12 1 - 20 of 27
rss atomLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
  • Mukhtar-Landgren, Dalia
    et al.
    Lunds universitet, SWE.
    Berglund Snodgrass, Lina
    Blekinge Institute of Technology, Faculty of Engineering, Department of Spatial Planning.
    Kräver hållbar mobilitet nya roller för den kommunala planeringen?2018In: PLAN, ISSN 0032-0560, no 2-3, p. 93-94Article in journal (Other (popular science, discussion, etc.))
  • Public defence: 2019-01-08 14:00 Karlskrona
    Minhas, Nasir Mehmood
    Blekinge Institute of Technology, Faculty of Computing, Department of Software Engineering.
    Regression Testing Challenges and Solutions: An Industry-Academia Perspective2019Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Background: Software quality assurance (QA) is an essential activity in the software development lifecycle. Among the different QA activities, regression testing is a challenging task for large-scale software development. Regression testing is a well-researched area, and a large number of techniques have been proposed to fulfill the needs of industry. Despite the extensive research, the adoption of proposed regression testing techniques in the industry is limited. Studies show that there is a visible gap between research and practice.

    Objective: This work aims at reducing the gap between industry and academia in regression testing. To fulfill this aim we have the following objectives:

    1) Understanding the practitioners' goals regarding regression testing.

    2) Understanding the current state of regression testing practice and challenges in the industry.

    3) Investigating the testing research applicable in an industrial context.

    Method: We conducted multiple studies using different methods.

    To explore the industry perspective on regression testing we used focus group and interview-based studies. To explore solutions from the literature, we used the systematic literature review and systematic mapping study.

    Results: This thesis presents the practitioners' specific regression testing goals. The identified goals are confidence, controlled fault slippage, effectiveness, efficiency, and customer satisfaction. The challenges identified in the thesis are of two categories, 1) management related challenges and 2) technical challenges. Technical challenges relate to test suite maintenance, test case selection, test case prioritization, evaluation of regression testing.

    We have mapped 26 empirically evaluated regression testing techniques to the context, effect, and information taxonomies, and provided a guide to the practitioners regarding the adoption of the techniques in an industrial setting. We have also classified 56 model-based test case generation techniques regarding their strengths/limitations, input/intermediate models used, and relevance to the industrial context.

    Conclusions: The challenges identified in this study are not new for research and practice. There could be two reasons regarding the presence of recurring challenges: 1) regression testing techniques proposed in the literature do not fit the companies’ context, 2) or, companies are not aware of the availability of the techniques that could be suitable for their context. To support the adoption of existing research on regression testing in the industry, we have presented three taxonomies. These taxonomies, allow the characterization of regression testing techniques and enable to determine which of these techniques might be suitable in a given context. Furthermore, the identification of information needs for these techniques would be helpful to learn the implications regarding the cost of adoption. Regarding the support in test case generation, we conclude that current research on interaction model-based test case generation techniques did not illustrate the use of rigorous methodology, and currently, model-based test case generation techniques have low relevance for the industrial problems.

  • Paxling, Linda
    Blekinge Institute of Technology, Faculty of Computing, Department of Technology and Aesthetics.
    Transforming technocultures: Feminist Technoscience, Critical Design Practices and Caring Imaginaries2019Doctoral thesis, monograph (Other academic)
  • Silvander, Johan
    Blekinge Institute of Technology, Faculty of Computing, Department of Software Engineering.
    Component Selection with Fuzzy Decision Making2018In: Procedia Computer Science, Elsevier B.V. , 2018, Vol. 126, p. 1378-1386Conference paper (Refereed)
    Abstract [en]

    In many situations a decision maker (DM) would like to grade a component, or rank several components of the same type. Often a component type has many features, which are deemed as valuable by the DM. Other vital features are not known by the DM but are needed for the component to function. However, it should be possible to guide the DM to find the desired business solution, without putting a requirement of detailed knowledge of the component type on the DM. We propose a framework for component selection with the help of fuzzy decision making. The work is based on algorithms from fuzzy decision making, which we have adapted or extended. The framework was validated by practitioners, which found the framework useful. © 2018 The Author(s).

  • Wagner, Stefan
    Blekinge Institute of Technology, Faculty of Engineering, Department of Mathematics and Natural Sciences.
    Extending characters of fixed point algebras2018In: Axioms, ISSN 2075-1680, Vol. 7, no 4, article id 79Article in journal (Refereed)
    Abstract [en]

    A dynamical system is a triple (A, G, α) consisting of a unital locally convex algebra A, a topological group G, and a group homomorphism α: G → Aut(A) that induces a continuous action of G on A. Furthermore, a unital locally convex algebra A is called a continuous inverse algebra, or CIA for short, if its group of units A× is open in A and the inversion map i: A× → A×, a → a-1 is continuous at 1A. Given a dynamical system (A, G, α) with a complete commutative CIA A and a compact group G, we show that each character of the corresponding fixed point algebra can be extended to a character of A. © 2018 by the authors.

  • Ouriques, Raquel
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Software Engineering.
    Wnuk, Krzysztof
    Blekinge Institute of Technology, Faculty of Computing, Department of Software Engineering.
    Gorschek, Tony
    Blekinge Institute of Technology, Faculty of Computing, Department of Software Engineering.
    Berntsson Svensson, Richard
    Chalmers, SWE.
    Knowledge Management Strategies and Processes in Agile Software Development: A Systematic Literature Review2018In: International journal of software engineering and knowledge engineering, ISSN 0218-1940Article in journal (Refereed)
    Abstract [en]

    Knowledge-intensive companies that adopt Agile Software Development (ASD) relay on efficient implementation of Knowledge Management (KM) strategies to promotes different Knowledge Processes (KPs) to gain competitive advantage. This study aims to explore how companies that adopt ASD implement KM strategies utilizing practices that promote the KPs in the different organizational layers. Through a systematic literature review, we analyzed 32 primary studies, selected by automated search and snowballing in the extant literature. To analyze the data, we applied narrative synthesis. Most of the identified KM practices implement personalization strategies (81 %), supported by codification (19 %). Our review shows that the primary studies do not report KM practices in the strategic layer and two of them in the product portfolio layer; on the other hand, in the project layer, the studies report 33 practices that implement personalization strategy, and seven practices that implement codification. KM strategies in ASD promote mainly the knowledge transfer process with practices that stimulate social interaction to share tacit knowledge in the project layer. As a result of using informal communication, a significant amount of knowledge can be lost or not properly transferred to other individuals and, instead of propagating the knowledge, it remains inside a few individuals minds.

  • Public defence: 2019-01-18 14:00 sal G340, Karlskrona
    Tell, Johanna
    Blekinge Institute of Technology, Faculty of Engineering, Department of Health.
    Implementation and use of Web-based National Guidelines in Child Healthcare2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In Sweden, child healthcare (CHC) is an important health promotion setting, providing universal and targeted interventions. High demands on child healthcare and the competences of CHC nurses, highlight the importance of access to supportive web-based guidelines in everyday work. The implementation of web-based guidelines is affected by various factors and can be challenging. The Swedish Rikshandbokenis national guidelines for CHC that are in the process of being implemented. The overall aim of this thesis was to investigate the CHC provided in Sweden before the implementation of the national CHC programme, and the implementation and usage of web-based national guidelines for CHC. Study Iaimed to investigate whether the Swedish CHC programme was equal and which methods for health surveillance the county councils offered. A web-survey distributed to CHC coordinators was used, and the data were analyzed with descriptive statistics. Study IIaimed to investigate how nurses in CHC use Rikshandboken and factors affecting its use. A web survey was used and analysed using descriptive and analytical statistics. Study IIIaimed to investigate CHC coordinators´ experiences of being a facilitator in the implementation of a new national CHC programme in the form of a web-based guide. Focus group interviews via Skype for Business were conducted and analyzed using qualitative content analysis. Study IVaimed to examine CHC nurses´ use and ways of understanding the national web-based guidelines, Rikshandboken. A mixed method with sequential explanatory design in two phases was used; a web-survey with descriptive statistics followed by telephone interviews with phenomenographic analysis. Study Vaimed to investigate the usage of the national web-based guidelines, Rikshandboken. The data were collected from Google Analytics, and analyzed using descriptive statistics. The results of the studies show that Rikshandbokenis widely used and that its usage has increased. CHC nurses are generally satisfied with the website and emphasizes the importance of national guidelines for CHC. Factors needed to be developed to improve Rikshandbokenwere suggested as well as prerequisites that are needed in the local context to use Rikshandbokenfully. It must be reliable, useful and relevant why the end users need to be involved in the development. With the right conditions, Rikshandbokencould be a resource for learning and a tool in everyday work for CHC nurses. The result also shows that the CHC is provided unequally, and that the CHC programme is challenging to implement in the local context. The CHC coordinators´ task is to facilitate the implementation of the web-based national guidelines; however, this responsibility is complex. Changing the content, structure and access to Rikshandbokenis not sufficient, in the local context, prerequisites for the use of these web-based national guidelines must exist, and only then can Rikshandbokenbe a contributing determinant to an equal CHC.

  • Schulte, Jesko
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Strategic Sustainable Development.
    Hallstedt, Sophie
    Blekinge Institute of Technology, Faculty of Engineering, Department of Strategic Sustainable Development.
    Self-Assessment Method for Sustainability Implementation in Product Innovation2018In: Sustainability, ISSN 2071-1050, E-ISSN 2071-1050, Vol. 10, no 12, article id 4336Article in journal (Refereed)
    Abstract [en]

    Companies, striving towards an effective and systematic integration of a strategic sustainability perspective in product innovation, need to treat the implementation of necessary processes and tools, as well as their continuous improvement, as a project in itself. An efficient way to measure the current sustainability implementation level in the organization, as well as guidance for progression, is required. To meet this need, a novel self-assessment was developed, which provides companies with a tool to assess and visualize their current capabilities in relation to key elements for successful sustainability integration in the product innovation process. It includes a scale of different sustainability implementation levels to support building a roadmap for systematic implementation, and to measure progress over time. This research is based on results from previous descriptive work within the area of sustainable product development and learning from applying strategic and tactical assessment tools for eco-design and sustainability maturity. Besides the contribution to practice, this study also contributes to knowledge by specifying detailed aspects for each key element that must be considered to guide sustainability integration. Also, insights from applying different existing tools in real cases are provided. The newly-developed self-assessment method was applied and validated at two case companies. Independent and continuous use of it by the companies beyond this particular study indicate the practical value of the method.

  • Tell, Johanna
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Health.
    Anderberg, Peter
    Blekinge Institute of Technology, Faculty of Engineering, Department of Health.
    Olander, Ewy
    Blekinge Institute of Technology, Faculty of Engineering, Department of Health.
    Sanmartin Berglund, Johan
    Blekinge Institute of Technology, Faculty of Engineering, Department of Health.
    The usage of web-based national guidelines for child healthcare: A web analytic study2018In: Article in journal (Refereed)
    Abstract [en]

    The development and dissemination of information- and communication technologies in healthcare is rapid. The purpose of web-based national guidelines is to support professionals in everyday work providing equivalent, safe and qualitative healthcare. Web-based national guidelines are often not implemented effectively in healthcare why studies reflecting different aspects of use and implementation is needed. The aim of this study was to investigate the usage of web-based national guidelines for child healthcare, Rikshandboken i barnhälsovård. In this case study with cross-sectional design, usage pattern of the web-based guidelineswas studied for one year using the web analytic tool, Google Analytics. The usage data were analysed with descriptive statistics. The study showed the general usage pattern of RHB, changes in usage through the year and various usage pattern in different user groups. The usage of RHB had increased, the web-based guidelines was used in all county councils/regions and the most common visited web-page was the new national child healthcare programme. This tendency suggests a positive direction towards the RHB aim to contribute to equal , equitable and high-qualitative CHC.The result also showed the importance to study different user groups as the usage pattern differs. This provide valuable knowledge in the development of web-based national guidelines making them useful and relevant for all its users. 

  • Tell, Johanna
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Health.
    Olander, Ewy
    Blekinge Institute of Technology, Faculty of Engineering, Department of Health.
    Anderberg, Peter
    Blekinge Institute of Technology, Faculty of Engineering, Department of Health.
    Sanmartin Berglund, Johan
    Blekinge Institute of Technology, Faculty of Engineering, Department of Health.
    Nurses´ use and ways of understanding web-based national guidelines for child healthcareIn: Article in journal (Refereed)
    Abstract [en]

    The national Rikshandbokenfor child healthcare, is a web-based guideline for child health care in Sweden containing knowledge- and methodological guidance and a national child health care program in progress to be implemented. The aim with the study was to examine child health care nurses use and ways of understanding the national web-basedRikshandbokenfor child health care.  Mixed method with sequential explanatory design in two phases was used; a web-survey with descriptive statistic followed by telephone interviews with phenomenographic analysis. The study showed variations in use and contribute with deeper knowledge of child healthcare nurse´s ways of understanding the unit RHB whose varied parts interact with each other. To be reliable, useful and relevant for nurses in their context, Rikshandbokenmust be kept updated and involve the end-users in the development process. Access to technical devices and optimal use of the possibilities with information and communication technology, the national web-based Rikshandbokencan be a resource for continuing learning and a tool in everyday work and a possible determinant to an equal child healthcare. The study contributes with valuable knowledge when designing web-based clinical practice guidelines for healthcare, making them useful and relevant for the end-users

  • Tell, Johanna
    et al.
    Landstinget, Blekinge.
    Magnusson, Margaretha
    Uppsala university.
    Lindfors, Anncharlotte
    Stockholm county council.
    Stora skillnader i svensk barnhälsovård: Barnhälsovårdsenheterna avgör själva- oroande att nationellt program saknas2011In: Läkartidningen, ISSN 0023-7205, E-ISSN 1652-7518, ISSN 0023-7205, Vol. 108, no 35, p. 1618-1621Article in journal (Refereed)
    Abstract [sv]

    I dag saknas ett nationellt program för barnhälsovården. Professionen har startat ett arbete, och Socialdepartementet har i ett regleringsbrev för 2009 givit Socialstyrelsen i uppdrag att tillse att vägledningar, rekommendationer och kunskapsöversikter för barnhälsovård finns utarbetade, tillgängliga och uppdaterade. 

    Våren 2010 skickades ett webbaserat frågeformulär till samtliga barnhälsovårdsenheter i Sverige i syfte att undersöka om barnhälsovårdsprogrammet är jämlikt och vilka metoder för hälso­övervakning som erbjuds i det generella basprogrammet. 

    Trots att den svenska barnhälsovården ofta beskrivs som generell och likartad, visar resultatet att det finns stora skillnader i landet vad gäller såväl utbud och metoder som uppföljning.

  • Kusetogullari, Hüseyin
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering. Blekinge Inst Technol, Dept Comp Sci & Engn, S-37141 Karlskrona, Sweden..
    Unsupervised Text Binarization in Handwritten Historical Documents Using k-Means Clustering2018In: PROCEEDINGS OF SAI INTELLIGENT SYSTEMS CONFERENCE (INTELLISYS) 2016, VOL 2 / [ed] Bi, Y Kapoor, S Bhatia, R, SPRINGER INTERNATIONAL PUBLISHING AG , 2018, p. 23-32Conference paper (Refereed)
    Abstract [en]

    In this paper, we propose a novel technique for unsupervised text binarization in handwritten historical documents using k-means clustering. In the text binarization problem, there are many challenges such as noise, faint characters and bleed-through and it is necessary to overcome these tasks to increase the correct detection rate. To overcome these problems, preprocessing strategy is first used to enhance the contrast to improve faint characters and Gaussian Mixture Model (GMM) is used to ignore the noise and other artifacts in the handwritten historical documents. After that, the enhanced image is normalized which will be used in the postprocessing part of the proposed method. The handwritten binarization image is achieved by partitioning the normalized pixel values of the handwritten image into two clusters using k-means clustering with k = 2 and then assigning each normalized pixel to the one of the two clusters by using the minimum Euclidean distance between the normalized pixels intensity and mean normalized pixel value of the clusters. Experimental results verify the effectiveness of the proposed approach.

  • Ghazi, Ahmad Nauman
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Software Engineering.
    Petersen, Kai
    Blekinge Institute of Technology, Faculty of Computing, Department of Software Engineering.
    Reddy, Sri Sai Vijay Raj
    Blekinge Institute of Technology, Faculty of Computing, Department of Software Engineering.
    Nekkanti, Harini
    Blekinge Institute of Technology, Faculty of Computing, Department of Software Engineering.
    Survey Research in Software Engineering: Problems and Mitigation Strategies2018In: IEEE Access, E-ISSN 2169-3536Article in journal (Refereed)
    Abstract [en]

    Background: The need for empirical investigations in software engineering is growing. Many researchers nowadays, conduct and validate their solutions using empirical research. The Survey is an empirical method which enables researchers to collect data from a large population. The main aim of the survey is to generalize the findings.

    Aims: In this study, we aim to identify the problems researchers face during survey design and mitigation strategies.

    Method: A literature review, as well as semi-structured interviews with nine software engineering researchers, were conducted to elicit their views on problems and mitigation strategies. The researchers are all focused on empirical software engineering.

    Results: We identified 24 problems and 65 strategies, structured according to the survey research process. The most commonly discussed problem was sampling, in particular, the ability to obtain a sufficiently large sample. To improve survey instrument design, evaluation and execution recommendations for question formulation and survey pre-testing were given. The importance of involving multiple researchers in the analysis of survey results was stressed.

    Conclusions: The elicited problems and strategies may serve researchers during the design of their studies. However, it was observed that some strategies were conflicting. This shows that it is important to conduct a trade-off analysis between strategies.

  • Schulte, Jesko
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Strategic Sustainable Development.
    Hallstedt, Sophie
    Blekinge Institute of Technology, Faculty of Engineering, Department of Strategic Sustainable Development.
    Company Risk Management in Light of the Sustainability Transition2018In: Sustainability, ISSN 2071-1050, E-ISSN 2071-1050, Vol. 10, article id 4137Article in journal (Refereed)
    Abstract [en]

    Many of the most important business and economic risks are directly linked to environmental and social issues. This includes both threats and opportunities, not only in relation to reputation, which is often mentioned in this context, but, even more importantly, in relation to innovation capability and legislative change on inevitably more and more sustainability-driven markets. It is, however, unclear through which mechanisms such sustainability risks currently affect companies and how they can be systematically identified and managed. Based on the Framework for Strategic Sustainable Development, this study investigates the dynamics and implications of society’s sustainability transition from a company risk management perspective. In addition, exploratory and descriptive studies were conducted at two large product innovation companies to identify current risk management practices and preconditions for sustainability integration. The results reveal that a society moving closer towards a collapse of environmental and social systems leads to increasing sustainability-related threats for unsustainable businesses and increasing opportunities for sustainable businesses. Also, risk management is found to be a promising way for maneuvering in a smart zone between being too passive and being too pro-active in relation to sustainable innovation.The study participants at the case companies were knowledgeable about risk management in general but were largely unfamiliar with risks associated with sustainability and no processes or support tools exist to work systematically with such risks. Key steps to accomplishing an integration of a strategic sustainability perspective into risk management are proposed as: (i) identifying the effects of sustainability issues on internal and external stakeholder value; (ii) actively including sustainability in objective setting and cascading objectives across the levels of the organizational hierarchy; and (iii) developing concrete support for identifying, assessing, and managing economic sustainability risks. Thereby, companies can enhance their competitiveness while providing leadership in the sustainability transition.

  • Public defence: 2019-01-16 13:00
    Shirinbab, Sogand
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
    Performance Implications of Virtualization2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Virtualization is a component of cloud computing. Virtualization transforms traditional inflexible, complex infrastructure of individual servers, storage, and network hardware into a flexible virtual resource pool and increases IT agility, flexibility, and scalability while creating significant cost savings. Additional benefits of virtualization include, greater work mobility, increased performance and availability of resources, and automated operations. Many virtualization solutions have been implemented. There are plenty of cloud providers using different virtualization solutions to provide virtual machines (VMs) and containers, respectively. Various virtualization solutions have different performance overheads due to their various implementations of virtualization and supported features. A cloud user should understand performance overheads of different virtualization solutions and the impact on the performance caused by different virtualization features, so that it can choose appropriate virtualization solution, for the services to avoid degrading their quality of services (QoSs). In this research, we investigate the impacts of different virtualization technologies such as, container-based, and hypervisor-based virtualization as well as various virtualization features such as, over-allocation of resources, live migration, scalability, and distributed resource scheduling on the performance of various applications for instance, Cassandra NoSQL database, and a large telecommunication application. According to our results, hypervisor-based virtualization has many advantages and is more mature compare to the recently introduced container-based virtualization. However, impacts of the hypervisorbased virtualization on the performance of the applications is much higher than the container-based virtualization as well as the non-virtualized solution. The findings of this research should be of benefit to the ones who provide planning, designing, and implementing of the IT infrastructure.

  • Sun, Bin
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies.
    Automated Traffic Time Series Prediction2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Intelligent transportation systems (ITS) are becoming more and more effective. Robust and accurate short-term traffic prediction plays a key role in modern ITS and demands continuous improvement. Benefiting from better data collection and storage strategies, a huge amount of traffic data is archived which can be used for this purpose especially by using machine learning.

    For the data preprocessing stage, despite the amount of data available, missing data records and their messy labels are two problems that prevent many prediction algorithms in ITS from working effectively and smoothly. For the prediction stage, though there are many prediction algorithms, higher accuracy and more automated procedures are needed.

    Considering both preprocessing and prediction studies, one widely used algorithm is k-nearest neighbours (kNN) which has shown high accuracy and efficiency. However, the general kNN is designed for matrix instead of time series which lacks the use of time series characteristics. Choosing the right parameter values for kNN is problematic due to dynamic traffic characteristics. This thesis analyses kNN based algorithms and improves the prediction accuracy with better parameter handling using time series characteristics.

    Specifically, for the data preprocessing stage, this work introduces gap-sensitive windowed kNN (GSW-kNN) imputation. Besides, a Mahalanobis distance-based algorithm is improved to support correcting and complementing label information. Later, several automated and dynamic procedures are proposed and different strategies for making use of data and parameters are also compared.

    Two real-world datasets are used to conduct experiments in different papers. The results show that GSW-kNN imputation is 34% on average more accurate than benchmarking methods, and it is still robust even if the missing ratio increases to 90%. The Mahalanobis distance-based models efficiently correct and complement label information which is then used to fairly compare performance of algorithms. The proposed dynamic procedure (DP) performs better than manually adjusted kNN and other benchmarking methods in terms of accuracy on average. What is better, weighted parameter tuples (WPT) gives more accurate results than any human tuned parameters which cannot be achieved manually in practice. The experiments indicate that the relations among parameters are compound and the flow-aware strategy performs better than the time-aware one. Thus, it is suggested to consider all parameter strategies simultaneously as ensemble strategies especially by including window in flow-aware strategies.

    In summary, this thesis improves the accuracy and automation level of short-term traffic prediction with proposed high-speed algorithms.

  • Shirinbab, Sogand
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
    Lundberg, Lars
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
    Scheduling Tasks with Hard Deadlines in CloudBased Virtualized Software SystemsManuscript (preprint) (Other academic)
    Abstract [en]

    There is scheduling on two levels in real-time applications executing in a virtualized environment: traditional real-time scheduling of the tasks in the realtime application, and scheduling of different Virtual Machines (VMs) on the hypervisor level. In this paper, we describe a technique for calculating a period and an execution time for a VM containing a real-time application with hard deadlines. This result makes it possible to apply existing real-time scheduling theory when scheduling VMs on the hypervisor level, thus making it possible to guarantee that the real-time tasks in a VM meet their deadlines. If overhead for switching from one VM to another is ignored, it turns out that (infinitely) short VM periods minimize the utilization that each VM needs to guarantee that all real-time tasks in that VM will meet their deadlines. Having infinitely short VM periods is clearly not realistic, and in order to provide more useful results we have considered a fixed overhead at the beginning of each execution of a VM. Considering this overhead, a set of real-time tasks, the speed of each processor core, and a certain processor utilization of the VM containing the real-time tasks, we present a simulation study and some performance bounds that make it possible to determine if it is possible to schedule the real-time tasks in the VM, and in that case for which periods of the VM that this is possible.

  • Shirinbab, Sogand
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
    Lundberg, Lars
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
    Scheduling Tasks with Hard Deadlines in Virtualized Software SystemsIn: Article in journal (Refereed)
    Abstract [en]

    There is scheduling on two levels in real-time applications executing in a virtualized environment: traditional real-time scheduling of the tasks in the real-time application, and scheduling of different Virtual Machines (VMs) on the hypervisor level. In this paper, we describe a technique for calculating a period and an execution time for a VM containing a real-time application with hard deadlines. This result makes it possible to apply existing real-time scheduling theory when scheduling VMs on the hypervisor level, thus making it possible to guarantee that the real-time tasks in a VM meet their deadlines. If overhead for switching from one VM to another is ignored, it turns out that (infinitely) short VM periods minimize the utilization that each VM needs to guarantee that all real-time tasks in that VM will meet their deadlines. Having infinitely short VM periods is clearly not realistic, and in order to provide more useful results we have considered a fixed overhead at the beginning of each execution of a VM. Considering this overhead, a set of real-time tasks, the speed of  each processor core, and a certain processor utilization of the VM containing the real-time tasks, we present a simulation study and some performance bounds that make it possible to determine if it is possible to schedule the real-time tasks in the VM, and in that case for which periods of the VM that  is possible.

  • Shirinbab, Sogand
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
    Lundberg, Lars
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
    Casalicchio, Emiliano
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
    Performance Comparison between Horizontal Scaling of Hypervisor and Container Based Virtualization using Cassandra NoSQL Database2018In: Proceeding of the 3rd International Conference on Virtualization Application and Technology, 2018, , p. 6Conference paper (Refereed)
    Abstract [en]

    Cloud computing promises customers the ondemand ability to scale in face of workload variations. There are different ways to accomplish scaling, one is vertical scaling and the other is horizontal scaling. The vertical scaling refers to buying more power (CPU, RAM), buying a more expensive and robust server, which is less challenging to implement but exponentially expensive. While, the horizontal scaling refers to adding more servers with less processor and RAM, which is usually cheaper overall and can scale very well. The majority of cloud providers prefer the horizontal scaling approach, and for them would be very important to know about the advantages and disadvantages of both technologies from the perspective of the application performance at scale. In this paper, we compare performance differences caused by scaling of the different virtualization technologies in terms of CPU utilization, latency, and the number of transactions per second. The workload is Apache Cassandra, which is a leading NoSQL distributed database for Big Data platforms. Our results show that running multiple instances of the Cassandra database concurrently, affected the performance of read and write operations differently; for both VMware and Docker, the maximum number of read operations was reduced when we ran several instances concurrently, whereas the maximum number of write operations increased when we ran instances concurrently.

  • Quoreshi, Shahiduzzaman
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Industrial Economics. Blekinge Tekniska Högskola.
    Mollah, Sabur
    Swansea University, GBR.
    Conditional Heteroskedasticity in Long Memory Model ‘FIMACH’ for Return Volatilities in Equity Markets2018Conference paper (Refereed)
    Abstract [en]

    This paper incorporates conditional heteroscedasticity properties in the long memory model and applies the model on squared returns of BRICS (Brazil, Russia, India, China, and South Africa), UK and USA equity markets to capture the volatility of stock return. The conditional first- and second-order moments are provided. The CLS, FGLS and QML are discussed and 2SQML estimator is proposed. The simulation study suggests that the proposed 2SQML estimator performs better than the other three estimators. Both in simulation and empirical studies, we find that the proposed model FIMACH outperforms FIGARCH in terms of eliminating serial correlations.