• Journal of the Korean Society of Safety
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• v.11 no.4
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• pp.107-114
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• 1996

A study to Improve the safety of the ceramic heat exchanger In the high temperature heat recovery system was performed in terms of air flow passes. The numerical and finite element analyses on the heat transfer and thermal stresses in the ceramic core related with air passes were carried out. The results showed that the stresses in the ceramic core induced by the thermal expansion are large enough to cause failure of the brittle ceramic core. The imployment of triple-pass air flow for the same ceramic core could increase the efficiency and effectively release approximately 20% of the maximum thermal stressess, thus improving the safety of the ceramic heat exchanger. The use of triple-pass, however, is limited by the amount of air flow due to the increase of pressure drop.

• Journal of the Korean Society of Safety
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• v.37 no.4
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• pp.113-119
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• 2022

Sudden intrusion of a large amount of surface water into a flood defensive tunnel or pipeline system can compress the residual air. The compressed air may explode along with water through the inlet or air vent, resulting in hydraulic capacity degradation or safety hazards. This study aims to investigate the behavior of compressed air body in pipelines according to the residual air condition with a series of laboratory experiments measuring pressure variation. It has been found that flow characteristics and residual air conditions have a dominant influence on the magnitude and periodicity of the pressure variation. A proper measure to effectively control the residual air is required for securing the design capacity of flood defensive pipeline systems, since the peak pressure is predominantly affected by residual air conditions.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.29 no.2
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• pp.111-116
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• 2021

Normal Operation Safety Survey (NOSS) is a safety management tool used by air traffic control organizations to measure data related to threats and errors to proactively prevent accidents before they occur. NOSS was developed to be applied to the air traffic control field according to the concept of Line Operation Safety Audit (LOSA) conducted by airlines to reduce human errors in the cockpits. Safety management based on data is crucial for the prevention of control-related accidents, and the competency of observers for this is important for the successful implementation of NOSS. Based on LOSA implementation experiences and expert interviews, this paper introduces the international NOSS methods and discusses the key factors required for effective observation and the implementation methods and implications of NOSS observer training.

• Journal of Environmental Health Sciences
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• v.49 no.2
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• pp.78-88
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• 2023

Background: Exposure to volatile organic compounds (VOCs) can have acute and chronic health effects on human beings in general and in working environments. In particular, VOCs are often emitted in large quantities in industrial settings. In such circumstances, there is a need to improve the indoor air quality at workplaces. Objectives: The purposes of this study were to verify the effectiveness of air cleaning devices in workplaces and provide alternative solutions for improving working environments. Methods: Personal exposure and area level of VOCs for workers were evaluated in a car-part adhesive process before and after installing an air cleaning device with a TiO₂-coated filter. Passive samplers and direct reading instruments were used to collect and analyze the VOCs, and the removal efficiency and improvement of air quality were evaluated. We also calculated the exposure index (EI) to assess the risk level in the workplace. Results: The removal efficiency for VOCs through the installation of the air cleaning device was approximately 26.9~69.0% as determined by the concentration levels before and after installation. The measured substances did not exceed the exposure limits for the work environment and the EI was less than 1. However, carcinogenic substances such as benzene, formaldehyde, carbon tetrachloride, and trichloroethylene were detected. Conclusions: The application of an air cleaning device can be a solution for controlling the indoor air quality in a workplace, particularly in cases where ventilation systems cannot be installed due to process limitations.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.29 no.4
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• pp.37-44
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• 2021

In case of South Korea, the airspace which airlines can operate is extremely limited due to the military operational area located within the Incheon flight information region. As a result, safety problems such as mid-air collision between aircraft or Traffic alert and Collision Avoidance System Resolution Advisory (TCAS RA) may occur with higher probability than in wider airspace. In order to prevent such safety problems, an mid-air collision risk detection model based on Detect-And-Avoid (DAA) well clear metrics is investigated. The model calculates the risk of mid-air collision between aircraft using aircraft trajectory data. In this paper, the practical use of DAA well clear metrics based model has been validated. Aviation safety data such as aviation safety mandatory report and Automatic Dependent Surveillance Broadcast is used to measure the performance of the model. The attributes of individual aircraft track data is analyzed to correct the threshold of each parameter of the model.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.29 no.2
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• pp.55-66
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• 2021

ICAO recommended that airspace monitoring and periodic safety assessments in each Contracting State ensure the stability of the airspace, since reducing the aircraft lateral and vertical separation intervals would rather increase the risk of collision. The target level of safety of the AKARA-FUKUE Corridor at the southern end of Jeju was 247×10^-9. In simple comparison, this means that the risk of an aircraft collision in this area (international safety standards, 5.0×10^-9) is about 50 times higher. The scope of this study is to organize the concept of terms, analyze the air traffic volume, the current status of navigational safety facility usage fees, and investigations of an aircraft collision risk in Jeju southern air corridor. Analyzing government policies and overseas evaluations, revising some of the existing contents, presenting some of the additional contents of new routes, and changing the instrument procedure for Korean-Chinese routes, change of arrive/departure route between Incheon Airport and Shanghai Airport, reduce the risk of aircraft collisions. We hope to restore airspace sovereignty, contribute to policies for the government to take the lead in solving this problem, and expect stability and operational efficiency in air traffic.

• Journal of the Korea Safety Management & Science
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• v.14 no.3
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• pp.85-92
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• 2012

In this study the real situation of apartment house in seoul is reproduced with multi-zone modeling program contam2.4. This model include immune building system(disinfection system) which is consist of dilution, Filter Technology and UVGI(ultra violet germicidal irrdiation). In this study experiments design method used for estimating interaction of HRV air change rate, UVGI air change rate and UVGI grade. Result show that HRV air change rate and UVGI air change rate is most influence factor for remove rate. also Interaction of HRV air change rate and UVGI air change rate is ost influence factor for remove rate.

• Journal of the Korean Society of Safety
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• v.23 no.5
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• pp.49-53
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• 2008

Glow discharge has lots of attractive properties, such as lower discharge sustaining voltage, no generation of ozone, and so on. And more, ionizer was developed recently using an atmospheric pressure glow discharge. On the other hand, ionizer needs a compressed or blown air to transport ion for charged objects. This air is very useful in explosive hazardous area to prevent the explosion of flammable gas and/or vapor by ignition sources, e.g. electrical spark. In this paper, we investigated the ionizing characteristic of atmospheric pressure glow discharge by controlled air flow rate from 5 liters to 60 liters a minute, and compared with decay time between the corona discharge and glow discharge as a function of some direction and distance from discharge ion source. We confirmed that an air flow rate needs 25 liters a minute to sustain the most suitable atmospheric pressure glow discharge and to increase an ionizing efficiency.

• Journal of the Korea Safety Management & Science
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• v.24 no.4
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• pp.101-107
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• 2022

To test a flameproof enclosure for the safety certificate, a reference pressure of explosion needs to be determined. However, the explosion pressure may be changed according to relative humidity of explosive gases. Therefore, the guideline on relative humidity should be recommended for measuring the explosion pressure for accurate and reproducible testings. This study examined the relationship of explosion pressure with relative humidity of hydrogen (31 vol %)-air and acetylene (14 vol %)-air mixture gases. The explosion pressures were measured by increasing the relative humidity of the gases by 10 % from dry state to 80 % in a cylindrical explosion enclosure of 2.3 L. on ambient temperature and atmospheric pressure (1 atm). The maximum explosive pressures were remained almost constant until the relative humidity reached 10 % for the hydrogen-air mixture and 20 % for the acetylene-air mixture. However, the maximum explosive pressures linearly decreased as the relative humidity increased. Based on the results of the study, it would be recommended to use 10 % relative humidity for the hydrogen-air mixture and 20 % for the acetylene-air mixture as the critical value in testing a flameproof enclosure.

• Nuclear Engineering and Technology
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• v.55 no.1
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• pp.71-79
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• 2023

Air ingress incidents are major safety accidents in very-high-temperature reactors (VHTRs). Air containing a high volume fraction of oxygen may cause severe oxidation of core components at the VHTR, especially for the significantly thin alloy tube wall in the intermediate heat exchanger (IHE). The research objects of this study are Inconel 617 and Incoloy 800H, two candidate alloys for IHE in VHTR. The air ingress accident scenario is simulated with high-temperature air flow at 950 ℃. A continuous oxide scale was formed on the surfaces of both the alloys after the experiment. Because the oxide scale of Inconel 617 has a loose structure, whereas that of Incoloy 800H is denser, Inconel 617 exhibited significantly more severe internal oxidation than Incoloy 800H. Further, Inconel 617 showed a significant decrease in ultimate tensile strength and plasticity after aging for 200 h, whereas Incoloy 800H maintained its tensile properties satisfactorily. Through control experiment under vacuum, we preliminarily concluded that serious internal oxidation is the primary reason for the decline in the tensile properties of Inconel 617.