检索结果-内蒙古大学图书馆

A new continuous optimization method of standardized cubic permanent magnets for stellarators

NUCLEAR FUSION 2025年第2期65卷 026060-026060页

作者： Zhang, Xiangyu Chen, Dehong Xu, Guosheng Lu, Zhiyuan Zhu, Caoxiang Chen, Liang Ye, Minyou Wan, Baonian Chinese Acad Sci Inst Plasma Phys Hefei 230031 Peoples R China Univ Sci & Technol China Hefei 230026 Peoples R China

Stellarator configurations can be realized using permanent magnets in combination with tokamak-like planar coils. From the perspective of engineering feasibility and cost-effectiveness, using standardized cubic permanent magnets with a finite number of magnetization directions is particularly advantageous. However, optimizing the discrete magnetization directions of tens of thousands of cubic magnets poses a significant challenge. This paper introduces a novel method that converts the discrete optimization problem into a continuous nonlinear optimization problem, enabling the direct application of well-established nonlinear optimization algorithms. This approach leverages a specially tailored continuous function to represent the magnetization moment and incorporates a penalty term to ensure the direction vector converges to one of the discrete points. Subsequently, a discrete solution for the magnetization direction distribution is derived by truncating the continuous solution and eliminating adjacent magnets with opposing magnetization directions. The proposed optimization method is validated using the ESTELL stellarator configuration as a case study. The results demonstrate that the designed distribution of cubic permanent magnets can accurately reproduce the intended magnetic field configuration.

关键词： stellarator permanent magnet numerical optimization polarization function

来源：评论

学校读者我要写书评

暂无评论

Massive quark production in electron positron annihilation to order α_s²

引用

EUROPEAN PHYSICAL JOURNAL C 1998年第1期2卷 137-150页

作者： Chetyrkin, KG Hoang, AH Kuhn, JH Steinhauser, M Teubner, T Univ Karlsruhe Inst Theoret Teilchenphys D-76128 Karlsruhe Germany Russian Acad Sci Inst Nucl Res Moscow 117312 Russia Univ Calif San Diego Dept Phys La Jolla CA 92093 USA Max Planck Inst Phys Werner Heisenberg Inst Phys D-80805 Munich Germany DESY D-22603 Hamburg Germany

Recent analytical and numerical results for the three-loop polarization function allow to present a phenomenological analysis of the cross section for massive quark production in electron positron annihilation to order alpha(s)(2). Numerical predictions based on fixed order perturbation theory are presented for charm and bottom production above 5 and 11.5 GeV, respectively. The contribution from these energy regions to alpha(M-Z(2)), the running QED coupling constant at scale M-Z, are given. The dominant terms close to threshold, i.e. in an expansion for small quark velocity beta, are presented.

关键词： Perturbation Theory Energy Region Massive Quark polarization function Numerical Prediction

来源：评论

学校读者我要写书评

暂无评论

Laurent series expansion of sunrise-type diagrams using configuration space techniques

引用

EUROPEAN PHYSICAL JOURNAL C 2004年第4期36卷 471-482页

作者： Groote, S Körner, JG Pivovarov, AA Johannes Gutenberg Univ Mainz Inst Phys D-55099 Mainz Germany Tartu Ulikool Fuusika Keemiateaduskond EE-51010 Tartu Estonia Russian Acad Sci Inst Nucl Res Moscow 117312 Russia

We show that configuration space techniques can be used to efficiently calculate the complete Laurent series epsilon-expansion of sunrise-type diagrams to any loop order in D-dimensional space-time for any external momentum and for arbitrary mass configurations. For negative powers of epsilon the results are obtained in analytical form. For positive powers of epsilon including the finite epsilon(0) contribution the result is obtained numerically in terms of low-dimensional integrals. We present general features of the calculation and provide exemplary results up to five-loop order which are compared to available results in the literature.

关键词： MULTILOOP FEYNMAN-INTEGRALS CHIRAL PERTURBATION-THEORY EFFECTIVE-FIELDTHEORY SUNSET-TYPE DIAGRAMS TO-LEADING ORDER RECURRENCE RELATIONS NUMERICAL EVALUATION DIFFERENTIAL-EQUATIONS SUM-RULES polarization function

来源：评论

学校读者我要写书评

暂无评论

Coulomb Screening and Plasmon Excitation in Graphene at Finite Temperature

引用

Communications in Theoretical Physics 2009年第8期52卷 361-364页

作者： LI Zhao-Zhe School of Physics Peking University Beijing 100871 China

By using the random phase approximation (RPA) in many-body perturbation theory,we calculate thepolarization function of the electron gas in graphene at finite *** on this,we calculate the temperaturedependent dielectric function ∈(q).The thermal effect on ∈(q) in various q regions is *** temperaturedependence is found to be *** also investigate the plasmon dispersion relation at finite temperature,with thezero-temperature relation as a special *** result is in good agreement with recent experimental data.

关键词： graphene polarization function dielectric function plasmon

来源：评论

学校读者我要写书评

暂无评论

Exploiting Discriminating Features for Fine-Grained Ship Detection in Optical Remote Sensing Images

引用

IEEE JOURNAL OF SELECTED TOPICS IN APPLIED EARTH OBSERVATIONS AND REMOTE SENSING 2024年 17卷 20098-20115页

作者： Liu, Ying Liu, Jin Li, Xingye Wei, Lai Wu, Zhongdai Han, Bing Dai, Wenjuan Shanghai Maritime Univ Coll Informat Engn Shanghai 201306 Peoples R China Shanghai Ship & Shipping Res Inst Co Ltd Shanghai 200135 Peoples R China Minist Nat Resources East China Sea Area & Isl Ctr Key Lab Marine Ecol Monitoring & Restorat Technol Shanghai 201206 Peoples R China

Fine-grained remote sensing ship detection is crucial in a variety of fields, such as ship safety, marine environmental protection, and maritime traffic management. Despite recent progress, current research suffers from the following three major challenges: insufficient features representation, conflicts in shared features, and inappropriate anchor labeling strategy, which significantly impede accurate fine-grained ship detection. To address these issues, we propose FineShipNet as a solution. Specifically, we first propose a novel blend synchronization module, which aims to facilitate the coutilization of semantic information from top-level and bottom-level features and minimize information redundancy. Subsequently, the blend feature maps are fed into a novel polarized feature focusing module, which decouples the features used in classification and regression to create task-specific discriminating features maps. Meanwhile, we adopt the adaptive harmony anchor labeling and propose a novel metric, harmony score, to choose high-quality anchors that can effectively capture the discriminating features of the target. Extensive experiments on four fine-grained remote sensing ship datasets (HRSC2016, DOSR, FGSD2021, and ShipRSImageNet) demonstrate that our FineShipNet outperforms current state-of-the-art object detection methods, achieving superior performance with mean average precision scores of 81.3%, 68.5%, 85.7%, and 63.9%, respectively.

关键词： Marine vehicles Feature extraction Labeling Remote sensing Attention mechanisms Accuracy Semantics Training Object detection Location awareness Anchor labeling strategy discriminating features fine-grained object detection polarization function ship detection

来源：评论

学校读者我要写书评

暂无评论

Modeling of the interband transitions in the optical conductivity of doped two-dimensional materials in the terahertz to the infrared frequency range: the case studies of graphene and phosphorene

引用

RADIATION EFFECTS AND DEFECTS IN SOLIDS 2023年第1-2期178卷 54-71页

作者： Miskovic, Z. L. Moshayedi, M. Rivas, M. R. Preciado Jakovac, J. Radovic, I. Despoja, V. Univ Waterloo Dept Appl Math Waterloo ON Canada Univ Waterloo Waterloo Inst Nanotechnol Waterloo ON Canada Inst Phys Zagreb Croatia Univ Belgrade VINCA Inst Nucl Sci Natl Inst Republ Serbia Dept Atom Phys Belgrade Serbia Donostia Int Phys Ctr DIPC San Sebastian Spain

We use Kramers-Kronig analysis and ab initio calculations to develop a simple analytical method for including the effects of high-energy interband electron transitions in the density polarization function of doped graphene and doped phosphorene in the optical limit. The resulting formulas are suitable for applications in the terahertz to the mid-infrared range of frequencies, where the interband electron transitions are shown to give rise to static screening with a suitably chosen in-plane polarizability. In the case of phosphorene, each component of its static polarizability tensor can be computed from a sum-rule-like formula using the ab initio data for the real part of the corresponding component of the full optical interband conductivity tensor of that material.

关键词： polarization function conductivity interband transitions graphene phosphorene

来源：评论

学校读者我要写书评

暂无评论

Vibrational and theoretical studies of urea and magnesium-urea complexes

引用

THEORETICAL CHEMISTRY ACCOUNTS 2000年第2期105卷 156-164页

作者： Raptis, SG Anastassopoulou, J Theophanides, T Natl Tech Univ Athens Dept Chem Engn Radiat Chem & Biospect GR-15773 Athens Greece

The molecular structure and IR spectra of urea, H2NCONH2, in gas phase and in acetonitrile solution, as well as of the two complexes [MgU4Cl2] and [MgU6]Cl-2 have been observed. The influence of environmental changes to geometry and spectra are shown. Various basis sets have been employed to safeguard the validity of the reported findings, using polarization functions for all calculations to get the correct pyramidal amide configuration. The erroneous low energy of the C-2v symmetry group, after the addition of the ZPVE correction, is discussed. For the solvated urea molecule a reduction of the energy barrier, compared to the gas phase urea, between the two minimum configurations, C-2 and C-S, and the planar geometry, is observed. The lowest energy minimum in acetonitrile is found to be the C-2 symmetry group, while for the two complexes, the local symmetry of urea is C-S or C-2 depending on the complex, or even on the coordination position of urea in the complex. The wagging motion of the amide group is also discussed in all the studied urea species. The computed geometries and most of the spectroscopic results are in good agreement with the available experimental data.

关键词： Urea Amide Symmetry Group Amide Group polarization function

来源：评论

学校读者我要写书评

暂无评论

DIATOMIC INTERACTIONS IN MOMENTUM SPACE - THE EFFECT OF polarization AND FLOATING functionS

引用

THEORETICA CHIMICA ACTA 1982年第1期62卷 39-53页

作者： KOGA, T SHIMOKAWA, K INAGAWA, I MORITA, M MURORAN INST TECHNOL DEPT APPL SCI ENERGYMURORANHOKKAIDO 050JAPAN

The method of momentum density for interatomic interactions is used to investigate the pictures and roles of the polarization and floating functions in momentum (p-) space. Referring to the previous results from the minimal LCAO (Finkelstein-Horowitz) momentum density, we quantitatively discuss the effect of these functions for the bonding process in the ground state of H 2 + system. The essence of the polarization and floating effects is found to be a modulation of the oscillation in the two-center part of the momentum density. The polarization function introduces a term with a phase and the floating function enlarges the period of the oscillation. An increased migration of the density from the one-center to the two-center part is also important. As a result, both the functions contribute to emphasize the contraction and expansion of momentum density observed previously. However, the floating function disturbs the density distribution in high momentum region, reflecting the destruction of cusps in position (r-) space. We point out an error in the pioneer work of Duncanson.

关键词： Floating function Momentum density polarization function

来源：评论

学校读者我要写书评

暂无评论

QCD, α_s, heavy quark mass and sum rules

引用

Nuclear and Particle Physics Proceedings 2015年 260卷 121-124页

作者： Sturm, Christian Universität Würzburg Institut für Theoretische Physik und Astrophysik Emil-Hilb-Weg 22 Würzburg D-97074 Germany

We discuss the determination of the heavy charm- and bottom-quark masses from the sum rule approach as well as the determination of the strong coupling constant from the measurable R-ratio, hadronic τ-lepton decays and Z-boson decays. From theory side these determinations require the calculation of the vacuum polarization function in the low- and high-energy limit, respectively. © 2015 Elsevier B.V.

关键词： Heavy quark mass polarization function Strong coupling constant

来源：评论

学校读者我要写书评

暂无评论

Magnetoplasmons for the α-T3 model with filled Landau levels

引用

JOURNAL OF PHYSICS-CONDENSED MATTER 2020年第48期32卷 485301-485301页

作者： Balassis, Antonios Dahal, Dipendra Gumbs, Godfrey Iurov, Andrii Huang, Danhong Roslyak, Oleksiy Fordham Univ Dept Phys & Engn Phys 441 East Fordham Rd Bronx NY 10458 USA CUNY Hunter Coll Dept Phys & Astron 695 Pk Ave New York NY 10065 USA Donostia Int Phys Ctr DIPC P de Manuel Lardizabal 4 San Sebastian 20018 Basque Country Spain CUNY Medgar Evers Coll Dept Phys & Comp Sci Brooklyn NY 11225 USA US Air Force Res Lab Space Vehicles Directorate Kirtland AFB NM 87117 USA

Using the alpha-T-3 model, we carried out analytical and numerical calculations for the static and dynamic polarization functions in the presence of a perpendicular magnetic field. The model involves a parameter alpha which is the ratio of the hopping strength from an atom at the center of a honeycomb lattice to one of the atoms on the hexagon to the hopping strength around its rim. Our results were employed to determine the longitudinal dielectric function and the magnetoplasmon dispersion relation. The magnetic field splits the continuous valence, conduction and flat energy subband into discrete Landau levels which present significant effects on the polarization function and magnetoplasmon dispersion. This includes the fact that the energies of the Landau levels are valley dependent which leads to different behaviors of the polarization function as the hopping parameter alpha(or phi= tan(-1)alpha) is reduced continuously toward zero. This essential critical behavior of the polarization function leads to a softening of a magnetoplasmon mode. We present results for a doped layer in the integer quantum Hall regime for fixed hopping parameter alpha and various magnetic fields as well as chosen magnetic field and different alpha in the random phase approximation.

关键词： alpha-T3 lattice dice lattice polarization function magnetoplasmon dispersion

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：