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Deep MARL-Based Resilient Motion Planning for Decentralized Space Manipulator

Space(science & technology) 2024年第1期4卷 160-169页

作者： Jiawei Zhang Chengchao Bai C.Patrick Yue Jifeng Guo The School of Astronautics Harbin Institute of TechnologyHarbinChina Department of Electronic and Computer Engineering Hong Kong University of Science and TechnologyHong KongChina

Space manipulators play an important role in the on-orbit services and planetary surface *** the extreme environment of space,space manipulators are susceptible to a variety of unknown *** to have a resilient guarantee in failure or disturbance is the core capability of its future *** with traditional motion planning,learning-based motion planning has gradually become a hot spot in current ***,no matter what kind of research ideas,the single robotic manipulator is studied as an independent agent,making it unable to provide sufficient flexibility under conditions such as external force disturbance,observation noise,and mechanical ***,this paper puts forward the idea of“discretization of the traditional single manipulator”.Different discretization forms are given through the analysis of the multi-degree-of-freedom single-manipulator joint relationship,and a single-manipulator representation composed of multiple new subagents is ***,to verify the ability of the new multiagent representation to deal with interference,we adopted a centralized multiagent reinforcement learning *** influence of the number of agents and communication distances on learning-based planning results is analyzed in *** addition,by imposing joint locking failures on the manipulator and introducing observation and action interference,it is verified that the“multiagent robotic manipulator”obtained after discretization has stronger antidisturbance resilient capability than the traditional single manipulator.

关键词： planetary surface motion planning multiagent reinforcement learning space manipulators resilient motion planning robotic manipula decentralized space manipulator deep marl

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Microstructure evolution of extruded Mg-RE-Ag alloy during short-time heat treatment

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Journal of Rare Earths 2024年第12期42卷 2350-2361,I0006页

作者： Zehua Li Jinghuai Zhang Shujuan Liu Jiaming Hao Liyuan Liu Yuying He Haodong Zhang Xingkai Jiao Xiaobo Zhang Ruizhi Wu Key Laboratory of Superlight Material and Surface Technology Ministry of EducationCollege of Material Science and Chemical EngineeringHarbin Engineering UniversityHarbin150001China School of Materials Science and Engineering Harbin Institute of TechnologyHarbin150001China Jiangsu Key Laboratory of Advanced Structural Materials and Application Technology Nanjing Institute of TechnologyNanjing211167China

Microstructure regulation via short-time heat treatment is conducive to the optimization in the microstructure and properties of precipitable magnesium(Mg)alloys,but there is currently a lack of relevant *** this work,the microstructure evolution of a Mg-RE-Ag alloy during different short-time heat treatments was characterized and *** results show that extreme short-time heat treatment(ESHT,e.g.,2 min)at 450-480℃can greatly increase solute concentration in Mg matrix through the rapid re-dissolution of the second-phase and simultaneously maintain fine grains,while the ESHT at a too high temperature(e.g.,510℃)is not suitable due to excessive grain growth and coarse second phase regenerated at grain *** is found that 480℃is the approximate critical temperature for appropriate ESHT,and further prolongation of the time will lead to excessive grain *** is suggested that in addition to grain boundary migration,grain rotation is activated,resulting in the annihilation of high-angle grain boundaries with relatively low misorientation,as well as the reduction in the ability of the residual second phase to pin grain *** addition,the reasons for the abnormal grain boundary segregation and grain boundary continuous phase were analyzed from the perspective of interfacial *** study provides a basis for effective microstructure regulation of Mg-RE alloys.

关键词： Magnesium alloy Rare earths Microstructure Heat treatment Precipitates

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Microstructures and properties of Nb-Si-based alloys with B addition

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Rare Metals 2023年第8期42卷 2801-2808页

作者： Liang-Shun Luo Fu-Xin Wang Xian-Yu Meng Yan-Jin Xu Liang Wang Yan-Qing Su Jing-Jie Guo Heng-Zhi Fu School of Materials Science and Engineering Harbin Institute of TechnologyHarbin 150001China AVIC Manufacturing Technology Institute Beijing 100024China

The Nb-16Si-18Ti-xB(at%,similarly hereinafter,x=0,1,2,3)alloys were prepared by arc melting in a water-cooled copper *** influences of B addition on their microstructures and properties were based on the data of X-ray diffraction(XRD),field emission scanning electron microscopy(FESEM),and electronic universal material testing *** is found that the addition of B promotes the formation ofα-Nb5Si3phase and suppresses the formation of Nb3Si phase.B addition also tends Nb-16Si-18Ti alloy to form the hypereutectic *** content of silicide phases shows a trend of firstly decreasing and then increasing in Nb-16Si-18Ti-xB(x=0,1,2,3)*** size of Nb solid solution(Nbss)phase increases in Nb-16Si-18Ti-xB(x=0,1,2,3)alloys after heat treatment at 1523 K for 10 *** room temperature compression strength of Nb-16Si-18Ti alloy increases firstly and then decreases with B *** high-temperature compression strength of Nb-16Si-18Ti alloy decreases firstly and then increases with B *** is found that the volume and size of silicide phases have a synergistic effect on the compression strength of Nb-TiSi-based alloys.

关键词： Nb-Si alloys B element Phase stability Compression yield strength

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Insights into the deformation mechanisms of an Al1Mg0.4Si alloy at cryogenic temperature:An integration of experiments and crystal plasticity modeling

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Journal of Materials science & technology 2024年第33期200卷 69-82页

作者： Youhong Peng Danyang Li He Wu Kesong Miao Chenglu Liu Li Wang Wei Liu Chao Xu Lin Geng Peidong Wu Guohua Fan School of Materials Science and Engineering Harbin Institute of TechnologyHarbin 150001China Laboratory for Space Environment and Physical Sciences Harbin Institute of TechnologyHarbin 150001China Key Laboratory for Light-Weight Materials Nanjing Tech UniversityNanjing 211816China

In this work,we investigated the mechanical properties and corresponding deformation mechanisms of an Al1Mg0.4Si alloy,which exhibited significantly higher strength and outstanding strain hardening capacity at 77 K compared to its counterparts at 298 *** deformation mechanisms responsible for the excellent strength-ductility synergy and extraordinary strain hardening capacity at cryogenic temperature were elucidated through a combined experimental and simulation *** results reveal the presence of numerous slip traces and microbands throughout grain surfaces during deformation at 298 K,whereas at 77 K,vague grain surfaces dominate,indicating the simultaneous operation of multiple slip *** electron microscopy(TEM)analysis using the two-beam diffraction technique demonstrates the presence of dislocations with several different Burgers vectors inside a grain at cryogenic temperature,confirming the activation of multiple slip *** accumulation of dislocations facilitated by these multiple slip systems,combined with the high dislocation density,contributes to strain hardening and remarkable uniform elongation at 77 K.A modified dislocation density-based crystal plasticity model,incorporating the effect of grain boundary hardening(GBH)and temperature,was developed to gain a better understanding of the underlying mechanisms governing alloy’s strength and *** GBH effect significantly enhances statistically stored dislocation(SSD)density and screw dislocation proportion,which promote homogeneous deformation and enhance strain hardening capacity at cryogenic *** findings deepen the understanding of plastic deformation at cryogenic temperatures and pave the way for the development of ultrahigh-performance metallic materials for cryogenic applications.

关键词： Aluminum alloy Cryogenic temperature Grain boundary hardening effect Deformation mechanism Crystal plasticity modeling

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Self-supported copper-based gas diffusion electrodes improve the local CO_(2)concentration for efficient electrochemical CO_(2)reduction

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Frontiers of Chemical science and Engineering 2024年第3期18卷 51-62页

作者： Azeem Mustafa Bachirou Guene Lougou Yong Shuai Zhijiang Wang Haseeb-ur-Rehman Samia Razzaq Wei Wang Ruming Pan Jiupeng Zhao Key Laboratory of Aerospace Thermophysics of MIIT Harbin Institute of TechnologyHarbin150001China School of Energy Science and Engineering Harbin Institute of TechnologyHarbin150001China MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage School of Chemistry and Chemical EngineeringHarbin Institute of TechnologyHarbin150001China Mechanical Engineering Department University of Engineering and TechnologyTaxila47050Pakistan School of Aerospace Mechanical and Mechatronics EngineeringUniversity of SydneySydney2006Australia

Electrochemical CO_(2)reduction is a sustainable approach in green chemistry that enables the production of valuable chemicals and fuels while mitigating the environmental impact associated with CO_(2)*** its several advantages,this technology suffers from an intrinsically low CO_(2)solubility in aqueous solutions,resulting in a lower local CO_(2)concentration near the electrode,which yields lower current densities and restricts product *** diffusion electrodes(GDEs),particularly those with tubular architectures,can solve these issues by increasing the local CO_(2)concentration and triple-phase interface,providing abundant electroactive sites to achieve superior reaction *** this study,robust and self-supported Cu flow-through gas diffusion electrodes(FTGDEs)were synthesized for efficient formate production via electrochemical CO_(2)*** were further compared with traditional Cu electrodes,and it was found that higher local CO_(2)concentration due to improved mass transfer,the abundant surface area available for the generation of the triple-phase interface,and the porous structure of Cu FTGDEs enabled high formate Faradaic efficiency(76%)and current density(265 mA¸cm^(−2))at–0.9 V *** hydrogen electrode(RHE)in 0.5 mol·L^(−1)*** combined phase inversion and calcination process of the Cu FTGDEs helped maintain a stable operation for several *** catalytic performance of the Cu FTGDEs was further investigated in a non-gas diffusion configuration to demonstrate the impact of local gas concentration on the activity and performance of electrochemical CO_(2)*** study demonstrates the potential of flow-through gas-diffusion electrodes to enhance reaction kinetics for the highly efficient and selective reduction of CO_(2),offering promising applications in sustainable electrochemical processes.

关键词： CO_(2)electroreduction flow-through delivery hollow fiber structure local concentration formate

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Investigation into enhancing the sensitivity method for monitoring trace erosion product concentration in the ceramic channel of a Hall thruster

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Plasma science and technology 2025年第4期27卷 95-104页

作者： Wei XI Ximing ZHU Bowen ZHENG Zhongxi NING Daren YU School of Energy Science and Engineering Harbin Institute of TechnologyHarbin 150001People’s Republic of China Key Laboratory of Aerospace Plasma Propulsion Ministry of Industry and Information TechnologyHarbin 150001People’s Republic of China

An optical emission spectroscopy(OES)method with a non-invasive measurement capability,without inducing disturbance to the discharge,represents an effective method for material ***,when the OES method is employed to monitor the trace erosion product within the ceramic channel of a Hall thruster,it becomes challenging to distinguish between signal and *** this study,we propose a model filtering method based on the signal characteristics of the Hall thruster plume *** method integrates the slit imaging and spectral resolution features of the *** this method,we extract the spectral signals of the erosion product and working gas from the Hall thruster under different operating *** results indicate that our new method performs comparably to the traditional method without model filtering when extracting atom signals from strong xenon working ***,for trace amounts of the erosion product,our approach significantly enhances the signal-to-noise ratio(SNR),enabling the identification of extremely weak spectral signals even under low mass flow rate and low-voltage *** obtain boron atom concentration of 3.91×10^(-3) kg/m^(3) at a mass flow rate of 4×10^(-7) kg/s and voltage of 200 V while monitoring a wider range of thruster operating *** new method proposed in this study is suitable for monitoring other low-concentration elements,making it valuable for materials processing,environmental monitoring and space propulsion applications.

关键词： model filtering method optical emission spectroscopy Hall thruster advanced actinometry method trace erosion product concentration(Some figures may appear in colour only in the online journal)

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Cu-Cu low-temperature diffusion bonding by spark plasma sintering:Void closure mechanism and mechanical properties

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Journal of Materials science & technology 2023年第8期139卷 210-223页

作者： Wendi Li Yuxin Liang Yang Bai Tiesong Lin Bangsheng Li Jicai Feng School of Materials Science and Engineering Harbin Institute of TechnologyHarbin 150001China State Key Laboratory of Advanced Welding and Joining Harbin Institute of TechnologyHarbin 150001China National Key Laboratory for Precision Hot Processing of Metals Harbin Institute of TechnologyHarbin 150001China

In this study,combining the single point diamond turning(SPDT)and spark plasma sintering(SPS),we achieved high-strength diffusion bonding of copper at an ultra-low temperature of 202℃(0.35 T_(m),T_(m):absolute temperature of the melting point).Additionally,the closure mechanism of interfacial micro-and nano-voids during the Cu-Cu SPS diffusion bonding is systematically revealed for the first *** micro-voids,the pulsed current is found to induce additional diffusion flux and plastic deformation,thereby facilitating the void *** dynamics(MD)simulation revealed that at the atomic scale,high-energy Cu atoms induced by the pulsed current can significantly promote the diffusion of low-energy atoms in their vicinity and accelerate the void *** study also proposes a novel“evaporation-deposition”nano-void closure mechanism for the previously unstudied nano-void closure *** results show that the synergistic effect of the pulsed current and nanoscale surface rough-ness can significantly improve joint *** a low temperature of 405℃(0.5 T_(m)),on combining the computerized numerical control(CNC)turning and SPS diffusion bonding,the joint strength can reach 212 MPa,while that for the joint obtained by traditional hot pressing diffusion bonding at the same tem-perature is only 47 *** obtained an ultra-high joint strength of 271 MPa using the combined process of SPDT and SPS diffusion bonding at an ultra-low temperature of 202℃(0.35 T_(m)),which is approximately 600℃ lower than the traditional diffusion bonding process temperature of 800℃(0.79 T_(m)).To sum up,this study provides a novel method and theoretical support for realizing low-temperature high-strength diffusion bonding.

关键词： Spark plasma sintering Diffusion bonding Void closure mechanism Mechanical property Molecular dynamics

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Research on stock trend prediction method based on optimized random forest

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CAAI Transactions on Intelligence technology 2023年第1期8卷 274-284页

作者： Lili Yin Benling Li Peng Li Rubo Zhang School of Computer and Science and Technology Harbin University of Science and TechnologyHarbinChina Department of Computer Science and Engineering Dalian Nationalities UniversityDalianChina

As a complex hot problem in the financial field,stock trend forecasting uses a large amount of data and many related indicators;hence it is difficult to obtain sustainable and effective results only by relying on empirical *** in the field of machine learning have proved that random forest can form better judgements on this kind of problem,and it has an auxiliary role in the prediction of stock *** study uses historical trading data of four listed companies in the USA stock market,and the purpose of this study is to improve the performance of random forest model in medium-and long-term stock trend *** study applies the exponential smoothing method to process the initial data,calculates the relevant technical indicators as the characteristics to be selected,and proposes the D-RF-RS method to optimize random *** the random forest is an ensemble learning model and is closely related to decision tree,D-RF-RS method uses a decision tree to screen the importance of features,and obtains the effective strong feature set of the model as ***,the parameter combination of the model is optimized through random parameter *** experimental results show that the average accuracy of random forest is increased by 0.17 after the above process optimization,which is 0.18 higher than the average accuracy of light gradient boosting machine *** with the performance of the ROC curve and Precision–Recall curve,the stability of the model is also guaranteed,which further demonstrates the advantages of random forest in medium-and long-term trend prediction of the stock market.

关键词： ensemble learning finance random forest random search technical indicator

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Achieving ultrahigh electromechanical properties with high TC in PNN-PZT textured ceramics

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Journal of Materials science & technology 2024年第8期175卷 258-265页

作者： Q.Wang L.Bian K.Li Y.C.Liu Y.L.Yang B.Yang W.W.Cao School of Instrumentation Science and Engineering Harbin Institute of TechnologyHarbin 150080China Guangdong Provincial Key Laboratory of Electronic Functional Materials and Devices Huizhou UniversityHuizhou 516001China Conversion and Storage School of Chemistry and Chemical EngineeringHarbin Institute of TechnologyHarbin 150080China

textured Pb(Ni_(1/3)Nb_(2/3))O_(3)-PbZrO_(3)-PbTiO_(3)(PNN-PZT)ceramics were prepared by templated grain growth(TGG)technique using 0.36PNN-x PZ-(0.64-x)PT(x=0.23,0.25 and 0.27)powder *** template content was derived ... 详细信息

<001>textured Pb(Ni_(1/3)Nb_(2/3))O_(3)-PbZrO_(3)-PbTiO_(3)(PNN-PZT)ceramics were prepared by templated grain growth(TGG)technique using 0.36PNN-x PZ-(0.64-x)PT(x=0.23,0.25 and 0.27)powder *** template content was derived to achieve the best electromechanical properties of textured *** piezoelectric coefficient d33=1165 pC/N,Curie temperature T_(C)=197℃,longitudinal mode electrome-chanical coupling factor k33=0.86 and a very large effective piezoelectric strain coefficient d_(33)^(*)=2041 pm/V were simultaneously achieved at the morphotropic phase boundary(MPB)composition(x=0.25)with 3 vol.%BaTiO_(3)(BT)*** structures of textured ceramics were analyzed in detail to reveal the origin of these high piezoelectric and electromechanical properties.

关键词： Pb(Ni_(1/3)Nb_(2/3))O_(3)-PbZrO_(3)-PbTiO_(3)(PNN-PZT) ceramics MPB composition Texture engineering Electromechanical properties Domain structure

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Insights into grain boundary segregation and solubility limit of Cr in(TiZrNbTaCr)C

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Journal of Materials science & technology 2023年第8期139卷 1-9页

作者： Wentao Su Lei Chen Wen Zhang Sijia Huo Yujin Wang Yu Zhou Institute for Advanced Ceramics School of Materials Science and EngineeringHarbin Institute of TechnologyHarbin 150001China Key Laboratory of Advanced Structure-Function Integrated Materials and Green Manufacturing Technology Harbin Institute of TechnologyHarbin 150001China

Dense(TiZrNbTaCr)C with Cr segregation along grain boundaries(GBs)has been first proposed and fabri-cated by pressureless sintering at 1800-2000℃,utilizing the self-synthesized carbide powders obtained by carbothermal *** segregation along GBs is successfully realized as expected via optimizing the initial Cr *** Cr content is more than 11.12 at.%,Cr addition is excessive and results in Cr-rich second phase formation at triple *** analyze the Cr solubility dependence on tempera-ture and initial Cr content,the Cr content in(TiZrNbTaCr)C grains is investigated by *** solubility limit of Cr in(TiZrNbTaCr)C is about 3.8 at.%at 1900℃.Finally,Vickers hardness of all the samples is measured to assess the mechanical property of(TiZrNbTaCr)C *** basic understanding of the Cr solubility limit and GB segregation feature in(TiZrNbTaCr)C have been preliminarily clarified,which may pave a potential way to design and tailor microstructure and GB feature of(TiZrNbTaCr)C for the purpose of enhancing its properties in the future.

关键词： High-entropy carbide Grain boundary segregation Solubility limit Microstructure

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