State Space Analysis of Forest Fires

This paper studies forest fires from the perspective of dynamical systems. Burnt area, precipitation and atmospheric temperatures are interpreted as state variables of a complex system and the correlations between them are investigated by means of different mathematical tools. First, we use mutual information to reveal potential relationships in the data. Second, we adopt the state space portrait to characterize the system’s behavior. Third, we compare the annual state space curves and we apply clustering and visualization tools to unveil long-range patterns. We use forest fire data for Portugal, covering the years 1980–2003. The territory is divided into two regions (North and South), characterized by different climates and vegetation. The adopted methodology represents a new viewpoint in the context of forest fires, shedding light on a complex phenomenon that needs to be better understood in order to mitigate its devastating consequences, at both economical and environmental levels.

Multilevel model of safety climate for furniture industries

BACKGROUND: Furniture companies can analyze their safety status using quantitative measures. However, the data needed are not always available and the number of accidents is under-reported. Safety climate scales may be an alternative. However, there are no validated Portuguese scales that account for the specific attributes of the furniture sector. OBJECTIVE: The current study aims to develop and validate an instrument that uses a multilevel structure to measure the safety climate of the Portuguese furniture industry. METHODS: The Safety Climate in Wood Industries (SCWI) model was developed and applied to the safety climate analysis using three different scales: organizational, group and individual. A multilevel exploratory factor analysis was performed to analyze the factorial structure. The studied companies’ safety conditions were also analyzed. RESULTS: Different factorial structures were found between and within levels. In general, the results show the presence of a group-level safety climate. The scores of safety climates are directly and positively related to companies’ safety conditions; the organizational scale is the one that best reflects the actual safety conditions. CONCLUSIONS: The SCWI instrument allows for the identification of different safety climates in groups that comprise the same furniture company and it seems to reflect those groups’ safety conditions. The study also demonstrates the need for a multilevel analysis of the studied instrument.

Mechanical properties of chemically modified portuguese pinewood

To turn wood into a construction material with enhanced properties, many methods of chemical modification have been developed in the last few decades. In this work, mechanical properties of pine wood were chemically modified, compared and evaluated. Maritime pine wood (Pinus pinaster) was modified with four chemical processes: 1,3-dimethylol-4,5- dihydroxyethyleneurea, N-methylol melamine formaldehyde, tetra-alkoxysilane and wax. The following mechanical properties were assessed experimentally: Modulus of elasticity measured statically, stiffness stabilization efficiency in different climates (30 and 87% of relative humidity), modulus of rupture, work maximum load, impact bending strength, compression, tensile and shear strength at indoor conditions (65% of relative humidity). In both types of active principle of modification, cell wall or lumen fill, no significant changes on the bending stiffness (modulus of elasticity) were found. In the remaining properties analysed significant changes in the modified wood-material took place compared to unmodified wood control: - Cell wall modification was the most effective method to achieve high stiffness stabilization efficiency (up to 60%) and also increased compression strength (up to 230%). However, modulus of rupture, tensile, shear and the impact bending strength were reduced by both resins, but in a varying extent, where the N-methylol melamine formaldehyde endured less reduction than 1,3-dimethylol-4,5-dihydroxyethyleneurea resin. In the latter, reduction up to 60% can take place. - In the lumen fill modification: tetra-alkoxysilane has no effect in the mechanical properties. Although, a slight increase in shear strength parallel to the grain was found. Wax specimens have shown a slight increase in bending strength, compression, tensile and shear strength as well as in the absorption energy capacity.

Caracterização da tecnologia de frio comercial e profissional

Hoje em dia a preocupação ambiental e a economia são fatores de sustentabilidade que são tidos em conta em países desenvolvidos, especialmente no seio da União Europeia. Reduzir os consumos de energia é, portanto, um ponto-chave para a redução das emissões de gases com efeito de estufa e aumentar a dependência das energias renováveis. Consequentemente surge então a necessidade de aumentar a eficiência dos equipamentos, em particular no presente caso, equipamentos de refrigeração. Para isso foi adotado pela Comissão Europeia uma rotulagem nos produtos consumidores de energia, em particular na refrigeração, os frigoríficos e congeladores domésticos permitindo informar o consumidor para os equipamentos mais eficientes. Mais recentemente, frigoríficos comerciais e profissionais também terão obrigatoriedade de incluir um rótulo energético na parte externa dos mesmos. Nesses rótulos estão incluídas várias informações técnicas do aparelho representadas de uma forma compreensível e lúdica aos olhos do consumidor mais leigo, entre as quais as classes de eficiência energética. As classes de eficiência energética caracterizam-se pela componente tecnológica dos frigoríficos. Perceber quais os componentes e materiais em particular que promovem uma melhor eficiência, quantificar a sua influência e avaliar os seus custos de integração torna-se assim essencial para toda a cadeia envolvida na produção destes equipamentos. Os fluídos frigorigénios e compressores aparentam ser os que mais exercem influência na eficiência de frigoríficos de baixa potência. Tubos capilares com trocador de calor são uma escolha mais eficiente comparado com o tubo capilar padrão que é utilizado nestes frigoríficos. Por forma a obter informação adicional e relevante do ponto de vista da análise energética realizaram-se simulações para determinação do consumo elétrico anual com recurso ao software Pack Calculation Pro. Entre os fluídos frigorigénios R-134a, R-22 e R-410a, os compressores scroll apresentaram consumos mais reduzidos (no máximo de 16%) do que os compressores alternativos. No caso do amoníaco (R-717) os compressores alternativos consumiram em média 14% menos do que os compressores parafuso. O recurso a velocidade variável em compressores permite reduzir o consumo na ordem dos 25%. Válvulas de expansão eletrónicas trazem reduções no consumo de 1,5% quando comparadas com válvulas de expansão termostáticas em compressores de velocidade variável. O propano (R-290) é um gás que mostra ter um melhor desempenho do que o R-134a e R404a em vários compressores, consumindo 16% menos do que o R-404a. Em função da temperatura exterior, o R-290 também apresentou um bom desempenho consumindo em climas quentes (Belém, Brasil) 24% menos do que o R-404a.