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  • 101.
    Andersson Naesseth, Christian
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Lindsten, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Schön, Thomas
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Capacity estimation of two-dimensional channels using Sequential Monte Carlo2014Inngår i: 2014 IEEE Information Theory Workshop, 2014, s. 431-435Konferansepaper (Fagfellevurdert)
    Abstract [en]

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

  • 102.
    Andersson Naesseth, Christian
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Lindsten, Fredrik
    The University of Cambridge, Cambridge, United Kingdom.
    Schön, Thomas
    Uppsala University, Uppsala, Sweden.
    Nested Sequential Monte Carlo Methods2015Inngår i: Proceedings of The 32nd International Conference on Machine Learning / [ed] Francis Bach, David Blei, Journal of Machine Learning Research (Online) , 2015, Vol. 37, s. 1292-1301Konferansepaper (Fagfellevurdert)
    Abstract [en]

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

  • 103.
    Andersson Naesseth, Christian
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Lindsten, Fredrik
    University of Cambridge, Cambridge, UK.
    Schön, Thomas
    Uppsala University, Uppsala, Sweden.
    Sequential Monte Carlo for Graphical Models2014Inngår i: Advances in Neural Information Processing Systems, 2014, s. 1862-1870Konferansepaper (Fagfellevurdert)
    Abstract [en]

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

  • 104.
    Andersson Naesseth, Christian
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten. Columbia University, USA.
    Ruiz, Francisco
    Columbia University, USA, University of Cambridge, UK.
    Linderman, Scott
    Columbia University, USA.
    Blei, David
    Columbia University, USA.
    Reparameterization Gradients through Acceptance-Rejection Sampling Algorithms2017Inngår i: Proceedings of the 20th International Conference on Artificial Intelligence and Statistics, 2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Variational inference using the reparameterization trick has enabled large-scale approximate Bayesian inference in complex probabilistic models, leveraging stochastic optimization to sidestep intractable expectations. The reparameterization trick is applicable when we can simulate a random variable by applying a differentiable deterministic function on an auxiliary random variable whose distribution is fixed. For many distributions of interest (such as the gamma or Dirichlet), simulation of random variables relies on acceptance-rejection sampling. The discontinuity introduced by the accept-reject step means that standard reparameterization tricks are not applicable. We propose a new method that lets us leverage reparameterization gradients even when variables are outputs of a acceptance-rejection sampling algorithm. Our approach enables reparameterization on a larger class of variational distributions. In several studies of real and synthetic data, we show that the variance of the estimator of the gradient is significantly lower than other state-of-the-art methods. This leads to faster convergence of stochastic gradient variational inference.

  • 105.
    Andersson, Nisa
    et al.
    Linköpings universitet, Institutionen för datavetenskap.
    Broman, Nils
    Björn, Martin
    Linköpings universitet, Institutionen för datavetenskap.
    Byström, Adrian
    Linköpings universitet, Institutionen för datavetenskap.
    Markfjärd, Gabriel
    Linköpings universitet, Institutionen för datavetenskap.
    Rasmussen, Christian
    Linköpings universitet, Institutionen för datavetenskap.
    Sundberg, Simon
    Linköpings universitet, Institutionen för datavetenskap.
    Prediktion av priset på höstvete2019Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    I denna rapport finnes resultatet av kandidatprojektet i kursen TDDD96 som ges av Linköpings universitet. Projektet har utförts av sju studenter på Civilingenjörsprogrammet inom Datateknik och Civilingenjörsprogrammet inom Mjukvaruteknik. Projektet som utförts var ett mjuvaruutvecklingsprojekt, där studenterna utvecklade en webb-applikation för visningen av historisk data från källor relaterade till lantbruk, med fokus på grödan höstvete. Projektet har dessutom innefattat en studie som, med hjälp av enkla maskininlärningstekniker, undersökt om datan är tillräcklig för att ge en prediktion på vad priset kan tänkas vara i framtiden. Rapporten behandlar de tekniska, gruppadministrativa, och informationsinsamlande val som gjorts, samt hur arbetet med utvecklingen har genomförts och vad resultatet av projektet blev. Rapporten innehåller även sju individuella delar, tillhörande var och en av de sju studenterna, där de genomfört en studie på en egen frågeställning. Dessa finnes i slutet av dokumentet.

  • 106.
    Andersson, Olov
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Artificiell intelligens och integrerad datorsystem. Linköpings universitet, Tekniska högskolan.
    Heintz, Fredrik
    Linköpings universitet, Institutionen för datavetenskap, Artificiell intelligens och integrerad datorsystem. Linköpings universitet, Tekniska högskolan.
    Doherty, Patrick
    Linköpings universitet, Institutionen för datavetenskap, Artificiell intelligens och integrerad datorsystem. Linköpings universitet, Tekniska högskolan.
    Model-Based Reinforcement Learning in Continuous Environments Using Real-Time Constrained Optimization2015Inngår i: Proceedings of the Twenty-Ninth AAAI Conference on Artificial Intelligence (AAAI) / [ed] Blai Bonet and Sven Koenig, AAAI Press, 2015, s. 2497-2503Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Reinforcement learning for robot control tasks in continuous environments is a challenging problem due to the dimensionality of the state and action spaces, time and resource costs for learning with a real robot as well as constraints imposed for its safe operation. In this paper we propose a model-based reinforcement learning approach for continuous environments with constraints. The approach combines model-based reinforcement learning with recent advances in approximate optimal control. This results in a bounded-rationality agent that makes decisions in real-time by efficiently solving a sequence of constrained optimization problems on learned sparse Gaussian process models. Such a combination has several advantages. No high-dimensional policy needs to be computed or stored while the learning problem often reduces to a set of lower-dimensional models of the dynamics. In addition, hard constraints can easily be included and objectives can also be changed in real-time to allow for multiple or dynamic tasks. The efficacy of the approach is demonstrated on both an extended cart pole domain and a challenging quadcopter navigation task using real data.

  • 107.
    Andersson, Olov
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Artificiell intelligens och integrerade datorsystem. Linköpings universitet, Tekniska fakulteten.
    Wzorek, Mariusz
    Linköpings universitet, Institutionen för datavetenskap, Artificiell intelligens och integrerade datorsystem. Linköpings universitet, Tekniska fakulteten.
    Doherty, Patrick
    Linköpings universitet, Institutionen för datavetenskap, Artificiell intelligens och integrerade datorsystem. Linköpings universitet, Tekniska fakulteten.
    Deep Learning Quadcopter Control via Risk-Aware Active Learning2017Inngår i: Proceedings of The Thirty-first AAAI Conference on Artificial Intelligence (AAAI) / [ed] Satinder Singh and Shaul Markovitch, AAAI Press, 2017, Vol. 5, s. 3812-3818Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Modern optimization-based approaches to control increasingly allow automatic generation of complex behavior from only a model and an objective. Recent years has seen growing interest in fast solvers to also allow real-time operation on robots, but the computational cost of such trajectory optimization remains prohibitive for many applications. In this paper we examine a novel deep neural network approximation and validate it on a safe navigation problem with a real nano-quadcopter. As the risk of costly failures is a major concern with real robots, we propose a risk-aware resampling technique. Contrary to prior work this active learning approach is easy to use with existing solvers for trajectory optimization, as well as deep learning. We demonstrate the efficacy of the approach on a difficult collision avoidance problem with non-cooperative moving obstacles. Our findings indicate that the resulting neural network approximations are least 50 times faster than the trajectory optimizer while still satisfying the safety requirements. We demonstrate the potential of the approach by implementing a synthesized deep neural network policy on the nano-quadcopter microcontroller.

  • 108.
    Andersson, Olov
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Artificiell intelligens och integrerade datorsystem. Linköpings universitet, Tekniska fakulteten.
    Wzorek, Mariusz
    Linköpings universitet, Institutionen för datavetenskap, Artificiell intelligens och integrerade datorsystem. Linköpings universitet, Tekniska fakulteten.
    Rudol, Piotr
    Linköpings universitet, Institutionen för datavetenskap, Artificiell intelligens och integrerade datorsystem. Linköpings universitet, Tekniska fakulteten.
    Doherty, Patrick
    Linköpings universitet, Institutionen för datavetenskap, Artificiell intelligens och integrerade datorsystem. Linköpings universitet, Tekniska fakulteten.
    Model-Predictive Control with Stochastic Collision Avoidance using Bayesian Policy Optimization2016Inngår i: IEEE International Conference on Robotics and Automation (ICRA), 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, s. 4597-4604Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Robots are increasingly expected to move out of the controlled environment of research labs and into populated streets and workplaces. Collision avoidance in such cluttered and dynamic environments is of increasing importance as robots gain more autonomy. However, efficient avoidance is fundamentally difficult since computing safe trajectories may require considering both dynamics and uncertainty. While heuristics are often used in practice, we take a holistic stochastic trajectory optimization perspective that merges both collision avoidance and control. We examine dynamic obstacles moving without prior coordination, like pedestrians or vehicles. We find that common stochastic simplifications lead to poor approximations when obstacle behavior is difficult to predict. We instead compute efficient approximations by drawing upon techniques from machine learning. We propose to combine policy search with model-predictive control. This allows us to use recent fast constrained model-predictive control solvers, while gaining the stochastic properties of policy-based methods. We exploit recent advances in Bayesian optimization to efficiently solve the resulting probabilistically-constrained policy optimization problems. Finally, we present a real-time implementation of an obstacle avoiding controller for a quadcopter. We demonstrate the results in simulation as well as with real flight experiments.

  • 109.
    Andersson, Per
    Linköpings universitet, Institutionen för datavetenskap.
    Design och utvärdering av en självbetjänings-terminal för mammografiundersökningar – en fallstudie2010Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Självbetjäningsterminaler tar över efter traditionella kassor och receptioner på allt fler platser i dagens samhälle. Vare sig du ska handla möbler på IKEA, låna böcker från biblioteket eller besiktiga bilen är sannolikheten stor att du stöter på en terminal. Dess användare anser många gånger att självbetjäningen är snabbare än och effektivare än dess traditionella motsvarighet, medan motståndarna anser att en maskin aldrig kan ersätta den personliga service en människa ger.

    Den här rapporten försöker dels besvara frågan om en självbetjäningsterminal tillför något positivt för personal respektive patienter på en mammografiklinik, och dels redogör den för de problem patienterna upplevde medan de använde terminalen.

    De patienter som rör sig på en mammografiklinik är i allmänhet äldre kvinnor med väldigt varierande förutsättningar vad det gäller datorvana. För att få så stort antal testpatienter som möjligt under utvärderingsperioden, stängdes klinikens ordinarie reception ner och samtliga patienter blev istället hänvisade till en av två självbetjäningsterminaler. Totalt användes terminalerna av 425 kvinnor i åldrarna 21 – 83 år, där medelåldern låg på knappt 54 år.

    Utvärderingen visar att patienternas största problem i allmänhet var att först och främst hitta terminalen, och därefter att förstå att de skulle trycka på terminalens pekskärm för att interagera med den. När patienterna väl har klarat sig över den tröskeln går resten av processen smidigt för de flesta, även om det förekommer undantag från den regeln.

    Personalen som arbetar på kliniken var till en början väldigt skeptiska till terminalernas intåg, men under utvärderingsperioderna upptäcktes flera fördelar jämfört med en traditionell reception. En del av uppgifterna som utförs i receptionen kan i dagsläget inte utföras av en terminal. Terminalerna kan därför inte ersätta receptionen, utan snarare fungera som ett komplement och en avlastning.

  • 110.
    Andersson, Peter
    Linköpings universitet, Institutionen för datavetenskap, CASL - Cognitive Autonomous Systems Laboratory. Linköpings universitet, Tekniska högskolan.
    Hazard: a Framework Towards Connecting Artificial Intelligence and Robotics2005Inngår i: IJCAI Workshop on Reasoning, Representation and Learning in Computer Games, 2005Konferansepaper (Fagfellevurdert)
  • 111.
    Andersson, Peter
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, CASL - Cognitive Autonomous Systems Laboratory.
    Hazard: A Framework Towards Connecting Artificial Intelligence and Robotics2005Inngår i: Proceedings of the 1st International Workshop on Multi-Agent Robotic Systems (MARS), Barcelona: INSTICC PRESS , 2005, s. 171-Konferansepaper (Fagfellevurdert)
  • 112.
    Andersson, Robin
    Linköpings universitet, Institutionen för datavetenskap.
    Implementation av ett kunskapsbas system för rough set theory med kvantitativa mätningar2004Independent thesis Basic level (professional degree)Oppgave
    Abstract [en]

    This thesis presents the implementation of a knowledge base system for rough sets [Paw92]within the logic programming framework. The combination of rough set theory with logic programming is a novel approach. The presented implementation serves as a prototype system for the ideas presented in [VDM03a, VDM03b]. The system is available at "http://www.ida.liu.se/rkbs".

    The presented language for describing knowledge in the rough knowledge base caters for implicit definition of rough sets by combining different regions (e.g. upper approximation, lower approximation, boundary) of other defined rough sets. The rough knowledge base system also provides methods for querying the knowledge base and methods for computing quantitative measures.

    We test the implemented system on a medium sized application example to illustrate the usefulness of the system and the incorporated language. We also provide performance measurements of the system.

  • 113. Andersson, Robin
    et al.
    Vitoria, Aida
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    Maluszynski, Jan
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, TCSLAB - Laboratoriet för teoretisk datalogi.
    Komorowski, Henryk Jan
    RoSy: A Rough Knowledge Base System2005Inngår i: Rough Sets, Fuzzy Sets, Data Mining, and Granular-Soft Computing,2005, Berlin: Springer , 2005, s. 48-Konferansepaper (Fagfellevurdert)
  • 114.
    Andersson, Sara
    Linköpings universitet, Institutionen för datavetenskap.
    Data Transformation Portal2010Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The purpose with this report is to present the findings from the thesis work performed at Ipendo Systems. The goal was to develop a methodological support for the migration process and implement a web portal for migration of data.

    When a company acquires a new application to perhaps replace a legacy system, or to improve their efficiency and there by their competitiveness, the company’s data need to be transferred into the new application. The process of transfer the data from a source to a target is called data migration. Because the source and target systems probably have a somewhat different architecture some transformation to the data has to be made.

    The thesis is divided in two parts, a theoretical part where I learned about data migration and developed a methodological support for data migration projects. The second part of the thesis work was practical designed and I developed a data transformation portal.

    Data migrations are often a somewhat forgotten activity in a project. It is sometimes carried out without a proper plan or structure. To bring some structure to this important process I developed a methodological support. The methodological support is made like a guide for how to conduct data migration projects. The purpose of the methodological support is to make data migrations more visible as an own project and add more structure to it. The methodological support is divided into five phases. The five phases are planning, analysis, design, implementation and validation. Every step has its own milestones and deliverables so the support could be used as a sort of checklist during the project.

    have also developed a web portal in SharePoint. The purpose with a data transformation portal is to gather all data migration to one common area without a third-party migration tool and minimize the technical complexity associated with data migration projects. I have developed two modules for the portal. The first module concerns migration from an Excel document to a SharePoint list. The second module handles upload of documents to a SharePoint document library. The portal has functionality like data mapping, validation and setting of metadata. Migration of data is a specific process, depending of the type of data that should be migrated it requires a somewhat different approach. A data transformation portal which can visually monitor, filter, transform and import various types of data to and from various data sources would facilitate the migration process.

  • 115.
    Andersson, Tim
    et al.
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Arnesson, Gustav
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Brengdahl, Pontus
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Ekelund, Anna
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Kallström, Claes
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Olsson, Kalle
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Thudén, Julia
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Wallvik, Erik
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Experiences from the Development of a Webshop Using Scrum Methodology2014Independent thesis Basic level (degree of Bachelor), 12 poäng / 18 hpOppgave
    Abstract [en]

    This is a report concerning the software development project Eldflugan, a system developed by eight students at Linköping University. It addresses experience from developing a web-based e-commerce using Scrum, an agile development method, which was used throughout the project. The teams work, how Scrum was applied with both advantages and disadvantages is being lifted. Different development environments have been used due to separate issues and opportunities, which is described. The database management systems, MySQL, and the local version, SQLite, are discussed as well as AJAX and PJAX, tools for giving the users a better and faster experience. To prepare Eldflugan for entering the e-commerce market, a marketing plan including environmental scanning, a SWOT analysis and a STP, has been made. Ethical aspects such as legal, use and handling of personal information and how it is communicated are also being addressed. Finally the report discusses product weaknesses, future opportunities, implementation difficulties and how those could have been prevented. It was found that Scrum is best used when it is utilized fully and a risk analysis can prevent unexpected problems to surface. 

  • 116.
    Andersson, Ulf
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska högskolan.
    Betalkort: Slutrapport1980Rapport (Annet vitenskapelig)
    Abstract [sv]

    Idén till Universalkort uppkom för cirka tre år sedan, som en följd av ett examensarbete med namnet "ID- kort med minne". Där undersöktes möjligheten att placera ett nonvolatilt minne på ett kort. Fortsättningen på det projektet beskrivs kort under rubriken ”Existerande hårdvarusystem”.

    Utvecklingen av Betal- och Universalkortsidén har sedan dess bedrivits i samarbete med personal på Institutionen för Systemteknik inom ämnesområdet informationsteori vid LiTH. Jag vill rikta ett varmt tack till dessa och speciellt till Rolf Blom , Robert Forchheimer och Ingemar Ingemarsson för deras bidrag till arbetet.

  • 117.
    Andersson, Viktor
    et al.
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Berg, Emil
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Bergsten, Emanuel
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Classon, Johan
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Fredriksson, Tony
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Halldén, Max
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Ljungberg, Niklas
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Övervakningsfunktion för en mätplattform för mätning i bil – erfarenhetsrapport från kandidatprojekt i programvaruutveckling2014Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Denna rapport innehåller de samlade erfarenheterna från ett produktutvecklingsprojekt i kursen TDDD77 vid Linköpings universitet. Projektets mål var att skapa en applikation för att visualisera mätdata från en specialutrustad bil på en surfplatta. Detta var önskvärt då det inte fanns något sätt att se om någon sensor slutade fungera mitt i ett test. Projektet delades upp i en förstudie följd av tre iterationer, där en färdig produkt presenterades på en teknisk mässa i slutet av iteration 3.

    Resultaten visar att Essence Kernel Alpha States kunde användas som en hälsokontroll för projektet, men då de kunde ses som rätt vaga och lämnade rum för tolkning passade det bäst som ett komplement till exempelvis milstolpar.

    Att använda Google Protocol Buffers sågs som ett viktigt tekniskt val tillsammans med uppdelningen av klienten i front- och back-end. Protobuf underlättade kommunikationen mellan server och klient som annars krävt ett nyskapat protokoll.

    Uppdelningen av front- och back-end underlättade inte bara resursfördelningen vid utveckling utan även vid felsökning då det i många fall blev lättare att se precis var felet uppkom. Back-ends uppbyggnad gjorde även att den går att återanvända vid eventuell utveckling till flertalet plattformar.

    Den arbetsprocess som följdes ses som en hybrid mellan agila metoder och vattenfallsmodellen.

    Mycket erfarenhet finns att hämta från projektet, bland annat hur krav kan ändras och hur en prototyp kan styra mjukvaruutvecklingen åt rätt håll.

    På grund av att surfplattan distraherar användaren under körning av bil har designen utgått från att minimera interaktionen som krävs med surfplattan under mätning.

  • 118.
    Andrasko, Jan
    et al.
    GC UV Centre, Kobergsgränd 2, SE-58731 Linkoping, Sweden.
    Lagesson-Andrasko, Ludmila
    GC UV Centre, Kobergsgränd 2, SE-58731 Linkoping, Sweden.
    Dahlén, Johan
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemi. Linköpings universitet, Tekniska fakulteten.
    Jonsson, Bengt-Harald
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemi. Linköpings universitet, Tekniska fakulteten.
    Analysis of Explosives by GC-UV2017Inngår i: Journal of Forensic Sciences, ISSN 0022-1198, E-ISSN 1556-4029, Vol. 62, nr 4, s. 1022-1027Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A mixture of explosives was analyzed by gas chromatography (GC) linked to ultraviolet (UV) spectrophotometry that enabled detection in the range of 178-330 nm. The gas-phase UV spectra of 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (DNT), ethylene glycol dinitrate (EGDN), glycerine trinitrate (NG, nitroglycerine), triacetone triperoxide (TATP), and pentaerythritol tetranitrate (PETN) were successfully recorded. The most interesting aspect of the current application is that it enabled simultaneous detection of both the target analyte and its decomposition products. At suitable elevated temperatures of the transfer line between the GC instrument and the UV detector, a partial decomposition was accomplished. Detection was made in real time and resulted in overlaid spectra of the mother compound and its decomposition product. Hence, the presented approach added another level to the qualitative identification of the explosives in comparison with traditional methods that relies only on the detection of the target analyte. As expected, the decomposition product of EGDN, NG, and PETN was NO, while TATP degraded to acetone. DNT and TNT did not exhibit any decomposition at the temperatures used.

  • 119.
    Andreasson, Daniel
    Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system. Linköpings universitet, Tekniska högskolan.
    Slack-time aware dynamic routing schemes for on-chip networks2007Licentiatavhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    Network-on-Chip (NoC) is a new on-chip communication paradigm for future IP-core based System-on-Chip (SoC), designed to remove a number of limitations of today-s on-chip interconnect solutions. A Nointerconnects cores by means of a packet switched micro-network, which improves scalability and reusability, resulting in a shorter time to market. A typical NoC will be running many applications concurrently, which results in shared network capacity between different kinds of traffic flows. Due to the diverse characteristic of applications, some traffic flows will require real-time communication guarantees while others are tolerant to even some loss of data. In order to provide different levels of Quality-of-Service (QoS) for traffic flows, the communication traffic is separated into different service classes. Traffic in NoC is typically classified into two service classes: the guaranteed throughput (GT) and the best-effort (BE) service class. The GT class offers strict QoS guarantees by setting up a virtual path with reserved bandwidth between the source (GT-producer) and destination (GT-consumer), called a GT-path. The BE class offers no strict QoS guarantees, but tries to efficiently use any network capacity which may become available from the GT traffic. The GT traffic may not fully utilize its bandwidth reservation if its communication volume varies, leading to time intervals where there is no GT traffic using the bandwidth reservation. These intervals are referred to as slack-time. If the slack can not be used this leads to unnecessarily reduced performance of BE traffic, since a part of the available network capacity becomes blocked. This thesis deals with methods to efficiently use the slack-time for BE traffic. The contributions include three new dynamic schemes for slack distribution in NoC. First, a scheme to inform the routers of a GT-path about available slack is evaluated. The GT-producer plans its traffic using a special playout buffer and issues control packets containing the actual amount of slack-time available. The results show that this scheme leads to decreased latency, jitter and packet drops for BE traffic. Secondly, an extension to this scheme is evaluated, where slack is distributed among multiple GT-paths (slack distribution in space). This opens up the possibility to balance the QoS of BE traffic flows which overlap with the GT-paths. Thirdly, a scheme to distribute slack among the links of a GT-path (slack distribution in time) is proposed. In this approach, arriving GT-packets, at a certain router along the GT-path, can wait for a maximum defined amount of time. During this time, any waiting BE traffic in the buffers can be forwarded over the GT-path. The results confirm that this is especially important during high BE-traffic load, where this technique decreases the jitter of BE traffic considerably.    

  • 120.
    Andrei, Alexandru
    Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system. Linköpings universitet, Tekniska högskolan.
    Energy Efficient and Predictable Design of Real-Time Embedded Systems2007Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    This thesis addresses several issues related to the design and optimization of embedded systems. In particular, in the context of time-constrained embedded systems, the thesis investigates two problems: the minimization of the energy consumption and the implementation of predictable applications on multiprocessor system-on-chip platforms.

    Power consumption is one of the most limiting factors in electronic systems today. Two techniques that have been shown to reduce the power consumption effectively are dynamic voltage selection and adaptive body biasing. The reduction is achieved by dynamically adjusting the voltage and performance settings according to the application needs. Energy minimization is addressed using both offline and online optimization approaches. Offline, we solve optimally the combined supply voltage and body bias selection problem for multiprocessor systems with imposed time constraints, explicitly taking into account the transition overheads implied by changing voltage levels. The voltage selection technique is applied not only to processors, but also to buses with repeaters and fat wires. We investigate the continuous voltage selection as well as its discrete counterpart. While the above mentioned methods minimize the active energy, we propose an approach that combines voltage selection and processor shutdown in order to optimize the total energy.

    In order to take full advantage of slack that arises from variations in the execution time, it is important to recalculate the voltage and performance settings during run-time, i.e., online. However, voltage scaling is computationally expensive, and, thus, performed at runtime, significantly hampers the possible energy savings. To overcome the online complexity, we propose a quasi-static voltage scaling scheme, with a constant online time complexity O(1). This allows to increase the exploitable slack as well as to avoid the energy dissipated due to online recalculation of the voltage settings.

    Worst-case execution time (WCET) analysis and, in general, the predictability of real-time applications implemented on multiprocessor systems has been addressed only in very restrictive and particular contexts. One important aspect that makes the analysis difficult is the estimation of the system’s communication behavior. The traffic on the bus does not solely originate from data transfers due to data dependencies between tasks, but is also affected by memory transfers as result of cache misses. As opposed to the analysis performed for a single processor system, where the cache miss penalty is constant, in a multiprocessor system each cache miss has a variable penalty, depending on the bus contention. This affects the tasks’ WCET which, however, is needed in order to perform system scheduling. At the same time, the WCET depends on the system schedule due to the bus interference. In this context, we propose, an approach to worst-case execution time analysis and system scheduling for real-time applications implemented on multiprocessor SoC architectures.

  • 121.
    Andrei, Alexandru
    et al.
    Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system. Linköpings universitet, Tekniska högskolan.
    Eles, Petru Ion
    Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system. Linköpings universitet, Tekniska högskolan.
    Peng, Zebo
    Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system. Linköpings universitet, Tekniska högskolan.
    Rosén, Jakob
    Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system. Linköpings universitet, Tekniska högskolan.
    Predictable Implementation of Real-Time Applications on Multiprocessor Systems on Chip2008Inngår i: VLSI Design, 2008. VLSID 2008, IEEE Computer Society, 2008, s. 103-110Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Worst-case execution time (WCET) analysis and, in general, the predictability of real-time applications implemented on multiprocessor systems has been addressed only in very restrictive and particular contexts. One important aspect that makes the analysis difficult is the estimation of the system-s communication behavior. The traffic on the bus does not solely originate from data transfers due to data dependencies between tasks, but is also affected by memory transfers as result of cache misses. As opposed to the analysis performed for a single processor system, where the cache miss penalty is constant, in a multiprocessor system each cache miss has a variable penalty, depending on the bus contention. This affects the tasks- WCET which, however, is needed in order to perform system scheduling. At the same time, the WCET depends on the system schedule due to the bus interference. In this context, we propose, for the first time, an approach to worst-case execution time analysis and system scheduling for real-time applications implemented on multiprocessor SoC architectures.

  • 122.
    Andrei, Alexandru
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system.
    Eles, Petru Ion
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system.
    Peng, Zebo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system.
    Schmitz, Marcus
    Diesel Systems for Commercial Vehicles Robert Bosch GmbH, Germany.
    Al-Hashimi, Bashir
    Computer Engineering Dept. Southampton University, UK.
    Voltage Selection for Time-Constrained Multiprocessor Systems on Chip2007Inngår i: Designing Embedded Processors: A Low Power Perspective / [ed] Jörg Henkel, Sri Parameswaran, Dordrecht: Springer , 2007, s. 259-286Kapittel i bok, del av antologi (Annet vitenskapelig)
    Abstract [en]

    As we embrace the world of personal, portable, and perplexingly complex digital systems, it has befallen upon the bewildered designer to take advantage of the available transistors to produce a system which is small, fast, cheap and correct, yet possesses increased functionality. Increasingly, these systems have to consume little energy.

    Designers are increasingly turning towards small processors, which are low power, and customize these processors both in software and hardware to achieve their objectives of a low power system, which is verified, and has short design turnaround times. Designing Embedded Processors examines the many ways in which processor based systems are designed to allow low power devices.

    It looks at processor design methods, memory optimization, dynamic voltage scaling methods, compiler methods, and multi processor methods. Each section has an introductory chapter to give a breadth view, and have a few specialist chapters in the area to give a deeper perspective. The book provides a good starting point to engineers in the area, and to research students embarking upon the exciting area of embedded systems and architectures.

  • 123.
    Andrei, Alexandru
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system.
    Schmitz, Marcus
    IDA Linköpings Universitet.
    Eles, Petru Ion
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system.
    Peng, Zebo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system.
    Al Hashimi, Bashir M.
    Dept. of Electronics and Computer Science University of Southampton.
    Overhead-Conscious Voltage Selection for Dynamic and Leakage Energy Reduction of Time-Constrained Systems2004Inngår i: Design, Automation and Test in Europe DATE 2004,2004, Paris, France: IEEE Computer Society Press , 2004, s. 518-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Dynamic voltage scaling and adaptive body biasing have been shown to reduce dynamic and leakage power consumption effectively. In this paper, we optimally solve the combined supply voltage and body bias selection problem for multi-processor systems with imposed time constraints, explicitly taking into account the transition overheads implied by changing voltage levels. Both energy and time overheads are considered. We investigate the continuous voltage scaling as well as its discrete counterpart, and we prove NP-hardness in the discrete case. Furthermore, the continuous voltage scaling problem is formulated and solved using nonlinear programming with polynomial time complexity, while for the discrete problem we use mixed integer linear programming. Extensive experiments, conducted on several benchmarks and a real-life example, are used to validate the approaches.

  • 124.
    Andrei, Alexandru
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system.
    Schmitz, Marcus
    Dept. of Electronics and Computer Science University of Southampton.
    Eles, Petru Ion
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system.
    Peng, Zebo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system.
    Al Hashimi, Bashir M.
    Dept. of Electronics and Computer Science University of Southampton.
    Overhead-Conscious Voltage Selection for Dynamic and Leakage Energy Reduction of Time-Constrained Systems2005Inngår i: IEE Proceedings - Computers and digital Techniques, ISSN 1350-2387, E-ISSN 1359-7027, Vol. 152, nr 01, s. 28-38Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Dynamic voltage scaling and adaptive body biasing have been shown to reduce dynamic and leakage power consumption effectively. In this paper, we optimally solve the combined supply voltage and body bias selection problem for multi-processor systems with imposed time constraints, explicitly taking into account the transition overheads implied by changing voltage levels. Both energy and time overheads are considered. We investigate the continuous voltage scaling as well as its discrete counterpart, and we prove NP-hardness in the discrete case. Furthermore, the continuous voltage scaling problemis formulated and solved using nonlinear programming with polynomial time complexity, while for the discrete problem we use mixed integer linear programming. Extensive experiments, conducted on several benchmarks and a real-life example, are used to validate the approaches.

  • 125.
    Andrei, Alexandru
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system.
    Schmitz, Marcus
    Dept. of Electronics and Computer Science University of Southampton.
    Eles, Petru Ion
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system.
    Peng, Zebo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system.
    Al Hashimi, Bashir M.
    Dept. of Electronics and Computer Science University of Southampton.
    Quasi-Static Voltage Scaling for Energy Minimization with Time Constraints2005Inngår i: Design Automation and Test in Europe Conference DATE 2005,2005, Munich, Germany: IEEE Computer Society Press , 2005, s. 514-Konferansepaper (Fagfellevurdert)
  • 126.
    Andrei, Alexandru
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system.
    Schmitz, Marcus
    IDA Linköpings Universitet.
    Eles, Petru Ion
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system.
    Peng, Zebo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system.
    Al Hashimi, Bashir M.
    Dept. of Electronics and Computer Science University of Southampton.
    Simultaneous Communication and Processor Voltage Scaling for Dynamic and Leakage Energy Reduction in Time-Constrained Systems2004Inngår i: International Conference on Computer Aided Design ICCAD 2004,2004, San Jose, USA: IEEE Computer Society Press , 2004, s. 362-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we propose a new technique for the combined voltage scaling of processors and communication links, taking into account dynamic as well as leakage power consumption. The voltage scaling technique achieves energy efficiency by simultaneously scaling the supply and body bias voltages in the case of processors and buses with repeaters, while energy efficiency on fat wires is achieved through dynamic voltage swing scaling. We also introduce a set of accurate communication models for the energy estimation of voltage scalable embedded systems. In particular, we demonstrate that voltage scaling of bus repeaters and dynamic adaption of the voltage swing on fat wires can significantly influence the system's energy consumption. Experimental results, conducted on numerous generated benchmarks and a real-life example, demonstrate that substantial energy savings can be achieved with the proposed techniques.

  • 127.
    Andrzejewski, Jakub
    Linköpings universitet, Institutionen för datavetenskap.
    Designing a User Interface for Smartphones. A Balance Between the Pragmatic and the Hedonic Dimension of Usability: A Case Study2004Independent thesis Basic level (university diploma), 20 poäng / 30 hpOppgave
    Abstract [en]

    Recent research in the usability engineering field tends to emphasize, somewhat neglected, the need of incorporating the joy-of-use factor (the hedonic dimension of usability) into the design of user interfaces. However such design decisions have to be applied with care and proper modesty as they may diminish the product’s overall quality of use. Notions of pleasure and joy are non-task related and partially incompatible with pragmatic usability qualities hence achieving a proper balance is essential.

    The thesis explores the question of how to establish a balance between pragmatic and hedonic dimensions of usability and whether it is possible to design a user interface which is both highly usable and enjoyable.

    In order to address these questions a case study was performed, which required further development of an existing prototype, the Zenterio Halfpipe Desktop; an innovative, patented, cross-platform user interface. To achieve high product usability, principles of Human-Computer Interaction and User-Centered Design were applied.

    The results of the study suggest that ensuring a high level of both aspects of usability: the pragmatic values (such as simplicity or controllability) as well as the hedonic values (such as originality or innovativeness), can result in a product which is perceived as highly usable and fun-to-use. The practical application of involving the joy-of-use factor shows a significant increase in the perceived software appeal.

    Finally, shortcomings and limitations of the study are discussed followed by future work proposals.

  • 128.
    André-Jönsson, Henrik
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Indexing strategies for time series data2002Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    Traditionally, databases have stored textual data and have been used to store administrative information. The computers used. and more specifically the storage available, have been neither large enough nor fast enough to allow databases to be used for more technical applications. In recent years these two bottlenecks have started to di sappear and there is an increasing interest in using databases to store non-textual data like sensor measurements or other types of process-related data. In a database a sequence of sensor measurements can be represented as a time series. The database can then be queried to find, for instance, subsequences, extrema points, or the points in time at which the time series had a specific value. To make this search efficient, indexing methods are required. Finding appropriate indexing methods is the focus of this thesis.

    There are two major problems with existing time series indexing strategies: the size of the index structures and the lack of general indexing strategies that are application independent. These problems have been thoroughly researched and solved in the case of text indexing files. We have examined the extent to which text indexing methods can be used for indexing time series.

    A method for transforming time series into text sequences has been investigated. An investigation was then made on how text indexing methods can be applied on these text sequences. We have examined two well known text indexing methods: the signature files and the B-tree. A study has been made on how these methods can be modified so that they can be used to index time series. We have also developed two new index structures, the signature tree and paged trie structures. For each index structure we have constructed cost and size models. resulting in comparisons between the different approaches.

    Our tests indicate that the indexing method we have developed. together with the B-tree structure. produces good results. It is possible to search for and find sub-sequences of very large time series efficiently.

    The thesis also discusses what future issues will have to be investigated for these techniques to be usable in a control system relying on time-series indexing to identify control modes.

  • 129.
    Angelakis, Vangelis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Askoxylakis, Ioannis
    FORTH, Institute of Computer Science, Greece.
    Fowler, Scott
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Gundlegård, David
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Traganitis, Apostolos
    FORTH, Institute of Computer Science, Greece.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Security and Resilience in Cognitive Radio Networks2011Inngår i: European Research Consortium for Informatics and Mathematics Magazine, ISSN 0926-4981, nr 85, s. 48-49Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    After more than a decade of research, system securityand resilience is now the major technological barrier forthe Cognitive Radio (CR) to be adopted by the telecommunication industry. New ideas are required tomake CR networks secure and robust against attacks taking advantage the inherent characteristics of the CR functionality. This work explores key points that urgentlyneed to be addressed.

  • 130.
    Angelsmark, Ola
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, TCSLAB - Laboratoriet för teoretisk datalogi.
    Constraints, Adjunctions and (Co)algebras2000Inngår i: Coalgebraic Methods in Computer Science CMCS-2000,2000, Science Direct , 2000, s. 3-12Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The connection between constraints and universal algebra has been looked at in, e.g Jeavons, Cohen and Pearson, 1998, and has given interesting results. Since the connection between universal algebra and category theory is so obvious, we will in this paper investigate if the usage of category theory has any impact on the results and/or reasoning and if anything can be gained from this approach. We construct categories of problem instances and of solutions to these, and, via an adjunction between these categories, note that the algebras give us a way of describing 'minimality of a problem,' while the coalgebras give a criterion for deciding if a given set of solutions can be expressed by a constraint problem of a given arity. Another pair of categories, of sets of relations and of sets of operations on a fixed set, is defined, and this time the algebras we get give an indication of the 'expressive power' of a set of constraint types, while the coalgebras tell us about the computational complexity of the corresponding constraint problem.

  • 131.
    Angelsmark, Ola
    Linköpings universitet, Institutionen för datavetenskap, TCSLAB. Linköpings universitet, Tekniska högskolan.
    Constructing Algorithms for Constraint Satisfaction and Related Problems: Methods and Applications2005Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    In this thesis, we will discuss the construction of algorithms for solving Constraint Satisfaction Problems (CSPs), and describe two new ways of approaching them. Both approaches are based on the idea that it is sometimes faster to solve a large number of restricted problems than a single, large, problem. One of the strong points of these methods is that the intuition behind them is fairly simple, which is a definite advantage over many techniques currently in use.

    The first method, the covering method, can be described as follows: We want to solve a CSP with n variables, each having a domain with d elements. We have access to an algorithm which solves problems where the domain has size e < d, and we want to cover the original problem using a number of restricted instances, in such a way that the solution set is preserved. There are two ways of doing this, depending on the amount of work we are willing to invest; either we construct an explicit covering and end up with a deterministic algorithm for the problem, or we use a probabilistic reasoning and end up with a probabilistic algorithm.

    The second method, called the partitioning method, relaxes the demand on the underlying algorithm. Instead of having a single algorithm for solving problems with domain less than d, we allow an arbitrary number of them, each solving the problem for a different domain size. Thus by splitting, or partitioning, the domain of the large problem, we again solve a large number of smaller problems before arriving at a solution.

    Armed with these new techniques, we study a number of different problems; the decision problems (d, l)-CSP and k-Colourability, together with their counting counterparts, as well as the optimisation problems Max Ind CSP, Max Value CSP, Max CSP, and Max Hamming CSP. Among the results, we find a very fast, polynomial space algorithm for determining k-colourability of graphs.

  • 132.
    Angelsmark, Ola
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, TCSLAB - Laboratoriet för teoretisk datalogi.
    Partitioning based algorithms for some colouring problems2005Inngår i: Proceedings of the Joint Annual Workshop of {ERCIM/CoLogNet} on Constraint Solving and Constraint Logic Programming,2005, ERCIM , 2005, s. 28-42Konferansepaper (Fagfellevurdert)
  • 133.
    Angelsmark, Ola
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, TCSLAB - Laboratoriet för teoretisk datalogi.
    Dahllöf, Vilhelm
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, TCSLAB - Laboratoriet för teoretisk datalogi.
    Jonsson, Peter
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, TCSLAB - Laboratoriet för teoretisk datalogi.
    Finite Domain Constraint Satisfaction Using Quantum Computation2002Inngår i: Mathematical Foundations of Computer Science, 27th International Symposium MFCS-2002,2002, Heidelberg: Springer Verlag , 2002, s. 93-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We present a quantum algorithm for finite domain constraint solving, where the constraints have arity 2. It is complete and runs in time, where d is size of the domain of the variables and n the number of variables. For the case of d=3 we provide a method to obtain an upper time bound of . Also for d=5 the upper bound has been improved. Using this method in a slightly different way we can decide 3-colourability in O(1.2185^n) time.

  • 134.
    Angelsmark, Ola
    et al.
    Linköpings universitet, Institutionen för datavetenskap, TCSLAB - Laboratoriet för teoretisk datalogi. Linköpings universitet, Tekniska högskolan.
    Jonsson, Peter
    Linköpings universitet, Institutionen för datavetenskap, TCSLAB - Laboratoriet för teoretisk datalogi. Linköpings universitet, Tekniska högskolan.
    Improved algorithms for counting solutions in constraint satisfaction problems2003Inngår i: Principles and Practice of Constraint Programming, 9th International Conference CP 2003,2003, Springer, 2003, Vol. 2833, s. 81-95Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Counting the number of solutions to CSP instances has vast applications in several areas ranging from statistical physics to artificial intelligence. We provide a new algorithm for counting the number of solutions to binary CSP s which has a time complexity ranging from O ((d/4 . alpha(4))(n)) to O((alpha + alpha(5) + [d/4 - 1] . alpha(4))(n)) (where alpha approximate to 1.2561) depending on the domain size d greater than or equal to 3. This is substantially faster than previous algorithms, especially for small d. We also provide an algorithm for counting k-colourings in graphs and its running time ranges from O ([log(2) k](n)) to O ([log(2) k + 1](n)) depending on k greater than or equal to 4. Previously, only an O(1.8171(n)) time algorithm for counting 3-colourings were known, and we improve this upper bound to O(1.7879(n)).

  • 135.
    Angelsmark, Ola
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, TCSLAB - Laboratoriet för teoretisk datalogi.
    Jonsson, Peter
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, TCSLAB - Laboratoriet för teoretisk datalogi.
    Linusson, Svante
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Matematiska institutionen, Tillämpad matematik.
    Thapper, Johan
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Matematiska institutionen, Tillämpad matematik.
    Determining the Number of Solutions to Binary CSP Instances2002Inngår i: Principles and Practice of Constraint Programming, 8th International Conference CP-2002,2002, Heidelberg: Springer Verlag , 2002, s. 327-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Counting the number of solutions to CSP instances has applications in several areas, ranging from statistical physics to artificial intelligence. We give an algorithm for counting the number of solutions to binary CSPs, which works by transforming the problem into a number of 2-SAT instances, where the total number of solutions to these instances is the same as those of the original problem. The algorithm consists of two main cases, depending on whether the domain size d is even, in which case the algorithm runs in O(1.3247^n*(d/2)^n) time, or odd, in which case it runs in O(1.3247^n*((d^2+d+2)/4)^(n/2)) if d=4*k+1, and O(1.3247^n*((d^2+d)/4)^(n/2)) if d=4*k+3. We also give an algorithm for counting the number of possible 3-colourings of a given graph, which runs in O(1.8171^n), an improvement over our general algorithm gained by using problem specific knowledge. 

  • 136.
    Angelsmark, Ola
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, TCSLAB - Laboratoriet för teoretisk datalogi.
    Thapper, Johan
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Matematiska institutionen, Tillämpad matematik.
    A Microstructure Based Approach to Constraint Satisfaction Optimisation Problems2005Inngår i: The 18th International FLAIRS Conference,2005, Menlo Park, CA, USA: AAAI Press , 2005, s. 155-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We study two constraint satisfaction optimisation problems: The Max Value problem for CSPs, which, somewhat simplified, aims at maximising the sum of the (weighted) variable values in the solution, and the Max Ind problem, where the goal is to find a satisfiable subinstance of the original instance containing as many variables as possible. Both problems are NP-hard to approximate within n^(1-e), e>0, where n is the number of variables in the problems, which implies that it is of interest to find exact algorithms. By exploiting properties of the microstructure, we construct algorithms for solving instances of these problems with small domain sizes, and then, using a probabilistic reasoning, we show how to get algorithms for more general versions of the problems. The resulting algorithms have running times of O((0.585d)^n) for Max Value (d,2)-CSP, and O((0.503d)^n) for MaxInd (d,2)-CSP. Both algorithms represent the best known theoretical bounds for their respective problem, and, more importantly, the methods used are applicable to a wide range of optimisation problems. 

  • 137.
    Angelsmark, Ola
    et al.
    Linköpings universitet, Institutionen för datavetenskap, TCSLAB - Laboratoriet för teoretisk datalogi. Linköpings universitet, Tekniska högskolan.
    Thapper, Johan
    Linköpings universitet, Matematiska institutionen, Tillämpad matematik. Linköpings universitet, Tekniska högskolan.
    Algorithms for the Maximum Hamming Distance Problem2006Inngår i: Recent Advances in Constraints: Joint ERCIM/CoLogNet International Workshop on Constraint Solving and Constraint Logic Programming, CSCLP 2004, Lausanne, Switzerland, June 23-25, 2004, Revised Selected and Invited Papers / [ed] Boi V. Faltings, Adrian Petcu, François Fages and Francesca Rossi, Springer Berlin/Heidelberg, 2006, s. 128-141Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    This book constitutes the thoroughly refereed and extended post-proceedings of the Joint ERCIM/CoLogNet International Workshop on Constraint Solving and Constraint Logic Programming, CSCLP 2005, held in Uppsala, Sweden in June 2005.

    Besides papers taken from the workshop, others are submitted in response to an open call for papers after the workshop.

    The 12 revised full papers presented were carefully reviewed and selected for inclusion in the book. The papers are organized in topical sections on global constraints, search and heuristics, language and implementation issues, and modeling.

  • 138.
    Angelsmark, Ola
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, TCSLAB - Laboratoriet för teoretisk datalogi.
    Thapper, Johan
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Matematiska institutionen, Tillämpad matematik.
    New Algorithms for the Maximum Hamming Distance Problem2004Inngår i: Joint Annual Workshop of ERCIMCoLogNet on Constraint Solving and Constraint Logic Programming,2004, 2004, s. 271-285Konferansepaper (Fagfellevurdert)
  • 139.
    Angerborn, Felix
    Linköpings universitet, Institutionen för datavetenskap, Interaktiva och kognitiva system.
    Better text formatting for the mobile web with javascript2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    As people read more and longer texts on the web, the simple formatting options that exists in todays browsers creates worse results than necessary. On behalf of Opera Software in Linköping, a better algorithm has been implemented in Javascript with the purpose of delivering a visually better experience for the reader. The implementation is first and foremost for mobile devices and therefore a large part of the thesis has been the evaluation and optimization of performance. 

  • 140.
    Anggreeni, Irene
    Linköpings universitet, Institutionen för datavetenskap.
    Prototyping Tools for the Early Stages of Web Design2006Independent thesis Basic level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    There is a gap between low-fidelity prototyping using paper and high-fidelity prototyping using computers in web design. Both serve well in different stages of web design, but are not well integrated. Prior studies have examined the practice of web designers. The studies resulted in a number of alternative prototyping tools, which focus on informal representation and try to prolong sketching in the design process.

    The thesis proposes a design of a prototyping tool that makes use of existing paper sketches. In paper prototyping, a human who acts as the “computer” makes the sketches interactive. In the prototyping tool put forward in the thesis, the interactivity of the sketches is instead created on the computer. The novel prototyping tool needs to support the interactions and behaviours used in web design, and it must be easy to use so that the web designers do not have to invest too much time learning it.

    The prototype of the tool is a sketch-and-scan interface, thus allowing the use of paper the way it is. The functionality supports both documentation and computer interactivity. Usability tests and expert reviews were conducted, involving students, lecturers and researchers in human-computer interaction.

    The results elaborate previous research on prototyping practice, and a designers’ wish list was formulated. A prototyping tool is expected to support communication between users, designers and developers; as well as to reduce a designer’s need to change his work practice when using the tool.

  • 141.
    Antelius, Daniel
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Link Extraction for Crawling Flash on the Web2015Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    The set of web pages not reachable using conventional web search engines is usually called the hidden or deep web. One client-side hurdle for crawling the hidden web is Flash files.

    This thesis presents a tool for extracting links from Flash files up to version 8 to enable web crawling. The files are both parsed and selectively interpreted to extract links. The purpose of the interpretation is to simulate the normal execution of Flash in the Flash runtime of a web browser. The interpretation is a low level approach that allows the extraction to occur offline and without involving automation of web browsers. A virtual machine is implemented and a set of limitations is chosen to reduce development time and maximize the coverage of interpreted byte code.

    Out of a test set of about 3500 randomly sampled Flash files the link extractor found links in 34% of the files. The resulting estimated web search engine coverage improvement is almost 10%.

  • 142.
    Anton, Stevensson
    Linköpings universitet, Institutionen för datavetenskap, Interaktiva och kognitiva system.
    Distributed User Interfaces for the Web2017Independent thesis Basic level (degree of Bachelor), 10,5 poäng / 16 hpOppgave
    Abstract [en]

    New ways of interaction between users and their computing devices has revealed that users are not only interested in sharing their data, but their user interfaces as well. This calls for an extension of the traditional notion of user interfaces, to a notion where user interfaces span over multiple devices: Distributed User Interfaces (DUIs). The purpose of this thesis is to identify challenges in developing Web based DUIs, and the result is a JavaScript library that aids the development of these types of interfaces. The development has been driven in an explorative fashion, to discover techniques that is appropriate to use, when moving ideas from existing DUI frameworks for the desktop, to the Web. Soundness of the implementation has been evaluated by measuring properties of the library source code that indicates maintainability and extensibility. The conclusion is that the library has the potential of answering the needs for future DUI development targeting the Web.

  • 143.
    Anzaldi, Davide
    Linköpings universitet, Institutionen för datavetenskap, RTSLAB - Laboratoriet för realtidssystem.
    ORWAR: a delay-tolerant protocol implemented on the Android platform2010Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The Aim of this thesis is to implement the "Opportunistic DTN Routing with Window-aware Adaptive Replication" (ORWAR) protocol on the Android platform.Delay-Tolerant Networks (DTNs) are particular mobile ad-hoc network (MANET) architectures that try to solve the issues related to the lack of point to point connectivity between the nodes of the network or between its sub-networks (partitions). The general approach is based on techniques of store-carry-forward of the messages whereby delivery can be achieved even in partitioned networks, though with mobility-dependent delays. DTNs can be considered as a means of communication for scenarios where infrastructure-based networks cannot be deployed or get dysfunctional for some reasons, such as in the case of a natural disaster or highly overloaded infrastructure. ORWAR is a DTN protocol that tries to exploit knowledge about the context of mobile nodes (speed, direction of movement and radio range) to estimate the size of a contact window in order to avoid the energy waste deriving from partial transmissions. This report presents the design and the implementation of the protocol on the Android platform. It then describes some functional tests together with an analysis of the energy consumption and the performance reachable on our test device Android Development Phone 1.

  • 144.
    Appelgren, Leif
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, EISLAB - Economic Information Systems.
    Audit Strategies for the Taxation of Investment2004Inngår i: Bournemouth Tax Research Network Conference 2004 September 16-17,2004, 2004Konferansepaper (Annet vitenskapelig)
  • 145.
    Aragon, Elena
    et al.
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Jimenez, Juan M.
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Maghazeh, Arian
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Rasmusson, Jim
    Sony Mobile Communications, Sweden.
    Bordoloi, Unmesh D.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Pattern matching in OpenCL: GPU vs CPU energy consumption on two mobile chipsets2014Inngår i: Proceedings of the International Workshop / OpenCL 2013 & 2014 (IWOCL '14), ACM Digital Library, 2014, s. Article No. 5-Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Adaptations of the Aho-Corasick (AC) algorithm on high performance graphics processors (also called GPUs) have garnered increasing attention in recent years. However, no results have been reported regarding their implementations on mobile GPUs. In this paper, we show that implementing a state-of-the-art Aho-Corasick parallel algorithm on a mobile GPU delivers significant speedups. We study a few implementation optimizations some of which may seem counter-intuitive to standard optimizations for high-end GPUs. More importantly, we focus on measuring the energy consumed by different components of the OpenCL application rather than reporting the aggregate. We show that there are considerable energy savings compared to the CPU implementation of the AC algorithm.

  • 146.
    Ardi, Shanai
    Linköpings universitet, Institutionen för datavetenskap, IISLAB - Laboratoriet för intelligenta informationssystem. Linköpings universitet, Tekniska högskolan.
    A Model and Implementation of a Security plug-in for the Software Life Cycle2008Licentiatavhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    Currently, security is frequently considered late in software life cycle. It is often bolted on late in development, or even during deployment or maintenance, through activities such as add-on security software and penetration-and-patch maintenance. Even if software developers aim to incorporate security into their products from the beginning of the software life cycle, they face an exhaustive amount of ad hoc unstructured information without any practical guidance on how and why this information should be used and what the costs and benefits of using it are. This is due to a lack of structured methods.

    In this thesis we present a model for secure software development and implementation of a security plug-in that deploys this model in software life cycle. The model is a structured unified process, named S3P (Sustainable Software Security Process) and is designed to be easily adaptable to any software development process. S3P provides the formalism required to identify the causes of vulnerabilities and the mitigation techniques that address these causes to prevent vulnerabilities. We present a prototype of the security plug-in implemented for the OpenUP/Basic development process in Eclipse Process Framework. We also present the results of the evaluation of this plug-in. The work in this thesis is a first step towards a general framework for introducing security into the software life cycle and to support software process improvements to prevent recurrence of software vulnerabilities.

  • 147.
    Ardi, Shanai
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik.
    Byers, David
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik.
    Meland, Per Håkon
    SINTEF ICT, Trondheim, Norway.
    Tøndel, Inger Anne
    SINTEF ICT, Trondheim, Norway.
    Shahmehri, Nahid
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    How can the developer benefit from security modeling?2007Inngår i: Second International Conference on Availability, Reliability and Security, 2007, IEEE Computer Society, 2007, s. 1017-1025Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Security has become a necessary part of nearly every software development project, as the overall risk from malicious users is constantly increasing, due to increased consequences of failure, security threats and exposure to threats. There are few projects today where software security can be ignored. Despite this, security is still rarely taken into account throughout the entire software lifecycle; security is often an afterthought, bolted on late in development, with little thought to what threats and exposures exist. Little thought is given to maintaining security in the face of evolving threats and exposures. Software developers are usually not security experts. However, there are methods and tools available today that can help developers build more secure software. Security modeling, modeling of e.g., threats and vulnerabilities, is one such method that, when integrated in the software development process, can help developers prevent security problems in software. We discuss these issues, and present how modeling tools, vulnerability repositories and development tools can be connected to provide support for secure software development

  • 148.
    Ardi, Shanai
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik.
    Byers, David
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik.
    Shahmehri, Nahid
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Towards a Structured Unified Process for Software Security2006Inngår i: ICSE Workshop on Software Engineering for Secure Systems,2006, ACM , 2006, s. 3-10Konferansepaper (Fagfellevurdert)
  • 149.
    Ardi, Shanai
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik.
    Shahmehri, Nahid
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    A post-mortem incident modeling method2009Inngår i: 2009 International Conference on Availability, Reliability and Security (ARES),  Vol. 1-2, IEEE , 2009, s. 1018-1023Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Incident post-mortem analysis after recovery from incidents is recommended by most incident response experts. An analysis of why and how an incident happened is crucial for determining appropriate countermeasures to prevent the recurrence of the incident. Currently, there is a lack of structured methods for such an analysis, which would identify the causes of a security incident. In this paper, we present a structured method to perform the post-mortem analysis and to model the causes of an incident visually in a graph structure. This method is an extension of our earlier work on modeling software vulnerabilities. The goal of modeling incidents is to develop an understanding of what could have caused the security incident and how its recurrence can be prevented in the future. The method presented in this paper is intended to be used during the post-mortem analysis of incidents by incident response teams.

  • 150.
    Ardi, Shanai
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik.
    Shahmehri, Nahid
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Integrating a security plug-in with the OpenUP/Basic development process2008Inngår i: Third International Conference on Availability, Reliability and Security, 2008, IEEE Computer Society, 2008, s. 284-291Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we present a security plug-in for the OpenUP/Basic development process. Our security plug-in is based on a structured unified process for secure software development, named S3P (sustainable software security process). This process provides the formalism required to identify the causes of vulnerabilities and the mitigation techniques that prevent these vulnerabilities. We also present the results of an expert evaluation of the security plug-in. The lessons learned from development of the plug-in and the results of the evaluation will be used when adapting S3P to other software development processes.

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