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Stirling engine technologies have been applied to cogeneration systems mainly for residential applications. The performance of Stirling engines has been evaluated considering different operational conditions, which include the electrical and thermal production, working fluid pressure, components geometrical sizing and others. Thermal-economic evaluation represents an effective tool to optimize a power plant with this type of technology. This study presents a mathematical model that encloses the physical variable equations able to simulate the thermodynamic transformations of the cycle, and a set of equations that define the purchase cost of the main plant components. The paper presents a numerical study faithfully simulating a micro-cogeneration unit based on an alpha type Stirling Engine. The simulations were performed through a Mat Lab code able to disclose the best economic output for the best combination of decision variables. Stirling engine performance is affected by geometrical and operational parameters optimization is required in order to obtain the best performance. Results show that the implemented mathematical model reached an optimal solution disclosing a positive profit for the best physical configuration of the system. Also, the cost estimation based on sizing and quality parameters shows a good correlation with the capital investment costs of commercial models.

Stirling engine technologies have been applied to cogeneration systems mainly for residential applications. The performance of Stirling engines has been evaluated considering different operational conditions, which include the electrical and thermal production, working fluid pressure, components geometrical sizing and others. Thermal-economic evaluation represents an effective tool to optimize a power plant with this type of technology. This study presents a mathematical model that encloses the physical variable equations able to simulate the thermodynamic transformations of the cycle, and a set of equations that define the purchase cost of the main plant components. The paper presents a numerical study faithfully simulating a micro-cogeneration unit based on an alpha type Stirling Engine. The simulations were performed through a Mat Lab code able to disclose the best economic output for the best combination of decision variables. Stirling engine performance is affected by geometrical and operational parameters optimization is required in order to obtain the best performance. Results show that the implemented mathematical model reached an optimal solution disclosing a positive profit for the best physical configuration of the system. Also, the cost estimation based on sizing and quality parameters shows a good correlation with the capital investment costs of commercial models.

Abstract Nanoscale measurements using atomic force microscopy are performed in order to scrutinize the friction phenomena observed in microscale ball-on-disc tribological tests under (boundary lubrication) BL regime. Two reference biodiesels, one derived from a vegetable source (soybean) and the other from animal fat, are compared. A linear dependence of the friction coefficient ( μ ) with the Stribeck parameter ( S = viscosity × velocity/load) is observed: μ = 0.11 − 26.54 × S for the animal fat and μ = 0.12 − 51.56 × S for the soybean biodiesel. The nanotribological tests allowed highlighting the cohesion component of friction force in the BL regime that is associated to the intrinsic characteristics of the biodiesels, the respective friction coefficients being μ = 0.0206 for the animal fat and μ = 0.0233 for the soybean biodiesel. The better lubricity of the animal fat biodiesel compared to the soybean observed in microscale is attributed to the presence of sulfur and to the higher amount of mono- and di-glycerides contaminants in it. The polarity and/or chemical affinity of the respective sulfur and OH groups facilitate them to reacting with the steel surfaces during the rubbing action. At nanoscale level, the same ranking in friction is observed among the biodiesels, being that here the friction phenomena are attributed to the cohesive forces other than those related to viscosity.

Abstract Nanoscale measurements using atomic force microscopy are performed in order to scrutinize the friction phenomena observed in microscale ball-on-disc tribological tests under (boundary lubrication) BL regime. Two reference biodiesels, one derived from a vegetable source (soybean) and the other from animal fat, are compared. A linear dependence of the friction coefficient ( μ ) with the Stribeck parameter ( S = viscosity × velocity/load) is observed: μ = 0.11 − 26.54 × S for the animal fat and μ = 0.12 − 51.56 × S for the soybean biodiesel. The nanotribological tests allowed highlighting the cohesion component of friction force in the BL regime that is associated to the intrinsic characteristics of the biodiesels, the respective friction coefficients being μ = 0.0206 for the animal fat and μ = 0.0233 for the soybean biodiesel. The better lubricity of the animal fat biodiesel compared to the soybean observed in microscale is attributed to the presence of sulfur and to the higher amount of mono- and di-glycerides contaminants in it. The polarity and/or chemical affinity of the respective sulfur and OH groups facilitate them to reacting with the steel surfaces during the rubbing action. At nanoscale level, the same ranking in friction is observed among the biodiesels, being that here the friction phenomena are attributed to the cohesive forces other than those related to viscosity.

Green Infrastructure has recently gained importance as a planning tool at the regional and local levels. While it provides a range of ecosystem services, greater attention is needed on integrating the economic, environmental and social benefits produced, particularly in the context of climate change adaptation and mitigation. This paper maps out the urban green infrastructure as a delivery mechanism of ecosystem services and identifies a number of measures for ecosystem services improvement using the strengths, weaknesses, opportunities and threats approach for the city of Faro within the context of the Algarve region. The absence of an integrated strategy for the urban built and green areas and the low connectivity with the hinterland green areas were the main weaknesses of the city. The solutions, identified by means of ecosystem services regulation functions, address the related measures, anticipate the climate change challenges and enhance the city’s resilience. Social, economic, health and visual-aes...

Green Infrastructure has recently gained importance as a planning tool at the regional and local levels. While it provides a range of ecosystem services, greater attention is needed on integrating the economic, environmental and social benefits produced, particularly in the context of climate change adaptation and mitigation. This paper maps out the urban green infrastructure as a delivery mechanism of ecosystem services and identifies a number of measures for ecosystem services improvement using the strengths, weaknesses, opportunities and threats approach for the city of Faro within the context of the Algarve region. The absence of an integrated strategy for the urban built and green areas and the low connectivity with the hinterland green areas were the main weaknesses of the city. The solutions, identified by means of ecosystem services regulation functions, address the related measures, anticipate the climate change challenges and enhance the city’s resilience. Social, economic, health and visual-aes...

Pathogens represent a significant threat to human health leading to the emergence of strategies designed to help manage their negative impact. We examined how spiritual beliefs developed to explain and predict the devastating effects of pathogens and spread of infectious disease. Analysis of existing data in studies 1 and 2 suggests that moral vitalism (beliefs about spiritual forces of evil) is higher in geographical regions characterized by historical higher levels of pathogens. Furthermore, drawing on a sample of 3140 participants from 28 countries in study 3, we found that historical higher levels of pathogens were associated with stronger endorsement of moral vitalistic beliefs. Furthermore, endorsement of moral vitalistic beliefs statistically mediated the previously reported relationship between pathogen prevalence and conservative ideologies, suggesting these beliefs reinforce behavioural strategies which function to prevent infection. We conclude that moral vitalism may be adaptive: by emphasizing concerns over contagion, it provided an explanatory model that enabled human groups to reduce rates of contagious disease.