Fracture mechanical and mechanical characterisation of Alloy 52 dissimilar metal welds

Dissimilar metal welds(DMW) in nuclear power plants have been identified to be prone to failure by cracking. Generally cracks grow straight, unless a weaker microstructure is adjacent. In DMWs cracks have propagated to the fusion line. Fracture toughness of weldments has been reported to sink in the same location. It has been shown that hardness can be used to predict strength of a homogeneous material. In this thesis, such model was applied to DMWs. On the other hand, fracture toughness and crack propagation was studied for both ductile and brittle specimens. Two DMWs were studied, MU1 and NI1. They shared the same SS base metal and Alloy 52 weld metal. Furthermore the LAS base metals were very similar: 18MND5 and SA508 for MU1 and NI1, respectively. NI1 specimens were studied in three different ageing conditions. Some of the data was reutilized from previous projects. Vickers hardness was measured over the LAS fusion line. To be able to utilize hardness measurements without knowledge of their distribution, the data was bootstrapped. The means of the bootstrapped medians provided estimates of the average hardness and its deviation. Three tensile specimens were tested from four different locations. Tensile results were compared to strength predictions from hardness. The VTT model developed for homogeneous materials predicted strength from hardness inadequately in its original form. However, once the parameters were varied, predictions agreed with measurements. Ductile specimens were made from both MU1 and NI1. Temperatures for testing were 300°C and 20°C for MU1 and NI1 respectively. Their fracture toughness was determined with JIc, which is defined in ASTM E1820. Crack path was studied with either cross-cutting or profilometry. In the case of profilometry, the specimens were profiled from three different locations and the mean of results was used. Brittle specimens were all from NI1. ASTM E1921 determines cleavage fracture toughness Jc. Test temperatures were between −80°C and −130°C. Crack path was studied with profilometry. Profiling location was at cleavage nucleation point. The point was determined with scanning electron microscope. The accuracy of profilometry itself was confirmed by comparing the results to specimen cross-cuts. Linear correlation between fracture toughnesses and crack jumps towards fusion line was established successfully for most datasets. Ageing of the specimens reduced the fracture toughness of brittle specimens, but not of ductile ones. Instead, ductile fracture toughness increased with test temperature

Exploring Students' Experiences of Self-Regulated Learning during a Large Flipped Classroom Course in Teacher Education

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Kristinuskon historia

Miten kristinuskosta tuli Rooman valtakunnan uskonto? Miksi ristiretkiä tehtiin? Miksi kirkko poltti noitia ja harhaoppisia? Kumosiko tiede uskonnon? Miten kirkolle kävi Neuvostoliitossa ja miten kristinusko levisi Aasiaan ja Afrikkaan? Kristinuskon historia vastaa näihin ja moniin muihin kysymyksiin. Kirja on ensimmäinen kristinuskon historian kokonaisesitys, jonka tekijä on suomalainen ja joka tarkastelee aihetta pohjoismaisesta näkökulmasta. Se on perusteos, joka antaa tietoa suurimmasta maailmanuskonnosta ja sen vaikutuksesta Euroopan ja koko maailman kulttuuriin ja kehitykseen. Yleistajuinen ja selkeä kirja perustuu uusimpaan tutkimukseen ja soveltuu yliopiston oppikirjaksi.2. paino

Numerical and Experimental Study on Inertial Impactors

One of the most important physical properties that defines the behavior of an aerosol particle is its size. Size defines to a great extent how particles behave in physical and chemical processes. Applying experimental and numerical methods, this thesis studies the fundamentals of the operation of impactors, the instruments that are used to measure the size of aerosol particles.The first part of the thesis develops a CFD simulation approach, which is suitable for low pressure impactors and their verification. The CFD model is then used to the study parameters that affect the shape of a low pressure impactor’s collection efficiency curve. The second part focuses on the applications of these findings by introducing two new impactors: a variable nozzle area impactor (VNAI), designed for detailed study of particle behavior in collisions, and a high-resolution low-pressure cascade impactor (HRLPI), used in combination with electrical detection to measure nanoparticle size distribution.Simulations showed that the steepness of the collection efficiency curve depends on the uniformity of the impaction conditions in the impactor jet. Conditions were defined in terms of static pressure, velocity, and particle stopping distance profiles in the cross section of the jet. Uniform impaction conditions and a steep cut-curve were achieved at a short throat, low pressure impactor stage.In the devised VNAI impactor, particles showed very uniform impaction velocities, a fact that was used to examine the critical velocity of the rebound of spherical silver particles. The critical velocities were several orders of magnitude lower than those for micron sized particles. This may be explained by a different material pair used in the experiments and previous studies. The HRLPI was designed based on instrument response simulations to gain maximum information on aerodynamic size distribution and to guarantee robust inversion characteristics in real-time measurement. This was achieved with roughly ten stages per size decade and with slit type, short-throat nozzles.This thesis sheds light on some still unanswered questions in impactor theory and successfully applies the theory to practise by introducing new high resolution impactors for nanoparticle research.<br/

Foot-related diabetes complications : care pathways, patient profiles and costs

Publisher Copyright: © 2022, The Author(s).Background: Foot-related diabetes complications reduce individual well-being, increase mortality and results in increased healthcare costs. Despite their notable stress on health services, studies examining the foot complication care pathways, especially from the viewpoint of health services, are limited. We aimed to identify the most typical care pathways following an initial foot-related diabetes complication, to characterize the patients on each pathway and calculate the related healthcare costs. Methods: The identification of pathways was based on population-wide register-based data including all persons diagnosed with diabetes in Finland from 1964 to 2017. For each patient, initial foot-related complication from 2011–2016 was identified using the ICD-10 codes and related healthcare episodes were followed for two years until the end of 2017 or death. A sequence analysis was conducted on care episodes resulting in groups of typical care pathways, as well as their patient profiles. The costs of pathways resulting from the care episodes were calculated based on the data and the reported national unit costs and analyzed using linear models. Results: We identified six groups of typical pathways each comprising mainly single type of care episodes. Three of the groups comprised over 10 000 patients while the remaining groups ranged from a few hundred to a few thousand. Majority of pathways consisted only single care episode. However, among the rest of the care pathways variability in length of care pathways was observed between and within group of pathways. On average, the patients were over 65 years of age and were diagnosed with diabetes for over a decade. The pathways resulted in an annual cost of EUR 13 million. The mean costs were nearly 20-fold higher in the group with the highest costs (EUR 11 917) compared to the group with the lowest costs (EUR 609). Conclusions: We identified groups of typical care pathways for diabetic foot and discovered notable heterogeneity in the resource use within the groups. This information is valuable in guiding the development of diabetes care to meet the growing need. Nevertheless, reasons underlying the observed heterogeneity requires further examination. Since foot complications are largely preventable, substantial savings could be achieved using cost-effective technologies and more efficient organization of care.Peer reviewe