• Journal of Chest Surgery
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• v.41 no.6
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• pp.724-728
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• 2008

Background: The purpose of this study was to identify factors associated with recurrent pneumothorax after wedge resection in primary spontaneous pneumothorax in our hospital. Material and Method: Two hundred thirty-five consecutive patient (98% males; mean age, $23.9{\pm}4.5$ years) who had undergone video-assisted thoracoscopic surgery (VATS) were reviewed retrospectively. The two groups were divided as follows: group A, non-recurrent patients (225 patients [96%]); and group B, recurrent group (10 patients [4%]); the risk factors were compared between the two groups. The single and multiple factors that influenced the recurrence rate were analyzed using Cox's proportional hazard model. Result: There were no significant differences between the recurrent and non-recurrent groups in terms of gender, smoking, site of recurrence, degree of collapse, operative time, and number or weight of resected bullae. The recurrence rate was significantly more common in the following: younger ages, increased height/weight ratio, longer initial air leakage period, and shorter duration of chest drainage. Early aggressive exercise (<30 days) of patients after wedge resection increased the tendency for recurrence. Conclusion: Thoracoscopic wedge resection does not have a higher recurrence rate than open thoracotomy. However, young age, height/weight ratio, continuous air, and duration of chest tube placement were risk factors for a recurrent pneumothorax.

• Journal of the Korean Institute of Gas
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• v.23 no.6
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• pp.74-80
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• 2019

Hydrogen refueling stations that use compressed hydrogen at high pressure provide safety distances between facilities in order to ensure safety. Most accidents occurring in hydrogen stations are accidental leaks. When a leak occurs, various types of ignition sources generate a jet flame. Therefore, the analysis of leaked gas diffusion and jet flame due to high pressure hydrogen leakage is one of the most important factor for setting the safety distance. In this study, the leakage accidents that occur in the hydrogen refueling station operated in high pressure environment are simulated for various leakage source sizes. The results of this study will be used as a reference for the future safety standards.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06c
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• pp.13-16
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• 2011

에너지플랜트는 위험성이 높은 유해화학물질을 취급해서 누출사고가 발생 할 가능성이 높다. 유해화학물질이 누출되어 대기 중에 확산되면 강한 유독성으로 인해 대형피해를 불러온다. 유해화학물질의 누출로 인한 대기 중의 확산피해 최소화하는 방안에는 확산 될 범위를 산출하여 적절한 사고대응조치를 취하는 것이다. 대기확산모델의 시뮬레이션을 이용한 대기확산범위 산출은 가상으로 설정 된 시나리오의 데이터를 사용자가 수동으로 입력하여 결과를 도출한다. 가상 데이터로 산출 된 결과는 정확성이 결여 될 수 있으며 실시간 대기확산범위 산출이 불가능하다. 본 연구에서는 유해화학물질의 대기확산범위를 즉각적으로 산출 할 수 있는 실시간 대기확산시스템을 설계하고 구현한다. 대기확산범위 산출에 필요한 데이터는 실시간으로 수집 된 실제 데이터를 이용한다. 실시간으로 수집된 실 데이터를 토대로 데이터마이닝기법을 통해 자율적인 누출사고를 탐지하고 누출지점을 특정 할 수 있는 지능화모듈을 설계한다. 대기확산모델은 유해화학물질의 증기운의 무게에 따라 가우시안과 SLAB모델을 이용한다. 실시간으로 산출 된 대기확산범위는 ERPG의 각 단계의 농도 기준에 근거하여 총 3단계로 구분해서 GIS맵 상의 유저인터페이스에 표현한다. 산출된 대기확산피해범위는 현장 작업자의 모바일기기로 사고와 관련 된 대응조치와 함께 신속히 전파할 수 있도록 구현해서 누출로 인한 유해화학물질의 확산사고피해 최소화를 도모한다.

• Journal of the Korean Institute of Gas
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• v.23 no.2
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• pp.17-27
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• 2019

In recent years, dangerous materials and gas leak accidents have been frequently occurred. The hazardous materials storage facility accidents are not rapidly controlled when a leak is detected, unlike other chemical plants can be controled. Externally, the human has to approach and respond to the source of leaking directly. As a result, the human and material damage are likely to larger result in the process. The current approach has been passive response after ringing the alarm. In this study, the suggested tracking system of the leak resource is designed system to track the resource actively by utilizing the mobile sensor robot platform, which can be made easily through recent rapid development technology, is verified through prototype system. Thus, a suggested system should pave the way for minimizing the spread and damage of the accident based on the exact site situation of the initial leak and quick and early measures.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.4
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• pp.305-316
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• 2022

Hydrogen energy is emerging as an alternative to the depletion of fossil fuels and environmental problems, and the use of hydrogen vehicles is increasing in the automobile industry as well. However, since hydrogen has a wide flammability limit of 4 to 75%, there is a high concern about safety in case of a hydrogen car accident. In particular, in semi-enclosed spaces such as tunnels and underground parking lots, a fire or explosion accompanied by hydrogen leakage is highly likely to cause a major accident. Therefore, it is necessary to review hydrogen safety through analysis of flammability areas caused by hydrogen leakage. Therefore, in this study, the effect of the air velocity in the tunnel on the flammability area was investigated by analyzing the hydrogen concentration according to the hydrogen leakage conditions of hydrogen vehicles and the air velocity in the tunnel in a road tunnel with standard section. Hydrogen leakage conditions were set as one tank leaking and three tanks leaking through the TPRD at the same time and a condition in which a large crack occurred and leaked. And the air velocity in the tunnel were considered 0, 1, 2.5, and 4.0 m/s. As a result of the analysis of the flammability area, it is shown that when the air velocity of 1 m/s or more exists, it is reduced by up to 25% compared to the case of air velocity of 0 m/s. But there is little effect of reducing the flammability area according to the increase of the wind speed. In particular, when a large crack occurs and completely leaks in about 2.5 seconds, the flammability area slightly increases as the air velocity increases. It was found that in the case of downward ejection, hydrogen gas remains under the vehicle for a considerably long time.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1997.11a
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• pp.59-64
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• 1997

화학관련분야의 공정안전에 관하여 오랜 역사를 가진 AIChE는 관련산업분야의 안전규정을 예방적인 측면과 사고원인을 규명하기 위한 측면에서 근원적인 자료를 제시하였고 1955년 AIChE에 의해 설립된 CCPS(center for chemical process safety)는 이에 관한 기술적인 면에 더욱 발달된 정보를 제공하게 되었다. 이런 정보들 가운데 사업장의 위험물질이 지니고 있는 위험성을 어떻게 평가할 것인가에 관하여 CPQRA(chemical process quantitative risk analysis)방법이 제시되어 있다. 1) CPQRA는 양적인 의미에서 위험성의 정의, 분석, 평가, 통제 및 관리방법 등에 대비해 잠재적인 방법을 제시한 것이다. (중략)

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2000.11a
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• pp.373-376
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• 2000

현대의 화학산업시설에서는 다양한 잠재위험으로 인하여 화재, 폭발, 독성물질 누출 등의 중대산업사고의 발생 가능성 및 사고결과의 피해 범위가 증가되고 있다. 만약 사고가 발생한다면, 현장의 근로자, 인근지역 주민, 주변의 환경에 심각한 영향을 미칠 수 있으며, 사회적·경제적 불안 요소를 제공하게 된다. 지금까지는 정량적 위험성 평가라는 방법을 사용하여 화학공장의 안전관리를 수행하였으나 이번 연구에서는 이러한 사고의 위험도를 낮추기 위하여 RBI라는 기법을 사용하여 효과적이고 효율적인 안전성 향상 모델을 제시하고자 한다.(중략)

• Journal of the Korean Institute of Gas
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• v.5 no.2 s.14
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• pp.36-42
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• 2001

A leak of fuel gas in partially confined area creates a flammable atmosphere and give rise to an explosion, which is one of the most common accident in domestic. Observations from accident in domestic suggest that some explosions are caused by a quantify of fuel significantly less than lower explosion limit(LEL) amount required to fill the room, which is attributed to inhomogeneous mixing of leaked gas. The minimum amount of leaked gas for explosion is highly dependent on the mixing degree in the area. For lighter gas, such as methane, a high concentration tends to build up in the space from ceiling of room. But heavy gas, such as propane, a high concentration tends to build up in the space from bottom of room. This paper presents a method for analysing the explosion hazard in a room with very small amount of leaked gas. Based on explosion limit concentration, the gaussian distribution model is used to estimate the minimum amount of leak which yields a specified explosion pressure. The results demonstrate that catastrophic structural damage can be achieved with a volume of fuel gas which is less than 0.5 percent of the total enclosed volume in domestic. The method will help analyzing hazard to develop new safe device as well as investigating accident.

• Journal of the Korean Institute of Gas
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• v.25 no.4
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• pp.57-62
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• 2021

In this study, risk assessment was conducted in case of leakage of storage facilities (tube trailer) using the HyKoRAM program developed through international joint research. The high-pressure gas facilities in the hydrogen filling station are divided into four main categories: storage facilities (tube trailers), processing facilities (compressors), compressed gas facilities, and filling facilities (dispensers). Among them, the design specifications of the tube trailer, which is a storage facility, and the surrounding environmental conditions were reflected to construct an accident scenario with previously occurring accidents and potential accidents. Through this, we identify the risks of storage facilities at hydrogen refueling stations and suggest measures to improve the safety of hydrogen charging stations.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.4
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• pp.610-619
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• 2022

Hydrogen is emerging as an alternative fuel for eco-friendly ships because it reacts with oxygen to produce electrical energy and only water as a by-product. However, unlike regular fossil fuels, hydrogen has a material with a high risk of explosion due to its low ignition point and high flammability range. In order to safely use hydrogen in ships, it is an essential task to study the flow characteristics of hydrogen leakage and diffusion need to be studied. In this study, a numerical analysis was performed on the effect of leakage, ventilation, etc. on ventilation performance when hydrogen leaks in an enclosed space such as inside a ship. ANSYS CFX ver 18.1, a commercial CFD software, was used for numerical analysis. The leakage rate was changed to 1 q, 2 q, and 3 q at 1 q = 1 g/s, the ventilation rate was changed to 1 Q, 2 Q and 3 Q at 1 Q = 0.91 m/s, and the ventilation method was changed to type I, type II, type III to analyze the ventilation performance was analyzed. As the amount of leakage increased from 1 q to 3 q, the HMF in the storage room was about 2.4 to 3.0 times higher. Furthermore, the amount of ventilation to reduce the risk of explosion should be at least 2 Q, and it was established that type III was the most suitable method for the formation of negative pressure inside the hydrogen tank storage room.