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Ensemble successor representations for task generalization in offline-to-online reinforcement learning

Science China(Information Sciences) 2024年第7期67卷 240-255页

作者： Changhong WANG Xudong YU Chenjia BAI Qiaosheng ZHANG Zhen WANG Space Control and Inertial Technology research Center Harbin Institute of Technology Shanghai Artificial Intelligence Laboratory Shenzhen research Institute of Northwestern Polytechnical University school of Cybersecurity Northwestern Polytechnical University

In reinforcement learning(RL), training a policy from scratch with online experiences can be inefficient because of the difficulties in exploration. Recently, offline RL provides a promising solution by giving an initialized offline policy, which can be refined through online interactions. However, existing approaches primarily perform offline and online learning in the same task, without considering the task generalization problem in offline-to-online adaptation. In real-world applications, it is common that we only have an offline dataset from a specific task while aiming for fast online-adaptation for several tasks. To address this problem, our work builds upon the investigation of successor representations for task generalization in online RL and extends the framework to incorporate offline-to-online learning. We demonstrate that the conventional paradigm using successor features cannot effectively utilize offline data and improve the performance for the new task by online fine-tuning. To mitigate this, we introduce a novel methodology that leverages offline data to acquire an ensemble of successor representations and subsequently constructs ensemble Q functions. This approach enables robust representation learning from datasets with different coverage and facilitates fast adaption of Q functions towards new tasks during the online fine-tuning *** empirical evaluations provide compelling evidence showcasing the superior performance of our method in generalizing to diverse or even unseen tasks.

关键词： offline reinforcement learning online fine-tuning task generalization successor representations ensembles

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Nrf2 as a potential target for the treatment of epilepsy

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Neural Regeneration research 2024年第9期19卷 1865-1866页

作者： Prince Kumar Singh Tawfeeq Shekh-Ahmad Institute for Drug research School of PharmacyFaculty of MedicineThe Hebrew University of JerusalemJerusalemIsrael

Epilepsy is a prevalent chronic brain disorder that is characterized by a persistent predisposition to recurrently generate epileptic seizures and is often associated with cognitive and psychological *** affects approximately 65 million individuals,including both males and females of all ages worldwide,and poses a significant burden on patients,their families,and the health system(Vezzani et al.,2019).

关键词： epilepsy Nrf2

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Ion heat transport in electron cyclotron resonance heated L-mode plasma on the T-10 tokamak

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Plasma Science and Technology 2024年第4期26卷 52-60页

作者： V.A.KRUPIN M.R.NURGALIEV A.R.NEMETS I.A.ZEMTSOV S.D.SUNTSOV T.B.MYALTON D.S.SERGEEV N.A.SOLOVEV D.V.SARYCHEV D.V.RYJAKOV S.N.TUGARINOV N.N.NAUMENKO National research Centre“Kurchatov Institute” Moscow 123182Russia Bauman Moscow State technical University Moscow 105005Russia Institution“Project Center ITER” Moscow 123098Russia JSC“SOLAR” Minsk 220034Belarus

Anomalous ion heat transport is analyzed in the T-10 tokamak plasma heated with electron cyclotron resonance heating(ECRH) in second-harmonic extra-ordinary mode. Predictive modeling with empirical scaling for Ohmical heat conductivity shows that in ECRH plasmas the calculated ion temperature could be overestimated, so an increase of anomalous ion heat transport is required. To study this effect two scans are presented: over the EC resonance position and over the ECRH power. The EC resonance position varies from the high-field side to the low-field side by variation of the toroidal magnetic field. The scan over the heating power is presented with on-axis and mixed ECRH regimes. Discharges with high anomalous ion heat transport are obtained in all considered regimes. In these discharges the power balance ion heat conductivity exceeds the neoclassical level by up to 10 times. The high ion heat transport regimes are distinguished by three parameters: the ratio Te/Ti, the normalized electron density gradient R/■, and the ion–ion collisionality νii~*. The combination of high Te/Ti, high νii~*, and R/■=6-10 results in values of normalized anomalous ion heat fluxes up to 10 times higher than in the low transport scenario.

关键词： tokamak L-mode electron cyclotron resonance heating ion heat transport

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Game theory based finite-time formation control using artificial potentials for tethered space net robot

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Chinese Journal of Aeronautics 2024年第8期37卷 358-372页

作者： Yifeng MA Yizhai ZHANG Panfeng HUANG Ya LIU Fan ZHANG The research Center for Intelligent Robotics School of AstronauticsNorthwestern Polytechnical UniversityXi’an 710072China school of Electronic Information and Electrical Engineering Shanghai Jiao Tong UniversityShanghai 200240China

The Tethered Space Net Robot(TSNR)is an innovative solution for active space debris capture and *** large envelope and simple capture method make it an attractive option for this ***,capturing maneuverable debris with the flexible and elastic underactuated net poses significant *** address this,a novel formation control method for the TSNR is proposed through the integration of differential game theory and robust adaptive control in this ***,the trajectory of the TSNR is obtained through the solution of a real-time feedback pursuit-evasion game with a dynamic target,where the primary condition is to ensure the stability of the ***,to minimize tracking errors and maintain a specific configuration,a robust adaptive formation control scheme with Artificial Potential Field(APF)based on a Finite-Time Convergent Extended State Observer(FTCESO)is *** proposed control method has a key advantage in suppressing complex oscillations by a new adaptive law,thus precisely maintaining the ***,numerical simulations are performed to demonstrate the effectiveness of the proposed scheme.

关键词： Game theory Formation control Artificial potential field Relative distance constraint Tethered space net robot(TSNR)

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Progress in the application of graphene material in oilfield chemistry:A review

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Petroleum 2024年第2期10卷 175-190页

作者： Jinsheng Sun Yuanwei Sun Yong Lai Li Li Gang Yang Kaihe Lv Taifeng Zhang Xianfa Zhang Zonglun Wang Zhe Xu Zhiwen Dai Jingping Liu school of Petroleum Engineering China University of Petroleum (East China) CNPC Engineering Technology R&D Company Limited Nanchong Vocational and technical College Oil & Gas Technology research Institute of Changqing Oilfield Company CNPC Greatwall Drilling Fluids Company

Graphene is a single atom thick crystal composed of carbon atoms. It is the lightest, thinnest, strongest material that conducts heat and electricity well heretofore. In terms of application, by introducing oxygen-containing groups, graphene can be well dispersed in solvents, can be chemically modified and functionalized, or connected with other electroactive substances through covalent bond or non-covalent bond to form composite materials, which is conducive to further processing and promotion. The application of graphene in oilfield chemistry started late, but developed rapidly. Graphene has played an active role in drilling fluid, cementing fluid, fracturing fluid, displacement fluid and other oilfield working fluids. It can enhance the temperature and salt resistance of working fluid and improve the effect of working fluid. In this paper, several directions of graphene applications in oilfield chemistry, such as modified graphene, graphene copolymers and graphene nanoparticles, are reviewed in detail from the synthesis methods, action mechanisms and effects of graphene and its derivatives, and the frontier cases at this stage are given. On the basis of the existing research, suggestions for the development direction of graphene materials in oilfield chemistry are given for a variety of graphene materials, aiming to provide guidance for the application of graphene in oilfield chemistry.

关键词： Oilfield chemistry Graphene Action mechanism Application Prospect

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Microstructure， electrochemical， wear and corrosive wear performance of laser-based powder bed fusion(lpbf) and wrought biomedical Ti-6Al-4V alloys

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Transactions of Nonferrous Metals Society of China 2024年

作者： A.G.Lekatou B.V.Efremenko V.Haoui V.G.Efremenko S.Emmanouilidou V.I.Zurnadzhy I.Petryshynets Yu.G.Chabak I.I.Sili Laboratory of Applied Metallurgy， Department of Materials Science and Engineering， school of Engineering， University of Ioannina Institute of Materials Science and Computing， University research Center of Ioannina (URCI) Pryazovskyi State technical University， Department of Physics Institute of Materials research of Slovak Academy of Sciences

Wrought and laser powder bed fusion （LPBF） Ti-6Al-4V specimens were comparatively evaluated， with the objective to determine LPBF Ti-6-4’s suitability for biomedical applications. Testing included nanoindentation， cyclic polarization in simulated body fluid （SBF， 37 ℃ ）， and dry and SBF “Ball-on-Plate” sliding. Wrought Ti-6-4 exhibited a lamellar （α+β） microstructure， whereas LPBF displayed a fine-grained α'-martensite microstructure. LPBF Ti-6-4 demonstrated ～3% higher indentation modulus and ～32% higher hardness， while wrought Ti-6-4 showed ～8% higher plasticity. Both alloys exhibited low corrosion rates (10–5mA/cm2order) and true passivity (10–4mA/cm2order). No localized corrosion was observed in either alloy， except for occasional metastable pitting in the LPBF alloy. However， LPBF Ti-6-4 presented higher corrosion rate and passive current， ascribed to its martensitic structure. During dry sliding， LPBF Ti-6-4 exhibited ～14% lower volume loss compared to wrought Ti-6-4. Sliding in SBF increased volume losses for both alloys， with wear resistances nearly equalized， as the advantage of LPBF Ti-6-4 decreased due to more intensive wear-accelerated corrosion induced by the stressed martensite. Overall， the results demonstrate the suitability of LPBF Ti-6Al-4V for biomedical uses.

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Realization of Low in-Band Harmonic for Compact 6–18-GHz T/R Module Under TX-Mode Operation

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Chinese Journal of Electronics 2024年第2期33卷 380-384页

作者： Jinming LAI Zhiyou LI Chaojie WANG Hailong WANG Xiaohua MA school of Microelectronics Xidian University CETC 29th research Institute

Wideband high power amplifier(PA) with poor harmonic suppression will degrade the performance of the active electronically scanned array(AESA) due to its harmonic products falling into the operating bandwidth of a wideband T/R module. In view of this, a compact reconfigurable harmonic suppress circuit(HSC) is proposed to achieve low in-band harmonic for compact T/R module with multiple octaves under TX-mode operation. The HSC consists of eight microstrip resonant stubs with high impedance and multiple p-i-n switches. By controlling the p-i-n switches, the HSC can work in three states. When six of the used p-i-n switches are “ON” state, the corresponding microstrip resonant stubs are loaded onto the 50 Ω transmission line, which performs a bandstop filter(BSF). For verification, the HSC with bandwidth of 12–15 GHz/15–18 GHz is designed to apply to a 6–18 GHz T/R module. As a result, the second harmonic of 6–9 GHz transmitting signal can be suppressed below 32 d Bc when compared to the PA's fundamental output. While the p-i-n switches are “OFF” state, the HSC is almost the same as a 50 Ω transmission line, which will have a little effect on the 9–18 GHz transmitting signal. The measurement results approximately agree with the calculated results and simulated results, which demonstrate the validity of the proposed HSC.

关键词： Microstrip filters Harmonics suppression Power transmission lines PIN photodiodes Switches Harmonic analysis Transmission line measurements

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Fe-Induced Electronic Transfer and Structural Evolution of Lotus Pod-Like CoNiFePx@P,N-C Heterostructure for Sustainable Oxygen Evolution

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Energy & Environmental Materials 2024年第3期7卷 186-193页

作者： Xiaojun Zeng Qingqing Zhang Chulong Jin Hui Huang Yanfeng Gao Advanced Ceramic Materials research Institute School of Materials Science and EngineeringJingdezhen Ceramic University Singapore Institute of Technology school of Materials Science and Engineering Shanghai University

Transition metal phosphides with metallic properties are a promising candidate for electrocatalytic water oxidation,and developing highly active and stable metal phosphide-based oxygen evolution reaction catalysts is still ***,we present a facile ion exchange and phosphating processes to transform intestine-like CoNiPx@P,N-C into lotus pod-like CoNiFePx@P,N-C heterostructure in which numerous P,N-codoped carboncoated CoNiFePxnanoparticles tightly anchors on the 2D carbon ***,the as-prepared CoNiFePx@P,N-C enables a core-shell structure,high specific surface area,and hierarchical pore structure,which present abundant heterointerfaces and fully exposed active ***,the incorporation of Fe can also induce electron transfer in CoNiPx@P,IM-C,thereby promoting the oxygen evolution ***,CoNiFePx@P,IM-C delivers a low overpotential of 278 mV （vs RHE） at a current density of10 mA cm-1and inherits excellent long-term stability with no observable current density decay after 30 h of chronoamperometry *** work not only highlights heteroatom induction to tune the electronic structure but also provides a facile approach for developing advanced and stable oxygen evolution reaction electrocatalysts with abundant heterointerfaces.

关键词： electronic transfer Fe exchange multi-metal phosphides OER electrocatalysts structural evolution

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Livelihood Vulnerability and Adaptation for Households Engaged in Forestry in Ecological Restoration Areas of the Chinese Loess Plateau

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Chinese Geographical Science 2024年第5期34卷 849-868页

作者： YANG Qingqing CHEN Yang LI Xiaomin YANG Jie GAO Yanhui Northwest Land and Resources research Center Global Regional and Urban Research InstituteShaanxi Normal UniversityXi’an 710119China school of Geographical Science and Tourism Shaanxi Normal UniversityXi’an 710119China school of Tour-ism and research Institute of Human Geography Xi’an International Studies UniversityXi’an 710128China

Chinese Loess Plateau has achieved a win-win situation concerning ecological restoration and socio-economic ***,synergistic development may not be realized at the local *** areas undergoing ecological restoration,livelihood vulner-ability may be more pronounced due to the inflexibility,policy protection,and susceptibility to climate and market changes in forestry *** this issue has attracted academic interest,empirical studies are relatively *** study,centered on Jiaxian County,Shaanxi Province of China explored the households’livelihood vulnerability and coping strategies and group heterogeneity con-cerned with livelihood structures or forestry resources through field investigation,comprehensive index assessment,and nonparametric *** showed that:1)the percentage of households with high livelihood vulnerability indicator(LVI)(>0.491)reached 46.34%.2)Eight groups in livelihood structures formed by forestry,traditional agriculture,and non-farm activities were significantly different in LVI,land resources(LR),social networks(SN),livelihood strategies(LS),housing characteristics(HC),and socio-demo-graphic profile(SDP).3)The livelihood vulnerability of the groups with highly engaged/reliance on jujube(Ziziphus jujuba)forest demonstrated more prominent livelihood vulnerability due to the increased precipitation and cold market,where the low-engaged with reliance type were significantly more vulnerable in LVI,SDP,LR,and HC.4)The threshold of behavioral triggers widely varied,and farmers dependent on forestry livelihoods showed negative coping ***,the cutting behavior was strongly associated with lagged years and government subsidies,guidance,and high returns of ***,the findings can provide guidance on the dir-ection of livelihood vulnerability mitigation and adaptive government management in ecologically restored *** issue of farmers’livelihood sustainability in the context of ecologi

关键词： livelihood vulnerability forestry coping behaviors climate change market change Jiaxian County

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Temporal and spatial evolution of global major grain trade patterns

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Journal of Integrative Agriculture 2024年第3期23卷 1075-1086页

作者： Ziqi Yin Jiaxuan Hu Jing Zhang Xiangyang Zhou Lingling Li Jianzhai Wu Agricultural Information Institute Chinese Academy of Agricultural SciencesBeijing 100081China Institute of Scientific and technical Information of China Beijing 100038China Zibo Agricultural Science research Institute Zibo 255000China Zibo Institute for Digital Agriculture and Rural research Zibo 255000China

The complex and volatile international landscape has significantly impacted global grain supply security. This study uses a complex network analysis model to examine the evolution and trends of the global major grain trade from 1990 to 2020, focusing on network topology, centrality ranking, and community structure. There are three major findings. First, the global major grain trade network has expanded in scale, with a growing emphasis on diversification and balance. During the study period, the United States, Canada, China, and Brazil were the core nodes of the network. Grain-exporting countries were mainly situated in Asia, the Americas, and Europe, and importing countries in Asia, Africa, and Europe. Second, a significant increase in the number of high centrality countries with high export capacity occurred, benefiting from natural advantages such as fertile land and favorable climates. Third, the main global grain trade network is divided into four communities, with the Americas-Europe community being the largest and most widespread. The formation of the community pattern was influenced by geographic proximity, driven by the core exporting countries. Therefore, the world needs to enhance the existing trade model, promote the multi-polarization of the grain trade network, and establish a global vision for the future community. Countries and regions should participate actively in global grain trade security governance and institutional reform, expand trade links with other countries, and optimize import and export policies to reduce trade risks.

关键词： grain trade pattern evolution complex network

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