Opportunities exist for forestry companies to vertically integrate operations to include both forest estate management and timber processing. However, forest supply chains have traditionally functioned in a decoupled ...
详细信息
Opportunities exist for forestry companies to vertically integrate operations to include both forest estate management and timber processing. However, forest supply chains have traditionally functioned in a decoupled manner where forest operations and timber processing are uncoordinated in their planning and operation, leading to sub-optimal supply chain configuration and outcomes. To maximize the benefits of vertically integrated forest supply chains, the planning method needs to include both strategic and tactical decisions simultaneously. This paper demonstrates a mixedintegerlinearprogramming integrated forest planning model that integrates strategic level forest management on a long 40-year planning horizon with sawmill operations in the tactical level decision over multiple shorter horizons with the 40 year overall planning period to cover the decisions related to forest and the wood processing plant. The results show that when compared to uncoordinated forestry and processing model outcomes, the incorporation of forestry and processing operations in an integrated optimization model can increase the NPV of the combined enterprise over 20%. The results are tested to a range of sensitivities, including discount rate, harvest cost and harvest volume. The revenue from selling processed wood products made possible when a forest management firm owns its own timber mill accounts for the integrated model profitability increase, which is not available in the strategic model representing a forest firm without timber processing capacity. The results emphasize that the integrated planning method could bring more economic returns and support forest managers' decision-making.
This work presents a bi-objective time-dependent vehicle routing problem with delivery failure probabilities (TDVRPDFP). Two objectives are jointly minimized: operational costs and delivery failure rates. Both travel ...
详细信息
This work presents a bi-objective time-dependent vehicle routing problem with delivery failure probabilities (TDVRPDFP). Two objectives are jointly minimized: operational costs and delivery failure rates. Both travel times and costs, as well as the probabilities of delivery failure and service times and costs, are considered time-dependent. A mixed-integerlinearprogrammingmodel is proposed to obtain sets of non-dominated solutions for small-size instances, while a multi-objective genetic algorithm, NSGA-II, is implemented to obtain approximate sets of non-dominated for large-size instances. Five sets of instances are proposed and used to evaluate the solution approaches. Our results indicate that the implemented NSGA-II algorithm can optimally solve small and large instances and find large Pareto fronts for instances with more than 25 nodes and 40-time intervals.
The fundamental function of a natural gas pipeline network is to transport enough natural gas to users. Therefore, user characteristics should be considered in the formulation of the flow allocation plan of the pipeli...
详细信息
The fundamental function of a natural gas pipeline network is to transport enough natural gas to users. Therefore, user characteristics should be considered in the formulation of the flow allocation plan of the pipeline network under accident conditions. However, user characteristics have usually not been considered in previous flow allocation models. In this study, a mixed integer linear programming model is developed to determine the optimal flow allocation plan of a large-scale and complex natural gas pipeline network under accident conditions, and the user characteristics are considered as well. The optimization objective is to maximize the weighted sum of the amount of natural gas transported to the consumers under accident conditions, and the weights of the natural gas users are obtained by user characteristics analysis. The model constraints include flow constraints, gas source supply capacity constraints, user demand constraints, pipeline transmission capacity constraints, pressure constraints, and pipeline hydraulic constraint. For the sake of model simplification, the hydraulic constraints are treated piecewise linearly. Furthermore, the model is set into a real-world situation, which is the natural gas pipeline network located in China, and the user characteristics are considered in the optimal flow allocation plan under accident condition. The impact of user characteristics is further investigated by calculating and comparing the flow allocation plan when considering and ignoring user characteristics. The study indicates that when user characteristics are considered, the natural gas pipeline network will tend to give higher priority to those crucial users.
End-of-life products have a severe impact on the ecological system. Potential production policies and distribution strategies for the newly manufactured product have attracted significant attention to sustainable deve...
详细信息
End-of-life products have a severe impact on the ecological system. Potential production policies and distribution strategies for the newly manufactured product have attracted significant attention to sustainable development. Sustainability in supply chain management has much importance to achieve eco-friendly goals. In this study, we have developed sustainable objectives in the supply chain optimization framework with different constraints. The trade-off between economic, environmental and social effects objectives have identified by ensuring the optimal allocation of different products among various levels. In this regard, a new sustainability multi-objective mixed-integerlinearprogramming mathematical model in the medicine supply chain network is developed. Although the proposed model is an NP-hard problem, we develop a novel hybrid Particle Swarm Optimization and Genetic Algorithm to achieve Pareto solutions. Then, to adjust the important parameters of the algorithms and chose the optimum levels of the significant factors for more efficiency is employed the Taguchi method. The results show that the economic and environmental effects tend to be decreased and the social impacts tend to be increased in the medicine supply chain network which can exhibit the best sustainability performance. The various outcomes of numerical experiments indicate that the proposed solution algorithm is more reliable than other algorithms. The solution methods are complemented with several sensitivity analyses on the input parameters of the model.
暂无评论