Página 1 dos resultados de 16425 itens digitais encontrados em 0.052 segundos

## Análise de erro de funções de pedotransferência na estimativa de retenção de água no solo por meio de árvore de decisão; Error analysis of pedotransfer functions in estimating soil water retention by using decision tree

Fonte: Biblioteca Digital da Unicamp
Publicador: Biblioteca Digital da Unicamp

Tipo: Tese de Doutorado
Formato: application/pdf

Publicado em 18/03/2014
PT

Relevância na Pesquisa

65.89%

#Análise de erros (Matemática)#Mineração de dados (Computação)#Soil water#Error analysis#Data mining

O conhecimento das propriedades hidráulicas do solo é indispensável para modelagem do sistema solo-planta-atmosfera. A determinação destas propriedades de forma direta é problemática: ¬exigem métodos caros, laboriosos e grandes demandantes de tempo. O uso de funções, que estimam estas propriedades a partir de outras, facilmente obtidas, tem sido objeto de várias pesquisas. Estas funções são denominadas de funções de pedotransferência (PTF). As PTF são normalmente avaliadas em função dos valores observados e estimados; pouca atenção tem sido dada à análise do erro em função das propriedades do solo. Este tipo de análise pode revelar detalhes importantes sobre o desempenho de uma PTF, podendo contribuir para melhorar sua capacidade preditiva. A hipótese científica deste trabalho foi que é possível identificar e avaliar padrões nos erros das PTF utilizadas para estimar a retenção de água no solo, por meio de modelos baseados em árvore de decisão. Outra hipótese é que a identificação dos padrões nos erros das PTF fornecerá subsídios para o uso de tais funções de forma mais confiável e precisa. O objetivo geral deste trabalho, portanto, foi obter árvores de decisão capazes de auxiliar na compreensão de quais atributos do solo afetam o desempenho das PTF na estimativa de retenção de água no solo. A metodologia foi baseada no modelo CRISP-DM e foram avaliadas PTF disponíveis na literatura...

Link permanente para citações:

## Error Analysis of a Partial Pivoting Method for Structured Matrices

Fonte: Universidade Nacional da Austrália
Publicador: Universidade Nacional da Austrália

Tipo: Working/Technical Paper
Formato: 322757 bytes; 356 bytes; application/pdf; application/octet-stream

EN_AU

Relevância na Pesquisa

65.86%

Many matrices that arise in the solution of signal processing problems have a special displacement structure. For example, adaptive filtering and direction-of-arrival estimation yield matrices of Toeplitz type. A recent method of Gohberg, Kailath and Olshevsky (GKO) allows fast Gaussian elimination with partial pivoting for such structured matrices. In this paper, a rounding error analysis is performed on the Cauchy and Toeplitz variants of the GKO method. It is shown the error growth depends on the growth in certain auxiliary vectors, the generators, which are computed by the GKO algorithms. It is also shown that in certain circumstances, the growth in the generators can be large, and so the error growth is much larger than would be encountered with normal Gaussian elimination with partial pivoting. A modification of the algorithm to perform a type of row-column pivoting is proposed which may ameliorate this problem.; no

Link permanente para citações:

## Critical evaluation of parameter consistency and predictive uncertainty in hydrological modeling: A case study using Bayesian total error analysis

Fonte: Amer Geophysical Union
Publicador: Amer Geophysical Union

Tipo: Artigo de Revista Científica

Publicado em //2009
EN

Relevância na Pesquisa

55.85%

#parameter consistency#calibration#hydrological model#uncertainty assessment#Bayesian analysis#predictive uncertainty

The lack of a robust framework for quantifying the parametric and predictive uncertainty of conceptual rainfall‐runoff (CRR) models remains a key challenge in hydrology. The Bayesian total error analysis (BATEA) methodology provides a comprehensive framework to hypothesize, infer, and evaluate probability models describing input, output, and model structural error. This paper assesses the ability of BATEA and standard calibration approaches (standard least squares (SLS) and weighted least squares (WLS)) to address two key requirements of uncertainty assessment: (1) reliable quantification of predictive uncertainty and (2) reliable estimation of parameter uncertainty. The case study presents a challenging calibration of the lumped GR4J model to a catchment with ephemeral responses and large rainfall gradients. Postcalibration diagnostics, including checks of predictive distributions using quantile‐quantile analysis, suggest that while still far from perfect, BATEA satisfied its assumed probability models better than SLS and WLS. In addition, WLS/SLS parameter estimates were highly dependent on the selected rain gauge and calibration period. This will obscure potential relationships between CRR parameters and catchment attributes and prevent the development of meaningful regional relationships. Conversely...

Link permanente para citações:

## Inertial Sensors in Estimating Spatio-Temporal Parameters of Walking: Performance Evaluation and Error Analysis

Fonte: Quens University
Publicador: Quens University

Tipo: Tese de Doutorado

EN; EN

Relevância na Pesquisa

55.95%

The portability, ease of use and improved accuracy of miniature inertial sensors brought by current microelectromechanical system (MEMS) technology has inspired researchers to develop human movement monitoring system with body-fixed sensors. Although a large number of studies have attempted to explore the use of miniature inertial sensors in estimating walking speed for the past two decades, there still remain some questions regarding applying inertial sensors in estimating walking speed under different walking conditions and for different subject populations. In this thesis, I focus on evaluating and improving the performance of a shank-mounted mounted inertial measurement unit (IMU) based walking speed estimation method. My research can be divided into four parts. The first part was a systematic review regarding the state of the art of current development of the inertial sensor based walking speed estimation method. A total of 16 articles were fully reviewed in terms of sensor specification, sensor attachment location, experimental design and spatial parameter estimation algorithm. In the second part, a comprehensive performance evaluation was conducted, which included the treadmill and overground walking experiments with constraint on the walking speed...

Link permanente para citações:

## A low-order mixed finite element method for a class of quasi-Newtonian Stokes flows. Part II: a posteriori error analysis

Fonte: Elsevier BV
Publicador: Elsevier BV

Tipo: Artigo de Revista Científica

ENG

Relevância na Pesquisa

65.79%

#Mixed finite element method#Mixed finite element method#Twofold saddle point formulation#A posteriori error analysis

[Abstract] This is the second part of a work dealing with a low-order mixed finite element method for a class of nonlinear Stokes models arising in quasi-Newtonian fluids. In the first part we showed that the resulting variational formulation is given by a twofold saddle point operator equation, and that the corresponding Galerkin scheme becomes well posed with piecewise constant functions and Raviart–Thomas spaces of lowest order as the associated finite element subspaces. In this paper we develop a Bank–Weiser type a posteriori error analysis yielding a reliable estimate and propose the corresponding adaptive algorithm to compute the mixed finite element solutions. Several numerical results illustrating the efficiency of the method are also provided.

Link permanente para citações:

## Error analysis of nonconforming and mixed FEMs for second-order linear non-selfadjoint and indefinite elliptic problems

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 20/01/2014

Relevância na Pesquisa

55.88%

The state-of-the art proof of a global inf-sup condition on mixed finite
element schemes does not allow for an analysis of truly indefinite,
second-order linear elliptic PDEs. This paper, therefore, first analyses a
nonconforming finite element discretization which converges owing to some a
priori $L^2$ error estimates even for reduced regularity on non-convex
polygonal domains. An equivalence result of that nonconforming finite element
scheme to the mixed finite element method (MFEM) leads to the well-posedness of
the discrete solution and to a priori error estimates for the MFEM. The
explicit residual-based a posteriori error analysis allows some reliable and
efficient error control and motivates some adaptive discretization which
improves the empirical convergence rates in three computational benchmarks.; Comment: 35 pages, 8 figures

Link permanente para citações:

## Backward error analysis and the substitution law for Lie group integrators

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Relevância na Pesquisa

55.81%

Butcher series are combinatorial devices used in the study of numerical
methods for differential equations evolving on vector spaces. More precisely,
they are formal series developments of differential operators indexed over
rooted trees, and can be used to represent a large class of numerical methods.
The theory of backward error analysis for differential equations has a
particularly nice description when applied to methods represented by Butcher
series. For the study of differential equations evolving on more general
manifolds, a generalization of Butcher series has been introduced, called
Lie--Butcher series. This paper presents the theory of backward error analysis
for methods based on Lie--Butcher series.; Comment: Minor corrections and additions. Final version

Link permanente para citações:

## Global Error Analysis and Inertial Manifold Reduction

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 28/11/2015

Relevância na Pesquisa

55.93%

Four types of global error for initial value problems are considered in a
common framework. They include classical forward error analysis and shadowing
error analysis together with extensions of both to rescaling of time. To
determine the amplification of the local error that bounds the global error we
present a linear analysis similar in spirit to condition number estimation for
linear systems of equations. We combine these ideas with techniques for
dimension reduction of differential equations via a boundary value formulation
of numerical inertial manifold reduction. These global error concepts are
exercised to illustrate their utility on the Lorenz equations and inertial
manifold reductions of the Kuramoto-Sivashinsky equation.

Link permanente para citações:

## A Frame Work for the Error Analysis of Discontinuous Finite Element Methods for Elliptic Optimal Control Problems and Applications to $C^0$ IP methods

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 04/11/2014

Relevância na Pesquisa

55.87%

In this article, an abstract framework for the error analysis of
discontinuous Galerkin methods for control constrained optimal control problems
is developed. The analysis establishes the best approximation result from a
priori analysis point of view and delivers reliable and efficient a posteriori
error estimators. The results are applicable to a variety of problems just
under the minimal regularity possessed by the well-posed ness of the problem.
Subsequently, applications of $C^0$ interior penalty methods for a boundary
control problem as well as a distributed control problem governed by the
biharmonic equation subject to simply supported boundary conditions are
discussed through the abstract analysis. Numerical experiments illustrate the
theoretical findings. Finally, we also discuss the variational discontinuous
discretization method (without discretizing the control) and its corresponding
error estimates.; Comment: 23 pages, 5 figures, 1 table

Link permanente para citações:

## Parallelization, processor communication and error analysis in lattice kinetic Monte Carlo

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 05/08/2012

Relevância na Pesquisa

55.87%

In this paper we study from a numerical analysis perspective the Fractional
Step Kinetic Monte Carlo (FS-KMC) algorithms proposed in [1] for the parallel
simulation of spatially distributed particle systems on a lattice. FS-KMC are
fractional step algorithms with a time-stepping window $\Delta t$, and as such
they are inherently partially asynchronous since there is no processor
communication during the period $\Delta t$. In this contribution we primarily
focus on the error analysis of FS-KMC algorithms as approximations of
conventional, serial kinetic Monte Carlo (KMC). A key aspect of our analysis
relies on emphasising a goal-oriented approach for suitably defined macroscopic
observables (e.g., density, energy, correlations, surface roughness), rather
than focusing on strong topology estimates for individual trajectories.
One of the key implications of our error analysis is that it allows us to
address systematically the processor communication of different parallelization
strategies for KMC by comparing their (partial) asynchrony, which in turn is
measured by their respective fractional time step $\Delta t$ for a prescribed
error tolerance.; Comment: 32 pages, 4 figures

Link permanente para citações:

## Error analysis of a partial pivoting method for structured matrices

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 05/05/2010

Relevância na Pesquisa

55.85%

#Mathematics - Numerical Analysis#Computer Science - Numerical Analysis#65F05 (Primary) 15B05, 65G50 (Secondary)#F.2.1

Many matrices that arise in the solution of signal processing problems have a
special displacement structure. For example, adaptive filtering and
direction-of-arrival estimation yield matrices of Toeplitz type. A recent
method of Gohberg, Kailath and Olshevsky (GKO) allows fast Gaussian elimination
with partial pivoting for such structured matrices. In this paper, a rounding
error analysis is performed on the Cauchy and Toeplitz variants of the GKO
method. It is shown the error growth depends on the growth in certain auxiliary
vectors, the generators, which are computed by the GKO algorithms. It is also
shown that in certain circumstances, the growth in the generators can be large,
and so the error growth is much larger than would be encountered with normal
Gaussian elimination with partial pivoting. A modification of the algorithm to
perform a type of row-column pivoting is proposed; it may ameliorate this
problem.; Comment: 18 pages. An old Technical Report, submitted for archival purposes.
For further details see http://wwwmaths.anu.edu.au/~brent/pub/pub157.html

Link permanente para citações:

## Robust error analysis of coupled mixed methods for Biot's consolidation model

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 07/12/2015

Relevância na Pesquisa

55.87%

We study the a priori error analysis of finite element methods for Biot's
consolidation model. We consider a formulation which has the stress tensor, the
fluid flux, the solid displacement, and the pore pressure as unknowns. Two
mixed finite elements, one for linear elasticity and the other for mixed
Poisson problems are coupled for spatial discretization, and we show that any
pair of stable mixed finite elements is available. The novelty of our analysis
is that the error estimates of all the unknowns are robust for material
parameters. Specifically, the analysis does not need a uniformly positive
storage coefficient, and the error estimates are robust for nearly
incompressible materials. Numerical experiments illustrating our theoretical
analysis are included.; Comment: 21 pages

Link permanente para citações:

## On an a posteriori error analysis of a mixed finite element Galerkin approximations to a second order wave equation

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 08/04/2015

Relevância na Pesquisa

55.83%

In this article, a posteriori error analysis is developed for mixed finite
element Galerkin approximations to a second order linear hyperbolic equation.
Based on mixed elliptic reconstructions and an integration tool, which is a
variation of Baker's technique introduced earlier by G. Baker ( SIAM J. Numer.
Anal., 13 (1976), 564-576) in the context of a priori estimates for a second
order wave equation, a posteriori error estimates of the displacement in
L{\infty}(L2)-norm for the semidiscrete scheme are derived under minimal
regularity. Finally, a first order implicit-in-time discrete scheme is analyzed
and a posteriori error estimators are established.

Link permanente para citações:

## Optimal Control of a Free Boundary Problem with Surface Tension Effects: A Priori Error Analysis

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Relevância na Pesquisa

55.85%

#Mathematics - Optimization and Control#Mathematics - Numerical Analysis#49J20, 35Q93, 35Q35, 35R35, 65N30

We present a finite element method along with its analysis for the optimal
control of a model free boundary problem with surface tension effects,
formulated and studied in \cite{HAntil_RHNochetto_PSodre_2014a}. The state
system couples the Laplace equation in the bulk with the Young-Laplace equation
on the free boundary to account for surface tension. We first prove that the
state and adjoint system have the requisite regularity for the error analysis
(strong solutions). We discretize the state, adjoint and control variables via
piecewise linear finite elements and show optimal $O(h)$ error estimates for
all variables, including the control. This entails using the second order
sufficient optimality conditions of \cite{HAntil_RHNochetto_PSodre_2014a}, and
the first order necessary optimality conditions for both the continuous and
discrete systems. We conclude with two numerical examples which examine the
various error estimates.

Link permanente para citações:

## Error analysis of tau-leap simulation methods

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Relevância na Pesquisa

55.82%

We perform an error analysis for numerical approximation methods of
continuous time Markov chain models commonly found in the chemistry and
biochemistry literature. The motivation for the analysis is to be able to
compare the accuracy of different approximation methods and, specifically,
Euler tau-leaping and midpoint tau-leaping. We perform our analysis under a
scaling in which the size of the time discretization is inversely proportional
to some (bounded) power of the norm of the state of the system. We argue that
this is a more appropriate scaling than that found in previous error analyses
in which the size of the time discretization goes to zero independent of the
rest of the model. Under the present scaling, we show that midpoint tau-leaping
achieves a higher order of accuracy, in both a weak and a strong sense, than
Euler tau-leaping; a result that is in contrast to previous analyses. We
present examples that demonstrate our findings.; Comment: Published in at http://dx.doi.org/10.1214/10-AAP756 the Annals of
Applied Probability (http://www.imstat.org/aap/) by the Institute of
Mathematical Statistics (http://www.imstat.org)

Link permanente para citações:

## Preasymptotic error analysis of higher order FEM and CIP-FEM for Helmholtz equation with high wave number

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 17/01/2014

Relevância na Pesquisa

55.83%

A preasymptotic error analysis of the finite element method (FEM) and some
continuous interior penalty finite element method (CIP-FEM) for Helmholtz
equation in two and three dimensions is proposed. $H^1$- and $L^2$- error
estimates with explicit dependence on the wave number $k$ are derived. In
particular, it is shown that if $k^{2p+1}h^{2p}$ is sufficiently small, then
the pollution errors of both methods in $H^1$-norm are bounded by
$O(k^{2p+1}h^{2p})$, which coincides with the phase error of the FEM obtained
by existent dispersion analyses on Cartesian grids, where $h$ is the mesh size,
$p$ is the order of the approximation space and is fixed. The CIP-FEM extends
the classical one by adding more penalty terms on jumps of higher (up to $p$-th
order) normal derivatives in order to reduce efficiently the pollution errors
of higher order methods. Numerical tests are provided to verify the theoretical
findings and to illustrate great capability of the CIP-FEM in reducing the
pollution effect.

Link permanente para citações:

## Unconditionally optimal error analysis of fully discrete Galerkin methods for general nonlinear parabolic equations

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 26/03/2013

Relevância na Pesquisa

55.85%

The paper focuses on unconditionally optimal error analysis of the fully
discrete Galerkin finite element methods for a general nonlinear parabolic
system in $\R^d$ with $d=2,3$. In terms of a corresponding time-discrete system
of PDEs as proposed in \cite{LS1}, we split the error function into two parts,
one from the temporal discretization and one the spatial discretization. We
prove that the latter is $\tau$-independent and the numerical solution is
bounded in the $L^{\infty}$ and $W^{1,\infty}$ norms by the inverse
inequalities. With the boundedness of the numerical solution, optimal error
estimates can be obtained unconditionally in a routine way. Several numerical
examples in two and three dimensional spaces are given to support our
theoretical analysis.

Link permanente para citações:

## Recovery of North-East Atlantic temperature fields from profiling floats: Determination of the optimal float number from sampling and instrumental error analysis

Fonte: Elsevier
Publicador: Elsevier

Tipo: Artículo
Formato: 131118 bytes; application/pdf

ENG

Relevância na Pesquisa

55.83%

12 pages, 4 figures, 1 table.-- Available online Oct 12, 2006.-- Issue title: "Marine Environmental Monitoring and Prediction - Selected papers from the 36th International Liège Colloquium on Ocean Dynamics" (May 3-7, 2004).-- Full-text version available Open Access at: http://www.icm.csic.es/files/oce/almacen/papers/AR-2007-04.pdf; Argo is an international project that is deploying an array of temperature and salinity profiling floats over the global ocean. Here we use the error formulation derived from Optimal Statistical Interpolation to estimate statistical errors associated with the recovery of the temperature field in the North-East Atlantic ocean. Results indicate that with the present distribution of floats (119 in the considered domain), scales of wavelength larger than 500 km can be recovered with a relative uncertainty (rms error relative to the standard deviation of the field) of about 7% at 50 m, 8% at 200 m and 10% at 1000 m. This corresponds to mean absolute errors of 0.111°C at 50 m, 0.104°C at 200 m and 0.073°C at 1000 m.; The splitting of total errors into instrumental and sampling contributions reveals that, in the present scenario, errors are more due to the small number of floats than to instrumental errors...

Link permanente para citações:

## Human reliability analysis in healthcare: Application of the cognitive reliability and error analysis method (CREAM) in a hospital setting

Fonte: Rochester Instituto de Tecnologia
Publicador: Rochester Instituto de Tecnologia

Tipo: Tese de Doutorado

EN_US

Relevância na Pesquisa

55.92%

#Healthcare#Human reliability analysis#Medical error#NYPORTS#Organizational factors#Root cause analysis#R729.8 .D44 2012#Medical errors--Prevention#Medical errors--Psychological aspects#Biomedical engineering#Human engineering

Patient safety is a concern within the healthcare domain as it is estimated that tens of thousands of people die annually from preventable medical errors. For over ten years, traditional Human Reliability Analysis (HRA) techniques (e.g., Root Cause Analysis and Failure Mode and Effect Analysis) have been used in hospitals nationwide in an attempt to explain why these errors occur and what can be done to prevent them. Still, patient safety has not improved significantly.
Traditional HRA techniques are limited as analysis tools. They do not consider the context in which workers operate. They are also not based on a valid psychological model that could explain human cognitive function. The Cognitive Reliability and Error Analysis Method (CREAM) is an HRA technique that allows analysts to examine worker actions through the context of performance-shaping factors. The CREAM also employs a cognitive model to explain cognitive failures.
This research used the CREAM to re-analyze events containing identifiable error modes that were previously analyzed by hospital team members using the RCA technique. The results of the re-analyses using the CREAM were compared with the previous analyses from RCA events. Additionally, several RCA events were observed and detailed written narratives of the observations were used to perform further independent analyses by three independent analysts in an effort to calculate inter-rater agreement. The results exposed a gap within categories of causal factors between the two techniques. The CREAM identified organizational factors as contributing to error in the events whereas those factors were either minimized or ignored in the RCA. The results also failed to demonstrate any significant inter-rater agreement among independent analysts performing the CREAM analyses. Due to serious data limitations...

Link permanente para citações:

## An error analysis in the early grades mathematics - A learning opportunity?

Fonte: South African Journal of Childhood Education
Publicador: South African Journal of Childhood Education

Tipo: Artigo de Revista Científica
Formato: text/html

Publicado em 01/01/2014
EN

Relevância na Pesquisa

65.92%

Error analysis is the study of errors in learners' work with a view to looking for possible explanations for these errors. It is a multifaceted activity involving analysis of correct, partially correct and incorrect processes and thinking about possible remediating strategies. This paper reports on such an analysis of learner tests. The tests were administered as part of the evaluation of an intervention project that aimed to teach mathematical problem solving skills to grade 1-4 learners. Quantitative error analysis was carried out using a coding sheet for each grade. A reliability coefficient was found for each test, as were item means and discrimination indexes for each item. The analysis provided some insight into the more common procedural and conceptual errors evidenced in the learners' scripts. Findings showed similar difficulties across intervention and control schools and highlighted particular areas of difficulty. The authors argue that this analysis is an example of large-scale error analysis, but that the analysis method could be adopted by teachers of grades 1-4.

Link permanente para citações: