| 1. |
- Blom Johansson, Monica, 1965-
(author)
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Aphasia and Communication in Everyday Life : Experiences of persons with aphasia, significant others, and speech-language pathologists
- 2012
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Doctoral thesis (other academic/artistic)abstract
- The aims of this thesis were to describe the experiences of persons with aphasia and their significant others of their conversations and use of communication strategies, examine current practice of family-oriented speech-language pathology (SLP) services, and test a family-oriented intervention in the early phase of rehabilitation.The persons with aphasia valued having conversations despite perceiving their aphasia as a serious social disability. They acknowledged the importance of the communication partners’ knowledge and understanding of aphasia and their use of supporting conversation strategies. Their own use of communication strategies varied considerably. The persons with aphasia longed to regain language ability and to be active participants in society.A majority of the significant others perceived their conversations with the person with aphasia as being less stimulating and enjoyable than conversations before stroke onset. Aphasia was considered a serious problem. The significant others took on increased communicative responsibility, where two thirds had changed their communicative behaviour to facilitate conversations. Type and severity of aphasia were especially related to the communicative experiences of the significant others and their motivation to be involved in SLP services.Thirty percent of the speech-language pathologists worked with people with aphasia and typically met with their families. They considered the involvement of significant others in SLP services as very important, especially in providing information about aphasia and communication partner training (CPT). However, involvement of significant others was restricted because of a time shortage and perceived limited skills and knowledge. In addition, there were national differences regarding aphasia rehabilitation services.The intervention consisted of three sessions directed to significant others (primarily emotional support and information) and three directed to the dyads (a person with aphasia and a significant other) (primarily CPT). All six participants (three dyads) felt that their knowledge and understanding of aphasia had increased and that their conversations had improved. These improvements were also evident to some extent with formal assessments.These results suggest the following: CPT should be an integral part of SLP services, national clinical guidelines are needed, and further education of speech-language pathologists and implementation of new knowledge into clinical practice requires consideration.
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| 2. |
- Hägglund, Patricia, 1989-
(author)
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Swallowing dysfunction among older people in short-term care : prevalence, effect of intervention, and risk of mortality
- 2019
-
Doctoral thesis (other academic/artistic)abstract
- Objectives: Swallowing dysfunction (dysphagia) is a common, but often neglected condition among geriatric patients that can cause severe complications such as malnutrition, aspiration pneumonia and death. The aims of this thesis were to (i) describe the study design and method of the multidisciplinary and multicenter project SOFIA (Swallowing function, Oral health, and Food Intake in old Age), (ii) study the prevalence of and the relationship between swallowing dysfunction and risk of undernutrition among older individuals in short-term care, (iii) study the effect of oral neuromuscular training on swallowing dysfunction among older individuals, and (iv) to investigate the association between poor oral health, swallowing dysfunction and mortality.Methods: This thesis includes four original papers that are all part of the SOFIA project. Paper Iis the study protocol. In total, 391 individuals aged 65 or older, from 36 short-term care units were included in the project. At baseline the participants’ status regarding swallowing function (assessed with the Timed Water Swallow Test, TWST), oral health (using the Revised Oral Assessment Guide, ROAG) and nutrition (assessed with the Minimal Eating Observation and Nutrition Form-version II, MEONF-II) were assessed and collected by calibrated professionals. Clinical data were also collected. Paper IIwas a cross-sectional study where the baseline assessments of the participants’ swallowing function and nutritional status were obtained and the relationship analyzed. Paper IIIwas a cluster randomized, controlled trial (cRCT) that included 116 participants identified with swallowing dysfunction in paper II. These participants were randomly assigned to either usual care (control group) or oral neuromuscular training (intervention group). All participants were assessed at baseline, after five weeks’ training and six months after end-of-treatment, regarding swallowing function and swallowing-related quality of life (QOL). Paper IVwas a prospective cohort study where all participants were followed-up 1-year after inclusion to investigate risk factors for mortality by analysis of the associations between swallowing dysfunction, poor oral health, and 1-year survival. Results: Paper II:The median age of the 391 participants was 84 years (Interquartile range [IQR] 11) and 209 (53%) were females. In total, 248 of the 385 (64%) participants showed swallowing dysfunction, and risk of undernutrition was observed in 91 of 390 (23%) participants. The adjusted logistics regression model revealed that participants with swallowing dysfunction had significantly higher odds of undernutrition than those with normal swallowing (Odds ratio [OR]: 1.74, 95% Confidence interval [CI] 1.04 to 2.92, P=0.034).Paper III: At end-of-treatment, a linear mixed model showed significant between-group differences of changes in swallowing efficacy between baseline and after completed treatment period (Ratio 1.60, 95% CI 1.15 to 2.29, P=0.007); indicating a 60% higher swallowing efficacy in the intervention group compared with the control group. Paper IV: A mixed effects Cox model showed that swallowing dysfunction and poor oral health were both independently associated with 1-year mortality (adjusted Hazard Ratio [aHR]: 1.67, 95% CI 1.02 to 2.75,P=0.041 and aHR: 1.98, 95% CI 1.07 to 3.65, P=0.029, respectively). In addition, swallowing dysfunction and poor oral health in combination predicted the highest mortality rate (35%, P<0.001).Conclusion: Swallowing dysfunction is highly prevalent and a risk factor for undernutrition among older people in short-term care. Oral neuromuscular training improves swallowing dysfunction and is thus a promising method of swallowing rehabilitation for older people with impaired swallowing. Swallowing dysfunction and poor oral health are independent risk factors for 1-year morality among older people in short-term care. Therefore, systematic screening and intervention to improve swallowing dysfunction and poor oral health are important to achieve healthy aging and to prevent undernutrition and early death.
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| 3. |
- Niméus, Emma, et al.
(author)
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Gene expression profiling in primary breast cancer distinguishes patients developing local recurrence after breast-conservation surgery, with or without postoperative radiotherapy
- 2008
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In: Breast Cancer Research. - : Springer Science and Business Media LLC. - 1465-5411 .- 1465-542X. ; 10:2
-
Journal article (peer-reviewed)abstract
- IntroductionSome patients with breast cancer develop local recurrence after breast-conservation surgery despite postoperative radiotherapy, whereas others remain free of local recurrence even in the absence of radiotherapy. As clinical parameters are insufficient for identifying these two groups of patients, we investigated whether gene expression profiling would add further information.MethodsWe performed gene expression analysis (oligonucleotide arrays, 26,824 reporters) on 143 patients with lymph node-negative disease and tumor-free margins. A support vector machine was employed to build classifiers using leave-one-out cross-validation.ResultsWithin the estrogen receptor-positive (ER+) subgroup, the gene expression profile clearly distinguished patients with local recurrence after radiotherapy (n = 20) from those without local recurrence (n = 80 with or without radiotherapy). The receiver operating characteristic (ROC) area was 0.91, and 5,237 of 26,824 reporters had a P value of less than 0.001 (false discovery rate = 0.005). This gene expression profile provides substantially added value to conventional clinical markers (for example, age, histological grade, and tumor size) in predicting local recurrence despite radiotherapy. Within the ER- subgroup, a weaker, but still significant, signal was found (ROC area = 0.74). The ROC area for distinguishing patients who develop local recurrence from those who remain local recurrence-free in the absence of radiotherapy was 0.66 (combined ER+/ER-).ConclusionA highly distinct gene expression profile for patients developing local recurrence after breast-conservation surgery despite radiotherapy has been identified. If verified in further studies, this profile might be a most important tool in the decision making for surgery and adjuvant therapy.
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| 4. |
- van de Beek, Jaap, et al.
(author)
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A conceptual study of OFDM-based multiple access schemes : Part 4: Tracking of time and frequency offset
- 1996
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Reports (other academic/artistic)abstract
- This paper is part of a conceptual study of a multiuser OFDM system. In previous reports we have examined requirements for the air interface and presented uncoded performance (in terms of bit error rate) for the uplink of such systems. In this report we adopt the user allocation structure from the previous parts of the study and examine the role of channel coding. We present performance simulations that illustrate the effects of a convolutional code exploiting channel diversity, and channel estimator performance exploiting the channel correlation.
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| 5. |
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| 6. |
- van de Beek, Jan-Jaap, et al.
(author)
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A time and frequency synchronization scheme for multiuser OFDM
- 1999
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In: IEEE Journal on Selected Areas in Communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8716 .- 1558-0008. ; 17:11, s. 1900-1914
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Journal article (peer-reviewed)abstract
- We present a multiuser synchronization scheme for tracking the mobile's uplink time and frequency offsets. It uses the redundancy introduced by the cyclic prefix and does not need additional pilots. We show performance results of an orthogonal frequency division multiplexing (OFDM)-based radio interface based on universal mobile telecommunication system (UMTS) parameters. For a UMTS-typical mobile channel environment, the performance of a coherent system employing the scheme is virtually indistinguishable from the performance of a perfectly synchronized system. In a differentially modulated system, synchronization errors decrease the system performance by about 0.7 dB compared to a perfectly synchronized system. Index Terms - Communication system, delay estimation, frequency estimation, multicarrier, multiuser system, orthogonal frequency division multiplexing (OFDM), synchronization, universal mobile telecommunication system (UMTS).
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| 7. |
- van de Beek, Jaap, et al.
(author)
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Synchronization of a TDMA-OFDM frequency hopping system
- 1998
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In: Pathway to a global wireless revolution. - Piscataway, NJ : IEEE Communications Society. - 0780343204 ; , s. 1290-1294
-
Conference paper (peer-reviewed)abstract
- In this paper we present a Time Division Multiple Access-Orthogonal Frequency Division Multiplexing (TDMA-OFDM)-based radio interface proposal for the Universal Mobile Telecommunication System (UMTS). We focus on synchronization and present an implementable algorithm for the tracking of the mobiles' time and frequency offsets at the base station in the uplink. This algorithm is based on recently developed estimation methods that use redundancy introduced by the cyclic prefix. A modified Maximum Likelihood (ML) estimator for the Additive White Gaussian Noise (AWGN) channel is used to meet both implementational requirements and performance requirements for frequency-selective fading multiuser environments. Simulation results for a typical UMTS mobile channel environment show that the uncoded symbol error rate of a coherently modulated system using our synchronization scheme is virtually indistinguishable from that of a system with no time and frequency offset.
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| 8. |
- Beldiceanu, Nicolas, et al.
(author)
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Assistant: Learning and robust decision support system for agile manufacturing environments
- 2021
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In: IFAC-PapersOnLine. - : Elsevier. ; , s. 641-646
-
Conference paper (peer-reviewed)abstract
- The European project ASSISTANT will provide a set of AI-based digital twins that helps process engineers and production planners to operate collaborative mixed-model assembly lines based on the data collected from IoT devices and external data sources. Such a tool will help planners to design the assembly line, plan the production, operate the line, and improve process tuning. In addition, the system monitors the line in real-time, ensures that all required resources are available, and allows fast re-planning when necessary. ASSISTANT aims to make cost-effective decisions while ensuring product quality, safety and wellbeing of the workers, and managing the various sources of uncertainties. The resulting digital twin systems will be data-driven, agile, autonomous, collaborative and explainable, safe but reactive.
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| 9. |
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| 10. |
- Blom Johansson, Monica, 1965-, et al.
(author)
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A multiple-case study of a family-oriented intervention practice in the early rehabilitation phase of persons with aphasia
- 2013
-
In: Aphasiology. - : Informa UK Limited. - 0268-7038 .- 1464-5041. ; 27:2, s. 201-226
-
Journal article (peer-reviewed)abstract
- Background:Having a family member with aphasia severely affects the everyday life of the significant others, resulting in their need for support and information. Family-oriented intervention programmes typically consist of support, information, and skill training, such as communication partner training (CPT). However, because of time constraints and perceived lack of skills and routines, such programmes, especially CPT, are not common practice among speech-language pathologists (SLPs).Aims:To design and evaluate an early family-oriented intervention of persons with stroke-induced moderate to severe aphasia and their significant others in dyads. The intervention was designed to be flexible to meet the needs of each participant, to emotionally support the significant others and supply them with information needed, to include CPT that is easy to learn and conduct for SLPs, and to be able to provide CPT when the persons with aphasia still have access to SLP services.Methods & Procedures:An evaluative multiple-case study, involving three dyads, was conducted no more than 2 months after the onset of aphasia. The intervention consisted of six sessions: three sessions directed to the significant other (primarily support and information) and three to the dyad (primarily CPT). The intervention was evaluated both qualitatively and quantitatively based on video recordings of conversations and self-assessment questionnaires.Outcomes & Results:The importance of emotional support as well as information about stroke/aphasia was clearly acknowledged, especially by the significant others. All significant others perceived increased knowledge and understanding of aphasia and related issues.Communicative skills (as manifested in the video recordings) showed improvements from pre- to post-intervention.Conclusions:The results corroborate the need for individualised and flexible family-oriented SLP services that are broad in content. Furthermore, the results support the early initiation of such services with recurrent contact. The usefulness of CPT this early in the rehabilitation process was indicated but is yet to be proved.
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| 11. |
- Blom Johansson, Monica, 1965-, et al.
(author)
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Communication changes and SLP-services according to significant others of persons with aphasia
- 2012
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In: Aphasiology. - : Informa UK Limited. - 0268-7038 .- 1464-5041. ; 26:8, s. 1005-1028
-
Journal article (peer-reviewed)abstract
- Background: Significant others are important to persons with aphasia. For several reasons they should be involved in speech-language pathology (SLP) services, including acquiring facilitating communicative strategies and receiving support. In order to further adapt SLP services there is a need to know the perceptions and views of the significant others. Little is known about how they perceive changes in communication as well as received SLP services and in what way they want to be involved in these services.Aims: The study aimed to investigate which communicative changes significant others of persons with aphasia had experienced after a stroke event and to what extent these changes were experienced. A further aim was to describe the significant others’ experiences of SLP services and their motivation to participate in these services. Finally, the significant others’ experiences were compared in terms of sex, age, type of relationship, time since stroke onset, and type and severity of aphasia.Methods & Procedures: An 80-item study-specific questionnaire was answered by 173 significant others of persons with aphasia living throughout Sweden (response rate 69%). Of these, 33% were male and 67% female. Mean age was 64.2 years (range 33–87 years) and 85.5% of the participants were a cohabiting partner to a person with aphasia.Outcomes & Results: A total of 64% of participants perceived their conversations as being less stimulating and enjoyable compared with conversations before stroke onset. Aphasia was considered a substantial or very substantial problem by 64%. The participants took on an increased communicative responsibility, and 70% had changed their communicative behaviour in order to facilitate conversations. A total of 75% (n = 130) had met with the SLP of the person with aphasia. Of those, 63% perceived their own support from SLP services to be adequate; 87% considered language ability training as the most important SLP service. Type and severity of aphasia were especially related to the communicative experiences of the participants and their motivation to be involved in SLP services.Conclusions: The substantial decrease from pre- to post-stroke regarding enjoyment and meaningfulness of conversations suggests the need to further improve SLP services in order to help the people in question communicate at an optimal level. We suggest that clinicians should put more emphasis on explaining the benefits and availability of different kinds of aphasia rehabilitation services, such as functional communication training and communication partner training in addition to language ability training.
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| 12. |
- Blom Johansson, Monica, 1965-, et al.
(author)
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Self-reported changes in everyday life and health of significant others of people with aphasia : a quantitative approach
- 2022
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In: Aphasiology. - : Taylor & Francis. - 0268-7038 .- 1464-5041. ; 36:1, s. 76-94
-
Journal article (peer-reviewed)abstract
- Background: Changes in the everyday life and health of the significant others (SOs) of people living with stroke sequalae have been widely investigated. However, information regarding the frequency of the changes in daily life and the variables most associated with these perceived life changes is limited. Aims: To examine the extent to which SOs of persons with aphasia (PWAs) experience changes in everyday life and health after the stroke event and how they evaluate these changes and to identify which variables are associated with these perceived life changes. Methods & Procedures: A study-specific questionnaire about perceived changes in everyday life and health was completed by 173 SOs of PWAs living in Sweden (response rate 67.8%). The items concerned the SO’s working and financial situation, leisure time and social life, relationship with the PWA, household work and responsibility, and health and quality of life. Outcomes & Results: The everyday life and health of the SOs were greatly affected by the stroke event. The changes the SOs experienced were mainly appraised negatively. The relationships with the PWA and immediate family were least affected by the stroke. The perceived existence and severity of physical, cognitive, and language impairments of the PWA were the variables most strongly associated with the everyday life situation of the participants. The sex and age of the participants and the nature of the relationship with the PWA were only marginally associated with the experience of the situation. Conclusions: SOs’ perceptions of the PWA’s stroke-related disabilities and need for assistance may be a key factor in identifying SOs who may require support and guidance to help them cope with their new life situation.
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| 13. |
- Bodnaruk, Andriy, et al.
(author)
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Does Investor Recognition Predict Excess Returns?
- 2024
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In: SSRN Electronic Journal. - : Elsevier BV. - 1556-5068.
-
Other publication (other academic/artistic)abstract
- We test Merton's (1987) hypothesis using individual level stockholdings of Swedish investors. Controlling for size and other factors, we find that lower levels of investor recognition lead to greater future excess returns. Positive (negative) changes in investor recognition are followed by lower (higher) excess returns. The effect of investor recognition is more pronounced for young firms. We demonstrate that investor recognition is conditionally priced.
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| 14. |
- Bodnaruk, Andriy, et al.
(author)
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Investor Recognition and the Long-Run Performance of Repurchases
- 2004
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Other publication (other academic/artistic)abstract
- Theory suggests that firms with lower investor recognition should provide investors with higher returns. Using U.S. data we document a strong negative relationship between changes in investor recognition and asset returns. We demonstrate that investor recognition is a priced factor in asset returns different from the traditional ones. Undertaking a repurchase significantly reduces the firm's investor recognition. Accounting for changes in investor recognition reduces the abnornlal performance of firms undertaking a repurchase by 1.4% over one year.
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| 15. |
- Byrne, James, et al.
(author)
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A review of cloud computing simulation platforms and related environments
- 2017
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In: Proceedings of the 7th International Conference on Cloud Computing and Services Science. - : SciTePress. - 9789897582431 ; , s. 679-691
-
Conference paper (peer-reviewed)abstract
- Recent years have seen an increasing trend towards the development of Discrete Event Simulation (DES) platforms to support cloud computing related decision making and research. The complexity of cloud environments is increasing with scale and heterogeneity posing a challenge for the efficient management of cloud applications and data centre resources. The increasing ubiquity of social media, mobile and cloud computing combined with the Internet of Things and emerging paradigms such as Edge and Fog Computing is exacerbating this complexity. Given the scale, complexity and commercial sensitivity of hyperscale computing environments, the opportunity for experimentation is limited and requires substantial investment of resources both in terms of time and effort. DES provides a low risk technique for providing decision support for complex hyperscale computing scenarios. In recent years, there has been a significant increase in the development and extension of tools to support DES for cloud computing resulting in a wide range of tools which vary in terms of their utility and features. Through a review and analysis of available literature, this paper provides an overview and multi-level feature analysis of 33 DES tools for cloud computing environments. This review updates and extends existing reviews to include not only autonomous simulation platforms, but also on plugins and extensions for specific cloud computing use cases. This review identifies the emergence of CloudSim as a de facto base platform for simulation research and shows a lack of tool support for distributed execution (parallel execution on distributed memory systems).
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| 16. |
- Castañé, G., et al.
(author)
-
The ASSISTANT project: AI for high level decisions in manufacturing
- 2023
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In: International Journal of Production Research. - : Taylor & Francis. - 0020-7543 .- 1366-588X. ; 61:7, s. 2288-2306
-
Journal article (peer-reviewed)abstract
- This paper outlines the main idea and approach of the H2020 ASSISTANT (LeArning and robuSt deciSIon SupporT systems for agile mANufacTuring environments) project. ASSISTANT is aimed at the investigation of AI-based tools for adaptive manufacturing environments, and focuses on the development of a set of digital twins for integration with, management of, and decision support for production planning and control. The ASSISTANT tools are based on the approach of extending generative design, an established methodology for product design, to a broader set of manufacturing decision making processes; and to make use of machine learning, optimisation, and simulation techniques to produce executable models capable of ethical reasoning and data-driven decision making for manufacturing systems. Combining human control and accountable AI, the ASSISTANT toolsets span a wide range of manufacturing processes and time scales, including process planning, production planning, scheduling, and real-time control. They are designed to be adaptable and applicable in a both general and specific manufacturing environments.
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| 17. |
- Charas, Philippe, et al.
(author)
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A Philosophy of Public Service - Architectural Principles for Digital Democracy
- 2007
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In: International Journal of Public Information Systems. - Sundsvall : Mittuniversitetet. - 1653-4360. ; 3:2, s. 89-99
-
Journal article (peer-reviewed)abstract
- This paper sets down architectural principles as seen from the perspective of a Public Service being part of a constitutional framework and aims at defining Public Service from the viewpoint of IT Architecture. The key features are the concepts of Policy and Policy Enforcement, which are integral parts of the Architecture while also introducing a hitherto missing component, namely the Legal Dimension.
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| 18. |
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| 19. |
- Domaschka, Jörg, et al.
(author)
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Towards an Architecture for Reliable Capacity Provisioning for Distributed Clouds
- 2020
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In: Managing Distributed Cloud Applications and Infrastructure. - Cham : Palgrave Macmillan. - 9783030398620 - 9783030398637 ; , s. 1-25
-
Book chapter (peer-reviewed)abstract
- The complexity of computing along the cloud-to-edge continuum presents significant challenges to ICT operations and in particular reliable capacity planning and resource provisioning to meet unpredictable, fluctuating, and mobile demand. This chapter presents a high-level conceptual overview of RECAP—an architectural innovation to support reliable capacity provisioning for distributed clouds—and its operational modes and functional building blocks. In addition, the major design concepts informing its design—namely separation of concerns, model-centricism, modular design, and machine learning and artificial intelligence for IT operations—are also discussed.
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| 20. |
- Edmark, Lennart, 1954-, et al.
(author)
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Pressure-controlled versus manual facemask ventilation for anaesthetic induction in adults : A randomised controlled non-inferiority trial
- 2023
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In: Acta Anaesthesiologica Scandinavica. - : John Wiley & Sons. - 0001-5172 .- 1399-6576. ; 67:10, s. 1356-1362
-
Journal article (peer-reviewed)abstract
- Background: Pressure-controlled face mask ventilation (PC-FMV) with positive end-expiratory pressure (PEEP) after apnoea following induction of general anaesthesia prolongs safe apnoea time and reduces atelectasis formation. However, depending on the set inspiratory pressure, a delayed confirmation of a patent airway might occur. We hypothesised that by lowering the peak inspiratory pressure (PIP) when using PC-FMV with PEEP, confirmation of a patent airway would not be delayed as studied by the first return of CO2, compared with manual face mask ventilation (Manual FMV).Methods: This was a single-centre, randomised controlled non-inferiority trial. Seventy adult patients scheduled for elective day-case surgery under general anaesthesia with body mass index between 18.5 and 29.9 kg m(-2), American Society of Anesthesiologists (ASA) classes I-III, and without anticipated difficult FMV, were included. Before the start of pre-oxygenation and induction of general anaesthesia, participants were randomly allocated to receive ventilation with either PC-FMV with PEEP, at a PIP of 11 and a PEEP of 6 cmH(2)O or Manual FMV, with the adjustable pressure-limiting valve set at 11 cmH(2)O. The primary outcome variable was the number of ventilatory attempts needed until confirmation of a patent airway, defined as the return of at least 1.3 kPa CO2.Results: The return of >= 1.3 kPa CO2 on the capnography curve was observed after mean +/- SD, 3.6 +/- 4.2 and 2.5 +/- 1.9 ventilatory attempts/breaths with PC-FMV with PEEP and Manual FMV, respectively. The difference in means (1.1 ventilatory attempts/breaths) had a 99% CI of similar to 1.0 to 3.1, within the accepted upper margin of four breaths for non-inferiority.Conclusion: Following induction of general anaesthesia, PC-FMV with PEEP was used without delaying a patent airway as confirmed with capnography, if moderate pressures were used.
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| 21. |
- Elmroth, Erik, 1964-, et al.
(author)
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A composable service-oriented architecture for middleware-independent and interoperable grid job management
- 2010
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Other publication (other academic/artistic)abstract
- We propose a composable, loosely coupled Service-Oriented Architecture for middleware-independent Grid job management. The architecture is designed for use in federated Grid environments and aims to decouple Grid appli- cations from Grid middlewares and other infrastructure components. The notion of an ecosystem of Grid infrastructure components is extended, and Grid job management software design is discussed in this context. Non- intrusive integration models and abstraction of Grid middleware function- ality through hierarchical aggregation of autonomous Grid job management services are emphasized, and service composition techniques facilitating this process are explored. Earlier efforts in Service-Oriented Architecture design are extended upon, and implications of these are discussed throughout the paper. A proof-of-concept implementation of the proposed architecture is presented along with a technical evaluation of the performance of the proto- type, and a details of architecture implementation are discussed along with trade-offs introduced by the service composition techniques used.
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| 22. |
- Elmroth, Erik, 1964-, et al.
(author)
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Designing general, composable, and middleware-independent Grid infrastructure tools for multi-tiered job management
- 2007
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In: Towards Next Generation Grids. - : Springer-Verlag. - 9780387724973 ; , s. 175-184
-
Conference paper (peer-reviewed)abstract
- We propose a multi-tiered architecture for middleware-independent Grid job management. The architecture consists of a number of services for well-defined tasks in the job management process, offering complete user-level isolation of servicecapabilities, multiple layers of abstraction, control, and fault tolerance. The middleware abstraction layer comprises components for targeted job submission, job control and resource discovery. The brokered job submission layer offers a Grid view on resources, including functionality for resource brokering and submission of jobs to selected resources. The reliable job submission layer includes components for fault tolerant execution of individual jobs and groups of independentjobs, respectively. The architecture is proposed as a composable set of tools rather than a monolithic solution, allowing users to select the individual components of interest. The prototype presented is implemented using the Globus Toolkit 4, integrated with the Globus Toolkit 4 and NorduGrid/ARC middlewares and based on existing and emerging Grid standards. A performance evaluation reveals that the overhead for resource discovery, brokering, middleware-specific format conversions, job monitoring, fault tolerance, and management of individual and groups of jobs is sufficiently small to motivate the use of the framework.
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| 23. |
- Elmroth, Erik, 1964-, et al.
(author)
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Designing service-based resource management tools for a healthy grid ecosystem
- 2008
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In: Parallel processing and applied mathematics. - Berlin, Heidelberg : Springer-Verlag. ; , s. 259-270
-
Conference paper (peer-reviewed)abstract
- We present an approach for development of Grid resource management tools, where we put into practice internationally established high-level views of future Grid architectures. The approach addresses fundamental Grid challenges and strives towards a future vision of the Grid where capabilities are made available as independent and dynamically assembled utilities, enabling run-time changes in the structure, behavior, and location of software. The presentation is made in terms of design heuristics, design patterns, and quality attributes, and is centered around the key concepts of co-existence, composability, adoptability, adaptability, changeability, and interoperability. The practical realization of the approach is illustrated by five case studies (recently developed Grid tools) high-lighting the most distinct aspects of these key concepts for each tool. The approach contributes to a healthy Grid ecosystem that promotes a natural selection of “surviving” components through competition, innovation, evolution, and diversity. In conclusion, this environment facilitates the use and composition of components on a per-component basis.
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| 24. |
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| 25. |
- Elmroth, Erik, 1964-, et al.
(author)
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Dynamic and transparent service compositions techniques for service-oriented grid architectures
- 2008
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In: Integrated research in Grid computing. - : Crete University Press. ; , s. 323-334
-
Book chapter (peer-reviewed)abstract
- With the introduction of the Service-Oriented Architecture design paradigm, service composition has become a central methodology for developing Grid software. We present an approach to Grid software development consisting of architectural design patterns for service de-composition and service re-composition. The patterns presented can each be used individually, but provide synergistic effects when combined as described in a unified framework. Software design patterns are employed to provide structure in design for service-based software development. Service APIs and immutable data wrappers are used to simplify service client development and isolate service clients from details of underlying service engine architectures. The use of local call structures greatly reduces inter-service communication overhead for co-located services, and service API factories are used to make local calls transparent to service client developers. Light-weight and dynamically replaceable plug-ins provide structure for decision support and integration points. A dynamic configuration scheme provides coordination of service efforts and synchronization of service interactions in a user-centric manner. When using local calls and dynamic configuration for creating networks of cooperating services, the need for generic service monitoring solutions becomes apparent and is addressed by service monitoring interfaces. We present these techniques along with their intended use in the context of software development for service-oriented Grid architectures.
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| 26. |
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| 27. |
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| 28. |
- Espling, Daniel, 1983-, et al.
(author)
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Integration and Evaluation of Decentralized Fairshare Prioritization (Aequus)
-
Other publication (other academic/artistic)abstract
- Fairshare is commonly one of the factors used by cluster resource management systems to prioritize jobs during scheduling. Despite the grid vision of a transparent and unified infrastructure, fairshare is normally calculated and enforced at the local cluster level rather than at a grid-wide scale. Aequus is a self-contained decentralized system for grid-wide fairshare job prioritization. Using Aequus, detailed global share policies can be combined with local cluster policies to offer a unified grid fairshare prioritization system where local administrations retain control over their clusters. This work shows how Aequus can be integrated with local resource management systems such as SLURM and Maui with minimal intrusion. Early results from production use are presented, and the system is further tested and evaluated for use at a nation-wide scale. Statistical models are created based on historical national grid usage data, and synthetic traces based on these models are used to create a diverse input set used to exemplify system behavior. The system is shown to behave consistently despite great variations in job arrival patterns and partial participation of some of the collaborating installations.
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| 29. |
- Espling, Daniel, et al.
(author)
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Integration and evaluation of decentralized fairshare prioritization (Aequus)
- 2014
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In: Proceedings of the IEEE 28th International Parallel & Distributed Processing Symposium Workshops IPDPSW 2014. - : IEEE Computer Society. - 9781479941162 ; , s. 1198-1207
-
Conference paper (peer-reviewed)abstract
- Fairshare is commonly one of the factors used by cluster resource management systems to prioritize jobs during scheduling. Despite the grid vision of a transparent and unified infrastructure, fairshare is normally calculated and enforced at the local cluster level rather than at a grid-wide scale. Aequus is a self-contained decentralized system for grid-wide fairshare job prioritization. Using Aequus, detailed global share policies can be combined with local cluster policies to offer a unified grid fairshare prioritization system where local administrations retain control over their clusters. This work shows how Aequus can be integrated with local resource management systems such as SLURM and Maui with minimal intrusion. Early results from production help assess the maturity of the system, and the system is further tested and evaluated for use at a nation-wide scale using workload modeling techniques. Statistical models are created based on historical national grid usage data, and synthetic traces based on these models are used to create a diverse input set used to exemplify system behavior. The system is shown to behave consistently despite great variations in job arrival patterns and partial participation of some of the collaborating installations.
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| 30. |
- Fernaeus, Sven-Erik, et al.
(author)
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Cut the coda : early fluency intervals predict diagnoses
- 2008
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In: Cortex. - : Elsevier BV. - 0010-9452 .- 1973-8102. ; 44:2, s. 161-169
-
Journal article (peer-reviewed)abstract
- The aim of this study was threefold: (i) to clarify whether letter and category fluency tap different cognitive abilities; (ii) to make diagnostic comparisons and predictions using temporally resolved fluency data; (iii) to challenge and test the widely made assumption that 1-min sum scores are the fluency test measure of choice in the diagnosis of dementia. Scores from six 10-sec intervals of letter and category fluency tests were obtained from 240 participants including cognitive levels ranging from mild subjective cognitive complaints to Alzheimer's disease. Factor analysis revealed clearly separate factors corresponding to letter and category fluency. Category fluency was markedly impaired in Alzheimer's disease but not in Mild Cognitive Impairment. Only scores from relatively early intervals predicted Alzheimer's disease and Mild Cognitive Impairment. The conclusions are (i) letter and category fluency are different tests, category fluency being the best diagnostic predictor; (ii) it would be possible to administer category fluency tests only for 30 sec, because after this point the necessary differential diagnostic information about the patient's word fluency capacity has already been gathered.
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| 31. |
- Fernaeus, Sven-Erik, et al.
(author)
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Memory factors in Rey AVLT : implications for early staging of cognitive decline
- 2014
-
In: Scandinavian Journal of Psychology. - : Wiley. - 0036-5564 .- 1467-9450. ; 55:6, s. 546-553
-
Journal article (peer-reviewed)abstract
- Supraspan verbal list learning is widely used to assess dementia and related cognitive disorders where declarative memory deficits are a major clinical sign. While the overall learning rate is important for diagnosis, serial position patterns may give insight into more specific memory processes in patients with cognitive impairment. This study explored these patterns in a memory clinic clientele. One hundred eighty three participants took the Rey Auditory-Verbal Learning Test (RAVLT). The major groups were patients with Alzheimer's disease (AD), Vascular Dementia (VD), Mild Cognitive Impairment (MCI), and Subjective Cognitive Impairment (SCI) as well as healthy controls (HC). Raw scores for the five trials and five serial partitions were factor analysed. Three memory factors were found and interpreted as Primacy, Recency, and Resistance to Interference. AD and MCI patients had impaired scores in all factors. SCI patients were significantly impaired in the Resistance to Interference factor, and in the Recency factor at the first trial. The main conclusion is that serial position data from word list testing reflect specific memory capacities which vary with levels of cognitive impairment.
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| 32. |
- Fernaeus, Sven-Erik, et al.
(author)
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The AMQ : a four-factor inventory of absentmindedness and memory
- 2009
-
In: Scandinavian Journal of Psychology. - : Wiley. - 0036-5564 .- 1467-9450. ; 50:3, s. 193-202
-
Journal article (peer-reviewed)abstract
- The Absentmindedness and Memory Questionnaire (AMQ) is a new self-rating scale designed to evaluate everyday memory problems related to absentmindedness. It includes 24 items and is based on studies of different samples (N= 623). Its test-retest reliability is high and it has consistently shown similar factor structure. The AMQ thus measures four weakly correlated factors: Absentmindedness, Persons, Locations and Codes/Addresses. Factor analysis further indicates that Absentmindedness may include two subfactors: momentary attention deficit and prospective forgetfulness or impaired agenda memory. Gender differences were found in Persons (Female+) and Locations (Male+) but not in Absentmindedness or Codes/Addresses. The current version of AMQ has seven interindividually comparable response alternatives for each item in the questionnaire. This makes it useful as a measure of subjective absentmindedness or forgetfulness as well as a complementary measure of subjective memory for persons, locations, and codes/addresses/stories, especially at follow-up examinations.
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| 33. |
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| 34. |
- Fägerstam, Patrik, et al.
(author)
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Similar inhibition of platelet adhesion, P-selectin expression and plasma coagulation by ioversol, iodixanol and ioxaglate
- 2010
-
In: The British Journal of Radiology. - : British Institute of Radiology. - 0007-1285 .- 1748-880X. ; 83:989, s. 401-410
-
Journal article (peer-reviewed)abstract
- Contrast media (CM) are reported to possess both pro-thrombotic and anticoagulant properties. The mechanisms are not clearly understood and early reports are contradictory. To study the effects of CM on haemostasis, we analysed the ex vivo effects of ioversol and iodixanol on platelet adhesion and P-selectin expression, and the in vitro effects of ioversol, iodixanol and ioxaglate on platelet adhesion, P-selectin expression and plasma coagulation. A novel enzymatic assay was used to measure platelet adhesion to protein surfaces and an enzyme-linked immunosorbent assay was used to measure platelet P-selectin surface expression. Pro-thrombin time (PT) and activated partial thromboplastin time (APTT) were used to measure plasma coagulation. The ex vivo study consisted of blood from 27 outpatients administered ioversol and 9 patients administered iodixanol intravenously. Samples were collected before and 5 min after CM administration. Healthy donors were used for the in vitro studies on the effects of CM. The ex vivo study showed significantly (p<0.05) decreased platelet adhesion and P-selectin expression after administration of ioversol and iodixanol. Adhesion was more affected than P-selectin expression. The in vitro study showed that ioversol, iodixanol and ioaxaglate significantly (p<0.05) and dose dependently (beginning at 3 mg ml(-1)) decreased platelet adhesion and P-selectin expression. APTT and PT were significantly (p<0.01) prolonged at concentrations of 10 mg ml(-1) and 30 mg ml(-1), respectively. In conclusion, ioversol, iodixanol and ioxaglate inhibit platelet adhesion and P-selectin expression, as well as plasma coagulation. Platelets are more sensitive in relation to the inhibiting effect on plasma coagulation.
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| 35. |
- Gonzalo P., Rodrigo, 1980-
(author)
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HPC scheduling in a brave new world
- 2017
-
Doctoral thesis (other academic/artistic)abstract
- Many breakthroughs in scientific and industrial research are supported by simulations and calculations performed on high performance computing (HPC) systems. These systems typically consist of uniform, largely parallel compute resources and high bandwidth concurrent file systems interconnected by low latency synchronous networks. HPC systems are managed by batch schedulers that order the execution of application jobs to maximize utilization while steering turnaround time. In the past, demands for greater capacity were met by building more powerful systems with more compute nodes, greater transistor densities, and higher processor operating frequencies. Unfortunately, the scope for further increases in processor frequency is restricted by the limitations of semiconductor technology. Instead, parallelism within processors and in numbers of compute nodes is increasing, while the capacity of single processing units remains unchanged. In addition, HPC systems’ memory and I/O hierarchies are becoming deeper and more complex to keep up with the systems’ processing power. HPC applications are also changing: the need to analyze large data sets and simulation results is increasing the importance of data processing and data-intensive applications. Moreover, composition of applications through workflows within HPC centers is becoming increasingly important. This thesis addresses the HPC scheduling challenges created by such new systems and applications. It begins with a detailed analysis of the evolution of the workloads of three reference HPC systems at the National Energy Research Supercomputing Center (NERSC), with a focus on job heterogeneity and scheduler performance. This is followed by an analysis and improvement of a fairshare prioritization mechanism for HPC schedulers. The thesis then surveys the current state of the art and expected near-future developments in HPC hardware and applications, and identifies unaddressed scheduling challenges that they will introduce. These challenges include application diversity and issues with workflow scheduling or the scheduling of I/O resources to support applications. Next, a cloud-inspired HPC scheduling model is presented that can accommodate application diversity, takes advantage of malleable applications, and enables short wait times for applications. Finally, to support ongoing scheduling research, an open source scheduling simulation framework is proposed that allows new scheduling algorithms to be implemented and evaluated in a production scheduler using workloads modeled on those of a real system. The thesis concludes with the presentation of a workflow scheduling algorithm to minimize workflows’ turnaround time without over-allocating resources.
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| 36. |
- Gonzalo P., Rodrigo, 1980-, et al.
(author)
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ScSF : a scheduling simulation framework
- 2018
-
In: Job Scheduling Strategies for Parallel Processing. - Cham : Springer. - 9783319773971 - 9783319773988 ; , s. 152-173
-
Conference paper (peer-reviewed)abstract
- High-throughput and data-intensive applications are increasingly present, often composed as workflows, in the workloads of current HPC systems. At the same time, trends for future HPC systems point towards more heterogeneous systems with deeper I/O and memory hierarchies. However, current HPC schedulers are designed to support classical large tightly coupled parallel jobs over homogeneous systems. Therefore, There is an urgent need to investigate new scheduling algorithms that can manage the future workloads on HPC systems. However, there is a lack of appropriate models and frameworks to enable development, testing, and validation of new scheduling ideas.In this paper, we present an open-source scheduler simulation framework (ScSF) that covers all the steps of scheduling research through simulation. ScSF provides capabilities for workload modeling, workload generation, system simulation, comparative workload analysis, and experiment orchestration. The simulator is designed to be run over a distributed computing infrastructure enabling to test at scale. We describe in detail a use case of ScSF to develop new techniques to manage scientific workflows in a batch scheduler. In the use case, such technique was implemented in the framework scheduler. For evaluation purposes, 1728 experiments, equivalent to 33 years of simulated time, were run in a deployment of ScSF over a distributed infrastructure of 17 compute nodes during two months. Finally, the experimental results were analyzed in the framework to judge that the technique minimizes workflows’ turnaround time without over-allocating resources. Finally, we discuss lessons learned from our experiences that will help future researchers.
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| 37. |
- Grunér, Sofia, et al.
(author)
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The Compensatory Effect of Text-to-Speech Technology on Reading Comprehension and Reading Rate in Swedish Schoolchildren With Reading Disability : The Moderating Effect of Inattention and Hyperactivity Symptoms Differs by Grade Groups
- 2018
-
In: Journal of Special Education Technology. - : SAGE Publications. - 0162-6434 .- 2381-3121. ; 33:2, s. 98-110
-
Journal article (peer-reviewed)abstract
- The purpose of this study was (i) to investigate if the compensatory effect of text-to-speech (TTS) technology on reading comprehension and reading rate in schoolchildren with reading disability is influenced by problems with inattention and hyperactivity and (ii) to examine whether a potentially moderating effect of such symptoms differ between grade groups. Participants (N = 49) were randomized into one of the two experimental conditions: Group A listened to a text with TTS, and Group B read the text themselves. The conditions were then switched. Inattention and hyperactivity symptoms were assessed with the Strengths and Difficulties Questionnaire (SDQ). Statistical analyses were performed both on the whole group and within-grade groups (Grades 3–5 and 6–9). Using TTS technology had a positive effect on reading rate for both grade groups, and this effect was not influenced by attention-deficit/hyperactivity disorder (ADHD) symptoms. As for reading comprehension, the two groups differed both with respect to the amount of improvement seen in the TTS condition and with respect to the moderating effect of ADHD symptoms. Reading with TTS improved reading comprehension significantly in the younger group, whereas no effect on reading comprehension was found in the older group. A higher score on the SDQ ADHD Scale was associated with less improvement in reading comprehension in the younger group and with greater improvement in reading comprehension in the older group. The results indicate that symptoms of inattention and hyperactivity, as well as the child’s grade level, are factors that should be taken into account when planning and introducing TTS technology.
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| 38. |
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| 39. |
- Hybbinette, Helena, et al.
(author)
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Longitudinal changes in functional connectivity in speech motor networks in apraxia of speech after stroke
- 2022
-
In: Frontiers in Neurology. - : Frontiers Media S.A.. - 1664-2295. ; 13
-
Journal article (peer-reviewed)abstract
- ObjectiveThe cerebral substrates of apraxia of speech (AOS) recovery remain unclear. Resting state fMRI post stroke can inform on altered functional connectivity (FC) within cortical language networks. Some initial studies report reduced FC between bilateral premotor cortices in patients with AOS, with lowest FC in patients with the most severe AOS. However, longitudinal FC studies in stroke are lacking. The aims of the present longitudinal study in early post stroke patients with AOS were (i) to compare connectivity strength in AOS patients to that in left hemisphere (LH) lesioned stroke patients without a speech-language impairment, (ii) to investigate the relation between FC and severity of AOS, aphasia and non-verbal oral apraxia (NVOA) and (iii) to investigate longitudinal changes in FC, from the subacute phase to the chronic phase to identify predictors of AOS recovery. MethodsFunctional connectivity measures and comprehensive speech-language assessments were obtained at 4 weeks and 6 months after stroke in nine patients with AOS after a LH stroke and in six LH lesioned stroke patients without speech-language impairment. Functional connectivity was investigated in a network for speech production: inferior frontal gyrus (IFG), anterior insula (aINS), and ventral premotor cortex (vPMC), all bilaterally to investigate signs of adaptive or maladaptive changes in both hemispheres. ResultsInterhemispheric vPMC connectivity was significantly reduced in patients with AOS compared to LH lesioned patients without speech-language impairment. At 6 months, the AOS severity was associated with interhemispheric aINS and vPMC connectivity. Longitudinal changes in FC were found in individuals, whereas no significant longitudinal change in FC was found at the group level. Degree of longitudinal AOS recovery was strongly associated with interhemispheric IFG connectivity strength at 4 weeks. ConclusionEarly interhemispheric IFG connectivity may be a strong predictor of AOS recovery. The results support the importance of interhemispheric vPMC connection in speech motor planning and severity of AOS and suggest that also bilateral aINS connectivity may have an impact on AOS severity. These findings need to be validated in larger cohorts.
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| 40. |
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| 41. |
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| 42. |
- Kristensson, Joana, 1972, et al.
(author)
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Naming vs. non-naming treatment in aphasia in a group setting–A randomized controlled trial
- 2022
-
In: Journal of Communication Disorders. - : Elsevier BV. - 0021-9924 .- 1873-7994. ; 97
-
Journal article (peer-reviewed)abstract
- Introduction: Anomia affects numerous persons with aphasia. Treatment effects of anomia group therapy have been reported, but the evidence is not comprehensive. This study aimed to explore treatment effects of a naming treatment compared with a non-naming treatment delivered in a group setting. Methods: In a randomized controlled trial, 17 participants with chronic poststroke aphasia underwent group therapy, 2 hours a session, 3 times per week, for a total of 20 hours. The treatment given in the naming group was modified semantic feature analysis (SFA). Treatment content in the non-naming group comprised auditory comprehension, copying text, and reading. The primary outcome measure was accuracy in confrontation naming of participant-selected trained nouns and verbs. Generalization effects were evaluated in single-word naming, connected speech, and everyday communication. Results: Participants in both groups significantly improved their naming of trained items. There were no differences between the groups. The treatment effect did not remain at follow-up 10 weeks after therapy. No other statistically significant changes occurred in either group. Conclusions: Group intervention can improve naming ability in individuals with chronic aphasia. However, similar treatment effects can be achieved using a non-naming treatment as using a naming treatment, such as modified SFA. Further research is warranted to identify the most important elements of anomia group therapy.
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| 43. |
- Krzywda, Jakub, et al.
(author)
-
A Sensor-Actuator Model for Data Center Optimization
- 2015
-
In: 2015 International Conference on Cloud and Autonomic Computing (ICCAC). - : IEEE Computer Society. - 9781467395663 ; , s. 192-195
-
Conference paper (peer-reviewed)abstract
- Cloud data centers commonly use virtualization technologies to provision compute capacity with a level of indirection between virtual machines and physical resources. In this paper we explore the use of that level of indirection as a means for autonomic data center configuration optimization and propose a sensor-actuator model to capture optimization-relevant relationships between data center events, monitored metrics (sensors data), and management actions (actuators). The model characterizes a wide spectrum of actions to help identify the suitability of different actions in specific situations, and outlines what (and how often) data needs to be monitored to capture, classify, and respond to events that affect the performance of data center operations.
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| 44. |
- Krzywda, Jakub, 1989-, et al.
(author)
-
ALPACA : Application Performance Aware Server Power Capping
- 2018
-
In: ICAC 2018. - : IEEE Computer Society. - 9781538651391 ; , s. 41-50
-
Conference paper (peer-reviewed)abstract
- Server power capping limits the power consumption of a server to not exceed a specific power budget. This allows data center operators to reduce the peak power consumption at the cost of performance degradation of hosted applications. Previous work on server power capping rarely considers Quality-of-Service (QoS) requirements of consolidated services when enforcing the power budget. In this paper, we introduce ALPACA, a framework to reduce QoS violations and overall application performance degradation for consolidated services. ALPACA reduces unnecessary high power consumption when there is no performance gain, and divides the power among the running services in a way that reduces the overall QoS degradation when the power is scarce. We evaluate ALPACA using four applications: MediaWiki, SysBench, Sock Shop, and CloudSuite’s Web Search benchmark. Our experiments show that ALPACA reduces the operational costs of QoS penalties and electricity by up to 40% compared to a non optimized system.
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| 45. |
- Krzywda, Jakub, 1989-
(author)
-
Analysing, modelling and controlling power-performance tradeoffs in data center infrastructures
- 2017
-
Licentiate thesis (other academic/artistic)abstract
- The aim of this thesis is to analyse the power-performance tradeoffs in datacenter servers, create models that capture these tradeoffs, and propose controllers to optimise the use of data center infrastructures taking the tradeoffs into consideration. The main research problem that we investigate in this thesis is how to increase the power efficiency of data center servers taking into account the power-performance tradeoffs.The main cause for this research is the massive power consumption of data centers that is a concern both from the financial and environmental footprint perspectives. Irrespectively of the approaches taken to enhance data center power efficiency, substantial reductions in the power consumption of data center servers easily lead to performance degradation of hosted applications, which causes customers dissatisfaction. Therefore, it is crucial for the data center operators to understand and control the power-performance tradeoffs.The research methods used in this thesis include experiments on real testbeds, applying statistical methods to create power-performance models, development of various optimisation techniques to improve the energy-efficiency of servers, and simulations to evaluate proposed solutions at scale.As a result of the research presented in this thesis, we propose taxonomies for selected aspects of data center configurations, events, management actions, and monitored metrics. We discuss the relationships between these elements and to support the analysis present results from a set of testbed experiments.We show limitations in the applicability of various data center management actions, including Dynamic Voltage Frequency Scaling (DVFS), Running Average Power Limit (RAPL), CPU Pinning, horizontal and vertical scaling. Finally, we propose a power budgeting controller that minimizes the performance degradation while enforcing the power limits.The outcomes of this thesis can be used by the data center operators to improve the energy-efficiency of servers and reduce the overall power consumption with minimized performance degradation. Moreover, the software artifacts including virtual machine images, scripts, and simulator are available online.Future work includes further investigation of the problem of graceful performance degradation under power limits, incorporating multi-layer applications spread among several servers and load balancing controller.
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| 46. |
- Krzywda, Jakub, 1989-
(author)
-
May the power be with you : managing power-performance tradeoffs in cloud data centers
- 2019
-
Doctoral thesis (other academic/artistic)abstract
- The overall goal of the work presented in this thesis was to find ways of managing power-performance tradeoffs in cloud data centers. To this end, the relationships between the power consumption of data center servers and the performance of applications hosted in data centers are analyzed, models that capture these relationships are developed, and controllers to optimize the use of data center infrastructures are proposed.The studies were motivated by the massive power consumption of modern data centers, which is a matter of significant financial and environmental concern. Various strategies for improving the power efficiency of data centers have been proposed, including server consolidation, server throttling, and power budgeting. However, no matter what strategy is used to enhance data center power efficiency, substantial reductions in the power consumption of data center servers can easily degrade the performance of hosted applications, causing customer dissatisfaction. It is therefore crucial for data center operators to understand and control power-performance tradeoffs.The research methods used in this work include experiments on real testbeds, the application of statistical methods to create power-performance models, development of various optimization techniques to improve the power efficiency of servers, and simulations to evaluate the proposed solutions at scale.This thesis makes multiple contributions. First, it introduces taxonomies for various aspects of data center configuration, events, management actions, and monitored metrics. We discuss the relationships between these elements and support our analysis with results from a set of testbed experiments. We demonstrate limitations on the usefulness of various data center management actions for controlling power consumption, including Dynamic Voltage Frequency Scaling (DVFS) and Running Average Power Limit (RAPL). We also demonstrate similar limitations on common measures for controlling application performance, including variation of operating system scheduling parameters, CPU pinning, and horizontal and vertical scaling. Finally, we propose a set of power budgeting controllers that act at the application, server, and cluster levels to minimize performance degradation while enforcing power limits.The results and analysis presented in this thesis can be used by data center operators to improve the power-efficiency of servers and reduce overall operational costs while minimizing performance degradation. All of the software generated during this work, including controller source code, virtual machine images, scripts, and simulators, has been open-sourced.
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| 47. |
- Krzywda, Jakub, 1989-, et al.
(author)
-
Modeling and Simulation of QoS-Aware Power Budgeting in Cloud Data Centers
- 2020
-
In: 28th Euromicro International Conference on Parallel, Distributed and Network-Based Processing (PDP). - : IEEE conference proceedings. ; , s. 88-93
-
Conference paper (peer-reviewed)abstract
- Power budgeting is a commonly employed solution to reduce the negative consequences of high power consumption of large scale data centers. While various power budgeting techniques and algorithms have been proposed at different levels of data center infrastructures to optimize the power allocation toservers and hosted applications, testing them has been challengingwith no available simulation platform that enables such testingfor different scenarios and configurations. To facilitate evaluationand comparison of such techniques and algorithms, we introducea simulation model for Quality-of-Service aware power budgetingand its implementation in CloudSim. We validate the proposedsimulation model against a deployment on a real testbed, showcase simulator capabilities, and evaluate its scalability.
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| 48. |
- Krzywda, Jakub, 1989-, et al.
(author)
-
Modeling and Simulation of QoS-AwarePower Budgeting in Cloud Data Centers
-
Other publication (other academic/artistic)abstract
- Power budgeting is a commonly employed solution to reduce the negative consequences of high power consumption of large scale data centers. While various power budgeting techniques and algorithms have been proposed at different levels of data center infrastructures to optimize the power allocation to servers and hosted applications, testing them has been challenging with no available simulation platform that enables such testing for different scenarios and configurations. To facilitate evaluation and comparison of such techniques and algorithms, we introduce a simulation model for Quality-of-Service aware power budgeting and its implementation in CloudSim. We validate the proposed simulation model against a deployment on a real testbed, showcase simulator capabilities, and evaluate its scalability.
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| 49. |
- Krzywda, Jakub, 1989-, et al.
(author)
-
Power-performance tradeoffs in data center servers : DVFS, CPUpinning, horizontal, and vertical scaling
- 2018
-
In: Future generations computer systems. - : Elsevier BV. - 0167-739X .- 1872-7115. ; 81, s. 114-128
-
Journal article (peer-reviewed)abstract
- Dynamic Voltage and Frequency Scaling (DVFS), CPU pinning, horizontal, and vertical scaling, are four techniques that have been proposed as actuators to control the performance and energy consumption on data center servers. This work investigates the utility of these four actuators, and quantifies the power-performance tradeoffs associated with them. Using replicas of the German Wikipedia running on our local testbed, we perform a set of experiments to quantify the influence of DVFS, vertical and horizontal scaling, and CPU pinning on end-to-end response time (average and tail), throughput, and power consumption with different workloads. Results of the experiments show that DVFS rarely reduces the power consumption of underloaded servers by more than 5%, but it can be used to limit the maximal power consumption of a saturated server by up to 20% (at a cost of performance degradation). CPU pinning reduces the power consumption of underloaded server (by up to 7%) at the cost of performance degradation, which can be limited by choosing an appropriate CPU pinning scheme. Horizontal and vertical scaling improves both the average and tail response time, but the improvement is not proportional to the amount of resources added. The load balancing strategy has a big impact on the tail response time of horizontally scaled applications.
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| 50. |
- Krzywda, Jakub, 1989-, et al.
(author)
-
Power Shepherd : Application Performance Aware Power Shifting
- 2019
-
In: Proceedings of the International Conference on Cloud Computing Technology and Science, CloudCom. - : IEEE Computer Society. - 9781728150116 ; , s. 45-53
-
Conference paper (peer-reviewed)abstract
- Constantly growing power consumption of data centers is a major concern from environmental and economical reasons. Current approaches to reduce negative consequences of high power consumption focus on limiting the peak power consumption. During high workload periods, power consumption of highly utilized servers is throttled to stay within the power budget. However, the peak power reduction affects performance of hosted applications and thus leads to Quality of Service violations. In this paper, we introduce Power Shepherd, a hierarchical system for application performance aware power shifting. Power Shepherd reduces the data center operational costs by redistributing the available power among applications hosted in the cluster. This is achieved by, assigning server power budgets by the cluster controller, enforcing these power budgets using Running Average Power Limit (RAPL), and prioritizing applications within each server by adjusting the CPU scheduling configuration. We implement a prototype of the proposed solution and evaluate it in a real testbed equipped with power meters and using representative cloud applications. Our experiments show that Power Shepherd has potential to manage a cluster consisting of thousands of servers and limit the increase of operational costs by a significant amount when the cluster power budget is limited and the system is overutilized. Finally, we identify some outstanding challenges regarding model sensitivity and the fact that this approach in its current from is not beneficial to be used in all situations, e.g., when the system is underutilized.
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