Opin vísindi
Opin vísindi er varðveislusafn vísindaefnis og doktorsritgerða í opnum aðgangi á vegum íslenskra háskóla og Landsbókasafns Íslands - Háskólabókasafns.
Opinn aðgangur að rannsóknaniðurstöðum er í samræmi við 10. gr. laga nr. 3/2003 um opinberan stuðning við vísindarannsóknir sem og kröfur innlendra og erlendra rannsóknasjóða. Markmiðið með opnum aðgangi er að niðurstöður rannsókna séu aðgengilegar sem flestum óhindrað og án endurgjalds á rafrænu formi. Vistun í varðveislusafninu er varanleg og ætlað að tryggja aðgang að vísindaefni íslenskra háskóla í opnum aðgangi um ókomna tíð. Varðveislusafnið Opin vísindi er tengt við rannsóknagáttina IRIS og rannsóknaniðurstöður í opnum aðgangi sem eru skráðar í IRIS eru um leið vistaðar og gerðar aðgengilegar til framtíðar í varðveislusafninu. Með því að safna þessu efni saman í eitt safn verður aðgangur að því einfaldur og þægilegur fyrir alla sem vilja kynna sér það og geta þannig notið þess öfluga vísindastarfs sem fram fer í háskólum landsins.
Varðveislusafnið er OpenAIRE / OpenAIREplus samhæft og samrýmist kröfum sem gerðar eru um birtingu rannsóknaniðurstaðna úr verkefnum sem styrkt eru úr evrópsku rannsóknaáætlununum FP7 og H2020.
Varðveislusafnið notar opna hugbúnaðinn DSpace.
Opinn aðgangur að rannsóknaniðurstöðum er í samræmi við 10. gr. laga nr. 3/2003 um opinberan stuðning við vísindarannsóknir sem og kröfur innlendra og erlendra rannsóknasjóða. Markmiðið með opnum aðgangi er að niðurstöður rannsókna séu aðgengilegar sem flestum óhindrað og án endurgjalds á rafrænu formi. Vistun í varðveislusafninu er varanleg og ætlað að tryggja aðgang að vísindaefni íslenskra háskóla í opnum aðgangi um ókomna tíð. Varðveislusafnið Opin vísindi er tengt við rannsóknagáttina IRIS og rannsóknaniðurstöður í opnum aðgangi sem eru skráðar í IRIS eru um leið vistaðar og gerðar aðgengilegar til framtíðar í varðveislusafninu. Með því að safna þessu efni saman í eitt safn verður aðgangur að því einfaldur og þægilegur fyrir alla sem vilja kynna sér það og geta þannig notið þess öfluga vísindastarfs sem fram fer í háskólum landsins.
Varðveislusafnið er OpenAIRE / OpenAIREplus samhæft og samrýmist kröfum sem gerðar eru um birtingu rannsóknaniðurstaðna úr verkefnum sem styrkt eru úr evrópsku rannsóknaáætlununum FP7 og H2020.
Varðveislusafnið notar opna hugbúnaðinn DSpace.
Nýlega bætt við
Fast All-Digital Clock Frequency Adaptation Circuit for Voltage Droop Tolerance
(2022-08-01) Fugger, Matthias; Kinali, Attila; Lenzen, Christoph; Wiederhake, Ben; Department of Computer Science
In classical synchronous designs, supply voltage droops can be handled by accounting for them in clock margins. However, this results in a significant performance hit even if droops are rare. In contrast, adaptive strategies detect such potentially hazardous events and either initiate a rollback to a previous state or proactively reduce clock speed in order to prevent timing violations. The performance of such solutions critically depends on a very fast response to droops. State-of-the-art solutions incur synchronization delays in the order of several clock cycles to avoid, with sufficient probability, that the clock signal is affected by metastability. We present an all-digital circuit that can respond to droops within a fraction of a clock cycle. This is achieved by using potentially metastable measurement values to delay clock signals while they undergo synchronization, instead of after they are synchronized. The challenge is to ensure that this strategy does not lead to harmful glitches or metastable upsets within the circuit. To this end, we verify our solution by formally proving correctness. We complement our findings by simulations of a 65-nm ASIC design confirming the results of our analysis.
Optimal Clock Synchronization with Signatures
(Association for Computing Machinery, 2022-07-21) Lenzen, Christoph; Loss, Julian; Department of Computer Science
Cryptographic signatures can be used to increase the resilience of distributed systems against adversarial attacks, by increasing the number of faulty parties that can be tolerated. While this is well-studied for consensus, it has been underexplored in the context of fault-tolerant clock synchronization, even in fully connected systems. Here, the honest parties of an n-node system are required to compute output clocks of small skew (i.e., phase offset) despite local clock rates varying between 1 and ' > 1, end-to-end communication delays varying between d - u and d, and the interference from malicious parties. Known algorithms with (trivially optimal) resilience of [n/2] - 1 improve over the tight bound of [n/3] - 1 holding without signatures for any skew bound [6, 18], but incur skew d [1] or ω(n(u + ( ' - 1)d)) [14]. Since typically d >> u and ' - 1 « 1, this is far from the lower bound of u + ( ' - 1)d that applies even in the fault-free case [3].
Brief Announcement : (1+)-Approximate Shortest Paths in Dynamic Streams.
(Association for Computing Machinery, 2022-07-21) Elkin, Michael; Trehan, Chhaya; Department of Computer Science
Computing approximate shortest paths in the dynamic streaming setting is a fundamental challenge that has been intensively studied. Currently existing solutions for this problem either build a sparse multiplicative spanner of the input graph and compute shortest paths in the spanner offline, or compute an exact single source BFS tree. Solutions of the first type are doomed to incur a stretch-space tradeoff of 2k - 1 versus n1+1/k , for an integer parameter k. (In fact, existing solutions also incur an extra factor of 1+ in the stretch for weighted graphs, and an additional factor of logO(1) n in the space.) The only existing solution of the second type uses n1/2-O(1/k) passes over the stream (for space O(n1+1/k )), and applies only to unweighted graphs.
A Recursive Early-Stopping Phase King Protocol
(Association for Computing Machinery, 2022-07-21) Lenzen, Christoph; Sheikholeslami, Sahar; Department of Computer Science
Early-stopping consensus protocols guarantee termination within a number of rounds that depends only on the actual number f of faulty nodes in a run, not the maximum number of faults that can be tolerated. We consider early-stopping deterministic synchronous consensus with Byzantine faults in a fully connected message passing system of n nodes. Many such protocols are known, but so far none combine early-stopping in O(f+1) rounds with optimal resilience and a bit complexity of o(n2(f+1)). We provide two solutions to the above problem. The first is fairly simple and almost matches the above goals, but has worst-case message and bit complexities of Θ(n2 log (f+2)). The second reduces the bit complexity further to O(n2) by calling itself recursively at most twice on Θ(n)-sized subsets. The result is the first protocol that is simultenously optimally resilient, asymptotically optimally early-stopping, and asymptotically bit- and message-optimal.
Lockdown Duration and Training Intensity Affect Sleep Behavior in an International Sample of 1,454 Elite Athletes
(2022-06-15) Romdhani, Mohamed; Fullagar, Hugh H.K.; Vitale, Jacopo A.; Nédélec, Mathieu; Rae, Dale E.; Ammar, Achraf; Chtourou, Hamdi; Al Horani, Ramzi A.; Ben Saad, Helmi; Bragazzi, Nicola Luigi; Dönmez, Gürhan; Dergaa, Ismail; Driss, Tarak; Farooq, Abdulaziz; Hammouda, Omar; Harroum, Nesrine; Hassanmirzaei, Bahar; Khalladi, Karim; Khemila, Syrine; Mataruna-Dos-Santos, Leonardo Jose; Moussa-Chamari, Imen; Mujika, Iñigo; Muñoz Helú, Hussein; Norouzi Fashkhami, Amin; Paineiras-Domingos, Laisa Liane; Khaneghah, Mehrshad Rahbari; Saita, Yoshitomo; Souissi, Nizar; Trabelsi, Khaled; Washif, Jad Adrian; Weber, Johanna; Zmijewski, Piotr; Taylor, Lee; Garbarino, Sergio; Chamari, Karim; Department of Sport Science
Objective: To investigate the effect of 1) lockdown duration and 2) training intensity on sleep quality and insomnia symptoms in elite athletes. Methods: 1,454 elite athletes (24.1 ± 6.7 years; 42% female; 41% individual sports) from 40 countries answered a retrospective, cross-sectional, web-based questionnaire relating to their behavioral habits pre- and during- COVID-19 lockdown, including: 1) Pittsburgh sleep quality index (PSQI); 2) Insomnia severity index (ISI); bespoke questions about 3) napping; and 4) training behaviors. The association between dependent (PSQI and ISI) and independent variables (sleep, napping and training behaviors) was determined with multiple regression and is reported as semi-partial correlation coefficient squared (in percentage). Results: 15% of the sample spent < 1 month, 27% spent 1–2 months and 58% spent > 2 months in lockdown. 29% self-reported maintaining the same training intensity during-lockdown whilst 71% reduced training intensity. PSQI (4.1 ± 2.4 to 5.8 ± 3.1; mean difference (MD): 1.7; 95% confidence interval of the difference (95% CI): 1.6–1.9) and ISI (5.1 ± 4.7 to 7.7 ± 6.4; MD: 2.6; 95% CI: 2.3–2.9) scores were higher during-compared to pre-lockdown, associated (all p < 0.001) with longer sleep onset latency (PSQI: 28%; ISI: 23%), later bedtime (PSQI: 13%; ISI: 14%) and later preferred time of day to train (PSQI: 9%; ISI: 5%) during-lockdown. Those who reduced training intensity during-lockdown showed higher PSQI (p < 0.001; MD: 1.25; 95% CI: 0.87–1.63) and ISI (p < 0.001; MD: 2.5; 95% CI: 1.72–3.27) scores compared to those who maintained training intensity. Although PSQI score was not affected by the lockdown duration, ISI score was higher in athletes who spent > 2 months confined compared to those who spent < 1 month (p < 0.001; MD: 1.28; 95% CI: 0.26–2.3). Conclusion: Reducing training intensity during the COVID-19-induced lockdown was associated with lower sleep quality and higher insomnia severity in elite athletes. Lockdown duration had further disrupting effects on elite athletes’ sleep behavior. These findings could be of relevance in future lockdown or lockdown-like situations (e.g., prolonged illness, injury, and quarantine after international travel).
Flokkar í Opnum vísindum
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- University of Iceland
- University of Akureyri
- Bifröst University
- Hólar University College
- IRIS
- Agricultural University of Iceland
- National and University Library of Iceland
- Iceland University of the Arts