• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.3
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• pp.237-242
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• 2015

With the rapid development of modern society, subway has become one of the most typical urban transport systems. Since fire accident occurred at Daegu subway in 2003, importance of life safety and disaster prevention have been widely recognized and many studies have been carried out. As a result of these studies, fire-retardant and non-combustible interior material and platform screen door with passenger guide indication device have been developed, but studies on a subway evacuation criteria have been in a stalemate. Therefore, this study is intended to improve the subway evacuation standard. It is very difficult to take into account whole subway system, so a typological approach to a ticket was carried out referring to previous studies focused on a subway platform. this paper selected the most common subway platforms and estimated evacuation time among 10 platforms from previous studies and 8 from this study. As a result, evacuation time exceeded 6 minutes which is the guideline of existing standard. Therefore, it is necessary to update the standard for evacuation time and add supplementary conditions which can help establishing the measures for safety facilities and prevention measures.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.6
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• pp.659-677
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• 2022

Hydrogen is emerging as a next-generation energy source and development and supply of FCEV (hydrogen fuel cell electric vehicle) is expected to occur rapidly. Accordingly, measures to respond to hydrogen car accidents are required and researches on the safety of hydrogen cars are being actively conducted. In this study, In this study, we developed a hydrogen car accident scenarios suitable for domestic conditions for the safety evaluation of hydrogen car in road tunnels through analysis of existing experiments and research data and analyzed and presented the hazard distance according to the accident results of the hydrogen car accident scenarios. The accident results according to the hydrogen car accident scenario were classified into minor accidents, general fires, jet flames and explosions. The probability of occurrence of each accident results are predicted to be 93.06%, 1.83%, 2.25%, and 2.31%. In the case of applying the hydrogen tank specifications of FCEV developed in Korea, the hazard distance for explosion pressure (based on 16.5 kPa) is about 17.6 m, about 6 m for jet fire, up to 35 m for fireball in road tunnel with a standard cross section (72 m²).

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.6
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• pp.1161-1175
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• 2018

An unexpected event could be easily followed by a large secondary accident due to the limitation in sight of drivers in road tunnels. Therefore, a series of automated incident detection systems have been under operation, which, however, appear in very low detection rates due to very low image qualities on CCTVs in tunnels. In order to overcome that limit, deep learning based tunnel incident detection system was developed, which already showed high detection rates in November of 2017. However, since the object detection process could deal with only still images, moving direction and speed of moving vehicles could not be identified. Furthermore it was hard to detect stopping and reverse the status of moving vehicles. Therefore, apart from the object detection, an object tracking method has been introduced and combined with the detection algorithm to track the moving vehicles. Also, stopping-reverse discrimination algorithm was proposed, thereby implementing into the combined incident detection processes. Each performance on detection of stopping, reverse driving and fire incident state were evaluated with showing 100% detection rate. But the detection for 'person' object appears relatively low success rate to 78.5%. Nevertheless, it is believed that the enlarged richness of image big-data could dramatically enhance the detection capacity of the automatic incident detection system.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.1
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• pp.1-29
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• 2019

Related to the previous paper on the typical crack pattern of tunnel lining with NATM, the characteristic defects in reinforced cement concrete lining of NATM tunnel have analyzed with the precise inspection with safety and diagnosis (PISD) by KISTEC. Depending on the reinforcing materials, steel rebar, steel fiber, and glass fiber have been implemented to reinforcing lining in various NATM tunnel constructions. Reinforcing lining with rebar are prevailed on NATM tunnel to countermeasure the weak geological circumstances, to pursuit the economical tunnel sections, and to resist the risk of tunnel deterioration. By the special act on the safety control of public facilities, the reinforced NATM tunnels for more than 1 km length are scrutinized closely to characterize defects; crack, reinforcement exposure, and lack of lining. Crack resistance by reinforcing is shown in comparison with the normalized crack to the length of tunnel. Typical exposed reinforcements in lining have exemplified with various sections. The lack of lining due to the mal-construction, spalling, fire, earthquake and leaching has been analyzed. The cause and mechanism with the field inspections and other studies has also been verified. Detailed cases are selected by the above concerns as well as the basic information from FMS (Facilities Management System). Likewise the previous paper, this study provides specialized defects in reinforced lining of NATM and it can be widely used in spreading the essential technics and reporting skills. Furthermore, it would be advised and amended for the detail guideline of Safety Diagnosis and PISD (tunnel).

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.3
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• pp.419-432
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• 2019

Most of deep learning model training was proceeded by supervised learning, which is to train labeling data composed by inputs and corresponding outputs. Labeling data was directly generated manually, so labeling accuracy of data is relatively high. However, it requires heavy efforts in securing data because of cost and time. Additionally, the main goal of supervised learning is to improve detection performance for 'True Positive' data but not to reduce occurrence of 'False Positive' data. In this paper, the occurrence of unpredictable 'False Positive' appears by trained modes with labeling data and 'True Positive' data in monitoring of deep learning-based CCTV accident detection system, which is under operation at a tunnel monitoring center. Those types of 'False Positive' to 'fire' or 'person' objects were frequently taking place for lights of working vehicle, reflecting sunlight at tunnel entrance, long black feature which occurs to the part of lane or car, etc. To solve this problem, a deep learning model was developed by simultaneously training the 'False Positive' data generated in the field and the labeling data. As a result, in comparison with the model that was trained only by the existing labeling data, the re-inference performance with respect to the labeling data was improved. In addition, re-inference of the 'False Positive' data shows that the number of 'False Positive' for the persons were more reduced in case of training model including many 'False Positive' data. By training of the 'False Positive' data, the capability of field application of the deep learning model was improved automatically.

• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.4
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• pp.395-401
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• 2009

One of the key design factors for the ventilation and safety system at extra long tunnel is the airflow velocity induced by the natural ventilation force. Despite of the importance, it has not been widely studied due to the complicated influencing variables and the relationship among them is difficult to quantify. At this moment none of the countries in the world defines its specific value on verified ground. It is also the case in Korea. The recent worldwide disasters by tunnel fires and demands for better air quality inside tunnel by users require the optimization of the tunnel ventilation system. This indicates why the natural ventilation force is necessary to be thoroughly studied. This paper aims at predicting the natural ventilation force at a 11 km-long tunnel which is in the stage of detailed design and will be the longest vehicle tunnel in Korea. The concept of barometric barrier which can provide the maximum possible natural ventilation force generated by the topographic effect on the external wind is applied to estimate the effect of wind pressure and the chimney effect caused by the in and outside temperature difference is also analyzed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2000.04a
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• pp.16-16
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• 2000

충격파를 포함하는 초음속 유동을 해석하는 수치해법 중에서 많이 사용되어진 것은 엄밀 및 근사 리만 해법과 플럭스 분할 기법들로서 이들은 Euler 방정식에 기반을 두고 선형 또는 비선형파의 상호작용을 풍상 차분법으로 기술하는 방법들이다. 이러한 수치기법들은 과거 광범위하게 사용되어 왔으나 최근 여러 가지 단점이 발견되었다. 이와 같은 문제점을 극복하고자 입자의 통계적인 운동을 기술하는 기체 운동론에 근거하여 BGK 수치기법이 제시되었다. 이는 비충돌 볼츠만 방정식으로부터 입자의 수준에서 플럭스 분할 기법 형태의 풍상차분법을 구현하는 것으로 볼츠만 방정식의 충돌항을 BGK 모델로 대치하고 이것의 적분해로부터 수치 플럭스를 구한다. 이 수치기법은 기존의 리만해법에 비하여 수치적으로나 물리적으로 매우 타당한 성질인 강건성, 정확성, 엔트로피 조건, 양수보존성 등을 가지고 있음이 밝혀졌다. 이와 같은 수치기법을 사용하여 로켓 노즐 내의 아음속, 천이음속, 초음속에서의 유동장 해석을 위한 프로그램을 작성하였다. 시간 적분에 대하여는 정상 상태의 계산을 위하여 내재적 시간 적분 방법을 사용하였으며, 공간 이산화 방법으로는 임의의 제어체적에 대하여 적분형 보존 방정식을 적용하는 유한 체적법을 사용하였다. 초음속 입구 유동과 출구에서 초음속과 저음속 유동의 두가지 경우를 고려하여 얻은 결과를 기존의 연구 결과와 비교하여 본 결과 잘 일치하였다. 입구 유동이 저음속이고 출구 유동이 초음속인 경우에 대하여도 해석결과가 실험결과와 잘 일치하였다. 상대적으로 낮은 온도, 압력 조건과 높은 온도, 압력 조건을 가지는 고체 로켓 모터 노즐 내의 유동을 해석하였다. 이들 해석 결과를 전압, 전온도로 표준화시킨 결과 서로 일치하였으며, 파라서 저온, 저압에서 얻은 결과도 표준화시킬 경우, 고온, 고압에서도 사용될 수 있음을 알 수 있었다.의 영향에 초점을 맞추었다.다고 판단되며 배기 가스 자체에 대기 공기중에 함유되어 있던 습기가 얼어붙는(Icing화) 문제가 발생하기 때문에 배기가스의 Icing을 방지하기 위하여 압축기 끝단에서 공기를 추출하여 배기부분에 송출할 필요성이 있는 것으로 판단되었다. 출구가스의 기체 유동속도가 매우 빠르므로 (100-l10m.sec) 이를 완화하기 위한 디퓨저의 설계가 요구된다고 판단된다. 또 연소기 후방에 물을 주입하는 경우 열교환기 및 기타 부분품에 발생할 수 있는 부식 및 열교환 효율 저하도 간과할 수 없는 문제로 파악되었다. 이러한 기술적 문제가 적절히 해결되는 경우 비활성 가스 제너레이터는 민수용으로는 대형 빌딩, 산림, 유조선 등의 화재에 매우 적절히 사용되어 질 수 있을 뿐 아니라 군사적으로도 군사작전 중 및 공군 기지의 화재 그리고 지하벙커에 설치되어 있는 고급 첨단 군사 장비 등의 화재 뿐 아니라 대간첩작전 등에 효과적으로 활용될 수 있을 것으로 판단된다.가 작으며, 본 연소관에 충전된 RDX/AP계 추진제의 경우 추진제의 습기투과에 의한 추진제 물성 변화는 미미한 것으로 나타났다.의 향상으로, 음성개선에 효과적이라고 사료되었으며, 이 방법이 편측 성대마비 환자의 효과적인 음성개선의 치료방법의 하나로 응용될 수 있으리라 생각된다..7%), 혈액투석, 식도부분절제술 및 위루술·위회장문합술을 시행한 경우가 각 1례(2.9%)씩이었다. 13) 심각한 합병증은 9례(26.5%)에서 보였는데 그중 식도협착증이 6례(17.6%), 급성신부전증 1례(2.9%), 종격동기흉과 폐염이 병발한 경우와 폐염이 각 1례(2.9%)였다. 14) 식도경 시행회수는 1회가 17례(54.8%), 2회가 9례(29.0%), 3회 이상이 5례(16.1%)였다.EX>$IC_{50}$/ 값이 210 $\mu\textrm{g}$<

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.4
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• pp.347-365
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• 2020

In order to resolve traffic problems in urban areas and to increase the area of green spaces, tunnels in downtown areas are being increased. Additionally, the application of large port smoke extraction ventilation systems is increasing as a countermeasure to smoke extraction ventilation for tunnels with high potential for traffic congestion. It is known that the smoke extraction performance of the large port smoke extraction system is influenced not only by the amount of the extraction flow rate, but also by various factors such as the shape of the extraction port (damper) and the extraction air velocity through a damper. Therefore, in this study, the design standards and installation status of each country were investigated. When the extraction air flow rate was the same, the smoke extraction performance according to the size of the damper was numerically simulated in terms of smoke propagation distance, compared and evaluated, and the following results were obtained. As the cross-sectional area of the smoke damper increases, the extraction flow rate is concentrated in the damper close to the extraction fan, and the smoke extraction rate of the damper in downstream decreases, thereby increasing the smoke propagation distance on the downstream side. In order to prevent such a phenomenon, it is necessary to reduce the cross-sectional area of the smoke damper and increase the velocity of passing air through the damper so that the pressure loss passing through the damper increases, thereby reducing the non-uniformity of smoke extraction flow rate in the extraction section. In this analysis, it was found that when the interval distance of the extraction damper was 50 m, the air velocity passing through damper was 4.4 m/s or more, and when the interval distance of the extraction dampers was 100 m, the air velocity passing through damper was greater than 4.84 m/s, it was found to be advantageous to ensure smoke extraction performance.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.6
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• pp.517-534
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• 2021

Hydrogen fuel is emerging as an new energy source to replace fossil fuels in that it can solve environmental pollution problems and reduce energy imbalance and cost. Since hydrogen is eco-friendly but highly explosive, there is a high concern about fire and explosion accidents of hydrogen fueled vehicles. In particular, in semi-enclosed spaces such as tunnels, the risk is predicted to increase. Therefore, this study was conducted on the applicability of the equivalent TNT model and the numerical analysis method to evaluate the hydrogen explosion pressure in the tunnel. In comparison and review of the explosion pressure of 6 equivalent TNT models and Weyandt's experimental results, the Henrych equation was found to be the closest with a deviation of 13.6%. As a result of examining the effect of hydrogen tank capacity (52, 72, 156 L) and tunnel cross-section (40.5, 54, 72, 95 m²) on the explosion pressure using numerical analysis, the explosion pressure wave in the tunnel initially it propagates in a hemispherical shape as in open space. Furthermore, when it passes the certain distance it is transformed a plane wave and propagates at a very gradual decay rate. The Henrych equation agrees well with the numerical analysis results in the section where the explosion pressure is rapidly decreasing, but it is significantly underestimated after the explosion pressure wave is transformed into a plane wave. In case of same hydrogen tank capacity, an explosion pressure decreases as the tunnel cross-sectional area increases, and in case of the same cross-sectional area, the explosion pressure increases by about 2.5 times if the hydrogen tank capacity increases from 52 L to 156 L. As a result of the evaluation of the limiting distance affecting the human body, when a 52 L hydrogen tank explodes, the limiting distance to death was estimated to be about 3 m, and the limiting distance to serious injury was estimated to be 28.5~35.8 m.

• Journal of Science and Technology Studies
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• v.10 no.2
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• pp.77-105
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• 2010

This essay aims to look into the possibility and limit of a technological fix with the PSD (platform screen door), which was proposed as the solution of subway risk problems. Subway risk problems may be classified into five categories-on-rail accidents, in-station accidents, platform accidents, spatial risks in underground, and risks due to a crime or terror-, and the platform accidents, which happens at the interface between the rail and the station, is the most serious and prominent. The PSD is considered as an effective technical means to prevent platform accidents. However, there remains a possibility of aggravating unexpected and invisible risks. When a fire breaks out in platforms, especially at exchange stations during the rush hour, the PSD can become a "wall of outcrying", since it may act as the "safety shutter" which killed many people in the 2003 Daegu subway disaster. This is why we need to look into the limit of a technological fix with the PSD.