• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.8
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• pp.78-85
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• 2018

In this study, we investigated the cases where there were many opinions in the judgment of the cause of ignition in the case of 20 cases of frozen warehouse fire that occurred in 2017.The research methodology is the scientific fire survey method prescribed by the NFPA 921 CODE. Scientific fire investigation method is fire investigation method by logical reasoning through hypothesis setting, minimizing errors in judgment of ignition source. On the other hand, unscientific fire investigation methods cause many errors by the intervention of irrational factors such as subjective estimation, reasoning judgment, etc. This eventually leads to the problem of human and material responsibility and academic deterioration. In particular, fire not seen as compared to sighted fire makes more errors in ignition sources in the cause investigation. In this study, we set the hypothesis A and hypothesis B based on the review of the fire investigation report and the field survey on the fire case of the cold storage warehouse front line that occurred at ** city ** Mart in 2017.The set hypothesis was tested by the NFPA 921 code. This analytical method will be constructed by NEW Paradigm as a source of fire that is not seen in the future and a source of ignorant fire.In addition, the experimental data of this study will be used to inform the manufacturer and operator of the refrigeration warehouse and serve as basic data for fire prevention.

• Journal of The Korean Astronomical Society
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• v.35 no.4
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• pp.175-185
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• 2002

Almost half of primeval galaxies show P-Cygni type profiles in the Ly$\alpha$ emission line. The main underlying mechanism for the profile formation in these systems is thought to be the frequency re-distribution of the line photons in expanding scattering media surrounding the emission source. A Monte Carlo code is developed to investigate the Ly$\alpha$ line transfer in an optically thick and moving medium with a careful consideration of the scattering in the damping wings. Typical column densities and expansion velocities of neutral hydrogen investigated in this study are $N_{H1}{\~}10^{17-20}\;cm^{-2}$ and ${\Delta}V{\~} 100 km\;s^{-1}$. We investigate the dependence of the emergent profiles on the kinematics and on the column density. Our numerical results are applied to show that the damped Ly$\alpha$ absorbers may possess an expanding H I supershell with bulk flow of ${\~}200 km\;s^{-l}$ and H I column density $N_{H1}{\~}10^{19}\;cm^{-2}$. We briefly discuss the observational implications.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.915-920
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• 2001

A spent fuel problem has prevented the nuclear power from claiming to be a completely clean energy source. The nuclear transmutation technology to incinerate the long lived radioactive nuclides and produce energy during the incineration process is believed to be one or the best solutions. HYPER(Hybrid Power Extraction Reactor) is the accelerator driven transmutation system which is being developed by KAERI(Korea Atomic Energy Research Institute). Some major feature of HYPER have been developed and employed. On-power fueling concepts are employed to keep system power constant with minimum variation of accelerator power. A hollow cylinder-type metal fuel is designed for the on-line refueling concept. Lead-bismuth(Pb-Bi) is adopted as a coolant and Spallation target material. HYPER is a subcritical reactor which needs an external neutron source. 1GeV proton beam is irradiated to Lead-bismuth(Pb-Bi) target inside HYPER, and spallation neutrons are produced. When proton beams are irradiated, much heat is also deposited in the Pb-Bi target and beam window which separates Pb-Bi and accelerator vacuum. Therfore, an effective cooling is needed for HYPER target. In this paper, we performed the thermal-hydraulic analysis of HYPER target using FLUENT code, and also calculated thermal and mechanical stress of the beam window using ANSYS code.

• Journal of the Korea Society of Computer and Information
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• v.13 no.4
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• pp.1-9
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• 2008

Most consumer electronics companies hold numerous line-ups to cope with divergent customer's needs. To cope with current situation, most products are derived from the 'base product' which is developed for brand new features with respect to the change requests. That is called derivation. After 'base code' is developed for newly introduced products, some modification will occur corresponding to the derivative product models. So, quality attributes of 'base code' affects quality and productivity of 'derived code'. But in the middle of continuous modification to 'base code', violation of architectural design decision and unauthorized or maybe unsophisticated change to source code willing to happen and thus it cause critical problem. Those code has 'aging symptom' both architectural and code level in nature. In this paper, we introduced reengineering framework which guide the procedure and tactics to find and fix 'aging symptom' for improvement on quality attribute of 'base code'.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.1773-1780
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• 2008

When the fire occur in the deeply underground subway station, the difficulties of passenger evacuation are expected because of many stairs to the exit. In this study, SOONGSIL-University station (7 line, 47m depth) is the one of the deepest subway stations of the each line in the Seoul metro. The numerical computational-simulation was performed for the fire driven flow in the subway station. Hot and smoke flow was analyzed from the simulation results. The proper plan of evacuation against fire was considered through the results. The fire driven flow was simulated using FDS code in which LES method was applied. The Heat Release Rate was 10MW and the ultrafast model was applied for the growing model of the fire source. The proper mesh size was determined from the characteristic length of fire size. The parallel computational method was employed to compute the flow and heat eqn's in the meshes, which are about 10,000,000, with 6cpu of the linux clustering machine.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.22 no.1
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• pp.81-91
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• 2012

Presently in 2011, there are countless attacking tools oriented to invading security on the internet. And most of the tools are possible to conduct the actual invasion. Also, as the program sources attacking the weaknesses of PS3 were released in 2010 and also various sources for attacking agents and attacking tools such as Stuxnet Source Code were released in 2011, the part for defense has the greatest burden; however, it can be also a chance for the defensive part to suggest and develop methods to defense identical or similar patterned attacking by analyzing attacking sources. As a way to cope with such attacking, this study divides the network areas targeted for attack based on load balancing by the approach gateways and communication lines according to the defensive policies by attacking types and also suggests methods to multiply communication lines. The result of this paper will be provided as practical data to realize defensive policies based on high hardware performances through enhancing the price competitiveness of hardware infrastructure with 2010 as a start.

• Progress in Medical Physics
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• v.22 no.4
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• pp.190-197
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• 2011

Currently, the dose distribution calculation used by commercial treatment planning systems (TPSs) for high-dose rate (HDR) brachytherapy is derived from point and line source approximation method recommended by AAPM Task Group 43 (TG-43). However, the study of Monte Carlo (MC) simulation is required in order to assess the accuracy of dose calculation around three-dimensional Ir-192 source. In this study, geometry factor was calculated using segmented sources integration method by dividing microSelectron HDR Ir-192 source into smaller parts. The Monte Carlo code (MCNPX 2.5.0) was used to calculate the dose rate $\dot{D}(r,\theta)$ at a point ($r,\theta$) away from a HDR Ir-192 source in spherical water phantom with 30 cm diameter. Finally, anisotropy function and radial dose function were calculated from obtained results. The obtained geometry factor was compared with that calculated from line source approximation. Similarly, obtained anisotropy function and radial dose function were compared with those derived from MCPT results by Williamson. The geometry factor calculated from segmented sources integration method and line source approximation was within 0.2% for $r{\geq}0.5$ cm and 1.33% for r=0.1 cm, respectively. The relative-root mean square error (R-RMSE) of anisotropy function obtained by this study and Williamson was 2.33% for r=0.25 cm and within 1% for r>0.5 cm, respectively. The R-RMSE of radial dose function was 0.46% at radial distance from 0.1 to 14.0 cm. The geometry factor acquired from segmented sources integration method and line source approximation was in good agreement for $r{\geq}0.1$ cm. However, application of segmented sources integration method seems to be valid, since this method using three-dimensional Ir-192 source provides more realistic geometry factor. The anisotropy function and radial dose function estimated from MCNPX in this study and MCPT by Williamson are in good agreement within uncertainty of Monte Carlo codes except at radial distance of r=0.25 cm. It is expected that Monte Carlo code used in this study could be applied to other sources utilized for brachytherapy.

• Journal of the Optical Society of Korea
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• v.13 no.3
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• pp.361-366
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• 2009

We propose the performance enhancing method optimization of an asynchronous 2.5 Gbps/1.25 Gbps optical subscriber network with inverse RZ (Return to Zero) coded downstream and NRZ (Non Return to Zero) upstream re-modulation by adjusting threshold level control of a receiver. We theoretically analyze the BER (Bit Error Rate) performance by modeling the occurrence of BER by simulation with MATLAB according to the types of downstream data. The results have shown that the normalized threshold level in an optical receiver could be saturated at 1/3 as the SNR (Signal to Noise Ratio) increases. The needed SNR for obtaining the BER $10^{-9}$ can be reduced by $\sim$5 dB by optimizing the normalized threshold level at 1/3 instead of by using the conventional receiver with threshold level of 0.5. The proposed system can be a useful technology for asynchronous optical access networks with asymmetric upstream and downstream data rates, because the improved minimum receiving power could replace a light source with a source with lower power and lower cost in an OLT (Optical Line Termination).

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.3142-3147
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• 2008

A simple transient simulation of ground source heat pump system was carried out to investigate the effects of ground thermal conductivity on its performance. The TRNSYS code with a simple water to water heat pump model was used to compare the COP variation of the system. A new ground heat exchanger called by semi-closed loop was proposed and constructed in the real site. The effective thermal conductivity was measured using the test equipment developed by according to the line source model. The simulation results showed that highly efficient thermal conductivity of the grout material could increase the performance of the heat pump system very well. And the new ground heat exchanger showed the increased effective thermal conductivity as the penetration water flow rate(PWFR) was increased. Therefore, the performance improvement of the heat pump system using the proposed ground heat exchanger can be expected.

• Journal of KSNVE
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• v.10 no.1
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• pp.49-56
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• 2000

In this paper performance of the noise barrier which is 53 m long and 6m high, and is located between the high rise apartment and road, is studied by using experimental and analytic method. The insertion loss is measured by using the direct method in accordance with the ISO code, while theoretical prediction is based on Muradali and Fyfe's method (Applied Acoustics, Vol. 53, 49~75, 1998). In addition to the diffraction at the top of the barrier, the waves are reflected infinite times between the building and the barrier, which is equivalent to replacing the building by the infinite series of the image receiver points. In two-dimensional study, the prediction of the insertion loss results in significantly overestimated values compared with the measurement. However three-dimensional analysis shows reasonable agreements, where traffic noise is assumed as incoherent line source and the length of the source is larger than that of the barrier.