To study the dynamics of mixed traffic flow consisting of motorized and non-motorized vehicles, a carfollowing model based on the principle of collision free and cautious driving is proposed. Lateral friction and over...To study the dynamics of mixed traffic flow consisting of motorized and non-motorized vehicles, a carfollowing model based on the principle of collision free and cautious driving is proposed. Lateral friction and overlapping driving are introduced to describe the interactions between motorized vehicles and non-motorized vehicles. By numerical simulations, the flux-density relation, the temporal-spatial dynamics, and the velocity evolution are investigated in detail The results indicate non-motorized vehicles have a significant impact on the motorized vehicle flow and cause the maximum flux to decline by about 13%. Non-motorized vehicles can decrease the motorized vehicle velocity and cause velocity oscillation when the motorized vehicle density is low. Moreover, non-motorized vehicles show a significant damping effect on the oscillating velocity when the density is medium and high, and such an effect weakens as motorized vehicle density increases. The results also stress the necessity for separating motorized vehicles from non-motorized vehicles.展开更多
Athens, a metropolis characterized by agglutination and compactness, but at the same time facing numerous urban and transport issues, saw its population swell during the 20th century which led to extensive urbanizatio...Athens, a metropolis characterized by agglutination and compactness, but at the same time facing numerous urban and transport issues, saw its population swell during the 20th century which led to extensive urbanization phenomena. This continued urbanization increases profoundly all urban activities with transportation being the key driver in energy consumption. Theories for sustainable cities prerequisite are the integration of a number of acts in order to reduce energy consumption, with mobility being the first consideration among others. The aim of this paper is to critically explore implemented policies and plans as well as forthcoming strategic plans in terms of sustainable mobility as imposed in large scale regeneration plans in contemporary Athens. Research focuses on strategic interventions since the 1980s, such as the Athenian Daktylios (ring road for circulation management) and its later adjustments, the upcoming pedestrianization and unification of the commercial triangle and its subsequent tram line extension as well as the notable implementation of the metropolitan cycling network. Moreover, the discussion takes into consideration the implications of the Greek economic crisis in mobility choices, as aimless travels have been reduced to a minimum, several cars have been abandoned and cyclists seem to tentatively claim some space in the urban environment. What will likely be the next day in the Athenian historic centre? Considering the transformations that are expected in the immediate future, this research paper explores their potential to enhance urban environment, reduce climate change impacts and amplify resilience.展开更多
In this study,a general circulation model coupled with a gas-phase module and an aerosol chemistry module was employed to investigate the impacts of anthropogenic emission sectors on aerosol direct radiative forcing a...In this study,a general circulation model coupled with a gas-phase module and an aerosol chemistry module was employed to investigate the impacts of anthropogenic emission sectors on aerosol direct radiative forcing at the top of atmosphere (TOA) in the present-day climate.The predictions were based on the emission inventories developed in support of the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5).Six emission sectors-agriculture,open biomass burning,domestic activities,industry,energy generation,and transport-were considered,with a special focus on nitrate aerosol that shows large uncertainties in current models.The results show that the energy sector accounts for the largest contribution (-222 mW m-2) to global aerosol radiative forcing,with substantial negative forcing from sulfate.Inclusion of nitrate results in the transport sector yielding a global nitrate radiative forcing of-92 mW rm-2 and an internally mixed aerosol radiative forcing of-85 mW m-2,which is opposite to the positive radiative forcing predicted in the past,indicating that the transport emissions could not be a potential control target to counteract climate warming as expected before.The maximum change in nitrate burden is found to be associated with agricultural emissions,which accounts for about 75% of global ammonia gas (NH3) emissions.Agricultural emissions account for global nitrate radiative forcing of-186 mW m-2 and internally mixed aerosols direct radiative forcing of-149 mW m-2.Such agricultural radiative forcing exceeds the radiative forcing of the industrial sector and is responsible for a large portion of negative radiative forcing over the Northern Hemisphere.展开更多
Accompanying with the economic development and the process of industrialization and urbanization in China, the energy consumption and greenhouse gases emission of transport sector increased rapidly. From the viewpoint...Accompanying with the economic development and the process of industrialization and urbanization in China, the energy consumption and greenhouse gases emission of transport sector increased rapidly. From the viewpoint of how the urban traffic management department should cope with the global climate change, based on the economy, institutional reform, planning and policies in China, the paper analyzed the main important problems and obstacles in the development of urban transport, put forward the corresponding policy recommendations which could lead the urban transport system transform to low carbon emission and become more suitable to the climate change.展开更多
基金Supported by the National Basic Research Program of China under Grant No.2006CB705500the National Natural Science Foundation of China under Grant Nos.70631001 and 70701004
文摘To study the dynamics of mixed traffic flow consisting of motorized and non-motorized vehicles, a carfollowing model based on the principle of collision free and cautious driving is proposed. Lateral friction and overlapping driving are introduced to describe the interactions between motorized vehicles and non-motorized vehicles. By numerical simulations, the flux-density relation, the temporal-spatial dynamics, and the velocity evolution are investigated in detail The results indicate non-motorized vehicles have a significant impact on the motorized vehicle flow and cause the maximum flux to decline by about 13%. Non-motorized vehicles can decrease the motorized vehicle velocity and cause velocity oscillation when the motorized vehicle density is low. Moreover, non-motorized vehicles show a significant damping effect on the oscillating velocity when the density is medium and high, and such an effect weakens as motorized vehicle density increases. The results also stress the necessity for separating motorized vehicles from non-motorized vehicles.
文摘Athens, a metropolis characterized by agglutination and compactness, but at the same time facing numerous urban and transport issues, saw its population swell during the 20th century which led to extensive urbanization phenomena. This continued urbanization increases profoundly all urban activities with transportation being the key driver in energy consumption. Theories for sustainable cities prerequisite are the integration of a number of acts in order to reduce energy consumption, with mobility being the first consideration among others. The aim of this paper is to critically explore implemented policies and plans as well as forthcoming strategic plans in terms of sustainable mobility as imposed in large scale regeneration plans in contemporary Athens. Research focuses on strategic interventions since the 1980s, such as the Athenian Daktylios (ring road for circulation management) and its later adjustments, the upcoming pedestrianization and unification of the commercial triangle and its subsequent tram line extension as well as the notable implementation of the metropolitan cycling network. Moreover, the discussion takes into consideration the implications of the Greek economic crisis in mobility choices, as aimless travels have been reduced to a minimum, several cars have been abandoned and cyclists seem to tentatively claim some space in the urban environment. What will likely be the next day in the Athenian historic centre? Considering the transformations that are expected in the immediate future, this research paper explores their potential to enhance urban environment, reduce climate change impacts and amplify resilience.
基金supported by the National Basic Research Program of China(973 Program,2010CB950804)
文摘In this study,a general circulation model coupled with a gas-phase module and an aerosol chemistry module was employed to investigate the impacts of anthropogenic emission sectors on aerosol direct radiative forcing at the top of atmosphere (TOA) in the present-day climate.The predictions were based on the emission inventories developed in support of the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5).Six emission sectors-agriculture,open biomass burning,domestic activities,industry,energy generation,and transport-were considered,with a special focus on nitrate aerosol that shows large uncertainties in current models.The results show that the energy sector accounts for the largest contribution (-222 mW m-2) to global aerosol radiative forcing,with substantial negative forcing from sulfate.Inclusion of nitrate results in the transport sector yielding a global nitrate radiative forcing of-92 mW rm-2 and an internally mixed aerosol radiative forcing of-85 mW m-2,which is opposite to the positive radiative forcing predicted in the past,indicating that the transport emissions could not be a potential control target to counteract climate warming as expected before.The maximum change in nitrate burden is found to be associated with agricultural emissions,which accounts for about 75% of global ammonia gas (NH3) emissions.Agricultural emissions account for global nitrate radiative forcing of-186 mW m-2 and internally mixed aerosols direct radiative forcing of-149 mW m-2.Such agricultural radiative forcing exceeds the radiative forcing of the industrial sector and is responsible for a large portion of negative radiative forcing over the Northern Hemisphere.
基金Funded by Volvo Research and Educational Foundations (VREF)
文摘Accompanying with the economic development and the process of industrialization and urbanization in China, the energy consumption and greenhouse gases emission of transport sector increased rapidly. From the viewpoint of how the urban traffic management department should cope with the global climate change, based on the economy, institutional reform, planning and policies in China, the paper analyzed the main important problems and obstacles in the development of urban transport, put forward the corresponding policy recommendations which could lead the urban transport system transform to low carbon emission and become more suitable to the climate change.