In cutting processes, one of the strategies to reduce raw material waste is to generate leftovers that are large enough to return to stock for future use. The length of these leftovers is important since waste is expe...
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In cutting processes, one of the strategies to reduce raw material waste is to generate leftovers that are large enough to return to stock for future use. The length of these leftovers is important since waste is expected to be minimal when cutting these objects in the future. However, in several situations, future demand is unknown and evaluating the best length for the leftovers is challenging. Furthermore, it may not be economically feasible to manage a stock of leftovers with multiple lengths that may not result in minimal waste when cut. In this paper, we approached the cutting stock problem with the possibility of generating leftovers as a two-stage stochastic program with recourse. We approximated the demand levels for the different items by employing a finite set of scenarios. Also, we modeled different decisions made before and after uncertainties were revealed. We proposed a mathematical model to represent this problem and developed a column generation approach to solve it. We ran computational experi-ments with randomly generated instances, considering a representative set of scenarios with a varying probability distribution. The results validated the efficiency of the proposed approach and allowed us to derive insights on the value of modeling and tackling uncertainty in this problem. Overall, the results showed that the cutting stock problem with usable leftovers benefits from a modeling approach based on sequential decision-making points and from explicitly considering uncertainty in the model and the solution method. (c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license ( http://***/licenses/by-nc-nd/4.0/ )
There will always be stochastic programs that are too large or complex to be solved in their basic form. In this article, we review, discuss, and compare different ways such stochastic programs can be handled using bo...
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There will always be stochastic programs that are too large or complex to be solved in their basic form. In this article, we review, discuss, and compare different ways such stochastic programs can be handled using bounds and approximations, all based on manipulations of the random variables. We are particularly interested in how methods based on different underlying ideas can be combined or possibly are the same.
Errors in forest inventory data can lead to sub-optimal management decisions and dramatic economic losses. Forest inventory approaches are typically evaluated by their levels of precision and accuracy;however, this ov...
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Errors in forest inventory data can lead to sub-optimal management decisions and dramatic economic losses. Forest inventory approaches are typically evaluated by their levels of precision and accuracy;however, this overlooks the specific usefulness of the data in decision-making. By evaluating the value of information (VoI), we can assess the usefulness of the data for specific decision-making problems. We evaluated the VoI through stochastic programming for four airborne laser scanning-based inventory approaches. The stochastic programming model explored the trade-off between the maximal net present value and the minimal conditional value at risk of meeting specified periodic income targets. We evaluated a range of periodic targets and risk aversion preference levels. To compare the performance of the inventory approaches, we used a reference dataset that was acquired using a forest harvester with precise positioning. For a wide range of the trade-offs, inventory approaches with higher-quality information provided the best overall performance. If only one of the extreme objectives was desired, less precise inventory approaches were sufficient to produce high-quality solutions.
stochastic programming has been widely used in various application scenarios and theoretical research works. However, these excellent methods depend on specific explicit probability modeling with complete knowledge of...
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stochastic programming has been widely used in various application scenarios and theoretical research works. However, these excellent methods depend on specific explicit probability modeling with complete knowledge of uncertainty, which is very limited in practical problem since there is usually no way to abstract complex uncertainties into the commonly used known probability models. In this paper, a novel generative model named the Adaptive Discrete Approximation Rejection Sampling is proposed for stochastic programming with incomplete knowledge of uncertainty, which can not only simulate uncertain scenarios from a complex explicit probability model that cannot meet the constraints of existing sampling methods, but also even simulate scenarios from a sample set related to uncertainty when the specific explicit probability model of uncertainty is missing or unavailable. The method is to establish the easy-to-sample proposal distribution by approximately transforming the complex hard-to-sample target probability model, to make the proposal distribution close enough to the target distribution, so as to achieve an efficient sampling while ensuring the performance of the model. On this basis, combining the Monte Carlo method and heuristic optimization, an uncertain optimization model for stochastic programming with incomplete knowledge of uncertainty is further constructed, to solve the unavailability of the existing stochastic programming methods in the absence of explicit probability model of uncertainty. Experimental results show the advantages of the proposed method in terms of applicability, adaptability, accuracy, efficiency and model performance.
We propose a new stochastic mixed -integer linear programming model for a home service fleet sizing and appointment scheduling problem (HFASP) with random service and travel times. Specifically, given a set of provide...
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We propose a new stochastic mixed -integer linear programming model for a home service fleet sizing and appointment scheduling problem (HFASP) with random service and travel times. Specifically, given a set of providers and a set of geographically distributed customers within a service region, our model solves the following problems simultaneously: (i) a fleet sizing problem that determines the number of providers required to serve customers;(ii) an assignment problem that assigns customers to providers;and (iii) a sequencing and scheduling problem that decides the sequence of appointment times of customers assigned to each provider. The objective is to minimize the fixed cost of hiring providers plus the expectation of a weighted sum of customers' waiting time and providers' travel time, overtime, and idle time. We compare our proposed model with an extension of an existing model for a closely related problem in the literature, theoretically and empirically. Specifically, we show that our newly proposed model is more compact (i.e., has fewer variables and constraints) and provides a tighter linear programming relaxation. Furthermore, to handle large instances observed in other application domains, we propose two optimization -based heuristics that decompose the HFASP decision process into two steps. The first step involves determining fleet sizing and assignment decisions, and the second constructs a routing plan and a schedule for each provider. We present extensive computational results to show the size and characteristics of HFASP instances that can be solved with our proposed model, demonstrating its computational efficiency over the extension. Results also show that the proposed heuristics can quickly produce high -quality solutions to large instances with an optimality gap not exceeding 5% on tested instances. Finally, we use a case study based on a service region in Lehigh County to derive insights into the HFASP.
To mitigate outpatient care delivery inefficiencies induced by resource shortages and demand heterogeneity, this paper focuses on the problem of allocating and sequencing multiple medical resources so that patients sc...
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To mitigate outpatient care delivery inefficiencies induced by resource shortages and demand heterogeneity, this paper focuses on the problem of allocating and sequencing multiple medical resources so that patients scheduled for clinical care can experience efficient and coordinated care with minimum total waiting time. We leverage highly granular location data on people and medical resources collected via Real-Time Location System technologies to identify dominant patient care pathways. A novel two-stage stochastic Mixed Integer Linear programming model is proposed to determine the optimal patient sequence based on the available resources according to the care pathways that minimize patients' expected total waiting time. The model incorporates the uncertainty in care activity duration via sample average *** employ a Monte Carlo Optimization procedure to determine the appropriate sample size to obtain solutions that provide a good trade-off between approximation accuracy and computational time. Compared to the conventional deterministic model, our proposed model would significantly reduce waiting time for patients in the clinic by 60%, on average, with acceptable computational resource requirements and time complexity. In summary, this paper proposes a computationally efficient formulation for the multi-resource allocation and care sequence assignment optimization problem under uncertainty. It uses continuous assignment decision variables without timestamp and position indices, enabling the data-driven solution of problems with real-time allocation adjustment in a dynamic outpatient environment with complex clinical coordination constraints.
In metal recycling plants, equipment problems originating from materials are not infrequent when recycling various types of input materials. Appropriate scheduling is required while taking such uncertainties into acco...
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ISBN:
(纸本)9798350379068;9798350379051
In metal recycling plants, equipment problems originating from materials are not infrequent when recycling various types of input materials. Appropriate scheduling is required while taking such uncertainties into account. In this study, the recycling process is modeled as a mixed integer programming problem and then as a two-stage stochastic programming problem that takes into account the uncertainty caused by troubles and the overtime caused by delays. Since the two-stage stochastic programming model becomes more difficult to derive the optimal solution as the problem size increases, a sampling-based solution method is used to reduce computation time by applying the integer variable values of the solution obtained by optimization in a small number of scenarios as constants to a model that includes all scenarios. The effectiveness of the model is examined through numerical experiments based on actual factory operations.
The agent routing process considering weather conditions is a multi-objective optimization problem constrainedly, which various optimization criteria and constraints should be considered. The quality of the given rout...
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In supply chain management, risk management is crucial to ensure a stable product supply while considering economic efficiency. It is essential to design resilient supply chains that can maintain production capacity b...
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In supply chain management, risk management is crucial to ensure a stable product supply while considering economic efficiency. It is essential to design resilient supply chains that can maintain production capacity by preparing for and responding to predictable risks. Our group has proposed strategic planning methodologies for the selection of appropriate material suppliers and the optimization of inventory levels across the supply chain, including suppliers, manufacturers, and wholesalers, with considering potential risks. We have introduced a planning method for resilient supply chain networks using two-stage stochastic programming. This paper extends the proposed method to accommodate supply chains managing multiple products, aiming for more realistic conditions. The effectiveness of the extended method is assessed through computational experiments.
In the scenario-based stochastic programming problems, the computational burden increase as the number of scenarios increases, which involves necessary scenario reduction operations. For the scenario reduction problem...
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ISBN:
(纸本)9798350387780;9798350387797
In the scenario-based stochastic programming problems, the computational burden increase as the number of scenarios increases, which involves necessary scenario reduction operations. For the scenario reduction problem with high-dimensional random vector, an optimal reduction framework is presented to eliminate redundant scenarios. In this framework, the concept of probabilistic similarity function is firstly proposed to solve the problem that scenarios cannot be clearly distinguished by traditional distance-based reduction methods in the high-dimensional scenario clustering process. The relative distance under each dimension of scenarios is considered in the computation of probabilistic similarity function, which depends not only on the values of two scenario vectors but also on the overall scenario set. The proposed recursive-type reduction method aims at maximizing the probabilistic similarity between the original scenario set and reduced scenario set. The numerical results demonstrate that our method can exhibit better performance than distance-based methods and have good universality for different stochastic programming problems.
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