• Journal of the Society of Naval Architects of Korea
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• v.36 no.2
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• pp.1-8
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• 1999

Extensive resistance tests for a passenger boat(now in service at Chung-Ju lake) have been performed in a towing tank to investigate the effect of an artificial air cavity attached to the hull bottom on the reduction of the ship resistance. The attached air cavity has been observed at various air sully rates, from which we have determined a proper shape of an air supply device. In order to prevent the supplied air from leaking near the bilge of the ship, longitudinal barrier strips have been attached to both sides of the device. The investigation on their effectiveness reveals that a cascade system of the air supply device reduces the resistance of the ship furthermore. Energy saving of more than 10% is achieved at the design speed in spite of the additional power necessary for the air supply.

• Journal of the Korean Institute of Gas
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• v.22 no.4
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• pp.55-62
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• 2018

There is growing interest in solar power generation due to global warming. As a result, demand for polysilicon, which is the core material for solar cells, is increasing day by day. As the market grows, large and small accidents occurred in the production process. In 2013, hydrochloric acid leaked from the polysilicon manufacturing plant in SangJu. In 2014, a fire occurred at a polysilicon manufacturing plant in Yeosu, and in 2015, STC(Silicon Tetrachloride) leaked at a polysilicon manufacturing plant in Gunsan City. Leakage of chemicals in the polysilicon manufacturing process can affect not only the workplace but also the surrounding area. Therefore, in this study, we identified the hazardous materials used in the polysilicon manufacturing process and quantitatively estimate the amount of leakage and extent of damage when the worst case scenario is applied. As a result, the damage distance by explosion was estimated to be 726 m, and the damage distance to toxicity was estimated to be 4,500 m. And, if TCS(Trichlorosilane), STC(Silicon Tetrachloride), DCS(Dichlorosilane) leaks into the air and reacts with water to generate HCl, the damage distance is predicted to 5.7 km.

• Journal of the Korea Convergence Society
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• v.10 no.10
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• pp.7-13
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• 2019

The natural gas (NG), mostly methane leaks into the air, it is a big problem for the climate. detected NG leaks under U.S. city streets and collected data. In this paper, we introduced a Deep Neural Network (DNN) classification of prediction for a level of NS leak. The proposed method is OrdinalEncoder(OE) based K-means clustering and Multilayer Perceptron(MLP) for predicting NG leak. The 15 features are the input neurons and the using backpropagation. In this paper, we propose the OE method for labeling target data using k-means clustering and compared normalization methods performance for NG leak prediction. There five normalization methods used. We have shown that our proposed OE based MLP method is accuracy 97.7%, F1-score 96.4%, which is relatively higher than the other methods. The system has implemented SPSS and Python, including its performance, is tested on real open data.

• The tire
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• s.48
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• pp.7-13
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• 1973

자동차 타이어의 최대의 특질은 공기라고 하는 천연의 기체를 충분히 활용하고 있는 점이다. 이 공기를 밖으로 누출함이 없이 수 10톤으로부터 수 100톤에나 달하는 중량물을 지탱하고 또한 시속 수 100km로 주파한다고 하는 마술에 가까운 묘기는 유독 타이어 만으로 이룩하고 있는 것은 아니고 갖가지 관련기술과의 공동의 연구 위에서 성립되어 있는 것이다. 그래서 금번은 타이어의 공기조정자로서 타이어와 함께 걸어온 타이어 발브와 발브코어를 취급해본다. 공기입 타이어의 발명은 상당히 옛날의 일이다. 그때 이미 타이어발브는 하차용으로서 존재하고 있었든 것 같다. 또 일본의 자동차발흥기에는 발브의 전부를 수입에 의존했다고 한다. 이것이 태평양공업주식회사이다. 하나 자동차와 함께 타이어의 진보도 눈부시다. 물론 그 그늘에 발브의 진보가 있었는 것도 간과할 수 없다. 특히 튜우브레스는 ……이다. 또한 타이어의 진보는 금후 더욱 가혹한 요구를 발브에도 요구하고 있는 중이다. -이에도 발브는 발브기술로서 충분히 부응할 용의가 있다고 한다…….

• Journal of the Korean Institute of Gas
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• v.18 no.5
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• pp.85-90
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• 2014

Turbo chiller is widely used for the air conditioner and uses hydrochlorofluorocarbon 123 (HCFC-123) as a refrigerant. HCFC-123 is one of the chemicals being considered as a replacement for the chlorofluorocarbons. High concentrations of HCFC-123 cause a deficiency of oxygen with the risk of unconsciousness or death, the vapour is heavier than air and may accumulate in low ceiling spaces causing deficiency of oxygen. In this study, the concentration distribution of oxygen indoor was investigated by using computational fluid dynamics(CFD) as four workers were killed in HCFC-123 gas leaks at machine room of hypermarket in 2011.

• Restorative Dentistry and Endodontics
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• v.27 no.5
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• pp.530-534
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• 2002

최근 치근단 와동 형성 시 초음파 또는 음파 기구를 이용하는 것이 보편화되어 있고 여러 측면에서 평가되어져 왔다. 본 연구의 목적은 혐기성 세균을 이용한 미세 누출 모델을 이용하여 초음파와 음파 기구를 사용, 치근단 와동 형성을 하였을 때 두 기구의 사용이 충전된 치근단 와동의 미세 누출에 미치는 영향을 비교 평가하는 것이다. 48개의 단근치의 근관을 crown-down방법을 이용 Profile로 .06 black까지 근관 성형을 시행하고 수직 가압법을 사용하여 gutta-percha와 AH26 sealer를 이용하여 근관 충전을 시행하였다. 각 충전된 시편의 치근단 3mm를 절제하였다. 각 시편은 이미로 4군으로 나누었으며 1군에서는 치근단 와동을 초음파 기구로 형성하였고 2군에서는 음파 기구로 형성하였다. 3군은 음성대조군으로 4군은 양성대조군으로 분류하였다. 형성된 치근단 와동은 공기 분사침을 이용하여 건조 후 super EBA 시멘트로 충전하였으며 Anaerobic chamber에서 Fusobacterium nucleatum (VPI 10197)을 사용한 혐기성 세균 미세누출 모델을 이용하여 30일간 미세 누출을 관찰한 결과, 초음파 기구를 사용한 군에서는 80%에서 음파 기구를 사용한 군에서는 75%에서 미세누출이 나타났으나 통계적으로 유의성 있는 차이는 보이지 않았다.

• Journal of Korean Society of Disaster and Security
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• v.10 no.2
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• pp.29-34
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• 2017

LPG is a substance that requires a lot of attention because it can cause fatal damage to people and environment when an accident occurs. LPG is frequently accidents in transportation facilities as well as fixed facilities, among which LPG tank lorries are the most frequent accidents. When the LPG tank is evacuated, the LP gas leaks into two phases, leaks mostly to the gas and leaks to some liquid. At this time, the leaked gas will also sink downward because it is heavier than air, and if it continues to leak, it may form an explosion and explode by the ignition source. The purpose of this study is to present the evacuation distance by analyzing the effect distance of the LPG liquefied petroleum gas in the event of explosion. As a result of calculation of the scattering radius of the fragment, the cylinder fragment was scattered up to 561 m. Therefore, it is appropriate to set the distance to be escaped when the LPG tanker leaks to 561m or more.

• Journal of the Korea Convergence Society
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• v.11 no.12
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• pp.23-30
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• 2020

In this study, the relationship between natural gas (NG) data and gas-related environmental elements was performed using machine learning algorithms to predict the level of gas leakage risk without directly measuring gas leakage data. The study was based on open data provided by the server using the IoT-based remote control Picarro gas sensor specification. The naturel gas leaks into the air, it is a big problem for air pollution, environment and the health. The proposed method is multivariate outlier removing method based Random Forest (RF) classification for predicting risk of NG leak. After, unsupervised k-means clustering, the experimental dataset has done imbalanced data. Therefore, we focusing our proposed models can predict medium and high risk so best. In this case, we compared the receiver operating characteristic (ROC) curve, accuracy, area under the ROC curve (AUC), and mean standard error (MSE) for each classification model. As a result of our experiments, the evaluation measurements include accuracy, area under the ROC curve (AUC), and MSE; 99.71%, 99.57%, and 0.0016 for MOL_RF respectively.

• Tunnel and Underground Space
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• v.21 no.5
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• pp.394-405
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• 2011

In this paper, we applied coupled non-isothermal, multiphase fluid flow and geomechanical numerical modeling using TOUGH-FLAC coupled analysis to study the complex thermodynamic and geomechanical performance of underground lined rock caverns (LRC) for compressed air energy storage (CAES). Mechanical stress in concrete linings as well as pressure and temperature within a storage cavern were examined during initial and long-term operation of the storage cavern for CAES. Our geomechanical analysis showed that effective stresses could decrease due to air penetration pressure, and tangential tensile stress could develop in the linings as a result of the air pressure exerted on the inner surface of the lining, which would result in tensile fracturing. According to the simulation in which the tensile tangential stresses resulted in radial cracks, increment of linings' permeability and air leakage though the linings, tensile fracturing occurred at the top and at the side wall of the cavern, and the permeability could increase to $5.0{\times}10^{-13}m^2$ from initially prescribed $10{\times}10^{-20}m^2$. However, this air leakage was minor (about 0.02% of the daily air injection rate) and did not significantly impact the overall storage pressure that was kept constant thanks to sufficiently air tight surrounding rocks, which supports the validity of the concrete-lined underground caverns for CAES.

• Journal of Chest Surgery
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• v.31 no.10
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• pp.995-998
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• 1998

Background: Prolonged air leak is a common complication after thoracoscopic bullectomy. Materials and methods: A technique is described to minimize postoperative air leak in thoracoscopic surgery for the treatment of recurrent or persistent spontaneous pneumothorax. Results: A 3.5cm utility incision is made in the anterior axillary line at the level of the third intercostal space, and blebs and bullae are stapled and sutured without excision, using standard surgical instruments and stapler. Conclusions: This technique may be useful to reduce prolonged air leak after removal of the bleb and bullous lesion, and may minimize the delayed recurrence of ipsilateral pneumothorax.