1,720,977 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
シリコンエピタキシャル成長に関わる輸送現象と表面化学反応
Full text linkTransport phenomena, surface chemical processes, dopant concentration profiles and surface roughness of substrate for silicon epitaxial growth are discussed theoretically and experimentally. The objective of this thesis is to develop the models to predict various phenomena relating to the silicon epitaxial wafer. The major part of discussion is based on the calculations of the transport phenomena and the chemical reactions at the surface. At first, the transport phenomena in a pancake reactor and in a single-wafer horizontal reactor are discussed. Secondary, the substrate rotation and the chemical reactions for the epitaxial growth are discussed to describe the growth rate and the film thickness. For further studies, the epitaxial wafer's qualities, the dopant distribution and the surface roughness of silicon substrate, are investigated.
The transport phenomena in a pancake reactor are discussed based on a gas flow visualization technique using a high-sensitivity analogue camera, and numerical calculations. At room temperature and the epitaxial growth temperature of 1423 K, a large recirculation exists in the reactor chamber, in which the gases near the susceptor flow from the outside toward the center of the susceptor. The profile of the epitaxial film growth rate observed agrees qualitatively with that predicted by visualization and calculations.
An evaluation of silicon epitaxial thin-film growth using the SiHCl3-H2 system in a single-wafer horizontal reactor is discussed by solving the transport equations for gas velocity, temperature and concentration of chemical species taking into account of the dependence of gas properties on temperature and composition, assuming a simple Arrhenius-type expression for the chemical reaction of SiHCl3 and H2 on a substrate. Non-Linear increase in the growth rate due to changes in thermal diffusion and diffusion is found to become significant as the SiHCl3 concentration in the reactor increases.
For an enhancement of studies, the effect of substrate rotation on transport of reactive gases and epitaxial growth rate is investigated for a single-wafer horizontal reactor using a model and experiments. The rotating substrate causes a circulating gas flow region above itself, in which an asymmetric and nonuniform SiHCl3 distribution is formed by thermal diffusion and species consumption due to the surface chemical reaction, even when the growth rate profile on the substrate surface is nearly uniform. The good uniformity in the film thickness observed in calculation and measurement is mainly attributed to the averaging effect by integrating the local growth rate along a concentric circle on the substrate surface, and partially by the species concentration distribution change, both of which are caused by the rotating motion of the substrate.
For the discussion of the dependence of the epitaxial growth rate on the source species concentrations, a transport and epitaxy model following Eley-Rideal to describe silicon epitaxial film growth in an SiHCl3-H2 system is developed by numerical calculations and comparison with experiments. The state of the surface during the epitaxial growth is also discussed considering the intermediate species, elementary reactions and rate limiting processes.
The boron concentration profile in silicon epitaxial films grown on a p-type substrate under atmospheric pressure is investigated in two types of epitaxial reactors, a single-wafer horizontal reactor and a pancake reactor. It is concluded thst large amounts of recirculation of gas in an epitaxial reactor should be avoided to obtain an abrupt boron concentration profile.
Since silicon surface after the epitaxial growth must be very smooth and fiat, surface roughness of a silicon wafer heated at 800-1100 °C under atmospheric pressure in hydrogen ambient is studied. AFM images show that the surface heated at 900°C has many small pits which are formed due to the difference in the chemical reaction rates between hydrogen-silicon and hydrogen-silicon dioxide. The behavior of surface roughness with pressure and heating time agrees well with that predicted by the pit formation model in this study.論文目録
Abstract / p2
CONTENTS / p5
Chapter1 Introduction / p1
1.1 Background / p2
1.2 Scope of this thesis / p15
References / p17
Chapter2 Gas Flow and Heat Transfer in a Pancake Reactor / p23
2.1 Introduction / p24
2.2 Gas flow visualization / p24
2.3. Basic equations governing the epitaxial reactor / p28
2.4 Results and discussion / p31
2.5 Conclusions / p37
Nomenclature / p39
References / p40
Chapter3 Numerical Evaluation of Silicon Thin-film growth from SiHCl₃-H₂ Gas Mixture in a Single-Wafer Horizontal Reactor / p41
3.1 Introduction / p42
3.2 Preparation of epitaxial silicon thin-film / p42
3.3 Results and discussion / p48
3.4 Conclusions / p60
Nomenclature / p61
References / p63
Chapter4 Modeling of Epitaxial Silicon Thin-Film Growth on a Rotating Substrate in a Single-Wafer Horizontal Reactor / p65
4.1 Introduction / p66
4.2 Silicon epitaxial thin-film growth process / p66
4.3 Results and discussion / p74
4.4 Conclusions / p84
Nomenclature / p85
References / p87
Chapter5 Model on Transport phenomena and Silicon Epitaxial Growth of Thin-Film in SiHCl₃H₂ System under Atmospheric Pressure / p89
5.1 Introduction / p90
5.2 Preparation of silicon epitaxial thin-films / p90
5.3 Basic equations governing the epitaxial reactor / p91
5.4 Mathematical model of the rate process / p95
5.5 Reasults and discussion / p102
5.6 Summary / p111
Nomenclature / p112
References / p114
Chapter6 Effect of Transport Phenomena on Boron Concentration Pro-files in Silicon Epitaxial Wafers / p117
6.1 Introduction / p118
6.2 Basic equation for solid-state diffusion / p118
6.3 Preparation of epitaxial silicon thin-film / p121
6.4 Analysis of gas flow / p122
6.5 Results and discussion / p123
6.6 Conclusions / p130
References / p131
Chapter7 Roughness of Silicon Surface Heated in Hydrogen Ambient / p133
7.1 Introduction / p134
7.2 Experimental / p134
7.3 Results and discussion / p136
7.4 Conclusions / p149
References / p150
Summary and Conclusions / p153広島大学(Hiroshima University)博士(工学)Engineeringdoctora
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
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
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
- …
