| 1. |
- Lindholm, Anna, et al.
(författare)
-
Hierarchical scheduling and utility disturbance management in the process industry
- 2013
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Ingår i: 7th IFAC Conference on Manufacturing Modelling, Management, and Control, 2013. - : Elsevier. - 1474-6670. - 9783902823359 ; , s. 140-145
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Konferensbidrag (refereegranskat)abstract
- The integration of scheduling and control in the process industry is a topic that has been frequently discussed during the recent years, but many challenges remain in order to achieve integrated solutions that can be implemented for large-scale industrial sites. In this paper we consider production control under disturbances in the supply of utilities at integrated sites together with the integration towards production scheduling. Utilities, such as steam and cooling water, are often shared between the production areas of a site, which enables formulation of an optimization problem for determining the optimal supply of utilities to each area at the occurrence of a disturbance. Optimization in two timescales is suggested to handle the scheduling and disturbance management problems in a hierarchical fashion. The suggested structure has been discussed with companies within the chemical process industry. A simple example is provided to show how the structure may be used.
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| 2. |
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| 3. |
- Akram, Usman, 1984-, et al.
(författare)
-
Closing Pakistan’s yield gaps through nutrient recycling
- 2018
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Ingår i: Frontiers in Sustainable Food Systems. - : Frontiers Media S.A.. - 2571-581X. ; , s. 1-14
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Tidskriftsartikel (refereegranskat)abstract
- Achieving food security will require closing yield gaps in many regions, including Pakistan. Although fertilizer subsidies have facilitated increased nitrogen (N) application rates, many staple crop yields have yet to reach their maximum potential. Considering that current animal manure and human excreta (bio-supply) recycling rates are low, there is substantial potential to increase the reuse of nutrients in bio-supply. We quantified 2010 crop N, phosphorus (P), and potassium (K) needs along with bio-supply nutrient availability for Pakistani districts, and compared these values to synthetic fertilizer use and costs. We found that synthetic fertilizer use combined with low bio-supply recycling resulted in a substantial gap between nutrient supply and P and K crop needs, which would cost 3 billion USD to fill with synthetic fertilizers. If all bio-supply was recycled, it could eliminate K synthetic fertilizer needs and decrease N synthetic fertilizer needs to 43% of what was purchased in 2010. Under a full recycling scenario, farmers would still require an additional 0.28 million tons of synthetic P fertilizers, costing 2.77 billion USD. However, it may not be prohibitively expensive to correct P deficiencies. Pakistan already spends this amount of money on fertilizers. If funds used for synthetic N were reallocated to synthetic P purchases in a full bio-supply recycling scenario, crop needs could be met. Most recycling could happen within districts, with only 6% of bio-supply requiring between-district transport when optimized to meet national N crop needs. Increased recycling in Pakistan could be a viable way to decrease yield gaps.
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| 4. |
- Berglund, Per, et al.
(författare)
-
Linking Education and Research : A Roadmap for Higher Education Institutions at the Dawn of the Knowledge Society
- 2019
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Ingår i: Linking education and research. - Basel, Switzerland : MDPI. ; , s. 11-33
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- In an era characterized by a move towards a “knowledge society”, universities are central in fostering “knowledgeability”, that is the reflexive understanding of knowledge in knowledge societies. The objective of “knowledgeability” can be met through creating a stronger link between education and research. Furthermore, overall student performance, for example in critical thinking and problem solving, can be improved if research-related activities are incorporated into the curriculum.The aim of this paper is to use international examples to discuss the research- education nexus from four different perspectives, namely context, policy, implementation and quality, with case studies from higher education institutions in Singapore and Sweden.We suggest that different integrative technologies can be used to enhance the links, but it will be essential to consider the inputs of training, service and support in using new technology. Interestingly, the act of evaluating the link between education and research will increase awareness of this linkage by stakeholders involved in both education and research. In turn the link can be strengthened, contributing to increased quality in both education and research.
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| 5. |
- Holmström, Kenneth, 1954-, et al.
(författare)
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An adaptive radial basis algorithm (ARBF) for expensive black-box mixed-integer constrained global optimization
- 2008
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Ingår i: Optimization and Engineering. - : Springer US. - 1389-4420 .- 1573-2924. ; 9:4, s. 311-339
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Tidskriftsartikel (refereegranskat)abstract
- Response surface methods based on kriging and radial basis function (RBF) interpolationhave been successfully applied to solve expensive, i.e. computationally costly,global black-box nonconvex optimization problems.In this paper we describe extensions of these methods to handle linear, nonlinear, and integer constraints. In particular, algorithms for standard RBF and the new adaptive RBF (ARBF) aredescribed. Note, however, while the objective function may be expensive, we assume that any nonlinear constraints are either inexpensive or are incorporated into the objective function via penalty terms. Test results are presented on standard test problems, both nonconvexproblems with linear and nonlinear constraints, and mixed-integernonlinear problems (MINLP). Solvers in the TOMLAB OptimizationEnvironment (http://tomopt.com/tomlab/) have been compared,specifically the three deterministic derivative-free solversrbfSolve, ARBFMIP and EGO with three derivative-based mixed-integernonlinear solvers, OQNLP, MINLPBB and MISQP, as well as the GENOsolver implementing a stochastic genetic algorithm. Results showthat the deterministic derivative-free methods compare well with thederivative-based ones, but the stochastic genetic algorithm solver isseveral orders of magnitude too slow for practical use.When the objective function for the test problems is costly to evaluate, the performance of the ARBF algorithm proves to be superior.
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| 6. |
- Holmström, Kenneth, 1954-, et al.
(författare)
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The influence of Experimental Designs on the Performance of Surrogate Model Based Costly Global Optimization Solvers
- 2009
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Ingår i: Studies in Informatics and Control. - : National Institute for Research & Development in Informatics. - 1220-1766 .- 1841-429X. ; 18:1, s. 87-95
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Tidskriftsartikel (refereegranskat)abstract
- When dealing with costly objective functions in optimization, one good alternative is to use a surrogate model approach. A common feature for all such methods is the need of an initial set of points, or "experimental design", in order to start the algorithm. Since the behavior of the algorithms often depends heavily on this set, the question is how to choose a good experimental design. We investigate this by solving a number of problems using different designs, and compare the outcome with respect to function evaluations and a root mean square error test of the true function versus the surrogate model produced. Each combination of problem and design is solved by 3 different solvers available in the TOMLAB optimization environment. Results indicate two designs as superior.
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| 7. |
- Häll, Carl Henrik, 1978-, et al.
(författare)
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Adjustments of public transit operations planning process for the use of electric buses
- 2019
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Ingår i: Journal of Intelligent Transportation Systems / Taylor & Francis. - : Taylor & Francis. - 1547-2450 .- 1547-2442. ; 23:3, s. 216-230
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Tidskriftsartikel (refereegranskat)abstract
- This work investigates and discusses how the introduction of electric buses (EB), both battery and plug-in hybrid EB, will and should change the operations planning of a public transit system. It is shown that some changes are required in the design of a transit route network, and in the timetabling and vehicle scheduling processes. Other changes are not required, but are advisable, using this opportunity upon the introduction of EB. The work covers the main characteristics of different types of EB with a short description, including the most popular charging technologies, and it presents the generally accepted transit operations planning process. Likewise, it describes and analytically formulates new challenges that arise when introducing EB. The outcome of the analyses shows that multiple new considerations must take place. It is also shown that the different charging techniques will influence the operations planning process in different ways and to a varying extent. With overnight, quick and continuous charging, the main challenges are in the network route design step, given the possibility of altering the existing network of routes, with efficient and optimal changes of the timetabling and vehicle scheduling components. An illustrative example, based on four bus lines in Norrköping, Sweden, is formulized and introduced using three problem instances of 48, 82, and 116 bus trips. The main results exhibit the minimum number of vehicles required using different scenarios of charging stations.
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| 8. |
- Larsson, Madeleine, 1984-, et al.
(författare)
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Towards a more circular biobased economy and nutrient use on Gotland : finding suitable locations for biogas plants
- 2023
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In this study we have investigated the role of biogas solutions to support increased resource efficiency on the island Gotland, including recovery and redistribution of nitrogen (N) and phosphorus (P) within the agricultural sector. First, we analyzed the potential for expanding energy and nutrient recovery from organic residues using biogas solutions. Our findings suggest that the biogas production could expand to 165 GWh, from the current 36 GWh (2020), with manure accounting for a potential 110 GWh biogas annually if all were digested. Comparing the nutrients contained in organic feedstock with the crop nutrient demand on Gotland showed that for N the demand is 2.4 times higher than the supply. In contrast, the calculations showed a 137 tonnes P surplus, with distinct excess areas in the center and southern part of the island.We then compared scenarios with different numbers (3 - 15) of biogas plants with respect to efficient nutrient redistribution and transport costs. Spatial constraints for new plants, e.g. need for roads with a certain capacity and permit issues, were accounted for by adding local information to a national data set. We identified 104 potential locations (1 km$^2$ grid cells) and used an optimization model to identify the most suitable locations for minimized transport costs. Optimal (meeting the crop demand with no excess) redistribution of all nutrients contained in the feedstock, as raw digestate from biogas plants, would result in an export of 127 tonnes of P from the island. The model results indicated that if all potential feedstock would be digested in three additional biogas plants and nutrients redistributed for optimal reuse, the total transport cost would be 2.6 million SEK annually, excluding the costs for nutrient export from the island (3.7 million SEK). If instead 10 or 15 smaller plants would be built, the transport cost would drop to 1.8 million SEK, with the same amount of P being exported. Comparing the scenarios with different number of biogas plants (3 - 15), showed that some locations are more suitable than others in terms of distance to feedstock andto fields with fertilizer demands. Finally, a preliminary analysis of the amount of crop residues indicated that this type of feedstock could add a substantial amount of biogas production, but more extensive analyses are needed to assess the feasibility to realize part of that potential.
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| 9. |
- Lindholm, Anna, et al.
(författare)
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Hierarchical Production Scheduling - A Case Study at Perstorp
- 2014
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Ingår i: 24th European Symposium on Computer Aided Process Engineering, PTS A and B. - : Elsevier. - 1570-7946. ; 33, s. 511-516, s. 511-516
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Konferensbidrag (refereegranskat)abstract
- Planning and scheduling are functions that have large economic impact in the chemical process industry. For integrated sites with many interconnected production areas, obtaining production schedules that respect all production-related constraints is a complex task. One important issue is the constraints due to disturbances in utilities, such as steam and cooling water. These are often site-wide disturbances that may make it impossible to maintain desired production rates in several production areas at a site. In this study, scheduling at two levels of the functional hierarchy at a site of a world lead chemical industry, Perstorp, is handled. The activities are denoted production scheduling (PS) and detailed production scheduling (DPS). Real data of incoming orders and utility disturbances are used to produce a production schedule and detailed production schedule for one month. The PS and DPS problems are formulated as optimization problems, where production-related constraints such as production rate constraints, inventory limitations, and start-up costs are included. The objective functions of the PS and DPS problems are formulated to reflect the importance of different issues at the site. The procedure aims to show how the hierarchical optimization framework may be used to provide decision support for how to operate the production at a site in order to maximize profit while minimizing the effects of site-wide disturbances.
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| 10. |
- Lindholm, Anna, et al.
(författare)
-
Production scheduling in the process industry
- 2013
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Ingår i: Proceedings for 22nd International Conference on Production Research, 2013.
-
Konferensbidrag (refereegranskat)abstract
- The purpose of this paper is to formulate an optimization model for the production scheduling problem at continuous production sites. The production scheduling activity should produce a monthly schedule that accounts for orders and forecasts of all products. The plan should be updated every day, with feedback on the actual production the previous day. The actual daily production may be lower than the planned production due to disturbances, e.g. disruptions in the supply of a utility. The work is performed in collaboration with Perstorp, a world-leading company within several sectors of the specialty chemicals market. Together with Perstorp, a list of specifications for the production scheduling has been formulated. These are formulated mathematically in a mixed-integer linear program that is solved in receding horizon fashion. The formulation of the model aims to be general, such that it may be used for any process industrial site.
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| 11. |
- Metson, Genevieve S., 1988-, et al.
(författare)
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Optimizing transport to maximize nutrient recycling and green energy recovery
- 2020
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Ingår i: Resources, Conservation & Recycling: X. - : Elsevier. - 2590-289X. ; 9-10
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Tidskriftsartikel (refereegranskat)abstract
- A circular biobased economy must be able to sustainably manage multiple resources simultaneously. Nutrient (nitrogen, phosphorus, and potassium) recycling and renewable energy production (biogas) can be compatible practices but require substantial transport of heavy organic waste. We combine a spatial optimization model and Life Cycle Assessment (LCA) to explore how Sweden could maximize its use of excreta resources. We use 10×10 km2 resolution data on the location of animal and human excreta and crop demand and model both optimal biogas plant locations and transport of nutrients to and from these plants. Each type of biogas plant (given 4 realistic mixes of excreta) is then evaluated for global warming potential, primary energy use and financial resource costs. Moving excreta through biogas plants, as opposed to simply reapplying on fields, to meet crop nutrient demands comes at a similar cost but the climate and primary energy savings are substantial. As much as 91% of phosphorus and 44% of nitrogen crop demand could be met via optimally transported excreta and the country would avoid about 1 450 kt of CO2-eq, save 3.6 TWh (13 000 tera-joules) of primary energy, and save 90 million euros per year. Substituting mineral fertilizers with recycled nutrients results in savings across all indicators, but the added energy and avoided greenhouse gas emissions associated with biogas production make a large difference in the attractiveness of nutrient recycling. Although the numeric values are theoretical, our results indicate that carefully coordinated and supported biogas production could help maximize multi-resource benefits.
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| 12. |
- Ngulo, Uledi, 1983-, et al.
(författare)
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A Dissection of the Duality Gap of Set Covering Problems
- 2020
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Ingår i: Operations Research Proceedings 2019. - Cham : Springer International Publishing. - 9783030484385 ; , s. 175-181
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Konferensbidrag (refereegranskat)abstract
- Set covering problems are well-studied and have many applications. Sometimes the duality gap is significant and the problem is computationally challenging. We dissect the duality gap with the purpose of better understanding its relationship to problem characteristics, such as problem shape and density. The means for doing this is a set of global optimality conditions for discrete optimization problems. These decompose the duality gap into two terms: near-optimality in a Lagrangian relaxation and near-complementarity in the relaxed constraints. We analyse these terms for numerous instances of large size, including some real-life instances. We conclude that when the duality gap is large, typically the near-complementarity term is large and the near-optimality term is small. The large violation of complementarity is due to extensive over-coverage. Our observations should have implications for the design of solution methods, and especially for the design of core problems.
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| 13. |
- Ngulo, Uledi, 1983-
(författare)
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Decomposition Methods for Combinatorial Optimization
- 2021
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis aims at research in the field of combinatorial optimization. Problems within this field often posses special structures allowing them to be decomposed into more easily solved subproblems, which can be exploited in solution methods. These structures appear frequently in applications. We contribute with both re-search on the development of decomposition principles and on applications. The thesis consists of an introduction and three papers. In Paper I, we develop a Lagrangian meta-heuristic principle, which is founded on a primal-dual global optimality condition for discrete and non-convex optimization problems. This condition characterizes (near-)optimal solutions in terms of near-optimality and near-complementarity measures for Lagrangian relaxed solutions. The meta-heuristic principle amounts to constructing a weighted combination of these measures, thus creating a parametric auxiliary objective function (which is a close relative to a Lagrangian function), and embedding a Lagrangian heuristic in a search procedure in the space of the weight parameters. We illustrate and assess the Lagrangian meta-heuristic principle by applying it to the generalized assignment problem and to the set covering problem. Our computational experience shows that the meta-heuristic extension of a standard Lagrangian heuristic principle can significantly improve upon the solution quality. In Paper II, we study the duality gap for set covering problems. Such problems sometimes have large duality gaps, which make them computationally challenging. The duality gap is dissected with the purpose of understanding its relationship to problem characteristics, such as problem shape and density. The means for doing this is the above-mentioned optimality condition, which is used to decompose the duality gap into terms describing near-optimality in a Lagrangian relaxation and near-complementarity in the relaxed constraints. We analyse these terms for numerous problem instances, including some large real-life instances, and conclude that when the duality gap is large, the near-complementarity term is typically large and the near-optimality term small. The large violation of complementarity is due to extensive over-coverage. Our observations have implications for the design of solution methods, especially for the design of core problems. In Paper III, we study a bi-objective covering problem stemming from a real-world application concerning the design of camera surveillance systems for large-scale outdoor areas. It is prohibitively costly to surveil the entire area, and therefore relevant to be able to present a decision-maker with trade-offs between total cost and the portion of the area that is surveilled. The problem is stated as a set covering problem with two objectives, describing cost and portion of covering constraints that are fulfilled, respectively. Finding the Pareto frontier for these objectives is very computationally demanding and we therefore develop a method for finding a good approximate frontier in a reasonable computing time. The method is based on the ε−constraint reformulation, an established heuristic for set covering problems, and subgradient optimization.
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| 14. |
- Quttineh, Nils-Hassan, 1979-, et al.
(författare)
-
Aircraft Mission Planning
- 2012
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This paper deals with a Military Aircraft Mission Planning Problem, where the problem is to find time efficient flight paths for a given aircraft fleet that should attack a number of ground targets. Due to the nature of the attack, two aircraft need to rendezvous at the target, that is, they need to be synchronized in both space and time. At the attack, one aircraft is launching a guided weapon, while the other is illuminating the target. Each target is associated with multiple attack and illumination options. Further, there may be precedence constraints between targets, limiting the order of the attacks. The objective is to maximize the outcome of the entire attack, while also minimizing the mission time span. We present two mathematical models for this problem and compare their efficiency on some small test cases. We also provide some heuristic approaches since direct application of a general MIP solver to the mathematical model is only practical for smaller scenarios. The heuristics are compared and they successfully provide solutions to a number of scenarios.
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| 15. |
- Quttineh, Nils-Hassan, 1979-
(författare)
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Algorithms for Costly Global Optimization
- 2009
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- There exists many applications with so-called costly problems, which means that the objective function you want to maximize or minimize cannot be described using standard functions and expressions. Instead one considers these objective functions as ``black box'' where the parameter values are sent in and a function value is returned. This implies in particular that no derivative information is available.The reason for describing these problems as expensive is that it may take a long time to calculate a single function value. The black box could, for example, solve a large system of differential equations or carrying out a heavy simulation, which can take anywhere from several minutes to several hours!These very special conditions therefore requires customized algorithms. Common optimization algorithms are based on calculating function values every now and then, which usually can be done instantly. But with an expensive problem, it may take several hours to compute a single function value. Our main objective is therefore to create algorithms that exploit all available information to the limit before a new function value is calculated. Or in other words, we want to find the optimal solution using as few function evaluations as possible.A good example of real life applications comes from the automotive industry, where on the development of new engines utilize advanced models that are governed by a dozen key parameters. The goal is to optimize the model by changing the parameters in such a way that the engine becomes as energy efficient as possible, but still meets all sorts of demands on strength and external constraints.
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| 16. |
- Quttineh, Nils-Hassan, 1979-, et al.
(författare)
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Approximating the Pareto frontier for a challenging real-world bi-objective covering problem
- 2022
-
Ingår i: INFOR. Information systems and operational research. - : Taylor & Francis Inc. - 0315-5986 .- 1916-0615. ; 60:3, s. 342-358
-
Tidskriftsartikel (refereegranskat)abstract
- We study a bi-objective covering problem stemming from a real-world application concerning the design of camera surveillance systems for large-scale outdoor areas. It is in this application prohibitively costly to surveil the entire area, and therefore necessary to be able to present a decision-maker with trade-offs between total cost and the portion of the area that is surveilled. The problem can be stated as a set covering problem with two objectives, describing cost and portion of covering constraints that are fulfilled. Finding the Pareto frontier for these objectives is very computationally demanding and we therefore derive a method for finding a good approximate frontier in a practically feasible computing time. The method is based on the epsilon-constraint reformulation, an established heuristic for set covering problems, and subgradient optimization.
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| 17. |
- Quttineh, Nils-Hassan, 1979-, et al.
(författare)
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Combined Timetabling and Vehicle Scheduling for Electric Buses
- 2017
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Ingår i: Proceedings of the 22nd International Conference of Hong Kong Society for Transportation Studies (HKSTS), December 9-11, 2017, Hong Kong, China. - Hong Kong : HKSTS.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this paper we present a novel mathematical model, integrating the timetabling and vehicle schedulingproblems for electric buses. The objective is to minimize the number of buses while satisfying constraintsconcerning routing and charging, including design choices of where to install charging equipment. Weillustrate the different effects of tackling the timetabling and vehicle scheduling of electric buses as separateproblems or as a joint problem, both for fixed and variable headways. To do so, tests are performed with: (i) given timetable, i.e. solving only the vehicle scheduling problem, (ii) fixed headways for each line, (iii) variable headways. For these tests, a small case based on four bidirectional bus lines is used.
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| 18. |
- Quttineh, Nils-Hassan, 1979-, et al.
(författare)
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Dissecting the duality gap : the supporting hyperplane interpretation revisited
- 2022
-
Ingår i: Optimization Letters. - : Springer Nature. - 1862-4472 .- 1862-4480. ; 16, s. 1093-1102
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Tidskriftsartikel (refereegranskat)abstract
- We revisit the classic supporting hyperplane illustration of the duality gap for non-convex optimization problems. It is refined by dissecting the duality gap into two terms: the first measures the degree of near-optimality in a Lagrangian relaxation, while the second measures the degree of near-complementarity in the Lagrangian relaxed constraints. We also give an example of how this dissection may be exploited in the design of a solution approach within discrete optimization.
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| 19. |
- Quttineh, Nils-Hassan, 1979-, et al.
(författare)
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Effect Oriented Planning
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The problem setting concerns the tactical planning of a military operation. Imagine a big wide open area where a number of interesting targets are positioned. It could be radar stations or other surveillance equipment, with or without defensive capabilities, which the attacker wishes to destroy. Moreover, the targets are possibly guarded by defending units, like Surface-to-Air Missile (SAM) units. The positions of all units, targets and defenders, are known. We consider the problem of the attacker, where the objective is to maximize the expected outcome of a joint attack against the enemy, subject to a limited amount of resources (i.e. aircraft, tanks). We present a mathematical model for this problem, together with alternative model versions which provide optimistic and a pessimistic approximations. The model is not efficient for large problem instances, hence we also provide heuristic solution approaches and successfully provide solutions to a number of scenarios.
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| 20. |
- Quttineh, Nils-Hassan, 1979-, et al.
(författare)
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Effect Oriented Planning of Joint Attacks
- 2013
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Ingår i: Optimization Theory, Decision Making, and Operations Research Applications. - New York, NY : Springer-Verlag New York. - 9781461451334 - 9781461451341 ; , s. 49-70
-
Konferensbidrag (refereegranskat)abstract
- We consider tactical planning of a military operation on a large target scene where a number of specific targets of interest are positioned, using a given number of resources which can be, for example, fighter aircraft, unmanned aerial vehicles, or missiles. The targets could be radar stations or other surveillance equipment, with or without defensive capabilities, which the attacker wishes to destroy. Further, some of the targets are defended, by, for example, Surface-to-Air Missile units, and this defense capability can be used to protect also other targets. The attacker has knowledge about the positions of all the targets and also a reward associated with each target. We consider the problem of the attacker, who has the objective to maximize the expected outcome of a joint attack against the enemy. The decisions that can be taken by the attacker concern the allocation of the resources to the targets and what tactics to use against each target. We present a mathematical model for the attacker’s problem. The model is similar to a generalized assignment problem, but with a complex objective function that makes it intractable for large problem instances. We present approximate models that can be used to provide upper and lower bounds on the optimal value, and also provide heuristic solution approaches that are able to successfully provide near-optimal solutions to a number of scenarios.
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| 21. |
- Quttineh, Nils-Hassan, 1979-, et al.
(författare)
-
Implementation of a One-Stage Efficient Global Optimization (EGO) Algorithm
- 2009
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Almost every Costly Global Optimization (CGO) solver utilizes a surrogate model, or response surface, to approximate the true (costly) function. The EGO algorithm introduced by Jones et al. utilizes the DACE framework to build an approximating surrogate model. By optimizing a less costly utility function, the algorithm determines a new point where the original objective function is evaluated. This is repeated until some convergence criteria is fulfilled.The original EGO algorithm finds the new point to sample in a two-stage process. In its first stage, the estimates of the interpolation parameters are optimized with respect to already sampled points. In the second stage, these estimated values are considered true in order to optimize the location of the new point. The use of estimate values as correct introduces a source of error.Instead, in the One-stage EGO algorithm, both parameter values and the location of a new point are optimized at the same time, removing the source of error. This new subproblem becomes more difficult, but eliminates the need of solving two subproblems.Difficulties in implementing a fast and robust One-Stage EGO algorithm in TOMLAB are discussed, especially the solution of the new subproblem.
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| 22. |
- Quttineh, Nils-Hassan, 1979-, et al.
(författare)
-
Military Aircraft Mission Planning : Efficient model-based metaheuristics approaches
- 2015
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Ingår i: Optimization Letters. - Berlin Heidelberg : Springer Berlin/Heidelberg. - 1862-4472 .- 1862-4480. ; 9:8, s. 1625-1639
-
Tidskriftsartikel (refereegranskat)abstract
- We consider a military mission planning problem where a given fleet of aircraft should attack a number of ground targets. At each attack, two aircraft need to be synchronized in both space and time. Further, there are multiple attack options against each targets, with different target effects. The objective is to maximize the outcome of the entire attack, while also minimizing the mission timespan. Real-life mission planning instances involve only a few targets and a few aircraft, but are still computationally challenging. We present metaheuristic solution methods for this problem, based on an earlier presented model. The problem includes three types of decisions: attack directions, task assignments and scheduling, and the solution methods exploit this structure in a two-stage approach. In an outer stage, a heuristic search is performed with respect to attack directions, while in an inner stage the other two decisions are optimized, given the outer stage decisions. The proposed metaheuristics are capable of producing high-quality solutions and are fast enough to be incorporated in a decision support tool.
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| 23. |
- Quttineh, Nils-Hassan, 1979-, et al.
(författare)
-
Military aircraft mission planning : a generalized vehicle routing model with synchronization and precedence
- 2013
-
Ingår i: EURO Journal on Transportation and Logistics. - : Springer. - 2192-4376 .- 2192-4384. ; 2:1-2, s. 109-127
-
Tidskriftsartikel (refereegranskat)abstract
- We introduce a military aircraft mission planning problem where agiven fleet of aircraft should attack a number of ground targets. Due to the nature of the attack, two aircraft need to rendez-vous at the target, that is, they need to be synchronized in both space and time. At the attack, one aircraft is launching a guided weapon, while the other is illuminating the target. Each target is associated with multiple attack and illumination options. Further, there may be precedence constraints between targets, limiting the order of the attacks. The objective is to maximize the outcome of the entire attack, while also minimizing the mission timespan. We give a linear mixed integer programming model of the problem, which can be characterized as ageneralized vehicle routing problem with synchronization and precedence side constraints. Numerical results are presented for problem instances of realistic size.
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| 24. |
- Quttineh, Nils-Hassan, 1979-
(författare)
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Models and Methods for Costly Global Optimization and Military Decision Support Systems
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The thesis consists of five papers. The first three deal with topics within costly global optimization and the last two concern military decision support systems.The first part of the thesis addresses so-called costly problems where the objective function is seen as a “black box” to which the input parameter values are sent and a function value is returned. This means in particular that no information about derivatives is available. The black box could, for example, solve a large system of differential equations or carry out timeconsuming simulation, where a single function evaluation can take several hours! This is the reason for describing such problems as costly and why they require customized algorithms. The goal is to construct algorithms that find a (near)-optimal solution using as few function evaluations as possible. A good example of a real life application comes from the automotive industry, where the development of new engines utilizes advanced mathematical models that are governed by a dozen key parameters. The objective is to optimize the engine by changing these parameters in such a way that it becomes as energy efficient as possible, but still meets all sorts of demands on strength and external constraints. The first three papers describe algorithms and implementation details for these costly global optimization problems.The second part deals with military mission planning, that is, problems that concern logistics, allocation and deployment of military resources. Given a fleet of resource, the decision problem is to allocate the resources against the enemy so that the overall mission success is optimized. We focus on the problem of the attacker and consider two separate problem classes. In the fourth paper we introduce an effect oriented planning approach to an advanced weapon-target allocation problem, where the objective is to maximize the expected outcome of a coordinated attack. We present a mathematical model together with efficient solution techniques. Finally, in the fifth paper, we introduce a military aircraft mission planning problem, where an aircraft fleet should attack a given set of targets. Aircraft routing is an essential part of the problem, and the objective is to maximize the expected mission success while minimizing the overall mission time. The problem is stated as a generalized vehicle routing model with synchronization and precedence side constraints.
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| 25. |
- Quttineh, Nils-Hassan, 1979-, et al.
(författare)
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Supply Chain Modeling for a Process Industry
- 2017
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Ingår i: International Journal of Operations Research and Information Systems. - : IGI Global. - 1947-9328 .- 1947-9336. ; 8:2, s. 36-55
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Tidskriftsartikel (refereegranskat)abstract
- Process industries of today differ from other industries in many aspects. The purpose of this paper is to consider these special properties of process industries when developing a mathematical model that can be used as a decision support tool for the supply chain planning for a chemical process industry in Sweden. A mixed-integer linear programming model is developed, and solutions to the model present how the products will be transported between the different sites of the company, the levels of the inventories, the setups and purchases from the external suppliers and also the production rates. The mathematical model takes many special properties regarding process industries into account. By using the results from the model and test different scenarios, the model can be used as an important support tool when making decisions. The decision support tool can for example be used in the company's budget process and thereby improve the chances of future profits increases.
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| 26. |
- Quttineh, Nils-Hassan, 1979-, et al.
(författare)
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Supply Chain Planning at a Chemical Process Industry
- 2013
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Ingår i: <em>Proceedings for Decision Science Institute (DSI 2013), The 44th Annual Meeting, 2013</em>. - : Decision Sciences Institute. ; , s. 671895 - 1-671895 - 19
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The purpose of this paper is to develop a mathematical optimization model that can be used as a decision support tool for the supply chain planning at Perstorp Oxo AB, a global company in the process industry. At their site in Stenungsund, Perstorp Oxo AB produce chemicals to customers in a variety of branches and for further refinement at other Perstorp sites in Gent, Castellanza and Perstorp. The customers are mainly in branches such as food and feed, leather and textile, plastic and safety glass production. Since Perstorp Oxo sells products to customers worldwide, two large inventory facilities are located in Antwerp (Belgium)and Tees (United Kingdom) for five product types each and two smaller facilities in Philadelphia (USA) and Aveiro (Portugal) for one type respectively. The developed model is a mixed-integer linear program, where the objective function maximizes the profit margin, that is, the difference between the selling price and the cost of production, transportation, inventory carrying and outsourcing. A solution to the model shows the quantities to be transported between the different sites, production rates, inventory levels, setups and purchases from external suppliers, each with its respective cost. The results of a baseline scenario show that there is a potential to increase profit margin by using a decision support tool based on an optimization model.
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| 27. |
- Quttineh, Nils-Hassan, 1979-, et al.
(författare)
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Using rolling horizon techniques in the planning process for a chemical process industry
- 2014
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Ingår i: <em>Pre-Prints, Vol.1, 18th International Working Seminars on Production Economics, Innsbruck, Austria, February 2014</em>.. ; , s. 381-393
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Konferensbidrag (refereegranskat)abstract
- We present a mathematical optimization model that can be used as a decision support tool for the supply chain planning at Perstorp Oxo AB, a global company in the process industry. At their site in Stenungsund, Perstorp Oxo AB produce chemicals to customers in a variety of branches and for further refinement at other Perstorp sites in Gent, Castellanza and Perstorp. The customers are mainly in branches such as food and feed, leather and textile, plastic and safety glass production. Since Perstorp Oxo sells products to customers worldwide, two large inventory facilities are located in Antwerp (Belgium) and Tees (United Kingdom) for five product types each and two smaller facilities in Philadelphia (USA) and Aveiro (Portugal) for one type respectively. The developed model is a mixed-integer linear program, where the objective function maximizes the profit. A solution to the model shows the quantities to be transported between the different sites, production rates, inventory levels, setups and purchases from external suppliers, each with its respective cost. Based on actual sales data from Perstorp Oxo AB, we use rolling horizon techniques to simulate how customer demands vary over a time horizon of one year, and show that our optimization model is able to find feasible and profitable production plans. The results show that there is a potential to increase profit margin by using a decision support tool based on an optimization model.
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