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  • 251.
    Martin, Eva Garcia
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Lavesson, Niklas
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Doroud, Mina
    Twitter Inc, San Francisco, CA USA..
    Hashtags and followers: An experimental study of the online social network Twitter2016Ingår i: SOCIAL NETWORK ANALYSIS AND MINING, ISSN 1869-5450, Vol. 6, nr 1, artikel-id UNSP 12Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have conducted an analysis of data from 502,891 Twitter users and focused on investigating the potential correlation between hashtags and the increase of followers to determine whether the addition of hashtags to tweets produces new followers. We have designed an experiment with two groups of users: one tweeting with random hashtags and one tweeting without hashtags. The results showed that there is a correlation between hashtags and followers: on average, users tweeting with hashtags increased their followers by 2.88, while users tweeting without hashtags increased 0.88 followers. We present a simple, reproducible approach to extract and analyze Twitter user data for this and similar purposes.

  • 252.
    Martin Sagayam, K.
    et al.
    Karunya University, IND.
    Ho, Chung Ching
    Multimedia University, MYS.
    Henesey, Lawrence
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Bestak, Robert
    Ceske vysoke uceni technicke v Praze, CZE.
    3D scenery learning on solar system by using marker based augmented reality2018Ingår i: 4th International Conference of the Virtual and Augmented Reality in Education, VARE 2018, Dime University of Genoa , 2018, s. 139-143Konferensbidrag (Refereegranskat)
    Abstract [en]

    Augmented reality (AR) is the technology that works on computer vision based recognition algorithms to augment sound, video, graphics and other sensor based inputs and real world objects using the camera of your device. AR applications can become the backbone of education industry. Apps are being developed which are embed text, images and videos, as well as the real-world curriculums. With help of AR, travellers can access real-time information of historical places just by pointing their camera viewfinder to subjects. There are two major forms of augmented reality, marker-based AR and markerless AR. A marker based AR works on concept of target recognition. The target can be 3D object, text, image, QR Code or human-face called markers. Whereas marker-less AR, also known as location-based AR, uses GPS of mobile devices to record the device position and displays information relative to that location. Few drawbacks in marker-less AR like house resolution, size variation and time delay can be solved using marker based algorithms such as marker detection, triangle similarity for marker to camera distance and corner detection. Copyright © (2015) by CAL-TEK S.r.l.All rights reserved. . All Rights Reserved.

  • 253.
    Martin Sagayam, K.
    et al.
    Karunya Institute of Technology and Sciences, IND.
    Vedha Viyas, T.
    Karunya University, IND.
    Ho, Chiung Ching
    Karunya University, IND.
    Henesey, Lawrence
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Virtual Robotic Arm Control with Hand Gesture Recognition and Deep Learning Strategies2017Ingår i: Deep Learning for Image Processing Applications, IOS Press BV , 2017, Vol. 31, s. 50-67Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Hand gestures and Deep Learning Strategies can be used to control a virtual robotic arm for real-time applications. A robotic arm which is portable to carry various places and which can be easily programmed to do any work of a hand and is controlled by using deep learning techniques. Deep hand is a combination of both virtual reality and deep learning techniques. It estimated the active spatio-temporal feature and the corresponding pose parameter for various hand movements, to determine the unknown pose parameter of hand gestures by using various deep learning algorithms. A novel framework for hand gestures has been made to estimate by using a deep convolution neural network (CNN) and a deep belief network (DBN). A comparison in terms of accuracy and recognition rate has been drawn. This helps in analyzing the movement of a hand and its fingers which can be made to control a robotic arm with high recognition rate and less error rate. © 2017 The authors and IOS Press. All rights reserved.

  • 254.
    Martinsen, Jan Kasper
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Design and Implementation of Thread-Level Speculation in JavaScript Engines2014Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Two important trends in computer systems are that applications are moved to the Internet as web applications, and that computer systems are getting an increasing number of cores to increase the performance. It has been shown that JavaScript in web applications has a large potential for parallel execution despite the fact that JavaScript is a sequential language. In this thesis, we show that JavaScript execution in web applications and in benchmarks are fundamentally different and that an effect of this is that Just-in-time compilation does often not improve the execution time, but rather increases the execution time for JavaScript in web applications. Since there is a significant potential for parallel computation in JavaScript for web applications, we show that Thread-Level Speculation can be used to take advantage of this in a manner completely transparent to the programmer. The Thread-Level Speculation technique is very suitable for improving the performance of JavaScript execution in web applications; however we observe that the memory overhead can be substantial. Therefore, we propose several techniques for adaptive speculation as well as for memory reduction. In the last part of this thesis we show that Just-in-time compilation and Thread-Level Speculation are complementary techniques. The execution characteristics of JavaScript in web applications are very suitable for combining Just-in-time compilation and Thread-Level Speculation. Finally, we show that Thread-Level Speculation and Just-in-time compilation can be combined to reduce power usage on embedded devices.

  • 255.
    Martinsen, Jan Kasper
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Grahn, Håkan
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Isberg, Anders
    Sony Mobile Communications AB.
    An argument for thread-level speculation and just-in-time compilation in the google's v8 javascript engine2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    Thread-Level Speculation can be used to take advantage of multicore architectures for web applications. We have implemented Thread-Level Speculation in the state-of-the-art JavaScript engine V8 instead of using an interpreted JavaScript engine. We evaluate the implementation with the Chromium web browser on 15 popular web applications for 2, 4, and 8 cores. The results show that it is benecial to combine Thread-Level Speculation and Just-in-time compi-lation and that it is possible to take advantage of multicore architectures while hiding the details of parallel program-ming from the programmer of web applications.

  • 256.
    Martinsen, Jan Kasper
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Grahn, Håkan
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Isberg, Anders
    Sony Mobile Communications AB Lund, SWE.
    Combining thread-level speculation and just-in-time compilation in Google’s V8 JavaScript engine2017Ingår i: Concurrency and Computation, ISSN 1532-0626, E-ISSN 1532-0634, Vol. 29, nr 1, artikel-id e3826Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Summary: Thread-level speculation can be used to take advantage of multicore architectures for JavaScript in web applications. We extend previous studies with these main contributions; we implement thread-level speculation in the state-of-the art just-in-time-enabled JavaScript engine V8 and make the measurements in the Chromium web browser both from Google instead of using an interpreted JavaScript engine. We evaluate the thread-level speculation and just-in-time compilation combination on 15 very popular web applications, 20 HTML5 demos from the JS1K competition, and 4 Google Maps use cases. The performance is evaluated on two, four, and eight cores. The results clearly show that it is possible to successfully combine thread-level speculation and just-in-time compilation. This makes it possible to take advantage of multicore architectures for web applications while hiding the details of parallel programming from the programmer. Further, our results show an average speedup for the thread-level speculation and just-in-time compilation combination by a factor of almost 3 on four cores and over 4 on eight cores, without changing any of the JavaScript source code.

  • 257.
    Martinsen, Jan Kasper
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Grahn, Håkan
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Isberg, Anders
    Sony Mobile Communications AB.
    The Effects of Parameter Tuning in Software Thread-Level Speculation in JavaScript Engines2015Ingår i: ACM Transactions on Architecture and Code Optimization, ISSN 1544-3566, Vol. 11, nr 4Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    JavaScript is a sequential programming language that has a large potential for parallel execution in Web applications. Thread-level speculation can take advantage of this, but it has a large memory overhead. In this article, we evaluate the effects of adjusting various parameters for thread-level speculation. Our results clearly show that thread-level speculation is a useful technique for taking advantage of multicore architectures for JavaScript in Web applications, that nested speculation is required in thread-level speculation, and that the execution characteristics of Web applications significantly reduce the needed memory, the number of threads, and the depth of our speculation.

  • 258.
    Martinsen, Jan Kasper
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Grahn, Håkan
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Isberg, Anders
    Sony Mobile Communications AB.
    Sundström, Henrik
    Sony Mobile Communications AB.
    Reducing Memory in Software-Based Thread-Level Speculation for JavaScript Virtual Machine Execution of Web Applications2014Ingår i: 2014 IEEE INTERNATIONAL CONFERENCE ON HIGH PERFORMANCE COMPUTING AND COMMUNICATIONS, 2014 IEEE 6TH INTL SYMP ON CYBERSPACE SAFETY AND SECURITY, 2014 IEEE 11TH INTL CONF ON EMBEDDED SOFTWARE AND SYST (HPCC,CSS,ICESS), Elsevier, 2014, s. 181-184Konferensbidrag (Refereegranskat)
    Abstract [en]

    Thread-Level Speculation has been used to take advantage of multicore processors in virtual execution environments for the sequential JavaScript scripting language. While the results are promising the memory overhead is high. Here we propose to reduce the memory usage by limiting the checkpoint depth based on an in-depth study of the memory and execution time effects. We also propose an adaptive heuristic to dynamically adjust the checkpoints. We evaluate this using 15 web applications on an 8-core computer. The results show that the memory overhead is reduced for Thread-Level Speculation by over 90% as compared to storing all checkpoints. Further, the performance is often better than when storing all the checkpoints and at worst 4% slower.

  • 259.
    Mbiydzenyuy, Gideon
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Persson, Jan A.
    Davidsson, Paul
    Exploring synergy relationships between telematic services and functionalities using cluster analysis2015Ingår i: IET Intelligent Transport Systems, ISSN 1751-956X, E-ISSN 1751-9578, Vol. 9, nr 4, s. 366-374Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A method for assessing potential synergies among different sets of transport telematic services (TTSs) is suggested. An Intelligent Transport System enhances transport by delivering one or more TTSs. The ability to deliver multiple TTSs to address a wide range of stakeholder needs is gaining momentum, not only from a marketing perspective but also from a technological perspective. The total cost of TTSs can be reduced if they share functionalities (i.e., sub-services provided by telematic systems). We show how this synergy can be assessed with the help of clustering methods. Knowledge about possible synergies of functionalities is useful in the (re)design and eventual deployment of TTSs, especially when the underlying telematic systems are able to support multiple TTSs. To adapt the clustering method for this purpose, we suggest a mathematical formulation of synergy among functionalities of TTSs. By applying the method to a set of 32 TTSs, we obtain a cluster formation of these TTSs according to their synergy measures. Overall, the results suggest that the joint implementation of TTSs targeted toward some problem domains can lead to significant cost savings, for example, Road User Charging, Infrastructure Repair and Maintenance, and Information on the Transport of extra large goods for the management of road transport infrastructure. © The Institution of Engineering and Technology 2015.

  • 260.
    Medina Chirinos, Jorge Alberto
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Deconstructing Open vSwitch for Isolated Enclaves: A security enabler for SDN data plane2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 261.
    Mehri, Seyedeh Marjaneh Ahmadi
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Effect of packet loss on VP8 encoded videos using HTML5 based streaming2014Självständigt arbete på grundnivå (kandidatexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    HTML5 based streaming gives opportunity to users for watching videos without using any plugins. HTML5 supports three different formats of video. One of them is VP8, which is owned by Google and is used in this thesis. Quality of experience of videos transmitted through the network can be affected by network distortions. Packet loss is one of the main distortions in communication networks. In this project, the effect of packet loss on video, encoded/decoded by VP8, with different resolutions and bitrates, has been investigated using subjective tests.

  • 262.
    Mehri, Vida. A.
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Ilie, Dragos
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Tutschku, Kurt
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Designing a Secure IoT System Architecture from a Virtual Premise for a Collaborative AI Lab2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    IoT systems are increasingly composed out of flexible, programmable, virtualised, and arbitrarily chained IoT elements and services using portable code. Moreover, they might be sliced, i.e. allowing multiple logical IoT systems (network + application) to run on top of a shared physical network and compute infrastructure. However, implementing and designing particularly security mechanisms for such IoT systems is challenging since a) promising technologies are still maturing, and b) the relationships among the many requirements, technologies and components are difficult to model a-priori.

    The aim of the paper is to define design cues for the security architecture and mechanisms of future, virtualised, arbitrarily chained, and eventually sliced IoT systems. Hereby, our focus is laid on the authorisation and authentication of user, host, and code integrity in these virtualised systems. The design cues are derived from the design and implementation of a secure virtual environment for distributed and collaborative AI system engineering using so called AI pipelines. The pipelines apply chained virtual elements and services and facilitate the slicing of the system. The virtual environment is denoted for short as the virtual premise (VP). The use-case of the VP for AI design provides insight into the complex interactions in the architecture, leading us to believe that the VP concept can be generalised to the IoT systems mentioned above. In addition, the use-case permits to derive, implement, and test solutions. This paper describes the flexible architecture of the VP and the design and implementation of access and execution control in virtual and containerised environments. 

  • 263.
    Mehri, Vida. A.
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Tutschku, Kurt
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Flexible Privacy and High Trust in the Next Generation Internet: The Use Case of a Cloud-based Marketplace for AI2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    Cloudified architectures facilitate resource ac-cess and sharing which is independent from physical lo-cations. They permit high availability of resources at lowoperational costs. These advantages, however, do not comefor free. End users might fear that they lose control overthe location of their data and, thus, of their autonomy indeciding to whom the data is communicate to. Thus, strongprivacy and trust concerns arise for end users.In this work we will review and investigate privacy andtrust requirements for Cloud systems in general and for acloud-based marketplace (CMP) for AI in particular. We willinvestigate whether and how the current privacy and trustdimensions can be applied to Clouds and for the design ofa CMP. We also propose the concept of a "virtual premise"for enabling "Privacy-by-Design" [1] in Clouds. The ideaof a "virtual premise" might probably not be a universalsolution for any privacy requirement. However, we expectthat it provides flexibility in designing privacy in Cloudsand thus leading to higher trust.

  • 264.
    Mehri, Vida. A.
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Tutschku, Kurt
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Privacy and trust in cloud-based marketplaces for AI and data resources2017Ingår i: IFIP Advances in Information and Communication Technology, Springer New York LLC , 2017, Vol. 505, s. 223-225Konferensbidrag (Refereegranskat)
    Abstract [en]

    The processing of the huge amounts of information from the Internet of Things (IoT) has become challenging. Artificial Intelligence (AI) techniques have been developed to handle this task efficiently. However, they require annotated data sets for training, while manual preprocessing of the data sets is costly. The H2020 project “Bonseyes” has suggested a “Market Place for AI”, where the stakeholders can engage trustfully in business around AI resources and data sets. The MP permits trading of resources that have high privacy requirements (e.g. data sets containing patient medical information) as well as ones with low requirements (e.g. fuel consumption of cars) for the sake of its generality. In this abstract we review trust and privacy definitions and provide a first requirement analysis for them with regards to Cloud-based Market Places (CMPs). The comparison of definitions and requirements allows for the identification of the research gap that will be addressed by the main authors PhD project. © IFIP International Federation for Information Processing 2017.

  • 265.
    Mendes, Emilia
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik. Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för programvaruteknik.
    Rodriguez, Pilar
    University of Oulu, FIN.
    Freitas, Vitor
    University of Oulu, FIN.
    Baker, Simon
    University of Cambridge, GBR.
    Atoui, Mohamed Amine
    University of Oulu, FIN.
    Correction to: Towards improving decision making and estimating the value of decisions in value-based software engineering: the VALUE framework (Software Quality Journal, (2018), 26, 2, (607-656), 10.1007/s11219-017-9360-z)2018Ingår i: Software quality journal, ISSN 0963-9314, E-ISSN 1573-1367, Vol. 26, nr 4, s. 1595-1596Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    The original version of this article unfortunately contained a mistake in Figs. 1 and 21. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.

  • 266.
    Mendes, Emilia
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Rodriguez, Pilar
    University of Oulu, FIN.
    Freitas, Vitor
    University of Oulu, FIN.
    Baker, Simon
    University of Cambridge, GBR.
    Atoui, Mohamed Amine
    University of Oulu, FIN.
    Towards improving decision making and estimating the value of decisions in value-based software engineering: the VALUE framework2018Ingår i: Software quality journal, ISSN 0963-9314, E-ISSN 1573-1367, Vol. 26, nr 2, s. 607-656Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To sustain growth, maintain competitive advantage and to innovate, companies must make a paradigm shift in which both short- and long-term value aspects are employed to guide their decision-making. Such need is clearly pressing in innovative industries, such as ICT, and is also the core of Value-based Software Engineering (VBSE). The goal of this paper is to detail a framework called VALUE—improving decision-making relating to software-intensive products and services development—and to show its application in practice to a large ICT company in Finland. The VALUE framework includes a mixed-methods approach, as follows: to elicit key stakeholders’ tacit knowledge regarding factors used during a decision-making process, either transcripts from interviews with key stakeholders are analysed and validated in focus group meetings or focus-group meeting(s) are directly applied. These value factors are later used as input to a Web-based tool (Value tool) employed to support decision making. This tool was co-created with four industrial partners in this research via a design science approach that includes several case studies and focus-group meetings. Later, data on key stakeholders’ decisions gathered using the Value tool, plus additional input from key stakeholders, are used, in combination with the Expert-based Knowledge Engineering of Bayesian Network (EKEBN) process, coupled with the weighed sum algorithm (WSA) method, to build and validate a company-specific value estimation model. The application of our proposed framework to a real case, as part of an ongoing collaboration with a large software company (company A), is presented herein. Further, we also provide a detailed example, partially using real data on decisions, of a value estimation Bayesian network (BN) model for company A. This paper presents some empirical results from applying the VALUE Framework to a large ICT company; those relate to eliciting key stakeholders’ tacit knowledge, which is later used as input to a pilot study where these stakeholders employ the Value tool to select features for one of their company’s chief products. The data on decisions obtained from this pilot study is later applied to a detailed example on building a value estimation BN model for company A. We detail a framework—VALUE framework—to be used to help companies improve their value-based decisions and to go a step further and also estimate the overall value of each decision. © 2017 The Author(s)

  • 267.
    Mendes, Emilia
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Vaz, Veronica Taquete
    UFRJ Fed Univ Rio De Janeiro, POB 68511, Rio De Janeiro, Brazil..
    Muradas, Fernando
    Naval Syst Anal Ctr, BR-20091000 San Diego, CA, Brazil..
    An Expert-Based Requirements Effort Estimation Model Using Bayesian Networks2016Ingår i: SOFTWARE QUALITY: THE FUTURE OF SYSTEMS- AND SOFTWARE DEVELOPMENT, 2016, s. 79-93Konferensbidrag (Refereegranskat)
    Abstract [en]

    [Motivation]: There are numerous software companies worldwide that split the software development life cycle into at least two separate projects an initial project where a requirements specification document is prepared; and a follow-up project where the previously prepared requirements document is used as input to developing a software application. These follow-up projects can also be delegated to a third party, as occurs in numerous global software development scenarios. Effort estimation is one of the cornerstones of any type of project management; however, a systematic literature review on requirements effort estimation found hardly any empirical study investigating this topic. [Objective]: The goal of this paper is to describe an industrial case study where an expert-based requirements effort estimation model was built and validated for the Brazilian Navy. [Method]: A knowledge engineering of Bayesian networks process was employed to build the requirements effort estimation model. [Results]: The expert-based requirements effort estimation model was built with the participation of seven software requirements analysts and project managers, leading to 28 prediction factors and 30+ relationships. The model was validated based on real data from 11 large requirements specification projects. The model was incorporated into the Brazilian navy's quality assurance process to be used by their software requirements analysts and managers. [Conclusion]: This paper details a case study where an expert-based requirements effort estimation model based solely on knowledge from requirements analysts and project managers was successfully built to help the Brazilian Navy estimate the requirements effort for their projects.

  • 268.
    Mendes, Emilia
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik. Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för programvaruteknik.
    Viana, Davi
    Univ Fed Maranhao, BRA.
    Vishnubhotla, Sai Datta
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Lundberg, Lars
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Realising Individual and Team Capability in Agile Software Development: A Qualitative Investigation2018Ingår i: Proceedings - 44th Euromicro Conference on Software Engineering and Advanced Applications, SEAA 2018 / [ed] Bures, T Angelis, L, IEEE , 2018, s. 183-190Konferensbidrag (Refereegranskat)
    Abstract [en]

    Several studies have shown that both individual and team capability can affect software development performance and project success; a deeper understating of such phenomena is crucial within the context of Agile Software Development (ASD), given that its workforce is a key source of agility. This paper contributes towards such understanding by means of a case study that uses data from 14 interviews carried out at a large telecommunications company, within the context of a mobile money transfer system developed in Sweden and India, to identify individual and team capability measures used to form productive teams. Our results identified 10 individual and five team capability measures, of which, respectively, five and four have not been previously characterised by a systematic literature review (SLR) on this same topic. Such review aggregated evidence for a total of 133 individual and 28 team capability measures. Further work entails extending our findings via interviewing other software/software-intensive industries practicing ASD.

  • 269.
    Mendes, Emilia
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik. Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för programvaruteknik.
    Winkler, Dietmar
    Technische Universitat Wien, AUT.
    Special issue on “software quality in software-intensive systems”2018Ingår i: Software quality journal, ISSN 0963-9314, E-ISSN 1573-1367, Vol. 26, nr 2, s. 657-660Artikel i tidskrift (Refereegranskat)
  • 270. Minku, Leandro
    et al.
    Sarro, Federica
    Mendes, Emilia
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Ferrucci, Filomena
    How to Make Best Use of Cross-Company Data for Web Effort Estimation?2015Ingår i: 2015 ACM/IEEE INTERNATIONAL SYMPOSIUM ON EMPIRICAL SOFTWARE ENGINEERING AND MEASUREMENT (ESEM), 2015, s. 172-181Konferensbidrag (Refereegranskat)
    Abstract [en]

    [Context]: The numerous challenges that can hinder software companies from gathering their own data have motivated over the past 15 years research on the use of cross-company (CC) datasets for software effort prediction. Part of this research focused on Web effort prediction, given the large increase worldwide in the development of Web applications. Some of these studies indicate that it may be possible to achieve better performance using CC models if some strategy to make the CC data more similar to the within-company (WC) data is adopted. [Goal]: This study investigates the use of a recently proposed approach called Dycom to assess to what extent Web effort predictions obtained using CC datasets are effective in relation to the predictions obtained using WC data when explicitly mapping the CC models to the WC context. [Method]: Data on 125 Web projects from eight different companies part of the Tukutuku database were used to build prediction models. We benchmarked these models against baseline models (mean and median effort) and a WC base learner that does not benefit of the mapping. We also compared Dycom against a competitive CC approach from the literature (NN-filtering). We report a company-by-company analysis. [Results]: Dycom usually managed to achieve similar or better performance than a WC model while using only half of the WC training data. These results are also an improvement over previous studies that investigated the use of different strategies to adapt CC models to the WC data for Web effort estimation. [Conclusions]: We conclude that the use of Dycom for Web effort prediction is quite promising and in general supports previous results when applying Dycom to conventional software datasets.

  • 271.
    Mohanty, Biswajeet
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Impact of Cassandra Compaction on Dockerized Cassandra’s performance: Using Size Tiered Compaction Strategy2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Context. Cassandra is a NoSQL Database which handles large amount of data simultaneously and provides high availability for the data present. Compaction in Cassandra is a process of removing stale data and making data more available to the user. This thesis focusses on analyzing the impact of Cassandra compaction on Cassandra’s performance when running inside a Docker container.

    Objectives. In this thesis, we investigate the impact of Cassandra compaction on the database performance when it is used within a Docker based container platform. We further fine tune Cassandra’s compaction settings to arrive at a sub-optimal scenario which maximizes its performance while operating within a Docker.

    Methods. Literature review is performed to enlist different compaction related metrics and compaction related parameters which have an effect on Cassandra’s performance. Further, Experiments are conducted using different sets of mixed workload to estimate the impact of compaction over database performance when used within a Docker. Once these experiments are conducted, we modify compaction settings while operating under a write heavy workload and access database performance in each of these scenarios to identify a sub-optimal value of parameter for maximum database performance. Finally, we use these sub-optimal parameters to perform an experiment and access the database performance.

    Results. The Cassandra and Operating System related parameters and metrics which affect the Cassandra compaction are listed and their effect on Cassandra’s performance has been tested using some experiments. Based on these experiments, few sub-optimum values are proposed for the listed metrics.

    Conclusions. It can be concluded that, for better performance of Dockerized Cassandra, the proposed values for each of the parameters in the results (i.e. 5120 for Memtable_heap_size_in_mb, 24 for concurrent_compactors, 16 for compaction_throughput_mb_per_sec, 6 for Memtable_flush_writers and 0.14 for Memtable_cleaup _threshold) can be chosen separately but not the union of those proposed values (confirmed from the experiment performed). Also the metrics and parameters affecting Cassandra performance are listed in this thesis. 

  • 272.
    Molléri, Jefferson Seide
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för programvaruteknik.
    Felderer, Michael
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för programvaruteknik.
    Mendes, Emilia
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik. Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för programvaruteknik.
    Petersen, Kai
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för programvaruteknik.
    Reasoning about Research Quality Alignment in Software EngineeringIngår i: Journal of Systems and Software, ISSN 0164-1212, E-ISSN 1873-1228Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Context: Research quality is intended to assess the design and reporting of studies. It comprises a series of concepts such as methodological rigor, practical relevance, and conformance to ethical standards. Depending on the perspective, different views of importance are given to the conceptual dimensions of research quality.

    Objective: We aim to better understand what constitutes research quality from the perspective of the empirical software engineering community. In particular, we intend to assess the level of alignment between researchers with regard to a conceptual model of research quality.

    Method: We conducted a mixed methods approach comprising an internal case study and a complementary focus group. We carried out a hierarchical voting prioritization based on the conceptual model to collect relative values for importance. In the focus group, we also moderate discussions with experts to address potential misalignment.

    Results: We provide levels of alignment with regard to the importance of quality dimensions in the view of the participants. Moreover, the conceptual model fairly expresses the quality of research but has limitations with regards the structure and description of its components.

    Conclusion: Based on the results, we revised the conceptual model and provided an updated version adjusted to the context of empirical software engineering research. We also discussed how to assess quality alignment in research using our approach, and how to use the revised model of quality to characterize an assessment instrument.

  • 273.
    Molléri, Jefferson Seide
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för programvaruteknik.
    Mendes, Emilia
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik. Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för programvaruteknik.
    Petersen, Kai
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för programvaruteknik.
    Felderer, Michael
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för programvaruteknik.
    Aligning the Views of Research Quality in Empirical Software EngineeringIngår i: ACM Transactions on Software Engineering and Methodology, ISSN 1049-331X, E-ISSN 1557-7392Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Context: Research quality is intended to assess the design and reporting of studies. It comprises a series of concepts such as methodological rigor, practical relevance, and conformance to ethical standards. Depending on the perspective, different views of importance are given to the conceptual dimensions of research quality.

    Objective: We intend to assess the level of alignment between researchers with regard to a conceptual model of research quality. This includes aligning the definition of research quality and reasoning on the relative importance of quality characteristics.

    Method: We conducted a mixed methods approach comprising an internal case study and a complementary focus group. We carried out a hierarchical voting prioritization based on the conceptual model to collect relative values for importance. In the focus group, we also moderate discussions with experts to address potential misalignment.

    Results: The alignment at the research group level was higher compared to that at community level. Moreover, the interdisciplinary conceptual quality model was seeing to express fairly the quality of research, but presented limitations regarding its structure and components' description, which resulted in an updated model. 

    Conclusion: The interdisciplinary model used was suitable for the software engineering context. The process used for reflecting on the alignment of quality with respect to definitions and priorities was working well. 

  • 274.
    Molléri, Jefferson Seide
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för programvaruteknik.
    Petersen, Kai
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för programvaruteknik.
    Mendes, Emilia
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik. Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för programvaruteknik.
    An Empirically Evaluated Checklist for Surveys in Software EngineeringIngår i: Information and Software Technology, ISSN 0950-5849, E-ISSN 1873-6025Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Context: Over the past decade Software Engineering research has seen a steady increase in survey-based studies, and there are several guidelines providing support for those willing to carry out surveys. The need for auditing survey research has been raised in the literature. Checklists have been used to assess different types of empirical studies, such as experiments and case studies.

    Objective: This paper proposes a checklist to support the design and assessment of survey-based research in software engineering grounded in existing guidelines for survey research. We further evaluated the checklist in the research practice context.

    Method: To construct the checklist, we systematically aggregated knowledge from 12 methodological studies supporting survey-based research in software engineering. We identified the key stages of the survey process and its recommended practices through thematic analysis and vote counting. To improve our initially designed checklist we evaluated it using a mixed evaluation approach involving experienced researchers.

    Results: The evaluation provided insights regarding the limitations of the checklist in relation to its understanding and objectivity. In particular, 19 of the 38 checklist items were improved according to the feedback received from its evaluation. Finally, a discussion on how to use the checklist and what its implications are for research practice is also provided.

    Conclusion: The proposed checklist is an instrument suitable for auditing survey reports as well as a support tool to guide ongoing research with regard to the survey design process.

  • 275.
    Molléri, Jefferson Seide
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för programvaruteknik.
    Petersen, Kai
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för programvaruteknik.
    Mendes, Emilia
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik. Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för programvaruteknik.
    CERSE - Catalog for empirical research in software engineering: A Systematic mapping study2019Ingår i: Information and Software Technology, ISSN 0950-5849, E-ISSN 1873-6025, Vol. 105, s. 117-149Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Context Empirical research in software engineering contributes towards developing scientific knowledge in this field, which in turn is relevant to inform decision-making in industry. A number of empirical studies have been carried out to date in software engineering, and the need for guidelines for conducting and evaluating such research has been stressed. Objective: The main goal of this mapping study is to identify and summarize the body of knowledge on research guidelines, assessment instruments and knowledge organization systems on how to conduct and evaluate empirical research in software engineering. Method: A systematic mapping study employing manual search and snowballing techniques was carried out to identify the suitable papers. To build up the catalog, we extracted and categorized information provided by the identified papers. Results: The mapping study comprises a list of 341 methodological papers, classified according to research methods, research phases covered, and type of instrument provided. Later, we derived a brief explanatory review of the instruments provided for each of the research methods. Conclusion: We provide: an aggregated body of knowledge on the state of the art relating to guidelines, assessment instruments and knowledge organization systems for carrying out empirical software engineering research; an exemplary usage scenario that can be used to guide those carrying out such studies is also provided. Finally, we discuss the catalog's implications for research practice and the needs for further research. © 2018 Elsevier B.V.

  • 276.
    Molléri, Jefferson Seide
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för programvaruteknik.
    Petersen, Kai
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för programvaruteknik.
    Mendes, Emilia
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik. Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för programvaruteknik.
    Towards understanding the relation between citations and research quality in software engineering studies2018Ingår i: Scientometrics, ISSN 0138-9130, E-ISSN 1588-2861Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The importance of achieving high quality in research practice has been highlighted in different disciplines. At the same time, citations are utilized to measure the impact of academic researchers and institutions. One open question is whether the quality in the reporting of research is related to scientific impact, which would be desired. In this exploratory study we aim to: (1) Investigate how consistently a scoring rubric for rigor and relevance has been used to assess research quality of software engineering studies; (2) Explore the relationship between rigor, relevance and citation count. Through backward snowball sampling we identified 718 primary studies assessed through the scoring rubric. We utilized cluster analysis and conditional inference tree to explore the relationship between quality in the reporting of research (represented by rigor and relevance) and scientiometrics (represented by normalized citations). The results show that only rigor is related to studies’ normalized citations. Besides that, confounding factors are likely to influence the number of citations. The results also suggest that the scoring rubric is not applied the same way by all studies, and one of the likely reasons is because it was found to be too abstract and in need to be further refined. Our findings could be used as a basis to further understand the relation between the quality in the reporting of research and scientific impact, and foster new discussions on how to fairly acknowledge studies for performing well with respect to the emphasized research quality. Furthermore, we highlighted the need to further improve the scoring rubric. © 2018, The Author(s).

  • 277.
    Moraes, Ana Louiza Dallora
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Eivazzadeh, Shahryar
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för hälsa.
    Mendes, Emilia
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Sanmartin Berglund, Johan
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för hälsa.
    Anderberg, Peter
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för hälsa.
    Prognosis of Dementia Employing Machine Learning and Microsimulation Techniques: A Systematic Literature Review2016Ingår i: Procedia Computer Science / [ed] Martinho R.,Rijo R.,Cruz-Cunha M.M.,Bjorn-Andersen N.,Quintela Varajao J.E., Elsevier, 2016, Vol. 100, s. 480-488Konferensbidrag (Refereegranskat)
    Abstract [en]

    OBJECTIVE: The objective of this paper is to investigate the goals and variables employed in the machine learning and microsimulation studies for the prognosis of dementia. METHOD: According to preset protocols, the Pubmed, Socups and Web of Science databases were searched to find studies that matched the defined inclusion/exclusion criteria, and then its references were checked for new studies. A quality checklist assessed the selected studies, and removed the low quality ones. The remaining ones (included set) had their data extracted and summarized. RESULTS: The summary of the data of the 37 included studies showed that the most common goal of the selected studies was the prediction of the conversion from mild cognitive impairment to Alzheimer's Disease, for studies that used machine learning, and cost estimation for the microsimulation ones. About the variables, neuroimaging was the most frequent used. CONCLUSIONS: The systematic literature review showed clear trends in prognosis of dementia research in what concerns machine learning techniques and microsimulation.

  • 278.
    Moraes, Ana Luiza Dallora
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Supplementary Material of: “Prognosis of dementia with machine learning and microssimulation techniques: a systematic literature review”.2016Övrigt (Övrigt vetenskapligt)
    Abstract [en]

     This document contains the supplementary material regarding the systematic literature review entitled: “Prognosis of dementia with machine learning and microssimulation techniques: a systematic literature review”.

  • 279.
    Moraes, Ana Luiza Dallora
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Systematic Literature Review Protocol:  Machine Learning and Microsimulation Techniques on the Prognosis of Dementia: A Systematic Literature Review2016Övrigt (Övrigt vetenskapligt)
    Abstract [en]

     This document contains the protocol followed to conduct the systematic literature review entitled: “Machine Learning and Microsimulation Techniques on the Prognosis of Dementia: A Systematic Literature Review”.

  • 280.
    Moraes, Ana Luiza Dallora
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Eivazzadeh, Shahryar
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för hälsa.
    Mendes, Emilia
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik. Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för programvaruteknik.
    Berglund, Johan
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för hälsa.
    Anderberg, Peter
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för hälsa.
    Machine learning and microsimulation techniques on the prognosis of dementia: A systematic literature review2017Ingår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 12, nr 6, artikel-id e0179804Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Background Dementia is a complex disorder characterized by poor outcomes for the patients and high costs of care. After decades of research little is known about its mechanisms. Having prognostic estimates about dementia can help researchers, patients and public entities in dealing with this disorder. Thus, health data, machine learning and microsimulation techniques could be employed in developing prognostic estimates for dementia. Objective The goal of this paper is to present evidence on the state of the art of studies investigating and the prognosis of dementia using machine learning and microsimulation techniques. Method To achieve our goal we carried out a systematic literature review, in which three large databases -Pubmed, Socups and Web of Science were searched to select studies that employed machine learning or microsimulation techniques for the prognosis of dementia. A single backward snowballing was done to identify further studies. A quality checklist was also employed to assess the quality of the evidence presented by the selected studies, and low quality studies were removed. Finally, data from the final set of studies were extracted in summary tables. Results In total 37 papers were included. The data summary results showed that the current research is focused on the investigation of the patients with mild cognitive impairment that will evolve to Alzheimer's disease, using machine learning techniques. Microsimulation studies were concerned with cost estimation and had a populational focus. Neuroimaging was the most commonly used variable. Conclusions Prediction of conversion from MCI to AD is the dominant theme in the selected studies. Most studies used ML techniques on Neuroimaging data. Only a few data sources have been recruited by most studies and the ADNI database is the one most commonly used. Only two studies have investigated the prediction of epidemiological aspects of Dementia using either ML or MS techniques. Finally, care should be taken when interpreting the reported accuracy of ML techniques, given studies' different contexts. © 2017 Dallora et al.This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

  • 281.
    Mourao, Erica
    et al.
    Fluminense Fed Univ, BRA.
    Kalinowski, Marcos
    Pontifical Catholic Univ Rio de Janeiro PUC Rio, BRA.
    Murta, Leonardo
    Fluminense Fed Univ, BRA.
    Mendes, Emilia
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik. Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för programvaruteknik.
    Wohlin, Claes
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för programvaruteknik. Blekinge Inst Technol, Karlskrona, Sweden..
    Investigating the Use of a Hybrid Search Strategy for Systematic Reviews2017Ingår i: 11TH ACM/IEEE INTERNATIONAL SYMPOSIUM ON EMPIRICAL SOFTWARE ENGINEERING AND MEASUREMENT (ESEM 2017), IEEE , 2017, s. 193-198Konferensbidrag (Refereegranskat)
    Abstract [en]

    [Background] Systematic Literature Reviews (SLRs) are one of the important pillars when employing an evidence-based paradigm in Software Engineering. To date most SLRs have been conducted using a search strategy involving several digital libraries. However, significant issues have been reported for digital libraries and applying such search strategy requires substantial effort. On the other hand, snowballing has recently arisen as a potentially more efficient alternative or complementary solution. Nevertheless, it requires a relevant seed set of papers. [Aims] This paper proposes and evaluates a hybrid search strategy combining searching in a specific digital library (Scopus) with backward and forward snowballing. [Method] The proposed hybrid strategy was applied to two previously published SLRs that adopted database searches. We investigate whether it is able to retrieve the same included papers with lower effort in terms of the number of analysed papers. The two selected SLRs relate respectively to elicitation techniques (not confined to Software Engineering (SE)) and to a specific SE topic on cost estimation. [Results] Our results provide preliminary support for the proposed hybrid search strategy as being suitable for SLRs investigating a specific research topic within the SE domain. Furthermore, it helps overcoming existing issues with using digital libraries in SE. [Conclusions] The hybrid search strategy provides competitive results, similar to using several digital libraries. However, further investigation is needed to evaluate the hybrid search strategy.

  • 282.
    Munir, Sameer
    et al.
    Univ Faisalabad, Sch Elect Engn, Faisalabad, Pakistan..
    Khan, Faraz
    Univ Faisalabad, Sch Elect Engn, Faisalabad, Pakistan..
    Riaz, Muhammad Atif
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    An Instance Based Schema Matching Between Opaque Database Schemas2014Ingår i: 2014 4TH INTERNATIONAL CONFERENCE ON ENGINEERING TECHNOLOGY AND TECHNOPRENEURSHIP (ICE2T), IEEE Computer Society, 2014, s. 177-182Konferensbidrag (Refereegranskat)
    Abstract [en]

    Schema matching is always needed amoung schemas of relational datasets in database integration applications. Heterogeneous database integration involves a significant role of schema matching Most of the previous solution to schema matching problem based on the identification of similarity between the columns names or by recognizing common domains in the data stored in the schemas. These approaches are not applicable on those datasets with unaligned schemas where the name of the columns in the schemas and the data in the columns are opaque. In this paper we proposed an instance based approach to find the matching between the schemas of heterogeneous datasets that share a common primary keys but it is unknown which columns are primary keys. The proposed approach consists of two main phases Row Similarity and Attribute Similarity. In the row similarity phase proposed approach determines all the pairs of rows among datasets that are representing same real world entity based on the same primary keys values. In attribute similarity phase, by comparing the data values within those similar pairs of rows our approach able to find the corresponding attributes. Different experiments are performed to validate proposed approach by using real world datasets. The results demonstrated the viability of the proposed approach.

  • 283.
    Muñoz, Álvaro Aranda
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Comparing 3D interfaces of virtual factories: an iconic 3D interface against an abstract 3D visualisation2014Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [sv]

    This thesis explores and compares two prototypes that present a visualisation of the process state of a factory. The first prototype presents a generic interface in which primitive 3D shapes convey the information of the factory status. The second prototype is complemented with specific and iconic 3D models of the factory that help the users associating the conveyed information to the factory flow. The motivation behind this dissertation is that the type of generic interface presented can lead to more reusable interfaces in the future.

  • 284.
    Márquez, Ángela Marqués
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    A Machine Learning Approach for Studying Linked Residential Burglaries2014Självständigt arbete på avancerad nivå (magisterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    Context. Multiple studies demonstrate that most of the residential burglaries are committed by a few offenders. Statistics collected by the Swedish National Council for Crime Prevention show that the number of residential burglary varies from year to year. But this value normally increases. Besides, around half of all reported burglaries occur in big cities and only some burglaries occur in sparsely-populated areas. Thus, law enforcement agencies need to study possible linked residential burglaries for their investigations. Linking crime-reports is a difficult task and currently there is not a systematic way to do it. Objectives. This study presents an analysis of the different features of the collected residential burglaries by the law enforcement in Sweden. The objective is to study the possibility of linking crimes depending on these features. The characteristics used are residential features, modus operandi, victim features, goods stolen, difference of days and distance between crimes. Methods. To reach the objectives, quasi experiment and repeated measures are used. To obtain the distance between crimes, routes using Google maps are used. Different cluster methods are investigated in order to obtain the best cluster solution for linking residential burglaries. In addition, the study compares different algorithms in order to identify which algorithm offers the best performance in linking crimes. Results. Clustering quality is measured using different methods, Rule of Thumb, the Elbow method and Silhouette. To evaluate these measurements, ANOVA, Tukey and Fisher’s test are used. Silhouette presents the greatest quality level compared to other methods. Other clustering algorithms present similar average Silhouette width, and therefore, similar quality clustering. Results also show that distance, days and residential features are the most important features to link crimes. Conclusions. The clustering suggestion denotes that it is possible to reduce the amount of burglaries cases. This reduction is done by finding linked residential burglaries. Having done the clustering, the results have to be investigated by law enforcement.

  • 285.
    Mårtensson, Anders
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Flying Penguins: Building and Evaluating the Viability of a Linux-based Drone2016Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Traditional quadcopter flight controllers use microcontrollers to run the code that keeps the drone in the air, and when more processing power or versatility is needed the same microcontrollers are used in tandem with Linux-based single-board computers. It would be cheaper and reduce complexity if the single-board computer could entirely replace the microcontrollers.

    We investigate whether it is possible to run a quadcopter using a Linux single-board computer as the flight controller, with no microcontrollers and otherwise the same hardware as used in hobby-grade quadcopters. We attempt to find out what the potential issues are and how to get around or mitigate them.

    To test it, a quadcopter will be built from hobby parts and the flight control software to be run on the flight controller will be developed.

    More specifically, the pulse-width modulation signals to the motor speed controllers are checked for stability and various methods of acquiring the radio control input in the form of pulse-width modulation signals are evaluated. The speed at which the flight control software is running is measured under different circumstances—with and without load and with and without mitigative measures active.

    We conclude that it was not possible to run a quadcopter using only the chosen Linux SBC as flight controller. The reason was because we could not accurately measure the radio control input, although there may be other additional issues. We did find that CPU time did not seem to be an issue even when an artificial stress was placed on the system, despite not being a real time system, and even less of an issue when the mitigation techniques discussed were applied.

  • 286.
    nagadevara, venkatesh
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Evaluation of Intrusion Detection Systems under Denial of Service Attack in virtual  Environment2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Context. The intrusion detection systems are being widely used for detecting the malicious

    traffic in many industries and they use a variety of technologies. Each IDs had different

    architecture and are deployed for detecting malicious activity. Intrusion detection system has

    a different set of rules which can defined based on requirement. Therefore, choosing intrusion

    detection system for and the appropriate environment is not an easy task.

    Objectives. The goal of this research is to evaluate three most used open source intrusion

    detection systems in terms of performance. And we give details about different types of attacks

    that can be detected using intrusion detection system. The tools that we select are Snort,

    Suricata, OSSEC.

    Methods. The experiment is conducted using TCP, SCAN, ICMP, FTP attack. Each

    experiment was run in different traffic rates under normal and malicious traffics all rule are

    active. All these tests are conducted in a virtual environment.

    Results. We can calculate the performance of IDS by using CPU usage, memory usage, packet

    loss and a number of alerts generated. These results are calculated for both normal and

    malicious traffic.

    Conclusions. We conclude that results vary in different IDS for different traffic rates.

    Specially snort showed better performance in alerts identification and OSSEC in the

    performance of IDS. These results indicated that alerts are low when the traffic rates high are

    which indicates this is due to the packet loss. Overall OSSEC provides better performance.

    And Snort provides better performance and accuracy for alert detection.

  • 287.
    Nardelli, Matteo
    et al.
    Università degli Studi di Roma Tor Vergata, ITA.
    Cardellini, Valeria
    Università degli Studi di Roma Tor Vergata, ITA.
    Casalicchio, Emiliano
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Multi-Level Elastic Deployment of Containerized Applications in Geo-Distributed Environments2018Ingår i: Proceedings - 2018 IEEE 6th International Conference on Future Internet of Things and Cloud, FiCloud 2018, Institute of Electrical and Electronics Engineers Inc. , 2018, s. 1-8Konferensbidrag (Refereegranskat)
    Abstract [en]

    Containers are increasingly adopted, because they simplify the deployment and management of applications. Moreover, the ever increasing presence of IoT devices and Fog computing resources calls for the development of new approaches for decentralizing the application execution, so to improve the application performance. Although several solutions for orchestrating containers exist, the most of them does not efficiently exploit the characteristics of the emerging computing environment. In this paper, we propose Adaptive Container Deployment (ACD), a general model of the deployment and adaptation of containerized applications, expressed as an Integer Linear Programming problem. Besides acquiring and releasing geo-distributed computing resources, ACD can optimize multiple run-time deployment goals, by exploiting horizontal and vertical elasticity of containers. We show the flexibility of the ACD model and, using it as benchmark, we evaluate the behavior of several greedy heuristics for determining the container deployment. © 2018 IEEE.

  • 288.
    Navarro, Diego
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Improving Player Performance by Developing Gaze Aware Games2014Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    Context. Eye tracking technology has been applied to video games, mainly, as an offline analysis tool or as an input for game control. Nevertheless, eye tracking systems applied to video games is a topic considered to be on an infant state that requires further development. The following study explore a different approach in how eye tracking systems can be used for video game interaction. Objectives. By implementing a gaze based interaction technique, a gaze aware space shooting game will be developed in order to provide in-game assistance that could improve player's performance. Method. With the help of a Tobii REX eye traking system, a set of 26 volunteers played two video games in a controlled environment. Both of the games had the same mechanics and elements, but only one of them implemented the gaze based interaction technique. The player performance was calculated in terms of the time needed by the players to finish each of the games. A statistic significance analysis was done in order to determine if the testing data provided sufficient evidence to conclude a performance improvement. Results. The results showed a reduction on the time needed to finish the game on the gaze aware prototype, having an average time difference of 74.03 seconds and overcoming a confidence level of 99.9\% when submitting the testing data to a paired t-Test. Also, the majority of the players chose the gaze aware game as the most enjoyable, in terms of their personal preferences. Conclusions. The testing results provided sufficient evidence to conclude that the gaze aware game improved the performance of all of the selected participants. This study provides a starting point for further development of eye tracking systems as a task assisting method on video game interaction.

  • 289.
    Nejman, Dawid
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Automation of data processing in the network of geospatial web services2013Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    Geoinformatics field of science becomes more and more important nowadays. This is not only because it is crucial for industry, but it also plays more important role in consumer electronics than ever before. The ongoing demand for complex solutions gave a rise to SOA1 architecture in enterprise and geographical field. The topic that is currently being studied is interoperability between different geospatial services. This paper makes a proposal for a master thesis that tries to add another way of chaining different geospatial services. It describes the current state of knowledge, possible research gap and then goes into the details on design and execution part. Final stage is the summary of expected outcomes. The result of this proposal is a clearly defined need for a research in the outlined area of knowledge.

  • 290.
    Nermansson, Niklas
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Evaluating how Non-player Character personalities affect the game experience in Future Happiness Challenge2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Artificiell intelligens (AI) används i många spel och det är vanligt att datorstyrda karaktärer (Non-Player Characters) föreställer människor. För att göra dessa karaktärer trovärdiga och ge känslan av att leva så behöver deras beteenden göras så mänskliga som möjligt. Tre egenskaper som ofta används för att göra karaktärerna mänskliga är behov, såsom att äta eller sova, sociala relationer och personligheter. Målet med det här arbetet var att skapa en AI med olika personligheter som karaktärerna kan ha i spelet Future Happiness Challenge (FHC) och jämföra dessa personligheter samt försöka ta reda på om personligheter ökar spelupplevelsen. Tre olika personligheter implementerades; självisk, osjälvisk och balanserad. Dessa valdes då FHC ger spelaren möjligheten att spela antingen själviskt eller osjälviskt. Det kan spelas som ett lag eller som en egoist som inte bryr sig om de andra. Denna rapport försöker svara på frågan om spelaren föredrar en osjälvisk karaktär över en självisk i ett spel där denna möjlighet finns. Dessa extrema personligheter jämförs också med en balanserad. Under utvecklingen av AIn och personligheterna användes tekniken Behaviour Tree (BT) och större delen av implementationen är presenterad i detta arbete för att ge ett exempel på hur personligheter kan implementeras i ett spel som FHC. Resultaten föreslår att personligheter ökar spelupplevelsen och ett intressant samband kan ses mellan spelarnas preferens av NPC och spelarnas personligheter i FHC. Istället för att alltid föredra en självisk eller osjälvisk NPC, verkar spelarna föredra den NPC som har en personlighet lik sin egen i spelet.

  • 291. Nia, Roozbeh
    et al.
    Erlandsson, Fredrik
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Bhattacharyya, Prantik
    Rahman, Mohammad Rezaur
    Johnson, Henric
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Wu, S. Felix
    SIN: A Platform to Make Interactions in Social Networks Accessible2012Ingår i: Proceedings of the 2012 ASE International Conference on Social Information, IEEE conference proceedings, 2012, s. 205-214Konferensbidrag (Refereegranskat)
    Abstract [en]

    Online Social Networks (OSNs) are popular platforms for interaction, communication and collaboration between friends. In this paper we develop and present a new platform to make interactions in OSNs accessible. Most of today's social networks, including Facebook, Twitter, and Google+ provide support for third party applications to use their social network graph and content. Such applications are strongly dependent on the set of software tools and libraries provided by the OSNs for their own development and growth. For example, third party companies like CNN provide recommendation materials based on user interactions and user's relationship graph. One of the limitations with this graph (or APIs) is the segregation from the shared content. We believe, and present in this paper, that the content shared and the actions taken on the content, creates a Social Interaction Network (SIN). As such, we extend Facebook's current API in order to allow applications to retrieve a weighted graph instead of Facebooks unweighted graph. Finally, we evaluate the proposed platform based on completeness and speed of the crawled results from selected community pages. We also give a few example uses of our API on how it can be used by third party applications.

  • 292. Nia, Roozbeh
    et al.
    Erlandsson, Fredrik
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Johnson, Henric
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Wu, S. Felix
    Leveraging Social Interactions to Suggest Friends2013Ingår i: IEEE 33rd International Conference on Distributed Computing Systems Workshops (ICDCSW), IEEE Computer Society, 2013, s. 386-391Konferensbidrag (Refereegranskat)
    Abstract [en]

    Over the past decade Online Social Networks (OSNs) have made it possible for people to stay in touch with people they already know in real life; although, they have not been able to allow users to grow their personal social network. Existence of many successful dating and friend finder applications online today show the need and importance of such applications. In this paper, we describe an application that leverages social interactions in order to suggest people to users that they may find interesting. We allow users to expand their personal social network using their own interactions with other users on public pages and groups in OSNs. We finally evaluate our application by selecting a random set of users and asking them for their honest opinion.

  • 293.
    Nieznanska, Marta
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Experimental evaluation of the smartphone as a remote game controller for PC racing games2014Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    Context. Both smartphones and PC games are increasingly commonplace nowadays. There are more and more people who own smartphones and – at the same time – like playing video games. Since the smartphones are becoming widely affordable and offer more and more advanced features (such as multi-touch screens, a variety of sensors, vibration feedback, and others), it is justifiable to study their potential in new application areas. The aim of this thesis is to adapt the smartphone for the use as a game controller in PC racing games and evaluate this solution taking into account such aspects as race results and user experience. Objectives. To this end, two applications were developed - a game controller application for Android‑based smartphones (i.e. the client application) and a PC server application. The applications support a selected open-source PC racing game called SuperTuxKart. The evaluation of the smartphone encompasses both race results (whether the smartphone enables players to achieve comparable results to the keyboard – a standard game controller) and user experience (whether this game controller may be satisfying to players). Methods. An experiment was conducted where 20 participants controlled the SuperTuxKart game using first the smartphone, and then the keyboard or vice versa. The experiment was followed by a questionnaire-based survey of the user experience. Results. The experiment results indicate that the smartphone may achieve results which are comparable to those achieved by the keyboard. The race times corresponding to the smartphone were somewhat longer than those obtained with the keyboard, but the average relative difference was below 18%. The questionnaire results show that more than half of the participants enjoyed the smartphone more than the keyboard, despite the fact that the smartphone turned out to be a more challenging game controller for many players and did not provide so good control of the racing game as the keyboard. Conclusions. Overall, this study shows that the smartphone has a potential to be a suitable, satisfying and enjoyable controller for PC racing games.

  • 294.
    Nilsson, Adam
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Assessment of the Microsoft Kinect v1 RGB-D Sensor and 3D Object Recognition as a Means of Drift Correction in Head mounted Virtual Reality Systems2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Context. The release of the Oculus Rift Development Kits and other similar hardware has led to something of a resurrection of interest in virtual reality hardware, but such hardware has problems in the form of, for example, drift errors, where the estimated forward direction veers of in an arbitrary direction. These drift errors accumulate over time and can lead to reduced user immersion and a need for the user to continuously calibrate the hardware. Objective. This study aims to investigate the possibility of drift error correction through the use of the Microsoft Kinect v1 RGB-D sensor and 3D object tracking technology. Method. Through the creation of a prototype application that utilizes object recognition to find the Oculus Rift DK1 on the user’s head and calculates its estimated six degrees of freedom, a "real world" forward vector can be produced. This vector’s authenticity can then be evaluated through an experiment that compares it to the forward direction reported by the Oculus Rift DK1. Result. The result is an application that can successfully recognize the Oculus Rift DK1 in a scene and deduce what its forward direction is. Due to what is suspected to be hardware malfunctions in the Oculus Rift DK1 the test results are not satisfactory, although observations still indicate that the application would perform within the set boundaries should the malfunctions not be present. Conclusion. Even though the experiment’s results are not ideal, the application shows promise and should be studied further with more accurate measuring equipment.

  • 295.
    Nilsson, Alexander
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Andersson, Marcus
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Axelsson, Stefan
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Key-hiding on the ARM platform2014Ingår i: Digital Investigation. The International Journal of Digital Forensics and Incident Response, ISSN 1742-2876, E-ISSN 1873-202X, Vol. 11, nr Supplement 1, s. S63-S67Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To combat the problem of encryption key recovery from main memory using cold boot-attacks, various solutions has been suggested, but most of these have been implemented on the x86 architecture, which is not prevalent in the smartphone market, where instead ARM dominates. One existing solution does exist for the ARM architecture but it is limited to key sizes of 128 bits due to not being able to utilise the full width of the CPU registers used for key storage. We developed a test-implementation of CPU-bound key storage with 256-bit capacity, without using more hardware resources than the previous solution. We also show that access to the key can be restricted for programs executing outside the kernel space.

  • 296.
    Nilsson, Eric
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Paravirtualizing OpenGL ES in Simics2014Studentuppsats (Examensarbete)
    Abstract [sv]

    Arkitekturella simulatorer förser utvecklare med medel till snabbare utvecklingscykler genom att tillåta utveckling av mjukvara för nya plattformar innan dessa finns tillgängliga. Dessvärre finns det få lösningar för GPU-accelerering i moderna virtuella plattformar; vilket leder till prestandaproblem som kan hämma de fördelar som virtuella plattformar har över exekvering på hårdvara. Denna uppsats angår implementering av grafikaccelerering genom paravirtualisering av OpenGL ES 2.0 i systemsimulatorn Simics. Studien sammanfattar fördelar och nackdelar av paravirtualiserade metoder, med hänsyn till prestandaanalys och jämförelse med Android-emulatorn; som också nyttjar paravirtualisering för att accelerera simulerad grafik. Vi föreslår grafikaccelering genom paravirtualisering m.h.a. magiska instruktioner; vars implementation sammanfattas i uppsatsen. Vidare presenteras tre utvärderingsprov vars syfte är att påfresta nyckelpunkter i den paravirtualiserade lösningen, så som systemlatens och bandbredd i kommunikation mellan simulering och den verkliga världen. Lösningen evalueras även baserat på ett prestandakrävande utvärderingstest. För experimentet, som presenteras i denna uppsats, samlas uppdateringsfrekvens för de grafiska utvärderingstesten och jämförs med exekvering på fyra olika plattformar. Dessa plattformar omfattar ett hårdvaruaccelerat referens-system, paravirtualiserad simulering m.h.a. Android-emulator, mjukvarurastrerad Simics-simulering, och paravirtualiserad Simics-simulering. Uppsatsen fastställer paravirtualisering som en god metod för att uppnå grafikaccelering i virtuella plattformar. Studien påvisar prestandaförbättringar motsvarande 34 gånger jämförelsevis med dess mjukvarurastrerade motpart. Vidare presenterar uppsatsen magiska instruktioner som den primära flaskhalsen i den utvecklade lösningen.

  • 297.
    Nilsson, Eric
    et al.
    Intel Corp., SWE.
    Aarno, Daniel
    Intel Corp., SWE.
    Carstensen, Erik
    Intel Corp., SWE.
    Grahn, Håkan
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Accelerating Graphics in the Simics Full-System Simulator2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    Virtual platforms provide benefits to developers in terms of a more rapid development cycle since development may begin before next-generation hardware is available. However, there is a distinct lack of graphics virtualization in industry-grade virtual platforms, leading to performance issues that may reduce the benefits virtual platforms otherwise have over execution on actual hardware. This paper demonstrates graphics acceleration by the means of paravirtualizing OpenGL ES in the Wind River Simics full-system simulator. We propose a solution for paravirtualized graphics using magic instructions to share memory between target and host systems, and present an implementation utilizing this method. The study illustrates the benefits and drawbacks of paravirtualized graphics acceleration and presents a performance analysis of strengths and weaknesses compared to software rasterization. Additionally, benchmarks are devised to stress key aspects in the solution, such as communication latency and computationally intensive applications. We assess paravirtualization as a viable method to accelerate graphics in system simulators, this reduces frame times up to 34 times compared to that of software rasterization. Furthermore, magic instructions are identified as the primary bottleneck of communication latency in the implementation.

  • 298. Niyizamwiyitira, C.
    et al.
    Lundberg, Lars
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Lennerstad, Håkan
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för matematik och naturvetenskap.
    Utilization-Based Schedulability Test of Real-Time Systems on Virtual Multiprocessors2015Ingår i: 2015 44TH INTERNATIONAL CONFERENCE ON PARALLEL PROCESSING WORKSHOPS, IEEE Computer Society, 2015, Vol. 2015-January, s. 267-276Konferensbidrag (Refereegranskat)
    Abstract [en]

    The number of applications that use virtual systems is growing, and one would like to use this kind of systems also for real-time applications with hard deadlines. Virtual machines with many cores are interesting since the underlying physical infrastructure usually contains many cores. We consider hard real-time tasks that execute on a virtual machine with m cores. Tasks are scheduled globally on the cores using fixed-priority preemptive scheduling. This means that a task can execute on different virtual cores at different instances in time. In order to avoid Dhall’s effect, which may cause task sets with even very low utilization to miss deadlines, we classify tasks into two priority classes, namely heavy and light tasks. Heavy tasks have higher priority than light tasks. For light tasks we use rate monotonic priority assignment. In this paper we propose a utilization-based test that shows if a task set is schedulable or not. If the task set is schedulable the test provides the priority for each task. The input to the test is the task set, the number of cores in the virtual machine (m), a period for the virtual machine with m cores, and the blocking time when a virtual machine does not have access to the underlying hardware in each period. © 2015 IEEE.

  • 299.
    Niyizamwiyitira, Christine
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Performance Aspects of Databases and Virtualized Real-time Applications2018Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Context: High computing system performance depends on the interaction between software and hardware layers in modern computer systems. Two strong trends that effect different layers in computer systems are that single processors are now more or less completely replaced by multiprocessors, which are often organized into clusters, and virtualization of resources. The performance evaluation of different software on such physical and virtualized resources, is the focus of this thesis.

    Objectives: The objectives of this thesis are to investigate the performance evaluation of SQL and No SQL database management systems, namely Cassandra, CouchDB, MongoDB, PostgreSQL, and RethinkDB; and soft real-time application namely, voice-driven web. Scheduling algorithms for resource allocation for hard real-time applications on virtual processor are also investigated.

    Methods: Experiment is used to measure the performance of SQL and No SQL management systems on cluster. It is also used to develop a prototype and predicts processor performance of voice-driven web on multiprocessors. Theoretical methods are used to model and design algorithms to schedule real-time applications on the virtual processor machine. Simulation is used to quantify the performance implications of certain parameter values in our theoretical results and to compare expected performance with theoretical bounds in our schedulability tests.

    Results:The performance of Cassandra, CouchDB, MongoDB, 2

    PostgreSQL, and RethinkDB is evaluated in terms of writing and reading throughput and latencies in cluster computing. For reading throughput, all database systems are horizontally scalable as the cluster’s nodes number increases, however, only Cassandra and couchDB exhibit scalability for data writing. The overall evaluation shows that Cassandra has the most writing scalable throughput as the number of nodes increases with a relative low latency, whereas PostgreSQL has the lowest writing latency, and MongoDB has the lowest reading latency.

    The architectures’ tradeoffs of voice-driven web show that the voice engine should be installed on the server instead of being on the mobile device, and performance evaluations show that speech engine scales with respect to the number of cores in the multiprocessor with and without hyperthreading.

    The thesis presents scheduling techniques for real-time applications that runs in virtual machines which are time sharing the processor. Each virtual machine’s period and execution time that allow real-time applications to meet their deadlines can be defined using these techniques. Simulation results show the impact of the length of different VM periods with respect to overhead. The tradeoffs between resources consumption and period length are also given. Furthermore, a utilization based test for scheduling real-time application on virtual multiprocessor is presented. This test determines if a task set is schedulable or not. If the task set is schedulable the algorithm provides the priority for each task. This algorithm avoids Dhall’s effect, which may cause task sets with even very low utilization to miss deadlines.

    Conclusions: The thesis presented the performance evaluation of reading and writing throughput and latencies for SQL and NoSQL management systems in the cluster computing. The thesis quantifies the tradeoffs of voice-driven web architectures and the performance scalability of the speech engine with respect to number of cores of the multiprocessor. Furthermore, this thesis proposes scheduling algorithms for real-time 3

    application with hard deadline on virtual processors, either as a single core processor or as a multicore processor.

  • 300.
    Niyizamwiyitira, Christine
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Lundberg, Lars
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    “Performance Evaluation of SQL and NoSQL Database Management Systems in a Cluster2017Ingår i: International Journal of Database Management Systems, ISSN 0975-5705, Vol. 9, nr 6, s. 1-24Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In  this  study,  we  evaluate  the  performance  of  SQL  and  NoSQL  database  management  systems  namely; Cassandra, CouchDB, MongoDB, PostgreSQL, and RethinkDB.  We use a cluster of  four  nodes to run the database  systems,  with  external  load  generators.The  evaluation  is  conducted  using  data  from  Telenor Sverige,  a  telecommunication  company  that  operates in  Sweden.  The  experiments  are  conducted  using three  datasets  of  different  sizes.The  write  throughput  and  latency  as  well  as  the  read  throughput  and latency are evaluated for four queries; namely distance query, k-nearest neighbour query, range query, and region  query.  For  write  operations  Cassandra  has  the  highest  throughput  when  multiple  nodes  are  used, whereas  PostgreSQL  has  the  lowest  latency  and  the  highest  throughput  for  a  single  node.  For  read operations  MongoDB  has  the  lowest  latency  for  all  queries.  However,  Cassandra  has  the  highest throughput  for  reads.  The  throughput  decreasesas  the  dataset  size  increases  for  both  write  and  read,  for both  sequential  as  well  as  random  order  access.  However,  this  decrease  is  more  significant  for  random read and write. In this study, we present the experience we had with these different database management systems including setup and configuration complexity.

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