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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.
    Ekvall, Staffan
    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.
    Adaptive virtual fixtures for machine-assisted teleoperation tasks2005In: 2005 IEEE International Conference on Robotics and Automation (ICRA), Vols 1-4, 2005, p. 1139-1144Conference paper (Refereed)
    Abstract [en]

    It has been demonstrated in a number of robotic areas how the use of virtual fixtures improves task performance both in terms of execution time and overall precision, [1]. However, the fixtures are typically inflexible, resulting in a degraded performance in cases of unexpected obstacles or incorrect fixture models. In this paper, we propose the use of adaptive virtual fixtures that enable us to cope with the above problems. A teleoperative or human machine collaborative setting is assumed with the core idea of dividing the task, that the operator is executing, into several subtasks. The operator may remain in each of these subtasks as long as necessary and switch freely between them. Hence, rather than executing a predefined plan, the operator has the ability to avoid unforeseen obstacles and deviate from the model. In our system, the probability that the user is following a certain trajectory (subtask) is estimated and used to automatically adjusts the compliance. Thus, an on-line decision of how to fixture the movement is provided.

  • 4.
    Aarno, Daniel
    et al.
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for Autonomous Systems, CAS. KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP.
    Kragic, Danica
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for Autonomous Systems, CAS. KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP.
    Layered HMM for motion intention recognition2006In: 2006 IEEE/RSJ International Conference on Intelligent Robots and Systems, Vols 1-12, NEW YORK: IEEE , 2006, p. 5130-5135Conference paper (Refereed)
    Abstract [en]

    Acquiring, representing and modeling human skins is one of the 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 subtasks in order to provide manageable modeling. In this paper we consider the use of a Layered Hidden Markov Model (LHMM) to model human skills. We evaluate a gestem classifier that classifies motions into basic action-primitives, or gestems. The gestem classifiers are then used in a LHMM to model a simulated teleoperated task. We investigate the online and offline classilication performance with respect to noise, number of gestems, type of HAIM and the available number of training sequences. We also apply the LHMM 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 LHMM is suitable for modeling teleoperative trajectory-tracking tasks and that the difference in classification performance between one and multi dimensional HMMs for gestem classification is small. It can also be seen that the LHMM is robust w.r.t misclassifications in the underlying gestem classifiers.

  • 5.
    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.
    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.
    Motion intention recognition in robot assisted applications2008In: Robotics and Autonomous Systems, ISSN 0921-8890, E-ISSN 1872-793X, Vol. 56, no 8, p. 692-705Article in journal (Refereed)
    Abstract [en]

    Acquiring, representing and modelling human skills is one of the key research areas in teleoperation, programming-by-demonstration and human-machine collaborative settings. The problems are challenging mainly because of the lack of a general mathematical model to describe human skills. One of the common approaches is to divide the task that the operator is executing into several subtasks or low-level subsystems in order to provide manageable modelling. In this paper we consider the use of a Layered Hidden Markov Model (LHMM) to model human skills. We evaluate a gesteme classifier that classifies motions into basic action-primitives, or gestemes. The gesteme classifiers are then used in a LHMM to model a teleoperated task. The proposed methodology uses three different HMM models at the gesteme level: one-dimensional HMM, multi-dimensional HMM and multidimensional HMM with Fourier transform. The online and off-line classification performance of these three models is evaluated with respect to the number of gestemes, the influence of the number of training samples, the effect of noise and the effect of the number of observation symbols. We also apply the LHMM to data recorded during the execution of a trajectory tracking task in 2D and 3D with a mobile manipulator in order to provide qualitative as well as quantitative results for the proposed approach. The results indicate that the LHMM is suitable for modelling teleoperative trajectory-tracking tasks and that the difference in classification performance between one and multidimensional HMMs for gesteme classification is small. It can also be seen that the LHMM is robust with respect to misclassifications in the underlying gesteme classifiers.

  • 6.
    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.
    Lingelbach, F.
    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.
    Constrained path planning and task-consistent path adaptation for mobile manipulators2005In: 2005 12th International Conference on Advanced Robotics, 2005, p. 268-273Conference paper (Refereed)
    Abstract [en]

    This paper presents our ongoing research in the design of a versatile service robot capable of operating in a home or office environment. Ideas presented here cover architectural issues and possible applications for such a robot system with focus on tasks requiring constrained end-effector motions. Two key components of such system is a path planner and a reactive behavior capable of force relaxation and path adaptation. These components are presented in detail along with an overview of the software architecture they fit into.

  • 7.
    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, p. 91-105Conference 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.

  • 8.
    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.

  • 9. Abbeloos, W.
    et al.
    Caccamo, Sergio
    KTH, School of Computer Science and Communication (CSC), Robotics, perception and learning, RPL.
    Ataer-Cansizoglu, E.
    Taguchi, Y.
    Feng, C.
    Lee, T. -Y
    Detecting and Grouping Identical Objects for Region Proposal and Classification2017In: 2017 IEEE Computer Society Conference on Computer Vision and Pattern Recognition Workshops, IEEE Computer Society, 2017, Vol. 2017, p. 501-502, article id 8014810Conference paper (Refereed)
    Abstract [en]

    Often multiple instances of an object occur in the same scene, for example in a warehouse. Unsupervised multi-instance object discovery algorithms are able to detect and identify such objects. We use such an algorithm to provide object proposals to a convolutional neural network (CNN) based classifier. This results in fewer regions to evaluate, compared to traditional region proposal algorithms. Additionally, it enables using the joint probability of multiple instances of an object, resulting in improved classification accuracy. The proposed technique can also split a single class into multiple sub-classes corresponding to the different object types, enabling hierarchical classification.

  • 10.
    Abdelmassih, Christian
    et al.
    KTH, School of Computer Science and Communication (CSC).
    Hultman, Axel
    KTH, School of Computer Science and Communication (CSC).
    Förutspå golfresultat med hjälp av sentimentanalys på Twitter2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In this study we examine the relationship between the sentiment value of golf players’ tweets and their sports results to evaluate the predictive power of the their twitter accounts. Findings on this topic may be of value to bookmakers, gamblers, coaches and fans of sport. Our study is based on two datasets: PGA­tour golf statistics and 112 101 tweets made by 155 profesional golfers over the course of two seasons. The golf players’ sentiment was quantified using the lexical sentiment analysis method AFINN.

    In contrast to other research with similiar methods, our findings suggest that there is low correlation betweet the datasets and that the methods used in our study have low predictive power. Our recommendation is that future studies use additional prediction variables besides sentiment score to better evaluate the predictive power of golf players’ tweets. 

  • 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.
    Abdulaziz Ali Haseeb, Mohamed
    KTH, School of Computer Science and Communication (CSC), Robotics, perception and learning, RPL.
    Passive gesture recognition on unmodified smartphones using Wi-Fi RSSI2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The smartphone is becoming a common device carried by hundreds of millions of individual humans worldwide, and is used to accomplish a multitude of different tasks like basic communication, internet browsing, online shopping and fitness tracking. Limited by its small size and tight energy storage, the human-smartphone interface is largely bound to the smartphones small screens and simple keypads. This prohibits introducing new rich ways of interaction with smartphones.

     

    The industry and research community are working extensively to find ways to enrich the human-smartphone interface by either seizing the existing smartphones resources like microphones, cameras and inertia sensors, or by introducing new specialized sensing capabilities into the smartphones like compact gesture sensing radar devices.

     

    The prevalence of Radio Frequency (RF) signals and their limited power needs, led us towards investigating using RF signals received by smartphones to recognize gestures and activities around smartphones. This thesis introduces a solution for recognizing touch-less dynamic hand gestures from the Wi-Fi Received Signal Strength (RSS) received by the smartphone using a recurrent neural network (RNN) based probabilistic model. Unlike other Wi-Fi based gesture recognition solutions, the one introduced in this thesis does not require a change to the smartphone hardware or operating system, and performs the hand gesture recognition without interfering with the normal operation of other smartphone applications.

     

    The developed hand gesture recognition solution achieved a mean accuracy of 78% detecting and classifying three hand gestures in an online setting involving different spatial and traffic scenarios between the smartphone and Wi-Fi access points (AP). Furthermore the characteristics of the developed solution were studied, and a set of improvements have been suggested for further future work.

  • 13. Abdullah, Matin
    et al.
    Feig, Michael
    Pettitt, Montgomery
    Johnsson, Lennart
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    SimDB: A Problem Solving Environment for Molecular Dynamics Simulation and Analysis2000Conference paper (Refereed)
    Abstract [en]

    The design of a software environment, SimDB, for molecular dynamics simulation and analysis is presented as an example of virtual laboratories enabled by high-speed networks connecting substantial computing and storage resources with more modest local compuation and visualization resources available to research groups. SimDB includes large-scale, dynamic, distributed data repositories. The simulated data sets, trajectories, are usually interpreted through reduced data sets, processed data sets, calculated by analysis functions. Both trajectory data and processed data are saved, but in differnt data bases, with processed data bases having several smaller objects for each trajectory. A browser based user interface with a well defined API allows for a wide array of analysis functions. Analysis functions are executed only if the requested analysis result is not available. The ability to incorporate user defined functions is a critical feature of SimDB.

  • 14. Abedan Kondori, Farid
    et al.
    Yousefi, Shahrouz
    KTH, School of Computer Science and Communication (CSC), Media Technology and Interaction Design, MID. Department of Applied Physics and Electronics, Umeå University, Umeå, Sweden.
    Smart Baggage in Aviation2011In: Proceedings - 2011 IEEE International Conferences on Internet of Things and Cyber, Physical and Social Computing, 2011Conference paper (Refereed)
    Abstract [en]

    Nowadays, the Internet has dramatically changed the way people take the normal course of actions. By the recent growth of the Internet, connecting different objects to users through mobile phones and computers is no longer a dream. Aviation industry is one of the areas which have a strong potential to benefit from the Internet of Things. Among many problems related to air travel, delayed and lost luggage are the most common and irritating. Therefore, this paper suggests anew baggage control system, where users can simply track their baggage at the airport to avoid losing them. Attaching a particular pattern on the bag, which can be detected and localized from long distance by an ordinary camera, users are able to track their baggage. The proposed system is much cheaper than previous implementations and does not require sophisticated equipment.

  • 15. Abedan Kondori, Farid
    et al.
    Yousefi, Shahrouz
    KTH, School of Computer Science and Communication (CSC), Media Technology and Interaction Design, MID.
    Li, Haibo
    KTH, School of Computer Science and Communication (CSC), Media Technology and Interaction Design, MID.
    Direct Head Pose Estimation Using Kinect-type Sensors2014In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911XArticle in journal (Refereed)
  • 16. Abedan Kondori, Farid
    et al.
    Yousefi, Shahrouz
    KTH, School of Computer Science and Communication (CSC), Media Technology and Interaction Design, MID.
    Liu, Li
    Li, Haibo
    KTH, School of Computer Science and Communication (CSC), Media Technology and Interaction Design, MID. Nanjing University of Posts and Telecommunications, Nanjing, China .
    Head Operated Electric Wheelchair2014In: Proceedings of the IEEE Southwest Symposium on Image Analysis and Interpretation, 2014, p. 53-56Conference paper (Refereed)
    Abstract [en]

    Currently, the most common way to control an electric wheelchair is to use joystick. However, there are some individuals unable to operate joystick-driven electric wheelchairs due to sever physical disabilities, like quadriplegia patients. This paper proposes a novel head pose estimation method to assist such patients. Head motion parameters are employed to control and drive an electric wheelchair. We introduce a direct method for estimating user head motion, based on a sequence of range images captured by Kinect. In this work, we derive new version of the optical flow constraint equation for range images. We show how the new equation can be used to estimate head motion directly. Experimental results reveal that the proposed system works with high accuracy in real-time. We also show simulation results for navigating the electric wheelchair by recovering user head motion.

  • 17.
    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.

  • 18. Abeywardena, D.
    et al.
    Wang, Zhan
    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.
    Dissanayake, G.
    Waslander, S. L.
    Kodagoda, S.
    Model-aided state estimation for quadrotor micro air vehicles amidst wind disturbances2014Conference paper (Refereed)
    Abstract [en]

    This paper extends the recently developed Model-Aided Visual-Inertial Fusion (MA-VIF) technique for quadrotor Micro Air Vehicles (MAV) to deal with wind disturbances. The wind effects are explicitly modelled in the quadrotor dynamic equations excluding the unobservable wind velocity component. This is achieved by a nonlinear observability of the dynamic system with wind effects. We show that using the developed model, the vehicle pose and two components of the wind velocity vector can be simultaneously estimated with a monocular camera and an inertial measurement unit. We also show that the MA-VIF is reasonably tolerant to wind disturbances, even without explicit modelling of wind effects and explain the reasons for this behaviour. Experimental results using a Vicon motion capture system are presented to demonstrate the effectiveness of the proposed method and validate our claims.

  • 19. Abrahamsson, H
    et al.
    Hagsand, Olof
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    Marsh, Ian
    TCP over high speed variable capacity links: A simulation study for bandwidth allocation2002Conference paper (Refereed)
    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.

  • 20. 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, p. 343-347Chapter in book (Refereed)
  • 21.
    Abreu, Rodrigo
    et al.
    KTH, School of Computer Science and Communication (CSC), Numerical Analysis, NA (closed 2012-06-30).
    Jansson, Niclas
    KTH, School of Computer Science and Communication (CSC), Numerical Analysis, NA (closed 2012-06-30).
    Hoffman, Johan
    KTH, School of Computer Science and Communication (CSC), Numerical Analysis, NA (closed 2012-06-30).
    Adaptive computation of aeroacoustic sources for a rudimentary landing gear using lighthill's analogy2011In: 17th AIAA/CEAS AeroacousticsConference 2011: 32nd AIAA Aeroacoustics Conference, 2011Conference paper (Refereed)
    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.

  • 22.
    Absillis, Eline
    KTH, School of Computer Science and Communication (CSC).
    How Can Event Companies Use Facebook’s Ad Manager to Optimise the Click-Through-Rates of their Native Instagram Ads?2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Marketers have come to realise that an abundance of potential customers can be reached through Facebook advertising. Although a new player, Instagram is quickly catching up to Facebook’s success with its native ads. Despite this, there is a scarcity in the amount of academic literature that explores the use of them. This thesis aims to rectify that, by contributing to the academic discourse surrounding Instagram ads.

    Shownight, a live event promotion company, had yet to run ads on Instagram. Using split-testing, this thesis was aimed to figure out which ad features generated the highest click-through-rates. The tests were carried out through Facebook’s ad manager. Although a unique platform, functioning with both drawbacks and benefits, it provided this study with an efficient tool to split-test ads.

    The results from this study demonstrated Instagram to be a suitable platform on which to advertise live events. Furthermore, the findings revealed targeting through lookalikes as well as behaviour, results in the highest click-through-rate. Moreover, using a video with 4 hashtags for lookalikes targeting, and an image with up to 3 hashtags for behaviour targeting, were the best ad set combinations. A call-to-action, portraying some degree of urgency, should also be employed within the caption.

    Nevertheless, this study has its limitations. Including being restricted demographically, as well as being confined to Shownight’s target audience, and advertising content. Furthermore, Facebook’s ad manager poses its own limitations as a split-testing platform, in terms of even audience distribution. 

  • 23.
    Abu Nijmeh, Jonas
    et al.
    KTH, School of Computer Science and Communication (CSC).
    Catalan Canales, Diego
    KTH, School of Computer Science and Communication (CSC).
    Prokrastinering i form av medieanvändning: En jämförelsestudie kring kön och sysselsättning2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    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.

  • 24.
    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. 

  • 25.
    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.

  • 26.
    Ackland, Patrik
    KTH, School of Computer Science and Communication (CSC).
    Fast and Scalable Static Analysis using Deterministic Concurrency2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    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.

  • 27. Adams, Henry
    et al.
    Tausz, Andrew
    Vejdemo-Johansson, Mikael
    KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP. Institut Jozef Stefan, Slovenia .
    javaPlex: A Research Software Package for Persistent (Co) Homology2014Conference paper (Refereed)
    Abstract [en]

    The computation of persistent homology has proven a fundamental component of the nascent field of topological data analysis and computational topology. We describe a new software package for topological computation, with design focus on needs of the research community. This tool, replacing previous jPlex and Plex, enables researchers to access state of the art algorithms for persistent homology, cohomology, hom complexes, filtered simplicial complexes, filtered cell complexes, witness complex constructions, and many more essential components of computational topology. We describe, herewithin, the design goals we have chosen, as well as the resulting software package, and some of its more novel capabilities.

  • 28.
    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.

  • 29. Addessi, A. R.
    et al.
    Anelli, F.
    Benghi, D.
    Friberg, Anders
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH.
    Corrigendum: Child-computer interaction at the beginner stage of music learning: Effects of reflexive interaction on children's musical improvisation [Front. Psychol.8 (2017)(65)]. Doi: 10.3389/fpsyg.2017.000652017In: Frontiers in Psychology, ISSN 1664-1078, E-ISSN 1664-1078, Vol. 8, no MAR, article id 399Article in journal (Refereed)
    Abstract [en]

    A corrigendum on Corrigendum: Child-Computer Interaction at the Beginner Stage of Music Learning: Effects of Reflexive Interaction on Children's Musical Improvisation by Addessi, A. R., Anelli, F., Benghi, D., and Friberg, A. (2017). Front. Psychol. 8:65. doi: 10.3389/fpsyg.2017.00065 In the original article, there was an error. "she plays C3" was used instead of "it plays C3." A correction has been made to Observation and Theoretical Framework of Reflexive Interaction, paragraph 3: The little girl plays two consecutive notes, C2 and A2, and then stops to wait for the response of the system. The system responds by repeating the same notes. The child then play a single note, G2, and the system responds with a single note but this time introduces a variation: it plays C3, thus introducing a higher register. The girl, following the change introduced by the system, moves toward the higher register and plays a variant of the initial pattern, namely: D2-A2-E2-C3, and introduces a particular rhythm pattern. This "reflexive" event marks the beginning of a dialogue based on repetition and variation: the rhythmic-melodic pattern will be repeated and varied by both the system and the child in consecutive exchanges, until acquiring the form of a complete musical phrase. At some point in the dialogue, the child begins to accompany the system's response with arm movements synchronized with the rhythmic-melodic patterns, creating a kind of music-motor composition. In addition, EG1 and EG2 are incorrectly referred to within the text. A correction has been made to Duet Task, sub-section Results for Each Evaluative Criterion of the Duet Task, paragraph Reflexive Interaction: The data of Reflexive Interaction show that the EG2 obtained the highest score (4.17), followed by the CG (3.33) and the EG1 (2.61); see Table 6 and Figure 7. The difference between EG2, which only use the system with reflexive interaction, and EG1, which did not use the system with reflexive interaction, is significant (p = 0.043). Therefore, it could be said that the use of MIROR-Impro can enhance the use of the reflexive behaviors: mirroring, turn-taking, and co-regulation. We observed a statistically significant correlation between the Reflexive Interaction and the total score (r = 0.937; p < 0.01), and all other evaluative criteria, with correlations ranging from r = 0.87 (p < 0.01) for Musical Quality to r = 0.92 (p < 0.01) for Musical Organization. Thus, the higher the children's use of reflexive interaction, the better their results in each criterion and in the ability to improvise. This result can support the hypothesis that reflexive interaction is a fundamental component of musical improvised dialog. Instead, although the differences between the CG and the Experimental Groups 1 and 2 indicate that the use of the MIROR Impro appears to be "necessary" (CG > EG1) and "sufficient" (CG < EG2) to improve the ability to improvise, we cannot generalize these results because the results are not statistically significant (t-test, comparing CG and EG1: p = 0.388; CG and EG2: p = 0.285). Finally, due to the resolution of Figures 5-9 being low, they have been replaced with new figures with a higher resolution. The corrected Figures, Figures 5-9 appear below. The authors apologize for these errors and state that these do not change the scientific conclusions of the article in any way.

  • 30. Addessi, Anna Rita
    et al.
    Anelli, Filomena
    Benghi, Diber
    Friberg, Anders
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH.
    Child-Computer Interaction at the Beginner Stage of Music Learning: Effects of Reflexive Interaction on Children's Musical Improvisation2017In: Frontiers in Psychology, ISSN 1664-1078, E-ISSN 1664-1078, Vol. 8, article id 65Article in journal (Refereed)
    Abstract [en]

    In this article childrens musical improvisation is investigated through the reflexive interaction paradigm. We used a particular system, the MIROR-Impro, implemented in the framework of the MIROR project (EC-FP7), which is able to reply to the child playing a keyboard by a reflexive output, mirroring (with repetitions and variations) her/his inputs. The study was conducted in a public primary school, with 47 children, aged 6-7. The experimental design used the convergence procedure, based on three sample groups allowing us to verify if the reflexive interaction using the MIROR-Impro is necessary and/or sufficient to improve the childrens abilities to improvise. The following conditions were used as independent variables: to play only the keyboard, the keyboard with the MIROR-Impro but with not-reflexive reply, the keyboard with the MIROR-Impro with reflexive reply. As dependent variables we estimated the childrens ability to improvise in solos, and in duets. Each child carried out a training program consisting of 5 weekly individual 12 min sessions. The control group played the complete package of independent variables; Experimental Group 1 played the keyboard and the keyboard with the MIROR-Impro with not-reflexive reply; Experimental Group 2 played only the keyboard with the reflexive system. One week after, the children were asked to improvise a musical piece on the keyboard alone (Solo task), and in pairs with a friend (Duet task). Three independent judges assessed the Solo and the Duet tasks by means of a grid based on the TAI-Test for Ability to Improvise rating scale. The EG2, which trained only with the reflexive system, reached the highest average results and the difference with EG1, which did not used the reflexive system, is statistically significant when the children improvise in a duet. The results indicate that in the sample of participants the reflexive interaction alone could be sufficient to increase the improvisational skills, and necessary when they improvise in duets. However, these results are in general not statistically significant. The correlation between Reflexive Interaction and the ability to improvise is statistically significant. The results are discussed on the light of the recent literature in neuroscience and music education.

  • 31. Adhikari, P. R.
    et al.
    Upadhyaya, B. B.
    Meng, Chen
    KTH, School of Computer Science and Communication (CSC), Computational Biology, CB.
    Hollmén, J.
    Gene selection in time-series gene expression data2011In: 6th IAPR International Conference on Pattern Recognition in Bioinformatics, PRIB 2011, 2011, p. 145-156Conference paper (Refereed)
    Abstract [en]

    The dimensionality of biological data is often very high. Feature selection can be used to tackle the problem of high dimensionality. However, majority of the work in feature selection consists of supervised feature selection methods which require class labels. The problem further escalates when the data is time-series gene expression measurements that measure the effect of external stimuli on biological system. In this paper we propose an unsupervised method for gene selection from time-series gene expression data founded on statistical significance testing and swap randomization. We perform experiments with a publicly available mouse gene expression dataset and also a human gene expression dataset describing the exposure to asbestos. The results in both datasets show a considerable decrease in number of genes.

  • 32.
    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.

  • 33. 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, p. 187-196Conference 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.

  • 34.
    Adrup, Joakim
    et al.
    KTH, School of Computer Science and Communication (CSC).
    Skogström, Charlotte
    KTH, School of Computer Science and Communication (CSC).
    Effekterna av spelmekanismerna ledartavlor, serier och certifikat på det dagliga stegantalet hos högskolestuderande studenter2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Gamification is becoming a recognized concept, especially in research areas such as HCI (Human Computer Interaction). This paper discusses and compares three different game mechanics through the daily step count. The game mechanisms included are leaderboards, streaks and badges. The study applies quantitative and qualitative methods to investigate how the above named game mechanisms affect the daily step count of students studying at a university level.

    The study shows that gamification is preferable in terms of awareness and pleasure, but that gamification must not interfere with the basic functions of the original product. On the contrary, gaming mechanisms should be used to support the products existing features, not just to make the product more entertaining and motivating. The general conclusion of the collected quantitative data is that gamification does not influence the daily step count.

    Finally, the article discusses what factors should be implemented to make gamification work in a motivating way. The article also discusses how game developers can use game design to create interesting and engaging applications.

  • 35.
    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.

  • 36. Aebischer, B.
    et al.
    Hilty, Lorenz
    KTH, School of Computer Science and Communication (CSC), Centres, School of Architecture and the Built Environment (ABE), Centres, Centre for Sustainable Communications, CESC. University of Zurich, Switzerland .
    The energy demand of ICT: A historical perspective and current methodological challenges2015In: ICT Innovations for Sustainability, Springer, 2015, p. 71-103Chapter in book (Refereed)
    Abstract [en]

    This chapter provides an overview of energy demand issues in the field of ICT with a focus on the history of measuring, modelling and regulating ICT electricity consumption and the resulting methodological challenges. While the energy efficiency of ICT hardware has been dramatically improving and will continue to improve for some decades, the overall energy used for ICT is still increasing. The growing demand for ICT devices and services outpaces the efficiency gains of individual devices. Worldwide per capita ICT electricity consumption exceeded 100 kWh/year in 2007 (a value which roughly doubles if entertainment equipment is included) and is further increasing. Methodological challenges include issues of data collection and modelling ICT devices and services, assessing the entire life cycle of ICT devices and infrastructures, accounting for embedded ICT, and assessing the effect of software on ICT energy consumption.

  • 37.
    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.

  • 38.
    Afkham, Heydar Maboudi
    et al.
    KTH, School of Biotechnology (BIO), Gene Technology.
    Ek, Carl Henrik
    KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP.
    Carlsson, Stefan
    KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP.
    A topological framework for training latent variable models2014In: Proceedings - International Conference on Pattern Recognition, 2014, p. 2471-2476Conference paper (Refereed)
    Abstract [en]

    We discuss the properties of a class of latent variable models that assumes each labeled sample is associated with a 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 examples of such models. These models are usually considered to be expensive to train and very sensitive to the initialization. In this paper, we focus on the learning of such models by introducing a topological framework and show how it is possible to both reduce the learning complexity and produce more robust decision boundaries. We will also argue how our framework can be used for producing robust decision boundaries without exploiting the dataset bias or relying on accurate annotations. To experimentally evaluate our method and compare with previously published frameworks, we focus on the problem of image classification with object localization. In this problem, the correct location of the objects is unknown, during both training and testing stages, and is considered as a latent variable. ©

  • 39.
    Afkham, Heydar Maboudi
    et al.
    KTH, School of Biotechnology (BIO), Gene Technology.
    Ek, Carl Henrik
    KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP.
    Carlsson, Stefan
    KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP.
    Gradual improvement of image descriptor quality2014In: ICPRAM 2014 - Proceedings of the 3rd International Conference on Pattern Recognition Applications and Methods, 2014, p. 233-238Conference paper (Refereed)
    Abstract [en]

    In this paper, we propose a framework for gradually improving the quality of an already existing image descriptor. The descriptor used in this paper (Afkham et al., 2013) uses the response of a series of discriminative components for summarizing each image. As we will show, this descriptor has an ideal form in which all categories become linearly separable. While, reaching this form is not feasible, we will argue how by replacing a small fraction of these components, it is possible to obtain a descriptor which is, on average, closer to this ideal form. To do so, we initially identify which components do not contribute to the quality of the descriptor and replace them with more robust components. Here, a joint feature selection method is used to find improved components. As our experiments show, this change directly reflects in the capability of the resulting descriptor in discriminating between different categories.

  • 40.
    Afkham, Heydar Maboudi
    et al.
    KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP.
    Ek, Carl Henrik
    KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP.
    Carlsson, Stefan
    KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP.
    Initialization framework for latent variable models2014In: ICPRAM 2014 - Proceedings of the 3rd International Conference on Pattern Recognition Applications and Methods, 2014, p. 227-232Conference paper (Refereed)
    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.

  • 41.
    Afkham, Heydar Maboudi
    et al.
    KTH, School of Computer Science and Communication (CSC).
    Qiu, Xuanbin
    KTH, School of Computer Science and Communication (CSC).
    The, Matthew
    KTH, School of Biotechnology (BIO), Gene Technology. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Käll, Lukas
    KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Uncertainty estimation of predictions of peptides' chromatographic retention times in shotgun proteomics2017In: Bioinformatics, ISSN 1367-4803, E-ISSN 1367-4811, Vol. 33, no 4, p. 508-513Article in journal (Refereed)
    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.

  • 42. Agarwal, A.
    et al.
    Dowling, A. P.
    Shin, H. -C
    Graham, W.
    Sefi, Sandy
    KTH, School of Computer Science and Communication (CSC), Numerical Analysis and Computer Science, NADA.
    A ray tracing approach to calculate acoustic shielding by the silent aircraft airframe2006In: Collection of Technical Papers - 12th AIAA/CEAS Aeroacoustics Conference, 2006, p. 2799-2818Conference paper (Refereed)
    Abstract [en]

    The Silent Aircraft is in the form of a flying wing with a large wing planform and a propulsion system that is embedded in the rear of the airframe with intakes on the upper surface of the wing. Thus a large part of the forward-propagating noise from the intake ducts is expected to be shielded from observers on the ground by the wing. Acoustic shielding effects can be calculated by solving an external acoustic scattering problem for a moving aircraft. In this paper, acoustic shielding effects of the Silent Aircraft airframe are quantified by a ray-tracing method. The dominant frequencies from the noise spectrum of the engines are sufficiently high for ray theory to yield accurate results. It is shown that for low-Mach number homentropic flows, a condition satisfied approximately by the Silent Aircraft during take-off and approach, the acoustic rays propagate in straight lines. Thus, from Fermat's principle it is clear that classical Geometrical Optics and Geometrical Theory of Diffraction solutions are applicable to this moving-body problem as well. The total amount of acoustic shielding at an observer located in the shadow region is calculated by adding the contributions from all the diffracted rays (edge-diffracted and creeping rays) and then subtracting the result from the incident field without the airframe. Experiments on a model-scale geometry have been conducted in an anechoic chamber to test the applicability of the ray-tracing technique. The three-dimensional ray-tracing solver is validated by comparing the numerical solution with analytical high-frequency asymptotic solutions for canonical shapes.

  • 43. Agarwal, Anurag
    et al.
    Dowling, Ann P.
    Shin, Ho-Chul
    Graham, Will
    Sefi, Sandy
    KTH, School of Computer Science and Communication (CSC), Numerical Analysis and Computer Science, NADA.
    Ray-tracing approach to calculate acoustic shielding by a flying wing airframe2007In: AIAA Journal, ISSN 0001-1452, E-ISSN 1533-385X, Vol. 45, no 5, p. 1080-1090Article in journal (Refereed)
    Abstract [en]

    The "silent aircraft" is in the form of a flying wing with a large wing planform and a propulsion system that is embedded in the rear of the airframe with intakes on the upper surface of the wing. Thus a large part of the forward-propagating noise from the intake ducts is expected to be shielded from observers on the ground by the wing. Acoustic shielding effects can be calculated by solving an external acoustic scattering problem for a moving aircraft. In this paper, acoustic shielding effects of the silent aircraft airframe are quantified by a ray-tracing method. The dominant frequencies from the noise spectrum of the engines are sufficiently high for ray theory to yield accurate results. It is shown that, for low-Mach number homentropic flows, a condition satisfied approximately during takeoff and approach, the acoustic rays propagate in straight lines. Thus, from Fermat's principle it is clear that classical geometrical optics and geometrical theory of diffraction solutions are applicable to this moving-body problem as well. The total amount of acoustic shielding at an observer located in the shadow region is calculated by adding the contributions from all the diffracted rays (edge-diffracted and creeping rays) and then subtrading the result from the incident field without the airframe. The three-dimensional ray-tracing solver is validated by comparing the numerical solutions with analytical high-frequency asymptotic solutions for canonical shapes. Experiments on a model-scale geometry have been conducted in an anechoic chamber to test the applicability of the ray-tracing technique. The results confirm the accuracy of the approach, which is then applied to a CAD representation of a prototype silent aircraft design. As expected, the flying wing configuration provides very significant ground shielding (in excess of 10 dB at all locations) of a source above the airframe.

  • 44. Agarwal, P.
    et al.
    Al Moubayed, Samer
    KTH, School of Computer Science and Communication (CSC), Robotics, perception and learning, RPL.
    Alspach, A.
    Kim, J.
    Carter, E. J.
    Lehman, J. F.
    Yamane, K.
    Imitating human movement with teleoperated robotic head2016In: 25th IEEE International Symposium on Robot and Human Interactive Communication, RO-MAN 2016, IEEE, 2016, p. 630-637Conference paper (Refereed)
    Abstract [en]

    Effective teleoperation requires real-time control of a remote robotic system. In this work, we develop a controller for realizing smooth and accurate motion of a robotic head with application to a teleoperation system for the Furhat robot head [1], which we call TeleFurhat. The controller uses the head motion of an operator measured by a Microsoft Kinect 2 sensor as reference and applies a processing framework to condition and render the motion on the robot head. The processing framework includes a pre-filter based on a moving average filter, a neural network-based model for improving the accuracy of the raw pose measurements of Kinect, and a constrained-state Kalman filter that uses a minimum jerk model to smooth motion trajectories and limit the magnitude of changes in position, velocity, and acceleration. Our results demonstrate that the robot can reproduce the human head motion in real time with a latency of approximately 100 to 170 ms while operating within its physical limits. Furthermore, viewers prefer our new method over rendering the raw pose data from Kinect.

  • 45. Agarwal, Priyanshu
    et al.
    Al Moubayed, Samer
    KTH, School of Computer Science and Communication (CSC), Robotics, perception and learning, RPL.
    Alspach, Alexander
    Kim, Joohyung
    Carter, Elizabeth J.
    Lehman, Jill Fain
    Yamane, Katsu
    Imitating Human Movement with Teleoperated Robotic Head2016In: 2016 25TH IEEE INTERNATIONAL SYMPOSIUM ON ROBOT AND HUMAN INTERACTIVE COMMUNICATION (RO-MAN), 2016, p. 630-637Conference paper (Refereed)
    Abstract [en]

    Effective teleoperation requires real-time control of a remote robotic system. In this work, we develop a controller for realizing smooth and accurate motion of a robotic head with application to a teleoperation system for the Furhat robot head [1], which we call TeleFurhat. The controller uses the head motion of an operator measured by a Microsoft Kinect 2 sensor as reference and applies a processing framework to condition and render the motion on the robot head. The processing framework includes a pre-filter based on a moving average filter, a neural network-based model for improving the accuracy of the raw pose measurements of Kinect, and a constrained-state Kalman filter that uses a minimum jerk model to smooth motion trajectories and limit the magnitude of changes in position, velocity, and acceleration. Our results demonstrate that the robot can reproduce the human head motion in real time with a latency of approximately 100 to 170 ms while operating within its physical limits. Furthermore, viewers prefer our new method over rendering the raw pose data from Kinect.

  • 46.
    Agelfors, Eva
    et al.
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH.
    Beskow, Jonas
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH.
    Karlsson, Inger
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH.
    Kewley, Jo
    Salvi, Giampiero
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH.
    Thomas, Neil
    User evaluation of the SYNFACE talking head telephone2006In: Computers Helping People With Special Needs, Proceedings / [ed] Miesenberger, K; Klaus, J; Zagler, W; Karshmer, A, 2006, Vol. 4061, p. 579-586Conference paper (Refereed)
    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.

  • 47.
    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.

  • 48.
    Aghazadeh, Omid
    KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP.
    Data Driven Visual Recognition2014Doctoral thesis, comprehensive summary (Other academic)
    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.

  • 49.
    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
  • 50.
    Aghazadeh, Omid
    et al.
    KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP.
    Azizpour, Hossein
    KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP.
    Sullivan, Josephine
    KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP.
    Carlsson, Stefan
    KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP.
    Mixture component identification and learning for visual recognition2012In: Computer Vision – ECCV 2012: 12th European Conference on Computer Vision, Florence, Italy, October 7-13, 2012, Proceedings, Part VI, Springer, 2012, p. 115-128Conference paper (Refereed)
    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.

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