1,721,202 research outputs found
Cho, Jun-Ho
No full text학위논문(석사)--아주대학교 일반대학원 일반대학원 :산업공학과,2007. 8주성분분석을 이용한 Hotelling T² 관리도는 지금껏 다변량 공정 모니터링으로 가장 널리 사용되어왔다. 그러나 최근 독립성분분석이라는 기법이 제안되고, 이를 이용한 공정 모니터링이 나오면서 PCA를 이용한 공정 모니터링을 대체하고 있다. 하지만 아직 두 공정 모니터링을 체계적으로 비교 분석하여 성능을 비교한 연구는 이루어지지 않았다.
본 연구에서는 공정 데이터를 생성하여 여러 상황을 설정한 후 각상황 하에서 어떤 공정 모니터링이 더 나은 성능을 보이는지 모의실험을 통해 비교, 분석한다.
본 연구에서 사용한 데이터는 실제 공정 데이터와 비슷한 다변량 자기상관이 존재하는 데이터와 이론적으로 많이 사용되는 다변량 정규분포를 따르는 데이터를 생성한다. 각 데이터는 2단계로 이루어진 공정 데이터로 3개의 원인 변수와 2개의 결과 변수로 이루어진다.
각 공정 변수에 이상 상황을 가정하여 2종 과오를 측정한다. 각 상황은 1)모든 변수가 변하였을 때, 2)변수 일부가 변하였을 때, 3)데이터에 갑자기 이상치가 주어졌을 때, 4)데이터의 분산이 변하였을 때 이렇게 4가지의 이상상황을 가정한다. 각 상황의 공정 변화는 3수준으로 10회 반복하여 각 데이터마다 총 120회 실험을 실시한다.
1종 과오의 경우 PCA가 약간 좋은 결과를 보였다. 2종 과오의 경우 변수 일부가 변하였을 때에는 ICA가 모델에 관계없이 좋은 성능을 보였고 모든 변수가 변하였을 때와 산포가 변화했을 때에는 AR모델에서는 ICA가 약가 좋은 성능을 보였고 정규분포에서는 PCA가 좋은 성능을 보였다. 이상치가 주어졌을 경우는 AR모델은 PCA, 정규분포는 ICA가 좋은 성능을 보였다.제1장 서론 = 1
1.1 연구의 목적 및 배경 = 1
1.2 기존 연구 고찰 = 2
1.3 연구 범위 및 내용 = 3
1.4 연구의 구성 = 4
제2장 PCA를 이용한 다변량 공정 모니터링 = 5
2.1 T² 관리도 = 5
2.2 PCA를 이용한 다변량 공정 모니터링 = 10
제3장 ICA를 이용한 다변량 공정 모니터링 = 15
3.1 독립성분분석 = 15
3.1.1 개요 = 16
3.1.2 ICA의 기본원리 = 17
3.1.3 비정규성 척도 = 19
3.1.4 Centering & Whitening = 20
3.1.5 Fast ICA = 21
3.2 ICA를 이용한 다변량 공정 모니터링 = 22
제4장 모의실험 = 25
4.1 데이터 생성 = 25
4.1.1 VAR(Vector Autoregressive) 가정 = 25
4.1.2 다변량 정규분포 가정 = 26
4.2 성능비교 = 28
4.2.1 제 1종 과오 = 28
4.2.2 제 2종 과오 = 30
4.3 모의실험 결과 = 35
4.3.1 모의실험 결과 비교 분석 = 35
4.3.2 ICA, PCA의 정성적 비교 = 47
제5장 결과 및 향후 연구과제 = 49
참고문헌 = 51
Abstract = 56MasterThe objective of this research is to compare and analyze performance of PCA and ICA process monitoring techniques. Formerly, Hotelling's T2 control chart based on PCA has been used for multivariate statistical process monitoring. Recently, ICA based monitoring is introduced for process control monitoring, especially for chemical processes. However, there have been no researches conducted to compare the performance of PCA and ICA process monitoring.
In this research, simulation is carried out to generate process data and analyze the behaviors of two monitoring techniques. Two different cases are considered: in first case, data are generated by AR model and in second case, by multivariate normal distribution. The process is assumed to have three input (control) variables and two output characteristics. To find out type II error in the given process, four out-of-control cases are considered: a) all variables are changed b) some variables are changed c) sudden change in data, and d) change in variance.
The results are obtained after ten simulation test in the range of three degrees: small change, standard change, and huge change. Which shows performance of ICA is better than PCA in both AR and normal model, in case a). Similarly, in case b) and d) ICA little outperform PCA in AR model, whereas, PCA is better than ICA in normal model. As in case (c), ICA is more preferable to PCA in normal model; however, PCA is superior to ICA in AR model
Study on the 3-dimensional metallic photonic crystal
No full text학위논문(석사) - 한국과학기술원 : 물리학과, 2005.2, [ v, 27 p. ]광자 결정에서 큰 폭의 밴드갭을 얻기 위해서 금속을 이용한 광자 결정에 많은 연구가 이루어 지고 있다. 그 중 3차원의금속 광자 결정은 제작상의 어려움이 존재하여 이론적인 연구가 함께 진행되고 있다. 본 논문에서는 3차원 금속 광자 결정의 광학적인 특성을 연구하기 위해서 KKR방법을 이용하여 전자기파의 진행 특성을 계산하였다. 이 때 2차원 주기적인 구조에서 표면모드가 발생되는 것을 알아보았다. 그리고 표면모드에 의한 투과율 특성이 3차원적으로 배열된 구조에서 어떠한 영향을 미치는 보고 3차원 구조에서의 전자기파의 진행 특성을 살펴보았다.한국과학기술원 : 물리학과
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
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
Comprehensive Genome-Wide Approaches to Activity-Dependent Translational Control in Neurons
Full text linkActivity-dependent regulation of gene expression is critical in experience-mediated changes in the brain. Although less appreciated than transcriptional control, translational control is a crucial regulatory step of activity-mediated gene expression in physiological and pathological conditions. In the first part of this review, we overview evidence demonstrating the importance of translational controls under the context of synaptic plasticity as well as learning and memory. Then, molecular mechanisms underlying the translational control, including post-translational modifications of translation factors, mTOR signaling pathway, and local translation, are explored. We also summarize how activity-dependent translational regulation is associated with neurodevelopmental and psychiatric disorders, such as autism spectrum disorder and depression. In the second part, we highlight how recent application of high-throughput sequencing techniques has added insight into genome-wide studies on translational regulation of neuronal genes. Sequencing-based strategies to identify molecular signatures of the active neuronal population responding to a specific stimulus are discussed. Overall, this review aims to highlight the implication of translational control for neuronal gene regulation and functions of the brain and to suggest prospects provided by the leading-edge techniques to study yet-unappreciated translational regulation in the nervous system
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
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