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| 6. |
- Bengtsson, Magnus, et al.
(författare)
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Fluorescence lidar imaging of fungal growth on high-voltage outdoor composite insulators
- 2005
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Ingår i: Optics and Lasers in Engineering. - : Elsevier BV. - 0143-8166 .- 1873-0302. ; 43:6, s. 624-632
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Tidskriftsartikel (refereegranskat)abstract
- Remote fluorescence imaging of fungal growth on polymeric high-voltage insulators was performed using a mobile lidar system with a laser wavelength of 355 nm. Insulator areas contaminated by fungal growth could be distinguished from clean surfaces and readily be imaged. The experiments were supported by detailed spectral studies performed in laboratory using a fibre-optic fluorosensor incorporating an optical multi-channel analyser system (OMA) and a nitrogen laser emitting radiation at 33 7 nm.
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| 7. |
- Bengtsson, Magnus, et al.
(författare)
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Fungus covered insulator materials studied with laser-induced fluorescence and principal component analysis
- 2005
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Ingår i: Applied Spectroscopy. - : SAGE Publications. - 0003-7028 .- 1943-3530. ; 59:8, s. 1037-1041
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Tidskriftsartikel (refereegranskat)abstract
- A method combining laser-induced fluorescence and principal component analysis to detect and discriminate between algal and fungal growth on insulator materials has been studied. Eight fungal cultures and four insulator materials have been analyzed. Multivariate classifications were utilized to characterize the insulator material, and fungal growth could readily be distinguished from a clean surface. The results of the principal component analyses make it possible to distinguish between algae infected, fungi infected, and clean silicone rubber materials. The experiments were performed in the laboratory using a fiber-optic fluorosensor that consisted of a nitrogen laser and an optical multi-channel analyzer system.
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| 8. |
- Bengtsson, Magnus, et al.
(författare)
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Lidar fluorescence measurements of algal growth on electrical insulators
- 2003
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Ingår i: 2003 Conference on Lasers and Electro-Optics Europe (CLEO/Europe 2003) (IEEE Cat. No.03TH8666). - 0780377346 ; , s. 473-473
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Konferensbidrag (refereegranskat)abstract
- Fluorescence measurements using lidar techniques have been shown to be useful for monitoring of algal growth on e.g. historical monuments. In this experiment similar measurements were performed on electrical insulators to examine the correlation between algal growth and the quality of the insulator, a factor of importance in the high-voltage grid management
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| 9. |
- Bengtsson, Magnus, et al.
(författare)
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Remote laser-induced breakdown spectroscopy for the detection and removal of salt on metal and polymeric surfaces
- 2006
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Ingår i: Applied Spectroscopy. - : SAGE Publications. - 1943-3530 .- 0003-7028. ; 60:10, s. 1188-1191
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Tidskriftsartikel (refereegranskat)abstract
- The detection of contamination such as salt in outdoor high-voltage insulator systems and its subsequent removal are vital for a reliable transmission of electric power. Remote detection of salt on a copper metal surface was carried out by using a mobile laser-induced breakdown spectroscopy (LIBS) Lidar system with a laser wavelength of 355 nm. Detection of salt on a polymeric high-voltage insulator was obtained when an additional lens was inserted into the beam path, and the number of photons that was detected could be calculated by using a calibrated white light source. Ablative cleaning could readily be carried out with LIBS and was verified by observing the disappearance of the sodium D-line emission.
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| 12. |
- Dernfalk, Andreas, 1975, et al.
(författare)
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Laser-induced fluorescence spectroscopy for detection of biological contamination on composite insulators
- 2003
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Ingår i: In Proc. 13th International Symposium on High Voltage Engineering, Delft, Netherlands.
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Konferensbidrag (refereegranskat)abstract
- A new technique for remote detection of biological contamination on high-voltage outdoor insulators has been investigated. The technique, which is based on laser-induced fluorescence (LIF) spectroscopy, has been applied to study surfaces of real silicon rubber insulators from a distance of approximately 60 m. Measurements were performed outdoors on a number of clean, as well as, biologically contaminated insulators. Several types of biological contamination were included, as five of the studied insulators had become covered when installed in Sweden, and another three had been contaminated by fungal growth in laboratory. Fluorescence spectra obtained from the surfaces of the described insulators are presented and the applicability of the technique is discussed and compared with photographic methods.
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| 13. |
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| 14. |
- Fernstål, Lotta, et al.
(författare)
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Inledning : Om Sverige i tiden
- 2015
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Ingår i: Sverige i tiden. - Stockholm : Historiska museets förlag. - 9789189176591 ; , s. 9-15
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 18. |
- Grönlund, Rasmus, et al.
(författare)
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Remote LIBS and Raman imaging for assessment of cultural heritage
- 2005
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Ingår i: 2005 Conference on Lasers and Electro-Optics Europe. - 0780389743 ; , s. 684-684
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Konferensbidrag (refereegranskat)abstract
- In this paper, we propose to perform remote laser-induced breakdown spectroscopy (LIBS) and Raman imaging of historical monuments to assess the state of a building. The lidar system is equipped with a Nd:YAG pumped optical parametrical oscillator (OPO) system, allowing laser radiation in the wavelength range 220 nm-4 μm. The laser radiation can be sent through a roof-top dome which can steer the radiation onto the point of interest
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| 22. |
- Härelind Ingelsten, Hanna, 1973, et al.
(författare)
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Kinetics of the formation of nano-sized platinum particles in water-in-oil microemulsions
- 2001
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 241:1, s. 104-111
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Tidskriftsartikel (refereegranskat)abstract
- The effect of surfactant type and temperature on the kinetics of the formation of platinum nanoparticles in water-in-oil microemulsions by chemical reduction of PtCl6(2-) were examined with time-resolved UV-vis absorption spectroscopy. The surfactants used were poly(ethylene glycol)monododecyl ethers (C12E4, C12E5, C12E6), sodium bis(2-ethylhexyl)sulphosuccinate (AOT), and mixtures of the alcohol ethoxylates and AOT. The oil domain was n-heptane. The microemulsion droplet size was measured by a dynamic light scattering technique (photon correlation spectroscopy) and the final platinum particle size was determined by transmission electron microscopy. The reaction rate for platinum particle formation was approximately the same in microemulsions based on either of the alcohol ethoxylates but considerably lower for microemulsions based on AOT. In microemulsions based on mixtures of an alcohol ethoxylate and AOT the reaction rate was similar to that obtained when alcohol ethoxylate was the sole surfactant. The reaction was observed to be particularly rapid in microemulsions based on combinations of AOT and C12E5 or C12E6, and the rate was relatively independent of the ratio of the nonionic and anionic surfactants. The reaction was found to be of first order for platinum nanoparticles formed in alcohol ethoxylate-, AOT-C12E5-, and AOT-C12E6-based microemulsions, whereas in microemulsions with AOT and AOT-C12E4 the reaction rate seemed to be of higher reaction order. The platinum particles were found to be less than 5 nm in average diameter, which was consistent with the microemulsion droplet size.
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| 23. |
- Jönsson, Robert, et al.
(författare)
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Påverkan på bärighet hos torvjord vid inblandning av gjuterisand samt effekt på koldioxidemission ur marken
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Odlade organogena jordar står för en betydande del av Sveriges utsläpp av växthusgaser. Att minska dessa utsläpp är mycket intressant och en möjlig åtgärd skulle kunna vara att höja grundvattenytan. När vattenhalten ökar i torvjordar fås dock stora bärighetsproblem vilket innebär att man inte kan använda tunga jordbruksmaskiner på dessa jordar. Sveriges gjuterier lägger varje år 77 000 ton sand på deponi, något som kan bli kostsamt om de i framtiden inte längre skulle vara befriade från att betala deponiskatt. Ett möjligt användningsområde för denna gjuterisand skulle kunna vara inblandning i torvjord då sandinblandning är en beprövad metod för att öka bärigheten i dessa jordar. På så sätt skulle man kunna höja grundvattenytan, vilket skulle minska koldioxidemissionen från dessa jordar, men ändå kunna fortsätta odla. Detta förutsatt att önskad effekt fås på bärigheten och att koldioxidemissionen inte ökar. I detta projekt undersöktes tre olika sandinblandningars effekt på bärighet och koldioxidemission från torv genom försök i labb och i fält. Koldioxidflöde och skjuvmotstånd mättes både i labb- och fältförsök. I fält mättes även spårdjup från cykel. De sandinblandningar som undersöktes var 13 %, 33 % och 46 %. Mätningarna i labb genomfördes på två olika dräneringsdjup, 20 och 40 cm. Cykelspårsmätningarna gav så osäkra resultat att det inte gick att dra några slutsatser utifrån dem. Skjuvtesterna i både labb och i fält visade att skjuvmotståndet ökade vid ökad sandinblandning vilket tyder på att bärigheten förbättrades. Koldioxidmätningarna i labb visade på en minskning av koldioxidemissionen när sand blandades in. Minskningen var ungefär lika stor för samtliga sandinblandningar. I resultaten från fältförsöken syns en kraftig ökning av koldioxidemission när gjuterisand blandats in, vilket berodde på att den sura torven reagerade med kalciumkarbonat i sanden. Den stora emissionen av koldioxid minskade efter ett par dagar och närmade sig efter en tid koldioxidemissionen för torv utan tillsats av gjuterisand. Då försöken i labb och i fält gav olika resultat är det svårt att dra någon riktig slutsats om vad som egentligen hände med koldioxidemissionen när torven blandades med gjuterisand. Inom tidsramen för detta experiment tyder dock inget på att koldioxidemissionen ökar på lång sikt.
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| 24. |
- Kishwar, Sultana, et al.
(författare)
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Biotoxicity of nanometallic oxides and their ligands with photosensitizers in osteosarcom a cells
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The cytotoxic effects in osteosarcoma (U2OS) cells to different nanosized metallic oxides e.g. zinc oxide nanowires (ZnO-NWs), manganese di-oxide nanowires (MnO2 NWs), ferric oxide nanoparticles (Fe2O3 NPs) individually and their complex forms with photosensitizers photofrin®, 5-Aminolevulinic acid (5-ALA), and protoporphyrin IX (Pp IX) were studied. The cellular effects were assayed by analyzing the cellular morphology. The reactive oxygen species (ROS) were detected using 2', 7'-Dichlorofluorescein diacetate, and cell viability were assessed using MTT assay under ultraviolet (UV), visible light and laser exposed conditions. Prominent cell death with above cited nanomaterials in their complex forms with photosensitizer was observed in labeled U2OS cells. This cell death might be due to their synergetic effect via the release of singlet oxygen species in osteosarcoma cells showing their anticancer-cell effects.
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| 25. |
- Larsson, Lars, et al.
(författare)
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Hall, harg eller hof. Ett kulthus i Uppåkra
- 2006
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Ingår i: Kulthus & dödshus. Det ritualiserade rummets teori och praktik. - 9172094281 ; , s. 143-152
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 26. |
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| 29. |
- Svanberg, J. Magnus
(författare)
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Predictions of manufacturing induced shape distortions : high performance thermoset composites
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- High performance composites usually consist of continuous fibres and a thermoset matrix. A well-known example is carbon fibre epoxy composites. When this kind of material is cured residual stresses and/or shape distortions are produced owing to thermally and chemically induced volumetric strains. The cure means the manufacturing step where the thermoset matrix is transformed from a liquid to a solid material. It is a quite complex thermal- chemical- mechanical process that in addition to volumetric strains, involves heat generation and dramatic changes in mechanical properties. For manufacturing of parts with high shape tolerances, such as aircraft components, the geometry of the mould is compensated to accommodate for shape distortions. Today this is made based on thumb rules and experience followed by trials. This is time consuming and expensive. Development of a tool for prediction of shape distortions and residual stresses is therefore an important step towards more optimised manufacturing of composites. The present thesis, consisting of five papers, describes the development and validation of a simulation tool for prediction of shape distortion and residual stresses. In the first paper a typical material and manufacturing process for high performance composites was used to experimentally investigate the effects from the cure temperature on spring-in of angle sections. The experimental results were interpreted in terms of mechanisms responsible for shape distortions. Based on the observations, a process model including a new mechanical constitutive model for predictions of residual stresses and shape distortions was proposed and implemented in a general purpose FE-program, as presented in the second paper. In the third paper, the model was validated by comparing spring-in predictions with the experimental results of the first paper complemented by same new experiments. The third paper also embraces a numerical investigation of the effect from the mechanical boundary conditions during cure. So far (in the three first papers), the curing conditions were kept isothermal. When a thick component is cured, the conditions are no longer isothermal owing to heat generated by the exothermal cure reaction. Hence, in the fourth paper the process model was validated against experimental results for a non-isothermally cured component. Finally, in the last paper shape distortions of a complex aircraft component was studied. This was made to both get further validation of the process model as well as investigate the feasibility to simulate large parts of complex shape.
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| 30. |
- Svanberg, J. Magnus
(författare)
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Residual stresses and shape distortion in composite structures
- 2000
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- High performance composites usually consist of continuous fibres and a thermoset matrix. One well-known example from the aerospace industry is carbon fibre epoxy composites. For that reason the manufacturing processes of thermoset composites are subject to extensive research. During the last decades process models have been developed for several different manufacturing methods. These process models are either based on linear elasticity or visco-elasticity. Linear elasticity is however too simple to accurately describe the material behaviour during processing. Visco-elasticity on the other hand requires extensive material characterisation and large computer resources for simulation. Residual stresses are formed during manufacturing of thermoset composites due to a number of factors. The crosslinking of the polymer leads to chemical shrinkage. Further shrinkage will add to this during cooling from the cure temperature to room temperature. During cure when the part usually is constrained by a mould, thermal and chemical shrinkage result in residual stresses. At demoulding the in-mould cure stresses are fully or partially released and shape distortions are formed. If the geometry of the component prohibits these shape distortions, residual stresses may lead to an apparent strength reduction or premature failure of the final product. To avoid problems related to residual stresses and shape distortions it is essential with a good understanding of the manufacturing process. This thesis, demonstrate that models for residual stress development and shape distortions must account for following mechanisms; thermal expansion (different in glassy and rubbery state), chemical shrinkage due to the crosslinking reaction and frozen-in deformations. Measured shape distortion of single shaped angle brackets manufactured at different in-mould temperatures have been used to identify and illustrate these mechanisms. The present thesis also presents a simple mechanical constitutive relation, suitable for implementation in a general purpose FE-package. The new mechanical constitutive relation accounts for all mechanisms identified in the first part of the thesis. The constitutive relation is based on linear visco-elasticity where the explicit time dependence is replaced by a path dependence on degree of cure and temperature. This means significant savings in computational time, memory requirements and costs for material characterisation compared to the visco-elastic models that has been commonly used for process modelling.
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| 31. |
- Svanberg, J. Magnus
(författare)
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Shape distortion of non-isothermally cured composite angle bracket
- 2002
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Ingår i: Plastics, rubber and composites. - : Informa UK Limited. - 1465-8011 .- 1743-2898. ; 31:9, s. 398-404
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Tidskriftsartikel (refereegranskat)abstract
- A simulation tool for prediction of shape distortion and residual stresses has been developed by implementing a new material model in the general purpose FE package ABAQUS. To validate the simulation tool, three thick wailed angle brackets were manufactured under non-isothermal conditions. Predicted temperatures, degree of cure, and shape distortions were then compared with the experimental values for the thick walled angle brackets. Predicted and experimental values show good agreement, which verifies that the simulation procedure is reliable under non-isothermal curing conditions
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| 32. |
- Svanberg, Magnus, et al.
(författare)
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An experimental investigation on mechanisms for manufacturing induced shape distortions in homogeneous and balanced laminates
- 2001
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Ingår i: Composites. Part A, Applied science and manufacturing. - 1359-835X .- 1878-5840. ; 32:6, s. 827-838
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Tidskriftsartikel (refereegranskat)abstract
- Manufacturing induced shape distortions is a common problem for composite manufacturers. For single curved geometries the phenomenon is known as spring-in. Today a lot of effort is spent to develop modelling tools for prediction of spring-in and shape distortions in general. However, good experimental data is rare in the literature and there are no established constitutive models capable of account for the effect from different cure schedules. In this paper, experimental data for spring-in of glass-fibre epoxy composites are presented. The experiments were performed with angle brackets manufactured by RTM, in a steel mould with accurate temperature control. Different in-mould temperature have been used to point out and separate different mechanisms responsible for spring-in. © 2001 Elsevier Science Ltd.
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| 40. |
- Svanberg, Magnus, et al.
(författare)
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Prediction of shape distortions for a curved composite C-spar
- 2005
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Ingår i: Journal of reinforced plastics and composites (Print). - : SAGE Publications. - 0731-6844 .- 1530-7964. ; 24:3, s. 323-339
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents predictions and validations of shape distortions of a curved C-spar, using a simulation tool developed in the general purpose FE-program ABAQUS. The simulation tool is based on a simplified mechanical constitutive model that accounts for the mechanisms identified in a previous experimental study concerning the influence from the cure schedule on shape distortions. The main objective of the present paper is to validate the simplified constitutive model and a simplified simulation approach. The feasibility for simulation of shape distortions of a component with relatively complex shape has also been investigated. © 2005 Sage Publications.
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| 41. |
- Svanberg, Magnus, et al.
(författare)
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Prediction of shape distortions Part I. FE-implementation of a path dependent constitutive model
- 2004
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Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 35:6, s. 711-721
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Tidskriftsartikel (refereegranskat)abstract
- There is a great interest, especially from the aircraft industry, to increase the ability to understand and predict development of shape distortions and residual stresses during manufacture of polymer composite components. An increased ability to predict shape distortions will result in more cost efficient development, improved performance and optimised manufacturing of composites. To be able to predict residual stresses and shape distortions a model is needed that accounts for all important mechanisms involved. In a previous work by the authors, it was demonstrated that such - models must account for thermal expansion (different in glassy and rubbery state), chemical shrinkage due to the crosslinking reaction and finally frozen-in deformations. The present paper presents a simple mechanical constitutive model that accounts for the mechanisms mentioned above. The model is a limiting case of linear visco-elasticity that permits us to replace the rate dependence by a path dependence on the state variables: strain, degree of cure and temperature. This means significant savings in computational time, memory requirements and costs for material characterisation as compared to conventional visco-elastic models. This is the first of two papers, the second paper deals with experimental validation and analysis of mechanical boundary conditions during prediction of shape distortion. © 2004 Elsevier Ltd. All rights reserved.
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| 42. |
- Svanberg, Magnus, et al.
(författare)
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Prediction of shape distortions. Part II. Experimental validation and analysis of boundary conditions
- 2004
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Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 35:6, s. 723-734
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Tidskriftsartikel (refereegranskat)abstract
- During cure of thermoset composite structures residual stresses and/or shape distortions are always present. Residual stresses can cause apparent strength reduction or failure, even prior demoulding, respectively, shape distortions can deform a component so that the component becomes useless. For this reason a lot of effort has been spent to develop simulation tools to be able to foresee problems related to residual stresses and/or shape distortions and make the first part right. In a companion paper a process model for shape distortion predictions was developed and implemented into ABAQUS. In the present paper the model is validated for a material and cure schedule typical for RTM and autoclave processes. Comparisons between predicted and experimental shape distortion shows that the model and simulation approach used capture both effects from different cure schedules as well as the mechanical interaction between composite and tooling during in-mould cure. The results show that changing the mechanical boundary conditions significantly affects the shape distortion prediction. Therefore accurate modelling of the composite-tooling interaction is an important part of a shape distortion analysis. © 2004 Elsevier Ltd. All rights reserved.
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| 45. |
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| 46. |
- Svanberg, Magnus
(författare)
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Shape distortion of a non-isothermally cured composite angle bracket
- 2002
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Ingår i: FRC 2002. - : Conference Design Consultants. - 954045920 ; , s. 329-336
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Konferensbidrag (refereegranskat)abstract
- A general numerical tool based on ABAQUS to predict shape distortions and residual stresses have been developed. To validate the simulation tool three thick walled angle brackets were manufactured under non-isothermal conditions. Predicted temperatures, degree of cure and shape distortions were then compared with the experimental values for the thick walled angle brackets. Predicted and experimental values show good agreement. Curing of a composite involves thermal expansion, chemical shrinkage and a severe change in the mechanical properties when the resin transforms from a liquid via a rubber like solid into glassy solid as well as heat generation from the cross linking reaction. In other words curing a composite is a quite complex thermal-chemical-mechanical process, which cause challenges in form of residual stresses and sahped distortions. For that reason, there is an interest to use simulation tools to forecast problems owing to residual stresses and/or shape distortions. The mechanical behavior of a thermoset polymer during cure is visoelastic and rather complicated to model accurately for c composite and anisotropic viscoelastic models demands extensive material characterisation, long calculation times and requires large memory for storage of internal state variables.
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