• Fire Science and Engineering
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• v.28 no.4
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• pp.14-20
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• 2014

The purpose of this study is to analyze combustion patterns by filling a specific container with a flammable liquid and performing combustion tests in a divided space. The container used for the test is made of plastic, 20 mm in depth and 150 mm in width. After the liquid was ignited, its combustion process was photographed using a digital camera and video camera. It was found that in the case of benzene, the flame reached its peak at the fastest speed about 60 s while in the case of alcohol, the flame reached its peak at the lowest speed about 360 s, which is approximately six times slower than the benzene. In most cases, when the flame reached its peak, smoke generated was dark as the plastic container and flammable liquid were combusted simultaneously. After completion of the combustion, it was possible to sample oil vapor from all flammable liquids excluding soybean oil as a result of the examination of oil vapor using a crime investigation tube. That is, it can be seen that there is significant difference in flame propagation speed, pattern, etc., depending on the combustible substances.

• Journal of Animal Environmental Science
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• v.9 no.2
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• pp.79-84
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• 2003

1.퇴비 온도의 상승에 비례하여 폐사계 체내의 온도도 상승하여 퇴적식 퇴비단의 경우 $55^{\circ}C$내외의 고온지속기간이 약 30일정도 유지되었다. 반면에 토양 중에 매립된 폐사계의 체내 온도는 발효 전 기간 동안 $30^{\circ}C$ 이상으로 상승하지 못한 채 주변토양 온도와 거의 비슷한 수준을 유지하였다. 토양온도는 외기온의 변화에 즉각적인 반응을 보이지 않았다. 2. 시험용 발효조 내에서의 송풍여부에 따른 퇴비의 발효온도 변화추이는 송풍 처리구에서는 퇴비화 3일째에 최고온도 $68^{\circ}C$를 기록한 반면에 무송풍구에서는 퇴비화 5일째에 최고온도 $72^{\circ}C$를 기록하였다. 3. 퇴비단 표층에서 채취된 시료에서 검출된 $H_2S$와 $CH_3$SH 농도는 송풍 처리구에 있어서는 퇴비화 개시 후 20일 경과 후 각 각 28.5, 16.0 ppb 수준을 나타냈고 35일 경과 시에는 각각 57.7, 11.7 ppb, $CH_3SH$의 경우에는 23.7, 9.9 ppb 수준의 발생량을 기록하는 등 전반적으로 송풍처리구가 무송풍 처리구에 비해 악취가스의 발생량이 상대적으로 낮았다. 4. 폐사계를 밀폐용기 내에서 발표 시 수거된 침출수 중의 미생물 수가 토양매립 상태 하에서 수거된 침출수 중의 미생물 수보다 더 적은 경향을 보이고 있다. 5. 퇴비단 내에서 발효에 따른 폐사계 중량은 최초 3일간에 급격히 감소하고 시간의 경과에 따라 그 감소속도는 줄어든다. 발효온도가 높을수록 조직의 분해속도가 빨라지고 폐사계의 중량감소 속도도 빨라졌다. 6. 일반 퇴비와 폐사계를 발효시킨 퇴비 사이에 비료성분과 중금속 함량의 유의적인 차이는 발견되지 않았다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.4
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• pp.145-149
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• 2016

The effect of process parameters such as plasma composition, ICP (Inductively Coupled Plasma) source power and rf chuck power on the etch characteristics of GaN epitaxy layer was studied. $Cl_2/Ar$ ICP discharges showed higher etch rates than $SF_6/Ar$ discharges because of the higher volatility of $GaCl_x$ etch products than $GaF_x$ compounds. As the Ar ratio increases in the $Cl_2/Ar$ ICP discharges, the etch anisotropy was enhanced due to the improved physical component of the etching. For both plasma chemistries, the GaN etch rate increased continuously as both the ICP source power and rf chuck power increased, and a maximum etch rate of 251.9 nm/min was obtained at $13Cl_2/2Ar$, 750W ICP power, 400W rf chuck power and 10 mTorr condition.

• Korean Journal of Microbiology
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• v.35 no.1
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• pp.47-52
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• 1999

The study on the bacterial distribution was performed to evaluate the bacteriological safety in 4 deep confined aquifers drilled for drinking. All the investigated aquifers were oligotrophic, howevec bacterial densities and activities and the number of indicator bacteria in C-2 boreholes were much higher than those in other boreholes. Fecal pollution was observed in 3 boreholcs except C-1 borehole. The ratio of gram positive bacteria of the C-2 borehole was much lower than those 01 another boreholes. The numbers of total colifonns, fecal coliforms, and fecal Slreptococcus in the C-2 boreholes were 61, 33, 55 CFU (250 ml)$^{-1}$

• Applied Biological Chemistry
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• v.34 no.3
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• pp.235-241
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• 1991

Several spices in the range of $1{\sim}3%\;(w/w)$ were added during Kimchi preparation in order to investigate their effects on the chemical changes and fermentation rate. The results showed that addition of red pepper powder by 2% slightly increased the fermentation rate reaching max. value after 36 hours, while 3% addition gradually increased its rate without max. point. Generally higher reducing sugar and acidity were measured for red pepper added Kimchi. The fermentation rate and its max. point were significantly increased as more garlic added and the max. value of ascorbic acid produced was also increased. Little effects were found for Welsh onion and ginger on Kimchi fermentation.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.1
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• pp.104-111
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• 2017

This research focuses on simulation and visualization of flow field characteristics inside a centrifugal pump. The 3D numerical analysis was carried out by using a numerical CFD tool, addressing a Reynolds Average Navier-Stock code with a standard k-${\varepsilon}$ two-equation turbulence model. The simulation accounts for friction head loss due to rough walls at suction, impeller, discharge areas and volumetric head loss at impeller wear ring. A comparison of performance curves between simulation and experimentation is included, and it reveals a same trend of those results with a small difference of maximum 5 %. At best efficiency point, velocity vectors are smooth but it changes significantly under off-design point, a strong recirculation appears at the outlet of impeller passages near tongue area. A relatively uniform preassure distribution was observed around the impeller in despite of the tongue. Within the volute, because of its geometry, spiral vortexes formed, proving that the flow field in this region was relatively turbulent and unsteady.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.951-954
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• 2005

This paper presents a study on the accuracy position Controller design for the Composite Smoke Bomb Rotational driving system using a BLDC servo motor. Function of Smoke Bomb is blind in the enermy's sight so that need to high response. The BLDC servo motor controller was designed with DSP(TMS320VC33), IGBT(Insulated Gate Bipolar. Transistor), IGBT gate driver and CPLD(EPM7128). This paper implements those control with vector control and MIN-MAX PWM. Vector control requires information about rotor positions, a resolver should be used to achieve that. The main controller is implemented with a TMS320VC33 high performance floating-point DSP(Digital Signal Process) and PWM Generator is embodied using EPM7128.

• Journal of Korea Multimedia Society
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• v.9 no.7
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• pp.808-817
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• 2006

Although the generally used the velocity index of doppler effect is a very significant factor in the functional evaluation of the left ventricle, it depends on the subjective evaluation of an inspector. The objective data of the motility can be obtained from the gated myocardial SPECT images by quantitative analysis. However, it is difficult to image visual of the velocity of the motion. The aim of our study is to develop a new method for the imaging velocity using the gated myocardial SPECT images and use it as an evaluation index for analyzing motility. First we visualized left ventricle into 3 dimensions using the coordinates of the points which were obtained through a segmentation of myocardium. Each point was represented by the different colors, according to the velocity of each point. We performed a validation study using 7 normal subjects and 15 myocardial infarction patients. To analyze motility, we used the average of the moved distance and the velocity. In normal cases, the average of the moved distance was 4.3mm and the average of the velocity was 11.9mm. In patient cases, the average of the moved distance was 3.9mm and the average of the velocity was 10.5mm. These results show that the motility of normal subjects is higher than the abnormal subjects. We expect that our proposed method could become a way to improve the accuracy and reproducibility for the functional evaluation of myocardial wall.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.37 no.5
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• pp.54-63
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• 2000

We present a multi-resolution block matching algorithm (BMA) for fast motion estimation At the coarsest level, a motion vector (MV) having minimum matching error is chosen via a full search, and a MV with minimum matching error is concurrently found among the MVs of the spatially adjacent blocks Here, to examine the spatial MVs accurately, we propose an efficient method for searching full resolution MV s without MV quantization even at the coarsest level The chosen two MV s are used as the initial search centers at the middle level At the middle level, the local search is performed within much smaller search area around each search center If the method used at the coarsest level is adopted here, the local searches can be done at integer-pel accuracy A MV having minimum matching error is selected within the local search areas, and then the final level search is performed around this initial search center Since the local searches are performed at integer-pel accuracy at the middle level, the local search at the finest level does not take an effect on the overall performance So we can skip the final level search without performance degradation, thereby the search speed increases Simulation results show that in comparison with full search BMA, the proposed BMA without the final level search achieves a speed-up factor over 200 with minor PSNR degradation of 02dB at most, under a normal MPEG2 coding environment Furthermore, our scheme IS also suitable for hardware implementation due to regular data-flow.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.2
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• pp.119-124
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• 2015

Numerical study on the new design of the liquid mass flow meter in infinitesimal flow rate for semiconductor production is performed. The heater and thermistor are wired on the circular tube about 0.3mm inner diameter with designed gap between them. After the time interval from the single pulse heating the thermistor reaches its peak temperature and this time interval is almost inversely proportional to the liquid mass flow rate. The axial conduction in tube wall and convection through the flow is combined. As a result, the peak temperature moving velocity is much smaller than flow mean velocity and there is no linear relationship between them. In this study, the effects of design parameters such as the tube inner/outer diameter, wired heater width, and the gap between heater and thermistor are investigated and the trends of optimization in these parameters are discussed.