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Research on the mechanism of the two-dimensional ultrasonic surface burnishing process to enhance the wear resistance for aluminum alloy

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Friction 2024年第3期12卷 490-509页

作者： Zhen-yu ZHOU Qiu-Yang ZHENG yu LI Cong DING Guang-Jian PENG zhong-yu piao College of Mechanical Engineering Zhejiang University of TechnologyHangzhou 310023China Key Laboratory of Special Purpose Equipment and Advanced Processing Technology Ministry of Education and Zhejiang ProvinceZhejiang University of TechnologyHangzhou 310014China

The gradient nanostructure is machined on the aluminum(Al)alloy by the two-dimensional ultrasonic surface burnishing process(2D-USBP).The mechanism of why the gradient nanostructure enhances wear resistance is *** mechanical properties and microstructure characterization for the gradient nanostructure are performed by operating a nanoindenter,transmission electron microscopy(TEM),and electron backscattered diffraction(EBSD).Dry wear tests are performed on the samples before and after machining to evaluate the wear resistance and *** effect of the gradient nanostructure on the wear resistance is explored by developing the crystal plasticity(CP)finite element and molecular dynamics(MD)*** characterization results show that the 2D-USBP sample prepared a gradient structure of~600μm thick on the aluminum surface,increasing the surface hardness from 1.13 to 1.71 GPa and reducing the elastic modulus from 78.84 to 70.14 *** optimization of the surface microstructure and the increase of the mechanical properties effectively enhance the wear resistance of the sample,with 41.20%,39.07%,and 54.58% of the wear scar areas for the 2D-USBP treated samples to the original samples under 5,10,and 15 N loads,*** gradient nanostructure hinders the slip of dislocations inside the sample during the wear process and reduces the size and scope of plastic deformation;meanwhile,the resistance to deformation,adhesion,and crack initiation and propagation of the sample surface is improved,resulting in enhanced wear resistance.

关键词： structural superlubricity lattice registry elastic deformation strained solitons crystal plasticity molecular dynamics simulations

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Accumulated damage process of thermal sprayed coating under rolling contact by acoustic emission technique

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Frontiers of Mechanical Engineering 2016年第3期11卷 227-232页

作者： Jia XU Zhen-yu ZHOU zhong-yu piao Key Laboratory of Special Purpose Equipment and Advanced Processing Technology (Zhejiang University of Technology) Ministry ofEducation and Zhejiang Province Hangzhou 310014 China Key Laboratory of Special Purpose Equipment and Advanced Processing Technology (Zhejiang University of Technology) Ministry ofEducation and Zhejiang Province Hangzhou 310014 China The StateKey Laboratory of Fluid Power Transmission and Control Hangzhou310027 China

The accumulated damage process of rolling contact fatigue （RCF） of plasma-sprayed coatings was investigated. The influences of surface roughness, loading condition, and stress cycle frequency on the accumulated damage status of the coatings were discussed. A ball-on- disc machine was employed to conduct RCF experiments. Acoustic emission （AE） technique was introduced to monitor thc RCF process of the coatings. AE signal characteristics were investigated to reveal the accumulated damage process. Result showed that the polished coating would resist the asperity contact and remit accumulated damage. The RCF lifetime would then extend. Heavy load would aggravate the accumulated damage status and induce surface fracture. Wear became the main failure mode that reduced the RCF lifetime. Frequent stress cycle would aggravate the accumulated damage status and induce interface fracture. Fatigue then became the main failure mode that also reduced the RCF lifetime.

关键词： accumulated damage spray coating rolling contact fatigue acoustic emission

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Clinical characteristics and treatment of splenic infarction in children with systemic lupus erythematosus

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World Journal of Pediatrics 2024年第5期20卷 525-531页

作者： Yan Li yu-Rong piao Tong-Xin Han Hua-Wei Mao Department of Immunology Ministry of Education Key Laboratory of Major Diseases in ChildrenBeijing Key Laboratory for Genetics of Birth DefectsNational Center for Children’s HealthBeijing Children’s HospitalCapital Medical UniversityNo.56 Nan Li Shi LuBeijing100045China

Splenic infarction(SI)is a rare clinical phenomenon that occurs when the blood supply to the spleen is interrupted,resulting in tissue ischemia and necrosis[1].There are many causes of SI;in adult patients,cardioembolism,hematological malignancy,and infectious disease are the most common[2].Rheumatic diseases,especially systemic lupus erythematosus(SLE)and granulomatosis with polyangitis,can also lead to SI[3];however,only a few cases have been *** are currently no statistically meaningful data on the etiology of SI in *** most patients with SI can recover after conservative treatment,a small number of patients develop complications,such as splenic abscess,splenic rupture,splenic hemorrhage,and hemoperitoneum,and may even undergo splenectomy in severe cases.

关键词： erythematosus lupus treatment

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Does the continuous wetting of the Tibetan Plateau contribute to the accelerated degradation of permafrost?

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Science China Earth Sciences 2024年第5期67卷 1714-1718页

作者： yuyang WANG Jinzhi DING Shilong piao Sino-French Institute for Earth System Science College of Urban and Environmental SciencesPeking UniversityBeijing 100871China State Key Laboratory of Tibetan Plateau Earth System Environment and ResourcesInstitute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100101China

Global warming is causing the Tibetan permafrost to degrade, as evidenced by rising ground temperatures, thicker active layer thickness, thinner permafrost layer, and melting underground ice, etc.(Ran et al., 2018;Wang et al., 2020).The degradation of permafrost not only profoundly alters the carbon cycling processes in high-altitude ecosystems,thereby influencing the regional climate system, but also affects landscape hydrological connectivity。

关键词： Tibetan landscape altitude

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A Unified Motion Generation Approach for Quadruped L-S Walk and Trot Gaits Based on Linear Model Predictive Control

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Journal of Bionic Engineering 2024年第4期21卷 1707-1719页

作者： Yapeng Shi Zhicheng He Xiaokun Leng Songhao piao Lining Sun Harbin Institute of Technology No.92 West Dazhi StreetHarbin150001HeilongjiangChina Yanshan University No.438 West Hebei AvenueQinhuangdao066004HebeiChina

The goal of this paper is to develop a unified online motion generation scheme for quadruped lateral-sequence walk and trot gaits based on a linear model predictive control ***,the dynamics of the linear pendulum model is formulated over a predictive horizon by dimensional *** gait pattern conversion,the lateral-sequence walk and trot gaits of the quadruped can be regarded as unified biped gaits,allowing the dynamics of the linear inverted pendulum model to serve quadruped motion *** addition,a simple linearization of the center of pressure constraints for these quadruped gaits is developed for linear model predictive control ***,the motion generation problem can be solved online by quadratic programming with foothold *** is demonstrated that the proposed unified scheme can generate stable locomotion online for quadruped lateral-sequence walk and trot gaits,both in simulation and on *** results show significant performance improvements compared to previous ***,the results also suggest the linearly simplified scheme has the ability to robustness against unexpected disturbances.

关键词： Motion generation Gait pattern conversion Model predictive control Quadruped locomotion

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Impacts of land surface darkening on frozen ground and ecosystems over the Tibetan Plateau

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Science China Earth Sciences 2024年第10期67卷 3213-3225页

作者： Shuchang TANG Tao WANG Dan LIU Tandong YAO Shilong piao Sino-French Institute for Earth System Science College of Urban and Environmental SciencesPeking UniversityBeijing 100101China State Key Laboratory of Tibetan Plateau Earth System Resources and EnvironmentInstitute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100101China

Tibetan Plateau(TP) is known as the “Third Pole” of the Earth. Any changes in land surface processes on the TP can have an unneglectable impact on regional and global climate. With the warming and wetting climate, the land surface of the TP saw a darkening trend featured by decreasing surface albedo over the past decades, primarily due to the melting of glaciers, snow,and greening vegetation. Recent studies have investigated the effects of the TP land surface darkening on the field of climate, but these assessments only address one aspect of the feedback loop. How do these darkening-induced climate changes affect the frozen ground and ecosystems on the TP? In this study, we investigated the impact of TP land surface darkening on regional frozen ground and ecosystems using the state-of-the-art land surface model ORCHIDEE-MICT. Our model results show that darkening-induced climate changes on the TP will lead to a reduction in the area of regional frozen ground by 1.1×10~4±0.019×10~4km~2, a deepening of the regional permafrost active layer by 0.06±0.0004 m, and a decrease in the maximum freezing depth of regional seasonal frozen ground by 0.06±0.0016 m compared to the scenario without TP land surface ***, the darkening-induced climate change on the TP will result in an increase in the regional leaf area index and an enhancement in the regional gross primary productivity, ultimately leading to an increase in regional terrestrial carbon stock by0.81±0.001 PgC. This study addresses the remaining piece of the puzzle in the feedback loop of TP land surface darkening, and improves our understanding of interactions across multiple spheres on the TP. The exacerbated regional permafrost degradation and increasing regional terrestrial carbon stock induced by TP land surface darkening should be considered in the development of national ecological security barrier.

关键词： Tibetan Plateau Albedo Land surface darkening Frozen ground Ecosystem

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A Case of Brucellosis Concomitant with Severe Fever with Thrombocytopenia Syndrome—Weifang City,Shandong Province,China,2023

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China CDC weekly 2024年第27期6卷 677-680页

作者： Qingqing Xu Cuiping Wu Hui Liu Chao Geng Jinhui Zhang Dongri piao Hongyan Zhao yu Fan Guozhong Tian Hai Jiang National Key Laboratory of Intelligent Tracing and Forecasting for Infectious Diseases National Institute for Communicable Disease Control and PreventionChinese Center for Disease Control and PreventionBeijingChina Department of Infectious Diseases Yidu Central Hospital of WeifangWeifang CityShandong ProvinceChina Institute of Bacterial Disease Jinan Center for Disease Control and PreventionJinan CityShandong ProvinceChina Tongliao Center for Disease Control and Prevention Tongliao CityInner Mongolia Autonomous RegionChina

Summary What is already known about this topic?Brucellosis and severe fever with thrombocytopenia syndrome(SFTS)are neglected zoonoses,attributable respectively to Brucella and the SFTS virus(SFTSV).While the incidence of these diseases has been rising,instances of co-infection remain *** is added by this report?This represents the first documented case of a rare coinfection involving Brucella and SFTSV.

关键词： neglected instance Shandong

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UAV maneuvering decision-making algorithm based on deep reinforcement learning under the guidance of expert experience

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Journal of Systems Engineering and Electronics 2024年第3期35卷 644-665页

作者： ZHAN Guang ZHANG Kun LI Ke piao Haiyin School of Electronics and Information Northwestern Polytechnical UniversityXi’an 710072China Science and Technology on Electro-Optic Control Laboratory Luoyang 471009China

Autonomous umanned aerial vehicle(UAV) manipulation is necessary for the defense department to execute tactical missions given by commanders in the future unmanned battlefield. A large amount of research has been devoted to improving the autonomous decision-making ability of UAV in an interactive environment, where finding the optimal maneuvering decisionmaking policy became one of the key issues for enabling the intelligence of UAV. In this paper, we propose a maneuvering decision-making algorithm for autonomous air-delivery based on deep reinforcement learning under the guidance of expert experience. Specifically, we refine the guidance towards area and guidance towards specific point tasks for the air-delivery process based on the traditional air-to-surface fire control ***, we construct the UAV maneuvering decision-making model based on Markov decision processes(MDPs). Specifically, we present a reward shaping method for the guidance towards area and guidance towards specific point tasks using potential-based function and expert-guided advice. The proposed algorithm could accelerate the convergence of the maneuvering decision-making policy and increase the stability of the policy in terms of the output during the later stage of training process. The effectiveness of the proposed maneuvering decision-making policy is illustrated by the curves of training parameters and extensive experimental results for testing the trained policy.

关键词： unmanned aerial vehicle(UAV) maneuvering decision-making autonomous air-delivery deep reinforcement learning reward shaping expert experience

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Trajectory Time Series Compression Algorithm Based on Unsupervised Segmentation

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Journal of Systems Science and Information 2024年第3期12卷 360-378页

作者： Shuang SUN Yan CHEN Zaiji piao School of Maritime Economics and Management Dalian Maritime UniversityDalian 116026China School of Software Dalian University of Foreign LanguagesDalian 116044China

Aiming at the problem of ignoring the importance of starting point features of trajecory segmentation in existing trajectory compression algorithms,a study was conducted on the preprocessing process of trajectory time ***,an algorithm improvement was proposed based on the segmentation algorithm GRASP-UTS(Greedy Randomized Adaptive Search Procedure for Unsupervised Trajectory Segmentation).On the basis of considering trajectory coverage,this algorithm designs an adaptive parameter adjustment to segment long-term trajectory data reasonably and the identification of an optimal starting point for *** the compression efficiency of typical offline and online algorithms,such as the Douglas-Peucker algorithm,the Sliding Window algorithm and its enhancements,was compared before and after *** experimental findings highlight that the Adaptive Parameters GRASP-UTS segmentation approach leads to higher fitting precision in trajectory time series compression and improved algorithm efficiency ***,the compression performance of the Improved Sliding Window algorithm post-segmentation showcases its suitability for trajectories of varying scales,providing reasonable compression accuracy.

关键词： trajectory time series unsupervised segmentation trajectory compression greedy ran-domized adaptive search

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Tube-based robust reinforcement learning for autonomous maneuver decision for UCAVs

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Chinese Journal of Aeronautics 2024年第7期37卷 391-405页

作者： Lixin WANG Sizhuang ZHENG Haiyin piao Changqian LU Ting yuE Hailiang LIU School of Aeronautical Science and Engineering Beihang UniversityBeijing 100191China Shenyang Aircraft Design&Research Institute Shenyang 110035China

Reinforcement Learning(RL)algorithms enhance intelligence of air combat AutonomousManeuver Decision(AMD)policy,but they may underperform in target combat environmentswith *** enhance the robustness of the AMD strategy learned by RL,thisstudy proposes a Tube-based Robust RL(TRRL)***,this study introduces a tube todescribe reachable trajectories under disturbances,formulates a method for calculating tubes basedon sum-of-squares programming,and proposes the TRRL algorithm that enhances robustness byutilizing tube size as a quantitative ***,this study introduces offline techniques forregressing the tube size function and establishing a tube library before policy learning,aiming toeliminate complex online tube solving and reduce the computational burden during ***,an analysis of the tube library demonstrates that the mitigated AMD strategy achievesgreater robustness,as smaller tube sizes correspond to more cautious *** finding highlightsthat TRRL enhances robustness by promoting a conservative *** effectively balanceaggressiveness and robustness,the proposed TRRL algorithm introduces a“laziness factor”as aweight of ***,combat simulations in an environment with disturbances confirm thatthe AMD policy learned by the TRRL algorithm exhibits superior air combat performance comparedto selected robust RL baselines.

关键词： Air combat Autonomous maneuver decision Robust reinforcement learning Tube-based algorithm Combat simulation

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