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  • 11651.
    Yevseyeva, Iryna
    et al.
    Department of Mathematical Information Technology, University of Jyväskylä, Finland.
    Miettinen, Kaisa
    Helsinki School of Economics.
    Salminen, Pekka
    School of Business and Economics, University of Jyväskylä.
    Lahdelma, Risto
    Department of Information Technology, University of Turku.
    SMAA-Classification - A New Method for Nominal Classification2007Rapport (Annet vitenskapelig)
    Abstract [en]

    We have developed a multicriteria decision aiding method for nominal classification for situations where prefer-ence information is imprecise, uncertain or absent. Such situations may appear, for instance, when the decisionmaker is not sure about his or her preferences or when there are multiple decision makers who have difficulties inagreeing about their common preference. The new SMAA-Classification method extends Stochastic Multicrite-ria Acceptability Analysis (SMAA) methodology for classification problems. The method provides the decisionmaker with descriptive information in the form of acceptability index for each alternative to be classified intoeach predefined class. We test the new method with several applications.

  • 11652.
    Yi, Xinlei
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Yang, Tao
    Univ North Texas, Dept Elect Engn, Denton, TX 76203 USA..
    Wu, Junfeng
    Zhejiang Univ, Coll Control Sci & Engn, Hangzhou 310027, Zhejiang, Peoples R China..
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Distributed event-triggered control for global consensus of multi-agent systems with input saturation2019Inngår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 100, s. 1-9Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The global consensus problem for first-order continuous-time multi-agent systems with input saturation is considered. In order to reduce the overall need of communication and system updates, we propose an event-triggered consensus protocol and a triggering law, which do not require any a priori knowledge of global network parameters. It is shown that Zeno behavior is excluded for these systems and that the underlying directed graph having a directed spanning tree is a necessary and sufficient condition for global consensus. We use a new Lyapunov function to show the sufficient condition and it inspires the triggering law. Numerical simulations are provided to illustrate the effectiveness of the theoretical results.

  • 11653.
    Yi, Xinlei
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Yao, Lisha
    Univ North Texas, Dept Elect Engn, Denton, TX 76203 USA..
    Yang, Tao
    Univ North Texas, Dept Elect Engn, Denton, TX 76203 USA..
    George, Jemin
    US Army Res Lab, Adelphi, MD 20783 USA..
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Distributed Optimization for Second-Order Multi-Agent Systems with Dynamic Event-Triggered Communication2018Inngår i: 2018 IEEE CONFERENCE ON DECISION AND CONTROL (CDC), IEEE , 2018, s. 3397-3402Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we propose a fully distributed algorithm for second-order continuous-time multi-agent systems to solve the distributed optimization problem. The global objective function is a sum of private cost functions associated with the individual agents and the interaction between agents is described by a weighted undirected graph. We show the exponential convergence of the proposed algorithm if the underlying graph is connected, each private cost function is locally gradient-Lipschitz- continuous, and the global objective function is restricted strongly convex with respect to the global minimizer. Moreover, to reduce the overall need of communication, we then propose a dynamic event-triggered communication mechanism that is free of Zeno behavior. It is shown that the exponential convergence is achieved if the private cost functions are also globally gradient-Lipschitz- continuous. Numerical simulations are provided to illustrate the effectiveness of the theoretical results.

  • 11654.
    Yilmaz, Oya
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Access Selection in Multi-Access Cellular and WLAN Networks2005Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    To meet the requirements of future data-rich applications and terminals with improved multimedia,  future wireless networks are expected to combine multiple access technologies.  When several radio access technologies are available, the assignment and the handover of  users among these technologies become fundamental problems. The solutions have a major  impact on the system performance as well as on the architecture of future networks. This  thesis focuses on access selection criteria in combined wide area coverage cellular and local  area coverage Wireless LAN networks. More specifically, involvement of traffic load information  on top of signal quality information during selection process is studied. A rough  but wide-ranging theory for what gains may be expected in different scenarios is first derived  through qualitative reasoning. Then, to verify the theory, a number of different signal  quality based and both signal quality and load based access selection algorithms are evaluated  in terms of achievable bitrate characteristics and system capacity via simulations. The  algorithms are compared for a set of different user behavior scenarios. Results indicate that  in scenarios with high traffic load concentrated to the hotspots or cellular access technologies  offering bitrates in the same order as WLANs, principles taking signal quality and traffic  load into account can provide gains around 20% both in capacity and in achievable bitrates.  In scenarios with more evenly distributed traffic or WLAN bitrates exceeding those of  cellular, smaller gains are achieved,

  • 11655.
    Yim, Man Yi
    et al.
    University of Hong Kong, Hong Kong.
    Kumar, Arvind
    Bernstein Center Freiburg, University of Freiburg, Germany .
    Aertsen, Ad
    Rotter, Stefan
    Impact of correlated inputs to neurons: modeling observations from in vivo intracellular recordings2014Inngår i: Journal of Computational Neuroscience, ISSN 0929-5313, E-ISSN 1573-6873, Vol. 37, nr 2, s. 293-304Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In vivo recordings in rat somatosensory cortex suggest that excitatory and inhibitory inputs are often correlated during spontaneous and sensory-evoked activity. Using a computational approach, we study how the interplay of input correlations and timing observed in experiments controls the spiking probability of single neurons. Several correlation-based mechanisms are identified, which can effectively switch a neuron on and off. In addition, we investigate the transfer of input correlation to output correlation in pairs of neurons, at the spike train and the membrane potential levels, by considering spike-driving and non-spike-driving inputs separately. In particular, we propose a plausible explanation for the in vivo finding that membrane potentials in neighboring neurons are correlated, but the spike-triggered averages of membrane potentials preceding a spike are not: Neighboring neurons possibly receive an ongoing bombardment of correlated subthreshold background inputs, and occasionally uncorrelated spike-driving inputs.

  • 11656. Yin, D.
    et al.
    Chen, B.
    Huang, Z.
    Lin, Xin
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Geoinformatik (stängd 20110301). Peking University,China.
    Fang, Y.
    Utility based query dissemination in spatial data grid2007Inngår i: Proceedings of the 6th International Conference on Grid and Cooperative Computing, GCC 2007, IEEE Computer Society, 2007, s. 574-581Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Spatial Information Grid is an ideal infrastructure to handle the data-intensive and computing-intensive geo-spatial processing. In order that each agency could ad hoc connect to this computing environment and make autonomous decision, we build a Geospatial Data Grid in peer-to-peer way. The query processor module in each peer can decompose the user's query into sub-queries that executed in different nodes. One problem in the parallel spatial join query optimization is how to determine an appropriate node group to disseminate the sub-queries. Especially, if there is more than one node sharing the same area of interest, there is a dilemma: on the one hand, the task scheduler tends to decompose this query into sub-queries and disseminate them to as many as possible nodes so that they could process the user's query in parallel; on the other hand, recruiting too many nodes will also bring in overhead in repetitive computing, redundant data transmission, and the result merging. Based on the study of trade-off between increasing parallelism and reducing redundancy using the Utility Theory in economics, we put forward a fast node selection algorithm for the parallel spatial join query dissemination. The test in our system shows this strategy could balance the above two conflict demands and is appropriate for use in Data Grid.

  • 11657.
    Yin, Ji
    KTH, Skolan för elektroteknik och datavetenskap (EECS).
    Trajectory Planning for Off-road Autonomous Driving2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The thesis develops a trajectory planner which operates in a formula racing scenario. The proposed trajectory planner gives time-optimal off-road trajectory planning solutions and generates sequences of control signals for the vehicle to follow the trajectory. Outputs of the trajectory planner are time-optimal trajectory, steering angle, resultant force of brake and throttle. The trajectory planner is designed to have two modes, the Exploring mode which is based on Rapidly-exploring Random Tree (RRT), and the optimization mode which is built upon optimal Rapidly-exploring random tree (RRT*). The exploring mode can generate a valid and safe trajectory in real  time, but the solution is not optimal; optimization mode gives optimal trajectories but it can only do offline planning.

    The system structure makes it possible that the exploring mode keeps running while the optimization mode runs in the background; once the optimization process is complete, the vehicle could then follow the optimal trajectory. A local trajectory planning method which considers the constraint of off-road vehicle dynamics is designed and integrated in the planner. System performance is evaluated by simulations on a racing track. Many aspects including time optimality, vehicle stability have been taken into account. A new, fast, local steering method has been proposed; the method generates trajectory based on random input. By a more efficient implementation of the planner in the future, for example by using parallel computing, the optimization mode is promising for real-time trajectory generation.

  • 11658.
    Yip, Eugene
    et al.
    University of Auckland.
    Kuo, Matthew M Y
    University of Auckland.
    Roop, Partha S
    University of Auckland.
    Broman, David
    University of California, Berkeley and Linköping University.
    Relaxing the Synchronous Approach for Mixed-Criticality Systems2014Inngår i: Proceedings of the 20th IEEE Real-Time and Embedded Technology and Application Symposium (RTAS), IEEE conference proceedings, 2014, s. 89-100Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Synchronous languages are widely used to design safety-critical embedded systems. These languages are based on the synchrony hypothesis, asserting that all tasks must complete instantaneously at each logical time step. This assertion is, however, unsuitable for the design of mixed-criticality systems, where some tasks can tolerate missed deadlines. This paper proposes a novel extension to the synchronous approach for supporting three levels of task criticality: life, mission, and non-critical. We achieve this by relaxing the synchrony hypothesis to allow tasks that can tolerate bounded or unbounded deadline misses. We address the issue of task communication between multi-rate, mixed-criticality tasks, and propose a deterministic lossless communication model. To maximize system utilization, we present a hybrid static and dynamic scheduling approach that executes schedulable tasks during slack time. Extensive benchmarking shows that our approach can schedule up to 15% more task sets and achieve an average of 5.38% better system utilization than the Early-Release EDF (ER-EDF) approach. Tasks are scheduled fairer under our approach and achieve consistently higher execution frequencies, but require more preemptions.

  • 11659.
    Yli-Luoma, Petti
    et al.
    University of Oulu, Finland.
    Naeve, Ambjörn
    KTH, Skolan för datavetenskap och kommunikation (CSC), Medieteknik och grafisk produktion, Media.
    Towards a semantic e-learning theory by using a modelling approach2006Inngår i: British Journal of Educational Technology, ISSN 0007-1013, E-ISSN 1467-8535, Vol. 37, nr 3, s. 445-459Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present study, a semantic perspective on e-learning theory is advanced and a modelling approach is used. This modelling approach towards the new learning theory is based on the four SECI phases of knowledge conversion: Socialisation, Externalisation, Combination and Internalisation, introduced by Nonaka in 1994, and involving two levels of knowledge-tacit and explicit. In the Socialisation phase, the teacher-student interaction activates the exploratory learning behaviour. This phase is emotionally and socially loaded. The Externalisation phase is partly emotional but a cognitive dimension is also needed, which requires creativity. This phase works optimally if it is collaborative in nature. In the Combination phase, an ability for hypothetical-deductive thinking is needed for the modelling approach. During the Internalisation phase, the learning process requires that students engage in seeking to understand and explain natural phenomena, which further demands testing of the theoretical concepts.

  • 11660.
    Yngström, Louise
    KTH, Tidigare Institutioner, Data- och systemvetenskap, DSV. Stockholm University, Sweden.
    An holistic approach to an international doctoral program2004Inngår i: Information security management, education and privacy: IFIP 18th World Computer Congress : TC11 19th International Information Security Workshops, 22-27 August 2004, Toulouse, France, Springer-Verlag New York, 2004, s. 117-132Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The paper discusses forms and structures for an international doctoral program with specialization in information security and information assurance based on an analysis of international educational efforts in the area 1995-2003. The presentation underlines the need for holistic approaches to the IT security area and presents, as an example, the Systemic-Holistic Approach, SHA.

  • 11661.
    Yngström, Louise
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Data- och systemvetenskap, DSV.
    Can we tune information security management into meeting corporate governance needs?: (invited paper)2005Inngår i: SECURITY MANAGEMENT, INTEGRITY, AND INTERNAL CONTROL IN INFORMATION SYSTEMS / [ed] Dowland, P; Furnell, S; Thuraisingham, B; Wang, XS, 2005, Vol. 193, s. 237-245Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper intends to stimulate discussion, research and new points-of-action for IS/IT security management from the background of corporate governance, contemporary debates of how to express observable consequences of IT and IT security, and of didactic issues. It is concluded that empirical research within IT security management is rare as compared to theoretical approaches but needed in order to have IS/IT security management on par with general management.

  • 11662. Yosef, Nir
    et al.
    Käll, Lukas
    KTH, Skolan för bioteknologi (BIO), Genteknologi.
    From sequence to structure to networks2008Inngår i: Genome Biology, ISSN 1465-6906, E-ISSN 1474-760X, Vol. 9, nr 11Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A report on the 7th European Conference on Computational Biology (ECCB), Cagliari, Italy, 22-26 September 2008.

  • 11663. Yoshida, Motoharu
    et al.
    Fransén, Erik
    KTH, Skolan för datavetenskap och kommunikation (CSC), Beräkningsbiologi, CB.
    Hasselmo, Michael E.
    mGluR-dependent persistent firing in entorhinal cortex layer III neurons2008Inngår i: European Journal of Neuroscience, ISSN 0953-816X, E-ISSN 1460-9568, Vol. 28, nr 6, s. 1116-1126Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Persistent firing is believed to be a crucial mechanism for memory function including working memory. Recent in vivo and in vitro findings suggest an involvement of metabotropic glutamate receptors (mGluRs) in persistent firing. Using whole-cell patch-recording techniques in a rat entorhinal cortex (EC) slice preparation, we tested whether EC layer III neurons display persistent firing due to mGluR activation, independently of cholinergic activation. Stimulation of the angular bundle drove persistent firing in 90% of the cells in the absence of a cholinergic agonist. The persistent firing was typically stable for > 4.5 min at which point persistent firing was terminated by the experimenter. The average frequency of the persistent firing was 2.1 Hz, ranging from 0.4 to 5.5 Hz. This persistent firing was observed even in the presence of atropine (2 mu M), suggesting that the persistent firing can occur independent of cholinergic activation. Furthermore, ionotropic glutamate and GABAergic synaptic blockers (2 mm kynurenic acid, 100 mu M picrotoxin and 1 mu M CGP55845) did not block the persistent firing. On the other hand, blockers of group I mGluRs (100 mu M LY367385 and 20 mu M MPEP) completely blocked or suppressed the persistent firing. An agonist of group I mGluRs (20 mu M DHPG) greatly enhanced the persistent firing induced by current injection. These results indicate that persistent firing can be driven through group I mGluRs in entorhinal layer III neurons, suggesting that glutamatergic synaptic input alone could enable postsynaptic neurons to hold input signals in the form of persistent firing.

  • 11664.
    You, Yang
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Teknisk informationsvetenskap.
    Qin, Chong
    Gong, Yi
    Resource Allocation for a Full-Duplex Base Station Aided OFDMA System2017Inngår i: PROCEEDINGS OF THE 2ND INTERNATIONAL CONFERENCE ON EDUCATIONAL MANAGEMENT AND ADMINISTRATION (COEMA 2017) / [ed] Kusumaningrum, D E, ATLANTIS PRESS , 2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Exploiting full-duplex (FD) technology on base stations (BSs) is a promising solution to enhancing the system performance. Motivated by this, we revisit a full-duplex base station (FD-BS) aided OFDMA system, which consists of one BS, several uplink/downlink users and multiple subcarriers. A joint 3-dimensional (3D) mapping scheme among subcarriers, down-link users (DUEs), uplink users (UUEs) is considered as well as an associated power allocation optimization. In detail, we first decompose the complex 3D mapping problem into three 2-dimensional sub ones and solve them by using the iterative Hungarian method, respectively. Then based on the Lagrange dual method, we sequentially solve the power allocation and 3-dimensional mapping problem by fixing a dual point. Finally, the optimal solution can be obtained by utilizing the sub-gradient method. Unlike existing work that only solves either 3D mapping or power allocation problem but with a high computation complexity, we tackle both of them and have successfully reduced computation complexity from exponential to polynomial order. Numerical simulations are conducted to verify the proposed scheme.

  • 11665.
    You, Yantian
    KTH, Skolan för elektroteknik och datavetenskap (EECS).
    Cloud Auto-Scaling Control Engine Based on Machine Learning2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    With the development of modern data centers and networks, many service providers have moved most of their computing functions to the cloud.  Considering the limitation of network bandwidth and hardware or virtual resources, how to manage different virtual resources in a cloud environment so as to achieve better resource allocation is a big problem.  Although some cloud infrastructures provide simple default auto-scaling and orchestration mechanisms, such as OpenStack Heat service, they usually only depend on a single parameter, such as CPU utilization and cannot respond to the network changes in a timely manner.<p> This thesis investigates different auto-scaling mechanisms and designs an on-line control engine that cooperates with different OpenStack service APIs based on various network resource data.  Two auto-scaling engines, Heat orchestration based engine and machine learning based online control engine, have been developed and compared for different client requests patterns.  Two machine learning methods, neural network, and linear regression have been considered to generate a control signal based on real-time network data.  This thesis also shows the network’s non-linear behaviors for heavy traffic and proposes a scaling policy based on deep network analysis.<p> The results show that for offline training, the neural network and linear regression provide 81.5% and 84.8% accuracy respectively.  However, for online testing with different client request patterns, the neural network results are different than we expected, while linear regression provided us with much better results.  The model comparison showed that these two auto-scaling mechanisms have similar behavior for a SMOOTH-load Pattern.  However, for the SPIKEY-load Pattern, the linear regression based online control engine responded faster to network changes while heat orchestration service shows some delay.  Compared with the proposed scaling policy with fewer web servers in use and acceptable response latency, both of the two auto-scaling models waste network resources.

  • 11666.
    You, Yantian
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Sparsity Analysis of Deep Learning Models and Corresponding Accelerator Design on FPGA2016Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [en]

    Machine learning has achieved great success in recent years, especially the deep learning algorithms based on Artificial Neural Network. However, high performance and large memories are needed for these models , which makes them not suitable for IoT device, as IoT devices have limited performance and should be low cost and less energy-consuming. Therefore, it is necessary to optimize the deep learning models to accommodate the resource-constrained IoT devices.

    This thesis is to seek for a possible solution of optimizing the ANN models to fit into the IoT devices and provide a hardware implementation of the ANN accelerator on FPGA. The contribution of this thesis mainly lies in two aspects: 1). analyze the sparsity in the two mainstream deep learning models – DBN and CNN. The DBN model consists of two hidden layers with Restricted Boltzmann Machines while the CNN model consists of 2 convolutional layers and 2 sub-sampling layer. Experiments have been done on the MNIST data set with the sparsity of 75%. The ratio of the multiplications resulting in near-zero values has been tested. 2). FPGA implementation of an ANN accelerator. This thesis designed a hardware accelerator for the inference process in ANN models on FPGA (Stratix IV: EP4SGX530KH40C2). The main part of hardware design is the processing array consists of 256 Multiply-Accumulators array, which can conduct multiply-accumulate operations of 256 synaptic connections simultaneously. 16-bit fixed point computation is used to reduce the hardware complexity, thus saving power and area.

    Based on the evaluation results, it is found that the ratio of the multiplications under the threshold of 2-5 is 75% for CNN with ReLU activation function, and is 83% for DBN with sigmoid activation function, respectively. Therefore, there still exists large space for complex ANN models to be optimized if the sparsity of data is fully utilized. Meanwhile, the implemented hardware accelerator is verified to provide correct results through 16-bit fixed point computation, which can be used as a hardware testing platform for evaluating the ANN models.

  • 11667. Younas, I.
    et al.
    Kamrani, F.
    Bashir, M.
    Schubert, J.
    KTH, Skolan för elektroteknik och datavetenskap (EECS). Swedish Defence Research Agency, Stockholm Sweden.
    Efficient genetic algorithms for optimal assignment of tasks to teams of agents2018Inngår i: Neurocomputing, ISSN 0925-2312, E-ISSN 1872-8286, Vol. 314, s. 409-428Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The problem of optimally assigning agents (resources) to a given set of tasks is known as the assignment problem (AP). The classical AP and many of its variations have been extensively discussed in the literature. In this paper, we examine a specific class of the problem, in which each task is assigned to a group of collaborating agents. APs in this class cannot be solved using the Hungarian or other known polynomial time algorithms. We employ the genetic algorithm (GA) to solve the problem. However, we show that if the size of the problem is large, then standard crossover operators cannot efficiently find near-optimal solutions within a reasonable time. In general, the efficiency of the GA depends on the choice of genetic operators (selection, crossover, and mutation) and the associated parameters. In order to design an efficient GA for determining the near-optimal assignment of tasks to collaborative agents, we focus on the construction of crossover operators. We analyze why a naive implementation with standard crossover operators is not capable of sufficiently solving the problem. Furthermore, we suggest modifications to these operators by adding a shuffled list and introduce two new operators (team-based and team-based shuffled list). We demonstrate that the modified and new operators with shuffled lists perform significantly better than all operators without shuffled lists and solve the presented AP more efficiently. The performance of the GA can be further enhanced by using chaotic sequences. Moreover, the GA is also compared with the particle swarm optimization (PSO) and differential evolution (DE) algorithms, demonstrating the superiority of the GA over these search algorithms. 

  • 11668.
    Younas, Irfan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster, Programvaru- och datorsystem, SCS.
    Ayani, Rassul
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster, Programvaru- och datorsystem, SCS.
    Schubert, Johan
    Swedish Defence Research Agency, Stockholm, Sweden.
    Using Genetic Algorithms for investigating specific regions of the solution space2011Inngår i: Proceedings of the 2011 African Conference on Software Engineering and Applied Computing (ACSEAC 2011), 2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In many practical cases decision makers are interested to understand the whole solution space, including possible outliers. By outlier we mean there is a solution that is theoretically possible, though with very low probability that it occurs. In many combinatorial problems, this is a very challenging task. During the past decade, the Data Farming community has done substantial work on developing methods and techniques for better understanding of the solution space. The data farming community has also looked at the design of experiments and used Latin hypercube (LH) techniques for this purpose. The LH is proven to be one of the important sampling methods for selecting a representative subset of the input space. In this paper, we consider a company X that wants to outsource m subprojects of a given project P. We assume that there are n potential subcontractors for each subproject. Thus, there will be n^m ways to assign the subprojects to the potential subcontractors. The project manager is interested to find those assignments that complete the project within a given time and a given cost frame. An exhaustive examination of all assignments is not feasible, if m and n are big numbers. We propose an objective-based genetic algorithm (GA) for finding the set of assignments that are mapped onto a given subset of the solution space. It means, as opposed to the design of experiment techniques, we start from the solution space and try to find the combinations of the input parameter values that can lead to a specific region of the solution space. By some numerical examples, we show how our GA identifies the set of such feasible assignments.

  • 11669.
    Younas, Irfan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Ayani, Rassul
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Schubert, Johan
    Swedish Defense Research Agency (FOI).
    Asadi, Hirad
    Swedish Defense Research Agency (FOI).
    Using genetic algorithms in effects-based planning2013Inngår i: Proceedings of the 2013 IEEE International Conference on Systems, Man, and Cybernetics (SMC), IEEE Computer Society, 2013, s. 438-443Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we propose a genetic algorithm-based method for evaluation of operational plans within effects-based planning. We formulate the effects-based planning problem as a bi-objective optimization problem, in which the distance from the initial state to the current state (g) and the distance from the current state to the desired end state (h) are minimized. To solve the problem, we adopt Non-dominated Sorting Genetic Algorithm-II (NSGA-II). Considering an expeditionary operation scenario, we simulate a subset of possible plans and present the decision maker with a set of promising plans which are capable of approaching the desired end state efficiently. In order to discuss the efficiency and effectiveness of the algorithm, we compare the results of NSGA-II with the results of A*. The computational results show that NSGA-II is much more efficient than A* with regard to g. On the other hand A* is a little more effective with regard to h.

  • 11670.
    Younas, Irfan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Kamrani, Farzad
    Swedish Defence Research Agency, Stockholm, Sweden.
    Ayani, Rassul
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Optimization of assignment of tasks to teams using multi-objective metaheuristics2013Inngår i: GECCO 2013 - Proceedings of the 2013 Genetic and Evolutionary Computation Conference Companion, Association for Computing Machinery (ACM), 2013, s. 103-104Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A highly interesting but not thoroughly addressed optimization problem is a variation of the Assignment Problem (AP) where tasks are assigned to groups of collaborating agents (teams). In this paper, we address this class of AP as a bi-objective optimization problem, in which the cost is minimized and the quality is maximized. To solve the model, we adopt Non-dominated Sorting Genetic Algorithm-II (NSGAII) and Strength Pareto Evolutionary Algorithm 2 (SPEA2). We conduct several experiments on problems with varying sizes to compare the NSGA-II and SPEA2 algorithms.

  • 11671.
    Younas, Irfan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Kamrani, Farzad
    Swedish Defense Research Agency (FOI).
    Moradi, Farshad
    Swedish Defense Research Agency (FOI).
    Ayani, Rassul
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Schubert, Johan
    Swedish Defense Research Agency (FOI).
    Håkansson, Anne
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Solving Battalion Rescheduling Problem Using Multi-objective Genetic Algorithms2013Inngår i: Asiasim 2013: 13th International Conference on Systems Simulation. Proceedings, Singapore, November 6-8, 2013., Springer Berlin/Heidelberg, 2013, s. 93-104Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we consider the problem of rescheduling human resources in a battalion where new activities are assigned to the battalion by higher headquarters, requiring modification of an existing original schedule. The problem is modeled as a multi-criteria optimization problem with three objectives: (i) maximizing the number of tasks that are performed, (ii) minimizing the number of high-priority tasks that are missed, and (iii) minimizing the difference between the original schedule and the modified one. In order to solve the optimization model, we adopt Non-dominated Sorting Genetic Algorithm-II (NSGA-II). The accuracy of NSGA-II in this context is verified by considering a small-sized problem where it is easy to verify solutions. Furthermore, we consider a realistic problem instance for a battalion with 400 agents and 66 tasks in the initial schedule. We present the computational result of rescheduling when unpredictable activities emerge.

  • 11672.
    Younas, Irfan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Kamrani, Farzad
    Swedish Defence Research Agency, Stockholm, Sweden.
    Schulte, Christian
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Ayani, Rassul
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Efficient Genetic Algorithms for Optimal Assignment of Tasks to Teamsof AgentsManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    The problem of optimally assigning agents (resources) to a given set oftasks is known as the Assignment Problem (AP). The classical AP and manyof its variations have been discussed extensively in the literature. In thispaper, we present a specific class of Assignment Problems (APs) in which eachtask is assigned to a group of collaborating agents. In this AP, collaborationof all agents is required to perform the task and an agent cannot individuallydo it.

    We present a mathematical model for this type of AP and use GeneticAlgorithm (GA) to solve the model, since there are no known polynomial timealgorithms for this class of APs. We show that for larger instances of the problem,the GA with one-point crossover operator cannot efficiently find nearoptimalsolutions. In general, the efficiency of the GA depends on the choiceof genetic operators (selection, crossover, mutation) and associated parameters.In order to design an efficient GA for finding near optimal assignment oftasks to collaborative teams, we focus on construction of crossover operators.We compare and analyze the efficiency of several well-known crossover operatorssuch as one-point, two-point, three-point, position-based and order-basedcrossover operators. We suggest modifications to these operators by addinga shuffled repair list to them and show that their efficiency is enhanced forsolving the presented AP. Furthermore, we introduce two new crossover operators,team-based and team-based shuffled list crossover operators, whichsolve large-scale models of our AP efficiently.

  • 11673.
    Younas, Irfan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster (Stängd 20120101), Programvaru- och datorsystem, SCS (Stängd 20120101).
    Kamrani, Farzad
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster (Stängd 20120101), Programvaru- och datorsystem, SCS (Stängd 20120101).
    Schulte, Christian
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster (Stängd 20120101), Programvaru- och datorsystem, SCS (Stängd 20120101).
    Ayani, Rassul
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster (Stängd 20120101), Programvaru- och datorsystem, SCS (Stängd 20120101).
    Optimization of Task Assignment to Collaborating Agents2011Inngår i: IEEE SSCI 2011 - Symposium Series on Computational Intelligence - CISched 2011, Paris, France: IEEE Computational Intelligence Society , 2011, s. 17-24Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The classic task assignment problem (AP) assigns m agents to n tasks, where each task is assigned to exactly one agent. This problem and many of its variations, including the case where a task is assigned to a group of agents working independently, have been discussed extensively in the literature. We consider a specific class of task assignment problems where each task is assigned to a group of collaborating agents that work as a team. Thus, changing one of the group members may have a vital impact on the output of the group. We assume that each agent has a set of capabilities and each task has certain requirements. The objective is to assign agents to teams such that the gain is maximized.

    We suggest a Genetic Algorithm (GA) for finding a near optimal solution to this class of task assignment problems. To the best of our knowledge, this class of APs has not been considered in the literature, probably due to the difficulty of evaluating the performance of a team of agents. Recently, we have developed a formal method for measuring performance of a team which is used in this paper to formulate the objective function of our GA. We analyze the quality of the obtained solution by comparing the result of our GA with (a) the exact solution of some smaller problems, and (b) with the results of the exact solution of specific cases that can be obtained by the Hungarian algorithm. We provide experimental results on efficiency, stability, robustness and scalability of the solution obtained by our GA.

  • 11674.
    Yousef, Andy
    et al.
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    Lansner, Erik
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    Detektion av “troll” i Twitterflöden med hjälp av klusteralgoritm: Metod för att detektera personer som sprider desinformation2016Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Sociala medier har alltid varit en plats där personer kan diskutera fritt om sina åsikter och dela nyheter med många. Lätt spridning av nyheter från alla hörn i världen kan komma vara användbart för att ha möjlighet att få opartiska nyheter. Även om det finns klara fördelar med exempelvis Twitter så kan det vara problematiskt med falska och uppgjorda nyheter. Ryktesspridning eller uppgjorda nyheter förekommer i stor utsträckning fortfarande, här testas metod(er) för att upptäcka vilka som kan tänkas sprida desinformation, så kallade ’trolls’. För att kunna upptäcka trolls i Twitter undersöks några attributer som tidigare använts för att detektera spammare. Problem uppstår då det inte finns några fastställda troll att jämföra med. Datasamling från Twitter utfördes och analyserats, genom att klustra data med viktiga attribut som skulle indikera på förekomst av trolls som exempelvis antalet tweets varje dag eller hur ofta det retweetas. Men klustringen ger inte 100% indikation på att det finns trolls utan att det skulle kunna öka sannolikheten att hitta trolls i ett kluster där en typisk twitterkonto har hög andel retweets eller följare genom vänner. Slutsatsen blev att metoden kan inte hitta trolls på egen hand men kan hjälpa till att isolera användare med specifika beteenden som kan vara mer eller mindre troll-lika.

  • 11675.
    Yousefi, Shahrouz
    et al.
    KTH, Skolan för datavetenskap och kommunikation (CSC), Medieteknik och interaktionsdesign, MID.
    Li, Haibo
    KTH, Skolan för datavetenskap och kommunikation (CSC), Medieteknik och interaktionsdesign, MID.
    3D Hand Gesture Analysis Through a Real-time Gesture Search Engine2015Inngår i: International Journal of Advanced Robotic Systems, ISSN 1729-8806, E-ISSN 1729-8814, Vol. 12, artikkel-id 67Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    3D gesture recognition and tracking are highly desired features of interaction design in future mobile and smart environments. Specifically, in virtual/augmented reality applications, intuitive interaction with the physical space seems unavoidable and 3D gestural interaction might be the most effective alternative for the current input facilities such as touchscreens. In this paper, we introduce a novel solution for real-time 3D gesture-based interaction by finding the best match from an extremely large gesture database. This database includes images of various articulated hand gestures with the annotated 3D position/orientation parameters of the hand joints. Our unique matching algorithm is based on the hierarchical scoring of the low-level edge-orientation features between the query frames and database and retrieving the best match. Once the best match is found from the database in each moment, the pre-recorded 3D motion parameters can instantly be used for natural interaction. The proposed bare-hand interaction technology performs in real time with high accuracy using an ordinary camera.

  • 11676.
    Yousefi, Shahrouz
    et al.
    KTH, Skolan för datavetenskap och kommunikation (CSC), Medieteknik och interaktionsdesign, MID.
    Li, Haibo
    KTH, Skolan för datavetenskap och kommunikation (CSC), Medieteknik och interaktionsdesign, MID.
    3D Interaction Through a Real-Time Gesture Search Engine2015Inngår i: COMPUTER VISION - ACCV 2014 WORKSHOPS, PT II, [Yousefi, Shahrouz; Li, Haibo] KTH Royal Inst Technol, S-10044 Stockholm, Sweden., 2015, s. 199-213Konferansepaper (Fagfellevurdert)
    Abstract [en]

    3D gesture recognition and tracking are highly desired features of interaction design in future mobile and smart environments. Specifically, in virtual/augmented reality applications, intuitive interaction with the physical space seems unavoidable and 3D gestural interaction might be the most effective alternative for the current input facilities such as touchscreens. In this paper, we introduce a novel solution for real-time 3D gesture-based interaction by finding the best match from an extremely large gesture database. This database includes the images of various articulated hand gestures with the annotated 3D position/orientation parameters of the hand joints. Our unique matching algorithm is based on the hierarchical scoring of the low-level edge-orientation features between the query frames and database and retrieving the best match. Once the best match is found from the database in each moment, the pre-recorded 3D motion parameters can instantly be used for natural interaction. The proposed bare-hand interaction technology performs in real-time with high accuracy using an ordinary camera.

  • 11677.
    Yousefi, Shahrouz
    et al.
    KTH, Skolan för datavetenskap och kommunikation (CSC), Medieteknik och interaktionsdesign, MID.
    Li, Haibo
    KTH, Skolan för datavetenskap och kommunikation (CSC), Medieteknik och interaktionsdesign, MID.
    Liu, L.
    3D gesture analysis using a large-scale gesture database2014Inngår i: Advances in Visual Computing (ISVC 2014), Pt 1, Springer, 2014, Vol. 8887, s. 206-217Konferansepaper (Fagfellevurdert)
    Abstract [en]

    3D gesture analysis is a highly desired feature of future interaction design. Specifically, in augmented environments, intuitive interaction with the physical space seems unavoidable and 3D gestural interaction might be the most effective alternative for the current input facilities. This paper, introduces a novel solution for real-time 3D gesture analysis using an extremely large gesture database. This database includes the images of various articulated hand gestures with the annotated 3D position/orientation parameters of the hand joints. Our unique search algorithm is based on the hierarchical scoring of the low-level edge-orientation features between the query input and database and retrieving the best match. Once the best match is found from the database in real-time, the pre-calculated 3D parameters can instantly be used for gesture-based interaction.

  • 11678.
    Ytterberg, Kim
    KTH, Skolan för elektroteknik och datavetenskap (EECS).
    Procedurers inverkan på kodförståelse i Java: En studie med eye-tracking2018Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    I programvarans livscykel spenderas mycket tid i det sista steget, underhållsfasen. I detta stadie är mjukvaran färdigutvecklad och behöver kontinuerligt underhåll för att säkerställa programvarans ständiga funktionalitet och effektivitet [25]. Det är därför viktigt att programvaran är så läsbar som möjligt då nya programmerare oftast tillkommer till projekten och för att snabbt kunna felsöka koden. Procedurer (metoderi Java) lärs ut som ett sätt att hålla koden strukturerad och lättläst. Läsbarhet av kod har blivit mer och mer studerat under de senaste åren och med hjälp av eye-tracking har läsbarhet av kod kunnat studerats på ett konkret sätt. I denna rapport har procedurers inverkan på läsbarhet av kod undersökts vilket har gjorts genom att undersöka tio testpersoners ögonrörelser vid tolkning av ett antal problem i Java, där problemen skilt sig till användandet av procedurer eller ej. Metodiken som valts har varit ett kontrollerat experiment där de tilldelade problemen involverat tolkning av kod samtidigt som deltagarnas ögonrörelser studerats och presenteras som bilder och data i form av diagram över punkter där blicken fixerats i koden. Resultaten visar attnybörjare generellt sett tar längre tid på sig att läsa procedurer jämfört med monolitisk kod (sekventiell kod, motsatsen till proceduruppdelad kod), medan erfarna programmerare inte skilde sig i lika hög gradeller var till och med snabbare på att lösa de procedurellt uppdelade kodsegmenten. Man kan även tyda att erfarna programmerare har ett annat sätt att läsa kod jämfört med nybörjare vilket kan vara intressant att studera ytterligare. Slutsatsen för experimentet är att kontrollflödesabstraktioner i form av procedurer gör det lättare för programmerare att läsa kod men det krävs tid och vana för att ta del av de gynnsamma effekterna utav dem.

  • 11679.
    Yu, Hang
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    A/B testing data-driven user experinece2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    A/B testing was an unpopular part in big data area in the past. Because of the unequal investment (finance and techniques) return have always been disappointing to the market. Fortunately, in recent years with lowering barriers to entry, many companies have the ability to initiate A/B testing. The barriers are expressed as specific cost on techniques and financial. A/B testing has become an emerging technique of optimizing web pages or applications. However, the feedback from real market is less productive in some ways than we anticipated. One of the important reasons leading to the rising complaints is that A/B testing is abused. At present, more developers step into A/B testing thinking it can easily help them to increase the conversion rate by using popular A/B testing analysis tools such as Google Analytics and Optimizely, but the important knowledge and research before testing are ignored. A/B testing is based on hypothesis and the outcome of the hypothesis belongs to predictive conclusion. So the test initiating from an arbitrary hypothesis will inevitably lead to errors. What is worse is that with increasing business needs, sometimes only one metric is not enough to decide whether the change is good or not. Also, when more metrics are involved into the evaluation system, the decision making becomes more complicated. Therefore, the decision engine is implemented for solving these kind of problems by selection of representative testing scenarios and related metrics, statistical significance of sample and algorithms applicability. In comparison to popular analysis tools, the decision engine is more comprehensive, it is guidance and algorithms selective. It also has the ability to run multiple metrics simultaneously. The data-driven decision engine evolves A/B testing to the next generation.

  • 11680.
    Yu, Hong
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Creating Public Trust in Electronic Voting Systems2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    There are many positive aspects of electronic voting systems: security, verifiability, convenience, resource conservation, and the like. However, there is still lack of trust for electronic voting systems within the public. One of the reasons could be that the notions involved in electronic voting are challenging to understand for the general public. In this project, we tried to create public trust through an explanation system.

    An explanation system was made to explain how a modern electronic voting system works. User testing was performed after that, to verify whether this explanation system is able to increase people’s trust in electronic voting system. After analysing the data collected through the user testing, we got promising results to believe that this explanation can be used to create public trust in electronic voting systems.

  • 11681.
    Yu, Jiayao
    KTH, Skolan för elektroteknik och datavetenskap (EECS).
    Gaze-typing for Everyday Use: Keyboard Usability Observations and a “Tolerant” Keyboard Prototype2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Gaze-typing opens up a new input channel, but its keyboard designs are not ready for everyday use. To investigate the gaze-typing keyboards for such use that are easy to learn, fast to type, and robust to use differences, I analyzed the usability of three widely used gaze-typing keyboards by a user study with typing performance measurements, synthesized the design space of everyday used gaze-typing keyboards under the topics of typing schemes and keyboard letter layouts, feedback, ease of text editing, and system design. In particular, I found gaze-typing keyboards need “tolerant” designs that allow implicit gaze control and balance between input ambiguity and typing efficiency. Therefore, I prototyped a gaze-typing keyboard using a shape-writing scheme meant for everyday typing by gaze gestures, with the adaption on segmenting the gaze locus when writing a word from continuous gaze data stream. The system affords real-time shape-writing in the speed of 11.70 WPM and the error rate of 0.14 evaluated with an experienced user and supports to type 20000+ words from the lexicon.

  • 11682.
    Yu, Pian
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Explicit computation of sampling period in periodic event-triggered multi-agent control under limited data rate2018Inngår i: IEEE Transactions on Control of Network Systems, E-ISSN 2325-5870Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper investigates the coordination of nonlinear sampled-data multi-agent systems subject to data rate constraint. The purpose is to design resource-efficient communication and control strategies that guarantee exponential synchronization. Two implementation scenarios are considered, the period time-triggered control and the period event-triggered control. One of the main difficulties of the problem is to obtain an explicit formula for the maximum allowable sampling period (MASP). To this end, an approach on finding the MASP for periodic time-triggered control is proposed first. Then, an asynchronous period event-triggered control strategy is formulated, a communication function and a control function are designed for each agent to determine respectively whether or not the sampled data and the control input should be transmitted at each sampling instant. Finally, the constraint of limited data rate is considered. An observer-based encoder-decoder and a finite-level quantizer are designed respectively for the Sensor-Controller communication and the Controller-Actuator communication such that certain constraint on the data rate is satisfied. It is shown that exponential synchronization can still be achieved in the presence of data rate constraint. A simulation example is given to illustrate the effectiveness of the theoretical results

  • 11683.
    Yu, Pian
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS).
    Dimarogonas, Dimos V.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Time-constrained multi-agent task scheduling based on prescribed performance control2018Inngår i: 2018 IEEE CONFERENCE ON DECISION AND CONTROL (CDC), IEEE , 2018, s. 2593-2598Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The problem of time-constrained multi-agent task scheduling and control synthesis is addressed. We assume the existence of a high level plan which consists of a sequence of cooperative tasks, each of which is associated with a deadline and several Quality-of-Service levels. By taking into account the reward and cost of satisfying each task, a novel scheduling problem is formulated and a path synthesis algorithm is proposed. Based on the obtained plan, a distributed hybrid control law is further designed for each agent. Under the condition that only a subset of the agents are aware of the high level plan, it is shown that the proposed controller guarantees the satisfaction of time constraints for each task. A simulation example is given to verify the theoretical results.

  • 11684.
    Yu, Xingang
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Chung, Il-Sug
    Mork, Jesper
    Xiang, Yu
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Berggren, Jesper
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Hammar, Mattias
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Single-mode InGaAs/GaAs 1.3-mu m VCSELs Based on a Shallow Intracavity Patterning2010Inngår i: SEMICONDUCTOR LASERS AND LASER DYNAMICS IV / [ed] Panajotov, K; Sciamanna, M; Valle, AA; Michalzik, R, 2010, Vol. 7720, s. 772021-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A high-power single-mode 1.3-mu m InGaAs/GaAs vertical-cavity surface-emitting laser (VCSEL) structure employing a novel concept of engineering the optical mode profile to match the gain profile is suggested and demonstrated experimentally and theoretically. In contrast to various singlemode VCSEL approaches reported in the literature so far, based on selective loss or anti-resonant effects to suppress higher order modes, it is due to a novel design to increase the active region size while maintaining single mode emission. The shape of the fundamental mode profile is engineered to be similar to the gain profile which resembles a doughnut shape especially in intra-cavity contacted devices. In this way, the fundamental mode with the best fit to the gain profile can reach the lasing condition earliest and consume all the optical gain, leading to a suppression of higher order modes. Notably, despite this engineered shape of the mode profile, the far field shape remains close to Gaussian. The mode shaping can be achieved by introducing a shallow intracavity patterning before depositing the top mirror. Fabricated device structures consist of a A-Si/SiN/SiO(2) top mirror, modulation-doped current spreading layers, re-grown current confinement layers, three InGaAs/GaAs quantum wells, and a GaAs/AlGaAs bottom mirror. Single mode operation is demonstrated even for devices with active region as large as 10 mu m.

  • 11685.
    Yu, Yang
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektronik, Elektronik och inbyggda system.
    Dubrova, Elena
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektronik, Elektronik och inbyggda system.
    Näslund, Mats
    KTH, Skolan för elektroteknik och datavetenskap (EECS).
    Tao, Sha
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektronik, Elektronik och inbyggda system. Royal Inst Technol, Sch EECS, S-16440 Stockholm, Sweden..
    On Designing PUF-Based TRNGs with Known Answer Tests2018Inngår i: 2018 IEEE Nordic Circuits and Systems Conference, NORCAS 2018: NORCHIP and International Symposium of System-on-Chip, SoC 2018 - Proceedings / [ed] Nurmi, J Ellervee, P Mihhailov, J Jenihhin, M Tammemae, K, Institute of Electrical and Electronics Engineers (IEEE), 2018, artikkel-id 8573489Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Random numbers are widely used in cryptographic algorithms and protocols. A faulty true random number generator (TRNG) may open a door into a system in spite of cryptographic protection. It is therefore important to design TRNGs so that they can be tested at different stages of their lifetime to assure their trustworthiness. In this paper, we propose a method for designing physical unclonable function (PUF)-based TRNGs which can be tested in-field by known answer tests. We present a prototype FPGA implementation of the proposed TRNG based on an arbiter PUF which passes all NIST 800-22 statistical tests and has the minimal entropy of 0.918 estimated according to NIST 800-90B recommendations. This is a nontrivial achievement given that arbiter PUFs are notoriously hard to place in a symmetric manner in FPGAs.

  • 11686.
    Yu, Yiting
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Energy- and Cost-Efficient 5G Networks in Rural Areas2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Energy- and cost-efficiency is becoming a criteria of ever increasing importance in the design of 5G wireless solutions, especially for suburban and rural areas where the realistic barrier of providing mobile broadband service lies in the economic drawback of low revenue potential. Thus net-work operators are highly sensitive to the energy performance and economic affordability of potential solutions in futuristic 5G wireless network.In this thesis, we investigate the energy performance of 5G wireless networks with two key technical components (massive beamforming and ultra-lean design) in a rural environment for two real-life cases commonly faced by network operators: (1) A hardware upgrade to 5G in existing LTE sites (2) 5G greeneld deployments. The results are compared with a currently deployed LTE network in rural environment.

    Furthermore, we conduct economic viability evaluations in a study of energy-cost trade-off in rural scenario to derive the condition when the proposed energy-efficient 5G solutions are also cost-efficient. The analysis are performed separately in two cases based on different methods.

    The simulation results indicate that 5G systems provides much better energy performance compared with LTE systems, achieving maximum 56% and 64% reduction in daily average area power consumption in hardware upgrade case and greenfield deployment case respectively. The significant saving mainly comes from the incorporated effect of beamforming technology and possibility of longer sleep durations.

    For cost-efficiency, a hardware upgrade to 5G is economically highly motivated in higher energy-pricing regions or in systems with longer sleep durations. In greenfield deployments, the analysis result shows that itis always cost-efficient to deploy 5G solutions other than LTE solutions in rural areas despite of the variation in regional energy prices, network lifetime expectation and the DTX factor in 5G solutions.

  • 11687.
    Yu, Zhongxing
    et al.
    Inria Lille Nord Europe, Ave Halley, F-59650 Villeneuve Dascq, France..
    Martinez, Matias
    Univ Valenciennes, Malvache Bldg,Campus Mont Houy, F-59313 Valenciennes 9, France..
    Danglot, Benjamin
    Inria Lille Nord Europe, Ave Halley, F-59650 Villeneuve Dascq, France..
    Durieux, Thomas
    Inria Lille Nord Europe, Ave Halley, F-59650 Villeneuve Dascq, France..
    Monperrus, Martin
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Teoretisk datalogi, TCS.
    Alleviating patch overfitting with automatic test generation: a study of feasibility and effectiveness for the Nopol repair system2019Inngår i: Journal of Empirical Software Engineering, ISSN 1382-3256, E-ISSN 1573-7616, Vol. 24, nr 1, s. 33-67Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Among the many different kinds of program repair techniques, one widely studied family of techniques is called test suite based repair. However, test suites are in essence input-output specifications and are thus typically inadequate for completely specifying the expected behavior of the program under repair. Consequently, the patches generated by test suite based repair techniques can just overfit to the used test suite, and fail to generalize to other tests. We deeply analyze the overfitting problem in program repair and give a classification of this problem. This classification will help the community to better understand and design techniques to defeat the overfitting problem. We further propose and evaluate an approach called UnsatGuided, which aims to alleviate the overfitting problem for synthesis-based repair techniques with automatic test case generation. The approach uses additional automatically generated tests to strengthen the repair constraint used by synthesis-based repair techniques. We analyze the effectiveness of UnsatGuided: 1) analytically with respect to alleviating two different kinds of overfitting issues; 2) empirically based on an experiment over the 224 bugs of the Defects4J repository. The main result is that automatic test generation is effective in alleviating one kind of overfitting, issue-regression introduction, but due to oracle problem, has minimal positive impact on alleviating the other kind of overfitting issue-incomplete fixing.

  • 11688. Yuan, H.
    et al.
    Furdek, Marija
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Muhammad, Ajmal
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Saljoghei, A.
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Zervas, G.
    Space-division multiplexing in data center networks: On multi-core fiber solutions and crosstalk-suppressed resource allocation2018Inngår i: Journal of Optical Communications and Networking, ISSN 1943-0620, E-ISSN 1943-0639, Vol. 10, nr 4, s. 272-288Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The rapid growth of traffic inside data centers caused by the increasing adoption of cloud services necessitates a scalable and cost-efficient networking infrastructure. Space-division multiplexing (SDM) is considered as a promising solution to overcome the optical network capacity crunch and support cost-effective network capacity scaling. Multi-core fiber (MCF) is regarded as the most feasible and efficient way to realize SDM networks, and its deployment inside data centers seems very likely as the issue of inter-core crosstalk (XT) is not severe over short link spans (<1 km) compared to that in long-haul transmission. However, XT can still have a considerable effect in MCF over short distances,which can limit the transmission reach and in turn the data center's size. XT can be further reduced by bi-directional transmission of optical signals in adjacent MCF cores. This paper evaluates the benefits of MCF-based SDM solutions in terms of maximizing the capacity and spatial efficiency of data center networks. To this end, we present an analytical model for XT in bi-directional normal step-index and trench-assisted MCFs and propose corresponding XT-aware core prioritization schemes. We further develop XT-aware spectrum resource allocation strategies aimed at relieving the complexity of online XT computation. These strategies divide the available spectrum into disjoint bands and incrementally add them to the pool of accessible resources based on the network conditions. Several combinations of core mapping and spectrum resource allocation algorithms are investigated for eight types of homogeneous MCFs comprising 7-61 cores, three different multiplexing schemes, and three data center network topologies with two traffic scenarios. Extensive simulation results showthat combining bi-directional transmission in dense core fibers with tailored resource allocation schemes significantly increases the network capacity. Moreover, a multiplexing scheme that combines SDM and WDM can achieve up to 33 times higher link spatial efficiency and up to 300 times greater capacity compared to a WDM solution.

  • 11689. Yuan, Qilong
    et al.
    Chen, I-Ming
    Lembono, Teguh Santoso
    Landén, Simon Nelson
    KTH, Skolan för industriell teknik och management (ITM).
    Malmgren, Victor
    KTH, Skolan för industriell teknik och management (ITM).
    Strategy for robot motion and path planning in robot taping2016Inngår i: FRONTIERS OF MECHANICAL ENGINEERING, ISSN 2095-0233, Vol. 11, nr 2, s. 195-203Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Covering objects with masking tapes is a common process for surface protection in processes like spray painting, plasma spraying, shot peening, etc. Manual taping is tedious and takes a lot of effort of the workers. The taping process is a special process which requires correct surface covering strategy and proper attachment of the masking tape for an efficient surface protection. We have introduced an automatic robot taping system consisting of a robot manipulator, a rotating platform, a 3D scanner and specially designed taping end- effectors. This paper mainly talks about the surface covering strategies for different classes of geometries. The methods and corresponding taping tools are introduced for taping of following classes of surfaces: Cylindrical/ extended surfaces, freeform surfaces with no grooves, surfaces with grooves, and rotational symmetrical surfaces. A collision avoidance algorithm is introduced for the robot taping manipulation. With further improvements on segmenting surfaces of taping parts and tape cutting mechanisms, such taping solution with the taping tool and the taping methodology can be combined as a very useful and practical taping package to assist humans in this tedious and time costly work.

  • 11690.
    Yuan, Weihao
    et al.
    Hong Kong Univ Sci & Technol, ECE, Robot Inst, Hong Kong, Peoples R China..
    Hang, Kaiyu
    Yale Univ, Mech Engn & Mat Sci, New Haven, CT USA..
    Kragic, Danica
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, Centrum för autonoma system, CAS. KTH, Skolan för elektroteknik och datavetenskap (EECS), Robotik, perception och lärande, RPL.
    Wang, Michael Y.
    Hong Kong Univ Sci & Technol, ECE, Robot Inst, Hong Kong, Peoples R China..
    Stork, Johannes A.
    Orebro Univ, Ctr Appl Autonomous Sensor Syst, Orebro, Sweden..
    End-to-end nonprehensile rearrangement with deep reinforcement learning and simulation-to-reality transfer2019Inngår i: Robotics and Autonomous Systems, ISSN 0921-8890, E-ISSN 1872-793X, Vol. 119, s. 119-134Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nonprehensile rearrangement is the problem of controlling a robot to interact with objects through pushing actions in order to reconfigure the objects into a predefined goal pose. In this work, we rearrange one object at a time in an environment with obstacles using an end-to-end policy that maps raw pixels as visual input to control actions without any form of engineered feature extraction. To reduce the amount of training data that needs to be collected using a real robot, we propose a simulation-to-reality transfer approach. In the first step, we model the nonprehensile rearrangement task in simulation and use deep reinforcement learning to learn a suitable rearrangement policy, which requires in the order of hundreds of thousands of example actions for training. Thereafter, we collect a small dataset of only 70 episodes of real-world actions as supervised examples for adapting the learned rearrangement policy to real-world input data. In this process, we make use of newly proposed strategies for improving the reinforcement learning process, such as heuristic exploration and the curation of a balanced set of experiences. We evaluate our method in both simulation and real setting using a Baxter robot to show that the proposed approach can effectively improve the training process in simulation, as well as efficiently adapt the learned policy to the real world application, even when the camera pose is different from simulation. Additionally, we show that the learned system not only can provide adaptive behavior to handle unforeseen events during executions, such as distraction objects, sudden changes in positions of the objects, and obstacles, but also can deal with obstacle shapes that were not present in the training process.

  • 11691.
    Yuan, Zhengwu
    et al.
    Chongqing University of Posts and Telecommunications / College of Computer Science and Technology.
    Jiang, Yanli
    Chongqing University of Posts and Telecommunications / College of Computer Science and Technology.
    Gidofalvi, Gyözö
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Geodesi och geoinformatik.
    Geographical and Temporal Similarity Measurement on Location-based Social Networks2013Inngår i: Proceedings of the Second ACM SIGSPATIAL International Workshop on Mobile Geographic Information Systems / [ed] Chi-Yin Chow and Shashi Shekhar, New York, NY, USA: Association for Computing Machinery (ACM), 2013, s. 30-34Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Using "check-in" data gathered from location-based social networks, this paper proposes to measure the similarity of users by considering the geographical and the temporal aspect of their geographical and temporal aspects of their "check-ins". Temporal neighborhood is added to support the time dimension on the basis of the traditional DBSCAN clustering algorithm, which determines the similarity among users at different scales using the classical Vector Space Model (VSM) with vectors composed of the amount of visits in different cluster area. The spatio-temporal similarity of the user behaviors are obtained through overlapping the different weighted user similarity values. The experimental results show that the proposed approach is effective in measuring user similarity in location-based social networks.

  • 11692.
    Yun, Ruida
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik- och datorsystem, ECS.
    Qin, Yajie
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik- och datorsystem, ECS.
    Signell, Svante
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik- och datorsystem, ECS.
    LMS-based calibration of pipelined ADCs including linear and nonlinear errors2007Inngår i: 2007 European Conference On Circuit Theory And Design: Vols 1-3, 2007, s. 348-351Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A least mean square (LMS) based calibration algorithm is proposed to calibrate most known error sources in 1.5 bit/stage pipelined ADCs, known to be immune to moderate comparator offsets. The error sources include linear gain errors, reference voltage errors, systematic offset errors and amplifier non-linear errors of each pipeline stage. LMS is used to estimate the error parameters in the digital domain. After estimation the proposed algorithm calibrate the pipelined ADC using the estimated parameter errors. Simulation results show that the proposed algorithm can improve the ENOB from 6.6 bits to 13.9 bits for a 14 bit 1.5 bits/stage pipelined ADC.

  • 11693.
    Yun, Se-Young
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Proutiere, Alexandre
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Distributed Load Balancing in Heterogenous Systems2014Inngår i: 2014 48TH ANNUAL CONFERENCE ON INFORMATION SCIENCES AND SYSTEMS (CISS), 2014, s. 6814133-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We consider the problem of distributed load balancing in heterogenous parallel server systems, where the service rate achieved by a user at a server depends on both the user and the server. Such heterogeneity typically arises in wireless networks (e.g., servers may represent frequency bands, and the service rate of a user varies across bands). Users select servers in a distributed manner. They initially attach to an arbitrary server. However, at random instants of time, they may probe the load at a new server and migrate there to improve their service rate. We analyze the system dynamics under the natural Random Local Search (RLS) migration scheme, introduced in [5]. Under this scheme, when a user has the opportunity to switch servers, she does it only if this improves her service rate. The dynamics under RLS may be interpreted as those generated by strategic players updating their strategy in a load balancing game. We show that this game has pure Nash Equilibriums (NEs), and we analyze their efficiency. We further prove that when the user population grows large, pure NEs get closer to a Proportionally Fair (PF) allocation of users to servers, and we characterize the gap between equilibriums and this ideal allocation depending on user population. Under the RLS algorithm, the system converges to pure NEs: we study the time it takes for the system to reach the PF allocation within a certain margin.

  • 11694.
    Yun, Seyoung
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Shin, J.
    Yi, Y.
    CSMA over time-varying channels: Optimality, uniqueness and limited backoff rate2013Inngår i: MobiHoc '13 Proceedings of the fourteenth ACM international symposium on Mobile ad hoc networking and computing, ACM Press, 2013, s. 137-146Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Recent studies on MAC scheduling have shown that carrier sense multiple access (CSMA) algorithms can be throughput optimal for arbitrary wireless network topology. However, these results are highly sensitive to the underlying assumption on 'static' or 'fixed' system conditions. For example, if channel conditions are time-varying, it is unclear how each node can adjust its CSMA parameters, so-called backoff and channel holding times, using its local channel information for the desired high performance. In this paper, we study 'channel-aware' CSMA (A-CSMA) algorithms in time-varying channels, where they adjust their parameters as some function of the current channel capacity. First, we show that the achievable rate region of A-CSMA equals to the maximum rate region if and only if the function is exponential. Furthermore, given an exponential function in ACSMA, we design updating rules for their parameters, which achieve throughput optimality for an arbitrary wireless network topology. They are the first CSMA algorithms in the literature which are proved to be throughput optimal under time-varying channels. Moreover, we also consider the case when back-off rates of A-CSMA are highly restricted compared to the speed of channel variations, and characterize the throughput performance of A-CSMA in terms of the underlying wireless network topology. Our results not only guide a high-performance design on MAC scheduling under highly time-varying scenarios, but also provide new insights on the performance of CSMA algorithms in relation to their backoff rates and underlying network topologies.

  • 11695.
    Yun, Seyoung
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Shin, J.
    Yi, Y.
    CSMA using the Bethe approximation for utility maximization2013Inngår i: IEEE International Symposium on Information Theory: Proceedings, IEEE conference proceedings, 2013, s. 206-210Konferansepaper (Fagfellevurdert)
    Abstract [en]

    CSMA (Carrier Sense Multiple Access), which resolves contentions over wireless networks in a fully distributed fashion, has recently gained a lot of attentions since it has been proved that appropriate control of CSMA parameters guarantees optimality in terms of system-wide utility. Most algorithms rely on the popular MCMC (Markov Chain Monte Carlo) technique, which enables one to find optimal CSMA parameters through iterative loops of simulation-and-update. However, such a simulation-based approach often becomes a major cause of exponentially slow convergence, being poorly adaptive to flow/topology changes. In this paper, we develop a distributed iterative algorithm which produces approximate solutions with convergence in polynomial time. Our approach is motivated by a scheme in statistical physics, referred to as the Bethe approximation, allowing us to express approximate solutions via a certain non-linear system with polynomial size. We provide numerical results to show that the algorithm produces highly accurate solutions and converges much faster than prior ones.

  • 11696.
    Yunus, Ender
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    THE ROLE OF SOCIAL MEDIA IN CREATING POLITICAL AWARENESS AND MOBILIZING POLITICAL PROTESTS: A Focus on Turkey2013Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In the recent years, the internet penetration, social media production and consumption have increased dramatically all over the world. This increase has affected the politics in most parts of the world in many ways. Social media became a tool for politicians to carry out their political campaigns and for activists to create awareness on political issues and mobilize protests. Today almost in all social movements in the countries with high rate of internet access, the role of social media is being discussed. Social media has become a costless and extremely effective tool in reaching mass audiences with political purposes.

    This thesis research focuses on the strength of social media in creating political awareness and mobilizing political protests in Turkey. In this study the recent social movements in Turkey are examined as case studies, to understand the role of social media in political movements, to be able to make predictions for the future. The prob-lem was approached with combining qualitative and quantitative research methods. Literature review regarding the subjects related to the social media and politics and information flow in social networks was conducted. After that, two interviews, a sur-vey and a social network analysis to comprehend the role of social media in the two recent major social movements in Turkey, Gezi Parki Protests and Internet Censor-ship Protests, were carried out.

    Depending on the results from research methods conducted, it was found that social media has already become a fundamental part of social movements in Turkey. The young generation in Turkey is extremely interested in joining online social networks. These social networks establish connections between people that are related with weak ties. These connections enable political information to flow on these networks virally, costless and rapidly. Information can be on political news or thoughts to cre-ate political awareness and also to mobilize political protests. These advantages of social media combined with biased and ignorant attitude of mainstream media on po-litical events; social media created an alternative source of information in the eyes of the society. Considering the increasing internet penetration, smart phone and social media use for political purposes, the strength of social media in creating political awareness and mobilizing political protests is expected to rise in the future as well.

  • 11697.
    Yus, Diego
    KTH, Skolan för elektroteknik och datavetenskap (EECS).
    Long-term vehicle movement prediction using Machine Learning methods2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The problem of location or movement prediction can be described as the task of predicting the future location of an item using the past locations of that item. It is a problem of increasing interest with the arrival of location-based services and autonomous vehicles. Even if short term prediction is more commonly studied, especially in the case of vehicles, long-term prediction can be useful in many applications like scheduling, resource managing or traffic prediction.

    In this master thesis project, I present a feature representation of movement that can be used for learning of long-term movement patterns and for long-term movement prediction both in space and time. The representation relies on periodicity in data and is based on weighted n-grams of windowed trajectories.

    The algorithm is evaluated on heavy transport vehicles movement data to assess its ability to from a search index retrieve vehicles that with high probability will move along a route that matches a desired transport mission. Experimental results show the algorithm is able to achieve a consistent low prediction distance error rate across different transport lengths in a limited geographical area under business operation conditions. The results also indicate that the total population of vehicles in the index is a critical factor in the algorithm performance and therefore in its real-world applicability.

  • 11698.
    Yusuf Isse, Jamila
    et al.
    KTH, Skolan för datavetenskap och kommunikation (CSC), Teoretisk datalogi, TCS.
    El Ghouch, Chaimae
    KTH, Skolan för datavetenskap och kommunikation (CSC), Teoretisk datalogi, TCS.
    Information Theoretic Similarity Measures for Robust Image Matching: Multimodal Imaging - Infrared and Visible light2016Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    Abstract

    This study aimed to investigate the applicability of three different information theoretic similarity measures in image matching, mutual information (MI), cross-cumulative residual entropy (CCRE) and sum of conditional variances (SCV). An experiment was conducted to assess the impact on the performances of the similarity measures when dealing with multimodality, in this case in the context of infrared and visible light. This was achieved by running simulations of four different scenarios using images taken in infrared and visible light, and additionally with variations in amount of details to create different experimental setups. Namely experimental setup A: unimodal data sets with more and less details and experimental setup B: multimodal datasets with more and less details.

    The result showed that the concept of multimodality gives a statistically significant effect on the performances of all similarity measures. Observations were made that the similarity measures performances also, when trying to match images with different amount of details, differed from each other. This provided a basis for judgement on what measure to use as to give as clear and sound results as possible depending on the variation of detail amount in the data. With this study, it was concluded that the similarity measure CCRE gave the most clear and sound results in the context of multimodality concerning infrared and visible light for both cases of more or less details. Even though the other similarity measures performed well in some cases, CCRE would be to recommend as observed by this study.

    Keywords : Image matching, image registration, information theoretic similarity measures, multimodal imaging, similarity measures, MI, CCRE, SCV, infrared, visible light.

  • 11699.
    Zacarias, Orlando P.
    et al.
    Stockholms universitet, Institutionen för data- och systemvetenskap.
    Boström, Henrik
    Stockholms universitet, Institutionen för data- och systemvetenskap.
    Comparing Support Vector Regression and Random Forests for Predicting Malaria Incidence in Mozambique2013Inngår i: 2013 International Conference on Advances in ICT for Emerging Regions (ICTer), IEEE Computer Society, 2013, s. 217-221, artikkel-id 6761181Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Accurate prediction of malaria incidence is essential for the management of several activities in the ministry of health in Mozambique. This study investigates the comparison of support vector machines (SVMs) and random forests (RFs) for this purpose. A dataset with records of malaria cases covering the period 1999-2008 was used to evaluate predictive models on the last year when developed from one up to nine years of historical data. Mean squared error (MSE) was used as the performance metric. The scheme for estimating variable importance commonly employed for RFs was also adopted for SVMs. SVMs developed from two years of historical data obtained the best prediction accuracy. Hence, if we are interested in predicting the actual number of malaria cases the support vector machines model should be chosen. In the analysis of variable importance, Indoor Residual Spray (IRS), the districts of Manhiça and Matola and month of January turned out to be the most important predictors in both the SVM and RF models.

  • 11700.
    Zacarias, Orlando P.
    et al.
    Stockholms universitet, Institutionen för data- och systemvetenskap.
    Boström, Henrik
    Stockholms universitet, Institutionen för data- och systemvetenskap.
    Generalization of Malaria Incidence Prediction Models by Correcting Sample Selection Bias2013Inngår i: Advanced Data Mining and Applications: Proceedings, Part II / [ed] Hiroshi Motoda et al., Springer Berlin/Heidelberg, 2013, Vol. 8347, s. 189-200Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Performance measurements obtained from dividing a single sample into training and test sets, e.g. by employing cross-validation, may not give an accurate picture of the performance of any model developed from the sample, on the set of examples to which the model will be applied. Such measurements, which are due to that training and test samples are drawn according to different distributions may hence be misleading. In this study, two support vector machine models for predicting malaria incidence developed from certain regions and time periods in Mozambique are evaluated on data from novel regions and time periods, and the use of selection bias correction is investigated. It is observed that significant reductions in the predicted error can be obtained using the latter approach, strongly suggesting that techniques of this kind should be employed if test data can be expected to be drawn from some other distribution than what is the origin of the training data.

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