• Proceedings of the KIEE Conference
• /
• 2008.07a
• /
• pp.2102-2103
• /
• 2008

The major causes of electrical fire are classified to short circuit fault, overload fault, electric leakage and electric contact failure. The occurrence factor of the fire is electric arc or spark accompanied with electrical faults. Residual Current Protective Device(RCD) of high sensitivity type used at low voltage wiring cuts off earth leakage and overload, but the RCD can't cut off electric arc or spark to be a major factor of electrical fire. As the RCDs which are applied low voltage distribution panel are prescribed to rated breaking time about 30[ms](KS C 4613), the RCDs can't perceive to the periodic electric arc or spark of more short wavelength level. To be improved on such problem, this paper is proposed to a electrical fire disaster prevention device(EFDPD) for a RCD trip or a self circuit-breaking function on electric arc or spark due to electrical fire. Some experimental results of the proposed apparatus is confirmed to the validity of the analytical results.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.16 no.3
• /
• pp.440-447
• /
• 2012

Numerical model experiments of wave transformation due to the reclamation and the construction of breakwater in case of 50 years design wave were performed using time dependent mild slope equation included shoaling, refraction, diffraction, reflection and wave breaking. As waves propagate to the shore, wave height gradually diminishes by the bottom friction and wave breaking etc.. After the reclamation and the construction of 75 m length breakwater, wave height distributions in the lee of breakwater have the range of 29~128 cm. To make better the harbor tranquility the length of breakwater needs to extend more than 100 m. After the construction of breakwater, wave height in the lee of the structure was deduced over 80%.

• Proceedings of the KSR Conference
• /
• 2009.05a
• /
• pp.457-465
• /
• 2009

Subway system including light-rail transit system is the representative public urban transportation. Accordingly, Nothing is more important than the safety operation as well as passengers' convenience. Due to the fire disaster of Daegu subway on 2003, more strict regulations of detecting fire and of conducting on emergency circumstances. However, regardless of this improved management, it was reported that installations of lots of fire-detection facilities may be harm than good to operate subway system due to frequent malfunction of some fire-detection facilities. It may cause mis-alarm for fire and induces abnormal operation of subway due to the strict regulation; the train shall be stopped on emergency circumstances. Therefore, in this paper, new scheme on surveiling breaking-out-of fire in the station is suggested with new IT technologies, Wireless Sensor Network(WSN) and CCTVs. which were integrated with an intelligent software. This intelligent system enables to surveil breaking-out-of fire in real time through sensor network technology and watch the emergency site on CCTV as well. Through this system, subway organizers could cope with the emergency circumstance rapidly as well as judge precisely whether fire breaks out or not.

• Journal of the Korean Chemical Society
• /
• v.62 no.2
• /
• pp.93-98
• /
• 2018

Bis-GMA, TEGDMA, and camphorquinone were used as the main material, cross-linking agent, and photoinitiator, respectively. In addition, 2-isocyanatoethyl methacrylate was used as an additive for high strength, while the 3-hydroxypyridine was used as an additive for antibacterial activity. Photopolymerization was also carried out at a 440-480 nm wavelength and at about $1000mW/cm^2$ intensity for about 40 seconds. The breaking strength measurement of the samples showed that the breaking strength increased along with increasing the addition ratio of IEM, while it took less time until the polymerization was complete, thereby suggesting that the degree of polymerization has the tendency to increase. And also, compared to the size of the clear zone formed by ampicillin, the 3-hydroxypyridine group exhibited antimicrobial activity induced by ampicillin. The results of this study suggest that the use of 2-isocyanatoethyl methacrylate as an additive for high strength and 3-hydroxypyridine as an additive for improved antibacterial activity would improve the usability of the fabricated polymer as a dental resin cement material with high functionality.

• Journal of Applied Biological Chemistry
• /
• v.43 no.3
• /
• pp.156-160
• /
• 2000

The possible mechanism of the DNA strand breaking activity of the hot-water extract of Fructus Chaenomelis (dried fruit of Chaenomeles sinensis) in a closed circular duplex replica form DNA (RFI DNA) was studied through agarose gel electrophresis under various conditions. Induction of DNA strand scission by the hot-water extract of C. sinensis occurred in dose and time-dependent manners. $Cu^{2+}$ was indispensable for the induction of DNA strand breakage. Exogeneous chelating agents inhibited the DNA breaking activity, conforming the catalytic action of $Cu^{2+}$ on generation of free radicals responsible for oxidative damage. Antioxidant enzymes and some radical scavengers were used to investigate the major radical species triggering the DNA strand scission, demonstrating that a highest inhibitory activity was found in the presence of catalase, while less in the presence of tiron (a scavenger for superoxide radical), 2-aminoethyl-isothiuroniumbromide-HBr, cysteamine (scavengers for hydroxyl radical), and 1,4-diazabicyclo [2,2,2] octane (a scavenger for singlet oxygen) in decreasing order. The findings implied that oxygen radical species generated in presence of transition divalent cation during the oxidation of some compounds contained in the hot-water extract of C. sinensis is mainly responsible for inducing genotoxicity.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.23 no.5
• /
• pp.299-304
• /
• 2018

An ideal circuit breaker should supply electric power to loads without losses in a conduction state and completely isolate the load from the power source by providing insulation strength in a break state. Fault current is relatively easy to break in an Alternating Current (AC) circuit breaker because the AC current becomes zero at every half cycle. However, fault current in DC circuit breaker (DCCB) should be reduced by generating a high arc voltage at the breaker contact point. Large fire may occur if the DCCB does not take sufficient arc voltage and allows the continuous flow of the arc fault current with high temperature. A semiconductor circuit breaker with a power electronic device has many advantages. These advantages include quick breaking time, lack of arc generation, and lower noise than mechanical circuit breakers. However, a large load capacity cannot be applied because of large conduction loss. An extinguishing technology of DCCB with polymeric positive temperature coefficient (PPTC) device is proposed and evaluated through experiments in this study to take advantage of low conduction loss of mechanical circuit breaker and arcless breaking characteristic of semiconductor devices.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.11 no.2
• /
• pp.87-94
• /
• 1999

The Morison's formula has been commonly used in the determination of wave forces of sinusoidal waves acting on coastal or ocean structures of pile-supported type. In the case that plunging breakers are incident, the structures are subjected to impulsive breaking wave forces which are normally much larger than the Morison's. However, the impulsive breaking wave forces act in a very short time, and hence a dynamic structural analysis should be done to determine whether or not to include the forces in the design force items. In the present study, numerical methods for calculating the dynamic response of a vertically located cylindrical pile are developed. Static and dynamic displacements are then compared through several example analyses varying the structural properties of pile.

• Journal of the Korea Furniture Society
• /
• v.17 no.1
• /
• pp.23-32
• /
• 2006

This study was carried out to explore a new application of traditional Hanji and obtain fundamental properties for producing Hanji wallpaper by incorporating ceramics from wood and rice-husk as an interior building material. The results of properties determined were summarized as follows: The addition of ceramics in Hanji paper reduced its apparent density, but increased bulk density due to the ceramic particles distributed on the surface and inside the fiber of Hanji wallpapers. In particular, woodceramic particles were specifically distributed on the fiber surface, while particles of rice-husk ceramics were permeated into the inside surface of fibers. The density of rice-husk ceramics were greater than that of woodceramics. The physical properties of Hanji wallpapers, such as breaking strength, wet breaking strength, burst strength, tear index and folding endurance were deteriorated with the addition of ceramics. However, the addition of woodceramics in the Hanji wallpaper resulted in better strength in most cases than that of rice-husk ceramics, except tear strength. Therefore, an optimum addition level of woodceramics into the wallpaper was found to be 5% on the basis of intensity. The addition of ceramics also prolonged the combustion time because it lowered air permeability and brightness of the wallpaper.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.8 no.1
• /
• pp.87-94
• /
• 1996

Random wave breaking is one of the most important phenomena in coastal engineering. For two and half decades, various models have been proposed to predict wave height variations in the surf zone. However, some models are applicable to plane beaches only, some requires clumsy computation for a joint probability density of wave heights and periods, and some others need calibration with individual wave data. The present study aims at formulating a model simple enough but reasonably accurate. The merits of the present model are as follows: It is applicable to any shapes of bottom profiles; It requires the input data of incident wave heights and periods only without necessity of coefficient calibration with field data; and its computation time is minimal because it deals with representative waves directly.

• Journal of the Society of Naval Architects of Korea
• /
• v.43 no.1 s.145
• /
• pp.96-102
• /
• 2006

In this study, an optimization routine with genetic algorithms is coupled for the selection of free variables for the production of a control signal for the motion of wave board in the numerical wave tank. An excitation function for the controlling of the wave board is formulated on basis of amplitude modulation for the generation of nonlinear wave packets. The found variables by the optimization serve for the determination of wave board motion both with the computation and with the experiment. The breaking criterion of the water waves is implemented as boundary condition for the optimization procedure. With the analysis of the time registration on the local position in the wave tank the optimization routine is accomplished until the given design wave with defined surface elevation is found. Water surface elevation and associated fields of velocity and pressure are numerically computed.