• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.888-892
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• 2008

If gas hydrate dissociates due to natural and/or human activities, it generates large amount of gas and water. Upon gas hydrate dissociation, a generated pore water pressure between soil particles increases and results in the loss of an effective stress and degradation of soil stiffness and strength. In order to predict the generated excess pore water pressure due to gas hydrate dissociation, two methods based on small hydrate concept (SHC) and large hydrate concept (LHC) are proposed. An excess pore water pressure generated by the gas hydrate dissociation in the Storegga Slide was calculated using two proposed methods.

• Journal of the Korean Institute of Gas
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• v.22 no.6
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• pp.16-27
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• 2018

Since 2014, the Korean government has begun distributing LPG pipelines and LPG tankers to mountainous or island areas where it is difficult to open urban gas supply chains. When installing LPG supply facilities at village level and county level, it supplied consumers with 10 times higher quasi-low pressure (25 kPa to 100 kPa) than conventional gas supply pressure, increasing the risk of gas accident. Due to the pressure that is 10 times higher than the conventional gas supply pressure, large amounts of gas are released at a faster rate when leaked. In order to secure safety of quasi-low-pressure gas pipes, excess flow valves for quasi-low-pressure gas pipes are not developed and are not supplied in Korea. Therefore, Korea Gas Safety Corporation is investigating the performance standards and products of the excess flow valves in order to localize the excess flow valves.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.70.2-70.2
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• 2012

Ram pressure is known as one of the most efficient mechanisms to deplete the atomic gas of galaxies in the cluster environment. However, the influence of the ram pressure on the molecular gas is not yet clear. Since the molecular gas resides in the galactic center, thus in the deeper potential well, and has higher surface density than the atomic hydrogen, it has been known as that the molecular gas is not easily affected and/or stripped away by the ICM-ISM interaction. To investigate the influence of the ram pressure on the gas properties of galaxies, we compare HI and $^{12}CO$(J=1-0) distribution of NGC 4654 which is experiencing on-going ram pressure and shows distinct HI, CO, optical, and $H_2$ features due to the ram pressure. We discuss the possibilities of H2 formation from HI by the ram pressure and also the star formation activities.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.399-404
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• 2008

The influence of gas hydrate dissociation on submarine slope stability was studied in this paper. Gas hydrates are stable under high pressure and low temperature conditions. Once gas hydrate dissociates due to natural or human activities, it generates large amount of gas and water. During gas hydrate dissociation, a pore pressure between soil particles increases and results in the loss of an effective stress and degradation of soil stiffness. A pore pressures model was proposed to calculated excess pore pressures generated by gas hydrate dissociation at the Storegga Slide. A slope stability analysis for the Storegga Slide using a two dimensional finite difference method was carried out by considering excess pore pressures due to gas hydrate dissociation. Since the excess pore pressure calculated by the proposed method resulted in the considerable loss of stiffness and strength in slope, a submarine slope failure occurred at the Storegga slide was well simulated.

• Journal of the Korea Society of Computer and Information
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• v.25 no.4
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• pp.19-27
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• 2020

In this paper, we propose a machine learning method for diagnosing the failure of a gas pressure regulator. Originally, when implementing a machine learning model for detecting abnormal operation of a facility, it is common to install sensors to collect data. However, failure of a gas pressure regulator can lead to fatal safety problems, so that installing an additional sensor on a gas pressure regulator is not simple. In this paper, we propose various machine learning approach for diagnosing the abnormal operation of a gas pressure regulator with only the flow rate and gas pressure data collected from a gas pressure regulator itself. Since the fault data of a gas pressure regulator is not enough, the model is trained in all classes by applying the over-sampling method. The classification model was implemented using Gradient boosting, 1D Convolutional Neural Networks, and LSTM algorithm, and gradient boosting model showed the best performance among classification models with 99.975% accuracy.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.58.3-59
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• 2015

Dynamical expansion of H II regions plays a key role in dispersing surrounding gas and therefore in limiting the efficiency of star formation in molecular clouds. We use analytic methods and numerical simulations to explore expansions of spherical dusty H II regions, taking into account the effects of direct radiation pressure, gas pressure, and total gravity of the gas and stars. Simulations show that the structure of the ionized zone closely follows Draine (2011)'s static equilibrium model in which radiation pressure acting on gas and dust grains balances the gas pressure gradient. Strong radiation pressure creates a central cavity and a compressed shell at the ionized boundary. We analytically solve for the temporal evolution of a thin shell, finding a good agreement with the numerical experiments. We estimate the minimum star formation efficiency required for a cloud of given mass and size to be destroyed by an HII region expansion. We find that typical giant molecular clouds in the Milky Way can be destroyed by the gas-pressure driven expansion of an H II region, requiring an efficiency of less than a few percent. On the other hand, more dense cluster-forming clouds in starburst environments can be destroyed by the radiation pressure driven expansion, with an efficiency of more than ~30 percent that increases with the mean surface density, independent of the total (gas+stars) mass. The time scale of the expansion is always smaller than the dynamical time scale of the cloud, suggesting that H II regions are likely to be a dominant feedback process in protoclusters before supernova explosions occurs.

• Korean Journal of Materials Research
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• v.28 no.1
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• pp.1-5
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• 2018

Gas detection is necessary for various reasons, including the prevention of gas leakages and the creation of necessary environmental conditions. Among the gas detection methods, leakage of gas can be confirmed using materials that undergo color changes that are easily distinguished by the naked eye. Metal nanoparticles (NPs) experience variations in their absorption wavelengths under the localized surface plasmon effect (LSPR) with mechanical stresses, which change the distance between NPs. In this study, we attempted to detect the presence of gas utilizing the LSPR-related color change of a chain of Au NPs. The assembly of Au NPs, arranged in a chain shape, experienced a color change from dark blue to purple with a change in the distance between the NPs by applying a physical force, i.e., compression, stretching, and gas pressure. As the force of compression and the degree of stretching increased, the absorption wavelength shifted from doublet peaks at 650 and 550 nm to a singlet peak at 550 nm. Further, applying gas pressure caused an identical color change. With this result, we propose a method that could be applied to all gases that require detection based on gas pressure.

• Journal of the Korean Society for Heat Treatment
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• v.13 no.3
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• pp.143-150
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• 2000

Ferritic plasma nitrocarburising was performed on pure iron using a modified DC plasma unit. This investigation was carried out with various gas compositions which consisted of nitrogen, hydrogen and carbon monoxide gases, and various gas pressures for 3 hours at $570^{\circ}C$. After treatment, the different cooling rates(slow cooling and fast cooling) were used to investigate its effect on the structure of the compound layer. The ${\varepsilon}$ phase occupied the outer part of the compound layer and ${\gamma}^{\prime}$ phase existed between the ${\varepsilon}$ phase and the diffusion zone. The gas composition of the atmosphere influenced the constitution of the compound layer produced, i.e. high nitrogen contents were essential for the production of ${\varepsilon}$ phase compound layer. It was found that with increasing carbon content in the gas mixture the compound layer thickness increased up to 10%. In the gas pressure around 3 mbar, the compound layer characteristics were slightly effected by gas pressure. However, in the low gas pressure and high gas pressure, the compound layer characteristics were significantly changed. The constitution of the compound layer was altered by varying the cooling rate. A large amount of ${\gamma}^{\prime}$ phase was transformed from the ${\varepsilon}$ phase during slow cooling.

• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.363-369
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• 2002

Orifice meter is the most widely used flowmeter in custody transfer between KOGAS and city gas companies. Absolute pressure value is needed to calculate the gas flow of orifice metering system, but the gauge pressure transmitters are mainly used in the field. In case that the gauge pressure transmitters are used, the fixed value as standard atmospheric pressure(101.325kPa) is applied for the absolute pressure value. The real, local atmospheric pressures of each metering station are different from the standard condition as the altitude and weather conditions. In this study the flow calculation errors were quantitatively analyzed through examining the atmospheric pressures of 50 stations of KOGAS. The data for analysis are such like the time data of supplied gas amount, the altitude of each metering station, the time data of atmospheric pressures and altitudes of each weather observatory. The results showed that the local atmospheric pressures were different from the standard value and the gas flow calculation errors were distributed between $-0.024\%{\~}0.025\%$ based on the supplied gas amount in the year 1999 and 2000.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.1067-1070
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• 1999

Anesthesia gas to pour to patients affects the flow and volume as the pressure difference of an oxygen and an anesthesia gas. An anesthesia gas, being injurious and polluting an environment, must control the pressure of an oxygen gas because of being used by closing up tight. But a pressure sensor to use for measuring an oxygen gas appears other pressure as the characteristic and the error difference of elements to use for implementing an system. A medical machine such as an anesthesia ventilator must be accurate because of using for the person's body. So we intend to implement an system for a sensor pressure measurement not to be change regardless of an environment. This papers is the target that a sensor pressrue measurement to be changed in environment is equal to actual sensor pressure measurement. So an implemented system is using analog filter and digital filter to reduce a noise. And we are using auto-zeroing and calibration to correct a sensor pressure which is changed in environment. Through such a process we increase the accuracy and the confidence of an anesthesia ventilator by controlling the flow of an anesthesia gas.