• Tunnel and Underground Space
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• v.23 no.1
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• pp.13-30
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• 2013

Increase of pore fluid pressure resulting from injection of $CO_2$ may reactivate pre-existing faults, and the induced seismic activities can raise the safety issues such as seal integrity, restoration of storage capacity, and, in the worst case, removal of previously injected $CO_2$. Thus, fault stability and potential for $CO_2$ leakage need to be assessed at the stage of site selection and planning of injection pressure, based on the results of large-scale site investigations and numerical modeling for various scenarios. In this report, studies on the assessment of fault stability during injection of $CO_2$ were reviewed. The seismic activities associated with an artificial injection of fluids or a release of naturally trapped high-pressure fluids were first examined, and then site investigation methods for the magnitude and orientation of in situ stresses, the distribution and change of pore fluid pressure, and the location of faults were generally summarized. Recent research cases on possibility estimation of fault reactivation, prediction of seismic magnitude, and modeling of $CO_2$ leakage through a reactivated fault were presented.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.7
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• pp.863-868
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• 2016

In this study, the precise shapes of sunken ships and information on seafloor topography were analyzed using data obtained from a multi-beam echo sounder. The state of each sunken ship was analyzed by processing diverse imagery data which was compared with data obtained from past investigations to determine changes in the state and circumjacent seafloor topography. Apparent changes in the seafloor topography around one sunken ship, the "Pacific Friend", were found from stern to bow as a result of continued submarine erosion and sedimentation. In the case of sunken ship "No. 7 Haeseong", the partial collapse of the bow was revealed in the seabed images captured in 2015, though it had still been intact in images captured during the Korea Hydrographic and Oceanographic Agency's investigation in 2011. This partial collapse was presumed to have resulted from the effects of continued tidal currents, the cargo load of the ship and continued corrosion of the ship over a long time on the seabed. Continuous monitoring of residual fuel inside the ship is necessary to avoid leakage and potential marine pollution. By conducting image analysis on these sunken ships, it has been determined that the structural safety of the ships is seriously influenced by tidal currents and seafloor topography, while the hulls will be continuously changed by corrosion. As a result, it can be concluded that the development of prediction and response techniques that take into consideration residual fuel leakage and environmental changes according to the geological characteristics of sunken ships is necessary.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.9
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• pp.440-446
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• 2016

Military secrets or confidential data of any organization are extremely important assets. They must be discluded from outside. To do this, methods for detecting anomalous attacks and intrusions inside the network have been proposed. However, most anomaly-detection methods only cover aspects of intrusion from outside and do not deal with internal leakage of data, inflicting greater damage than intrusions and attacks from outside. In addition, applying conventional anomaly-detection methods to data exfiltration creates many problems, because the methods do not consider a number of variables or the internal network environment. In this paper, we describe issues considered in data exfiltration detection for anomaly detection (DEDfAD) to improve the accuracy of the methods, classify the methods as profile-based detection or machine learning-based detection, and analyze their advantages and disadvantages. We also suggest future research challenges through comparative analysis of the issues with classification of the detection methods.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.4
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• pp.771-781
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• 1994

The heat generation of cement causes the internal temperature rise and volume change at early age, particulary in massive concrete structures. As the results of the temperature rise and restraint conditions, the thermal stress may induce cracks in concrete. Therefore, the prediction of the thermal stress is very important in the design and construction in order to control the cracks developed in mass concrete. In case of young concrete, creep effect by the temperature load is larger than that of old concrete. Thus, the effect of creep must be considered for checking the cracks, serviceability, durability and leakage. This paper is concentrated on the development of a finite element program which is capable of simulating the temperature history and the thermal stress considering creep and the modified elastic modulus due to inner temperature change and maturity. The analytical results in the inner parts highest important to control cracks are in good agreement with experimental data. Therefore this study may provide available method to control the cracks.

• Journal of Korean Society of Disaster and Security
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• v.9 no.2
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• pp.23-32
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• 2016

Today the issue of deterioration of industrial complexes that are located close to life space of residents has been raised as a cause of threats to the safety of local communities. In this study, in order to improve the current risk analysis and scope of community notification, simulated threat zones were comparatively analyzed by utilizing the threat zones of alternative accident scenarios and modes of seasonal weather, and the area with a high probability of damage upon the leakage of toxic substances was predicted by examining wind directions observed at each time slot for each season. In addition, limit evacuation time and minimum separation distance to minimize casualties were suggested, and a proposal to enable more reasonable safety measures for on-site workers and nearby residents made by reviewing the risk management plan currently utilized for emergency response.

• Journal of Chest Surgery
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• v.50 no.6
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• pp.424-429
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• 2017

Background: The surgical treatment of secondary spontaneous pneumothorax (SSP) can be complicated by fragile lung parenchyma. The preoperative prediction of air leakage could help prevent intraoperative lung injury during manipulation of the lung. Common sites of bulla development and ruptured bullae were investigated based on computed tomography (CT) and intraoperative findings. Methods: The study enrolled 208 patients with SSP who underwent air leak control through video-assisted thoracoscopic surgery (VATS). We retrospectively reviewed the sites of bulla development on preoperative CT and the rupture sites during VATS. Results: Of the 135 cases of right-sided SSP, the most common rupture site was the apical segment (31.9%), followed by the azygoesophageal recess (27.4%). Of the 75 cases on the left side, the most common rupture site was the apical segment (24.0%), followed by the anterior basal segment (17.3%). Conclusion: The azygoesophageal recess and parenchyma along the cardiac border were common sites of bulla development and rupture. Studies of respiratory lung motion to measure the pleural pressure at the lung surface could help to determine the relationship between cardiogenic and diaphragmatic movement and bulla formation or rupture.

• Journal of Environmental Health Sciences
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• v.46 no.1
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• pp.78-87
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• 2020

Objectives: To identify the degree of physical burden, a determination was undertaken of dust collection efficiency, inhalation pressure, and CO₂ concentration related to health masks certified by the Ministry of Food and Drug Safety (MFDS). Methods: Twenty health masks were purchased on the market. Dust collection efficiency and inhalation pressure were determined in the same manner as in MFDS certification testing, respectively using TSI Model 8130 (TSI, U.S.) and ART Plus (Korea). CO₂ concentrations for 20 subjects using a CO₂ analyzer (G100, G150, Geotechnical Instrument Ltd., UK) were measured with a similar method as a total inward leakage test. In addition to CO₂ levels, dead space volumes in the masks was determined for predicting concentrations of CO₂ in inhalation air. Results: Most of the dust collection efficiencies found for the 20 masks were far higher than the standard. Four KF94s met KF99 and four KF80s even met KF94. Most inhalation pressures were also much lower than the standard, with many almost one-half of the standard. The mean and standard deviation of CO₂ concentration in the mask were 2.9±0.44%. Considering dead volume, the prediction for CO₂ concentration in the inhalation air was 4,395±1,266 ppm. Conclusions: For healthy men and women, the dust collection efficiency and inhalation pressure of health masks were not at a level that would affect their health. Although CO₂ levels in the inhalation air were predicted not to affect health, research on the physiological effects of health masks on Koreans is needed for more precise research.

• Journal of the Korean Institute of Gas
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• v.24 no.5
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• pp.47-55
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• 2020

Hazardous materials accidents are not limited to the leakage of the material, but if the early response is not appropriate, it can lead to a fire or an explosion, which increases the scale of the damage. However, as the 4th industrial revolution and the rise of the big data era are being discussed, systematic analysis of hazardous materials accidents based on new techniques has not been attempted, but simple statistics are being collected. In this study, we perform the systematic analysis, using machine learning, on the fire accident data for the past 11 years (2008 ~ 2018), accumulated by the National Fire Service. The analysis results are visualized and presented through text mining analysis, and the possibility of developing a damage-scale prediction model is explored by applying the regression analysis method, using the main factors present in the hazardous materials fire accident data.

• Journal of Korean Society for Atmospheric Environment
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• v.21 no.6
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• pp.573-583
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• 2005

Fugitive dust, which is emitted in the ambient air without first passing through a stack or duct designed to control flow, is frequently generated by means of wind erosion from storage yards at Pohang Steel Wokrs. The size distribution of fugitive dust is mostly in the range of coarse particulate which is deposited as soon as emitted and less harm to human health; however $20\%$ of fugitive dust contains PM 10 known as one of most harmful airborne pollutant. Consequently, effective control and reduction of fugitive dust is strongly requested by the local society, but it is not easy so far because the generation and dispersion of fugitive dust highly depends on meteorological conditions, and it being occurred for irregularity. This research presented a fugitive dust control system for each meteorological condition by providing statistical prediction data obtained from a statistical analysis on the probability of generating the threshold velocity at which the fugitive dust begins to occur, and the frequency occurring by season and by time of the wind direction that can generate atmospheric pollution when the dispersed dust spreads to adjacent residential areas. The research also built a fugitive dust detection system which monitors the weather conditions surrounding storage yards and the changes in air quality on a real-time basis and issues a warning message by identifying a situation where the fugitive dust disperses outside the site boundary line so that appropriate measures can be taken on a timely basis. Furthermore, in respect to the spraying of water to prevent the generation of fugitive dust from the storage piles at the storage yard, an advanced statistical meteorological analysis on the weather conditions in Pohang area and a case study of fugitive dust dispersion toward outside of working field during $2002\∼2003$ were carried out in order to decide an optimal water-spraying time and the number of spraying that can prevent the origin of fugitive dust emission. The results of this research are expected to create extremely significant effects in improving surrounding environment through actual reduction of the fugitive dust produced from the storage yard of Pohang Steel Works by providing a high-tech warning system capable of constantly monitoring the leakage of fugitive dust and water-spray guidance that can maximize the water-spraying effects.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.4
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• pp.1480-1487
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• 2012

Recently, the safety of the coal-mining tunnels has been improved greatly, but accidents occur continually. Most tunnel support failures occur because the fish plate part that connects the I-beams is unable to withstand ground pressure. In the case of XX coal mine, the arch part of tunnel support bends to the upper direction. In such a case, excessive horizontal load as well as vertical load acts on the tunnel support. Horizontal load is caused by the sudden loosing of underground rock mass or the leakage of underground water, so it is fairly complex to predict horizontal loading on a tunnel support. To predict the horizontal load on this component is defined as the problem that determines the horizontal load conditions in wedges of tunnel support. This is an optimization problem in which maximum bending stress and horizontal load are considered by an objective function and design variables, respectively. Therefore, in this study, design of experiments and optimization algorithm were applied to identify the horizontal load in tunnel support.