• Korean Security Journal
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• no.2
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• pp.83-98
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• 1999

The LPG station's explosion at Bucheon city was a major accident which with rare frequency of occurrence but large damage effect. Therefore, to prevent similar accident in the future from LPG chargings stations which located at inner urban area, it needs to identify the damage effects of such facilities by comparing theoretically quantities risks-PHAST. The BLEVE effects from the accident showed similar level in case of heat flux, however, the over pressure level reflected at reduced distance. The structure damage to the nearby area showed comparatively large reduction of concrete strength and shape changes through by heat effect while the overpressure effect was small.

• Proceedings of the KAIS Fall Conference
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• 2010.05b
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• pp.1045-1048
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• 2010

본 연구는 LPG 충전소 등에서 운용하는 저장탱크에 대하여 퓨방법을 통하여, 기존의 지상형과 지하형의 장점과 단점을 비교 판정하여 혁신시공법으로 고객만족을 실현시키기 위함이다. 자동차 연료로서 LPG(Liquefied Petroleum Gas)의 사용은 대기오염을 줄이는데 효과적으로 사용이 빠르게 확산되고 있다. 하지만 가스사용이 늘어나면서 폭발과 화재에 의한 인명피해가 해마다 발생하고 있으며, 특히 대규모 저장시설에서의 가스사고는 사회적으로 심각한 문제를 야기하고 있다. 따라서, 본 연구는 LPG를 대량으로 취급 저장하는 시설에서 운용하는 저장탱크의 설치방법을 개선하기 위하여 아이디어 판단기법중 하나인 퓨(Pugh) 방법으로 판단하면 기존의 지상형과 지하매몰형, 지하격납형에서 안전성과 토지이용률이 우수한 지하격납저장탱크가 가장 효과적임을 알 수 있다.

• Proceedings of the KIPE Conference
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• 2018.11a
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• pp.221-222
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• 2018

본 논문은 전기자동차용 2.8kW 양방향 LDC (Low-voltage DC-DC Converter) 개발에 대한 내용을 다루고 있다. 양방향 토폴로지는 충전소까지 갈 수 있는 전력이 부족할 때 저전압단에서의 전력을 공유함으로써 위급한 상황을 탈피할 수 있다는 장점이 있다. 양방향 LDC는 변압기에 의한 절연이 가능하고 에너지변환 효율이 높은 Full-bridge DC-DC Converter 방식을 선정하였다. PWM 스위칭 방식은 위상천이방식(Phase Shift PWM)을 사용하였고 기존의 2차측 다이오드를 MOSFET 스위치로 구성하여 양방향 전력전달이 가능하게 하였다.

• Journal of the korean academy of Pediatric Dentistry
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• v.43 no.2
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• pp.129-136
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• 2016

The purpose of this study is to examine the sealing effect and efficiency of root canal filling MTA (Endoseal, Endoseal MTA). A total of 106 extracted single rooted teeth were used and classified with group AH (AH-26), group PR (ProRoot MTA), group ES (Endoseal) and group EM (Endoseal MTA) depending on filled sealers. Time was measured in each group when sealers were filled. The groups were divided into subgroup A and subgroup B. The sealing of root canal walls and penetration of sealer in the dentinal tubule were evaluated, respectively. According to the results, the sealing of root canal walls and dentinal tubule penetration of root canal filling MTA were inferior to AH-26 (p < 0.05). When compared with ProRoot MTA, however, there was no significant difference in sealing of root canal walls (p > 0.05), but dentinal tubule penetration was high (p < 0.05). Working time was shorter in root canal filling MTA than ProRoot MTA and AH-26 (p < 0.05). In conclusion, root canal filling MTA has lower root canal sealing effect than resin-based sealer, however, when in MTA needed root canal filling, it could be an effective alternative.

• Restorative Dentistry and Endodontics
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• v.23 no.1
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• pp.54-67
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• 1998

The purposes of this study were to evaluate the efficiency of dentin cutting and root-end cavity preparation, and to determine the incidence of tooth crack when root-end retrograde cavity preparation was done with. ultrasonic diamond instruments. To evaluate the efficiency of dentin cutting, ultrasonic diamond and stainless steel instruments were applied to 20 exposed bovine dentin surfaces perpendicularly or parallely at the low, and medium power settings for 1 minute ($Miniendo^{TM}$, EIE, CA, U.S.A.). The resultant cavity depth was measured. To evaluate the efficiency of cavity preparation and to investigate the incidence of tooth crack, 165 mesiobuccal, distobuccal and palatal root-ends of extracted human maxillary first molars were resected by 3 mm perpendicularly to the long axis of tooth using a slow speed diamond saw after root canal preparation and filling. Retrocavities were prepared using a ultrasonic diamond instrument or a stainless steel one of the low- or medium power settings of 2 or 6. Time consumed and the number of strokes used for the cavity preparation were measured and the incidence of tooth cracks was evaluated under a stereomicroscope. The results were as follows: Both at the low and medium power settings, and both with perpendicularly- and parallely applied tips to dentin, diamond instruments showed higher dentin cutting efficiency than stainless steel ones did (p<0.01). When tips were applied to dentin perpendicularly, both diamond instrument and stainless steel one showed higher cutting efficiency with medium power setting than with low power one (p<0.01). Both at the low- and medium power settings, both diamond instrument and stainless steel one showed higher cutting efficiency when tips were applied perpendicularly to dentin surface than applied parallely (p<0.01). At the medium power setting, the number of stroke and time consumed were less with diamond instrument than with stainless steel one (p<0.05) for the retrograde cavity preparation. At the low power setting, diamond instrument induced less tooth cracks than stainless steel one did (p<0.01).

• Journal of Internet Computing and Services
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• v.24 no.6
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• pp.171-180
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• 2023

Hydrogen energy technology is gaining importance in the era of the Fourth Industrial Revolution, offering military advantages when applied to military vehicles due to its characteristics such as reduced greenhouse gas emissions, noise, and low vibration. Korea's military has initiated the Army Tiger 4.0 plan, focusing on hydrogen application, downsizing, and AI-based smart features. The Ministry of National Defense plans to collaborate with the Ministry of Environment to expand hydrogen charging stations nationwide, anticipating increased deployment of military hydrogen vehicles. However, considering the Jet Fire and VCE(Vapor Cloud Explosion) nature of hydrogen, ensuring safety during installation is crucial. Current military guidelines specify a minimum safety distance of 2m from adjacent buildings for charging stations. Scientific methods have been employed to quantitatively assess the accident damage range of hydrogen, proposing a minimum safety distance beyond the affected area.

• Journal of the Korean Society of Radiology
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• v.10 no.2
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• pp.117-124
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• 2016

The purpose of this study was tried to evaluate the filling sodium states inside the fuel rod of sodium-cooled fast reactor by digital medical X-ray. We used the diagnostic X-ray generators in digital radiography (DR). This study have found the optimal conditions by changing the effective focal spot size of X-ray tube and post-processing of the DR method with a tungsten edge plate in order to ensure excellent sharpness At this time, the sharpness and resolution were evaluated using the MTF (modulation transfer function). As a result, this study obtained a spatial resolution of 3.871 lp/mm (0.1 MTF), 3.290 lp/mm (0.5 MTF) when implemented the contrast strengthen post-processing in small focal spot. In this research, the result is able to evaluate the level of sodium inside the fuel rod by using the diagnostic X-ray generators in medical digital radiographic images.

• Journal of the Korean Institute of Gas
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• v.12 no.4
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• pp.29-33
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• 2008

The focus of this study is to develop a virtual reality program for safe training and virtual reality of hydrogen station. This programme consists of 4 modules such as hydrogen and safety module, hydrogen station module, hypothetical experience module, and accident scenarios module for hydrogen experts. User can experience with principles and operation condition and collect the information of hydrogen station by this programme and can simultaneously study the probable scenarios, emergency response plan/standard operating procedure about hydrogen stations. It makes it possible to educate and safety publicity for the trainee. This virtual reality program will be expected to be helpful for hydrogen station's construction propagation and technology development which is essential for hydrogen energy induction.

• The Journal of Engineering Geology
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• v.8 no.3
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• pp.207-213
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• 1998

A study was conducted to determine the characteristics of acoustic emission(AE) events generated by the expansive cement induced rock fracturing. The dominant frequency and the maximum amplitude of the AE events are changed in relation to the rate of expansive pressure development in the hole. The dominant frequencies are in the range of 150∼230kHz for the small hole tests and 400∼500kHz for the large hole test. The maximum amplitudes are in the range of 0.015∼0.050cm/sec and 0.025∼0.064cm/sec, respectively. The fact that AE events of higher amplitude with higher frequency on the large hole test and lower amplitude with lower frequency on the small hole tests were detected, may strongly imply that the amount of energy consumed for a macro-crack in both tests may be similar. The expansive cement induced crack propagates stably without any distinguished event having higher amplitude and this implies that a macro-crack is a result of stable growth of micro cracks.

• Journal of Digital Convergence
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• v.11 no.7
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• pp.141-148
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• 2013

Smart grid can two-way communication using ICT(Information & Communication Technology). Also, smart grid can supply to dynamic power that grafted to electric vehicle can activate to electric vehicle charging infrastructure and used to storage battery of home. Storage battery of home can resale to power provider. These electric vehicle charging infrastructure locate fixed on home, apartment, building, etc charging infrastructure that used fluid on user. If don't authentication for user of fluid user use to charging infrastructure, electric charging service can occurred to illegal use, electric charges and leakgage of electric information. In this paper, we propose smartcard and dynamic ID based user authentication scheme for used secure to electric vehicle service in smart grid environment.