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- Fischer, S, et al.
(författare)
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Collector test method under quasi dynamic conditions according to the European Standard EN 12975-2
- 2004
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Ingår i: Solar Energy. - : Elsevier BV. - 0038-092X. ; 76, s. 117-123
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Konferensbidrag (refereegranskat)abstract
- In April 2001 the new European Standard EN 12975:2000: ''Thermal solar systems and components--Solar Collectors'' was established. With the publication of this European standard all national standards, related to the same topic, have to be withdrawn by the nations of the European Community. Now only one standard for testing solar collectors is valid throughout Europe.This European Standard specifies test methods for validating the durability, reliability and safety requirements for liquid heating collectors. The standard also includes two alternative test methods for the thermal performance characterization for liquid heating collectors. Apart from the well-known test method under steady-state conditions according to ISO 9806-1, ISO 9806-3 and ASHRAE 93-77 the EN 12975 permits a quasi-dynamic test method for the thermal performance characterization of solar thermal collectors.This paper presents the improved approach to outdoor performance testing of solar thermal collectors under quasi-dynamic test conditions. The test requirements and collector theory are closely connected to those long agreed on for steady-state testing, as described in the ISO and ASHRAE standards mentioned above. The most important effects for the all day performance of the collector are taken into account. The test method covers most collector designs on the market today (except ICS type). Only some correction terms are added to the basic collector models of the present steady-state test methods. Still this limited change will allow test data to be collected and used from whole days.An important fact is that the collector model used for the parameter identification is written so that the error in collector output power is minimized. Therefore an accurate long-term prediction of the collector performance can be an integral part of the test method, where the same collector model and parameters are used for both testing and prediction.
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- Adsten, M, et al.
(författare)
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Measurement of radiation distribution on the absorber in an asymmetric CPC collector
- 2004
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Ingår i: Solar Energy. - : Elsevier BV. - 0038-092X .- 1471-1257. ; 76:1-3, s. 199-206
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Tidskriftsartikel (refereegranskat)abstract
- A method to estimate the annual collected energy and the annual average optical efficiency factor is suggested. The radiation distribution on the absorber of an asymmetric CPC collector with a flat bi-facial absorber is measured for three different absorber mounting angles using a photo diode. The annual optical efficiency factors and a relative measure of the annual collected energy are determined for collectors with the absorber fin thickness 0.5 and 1 mm, and for a collector with a teflon convection suppression film mounted around the absorber. With the local optical efficiency factors and the annual incident solar energy distribution considered, the analysis indicates that the energy gain for a mounting angle of 20 is higher than for a collector with 65 absorber mounting angle. The annual collected energy is increased with 6-8% if the absorber fin thickness is increased from 0.5 to 1 mm. The annual average optical efficiency factor is relatively independent of the absorber mounting angle. It was found to be 0.87-0.88 for a collector with a 0.5 mm thick absorber fin and 0.92 for a collector with a 1 mm thick absorber fin or for a collector with 0.5 mm thick absorber fin with a teflon convection suppression film added. The low annual average optical efficiency factor is not caused by the uneven irradiance distribution but by the relatively high U-L-values. (C) 2003 Elsevier Ltd. All rights reserved.
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- Agreus, Lars, et al.
(författare)
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Towards a healthy stomach? : Helicobacter pylori prevalence has dramatically decreased over 23 years in adults in a Swedish community
- 2016
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Ingår i: United European Gastroenterology journal. - : Wiley. - 2050-6406 .- 2050-6414. ; 4:5, s. 686-696
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Tidskriftsartikel (refereegranskat)abstract
- Background In Western countries the prevalence of Helicobacter pylori (H. pylori) infection may be declining but there is a lack of recent longitudinal population studies. We evaluated the changing epidemiology over a 23-year period in Sweden.Materials and methods In 1989, the validated Abdominal Symptom Questionnaire (ASQ) was mailed to a random sample of inhabitants (ages 22-80 years) in a Swedish community, and 1097 (87%) responded. H. pylori serology was analysed in a representative subsample (n=145). Twenty-three years later, the ASQ was mailed again using similar selection criteria, and 388 out of 1036 responders had an upper endoscopy with assessment of H. pylori and corpus atrophy status.Results The prevalence of positive H. pylori serology decreased from 37.9% (1989) to 15.8% (2012), corresponding to a decrease in odds of 75% per decade (odds ratio (OR): 0.25; 95% confidence interval (CI): 0.11-0.59, p=0.001) independent of age, gender, body mass index (BMI) and level of education, with a pattern consistent with a birth cohort effect. The prevalence increased with increasing age (p=0.001). The prevalence of H. pylori on histology in 2012 was 11.4% (95% CI 8.6-15.0). The prevalence of corpus atrophy on serology and/or histology in 2012 was 3.2% (95% CI 1.8-5.5); all cases were 57 years old.Conclusion The stomach is healthier in 2012 compared with 1989. H. pylori prevalence in adults has decreased over the last two decades to a level where clinical management might be affected.
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| 10. |
- Andreasson, Anna, et al.
(författare)
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An Increasing Incidence of Upper Gastrointestinal Disorders Over 23 Years : A Prospective Population-Based Study in Sweden
- 2021
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Ingår i: American Journal of Gastroenterology. - : Ovid Technologies (Wolters Kluwer Health). - 0002-9270 .- 1572-0241. ; 116:1, s. 210-213
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Tidskriftsartikel (refereegranskat)abstract
- INTRODUCTION: We hypothesized that the prevalence of functional dyspepsia and gastroesophageal reflux disease in the community may be increasing.METHODS: Randomly selected adults were surveyed on 4 occasions: 1988 (n = 1,151, 21–79 years, response rate [rr] = 90%), 1989 (n = 1,097, 22–80 years, rr = 87%), 1995 (n = 1,139, 20–85 years, rr = 76%), and 2011 (n = 1,175, 20–93 years, rr = 63%).RESULTS: In functional dyspepsia, the odds of postprandial distress syndrome tripled over 23 years' follow-up (odds ratio [OR]: 3.55; 95% confidence interval [CI]: 2.60–4.84, mixed-effect regression analysis), whereas a small decrease in epigastric pain syndrome was observed (OR: 0.65, 95% CI: 0.42–1.00). The odds of reporting gastroesophageal reflux disease doubled (OR: 2.02; 95% CI: 1.50–2.73).DISCUSSION: The underlying mechanisms behind the increase in postprandial distress syndrome and gastroesophageal reflux disease remain to be determined.
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