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  • 51.
    Abraham, Johannes
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem, Hälsoinformatik och logistik.
    Romano, Robin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem, Hälsoinformatik och logistik.
    Automatisk kvalitetssäkring av information för järnvägsanläggningar: Automatic quality assurance of information for railway infrastructure2019Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Järnvägsbranschen står i dagsläget inför stora utmaningar med planerade infrastrukturprojekt och underhåll av befintlig järnväg. Med ökade förväntningar på  utbyggnaden av den framtida järnvägen, medför det en ökad risk för belastning på det nuvarande nätet. Baksidan av utbyggnaden kan bli fler inställda resor och  förseningar. Genom att dra nytta av tekniska innovationer såsom digitalisering och  automatisering kan det befintliga system och arbetsprocesser utvecklas för en  effektivare hantering.  Trafikverket ställer krav på Byggnadsinformationsmodeller (BIM) i upphandlingar. Projektering för signalanläggningar sker hos Sweco med CAD-programmet  Promis.e. Från programmet kan Baninformationslistor (BIS-listor) innehållande  information om objekts attribut hämtas. Trafikverket ställer krav på att attributen ska bestå av ett visst format eller ha specifika värden. I detta examensarbete  undersöks metoder för att automatisk verifiera ifall objekt har tillåtna värden från projekteringsverktyget samt implementering av en metod. Undersökta metoder  innefattar kalkyleringsprogrammet Excel, frågespråket Structured Query Language (SQL) och processen Extract, Transform and Load (ETL).  Efter analys av metoder valdes processen ETL. Resultatet blev att ett program  skapades för att automatiskt välja vilken typ av BIS-lista som skulle granskas och för att verifiera om attributen innehöll tillåtna värden. För att undersöka om kostnaden för programmen skulle gynna företaget utöver kvalitetssäkringen utfördes en  ekonomisk analys. Enligt beräkningarna kunde valet av att automatisera  granskningen även motiveras ur ett ekonomiskt perspektiv.

  • 52.
    Abrahamsson, Felix
    KTH, Skolan för elektroteknik och datavetenskap (EECS).
    Designing a Question Answering System in the Domain of Swedish Technical Consulting Using Deep Learning2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Question Answering systems are greatly sought after in many areas of industry. Unfortunately, as most research in Natural Language Processing is conducted in English, the applicability of such systems to other languages is limited. Moreover, these systems often struggle in dealing with long text sequences.

    This thesis explores the possibility of applying existing models to the Swedish language, in a domain where the syntax and semantics differ greatly from typical Swedish texts. Additionally, the text length may vary arbitrarily. To solve these problems, transfer learning techniques and state-of-the-art Question Answering models are investigated. Furthermore, a novel, divide-and-conquer based technique for processing long texts is developed.

    Results show that the transfer learning is partly unsuccessful, but the system is capable of perform reasonably well in the new domain regardless. Furthermore, the system shows great performance improvement on longer text sequences with the use of the new technique.

  • 53. Abrahamsson, H
    et al.
    Hagsand, Olof
    KTH, Skolan för datavetenskap och kommunikation (CSC), Teoretisk datalogi, TCS.
    Marsh, Ian
    TCP over high speed variable capacity links: A simulation study for bandwidth allocation2002Konferansepaper (Fagfellevurdert)
    Abstract [en]

     New optical network technologies provide opportunities for fast, controllable bandwidth management. These technologies can now explicitly provide resources to data paths, creating demand driven bandwidth reservation across networks where an applications bandwidth needs can be meet almost exactly. Dynamic synchronous Transfer Mode (DTM) is a gigabit network technology that provides channels with dynamically adjustable capacity. TCP is a reliable end-to-end transport protocol that adapts its rate to the available capacity. Both TCP and the DTM bandwidth can react to changes in the network load, creating a complex system with inter-dependent feedback mechanisms. The contribution of this work is an assessment of a bandwidth allocation scheme for TCP flows on variable capacity technologies. We have created a simulation environment using ns-2 and our results indicate that the allocation of bandwidth maximises TCP throughput for most flows, thus saving valuable capacity when compared to a scheme such as link over-provisioning. We highlight one situation where the allocation scheme might have some deficiencies against the static reservation of resources, and describe its causes. This type of situation warrants further investigation to understand how the algorithm can be modified to achieve performance similar to that of the fixed bandwidth case.

  • 54. Abrahamsson, M.
    et al.
    Sundberg, Johan
    KTH, Skolan för datavetenskap och kommunikation (CSC), Tal, musik och hörsel, TMH, Musikakustik.
    Subglottal pressure variation in actors’ stage speech2007Inngår i: Voice and Gender Journal for the Voice and Speech Trainers Association / [ed] Rees, M., VASTA Publishing , 2007, s. 343-347Kapittel i bok, del av antologi (Fagfellevurdert)
  • 55.
    Abrahamyan, Lilit
    et al.
    University of Amsterdam.
    Schaap, Jorrit A.
    Hoekstra, Alfons G.
    Shamonin, Denis
    M.A.Box, Frieke
    Van der Geest, Rob J.
    H.C. Reiber, Johan
    M.A. Sloot, Peter
    A Problem Solving Environment for Image-Based Computational Hemodynamics2005Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We introduce a complete problem solving environment designed for pulsatile flows in 3D complex geometries, especially arteries. Three-dimensional images from arteries, obtained from e.g. Magnetic Resonance Imaging, are segmented to obtain a geometrical description of the arteries of interest. This segmented artery is prepared for blood flow simulations in a 3D editing tool, allowing to define in- and outlets, to filter and crop part of the artery, to add certain structures ( e.g. a by-pass, or stents ), and to generate computational meshes as input to the blood flow simulators. Using dedicated fluid flow solvers the time dependent blood flow in the artery during one systole is computed. The resulting flow, pressure and shear stress fields are then analyzed using a number of visualization techniques. The whole environment can be operated from a desktop virtual reality system, and is embedded in a Grid computing environment.

  • 56.
    Abreu, Rodrigo
    et al.
    KTH, Skolan för datavetenskap och kommunikation (CSC), Numerisk analys, NA (stängd 2012-06-30).
    Jansson, Niclas
    KTH, Skolan för datavetenskap och kommunikation (CSC), Numerisk analys, NA (stängd 2012-06-30).
    Hoffman, Johan
    KTH, Skolan för datavetenskap och kommunikation (CSC), Numerisk analys, NA (stängd 2012-06-30).
    Adaptive computation of aeroacoustic sources for a rudimentary landing gear using lighthill's analogy2011Inngår i: 17th AIAA/CEAS AeroacousticsConference 2011: 32nd AIAA Aeroacoustics Conference, 2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We present our simulation results for the benchmark problem of the ow past a Rudimentary Landing Gear (RLG) using a General Galerkin (G2) nite element method, also referred to as Adaptive DNS/LES. In G2 no explicit subgrid model is used, instead the compuational mesh is adaptively re ned with respect to an a posteriori error es-timate of a quantity of interest in the computation, in this case the drag force on the RLG. Turbulent boundary layers are modeled using a simple wall layer model with the shear stress at walls proportional to the skin friction, which here is assumed to be small and, therefore, can be approximated by zero skin friction. We compare our results with experimental data and other state of the art computations, where we nd good agreement in sound pressure levels, surface velocities and ow separation. We also compare with detailed surface pressure experimental data where we nd largely good agreement, apart from some local dierences for which we discuss possible explanations.

  • 57.
    Abu Nijmeh, Jonas
    et al.
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    Catalan Canales, Diego
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    Prokrastinering i form av medieanvändning: En jämförelsestudie kring kön och sysselsättning2017Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    Procrastination has long been a problem for many. Whether it is school work, training or something else, most individuals have experienced that they deliberately postpone a task for a later occasion. This phenomenon has in recent time been integrated into our society in a negative way. In our media-centered society we are becoming more connected where nowadays almost all of Sweden's population has access to the internet. Technology has brought many opportunities, but it has also opened up for new ways to procrastinate.

    This study aimed to investigate procrastination in the form of media usage by a large target group. We intended to find out eventual differences in procrastination habits between the sexes, but also between workers and students. Previous research has already shown that procrastination differs with age and occupation. With this in mind we seek to answer the question: Which digital media does people use when they procrastinate and on which technical platforms does this happen? In order to answer this question, we conducted a preliminary study on a smaller group of people to get a better understanding of what matters were relevant in this context. This preliminary study then formed the basis for a survey of 91 participants.

    The results showed clear differences between both men and women and between students and workers. Differences regarding both media usage and procrastination habits were seen where some differences were more notable than others. The result confirms previous studies in several aspects and gives us some insight into how different procrastination habits might look.

  • 58.
    Acharya, Jaldeep
    et al.
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    Fröberg, Ludvig
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    A comparison of interfaces in choice driven games: Investigating possible future applications of NLIs in choice driven games by comparing a menu- based interface with an NLI in a text-based game2016Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    Natural language processing has for a long time been a field of research and has been regarded as a thing of the future. Due to its complexity it stopped being featured in computer games in the early 2000s. It has however had a recent revival as a consequence of advancements made in speech recognition, making the possible applications of natural language processing much larger. One market that hasn’t seen much in the way of natural language interfaces recently is that of computer games. This report covers the basics of natural language processing needed to implement two versions of a simple text-based adventure game, one with a menu-based interface and one with a natural lan- guage interface. These were then played by a test group from which usability statistics were gathered to determine if it is likely that NLP will find its way back in to choice driven games in the future.

    The results showed that even though the menu-based interface has a faster rate of progression, the NLI version of the game was perceived as more enjoyable by users with experience in gaming. The reason being that the NLI al- lowed for more thinking on the user’s part and therefore the game presented a greater challenge, something that is perceived as attractive by users with experience in com- puter games. Also the measured usability was roughly the same for both interfaces while it was feared that it would be much lower for NLIs. Therefore, the conclusion was that it is highly plausible that NLI will find its way back into the gaming world, since it adds a new dimension to adventure games, which is something that attracts users. However, this is given that NLP development continues in the same fast pace as it is today, making it possible to implement a more accurate NLI. 

  • 59. Achilleos, Antonis
    et al.
    Lampis, Michael
    City University of New York.
    Mitsou, Valia
    Parameterized Modal Satisfiability2010Inngår i: ICALP 2010, Bordeaux, France, July 6-10, 2010, Proceedings, Part II, 2010, s. 369-380Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We investigate the parameterized computational complexity of the satisfiability problem for modal logic and attempt to pinpoint relevant structural parameters which cause the problem’s combinatorial explosion, beyond the number of propositional variables v. To this end we study the modality depth, a natural measure which has appeared in the literature, and show that, even though modal satisfiability parameterized by v and the modality depth is FPT, the running time’s dependence on the parameters is a tower of exponentials (unless P=NP). To overcome this limitation we propose possible alternative parameters, namely diamond dimension and modal width. We show fixed-parameter tractability results using these measures where the exponential dependence on the parameters is much milder (doubly and singly exponential respectively) than in the case of modality depth thus leading to FPT algorithms for modal satisfiability with much more reasonable running times. We also give lower bound arguments which prove that our algorithms cannot be improved significantly unless the Exponential Time Hypothesis fails.

  • 60. Achilleos, Antonis
    et al.
    Lampis, Michail
    City University of New York.
    Mitsou, Valia
    Parameterized Modal Satisfiability2012Inngår i: Algorithmica, ISSN 0178-4617, E-ISSN 1432-0541, Vol. 64, nr 1, s. 38-55Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We investigate the parameterized computational complexity of the satisfiability problem for modal logic and attempt to pinpoint relevant structural parameters which cause the problem’s combinatorial explosion, beyond the number of propositional variables v. To this end we study the modality depth, a natural measure which has appeared in the literature, and show that, even though modal satisfiability parameterized by v and the modality depth is FPT, the running time’s dependence on the parameters is a tower of exponentials (unless P=NP). To overcome this limitation we propose pos- sible alternative parameters, namely diamond dimension and modal width. We show fixed-parameter tractability results using these measures where the exponential dependence on the parameters is much milder (doubly and singly exponential respectively) than in the case of modality depth thus leading to FPT algorithms for modal satisfiability with much more reasonable running times. We also give lower bound arguments which prove that our algorithms cannot be improved significantly unless the Exponential Time Hypothesis fails.

  • 61.
    Acin, Medya
    et al.
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    Stansvik, Elvis
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    Improving Player Engagement inTetris Through EDR Monitoring2013Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    When designing computer games, one is often interested in evoking feelings of

    engagement, enjoyment and challenge in the player. One way of doing so is

    dynamically adjusting the difficulty of the game. Traditionally, this adjustment

    has been based on the performance of the player. However, in recent years there

    has been an increased interest in dynamically adjusting the difficulty level of a

    game based on physiological signals from the player. In this Bachelor’s project,

    we have studied the effect of using an electrodermal activity (EDA) wristband

    sensor as the source signal for the difficulty adjustment algorithm and compared

    it to the traditional approach of using the performance of the player.

    We developed two Tetris games, one EDA controlled and one performance controlled,

    and let participants play them both. Each game session was followed

    by a questionnaire. Our results show that, although participants reported an

    increased sense of engagement and challenge when playing the EDA version,

    further research is necessary before the usefulness of EDA in this setting can be

    established.

  • 62.
    Ackland, Patrik
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    Fast and Scalable Static Analysis using Deterministic Concurrency2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This thesis presents an algorithm for solving a subset of static analysis data flow problems known as Interprocedural Finite Distribute Subset problems. The algorithm, called IFDS-RA, is an implementation of the IFDS algorithm which is an algorithm for solving such problems. IFDS-RA is implemented using Reactive Async which is a deterministic, concurrent, programming model. The scalability of IFDS-RA is compared to the state-of-the-art Heros implementation of the IFDS algorithm and evaluated using three different taint analyses on one to eight processing cores. The results show that IFDS-RA performs better than Heros when using multiple cores. Additionally, the results show that Heros does not take advantage of multiple cores even if there are multiple cores available on the system.

  • 63.
    Ackva, Adrian
    KTH, Skolan för elektroteknik och datavetenskap (EECS).
    WinBro: A Window and Broadcast-based Parallel Streaming Graph Partitioning Framework for Apache Flink2019Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The past years have shown an increasing demand to process data of various kinds and size in real-time. A common representation for many real-world scenarios is a graph, which shows relations between entities, such as users of social networks or pages on the Internet. These graphs increase in size over time and can easily exceed the capacity of single machines.Graph partitioning is used to divide graphs into multiple subgraphs on different servers. Traditional partitioning techniques work in an offline manner where the whole graph is processed before partitioning. Due to the recently increased demand for real-time analysis, online partitioning algorithms have been introduced. They are able to partition a graph arriving as a stream, also referred to as a streaming graph, without any pre-processing step.The goal of a good graph partitioning algorithm is to maintain the data locality and to balance partitions’ load at the same time. Although different algorithms have proven to achieve both goals for real-world graphs, they often require to maintain a state. However, modern stream processing systems, such as Apache Flink, work with a shared-nothing architecture in a data-parallel manner. Therefore, they do not allow to exchange information along with parallel computations. These systems usually use Hash-based partitioning, that is a fast stateless technique but ignores the graph structure. Hence, it can lead to longer analysis times for streaming applications which could benefit from preserved structures.This work aims to develop a state-sharing parallel streaming graph partitioner for Apache Flink, called WinBro, implementing well-performing partitioning algorithms. In order to do this, existing streaming graph algorithms are studied for possible implementation and then integrated into WinBro.For validation, different experiments were made with real-world graphs. In these experiments, the partitioning quality, and partitioning speed were measured. Moreover, the performance of different streaming applications using WinBro was measured and compared with the default Hash-based partitioning method.Results show that the new partitioner WinBro provides better partitioning quality in terms of data locality and also higher performance for applications with requirements for locality-based input data. Nonetheless, the Hash-based partitioner shows the highest throughput and better performance for data localityagnostic streaming applications.

  • 64.
    Adamsson, Marcus
    KTH, Skolan för elektroteknik och datavetenskap (EECS).
    Curriculum learning for increasing the performance of a reinforcement learning agent in a static first-person shooter game2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In this thesis, we trained a reinforcement learning agent using one of the most recent policy gradient methods, proximal policy optimization, in a first-person shooter game with a static player. We investigated how curriculum learning can be used to increase performance of a reinforcement learning agent. Two reinforcement learning agents were trained in two different environments. The first environment was constructed without curriculum learning and the second environment was with curriculum learning. After training the agents, the agents were placed in the same environment where we compared them based on their performance. The performance was measured by the achieved cumulative reward. The result showed that there is a difference in performance between the agents. It was concluded that curriculum learning can be used to increase the performance of a reinforcement learning agent in a first-person shooter game with a static player.

  • 65.
    Adamsson, Marcus
    et al.
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    Vorkapic, Aleksandar
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    A comparison study of Kd-tree, Vp-tree and Octree for storing neuronal morphology data with respect to performance2016Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    In this thesis we investigated performance of Kdtree, Vptree and Octree for storing neuronal morphology data. Two naive list structures were implemented to compare with the space partition data structures. The performance was measured with different sizes of neuronal networks and different types of test cases. A comparison with focus on cache misses, average search time and memory usage was made. Furthermore, measurements gathered quantitative data about each data structure. The results showed significant difference in performance of each data structure. It was concluded that Vptree is more suitable for searches in smaller populations of neurons and for specific nodes in larger populations, while Kdtree is better for volume searches in larger populations. Octree had highest average search time and memory requirement.

  • 66.
    Adaszynski, Wojciech
    KTH, Skolan för elektroteknik och datavetenskap (EECS).
    Interactive visualization of radio waves propagation in 5G massive MIMO2019Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The complexity of advanced antenna techniques used in the new generation of wireless networks (5G) makes communication between experts and non-technical staff more difficult than ever. As cooperation between network vendors and network operators affects the adoption of the new standard, a need for a new tool has emerged to make technical presentations more engaging and compelling. This thesis presents an exploratory study that aims to examine various design options for an interactive visualization of radiowave propagation to be used by advanced antenna systems experts. Through a Research-oriented Design, functional and non-functional requirements were identified with the help of domain expert. Later, an interactive prototype was designed and developed using a participatory design approach. Qualitative and quantitative data was gathered through usability testing, System Usability Scale (SUS) questionnaires and semi-structured interviews conducted with 12 researchers and engineers at Ericsson AB a multinational telecommunication company. User evaluation proved that such a tool could facilitate communication between technical experts and non-technical staff. The developed prototype was considered intuitive and useful by the majority of study participants as measured by interviews and the SUS survey. Future research is encouraged to include the target audience representatives in order to measure their engagement while using the tool.

  • 67. Addario-Berry, L
    et al.
    Chor, B
    Hallett, M
    Lagergren, Jens
    KTH, Tidigare Institutioner, Numerisk analys och datalogi, NADA.
    Panconesi, A
    Wareham, T
    Ancestral maximum likelihood of evolutionary trees is hard2004Inngår i: Journal of Bioinformatics and Computational Biology, ISSN 0219-7200, E-ISSN 1757-6334, Vol. 2, nr 2, s. 257-271Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Maximum likelihood (ML) (Felsenstein, 1981) is an increasingly popular optimality criterion for selecting evolutionary trees. Finding optimal ML trees appears to be a very hard computational task - in particular, algorithms and heuristics for ML take longer to run than algorithms and heuristics for maximum parsimony (MP). However, while MP has been known to be NP-complete for over 20 years, no such hardness result has been obtained so far for ML. In this work we make a first step in this direction by proving that ancestral maximum likelihood (AML) is NP-complete. The input to this problem is a set of aligned sequences of equal length and the goal is to find a tree and an assignment of ancestral sequences for all of that tree's internal vertices such that the likelihood of generating both the ancestral and contemporary sequences is maximized. Our NP-hardness proof follows that for MP given in (Day, Johnson and Sankoff, 1986) in that we use the same reduction from VERTEX COVER; however, the proof of correctness for this reduction relative to AML is different and substantially more involved.

  • 68.
    Aden Hassan, Abdullahi
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS).
    Karlsson Källqvist, Rasmus
    KTH, Skolan för elektroteknik och datavetenskap (EECS).
    Evaluating LoRa Physical as a Radio Link Technology for use in a Remote-Controlled Electric Switch System for a Network Bridge Radio-Node2019Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    This report explores the design of a system for remotely switching electronics on and off within a range of at least 15 km, to be used with battery driven radio nodes for outdoor Wi-Fi network bridging. The application of the network bridges are connecting to remote networks, should Internet infrastructure fail during an emergency.The problem statement for the report was “What is a suitable radio link technology for use in a remote controlled electrical switch system and how should it best be put to use?” To answer the question, delimitation was done to exploring Low Power Wide Area Network (LPWAN) link technologies, due to their prior use within power constrained devices.Long Range-radio, abbreviated LoRa, is a LPWAN radio modulation technique and was determined to be a good candidate as a suitable link technology for the remote electrical switch system. The range of LoRa is achieved by drastically lowering the data rate of the transmission, and is suitable for battery-powered or energy harvesting devices such as those found in the field of Internet of Things.A LoRa-based transmitter and receiver pair was implemented, and measured to have a packet delivery ratio of over 95% at a distance of 2 km, measured between two bridges. Data at further distances could not be accurately determined, because of the LoRa transceiver giving faulty readings.No conclusion could be made about the suitability for using a LoRa based system to solve the problem, partially due to an improper method for testing the radio performance was used, and partially due to an inconclusive measurement result.

  • 69.
    Adida, Ben
    et al.
    MIT, Comp Sci & Artificial Intelligence Lab, Cambridge, MA 02139 USA.
    Wikström, Douglas
    ETH Zürich, Department of Computer Science.
    How to shuffle in public2007Inngår i: THEORY OF CRYPTOGRAPHY, PROCEEDINGS, 2007, s. 555-574Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We show how to obfuscate a secret shuffle of ciphertexts: shuffling becomes a public operation. Given a trusted party that samples and obfuscates a shuffle before any ciphertexts are received, this reduces the problem of constructing a mix-net to verifiable joint decryption. We construct public-key obfuscations of a decryption shuffle based on the Boneh-Coh-Nissim (BGN) cryptosystem and a re-encryption shuffle based on the Paillier cryptosystem. Both allow efficient distributed verifiable decryption. Finally, we give a distributed protocol for sampling and obfuscating each of the above shuffles and show how it can be used in a trivial way to construct a universally composable mix-net. Our constructions are practical when the number of senders N is small, yet large enough to handle a number of practical cases, e.g. N = 350 in the BGN case and N = 2000 in the Paillier case.

  • 70.
    Adida, Ben
    et al.
    Harvard Univ, Ctr Res Computat & Soc, Cambridge, MA 02138 USA.
    Wikström, Douglas
    Harvard Univ, Ctr Res Computat & Soc, Cambridge, MA 02138 USA.
    Offline/online mixing2007Inngår i: AUTOMATA, LANGUAGES AND PROGRAMMING, PROCEEDINGS, 2007, s. 484-495Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We introduce an offline precomputation technique for mix-nets that drastically reduces the amount of online computation needed. Our method can be based on any additively homomorphic cryptosystem and is applicable when the number of senders and the maximal bit-size of messages are relatively small.

  • 71.
    Adikari, Jithra
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Data- och systemvetenskap, DSV.
    Efficient non-repudiation for techno-information environment2006Inngår i: 2006 International Conference on Industrial and Information Systems, Vols 1 and 2, NEW YORK: IEEE , 2006, s. 454-458Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Non-repudiation means that a person is unable to deny a certain action that he has done under any circumstances. There are several mechanisms, standards and protocols to achieve non-repudiation in techno-information enviromnent. However efficiency in non-repudiation in legal framework was not considerably addressed within the context of those mechanisms. Lack of efficient non-repudiation in the legal framework for techno-information environment makes legal issues when evidence is generated maintained. It can be derived that traditional non-repudiation mechanism delivers efficient non-repudiation. Efficient non-repudiation in techno-information environment is achieved by mapping traditional non-repudiation. Evaluation methodology for efficiency of non-repudiation mechanisms has been improved during this work. Further most significant finding of this research is the Efficient Non-Repudiation Protocol.

  • 72.
    Aditya Wardana, I Wayan Kurniawan
    KTH, Skolan för elektroteknik och datavetenskap (EECS).
    Visualizing Error in Real-Time Video Streaming Data for a Monitoring System2019Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The aim of this master thesis is to investigate the affordances and limitations of using information visualization methods to visualize errors in real-time video streaming data. The study was carried in Red Bee Media company by following several steps including user research, prototyping, and user evaluation. The user research produced design requirements and basic tasks for the prototype. The prototype had to follow the design requirements and use information visualization techniques to visualize the error data. Next, the prototype was evaluated by 5 expert users, all Red Bee Media employees with 1,5 to 3 years experience of working with the existing Red Bee Media system. The results show the prototype obtained a higher SUS score compared to the Red Bee Media monitoring system. Based on a comparison questionnaire, the prototype also had a better visualization for each basic task compared to Red Bee Media monitoring system. The comments from the user evaluation have been categorized into 4 different labels. Those labels listed several usabilities need to be focused on when developing a video monitoring system.

  • 73.
    Adler, Jonas
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Matematik (Avd.). Elekta Instrument AB, Stockholm, Sweden.
    Öktem, Ozan
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Matematik (Avd.).
    Learned Primal-Dual Reconstruction2018Inngår i: IEEE Transactions on Medical Imaging, ISSN 0278-0062, E-ISSN 1558-254X, Vol. 37, nr 6, s. 1322-1332Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We propose the Learned Primal-Dual algorithm for tomographic reconstruction. The algorithm accounts for a (possibly non-linear) forward operator in a deep neural network by unrolling a proximal primal-dual optimization method, but where the proximal operators have been replaced with convolutional neural networks. The algorithm is trained end-to-end, working directly from raw measured data and it does not depend on any initial reconstruction such as filtered back-projection (FBP). We compare performance of the proposed method on low dose computed tomography reconstruction against FBP, total variation (TV), and deep learning based post-processing of FBP. For the Shepp-Logan phantom we obtain >6 dB peak signal to noise ratio improvement against all compared methods. For human phantoms the corresponding improvement is 6.6 dB over TV and 2.2 dB over learned post-processing along with a substantial improvement in the structural similarity index. Finally, our algorithm involves only ten forward-back-projection computations, making the method feasible for time critical clinical applications.

  • 74.
    Adlers, Jacob
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS).
    Pihl, Gustaf
    KTH, Skolan för elektroteknik och datavetenskap (EECS).
    Prediction of training time for deep neural networks in TensorFlow2018Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    Machine learning has gained a lot of interest over the past years and is now used extensively in various areas. Google has developed a framework called TensorFlow which simplifies the usage of machine learning without compromising the end result. However, it does not resolve the issue of neural network training being time consuming. The purpose of this thesis is to investigate with what accuracy training times can be predicted using TensorFlow. Essentially, how effectively one neural network in TensorFlow can be used to predict the training times of other neural networks, also in TensorFlow. In order to do this, training times for training different neural networks was collected. This data was used to create a neural network for prediction. The resulting neural network is capable of predicting training times with an average accuracy of 93.017%.

  • 75.
    Adolfsson, Fredrik
    KTH, Skolan för elektroteknik och datavetenskap (EECS).
    WebTaint: Dynamic Taint Tracking for Java-based Web Applications2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The internet is a source of information and it connects the world through a single platform. Many businesses have taken advantage of this to share information, to communicate with customers, and to create new business opportunities. However, this does not come without drawbacks as there exists an elevated risk to become targeted in attacks.

    The thesis implemented a dynamic taint tracker, named WebTaint, to detect and prevent confidentiality and integrity vulnerabilities in Java-based web applications. We evaluated to what extent WebTaint can combat integrity vulnerabilities. The possible advantages and disadvantages of using the application is introduced as well as an explication whether the application was capable of being integrated into production services.

    The results show that WebTaint helps to combat SQL Injection and Cross-Site Scripting attacks. However, there are drawbacks in the form of additional time and memory overhead. The implemented solution is therefore not suitable for time or memory sensitive domains. WebTaint could be recommended for use in test environments where security experts utilize the taint tracker to find TaintExceptions through manual and automatic attacks.

  • 76.
    Adolfsson, Fredrik
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Johansson, Tobias
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Grafisk visualisering av små fiberoptiska nätverk2016Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    To graphically visualize small fiber optic networks, in a simple and clear way, can be problematic. The information presented in a graph must not be superfluous nor lacking. The purpose of this report is to present what should be considered when creating graphical visualizations, which refers to layout structure, color and shape. The work was conducted through a literature study, collecting information regarding different types of visualizations. With the help of the information solutions about the graph structure and component appearance were discussed and through this a prototype was built. Based on the creation of the prototype an implementation in JavaScript was performed. The result of the appearance, that the implementation generates, results in the recommended layout for visualization of small fiber optic network.

    The report is divided into the parts: a literature study, the development of the prototype, deciding the JavaScript library to use and finally the implementation of the prototype. The result is a graph based on orthogonal and hierarchy layout where symmetry was pursued. The components are distinguished, among other things, by unique shapes and colors.

    One of the conclusions that is drawn is that the developed visualization is a suitable alternative to visualize a small fiber optic network. To say that it is the obvious alternative is not possible without any kind of study based on interaction between users and the visualization.

  • 77.
    ADORF, JULIUS
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    Motion Segmentation of RGB-D Videosvia Trajectory Clustering2014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Motion segmentation of RGB-D videos can be a first step towards object reconstruction in dynamic scenes. The objective in this thesis is to end an ecient motion segmentation method that can deal with a moving camera. To this end, we adopt a feature-based approach where keypoints in the images are tracked over time. The variation in the observed pairwise 3-d distances is used to determine which of the points move similarly. We then employ spectral clusteringto group trajectories into clusters with similar motion, thereby obtaining a sparse segmentation of the dynamic objectsin the scene. The results on twenty scenes from real world datasets and simulations show that while the method needs more sophistication to segment all of them, several dynamic scenes have been successfully segmented at a processing speed of multiple frames per second.

  • 78. Adrian, K.
    et al.
    Chocron, P.
    Confalonieri, R.
    Ferrer, X.
    Giraldez-Cru, J.
    KTH, Skolan för datavetenskap och kommunikation (CSC), Teoretisk datalogi, TCS.
    Link prediction in evolutionary graphs the case study of the CCIA network2016Inngår i: 19th International Conference of the Catalan Association for Artificial Intelligence, CCIA 2016, IOS Press, 2016, s. 187-196Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Studying the prediction of new links in evolutionary networks is a captivating question that has received the interest of different disciplines. Link prediction allows to extract missing information and evaluate network dynamics. Some algorithms that tackle this problem with good performances are based on the sociability index, a measure of node interactions over time. In this paper, we present a case study of this predictor in the evolutionary graph that represents the CCIA co-authorship network from 2005 to 2015. Moreover, we present a generalized version of this sociability index, that takes into account the time in which such interactions occur. We show that this new index outperforms existing predictors. Finally, we use it in order to predict new co-authorships for CCIA 2016.

  • 79.
    Adrup, Joakim
    KTH, Skolan för elektroteknik och datavetenskap (EECS).
    Visualization and Interaction with Temporal Data using Data Cubes in the Global Earth Observation System of Systems2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The purpose of this study was to explore the usage of data cubes in the context of the Global Earth Observation System of Systems (GEOSS). This study investigated what added benefit could be provided to users of the GEOSS platform by utilizing the capabilities of data cubes. Data cubes in earth observation is a concept for how data should be handled and provided by a data server. It includes aspects such as flexible extraction of subsets and processing capabilities. In this study it was found that the most frequent use case for data cubes was time analysis. One of the main services provided by the GEOSS portal was the discovery and inspection of datasets. In the study a timeline interface was constructed to facilitate the exploration and inspection of datasets with a temporal dimension. The datasets were provided by a data cube, and made use of the data cubes capabilities in retrieving subsets of data along any arbitrary axis. A usability evaluation was conducted on the timeline interface to gain insight into the users requirements and user satisfaction. The results showed that the design worked well in many regards, ranking high in user satisfaction. On a number of points the study highlighted areas of improvement. Providing insight into important design limitations and challenges together with suggestions on how these could be approached in different ways.

  • 80.
    Adrup, Joakim
    et al.
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    Skogström, Charlotte
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    Effekterna av spelmekanismerna ledartavlor, serier och certifikat på det dagliga stegantalet hos högskolestuderande studenter2016Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Spelifiering börjar bli ett vedertaget begrepp, speciellt inom forskningsområden såsom MDI (Människa-datorinteraktion). I den här uppsatsen diskuteras och jämförs tre olika spelmekanismer genom det dagliga stegantalet. Spelmekanismerna är ledartavlor, serier och certifikat. Studien tillämpar kvantitativa och kvalitativa metoder för att undersöka hur de ovannämnda spelmekanismerna påverkar det dagliga stegantalet hos studenter som studerar på en högskolenivå.

    Av studien framgår att spelifiering är att föredra när det gäller medvetenhet och nöje, men att spelifiering ej får störa de grundläggande funktionerna hos den ursprungliga produkten. Tvärtom bör spelmekanismer användas för att stödja produktens befintliga funktioner, och inte enbart för att göra produkten mer underhållande och motiverande. Den generella konklusionen av all insamlad kvantitativ data är att spelifiering inte influerar det dagliga stegantalet.

    Slutligen diskuterar artikeln vilka faktorer som bör implementeras för att spelifiering ska verka i motiverande syfte. Artikeln diskuterar även hur spelutvecklare kan nyttja speldesign för att skapa intressanta och engagerande applikationer.

  • 81.
    Adzemovic, Haris
    et al.
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    Sandor, Alexander
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    Comparison of user and item-based collaborative filtering on sparse data2017Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    Recommender systems are used extensively today in many areas to help users and consumers with making decisions. Amazon recommends books based on what you have previously viewed and purchased, Netflix presents you with shows and movies you might enjoy based on your interactions with the platform and Facebook serves personalized ads to every user based on gathered browsing information. These systems are based on shared similarities and there are several ways to develop and model them. This study compares two methods, user and item-based filtering in k nearest neighbours systems.The methods are compared on how much they deviate from the true answer when predicting user ratings of movies based on sparse data. The study showed that none of the methods could be considered objectively better than the other and that the choice of system should be based on the data set.

  • 82.
    af Sandeberg, Jonas
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    Riksdagsval via Internet – Ett system för säkra val via Internet i Sverige.2012Independent thesis Advanced level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [en]

    In this essay a system for voting via the Internet in Sweden is designed. To do this the current Swedish election system is examined. Research is also done on what technologies can be used to build such a system. Lastly systems already used for Internet voting in other countries are examined. Based on the result of the research a system for voting via the Internet in Sweden is designed. The system is designed to follow all safety regulations demanded by a democtratic election. The essay shows that it is possible to design a system for voting via the Internet in Sweden and also that such a system likely would increase the turnout in elections.

  • 83.
    af Sandeberg, Jonas
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Speeding Up Value at Risk Calculations Using Accelerators2014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Calculating Value at Risk (VaR) can be a time consuming task. Therefore it is of interest to find a way to parallelize this calculation to increase performance. Based on a system built in Java, which hardware is best suited for these calculations?

    This thesis aims to find which kind of processing unit that gives optimal performance when calculating scenario based VaR. First the differences of the CPU, GPU and coprocessor is examined in a theoretical study. Then multiple versions of a parallel VaR algorithm are implemented for a CPU, a GPU and a coprocessor trying to make use of the findings from the theoretical study.

    The performance and ease of programming for each version is evaluated and analyzed. By running performance tests it is found that the CPU was the winner when coming to performance while running the chosen VaR algorithm and problem sizes.

  • 84.
    Afework, Miriam
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Medieteknik och interaktionsdesign, MID.
    Using Magic Machines to Elaborate Menstrual Self-Tracker­s for Women with Endometriosis2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Existing self-tracking tools for women concentrate on one’s general well-being and keeping track of ovulation and periods. With around 10% of women worldwide suffering from endometriosis there is an unmet need to leverage self-tracking for women whose cycles are affected by more variables. The disease is enigmatic with an unknown cause and cure and the ill­ness differs for each individual in symptoms and working treatments. It is therefore critical to understand how women can learn about their bodies and how to treat their condition. In this research I work with two sufferers to identify their secret de­sires through a workshop and a series of interviews. Results suggest that women with endometriosis could benefit from ex­perimenting with different habits and make personalized routines to suit their own needs. Finally I present design implica­tions for an existing menstrual app in the form of an add-on. The steps of the add-on tool included three steps. Firstly, choosing variables of one’s well being to track (mood, energy, pain etc.), choosing activities for one or more cycles (gluten-free diet, exercising etc.), and lastly viewing an analysis of any changes in the body.

  • 85.
    Afkham, Heydar Maboudi
    et al.
    KTH, Skolan för datavetenskap och kommunikation (CSC), Datorseende och robotik, CVAP.
    Ek, Carl Henrik
    KTH, Skolan för datavetenskap och kommunikation (CSC), Datorseende och robotik, CVAP.
    Carlsson, Stefan
    KTH, Skolan för datavetenskap och kommunikation (CSC), Datorseende och robotik, CVAP.
    Initialization framework for latent variable models2014Inngår i: ICPRAM 2014 - Proceedings of the 3rd International Conference on Pattern Recognition Applications and Methods, 2014, s. 227-232Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we discuss the properties of a class of latent variable models that assumes each labeled sample is associated with set of different features, with no prior knowledge of which feature is the most relevant feature to be used. Deformable-Part Models (DPM) can be seen as good example of such models. While Latent SVM framework (LSVM) has proven to be an efficient tool for solving these models, we will argue that the solution found by this tool is very sensitive to the initialization. To decrease this dependency, we propose a novel clustering procedure, for these problems, to find cluster centers that are shared by several sample sets while ignoring the rest of the cluster centers. As we will show, these cluster centers will provide a robust initialization for the LSVM framework.

  • 86.
    Afkham, Heydar Maboudi
    et al.
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    Qiu, Xuanbin
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    The, Matthew
    KTH, Skolan för bioteknologi (BIO), Genteknologi. KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Käll, Lukas
    KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Uncertainty estimation of predictions of peptides' chromatographic retention times in shotgun proteomics2017Inngår i: Bioinformatics, ISSN 1367-4803, E-ISSN 1367-4811, Vol. 33, nr 4, s. 508-513Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Motivation: Liquid chromatography is frequently used as a means to reduce the complexity of peptide-mixtures in shotgun proteomics. For such systems, the time when a peptide is released from a chromatography column and registered in the mass spectrometer is referred to as the peptide's retention time. Using heuristics or machine learning techniques, previous studies have demonstrated that it is possible to predict the retention time of a peptide from its amino acid sequence. In this paper, we are applying Gaussian Process Regression to the feature representation of a previously described predictor ELUDE. Using this framework, we demonstrate that it is possible to estimate the uncertainty of the prediction made by the model. Here we show how this uncertainty relates to the actual error of the prediction. Results: In our experiments, we observe a strong correlation between the estimated uncertainty provided by Gaussian Process Regression and the actual prediction error. This relation provides us with new means for assessment of the predictions. We demonstrate how a subset of the peptides can be selected with lower prediction error compared to the whole set. We also demonstrate how such predicted standard deviations can be used for designing adaptive windowing strategies.

  • 87.
    Afrem, Bassel
    KTH, Skolan för elektroteknik och datavetenskap (EECS).
    Designing a Suitable Help Desk Software2019Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    In growing help desk companies, how to handle customer requests is a mark of success. Thus, each company should have an organized system to efficiently handle the communication between the company and its customers.There are many variants of help desk service software that serve different kinds of business model. Therefore, this thesis will be a study about what types of help desk software there are and what functionalities they have, in order to reach the goal of the project which was designing a suitable help desk software for a company Amplius Field Services, based on its business model.The chosen method to solve the problem consisted of a literature study about help desk software and business models, followed by a case study about the different types of help desk software that are already developed and provided and what functions they fulfill by analyzing their pros and cons and evaluate the kind of functionalities they serve. Then, based on the performed study, a general model for a help desk software containing the most important functionalities, was provided. The provided general model should be basically applicable for all different help desk companies, with possibility to be improved by adding other functionalities as required or desired by the company itself. It is intended to companies that desire to build their own application. Finally, the general model was applied for Amplius after studying its business model.The result of the project was finding a general design of a help desk software based on the result of the case study, then, the model was applied to Amplius after setting the requirements through studying its business model’s components. This gave the tailored design for Amplius, and it was supposed to be implemented and tested, but the project time was not sufficient.

  • 88.
    Afroze, Tonima
    et al.
    KTH, Skolan för teknik och hälsa (STH).
    Rosén Gardell, Moa
    KTH, Skolan för teknik och hälsa (STH).
    Algorithm Construction for Efficient Scheduling of Advanced Health Care at Home2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Providing advanced health care at home rather than in a hospital creates a greater quality of life for patients and their families. It also lowers the risk of hospital-acquired infections and accelerates recovery. The overall cost of care per patient is decreased. Manual scheduling of patient visits by health care professionals (HCPs) has become a bottleneck for increased patient capacity at SABH, a ward providing advanced pediatric health care at home (“Sjukhusansluten Avancerad Barnsjukvård i Hemmet” in Swedish), since many parameters need to be taken into account during scheduling. This thesis aims to increase the efficiency of SABH’s daily scheduling of personnel and resources by designing an automated scheduler that constructs a daily schedule and incorporates changes in it when needed in order to remove scheduling as a limitation for increased patient capacity. Requirements on a feasible schedule are identified in cooperation with SABH and literature is investigated about similar areas where the scheduling process has been automated. The scheduling is formulated as a computerized problem and investigated from the perspective of theoretical computer science. We show that the scheduling problem is NP-hard and can therefore not be expected to be solved optimally. The algorithm for scheduling the visits minimizes violations of time windows and travel times, and maximizes person continuity and workload balancing. The algorithm constructs an initial solution that fulfills time constraints using a greedy approach and then uses local search, simulated annealing, and tabu search to iteratively improve the solution. We present an exact rescheduling algorithm that incorporates additional visits after the original schedule has been set. The scheduling algorithm was implemented and tested on real data from SABH. Although we found the algorithm to be efficient, automatic transfer of data from the patient journal system is an imperative for the scheduler to be adopted.

  • 89.
    Agelfors, Eva
    et al.
    KTH, Tidigare Institutioner, Tal, musik och hörsel.
    Beskow, Jonas
    KTH, Tidigare Institutioner, Tal, musik och hörsel.
    Dahlquist, Martin
    KTH, Tidigare Institutioner, Tal, musik och hörsel.
    Granström, Björn
    KTH, Tidigare Institutioner, Tal, musik och hörsel.
    Lundeberg, Magnus
    Salvi, Giampiero
    KTH, Tidigare Institutioner, Tal, musik och hörsel.
    Spens, Karl-Erik
    KTH, Tidigare Institutioner, Tal, musik och hörsel.
    Öhman, Tobias
    A synthetic face as a lip-reading support for hearing impaired telephone users - problems and positive results1999Inngår i: European audiology in 1999: proceeding of the 4th European Conference in Audiology, Oulu, Finland, June 6-10, 1999, 1999Konferansepaper (Fagfellevurdert)
  • 90.
    Agelfors, Eva
    et al.
    KTH, Tidigare Institutioner, Tal, musik och hörsel.
    Beskow, Jonas
    KTH, Tidigare Institutioner, Tal, musik och hörsel.
    Granström, Björn
    KTH, Tidigare Institutioner, Tal, musik och hörsel.
    Lundeberg, Magnus
    KTH, Tidigare Institutioner, Tal, musik och hörsel.
    Salvi, Giampiero
    KTH, Tidigare Institutioner, Tal, musik och hörsel.
    Spens, Karl-Erik
    KTH, Tidigare Institutioner, Tal, musik och hörsel.
    Öhman, Tobias
    KTH, Tidigare Institutioner, Tal, musik och hörsel.
    Synthetic visual speech driven from auditory speech1999Inngår i: Proceedings of Audio-Visual Speech Processing (AVSP'99)), 1999Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We have developed two different methods for using auditory, telephone speech to drive the movements of a synthetic face. In the first method, Hidden Markov Models (HMMs) were trained on a phonetically transcribed telephone speech database. The output of the HMMs was then fed into a rulebased visual speech synthesizer as a string of phonemes together with time labels. In the second method, Artificial Neural Networks (ANNs) were trained on the same database to map acoustic parameters directly to facial control parameters. These target parameter trajectories were generated by using phoneme strings from a database as input to the visual speech synthesis The two methods were evaluated through audiovisual intelligibility tests with ten hearing impaired persons, and compared to “ideal” articulations (where no recognition was involved), a natural face, and to the intelligibility of the audio alone. It was found that the HMM method performs considerably better than the audio alone condition (54% and 34% keywords correct respectively), but not as well as the “ideal” articulating artificial face (64%). The intelligibility for the ANN method was 34% keywords correct.

  • 91.
    Agelfors, Eva
    et al.
    KTH, Skolan för datavetenskap och kommunikation (CSC), Tal, musik och hörsel, TMH.
    Beskow, Jonas
    KTH, Skolan för datavetenskap och kommunikation (CSC), Tal, musik och hörsel, TMH.
    Karlsson, Inger
    KTH, Skolan för datavetenskap och kommunikation (CSC), Tal, musik och hörsel, TMH.
    Kewley, Jo
    Salvi, Giampiero
    KTH, Skolan för datavetenskap och kommunikation (CSC), Tal, musik och hörsel, TMH.
    Thomas, Neil
    User evaluation of the SYNFACE talking head telephone2006Inngår i: Computers Helping People With Special Needs, Proceedings / [ed] Miesenberger, K; Klaus, J; Zagler, W; Karshmer, A, 2006, Vol. 4061, s. 579-586Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The talking-head telephone, Synface, is a lip-reading support for people with hearing-impairment. It has been tested by 49 users with varying degrees of hearing-impaired in UK and Sweden in lab and home environments. Synface was found to give support to the users, especially in perceiving numbers and addresses and an enjoyable way to communicate. A majority deemed Synface to be a useful product.

  • 92.
    Agerblad, Josefin
    et al.
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    Andersen, Martin
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    Provably Secure Pseudo-Random Generators 2013Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    This report is a literary study on provably secure pseudo-random generators. In the report we explain what provably secure pseudo-random generators are and what they are most commonly used for. We also discuss one-way functions which are closely related to our subject. Furthermore, two well-known generators are described and compared, one generator by Blum and Micali, and one by Blum, Blum and Shub. What we have concluded is that the x

    2 mod N generator by Blum, Blum and Shub seems to be the better one concerning speed, security and application areas. You will also be able to read about how the Blum-Blum-Shub generator can be implemented and why we believe that implementation is suitable.

  • 93.
    Agevik, Niklas
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Shared UMTS Networks - A Techno-Economic Study on Mobile Network Operators’ Possibilities to Deliver Unique Products and Services2005Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Historically, there has been a one-to-one mapping between a mobile network and the reseller of the network’s services. Recent developments challenge this model. Virtual operators have emerged in GSM networks and during the rollout of UMTS networks, many operators built shared UMTS networks. This study analyses the impact of shared networks on the mobile network operators’ abilities to deliver unique products and services to their customers. Four sharing models that are in use today are analysed and presented in detail. These are site sharing, geographical split networks, shared RAN and spectrum sharing.

    The research in this study has been done in two steps. In the first step, possible differentiation opportunities are identified through literature studies and interviews with key persons at network operators, equipment manufacturers, business analysts and the Swedish national post and telecom agency. In the second step, this study compares the implementation of these opportunities in the four forms of shared networks with their implementations in a wholly owned network. The opportunities are grouped in three categories: products, quality of service differentiation and multiaccess networks.

    By setting quality of service attributes on bearers, such as latency and the attention/retention policy, quality of service differentiation is a possibility in common shared networks and geographical split networks. Although unlicensed access technologies, such as WLAN standards, can provide coverage differentiation in one sense, this study shows that this is not economical compared to UMTS pico-cells.

    The study finds that implementing features in the underlying network requires extensive cooperation between operators in all sharing models except for site sharing. Certain services require quality of service parameters that are mutually exclusive without over-provisioning in terms of network resources. Such parameters include for example latency and capacity. Even though the 3GPP UMTS standard allow for a separation of the service creation layer and the underlying network, this study argues that many services will still be dependent upon network features, thus mitigating the advantage of developing services in the unshared domain.

  • 94.
    Aghazadeh, Omid
    KTH, Skolan för datavetenskap och kommunikation (CSC), Datorseende och robotik, CVAP.
    Data Driven Visual Recognition2014Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis is mostly about supervised visual recognition problems. Based on a general definition of categories, the contents are divided into two parts: one which models categories and one which is not category based. We are interested in data driven solutions for both kinds of problems.

    In the category-free part, we study novelty detection in temporal and spatial domains as a category-free recognition problem. Using data driven models, we demonstrate that based on a few reference exemplars, our methods are able to detect novelties in ego-motions of people, and changes in the static environments surrounding them.

    In the category level part, we study object recognition. We consider both object category classification and localization, and propose scalable data driven approaches for both problems. A mixture of parametric classifiers, initialized with a sophisticated clustering of the training data, is demonstrated to adapt to the data better than various baselines such as the same model initialized with less subtly designed procedures. A nonparametric large margin classifier is introduced and demonstrated to have a multitude of advantages in comparison to its competitors: better training and testing time costs, the ability to make use of indefinite/invariant and deformable similarity measures, and adaptive complexity are the main features of the proposed model.

    We also propose a rather realistic model of recognition problems, which quantifies the interplay between representations, classifiers, and recognition performances. Based on data-describing measures which are aggregates of pairwise similarities of the training data, our model characterizes and describes the distributions of training exemplars. The measures are shown to capture many aspects of the difficulty of categorization problems and correlate significantly to the observed recognition performances. Utilizing these measures, the model predicts the performance of particular classifiers on distributions similar to the training data. These predictions, when compared to the test performance of the classifiers on the test sets, are reasonably accurate.

    We discuss various aspects of visual recognition problems: what is the interplay between representations and classification tasks, how can different models better adapt to the training data, etc. We describe and analyze the aforementioned methods that are designed to tackle different visual recognition problems, but share one common characteristic: being data driven.

  • 95.
    Aghazadeh, Omid
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    Object Segmentation using Spatial and Spatio-Temporal Features.2011Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 96.
    Aghazadeh, Omid
    et al.
    KTH, Skolan för datavetenskap och kommunikation (CSC), Datorseende och robotik, CVAP.
    Azizpour, Hossein
    KTH, Skolan för datavetenskap och kommunikation (CSC), Datorseende och robotik, CVAP.
    Sullivan, Josephine
    KTH, Skolan för datavetenskap och kommunikation (CSC), Datorseende och robotik, CVAP.
    Carlsson, Stefan
    KTH, Skolan för datavetenskap och kommunikation (CSC), Datorseende och robotik, CVAP.
    Mixture component identification and learning for visual recognition2012Inngår i: Computer Vision – ECCV 2012: 12th European Conference on Computer Vision, Florence, Italy, October 7-13, 2012, Proceedings, Part VI, Springer, 2012, s. 115-128Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The non-linear decision boundary between object and background classes - due to large intra-class variations - needs to be modelled by any classifier wishing to achieve good results. While a mixture of linear classifiers is capable of modelling this non-linearity, learning this mixture from weakly annotated data is non-trivial and is the paper's focus. Our approach is to identify the modes in the distribution of our positive examples by clustering, and to utilize this clustering in a latent SVM formulation to learn the mixture model. The clustering relies on a robust measure of visual similarity which suppresses uninformative clutter by using a novel representation based on the exemplar SVM. This subtle clustering of the data leads to learning better mixture models, as is demonstrated via extensive evaluations on Pascal VOC 2007. The final classifier, using a HOG representation of the global image patch, achieves performance comparable to the state-of-the-art while being more efficient at detection time.

  • 97.
    Aghazadeh, Omid
    et al.
    KTH, Skolan för datavetenskap och kommunikation (CSC), Datorseende och robotik, CVAP.
    Carlsson, Stefan
    KTH, Skolan för datavetenskap och kommunikation (CSC), Datorseende och robotik, CVAP.
    Large Scale, Large Margin Classification using Indefinite Similarity MeasurensManuskript (preprint) (Annet vitenskapelig)
  • 98.
    Aghazadeh, Omid
    et al.
    KTH, Skolan för datavetenskap och kommunikation (CSC), Datorseende och robotik, CVAP.
    Carlsson, Stefan
    KTH, Skolan för datavetenskap och kommunikation (CSC), Datorseende och robotik, CVAP.
    Properties of Datasets Predict the Performance of Classifiers2013Inngår i: BMVC 2013 - Electronic Proceedings of the British Machine Vision Conference 2013, British Machine Vision Association, BMVA , 2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    It has been shown that the performance of classifiers depends not only on the number of training samples, but also on the quality of the training set [10, 12]. The purpose of this paper is to 1) provide quantitative measures that determine the quality of the training set and 2) provide the relation between the test performance and the proposed measures. The measures are derived from pairwise affinities between training exemplars of the positive class and they have a generative nature. We show that the performance of the state of the art methods, on the test set, can be reasonably predicted based on the values of the proposed measures on the training set. These measures open up a wide range of applications to the recognition community enabling us to analyze the behavior of the learning algorithms w.r.t the properties of the training data. This will in turn enable us to devise rules for the automatic selection of training data that maximize the quantified quality of the training set and thereby improve recognition performance.

  • 99.
    Aghazadeh, Omid
    et al.
    KTH, Skolan för datavetenskap och kommunikation (CSC), Datorseende och robotik, CVAP.
    Carlsson, Stefan
    KTH, Skolan för datavetenskap och kommunikation (CSC), Datorseende och robotik, CVAP.
    Properties of Datasets Predict the Performance of Classifiers2013Manuskript (preprint) (Annet vitenskapelig)
  • 100.
    Aghazadeh, Omid
    et al.
    KTH, Skolan för datavetenskap och kommunikation (CSC), Datorseende och robotik, CVAP.
    Sullivan, Josephine
    KTH, Skolan för datavetenskap och kommunikation (CSC), Datorseende och robotik, CVAP.
    Carlsson, Stefan
    KTH, Skolan för datavetenskap och kommunikation (CSC), Datorseende och robotik, CVAP.
    Multi view registration for novelty/background separation2012Inngår i: Computer Vision and Pattern Recognition (CVPR), 2012 IEEE Conference on, IEEE Computer Society, 2012, s. 757-764Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We propose a system for the automatic segmentation of novelties from the background in scenarios where multiple images of the same environment are available e.g. obtained by wearable visual cameras. Our method finds the pixels in a query image corresponding to the underlying background environment by comparing it to reference images of the same scene. This is achieved despite the fact that all the images may have different viewpoints, significantly different illumination conditions and contain different objects cars, people, bicycles, etc. occluding the background. We estimate the probability of each pixel, in the query image, belonging to the background by computing its appearance inconsistency to the multiple reference images. We then, produce multiple segmentations of the query image using an iterated graph cuts algorithm, initializing from these estimated probabilities and consecutively combine these segmentations to come up with a final segmentation of the background. Detection of the background in turn highlights the novel pixels. We demonstrate the effectiveness of our approach on a challenging outdoors data set.

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