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Diagnosing ratio of electron density to collision frequency of plasma surrounding scaled model in a shock tube using low-frequency alternating magnetic field phase shift

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Chinese Physics B 2024年第5期33卷 519-530页

作者：吴明兴谢楷刘艳徐晗张宝田得阳 School of aerospace Science and Technology Xidian UniversityXi'an 710071China Hypervelocity Aerodynamics Institute China Aerodynamics Research and Development CenterMianyang 621000China

A non-contact low-frequency(LF)method of diagnosing the plasma surrounding a scaled model in a shock tube is *** method utilizes the phase shift occurring after the transmission of an LF alternating magnetic field through the plasma to directly measure the ratio of the plasma loop average electron density to collision *** equivalent circuit model is used to analyze the relationship of the phase shift of the magnetic field component of LF electromagnetic waves with the plasma electron density and collision *** applicable range of the LF method on a given plasma scale is *** upper diagnostic limit for the ratio of the electron density(unit:m^(-3))to collision frequency(unit:Hz)exceeds 1×10^(11),enabling an electron density to exceed 1×10^(20)m^(-3)and a collision frequency to be less than 1 *** this work,the feasibility of using the LF phase shift to implement the plasma diagnosis is also *** experiments on shock tube equipment are conducted by using both the electrostatic probe method and LF *** comparing the diagnostic results of the two methods,the inversion results are relatively consistent with each other,thereby preliminarily verifying the feasibility of the LF *** ratio of the electron density to the collision frequency has a relatively uniform distribution during the plasma *** LF diagnostic path is a loop around the model,which is suitable for diagnosing the plasma that surrounds the ***,the causes of diagnostic discrepancy between the two methods are *** proposed method provides a new avenue for diagnosing high-density enveloping plasma.

关键词： low-frequency alternating magnetic field phase shift shock-tube plasma diagnosis electron density collision frequency

Comprehensively Deepening Reform Fundamental Driving Force for Chinese Modernization

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China News Release 2024年第8期 28-32页

作者： Yang Yiyong Academy of Macroeconomic research under the national development and Reform commission

Chinese President Xi Jinping stresses that"comprehensively deepening reform should be taken as a fundamental driving force for Chinese modernization."He asserts that reform can remove institutional barriers in all respects and provide an inexhaustible impetus for Chinese ***,measures such as deepening the reform of state institutions,improving and perfecting the socialist system with Chinese characteristics,and advancing the modernization of China's governance system and capacity can continuously strengthen the driving force and vitality of socialist modernization,and better transform China's institutional advantages into effective national governance.

关键词： deepening driving remove

Fast and Adaptive Multi-Agent Planning under Collaborative Temporal Logic Tasks via Poset Products

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research 2024年第2期2024卷 81-94页

作者： Zesen Liu Meng Guo Weimin Bao Zhongkui Li Deparment of Mechanics and Engineering Science College of EngineeringPeking UniversityBejing 0081 China Science and Technology commission of China aerospace Science and Technology Corporation Beijing 100048China

Efficient coordination and planning is essential for large-scale multi-agent systems that collaborate in a shared dynamic environment. Heuristic search methods or learning-based approaches often lack the guarantee on correctness and performance. Moreover, when the collaborative tasks contain both spatial and temporal requirements, e.g., as linear temporal logic (LTL) formulas, formal methods provide a verifiable framework for task planning. However, since the planning complexity grows exponentially with the number of agents and the length of the task formula, existing studies are mostly limited to small artificial cases. To address this issue, a new planning paradigm is proposed in this work for system-wide temporal task formulas that are released online and continually. It avoids two common bottlenecks in the traditional methods, i.e., (a) the direct translation of the complete task formula to the associated B點hi automaton and (b) the synchronized product between the B點hi automaton and the transition models of all agents. Instead, an adaptive planning algorithm is proposed, which computes the product of relaxed partially ordered sets (R-posets) on-the-fly and assigns these subtasks to the agents subject to the ordering constraints. It is shown that the first valid plan can be derived with a polynomial time and memory complexity with respect to the system size and the formula length. Our method can take into account task formulas with a length of more than 400 and a fleet with more than 400 agents, while most existing methods fail at the formula length of 25 within a reasonable duration. The proposed method is validated on large fleets of service robots in both simulation and hardware experiments.

关键词： hardware service system

Ballistic design and testing of a composite armour reinforced by CNTs suitable for armoured vehicles

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Defence Technology（防务技术） 2024年第2期32卷 173-195页

作者： Evangelos Ch.Tsirogiannis Evangelos Daskalakis Mohamed H.Hassan Abdalla M.Omar Paulo Bartolo EODH SA Research and Development DepartmentLakkoma Chalkidikis63080Greece School of Mechanical Aerospace and Civil EngineeringUniversity of ManchesterManchesterM139PLUK Singapore Centre for 3D Printing School of Mechanical and Aerospace EngineeringNanyang Technological University639798Singapore

This paper is investigating the use of composite armour reinforced by nanomaterials, for the protection of light armoured(LAV) and medium armoured military vehicles(MAV), and the interaction between the composite materials and high-performance ballistic projectiles. Four armour materials, consisted of front hybrid fibre reinforced polymer cover layer, ceramic strike-face, fibre reinforced polymer intermediate layer and the metal matrix composite reinforced backplate, were manufactured and assembled by adhesive technology. The proposed laminated protection system is suitable for armoured ground vehicles;however, it could be used as armour on ground, air and naval platforms. The design of the protection system, including material selection and thickness, was elaborated depending on the performance requirements of Level 4 + STANAG 4569 military standard(projectile 14.5 mm × 114 mm API B32) and especially on a design philosophy which is analysed with the specifications. The backplate of this new composite is a hybrid material of Metal Matrix Composite(MMC) reinforced with carbon nanotubes(CNTs), manufactured with the use of powder metallurgy technique. The composite backplate material was morphologically, mechanically and chemically analysed. Results show that all plates are presenting high mechanical properties and ballistic characteristics, compared to commonly used armour plates. Real military ballistic tests according to AEP-STANAG 4569 were carried out for the total composite armour systems. After the ballistic tests, AA2024-CNT3 showed the best protection results, compared with the other plates(AA2024-CNT1 and AA2024-CNT2), with the projectile being unable to fully penetrate the composite plate.

关键词： Passive armour protection Protective armour Ballistic performance Hybrid composites Vehicle protection

Electrical stimulation for brighter persistent luminescence

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Light(Science & Applications) 2024年第8期13卷 1590-1601页

作者： Xilin Ma Yuhua Wang Takatoshi Seto Key Laboratory for Special Function Materials and Structural Design of the Ministry of Education National&Local Joint Engineering Laboratory for Optical Conversion Materials and Technology of National Development and Reform CommissionDepartment of Materials ScienceSchool of Materials and EnergyLanzhou UniversityNo.222South Tianshui RoadLanzhouGansu 730000China

An immature understanding of the mechanisms of persistent luminescence(PersL)has hindered the development of new persistent luminescent materials(PersLMs)with increased *** this regard,in-situ direct current(DC)electric field measurements were conducted on a layered structure composed of the SrAl_(2)O_(4):Eu^(2+),Dy^(3+)phosphor,and an *** this study,the photoluminescence(PL)and afterglow properties were investigated with respect to voltage by analyzing the current signal and thermoluminescence(TL)*** intensity of PersL increased due to a novel phenomenon known as“external electric field stimulated enhancement of initial brightness of afterglow”.This dynamic process was illustrated via the use of a rate equation approach,where the electrons trapped by the ultra-shallow trap at 0.022 eV could be transferred through the conduction band during long *** afterglow intensity could reach 0.538 cdm^(-2)at a 6 V electric *** design of an electric field stimulation technique enables the enhancement of the intensity of PersLMs and provides a new perspective for exploring the fundamental mechanics of certain established PersLMs.

关键词： spectroscopy luminescence conduction

Iterative Model Predictive Control for Automatic Carrier Landing of Carrier-Based Aircrafts Under Complex Surroundings and Constraints

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Journal of Shanghai Jiaotong university(Science) 2024年第4期29卷 712-724页

作者： ZHANG Xiaotian HE Defeng LIAO Fei College of Information Engineering Zhejiang University of TechnologyHangzhou310023China aerospace Technology Institute China Aerodynamics Research and Development CenterMianyang621000SichuanChina

This paper considers the automatic carrier landing problem of carrier-based aircrafts subjected to constraints,deck motion,measurement noises,and unknown *** iterative model predictive control(MPC)strategy with constraints is proposed for automatic landing control of the ***,the long short-term memory(LSTM)neural network is used to calculate the adaptive reference trajectories of the *** the Sage-Husa adaptive Kalman filter and the disturbance observer are introduced to design the composite ***,an iterative optimization algorithm is presented to fast solve the receding horizon optimal control problem of MPC based on the Lagrange’s ***,some sufficient conditions are derived to guarantee the stability of the landing system in a closed loop with the ***,the simulation results of F/A-18A aircraft show that compared with the conventional MPC,the presented MPC strategy improves the computational efficiency by nearly 56%and satisfies the control performance requirements of carrier landing.

关键词： automatic carrier landing model predictive control(MPC) long short-term memory(LSTM)neural network stability computational efficiency

A dataset of lake level changes in China between 2002 and 2023 using multi-altimeter data

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Big Earth Data 2024年第1期8卷 166-188页

作者： Shanmu Ma Jingjuan Liao Ruofan Jing Jiaming Chen Key Laboratory of Digital Earth Science Aerospace Information Research InstituteChinese Academy of SciencesBeijingChina International research Center of Big Data for Sustainable development Goals BeijingChina University of Chinese Academy of Sciences BeijingChina

Lake water levels are an important indicator of water balance and water cycles,and are essential for climate and environmental change studies and water resource ***,lake level measurements are scarce or inconsistent throughout the country,and traditional gauge measurements of many lakes are not feasible,so satellite altimetry is a vital alternative to gauge lake ***,the accuracy and sam-pling frequency of lake level time series are usually low because of time and space coverage limitations;therefore,it is necessary to utilize multialtimeter data to monitor lake levels and obtain lake level changes over long time *** this study,we extracted the water level changes in 988 lakes(>10 km^(2))in China between 2002 and 2023 based on ICESat/-2,Cryosat-2,Jason-1/2/3,and Sentinel-3A/3B altimetry data using waveform retracking,lake level extraction,lake level time series construction,the fusion of multi-altimeter lake level time series,and outlier removal.A total of 55%of the lakes in this dataset have been monitored for more than 10 years,and 34%have more than 12 times the annual average water level *** the same time,in situ data from 21 lakes were used for validation,and the average root mean square error(RMSE)for each of the datasets of ICESat/-2,Cryosat-2,Jason-1/2/3,and Sentinel-3A/3B versus the in situ lake levels are 0.223 m,0.163 m,0.207 m,0.596 m,0.295 m,0.275 m,0.243 m,and 0.317 m,respectively,and the mean RMSE of the fused lake levels reaches 0.332 *** the monitoring period,the water levels in Chinese lakes generally *** overall annual average rate of change at the 20 and 10-year scales was 0.123 m/a and 0.151 m/a,respectively,among which the overall water levels in large lakes increased *** lakes with a faster rate of decline in the water level were primarily *** water storage in each lake region in China shows an upward trend,with the most significant increase in the Tibetan Plateau reg

关键词： Lake level multi-altimeter China spatiotemporal variation

Noteworthy phenomena in pediatric inherited cardiomyopathy

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World Journal of Pediatrics 2024年第6期20卷 635-637页

作者： Jin-Hang Jiang Jie Tian Bo Pan Department of Pediatric Cardiology National Clinical Key Cardiovascular SpecialtyNational Clinical Research Center for Child Health and DisordersMinistry of Education Key Laboratory of Child Development and DisordersChildren's Hospital of Chongqing Medical University136 Zhongshan Er RoadYuzhong DistirctChongqing 400014China Key Laboratory of Children's Important Organ development and Diseases Chongqing Municipal Health CommissionChongqingChina

Pediatric cardiomyopathy has an early onset and poor ***,it was referred to as idiopathic cardiomyopathy due to unknown ***,recent advances in molecular genetics and molecular biology have demonstrated that most pediatric cardiomyopathy cases are related to genetic factors,mainly involving single gene and single nucleotide mutations[1,2].Although the pathogenicity of some gene mutations in patients has not been fully elucidated,genetic factors are still considered the main cause of pediatric cardiomyopathy.

关键词： cardiomyopathy pediatric etiology

Aircraft parameter estimation using a stacked long short-term memory network and Levenberg-Marquardt method

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Chinese Journal of Aeronautics 2024年第2期37卷 123-136页

作者： Zhe HUI Yinan KONG Weigang YAO Gang CHEN School of aerospace Science and Technology Xidian UniversityXi’an 710071China Computation Aerodynamics Institution China Aerodynamics Research and Development CenterMianyang 621000China Faculty of Computing Engineering and MediaDe Montfort UniversityLeicester LE19BHUnited Kingdom School of aerospace Engineering Xi’an Jiaotong UniversityXi’an 710049China

To effectively estimate the unknown aerodynamic parameters from the aircraft’s flight data,this paper proposes a novel aerodynamic parameter estimation method incorporating a stacked Long Short-Term Memory(LSTM)network model and the Levenberg-Marquardt(LM)*** stacked LSTM network model was designed to realize the aircraft dynamics modeling by utilizing a frame of nonlinear functional mapping based entirely on the measured input-output data of the aircraft system without requiring explicit postulation of the *** LM method combines the already-trained LSTM network model to optimize the unknown aerodynamic *** proposed method is applied by using the real flight data,generated by ATTAS aircraft and a bio-inspired morphing Unmanned Aerial Vehicle(UAV).The investigation reveals that for the two different flight data,the designed stacked LSTM network structure can maintain the efficacy of the network prediction capability only by appropriately adjusting the dropout rates of its hidden layers without changing other network parameters(i.e.,the initial weights,initial biases,number of hidden cells,time-steps,learning rate,and number of training iterations).Besides,the proposed method’s effectiveness and potential are demonstrated by comparing the estimated results of the ATTAS aircraft or the bio-inspired morphing UAV with the corresponding reference values or wind-tunnel results.

关键词： Parameter estimation LSTM network model LM method Aerodynamic parameters Flight data Aircraft dynamics modeling Network prediction capability Network parameters