检索结果-内蒙古大学图书馆

A limited-feedback approximation scheme for optimal switching problems with execution delays

MATHEMATICAL METHODS OF OPERATIONS RESEARCH 2018年第3期87卷 347-382页

作者： Perninge, Magnus Linnaeus Univ Dept Phys & Elect Engn PG Vejdes Plats S-35252 Vaxjo Sweden

We consider a type of optimal switching problems with non-uniform execution delays and ramping. Such problems frequently occur in the operation of economical and engineering systems. We first provide a solution to the problem by applying a probabilistic method. The main contribution is, however, a scheme for approximating the optimal control by limiting the information in the state-feedback. In a numerical example the approximation routine gives a considerable computational performance enhancement when compared to a conventional algorithm.

关键词： Optimal switching Impulse control Real options Delivery lag Execution delay Stopping time Snell envelope numerical algorithm

来源：评论

学校读者我要写书评

暂无评论

Variational assimilation with covariance matrices of observation data errors for the model of the Baltic Sea dynamics

引用

RUSSIAN JOURNAL OF numerical ANALYSIS AND MATHEMATICAL MODELLING 2018年第3期33卷 149-160页

作者： Agoshkov, Valery I. Parmuzin, Eugene I. Zakharova, Natalia B. Shutyaev, Victor P. RAS Inst Numer Math Moscow 119333 Russia Moscow Inst Phys & Technol Dolgoprudnyi 141701 Moscow Region Russia

The mathematical model of the Baltic Sea dynamics developed at the Institute of numerical Mathematics of RAS is considered. The problem of variational assimilation of average daily data for the sea surface temperature (SST) is formulated and studied with the use of covariance matrices of observation data errors. Based on variational assimilation of satellite observation data, we propose an algorithm for solving the inverse problem of the heat flux reconstruction on the sea surface. The results of numerical experiments on reconstruction of the heat flux function are presented for the problem of variational assimilation of observation SST data.

关键词： Variational assimilation covariance matrices numerical algorithm determination of heat fluxes sea surface temperature

来源：评论

学校读者我要写书评

暂无评论

Novel algorithms to estimate nonlinear FDEs: Applied to fractional order nutrient-phytoplankton-zooplankton system

引用

JOURNAL OF COMPUTATIONAL AND APPLIED MATHEMATICS 2018年 339卷 193-207页

作者： Asl, Mohammad Shahbazi Javidi, Mohammad Univ Tabriz Fac Math Sci Tabriz Iran

In this paper, dynamical behavior of a mathematical model for the interaction of nutrient phytoplankton and its predator zooplankton is investigated numerically. Stability analysis of the phytoplankton-zooplankton model is studied by using the fractional Routh-Hurwitz stability conditions. We have studied the local stability of the equilibrium points. Then a new numerical algorithm, as well as its modification for solving fractional differential equations (FDEs) based on the polynomial interpolation, is proposed. The algorithms are designed to estimate linear and nonlinear FDEs and they have the capability to apply for solving fractional order systems. The convergence order and stability of the fractional higher order algorithms are proved and stability regions of the algorithms are achieved. Extensive numerical simulation results are provided and compared with the literature for illustrating the effectiveness and applicability of the presented algorithms to solve fractional differential equations. The obtained analytical results are validated by numerical simulations and the global dynamics of the model system is studied. (C) 2017 Elsevier B.V. All rights reserved.

关键词： Nutrient Plankton numerical algorithm Fractional order system Stability

来源：评论

学校读者我要写书评

暂无评论

Two-dimensional shifted Legendre polynomials operational matrix method for solving the two-dimensional integral equations of fractional order

引用

APPLIED MATHEMATICS AND COMPUTATION 2018年 322卷 40-54页

作者： Hesameddini, Esmail Shahbazi, Mehdi Shiraz Univ Technol Dept Math Sci POB 71555-313 Shiraz Iran

This work approximates the unknown functions based on the two-dimensional shifted Legendre polynomials operational matrix method (2D-SLPOM) for the numerical solution of two-dimensional fractional integral equations. The present method reduces these equations to a system of algebraic equations and then this system will be solved numerically by Newton's method. Moreover, an estimation of the error bound for this algorithm will be shown by preparing some theorems. Some examples are presented to demonstrate the validity and applicability of the proposed method with respect to the two-dimensional block pulse functions method (2D-BPFs) and two-dimensional Bernstein polynomials operational matrix method (2D-BPOM). (C) 2017 Elsevier Inc. All rights reserved.

关键词： Two-dimensional shifted Legendre polynomials Two-dimensional fractional integral equations Error estimate numerical algorithm

来源：评论

学校读者我要写书评

暂无评论

Identification of atypical (rare) elements-a conditional, distribution-free approach

引用

IMA JOURNAL OF MATHEMATICAL CONTROL AND INFORMATION 2018年第3期35卷 923-937页

作者： Kulczycki, Piotr Charytanowicz, Malgorzata Kowalski, Piotr A. Lukasik, Szymon Polish Acad Sci Syst Res Inst Ctr Informat Technol Data Anal Methods Warsaw Poland AGH Univ Sci & Technol Fac Phys & Appl Comp Sci Div Informat Technol & Syst Res Krakow Poland Catholic Univ Lublin Fac Math Comp Sci & Landscape Inst Math & Comp Sci Lublin Poland

The discovery of atypical elements has become one of the most important challenges in data analysis and exploration. At the same time it is not an easy matter with difficult conditions, and not even strictly defined. This article presents a ready-to-use procedure for identifying atypical elements in the sense of rarely occurring. The issue is considered in a conditional approach, where describing and conditioning variables can be multidimensional continuous with the second type also potentially categorical. The application of nonparametric concepts frees the investigated procedure from distributions of describing and conditioning variables. Ease of interpretation and completeness of the presented material lend themselves to the use of the worked out method in a wide range of tasks in various applications of data analysis in science and practice.

关键词： atypical element rare element outlier atypical element identification conditional approach nonparametric method distribution-free method numerical algorithm

来源：评论

学校读者我要写书评

暂无评论

On Lie symmetry mechanics for Navier-Stokes equations unified with non-Newtonian fluid model: A classical directory

引用

PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS 2019年 535卷 122469-000页

作者： Rehman, Khalil Ur Malik, M. Y. King Khalid Univ Coll Sci Dept Math Abha Saudi Arabia Air Univ Dept Math PAF Complex E-9 Islamabad 44000 Pakistan

It is noticed that the most of the researchers having affiliation with the field of fluid science formulate the physical problems by coupling the constitutive relation of the fluid models with the Navier-Stokes equations. The ultimate system of partial differential equations in this direction becomes non-linear in nature due to which investigators always faced problem to narrate the flow field properties. Therefore, in this article we propose the symmetry toolkit to obtain the one parameter group of transformations for the flow controlling differential equations rather than to move-on with the so-called transformations available in literature. To propose idea we have considered the thermally magnetized Williamson fluid flow field along with heat source/sink and chemical reaction effects. The mathematical model is constructed by coupling the constitutive relation of Williamson fluid model with the Navier-Stokes equations in terms of partial differential equations. Such equations are reduced into system of ordinary differential equations by using self-constructed scaling group of transformations via symmetry analysis. The reduced system is solved by numerical algorithm. The key observations are added by means of graphs and tables. It is observed that both Weissenberg number and Hartmann number has same impact of Williamson fluid velocity. Further, Williamson fluid concentration reflects decline magnitude towards higher values of both Schmidt number and chemical reaction parameter. It is well trusted that the structuring of one parameter group of transformations for the particular flow problem will be helpful to report complete description as compared to utilizing the so-called transformations from an existing work. (C) 2019 Elsevier B.V. All rights reserved.

关键词： Symmetry analysis Williamson fluid model Magnetized flow field Heat source/sink Chemical reaction numerical algorithm

来源：评论

学校读者我要写书评

暂无评论

Identification of the Thermal Conductivity Coefficient Using a Given Surface Heat Flux

引用

COMPUTATIONAL MATHEMATICS AND MATHEMATICAL PHYSICS 2018年第12期58卷 2031-2042页

作者： Albu, A. F. Zubov, V. I. Russian Acad Sci Fed Res Ctr Comp Sci & Control Dorodnicyn Comp Ctr Moscow 119333 Russia State Univ Moscow Inst Phys & Technol Dolgoprudnyi 141700 Moscow Oblast Russia

The inverse problem of determining a temperature-dependent thermal conductivity coefficient is studied. The study is based on the Dirichlet boundary value problem for the two-dimensional nonstationary heat equation. The cost functional is defined as the rms deviation of the surface heat flux from experimental data. For the numerical solution of the problem, an algorithm based on the modern fast automatic differentiation technique is proposed. Examples of solving the posed problem are given.

关键词： heat conduction inverse coefficient problems gradient heat equation adjoint equations numerical algorithm

来源：评论

学校读者我要写书评

暂无评论

Heat spreading path optimization of IGBT thermal network model

引用

MICROELECTRONICS RELIABILITY 2019年 103卷 113511-000页

作者： Cui, Haoyang Hu, Fengye Zhang, Yu Zhou, Kun Shanghai Univ Elect Power Sch Elect & Informat Engn Shanghai Peoples R China

This paper presents a theoretical study on the thermal reliability of Insulated-gate bipolar transistor (IGBT) power modules. Although the Cauer thermal network (CTN) model is widely recognized as an essential tool to analyze the thermal performance of IGBT, the heat propagation path, however, deviates from the actual situation and causing an error calculation of junction temperature. Therefore, the thermal resistance (R-th) and thermal capacity (C-th) values are optimized by the heat spreading angle of each material layer, and the influence of baseplate heat dissipation effects is fully considered by adding the heat convection mechanism to the CTN model, which includes interaction between heat conduction and heat convection, thus achieving the integrity of the heat spreading path. Effectiveness of proposed model is validated by simulation studies of finite element analysis and Simulink, the junction temperature estimation results show that the proposed model is more accurate than the conventional CTN model especially in the good dissipation conditions. Thus, accurate thermal behavior estimation could be fairly interpreted by the optimized heat spreading path.

关键词： IGBT module Spreading angle Thermal network model Transient thermal impedance numerical algorithm

来源：评论

学校读者我要写书评

暂无评论

Identification of Thermal Conductivity Coefficient Using a Given Temperature Field

引用

COMPUTATIONAL MATHEMATICS AND MATHEMATICAL PHYSICS 2018年第10期58卷 1585-1599页

The problem of determining the temperature-dependent thermal conductivity coefficient is studied. The study is based on the Dirichlet boundary value problem for the two-dimensional nonstationary heat equation. The cost functional is defined as the rms deviation of the temperature field from experimental data. For the numerical solution of the problem, an algorithm based on the modern fast automatic differentiation technique is proposed. Examples of solving the posed problem are given.

关键词： heat conduction inverse coefficient problems gradient heat equation adjoint equations numerical algorithm

来源：评论

学校读者我要写书评

暂无评论

The Dissection algorithm for the Second-Born Self-Energy

引用

PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS 2019年第7期256卷 1800573-1800573页

作者： Perfetto, Enrico Stefanucci, Gianluca CNR ISM Div Ultrafast Proc Mat FLASHit Area Ric Roma 1 Monterotondo Italy Univ Roma Tor Vergata Dipartimento Fis Via Ricerca Sci I-00133 Rome Italy INFN Sez Roma Tor Vergata Via Ric Sci 1 I-00133 Rome Italy

Here, an algorithm to efficiently compute the second-Born self-energy of many-body perturbation theory is described. The core idea consists in dissecting the set of all four-index Coulomb integrals into properly chosen subsets, thus avoiding to loop over those indices for which the Coulomb integrals are zero or negligible. The scaling properties of the algorithm with the number of basis functions is discussed. The computational gain is demonstrated in the case of one-particle Kohn-Sham basis for organic molecules.

关键词： nonequilibrium Green's functions numerical algorithm second-Born self-energy

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：