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

• Earthquakes and Structures
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• v.3 no.5
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• pp.675-694
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• 2012

The 2008 Iwate-Miyagi Nairiku earthquake ($M_w$ 6.9, $M_{jma}$ 7.2) occurred on 14 June 2008 in Japan. The amplification and asymmetric waveform of the vertical acceleration at the ground surface recorded by accelerometers at station IWTH25, situated 3 km from the source, were remarkable in two ways. First, the vertical acceleration was extremely large (PGA = 38.66 $m/s^2$ for the vertical component, PGA = 42.78 $m/s^2$ for the sum of the three components). Second, an unusual asymmetric waveform, which is too far above the zero acceleration axis, as well as large upward spikes were observed. Using a multidegree-of-freedom (MDF) system consisting of a one-dimensional continuum subjected to vertical acceleration recorded at a depth of 260 m below ground level, the present paper clarifies numerically that these singular phenomena in the surface vertical acceleration records occurred as a result of the jumping and collision of a layer in vertical motion. We herein propose a new mechanism for such jumping and collision of ground layers. The unexpected extensive landslides that occurred in the area around the epicenter are believed to have been produced by such jumping under the influence of vertical acceleration.

• Korean Journal of Materials Research
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• v.29 no.5
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• pp.304-310
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• 2019

Chemical vapor deposition method using $CH_4$ gaseous hydrocarbons is generally used to synthesize large-area graphene. Studies using non-gaseous materials such as ethanol, hexane and camphor have occasionally been conducted. In this study, large-area graphene is synthesized via chemical vapor deposition using polyethylene as a carbon precursor. In particular, we used a poly glove, which is made of low-density polyethylene. The characteristics of the synthesized graphene as functions of the growth time of graphene and the temperature for vaporizing polyethylene are evaluated by optical microscopy and Raman spectroscopy. When the polyethylene vaporizing temperature is over $150^{\circ}C$, large-area graphene with excellent quality is synthesized. Raman spectroscopy shows that the D peak intensity increased and the 2D peak intensity decreased with increasing growth time. The reason for this is that sp3 bonds in the graphene can form when the correct amount of carbon source is supplied. The quality of the graphene synthesized using polyethylene is similar to that of graphene synthesized using methane gas.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.8
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• pp.1170-1179
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• 2009

The purpose of this work is to predict the low frequency aero-acoustic noise generated from the horizontal axis wind turbine, NREL Phase VI for the whole operating conditions of various wind speeds using large eddy simulation and Ffowcs-Williams and Hawkings model provided in the commercial code, FLUENT. Because there is no experimental data about wind turbine noise, we first of all compared aerodynamic performance such as shaft torque and power with experimentally measured value. Performance results show a good agreement with experimental data within about 0.8%. As the wind speed increases, the overall sound pressure level and the sound pressure level by the quadrupole and dipole source show a increasing tendency. Also, sound pressure level is proportional to $r^{-2}$ in the near field and $r^{-1}$ in the far field according to the increase of distance from the center of hub of wind turbine. According to 2 times increase of distance, sound pressure level is reduced by about 6dB.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.3
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• pp.379-387
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• 2013

In large-scale wireless sensor networks, tremendous amount of dummy packets is usually accompanied by keeping location privacy of the communication source and destination against global eavesdropping. In our earlier work we designed a location privacy routing protocol, ELPR(End-node Location Privacy Routing) in which the generation of dummy packets at each idle time-slot while transferring data packets are restricted to only the nodes within certain areas of encompassing the source and destination, respectively. In this paper, it is given that ELPR provides various degrees of location privacy while PCM(Periodic Collection Method) allows the only fixed level. Simulation results show that as the number of nodes or data packets increases ELPR permits in terms of the number of generated packets more cost-effective location privacy than PCM.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.69.1-69.1
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• 2015

Classical T Tauri star DG Tau is suggested as the driving source of parsec-scale jet which expands up to 650" (0.4 pc). To investigate the kinematics and physical properties of the jet, we have obtained the optical emission lines of $H{\alpha}$, [O I] ${\lambda}{\lambda}$6300, 6363, [N II] ${\lambda}{\lambda}$6548,6584, and [S II] ${\lambda}{\lambda}$6716, 6731 from HH 158 ad HH 702. The radial velocity of HH 158 is in the range of -50 to $-250km\;s^{-1}$. For HH 702, located at 650" from the source, it shows ~ $-80km\;s^{-1}$. In HH 158, the electron density ($n_e$) close to the star is ${\sim}10^4cm^{-3}$ and it decreases to ${\sim}10^2cm^{-3}$ at 14" away from the star. Electron temperature ($T_e$) is decreasing from >15,000 K to ~5,000 K with distance. Ionization fraction ($x_e$) is increasing from almost zero to > 0.4 along the distance. In HH 702, the values of $n_e$, $T_e$, and $x_e$ are similar to those estimated at 14" from source, where knot C of HH 158 is located. This may imply that the physical properties of the knot could persist through such a long distance in the space, and the gas could be re-excited by the shock during propagation of the jet. On the other hand, we cannot avoid the possibility that HH 702 is driven by another source rather than DG Tau because HH 158 and HH 702 show somewhat large difference in their inclination angles (${\Delta}i=21-35^{\circ}$).

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.5
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• pp.439-444
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• 2003

Acoustic emission(AE) ran be very effectively applied to locate the damaged area in large structures by detecting the elastic waves generated during the damage process within solids. Source location in the composite structures has been, however, extremely difficult due to the acoustic anisotropy with the velocity dependence on fiber orientations. In this study, it has been shown that a newly proposed method for 2-D source location of anisotropic structures is practically applicable to the real structure. The method employes wave velocities obtained with different velocities from $0^{\circ}\;to\;90^{\circ}$ for a filament wound composite pressure vessel under the air-filled and the water-filled conditions.

• Microbiology and Biotechnology Letters
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• v.46 no.1
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• pp.29-39
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• 2018

Vibrio vulnificus needs various responsive mechanisms to survive and transmit successfully in alternative niches of human and marine environments, and to ensure the acquisition of steady energy supply to facilitate such unique life style. The bacterium had genetic constitution very different from that of Escherichia coli regarding metabolism of glycogen, a major energy reserve. V. vulnificus accumulated more glycogen than other bacteria and at various levels according to culture medium and carbon source supplied in excess. Glycogen was accumulated to the highest level in Luria-Bertani (3.08 mg/mg protein) and heart infusion (4.30 mg/mg protein) complex media supplemented with 1% (w/v) maltodextrin at 3 h into the stationary phase. Regarding effect of carbon source, more glycogen was accumulated when maltodextrin (2.34 mg/mg protein) was added than when glucose or maltose (0.78.1-14 mg/mg protein) was added as an excessive carbon source to M9 minimal medium, suggesting that maltodextrin metabolism might affect glycogen metabolism very closely. These results were supported by the analysis using the malP (encoding a maltodextrin phosphorylase) and malQ (encoding a 4-${\alpha}$-glucanotransferase) mutants, which accumulated much less glycogen than wild type when either glucose or maltodextrin was supplied as an excessive carbon source, but at different levels (3.1-80.3% of wild type glycogen). Therefore, multiple pathways for glycogen metabolism were likely to function in V. vulnificus and that responding to maltodextrin might be more efficient in synthesizing glycogen. All of the glycogen samples from 3 V. vulnificus strains under various conditions showed a narrow side chain length distribution with short chains (G4-G6) as major ones. Not only the comparatively large accumulation volume but also the structure of glycogen in V. vulnificus, compared to other bacteria, may explain durability of the bacterium in external environment.

• Journal of The Korean Society of Agricultural Engineers
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• v.47 no.4
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• pp.65-74
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• 2005

AnnAGNPS model was applied to a catchment mainly occupied with bushland for modeling non-point source pollution. Since the single event model cannot handle events longer than 24 hours duration, the event-based calibration was carried out using the continuous mode. As event flows affect sediment and nutrient generation and transport, the calibration of the model was performed in three steps: Hydrologic, Sediment and Nutrient calibrations. The results from hydrologic calibration for the catchment indicate a good prediction of the model with average ARE(Absolute Relative Error) of $24.6\%$ fur the runoff volume and $12\%$ for the peak flow. For the sediment calibration, the average ARE was $198.8\%$ indicating acceptable model performance for the sediment prediction. The predicted TN(Total Nitrogen) and TP(Total Phosphorus) were also found to be acceptable as the average ARE for TN and TP were $175.5\%\;and\;126.5\%$, respectively. The AnnAGNPS model was therefore approved to be appropriate to model non-point source pollution in bushland catchments. In general, the model was likely to result in underestimation for the larger events and overestimation fur the smaller events for the water quality predictions. It was also observed that the large errors in the hydrologic prediction also produced high errors in sediment and nutrient prediction. This was probably due to error propagation in which the error in the hydrologic prediction influenced the generation of error in the water quality prediction. Accurate hydrologic calibration should be hence obtained for a reliable water quality prediction.

• Asian-Australasian Journal of Animal Sciences
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• v.15 no.1
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• pp.89-93
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• 2002

A total of six crossbred barrows ($Duroc{\times}Landrace{\times}Large$ White, $44.17{\pm}1.94kg$ BW) were housed conducted to evaluate apparent fecal digestibilities of Brown Rice (BR) as an alternative energy source in growing pigs. Pigs were housed individually on metabolism crate on the basis of body weight. Four treatments contained: 1) 100% of corn-soybean meal (C100; Control diet), 2) 75% of corn-soybean meal diet plus 25% of corn meal (C25), 3) 100% of brown rice-soybean meal diet (BR100), 4) 75% of brown rice-soybean meal diet plus 25% of brown rice meal (BR25). Brown rice has an excellent gross energy and crude protein composition compared to corn. The BR used had 3,801 kcal of gross energy/kg, 8.0% crude protein, 2.6% of ether extract, 0.035% calcium and 0.35% total phosphorus. The best digestibilities of energy (87.75%), DM (81.71%) and CP (78.57%) were observed in BR 100 group and the worst were found in Corn 25 group. The nutrient digestibility was not significantly different in most nutrients. Through this experiment, BR appeared a good alternative energy source that can replace corn yellow to 100% in growing pigs. Therefore, the price relationship between corn and BR may provide an excellent opportunity for pork producers to use BR in order to reduce feed costs provided that diet has been balanced for digestible amino acids.