Opin vísindi

 

Nýlega bætt við

Verk
Induced seismicity risk analysis of the hydraulic stimulation of a geothermal well on Geldinganes, Iceland
(2020-06-04) Broccardo, Marco; Mignan, Arnaud; Grigoli, Francesco; Karvounis, Dimitrios; Rinaldi, Antonio Pio; Danciu, Laurentiu; Hofmann, Hannes; Milkereit, Claus; Dahm, Torsten; Zimmermann, Gunter; Hjörleifsdóttir, Vala; Wiemer, Stefan; Department of Engineering
The rapid increase in energy demand in the city of Reykjavik has posed the need for an additional supply of deep geothermal energy. The deep-hydraulic (re-)stimulation of well RV-43 on the peninsula of Geldinganes (north of Reykjavik) is an essential component of the plan implemented by Reykjavik Energy to meet this energy target. Hydraulic stimulation is often associated with fluid-induced seismicity, most of which is not felt on the surface but which, in rare cases, can be a nuisance to the population and even damage the nearby building stock. This study presents a first-of-its-kind pre-drilling probabilistic induced seismic hazard and risk analysis for the site of interest. Specifically, we provide probabilistic estimates of peak ground acceleration, European microseismicity intensity, probability of light damage (damage risk), and individual risk. The results of the risk assessment indicate that the individual risk within a radius of 2km around the injection point is below 0.1 micromorts, and damage risk is below 10-2 for the total duration of the project. However, these results are affected by several orders of magnitude of variability due to the deep uncertainties present at all levels of the analysis, indicating a critical need in updating this risk assessment with in situ data collected during the stimulation. Therefore, it is important to stress that this a priori study represents a baseline model and starting point to be updated and refined after the start of the project.
Verk
Evaluating the Effect of Timeline Shape on Visualization Task Performance
(Association for Computing Machinery, 2020-04-21) Di Bartolomeo, Sara; Pandey, Aditeya; Leventidis, Aristotelis; Saffo, David; Syeda, Uzma Haque; Carstensdottir, Elin; Seif El-Nasr, Magy; Borkin, Michelle A.; Dunne, Cody; Department of Computer Science
Timelines are commonly represented on a horizontal line, which is not necessarily the most effective way to visualize temporal event sequences. However, few experiments have evaluated how timeline shape influences task performance. We present the design and results of a controlled experiment run on Amazon Mechanical Turk (n=192) in which we evaluate how timeline shape affects task completion time, correctness, and user preference. We tested 12 combinations of 4 shapes - - horizontal line, vertical line, circle, and spiral A- and 3 data types A- recurrent, non-recurrent, and mixed event sequences. We found good evidence that timeline shape meaningfully affects user task completion time but not correctness and that users have a strong shape preference. Building on our results, we present design guidelines for creating effective timeline visualizations based on user task and data types. A free copy of this paper, the evaluation stimuli and data, and code are available https://osf.io/qr5yu/
Verk
Hot, tired and hungry : The snacking behaviour and food cravings of firefighters during multi-day simulated wildfire suppression
(2020-04) Gupta, Charlotte C.; Ferguson, Sally A.; Aisbett, Brad; Dominiak, Michelle; Chappel, Stephanie E.; Sprajcer, Madeline; Fullagar, Hugh H.K.; Khalesi, Saman; Guy, Joshua H.; Vincent, Grace E.; Department of Sport Science
Firefighters are exposed to numerous stressors during wildfire suppression, including working in hot temperatures and sleep restricted conditions. Research has shown that when sleep restricted, individuals choose foods higher in carbohydrates, fat, and sugar, and have increased cravings for calorie dense foods. However, there is currently no research on the combined effect of heat and sleep restriction on snacking behaviour. Conducting secondary analyses from a larger study, the current study aimed to investigate the impact of heat and sleep restriction on snacking behaviour and food cravings. Sixty-six firefighters completed three days of simulated physically demanding firefighting work and were randomly allocated to either the control (n = 18, CON; 19 °C, 8h sleep opportunity), sleep restricted (n = 16, SR; 19 °C, 4-h sleep opportunity), hot (n = 18, HOT; 33 °C, 8h sleep opportunity), or hot and sleep restricted (n = 14 HOT + SR; 33 °C, 4-h sleep opportunity) condition. During rest periods firefighters were able to self-select sweet, savoury, or healthy snacks from a ration pack and were asked to rate their hunger, fullness, and cravings every two hours (eating block). Mixed model analyses revealed no difference in total energy intake between conditions, however there was a significant interaction between eating block and condition, with those in the CON, HOT, and HOT + SR condition consuming significantly more energy between 1230 and 1430 compared to the SR condition (p = 0.002). Sleep restriction and heat did not impact feelings of hunger and fullness across the day, and did not lead to greater cravings for snacks, with no differences between conditions. These findings suggest that under various simulated firefighting conditions, it is not the amount of food that differs but the timing of food intake, with those that are required to work in hot conditions while sleep restricted more likely to consume food between 1230 and 1430. This has potential implications for the time of day in which a greater amount of food should be available for firefighters.
Verk
Optimal Metastability-Containing Sorting via Parallel Prefix Computation
(2020-02-01) Bund, Johannes; Lenzen, Christoph; Medina, Moti; Department of Computer Science
Friedrichs et al. (TC 2018) showed that metastability can be contained when sorting inputs arising from time-to-digital converters, i.e., measurement values can be correctly sorted without resolving metastability using synchronizers first. However, this work left open whether this can be done by small circuits. We show that this is indeed possible, by providing a circuit that sorts Gray code inputs (possibly containing a metastable bit) and has asymptotically optimal depth and size. Our solution utilizes the parallel prefix computation (PPC) framework (JACM 1980). We improve this construction by bounding its fan-out by an arbitrary f\geq 3f≥3, without affecting depth and increasing circuit size by a small constant factor only. Thus, we obtain the first PPC circuits with asymptotically optimal size, constant fan-out, and optimal depth. To show that applying the PPC framework to the sorting task is feasible, we prove that the latter can, despite potential metastability, be decomposed such that the core operation is associative. We obtain asymptotically optimal metastability-containing sorting networks. We complement these results with simulations, independently verifying the correctness as well as small size and delay of our circuits. Proofs are omitted in this version; the article with full proofs is provided online at http://arxiv.org/abs/1911.00267.
Verk
Environmental and individual correlates of depressive symptoms in Iceland : The role of season, environmental mood responses and circadian preference
(University of Akureyri, 2026-11) Zelinski, Lada; Höller, Yvonne; Ólafsson, Ragnar P.; Bathke, Arne C.; Centre for Doctoral Studies
Í þessari ritgerð er sjónum beint, í þremur rannsóknum, að umhverfis- og eintaklingsbundnum þáttum í þunglyndiseinkennum á Íslandi -landi sem liggur norðarlega og mikill munur er á dagsbirtu og veðurfari eftir árstíðum. Í fyrstu rannsókninni var notaður skimunarlisti ásamt hálfstöðluðu geðgreiningarviðtali til að meta árstíðabundnar sveiflur í þunglyndiseinkennum og þunglyndisröskun í lagskiptu úrtaki Íslendinga. Vegið algengi árstíðabundins þunglyndis var mun hærra samkvæmt skimunarlista, eða 17,86%, heldur en samkvæmt geðgreiningarviðtali, eða 2,24%, sem er í samræmi við rannsóknir í löndum nær miðbaug og bendir til ofmats á áhrifum hnattlegu landa á þunglyndi, ef sjálfsmatsskimunarlistar eru eingöngu notaðir. Í annarri rannsókninni voru skoðuð tengsl skaps fólks við staðbundið hita- og birtustig og hvort þeir þættir tengdust alvarleika þunglyndiseinkenna. Niðurstöður sýndu að verra skap þegar kalt var í veðri og dagsbirta minni, tengdist alvarlegri einkennum og að tengsl hitastigs og þunglyndiseinkenna var háð (ó)þoli fólks fyrir kaldara hitastigi. Í þriðju rannsókninni var dægursveifluhneigð og neysla orkudrykkja skoðuð í tengslum við einkenni þunglyndis og svefnleysis með árstíðabundnum mælingum í eitt ár. Niðurstöður sýndu að kvöldhneigt fólk hafði meiri þunglyndiseinkenni á grunnlínu að sumri og að neysla orkudrykkja tengdist þunglynlyndiseinkennum þegar tók að hausta, sér í lagi hjá kvöldheigðu fólki. Samantekið, benda niðurstöður þessara þriggja rannsókna til að árstíðabundið þunglyndi, greint sem geðröskun í geðgreiningarviðtali, sé tiltölulega sjaldgæft en að sveiflur í þunglyndiseinkennum eftir árstíðum sé mun algengari þegar miðað er við sjálfsmat fólks. Niðurstöðurnar benda einnig til að áhrif umhverfisþátta á þunglyndiseinkenni séu háð einstaklingsbundnu mati og þoli fólks, frekar en þáttunum einum og sér og að tengsl orkudrykkja við þunglyndiseinkenni séu háð dægursveifluhneigð og árstíðum. Niðurstöður rannsóknaverkefnisins benda til að tengsl árstíðabundninna umhverfisþátta og þunglyndiseinkenna séu háð einstaklingsbundnum tilhneigingum. Loftslagsbreytingar móta umhverfi og aðstæður fólks. Aukinn skilningur á samspili umhverfis og einstaklingsbundinna þátta er því mikilvægur og getur nýst til að afmarka viðkvæma hópa og veita markvissari fræðslu og stuðning.

Flokkar í Opnum vísindum

Veldu flokk til að skoða.

Niðurstöður 1 - 9 af 9