1,721,949 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Study of pi+pi-, K+K-, ppbar and pi+pi+pi-pi- production in central exclusive processes with the STAR detector at RHIC
Full text linkTato práce se zabývá prvním měřením centrální exkluzivní produkce v proton-protonových srážkách při energii sqrt s = 510 GeV naměřených na experimentu STAR. Při této energie dominuje dvojitá výměna pomeronů. Z toho důvodu jsou tyto srážky velmi slibné pro hledání vázaných stavů gluonů, glueballů. Experimentální potvrzení jejich existence by silně podpořilo platnost kvantové chromodynamiky. Difrakčně rozptýlené protony pohybující se neporušeny uvnitř svazkové trubice byly změřeny pomocí detektorů Roman Pot, což umožnilo plnou kontrolu nad kinematikou interakce a tedy ověření exkluzivity. První výsledky ve formě distribuce invariantní hmotnosti centrálně produkovaných pi+pi-, K+K− a ppbar párů jsou prezentovány v této práci.This thesis is dedicated to the first measurement of the central exclusive production process in proton-proton collisions at RHIC with the STAR detector at sqrt s = 510 GeV. At this energy, this process is dominated by a Double Pomeron Exchange mechanism. Therefore, it is very promising for the search of gluon bound states, glueballs. The experimental confirmation of their existence would be yet another strong support for the validity of the quantum chromodynamics theory. The diffractively scattered protons, moving intact inside the RHIC beam pipe after the collision, were measured in the Roman Pots system allowing full control of the interaction’s kinematics, and thus verification of the exclusivity. The preliminary results on the invariant mass distributions of centrally exclusively produced pi+pi−, K+K− and ppbar pairs measured within the STAR acceptance are presented in this thesis
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Calibration of Straw detector for studies of DVCS process at COMPASS experiment
No full textCOMPASS je terčíkový experiment, který používá urychlené protony z SPS urychlovače v CERNu k produkci mionového, pionového a elektronového svazku. Fyzikální program COMPASSu je zameren na výzkum struktury hadronu a hadronovou spektroskopii. Pro studium obecných partonových distribucí prostrednictvím hluboce virtuálního Comptonova rozptylu (DVCS) je zapotrebí ruzných detektoru, jež se rozprostírají na délce padesáti metru. Jedním z nich je dráhový detektor Straw 3 sestávající z mnoha driftových komor. Detektor Straw je hlavním predmetem této práce. Kalibrace jeho RT závislosti pro data z roku 2016 byla overena. Dále byla na základe dat z roku 2016 provedena analýza kinematických velicin, které hrají významnou roli pri studiu DVCS událostí a následné analýze obecných partonových distribucí.COMPASS is a fixed target experiment which uses protons from the CERN SPS accelerator for production of muon, pion or either electron beam. Its physical program is focused on hadron structure and hadron spectroscopy. To study the Generalized Parton Distributions (GPDs) via measurements of Deeply Virtual Compton Scattering (DVCS), various detectors at length of more than fifty meters are needed. One of them is tracking detector Straw 3 consisting of straw drift chambers. This thesis is mainly focused on the Straw detector. The verification of its calibration of RT relation for the 2016 data was done. Additionally, the thesis deals with analysis of kinematic variables, based on 2016 data, which are important for studies of DVCS events an subsequent GPD analysis
Meson production at the COMPASS experiment, calibration of the Straw detector
Full text linkTato práce se zabývá terčovým experimentem COMPASS, který je součástí CERN (Evropské organizace pro jaderný výzkum). Fyzikální program experimentu COMPASS je zaměřen na výzkum struktury hadronů a hadronovou spektroskopii. Pro tento účel jsou studovány výlučné procesy, jako jsou např. mezonové produkce a hluboce virtuální Comptonův rozptyl. Ty lze měřit pomocí rozsáhlého spektrometru tvořeného mnoha detektory. Jedním z nich je detektor Straw skládající se z trubičkových driftových komor. Kalibrace jeho RT závislosti pro rok 2021 byla ověřena pomocí dat z roku 2018. Dále byl proveden výpočet z měření survey z roku 2021, který slouží určení polohy detektoru, což je základní požadavek pro úspěšnou kalibraci a co nejvyšší účinnost při dráhové rekonstrukci.This thesis deals with the target experiment COMPASS, which is a part of CERN (European Organization for Nuclear Research). The physics program of the COMPASS experiment is focused on the research of the hadrons structure and hadrons spectroscopy. For this purpose, exclusive processes such as productions of mesons and deeply virtual Compton scattering are studied. These processes can be measured using an extensive spectrometer consisting of many detectors. One of them is the detector Straw composed of tube drift chambers. The calibration of its RT relation for the year 2021 was verified using the data from the 2018 run. Furthermore, a calculation from the 2021 survey measurement was performed. It serves to determine the position of the detector, which is essential for successful calibration and for high efficiency of the chamber in track reconstruction
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Analysis of the Exclusive Omega Meson Muoproduction at COMPASS experiment
Full text linkTato diplomová práce se zabývá exkluzivní produkcí omega mezonu na základě dat z experimentu COMPASS, který je součástí výzkumného střediska CERN (Evropské organizace pro jaderný výzkum). Práce se zaměřuje na exkluzivní produkci omega mezonu při interakci mionového svazku s nepolarizovaným kapalným vodíkovým terčíkem, selekci odpovídajících událostí z dat z roku 2016 a vykreslení kinematických proměnných a invariantních hmotností z vybraných událostí. Tyto výsledky jsou následně porovnány s Monte Carlo simulacemi. Dále se práce věnuje účinnému průřezu tohoto procesu, určení pozadí exkluzivní omega produkce a extrakci Spin Density Matrix Elements (SDMEs), přičemž zdůrazňuje jejich význam pro pochopení dynamiky reakce a podrobně popisuje jejich experimentální určení.This diploma thesis investigates exclusive production of omega meson using data from the COMPASS experiment, which is a part of CERN (European Organization for Nuclear Research). The study focuses on the exclusive omega production for the interaction of muon beam on unpolarized liquid hydrogen target, selection of the corresponding events for 2016 data, and plots of kinematic variables and invariant masses from selected events. The results are afterwards compared to Monte Carlo simulations. Additionally, the thesis explores the cross section of the production process, background of the exclusive omega production and the extraction of Spin Density Matrix Elements (SDMEs), emphasizing their importance in understanding the reaction dynamics and detailing their experimental determination
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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