Search results for " Models"
showing 10 items of 4240 documents
La importància dels equips de treball en les organitzacions: models d'efectivitat grupal
2016
espanolEl creciente uso de los equipos de trabajo como unidades de operacion basica en las organizaciones ha generado una gran cantidad de literatura centrada en el estudio del pequeno grupo y los grupos, en general. No obstante, aunque en la actualidad la investigacion centrada en los equipos de trabajo recobra un interes renovado, sus origenes se remontan a los anos 30 coincidiendo con los modelos socio-tecnicos. Aun asi, su uso no se puede considerar lineal, aunque sin duda los expertos en grupos coinciden en senalar: (1) 1980, como el momento mas algido en lo que al interes por los equipos de trabajo se refiere, y (2) un continuo y vertiginoso ascenso en la actualidad (Bell y Kozlowski,…
Volatility transmission patterns and terrorist attacks
2009
The objective of this study is to analyze volatility transmission between the US and Eurozone stock markets considering the effects of the September 11, March 11 and July 7 financial crises. In order to do this, we use a multivariate GARCH model and take into account the asymmetric volatility phenomenon, the non-synchronous trading problem and the crises themselves. Moreover, a graphical analysis of the Asymmetric Volatility Impulse-Response Functions (AVIRF) is introduced, which takes into consideration the crisis effect. Results suggest that there is bidirectional and asymmetric volatility transmission and show the different impact that terrorist attacks had on both markets. El objetivo d…
Estimation of the Velocity of a Walking Person in Non-Stationary Indoor Environments from the Received RF Signal
2018
Accurate estimation of the time-variant (TV) velocity, i.e., TV speed and TV direction of motion, of walking persons in indoor environment is of great importance in a variety of wireless indoor applications. This paper presents a novel method for estimating the velocity of a walking person in three-dimensional indoor environments, which are assumed to be equipped with a distributed 3 × 3 multiple-input multiple-output (MIMO) system. The approach estimates the TV speed, TV vertical angle-of-motion (VAOM), and TV horizontal angle-of-motion (HAOM) by fitting the spectrogram of the complex channel gain of a non-stationary indoor channel model to the spectrogram obtained from the received radio …
Labor productivity and firm-level TFP with technology-specific production functions
2020
Abstract We investigate the technological dimension of productivity, presenting an empirical methodology based on mixture models to disentangle the labor productivity differences associated with the firm's choice of technology (BTFP) and those related to the firm's ability to exploit the adopted technology (WTFP). The estimation endogenously determines the number of technologies (in the sector) and degree of technology sharing across firms (i.e., for each firm, the probability of using a given technology). By using comparable data for about 35,000 firms worldwide distributed across 22 (two-digit) sectors, we show BTFP to be at least as important as WTFP in explaining the labor productivity …
Estimation of ordered response models with sample selection
2011
We introduce two new Stata commands for the estimation of an ordered response model with sample selection. The opsel command uses a standard maximum-likelihood approach to fit a parametric specification of the model where errors are assumed to follow a bivariate Gaussian distribution. The snpopsel command uses the semi-nonparametric approach of Gallant and Nychka (1987, Econometrica 55: 363–390) to fit a semiparametric specification of the model where the bivariate density function of the errors is approximated by a Hermite polynomial expansion. The snpopsel command extends the set of Stata routines for semi-nonparametric estimation of discrete response models. Compared to the other semi-n…
Dealing with spatial data pooled over time in statistical models
2012
Recent developments in spatial econometrics have been devoted to spatio-temporal data and how spatial panel data structure should be modeled. Little effort has been devoted to the way one must deal with spatial data pooled over time. This paper presents the characteristics of spatial data pooled over time and proposes a simple way to take into account unidirectional temporal effect as well as multidirectional spatial effect in the estimation process. An empirical example, using data on 25,357 single family homes sold in Lucas County, OH (USA), between 1993 and 1998 (available in the MatLab library), is used to illustrate the potential of the approach proposed.
Crash modeling for urban roundabouts: a case study
2013
In many cities and towns, a large number of intersections are considered sites with promise for safety and operational improvements. Several studies have been carried out in many countries to establish relationships between crashes and flow and non-flow explanatory variables, using statistical tools to investigate factors critical to road safety. Starting from a brief review of existing information and analysis on the issue, this article summarizes the findings of an exploratory analysis aimed at modeling injury crashes for a sample of urban roundabouts. The methodological path followed in this research allowed to handle issues associated with the estimation of a safety performance function…
Mathematical modeling and parameters estimation of a car crash using data-based regressive model approach
2011
Author's version of an article in the journal: Applied Mathematical Modelling. Also available from the publisher at: http://dx.doi.org/10.1016/j.apm.2011.04.024 n this paper we present the application of regressive models to simulation of car-to-pole impacts. Three models were investigated: RARMAX, ARMAX and AR. Their suitability to estimate physical system parameters as well as to reproduce car kinematics was examined. It was found out that they not only estimate the one quantity which was used for their creation (car acceleration) but also describe the car's acceleration, velocity and crush. A virtual experiment was performed to obtain another set of data for use in further research. An A…
Explicación teórica y compromisos ontológicos : un modelo estructuralista
2021
En este ensayo me propongo esbozar un modelo de «explicación teórica con compromisos ontológicos». No se pretende que tal modelo tenga aplicación al uso de 'explicación' en la vida cotidiana, y ni siquiera que sea aplicable a todos los contextos científicos, tan sólo que tiene una significación genuina en grandes porciones de las ciencias naturales, particularmente en la física, y más generalmente en aquellas disciplinas que han sido matematizadas más o menos sistemáticamente. Mi tesis general, que voy a tratar de articular en lo que sigue, es simplemente la siguiente: al menos en muchos contextos de la ciencia teórica, la explicación adopta la forma de la inserción de una estructura de dat…
Revisión de modelos de evaluación del impacto de la formación en el ámbito sanitario: de lo general a lo específico
2004
El presente artículo tiene como objetivo hacer una revisión de los modelos de evaluación del impacto de la formación en ámbito sanitario. Esta revisión comenzará por los modelos más generales de evaluación para, a continuación, continuar con los modelos más utilizados en la evaluación del impacto de la formación en el ámbito sanitario.