检索结果-内蒙古大学图书馆

Thickness-driven first-order phase transitions in manganite ultrathin films

Physical Review B 2019年第21期99卷 214419-214419页

作者： Hongyan Chen Yang Yu Zhe Wang Yu Bai Hanxuan Lin Xiaolong Li Hao Liu Tian Miao Yunfang Kou Yongsheng Zhang Yan Li Jin Tang Zechao Wang Peng Cai Yinyan Zhu Zhaohua Cheng Xiaoyan Zhong Wenbin Wang Xingyu Gao Lifeng Yin Ruqian Wu Jian Shen State Key Laboratory of Surface Physics and Department of Physics Fudan University Shanghai 200433 China Shanghai Institute of Applied Physics Chinese Academy of Sciences Shanghai 201204 China Beijing National Laboratory for Condensed Matter Physics Chinese Academy of Sciences Beijing 100190 China National Center for Electron Microscopy in Beijing Key Laboratory of Advanced Materials (MOE) The State Key Laboratory of New Ceramics and Fine Processing School of Materials Science and Engineering Tsinghua University Beijing 100084 People's Republic of China Institute for Nanoelectronics Devices and Quantum Computing Fudan University Shanghai 200433 China Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing 210093 China

We report thickness dependent inhomogeneous antiferromagnetic (AFM) to ferromagnetic (FM) phase transitions in ultrathin La0.7Sr0.3MnO3 (LSMO) films grown on the SrTiO3 substrate. When the films are 4–7 unit cells (UCs) thick, FM domains appear as isolated nanodisks in the AFM matrix that together floats on top of the three AFM base UCs, leading a superparamagnetic blocking behavior. Our first principles calculations unravel the rather counterintuitive physical origin of this mixed phase state; the formation of FM/AFM domain boundaries is energetically favorable. At 8 UCs, an abrupt shear strain relief occurs in the LSMO thin film and twinning patterns with two unit cell periodicity form along the [010] and [100] directions. Our studies reveal the complexity of the magnetic phase transition at the nanometer scale and open a door for the development of quantum devices and statistical theories.

关键词： Magnetic phase transitions Phase separation Phase transitions Magnetic systems Ultrathin films Atomic force microscopy Density functional calculations Magnetic force microscopy Magnetization measurements

来源：评论

学校读者我要写书评

暂无评论

Macroscopic Assembled Graphene for Silicon Mid-Infrared Photodetectors

Research Square

引用

Research Square 2020年

作者： Gao, Chao Peng, Li Du, Sichao Liu, Lixiang Bodepudi, Srikrishna Chanakya Li, Lingfei Liu, Wei Cong, Xin Lai, Runchen Fang, Wenzhang Cao, Xiaoxue Liu, Xinyu Abid, Muhammad Lv, Jianhang Liu, Junxue Jin, Shengye Wu, Kaifeng Zhou, Qiaohui Zhu, Haiming Lin, Miao-Ling Tan, Ping-Heng Xiong, Qihua Wang, Xiaomu Hu, Weida Duan, Xiangfeng Yu, Bin Yin, Wenyan Xu, Zhen Xu, Yang MOE Key Laboratory of Macromolecular Synthesis and Functionalization Department of Polymer Science and Engineering Zhejiang University Hangzhou310027 China Colleges of ISEE and Microelectronics State Key Laboratories of Modern Optical Instrumentation and Silicon Materials Hangzhou Global Scientific and Technological Innovation Center ZJU-UIUC Joint Institute Zhejiang University Hangzhou310027 China State Key Laboratory of Superlattices and Microstructures Institute of Semiconductors Chinese Academy of Sciences Beijing100083 China State Key Laboratory of Molecular Reaction Dynamics and Dynamics Dalian Institute of Chemical Physics Chinese Academy of Sciences Dalian116023 China Department of Chemistry Zhejiang University Hangzhou310027 China Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University 637371 Singapore National Laboratory of Solid State Microstructures Collaborative Innovation Center of Advanced Microstructure School of Electronic Science and Engineering Nanjing University Nanjing210093 China National Laboratory for Infrared Physics Shanghai Institute of Technical Physics Chinese Academy of Sciences Shanghai200083 China Department of Chemistry and Biochemistry California Nanosystems Institute University of California Los Angeles90095 United States

Graphene with linear energy dispersion and weak electron-phonon interaction is highly anticipated to harvest hot-electrons in a broad wavelength range from ultraviolet to terahertz1,2. However, the limited absorption (~2.3%) and serious backscattering of hot-electrons associated with single-layer graphene result in inadequate quantum yields3-5, impeding their practically broadband photodetection, especially in the mid-infrared range. Here, we report a macroscopic assembled graphene (MAG)/silicon heterojunction for ultrafast mid-infrared photodetection. The highly crystalline 2-inch scale MAG with tunable thickness from 10 to 60 nm is produced by scalable wet-assembly of commercial graphene oxide followed by thermal annealing. The MAG/Si Schottky diode exhibits broadband photodetection capability in 1-10 μm at room temperature with fast response (120-130 ns, 4 mm2 window) and high detectivity (1011 to 106 Jones), outperforming single-layer graphene/Si photodetectors by 2 to 8 orders in transient photocurrent. This optoelectronic performance is attributed to the superior advantages of MAG (~40% of light absorption, ~23 ps of carrier relaxation time, and high quasi-equilibrated hot-carrier-multiplication gain), atomic-scale contact interface of MAG and silicon, and impact-ionization avalanche gain (~102 times) from silicon. The MAG provides a long-range platform to understand the hot-carrier dynamics in stacked 2D materials, leading to next-generation broadband silicon-based image sensors. © 2020, CC BY.

关键词： Graphene

来源：评论

学校读者我要写书评

暂无评论

Discrete unified gas kinetic scheme for nonlinear convection-diffusion equations

arXiv

引用

arXiv 2019年

作者： Shang, Jinlong Chai, Zhenhua Wang, Huili Shi, Baochang School of Mathematics and Statistics Huazhong University of Science and Technology Wuhan430074 China Hubei Key Laboratory of Engineering Modeling and Scientific Computing Huazhong University of Science and Technology Wuhan430074 China School of Mathematics and Computer Science Wuhan Textile University Wuhan430073 China

In this paper, we develop a discrete unified gas kinetic scheme (DUGKS) for general nonlinear convection-diffusion equation (NCDE), and show that the NCDE can be recovered correctly from the present model through the Chapman-Enskog analysis. We then test the present DUGKS through some classic convection-diffusion equations, and find that the numerical results are in good agreement with analytical solutions and the DUGKS model has a second-order convergence rate. Finally, as a finite-volume method, DUGKS can also adopt the nonuniform mesh. Besides, we performed some comparisons among the DUGKS, finite-volume lattice Boltzmann model (FV-LBM), single-relaxation-time lattice Boltzmann model (SLBM) and multiple-relaxation-time lattice Boltzmann model (MRT-LBM). The results show that the DUGKS model is more accurate than FV-LBM, more stable than SLBM, and almost has the same accuracy as the MRT-LBM. Besides, the using of non-uniform mesh may make DUGKS model more flexible. Copyright © 2019, The Authors. All rights reserved.

关键词： Finite volume method

来源：评论

学校读者我要写书评

暂无评论

A finite-difference lattice Boltzmann model with second-order accuracy of time and space for incompressible flow

arXiv

引用

arXiv 2019年

作者： Chen, Xinmeng Chai, Zhenhua Wang, Huili Shi, Baochang School of Mathematics and Statistics Huazhong University of Science and Technology Wuhan430074 China Hubei Key Laboratory of Engineering Modeling and Scientific Computing Huazhong University of Science and Technology Wuhan430074 China School of Mathematics and Computer Science Wuhan Textile University Wuhan430073 China

In this paper, a kind of finite-difference lattice Boltzmann method with the second-order accuracy of time and space (T2S2-FDLBM) is proposed. In this method, a new simplified two-stage fourth order time-accurate discretization approach is applied to construct time marching scheme, and the spatial gradient operator is discretized by a mixed difference scheme to maintain a second-order accuracy both in time and space. It is shown that the previous finite-difference lattice Boltzmann method (FDLBM) proposed by Guo [1] is a special case of the T2S2-FDLBM. Through the von Neumann analysis, the stability of the method is analyzed and two specific T2S2-FDLBMs are discussed. The two T2S2-FDLBMs are applied to simulate some incompressible flows with the nonuniform grids. Compared with the previous FDLBM and SLBM, the T2S2-FDLBM is more accurate and more stable. The value of the Courant-Friedrichs-Lewy condition number in our method can be up to 0.9, which also significantly improves the computational efficiency. Copyright © 2019, The Authors. All rights reserved.

关键词： Incompressible flow

来源：评论

学校读者我要写书评

暂无评论

Comparative modelling and verification of Pthreads and Dthreads

Comparative modelling and verification of Pthreads and Dthre...

引用

作者： Fei, Yuan Zhu, Huibiao Wu, Xi Fang, Huixing Qin, Shengchao Shanghai Key Laboratory of Trustworthy Computing MOE International Joint Laboratory of Trustworthy Software International Research Center of Trustworthy Software East China Normal University Shanghai China School of Computing University of Teesside Middlesbrough United Kingdom School of Computer Science and Software Engineering Shenzhen University Shenzhen China School of Information Technology and Electrical Engineering University of Queensland Brisbane Australia School of Information Engineering Yangzhou University Jiangsu China

The POSIX threads (Pthreads) library is a thread API for C/C++ to control parallel threads and spawn concurrent process flows. Programming in Pthreads usually suffers from undesirable deadlock, data race, and race condition problems due to the potential nondeterministic execution behaviors between parallel threads. Dthreads, as another multithreading model that re-implements Pthreads, was proposed by Liu et al for efficient deterministic multithreading. They found out that, under specific test cases, Dthreads can effectively prevent data races. However, no comparison test has been made with Pthreads. To perform a formal comparison between Pthreads and Dthreads over deadlocks, data races, and race conditions, in this paper, we adopt CSP (communicating sequential processes) as a formal model for specifying part of API functions in Pthreads and Dthreads and illustrate the model construction using 4 classical example programs. By feeding the models into the model checker PAT (process analysis toolkit), we have verified that deadlocks and data races exist in Pthreads, but do not exist in Dthreads, for the considered programs. We have also found that neither of them can prevent race conditions. Our comparative modelling and verification of Pthreads and Dthreads show that though Dthreads cannot prevent all the deadlock situations, shown by verification results of another 2 example programs, Dthreads is better than Pthreads on eliminating data races and preventing deadlocks. Considering limited scalability of Dthreads, we have introduced a new programming model to support coarse granularity in bank transfer. Our modelling is also extended by covering the synchronization operations in Liu et al work. Copyright © 2017 John Wiley & Sons, Ltd.

关键词： C++ (programming language)

来源：评论

学校读者我要写书评

暂无评论

Modeling subgrid-scale force and divergence of heat flux of compressible isotropic turbulence by artificial neural network

引用

Physical Review Fluids 2019年第10期4卷 104605-104605页

作者： Chenyue Xie Ke Li Chao Ma Jianchun Wang Shenzhen Key Laboratory of Complex Aerospace Flows Center for Complex Flows and Soft Matter Research Department of Mechanics and Aerospace Engineering Southern University of Science and Technology Shenzhen 518055 People's Republic of China Institute of Computational Mathematics and Scientific Engineering Computing Chinese Academy of Sciences Beijing 100190 People's Republic of China The Program in Applied and Computational Mathematics Princeton University Princeton New Jersey 08544 USA

In this paper, the subgrid-scale (SGS) force and the divergence of SGS heat flux of compressible isotropic turbulence are modeled directly by an artificial neural network (ANN), which serves as a data-driven SGS modeling tool for large-eddy simulations (LESs). The unclosed SGS force and divergence of SGS heat flux are modeled based on the local stencil geometry with Galilean invariance. The input features include the first-order and second-order derivatives of filtered velocity and temperature, filtered density, and its first-order derivative. It is shown that the proposed ANN-F7 model shows an advantage over the gradient model in the a priori test. Specifically, the ANN-F7 model gives larger correlation coefficients and smaller relative errors than the gradient model. In an a posteriori analysis, the ANN-F7 model performs better than the dynamic Smagorinsky model (DSM) and dynamic mixed model (DMM) in the prediction of the statistical properties of flow fields at the Taylor microscale Reynolds number Reλ ranging from 180 to 250. The DSM and DMM models lead to the typical tilted spectral distribution of velocity, where low wave numbers are too energy rich, while those near the cutoff are damped too strongly. In contrast, it is shown that the velocity spectrum predicted by the ANN-F7 model almost overlaps with the filtered direct numerical simulation data. Besides, the ANN-F7 model reconstructs the probability density functions of SGS force and divergence of SGS heat flux much better than the DSM and DMM models. An artificial neural network with reasonable physical input features can deepen our understanding of turbulence modeling.

关键词： Compressible flows Turbulence Artificial neural networks

来源：评论

学校读者我要写书评

暂无评论

Bayesian inference and uncertainty quantification for medical image reconstruction with Poisson data

arXiv

引用

arXiv 2019年

作者： Zhou, Qingping Yu, Tengchao Zhang, Xiaoqun Li, Jinglai School of Mathematical Sciences Institute of Natural Sciences Shanghai Jiao Tong University 800 Dongchuan Rd Shanghai200240 China Institute of Natural Sciences School of Mathematical Sciences MOE Key Laboratory of Scientific and Engineering Computing Shanghai Jiao Tong University 800 Dongchuan Rd Shanghai200240 China Department of Mathematical Sciences University of Liverpool LiverpoolL69 7ZL United Kingdom

We provide a complete framework for performing infinite-dimensional Bayesian inference and uncertainty quantification for image reconstruction with Poisson data. In particular, we address the following issues to make the Bayesian framework applicable in practice. We first introduce a positivity-preserving reparametrization, and we prove that under the reparametrization and a hybrid prior, the posterior distribution is well-posed in the infinite dimensional setting. Second we provide a dimension-independent MCMC algorithm, based on the preconditioned Crank-Nicolson Langevin method, in which we use a primal-dual scheme to compute the offset direction. Third we give a method combining the model discrepancy method and maximum likelihood estimation to determine the regularization parameter in the hybrid prior. Finally we propose to use the obtained posterior distribution to detect artifacts in a recovered image. We provide an example to demonstrate the effectiveness of the proposed method. Copyright © 2019, The Authors. All rights reserved.

关键词： Uncertainty analysis

来源：评论

学校读者我要写书评

暂无评论

Ergodic optimization theory for a class of typical maps

arXiv

引用

arXiv 2019年

作者： Huang, Wen Lian, Zeng Ma, Xiao Xu, Leiye Zhang, Yiwei Wu Wen-Tsun Key Laboratory of Mathematics USTC Chinese Academy of Sciences Department of Mathematics University of Science and Technology of China Hefei Anhui China College of Mathematical Sciences Sichuan University Chengdu Sichuan610016 China School of Mathematics and Statistics Center for Mathematical Sciences Hubei Key Laboratory of Engineering Modeling and Scientific Computing Huazhong University of Sciences and Technology Wuhan430074 China

In this article, we consider the weighted ergodic optimization problem of a class of dynamical systems T: X → X where X is a compact metric space and T is Lipschitz continuous. We show that once T: X → X satisfies both the Anosov shadowing property (ASP) and the Mañé-Conze-Guivarc'h-Bousch property (MCGBP), the minimizing measures of generic Hölder observables are unique and supported on a periodic orbit. Moreover, if T: X → X is a subsystem of a dynamical system f: M → M (i.e. X ⊂ M and f|X= T ) where M is a compact smooth manifold, the above conclusion holds for C1observables. Note that a broad class of classical dynamical systems satisfies both ASP and MCGBP, which includes Axiom A attractors, Anosov diffeomorphisms and uniformly expanding maps. Therefore, the open problem proposed by Yuan and Hunt in [YH] for C1-observables is solved consequentially. Copyright © 2019, The Authors. All rights reserved.

关键词： Dynamical systems

来源：评论

学校读者我要写书评

暂无评论

UNIFORM STRUCTURAL STABILITY OF HAGEN-POISEUILLE FLOWS IN A PIPE

arXiv

引用

arXiv 2019年

作者： Wang, Yun Xie, Chunjing School of Mathematical Sciences Center for dynamical systems and differential equations Soochow University Suzhou China School of mathematical Sciences Institute of Natural Sciences Ministry of Education Key Laboratory of Scientific and Engineering Computing and SHL-MAC Shanghai Jiao Tong University 800 Dongchuan Road Shanghai China

In this paper, we prove the uniform nonlinear structural stability of Hagen-Poiseuille flows with arbitrary large fluxes in the axisymmetric case. This uniform nonlinear structural stability is the first step to study Liouville type theorem for steady solution of Navier-Stokes system in a pipe, which may play an important role in proving the existence of solutions for the Leray’s problem, the existence of solutions of steady Navier-Stokes system with arbitrary flux in a general nozzle. A key step to establish nonlinear structural stability is the a priori estimate for the associated linearized problem for Navier-Stokes system around Hagen-Poiseuille flows. The linear structural stability is established as a consequence of elaborate analysis for the governing equation for the partial Fourier transform of the stream function. The uniform estimates are obtained based on the analysis for the solutions with different fluxes and frequencies. One of the most involved cases is to analyze the solutions with large flux and intermediate frequency, where the boundary layer analysis for the solutions plays a crucial role. Copyright © 2019, The Authors. All rights reserved.

关键词： Stability

来源：评论

学校读者我要写书评

暂无评论

Activating Bip-orbitals in Dispersed Clusters of Amorphous BiOxfor Electrocatalytic Nitrogen Reduction

引用

Angewandte Chemie 2023年第15期135卷

作者： Dr. Jianxin Kang Xiangyu Chen Rutong Si Prof. Xiang Gao Prof. Shuo Zhang Prof. Gilberto Teobaldi Prof. Annabella Selloni Li-Min Liu Prof. Lin Guo School of Chemistry Beijing Advanced Innovation Center for Biomedical Engineering Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology Beihang University Beijing 100191 China Beijing Computational Science Research Center Beijing 100193 China School of Physics Beihang University Beijing 100191 China Center for High Pressure Science and Technology Advanced Research Beijing 100190 China Shanghai Synchrotron Radiation Facility Shanghai Institute of Applied Physics Chinese Academy of Sciences Shanghai 201204 China Scientific Computing Department STFC UKRI Rutherford Appleton Laboratory Didcot OX11 0QX UK School of Chemistry University of Southampton Highfield Southampton SO17 1BJ UK Department of Chemistry Princeton University Princeton NJ 08544 USA

Catalytic strategies based on main group metals are significantly less advanced than those of transition metal catalysis, leaving untapped areas of potentially fruitful research. We here demonstrate an effective approach for the modulation of Bi 6p energy levels during the construction of atomically dispersed clusters of amorphous BiO x . Bi oxidation state is proposed to strongly affects the nitrogen fixation activity, with the half-occupied p z orbitals of the Bi 2+ ions being highly efficient toward electron injection into the inert N 2 molecule. With sufficient catalytic sites to adsorb and activate N 2 , the bonding between N 2 and catalyst is able to be in situ identified. The catalyst shows an outstanding Faraday efficiency (≈30 %) and high yield (≈113 μg h −1 mg −1 cat ) in NH 3 production, outperforming most of the existing catalysts in aqueous solution. These results lay the basis for developing the potential of p- block elements for catalysis of multi-electron reactions.

关键词： Amorphous Nanomaterial Electrocatalysis In Situ Identification Nitrogen Fixation p-Orbitals

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：