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Astronomical time scale of the Turonian constrained by multiple paleoclimate proxies

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Geoscience Frontiers 2020年第4期11卷 1345-1352页

作者： chao ma Mingsong Li Department of Computer Science University of IdahoMoscowID83843USA Department of Geosciences The Pennsylvania State UniversityUniversity ParkPA16802USA

One of the clocks that record the Earth history is(quasi-) periodic astronomical *** cycles influence the climate that can be ultimately stored in sedimentary *** cracking these(quasi-) periodic sedimentation signals,high resolution astronomical time scale(ATS) can be *** proxies are widely used to extract astronomical *** different proxies may respond differently to astronomical signals and nonastronomical noises including tectonics,diagenesis,and measurement error among *** time scale constructed based on a single proxy where its signal-to-noise ratio is low may have uncertainty that is difficult to evaluate but can be revealed by utilizing other ***,we test eight astronomical age models using two astrochro no logical methods from four paleoclimate proxies(i.e.,color reflection L~* and b~*,natural gamma radiation,and bulk density) from the Turonian to the Coniacian of the Cretaceous Period at the Demerara Rise in the equatorial *** two astrochronological methods are time calibration using long eccentricity bandpass filtering(E1 bandpass) and tracking the long eccentricity from evolutive harmonic analysis(tracking EHA).The statistical mean and standard deviation of four age models from the four proxies are calculated to construct one integrated age model with age uncertainty in each *** demonstrate that extracting astronomical signals from multiple paleoclimate proxies is a valid method to estimate age model *** at the Cenomanian/Turonian boundary with an age of 93.9 ± 0.15 ma from biostratigraphy,the ages for CC11/CC12(calcareous nannofossil zones),Turonian/Coniacian(CC12/CC13),CC13/CC14,and Coniacian/Santonian boundaries are 91.25±0.20 ma,89.87±0.20 ma,86.36±0.33 ma,and 86.03±0.32 ma in E1 bandpass method,compared with 91.17±0.36 ma,89.74±0.38 ma,86.13±1.31 ma,and 85.80±1.33 ma respectively in tracking EHA *** results are consistent with previous st

关键词： Astrochronology Astronomical time scale Uncertainty Cretaceous Turonian Demerara rise

ACHIEVING ADVERSARIAL ROBUSTNESS REQUIRES AN ACTIVE TEACHER

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Journal of Computational mathematics 2021年第6期39卷 880-896页

作者： chao ma Lexing Ying Department of mathematics Stanford UniversityCaliforniaUSA

A new understanding of adversarial examples and adversarial robustness is proposedby decoupling the data generator and the label generator (which we call the teacher). Inour framework, adversarial robustness is a conditional concept—the student model is notabsolutely robust, but robust with respect to the teacher. Based on the new understanding, we claim that adversarial examples exist because the student cannot obtain sufficientinformation of the teacher from the training data. Various ways of achieving robustness iscompared. Theoretical and numerical evidence shows that to efficiently attain robustness,a teacher that actively provides its information to the student may be necessary.

关键词： Adversarial robustness Decoupled supervised learning Active teacher

Physical Properties of Polymers under Soft and Hard Nanoconfinement: A Review

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Chinese Journal of Polymer Science 2020年第6期38卷 565-578页

作者： Ming-chao ma Yun-Long Guo University o f Michigan-Shanghai Jiao Tong University Joint Institute Shanghai Jiao Tong UniversityShanghai 200240China School of materials Science and Engineering Shanghai Jiao Tong UniversityShanghai200240China

Polymeric materials under nanoconfinements have substantially deviated physical properties with respect to the bulk,especially glass transition temperature,physical aging,and crystallization *** we highlight the leading methods for creating various confinement *** these systems,recent advances on hard and soft confinement effect for glass transition,physical aging,mechanical properties and crystallization of polymers are reviewed in ***,as nanoconfined systems in extreme conditions are experimentally inaccessible,simulation results describing confinement effect on such systems are also discussed.

关键词： Nanoconfinement Glass transition temperature Physical aging Mechanical properties Crystallization

A high-order scheme based on lattice Boltzmann flux solver for viscous compressible flow simulations

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Applied mathematics and Mechanics(English Edition) 2022年第10期43卷 1601-1614页

作者： Jian QIN Jie WU chao ma State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and AstronauticsNanjing210016China Key Laboratory of Unsteady Aerodynamics and Flow Control Ministry of Industry and Information TechnologyNanjing University of Aeronautics and AstronauticsNanjing210016China Department of Aerodynamics Nanjing University of Aeronautics and AstronauticsNanjing210016China

In this paper,a high-order scheme based on the lattice Boltzmann flux solver(LBFS)is proposed to simulate viscous compressible *** flux reconstruction(FR)approach is adopted to implement the spatial *** LBFS is employed to compute the inviscid flux by using the local reconstruction of the lattice Boltzmann equation solutions from macroscopic flow ***,a switch function is used in LBFS to adjust the magnitude of the numerical ***,it is more beneficial to capture both strong shock waves and thin boundary ***,the viscous flux is computed according to the local discontinuous Galerkin *** typical compressible viscous problems,including manufactured solution case,lid-driven cavity flow,supersonic flow around a cylinder and subsonic flow over a NACA0012 airfoil,are simulated to demonstrate the accuracy and robustness of the proposed FR-LBFS.

关键词： high-order method flux reconstruction lattice Boltzmann flux solver(LBFS) viscous compressible flow

Optimal integrability of some system of integral equations

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Frontiers of mathematics in China 2014年第1期9卷 81-91页

作者： Yutian LEI chao ma Institute of mathematics School of Mathematical Sciences Nanjing Normal UniversityNanjing 210023 China Depar(ment of mathematics University of Colorado at Boulder Boulder CO 80309 USA

We obtain the optimal integrability for positive solutions of the Euler-Lagrange system of the weighted Hardy-Littlewood-Sobolev inequality in R^n ：{u（x）=1/｜x｜^α｜∫R^n v（y）^q｜y｜^β｜x-y｜^λdy,v（x）=1/｜x｜^β∫R^n u（y）^p｜y｜^α｜x-y｜^λdy.C. Jin and C. Li [Calc. Var. Partial Differential Equations, 2006, 26： 447-457] developed some very interesting method for regularity lifting and obtained the optimal integrability for p, q 〉 1. Here, based on some new observations, we overcome the difficulty there, and derive the optimal integrability for the case of p, q ≥1 and pq ≠1. This integrability plays a key role in estimating the asymptotic behavior of positive solutions when ｜x｜ →0 and when ｜x｜→∞.

关键词： Integral equation weighted Hardy-Littlewood-Sobolev inequality integrability interval

Intelligent optimization of seam-line finding for orthophoto mosaicking with LiDAR point clouds

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Journal of Zhejiang University-Science C(Computers and Electronics) 2011年第5期12卷 417-429页

作者： Hong-chao ma Jie SUN School of Remote Sensing Wuhan University Wuhan 430079 China State Key Lab for Surveying Mapping and Remote Sensing Wuhan University Wuhan 430079 China

A detailed study was carried out to find optimal seam-lines for mosaicking of images acquired by an airborne light detection and ranging (LiDAR) *** ground objects labeled as obstacles can be identified by delineating black holes from filtered point clouds obtained by filtering the raw laser scanning *** innovative A algorithm is proposed that can automatically make the seam-lines keep away from these obstacles in the registered *** method can intelligently optimize the selection of seam-lines and improve the quality of orthophotos.A simulated grid image was first used to analyze the effect of different heuristic functions on path *** subsets of LiDAR data from Xi'an,Dunhuang,and Changyang in Northwest China were obtained.A quantitative method including pixel intensity,hue,and texture was *** our proposed method,9.4%,8.7%,and 9.8% improvements were achieved in Dunhuang,Xi'an,and Changyang,respectively.

关键词： Light detection and ranging (EiDAR) Filter A* algorithm Mosaicking Seam-line

The NGC 7742 star cluster luminosity function： a population analysis revisited

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Research in Astronomy and Astrophysics 2018年第2期18卷 1-6页

作者： Richard de Grijs chao ma Kavli Institute for Astronomy & Astrophysics Peking University Beijing 100871 China Department of Astronomy Peking University Beijing 100871 China International Space Science Institute-Beijing Beijing 100190 China

We re-examine the properties of the star cluster population in the circumnuclear starburst ring in the face-on spiral galaxy NGC 7742, whose young cluster mass function has been reported to exhibit significant deviations from the canonical power law. We base our reassessment on the clusters＇ luminosi- ties （an observational quantity） rather than their masses （a derived quantity）, and confirm conclusively that the galaxy＇s starburst-ring clusters--and particularly the youngest subsample, log（t yr-1） ≤7.2- show evidence of a turnover in the cluster luminosity function well above the 90% completeness limit adopted to ensure the reliability of our results. This confirmation emphasizes the unique conundrum posed by this unusual cluster population.

关键词： globular clusters: general - galaxies: evolution - galaxies: individual (NGC 7742)--galaxies: star clusters: general -- galaxies: star formation

A comparative analysis of optimization and generalization properties of two-layer neural network and random feature models under gradient descent dynamics

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Science China mathematics 2020年第7期63卷 1235-1258页

作者： Weinan E chao ma Lei Wu Department of mathematics Princeton UniversityPrincetonNJ 08544USA The Program in Applied and Computational mathematics Princeton UniversityNJ 08544USA Beijing Institute of Big Data Research Beijing 100871China

A fairly comprehensive analysis is presented for the gradient descent dynamics for training two-layer neural network models in the situation when the parameters in both layers are *** initialization schemes as well as general regimes for the network width and training data size are *** the overparametrized regime,it is shown that gradient descent dynamics can achieve zero training loss exponentially fast regardless of the quality of the *** addition,it is proved that throughout the training process the functions represented by the neural network model are uniformly close to those of a kernel *** general values of the network width and training data size,sharp estimates of the generalization error are established for target functions in the appropriate reproducing kernel Hilbert space.

关键词： two-layer neural network random feature model Gram matrix generalization error

An overview of grid-forming technology and its application in new-type power system

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Global Energy Interconnection 2024年第5期7卷 541-552页

作者： Zehong Liu Yu Sun chao ma Global Energy Interconnection Development and Cooperation Organization Xicheng DistrictBeijing 100031P.R.China Southwest Electric Power Design Institute Co. Ltd.of China Power Engineering Consulting GroupP.R.China

To address the global climate crisis,achieving energy transitions is *** a new-type power system is a key measure to achieve CO_(2) emissions peaking and carbon *** core goal is to transform renewable energy resources into primary power *** large-scale integration of high proportions of renewable energy sources and power electronic devices will dramatically change the operational mechanisms and control strategies of power *** wind and solar converters mostly adopt the grid-following control mode,which leads to significant challenges in system security and stability as it is insufficient to support the frequency and voltage of the *** the other hand,grid-forming control technology(GFM)can provide voltage and frequency support for the system,and thus becomes an effective measure to improve the inertia and damping characteristics of power *** paper illustrates the principles,control strategies,equipment types,application scenarios,and project implementation of grid-forming *** simulation and analysis based on a renewable-dominated real new-type power system show that GFM can significantly enhance the frequency and voltage support capacity of the power system,improve renewable energy accommodation capacity and grid transmission capacity under weak grid conditions,and play an important role in enhancing the stability and power supply reliability of renewable-dominated new-type power systems.

关键词： New-type power system Renewable energy resources Grid-Forming(GFM) Control strategy