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1.
  • Adman, Per, et al. (författare)
  • 171 forskare: ”Vi vuxna bör också klimatprotestera”
  • 2019
  • Ingår i: Dagens nyheter (DN debatt). - Stockholm. - 1101-2447.
  • Tidskriftsartikel (populärvet., debatt m.m.)abstract
    • DN DEBATT 26/9. Vuxna bör följa uppmaningen från ungdomarna i Fridays for future-rörelsen och protestera eftersom det politiska ledarskapet är otillräckligt. Omfattande och långvariga påtryckningar från hela samhället behövs för att få de politiskt ansvariga att utöva det ledarskap som klimatkrisen kräver, skriver 171 forskare i samhällsvetenskap och humaniora.
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2.
  • Högberg, Johan, 1994, et al. (författare)
  • Restoring Knee Flexor Strength Symmetry Requires 2 Years After ACL Reconstruction, But Does It Matter for Second ACL Injuries? A Systematic Review and Meta-analysis
  • 2024
  • Ingår i: Sports Medicine – Open. - Heidelberg : SpringerOpen. - 2199-1170 .- 2198-9761. ; 10
  • Forskningsöversikt (refereegranskat)abstract
    • Background: It is unknown whether knee flexor strength recovers after anterior cruciate ligament (ACL) reconstruction with a hamstring tendon (HT) autograft and whether persistent knee flexor strength asymmetry is associated to a second ACL injury. Objective: We aimed to systematically review (1) whether knee flexor strength recovers after ACL reconstruction with HT autografts, and (2) whether it influences the association with a second ACL injury. A third aim was to summarize the methodology used to assess knee flexor strength. Design: Systematic review and meta-analysis reported according to PRISMA. Methods: A systematic search was performed using the Cochrane Library, Embase, Medline, PEDRo, and AMED databases from inception to December 2021 and until completion in January 2023. Human clinical trials written in English and conducted as randomized controlled trials, longitudinal cohort, cross-sectional, and case–control studies on patients with index ACL reconstructions with HT autografts harvested from the ipsilateral side were considered. Knee flexor strength was measured isokinetically in both the reconstructed and uninjured limb to enable the calculation of the limb symmetry index (LSI). The Risk of Bias Assessment Tool for Non-Randomized Studies was used to assess risk of bias for non-randomized studies and the revised Cochrane Risk of Bias tool was used for randomized controlled trials. For the meta-analysis, the LSI (mean ± standard error) for concentric knee flexor strength at angular velocities of 60°/second (s) and 180°/s preoperatively and at 3 months, 6 months, 12 months, and 24 months were pooled as weighted means with standard errors. Results: The search yielded 64 studies with a total of 8378 patients, which were included for the assessment of recovery of knee flexor strength LSI, and a total of 610 patients from four studies that investigated the association between knee flexor strength and second ACL injuries. At 1 year after ACL reconstruction, the knee flexor strength LSI had recovered to 89.0% (95% CI 87.3; 90.7%) and 88.3% (95% CI 85.5; 91.1%) for the velocities of 60°/s and 180°/s, respectively. At 2 years, the LSI was 91.7% (95% CI 90.8; 92.6%) and 91.2% (95% CI 88.1; 94.2%), for velocities of 60°/s and 180°/s, respectively. For the association between knee flexor strength and second ACL injuries, there was insufficient and contradictory data. Conclusions: There was low to very low certainty of evidence indicating that the recovery of knee flexor strength LSI, defined as ≥ 90% of the uninjured side, takes up to 2 years after ACL reconstruction with HT autografts. Whether knee flexor strength deficits influence the association of second ACL injuries is still uncertain. There was considerable heterogeneity in the methodology used for knee flexor strength assessment, which together with the low to very low certainty of evidence, warrants further caution in the interpretation of our results. Registration number: CRD42022286773. © 2024, The Author(s).
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3.
  • Saarimäki, Jonas (författare)
  • Effect of Dwell-times on Crack Propagation in Superalloys
  • 2015
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Gas turbines are widely used in industry for power generation and as a power source at "hard to reach" locations where other possibilities for electrical supply are insufficient. There is a strong need for greener energy, considering the effect that pollution has had on global warming, and we need to come up with ways of producing cleaner electricity. A way to achieve this is by increasing the combustion temperature in gas turbines. This increases the demand on the high temperature performance of the materials used e.g. superalloys in the turbine. These high combustion temperatures can lead to detrimental degradation of critical components. These components are commonly subjected to cyclic loading of different types e.g. combined with dwell-times and overloads at elevated temperatures, which influence the crack growth. Dwell-times have shown to accelerate crack growth and change the cracking behaviour in both Inconel 718 and Haynes 282. Overloads at the beginning of the dwell-time cycle have shown to retard the dwell time effect on crack growth in Inconel 718. To understand these effects more microstructural investigations are needed.The work presented in this licentiate thesis was conducted under the umbrella of the research program Turbo Power; "High temperature fatigue crack propagation in nickel-based superalloys", concentrating on fatigue crack growth mechanisms in superalloys during dwell-times, which have shown to have a devastating effect on the crack propagation behaviour. Mechanical testing was performed under operation-like conditions in order to achieve representative microstructures and material data for the subsequent microstructural work. The microstructures were microscopically investigated in a scanning electron microscope (SEM) using electron channeling contrast imaging (ECCI) as well as using light optical microscopy.The outcome of this work has shown that there is a significant increase in crack growth rate when dwell-times are introduced at the maximum load (0% overload) in the fatigue cycle. With the introduction of a dwell-time there is also a shift from transgranular to intergranular crack growth for both Inconel 718 and Haynes 282. When an overload is applied prior to the dwell-time, the crack growth rate decreases with increasing overload levels in Inconel 718. At high temperature crack growth in Inconel 718 took place as intergranular crack growth along grain boundaries due to oxidation and the creation of nanometric voids. Another observed growth mechanism was crack advance along phase boundaries with subsequent severe oxidation of the phase.This thesis comprises two parts. The first giving an introduction to the field of superalloys and the acting microstructural mechanisms that influence fatigue during dwell times. The second part consists of two appended papers, which report the work completed so far in the project.
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4.
  • Simonsson, Kjell, et al. (författare)
  • Kamratutvärdering i kurser med stort datorlaborativt inslag
  • 2014
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • De mångfacetterade krav som idag ställs på yrkesverksamma högskole- och civilingenjörer handlar inte enbart om rena ämnesmässiga kunskaper och förmågor, utan även om t.ex. erfarenhet och förmåga att delta i och leda projekt samt (kopplat till detta) kommunikativ skicklighet (såväl muntlig som skriftlig). En annan uppgift som yrkesverksamma ingenjörer måste kunna bemästra i sin profession är att (individuellt, eller som medlemmar i olika typer av styrgrupper) bedöma och utvärdera andras ingenjörsmässiga arbete, en oerhört central uppgift i ett projekt- och kvalitetssäkringsperspektiv.Det övergripande syftet med arbetet har varit att studera hur kamratbedömning kan implementeras i redan existerande kurser, för att på så sätt ge de studerande möjlighet att träna på att ge och ta emot kritisk bedömning, att förbättra de studerandes lärande via ett större aktivt engagemang under kursen samt att se om potential finns att effektivisera undervisningen m.a.p. lärarinsatsen, genom att lyfta över en del av enklare rutinkontroller till de studerande själva.Kamratbedömning har implementerats i två sinsemellan likartade kurser inom beräkningsmekanik vid högskole- resp. civilingenjörsprogrammen i Maskinteknik, LiTH (600 studenter ingick i studien). Mer specifikt har till två enklare inledande laborationsuppgifter inkluderats ett moment av kamratbedömning. Utvärderingen av det genomförda arbetet har skett via en kvalitativ studie, där de studerandes perspektiv/synpunkter inhämtats i samband med skriftlig redovisning av inlämningsuppgifter. Utöver detta har den kursansvarige gjort observationer av hur kamratutvärderingsarbetet fortskridit under laborationstid.Resultatet visar att de studerande har uppskattat granskningen av såväl det egna som kamraternas arbeten, och att de sett det som ett led i lärandeprocessen. Även professionsperspektivet har lyfts fram där de studerande betonar vikten av moment och uppgifter i utbildningen som har en direkt relevans i det kommande yrkeslivet. Den kursansvariges bedömning är vidare att andelen ”viktiga” och ”relevanta” frågor ökat, vilket ger indikationer på att kamratbedömning kan vara en såväl pedagogiskt som effektivitetsmässigt gynnsam metodik. De studerande har dock upplevt logistiken/administrationen kring kamratvärderingen som i vissa avseenden besvärlig.Sammanfattningsvis är det vår slutsats att kamratbedömning har en stor potential att berika utbildningar m.a.p. förmåga till kritisk granskning, djupinlärning och effektivisering, men att verksamheten inte bara skall implementeras kursvis (med risk för suboptimering och ineffektivitet), utan att den bör inlemmas i ett större perspektiv, med progression genom utbildningen som riktmärke.
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5.
  • Török, Sandra, et al. (författare)
  • Investigation of the absorption Ångström exponent and its relation to physicochemical properties for mini-CAST soot
  • 2018
  • Ingår i: Aerosol Science and Technology. - : Informa UK Limited. - 0278-6826 .- 1521-7388. ; 52:7, s. 757-767
  • Tidskriftsartikel (refereegranskat)abstract
    • In this work, a mini-CAST soot generator was used to produce soot with different optical and physicochemical characteristics. Absorption Ångström exponents (AAE) expressing the absorption wavelength dependence were assessed by multiwavelength in-situ and filter-based (aethalometer) laser extinction. The two optical techniques showed good agreement. For the chosen mini-CAST operating conditions, AAEs between 1 and 3.5 were found. Soot with high mass-fractions of organic carbon (OC) and pyrolytic carbon (PC) determined with thermal optical analysis were associated with AAEs significantly higher than 1. Heating to 250 and 500°C removed the majority of polycyclic aromatic hydrocarbons. However, the thermal-optical analysis revealed that OC and PC were abundant in the soot with AAE > 2 also after heating the aerosol. Analysis of mass absorption cross section ratios for elemental carbon and OC indicated that elevated AAEs also after heating to 500°C could be related to persistent OC and PC components and/or the refractory soot. By comparing the mini-CAST soot optical properties with soot properties derived from in-situ extinction measurements in a premixed flame, mini-CAST soot with a higher AAE could be identified as less mature soot.
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6.
  • Andreasson, Martin, 1993-, et al. (författare)
  • Dynamics of related and unrelated digital diversification in established firms : Strategies, programs, process, and outcomes
  • 2024
  • Ingår i: Technological forecasting & social change. - : Elsevier. - 0040-1625 .- 1873-5509. ; 202
  • Tidskriftsartikel (refereegranskat)abstract
    • Research on digital transformation focuses on business models and technological innovation but it often lacks a detailed exploration of how firms develop, execute, and evaluate related and unrelated digital diversification strategies. To address this gap, this study employs a multiple case study approach to uncover the varied processes and outcomes of implementing digital diversification programs in established firms. The findings reveal that established firms frequently refine and adjust their digital diversification strategies to achieve desired results. Specifically, related digital diversification strategies benefit from well-defined market segments, clear technological focus, and robust senior management support. In contrast, unrelated digital diversification strategies thrive through extensive exploration and experimentation with novel digital technologies and markets, reduced senior managerial intervention and increased middle- and lower-level management involvement. Semi-related digital diversification strategies, which incorporate elements of both related and unrelated approaches, often encounter tensions owing to conflicting traditional and new program execution methods, posing significant realization challenges. Key factors identified as instrumental in the success of digital diversification strategies include technology, markets, management & organization, and program execution. The study concludes by discussing the managerial and academic implications and offers recommendations for future research in this domain.
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7.
  • Baccarani, Michele, et al. (författare)
  • Comparison of imatinib 400 mg and 800 mg daily in the front-line treatment of high-risk, Philadelphia-positive chronic myeloid leukemia : a European LeukemiaNet Study
  • 2009
  • Ingår i: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 113:19, s. 4497-4504
  • Tidskriftsartikel (refereegranskat)abstract
    • Imatinib mesylate (IM), 400 mg daily, is the standard treatment of Philadelphia-positive (Ph(+)) chronic myeloid leukemia (CML). Preclinical data and results of single-arm studies raised the suggestion that better results could be achieved with a higher dose. To investigate whether the systematic use of a higher dose of IM could lead to better results, 216 patients with Ph(+) CML at high risk (HR) according to the Sokal index were randomly assigned to receive IM 800 mg or 400 mg daily, as front-line therapy, for at least 1 year. The CCgR rate at 1 year was 64% and 58% for the high-dose arm and for the standard-dose arm, respectively (P = .435). No differences were detectable in the CgR at 3 and 6 months, in the molecular response rate at any time, as well as in the rate of other events. Twenty-four (94%) of 25 patients who could tolerate the full 800-mg dose achieved a CCgR, and only 4 (23%) of 17 patients who could tolerate less than 350 mg achieved a CCgR. This study does not support the extensive use of high-dose IM (800 mg daily) front-line in all CML HR patients. This trial was registered at www.clinicaltrials.gov as #NCT00514488.
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8.
  • Bladh, Henrik, et al. (författare)
  • Probing the smallest soot particles in low-sooting premixed flames using laser-induced incandescence
  • 2015
  • Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 35, s. 1843-1850
  • Tidskriftsartikel (refereegranskat)abstract
    • In this work we investigate nascent soot particles by analyzing laser-induced incandescence (LII) signals obtained in low-sooting premixed flames. The analysis covers two data sets obtained in separate experimental campaigns. The first data set was obtained in a previous work (Mouton et al., 2013) in methane/oxygen/nitrogen flames (equivalence ratio range 1.95 < Phi < 2.32) at 26.7 kPa, whereas the second was performed in atmospheric ethylene/air flames (1.77 < Phi < 2.00). Both studies show similar trends, i.e. a gradual change of the fluence curves (evolution of the LII signal as function of the laser fluence) from the well-known S-shaped curve for mature soot found at high heights above the burner (HAB) and high equivalence ratio, to a nearly linear behavior for nascent soot found at low HAB and reduced equivalence ratio. With this change comes a decrease in the LII decay time (and hence inferred particle size). Also, this decay time appears to be almost constant with HAB in flames having the lowest equivalence ratio at which the incandescence signal could be detected. In these flames, so-called nucleation flames, the stability of the particle size with HAB suggests that recently nucleated particles have undergone marginal surface growth and coagulation. Existence of such nucleation flames is of great interest for improving the theoretical description of the nucleation step. Experimental results are analyzed by using a theoretical model for LII to determine the particle size evolution throughout the flame at various experimental conditions. We highlight the size difference from nascent soot particles up to mature soot, giving insight into the particle nucleation and the surface growth processes as a function of reaction time and flame conditions. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
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9.
  • Boreström, Cecilia, 1974, et al. (författare)
  • Footprint-Free Human Induced Pluripotent Stem Cells From Articular Cartilage With Redifferentiation Capacity: A First Step Toward a Clinical-Grade Cell Source.
  • 2014
  • Ingår i: Stem cells translational medicine. - : Oxford University Press (OUP). - 2157-6564 .- 2157-6580. ; 3:4, s. 433-447
  • Tidskriftsartikel (refereegranskat)abstract
    • Human induced pluripotent stem cells (iPSCs) are potential cell sources for regenerative medicine; however, clinical applications of iPSCs are restricted because of undesired genomic modifications associated with most reprogramming protocols. We show, for the first time, that chondrocytes from autologous chondrocyte implantation (ACI) donors can be efficiently reprogrammed into iPSCs using a nonintegrating method based on mRNA delivery, resulting in footprint-free iPSCs (no genome-sequence modifications), devoid of viral factors or remaining reprogramming molecules. The search for universal allogeneic cell sources for the ACI regenerative treatment has been difficult because making chondrocytes with high matrix-forming capacity from pluripotent human embryonic stem cells has proven challenging and human mesenchymal stem cells have a predisposition to form hypertrophic cartilage and bone. We show that chondrocyte-derived iPSCs can be redifferentiated in vitro into cartilage matrix-producing cells better than fibroblast-derived iPSCs and on par with the donor chondrocytes, suggesting the existence of a differentiation bias toward the somatic cell origin and making chondrocyte-derived iPSCs a promising candidate universal cell source for ACI. Whole-genome single nucleotide polymorphism array and karyotyping were used to verify the genomic integrity and stability of the established iPSC lines. Our results suggest that RNA-based technology eliminates the risk of genomic integrations or aberrations, an important step toward a clinical-grade cell source for regenerative medicine such as treatment of cartilage defects and osteoarthritis.
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10.
  • Busse, Christian, et al. (författare)
  • A FINITE ELEMENT STUDY OF THE EFFECT OF CRYSTAL ORIENTATION AND MISALIGNMENT ON THE CRACK DRIVING FORCE IN A SINGLE-CRYSTAL SUPERALLOY
  • 2016
  • Ingår i: PROCEEDINGS OF THE ASME TURBO EXPO: TURBINE TECHNICAL CONFERENCE AND EXPOSITION, 2016, VOL 7A. - : AMER SOC MECHANICAL ENGINEERS. - 9780791849835
  • Konferensbidrag (refereegranskat)abstract
    • The elastic and plastic anisotropy of the single-crystal materials bring many difficulties in terms of modeling, evaluation and prediction of fatigue crack growth. In this paper a single-crystal material model has been adopted to a finite element-environment, which is paired with a crack growth tool. All simulations are performed in a three-dimensional context. This methodology makes it possible to analyze complex finite element-models, which are more application-near than traditional two-dimensional models. The influence of the crystal orientation, as well as the influence of misalignments of the crystal orientation due to the casting process are investigated. It is shown that both the crystal orientation and the misalignment from the ideal crystal orientation are important for the crack driving force. The realistic maximum limit of 10 degrees misalignment is considered. It can be seen that crack growth behavior is highly influenced by the misalignment. This knowledge is of great interest for the industry in order to evaluate the crack growth in single-crystal components more accurately.
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11.
  • Busse, Christian, 1989- (författare)
  • Aspects of Crack Growth in Single-Crystal Nickel-Base Superalloys
  • 2017
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • This Licentiate of Engineering thesis is a product of the results generated in the research project KME-702, which comprises modelling, microstructure investigations and material testing of cast nickel-base superalloys.The main objective of this work is to model the fatigue crack propagation behaviour in single-crystal nickel-base superalloys. To achieve this, the influence of the crystal orientations on the cracking behaviour is assessed. The results show that the crystal orientation is strongly affecting the material response and must be accounted for. Furthermore, a linear elastic crack driving force parameter suitable for describing crystallographic cracking has been developed. This parameter is based on resolved anisotropic stress intensity factors and is able to predict the correct crystallographic cracking plane after a transition from a Mode I crack. Finally, a method to account for inelastic deformations in a linear elastic fracture mechanics context was investigated. A residual stress field is extracted from an uncracked finite-element model with a perfectly plastic material model and superimposed on the stress field from the cracked model with a linear elastic material model to account for the inelastic deformations during the determination of the crack driving force. The modelling work is validated by material testing on two different specimen geometries at different temperatures.This Licentiate of Engineering thesis consists of two parts, where Part I gives an introduction and background to the research area, while Part II consists of three papers.
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12.
  • Busse, Christian, et al. (författare)
  • Criteria evaluation for the transition of cracking modes in a single-crystal nickel-base superalloy
  • 2020
  • Ingår i: Theoretical and applied fracture mechanics (Print). - : ELSEVIER. - 0167-8442 .- 1872-7638. ; 106
  • Tidskriftsartikel (refereegranskat)abstract
    • Single-crystal nickel-base superalloys frequently experience two distinct fatigue crack growth modes. It has been observed that, under certain conditions, cracks transition from a path perpendicular to the loading direction to a crystallographic slip plane. As crystallographic cracking is associated with an increased fatigue crack growth rate, it is important to be able to predict when this transition occurs. In this work three different criteria for crystallographic cracking based on resolved anisotropic stress intensity factors are evaluated in a three-dimensional finite element context. The criteria were calibrated and evaluated using isothermal fatigue experiments on two different specimen geometries. It is suggested by the results, that a threshold value of a resolved shear stress intensity factor can act as a conservative criterion indicating cracking mode transition. Further, a trend hinting towards a loading frequency dependency could be observed.
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13.
  • Busse, Christian, et al. (författare)
  • Three-Dimensional LEFM Prediction of Fatigue Crack Propagation in a Gas Turbine Disk Material at Component Near Conditions
  • 2016
  • Ingår i: Journal of engineering for gas turbines and power. - : ASME. - 0742-4795 .- 1528-8919. ; 138:4
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, the possibility to use linear elastic fracture mechanics (LEFM), with and without a superimposed residual stress field, to predict fatigue crack propagation in the gas turbine disk material Inconel 718 has been studied. A temperature of 400 degrees C and applied strain ranges corresponding to component near conditions have been considered. A three-dimensional crack propagation software was used for determining the stress intensity factors (SIFs) along the crack path. In the first approach, a linear elastic material behavior was used when analyzing the material response. The second approach extracts the residual stresses from an uncracked model with perfectly plastic material behavior after one loading cycle. As a benchmark, the investigated methods are compared to experimental tests, where the cyclic lifetimes were calculated by an integration of Paris law. When comparing the results, it can be concluded that the investigated approaches give good results, at least for longer cracks, even though plastic flow was taking place in the specimen. The pure linear elastic simulation overestimates the crack growth for all crack lengths and gives conservative results over all considered crack lengths. Noteworthy with this work is that the 3D-crack propagation could be predicted with the two considered methods in an LEFM context, although plastic flow was present in the specimens during the experiments.
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14.
  • Casetou, Sophie, et al. (författare)
  • Comparison of measured (XRPD) and modeled (A2M) soil mineralogies : A study of some Swedish forest soils in the context of weathering rate predictions
  • 2018
  • Ingår i: Geoderma. - : Elsevier BV. - 0016-7061 .- 1872-6259. ; 310, s. 77-88
  • Tidskriftsartikel (refereegranskat)abstract
    • Quantitative soil mineralogy has been identified as a key factor influencing PROFILE weathering estimates, and is often calculated with normative methods, such as the “Analysis to Mineralogy” (‘A2M’) model. In Sweden and other countries, there is a large request for accurate base cation weathering estimates in order to establish how sustainable harvest of biomass should be performed in the future. However, there is a lack of knowledge around the accuracy of the arithmetic mean output of A2M estimates, the most common A2M solution used in weathering studies. To our knowledge, a thorough investigation of how A2M input data affect the arithmetic mean output (center of gravity of the A2M solution space) is missing. In this study, the indirect geochemical normative method (A2M) was compared with a direct x-ray powder diffraction method (XRPD) to quantify soil mineralogy at two sites and 8 soil profiles, at a 10 cm depth interval. We explored the hypothesis that normative calculations performed with A2M produce an output in closer agreement with the mineralogy obtained from XRPD, if site specific mineralogical input data are used rather than regional data. Site-specific mineralogical input data consisted of mineral stoichiometry data measured by electron microprobe analysis (EMPA) and mineral identity determined by XRPD, whereas regional mineral input data were based on previously reported data on mineral stoichiometry and mineral identity, derived from three geological regions in Sweden. The results from this comparison showed that the site-specific approach yielded relatively low average biases and root mean square errors (RMSE) for most minerals, with the exception of quartz (Average bias of − 4.8 wt%, RMSE of 5.3 wt%) at the Asa site. The regional approach yielded deviating results for K-feldspar and dioctahedral mica, with high average biases and RMSE for dioctahedral mica (Asa: 7.8 wt%, 9.0 wt%; Flakaliden: 12.8 wt%, 15.5 wt%) and for K-feldspar (Asa: − 5.2 wt%, 6.1 wt%; Flakaliden: − 5.6 wt%, 6.7 wt%). The results from this study were supported by a close agreement between measured geochemistry and normalized geochemistry derived from a back calculation of the XRPD mineralogy (i.e. mineral budgeting). In conclusion, our findings suggest that A2M results in combination with site-specific mineralogical input data are improved independent of study site and soil profile. However, for future weathering studies it might be beneficial to find constraints of how to select a solution from the entire A2M solution space which is in better agreement with the XRPD mineralogy.
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15.
  • Casetou, Sophie, et al. (författare)
  • Current, steady-state and historical weathering rates of base cations at two forest sites in northern and southern Sweden: a comparison of three methods
  • 2020
  • Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 17, s. 281-304
  • Tidskriftsartikel (refereegranskat)abstract
    • Reliable and accurate methods for estimating soil mineral weathering rates are required tools in evaluating the sustainability of increased harvesting of forest biomass and assessments of critical loads of acidity. A variety of methods that differ in concept, temporal and spatial scale, and data requirements are available for measuring weathering rates. In this study, causes of discrepancies in weathering rates between methods were analysed and were classified as being either conceptual (inevitable) or random. The release rates of base cations (BCs; Ca, Mg, K, Na) by weathering were estimated in podzolised glacial tills at two experimental forest sites, Asa and Flakaliden, in southern and northern Sweden, respectively. Three different methods were used: (i) historical weathering since deglaciation estimated by the depletion method, using Zr as the assumed inert reference; (ii) steady-state weathering rate estimated with the PROFILE model, based on quantitative analysis of soil mineralogy; and (iii) BC budget at stand scale, using measured deposition, leaching and changes in base cation stocks in biomass and soil over a period of 12 years. In the 050 cm soil horizon historical weathering of BCs was 10.6 and 34.1 mmolc m(-2) yr(-1), at Asa and Flakaliden, respectively. Corresponding values of PROFILE weathering rates were 37.1 and 42.7 mmolc m(-2) yr(-1). The PROFILE results indi- cated that steady-state weathering rate increased with soil depth as a function of exposed mineral surface area, reaching a maximum rate at 80 cm (Asa) and 60 cm (Flakaliden). In contrast, the depletion method indicated that the largest postglacial losses were in upper soil horizons, particularly at Flakaliden.With the exception of Mg and Ca in shallow soil horizons, PROFILE produced higher weathering rates than the depletion method, particularly of K and Na in deeper soil horizons. The lower weathering rates of the depletion method were partly explained by natural and anthropogenic variability in Zr gradients. The base cation budget approach produced significantly higher weathering rates of BCs, 134.6 mmolc m(-2) yr(-1) at Asa and 73.2 mmolc m(-2) yr(-1) at Flakaliden, due to high rates estimated for the nutrient elements Ca, Mg and K, whereas weathering rates were lower and similar to those for the depletion method (6.6 and 2.2 mmolc m(-2) yr(-1) at Asa and Flakaliden). The large discrepancy in weathering rates for Ca, Mg and K between the base cation budget approach and the other methods suggests additional sources for tree uptake in the soil not captured by measurements.
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16.
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17.
  • Druker, Brian J., et al. (författare)
  • Five-year follow-up of patients receiving imatinib for chronic myeloid leukemia
  • 2006
  • Ingår i: New England Journal of Medicine. - 0028-4793 .- 1533-4406. ; 355:23, s. 2408-2417
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: The cause of chronic myeloid leukemia (CML) is a constitutively active BCR-ABL tyrosine kinase. Imatinib inhibits this kinase, and in a short-term study was superior to interferon alfa plus cytarabine for newly diagnosed CML in the chronic phase. For 5 years, we followed patients with CML who received imatinib as initial therapy. METHODS: We randomly assigned 553 patients to receive imatinib and 553 to receive interferon alfa plus cytarabine and then evaluated them for overall and event-free survival; progression to accelerated-phase CML or blast crisis; hematologic, cytogenetic, and molecular responses; and adverse events. RESULTS: The median follow-up was 60 months. Kaplan-Meier estimates of cumulative best rates of complete cytogenetic response among patients receiving imatinib were 69% by 12 months and 87% by 60 months. An estimated 7% of patients progressed to accelerated-phase CML or blast crisis, and the estimated overall survival of patients who received imatinib as initial therapy was 89% at 60 months. Patients who had a complete cytogenetic response or in whom levels of BCR-ABL transcripts had fallen by at least 3 log had a significantly lower risk of disease progression than did patients without a complete cytogenetic response (P<0.001). Grade 3 or 4 adverse events diminished over time, and there was no clinically significant change in the profile of adverse events. CONCLUSIONS: After 5 years of follow-up, continuous treatment of chronic-phase CML with imatinib as initial therapy was found to induce durable responses in a high proportion of patients. (ClinicalTrials.gov number, NCT00006343 [ClinicalTrials.gov].)
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18.
  • Engström, Annika, 1964-, et al. (författare)
  • A learning perspective on the interdependency between technology-driven and managerial- driven AI-transformation
  • 2022
  • Ingår i: International Conference on Work Integrated Learning. - Trollhättan : University West. - 9789189325302 ; , s. 122-124
  • Konferensbidrag (refereegranskat)abstract
    • Introduction Moving from manual, to automated, to connected AI operations systems implies a significant transformation in the organisation of work (European Parliament, 2015:8) (Brock & von Wangenheim). To understand these “realistic AI” processes, to build competence for certain tasks. it is crucial to understand what organisational competencies that are needed and how to organize knowledge creation processes in practice (Ellström, 2001) Schön used the concept of “knowing–in-action” is nonreflective and solving most everyday practical problems, here understood as executional learning (Engström & Wikner, 2017). Thus, this knowing, according to Schön (1983), is not enough to meet more complex situations. To be aware of tacit knowledge, we need to distance ourselves and learn to reflect. More complex, uncertain and unclear tasks require “knowing-on-action” and collaboration between several competences to create new knowledge or to reach a new solution here understood as developmental learning (Engström&Wikner).. Anton et al. (2020) state that in many organisations there is a lack of AI-related competencies that prevent development of the full AI potential. For the development of the field, it is important to study the dynamic interplay between advanced technology and the social side of work from a learning and competence perspective. Therefore, this paper aims to explore how industrial organisations understand their competencies in relation to AI transformation from a knowledge creation perspective.Research method The study was part of a collaborative research project with an interdisciplinary research team and representatives from five industrial partners. In four-month cycles the industrial partners engaged in “homework” presented, analysed and discussed in common workshops. For this study, the homework was guided by the DIGITAL approach (Brock & von Wangenheim, 2019) and based on the explanatory model (Anton et al., 2020). The industrial partners studied how resources and competencies related to specific organisational tasks in their own organisations could be identified and defined. To aid the data collection (that was done by the industrial partners themselves) a framework capturing Anton et al.’s (2020) 13 dimensions of competencies (Leadership, Communication, Customer-focused decision making, Business development, Data science/STEM, Agile software development, Initiative and engagement, AI technology, Programming, Digital analysis tools, Data and network technology, Digital competencies, and Data management) was used. For each dimension the partners assesses the competence level: Competence central to the process; Competence exists internally; Competence partly exists internally; Competence does not exist internally; Competence can be gained by development internally; Competence needs to be sourced externally. These were in line with Brock & von Wangenheim’s (2019) logic that managers when starting AI project should do “internal resources check”. The data was analysed in four steps. First, focus group data was analysed by the facilitators at each industrial partner. Second, the competence mapping was analysed by the “working groups” at each industrial partner. Third, the transcribed data from the two industrial partners used in this paper were reviewed individually by t he authors. Fourth, the cross-disciplinary group of authors from both academia and industrial partners gathered for a common analysis session. This session primarily focused on the data from the competence mapping but also cross-checked with the input from the cross-functional focus groups to triangulate the outcome. During the common analysis the conceptual framework presented in the discussion section was developed through iterations between the theoretical framework based on the findings by Anton et al. (2020), and the data from the project.Findings The preliminary findings show differences among the industrial partners in how they view their own competencies. For some organisations organisational structures are in place, e.g., dedicated AI Labs, where the work with understanding the benefits and usage of the technology is ongoing on a rather advanced level. In other organisations the work has just been initiated. Overall, all representatives stress the importance of top management support and the need for dedicated forums. Among the organisations that have come the farthest in their AI transformation the structure given by the proposed framework is not enough. They emphasise the need to further frame it into also understanding what the competence is associated with and why it is needed. They view the leadership as almost having to have an evangelistic approach to it, where it does not seem to be enough with “only” technical experts. A conceptual framework, consisting of the relationship between the two dimensions: the managerial competencies and the technical competencies, is developed (Figure 1). The managerial competencies dimension concerns organisation and organising. The technical competencies dimension on the other hand captures the complexity level of the technology that is needed, the system of systems. The diagonal illustrates the relationship between these two dimensions, that is, the relation between technological complexity and organisational ability. The lower part of the diagonal captures isolated, simple processes (presumably internal) while the upper part of the diagonal captures integrated, complex processes (presumably primarily related to external parts and/or actors).. For high levels of technical complexity that requires high levels of technical competencies within the organisation the organisation also needs to advance the managerial competencies and the developmental learning processes. However, while in the long-term perspective we suggest that going off the diagonal will be inefficient and ineffective, hence, waste, it might be needed to do that temporarily, as the organisation develops. We believe that this developmentcan be either technology-driven or organisation-driven.The proposed conceptual framework is intended to help organisations plot their own current position based on the two dimensions and identify what changes are needed to reach the diagonal. It can also be used to define where on the diagonal the organisation ultimately wants to end up. It is not relevant for all companies or even for all sectors overall to be at the top right side. We believe that AI transformation cannot be approached as either technologydriven or managerial-driven, but as an e interdependent process of both dimensions.
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19.
  • Eriksson, Robert, et al. (författare)
  • Evaluation of notch effects in low cycle fatigue of alloy 718 using critical distances
  • 2018
  • Ingår i: 12TH INTERNATIONAL FATIGUE CONGRESS (FATIGUE 2018). - : E D P SCIENCES.
  • Konferensbidrag (refereegranskat)abstract
    • Gas turbine disks contain many notch-like features acting as stress raisers. The fatigue life based on the notch root stress may be overly conservative as the steep stress gradient in front of the notch may give rise to so-called notch support. In the current work, the theory of critical distances was applied to the prediction of the total fatigue life of low cycle fatigued, notched specimens made from alloy 718. The fatigue tests were performed at 450 degrees C and 550 degrees C. It was found that, for lives shorter than 5000-10000 cycles, the notched specimens had longer lives than would have been expected based on the notch root strain. For lives longer than 5000-10000 cycles, there were no notch support. The life prediction for notched specimens could be significantly improved by basing the prediction on the strain chosen some distance from the notch (the critical distance). An expression for calculating the critical distance based on the notch root strain was suggested.
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20.
  • Ewest, D., et al. (författare)
  • A modified compliance method for fatigue crack propagation applied on a single edge notch specimen
  • 2016
  • Ingår i: International Journal of Fatigue. - London : ELSEVIER SCI LTD. - 0142-1123 .- 1879-3452. ; 92, s. 61-70
  • Tidskriftsartikel (refereegranskat)abstract
    • Crack length measurements with high accuracy are often difficult to achieve during fatigue crack propagation testing under non-isothermal conditions. In this work a modified approach to the compliance method defined in e.g. ASTM E647 is described, which is better suited for high loads, varying temperatures and for taking the scatter in Youngs modulus into account. A numerical finite element study is performed for a single edge notch specimen, to investigate the influence of initiation locations on the accuracy of the method. The change in cracked area versus change in stiffness for three different cases are numerically shown to collapse to one curve, i.e. the result is not significantly affected by how the crack is initiated. The numerical study is compared to results from two experiments using different materials, with heat tinting during the tests for extracting snapshots of the crack fronts. A good agreement between the experiments and the numerical study is shown. A new compliance curve and a new geometry function for the stress intensity factor is proposed for the single edge notch specimen. (C) 2016 Elsevier Ltd. All rights reserved.
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21.
  • Felton, Adam, et al. (författare)
  • Correction to: Keeping pace with forestry : Multi-scale conservation in a changing production forest matrix (vol 49, pg 1050, 2020)
  • 2020
  • Ingår i: Ambio. - : Springer. - 0044-7447 .- 1654-7209. ; 49:5, s. 1065-1066
  • Tidskriftsartikel (refereegranskat)abstract
    • In the original published article, the sentence “Nevertheless, semi-natural forest remnants continue to be harvested and fragmented (Svensson et al. 2018; Jonsson et al. 2019), and over 2000 forest-associated species (of 15 000 assessed) are listed as threatened on Sweden’s red-list, largely represented by macro-fungi, beetles, lichens and butterflies (Sandström 2015).”under the section Introduction was incorrect. The correct version of the sentence is “Nevertheless, semi-natural forest remnants continue to be harvested and fragmented (Svensson et al. 2018; Jonsson et al. 2019), and approximately 2000 forest-associated species (of 15 000 assessed) are on Sweden’s red-list, largely represented by macro-fungi, beetles, lichens and butterflies (Sandström 2015).”
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22.
  • Felton, Adam, et al. (författare)
  • Keeping pace with forestry : Multi-scale conservation in a changing production forest matrix
  • 2020
  • Ingår i: Ambio. - : Springer. - 0044-7447 .- 1654-7209. ; 49:5, s. 1050-1064
  • Tidskriftsartikel (refereegranskat)abstract
    • The multi-scale approach to conserving forest biodiversity has been used in Sweden since the 1980s, a period defined by increased reserve area and conservation actions within production forests. However, two thousand forest-associated species remain on Sweden's red-list, and Sweden's 2020 goals for sustainable forests are not being met. We argue that ongoing changes in the production forest matrix require more consideration, and that multi-scale conservation must be adapted to, and integrated with, production forest development. To make this case, we summarize trends in habitat provision by Sweden's protected and production forests, and the variety of ways silviculture can affect biodiversity. We discuss how different forestry trajectories affect the type and extent of conservation approaches needed to secure biodiversity, and suggest leverage points for aiding the adoption of diversified silviculture. Sweden's long-term experience with multi-scale conservation and intensive forestry provides insights for other countries trying to conserve species within production landscapes.
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23.
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24.
  • Frykholm, Erik, 1985-, et al. (författare)
  • Applicability of a supramaximal high-intensity interval training program for older adults previously not engaged in regular exercise : analyses of secondary outcomes from the Umeå HIT Study
  • 2024
  • Ingår i: Psychology of Sport And Exercise. - : Elsevier. - 1469-0292 .- 1878-5476. ; 73
  • Tidskriftsartikel (refereegranskat)abstract
    • This analysis of secondary outcomes investigated the applicability of supramaximal high-intensity interval training (HIT) with individually prescribed external intensity performed on stationary bicycles. Sixty-eight participants with a median (min; max) age of 69 (66; 79), at the time not engaged in regular exercise were randomized to 25 twice-weekly sessions of supramaximal HIT (20-min session with 10 × 6-s intervals) or moderate-intensity training (MIT, 40-min session with 3 × 8-min intervals). The primary aim was outcomes on applicability regarding; adherence to prescribed external interval intensity, participant reported positive and negative events, ratings of perceived exertion (RPE 6–20), and affective state (Feeling Scale, FS -5–5). A secondary aim was to investigate change in exercise-related self-efficacy (Exercise Self-Efficacy Scale) and motivation (Behavioural Regulations in Exercise Questionnaire-2). Total adherence to the prescribed external interval intensity was [median (min; max)] 89 % (56; 100 %) in supramaximal HIT, and 100 % (95; 100 %) in MIT. The supramaximal HIT group reported 60 % of the positive (112 of 186) and 36 % of the negative (52 of 146) events. At the end of the training period, the median (min; max) session RPE was 15 (12; 17) for supramaximal HIT and 14 (9; 15) for MIT. As for FS, the median last within-session rating was 3 (−1; 5) for supramaximal HIT and 3 (1; 5) for MIT. Exercise-related motivation increased (mean difference in Relative Autonomy Index score = 1.54, 95 % CI [0.69; 2.40]), while self-efficacy did not change (mean difference = 0.55, 95 % CI [-0.75; 1.82]), regardless of group. This study provide support for supramaximal HIT in supervised group settings for older adults.
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25.
  • Gallo, Yann, et al. (författare)
  • A Study of In-Cylinder Soot Oxidation by Laser Extinction Measurements During an EGR-Sweep in an Optical Diesel Engine
  • 2015
  • Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191.
  • Tidskriftsartikel (refereegranskat)abstract
    • Two competing in-cylinder processes, soot formation and soot oxidation, govern soot emissions from diesel engines. Previous studies have shown a lack of correlation between the soot formation rate and soot emissions. The current experiment focuses on the correlation between soot oxidation rates and soot emissions. Laser extinction is measured using a red (690nm) laser beam, which is sent vertically through the cylinder. This wavelength is long enough to minimize absorption interference from poly-aromatic hydrocarbons, while still in the visible regime. It is modulated at 72 kHz in order to produce 10 pulses per crank angle degree at an engine speed of 1200 rpm. The intake oxygen concentration is varied between 9% and 21%. The time resolved extinction measurements are used to estimate soot oxidation rates during expansion. High-speed video imaging is used in conjunction with the laser-extinction technique to indicate the location of the sooting regions, and to assess beam steering effects. The oxidation processes are described using single exponential decay fits and an attempt to correlate them with the late cycle rate of heat release was made.
  •  
26.
  • Gallo, Yann, et al. (författare)
  • Investigation of Late-Cycle Soot Oxidation Using Laser Extinction and In-Cylinder Gas Sampling at Varying Inlet Oxygen Concentrations in Diesel Engines
  • 2017
  • Ingår i: Fuel. - : Elsevier BV. - 1873-7153 .- 0016-2361. ; 193, s. 308-314
  • Tidskriftsartikel (refereegranskat)abstract
    • This study focuses on the relative importance of O2 and OH as oxidizers of soot during the late cycle in diesel engines, where the soot oxidation is characterized in an optically accessible engine using laser extinction measurements. These are combined with in cylinder gas sampling data from a single cylinder engine fitted with a fast gas sampling valve. Both measurements confirm that the in-cylinder soot oxidation slows down when the inlet concentration of O2 is reduced. A 38% decrease in intake O2 concentration reduces the soot oxidation rate by 83%, a non-linearity suggesting that O2 in itself is not the main soot oxidizing species. Chemical kinetics simulations of OH concentrations in the oxidation zone and estimates of the OH soot oxidation rates point towards OH being the dominant oxidizer.
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27.
  • Giandomenico, Valeria, et al. (författare)
  • Coactivator-dependent acetylation stabilizes members of the SREBP family of transcription factors
  • 2003
  • Ingår i: Molecular and Cellular Biology. - 0270-7306 .- 1098-5549. ; 23:7, s. 2587-2599
  • Tidskriftsartikel (refereegranskat)abstract
    • Members of the SREBP family of transcription factors control cholesterol and lipid homeostasis and play important roles during adipocyte differentiation. The transcriptional activity of SREBPs is dependent on the coactivators p300 and CBP. We now present evidence that SREBPs are acetylated by the intrinsic acetyltransferase activity of p300 and CBP. In SREBP1a, the acetylated lysine residue resides in the DNA-binding domain of the protein. Coexpression with p300 dramatically increases the expression of both SREBP1a and SREBP2, and this effect is dependent on the acetyltransferase activity of p300, indicating that acetylation of SREBPs regulates their stability. Indeed, acetylation or mutation of the acetylated lysine residue in SREBP1a stabilizes the protein. We demonstrate that the acetylated residue in SREBP1a is also targeted by ubiquitination and that acetylation inhibits this process. Thus, our studies define acetylation-dependent stabilization of transcription factors as a novel mechanism for coactivators to regulate gene expression.
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28.
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29.
  • Gunnarsson, Adrian, 1990, et al. (författare)
  • Radiative Heat Transfer Modeling and in Situ Diagnostics of Soot in an 80 kWth Propane Flame with Varying Feed-Gas Oxygen Concentration
  • 2018
  • Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 57:36, s. 12288-12295
  • Tidskriftsartikel (refereegranskat)abstract
    • This work presents experimental measurements of various 80 kWth propane flames, using a swirl burner, and modeling of the radiative heat transfer. The combustion conditions were altered by varying the oxygen concentration in the oxidant within range of 21-32%, while keeping the thermal input and oxygen-to-fuel ratio constant. Temperature, gas composition, and radiative intensity were measured using probes, while the soot volume fraction was quantified using nonintrusive laser-induced incandescence. The radiative intensity and the soot volume fraction increased with an increased oxygen concentration in the flame. When the oxygen concentration exceeded 27% the soot volume fraction was increased more than 14-fold. The results reveal the potential of promoting radiative heat transfer by increasing the oxygen concentration; the total radiative intensity becomes dominated by the soot particle contribution. In addition, laser-induced incandescence was successfully used for instantaneous and spatially resolved soot measurements in this type of furnace being at a technical scale.
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30.
  • Gunnarsson, Adrian, 1990, et al. (författare)
  • Soot Formation and Radiative Heat Transfer in Oxy-Fuel and Oxygen-Enhanced Propane Flames
  • 2018
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • This work aims to determine radiation-related properties of various propane flames, where the measurements were conducted in a down-fired and cylindrical 100 kW furnace equipped with a swirl burner. The combustion conditions were varied by altering the composition of the oxidant. For six cases, oxygen-enhanced air was used, step-wise varying the oxygen concentration in the oxidant from 21% to 32%. Also for six cases, the furnace was operated in oxy-fuel mode, recirculating dry flue gas and varying the oxygen concentration from 25% to 42%. All measurements were conducted at an axial distance of 384 mm from the burner. Temperature, gas composition and radiative intensity were measured (by intrusive instruments) along the furnace diameter using probes while the soot volume fraction was quantified using non-intrusive laser induced incandescence (LII). An Nd:YAG laser at wavelength 1064 nm was used for the LII measurements, and a diode laser at wavelength 808 nm was used for extinction measurements for absolute calibration of the LII-signal. Two-dimensional images of the LII-signal were captured using an intensified CCD-camera and radial profiles of the soot volume fraction were achieved. The soot volume fraction increased with increasing oxygen concentration in the feed gas, and, when the oxygen concentration exceeded 30 and 42% for the oxygen-enriched air and oxy-fuel cases, respectively, the soot formation was substantially enhanced with volume fractions more than 10 times higher than for lower oxygen concentrations. The higher oxygen concentration required for the increased soot production in the oxy-fuel combustion cases is mainly due to the higher heat capacity of carbon dioxide that lowers the flame temperatures. The data collected from the measurements was used to model the radiative intensity using a discrete transfer model. In this model, gas properties are calculated using a statistical narrow-band model and particle properties are calculated using Rayleigh theory. Good agreement was achieved between the modeled and measured radiative intensity for most flames and the use of an LII-system to measure the soot volume fraction in this type of furnace was successful.
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31.
  • Gustafsson, David, 1983- (författare)
  • Constitutive and fatigue crack propagation behaviour of Inconel 718
  • 2010
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • In this licentiate thesis the work done in the TURBO POWER project Influence of high temperature hold times on the fatigue life of nickel-based superalloys will be presented. The overall objective of this project is to develop and evaluate tools for designing against fatigue in gas turbine applications, with special focus on the nickel-based superalloy Inconel 718. Firstly, the constitutive behaviour of the material has been been studied, where focus has been placed on trying to describe the mean stress relaxation and initial softening of the material under intermediate temperatures. Secondly, the fatigue crack propagation behaviour under high temperature hold times has been studied. Focus has here been placed on investigating the main fatigue crack propagation phenomena with the aim of setting up a basis for fatigue crack propagation modelling.This thesis is divided into two parts. The first part describes the general framework, including basic constitutive and fatigue crack propagation behaviour as well as a theoretical background for the constitutive modelling of mean stress relaxation. This framework is then used in the second part, which consists of the four included papers.
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32.
  • Gustafsson, David, et al. (författare)
  • Fatigue Crack Growth behaviour of Inconel 718 - the Concept of a Damaged Zone Caused by High Temperature Hold Times
  • 2011
  • Ingår i: Procedia Engineering. - : Elsevier. - 1877-7058. ; 10, s. 2821-2826
  • Tidskriftsartikel (refereegranskat)abstract
    • Fatigue crack growth testing of Inconel 718 has been carried out at the temperatures 550 °C and 650 °C. The tests were conducted using a mix of hold times and pure cyclic loading, referred to as block tests. From the test results, the existence of an embrittled volume or damaged zone in the vicinity of the crack tip has been revealed. It has been found that the evolution of this damaged zone can be sufficiently well described using a power law function with an exponent n = 0.25.
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33.
  • Gustafsson, David, 1983, et al. (författare)
  • Fatigue crack growth behaviour of Inconel 718 with high temperature hold times
  • 2010
  • Ingår i: Procedia Engineering. - : Elsevier BV. - 1877-7058. ; 2:1, s. 1095-1104
  • Konferensbidrag (refereegranskat)abstract
    • In this work, fatigue crack growth measurements have been made on center-cracked tension specimens of Inconel 718, where the focus has been to observe the effect of high temperature hold times on the fatigue crack growth behaviour of the material. The material testing has been done at three different temperatures, namely 450 °C, 550 °C and 650 °C. All testing were done in an isothermal LCF context with a standard test method for measuring the fatigue crack growth rates. © 2010 Published by Elsevier Ltd.
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34.
  • Gustafsson, David, 1983- (författare)
  • High temperature fatigue crack propagation behaviour of Inconel 718
  • 2013
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The overall objective of this work has been to develop and evaluate tools for designing against fatigue in gas turbine applications, with special focus on the nickel-based superalloy Inconel 718. The fatigue crack propagation behaviour under high temperature hold times has been studied. Firstly, the main fatigue crack propagation phenomena have been investigated with the aim of setting up a basis for fatigue crack propagation modelling. Secondly, modelling of the observed behaviour has been performed. Finally, the constitutive behaviour of the material has been studied, where focus has been placed on trying to describe the mean stress relaxation and initial softening of the material under intermediate temperatures.This thesis is divided into two parts. The first part describes the general framework, including basic observed fatigue crack propagation behaviour of the material when subjected to hold times at high temperature as well as a background for the constitutive modelling of mean stress relaxation. This framework is then used in the second part, which consists of the seven included papers.
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35.
  • Gustafsson, David, et al. (författare)
  • Influence of high temperature hold times on the fatigue crack propagation in Inconel 718
  • 2011
  • Ingår i: International Journal of Fatigue. - : Elsevier. - 0142-1123 .- 1879-3452. ; 33:11, s. 1461-1469
  • Tidskriftsartikel (refereegranskat)abstract
    • High temperature fatigue crack growth in Inconel 718 has been studied at the temperatures 450 degrees C, 500 degrees C, 550 degrees C and 650 degrees C. The tests were conducted both without hold times and with hold times of different lengths and with a mix of both. Focus has been on quantifying the effect the hold time has upon the crack growth rate and how much it damages the material. Furthermore, it has been investigated how this damage influences the actual cracking behavior, i.e. where in the loading cycle the damage contributes most to the crack growth. This damage is related to the concept of a damaged zone in front of the crack tip. The size of the damaged zone has been derived from the tests and a microscopy study to confirm the findings has also been carried out. It is found that the concept of a damaged zone can be a successful explanatory model for the observed crack growth behavior under high temperature hold time.
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36.
  • Gustafsson, David, 1983-, et al. (författare)
  • Modeling of the Constitutive Behavior of Inconel 718 at Intermediate Temperatures
  • 2011
  • Ingår i: Journal of engineering for gas turbines and power. - : ASME. - 0742-4795 .- 1528-8919. ; 133, s. 094501-1-094501-4
  • Tidskriftsartikel (refereegranskat)abstract
    • Turbine disks are of large importance to turbine designers as theyare exposed to hot environment and subjected to high loads. Inorder to analyze such components with respect to fatigue crackinitiation, the work generally starts with a rigorous analysis of thefirst few cycles, during which an important stress redistributionwill always take place in an inelastic structure. In this work, thenonlinear kinematic hardening law by Ohno and Wang (1998,“Constitutive Modeling of Cyclic Plasticity With Emphasis onRatchetting,” Int. J. Mech. Sci., 40, pp. 251–261) has been used incombination with an isotropic softening law for describing theinitial stress-strain distribution for strain controlled uniaxial testsof the material Inconel 718. Focus has been placed on finding asimple model with few material parameters and to describe theinitial softening and the comparatively small mean stress relaxationobserved during the material testing. The simulation resultsobtained by using the model fit the experimental resultswell.
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37.
  • Henriksson, Andreas, 1979, et al. (författare)
  • RIFEL - Ripple and Electromagnetic Fields in Electric Vehicles
  • 2018
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • The electrical system in an electrified vehicle consists of high voltage (HV) components interacting in a complex way. The switching interaction in the power electronics results in ripple causing electromagnetic fields, disturbing other electronics and degradation of components. An overview of this can first be obtained when a physical system is built which could lead to unintentional over- or under dimensioning of HV components. This lack of information within the electrical system can lead to late verifications in the project causing substantial cost if changes are needed. This project aims at improving early evaluation of new concepts, create tools and build the necessary competence for a virtual system model that includes the key HV components: battery, electrical motor and power electronics, a simple load along with cable and connectors. This virtual model shall be able to simulate voltage and current ripple generated by the power electronics, initially in a frequency range up to 100 kHz. Results from the simulations shall be presented both in time and frequency domain as well as be expressed in RMS values for easier comparison to measured results. Some of the more important findings are briefly summarised below; For the high voltage battery, the electrical characteristics up to a frequency of roughly 1000 Hz was well determined using an impedance spectroscopy instrument at cell level and then multiplied by the numbers of cells.  However for finding the impedance behaviour for frequencies above 1000 Hz, the determination must be done on the battery pack level since bus bars and other component in the complete battery pack will be dominating in this frequency range. From measurements of differential mode impedance in high voltage cables it is found that it is important that the mutual inductance between the centre conductor and shield is included in the model to describe cable impedance below 10 kHz properly. The control of the inverter is very important for the overall behaviour and in this project SVM was used which has been shown to give the lowest current and voltage ripple of the traditional switching schemes. And for the machine model, the temperature variations must be taken into account since the machine parameters has been found to vary with ~20 % over the specified temperature range. The system model is found to agree well with rig measurements well up to 1 MHz with regards to both currents and voltages at the DC and AC sides. Furthermore, measurements in a real car match those in the rig. For time domain simulations, it was decided to use Ansys Simplorer since it can handle the inverter and the electrical machine simulations very well and for frequency domain simulations, it was decided to use LTspice since it is freeware, has support for AC-sweeps, improved switching compared to other SPICE-simulators, and is easy to use. Magnetic field simulations have been calculated and compared to measurements in the driveline rig at Chalmers. It was a good match across the investigated frequency range 10 Hz to 100 kHz. In this project, only internally developed component models were considered. To expand the functionality of the system modelling tool, international interface standards such as the Functional Mockup Interface (FMI) need to be investigated. Consequently, it would be a good idea to include additional automotive OEMs as well as suppliers and software vendors in future research collaborations.
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38.
  • Hjorth-Hansen, Henrik, et al. (författare)
  • Dasatinib induces fast and deep responses in newly diagnosed chronic myeloid leukaemia patients in chronic phase: clinical results from a randomised phase-2 study (NordCML006)
  • 2015
  • Ingår i: European Journal of Haematology. - : Wiley. - 1600-0609 .- 0902-4441. ; 94:3, s. 243-250
  • Tidskriftsartikel (refereegranskat)abstract
    • We randomised 46 newly diagnosed patients with chronic myeloid leukaemia (median age 56) to receive dasatinib 100mg QD or imatinib 400mg QD and report outcome as an intention-to-treat analysis with 36months follow-up. Early cytogenetic and molecular responses were superior in the dasatinib group, with a tendency that imatinib patients caught up with time. For instance, MR3.0 was reached at 3months in 36% vs. 8% (P=0.02), at 12months in 81% vs. 46% (P=0.02) and at 18months in 73% vs. 65% (n.s.) of the patients in the two groups. In contrast, MR4.5 was consistently superior in the dasatinib group at all time points from 6months onwards, reaching 61% vs. 21% (P<0.05) at 36months. Sixty-four vs. 71% of the patients in the dasatinib and imatinib arms, respectively, remained on assigned drug. Dasatinib dose was frequently reduced, but with maintained excellent effect. One imatinib patient progressed to blastic phase, but no CML-related deaths occurred. In conclusion, our data compare favourably with those of the dasatinib registration study, DASISION. The fast and deep molecular responses induced by dasatinib compared with imatinib may be exploited to increase the proportion of patients who can achieve a treatment-free remission after treatment discontinuation.
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39.
  • Högberg, Johan, 1994, et al. (författare)
  • No Association Between Hamstrings-to-Quadriceps Strength Ratio and Second ACL Injuries After Accounting for Prognostic Factors : A Cohort Study of 574 Patients After ACL-Reconstruction
  • 2024
  • Ingår i: Sports Medicine - Open. - Heidelberg : Springer. - 2199-1170 .- 2198-9761. ; 10
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: The stress on the anterior cruciate ligament (ACL) induced by the quadriceps can be attenuated by activation of the hamstrings by exerting an opposing torque to the anterior translation of tibia. Consequently, considering the ratio between strength of the hamstrings-to-quadriceps (HQ-ratio) may be of value to reduce the odds of second ACL injuries. The objective was therefore to evaluate (1) the association between HQ-ratio and the occurrence of a second ACL injury in patients after ACL-reconstruction within 2 years of return to preinjury sport level and (2) to compare the HQ-ratio between males and females after ACL reconstruction. Methods: Patients who had undergone primary ACL reconstruction and participated in knee-strenuous activity preinjury were included. Demographics, the occurrence of a second ACL injury, and muscle strength test results before returning to preinjury sport level were extracted from a rehabilitation registry. The endpoint was set at a second ACL injury or 2 years after return to preinjury sport level. A multivariable logistic regression was used to analyze the association between the HQ-ratio and a second ACL injury. Results: A total of 574 patients (50.0% female) with a mean age of 24.0 ± 9.4 years at primary ACL reconstruction were included. In the univariable logistic regression analysis, the odds of sustaining a second ACL injury decreased by 3% for every 1% increase in the HQ-ratio (OR 0.97 [95% CI 0.95–1.00], p = 0.025). After adjusting for the time from reconstruction to return to preinjury sport level, sex, preinjury sport level, graft choice, age, and body mass index, the results were no longer significant (OR 0.98 [95% CI 0.95–1.01], p = 0.16). Females had a higher HQ-ratio compared with males for both the ACL-reconstructed and uninjured side (3.7% [95% CI 5.7; 1.8%], p = 0.0002 and 3.3% [95% CI 4.6; 2.1], p < 0.001, respectively). Conclusion: The HQ-ratio did not significantly affect the odds for sustaining a second ACL injury upon return to preinjury sports level after primary ACL reconstruction. Females had a significant higher HQ-ratio than males for both the ACL reconstructed and uninjured side. © 2024, The Author(s).
  •  
40.
  • Högberg, Johan, 1994, et al. (författare)
  • Relationship between hamstring strength and hop performance at 8 and 12 months after ACL reconstruction with hamstring tendon autografts
  • 2024
  • Ingår i: BMC SPORTS SCIENCE MEDICINE AND REHABILITATION. - 2052-1847. ; 16:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Background The relationship between hamstring strength and hop performance after anterior cruciate ligament (ACL) reconstruction with hamstring tendon (HT) autografts has not been well elucidated. The aim was to investigate the relationship between eccentric hamstring strength, assessed with the NordBord, and concentric hamstring strength, assessed with the Biodex, with hop performance at 8 and 12 months after ACL reconstruction.Methods Registry study. Patients >= 16 years who had undergone primary ACL reconstruction with HT autograft, followed by muscle strength and hop tests at 8 and 12 months were included. Correlations of the relative hamstring strength (Nm/kg or N/kg) and limb symmetry index (LSI) with hop performance were analyzed. Pearson's correlation coefficient, and coefficient of determination (r2) were used for statistical analysis.Results A total of 90 patients were included, of which 48 (53%) were women. The mean age at ACL reconstruction was 27.0 +/- 8.0 years. Relative hamstring strength had significant positive correlations with hop performance, ranging from r = 0.25-0.66, whereas hamstring strength LSI had significant positive correlations which ranged from r = 0.22-0.37 at 8 and 12 months after ACL reconstruction. At 12 months, the relative hamstring strength in the Biodex explained 32.5-43.6% of the hop performance in vertical hop height, hop for distance relative to height, and the total number of side hops, whereas the relative hamstring strength in the NordBord explained 15.2-23.0% of the hop performance.Conclusion The relative hamstring strength in the Biodex test explained 32.5-43.6% of the hop performance, whereas the relative hamstring strength in the NordBord explained 15.2-23.0%. Thus, our findings suggest that relative hamstring strength, especially in the hip-flexed position may be a better indicator of hop performance at 8 and 12 months after ACL reconstruction in patients treated with HT autograft.
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41.
  • Högberg, Johan, 1994, et al. (författare)
  • The NordBord test reveals persistent knee flexor strength asymmetry when assessed two and five years after ACL reconstruction withhamstring tendon autograft
  • 2024
  • Ingår i: Physical Therapy in Sport. - 1466-853X .- 1873-1600. ; 66, s. 53-60
  • Tidskriftsartikel (refereegranskat)abstract
    • Objective: Comparison of knee flexor strength limb symmetry index (LSI) between the NordBord-test and the Biodex-test, and to determine the relationship between knee flexor strength and function in patients 2 and 5 years after anterior cruciate ligament reconstruction (ACL-R) with hamstring tendon (HT) autografts. Design: Observational registry study. Setting: Primary care. Patients: Cross-sectional data from 96 patients (55% women) participating in a rehabilitation-registry after ACL-R with HT autografts. Main outcome measures: Comparison of knee flexor strength symmetry between the Biodex-test and the NordBord-test. Secondly, the relationship between knee flexor strength test and perceived knee function, activity level, and hop performance. Results: The NordBord-test demonstrated greater strength deficits compared to the Biodex-test with a mean difference of 12.5% ± 15.1% 95 % CI [8.1; 16.9%] at 2 years, and 11.1% ± 11.9% 95 % CI [7.7; 14.6 %] at 5 years after ACL-R. Relative concentric knee flexor strength (Nm/kg) in the Biodex demonstrated significant weak-to-moderate correlations with activity level and hop performance (r = 0.33–0.67) at 2 and 5 years. Conclusion: The NordBord-test identified deficits in knee flexor strength LSI not seen with the Biodex-test at 2 and 5 years after ACL-R. No significant correlations were found between the persistent knee flexor strength asymmetry and perceived function, activity level or hop performance.
  •  
42.
  • Höglund, Martin, et al. (författare)
  • Tyrosine kinase inhibitor usage, treatment outcome, and prognostic scores in CML: report from the population-based Swedish CML registry
  • 2013
  • Ingår i: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 122:7, s. 1284-1292
  • Tidskriftsartikel (refereegranskat)abstract
    • Clinical management guidelines on malignant disorders are generally based on data from clinical trials with selected patient cohorts. In Sweden, more than 95% of all patients diagnosed with chronic myeloid leukemia (CML) are reported to the national CML registry, providing unique possibilities to compile population-based information. This report is based on registry data from 2002 to 2010, when a total of 779 patients (425 men, 354 women; median age, 60 years) were diagnosed with CML (93% chronic, 5% accelerated, and 2% blastic phase) corresponding to an annual incidence of 0.9/100 000. In 2002, approximately half of the patients received a tyrosine kinase inhibitor as initial therapy, a proportion that increased to 94% for younger (andlt;70 years) and 79% for older (andgt;80 years) patients during 2007-2009. With a median follow-up of 61 months, the relative survival at 5 years was close to 1.0 for patients younger than 60 years and 0.9 for those aged 60 to 80 years, but only 0.6 for those older than 80 years. At 12 months, 3% had progressed to accelerated or blastic phase. Sokal, but not European Treatment and Outcome Study, high-risk scores were significantly linked to inferior overall and relative survival. Patients living in university vs nonuniversity catchment areas more often received tyrosine kinase inhibitors up front but showed comparable survival.
  •  
43.
  • Janson Olstam, Johan, et al. (författare)
  • Simulerad trafik till VTI:s körsimulator : en förstudie
  • 2003
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • A driving simulator is an advanced piece of equipment used to createrealistic driver sensations in a laboratory environment. The the SwedishNational Road and Transport Research Institute, (VTI) driving simulator hasan advanced motion system. Today the VTI driving simulator does not includeany model that generates and simulates ambient traffic. The aim of thismaster thesis was to construct a model that generates and simulates vehiclesfor the VTI driving simulator. In order to achieve this, a survey of othersimilar models around the world was performed. We found that there are atleast ten similar models. Our model is valid for a straight, dry and planemotorway without any entering and exiting lanes. The model is namedIntelligent Traffic Generator, INTRAG. There are five different areas ofthree types in INTRAG. The three types are: simulated area, candidate areaand generation area. The area closest to the driving simulator is thesimulated area. In this area the vehicles are simulated according to modelsfor driving behavior. The models that we have used for car-following, lanechanging and acceleration are based on the model Traffic Performance on MajorArterials, TPMA, and the VTI Traffic Simulation Model. INTRAG also includesmodels for deceleration, transformation of basic desired speed andcommunication between vehicles with turn and brake signals. The areas on bothsides of the simulated area are the candidate areas. These areas are bufferzones of vehicles. The vehicles in these areas are seldom updated. Whenupdated, this is not done according to any models for driving behavior. Thereare two generation areas in INTRAG, one at the end of each candidate area. Inthese areas, new vehicles are generated. Vehicles that have traveled out ofthe model are removed in this area. The thesis also includes the task toconstruct a communication link between INTRAG and the driving simulator. Wehave chosen to use the Internet protocol IP and the transport protocol UDP.The packages that are sent between INTRAG and the driving simulator are builtaccording to a structure that we have developed. INTRAG has been implementedin the programming environment Borland Delphi 5. An application that can beused as a substitute for a real driving simulator was created to test INTRAG.The substitute has also been used during the model verification andvalidation. We found, during the model verification, that the flow in averageis 3.6 to 9.9 % too low. The reason is probably non-valid measurementmethods. Besides this, the model seems to be implemented correctly. INTRAGhas not yet been tested within the VTI driving simulator. The tests that havebeen done with the substitute provide an indication that the model may be agood representation of the reality.
  •  
44.
  • Jensen, Patrik, et al. (författare)
  • Improving buildability with platforms and configurators
  • 2013
  • Ingår i: Proceedings IGLC-21. - Fortaleza, Brazil. ; , s. 771-780
  • Konferensbidrag (refereegranskat)abstract
    • The different stages in construction projects are often separated with little interaction between the different trades. Many researchers proclaim that this separation between design and production limits the buildability of construction designs. Thus there is a need for providing knowledge of rules and constraints imposed from production in the design of construction products. A way of integration of production knowledge in the design is by implementing product platforms and configurators in construction projects. This paper describes the development of a configurator for a modularized concrete bridge that can be produced efficiently. Production of bridges can be selected to be built either on site or prefabricated. Previous work to develop configurators has mainly focused on the efficiency of the design phase and is usually not linked to production improvements and simplifications. By defining the product platform for a certain bridge variant within its market segment, the technical solutions can be designed to be flexible while ensuring the buildabuility in the construction phase.The developed configurator is built in SolidWorks and parametrically coupled using Tacton Studio. The first version generates geometrical drawings. Whereas validation show that parametric modelling configurators can be used for increasing buildability and efficiency at site, and also increasing the range of feasible alternatives and for speeding up the design process.
  •  
45.
  • Johansson, Sten, et al. (författare)
  • Investigation of localized damage in single crystals subjected to thermalmechanical fatigue (TMF)
  • 2010
  • Ingår i: Procedia Engineering. - : ELSEVIER SCIENCE BV. - 1877-7058. ; 2:1, s. 657-666
  • Tidskriftsartikel (refereegranskat)abstract
    • The deformation and damage mechanisms arising during thermalmechanical fatigue (TMF) of a CMSX-4 and high-Cr single crystal super alloy, SCA425 have been investigated and a completely new failure mechanism involving recrystallization and oxidation has been discovered. The primary deformation mechanism is slip along the {111} planes. The deformation is highly localised to a number of bands, where recrystallization eventually occur during the thermalmechanical fatigue process. When the final failure occurs along these recrystallized bands it is accompanied by the formation of voids due to the presence of grain boundaries. The damage process is further enhanced by oxidation, since recrystallization occurs more easily in the gamma depleted zone under the oxide scale. The macroscopic as well as the microscopic damage and fracture mechanisms are varying with alloy and heat treatment. The aim of this work is to further investigate, discuss the local damage mechanisms responsible for TMF damage. Of special interest is the localisation of damage into twins and extremely localized rafted deformation bands.
  •  
46.
  • Kirejev, Vladimir, 1984, et al. (författare)
  • Multiphoton microscopy – a powerful tool in skin research and topical drug delivery science
  • 2012
  • Ingår i: Journal of Drug Delivery Science and Technology. - 1773-2247. ; 22:3, s. 250-259
  • Tidskriftsartikel (refereegranskat)abstract
    • Multiphoton microscopy (MPM) has become a powerful complementary tool in biomedical research, enabling non-invasive three-dimensional imaging of tissue with high resolution. The major advantage is that investigations and visualization can be performed without mechanical destruction of the sample through tissue sectioning. This review will give a brief introduction to the technology, accompanied by examples of how the technique can be implemented within the field of skin research. Specifically, MPM has already made it possible to visualize cellular morphology and the cutaneous distribution of topically applied compounds applied to intact skin. MPM provides information that can be used to assess the bioavailability of drugs and to visualize drug penetration pathways into skin. MPM has also been implemented as a tool for obtaining non-invasive tissue biopsy based on skin autofluorescence in connection to diagnostics of skin cancer. We will also briefly present some recent results where MPM has been used to track cyclodextrin based drugs applied topically. Finally, we will discuss some future challenges of the technology, including label-free imaging, multimodal techniques, and quantitative imaging.
  •  
47.
  • Lagerkvist, Johan, 1983, et al. (författare)
  • Climate impact estimation – from feasibility study to handover
  • 2021
  • Ingår i: IABSE Congress, Ghent 2021: Structural Engineering for Future Societal Needs. - Zurich, Switzerland : International Association for Bridge and Structural Engineering (IABSE). ; , s. 622-628
  • Konferensbidrag (refereegranskat)abstract
    • Responsible for 1/5 of the total CO2-equivalents emissions and 50% of the materials resources used globally, the construction industry plays a vital role for a sustainable future. All parties in the construction industry address the challenge from their perspective and national transport administrations are often considered as the driver toward a fossil free industry. In this study, three Swedish infrastructure projects are studied by means of interviews, focusing on the usage and acceptance of the recently implemented climate estimation process. From the interviews, it is found that currently there is a lack of knowledge regarding climate estimations among bridge and environmental specialists as well as project managers. To address this challenge, it is important to educate the industry and increase the knowledge about climate estimations and declarations as well as inform which actions have the largest impact to reduce the CO2-equivalents emissions.
  •  
48.
  • Lagerkvist, Johan, 1983, et al. (författare)
  • Important parameters for increased productivity in bridge design and production
  • 2022
  • Ingår i: IABSE Congress Nanjing 2022 - Bridges and Structures: Connection, Integration and Harmonisation, Report. ; , s. 80-88
  • Konferensbidrag (refereegranskat)abstract
    • There is great potential for increased productivity in the production of bridges in terms of optimizing material use, time and cost for design and production. Hence, the environmental impact and cost can be optimized. To find out how standardisation of parts of bridges and which parameters are of most importance for increased productivity in the production of bridges, a quantitate study was performed on the Swedish bridge construction industry. The questionnaire received 151 responses. The results show in which aspects and parameters the industry’s three major actors – engineers, contractors, and clients – see greatest potential in order to increase the productivity. By standardising parts in bridges, there is great potential in making the construction of bridges more productive.
  •  
49.
  • Larsson, Johan, et al. (författare)
  • Barriers and drivers for increased use of off-site bridge construction in Sweden
  • 2012
  • Ingår i: Association of Researchers in Construction Management (ARCOM). - : Association of Researchers in Construction Management. - 9780955239069 ; , s. 751-761
  • Konferensbidrag (refereegranskat)abstract
    • There is great pressure to change the civil engineering industry in Sweden, which is said not to follow efficiency growth other manufacturing sectors are achieving. This increases a demand for innovative construction methods and a growing industrialised thinking for sustainable construction. By implementing off-site manufacturing (OSM) into bridge construction, client satisfaction can increase, bridges can be constructed faster using less resource, and more bridges for the same invested capital can be realised. A questionnaire survey and a workshop have been undertaken partly to identify benefits and drawbacks for OSM in bridge construction and partly to study if OSM satisfies the client better than on-site construction. The outcome shows that drivers of OSM meet client needs better than on-site construction alternatives. Time, cost and working environment are large drivers, correlating well with previous surveys undertaken. However, quality, as in other surveys tend to stand out as a driver, is a barrier in comparison with on-site construction. This opinion may be due to both the generally negative views for OSM bridges in Sweden and also due to previous bad experiences. Despite these negative views, results show that the hypothesis of OSM being a better alternative for satisfying the client is true. To increase its market share, barriers like reduced quality and not aesthetically pleasing must be overcome. OSM bridges are to date a rare feature in Sweden, but by display the drivers, it could become a common construction method in Sweden.
  •  
50.
  • Larsson, Johan, et al. (författare)
  • Decreasing complexity of the on-site construction process using prefabrication : a case study
  • 2012
  • Ingår i: Proceedings IGLC-20. - 9780744217445 ; , s. 841-850
  • Konferensbidrag (refereegranskat)abstract
    • Implementing prefabrication is by many seen as means to improve construction in terms of managing variability and productivity. However, regarding Swedish civil engineering works this has not been adequately documented to date. This case study uses Value Stream Mapping (VSM) to document the construction of a semi-prefabricated superstructure. The intention of the project is to investigate if the bridge construction process becomes less complex to manage and control when using prefabrication instead of traditional on-site construction.By relocating parts of traditional on-site construction to a factory, the time spent on site performing traditional work tasks such as constructing formwork, mounting and fixing of rebar and casting concrete, could be decreased. Nevertheless, mapping the process revealed shortcomings such as problems placing the prefabricated beams onto the on-site constructed plate structures and also that clear communication between actors tend to increase in importance when choosing prefabrication as construction method.Results from the VSM show that the semi-prefabricated superstructure, future state, became less complex compared to current state construction and also 75% quicker to construct on-site. By redesigning the bridge to eliminate some of the infant “diseases”, prefabrication will become more common in the future of small bridge construction in Sweden.
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