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  • 251.
    Connors, Richard
    et al.
    Institute for Transport Studies, Leeds University, Leeds, England, UK.
    Patriksson, Michael
    Department of Mathematical Sciences, Chalmers University of Technology, Gothenburg, Sweden.
    Rydergren, Clas
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Sumalee, Agachai
    King Mongkut’s Institute of Technology Ladkrabang, Thailand.
    Watling, David
    Institute for Transport Studies, Leeds University, Leeds, England, UK.
    Sensitivity Analysis of Welfare, Equity, and Acceptability Level of Transport Policies2015In: Optimization, Control, and Applications in the Information Age: In Honor of Panos M. Pardalos’s 60th Birthday / [ed] Athanasios Migdalas, Athanasia Karakitsiou, London: Springer Publishing Company, 2015, p. 39-65Chapter in book (Refereed)
    Abstract [en]

    Transport planners face a major challenge to devise policies to meet multiple expectations and objectives. While we know that transport networks are complex, multi-modal, and spatially distributed systems, there is now a long history of mathematical tools which assist planners in understanding travel movements. However, the objectives that they are asked to achieve do not always admit such a quantification, and so there is a potential mismatch between seemingly qualitatively driven objectives and quantitatively expressed models of the transport system. In the present chapter we address this mismatch, by focusing on three objectives that we believe represent the typical interests of a planner. These are namely: is the policy economically justifiable (efficient), is it “fair” (equitable), and is it justifiable to a democratic society (acceptable)? We provide mathematical representations of these three objectives and link them to mathematical theory of transport networks, in which we may explore the sensitivity of travel behaviour (and hence the objectives) to various multi-modal transport policies. The detailed steps for representing the policy objectives and sensitivities in the network are set out, and the results of a case study reported in which road tolls, road capacities, and bus fares are the policy variables. Overall, the chapter sets out a systematic method for planners to choose between multi-modal policies based on these three objectives.

  • 252.
    Corneliusson, Malin
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Emanuelsson, Karin
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    An analysis of flow of information at material receiving: with focus on a third party logistics within industry- and construction support2018Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    Allt fler företag väljer att lägga ut sin logistikverksamhet på ett tredjepartlogistikföretag för att möta kundbehovet. Ett av dessa företag är Servistik. Servistik vill utveckla informationshantering för att skapa ytterligare effektivitet. Detta examensarbete syftar till att ge förståelse för hur information hanteras i nuläget, likheter och skillnader i informationshantering och hur det påverkar Servistik. Examensarbetet är avgränsat till informationshantering på fyra godsmottagningar tillhörande två av Servistiks dotterbolag. För att samla in data gällande informationshanteringen i nuläget har alla fyra godsmottagningar besökts och intervjuer samt observationer har genomförts. Två olika metoder används för att säkerställa sanningshalten i insamlad data. Ytterligare har även olika personer inom liknande områden observerats och intervjuats för att nå hög tillförlitlighet. Datainsamlingen har skapat förståelse för nuläget och vilka moment som ingår i godsmottagningsprocessen. De moment som ingår är lossning, ankomstregistrering, skanning och inre spridning. Likheter och skillnader har identifierats; en av likheterna är bristande inflöde av information. Det skapar problem och avbrott inom alla moment samt mer arbete för både godsmottagare och kund då de behöver tillhandahålla information som saknas. De likheter och skillnader som har identifierats påverkar främst Servistiks möjlighet till ökad effektivitet. De faktorer som påverkas är bättre och förenklad hantering kring information, inhämtandet av information samt förmedlade av information. I nuläget används verktyg på godsmottagningarna som kan bidra till ökad effektivitet. Genom att ta del av varandras verktyg kan godsmottagningarna och medarbetarna utvecklas till att arbeta på ett standardiserat sätt. Detta bidrar även till social hållbarhet inom företaget då alla arbetar mot gemensamma mål. För att effektivisera informationshanteringen kan det tillgängliga IT-systemet utvecklas för att möta grundläggande standarder som specificeras efter branschens behov. IT-system kan skapa statistik i samband med att ett moment utförs och skapa ett underlag hur väl godsmottagningarna presterar. Underlaget kan även användas för att tydliggöra fel och brister som finns och uppstår vid informationshantering.

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    An analysis of flow of information at material receiving: with focus on a third party logistics within industry- and construction support
  • 253.
    Daescu, Ovidiu
    et al.
    University of Texas at Dallas, Richardson, TX, USA.
    Friedrichs, Stephan
    Max Planck Institute for Informatics, Saarbrücken, Germany; Saarbrücken Graduate School of Computer Science, Saarbrücken, Germany.
    Malik, Hemant
    University of Texas at Dallas, Richardson, TX, USA.
    Polishchuk, Valentin
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Schmidt, Christiane
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Altitude Terrain Guarding and Guarding Uni-Monotone Polygons2019In: Computational geometry, ISSN 0925-7721, E-ISSN 1879-081XArticle in journal (Refereed)
    Abstract [en]

    We present an optimal, linear-time algorithm for the following version of terrain guarding: given a 1.5D terrain and a horizontal line, place the minimum number of guards on the line to see all of the terrain. We prove that the cardinality of the minimum guard set coincides with the cardinality of a maximum number of “witnesses”, i.e., terrain points, no two of which can be seen by a single guard. We show that our results also apply to the Art Gallery problem in “monotone mountains”, i.e., x-monotone polygons with a single edge as one of the boundary chains. This means that any monotone mountain is “perfect” (its guarding number is the same as its witness number); we thus establish the first non-trivial class of perfect polygons.

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  • 254.
    Dahl, Valerie
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Davidsson, Mikael
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Route flow estimation based on time-dependent route choice sets and historical travel times2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Since congestion leads to variations in travel time which gives a variation in the traffic flow, it is interesting to estimate the traffic flow in larger cities where cars drive in a limited space. In order to estimate the traffic flow, different traffic models are usually used. These models often use volume-delay functions which calculate the travel times for each link depending on the current traffic flow. However, in these models, the process for reaching equilibrium can be time consuming and it is hard to calibrate the volume-delay functions for a road network with a large set of links. Instead, we assume that it is relatively simply to measure or collect historical time-dependent travel times on a large set of links. With this assumption, a method that uses time-dependent route choice sets and time-dependent travel times in order to estimate time-dependent route flows, is developed.

    In this thesis, the method was applied to Stockholm County where it is interesting to study the route choice since congestion occurs in the area which generate variations in travel time. In order to estimate time-dependent route flows, a time-sliced OD-matrix was created by dividing the matrix for the peak hour using two different time-slicing distributions.

    The time-dependent route choice set with time-dependent travel times was created by using an existing route planning tool. These routes were mapped to the links in a road network in order to estimate link flows. The mapping was done by using map matching and a shortest path algorithm. Route shares were decided by using a method that splits the demand equally among the routes in the route choice set for an OD-pair, and with a logit model that takes travel time into account with the assumption that the travel time can affect a traveler’s route choice.

    The evaluation of the resulting link flows was done by comparing these link flows with observed link flows using different time-slicing distributions and route share models. Furthermore, the method’s resulting link flows was evaluated against the resulting link flows from a scenario where all travelers are assumed to choose the shortest path, in terms of free flow travel time, between each OD-pair.

    The developed method can estimate link flows so that 27.9 % of the links have a GEH value less than 5, which can be compared to the commonly used acceptance criteria of 85 %. This shows that the method needs to be developed further in order to achieve link flow estimations that fulfills the acceptance criteria. Even though the overall result show that the developed method does not fulfill the acceptance criteria, the method works well on some individual links. Furthermore, the resulting link flows from the developed method match the observed link flows better than the resulting link flows from the scenario where all travelers are assumed to choose the shortest path.

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  • 255. Order onlineBuy this publication >>
    Dahlberg, Joen
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Cooperative Transportation Planning and Cost Allocation2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    A freight forwarder may consolidate its goods transportations in order to achieve a more efficient operation. When goods transportations are consolidated, they may reduce operational costs, e.g. labor and fuel. This can be further improved if a number of freight forwarders cooperate and consolidate their collective goods transportations, i.e. it is a cooperation between competitors, a coopetition. In order to maintain the cooperation, a suitable business model, in which fair cost allocations plays an important role is essential. The potential by cooperating is not exclusive to freight forwarders, but in fact, any type of goods transportation planning may benefit from cooperation. In this thesis, cooperative game theory is used as an academic tool to study cooperation between stakeholders in different transportation planning applications. Cooperative game theory defines a number of criteria for fair cost allocations.

    In Paper 1, the role of the municipality as an enabler of a cooperation between fictitious freight forwarders in an urban area, is studied. In this case, the municipality acts as a stakeholder with unusual characteristics. It is shown that a stable cooperation can be achieved if the municipality is willing to carry some of the cost. This cost is specified and discussed in Paper 1. The results of Paper 2 contribute to game theory by introducing a further development of a cost allocation method. Some small numerical examples are presented in order to illustrate the resulting changes. In Paper 3, the process of establishing a cooperation is studied, where the stakeholders, in this case forest companies, join the cooperation sequentially. Who will join and in what order, is not predetermined. It is shown that a stable cooperation can be achieved despite the uncertainty. This is done by using the cost allocation methods presented.

    List of papers
    1. Consolidation in Urban Freight Transportation - Cost Allocation Models
    Open this publication in new window or tab >>Consolidation in Urban Freight Transportation - Cost Allocation Models
    2018 (English)In: Asia-Pacific journal of operational research, ISSN 0217-5959, E-ISSN 1793-7019, Vol. 35, no 4, article id 1850023Article in journal (Refereed) Published
    Abstract [en]

    In this paper, the focus is on the role of the municipality, as an enabler of a collaboration between freight forwarders and the municipality in which the consolidation of goods is considered as a means for goods flow improvement in urban freight transportation. We present a cost allocation model that is based on solution concepts from cooperative game theory, for allocating the operational costs associated with the collaboration. It is assumed that the municipality is willing to carry some cost to ensure a stable collaboration for the potential benefits received, e.g., reduced traffic congestion in the city. The model is applied to some illustrative examples, and the cost allocation results are discussed. It is shown that the role of the municipality may be decisive in achieving a stable collaboration between the freight forwarders, and further that the municipality does not necessarily need to contribute to covering the costs.

    Place, publisher, year, edition, pages
    WORLD SCIENTIFIC PUBL CO PTE LTD, 2018
    Keywords
    Collaboration; cost allocation; city distribution center; municipality
    National Category
    Transport Systems and Logistics
    Identifiers
    urn:nbn:se:liu:diva-150486 (URN)10.1142/S0217595918500239 (DOI)000441395200005 ()
    Note

    Funding Agencies|Swedish Energy Agency; VINNOVA

    Available from: 2018-08-24 Created: 2018-08-24 Last updated: 2018-12-13
    2. A note on the nonuniqueness of the Equal Profit Method
    Open this publication in new window or tab >>A note on the nonuniqueness of the Equal Profit Method
    2017 (English)In: Applied Mathematics and Computation, ISSN 0096-3003, E-ISSN 1873-5649, Vol. 308, p. 84-89Article in journal (Refereed) Published
    Abstract [en]

    When a set of players cooperate, they need to decide how the collective cost should be allocated amongst them. Cooperative game theory provides several methods or solution concepts, that can be used as a tool for cost allocation. In this note, we consider a specific solution concept called the Equal Profit Method (EPM). In some cases, a solution to the EPM is any one of infinitely many solutions. That is, it is not always unique. This leads to a lack of clarity in the characterization of the solutions obtained by the EPM. We present a modified version of the EPM, which unlike its precursor ensures a unique solution. In order to illustrate the differences, we present some numerical examples and comparisons between the two concepts.

    Keywords
    Game Theory, Unique Solution, Solution Concept, EPM, Linear Programming, Lexicography
    National Category
    Transport Systems and Logistics
    Identifiers
    urn:nbn:se:liu:diva-121557 (URN)10.1016/j.amc.2017.03.018 (DOI)000399591500007 ()
    Note

    Funding agencies: Swedish Energy Agency

    Available from: 2015-09-24 Created: 2015-09-24 Last updated: 2018-12-13
    3. Incitements for transportation collaboration by cost allocation
    Open this publication in new window or tab >>Incitements for transportation collaboration by cost allocation
    Show others...
    2019 (English)In: Central European Journal of Operations Research, ISSN 1435-246X, E-ISSN 1613-9178, Vol. 27, no 4, p. 1009-1032Article in journal (Refereed) Published
    Abstract [en]

    In this paper, we focus on how cost allocation can be used as a means to create incentives for collaboration among companies, with the aim of reducing the total transportation cost. The collaboration is assumed to be preceded by a simultaneous invitation of the companies to collaborate. We make use of concepts from cooperative game theory, including the Shapley value, the Nucleolus and the EPM, and develop specific cost allocation mechanisms aiming to achieve large collaborations among many companies. The cost allocation mechanisms are tested on a case study that involves transportation planning activities. Although the case study is from a specific transportation sector, the findings in this paper can be adapted to collaborations in other types of transportation planning activities. Two of the cost allocation mechanisms ensure that any sequence of companies joining the collaboration represents a complete monotonic path, that is, any sequence of collaborating companies is such that the sequences of allocated costs are non-increasing for all companies.

    Place, publisher, year, edition, pages
    Springer, 2019
    Keywords
    Collaboration, Transportation planning, Monotonic Path, Cost Allocation, Cooperative game theory
    National Category
    Transport Systems and Logistics
    Identifiers
    urn:nbn:se:liu:diva-121558 (URN)10.1007/s10100-018-0530-2 (DOI)000482948100006 ()
    Funder
    Swedish Energy AgencyVinnova
    Note

    Funding agencies: Swedish Energy Agency and Swedens innovation agency (Vinnova)

    Available from: 2015-09-24 Created: 2015-09-24 Last updated: 2019-09-23Bibliographically approved
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  • 256. Order onlineBuy this publication >>
    Dahlberg, Joen
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Cost allocation methods in cooperative transportation planning2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Transportation, together with transportation planning for goods, provides good conditions for economic growth and is a natural part of modern society. However, transportation has negative side effects, including emissions and traffic congestion. A freight forwarder may consolidate shippers’ goods in order to reduce some of the negative side effects, thus reducing emissions and/or congestion as well as operational costs. The negative side effects as well as operational costs can be further reduced if a number of freight forwarders cooperate and consolidate their collective goods flows. Consolidation refers to the process of merging a number of the freight forwarders’ shipments of goods into a single shipment. In this case, the freight forwarders are cooperating with competitors (the other freight forwarders).

    Fair cost allocations are important for establishing and maintaining cost-efficient cooperation among competing stakeholders. Cooperative game theory defines a number of criteria for fair cost allocations and the problem associated with the decision process for allocating costs is referred to as the cost allocation problem. In this thesis, cooperative game theory is used as an academic tool to study cooperation among stakeholders in two transportation planning applications, namely 1) the distribution of goods bound for urban areas and 2) the transportation of wood between harvest areas and industries.

    In transportation planning application 1, there is a cooperation among a number of freight forwarders and a municipality. Freight forwarders’ goods bound for an urban area are consolidated at a facility located just outside the urban area. In this thesis, operational costs for distributing the goods are assessed by solving vehicle routing problems. Common methods from cooperative game theory are used for allocating the operational costs among the freight forwarders and the municipality. In transportation planning application 2, forest companies cooperate in terms of the supply and transportation of common resources, or more specifically, different types of wood. Each forest company has harvest areas and industries to which the wood is transported. The resources may be bartered, that is, the forest companies may transport wood from each other’s harvest areas.

    In the cooperative game theory literature, the stakeholders are often treated equally in the context of transportation planning. However, there seems to be a lack of studies on cooperations where at least one stakeholder differs from the other stakeholders in some fundamental way, for instance, as an initiator or an enabler of the cooperation. Such cooperations are considered in this thesis. The municipality and one of the forest companies are considered to be the initiators in their respective applications.

    Five papers are appended to this thesis and the overall aim is to contribute to the research into cooperative transportation planning by using concepts from cooperative game theory to develop methods for allocating costs among cooperating stakeholders. The purpose of this thesis is to provide decision support for planners in the decisionmaking process of transportation planning to establish cost-efficient and stable cooperations.

    Some of the main outcomes of this thesis are viable and practical methods that could be used in real-life situations to allocate costs among cooperating stakeholders, as well as support for decisionmakers who are concerned with transportation planning. This is done by demonstrating the potential of cooperation, such as cost reduction, and by suggesting how costs can be allocated fairly in the transportation planning applications considered. Lastly, a contribution to cooperative game theory is provided; the introduction of a development of the equal profit method for allocating costs. The proposed version is the equal profit method with lexicography, which, in contrast to the former, guarantees to yield at most one solution to any cost allocation problem. Lexicography is used to rank potential cost allocations and the unambiguously best cost allocation is chosen.  

    List of papers
    1. Consolidation in Urban Freight Transportation - Cost Allocation Models
    Open this publication in new window or tab >>Consolidation in Urban Freight Transportation - Cost Allocation Models
    2018 (English)In: Asia-Pacific journal of operational research, ISSN 0217-5959, E-ISSN 1793-7019, Vol. 35, no 4, article id 1850023Article in journal (Refereed) Published
    Abstract [en]

    In this paper, the focus is on the role of the municipality, as an enabler of a collaboration between freight forwarders and the municipality in which the consolidation of goods is considered as a means for goods flow improvement in urban freight transportation. We present a cost allocation model that is based on solution concepts from cooperative game theory, for allocating the operational costs associated with the collaboration. It is assumed that the municipality is willing to carry some cost to ensure a stable collaboration for the potential benefits received, e.g., reduced traffic congestion in the city. The model is applied to some illustrative examples, and the cost allocation results are discussed. It is shown that the role of the municipality may be decisive in achieving a stable collaboration between the freight forwarders, and further that the municipality does not necessarily need to contribute to covering the costs.

    Place, publisher, year, edition, pages
    WORLD SCIENTIFIC PUBL CO PTE LTD, 2018
    Keywords
    Collaboration; cost allocation; city distribution center; municipality
    National Category
    Transport Systems and Logistics
    Identifiers
    urn:nbn:se:liu:diva-150486 (URN)10.1142/S0217595918500239 (DOI)000441395200005 ()
    Note

    Funding Agencies|Swedish Energy Agency; VINNOVA

    Available from: 2018-08-24 Created: 2018-08-24 Last updated: 2018-12-13
    2. A note on the nonuniqueness of the Equal Profit Method
    Open this publication in new window or tab >>A note on the nonuniqueness of the Equal Profit Method
    2017 (English)In: Applied Mathematics and Computation, ISSN 0096-3003, E-ISSN 1873-5649, Vol. 308, p. 84-89Article in journal (Refereed) Published
    Abstract [en]

    When a set of players cooperate, they need to decide how the collective cost should be allocated amongst them. Cooperative game theory provides several methods or solution concepts, that can be used as a tool for cost allocation. In this note, we consider a specific solution concept called the Equal Profit Method (EPM). In some cases, a solution to the EPM is any one of infinitely many solutions. That is, it is not always unique. This leads to a lack of clarity in the characterization of the solutions obtained by the EPM. We present a modified version of the EPM, which unlike its precursor ensures a unique solution. In order to illustrate the differences, we present some numerical examples and comparisons between the two concepts.

    Keywords
    Game Theory, Unique Solution, Solution Concept, EPM, Linear Programming, Lexicography
    National Category
    Transport Systems and Logistics
    Identifiers
    urn:nbn:se:liu:diva-121557 (URN)10.1016/j.amc.2017.03.018 (DOI)000399591500007 ()
    Note

    Funding agencies: Swedish Energy Agency

    Available from: 2015-09-24 Created: 2015-09-24 Last updated: 2018-12-13
    3. Incitements for transportation collaboration by cost allocation
    Open this publication in new window or tab >>Incitements for transportation collaboration by cost allocation
    Show others...
    2019 (English)In: Central European Journal of Operations Research, ISSN 1435-246X, E-ISSN 1613-9178, Vol. 27, no 4, p. 1009-1032Article in journal (Refereed) Published
    Abstract [en]

    In this paper, we focus on how cost allocation can be used as a means to create incentives for collaboration among companies, with the aim of reducing the total transportation cost. The collaboration is assumed to be preceded by a simultaneous invitation of the companies to collaborate. We make use of concepts from cooperative game theory, including the Shapley value, the Nucleolus and the EPM, and develop specific cost allocation mechanisms aiming to achieve large collaborations among many companies. The cost allocation mechanisms are tested on a case study that involves transportation planning activities. Although the case study is from a specific transportation sector, the findings in this paper can be adapted to collaborations in other types of transportation planning activities. Two of the cost allocation mechanisms ensure that any sequence of companies joining the collaboration represents a complete monotonic path, that is, any sequence of collaborating companies is such that the sequences of allocated costs are non-increasing for all companies.

    Place, publisher, year, edition, pages
    Springer, 2019
    Keywords
    Collaboration, Transportation planning, Monotonic Path, Cost Allocation, Cooperative game theory
    National Category
    Transport Systems and Logistics
    Identifiers
    urn:nbn:se:liu:diva-121558 (URN)10.1007/s10100-018-0530-2 (DOI)000482948100006 ()
    Funder
    Swedish Energy AgencyVinnova
    Note

    Funding agencies: Swedish Energy Agency and Swedens innovation agency (Vinnova)

    Available from: 2015-09-24 Created: 2015-09-24 Last updated: 2019-09-23Bibliographically approved
    Download full text (pdf)
    Cost allocation methods in cooperative transportation planning
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    presentationsbild
  • 257.
    Dahlberg, Joen
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Andersson Granberg, Tobias
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Polishchuk, Tatiana
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Schmidt, Christiane
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Sedov, Leonid
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Capacity-Driven Automatic Design of Dynamic Aircraft Arrival Routes2018In: 2018 IEEE/AIAA 37TH DIGITAL AVIONICS SYSTEMS CONFERENCE (DASC), IEEE , 2018, p. 1194-1202Conference paper (Refereed)
    Abstract [en]

    We present a Mixed-Integer Programming framework for the design of aircraft arrival routes in a Terminal Maneuvering Area (TMA) that guarantee temporal separation of aircraft. The output routes constitute operationally feasible merge trees, and guarantee that the overall traffic pattern in the TMA can be monitored by air traffic controllers; in particular, we ensure that all aircraft on the arrival routes are separated in time and all merge points are spatially separated. We present a proof of concept of our approach, and demonstrate its feasibility by experiments for arrival routes during one hour at Stockholm TMA.

  • 258.
    Dahlberg, Joen
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Engevall, Stefan
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Göthe-Lundgren, Maud
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Consolidation in Urban Freight Transportation - Cost Allocation Models2018In: Asia-Pacific journal of operational research, ISSN 0217-5959, E-ISSN 1793-7019, Vol. 35, no 4, article id 1850023Article in journal (Refereed)
    Abstract [en]

    In this paper, the focus is on the role of the municipality, as an enabler of a collaboration between freight forwarders and the municipality in which the consolidation of goods is considered as a means for goods flow improvement in urban freight transportation. We present a cost allocation model that is based on solution concepts from cooperative game theory, for allocating the operational costs associated with the collaboration. It is assumed that the municipality is willing to carry some cost to ensure a stable collaboration for the potential benefits received, e.g., reduced traffic congestion in the city. The model is applied to some illustrative examples, and the cost allocation results are discussed. It is shown that the role of the municipality may be decisive in achieving a stable collaboration between the freight forwarders, and further that the municipality does not necessarily need to contribute to covering the costs.

  • 259.
    Dahlberg, Joen
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. The Swedish National Road and Transport Research Institute, Linköping, Sweden.
    Engevall, Stefan
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Göthe-Lundgren, Maud
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Jörnsten, Kurt
    Norwegian School of Economics and Business Administration, Bergen, Norway.
    Rönnqvist, Mikael
    Dpartement de gnie mcanique, Universit Laval, Qubec, Canada.
    Incitements for transportation collaboration by cost allocation2019In: Central European Journal of Operations Research, ISSN 1435-246X, E-ISSN 1613-9178, Vol. 27, no 4, p. 1009-1032Article in journal (Refereed)
    Abstract [en]

    In this paper, we focus on how cost allocation can be used as a means to create incentives for collaboration among companies, with the aim of reducing the total transportation cost. The collaboration is assumed to be preceded by a simultaneous invitation of the companies to collaborate. We make use of concepts from cooperative game theory, including the Shapley value, the Nucleolus and the EPM, and develop specific cost allocation mechanisms aiming to achieve large collaborations among many companies. The cost allocation mechanisms are tested on a case study that involves transportation planning activities. Although the case study is from a specific transportation sector, the findings in this paper can be adapted to collaborations in other types of transportation planning activities. Two of the cost allocation mechanisms ensure that any sequence of companies joining the collaboration represents a complete monotonic path, that is, any sequence of collaborating companies is such that the sequences of allocated costs are non-increasing for all companies.

  • 260.
    Dahlberg, Joen
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. The Swedish National Road and Transport Research Institute, Linköping, Sweden.
    Göthe-Lundgren, Maud
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Engevall, Stefan
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    A note on the nonuniqueness of the Equal Profit Method2017In: Applied Mathematics and Computation, ISSN 0096-3003, E-ISSN 1873-5649, Vol. 308, p. 84-89Article in journal (Refereed)
    Abstract [en]

    When a set of players cooperate, they need to decide how the collective cost should be allocated amongst them. Cooperative game theory provides several methods or solution concepts, that can be used as a tool for cost allocation. In this note, we consider a specific solution concept called the Equal Profit Method (EPM). In some cases, a solution to the EPM is any one of infinitely many solutions. That is, it is not always unique. This leads to a lack of clarity in the characterization of the solutions obtained by the EPM. We present a modified version of the EPM, which unlike its precursor ensures a unique solution. In order to illustrate the differences, we present some numerical examples and comparisons between the two concepts.

  • 261.
    Dahlberg, Joen
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Polishchuk, Tatiana
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Polishchuk, Valentin
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Schmidt, Christiane
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Stakeholder Cooperation for Improved Predictability and Lower Cost Remote Services2017Conference paper (Refereed)
  • 262.
    Dahlgren, Martin
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Westin, Viktor
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Mapping of environmental KPIs2015Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The aviation industry is facing many challenges concerning environmental effects associated to an overall increase in air travel. In order to analyse these environmental effects, the possibility for measurement in the areas connected to the aviation industry is essential. Metrics measuring progress towards meeting goals, called key performance indicators, are used in order to meet this requirement. The purpose of the thesis is to map and evaluate the various environmental key performance indicators that are utilised within European Air Traffic Management today, and the development underway for the future. Suggestions to LFV regarding suitable e-KPIs, and how they can be used within their organisation are also provided. Several organisations and initiatives, including the European Union, EUROCONTROL, Single European Sky, the International Civil Aviation Organisation and the Civil Air Navigation Service Organisation, as well as the British and French air navigation service providers, in addition to other stakeholders within the industry, have been investigated in terms of their work in the environmental area and which indicators they utilise. The investigation is based on a literature study and interviews conducted with stakeholders within previously mentioned organisations. Out of 39 indicators found during the mapping, seven remain after an initial selection and an analysis based on the utilisation of the SMART-model. In addition to the use of the SMART-model, the choice of suitable indicators is also based on the fact that the whole spectrum of a flight, meaning all phases, including planning, taxi-out, departure, en route, descent and arrival as well as taxi-in, should be taken into consideration.

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  • 263.
    Daneshfar, Nader
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Pappas, Nikolaos
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Resource Allocation with Service Availability & QoS Constraints in Mobile Fog Networks2017In: 2017 IEEE CONFERENCE ON COMPUTER COMMUNICATIONS WORKSHOPS (INFOCOM WKSHPS), IEEE , 2017, p. 1018-1019Conference paper (Refereed)
    Abstract [en]

    The evolution of the Internet of Things (IoT) is bringing Cloud services closer to the networks edge. Thus, fog networking presents itself as an approach aiming to utilize more and more resources in network edge devices to provide various networking tasks. This work presents an optimization formulation that minimizes the cost of executing a set of services, taking into account the availability of resources in mobile edge devices.

  • 264.
    Daneshfar, Nader
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Pappas, Nikolaos
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Polishchuk, Valentin
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Service Allocation in a Mobile Fog Infrastructure under Availability and QoS Constraints2018In: 2018 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM), IEEE , 2018Conference paper (Refereed)
    Abstract [en]

    The next generation of mobile networks, namely SG, together with the Internet of Things (IoT) come with a large number of delay sensitive services. To meet their requirements, cloud services are migrating to the edge of the networks to reduce latency. The notion of fog computing, where the edge plays an active role in the execution of services, comes to meet the needs for the stringent requirements. Thus, it becomes of a high importance to address the problem of mapping services demands to infrastructure resources supply. This work addresses it taking into account the randomness of resource availability in a fog infrastructure. We introduce an integer optimization formulation to minimize the total cost under a guarantee of service execution despite the uncertainty of resources availability. Our results illustrate the effect of various system parameters, such as the diversity of the infrastructure server set, the availability of different infrastructure servers in the set, and the probability of service completion required by each service.

  • 265.
    Datsika, Eftychia
    et al.
    IQUADRAT Informat SL, Spain.
    Antonopoulos, Angelos
    Telecommun Technol Ctr Catalonia CTTC CERCA, Spain.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Verikoukis, Christos
    Telecommun Technol Ctr Catalonia CTTC CERCA, Spain.
    Matching Theory for Over-the-Top Service Provision in 5G Networks2018In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 17, no 8, p. 5452-5464Article in journal (Refereed)
    Abstract [en]

    Modern over-the-top (OTT) applications can be accessed via Internet connections over cellular networks, possibly shared and managed by multiple mobile network operators (MNOs). The OTT service providers (OSPs) need to interact with MNOs, requesting resources for serving users of different categories and with different quality-of-service requirements. For this purpose, OSPs need OTT application flow prioritization in resource allocation, while the network resource scheduling should respect network neutrality that forbids OSP prioritization. OSPs also need to request resources periodically, according to their performance goals, i.e., grade-of-service (GoS) level (blocking probability), causing delay in flows accommodation due to: 1) the time required for information exchange between OSPs and MNOs, affected by network congestion, and 2) the time required for flows to receive resources, affected by the number of concurrently active flows. Acknowledging the lack of OSP-oriented resource management approaches, we: 1) introduce a novel matching theoretic flow prioritization (MTFP) algorithm that respects network neutrality and 2) design analytical models that enable the thorough investigation of the GoS and delay performance in various scenarios. Our results (analytical and simulation) show that MTFP improves both metrics compared to the best effort approach, whereas its performance is affected by the number of flows and the resource allocation frequency.

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  • 266.
    Davidsson, Josefin
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Delén, Caroline
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Using Volunteers in Emergencies – A Study on Dispatching Routines and Requirements2018Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    När det sker en olycka är det viktigt att en första insats kan påbörjas snabbt. På glesbyggden kan det vara svårt för polis, ambulans och räddningstjänst (blåljusmyndigheter) att vara på plats inom en rimlig tid då körsträckorna är långa. För att en första insats ska kunna påbörjas så tidigt som möjligt har det på flera håll i Sverige organiserats verksamheter med frivilliga som kan vara behjälpliga vid vissa olyckor och en av dessa verksamheter är civil insatsperson (CIP). I detta arbete har CIP-verksamheten i västra Sörmland studerats för att se hur verksamheten ser ut idag och hur den skulle kunna utvecklas. Fokus är utlarmningsprocessen och vilka som ska larmas till olika typer av olyckor. När det sker en olycka i ett område med CIP-verksamhet och det är ett relevant larm för CIP att åka på larmas alla som är CIP i det område där olyckan skett. Det innebär att CIP får meddelande om olyckor i deras område även om de inte är i närheten vid tillfället för larmet. CIP kan heller inte meddela SOS Alarm om de kommer att åka på larmet eller inte i dagsläget. En beslutsmodell har utformats för att CIP genom en applikation i mobiltelefonen ska kunna bli larmade till lämpliga olyckor. Här larmas de CIP som kan vara vid olycksplatsen före blåljusmyndigheterna och vidare får de information om vilka kvalifikationer som är av värde vid olyckan och får klicka i om de kan ta med sig några av dessa. Denna studie ger indikationer på att det går att utveckla CIP-verksamheten genom en beslutsmodell och därigenom även att underlätta spridningen av CIP-verksamheten till övriga delar av landet. Med en beslutsmodell som underlättar utlarmningsprocessen underlättas räddningsinsatser och CIP kan bidra med effektivare hjälp.

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    Using Volunteers in Emergencies – A Study on Dispatching Routines and Requirements
  • 267.
    Dervic, Amina
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Rank, Alexander
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    ATC complexity measures: Formulas measuring workload and complexity at Stockholm TMA2015Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Workload and complexity measures are, as of today, often imprecise and subjective. Currently, two commonly used workload and complexity measuring formulas are Monitor Alert Parameter and the “Bars”, both using the same measurement variables; amount of aircraft and time. This study creates formulas for quantifying ATC complexity. The study is done in an approach environment and is developed and tested on Stockholm TMA by the creation of 20 traffic scenarios. Ten air traffic controllers working in Stockholm TMA studied the complexity of the scenarios individually and ranked the scenarios in reference to each other. Five controllers evaluated scenario A1-A10. These scenarios were used as references when creating the formulas. The other half of the scenarios, B1-B10, ranked by another five controllers, was used as validation scenarios. Factors relevant to an approach environment were identified, and the data from the scenarios were extracted according to the identified factors. Moreover, a regression analysis was made with the ambition to reveal appropriate weights for each variable. At the first regression, called formula #1, some parameter values were identical. Also, some parameter weights became negative in the regression analysis. The basic requirements were not met and consequently, additional regressions were done; eventually forming formula #2. Formula #2 showed stable values and plausible parameter weights. When compared to a workload measuring model of today, formula #2 showed better performance. Despite the small amount of data samples, we were able to prove a genuine relation between three, of each other independent, variables and the traffic complexity.

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  • 268.
    Dimitriou, Ioannis
    et al.
    Univ Patras, Greece.
    Pappas, Nikolaos
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    A Queue-based Random Access Scheme in Network-level Cooperative Wireless Networks2019In: ICC 2019 - 2019 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC), IEEE , 2019Conference paper (Refereed)
    Abstract [en]

    In this work, we consider a relay assisted adaptive queue-aware cooperative random access wireless network with multipacket (MPR) reception capabilities. The network consists of N sources transmitting packets to a common destination node with the aid of two relay nodes equipped with queues. The relays assist the sources by forwarding the packets that failed to reach the destination, by using a queue-based transmission control mechanism. Moreover, the relays have also their own traffic. We investigate the stability conditions and the throughput performance of the network for the full MPR channel model. Moreover, we derive expressions for the average queueing delay with the aid of the theory of boundary value problems for the asymmetric two-user network. We evaluate numerically the presented theoretical analysis.

  • 269.
    Dimitriou, Ioannis
    et al.
    Univ Patras, Greece.
    Pappas, Nikolaos
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Performance analysis of a cooperative wireless network with adaptive relays2019In: Ad hoc networks, ISSN 1570-8705, E-ISSN 1570-8713, Vol. 87, p. 157-173Article in journal (Refereed)
    Abstract [en]

    In this work, we investigate a slotted-time relay assisted cooperative random access wireless network with multipacket (MPR) reception capabilities. MPR refers to the capability of a wireless node to successfully receive packets from more than two other modes that transmit simultaneously at the same slot. We consider a network of N saturated sources that transmit packets to a common destination node with the cooperation of two infinite capacity relay nodes. The relays assist the sources by forwarding the packets that failed to reach the destination. Moreover, the relays have also packets of their own to transmit to the destination. We further assume that the relays employ a state-dependent retransmission control mechanism. In particular, a relay node accordingly adapts its transmission probability based on the status of the other relay. Such a protocol is towards self-aware networks and leads to substantial performance gains in terms of delay. We investigate the stability region and the throughput performance for the full MPR model. Moreover, for the asymmetric two-sources, two-relay case we derive the generating function of the stationary joint queue-length distribution with the aid of the theory of boundary value problems. For the symmetric case, we obtain explicit expressions for the average queueing delay in a relay node without solving a boundary value problem. Extensive numerical examples are presented and provide insights on the system performance. (C) 2018 Elsevier B.V. All rights reserved.

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  • 270.
    Dimitriou, Ioannis
    et al.
    Department of Mathematics, University of Patras, 26500, Patras, Greece.
    Pappas, Nikolaos
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Performance Analysis of an Adaptive Queue-Aware Random Access Scheme with Random Traffic2018In: 2018 IEEE International Conference on Communications (ICC) Proceedings Kansas City, MO, USA 20–24 May 2018, IEEE Communications Society, 2018, p. 1-6Conference paper (Refereed)
    Abstract [en]

    In this work, we consider an adaptive two-user random access scheme with multipacket reception (MPR) ca- pabilities. A user adapts its transmission characteristics based on the status of the other user. The users have external random traffic stored in their queues. We derive the stable throughput region of the system and the convexity conditions of this region. We derive analytically the queueing delay by formulating and solving a Riemann-Hilbert boundary value problem. Finally, we evaluate numerically the presented theoretical results. 

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    Performance Analysis of an Adaptive Queue-Aware Random Access Scheme with Random Traffic
  • 271.
    Dimitriou, Ioannis
    et al.
    Univ Patras, Greece.
    Pappas, Nikolaos
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Stability and Delay Analysis of an Adaptive Channel-Aware Random Access Wireless Network2017In: ANALYTICAL AND STOCHASTIC MODELLING TECHNIQUES AND APPLICATIONS, ASMTA 2017, SPRINGER INTERNATIONAL PUBLISHING AG , 2017, Vol. 10378, p. 63-80Conference paper (Refereed)
    Abstract [en]

    In this work, we consider an asymmetric two-user random access wireless network with interacting nodes, time-varying links and multipacket reception capabilities. The users are equipped with infinite capacity buffers where they store arriving packets that will be transmitted to a destination node. Moreover, each user employs a general transmission control protocol under which, it adapts its transmission probability based both on the state of the other user, and on the channel state information according to a Gilbert-Elliot model. We study a two-dimensional discrete time Markov chain, investigate its stability condition, and show that its steady state performance is expressed in terms of a solution of a Riemann-Hilbert boundary value problem. Moreover, for the symmetrical system, we provide closed form expressions for the average delay at each user node. Numerical results are obtained and show insights in the system performance.

  • 272.
    Dimitriou, Ioannis
    et al.
    Department of Mathematics, University of Patras, Greece.
    Pappas, Nikolaos
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Stable Throughput and Delay Analysis of a Random Access Network With Queue-Aware Transmission2018In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 17, no 5, p. 3170-3184Article in journal (Refereed)
    Abstract [en]

    In this work we consider a two-user and a three-user slotted ALOHA network with multi-packet reception (MPR) capabilities and a queue-aware transmission control. In this setting, the nodes can adapt their transmission probabilities and their transmission parameters based on the status of the other nodes. Each user has external bursty arrivals that are stored in their infinite capacity queues. We focus on the fundamental problem of characterizing the stable throughput region, as well as of investigating the queueing delay. For the two- and the three-user cases we obtain the exact stability region, whereas in the former case we also provide the conditions under which the stability region is a convex set. We perform a detailed mathematical analysis to study the queueing delay in the two-user case by formulating two boundary value problems, the solution of which provide the generating function of the joint stationary probability distribution of the queue size at user nodes. Furthermore, for the two-user symmetric case with MPR we obtain a lower and an upper bound for the average delay without the need of solving a boundary value problem. In addition, we provide a closed form expression for the gap between the lower and the upper bound. The bounds as it is seen in the numerical results appear to be tight. Explicit expressions for the average delay are obtained for the symmetrical model with capture effect. We also provide a closed form expression for the optimal transmission probability that minimizes the average delay in the symmetric capture case. Finally, we evaluate numerically the presented theoretical results.

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  • 273.
    Djordjevic, Miroljub
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems.
    Häggqvist, Johan
    Linköping University, Department of Science and Technology, Communications and Transport Systems.
    Simuleringsbaserad material och produktionsstyrning2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Gruppen Kvantitativ Logistik (KL) vid Linköpings Universitet har under en längre tid efterfrågat en simuleringsbaserad utbildningsmiljö där produktionsplanering kan upplevas i form av planering, omplanering och kapacitetsberäkningar. 

    Denna utbildningsmiljö ska framförallt användas för att utbilda andra studenter inom produktionsplanering. Miljön ska bestå av ett användarinterface där all data om produktionen framgår, en simuleringsmodell som utgör själva fabriken samt en sammanhållande struktur som möjliggör styrning av de båda komponenterna. Dessutom skall ett antal scenarion skapas som skall ligga till grund för de lärandemoment som MPCW hanterar.

    Fyra fiktiva produktstruktur skapades, på så sätt att deras komplexitet och djup var tillfredsställande. Dessa strukturer ligger till grund för de MRP- och sedermera CRP-beräkningar som används för att styra de ursprungliga aktiviteterna.

    Resultatet av examensarbetet är ett verktyg som kan användas för att simulera produktionsplaneringsarbete. Verktyget består av två huvuddelar, den ena är ett GUI (Graphical User Interface) i Excel som kallas för MPCW (Material Planning and Control Workbench) och en simuleringsmodell. Dessa delar jobbar tillsammans via Excel och VBA. Allt kontrolleras genom MPCW:s GUI och det är i MPCW som användaren sitter och styr produktionsplaneringen genom att analysera och bearbeta tillgänglig information. Användaren har möjlighet att erhålla information i MPCW i form av MRP tablåer som bygger på en huvudplan, information om produktionskapacitet och beläggning på maskinerna i fabriken.

    Vad gäller vidare arbete med modellen, så kommer det alltid finnas utrymme för förbättring, framförallt vad gäller fabriken. Detta då en simulerad fabrik naturligtvis aldrig kan avbilda en riktig fabrik helt och hållet, särskilt då den modellerade fabriken inte bygger på en verklig fabrik.

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  • 274.
    Dong, Yao
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Sadegh Aminian, Mohammad
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Routing in Terrestrial Free Space Optical Ad-Hoc Networks2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Terrestrial free-space optical (FSO) communication uses visible or infrared wavelengths to broadcast high speed data wirelessly through the atmospheric channel. The performance of terrestrial FSO channel mainly depends on the local atmospheric conditions. Ad hoc networks offer cost-effective solutions for communications in areas where infrastructure is unavailable, e.g., intelligent transport system, disaster recovery and battlefield scenarios. Traditional ad hoc networks operate in the radio frequency (RF) spectrum, where the available bandwidth faces the challenge of rapidly increasing demands. FSO is an attractive alternative for RF in ad-hoc networks because of its high bandwidth and interference-free operation. This thesis investigates the influencing factors for routing traffic from given s-d pair while satisfying certain Quality of Services in terrestrial FSO ad hoc mesh networks under the effect of stochastic atmospheric turbulence. It starts with a comprehensive review of FSO technology, including the history, application, advantages and limitations. Subsequently the principle of operation, the building blocks and safety of FSO communication systems are discussed. The physics of atmosphere is taken into account to investigate how propagation of optical signals is affected in terrestrial FSO links. A propagation model is developed to grade the performance and reliability of the FSO ad hoc links in the network. Based on that model and the K-th shortest path algorithm, the performance of the path with highest reliability, the path with a second highest possible reliability and an independent path with no common links shared with the former two paths, were compared according to the simulation scenarios in node-dense area and node-sparse area. Matlab simulation shows that the short/long range dependent transmission delay are positively proportional to number of hops of the paths. Lower path reliability only dominate the cause of severe delay when traffic flow approaches near its upper link capacity in node-sparse area. In order to route traffic from given s-d pairs with satisfying certain Quality of Services, the path with highest reliability may not be the best choices since they may hold more hops which will degrade the QoS. Meanwhile, in case of exponential traffic congestion, it is recommended that both traffic demand and traffic flow propagating through the links should be pressed below a value close to the effective capacity, where the nonlinearity of the transmission delay curve starts to obviously aggravate.

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  • 275.
    Drageryd, Lars
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Using public transport tap-in data to improve a travel demand model: A Norrköping case study2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With reliable models to forecast travel demand, traffic planners and decision-makers can be assisted in choosing the best solutions to obtain traffic performance goals. Practitioners have traditionally been relying on infrequent, costly and respondent pressurized travel surveys as their main source of data for these models. The drawbacks of the data collection method highlight a need to search for alternative sources of data used for the purpose. One such source is public transport “tap-in” data. This thesis executed a case study with the target of improving the travel demand model of Norrköping via public transport data. An algorithm that estimates the alighting station of travellers was applied to a data set provided by the public transport operator of the city. By allocating the OD-demand from stations to the traffic analysis zones used in the model a straightforward integration method using the tap-in estimate as a reference matrix could be used. The target with the method was to redistribute the demand in such a way that the public transport demand approached the tap-in estimate but that the total demand for all modes for the OD-pair remained unchanged. The results gave some indication that the integration of tap-in data improved the model performance from the perspective of public transports. In a regression analysis comparing the number of entries per station the integration of tap-in data increased the correlation coefficient from 0,845 to 0,864. Further was the performance for other transport modes seemingly not worsened by the integration of tap-in data. Finding an allocation procedure that was generic but still accurate proved complex. Further were drawbacks with the integration procedure highlighted where the method executed affected the results of the model, not its behaviour. The consequence of this is that, though the model might be an accurate representation of the current state of traffic, it is difficult to execute the same procedure when investigating future states. Still, the thesis stressed some of the potential for public transport data in modelling contexts, where the role of the data, given the procedure executed, still is of complementary character to travel surveys.

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    Using public transport tap-in data to improve a travel demand model: A Norrköping case study
  • 276.
    Dukic, Tania
    et al.
    VTI, Göteborg.
    Ahlström, Christer
    VTI, Linköping.
    Björketun, Urban
    VTI, Linköping.
    Kettwich, Carmen
    Karlsruhe Institute of Technology.
    Yahya, Mohammad-Reza
    VTI, Linköping.
    Patten, Christofer
    VTI, Borlänge.
    Tapani, Andreas
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Vadeby, Anna
    VTI, Linköping.
    Inverkan av elektroniska reklamskyltar på trafiksäkerhet: En studie på E4 i Stockholm2011Report (Refereed)
  • 277.
    Dully, Michael
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Traffic Safety Evaluation of Future Road Lighting Systems2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    While new road lighting technologies, either LED or adaptive road lighting systems, offer a wide range of unique potential benefits (mainly in terms of energy savings), it is necessary to evaluate the safety impacts of these technologies on road users. The literature survey shows that providing light on previous unlit roads has a positive effect on traffic safety. Reducing the amount of light has the opposite effect. These studies are usually conducted by using crash numbers, which makes it impossible to draw conclusions on changes in driving behaviour. Driving behaviour analyses need special approaches and indicators. Therefore indirect indicators such as speed and safety relationship, jerky driving and traffic conflict parameters are presented. The individual character of such data is difficult to deal with and limits big scale analyses. In order to have a practical example of such indicators a case study is conducted. Floating car data collected in Vienna is used to analyse travel speeds of taxi drivers at two LED test sites. A simple before-after analysis is used with data from January 2011 to May 2012 in order to examine an expected increase in speed due to a better visual performance of LED light. However the results show either no changes at all or a trend in speed reduction of 1km/h in average. Unfavourable test site locations might limit the significance of the results.

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  • 278.
    Dzeko, Jasmin
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Scheduling of Norrköping Airport2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    For Securitas AB case to maintain their position in Norrkoping Airport is it important to effectives their staffing and schedules. This is required to achieve cost reductions which will in turn give them the competitive edge to maintain their position at the annual contracts concluded between the municipality and the airport. To effectives their staffing and schedules are theoretical parts going to be used to control their groups and business better. The theoretical parts are in the form of scheduling principles.

    At the streamlining of operations is an optimization model going to be used that has several features that enable a comprehensive optimization solution to embarrass the most costeffective staffing for the schedule planning. A technical system as an information system will also be used to structure Securitas work more efficiently with a better accounting of the employees and to facilitate the implementation of a standardized approach. The importance of standardized work is treated much in the LEAN philosophy and is considered important in this case to obtain the theoretical aspects and the information system to work together smoothly. A scheduling policy that is recommended that Securitas uses is the Perceptual Control Theory as it has proven to be successful by companies that applied it.

    The solution to Securitas Problem is a combination of theory and quantitative methods that can be used to count on. Optimization model and information system will together with the scheduling principles create better conditions for Securitas to set up a new optimal schedule to reduce costs by 10 % and increase the efficiency for Securitas operations in the airport. These actions are going to lead to higher profitability and will result that Securitas wins the annual procurements in Norrkoping Airport.

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  • 279.
    Ecker, Grit
    et al.
    INFORM GmbH, Germany.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering. Uppsala Univ, Sweden.
    Koster, Arie M. C. A.
    Rhein Westfal TH Aachen, Germany.
    Schmeink, Anke
    Rhein Westfal TH Aachen, Germany.
    Accurate optimization models for interference constrained bandwidth allocation in cellular networks2019In: Computers & Operations Research, ISSN 0305-0548, E-ISSN 1873-765X, Vol. 101Article in journal (Refereed)
    Abstract [en]

    In cellular networks, the signal-to-interference-plus-noise ratio (SINR) is a key metric for link availability and quality. For network planning purposes, a straightforward modeling unfortunately yields numerically difficult optimization models. Further, given a required data rate of a link, its bandwidth consumption depends nonlinearly on the SINR. In this paper, we develop two novel approaches to jointly model SINR-based link availability and bandwidth requirements accurately. The first approach is a set-wise formulation from a users point of view, while the second one exploits discrete channel quality indicators. We compare these formulations with three known approximate approaches numerically, revealing the clear outperformance of our approaches in terms of exactness. Moreover, since the exact models comprise an exponential number of either variables or constraints, we discuss their pros and cons in a further computational study and develop a more efficient algorithm dealing implicitly with the involved constraints. (C) 2018 Elsevier Ltd. All rights reserved.

    The full text will be freely available from 2021-08-22 11:09
  • 280.
    Edberg, Robin
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Qvint, Magnus
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Article Placement in Storage2012Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Beijer Byggmaterial is a company with potential for improvement regarding inventory management. Since stockks and customer service are central to the company’s purpose, profitability can be achieved in more efficient inventory management.

    The purpose of the report has been to reduce the time for picking items from a customer perspective in one of Beijer Byggmaterial’s warehouses. On this basis, a number of issues discussed were that this report will answer if it’s profitable for the company to overlook an article placement of its products. The procedure was done through three different stages, the first phase dealt with the collection of data. This was followed by various calculations and analyzes regarding article placement of stock. The last phase is considered the solution proposed by the authors.

    In the current situation, articles at Beijer are placed in different groups without being based on frequency. The proposed solutions in this report show that it’s profitable for the company to place articles based on frequency. This has been implemented by a number of ABCanalyzes with a number of criteria which the articles with the highest frequency being classified as A-items and are therefore placed in a suitable location.

    Through the support of theories frequency orientation and article placement have resulted in shorter retrieval times for both customers and staff, and a higher customer service thought the warehouse.

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  • 281.
    Edh Mirzaei, Nina
    et al.
    Chalmers University of Technology, Gothenburg, Sweden.
    Fredriksson, Anna
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Winroth, Mats
    Chalmers University of Technology, Gothenburg, Sweden.
    Strategic consensus on manufacturing strategy content: including the operators' perceptions2016In: International Journal of Operations & Production Management, ISSN 0144-3577, E-ISSN 1758-6593, Vol. 36, no 4, p. 429-466Article in journal (Refereed)
    Abstract [en]

    Purpose – Strategic consensus between operators and managers is an important means to accomplish a successful manufacturing strategy (MS) process. Previous studies largely left out individual operators from this concept. Therefore, the purpose of this paper was to empirically examine the level of strategic consensus on the MS within the operations function, that is, the operators’ and managers’ perceptions of MS.

    Design/methodology/approach – Interviews were conducted with both operators and managers at three small and medium-sized enterprises in Sweden. The MS dimensions were selected based on previous research; the data was analysed by using thematic coding.

    Findings – The study shows that the levels of strategic consensus on the MS vary among companies. Even when strategic consensus exists between operators and managers, their underlying reasons often differ. Furthermore, the levels of strategic consensus vary among MS dimensions. The companies’ usage of information-sharing channels, along with their size and position in the supply chain, can be important for the level of strategic consensus.

    Originality/value – This paper contributes to the body of knowledge in three ways. First, it expands the scope of the MS dimensions under study, thus offering a stronger, resource-based perspective on MS and strategic consensus than what earlier studies showed. Second, it goes beyond the management level by including both managers and operators as the unit of analysis. Third, compared to previous research, it focuses on a new context and is based on indepth case studies.

  • 282.
    Edh, Nina
    et al.
    Chalmers Tekniska Högskola, Gothenburg, Sweden.
    Fredriksson, Anna
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    The people dimension in manufacturing strategy:contextual factors influencing a joint view2014In: Proceedings of EurOMA, 2014, 2014Conference paper (Refereed)
    Abstract [en]

    This paper explicates the contextual factors influencing the workers’ perceptions of the MS, and hence, the possibilities for a joint view between workers and managers. The paper is based on in depth interviews with 16 workers in four metal working SMEs in Sweden. The contextual factors can be viewed at two levels: individual and organisational. This paper contributes to richer descriptions of what the individual and organisational contextual factors incorporate, and to the clarification of the important role communication channels plays for the possibilities of a joint view. Thereby, contributing to increased knowledge on the manufacturing strategy formation process.

  • 283.
    Efrat, Alon
    et al.
    University of Arizona, AZ 85721 USA.
    Fekete, Sandor P.
    Braunschweig University of Technology, Germany; TU Braunschweig, Germany.
    Mitchell, Joseph S. B.
    SUNY Stony Brook, NY 11794 USA.
    Polishchuk, Valentin
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Suomela, Jukka
    Aalto University, Finland.
    Improved Approximation Algorithms for Relay Placement2016In: ACM Transactions on Algorithms, ISSN 1549-6325, E-ISSN 1549-6333, Vol. 12, no 2, p. 20-Article in journal (Refereed)
    Abstract [en]

    In the relay placement problem, the input is a set of sensors and a number r >= 1, the communication range of a relay. In the one-tier version of the problem, the objective is to place a minimum number of relays so that between every pair of sensors there is a path through sensors and/or relays such that the consecutive vertices of the path are within distance r if both vertices are relays and within distance 1 otherwise. The two-tier version adds the restrictions that the path must go through relays, and not through sensors. We present a 3.11-approximation algorithm for the one-tier version and a polynomial-time approximation scheme (PTAS) for the two-tier version. We also show that the one-tier version admits no PTAS, assuming P not equal NP.

  • 284.
    Egerud, Rebecca
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Södergren, Erik
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Cost differences between Miljöbyggnad Guld and BBR2017Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Denna rapport är en jämförelse mellan BBR och Miljöbyggnad nivå Guld. Tre frågeställningar besvaras, Vad är skillanden mellan BBR och Miljöbyggnad nivå guld, vad är mervärdet och merkostnaden av Miljöbyggnad nivå Guld. Studien är utförd på en fallstudie av Studenthuset som byggs på Linköpings Universitet. Resultaten av studien visar att skillanderna mellan de två är stora, mervärdet för Miljöbyggnad nivå Guld är stort samt att merkostnaden är 2.5 - 3.0 % för Miljöbyggnad nivå GUld

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    Cost differences between Miljöbyggnad Guld and BBR
  • 285.
    Egnell, Karl
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Standardized Technical Building Requirement2016Independent thesis Basic level (university diploma), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Denna rapport behandlar tekniska beskrivningar. Främst med fokus på problematiken för att skapa dessa på national men även global nivå samt utvecklingspotentialen med att standardisera dessa. Rapporten inriktar sig på stora industriella aktörer med en repetitiv hantering av byggprojekt för att på minsta möjliga sätt hindra sin kärnverksamhet men även underlätta utveckling och utökning av sin produktion. Rapporten tar upp fördelar men även potentiella nackdelar med ett standardiserat förfarande, därigenom vad företag måste tänka på och säkerställa för att få en fungerande och utvecklande process. I syfte att motivera företagens arbete med standardiserade beskrivningar visar rapporten vilka riktvärden som kan påverkas. Riktvärden som baseras på kompetenta personers erfarenhet inom branschen. Med detta förklaras även vikten i att sätta upp mål för utvecklingen och samtidigt processer för att följa upp så att uppsatta mål uppnås men även återkopplas genom erfarenhetsåterföring och revidering. Tre större industriella aktörer har medverkat i arbetet med rapporten, alla tre med ett stort fokus på vad en standardisering kan innebära för deras verksamhet. Där av har rapportens kärndelar anpassats efter att stämma överens med företagens frågeställningar. Då tekniska beskrivningar inom branschen inte är något nytt fenomen men att standardisera dessa ännu ej är i bruk, konstateras att ämnet måste undersökas mer samt testas i praktiken för att helt kunna följa upp att företagen mål uppnås. Dock kan av rapportens slutsatser dras att det finns stora besparingar och effektiviseringar som potentiellt kan påverkas. Detta med utgångspunkt av digniteten för de projekt företagen kommer i kontakt med.

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  • 286.
    Ehliar, Lars-Johan
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Wagner, Tobias
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Key performance indicators for the evaluation of an air navigation service providers' safety management system2016Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Safety is the main concern of the aviation industry. All Air Navigation Service Providers must have a Safety Management System (SMS) which states how safety is handled, promoted and prioritized. By developing Key Performance indicators (KPIs), it is possible to quantify the effectiveness of a SMS, discover potential flaws and improvement measures. This thesis identifies principles behind the SMS, the development of KPIs and suggest potential KPIs for the Swedish air navigation service provider LFVs’ SMS.

    A literature study was performed and organisation specific documents were analysed to develop potential KPIs within the areas timely compliance with international obligations, competency and adoption and sharing of best practices based on an EASA questionnaire. This work presents a set of 27 performance indicators and recommends 6 as potential KPIs for the three areas together. The KPIs are developed specifically for LFV but could be applicable for other organisations with similar SMS structure and processes. They should be analysed within the organisation and, potentially, have thresholds set before implementation.

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  • 287.
    Eidner, Albin
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Engman, Markus
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    En studie i energieffektivisering av miljonprogrammet2018Independent thesis Basic level (university diploma), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    Vi står idag inför stora utmaningar för att minska miljöpåverkan. Fastigheter och främst flerbostadshus står för en stor del av energiåtgången i världen. Det krävs därför åtgärder för att effektivisera deras energianvändning. I Sverige byggdes en miljon bostäder mellan åren 1965 och 1974, en stor del av dessa bostäder var flerbostadshus. Dessa bostäder har med dagens mått mätt dålig energiprestanda och en stor del av beståndet kommer även att behöva omfattande renoveringar under de kommande åren. I denna studie undersöker vi hur renoveringar har gjorts när energieffektivisering dessa bostäder har skett. Vi har studerat olika projekt där man har energioptimerat på olika sätt. Vi har också studerat olika tänkbara lösningar för att energioptimera ett lamellhus i två våningar uppfört 1973. Rapporten presenterar tre olika förslag på tänkbara lösningar för att energioptimera fastigheten. De åtgärder som undersökts är fönsterbyte, tilläggsisolering av väggar både invändigt och utvändigt, tilläggsisolering av plattan invändigt samt tilläggsisolering av sockeln utvändigt.

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    En studie i energieffektivisering av miljonprogrammet
  • 288.
    Ekelin, Svante
    et al.
    Ericsson Research, Stockholm, Sweden, Mälardalen University, Västerås, Sweden.
    Nilsson, Martin
    Swedish Institute of Computer Science (SICS), Stockholm, Sweden, Mälardalen University, Västerås, Sweden .
    Hartikainen, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology, Communications and Transport Systems. Ericsson Research, Stockholm, Sweden.
    Johnsson, Andreas
    Mälardalen University, Västerås, Sweden .
    Mångs, Jan-Erik
    Ericsson Research, Stockholm, Sweden .
    Melander, Bob
    Ericsson Research, Stockholm, Sweden, Mälardalen University, Västerås, Sweden.
    Björkman, Mats
    Mälardalen University, Västerås, Sweden .
    Real-Time Measurement of End-to-End Available Bandwidth using Kalman Filtering2006In: 10th IEEE/IFIP Network Operations and Management Symposium, 2006. NOMS 2006., Piscataway, New Jersey, USA: IEEE Computer Society, 2006, p. 73-84Conference paper (Refereed)
    Abstract [en]

    This paper presents a new method, BART (bandwidth available in real-time), for estimating the end-to-end available bandwidth over a network path. It estimates bandwidth quasi-continuously, in real-time. The method has also been implemented as a tool. It relies on self-induced congestion, and repeatedly samples the available bandwidth of the network path with sequences of probe packet pairs, sent at randomized rates. BART requires little computation in each iteration, is lightweight with respect to memory requirements, and adds only a small amount of probe traffic. The BART method uses Kalman filtering, which enables real-time estimation (a.k.a. tracking). It maintains a current estimate, which is incrementally improved with each new measurement of the inter-packet time separations in a sequence of probe packet pairs. The measurement model has a strong non-linearity, and would not at first sight be considered suitable for Kalman filtering, but we show how this non-linearity can be handled. BART may be tuned according to the specific needs of the measurement application, such as agility vs. stability of the estimate. We have tested an implementation of BART in a physical test network with carefully controlled cross traffic, with good accuracy and agreement. Test measurements have also been performed over the Internet. We compare the performance of BART with that of pathChirp, a state-of-the-art tool for measuring end-to-end available bandwidth in real-time

  • 289. Order onlineBuy this publication >>
    Ekeskär, Andreas
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Exploring Third-Party Logistics and Partnering in Construction: A Supply Chain Management Perspective2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The construction industry is associated with problems such as low productivity and high costs. This has been highlighted in several government-funded reports in both Sweden and in the UK during the course of over two decades. The construction industry is a large industry sector employing hundreds of thousands and a large contributor to a country’s GDP. The problems therefore have a large impact on society. Some of the problems are rooted in the organizational structure of the construction industry. Compared to other manufacturing industries, the construction industry is organized in temporary organizations. The temporary organizations cause temporary supply chains, fragmentation among construction industry actors and adversarial relationships between those actors. Partnering has been but forward as a solution to overcome the temporariness and the adversarial relationships in the construction. Another solution to mitigate the problems suggested in the reports is supply chain management (SCM). Both concepts have been taken from the manufacturing industries and partnering has been more successful compared to SCM in the construction industry. In the construction industry the progress towards SCM has focused on logistics. In recent years dedicated third-party logistics (TPL) solutions have emerged in the Swedish construction industry, where a company is hired to manage the logistics in a construction project.

    The purpose with the research presented in this licentiate thesis is to explore how client initiated TPL solutions and partnering can be facilitators for SCM in the construction industry. Being a new phenomenon in the construction industry TPL solutions provide a logistical competence not necessarily included in a traditional construction project. Therefore, TPL solutions are of particular interest when studying the realization of SCM in the construction industry. In the process of realizing SCM in the construction industry, the construction clients have been put forward as having a crucial and important role. The clients are the initiator and funder of construction projects and as such the client can influence the course of a construction project. Therefore, it is of interest to study how the client can take an active role in this process. Initiating a TPL solution in a construction project is one way for a client to take an active part in the realization of SCM in construction.

    However, in order to study how clients can take an active role towards the realization of SCM in the construction industry, there have to be an understanding of how SCM is to be adopted to the construction industry context. SCM that derives from the manufacturing industry is designed to be used in long-term relationships with permanent organizational structures. The construction industry on the other hand is associated with short-term relationships and a temporary organizational structure. Partnering that is designed to mitigate the temporariness and establish long-term relationships have been quite successful in the construction industry, and could therefore be used as a facilitator for SCM in construction.

    To study the use of client initiated TPL-solutions in construction and the realization of SCM in the construction industry the following research questions have been addressed:

    • RQ1: To what extent can a third-party logistics solution be a facilitator for client driven SCM in the construction industry?
    • RQ2: How will upstream and downstream tiers be affected when a thirdparty logistics provider is used in a construction project?
    • RQ3: How can partnering be used a mean to facilitate the realization of SCM in the construction industry?

    To answer the research questions two main methodologies have been used; case study for the empirically grounded research and conceptual studies for the analysis of the case studies as well as for comparing the two concepts of partnering and SCM. All questions have been grounded in literature and previous research. The findings of this research is therefore grounded in both theory and in practice. The main findings of this research is that TPL solutions are not a quick fix for realizing SCM in the construction industry. However, if used right a TPL solution can be an effective tool to address logistical issues in a construction project and to establish an interface between the supply chain and the construction site. By initiating a TPL solution the client addresses the importance of logistical competence in a construction project. A TPL solution does not have a purpose of its own; a TPL solution is a service function to the construction project, providing expertise on logistics management. There are also a number of driving forces and concerns that have been identified, if they are addressed prior to a TPL solution is implemented, the likelihood of its success will increase.

    Furthermore, both partnering and SCM rely on high trust and share several key components and issues that have to be addressed. Partnering on strategic level with several suppliers included can even be hard to distinguish from SCM. Wherefore, partnering is considered a facilitator for the realization of SCM in construction. By addressing the necessary issues in both concepts a good foundation for SCM is established.

    List of papers
    1. Third-party logistics in construction: the case of a large hospital project
    Open this publication in new window or tab >>Third-party logistics in construction: the case of a large hospital project
    2016 (English)In: Construction Management and Economics, ISSN 0144-6193, E-ISSN 1466-433X, Vol. 34, no 3, p. 174-191Article in journal (Refereed) Published
    Abstract [en]

    The construction supply chain is of temporary nature and complex, with many interactions between multiple actors in different construction projects. This challenging context typically leads to relatively higher costs and lower productivity, compared to other industries. Supply chain management (SCM) has been put forward as a mean to better handle this challenging context. As a part of SCM initiatives some construction industry stakeholders have turned to third-party logistics (TPL) providers, especially in large construction projects. The use of TPL providers is a new, and under-investigated, phenomenon in the construction industry. The main purpose of this study is thus to explore the use of a TPL provider in a large construction project and to analyse its resulting effects. Driving forces and possible concerns for implementing TPL are identified and the possibility for TPL to be a facilitator for implementing SCM in construction is investigated. The research is based on a literature review and an explorative case study of a large hospital project in Sweden, where the client and the main contractor have initiated the use of a TPL provider to coordinate sourcing and materials handling activities on site. The results show positive effects on establishing an effective interface between the construction site and the supply chain. The results also show that a TPL solution facilitates an increase in productive work at the construction site itself, a reduction of costs and an increased utilisation of site assets. On the downside, the study also shows a lack of SCM knowledge amongst the involved actors in the project, hindering them to reap the full potential of TPL.

    Place, publisher, year, edition, pages
    Routledge, 2016
    Keywords
    Case study, construction logistics, construction supply chain, supply chain management, third-party logistics
    National Category
    Construction Management Transport Systems and Logistics Business Administration
    Identifiers
    urn:nbn:se:liu:diva-128817 (URN)10.1080/01446193.2016.1186809 (DOI)
    Available from: 2016-05-31 Created: 2016-05-31 Last updated: 2017-11-30
    2. Third-party logistics in construction: Perspectives from suppliers and transport providers
    Open this publication in new window or tab >>Third-party logistics in construction: Perspectives from suppliers and transport providers
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Suppliers and transport providers are key parties in the construction supply chain, and

    their respective roles when employing third-party logistics (TPL) is investigated. The

    purpose is to analyze how they are affected by the TPL solution in terms of their

    attitudes towards the use of TPL, the experienced effects from the TPL solution, and

    their level of supply chain management (SCM) maturity. This is done by a literature

    review and an explorative case study at a large construction project employing a TPL

    solution. Results show a positive attitude and that they actively address SCM issues,

    whereas actual effects are inconclusive.

    Keywords
    Construction management, Supply chain management, Third-party logistics, Case study
    National Category
    Construction Management Transport Systems and Logistics Business Administration
    Identifiers
    urn:nbn:se:liu:diva-128818 (URN)
    Available from: 2016-05-31 Created: 2016-05-31 Last updated: 2016-06-01
    3. Partnering as a mean towards the use of supply chain management in temporary construction organizations
    Open this publication in new window or tab >>Partnering as a mean towards the use of supply chain management in temporary construction organizations
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    The construction industry is a complex industry typically working in temporary

    organizations. The temporary organizational structure of the construction industry affects

    the outcome of construction projects. In recent years the construction industry has been

    associated with problems such as low productivity, high costs, high waste and poorly

    managed supply chains. To overcome these problems, several government funded reports

    and research reports have addressed the problems. Two concepts have gained a lot of

    interest in these reports: partnering and supply chain management (SCM). However,

    partnering, that have been introduced to overcome the temporariness in the construction

    industry has been more successful than SCM. A reason behind this could be that SCM

    derives from the manufacturing industry and is directed towards long-term relationships

    and permanent organizational structures. By a conceptual literature review it is

    investigated if the realization of SCM in construction could be facilitated by the use of

    partnering. Both concepts share many components and partnering has been a successful

    approach to overcome the boundaries temporary organizations imply. The two concepts

    are in fact so similar that it can be argued that partnering is a subset of SCM focusing

    relationships. The question would then be what type of partnering approach is most

    suitable when realizing SCM in construction.

    Keywords
    Partnering, Supply chain management, Temporary organizations, Construction management, Construction industry
    National Category
    Construction Management Transport Systems and Logistics Business Administration
    Identifiers
    urn:nbn:se:liu:diva-128819 (URN)
    Available from: 2016-05-31 Created: 2016-05-31 Last updated: 2016-06-01
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  • 290.
    Ekeskär, Andreas
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology. Linköping University, Faculty of Science & Engineering.
    Partnering as a mean towards the use of supply chain management in temporary construction organizationsManuscript (preprint) (Other academic)
    Abstract [en]

    The construction industry is a complex industry typically working in temporary

    organizations. The temporary organizational structure of the construction industry affects

    the outcome of construction projects. In recent years the construction industry has been

    associated with problems such as low productivity, high costs, high waste and poorly

    managed supply chains. To overcome these problems, several government funded reports

    and research reports have addressed the problems. Two concepts have gained a lot of

    interest in these reports: partnering and supply chain management (SCM). However,

    partnering, that have been introduced to overcome the temporariness in the construction

    industry has been more successful than SCM. A reason behind this could be that SCM

    derives from the manufacturing industry and is directed towards long-term relationships

    and permanent organizational structures. By a conceptual literature review it is

    investigated if the realization of SCM in construction could be facilitated by the use of

    partnering. Both concepts share many components and partnering has been a successful

    approach to overcome the boundaries temporary organizations imply. The two concepts

    are in fact so similar that it can be argued that partnering is a subset of SCM focusing

    relationships. The question would then be what type of partnering approach is most

    suitable when realizing SCM in construction.

  • 291.
    Ekeskär, Andreas
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Rudberg, Martin
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Third-party logistics in construction: Perspectives from suppliers and transport providers2015In: Proceedings of the 22nd EurOMA Conference: Operations Management for Sustainable Comeptitivness, 2015Conference paper (Refereed)
    Abstract [en]

    Suppliers and transport providers are key parties in the construction supply chain, and their respective roles when employing third-party logistics (3PL) is investigated. The purpose is to analyze how they are affected by the 3PL solution in terms of their attitudes towards the use of 3PL, the experienced defects from the 3PL solution, and their level of supply chain management (SCM) maturity. This is done by a literature review and an explorative case study at a large construction project employing a 3PL solution. Results show a positive attitude and that they actively address SCM issues, whereas actual effects are inconclusive.

  • 292.
    Ekeskär, Andreas
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology. Linköping University, Faculty of Science & Engineering.
    Rudberg, Martin
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Third-party logistics in construction: Perspectives from suppliers and transport providersManuscript (preprint) (Other academic)
    Abstract [en]

    Suppliers and transport providers are key parties in the construction supply chain, and

    their respective roles when employing third-party logistics (TPL) is investigated. The

    purpose is to analyze how they are affected by the TPL solution in terms of their

    attitudes towards the use of TPL, the experienced effects from the TPL solution, and

    their level of supply chain management (SCM) maturity. This is done by a literature

    review and an explorative case study at a large construction project employing a TPL

    solution. Results show a positive attitude and that they actively address SCM issues,

    whereas actual effects are inconclusive.

  • 293.
    Ekeskär, Andreas
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Rudberg, Martin
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Third-party logistics in construction: the case of a large hospital project2016In: Construction Management and Economics, ISSN 0144-6193, E-ISSN 1466-433X, Vol. 34, no 3, p. 174-191Article in journal (Refereed)
    Abstract [en]

    The construction supply chain is of temporary nature and complex, with many interactions between multiple actors in different construction projects. This challenging context typically leads to relatively higher costs and lower productivity, compared to other industries. Supply chain management (SCM) has been put forward as a mean to better handle this challenging context. As a part of SCM initiatives some construction industry stakeholders have turned to third-party logistics (TPL) providers, especially in large construction projects. The use of TPL providers is a new, and under-investigated, phenomenon in the construction industry. The main purpose of this study is thus to explore the use of a TPL provider in a large construction project and to analyse its resulting effects. Driving forces and possible concerns for implementing TPL are identified and the possibility for TPL to be a facilitator for implementing SCM in construction is investigated. The research is based on a literature review and an explorative case study of a large hospital project in Sweden, where the client and the main contractor have initiated the use of a TPL provider to coordinate sourcing and materials handling activities on site. The results show positive effects on establishing an effective interface between the construction site and the supply chain. The results also show that a TPL solution facilitates an increase in productive work at the construction site itself, a reduction of costs and an increased utilisation of site assets. On the downside, the study also shows a lack of SCM knowledge amongst the involved actors in the project, hindering them to reap the full potential of TPL.

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  • 294.
    Ekeskär, Andreas
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Rudberg, Martin
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Vennström, Anders
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Third-party logistics in large construction projects: A SCM perspective2014In: Proceedings of the 21st EurOMA Conference: Operations Management in an innovative economy, 2014Conference paper (Refereed)
    Abstract [en]

    The purpose of this paper is to investigate the use of 3PL providers in large construction projects, and to identify main drivers and barriers, as well as the resulting effects, when implementing SCM by the use of 3PL providers. This is done by the means of a literature review and an explorative case study, the latter being a large hospital construction project. The results show positive performance effects in terms of increased productivity, resources utilization, and delivery performance, but also that there are challenges when it comes to organizational setting, policy adherence and supply chain coordination.

  • 295.
    Ekman, Anna-Karin
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Calibration of traffic models in SIDRA2013Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis studies calibration of SIDRA Intersection roundabout models. The calibration has been performed with three different methods; manual calibration of gap-acceptance parameters, manual calibration of the parameter environment factor and automatic calibration of the environment factor based on optimization. The main aim has been to evaluate and compare 3 the three methods. One part of the purpose was also to test the possibility of finding a general value of environment factor by testing a few different types of models. SIDRA Intersection is a micro-analytical model used for capacity and performance estimations. The capacity model is based on gap-acceptance theory where follow-up headway and critical gap have a great impact. An application for automatic calibration was developed in Microsoft Excel/VBA. The calibration process is based Differential evolution and the cost function uses root mean square percent error where capacity and average delay are used as performance measures. The application has been tested with a test model at first to make sure the calibration is correct. The application has then been tested on data from a site in Farsta, Stockholm. For this site all three calibration methods, the two manual and the automatic, has been tested. The results show that all three methods performed equally well, with only small differences in precision. The most effective method considering results and time required for process was the manual calibration of environment factor.In the last part of this project the method for manual calibration of environment factor was tested with three more models with different characteristics in order to investigate the possibility of finding one value for environment factor suitable for all approaches. However the tests show difference in environment factor between small and large roundabouts and difficulties to set one value for environment factor for two-lane approaches.

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  • 296.
    Ekman, Harald
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Effektiv dimensionering av stånginfästningar i Excel2018Independent thesis Basic level (university diploma), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    Byggbranschen anses ofta som långsam, dyr och ineffektiv, vilket skapar möjligheter till förbättring. Denna uppsats angriper projekteringsskedet då konstruktionsritningar skapas. Dimensionering av stålanslutningar kan upplevas som en komplicerad och lång process, speciellt vid handberäkning Det lämnar utrymme för effektivisering som på så sätt sparar både tid och pengar. Uppsatsen avgränsas till stålanslutningen stånginfästning som är vanligt förekommande i fackverkskonstruktioner av olika slag. Exempel på sådana konstruktioner är fackverkstakstolar, fackverksbroar samt vid stagning av andra konstruktioner med hänsyn till vippning och knäckning. En genomgång av dimensioneringsgången har gjorts och exempeluppgifter har skapats för att kunna tillämpa kunskaperna. Därefter programmerades samma dimensioneringsgång i Excel för att undersöka vilka möjligheter till effektivisering som finns med programvaran. En avgörande faktor till knutpunktens kapacitet uppmärksammades. Knutpunktens kapacitet beror till stor del av stängernas utformning i förhållande till varandra. Vidare observerades goda dimensioneringsmöjligheter i Excel där kontroller och dimensionering av alla möjliga stålprofiler utförs på ett ögonblick. Dessutom ges en visuell överblick av möjliga alternativ hållfasthetsmässigt men också ur ett ekonomiskt perspektiv. Stålprofilerna ställs mot varandra i grafer för att på så sätt förenkla valet av profil. Då fråga om tillgänglighet eller behov av anpassad redovisning av dimensioneringsberäkningar är aktuellt rekommenderas Excel.

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    Effektiv dimensionering av stånginfästningar i Excel
  • 297.
    Ekstedt, Alexander
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Mucerenge, Sonia
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Improved article placement through ABC analysis - a case study at Hellman´s förlag2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    En viktig del av lagerhållning är att placera artiklar på ett sådant sätt att materialhanteringen i lagret sker så effektivt som möjligt, t.ex. genom minskad tid för plockning av artiklar. När artiklar ska plockas, för att packas och avsändas, kan det ske utifrån olika strategier, t.ex. med utgångspunkt i varje order som kunden lägger. Beroende på hur plockningen går till kan artiklar placeras på ett sätt som effektiviserar plockningen och därmed minskar plocktiden. Hellmans förlag är ett tredjepartslogistikföretag som lagerhåller utbildningsmaterial. Många av deras artiklar med låg plockfrekvens är placerade på åtkomliga lagerplatser medan artiklar med högre plockfrekvens är placerade på mindre åtkomliga platser. Vidare är andra artiklar placerade utspridda på ett flertal hyllor som i praktiken till stor del är tomma. Syftet med studien var att undersöka artikelplaceringen i Hellmans lager samt att med hjälp av ABC-analyser föreslå bättre artikelplaceringar för att reducera plocktiden. För att utföra passande ABC-analyser studerades relevanta klassificeringskriterier. Observationer och intervjuer genomfördes i Hellmans lager för att beskriva artikelplaceringen i dagsläget samt för att se möjligheter till förbättrad artikelplacering. Med hjälp av historiska data genomfördes ABC-analyser i lagret som utgjorde grunden för en ny artikelplacering. Artikelplaceringen i Hellmans buffertlager saknar särskild artikelnummerordning eller klassificering av något slag. I plocklagret är hyllorna till stor del tomma eftersom endast 12 % av lagerplatserna faktiskt ockuperas. Vidare är nästan 90 % av antalet artiklar placerade på den bortre halvan av hyllsektionerna. Med artiklars plockfrekvens som kriterium utfördes ABC-analyser för att klassificera artiklarna och föreslå nya placeringar. Förbrukning av artiklar användes som sekundärkriterium i dubbla ABC-analyser men bedömdes missvisande och användes därför inte i förbättringsförslagen. Med de endimensionella ABC-analyserna som grund förslås att placera artiklar utifrån fallande plockfrekvens samtidigt som någon typ av artikelnummerordning uppehålls samt att den höjdnivå som är närmast åtkomlig prioriteras.

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    mproved article placement through ABC analysis - a case study at Hellman´s förlag
  • 298.
    Ekström, Joakim
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    A MILP approximation approach for finding optimal toll locations and levels in elastic demand traffic networks2010In: TRANSPORTATION AND URBAN SUSTAINABILITY: Proceedings of the 15th International Conference of Hong Kong Society for Transportation Studies (HKSTS) / [ed] Sumalee, A; Lam, WHK; Ho, HW; Siu, B, Hong Kong, China: Hong Kong Society for Transportation Studies , 2010, p. 107-114Conference paper (Refereed)
    Abstract [en]

    The toll design problem (TDP) is to find optimal toll locations and corresponding toll levels in a congestion pricing scheme. The TDP can be formulated as a non-convex mathematical program, in which the road users are assumed to be distributed according to a user-equilibrium with elastic demand. This program is hard to solve due to non-convexity and non-smoothness. In this paper, the TDP is approximated by a mixed integer linear program (MILP), in which the non-linear functions of the TDP are approximated by piecewise linear ones. The MILP can be solved to its global optimal solution by known methods, and its optimal solution will give a lower bound on the optimal solution to the TDP. By iteratively updating the MILP approximation, the error introduced by the approximation is reduced, and for a test network with nine nodes and 18 links, the global optimal solution is obtained.

  • 299.
    Ekström, Joakim
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Comparison of usage-based congestion pricing schemes2018In: Proceedings Transportation Research Board 97th Annual Meeting, Washington D.C., 2018Conference paper (Refereed)
    Abstract [en]

    This paper investigates how usage-based pricing can be applied in order to improve the efficiency of the transportation system. Distance-based, travel time-based and delayed-based pricing schemes are investigated, both from a one-link and network perspective. A static modeling framework is adopted, based on user-equilibrium, and a simplified emission model based on the HBEFA emission model is used. Optimal usage-based fees are calculated using a surrogate-based optimization framework, and determination of zone layout is done using k-means clustering. The results for a Stockholm region network show that already with network wide pricing a large proportion of the maximum improvement of social surplus achievable with first-best pricing, can be reached. Delay-based pricing, in which the users are charged based on the excess travel time in comparison to free flow travel times, achieves 99% of the maximum improvement, already with one single fee across the whole network. With clustering of links based on their first-best optimal fees, the benefits of both distance and travel time-based fees can significantly be improved.

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  • 300.
    Ekström, Joakim
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Finding second-best toll locations and levels by relaxing the set of first-best feasible toll vectors2014In: European Journal of Transport and Infrastructure Research, ISSN 1567-7133, E-ISSN 1567-7141, Vol. 14, no 1, p. 7-29Article in journal (Refereed)
    Abstract [en]

    This paper provides a framework for optimizing toll locations and levels in congestion pricing schemes for large urban road networks, with the objective to maximize the social surplus. This optimization problem is referred to as the toll location and level setting problem (TLLP) and is both non-convex, non-smooth and involves binary decision variables, and is therefore considered as a hard problem to solve. In this paper a solution approach is provided which instead of directly solving the TLLP, makes use of the first-best toll level solution, in which no restrictions are imposed on toll locations or levels. A first-best pricing scheme can be obtained by solving a convex program, and it has previously been shown that for the used routes in the network, the first-best toll levels on a route level are unique. By formulating an optimization problem, which instead of maximizing the social surplus, tries to find the link toll levels which minimize the deviation from first-best route tolls, a mixed integer linear program is obtained, and if the toll locations are predetermined the resulting optimization problem is a linear program.

    The approach of minimizing the deviation from first--best route tolls is applied for two different network models, and results are provided to show the applicability of the approach, as well as to compare with other approaches. Also, it is shown that for the Stockholm network, virtually the first-best level of social surplus can be obtained with a significantly reduced number of located tolls.

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