| 1. |
- Lindholm, Anna, et al.
(författare)
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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)
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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. |
- Akram, Usman, et al.
(författare)
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Enhancing nutrient recycling from excreta to meet crop nutrient needs in Sweden - a spatial analysis
- 2019
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Ingår i: Scientific Reports. - : NATURE PUBLISHING GROUP. - 2045-2322. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Increased recycling of nutrient-rich organic waste to meet crop nutrient needs is an essential component of a more sustainable food system. However, agricultural specialization continues to pose a significant challenge to balancing crop nutrient needs and the nutrient supply from animal manure and human excreta locally. For Sweden, this study found that recycling all excreta (in 2007) could meet up to 75% of crop nitrogen and 81% of phosphorus needs, but that this would exceed crop potassium needs by 51%. Recycling excreta within municipalities could meet 63% of crop P nutrient needs, but large regional differences and imbalances need to be corrected to avoid over or under fertilizing. Over 50% of the total nitrogen and phosphorus in excreta is contained in just 40% of municipalities, and those have a surplus of excreta nutrients compared to crop needs. Reallocation of surpluses (nationally optimized for phosphorus) towards deficit municipalities, would cost 192 million USD (for 24 079 km of truck travel). This is 3.7 times more than the total NPK fertilizer value being transported. These results indicate that Sweden could reduce its dependence on synthetic fertilizers through investments in excreta recycling, but this would likely require valuing also other recycling benefits.
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| 5. |
- Akram, Usman, et al.
(författare)
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Optimizing Nutrient Recycling From Excreta in Sweden and Pakistan : Higher Spatial Resolution Makes Transportation More Attractive
- 2019
-
Ingår i: Frontiers in Sustainable Food Systems. - : Frontiers Media SA. - 2571-581X. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- Recycling essential plant nutrients like nitrogen (N), phosphorus (P), and potassium (K) from organic waste such as human and animal excreta will be an essential part of sustainable food systems and a circular economy. However, transportation is often cited as a major barrier to increased recycling as organic waste is heavy and bulky, and distances between areas of abundant waste may be far from areas with a need for fertilizers. We investigated the effect of increased input data spatial resolution to an optimization model on the weight, distance, and spatial patterns of transport. The model was run in Sweden and in Pakistan to examine cost-effectiveness of transporting excess excreta to areas of crop need after local recycling. Increasing the resolution of input data from political boundaries (municipalities and districts) to 0.083 decimal grids increased the amount of N requiring transport by 12% in Pakistan and increased P requiring transport by 14% in Sweden. The average distance decreased by 67% (to 44 km) in Pakistan but increased by 1 km in Sweden. Further increasing the resolution to 5 km grids in Sweden decreased the average transportation distance by 9 km (down to 123 km). In both countries, increasing resolution also decreased the number of long-distance heavy transports, and as such costs did not increase as much as total distance and weight transported. Ultimately, transportation in Pakistan seemed financially beneficial: the cost of transport only represented 13% of the NPK fertilizer value transported, and total recycling could even cover 78% of additional fertilizer purchases required. In Sweden, the cost of transporting excreta did not seem cost effective without valuing other potential benefits of increased recycling: costs were three times higher than the fertilizer value transported in excreta at the 5 km resolution. In summary, increasing input data resolution created a more realistic picture of recycling needs. This also highlighted more favorable cost to fertilizer value ratios which could make it easier to move forward with industry and government partners to facilitate productive recycling. Our analysis shows that in both countries increased recycling can result in better spatial nutrient balances.
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| 6. |
- Berg, Sofia, et al.
(författare)
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Ekologisk funktionalitet av värdekärnor för barrskogar inom Västra Götalands län : Ett strategiskt underlag för planering av förändrad skogsskötsel av barrskogsområden inom Västra Götalands län i syfte att stärka skogarnas förutsättningar att stödja biologisk mångfald och skogens klimatnytta
- 2022
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Rapport (populärvet., debatt m.m.)abstract
- Skogsstyrelsen redovisar i sin utvärdering av miljömålet Levande skogar 2019 att centrala hinder för uppfyllelse av miljömålet är minskande och fragmenterade livsmiljöer och minskande och/eller små populationer av ett antal hotade arter knutna till skogsekosystemet. En väg framåt för att vända denna trend är att framtidens skogsbruk bland annat bör utvecklas utifrån ett landskapsperspektiv och där hyggesfria skogsbruksmetoder ökar i omfattning.Länsstyrelserna i Sverige har genom sitt arbete med regionala handlingsplaner för grön infrastruktur identifierat så kallade värdekärnor – områden av stor betydelse för skogsarternas överlevnad. I denna studie har Västra Götalands läns värdekärnor analyserats med avseende på deras förmåga att stödja biologisk mångfald i ett landskapsperspektiv. Arbetet har gjorts i samverkan med Länsstyrelsen för Västra götalands län.Metoden som använts är Biotope Biodiversity Capacity Indicator (BBCI). Metoden har utvecklats inom forskningsprojektet “Landscape biodiversity capacity: a tool for measuring, monitoring and managing” finansierat av Naturvårdsverkets miljöforskningsanslag (2019-2022).Resultaten visar vilka geografiskt avgränsade värdekärnor som idag har hög ekologisk funktionalitet och som utgör biologiska överlevnads- och spridningshotspots för arter knutna till barrskogar. Vidare visar resultaten att endast sju kommuner har BBCI-värden över 1, det vill säga, ett hållbart skogslandskap som kan hålla fokusarten i ett 100-årsperspektiv.För att nå de svenska miljömålen Levande skogar och Ett rikt växt- och djurliv samt skapa bättre förutsättningar för skogens biologiska mångfald att fortleva behöver nuvarande skogsmetoder med trakthyggesbruk anpassas till brukningsformer som tar större hänsyn till skogens ekosystem. Resultaten från denna studie kan ge prioriteringsunderlag för inom vilka produktionsskogar en så kallad återvildning genom förändrad brukningsmetod skulle kunna resultera i betydelsefull ökad ekologisk funktionalitet på landskapsnivå för de västgötska barrskogarna.
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| 7. |
- Berglund, Per, et al.
(författare)
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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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| 8. |
- Ekström, Joakim, 1980-, et al.
(författare)
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Simulation based optimisation of toll levels in urban road traffic networks
- 2014
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- There has recently been a growing interest in analysing road pricing schemes in urban areas using dynamic traffic assignment (DTA) tools. The motivation behind this development is the problem for static transportation models to accurately predict travel time savings, from introducing road pricing, in networks with severe congestion. Finding optimal toll levels and locations in urban road traffic networks has so far mainly been studied using either derivative-free heuristics (e.g. genetic algorithms and simulated annealing) or ascent methods. Both approaches rely on fast computations of the road users response (traffic flows, travel times and demands), given the road pricing scheme, and for the case of ascent methods, the methods also rely on fast computations (or rather approximation) of derivatives. Using DTA tools for evaluating the road users’ response to a pricing scheme is, however, very computationally expensive. Previously developed methods are therefore not suitable to use together with DTA.Surrogate models, e.g. in terms of response surfaces, are commonly used for optimisation problems with expensive-to-evaluate objective functions. The surrogate model is used for approximating the expensive-to-evaluate objective function, and the optimisation is then done on the surrogate model instead. The performances of optimisation methods based on surrogate models are, however, dependent on experimental design, infill strategy and choice of surrogate model itself. The experimental design will give the initial set of toll levels, for which the DTA needs to be evaluated, the infill strategy determined additional toll levels to be evaluated by the DTA, and the choice of surrogate model will give the functional form to be fitted to the sampled toll levels.We apply a surrogate model framework for optimising toll levels in a multiple cordon pricing scheme. In the first stage we evaluate the experimental design, infill strategy and choice of surrogate model, using a static macroscopic traffic model. This allows a large number of experiments to be carried out, which would not be possible with a DTA tool. It also allows us to compare the performance of the surrogate modelling approach with other global optimisation methods. In the second stage, the insight which has been gained from the experiments with the static model is used when applying the surrogate modelling approach to a DTA model of Stockholm.Computational results are presented for a Stockholm network with three cordons, each with differentiated toll level in both directions, resulting in a total of six toll level variables. Surrogate models in the form of Radial Basis Functions and Kriging models are evaluated with a static model of Stockholm, for different initial experimental designs, infill strategies and choice of surrogate models. In comparison with previously developed derivative based methods for static models, our results show that the surrogate based optimisation approach performs better, since it allows for metaheuristic methods to search for global optimal solutions efficiently.
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| 9. |
- Ekström, Joakim, 1980-, et al.
(författare)
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Surrogatbaserad optimering av avgiftsnivåer i trängselavgiftssystem
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Trängselskatt finns idag i både Stockholm och Göteborg, och det är troligt att utformningen av dessa trängselskattesystem kommer att justeras framöver med avseende på avgiftsnivå, placering och tidpunkt. För Stockholm finns beslut om ändring från januari 2016 och i Göteborg ändrades avgiftsnivåerna i januari 2015. I detta projekt utvecklas metoder som ska kunna ge stöd vid justering av avigiftsnivåer, så att en så stor samhällsekonomisk nytta som är möjligt uppnås med trängselskattesystemet.För storstadsområden, där det under rusningstrafik är trängsel i delar av nätverket, är trängselskatt främst intressant att analysera med dynamiska transportmodeller. Tidigare utveckling av metoder för optimal avgiftssättning har dock främst fokuserat på statiska modeller, exempelvis Emme, som har kända problem med att korrekt uppskatta förändring i restider när det är trängsel i delar av trafiknätverket. I detta projekt har vi därför tillämpat surrogat-baserad optimering, som är en metodansats som ställer få krav på vilken transportmodell som används. Den dynamiska transportmodellen Regent/VisumDUE finns sedan tidigare implementerad för Stockholmsregionen, och har därför även använts i detta projekt. VisumDUE är en makroskopisk nätutläggningsmodell med dynamiskt ruttval, och Regent är en efterfrågemodell som innehåller resgenerering, färdmedelsval och destinationsval för arbetsresor[1].Surrogat-baserad optimering erbjuder ett ramverk för optimering av problem med beräkningsmässigt kostsamma målfunktioner. Genom att approximera en funktionsyta till samplade punkter från den kostsamma målfunktionen, kan optimeringen istället göras över den approximerade funktionsytan. För Regent/VisumDUE tar utvärderingen av ett givet trängselskattescenario ca tio timmar, och det är denna beräkningstid som gör målfunktionen kostsam. Givet ett antal samplade punkter, görs ytterligare sampling utifrån en given strategi för att förbättra approximationen, så kallad iterativ sampling. Inom ramverket finns dock en mängd möjligheter för hur de olika komponenterna designas. Därför är det svårt att utvärdera surrogat-baserad optimering med endast Regent/VisumDUE. En statisk transportmodell har därför använts för att utvärdera ett antal kombinationer av samplingsstrategi och funktionsyta. Den mest lovande kombinationen har sedan även utvärderats med Regent/VisumDUE. För att vara praktiskt tillämpbart i framtiden har fokus i projektet varit att utvärdera hur metodansatsen fungerar när antalet möjliga tulluppsättningar är kraftigt begränsat (20-40 stycken).Det scenario som har använts som grund i projektet är trängselskatt i Stockholm på nuvarande tullring, på Essingeleden samt på innerstadsbroarna. Skatten är differentierad med avseende på riktning, vilket ger sex olika skattenivåer att optimera. Optimeringen har gjorts för trängselskattenivå under maxtimmen. I det dynamiska fallet har trängselskattens nivå utanför maxtimme funnits med som indata, men samma tidsprofil som på nuvarande tullring har antagits i alla scenarier (avgiftstrappa 50%, 75%, 100%, 75%, 50%). Utvärderingen med den statiska transportmodellen visar att lösningar nära globalt optimum kan uppnås med endast 40 utvärderade trängselskattenivåer, och en tydlig förbättring av den samhällsekonomiska nyttan uppnås redan vid 20 utvärderade trängselskattenivåer.Även med ett kraftigt begränsat antal utvärderingar av den kostsamma målfunktionen i Regent/VisumDUE, har vi visat att det är möjligt att använda metodansatsen. En tydlig förbättring av den samhällsekonomiska nyttan uppnås med endast 22 utvärderade trängselskattenivåer. Ytterligare experiment skulle dock behövas för att undersöka hur stor denna förbättring är i förhållande till vad som skulle kunna uppnås.
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| 10. |
- Ekström, Joakim, 1980-, et al.
(författare)
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Surrogate-based optimisation of toll levels in congestion pricing schemes
- 2014
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Ingår i: Transportation Infrastructure. - Hong Kong : Hong Kong Society of Transportation Studies Limited. - 9789881581433 ; , s. 209-216
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Konferensbidrag (refereegranskat)abstract
- There has recently been a growing interest in analysing road pricing schemes in urban areas using dynamic traffic assignment (DTA) tools. Finding optimal toll levels in cordon based road pricing schemes has so far mainly been studied using either derivative-free heuristics or ascent methods. For future use of DTA tools such methods are not suitable and in this paper we investigate how a surrogate modelling framework can be used instead. We focus on cases when the number of costly objective function evaluations is limited to between 20 and 40. In order to allow a large number of different configurations of the surrogate modelling framework to be evaluated, a static user equilibrium model is used for simulating the road users’ response to a given pricing scheme. The results show that for a realistic scenario, valuable information on close to optimal toll levels can be achieved with only 20 costly function evaluations.
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| 11. |
- Ekström, Joakim, et al.
(författare)
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Surrogate-based optimization of cordon toll levels in congested traffic networks
- 2016
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Ingår i: Journal of Advanced Transportation. - : John Wiley & Sons. - 0197-6729 .- 2042-3195. ; 50:6, s. 1008-1033
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Tidskriftsartikel (refereegranskat)abstract
- The benefit, in terms of social surplus, from introducing congestion charging schemes in urban networks is depending on the design of the charging scheme. The literature on optimal design of congestion pricing schemes is to a large extent based on static traffic assignment, which is known for its deficiency in correctly predict travel times in networks with severe congestion. Dynamic traffic assignment can better predict travel times in a road network, but are more computational expensive. Thus, previously developed methods for the static case cannot be applied straightforward. Surrogate-based optimization is commonly used for optimization problems with expensive-to-evaluate objective functions. In this paper, we evaluate the performance of a surrogate-based optimization method, when the number of pricing schemes, which we can afford to evaluate (because of the computational time), are limited to between 20 and 40. A static traffic assignment model of Stockholm is used for evaluating a large number of different configurations of the surrogate-based optimization method. Final evaluation is performed with the dynamic traffic assignment tool VisumDUE, coupled with the demand model Regent, for a Stockholm network including 1240 demand zones and 17 000 links. Our results show that the surrogate-based optimization method can indeed be used for designing a congestion charging scheme, which return a high social surplus.
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| 12. |
- Holmström, Kenneth, 1954-, et al.
(författare)
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Adaptive Radial Basis Algorithms (ARBF) for Expensive Black-Box Global MINLP Optimization
- 2008
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Ingår i: SIOPT08 - Abstracts. ; , s. 132-
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Konferensbidrag (refereegranskat)abstract
- Improvements of the adaptive radial basis function algo-rithm (ARBF) for computationally costly optimization are presented. A new target value search algorithm and modifications to improve robustness and speed are discussed. The algoritm is implemented in solver ARBFMIP in the TOM-LAB Optimization Environment (http://tomopt.com/). Solvers in TOMLAB are used to solve global and local subproblems. Results and comparisons with other solvers are presented for global optimization test problems. Performance on costly real-life applications are reported.
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| 13. |
- 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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| 14. |
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| 15. |
- 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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| 16. |
- 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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| 17. |
- Häll, Carl Henrik, 1978-, et al.
(författare)
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Adjustments of Public Transit Operations Planning Process for the Use of Electric Buses
- 2017
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Ingår i: TRB Annual Meeting Online, 2017. - : Transportation Research Board.
-
Konferensbidrag (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.
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| 18. |
- Jonsson, Annie, et al.
(författare)
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Landskapets förmåga att hålla biologisk mångfald : – en indikator för biologisk mångfald och ett planeringsverktyg för prioritering av markanvändning
- 2022
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Rapporten beskriver ett nytt verktyg framtaget för att underlätta planering av grön infrastruktur på landskapsnivå och ger via fallstudier exempel på hur verktyget kan användas. Projektet har utförts i ett samarbete med expertis inom teoretisk ekologi, ekologi, biodiversitetsinformatik och tillämpad matematik.Forskningsprojektet har utvecklat en modell för att uppskatta ett landskaps för-måga att hålla biologisk mångfald i dess olika biotoper (Biotope Biodiversity Capacity Indicator, BBCI). Ett teoretiskt ramverk baserat på ekologisk kunskap har tagits fram som grund för modellen.Syftet med BBCI är att modellen ska kunna användas som ett planeringsverktyg för att:stärka biologisk mångfald i ett landskap,förbättra förutsättningarna för arter att använda hela landskapet ochskapa bättre förutsättningar för hänsyn till biologisk mångfald i samband med samhällsutveckling.För att testa och beskriva verktygets användbarhet har fyra fallstudier genomförts med olika fokus:Analys av fragmenteringen i ett barrskogslandskap som sköts med särskild naturhänsyn i Västernorrlands län.Analys av barrskogsvärdekärnors kapacitet för biologisk mångfald inom Västra Götalands län som synliggör vikten av kommunöverskridande samverkan.Analys av potentiella målkonflikter mellan två biotoper, ädellövskog och öppen mark med skyddsvärda träd i Valle.Analys av kapacitet för biologisk mångfald hos äldre ädellövträd i ett landskap mixat med urbana miljöer och landsbygd, Mjölby kommun.Parallellt med utvcklingen av BBCI har en tät dialog och samverkan skett med olika intressenter och slutanvändare. Den breda dialogen har medfört ett effektivt kun-skapsutbyte mellan olika parter.Rapporten avslutas med att beskriva utmaningar och verktygets utvecklings-potential både avseende pedagogik och teknik men även hur modellen kan byggas på och utvecklas med ytterligare funktioner för en breddad tillämpning.
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| 19. |
- 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
-
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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| 20. |
- Larsson, Torbjörn, et al.
(författare)
-
A Lagrangian bounding and heuristic principle for bi-objective discrete optimization
- 2024
-
Ingår i: Operational Research. - : SPRINGER HEIDELBERG. - 1109-2858 .- 1866-1505. ; 24:2
-
Tidskriftsartikel (refereegranskat)abstract
- Lagrangian relaxation is a common and often successful way to approach computationally challenging single-objective discrete optimization problems with complicating side constraints. Its aim is often twofold; first, it provides bounds for the optimal value, and, second, it can be used to heuristically find near-optimal feasible solutions, the quality of which can be assessed by the bounds. We consider bi-objective discrete optimization problems with complicating side constraints and extend this Lagrangian bounding and heuristic principle to such problems. The Lagrangian heuristic here produces non-dominated candidates for points on the Pareto frontier, while the bounding forms a polyhedral outer approximation of the Pareto frontier, which can be used to assess the quality of the candidate points. As an illustration example we consider a facility location problem in which both CO2 emission and cost should be minimized. The computational results are very encouraging, both with respect to bounding and the heuristically found non-dominated solutions. In particular, the Lagrangian bounding is much stronger than the outer approximation given by the Pareto frontier of the problem's linear programming relaxation.
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| 21. |
- Larsson, Torbjörn, et al.
(författare)
-
A theoretical justification of the set covering greedy heuristic of Caprara et al
- 2022
-
Ingår i: Discrete Optimization. - : Elsevier. - 1572-5286 .- 1873-636X. ; 45
-
Tidskriftsartikel (refereegranskat)abstract
- Large scale set covering problems have often been approached by constructive greedy heuristics, and much research has been devoted to the design and evaluation of various greedy criteria for such heuristics. A criterion proposed by Caprara et al. (1999) is based on reduced costs with respect to the yet unfulfilled constraints, and the resulting greedy heuristic is reported to be superior to those based on original costs or ordinary reduced costs. We give a theoretical justification of the greedy criterion proposed by Caprara et al. by deriving it from a global optimality condition for general nonconvex optimisation problems. It is shown that this criterion is in fact greedy with respect to incremental contributions to a quantity which at termination coincides with the deviation between a Lagrangian dual bound and the objective value of the feasible solution found.
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| 22. |
- Larsson, Torbjörn, et al.
(författare)
-
Column generation extensions of set covering greedy heuristics
- 2022
-
Ingår i: Operations Research Letters. - : Elsevier. - 0167-6377 .- 1872-7468. ; 50:6, s. 738-744
-
Tidskriftsartikel (refereegranskat)abstract
- Large-scale set covering problems are often approached by constructive greedy heuristics, and many selection criteria for such heuristics have been considered. These criteria are typically based on measures of the cost of setting an additional variable to one in relation to the number of yet unfulfilled constraints that it will satisfy. We show how such greedy selections can be performed on column-oriented set covering models, by using a fractional optimization formulation and solving sequences of ordinary column generation problems for the application at hand.
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| 23. |
- Larsson, Torbjörn, et al.
(författare)
-
One-parametric analysis of column-oriented linear programs
- 2023
-
Ingår i: Oncoscience. - : ELSEVIER. - 0255-0156 .- 2214-7160. ; 10
-
Tidskriftsartikel (refereegranskat)abstract
- A linear optimization problem which is amenable to column generation and contains a single parameter in the objective function is considered. We extend and adapt the standard linear programming column generation scheme to effectively and efficiently solve this problem for all values of the parameter. As a potential application we consider bi-objective discrete optimization and describe how the one-parametric column generation scheme can be used to form an outer approximation of the Pareto frontier for such a problem.
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| 24. |
- Lindholm, Anna, et al.
(författare)
-
Hierarchical Production Scheduling - A Case Study at Perstorp
- 2014
-
Ingår i: 24th European Symposium on Computer Aided Process Engineering, PTS A and B. - : Elsevier. - 1570-7946. ; 33, s. 511-516, s. 511-516
-
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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| 25. |
- Lindholm, Anna, et al.
(författare)
-
Production scheduling in the process industry
- 2013
-
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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| 26. |
- Metson, Genevieve, et al.
(författare)
-
Not all sites are created equal - Exploring the impact of constraints to suitable biogas plant locations in Sweden
- 2022
-
Ingår i: Journal of Cleaner Production. - : Elsevier Science Ltd. - 0959-6526 .- 1879-1786. ; 349
-
Tidskriftsartikel (refereegranskat)abstract
- Biogas production from manure is attractive to support plans towards a circular economy as it allows for renewable energy production and nutrient recycling in agriculture. Finding optimal locations for biogas plants, which minimize transport distances to and from farms, while accounting for multiple feasibility constraints, remains a challenge. We developed 1 km2 spatially-explicit datasets for known feasibility constraints such as distance to housing, compatible land-use zoning, and the presence of roads with sufficient weight bearing capacity. These datasets were used to improve the realism of an optimization model designed to minimize transportation costs in Sweden. At a national level, the presence of durable enough roads most limited the number of suitable locations for a plant. We further focused our analysis on a case study region where a company wanted to invest in a new manure-based biogas plant. In contrast to the national level, the constraint for remaining at least 500 m from housing/buildings had the greatest limiting impact, excluding 71% of grids in the Sjo center dot bo or Tomelilla municipalities of Southern Sweden. Still, we identified 105 suitable locations for a new biogas plant. The most suitable location, accounting for feasibility and minimized transportation costs, changed when simultaneously accounting for another proposed plant in a neighboring municipality. Our results indicate that utilizing both local and national datasets can help narrow down potential biogas development sites and that long-term planning is necessary for actors with ambitions to build several plants to minimize costs and maximize energy and nutrient recycling benefits.
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| 27. |
- Metson, Genevieve S., 1988-, et al.
(författare)
-
Optimizing transport to maximize nutrient recycling and green energy recovery
- 2020
-
Ingår i: Resources, Conservation & Recycling: X. - : Elsevier. - 2590-289X. ; 9-10
-
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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| 28. |
- Metson, Genevieve, et al.
(författare)
-
Swedish food system transformations : Rethinking biogas transport logistics to adapt to localized agriculture
- 2022
-
Ingår i: Sustainable Production and Consumption. - : Elsevier. - 2352-5509. ; 29, s. 370-386
-
Tidskriftsartikel (refereegranskat)abstract
- Ensuring future food and energy security will require large changes in consumption and production pat-terns, including enhanced animal and human excreta recycling. Although these shifts are considered in many scenario studies, their implications on the logistical requirements for effective recycling are rarely analysed. Here we translated two existing stakeholder co-designed food system scenarios for Sweden to 5 x 5 km resolution maps of animals, crops, and humans. We used optimization modelling to identify biogas plant locations to minimize transport costs and maximize nutrient reuse. We then compared sce-narios, including full recycling under current landscape configuration, through Life Cycle Assessment. The reduction in meat consumption and imported food in both co-designed scenarios, by definition, led to less nutrients available in manure for recycling back on cropland, and less material available for diges-tion. Less excreta meant lower national benefits, for example 50% less greenhouse gas emissions savings in the most divergent scenario. However on a per transport basis the benefits of recycling were more important: recycling remained a net financial benefit even if transport costs were to increase. Although fewer biogas plant locations were necessary (184 and 228 for alternative futures, vs 236 under current conditions) to process human and animal excreta, the regional clustering of locations did not change substantially across scenarios. Regions such as Skane and Vastra Gotaland consistently required the most biogas plant locations across scenarios. Focusing early construction investments in these regions would be resilient to a large array of food system futures. Our spatially-explicit open access scenario maps can be used to explore logistics for such planning, and explore the impact of landscape configuration on other sustainability priority areas. (C) 2021 The Author(s). Published by Elsevier B.V. on behalf of Institution of Chemical Engineers.
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| 29. |
- Ngulo, Uledi, 1983-, et al.
(författare)
-
A Dissection of the Duality Gap of Set Covering Problems
- 2020
-
Ingår i: Operations Research Proceedings 2019. - Cham : Springer International Publishing. - 9783030484385 ; , s. 175-181
-
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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| 30. |
- Ngulo, Uledi, 1983-
(författare)
-
Decomposition Methods for Combinatorial Optimization
- 2021
-
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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| 31. |
- Olsson, Jonas, et al.
(författare)
-
Automating the planning of container loading for Atlas Copco: Coping with real-life stacking and stability constraints
- 2020
-
Ingår i: European Journal of Operational Research. - : ELSEVIER. - 0377-2217 .- 1872-6860. ; 280:3, s. 1018-1034
-
Tidskriftsartikel (refereegranskat)abstract
- The Atlas Copco* distribution center in Allen, TX, supplies spare parts and consumables to mining and construction companies across the world. For some customers, packages are shipped in sea containers. Planning how to load the containers is difficult due to several factors: heterogeneity of the packages with respect to size, weight, stackability, positioning and orientation; the set of packages differs vastly between shipments; it is crucial to avoid cargo damage. Load plan quality is ultimately judged by shipping operators. This container loading problem is thus rich with respect to practical considerations. These are posed by the operators and include cargo and container stability as well as stacking and positioning constraints. To avoid cargo damage, the stacking restrictions are modeled in detail. For solving the problem, we developed a two-level metaheuristic approach and implemented it in a decision support system. The upper level is a genetic algorithm which tunes the objective function for a lower level greedy-type constructive placement heuristic, to optimize the quality of the load plan obtained. The decision support system shows load plans on the forklift laptops and has been used for over two years. Management has recognized benefits including reduction of labour usage, lead time, and cargo damage risk. (C) 2019 Elsevier B.V. All rights reserved.
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| 32. |
- Quttineh, Nils-Hassan, et al.
(författare)
-
A Time-Indexed Generalized Vehicle Routing Model and Stabilized Column Generation for Military Aircraft Mission Planning
- 2015
-
Ingår i: OPTIMIZATION, CONTROL, AND APPLICATIONS IN THE INFORMATION AGE: IN HONOR OF PANOS M. PARDALOSS 60TH BIRTHDAY. - Cham : SPRINGER. - 9783319185675 - 9783319185668 ; , s. 299-314
-
Konferensbidrag (refereegranskat)abstract
- We introduce a time-indexed mixed-integer linear programming model for a military aircraft mission planning problem, where a fleet of cooperating aircraft should attack a number of ground targets so that the total expected effect is maximized. The model is a rich vehicle routing problem and the direct application of a general solver is practical only for scenarios of very moderate sizes. We propose a Dantzig-Wolfe reformulation and column generation approach. A column here represents a specific sequence of tasks at certain times for an aircraft, and to generate columns a longest path problem with side constraints is solved. We compare the column generation approach with the time-indexed model with respect to upper bounding quality of their linear programming relaxations and conclude that the former provides a much stronger formulation of the problem.
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| 33. |
- Quttineh, Nils-Hassan, et al.
(författare)
-
Adaptive Radial Basis Algorithm (ARBF) for Expensive Black-Box Mixed-Integer Constrained Global Optimization
- 2007
-
Ingår i: 2nd Mathematical Programming SocietyInternational Conference on Continuous Optimization ICCOPT 07 - MOPTA 07. ; , s. 30-
-
Konferensbidrag (refereegranskat)abstract
- Response surface methods based on kriging and radial basis function (RBF) interpolation have been successfully applied to solve expensive, i.e. com-putationally costly, global black-box nonconvex optimization problems. We describe extensions of these methods to handle linear, nonlinear and integer constraints. In particular standard RBF and new adaptive RBF (ARBF) algorithms are discussed. Test results are presented on standard test problems, both nonconvex problems with linear and nonlinear constraints, and mixed-integer nonlinear problems. Solvers in the TOMLAB Optimization Environment (http://tomopt.com/tomlab/) are compared; the three deterministic derivative-free solvers rbfSolve, ARBFMIP and EGO with three derivative-based mixed-integer nonlinear solvers, OQNLP, MINLPBB and MISQP as well as GENO implementing a stochastic genetic algorithm. Assuming that the objective function is costly to evaluate the performance of the ARBF algorithm proves to be superior.
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| 34. |
|
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| 35. |
- 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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| 36. |
- Quttineh, Nils-Hassan, 1979-
(författare)
-
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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| 37. |
- Quttineh, Nils-Hassan, et al.
(författare)
-
An optimization approach to the design of outdoor thermal fire detection systems
- 2022
-
Ingår i: Fire safety journal. - : Elsevier Science Ltd. - 0379-7112 .- 1873-7226. ; 129
-
Tidskriftsartikel (refereegranskat)abstract
- With the recent growing usage of bio-fuels the need for fire detection in outdoor bio-fuel depots has increased, and several fire detection technologies for this purpose have been proposed. We consider the use of thermal cameras and present the problem of designing the placement of such cameras. Bio-fuel depots are often large and it might be prohibitively expensive to surveil the complete areas of interest, and it is therefore required to generate compromise solutions between area coverage and cost, to be presented to a customer. We give a bi-objective mathematical optimization formulation of the problem and fast heuristics that find compromise solutions, and present results from calculating camera placements for several real-world bio-fuel depots. Our approach has been implemented in a decision support software, which is currently in use.
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| 38. |
- Quttineh, Nils-Hassan, et al.
(författare)
-
Applying heuristics in supply chain planning in the process industry
- 2020
-
Ingår i: International Journal of Industrial Engineering Computations. - : GROWING SCIENCE. - 1923-2926 .- 1923-2934. ; 11:4, s. 585-606
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper a mixed-integer linear programming (MILP) model is developed to be used as a decision support tool for the chemical company Perstorp Oxo AB. The intention with the mathematical model is to maximize the profit and the model can be used in the process of planning the supply chain for the company. Perstorp Oxo is classified as a global company in the process industry and is has production sites in Gent, Castellanza, Stenungsund and Perstorp. The site in Stenungsund is in focus in this paper. The company produces chemicals that later are used for example in textiles, plastic and glass production. Perstorp Oxo also uses inventories in other countries for enabling the selling abroad. It has two larger inventories in Antwerp and in Tees and two smaller in Philadelphia and in Aveiro. The larger facilities store five different products and the smaller take care of one type each. To be able to find feasible and profitable production plans for the company we have developed and implemented rolling horizon techniques for a time horizon of one year and used real sales data. The outcomes from the model show the transportation of products between different production sites, the different production rates, the levels of inventory, setups and purchases from external suppliers. The numerical results are promising and we conclude that a decision support tool based on an optimization model could improve the situation for the planners at Perstorp Oxo AB. (C) 2020 by the authors; licensee Growing Science, Canada
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| 39. |
- Quttineh, Nils-Hassan, 1979-, et al.
(författare)
-
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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| 40. |
- Quttineh, Nils-Hassan, 1979-, et al.
(författare)
-
Combined Timetabling and Vehicle Scheduling for Electric Buses
- 2017
-
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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| 41. |
- Quttineh, Nils-Hassan, 1979-, et al.
(författare)
-
Dissecting the duality gap : the supporting hyperplane interpretation revisited
- 2022
-
Ingår i: Optimization Letters. - : Springer Nature. - 1862-4472 .- 1862-4480. ; 16, s. 1093-1102
-
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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| 42. |
- Quttineh, Nils-Hassan, 1979-, et al.
(författare)
-
Effect Oriented Planning
- 2012
-
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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| 43. |
- Quttineh, Nils-Hassan, 1979-, et al.
(författare)
-
Effect Oriented Planning of Joint Attacks
- 2013
-
Ingår i: Optimization Theory, Decision Making, and Operations Research Applications. - New York, NY : Springer-Verlag New York. - 9781461451334 - 9781461451341 ; , s. 49-70
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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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| 44. |
- Quttineh, Nils-Hassan, 1979-, et al.
(författare)
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Implementation of a One-Stage Efficient Global Optimization (EGO) Algorithm
- 2009
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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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| 45. |
- Quttineh, Nils-Hassan, et al.
(författare)
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Integrated solution for electric bus timetabling and vehicle scheduling combined with choices of charging locations
- 2023
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Ingår i: Journal of Public Transportation. - : ELSEVIER. - 1077-291X. ; 25
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a novel mathematical model, integrating timetabling and vehicle scheduling problems for electric buses. The objective is to minimize the number of buses while satisfying constraints concerning routing and charging, including design choices for where to install charging stations. The aim of the paper is to illustrate and discuss the effects of solving the timetabling and vehicle scheduling of electric buses (including where to install charging infrastructure) separately, compared to solving them jointly in one single step. For that purpose, we perform tests with: i) given timetable, that is, solving only the vehicle scheduling problem, ii) fixed headways for each line, and iii) variable headways. A small test case based on actual bus lines from Va center dot stra Fro center dot lunda, Gothenburg, Sweden, is used. From the numerical experiments, we verify that combining the two planning steps can significantly reduce the number of vehicles needed.
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| 46. |
- Quttineh, Nils-Hassan, 1979-, et al.
(författare)
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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
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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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| 47. |
- Quttineh, Nils-Hassan, 1979-, et al.
(författare)
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Military aircraft mission planning : a generalized vehicle routing model with synchronization and precedence
- 2013
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Ingår i: EURO Journal on Transportation and Logistics. - : Springer. - 2192-4376 .- 2192-4384. ; 2:1-2, s. 109-127
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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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| 48. |
- 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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| 49. |
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| 50. |
- 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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