• Bulletin of the Korean Mathematical Society
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• v.38 no.3
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• pp.449-461
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• 2001

The purpose of this paper is to study several geometric properties for the new class $G_{\kappa}(\beta)$ including geometric interpretation, coefficient estimates, radius of convexity, distortion property and covering theorem.

• Journal of the Korean Ceramic Society
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• v.40 no.4
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• pp.393-397
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• 2003

To investigate the effect of AIN c-axis orientation on the resonance performance of film bulk acoustic wave resonators, solidly mounted resonators with crybtallographically different AIN piezoelectric films were prepared by changing only the bottom electrode surface conditions. As increasing the degree of c-axis texturing, the effective electromechanical coupling coefficient ($\kappa$$\_$eff/)$^2$ in resonators increased gradually. The least 4 degree of full width at half maximum in an AIN(002) rocking curve, which corresponds to $\kappa$$^2$$\_$eff/ of above 5%, was measured to be necessary for band pass filter applications in wireless communication system. The longitudinal acoustic wave velocity of AIN films varied with the degree of c-axis texturing. The velocity of highly c-axis textured AIN film was extracted to be about 10200 n/s by mathematical analysis using Matlab.

• The Journal of Korean Physical Therapy
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• v.22 no.5
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• pp.83-93
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• 2010

Purpose: The purpose of this study was to determine the reliability and validity of the Functional Movement Screen (FMS) for assessing Korean athletes. Methods: A total of 48 patients (37 males and 11 females) participated in this study. Data were acquired after translation of the FMS from English to Korean and cross-cultural adaptation of the this questionnaire. To determine inter-rater reliability, the relationship between the FMS scores obtained by two raters was evaluated using the Kappa coefficient, which was in total agreement with the Intra-Correlation Coefficient (ICC3,1). Concurrent validity was examined by correlating the FMS scores with the Oswestry disability index (ODI) scores and Visual analogue scale (VAS) scores. Results: The raters demonstrated excellent agreement on 7 (above 90%) of the 17 test (72.9 to 97.9%) components. Substantial agreement was seen in 11 of the 17 tests. Two components of the In-line lunge and rotatory stability tests demonstrated moderate agreement. It showed good inter-rater reliability: the Kappa coefficients ranged from 0.42 to 0.97. ICC3,1=0.42~0.99 and 0.93 (total FMS score). Cronbach's alpha for FMS was 0.80. It was not correlated with ODI or VAS. Conclusion: The Korean version of the FMS is a reliable instrument for measuring movement patterns of Korean athletes and for making decisions related to interventions for performance enhancement.

• Korean Journal of Remote Sensing
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• v.31 no.4
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• pp.337-346
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• 2015

Water body extraction based on backscatter information is an essential process to analyze floodaffected areas from Synthetic Aperture Radar (SAR) image. Water body in SAR image tends to have low backscatter values due to homogeneous surface of water, while non-water body has higher backscatter values than water body. Non-water body, however, may also have low backscatter values in high resolution SAR image such as Kompsat-5 image, depending on surface characteristic of the ground. The objective of this paper is to present a method to increase backscatter contrast between water body and non-water body and also to remove efficiently misclassified pixels beyond true water body area. We create an entropy image using a Gray Level Co-occurrence Matrix (GLCM) and classify the entropy image into water body and non-water body pixels by thresholding of the entropy image. In order to reduce the effect of threshold value, we also propose Water Body Texture Index (WBTI), which measures simultaneously the occurrence of repeated water body pixel pair and the uniformity of water body in the binary entropy image. The proposed method produced high overall accuracy of 99.00% and Kappa coefficient of 90.38% in water body extraction using Kompsat-5 image. The accuracy analysis indicates that the proposed WBTI method is less affected by the choice of threshold value and successfully maintains high overall accuracy and Kappa coefficient in wide threshold range.

• Korean Journal of Remote Sensing
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• v.34 no.4
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• pp.601-610
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• 2018

The national accuracy of global land cover (GLC) products is of great importance to ecological and environmental research. However, GLC products that are derived from different satellite sensors, with differing spatial resolutions, classification methods, and classification schemes are certain to show some discrepancies. The goal of this study is to assess the accuracy of four commonly used GLC datasets in South Korea, GLC2000, GlobCover2009, MCD12Q1, and GlobeLand30. First, we compared the area of seven classes between four GLC datasets and a reference dataset. Then, we calculated the accuracy of the four GLC datasets based on an aggregated classification scheme containing seven classes, using overall, producer's and user's accuracies, and kappa coefficient. GlobeLand30 had the highest overall accuracy (77.59%). The overall accuracies of MCD12Q1, GLC2000, and GlobCover2009 were 75.51%, 68.38%, and 57.99%, respectively. These results indicate that GlobeLand30 is the most suitable dataset to support a variety of national scientific endeavors in South Korea.

• Nuclear Engineering and Technology
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• v.41 no.7
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• pp.907-920
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• 2009

This study was performed to evaluate the prediction capability of a commercial CFD code and to investigate the effects of different geometries such as a 4.4 mm tube and an 8/10 mm annular channel on the detailed flow structures. A numerical simulation was performed for the conditions, at which the experimental data was produced by the test facility SPHINX. A 2-dimensional axisymmetric steady flow was assumed for computational simplicity. The RNG $\kappa-\varepsilon$ turbulence model (RNG) with an enhanced wall treatment option, SST $\kappa-\omega$ (SST) and low Reynolds Abid turbulence model (ABD) were employed and the numerical predictions were compared with the experimental data generated from the experiment. The effects of the geometry on heat transfer were investigated. The flow and temperature fields were also examined in order to investigate the mechanism of heat transfer near the wall. The local heat transfer coefficient predicted by the RNG model is very close to the measurement result for the tube. In contrast, the local heat transfer coefficient predicted by the SST and ABD models is closer to the measurement for the annular channel.

• Journal of the Korean Society of Propulsion Engineers
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• v.7 no.2
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• pp.7-14
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• 2003

Computational work using the axisymmetric, compressible, Navier-Stokes Equations is carried out to predict the discharge coefficient of mass flow through a micro-critical nozzle. Several kinds of turbulence models and wall functions are employed to validate the computational predictions. The computed results are compared with the previous experimented ones. The present computations predict the experimental discharge coefficients with a reasonable accuracy. It is found that the standard $\kappa$-$\varepsilon$turbulence model with the standard wall function gives a best prediction of the discharge coefficients. The displacement thickness of the nozzle wall boundary layer is evaluated at the nozzle throat and is well compared to a prediction obtained by an empirical equation. The resulting displacement thickness of the wall boundary layer is about 2% to 0.6% of the diameter of the nozzle throat for the Reynolds numbers of 2000 to 20000.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.6
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• pp.886-895
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• 2009

The purpose of this work is to compare and analyze computed results with experimental data of NREL (National Renewable Energy Laboratory) Phase VI for the whole operating conditions of various wind speeds using $\kappa-\omega$ turbulence model provided in the commercial code, FLUENT. Performance results such as power coefficient, shaft torque, pressure coefficient show a good agreement with experimental data. But, root bending moment is over-predicted than the experimentally measured value by about 30% for the whole operating conditions because of indefinite measurement reference. Nevertheless, these results qualitatively show a good tendency in the aspect of aerodynamic performance. As wind speed increases, streamlines on the surface of blade show more and more complex pattern.

• The Journal of the Korea Contents Association
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• v.13 no.5
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• pp.354-365
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• 2013

The purpose of the study was to develop the home fall prevention checklist for community-dwelling older adults. And the validity and reliability of the checklist were tested. The preliminary questions were developed through content validity by twenty experts using the CVI(Content Validity Index). Following the establishment of content validity, 52 items of the checklist were developed. Responses of 299 community-dwelling older adults were analyzed to further establish both reliability and validity of the checklist. Reliability using cohen's kappa coefficient and test-retest reliability(rate of concordance(%)), and construct validity using known-group comparison technique were tested. 51 items were over 0.80 in the cohen's kappa coefficient of the checklist, 45 items were over 80.0% in test-retest reliability. Construct validity was established by known-group comparison(t=3.50, p=.001). Validity and reliability of the checklist were confirmed. This checklist will help further studies to develop more safe environment to prevent falls.

• Physical Therapy Korea
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• v.21 no.3
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• pp.73-79
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• 2014

The purposes of the current study were to (1) estimate the inter-rater agreement for visual assessment of scapular downward rotation (SDR), (2) develop the scapular downward rotation index (SDRI) as a method to measure SDR objectively and quantitatively, and (3) analyze the intra- and inter-rater reliability of the SDRI. Twenty subjects with scapular downward rotation syndrome (SDRS) were recruited for this study. The visual assessment and the measurement for the SDRI were conducted by two examiners in two sessions each. The SDRI [$(a-b){\div}a{\times}100$] is calculated with the measurement of two linear distances: One is a perpendicular distance from the root of the scapular spine to the thoracic mid-line (a), and the other is a perpendicular distance from the inferior angle of the scapula to the thoracic mid-line (b). Cohen's kappa coefficient was calculated to estimate the inter-rater agreement for visual assessment. Intra-class correlation coefficients (ICCs) with a 95% confidence interval (CI), the standard error of measurement, and minimal detectable differences were calculated to assess intra- and inter-rater reliability of SDR measurement using the SDRI. The results indicated that the kappa coefficient of inter-rater agreement for visual assessment was fair (${\kappa}=.21$). The intra-rater reliability of SDR measurement using the SDRI was excellent for examiner 1 (ICC=.92, 95% CI=.78~.97) and good for examiner 2 (ICC=.82, 95% CI=.55~.93). The inter-rater reliability was moderate (ICC=.73, 95% CI=.32~.89). These findings showed that SDR measurement using the SDRI for subjects with SDRS may be considered reliable and better than the visual assessment.