• Journal of the Society of Disaster Information
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• v.10 no.3
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• pp.466-480
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• 2014

In addition to aging social problem, the problem of older age structure ratio in the fire service organization playing the leading role of the disaster response activities is also expected to be this serious situation. In the case of Seoul fire fighting organization, it is expected that the ratio of over the age 50 reaches 31% or 40% between from 10 to 15 years later from now on, but this will be a serious problem in the fire fighting personnel needing a healthy body and physical strength in the disaster situation unlike the civil servants of general staff. Therefore, the purpose of this study is to take measures that can adapt to a new disaster environment of Increasing proportion of the elderly population by presenting the criteria of age limit of fire fighting field activities to analyze the relevance of the ability to perform on-site activities and age of Seoul fire civil servants, by using three analysis criteria.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.6
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• pp.2528-2534
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• 2011

This paper investigates the relationship between the change of age structure of population and the efficiency of education investment, using cross-section of 106 countries. Based on the existing theoretical arguments, we establish a hypothesis concerning the relationship between age structure and education investment efficiency. The regression results suggest that a country's with a higher ratio of young age to total population results in a lower level of the efficiency of education investment. However, there exists a positive and significant relationship between the ratio of old age to total population and the efficiency of education investment. Therefore, it does suggest that countries experiencing reducing in fertility rate and increasing in expected longevity, such as Korea, not only should be maximized the education efficiency but also contrived for the institutional system for maximization the efficiency of education performance.

• Journal of Korean Society of Rural Planning
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• v.25 no.4
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• pp.99-107
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• 2019

This paper analyzed the characteristics of population change from 2000 to 2018 in 466 mountainous areas using resident registration data from the Ministry of the Interior and Safety, and projected the population in those areas through 2050 with the cohort change ratio method. The population had dramatically decreased from 2000 to 2009. With the slowing population decrease after 2010, the population has increased gradually since 2014. Especially the population of ages over 65 in 2018 had increased 34% compared to 2000, while the working age population had decreased 29%. This shows that population aging becomes serious problems in the mountainous area. Assuming the cohort change ratios from 2010 to 2015 and child-woman ratio in 2015 remain constant, it appeared that the projected population of the mountainous area dropped to 1.26 million in 2030 and 820,000 in 2050. It is expected to have a population with an inverted pyramid structure showing a gender imbalance with more females in 60's and 70's. Although it continues to show the recent population growth in mountainous area, population in mountainous area is expected to consistently decrease. Therefore, it is required to develop policies and strategies to promote an influx of people into mountainous area for maintaining functionality and sustainability of mountainous areas.

• Food Science of Animal Resources
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• v.38 no.5
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• pp.1080-1091
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• 2018

The eggshell, which is a complex and highly ordered structure, is very important factor for food safety and egg marketing. This study investigated the changes in eggshell structure and shell components in relationship to hen age. For this study, we examined the histological change of the endometrium of the 30-, 60-, and 72-wk-old commercial layers, and analyzed the ultrastructure and ionic composition of their eggshells. The results showed that histological deformation, fibrosis, atrophy and elimination of micro-villi in the uterus endometrium were found through microscopic observation that was associated with increasing hen age. Concentration of blood-ion components such as $Ca^{2+}$, $Na^+$, $K^+$, and $Cl^-$ ions did not change with age. Along with the results from the ultrastructure analysis of the eggshell, the palisade layer ratio and the density of mammillary knobs were significantly decreased in older hens. In addition, the type B mammillary knobs were frequently observed with increasing hen age. In the mineral element assay from the eggshell, $Ca^{2+}$, $S^{2-}$, and $Co^{2+}$ significantly decreased with increasing hen age, whereas $Na^+$, $K^+$, and $V^{2+}$ significantly increased. Therefore, the damages of endometrial tissue inhibit the processes of ion transmission and the crystallization of eggshell formation, resulting in a large and non-uniform mammillary knob formation. This means the conditions of endometrial cells affect the formation of the eggshell structure. In conclusion, hen aging causes the weakness of the eggshell and degrades the eggshell quality.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.132-135
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• 2004

High-performance concrete (HPC) may be expected to differ from usual concrete with respect to shrinkage behavior, and it shows high autogenous shrinkage due to the use of very low water-binder ratio (w/b) and various admixtures. Therefore, in order to minimize the shrinkage stress and to ensure the service life of concrete structure, volumetric change of HPC should be understood. In this study, small prisms made of HPC with w/b of 0.32 and blast-furnace slag content of $0\%,\;30\%,\;and\;50\%$ were prepared to measure the volumetric changes such as autogenous shrinkage, drying shrinkage, and swelling under three different curing conditions. It was observed that the concrete cured. sealed condition showed only autogenous shrinkage while the concrete let to dry condition at temperature of $20^{\circ}C$ and relative humidity of $60\%$ during the test period showed both autogenous and drying shrinkage. Moreover, the concrete exposed to dry condition after 2-day water curing swelled and then started to shrink with age. The total shrinkage (autogenous+drying) of this concrete was smaller than that of the concrete cured dry condition, especially at early-age. Therefore, the early-age moisture curing is very effective to control or minimize the volumetric change and its induced stress of HPC.

• Journal of the Korean Institute of Rural Architecture
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• v.19 no.2
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• pp.25-33
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• 2017

This study aims to find out the change trend of the existing vacant houses in the small and medium sized farming city. And the using method of those houses is proposed in this paper. Especially to find out the change trend ratio of vacant houses in the case, the historic conservation area - Keumma village is selected as the research target area. To carry out this study, it was surveyed in 2013 when they were not designated as the special area first. And it is reviewed in 2017 when it is designated. The contents of the survey were their use, old age, structure, materials, color, roof of the main building and wall. they were surveyed by direct and interview survey. And thew were analyzed and synthesized. It is concluded that the 142 vacant houses in 2013 were declined 46houses in 2017. It is caused by the government support. And they will be declined continuously. The architectural statues of vacant houses between in 2013 and in 2017 are almost same in it's use, old age, structure, materials, color, roof of the main building and wall. In the use ratio of the vacant houses that of residence is most high, and that of warehouses, commerce are followed in turn. The reason of that statues is moving out is the first and the death of house holder, the difficulty of managing are followed. As the their re-use plan of owners, the selling is the first, constructing new buildings and the renovation them are followed. As the method of their use, re-use, community facilities, managing in the vacant houses bank are proposed. As the vacant houses are the reason of bad elements in the rural landscape in the farm village, the method of its improvement will be carried out.

• Journal of the Korea Concrete Institute
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• v.17 no.5 s.89
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• pp.853-856
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• 2005

A low water/cement ratio leads to autogenous shrinkage of cement paste at an early age. This autogenous shrinkage is related to the change of relative humidity in the pore structure that is formed during the hydration process. The relationship between autogenous shrinkage and relative humidity change are relatively well defined today, but the effects of temperature on autogenous shrinkage, relative humidity, and pore structures have been studied less systematically. This study focused on correlating alterations of these properties of cement paste hydrated at constant temperatures of 20, 40, and $60^{\circ}C$. The test results clearly indicate that increasing curing temperature resulted in increased porosity, particularly for pores between 5 to 50 nm as measured by MIP, and increased autogenous shrinkages, as a consequence of a reduction of relative humidity at early ages.

• Sleep Medicine and Psychophysiology
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• v.17 no.1
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• pp.21-27
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• 2010

Objectives: It is well established that primary insomnia affects the activity of autonomic nervous system. We tried to know how the activity of autonomic nervous system during night sleep changes by analyzing correlation between heart rate variability (HRV) index and the variables related with sleep structure in primary insomnia. Methods: Thirty three subjects (mean age: $36.2{\pm}14.2$ years, male:female=15:18) who were diagnosed with primary insomnia were selected for the study. Nocturnal polysomnography (NPSG) was carried out on each subject and correlation was analyzed between high frequency/low frequency ratio (LF/HF ratio), one of HRV indices and the variables related with sleep structure which were calculated from NPSG. Results: When age and sex were controlled, LF/HF ratio showed negative correlations with slow wave sleep and stage 2 sleep, respectively ($r_p$=-0.43, p=0.01; $r_p$=-0.37, p=0.04). On the other hands LF/HF ratio showed a positive correlation with arousal index ($r_p$=0.65, p<0.001). The activity of autonomic nervous system responded differentially depending on the change of sleep structure in primary insomnia. Especially the increase of arousal index and the decrease of slow wave sleep and stage 2 sleep which are the components of non-REM sleep provoked hyperactivity of sympathetic nervous system. Conclusion: This study suggests that the typical change of sleep structure in primary insomnia can negatively impact on cardiovascular system.

• Journal of the Korea Safety Management & Science
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• v.10 no.2
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• pp.225-235
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• 2008

It is expected that the change of industrial structure of Knowledge based economy, and service based economy would affect on economic life of physically-challenged person with no exceptions. There have been some former studies which have been misunderstood the employment of disabled due to the declining employment of the disabled and prejudice to the disabled based on biased perspective and public opinion. This study have analyzed the employment conditions of the ordinary workers and disabled workers out of those prejudices and biased opinions. Wage, economic activity ratio, age, educational background and industry those 5 parameters are brought for analyzing the two comparison group. Each parameter have compared based on the statistical data of ordinary workers and disabled workers for past 7 years. Weight between each parameter have been drawn by collecting the experts' opinion using AHP(Analytic Hierarchy Process), and utility of employment of two comparison groups have been estimated through progress inclination of each parameter. Through the estimated outcome, present condition and controversial issues and way of improvement of domestic employment of ordinary workers and the disabled is mentioned.

• Proceedings of the Safety Management and Science Conference
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• 2008.11a
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• pp.405-419
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• 2008

It is expected that the change of industrial structure of Knowledge based economy, and service based economy would affect on economic life of physically-challenged person with no exceptions. There have been some former studies which have been misunderstood the employment of disabled due to the declining employment of the disabled and prejudice to the disabled based on biased perspective and public opinion. This study have analyzed the employment conditions of the ordinary workers and disabled workers out of those prejudices and biased opinions. Wage, economic activity ratio, age, educational background and industry those 5 parameters are brought for analyzing the two comparison group. Each parameter have compared based on the statistical data of ordinary workers and disabled workers for past 7 years. Weight between each parameter have been drawn by collecting the experts' opinion using AHP(Analytic Hierarchy Process), and utility of employment of two comparison groups have been estimated through progress inclination of each parameter. Through the estimated outcome, present condition and controversial issues and way of improvement of domestic employment of ordinary workers and the disabled is mentioned.