1,721,029 research outputs found
강자장 저차원계의 전자 상관 효과에 대한 이론연구
No full text학위논문(박사) - 한국과학기술원 : 물리학과, 1998.8, [ vii, 59 p. ]We investigate theoretically the physical properties of the low dimensional system for zero-dimensional quantum dot, one-diemnsional quantum Hall edge states, and two-dimensional quantum Hall system especially for the systems at high magnetic fields. In the low dimensional system where the electron-electron interactions are significant, careful theoretical studies are needed for understanding the phenomena which can not be explained in independent-electron models. For the zero-dimensional quantum dot system, through a calculational method developed by us, we investigate the effects of electron correlations on the ground state energy and the chemical potential of a droplet confined by a parabolic potential at high magnetic fields. We demonstrate the importance of correlations in estimating the transition field at which the first edge reconstruction of the maximum density droplet occurs in the spin polarized regime. The spectral weight matrix for quantum dot is also calculated and we find that electron tunneling is strongly spin-related due to electron correlation. Our calculational results are in good agreement with the experiments.
For one-dimensional quantum Hall edge states, we investigate the effect of contact hyperfine interaction at the edge of the filling factor ν=2. We find that the contact interaction breaks the U(1) symmetry in the system, so that the compact ground state at ν=2 can be unstable. Due to the electron-electron interactions, there is spontaneous spin polarization at the edge of ν=2. The contact hyperfine interactions can be divided into two parts, static and dynamical parts. The size of the spin-polarized region can be enhanced by the static part of contact interactions, which is an Overhauser effect. The dynamical part of contact interaction is relatively small compared to other interactions and it reduces the size of spin-polarized region.
For the two-dimensional quantum Hall system, we study charged spin texture (skyrmion) which have ...한국과학기술원 : 물리학과
Fractional quantum hall 영역에 있는 이차원 양자점에서의 전자 상호작용에 관한 연구
No full text학위논문(석사) - 한국과학기술원 : 물리학과, 1995.2, [ 26 p. ]We examine the effect of electron-electron interactions on the ground state property of a two-dimensional quantum dot in the fractional quantum Hall regime. For quantum dots containing up to six electrons at filling factors between 1 and , the many-body wave functions are made of the lowest Landau levels and the higher Landau levels are effectively included by a Jastrow factor. We find that some bumps observed in Single Electron Capacitance Spectroscopy (SECS) experiments are related to the chemical potential discontinuity, , which was shown in the fractional quantum Hall system. We find the precursor of the incompressibility at a filling factor , which is responsible for the fractional quantum Hall effect. A quasi-hole creation results in the phase transition from the state to the state. The effect of a quasi-hole creation on compressibility is also discussed. In order to avoid the problem with the tunneling rate decrease in SECS experiments, which makes the quasi-hole creation hardly detectable, we suggest that weaker confining potentials are important.한국과학기술원 : 물리학과
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Variations on the Author
Get PDF“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
Get PDFWe 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
Get PDFWe 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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