Assisted by framework of multimedia total exposure model for hazard waste sites(CalTOX),potential influences of scenario-uncertainty on multimedia health risk assessment(MHRA) and decision-making were quantitatively a...Assisted by framework of multimedia total exposure model for hazard waste sites(CalTOX),potential influences of scenario-uncertainty on multimedia health risk assessment(MHRA) and decision-making were quantitatively analyzed in a primary extent under the Chinese scenario case by deliberately varying the two key scenario-elements,namely conceptual exposure pathways combination and aim receptor cohorts choice.Results show that the independent change of one exposure pathway or receptor cohort could lead variation of MHRA results in the range of 3.6×10-6-1.4×10-5 or 6.7×10-6-2.3×10-5.And randomly simultaneous change of those two elements could lead variation of MHRA results at the range of 7.7×10-8-2.3×10-5.On the basis of the corresponding sensitivity analysis,pathways which made a valid contribution to the final modeling risk value occupied only 16.7% of all considered pathways.Afterwards,comparative analysis between influence of parameter-uncertainty and influence of scenario-uncertainty was made.In consideration of interrelationship among all types of uncertainties and financial reasonability during MHRA procedures,the integrated method how to optimize the entire procedures of MHRA was presented innovatively based on sensitivity analysis,scenario-discussion and nest Monte Carlo simulation or fuzzy mathematics.展开更多
In recent years,there have been important developments in the joint analysis of the travel behavior based on discrete choice models as well as in the formulation of increasingly flexible closed-form models belonging t...In recent years,there have been important developments in the joint analysis of the travel behavior based on discrete choice models as well as in the formulation of increasingly flexible closed-form models belonging to the generalized extreme value class.The objective of this work is to describe the simultaneous choice of shopping destination and travel-to-shop mode in downtown area by making use of the cross-nested logit(CNL) structure that allows for potential spatial correlation.The analysis uses data collected in the downtown areas of Maryland-Washington,D.C.region for shopping trips,considering household,individual,land use,and travel-related characteristics.The estimation results show that the dissimilarity parameter in the CNL model is 0.37 and significant at the 95% level,indicating that the alternatives have high spatial correlation for the short shopping distance.The results of analysis reveal detailed significant influences on travel behavior of joint choice shopping destination and travel mode.Moreover,a Monte Carlo simulation for a group of scenarios arising from transportation policies and parking fees in downtown area,was undertaken to examine the impact of a change in car travel cost on the shopping destination and travel mode switching.These findings have important implications for transportation demand management and urban planning.展开更多
基金Projects(50978088,51039001,51178172,51009063) supported by the National Natural Science Foundation of ChinaProject(NCET-08- 180) supported by the Program for New Century Excellent Talents in University from the Ministry of Education of China
文摘Assisted by framework of multimedia total exposure model for hazard waste sites(CalTOX),potential influences of scenario-uncertainty on multimedia health risk assessment(MHRA) and decision-making were quantitatively analyzed in a primary extent under the Chinese scenario case by deliberately varying the two key scenario-elements,namely conceptual exposure pathways combination and aim receptor cohorts choice.Results show that the independent change of one exposure pathway or receptor cohort could lead variation of MHRA results in the range of 3.6×10-6-1.4×10-5 or 6.7×10-6-2.3×10-5.And randomly simultaneous change of those two elements could lead variation of MHRA results at the range of 7.7×10-8-2.3×10-5.On the basis of the corresponding sensitivity analysis,pathways which made a valid contribution to the final modeling risk value occupied only 16.7% of all considered pathways.Afterwards,comparative analysis between influence of parameter-uncertainty and influence of scenario-uncertainty was made.In consideration of interrelationship among all types of uncertainties and financial reasonability during MHRA procedures,the integrated method how to optimize the entire procedures of MHRA was presented innovatively based on sensitivity analysis,scenario-discussion and nest Monte Carlo simulation or fuzzy mathematics.
基金Projects(JCYJ20120615145601342,JCYJ20130325151523015)supported by Shenzhen Science and Technology Development Funding-Fundamental Research Plan,ChinaProject(2013U-6)supported by Key Laboratory of Eco Planning & Green Building,Ministry of Education(Tsinghua University),China
文摘In recent years,there have been important developments in the joint analysis of the travel behavior based on discrete choice models as well as in the formulation of increasingly flexible closed-form models belonging to the generalized extreme value class.The objective of this work is to describe the simultaneous choice of shopping destination and travel-to-shop mode in downtown area by making use of the cross-nested logit(CNL) structure that allows for potential spatial correlation.The analysis uses data collected in the downtown areas of Maryland-Washington,D.C.region for shopping trips,considering household,individual,land use,and travel-related characteristics.The estimation results show that the dissimilarity parameter in the CNL model is 0.37 and significant at the 95% level,indicating that the alternatives have high spatial correlation for the short shopping distance.The results of analysis reveal detailed significant influences on travel behavior of joint choice shopping destination and travel mode.Moreover,a Monte Carlo simulation for a group of scenarios arising from transportation policies and parking fees in downtown area,was undertaken to examine the impact of a change in car travel cost on the shopping destination and travel mode switching.These findings have important implications for transportation demand management and urban planning.
