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Perturbed low-thrust geostationary orbit transfer guidance via polynomial costate estimation

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Chinese Journal of Aeronautics 2024年第3期37卷 181-193页

作者： Zhao li Hengnian li fanghua JIANG Junfeng li State Key Laboratory of Astronautic Dynamics Xi’an Satellite Control CenterXi’an 710043China School of Aerospace Engineering Tsinghua UniversityBeijing 100084China

This paper proposes an optimal,robust,and efficient guidance scheme for the perturbed minimum-time low-thrust transfer toward the geostationary orbit.The Earth’s oblateness perturbation and shadow are taken into account.It is difficult for a Lyapunov-based or trajectory-tracking guidance method to possess multiple characteristics at the same time,including high guidance optimality,robustness,and onboard computational efficiency.In this work,a concise relationship between the minimum-time transfer problem with orbital averaging and its optimal solution is identified,which reveals that the five averaged initial costates that dominate the optimal thrust direction can be approximately determined by only four initial modified equinoctial orbit elements after a coordinate transformation.Based on this relationship,the optimal averaged trajectories constituting the training dataset are randomly generated around a nominal averaged trajectory.Five polynomial regression models are trained on the training dataset and are regarded as the costate estimators.In the transfer,the spacecraft can obtain the real-time approximate optimal thrust direction by combining the costate estimations provided by the estimators with the current state at any time.Moreover,all these computations onboard are analytical.The simulation results show that the proposed guidance scheme possesses extremely high guidance optimality,robustness,and onboard computational efficiency.

关键词： Low thrust Orbital transfer Trajectory optimization Guidance Indirect method Orbital averaging Machine learning Geostationary satellites

All boron-based 2D material as anode material in li-ion batteries

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Journal of Energy Chemistry 2018年第6期27卷 1651-1654页

作者： Ning Jiang Biao li fanghua Ning Dingguo Xia Beijing Key Lab of Theory and Technology for Advanced Batteries Materials College of Engineering Peking University Beijing 100874China

To design the high-energy-density li-ion batteries, the anode materials with high specific capacity haveattracted much attention. In this work, we adopt the first principles calculations to investigate the pos-sibility of a new two dimensional boron material, named Be, as anode material for li-ion batteries. Thecalculated results show that the maximum theoretical specific capacity of Bc is 1653mAh g-1 （liBl.s）.Additionally, the energy barriers of li ion and li vacancy diffusion are 330 meV and 110 meV, respec-tively, which imply fast charge and discharge ability for B6 as an anode material. The theoretical findingsreported in this work suggest that BG is a potential candidate as anode material of high-energy-density li-ion batteries.

关键词： Ali boron-based 2D material Anode materials li-ion batteries First principles calculations

Comparative transcriptomic insights into the mechanisms of electron transfer in Geobacter co-cultures with activated carbon and magnetite

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Science China(life Sciences) 2018年第7期61卷 787-798页

作者： Shiling Zheng fanghua liu Meng li Leilei Xiao Oumei Wang Key Laboratory of Coastal Biology and Biological Resources Utilization Yantai Institute of Coastal Zone ResearchChinese Academy of SciencesYantai 264003China Institute for Advanced Study Shenzhen UniversityShenzhen 518060China Binzhou Medical University Yantai 264003China

Both activated carbon and magnetite have been reported to promote the syntrophic growth of Geobacter metallireducens and Geobacter sulfurreducens co-cultures, the first model to show direct interspecies electron transfer (DIET); however, differential transcriptomics of the promotion on co-cultures with these two conductive materials are unknown. Here, the comparative transcriptomic analysis of G. metallireducens and G. sulfurreducens co-cultures with granular activated carbon (GAC) and magnetite was reported. More than 2.6-fold reduced transcript abundances were determined for the uptake hydrogenase genes of G. sulfurreducens as well as other hydrogenases in those co-cultures to which conductive materials had been added. This is consistent with electron transfer in G. metallireducens-G. sulfurreducens co-cultures as evinced by direct interspecies electron transfer (DIET). Transcript abundance for the structural component of electrically conductive pili (e-pili), PilA, was 2.2-fold higher in G. metallireducens, and, in contrast, was 14.9-fold lower in G. sulfurreducens in co-cultures with GAC than in Geobacters co-cultures without GAC. However, it was 9.3-fold higher in G. sulfurreducens in co-cultures with magnetite than in Geobacters co-cultures. Mutation results showed that GAC can be substituted for the e-pili of both strains but magnetite can only compensate for that of G. sulfurreducens, indicating that the e-pili is a more important electron acceptor for the electron donor strain of G. metallireducens than for G. sulfurreducens. Transcript abundance for G. metallireducens c-type cytochrome gene GMET_RS14535, a homologue to c-type cytochrome gene omcE of G. sulfurreducens was 9.8-fold lower in co-cultures with GAC addition, while that for OmcS of G. sulfurreducens was 25.1-fold higher in co-cultures with magnetite, than in that without magnetite. Gene deletion studies showed that neither GAC nor magnetite can completely substitute the cytochrome (OmcE homologous) of G. metallireducens but compensate for the

关键词：电子转移磁铁矿文化合作激活色素基因细胞色素碳

Recent advances in MXenes-based glucose biosensors

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中国化学快报:英文版 2023年第10期34卷 2-11页

作者： Shunyao Tian Meng Wang Paolo Fornasiero Xiaoyu Yang Seeram Ramakrishna Shih-Hsin Ho fanghua li State Key Laboratory of Urban Water Resource and Environment School of EnvironmentHarbin Institute of TechnologyHarbin 150090China Department of Chemical and Pharmaceutical Sciences University of TriesteVia L.Giorgieri 1Trieste 34127Italy Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali(INSTM) Unit of Triestevia L.Giorgieri 1Trieste 34127Italy School of Chemical and Environmental Engineering China University of Mining and TechnologyBeijing 100083China Center for Nanotechnology and Sustainability Department of Mechanical EngineeringNational University of SingaporeSingapore 119077Singapore

It is established that monitoring blood glucose on a daily basis is one of the most effective solutions to prevent and treat diabetes.Consequently,developing a glucose sensing platform with outstanding sensing performance occupies an indispensable position for the early diagnosis and risk assessment of diabetes.Recently,biosensor has been deemed as a promising apparatus to acquire the signals for glucose monitoring based on 2D materials.However,it is unsatisfied to deploy some materials widely as a result of some inherent defects.Carbon nanotubes have comparatively high toxicity.MoS_(2) with unfavourable biocompatibility are still arduously implemented on being functionalized.Fortunately,MXene,a brand-new and rapidly developing two-dimensional material,exhibits marvellous application potential in the domain of biosensing.Therefore,it has exerted tremendous attention from diverse scientific fields owning to its remarkable properties,such as excellent hydrophilicity,metal-like conductivity,abundant surface functional groups,unique layered structure,large specific surface area and remarkable biocompatibility.This review mainly focuses on the main synthetic route of MXenes,as well as the recent advancements of biosensors involving MXenes as an electrode modifier for glucose detection.In addition,the promising prospects and challenges of glucose sensing technology based on MXenes are also discussed.

关键词： MXenes Biosensor Mechanism Blood glucose Glucose detection

The impact of ocean data assimilation on seasonal predictions based on the National Climate Center climate system model

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Acta Oceanologica Sinica 2021年第5期40卷 58-70页

作者： Wei Zhou Jinghui li fanghua Xu Yeqiang Shu Yang Feng Equipment Public Service Center South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou 510301China Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou) Guangzhou 511458China Ministry of Education Key Laboratory for Earth System Modeling Department of Earth System ScienceTsinghua UniversityBeijing 100084China State Key Laboratory of Tropical Oceanography South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou 510301China

An ensemble optimal interpolation(EnOI)data assimilation method is applied in the BCCCSM1.1 to investigate the impact of ocean data assimilations on seasonal forecasts in an idealized twin experiment framework.Pseudoobservations of sea surface temperature(SST),sea surface height(SSH),sea surface salinity(SSS),temperature and salinity(T/S)profiles were first generated in a free model run.Then,a series of sensitivity tests initialized with predefined bias were conducted for a one-year period;this involved a free run(CTR)and seven assimilation runs.These tests allowed us to check the analysis field accuracy against the"truth".As expected,data assimilation improved all investigated quantities;the joint assimilation of all variables gave more improved results than assimilating them separately.One-year predictions initialized from the seven runs and CTR were then conducted and compared.The forecasts initialized from joint assimilation of surface data produced comparable SST root mean square errors to that from assimilation of T/S profiles,but the assimilation of T/S profiles is crucial to reduce subsurface deficiencies.The ocean surface currents in the tropics were better predicted when initial conditions produced by assimilating T/S profiles,while surface data assimilation became more important at higher latitudes,particularly near the western boundary currents.The predictions of ocean heat content and mixed layer depth are significantly improved initialized from the joint assimilation of all the variables.Finally,a central Pacific El Ni?o was well predicted from the joint assimilation of surface data,indicating the importance of joint assimilation of SST,SSH,and SSS for ENSO predictions.

关键词： global ocean data assimilation EnOI twin experiments

China’s local governments are combating COVID-19 with unprecedented responses——from a Wenzhou governance perspective

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Frontiers of Medicine 2020年第2期14卷 220-224页

作者： fanghua Gong Yong Xiong Jian Xiao li lin Xiaodong liu Dezhong Wang Xiaokun li School of Pharmaceutical Sciences Wenzhou Medical UniversityWenzhou 325035China Biomedicine Collaborative Innovation Center Wenzhou 325035China School of Public Health and Management Wenzhou Medical UniversityWenzhou 325035China

The COVID-19 caused by a novel strain of coronavirus has been spreading rapidly since its occurrence in December 2019.It is highly communicable through human-to-human transmission.China has been making unprecedented efforts in treating the confirmed cases,identifying and isolating their close contacts and suspected cases to control the source of infection and cut the route of transmission.China’s devotion in handling this epidemic has effectively and efficiently curbed communication domestically and across the border.Representative measures adopted by Wenzhou,the worst hit city out of Hubei Province,are examined to elucidate those massive undertakings with the aim of enhancing international understanding and building global rapport in fighting this evolving epidemic situation.

关键词： COVID-19 novel coronavirus pneumonia 2019-nCoV epidemic management

Electron Crystallography Study on the Structure Determination of Minute Crystals

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Science Foundation in China 2007年第1期15卷 24-28页

作者： Li Fanghua Institute of physics Chinese Academy of Sciences Beijing 100080 China

Introduction In the paper the research project 'Electron crys- tallography study on the structure determination of minute crystals' is briefly introduced. (1)Historical background and purpose Here minute crystals mean the crystals with di- mensions less than 1 micron.Hence,it is not suitable to determine the structures of such crystals by

关键词：电子晶体学晶体结构电子衍射高分辨率电子显微镜

An identifier-actor-optimizer policy learning architecture for optimal control of continuous-time nonlinear systems

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Science China(Physics,Mechanics & Astronomy) 2020年第6期63卷 42-53页

作者： lin Cheng ZhenBo Wang fanghua Jiang JunFeng li School of Aerospace Engineering Tsinghua UniversityBeijing 100084China Department of Mechanical Aerospaceand Biomedical EngineeringUniversity of TennesseeKnoxville TN 37996USA

An intelligent solution method is proposed to achieve real-time optimal control for continuous-time nonlinear systems using a novel identifier-actor-optimizer(IAO)policy learning architecture.In this IAO-based policy learning approach,a dynamical identifier is developed to approximate the unknown part of system dynamics using deep neural networks(DNNs).Then,an indirect-method-based optimizer is proposed to generate high-quality optimal actions for system control considering both the constraints and performance index.Furthermore,a DNN-based actor is developed to approximate the obtained optimal actions and return good initial guesses to the optimizer.In this way,the traditional optimal control methods and state-of-the-art DNN techniques are combined in the IAO-based optimal policy learning method.Compared to the reinforcement learning algorithms with actor-critic architectures that suffer hard reward design and low computational efficiency,the IAO-based optimal policy learning algorithm enjoys fewer user-defined parameters,higher learning speeds,and steadier convergence properties in solving complex continuous-time optimal control problems(OCPs).Simulation results of three space flight control missions are given to substantiate the effectiveness of this IAO-based policy learning strategy and to illustrate the performance of the developed DNN-based optimal control method for continuous-time OCPs.

关键词： continous-time nonlinear systems identifier-actor-optimizer architecture intelligent optimal control deep neural net-works

贫困家庭高中阶段教育选择:基于行为经济学的视角

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经济研究 2022年第12期57卷 180-200页

作者：李芳华肖寒澳大利亚新南威尔士大学经济学院 2052 中国人民大学应用经济学院 100872

本文使用河南省某样本县2012—2019年全部初中毕业生的中考成绩和高中录取数据,基于普通高中第一轮录取的分数线可能对学生家庭造成的关于“考上大学”主观概率的冲击,以及2016年针对建档立卡户的普通高中学费减免政策这一准自然实验,... 详细信息

本文使用河南省某样本县2012—2019年全部初中毕业生的中考成绩和高中录取数据,基于普通高中第一轮录取的分数线可能对学生家庭造成的关于“考上大学”主观概率的冲击,以及2016年针对建档立卡户的普通高中学费减免政策这一准自然实验,采用“断点-差分法”和“双重差分法”研究后发现:面对同等的来自“考上大学”概率的负面冲击,贫困家庭的学生有更大的概率选择职业高中;当贫困家庭普通高中学费减免(即普通高中的净收益增加)时,这一概率差大幅下降。在排除了贴现因子差异、收入水平上升、教育观念突变与信息不足四种可能的解释后,本文充分证明,造成贫困家庭与一般家庭高中选择差异的原因在于贫困家庭更高的风险厌恶程度。本研究厘清了高中阶段教育决策的微观机制,为研究低收入群体的风险偏好提供了来自中国的证据,对于普职协调发展和加强技能型人才培养具有鲜明政策启示。

关键词：贫困教育选择职业高中