7,338 research outputs found
Technical Efficiency in Portuguese Dairy Farms
This paper addresses issues related to efficiency measurement from an empirical point of view. A stochastic frontier production model using a translog is estimated for a group of Portuguese dairy farms. Farm level survey data for the period 1988 -2005 is used. Stochastic Frontier estimates address behaviour across all periods so the empirical model allows for time varying efficiency as well as technical change. Previous empirical studies use either the value of production or the quantity of milk produced in a single output framework. The value of production approach bundles together decision regarding the quantity and quality components as well as CAP subsidies. Using both approaches for the same data set produce substantial differences in efficiency measurement. The analysis shows that while farmers are quite efficient maximizing quantity produced they are much less efficient when allowing for quality. Sensitivity of estimates to the heterogeneity of the panel data sample as well as to the specification of the dependent variable is discussed. Average efficiency is 84% which indicates a close proximity to the production frontier for 71% of dairy farms but one can not reject the hypothesis that efficiency is decreasing over time and the rate of technical change is negative and close to 2%.
Singular value demodulation of phase-shifted holograms
We report on phase-shifted holographic interferogram demodulation by singular
value decomposition. Numerical processing of optically-acquired interferograms
over several modulation periods was performed in two steps : 1- rendering of
off-axis complex-valued holograms by Fresnel transformation of the
interferograms; 2- eigenvalue spectrum assessment of the lag-covariance matrix
of hologram pixels. Experimental results in low-light recording conditions were
compared with demodulation by Fourier analysis, in the presence of random phase
drifts.Comment: 4 pages, 3 figure
MONETARY POLICY AND EXTERNAL VULNERABILITY IN BRAZIL
This paper analyses monetary policy in Brazil, investigating why interest rates were so high and volatile from 1995 to 1998. We identify in monetary policy an overreaction to external shocks, where exogenous changes in international liquidity triggered sharp movements on domestic interest rates. We also show that the Brazilian policy response to these shocks was far more intense than in Argentina and Mexico. We argue that Brazil was caught in a high interest rates trap, which culminated in a currency crisis in January 1999.
A Kolmogorov-Smirnov test for the molecular clock on Bayesian ensembles of phylogenies
Divergence date estimates are central to understand evolutionary processes
and depend, in the case of molecular phylogenies, on tests of molecular clocks.
Here we propose two non-parametric tests of strict and relaxed molecular clocks
built upon a framework that uses the empirical cumulative distribution (ECD) of
branch lengths obtained from an ensemble of Bayesian trees and well known
non-parametric (one-sample and two-sample) Kolmogorov-Smirnov (KS)
goodness-of-fit test. In the strict clock case, the method consists in using
the one-sample Kolmogorov-Smirnov (KS) test to directly test if the phylogeny
is clock-like, in other words, if it follows a Poisson law. The ECD is computed
from the discretized branch lengths and the parameter of the expected
Poisson distribution is calculated as the average branch length over the
ensemble of trees. To compensate for the auto-correlation in the ensemble of
trees and pseudo-replication we take advantage of thinning and effective sample
size, two features provided by Bayesian inference MCMC samplers. Finally, it is
observed that tree topologies with very long or very short branches lead to
Poisson mixtures and in this case we propose the use of the two-sample KS test
with samples from two continuous branch length distributions, one obtained from
an ensemble of clock-constrained trees and the other from an ensemble of
unconstrained trees. Moreover, in this second form the test can also be applied
to test for relaxed clock models. The use of a statistically equivalent
ensemble of phylogenies to obtain the branch lengths ECD, instead of one
consensus tree, yields considerable reduction of the effects of small sample
size and provides again of power.Comment: 14 pages, 9 figures, 8 tables. Minor revision, additin of a new
example and new title. Software:
https://github.com/FernandoMarcon/PKS_Test.gi
O reconhecimento dos nĂveis de competĂȘncia linguĂstica atribuĂdos pela FAP Ă luz dos novos requisitos ICAO
A Organização da Aviação Civil Internacional (ICAO) introduziu recentemente
uma alteração ao seu Anexo 1 â Personnel Licensing, estabelecendo a obrigatoriedade de
demonstração de um nĂvel de competĂȘncia mĂnimo na lĂngua inglesa para os agentes
aeronĂĄuticos que, em voos internacionais, tĂȘm de efectuar comunicaçÔes via rĂĄdio. ApĂłs
décadas de atenção centrada essencialmente na fraseologia, a ICAO vem assim reconhecer
a importĂąncia vital de um conhecimento mais abrangente da lĂngua normalmente utilizada
no contexto aeronåutico internacional. Resultados das investigaçÔes efectuadas às causas
de diversos acidentes e incidentes registados nos Ășltimos anos apontam para a existĂȘncia de
problemas de comunicação entre tripulaçÔes e controladores de trĂĄfego aĂ©reo, devido Ă
fraca competĂȘncia na lĂngua inglesa.
A Força AĂ©rea Portuguesa (FAP) tem vindo a seguir uma polĂtica que visa o
reconhecimento por entidades civis das competĂȘncias adquiridas no Ăąmbito militar. Nessa
medida, a vasta experiĂȘncia da FAP no campo da avaliação da competĂȘncia linguĂstica,
através do STANAG 6001, tem aqui uma oportunidade para dar o seu contributo ao
prosseguimento dessa polĂtica, com evidentes vantagens para a organização, em particular
no que se refere ao aumento da segurança de voo.
Este trabalho de investigação estabelece uma ligação entre os requisitos linguĂsticos
definidos pela ICAO e o sistema de avaliação da competĂȘncia linguĂstica utilizado pela
FAP, atravĂ©s da construção de uma tabela de equivalĂȘncias. A aceitação da validade desta
tabela pela autoridade nacional competente â o INAC â permitirĂĄ o reconhecimento dos
nĂveis de competĂȘncia linguĂstica atribuĂdos pela FAP e, consequentemente, a
conformidade com a alteração preconizada pela ICAO.
Seguindo o mĂ©todo de investigação em ciĂȘncias sociais de Raymond Quivy, este
estudo parte da questĂŁo central e faz uma anĂĄlise do STANAG 6001 e do sistema ICAO,
relacionando depois os dois sistemas de avaliação. Por fim, as hipóteses formuladas são
verificadas e validadas em função dos resultados obtidos.
A principal conclusĂŁo deste trabalho reside na validação da tabela de equivalĂȘncias
da competĂȘncia linguĂstica proposta, abrindo assim caminho ao reconhecimento dos nĂveis
atribuĂdos pela FAP Ă luz dos novos requisitos ICAO. Abstract: The International Civil Aviation Organization (ICAO) has recently introduced an
amendment to its Annex 1 â Personnel Licensing, establishing that aviation professionals
who make radiotelephony communications in international flights shall demonstrate a
minimum proficiency level in the English language. After decades of attention mainly
dedicated to phraseology, ICAO thus recognizes the vital importance of a more
comprehensive approach to the language normally used in the international aviation
context. Results of investigations on the causes of several accidents and incidents that took
place in the last few years indicate the existence of communication problems between
flight crews and air traffic controllers due to lack of proficiency in the English language.
The Portuguese Air Force (PRTAF) has been following a policy aimed at the
recognition by civilian entities of competences acquired in the military context. In this
sense, the vast experience of the PRTAF in the field of language proficiency testing,
through STANAG 6001, now has an opportunity to give its contribution to this policy,
with obvious advantages for the organization, particularly with regard to an increase in
flight safety.
This research establishes a connection between the ICAO language proficiency
requirements and the language proficiency evaluation system used by the PRTAF, through
the development of an equivalence table. The acceptance of the validity of this table by the
national competent authority â INAC â will allow for the recognition of the language
proficiency levels awarded by the PRTAF and, consequently, the conformity with the
ICAO amendment.
Following Raymond Quivyâs social science research method, this study starts from
the research question and analyses the STANAG 6001 and the ICAO system, relating both
systems of language proficiency evaluation. Finally, the hypotheses formulated are verified
according to the results obtained.
The main conclusion of this research lies in the validation of the language
proficiency equivalence table that is proposed, thus making way for the recognition of the
levels awarded by the PRTAF in light of the new ICAO requirements
From wholesale energy markets to local flexibility markets: structure, models and operation
Most energy markets (EMs) across Europe are based on a design framework involving day-ahead, intraday, and bilateral markets, operating together with balancing markets. This framework was set out, however, when the vast majority of generation units were controllable and fuel-based. The increasing levels of renewable generation create unique challenges in the operation of EMs. In this context, flexibility markets are starting to be recognized as a promising and powerful tool to adequately valorize demand-side flexibility. This chapter describes the models underlying both centralized and bilateral markets, analyzes the operation of several European markets, introduces some energy management tools, analyzes the pressing issue of flexibility in system operation, and describes various pioneering flexibility platforms.info:eu-repo/semantics/publishedVersio
A continuous-stress tetrahedron for finite strain problems
A finite-strain tetrahedron with continuous stresses is proposed and analyzed. The complete stress tensor is now a nodal tensor degree-of-freedom, in addition to displacement. Specifically, stress conjugate to the relative Green-Lagrange strain is used within the framework of the Hellinger-Reissner variational principle. This is an extension of the Dunham and Pister element to arbitrary constitutive laws and finite strain. To avoid the excessive continuity shortcoming, outer faces can have null stress vectors. The resulting formulation is related to the nonlocal approaches popularized as smoothed finite element formulations. In contrast with smoothed formulations, the interpolation and integration domain is retained. Sparsity is also identical to the classical mixed formulations. When compared with variational multiscale methods, there are no parameters. Very high accuracy is obtained for four-node tetrahedra with incompressibility and bending benchmarks being successfully solved. Although the ad-hoc factor is removed and performance is highly competitive, computational cost is high, as each tetrahedron has 36 degrees-of-freedom. Besides the inf-sup test, four benchmark examples are adopted, with exceptional results in bending and compression with finite strains
A instituição do Espaço LĂrico na Narrativa Breve de Domingos Monteiro
A obra de Domingos Monteiro (Barqueiros, MesĂŁo Frio, 06/11/1903 â Lisboa 17/08/1980) nĂŁo tem merecido por parte da crĂtica, pelo menos em quantidade, uma atenção homĂłloga Ă qualidade estĂ©tico-literĂĄria e axiolĂłgica que, apesar de tudo, ensaĂstas de nomeada lhe reconheceram, alguns ainda em vida do autor.
A par desta precariedade, sĂŁo de realçar, entretanto, os dois trabalhos de maior fĂŽlego, ou de maior abrangĂȘncia, levados a cabo, em Ă©pocas muito diferentes, por Ălvaro Ribeiro (1965) e Teresa Seruya (2003), sobre o escritor-jurisconsulto, que tambĂ©m foi historiador, crĂtico literĂĄrio, autor de textos doutrinĂĄrios, membro da Academia das CiĂȘncias, diretor de Serviços das Bibliotecas Itinerantes da Fundação Calouste Gulbenkian, entre outras funçÔes de destaque.
Domingos Monteiro, apesar de ter feito tambĂ©m incursĂ”es pela poesia (de que as primeiras publicaçÔes sĂŁo um fulgurante testemunho: OraçÔes do CrepĂșsculo, em 1920, e Nau Errante, em 1921 â acervo acrescido mais tarde pelos volumes EvasĂŁo e Sonetos, respetivamente em 1953 e 1978), foi sobretudo um prĂłcere no conto e na novela, tendo merecido, por isso, o encĂłmio do professor e escritor EugĂ©nio Lisboa de âum dos maiores ficcionistas de sempre e, seguramente, o maior contista portuguĂȘs do sĂ©culo XXâ.
De facto, o escritor teve outras aventuras genolĂłgicas, como o drama A Traição InverosĂmil e o romance O Caminho para LĂĄ; no entanto, e como afirmou, em relação a este Ășltimo volume, Teresa Seruya, âo fĂŽlego romanesco Ă© demasiado exigente para o talento sintĂ©tico de Domingos Monteiroâ.
O vetor hermenĂȘutico de que nos ocupamos prende-se, entĂŁo, com o corpus textual dos Contos e Novelas de Monteiro, materializado em quinze tĂtulos, num total de sessenta histĂłrias, relativamente Ă s quais iremos, como parece razoĂĄvel, proceder a uma triagem que se revele representativa da tal instituição do espaço lĂrico que julgamos patente, de forma indelĂ©vel, em fragmentos textuais diversos.
Assim, a nĂvel do espaço, pretendemos, com esta investigação, mostrar como Domingos Monteiro construiu um espaço lĂrico e poĂ©tico, em relação ao campo e Ă cidade do paĂs natal e Ă s altas planĂcies de Castela, a que nĂŁo faltam tambĂ©m alusĂ”es ao Brasil, a Ăfrica e a certos paĂses europeus.
Nesta perspetiva, Ă© nosso objetivo mostrar como o autor de O Mal e o Bem conseguiu conciliar simultaneamente a sua invulgar capacidade de efabulação com a mestria de transfigurar o real, resultando desta fusĂŁo uma liricização, em que a narratividade nĂŁo se perde e a emotividade flui, ora nas personagens, ora no narrador, que muitas vezes tambĂ©m Ă© personagem. Por outras palavras: talvez a recorrĂȘncia de certos espaços na narrativa breve de Domingos Monteiro derive de uma intromissĂŁo da voz lĂrica do autor na sua criação ficcional
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