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A survey on model-based reinforcement learning

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Science China(Information Sciences) 2024年第2期67卷 59-84页

作者： Fan-ming luo Tian XU Hang LAI Xiong-Hui CHEN Weinan ZHANG Yang YU National Key Laboratory for Novel Software Technology Nanjing University Polixir. ai Department of Computer Science and Engineering Shanghai Jiao Tong University

Reinforcement learning(RL) interacts with the environment to solve sequential decision-making problems via a trial-and-error approach. Errors are always undesirable in real-world applications, even though RL excels at playing complex video games that permit several trial-and-error attempts. To improve sample efficiency and thus reduce errors, model-based reinforcement learning(MBRL) is believed to be a promising direction, as it constructs environment models in which trial-and-errors can occur without incurring actual costs. In this survey, we investigate MBRL with a particular focus on the recent advancements in deep RL. There is a generalization error between the learned model of a non-tabular environment and the actual environment. Consequently, it is crucial to analyze the disparity between policy training in the environment model and that in the actual environment, guiding algorithm design for improved model learning, model utilization, and policy training. In addition, we discuss the recent developments of model-based techniques in other forms of RL, such as offline RL, goal-conditioned RL, multi-agent RL, and meta-RL. Furthermore,we discuss the applicability and benefits of MBRL for real-world tasks. Finally, this survey concludes with a discussion of the promising future development prospects for MBRL. We believe that MBRL has great unrealized potential and benefits in real-world applications, and we hope this survey will encourage additional research on MBRL.

关键词： reinforcement learning model-based reinforcement learning planning model learning model learning with reduced error model usage

Supramolecular polymer network constructed by a functionalized polyimidazolium salt derived from metal-carbene template approach

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Science China Chemistry 2024年第4期67卷 1224-1228页

作者： ming-ming Gan Zi-En Zhang yi-Fan Zhang Heng Zhang Li-ying Sun ying-Feng Han Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of the Ministry of Education Xi’an Key Laboratory of Functional Supramolecular Structure and MaterialsCollege of Chemistry and Materials ScienceNorthwest UniversityXi’an 710127China

In this study,we present a supramolecular templating approach for constructing polyimidazolium salt containing crown ether and cyclobutane *** strategy involves the formation of metal-carbene templates,photochemical cycloaddition,and subsequent demetallation of metal *** by the host-guest chemistry between crown ether units and ammonium salts,we successfully fabricated a supramolecular polymer SPN1,which features imidazolium receptors and cyclobutane *** obtained SPN1 demonstrates outstanding reversible stimulus-response,antibacterial behavior and conductivity.

关键词： metal-carbene template crown ether polyimidazolium salt host-guest chemistry

Understanding Simulated Causes of Damaging Surface Winds in a Derecho-Producing Mesoscale Convective System near the East China Coast Based on Convection-Permitting Simulations

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Advances in Atmospheric Sciences 2024年第11期41卷 2112-2130页

作者： Liping luo ming XUE Xin XU Lijuan LI Qiang ZHANG Ziqi FAN College of Civil Aviation Nanjing University of Aeronautics and AstronauticsNanjing 211106China State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China Key Laboratory of Mesoscale Severe Weather/Ministry of Education and School of Atmospheric Sciences Nanjing UniversityNanjing 210023China Center for Analysis and Prediction of Storms and School of Meteorology University of OklahomaNormanOklahoma 73072USA Civil Aviation North China Air Traffic Management Bureau Meteorological Center Beijing 100621China

A mesoscale convective system(MCS) occurred over the East China coastal provinces and the East China Sea on 30April 2021, producing damaging surface winds near the coastal city Nantong with observed speeds reaching 45 m s^(–1). A simulation using the Weather Research and Forecasting model with a 1.5-km grid spacing generally reproduces the development and subsequent organization of this convective system into an MCS, with an eastward protruding bow segment over the sea. In the simulation, an east-west-oriented high wind swath is generated behind the gust front of the MCS. Descending dry rear-to-front inflows behind the bow and trailing gust front are found to feed the downdrafts in the main precipitation regions. The inflows help to establish spreading cold outflows and enhance the downdrafts through evaporative cooling. Meanwhile, front-to-rear inflows from the south are present, associated with severely rearward-tilted updrafts initially forming over the gust front. Such inflows descend behind(north of) the gust front, significantly enhancing downdrafts and near-surface winds within the cold pool. Consistently, calculated trajectories show that these parcels that contribute to the derecho originate primarily from the region ahead(south) of the east-west-oriented gust front, and dry southwesterly flows in the low-to-middle levels contribute to strong downdrafts within the MCS. Moreover, momentum budget analyses reveal that a large westward-directed horizontal pressure gradient force within the simulated cold pool produced rapid flow acceleration towards Nantong. The analyses enrich the understanding of damaging wind characteristics over coastal East China and will prove helpful to operational forecasters.

关键词： damaging surface winds convection-permitting simulations mesoscale convective system gust front cold pool

Ultrafast laser processing of camouflaged metals by topography inherited multistep removal for information encryption

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Nano Research 2024年第8期17卷 7242-7249页

作者： Guangzhi He Jianfeng Yan Jiawang Xie ming Qiao Ma luo Yuzhi Zhao Haoze Han State Key Laboratory of Tribology in Advanced Equipment Department of Mechanical EngineeringTsinghua UniversityBeijing 100084China

Surfaces with micro-nanoscale structures show different optical responses,including infrared reflection,thermal radiation,and protective *** realization of structure camouflage is important for material ***,external cloaks or coatings are necessary in structure camouflage,which limits the surface ***,we propose a novel strategy for the direct structure camouflage through topography inherited removal(TIR)with ultrafast laser,featuring pristine topography preservation and scattering surface *** multistep TIR,pristine topographies are partially and uniformly removed to preserve the original designed *** response changes show the suppression of specular reflection by uniformizing reflected light intensity to a low level on the inherited *** produce various structure camouflages on large scaled substrates,and demonstrate applications of information encryption in code extraction and word recognition through structure *** proposed strategy opens opportunities for infrared camouflage and other technologies,such as thermal management,device security,and information encryption.

关键词： topography inherited removal ultrafast laser structure camouflage optical response information encryption

Vasospastic angina with J waves formation in patients with sudden loss of consciousness

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Journal of Geriatric Cardiology 2015年第3期12卷 313-318页

作者： Dan ZHU yi-ming luo Ke-Hu A Ling-Yun ZU Yan-Hui ZHANG Li-Jun GUO Wei GAO Yuan ZHANG Key Laboratory of Cardiovascular Molecular Biology and Regulatory Peptides Department of Cardiology Peking University Third Hospital Beijing China

Vasospastic angina is caused by sudden occlusive vasoconstriction of a segment of an epicardial artery, which can present with a wide spectrum of clinical scenario. We report the cases of two patients diagnosed with vasospastic angina, with one of which presenting with sudden cardiac arrest, while the other presenting with a relatively benign syncope. But both of them have J waves formation on ECG during active ischemia. The diagnosis and management of vasospastic angina, as well as the proposed clinical significance of J waves during coro- nary soasm are discussed.

关键词： Angina Consciousness loss J wave Osbom wave

Structural engineering of hard carbon through spark plasma sintering for enhanced sodium-ion storage

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Rare Metals 2024年第9期43卷 4274-4285页

作者： Hao-ming Xiao Heng Zheng Ping Yuan Jun-Hui luo Lin-Lin Shen Jie-Feng Tan Xian-You luo De Li Yong Chen Guangdong Key Laboratory for Hydrogen Energy Technologies School of Materials Science and Hydrogen EnergyFoshan UniversityFoshan 528000China State Key Laboratory of Marine Resource Utilization in South China Sea Hainan Provincial Key Laboratory of Research on Utilization of Si-Zr-Ti ResourcesHainan UniversityHaikou 570228China

Hard carbon(HC)has emerged as one of the superior anode materials for sodium-ion batteries(SIBs),with its electrochemical performance significantly influenced by the presence of oxygen functional groups and its closed pore ***,current research on the structural adjustment of these oxygen functional groups and the closed pore architecture within HC remains ***,energy-efficient and contamination-free spark plasma sintering technology was employed to tune the structure of coconut-shell HC,resulting in significant adjustments to the content of carboxyl(decreasing from 5.71 at%to 2.12 at%)and hydroxyl groups(decreasing from 7.73 at%to 6.26 at%).Crucially,these modifications reduced the irreversible reaction of oxygen functional groups with Na^(+).Simultaneously,a substantial number of closed pores with an average diameter of 1.22 nm were generated within the HC,offering an ideal environment for efficient Na^(+)*** structural changes resulted in a remarkable improvement in the electrochemical performance of the modified *** reversible specific capacity of the modified HC surged from 73.89 mAh·g^(-1)to an impressive 251.97 m Ah·g^(-1)at a current density of 50 mA·g^(-1).Even at 400 mA·g^(-1),the reversible specific capacity increased significantly from 14.55 to 85.44 mAh·g^(-1).Hence,this study provides a novel perspective for designing tailored HC materials with the potential to develop high-performance SIBs.

关键词： Hard carbon Spark plasma sintering Sodiumion batteries Closed pores Oxygen functional groups

Effectiveness of colonoscopy,immune fecal occult blood testing,and risk-graded screening strategies in colorectal cancer screening

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World Journal of Gastrointestinal Surgery 2024年第7期16卷 2270-2280页

作者： ming Xu Jing-yi Yang Tao Meng Department of Colorectal Surgery Qilu Hospital(Qingdao)Cheeloo College of MedicineQingdao 266000Shandong ProvinceChina Department of Gastrointestinal Surgery The First Affiliated Hospital of Zhengzhou UniversityZhengzhou 450052Henan ProvinceChina

BACKGROUND Colorectal cancer(CRC)is one of the most common malignant tumors,and early screening is crucial to improving the survival rate of *** combination of colonoscopy and immune fecal occult blood detection has garnered significant attention as a novel method for CRC *** and fecal occult blood tests,when combined,can improve screening accuracy and early detection rates,thereby facilitating early intervention and ***,certain risks and costs accompany it,making the establishment of a risk classification model crucial for accurate classification and management of screened *** To evaluate the feasibility and effectiveness of colonoscopy,immune fecal occult blood test(FIT),and risk-graded screening strategies in CRC *** Based on the randomized controlled trial of CRC screening in the population conducted by our hospital May 2020 to May 2023,participants who met the requirements were randomly assigned to a colonoscopy group,an FIT group,or a graded screening group at a ratio of 1:2:2(after risk assessment,the high-risk group received colonoscopy,the low-risk group received an FIT test,and the FITpositive group received colonoscopy).The three groups received CRC screening with different protocols,among which the colonoscopy group only received baseline screening,and the FIT group and the graded screening group received annual follow-up screening based on baseline *** primary outcome was the detection rate of advanced tumors,including CRC and advanced *** population participation rate,advanced tumor detection rate,and colonoscopy load of the three screening programs were *** A total of 19373 subjects who met the inclusion and exclusion criteria were enrolled,including 8082 males(41.7%)and 11291 females(58.3%).The mean age was 60.05±6.5 *** them,3883 patients were enrolled in the colonoscopy group,7793 in the FIT group,and 7697 in the graded screening *** rounds

关键词： Colorectal tumor Immune fecal occult blood testing Colonoscopy Hierarchical screening Risk assessment

Copper-coated Porous Polyimide as Ultralight and Safe Current Collectors for Advanced LIBs

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Chinese Journal of Polymer Science 2024年第4期42卷 521-531页

作者： Cun-Sheng Liu Jun-Qi Hu Ting-Ting Mao Song-yi Liao Ru-ming Feng yi-Dong Liu Yong-Gang Min School of Materials and Energy Guangdong University of TechnologyGuangzhou510006China College of Chemistry and Chemical Engineering Zhongkai University of Agriculture and EngineeringGuangzhou510225China Shanwei Branch of Advanced Energy Science and Technology Guangdong Laboratory Shanwei516600China

Metallic copper is widely used as current collector(CC) for graphite anode of lithium-ion batteries(LIBs) due to its high electrical conductivity and electrochemical stability. However, the large volume density of commercial copper foil(~8.9 g·cm^(-3)) limits the increase of energy density of battery. Here, copper-coated porous polyimide(Cu@PPI) was prepared by vacuum evaporation as collector for the graphite anode. The sandwich structure connects the copper metal on both sides of the collector with excellent electrical conductivity. Compared to commercial Cu foil, Cu@PPI has lighter mass(≤3.9 mg for disc of 12 mm diameter versus 9.9 mg of ~10 μm Cu foil) and lower volume density(≤3.3 g·cm^(-3)). In addition, the porous structure allows of better adhesion of reactive substances and electrochemical properties than pure Cu foils. It is estimated that the energy density of Cu@PPI should be much higher than that of Cu foil. This strategy should be applicable for other current collectors.

关键词： Copper-coated Vacuum evaporation Porous polyimide(PPI) Current collector(CC) LIBs

A novel dandelion-based bionic proppant and its transportation mechanism in different types of fractures

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Petroleum Science 2024年第4期21卷 2583-2599页

作者： Jun Li ming-yi Wu Xu Han Si-Yuan He Ze-Yu Lin State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation Southwest Petroleum University Sichuan Particles Energy and Technology Co. Ltd Chongqing Industry Polytechnic College Petroleum Systems Engineering Faculty of Engineering and Applied Science University of Regina

Low-permeability reservoirs are generally characterized by low porosity and low permeability. Obtaining high production using the traditional method is technologically challenging because it yields a low reservoir recovery factor. In recent years, hydraulic fracturing technology is widely applied for efficiently exploiting and developing low-permeability reservoirs using a low-viscosity fluid as a fracturing ***, the transportation of the proppant is inefficient in the low-viscosity fluid, and the proppant has a low piling-up height in fracture channels. These key challenges restrict the fluid(natural gas or oil) flow in fracture channels and their functional flow areas, reducing the profits of hydrocarbon *** study aimed to explore and develop a novel dandelion-bionic proppant by modifying the surface of the proppant and the fiber. Its structure was similar to that of dandelion seeds, and it had high transport and stacking efficiency in low-viscosity liquids compared with the traditional ***, the transportation efficiency of this newly developed proppant was investigated experimentally using six different types of fracture models(tortuous fracture model, rough fracture model,narrow fracture model, complex fracture model, large-scale single fracture model, and small-scale single fracture model). Experimental results indicated that, compared with the traditional proppant, the transportation efficiency and the packing area of the dandelion-based bionic proppant significantly improved in tap water or low-viscosity fluid. Compared with the traditional proppant, the dandelionbased bionic proppant had 0.1-4 times longer transportation length, 0.3-5 times higher piling-up height, and 2-10 times larger placement area. The newly developed proppant also had some other extraordinary features. The tortuosity of the fracture did not influence the transportation of the novel proppant. This proppant could easily enter the branch fracture and n

关键词： Dandelion-based bionic proppant Low-viscosity fracturing fluid Unconventional reservoir Volumetric fracturing stimulation