721 resultados para Dymanic panel data


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Using data on Polish firms this paper examines the relationship between corporate control structures, sales growth and the determinants of employment change. Privatised and de novo firms are the main drivers of employment growth; in the case of de novo firms, it is foreign ownership which underpins the result. Being privatised has a positive impact on employment but this is concentrated within a range of 3–6 years after privatisation. There are no systematic differences in employment response to negative sales growth across the ownership categories. Employment in state firms is less responsive to positive sales growth. From these results we infer that the behaviour of state firms is affected by both insider rent sharing and binding budget constraints.

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Renewable energy forms have been widely used in the past decades highlighting a "green" shift in energy production. An actual reason behind this turn to renewable energy production is EU directives which set the Union's targets for energy production from renewable sources, greenhouse gas emissions and increase in energy efficiency. All member countries are obligated to apply harmonized legislation and practices and restructure their energy production networks in order to meet EU targets. Towards the fulfillment of 20-20-20 EU targets, in Greece a specific strategy which promotes the construction of large scale Renewable Energy Source plants is promoted. In this paper, we present an optimal design of the Greek renewable energy production network applying a 0-1 Weighted Goal Programming model, considering social, environmental and economic criteria. In the absence of a panel of experts Data Envelopment Analysis (DEA) approach is used in order to filter the best out of the possible network structures, seeking for the maximum technical efficiency. Super-Efficiency DEA model is also used in order to reduce the solutions and find the best out of all the possible. The results showed that in order to achieve maximum efficiency, the social and environmental criteria must be weighted more than the economic ones.

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In this thesis, a numerical program has been developed to simulate the wave-induced ship motions in the time domain. Wave-body interactions have been studied for various ships and floating bodies through forced motion and free motion simulations in a wide range of wave frequencies. A three-dimensional Rankine panel method is applied to solve the boundary value problem for the wave-body interactions. The velocity potentials and normal velocities on the boundaries are obtained in the time domain by solving the mixed boundary integral equations in relation to the source and dipole distributions. The hydrodynamic forces are calculated by the integration of the instantaneous hydrodynamic pressures over the body surface. The equations of ship motion are solved simultaneously with the boundary value problem for each time step. The wave elevation is computed by applying the linear free surface conditions. A numerical damping zone is adopted to absorb the outgoing waves in order to satisfy the radiation condition for the truncated free surface. A numerical filter is applied on the free surface for the smoothing of the wave elevation. Good convergence has been reached for both forced motion simulations and free motion simulations. The computed added-mass and damping coefficients, wave exciting forces, and motion responses for ships and floating bodies are in good agreement with the numerical results from other programs and experimental data.

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Peer effects in adolescent cannabis are difficult to estimate, due in part to the lack of appropriate data on behaviour and social ties. This paper exploits survey data that have many desirable properties and have not previously been used for this purpose. The data set, collected from teenagers in three annual waves from 2002-2004 contains longitudinal information about friendship networks within schools (N = 5,020). We exploit these data on network structure to estimate peer effects on adolescents from their nominated friends within school using two alternative approaches to identification. First, we present a cross-sectional instrumental variable (IV) estimate of peer effects that exploits network structure at the second degree, i.e. using information on friends of friends who are not themselves ego’s friends to instrument for the cannabis use of friends. Second, we present an individual fixed effects estimate of peer effects using the full longitudinal structure of the data. Both innovations allow a greater degree of control for correlated effects than is commonly the case in the substance-use peer effects literature, improving our chances of obtaining estimates of peer effects than can be plausibly interpreted as causal. Both estimates suggest positive peer effects of non-trivial magnitude, although the IV estimate is imprecise. Furthermore, when we specify identical models with behaviour and characteristics of randomly selected school peers in place of friends’, we find effectively zero effect from these ‘placebo’ peers, lending credence to our main estimates. We conclude that cross-sectional data can be used to estimate plausible positive peer effects on cannabis use where network structure information is available and appropriately exploited.

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Composites are fast becoming a cost effective option when considering the design of engineering structures in a broad range of applications. If the strength to weight benefits of these material systems can be exploited and challenges in developing lower cost manufacturing methods overcome, then the advanced composite systems will play a bigger role in the diverse range of sectors outside the aerospace industry where they have been used for decades.
This paper presents physical testing results that showcase the advantages of GRP (Glass Reinforced Plastics), such as the ability to endure loading with minimal deformation. The testing involved is a cross comparison of GRP grating vs. GRP encapsulated foam core. Resulting data gained within this paper will then be coupled with design optimization (utilising model simulation) to bring forward layup alterations to meet the specified load classifications involved.

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On 2 July 2009, the EFSA Panel on Dietetic products, Nutrition and Allergies (NDA) endorsed a draft Opinion on Dietary Reference Values for fats to be released for public consultation. This Scientific Report summarises the comments received through the public consultation and outlines how these were taken into account in the final opinion. EFSA had received contributions from 40 interested parties (individuals, non-governmental organisations, industry organisations, academia and national assessment bodies). The main comments which were received during the public consultation related to: the availability of more recent data, the nomenclature used, the use of a non-European food composition data base, the impact of genetic factors in modulating the absorption, metabolism and health effects of different fatty acids, the definition of “nutritionally adequate diet”, the use of Dietary Reference Values in the labelling of foods, the translation of advice into food-based dietary guidelines, nutrient goals and recommendations, certain risk management issues, and to Dietary Reference Values of fats, individual fatty acids, and cholesterol. All the public comments received that related to the remit of EFSA were assessed and the Opinion on Dietary Reference Values for fats has been revised taking relevant comments into consideration.

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The European Multidisciplinary Seafloor and water-column Observatory (EMSO) European Research Infrastructure Consortium (ERIC) provides power, communications, sensors, and data infrastructure for continuous, high-resolution, (near-)real-time, interactive ocean observations across a multidisciplinary and interdisciplinary range of research areas including biology, geology, chemistry, physics, engineering, and computer science, from polar to subtropical environments, through the water column down to the abyss. Eleven deep-sea and four shallow nodes span from the Arctic through the Atlantic and Mediterranean, to the Black Sea. Coordination among the consortium nodes is being strengthened through the EMSOdev project (H2020), which will produce the EMSO Generic Instrument Module (EGIM). Early installations are now being upgraded, for example, at the Ligurian, Ionian, Azores, and Porcupine Abyssal Plain (PAP) nodes. Significant findings have been flowing in over the years; for example, high-frequency surface and subsurface water-column measurements of the PAP node show an increase in seawater pCO2 (from 339 μatm in 2003 to 353 μatm in 2011) with little variability in the mean air-sea CO2 flux. In the Central Eastern Atlantic, the Oceanic Platform of the Canary Islands open-ocean canary node (aka ESTOC station) has a long-standing time series on water column physical, biogeochemical, and acidification processes that have contributed to the assessment efforts of the Intergovernmental Panel on Climate Change (IPCC). EMSO not only brings together countries and disciplines but also allows the pooling of resources and coordination to assemble harmonized data into a comprehensive regional ocean picture, which will then be made available to researchers and stakeholders worldwide on an open and interoperable access basis.

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This article reports the preliminary results of a technical and material study carried out on a 17th century panel painting located at the Chapel of the Souls in the main church of Vila Nova da Baronia (30 km away from Evora city, in southern Portugal). This painting is attributed to Jose the Escovar, a painter that worked for Evora Archiepiscopate between 1583 and 1622. Jose the Escovar is known by his mural paintings all across the Alentejo region. This is the first time that a panel painting made by this artist was studied. Analytical methods used included in situ technical photography (visible (Vis), raking light (RAK), infrared (IR), and ultraviolet (UV)), optical microscopy of cross sections, scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDS), micro Raman spectroscopy, and micro Fourier transform infrared spectroscopy (m-FT-IR). The goal was to ascertain the techniques and colored materials used by Escovar on this painting so that the data can be used in future comparisons with others works attributed to this painter based on stylistic aspects.

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Recent data indicate that levels of overweight and obesity are increasing at an alarming rate throughout the world. At a population level (and commonly to assess individual health risk), the prevalence of overweight and obesity is calculated using cut-offs of the Body Mass Index (BMI) derived from height and weight. Similarly, the BMI is also used to classify individuals and to provide a notional indication of potential health risk. It is likely that epidemiologic surveys that are reliant on BMI as a measure of adiposity will overestimate the number of individuals in the overweight (and slightly obese) categories. This tendency to misclassify individuals may be more pronounced in athletic populations or groups in which the proportion of more active individuals is higher. This differential is most pronounced in sports where it is advantageous to have a high BMI (but not necessarily high fatness). To illustrate this point we calculated the BMIs of international professional rugby players from the four teams involved in the semi-finals of the 2003 Rugby Union World Cup. According to the World Health Organisation (WHO) cut-offs for BMI, approximately 65% of the players were classified as overweight and approximately 25% as obese. These findings demonstrate that a high BMI is commonplace (and a potentially desirable attribute for sport performance) in professional rugby players. An unanswered question is what proportion of the wider population, classified as overweight (or obese) according to the BMI, is misclassified according to both fatness and health risk? It is evident that being overweight should not be an obstacle to a physically active lifestyle. Similarly, a reliance on BMI alone may misclassify a number of individuals who might otherwise have been automatically considered fat and/or unfit.

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In this paper, a singularly perturbed ordinary differential equation with non-smooth data is considered. The numerical method is generated by means of a Petrov-Galerkin finite element method with the piecewise-exponential test function and the piecewise-linear trial function. At the discontinuous point of the coefficient, a special technique is used. The method is shown to be first-order accurate and singular perturbation parameter uniform convergence. Finally, numerical results are presented, which are in agreement with theoretical results.