• Wind and Structures
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• v.18 no.6
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• pp.651-668
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• 2014

Wind tunnel tests are conducted to investigate the wind loads on vertical fixed-roof cylindrical tanks with a very low aspect ratio of 0.275, which is a typical ratio for practical tanks with a volume of $100,000m^3$. Both the flat-roof tank and the dome-roof tank are investigated in present study. The first four moments of the measured wind pressure, including the mean and normalized deviation pressure, kurtosis and skewness of the pressure signal, are obtained to study the feature of the wind loads. It is shown that the wind loads are closely related to the behavior of flow around the structure. For either tank, the mean wind pressures on the cylinder are positive on the windward area and negative on the sides and the wake area, and the mean wind pressures on the whole roof are negative. The roof configurations have no considerable influence on the mean pressure distributions of cylindrical wall in general. Highly non-Gaussian feature is found in either tank. Conditional sampling technique, envelope method, and the proper orthogonal decomposition (POD) analysis are employed to investigate the characteristics of wind loads on the cylinder in more detail. It is shown that the patterns of wind pressure obtained from conditional sampling are similar to the mean pressure patterns.An instantaneous pressure coefficient can present a wide range from the maximum value to the minimum value. The quasi-steady assumption is not valid for structures considered in this paper according to the POD analysis.

• Journal of Distribution Science
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• v.19 no.1
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• pp.27-35
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• 2021

Purpose: This study is to investigate the effect of managerial ownership level in distribution and service companies on the stock price crash. The managerial ownership level affects the firm's information disclosure policy. If managers conceal or withholds business-related unfavorable factors over a long period, the firm's stock price is likely to plummet. In a similar vein, management's equity affects information opacity, and information asymmetry affects stock price collapse. Research design, data, and methodology: A regression analysis is conducted using the data on companies listed on the Korea Composite Stock Price Index (KOSPI) between 2012-2017 to examine the effect of the managerial ownership level on stock price crash risks. Results: Logistic and regression results indicate that the stock price crash risk was reduced as managerial ownership levels are increased. The managerial ownership level has a significant negative coefficient on stock price crash risk, negative conditional return skewness of firm-specific weekly return distribution, and asymmetric volatility between positive and negative price-to-earnings ratios. Conclusions: As the ownership and management align, the likeliness of withholding business-related information is reduced. This study's results imply that the stock price crash risk reduces as the managerial ownership level increases because shareholder and manager interests coincide, thereby reducing information asymmetry.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1880-1884
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• 2000

The discrete wavelet transform is utilized as preprocessing of Neural Network(NN) to identify aging state of internal partial discharge in transformer. The discrete traveler transform is used to produce wavelet coefficients which are used for Classification. The statistical parameters (maximum of wavelet coefficients, average value, dispersion, skewness, kurtosis) using the wavelet coefficients are input into an back-propagation neural network. The neurons whose weights have obtained through Result of Cross-Validation. The Neural Network learning stops either when the error rate achieves an appropriate minimum or when the learning time overcomes a constant value. The networks, after training, can decide if the test signal is Early Aging State or Last Aging State or normal state.

• Journal of The Korean Association For Science Education
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• v.41 no.6
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• pp.533-542
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• 2021

This study aims to develop an instrument for measuring high school students' action competence on climate change (ACoCC). The instrument is defined as the construct comprised of seven factors and thirty-five items and takes approximately 15 minutes to fill out. A panel of experts and students' content validation were undertaken to modify the items. Five hundred and twenty-eight first and second graders in Korean high schools participated in the instrument survey. To assess the reliability and validity of ACoCC instrument, item analysis (mean, skewness, kurtosis, item-total correlation), internal consistency estimate, and confirmatory factor analysis were used. It was appropriate to use the 7-dimensional ACoCC instrument (knowledge about climate change, climate change sensibility, reflection, communication, integrated thinking, willingness, decision making), with 35 items for high school students. The following instrument was self-report given in the 5-point Likert scale (1=strongly disagree, 2=disagree, 3=neutral, 4=agree, 5=strongly agree). The internal consistency coefficient was shown as a whole was shown as 0.953, and the subscale's internal consistency coefficient ranged from 0.786 to 0.862.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.2
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• pp.112-123
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• 2006

Double-peak normal distribution function was suggested as the probability density function of the non-tidal components (NTC) data in Korean coastal zone. Frequency distribution analysis of the NTC data was carried out using hourly tidal elevation data of the ten tidal gauging stations, i.e., Incheon, Gunsan, Mokpo, Jeju, Yeosu, Masan, Gadeokdo, Busan, Pohang, and Sokcho which were served through the Internet Homepage by the National Ocean Research Institute. NTC data is defined as the difference between the measured tidal elevation data and the astronomical tidal elevation data using 64 tidal constituents information. Based on the RMS error and R2 value comparison analysis, it was found that this suggested function as the probability density function of the NTC data was found to be more appropriate than the normal distribution function. The parameters of the double-peak function were estimated optimally using Levenberg-Marquardt method which was modified from the Newton method. The standard deviation and skewness coefficient were highly correlated with the non-tidal constants of the tidal gauging stations except Mokpo, Jeju and Sokcho stations.

• Journal of the Korean Society of Radiology
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• v.83 no.1
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• pp.112-126
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• 2022

Purpose To determine the value of 3 Tesla (T) MRI texture analysis for predicting tumor margin infiltration in soft tissue sarcomas. Materials and Methods Thirty-one patients who underwent 3T MRI and had a pathologically confirmed diagnosis of soft tissue sarcoma were included in this study. Margin infiltration on pathology was used as the gold standard. Texture analysis of soft tissue sarcomas was performed on axial T1-weighted images (WI) and T2WI, fat-suppressed contrast-enhanced (CE) T1WI, diffusion-weighted images (DWI) with b-value of 800 s/mm², and apparent diffusion coefficient (ADC) was mapped. Quantitative parameters were compared between sarcomas with infiltrative margins and those with circumscribed margins. Results Among the 31 patients with soft tissue sarcomas, 23 showed tumor margin infiltration on pathology. There were significant differences in kurtosis with the spatial scaling factor (SSF) of 0 and 6 on T1WI, kurtosis (SSF, 0) on CE-T1WI, skewness (SSF, 0) on DWI, and skewness (SSF, 2, 4) on ADC between sarcomas with infiltrative margins and those with circumscribed margins (p ≤ 0.046). The area under the receiver operating characteristic curve based on MR texture features for identification of infiltrative tumor margins was 0.951 (p < 0.001). Conclusion MR texture analysis is reliable and accurate for the prediction of infiltrative margins of soft tissue sarcomas.

• Investigative Magnetic Resonance Imaging
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• v.25 no.2
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• pp.118-128
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• 2021

Purpose: To investigate the value of MR textural analysis, including use of diffusion-weighted imaging (DWI) to differentiate malignant from benign soft-tissue tumors on 3T MRI. Materials and Methods: We enrolled 69 patients (25 men, 44 women, ages 18 to 84 years) with pathologically confirmed soft-tissue tumors (29 benign, 40 malignant) who underwent pre-treatment 3T-MRI. We calculated MR texture, including mean, standard deviation (SD), skewness, kurtosis, mean of positive pixels (MPP), and entropy, according to different spatial-scale factors (SSF, 0, 2, 4, 6) on axial T1- and T2-weighted images (T1WI, T2WI), contrast-enhanced T1WI (CE-T1WI), high b-value DWI (800 sec/mm²), and apparent diffusion coefficient (ADC) map. We used the Mann-Whitney U test, logistic regression, and area under the receiver operating characteristic curve (AUC) for statistical analysis. Results: Malignant soft-tissue tumors had significantly lower mean values of DWI, ADC, T2WI and CE-T1WI, MPP of ADC, and CE-T1WI, but significantly higher kurtosis of DWI, T1WI, and CE-T1WI, and entropy of DWI, ADC, and T2WI than did benign tumors (P < 0.050). In multivariate logistic regression, the mean ADC value (SSF, 6) and kurtosis of CE-T1WI (SSF, 4) were independently associated with malignancy (P ≤ 0.009). A multivariate model of MR features worked well for diagnosis of malignant soft-tissue tumors (AUC, 0.909). Conclusion: Accurate diagnosis could be obtained using MR textural analysis with DWI and CE-T1WI in differentiating benign from malignant soft-tissue tumors.

• Journal of the Korean Society of Food Science and Nutrition
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• v.19 no.3
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• pp.248-262
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• 1990

General purpose of the study was to understend nutritional status of the Korean farmers and thus provide rural nutrition intervention programs with more useful in formation and data. The data for the study was collected two times from the 603 sample farm households in 1982 and 1987. The main results of the study were as follows ; 1) Food intake of the Korean farmers was highly dependent upon vegetable foods especially on cereals and gains. However the unbalanced food intake pattern was gradually improved as consumption of vegetable foods was decreased from 992.8 grams per person per day in 1982 to 946.4g in 1987 and that of animal foods increased from 54.2g to 91.4g . 2) In mean value analysis on nutrient intake of the farmeres intakes of energy and protein were nearly reached to Recommended Dietary Allowances(RDA) level; intakes of calcium vitamin A and riboflavin were quite deficient whereas iron thiamin niacin and ascorbic acid were well over. From 1982 to 1987 intakes of all nutrients except energy were increased. 3) In distribution analysis on nutrient intake coefficient of variation(CV) of all nutrients except iron was increased. skewness(SK) the coefficients of calcium iron vitamin A riboflavin and ascorbic acid were decreased Kurtosis (Ku) of iron and vitamin A was increased. On the whole distributions of nutrient intake of the farmers were changed in undesirable ways although the mean values of the nutrient intake were improved 4) In relationship analysis among 115 relationships 76 relationships were consistent between 1982 and 1987. Of 76 consistent relationships only 10 relationship were significant at 5% level such as the protein intake level and the balance of food intake calcium intake level and the age etc.

• Magazine of the Korean Society of Agricultural Engineers
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• v.40 no.4
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• pp.45-57
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• 1998

This study was conducted to derive optimal design floods by Generalized Extreme Value (GEV) distribution for the annual maximum series at ten watersheds along Han, Nagdong, Geum, Yeongsan and Seomjin river systems. Adequacy for the analysis of flood data used in this study was established by the tests of Independence, Homogeneity, detection of Outliers. L-coefficient of variation, L-skewness and L-kurtosis were calculated by L-moment ratio respectively. Parameters were estimated by the Methods of Moments and L-Moments. Design floods obtained by Methods of Moments and L-Moments using different methods for plotting positions in GEV distribution were compared by the Relative Mean Errors(RME) and Relative Absolute Errors(RAE). The results were analyzed and summarized as follows. 1. Adequacy for the analysis of flood data was acknowledged by the tests of Independence, Homogeneity and detection of Outliers. 2. GEV distribution used in this study was found to be more suitable one than Pearson type 3 distribution by the goodness of fit test using Kolmogorov-Smirnov test and L-Moment ratios diagram in the applied watersheds. 3. Parameters for GEV distribution were estimated using Methods of Moments and L-Moments. 4. Design floods were calculated by Methods of Moments and L-Moments in GEV distribution. 5. It was found that design floods derived by the method of L-Moments using Weibull plotting position formula in GEV distribution are much closer to those of the observed data in comparison with those obtained by method of moments using different formulas for plotting positions from the viewpoint of Relative Mean Errors and Relative Absolute Errors.

• Atmosphere
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• v.24 no.3
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• pp.317-329
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• 2014

Eddy covariance data have been analyzed to investigate the influence of surface heterogeneity on turbulent transfer over farmland and industrial sites near Nakdong river, Korea, where both large and small scale heterogeneities co-exist. For this purpose, basic turbulent statistics, quadrant analysis and multi-resolution decomposition have been analyzed during the daytime. Basic turbulent statistics were compared with typical turbulent statistics in the surface layer. Such comparisons were in close agreement for momentum and heat at both sites but not for water vapor at industrial site. The correlation coefficient between water vapor and vertical velocity ($r_{wq}$) is relatively low and skewness of water vapor ($sk_q$) is very low at industrial site, possibly due to limited water source. For heat at both sites and water vapor at farmland, the quadrant analysis show similar behavior to that over homogeneous site but for water vapor at industrial site, the presence of river and limited water source at industrial site seems to influence on water vapor transfer by coherent eddy motion by increasing sweep contribution and decreasing ejection contribution. Multi-resolution decomposition analysis shows that large scale heterogeneity leads to low $r_{Tq}$ at large averaging time regardless of season at both sites and there are seasonal changes of $r_{Tq}$ in mid-averaging times at industrial site, possibly due to seasonal change of trees and grasses near the site.