• Journal of the Korean Mathematical Society
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• v.44 no.4
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• pp.747-756
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• 2007

In this paper we give an example of imaginary quadratic number field k such that every ideal of k becomes principal in some proper subfields of the Hilbert class field of k.

• Kyungpook Mathematical Journal
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• v.18 no.2
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• pp.201-205
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• 1978

• Journal of Environmental Impact Assessment
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• v.21 no.5
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• pp.609-615
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• 2012

In recent years, the development of computer technique was possible to the simulation analysis of the structure caused by ground vibration. Generally, finite element method(FEM) has been used in these structural analysis. In this study, it was calculated to the vibration energy as measuring vibration waveform, and estimated about principal stress due to medium characteristics of the ground as processing dynamic analysis by the vibration energy. The results are as follows : Firstly, the principal stress distribution in all mediums was different due to a medium condition, and the principal stress at concrete medium was represented to difference due to physical characteristics. Secondly, the principal stress by time increasing was represented to maximum amplitude within 0.03 second. And also, the principal stress after maximum amplitude was very large at concrete medium, which was considered to be formed compression or tension range at a medium boundary. Thirdly, the variation of principal stress at concrete medium was represented in the order of RC medium, NC=H medium, NC=S medium. It was considered that the vibration energy propagated fast when a medium have a big elasticity and density.

• The Journal of the Acoustical Society of Korea
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• v.15 no.1
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• pp.23-33
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• 1996

In this paper we point out that if the classical principal domain for bispectra is utilized to determine a second-order Volterra model's output, such and output will be incomplete. This deficiency is associated with the periodic nature of the DFT. For this reason, the objective of this paper is to present an "extended" principal domain for Volterra kernels which leads to an improved estimate of the nonlinear system's response. In order to define the extended principal domain, we derive a new discrete frequency-domain Volterra model from a discrete time-domain Volterra model utilizing 2-dimensional DFT and the relationship between the quadratic component of the Volterra model and a square filter. The effect of the extended domain on the model output is interpreted in terms of the periodicity of DFT. Through computer simulations, we demonstrate the effects of the extended principal domain on the Volterra modeling. The simulation results indicate that the extended principal domain plays and important role in computing Volterra model outputs and estimating Volterra model coefficients.

• Journal of the Korean Data and Information Science Society
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• v.14 no.4
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• pp.773-787
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• 2003

Principal component analysis, factor analysis and cluster analysis have been performed to analyze the relationship between air pollutants and meteorological variables measured in 1999 in Seoul. In principal analysis, the first principal has been shown the contrast effect between $O_3$ and the other pollutants, the second principal has been shown the contrast effect between CO, $SO_2$, $NO_2$ and $O_3$, PM10, TSP. In factor analysis, the first factor has been found as PM10, TSP, $NO_2$ concentrations which are related with suspended particulates. As a result of cluster analysis, three clusters respectively have represented different air pollution levels, seasonal characteristics of air pollutants and meteorological situations.

• Animal cells and systems
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• v.2 no.4
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• pp.439-449
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• 1998

To discuss the taxonomic dispositions of Korean Isopyroideae (Ranunculaceae) taxa, principal components analysis and cluster analysis were performed using quantitative and qualitative morphological characters. The principal components analysis revealed that the size and number of ovule, ovary width, ratio of style length/ovary length, filament length, sepal size, style length, leaf size, and ovary length are important characters to distinguish Korean Isopyroideae taxa. The cluster and principal components analyses based on both quantitative and quantitative characters demonstrate that lsopyrum mandshuricum is more closely related to Enemion raddeanum than to Semiaquilegia adoxoides. Even though Enemion s not separated from Isopyrum by uantitative characters, they are distinguished by qualitative characters, suggesting that our taxa, Enemion, Semiaquilegia, Isopyrum and Aquilegia, should be recognized in Korean Isopyroideae. In addition, cluster analyses suggest that S. adoxoides could be separated from Aquilegia buergeriana var, oxysepala.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.36 no.11
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• pp.813-818
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• 1987

In this paper, high resolution spectral estimation by AR modelling and principal comonent analysis is proposed. The given data can be expanded by the eigenvectors of the estimated covariance matrix. The eigenspectrum is obtained for each eigenvector using the Autoressive(AR) spectral estimation technique. The final spectrum estimate is obtained by weighting each eigenspectrum with the corresponding eigenvalue and summing them. Although the proposed method increases in computational complexity, it shows good frequency resolution especially for short data records and narrow-band data whose signal-to-noise ratio is low.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.1035-1036
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• 2010

• The Journal of Asian Finance, Economics and Business
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• v.9 no.7
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• pp.145-152
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• 2022

The purpose of this study is to assess the impact of the principal's democratic leadership style, teacher competency, work discipline, and work environment on teacher performance during the pandemic. Using the proportional random sampling strategy, a sample of 468 respondents consisted of kindergarten teachers, elementary school teachers, junior high school teachers, junior high school teachers, and high school/vocational school teachers. The study revealed that the principal's democratic leadership style, teacher competence, work discipline, and work environment substantially impact teacher performance. However, the principal's democratic leadership style does not affect teacher performance, whereas teacher competence, work discipline, and work environment have a minor impact on teacher performance. Furthermore, during the COVID-19 pandemic, work discipline is the most critical variable influencing teacher performance. The findings of this study suggest that the principal's democratic leadership style, teacher competence, work discipline, and work environment have a positive impact on teacher performance during the pandemic. During the COVID-19 pandemic, work discipline is the most important variable influencing teacher performance. Considering that democratic leadership has no effect on teacher performance and that this leadership style is widely used by school principals in the world of education, it is assumed that there is no effect on teacher performance.

• Journal of Pharmaceutical Investigation
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• v.37 no.6
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• pp.377-395
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• 2007

Near infrared(NIR) spectral data have been used for the noninvasive analysis of various biological samples. Nonetheless, absorption bands of NIR region are overlapped extensively. It is very difficult to select the proper wavelengths of spectral data, which give the best PCR(principal component regression) models for the analysis of constituents of biological samples. The NIR data were used after polynomial smoothing and differentiation of 1st order, using Savitzky-Golay filters. To find the best PCR models, all-possible combinations of available principal components from the given NIR spectral data were derived by in-house programs written in MATLAB codes. All of the extensively generated PCR models were compared in terms of SEC(standard error of calibration), $R^2$, SEP(standard error of prediction) and SECP(standard error of calibration and prediction) to find the best combination of principal components of the initial PCR models. The initial PCR models were found by SEC or Malinowski's indicator function and a priori selection of spectral points were examined in terms of correlation coefficients between NIR data at each wavelength and corresponding concentrations. For the test of the developed program, aqueous solutions of BSA(bovine serum albumin) and glucose were prepared and analyzed. As a result, the best PCR models were found using a priori selection of spectral points and the final model selection by SEP or SECP.