1,722,242 research outputs found
SIS 죠셉슨 접합을 위한 Al이 도핑된 박막에 관한 연구
No full text학위논문(박사) - 한국과학기술원 : 재료공학과, 2002.2, [ viii, 112 p. ]I have vacuum-deposited c-axis and (110) oriented thin films on (001) and (110) substrates by rf-sputtering and Pulsed Laser Deposition (PLD). The initial growth stage in PLD process was studied by Atomic Force Microscopy (AFM) method. The oxygen partial pressure and thickness effect on thin film surface and property also has been studied. The surface smoothness and crystallinity decreased as thin film thickness increases. Thickness and stoichiometry distribution of the thin films were studied by Rutherford Backscattering Spectrometry (RBS) measurement. From the temperature dependence of electrical resistivities for both the target and the films, we found that the electrical conduction was mainly through the variable range phonon-assisted hopping mechanism. This suggests that Al-doping in this material has given rise to extensive impurity states in the band gap, which, in turn, localized the charge carriers, especially at lower temperatures. The resistivity of the doped (PBCO) is much higher than the pure PBCO, ranged from ~1 Ω -cm at room temperature to about five orders of magnitudes higher at ~30 K. The electronic structure of the samples was studied through measuring the optical absorption coefficients vs. photon energy from which the band gap and defect state energies were inferred. Soft x-ray emission spectra obtained for pure and Al-doped PBCO thin films show shift in Cu Lα peak position and change in Cu Lα / intensity ratio upon doping. This indicates the change of Cu-O bonding due to the partial Al substitution. In addition, Raman spectra from the Al-doped PBCO thin films exhibit an additional peak near the apical oxygen peak, a result suggestive of the broken symmetry of the Cu-O chains caused by the partial replacement of Cu-atoms with the Al on the Cu-O chains. C-axis oriented YBCO films are very common but not well suited for the fabrication of sandwich-type superconductor-no...한국과학기술원 : 재료공학과
화학적 방법에 의한 단분산 구형의 세라믹스 분말 합성
No full text최근 산업의 고도화 및 첨단화가 급속히 진행됨에 따라 그에 사용되는 세라믹 재료 역시 고기능화를 탈성하기 위하여 과거에 비해 훨씬 엄밀한 제어， 고성능화의 필연성을 해결하지 않으면 않되게 되었다. 따라서 출발물질로써 특성이 고도로 제어된 세라믹 분말이 요구되게 되었다. 일반적으로 세라믹을 제조시 나타나는 낮은 신뢰도와 재현성은 설제 사용시 문제점으후 지적되어 왔으며， 이는 원료분말의 특성과 성형체의 충전상태에 의해 크게 영향을 받는다. 최근에는 응집이 없고 업도분포가 좁으며 구형인 분말이 세라믹스의 소결 및 성형에 이상척이라는것이 공통된 인식이다. 따라서 이러한 요구조건을 만족시키는 분말을 제조하기 위한 연구가 활발히 진행되고 있다.
기존의 고상법에 의하여 제조된 분말은 업자의 업경이 크고， 업도 분포가 넓으며， 불규칙한 행상을 가지며， 화학적 조성이 균일하지 못하고 또한 순도도 낮다. 이러한 문제점을 해결하기 위하여 액상볍 및 기상법을 이용하여 분말의 형상 및 크기를 제어할 수 었는 새로운 분말 제조법의 개발이 주된 과제가 되였다. 이중 액상법은 액상에서 얼어나는 화학반응을 통하여 분말을 제조하는 방법으로서 기상법에 비해 대량생산이 용이하기 때문에 상업적으로도 활발히 응용되고 있다. 액상법에 의한 단분산 구형 Zr02. Ti02 분말의 기존 연구 방향을 살펴보면， 주로 알콕사이드를 출발물질로 한비수성계의 졸-겔법이 가장 많이 연구되었으며， 비교적 성공적인 결과를 보이고 였으나， 반응조건이 까다롭고 출발물질이 고가이기 때문에 실제 응용에 큰 제약이 되고 있다. Barringer와 Bowen은 얄코올 용액에서 타이타늄 얄콕사이드를 가수분해시킴으로써 단분산 구형의 Ti02 분말을 얻을 수 있었다. 그러나 이 방법은 재현성이 떨어진다는 것이 몇몇 다른 연구자틀에 의하여 보고되었으며，분말의 형상은 용매의 성질에 영향을 받는 것으로 알려졌다. Ogihara 등은 졸-겔법을 이용하여 지르코늄 부톡사이드(zirconium butoxide)로 부터 단분산 구형의 Zr02 분말을 성공적으로 제조하였다. 분말의 특성은 알콕사이드의 농도 및 물과 알코올의 비에 만감한 것으로 알려져 있으며， 단분산의 분말을 얻기 위해서는 알콕사이드의 농도가 0.1 M 이하이어야 한다
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
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
DS_DISC767843 – Supplemental material for The Development of a Biotinylated NAD<sup>+</sup>-Applied Human Poly(ADP-Ribose) Polymerase 3 (PARP3) Enzymatic Assay
No full textSupplemental material, DS_DISC767843 for The Development of a Biotinylated NAD+-Applied Human Poly(ADP-Ribose) Polymerase 3 (PARP3) Enzymatic Assay by Ming Ji, Liyuan Wang, Nina Xue, Fangfang Lai, Sen Zhang, Jing Jin and Xiaoguang Chen in SLAS Discovery</p
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
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