• Korean Journal of Materials Research
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• v.27 no.7
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• pp.359-363
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• 2017

The resistance of metallic materials to ballistic penetration generally depends on a number of parameters related to projectile, impact, and armor plate. Recently, armor materials have been required to have various properties such as hardness, strength, and impact toughness in order to maintain an excellent ballistic resistance even after impact. In the present study, the influence of tempering on the microstructure and mechanical properties of an ARMOX 500T armor steel plate was investigated and then compared with those of S45C and SCM440 steels. As the tempering temperature increased, the hardness and strength gradually decreased, whereas the ductility and impact toughness clearly increased because the hardness, tensile, and impact properties were affected by the microstructural evolution and precipitation occurring during tempering. On the other hand, temper embrittlement appeared at tempering temperatures of 300 to $400^{\circ}C$ for the impact specimens tested at low temperature.

• Journal of Home Health Care Nursing
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• v.8 no.2
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• pp.135-147
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• 2001

The aim of this descriptive study was to identify the impact of chronic illness on children and their families. Mothers of 177 children with chronic disease were recruited from aged one to 17 years hospitalizing the pediatric nursing unit at one university hospital. 28 questions. a self-complete maternal questionnaire developed by researchers based on literatures and 'The Impact of Childhood Illness Scale' (Hoare & Russell, 1995) assess four aspects of the child's and family's lifestyle with two dimensions for each question. the frequency of the problem and its importance of concern that it cause. In the data analysis. Pearson correlation coefficients and analysis of variance were used to test any association and a statistical comparisons. between individual variables and the impact on child's and family's lifestyle. The results were as follows: 1) There were the higher mean scores on the importance dimension than on the frequency dimension on total impact on child's and family's lifestyle. On the importance dimension. mothers had much higher levels of concern about impact on child's development and adjustment among subscales. On the frequency dimension, mothers had much higher levels of concern about impact on the family daily living on subscales. 2) The impact on child's and family's lifestyle related on individual variables were: (1) On the importance dimension. there was statistically significant low in the impact on child's development and adjustment among subscales in older parent group compared with it of younger parent group. (2) On the frequency dimension. there were statistically significant high in the impact on child's development and adjustment among subscales in the children with leukemia or cancer compared with it of the other children who had another chronic illnesses. And there were statistically significant high in the impact on child's development and adjustment among subscales in less than high school educated mothers compared with it of mothers who was educated college level. (3) On the frequency dimension. There were statistically significant high in the impact on family's daily living among subscales and total impact on child's and family's lifestyle in female children. (4) There was positive correlation between impact on parents daily living and frequency of child's hospitalization on the frequency dimension. but there was negative correlation between the two variables on the importance dimension. (5) There was positive correlation between impact of chronic illness and its treatment and duration of child's hospitalization on the frequency dimension. In conclusion. these results were reflected by the high level of concerns about impact on child's development and adjustment although mothers had frequently responded about the impact on the family daily living. We suggest consistent intervening program that help the family empowering to make children live with and adjust to their chronic illnesses from the point of diagnosis and after discharge from the hospital. We also suggest these results can be utilized as a useful data in the practice of home health nursing for children who have chronic illnesses and their families.

• Journal of Korean Society of Rural Planning
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• v.30 no.2
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• pp.69-77
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• 2024

As impervious area increases due to urbanization, rainfall on the impervious area does not infiltrate into the ground, and stormwater drains quickly. Low impact development (LID) practices have been suggested as alternatives to infiltrate and store water in soil layers. The practices in South Korea is applied to urban development projects, urban renewal projects, urban regeneration projects, etc., it is required to perform literature research, watershed survey, soil quality, etc. for the LID practices implementation. Prior to the LID implementation at fields, there is a need to simulate its' effect on watershed hydrology, and Storm Water Management Model (SWMM) provides an opportunity to simulate LID practices. The LIDs applied in South Korea are infiltration-based practices, vegetation-based practices, rainwater-harvesting practices, etc. Vegetation-based practices includes bio-retention cell and rain garden, bio-retention cells are mostly employed in the model, adjusting the model parameters to simulate various practices. The bio-retention cell requires inputs regarding surface layer, soil layer, and drain layer, but the inputs for the drain layer are applied without sufficient examination, while the model parameters or inputs are somewhat influential to the practice effects. Thus, the approach to simulate vegetation-based LID practices in SWMM uses was explored and suggested for better LID simulation in South Korea.

• Journal of Environmental Impact Assessment
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• v.21 no.3
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• pp.445-460
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• 2012

In order to evaluate and predict the environmental impact of the low-trophic-level ecosystem to environmental changes in the Yellow Sea and the East China Sea, an ecological modelling study was undertaken. Simulation results of average distribution patterns and concentrations of water quality factors during the summer by the model were acceptable. Phytoplankton and remineralization rate of organic matter were very important parameters by a sensitivity analysis. Water quality factors showed high values in the estuary of the Yangtze River and in the West and South Sea of Korea and low values in the central area of the Yellow Sea. There is a plume of high values, especially nutrients, off the mouth of the Yangtze that expands or contracts with changes in the discharge strength. Characteristics of responses of water quality factors vary for different scenarios of environmental change, such as land-based pollution sources and atmospheric forcing. It is suggested that changes of light intensity, discharges of input sources, and wind play an important role in the marine ecosystem.

• Steel and Composite Structures
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• v.18 no.5
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• pp.1291-1303
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• 2015

Damage caused by low velocity impact is so dangerous in composites because although in most cases it is not visible to the eye, it can greatly reduce the strength of the composite material. In this paper, damage development in U-section glass/polyester pultruded beams subjected to low velocity impact was considered. Different failure criteria such as Maximum stress, Maximum strain, Hou, Hashin and the combination of Maximum strain criteria for fiber failure and Hou criteria for matrix failure were programmed and implemented in ABAQUS software via a user subroutine VUMAT. A suitable degradation model was also considered for reducing material constants due to damage. Experimental tests, which performed to validate numerical results, showed that Hashin and Hou failure criteria have better accuracy in predicting force-time history than the other three criteria. However, maximum stress and Hashin failure criteria had the best prediction for damage area, in comparison with the other three criteria. Finally in order to compare numerical model with the experimental results in terms of extent of damage, bending test was performed after impact and the behavior of the beam was considered.

• Composites Research
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• v.31 no.5
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• pp.215-220
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• 2018

In this study, finite element analysis of Carbon-Steel Laminates with different layup pattern was conducted to verify similarity to the results of previous studies and to develop the effective model for low-velocity impact analysis. As in the experiment, Finite element analysis of the Fiber metal laminates (FMLs) with five different lamination patterns was carried out, and the impact resistance of the FMLs was confirmed by comparing the energy absorption ratio. The FMLs showed the higher energy absorption ratio than the mild steel having the same thickness, and it was confirmed that all the FMLs had the high energy absorption ratio over than 96%. In addition, the low-velocity impact analysis model proposed in this study can be effectively used to study composite forms and automotive structures.

• Journal of Auto-vehicle Safety Association
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• v.4 no.2
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• pp.37-43
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• 2012

The purpose of this research is to obtain and analyze dynamic responses from human volunteers for the development of the human-like mechanical or mathematical model for Korean males in automotive rear collisions. This paper focused on the introduction to a low-speed rear impact sled test involving Korean male subjects, and the accumulation of the motion of head and neck. A total of 50 dynamic rear impact sled tests were performed with 50 human volunteers, who are 30-50 year-old males. Each subject can be involved in only one case to prevent any injury in which he was exposed to the impulse that was equivalent to a low-speed rear-end collision of cars at 5-8 km/h for change of velocity, so called, ${\Delta}V$. All subjects were examined by an orthopedist to qualify for the test through the medical check-up of their necks and low backs prior to the test. The impact device is the pendulum type, tuned to simulate the crash pulse of a real vehicle. All motions and impulses were captured and measured by motion capture systems and pressure sensors on the seat. Dynamic responses of head and T1 were analyzed in two cases(5 km/h, 8 km/h) to compare with the results in the previous studies. After the experiments, human subjects were examined to check up any change in the post medical analysis. As a result, there was no change in MRI and no injury reported. Six subjects experienced a minor stiffness on their back for no more than 2 days and got back to normal without any medical treatment.

• Journal of Korean Society on Water Environment
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• v.29 no.4
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• pp.466-475
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• 2013

Non-point source pollution management is one of the most important issues in Korean water quality/watershed management. In recent years, Low Impact Development (LID) has emerged as an effective approach to control stormwater in an urban area. This study illustrates how to design and evaluate the effect of non-point pollutant management using EPA-SWMM LID module and suggests design parameters for modeling LID facilities. In addition, optimal installation locations of LID can be determined by a simple distributed hydrologic model by using SWMM for a long-term.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.181-181
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• 2015

최근 계속적인 도시화와 개발로 인해 불투수층이 증가함에 따라, 도시비점오염물질이 동반된 표면유출수가 증가하고 있다. 또한 도시 오염물질 배출특성 중 하나인 초기세척효과(First Flush Effect)가 대두되고 있다. 초기세척효과란 강우 시 강우초반에 고농도의 오염물질 나타나는 현상을 의미한다. 최근 이와 같은 도시 오염물질을 관리 및 저감을 위해 저영향개발(Low Impact Development)이 대안으로 나타나고 있다. 하지만 이러한 저영향개발을 분석 및 정량하기 위해서는 많은 실험적인 연구와 모델링이 필요하다. 본 연구에서는 광주광역시에 위치한 상업지구에 대해 모니터링과 LID 모델링을 실시하였고, 또한 Mass First Flush (MFF)라는 지표를 이용하여 최적 LID 크기를 산정하였다. 본 연구에선 나온 LID 크기는 1.2 mm부터 3.0 mm 정도로 나타났다. 이 결과는 향후 초기세척처리를 LID의 가이드라인으로 유용할 것이다.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.391-391
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• 2021

최근에는 도시에는 불투수 면적의 증가로 지면 침투량이 줄어들고 유출량이 증가되고 있다. 또한 지면에서의 먼지 등 비점오염원의 유출로 인한 수질악화도 진행되는 경우가 많다. 그러므로 도시의 개발에 따른 악영향을 최소화하기 위해 다양한 저영향개발기법(Low Impact Development)을 도입하여 도시 물순환 건전성을 확보하기 위해 노력하고 있다. 본 연구에서는 도시 유역에서의 유출량 분석을 위해 저영향개발기법 중 투수성포장과 옥상녹화 등을 적용하여 침투량의 증가와 유출량 감소 결과를 분석하였다. 투수성포장과 옥상녹화의 영향이 크지는 않지만, 도시에서의 유출량 저감에 영향을 미칠 수 있는 것으로 분석되었으며, 향후 지속적인 도시 물순환 건 전성 확보연구의 기초 자료로 활용될 수 있을 것으로 보인다. 그 결과는 도시 개발 계획의 우선순위를 결정하는데 사용될 수 있어서, 도시 공간의 삶의 질이 향상될 것이다.