• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.3
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• pp.147-154
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• 2014

In the context of an increasing need for safety in concrete structures under blast and impact loading condition, the behavior of concrete under high strain rate condition has been an important issue. Since concrete subjected to impact loading associated with high strain rate shows quite different material behavior from that in the static state, several material models are proposed and used to describe the high strain rate behavior under blast and impact loading. In the process of modelling high strain rate conditions with these material models, mesh dependency in the used finite element(FE) is the key problem because simulation results under high strain-rate condition are quite sensitive to applied FE mesh size. This paper introduces an criterion which can minimize the mesh-dependency of simulation results on the basis of the fracture energy concept, and HJC(Holmquist Johnson Cook) model is examined to trace sensitivity to the used FE mesh size. To coincide with the purpose of the perforation simulation with a concrete plate under a projectile(bullet), the residual velocities of projectile after perforation are compared. The analytical results show that the variation of residual velocity with the used FE mesh size is quite reduced and accuracy of simulation results are improved by applying a unique failure strain value determined according to the proposed criterion.

• Journal of Environmental Health Sciences
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• v.45 no.6
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• pp.668-674
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• 2019

Objectives: Modern people spend most of their day indoors. As the health impact of radon becomes an issue, public interest also has been growing. The primary route of potential human exposure to radon is inhalation. Long-term exposure to high levels of radon increases the risk of developing lung cancer. Radon exposure is known to be the second-leading cause of lung cancer, following tobacco smoke. This study measures the indoor radon concentrations in detached houses in area A of Chungcheongbuk-do Province considering the construction year, cracks in the houses, the location of installed detectors, and seasonal effects. Methods: The survey was conducted from September 2017 to April 2018 on 1,872 private households located in selected areas in northern Chungcheongbuk-do Province to figure out the year of building construction and the location of detector installed and identify the factors which affect radon concentrations in the air within the building. Radon was measured using a manual alpha track detector (Raduet, Hungary) with a sampling period of longer than 90 days. Results: Indoor radon concentrations in winter within area A was surveyed to be 168.3±193.3 Bq/㎥. There was more than a 2.3 times difference between buildings built before 1979 and those built after 2010. The concentration reached 195.4±221.9 Bq/㎥ for buildings with fractures and 167.2±192.4 Bq/㎥ for buildings without fractures. It was found that detectors installed in household areas with windows exhibited a lower concentration than those installed in concealed spaces. Conclusion: High concentrations of indoor radon were shown when there was a crack in the house. Also, ventilation seems to significantly affect radon concentrations because when the location of the detector in the installed site was near windows compared to an enclosed area, radon concentration variation increased. Therefore, it is considered that radon concentration is lower in summer because natural ventilation occurs more often than in winter.

• Journal of the Economic Geographical Society of Korea
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• v.18 no.2
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• pp.168-189
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• 2015

The job creation has been the most pressing issue after financial crisis in many countries around the world. Various policies for creating jobs have been implemented in order to revitalize regional economy in Korea. It has been known that the jobs have been created more in low-wage and part-time work than high-wage and full-time work. The purpose of this study is to analyze the differentiation of startups job in local labor market areas(LLMAs) in terms of job quantity as well as job quality. As the spatial unit, 121 local labor market areas which were delineated based on self-containment rate(demand and supply side of labor market) and numbers of resident workers are used. Also due to difference of the size of employment, LLMAs are classified into 3 groups: large, Medium, small LLMAs. The major results are as follows: First, the characteristics of the job creation are varied among 3 groups in terms of the quantitative and qualitative aspects. Highly waged and highly value-added jobs have been created more in large LLMAs, but full-time jobs created more in small LLMAs. Secondly, the job creation of LLMAs is somewhat weakly correlated to regional economic performance. While the quality of jobs is correlated to regional economic performance in Medium LLMAs, the quantity of jobs is significantly correlated to regional economic performance in small LLMAs. The results of this research give some implications for implementing the effective policy to create jobs related to regional economy, indicating that differentiated strategies for 3 groups of LLMAs is critically important.

• Resources Recycling
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• v.18 no.3
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• pp.11-19
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• 2009

Recently the problem of global environment is became by social issue. Accordingly the interests to recycling and saving of resources are growing from daily life to varieties field of industry. To preserve the global environment, prevent global warming, environmental destruction, environmental pollution by wastes, the drain of aggregate, plasticity energy of cement and decrease in carbon dioxide are an urgent problem that must be resolved. So there is to a field of building industry and stands but on the inside of the building the many double meaning resources usefully, applies. Also the seller masterpiece building where the service life is long planned is safe and comfortably, maintenance, suppresses the construction which is not necessary is unnecessary. Also the seller masterpiece building where the service life is long planned is safe and comfortably, maintenance, suppresses the construction which is not necessary is unnecessary. By revitalizing effective use of limited earth resources, recycling and controling production of construction waste, this study introduced to a method for Long-Term Durability of Construction Structure and Effective Use of Technology for Construction Waste considering architectural demand and earth environment. It is for reduction of an earth environment load from the side of construction production and performance design of a structure.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.2
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• pp.679-689
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• 2013

To relieve Green-house Gas Emission is the key issue in urban area. Urban transport policies have focused on the reduction of private car use. The most common of these is Travel Demand Management(e.g., congestion charge, environmental tax, etc.) that forces individuals to reduce their private car use. An alternative way is Mobility Management(MM) that induces individuals to voluntarily change their car use through communications. MM is founded on social psychology theory and focuses on individuals' decision making processes to change their perception and attitude on private car use. Although some researchers have reported the relevance of MM approach, still few researches have explicitly studied on individuals' decision making processes. Therefore, the aims of the paper are to analyze the decision making process of individuals and to provide the basis of introducing MM approach in Korea. Structural equation model(SEM) is applied for the analysis of individuals' decision making process. A empirical study shows that psychological factors such as perception/attitude on global environment or individual norms impact significantly to reduce private car use and accordingly the relevance of introducing MM approach instead of imposing regulations or expanding transport facilities.

• Journal of the Korean Society for Railway
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• v.16 no.4
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• pp.340-347
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• 2013

This paper studied the causes of job stress of driving crews working in Metropolitan Transit Authorities in Daejeon, Daegu, Seoul Metro Line 9, and Incheon, analyzing psychological, physical, and environmental factors, along withdriving crews' assignments. Regarding driving crews' assignments, it was found that driving crews had strong senses of obligation for their job, and hence their aptitude for their job was in accordance, and also it was found that most driving crews worked devotedly with a desirable occupational view and pride. However, psychological and physical factors that contributed to stress were identified: lack of sleep, high task burden, physical fatigue, and boring daily life. Furthermore, the driving crews' irregular working conditions and irregular meal time and burden related to on-time transit service with prolonged immobilization raised their stress levels. In terms of external environmental factors, it was found that driving crews' anxiety due to possible accidents caused a roughly four-fold increase in stress levels compared to other factors. Furthermore, personnel system and salary issue were also found to be closely related to the driving crews' job stress.

• The Journal of Engineering Geology
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• v.18 no.2
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• pp.191-196
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• 2008

This study is a case study for application of the RTI warning model to Korea which was previously developed to predict landslide potential and occurrence time during a rainfall event. The rainfall triggering index (RTI) is defined as the product of the rainfall intensity I (mm/hr) and the effective accumulated rainfall $R_t$ (mm). This index is used to evaluate the landslide and debris-flow occurrence potential at time t during a rainfall event. The upper critical value ($RTI_{UC}$) of RTI and the lower critical value ($RTI_{LC}$) of RTI can be determined by historical rainfall data of a certain area. When the rainfall intensity exceeds the upper critical value, there are high potential to occur land-slides. The analysis result can predict landslide occurrence time of an area during a rainfall event as well as land-slide potential. The result can also be used as an important data to issue early-warning of landslides. In order to apply the RTI warning model to Korea this study analyzed rainfall data and landslides data in Inje county, Gangwon province, Korea from July 13 to July 19, 2006. According to the analysis result, the rainfall intensity exceeded the upper critical value 23 hours ago, 11 hours ago, and 9 hours ago from 11:00 in the morning, July 16. Therefore, landslide warnings would be issued three times for people evacuation for avoiding or reducing hurts and dam-ages from landslides in mountainous areas of Inje.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.2
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• pp.1176-1187
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• 2014

In Contemporary residential area, especially apartment commplex, crime affect the quality of life and sustainability of cities. So our interest is an all-time high in the role that planning processes and the design of the physical environment can play in reducing the opportunity for crime. The purpose of this study try to find the possibility of application of CPTED in Urban Apartment Complex. Recently, as increase of residencial density, diverse and new types of crime are increasing in urban apartment complex. It is the current of times which demand our serious consideration. This research focused on crime reduction through the physical environmental control methods. And the concepts and contents of CPTED are studied and the case studies of developed countries are surveyed. For groping in the practical application, researched into the case study of apartment blocks in medium sized city, Cheongju. Also Local crime prevention initiatives require partnership working, both between professionals and with local communities. The result of this study has implicated, increasing importance on daily safety issue in urban life and examining the possibility of applying crime prevention and reduction program and systems.

• Korean Journal of Environmental Agriculture
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• v.40 no.4
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• pp.335-344
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• 2021

BACKGROUND: Cyantraniliprole is a systemic diamide insecticide that has been used to control lepidopteran pests in agriculture. Cyantraniliprole has become an issue due to its potentiality of unexpectable contamination in rotational crop cultivation. Thus, studies on the evaluation of cyantraniliprole translocated from soil into rotational crops are required. METHODS AND RESULTS: Cyantraniliprole was treated at a yearly maximum application level onto bare soil under greenhouse conditions in two geographically different regions. Lettuce was transplanted and spinach and radish were sown onto the soil 30 and 60 days-plant back intervals (PBIs) after cyantraniliprole treatment. The QuEChERS method was modified and coupled with LC/MS/MS analysis to determine the residues of cyantraniliprole in soil and plant samples. The methods for sample preparation and instrumental conditions were validated to meet the criteria of Codex guidelines and were successful to determine cyantraniliprole quantitatively and qualitatively in the samples. Cyantraniliprole residues in lettuce samples were 0.01 mg/kg for PBI 60 and 0.02 mg/kg for PBI 30, respectively. The residues in spinach samples were 0.01 mg/kg for PBI 60 and 0.01~0.02 mg/kg for PBI 30, respectively. Less than limit of the quantitation (LOQ) level (0.01 mg/kg) of cyantraniliprole was observed in radish samples. The residues in the plant samples were found as the levels less than maximum residue limit (MRL) for leafy and root vegetables. CONCLUSION(S): This study suggests PBI 30~60 days for rotational cultivation of lettuce, spinach and radish in greenhouse soil treated with cyantraniliprole at a yearly maximum application level.

• Korean Journal of Environmental Agriculture
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• v.40 no.3
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• pp.211-218
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• 2021

BACKGROUND: Fine particulate matter (PM_2.5) is produced by chemical reactions between various precursors. PM_2.5 has been found to create greater human risk than particulate matter (PM₁₀), with diameters that are generally 10 micrometers and smaller. Ammonia (NH₃) and nitrogen oxides (NOx) are the sources of secondary generation of PM_2.5. These substances generate PM_2.5 through some chemical reactions in the atmosphere. Through chemical reactions in the atmosphere, NH₃ generates PM_2.5. It is the causative agent of PM_2.5. In 2017 the annual ammonia emission recorded from the agricultural sector was 244,335 tons, which accounted for about 79.3% of the total ammonia emission in Korea in that year. To address this issue, the agricultural sector announced the inclusion of reducing fine particulate matter and ammonia emissions by 30% in its targets for the year 2022. This may be achieved through analyses of its emission characteristics by monitoring the PM_2.5 and NH₃. METHODS AND RESULTS: In this study, the PM_2.5 concentration was measured real-time (every 1 hour) by using beta radiation from the particle dust measuring device (Spirant BAM). NH₃ concentration was analyzed real-time by Cavity Ring-Down Spectroscopy (CRDS). The concentrations of ozone (O₃) and nitrogen dioxide (NO₂) were continuously measured and analyzed for the masses collected on filter papers by ultraviolet photometry and chemiluminescence. CONCLUSION: This study established air pollutant monitoring system in agricultural areas to analyze the NH₃ emission characteristics. The amount of PM_2.5 and NH₃ emission in agriculture was measured. Scientific evidence in agricultural areas was obtained by identifying the emission concentration and characteristics per season (monthly) and per hour.