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Mode transitions in Hall effect thrusters by Varying duty ratio under pulsating operation

Advances in Space Research 2025年第10期75卷 7466-7472页

作者： Ma, Haochen Zheng, He Liang, Tiance Li, Jiapeng Wei, Liqiu Han, Liang Li, Hong Ding, Yongjie School of Energy Science and Engineering Harbin Institute of Technology Heilongjiang Harbin150001 China Key Laboratory of Aerospace Plasma Propulsion Ministry of Industry and Information Technology Harbin150001 China Beijing Institute of Control Engineering China Aerospace Science and Technology Corporation Beijing100089 China

During the operation of a Hall effect thruster, small changes in discharge voltage, mass flow, or magnetic field cause significant changes in the discharge mode of the thruster. Keeping other working conditions unchanged, the discharge mode of the Hall effect thruster can be triggered by changing the duty ratio. The experimental results show that at different frequencies, a small change in the duty ratio caused a significant increase in the discharge current and discharge oscillation amplitude. When the duty ratio changed from 70 % to 68 % at 90 kHz, the discharge mode changed from high- to low-oscillation mode. The discharge current oscillation decreased from 1.03 to 0.66, and the anode efficiency increased from 24.5 % to 25.8 %. When the duty ratio was changed from 64 % to 58 % at a pulse frequency of 70 kHz, the discharge current oscillation decreased from 1.26 to 0.85, and the anode efficiency increased from 23.5 % to 24.8 %. In the low-oscillation mode, the discharge current and anode voltage of the thruster were at the same frequency, and the discharge oscillation of the thruster was significantly reduced. Furthermore, the Faraday probe measurement results showed that the ion current density distribution of the thruster was more focused. The match between the supply of the working medium and the ionization rate improved the degree of ionization, leading to an improvement in thrust performance. Maintaining the Hall effect thruster in low-oscillation mode is of great significance for improving the reliability of the thruster. © 2025 COSPAR

关键词： Hall thrusters

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Maximum Entropy Deep Reinforcement Learning Based Power Allocation for NOMA Maritime Network 14th

Maximum Entropy Deep Reinforcement Learning Based Power Allo...

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14th EAI International Conference on Wireless and Satellite systems, WiSATS 2024

作者： He, Jiayi Zhang, Yakai Liu, Zhiyong School of Information Science and Engineering of HIT Weihai264209 China Shandong Provincial Key Laboratory of Marine Electronic Information and Intelligent Unmanned Systems Weihai264209 China Key Laboratory of Cross Domain Synergy and Comprehensive Support for Unmanned Marine Systems of Ministry of Industry and Information Technology Weihai264209 China

ISBN: (纸本)9783031862021

In order to address the challenges of high propagation delays and limited service capabilities in maritime satellite communications, unmanned aerial vehicles have been proposed as an airborne backhaul solution to enhance communications between satellites and maritime base stations. The non-orthogonal multiple access (NOMA) framework can solve the user sparsity problem in maritime networks. In this paper, a deep reinforcement learning algorithm is used to solve the nonconvex power allocation problem under NOMA. In order to mitigate the risk of overestimation of Q values and local optimal convergence of Deep Q Network (DQN) algorithm, we propose an algorithm called Soft Agent Critical Ocean Satellite Communication Power Allocation (SAC-OSCPA) based on the idea of maximum entropy and compare it with the traditional DQN algorithm. The main goal of this research is to maximize network throughput in scenarios with randomly distributed users. Simulation results show that the average system throughput is improved by 13.18% with the SAC-OSCPA algorithm, and the average throughput of the worst performing user is significantly improved by 41.59%. These results demonstrate the efficacy of the proposed algorithm in optimizing the communication performance of maritime satellite networks. © ICST Institute for Computer sciences, Social Informatics and Telecommunications engineering 2025.

关键词： Deep reinforcement learning

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CNN-Based Multi-Output and Multi-Task Regression for Supershape Reconstruction from 3D Point Clouds

Informatica (Slovenia)

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Informatica (Slovenia) 2025年第5期49卷 37-48页

作者： Remmach, Hassnae Razak, Siti Fatimah Abdul Ullah, Arif Yogarayan, Sumendra Sayeed, Md Shohel Mrhari, Amine Computer Systems Engineering Laboratory Cadi Ayyad University Marrakesh40000 Morocco Faculty of Information Science and Technology Multimedia University Ayer Keroh75450 Malaysia Research in Computer Science Laboratory Faculty of Sciences Ibn Tofail University Kenitra Morocco

In a number of industries, including computer graphics, robotics, and medical imaging, three-dimensional reconstruction is essential. In this research, a CNN-based Multi-output and Multi-Task Regressor with deep learning capabilities is proposed for three-dimensional object reconstruction from 3D point cloud. Our approach is grounded in the original Point Net architecture, which addresses the difficulties associated with convolution when applied to point clouds. Firstly, this paper is modified using a Multi-Output Regressor to accurately recreate Super forms from 3D point clouds. Using this method, we first extract features from the 3D point cloud using Point Net. After that, a Multi-Output Regressor receives these data and uses them to anticipate the Super shape parameters needed to reconstruct the shape. Taking in the data, the Multi-Output Regressor retrieved characteristics from Point Net and simultaneously predicts several outcomes. Second, a Multi-Task Regressor is used to modify the Point Net. The network gains from the capacity to transfer knowledge from one task to another, improving the model's overall performance. The model would forecast the ten parameters needed to create the shape in the case of rebuilding Super shapes. The test findings were better than expected;they are intriguing in terms of prediction accuracy and cost, and they update the result by 80%, which is a good accomplishment for the study. © 2025 Slovene Society Informatika. All rights reserved.

关键词： 3D reconstruction

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Decoding the physical mechanisms responsible for oxide ion conduction in NaNbO3-based ceramics

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Ceramics International 2025年第9期51卷 12019-12028页

作者： Qiao, Peng Wang, Jing Guo, Yifan Duan, Yizhuo Yang, Zupei Chao, Xiaolian Wu, Wenwen Liang, Pengfei School of Physics & Information Technology Shaanxi Normal University Shaanxi Xi'an710062 China Key Laboratory for Macromolecular Science of Shaanxi Province and Shaanxi Key Laboratory for Advanced Energy Devices School of Materials Science and Engineering Shaanxi Normal University Shaanxi Xi'an710062 China

NaNbO3 usually exhibits relatively high leakage current due to the volatilization of sodium oxides and the existence of oxygen vacancies in the crystal lattice. A large amount of research works have been devoted to reducing its conductivity and in turn optimized piezo/ferroelectric and energy storage performance, while neglecting the potential research value of high conductivity. Interestingly, our group recently evidenced that A-site bismuth doping could convert it to be pure oxygen ion conductor and the samples showed superior ionic conductivity at intermediate-temperature range. In this paper, the physical mechanisms responsible for oxygen ion conduction were elucidated in detail. It is clarified that oxygen vacancies from bismuth and sodium oxides volatilization act as oxide ion migration pathways. Meanwhile, high polarization of bismuth ion, microstructure and defect complexes also have significant effects on oxide ion conductivity in bismuth-doped sodium niobate. Combining dielectric loss and coupling theory analysis were given to obtain the migration energy of individual oxide ion between oxygen vacancies. Moreover, the ionic conductivity was slightly improved by Mg or Fe doping at B-site based on the enhancement of oxygen vacancy concentration. © 2025 Elsevier Ltd and Techna Group S.r.l.

关键词： Activation energy

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Continuous Monitoring of Blood Pressure by Measuring Local Pulse Wave Velocity Using Wearable Micromachined Ultrasonic Probes

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IEEE Transactions on Biomedical engineering 2025年第5期72卷 1615-1624页

作者： Zhou, Jie Qu, Mengjiao Liu, Weiting Wang, Yancheng Zhang, Guojun Zheng, Yinfei Xie, Jin Zhejiang University State Key Laboratory of Fluid Power and Mechatronic Systems Zhejiang China North University of China State Key Laboratory of Dynamic Measurement Technology China Zhejiang University College of Biomedical Engineering and Instrument Science Zhejiang China Zhejiang University State Key Laboratory of Fluid Power and Mechatronic Systems Hangzhou310027 China

Continuous monitoring of dynamic blood pressure (BP) is crucial for cardiovascular status analysis and holds significant value in the clinical prevention and diagnosis of cardiovascular diseases. However, existing methods are often limited by their bulky design and complex procedures, which are incompatible with the demands of smart, portable devices. Here, we present a wearable, non-invasive, and continuous BP monitoring system based on piezoelectric micromachined ultrasound transducer (PMUT) with flexible encapsulation. This device is compact, lightweight (29 dB), enabling it to capture distinct echoes from different arterial sites. The system adopts ultrasonic pulse-echo to record arterial diameter waveforms from dual sites and calculates the incremental local pulse wave velocity (PWV) beat-to-beat to determine arterial stiffness index and BP. When benchmarked against a cuff sphygmomanometer, our device demonstrates a mean absolute error and standard deviation for systolic BP and diastolic BP measurements of less than 4 mmHg and 3 mmHg, respectively, and a heart rate error of less than 3 bpm. Compared with a photoplethysmography finger clip as waveform references, the correlation coefficients for all measurements range from 0.951 to 0.998, and the root mean square error falls within an error band of ±5 mmHg, validating the reliability and stability of our device. Furthermore, the capability to track large-range dynamic changes in BP is also verified, highlighting its potential for daily BP management. © 1964-2012 IEEE.

关键词： Blood pressure

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Kolmogorov-Arnold Networks Based Signal Detection for OTFS systems in LEO Satellite Communications 14th

Kolmogorov-Arnold Networks Based Signal Detection for OTFS ...

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14th EAI International Conference on Wireless and Satellite systems, WiSATS 2024

作者： Zhang, Yakai He, Jiayi Liu, Zhiyong School of Information Science and Engineering of HIT Weihai264209 China Shandong Provincial Key Laboratory of Marine Electronic Information and Intelligent Unmanned Systems Weihai264209 China Key Laboratory of Cross-Domain Synergy and Comprehensive Support for Unmanned Marine Systems of Ministry of Industry and Information Technology Weihai264209 China

ISBN: (纸本)9783031861956

In numerous studies, orthogonal time-frequency space (OTFS) has been utilized in satellite-terrestrial communication systems with high mobility due to its strong adaptability to Doppler shifts and delays. Signal detection, a crucial technology influencing OTFS performance, is often hindered by high complexity or suboptimal detection capabilities. To address this, we propose a Kolmogorov-Arnold Networks (KANs)-based OTFS signal detection method for low Earth orbit satellite (LEO-Sat) communication systems. KANs employ learnable activation functions instead of traditional learnable linear weights between network nodes, enabling dynamic activation functions to enhance model accuracy. We integrate KANs, trained offline, into the LEO-Sat system to recover distorted signals at the receiver, facilitating effective signal detection. Compared to conventional detection algorithms, the proposed method demonstrates superior Bit Error Rate (BER) performance. Additionally, KANs are more parameter-efficient than DNNs, using significantly fewer parameters. © ICST Institute for Computer sciences, Social Informatics and Telecommunications engineering 2025.

关键词： Bit error rate

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Density waves of vortex fluids on a sphere

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Communications in Theoretical Physics 2025年第4期77卷 159-166页

作者： Yanqi Xiong Zhijun Zou Liang Luo Key Laboratory of Hunan Province on Information Photonics and Freespace Optical Communications School of Physics and Electronic ScienceHunan Institute of Science and TechnologyYueyang 414006China Graduate School of China Academy of Engineering Physics Beijing 100193China

We aim to find one highly nontrivial example of the solutions to the vortex fluid dynamical equation on the unit sphere(S^(2))and compare it with the numerical *** the rigid rotating steady solution for vortex fluids on S^(2)is already known to us,we consider the perturbations above *** decomposing the perturbation of the vortex number density and vortex charge density into spherical harmonics,we find that the perturbations are propagating *** be precise,the velocities for different single-mode vortex number density waves are all the same,while the velocities for single-mode vortex charge density waves depend on the degree of the spherical harmonics l,which is a signal of the existence of ***,we find that there is a beat phenomenon for the positive(or negative)vortex density *** simulation based on the canonical equations for the point vortex model agrees perfectly with our theoretical calculations.

关键词： quantum vortex 2D sphere superfluid density wave dispersion ome

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High-precision magnetic field measurement system based on a coherent population trapping magnetometer onboard the SATech-01 satellite

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science China(Technological sciences) 2025年第2期68卷 227-242页

作者： Hongbo XUE Wei SONG Haoran ZHAO Yiteng ZHANG Shanzhi YE Jindong WANG Ran TAO Peng SANG Keli CHEN Xingzi BI Bingjun CHENG Bin ZHOU Yongliang XUE Yingying TANG Liu LIU Jinsong LI Xiaocheng ZHU Baoquan LI Jinguo LIU Wen CHEN Xiaofeng ZHANG Yonghe ZHANG Lei LI State Key Laboratory of Space Weather National Space Science CenterChinese Academy of SciencesBeijing 100190China Key Laboratory of Solar Activity and Space Weather National Space Science CenterChinese Academy of SciencesBeijing 100190China Key Laboratory of Electronics and Information Technology for Space Systems National Space Science CenterChinese Academy of SciencesBeijing 100190China State Key Laboratory of Robotics Shenyang Institute of AutomationChinese Academy of SciencesShenyang 110016China Innovation Academy for Microsatellites Chinese Academy of SciencesShanghai 201304China

On July 27,2022,a high-precision system for measuring the magnetic field based on a coherent population trapping magnetometer(referred to as the CPT system)was launched onboard the Space Advanced technology demonstration satellite(SATech-01)by a ZK-1A *** payload comprises a scalar coherent population trapping magnetometer(CPTM),triaxial anisotropic magnetoresistance magnetometer(AMRM),and nano star tracker mounted on a non-magnetic telescopic tubular *** configuration enables synchronized measurement of scalar and vector geomagnetic fields,as well as the attitude,making the payload with its compact sensors suitable for applications on miniature satellite *** November 7,2022,the novel telescopic tubular mast was deployed in orbit,extending to a length of 5.28 *** CPTM,an absolute scalar magnetometer with an omnidirectional sensor,is the first China-developed quantum/atomic magnetometer successfully operating in *** orbit,the CPTM has sensitivity of~10 pT/Hz^(1/2) and can automatically operate under complex magnetic field *** difference between the scalar fields obtained using the CPTM and CHAOS model has a mean deviation of -3.73 nT and a standard deviation of 26.11 nT(1σ),without on-orbit calibration or *** miniaturized AMRM has a sensitivity of~0.3 nT/Hz^(1/2) and maintains stable and reliable operation in *** low-power and miniaturized nano star tracker has a measurement uncertainty of 14.23″(1σ)in *** mission has realized the on-orbit technical verification of the integrated and synchronized detection of the vector magnetic field and attitude and fully validated the system’s performance,automation level,and reliability.

关键词： magnetic field measurement system coherent population trapping magnetometer anisotropic magnetoresistance magnetometer nano star tracker non-magnetic telescopic tubular mast satellite

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Goal-Oriented Communication, Estimation, and Control Over Bidirectional Wireless Links

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IEEE Transactions on Communications 2025年第5期73卷 3031-3045页

作者： Cao, Jie Kurniawan, Ernest Boonkajay, Amnart Pappas, Nikolaos Sun, Sumei Popovski, Petar School of Electronic and Information Engineering Guangdong Provincial Key Laboratory of Aerospace Communication and Networking Technology Shenzhen518055 China Institute of Infocomm Research Agency for Science Technology and Research Fusionopolis 138632 Singapore Linköping University Department of Computer and Information Science Linköping58183 Sweden Aalborg University Department of Electronic Systems Aalborg9220 Denmark

We consider a wireless networked control system (WNCS) with imperfect bidirectional links for real-time applications such as smart grids. To maintain the stability of WNCS, captured by the probability that plant state violates preset values, at minimal cost, heterogeneous physical processes are monitored by multiple sensors. This status information, such as dynamic plant state and Markov Process-based context information, is then received/estimated by the controller for remote control. However, scheduling multiple sensors and designing the controller with limited resources is challenging due to their coupling, delay, and transmission loss. We formulate a Constrained Markov Decision Problem (CMDP) to minimize violation probability with cost constraints. We reveal the relationship between the goal and different updating actions by analyzing the significance of information that incorporates goal-related usefulness and contextual importance. Subsequently, a goal-oriented deterministic scheduling policy is proposed. Two sensing-assisted control strategies and a control-aware estimation policy are proposed to improve the violation probability-cost tradeoff, integrated with the scheduling policy to form a goal-oriented co-design framework. Additionally, we explore retransmission in downlink transmission and qualitatively analyze its preference scenario. Simulation results demonstrate that the proposed goal-oriented co-design policy outperforms previous work in simultaneously reducing violation probability and cost. © 1972-2012 IEEE.

关键词： Markov processes

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Solving Overlapping Coalition Structure Generation in Task-Based Settings

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Journal of Artificial Intelligence Research 2025年 82卷 2125-2166页

作者： Zhang, Guofu Su, Zhaopin Song, Xiaoxiao Gao, Zixuan Li, Miqing Yao, Xin School of Computer Science and Information Engineering Hefei University of Technology Anhui Hefei China Intelligent Interconnected Systems Laboratory of Anhui Province Anhui Hefei China Anhui Province Key Laboratory of Industry Safety and Emergency Technology Anhui Hefei China CERCIA School of Computer Science University of Birmingham Birmingham United Kingdom School of Data Science Lingnan University Hong Kong

The overlapping coalition structure generation problem (OCSGP) is a challenging computational problem in multi-agent systems. It focuses on selecting possibly overlapping coalitions from a set of agents to maximize the social welfare of all coalitions while containing all agents. However, in practical applications, coalitions may be formed to selectively respond to tasks from a pool of potential tasks assigned to agents. Consequently, this study considers OCSGP in a task-based setting, where each agent has finite resources and can only respond to tasks of interest, and each coalition can only take on mutually disjoint subsets of tasks. Specifically, we first present a model of the task-based OCSGP and investigate its computational complexity. Our theoretical results demonstrate that this specific OCSGP remains intractable even under restrictive assumptions. Subsequently, we develop a generic evolutionary algorithm framework (EAF) to find an approximately optimal overlapping coalition structure (OCS) in time quartic polynomial in the size of the instance. Particularly, we devise a specific solution-repair based heuristic of cubic time complexity to generate a feasible OCS. Finally, we compare the proposed EAF with a task-oriented heuristic and a hybrid algorithm for OCSGP, and examine its applicability in the pursuit-evasion problem. The experimental results reveal that the proposed EAF exhibits superior performance in finding feasible OCSs and demonstrates flexible adaptability to problem size and resource status. ©2025 The Authors.

关键词： Heuristic algorithms

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