Search results for "FREQUENCY"
showing 8 items of 2158 documents
Diversity in warning coloration: selective paradox or the norm?
2019
Aposematic theory has historically predicted that predators should select for warning signals to converge on a single form, as a result of frequency-dependent learning. However, widespread variation in warning signals is observed across closely related species, populations and, most problematically for evolutionary biologists, among individuals in the same population. Recent research has yielded an increased awareness of this diversity, challenging the paradigm of signal monomorphy in aposematic animals. Here we provide a comprehensive synthesis of these disparate lines of investigation, identifying within them three broad classes of explanation for variation in aposematic warning signals: …
Structure and dynamics in liquid bismuth and Bin clusters: A density functional study
2014
Density functional/molecular dynamics simulations with more than 500 atoms have been performed on liquid bismuth at 573, 773, 923, and 1023 K and on neutral Bi clusters with up to 14 atoms. There are similar structural patterns (coordination numbers, bond angles, and ring patterns) in the liquid and the clusters, with significant differences from the rhombohedral crystalline form. We study the details of the structure (structure factor, pair, and cavity distribution functions) and dynamical properties (vibration frequencies, diffusion constants, power spectra), and compare with experimental results where available. While the three short covalent bonds typical to pnictogens are characteristi…
Sustaining Attention for a Prolonged Duration Affects Dynamic Organizations of Frequency-Specific Functional Connectivity
2020
Sustained attention encompasses a cascade of fundamental functions. The human ability to implement a sustained attention task is supported by brain networks that dynamically formed and dissolved through oscillatory synchronization. The decrement of vigilance induced by prolonged task engagement affects sustained attention. However, little is known about which stage or combinations are affected by vigilance decrement. Here, we applied an analysis framework composed of weighted phase lag index (wPLI) and tensor component analysis (TCA) to an EEG dataset collected during 80 min sustained attention task to examine the electrophysiological basis of such effect. We aimed to characterize the phase…
Sensitivity Analysis and Frequency Dynamics of Grid-Connected Converters with Virtual Inertia
2021
For the participation in the frequency control of the system, power converters can be controlled with different strategies and methods, sharing the common concept of virtual inertia capability. In this work, a sensitivity analysis of two main categories of converter controls with virtual inertia is presented. The considered schemes are a grid-following current vector control with additional virtual inertia block and a grid-forming control scheme based on virtual synchronous machine concept. A proper basis for the comparison is first assessed providing an analytical correlation between the control parameters of the two schemes. For the two control strategies, the sensitivity analysis of the …
Energy Efficient Optimization for Wireless Virtualized Small Cell Networks With Large-Scale Multiple Antenna
2017
Wireless network virtualization is envisioned as a promising framework to provide efficient and customized services for next-generation wireless networks. In wireless virtualized networks (WVNs), limited radio resources are shared among different services providers for providing services to different users with heterogeneous demands. In this paper, we propose a resource allocation scheme for an orthogonal frequency division multiplexing-based WVN, where one small cell base station equipped with a large number of antennas serves the users with different service requirements. In particular, with the objective to obtain the energy efficiency in the uplink, a joint power, subcarrier, and antenn…
Pastāvīgo vārdu biežums laikrakstu tiešsaistes publikācijas un to diskusiju ziņās
2016
Šis darbs iepazīstina ar laikraksta The Guardian tiešsiastes publikāciju analīzi. Šī darba mērķis ir izanalizēt pastāvīgo vārdu (lietvārdu, darbības vārdu un īpašības vārdu) biežumu laikrakstu publikācijas un to diskusiju ziņās. Galvenā pētījuma metode bija korpusa-lingvistiskā metode, kas balstīta uz Makenerija (2006) teoriju. Šī darba autors izveidoja mini-korpusu, kas sastāvēja no divām teksta grupām: laikrakstu publikācijām un diskusiju ziņām. Vārdšķiru biežuma sadalījums korpusā, norāda uz formalitātes līmeņu atšķirību starp laikrakstu publikācijām un to diskusiju ziņām. Iegūtie rezultāti norāda uz reģistra variāciju izanalizētājos korpusa žanra tekstos. Lai identificētu līdzības un at…
Vain yksi voimaharjoitus viikossa riittää toimintakyvyn ylläpitämiseen ikääntyneillä
2018
Tutkimuksella selvitimme, parantaako voimaharjoittelu iäkkäiden toimintakykyä, ja onko harjoitusmäärillä vaikutusta toimintakyvyn muutoksiin. Tutkimukseen osallistui 106 koehenkilöä (65–75 v.), jotka satunnaistettiin neljään ryhmään: 1x/vko (H1, n=26), 2x/vko (H2, n=27) ja 3x/vko (H3, n=28) harjoitteleviin ja kontrolliryhmään (K, n=25). Ensimmäisen kolmen kuukauden ajan kaikki harjoitteluryhmät voimaharjoittelivat valvotusti kahdesti viikossa (H, n=81), jonka jälkeen ryhmät harjoittelivat kuusi kuukautta (3 kk–9 kk) nimensä mukaisesti kerran, kahdesti tai kolmesti viikossa. Koehenkilöille suoritettiin testit 0 kk, 3 kk ja 9 kk. Toimintakykyä testattiin etuperinkävelyllä (E), takaperinkävely…
High frequency data entry: statistical findings at high frequency
2010
We introduce some of the most common types of high-frequency financial data: tick-by-tick data, trade andquote data, order bookdata, andmarket member data. We describe the types of variables that are usually available in the most popular high-frequency financial databases. We discuss the issues related to the handling of these data, including cleaning protocols, timing issues, and issues related to data size. We then briefly consider the issues related to the stylized facts detected in the empirical analysis of high- frequency data. Specifically, we consider (i) the irregular temporal spacing of the events at high frequency and its relevance for the econometric modeling of financial variables, (…