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Autonomous navigation method of satellite constellation based on adaptive forgetting factors

Chinese Journal of Aeronautics 2024年第7期37卷 317-332页

作者： Dong WANG Jing YANG kai XIONG School of Automation Science and Electrical Engineering Beihang UniversityBeijing 100191China Science and Technology on Space Intelligent Control Laboratory Beijing Institute of Control EngineeringBeijing 100094China

To address the problem that model uncertainty and unknown time-varying system noise hinder the filtering accuracy of the autonomous navigation system of satellite constellation,an autonomous navigation method of satellite constellation based on the Unscented Kalman Filter with Adaptive Forgetting Factors(UKF-AFF)is *** process noise covariance matrix is estimated online with the strategy that combines covariance matching and adaptive adjustment of forgetting *** adaptive adjustment coefficient based on squared Mahalanobis distance of state residual is employed to achieve online regulation of forgetting factors,equipping this method with more *** intersatellite direction vector obtained from photographic observations is introduced to determine the constellation satellite orbit together with the distance measurement to avoid rank deficiency *** that the number of available measurements varies online with intersatellite visibility in practical applications such as time-varying constellation configurations,the smooth covariance matrix of state correction determined by innovation and gain is adopted and constructed *** analysis of the proposed method is also *** effectiveness of the proposed method is verified by the Monte Carlo simulation and comparison *** estimation accuracy of constellation position and velocity of UKF-AFF is improved by 3.%and 44%respectively compared to those of the extended Kalman filter,and the method proposed is also better than other several adaptive filtering methods in the presence of significant model uncertainty.

关键词： Constellation autonomous navigation Unscented Kalman filter Adaptive forgetting factor Model uncertainty Stability analysis

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Robustness of the octupole collectivity in 144Ba within the cranking covariant density functional theory in 3. lattice

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Nuclear Science and Techniques 2024年第8期35卷 124-131页

作者： Ze‑kai Li Yuan‑Yuan Wang Mathematics and Physics Department North China Electric Power UniversityBeijing 102206China Hebei Key Laboratory of Physics and Energy Technology North China Electric Power UniversityBaoding 071000China

The octupole deformation and collectivity in octupole double-magic nucleus 144Ba are investigated using the Cranking covariant density functional theory in a three-dimensional lattice *** reduced B(E3.transition probability is implemented for the first time in semiclassical approximation based on the microscopically calculated electric octupole *** available data,including the I-ωrelation and electric transitional probabilities B(E2)and B(E3.are well ***,it is shown that the ground state of 144Ba exhibits axial octupole and quadrupole deformations that persist up to high spins(I≈24h).

关键词： Octupole collectivity Cranking covariant density functional theory Rotational spectrum Electric transitional probabilities

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Impact of the Political Risk on Food Reserve Ratio:Evidence Across Countries

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Journal of Systems Science & Complexity 2024年第5期37卷 2071-2103页

作者： XING kai LI Shang YANG Xiaoguang School of Economics&Management Nanchang UniversityNanchang330031China Department of Statistics and Data Science National University of Singapore119077Singapore Academy of Mathematics and Systems Science Chinese Academy of SciencesBeijing100190China University of Chinese Academy of Sciences Beijing100190China

Using an unbalanced panel data covering 75 countries from 1991 to 2019,the authors explore how the political risk impacts on food reserve *** empirical findings show that an increasing political risk negatively affects food reserve ratio,and the same effects hold for both internal risk and external ***,the authors find that the increasing external or internal risks both negatively affect food production and food exports,but external risk does not significantly impact food imports and it positively impacts food consumption,while internal risk negatively impacts food imports and food *** results suggest that most governments have difficulty raising subsequent food reserve ratios in face of an increasing political risk,no matter if it is an internal risk or an external risk although the mechanisms behind the impacts are different.

关键词： External risk food reserve ratio internal risk political risk

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Fusion of Spiral Convolution-LSTM for Intrusion Detection Modeling

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Computers, Materials & Continua 2024年第5期79卷 2315-2329页

作者： Fei Wang zhen Dong School of Cyberspace Security Gansu University of Political Science and LawLanzhou73000China

Aiming at the problems of low accuracy and slow convergence speed of current intrusion detection models,SpiralConvolution is combined with Long Short-Term Memory Network to construct a new intrusion detection *** dataset is first preprocessed using solo thermal encoding and normalization *** the spiral convolution-Long Short-Term Memory Network model is constructed,which consists of spiral convolution,a two-layer long short-term memory network,and a *** is shown through experiments that the model is characterized by high accuracy,small model computation,and fast convergence speed relative to previous deep learning *** model uses a new neural network to achieve fast and accurate network traffic intrusion *** model in this paper achieves 0.9706 and 0.843. accuracy rates on the NSL-KDD dataset and the UNSWNB-15 dataset under five classifications and ten classes,respectively.

关键词： Intrusion detection deep learning spiral convolution long and short term memory networks 1D-spiral convolution

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First Passage Density of Brownian Motion with Two-sided Piecewise Linear Boundaries

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Acta Mathematica Sinica,English Series 2024年第6期40卷 1505-1520页

作者： zhen YU Mao Zai TIAN Center for Applied Statistics School of StatisticsRenmin University of ChinaBeijing 100872P.R.China School of Mathematics and Data Science Changji UniversityChangji 831100P.R.China

The first passage time has many applications in fields like finance,econometrics,statistics,and ***,explicit formulas for the first passage density have only been obtained for a few *** paper derives an explicit formula for the first passage density of Brownian motion with twosided piecewise continuous boundaries which may have some points of *** are used to obtain a simplified formula for estimating the first passage ***,the results are also generalized to the case of two-sided general nonlinear *** can be easily carried out with Monte Carlo method and it is demonstrated for several typical two-sided boundaries that the proposed approximation method offers a highly accurate approximation of first passage density.

关键词： Boundary non-crossing probability first density passage density two-sided piecewise continuous boundaries Brownian motion

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Bivariate attribution of the compound hot and dry summer of 2022 on the Tibetan Plateau

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Science China Earth Sciences 2024年第7期67卷 2122-2136页

作者： Baiquan ZHOU Panmao ZHAI zhen LIAO State Key Laboratory of Severe Weather Chinese Academy of Meteorological SciencesChina Meteorological AdministrationBeijing 100081China

The extraordinarily high temperatures experienced during the summer of 2022 on the Tibetan Plateau(TP)demand attention when compared with its typical climatic *** absence of precipitation alongside the elevated temperatures resulted in 2022 being the hottest and driest summer on record on the TP since at least *** the susceptibility of the TP to climate change,this study employed large-ensemble simulations from the HadGEM3.A-N216 attribution system,together with a copula-based joint probability distribution,to investigate the influence of anthropogenic forcing,primarily global greenhouse gas emissions,on this unprecedented compound hot and dry event(CHDE).Findings revealed that the return period for the 2022 CHDE on the TP exceeds 4000 years,as determined from the fitted joint distributions derived using observational data spanning *** CHDE was directly linked to large-scale circulation anomalies,including the control of equivalent-barotropic high-pressure anomalies and the northward displacement of the subtropical westerly jet ***,anthropogenic forcing has,to some extent,promoted the surface warming and increased variability in precipitation on the TP in summer,establishing conditions conducive for the 2022 CHDE from a long-term climate change *** return period for a 2022-like CHDE on the TP was estimated to be approximately 283.years(142-613.years)by the large ensemble forced by both anthropogenic activities and natural ***,ensemble simulations driven solely by natural forcing indicated that the likelihood of occurrence of a 2022-like CHDE was almost *** outcomes underscore that the contribution of anthropogenic forcing to the probability of a 2022-like CHDE was 100%,implying that without anthropogenically induced global warming,a comparable CHDE akin to that observed in 2022 on the TP would not be possible.

关键词： Compound hot and dry event Tibetan Plateau Bivariate event attribution Anthropogenic forcing

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纳米多孔介质中的流体流动

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Engineering 2024年第1期32卷 138-151页

作者： Weiyao Zhu Bin Pan zhen Chen Wengang Bu Qipeng Ma kai Liu Ming Yue School of Civil and Resource Engineering University of Science and Technology BeijingBeijing 100083China

Fluid flow at nanoscale is closely related to many areas in nature and technology(e.g.,unconventional hydrocarbon recovery,carbon dioxide geo-storage,underground hydrocarbon storage,fuel cells,ocean desalination,and biomedicine).At nanoscale,interfacial forces dominate over bulk forces,and nonlinear effects are important,which significantly deviate from conventional *** the past decades,a series of experiments,theories,and simulations have been performed to investigate fluid flow at nanoscale,which has advanced our fundamental knowledge of this ***,a critical review is still lacking,which has seriously limited the basic understanding of this *** herein,we systematically review experimental,theoretical,and simulation works on single-and multi-phases fluid flow at *** also clearly point out the current research gaps and future *** insights will promote the significant development of nonlinear flow physics at nanoscale and will provide crucial guidance on the relevant areas.

关键词： Transport in nanoporous media Multi-phase fluid dynamics Nonlinear flow mechanisms Nonlinear flow conservation equations Interfacial forces Molecular dynamics simulation

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Revisiting the island of hexadecapoledeformation nuclei in the A≈150 mass region:focusing on the model application to nuclear shapes and masses

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Communications in Theoretical Physics 2024年第2期76卷 74-88页

作者： Xiao-Yang Wei Hua-Lei Wang zhen-zhen Zhang Min-Liang Liu School of Physics and Microelectronics Zhengzhou UniversityZhengzhou 450001China Key Laboratory of High Precision Nuclear Spectroscopy Institute of Modern PhysicsChinese Academy of SciencesLanzhou 730000China School of Nuclear Science and Technology University of Chinese Academy of SciencesBeijing 100049China

Based on the potential-energy-surface calculation,the impact of different deformation degrees of freedom on a single-particle structure and binding energies in nuclei around^(152)Nd,located on one of the hexadecapole-deformation islands,is analyzed in a multi-dimensional deformation *** energy maps,curves and tables are presented to indicate nuclear *** calculated equilibrium deformations and binding energies with different potential parameters are compared with experimental data and other *** is found that the inclusion of the hexadecapole deformations,especially the axial one,can improve the theoretical description of both nuclear shapes and *** addition,our calculated potential-energy curve shows that a critical deformation-point,β_(2)≈0.4,exists—the triaxial(hexadecapole)deformation effect can be neglectable but the hexadecapole(triaxial)one plays an important role before(after)such a critical point.

关键词： hexadecapole deformation binding energy potential-energy-surface calculation nuclear property

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Corrosion behavior of Gd_(2)Zr_(2)O_(7)thermal barrier coatings under Fe-containing environmental sediment attack

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Journal of Advanced Ceramics 2024年第4期13卷 447-462页

作者： Lei Guo Yanyan Li kai Yan School of Materials Science and Engineering Tianjin UniversityTianjin 300072China Tianjin Key Laboratory of Advanced Joining Technology Key Lab of Advanced Ceramics and Machining Technology of Ministry of EducationTianjin 300072China Key Laboratory of Special Equipment Safety and Energy-saving for State Market Regulation China Special Equipment Inspection&Research InstituteBeijing 100029China

Environmental sediments mainly consisting of CaO–MgO–Al_(2)O_(3.–SiO_(2)(CMAS)corrosion are a serious threat to thermal barrier coatings(TBCs),in which Fe element is usually ***_(2)Zr_(2)O_(7)TBCs are famous for their excellent CMAS *** this study,the characteristics of Fe-containing environmental sediments(CMAS-Fe)and their corrosiveness to Gd_(2)Zr_(2)O_(7)coatings were *** types of CMAS-Fe glass with different Fe contents were *** melting points were measured to be 13.2–13.4℃,and the high-temperature viscosity showed a decreasing trend with increasing Fe *** corrosion behavior of four types of CMAS-Fe to Gd_(2)Zr_(2)O_(7)coatings at 13.0℃was *** the initial corrosion stage(0.1 h),anorthite was precipitated in CMAS-Fe with a high Ca:Si ratio,while Fe-garnet was formed in the melt with the highest Fe *** the corrosion time resulted in the formation of a reaction layer,which exhibited an interpenetrating network composed of Gd-oxyapatite,ZrO_(2),and residual *** spinel was precipitated within the reaction *** 1 h or even longer time,the reaction layers tended to be stable and compact,which had comparable hardness and fracture toughness to those of Gd_(2)Zr_(2)O_(7)*** the cyclic CMAS-Fe attack,the residual CMAS-Fe in the interpenetrating network provided a pathway for the redeposited CMAS-Fe infiltration,resulting in the continuous growth of the reaction *** a result,the Gd_(2)Zr_(2)O_(7)coatings had a large consumption in the thickness,degrading the coating ***,the Gd_(2)Zr_(2)O_(7)coatings exhibit unsatisfactory corrosion resistance to CMAS-Fe attack.

关键词： thermal barrier coatings(TBCs) Gd_(2)Zr_(2)O_(7) Fe-containing CaO-MgO-Al2O3.SiO_(2)(CMAS) corrosion resistance reaction layer

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Nuclei-rich galvanizing strategy for suppressing zinc dendrite growth

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Rare Metals 2024年第8期43卷 4016-4018页

作者： Hai-Xia Wu kai-Lu Guo College of Chemistry and Chemical Engineering Henan Key Laboratory of Function-Oriented Porous MaterialsLuoyang Normal UniversityLuoyang 471934China

The uncontrolled growth of zinc dendrites on zinc anode hinders the application of zinc ion *** solve this problem,Lu's group proposed a nuclei-rich galvanizing strategy for suppressing the zinc dendrite *** allows the nuclei-rich zinc electrode to cycle steadily for1200 h and have a high Coulombic efficiency of 99.7%at15 mA·cm^(-2)with a deposited amount of 10 mAh·cm^(-2).Moreover,the Zn-MnO_(2) battery with a low N/P ratio of 1.9exhibited sustained cycling life.

关键词： cycling sustained battery

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