• The Korean Journal of Applied Statistics
• /
• v.21 no.2
• /
• pp.183-200
• /
• 2008

Research for efficient management of the National Pension has been emphasized as the current society trends toward aging and low birth rate. In this article, we suggest a statistical model for effective classification and prediction of the reserve for the survivor's pension in Korea. Logistic regression model is incorporated; correct classification rate, and distribution of the posterior probability for the reserve of survivor's pension are investigated and compared with the results from the general logistic models. Assessment of predictive model is also done with lift graph, ROC curve and K-S statistic. We suggest strategies for reducing financial risks in managing and planning the pension as an application of the suggested model.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.29 no.3
• /
• pp.177-182
• /
• 1993

In order to estimate the mesh selectivity master curves and the optimum mesh size, experiments were made by the cover net method with the cod-ends of the five different the opening mesh sizes(51.2mm, 70.2mm, 77.6mm, 88.0mm and 111.3mm). After that 163 hauling were performed and there by investigated, on the training vessel Saebada in the Southern Korean Sea and East China Sea from June 1991 to August 1992. In this report, the mesh selectivity master curves were fitted by using logistic function(S=1/(1+exp super(-(aR+b))), R=(L-L sub(0))/(M-M sub(0)) and the optimum mesh sizes were estimated from each master curve. In this case, a and b are the selection parameters, M is the mesh size of each experimental cod-end. L is body length, L sub(0) and M sub(0) is the distance from the coordinate origine to intersection of linear regression between 25% and 50% selection length. The results obtained are summarized as follows; 1. Trachurus japonicus: Mesh selectivity master curve parameters: a and b were 2. 25, -4.73 respectively and optimum mesh size was estimated to be 79.3mm. 2. Trichiurus lepturus: Mesh selectivity master curve parameters: a and b were 0.81, -3.17 respectively and optimum mesh size was estimated to be 64.5mm. 3. Photololigo edulis: Mesh selectivity master curve parameters: a and b were 1.30m, -4.10 respectively and optimum mesh size was estimated to be 89.9mm. 4. Todarodes pacificus: Mesh selectivity master curve parameters: a and b were 1. 35, -3.45 respectively and optimum mesh size was estimated to be 89.4mm.

• Asian-Australasian Journal of Animal Sciences
• /
• v.28 no.9
• /
• pp.1252-1258
• /
• 2015

The Liangshan pig is a traditional Chinese small-sized breed; it has a relatively long feeding period and low meat production ability but superior meat quality. This study utilized three non-linear growth models (Von Bertalanffy, Gompertz, and logistic) to fit the growth curve of Liangshan pigs from an unselected, random-bred pig population and estimate the pigs most suitable slaughter weight. The growth development data at 20 time points of 275 Liangshan pigs (from birth to 250 d) were collected. To analyze the relative gene expression related to development, seven slaughter weight phases (50, 58, 66, 74, 82, 90, and 98 kg) (20 pigs per phase) were examined. We found that the Liangshan pig growth curve fit the typical S-curve well and that their growth turning point was 193.4 days at a weight of 62.5 kg, according to the best fit Von Bertalanffy model based on the goodness of fit criteria. Furthermore, we estimated that the most suitable slaughter weight was 62.5 to 74.9 kg based on the growth curve and the relative expression levels of growth-related genes.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.59 no.3
• /
• pp.189-195
• /
• 2023

This study quantitatively evaluated size selectivity for three netting shapes (T0; regular, T45, T90) and hanging ratio (35%, 70%) of T0 netting used for trawl codend. The size selectivity experiment was performed in a tank using a cube experimental model with a length of 50 cm on one side and 389 experimental individuals, jack mackerel (Trachurus japonicus). In the selectivity analysis, a selectivity curve was created based on the selection ratio using a logistic function, and the 25%, 50%, and 70% selection length and selection range (SR) were obtained. The T0 netting was 19.54 cm when the 50% selective length, which is a selectivity evaluation index, had a hanging ratio of 35%, a selection range of 0.51 cm, and 22.70 cm and 3.08 cm for the hanging ratio of 70%. The T45 netting was 24.34 cm and 2.13 cm, and the T90 netting was 23.51 cm and 2.84 cm. The results of the T45 netting and the T90 netting are similar, and the 50% selection length and selection range were relatively larger than the T0 netting. There was a significant difference in the correlation between the circumference of the inner circle of the mesh by the shape of the netting and the body girth of the experimental individual (Pearson test, r = 0.86, p < 0.05). There was no significant difference in the correlation between the selection ratio by the T0 netting, T45 netting, and T90 netting with a 70% hanging ratio (one-way ANOVA, p > 0.05). The results of this study showed that selectivity such as T45 netting and T90 netting appeared when the hanging ratio, which maximizes the area of T0 netting, was maintained at 70%.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.36 no.4
• /
• pp.267-273
• /
• 2000

The tooth selectivity of the dredge for catching venus clam (Gomphina melanaegis) was described in which the teeth penetrated the bottom and lifted the shell into the bag. Some factors affecting the selection action of the teeth of the dredge were analyzed related to shell length and shell height. The retention probability of venus clam not sifting through the gaps between the teeth was calculated for various shell lengths and was fitted to two parameter logistic selection curve. The formula obtained is as follows: $P= \frac{1}{1+exp[8.24](\frac{d}{L_1}-0.649)}$, where d is distance between teeth and $L_1$ is a shell length. For biological minimum size(25mm) of venus clam to be catchability 50% the distance between teeth was estimated 16.2mm from the logistic curve. Therefore it is desirable to extend that current spacing between teeth from 12mm to 16mm for the venus clam dredge. That space increasing enables fuel oil of vessel to drag a dredge to be reduced and also man power to sift through sifter smaller venus clams on boards to be reduced.

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

• The Korean Journal of Applied Statistics
• /
• v.30 no.4
• /
• pp.591-602
• /
• 2017

The concentration of fine dust has increased in Korea and people have become more concerned with respiratory diseases. This study selected risk factors for chronic obstructive pulmonary disease (COPD) through demographic and clinical features and constructed a nomogram. First, logistic regression analysis was performed using demographic and clinical feature and the pulmonary function test results of the Korean National Health and Nutrition Examination Survey (KNHANES) $6^{th}$ (2013-2015) and the nomogram was constructed to visualize the risk factors of chronic obstructive pulmonary disease in order to facilitate the interpretation of the analysis results. The ROC curve and calibration plot were also used to verify the nomogram of chronic obstructive pulmonary disease.

• Korean Journal of Remote Sensing
• /
• v.33 no.6_2
• /
• pp.1047-1060
• /
• 2017

In recent years, global warming has been continuing and abnormal weather phenomena are occurring frequently. Especially in the 21st century, the intensity and frequency of hydrological disasters are increasing due to the regional trend of water. Since the damage caused by disasters in urban areas is likely to be extreme, it is necessary to prepare a landslide susceptibility maps to predict and prepare the future damage. Therefore, in this study, we analyzed the landslide vulnerability using the logistic model and assessed the management plan after the landslide through the field survey. The landslide area was extracted from aerial photographs and interpretation of the field survey data at the time of the landslides by local government. Landslide-related factors were extracted topographical maps generated from aerial photographs and forest map. Logistic regression (LR) model has been used to identify areas where landslides are likely to occur in geographic information systems (GIS). A landslide susceptibility map was constructed by applying a LR model to a spatial database constructed through a total of 13 factors affecting landslides. The validation accuracy of 77.79% was derived by using the receiver operating characteristic (ROC) curve for the logistic model. In addition, a field investigation was performed to validate how landslides were managed after the landslide. The results of this study can provide a scientific basis for urban governments for policy recommendations on urban landslide management.

• Journal of Korean Neurosurgical Society
• /
• v.40 no.1
• /
• pp.16-21
• /
• 2006

Objective : Young neurosurgeons need to focus on the mortality and morbidity of aneurysmal neck clipping to develop a personal experience with an initial series. Methods : Total 88 aneurysms from 75 patients who underwent neck clipping by the same operator from 2001 to 2004 were reviewed. Patients were divided into three groups : first year [Group I], second year [Group II], and third year [Group III] in each group. Location of aneurysm, age, Fisher grade, Hunter-Hess grade [H-H grade], postoperative Glasgow outcome scale [GOS], and complications related to surgical procedures were evaluated with Chi-square and logistic regression analyses. Results : Fourteen patients had complications related to surgery [18.7%]. The major causes of mortality and morbidity related to surgery were cerebral infarction, hemorrhage and brain swelling due to intraoperative rupture, brain retraction and vasospasm. Among the 4 cases of mortality were 2 patients in Group I, 1 patient in Group II and 1 patient in Group III, and location of aneurysms were 2 internal carotid artery[ICA] and 2 posterior communicating artery[PCoA] aneurysms. There were 4 morbidity and new neurological deficits in Group I, 4 in Group II and 2 in Group III. Although mortality and morbidity during the learning curve had a statistical significance in H-H grade, age [>60 years old], and aneurysm location [especially ICA aneurysm] as variables, mortality mainly occurred in ICA and PCoA aneurysms. Conclusion : Experienced supervision or endovascular approach should be considered for the treatment of ICA and PCoA aneurysms during the learning curve.

• Smart Structures and Systems
• /
• v.24 no.3
• /
• pp.361-377
• /
• 2019

The stiffness of shape memory alloy (SMA) spring while in actuation is represented by an empirical model that is derived from the logistic differential equation. This model correlates the stiffness to the alloy temperature and the functionality of SMA spring as active variable stiffness actuator (VSA) is analyzed based on factors that are the input conditions (activation current, duty cycle and excitation frequency) and operating conditions (pre-stress and mechanical connection). The model parameters are estimated by adopting the nonlinear least square method, henceforth, the model is validated experimentally. The average correlation factor of 0.95 between the model response and experimental results validates the proposed model. In furtherance, the justification is augmented from the comparison with existing stiffness models (logistic curve model and polynomial model). The important distinction from several observations regarding the comparison of the model prediction with the experimental states that it is more superior, flexible and adaptable than the existing. The nature of stiffness variation in the SMA spring is assessed also from the Dynamic Mechanical Thermal Analysis (DMTA), which as well proves the proposal. This model advances the ability to use SMA integrated mechanism for enhanced variable stiffness actuation. The investigation proves that the stiffness of SMA spring may be altered under controlled conditions.