检索结果-内蒙古大学图书馆

arXiv 2023年

作者： Minta, F.N. Nozawa, S.I. Kozarev, K. Elsaid, A. Mahrous, A. Department of Space Environment Institute of Basic and Applied Sciences Egypt-Japan University of Science and Technology Alexandria21934 Egypt Department of Science Ibaraki University 2-1-1 Bunkyo Ibaraki Mito310-8512 Japan Institute of Astronomy with National Astronomical Observatory Bulgarian Academy of Sciences Sofia Bulgaria Department of Applied and Computational Mathematics Institute of Basic and Applied Sciences Egypt-Japan University of Science and Technology Alexandria21934 Egypt Mathematics & Engineering Physics Department Faculty of Engineering Mansoura University MansouraPO 35516 Egypt

The newly installed CALLISTO spectrometer, hosted by the department of Space Environment, Institute of Basic and applied Sciences- EJUST, commenced operation on August 14, 2021. The system contains a cross dipole long-wavelength array antenna with high sensitivity to monitor solar radio transients. Its antenna was strategically positioned and appeared to be in the center of the CALLISTO network of spectrometers. Moreover, in the northern section of Africa, the Egypt-Alexandria CALLISTO and ALGERIA-CRAAG stations are the only ones operating. There are no stations in the West African region, while stations in the eastern part of Africa are not working. Thus, Egypt- Alexandria station serves as a reference for other stations within the e-CALLISTO network. Despite the low solar activity, the instrument detected several solar radio bursts not limited to type II, type III, and type V. A vigorous case study was conducted on two selected radio burst events to validate the authenticity of the recorded events. Other solar radio stations at different geographical locations recorded all the radio bursts detected by the spectrometer. The case study included brief analyses that indicated a type II radio burst observed on October 09, 2021, between 06:30 and 07:00 UT, was associated with an M1.6 solar flare located at N18E08 within NOAA-AR 12882 and a CME with a shock front speed of ~978 km/s. However, the type III radio burst is neither CME nor solar flare associated. These analyses examine the instrument's capacity to provide real-time solar radio transient data 24 hours a day to mitigate the challenges of data gaps faced in the African continent. Hence, the instrument has become an integral part of space weather monitoring and forecasting over the region and other parts of the globe. © 2023, CC BY-NC-ND.

关键词： Solar energy

来源：评论

学校读者我要写书评

暂无评论

The Null Field and the Interior Field Methods For Mixed Types of Boundary Conditions of Laplace's Equations in Elliptic Domains with Elliptic Holes

The Null Field and the Interior Field Methods For Mixed Type...

引用

Joint International Conference on Trefftz Method Ⅶ and Method of Fundamental Solutions Ⅲ(Trefftz/MFS 2015)

作者： Liping Zhang Ming-Gong Lee Zi-Cai Li College of Science Zhejiang University of Technology Department of Leisure and Recreation Management Ph.D.Program in Engineering ScienceChung Hua University Department of Applied Mathematics Department of Computer Science and EngineeringNational Sun Yat-sen University

The particular solutions(PS) and fundamental solutions(FS) in polar coordinates can be found in many textbooks, but with much less coverage in elliptic coordinates [1]. Since the elliptic domains with elliptic holes may be found in some engineering problems, the PS and the FS expansions in elliptic coordinates are essential for numerical computations. For Dirichlet problems of Laplace's equation in elliptic domains, the null field method(NFM), the interior field method(IFM) and the collocation Trefftz method(CTM) are reported in [2]. There seems to exist very few reports for mixed problems, where the Dirichlet and Neumann conditions are assigned on the exterior and the interior boundaries, simultaneously. This paper is devoted to such mixed problems by the NFM and the IFM, and the explicit algebraic equations are derived for elliptic domains. Besides, other effective particular solutions(PS) are sought, and the collocation Trefftz method(CTM) [3] is employed. The CTM may be used for Robin problems in elliptic domains. The effective algorithms for the mixed problems of Laplace's equation on elliptic domains are the main goal of this paper.

关键词： Null field method Interior field method collocation Trefftz method circular domains elliptic domains Elliptic Holes fundamental solutions Particular Solutions Dirichlet condition Neumann condition Robin Problems

来源：评论

学校读者我要写书评

暂无评论

A POSTERIORI ERROR ANALYSIS FOR APPROXIMATIONS OF TIME-FRACTIONAL SUBDIFFUSION PROBLEMS

arXiv

引用

arXiv 2022年

作者： Banjai, Lehel Makridakis, Charalambos G. Maxwell Institute for Mathematical Sciences School of Mathematical & Computer Sciences Heriot-Watt University EdinburghEH14 4AS United Kingdom Institute for Applied and Computational Mathematics-FORTH Crete HeraklionGR 70013 Greece Department of Mathematics University of Sussex BrightonBN1 9QH United Kingdom

In this paper we consider a sub-diffusion problem where the fractional time derivative is approximated either by the L1 scheme or by Convolution Quadrature. We propose new interpretations of the numerical schemes which lead to a posteriori error estimates. Our approach is based on appropriate pointwise representations of the numerical schemes as perturbed evolution equations and on stability estimates for the evolution equation. A posteriori error estimates in L2(H) and L∞(H) norms of optimal order are derived. Extensive numerical experiments indicate the reliability and the optimality of the estimators for the schemes considered, as well as their efficiency as error indicators driving adaptive mesh selection locating singularities of the *** Codes 35R11, 65M06, 65M15 © 2022, CC BY.

关键词： Differential equations

来源：评论

学校读者我要写书评

暂无评论

Controlling the deformation of antiferromagnetic skyrmions in the high-velocity regime

引用

Physical Review B 2020年第2期101卷 024429-024429页

作者： A. Salimath Fengjun Zhuo R. Tomasello G. Finocchio A. Manchon King Abdullah University of Science and Technology (KAUST) Physical Science and Engineering Division (PSE) Thuwal 23955-6900 Saudi Arabia Institute of Applied and Computational Mathematics FORTH GR-70013 Heraklion-Crete Greece Department of Mathematical and Computer Sciences Physical Sciences and Earth Sciences University of Messina I-98166 Messina Italy

While antiferromagnetic skyrmions display appealing properties, their lateral expansion in the high-velocity regime hinders their potential for applications. In this work, we study the impact of spin Hall torque, spin transfer torque, and topological torque on the velocity-current relation of antiferromagnetic skyrmions with the aim of reducing this deformation. Using a combination of micromagnetic simulations and analytical derivations, we demonstrate that the lateral expansion of the antiferromagnetic skyrmion is reminiscent of the well-known Lorentz contraction identified in one-dimensional antiferromagnetic domain walls. We also show that in the flow regime the lateral expansion is accompanied by a progressive saturation of the skyrmion velocity when driven by spin Hall and topological torques. This saturation occurs at much smaller velocities when driven by the topological torque, while the lateral expansion is reduced, preventing the skyrmion size from diverging at large current densities. We extend this study toward synthetic antiferromagnets, where the weaker antiferromagnetic exchange leads to much larger lateral expansion at smaller current densities in all cases. This study suggests that a compromise must be made between skyrmion velocity and lateral expansion during the device design. In this respect, exploiting the topological torque could lead to better control of the skyrmion velocity in antiferromagnetic racetracks.

关键词： Skyrmions Spin transfer torque Spintronics Antiferromagnets

来源：评论

学校读者我要写书评

暂无评论

Covariant density and velocity perturbations of the quasi-Newtonian cosmological model in f(T) gravity

arXiv

引用

arXiv 2021年

作者： Sami, Heba Sahlu, Shambel Abebe, Amare Dunsby, Peter K.S. Center for Space Research North-West University South Africa Astronomy and Astrophysics Research Development Department Entoto Observatory and Research Center Ethiopian Space Science and Technology Institute Ethiopia Department of Physics College of Natural and Computational Science Wolkite University Ethiopia Cosmology and Gravity Group Department of Mathematics and Applied Mathematics University of Cape Town Rondebosch Cape Town7701 South Africa

We investigate classes of shear-free cosmological dust models with irrotational fluid flows within the framework of f(T) gravity. In particular, we use the 1+3 covariant formalism and present the covariant linearised evolution and constraint equations describing such models. We then derive the integrability conditions describing a consistent evolution of the linearised field equations of these quasi-Newtonian universes in the f(T) gravitational theory. Finally, we derive the evolution equations for the density and velocity perturbations of the quasi-Newtonian universe. We explore the behaviour of the matter density contrast for two models - f(T) = µT0(T/T0)n and the more generalised case, where f(T) = T + µT0(T/T0)n, with and without the application of the quasi-static approximation. Our numerical solutions show that these f(T) theories can be suitable alternatives to study the background dynamics, whereas the growth of energy density fluctuations change dramatically from the expected ΛCDM behaviour even for small deviations away from the general relativistic limits of the underlying f(T) theory. Moreover, applying the so-called quasi-static approximation yields exact-solution results that are orders of magnitude different from the numerically integrated solutions of the full system, suggesting that these approximations are not applicable here. Copyright © 2021, The Authors. All rights reserved.

关键词： Flow of fluids

来源：评论

学校读者我要写书评

暂无评论

Maximal violation of Clauser-Horne-Shimony-Holt inequality for four-level systems

引用

Physical Review A 2004年第3期69卷 034305-034305页

作者： Li-Bin Fu Jing-Ling Chen Shi-Gang Chen Institute of Applied Physics and Computational Mathematics P.O. Box 8009 (28) 100088 Beijing China Max-Planck-Institute for the Physics of Complex Systems Nöthnitzer Strasse 38 01187 Dresden Germany Department of Physics Faculty of Science University of Singapore 10 Kent Ridge Crescent Singapore 119260 Singapore

Clauser-Horne-Shimony-Holt inequality for bipartite systems of four dimensions is studied in detail by employing the unbiased eight-port beam splitters measurements. The uniform formulas for the maximum and minimum values of this inequality for such measurements are obtained. Based on these formulas, we show that an optimal nonmaximally entangled state is about 6% more resistant to noise than the maximally entangled one. We also give the optimal state and the optimal angles which are important for experimental realization.

关键词： Quantum theory

来源：评论

学校读者我要写书评

暂无评论

Dimension reduction of dynamical systems on networks with leading and non-leading eigenvectors of adjacency matrices

arXiv

引用

arXiv 2022年

作者： Masuda, Naoki Kundu, Prosenjit Department of Mathematics State University of New York BuffaloNY14260-2900 United States Computational and Data-Enabled Science and Engineering Program State University of New York at Buffalo BuffaloNY14260-5030 United States

Dimension reduction techniques for dynamical systems on networks are considered to promote our understanding of the original high-dimensional dynamics. One strategy of dimension reduction is to derive a low-dimensional dynamical system whose behavior approximates the observables of the original dynamical system that are weighted linear summations of the state variables at the different nodes. Recently proposed methods use the leading eigenvector of the adjacency matrix of the network as the mixture weights to obtain such observables. In the present study, we explore performances of this type of one-dimensional reductions of dynamical systems on networks when we use non-leading eigenvectors of the adjacency matrix as the mixture weights. Our theory predicts that non-leading eigenvectors can be more efficient than the leading eigenvector and enables us to select the eigenvector minimizing the error. We numerically verify that the optimal non-leading eigenvector outperforms the leading eigenvector for some dynamical systems and networks. We also argue that, despite our theory, it is practically better to use the leading eigenvector as the mixture weights to avoid misplacing the bifurcation point too distantly and to be resistant against dynamical noise. © 2022, CC BY.

关键词： Eigenvalues and eigenfunctions

来源：评论

学校读者我要写书评

暂无评论

Critical latitude in global quasi-geostrophic flow on a rotating sphere

arXiv

引用

arXiv 2024年

作者： Franken, Arnout D. Luesink, Erwin Ephrati, Sagy R. Geurts, Bernard J. Mathematics of Multiscale Modelling and Simulation Department of Applied Mathematics Faculty EEMCS University of Twente PO Box 217 Enschede7500 AE Netherlands Korteweg-de-Vries Institute University of Amsterdam PO Box 94248 Science Park 107 Amsterdam1090 GE Netherlands Department of Mathematical Sciences Chalmers University of Technology Gothenburg412 96 Sweden Multiscale Physics Center for Computational Energy Research Department of Applied Physics Eindhoven University of Technology Eindhoven Netherlands

In this paper, we study geostrophic turbulence without external forcing or dissipation, using a Casimir-preserving numerical method. The research examines the formation of large zonal jets, common in geophysical flows, especially in giant gas planets. These jets form due to the east-west stretching of vortices, influenced by the gradient of the Coriolis parameter, leading to a critical latitude beyond which jets do not form. Using a global quasi-geostrophic model with a fully latitude-dependent Coriolis parameter, we investigate this critical latitude, which is theorized to depend only on the product of the Rossby number and the Lamb parameter. By simulating random flow fields, the critical latitude was identified through zonally averaged zonal velocity profiles. Results align with geostrophic theory, especially near typical Rossby and Lamb parameter values for Earth’s atmosphere. However, in the regime of weak rotation (high Rossby numbers) and strong stratification (high Lamb values), no clear critical latitude emerges;instead, zonal jet amplitude and width decrease gradually towards the poles. This research paves the way for further study of jet dynamics under a fully latitude-dependent Coriolis parameter. Copyright © 2024, The Authors. All rights reserved.

关键词： Miocene

来源：评论

学校读者我要写书评

暂无评论

Extreme ultraviolet and visible spectroscopy of promethiumlike heavy ions

引用

Physical Review A 2015年第2期92卷 022510-022510页

作者： Yusuke Kobayashi Kai Kubota Kazuki Omote Akihiro Komatsu Junpei Sakoda Maki Minoshima Daiji Kato Jiguang Li Hiroyuki A. Sakaue Izumi Murakami Nobuyuki Nakamura Institute for Laser Science The University of Electro-Communications Chofu Tokyo 182-8585 Japan National Institute for Fusion Science Toki Gifu 509-5292 Japan Department of Fusion Science SOKENDAI (The Graduate University for Advanced Studies) Toki Gifu 509-5292 Japan Institute of Applied Physics and Computational Mathematics Beijing 100088 China

We present extreme ultraviolet and visible spectra of promethiumlike tungsten and gold obtained with an electron beam ion trap. Although the contributions from a few charge states are involved in the spectra, the charge state of the ion assigned to the observed lines is definitely identified by the time-of-flight (TOF) analysis of the ions performed at the same time with the spectroscopic measurements. Experimental results are compared with collisional-radiative model calculations as well as previous experimental and theoretical studies. Some ambiguous identifications in the previous observations have been clarified owing to the definite identification by the TOF analysis.

关键词： HEAVY ions OPTICAL spectroscopy ULTRAVIOLET spectroscopy TUNGSTEN GOLD ELECTRON beams ION traps

来源：评论

学校读者我要写书评

暂无评论

A Nodal Immersed Finite Element-Finite Difference Method

SSRN

引用

SSRN 2022年

作者： Wells, David Vadala-Roth, Ben Lee, Jae Ho Griffith, Boyce E. Department of Mathematics University of North Carolina Chapel HillNC United States U.S. Army Corps of Engineers Engineer Research and Development Center Coastal and Hydraulic Laboratory VicksburgMS United States Department of Mechanical Engineering Institute for Computational Medicine Johns Hopkins University BaltimoreMD United States Departments of Mathematics Applied Physical Sciences and Biomedical Engineering University of North Carolina Chapel HillNC United States Carolina Center for Interdisciplinary Applied Mathematics University of North Carolina Chapel HillNC United States Computational Medicine Program University of North Carolina Chapel HillNC United States McAllister Heart Institute University of North Carolina Chapel HillNC United States

The immersed finite element-finite difference (IFED) method is a computational approach to modeling interactions between a fluid and an immersed structure. The IFED method uses a finite element (FE) method to approximate the stresses and forces on a structural mesh and a finite difference (FD) method to approximate the momentum of the entire fluid-structure system on a Cartesian grid. The fundamental approach used by this method follows the immersed boundary framework for modeling fluid-structure interaction (FSI), in which a force spreading operator prolongs structural forces to a Cartesian grid, and a velocity interpolation operator restricts a velocity field defined on that grid back onto the structural mesh. With an FE structural mechanics framework, force spreading first requires that the force itself be projected onto the finite element space. Similarly, velocity interpolation requires projecting velocity data onto the FE basis functions. Consequently, evaluating either coupling operator requires solving a matrix equation at every time step. Mass lumping, in which the projection matrices are replaced by diagonal approximations, has the potential to accelerate this method considerably. This paper provides both numerical and computational analyses of the effects of this replacement for evaluating the force projection and for the IFED coupling operators. Constructing the coupling operators also requires determining the locations on the structure mesh where the forces and velocities are sampled. Here we show that sampling the forces and velocities at the nodes of the structural mesh is equivalent to using lumped mass matrices in the IFED coupling operators. A key theoretical result of our analysis is that if both of these approaches are used together, the IFED method permits the use of lumped mass matrices derived from nodal quadrature rules for any standard interpolatory element. This is different from standard FE methods, which require specialized treatments to

关键词： Fluid structure interaction

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：