We propose the REORIENT (REnewable resOuRce Investment for the ENergy Transition) model for energy systems planning with the following novelties: (1) integrating capacity expansion, retrofit and abandonment planning, ...
详细信息
We study the optimal supply chain design for a dual-channel retailer that operates physical and web-based stores and has traditionally managed each one separately. With increased pressures from customers and decreased...
详细信息
We study the optimal supply chain design for a dual-channel retailer that operates physical and web-based stores and has traditionally managed each one separately. With increased pressures from customers and decreased profits due to marked-down leftover inventories in each channel, the retailer considers integrating the supply chain operations of both channels and using in-store inventory more effectively across different channels. In contrast to the existing literature, we focus on the firm's choice of the best omni-channel strategies considering demand segmentation, cost structure, and, more importantly, the inventory rationing ability of the firm. We formulate our problem as a two-stage stochastic programming model and use first-order optimality conditions to study the optimal inventory ordering decisions. Based on different omni-channel strategy decisions, we explore four supply chain design options. We identify the optimal inventory ordering policy under each option and explicitly describe the optimality conditions on cost and demand under perfect and imperfect demand information. When the demand information is imperfect, the demand fulfillment decisions can be characterized as nested protection-level policies. First, we show that omni-channel strategies are not necessarily profitable under all settings as dictated by market conditions. Second, we demonstrate that when the company can allocate its inventory perfectly, running omni-channel strategies may help better serve web-based customers and in-store customers. Finally, we show that, in the worst case, the imperfect demand information may result in losing all the claimed inventory integration benefits when running omni-channel strategies.
This paper introduces a new exact algorithm to solve two-stage stochastic linear programs. Based on the multicut Benders reformulation of such problems, with one subproblem for each scenario, this method relies on a p...
详细信息
This paper introduces a new exact algorithm to solve two-stage stochastic linear programs. Based on the multicut Benders reformulation of such problems, with one subproblem for each scenario, this method relies on a partition of the subproblems into batches. The key idea is to solve at most iterations only a small proportion of the subproblems by detecting as soon as possible that a first-stage candidate solution cannot be proven optimal. We also propose a general framework to stabilize our algorithm, and show its finite convergence and exact behavior. We report an extensive computational study on large-scale instances of stochastic optimization literature that shows the efficiency of the proposed algorithm compared to nine alternative algorithms from the literature. We also obtain significant additional computational time savings using the primal stabilization schemes. (C) 2023 Elsevier B.V. All rights reserved.
We study optimal aircraft seat assignment for infectious diseases in view of the stochastic risk of infection for a passenger assigned to a seat. The stochastic risk is based on the passengers' vaccination status ...
详细信息
We study optimal aircraft seat assignment for infectious diseases in view of the stochastic risk of infection for a passenger assigned to a seat. The stochastic risk is based on the passengers' vaccination status and the different risk probability distributions corresponding to seat locations at window, middle, or aisle. In addition, the influence of groups of passengers who prefer to be seated together on the risk of infection in the cabin is also analyzed. A stochastic programming technique is applied to develop both non-grouped and grouped scenariobased models. The objective is to minimize the risk of infection for the worst-case scenario, as formulated by the Min-Max objective approach. Numerical tests utilizing statistical data from 2369 flights in Taiwan were performed. The results show that the consideration of passengers' vaccination status during seat assignment is useful, reducing the average risk of infection in the cabin by half. Grouped seat assignment does not seem to have a significant influence on the risk of infection, with an increase of only 1.28 and 1.25 times compared with nongrouped seat assignment. The recommendations are that more heavily vaccinated passengers be assigned to aisle seats, while passengers who have received fewer doses be assigned to window seats. In addition, considering the limited impact of group seating on the risk of infection, it may not be necessary for an airline to decline to accommodate such requests.
Hydropower producers need to plan several months or years ahead to estimate the opportunity value of water stored in their reservoirs. The resulting large-scale optimization problem is computationally intensive, and m...
详细信息
Hydropower producers need to plan several months or years ahead to estimate the opportunity value of water stored in their reservoirs. The resulting large-scale optimization problem is computationally intensive, and model simplifications are often needed to allow for efficient solving. Alternatively, one can look for near-optimal policies using heuristics that can tackle non-convexities in the production function and a wide range of modelling approaches for the price- and inflow dynamics. We undertake an extensive numerical comparison between the state-of-the-art algorithm stochastic dual dynamic programming (SDDP) and rolling forecast-based algorithms, including a novel algorithm that we develop in this paper. We name it Scenario-based Two-stage ReOptimization abbreviated as STRO. The numerical experiments are based on convex stochastic dynamic programs with discretized exogenous state space, which makes the SDDP algorithm applicable for comparisons. We demonstrate that our algorithm can handle inflow risk better than traditional forecast-based algorithms, by reducing the optimality gap from 2.5 to 1.3% compared to the SDDP bound.
In this paper, we study the stochastic optimization problem with multivariate second-order stochastic dominance (MSSD) constraints where the distribution of uncertain parameters is unknown. Instead, only some historic...
详细信息
In this paper, we study the stochastic optimization problem with multivariate second-order stochastic dominance (MSSD) constraints where the distribution of uncertain parameters is unknown. Instead, only some historical data are available. Using the Wasserstein metric, we construct an ambiguity set and develop a data-driven distributionally robust optimization model with multivariate second-order stochastic dominance constraints (DROMSSD). By utilizing the linear scalarization function, we transform MSSD constraints into univariate constraints. We present a stability analysis focusing on the impact of the variation of the ambiguity set on the optimal value and optimal solutions. Moreover, we carry out quantitative stability analysis for the DROMSSD problems as the sample size increases. Specially, in the context of the portfolio, we propose a convex lower reformulation of the corresponding DROMSSD models under some mild conditions. Finally, some preliminary numerical test results are reported. We compare the DROMSSD model with the sample average approximation model through out-of-sample performance, certificate and reliability. We also use real stock data to verify the effectiveness of the DROSSM model.
We present a novel framework for distributionally robust optimization (DRO), called cost-aware DRO (Cadro). The key idea of Cadro is to exploit the cost structure in the design of the ambiguity set to reduce conservat...
详细信息
We present a novel framework for distributionally robust optimization (DRO), called cost-aware DRO (Cadro). The key idea of Cadro is to exploit the cost structure in the design of the ambiguity set to reduce conservatism. Particularly, the set specifically constrains the worst-case distribution along the direction in which the expected cost of an approximate solution increases most rapidly. We prove that Cadro provides both a high-confidence upper bound and a consistent estimator of the out-of-sample expected cost, and show empirically that it produces solutions that are substantially less conservative than existing DRO methods, while providing the same guarantees.
A stochastic programming model for a price-taking, profit-maximizing hydropower producer participating in the Nordic day-ahead and balancing market is developed and evaluated by backtesting over 200 historical days. W...
详细信息
A stochastic programming model for a price-taking, profit-maximizing hydropower producer participating in the Nordic day-ahead and balancing market is developed and evaluated by backtesting over 200 historical days. We find that the producer may gain 0.07% by coordinating its trades in the day-ahead and balancing market, compared to considering the two markets sequentially. It is thus questionable whether a coordinated bidding strategy is worthwhile. However, the gain from coordinating trades is dependent on the quality of the forecasts for the balancing market. The limited gain of 0.07% comes from using an artificial neural network prediction model that is trained on historical data on seasonal effects, day-ahead market price, wind and temperature forecasts. To quantify the effect of the forecasting model on the gain of coordination, we therefore develop a benchmarking framework for two additional prediction models: a naive forecast predicting zero imbalance in expectation, and a perfect information forecast. Using the naive method, we estimate the lower bound of coordination to be 0.0% which coincides with theory. When having perfect information, we find that the upper bound for the gain is 3.8% which indicates that a substantial gain in profits can be obtained by coordinated bidding if accurate prediction methods could be developed.
We seek to provide practicable approximations of the two-stage robust stochastic optimization model when its ambiguity set is constructed with an f-divergence radius. These models are known to be numerically challengi...
详细信息
We seek to provide practicable approximations of the two-stage robust stochastic optimization model when its ambiguity set is constructed with an f-divergence radius. These models are known to be numerically challenging to various degrees, depending on the choice of the f-divergence function. The numerical challenges are even more pronounced under mixed-integer first-stage decisions. In this paper, we propose novel divergence functions that produce practicable robust counterparts, while maintaining versatility in modeling diverse ambiguity aversions. Our functions yield robust counterparts that have comparable numerical difficulties to their nominal problems. We also propose ways to use our divergences to mimic existing f-divergences without affecting the practicability. We implement our models in a realistic location-allocation model for humanitarian operations in Brazil. Our humanitarian model optimizes an effectiveness-equity trade-off, defined with a new utility function and a Gini mean difference coefficient. With the case study, we showcase (1) the significant improvement in practicability of the robust stochastic optimization counterparts with our proposed divergence functions compared to existing f-divergences, (2) the greater equity of humanitarian response that the objective function enforces and (3) the greater robustness to variations in probability estimations of the resulting plans when ambiguity is considered.
This study introduces a stochastic optimization model designed for enhancing coal procurement and logistics management at port-based coal-fired power plants. Addressing the dual pressures of economic efficiency and en...
详细信息
This study introduces a stochastic optimization model designed for enhancing coal procurement and logistics management at port-based coal-fired power plants. Addressing the dual pressures of economic efficiency and environmental sustainability, this model incorporates the complexities of maritime transportation uncertainties, varying demand, and stringent carbon emission controls. Through this framework, we effectively align procurement strategies with inventory management to optimize operations under dynamic conditions. The model's distinctiveness lies in its integration of real-time maritime variables and adaptive responses to environmental policies, setting a new standard for green logistics in the energy sector. Key results demonstrate the effectiveness of mixed coal procurement strategies across different demand scenarios, highlighting significant savings in carbon emissions and operational costs. Our findings provide valuable insights for policymakers and industry stakeholders aiming to achieve sustainable development goals in the energy sector.
暂无评论