• Elastomers and Composites
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• v.35 no.4
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• pp.272-280
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• 2000

The experimental kinetics was analyzed for commercial rubbers such as NR, IR, BR, SBR 1500, and SBR 1700. Kinetic analysis for the commercial rubbers was performed using a thermogravimetric method, which the activation energies of NR obtained by Kissinger, Friedman, ana Ozawa's method were 195.0, 198.3, and 186.3 kJ/mol, respectively. whereas that of SBR 1500 were 246.4, 247.5, and 254.8 kJ/mol, respectively. It was shown that the yield of pyrolytic oil was generally increased with increasing the final temperature. Considering the effect of heating rate. it was found that the yield of pyrolytic oil was not consistent for each sample. The number average molecular weight of pyrolitic oil of SBR 1500 was in the range of 740-2486. The calorific value of SBR 1500 was 39-40 kJ/g, and it might be a considerable energy potential although it was lower than the conventional fuel such as kerosene, diesel, light fuel, and heavy fuel.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.2
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• pp.91-97
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• 2013

Self-heating effects during operation of high current AlGaN/GaN power transistors degrade the current-voltage characteristics. In particular, this problem becomes serious when a low thermal conductivity Si substrate is used. In this work, AlGaN/GaN-on-Si devices were fabricated with various channel widths and Si substrate thicknesses in which the structure dependent self-heating effects were investigated by temperature dependent measurements as well as thermal simulation. Accordingly, a device structure that can effectively dissipate the heat was proposed in order to achieve the maximum current in a multi-channel, large area device. Employing via-holes and common electrodes with a 100 ${\mu}m$ Si substrate thickness improved the current level by 75% reducing the channel temperature by 68%.

• Fire Science and Engineering
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• v.17 no.4
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• pp.13-19
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• 2003

In this paper, we studied on the characteristics of RCD(Residual Current Device) case deteriorated by tracking, and compared the tracked samples between in the site of fire($S_1$) and in the reappearance experiment($E_1$). This experiment is applied to IEC Publ. 112 method. Electrical fire by tracking occurred after scintillation and dry-band generated. The insulation resistance between source terminals of RCD case was about 25.7Ω in $E_1$ and the resistance was about 58.6Ω in $S_1$.The exothermic peaks of $E_1$ appeared at $491.0^{\circ}C$ and $603.2^{\circ}C$. The exothermic peak at $603.2^{\circ}C$ was shown by tracking. And the exothermic peak of $S_1$ appeared at $593.1^{\circ}C$. In spectrum of $S_1$ and $E_1$, absorption peak didn't appear at near 1590 cm$^{-1}$ .

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.2203_2104
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• 2009

아크는 전원의 양단에 큰 전류가 흐를 때 공기의 이온화와 발열로 인하여 생성된 플리즈마로 정의될 수 있다. 최근 경제발전과 IT산업 발달로 큰 전력계통에서 안정적인 전력 공급이 중요하므로 이러한 아크가 발생하면 부하의 정전사태를 방지하기 위해 일시고장인지 영구 고장인지 빠르게 판단하여 재폐로를 수행하여야 한다. 이를 위해 아크에 대한 특성을 살펴보는 것은 반드시 필요한 사항이므로 본 논문에서는 아크가 발생하는 고장지점에 따른 아크의 특성 변화를 EMTP로 모델링 하여 살펴보고자 하였다. 일반적으로 아크는 특성상 매우 복잡한 구조를 가지며 여러 주위 조건들에 따라 그 특성이 변화한다. 아크의 발생 원인이 되는 사고는 크게 일시고장과 영구고장으로 나눌 수 있는데 여기서 모델링한 것은 스위칭 작용에 의한 2차아크가 발생하는 일시고장의 경우라고 가정하였다. 그리고 아크를 모델링함에 있어서 아크의 특성과 유사한 ZnO 아크 모델을 이용하여 송전선로의 한 상에 연결시켜 연구를 수행하였다.

• Pediatric Infection and Vaccine
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• v.11 no.1
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• pp.90-100
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• 2004

Objective : Urinary tract infection(UTI) is a frequent serious bacterial infection in young infants. The clinical presentation may be non-specific and variable, depends on factors such as the age and the level of infection. Children with renal involvement may be at risk of permanent renal damage. Experimental studies have shown that renal lesions caused by acute febrile UTI may be prevented or diminished by early diagnosis and treatment. Therefore, it is important to find a method that can permit early diagnosis and identification of patients who are at risk for progressive renal damage. We designed this study to identify related factors in culture positive UTI infants, and also to identify related factors in culture negative UTI infants, who are febrile with pyuria, by using renal imaging and functional studies including renal sonography, DMSA scan and VCUG. Methods : Retrospectively analyzed the medical records of 136 febrile infants with pyuria over 2 years(from January 2001 to February 2003). Urine culture was done in all cases, and regardless of urine culture findings, renal imaging study was done if symptomatic UTI suspected. Results : Total 57 organisms were isolated in 53 patients. E. coli was the most common organism(86%), followed by E. faecalis, M. morganii, Proteus species, P. aeruginosa, S. aureus and E. fergusonii. Most of the isolates had high sensitivity on cephalosporins or amikacin and had low sensitivities on aminopenicillins. Abnormal acute phase DMSA scan or VCUG findings were seen in both urine culture positive and negative group without statistical differences(P>0.05). In febrile infants with pyuria, fever over 48 hours, older age and high CRP related to abnormal acute phase DMSA scan findings regardless urine culture results. Conclusion : 1st or 3rd generation cephalosporins with amikacin could be the first choice of treatment for UTI. Febrile infants with positive urine culture dose mean urinary tract infection but not acute pyelonephritis which directly relates to cortical damage which could be confirmed by acute phase DMSA scan. Even cases with negative urine culture findings, acute pyelonephritis should be concerned in febrile infants with pyuria who are older than 3 months of age, has fever over 48 hours or high CRP level. And in such cases, acute phase DMSA scan and VCUG should be evaluated for early treatment and long term prognosis.

• Applied Chemistry for Engineering
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• v.25 no.5
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• pp.515-519
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• 2014

The fuel properties of biodiesel produced by changing the mixing ratio of methanol and ethanol in trans-esterification of soybean oil and lard were evaluated in this paper. The solubility of oil and fat in ethanol was higher than that in methanol. Also the more homogeneous biodiesel was produced as increasing the mole ratio of ethanol. The conversion characteristics of lard was the best at the mixing mole ratio of methanol and ethanol was 6 : 6 at the reaction temperature of $60^{\circ}C$. On the other hands, the best biodiesel conversion characteristics for soybean oil was obtained at the mixing mole ratio of 3 : 3. The kinematic viscosities of soybean oil and lard based biodiesel were 4.17~4.35 cSt and 4.69~4.93 cSt, respectively. The oxidation stability and higher heating value increased with increasing the mole ratio of ethanol. The oxidation stability satisfied the criteria of biodiesel quality of 6 hours. And finally, the higher heating value was approximately 40 MJ/kg.

• Fire Science and Engineering
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• v.29 no.4
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• pp.67-72
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• 2015

A series of fire tests was conducted to examine the fire characteristics of flaming and smoldering combustion of engineered wood products, which have been widely used for furniture and finishing materials in buildings. The engineered wood products of MDF, plywood, and chipboard were ignited by a radiant cone heater with incident heat flux of $50kW/m^2$. During the fire test, key parameters representing the fire characteristics such as the heat release rate, yield rate of combustion product, and effective heat of combustion were quantified in terms of thickness. The tests show two peak points of HRRPUA due to lateral fire propagation in the initial stage, followed by later fire penetration through the specimen thickness. The mass loss rate of flaming combustion was 5 times higher than that of smoldering combustion, while the CO yield rate of smoldering combustion was 10 times higher than that of flaming combustion. This study can contribute to the understanding of fire behavior of wood combustibles and provide useful data for fire analysis.

• Fire Science and Engineering
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• v.22 no.4
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• pp.54-60
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• 2008

In this study, damage characteristics of MCCB and terminal block due to poor contact were analyzed, and various poor contact detection techniques were suggested. Firstly, the detection techniques using thermocouple and infrared thermal camera were analyzed respectively. Also, thermo-cap during poor contact detected abnormal status effectively by changing its color, and the detection system using an odor detector and odor capsules was analyzed. Lastly, poor contact detection screw was made using characteristics of fusible alloy, and we applied the poor contact detection screw to terminal block. The above methods could prevent electrical fire caused by poor contact effectively if they are used properly.

• Journal of the Korean Society of Propulsion Engineers
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• v.1 no.2
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• pp.91-102
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• 1997

In order to evaluate the effects of aging on the ignition performance, pyrotechnic igniters were separated from twelve-year-old, fifteen-year-old, and sixteen-year-old live rocket motors. The characteristic values of the ignition material were measured, and the firing tests of the igniters were performed. The moisture content, the outer dimension, the crush strength, the thermal decomposition characteristics, and the heat of formation the B/$KNO_3$ ignition pellet were measured. The crush strength was increased and the heat of formation was reduced as aged, but no change was detected for other characteristic values. The burning test results of the igniter pellet in the closed bomb and the inert motor showed that the burning rate of the ignition pellet was increased by 10%, and the integration of pressure $P_t$ of the p-t curve was reduced by 15% for aged samples. It was inferred that the burning rate was increased as the crack was appeared in the pellet and $P_t$ could be proportionally decreased with the heat of explosion.

• Journal of the Korean Wood Science and Technology
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• v.39 no.6
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• pp.512-520
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• 2011

This study was preformed to investigate the characteristics of the green drying system for utilizing heat wasted during carbonization process. The green drying system utilizing waste heat is one of environment-friendly equipments because it needs no other energies from fossil fuel and etc. In this study, waste heat from three kilns was collected by stainless connection pipe, and in the green drying system the temperature and humidity was hardly changed. Charcoal charecteristics as fixed carbon, refining degree, hardness, pH, calorific value, and charcoal yield were analyzed to investigate kiln performance due to installation of green drying system. As a result, the green dry system installation hardly affected the characteristics of charcoal. In conclusion, the green drying system can be applied to maximize the profit of the farm household income and contribute to reduce fossil energy.