检索结果-内蒙古大学图书馆

SSRN 2023年

作者： Sun, Shiyao Fu, Chong Xu, Sen Wen, Yingyou Ma, Tao School of Computer Science and Engineering Northeastern University Shenyang110819 China Key Laboratory of Intelligent Computing in Medical Image Ministry of Education Northeastern University Shenyang110819 China Engineering Research Center of Security Technology of Complex Network System Ministry of Education China General Hospital of Northern Theatre Command Shenyang110016 China Medical Imaging Research Department Neusoft Research of Intelligent Healthcare Technology Co. Ltd. Shenyang China Dopamine Group Ltd. Auckland1542 New Zealand

Segmenting accurate thyroid nodules in medical ultrasound images is always non-trivial due to the large variation in size, shape and texture of nodules, and also the presence of surrounding tissues and organs with similar intensity values. Existing algorithms solve this by designing multi-scale spatial context modeling modules and introducing the emerging self-attention based paradigm, while failing to learn the class-wise relational context around nodules. To this end, we propose a novel coarse-to-fine framework, namely, CRSANet, which leverages both class-wise relational context and spatial multi-scale context for comprehensive context perception. Specifically, we first introduce the concept of Class Representations, which describe the overall representation of thyroid nodules in ultrasound images from a categorical perspective. Secondly, we propose a backbone-free dual-branch Class Representation Self-Attention Module (CRSA) to refine the coarse segmentation results from segmentation backbones. Concretely, Fine Class Region (FCR) branch is proposed to impose consistency between pixels and their corresponding Class Representations to correct the wrongly classified pixels. Meanwhile, Class Contextual Representation (CCR) branch is introduced to enhance the ability of pixel representations with the corresponding Class Representations. We evaluate the effectiveness and generality of CRSANet using three types of backbone networks. In the experiments, our proposed U-CRSANet achieves a mIoU of 78.86% and 81.35%, an accuracy of 97.11% and 98.63%, a Dice value of 74.26% and 87.57%, respectively, which outperforms most state-of-the-art methods on the public DDTI and TN-SCUI datasets. © 2023, The Authors. All rights reserved.

关键词： Pixels

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From first- to second-order phase transitions in hybrid improper ferroelectrics through entropy stabilization

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Physical Review B 2020年第1期102卷 014101-014101页

作者： Fernando Pomiro Chris Ablitt Nicholas C. Bristowe Arash A. Mostofi Choongjae Won Sang-Wook Cheong Mark S. Senn Department of Chemistry University of Warwick Gibbet Hill Coventry CV4 7AL United Kingdom School of Physical Sciences University of Kent Canterbury CT2 7NH United Kingdom Departments of Materials and Physics and the Thomas Young Centre for Theory and Simulation of Materials Imperial College London Exhibition Road London SW7 2AZ United Kingdom Laboratory for Pohang Emergent Materials and Max Planck POSTECH Center for Complex Phase Materials Pohang University of Science and Technology Pohang Korea Rutgers Center for Emergent Materials and Department of Physics and Astronomy Rutgers University Piscataway New Jersey 08854 USA

Hybrid improper ferroelectrics (HIFs) have been studied intensively over the past few years to gain an understanding of their temperature-induced phase transitions and ferroelectric switching pathways. Here we report a switching from a first- to a second-order phase transition pathway for HIFs Ca3−xSrxTi2O7, which is driven by the differing entropies of the phases that we identify as being associated with the dynamic motion of octahedral tilts and rotations. A greater understanding of the transition pathways in this class of layered perovskites, which host many physical properties that are coupled to specific symmetries and octahedral rotation and tilt distortions—such as superconductivity, negative thermal expansion, fast ion conductivity, ferroelectricity, among others—is a crucial step in creating novel functional materials by design.

关键词： Crystal structure Ferroelectricity First order phase transitions First-principles calculations Order parameters Second order phase transitions Ferroelectrics Density functional calculations X-ray powder diffraction

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Influence of Stagnant Zones on Transient and Asymptotic Dispersion in Macroscopically Homogeneous Porous Media

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Physical Review Letters 2002年第23期88卷 234501-234501页

作者： D. Kandhai D. Hlushkou A. G. Hoekstra P. M. A. Sloot H. Van As U. Tallarek Section Computational Science Faculty of Science University of Amsterdam Kruislaan 403 1098 SJ Amsterdam The Netherlands Kramers Laboratorium voor Fysische Technologie Faculty of Applied Sciences Delft University of Technology Prins Bernhardlaan 6 2628 BW Delft The Netherlands Max Planck Institute for the Dynamics of Complex Technical Systems Sandtorstrasse 1 39106 Magdeburg Germany Department of System Analysis Belarusian State University 4 Francisk Scoryna Avenue Minsk 220050 Belarus Laboratory of Molecular Physics and Wageningen NMR Centre Wageningen University Dreijenlaan 3 6703 HA Wageningen The Netherlands Lehrstuhl für Chemische Verfahrenstechnik Otto-von-Guericke Universität Magdeburg Universitätsplatz 2 39106 Magdeburg Germany

The role of stagnant zones in hydrodynamic dispersion is studied for creeping flow through a fixed bed of spherical permeable particles, covering several orders of characteristic time and length scales associated with fluid transport. Numerical simulations employ a hierarchical model to cope with the different temporal and spatial scales, showing good agreement with our experimental results on diffusion-limited mass transfer, transient, and asymptotic longitudinal dispersion. These data demonstrate that intraparticle liquid holdup in macroscopically homogeneous porous media clearly dominates over contributions caused by the intrinsic flow field heterogeneity and boundary-layer mass transfer.

关键词： Porous materials

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Preface

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Fuel Processing technology 2010年第8期91卷 799-799页

作者： Guangwen Xu Chun-Zhu Li Kinya Sakanishi State Key Laboratory of Multiphase Complex System Institute of Process Engineering Chinese Academy of Sciences China Curtin Centre for Advanced Energy Science and Engineering Curtin University of Technology Australia Biomass Technology Research Center National Institute of Advanced Industrial Science and Technology Japan

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Approaching the Fundamental Limit of Orbital Angular Momentum Multiplexing Through a Hologram Metasurface

arXiv

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arXiv 2021年

作者： Yuan, Shuai S.A. Wu, Jie Chen, Menglin L.N. Lan, Zhihao Zhang, Liang Sun, Sheng Huang, Zhixiang Chen, Xiaoming Zheng, Shilie Jiang, Li Jun Zhang, Xianmin Sha, Wei E.I. College of Information Science and Electronic Engineering Zhejiang University Hangzhou310027 China Ministry of Education The Key Laboratory of Electromagnetic Environmental Sensing Department of Education of Anhui Province Anhui University Hefei230039 China Department of Electrical and Electronic Engineering The University of Hong Kong Hong Kong Department of Electronic and Electrical Engineering University College London Torrington Place LondonWC1E 7JE United Kingdom Anhui Province Key Laboratory of Simulation and Design for Electronic Information System Hefei Normal University Hefei230601 China School of Electronic Science and Engineering University of Electronic Science and Technology of China Chengdu611731 China School of Information and Communications Engineering Xi’an Jiaotong University Xi’an710049 China

Establishing and approaching the fundamental limit of orbital angular momentum (OAM) multiplexing are necessary and increasingly urgent for current multiple-input multiple-output research. In this work, we elaborate the fundamental limit in terms of independent scattering channels (or the degrees of freedom of scattered fields) through angular-spectral analysis, in conjunction with a rigorous Green’s function method. The scattering-channel limit is universal for arbitrary spatial-mode multiplexing, which is launched by a planar electromagnetic device, such as antenna, metasurface, etc., with a predefined physical size. As a proof of concept, we demonstrate both theoretically and experimentally the limit by a phase-only metasurface hologram that transforms orthogonal OAM modes to plane-wave modes scattered at critically separated angular-spectral regions. Particularly, a minimax optimization algorithm is applied to suppress angular-spectrum aliasing, achieving good performances in both full-wave simulation and experimental measurement at microwave frequencies. This work offers a theoretical upper bound and corresponding approach route for engineering designs of OAM multiplexing. Copyright © 2021, The Authors. All rights reserved.

关键词： Spectrum analysis

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Existence of Hydroxymethanesulfonate (Hms) During Spring Haze and Sandstorm Events in Beijing: Implications for a Heterogeneous Formation Pathway on Mineral Aerosols

SSRN

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SSRN 2024年

作者： Xu, Yunzhi Ma, Tao Duan, Fengkui Wang, Shuxiao Jiang, Jingkun Cheng, Yafang Su, Hang An, Taicheng Ma, Yongliang Kimoto, Takashi Huang, Tao He, Kebin State Key Joint Laboratory of Environment Simulation and Pollution Control School of Environment State Environmental Protection Key Laboratory of Sources and Control of Air Pollution Complex Beijing Key Laboratory of Indoor Air Quality Evaluation and Control Tsinghua University Beijing100084 China Guangdong-Hong Kong-Macao Joint Laboratory for Contaminants Exposure and Health Guangdong Key Laboratory of Environmental Catalysis and Health Risk Control School of Environmental Science and Engineering Institute of Environmental Health and Pollution Control Guangdong University of Technology Guangzhou510006 China Minerva Research Group Max Planck Institute for Chemistry Mainz55128 Germany Institute of Atmospheric Physics Chinese Academy of Sciences Beijing100029 China Kimoto Electric Co. Ltd. 3-1 Funahashi-Cho Tennouji-Ku Osaka543-0024 Japan

Hydroxymethylsulfonate (HMS) is an abundant secondary organic aerosol from aqueous/heterogeneous processes and may be misidentified as sulfate in conventional measurements. High concentrations of HMS have been observed in humid winter and autumn haze in northern China, while its prevalence in other seasons is unclear and the production medium is controversial. In this study, our field measurements in Beijing during the 2021 spring first showed the presence of HMS in PM2.5 during both haze and sandstorm events despite the different atmospheric conditions. HMS accounted for 0.44% of PM2.5 during haze periods, higher than the proportion (0.097%) during sandstorms. The sum of HMS and sulfate was also higher during the haze (6.5 μg m−3) than during the sandstorm (2.6 μg m−3), while the HMS/sulfate molar ratio during the haze (0.021) was similar to the value during the sandstorm (0.019). HMS concentration showed a good positive correlation with aerosol water content (AWC), indicating heterogeneous production. During haze periods, relatively high AWC favored the formation of HMS. In contrast, relative humidity and AWC decreased significantly during sandstorm events, while high pH favored HMS formation. In addition, higher concentrations and proportions of HMS were observed in PM2.5−10 than in PM2.5. The presence of HMS in dust particles indicated a heterogeneous formation mechanism of HMS on mineral aerosols. Our findings broaden the prevalence of HMS in aerosols and indicate a new HMS formation mechanism from the perspective of observation. © 2024, The Authors. All rights reserved.

关键词： Aerosols

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Large-Scale Single Tree Information Extraction of Oil Palm in Malaysia Based on Sub-Meter Visible Light Satellite Images

SSRN

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SSRN 2024年

作者： Zhang, Sen Li, Nan Cui, Yaoping Dong, Jinwei Yu, Le Ran, Lishan Chen, Ziyue Niu, Jiqiang Yan, Wei Kanniah, Kasturi Devi Xiao, Xiangming Zhang, Yongguang Key Laboratory of Geospatial Technology for the Middle and Lower Yellow River Regions Henan University Ministry of Education Kaifeng475004 China College of Geography and Environmental Science Henan University Kaifeng475004 China Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application International Institute for Earth System Sciences Nanjing University Nanjing210023 China Key Laboratory of Land Surface Pattern and Simulation Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing100101 China Department of Earth System Science Ministry of Education Key Laboratory for Earth System Modeling Institute for Global Change Studies Tsinghua University Beijing100084 China Department of Geography The University of Hong Kong Pokfulam999077 Hong Kong State Key Laboratory of Earth Surface Processes and Resource Ecology College of Global Change and Earth System Science Beijing Normal University Beijing100875 China College of Geographic Sciences Xinyang Normal University Xinyang464000 China Department of Geoinformation Faculty of Built Environment & Surveying Universiti Teknologi Malaysia Johor Bahru81310 Malaysia Department of Microbiology and Plant Biology Center for Spatial Analysis University of Oklahoma NormanOK73019 United States College of Environment and Planning Faculty of Geoinformation and Real Estate

The distribution of specific tree species and single tree information can shift down the research scale of geography and ecology, bridging research from regional to local scales. However, efficiently and finely extracting the spatial distribution and single tree information for a tree species regionally has always been a challenge due to the constraints of data and algorithms. With sub-meter visible light satellite images (RGB bands) in 2021 to 2022, we constructed a novel method for extracting the spatial distribution and single tree information of oil palm across Malaysia, namely the Single Tree Extraction Method - Oil Palm (STEM-OP). We developed a graphic morphological algorithm based on gradient difference window detection to extract the spatial distribution of oil palms. Then, we proposed an algorithm of double ring sliding detection algorithm to identify the canopy texture features of single oil palm. Finally, an adaptive iterative erosion algorithm was employed to separate overlapping and adjacent canopies into single trees. The overall accuracy of both the spatial distribution and number of single oil palm extracted by STEM-OP exceeded 90%. Our study revealed that the total area of oil palm in Malaysia was 5.25 million hectares, with a total of 572.6 million trees and an average planting density of 109 palms per hectare. The STEM-OP addresses the computational inefficiencies of methods with training samples and limitations of satellite image bands. For the first time, our study extracts the refined spatial distribution of oil palm and obtains the planting density and single tree position on a national scale. All of these are of great value to the formulation of oil palm development policies and ecological protection measures. © 2024, The Authors. All rights reserved.

关键词： Morphology

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Amorphous alloys surpass E/10 strength limit at extreme strain rates

arXiv

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arXiv 2021年

作者： Zhu, Wenqing Li, Zhi Shu, Hua Gao, Huajian Wei, Xiaoding State Key Laboratory for Turbulence and Complex System Department of Mechanics and Engineering Science College of Engineering Peking University Beijing100871 China School of Mechanical and Aerospace Engineering College of Engineering Nanyang Technological University 70 Nanyang Drive 637457 Singapore Shanghai Institute of Laser Plasma China Academy of Engineering Physics Shanghai201102 China Institute of High Performance Computing A*STAR 138632 Singapore Beijing Innovation Center for Engineering Science and Advanced Technology Peking University Beijing100871 China Peking University Nanchang Innovation Institute Nanchang330000 China

Theoretical predictions of the ideal strength of materials range from E/30 to E/10 (E is Young’s modulus). However, despite intense interest over the last decade, the value of the ideal strength that can be attained experimentally for metals remains a mystery (1-5). In this study, we demonstrated the unprecedented strength of an amorphous Cu-Zr alloy that surpassed the E/10 limit. Laser-induced shock experiments were conducted on Cu50Zr50 to explore its strength and failure mechanisms at ultrahigh strain rates. The material demonstrated a high spall strength of 9.8 GPa, approximately 1/13 of its P-wave modulus (~ E/6), at strain rates greater than 107 s−1, which sets a new record for the elastic limit of metallic materials. Electron microscopy and large-scale molecular dynamics simulations revealed that void nucleation and growth, not shear-banding, comprised the major failure mechanism for metallic glasses at extremely fast strain rates. A new model for void formation under the control of surface energy explained the rate dependence of the material strength. The results of this study reveal new possible ways to use the amorphous phase in nanostructured metals in future applications under demanding mechanical conditions. Copyright © 2021, The Authors. All rights reserved.

关键词： Copper alloys

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DOUBLE PHASE IMPLICIT OBSTACLE PROBLEMS WITH CONVECTION AND MULTIVALUED MIXED BOUNDARY VALUE CONDITIONS

arXiv

引用

arXiv 2021年

作者： Zeng, Shengda Rǎdulescu, Vicenţiu D. Winkert, Patrick Guangxi Colleges Universities Key Laboratory of Complex System Optimization and Big Data Processing Yulin Normal University Guangxi Yulin537000 China Jagiellonian University in Krakow Faculty of Mathematics and Computer Science ul. Lojasiewicza 6 Krakow30-348 Poland Faculty of Applied Mathematics Agh University of Science and Technology Kraków30-059 Poland Department of Mathematics University of Craiova Craiova200585 Romania Technische Universität Berlin Institut für Mathematik Straße des 17. Juni 136 Berlin10623 Germany

In this paper we consider a mixed boundary value problem with a nonhomogeneous, nonlinear differential operator (called double phase operator), a nonlinear convection term (a reaction term depending on the gradient), three multivalued terms and an implicit obstacle constraint. Under very general assumptions on the data, we prove that the solution set of such implicit obstacle problem is nonempty (so there is at least one solution) and weakly compact. The proof of our main result uses the Kakutani-Ky Fan fixed point theorem for multivalued operators along with the theory of nonsmooth analysis and variational methods for pseudomonotone operators. Copyright © 2021, The Authors. All rights reserved.

关键词： Fixed point arithmetic

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Probing exotic phenomena at the interface of nuclear and particle physics with the electric dipole moments of diamagnetic atoms: A unique window to hadronic and semi-leptonic CP violation

arXiv

引用

arXiv 2017年

作者： Yamanaka, N. Sahoo, B.K. Yoshinaga, N. Sato, T. Asahi, K. Das, B.P. iTHES Research Group RIKEN Wako Saitama351-0198 Japan Complex Simulation Group School of Biomedicine Far Eastern Federal University Vladivostok690950 Russia Atomic Molecular and Optical Physics Division Physical Research Laboratory Ahmedabad380009 India Graduate School of Science and Engineering 255 Shimo-Okubo Sakura-ku Saitama City Saitama338-8570 Japan Nishina Center RIKEN 2-1 Hirosawa Wako-shi Saitama351-0198 Japan Department of Physics International Education Research Center of Science Tokyo Institute of Technology 2-12-1 Ookayama Meguro-ku Tokyo152-8550 Japan

The current status of electric dipole moments of diamagnetic atoms which involves the synergy between atomic experiments and three different theoretical areas – particle, nuclear and atomic is reviewed. Various models of particle physics that predict CP violation, which is necessary for the existence of such electric dipole moments, are presented. These include the standard model of particle physics and various extensions of it. Effective hadron level combined charge conjugation (C) and parity (P) symmetry violating interactions are derived taking into consideration different ways in which a nucleon interacts with other nucleons as well as with electrons. Nuclear structure calculations of the CP-odd nuclear Schiff moment are discussed using the shell model and other theoretical approaches. Results of the calculations of atomic electric dipole moments due to the interaction of the nuclear Schiff moment with the electrons and the P and time-reversal (T) symmetry violating tensor-pseudotensor electron-nucleus are elucidated using different relativistic many-body theories. The principles of the measurement of the electric dipole moments of diamagnetic atoms are outlined. Upper limits for the nuclear Schiff moment and tensor-pseudotensor coupling constant are obtained combining the results of atomic experiments and relativistic many-body theories. The coefficients for the different sources of CP violation have been estimated at the elementary particle level for all the diamagnetic atoms of current experimental interest and their implications for physics beyond the standard model is discussed. Possible improvements of the current results of the measurements as well as quantum chromodynamics, nuclear and atomic calculations are suggested. Copyright © 2017, The Authors. All rights reserved.

关键词： Electric dipole moments

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