Wind turbines are usually clustered in wind farms which causes the downstream turbines to operate in the turbulent wakes of upstream turbines. As turbulence is directly related to increased fatigue loads, knowledge of the turbulence in the wake and its evolution are important. Therefore, the main objective of this study is a comprehensive exploration of the turbulence evolution in the wind turbine’s wake to identify characteristic turbulence regions. For this, we present an experimental study of three model wind turbine wake scenarios that were scanned with hot-wire anemometry with a very high downstream resolution. The model wind turbine was exposed to three inflows: laminar inflow as a reference case, a central wind turbine wake, and half of the wake of an upstream turbine. A detailed turbulence analysis reveals four downstream turbulence regions by means of the mean velocity, variance, turbulence intensity, energy spectra, integral and Taylor length scales, and the Castaing parameter that indicates the intermittency, or gustiness, of turbulence. In addition, a wake core with features of homogeneous isotropic turbulence and a ring of high intermittency surrounding the wake can be identified. The results are important for turbulence modeling in wakes and optimization of wind farm wake control
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Studies among people with dementia demonstrated that the sleep quality and rhythm improves significantly when people are exposed to ambient bright light. Since almost half of the healthy older people also indicate to suffer from chronic sleep disorders, the question arises whether ambient bright light can be beneficial to healthy older people. Particularly the effect on sleep/wake rhythm in relation to the exposure to natural light is the focus. It was hypothesised that the sleep quality would be worse in winter due to a lower daylight dose than in summer due to the lower illuminance and exposure duration. A field study was conducted to examine the relationship between daylight exposure and sleep quality in 14 healthy older adults living independently in their own dwellings in the Netherlands. All participants were asked to take part of the study both during the summer period as well as during the winter period. Therefore, they had to wear an actigraph for five consecutive days which measured sleep, activity and light exposure. Results confirmed that people were significantly longer exposed to high illumination levels (>1000 lx) in summer than in winter. Sleep quality measures, however, did not differ significantly between summer and winter. A significant, positive correlation was found between exposure duration to high illuminance from daylight during the day and the sleep efficiency the following night in summer, implying that being exposed to high illuminance for a longer time period has a positive effect on sleep efficiency for the individual data. There was also a tendency of less frequent napping in case of longer exposure duration to light for both seasons. Sleep quality does not differ between summer and winter but is related to the duration of the exposure to bright light the day prior to the night. CC-BY Original article at http://solarlits.com/jd/5-14 http://dx.doi.org/10.15627/jd.2018.2 https://www.dehaagsehogeschool.nl/onderzoek/lectoraten/details/urban-ageing#over-het-lectoraat
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Stroke is the second most common cause of death and the third leading cause of disability worldwide,1,2 with the burden expected to increase during the next 20 years.1 Almost 40% of the people with stroke have a recurrent stroke within 10 years,3 making secondary prevention vital.3,4 High amounts of sedentary time have been found to increase the risk of cardiovascular disease,5–11 particularly when the sedentary time is accumulated in prolonged bouts.12–15 Sedentary behavior, is defined as “any waking behavior characterized by an energy expenditure ≤1.5 Metabolic Equivalent of Task (METs) while in a sitting, reclining or lying posture”.16,17 Studies in healthy people, as well as people with diabetes and obesity, have shown that reducing the total amount of sedentary time and/or breaking up long periods of uninterrupted sedentary time, reduces metabolic risk factors associated with cardiovascular disease.6,9,10,12–15 Recent studies have shown that people living in the community after stroke spend more time each day sedentary, and more time in uninterrupted bouts of sedentary time compared to age-matched healthy peers.18–20 Reducing sedentary time and breaking up long sedentary bouts with short bursts of activity may be a promising intervention to reduce the risk of recurrent stroke and other cardiovascular diseases in people with stroke. To develop effective interventions, it is important to understand the factors associated with sedentary time in people with stroke. Previous studies have found associations between self-reported physical function after stroke and total sedentary time, but inconsistent results with regards to the relationship of age, stroke severity, and walking speed with sedentary time.20,21 These results are from secondary analyses of single-site observational studies, not powered to address associations, and inconsistent in the methods used to determine waking hours; thus making direct comparisons between studies difficult.20,21 Individual participant data pooling, with consistent processing of wake time data, allows novel exploratory analyses of larger datasets with greater power. By pooling all available individual participant data internationally, this study aimed to comprehensively explore the factors associated with sedentary time in community-dwelling people with stroke. Specifically, our research questions were: (1) What factors are associated with total sedentary time during waking hours after stroke? (2) What factors are associated with time spent in prolonged sedentary bouts during waking hours?
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Coachingsgeprekken rond spiritueel – ritueel geladen handelen in de residentiele jeugdhulp. Vraagstukken rond jeugd, gezin en opvoeding zijn blijvend actueel. De vraag hoe het leven van jongeren eruit ziet en hoe zij voor hun leven en rol in de maatschappij worden gevormd, is daarbij wezenlijk. In mijn promotieonderzoek heb ik verslag gedaan van het dagelijks leven van adolescenten in de residentiele jeugdhulp en de rol van pedagogische medewerkers daarbij (Vierwind, 2019). Het perspectief van waaruit dat gebeurt is dat van de ritual studies. Naast dagelijkse- en overgangsrituelen worden in dit onderzoek ‘rituelen met een spirituele dimensie’ blootgelegd. De jongeren vertellen in de interviews hoe zij in situaties van tegenslag en verdriet overgaan tot spirituele handelingen waaraan zij moed en kracht ontlenen. Eerder onderzoek toont dat de adolescentietijd, onafhankelijk van eigen al of niet spirituele opvoeding, voor meerdere jongeren een periode van spiritueel ontwaken is. Religie en spiritualiteit blijken als coping mechanisme een bron van veerkracht. Een van de bevindingen in mijn onderzoek is dat pedagogisch medewerkers zeggen dat zij weten dat jongeren bij tegenslag en verdriet spirituele handelingen verrichten, maar daarbij expliciet benoemen dat ze in mentorgesprekken daar niet op afstemmen. Als een reden daarvoor wordt genoemd dat dit niet aansluit bij de eigen visie en levensrichting. Deze bevinding sluit aan bij eerder onderzoek waarin wordt geconcludeerd dat het kunnen hanteren van de eigen voorkeurstijl door pedagogisch medewerkers blijvend aandacht vraagt. Ook de door jongeren in eerder onderzoek uitgesproken behoefte om met hun begeleiders ‘echte gesprekken’ te kunnen hebben, is in dit verband noemenswaardig. Het hier voorgestelde onderzoek richt zich op de vraag hoe pedagogisch medewerkers in mentorgesprekken die binnen de residentiele jeugdhulp worden gevoerd kunnen afstemmen op het spiritueel handelen van jongeren. De resultaten van dit onderzoek zijn ook voor aanpalende beroepsgroepen van belang (Verpleegkunde, Onderwijs, Theologie).
