10,263 research outputs found
Symmetrically normalized instrumental-variable estimation using panel data
In this paper we discuss the estimation of panel data models with sequential moment restrictions using symmetrically normalized GMM estimators. These estimators are asymptotically equivalent to standard GMM but are invariant to normalization and tend to have a smaller finite sample bias. They also have a very different behaviour compared to standard GMM when the instruments are poor. We study the properties of SN-GMM estimators in relation to GMM, minimum distance and pseudo maximum likelihood estimators for various versions of the AR(1) model with individual effects by mean of simulations. The emphasis is not in assessing the value of enforcing particular restrictions in the model; rather, we wish to evaluate the effects in small samples of using alternative estimating criteria that produce asymptotically equivalent estimators for fixed T and large N. Finally, as an empírical illustration, we estimate by SN-GMM employment and wage equations using panels of UK and Spanish firms
Los efectos del consumo de alcohol, tabaco y cannabis en las patologías ocualres
El consumo de alcohol, tabaco y cannabis está ampliamente extendido en la sociedad hoy
en día
,
y son múltiples las consecuencias que esto supone en
la salud de los ciudadanos.
Son muchos los estudios que evidencian el efecto negativo que producen estas drogas en
el cerebro, sistema nervioso, sistema circulatorio y sistema digestivo; pero la relación de su
consumo con las principales enfermedades ocula
res no está del todo clara y faltan
evidencias científicas contundentes.
En este trabajo se revisa la bibliografía más actual para analizar de qué manera afecta el
consumo de estas sustancias en la aparición y desarrollo de las cataratas, la degeneración
macular asociada a la edad, la retinopatía diabética y el glaucoma.
Por otro lado, se expone el papel actual de los antioxidantes en la prevención y protección
de estas patologías, ya qu
e contribuyen a compensar el efecto
que las drogas
producen
mediante
el estrés oxidativo (principal mecanismo que produce daño celular en estas
enfermedades)Universidad de Sevilla. Grado en Óptica y Optometrí
Symmetrically normalized instrumental-variable estimation using panel data.
In this paper we discuss the estimation of panel data models with sequential moment restrictions using symmetrically normalized GMM estimators. These estimators are asymptotically equivalent to standard GMM but are invariant to normalization and tend to have a smaller finite sample bias. They also have a very different behaviour compared to standard GMM when the instruments are poor. We study the properties of SN-GMM estimators in relation to GMM, minimum distance and pseudo maximum likelihood estimators for various versions of the AR(1) model with individual effects by mean of simulations. The emphasis is not in assessing the value of enforcing particular restrictions in the model; rather, we wish to evaluate the effects in small samples of using alternative estimating criteria that produce asymptotically equivalent estimators for fixed T and large N. Finally, as an empírical illustration, we estimate by SN-GMM employment and wage equations using panels of UK and Spanish firms.Panel data; Instrumental variables; Symmetric normalization; Autoregressive models; Employment equations;
On the Whitham Hierarchies: Reductions and Hodograph Solutions
A general scheme for analyzing reductions of Whitham hierarchies is
presented. It is based on a method for determining the -function by means of
a system of first order partial differential equations. Compatibility systems
of differential equations characterizing both reductions and hodograph
solutions of Whitham hierarchies are obtained. The method is illustrated by
exhibiting solutions of integrable models such as the dispersionless Toda
equation (heavenly equation) and the generalized Benney system.Comment: 24 page
Generating Quadrilateral and Circular Lattices in KP Theory
The bilinear equations of the -component KP and BKP hierarchies and a
corresponding extended Miwa transformation allow us to generate quadrilateral
and circular lattices from conjugate and orthogonal nets, respectively. The
main geometrical objects are expressed in terms of Baker functions.Comment: 20 pages, 1 figure, LaTeX2e with AMSLaTeX, Babel, graphicx and psfrag
package
Implementation of Special Singular Finite Elements for Cracks along Adhesive Interfaces in Mode III
El MEF puede aplicarse a la Mecánica de la Fractura para simular tensiones en el entorno del borde
de grieta; así se puede calcular el Factor de Intensificación de Tensiones. Los elementos lineales
aportan tensiones constantes en su interior, por lo cual no son apropiados para captar la tendencia al infinito,
requiriéndose mallas densas. Para reducir el coste computacional, se diseñan Elementos Singulares, cuyas
funciones de forma y/o disposición de los nodos permite captar mejor las tensiones en torno al borde de
grieta con menor número de elementos.
Aun así, un comportamiento correcto de cualquier elemento singular es muy dependiente del mallado
de la pieza: forma, disposición y tamaño de los elementos alrededor de la región mallada con elementos
singulares, y el tamaño relativo entre elementos y grieta entre otros. El objetivo de este trabajo es desarrollar
un breve manual de uso de un nuevo Elemento Singular con singularidad logarítmica adaptado para interfases
adhesivas en modo III. Como objetivo secundario, el proceso de pruebas se generaliza para extrapolarse
fácilmente. Finalmente, los códigos y macros generados se adjuntan para que el proceso se aplique fácilmente
a nuevos Elementos Singulares.FEM can be applied to Fracture Mechanics to simulate stresses in the neighborhood of a crack tip; thus,
the Stress Intensity Factor can be estimated. Linear Elements bear constant tensions inside, so they are
not suitable for capturing the tendency to infinity, hence requiring dense meshes. To reduce computation
time, Singular Elements are designed, whose basis functions and/or nodal placing allow to better fit stresses
around the crack tip with a lesser number of elements.
However, the correct behavior of any Singular Element is heavily dependent on the part meshing: shape,
placing and size of the elements surrounding the singular-element-meshed region near the crack and the
relative size between elements and crack among others. The purpose of this work is to develop a series of
guidelines on the use of a newly programmed Singular Element with a logarithmic singularity adapted to
adhesive interfaces in mode III. As a secondary purpose, the testing process is generalized so that it can
be easily extrapolated. Finally, generated codes and macros are appended so that the process can be easily
applied to another element.Universidad de Sevilla. Grado Ingeniería Aerospacia
Crony capitalism and neoliberal paradigm (Part II)
This is the second and final part of Crony Capitalism and Neoliberal Paradigm, the first part was posted earlier on this very blog
European Union’s key figures
With the objective to draw some conclusions about macroeconomic stability and economic structure, this article examines for the 28 Member States of the European Union, the following aspects: GDP and AIC per capita, General Government Gross Debt, Labour Productivity (monetary units and percentages), Average Annual Wages, Annual Hours Worked, Jobless and Average Hourly labour Costs. To develop this analysis, Member States have been divided into three blocks by the number of inhabitants: less than 6 million, between 6 and 17 million and more than 17 million
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