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  • 1.
    Aalto, Erik
    KTH, School of Computer Science and Communication (CSC).
    Learning Playlist Representations for Automatic Playlist Generation2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Spotify is currently the worlds leading music streaming ser-vice. As the leader in music streaming the task of providing listeners with music recommendations is vital for Spotify. Listening to playlists is a popular way of consuming music, but traditional recommender systems tend to fo-cus on suggesting songs, albums or artists rather than pro-viding consumers with playlists generated for their needs.

    This thesis presents a scalable and generalizeable approach to music recommendation that performs song selection for the problem of playlist generation. The approach selects tracks related to a playlist theme by finding the charac-terizing variance for a seed playlist and projects candidate songs into the corresponding subspace. Quantitative re-sults shows that the model outperforms a baseline which is taking the full variance into account. By qualitative results the model is also shown to outperform professionally curated playlists in some cases.

  • 2.
    Aarno, Daniel
    KTH, School of Computer Science and Communication (CSC), Numerical Analysis and Computer Science, NADA.
    Intention recognition in human machine collaborative systems2007Licentiate thesis, monograph (Other scientific)
    Abstract [en]

    Robot systems have been used extensively during the last decades to provide automation solutions in a number of areas. The majority of the currently deployed automation systems are limited in that the tasks they can solve are required to be repetitive and predicable. One reason for this is the inability of today’s robot systems to understand and reason about the world. Therefore the robotics and artificial intelligence research communities have made significant research efforts to produce more intelligent machines. Although significant progress has been made towards achieving robots that can interact in a human environment there is currently no system that comes close to achieving the reasoning capabilities of humans.

    In order to reduce the complexity of the problem some researchers have proposed an alternative to creating fully autonomous robots capable of operating in human environments. The proposed alternative is to allow fusion of human and machine capabilities. For example, using teleoperation a human can operate at a remote site, which may not be accessible for the operator for a number of reasons, by issuing commands to a remote agent that will act as an extension of the operator’s body.

    Segmentation and recognition of operator generated motions can be used to provide appropriate assistance during task execution in teleoperative and human-machine collaborative settings. The assistance is usually provided in a virtual fixture framework where the level of compliance can be altered online in order to improve the performance in terms of execution time and overall precision. Acquiring, representing and modeling human skills are key research areas in teleoperation, programming-by-demonstration and human-machine collaborative settings. One of the common approaches is to divide the task that the operator is executing into several sub-tasks in order to provide manageable modeling.

    This thesis is focused on two aspects of human-machine collaborative systems. Classfication of an operator’s motion into a predefined state of a manipulation task and assistance during a manipulation task based on virtual fixtures. The particular applications considered consists of manipulation tasks where a human operator controls a robotic manipulator in a cooperative or teleoperative mode.

    A method for online task tracking using adaptive virtual fixtures is presented. Rather than executing a predefined plan, the operator has the ability to avoid unforeseen obstacles and deviate from the model. To allow this, the probability of following a certain trajectory sub-task) is estimated and used to automatically adjusts the compliance of a virtual fixture, thus providing an online decision of how to fixture the movement.

    A layered hidden Markov model is used to model human skills. A gestem classifier that classifies the operator’s motions into basic action-primitives, or gestemes, is evaluated. The gestem classifiers are then used in a layered hidden Markov model to model a simulated teleoperated task. The classification performance is evaluated with respect to noise, number of gestemes, type of the hidden Markov model and the available number of training sequences. The layered hidden Markov model is applied to data recorded during the execution of a trajectory-tracking task in 2D and 3D with a robotic manipulator in order to give qualitative as well as quantitative results for the proposed approach. The results indicate that the layered hidden Markov model is suitable for modeling teleoperative trajectory-tracking tasks and that the layered hidden Markov model is robust with respect to misclassifications in the underlying gestem classifiers.

  • 3.
    Aarno, Daniel
    et al.
    KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP. KTH, School of Computer Science and Communication (CSC), Centres, Centre for Autonomous Systems, CAS.
    Sommerfeld, Johan
    KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP. KTH, School of Computer Science and Communication (CSC), Centres, Centre for Autonomous Systems, CAS.
    Kragic, Danica
    KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP. KTH, School of Computer Science and Communication (CSC), Centres, Centre for Autonomous Systems, CAS.
    Pugeault, Nicolas
    Kalkan, Sinan
    Woergoetter, Florentin
    Krüger, Norbert
    Early reactive grasping with second order 3D feature relations2008In: Recent Progress In Robotics: Viable Robotic Service To Human / [ed] Lee, S; Suh, IH; Kim, MS, 2008, Vol. 370, 91-105 p.Conference paper (Refereed)
    Abstract [en]

    One of the main challenges in the field of robotics is to make robots ubiquitous. To intelligently interact with the world, such robots need to understand the environment and situations around them and react appropriately, they need context-awareness. But how to equip robots with capabilities of gathering and interpreting the necessary information for novel tasks through interaction with the environment and by providing some minimal knowledge in advance? This has been a longterm question and one of the main drives in the field of cognitive system development. The main idea behind the work presented in this paper is that the robot should, like a human infant, learn about objects by interacting with them, forming representations of the objects and their categories that are grounded in its embodiment. For this purpose, we study an early learning of object grasping process where the agent, based on a set of innate reflexes and knowledge about its embodiment. We stress out that this is not the work on grasping, it is a system that interacts with the environment based on relations of 3D visual features generated trough a stereo vision system. We show how geometry, appearance and spatial relations between the features can guide early reactive grasping which can later on be used in a more purposive manner when interacting with the environment.

  • 4. Aasi, Parisa
    et al.
    Nunes, Ivan
    Rusu, Lazar
    Hodosi, Georg
    Does Organizational Culture Matter in IT Outsourcing Relationships?2015In: 2015 48TH HAWAII INTERNATIONAL CONFERENCE ON SYSTEM SCIENCES (HICSS), IEEE Computer Society, 2015, 4691-4699 p.Conference paper (Refereed)
    Abstract [en]

    IT Outsourcing (ITO) is used widely by Multinational Companies (MNCs) as a sourcing strategy today. ITO relationship between service buyer and provider then becomes a crucial issue in achieving expected objectives. This research sheds light on the influence of organizational culture (OC) of the buyer company on its ITO relationship with the provider. More specifically, the influence that OC can have on four significant dimensions of trust, cooperation, communication and commitment in ITO is studied through a qualitative analysis. IT managers of six MNCs were interviewed which exposed the connection between OC and ITO relationship factors. An open communication culture, speed of adaption to change, receiving innovative solutions, flat or hierarchical structures and responsibility degree appeared as the most visible differences between OCs of MNCs influencing ITO relationships. The results can be used for improving the ITO by considering the influence of OC to gain more benefits from outsourcing.

  • 5.
    Abbas, Haider
    KTH, School of Information and Communication Technology (ICT), Computer and Systems Sciences, DSV.
    Threats and Security Measures Involved in VoIP-Telephony2006Independent thesis Advanced level (degree of Master (One Year)), 30 credits / 45 HE creditsStudent thesis
  • 6.
    Abbas, Haider
    KTH, School of Information and Communication Technology (ICT), Electronic Systems.
    Options-Based Security-Oriented Framework for Addressing Uncerainty Issues in IT Security2010Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Continuous development and innovation in Information Technology introduces novel configuration methods, software development tools and hardware components. This steady state of flux is very desirable as it improves productivity and the overall quality of life in societies. However, the same phenomenon also gives rise to unseen threats, vulnerabilities and security concerns that are becoming more critical with the passage of time. As an implication, technological progress strongly impacts organizations’ existing information security methods, policies and techniques, making obsolete existing security measures and mandating reevaluation, which results in an uncertain IT infrastructure. In order to address these critical concerns, an options-based reasoning borrowed from corporate finance is proposed and adapted for evaluation of security architecture and decision- making to handle them at organizational level. Options theory has provided significant guidance for uncertainty management in several domains, such as Oil & Gas, government R&D and IT security investment projects. We have applied options valuation technique in a different context to formalize optimal solutions in uncertain situations for three specific and identified uncertainty issues in IT security. In the research process, we formulated an adaptation model for expressing options theory in terms useful for IT security which provided knowledge to formulate and propose a framework for addressing uncertainty issues in information security. To validate the efficacy of this proposed framework, we have applied this approach to the SHS (Spridnings- och Hämtningssystem) and ESAM (E-Society) systems used in Sweden. As an ultimate objective of this research, we intend to develop a solution that is amenable to automation for the three main problem areas caused by technological uncertainty in information security: i) dynamically changing security requirements, ii) externalities caused by a security system, iii) obsoleteness of evaluation. The framework is general and capable of dealing with other uncertainty management issues and their solutions, but in this work we primarily deal with the three aforementioned uncertainty problems. The thesis presents an in-depth background and analysis study for a proposed options-based security-oriented framework with case studies for SHS and ESAM systems. It has also been assured that the framework formulation follows the guidelines from industry best practices criteria/metrics. We have also proposed how the whole process can be automated as the next step in development.

  • 7.
    Abbas, Haider
    et al.
    KTH, School of Information and Communication Technology (ICT), Electronic, Computer and Software Systems, ECS.
    Sundkvist, Stefan
    KTH, School of Information and Communication Technology (ICT).
    Increasing the Performance of Crab Linux Router Simulation Package Using XEN2006In: IEEE International Conference on Industrial and Information Systems, Kandy, Sri Lanka, 2006, 459-462 p.Conference paper (Refereed)
    Abstract [en]

    Nowadays hardware components are very expensive, especially if the prime purpose is to perform some routing related lab exercises. Physically connected network resources are required to get the desired results. Configuration of network resources in a lab exercise consumes much time of the students and scientists. The router simulation package Crab(1), based on KnoppW, Quagga' and User Mode Linux (UML) is designed for the students to facilitate them in performing lab exercises on a standalone computer where no real network equipment is needed. In addition to that it provides the facility of connection with the real network equipments. Crab also handles the pre configuration of different parts of the simulated networks like automatic IT addressing etc. This paper will describe the performance enhancing of Crab by replacing User Mode Linux virtual machine with XEN capable of providing ten virtual sessions concurrently using a standalone computer.

  • 8.
    Abbas, Haider
    et al.
    KTH, School of Information and Communication Technology (ICT), Electronic Systems.
    Yngström, Louise
    Hemani, Ahmed
    KTH, School of Information and Communication Technology (ICT), Electronic Systems.
    Empowering Security Evaluation of IT Products with Options Theory2009In: 30th IEEE Symposium on Security & Privacy, Oakland, USA, 2009Conference paper (Refereed)
  • 9.
    Abbasi, Azad Ismail
    KTH, School of Computer Science and Communication (CSC).
    Coffeepot for Masochists: A Study in User-Centered System Design2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Abstract

    Coffeepot for Masochists

    A Study in User-Centered System Design

     

    This master thesis is carried out in the field of “Human-Computer interaction”, more specifically the area “User-centered system design”. The focus has been on “usability” and useful graphical user interfaces. Current theories and definitions in the field have been considered. Literature studies contain well known authors and organisations in domains mentioned above; Jakob Nielsen, Donald A Norman and International Organization for Standardization ISO to mention some.

     

    Another source for this work from which the theories and way of working have been used is the book “User-Centered System Design” written by Jan Gulliksen and Bengt Göransson.

     

    The work started with a literature study followed by looking at methods to use. The next step was to do task and user analysis which followed by the development phase. The user has been given a central role in this project and, just as recommended, also been involved through the whole cycle. A useful method to get feedback from users, in addition to interviews and workshops, has been the “Heuristic Evaluation”.

     

    The final result and conclusion shows that the user-centered system design is a powerful tool to adapt when designing and developing interactive user interface.

  • 10. Abd El Ghany, M. A.
    et al.
    El-Moursy, M. A.
    Ismail, Mohammed
    KTH, School of Information and Communication Technology (ICT), Electronic Systems. Ohio State University, Columbus, United States .
    High throughput architecture for high performance NoC2009In: ISCAS: 2009 IEEE International Symposium on Circuits and Systems, IEEE , 2009, 2241-2244 p.Conference paper (Refereed)
    Abstract [en]

    High Throughput Butterfly Fat Tree (HTBFT) architecture to achieve high performance Networks on Chip (NoC) is proposed. The architecture increases the throughput of the network by 38% while preserving the average latency. The area of HTBFT switch is decreased by 18% as compared to Butterfly Fat Tree switch. The total metal resources required to implement HTBFT design is increased by 5% as compared to the total metal resources required to implement BFT design. The extra power consumption required to achieve the proposed architecture is 3% of the total power consumption of the BFT architecture.

  • 11.
    Abdlwafa, Alan
    et al.
    KTH, School of Computer Science and Communication (CSC).
    Edman, Henrik
    KTH, School of Computer Science and Communication (CSC).
    Distributed Graph Mining: A study of performance advantages in distributed data mining paradigms when processing graphs using PageRank on a single node cluster2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Distributed data mining is a relatively new area within computer science that is steadily growing, emerging from the demands of being able to gather and process various distributed data by utilising clusters. This report presents the properties of graph structured data and what paradigms to use for efficiently processing the data type, based on comprehensive theoretical studies applied on practical tests performed on a single node cluster. The results in the study showcase the various performance aspects of processing graph data, using different open source paradigm frameworks and amount of shards used on input. A conclusion to be drawn from this study is that there are no real performance advantages to using distributed data mining paradigms specifically developed for graph data on single machines. 

  • 12.
    Abenius, Erik
    KTH, Superseded Departments, Numerical Analysis and Computer Science, NADA.
    Time-Domain Inverse Electromagnetic Scattering using FDTD and Gradient-based Minimization2004Licentiate thesis, monograph (Other scientific)
    Abstract [en]

    The thesis addresses time-domain inverse electromagneticscattering for determining unknown characteristics of an objectfrom observations of the scattered .eld. Applications includenon-destructive characterization of media and optimization ofmaterial properties, for example the design of radar absorbingmaterials.A nother interesting application is the parameteroptimization of subcell models to avoid detailed modeling ofcomplex geometries.

    The inverse problem is formulated as an optimal controlproblem where the cost function to be minimized is thedi.erence between the estimated and observed .elds, and thecontrol parameters are the unknown object characteristics. Theproblem is solved in a deterministic gradient-basedoptimization algorithm using a parallel 2D FDTD scheme for thedirect problem.This approach is computationally intensive sincethe direct problem needs to be solved in every optimizationiteration in order to compute an estimated .eld.H ighlyaccurate analytical gradients are computed from the adjointformulation.In addition to giving better accuracy than .nitedi.erences, the analytical gradients also have the advantage ofonly requiring one direct and one adjoint problem to be solvedregardless of the number of parameters.

    When absorbing boundary conditions are used to truncate thecomputational domain, the equations are non-reversible and theentire time-history of the direct solution needs to be storedfor the gradient computation.Ho wever, using an additionaldirect simulation and a restart procedure it is possible tokeep the storage at an acceptable level.

    The inverse method has been successfully applied to a widerange of industrial problems within the European project,IMPACT (Inverse Methods for Wave Propagation Applications inTime-Domain).T he results presented here includecharacterization of layered dispersive media, determination ofparameters in subcell models for thin sheets and narrow slotsand optimization problems where the observed .eld is given bydesign objectives.

  • 13.
    Abensour Sellström, Gabriel
    et al.
    KTH, School of Computer Science and Communication (CSC).
    Runefelt Tõnisson, Meidi
    KTH, School of Computer Science and Communication (CSC).
    Analysis of Voting Algorithms: a comparative study of the Single Transferable Vote.2012Independent thesis Advanced level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    A voting system is defined as a procedure through which political power is distributed among candidates - from the ballot box to the parliament. This essay specifically seeks to contrast the Single Transferable Vote system with two other voting algorithms (Modified Sainte-Laguë and First-Past-The-Post), by constructing Java implementations of the algorithms and running example data through them. Thus, the suitability of a possible real-life implementation of the Single Transferable Vote method in a Swedish parliament context is evaluated. Furthermore, an alternative version of the original STV method which has been modified to fit these conditions is suggested. The effects of such an implementation on election outcomes are not entirely conclusive, and the conclusion is that more research is needed before a definite evaluation can be made.

  • 14.
    Abou Zliekha, M.
    et al.
    Damascus University/Faculty of Information Technology.
    Al Moubayed, Samer
    Damascus University/Faculty of Information Technology.
    Al Dakkak, O.
    Higher Institute of Applied Science and Technology (HIAST).
    Ghneim, N.
    Higher Institute of Applied Science and Technology (HIAST).
    Emotional Audio-Visual Arabic Text to Speech2006In: Proceedings of the XIV European Signal Processing Conference (EUSIPCO), Florence, Italy, 2006Conference paper (Refereed)
    Abstract [en]

    The goal of this paper is to present an emotional audio-visual. Text to speech system for the Arabic Language. The system is based on two entities: un emotional audio text to speech system which generates speech depending on the input text and the desired emotion type, and un emotional Visual model which generates the talking heads, by forming the corresponding visemes. The phonemes to visemes mapping, and the emotion shaping use a 3-paramertic face model, based on the Abstract Muscle Model. We have thirteen viseme models and five emotions as parameters to the face model. The TTS produces the phonemes corresponding to the input text, the speech with the suitable prosody to include the prescribed emotion. In parallel the system generates the visemes and sends the controls to the facial model to get the animation of the talking head in real time.

  • 15. Abrahamsson, M.
    et al.
    Sundberg, Johan
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH, Music Acoustics.
    Subglottal pressure variation in actors’ stage speech2007In: Voice and Gender Journal for the Voice and Speech Trainers Association / [ed] Rees, M., VASTA Publishing , 2007, 343-347 p.Chapter in book (Refereed)
  • 16.
    Acharya, Jaldeep
    et al.
    KTH, School of Computer Science and Communication (CSC).
    Fröberg, Ludvig
    KTH, School of Computer Science and Communication (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 credits / 15 HE creditsStudent thesis
    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. 

  • 17.
    Acin, Medya
    et al.
    KTH, School of Computer Science and Communication (CSC).
    Stansvik, Elvis
    KTH, School of Computer Science and Communication (CSC).
    Improving Player Engagement inTetris Through EDR Monitoring2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    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.

  • 18.
    Adamsson, Marcus
    et al.
    KTH, School of Computer Science and Communication (CSC).
    Vorkapic, Aleksandar
    KTH, School of Computer Science and Communication (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 credits / 15 HE creditsStudent thesis
    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.

  • 19.
    Adikari, Jithra
    KTH, School of Information and Communication Technology (ICT), Computer and Systems Sciences, DSV.
    Efficient non-repudiation for techno-information environment2006In: 2006 International Conference on Industrial and Information Systems, Vols 1 and 2, NEW YORK: IEEE , 2006, 454-458 p.Conference paper (Refereed)
    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.

  • 20.
    ADORF, JULIUS
    KTH, School of Computer Science and Communication (CSC).
    Motion Segmentation of RGB-D Videosvia Trajectory Clustering2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    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.

  • 21. Adrian, K.
    et al.
    Chocron, P.
    Confalonieri, R.
    Ferrer, X.
    Giraldez-Cru, J.
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    Link prediction in evolutionary graphs the case study of the CCIA network2016In: 19th International Conference of the Catalan Association for Artificial Intelligence, CCIA 2016, IOS Press, 2016, 187-196 p.Conference paper (Refereed)
    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.

  • 22.
    Adzemovic, Haris
    et al.
    KTH, School of Computer Science and Communication (CSC).
    Sandor, Alexander
    KTH, School of Computer Science and Communication (CSC).
    Comparison of user and item-based collaborative filtering on sparse data2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    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.

  • 23.
    af Sandeberg, Jonas
    KTH, School of Computer Science and Communication (CSC).
    Riksdagsval via Internet – Ett system för säkra val via Internet i Sverige.2012Independent thesis Advanced level (professional degree), 10 credits / 15 HE creditsStudent thesis
    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.

  • 24.
    Afroze, Tonima
    et al.
    KTH, School of Technology and Health (STH).
    Rosén Gardell, Moa
    KTH, School of Technology and Health (STH).
    Algorithm Construction for Efficient Scheduling of Advanced Health Care at Home2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    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.

  • 25.
    Agerblad, Josefin
    et al.
    KTH, School of Computer Science and Communication (CSC).
    Andersen, Martin
    KTH, School of Computer Science and Communication (CSC).
    Provably Secure Pseudo-Random Generators 2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    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.

  • 26.
    Aghazadeh, Omid
    KTH, School of Computer Science and Communication (CSC).
    Object Segmentation using Spatial and Spatio-Temporal Features.2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 27.
    Aguilar, Xavier
    et al.
    KTH, School of Computer Science and Communication (CSC), High Performance Computing and Visualization (HPCViz).
    Fuerlinger, Karl
    Laure, Erwin
    KTH, School of Computer Science and Communication (CSC), High Performance Computing and Visualization (HPCViz).
    Automatic On-Line Detection of MPI Application Structure with Event Flow Graphs2015In: EURO-PAR 2015: PARALLEL PROCESSING, Springer Berlin/Heidelberg, 2015, 70-81 p.Conference paper (Refereed)
    Abstract [en]

    The deployment of larger and larger HPC systems challenges the scalability of both applications and analysis tools. Performance analysis toolsets provide users with means to spot bottlenecks in their applications by either collecting aggregated statistics or generating loss-less time-stamped traces. While obtaining detailed trace information is the best method to examine the behavior of an application in detail, it is infeasible at extreme scales due to the huge volume of data generated. In this context, knowing the application structure, and particularly the nesting of loops in iterative applications is of great importance as it allows, among other things, to reduce the amount of data collected by focusing on important sections of the code. In this paper we demonstrate how the loop nesting structure of an MPI application can be extracted on-line from its event flow graph without the need of any explicit source code instrumentation. We show how this knowledge on the application structure can be used to compute postmortem statistics as well as to reduce the amount of redundant data collected. To that end, we present a usage scenario where this structure information is utilized on-line (while the application runs) to intelligently collect fine-grained data for only a few iterations of an application, considerably reducing the amount of data gathered.

  • 28.
    Aguilar, Xavier
    et al.
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    Schliephake, Michael
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    Vahtras, Olav
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    Gimenez, Judit
    Barcelona Supercomputing Center, Universitat Politecnica de Catalunya, Barcelona, Spain.
    Laure, Erwin
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    Scaling Dalton, a molecular electronic structure program2011In: Seventh International Conference on e-Science, e-Science 2011, 5-8 December 2011, Stockholm, Sweden, IEEE conference proceedings, 2011, 256-262 p.Conference paper (Refereed)
    Abstract [en]

    Dalton is a molecular electronic structure program featuring common methods of computational chemistry that are based on pure quantum mechanics (QM) as well as hybrid quantum mechanics/molecular mechanics (QM/MM). It is specialized and has a leading position in calculation of molecular properties with a large world-wide user community (over 2000 licenses issued). In this paper, we present a characterization and performance optimization of Dalton that increases the scalability and parallel efficiency of the application. We also propose asolution that helps to avoid the master/worker design of Daltonto become a performance bottleneck for larger process numbers and increase the parallel efficiency.

  • 29.
    Ahlberg, Michael
    et al.
    KTH, School of Information and Communication Technology (ICT), Electronic, Computer and Software Systems, ECS.
    Vlassov, Vladimir
    KTH, School of Information and Communication Technology (ICT), Electronic, Computer and Software Systems, ECS.
    Yasui, Terumasa
    Advanced Technology Research and Development Center, Mitsubishi Electric Corporation, Amagasaki, Japan.
    Router placement in wireless sensor networks2006In: 2006 IEEE International Conference on Mobile Adhoc and Sensor Systems, Vols 1 and 2, IEEE , 2006, 498-501 p.Conference paper (Refereed)
    Abstract [en]

    In this paper we propose and evaluate algorithms for placement of routers in a wireless sensor network. There are two major requirements on router placement First, a placement must guarantee connectivity, i.e. every sensor must be able to communicate through routers with a predefined computer-connected gateway node. Second, a placement must provide robust communication in the case of router failures. This is achieved by placing redundant routers that increase the number of possible routes. Both requirements should be met by placing as few routers as possible. The proposed algorithms compute placement in an efficient and reasonably fast way.

  • 30. Ahlgren, B.
    et al.
    Hidell, Markus
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Network Systems Laboratory (NS Lab).
    Ngai, E. C. -H
    Internet of Things for Smart Cities: Interoperability and Open Data2016In: IEEE Internet Computing, ISSN 1089-7801, E-ISSN 1941-0131, Vol. 20, no 6, 52-56 p., 7781549Article in journal (Refereed)
    Abstract [en]

    The Internet of Things (IoT) has become a promising technology for addressing societal challenges by connecting smart devices and leveraging Big Data analytics to create smart cities worldwide. As the IoT scales up, it's important to provide interoperability among different devices. Yet current simple standard protocols lack sufficient openness and interoperability. IoT for smart cities needs to guarantee the accessibility of open data and cloud services to allow industries and citizens to develop new services and applications. Here, the authors provide a case study of the GreenIoT platform in Uppsala, Sweden, to demonstrate the idea of interoperability and open data for smart cities.

  • 31.
    Ahlgren, Joel
    et al.
    KTH, School of Computer Science and Communication (CSC).
    Mikkola, Mattias
    KTH, School of Computer Science and Communication (CSC).
    Net Voting – Designing an Online Voting System.2011Independent thesis Advanced level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    We are currently in a time where old routines and ways are being converted to more easily accessible, digital ways. You can perform your bank errands and interact with authorities through the Internet. While many of our societies functions already have undergone this transformation, our elections are still very manual. In our report we present what we think are the biggest obstacles to implementing a net voting system in Sweden, how to solve these issues and present a system which we feel would be a good start to designing The Ultimate Net Voting System. We touch upon areas like authenticating voters, protecting their right to anonymous voting in sending and storing votes and ways to protect against attacks against this system. In the end, we present an abstract level of a system design which could begin to fulfill all requirements to make net voting a feasible solution.

  • 32.
    Ahlgren, Joel
    et al.
    KTH, School of Computer Science and Communication (CSC), Media technology and interaction design.
    Mikkola, Mattias
    KTH, School of Computer Science and Communication (CSC), Media technology and interaction design.
    Net Voting – Designing an Online Voting System.2011Independent thesis Advanced level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    We are currently in a time where old routines and ways are being converted to more easily accessible, digital ways. You can perform your bank errands and interact with authorities through the Internet. While many of our societies functions already have undergone this transformation, our elections are still very manual. In our report we present what we think are the biggest obstacles to implementing a net voting system in Sweden, how to solve these issues and present a system which we feel would be a good start to designing The Ultimate Net Voting System. We touch upon areas like authenticating voters, protecting their right to anonymous voting in sending and storing votes and ways to protect against attacks against this system. In the end, we present an abstract level of a system design which could begin to fulfill all requirements to make net voting a feasible solution.

  • 33.
    Ahlqvist, Oscar
    et al.
    KTH, School of Computer Science and Communication (CSC).
    Åkermark, Wilhelm
    KTH, School of Computer Science and Communication (CSC).
    Examining the Implications of Adding Sentiment Analysis when Clustering based on Party Affiliation through Twitter2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Political discussion is very common and a popular statistic for the politically interested are the surveys determining people’s party affiliation. Today they are done manually but it would be beneficial if there was an automated method which could produce the same or similar results. On the social network Twitter there are a lot of users discussing politics, all from political leaders and representatives to just regular people with an interest for the subject. Because of that and also for its convenience when it comes to collecting data, Twitter has been used before in previous work to cluster political users based on what they are discussing. What has not been done before which this thesis contributes is clustering with sentiment analysis. In other terms, trying to cluster people based on what they are discussing but also if their opinion is positive or negative. What was noted in this work was that the part of clustering without sentiment analysis, that had been done in previous studies, was successfully replicated. However adding the sentiment analysis did not give the desired effect and only worsened the results.

  • 34.
    Ahltorp, Magnus
    KTH, School of Computer Science and Communication (CSC).
    A Personalizable Reading Aid for Second Language Learners of Japanese.2012Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Magnus Ahltorp

    A Personalizable Reading Aid for Second Language Learners of Japanese

    Second language learners of Japanese today have access to vast amounts of authentic Japanese text, audio and video material. A challenge that the Japanese learner faces though, is that the process of looking up words in a dictionary is prohibitively slow. In this thesis, I describe a personalizable system that helps the user read Japanese text by providing pronunciation information and English explanations at the user's request. I also describe the user-centered development of the system and the results of each iteration of user testing. The resulting system and user testing show that it is feasible to provide an immersive reading experience that both beginners and more advanced language learners can use to take command of a crucial part of their own learning.

  • 35.
    Ahmad, Rezgar
    KTH, School of Computer Science and Communication (CSC).
    Con curdino – Utökning av tvärflöjtens tonförråd till kvartstoner genom perturbation av tonhålens geometri.2011Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The thesis describes the development and evaluation of a component ('kurdin') that provides flutists the opportunity to play quarter tones on the regular orchestra flute (Böhm flute). The flutist does not need a new instrument or learn a new playing technique.

    Quarter tones were obtained by reducing the diameter of some of the tone holes. The hole diameter is reduced by using the kurdin which is entered inside the flute. The kurdin consists of two parts which can reduce the diameter of two tone holes at the same time. Flutists can thereby extend the available set of scale notes with two quarter tones without changing the position of the kurdin.

    Systematic measurements of the fundamental frequency of four tones (E4, F^#4, A4 and B4) using an artificially blown flute and different versions of the kurdin showed that the pitch of these tones can be lowered a quarter tone (50 cents) with the same reduced hole diameter. The four quarter tones cover almost all scales called Maqamat in oriental music.

  • 36.
    Ahmad, Rezgar
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH.
    Con curdino – Utökning av tvärflöjtens tonförråd till kvartstoner genom perturbation av tonhålens geometri.2011Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The thesis describes the development and evaluation of a component ('kurdin') that provides flutists the opportunity to play quarter tones on the regular orchestra flute (Böhm flute). The flutist does not need a new instrument or learn a new playing technique.

    Quarter tones were obtained by reducing the diameter of some of the tone holes. The hole diameter is reduced by using the kurdin which is entered inside the flute. The kurdin consists of two parts which can reduce the diameter of two tone holes at the same time. Flutists can thereby extend the available set of scale notes with two quarter tones without changing the position of the kurdin.

    Systematic measurements of the fundamental frequency of four tones (E4, F^#4, A4 and B4) using an artificially blown flute and different versions of the kurdin showed that the pitch of these tones can be lowered a quarter tone (50 cents) with the same reduced hole diameter. The four quarter tones cover almost all scales called Maqamat in oriental music.

  • 37.
    Ahmed, Kachkach
    KTH, School of Computer Science and Communication (CSC).
    Analyzing user behavior and sentiment in music streaming services2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    These last years, streaming services (for music, podcasts, TV shows and movies) have been under the spotlight by disrupting traditional media consumption platforms. If the technical implications of streaming huge amounts of data are well researched, much remains to be done to analyze the wealth of data collected by these services and exploit it to its full potential in order to improve them. Using raw data about users’ interactions with the music streaming service Spotify, this thesis focuses on three main concepts: streaming context, user attention and the sequential analysis of user actions. We discuss the importance of each of these aspects and propose different statistical and machine learning techniques to model them. We show how these models can be used to improve streaming services by inferring user sentiment and improving recommender systems, characterizing user sessions, extracting behavioral patterns and providing useful business metrics.

  • 38.
    Ahmed, Laeeq
    et al.
    KTH, School of Computer Science and Communication (CSC), High Performance Computing and Visualization (HPCViz).
    Edlund, Åke
    KTH, School of Computer Science and Communication (CSC), High Performance Computing and Visualization (HPCViz).
    Laure, Erwin
    KTH, School of Computer Science and Communication (CSC), High Performance Computing and Visualization (HPCViz).
    Spjuth, O.
    Using iterative MapReduce for parallel virtual screening2013In: 2013 IEEE 5th International Conference on Cloud Computing Technology and Science (CloudCom), IEEE Computer Society, 2013, 27-32 p.Conference paper (Refereed)
    Abstract [en]

    Virtual Screening is a technique in chemo informatics used for Drug discovery by searching large libraries of molecule structures. Virtual Screening often uses SVM, a supervised machine learning technique used for regression and classification analysis. Virtual screening using SVM not only involves huge datasets, but it is also compute expensive with a complexity that can grow at least up to O(n2). SVM based applications most commonly use MPI, which becomes complex and impractical with large datasets. As an alternative to MPI, MapReduce, and its different implementations, have been successfully used on commodity clusters for analysis of data for problems with very large datasets. Due to the large libraries of molecule structures in virtual screening, it becomes a good candidate for MapReduce. In this paper we present a MapReduce implementation of SVM based virtual screening, using Spark, an iterative MapReduce programming model. We show that our implementation has a good scaling behaviour and opens up the possibility of using huge public cloud infrastructures efficiently for virtual screening.

  • 39.
    Ahmed, Rakiv
    et al.
    KTH, School of Computer Science and Communication (CSC).
    Aule, Jonas
    KTH, School of Computer Science and Communication (CSC).
    An Evaluation of the Framework Libgdx when Developing a Game Prototype for Android Devices.2011Independent thesis Advanced level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    An evaluation of the framework Libgdx

    when developing a game prototype for Android devices

    By: Rakiv Ahmed & Jonas Aule

    ABSTRACT

    This paper is about evaluation of the framework Libgdx, regarding 2D game development for the Android platform. Other frameworks are also investigated briefly. The game under development is an original game called Magnificent Marbles and is multi-modal as other games for smartphones. The Background section talks about the Android platform and its related tools along with game examples, also frameworks are introduced here. The main focus of this paper will be on the Implementation section and the actual usage of Libgdx. Methods and results for different development versions of the game will be displayed.

    The Discussion section concludes that Libgdx is a good framework due to its desktop support. Libgdx may not suitable for smaller game projects or when wanting to get started quickly without too much knowledge in other areas, such as OpenGL. Another issue is that one should not solely rely on Libgdx desktop support, but knowledge in other areas is required as well to utilize Libgdx to the fullest. The Appendix section includes different documents for more information about Magnificent Marbles.

  • 40.
    Ahnlund, Josefin
    KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP.
    Statistical Analysis of Conductor-Musician Interaction: With a Focus on Musical Expression2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The kind of interaction occurring between a conductor and musicians while performing a musical piece together is an unique instance of human non-verbal communication. This Musical Production Process (MPP) thus provides an interesting area of research, both from a communication perspective and by its own right. The long term goal of this project is to model the MPP with machine learning methods, for which large amounts of data are required. Since the amount of data available to this master thesis stems from a single recording session (collected at KTH May 2014) a direct modeling of the MPP is unfeasible. As such the thesis can instead be considered as a pilot project which examines pre-requisites for modeling of the MPP. The main aim of the thesis is to investigate how musical expression can be captured in the modeling of the MPP. Two experiments, as well as a theoretical investigation of the MPP, are performed to this end. The first experiment consists of a HMM classification of sound represented by expressive tone parameters extracted by the CUEX algorithm, and labeled by four emotions. This experiment complements the previous classification of conducting gesture in GP-LVM representation performed by Kelly Karipidou on the same data set. The result of the classification implicitly proves that expression has been transferred from conductor to musicians. As the first experiment considers expression over the musical piece as a whole, the second experiment investigates the transfer of expression from conductor to musician on a local level. To this end local representations of the sound and conducting gesture are extracted, the separability of the four emotions are calculated for both representations by use of the Bhattacharyya distance and the results are compared in search for correlation. Some indications of correlation between the representations of sound and gesture are found. The conclusion is nevertheless that the utilized representations of conducting gesture do not capture musical expression to a sufficient extent.

  • 41.
    Ahsant, Mehran
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    On-demand Restricted Delegation: A Framework for Dynamic, Context-Aware, Least-Privilege Delegation in Grids2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In grids, delegation is a key facility that can be used to authenticate and authorize requests on behalf of disconnected users. In current grid systems,delegation is either performed dynamically, in an unrestricted manner, or by a secure but static method. Unfortunately, the former compromises security and the latter cannot satisfy the requirements of dynamic grid application execution. Therefore, development of a delegation framework that enables a restricted and flexible delegation mechanism becomes increasingly urgent as grids are adopted by new communities and grow in size. The main barriers in development of such a mechanism are the requirements for dynamic execution of grid applications, which make it difficult to anticipate required access rights for completing tasks in advance.

    Another significant architectural requirement in grids is federated security and trust. A considerable barrier to achieving this is cross-organizational authentication and identification. Organizations participating in Virtual Organizations (VOs) may use different security infrastructures that implement different protocols for authentication and identification; thus, there exists a need to provide an architectural mechanism for lightweight, rapid and interoperable translation of security credentials from an original format to a format understandable by recipients.

    This thesis contributes the development of a delegation framework that utilizes a mechanism for determining and acquiring only required rights and credentials for completing a task, when they are needed. This is what we call an on-demand delegation framework that realizes a bottom-up delegation model and provides a just-in-time acquisition of rights for restricted and dynamic delegation.

    In this thesis, we further contribute the development of a credential mapping mechanism using off-the-shelf standards and technologies. This mechanism provides support for an on-the-fly exchange of different types of security credentials used by the security mechanisms of existing grids.

  • 42.
    Ahsant, Mehran
    et al.
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    Basney, Jim
    Workflows in Dynamic and Restricted Delegation2009In: 2009 INTERNATIONAL CONFERENCE ON AVAILABILITY, RELIABILITY, AND SECURITY (ARES), New York: IEEE , 2009, 17-24 p.Conference paper (Refereed)
    Abstract [en]

    Delegation is a key facility in dynamic, distributed and collaborative environments like e rids and enables an effective use of a wide range of dynamic applications. Traditional delegation frameworks approach a top-down model of delegation for delegating rights from a superior to a subordinate in advance before a delegate starts off a delegated task. However, a top-down model of delegation cannot meet all the requirements of dynamic execution of distributed applications, as in such environments. required access rights for completing a task cannot easily be anticipated in advance. Delegating fewer rights than required for completing a task may cause the task execution to fail while delegating more rights than needed may threaten abuse by malicious parties. It is therefore reasonable and more robust to utilize a mechanism that allows determining and acquiring only required rights and credentials for completing a task, when they are needed. This is what we call an on-demand delegation framework, which realizes a bottom-up delegation model and provides a just-in-time acquisition of rights for a restricted and dynamic delegation. In this paper we elaborate the concept of bottom-up delegation and describe how an on-demand delegation framework can leverage workflows to meet the requirements of the least privileges principle. We also discuss the vital need for dynamic and adaptive scientific workflows to support an on-demand delegation framework. We present three different models or bottom-up delegation, which cover a wide range or usage scenarios in Grids and dynamic collaborative environments. Using a standard RBAC authorization model and a graph-based workflow model (DAG), we define and analyze a formal model of our proposed bottom-up delegation approach.

  • 43.
    Ahsant, Mehran
    et al.
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    Basney, Jim
    Johnsson, Lennart
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    Dynamic, Context-Aware, Least-Privilege Grid Delegation2007In: 8th IEEE/ACM International Conference on Grid Computing, New York: IEEE , 2007, 209-216 p.Conference paper (Refereed)
    Abstract [en]

    Performing delegation in large scale, dynamic and distributed environments with large numbers of shared resources is more challenging than inside local administrative domains. In dynamic environments like Grids, on one hand, delegating a restricted set of rights reduces exposure to attack but also limits the flexibility and dynamism of the application; on the other hand, delegating all rights provides maximum flexibility but increases exposure. This issue has not yet been adequately addressed by current Grid security mechanisms and is becoming a very challenging and crucial issue for future Grid development. Therefore, providing an effective delegation mechanism which meets the requirements of the least privilege principle is becoming an essential need. Furthermore, we are witnessing a phenomenal increase in the automation of organizational tasks and decision making, as well as the computerization of information related services, requiring automated delegation mechanisms. In order to meet these requirements we introduce an Active Delegation Framework which extends our previous work on on-demand delegation, making it context-aware. The framework provides a just-in-time, restricted and dynamic delegation mechanism for Grids. In this paper we describe the development of this framework and its implementation and integration with the Globus Toolkit.

  • 44.
    Ahsant, Mehran
    et al.
    KTH, Superseded Departments, Numerical Analysis and Computer Science, NADA.
    Mulmo, Olle
    KTH, Superseded Departments, Numerical Analysis and Computer Science, NADA.
    Basney, Jim
    University of Illinois.
    Grid Delegation Protocol2004In: Workshop on Grid Security Practice and Experience, 2004, 81-91 p.Conference paper (Refereed)
    Abstract [en]

    We propose a delegation protocol based on the WS-Trust specification, which is applicablefor a wide range of Grid applications. The protocol is independent of underlying securitymechanisms and is therefore applicable to all security mechanisms of common use in Gridenvironments, such as X.509 proxy certificates, Kerberos based delegation, and SAML assertions.We emphasize that this is work in progress. In this paper, we document our thoughtsand current strategy, and we solicit comments and feedback on our approach.

  • 45.
    Ahsant, Mehran
    et al.
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    Mulmo, Olle
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    Johnsson, Lennart
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    Basney, Jim
    Lee, Adam J.
    Toward An On-demand Restricted Delegation Mechanism for Grids2006In: 2006 7TH IEEE/ACM INTERNATIONAL CONFERENCE ON GRID COMPUTING, New York: IEEE , 2006, 152-159 p.Conference paper (Refereed)
    Abstract [en]

    Grids are intended to enable cross-organizationalinteractions which makes Grid security a challenging and nontrivialissue. In Grids, delegation is a key facility that canbe used to authenticate and authorize requests on behalf ofdisconnected users. In current Grid systems there is a tradeoffbetween flexibility and security in the context of delegation.Applications must choose between limited or full delegation: onone hand, delegating a restricted set of rights reduces exposure toattack but also limits the flexibility/dynamism of the application;on the other hand, delegating all rights provides maximumflexibility but increases exposure. In this paper, we propose anon-demand restricted delegation mechanism, aimed at addressingthe shortcomings of current delegation mechanisms by providingrestricted delegation in a flexible fashion as needed for Grid applications.This mechanism provides an ontology-based solutionfor tackling one the most challenging issues in security systems,which is the principle of least privileges. It utilizes a callbackmechanism, which allows on-demand provisioning of delegatedcredentials in addition to observing, screening, and auditingdelegated rights at runtime. This mechanism provides supportfor generating delegation credentials with a very limited andwell-defined range of capabilities or policies, where a delegatoris able to grant a delegatee a set of restricted and limited rights,implicitly or explicitly.

  • 46.
    Ahsant, Mehran
    et al.
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    Mulmo, Olle
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    Nefedova, V.
    Ananthakrishnan, R.
    Liming, L.
    Madduri, R.
    Pearlman, L.
    Siebenlist, F.
    Streamlining Grid Operations: Definition and Deployment of a Portal-based User Registration Service2006In: Journal of Grid Computing, ISSN 1572-9814, Vol. 4, no 2, 135-144 p.Article in journal (Refereed)
    Abstract [en]

    Manual management of public key credentials can be a significant and often off-putting obstacle to Grid use, particularly for casual users. We describe the Portal-based User Registration Service (PURSE), a set of tools for automating user registration, credential creation, and credential management tasks. PURSE provides the system developer with a set of customizable components, suitable for integration with portals, that can be used to address the full lifecycle of Grid credential management. We describe the PURSE design and its use in portals for two systems, the Earth System Grid data access system and the Swegrid computational Grid. In both cases, the user is entirely freed from the need to create or manage public key credentials, thus simplifying the Grid experience and reducing opportunities for error. We argue that this capturing of common use cases in a reusable ‘solution’ can be a model for how Grid ease-of-use can be addressed in other domains as well.

  • 47.
    Ahsant, Mehran
    et al.
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    Talavera González, Esteban
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    Basney, Jim
    Security Credential Mapping in Grids2009In: 2009 INTERNATIONAL CONFERENCE ON AVAILABILITY, RELIABILITY, AND SECURITY (ARES), New York: IEEE , 2009, 481-486 p.Conference paper (Refereed)
    Abstract [en]

    Federating security and trust is one of the most significant architectural requirements in grids. In this regard, one challenging issue is the cross-organizational authentication and identification. Organizations participated in Virtual Organizations (VOs) may use different security infrastructures that implement different authentication and identification protocols. Thus, arises an architectural need to provide a mechanism for a lightweight, rapid and interoperable translation of security credentials from an original format to a format understandable by recipients. In this paper, we describe the development and the implementation of an architecture for credential mapping in grids using off-the-shelf technologies and standard specifications. Our open-source implementation of this architecture provides support for an on-the-fly exchange for different types of security credentials used by diverse grid security infrastructures'.

  • 48.
    Akay, Altug
    et al.
    KTH, School of Technology and Health (STH), Health Systems Engineering, Systems Safety and Management.
    Dragomir, A
    Erlandsson, Björn-Erik
    KTH, School of Technology and Health (STH), Health Systems Engineering, Systems Safety and Management.
    Network-Based Modeling and Intelligent Data Mining of Social Media for Improving Care2015In: IEEE journal of biomedical and health informatics, ISSN 2168-2194, E-ISSN 2168-2208, Vol. 19, no 1, 210-218 p.Article in journal (Refereed)
    Abstract [en]

    Intelligently extracting knowledge from social media has recently attracted great interest from the Biomedical and Health Informatics community to simultaneously improve healthcare outcomes and reduce costs using consumer-generated opinion. We propose a two-step analysis framework that focuses on positive and negative sentiment, as well as the side effects of treatment, in users' forum posts, and identifies user communities (modules) and influential users for the purpose of ascertaining user opinion of cancer treatment. We used a self-organizing map to analyze word frequency data derived from users' forum posts. We then introduced a novel network-based approach for modeling users' forum interactions and employed a network partitioning method based on optimizing a stability quality measure. This allowed us to determine consumer opinion and identify influential users within the retrieved modules using information derived from both word-frequency data and network-based properties. Our approach can expand research into intelligently mining social media data for consumer opinion of various treatments to provide rapid, up-to-date information for the pharmaceutical industry, hospitals, and medical staff, on the effectiveness (or ineffectiveness) of future treatments.

  • 49.
    Akay, Altug
    et al.
    KTH, School of Technology and Health (STH), Health Systems Engineering, Systems Safety and Management.
    Dragomir, Andrei
    Erlandsson, Björn-Erik
    KTH, School of Technology and Health (STH), Health Systems Engineering, Systems Safety and Management.
    Assessing Antidepressants Using Intelligent Data Monitoring and Mining of Online Fora2016In: IEEE journal of biomedical and health informatics, ISSN 2168-2194, E-ISSN 2168-2208, Vol. 20, no 4, 977-986 p.Article in journal (Refereed)
    Abstract [en]

    Depression is a global health concern. Social networks allow the affected population to share their experiences. These experiences, when mined, extracted, and analyzed, can be converted into either warnings to recall drugs (dangerous side effects), or service improvement (interventions, treatment options) based on observations derived from user behavior in depression-related social networks. Our aim was to develop a weighted network model to represent user activity on social health networks. This enabled us to accurately represent user interactions by relying on the data's semantic content. Our three-step method uses the weighted network model to represent user's activity, and network clustering and module analysis to characterize user interactions and extract further knowledge from user's posts. The network's topological properties reflect user activity such as posts' general topic as well as timing, while weighted edges reflect the posts semantic content and similarities among posts. The result, a synthesis from word data frequency, statistical analysis of module content, and the modeled health network's properties, has allowed us to gain insight into consumer sentiment of antidepressants. This approach will allow all parties to participate in improving future health solutions of patients suffering from depression.

  • 50. Akbarzadeh, Sara
    et al.
    Combes, Richard
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Altman, Zwi
    Self-organizing femtocell offloading at the flow level2013In: International Journal of Network Management, ISSN 1055-7148, E-ISSN 1099-1190, Vol. 23, no 4, 259-271 p.Article in journal (Refereed)
    Abstract [en]

    Femtocell technology is expected to be fully self-managed, empowered by self-organizing network functionalities. This paper proposes a solution for self-optimized offloading of macrocell traffic towards open/hybrid-access femtocells. A heterogeneous network comprising macro- and femtocells is modeled as parallel queues. The coverage area of the femtocells is self-optimized by dynamically adapting their pilot powers. A simple update equation for the pilot power is given and its convergence is studied using stochastic approximation techniques. The algorithm balances the load among the cells to improve network capacity. Simulation results illustrate the important performance gains brought about by the proposed scheme, using a dynamic network simulator.

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