• Communications of the Korean Mathematical Society
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• v.32 no.3
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• pp.709-714
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• 2017

For every interval [a, b], we denote by (${\bar{x}}_A,{\bar{y}}_A$) and (${\bar{x}}_L,{\bar{y}}_L$) the geometric centroid of the area under a catenary y = k cosh((x - c)/k) defined on this interval and the centroid of the curve itself, respectively. Then, it is well-known that ${\bar{x}}_L={\bar{x}}_A$ and ${\bar{y}}_L=2{\bar{y}}_A$. In this paper, we show that one of ${\bar{x}}_L={\bar{x}}_A$ and ${\bar{y}}_L=2{\bar{y}}_A$ characterizes the family of catenaries among nonconstant $C^2$ functions. Furthermore, we show that among nonconstant and nonlinear $C^2$ functions, ${\bar{y}}_L/{\bar{x}}_L=2{\bar{y}}_A/{\bar{x}}_A$ is also a characteristic property of catenaries.

• Proceedings of the Korea Concrete Institute Conference
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• 1990.10a
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• pp.57-62
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• 1990

This paper is to study the effect of rectilinear confinement in high-strength concrete subjected to a monotonically increasing compressive axial loads. To investigate behavior of columns rectilinearly confined with lateral ties and longitudinal rebars, twelve specimens including two plain concrete specimens were tested. The main variables in this study are volumetric ratio of lateral ties, cistribution of lateral ties, yield strength of logitudinal steel, ratio of area of longitudinal steel to the area of cross section. The test results were not only compared with an empirical model for the stress-strain curve of rectilinearly confined high-strength concrete but also the existing model. The empirical model used calculating column capacity shows better agreement with the test results tham the existing model.

• Journal of the Korean Data and Information Science Society
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• v.26 no.3
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• pp.749-754
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• 2015

This article presents Bayesian approach to regression splines with knots on a grid of equally spaced sample quantiles of the independent variables under functional measurement error model.We consider small area model by using penalized splines of non-linear pattern. Specifically, in a basis functions of the regression spline, we use radial basis functions. To fit the model and estimate parameters we suggest a hierarchical Bayesian framework using Markov Chain Monte Carlo methodology. Furthermore, we illustrate the method in an application data. We check the convergence by a potential scale reduction factor and we use the posterior predictive p-value and the mean logarithmic conditional predictive ordinate to compar models.

• Journal of Korean Academy of Nursing
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• v.33 no.2
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• pp.162-169
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• 2003

Purpose: This study was to compare the predictive validity of Norton Scale(1962), Cubbin & Jackson Scale(1991), and Song & Choi Scale(1991). Method: Data were collected three times per week from 48~72hours after admission based on the four pressure sore risk assessment scales and a skin assessment tool for pressure sore on 112 intensive care unit(ICU) patients in a educational hospital Ulsan during Dec, 11, 2000 to Feb, 10, 2001. Four indices of validity and area under the curve(AUC) of receiver operating characteristic(ROC) were calculated. Result: Based on the cut off point presented by the developer, sensitivity, specificity, positive predictive value, negative predictive value were as follows : Norton Scale : 97%, 18%, 35%, 93% respectively; Cubbin & Jackson Scale : 89%, 61%, 51%, 92%, respectively; and Song & Choi Scale : 100%, 18%, 36%, 100% respectively. Area under the curves(AUC) of receiver operating characteristic(ROC) were Norton Scale .737, Cubbin & Jackson Scale .826, Song & Choi Scale .683. Conclusion: The Cubbin & Jackson Scale was found to be the most valid pressure sore risk assessment tool. Further studies on patients with chronic conditions may be helpful to validate this finding.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.5
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• pp.3219-3221
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• 2013

Background: This study used receiver operating characteristic (ROC) curves to screen Surveillance, Epidemiology and End Results (SEER) skin melanoma data to identify and quantify the effects of socioeconomic factors on cause specific survival. Methods: 'SEER cause-specific death classification' used as the outcome variable. The area under the ROC curve was to select best pretreatment predictors for further multivariate analysis with socioeconomic factors. Race and other socioeconomic factors including rural-urban residence, county level % college graduate and county level family income were used as predictors. Univariate and multivariate analyses were performed to identify and quantify the independent socioeconomic predictors. Results: This study included 49,999 parients. The mean follow up time (SD) was 59.4 (17.1) months. SEER staging (ROC area of 0.08) was the most predictive foctor. Race, lower county family income, rural residence, and lower county education attainment were significant univariates, but rural residence was not significant under multivariate analysis. Living in poor neighborhoods was associated with a 2-4% disadvantage in actuarial cause specific survival. Conclusions: Racial and socioeconomic factors have a significant impact on the survival of melanoma patients. This generates the hypothesis that ensuring access to cancer care may eliminate these outcome disparities.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2003.10a
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• pp.89.2-90
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• 2003

Potato late blight, caused by Phytophthora infestans, is one of the important diseases in potato cultivation areas. Though the incidence of late blight was depend on the inoculums and climatic condition In each fields, the foliar blight was reached to 100％ under the severe disease pressure condition in 2003. Outbreak of foliar blight was concentrated from May and July and evaluation of ten fungicides to control of late blight was made at Daekwallryoung area in potato fields. Based on the company recommendation, those fungicides were applied by a sprayer at the recommended rates on a weekly application schedule. Effect of ten fungicides on foliar blight was based on area under disease progress curve (AUDPC). Across all fungicides was reduced by 77％ in AUDPC and dimethomorph was reduced by 92％ in AUDPC during the same period, respectively. Those fungicide were inhibited the mycelial growth of isolate with different rate in chemical amended medium and several fungicides were completely limited the growth of isolate.

• Korean Journal of Agricultural and Forest Meteorology
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• v.15 no.4
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• pp.219-233
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• 2013

We employed the ecological niche modeling framework using GARP (Genetic Algorithm for Ruleset Production) to model the current and future geographic distribution of Pinus densiflora based on environmental predictor variable datasets such as climate data including the RCP 8.5 emission climate change scenario, geographic and topographic characteristics, soil and geological properties, and MODIS enhanced vegetation index (EVI) at 4 $km^2$ resolution. National Forest Inventory (NFI) derived occurrence and abundance records from about 4,000 survey sites across the whole country were used for response variables. The current and future potential geographic distribution of Pinus densiflora, one of the tree species dominating the present Korean forest was modeled and mapped. Future models under RCP 8.5 scenarios for Pinus densiflora suggest large areas predicted under current climate conditions may be contracted by 2090 showing range shifts northward and to higher altitudes. Area Under Curve (AUC) values of the modeled result was 0.67. Overall, the results of this study were successful in showing the current distribution of major tree species and projecting their future changes. However, there are still many possible limitations and uncertainties arising from the select of the presence-absence data and the environmental predictor variables for model input. Nevertheless, ecological niche modeling can be a useful tool for exploring and mapping the potential response of the tree species to climate change. The final models in this study may be used to identify potential distribution of the tree species based on the future climate scenarios, which can help forest managers to decide where to allocate effort in the management of forest ecosystem under climate change in Korea.

• Tuberculosis and Respiratory Diseases
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• v.73 no.3
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• pp.143-150
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• 2012

Background: The release of interferon-gamma (IFN-${\gamma}$) by T lymphocytes increases after rechallenge with Mycobacterium tuberculosis antigen, especially, at a localized site of tuberculosis (TB) infection. We aimed to compare the clincial efficacy of two commercial IFN-${\gamma}$ release assays from pleural fluid for the diagnosis in tuberculous pleurisy. Methods: We performed T-SPOT.TB and QuantiFERON-TB Gold tests simultaneously on pleural fluid and peripheral blood samples from patients with pleural effusion, in South Korea, an area with intermediate TB burden. Results: Thirty-six patients were enrolled prospectively, and tuberculous pleurisy was found in 21 patients. Both the numbers of IFN-${\gamma}$ secreting T cells and the concentration of IFN-${\gamma}$ were greater in the pleural tuberculous group, comparing with the non-tuberculous group. Moreover, in the tuberculous group, there was a significant difference in IFN-${\gamma}$ producing spot-forming cells using the T-SPOT.TB method between pleural fluid and peripheral blood. The receiver operating characteristic (ROC) curve, was the greatest for pleural fluid T-SPOT.TB test, followed by peripheral blood T-SPOT.TB test, peripheral blood QuantiFERON-TB Gold test, and pleural fluid QuantiFERON-TB Gold test (area under the ROC curve of 0.956, 0.890, 0.743, and 0.721, respectively). The T-SPOT.TB assay produced less indeterminate results than did QuantiFERON-TB Gold assay in both pleural fluid and peripheral blood. Conclusion: These findings suggest that the pleural fluid T-SPOT.TB test could be the most useful test among the IFN-${\gamma}$ release assays for diagnosing tuberculous pleurisy in an area with an intermediate prevalence of TB infection.

• Membrane Journal
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• v.13 no.1
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• pp.20-28
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• 2003

In this study, we try to formularize simultaneous equations to make a prediction about pressure drop for designing intravascular artificial lung assist device. Designing parameters to predict the effect of pressure drop and designed modules under various conditions were studied through an experimental modeling before inserting the artificial lung assist device into as venous. We measured pressure drop in various number of hollow fiber membranes, when the inside diameter of shell is fixed in 3 cm, and tried to develope the prediction equations by curve fitting based on the correlation between the experimental pressure drop and the device frontal area or packing density. The results showed that pressure drop increased with 2nd order functional formula as the liquid flow rate, the frontal area, and the packing density increased. Also, we can estimate the pressure drop as a function of the frontal area or packing density. The pressure drop obtained from the experiment was similar to that from the equation, confirming the usefulness of the equation.

• Korean Journal of Radiology
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• v.22 no.5
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• pp.735-741
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• 2021

Objective: To evaluate circularity as a quantitative shape factor of small renal tumor on computed tomography (CT) in differentiating fat-poor angiomyolipoma (AML) from renal cell carcinoma (RCC). Materials and Methods: In 257 consecutive patients, 257 pathologically confirmed renal tumors (either AML or RCC less than 4 cm), which did not include visible fat on unenhanced CT, were retrospectively evaluated. A radiologist drew the tumor margin to measure the perimeter and area in all the contrast-enhanced axial CT images. In each image, a quantitative shape factor, circularity, was calculated using the following equation: 4 x π x (area ÷ perimeter²). The median circularity (circularity index) was adopted as a representative value in each tumor. The circularity index was compared between fat-poor AML and RCC, and the receiver operating characteristic (ROC) curve analysis was performed. Univariable and multivariable binary logistic regression analysis was performed to determine the independent predictor of fat-poor AML. Results: Of the 257 tumors, 26 were AMLs and 231 were RCCs (184 clear cell RCCs, 25 papillary RCCs, and 22 chromophobe RCCs). The mean circularity index of AML was significantly lower than that of RCC (0.86 ± 0.04 vs. 0.93 ± 0.02, p < 0.001). The mean circularity index was not different between the subtypes of RCCs (0.93 ± 0.02, 0.92 ± 0.02, and 0.92 ± 0.02 for clear cell, papillary, and chromophobe RCCs, respectively, p = 0.210). The area under the ROC curve of circularity index was 0.924 for differentiating fat-poor AML from RCC. The sensitivity and specificity were 88.5% and 90.9%, respectively (cut-off, 0.90). Lower circularity index (≤ 0.9) was an independent predictor (odds ratio, 41.0; p < 0.001) for predicting fat-poor AML on multivariable logistic regression analysis. Conclusion: Circularity is a useful quantitative shape factor of small renal tumor for differentiating fat-poor AML from RCC.