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Journal of Materials Science & Technology 2019年第5期35卷 946-956页

作者： Qing Liu Hejun Li Yulei Zhang Zhigang Zhao State Key Laboratory of Solidification Processing Carbon/Carbon Composites Technology Research Center Northwestern Polytechnical University

Multi-layer connected self-organizing feature maps(SOFMs) and the associated learning procedure were proposed to achieve efficient recognition and clustering of messily grown nanowire morphologies. The network is made up by several paratactic 2-D SOFMs with inter-layer connections. By means of Monte Carlo simulations, virtual morphologies were generated to be the training samples. With the unsupervised inner-layer and inter-layer learning, the neural network can cluster different morphologies of messily grown nanowires and build connections between the morphological microstructure and geometrical features of nanowires within. Then, the as-proposed networks were applied on recognitions and quantitative estimations of the experimental morphologies. Results show that the as-trained SOFMs are able to cluster the morphologies and recognize the average length and quantity of the messily grown nanowires within. The inter-layer connections between winning neurons on each competitive layer have significant influence on the relations between the microstructure of the morphology and physical parameters of the nanowires within.

关键词： Artificial neural networks Self-organizing feature maps Monte Carlo simulation Pattern recognition Messily grown nanowire morphologies

Hopf-flip bifurcation of high dimensional maps and application to vibro-impact systems

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Acta Mechanica Sinica 2005年第4期21卷 402-410页

作者： Jianhua Xie Wangcai Ding E.H. Dowell L. N. Virgin Department of Applied Mechanics and Engineering Southwest Jiaotong University Chengdu 610031 China School of Mechanical Engineering Lanzhou Jiaotong UniversityLanzhou 730070 China School of Engineering.Duke University. Durham NC27708-0300USA

This paper addresses the problem of Hopf-flip bifurcation of high dimensional maps. Using the center manifold theorem, we obtain a three dimensional reduced map through the projection technique. The reduced map is further transformed into its normal form whose coefficients are determined by that of the original system. The dynamics of the map near the Hopf-flip bifurcation point is approximated by a so called “time-2τ^2 map” of a planar autonomous differential equation. It is shown that high dimensional maps may result in cycles of period two, tori T^1 （Hopf invariant circles）, tori 2T^1 and tori 2T^2 depending both on how the critical eigenvalues pass the unit circle and on the signs of resonant terms＇ coefficients. A two-degree-of-freedom vibro-impact system is given as an example to show how the procedure of this paper works. It reveals that through Hopf-flip bifurcations, periodic motions may lead directly to different types of motion, such as subharmonic motions, quasi-periodic motions, motions on high dimensional tori and even to chaotic motions depending both on change in direction of the parameter vector and on the nonlinear terms of the first three orders.

关键词： maps Vibro-impact dynamics Hopf-flip bifurcation Torus Chaos

Efficient ray casting of volumetric images using distance maps for empty space skipping

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Computational Visual Media 2020年第1期6卷 53-63页

作者： Lachlan J.Deakin Mark A.Knackstedt Australian National University Canberra2601Australia

Volume and isosurface rendering are methods of projecting volumetric images to two dimensions for *** methods are common in medical imaging and scientific ***-mounted optical see-through displays have recently become an affordable technology and are a promising platform for volumetric image *** displayed on a head-mounted display must be presented at a high frame rate and with low latency to compensate for head *** latency can be jarring and may cause cybersickness which has similar symptoms to motion *** images can be very computationally expensive to render as they often have hundreds of millions of scalar ***,certain materials in images such as air surrounding an object boundary are often made transparent and need not be sampled,which improves rendering *** our previous work we introduced a novel ray traversal technique for rendering large sparse volumetric images at high frame *** method relied on the computation of an occupancy and distance map to speed up ray traversal through empty *** this work we achieve higher frame rates than our previous work with an improved method of resuming empty space skipping and the use of anisotropic Chebyshev distance *** optimised algorithm for computing Chebyshev distance maps on a graphical processing unit is introduced supporting real-time transfer function editing.

关键词： ray casting volume rendering isosurface rendering distance maps

Adaptable physics-based super-resolution for electron backscatter diffraction maps

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npj Computational Materials 2022年第1期8卷 2444-2452页

作者： Devendra K.Jangid Neal R.Brodnik Michael G.Goebel Amil Khan SaiSidharth Majeti McLean P.Echlin Samantha H.Daly Tresa M.Pollock B.S.Manjunath Electrical and Computer Engineering University California Santa BarbaraSanta Barbara93106-5050CAUSA Mechanical Engineering University California Santa BarbaraSanta Barbara93106-5050CAUSA Computer Science University California Santa BarbaraSanta Barbara93106-5050CAUSA Materials Department University California Santa BarbaraSanta Barbara93106-5050CAUSA

In computer vision,single-image super-resolution(SISR)has been extensively explored using convolutional neural networks(CNNs)on optical images,but images outside this domain,such as those from scientific experiments,are not well *** data is often gathered using non-optical methods,which alters the metrics for image *** such example is electron backscatter diffraction(EBSD),a materials characterization technique that maps crystal arrangement in solid materials,which provides insight into processing,structure,and property *** present a broadly adaptable approach for applying state-of-art SISR networks to generate super-resolved EBSD orientation *** approach includes quaternion-based orientation recognition,loss functions that consider rotational effects and crystallographic symmetry,and an inference pipeline to convert network output into established visualization formats for EBSD *** ability to generate physically accurate,high-resolution EBSD maps with super-resolution enables high-throughput characterization and broadens the capture capabilities for three-dimensional experimental EBSD datasets.

关键词： maps resolution networks

Deformation behavior and processing maps during isothermal compression of TC21 alloy

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Rare Metals 2017年第2期36卷 86-94页

作者： Jun Gao Miao-Quan Li Ge-Jun Liu Shao-Fei Liu School of Materials Science and Engineering Northwestern Polytechnical UniversityXi'an 710072China

In this study,isothermal compression tests were conducted at a Gleeble-1500 simulator at deformation temperatures ranging from 1073 to 1283 K,strain rates ranging from 0.01 to 5.00 s^（-1）,and height reductions ranging from 20%to 60%.The flow stress and apparent activation energy for deformation and constitutive equation were used to characterize the deformation behavior of TC21 alloy during the isothermal *** processing maps combined microstructure observations were established based on dynamic material model（DMM） over a range of strain rates and *** results show that an initial yield drop is observed above 1203 K or at higher strain rates ranging from 1.00 to 5.00 s^-1,and oscillatory flow curves are presented particularly at a strain rate of 5.00 s^-*** has some influence on the apparent activation energy for deformation during the isothermal compression of TC21 *** Q-values and microstructure observation confirm that dynamic recrystallization（DRX） occurs in the β single-phase *** constitutive equation during the isothermal compression of TC21 alloy is developed using the Zener-Hollomon parameter in the exponent-type *** maximum and minimum relative errors between the calculated and the experimental flow stress are 14.1%and 0.3%,*** peak efficiency of power dissipation at a strain of 0.7 is about 0.51 occurring at a deformation temperature of 1073 K and strain rate of 0.01 s^-1,corresponding to an optimal deformation condition of TC21 alloy.

关键词： TC21 alloy Flow stress Apparent activation energy for deformation Constitutive equation Processing maps

Rational holomorphic maps from B^2 into B^N with degree 2

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Science China Mathematics 2006年第11期49卷 1504-1522页

作者： CHEN Zhihua, Jl Shanyu & XU Dekang Department of Mathematics, Tongji University, Shanghai 200092, China Department of Mathematics, University of Houston, Houston, TX 77204, USA Department of Mathematics Tongji University Shanghai China Department of Mathematics University of Houston Houston USA

Rational proper holomorphic maps from the unit ball in C2 into the unit ball CN with degree 2 are studied. Any such map must be equivalent to one of the four types of maps.

关键词： rational holomorphic maps between balls.

Inferring Spatial Distribution Patterns in Web maps for Land Cover Mapping

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Computer Modeling in Engineering & Sciences 2019年第5期119卷 311-330页

作者： Yang Liu Zeying Lan Hanfa Xing Guangzhou Urban Planning&Design Survey Research Institute Guangzhou510060China College of Geography and Environment Shandong Normal UniversityJinan250300China School of Geography Sciences South China Normal UniversityGuangzhou510631China School of management Guangdong University of TechnologyGuangzhou510520China

Web maps represent an effective source for land cover mapping in capturing human ***,due to spatial heterogeneity,previous research has mainly focused on generating land cover maps in partial *** spatial distribution patterns in Web maps may provide an alternative perspective on improving map production on a larger *** paper represents a novel approach to investigating the spatial distribution in Web maps for land cover ***,linear features from Web maps are utilised to delineate parcels with insufficient Web map data for ***,spatial factors are constructed from point and polygon features to identify the spatial variety of Web maps,with an artificial neural network classifier being adopted to classify land cover *** cover mapping is finally proposed by combining classified parcels and existing polygon *** proposed method is applied in Guangzhou,Guangdong Province,using a Web map from *** results show an approximately 88%classification accuracy and an overall mapping accuracy of 85.06%.The results indicate that the proposed approach has the potential to be utilised in land cover mapping,and the constructed spatial factors are effective at characterising land cover information.

关键词： Land cover mapping Web maps spatial distribution spatial factors ANN classifier

Block maps and Fourier analysis

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Science China Mathematics 2019年第8期62卷 1585-1614页

作者： Chunlan Jiang Zhengwei Liu Jinsong Wu Department of Mathematics Hebei Normal University Shijiazhuang 050024 China Department of Physics and Department of Mathematics Harvard University Cambridge MA 02138 USA Institute for Advanced Study in Mathematics Harbin Institute of Technology Harbin 150001 China

We introduce block maps for subfactors and study their dynamic systems. We prove that the limit points of the dynamic system are positive multiples of biprojections and zero. For the Z2 case, the asymptotic phenomenon of the block map coincides with that of the 2 D Ising model. The study of block maps requires a further development of our recent work on the Fourier analysis of subfactors. We generalize the notion of sum set estimates in additive combinatorics for subfactors and prove the exact inverse sum set theorem. Using this new method, we characterize the extremal pairs of Young’s inequality for subfactors, as well as the extremal operators of the Hausdorff-Young inequality.

关键词： subfactors Fourier analysis planar algebras block maps quantum groups

A semantic geographical knowledge wiki system mashed up with Google maps

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Science China(Technological Sciences) 2010年第S1期53卷 52-60页

作者： GAO Yong,GAO Song,LI RunQiang & LIU YuInstitute of Remote Sensing and Geographical Information Systems,Peking University,Beijing 100871,China Institute of Remote Sensing and Geographical Information Systems Peking University Beijing China

A wiki system is a typical Web 2.0 application that provides a bi-directional platform for users to collaborate and share much useful information ***,computers cannot well understand the wiki pages in plain *** user-generated geographical content via wiki systems cannot be manipulated properly and efficiently unless the geographical semantics is explicitly *** this paper,a geographical semantic wiki system,Geo-Wiki,is introduced to solve this ***-Wiki is a semantic geographical knowledge-sharing web system based on geographical ontologies so that computers can parse and storage the multi-source geographical ***,Geo-Wiki mashed up with map services enriches the representation and helps users to find spatial distribution patterns,and thus can serve geospatial decision-making by customizing the Google maps APIs.

关键词： geo-ontology semantic wiki mashup Google maps

POSITIVE maps CONSTRUCTED FROM PERMUTATION PAIRS

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Acta Mathematica Scientia 2019年第1期39卷 148-164页

作者： Jinchuan HOU Haili ZHAO School of Mathematics Taiyuan University of Technology

A property(C) for permutation pairs is introduced. It is shown that if a pair{π_1, π_2} of permutations of(1,2,…,n) has property(C),then the D-type map Φ_(π_1,π_2) on n× n complex matrices constructed from {π_1,π_2} is positive. A necessary and sufficient condition is obtained for a pair {π_1,π_2} to have property(C),and an easily checked necessary and sufficient condition for the pairs of the form {π~p,π~q} to have property(C) is given, whereπ is the permutation defined by π(i) = i + 1 mod n and 1≤ p < q≤ n.

关键词： matrix algebras positive linear maps permutations quantum information