| 1. |
- Bengtsson, Magnus, et al.
(author)
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Fluorescence lidar imaging of fungal growth on high-voltage outdoor composite insulators
- 2005
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In: Optics and Lasers in Engineering. - : Elsevier BV. - 0143-8166 .- 1873-0302. ; 43:6, s. 624-632
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Journal article (peer-reviewed)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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| 2. |
- Ericsson, Stina, 1972, et al.
(author)
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Att analysera interaktion
- 2023
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Book (other academic/artistic)abstract
- Snart sagt alla situationer en människa befinner sig i präglas av interaktion. Människor pratar med varandra, rör sig genom ett rum, utbyter blickar, lär sig saker, arbetar, skämtar, håller i föremål ... Utmärkande för oss människor är nämligen att vi får saker och ting gjorda med vårt språk och våra kroppsliga resurser. Genom sådana handlingar påverkar vi vår omvärld och våra medmänniskor - och vi gör det tillsammans med dem. Det är studiet av denna mänskliga interaktion som boken handlar om. I första delen introduceras forskningsfältet interaktionsanalys och de arbetssätt, redskap och etiska ställningstaganden som hör till fältet. Den andra delen innehåller forskningsstudier som visar på bredden inom fältet och som pedagogiskt leder läsaren genom hela analysarbetet. Till boken hör även ett videomaterial som illustrerar några av bokens exempel, och som är tillgängligt för läsarens egna studier. Att analysera interaktion är avsedd för utbildningar inom språk vetenskap och angränsande ämnen som sociologi, utbildningsvetenskap och kommunikation.
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| 3. |
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| 4. |
- Karlsson, Stina, 1975, et al.
(author)
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CFD modelling of the Wurster bed coater.
- 2009
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In: AICHE Journal. - : Wiley. - 1547-5905 .- 0001-1541. ; 55:10, s. 2578-2590
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Journal article (peer-reviewed)abstract
- In the Wurster bed coater, the wetting, drying, and circulation of particles are combined to produce a high quality coating. The drying and wetting conditions in a laboratory scale Wurster bed coater are modeled and compared with experimental data. A model combining multiphase fluid dynamics with heat and mass transfer is developed to model the particle and gas motion and the transport of thermal energy and moisture. A wetting region is defined, where a specified moisture content is set in the particle phase, above the jet inlet, to describe the injection ofcoating liquid. The simulation shows the characteristic circulation of particles in the equipment, as well as the behavior of the moisture in the system and agrees well with measurements. The simulation indicates how different process conditions influence the drying regions. The results show that most ofthe drying, under typical operating conditions, takes place in the Wurster tube. © 2009 American Institute of Chemical Engineers.
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| 5. |
- Karlsson, Stina, 1975, et al.
(author)
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Characterization and mathematical modelling of single fluidised particle coating
- 2011
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In: Powder Technology. - : Elsevier BV. - 1873-328X .- 0032-5910. ; 207:1-3, s. 245-256
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Journal article (peer-reviewed)abstract
- A study was made of coating single particles with water-based dispersions under realistic fluid dynamic and well-defined operating conditions. The surfaces of the coated particles were observed with atomic force microscopy (AFM) and scanning electron microscopy (SEM). AFM was used to study the latex particle packing and the colloid particle coalescence at the nanoscale, while SEM was used to study the film at the droplet size level. The influence of temperature, moisture content and spray rate were investigated. The experiments showed a coating layer built up of rings of colloid particles for all cases studied except for high spray rate. A variation in the degree of coalescence between colloid particles with different glass transition temperatures, T-g, was shown in AFM. Cracks in the coating layer were observed when the temperature was lower than T-g. Mechanism evaluation using dimensionless numbers showed that a droplet will spread to the equilibrium angle without splashing; the colloid particles accumulate at the interface between the liquid and the air for all cases studied except air with 90% RH and 20 degrees C and a wet-bulb temperature in the coating layer. The evaluation indicated that no skin forms in any of the cases. A model of the drying of a single droplet was developed to describe the experimental results with rings of colloid particles. The simulation of the shape and height of the dried droplet agrees well with the experimental results. (C) 2010 Elsevier B.V. All rights reserved.
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| 6. |
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| 7. |
- Karlsson, Stina, 1975
(author)
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Particle Coating in a Wurster Type Bed
- 2007
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Doctoral thesis (other academic/artistic)abstract
- The Wurster bed process is frequently used for film coating. In the Wurster bed, particles circulate in the equipment and are sprayed with a liquid which forms a coating when dry. The procedure is repeated until the desired characteristics of the coating layer are obtained. The complex process involves zones of both high and low particle concentrations, as well as high and low velocities. To gain a better understanding of the mechanisms controlling the quality of the coating and how optimisation and scale-up of the process can be improved, both experimental and theoretical studies were made. To study the coating formation and investigate how the coating is affected by the spray and drying velocities, a new device for coating a single levitated particle under controlled conditions was designed and tested. The particle was levitated and droplets were sprayed from below, as in the Wurster process. Coating with a solution of HydroxyPropylCellulose (HPC) and a latex dispersion was investigated in the single particle coating device, and the influence of operating conditions was studied. Temperature, gas humidity and droplet frequency can be varied and are well defined. The experimental results show that both increased gas moisture content and increased droplet frequency give a smoother coating. The solvent in the coating liquid and the temperature also influenced the coating structure. A ring pattern was observed when the particle was coated with the dispersion. A model was developed to study the mechanism influencing the coating structure at the single particle level.Knowledge of the particle movement in the bed is needed in order to couple the single particle coating to the particle and gas dynamics in the process equipment. To study the particle movement, a laboratory Wurster bed of plexiglass, to allow optical access to the flow, was constructed. A technique was developed to track the particle in the laboratory scale bed. A small amount of particles are marked with fluorescence and the marked particles are tracked with a high-speed video camera. With this technique, particles can be followed in the zones with low particle concentration and near the walls; with image analysis, particle trajectories and velocities can be calculated. The technique can be used for the characterization of differences in process dynamics due to variation in operating conditions. The distribution of the maximum height of the particle trajectories was studied for selected parameters of particle loading, jet air velocity and position of the Wurster tube. A model of the Wurster bed coater, which combines the particle and gas dynamics with the wetting and drying, was developed. The model can be used to predict the influence of the operating conditions and geometric dimensions of the equipment. To simulate particle and gas motion, the Eulerian-Eulerian approach was used. The simulation indicates where the drying takes place in the equipment and how different process conditions influence the drying. The influence of spray rate, temperature and moisture content in the fluidised air was investigated. Results show that most of the drying takes place in the Wurster tube under typical operating conditions.
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| 8. |
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| 9. |
- Wallström, Stina, et al.
(author)
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Image analysis and laser induced fluorescence combined to determine biological growth on silicone rubber insulators
- 2005
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In: Polymer Degradation and Stability. - : Elsevier BV. - 1873-2321 .- 0141-3910. ; 88:3, s. 394-400
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Journal article (peer-reviewed)abstract
- High-voltage outdoor insulators made from silicone rubber are sometimes reported to be colonised by microorganisms. When the hydrophobic polymeric surface is covered by a hydrophilic biofilm, the electrical properties of the insulator are altered. In this work, mixed biofilms, similar to those formed on the surfaces of polymeric insulators in the field, were successfully grown on five types of silicone rubber substrates in the laboratory, using specially designed microenvironment chambers. Photography and digital image analysis were utilized to estimate the areas covered by the growth. It was found that direct UV-light exposure hindered growth of the biofilms. Further, growth was also hindered on samples where zinc borate had been added as flame retardant. In contrast, addition of ATH did not influence the growth. In parallel, LIF spectroscopy was explored as a tool for detection of biofilms on silicon rubber samples. Experiments revealed that even weak traces of growth, not visible to the naked eye, could be detected. Finally, it is believed that LIF spectroscopy in combination with image analysis can be used for field diagnostics of biological growth on insulators in service.
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