• Clinical and Experimental Pediatrics
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• v.54 no.6
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• pp.246-252
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• 2011

Purpose: The outcomes of small for gestational age (SGA) infants especially in extremely low birth weight infants (ELBWIs) are controversial. This study evaluated the mortality and morbidity of ELBWIs, focusing on whether or not they were also SGA. Methods: The medical records of 415 ELBWIs (birth weight<1,000 g), who were inborn and admitted to the Samsung Medical Center neonatal intensive care unit from January 2000 to December 2008, were reviewed retrospectively. Mortality and morbidities were compared by body size groups: very SGA (VSGA), birth weight ${\leq}$3rd percentile; SGA, 3rd to 10th percentile; and appropriate for gestational age (AGA) infants, >10th percentile for gestational age. For gestational subgroup analysis, groups were divided into infants with gestational age ${\leq}24^{+6}$ weeks (subgroup I), $25^{+0}$ to $26^{+6}$ weeks (subgroup II), and ${\geq}27^{+0}$ weeks (subgroup III) Results: Gestational age was $29^{+2}{\pm}2^{+6}$ weeks in the VSGA infants (n=49), $27^{+5}{\pm}2^{+2}$weeks in the SGA infants (n=45), and $25^{+4}{\pm}1^{+4}$ weeks in AGA infants (n=321). Birth weight was $692{\pm}186.6$ g, $768{\pm}132.9$ g, and $780{\pm}142.5$ g in the VSGA, SGA, and AGA groups, respectively. Cesarean section rate and maternal pregnancy-induced hypertension were more common in the VSGA and SGA than in AGA pregnancies. However, chorioamnionitis was more common in the AGA group. The mortalities of the lowest gestational group (subgroup I), and also of the lower gestational group (subgroup I+II) were significantly higher in the VSGA group than the SGA or AGA groups (P=0.020 and P=0.012, respectively). VSGA and SGA infants showed lower incidence in respiratory distress syndrome, ductal ligation, bronchopulmonary dysplasia, intraventricular hemorrhage than AGA group did. However, by multiple logistic regression analysis of each gestational subgroup, the differences were not significant. Conclusion: Of ELBWIs, extremely SGA in the lower gestational subgroups, had an impact on mortality, which may provide information useful for prenatal counseling.

• Journal of Korean Society for Atmospheric Environment
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• v.31 no.4
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• pp.378-384
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• 2015

The long-term variations of ozone and nitrogen oxides in Suwon city, the capital of Gyeong-gi province, were examined from 1991 to 2012. In this period, the annual average $O_3$ concentration increased from 13.8 ppbv to 22.7 ppbv and that of $99^{th}$ percentile increased from 58.0 ppbv to 80.0 ppbv. The monthly average and $99^{th}$ percentile of $O_3$ concentrations were the highest in June. The increase in $O_3$ concentration was the greatest in early summer (May and June) before monsoon season began. While the concentrations of NO and NOx have gradually decreased since 2000, $NO_2$ remained unchanged. As a result, $NO_2/NO_x$ ratio increased from 0.5 to 0.73 in 2012. The monthly $NO_2/NO_x$ ratio was the highest in early summer, when monthly average $O_3$ concentration was the highest. It suggests that the enhanced $NO_2/NO_x$ ratio is intimately coupled with increase in $O_3$ for the last two decades in Suwon.

• Journal of the Ergonomics Society of Korea
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• v.31 no.3
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• pp.437-444
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• 2012

The purpose of this study was to suggest appropriate human model for ergonomic evaluation considering working postures on 3D space. Background: Traditionally extreme design rules have been widely utilized at the stage of designing products. Body size of 5th percentile and 95th percentile in stature has been generally selected for controllability and clearance evaluation, respectively. However, these rules had limitations in reflecting working posture in ergonomic evaluation. Method: In order to define working posture on 3D space, not only sagittal plane but also lateral plane was considered. Kinematic linkage body model was utilized for representation of working posture. By utilizing the anthropometric data of 2,836 South Korean male populations, the point cloud for end points of linkage models was derived. The individuals who were lacking in certain controllability were selected as human models for the evaluation. Result: In case of standing posture it was found that conventional approach is proper for all controllability evaluations. Contrary to standing posture, tall people had less controllability on control location below shoulder point in sitting posture. Conclusion: From the derived proper range on controllability, ergonomic evaluation rule was suggested according to working posture especially in standing and sitting. Application: The results of the study are expected to aid in selection of appropriate human model for ergonomic evaluation and to improve the usability of products and work space.

• Journal of the Korean Geographical Society
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• v.39 no.5 s.104
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• pp.711-721
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• 2004

The aim of this study is to clarify whether frequency and/or severity of extreme climate events have changed significantly in Korea during recent years. Using the best available daily data, spatial and temporal aspects of ten climate change indicators are investigated on an annual and seasonal basis for the periods of 1954-1999. A systematic increase in the $90^{th}$ percentile of daily minimum temperatures at most of the analyzed areas has been observed. This increase is accompanied by a similar reduction in the number of frost days and a significant lengthening of the thermal growing season. Although the intra-annual extreme temperature range is based on only two observations, it provides a very robust and significant measure of declining extreme temperature variability. The five precipitation-related indicators show no distinct changing patterns for spatial and temporal distribution except for the regional series of maximum consecutive dry days. Interestingly, the regional series of consecutive dry days have increased significantly while the daily rainfall intensity index and the fraction of annual total precipitation due to events exceeding the $95^{th}$ percentile for 1901-1990 normals have insignificantly increased.

• International Journal of Automotive Technology
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• v.5 no.1
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• pp.33-46
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• 2004

A finite element model development of a 50th percentile male cervical spine is presented in this paper. The model consists of rigid, geometrically accurate vertebrae held together with deformable intervertibral disks, facet joints, and ligaments modeled as a series of nonlinear springs. These deformable structures were rigorously tuned, through failure, to mimic existing experimental data; first as functional unit characterizations at three cervical levels and then as a fully assembled c-spine using the experimental data from Duke University and other data in the NHTSA database. After obtaining satisfactory validation of the performance of the assembled ligamentous cervical spine against available experimental data, 22 cervical muscle pairs, representing the majority of the neck's musculature, were added to the model. Hill's muscle model was utilized to generate muscle forces within the assembled cervical model. The muscle activation level was assumed to be the same for all modeled muscles and the degree of activation was set to correctly predict available human volunteer experimental data from NBDL. The validated model is intended for use as a post processor of dummy measurement within the simulated injury monitor (SIMon) concept being developed by NHTSA where measured kinematics and kinetic data obtained from a dummy during a crash test will serve as the boundary conditions to "drive" the finite element model of the neck. The post-processor will then interrogate the model to determine whether any ligament have exceeded its known failure limit. The model will allow a direct assessment of potential injury, its degree and location thus eliminating the need for global correlates such as Nij.

• Journal of the Ergonomics Society of Korea
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• v.29 no.6
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• pp.831-841
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• 2010

Usability evaluation of physical products involves characterizing complex physical interactions between humans and products. Human models known as manikins have been widely utilized as usability evaluation tools for automobile interior package design. When combined with computer-aided design software programs, such manikins can be used to simulate driving postures and evaluate driver-interior fits early in the design process, and therefore, may greatly facilitate achieving high-quality design in a cost-efficient manner. The purpose of this study was to define a set of manikins for designing automobile interior packages for the South Korean male population. These manikins were conceptualized as "boundary" manikins, which represent individuals lacking in certain physical capacities or having usability-related issues (e.g., an individual with the 5th percentile forward reach capability, an individual with the 95th percentile shoulder width). Such boundary manikins can serve as an efficient tool for determining if an automobile interior design accommodates the majority of the population. The boundary manikins were selected from the large sample of Korean males whose anthropometric dimensions were described in the recent Size Korea anthropometric database. For each male in the database, his comfortable driving posture was represented using a kinematic body linkage model and various physical capacity measured and usability-related characteristics relevant to driver accommodation were evaluated. For each such measure, a boundary manikin was selected among the Korean males. The manikins defined in this study are expected to serve as tools for ergonomic design of automobile interior packages. The manikin selection method developed in this study was implemented as a generic software program useful for various product design applications.

• Journal of Preventive Medicine and Public Health
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• v.22 no.3 s.27
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• pp.303-312
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• 1989

To show the distribution and change of blood pressure according to age and to find factors affecting the level of blood pressure in primary school children, a follow-up study was conducted from 1986 to 1989 on 401 first grade children attending primary school in Kangwha County in 1986 and their parents. The blood pressure of the children was significantly increased according to age. The average annual increase was 1.8mmHg in systolic blood pressure and 2.5mmHg in diastolic blood pressure. The level of blood pressure did not show any significant difference in both sexes. Among children who were at or above the 80th percentile of blood pressure in the first grade, 35 and 30% of them have remained at the same level of systolic and diastolic blood pressure respectively in the fourth grade. But we could not find any significance in the tracking of blood pressure of children who were at or above the 90th percentile of blood pressure in the first grade. Weight and pulse rate were shown to be significant factors affecting systolic blood pressure in children of both sexes and mother's blood pressure and skinfold thickness were also affected systolic blood pressure in girls. The variables significantly affecting diastolic blood pressure were arm circumference and pulse rate for boys and height and pulse rate for girls.

• Journal of Climate Change Research
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• v.9 no.2
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• pp.157-169
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• 2018

This study explores the long?term trends of extreme temperatures of 270 observation stations in East Asia (China, Japan, and Korea) for 1961?2013. The 5th percentile of daily minimum temperatures (TN05%) and 95th percentile of daily maximum temperatures (TX95%), derived from the quantile regression, are particularly examined in term of their linear and nonlinear trends. The warming trends of TN05% are typically stronger than those of TX95% with more significant trends in winter than in summer for most stations. In both seasons, warming trends of TN05% tend to amplify with latitudes. The nonlinear trends, quantified by the $2^{nd}$?order polynomial fitting, exhibit different structures with seasons. While summer TN05% and TX95% were accelerated in time, winter TN05% underwent weakening of warming since the 2000s. These results suggest that extreme temperature trends in East Asia are not homogeneous in time and space.

• Safety and Health at Work
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• v.13 no.3
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• pp.308-314
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• 2022

Background: Occupational cancer is a global health issue. The Korean CARcinogen EXposure (K-CAREX), a database of CARcinogen EXposure, was developed for the Korean labor force to estimate the number of workers exposed to carcinogens by industry. The present study aimed to estimate the intensity of exposure to carcinogens by industry, in order to supply complementary information about CARcinogen EXposure intensity to the K-CAREX. Methods: We used nationwide workplace monitoring data from 2014 to 2016 and selected target carcinogens based on the K-CAREX list. We computed the 95th percentile levels of measurements for each industry by carcinogens. Based on the 95th percentile level relative to the occupational exposure limit, we classified the CARcinogen EXposure intensity into five exposure ratings (1-5) for each industry. Results: The exposure ratings were estimated for 21 carcinogenic agents in each of the 228 minor industry groups. For example, 3,058 samples were measured for benzene in the manufacturing industry of basic chemicals. This industry was assigned a benzene exposure rating of 3. Conclusions: We evaluated the CARcinogen EXposure ratings across industries in Korean workers. The results will provide information on the exposure intensity to carcinogens for integration into the K-CAREX. Furthermore, it will aid in prioritizing control efforts and identifying industries of concern.

• Journal of Environmental Health Sciences
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• v.49 no.4
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• pp.210-217
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• 2023

Background: N-nitrosamines are carcinogenic substances often found in rubber products. They are produced when certain additives of rubber products react with nitrite in saliva or air. Exposure assessment for the proper management and communication of N-nitrosamines in rubber balloons should be carried out. Objectives: This study was conducted to determine the concentrations of N-nitrosamines in rubber balloons in the South Korean market and assess exposure among Korean children. Methods: Forty eight rubber balloon products in the domestic market were purchased and a total of 68 balloons were analyzed for N-nitrosamines and N-nitrosatable substances. Chemical analysis was conducted by HPLC-MS/MS according to the method EN 71-12. For exposure assessment, an exposure algorithm and coefficients were obtained from previous studies. Results: Among the 68 rubber balloons, N-nitrosamines were detected in 18 (26.5%) with an average level of 60.77 ㎍/kg. N-Nitrosatable substances were detected in 44 products (64.7%) with an average level of 1353.33 ㎍/kg. As a result of the exposure evaluation, the exposure dose differed according to how exposure coefficients were applied. The median exposure (50th percentile) was higher in the age group of 6~12 years, and high exposure (95th percentile) was higher in the age group of 13~18. Conclusions: We evaluated the N-nitrosamines contained in rubber balloons purchased in the domestic market and assessed oral exposure among South Korean children. For integrated risk management of N-nitrosamines, further studies and discussion regarding exposure and risk assessment are required.