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Formation behaviors of rod-like reactive shaped charge penetrator and their effects on damage capability

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Defence technology（防务技术） 2024年第2期32卷 242-253页

作者： Tao Sun Haifu Wang Shipeng Wang Chao Ge Die Hu Pengwan Chen Yuanfeng Zheng Beijing institute of technology State Key Laboratory of Explosion Science and TechnologyBeijing100081China Xi'an institute of Electromechanical Information technology Xi'an710065China

Formation behaviors of rod-like reactive shaped charge penetrator(RRSCP)and their effects on damage capability are investigated by experiments and numerical *** pulsed X-ray technology and a spaced aluminum/steel plate with the thicknesses of 5 mm/100 mm are *** types of sphericalsegment aluminum-polytetrafluoroethylene-copper(Al-PTFE-Cu)reactive liners with Cu contents of 0%,46.6%,and 66%are fabricated and *** experimental results show that the reactive liners can form excellent rod-shaped penetrators with tail skirts under the shaped charge effect,but the tail skirts disappear over ***,rupturing damage to the aluminum plate and penetration to the steel plate are caused by the RRSCP *** simulation analysis,the RRSCP is formed by a mechanically and chemically coupled response with the reactive liner activated by shock in its outer walls and bottom and then backward overturning,forming a leading reactive penetrator and a following chemical energy *** unique formation structure determines the damage modes of the aluminum plate and the steel *** analysis indicates that the formation behaviors and damage capability of Al-PTFE-Cu RRSCP strongly depend on Cu *** increasing Cu content,the velocity,activation extent,and reaction extent of Al-PTFE-Cu RRSCP decrease,which contribute to elongation and alleviate the negative effects of chemical reactions on elongation,significantly increasing the length-diameter ratio and thus enhancing the capability of steel plate ***,the lower activation extent and energetic density will weaken the RRSCP's capability of causing rupturing damage to the aluminum plate.

关键词： Reactive materials Al-PTFE composites Reactive liner X-ray Penetration

Continuous advantage learning for minimum-time trajectory planning of autonomous vehicles

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Science China(Information Sciences) 2024年第7期67卷 285-294页

作者： Zhuo LI Weiran WU Jialin WANG Gang WANG Jian SUN School of Automation Beijing Institute of Technology Beijing institute of technology Chongqing Innovation Center China Academy of Launch Vehicle technology Intelligent Game and Decision Laboratory

This paper investigates the minimum-time trajectory planning problem of an autonomous vehicle. To deal with unknown and uncertain dynamics of the vehicle, the trajectory planning problem is modeled as a Markov decision process with a continuous action space. To solve it, we propose a continuous advantage learning(CAL) algorithm based on the advantage-value equation, and adopt a stochastic policy in the form of multivariate Gaussian distribution to encourage exploration. A shared actor-critic architecture is designed to simultaneously approximate the stochastic policy and the value function, which greatly reduces the computation burden compared to general actor-critic methods. Moreover, the shared actor-critic is updated with a loss function built as mean square consistency error of the advantage-value equation, and the update step is performed several times at each time step to improve data efficiency. Simulations validate the effectiveness of the proposed CAL algorithm and its better performance than the soft actor-critic algorithm.

关键词： trajectory planning continuous advantage learning stochastic policy shared actor-critic

Experimental investigation on weak shock wave mitigation characteristics of flexible polyurethane foam and polyurea

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Defence technology（防务技术） 2024年第1期31卷 179-191页

作者： Shiyu Jia Cheng Wang Wenlong Xu Dong Ma Fangfang Qi State Key Laboratory of Explosion Science and technology Beijing Institute of TechnologyBeijing100081China institute for Advanced technology Shandong UniversityJinan250061China

In recent years,explosion shock wave has been considered as a signature injury of the current military *** strong shock wave is lethal to the human body,weak shock wave can cause many more lasting *** investigate the protection ability and characteristics of flexible materials and structures under weak shock wave loading,the blast wave produced by TNT explosive is loaded on the polyurethane foam with the density of 200.0 kg/m3(F-200)and 400.0 kg/m3(F-400),polyurea with the density of 1100.0 kg/m^(3)(P-1100)and structures composed of the two materials,which are intended for individual *** results indicate that the shock wave is attenuated to weak pressure disturbance after interacting with the flexible materials which are not *** shock wave protective capability of single-layer materials is dependent on their thickness,density and microscopic *** overpressure,maximum pressure rise rate and impulse of transmitted wave decrease exponentially with increase in sample *** the same thickness,F-400 provides better protective capability than F-200 while P-1100 shows the best protective capability among the three *** this study,as the materials are not destroyed,F-200 with a thickness more than10.0 mm,F-400 with a thickness more than 4.0 mm,and P-1100 with a thickness more than 1.0 mm can attenuate the overpressure amplitude more than 90.0%.Further,multi-layer flexible composites are *** layer layouts of designed structures and layer thickness of the single-layer materials can affect the protective *** the research range,the structure in which polyurea is placed on the impact side shows the optimal shock wave protective performance,and the thicknesses of polyurea and polyurethane foam are 1.0 mm and 4.0 mm *** overpressure attenuation rate reached maximum value of 93.3%and impulse attenuation capacity of this structure are better than those of s

关键词： Free-field explosion Weak shock wave mitigation Polyurea Polyurethane foam Multi-layered composites

Effect of organic component(tartrate) addition on cerium nitrate's ability to inhibit corrosion of mild steel in NaCl solution

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Journal of Rare Earths 2024年第10期42卷 1995-2002页

作者： Minakshi Koundal Chhaya Sharma A.K.Singh Department of Applied Science and Engineering Indian Institute of Technology RoorkeeSaharanpur Campus Department of Pulp and Paper technology Indian institute of technology Roorkee Saharanpur Campus

Cerium tartrate（CeTar）,produced in this study by precipitating cerium nitrate with potassium sodium tartrate（KNaTar）,was examined as a corrosion *** loss tests show inhibition efficiency of 71.7% with Ce（NO3）3and 88.7% with CeTar inhibitor for one-month exposure to mild steel in 7 g/L NaCl *** inhibition efficiency drops to 28.6% with the fo rmer and remains around 8 7% with the latter inhibitor after six months of *** results from electrochemical testing indicate that the inhibition efficiency decreases by adding cerium ***,the cerium tartrate inhibitor demonstrates a nearly constant inhibition efficiency for up to 30 d,i.e.,≈90%.Electrochemical impedance spectroscopy（EIS） performed in these cases shows the following results:（ⅰ） with cerium nitrate,a film of iron and cerium oxide,which on prolonged exposure diminishes,and（ⅱ） with cerium tartrate,the formation of a bimetallic film（Fe-tartrate-Ce） and a mixture of cerium hydroxide and iro n oxide that protects steel for a longer *** inferences are based on the analyses of scanning electron microscopy/energydispersive X-ray analysis（SEM/EDAX）,X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FTIR）,X-ray photoelectron（XPS）,and Raman spectroscopy results.

关键词： Cerium nitrate Cerium tartrate Corrosion inhibition Inhibitor film characterization Mild steel Rare earths

An adaptive 3D reconstruction method for asymmetric dual-angle multispectral stereo imaging system on UAV platform

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Science China(Information Sciences) 2024年第8期67卷 285-299页

作者： Chen WANG Xian LI Yanfeng GU Zixu WANG School of Electronics and Information Engineering Harbin Institute of Technology Beijing institute of Control and Electronic technology

A multispectral imaging system often cannot capture 3D spatial information owing to hardware limitations, which diminishes the effectiveness across various domains. To address this problem, we have developed a multispectral stereo imaging system along with an adaptive 3D reconstruction algorithm. Unlike existing unmanned aerial vehicle stereo imaging systems, our multispectral stereo imaging system uses two multispectral cameras with asymmetric spectral bands positioned at different angles. This design enables the acquisition of a higher number of bands and lateral spatial information while maintaining a lightweight structure. This system introduces challenges such as large geometric distortions and intensity differences between multiple bands. To accurately recover 3D spatial information, we propose an adaptive 3D reconstruction method. This method employs a position and orientation system-assisted projection transformation and a normalized threshold adjustment strategy. Finally, mutual information is used to reconstruct the multispectral images densely, effectively addressing nonlinear differences and generating a comprehensive multispectral point cloud. Our stereo system was used for two real data collections in different regions, and the efficacy of the proposed 3D reconstruction method was validated by comparing it with existing methods and commercial software.

关键词： multispectral images 3D reconstruction stereo imaging system unmanned aerial vehicle feature extraction

Filtering and regret network for spacecraft component segmentation based on gray images and depth maps

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Chinese Journal of Aeronautics 2024年第7期37卷 439-449页

作者： Xiang LIU Hongyuan WANG Zijian WANG Xinlong CHEN Weichun CHEN Zhengyou XIE institute of Aeronautics Harbin Institute of TechnologyHarbin 150001China Qian Xuesen Laboratory of Space technology China Academy of Space TechnologyBeijing 100080China

Identifying and segmenting spacecraft components is vital in many on-orbit space missions,such as on-orbit maintenance and component *** depth maps with visual images has been proven effective in improving segmentation ***,existing methods ignore the noise and fallacy in collected depth maps,which interfere with the network to extract representative features,decreasing the final segmentation *** this end,this paper proposes a Filtering and Regret Network(FRNet)for spacecraft component *** FRNet incorporates filtering and regret mechanisms to suppress the abnormal depth response in shallow layers and selectively reuses the filtered cues in deep layers,avoiding the detrimental effects of low-quality depth information while preserving the semantic context inherent in depth ***,a two-stage feature fusion module is proposed,which involves information interaction and *** module effectively explores the feature correlation and unifies the multimodal features into a comprehensive ***,a large-scale spacecraft component recognition dataset is constructed for training and evaluating spacecraft component segmentation *** results demonstrate that the FRNet achieves a state-of-the-art performance with a mean Intersection Over Union(mIOU)of 84.13%and an average inference time of 133.2 ms when tested on an NVIDIA RTX 2080 SUPER GPU.

关键词： Spacecraft component recognition Multi-modal feature fusion Satellite dataset Intelligent systems Deep learning

Electrodeposition of rare refractory metals in low-temperature ionic liquids

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Rare Metals 2024年第10期43卷 4921-4933页

作者： Lin-Lin Wang Han-Dong Jiao Rui Yuan Le-Yang Li Man-Peng Lin Rui-Yang Sun Jiu-San Xiao Shu-Qiang Jiao institute of Advanced Structure technology Beijing Institute of Technology State Key Laboratory of Advanced Metallurgy University of Science and Technology Beijing

Rare refractory metals(RRMs) play a significant role in fundamental industries, including electronics,chemical industry, machinery, etc., and future advanced fields, such as aerospace and superconductivity. However,the traditional production processes of RRMs based on high-temperature thermal reduction cannot meet the requirements of low-energy consumption. This dilemma could be addressed efficiently by using a low-temperature electrodeposition strategy in ionic liquids(ILs). This review summarizes a panoramic view of the latest developments on the electrodeposition of RRMs in ILs after a brief review on the current industrial production methods of RRMs. Based on this, the electrochemical mechanism occurring at the cathode during the electrodeposition process of RRMs in different electrolytes and under different conditions is thoroughly discussed, because it is crucial for the successful production of pure RRMs. In addition, this review not only analyses the main challenges that hinder the industrial application of the electrodeposition of RRMs in ILs, but also proposes corresponding solutions. We hope this review can provide a valuable guidance for the fundamental research and industrial development of lowtemperature electrodeposition of RRMs.

关键词： Chemical industry

A new fluorocarbon adhesive:Inhibiting agglomeration during combustion of propellant via efficient F-Al_(2)O_(3) preignition reaction

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Carbon Energy 2024年第6期6卷 292-305页

作者： Qifa Yao Min Xia Chao Wang Fanzhi Yang Wei Yang Yunjun Luo School of Materials Science and Engineering Beijing Institute of TechnologyBeijingChina Key Laboratory of High Energy Density Materials Ministry of EducationBeijing Institute of TechnologyBeijingChina School of Aerospace Engineering Beijing Institute of TechnologyBeijingChina Advanced Research institute of Multidisciplinary Science Beijing Institute of TechnologyBeijingChina

Inhibiting the agglomeration of molten aluminum particles packed in the binder network is a promising scheme to achieve efficient combustion of solid *** this investigation,the hydroxyl-terminated structured fluorinated alcohol compound(PFD)was introduced to modify the traditional polyethylene glycol/polytetrahydrofuran block copolymerization(HTPE)binder;that is,a unique fluorinated polyether(FTPE)binder was synthesized by embedding fluorinated organic segments into the HTPE binder via crosslinking *** FTPE was applied in aluminum-based propellants for the first *** to the complete release of fluorinated organic active segments in the range of 300℃to 400℃,the burning rate of FTPEbased propellant increased from 4.07(0%PFD)to 6.36 mm/s(5%PFD),increased by 56.27%under 1 *** reaction heat of FTPE propellants increased from 5.95(0%PFD)to 7.18 MJ/kg(5%PFD)under 3.0 MPa,indicating that HTPE binder modified with PFD would be conducive to inhibiting the D90 of condensed combustion products(CCPs)dropped by 81.84%from 75.46(0%PFD)to 13.71μm(5%PFD)under 3.0 MPa,in consistent with the significant reduction of aluminum agglomerates observed on the quenched burning surface of the *** results demonstrated that a novel FTPE binder with PFD can release fluorinated organic active segments,which motivate preignition reaction with the alumina shell in the early stage of aluminum combustion,and then enhance the melting diffusion effect of aluminum to inhibit the agglomeration.

关键词： agglomeration characteristics aluminum particles combustion fluorine alcohol compounds HTPE propellants

Repeat-pass space-surface bistatic SAR tomography:accurate imaging and first experiment

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Science China(Information Sciences) 2024年第9期67卷 245-262页

作者： Zhiyang CHEN Yuanhao LI Cheng HU Shenglei WANG Xinpeng CHEN Mihai DATCU Andrea Virgilio MONTI-GUARNIERI Radar technology Research institute School of Information and Electronics Beijing Institute of Technology Beijing Key Laboratory of Embedded Real-Time Information Processing technology Beijing Institute of Technology Advanced technology Research institute Beijing Institute of Technology CEOSpace Tech University Politehnica of Bucharest Dipartimento di Elettronica Informazione e Bioingegneria Politecnico di Milano

Space-surface bistatic synthetic aperture radar(SS-BiSAR) offers an additional observation angle for monostatic spaceborne SAR, making it a promising technology for high-accuracy deformation retrieval technology in local regions. Repeat-pass SS-BiSAR tomography can accurately estimate the surfaces of buildings and steep areas, effectively removing terrain phases during deformation retrieving. However, inaccuracies in the orbital ephemeris can lead to image geometry distortion, reducing image pair coherence,introducing interferometric phase errors, and consequently deteriorating tomographic precision. This paper precisely models the image geometry distortion and interferometric phase error caused by repeat-pass ephemeris error. We propose an ephemeris correction method based on the chirp-Z transform to address these issues. Furthermore, we introduce an accurate tomography model to improve 3D reconstruction *** first SS-BiSAR tomography experiment, conducted using the Chinese Lutan-1 satellite, demonstrates that the correlation coefficient is improved by 0.16 after ephemeris error correction. Moreover, the density and precision of the tomographic point cloud are improved by 13.7% and 12.1%, respectively.

关键词： space-surface SAR tomography orbit error image distortion Lutan-1