Modelica como uma linguagem de engenharia: modelação de sistemas mecânicos/mecatrónicos

No presente artigo vão ser abordados alguns exemplos mecânicos/mecatrónicos básicos que podem ser encontrados nas bibliotecas do software Dymola 6.0 ou criados pelos autores, no sentido de serem verificadas as potencialidades do mesmo para a sua aplicação no projeto de sistemas/produtos.info:eu-repo/semantics/publishedVersio

Duration of Low Wage Employment: A Study Based on a Survival Model

This paper includes a survival analysis which attempts to explain the duration, as in the number of years a worker remains in a low wage situation. Explanatory variables take into account the characteristics of the employee, such as education, age, tenure with the company, gender and nationality, and the characteristics of the job and the company such as industry affiliation, number of employees, age of the company and location.low wage, survival, Portugal

All-optical trapping and acceleration of heavy particles

A scheme for fast, compact, and controllable acceleration of heavy particles in vacuum is proposed, in which two counterpropagating lasers with variable frequencies drive a beat-wave structure with variable phase velocity, thus allowing for trapping and acceleration of heavy particles, such as ions or muons. Fine control over the energy distribution and the total charge of the beam is obtained via tuning of the frequency variation. The acceleration scheme is described with a one-dimensional theory, providing the general conditions for trapping and scaling laws for the relevant features of the particle beam. Two-dimensional, electromagnetic particle-in-cell simulations confirm the validity and the robustness of the physical mechanism.Comment: 10 pages, 3 figures, to appear in New Journal of Physic

Books that Matter. The Case of Tocqueville’s Democracy in America

This article addresses a puzzle in the history of academic disciplines: Why is Alexis de Tocqueville’s Democracy in America, once considered a sociological classic, nowadays mostly praised as a classic in political philosophy? Existing approaches emphasize either aspects internal to the text or to the figure of the author, or external factors such as historical contexts and disciplinary dynamics. Our explanation questions the assumption that texts are stable and explores the pragmatic interplay between text-artifact-metaphor. The result is a pragmatic genealogy of the successive material incarnations of Democracy since 1945. This allows us to account for the various meanings that have been associated with Democracy (and Tocqueville) at key historical moments in terms of the cultural work of collectives of agents around the text and its material form so as to make it the icon of certain political and disciplinary projects

O Comportamento do Investidor é Influenciado por Fatores Psicológicos? Evidência Empírica no Mercado Português

No âmbito da teoria financeira tradicional os investidores são considerados racionais. No contexto das finanças comportamentais, os investidores tendem a afastar-se do princípio da racionalidade, já que as suas decisões se baseiam mais em fatores psicológicos do que em princípios de gestão de investimentos. Este trabalho pretende analisar se alguns dos comportamentos descritos pelas finanças comportamentais afetam a tomada de decisão de um grupo de investidores portugueses, inquirindo um conjunto de 300 indivíduos residentes no território nacional. Os resultados indicam que o comportamento dominante é o de aversão ao risco. Os indivíduos inquiridos manifestam alguma preferência por investimentos em títulos nacionais, o que indicia alguma evidência de patriotismo. Foi igualmente encontrada evidência de comportamentos de aversão a perdas, unidimensionalidade das atitudes face ao risco e excesso de confiança. Os resultados permitem concluir que os investidores cometem alguns erros cognitivos, afastando-se do conceito de racionalidade defendido pelas finanças tradicionais

Utilização de lodo de esgoto como fonte de fósforo na cultura de soja.

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Modeling of chemical wear in ferrous alloys/silicon nitride contacts during high speed cutting

The wear resistance of SisN4 in machining of iron alloys can be surprisingly low due to chemical affinity for dissolution in the metal. This limits the use of SisN4 inserts in high speed machining of steels, while Si3N4 retains the best performance of all cutting materials in turning of grey cast iron, a different ferrous alloy. The chemical wear of several ceramics has been investigated on the basis of dissolution in pure iron by Kramer and Suh. Nevertheless, the influence of alloy elements was not studied. In the present work, solid solution thermodynamics is applied to predict chemical wear of S&N4 by setting the influence of interaction coefficients of the alloy elements in the Henrian activity of Si and N in austenite. The model predicts the relative order of magnitude of the crater wear of SisN4 inserts in machining of tool steels, carbon steels and grey cast iron

Efeito da aplicação do herbicida sulfentrazona nos processos simbióticos associados à soja (Glycine max (L.) Merril)

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