In the literature on evacuation planning, a basic assumption is that all evacuees are fully compliant with respect to the officially planned evacuee-to-facility assignments. However, this assumption is challenged in r...
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In the literature on evacuation planning, a basic assumption is that all evacuees are fully compliant with respect to the officially planned evacuee-to-facility assignments. However, this assumption is challenged in reality. Hence, we propose two-stage stochastic evacuation pick-up point assignment models, which explicitly incorporate uncertain non-compliance behavior of evacuees. In the first stage, evacuees of each demand point are assigned to a specific transit pick-up point. In the second stage, imbalances of evacuees at each pick-up point are revealed based on the first-stage assignments and the realized non-compliance relevant scenarios. With numerical studies and a case study, we investigate the importance of including correlated stochastic noncompliance behavior in the models, illustrate that our models are effective to produce better pick-up point assignment plans and obtain managerial insights on evacuation planning and model applications.
Because of high volatility in oil price, oil companies should change their strategies along with changing oil prices. Thus, dynamic portfolio management is strongly recommended to increase the rate of oil production a...
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Due to the carbon neutral goals in many countries, a shift from traditional fuels to biomass is currently taking place in the energy sector. In this publication, we are looking at the long-term biomass contracting dec...
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Due to the carbon neutral goals in many countries, a shift from traditional fuels to biomass is currently taking place in the energy sector. In this publication, we are looking at the long-term biomass contracting decisions for combined heat and power plants and power producers. A major share of biomass contracts are long-term contracts with runtimes of around 1 year, so the actual biomass demand is still uncertain when the contracts are negotiated. The operators can select different types of contracts ranging from fixed contracts with fixed amounts and deliveries to more flexible contracts and call options that allow for some flexibility in terms of amount and delivery times. We propose a stochastic program to optimize the contract selection including amounts and deliveries taking the biomass storage and uncertain demand into account. We present results of a case study from industry and show how the model utilizes the contracts for flexibility to adapt to different demand scenarios. Furthermore, the model is used for investigating the tradeoff between storage restrictions and fulfilling the demand in all scenarios. We show why it is important to model this problem as a stochastic program and why considering an expected demand is not enough.
Designing a resilient power network is paramount for a stable power supply. The component hardening strategy has widespread applications in the resilience design of power networks to mitigate the impact of various nat...
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We consider the multistage stochastic programming problem where uncertainty enters the right-hand sides of the problem. stochastic Dual Dynamic programming (SDDP) is a popular method to solve such problems under the a...
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We consider the multistage stochastic programming problem where uncertainty enters the right-hand sides of the problem. stochastic Dual Dynamic programming (SDDP) is a popular method to solve such problems under the assumption that the random data process is stagewise independent. There exist two approaches to incorporate dependence into SDDP. One approach is to model the data process as an autoregressive time series and to reformulate the problem in stagewise independent terms by adding state variables to the model (TS-SDDP). The other approach is to use Markov Chain discretization of the random data process (MC-SDDP). While MC-SDDP can handle any Markovian data process, some advantages of statistical analysis of the policy under the true process are lost. In this work, we compare both approaches based on a computational study using the long-term operational planning problem of the Brazilian interconnected power systems. We found that for the considered problem the optimality bounds computed by the MC-SDDP method close faster than its TS-SDDP counterpart, and the MC-SDDP policy dominates the TS-SDDP policy. When implementing the optimized policies on real data, we observe that not only the method but also the quality of the stochastic model has an impact on policy performance and that using an Av@R formulation is effective in making the policy robust against a misspecified stochastic model. (C) 2018 Elsevier B.V. All rights reserved.
Nowadays, organisations try to find a proper method to increase their competitiveness. Lean, resilient, and sustainable are top-hole managerial practices in supply chain management. This paper tries to study the effec...
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Nowadays, organisations try to find a proper method to increase their competitiveness. Lean, resilient, and sustainable are top-hole managerial practices in supply chain management. This paper tries to study the effects of integrating lean, resilient, and sustainable practices in the supply chain network (SCN). To this end, a new multi-objective mixed-integer programming is developed in such a way that lean manufacturing is implemented in a resilient-sustainable SCN. The objective functions try to maximise job opportunities and minimise costs, environmental effects, and delivery time. Resilience has been taken into account to tackle the lack of raw materials during disruptions by implementing multiple sourcing in the model. Besides, to devote more attention to sustainable practices, backup suppliers have been prioritised based on sustainability criteria. The academics were enquired to rate sustainability criteria for selecting a backup supplier. Finally, a fuzzy TOPSIS method was used to rank the backup suppliers based on sustainability criteria. The improved version of augmented epsilon-constraint (AUGMECON2) was applied to cope with multi-objectivity of the problem. The results indicated a synergistic effect among leanness, resilience, and sustainability in the supply chain. Also, it turned out that sustainable backup supplier selection boosts the synergistic effect among these three concepts.
In the aftermath of a hurricane, humanitarian logistics plays a critical role in delivering relief items to the affected areas in a timely fashion. This paper proposes a novel stochastic look-ahead framework that impl...
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In the aftermath of a hurricane, humanitarian logistics plays a critical role in delivering relief items to the affected areas in a timely fashion. This paper proposes a novel stochastic look-ahead framework that implements a two-stage stochastic programming model in a rolling horizon approach to address the evolving uncertain logistics system state during the post-hurricane humanitarian logistics operations. The two-stage stochastic programming model that executes in this rolling horizon approach is formulated as a mixed-integer programming problem. The model aims to minimize the total cost incurred in the logistics operations, which consist of transportation cost and social cost. The social cost is measured as a function of deprivation for unsatisfied demand. Our extensive numerical results and sensitivity analysis demonstrate the effectiveness of the proposed approach in reducing the total cost incurred during the post-hurricane relief logistics operations compared to the two-stage stochastic programming model implemented in a static fashion.
This study focuses on the real-time operation of a microgrid (MG). A novel approximate dynamic programming based spatiotemporal decomposition approach is developed to incorporate efficient management of distributed en...
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This study focuses on the real-time operation of a microgrid (MG). A novel approximate dynamic programming based spatiotemporal decomposition approach is developed to incorporate efficient management of distributed energy storage systems into MG real-time operation while considering uncertainties in renewable generation. The original dynamic energy management problem is decomposed into single-period and single-unit sub-problems, and the value functions are used to describe the interaction among the sub-problems. A two-stage procedure is further designed for the real-time decisions of those sub-problems. In the first stage, empirical data is utilised offline to approximate the value functions. Then in the second stage, each sub-problem can make immediate and independent decision in both temporal and spatial dimensions to mitigate adverse effects of intermittent renewable generation in a MG. No central operator intervention is required, and the near optimal decisions can be obtained at a very fast speed. Case studies based on a six-bus MG and an actual island MG are conducted to demonstrate the effectiveness of the proposed algorithm.
The enhanced index tracking (EIT) represents a popular investment strategy designed to create a portfolio of assets that outperforms a benchmark, while bearing a limited additional risk. This paper analyzes the EIT pr...
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The enhanced index tracking (EIT) represents a popular investment strategy designed to create a portfolio of assets that outperforms a benchmark, while bearing a limited additional risk. This paper analyzes the EIT problem by the chance constraints (CC) paradigm and proposes a formulation where the return of the tracking portfolio is imposed to overcome the benchmark with a high probability value. Besides the CC-based formulation, where the eventual shortage is controlled in probabilistic terms, the paper introduces a model based on the Integrated version of the CC. Here the negative deviation of the portfolio performance from the benchmark is measured and the corresponding expected value is limited to be lower than a given threshold. Extensive computational experiments are carried out on different set of benchmark instances. Both the proposed formulations suggest investment strategies that track very closely the benchmark over the out-of-sample horizon and often achieve better performance. When compared with other existing strategies, the empirical analysis reveals that no optimization model clearly dominates the others, even though the formulation based on the traditional form of the CC seems to be very competitive.
In this paper, we aim to build confidence regions of the true solution to the stochastic variational inequalities problem (SVIP) when the sample average approximation (SAA) scheme is implemented. A new approach based ...
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In this paper, we aim to build confidence regions of the true solution to the stochastic variational inequalities problem (SVIP) when the sample average approximation (SAA) scheme is implemented. A new approach based on error bound conditions admitted by the SVIP is proposed. This so-called error bound approach provides an upper bound of the distance between SAA solutions and the true solution set through the distance between the SAA function and the true counterpart at the SAA solutions. Certain statistical tools such as central limit theorem and Owen's empirical likelihood theorem are then employed to construct the asymptotic confidence regions of the solutions to SVIP. In particular, if the SVIP admits a global error bound condition, the non-asymptotic (uniform) confidence regions of the solutions are also approachable. Different from the conventional normal map approach, our error bound approach does not require any information regarding the derivative of the solution mapping with respect to perturbations of involved functions in SVIP. For constructing component-wise confidence regions, the validity of the error bound approach is guaranteed for those cases where the functions own separable structures.
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