This study addresses the problem of creating single aircraft route within strict time constraints, taking into account the uncertainty of travel times. The approach involves a two-phase decision-making process: the in...
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This study addresses the problem of creating single aircraft route within strict time constraints, taking into account the uncertainty of travel times. The approach involves a two-phase decision-making process: the initial phase focuses on selecting airports from a pool of candidates by optimizing for maximum customer satisfaction;the subsequent phase involves arranging the sequence of itinerary to these airports, factoring in variable travel times to enhance the overall experience. To tackle this complex issue, we have developed a two-stage stochastic optimization model that incorporates probability-based constraints. This model is then analyzed using the sample average approximation method. To validate the efficacy of our proposed model, we compared its performance with two established benchmark models. Additionally, case studies focused on the U.S. airline network suggest that operators can optimize airline route recommendations by enhancing both customer utility and their own profitability. This approach demonstrates that strategic adjustments in route planning can lead to mutual benefits, effectively balancing customer satisfaction with financial performance.
This study considers a supply chain in which a credit-worthy buyer purchases goods from a capital-constrained supplier to satisfy her deterministic demand. The buyer simultaneously implements both cash in advance (CIA...
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This study considers a supply chain in which a credit-worthy buyer purchases goods from a capital-constrained supplier to satisfy her deterministic demand. The buyer simultaneously implements both cash in advance (CIA) and purchase order financing (POF) as part of their pre-shipment financing (PSF) schemes to fund the supplier's operation. This research classifies CIA based on refundability, considering the increasing use of mitigating services or platforms associated with these PSF schemes. The study provides guidelines for aligning these primary PSF schemes with purchasing decisions, strengthening the buyer's ability to develop suppliers in sectors with small vendors, such as agriculture and dairy farming. We reveal that whether or not a CIA agreement includes so-called refundability strongly affects buyer preferences for CIA and POF. Specifically, we summarize our findings as follows: (1) Pure CIA financing strategy is optimal when CIA is refundable, which implies refundable CIA dominates POF. (2) When CIA is non-refundable, POF is preferred over CIA because POF allows a buyer to share the financing risk with a bank, whereas non-refundable CIA involves high risk. (3) When CIA is non-refundable, we recommend the buyer implement a mixed financing strategy, with POF and CIA as primary and backup financing options, respectively.
Cogeneration systems have gained prominence in recent years driven by the simultaneous systematic production of heat and electricity, which are involved in industrial and commercial processes. Sugar and alcohol indust...
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Cogeneration systems have gained prominence in recent years driven by the simultaneous systematic production of heat and electricity, which are involved in industrial and commercial processes. Sugar and alcohol industry has become a reference in the use of cogeneration through the burning of sugarcane bagasse, with an important role in the future policies for generation expansion in Brazil. However, in the economic evaluation of this type of project, some previously ignored variables had a gain of relevance, such as the possibility of selling surplus energy produced by the plant. This paper presents a multiobjective stochastic optimization model using stochastic dynamic dual programming techniques, which seeks to maximize net revenue of a cogeneration project, indicating also the installed power adequate to the fuel availability and the needs of the plant, considering different energy scenarios in the spot market. The results indicate the best configuration for a cogeneration plant, considering the possibility of energy revenue, allowing an easy cost comparison of different alternatives for decision making from the investor's point of view.
The push for renewable energy emphasizes the need for energy storage systems(ESSs)to mitigate the unpre-dictability and variability of these sources,yet challenges such as high investment costs,sporadic utilization,an...
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The push for renewable energy emphasizes the need for energy storage systems(ESSs)to mitigate the unpre-dictability and variability of these sources,yet challenges such as high investment costs,sporadic utilization,and demand mismatch hinder their broader *** response,shared energy storage systems(SESSs)offer a more cohesive and efficient use of ESS,providing more accessible and cost-effective energy storage solutions to overcome these *** enhance the profitability of SESSs,this paper designs a multi-time-scale resource allocation strategy based on long-term contracts and real-time rental business *** initially construct a life cycle cost model for SESS and introduce a method to estimate the degradation costs of multiple battery groups by cycling numbers and depth of discharge within the ***,we design various long-term contracts from both capacity and energy perspectives,establishing associated models and real-time rental ***,multi-time-scale resource allocation based on the decomposition of user demand is *** analysis validates that the business model based on long-term contracts excels over models operating solely in the real-time market in economic viability and user satisfaction,effectively reducing battery degradation,and leveraging the aggregation effect for SESS can generate an additional increase of 10.7%in net revenue.
The primary purpose of oil sands mine planning and waste management is to provide ore from the mine pit to the processing plant while containing the tailings in an efficient manner in-pit. Incorporating waste manageme...
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The primary purpose of oil sands mine planning and waste management is to provide ore from the mine pit to the processing plant while containing the tailings in an efficient manner in-pit. Incorporating waste management in the mine plan is essential to maximize the economic potential of the mineral reserve and minimize waste management costs. However, spatial variability such as grade uncertainty results in ore tonnage variations, which leads to fluctuations in the quantity of ore to be processed and waste to be managed. This paper investigates the application of a stochastic mixed integer linear programming (SMILP) on oil sands mine planning to integrate bitumen grade uncertainty and waste management. Sequential Gaussian simulation is employed to quantitatively model the spatial variability of bitumen grade in the oil sands deposit. Multiple simulated orebody models are used as inputs for the SMILP model to generate optimal mine plans in the presence of grade uncertainty. The results demonstrate that the SMILP schedule generates 14% and 17% improvements in net present value compared to the E-type and ordinary kriging schedules, respectively. These results indicate that the SMILP model is a robust tool for optimizing stochastic integrated oil sands production schedules and waste management. L'objectif principal de la planification des mines de sables bitumineux et de la gestion des d & eacute;chets est de fournir du minerai de la mine & agrave;l'usine de traitement tout en confinant les r & eacute;sidus de mani & egrave;re efficace dans la fosse. L'int & eacute;gration de la gestion des d & eacute;chets dans le plan minier est essentielle pour maximiser le potentiel & eacute;conomique de la r & eacute;serve min & eacute;rale et de minimiser les co & ucirc;ts de gestion des d & eacute;chets. Cependant, la variabilit & eacute;spatiale comme l'incertitude de la teneur se traduit par des variations du tonnage de minerai, ce qui entra & icirc;ne des fluctuations de la qu
Renewable energy generation has attracted increasing attention in port energy systems due to the urgent need for sustainable development. This study focuses on an integrated energy system that involves wind energy, ph...
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Renewable energy generation has attracted increasing attention in port energy systems due to the urgent need for sustainable development. This study focuses on an integrated energy system that involves wind energy, photovoltaic energy, hydrogen energy and energy storage in the sustainable port. The multiple energy sources are used to generate electricity to support container loading and unloading in vessels. The realistic container loads are unknown to the port because of the uncertain arrival information, which affect the specific integrated energy scheduling. A twostage stochastic programming model is proposed to incorporate uncertain demand, multi-energy supply, electricity storage and sales. The vessel delay costs and the related energy costs that are generated from electricity consumption, storage and sales are minimized when allocating the integrated energy to serve berthing vessels. A metaheuristic algorithm based on the adaptive large neighborhood search (ALNS) framework is proposed for solving the model. The proposed metaheuristic algorithm fixes the decision variable values of the first-stage problem and allows transfers to solve sub-problems under all uncertain scenarios. The effectiveness of the proposed algorithm is demonstrated through small-scale, medium-scale, and large-scale numerical experiments in terms of solution quality and computation time. Some experiments are further conducted to analyze the impact of renewable energy generation, renewable energy sources, berthing vessel types, and vessel delay tolerances. Managerial insights can be obtained for optimizing the integrated energy scheduling schemes in sustainable ports. The findings can also provide implications for ports with different scales when optimizing the configurations of renewable energy supply.
We introduce an extension of stochastic dual dynamic programming (SDDP) to solve stochastic convex dynamic programming equations. This extension applies when some or all primal and dual subproblems to be solved along ...
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We introduce an extension of stochastic dual dynamic programming (SDDP) to solve stochastic convex dynamic programming equations. This extension applies when some or all primal and dual subproblems to be solved along the forward and backward passes of the method are solved with bounded errors (inexactly). This inexact variant of SDDP is described for both linear problems (the corresponding variant being denoted by ISDDP-LP) and nonlinear problems (the corresponding variant being denoted by ISDDP-NLP). We prove convergence theorems for ISDDP-LP and ISDDP-NLP for both bounded and asymptotically vanishing errors. Finally, we present the results of numerical experiments comparing SDDP and ISDDP-LP on a portfolio problem with direct transaction costs modeled as a multistage stochastic linear optimization problem. In these experiments, ISDDP-LP allows us to strike a different balance between policy quality and computing time, trading off the former for the latter.
Problem definition: Cloud computing is a multibillion-dollar business that draws substantial capital investments from large companies such as Amazon, Microsoft, and Google. Large cloud providers need to accommodate th...
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Problem definition: Cloud computing is a multibillion-dollar business that draws substantial capital investments from large companies such as Amazon, Microsoft, and Google. Large cloud providers need to accommodate the growing demand for computing resources while avoiding unnecessary overprovisioning of hardware and operational costs. The underlying decision processes are challenging, as they involve long-term hardware and infrastructure investments under future demand uncertainty. In this paper, we introduce the cloud server deployment problem. One important aspect of the problem is that the infrastructure preparation work has to be planned for before server deployments can take place. Furthermore, a combination of temporal constraints has to be considered together with a variety of physical constraints. Methodology/results: We formulate the underlying optimization problem as a two-stage stochastic program. After carefully examining the demand data and on-the-ground deployment operations, we distill two structural properties on deployment throughput constraints and provide tightness results on a convex relaxation of the second stage. Based on that, we develop efficient cutting-plane methods that exploit the special structure of the problem and can accommodate different risk measures. We test our algorithms with real production traces from Microsoft Azure and demonstrate sizeable cost reductions. We show empirically that the algorithms remain optimal even when the two properties are not fully satisfied. Managerial implications: Cloud supply chain operations were largely executed manually due to their complexity and dynamic nature. In this paper, we show that the key decision processes can be systematically optimized. In particular, we demonstrate that accounting for the stochastic nature of demands results in substantial cost reductions in cloud server deployments. Another benefit of our stochastic optimization approach is the ability to seamlessly integrate configu
We consider stochastic optimization problems with possibly nonsmooth integrands posed in infinite-dimensional decision spaces and approximate these stochastic programs via a sample- based approaches. We establish the ...
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We consider stochastic optimization problems with possibly nonsmooth integrands posed in infinite-dimensional decision spaces and approximate these stochastic programs via a sample- based approaches. We establish the asymptotic consistency of approximate Clarke stationary points of the sample-based approximations. Our framework is applied to risk-averse semilinear PDEconstrained optimization using the average value-at-risk and risk-neutral bilinear PDE-constrained optimization.
The integration of renewable energy sources into the manufacturing sector is a recent development, which is prompting companies to explore innovative approaches to enhance their production systems through efficient re...
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The integration of renewable energy sources into the manufacturing sector is a recent development, which is prompting companies to explore innovative approaches to enhance their production systems through efficient renewable energy utilization. Within this context, renewable energy-aware machine scheduling has emerged as a pivotal area requiring novel strategies for sustainability. This study aims to evaluate the effect of intermittent renewable energy supply on sustainable machine scheduling by incorporating the option of machine speed for the first time in the literature. A two-stage stochastic program is developed to model the problem and examine the value of the stochastic solution. Additionally, an efficient genetic algorithm is proposed for approximate problem solving. Extensive test study is conducted to explore and generalize the sustainable operational policies derived from the proposed method. The results reveal key scheduling strategies that promote sustainability in production by reducing non-renewable dependence. Notably, the study underlines the importance of considering uncertainties in renewable supply in scheduling, especially under conditions of substantial job and machine scales, high-capacity but variable renewable supply, and flexible job deadlines. As an illustration, in the context of test cases involving a significant number of jobs and machines, the stochastic solutions demonstrate a substantial impact on reducing energy expenditure. Failing to account for the stochastic nature of renewable energy supply would lead to considerable additional energy consumption from the grid. These findings offer valuable insights for corporate management and scheduling operations, particularly as they navigate the transition towards green manufacturing practices.
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