• Journal of Korean Society for Atmospheric Environment
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• v.12 no.3
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• pp.243-254
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• 1996

The main purpose of this study is to investigate the collection efficiency characteristics of a cylindrical ESP. To do that, it is necessary to analyze the electric field, gas flow field, and mechanism of particle movement by numerical simulation based on EHD model. For a gas flow field, Navier-Stokes equation involving the electric source term was solved by SIMPLE algorithm. In case of the electric field, the current continuity and electric field equations were solved by S.O.R. method. The analysis of particle movement was performed on the basis of PSI-CELL model from the Lagrangian viewpoint. The results showed that the influence on the gas flow field by the electric field is almost negligible in a cylindrical ESP. The particle drift velocity $V_P$ toward the collection surface is increased continuously by the electrostatic force due to the rise of particle charge as the particle is moving to the flow direction and the particle size becomes larger. The collection efficiency is to quitely higher with the increase of applied voltage for the same particle size, while becomes smaller as the inlet velocity is increased.

• Journal of Hydrogen and New Energy
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• v.19 no.3
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• pp.239-247
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• 2008

Hydrogen production facility using very high temperature gas cooled reactor lies in situation of high temperature and corrosion which makes hydrogen release easily. In that case of hydrogen release, there lies a danger of explosion. However, from the point of thermal-hydraulics view, the long distance of them makes lower efficiency result. In this study, therefore, outlines of hydrogen production using nuclear energy are researched. Several methods for analyzing the effects of hydrogen explosion upon high temperature gas cooled reactor are reviewed. Reliability physics model which is appropriate for assessment is used. Using this model, leakage probability, rupture probability and structure failure probability of very high temperature gas cooled reactor are evaluated and classified by detonation volume and distance. Also based on standard safety criteria which is value of $1{\times}10^{-6}$, safety distance between the very high temperature gas cooled reactor and the hydrogen production facility is calculated.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.6
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• pp.238-249
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• 1995

The gas pressure acting on the rings in internal combustion engine influences the friction and wear characteristics. Inter-ring pressure variation during engine operation results from cylinder gas flow through a piston-ring pack. The flow passages consist of ring end gaps and clearances between the ring and the piston groove. The gas flow in the clearance between the ring and the groove is directly affected by the axial motion of the ring in the groove. In this paper the asperity contact force is newly considered in the prediction of the clearence between the ring and the groove surface. This term must be taken into account physically in case that the clearance get narrow rather than asperity height between the ring and the groove surface. Finally, comparisons of calculated inter-ring gas pressures based on the analytical method are made with the measured ones. The agereement was found to be good below midium engine speed, 3000rpm. In order to obtain accurate analytical results to the extend of high rpm range, it is recommended to include oil ring motion as well as top and second ring in analytical model.

• Journal of Environmental Impact Assessment
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• v.21 no.2
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• pp.255-264
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• 2012

The present study attempts to understand the emission pattern of greenhouse gases in people's daily life through the estimation and analysis of the amount and characteristics of the greenhouse gases. Based on the survey of 1,000 people throughout the nation, monthly emission of greenhouse gases per-capita was estimated from their use of fuels, electricity, water, and personal and public transportation means in addition to their waste generation. In the case of personal car drivers, greenhouse gas emission was the greatest from their cars, followed by the emission from electricity, fuels, and public transportation. Emission from water consumption and waste generation was relatively low. Fuel consumption varied depending on the number of household members, their housing type, and the size of their living spaces. Results showed that single-person households emitted the largest amount of per-capita greenhouse gas while greenhouse gas emission from electricity was inversely proportional to the number of persons in a given household.

• Journal of The Korean Society of Clinical Toxicology
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• v.6 no.2
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• pp.99-103
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• 2008

Purpose: Chlorine gas is a common irritant that usually causes mild respiratory symptoms. One severe symptom, RADS (Reactive Airway Dysfunction Syndrome), is not well known to physicians. We analyzed the clinical features of chlorine gas exposure. Methods: We prospectively collected 25 cases of chlorine gas exposure near our emergency center on January 10th, 2007, and analyzed demographic data, event-to-ER interval, symptoms, and laboratory results based on medical records. Results: Only 2 patients out of 25 were admitted because of severe symptoms, the rest were discharged without complications. Sixty percent of them visited the ER within 12 h of exposure. The most common symptoms were chest discomfort (60%), headache (40%), nausea (40%), throat irritation (26%), and cough (32%). Two out of eight dyspnea cases showed abnormal pulmonary function, but only one case was diagnosed as RADS. Conclusion: Most symptoms after chlorine gas exposure can be treated conservatively. However, patients with chlorine exposure should be followed up long term for delayed complications.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.75.4-75.4
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• 2019

We present a quantitative analysis of the relationship between the gas dynamics and star formation history of DDO 210 which is an irregular dwarf galaxy in the local Universe. We perform profile analysis of an high-resolution neutral hydrogen (HI) data cube of the galaxy taken with the large Very Large Array (VLA) survey, LITTLE THINGS using newly developed algorithm based on a Bayesian Markov Chain Monte Carlo (MCMC) technique. The complex HI structure and kinematics of the galaxy are decomposed into multiple kinematic components in a quantitative way like 1) bulk motions which are most likely to follow the underlying circular rotation of the disk, 2) non-circular motions deviating from the bulk motions, and 3) kinematically cold and warm components with narrower and wider velocity dispersion. The decomposed kinematic components are then spatially correlated with the distribution of stellar populations obtained from the color-magnitude diagram (CMD) fitting method. The cold and warm gas components show negative and positive correlations between their velocity dispersions and the surface star formation rates of the populations with ages of < 40 Myr and 100~400 Myr, respectively. The cold gas is most likely to be associated with the young stellar populations. Then the stellar feedback of the young populations could influence the warm gas. The age difference between the populations which show the correlations indicates the time delay of the stellar feedback.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.12
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• pp.1667-1672
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• 2003

In contrast to the high demand for MEMS devices, microflow analysis is not feasible even for single-phase flow with conventional Navier-Stokes equation because of non-continuum effect when characteristic dimension is comparable with local mean free path. DSMC is one of particle based DNS(Direct Numerical Simulation) methods that uses no continuum assumption. In this paper, gas flow in microchannel is studied using DSMC. Interfacial shear and flow characteristics are observed and compared with the results of gas flow that is in contact with liquid case and solid wall case. The simulation is limited to the case of equilibrium steady state and evaporation/condensation coefficient is assumed to be the same and unity. System temperature remains constant and the interfacial shear appears to be small compared to the result with solid wall. This is because particles evaporated and reflected from the liquid surface form high density layer near the interface with liquid flow.

• Journal of the Korean Institute of Gas
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• v.22 no.1
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• pp.60-63
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• 2018

This paper presents the FEM analysis results on the strength safety of a gas valve for a LPG cylinder. Based on the FEM analysis, the maximum von Mises stress on the boundary zone between a safety valve and the upper area of the thread is 99.2 MPa for the supplied gas pressure of 3.5 MPa in which the gas valve is fully opened. The maximum von Mises stress of 99.2 MPa is considered as safety value, because that value is lower than the yield stress of a brass material. In this case, the maximum deformation at the upper right part of the pressure regulator is 0.002mm. The maximum deformation zone is not a meaning part of the sealing part such as an O-ring or a diaphragm of a gas valve and a pressure regulator. The proposed hybrid gas valve model in which is integrated with a conventional cut-off valve and a pressure regulator is recommended as a gas leakage free mechanism and minimized compact size for a LPG cylinder.

• Journal of the Korean Institute of Gas
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• v.4 no.4 s.12
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• pp.58-64
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• 2000

Data compression and retrieval method are investigated for the effective utilization of measured process data. In this paper, a new data compression method, Clustering Compression(CC), which is based on the k-means clustering algorithm and piecewise linear approximation method is suggested. Case studies on industrial data set showed the superior performance of clustering based techniques compared to other conventional methods and showed that CC could handle the compression of multi-dimensional data.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.12
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• pp.6079-6097
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• 2018

Safety-related systems (SRSs) has widely used in shipbuilding and power generation to prevent fatal accidents and to protect life and property. Thus, SRS performance is a high priority. The safety integrity level (SIL) is the relative performance level of an SRS with regard to its ability to operate reliably in a safe manner. In this article, we proposed an optimal design procedure to achieve the targeted SIL of SRSs. In addition, a more efficient failure mode and effects diagnostic analysis (FMEDA) process and optimization model were developed to improve cost efficiency. Based on previous IEC 61508 diagnostic analyses that revealed unnecessary costs associated with excessive reliability, the new approach consists of two phases: (i) SIL evaluation by FMEDA, and (ii) solution optimization for achieving the target SIL with minimal cost using integer-programming models. The proposed procedure meets the required safety level and minimizes system costs. A case study involving a gas-detection SRS was conducted to demonstrate the effectiveness of the new procedure.