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Load-dependent speed optimization in maritime inventory routing

COMPUTERS & OPERATIONS RESEARCH 2020年 123卷 105051-105051页

作者： Eide, Line Ardal, Gro Cesilie Hahjem Evsikova, Nataliia Hvattum, Lars Magnus Urrutia, Sebastian Molde Univ Coll Fac Logist Molde Norway Univ Fed Minas Gerais Comp Sci Dept Belo Horizonte MG Brazil

Maritime inventory routing problems involve determining optimal routes for seagoing vessels between ports while managing the inventory of each port. Normally, such problems are considered with the vessels operating at fixed sailing speeds. However, the speed of vessels can typically be adjusted within an interval, and the actual fuel consumption depends on both the load and the speed of the vessel. The fuel consumption function combines speed and load in a non-linear manner, but can be approximated through linearization. In this work, to evaluate the importance of taking into account that both speeds and load levels influence the fuel costs, the resulting solutions are contrasted with solutions from the case where speeds and travel costs are taken as constants, as well as the case where speed is a decision, but the cost considered to be independent of the load. For either of these cases, load-dependent speed optimization can be added as a post-processing step. Computational experiments show that combining speed and load do have an impact on the selection of routes in maritime inventory routing problems, and that proper modelling of the fuel consumption can reduce sailing costs significantly. On the test instances considered, taking into account speed while ignoring the load leads to cost savings of around 38%. Considering the fuel consumption as a function of speed and load when planning leads to additional cost savings of 28%. (C) 2020 The Authors. Published by Elsevier Ltd.

关键词： mixed integer programming Non-linear Fuel consumption Transport

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State-Of-The-Art in Microgrid-Integrated Distributed Energy Storage Sizing

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ENERGIES 2017年第9期10卷 1421页

作者： Alsaidan, Ibrahim Alanazi, Abdulaziz Gao, Wenzhong Wu, Hongyu Khodaei, Amin Univ Denver Dept Elect & Comp Engn Denver CO 80210 USA Kansas State Univ Dept Elect & Comp Engn Manhattan KS 66506 USA

Distributed energy storage (DES) plays an important role in microgrid operation and control, as it can potentially improve local reliability and resilience, reduce operation cost, and mitigate challenges caused by high penetration renewable generation. However, to ensure an acceptable economic and technical performance, DES must be optimally sized and placed. This paper reviews the existing DES sizing methods for microgrid applications and presents a generic sizing method that enables microgrid planners to efficiently determine the optimal DES size, technology, and location. The proposed method takes into consideration the impact of DES operation on its lifetime to enhance the obtained results accuracy and practicality. The presented model can be used for both grid-tied (considering both grid-connected and islanded modes) and isolated microgrids.

关键词： distributed energy storage depth of discharge microgrid expansion mixed integer programming optimal sizing

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Robust Direct Aperture Optimization for Radiation Therapy Treatment Planning

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INFORMS JOURNAL ON COMPUTING 2022年第4期34卷 2017-2038页

作者： Ripsman, Danielle A. Purdie, Thomas G. Chan, Timothy C. Y. Mahmoudzadeh, Houra Univ Waterloo Dept Management Sci Waterloo ON N2L 3G1 Canada Princess Margaret Canc Ctr Toronto ON M5G 2C1 Canada Univ Toronto Dept Mech & Ind Engn Toronto ON M5S 3G8 Canada

Intensity-modulated radiation therapy (IMRT) allows for the design of customized, highly conformal treatments for cancer patients. Creating IMRT treatment plans, however, is a mathematically complex process, which is often tackled in multiple, simpler stages. This sequential approach typically separates radiation dose requirements from mechanical deliverability considerations, which may result in suboptimal treatment quality. For patient health to be considered paramount, holistic models must address these plan elements concurrently, eliminating quality loss between stages. This combined direct aperture optimization (DAO) approach is rarely paired with uncertainty mitigation techniques, such as robust optimization, because of the inherent complexity of both parts. This paper outlines a robust DAO (RDAO) model and discusses novel methodologies for efficiently integrating salient constraints. Because the highly complex RDAO model is difficult to solve, an original candidate plan generation (CPG) heuristic is proposed. The CPG produces rapid, high-quality, feasible plans, which are immediately clinically viable and can also be used to generate a feasible incumbent solution for warm-starting the RDAO model. Computational results obtained using clinical patient data sets with motion uncertainty show the benefit of incorporating the CPG, in terms of both the first incumbent solution and final output plan quality.

关键词： intensity-modulated radiation therapy direct aperture optimization robust optimization mixed integer programming solution heuristics

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The Application of a MIP Model to Select the Optimum Auxiliary Fan and Operational Settings for Multiple Period Duties

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INFOR 2010年第2期48卷 95-102页

作者： Acuna, Enrique Hall, Stephen Hardcastle, Stephen Fava, Lorrie Univ Los Andes Santiago Chile Laurentian Univ MIRARCO Sudbury ON P3E 2C6 Canada Curtin Univ Technol WASM Perth WA 6845 Australia Nat Resources Canada CANMET MMSL Sudbury ON P3E 5P5 Canada

Ventilation systems can be the primary consumers of energy in underground mining operations Systematically reducing ventilation costs without impinging on production will significantly improve the profitability of an operation This paper presents an application of mixed integer programming model (MIP) to assist in the selection of the optimum auxiliary fan to supply the required pressure and airflow to an underground mining activity across multiple time periods The MIP model considers the pressures and airflows required to be delivered by the tan for each time period along with the associated capital and operational expenditure in selecting the optimum fan based on cost across all the operating conditions In the presented approach the nonlinear performance characteristic curves of the fans are discretized to permit the implementation of linear techniques in the selection of the fan operational points for every period A case study IN presented to test the proposed MIP model and its applicability plus show the potential savings that can be generated even over short time periods The solution obtained is optimal in the discretized solution space, but in the real life solution space the fan selection is feasible and near optimal outperforming the current practices

关键词： Auxiliary mine ventilation decision support systems mixed integer programming mine ventilation optimization

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Minimizing Airplane Boarding Time

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TRANSPORTATION SCIENCE 2022年第5期56卷 1196页

作者： Willamowski, Felix J. L. Tillmann, Andreas M. Rhein Westfal TH Aachen Lehrstuhl Operat Res D-52072 Aachen Germany Tech Univ Carolo Wilhelmina Braunschweig Cluster Excellence Sustainable & Energy Efficient D-38106 Braunschweig Germany Tech Univ Carolo Wilhelmina Braunschweig Inst Math Optimizat D-38106 Braunschweig Germany

The time it takes passengers to board an airplane is known to influence the turnaround time of the aircraft and thus bears a significant cost-saving potential for airlines. Although minimizing boarding time therefore is the most important goal from an economic perspective, previous efforts to design efficient boarding strategies apparently never tackled this task directly. In this paper, we first rigorously define the problem and prove its NP-hardness. Although this generally justifies the development of inexact solution methods, we show that all commonly discussed boarding strategies may in fact give solutions that are far from optimal. We complement these theoretical findings by a simple time-aware boarding strategy with guaranteed approximation quality (under reasonable assumptions) as well as a local improvement heuristic and an exact mixed-integer programming (MIP) formulation. Our numerical experiments with simulation data show that for several airplane cabin layouts, provably high-quality or even optimal solutions can be obtained within reasonable time in practice by means of our MIP approach. We also empirically assess the sensitivity of boarding strategies with respect to disruptions of the prescribed boarding sequences and identify robustness against such disruptions as a bottleneck for further improvements.

关键词： airplane boarding optimization complexity mixed integer programming

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A time-expanded network design model for staff allocation in mail centres

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JOURNAL OF THE OPERATIONAL RESEARCH SOCIETY 2024年第10期75卷 1949-1964页

作者： Thorburn, Hamish Sachs, Anna-Lena Fairbrother, Jamie Boylan, John E. Univ Lancaster STOR I Ctr Doctoral Training Lancaster England Univ Lancaster Dept Management Sci Lancaster England

We consider a staff allocation problem at a sequential sorting facility. In this facility, staff need to be assigned to work areas, through which commodities flow sequentially to be processed. Assigning staff optimally involves a trade-off between several different objectives, such as minimising the overall number of workers, as well as having fewer changes in the staff levels over time. While optimising for these, many operational requirements need to be met, including minimum processing volumes, correct ordering/processing of the commodities, and not exceeding staff resource constraints. We develop a deterministic time-expanded network flow model to solve the staff allocation problem. The model addresses the problem at a more granular timescale and with more operational constraints than previously used models. We use a lexicographical approach to deal with the multiple objectives. To demonstrate the model's value, we apply it to a staff problem of a UK mail centre, showing that in the majority of cases, our model improves on current staffing practises on both objectives. We also show how the model performs in several different scenarios, including increasing total mail volumes and changing the proportion of letters and parcels to be sorted.

关键词： Staff allocation rostering network flow model mixed integer programming lexicographic optimisation multi-objective optimisation

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Integrated short- and medium-term underground mine production scheduling

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JOURNAL OF THE SOUTHERN AFRICAN INSTITUTE OF MINING AND METALLURGY 2012年第5期112卷 365-378页

作者： Nehring, M. Topal, E. Kizil, M. Knights, P. Univ Queensland Sch Mech & Min Engn St Lucia Qld Australia Curtin Univ Technol Western Australia Sch Mines Kalgoorlie WA Australia Univ Queensland Sch Mech & Min Engn St Lucia Qld Australia Univ Queensland Sch Mech & Min Engn St Lucia Qld Australia

The development of short- and medium-term mine production schedules in isolation from each other has meant that only a local optimum can be achieved when each scheduling phase is carried out. The globally optimal solution, however, can be achieved when integrating scheduling phases and accounting for the interaction between short-term and medium-term activities simultaneously. This paper addresses the task of integrating short- and medium-term production plans by combining the short-term objective of minimizing deviation from targeted mill feed grade with the medium-term objective of maximizing net present value (NPV) into a single mathematical optimization model. A conceptual sublevel stoping operation comprising 30 stopes is used for trialling segregated and integrated scheduling approaches. Segregated medium- and short-term scheduling using separate models achieved an NPV of $42 654 456. The final scheduling approach involved integrating the two scheduling horizons using the newly-developed globally optimal integrated production scheduling model to achieve an NPV of $42 823 657 with smoother mill feed grade. The larger the stope data set, the larger the difference between the two scheduling approaches is likely to be. At the very least, an integrated approach ensures feasibility across the two scheduling horizons, which cannot always be assumed when using a segregated approach.

关键词： production scheduling optimization mixed integer programming integrated scheduling mine planning

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Production-Inventory control model for a supply chain network with economic production rates under no shortages allowed

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COMPUTERS & INDUSTRIAL ENGINEERING 2021年 160卷 107558-107558页

作者： Woo, Young-Bin Moon, Ilkyeong Kim, Byung Soo Seoul Natl Univ Dept Ind Engn Seoul South Korea Seoul Natl Univ Inst Ind Syst Innovat Seoul South Korea Incheon Natl Univ Dept Ind & Management Engn Songdo Dong 119 Acad Ro Incheon 22012 South Korea

This paper presents a new production-inventory control (PIC) model for a supply chain network (SCN) where multiple suppliers, manufacturers, and buyers are vertically integrated to provide multiple items to the market. The objective of the model is to simultaneously determine optimal replenishment quantities, replenishment cycles, and production rates in order to minimize the total network cost allowing no shortages of inventory and shutdown periods. We propose closed-form functions of the average annual inventory levels. A novel mixedinteger linear programming (MILP) formulation is developed based on these functions to solve the PIC model. In addition, an algorithm based on a decomposition approach was developed to solve a special case of the PIC model with a less computational burden. The results obtained by the algorithm are compared to the results of the existing models in literature to see if there is any improvement. A case study for designing an integrated SCN and controlling operational decisions is presented to demonstrate the application of the proposed PIC model.

关键词： Supply chain management Production-inventory control Economic production rate mixed integer programming Decomposition approach Scheduling

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Short-term planning optimization model for underground mines

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COMPUTERS & OPERATIONS RESEARCH 2020年 115卷 104642-000页

作者： Campeau, Louis-Pierre Gamache, Michel Polytech Montreal Gerad Boul Edouard Montpetit Montreal PQ 2900 Canada Polytech Montreal Dept Math & Genie Ind Boul Edouard Montpetit Montreal PQ 2900 Canada

Scheduling activities in an underground mine is a very complex task. Precedence relations, the great number of resources and the large number of work sites are some of the reasons for this complexity. This paper presents an optimization model for short-term planning that takes into consideration all parts of the development and production as well as specific limitations on equipment and workers. A preemptive mixed integer program is used in order to produce optimal planning over a short-term time horizon. Multiple tests made with various data sets and scenarios are then presented, including a comparison to a non-preemptive model and a case study. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： Mine planning Production scheduling mixed integer programming Short-term planning Underground mine Optimization

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Aggregating Harvest Activities in Long Term Forest Planning by Minimizing Harvest Area Perimeters

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SILVA FENNICA 2010年第1期44卷 77-89页

作者： Ohman, Karin Eriksson, Ljusk Ola Dept Forest Resource Management SE-90183 Umea Sweden

The study presents a new approach for aggregating stands for harvest in strategic forest planning. In fragmented landscapes this could benefit nature conservation as well as reduce costs. The approach is built on the idea of minimizing the outside perimeter of contiguous harvest areas. The formulation allows for the use of exact solution methods such as mixed integer programming. The method was tested in a landscape consisting of 2821 stands. The application showed that large and compact harvest areas were created with limited sacrifice of financial value. The mixed integer programs were in most cases solved within a couple of hours. The method needs to be tested on different landscapes with different degrees of fragmentation. It is also necessary to evaluate the long term consequences of the large clear cuts that appear to be a consequence of this problem formulation.

关键词： harvest scheduling mixed integer programming optimization spatial consideration trade off

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