is proved that the analog beamformer influences the AMR through its array gain, leading to the proposal of efficient beamforming algorithms aimed at maximizing the array gain to enhance the AMR.

关键词： Array signal processing Signal to noise ratio Multicast communication Radio frequency Symbols Small satellites Performance evaluation Analog beamforming finite-alphabet inputs multicast statistical channel state information (CSI)

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Optimization of image reconstruction method for dual-particle time-encode imager through adaptive response correction

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NUCLEAR ENGINEERING AND TECHNOLOGY 2023年第5期55卷 1587-1592页

作者： Zhao, Dong Jia, Wenbao Hei, Daqian Cheng, Can Cheng, Wei liang, xuwen Li, Ji Nanjing Univ Aeronaut & Astronaut Dept Nucl Sci & Technol Nanjing 211106 Peoples R China Lanzhou Univ Sch Nucl Sci & Technol Lanzhou 730000 Peoples R China Collaborat Innovat Ctr Radiat Med Jiangsu Higher E Suzhou 215000 Peoples R China Nucl Power Inst China Chengdu 610041 Peoples R China

Time-encoded imagers (TEI) are important class of instruments to search for potential radioactive sources to prevent illicit transportation and trafficking of nuclear materials and other radioactive sources. The energy of the radiation cannot be known in advance due to the type and shielding of source is unknown in practice. However, the response function of the time-encoded imagers is related to the energy of neutrons or gamma-rays. An improved image reconstruction method based on MLEM was proposed to correct for the energy induced response difference. In this method, the count vector versus time was first smoothed. Then, the preset response function was adaptively corrected according to the measured counts. Finally, the smoothed count vector and corrected response were used in MLEM to reconstruct the source distribution. A one-dimensional dual-particle time-encode imager was developed and used to verify the improved method through imaging an Am -Be neutron source. The improvement of this method was demonstrated by the image reconstruction results. For gamma-ray and neutron images, the angular resolution improved by 17.2% and 7.0%;the contrast-to-noise ratio improved by 58.7% and 14.9%;the signal-to-noise ratio improved by 36.3% and 11.7%, respectively.(c) 2023 Korean Nuclear Society, Published by Elsevier Korea LLC. This is an open access article under the CC BY-NC-ND license (http://***/licenses/by-nc-nd/4.0/).

关键词： Time -encoded imager Dual -particle imaging Response correction Image reconstruction

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Dynamic Channel Reservation Strategy Based on DQN Algorithm for Multi-Service LEO Satellite Communication System

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IEEE WIRELESS COMMUNICATIONS LETTERS 2021年第4期10卷 770-774页

作者： Li, Zongwang Xie, Zhuochen liang, xuwen Chinese Acad Sci Shanghai Engn Ctr Microsatellites Shanghai 201210 Peoples R China Univ Chinese Acad Sci Beijing 100049 Peoples R China

In this letter, a dynamic channel reservation (DCR) strategy based on deep Q network (DQN) is proposed for multi-service low earth orbit (LEO) satellite communication system. We develop a novel modeling method to represent DCR problem of multiple services as a reinforcement learning (RL) task. Based on this model, we calculate the influence of current channel allocation results on future environment and take it as one of the factors for channel allocation decision. Moreover, a corresponding neural network is designed as a decision evaluator to provide an end to end mapping of decision to its value, which effectively avoids the influence of artificial preconditions. Simulation results show that the proposed strategy can improve the overall quality of service (QOS) of the system.

关键词： Satellites Bandwidth Handover Low earth orbit satellites Channel allocation Resource management Heuristic algorithms Multi-service LEO satellite dynamic channel reservation strategy deep Q network

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Characterization of thermal neutron distribution of an Am-Be neutron source setup by CdZnTe detector

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APPLIED RADIATION AND ISOTOPES 2023年 196卷 110778页

作者： liang, xuwen Zhao, Dong Jia, Wenbao Hei, Daqian Cheng, Can Nanjing Univ Aeronaut & Astronaut Dept Nucl Sci & Technol Nanjing Peoples R China Jiangsu Higher Educ Inst Collaborat Innovat Ctr Radiat Med Suzhou 215000 Peoples R China Lanzhou Univ Sch Nucl Sci & Technol Lanzhou 730000 Peoples R China Nanjing Univ Aeronaut & Astronaut Coll Astronaut Nanjing 211106 Peoples R China

Owing to the developments in prompt gamma neutron activation analysis (PGNAA) and prompt gamma ray activation imaging (PGAI), it is necessary to develop an online thermal neutron distribution measurement method. The CdZnTe detector is considered as an alternative thermal neutron detector because of its high thermal neutron capture cross section. In this study, the thermal neutron field of an 241Am-Be neutron source was determined by CdZnTe detector. The intrinsic neutron detection efficiency of CdZnTe detector was calcu-lated by using indium foil activation, and the value was 3.65%. Then the characteristics of neutron source were conducted with the calibrated CdZnTe detector. The thermal neutron fluxes in front of beam port were measured at several distances ranging from 0 cm up to 28 cm. Thermal neutron field at distances of 1 cm and 5 cm were also measured. The experimental data were then compared with Monte Carlo simulation. The results demon-strated that the simulated data agree well with experimental measurements.

关键词： CdZnTe detector Monte Carlo simulation Am -Be neutron source Activation method Thermal neutron flux

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Microvibration streaming measurements using dynamic compressed sensing for satellites

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MEASUREMENT SCIENCE AND TECHNOLOGY 2023年第8期34卷 085015-085015页

作者： Li, Li Zhou, Miaomiao Zhu, Ye Tao, Lixuan liang, xuwen Chinese Acad Sci Innovat Acad Microsatellites Shanghai 201204 Peoples R China Shanghai Engn Ctr Microsatellites Shanghai 201204 Peoples R China Univ Chinese Acad Sci Beijing 100049 Peoples R China

Long-term monitoring of satellite microvibrations generates a significant amount of data streams, placing strain on satellites with limited transmission capacity. To relieve this transmission strain, a dynamic compressed sensing (CS) framework is proposed for measuring satellite microvibrations. Microvibration streams are measured block by block and then reconstructed using a dynamic recovery algorithm. The recovery solution of one block can be used as a priori knowledge for the next block, allowing for faster updates. However, existing dynamic recovery algorithms are only applicable in the real domain and cannot be applied to microvibrations projected on a Fourier basis in the complex domain. In light of this event, the dynamic homotopy algorithm is expanded to the complex domain to deal with microvibration signals that are sparse in the Fourier basis. In comparison to conventional uniform sampling methods, the experimental results show that the dynamic CS with the expanded recovery algorithm can achieve a maximum root-mean-square acceleration (Grms) deviation of 4% in power spectrum density with one-fifth of the sampling points. Compared to recovery algorithms applicable to fixed measurements, the dynamic algorithm can achieve comparable accuracy in about one-third of the computation time. The experimental findings demonstrate the feasibility of satellite microvibrations measurements using dynamic CS.

关键词： satellite microvibration compressed sensing dynamic homotopy algorithm streaming measurement

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