• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.5
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• pp.437-450
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• 2014

In this study, we developed a methodology to determine the reference parameter for an aircraft impact induced risk assessment of nuclear power plant (NPP) using finite element impact analysis of containment building. The target structure used to develop the method of reference parameter selection is one of the typical Korean PWR type containment buildings. We composed a three-dimensional finite element model of the containment building. The concrete damaged plasticity model was used for the concrete material model. The steels in the tendon, rebar, and liner were modeled using the piecewise-linear stress-strain curves. To evaluate the correlations between structural response and each candidate parameter, we developed Riera's aircraft impact force-time history function with respect to the variation of the loading parameters, i.e., impact velocity and mass of the remaining fuel. For each force-time history, the type of aircraft is assumed to be a Boeing 767 model. The variation ranges of the impact velocity and remaining fuel percentage are 50 to 200m/s, and 30 to 90%, respectively. Four parameters, i.e., kinetic energy, total impulse, maximum impulse, and maximum force are proposed for candidates of the reference parameter. The wellness of the correlation between the reference parameter and structural responses was formulated using the coefficient of determination ($R^2$). From the results, we found that the maximum force showed the highest $R^2$ value in most responses in the materials. The simplicity and intuitiveness of the maximum force parameter are also remarkable compared to the other candidate parameters. Therefore, it can be concluded that the maximum force is the most proper candidate for the reference parameter to assess the aircraft impact induced risk of NPPs.

• Journal of the Korean Society of Safety
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• v.37 no.2
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• pp.76-87
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• 2022

Lithium-ion batteries (LIBs) have attracted much interest for their high energy density (>150 mAh/g), high capacity, low self-discharge rate, and high coulombic efficiency. However, with the successful commercialization of LIBs, fire and explosion incidents are likely to increase. The thermal runaway is known as the major factor in battery-related accidents that can lead to a series of critical conditions. Considering this, recent studies have shown an increased interest in countering the safety issues associated with LIBs. Although safety standards for LIB use have recently been formulated, little attention has been paid to the safety around the manufacturing process for battery products. The present study introduces a risk assessment method suitable for assessing the safety of the LIB-manufacturing process. In the assessment method, a compensation parameter (Z-factor) is employed to correctly evaluate the process's safety on the basis of the type of material (e.g., metal anode, liquid electrolyte, solid-state electrolytes) utilized in a cell. The proposed method has been applied to an 18650 cell-manufacturing process, and three sub-processes have been identified as possibly vulnerable parts (risk index: >4). This study offers some crucial insights into the establishment of safety standards for battery-manufacturing processes.

• Journal of the Korean Dietetic Association
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• v.16 no.2
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• pp.122-132
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• 2010

Elderly people comprise an increasing proportion of the population, and nutritional impairments may contribute to health problems among this group. This study was conducted to evaluate the nutritional status by Mini-Nutritional Assessment (MNA) and to identify relationships among anthropometric measurements, biochemical indicators, bone Mineral Density (BMD) and MNA results among older adults (${\geq}$65 yrs, n=98, 66.7${\pm}$2.5 yrs; M=52, F=46, BMI 24.5${\pm}$2.8 $kg/m^2$) at a Health Care Center. A dietitian administered MNA and collected anthropometric measurements (weight, height, waist circumference), biochemical indicators (albumin, hemoglobin, hematocrit, TLC, glucose, lipids) and the BMD (spine, femur, F=46). Subjects were grouped into a normal nutrition group (0~2 risk factors of malnutrition) and a high risk of malnutrition group (>=3 risk factors of malnutrition) based on their risk factor status for malnutrition. The risk factors for malnutrition include age ${\geq}$65 years, PIBW <90%, albumin <3.5 g/dl, TLC <1,500%, Hgb <14 g/dl (men), Hgb <10 g/dl (women), loss of appetite and weight loss 1~3 kg/last 3 months. In addition, subjects were grouped into a normal, osteopenia and osteoporosis group by BMD. We found that 12% of the subjects were at risk of malnutrition (MNA score, 21.4${\pm}$2.1) and that 88% were well nourished (27.3${\pm}$1.5) according to the MNA. Full-MNA scores were positively and significantly (p<0.05) associated with BMI, mid-arm circumference (MAC), calf circumference (CC), albumin and hemoglobin, respectively. The full-MNA score of the high risk of malnutrition group (23.0${\pm}$3.8) was lower than that of the normal nutrition group (27.0${\pm}$2.1) (p<0.05). In addition, the Full-MNA score was negatively associated with the risk factor of malnutrition (r=－0.35, p=0.0004). We found that 39.1% of the subjects had osteoporosis, 45.7% had osteopenia and 15.2% were normal according to their BMD. The MNA score of osteoporosis group (24.58${\pm}$3.3) was lower than that of the normal (27.4${\pm}$1.1) and osteopenia group (26.9${\pm}$1.5) (p<0.05). These results suggested that MNA can be useful as a nutritional screening tool of older adults in Health Care Centers.

• Journal of Ecology and Environment
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• v.35 no.4
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• pp.307-311
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• 2012

This study was conducted to evaluate the dynamics of soil respiration (total soil and heterotrophic respiration) following fertilizer application in red pine forests. Fertilizer (N:P:K = 113:150:37 kg/ha), which reflects current practices in Korean forest, was applied in April 2011, and total soil and heterotrophic respiration rates were monitored from April 2011 to March 2012. Monthly variation of total soil and heterotrophic respiration rates were similar between the fertilizer and control treatments, as soil temperature was the dominant factor controlling the both rates. Total soil respiration rates during the study period were not significantly different between the fertilizer (0.504 g $CO_2\;m^{-2}\;h^{-1}$) and control (0.501 g $CO_2\;m^{-2}\;h^{-1}$) treatments. However, the proportion of heterotrophic respiration was higher in the fertilizer (78% of total soil respiration rates) than in the control (62% of total soil respiration rates) treatments. These results suggest that current fertilizer practices in Korea forest soil do not substantially affect total soil respiration rates.

• Asian Journal of Atmospheric Environment
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• v.5 no.2
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• pp.121-133
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• 2011

This study suggests criteria to conduct a risk assessment of VOCs and formaldehyde in uncontrolled public facilities. Pollutants and facilities were selected based on two years of monitoring data and exposure scenarios in 573 uncontrolled public facilities, composed of 10 types of public institutions. With the exception of social welfare facilities, lifetime ECRs of formaldehyde and benzene in each facility were higher in employees than in users, except in social welfare facilities. In social welfare facilities, the risk of benzene for users ($1{\times}10^{-5}$) was higher than that of workers ($1{\times}10^{-6}$) because facility users live in the facility 24 hours per day, compared to workers who spend an average of 8 hours per day in the facility. The risk of benzene to workers in restaurants, academies, performance halls, internet cafe and pubs were estimated as high as $1{\times}10^{-4}$ and the risk to workers in the theaters and karaoke bars were recorded as $1{\times}10^{-5}$. Because lifetime ECRs of carcinogens exceeded $1{\times}10^{-4}$ for workers and users in most facilities, risk management of formaldehyde and benzene in these facilities is necessary. Although HQs of toluene and xylenes did not exceed 1.0, their HQs did exceed 0.1 in some facilities, so they were evaluated as potentially harmful materials. Additionally, criteria for health protection in IAQ by facility are suggested at $60-100\;{\mu}g/m^3$ for formaldehyde, $400-500\;{\mu}g/m^3$ for TVOCs, $10-20\;{\mu}g/m^3$ for benzene, $150-170\;{\mu}g/m^3$ for toluene and $100\;{\mu}g/m^3$ for xylenes, based on the survey on IAQ and HRA methodology. The excess rates of IAQ to health protection criteria in all facilities were 16% for formaldehyde, 8% for TVOCs and benzene, 9% for toulene, and 5% for xylenes.

• Journal of The Korean Society of Agricultural Engineers
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• v.48 no.2
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• pp.77-87
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• 2006

The reuse of wastewater for agricultural irrigation may cause human health risk as a result of exposure to pathogens. This study conducted the quantitative microbial risk assessment in paddy field irrigated with treated wastewater. Six treatments were used to irrigate the paddy field from Year 2003 to Year 2005: biofilter-effluent, UV-disinfected water (6, 16, 40, 68 $mW s cm^{-2}$), pond-treated water, wetland-treated water, conventional irrigation water and tap water. Total coliforms, fecal coliforms and E. coli were monitored during rice growing period. Beta - Poisson model was employed to calculate the microbial risk of pathogens ingestion that may occur to farmers and neighbor children. Uncertainty of risk was estimated using Monte Carlo simulation. In this study, the microbial risk was higher during initial cultivation (end of May$\sim$June), and it decreased with time. Biofilter effluent (secondary effluent) irrigation showed higher risk values than others (>$10^{-4}$) and irrigation with UV-disinfected water has the lowest risk range ($10^{-6}{\sim}10^{-5}$). The risk value estimated in 2005 was lower than risk value in 2003 and 2004, it is likely due to clean tap water irrigation in initial transplanting stage. It is suggested that irrigation with UV-disinfected water and pond-treated water would reduce the microbial risk associated with wastewater irrigation in paddy field. In addition, the first irrigation water quality significantly affected the subsequent microbial risk.

• Transactions of the Korean hydrogen and new energy society
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• v.28 no.2
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• pp.166-173
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• 2017

For commercialization of hydrogen refuelling station (HRS), we need to reduce the clearance distance for jet fire in the real entities in the HRS. Thus, we revisited the current regulations of clearance distance for jet fire in the law. The law in korea has been set up by replica of japan, not by our own scientific basis. Recently, sandia lab developed Hydrogen Risk Assessment Model (HyRAM) tools and we simulated a series of circumstances such as 10 to 850 bar with several leak hole sizes. In 850 bar with 10 mm diameter hole leak cases, it shows $4,981kW/m^2$ at 12 m separation from leak source and $1,774kW/m^2$ at 17 m separation from leak source. In 850 bar with 1 mm diameter leak hole, it shows $0.102kW/m^2$ at 12 m separation and $0.044kW/m^2$ at 17 m separation. Current law may be acceptable with 1 mm hole size with 850 bar.

• Journal of Food Hygiene and Safety
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• v.34 no.2
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• pp.199-204
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• 2019

This study aimed to generate a probability distribution model based on temperature data of frozen food storage facility as input variables for microbial risk assessment (MRA). We visited 8 food-handling businesses to collect temperature data from their cold storage warehouses. The overall mean temperature inside the storage facilities was $-20.48{\pm}3.08^{\circ}C$, with 20.4% of the facilities having above $-18^{\circ}C$, with minimum and maximum temperature values of -10.3 and $-25.80^{\circ}C$ respectively. Temperature distributions by space locations of natural and forced convection were $-22.57{\pm}0.84$ and $-17.81{\pm}1.47^{\circ}C$, $-22.49{\pm}1.05$ and $-17.94{\pm}1.44^{\circ}C$, and $-22.68{\pm}1.03$ and $-18.08{\pm}1.42^{\circ}C$ in the upper (2.4~4 m), middle (1.5~2.4 m), and lower (0.7~1.5 m) shelves, respectively. Probability distributions from the temperature data were obtained using the program @RISK. Statistical ranking was determined using goodness of fit to determine the probability distribution model. Our results show that a log-normal distribution [5.9731, 3.3483, shift (-26.4281)] is most appropriate for relative MRA conduction.

• Journal of Korean Society of Disaster and Security
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• v.16 no.1
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• pp.71-80
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• 2023

Fuel cells are low-carbon power sources that can expand distributed energy system and electric vehicle charging infrastructure when installing fuel cells in gas stations. In order to ensure safety for fuel cells in gas stations, quantitative risk assessments were conducted after deriving accident scenarios based on accident data of domestic and foreign gas stations and fuel cells. It calculates the expected extent of damage from fire and explosion that can occur in reality, not the worst accident scenario, and analyzes the damage impact. The separation distance of more than 9.0 m from a dispenser, 15.5 m from a car under refueling, 4.1 m from the ventilation pipe, 1.1 m from the gas adjustment device prevent the severe damage caused by the expected accident. This study result can be used to deploy fuel cells in gas stations and establish safety measures.

• Journal of Microbiology and Biotechnology
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• v.13 no.4
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• pp.495-500
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• 2003

Tight junctions (TJ) between adjacent Sertoli cells in testis are important for the formation of the blood testis barrier (BTB). In an effort to verify the reproductive health risk of endocrine-active chemicals (EACs), changes in the transepithelial electrical resistance (TER) and the expression of TJ genes were examined by co-planar polychlorinated biphenyl (PCB) treatment in cultured mouse Sertoli cells. Although the increase in TER of Sertoli cells was accelerated by 10 nM co-planar PCB, it was downregulated by 100 nM co-planar PCB. The expression of claudin-1 was downregulated by co-planar PCB in a concentration-dependent manner. On the contrary, the expression of claudin-1 was increased in the Sertoli cells by 10 nM co-planar PCB treatment. These results suggest that the structure and function of TJ may be targeted by co-planar PCB in Sertoli cells. Assessment of the structure and function of TJ in Sertoli cells might be useful for screening the reproductive health risk of EACs.