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  • 51.
    Amankwah, Henry
    et al.
    Linköpings universitet, Matematiska institutionen, Optimeringslära. Linköpings universitet, Tekniska högskolan.
    Larsson, Torbjörn
    Linköpings universitet, Matematiska institutionen, Optimeringslära. Linköpings universitet, Tekniska högskolan.
    Textorius, Björn
    Linköpings universitet, Matematiska institutionen, Tillämpad matematik. Linköpings universitet, Tekniska högskolan.
    Open-Pit Mining with Uncertainty - A Conditional Value-at-Risk ApproachManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    The selection of a mine design is based on estimating net present values of all possible, technically feasible mine plans so as to select the one with the maximum value. It is a hard task to know with certainty the quantity and quality of ore in the ground. This geological uncertainty, and also the future market behaviour of metal prices and foreign exchange rates, which are impossible to be known with certainty, make mining a high risk business.

    Value-at-Risk (VaR) is a measure that is used in financial decisions to minimize the loss caused by inadequate monitoring of risk. This measure does however have certain drawbacks such as lack of consistency, nonconvexity, and nondifferentiability. Rockafellar and Uryasev (2000) introduce the Conditional Value-at-Risk (CVaR) measure as an alternative to the VaR measure. The CVaR measure gives rise to a convex problem.

    An optimization model that maximizes expected return while minimizing risk is important for the mining sector as this will help make better decisions on the blocks of ore to mine at a particular point in time. We present a CVaR approach to the uncertainty involved in open-pit mining. We formulate investment and design models for the open-pit mine and also give a nested pit scheduling model based on CVaR. Several numerical results based on our models are presented by using scenarios from simulated geological and price uncertainties.

  • 52.
    Amankwah, Henry
    et al.
    University of Cape Coast, Ghana .
    Larsson, Torbjörn
    Linköpings universitet, Matematiska institutionen, Optimeringslära. Linköpings universitet, Tekniska högskolan.
    Textorius, Björn
    Linköpings universitet, Matematiska institutionen, Matematik och tillämpad matematik. Linköpings universitet, Tekniska högskolan.
    Open-pit mining with uncertainty: A conditional value-at-risk approach2013Inngår i: Optimization Theory, Decision Making, and Operations Research Applications: Proceedings of the 1st International Symposium and 10th Balkan Conference on Operational Research / [ed] Athanasios Migdalas, Angelo Sifaleras, Christos K. Georgiadis, Jason Papathanasiou, Emmanuil Stiakakis, New York: Springer, 2013, s. 117-139Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The selection of a mine design is based on estimating net present values of all possible, technically feasible mine plans so as to select the one with the maximum value. It is a hard task to know with certainty the quantity and quality of ore in the ground. This geological uncertainty and also the future market behavior of metal prices and foreign exchange rates, which are always uncertain, make mining a high risk business. Value-at-Risk (VaR) is a measure that is used in financial decisions to minimize the loss caused by inadequate monitoring of risk. This measure does, however, have certain drawbacks such as lack of consistency, nonconvexity, and nondifferentiability. Rockafellar and Uryasev [J. Risk 2, 21-41 (2000)] introduce the Conditional Value-at-Risk (CVaR) measure as an alternative to the VaR measure. The CVaR measure gives rise to a convex optimization problem. An optimization model that maximizes expected return while minimizing risk is important for the mining sector as this will help make better decisions on the blocks of ore to mine at a particular point in time. We present a CVaR approach to the uncertainty involved in open-pit mining. We formulate investment and design models for the open-pit mine and also give a nested pit scheduling model based on CVaR. Several numerical results based on our models are presented by using scenarios from simulated geological and market uncertainties.

  • 53.
    Amankwah, Henry
    et al.
    Linköpings universitet, Matematiska institutionen, Optimeringslära. Linköpings universitet, Tekniska högskolan.
    Larsson, Torbjörn
    Linköpings universitet, Matematiska institutionen, Optimeringslära. Linköpings universitet, Tekniska högskolan.
    Textorius, Björn
    Linköpings universitet, Matematiska institutionen, Tillämpad matematik. Linköpings universitet, Tekniska högskolan.
    Rönnberg, Elina
    Linköpings universitet, Matematiska institutionen, Optimeringslära. Linköpings universitet, Tekniska högskolan.
    Open-Pit Production Scheduling - Suggestions for Lagrangian Dual Heuristic and Time Aggregation ApproachesManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Open-pit production scheduling deals with the problem of deciding what and when to mine from an open-pit, given potential profits of the different fractions of the mining volume, pit-slope restrictions, and mining capacity restrictions for successive time periods. We give suggestions for Lagrangian dual heuristic approaches for the open-pit production scheduling problem. First, the case with a single mining capacity restriction per time period is considered. For this case, linear programming relaxations are solved to find values of the multipliers for the capacity restrictions, to be used in a Lagrangian relaxation of the constraints. The solution to the relaxed problem will not in general satisfy the capacity restrictions, but can be made feasible by adjusting the multiplier values for one time period at a time. Further, a time aggregation approach is suggested as a way of reducing the computational burden of solving linear programming relaxations, especially for largescale real-life mine problems. For the case with multiple capacity restrictions per time period we apply newly developed conditions for optimality and nearoptimality in general discrete optimization problems to construct a procedure for heuristically constructing near-optimal intermediate pits.

  • 54.
    Amsallem, David
    et al.
    Department of Aeronautics and Astronautics, Stanford University, Stanford, CA 94305-4035, USA.
    Nordström, Jan
    Linköpings universitet, Matematiska institutionen, Beräkningsmatematik. Linköpings universitet, Tekniska fakulteten.
    Energy Stable Model Reduction of Neurons by Non-negative Discrete Empirical Interpolation2016Inngår i: SIAM Journal on Scientific Computing, ISSN 1064-8275, E-ISSN 1095-7197, Vol. 38, nr 2, s. B297-B326Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The accurate and fast prediction of potential propagation in neuronal networks is of prime importance in neurosciences. This work develops a novel structure-preserving model reduction technique to address this problem based on Galerkin projection and nonnegative operator approximation. It is first shown that the corresponding reduced-order model is guaranteed to be energy stable, thanks to both the structure-preserving approach that constructs a distinct reduced-order basis for each cable in the network and the preservation of nonnegativity. Furthermore, a posteriori error estimates are provided, showing that the model reduction error can be bounded and controlled. Finally, the application to the model reduction of a large-scale neuronal network underlines the capability of the proposed approach to accurately predict the potential propagation in such networks while leading to important speedups.

    Fulltekst (pdf)
    fulltext
  • 55.
    Amsallem, David
    et al.
    Department of Aeronautics and Astronautics, Stanford University, Stanford, USA.
    Nordström, Jan
    Linköpings universitet, Matematiska institutionen, Beräkningsmatematik. Linköpings universitet, Tekniska högskolan.
    High-order accurate difference schemes for the Hodgkin-Huxley equations2012Rapport (Annet vitenskapelig)
    Abstract [en]

    A novel approach for simulating potential propagation in neuronal branches with high accuracy is developed. The method relies on high-order accurate dierence schemes using the Summation-By-Parts operators with weak boundary and interface conditions applied to the Hodgkin-Huxley equations. This work is the rst demonstrating high accuracy for that equation. Several boundary conditions are considered including the non-standard one accounting for the soma presence, which is characterized by its own partial dierential equation. Well-posedness for the continuous problem as well as stability of the discrete approximation is proved for all the boundary conditions. Gains in terms of CPU times are observed when high-order operators are used, demonstrating the advantage of the high-order schemes for simulating potential propagation in large neuronal trees.

    Fulltekst (pdf)
    High-order accurate difference schmes for the Hodgkin-Huxley equations
  • 56.
    Amsallem, David
    et al.
    Department of Aeronautics and Astronautics, Stanford University, USA.
    Nordström, Jan
    Linköpings universitet, Matematiska institutionen, Beräkningsmatematik. Linköpings universitet, Tekniska högskolan.
    High-order accurate difference schemes for the Hodgkin-Huxley equations2013Inngår i: Journal of Computational Physics, ISSN 0021-9991, E-ISSN 1090-2716, Vol. 252, s. 573-590Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A novel approach for simulating potential propagation in neuronal branches with high accuracy is developed. The method relies on high-order accurate difference schemes using the Summation-By-Parts operators with weak boundary and interface conditions applied to the Hodgkin–Huxley equations. This work is the first demonstrating high accuracy for that equation. Several boundary conditions are considered including the non-standard one accounting for the soma presence, which is characterized by its own partial differential equation. Well-posedness for the continuous problem as well as stability of the discrete approximation is proved for all the boundary conditions. Gains in terms of CPU times are observed when high-order operators are used, demonstrating the advantage of the high-order schemes for simulating potential propagation in large neuronal trees.

    Fulltekst (pdf)
    fulltext
  • 57.
    Andersen, Lisa
    et al.
    Linköpings universitet, Matematiska institutionen, Matematik och tillämpad matematik. Linköpings universitet, Tekniska fakulteten.
    Tebring, Sandra
    Linköpings universitet, Matematiska institutionen, Matematik och tillämpad matematik. Linköpings universitet, Tekniska fakulteten.
    Metakognitiva förmågors påverkan på elevers prestationer i matematisk problemlösning2018Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Problemlösning är en central matematisk förmåga och anses av många vara matematikens kärna. I ett försök att finna svar på hur den optimala undervisningen i problemlösning borde bedrivas, uppkom idén att studera elevers prestationer inom problemlösning kopplat till metakognition. Metakognition kan beskrivas som tänkande över det egna tänkandet och är en nödvändig förmåga i flera olika sammanhang. Denna litteraturstudie har till syfte att undersöka om metakognitiv förmåga påverkar elevers prestationer i matematisk problemlösning.Studien utgår från åtta artiklar som hittades via databasen UniSearch och det är dessa åtta artiklar som utgör resultatet. Artiklarnas metoder skiljer sig från varandra då vissa jämför elevers metakognitiva förmåga med deras prestationer inom problemlösning, medan andra testar effekten av olika undervisningsmetoder baserade på metakognition. Trots detta visar studiens resultat på att det finns ett samband mellan god metakognitiv förmåga och att prestera väl inom matematisk problemlösning. Utifrån detta dras slutsatsen att det är av stor vikt att elever får undervisning i metakognition, speciellt de svaga eleverna.

    Fulltekst (pdf)
    fulltext
  • 58.
    Andersen, Lisa
    et al.
    Linköpings universitet, Matematiska institutionen. Linköpings universitet, Tekniska fakulteten.
    Tebring, Sandra
    Linköpings universitet, Matematiska institutionen. Linköpings universitet, Tekniska fakulteten.
    Metakognitiva strategier vid lösning av rika matematiska problem: Vilka strategier används och vilka för problemlösningsprocessen framåt?2020Independent thesis Advanced level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Sammanfattningsvis handlar denna studie om relationen mellan metakognition och matematisk problemlösning.Metakognition betyder kortfattat förmågan att tänka över det egna tänkandet och har visat sig vara en central del avarbete med problemlösning. Syftet med studien var att undersöka vilka metakognitiva strategier som elever användervid arbete med rika matematiska problem samt hur dessa påverkar huruvida problemlösningsprocessen förs framåt.Studien bygger på fyra observationer av 13 elever i årskurs åtta som arbetade med rika matematiska problem. Resultatet kodades med hjälp av ett analysverktyg som skapades med stöd i tidigare forskning och studien kom framtill att de vanligaste strategierna som eleverna använde var att identifiera relevant information samt att hitta ”nyckeln”i problemet. Dessa strategier var också de som förde problemlösningsprocessen framåt. Avslutningsvis dras slutsatsenatt elever som lyckas i sin problemlösning använder många olika metakognitiva strategier och att de behärskar detvå vanligaste strategierna, vilket leder till att de kan komma vidare i problemlösningen.

    Fulltekst (pdf)
    fulltext
  • 59.
    Anderskär, Erika
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Statistik och maskininlärning.
    Thomasson, Frida
    Linköpings universitet, Institutionen för datavetenskap, Statistik och maskininlärning.
    Inkrementell responsanalys av Scandnavian Airlines medlemmar: Vilka kunder ska väljas vid riktad marknadsföring?2017Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    Scandinavian Airlines has a large database containing their Eurobonus members. In order to analyze which customers they should target with direct marketing, such as emails, uplift models have been used. With a binary response variable that indicates whether the customer has bought or not, and a binary dummy variable that indicates if the customer has received the campaign or not conclusions can be drawn about which customers are persuadable. That means that the customers that buy when they receive a campaign and not if they don't are spotted. Analysis have been done with one campaign for Sweden and Scandinavia. The methods that have been used are logistic regression with Lasso and logistic regression with Penalized Net Information Value. The best method for predicting purchases is Lasso regression when comparing with a confusion matrix. The variable that best describes persuadable customers in logistic regression with PNIV is Flown (customers that have own with SAS within the last six months). In Lassoregression the variable that describes a persuadable customer in Sweden is membership level1 (the rst level of membership) and in Scandinavia customers that receive campaigns with delivery code 13 are persuadable, which is a form of dispatch.

    Fulltekst (pdf)
    fulltext
  • 60.
    Andersson, Aina
    et al.
    Linköpings universitet, Institutionen för beteendevetenskap och lärande. Linköpings universitet, Utbildningsvetenskap.
    Persson, Ing-Marie
    Linköpings universitet, Institutionen för beteendevetenskap och lärande. Linköpings universitet, Utbildningsvetenskap.
    Svagt arbetsminne - orsaken till matematiksvårigheter?2013Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Syftet med studien var att se om det finns ett samband mellan matematiksvårigheter och elevens arbetsminne. Utifrån ett befintligt resultat från screeningtest valdes 19 elever ut med matematiksvårigheter, och ytterligare 20 som kontrollgrupp. Därefter genomfördes arbetsminnestester samt test av antalsuppfattning. Undersökningarna utfördes i år 3 och 4 på två olika skolor. Arbetsminnestesterna testade den centrala exekutiven, fonologiska loopen, visuella skissblocket, process-hastighet. Resultaten som analyserades med variansanalys visade att det finns samband mellan arbetsminne och matematiksvårigheter. Studien visar på specifika störningar i centrala exekutiven, men också störningar i den medfödda antalsuppfattningen.

     

    Fulltekst (pdf)
    fulltext
  • 61.
    Andersson, Anna
    Linköpings universitet, Institutionen för beteendevetenskap och lärande.
    Ett laborativt arbetssätt i matematik: I skolår 1 och 22007Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Ett intresse för matematik och nyfikenhet över hur jag i framtiden ska kunna göra matematiklektionerna meningsfulla och vardagsnära för mina elever bidrog till att jag, när jag fick den, tog chansen att genomföra ett temaarbete med ett laborativt arbetssätt och göra en fallstudie över detta.

    Tidigare forskning visar att det är viktigt att utgå från elevers olika individuella förutsättningar, göra lektionerna vardagsnära, meningsfulla, varierande och även gärna lustfyllda. Forskningen visar även på kommunikationens betydelse, särskilt vikten av att kommunicera så att eleverna förstår både vad de förväntas lära och vad de kan utveckla.

    Detta examensarbete är skrivet utifrån ett sociokulturellt perspektiv efter att en fallstudie, inspirerad av aktionsforskning, bestående av såväl observationer, intervjuer, samtal och enkäter genomförts.

    Resultatet visar att ett laborativt arbetssätt gynnar alla elever, inte minst de svaga då det ger många möjligheter till att låta eleverna uppleva och upptäcka. Lärarna betonar vikten av att noggrant planera lektionerna samt att vara medveten om hur man kommunicerar undervisningsinnehållet. De menar också att ett laborativt arbetssätt ger goda möjligheter till individanpassning eftersom arbetet kan utgå från de enskilda elevernas individuella behov.

    Fulltekst (pdf)
    FULLTEXT01
  • 62.
    Andersson Granberg, Tobias
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Norin, Anna
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Värbrand, Peter
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Integrating optimization and simulation to gain more efficient airport logistics2009Inngår i: Eighth USA/Europe Air Traffic Management Research and Development Seminar (ATM2009), 2009, s. 1-10Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we present airport logistics, which is a framework of resource management in the air transportation system. Focus is on the processes supporting turn-around. A detailed simulation model of various processes involved in turn-around is developed, by which the interaction between these processes are analyzed. We show that integrating optimization and simulation is a powerful tool to demonstrate efficiency improvements in airport logistics, using scheduling de-icing trucks as an example. An optimization algorithm for scheduling de-icing trucks is developed and simulations are performed comparing different schedules. The schedule obtained when considering total airport performance in the optimization algorithm gives minimum flight delay and waiting times in the simulations.

  • 63.
    Andersson Hagiwara, Magnus
    et al.
    University of Borås, Sweden.
    Andersson Gare, Boel
    Jönköping University, Sweden.
    Elg, Mattias
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Logistik- och kvalitetsutveckling. Linköpings universitet, Tekniska fakulteten. Linköpings universitet, HELIX Vinn Excellence Centre.
    Interrupted Time Series Versus Statistical Process Control in Quality Improvement Projects2016Inngår i: Journal of Nursing Care Quality, ISSN 1057-3631, E-ISSN 1550-5065, Vol. 31, nr 1, s. E1-E8Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To measure the effect of quality improvement interventions, it is appropriate to use analysis methods that measure data over time. Examples of such methods include statistical process control analysis and interrupted time series with segmented regression analysis. This article compares the use of statistical process control analysis and interrupted time series with segmented regression analysis for evaluating the longitudinal effects of quality improvement interventions, using an example study on an evaluation of a computerized decision support system.

  • 64.
    Andersson, Hanna
    Linköpings universitet, Matematiska institutionen, Matematik och tillämpad matematik. Linköpings universitet, Tekniska fakulteten.
    Den flippade läxan: En systematisk litteraturstudie av läxor i det flippade matematikklassrummet2018Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Syftet med denna litteraturstudie är att redogöra för läxans roll i det flippade matematiklassrummet. Arbetsmetoden ”Flippat klassrum” karaktäriseras av en förflyttning av traditionella föreläsningar ut ur klassrummet. Direkta instruktioner ges istället som läxa, ”flippad läxa”, ofta i form av videoföreläsningar. Litteraturstudien baserar sig på nio artiklar och behandlar den flippade matematikläxans utformning, elevers åsikter om arbetsmetoden, och vilka fördelar respektive nackdelar flippad läxa har i förhållande till traditionell läxa. ”Flippad läxa” är fortfarande är ett relativt outforskat begrepp, vilket gör det svårt att dra generella slutsatser. Studiens resultat tyder dock på att metoden kan ha flera fördelar, bland annat i att videoföreläsningar som läxa ger eleverna ett större ansvar för sitt eget lärande, och att videons bestämda speltid har potential att minska skillnaden i den tid, som olika elever använder för att göra samma läxa.

    Fulltekst (pdf)
    fulltext
  • 65.
    Andersson, Helén
    Linköpings universitet, Institutionen för utbildningsvetenskap.
    Matematik: som eleven ser det Elevers uppfattningar om matematik och matematikundervisning2002Independent thesis Basic level (professional degree)Oppgave
    Abstract [sv]

    Studiens syftar till att undersöka elevers uppfattningar om matematik och matematikundervisning. Arbetet består av en litteraturgenomgång och en empirisk del där intervjuer med åtta elever ingår.

    Både den teoretiskaoch den empiriska delen behandlar tre områden. Dessa områden är:

    - Varför har vi matematik i skolan?

    - Vad är matematik?

    - Hur bedrivs matematikundervisning?

    Den teoretiska studien beskriver frågeställningarna utifrån hur forskare, författare och lärare ser på det. Inom denna del inryms även en beskrivning om hur undervisning skulle kunna se ut i praktiken.

    Den empiriska delen består av åtta intervjuer med elever i år åttta och år nio. Eleverna beskriver hur de uppfattar varför vi har matematik i skolan, vad matematik är och hur matematikundervisning bedrivs.

    Elevernas uppfattningar om varför vi har matematik i skolan, vad matematik är och hur matematikundervisning bedrivs stämmer i stort överens med litteraturen.

    Fulltekst (pdf)
    FULLTEXT01
  • 66. Bestill onlineKjøp publikasjonen >>
    Andersson, Henrik
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Coordinated Routing: applications in location and inventory management2006Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Almost everywhere, routing plays an important role in everyday life. This thesis consists of three parts, each studying different applications where routing decisions are coordinated with other decisions. A common denominator in all applications is that an intelligent utilization of a fleet of vehicles is crucial for the performance of the system. In the first part, routing and inventorymanagement decisions are coordinated, in the second part, routing decisions concerning different modes of transportation are coordinated with inventory management, and in the third part, location decision and routing are coordinated.

    In the first part, an application concerning waste management is presented. Many industries generate garbage, and instead of handling the waste disposal themselves, other companies, specialized in garbage collection, handle the disposal. Each industry rents containers from a company to be used for waste, and the garbage collection companies handle the collection. The industries buy a service including one or more containers at the industry and the garbage collection companies are obliged to make sure that the containers never become overfull. The idea is that the industries buy this service and in return, the garbage collection company can plan the collection so that the overall cost and the number of overfull containers is minimized. Two models for the problem facing the garbage collection company are proposed. The first is solved using a Lagrangean relaxation approach on a flow based model, and the second is solved using Benders decomposition on a column based model.

    The second part investigates a distribution chain management problem taken from the Swedish pulp industry. Given fixed production plans at the mills, and fixed customer demands, the problem is to minimize the distribution cost. Unlike many other models for marine distribution chains, the customers are not located at the harbors. This means that the model proposed also incorporates the distribution planning from the harbors to the customers. All customers are not served from the harbors; some are served directly from the mills using trucks and trains to distribute the pulp, and these decisions are also included. The problem is modeled as a mixed integer linear program and solved using a branch and price scheme. Due to the complexity of the problem, the solution strategy is divided into two phases, where the first emphasizes the generation of schedules for the vessels operated by the company, while the second deals with the chartering of vessels on the spot market.

    In the third part, routing is combined with location decisions in the location-routing problem. Special emphasis is given to strategic management where decision makers must make location, capacity and routing decisions over a long planning period. The studied application comes fromstrategic schoolmanagement, where the location and capacity of the schools as well as their catchment areas are under consideration. The problem is modeled as a mixed integer linear program. The computational study shows the importance of incorporating

    a routing component allowing multiple visits, as well as the danger of having a too short planning period.

    Delarbeid
    1. A Lagrangean Based Heuristic for the Inventory Routing Problem
    Åpne denne publikasjonen i ny fane eller vindu >>A Lagrangean Based Heuristic for the Inventory Routing Problem
    2006 (engelsk)Inngår i: European Journal of Operational Research, ISSN 0377-2217Artikkel i tidsskrift (Fagfellevurdert) Submitted
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-13900 (URN)
    Tilgjengelig fra: 2006-07-12 Laget: 2006-07-12
    2. A pseudo Benders Decomposition Approach
    Åpne denne publikasjonen i ny fane eller vindu >>A pseudo Benders Decomposition Approach
    2002 (engelsk)Inngår i: Proceedings of Nordic MPS ’02, 2002Konferansepaper, Publicerat paper (Annet vitenskapelig)
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-13901 (URN)
    Tilgjengelig fra: 2006-07-12 Laget: 2006-07-12
    3. A Distribution Chain Management Problem in the Swedish Pulp Industry
    Åpne denne publikasjonen i ny fane eller vindu >>A Distribution Chain Management Problem in the Swedish Pulp Industry
    2006 (engelsk)Artikkel i tidsskrift (Fagfellevurdert) Submitted
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-13902 (URN)
    Tilgjengelig fra: 2006-07-12 Laget: 2006-07-12
    4. Decision Support for Distribution Chain Management: the Swedish Pulp Industry
    Åpne denne publikasjonen i ny fane eller vindu >>Decision Support for Distribution Chain Management: the Swedish Pulp Industry
    2004 (engelsk)Inngår i: 7th International Conference on Intelligent Transport Systems, 2004, s. 1051-1056Konferansepaper, Publicerat paper (Annet vitenskapelig)
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-13903 (URN)
    Tilgjengelig fra: 2006-07-12 Laget: 2006-07-12 Sist oppdatert: 2009-04-23
    5. Location-Routing Problems: An Annotated Bibliography
    Åpne denne publikasjonen i ny fane eller vindu >>Location-Routing Problems: An Annotated Bibliography
    2006 (engelsk)Artikkel i tidsskrift (Fagfellevurdert) Submitted
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-13904 (URN)
    Tilgjengelig fra: 2006-07-12 Laget: 2006-07-12
    6. The Relocation-Routing Problem
    Åpne denne publikasjonen i ny fane eller vindu >>The Relocation-Routing Problem
    2006 (engelsk)Artikkel i tidsskrift (Fagfellevurdert) Submitted
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-13905 (URN)
    Tilgjengelig fra: 2006-07-12 Laget: 2006-07-12
    Fulltekst (pdf)
    FULLTEXT01
  • 67.
    Andersson, Johanna
    et al.
    Linköpings universitet, Institutionen för utbildningsvetenskap.
    Melin, Nina
    Linköpings universitet, Institutionen för utbildningsvetenskap.
    Elevers upplevelser gällande särskilt stöd i matematik: Ur barns perspektiv2007Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Syftet med undersökningen var att klarlägga om elever med särskilt stöd i matematik visste varför de fick särskild undervisning. Ett annat syfte var också att ta reda på barnens delaktighet i beslutet och vad de kände angående undervisningen och gruppindelningen. Undersökningen utgår från ett barns perspektiv därmed var ambitionen att barnens egna tankar och värderingar tydligt skulle komma fram. För att uppnå det syftet intervjuade vi sju barn i årskurs fyra. Vi utgick från tre frågeställningar: På vilket sätt har eleven varit delaktig i beslutet om särskilt stöd i matematikundervisning? På vilket sätt har eleven särskilt stöd i matematikundervisningen, enligt eleven själv? Vad känner eleven angående särskilt stöd? Vi använde oss av en kvalitativ forskningsansats med observationer och semistrukturerade intervjuer. Vi bearbetade intervjuerna utifrån de tre frågeställningarna. Resultatet blev sex stycken kategorier dessa är: ingen delaktighet, osäkerhet, stress, arbetsro, utmaning och självförtroende. Den första frågan handlar om att vara delaktig vid beslut om att vara i den lilla gruppen för att få särskilt stöd i matematik. Det visade sig att samtliga elever inte varit delaktiga vid beslutet. Den andra frågan handlar om elevens egen uppfattning om anledningar till varför den var placerad i den lilla gruppen. Samtliga elever hade olika tolkningar. Den tredje frågan handlar om elevens känslor angående att ha särskilt stöd i matematik. Någon elev kände att den lilla gruppen medförde arbetsro då ljudnivån blev lägre med färre elever. Några elever kände hjälplöshet då fröken inte hann med att hjälpa alla. Då läraren lät eleven hoppa över de uppgifter den redan kunde kände eleven att den fick en lagom utmaning. De flesta barn som intervjuades hade en positiv självkänsla när det gällde matematik. Barnen själva ansåg sig vara duktiga på matematik.

    Fulltekst (pdf)
    FULLTEXT01
  • 68.
    Andersson, Jonathan
    Linköpings universitet, Matematiska institutionen, Matematik och tillämpad matematik. Linköpings universitet, Tekniska fakulteten.
    Asymptotic behavior and effective boundaries forage-structured population models in aperiodically changing environment2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Human activity and other events can cause environmental changes to the habitat of organisms. The environmental changes effect the vital rates for a population. In order to predict the impact of these environmental changes on populations, we use two different models for population dynamics. One simpler linear model that ignores environmental competition between individuals and another model that does not. Our population models take into consideration the age distribution of the population and thus takes into consideration the impact of demographics. This thesis generalize two theorems, one for each model, developed by Sonja Radosavljevic regarding long term upper and lower bounds of a population with periodic birth rate ; see [6] and [5]. The generalisation consist in including the case where the periodic part of the birth rate can be expressed with a finite Fourier series and also infinite Fourier series under some constraints. The old theorems only considers the case when the periodic part of the birth rate can be expressed with one cosine term. From the theorems we discover a connection between the frequency of oscillation and the effect on population growth. From this derived connection we conclude that periodical changing environments can have both positive and negative effects on the population.

    Fulltekst (pdf)
    fulltext
  • 69.
    Andersson, Jonathan
    et al.
    Linköpings universitet, Matematiska institutionen, Matematik och tillämpad matematik. Linköpings universitet, Tekniska fakulteten.
    Kozlov, Vladimir
    Linköpings universitet, Matematiska institutionen, Matematik och tillämpad matematik. Linköpings universitet, Tekniska fakulteten.
    Radosavljevic, Sonja
    Stockholm Resilience Centre, Stockholm University, Stockholm, Sweden.
    Tkachev, Vladimir
    Linköpings universitet, Matematiska institutionen, Matematik och tillämpad matematik. Linköpings universitet, Tekniska fakulteten.
    Wennergren, Uno
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Biologi. Linköpings universitet, Tekniska fakulteten.
    Density-Dependent Feedback in Age-Structured Populations2019Inngår i: Journal of Mathematical Sciences, ISSN 1072-3374, E-ISSN 1573-8795, Vol. 242, nr 1, s. 2-24Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The population size has far-reaching effects on the fitness of the population, that, in its turn influences the population extinction or persistence. Understanding the density- and age-dependent factors will facilitate more accurate predictions about the population dynamics and its asymptotic behaviour. In this paper, we develop a rigourous mathematical analysis to study positive and negative effects of increased population density in the classical nonlinear age-structured population model introduced by Gurtin \& MacCamy in the late 1970s. One of our main results expresses the global stability of the system in terms of the newborn function only. We also derive the existence of a threshold population size implying the population extinction, which is well-known in population dynamics as an Allee effect.

  • 70.
    Andersson, Lars-Erik
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Matematiska institutionen, Tillämpad matematik.
    A quasistatic frictional problem with normal compliance penalization term1999Inngår i: Nonlinear Analysis, ISSN 0362-546X, E-ISSN 1873-5215, Vol. 37, s. 689-705Artikkel i tidsskrift (Fagfellevurdert)
  • 71.
    Andersson, Lars-Erik
    Linköpings universitet, Matematiska institutionen, Matematik och tillämpad matematik. Linköpings universitet, Tekniska högskolan.
    Critical bounds for frictional rate- and wedging problems2010Konferansepaper (Annet vitenskapelig)
  • 72.
    Andersson, Lars-Erik
    Linköpings universitet, Matematiska institutionen, Matematik och tillämpad matematik. Linköpings universitet, Tekniska högskolan.
    Existence and uniqueness for thermoelastic contact2013Inngår i: Encyclopedia of Thermal Stresses / [ed] Hetnarski, Richard B., Springer, 2013, s. -6643Kapittel i bok, del av antologi (Annet vitenskapelig)
    Abstract [en]

    The Encyclopedia of Thermal Stresses is an important interdisciplinary reference work.  In addition to topics on thermal stresses, it contains entries on related topics, such as the theory of elasticity, heat conduction, thermodynamics, appropriate topics on applied mathematics, and topics on numerical methods. The Encyclopedia is aimed at undergraduate and graduate students, researchers and engineers. It brings together well established knowledge and recently received results. All entries were prepared  by leading experts from all over the world, and are presented in an easily accessible format. The work is lavishly illustrated, examples and applications are given where appropriate, ideas for further development abound, and the work will challenge many students and researchers to pursue new results of their own. This work can also serve as a one-stop resource for all who need succinct, concise, reliable and up to date information in short encyclopedic entries, while the extensive references will be of interest to those who need further information. For the coming decade, this is likely to remain the most extensive and authoritative work on Thermal Stresses

  • 73.
    Andersson, Lars-Erik
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Matematiska institutionen, Tillämpad matematik.
    Quasistatic frictional contact problems with finitely many degrees of freedom.1999Rapport (Annet vitenskapelig)
    Abstract [en]

    In the present paper results on existence and uniqueness of solutions to discrete frictional quasi-static unilateral contact problems are given under a condition that the coefficients of friction are smaller than a certain upper bound. This upper bound is defined in terms of an influence matrix for the contact nodes. The results of existence and uniqueness may be ordered into two classes depending on whether regularity conditions for the applied forces are imposed or not. For general loading which has a time derivative almost everywhere it is shown that a solution exists which satisfies governing equations for almost all times. Uniqueness of the solution has been shown only when the problem is restricted to two degrees of freedom. For a loading which is right piecewise analytic, additional results can be obtained. For instance, if each contact node has only two degrees of freedom a unique solution which satisfies governing equeations for all times exists. For the constructed solutions a priori estimates of the displacement field and its time derivate in terms of the applied forces are also given.

    Fulltekst (pdf)
    Quasistatic frictional contact problems with finitely many degrees of freedom
  • 74.
    Andersson, Lars-Erik
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Matematiska institutionen, Tillämpad matematik.
    Quasistatic frictional contact problems with finitely many degrees of freedom. Existence and uniqueness2002Inngår i: WE-Hereus Seminar on Contact and Fracture Problems,2002, 2002Konferansepaper (Annet vitenskapelig)
  • 75.
    Andersson, Lars-Erik
    et al.
    Linköpings universitet, Matematiska institutionen, Matematik och tillämpad matematik. Linköpings universitet, Tekniska högskolan.
    Barber, J. R.
    University of Michigan, MI 48109 USA.
    Ponter, A. R. S.
    University of Leicester, England.
    Existence and uniqueness of attractors in frictional systems with uncoupled tangential displacements and normal tractions2014Inngår i: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 51, nr 21-22, s. 3710-3714Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We consider the class of two or three-dimensional discrete contact problems in which a set of contact nodes can make frictional contact with a corresponding set of rigid obstacles. Such a system might result from a finite element discretization of an elastic contact problem after the application of standard static reduction operations. The Coulomb friction law requires that the tractions at any point on the contact boundary must lie within or on the surface of a friction cone, but the exact position of any stuck node (i.e., a node where the tractions are strictly within the cone) depends on the initial conditions and/or the previous history of loading. If the long-term loading is periodic in time, we anticipate that the system will eventually approach a steady periodic cycle. Here we prove that if the elastic system is uncoupled, meaning that changes in slip displacements alone have no effect on the instantaneous normal contact reactions, the time-varying terms in this steady cycle are independent of initial conditions. In particular, we establish the existence of a unique permanent stick zone T comprising the set of all nodes that do not slip after some finite number of cycles. We also prove that the tractions and slip velocities at all nodes not contained in T approach unique periodic functions of time, whereas the (time-invariant) slip displacements in T may depend on initial conditions. Typical examples of uncoupled systems include those where the contact surface is a plane of symmetry, or where the contacting bodies can be approximated locally as half spaces and Dundurs mismatch parameter beta = 0. An important consequence of these results is that systems of this kind will exhibit damping characteristics that are independent of initial conditions. Also, the energy dissipated at each slipping node in the steady state is independent of initial conditions, so wear patterns and the incidence of fretting fatigue failure should also be so independent.

  • 76.
    Andersson, Lars-Erik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Matematiska institutionen, Tillämpad matematik.
    Khludnev, Alexander
    Lavrentiev Institute of Hydrodynamics Russian Academie of Sciences, Novosibirsk.
    On crack crossing a contact boundary. Fictitious domain method and invariant integrals (Russian) .2008Inngår i: Siberian journal of industrial mathematics, ISSN 1560-7518, Vol. 11, nr 3, s. 15-29Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

        

  • 77.
    Andersson, Lars-Erik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Matematiska institutionen, Tillämpad matematik.
    Klarbring, Anders
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Mekanik.
    A review of the theory of static and quasi-static frictional contact problems in elasticity2001Inngår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 359, s. 2519-2539Artikkel i tidsskrift (Fagfellevurdert)
  • 78.
    Andersson, Lars-Erik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Matematiska institutionen, Tillämpad matematik.
    Klarbring, Anders
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Mekanik.
    A Survey of Basic Mathematical Results for Frictional Contact Problems2001Inngår i: From Convexity to Nonconvexity / [ed] Robert P Gilbert; P D Panagiotopoulos; P M Pardalos, Dordrecht/Boston/London: Kluwer , 2001, s. -392Kapittel i bok, del av antologi (Annet vitenskapelig)
    Abstract [en]

    Contains a collection of invited papers dedicated to the memory of two great mathematicians, Gaetano Fichera and Panagis Panagiotopoulos. The book is centered around the seminal research of G Fichera on the Signorini problem, hemivariational inequalities, nonsmooth global optimization, and regularity results for variational inequatities.

  • 79.
    Andersson, Lars-Erik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Matematiska institutionen, Tillämpad matematik.
    Klarbring, Anders
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Mekanik.
    Existence and uniqueness for quasistatic contact problems with friction2001Inngår i: CMIS 2001, third Contact Mechanics International Symposiium,2001, Dordrecht: Kluwer , 2001, s. 245-Konferansepaper (Fagfellevurdert)
  • 80.
    Andersson, Lars-Erik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Matematiska institutionen, Tillämpad matematik.
    Klarbring, Anders
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Mekanik.
    Quasi-static Frictional Contact of Discrete Mechanical Structures2000Inngår i: European journal of mechanics. A, Solids, ISSN 0997-7538, E-ISSN 1873-7285, Vol. 19, s. S61-S67Artikkel i tidsskrift (Fagfellevurdert)
  • 81.
    Andersson, Lars-Erik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Matematiska institutionen, Tillämpad matematik.
    Peters, T.J.
    Computer Science Engineering University of Connecticut.
    Stewart, N.F.
    Dept IRO Universite de Montreal.
    Equivalence of topological form for curvilinear geometric objects2000Inngår i: International journal of computational geometry and applications, ISSN 0218-1959, Vol. 10, nr 6, s. 609-622Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Given a curvilinear geometric object in R3, made up of properly-joined parametric patches defined in terms of control points, it is of interest to know under what conditions the object will retain its original topological form when the control points are perturbed. For example, the patches might be triangular BΘzier surface patches, and the geometric object may represent the boundary of a solid in a solid-modeling application. In this paper we give sufficient conditions guaranteeing that topological form is preserved by an ambient isotopy. The main conditions to be satisfied are that the original object should be continuously perturbed in a way that introduces no self-intersections of any patch, and such that the patches remain properly joined. The patches need only have C0 continuity along the boundaries joining adjacent patches. The results apply directly to most surface modeling schemes, and they are of interest in several areas of application.

  • 82.
    Andersson, Lars-Erik
    et al.
    Linköpings universitet, Matematiska institutionen, Matematik och tillämpad matematik. Linköpings universitet, Tekniska högskolan.
    Pinto da Costa, A.
    University of Lisbon, Portugal.
    Agwa, M. A.
    Zagazig University, Egypt.
    Existence and uniqueness for frictional incremental and rate problems - sharp critical bounds2016Inngår i: Zeitschrift für angewandte Mathematik und Mechanik, ISSN 0044-2267, E-ISSN 1521-4001, Vol. 96, nr 1, s. 78-105Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We investigate frictional contact problems for discrete linear elastic structures, in particular the quasistatic incremental problem and the rate problem. It is shown that sharp conditions on the coefficients of friction for unique solvability of these problems are the same. We also give explicit expressions of these critical bounds by using a method of optimization. For the case of two spatial dimensions the conditions are formulated as a huge set of non symmetric eigenvalue problem. A computer program for solving these problems was designed and used to compute the critical bounds for some structures of relative small size, some of which appeared in the literature. The results of a variety of numerical experiments with uniform and non uniform distributions of the frictional properties are presented. (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • 83.
    Andersson, Lars-Erik
    et al.
    Linköpings universitet, Matematiska institutionen, Tillämpad matematik. Linköpings universitet, Tekniska högskolan.
    Rietz, Andreas
    Linköpings universitet, Matematiska institutionen, Tillämpad matematik. Linköpings universitet, Tekniska högskolan.
    Existence theorems for noncoercive incremental contact problems with Coulomb friction2006Inngår i: Analysis and Simulation of Contact Problems / [ed] Peter Wriggers and Udo Nackenhorst, Springer Berlin/Heidelberg, 2006, s. 121-128Kapittel i bok, del av antologi (Annet vitenskapelig)
    Abstract [en]

    For static or incremental contact problems with Coulomb friction there are satisfactory and well known existence results for the coercive case, i.e., when the elastic body is anchored so that rigid body motions are not possible, see [3, 1, 6, 7, 2]. The articles by Jaruusek and Cocu, [7, 2] indeed contain results for the noncoercive case, i.e., when rigid body motions are possible. However, the compatibility conditions which are used to ensure the existence of a solution, are the same that guarantee that the corresponding contact problem without friction has a solution. The condition is essentially that the applied force field should push the elastic body towards the obstacle. One of few previous articles containing friction-dependent compatibility conditions is.

  • 84.
    Andersson, Lars-Erik
    et al.
    Linköpings universitet, Matematiska institutionen, Matematik och tillämpad matematik. Linköpings universitet, Tekniska högskolan.
    Stewart, Neil F.
    Université de Montréal, Montréal, Canada.
    Introduction to the Mathematics of Subdivision Surfaces2010Bok (Annet vitenskapelig)
    Abstract [en]

    Subdivision surfaces permit a designer to specify the approximate form of a surface defining an object and to refine and smooth the form to obtain a more useful or attractive version of the surface.

    A considerable amount of mathematical theory is required to understand the characteristics of the resulting surfaces, and this book

    • provides a careful and rigorous presentation of the mathematics underlying subdivision surfaces as used in computer graphics and animation, explaining the concepts necessary to easily read the subdivision literature;

    • organizes subdivision methods into a unique and unambiguous hierarchy to facilitate insight and understanding;

    • gives a broad discussion of the various methods and is not restricted to questions related to regularity of subdivision surfaces at so-called extraordinary points.

    Introduction to the Mathematics of Subdivision Surfaces is excellent preparation for reading more advanced texts that delve more deeply into special questions of regularity. The authors provide exercises and projects at the end of each chapter. Course material, including solutions to the exercises, is available on an associated Web page.

  • 85.
    Andersson, Lars-Erik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Matematiska institutionen, Tillämpad matematik.
    Stewart, Neil F.
    IRO Universite de Montreal.
    Zidani, M.
    IRO Universite de Montreal.
    Conditions for use of a non-selfintersection conjecture2006Inngår i: Computer Aided Geometric Design, ISSN 0167-8396, E-ISSN 1879-2332, Vol. 23, nr 7, s. 599-611Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Volino and Thalmann have published a conjecture proposing sufficient conditions for non-selfintersection of surfaces. Such conditions may be used in solid modeling, computer graphics, and other application areas, as a basis for collision-detection algorithms. In this paper we clarify certain of the hypotheses of the proposed theorem, and give a proof. A brief summary of possible pitfalls related to using the conditions, when the hypotheses of the formal theorem given here are not satisfied, is also given. We also give examples, and show that the theorem can be extended to domains that are not simply connected. © 2006 Elsevier B.V. All rights reserved.

  • 86.
    Andersson, Lars-Erik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Matematiska institutionen, Tillämpad matematik.
    Stewart, Neil F.
    Departement IRO Universite de Montreal.
    Zidani, Malika
    Departement IRO Universite de Montreal.
    Error analysis for operations in solid modeling in the presence of uncertainty2008Inngår i: SIAM Journal on Scientific Computing, ISSN 1064-8275, E-ISSN 1095-7197, Vol. 29, nr 2, s. 811-826Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The problem of maintaining consistent representations of solids in computer-aided design and of giving rigorous proofs of error bounds for operations such as regularized Boolean intersection has been widely studied for at least two decades. One of the major difficulties is that the representations used in practice not only are in error but are fundamentally inconsistent. Such inconsistency is one of the main bottlenecks in downstream applications. This paper provides a framework for error analysis in the context of solid modeling, in the case where the data is represented using the standard representational method, and where the data may be uncertain. Included are discussions of ill-condition, error measurement, stability of algorithms, inconsistency of defining data, and the question of when we should invoke methods outside the scope of numerical analysis. A solution to the inconsistency problem is proposed and supported by theorems: it is based on the use of Whitney extension to define sets, called Quasi-NURBS sets, which are viewed as realizations of the inconsistent data provided to the numerical method. A detailed example illustrating the problem of regularized Boolean intersection is also given.    

  • 87.
    Andersson, Lars-Erik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Matematiska institutionen, Tillämpad matematik.
    Stewart, N.F.
    IRO Universite de Montreal.
    Zidani, M.
    IRO Universite de Montreal.
    Proof of a non-selfintersection conjecture2006Rapport (Annet vitenskapelig)
  • 88.
    Andersson, Malin
    Linköpings universitet, Institutionen för utbildningsvetenskap.
    Hur tänker flickor och pojkar om matematik? En enkät- och intervjustudie av elever i år 62002Independent thesis Basic level (professional degree)Oppgave
    Abstract [sv]

    Mitt syfte med det här arbetet har varit att ta reda på vad flickor och pojkar tänker om matematik. Mina frågeställningar har varit: Hur tänker flickor och pojkar om matematik? Hur kan läraren genom sin undervisning göra matematiken intressant och begriplig för både flickor och pojkar? För att söka svar på mina frågeställningar har jag valt att använda mig av litteraturstudier och mpiriska studier.

    Arbetet består först av en litteraturgenomgång, där jag tittat på vad tidigare forskning säger om flickors och pojkars tankar om matematik. Efter litteraturgenomgången kommer den empiriska delen, där resultatet från min enkätundersökning med 76 elever, och resultatet från min intervjuundersökning med 10 elever ingår.

    Flickornas och pojkarnas uppfattningar och tankar om matematiken från min undersökning stämmer i mångt och mycket överens med resultat från tidigare forskning. I min undersökning har jag kommit fram till att eleverna har ett emotionellt förhållningssätt till matematiken, och så ser de matematiken som ett skolämne. Det är viktigt med variation i undervisningen och att eleverna känner att de lär sig något. Nästan alla eleverna är överens om att matematik är ett viktigt ämne, men många har svårt att svara på varför. I min undersökning har jag tittat på likheter och skillnader mellan flickorna och pojkarna. Den största skillnaden jag hittat, är att pojkarna självvärderar sig högre än flickorna på matematiken.

    Fulltekst (pdf)
    FULLTEXT01
  • 89.
    Andersson, Mats
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska högskolan.
    Burdakov, Oleg
    Linköpings universitet, Matematiska institutionen, Optimeringslära. Linköpings universitet, Tekniska högskolan.
    Knutsson, Hans
    Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska högskolan.
    Zikrin, Spartak
    Linköpings universitet, Matematiska institutionen, Matematik och tillämpad matematik. Linköpings universitet, Tekniska högskolan.
    Global search strategies for solving multilinear least-squares problems2012Inngår i: Sultan Qaboos University Journal for Science, ISSN 1027-524X, Vol. 17, nr 1, s. 12-21Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The multilinear least-squares (MLLS) problem is an extension of the linear leastsquares problem. The difference is that a multilinear operator is used in place of a matrix-vector product. The MLLS is typically a large-scale problem characterized by a large number of local minimizers. It originates, for instance, from the design of filter networks. We present a global search strategy that allows for moving from one local minimizer to a better one. The efficiency of this strategy is illustrated by results of numerical experiments performed for some problems related to the design of filter networks.

    Fulltekst (pdf)
    TR2011-17
  • 90.
    Andersson, Mats
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska högskolan.
    Burdakov, Oleg
    Linköpings universitet, Matematiska institutionen, Optimeringslära. Linköpings universitet, Tekniska högskolan.
    Knutsson, Hans
    Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska högskolan.
    Zikrin, Spartak
    Linköpings universitet, Matematiska institutionen. Linköpings universitet, Tekniska högskolan.
    Global Search Strategies for Solving Multilinear Least-squares Problems2011Rapport (Annet vitenskapelig)
    Abstract [en]

    The multilinear least-squares (MLLS) problem is an extension of the linear least-squares problem. The difference is that a multilinearoperator is used in place of a matrix-vector product. The MLLS istypically a large-scale problem characterized by a large number of local minimizers. It originates, for instance, from the design of filter networks. We present a global search strategy that allows formoving from one local minimizer to a better one. The efficiencyof this strategy isillustrated by results of numerical experiments performed forsome problems related to the design of filter networks.

    Fulltekst (pdf)
    Global Search Strategies for Solving Multilinear Least-squares Problems
  • 91.
    Andersson, Mats
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Burdakov, Oleg
    Linköpings universitet, Matematiska institutionen, Optimeringslära. Linköpings universitet, Tekniska högskolan.
    Knutsson, Hans
    Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska högskolan.
    Zikrin, Spartak
    Linköpings universitet, Matematiska institutionen. Linköpings universitet, Tekniska högskolan.
    Sparsity Optimization in Design of Multidimensional Filter Networks2013Rapport (Annet vitenskapelig)
    Abstract [en]

    Filter networks is a powerful tool used for reducing the image processing time, while maintaining its reasonably high quality.They are composed of sparse sub-filters whose low sparsity ensures fast image processing.The filter network design is related to solvinga sparse optimization problem where a cardinality constraint bounds above the sparsity level.In the case of sequentially connected sub-filters, which is the simplest network structure of those considered in this paper, a cardinality-constrained multilinear least-squares (MLLS) problem is to be solved. If to disregard the cardinality constraint, the MLLS is typically a large-scale problem characterized by a large number of local minimizers. Each of the local minimizers is singular and non-isolated.The cardinality constraint makes the problem even more difficult to solve.An approach for approximately solving the cardinality-constrained MLLS problem is presented.It is then applied to solving a bi-criteria optimization problem in which both thetime and quality of image processing are optimized. The developed approach is extended to designing filter networks of a more general structure. Its efficiency is demonstrated by designing certain 2D and 3D filter networks. It is also compared with the existing approaches.

    Fulltekst (pdf)
    Sparsity Optimization in Design of Multidimensional Filter Networks (revised version)
  • 92.
    Andersson, Mats
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska högskolan. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Burdakov, Oleg
    Linköpings universitet, Matematiska institutionen, Optimeringslära. Linköpings universitet, Tekniska högskolan.
    Knutsson, Hans
    Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska högskolan.
    Zikrin, Spartak
    Linköpings universitet, Matematiska institutionen, Optimeringslära. Linköpings universitet, Tekniska högskolan.
    Sparsity Optimization in Design of Multidimensional Filter Networks2015Inngår i: Optimization and Engineering, ISSN 1389-4420, E-ISSN 1573-2924, Vol. 16, nr 2, s. 259-277Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Filter networks are used as a powerful tool used for reducing the image processing time and maintaining high image quality.They are composed of sparse sub-filters whose high sparsity ensures fast image processing.The filter network design is related to solvinga sparse optimization problem where a cardinality constraint bounds above the sparsity level.In the case of sequentially connected sub-filters, which is the simplest network structure of those considered in this paper, a cardinality-constrained multilinear least-squares (MLLS) problem is to be solved. Even when disregarding the cardinality constraint, the MLLS is typically a large-scale problem characterized by a large number of local minimizers, each of which is singular and non-isolated.The cardinality constraint makes the problem even more difficult to solve.

    An approach for approximately solving the cardinality-constrained MLLS problem is presented.It is then applied to solving a bi-criteria optimization problem in which both thetime and quality of image processing are optimized. The developed approach is extended to designing filter networks of a more general structure. Its efficiency is demonstrated by designing certain 2D and 3D filter networks. It is also compared with the existing approaches.

    Fulltekst (pdf)
    fulltext
  • 93.
    Andersson Naesseth, Christian
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Nowcasting using Microblog Data2012Independent thesis Basic level (degree of Bachelor), 10,5 poäng / 16 hpOppgave
    Abstract [en]

    The explosion of information and user generated content made publicly available through the internet has made it possible to develop new ways of inferring interesting phenomena automatically. Some interesting examples are the spread of a contagious disease, earth quake occurrences, rainfall rates, box office results, stock market fluctuations and many many more. To this end a mathematical framework, based on theory from machine learning, has been employed to show how frequencies of relevant keywords in user generated content can estimate daily rainfall rates of different regions in Sweden using microblog data.

    Microblog data are collected using a microblog crawler. Properties of the data and data collection methods are both discussed extensively. In this thesis three different model types are studied for regression, linear and nonlinear parametric models as well as a nonparametric Gaussian process model. Using cross-validation and optimization the relevant parameters of each model are estimated and the model is evaluated on independent test data. All three models show promising results for nowcasting rainfall rates.

    Fulltekst (pdf)
    fulltext
  • 94.
    Andersson Naesseth, Christian
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Statistik och maskininlärning. Linköpings universitet, Tekniska fakulteten.
    Lindsten, Fredrik
    Linköpings universitet, Institutionen för datavetenskap, Statistik och maskininlärning. Linköpings universitet, Tekniska fakulteten.
    Schon, Thomas B.
    Uppsala Univ, Sweden.
    High-Dimensional Filtering Using Nested Sequential Monte Carlo2019Inngår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 67, nr 16, s. 4177-4188Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sequential Monte Carlo (SMC) methods comprise one of the most successful approaches to approximate Bayesian filtering. However, SMC without a good proposal distribution can perform poorly, in particular in high dimensions. We propose nested sequential Monte Carlo, a methodology that generalizes the SMC framework by requiring only approximate, properly weighted, samples from the SMC proposal distribution, while still resulting in a correctSMCalgorithm. This way, we can compute an "exact approximation" of, e. g., the locally optimal proposal, and extend the class of models forwhichwe can perform efficient inference using SMC. We showimproved accuracy over other state-of-the-art methods on several spatio-temporal state-space models.

    Fulltekst (pdf)
    fulltext
  • 95.
    Andersson Naesseth, Christian
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Lindsten, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Schön, Thomas
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Capacity estimation of two-dimensional channels using Sequential Monte Carlo2014Inngår i: 2014 IEEE Information Theory Workshop, 2014, s. 431-435Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We derive a new Sequential-Monte-Carlo-based algorithm to estimate the capacity of two-dimensional channel models. The focus is on computing the noiseless capacity of the 2-D (1, ∞) run-length limited constrained channel, but the underlying idea is generally applicable. The proposed algorithm is profiled against a state-of-the-art method, yielding more than an order of magnitude improvement in estimation accuracy for a given computation time.

    Fulltekst (pdf)
    fulltext
  • 96.
    Andersson Naesseth, Christian
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Lindsten, Fredrik
    The University of Cambridge, Cambridge, United Kingdom.
    Schön, Thomas
    Uppsala University, Uppsala, Sweden.
    Nested Sequential Monte Carlo Methods2015Inngår i: Proceedings of The 32nd International Conference on Machine Learning / [ed] Francis Bach, David Blei, Journal of Machine Learning Research (Online) , 2015, Vol. 37, s. 1292-1301Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We propose nested sequential Monte Carlo (NSMC), a methodology to sample from sequences of probability distributions, even where the random variables are high-dimensional. NSMC generalises the SMC framework by requiring only approximate, properly weighted, samples from the SMC proposal distribution, while still resulting in a correct SMC algorithm. Furthermore, NSMC can in itself be used to produce such properly weighted samples. Consequently, one NSMC sampler can be used to construct an efficient high-dimensional proposal distribution for another NSMC sampler, and this nesting of the algorithm can be done to an arbitrary degree. This allows us to consider complex and high-dimensional models using SMC. We show results that motivate the efficacy of our approach on several filtering problems with dimensions in the order of 100 to 1 000.

    Fulltekst (pdf)
    fulltext
  • 97.
    Andersson Naesseth, Christian
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Lindsten, Fredrik
    University of Cambridge, Cambridge, UK.
    Schön, Thomas
    Uppsala University, Uppsala, Sweden.
    Sequential Monte Carlo for Graphical Models2014Inngår i: Advances in Neural Information Processing Systems, 2014, s. 1862-1870Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We propose a new framework for how to use sequential Monte Carlo (SMC) algorithms for inference in probabilistic graphical models (PGM). Via a sequential decomposition of the PGM we find a sequence of auxiliary distributions defined on a monotonically increasing sequence of probability spaces. By targeting these auxiliary distributions using SMC we are able to approximate the full joint distribution defined by the PGM. One of the key merits of the SMC sampler is that it provides an unbiased estimate of the partition function of the model. We also show how it can be used within a particle Markov chain Monte Carlo framework in order to construct high-dimensional block-sampling algorithms for general PGMs.

    Fulltekst (pdf)
    fulltext
  • 98.
    Andersson, Niclas
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Compilation of mathematical models to parallel code1996Licentiatavhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    Generating parallel code from high-level mathematical models is in its general form an intractable problem. Rather than trying to solve this problem, a more realistic approach is to solve specific problem instances for limited domains.In this thesis, we focus our efforts on problems where the main computation is to solve ordinary differential equation systems. When solving such a system of equations, the major part of the computing time is spent in application specific code, rather than in the serial solver kernel. By applying domain specific knowledge, we can generate efficient parallel code for numerical solution.We investigate automatic parallelisation of the computation of ordinary differential equation systems at three different levels of granularity: equation system level, equation level, and clustered task level. At the clustered task level we employ existing scheduling and clustering algorithms to partition and distribute the computation.Moreover, an interface is provided to express explicit parallelism through annotations in the the mathematical model.This work is performed in the context of ObjectMath, a programming environment and modelling language that supports classes of equation objects, inheritance of equations, and solving systems of equations. The environment is designed to handle realistic problems.

  • 99.
    Andersson, Niklas
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Statistik.
    Hansson, Josef
    Linköpings universitet, Institutionen för datavetenskap, Statistik.
    Metodik för detektering av vägåtgärder via tillståndsdata2010Independent thesis Advanced level (degree of Master (One Year)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The Swedish Transport Administration has, and manages, a database containing information of the status of road condition on all paved and governmental operated Swedish roads. The purpose of the database is to support the Pavement Management System (PMS). The PMS is used to identify sections of roads where there is a need for treatment, how to allocate resources and to get a general picture of the state of the road network condition. All major treatments should be reported which has not always been done.

    The road condition is measured using a number of indicators on e.g. the roads unevenness. Rut depth is an indicator of the roads transverse unevenness. When a treatment has been done the condition drastically changes, which is also reflected by these indicators.

    The purpose of this master thesis is to; by using existing indicators make predictions to find points in time when a road has been treated.

    We have created a SAS-program based on simple linear regression to analyze rut depth changes over time. The function of the program is to find levels changes in the rut depth trend. A drastic negative change means that a treatment has been made.

    The proportion of roads with an alleged date for the latest treatment earlier than the programs latest detected date was 37 percent. It turned out that there are differences in the proportions of possible treatments found by the software and actually reported roads between different regions. The regions North and Central have the highest proportion of differences. There are also differences between the road groups with various amount of traffic. The differences between the regions do not depend entirely on the fact that the proportion of heavily trafficked roads is greater for some regions.

    Fulltekst (pdf)
    FULLTEXT01
  • 100.
    Andersson, Per Gösta
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Matematiska institutionen, Matematisk statistik.
    A conditional perspective of weighted variance estimation of regression estimator2003Rapport (Annet vitenskapelig)
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