| 1. |
- Gustafsson, Stefan, et al.
(författare)
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Electromagnetic dispersion modeling and measurements for HVDC power cables
- 2014
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Ingår i: IEEE Transactions on Power Delivery. - : IEEE Press. - 0885-8977 .- 1937-4208. ; 29:6, s. 2439-2447
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Tidskriftsartikel (refereegranskat)abstract
- This paper provides a general framework for electromagnetic (EM) modeling, sensitivity analysis, computation, and measurements regarding the wave propagation characteristics of high-voltage direct-current (HVDC) power cables. The modeling is motivated by the potential use with transient analysis, partial-discharge measurements, fault localization and monitoring, and is focused on very long (10 km or more) HVDC power cables with transients propagating in the low-frequency regime of about 0-100 kHz. An exact dispersion relation is formulated together with a discussion on practical aspects regarding the computation of the propagation constant. Experimental time-domain measurement data from an 80-km-long HVDC power cable are used to validate the electromagnetic model, and a mismatch calibration procedure is devised to account for the connection between the measurement equipment and the cable. Quantitative sensitivity analysis is devised to study the impact of parameter uncertainty on wave propagation characteristics. The sensitivity analysis can be used to study how material choices affect the propagation characteristics, and to indicate which material parameters need to be identified accurately in order to achieve accurate fault localization. The analysis shows that the sensitivity of the propagation constant due to a change in the conductivity in the three metallic layers (the inner conductor, the intermediate lead shield, and the outer steel armor) is comparable to the sensitivity with respect to the permittivity of the insulating layer. Hence, proper modeling of the EM fields inside the metallic layers is crucial in the low-frequency regime of 0-100 kHz.
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| 2. |
- Nordebo, Sven, et al.
(författare)
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Low-frequency dispersion characteristics of a multilayered coaxial cable
- 2013
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Ingår i: Journal of Engineering Mathematics. - : Springer Netherlands. - 0022-0833 .- 1573-2703. ; 83:1, s. 169-184
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Tidskriftsartikel (refereegranskat)abstract
- This paper provides an exact asymptotic analysis regarding the low-frequency dispersion characteristics of a multilayered coaxial cable. A layer-recursive description of the dispersion function is derived that is well suited for asymptotic analysis. The recursion is based on two well-behaved (meromorphic) subdeterminants defined by a perfectly electrically conducting (PEC) and a perfectly magnetically conducting termination, respectively. For an open waveguide structure, the dispersion function is a combination of two such functions, and there is only one branch point that is related to the exterior domain. It is shown that if there is one isolating layer and a PEC outer shield, then the classical Weierstrass preparation theorem can be used to prove that the low-frequency behavior of the propagation constant is governed by the square root of the complex frequency, and an exact analytical expression for the dominating term of the asymptotic expansion is derived. It is furthermore shown that the same asymptotic expansion is valid to its lowest order even if the outer shield has finite conductivity and there is an infinite exterior region with finite nonzero conductivity. As a practical application of the theory, a high-voltage direct current (HVDC) power cable is analyzed and a numerical solution to the dispersion relation is validated by comparisons with the asymptotic analysis. The comparison reveals that the low-frequency dispersion characteristics of the power cable is very complicated and a first-order asymptotic approximation is valid only at extremely low frequencies (below 1 Hz). It is noted that the only way to come to this conclusion is to actually perform the asymptotic analysis. Hence, for practical modeling purposes, such as with fault localization, an accurate numerical solution to the dispersion relation is necessary and the asymptotic analysis is useful as a validation tool.
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| 3. |
- Granlund, Mats, 1954-, et al.
(författare)
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Tidig upptäckt - tidig insats (TUTI) : slutrapport
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Ur sammanfattningen: Små barns psykiska hälsa har de senaste åren uppmärksammats mer än tidigare. De insatser som görs för att stärka hälsa hos små barn har visat sig ge goda effekter på barns psykiska hälsa senare i livet. Förskolan har lyfts fram både som en miljö i vilken barns psykiska ohälsa tidigt kan upptäckas men också som en miljö som genom tidiga insatser kan främja god psykisk hälsa och ge skydd mot ohälsa. Angående små barn i Sverige saknas en samlad kunskap om väl validerade instrument för att mäta psykisk ohälsa hos små barn, förekomsten av psykisk ohälsa och även om de åtgärder som görs i förskolan för att skydda mot senare negativ utveckling av psykisk hälsa hos barnen. Uppdraget från Socialstyrelsen handlar om att validera ett instrument för att mäta beteendeproblem hos små barn och att kartlägga förekomsten av beteendeproblem hos små barn. Även åtgärder som utförs i förskolan för gruppen kartläggs. Fokus ligger alltså på tidig upptäckt och tidig insats (TUTI) när det gäller små barn som uppvisar beteendeproblem i förskolan.
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| 4. |
- Gustafsson, Berit, 1966-, et al.
(författare)
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Longitudinal pathways of engagement, social interaction skills,hyperactivity and conduct problems in preschool children
- 2021
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Ingår i: Scandinavian Journal of Psychology. - : Wiley. - 0036-5564 .- 1467-9450. ; 62:2, s. 170-184
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Tidskriftsartikel (refereegranskat)abstract
- Preschool children’s engagement/social interaction skills can be seen as aspects of positive functioning, and also act as protective aspects of functioning.On the other hand, hyperactivity/conduct problems are risk aspects that negatively affect children’s everyday functioning. Few studies have investigatedsuch orchestrated effects on mental health in young children over time. The aims of the study are rst, to identify homogeneous groups of children havingsimilar pathways in mental health between three time points. Second, to examine how children move between time points in relation to risk and protectivefactors. Alongitudinal study over 3 years, including 197 Swedish preschool children was used. Questionnaire data collected from preschool teachers.Statistical analysis using person-oriented methods with repeated cluster analyses. Children high in engagement/social skills and low in conduct problemscontinue to function well. Children with low engagement/social skills exhibiting both hyperactivity and conduct problems continue to have problems.Children with mixed patterns of protective factors and risk factors showed mixed outcomes. The stability of children’s pathways was quite high if theyexhibited many positive protective factors but also if they exhibited many risk factors. Children exhibiting a mixed pattern of protective and risk factorsmoved between clusters in a less predictable way. That stability in mental health was related to the simultaneous occurrence of either many protectivefactors or many risk factors supports the notion of orchestrated effects. The results indicate that early interventions need to have a dual focus, includingboth interventions aimed at enhancing child engagement and interventions focused on decreasing behavior problem.
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| 5. |
- Gustafsson, Berit M., 1966-, et al.
(författare)
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Hyperactivity precedes conduct problems in preschool children : a longitudinal study.
- 2018
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Ingår i: BJPsych Open. - : Cambridges Institutes Press. - 2056-4724. ; 4:4, s. 186-191
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Tidskriftsartikel (refereegranskat)abstract
- Background: Externalising problems are among the most common symptoms of mental health problems in preschool children.Aims: To investigate the development of externalising problems in preschool children over time, and the way in which conduct problems are linked to hyperactivity problems.Method: In this longitudinal study, 195 preschool children were included. Latent growth modelling of conduct problems was carried out, with gender and hyperactivity at year 1 as time-invariant predictors.Results: Hyperactivity was a significant predictor for the intercept and slope of conduct problems. Children with more hyperactivity at year 1 had more conduct problems and a slower reduction in conduct problems. Gender was a significant predictor for the slope of conduct problems.Conclusions: Children with more initial hyperactivity have less of a reduction in conduct problems over time. It is important to consider the role of hyperactivity in studies of the development of conduct problems.Declaration of interest: None.
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| 6. |
- Gustafsson, Jan-Eric, 1949, et al.
(författare)
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School, Learning and Mental Health : A systematic review
- 2010
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Rapporten presenterar resultaten från en systematisk översikt av forskning om skola, lärande och barns psykiska hälsa. Kungliga Vetenskapsakademiens Hälsoutskottet har givit uppdraget att genomföra en sådan översikt till en arbetsgrupp som har arbetat med uppdraget från hösten 2008 till mars 2009. Det första syftet med översikten är att genomföra en kartläggning av forskning inom det breda fält som behandlar frågor om skola, lärande och barns och ungdomars psykiska hälsa. Det andra syftet är att genomföra en narrativ syntes av forskning som undersökt orsaksförhållanden mellan psykisk hälsa å ena sidan och skolresultat och lärande å den andra sidan. Det tredje syftet är att redovisa resultat från forskning som har studerat svenska barns och ungdomars erfarenheter och upplevelser av skola och undervisningssituationer. För att uppnå de första två syftena genomfördes systematiska litteratursökningar i bibliografiska databaser av artiklar publicerade i vetenskapliga internationella tidskrifter inom olika discipliner. Det tredje syftet undersöktes med litteratursökningar av kvalitativa svenska studier i bibliografiska databaser. Slutsatser På grundval dels av kartläggningen av forskning om skola, lärande och psykisk hälsa, dels av de två fördjupade översikterna kan följande slutsatser dras: • Omfattningen av forskning som undersöker relationerna mellan olika aspekter av skola och psykisk hälsa är begränsad och i synnerhet gäller detta forskning som undersöker organisationsfaktorer och undervisnings-faktorer, aktiviteter, läroplaners utformning, resurser, specialpedagogiskt stöd, och olika former av betyg och bedömning. • Tidiga svårigheter i skolan och i synnerhet läs- och skrivsvårigheter kan orsaka internaliserande och externaliserande psykiska problem. • Svårigheter i skola och psykiska problem tenderar att vara stabila över tid. • Skolrelaterade hälsoproblem tenderar att minska när eleverna börjar på gymnasiet och får tillgång till nya områden av aktiviteter, roller och valmöjligheter. • Att genomföra stora ansträngningar utan att detta leder till resultat är relaterat till utveckling av depression. Problem i skolan med skolresultat och prestationer orsakar inter-naliserande symptom för flickor under tonåren. • Det finns samband mellan olika typer av psykiska problem och de är också relaterade till ett brett spektrum av somatiska och psykosomatiska symptom. • Internaliserande och externaliserande psykiska problem har negativa effekter på skolprestationer genom mekanismer som är delvis ålders- och genusspecifika. • Kompetenser och prestationer i skolan är relaterade till psykisk hälsa. • Goda resultat i skolan har en positiv effekt på självuppfattning. • En god självuppfattning bidrar inte direkt till bättre resultat, men andra faktorer som är relaterade till självuppfattning (motivation och upplevd inre/yttre kontroll) påverkar lärande och resultat • Relationer med klasskamrater och lärare bidrar till processer som kopplar skolmisslyckande till psykisk ohälsa. Relationer med kamrater och lärare kan också skydda mot utvecklingen av psykiska problem. • Jämförelser med klasskamrater påverkar självuppfattningen, med effekter som varierar beroende på gruppsammansättning och typ av skola.
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| 7. |
- Øvretveit, John, et al.
(författare)
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Implementing organization and management innovations in Swedish healthcare : Lessons from a comparison of 12 cases
- 2012
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Ingår i: Journal of Health Organization & Management. - : Emerald Group Publishing Limited. - 1477-7266 .- 1758-7247. ; 26:2, s. 237-257
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The purpose of this paper is to compare the implementation of twelve different "organization and management innovations" (OMIs) in Swedish healthcare, to discover the generic and specific factors important for successful healthcare improvement change in a public health system.Design/methodology/approach: Longitudinal cross-case comparison of twelve case studies was employed, where each case study used a common framework for collecting data about the process of change, the content of change, the context and the intermediate and final outcomes.Findings: Clinical leaders played a more important part in the development of these successful service innovations than managers. Strategies for and patterns of change implementation were found to differ according to the type of innovation. Internal organisational context factors played a significant role in the development of nearly all, but external factors did not. "Developmental evolution" better described the change process than "implementation".Research limitations/implications: The 12 cases were all of relatively successful change processes: some unsuccessful examples would have provided additional testing of of the hypotheses about what would predict successful innovation which were used in the case comparison. The cross-case comparative hypothesis testing method allows systematic comparison if the case data are collected using similar frameworks, but this approach to management research requires considerable resources and coordination.Practical implications: Management innovations that improve patient care can be carried out successfully by senior clinicians, under certain circumstances. A systematic approach is important both for developing and adapting an innovation to a changing situation. A significant amount of time was required for all involved, which could be reduced by "fast-tracking" approval for some type of change.Originality/value: This is the first empirical report comparing longitudinal and contextualised findings from a number of case studies of different organisational and management healthcare innovations. The findings made possible explanations for success factors and useful practical recommendations for conditions needed to nurture such innovation in public healthcare.
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