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A policy gradient algorithm integrating long and short-term rewards for soft continuum arm control

Science China(Technological Sciences) 2022年第10期65卷 2409-2419页

作者： DONG Xiang ZHANG Jing CHENG Long XU WenJun SU Hang MEI Tao School of Electrical Engineering and Automation Anhui UniversityHefei 230601China State Key Laboratory for Control and Management of Complex Systems Institute of AutomationChinese Academy of SciencesBeijing 100190China Robotics Research center Peng Cheng LaboratoryShenzhen 518055China

The soft continuum arm has extensive application in industrial production and human life due to its superior safety and flexibility. Reinforcement learning is a powerful technique for solving soft arm continuous control problems, which can learn an effective control policy with an unknown system model. However, it is often affected by the high sample complexity and requires huge amounts of data to train, which limits its effectiveness in soft arm control. An improved policy gradient method, policy gradient integrating long and short-term rewards denoted as PGLS, is proposed in this paper to overcome this issue. The shortterm rewards provide more dynamic-aware exploration directions for policy learning and improve the exploration efficiency of the algorithm. PGLS can be integrated into current policy gradient algorithms, such as deep deterministic policy gradient(DDPG). The overall control framework is realized and demonstrated in a dynamics simulation environment. simulation results show that this approach can effectively control the soft arm to reach and track the targets. Compared with DDPG and other model-free reinforcement learning algorithms, the proposed PGLS algorithm has a great improvement in convergence speed and performance. In addition, a fluid-driven soft manipulator is designed and fabricated in this paper, which can verify the proposed PGLS algorithm in real experiments in the future.

关键词： soft arm control Cosserat rod deep reinforcement learning policy gradient algorithm high sample complexity

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Is Dynesys dynamic stabilization system superior to posterior lumbar fusion in the treatment of lumbar degenerative diseases?

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World Journal of Clinical Cases 2020年第22期8卷 5496-5500页

作者： Bao-Gan Peng Chun-Hua Gao Department of Spinal Surgery The Third Medical CenterPeople’s Liberation Army General HospitalBeijing 100039China

Dynesys,a pedicle-based dynamic stabilization system,was introduced to overcome some undesirable complications of fusion procedures.Nevertheless,the theoretical advantages of Dynesys over fusion have not been clearly confirmed.The purpose of this editorial was to compare clinical and radiological outcomes of patients who underwent Dynesys system with those who underwent posterior lumbar fusion according to the existing literature and to see if the application of the Dynesys system is superior to the traditional lumbar fusion surgery.According to published clinical reports,the short-term effects of the Dynesys dynamic stabilization system are similar to that of traditional lumbar fusion surgery.Three comparative studies of Dynesys dynamic stabilization and fusion surgery with medium-term follow-up are encouraging.However,the results from four single-treatment-arm and small-sample studies of case series with long-term follow-up were not encouraging.In the present circumstances,it is not possible to conclude that the Dynesys dynamic stabilization system is superior to fusion surgery for lumbar degenerative diseases.

关键词： Dynamic stabilization system Lumbar fusion Lumbar degenerative diseases Complication

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A paleo-hydrological simulation experiment and its verification in an inland basin

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Research in Cold and Arid Regions 2019年第4期11卷 267-282页

作者： YuXin Zhang Yu Li XinZhong Zhang ChengQi Zhang WangTing Ye Yuan Liu Key Laboratory of Western China's Environmental Systems(Ministry of Education) College of Earth and Environmental SciencesCenter for Hydrologic Cycle and Water Resources in Arid RegionLanzhou UniversityLanzhouGansu 730000China Key Laboratory of Ecohydrology of Inland River Basin/Gansu Hydrology and Water Resources Engineering Research center Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhouGansu 730000China

Hydrological circulation,as the most basic material cycle and active natural phenomenon on earth,exerts a significant in fluence on climate change.The mid-Holocene is an important period to better understand modern environmental change;however,little research has focused on its quantitative simulation of paleo-hydrological process.In this research,we first collected chronological evidence and sediment records from six Holocene sedimentary sections in the Shiyang River Ba sin to reconstruct the mid-Holocene environment and terminal paleo-lake area.Secondly,we comprehensively analyzed modern pollen combinations and their propagation characteristics in surface soil,air,river and lacustrine sediments in the Shiyang River Basin,and combined the pollen records,as well as quantitatively reconstructed the millennial-scale vegeta tion zones.Finally,based on the land-cover adjustment results during the mid-Holocene,we successfully used the Soil and Water Assessment Tool(SWAT)model,a modern distributed hydrological watershed model,to simulate mid-Holocene runoff in the basin.Results show that the reconstructed climate in the basin was warmer and moister than that in recent times.Vegetation types in the mid-Holocene mainly consisted of sub-alpine shrub distributed between 2,550 m and 2,750 m,forest at an elevation of 2,550 2,750 m,steppe at an elevation of 1,550 2,150 m and desert steppe below 1,550 m.The up stream,midstream,downstream and average annual runoff of the mid-Holocene in the basin were 16.76×10^8 m^3,22.86×10^8 m^3,9.00×10^8 m^3 and 16.20×10^8 m^3 respectively,compared to 15.61×10^8 m^3 of modern annual runoff.Also,the area of terminal paleo-lake in the mid-Holocene was 628 km^2.Thus,this study provides a new quantitative method for paleo-hy drological simulation.

关键词： SWAT model inland basin vegetation reconstruction runoff simulation mid-Holocene

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A Research of Multi‐antenna Spoofing Detection Technology

A Research of Multi‐antenna Spoofing Detection Technology

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第五届中国卫星导航学术年会

作者： Fan Guangwei Yu.Baoguo Dengzhixin Wang Zhenhua The 54th Research Institute of CETC Satellite Navigation Technology and Equipment Engineering Technology Research center of Hebei province

ISBN: (纸本)9783642547362

This paper presented a method that supports multi‐element signal direction finding through power augmentation after the spoofing jamming signals are despread with the local codes,which is compared with the satellite position acquired by Ephemeris calculating.The conventional spoofing‐jamming detection methods are only effective to specific spoofing jamming.This algorithm utilizes the priori knowledge that the satellite navigation receiving system already has detected a number of spoofing jamming with the high‐resolution direction‐finding method.The simulation results show that this algorithm has good detection performance on both active spoofing and passivespoofing.

关键词： GNSS,direction of arrival,spoofing jamming despread.

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A multi-scale cholera model linking between-host and within-host dynamics

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International Journal of Biomathematics 2018年第3期11卷 53-75页

作者： Chayu Yang Drew Posny Feng Bao Jin Wang Department of Mathematics University of Tennessee at Chattanooga Chattanooga TN 37403 USA NSF center for Integrated Pest Management North Carolina State University Raleigh NC 27606 USA

We propose a multi-scale modeling framework to investigate the transmission dynamics of cholera. At the population level, we employ a SIR model for the between-host transmission of the disease. At the individual host level, we describe the evolution of the pathogen within the human body. The between-host and within-host dynamics are connected through an environmental equation that characterizes the growth of the pathogen and its interaction with the hosts outside the human body. We put a special emphasis on the within-host dynamics by making a distinction for each individual host. We conduct both mathematical analysis and numerical simulation for our model in order to explore various scenarios associated with cholera transmission and to better understand the complex, multi-scale disease dynamics. [ABSTRACT FROM AUTHOR]

关键词：动力学多尺度主人霍乱模型连接建模框架相互作用

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Recent improvements to the physical model of the Bohai Sea,the Yellow Sea and the East China Sea Operational Oceanography Forecasting System

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Acta Oceanologica Sinica 2021年第11期40卷 87-103页

作者： Ang Li Xueming Zhu Yunfei Zhang Shihe Ren Miaoyin Zhang Ziqing Zu Hui Wang Key Laboratory of Marine Hazards Forecasting National Marine Environmental Forecasting CenterMinistry of Natural ResourcesBeijing 100081China Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai) Zhuhai 519000China

In order to satisfy the increasing demand for the marine forecasting capacity,the Bohai Sea,the Yellow Sea and the East China Sea Operational Oceanography Forecasting System(BYEOFS)has been upgraded and improved to Version 2.0.Based on the Regional Ocean Modeling System(ROMS),a series of comparative experiments were conducted during the improvement process,including correcting topography,changing sea surface atmospheric forcing mode,adjusting open boundary conditions,and considering atmospheric pressure correction.(1)After the topography correction,the volume transport and meridional velocity maximum of Yellow Sea Warm Current increase obviously and the unreasonable bending of its axis around 36.1°N,123.5°E disappears.(2)After the change of sea surface forcing mode,an effective negative feedback mechanism is formed between predicted sea surface temperature(SST)by the ocean model and sea surface radiation fluxes fields.The simulation errors of SST decreased significantly,and the annual average of root-mean-square error(RMSE)decreased by about 18%.(3)The change of the eastern lateral boundary condition of baroclinic velocity from mixed Radiation-Nudging to Clamped makes the unreasonable westward current in Tsushima Strait disappear.(4)The adding of mean sea level pressure correction option which forms the mean sea level gradient from the Bohai Sea and the Yellow Sea to the western Pacific in winter and autumn is helpful to increasing the fluctuation of SLA and outflow of the Yellow Sea when the cold high air pressure system controls the Yellow Sea area.

关键词： Operational Oceanography Forecasting System East China Sea SST Yellow Sea Warm Current

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Tilting stability analysis and experiment of the 3-DOF lifting platform for hilly orchards

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International Journal of Agricultural and Biological Engineering 2018年第6期11卷 73-80页

作者： Zhenhua Duan Wei Qiu Weimin Ding Yande Liu Yuping Ouyang Liang Huang College of Engineering Nanjing Agricultural UniversityNanjing 210031China Co-Innovation center of the Intelligent Management and Equipment for Orchard on the Hilly Land in South China Nanchang330013China

An orchard-lifting platform is a type of mechanical equipment to assist growers in fruit picking,fruit tree pruning,flower thinning,and other operations.In its operational processes,the tilting stability directly affects the operational safety and adaptability under complex terrain conditions,while critical tilting angle is an important criterion to evaluate the tilting stability.Based on the structure and the operating characteristics of the three degree of freedom(3-DOF)lifting platform for hilly orchards,the tilting stability was analyzed in different parked states,and the theoretical expressions of critical tilting angle were obtained;in the theoretical expressions,the influencing factors on tilting stability were determined as the parked positionβ1,the manned worktable rotary positionβ2,the lifting height h,and the load m.Based on the multi-body dynamics principle,the tilting stability simulation was carried out.The relative error of tilting angles was approximately 4.6%between simulation and tilting verification experiment,which indicated that the results of tilting stability simulation were reliable.Therefore,the multi-body dynamics simulation was used for further clarifying the influencing factors on tilting stability.A virtual orthogonal test was designed,and the results showed that critical tilting angle ranged from 20°to 44°when the factors were at different values,which indicated that the 3-DOF lifting platform for hilly orchards had a high tilting stability performance and could adapt to the operating conditions of hills with slope angles from 5°to 20°.The results of the range analysis and ANOVA showed that the influence intensity of factors on tilting stability wasβ1>h>m>β2;at the same time,β1,h,and m exerted significant effect on tilting stability.The tilting stability first decreased and then either increased or decreased with the increasing lifting height;it gradually decreased with the increasing load.It also showed that the position of the manned worktable along the slope down always had the lo

关键词： orchard-lifting platform hills areas tiling stability influencing factors analysis and experiment

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Numerical Study of Gas Production from a Methane Hydrate Reservoir Using Depressurization with Multi-wells

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Acta Geologica Sinica(English Edition) 2021年第3期95卷 928-936页

作者： SHANG Shilong GU Lijuan LU Hailong College of Engineering Peking UniversityBeijing 100871China School of Earth and Space Sciences Peking UniversityBeijing 100871China Beijing International center for Gas Hydrate Peking UniversityBeijing 100871China

With the implementation of the production tests in permafrost and offshore regions in Canada,US,Japan,and China,the study of natural gas hydrate has progressed into the stage of technology development for industrial exploitation.The depressurization method is considered as a better strategy to produce gas from hydrate reservoirs based on production tests and laboratory experiments.Multi-well production is proposed to improve gas production efficiency,to meet the requirement for industrial production.For evaluating the applicability of multi-well production to hydrate exploitation,a 2D model is established,with numerical simulations of the performance of the multi-well pattern carried out.To understand the dissociation behavior of gas hydrate,the pressure and temperature distributions in the hydrate reservoir are specified,and the change in permeability of reservoir sediments is investigated.The results obtained indicate that multi-well production can improve the well connectivity,accelerate hydrate dissociation,enhance gas production rate and reduce water production as compared with single-well production.

关键词： oil and gas upstream unconventional resources natural gas hydrate numerical simulation depressurization

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Preparation,characterization and performance of poly(m-phenylene isophthalamide)/organically modified montmorillonite nanocomposite membranes in removal of perfluorooctane sulfonate

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Journal of Environmental Sciences 2016年第8期28卷 126-133页

作者： Qin Luo Yanxia Liu Guixia Liu Changwei Zhao Key Laboratory of Applied Chemistry and Nanotechnology at Universities of Jilin Province Changchun University of Science and Technology State Key Laboratory of Environmental Aquatic Chemistry Research Center for Eco-Environmental Sciences Chinese Academy of Sciences

Nanocomposite membranes containing poly（m-phenylene isophthalamide）（PMIA） and organically modified montmorillonite（OMMT） were prepared by a combination of solution dispersion and wet-phase inversion methods, and the effects of OMMT addition on the properties and performance of fabricated nanofiltration membranes were investigated. The membranes were characterized by contact angle measurements, scanning electron microscopy（SEM）, atomic force microscopy（AFM）, thermogravimetric analysis, and zeta potential.The performance of the membranes was elucidated by the removal of perfluorooctane sulfonate（PFOS） at neutral p H. Increasing OMMT concentration improved the thermal stability and hydrophilicity of the membranes. The permeation and rejection of PFOS were significantly improved. The performance of fabricated nanofiltration membranes in removal of PFOS varied depending on the solute and membrane properties as well as solution conditions. Finally,a comparison between fabricated membranes and a commercial NF membrane（ESNA1-K1,Hydecanme） proved that the OMMT addition is a convenient procedure for producing nanocomposite membranes with superior properties and performance.

关键词： Nanofiltration membrane Organically modified montmorillonite PFOS removal

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North Pacific Eastern Subtropical Mode Water simulation and future projection

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Acta Oceanologica Sinica 2015年第3期34卷 25-30页

作者： XIA Ruibin LIU Qinyu XU Lixiao LU Yiqun Physical Oceanography Laboratory/Qingdao Collaborative Innovation center of Marine Science and Technology Key Laboratory of Ocean-Atmosphere Interaction and Climate in Universities of ShandongOcean University of China

The present climate simulation and future projection of the Eastern Subtropical Mode Water （ESTMW） in the North Pacific are investigated based on the Geophysical Fluid Dynamics Laboratory Earth System Model （GFDL-ESM2M）. Spatial patterns of the mixed layer depth （MLD） in the eastern subtropical North Pacific and the ESTMW are well simulated using this model. Compared with historical simulation, the ESTMW is produced at lighter isopycnal surfaces and its total volume is decreased in the RCP8.5 runs, because the subduction rate of the ESTMW decreases by 0.82×10？6 m/s during February–March. In addition, it is found that the lateral induction decreasing is approximately four times more than the Ekman pumping, and thus it plays a dominant role in the decreased subduction rate associated with global warming. Moreover, the MLD during February–March is banded shoaling in response to global warming, extending northeastward from the east of the Hawaii Islands （20°N, 155°W） to the west coast of North America （30°N, 125°W）, with a max-imum shoaling of 50 m, and then leads to the lateral induction reduction. Meanwhile, the increased north-eastward surface warm current to the east of Hawaii helps strengthen of the local upper ocean stratification and induces the banded shoaling MLD under warmer climate. This new finding indicates that the ocean surface currents play an important role in the response of the MLD and the ESTMW to global warming.

关键词： eastern subtropical mode water global warming mixed layer depth subduction rate heat advection

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