| 1. |
- Paz, Maria Dolores, 1982, et al.
(författare)
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Investigating corrosion memory: The influence of previous boiler operation on current corrosion rate
- 2017
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Ingår i: Fuel Processing Technology. - : Elsevier BV. - 0378-3820. ; 156, s. 348-356
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Tidskriftsartikel (refereegranskat)abstract
- The selection of fuel is crucial for a Combined Heat and Power (CHP) plant in terms of cost and corrosion and the fuel will vary over time. The corrosiveness of different fuels has been studied extensively, however, not how a current corrosion attack is influenced by corrosion history (i.e. previous deposit buildup and oxide scale formation) instead of the influence of the current flue gas composition (i.e. the current fuel mix being used). This influence of the corrosion history effect can be called "corrosion memory". To investigate the corrosion memory effect on boilers, a novel setup was used. Air-cooled probe AISI304L samples were exposed in two different boilers to mimic different fuels. One boiler was a biomass-fired boiler representing a moderate corrosive fuel and the other was a waste-fired boiler representing a highly corrosive fuel. A three-step exposure program was performed in which a reference probe was exposed in the biomass-fired boiler for all three steps while another probe was exposed in the biomass-fired boiler for steps 1 + 3 and in the waste-fired boiler for the second step. All samples were investigated with material-loss measurements and SEM/EDX. The findings show that the deposit and oxide scales formed on the samples in the biomass-fired boiler had a mitigating effect on the corrosion attack. Consequently, corrosion history affects the future corrosion rate.
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| 2. |
- Alexopoulou, Sofia, 1984-
(författare)
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"Please Mind the Grey Digital Divide" : An Analysis of Digital Public Policies in Light of the Welfare State (Sweden and Greece)
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis examines the grey digital divide and digital policies in the divergent welfare regimes of Sweden and Greece. The grey digital divide is a serious problem not only for the individual but also for society. The grey digital divide signifies the inability of older people to utilize digital technology. In academic circles, the emphasis is mostly on the technological aspects of the grey digital divide or on the individual characteristics of older people as (non)users of digital tools. However, the problem is more complex in nature and is interconnected with the aging process and experience. The grey digital divide has multiple levels: the first concerns access, the second skills, and the third opportunities. This thesis concentrates mostly on the third level of digital divide because it touches on the welfare denominator. This particular level describes the encounters that older citizens need to have with the digital welfare state and the obstacles that they might face in doing this. Older digital “offliners” cannot take advantage of the welfare services that they need for their own well-being and cannot participate as equal citizens in digital space, which is expanding on a daily basis with new digital services.This thesis is situated in the discipline of political science and draws on various disciplines, such as political science (welfare regime theory, neo-institutionalism, and path-dependency), public policy (active aging paradigm), gerontology (disengagement), sociology (exclusion via the digital-by-default approach), and ICT studies (the phenomenon of digitalization and the third-level of the digital divide). The thesis is a compilation of papers and consists of two qualitative case studies, a comparative study, and a scoping literature review. The key findings are as follows: 1) older people are a heterogeneous group and this applies in the digital world as well, with the appearance of heterogeneous digital profiles; 2) the welfare regime seems to affect the manifestation of the grey digital divide and there is a path-dependency pattern in this; 3) the more digitalized a society, the greater the chance that older people not using technology will be excluded from the digital and social spheres; and 4) digital policies indicate the priorities of every society and how older people are perceived as a social group.
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| 3. |
- Alexopoulou, Sofia, 1984-, et al.
(författare)
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The grey digital divide and welfare state regimes : a comparative study of European countries
- 2022
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Ingår i: Information Technology and People. - : Emerald Group Publishing Limited. - 0959-3845 .- 1758-5813. ; 35:8, s. 273-291
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Technology access, digital skills, and digital services are increasingly prerequisites for public life and accessing public services. The digital divide in contemporary societies matters for efforts to digitalize the welfare state. Research has already mapped individual determinants of digital exclusion and the existence of an age-related digital divide. However, far less attention has been paid to variations in digital inclusion between countries and to their potential explanations related to political systems. This study explores the influence of variations in welfare regimes on the digital divide among seniors (aged 65+) in Europe.Design/methodology/approach: This article presents time-series cross-sectional analyses of the relationship between welfare state regimes and digital inclusion among seniors in European countries. The analyses are based on data from Eurostat, the World Bank, and the UN E-Government Survey.Findings: The authors find extensive variation in the digital inclusion of citizens between welfare regimes and argue that considering regime differences improves the understanding of these variations. The findings indicate that the age-related digital divide seems to be least evident in countries with more universalistic welfare regimes and most evident in countries where seniors rely more on their families.Originality/value: This is the first comparative study of the association between welfare state regimes and digital inclusion among seniors.
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| 4. |
- Almby, Kristina E., et al.
(författare)
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Effects of Gastric Bypass Surgery on the Brain : Simultaneous Assessment of Glucose Uptake, Blood Flow, Neural Activity, and Cognitive Function During Normo- and Hypoglycemia
- 2021
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 70:6, s. 1265-1277
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Tidskriftsartikel (refereegranskat)abstract
- While Roux-en-Y gastric bypass (RYGB) surgery in obese individuals typically improves glycemic control and prevents diabetes, it also frequently causes asymptomatic hypoglycemia. Previous work showed attenuated counterregulatory responses following RYGB. The underlying mechanisms as well as the clinical consequences are unclear. In this study, 11 subjects without diabetes with severe obesity were investigated pre- and post-RYGB during hyperinsulinemic normo-hypoglycemic clamps. Assessments were made of hormones, cognitive function, cerebral blood flow by arterial spin labeling, brain glucose metabolism by F-18-fluorodeoxyglucose (FDG) positron emission tomography, and activation of brain networks by functional MRI. Post- versus presurgery, we found a general increase of cerebral blood flow but a decrease of total brain FDG uptake during normoglycemia. During hypoglycemia, there was a marked increase in total brain FDG uptake, and this was similar for post- and presurgery, whereas hypothalamic FDG uptake was reduced during hypoglycemia. During hypoglycemia, attenuated responses of counterregulatory hormones and improvements in cognitive function were seen postsurgery. In early hypoglycemia, there was increased activation post- versus presurgery of neural networks in brain regions implicated in glucose regulation, such as the thalamus and hypothalamus. The results suggest adaptive responses of the brain that contribute to lowering of glycemia following RYGB, and the underlying mechanisms should be further elucidated.
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| 5. |
- Jonsson, Torbjörn, 1970, et al.
(författare)
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High-Temperature Oxidation of FeCr(Ni) Alloys : The Behaviour After Breakaway
- 2017
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Ingår i: Oxidation of Metals. - : Springer Nature. - 0030-770X .- 1573-4889. ; 87:3-4, s. 333-341
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Tidskriftsartikel (refereegranskat)abstract
- The oxidation of an austenitic FeCr(Ni) steel at 600 C in H2O ?KCl ? O2/H2 ? H2O ? Ar environments is studied up to 168 h. The oxidationbehaviour after ‘‘breakaway’’ is investigated by microstructural investigations, andthermodynamic calculations (Thermo-Calc) on the FeCr(Ni)–O system are used tointerpret the results. The characteristic ‘‘breakaway’’ scale morphology exhibits anoutward-growing iron oxide and a bottom layer consisting of inward-growing spineloxide and reaction zones containing Cr-rich oxide precipitates and Cr-depletedmetal. The equilibrium calculations show that a miscibility gap appears in the FeCrspinel oxide below 665 C influencing the microstructure of the inward-growingscale. Equilibrium calculations on the FeCrNi–O system show that Ni is notexpected to enter the spinel oxide in low oxygen activity conditions, in accordancewith observations
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| 6. |
- Jonsson, Torbjörn, 1970, et al.
(författare)
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Oxidation After Breakdown of the Chromium-Rich Scale on Stainless Steels at High Temperature: Internal Oxidation
- 2016
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Ingår i: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 85:5-6, s. 509-536
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Tidskriftsartikel (refereegranskat)abstract
- Breakaway oxidation of alloy 304L at 600 degrees C was studied in four environments (O-2 + H2O + KCl, O-2 + H2O + SO2 + KCl, H-2 + H2O + Ar, O-2 + K2CO3) for up to 168 h. The resulting scales were investigated by FIB/SEM, SEM/EDX, STEM/EELS, STEM/EDS and oxidation was elucidated by thermodynamic calculations (Thermo-Calc). The initial thin protective scale broke down in all cases. After breakaway, the scale consisted of two layers, i.e. an inward growing spinel/reaction zone and an outward growing iron-rich layer. The general features and microstructure of the scales after breakaway were similar in all environments and were explained in terms of: (1) Different diffusivities of Cr3+ and Fe2+ in the spinel oxide. (2) The appearance of a miscibility gap in the FeCr and FeCrNi spinel oxides. (3) The equilibrium composition of the spinel (at low pO(2) Ni is not present in the spinel).
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| 7. |
- Karlsson, Anette, 1986-, et al.
(författare)
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The effect on precision and T1 bias comparing two flip angles when estimating muscle fat infiltration using fat-referenced chemical shift-encoded imaging
- 2021
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Ingår i: NMR in Biomedicine. - : John Wiley & Sons. - 0952-3480 .- 1099-1492. ; 34:11
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Tidskriftsartikel (refereegranskat)abstract
- Investigation of the effect on accuracy and precision of different parameter settings is important for quantitative Magnetic Resonance Imaging. The purpose of this study was to investigate T1-bias and precision for muscle fat infiltration (MFI) using fat-referenced chemical shift magnetic resonance imaging at 5° and 10° flip angle. This [MB1] experimental study was done on forty postmenopausal women using 3T MRI test and retest images using 4-point 3D spoiled gradient multi-echo acquisition including real and imaginary images for reconstruction acquired at Flip angles 5° and 10°. Post-processing included T2* correction and fat-referenced calibration of the fat signal. The mean MFI was calculated in six different automatically segmented muscle regions using both the fat-referenced fat signal and the fat fraction calculated from the fat and water image pair for each acquisition. The variance of the difference between mean MFI from test and retest was used as measure of precision. The SNR characteristics were analyzed by measuring difference of the full width half maximum of the fat signal distribution using Student’s t-test.There was no difference in the mean fat-referenced MFI at different flip angles with the fat-referenced technique, which was the case using the fat fraction. No significant difference in the precision was found in any of the muscles analyzed. However, the full width half maximum of the fat signal distribution was significantly lower at 10° flip angle compared to 5°. Fat-referenced MFI is insensitive to T1 bias in chemical shift magnetic resonance imaging enabling usage of a higher and more SNR effective flip angle. The lower full-width-at half-maximum in fat-referenced MFI at 10° indicates that high flip angle acquisition is advantageous although no significant differences in precision was observed comparing 5° and 10°.
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| 8. |
- Karlsson, Sofia, 1982, et al.
(författare)
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A Laboratory Study of the in Situ Sulfation of Alkali Chloride Rich Deposits: Corrosion Perspective
- 2016
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 30:9, s. 7256-7267
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Tidskriftsartikel (refereegranskat)abstract
- The initial corrosive effect of small (1.35 mu mol/cm(2)) and large (13.5 mu mol/cm(2)) amounts of KCl on 304L has been investigated. The investigations were performed in both the absence and presence of 300 ppm of SO2 at 600 degrees C. The results showed that in the absence of SO2 KCl accelerates the rate of corrosion by means of two types of corrosion attack: a general attack and a steel grain boundary attack. The general attack has been proved to be initiated by K2CrO4 formation. Meanwhile, the steel grain boundary attack is suggested to be accelerated by HCl released due to the chromate formation which increased with higher amounts of KCl. The presence of KCl and SO2 resulted in the simultaneous formation of K2SO4 and K2CrO4. The chromate formation resulted in a general corrosion attack. However, the oxide growth was significantly reduced due to the very fast sulfation reaction. In contrast, the steel grain boundary attack increased in the presence of SO2. It is suggested that the attack is accelerated by HCl released from the sulfation reaction and by sulfidation of the steel grain boundaries.
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| 9. |
- Karlsson, Sofia, 1982, et al.
(författare)
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Alkali Induced High Temperature Corrosion of Stainless Steel: The Influence of NaCl, KCl and CaCl2
- 2012
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Ingår i: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 78:1-2, s. 83-102
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Tidskriftsartikel (refereegranskat)abstract
- The influence of KCl, NaCl and CaCl2 on the oxidation of 304-type (Fe18Cr10Ni) stainless steel at 600 A degrees C in 5 %O-2 + 40 %H2O was investigated. Prior to exposure, a small amount of the preferred salt (cation equivalent: 1.35 mu mol/cm(2)) was deposited on the samples. Exposure time was 1-168 h. The oxidized samples were analyzed by SEM/EDX, XRD, FIB and IC. The presence of KCl and NaCl strongly accelerates high temperature corrosion of 304L. Corrosion attack is initiated by the formation of alkali chromate through the reaction of alkali with the protective oxide. Chromate formation is a sink for chromium in the oxide and leads to a loss of its protective properties. Subsequently a rapidly growing scale forms, consisting of an outer hematite layer with chromate particles on top and an inner spinel oxide layer. In contrast to NaCl and KCl, CaCl2 is not very corrosive. At temperature, CaCl2 is rapidly converted to CaO. Small amounts of CaCrO4 form where CaO is in direct contact with the scale. CaO also reacts with the scale to form Ca2Fe2O5.
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| 10. |
- Karlsson, Sofia, 1982
(författare)
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High Temperature Corrosion of Stainless Steels - The Effects of Chloride Salts and SO2(g)
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- AbstractThe high corrosion rate of superheaters in waste- and biomass- fired plants is often linked to the presence of alkali chlorides. One way to mitigate the corrosion is to replace the superheater material with more corrosion- resistant materials. Another way is to change the corrosive environment by introducing fuel additives. In both cases it is important to know as much as possible about the corrosion process.This study, investigates the corrosive effect of alkali chlorides and the beneficial effect of using sulphur-containing additives by laboratory and field exposures. In the laboratory study, the influence of three chloride salts, KCl, NaCl and CaCl2, on the oxidation of 304L type (Fe18Cr10Ni) austenitic stainless at 600°C in O2 + H2O is investigated. The effect of sulphur is tested by adding 300 ppm SO2 to the KCl exposure. In the field study the effect of sulphur is investigated by adding sulfur-rich municipal sewage sludge to the fuel which is rich in alkali and chlorine.The laboratory results show that KCl and NaCl strongly accelerate the high temperature corrosion of 304L. The corrosion attack is initiated by the formation of alkali chromates through the reaction of alkali with the protective oxide. Chromate formation is a sink for chromium in the oxide; this leads to a loss of its protective properties. In contrast to NaCl and KCl, CaCl2 is not very corrosive under the exposure conditions tested. CaCl2 is rapidly converted to CaO and only small amounts of CaCrO4 were detected in areas where CaO was in direct contact with the scale. The addition of SO2 to the gas results in a drastic reduction of the corrosion rate of the KCl treated samples. The corrosion mitigating effect of SO2 in this environment is attributed mainly to the rapid conversion of KCl to K2SO4. Unlike KCl, K2SO4 does not deplete the protective oxide in chromium by forming K2CrO4. It is also suggested that the formation of a thin sulphate film on the oxide surface impedes chromium volatilization in O2 + H2O environment and that it may decrease the rate of oxygen reduction on the oxide surface. The field study shows that the addition of sulphur rich material to the fuel mitigates corrosion in the superheater region of the power plant. Without additives, a thick corrosion product layer formed and the deposit was dominated by alkali chlorides. With additives, the amount of alkali chlorides in the deposit layer was very low and the steel was protected by a thin oxide. It is concluded that the beneficial effects of sulphur observed in the field can be explained in analogy to the lab experiments.Keywords: Alkali induced corrosion, Sulphur additives, Biomass, Waste, Stainless Steels
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