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Structure and Inclination Angle of the Spiral Galaxy M31

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Chinese Physics Letters 2001年第10期18卷 1420-1422页

作者： ma Jun National Astronomical Observatories Chinese Academy of SciencesBeijing 100012 Joint Laboratory of Optical Astronomy Chinese Academy of SciencesBeijing 100012

The mathematical form, the symmetry of the spiral structure, and the projection of the galactic disc on the image of the spiral galaxy M31 have been directly studied. It is found that M31 has two symmetric arms, i.e. the pitch angles of the two arms are nearly equal;these are 7.7° and 8.0°, respectively. Using the method proposed in this letter, the inclination angle of the galactic disc ofM31 is also obtained, which is 77.5° and is in good agreement with previously published results.

关键词： M31 galactic galaxy

Cooperative effects of Mo,V and Zr additions on the microstructure and properties of multi-elemental Nb-Si based alloys

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Journal of materials Science & Technology 2023年第1期132卷 27-41页

作者： Rui ma Xiping Guo State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China

Eight multi-elemental Nb-Si-based alloys with various Mo,V and Zr contents were prepared by vacuum non-consumable arc *** cooperative alloying effects of Mo,V and Zr on the arc-melted and heat-treated microstructure,mechanical properties as well as oxidation resistance at 1250°C of the alloys were evaluated *** results show that except for adding Mo solely,additions of Mo,V and Zr change the microstructure from eutectic to *** additions of Mo,V and Zr suppress the formation ofα(Nb,X)5 Si 3(“X”represents the alloying elements that substitute for Nb in the lattices),whilst promoting the formation ofγ(Nb,X)5 Si *** heat treatment at 1450°C for 50 h promotes the formation of(Nb,X)3 Si phase in the Zr-containing *** with either Mo or Zr improves,and their composite additions more obviously improve the compressive yield strength at 1250°C as well as the microhardness ofγ(Nb,X)5 Si *** room temperature fracture toughness of the alloys is enhanced by sole and composite additions of V and Zr,while it is deteriorated by the addition of *** sole addition of Mo,V or Zr improves the oxidation resistance at 1250°C,the composite additions of V with Mo/Zr(especially V-Mo-Zr)degrade the oxidation resistance at 1250°C.

关键词： Multi-elemental Nb-Si based ultrahigh temperature alloy Alloying effect Microhardness Room temperature fracture toughness High-temperature compressive yield strength Oxidation resistance

bayesian compressive principal component analysis

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Frontiers of Computer Science 2020年第4期14卷 29-38页

作者： Di ma Songcan CHEN College of Computer Science and Technology Nanjing University of Aeronautics and AstronauticsNanjing211106China College of Computer Science and Technology Nanjing University of Aeronautics and AstronauticsMIIT Key Laboratory of Pattern Analysis and Machine IntelligenceNanjing211106China

Principal component analysis(PCA)is a widely used method for multivariate data analysis that projects the original high-dimensional data onto a low-dimensional subspace with maximum ***,in practice,we would be more likely to obtain a few compressed sensing(CS)measurements than the complete high-dimensional data due to the high cost of data acquisition and *** this paper,we propose a novel bayesian algorithm for learning the solutions of PCA for the original data just from these CS *** this end,we utilize a generative latent variable model incorporated with a structure prior to model both sparsity of the original data and effective dimensionality of the latent *** proposed algorithm enjoys two important advantages:1)The effective dimensionality of the latent space can be determined automatically with no need to be pre-specified;2)The sparsity modeling makes us unnecessary to employ multiple measurement matrices to maintain the original data space but a single one,thus being storage *** results on synthetic and real-world datasets show that the proposed algorithm can accurately learn the solutions of PCA for the original data,which can in turn be applied in reconstruction task with favorable results.

关键词： compressed sensing principal component analysis bayesian learning sparsity modeling

A Dynamic maintenance Strategy for Multi-Component Systems Using a Genetic Algorithm

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Computer Modeling in Engineering & Sciences 2023年第3期134卷 1899-1923页

作者： Dongyan Shi Hui ma Chunlong ma Department of Mechanical and Electrical Engineering.Harbin Engineer University Harbin150006China Department of Automotive Harbin Vocational&e Technical CollegeHarbin150000China

In multi-component systems,the components are dependent,rather than degenerating independently,leading to changes inmaintenance *** this situation,this study proposes a grouping dynamicmaintenance *** the structure of multi-component systems,the maintenance strategy is determined according to the importance of the *** strategy can minimize the expected depreciation cost of the system and divide the system into optimal groups that meet economic ***,multi-component models are ***,a failure probability model of multi-component systems is *** maintenance parameters in each maintenance cycle are updated according to the failure probability of the ***,the component importance indicator is introduced into the grouping model,and the optimization model,which aimed at a maximum economic profit,is established.A genetic algorithm is used to solve the non-deterministic polynomial(NP)-complete problem in the optimization model,and the optimal grouping is obtained through the initial grouping determined by random *** 11-component series and parallel system is used to illustrate the effectiveness of the proposed strategy,and the influence of the system structure and the parameters on the maintenance strategy is discussed.

关键词： Condition-based maintenance predictive maintenance maintenance strategy genetic algorithm NP-complete problems

Shamanskii-Like Levenberg-marquardt Method with a New Line Search for Systems of Nonlinear Equations

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Journal of Systems Science & Complexity 2020年第5期33卷 1694-1707页

作者： CHEN Liang ma Yanfang School of mathematical Sciences Huaibei Normal UniversityHuaibei 235000China School of Compuler Science and Technology Huaibei Normal UniversityHuaibei 235000China

To save the calculations of Jacobian,a multi-step Levenberg-marquardt method named Shamanskii-like LM method for systems of nonlinear equations was proposed by *** convergence properties have been proved by using a trust region technique under the local error bound ***,the authors wonder whether the similar convergence properties are still true with standard line searches since the direction may not be a descent *** this purpose,the authors present a new nonmonotone m-th order Armijo type line search to guarantee the global *** the same condition as trust region case,the convergence rate also has been shown to be m+1 by using this line search *** experiments show the new algorithm can save much running time for the large scale problems,so it is efficient and promising.

关键词： Armijo line search Levenberg-marquardt method local error bound condition systems of nonlinear equations unconstrained optimization

A data-efficient self-supervised deep learning model for design and characterization of nanophotonic structures

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Science China(Physics,Mechanics & Astronomy) 2020年第8期63卷 23-30页

作者： Wei ma Yongmin Liu College of Information Science and Electronic Engineering Zhejiang UniversityHangzhou 310027China Department of Mechanical and Industrial Engineering Northeastern UniversityMassachusetts 02115USA Department of Electrical and Computer Engineering Northeastern UniversityMassachusetts 02115USA

With its tremendous success in many machine learning and pattern recognition tasks,deep learning,as one type of data-driven models,has also led to many breakthroughs in other disciplines including physics,chemistry and material ***,the supremacy of deep learning over conventional optimization approaches heavily depends on the huge amount of data collected in advance to train the model,which is a common bottleneck of such a data-driven *** this work,we present a comprehensive deep learning model for the design and characterization of nanophotonic structures,where a self-supervised learning mechanism is introduced to alleviate the burden of data *** reflective metasurfaces as an example,we demonstrate that the self-supervised deep learning model can effectively utilize randomly generated unlabeled data during training,with the total test loss and prediction accuracy improved by about 15%compared with the fully supervised *** proposed self-supervised learning scheme provides an efficient solution for deep learning models in some physics-related tasks where labeled data are limited or expensive to collect.

关键词： nanophotonics metasurfaces self-supervised deep learning

On the Security of Homomorphic Encryption Schemes with Restricted Decryption Oracles

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Journal of Systems Science & Complexity 2024年第5期37卷 2240-2261页

作者： ma Guangsheng LI Hongbo School of mathematics and Physics North China Electric Power UniversityBeijing 100096China Academy of mathematics and Systems Science Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China

Fully homomorphic encryption(FHE)can be used for privacy-preserving aggregation of medical *** this typical application,the security against passive attacks has been well studied by Li and Micciancio(2021).In this paper,the authors further consider a“nearly passive”kind of attack,where the attacker may behave like a passive attacker in the view of the third-party *** capture the security against this hard-to-detect attack,the authors propose a new notion of IND-CPA^(rD)*** authors show that the standard LWE encryption and its related FHE schemes can not defend against IND-CPA^(rD)attack,even under a stricter rule limiting the content and number of queries made by the *** make the application of FHE schemes more secure,the authors discuss some possible modifications that may serve as countermeasures to IND-CPA^(rD)attack.

关键词： Homomorphic encryption privacy secure cloud computing security

Analytical solution of ground-borne vibration due to a spatially periodic harmonic moving load in a tunnel embedded in layered soil

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2023年第7期24卷 637-652页

作者： Lihui XU Meng ma Key Laboratory of Urban Underground Engineering of Ministry of Education Beijing Jiaotong UniversityBeijing 100044China School of Civil Engineering Beijing Jiaotong UniversityBeijing 100044China

In this study,we propose a novel coupled periodic tunnel–soil analytical model for predicting ground-borne vibrations caused by vibration sources in *** problem of a multilayered soil overlying a semi-infinite half-space was solved using the transfer matrix *** account for the interactions between the soil layer and tunnel structure,the transformation characteristics between cylindrical waves and plane waves were considered and used to convert the corresponding wave potentials into forms in terms of the Cartesian or cylindrical coordinate *** induced ground-borne vibration was obtained analytically by applying a spatially periodic harmonic moving load to the tunnel *** accuracy and efficiency of the proposed model were verified by comparing the results under a moving constant and harmonic load with those from previous ***,the response characteristics under a spatially periodic harmonic moving load were identified,and the effects of a wide range of factors on the responses were systematically *** numerical results showed that moving and Doppler effects can be caused by a spatially periodic harmonic moving *** critical frequency and frequency bandwidth of the response are affected by the load type,frequency,velocity,and wavenumber in one periodicity *** the tunnel depth is an efficient way to reduce ground-borne *** effect of vibration amplification on the free surface should be considered to avoid excessive vibration levels that disturb residents.

关键词： Coupled tunnel-soil model Spatially periodic load Transfer matrix method Wave transformation Parametric analysis

A review of recent advances in the effects of surface and interface properties on marine propellers

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Friction 2024年第2期12卷 185-214页

作者： manfu ZHU Liran ma State Key Laboratory of Tribology in Advanced Equipment Tsinghua UniversityBeijing 100084China

marine propellers are important propulsion devices for both surface ships and underwater *** severe environmental problems have required further performance enhancement for ***,traditional methods to improve propeller performances through geometrical and structural optimizations have been extensively investigated,while the underlying mechanisms of the effects of surface and interface properties on marine propellers are still far from being fully *** paper presented a comprehensive review of recent advances in the effects of surface and interface properties,such as surface roughness and surface wettability,on marine propellers with an emphasis on the significant improvements in both hydrodynamic and cavitation performances,hoping to arouse more in-depth investigations in the field of surface/interface science and technologies on marine propellers,and also promote the state-of-the-art technologies,such as superlubricity technology,into practical applications.

关键词： marine propellers hydrodynamics cavitation surface roughness surface wettability