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  • 251.
    Almqvist, Tom
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Utvärdering av metoder för temporär lagring av data i en webbapplikation2018Independent thesis Basic level (university diploma), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [sv]

    I databasapplikationer är det viktigt att kunna minska belastningen på en databas i syfte att minska responstiden. Detta kan exempelvis åstadkommas med hjälp av olika metoder för temporär lagring av data, något som studerats i detta arbete. De metoder som utvärderats och jämförts i detta arbete är Redis och memcached. Utvärderingen jämförde Redis och memcached med avseende på minnesanvändning, CPU-användning och tidsåtgång för hämtning av data i respektive cache. Dessa egenskaper beräknades med hjälp av verktygen SYSSTAT och valgrind. Det visade sig i slutändan att den interna fragmenteringen i memcached är dess största nackdel, medan Redis är något långsammare än memcached när det gäller att hämta stora mängder data. Utifrån de resultat som anskaffats var det tänkt att använda den metod som är mest lämpad för SysPartners ändamål, vilket ansågs vara Redis.

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  • 252.
    Al-Mter, Yusur
    Linköping University, Department of Computer and Information Science, The Division of Statistics and Machine Learning.
    Automatic Prediction of Human Age based on Heart Rate Variability Analysis using Feature-Based Methods2020Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Heart rate variability (HRV) is the time variation between adjacent heartbeats. This variation is regulated by the autonomic nervous system (ANS) and its two branches, the sympathetic and parasympathetic nervous system. HRV is considered as an essential clinical tool to estimate the imbalance between the two branches, hence as an indicator of age and cardiac-related events.This thesis focuses on the ECG recordings during nocturnal rest to estimate the influence of HRV in predicting the age decade of healthy individuals. Time and frequency domains, as well as non-linear methods, are explored to extract the HRV features. Three feature-based methods (support vector machine (SVM), random forest, and extreme gradient boosting (XGBoost)) were employed, and the overall test accuracy achieved in capturing the actual class was relatively low (lower than 30%). SVM classifier had the lowest performance, while random forests and XGBoost performed slightly better. Although the difference is negligible, the random forest had the highest test accuracy, approximately 29%, using a subset of ten optimal HRV features. Furthermore, to validate the findings, the original dataset was shuffled and used as a test set and compared the performance to other related research outputs.

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  • 253.
    Al-mufti, Summia
    et al.
    Linköping University, Department of Computer and Information Science.
    Jönsson, Rasmus
    Linköping University, Department of Computer and Information Science.
    HTTP/2, Server Push and Branched Video: Evaluation of using HTTP/2 Server Push in Dynamic Adaptive Streaming over HTTP with linear and non-linear prefetching algorithms2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The purpose of this thesis is to investigate and test the usage of HTTP/2 in dynamic adaptive video streaming as well as to take a look into how it can be used to benefit prefetching algorithms used with branched video. With a series of experiments the performance gains of using HTTP/2 rather than the older standard HTTP/1.1 has been investigated. The results has shown no significant change to player quality and buffer occupancy when using HTTP/2, though our tests has shown in a slight decrease in overall playback quality when using HTTP/2. When using a linear prefetch of two fragments an average quality improvement of 4.59% has been shown, however, the result is inconclusive due to variations in average quality between different values for how many fragments to prefetch. Average buffer occupancy has shown promise with a maximum increase of 12.58%, when using linear prefetch with three fragments. The values for buffer occupancy gains are conclusive. Two implementations for non-linear prefetching has been made. The first one uses HTTP/2 server push to deliver fragments for prefetching and the second one uses client-side invoked HTTP requests to pull fragments from the server. Using HTTP/2 server push has shown in a decrease of 2.5% in average total load time while using client-side pulling has shown in a decrease of 34% in average total load time.

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    HTTP/2, Server Push and Branched Video
  • 254.
    Alnervik, Erik
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Evaluation of the Configurable Architecture REPLICA with Emulated Shared Memory2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    REPLICA is a family of novel scalable chip multiprocessors with configurable emulated shared memory architecture, whose computation model is based on the PRAM (Parallel Random Access Machine) model.

    The purpose of this thesis is to, by benchmarking different types of computation problems on REPLICA, similar parallel architectures (SB-PRAM and XMT) and more diverse ones (Xeon X5660 and Tesla M2050), evaluate how REPLICA is positioned among other existing architectures, both in performance and programming effort. But it should also examine if REPLICA is more suited for any special kinds of computational problems.

    By using some of the well known Berkeley dwarfs, and input from unbiased sources, such as The University of Florida Sparse Matrix Collection and Rodinia benchmark suite, we have made sure that the benchmarks measure relevant computation problems.

    We show that today’s parallel architectures have some performance issues for applications with irregular memory access patterns, which the REPLICA architecture can solve. For example, REPLICA only need to be clocked with a few MHz to match both Xeon X5660 and Tesla M2050 for the irregular memory access benchmark breadth first search. By comparing the efficiency of REPLICA to a CPU (Xeon X5660), we show that it is easier to program REPLICA efficiently than today’s multiprocessors.

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  • 255.
    Alnervik, Jonna
    et al.
    Linköping University, Department of Computer and Information Science, Statistics.
    Nord Andersson, Peter
    Linköping University, Department of Computer and Information Science, Statistics.
    En retrospektiv studie av vilka patientgrupper som erhåller insulinpump2010Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Målsättning

    Att utreda skillnader i tillgänglighet till insulinpump mellan olika patientgrupper samt vad som orsakar ett byte till insulinpump.

    Metod

    Data från 7224 individer med typ 1 diabetes vid tio olika vårdenheter analyserades för att utreda effekterna av njurfunktion, kön, långtidsblodsocker, insulindos, diabetesduration samt ålder. Jämförelsen mellan patientgrupper utfördes med logistisk regression som en tvärsnittsstudie och Cox-regression för att utreda vad som föregått ett byte till pump.

    Resultat

    Genom logistisk regression erhölls en bild av hur skillnader mellan patienter som använder insulinpump och patienter som inte gör det ser ut i dagsläget. Cox-regressionen tar med ett tidsperspektiv och ger på så sätt svar på vad som föregått ett byte till insulinpump. Dessa analyser gav liknande resultat gällande variabler konstanta över tiden. Kvinnor använder pump i större utsträckning än män och andelen pumpanvändare skiljer sig åt vid olika vårdenheter. I dagsläget visar sig hög ålder sänka sannolikheten att använda insulinpump, vilket bekräftas vid den tidsberoende studien som visade hur sannolikheten att byta till pump är avsevärt lägre vid hög ålder. Långtidsblodsockret har också tydlig effekt på sannolikheten att gå över till pump där ett högt långtidsblodsocker medför hög sannolikhet att byta till insulinpump.

    Slutsatser

    I dagsläget finns det skillnader i andelen insulinpumpanvändare mellan olika patientgrupper och skillnader finns även i de olika gruppernas benägenhet att byta från andra insulinbehandlingar till insulinpump. Beroende av patienters njurfunktion, kön, långtidsblodsocker, insulindos, diabetesduration och ålder har dessa olika sannolikheter att byta till insulinpump.

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  • 256.
    Al-Omaishe, Allaa
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering. 860418-9061.
    The impacts of adopting large touch screens and tablets with access  to electronic healthcare records2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In the last decade modern information technology systems have been introduced to healthcare in order to improve it. The aim of this study is to present the impact of such information system’s adoption on patient safety and efficiency within healthcare.

    Interviews, observations along with literature study were conducted in order to study the impact of the adoption on patient safety and efficiency at hospital’s wards where a new information system is implemented.

    The conclusion of this study is that such information technology systems can improve patient safety. However it is believed that the information technology system can improve efficiency in some aspects such as the communication among medical care personnel while other aspects within efficiency can be achieved if some improvements are made. Moreover the ability to access Electronic Healthcare Records is considered to be important to improve the medical care, which can increase patient safety. 

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  • 257.
    Alsaadi, Sarah
    et al.
    Linköping University, Department of Computer and Information Science, The Division of Statistics and Machine Learning.
    Wänström, Linda
    Linköping University, Department of Computer and Information Science, The Division of Statistics and Machine Learning.
    Sjögren, Björn
    Linköping University, Department of Behavioural Sciences and Learning, Education, Teaching and Learning.
    Bjärehed, Marlene
    Linköping University, Department of Behavioural Sciences and Learning, Education, Teaching and Learning.
    Thornberg, Robert
    Linköping University, Department of Behavioural Sciences and Learning, Education, Teaching and Learning. Linköping University, Faculty of Educational Sciences.
    Collective moral disengagement and school bullying: An initial validation study of the Swedish scale version2016Conference paper (Refereed)
  • 258.
    Alsaadi, Sarah
    et al.
    Linköping University, Department of Computer and Information Science, The Division of Statistics and Machine Learning. Linköping University, Faculty of Arts and Sciences.
    Wänström, Linda
    Linköping University, Department of Computer and Information Science, The Division of Statistics and Machine Learning. Linköping University, Faculty of Arts and Sciences. Linköping University, Department of Behavioural Sciences and Learning, Education, Teaching and Learning. Linköping University, Faculty of Educational Sciences.
    Thornberg, Robert
    Linköping University, Department of Behavioural Sciences and Learning, Education, Teaching and Learning. Linköping University, Faculty of Educational Sciences.
    Sjögren, Björn
    Linköping University, Department of Behavioural Sciences and Learning, Education, Teaching and Learning. Linköping University, Faculty of Educational Sciences.
    Bjärehed, Marlene
    Linköping University, Department of Behavioural Sciences and Learning, Education, Teaching and Learning. Linköping University, Faculty of Educational Sciences.
    Forsberg, Camilla
    Linköping University, Department of Behavioural Sciences and Learning, Education, Teaching and Learning. Linköping University, Faculty of Educational Sciences.
    Collective moral disengagement at school: A validation of a scale for Swedish children2018Conference paper (Other academic)
    Abstract [en]

    The purpose of this study was to evaluate a recently developed classroom collective moral disengagement scale (CMD). The 18-item scale was evaluated on a sample of 1626 fourth grade students in Sweden. Through confirmatory factor analysis, the unidimensional structure of the scale was verified, and the internal consistency was good. The scale is related to individual moral disengagement and to bullying behavior both on an individual level, which supports the criteria validity of the scale and on class level, which supports the construct validity of the scale. Multigroup analyses demonstrated measurement invariance across gender. These results indicate that the scale can be used in studies on CMD, and girls’ and boys’ mean scores may be compared.

  • 259.
    Alshourbaji, Ibrahim
    et al.
    Univ Hertfordshire, England; Jazan Univ, Saudi Arabia.
    Helian, Na
    Univ Hertfordshire, England.
    Sun, Yi
    Univ Hertfordshire, England.
    Hussien, Abdelazim
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering. Fayoum Univ, Egypt.
    Abualigah, Laith
    Al Al Bayt Univ, Jordan; Lebanese Amer Univ, Lebanon; Al Ahliyya Amman Univ, Jordan; Middle East Univ, Jordan; Appl Sci Private Univ, Jordan; Univ Sains Malaysia, Malaysia; Sunway Univ, Malaysia.
    Elnaim, Bushra
    Prince Sattam Bin Abdulaziz Univ, Saudi Arabia.
    An efficient churn prediction model using gradient boosting machine and metaheuristic optimization2023In: Scientific Reports, E-ISSN 2045-2322, Vol. 13, no 1, article id 14441Article in journal (Refereed)
    Abstract [en]

    Customer churn remains a critical challenge in telecommunications, necessitating effective churn prediction (CP) methodologies. This paper introduces the Enhanced Gradient Boosting Model (EGBM), which uses a Support Vector Machine with a Radial Basis Function kernel (SVMRBF) as a base learner and exponential loss function to enhance the learning process of the GBM. The novel base learner significantly improves the initial classification performance of the traditional GBM and achieves enhanced performance in CP-EGBM after multiple boosting stages by utilizing state-of-the-art decision tree learners. Further, a modified version of Particle Swarm Optimization (PSO) using the consumption operator of the Artificial Ecosystem Optimization (AEO) method to prevent premature convergence of the PSO in the local optima is developed to tune the hyper-parameters of the CP-EGBM effectively. Seven open-source CP datasets are used to evaluate the performance of the developed CP-EGBM model using several quantitative evaluation metrics. The results showed that the CP-EGBM is significantly better than GBM and SVM models. Results are statistically validated using the Friedman ranking test. The proposed CP-EGBM is also compared with recently reported models in the literature. Comparative analysis with state-of-the-art models showcases CP-EGBMs promising improvements, making it a robust and effective solution for churn prediction in the telecommunications industry.

  • 260.
    Al-Shourbaji, Ibrahim
    et al.
    Jazan Univ, Saudi Arabia; Univ Hertfordshire, England.
    Kachare, Pramod
    Ramrao Adik Inst Technol, India.
    Fadlelseed, Sajid
    Univ Hertfordshire, England.
    Jabbari, Abdoh
    Jazan Univ, Saudi Arabia.
    Hussien, Abdelazim
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering. Fayoum Univ, Egypt.
    Al-Saqqar, Faisal
    Al Al Bayt Univ, Jordan.
    Abualigah, Laith
    Al Al Bayt Univ, Jordan; Sunway Univ Malaysia, Malaysia; Al Ahliyya Amman Univ, Jordan; Middle East Univ, Jordan; Appl Sci Private Univ, Jordan; Univ Sains Malaysia, Malaysia.
    Alameen, Abdalla
    Prince Sattam Bin Abdulaziz Univ, Saudi Arabia.
    Artificial Ecosystem-Based Optimization with Dwarf Mongoose Optimization for Feature Selection and Global Optimization Problems2023In: International Journal of Computational Intelligence Systems, ISSN 1875-6891, E-ISSN 1875-6883, Vol. 16, no 1, article id 102Article in journal (Refereed)
    Abstract [en]

    Meta-Heuristic (MH) algorithms have recently proven successful in a broad range of applications because of their strong capabilities in picking the optimal features and removing redundant and irrelevant features. Artificial Ecosystem-based Optimization (AEO) shows extraordinary ability in the exploration stage and poor exploitation because of its stochastic nature. Dwarf Mongoose Optimization Algorithm (DMOA) is a recent MH algorithm showing a high exploitation capability. This paper proposes AEO-DMOA Feature Selection (FS) by integrating AEO and DMOA to develop an efficient FS algorithm with a better equilibrium between exploration and exploitation. The performance of the AEO-DMOA is investigated on seven datasets from different domains and a collection of twenty-eight global optimization functions, eighteen CEC2017, and ten CEC2019 benchmark functions. Comparative study and statistical analysis demonstrate that AEO-DMOA gives competitive results and is statistically significant compared to other popular MH approaches. The benchmark function results also indicate enhanced performance in high-dimensional search space.

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  • 261.
    Alsén, Simon
    et al.
    Linköping University, Department of Computer and Information Science, The Division of Statistics and Machine Learning.
    Åkesson, Andreas
    Linköping University, Department of Computer and Information Science, The Division of Statistics and Machine Learning.
    Jämförelse av metoder för hantering av partiellt bortfall vid logistisk regressionsanalys2021Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Missing data is a common problem in research and can lead to loss of statistical power and bias in parameter estimates. Numerous methods have been developed for dealing with missing data, and the aim of this thesis is to evaluate how a number of these methods affect the parameter estimates in a logistic regression model, and whether these methods are suitable for the data in question. The methods included in this study are complete case analysis, MICE and missForest.

    For the purpose of evaluating the methods, missing values in varying proportions and under different missing mechanisms are generated in a real dataset consisting of 2987 observations and five variables. The performance of the methods is assessed by normalized root mean squared error (NRMSE), and by comparing the regression coefficients estimated using the original, true data set with the regression coefficients estimated using imputed data sets.

    missForest results in the lowest NRMSE. In the subsequent logistic regression analysis, however, MICE results in considerably lower bias than missForest.

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  • 262.
    Al-Trad, Anas
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    Optimized Composition of Parallel Components on a Linux Cluster2012Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    We develop a novel framework for optimized composition of explicitly parallel software components with different implementation variants given the problem size, data distribution scheme and processor group size on a Linux cluster. We consider two approaches (or two cases of the framework). 

    In the first approach, dispatch tables are built using measurement data obtained offline by executions for some (sample) points in the ranges of the context properties. Inter-/extrapolation is then used to do actual variant-selection for a given execution context at run-time.

    In the second approach, a cost function of each component variant is provided by the component writer for variant-selection. These cost functions can internally lookup measurements' tables built, either offline or at deployment time, for computation- and communication-specific primitives.

    In both approaches, the call to an explicitly parallel software component (with different implementation variants) is made via a dispatcher instead of calling a variant directly.

    As a case study, we apply both approaches on a parallel component for matrix multiplication with multiple implementation variants. We implemented our variants using Message Passing Interface (MPI). The results show the reduction in execution time for the optimally composed applications compared to applications with hard-coded composition. In addition, the results show the comparison of estimated and measured times for each variant using different data distributions, processor group and problem sizes.

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  • 263.
    Alvarsson, Albin
    Linköping University, Department of Computer and Information Science.
    Wizard-of-Oz system för interaktion på distans med den sociala roboten Furhat2022Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    In the last decades the average life expectancy of humans has increased significantly. There are more old people than ever before. At the same time there is a big staff shortage at nursing homes. A future study will examine the effect of introducing a socially intelligent robot called Furhat in such a home. In this work a so-called Wizard-of-Oz control system is developed which enables remote control of the normally autonomous Furhat. This control system will later be used in the future study. The Wizard-of-Oz control system is developed with the intention of reaching the lowest possible response time between the control system and Furhat to minimize the risk of unnatural conversation due to long wait times between actions. It is found that a response time at or above 500ms can have a clearly degrading effect on a conversation. By following code-standards with a focus on developing fast code an average response time in the range of 35-245ms depending on the action taken is reached.

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  • 264.
    Alvarsson, Andreas
    Linköping University, Department of Computer and Information Science.
    The development of a sports statistics web application: Sports Analytics and Data Models for a sports data web application2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Sports and technology have always co-operated to bring better and more specific sports statistics. The collection of sports game data as well as the ability to generate valuable sports statistics of it is growing. This thesis investigates the development of a sports statistics application that should be able to collect sports game data, structure the data according to suitable data models and show statistics in a proper way.

    The application was set to be a web application that was developed using modern web technologies. This purpose led to a comparison of different software stack solutions and web frameworks. A theoretical study of sports analytics was also conducted, which gave a foundation for how sports data could be stored and how valuable sports statistics could be generated.

    The resulting design of the prototype for the sports statistics application was evaluated. Interviews with persons working in sports contexts evaluated the prototype to be both user-friendly, functional and fulfilling the purpose to generate valuable statistics during sport games.

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  • 265.
    Alvehus, Johan
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    Mötets metaforer: en studie av berättelser om möten1999Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Although meetings are, for most, an important part of the daily routine, they are easily disregarded. When viewed as a form of interaction, meetings become more problematic. While the form of interaction is important for the interpretation of content, it also opens up possibilities for manipulation.

    The purpose of this study is to contribute to an increased understanding of the possibilities for constructing the form of interaction in meetings. This has been achieved through a study of narratives on meetings, here in terms of normative management literature.

    The literature on meeting management offers distinct views on how meetings supposedly function. These views can be expressed in terms of two metaphors: meetings as organisms and meetings as machines. Metaphors serve to both highlight and conceal certain aspects of a phenomenon. The organism metaphor highlights the homogeneity and dynamics of meetings. In contrast, the machine metaphor helps explain how meetings work, as well as how they can be measured and evaluated.

    Different metaphors are often portrayed as either totally distinct from, or directly related to each other. However, the literature on managing meetings reveals that the organism and machine metaphors are both related and discrete. Accordingly, the dialectics of highlighting and concealing aspects of a phenomenon must be complemented by the dialectics between the metaphors. The latter can be expressed in terms of links that integrate the metaphors, as well as links that separate the metaphors and define differences between them. In the literature these links emerge as options for action, i.e., alternatives for enacting a particular metaphor using specific techniques. Accordingly, certain techniques provide options for choosing the form of interaction. However, meetings in themselves can also be viewed as a kind of information technology in the same way as e-mail or videoconferencing technology. Normative statements, e.g. the literature on managing meetings, are important clues for the analysis of how different forms of social action can be designed.

    In studying interaction and communication, an analysis of conscious attempts to design or influence situations should be considered. Such analysis is facilitated by working with a refined concept of form-the double dialectics of form/content and form/form-along with the concept of techniques.

  • 266.
    Alvila, Markus
    et al.
    Linköping University, Department of Computer and Information Science.
    Johansson, Jonathan
    Linköping University, Department of Computer and Information Science.
    Johansson, Philip
    Linköping University, Department of Computer and Information Science.
    Lenz, Silas
    Linköping University, Department of Computer and Information Science.
    Lindmark, Sebastian
    Linköping University, Department of Computer and Information Science.
    Norberg, Emil
    Linköping University, Department of Computer and Information Science.
    Regard, Viktor
    Linköping University, Department of Computer and Information Science.
    Övervakning och bedömning av flygledares prestanda2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Möjligheten att fjärrstyra flygledartorn kommer att ställa högre krav på flygledares koncentrations- och simultanförmåga runt om i Sverige. Det är viktigt att åtgärder tas för att förhindra att en trött flygledare begår ett misstag och det är just detta som det framtagna systemet försöker att förhindra.

    Med hjälp av sensorer och modeller kan systemet bestämma flygledarens trötthet, stressnivå, uppmärksamhet och nuvarande arbetsuppgift. Alla värden presenteras i ett enkelt grafiskt gränssnitt. Tillsammans med resultaten för flygledarens hälsa presenteras även all sensordata i gränssnittet.

    Systemet är främst uppbyggt av två olika ramverk: Apache NiFi och Apache Spark. Vad de båda ramverken har gemensamt är att de har funktionalitet för att bygga kluster, vilket betyder att endast antalet noder sätter gränsen för hur många flygledare som kan vara uppkopplade samtidigt.

    Denna prototyp har inte all funktionalitet på plats för att behandla flera flygledare. Grunden är däremot lagd för att enkelt kunna implementera ytterligare funktionalitet och i slutändan ha flera flygledare uppkopplade samtidigt. Systemet öppnar upp möjligheter till att fördela arbetet på de flygledare som är mest fokuserade och kan därför bidra till att öka flygsäkerheten.

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    flygledares-prestanda
  • 267.
    Alvinge, Björn
    Linköping University, Department of Computer and Information Science.
    Is Speed a Magnitude?: Neurocognitive Estimations of Speed and its’ Connection to Time, Space and Numeric/Quantity Estimations2018Independent thesis Basic level (degree of Bachelor), 12 credits / 18 HE creditsStudent thesis
    Abstract [en]

    Associations between space, time, numbers and quantities have suggested that there must be a shared representational format which underlies them. One of the more prominent theories of an underlying system of representation is that of ATOM, which suggests that the there exists a generalized system of magnitude which processes these dimensions. However, there has been no study that examines whether speed is also processed within such a system. This study investigates this by seeing if a SNARC or Problem-Size effect arise in two speed estimation tests. The fundamental task for the participants in both tests was to judge which of two stimuli was the fastest, with the stimuli moving towards a wall located in the center of a computer screen. Their correct discrimination and response time was recorded. The results found that there were no significant results for either effect. This might be due to low sample size, methodological difficulties, and low robustness. Future research might amend these difficulties by having a more consistent setup with more trials reflecting the effect being tested and fix some potential problems with the test environment.

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  • 268.
    Amanda, Jaber
    Linköping University, Department of Computer and Information Science.
    Evaluating the Team Resilience Assessment Method for Simulation (TRAMS)2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The Team Resilience Assessment Method for Simulation (TRAMS) is an instrument that consist of several measurements, such as team-member exchange, workload, the TRAMS observation protocol etc. This thesis researches the observation protocol. The TRAMS protocol is an assessment method for resilience in simulation games. The aim of this protocol is to support the identification of resilience strategies used and developed by the participants in a simulation game. It is a challenge to assess resilience in teams and that is why the TRAMS protocol has been developed. The scenario of the simulation games is a disruption for 10 days in the card payment system. During the simulation games, the participants work in teams and have to try to cope with the disruption in the card payment system. During the course of this study, 14 simulation games have been conducted with seven different teams. Each of the simulation games has been executed during one whole day, and the participating teams have in total played two games each. During every simulation game there were three observers equipped with the TRAMS protocol. To interpret the data collected with the TRAMS protocol, two methods have been used: transcription and thematic analysis. As a result, guidelines and design changes was formed. In addition, results showed that the distribution and frequency of observations of resilience strategies made were similar, that the observations noted by the observers were similar, and lastly eight themes from the data collection could be extracted: Coordinate and collaborate, Payment options, Cash circulation, Safety, Fuel and transportation, Inform, communicate and the media, Hoarding and rationing, Vulnerable groups. In conclusion, the TRAMS protocol is still under development and 15 more simulation games are planned to be conducted within the ongoing CCRAAAFFTING project. However, the protocol has been applied in this study´s 14 simulation games so far, and the similarities in how the observers filled in the protocol and how similar the observations were, indicate that it hopefully can develop into a recognized research tool in the future. 

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  • 269.
    Amaral, Vasco
    et al.
    Univ Nova Lisboa, Portugal.
    Norberto, Beatriz
    Univ Nova Lisboa, Portugal.
    Goulao, Miguel
    Univ Nova Lisboa, Portugal.
    Aldinucci, Marco
    Univ Torino, Italy.
    Benkner, Siegfried
    Univ Vienna, Austria.
    Bracciali, Andrea
    Univ Stirling, Scotland.
    Carreira, Paulo
    Univ Lisbon, Portugal.
    Celms, Edgars
    Univ Latvia, Latvia.
    Correia, Luis
    Univ Lisbon, Portugal.
    Grelck, Clemens
    Univ Amsterdam, Netherlands.
    Karatza, Helen
    Aristotle Univ Thessaloniki, Greece.
    Kessler, Christoph
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Kilpatrick, Peter
    Queens Univ Belfast, North Ireland.
    Martiniano, Hugo
    Univ Lisbon, Portugal.
    Mavridis, Ilias
    Aristotle Univ Thessaloniki, Greece.
    Pllana, Sabri
    Linnaeus Univ, Sweden.
    Respicio, Ana
    Univ Lisbon, Portugal.
    Simao, Jose
    Inst Politecn Lisboa, Portugal.
    Veiga, Luis
    Univ Lisbon, Portugal.
    Visa, Ari
    Tampere Univ, Finland.
    Programming languages for data-Intensive HPC applications: A systematic mapping study2020In: Parallel Computing, ISSN 0167-8191, E-ISSN 1872-7336, Vol. 91, article id UNSP 102584Article in journal (Refereed)
    Abstract [en]

    A major challenge in modelling and simulation is the need to combine expertise in both software technologies and a given scientific domain. When High-Performance Computing (HPC) is required to solve a scientific problem, software development becomes a problematic issue. Considering the complexity of the software for HPC, it is useful to identify programming languages that can be used to alleviate this issue. Because the existing literature on the topic of HPC is very dispersed, we performed a Systematic Mapping Study (SMS) in the context of the European COST Action cHiPSet. This literature study maps characteristics of various programming languages for data-intensive HPC applications, including category, typical user profiles, effectiveness, and type of articles. We organised the SMS in two phases. In the first phase, relevant articles are identified employing an automated keyword-based search in eight digital libraries. This lead to an initial sample of 420 papers, which was then narrowed down in a second phase by human inspection of article abstracts, titles and keywords to 152 relevant articles published in the period 2006-2018. The analysis of these articles enabled us to identify 26 programming languages referred to in 33 of relevant articles. We compared the outcome of the mapping study with results of our questionnaire-based survey that involved 57 HPC experts. The mapping study and the survey revealed that the desired features of programming languages for data-intensive HPC applications are portability, performance and usability. Furthermore, we observed that the majority of the programming languages used in the context of data-intensive HPC applications are text-based general-purpose programming languages. Typically these have a steep learning curve, which makes them difficult to adopt. We believe that the outcome of this study will inspire future research and development in programming languages for data-intensive HPC applications. (C) 2019 Elsevier B.V. All rights reserved.

  • 270.
    Amaxilatis, Dimitrios
    et al.
    SparkWorks ITC Ltd, England.
    Tsironis, Nikolaos
    SparkWorks ITC Ltd, England.
    Papoulias, George
    Univ Patras, Greece.
    Hofs, Dennis
    Roessingh Res & Dev, Netherlands.
    Kovordanyi, Rita
    Linköping University, Department of Computer and Information Science, Human-Centered systems. Linköping University, Faculty of Science & Engineering.
    Marcos, Hugo
    Inst Pedro Nunes, Portugal.
    Jordao, Joao
    Inst Pedro Nunes, Portugal.
    Quintas, Joao
    Inst Pedro Nunes, Portugal.
    SmartWork: An IoT Enabled Unobtrusive Worker Health, Well-being and Functional Ability Monitoring Framework2021In: PROCEEDINGS OF THE 13TH INTERNATIONAL JOINT CONFERENCE ON COMPUTATIONAL INTELLIGENCE (IJCCI), SCITEPRESS , 2021, p. 398-408Conference paper (Refereed)
    Abstract [en]

    Staying healthy in our workplaces is one of the most important priorities both for employers and employees, especially after the recent COVID-19 pandemic. Especially for older workers, that are more vulnerable, not only due to COVID-19 but also due to their chronic conditions that may be affecting their performance and productivity. This is more prevalent in western societies where populations are aging and people and governments start to consider staying at work longer to stay as active members of the society and live independently in better conditions. In this paper we present the SmartWork software suite that aims at building a worker-centric Internet of Things enabled system for workability sustainability, integrating unobtrusive sensing and modeling of the worker state with a suite of novel services for context and worker-aware adaptive work support. SmartWork is a ready to use, software suite tested in real-world installations that combines off-the-shelf and novel software and hardware components to provide workers with guidance on how to improve both their personal and professional lives.

  • 271.
    Amcoff, Oscar
    Linköping University, Department of Computer and Information Science.
    I don’t know because I’m not a robot: I don’t know because I’m not a robot:A qualitative study exploring moral questions as a way to investigate the reasoning behind preschoolers’ mental state attribution to robots2022Independent thesis Basic level (degree of Bachelor), 12 credits / 18 HE creditsStudent thesis
    Abstract [en]

    Portrayals of artificially intelligent robots are becoming increasingly prevalent in children’s culture. This affects how children perceive robots, which have been found to affect the way children in school understand subjects like technology and programming. Since teachers need to know what influences their pupils' understanding of these subjects, we need to know how children’s preconceptions about robots affect the way they attribute mental states to them. We still know relatively little about how children do this. Based on the above, a qualitative approach was deemed fit. This study aimed to (1) investigate the reasoning and preconceptions underlying children’s mental state attribution to robots, and (2) explore the effectiveness of moral questions as a way to do this. 16 children aged 5- and 6 years old were asked to rate the mental states of four different robots while subsequently being asked to explain their answers. Half of the children were interviewed alone and half in small groups. A thematic analysis was conducted to analyze the qualitative data. Children’s mental state attribution was found to be influenced by preconceptions about robots as a group of entities lacking mental states. Children were found to perceive two robots, Atlas, and Nao, differently in various respects. This was argued to be because the children perceived these robots through archetypal frameworks. Moral questions were found successful as a way to spark reflective reasoning about the mental state attribution in the children. 

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  • 272.
    Amdahl, Per
    et al.
    Linköping University, Department of Computer and Information Science.
    Chaikiat, Per
    Linköping University, Department of Computer and Information Science.
    Personas as Drivers: - an alternative approach for creating scenarios for ADAS evaluation2007Independent thesis Advanced level (degree of Magister), 20 points / 30 hpStudent thesis
    Abstract [en]

    Research and development on vehicle safety has lately started to direct its focus towards how to actively support the driver and make it easier for her to drive safely through letting Advanced Driver Assistance Systems (ADAS) have effect on how the driver interacts with the vehicle and the surrounding traffic. This requires research on both how the driver and vehicle perform in different situations, in terms of psychology, cognition and individual differences. In addition, physical limitations and requirements of the driver and the vehicle must be taken into account. Therefore scenarios for evaluation of these systems are required. In the area of user-centered design a rather new method, Personas, is being adopted. This thesis tries to explore if the Persona method is a viable tool for creating scenarios for such evaluations. Experiences after completing this work imply that personas indeed is a viable way to include aspects and raise issues concerning individual variability and situational context in ADAS scenarios.

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  • 273.
    Ameur, Safia
    Linköping University, Department of Computer and Information Science.
    Picturing Words and Spelling out Pictures Semantic, phonological and spatial aspects of working memory capacity and processing and their implication for information layout2004Independent thesis Advanced level (degree of Magister)Student thesis
    Abstract [en]

    This study investigates verbal and visuospatial memory strategies used by individuals with perceptual or cognitive disabilities. The groups concentrated on in this study are deaf individuals who are native sign language users and individuals with dyslexia.

    The study comprises an experiment and an in-depth study in which a pre-test and a questionnaire were used. Nine deaf signers, two persons with dyslexia and 12 persons without any perceptual or cognitive constraints participated. Of these 23 persons, seven were selected to take part in the in-depth study.

    The results indicate individual differences in working memory capacity among the subjects and differences in performance and processing between native sign language users and hearing individuals. Further, all of the participants were using a number of different strategies and shifting between strategies in the experiment. The results demonstrate that the amount of information individuals are able to hold activated in working memory is dependent on a range of factors, both internal factors specific to the individual and external factors relating to how information is presented. Guidelines for information presentation to limit working memory demands based on the findings are suggested.

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  • 274. Order onlineBuy this publication >>
    Aminifar, Amir
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Analysis, Design, and Optimization of Embedded Control Systems2016Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Today, many embedded or cyber-physical systems, e.g., in the automotive domain, comprise several control applications, sharing the same platform. It is well known that such resource sharing leads to complex temporal behaviors that degrades the quality of control, and more importantly, may even jeopardize stability in the worst case, if not properly taken into account.

    In this thesis, we consider embedded control or cyber-physical systems, where several control applications share the same processing unit. The focus is on the control-scheduling co-design problem, where the controller and scheduling parameters are jointly optimized. The fundamental difference between control applications and traditional embedded applications motivates the need for novel methodologies for the design and optimization of embedded control systems. This thesis is one more step towards correct design and optimization of embedded control systems.

    Offline and online methodologies for embedded control systems are covered in this thesis. The importance of considering both the expected control performance and stability is discussed and a control-scheduling co-design methodology is proposed to optimize control performance while guaranteeing stability. Orthogonal to this, bandwidth-efficient stabilizing control servers are proposed, which support compositionality, isolation, and resource-efficiency in design and co-design. Finally, we extend the scope of the proposed approach to non-periodic control schemes and address the challenges in sharing the platform with self-triggered controllers. In addition to offline methodologies, a novel online scheduling policy to stabilize control applications is proposed.

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  • 275.
    Aminifar, Amir
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Self-Triggered Controllers, Resource Sharing, and Hard Guarantees2016In: 2016 2ND INTERNATIONAL CONFERENCE ON EVENT-BASED CONTROL, COMMUNICATION, AND SIGNAL PROCESSING (EBCCSP), IEEE , 2016Conference paper (Refereed)
    Abstract [en]

    Today, many control applications in embedded and cyber-physical systems are implemented on shared platforms, alongside other hard real-time or safety-critical applications. Having the resource shared among several applications, to provide hard guarantees, it is required to identify the amount of resource needed for each application. This is rather straightforward when the platform is shared among periodic control and periodic real-time applications. In the case of event-triggered and self-triggered controllers, however, the execution patterns and, in turn, the resource usage are not clear. Therefore, a major implementation challenge, when the platform is shared with self-triggered controllers, is to provide hard and efficient stability and schedulability guarantees for other applications. In this paper, we identify certain execution patterns for self-triggered controllers, using which we are able to provide hard and efficient stability guarantees for periodic control applications.

  • 276.
    Aminifar, Amir
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Bini, Enrico
    Scuola Super Sant Anna, Italy.
    Eles, Petru lon
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Analysis and Design of Real-Time Servers for Control Applications2016In: IEEE Transactions on Computers, ISSN 0018-9340, E-ISSN 1557-9956, Vol. 65, no 3, p. 834-846Article in journal (Refereed)
    Abstract [en]

    Today, a considerable portion of embedded systems, e.g., automotive and avionic, comprise several control applications. Guaranteeing the stability of these control applications in embedded systems, or cyber-physical systems, is perhaps the most fundamental requirement while implementing such applications. This is different from the classical hard real-time systems where often the acceptance criterion is meeting the deadline. In other words, in the case of control applications, guaranteeing stability is considered to be a main design goal, which is linked to the amount of delay and jitter a control application can tolerate before instability. This advocates the need for new design and analysis techniques for embedded real-time systems running control applications. In this paper, the analysis and design of such systems considering a server-based resource reservation mechanism are addressed. The benefits of employing servers are manifold: providing a compositional and scalable framework, protection against other tasks misbehaviors, and systematic bandwidth assignment and co-design. We propose a methodology for designing bandwidth-optimal servers to stabilize control tasks. The pessimism involved in the proposed methodology is both discussed theoretically and evaluated experimentally.

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  • 277.
    Aminifar, Amir
    et al.
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Bini, Enrico
    Lund University, Sweden.
    Eles, Petru
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Bandwidth-Efficient Controller-Server Co-Design with Stability Guarantees2014In: Design, Automation & Test in Europe, DATE 2014, IEEE Computer Society, 2014Conference paper (Refereed)
    Abstract [en]

    Many cyber-physical systems comprise several control applications implemented on a shared platform, for which stability is a fundamental requirement. This is as opposed to the classical hard real-time systems where often the criterion is meeting the deadline. However, the stability of control applications depends on not only the delay experienced, but also the jitter. Therefore, the notion of deadline is considered to be artificial for control applications that promotes the need for new techniques for designing cyber-physical systems. The approach in this paper is built on a server-based resource reservation mechanism, which provides compositionality, isolation, and the opportunity of systematic controller--server co-design. We address the controller--server co-design of such systems to obtain design solutions with the minimal bandwidth to guarantee stability.

  • 278.
    Aminifar, Amir
    et al.
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Bini, Enrico
    Lund University, Sweden.
    Eles, Petru
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Designing Bandwidth-Efficient Stabilizing Control Servers2013In: IEEE Real-Time Systems Symposium, RTSS 2013, IEEE , 2013, p. 298-307Conference paper (Refereed)
    Abstract [en]

    Guaranteeing stability of control applications in embedded systems, or cyber-physical systems, is perhaps the alpha and omega of implementing such applications. However, as opposed to the classical real-time systems where often the acceptance criterion is meeting the deadline, control applications do not primarily enforce hard deadlines. In the case of control applications, stability is considered to be the main design criterion and can be expressed in terms of the amount of delay and jitter a control application can tolerate before instability. Therefore, new design and analysis techniques are required for embedded control systems. In this paper, the analysis and design of such systems considering server-based resource reservation mechanism are addressed. The benefits of employing servers are manifold: (1) providing a compositional framework, (2) protection against other tasks misbehaviors, and (3) systematic bandwidth assignment. We propose a methodology for designing bandwidth-efficient servers to stabilize control tasks.

  • 279.
    Aminifar, Amir
    et al.
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Eles, Petru
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology. Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Jfair: A Scheduling Algorithm to Stabilize Control Applications2015In: 21st IEEE Real-Time and Embedded Technology and Applications Symposium, Cyber-Physical Systems Week, Seattle, WA, April 2015, IEEE Computer Society, 2015, p. 63-72Conference paper (Refereed)
    Abstract [en]

    Control applications are considered to be among the core applications in cyber-physical and embedded realtime systems, for which jitter is typically an important factor. This paper investigates whether it is possible to guarantee certain amount of jitter for a given set of applications on a shared platform. The effect of jitter on the stability of control applications and its relation with the latency will be discussed. The importance arises from the fact that it is considerably easier to manage the constant part of the delay (known as latency), while the process of coping with the varying part of the delay (known as jitter) is more involved. The proposed solution guarantees certain jitter limits, and at the same time does not lead to overly pessimistic latency values. The results are later used in a design optimization problem to minimize the resource utilized.

  • 280.
    Aminifar, Amir
    et al.
    Embedded Systems Laboratory, École Polytechnique Fédérale de Lausanne (EPFL), Switzerland.
    Eles, Petru
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Optimization of Message Encryption for Real-Time Applications in Embedded Systems2018In: IEEE Transactions on Computers, ISSN 0018-9340, E-ISSN 1557-9956, Vol. 67, no 5, p. 748-754Article in journal (Refereed)
    Abstract [en]

    Today, security can no longer be treated as a secondary issue in embedded and cyber-physical systems. Therefore, one of the main challenges in these domains is the design of secure embedded systems under stringent resource constraints and real-time requirements. However, there exists an inherent trade-off between the security protection provided and the amount of resources allocated for this purpose. That is, the more the amount of resources used for security, the higher the security, but the fewer the number of applications which can be run on the platform and meet their timing requirements. This trade-off is of high importance since embedded systems are often highly resource constrained. In this paper, we propose an efficient solution to maximize confidentiality, while also guaranteeing the timing requirements of real-time applications on shared platforms.

  • 281.
    Aminifar, Amir
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Eles, Petru
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Cervin, Anton
    Dept. of Automatic Control, Lund University, Sweden.
    Control-Quality Driven Design of Cyber-Physical Systems with Robustness Guarantees2013In: Design, Automation & Test in Europe (DATE 2013), IEEE , 2013, p. 1093-1098Conference paper (Refereed)
    Abstract [en]

    Many cyber-physical systems comprise several control applications sharing communication and computation resources. The design of such systems requires special attention due to the complex timing behavior that can lead to poor control quality or even instability. The two main requirements of control applications are: (1) robustness and, in particular, stability and (2) high control quality. Although it is essential to guarantee stability and provide a certain degree of robustness even in the worst-case scenario, a design procedure which merely takes the worst-case scenario into consideration can lead to a poor expected (average-case) control quality, since the design is solely tuned to a scenario that occurs very rarely. On the other hand, considering only the expected quality of control does not necessarily provide robustness and stability in the worst-case. Therefore, both the robustness and the expected control quality should be taken into account in the design process. This paper presents an efficient and integrated approach for designing high-quality cyber-physical systems with robustness guarantees.

  • 282.
    Aminifar, Amir
    et al.
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Eles, Petru
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Cervin, Anton
    Lund University, Sweden.
    Stability-Aware Analysis and Design of Embedded Control Systems2013In: Proceedings of the International Conference on Embedded Software (EMSOFT), 2013, IEEE conference proceedings, 2013, p. 1-10Conference paper (Refereed)
    Abstract [en]

    Many embedded systems comprise several controllers sharing available resources. It is well known that such resource sharing leads to complex timing behavior that can jeopardize stability of control applications, if it is not properly taken into account in the design process, e.g., mapping and scheduling. As opposed to hard real-time systems where meeting the deadline is a critical requirement, control applications do not enforce hard deadlines. Therefore, the traditional real-time analysis approaches are not readily applicable to control applications. Rather, in the context of control applications, stability is often the main requirement to be guaranteed, and can be expressed as the amount of delay and jitter a control application can tolerate. The nominal delay and response-time jitter can be regarded as the two main factors which relate the real-time aspects of a system to control performance and stability. Therefore, it is important to analyze the impact of variations in scheduling parameters, i.e., period and priority, on the nominal delay and response-time jitter and, ultimately, on stability. Based on such an analysis, we address, in this paper, priority assignment and sensitivity analysis problems for control applications considering stability as the main requirement.

  • 283.
    Aminifar, Amir
    et al.
    Embedded Systems Laboratory, École Polytechnique Fédérale de Lausanne (EPFL), Switzerland..
    Eles, Petru
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Cervin, Anton
    Department of Automatic Control, Lund University, Sweden.
    Årzén, Karl-Erik
    Department of Automatic Control, Lund University, Sweden.
    Control-Quality Driven Design of Embedded Control Systems with Stability Guarantees2018In: IEEE design & test, ISSN 2168-2356, E-ISSN 2168-2364, Vol. 35, no 4, p. 38-46Article in journal (Refereed)
    Abstract [en]

    Today, the majority of control applications in embedded systems, e.g., in the automotive domain, are implemented as software tasks on shared platforms. Ignoring implementation impacts during the design of embedded control systems results in complex timing behaviors that may lead to poor performance and, in the worst case, instability of control applications. This article presents a methodology for implementation-aware design of high-quality and stable embedded control systems on shared platforms with complex timing behaviors.

  • 284.
    Aminifar, Amir
    et al.
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, The Institute of Technology.
    Samii, Soheil
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, The Institute of Technology.
    Eles, Petru
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, The Institute of Technology.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, The Institute of Technology.
    Control-Quality Driven Task Mapping for Distributed Embedded Control Systems2011In: Embedded and Real-Time Computing Systems and Applications (RTCSA), 2011 IEEE 17th International Conference on, IEEE, 2011, p. 133-142Conference paper (Refereed)
    Abstract [en]

    Many embedded control systems are implemented on execution platforms with several computation nodes and communication components. Distributed embedded control systems typically comprise multiple control loops that share the available computation and communication resources of the platform. It is well known that such resource sharing leads to complex delay characteristics that degrade the control quality if not properly taken into account at design time. Scheduling in computation nodes and communication infrastructure, as well as execution periods of the controllers impact the delay characteristics and, consequently, the control quality. In addition, mapping of tasks on computation nodes affect both scheduling of tasks and messages, and the assignment of periods of the control applications. Therefore, control synthesis must be considered during mapping, scheduling, and period assignment in order to achieve high control quality. This paper presents a control-quality optimization approach for integrated mapping, scheduling, period selection, and control synthesis for distributed embedded control systems.

  • 285.
    Aminifar, Amir
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Samii, Soheil
    Linköping University, The Institute of Technology. Linköping University, Department of Computer and Information Science, Software and Systems.
    Eles, Petru
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Cervin, Anton
    Dept. of Automatic Control, Lund University, Sweden.
    Designing High-Quality Embedded Control Systems with Guaranteed Stability2012In: 33rd IEEE Real-Time Systems Symposium (RTSS 2012, 2012Conference paper (Refereed)
    Abstract [en]

    Many embedded systems comprise several controllers sharing available resources. It is well known that such resource sharing leads to complex timing behavior that degrades the quality of control, and more importantly, can jeopardize stability in the worst-case, if not properly taken into account during design. Although stability of the control applications is absolutely essential, a design flow driven by the worst-case scenario often leads to poor control quality due to the significant amount of pessimism involved and the fact that the worst-case scenario occurs very rarely. On the other hand, designing the system merely based on control quality, determined by the expected (average-case) behavior, does not guarantee the stability of control applications in the worst-case. Therefore, both control quality and worst-case stability have to be considered during the design process, i.e., period assignment, task scheduling, and control-synthesis. In this paper, we present an integrated approach for designing high-quality embedded control systems, while guaranteeing their stability.

  • 286.
    Aminifar, Amir
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Tabuada, Paulo
    University of California at Los Angeles, USA.
    Eles, Petru
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Self-Triggered Controllers and Hard Real-Time Guarantees2016In: PROCEEDINGS OF THE 2016 DESIGN, AUTOMATION & TEST IN EUROPE CONFERENCE & EXHIBITION (DATE), Institute of Electrical and Electronics Engineers (IEEE), 2016, p. 636-641Conference paper (Refereed)
    Abstract [en]

    It is well known that event-triggered and self-triggered controllers implemented on dedicated platforms can provide the same performance as the traditional periodic controllers, while consuming considerably less bandwidth. However, since the majority of controllers are implemented by software tasks on shared platforms, on one hand, it might no longer be possible to grant access to the event-triggered controller upon request. On the other hand, due to the seemingly irregular requests from self-triggered controllers, other applications, while in reality schedulable, may be declared unschedulable, if not carefully analyzed. The schedulability and response-time analysis in the presence of self-triggered controllers is still an open problem and the topic of this paper.

  • 287.
    Aminoff, Hedvig
    Linköping University, Department of Computer and Information Science.
    Coordination in Emergency Management from a Joint Cognitive Systems Perspective2007Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Emergency management (EM) can benefit from new information and communication technology (ICT). However, the complexity of the field poses high demands upon prospective system developers. The design of technological support in a field where roles and actions are entwined and never completely predetermined, requires an understanding of interactions in the socio-technical system as a whole.

    In this thesis, an attempt is made to work from a Cognitive Systems Engineering stance to identify important characteristics of coordination in intermunicipal EM. Applying perspectives from distributed cognition, joint activity and common ground, Hollnagel’s COCOM and ECOM models have been applied to identify points of entry into work practices. Working with data from a simulated forest-fire in a role-playing exercise, an analysis of dialogues uncovered ambiguity in how functions are handled in a large event, indicating vulnerabilities in face of larger crises. In addition, it became evident that functions moved across roles during the evolving event, and it was possible to uncover recognizable phases of a response. The results underline characteristics that should be supported by future ICT, and occurrences that can be explored in future studies.

    Download full text (pdf)
    FULLTEXT01
  • 288.
    Aminoff, Hedviq
    et al.
    Infocentret Ankaret.
    Johansson, Björn
    Linköping University, The Institute of Technology. Linköping University, Department of Computer and Information Science, CSELAB - Cognitive Systems Engineering Laboratory.
    Trnka, Jiri
    Linköping University, The Institute of Technology. Linköping University, Department of Computer and Information Science, GIS - Geographical Information Science Group.
    Understanding Coordination in Emergency Response2007In: European Annual Conference on Human Decision-Making and Manual Control,2007, Lyngby, Denmark: Technical University of Denmark , 2007Conference paper (Other academic)
    Abstract [en]

    This paper describes and discusses analysis of an emergency management exercise. In the exercise scenario, different emergency management organizations jointly try to cope with a forest fire and related incidents. The Extended Control Model is utilized for examination of the establishment of en emergent emergency response organization. Ambiguity in how functions are to be handled in a large event, indicating vulnerabilities in face of larger crises; functions moving across roles during the evolving event; and recognizable phases of a response are uncovered. This is assessed by utilizing episodic analysis of the communication between different functions and roles in the participating emergency management organizations. The results indicate requirements for future information and communication technologies, and occurrences that can be explored in future studies.

  • 289. Order onlineBuy this publication >>
    Amirijoo, Mehdi
    Linköping University, Department of Computer and Information Science, RTSLAB - Real-Time Systems Laboratory. Linköping University, The Institute of Technology.
    QoS Control of Real-Time Data Services under Uncertain Workload2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Real-time systems comprise computers that must generate correct results in a timely manner. This involves a wide spectrum of computing systems found in our everyday life ranging from computers in rockets to our mobile phones. The criticality of producing timely results defines the different types of realtime systems. On one hand, we have the so-called hard real-time systems, where failing to meet deadlines may result in a catastrophe. In this thesis we are, however, concerned with firm and soft real-time systems, where missing deadlines is acceptable at the expense of degraded system performance. The usage of firm and soft real-time systems has increased rapidly during the last years, mainly due to the advent of applications in multimedia, telecommunication, and e-commerce. These systems are typically data-intensive, with the data normally spanning from low-level control data, typically acquired from sensors, to high-level management and business data. In contrast to hard real-time systems, the environments in which firm and soft real-time systems operate in are typically open and highly unpredictable. For example, the workload applied on a web server or base station in telecommunication systems varies according to the needs of the users, which is hard to foresee. In this thesis we are concerned with quality of service (QoS) management of data services for firm and soft real-time systems. The approaches and solutions presented aim at providing a general understanding of how the QoS can be guaranteed according to a given specification, even if the workload varies unpredictably. The QoS specification determines the desired QoS during normal system operation, and the worst-case system performance and convergence rate toward the desired setting in the face of transient overloads. Feedback control theory is used to control QoS since little is known about the workload applied on the system. Using feedback control the difference between the measured QoS and the desired QoS is formed and fed into a controller, which computes a change to the operation of the real-time system. Experimental evaluation shows that using feedback control is highly effective in managing QoS such that a given QoS specification is satisfied. This is a key step toward automatic management of intricate systems providing real-time data services.

    List of papers
    1. Specification and Management of QoS in Real-Time Databases Supporting Imprecise Computations
    Open this publication in new window or tab >>Specification and Management of QoS in Real-Time Databases Supporting Imprecise Computations
    2006 (English)In: IEEE Transactions on Computers, ISSN 0018-9340, E-ISSN 1557-9956, Vol. 55, no 3, p. 304-319Article in journal (Refereed) Published
    Abstract [en]

    Real-time applications such as e-commerce, flight control, chemical and nuclear control, and telecommunication are becoming increasingly sophisticated in their data needs, resulting in greater demands for real-time data services that are provided by real-time databases. Since the workload of real-time databases cannot be precisely predicted, they can become overloaded and thereby cause temporal violations, resulting in damage or even a catastrophe. Imprecise computation techniques address this problem and allow graceful degradation during overloads. In this paper, we present a framework for QoS specification and management consisting of a model for expressing QoS requirements, an architecture based on feedback control scheduling, and a set of algorithms implementing different policies and behaviors. Our approach gives a robust and controlled behavior of real-time databases, even for transient overloads and with inaccurate runtime estimates of the transactions. Further, performance experiments show that the proposed algorithms outperform a set of baseline algorithms that uses feedback control.

    Keywords
    Real-time and embedded systems, real-time data services, imprecise computation, feedback control, modeling techniques
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-12635 (URN)10.1109/TC.2006.45 (DOI)
    Available from: 2007-10-17 Created: 2007-10-17 Last updated: 2023-03-28
    2. Experimental Evaluation of Linear Time-Invariant Models for Feedback Performance Control in Real-Time Systems
    Open this publication in new window or tab >>Experimental Evaluation of Linear Time-Invariant Models for Feedback Performance Control in Real-Time Systems
    2007 (English)In: Real-time systems, ISSN 0922-6443, E-ISSN 1573-1383, Vol. 35, no 3, p. 209-238Article in journal (Refereed) Published
    Abstract [en]

    In recent years a new class of soft real-time applications operating in unpredictable environments has emerged. Typical for these applications is that neither the resource requirements nor the arrival rates of service requests are known or available a priori. It has been shown that feedback control is very effective to support the specified performance of dynamic systems that are both resource insufficient and exhibit unpredictable workloads. To efficiently use feedback control scheduling it is necessary to have a model that adequately describes the behavior of the system. In this paper we experimentally evaluate the accuracy of four linear time-invariant models used in the design of feedback controllers. We introduce a model (DYN) that captures additional system dynamics, which a previously published model (STA) fails to include. The accuracy of the models are evaluated by validating the models with regard to measured data from the controlled system and through a set of experiments where we evaluate the performance of a set of feedback control schedulers tuned using these models. From our evaluations we conclude that second order models (e.g., DYN) are more accurate than first order models (e.g. STA). Further we show that controllers tuned using second order models perform better than controllers tuned using first order models.

    Place, publisher, year, edition, pages
    Springer Science+Business Media B.V., 2007
    Keywords
    Feedback control scheduling, Modeling, Model validation, System identification
    National Category
    Control Engineering
    Identifiers
    urn:nbn:se:liu:diva-12636 (URN)10.1007/s11241-006-9008-8 (DOI)
    Available from: 2007-10-17 Created: 2007-10-17 Last updated: 2017-12-14
    3. Robust Quality Management for Differentiated Imprecise Data Services
    Open this publication in new window or tab >>Robust Quality Management for Differentiated Imprecise Data Services
    2004 (English)In: Proceedings of the 25th IEEE International Real-Time Systems Symposium, 2004, p. 265-275Conference paper, Published paper (Refereed)
    Abstract [en]

    Several applications, such as Web services and e-commerce, are operating in open environments where the workload characteristics, such as the load applied on the system and the worst-case execution times, are inaccurate or even not known in advance. This implies that transactions submitted to a real-time database cannot be subject to exact schedulability analysis given the lack of a priori knowledge of the workload. In this paper we propose an approach, based on feedback control, for managing the quality of service of real-time databases that provide imprecise and differentiated services, given inaccurate workload characteristics. For each service class, the database operator specifies the quality of service requirements by explicitly declaring the precision requirements of the data and the results of the transactions. The performance evaluation shows that our approach provides reliable quality of service even in the face of varying load and inaccurate execution time estimates.

    Keywords
    Real-time systems, Real-time databases, Control theory, Realtidssystem, Realtidsdatabaser, Reglerteknik, CUGS
    National Category
    Control Engineering
    Identifiers
    urn:nbn:se:liu:diva-12637 (URN)10.1109/REAL.2004.49 (DOI)0-7695-2247-5 (ISBN)
    Conference
    25th IEEE International Real-Time Systems Symposium, Lisbon, Portugal, December 5-8, 2004
    Available from: 2007-10-17 Created: 2007-10-17 Last updated: 2018-08-30
    4. Generalized performance management of multi-class real-time imprecise data services
    Open this publication in new window or tab >>Generalized performance management of multi-class real-time imprecise data services
    Show others...
    2005 (English)In: Real-Time Systems Symposium, 2005. RTSS 2005. 26th IEEE International, 2005, p. 12-49Conference paper, Published paper (Other academic)
    Abstract [en]

    The intricacy of real-time data service management increases mainly due to the emergence of applications operating in open and unpredictable environments, increases in software complexity, and need for performance guarantees. In this paper we propose an approach for managing the quality of service of real-time databases that provide imprecise and differentiated services, and that operate in unpredictable environments. Transactions are classified into service classes according to their level of importance. Transactions within each service class are further classified into subclasses based on their quality of service requirements. In this way transactions are explicitly differentiated according to their importance and quality of service requests. The performance evaluation shows that during overloads the most important transactions are guaranteed to meet their deadlines and that reliable quality of service is provided even in the face of varying load and execution time estimation errors.

    Keywords
    real-time system, database, QoS, feedback control
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-12638 (URN)10.1109/RTSS.2005.23 (DOI)
    Available from: 2007-10-17 Created: 2007-10-17 Last updated: 2009-04-22
    5. Quantifying and Suppressing the Measurement Disturbance in Feedback Controlled Real-Time Systems
    Open this publication in new window or tab >>Quantifying and Suppressing the Measurement Disturbance in Feedback Controlled Real-Time Systems
    2008 (English)In: Real-time systems, ISSN 0922-6443, E-ISSN 1573-1383, Vol. 40, no 1, p. 44-76Article in journal (Refereed) Published
    Abstract [en]

    In the control of continuous and physical systems, the controlled system is sampled sufficiently fast to capture the dynamics of the system. In general, this property cannot be applied to the control of computer systems as the measured variables are often computed over a data set, e.g., deadline miss ratio. In this paper we quantify the disturbance present in the measured variable as a function of the data set size and the sampling period, and we propose a feedback control structure that suppresses the measurement disturbance. The experiments we have carried out show that a controller using the proposed control structure outperforms a traditional control structure with regard to performance reliability.

    Place, publisher, year, edition, pages
    Springer, 2008
    Keywords
    Adaptive scheduling, Feedback control, Measurement disturbance, System disturbance
    National Category
    Control Engineering
    Identifiers
    urn:nbn:se:liu:diva-12639 (URN)10.1007/s11241-008-9048-3 (DOI)
    Available from: 2007-10-17 Created: 2007-10-17 Last updated: 2017-12-14
    Download full text (pdf)
    FULLTEXT01
    Download (pdf)
    COVER01
  • 290.
    Amirijoo, Mehdi
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Computer and Information Science, RTSLAB - Real-Time Systems Laboratory.
    Brännström, Per
    Institutionen för datavetenskap Linköpings universitet.
    Hansson, Jörgen
    Linköping University, The Institute of Technology. Linköping University, Department of Computer and Information Science, RTSLAB - Real-Time Systems Laboratory.
    Gunnarsson, Svante
    Linköping University, The Institute of Technology. Linköping University, Department of Electrical Engineering, Automatic Control.
    Son, Sang
    Department of Computer Science University of Virginia.
    Toward Adaptive Control of QoS-Importance Decoupled Real-Time Systems2007In: IEEE International Workshop on Feedback Control Implementation and Design in Computing Systems and Networks,2007, 2007Conference paper (Refereed)
    Abstract [en]

    This paper deals with differentiated services in real-time systems. Tasks submitted to a real-time system are differentiated with respect to importance and QoS requirements. We use feedback control to enforce the requirements in QoS and ensure a hierarchical admission policy based on the importance of the tasks. The results show that the requirements are met during steady state when the workload is constant. The feedback control approach does not satisfactorily manage QoS when there is a sudden and significant workload change (transient state) due to the time-variant nature of the system. To address this, we present preliminary and promising results using adaptive control, and report on some challenges we are facing when applying the theory.

  • 291.
    Amirijoo, Mehdi
    et al.
    Linköping University, Department of Computer and Information Science, RTSLAB - Real-Time Systems Laboratory. Linköping University, The Institute of Technology.
    Chaufette, Nicolas
    Hansson, Jörgen
    Software Engineering Institute, Carnegie Mellon University, USA.
    Son, Sang H.
    Dept. of Computer Science, University of Virginia, Charlottesville, USA.
    Gunnarsson, Svante
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Generalized performance management of multi-class real-time imprecise data services2005In: Real-Time Systems Symposium, 2005. RTSS 2005. 26th IEEE International, 2005, p. 12-49Conference paper (Other academic)
    Abstract [en]

    The intricacy of real-time data service management increases mainly due to the emergence of applications operating in open and unpredictable environments, increases in software complexity, and need for performance guarantees. In this paper we propose an approach for managing the quality of service of real-time databases that provide imprecise and differentiated services, and that operate in unpredictable environments. Transactions are classified into service classes according to their level of importance. Transactions within each service class are further classified into subclasses based on their quality of service requirements. In this way transactions are explicitly differentiated according to their importance and quality of service requests. The performance evaluation shows that during overloads the most important transactions are guaranteed to meet their deadlines and that reliable quality of service is provided even in the face of varying load and execution time estimation errors.

  • 292.
    Amirijoo, Mehdi
    et al.
    Linköping University, Department of Computer and Information Science, RTSLAB - Real-Time Systems Laboratory. Linköping University, The Institute of Technology.
    Gunnarsson, Svante
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Hansson, Jörgen
    Software Engineering Institute, Carnegie Mellon University, Pittsburgh, PA, USA.
    Son, Sang H.
    University of Virginia, USA.
    Quantifying and Suppressing the Measurement Disturbance in Feedback Controlled Real-Time Systems2008In: Real-time systems, ISSN 0922-6443, E-ISSN 1573-1383, Vol. 40, no 1, p. 44-76Article in journal (Refereed)
    Abstract [en]

    In the control of continuous and physical systems, the controlled system is sampled sufficiently fast to capture the dynamics of the system. In general, this property cannot be applied to the control of computer systems as the measured variables are often computed over a data set, e.g., deadline miss ratio. In this paper we quantify the disturbance present in the measured variable as a function of the data set size and the sampling period, and we propose a feedback control structure that suppresses the measurement disturbance. The experiments we have carried out show that a controller using the proposed control structure outperforms a traditional control structure with regard to performance reliability.

  • 293.
    Amirijoo, Mehdi
    et al.
    Linköping University, Department of Computer and Information Science, RTSLAB - Real-Time Systems Laboratory. Linköping University, The Institute of Technology.
    Hansson, Jörgen
    Linköping University, Department of Computer and Information Science, RTSLAB - Real-Time Systems Laboratory. Linköping University, The Institute of Technology.
    Gunnarsson, Svante
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Son, Sang H.
    University of Virginia, VA, USA.
    Enhancing Feedback Control Scheduling Performance by On-line Quantification and Suppression of Measurement Disturbance2005In: Proceedings of the 11th IEEE Real-Time and Embedded Technology and Applications Symposium, 2005, p. 2-11Conference paper (Refereed)
    Abstract [en]

    In the control of continuous and physical systems, the controlled system is sampled sufficiently fast to capture the system dynamics. In general, this property cannot be applied to the control of computer systems as the measured variables are often computed over a data set, e.g., deadline miss ratio. In this paper we quantize the disturbance present in the measured variable as a function of the sampling period and we propose a measurement disturbance suppressive control structure. The experiments we have carried out show that a controller using the proposed control structure outperforms a traditional control structure with regard to performance reliability and adaptation.

  • 294.
    Amirijoo, Mehdi
    et al.
    Linköping University, Department of Computer and Information Science, RTSLAB - Real-Time Systems Laboratory. Linköping University, The Institute of Technology.
    Hansson, Jörgen
    Linköping University, Department of Computer and Information Science, RTSLAB - Real-Time Systems Laboratory. Linköping University, The Institute of Technology.
    Son, S. H.
    University of Virginia.
    Algorithms for Managing QoS for Real-Time Data Services Using Imprecise Computation2003In: Proceedings of the 9th International Conference on Real-Time and Embedded Computing Systems and Application (RTCSA 2003), Springer Verlag , 2003Conference paper (Refereed)
  • 295.
    Amirijoo, Mehdi
    et al.
    Linköping University, Department of Computer and Information Science, RTSLAB - Real-Time Systems Laboratory. Linköping University, The Institute of Technology.
    Hansson, Jörgen
    Linköping University, Department of Computer and Information Science, RTSLAB - Real-Time Systems Laboratory. Linköping University, The Institute of Technology.
    Son, Sang H
    University of Virginia.
    Algorithms for managing QoS for real-time data services using imprecise computation2004In: Real-Time and Embedded Computing Systems and Applications 9th International Conference, RTCSA 2003, Tainan City, Taiwan, February 18-20, 2003. Revised Papers / [ed] Jing Chen and Seongsoo Hong, Springer Berlin/Heidelberg, 2004, Vol. 2968, p. 136-157Chapter in book (Refereed)
    Abstract [en]

    Lately the demand for real-time data services has increased in applications where it is desirable to process user requests within their deadlines using fresh data. The real-time data services are usually provided by a real-time database (RTDB). Here, since the workload of the RTDBs cannot be precisely predicted, RTDBs can become overloaded. As a result, deadline misses and freshness violations may occur. To address this problem we propose a QoS-sensitive approach to guarantee a set of requirements on the behavior of RTDBs. Our approach is based on imprecise computation, applied on both data and transactions. We propose two algorithms to dynamically balance the workload and the quality of the data and transactions. Performance evaluations show that our algorithms give a robust and controlled behavior of RTDBs, in terms of transaction and data quality, even for transient overloads and with inaccurate run-time estimates of the transactions.

  • 296.
    Amirijoo, Mehdi
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Computer and Information Science, RTSLAB - Real-Time Systems Laboratory.
    Hansson, Jörgen
    Linköping University, The Institute of Technology. Linköping University, Department of Computer and Information Science, RTSLAB - Real-Time Systems Laboratory.
    Son, Sang H
    Dept. of Computer Science University of Virginia.
    Error-Driven QoS Management in Imprecise Real-Time Databases2003In: Euromicro Conference on Real-Time Systems,2003, Los Alamitos, CA, USA: IEEE Computer Society , 2003, p. 63-Conference paper (Refereed)
    Abstract [en]

    In applications such as web-applications, e-commerce, and engine control, the demand for real-time data services has increased. In these applications, requests have to be processed within their deadlines using fresh data. Since the workload of these systems cannot be precisely predicted, they can become overloaded and as a result, deadline and freshness violations may occur. To address this problem we propose a QoS-sensitive approach based on imprecise computation, applied on transactions and data objects. We propose two algorithms FCS-HEF and FCS-HEDF that give a robust and controlled behavior of RTDBs in terms of transaction and data preciseness, even for transient overloads and with inaccurate run-time estimates of the transactions. Further, performance experiments show that the proposed algorithms outperform a set of baseline algorithms including FCS-EDF, which schedules the transactions using EDF.

  • 297.
    Amirijoo, Mehdi
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Computer and Information Science, RTSLAB - Real-Time Systems Laboratory.
    Hansson, Jörgen
    Linköping University, The Institute of Technology. Linköping University, Department of Computer and Information Science, RTSLAB - Real-Time Systems Laboratory.
    Son, Sang H
    Dept. of Computer Science University of Virginia.
    Specification and Management of QoS in Imprecise Real-Time Databases2003In: International Database Engineering and Applications Symposium,2003, Los Alamitos, CA, USA: IEEE Computer Society , 2003, p. 192-Conference paper (Refereed)
    Abstract [en]

    Real-time applications such as e-commerce, flight control, chemical and nuclear control, and telecommunication are becoming increasingly sophisticated in their data needs, resulting in greater demands for real-time data services. Since the workload of real-time databases RTDBs, providing real-time data services, cannot be precisely predicted, they can become overloaded and thereby cause temporal violations, resulting in a damage or even a catastrophe. Imprecise computation techniques address this problem and allow graceful degradation during overloads. In this paper, we present a framework consisting of a model for expressing QoS requirements in terms of data and transaction preciseness, an architecture based on feedback control scheduling, and a set of algorithms implementing different policies and behaviors. Our approach gives a robust and controlled behavior of RTDBs, even for transient overloads and with inaccurate run-time estimates of the transactions. Further, performance experiments show that the proposed algorithms outperform a set of baseline algorithms, including FCS-EDF that schedules the transactions using EDF and feedback control.

  • 298.
    Amirijoo, Mehdi
    et al.
    Linköping University, Department of Computer and Information Science, RTSLAB - Real-Time Systems Laboratory. Linköping University, The Institute of Technology.
    Hansson, Jörgen
    Linköping University, Department of Computer and Information Science, RTSLAB - Real-Time Systems Laboratory. Linköping University, The Institute of Technology.
    Son, Sang H.
    Dept. of Computer Science, University of Virginia, Charlottesville, USA.
    Specification and Management of QoS in Real-Time Databases Supporting Imprecise Computations2006In: IEEE Transactions on Computers, ISSN 0018-9340, E-ISSN 1557-9956, Vol. 55, no 3, p. 304-319Article in journal (Refereed)
    Abstract [en]

    Real-time applications such as e-commerce, flight control, chemical and nuclear control, and telecommunication are becoming increasingly sophisticated in their data needs, resulting in greater demands for real-time data services that are provided by real-time databases. Since the workload of real-time databases cannot be precisely predicted, they can become overloaded and thereby cause temporal violations, resulting in damage or even a catastrophe. Imprecise computation techniques address this problem and allow graceful degradation during overloads. In this paper, we present a framework for QoS specification and management consisting of a model for expressing QoS requirements, an architecture based on feedback control scheduling, and a set of algorithms implementing different policies and behaviors. Our approach gives a robust and controlled behavior of real-time databases, even for transient overloads and with inaccurate runtime estimates of the transactions. Further, performance experiments show that the proposed algorithms outperform a set of baseline algorithms that uses feedback control.

  • 299.
    Amirijoo, Mehdi
    et al.
    Linköping University, Department of Computer and Information Science, RTSLAB - Real-Time Systems Laboratory. Linköping University, The Institute of Technology.
    Hansson, Jörgen
    Linköping University, Department of Computer and Information Science, RTSLAB - Real-Time Systems Laboratory. Linköping University, The Institute of Technology.
    Son, Sang H.
    University of Virginia, USA.
    Gunnarsson, Svante
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Experimental Evaluation of Linear Time-Invariant Models for Feedback Performance Control in Real-Time Systems2007In: Real-time systems, ISSN 0922-6443, E-ISSN 1573-1383, Vol. 35, no 3, p. 209-238Article in journal (Refereed)
    Abstract [en]

    In recent years a new class of soft real-time applications operating in unpredictable environments has emerged. Typical for these applications is that neither the resource requirements nor the arrival rates of service requests are known or available a priori. It has been shown that feedback control is very effective to support the specified performance of dynamic systems that are both resource insufficient and exhibit unpredictable workloads. To efficiently use feedback control scheduling it is necessary to have a model that adequately describes the behavior of the system. In this paper we experimentally evaluate the accuracy of four linear time-invariant models used in the design of feedback controllers. We introduce a model (DYN) that captures additional system dynamics, which a previously published model (STA) fails to include. The accuracy of the models are evaluated by validating the models with regard to measured data from the controlled system and through a set of experiments where we evaluate the performance of a set of feedback control schedulers tuned using these models. From our evaluations we conclude that second order models (e.g., DYN) are more accurate than first order models (e.g. STA). Further we show that controllers tuned using second order models perform better than controllers tuned using first order models.

  • 300.
    Amirijoo, Mehdi
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Computer and Information Science, RTSLAB - Real-Time Systems Laboratory.
    Son, Sang H.
    Department of Computer Science University of Virgina.
    Hansson, Jörgen
    Linköping University, The Institute of Technology. Linköping University, Department of Computer and Information Science, RTSLAB - Real-Time Systems Laboratory.
    QoD Adaptation for Achieving Lifetime Predictability of WSN Nodes Communicating over Satellite Links2007In: International Conference on Networked Sensing Systems INSS,2007, IEEE , 2007, p. 19-26Conference paper (Refereed)
    Abstract [en]

    In this paper we propose an architecture consisting of a particular type of node, namely a communication server that collects and aggregates data, and establishes a link between the users and the sensor nodes through satellite communication. A key challenge with satisfying a lifetime requirement of the communication server is the unpredictability of the sensor data volume arriving at the communication server and the transmission power of the satellite terminal. To provide lifetime predictability we propose an approach that automatically adjusts the quality of the data such that the specified lifetime if achieved. We have shown through an extensive evaluation that the approach manages to provide an actual lifetime within 2% of the specified lifetime despite variations in workload and communication link quality.

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