Yanfeng Ouyang | University of Illinois at Urbana-Champaign (original) (raw)
Papers by Yanfeng Ouyang
Biosystems Engineering, 2016
Center For Future Urban Transport Working Paper, 2012
Journal of Infrastructure Systems, May 15, 2012
ABSTRACT The bridge network, as part of the critical civil infrastructure, is susceptible to natu... more ABSTRACT The bridge network, as part of the critical civil infrastructure, is susceptible to natural and man-made hazards. It is essential that the network retains its traffic-carrying capacity after a disastrous earthquake to ensure efficient evacuation of at-risk population to safe zones and timely dispatch of emergency response resources to the impacted area. Because of limited resources, it is important to prioritize bridge retrofit projects and manage disaster mitigation resources under a strategic budget plan. This paper proposes a methodology to find the optimal bridge retrofit program that aims to maximize the postdisaster network evacuation capacity. The uncertainties of earthquake intensity, bridge structural damage, and bridge traffic-carrying capacities are addressed by using a Monte Carlo simulation framework with established bridge fragility curves and damage-functionality relationships, and the effectiveness of preserving evacuation capacity is calculated on the basis of a network design model. The proposed methodological framework is demonstrated with the transportation network in Memphis, Tennessee, and numerical experiments show that the proposed framework solves the problem efficiently. The modeling framework can help transportation agencies maximize the effectiveness of investment. Emergency managers can also use the model to enhance preparedness and emergency response efficiency, which in turn improves the infrastructure systems’ resilience against extreme events.
Transportation Research Record Journal of the Transportation Research Board, Feb 3, 2015
ABSTRACT
Operations Research, Sep 26, 2012
ABSTRACT
Computer-Aided Civil and Infrastructure Engineering, 2014
In congested urban areas, it remains a pressing challenge to reduce unnecessary vehicle circling ... more In congested urban areas, it remains a pressing challenge to reduce unnecessary vehicle circling for parking while at the same time maximize parking space utilization. In observance of new information technologies that have become readily accessible to drivers and parking agencies, we develop a dynamic non-cooperative bi-level model (i.e. Stackelberg leader-follower game) to set parking prices in real-time for effective parking access and space utilization. The model is expected to fit into an integrated parking pricing and management system, where parking reservations and transactions are facilitated by sensing and informatics infrastructures, that ensures the availability of convenient spaces at equilibrium market prices. It is shown with numerical examples that the proposed dynamic parking pricing model has the potential to virtually eliminate vehicle circling for parking, which results in significant reduction in adverse socioeconomic externalities such as traffic congestion and emissions.
European Journal of Operational Research, 2016
Jiefangjun Ligong Daxue Xuebao Journal of Pla University of Science and Technology, 2012
ABSTRACT This paper studies optimal spatial layout of transshipment facilities and their correspo... more ABSTRACT This paper studies optimal spatial layout of transshipment facilities and their corresponding service regions on an infinite homogeneous plane Re2\Re^2Re2 that minimizes the total cost for facility set-up, outbound delivery and inbound replenishment transportation. This paper first focuses on a Euclidean plane and proves the Gersho's conjecture, which states if the inbound transportation cost is ignored, the optimal shape of each service region should be a regular hexagon. When inbound transportation cost becomes non-negligible, however, a tight upper bound can be achieved by a type of elongated cyclic hexagons, while a cost lower bound based on relaxation and idealization is also obtained. The gap between the analytical upper and lower bounds is within 0.3%. This paper then shows that a similar elongated non-cyclic hexagon shape is actually optimal for service regions on a rectilinear metric plane. Numerical experiments and sensitivity analyses are conducted to verify the analytical findings and to draw managerial insights.
Environmental Science & Technology, 2015
Implementing public policies often involves navigating an array of choices that have economic and... more Implementing public policies often involves navigating an array of choices that have economic and environmental consequences that are difficult to quantify given the complexity of multiple system interactions. Implementing the mandate for cellulosic biofuel production in the Renewable Fuel Standard (RFS), and reducing hypoxia in the northern Gulf of Mexico by reducing riverine nitrate-N loads represent two such cases that overlap in the Mississippi River Basin. To quantify the consequences of these interactions, we developed a system of systems (SoS) model that incorporates interdependencies among the various subsystems, including biofuel refineries, transportation, agriculture, water resources and crop/ethanol markets. The model allows examination of the impact of nitrate-N load limits on the biofuel production system as a whole, including land use change and infrastructure needs. The synergies of crop choice (first versus second generation biofuel crops), infrastructure development, and environmental impacts (streamflow and nitrate-N load) were analyzed to determine the complementarities and trade-offs between environmental protection and biofuel development objectives. For example, the results show that meeting the cellulosic biofuel target in the RFS using Miscanthus x giganteus reduces system profits by 8% but reduces nitrate-N loads by 12%. However, the larger water consumption by Miscanthus is likely to reduce streamflow with potentially adverse environmental consequences that need to be considered in decision making.
Environmental science & technology, Jan 14, 2015
This work develops an integrated model approach to estimate emissions from long-haul freight truc... more This work develops an integrated model approach to estimate emissions from long-haul freight truck and rail transport in the U.S. between 2010 and 2050. We connect models of macroeconomic activity, freight demand by commodity, transportation networks, and emission technology to represent different pathways of future freight emissions. Emissions of particulate matter (PM), carbon monoxide (CO), nitrogen oxides (NOx), and total hydrocarbon (THC) decrease by 60%-70% from 2010 to 2030, as older vehicles built to less stringent emission standards retire. Climate policy, in the form of carbon tax that increases apparent fuel prices, causes a shift from truck to rail, resulting in a 30% reduction in fuel consumption and 10%-28% reduction in pollutant emissions by 2050, if rail capacity is sufficient. Eliminating high-emitting conditions in the truck fleet affects air pollutants by 20% to 65%; although these estimates are highly uncertain, they indicate the importance of durability in vehic...
Transportation Science, 2015
ABSTRACT This paper presents an integer program formulation of a reliable location-routing proble... more ABSTRACT This paper presents an integer program formulation of a reliable location-routing problem where built facilities are subject to the risk of probabilistic disruptions. The objective is to determine facility locations, outbound delivery routing, and backup plans under disruptions, so as to minimize the total cost including the facility set-up cost, the expected routing cost, and the customer penalty (if no delivery is possible). A variety of solution approaches (i.e., Lagrangian relaxation with embedded column generation, ring sweep heuristics, and local search) are proposed to solve the problem. The authors also present an alternative continuum approximation model for large-scale instances of this problem. This model not only provides analytical formulas to predict the optimal system cost but also can be used to generate high quality feasible solutions. A series of numerical case studies are conducted to test the performance of the proposed models and solution algorithms. Managerial insights are also drawn on how various system parameters impact the optimal solution.
Transportation Research Part B: Methodological, 2015
ABSTRACT
Transportation Research Record: Journal of the Transportation Research Board, 2014
sites and the supporting transportation infrastructure. In view of the interactive relationship b... more sites and the supporting transportation infrastructure. In view of the interactive relationship between transportation and the tourism industry, this paper proposes an integrated modeling framework to address tourism planning and transportation network design simultaneously. A bilevel optimization model was proposed to decide the optimal locations for tourism investment and highway capacity expansion. The upper-level problem minimized the total system cost while the lower-level model determined user equilibrium flow of tourist and nontourist road users under traffic congestion. A customized solution approach based on relaxation, reformulation, and approximation was developed. The proposed methodology was applied to an empirical case study for Heilongjiang Province, China, to show implications of the optimal strategies for tourism planning.
European Journal of Operational Research, 2015
ABSTRACT This paper analyzes the bullwhip effect in multi-echelon supply chains under a general c... more ABSTRACT This paper analyzes the bullwhip effect in multi-echelon supply chains under a general class of nonlinear ordering policies. A describing-function approach from control theory is used to derive closed-form formulas to predict amplification of order fluctuations along the supply chain. It is proven that with consideration of nonlinearity in the ordering policy, the magnitude of the bullwhip effect will eventually become bounded after growing through the first few stages of the supply chain. It is also proven that the average customer demand as well as the demand fluctuation frequency would directly affect the bounded magnitude, while the suppliers’ demand forecasting method has no effect at all. For illustration, analytical results for a class of order-up-to policies are derived and verified by numerical simulations. The proposed modeling framework holds the promise to not only explain empirical observations, but also serve as the basis for developing counteracting strategies against the bullwhip effect.
Transportation Research Part B: Methodological, 2014
Biosystems Engineering, 2016
Center For Future Urban Transport Working Paper, 2012
Journal of Infrastructure Systems, May 15, 2012
ABSTRACT The bridge network, as part of the critical civil infrastructure, is susceptible to natu... more ABSTRACT The bridge network, as part of the critical civil infrastructure, is susceptible to natural and man-made hazards. It is essential that the network retains its traffic-carrying capacity after a disastrous earthquake to ensure efficient evacuation of at-risk population to safe zones and timely dispatch of emergency response resources to the impacted area. Because of limited resources, it is important to prioritize bridge retrofit projects and manage disaster mitigation resources under a strategic budget plan. This paper proposes a methodology to find the optimal bridge retrofit program that aims to maximize the postdisaster network evacuation capacity. The uncertainties of earthquake intensity, bridge structural damage, and bridge traffic-carrying capacities are addressed by using a Monte Carlo simulation framework with established bridge fragility curves and damage-functionality relationships, and the effectiveness of preserving evacuation capacity is calculated on the basis of a network design model. The proposed methodological framework is demonstrated with the transportation network in Memphis, Tennessee, and numerical experiments show that the proposed framework solves the problem efficiently. The modeling framework can help transportation agencies maximize the effectiveness of investment. Emergency managers can also use the model to enhance preparedness and emergency response efficiency, which in turn improves the infrastructure systems’ resilience against extreme events.
Transportation Research Record Journal of the Transportation Research Board, Feb 3, 2015
ABSTRACT
Operations Research, Sep 26, 2012
ABSTRACT
Computer-Aided Civil and Infrastructure Engineering, 2014
In congested urban areas, it remains a pressing challenge to reduce unnecessary vehicle circling ... more In congested urban areas, it remains a pressing challenge to reduce unnecessary vehicle circling for parking while at the same time maximize parking space utilization. In observance of new information technologies that have become readily accessible to drivers and parking agencies, we develop a dynamic non-cooperative bi-level model (i.e. Stackelberg leader-follower game) to set parking prices in real-time for effective parking access and space utilization. The model is expected to fit into an integrated parking pricing and management system, where parking reservations and transactions are facilitated by sensing and informatics infrastructures, that ensures the availability of convenient spaces at equilibrium market prices. It is shown with numerical examples that the proposed dynamic parking pricing model has the potential to virtually eliminate vehicle circling for parking, which results in significant reduction in adverse socioeconomic externalities such as traffic congestion and emissions.
European Journal of Operational Research, 2016
Jiefangjun Ligong Daxue Xuebao Journal of Pla University of Science and Technology, 2012
ABSTRACT This paper studies optimal spatial layout of transshipment facilities and their correspo... more ABSTRACT This paper studies optimal spatial layout of transshipment facilities and their corresponding service regions on an infinite homogeneous plane Re2\Re^2Re2 that minimizes the total cost for facility set-up, outbound delivery and inbound replenishment transportation. This paper first focuses on a Euclidean plane and proves the Gersho's conjecture, which states if the inbound transportation cost is ignored, the optimal shape of each service region should be a regular hexagon. When inbound transportation cost becomes non-negligible, however, a tight upper bound can be achieved by a type of elongated cyclic hexagons, while a cost lower bound based on relaxation and idealization is also obtained. The gap between the analytical upper and lower bounds is within 0.3%. This paper then shows that a similar elongated non-cyclic hexagon shape is actually optimal for service regions on a rectilinear metric plane. Numerical experiments and sensitivity analyses are conducted to verify the analytical findings and to draw managerial insights.
Environmental Science & Technology, 2015
Implementing public policies often involves navigating an array of choices that have economic and... more Implementing public policies often involves navigating an array of choices that have economic and environmental consequences that are difficult to quantify given the complexity of multiple system interactions. Implementing the mandate for cellulosic biofuel production in the Renewable Fuel Standard (RFS), and reducing hypoxia in the northern Gulf of Mexico by reducing riverine nitrate-N loads represent two such cases that overlap in the Mississippi River Basin. To quantify the consequences of these interactions, we developed a system of systems (SoS) model that incorporates interdependencies among the various subsystems, including biofuel refineries, transportation, agriculture, water resources and crop/ethanol markets. The model allows examination of the impact of nitrate-N load limits on the biofuel production system as a whole, including land use change and infrastructure needs. The synergies of crop choice (first versus second generation biofuel crops), infrastructure development, and environmental impacts (streamflow and nitrate-N load) were analyzed to determine the complementarities and trade-offs between environmental protection and biofuel development objectives. For example, the results show that meeting the cellulosic biofuel target in the RFS using Miscanthus x giganteus reduces system profits by 8% but reduces nitrate-N loads by 12%. However, the larger water consumption by Miscanthus is likely to reduce streamflow with potentially adverse environmental consequences that need to be considered in decision making.
Environmental science & technology, Jan 14, 2015
This work develops an integrated model approach to estimate emissions from long-haul freight truc... more This work develops an integrated model approach to estimate emissions from long-haul freight truck and rail transport in the U.S. between 2010 and 2050. We connect models of macroeconomic activity, freight demand by commodity, transportation networks, and emission technology to represent different pathways of future freight emissions. Emissions of particulate matter (PM), carbon monoxide (CO), nitrogen oxides (NOx), and total hydrocarbon (THC) decrease by 60%-70% from 2010 to 2030, as older vehicles built to less stringent emission standards retire. Climate policy, in the form of carbon tax that increases apparent fuel prices, causes a shift from truck to rail, resulting in a 30% reduction in fuel consumption and 10%-28% reduction in pollutant emissions by 2050, if rail capacity is sufficient. Eliminating high-emitting conditions in the truck fleet affects air pollutants by 20% to 65%; although these estimates are highly uncertain, they indicate the importance of durability in vehic...
Transportation Science, 2015
ABSTRACT This paper presents an integer program formulation of a reliable location-routing proble... more ABSTRACT This paper presents an integer program formulation of a reliable location-routing problem where built facilities are subject to the risk of probabilistic disruptions. The objective is to determine facility locations, outbound delivery routing, and backup plans under disruptions, so as to minimize the total cost including the facility set-up cost, the expected routing cost, and the customer penalty (if no delivery is possible). A variety of solution approaches (i.e., Lagrangian relaxation with embedded column generation, ring sweep heuristics, and local search) are proposed to solve the problem. The authors also present an alternative continuum approximation model for large-scale instances of this problem. This model not only provides analytical formulas to predict the optimal system cost but also can be used to generate high quality feasible solutions. A series of numerical case studies are conducted to test the performance of the proposed models and solution algorithms. Managerial insights are also drawn on how various system parameters impact the optimal solution.
Transportation Research Part B: Methodological, 2015
ABSTRACT
Transportation Research Record: Journal of the Transportation Research Board, 2014
sites and the supporting transportation infrastructure. In view of the interactive relationship b... more sites and the supporting transportation infrastructure. In view of the interactive relationship between transportation and the tourism industry, this paper proposes an integrated modeling framework to address tourism planning and transportation network design simultaneously. A bilevel optimization model was proposed to decide the optimal locations for tourism investment and highway capacity expansion. The upper-level problem minimized the total system cost while the lower-level model determined user equilibrium flow of tourist and nontourist road users under traffic congestion. A customized solution approach based on relaxation, reformulation, and approximation was developed. The proposed methodology was applied to an empirical case study for Heilongjiang Province, China, to show implications of the optimal strategies for tourism planning.
European Journal of Operational Research, 2015
ABSTRACT This paper analyzes the bullwhip effect in multi-echelon supply chains under a general c... more ABSTRACT This paper analyzes the bullwhip effect in multi-echelon supply chains under a general class of nonlinear ordering policies. A describing-function approach from control theory is used to derive closed-form formulas to predict amplification of order fluctuations along the supply chain. It is proven that with consideration of nonlinearity in the ordering policy, the magnitude of the bullwhip effect will eventually become bounded after growing through the first few stages of the supply chain. It is also proven that the average customer demand as well as the demand fluctuation frequency would directly affect the bounded magnitude, while the suppliers’ demand forecasting method has no effect at all. For illustration, analytical results for a class of order-up-to policies are derived and verified by numerical simulations. The proposed modeling framework holds the promise to not only explain empirical observations, but also serve as the basis for developing counteracting strategies against the bullwhip effect.
Transportation Research Part B: Methodological, 2014