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14623. Velká data jako alternativa výběrových šetření v kvantitativním sociálněvědním výzkumu

Creator:
Johana Chylíková
Format:
print, bez média, and svazek
Type:
model:article and TEXT
Subject:
big data, kvalita dat, metodologie, data quality, methodology, survey, epistemology, 18, and 316.4/.7
Language:
Czech
Description:
The goal of this article is to inform social scientists, especially those of a quantitative orientation, about the basic characteristics of Big Data and to present the opportunities and limitations of using such data in social research. The paper informs about three basic types of Big Data as they are distinguished in contemporary methodological literature, namely administrative data, transaction data and social network data, and exemplifies how they can be utilized by quantitative social research. According to many, questionnaire-based sample survey as the dominant method of quantitative social research has found itself in a crisis, especially as response rates have decreased in most developed countries and public confidence in opinion polling has declined. The author presents the characteristics and specifics of Big Data compared to survey research - a method whose primary distinguishing characteristic is the capacity to quantify individual behaviour, social action and attitudes at the level of populations. In this context, the article draws attention to the differences between Big Data and survey data typically presented in scholarly literature, namely that datasets are not representative of known populations, the values of observed variables are systematically biased, there is a limited number of variables in Big Data sets, there is uncertainty about the meaning of observed values, and social environment has direct influence on the behaviours captured by Big Data. Attention is also paid to such characteristics of Big Data that pose an obstacle to smooth integration of this type of data in the social scientific mainstream. First, the collection, processing and analysis of Big Data is extremely demanding in terms of programming skills, something social scientists typically do not have. Second, the availability of Big Data is limited as they are normally possessed by private corporations, some of which (Facebook, Google) have undoubtedly come to form data oligopolies - and their management is mostly unwilling to share their data with traditional academics. Based on the above-mentioned specifics, differences and limitations, it is argued that Big Data currently do not have the potential of becoming a full-fledged source of social science data and replacing sample surveys as the dominant research method. Finally, the article draws attention to the specifics of different types of Big Data as they are primarily generated for purposes other than social research and result from specific situations framed by existing social relations - and it is from this perspective that Big Data should be viewed by social researchers., Johana Chylíková., and Obsahuje bibliografické odkazy
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

14626. Veľké zjednotenie, nezachovanie leptónového náboja/arómy a štruktúra jadra

Creator:
Šimkovic, F., Domin, P., and Šmotlák, M.
Format:
print, bez média, and svazek
Type:
model:article and TEXT
Subject:
Univerzita Komenského v Bratislave., Fakulta matematiky, fyziky a informatiky, jaderná fyzika, fyzika elementárních částic, leptony, nuclear physics, elementary particle physics, leptons, Slovensko, Slovakia, 6, and 53
Language:
Czech
Description:
F. Šimkovic, P. Domin, M. Šmotlák.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

14628. Velmi přesné obrábění ocelových slitin s minimální teplotní roztažností pomocí SPDT

Creator:
Doleček, Roman, Lédl, Vít, and Psota, Pavel
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
SPDT, ultrasonic assisted machining process, ultra precision turning, diamond turning, invar, velmi přesné obrábění, diamantové obrábění, and ultrazvuková asistence
Language:
Czech
Description:
This paper presents the single point diamond turning (SPDT) technology combined with an ultrasound-assisted machining process. The connection of both technologies allows ultra precision machining of steel alloy, reaching optical surface quality without the necessity of post polishing. The paper outlines results achieved by machining of different steel alloys with low thermal expansion. and Tento článek pojednává o možnostech a výsledcích aplikace technologie single point diamond turning (SPDT) kombinované s ultrazvukovou asistencí při obrábění materiálů invar a superinvar. Kombinace SPDT s ultrazvukovou asistencí umožňuje dosažení optické kvality povrchu bez nutnosti následného leštění při velmi přesném obrábění kovových materiálů s vysokým podílem železa. Vysoce hladké povrchy nejsou standardní technologií SPDT dosažitelné např. u ocelí, především proto, že dochází k velké chemické interakci diamantového nástroje a uhlíku obsaženého v oceli. Materiály invar a superinvar svým nízkým koeficientem teplotní roztažnosti a velkou tepelnou vodivostí jsou ideálními kandidáty pro realizaci metrologických referenčních povrchů, což byla i hlavní motivace pro provedení výzkumu jejich obrobitelnosti. V článku jsou prezentovány výsledky, které byly dosaženy při obrábění invaru a superinvaru technologií SPDT s ultrazvukovou asistencí.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

14629. Velmi velký dalekohled

Creator:
Kulhánek, Petr and Rozehnal, Jakub
Format:
print, bez média, and svazek
Type:
model:article and TEXT
Subject:
European Southern Observatory, astronomie, interferometrie, dalekohledy, astronomy, interferometry, telescopes, 6, and 53
Language:
Czech
Description:
Very Large Telescope (VLT) je zcela výjimečným dalekohledem postaveným organizací ESO na jižní polokouli v Atacamské poušti v chilských Andách ve výšce 2635 metrů. Jde o čtyři dalekohledy o průměru 8,2 metru, které v kombinovaném režimu odpovídají jednomu přístroji o průměru zrcadla 16 metrů. Do budoucna se plánuje ještě interferometrické propojení (VLTI - Very Large Telescope Interferometer) se základnou 200 metrů. Naše expedice PARACHI 2003 měla možnost VLT navštívit a vidět na vlastní oči současný stav tohoto astronomicky mimořádně cenného přístroje. and Petr Kulhánek, Jakub Rozehnal.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

14630. Velocity of body lean evoked by leg muscle vibration potentiate the effects of vestibular stimulation on posture

Creator:
Dzurková, O. and František Hlavačka
Format:
print, bez média, and svazek
Type:
article, články, model:article, and TEXT
Subject:
Fyziologie člověka a srovnávací fyziologie, fyziologie, vestibulární ústrojí, držení těla, physiology, vestibular apparatus, posture, postural control, muscle vibration, sensory interaction, 14, and 612
Language:
English
Description:
To investigate the vestibular and somatosensory interaction in human postural control, a galvanic vestibular stimulation of cosine bell shape resulting in a small forward or backward body lean was paired with three vibrations of both soleus muscles. The induced body lean was registered by the position of the center of foot pressure (CoP). During a quiet stance with eyes closed the vibration of both soleus muscles with frequency (of) 40 Hz, 60 Hz and 80 Hz resulted in the body lean backward with velocities related to the vibration frequencies. The vestibular galvanic stimulation with the head turned to the right caused forward or backward modification of CoP backward response to the soleus muscles vibration and peaked at 1.5-2 s following the onset of the vibration. The effect of the paired stimulation was larger than the summation of the vestibular stimulation during the quiet stance and a leg muscle vibration alone. The enhancement of the galvanic stimulation was related to the velocity of body lean induced by the leg muscle vibration. The galvanic vestibular stimulation during a faster body movement had larger effects than during a slow body lean or the quiet stance. The results suggest that velocity of a body postural movement or incoming proprioceptive signal from postural muscles potentiate the effects of simultaneous vestibular stimulations on posture., O. Dzurková, F. Hlavačka., and Obsahuje bibliografii a bibliografické odkazy
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

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