• Journal of the Korean Society of Hazard Mitigation
• /
• v.11 no.1
• /
• pp.101-105
• /
• 2011

Determination of ultrasonic frequency and experimental design approach to optimization of ultrasonic soil-washing process for remediation of diesel contaminated soil were investigated. Ultrasonic frequencies of 35, 72, and 100 kHz were used for determination of optimal frequency. $MINITAB^{(R)}$ program was used for experimental design of optimal washing condition. The optimal ultrasonic frequency was 35 kHz. Even though the number of cavitation bubble is little, however cavitation bubbles involving larger energy compared with high frequency was generated. Therefore, the removal efficiency at low frequency was higher than at high frequency. However the input energy has to be considered when the process is applied. The statistical tests from a factorial experiment shows that the application of ultrasound and mechanical mixing are the most important factor for design of an ultrasonic soil washing process. The lab-scale experiments are required to get the optimal condition of ultrasound and mechanical mixing for application of ultrasonic soil washing process.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.11 no.3
• /
• pp.157-163
• /
• 2011

In this study, after the target basin was divided into both overland and channel grids, the travel time from center of each grid cell to watershed's outlet was calculated based on the manning equation. Through this process, volumetric discharge was calculated according to the isochrones and finally, the direct runoff hydrograph was estimated considering watershed's hydrodynamic characteristics. Sanseong subwatershed located in main stream of Bocheong basin was selected as a target basin. The model parameters are only two: area threshold and channel velocity correction factor; the optimized values were estimated at 3,800 and 3.3, respectively. The developed model based on the tuned parameters led to well-matching results between observed and calculated hydrographs (mean of absolute error of peak discharge: 3.41%, mean of absolute error of peak time: 0.67 hr). Moreover, the analysis results regarding histogram of travel time-contribution area demonstrates that the proposed model characterizes relatively well hydrodynamic characteristics of the catchment due to effective rainfall.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.11 no.2
• /
• pp.93-101
• /
• 2011

Korea has about 70% of its land classified as the mountain area, which has led to cut-slope being the result of substantial road and railway construction. However, there is currently a lack of research about the seismic retrofit design of a slope, even though many earthquakes have recently occurred at home and abroad. In this study, in order to investigate the stabilizing effect of piles against sliding during an earthquake, a series of 1 g shaking table tests and pseudo-static analyses were carried out. As a result, the stabilizing effect of piles against sliding during an earthquake was verified by the 1 g shaking table tests and the most effective result from the pseudo-static analyses was that the installation of the piles on the central part of the slope, where the failure surface included piles unlike the lower part and upper part of the slope. Furthermore, when the pile was installed on the central part of the slope, the change of the safety factor depending on the distance between the center of two piles was evaluated.

• Journal of Biomedical Engineering Research
• /
• v.39 no.6
• /
• pp.243-249
• /
• 2018

The indoor radon concentration was measured in the lecture room of the university and the radon concentration was converted to the amount related to the radon exposure using the dose conversion convention and compared with the reference levels for the radon concentration control. The effect of indoor radon inhalation was evaluated by estimating the life effective dose and the risk of exposure. To measure the radon concentration, measurements were made with a radon meter and a dedicated analysis Capture Ver. 5.5 program in a university lecture room from January to February 2018. The radon concentration measurement was carried out for 5 consecutive hours for 24 hours after keeping the airtight condition for 12 hours before the measurement. Radon exposure risk was calculated using the radon dose and dose conversion factor. Indoor radon concentration, radon exposure risk, and annual effective dose were found within the 95% confidence interval as the minimum and maximum boundary ranges. The radon concentration in the lecture room was $43.1-79.1Bq/m^3$, and the maximum boundary range within the 95% confidence interval was $77.7Bq/m^3$. The annual effective dose was estimated to be 0.20-0.36 mSv/y (mean 0.28 mSv/y). The life-time effective dose was estimated to be 0.66-1.18 mSv (mean $0.93{\pm}0.08mSv$). Life effective doses were estimated to be 0.88-0.99 mSv and radon exposure risk was estimated to be 12.4 out of 10.9 per 100,000. Radon concentration was measured, dose effective dose was evaluated using dose conversion convention, and degree of health hazard by indoor radon exposure was evaluated by predicting radon exposure risk using nominal hazard coefficient. It was concluded that indoor living environment could be applied to other specific exposure situations.

• Journal of the Korean Society of Environmental Restoration Technology
• /
• v.22 no.1
• /
• pp.33-45
• /
• 2019

Compound disaster is the type that increases the impact affected by two or more hazard events, and attention to compound disaster and multi-hazards risk is growing due to potential damages which are difficult to predict. The objective of this study is to analyze the possible impacts of post-fire landslide scenario quantitatively by using TRIGRS (Transient Rainfall Infiltration and Grid-Based Regional Slope-Stability Analysis), a physics-based landslide model. In the case of wildfire, soil organic material and density are altered, and saturated hydraulic conductivity decrease because of soil exposed to high temperature. We have included the change of soil saturated hydraulic conductivity into the TRIGRS model through literature review. For a case study, we selected the area of $8km^2$ in Pyeongchang County. The landslide modeling process was calibrated before simulate the post-wildfire impact based on landslide inventory data to reduce uncertainty. As a result, the mean of the total factor of safety values in the case of landslide was 2.641 when rainfall duration is 1 hour with rainfall intensity of 100mm per day, while the mean value for the case of post-wildfire landslide was lower to 2.579, showing potential landslide occurrence areas appear more quickly in the compound disaster scenario. This study can be used to prevent potential losses caused by the compound disaster such as post-wildfire debris flow or landslides.

• Journal of Korean Society on Water Environment
• /
• v.37 no.6
• /
• pp.501-509
• /
• 2021

In 2018, total 263 micro and emerging contaminants were selected as target substances by the Ministry of Environment, and 80 of them were first-class substance including endocrine disruptors, residual Pharmaceuticals and Personal Care Products (PPCPs), residual organic pollutants, pesticides and heavy metals. In this study, in order to evaluate the Hazard Quotient (HQ) of the 80 types in the domestic water environment the concentration of discharged effluent and nearby water environment reported by Korean institutes since 2010 was investigated. There were 45 substances reported to be detected, and Measurement Environment Concentration (MEC) were obtained by collectively converting them into water environment concentration. For biotoxicity, half maximal Effective Dose (EC50) to Daphnia magna, a water fleas species widely adopted in Material Safety Data Sheet (MSDS) was applied. As for the biotoxicity level, the Predicted No-Effect Concentration (PNEC) was obtained by applying the Assessment Factor (AF) and the HQ was derived by dividing it from the MEC. As a result of calculating the HQ, more than 1 substances were Cabamazepine, Mefenamic acid, Acetaminophen, Ibuprofen, Nonylphenol, Nickel, Erythromycin, Acetylslic acid, etc. Meanwhile, perfluorinated compounds were identified as hazardous substances in the water env ironment, with 5 out of 14 species included in the 20 ranks of first-class substance.

• Nuclear Engineering and Technology
• /
• v.54 no.11
• /
• pp.4253-4264
• /
• 2022

Since the implementation of the phosphate project in Bled El-Hadba (BEH) deposit, western region of Tébessa, no detailed study has been conducted to assess the natural radioactivity distribution and the associated radiological risk parameter for this open-pit mine. For the sake of determining a credible premining reference database for the region of interest, 21 samples were collected from different geological layers of the above-mentioned deposit. Gamma Spectrometry was applied for measuring radioactivity using a high resolution HPGe semiconductor detector. The obtained activity results have shown a significant broad variation in the radioactive contents for the different phosphate samples. The total average concentrations (in Bq·kg^-1) for ²²⁶Ra, ²³⁸U, ²³⁵U, ²³²Th and ⁴⁰K computed for the different type of phosphate layers were found to be 570 ± 169, 788 ± 280, 52 ± 18, 66 ± 6 and 81 ± 18 respectively. The mean activity concentrations of the measured radionuclides were compared to other regional and worldwide deposits. The ratios between the detected radioisotopes have been calculated for spatial distribution of natural radionuclides in the study area. Based on the aforementioned activity concentrations, the corresponding radiation hazard parameters were assessed. Correlations between the obtained parameters were drawn and a multivariate statistical analysis (Pearson Correlation, Cluster and Factor analysis) was carried out in order to identify the existing relationships.

• Journal of Gastric Cancer
• /
• v.23 no.4
• /
• pp.584-597
• /
• 2023

Purpose: This study aimed to investigate the impact of different types of complications on long-term survival following total gastrectomy for gastric cancer. Materials and Methods: A total of 926 patients who underwent total gastrectomy between 2008 and 2016 were included. Patients were divided into the morbidity and no-morbidity groups, and long-term survival was compared between the 2 groups. The prognostic impact of postoperative morbidity was assessed using a multivariate Cox proportional hazard model, which accounted for other prognostic factors. In the multivariate model, the effects of each complication on survival were analyzed. Results: A total of 229 patients (24.7%) developed postoperative complications. Patients with postoperative morbidity showed significantly worse overall survival (OS) (5-year, 65.0% vs. 76.7%, P<0.001) and cancer-specific survival (CSS) (5-year, 74.2% vs. 83.1%, P=0.002) compared to those without morbidity. Multivariate analysis adjusting for other prognostic factors showed that postoperative morbidity remained an independent prognostic factor for OS (hazard ratio [HR], 1.442; 95% confidence interval [CI], 1.136-1.831) and CSS (HR, 1.463; 95% CI, 1.063-2.013). There was no significant difference in survival according to the severity of complications. The following complications showed a significant association with unfavorable long-term survival: ascites (HR, 1.868 for OS, HR, 2.052 for CSS), wound complications (HR, 2.653 for OS, HR, 2.847 for CSS), and pulmonary complications (HR, 2.031 for OS, HR, 1.915 for CSS). Conclusions: Postoperative morbidity adversely impacted survival following total gastrectomy for gastric cancer. Among the different types of complications, ascites, wound complications, and pulmonary complications exhibited significant associations with long-term survival.

• Annals of Hepato-Biliary-Pancreatic Surgery
• /
• v.26 no.2
• /
• pp.168-177
• /
• 2022

Backgrounds/Aims: The goal of the present study was to evaluate the prognostic value of lymph node ratio (LNR) in distal cholangiocarcinoma (DCC) after curative intended surgery. Methods: Clinicopathological data of 162 DCC patients who underwent radical intended surgery between 2012 and 2020 were analyzed retrospectively. Prognostic factors related to overall survival (OS) and disease-free survival (DFS) were evaluated. Results: Median OS time and DFS time were 41 and 29 months, and 5-year OS rate and DFS rate were 44.7% and 38.1%, respectively. In the univariate analysis, significant prognostic factors for OS were histologic differentiation, American Joint Committee on Cancer (AJCC) stage, positive lymph node count, LNR, R1 resection, and perineural invasion. Preoperative carcinoembryonic antigen, carbohydrate antigen 19-9, infiltrative type, histologic differentiation, AJCC stage, positive lymph node count, LNR, R1 resection, perineural invasion, and lymph-vascular invasion were significant prognostic factors for DFS in the univariate analysis. In the multivariate analysis, histologic differentiation, R1 resection, and LNR were the independent prognostic factors for both OS and DFS. The LNR ≥ 0.2 group had a significantly poor prognosis in terms of OS (hazard ratio, 3.915; p = 0.002) and DFS (hazard ratio, 5.840; p < 0.001). Conclusions: LNR has significant value as a prognostic factor of DCC related to OS and DFS. LNR has the potential to be used as a modified staging system with furthermore studies.

• Journal of Soil and Groundwater Environment
• /
• v.12 no.1
• /
• pp.64-72
• /
• 2007

Humans are exposed by a range of pollutants in soil via exposure routes such as ingestion, inhalation, and dermal contact. Risk assessment is a process of evaluating the adverse health effects of chemicals as a result of exposure to stressors, and it is a very useful tool to establish the cleanup goals in contaminated lands. In the exposure assessment that is one of main process in risk assessment, exposure factor plays a significant role to quantify the intake of soil pollutants. However there is a very limited study about the exposure factor applicable to Korea. In this study, we compared the exposure factors applied by the developed countries including the United States and representative European countries, and suggested the exposure factor that might be suitable in our situation. The exposure factors considered in this study include average lifetime, body weight, (exposed) skin surface area, life time, skin absorption, soil-skin adherence factor, and soil ingestion rate. This information is needed to quantitatively estimate the intake of soil pollutants in contaminated lands.