| 1. |
- Abas, Naeem, et al.
(författare)
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Dynamic simulation of solar water heating system using supercritical CO2 as mediating fluid under sub-zero temperature conditions
- 2019
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Ingår i: Applied Thermal Engineering. - Oxford, UK : Pergamon Press. - 1359-4311 .- 1873-5606. ; 161
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Tidskriftsartikel (refereegranskat)abstract
- CO2 is becoming increasingly important as a mediating fluid, and simulation studies are indispensable for corresponding developments. In this study, a simulation-based performance investigation of a solar water heating system using CO2 as a mediating fluid under sub-zero temperature condition is performed using the TRNSYS (R) software. The maximum performance is achieved at a solar savings fraction of 0.83 during July. The as lowest solar savingss fraction of 0.41 is obtained during December. The annual heat production of the proposed system under Fargo climate is estimated to be about 2545 kWh. An evacuated glass tube solar collector is designed, fabricated and tested for various climate conditions. Moreover, a detailed comparison of the system's performance at sub/supercritical and supercritical pressures shows that the annual heat transfer efficiency of the modeled system is 10% higher at supercritical pressure than at sub/supercritical pressures. This result can be attributd to the strong convection flow of CO2 caused by density inhomogeneities, especially in the near critical region. This condition resuls in high heat transfer rates.
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| 2. |
- Abrahamsson, Henrik, et al.
(författare)
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Connected Vehicles in Cellular Networks : Multi-Access Versus Single-Access Performance
- 2018
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Ingår i: TMA 2018 - Proceedings of the 2nd Network Traffic Measurement and Analysis Conference. - : Institute of Electrical and Electronics Engineers Inc.. - 9783903176096
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Konferensbidrag (refereegranskat)abstract
- Connected vehicles can make roads traffic safer and more efficient, but require the mobile networks to handle time-critical applications. Using the MONROE mobile broadband measurement testbed we conduct a multi-access measurement study on buses. The objective is to understand what network performance connected vehicles can expect in today's mobile networks, in terms of transaction times and availability. The goal is also to understand to what extent access to several operators in parallel can improve communication performance. In our measurement experiments we repeatedly transfer warning messages from moving buses to a stationary server. We triplicate the messages and always perform three transactions in parallel over three different cellular operators. This creates a dataset with which we can compare the operators in an objective way and with which we can study the potential for multi-access. In this paper we use the triple-access dataset to evaluate single-access selection strategies, where one operator is chosen for each transaction. We show that if we have access to three operators and for each transaction choose the operator with best access technology and best signal quality then we can significantly improve availability and transaction times compared to the individual operators. The median transaction time improves with 6% compared to the best single operator and with 61% compared to the worst single operator. The 90-percentile transaction time improves with 23% compared to the best single operator and with 65% compared to the worst single operator.
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| 3. |
- Ahmed, Bestoun S., 1982-, et al.
(författare)
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An evaluation of Monte Carlo-based hyper-heuristic for interaction testing of industrial embedded software applications
- 2020
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Ingår i: Soft Computing - A Fusion of Foundations, Methodologies and Applications. - : Springer. - 1432-7643 .- 1433-7479. ; 24:18, s. 13929-13954
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Tidskriftsartikel (refereegranskat)abstract
- Hyper-heuristic is a new methodology for the adaptive hybridization of meta-heuristic algorithms to derive a general algorithm for solving optimization problems. This work focuses on the selection type of hyper-heuristic, called the exponential Monte Carlo with counter (EMCQ). Current implementations rely on the memory-less selection that can be counterproductive as the selected search operator may not (historically) be the best performing operator for the current search instance. Addressing this issue, we propose to integrate the memory into EMCQ for combinatorial t-wise test suite generation using reinforcement learning based on the Q-learning mechanism, called Q-EMCQ. The limited application of combinatorial test generation on industrial programs can impact the use of such techniques as Q-EMCQ. Thus, there is a need to evaluate this kind of approach against relevant industrial software, with a purpose to show the degree of interaction required to cover the code as well as finding faults. We applied Q-EMCQ on 37 real-world industrial programs written in Function Block Diagram (FBD) language, which is used for developing a train control management system at Bombardier Transportation Sweden AB. The results show that Q-EMCQ is an efficient technique for test case generation. Addition- ally, unlike the t-wise test suite generation, which deals with the minimization problem, we have also subjected Q-EMCQ to a maximization problem involving the general module clustering to demonstrate the effectiveness of our approach. The results show the Q-EMCQ is also capable of outperforming the original EMCQ as well as several recent meta/hyper-heuristic including modified choice function, Tabu high-level hyper-heuristic, teaching learning-based optimization, sine cosine algorithm, and symbiotic optimization search in clustering quality within comparable execution time.
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| 4. |
- Ahmed, Bestoun S., 1982-, et al.
(författare)
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Constrained interaction testing : A systematic literature study
- 2017
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Ingår i: IEEE Access. - Sweden : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 2169-3536. ; 5, s. 25706-25730
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Tidskriftsartikel (refereegranskat)abstract
- Interaction testing can be used to effectively detect faults that are otherwise difficult to find by other testing techniques. However, in practice, the input configurations of software systems are subjected to constraints, especially in the case of highly configurable systems. Handling constraints effectively and efficiently in combinatorial interaction testing is a challenging problem. Nevertheless, researchers have attacked this challenge through different techniques, and much progress has been achieved in the past decade. Thus, it is useful to reflect on the current achievements and shortcomings and to identify potential areas of improvements. This paper presents the first comprehensive and systematic literature study to structure and categorize the research contributions for constrained interaction testing. Following the guidelines of conducting a literature study, the relevant data are extracted from a set of 103 research papers belonging to constrained interaction testing. The topics addressed in constrained interaction testing research are classified into four categories of constraint test generation, application, generation and application, and model validation studies. The papers within each of these categories are extensively reviewed. Apart from answering several other research questions, this paper also discusses the applications of constrained interaction testing in several domains, such as software product lines, fault detection and characterization, test selection, security, and graphical user interface testing. This paper ends with a discussion of limitations, challenges, and future work in the area.
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| 5. |
- Ahmed, Bestoun S., 1982-, et al.
(författare)
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Handling constraints in combinatorial interaction testing in the presence of multi objective particle swarm and multithreading
- 2017
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Ingår i: Information and Software Technology. - : Elsevier. - 0950-5849 .- 1873-6025. ; 86, s. 20-36
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Tidskriftsartikel (refereegranskat)abstract
- Context: Combinatorial testing strategies have lately received a lot of attention as a result of their diverse applications. In its simple form, a combinatorial strategy can reduce several input parameters (configurations) of a system into a small set based on their interaction (or combination). In practice, the input configurations of software systems are subjected to constraints, especially in case of highly configurable systems. To implement this feature within a strategy, many difficulties arise for construction. While there are many combinatorial interaction testing strategies nowadays, few of them support constraints. Objective: This paper presents a new strategy, to construct combinatorial interaction test suites in the presence of constraints. Method: The design and algorithms are provided in detail. To overcome the multi-judgement criteria for an optimal solution, the multi-objective particle swarm optimisation and multithreading are used. The strategy and its associated algorithms are evaluated extensively using different benchmarks and comparisons. Results: Our results are promising as the evaluation results showed the efficiency and performance of each algorithm in the strategy. The benchmarking results also showed that the strategy can generate constrained test suites efficiently as compared to state-of-the-art strategies. Conclusion: The proposed strategy can form a new way for constructing of constrained combinatorial interaction test suites. The strategy can form a new and effective base for future implementations. (C) 2017 Elsevier B.V. All rights reserved.
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| 6. |
- Al-Dulaimy, Auday, et al.
(författare)
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LOOPS : A Holistic Control Approach for Resource Management in Cloud Computing
- 2021
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Ingår i: ICPE 2021 - Proceedings of the ACM/SPEC International Conference on Performance Engineering. - New York, NY, USA : Association for Computing Machinery (ACM). - 9781450381949 ; , s. 117-124
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Konferensbidrag (refereegranskat)abstract
- In cloud computing model, resource sharing introduces major benefits for improving resource utilization and total cost of ownership, but it can create technical challenges on the running performance. In practice, orchestrators are required to allocate sufficient physical resources to each Virtual Machine (VM) to meet a set of predefined performance goals. To ensure a specific service level objective, the orchestrator needs to be equipped with a dynamic tool for assigning computing resources to each VM, based on the run-Time state of the target environment. To this end, we present LOOPS, a multi-loop control approach, to allocate resources to VMs based on the service level agreement (SLA) requirements and the run-Time conditions. LOOPS is mainly composed of one essential unit to monitor VMs, and three control levels to allocate resources to VMs based on requests from the essential node. A tailor-made controller is proposed with each level to regulate contention among collocated VMs, to reallocate resources if required, and to migrate VMs from one host to another. The three levels work together to meet the required SLA. The experimental results have shown that the proposed approach can meet applications' performance goals by assigning the resources required by cloud-based applications.
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| 7. |
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Algebra, Geometry, and Mathematical Physics 2010
- 2012
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6596 .- 1742-6588.
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Samlingsverk (redaktörskap) (övrigt vetenskapligt/konstnärligt)abstract
- This proceedings volume presents results obtained by the participants of the 6th Baltic–Nordic workshop 'Algebra, Geometry, and Mathematical Physics (AGMP-6)' held at the Sven Lovén Centre for Marine Sciences in Tjärnö, Sweden on October 25–30, 2010. The Baltic–Nordic Network AGMP 'Algebra, Geometry, and Mathematical Physics' http://www.agmp.eu was created in 2005 on the initiative of two Estonian universities and two Swedish universities: Tallinn University of Technology represented by Eugen Paal (coordinator of the network), Tartu University represented by Viktor Abramov, Lund University represented by Sergei Silvestrov, and Chalmers University of Technology and the University of Gothenburg represented by Alexander Stolin. The goal was to promote international and interdisciplinary cooperation between scientists and research groups in the countries of the Baltic–Nordic region in mathematics and mathematical physics, with special emphasis on the important role played by algebra and geometry in modern physics, engineering and technologies. The main activities of the AGMP network consist of a series of regular annual international workshops, conferences and research schools. The AGMP network also constitutes an important educational forum for scientific exchange and dissimilation of research results for PhD students and Postdocs. The network has expanded since its creation, and nowadays its activities extend beyond countries in the Baltic–Nordic region to universities in other European countries and participants from elsewhere in the world. As one of the important research-dissimilation outcomes of its activities, the network has a tradition of producing high-quality research proceedings volumes after network events, publishing them with various international publishers.
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| 8. |
- Aronsson, Gunnar, 1943-, et al.
(författare)
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Etiska dilemman får cheferi nom socialtjänsten att sluta sin anställning
- 2021
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Ingår i: Arbetsmarknad & Arbetsliv. - Karlstad : Karlstads universitet. - 1400-9692 .- 2002-343X. ; 27:4, s. 33-48
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Tidskriftsartikel (refereegranskat)abstract
- I denna enkätstudie undersöktes krav – kontroll och stödfaktorers betydelseför att chefer inom socialtjänsten lämnar sin anställning. Person – rollkonflikt som etisk konflikt mellan egna värderingar och krav i arbetsrollen, emotionell utmattning samt ålder framkom som signifikanta prediktorer för att ha slutat vid uppföljning efter ett år. Samma prediktorer framkom för intention att sluta plus chefsstöd medan ålder bortföll. En slutsats är att identifiering av etiska dilemman och bättre stöd i svåra beslutssitutioner kan minska andelen som överväger lämna sin chefsbefattning. Att kunna hantera dilemman har betydelse för hela verksamheten och potentiellt även för medborgarnas tillit till socialtjänsten.
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| 9. |
- Asp, Margareta, professor, 1958-, et al.
(författare)
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Physical mobility, physical activity, and obesity among elderly : findings from a large population-based Swedish survey
- 2017
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Ingår i: Public Health. - : Elsevier B.V.. - 0033-3506 .- 1476-5616. ; 147, s. 84-91
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Tidskriftsartikel (refereegranskat)abstract
- Objective To examine how physical activity and physical mobility are related to obesity in the elderly. Study design A cross-sectional study of 2558 men and women aged 65 years and older who participated in a population survey in 2012 was conducted in mid-Sweden with an overall response rate of 67%. Methods Obesity (body mass index ≥30 kg/m2) was based on self-reported weight and height, and physical activity and physical mobility on questionnaire data. Chi-squared test and multiple logistic regressions were used as statistical analyses. Results The overall prevalence of obesity was 19% in women and 15% in men and decreased after the age of 75 years. A strong association between both physical activity and obesity, and physical mobility and obesity was found. The odds for obesity were higher for impaired physical mobility (odds ratio [OR] 2.83, 95% confidence interval [CI] 2.14–3.75) than for physical inactivity (OR 1.63, 95% CI 1.28–2.08) when adjusted for gender, age, socio-economic status and fruit and vegetable intake. However, physical activity was associated with obesity only among elderly with physical mobility but not among those with impaired physical mobility. Conclusion It is important to focus on making it easier for elderly with physical mobility to become or stay physically active, whereas elderly with impaired physical mobility have a higher prevalence of obesity irrespective of physical activity.
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| 10. |
- Astvik, Wanja, et al.
(författare)
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Arbetsmiljön i tillitsbaserad styrning och ledning : exempel från socialtjänsten
- 2020
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Ingår i: Arbetsmarknad & Arbetsliv. - Karlstad : Karlstads universitet. - 1400-9692 .- 2002-343X. ; 26:4, s. 25-45
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Tidskriftsartikel (refereegranskat)abstract
- Studiens syfte är att via fallstudier av socialtjänsten undersöka konkreta ledningspraktiker som kan sägas falla inom ramen för Tillitsdelegationens definition av tillitsbaserad styrning och ledning och som har betydelse för att åstadkomma hållbara arbetsmiljöer i välfärden. Analysen visar att hållbar arbetsmiljö via tillitsbaserad styrning och ledning kan kopplas till organisationens säkerställande av förmåga, integritet och hjälpvillighet. Konkreta ledningspraktiker för säkerställande och hållbar arbetsmiljö var uppdragsdialog, systemperspektiv, integrering av arbetsmiljö och verksamkvalitet samt långsiktig ekonomisk styrning. Genom att ledningen agerar tillitsvärdigt via säkerställande av tillitsvärdigheten hos dem som är satta att utföra arbetet närmast medborgarna, erhålls goda arbetsmiljöer.
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