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System Boundaries (system + boundary)
Selected AbstractsRecovery of transition metal complex by reverse flow adsorptionAICHE JOURNAL, Issue 1 2008Jeroen Dunnewijk Abstract Reverse flow adsorption (RFA) is a technique with a definite potential to prevent the leaching of a homogenous catalyst. In this work, we model an RFA-process for a continuous ideally stirred tank reactor with an adsorption bed upstream and another one downstream from the reactor. The model parameters concerning adsorption equilibrium and kinetics are taken from previous experimental studies on CoCl2 adsorption on polymer-bound trifenylfosfine. We use this model to study the concentration profiles of CoCl2 in the adsorption beds during consecutive adsorption,desorption cycles. The model calculations show that the concentration profile eventually reaches a fixed position after a number of adsorption,desorption cycles, even though internal mass transfer was a limiting factor. Hence, the transition metal is kept within the system boundaries, which is an essential requirement for the application of RFA. © 2007 American Institute of Chemical Engineers AIChE J, 2008 [source] Variations in Kinship Networks Across Geographic and Social SpacePOPULATION AND DEVELOPMENT REVIEW, Issue 1 2008Michael Murphy This article analyzes variations in interaction with non-coresident adult kin based on comparable cross-national surveys conducted in 2001 in 27 countries. The two main dimensions of kin contact are considered: (1) overall levels and (2) the relative emphasis given to contacts with primary kin (parents, adult children, siblings) and secondary kin (aunts, cousins, in-laws). Age-adjusted variations in kin contact between countries are much greater than those within countries. These results do not confirm the commonly hypothesized existence of well-defined family system boundaries in Europe arising from historical factors. The similarity of patterns of countries outside Europe with European countries with which they have historical ties suggests cultural factors are important in explaining interaction with kin, whereas welfare regimes appear to have little explanatory value. Within Europe, kin contact levels are more strongly related to a north/south divide than to indicators of economic development or religiosity. The findings suggest that neither of the extreme assumptions,homogenizing pressures toward a nuclear family model or persistent well-defined groupings arising from historical contexts,can be substantiated. Rather, there is a continuum in family behaviors over a substantial range, related to a number of explanatory factors. [source] Industrial ecology, life cycles, supply chains: differences and interrelationsBUSINESS STRATEGY AND THE ENVIRONMENT, Issue 5 2004Stefan Seuring Within recent years, various concepts have arisen in environmental management that directly address the flow of material (and information) along life cycles or supply chains and thereby relate to inter-organizational management aspects. These include industrial ecology (IE), life-cycle management, closed-loop supply chains, integrated chain management and green/environmental or sustainable supply chain management. It is not clear how these concepts relate to each other and whether or how they are different. Starting with sustainable development three criteria are identified that allow the comparison of the four concepts. Building on definitions the concepts are discussed and analysed using the three criteria while also identifying a distinctive feature of each approach. The criteria reveal that the concepts take a specific approach to study material flows in their particular system boundaries. This also relates to the time frame usually applied within the concept as well as the relevant actor network taken into account. Beyond these differences, it arises that the concepts have their strengths on different levels, which leads to a framework for the interrelation of the concepts. Copyright © 2004 John Wiley & Sons, Ltd and ERP Environment. [source] Modelling and optimization of district heating and industrial energy system,an approach to a locally deregulated heat marketINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 5 2004Alemayehu Gebremedhin Abstract Regions with densely concentration of industries and district heating systems (DHS) could be interesting study object from the light of an integrated heat market on local basis. System analysis with a widened system boundary could be used as an approach to evaluate the benefit of an integrated heat supply system. In this study, an energy system model consisting of totally seven different participants is designed and the optimization results of the system analysis are presented. With applied data and assumptions, the study shows that a significant amount of the heat demand within two sub-systems can be covered by heat supply from the heat market (the entire heat comes from two industries). Shadow prices, which can be used for heat pricing, indicate the advantage of an integrated system. The system cost reduction through integration and the availability of several actors with diverse energy supply system, makes the region under study an interesting area to prove a locally deregulated heat market. Copyright © 2004 John Wiley & Sons, Ltd. [source] Evaluating environmental impacts of the Japanese beef cow,calf system by the life cycle assessment methodANIMAL SCIENCE JOURNAL, Issue 4 2007Akifumi OGINO ABSTRACT The objectives of this study were to evaluate the environmental impacts of a beef cow,calf system using a life cycle assessment (LCA) method and to investigate the effects of scenarios to reduce environmental impacts on the LCA results. The functional unit was defined as one marketed beef calf, and the processes associated with the cow,calf life cycle, such as feed production, feed transport, animal management, the biological activity of the animal and the treatment of cattle waste were included in the system boundary. The present results showed that the total contributions of one beef calf throughout its life cycle to global warming, acidification, eutrophication and energy consumption were 4550 kg of CO2 equivalents, 40.1 kg of SO2 equivalents, 7.0 kg of phosphate (PO4) equivalents and 16.1 GJ, respectively. The contribution of each process to the total environmental impact in each environmental impact category showed a similar tendency to the contribution of each process in each environmental category reported in the case of the beef fattening system as a whole. The results from this analysis showed that shortening calving intervals by 1 month reduced environmental impacts by 5.7,5.8% in all the environmental impact categories examined in the current study, and increasing the number of calves per cow also reduced environmental impacts in all the categories, although the effects were smaller. [source] Environmental impacts of a Japanese dairy farming system using whole-crop rice silage as evaluated by life cycle assessmentANIMAL SCIENCE JOURNAL, Issue 6 2008Akifumi OGINO ABSTRACT The objectives of this study were to assess and compare the environmental impacts of two types of dairy farming systems, one of which makes use of whole-crop rice silage and the other of which is conventional, using life cycle assessment (LCA). The functional unit was defined as 1 kg of 4% fat-corrected milk (FCM). The processes associated with the dairy farming life cycle, such as feed production, feed transport, animal management including biological activity of the animal, and waste treatment were included within the system's boundaries. Environmental impacts of the rice silage-using and conventional dairy farming systems were 987 and 972 g CO2 equivalents for global warming, 6.87 and 7.13 g SO2 equivalents for acidification, 1.19 and 1.23 g PO4 equivalents for eutrophication, and 5.53 and 5.81 MJ for energy consumption, respectively. Our results suggest that the dairy farming system using rice silage in Japan has smaller environmental impacts for acidification, eutrophication, and energy consumption, and a larger impact for global warming compared with conventional farming. Further interpretation integrating these impact categories suggested 1.1% lower environmental impact of the rice silage-using dairy farming system as a whole. [source] | ||||||||||