This article describes the integrated modeling approach for planning the size and the operation of constructed wetlands for maximizing retention of nonpoint source pollutant loads and reservoir water-quality improveme...This article describes the integrated modeling approach for planning the size and the operation of constructed wetlands for maximizing retention of nonpoint source pollutant loads and reservoir water-quality improvement at a catchment scale. The experimental field-scale wetland systems （four sets, 0.88 ha each） have been in operation since 2002, where water depth was maintained at 30-50 cm and hydraulic loading rate was at 6.3-18.8 cm/day. The wetland system was found to be adequate for treating polluted stream water with stable removal efficiency even during the winter. The integrated modeling system （modified-BASINS） was applied to the Seokmoon estuarine reservoir watershed and calibrated with monitoring data from constructed wetland, stream, and reservoir. The calibrated integrated modeling system estimated that constructing wetlands on 0.5% （about 114 ha） of the watershed area at the mouth of reservoir could reduce 11.61% and 13.49% of total external nitrogen and phosphorus loads, respectively. It also might improve the nitrogen and phosphorus concentration of the reservoir by 9.69% and 16.48%, respectively. The study suggested that about 0.1%-1.0% of the watershed area should be allocated for constructed wetland to meet specified water-quality standards for the estuarine reservoir at the polder area where land use planning is relatively less complicated.展开更多
In China, urbanization of agricultural land around city agglomerations increases rapidly. Rapid urbanization of agricultoral land affects food supply, land value and ecological balance in the society. In China, the ur...In China, urbanization of agricultural land around city agglomerations increases rapidly. Rapid urbanization of agricultoral land affects food supply, land value and ecological balance in the society. In China, the urban built-up area had increased by 40% from 1996 to 2003. This increase came predominantly from farmland surrounding the cities. How the ongoing urbanization of China affects its agricultural land is the focus of this paper. In current studies, we have found that population density; urbanization degree and personal income are key factors that influence the urbanization process. Based on this, relation model has been established and to predict the general trends of the urban area expansion in China in 2020.In 2020, the constructed urban area of China would be increased by 1.3 times compared wtth 2003. In 2020, this study anticipates the conversion of about 32,562 sq. kin. agricultural land of China for urban use.展开更多
The present work aims to investigate the influence of extended surfaces(fins)on the multi-objective optimization of a tubular heat exchanger network(THEN).An increase in the heat transfer area using various extended s...The present work aims to investigate the influence of extended surfaces(fins)on the multi-objective optimization of a tubular heat exchanger network(THEN).An increase in the heat transfer area using various extended surfaces(fins)to enhance the performance of the heat exchanger was used while considering the effectiveness and total heat transfer area as two objective functions.In addition to the simulation of simple fins,a new set of fins,called constructal fins,was designed based on the constructal theory.Tubular heat exchanger network design parameters were chosen as optimization variables,and optimization results were achieved in such a way as to enhance the effectiveness and decrease the total heat transfer area.The results show the importance of constructal fins in improving the objective functions of heat exchangers.For instance,the simple fins case enhances the effectiveness by up to 5.3%compared to that without fins(usual heat exchanger)while using constructal fins,in addition to the 7%increment of effectiveness,reduces the total heat transfer area by 9.47%.In order to optimize the heat exchanger,the heat transfer rate and cold fluid temperature must increase,and at the same time,the hot exiting fluid temperature should decrease at the same constant total heat transfer area,which is higher in the constructal fins case.Finally,optimized design variables were studied for different cases,and the effects of various fins were reported.展开更多
文摘This article describes the integrated modeling approach for planning the size and the operation of constructed wetlands for maximizing retention of nonpoint source pollutant loads and reservoir water-quality improvement at a catchment scale. The experimental field-scale wetland systems （four sets, 0.88 ha each） have been in operation since 2002, where water depth was maintained at 30-50 cm and hydraulic loading rate was at 6.3-18.8 cm/day. The wetland system was found to be adequate for treating polluted stream water with stable removal efficiency even during the winter. The integrated modeling system （modified-BASINS） was applied to the Seokmoon estuarine reservoir watershed and calibrated with monitoring data from constructed wetland, stream, and reservoir. The calibrated integrated modeling system estimated that constructing wetlands on 0.5% （about 114 ha） of the watershed area at the mouth of reservoir could reduce 11.61% and 13.49% of total external nitrogen and phosphorus loads, respectively. It also might improve the nitrogen and phosphorus concentration of the reservoir by 9.69% and 16.48%, respectively. The study suggested that about 0.1%-1.0% of the watershed area should be allocated for constructed wetland to meet specified water-quality standards for the estuarine reservoir at the polder area where land use planning is relatively less complicated.
基金This work is supported by the National Natural Science Foundation of China(GrantNo.70273012)Century Elitist Supporting Program of China education ministry.
文摘In China, urbanization of agricultural land around city agglomerations increases rapidly. Rapid urbanization of agricultoral land affects food supply, land value and ecological balance in the society. In China, the urban built-up area had increased by 40% from 1996 to 2003. This increase came predominantly from farmland surrounding the cities. How the ongoing urbanization of China affects its agricultural land is the focus of this paper. In current studies, we have found that population density; urbanization degree and personal income are key factors that influence the urbanization process. Based on this, relation model has been established and to predict the general trends of the urban area expansion in China in 2020.In 2020, the constructed urban area of China would be increased by 1.3 times compared wtth 2003. In 2020, this study anticipates the conversion of about 32,562 sq. kin. agricultural land of China for urban use.
文摘The present work aims to investigate the influence of extended surfaces(fins)on the multi-objective optimization of a tubular heat exchanger network(THEN).An increase in the heat transfer area using various extended surfaces(fins)to enhance the performance of the heat exchanger was used while considering the effectiveness and total heat transfer area as two objective functions.In addition to the simulation of simple fins,a new set of fins,called constructal fins,was designed based on the constructal theory.Tubular heat exchanger network design parameters were chosen as optimization variables,and optimization results were achieved in such a way as to enhance the effectiveness and decrease the total heat transfer area.The results show the importance of constructal fins in improving the objective functions of heat exchangers.For instance,the simple fins case enhances the effectiveness by up to 5.3%compared to that without fins(usual heat exchanger)while using constructal fins,in addition to the 7%increment of effectiveness,reduces the total heat transfer area by 9.47%.In order to optimize the heat exchanger,the heat transfer rate and cold fluid temperature must increase,and at the same time,the hot exiting fluid temperature should decrease at the same constant total heat transfer area,which is higher in the constructal fins case.Finally,optimized design variables were studied for different cases,and the effects of various fins were reported.
