1,720,990 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
Rapid and low-cost entropic coefficient measurement technique based on harmonic-dual-frequency electrothermal impedance spectroscopy
No full textThe rapid expansion of the global battery market, fueled by the rise of electric vehicles and energy storage systems, necessitates efficient battery recycling and repurposing to foster a sustainable circular economy. This paper presents an innovative, cost-effective, and rapid method for measuring the entropic coefficient of batteries using harmonic-dual-frequency electrothermal impedance spectroscopy. Unlike conventional methods requiring complex and costly setups, our technique utilizes a simple battery cycler, enhancing accessibility and ease of implementation. The proposed method surpasses current state-of-the-art techniques in speed, cost- efficiency, and simplicity without sacrificing accuracy. It facilitates precise entropymetry, which is essential for understanding battery electrode degradation. Additionally, this method holds notable promise for integration into existing sorting lines in recycling plants, potentially resolving current sorting challenges and significantly reducing recycling costs. This could lower production expenses, making batteries more affordable and aligning with circular economy principles by promoting material reuse and waste reduction. This novel method has the potential to transform battery diagnostics and recycling, offering substantial economic and environmental benefits. Future research will aim to refine this technique further and explore its broader adoption within the industry.
Topographical and crystalline change on surface by sandblasting improve flexural and shear bond strength of niobia-modified yttria-stabilized tetragonal zirconia polycrystal
No full textThis study aimed to investigate the effects of sandblasting on the physical properties and bond strength of two types of translucent zirconia: niobium-oxide-containing yttria-stabilized tetragonal zirconia polycrystals ((Y, Nb)-TZP) and 5 mol% yttria-partially stabilized zirconia (5Y-PSZ). Fully sintered disc specimens were either sandblasted with 125 μm alumina particles or left as-sintered. Surface roughness, crystal phase compositions, and surface morphology were explored. Biaxial flexural strength (n=10) and shear bond strength (SBS) (n=12) were evaluated, including thermocycling conditions. Results indicated a decrease in flexural strength of 5Y-PSZ from 601 to 303 MPa upon sandblasting, while (Y, Nb)-TZP improved from 458 to 544 MPa. Both materials significantly increased SBS after sandblasting (p<0.001). After thermocycling, (Y, Nb)-TZP maintained superior SBS (14.3 MPa) compared to 5Y-PSZ (11.3 MPa) (p<0.001). The study concludes that (Y, Nb)-TZP is preferable for sandblasting applications, particularly for achieving durable bonding without compromising flexural strength.N
Analgesic effects of ketorolac on renal colic according to the grade of ureteral obstruction
No full text의학과/석사[한글]
요로 결석은 요로를 자극하여 손상을 입히거나 요로 수축을 일으킨다. 결과적으로 요로의 부분 혹은 완전 폐색이 발생할 수 있다. 요로 폐색은 폐색 부위 상부에서 요로와 신장 피막의 팽창을 일으킨다. 이로 인해 발생하는 요로 결석 환자의 증상은 갑자기 시작되는 한쪽 옆구리의 매우 심한 통증과, 같은 쪽 샅고랑 부위의 방사통이다. Ketorolac은 비스테로이드성 진통소염제로 동물 실험에서 요로 폐색으로 인해 증가한 요로의 압력을 떨어뜨리고, 요로 결석 환자의 통증 조절에 있어 아편유사약물과 비슷하거나 더 좋은 결과를 보인다. 그러나 ketorolac의 투여만으로는 통증 조절이 되지 않아 아편유사약물의 추가 투여가 필요한 경우가 있다. 이에 연구자는 ketorolac만으로 통증 조절이 되지 않는 경우가 요로 폐색 정도와 연관이 있을 것이라는 생각으로 요로 결석 환자에게 ketorolac을 투여하여 요로 폐색 정도에 따라 진통 효과에 차이가 있는지, 실제 요로 폐색에 어떤 영향을 미치는지, 그리고 그 영향이 진통 효과와 연관이 있는지 알아보았다.2006년 11월 1일부터 2007년 3월 15일까지 서울에 있는 3차 병원 응급의료센터 2곳과 경기도 파주시에 있는 2차 병원 응급실 1곳에서 갑자기 발생한 옆구리 통증을 호소하며 내원한 환자 가운데 요로 결석이 확진된 76명을 대상으로 전향적 관찰 연구를 시행하였다. 내원 시 시각아날로그척도를 이용하여 통증 정도를, 초음파를 이용하여 수신증 정도를 조사한 후 바로 ketorolac(0.5 mg/Kg 혹은 1.0 mg/Kg)을 투여하고 30분 후에도 같은 항목을 조사 하였다. 수신증 정도는 0, I, II, III으로 구분하였다. 수신증 정도에 따라 나눈 군들 사이에서 시각아날로그척도 변화에는 차이가 없었다. 또한 수신증 정도의 변화와 통증의 감소와도 연관이 없었고, 증세 발현 기간과 시각아날로그척도 변화와도 연관이 낮았다. 이는 ketorolac의 진통효과가 요로 폐색 정도와 상관없다고 해석할 수 있으나 요로 폐색 정도와 수신증 정도의 비례 관계가 명확하지 않은 제한점이 있다. 그러므로 앞으로 요로 폐색과 수신증이 비례하는지에 대한 연구가 필요하다.
[영문]
Ureter stone causes a ureteral injury or a spasm. Consequently, a ureteral obstruction may occur. A ureteral obstruction distends the ureter and the renal capsule, which cause acute, colicky flank pain radiating to the groin. Prostagladins cause a ureter spasm, increase renal blood flow and renal pelvis pressure. As a nonsteroidal anti-inflammatory drug(NSAID), ketorolac inhibits prostaglandin synthesis which is occured during the ureteral obstruction in the renal medulla. However, analgesic effects of ketorolac in ureter stone patients are different ,case by case. The purpose of this study is to investigate analgesic effects of ketorolac on renal colic by the grade of ureteral obstruction.During the 5 months, we conducted a prospective observational study of 76 ureter stone patients in the ER diagnosed by intravenous pyelogram. We compared visual analog scale(VAS) and vital signs by the hydronephrosis grade on ER visit and after 30 minutes of ketorolac administration.Thirty minutes after the ketorolac treatment, VAS was reduced 8.2 to 3.6 and vital signs were also stabilized. There were no differences, however, in VAS and vital signs among the groups of hydronephrosis. There was no relationship between changes in hydronephrosis and changes in VAS. Therefore, we asummed there were no differences in analgesic effects of ketorolac on renal colic by the grade of ureteral obstruction. However, we need further study on the relationship among ureter pressure, pain intensity, and hydronephrosis due to the limitation of this study.ope
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
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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