Role of Sorption Isotherms in the Analysis of Coupled Heat and Mass Fluxes in Porous Media

The aim of this work is to show the importance of the sorption isotherms in the study of the heat and mass fluxes in unsaturated porous media. General forms of the heat and mass fluxes are presented in terms of experimentally accessible quantities. The role of the isotherm slope in the coupling of heat and mass fluxes and its influence on the effective permeability are shown. Separate relations for vapor and liquid fluxes through the porous medium are presented as functions of the temperature and the isotherm slopes. Nonstationary isothermal mass flux is also analyzed, a relaxation time for this process is identifled, and its relation to the isotherm slope is also discussed

The Effects of Foreign Direct Investment on the Host Country Economic Growth - Theory and Empirical Evidence

Foreign direct investment (FDI) influences the host country’s economic growth through the transfer of new technologies and know-how, formation of human resources, integration in global markets, increase of competition, and firms’ development and reorganization. Empirically, a variety of studies considers that FDI generate economic growth in the host country. However, there is also evidence that FDI is a source of negative effects. Given this ambiguity of results, the present paper makes a review of the existing theoretical and empirical literature on the subject, intending to shed light on the main explanations for the divergence of results in different studies. The main idea that stands out in this review is that the effects of FDI on economic growth are dependent on the existing or subsequently developed internal conditions of the host country (economic, political, social, cultural or other). Thus, the host countries authorities have a key role in creating the conditions that allow for the leverage of the positive effects or for the reduction of the negative effects of FDI on the host country’s economic growth.Foreign Direct Investment; Economic Growth; Literature Survey

Demand for Organic Milk Products in Portugal

Milk consumption patterns are changing in Portugal. Factors like convenience, quality and safety increasingly constitute the basis for the Portuguese consumer purchasing decision. Demand for organic milk products (OMP) is emerging while most of these products are supplied by foreign companies. This study explores the demand for OMP in Portugal using both direct market observation and multivariate methods, in particular factor and cluster analysis. It appears that there are specific emerging segments preferring OMP, as they are increasingly concerned by health attributes and environmental protection.Organic milk consumption, market segmentation, Portugal, Demand and Price Analysis, Food Consumption/Nutrition/Food Safety,

Meta-Modelo de Sequenciação de Actividades de Manutenção

Atingir níveis de eficiência que possam optimizar a manutenção dos Sistemas de Armas foi sempre um objectivo da Força Aérea Portuguesa. Este objectivo estrutural tem sido alvo de estudos que incidiram sobre a gestão dos recursos humanos e materiais, provocando, inclusive alterações na estrutura da Organização, sempre com o objectivo de potenciar a disponibilidade dos meios aéreos. O objectivo deste trabalho é investigar de que forma se poderão operar alterações na sequência das acções das Inspecções Programadas, introduzindo melhorias e tornando este processo mais fluído, propondo uma solução que possa ser aplicável a todas as frotas em operação. Este trabalho encontra-se estruturado em quatro capítulos e segue o método de investigação em ciências sociais, preconizado por Raymond Quivy e Luc Van Campenhoudt. Inicialmente, faz-se uma descrição da realidade da manutenção das frotas Alpha-Jet e P-3, identificadas como não tendo sido alvo de nenhuma reestruturação estruturada, especialmente na sequenciação das acções de manutenção. De seguida, é abordada a manutenção das frotas F-16, Alouette III e Epsilon, que recentemente sofreram alterações nos seus procedimentos de manutenção, com a intenção de atingir melhores níveis de eficiência e aumento na prontidão dos meios aéreos. Posteriormente, procede-se a uma análise comparativa destas duas realidades, onde se identificam as diferenças existentes, nomeadamente nas ferramentas informáticas que servem de apoio à decisão e à execução. Verifica-se que, com o recurso à ferramenta Value Stream Mapping, Mapeamento da Cadeia de Valor, procedimento retirado da metodologia Lean, é possível mapear, de forma integrada e consolidada, o fluxo de uma Inspecção Programada, com ganhos de eficiência nos meios materiais e humanos. Este método é identificado como estando alinhado com os objectivos estruturantes da Organização, na procura constante de processos optimizados em várias vertentes da manutenção de aeronaves. Para finalizar, são propostas algumas recomendações no sentido de traduzir para a prática, as conclusões deste trabalho. Abstract: Achieving levels of efficiency that optimize the maintenance of Weapons Systems has always been one of the Portuguese Air Force main objectives. Many studies centered on this theme have been made, including human resources and materiel management, resulting in structural changes within the Organization itself. The goal is always to enhance the availability of aircraft. The aim of this study is to investigate the best task sequence within the Programmed Inspections in order to improve the process and its flow, proposing a solution that can be applied to every fleet in operation. The work is divided in four chapters and follows the social sciences investigation method proposed by Raymond Quivy and Luc Van Campenhoudt. Initially it begins with a description about the maintenance process reality done on the Alpha-jet and P-3 fleet, identified as not having any evidence of a restructuring process in the past, especially where maintenance actions are concerned. In sequence an analysis is made on the F-16, Alouette III and Epsilon fleet that have recently suffered procedural maintenance changes. The goal is to achieve better efficiency levels and an increase on the aircraft availability. Afterwards these two realities are compared and analyzed, identifying the main differences, concerned mainly on the software tools used to support the decision and execution process. We can verify that using the Value Stream Mapping, procedure taken from the Lean methodology, it’s possible to map in an integrated and consolidated way the flow within a certain Programmed Inspection. This will result in efficiency gained in human and materiel resources. This method is aligned with the structural goals of the Organization, in a continuous search for optimized processes, applied to several areas regarding the aircraft maintenance. Finally a group of recommendations are proposed to translate, in a practical way, the conclusions of this work

Influences of cosmic radiation, artificial radioactivity and aerosol concentration upon the fair-weather atmospheric electric field in Lisbon (1955–1991)

The atmospheric electric field is influenced by cosmic radiation, radioactivity and aerosols. In this work we investigate the existence of: (i) correlations between relative anomalies of annual values of atmospheric electric field and cosmic radiation intensity, artificial radioactivity and aerosol concentration; (ii) seasonal correlations between relative anomalies of the atmospheric electric field and cosmic radiation intensity. We used data of the electric field strength recorded at the Portela meteorological station (Lisbon) in the period 1955–1991. We found statistically significant inverse correlations between atmospheric electric field and cosmic radiation in the period 1967–1991. We also found that the influence of cosmic radiation on the atmospheric electric field is strong in wintertime and very weak in summertime. The GCR–CN–CCN–Cloud Hypothesis and the wintertime reduced boundary layer convection are analyzed as possible explanations for this difference

REAS, o que são?

O presente artigo foca-se na definição do conceito de Recursos Educacionais Abertos, enquanto elemento norteador de uma aprendizagem sintonizada ao contexto social e educativo da sociedade em rede em que vivemos. Para tal, procurou-se triangular informações de diferentes referências bibliográficas para se atingir o objetivo central. Os resultados refletem que o futuro a aprendizagem atual, marcada pelo avanço tecnológico e digital, envolve Recursos Educacionais Abertos, recursos que promovem uma aprendizagem colaborativa e inovadora.This article focus on the definition of the concept of Open Educational Resources as a guiding element of a tuned learning social and educational context of the network society in which we live. In this sense, we tried to triangulate information from different references to achieve the main objective. The results reflect the future the current learning, marked by the technological and digital advances, involves Open Educational Resources, resources which promote a collaborative and innovative learning

Missão REA

O presente artigo foca-se no esclarecimento da missão dos Recursos Educacionais Abertos, enquanto elemento norteador de uma aprendizagem efetiva e de sucesso. Neste sentido, através da leitura de diversas fontes bibliográficas e da conjugação das suas informações, conclui-se que esta tipologia de recursos se apresenta como um movimento crescente em prol da democratização do conhecimento e do seu acesso generalizado. Assim, uma nova forma de aprender se desenvolve, mais colaborativa, participativa e inclusiva.This article focus on the clarification of the mission of Open Educational Resources as a guiding element of effective learning and success. In this regard, by reading different literature sources and the combination of its information, we concluded that this typology of resources presents itself as a growing movement to the knowledge democratization and its widespread access. Thus, a new way of learning develops, more collaborative, participatory and inclusive

Exergy cost of mineral resources

Mineral deposits are considered as natural capital whose value can be assessed in exergy terms. Historical industry experience provides evidence that exploitation of mineral deposits and the beneficiation of ores are essentially energy intensive. The persisting decline of the grade of the developed deposits demands increasing exergy replacement and processing costs. The results demonstrate how far processed ores and concentrates are from ideal behaviour, and technologies from reversibility conditions. The exploitation of mineral resources of declining quality for mineral commodities imply a long time trend of increasing mass and exergy inputs spent per unit product output, in line with a law of ‘diminishing returns’ on invested exergy