• Journal of The Korean Society of Agricultural Engineers
• /
• v.65 no.4
• /
• pp.1-10
• /
• 2023

As a result of climate change, non-point source pollution (NPS) from farmland with the steep slope during the rainy season is expected to have a significant impact on the water system. This study aimed to evaluate the effect of furrow mulching using alfalfa and PAM (Polyacrylamide) materials for each rainfall event, while considering the load characteristics of NPS. The study was conducted in Wanju-gun, Jeollabuk-do, in 2022, with a testbed that had a slope of 13%, sandy loam soil, and maize crops. The testbed was composed of four plots: bare soil (Bare), No mulching (Cont.), Vegetation mulching (VM), and PAM mulching (PM). Runoff was collected from each rainfall event using a 1/40 sampler and the NPS load was calculated by measuring the concentrations of SS, T-N, T-P, and TOC. During farming season, the reduction efficiency of NPS load was 37.1~59.5% for VM and 38.2~75.7% for PM. The analysis found that VM had a linear regression correlation (R²=0.28~0.86, P-value=0.01~0.1) with elapsed time of application, while PM had a quadratic regression correlation (R²=0.35~0.80, P-value=0.1). These results suggest that the selection of furrow mulch materials and the appropriate application method play a crucial role in reducing non-point pollution in farmland. Therefore, further studies on the time-series reduction effect based on the application method are recommended to develop more effective preemptive reduction technologies.

• Asian Pacific Journal of Cancer Prevention
• /
• v.13 no.8
• /
• pp.4045-4050
• /
• 2012

Objective: The impact of ablative oral cancer surgery was studied, with particular reference to recurrence and nodal metastasis, to assess survival probability and prognostic indicators and to elucidate if ethnicity influences the survival of patients. Methods: Patients who underwent major ablative surgery of the head and neck region with neck dissection were identified and clinical records were assessed. Inclusion criteria were stage I-IV oral and oropharyngeal malignancies necessitating resection with or without radiotherapy from 2004 to 2009. All individuals had a pre-operative assessment prior to the surgery. The post operative assessment period ranged from 1 year to 5 years. Survival distributions were analyzed using Kaplan-Meier curves. Results: 87 patients (males:38%; females:62%) were included in this study, with an age range of 21-85 years. Some 78% underwent neck dissections while 63% had surgery and radiotherapy. Nodal recurrence was detected in 5.7% while 20.5% had primary site recurrence within the study period. Kaplan-Meier survival analysis revealed that the median survival time was 57 months. One year overall survival (OS) rate was 72.7% and three year overall survival rate dropped to 61.5%. On OS analysis, the log-rank test showed a significant difference of survival between Malay and Chinese patients (Bonferroni correction p=0.033). Recurrence-free survival (RFS) analysis revealed that 25% of the patients have reached the event of recurrence at 46 months. One year RFS rate was 85.2% and the three year survival rate was 76.1%. In the RFS analysis, the log-rank test showed a significant difference in the event of recurrence and nodal metastasis (p<0.001). Conclusion: Conservative neck is effective, in conjunction with postoperative radiotherapy, for control of neck metastases. Ethnicity appears to influence the survival of the patients, but a prospective trial is required to validate this.

• Journal of Korean Society on Water Environment
• /
• v.35 no.1
• /
• pp.72-77
• /
• 2019

Soil type in LID infiltration practices plays a major role in runoff reduction efficacy. In this study, the effects of infiltration rate of foundation ground under bioretention on annual runoff reduction rate was evaluated using LIDMOD3 which is a simple excel based model for evaluating LID practices. A bioretention area of about 3.2 % was required to capture surface runoff from an impervious area for a 25.4 mm rainfall event. The relative error of runoff from bioretention using LIDMOD3 is 10 % less than that of SWMM5.1 for a total rainfall event of 257.1 mm during the period of Aug. 1 ~ 18, 2017, hence, the applicability of LIDMOD3 was confirmed. Annual runoff reduction rates for the period 2008 ~ 2017 were evaluated for various infiltration rates of foundation ground under the bioretention which ranged from 0.001 to 0.600 m/day and were converted to annual runoff reduction for hydrologic soil group. The runoff reduction rates within hydrologic soil group C and D were steeply increased through increased infiltration rate but not steep within hydrologic A and B with reduction rates ranging from 53 ~ 68 %. The estimated time required to completely empty a bioretention which has a storage depth of 0.632 m is 3.5 ~ 6.9 days and we could assume that the annual average of antecedent rainfall is longer than 3.5 ~ 6.9 days. Therefore, we recommended B type as the minimum hydrologic soil group installed LID infiltration practices for high runoff reduction rate.

• Explosives and Blasting
• /
• v.40 no.4
• /
• pp.27-34
• /
• 2022

The government is promoting various policies to reduce greenhouse gas emissions for carbon neutrality, one of the key tasks is to revitalize the hydrogen economy. As one of these policies the government has formulated a plan to incorporate hydrogen into existing city gas pipes, and aims to commercialize 20% hydrogen mixing by 2026. In preparation for the commercialization of city gas and hydrogen mixture, this study quantitatively predicts the scale of damage and the range of impact in the event of leakage of these two gas mixtures. The quantitative damage prediction method is to calculate the damage conversion distance through the calculation of the TNT equivalent by setting the leakage amount of the gas mixture in the event of an accident under a virtual scenario.

• Wind and Structures
• /
• v.37 no.6
• /
• pp.413-423
• /
• 2023

Wind turbines are usually steel hollow structures that can be vulnerable to dramatic failures due to high-intensity wind (HIW) events, which are classified as a category of localized windstorms that includes tornadoes and downbursts. Analyzing Wind Turbines (WT) under tornadoes is a challenging-to-achieve task because tornadoes are much more complicated wind fields compared with the synoptic boundary layer wind fields, considering that the tornado's 3-D velocity components vary largely in space. As a result, the supporting tower of the wind turbine and the blades will experience different velocities depending on the location of the event. Wind farms also extend over a large area so that the probability of a localized windstorm event impacting one or more towers is relatively high. Therefore, the built-in-house numerical code "HIW-WT" has been developed to predict the straining actions on the blades considering the variability of the tornado's location and the blades' pitch angle. The developed HIWWT numerical model incorporates different wind fields that were generated from developed CFD models. The developed numerical model was applied on an actual wind turbine under three different tornadoes that have different tornadic structure. It is found that F2 tornado wind fields present significant hazard for the wind turbine blades and have to be taken into account if the hazardous impact of this type of unexpected load is to be avoided.

• Journal of Korean Society of Water and Wastewater
• /
• v.21 no.2
• /
• pp.235-242
• /
• 2007

Road runoff water includes various heavy metals (zinc, Zn; lead, Pb; copper, Cu; chrome, Cr; cadmium, Cd; etc.) and pathogens (E-coli and coliform). Since these pollutants are significantly harmful to human beings and have negative impact on water streams, numerous studies have been conducted to determine the characterization of these non-point pollutants from road runoff water. However, since these non-point pollutant concentrations vary depending on road traffic, road construction, and road maintenance, measurement of pollutant loadings in different site is necessary to estimate the effect of road runoff water on drinking water source. The objective of this study was to examine the quality of road runoff water from a city bridge in Seoul, Korea. This study was conducted for two years to assess annual discharge pollution loads. In this study, five key heavy metals (Zn, Pb, Cu, Cr, and Cd) and two pathogens (E-coli and coliform) were measured at 18 different events. The pollutant load mass transported was always higher than the corresponding runoff volume for Zn, Cu, and Cd, while Pb and Cr showed similar values between the load mass transported and the corresponding runoff volume. The event mean concentrations were Zn (0.908 mg/L), Pb (0.092 mg/L), Cu (0.141 mg/L), Cr (0.023 mg/L), and Cd (0.006 mg/L). Like Zn, Cu, and Cd, E-coli and coliform values (relatively high in Summer and Fall) are higher at the beginning of each event and decrease afterwards.

• Journal of Korea Water Resources Association
• /
• v.46 no.6
• /
• pp.585-596
• /
• 2013

The objective of this study is to evaluate the hybrid downscaling method combined Step-Wise Scaling (SWS) method with Regional Climate Model (RCM) simulation data for climate change impact study on hydrology area. The SWS method is divided by 3 categories (extreme event, dry event and the others). The extreme events, wet-dry days and the others are corrected by using regression method, quantile mapping method, mean & variance scaling method. The application and evaluation of SWS method with 3 existing and popular statistical techniques (linear scaling method, quantile mapping method and weather generator method) were performed at the 61 weather stations. At the results, the accuracy of corrected simulation data by using SWS are higher than existing 3 statistical techniques. It is expected that the usability of SWS method will grow up on climate change study when the use of RCM simulation data are increasing.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.41 no.9
• /
• pp.740-746
• /
• 2013

Design with crashworthiness concept has been emphasized for almost aircraft and motor vehicles. However, crashes accompanied serious injury and death have been continuously occurred, and will be occurred subsequently. What was worse, it is a well-known fact that there were a good many crashes classified as survivable accidents in which fatal injuries were reported. But we cannot say that fatal injuries were inevitable consequences of those crashes. If crashworthy design for seat, restraint systems, and cabin strength were adequate or right, survivability in a crash event could be maximized greatly. To substantiate the right crashworthiness, we must thoroughly understand the characteristics of human tolerance under abrupt acceleration change, and the cabin design should be combined with proper use of energy absorbing technologies that reduce accelerations experienced by the occupants. In this paper, the emphasis on the human tolerance under abrupt accelerations as well as the necessity of change in design requirements for crash environment will be stressed to widen the belt of consensus for the right crashworthy design.

• Sleep Medicine and Psychophysiology
• /
• v.17 no.1
• /
• pp.28-33
• /
• 2010

Objectives: Working at other times than the regular day shift has been reported to be a stressor associated with health consequences and mental disorders as well as disturbance of sleep. In current study, we aimed at investigating the relationship between work schedule, sleep quality and depression among police officers. Methods: Eleven hundreds and forty five police officers (male: 1040, female: 105) completed questionnaires of basic socio-demographic data, Pittsburgh Sleep Quality Index (PSQI), Korean Scale of Occupational Stress (KOSS), Impact of Event Scale - Revised (IES-R) and Center for Epidemiologic Study-Depression (CES-D). Results: After controlling for age, sex and educational level, score of CES-D was correlated positively with the score of KOSS, PSQI and IES-R on partial correlation analysis (r=-0.077; p=0.009, r=0.262; p<0.000 and r=0.421, p<0.000, respectively). Logistic regression analysis revealed that female sex, age, the score of KOSS and IES-R and schedule of rotating shift work predicted higher score than 16 score of CES-D significantly in total subjects (p=0.023, p=0.015, p=0.000, p=0.000 and p=0.022, respectively). Conclusion: Current result suggested that not only female sex, age, higher occupational stress and impact of event scale but also rotating shift work schedule might be related to depression among police officers.

• Journal of Environmental Science International
• /
• v.28 no.1
• /
• pp.7-18
• /
• 2019

This study aimed to assess the impact of livestock excreta discharged from an Intensive Livestock Farming Area (ILFA) on river water quality during a rainfall event. The Bangcho River, which is one of the 7 tributaries in the Cheongmi River watershed, was the study site. The Cheongmi River watershed is the second largest area for livestock excreta discharge in Korea. Our results clearly showed that, during the rainfall event, the water quality of the Bangcho River was severely deteriorated due to the COD, $NH_4-N$, T-N, $PO_4-P$, T-P, and heavy metals (Cu, Zn, and Mn) in the run-off from nearby farmlands, where the soil comprised composted manure and unmanaged livestock excreta. In addition, stable isotope analysis revealed that most of nitrogen ($NH_4-N$ and $NO_3-N$) in the run-off was from the ammonium and nitrate in the livestock excreta. The values of ${\delta}^{15}N_{NH4}$ and ${\delta}^{15}N_{NO3}$ for the Bangcho River water sample, which was obtained from the downstream of mixing zone for run-off water, were lower than those for the run-off water. This indicates that there were other nitrogen sources upstream river in the river. It was assumed from ${\delta}^{15}N_{NH4}$ and ${\delta}^{15}N_{NO3}$ stable isotope analyses that these other nitrogen sources were naturally occurring soil nitrogen, nitrogen from chemical fertilizers, sewage, and livestock excreta. Therefore, the use of physicochemical characteristics and nitrogen stable isotopes in the water quality impact assessment enabled more effective analysis of nitrogen pollution from an ILFA during rainfall events.