• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 1993년도 Fifth International Fuzzy Systems Association World Congress 93
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• pp.857-860
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• 1993

In this paper, we apply the self generating neuro fuzzy model (SGNFM) to the dimension analysis of the chaotic time series. Firstly, we formulate a nonlinear time series identification problem with nonlinear autoregressive (NARMAX) model. Secondly, we propose an identification algorithm using SGNFM. We apply this method to the estimation of embedding dimension for chaotic time series, since the embedding dimension plays an essential role for the identification and the prediction of chaotic time series. In this estimation method, identification problems with gradually increasing embedding dimension are solved, and the identified result is used for computing correlation coefficients between the predicted time series and the observed one. We apply this method to the dimension estimation of a chaotic pulsation in a finger's capillary vessels.

• Communications for Statistical Applications and Methods
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• 제29권6호
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• pp.721-733
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• 2022

In this paper we compare parameter estimation by Grassmann manifold optimization and sequential candidate set algorithm in a structured principal fitted component (PFC) model. The structured PFC model extends the form of the covariance matrix of a random error to relieve the limits that occur due to too simple form of the matrix. However, unlike other PFC models, structured PFC model does not have a closed form for parameter estimation in dimension reduction which signals the need of numerical computation. The numerical computation can be done through Grassmann manifold optimization and sequential candidate set algorithm. We conducted numerical studies to compare the two methods by computing the results of sequential dimension testing and trace correlation values where we can compare the performance in determining dimension and estimating the basis. We could conclude that Grassmann manifold optimization outperforms sequential candidate set algorithm in dimension determination, while sequential candidate set algorithm is better in basis estimation when conducting dimension reduction. We also applied the methods in real data which derived the same result.

• 대한수학회지
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• 제37권5호
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• pp.857-870
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• 2000

In this paper, we estimate correlation dimensions of discrete quasi periodic ordits with frequencies, irrational numbers, which are called quasi Roth numbers. We specify the lower estimate valuse of the dimensions by using the parameters which are derived the rational approximable properties of the quasi Roth numbers.

• 한국지역지리학회지
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• 제11권6호
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• pp.530-542
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• 2005

본 연구에서는 지형이 위치별로 자기 상사성을 가진다는 전제하에 프랙탈 차원을 이용한 지형의 복잡성을 표현해 보고자 한다. 특히 수치지도 분석기법에서 표면적요소를 산정하여 프랙탈 차원을 산정하도록 한다. 또한 프랙탈 차원과 지형 형상요소들과의 관계를 규명하고, 프랙탈 차원의 통계적 대표치로서의 기능에 대해 고찰해 보려한다. 본 연구에서는 GIS기법을 적용하여 지형의 프랙탈 특성을 구하였다. 길이를 이용하여 하천이나 해안선의 1차원적 프랙탈 특성을 구하는 것에서 벗어나 면적의 개념 즉, 투영면적과 표면적을 이용하여 지형의 2차원적 프랙탈 특성을 구해보았다. 그리고 프랙탈 차원과 평균경사도와의 상관관계를 검토해 보았다. 연구결과 다음과 같은 결론을 얻게 되었다. 1) 프랙탈 차원을 구하기 위한 척도로서 표면적을 사용한 경우에서도 일반적 프랙탈 차원의 특성과 같이 지형의 복잡성과 비례관계의 성질을 나타내었다. 2) 본 연구에서 제안한 표면적을 이용한 프랙탈 차원은 영천지역에서는 $2.10{\sim}2.24$이고 의성지역은 $2.02{\sim}2.15$으로 나타났다. 이 값들은 통상 알려진 지형의 프랙탈 차원인 $2.10{\sim}2.20$의 범위에 든다. 3) 평균 경사도와 프랙탈 차원의 상관관계는 평균경사도가 $25^{\circ}$ 이상인 지역에서 결정계수 $R^2$값이 $25^{\circ}$ 이하인 지역에 비해 30% 정도 작아진다. 그러므로 모든 지형의 거침도를 표현하기 위해선 프랙탈 차원이 알맞을 것으로 본다. 본 연구결과를 통해 투영면적과 표면적을 이용한 프랙탈 차원 산정공식이 유효함을 확인하였다. 그러나 본 기법이 충분히 타당성을 인정받기 위해선 연구대상지역의 확대를 통하여 경사도와 표면적, 프랙탈 차원과의 상관관계를 더욱 명확히 할 필요가 있다. 향후 연구에선 지형의 복원에 적용 할 수 있을 것이며 fBm모델을 이용하여 교통류 해석에도 적용이 가능할 것이다.

• The Journal of Asian Finance, Economics and Business
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• 제7권9호
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• pp.499-504
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• 2020

Service quality of any institution is a pull factor for attracting and retaining the customer. The present study examines the customer satisfaction level toward the quality of service offered by the Islamic banks in Oman. It also aims to find out which dimension influences customer satisfaction more concerning the other dimension chosen for the study. To fulfil the need of the study, a structured questionnaire is distributed amongst 100 customers of Islamic banks. The random stratified sampling technique is used for the collection of the data. The collected data is analyzed using the correlation and the multiple linear regression techniques. The result of the study indicates that timely service provided by the banking personnel has a mean score of 4.57, bank staff readiness to serve the customer has a mean score of 4.36, and the security of the banking operation has a mean score of 4.37 occupies the highest rank in their respective dimension chosen for the study. The study reveals that all three dimensions of quality of service represented by Services Reliability, Services Responsiveness and Services Security have a positive and significant correlation with customer satisfaction. The regression results also indicate that all three dimensions influence customer satisfaction of the Islamic banks.

• 지질공학
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• 제9권2호
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• pp.101-118
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• 1999

본 연구는 덕산온천내에 수행된 28개 양수시험자료를 종합하여 덕산온천의 수리적 특성 및 매개변수를 파악하였다. 프락탈 모델, 누수성 프락탈 모델 그리고 정상류의 이중공극 프락탈 모델을 이용한 양수시험분석 결과, 대체로 온천의 중심부에서는 1.9 또는 2.0의 유동차원을 보이며, 주변부에서는 1.5∼l.7의 유동차원을 보인다. 2.0차원의 경우에, 투수량계수와 대수층 손실에 의한 산출계수의 상관성이 총 수위강하를 이용한 비양수량의 상관성보다 훨씬 높게 나타난다. 그러나, 1.9차원의 경우에는 일반화 투수량계수와 산출계수간의 상관성이 일반화 투수량계수와 비양수량간의 상관성과 비슷하게 나타나며 상관계수도 높게 나타난다.

• 한국해양공학회지
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• 제10권4호
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• pp.84-91
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• 1996

A fractal analysis on fracture surface of aluminium-particulate SiC composites was attempted. As the volume fraction of SiC in composites increases, the fractal dimension tends to increase. However, no correlation between the fractal dimension and the fracture toughness in terms of critical energy release rate was observed. Since the fractal dimension represents the roughness of fracture surface, the fracture toughness would be a function of not only fracture surface roughness but also additional parameters. Thus the applicability of fractal analysis to the estimation of fracture toughness must depend on the proper choice and interpretation of additioal paramerters. In this paper, the size of characteristic strctural unit for fracture was considered as an additional parameter. As a result, the size appeared to be a function of only volume fraction of SiC. Finally, a master curve for fracture toughness of aluminium-particulate SiC composites was proposed as a function of fractal dimension and volume fraction of SiC.

• 한국사회복지학
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• 제44권
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• pp.7-35
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• 2001

Little empirical study has been conducted concerning board function effectiveness and organizational performance in nonprofit nongovernmental human service organizations in Korea. Using the evaluations of 107 board members and 17 executive directors in Korean Community Chest and 16 regional community chests, this study attempted to examine the level of board function effectiveness and its relationship with organizational performance in these community chests. This study used board function scale developed by Holland and Jackson (1998) to measure board function effectiveness in the following 6 dimensions: contextual dimension: educational dimension: interpersonal dimension: analytical dimension: political dimension: and strategic dimension. This study showed that using 4 points scale, mean of overall board function effectiveness evaluated by board members is 2.62 and mean of overall board function effectiveness evaluated by executive directors is 2.73. That is, it showed that means of overall board function effectiveness are located in the middle point between negative evaluation and positive evaluation. On the other hand, using parametric correlation analysis method, it was found that in these community chests the association between board function effectiveness and organizational performance measured by fund-raising growth rate in $1999{\sim}2000\;and\;1998{\sim}2000$ is very weak and statistically nonsignificant. This study also revealed that using nonparametric correlation analysis method, the association between consensus level in evaluation by board members and executive directors about board function effectiveness, and organizational performance is still very weak and statistically nonsignificant. Finally, this study discussed the direction of future research in board function effectiveness and its relationship with organizational performance and the areas of board management that requires substantial efforts for promoting effectiveness of nonprofit human service organizations in Korea.

• Imaging Science in Dentistry
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• 제52권1호
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• pp.33-41
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• 2022

Purpose: This study aimed to evaluate the structural complexity of craniofacial trabecular bone in multiple myeloma by fractal analysis of panoramic and lateral skull radiography, and to compare the fractal dimension values of healthy patients (HPs), pre-treatment patients (PTPs), and patients during bisphosphonate treatment (DTPs). Materials and Methods: Pairs of digital panoramic and lateral skull radiographs of 84 PTPs and 72 DTPs were selected. After application of exclusion criteria, 43 panoramic and 84 lateral skull radiographs of PTPs, 56 panoramic and 72 lateral skull radiographs of DTPs, and 99 panoramic radiographs of age- and sex-matched HPs were selected. The fractal dimension values from panoramic radiographs were compared among HPs, PTPs, and DTPs and between anatomical locations within patient groups using analysis of variance with the Tukey test. Fractal dimension values from lateral skull radiographs were compared between PTPs and DTPs using the Student t-test. Pearson correlation coefficients were used to assess the relationship between the mandible from panoramic radiographs and the skull from lateral skull radiographs. Intra-examiner agreement was assessed using intraclass correlation coefficients (α=0.05). Results: The fractal dimension values were not significantly different among HPs, PTPs, and DTPs on panoramic radiographs or between PTPs and DTPs on lateral skull radiographs (P>0.05). The mandibular body presented the highest fractal dimension values (P≤0.05). The fractal dimension values of the mandible and skull in PTPs and DTPs were not correlated. Conclusion: Fractal analysis was not sensitive for distinguishing craniofacial trabecular bone complexity in multiple myeloma patients using panoramic and lateral skull radiography.

• Imaging Science in Dentistry
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• 제53권2호
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• pp.153-159
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• 2023

Purpose: The objective of this study was to assess the fractal dimension, lacunarity, trabecular microarchitecture parameters, and cortical linear measurements in the mandibles of male and female individuals to identify differences between them. Materials and Methods: In total, 116 cone-beam computed tomography scans of healthy individuals of different ages (57 men and 59 women, aged between 20 and 60 years) were selected. The following bone parameters were measured: 1) buccal, lingual, and basal cortical bone thickness in 5 standard parasagittal sections (the midline, the left and right sides of the lower lateral incisors, and the left and right sides of the lower canines); 2) the bone volume fraction of 10 sequential axial sections from each patient by creating a volume of interest in the area between the lower canines; and 3) fractal dimension and lacunarity using grayscale images of the same region of the volume of interest in the anterior mandible. Spearman correlation coefficients and the Mann-Whitney test were used. Results: A significant and positive correlation was found between age and cortical thickness, especially in the region of the central incisors. Significant differences between sexes in terms of fractal dimension, lacunarity, and bone volume were found. Women revealed lower fractal dimension values and higher lacunarity and bone volume ratio values than men. Conclusion: Fractal dimension, lacunarity, trabecular bone volume, and cortical thickness were different between men and women of different ages.