• Journal of The Korean Astronomical Society
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• v.49 no.3
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• pp.109-122
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• 2016

[Fe II] emission lines are prominent in the infrared (IR) and important as diagnostic tools for radiative atomic shocks. We investigate the emission characteristics of [Fe II] lines using a shock code developed by Raymond (1979) with updated atomic parameters. We first review general characteristics of the IR [Fe II] emission lines from shocked gas, and derive their fluxes as a function of shock speed and ambient density. We have compiled available IR [Fe II] line observations of interstellar shocks and compare them to the ratios predicted from our model. The sample includes both young and old supernova remnants in the Galaxy and the Large Magellanic Cloud and several Herbig-Haro objects. We find that the observed ratios of the IR [Fe II] lines generally fall on our grid of shock models, but the ratios of some mid-IR lines, e.g., [Fe II] 35.35 µm/[Fe II] 25.99 µm, [Fe II] 5.340 µm/[Fe II] 25.99 µm, and [Fe II] 5.340 µm/[Fe II] 17.94 µm, are significantly offset from our model grid. We discuss possible explanations and conclude that while uncertainties in the shock modeling and the observations certainly exist, the uncertainty in atomic rates appears to be the major source of discrepancy.

• Proceedings of KOSOMES biannual meeting
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• 2006.05a
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• pp.15-20
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• 2006

In this study, we had investigated several input factors and output factors, to maintain safety management, of domestic shipping companies, and then had analyzed the efficiency of performance of performance about each shipping companies' safety management system from 1998 year to 2004 year using DEA method As the result of analysis, the annual mean efficiency of total companies tended downward every year. Analysis was that the cause was increase of the cost of repairing ship, the cost of ship's stores and idle day of ship.

• Earthquakes and Structures
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• v.14 no.4
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• pp.305-312
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• 2018

Significant research efforts were undertaken to evaluate seismic performance of vertically irregular buildings on flat ground. However, there is scarcity of study on seismic performance of buildings on hill slopes. The present study attempts to investigate seismic behaviour of reinforced concrete irregular stepback building frames with different configurations on sloping ground. Based on extensive regression study of free vibration results of four hundred seventeen frames with varying ground slope, number of story and span number, a modification is proposed to the code based empirical fundamental time period estimation formula. The modification to the fundamental time period estimation formula is a simplified function of ground slope and a newly introduced equivalent height parameter to reflect the effect of stiffness and mass irregularity. The derived empirical formula is successfully validated with various combinations of slope and framing configurations of buildings. The correlation between the predicted and the actual time period obtained from the free vibration analysis results are in good agreement. The various statistical parameters e.g., the root mean square error, coefficient of determination, standard average error generally used for validation of such regression equations also ensure the prediction capability of the proposed empirical relation with reasonable accuracy.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2019.11a
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• pp.170-172
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• 2019

최근 우리나라에서는 해양사고의 효과적인 예방을 위하여 구축 중인 한국형 e-Navigation SV20-선내시스템 원격모니터링 서비스에서는 복원성, 화재, 침수, 과도경사, 항해장비의 이상과 같이 선박의 안전 운항과 직접적으로 관련이 있는 선박의 센서들을 수집, 분석하여 이상 상태와 긴급상황을 자동으로 식별하여 안전운항을 지원하는 기능이 있다. IMO 선박안전관리 시스템의 경우 선원의 인적 과실에 의한 해상에서 안전 및 해양환경 보호를 위한 핵심 요소로서 우리나라는 SOLAS 협약 제9장(선박의 안전운항을 위한 관리)및 ISM CODE를 1999년 2월 해사안전법에 수용하여 2002. 7. 1.부터 단계적으로 시행하고 있다. 이 연구에서는 이 둘의 융합 개념의 기술적 결합을 통한 체계적이고 자동화적으로 선박에서의 안전관리 능력을 제고하여 안전 사고 발생을 최소화 할 수 있는 여러 가지 시스템과 더불어 사고 발생시 효율적으로 대응할 수 있는 표준 토폴로지 기반 UI 및 항차 기반 위기대응 가이던스를 개발 하고자 한다.

• Journal of The Korean Astronomical Society
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• v.48 no.2
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• pp.139-154
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• 2015

We carry out three-dimensional hydrodynamic simulations of the supernova remnants (SNRs) produced inside molecular clouds (MCs) near their surface using the HLL code (Harten et al. 1983). We explore the dynamical evolution and the X-ray morphology of SNRs after breaking through the MC surface for ranges of the explosion depths below the surface and the density ratios of the clouds to the intercloud media (ICM). We find that if an SNR breaks out through an MC surface in its Sedov stage, the outermost dense shell of the remnant is divided into several layers. The divided layers are subject to the Rayleigh-Taylor instability and fragmented. On the other hand, if an SNR breaks through an MC after the remnant enters the snowplow phase, the radiative shell is not divided to layers. We also compare the predictions of previous analytic solutions for the expansion of SNRs in stratified media with our onedimensional simulations. Moreover, we produce synthetic X-ray surface brightness in order to research the center-bright X-ray morphology shown in thermal composite SNRs. In the late stages, a breakout SNR shows the center-bright X-ray morphology inside an MC in our results. We apply our model to the observational results of the X-ray morphology of the thermal composite SNR 3C 391.

• Journal of Ocean Engineering and Technology
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• v.22 no.3
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• pp.47-57
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• 2008

Many accidents occur on the oceans. Accidents involving ships can cause enormous damage. When an accident occurs, the cost of environmental restoration can bankrupt even a top-ranked international company. The potential damages resulting from ship accidents have resulted in many international agreements such as MARPOL, SOLAS, ISM Code, etc. The viability of damaged ships has become more and more important. A damaged ship's viability and cargo safety can be improved by a safety assessment design procedure. We consider th￡ shipbuilding industry's distributed characteristics to define a safety assessment system with software engineering-based requirements analysis. We used a distributed network-based simulation method (HLA - High level architecture), because of ease of reuse and expansion of existing components to other situations, and because it is a military standard. HLA is the standard for distributed network-based simulation in many countries including the United States, Canada, Israel, and Korea. The paper describes research to develop a prototype of a network-based safety assessment simulation system by software engineering based analysis.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.327-332
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• 2017

As Internet of Things (IoT) technology advances, there is a growing demand for location-based services (LBSs) to identify users' mobility and identity. The initial LBS system was mainly used to measure position information by measuring the phase of a signal transmitted from a global positioning system (GPS) satellite or by measuring distance to a satellite by tracking the code of a carrier signal. However, the use of GPS satellites is ineffective, because it is difficult to receive satellite signals indoors. Therefore, research on wireless communications systems like ultra-wide band (UWB), radio frequency identification (RFID), and ZigBee are being actively pursued for location recognition technology that can be utilized in an indoor environment. In this paper, we propose an LBS system that includes the 2.45GHz band for chirp spread spectrum (CSS), and the 3.1-10.6GHz band and the 250-750MHz bands for UWB using the IEEE 802.15.4a standard for low power-based location recognition. As a result, we confirmed that the 2.45GHz Industrial, Scientific and Medical (ISM) band RF transceiver and the ranging function can be realized in the hardware and has 0dBm output power.

• International Journal of Automotive Technology
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• v.6 no.1
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• pp.1-8
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• 2005

Recently, the HSDI (High Speed Direct Injection) diesel engine has been spotlighted as a next generation engine because it has a good potential for high thermal efficiency and fuel economy. This study was carried out to investigate the in-cylinder flow characteristics generated in a HSDI diesel engine with a 4-valve type cylinder head. The four kinds of cylinder head were manufactured to elucidate the effect of intake port geometry on the in-cylinder flow characteristics. The steady flow characteristics such as coefficient of flow rate $(C_{f})$, swirl ratio (Rs), and mass flow rate (m,) were measured by the steady flow test rig and the unsteady flow velocity within a cylinder was measured by PIV. In addition, the in-cylinder flow patterns were visualized by the visualization experiment and these results were compared with simulation results calculated by the commercial CFD code. The steady flow test results indicated that the mass flow rate of the cylinder head with a short distance between the two intake ports is $13\%$ more than that of the other head. However, the non-dimensional swirl ratio is decreased by approximately $15\%$. As a result of in-cylinder flow characteristics obtained by PIV and CFD calculation, we found that the swirl center was eccentric from the cylinder center and the position of swirl center was changed with crank angle. As the piston moves to near the TDC, the swirl center corresponded to the cylinder center and the velocity distribution became uniform. In addition, the results of the calculation are in good agreement with the experimental results.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.9
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• pp.1276-1283
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• 2002

Recently, HSDI (High Speed Direct Injection) diesel engine has been spotlighted as a next generation engine because it has a good potential for high thermal efficiency and fuel economy. This study was carried out to investigate the in-cylinder flow characteristics generated in a 4-valve small diesel cylinder head with a tangential and helical intake port. The flow characteristics such as coefficient of flow rate(Cf), swirl ratio (Rs), and mass flow rate (ms) were measured in the steady flow test rig using the impulse swirl meter and the analysis of in-cylinder flow field was conducted by experiment using the PIV and calculation using the commercial CFD code. As the results from steady flow test indicate, the mass flow rate of the cylinder head with a short distance between the two intake ports is increased over 13% than that of the other head. However, the non-dimensional swirl ratio is decreased approximately 15%. From in-cylinder flow characteristics obtained by PIV and CFD calculation, we found that the swirl center was eccentric from the cylinder center and the velocity distribution became uniform near the TDC. In addition, the results of the calculation are good agreement with the experimental results.

• Journal of the Korean Society of Marine Environment & Safety
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• v.13 no.2 s.29
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• pp.141-146
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• 2007

In this study, we have investigated several input factors and output factors to maintain safety management of domestic shipping companies, and then have analyzed the efficiency of performance about each shipping companies' safety management system from 1998 year to 2004 year using DEA method. The result of analysis shows that the annual mean efficiency index of total companies tended downward every year. Analysis was that the cause was increase of the cost of repairing ship, the cost of ship's stores and idle day of ship while the number of marine accidents and sanctions of PSC, ship's insurances and P&I insurances was decreased.