• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.5
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• pp.287-296
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• 2019

In this study, the effect of ground boundary conditions on the evaluation of blast resistance performance of precast arch structures was evaluated by a numerical analysis method. Two types of boundary conditions, namely, fixed boundary conditions and a perfectly matched layer (PML) were applied to numerical models. Blast loads that were much higher than the design load of the target structure were applied to compare the effects of the boundary conditions. The distribution and path of the ground explosion pressure, structural displacement, fracture of concrete, stress of concrete, and reinforcing bars were compared according to the ground boundary condition settings. As a result, the reflecting pressure shock wave at the ground boundaries could be effectively eliminated using PML elements; furthermore, the displacement of the foundation was reduced. However, no distinct difference could be observed in the overall structural behavior including the fracture and stress of the concrete and rebar. Therefore, when blast simulations are performed in the design of protective structures, it is rational to apply the fixed boundary condition on the ground boundaries as conservative design results can be achieved with relatively short computation times.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.1
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• pp.464-469
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• 2019

A remote monitoring panel and control system was developed to control various valves and access control chambers, including gas shutoff valves used in CBR(Chemical, Biological and Radiological) facilities. The remote monitoring panel consisted of a main panel installed in the NBC (Nuclear, Biological and Chemical) control room and auxiliary panel installed in the clean room, and the size was divided into pure control and control including CCTV. This system can be monitored and controlled remotely according to the situation where an explosion door and gas barrier door can occur during war and during normal times. This system is divided into normal mode and war mode. In particular, it periodically senses the operation status of various valves, sensors, and filters in the CBR facilities to determine if each apparatus and equipment is in normal operation, and remotely alerts situation workers when repair or replacement is necessary. Damage due to the abnormal operation of each device in the situation can be prevented. This enables control of the blower, supply and exhaust damper, emergency generator, and coolant pump according to the state of shutoff valve and positive pressure valve in the occurrence of NBC, and prevents damage caused by abrupt inflow of conventional weapons and nuclear explosions.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.36 no.6
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• pp.355-364
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• 2023

The arbitrary Lagrangian-Eulerian (ALE) method has been extensively researched owing to its capability to accurately predict the propagation of blast shock waves. Although the use of the ALE method for dynamic analysis can produce unreliable results depending on the mesh size of the finite element, few studies have explored the relationship between the mesh size for the air domain and the accuracy of numerical analysis. In this study, we propose a procedure to calculate the optimal mesh size based on the mean squared error between the maximum blast pressure values obtained from numerical simulations and experiments. Furthermore, we analyze the relationship between the weight of explosive material (TNT) and the optimal mesh size of the air domain. The findings from this study can contribute to estimating the optimal mesh size in blast simulations with various explosion weights and promote the development of advanced blast numerical analysis models.

• Journal of Nutrition and Health
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• v.36 no.1
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• pp.9-17
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• 2003

The preparation method of a soluble dietary fiber from oak wood (Quercus mongolica) and the effect of the soluble dietary fiber on physiological function in rat fed high cholesterol diets was investigated. The best condition for steam explosion method was 25 kgf/㎤ pressure for 6 min. The exploded samples were delignified by the filtration treatment with 1% NaOH for several times, which is the best condition. The enzymatic hydrolysis of Cellusoft cellulase was more effective than Onozuka R-10 cellulase. The manufactured soluble dietary fiber was assayed using gel permeation chromatography (GPC) and it was dissolved in water. Average molecular weight distribution of manufactured soluble dietary fiber was about 348-1,200 and it was assumed the oligomer form fraction. In order to compare the manufactured soluble dietary fiber with commercial soluble dietary fiber (pectin) on the physiological function, Sprague-Dawley male rats weighing 100$\pm$10 g were randomly assigned to one normal diet and five high cholesterol diet containing 1% cholesterol. The high cholesterol diet groups were classified to fiber free diet (FF group), 5% pectin (5P group), 10% pectin (l0P group), 5% manufactured soluble dietary fiber (5M group) and 10% manufactured soluble dietary fiber (10M group). Body weight gains in all soluble dietary fiber groups were lower than FF group. Food intakes were increased in all soluble dietary fiber groups than that of FF group. Food efficiency ratio (FER) was significantly decreased in all soluble dietary fiber groups than that of the FF group, and it was especially was highest in 10% supplemented soluble dietary fiber group. The weight of liver of the soluble dietary fiber supplemented groups were lower than those of the FF group, but weights of cecum and small intestine of all supplemented soluble dietary fiber groups were significantly increased, compared with that of FF group. The weights and water contents in feces were significantly increased by the soluble dietary fiber. The activity of the glutamic oxaloacetic transaminase in soluble dietary fiber groups were significantly decreased than those of FF group. The hepatic glutathione S-transferase activity in all soluble dietary fiber supplemented groups were higher than that of FF group. The physiological effects of the manufactured soluble dietary fiber are the same as the commercial soluble dietary fiber (pectin). The preparation method of the soluble dietary fiber from the oak chips suited to its purpose. (Korean J Nutrition 36(1) : 9~17, 2003)

• Korean Chemical Engineering Research
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• v.52 no.4
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• pp.467-474
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• 2014

Preliminary design in chemical process furnishes economic feasibility through calculation of both mass balance and energy balance and makes it possible to produce a desired product under the given conditions. Through this design stage, the process possesses unchangeable characteristics, since the materials, reactions, unit configuration, and operating conditions were determined. Unique characteristics could be very economic, but it also implies various potential risk factors as well. Therefore, it becomes extremely important to design process considering both economics and safety by integrating process simulation and quantitative risk analysis during preliminary design stage. The target of this study is LNG liquefaction process. By the simulation using Aspen HYSYS and quantitative risk analysis, the design variables of the process were determined in the way to minimize the inherent explosion risks and operating cost. Instead of the optimization tool of Aspen HYSYS, the optimization was performed by using stochastic optimization algorithm (Covariance Matrix Adaptation-Evolution Strategy, CMA-ES) which was implemented through automation between Aspen HYSYS and Matlab. The research obtained that the important variable to enhance inherent safety was the operation pressure of mixed refrigerant. The inherent risk was able to be reduced about 4~18% by increasing the operating cost about 0.5~10%. As the operating cost increases, the absolute value of risk was decreased as expected, but cost-effectiveness of risk reduction had decreased. Integration of process simulation and quantitative risk analysis made it possible to design inherently safe process, and it is expected to be useful in designing the less risky process since risk factors in the process can be numerically monitored during preliminary process design stage.

• Journal of the Korean Institute of Gas
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• v.16 no.6
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• pp.87-101
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• 2012

In gas industries, the potential risks of serious accidents have been increased due to high technology application and process complexities. Especially, in case of gas-related accidents, the extent of demage is out of control since gas plants handle and produce combustible, flammable, explosive and toxic materials in large amounts. The characteristics of this kind of disaster is that accident frequency is low, while the impact of damage is high, extending to the neighboring residents, environment and related industries as well as employees involved. The hydrogen gases treated important things and it used the basic material of chemical plants and industries. Since 2000, this gas stood in the spotlight the substitution energy for reduction of the global warming in particular however it need to compress high pressure(more than 150 bar.g) and store by using the special cylinders due to their low molecular weight. And this gas led to many times the fire and explosion due to leak of it. To reduce these kinds of risks and accidents, it is necessary to improve the new safety management system through a risk management after technically evaluating potential hazards in this process. This study is to carry out the quantitative risk assesment for hydrogen filling plant which are very dangerous(fire and explosive) and using a basic materials of general industries. As a results of this risk assessment, identified the elements important for safety(EIS) and suggested the practical management tools and verified the reliability of this risk assessment model through case study of accident.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.11
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• pp.259-272
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• 2019

Steel-concrete single-leaf blast-resistant doors are protective structures consisting of a steel box and reinforced concrete slab. By the domestic blast-resistant doors, the structure is not designed efficiently because few studies have examined the effects of variables, such as the blast pressure, rebar ratio, and steel plate thickness on the structural behavior. In this study, the structural behavior of the doors was analyzed using the FE method, and the support rotation and ductility ratio used to classify the structural performance were reviewed. The results showed that the deflection changes more significantly when the plate thickness increases than when the rebar spacing is a variable. This is because the strain energy absorbed by the door is reduced considerably when the plate thickness increases, and as a result, the maximum deflection becomes smaller. According to a comparison of the calculated values of the support rotation and the ductility ratio, the structural performance of the doors could be classified based on the support rotation of one degree and ductility ratio of three. On the other hand, more explosion tests and analytical studies will be needed to classify the damage level.

• Journal of Energy Engineering
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• v.27 no.2
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• pp.1-13
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• 2018

The proportion of natural gas-fueled power generation is expanding due to the change of domestic energy policy pursuing reduction of dust and increasing clean energy consumption. Natural gas fuels used for the combined-cycle power plants and the district-heating power plants are operated at high temperature and high pressure in the fuel supply system. Accidents due to leakage of the gas such as fire and explosion should be prevented by applying risk management techniques. In this study, risk assessment was performed on the natural gas fuel supply system of a combined power plant based on the API RP 581 RBI code. For the application of the API RBI code, lines and segments of the evaluation target system were identified. Operational data and input information were analyzed for the calculations of probability of failure and consequence of failure. The results of the risk assessment were analyzed over time from the initial installation time. In the code-based evaluation, the gas fuel supply system was mainly affected by thinning, external damage, and mechanical fatigue damage mechanisms. As the operating time passes, the risk is expected to increase due to the external damage caused by the CUI(Corrosion Under Insulation).

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.16 no.3
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• pp.233-244
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• 2006

Of many volatile organic detergents for metals, benzine(CAS No. 8030-30-6), of which the toxicity has not yet been proven, has been used as an alternative of the halide compounds in the consideration of toxic effects, global warming and the destruction of ozone layer. In order to evaluate the effects of the benzine on human body by investigating the subchronic inhalation toxicity, to obtain the basic data for establishing the criteria of exposure in working environments and to classify the hazardousness in compliance with the Industrial Safety and Health Act by evaluating the hazardousness, repeated inhalation exposure test was carried with SD rats. The rats were grouped by 10 females and males each. The repetitive inhalation exposures were carried out at 4 levels of concentration of 0 ppm, 60 ppm, 300 ppm, and 1,500 ppm, for 6 hours a day, 5 days a week, for 13 weeks. The results are described hereunder. 1. No death of the animals of the exposed and controlled groups in the test period. Not any specific clinical symptoms, change in feed intake quantity, abnormality in eye test, or change in activity were observed. 2. In the 300 ppm and 1,500 ppm groups, weight reduction in the female groups and weight increase of liver and kidney in the male groups compared with control group were observed with statistical significance(p<0.05). 3. In the blood test, the HCT increased in the male 300 ppm group and the number of hematocyte increased, MCV and MCH decreased in the male 1,500 ppm group. In the female 1,500 ppm group, the HB decreased and the distribution width of the hematocyte particle size increased. In the blood biochemistry test, the TP in the male 1,500 ppm group and the LDH in the female 1,500 ppm group were increased with statistical significance(p<0.05). 4. Under the test conditions of the present study with SD rats, the NOEL was evaluated to be from 60 ppm to 300 ppm for both male and female groups. By extrapolation, the NOEL for human who work 8 hours a day was evaluated to be from 128 ppm to 640 ppm 5. Since the NOEL evaluated in this study do not exceed 60ppm(0.184 mg/L) the test material does not belong to the classification of the hazardous substance "NOEL${\leq}$0.5mg/L/6hr/90day(rat), for continuous inhalation of 6hours a day for 90 days" nor to the basic hazardous chemical substance class 1(0.2 mg/L/6hr/90day(rat) defined by the GHS which is a criteria of classification and identification of chemical compounds. However, considering the boiling point($30-204^{\circ}C$), flashing point($-40^{\circ}C$), vapor pressure(40 mmHg), and the inflammable range(1.0 - 6.0 %), sufficient care should be taken for handling in the safety aspects including fire or explosion.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.5
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• pp.339-349
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• 2020

Double-leaf blast-resistant doors consisting of steel box and slab are application-specific structures installed at the entrances of protective facilities. In these structural systems, certain spacing is provided between the door and wall. However, variation in the boundary condition and structural behavior due to this spacing are not properly considered in the explosion analysis and design. In this study, the structural response and failure behavior based on two variables such as the spacing and blast pressure were analyzed using the finite element method. The results revealed that the two variables affected the overall structural behavior such as the maximum and permanent deflections. The degree of contact due to collision between the door and wall and the impact force applied to the door varied according to the spacing. Hence, the shear-failure behavior of the concrete slab was affected by this impact force. Doors with spacing of less than 10 mm were vulnerable to shear failure, and the case of approximately 15-mm spacing was more reasonable for increasing the flexural performance. For further study, tests and numerical research on the structural behavior are needed by considering other variables such as specifications of the structural members and details of the slab shear design.