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981.
In order to understand the complex transport phenomena in a passive direct methanol fuel cell (DMFC), a theoretical model is essential. The analytical model provides a computationally efficient framework with a clear physical meaning. For this, a non-isothermal, analytical model for the passive DMFC has been developed in this study. The model considers the coupled heat and mass transport along with electrochemical reactions. The model is successfully validated with the experimental data. The model accurately describes the various species transport phenomena including methanol crossover and water crossover, heat transport phenomena, and efficiencies related to the passive DMFC. It suggests that the maximum real efficiency can be achieved by running the cell at low methanol feed concentration and moderate current density. The model also accurately predicts the effect of various operating and geometrical parameters on the cell performance such as methanol feed concentration, surrounding temperature, and polymer electrolyte membrane thickness. The model predictions are in accordance with the findings of the other researchers. The model is rapidly implementable and can be used in real-time simulation and control of the passive DMFC. This comprehensive model can be used for diagnostic purpose as well.  相似文献   
982.
Pollution has taken on a global dimension, and the effects are most obvious in developing countries. The effects take a toll on human health, animals, and vegetation, as well as on soil, air, and water quality. The objective of this article is to discuss the current relationships among pollution, environmental quality, and human health within the frame of anthropogenic activities in developing countries. In addition to personal observations, we review relevant literature on conditions throughout the developing world and case studies on conditions and activities in Nigeria. Key findings show the significant, adverse contributions to human health and environmental risk from current waste generation and handling practices, indoor and outdoor air pollution, wastewater and effluent generation and disposal, the hazardous nature and pollution potential of wastes, and the human behaviors that contribute to pollution in developing countries. There is an urgent need to create awareness among the various segments of society of the human health hazards posed by pollution as well as a need for the comprehensive development and enforcement of appropriate policies to prevent a descent into an abyss of deteriorating human and environmental health.  相似文献   
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987.
Sand–gravel mining is a significant parameter of economic development and social welfare function in modern societies. As demand for aggregate increases in construction industry, conflicts for the availability of the resource and environmental impacts become more intense. The present paper describes the contested status quo in riverbed sand–gravel mining activities with an example from Greece, as a case study. The scope is to propose a methodology about good governance of the mining sector that promotes a sustainable sharing of aggregate resource by securing environment and safekeeping revenues in the mining trade market.  相似文献   
988.
In response to the extreme flood events of recent decades, the European Union has released the Floods Directive (2007/60/EC), which requires the creation of flood risk management plans. These plans do not yet exist in practice, as water management agencies have until 2015 to put them into action. This contribution will discuss two questions regarding the European flood risk management plan: First, how is the new instrument integrated into the various member states, particularly with respect to the scenario approach? Second, how prepared are the institutions for the collaborative planning paradigm of the flood risk management plan, particularly with respect to the river basin districts approach? Citing examples from France, Germany, the Netherlands, and Great Britain, this paper offers both a pessimistic and an optimistic perspective on the implementation of the new flood risk management instrument.  相似文献   
989.
The debate concerning the environmental effectiveness of environmental management systems (EMS) based on ISO 14001 is still open and scholars have called for further studies that can explain the contrasting evidence in previous research. As a response, this study aims to contribute knowledge about the effects of ISO 14001-based EMS by presenting fact-based environmental data. The study focuses on changes in performance over a period of 12 years and includes both firms with an EMS (66 firms) and firms without one (50 firms). Consideration is given to the improvement efforts in the firms before EMS adoption making it possible to neutralize any selection effects where better environmental performance precedes ISO 14001 adoption. Analysis has been carried out using statistical methods for six different environmental areas. No statistically significant differences between certified and non-certified firms concerning the change in the rate of improvement could be found in any of the six areas. However, it can be suspected that EMS adoption has positive effects on energy use and waste production whereas the non-adopting firms seem to perform better concerning air emissions. These mixed results mirrors previous research, which is rather worrying considering the worldwide popularity of EMS based on ISO 14001 in industry.  相似文献   
990.
General backcasting as a decision support and planning method starts from desired future states and simulates developments backwards until reaching the present state. Development pathways that reveal steps to be taken to reach a certain future state, and milestones that serve as interim goals, are created during the process. Backcasting has hitherto only been applied in workshops or as a theoretical framework and no spatially explicit backcasting model has previously been established. This paper presents the development of a spatially explicit backcasting model. The proposed model first creates a future scenario utilizing an agent-based model and then simulates backwards. It is implemented using the programming language Python. The model has been applied to a case study for sustainable land-use planning in Salzburg, Austria. The results of the model run show a successful backcasting of land-use classes from a future state back to the present, in 10 year time steps.  相似文献   
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