检索结果-内蒙古大学图书馆

Uncertainty in Simulating the Impact of Cultivar Improvement on Winter Wheat Phenology in the North China Plain

Journal of Meteorological Research 2018年第4期32卷 636-647页

作者： Dingrong WU Chunyi WANG Fang WANG Chaoyang JIANG Zhiguo HUO Peijuan WANG State Key Laboratory of Severe Weather Chinese Academy of Meteorological Sciences Beijing 100081 Hainan Meteorological Service Haikou 570203

The phenology model is one of the major tools in evaluating the impact of cultivar improvement on crop pheno-logy. Understanding uncertainty in simulating the impact is an important prerequisite for reliably interpreting the ef-fect of cultivar improvement and climate change on phenology. However, uncertainty induced by different temperat-ure response functions and parameterization methods have not been properly addressed. Based on winter wheat phen-ology observations during 1986-2012 in 47 agro-meteorology observation stations in the North China Plain （NCP）, the uncertainty of the simulated impacts caused by four widely applied temperature response functions and two para- meterization methods were investigated. The functions were firstly calibrated using observed phenology data during 1986-1988 from each station by means of two parameterization methods, and were then used to quantify the impact of cultivar improvement on wheat phenology during 1986-2012. The results showed that all functions and all para-meterization methods could reach acceptable precision （RMSE 〈 3 days for all functions and parameterization meth-ods）, however, substantial differences exist in the simulated impacts between different functions and parameteriza-tion methods. For vegetative growth period, the simulated impact is 0.20 day （10 yr）^-1 [95% confidence interval： -2.81-3.22 day （10 yr）^-1] across the NCP, while for reproductive period, the value is 1.50 day （10 yr）^-1 [-1.03-4.02 day （10 yr）^-1]. Further analysis showed that uncertainty can be induced by both different fimctions and parameteriza-tion methods, while the former has greater influence than the latter. During vegetative period, there is a significant positive linear relationship between ranges of simulated impact and growth period average temperature, while during reproductive period, the relationship is polynomial. This highlights the large inconsistency that exists in most impact quantifying functions and the urgent need to

关键词： observed phenology temperature response function parameterization method renewing cultivar

来源：评论

学校读者我要写书评

暂无评论

parameterization of Invariant Manifolds for Periodic Orbits (II): A Posteriori Analysis and Computer Assisted Error Bounds

引用

JOURNAL OF DYNAMICS AND DIFFERENTIAL EQUATIONS 2018年第4期30卷 1525-1581页

作者： Castelli, Roberto Lessard, Jean-Philippe James, Jason D. Mireles Vrije Univ Amsterdam Dept Math De Boelelaan 1081 NL-1081 HV Amsterdam Netherlands McGill Univ Dept Math & Stat 805 Sherbrooke O Montreal PQ H3A 0B9 Canada Florida Atlantic Univ Dept Math Sci Sci BldgRoom 234777 Glades Rd Boca Raton FL 33431 USA

In this paper we develop mathematically rigorous computer assisted techniques for studying high order Fourier-Taylor parameterizations of local stable/ unstable manifolds for hyperbolic periodic orbits of analytic vector fields. We exploit the numerical methods developed in Castelli et al. (SIAM J Appl Dyn Syst 14(1): 132-167, 2015) in order to obtain a high order Fourier-Taylor series expansion of the parameterization. The main result of the present work is an a-posteriori theorem which provides mathematically rigorous error bounds. The hypotheses of the theorem are checked with computer assistance. The argument relies on a sequence of preliminary computer assisted proofs where we validate the numerical approximation of the periodic orbit, its stable/ unstable normal bundles, and the jets of the manifold to some desired order M. We illustrate our method by implementing validated computations for two dimensional manifolds in the Lorenz equations in R3 and a three dimensional manifold of a suspension bridge equation in R-4.

关键词： Periodic orbits Stable unstable manifolds parameterization method Validated error bounds Truncation error analysis Computer assisted proof

来源：评论

学校读者我要写书评

暂无评论

Evaluating the Knot Vector to Synthesize the Cam Motion Using NURBS 7th

引用

7th International Workshop on Computational Kinematics (CK)

作者： Nguyen, T. T. N. Kurtenbach, S. Huesing, M. Corves, B. Rhein Westfal TH Aachen Dept Mech Theory & Dynam Machines Aachen Germany

ISBN: (纸本)9783319608679;9783319608662

A Non Uniform Rational B-Spline (NURBS) is used for synthesizing the motion curve of cam mechanisms because it is flexible and satisfies arbitrary boundary conditions from the working requirement of machinery systems. For using NURBS curve as motion curves of cam mechanisms, selecting the knot vector is very important. This work presents the effect of the knot vector on the displacement, velocity, acceleration, and jerk curves. The linear system of equations for solving the cam motion is also presented. A general computation of the knot vector of NURBS for synthesizing the motion curve is presented. Several examples illustrate this research.

关键词： parameterization method Knot vector NURBS Cam motion synthesis

来源：评论

学校读者我要写书评

暂无评论

A Two-Tier Hybrid parameterization Framework for Effective Data Classification 17

A Two-Tier Hybrid Parameterization Framework for Effective D...

引用

17th International Conference on New Trends in Intelligent Software methodology Tools, and Techniques (SoMeT)

作者： Mohamad, Masurah Selamat, Ali Univ Teknol Malaysia Fac Comp Johor Baharu 81310 Johor Malaysia Univ Teknol Malaysia Media & Game Innovat Ctr Excellence MaGICX Johor Baharu 81310 Johor Malaysia Univ Teknol MARA Perak Fac Comp & Math Sci Tapah Branch Tapah 45000 Perak Malaysia Univ Teknol Malaysia MJIIT Jalan Sultan Yahya Petra Kuala Lumpur Malaysia Univ Hradec Kralove Rokitanskeho 62 Hradec Kralove 50003 Czech Republic

ISBN: (纸本)9781614999003;9781614998990

The classification process is a decision-making task. In order to obtain a good decision, the classification process needs to be conducted by following a standard framework or approach. The selection of a good parameterization method plays an important role in executing an effective parameterization process. The parameterization process will generate an optimized parameter reduction set that helps the classifier in generating a significant result. However, the size and characteristics of the dataset might also influence the generation of results in the classification process. The process of parameterization becomes more complex when the dataset is big and consists of uncertain and inconsistent data. Therefore, these problems need to be considered during the decision-making process. Many solutions have been provided recently by researchers, but most of the research works did not consider the highlighted issues as problems that should be solved together through the use of a single framework. In this paper, an alternative framework was proposed for decision-makers in conducting the decision-making process. The framework was demonstrated by the use of a two-tier hybrid parameterization phase that involving two main processes for identifying the most optimized parameter set for uncertain and inconsistent big datasets. The results showed that the proposed framework can be implemented to significantly increase the classification performance by returning an accuracy rate of more than 70% for all datasets.

关键词： parameterization method soft set rough set classification hybrid big data

来源：评论

学校读者我要写书评

暂无评论

Analytic Continuation of Local (Un)Stable Manifolds with Rigorous Computer Assisted Error Bounds

引用

SIAM JOURNAL ON APPLIED DYNAMICAL SYSTEMS 2018年第1期17卷 157-202页

作者： Kalies, William D. Kepley, Shane James, J. D. Mireles Florida Atlantic Univ Dept Math Sci Boca Raton FL 33431 USA

We develop a validated numerical procedure for continuation of local stable/unstable manifold patches attached to equilibrium solutions of ordinary differential equations. The procedure has two steps. First we compute an accurate high order Taylor expansion of the local invariant manifold. This expansion is valid in some neighborhood of the equilibrium. An important component of our method is that we obtain mathematically rigorous lower bounds on the size of this neighborhood, as well as validated a posteriori error bounds for the polynomial approximation. In the second step we use a rigorous numerical integrating scheme to propagate the boundary of the local stable/unstable manifold as long as possible, i.e., as long as the integrator yields validated error bounds below some desired tolerance. The procedure exploits adaptive remeshing strategies which track the growth/decay of the Taylor coefficients of the advected curve. In order to highlight the utility of the procedure, we study the embedding of some two dimensional manifolds in the Lorenz system.

关键词： computer assisted proof parameterization method invariant manifolds analytic continuation radii polynomials heteroclinic connections

来源：评论

学校读者我要写书评

暂无评论

Validated Computation of Heteroclinic Sets

引用

SIAM JOURNAL ON APPLIED DYNAMICAL SYSTEMS 2017年第1期16卷 375-409页

作者： Capinski, Maciej J. James, J. D. Mireles AGH Univ Sci & Technol Fac Appl Math Al Mickiewicza 30 PL-30059 Krakow Poland Florida Atlantic Univ Dept Math Sci Boca Raton FL 33431 USA

In this work we develop a method for computing mathematically rigorous enclosures of some one dimensional manifolds of heteroclinic orbits for nonlinear maps. Our method exploits a rigorous curve following an argument built on high order Taylor approximation of the local stable/unstable manifolds. The curve following argument is a uniform interval Newton method applied on short line segments. The definition of the heteroclinic sets involve compositions of the map, and we use a Lohner-type representation to overcome the accumulation of roundoff errors. Our argument requires precise control over the local unstable and stable manifolds so that we must first obtain validated a posteriori error bounds on the truncation errors associated with the manifold approximations. We illustrate the utility of our method by proving some computer assisted theorems about heteroclinic invariant sets for a volume preserving map of R-3.

关键词： invariant manifolds heteroclinic orbits rigorous enclosure of level sets computer assisted proof validated numerics parameterization method Newton's method

来源：评论

学校读者我要写书评

暂无评论

Fourier-Taylor Approximation of Unstable Manifolds for Compact Maps: Numerical Implementation and Computer-Assisted Error Bounds

引用

FOUNDATIONS OF COMPUTATIONAL MATHEMATICS 2017年第6期17卷 1467-1523页

作者： James, J. D. Mireles Florida Atlantic Univ Dept Math Sci Boca Raton FL 33431 USA

We develop and implement a semi-numerical method for computing high-order Taylor approximations of unstable manifolds for hyperbolic fixed points of compact infinite-dimensional maps. The method can follow folds in the embedding and describes precisely the dynamics on the manifold. In order to ensure the accuracy of our computations in spite of the many truncation and round-off errors, we develop a posteriori error bounds for the approximations. Deliberate control of round-off errors (using interval arithmetic) in conjunction with explicit analytical estimates leads to mathematically rigorous computer-assisted theorems describing precisely the truncation errors for our approximation of the invariant manifold. The method is applied to the Kot-Schaffer model of population dynamics with spatial dispersion.

关键词： Unstable manifolds Compact maps Infinite dimensional dynamical systems parameterization method A posteriori analysis Computer-assisted proof

来源：评论

学校读者我要写书评

暂无评论

Coupled wind farm parameterization with a mesoscale model for simulations of an onshore wind farm

引用

APPLIED ENERGY 2017年 206卷 113-125页

作者： Yuan, Renyu Ji, Wenju Luo, Kun Wang, Jianwen Zhang, Sanxia Wang, Qiang Fan, Jianren Ni, MingJiang Cen, Kefa Zhejiang Univ State Key Lab Clean Energy Utilizat Hangzhou 310027 Zhejiang Peoples R China Inner Mongolia Univ Technol Sch Energy & Power Engn Hohhot 010051 Peoples R China Minist Educ & Inner Mongolia Construct Key Lab Wind & Solar Power Energy Utilizat Techno Hohhot 010051 Peoples R China

The mesoscale Weather Research and Forecasting (WRF) model coupled with wind farm parameterization is newly developed to simulate the wake flow and power production of a real onshore wind farm. First, wind farm flow field simulations are conducted with 1000 m, 500 m and 200 m horizontal resolutions, and the simulation results capture the wind farm observed data well. in addition, wind farm flow characteristics, power output, and influence on the atmosphere boundary layer (ABL) are resolved at a horizontal resolution of 200 m. The wake interactions, wind speed, and power output deficit in the wind farm are analyzed. The power comparison results prove that the proposed method can be applied to simulate the power output of a real onshore wind farm with high accuracy in real time. The influence of the wind farm on the ABL is also discussed. The results show that wind farm effects on the ABL occur mainly within the turbine rotor-spanned heights and the downstream regions behind the wind farm within 10 km, within which the speed deficit ratio can exceed 10%. For the region that is 18 km downstream of the wind farm, the average speed deficit ratio is only about 2%. This study is the first attempt to reproduce the wake flow and power output of a real onshore wind farm by the WRF model at such high resolution.

关键词： parameterization method WRF model Mesoscale model Onshore wind farm ABL High resolution

来源：评论

学校读者我要写书评

暂无评论

High-Order parameterization of Stable/Unstable Manifolds for Long Periodic Orbits of Maps

引用

SIAM JOURNAL ON APPLIED DYNAMICAL SYSTEMS 2017年第3期16卷 1748-1795页

作者： Gonzalez, J. L. James, J. D. Mireles Florida Atlantic Univ Dept Math Sci Boca Raton FL 33431 USA

This paper develops seminumerical methods for computing high-order polynomial approximations of stable/unstable manifolds attached to long periodic orbits in discrete time dynamical systems. Our approach extends a standard multiple shooting scheme for periodic orbits, allowing us to compute invariant manifolds for periodic orbits without considering compositions of the map. This leads to a system of conjugacy equations characterizing the complete collection of chart maps, with one chart attaching a local stable/unstable manifold to each point along the periodic orbit. We develop a formal series solution for the system of conjugacy equations and show that the coefficients of the series are determined by recursively solving certain linear systems of equations. We derive the recursive equations for a number of example problems in dimensions two and three, with both polynomial and transcendental nonlinearities, and present some numerical results which illustrate the utility of the method. We also highlight some technical issues such as controlling the decay rate of the coefficients and managing truncation errors via a posteriori indicators.

关键词： parameterization method periodic orbits of maps multiple shooting stable and unstable manifolds

来源：评论

学校读者我要写书评

暂无评论

Chebyshev-Taylor parameterization of Stable/Unstable Manifolds for Periodic Orbits: Implementation and Applications

引用

INTERNATIONAL JOURNAL OF BIFURCATION AND CHAOS 2017年第14期27卷 1730050-1730050页

作者： James, J. D. Mireles Murray, Maxime Florida Atlantic Univ Dept Math Sci 777 Glades Rd Boca Raton FL 33431 USA

This paper develops a Chebyshev-Taylor spectral method for studying stable/ unstable manifolds attached to periodic solutions of differential equations. The work exploits the parameterization method -a general functional analytic framework for studying invariant manifolds. Useful features of the parameterization method include the fact that it can follow folds in the embedding, recovers the dynamics on the manifold through a simple conjugacy, and admits a natural notion of a posteriori error analysis. Our approach begins by deriving a recursive system of linear differential equations describing the Taylor coefficients of the invariant manifold. We represent periodic solutions of these equations as solutions of coupled systems of boundary value problems. We discuss the implementation and performance of the method for the Lorenz system, and for the planar circular restricted three-and four-body problems. We also illustrate the use of the method as a tool for computing cycle-to-cycle connecting orbits.

关键词： Periodic orbit (un)stable manifold parameterization method boundary value problems automatic differentiation Chebyshev polynomials

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：