• Title/Summary/Keyword: maxium temperature

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Preparation and thermodynamics consideration of MgO-Al spinel by self-propagation high- temperature synthesis (자전고온연소합성법에 의한 MgO-Al 스피넬 제조 및 열역학적 고찰)

  • Byun, Hun-Soo;Choi, Tae-Hyun
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.8 no.4
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    • pp.573-580
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    • 1998
  • Self-propagating high temperature synthesis (SHS) technique was used to synthesize the spinel phase of $MgAl_2O_4$ from MgO and Al powder. Thermit reaction products of MgO and Al, The reaction products were heat treated at the temperature $800^{\circ}C$ preheating. Processing factors such as DTA/TG, combustium product and maxium temperature, synthesis of MgO and Al from "$MgO+2Al+3/2O_2$\rightarrow$MgAl_2O_4$". An activation energy (${\Delta}H^{\circ}$)-264.8 kcal/mol and reaction of maxium temperature 5634 K was calculated to form a $MgAl_2O_4$ spinel from unreacted materials. Pellet were increased volume 6% after thermit reaction. reaction.

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Effect of Temperature and Day-length on Antioxidants in Sesame (온도와 일장이 참깨의 항산화성분에 미치는 영향)

  • Ryu, Su-Rno;Lee, Jung-Il;Lee, Hyo-Sung
    • KOREAN JOURNAL OF CROP SCIENCE
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    • v.38 no.4
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    • pp.330-335
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    • 1993
  • Sesame cultivars were treated with temperature and daylength to determine the environmental variance of Antioxidant content The experiment was performed in phytotron with 11, 13, 15hours of daylength and 20/15, 25 120, 30/25$^{\circ}C (day / night) of temperature treatment. Varietal differences of antioxidant content were significant by the temperature and daylength treatment. Antioxidant content was incrased at higher temperature(25/2$0^{\circ}C$, 30/25$^{\circ}C) and daylength(13hours) but decreased at lower temperature (20/15$^{\circ}C), short daylength (l1hours) and long day length (15hours) condition. Sesamin content were showed 0.06% difference as maxium by the temperature treatment, while 0.03% by the daylength treatment. Sesamolin content were showed 0.03% difference as maxium by the temperature treatment, while 0.01% by the daylength treatment. The antioxidant content was influenced by the increased temperature than daylength.

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Effect of Additives and Cooling Rates on the Electrical Resistivity of $BaTiO_3$ Ceramics: (II) Multi-Component Systems of $TiO_2$, $SiO_2$ and $Al_2O_3$ Additives ($BaTiO_3$ 세라믹스의 전기저항에 미치는 첨가제와 냉각속도의 영향: (II) $TiO_2$, $SiO_2$$Al_2O_3$ 복합첨가)

  • 염희남;하명수;이재춘;정윤중
    • Journal of the Korean Ceramic Society
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    • v.28 no.10
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    • pp.803-809
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    • 1991
  • Microstructure, room temperature resistivity and temperature coefficient of resistance of BaTiO3 ceramics were characterized and measured in this study. The basic composition of the BaTiO3 cremics was formed by adding 0.25 mol% Dy2O3 and 0.07 mol% MnO2 to the BaTiO3 composition. Samples of the BaTiO3 ceramics were prepared by adding various amounts of the TiO2, SiO2 and Al2O3 to the basic composition. An addition of 1 mol% TiO2, 2 mol% SiO2 and 0.5 mol% Al2O3 to the basic composition resulted both the values of the room temperature resistivity and the temperatured coefficient being maxium. Meanwhile, an addition of 1 mol% TiO2 and 1 mol% Al2O3 to the basic composition resulted the value of the room temperature resistivity maxium and the temperature coefficient minimum. The temperature coefficient showed a maximum value as well as a minimum value when the three kinds of the additives were added together to the basic composition of the BaTiO3 ceramics. Maxed phases of BaTi3O7, BaTiSiO5 and BaAl2Si2O8 were present at the grain boundary.

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A Study on the Reduction of $NO_x$ Emission from Dual Fuel Engine for Co-generation System (열병합발적용 Dual Fuel Engine의 질소산화물 배출저감에 관한 연구)

  • 정일래;김용술;심용식
    • Journal of Korean Society for Atmospheric Environment
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    • v.7 no.1
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    • pp.31-40
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    • 1991
  • This study shows the correlation between $NO_x$ emission in the exhaust gas and various operation factors of dual fuel engine for Co-generation system. General tendency was shown that the thermal efficiency was lowered by the change of operation factors. However these were not confirmed on this experiment. Increasing T4 temperature (exhaust gas temperature at turbo-charger inlet) reduces $NO_x$ emission rate. The higher T4 temperature requires lower excess air as the excess air ratio is controlled by T4 temperature on gas mode operation. Another tendency was that $NO_x$ emission rate is reduced in case of increasing boost air temperature, quantity of pilot oil or bypassing flue gas through the exhaust gas boiler. The diameter of the fuel injection nozzle was changed smaller than design value and the injection timing was readjusted. Thus $NO_x$ emission rate could be reduced as retarding injection timing and changing hole diameter of fuel injection nozzle, however maxium engine out-put was decreased by changing fuel nozzle on the diesel mode operation.

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Prediction of Temperature Rise in Power Appratus (초고압 전력기기의 온도상승 예측)

  • Kim, S.W.;Park, J.H.;Hahn, S.C.;Lee, B.Y.;Park, K.Y.;Song, W.P.;Kim, J.B.
    • Proceedings of the KIEE Conference
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    • 2001.04a
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    • pp.113-115
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    • 2001
  • In order to design the power appratus such ac bus bar, the current carrying ampacity should be determined, Since it is limited by maxium operating temperature, it is very important to predict temperature-rise on it. The main causes to raise temperature are joule's loss in the current carrying conductor and induced circulating and eddy current in the tank. The heat transfer is divided into convection and radiation on boundary, determining convection heat transfer coefficient is not easy. This paper propose a new technique that can be used to estimate the temperature rise in the extra high voltage bus bar. The heat transfer coefficient is analytically calculated by applying Nusselt Number depending on temperature as well as model geometry. The analytic method which use heat transfer coefficient is coupled with finite element method. The temperature distribution in the bus bar by the proposed method shows good agreement with experimental data.

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The Temporal Variations of Summer Temperature in Central Area of Korea during the 20th Century (20세기 한반도 중부지방의 여름철 기온 변화)

  • 최광용;최종남;김종욱
    • Journal of the Korean Geographical Society
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    • v.35 no.4
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    • pp.519-528
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    • 2000
  • 본 연구에서는 지난 20세기 동안 한반도 중부 지방의 여름철 7월과 8월의 일최고기온과 일최저기온의 지역적 패턴을 조사하였다. 조사결과 연구기간 동안 여름철 일최고기온의 평균 및 일정 임계치 이상의 고온 특이일의 빈도가 감소하는 경향을 나타냈다. 반면, 여름철 일최저기온의 평균은 지속적으로 상승하여 결과적으로 이 지역의 여름철 일교차의 평균이 급격히 감소하는 경향을 보였다. 일최고기온의 감소 추세는 1950년대 이래로 진행되어온 조림사업으로 인한 삼림 임목 축적량의 증가와 관련성이 있는 것으로 추정되었다. 이 밖에도 본 연구에서는 현재의 도시화 지구온난화가 지속된다는 가정 하에 기온극값 발생빈도와 장기적인 패턴변화를 예측하는 모델을 제시하였다.

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Changes of the Physicochemical Characteristics of Cassia tora L. by Roasting Conditions (결명자 종실의 볶음조건에 따른 이화학적 특성변화)

  • 김종국;김귀영
    • Journal of the East Asian Society of Dietary Life
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    • v.6 no.3
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    • pp.317-323
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    • 1996
  • Physicochemical characteristics of Cassia tora seeds roasted at different conditions were investigated. Intact Cassia tora seeds were composed of water 11.6% crude protein 13.1%, crude fat 4.4%, curde fiber 13.8%, N-free extract 47.2% and ash 4.9%. Stacking volume ratio was increased generally by swelling, but soluble solids were decreased by rosating process L and B values decreased conspicuously as roasting temperature increase, but $\Delta$E value increased. The content of anthraquinones was 1, 200mg% in unroasted Cassia tora seeds, it increased as roasting time and temperature increase and reached maxium amount at 19$0^{\circ}C$-30min, 21$0^{\circ}C$-20min. and 23$0^{\circ}C$-10min. agter that it decreased remarkably. Optimum roasting condition of Cassia tora seeds was 21$0^{\circ}C$-20min.

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Physicochemical Properties of Modified Rice Powder for Rice-Based Infant Foods III -Acetylated-coss linkage treatment on rice powder (반고형 이유식의 개발을 위한 변형 쌀가루 제조 및 이화학적 특성 III - 초산-처리 쌀가루)

  • Choi, Jung-Sun;Sohn, Kyung-Hee;Choi, Hee-Sun
    • Journal of the Korean Society of Food Culture
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    • v.12 no.5
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    • pp.469-475
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    • 1997
  • The modification of rice powder was attempted by treatment of acetic acid and epichlorohydrin to improve the functional properties of baby food. The initial gelatinization temperature of rice powder determined by amylograph was decreased from $79.5^{\circ}C$ to $63^{\circ}C$ by modification. The apparent and maxium viscosity of rice paste at $95^{\circ}C$ before and after modification were increased from 92B.U. to 236B.U. and from 100B.U. to 202B.U., respectively. The light transmittance of modified rice paste was increased from the temperature of $60^{\circ}C$ and by increasing the degree of substitution at the fixed temperature, while decrease more or less by the treatment of epichlorohydrin. The degree of retrogradation of the paste was decreased from 28.7 to 18.0 upon modification. The rate of syneresis of modified rice powder was decreased with increasing the drgree of substitution and ,the extend of epichlorohydrin treatment. Syneresis was not observed when acetylated rice powder whose DS value is 0.048 was treated with 0.25% of epichlorohydrin for the formation of cross-linkage. The addition of modified rice powder in preparation of semi-solid type infant food could improve the quality without lowering overall digestibility.

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Structural and ferroelectric characteristics of sol-gel $Pb(Zr_{1-x}Ti_x)O_3$ thin films according to the sintering conditions and Zr/Ti mol% (소성 조건과 Zr/Ti 몰비에 따른 졸겔 $Pb(Zr_{1-x}Ti_x)O_3$ 박막의 구조 및 강유전 특성)

  • 김준한;윤현상;박정흠;장낙원;박창엽
    • Electrical & Electronic Materials
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    • v.9 no.8
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    • pp.836-850
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    • 1996
  • In this study, we have analyzed structural analysis and measured ferroelectric characteristics of PZT thin films prepared by sol gel process with different sintering conditions and different Zr/Ti mot%. When the Zr mot% of PZT thin film was increased, it was found that the remanent. polarization and coercive field were decreased and increased, respectively. Also, the maxium dielectric constant of PZT(50/50) thin film was 786.8. We got double hysteresis(anti-fcrroelectric) curve from PbZrO$_{3}$ thin film. As heating rate goes up, pyrochlore phase of PZT thin film was decreased and dielectric and ferroelectric characteristics were improved. As a result of variation of sintering temperature and time 500.deg. C-800.deg. C and 5 sec.-8 hours, respectively, we got optimal sintering temperature and time. The optimium sintering temperature and time of conventional furnace method and rapid thermal processing method were 650.deg. C-700.deg. C for 30-60 minutes and 700.deg. C/20 seconds-2 minutes, respectively.

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Study on Meteorological Factors affecting Estimation of Chinese Cabbage Yield (배추 생산량 추정에 영향을 미치는 기상요소 연구)

  • Kim, Yong Seok;Shim, Kyo Moon;Jung, Myung Pyo;Choi, In Tae
    • Journal of Climate Change Research
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    • v.6 no.4
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    • pp.277-281
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    • 2015
  • A Chinese cabbage is one of important vegetables which accounts for more than 60 percent of leaf vegetable. However, cultivation area and yield of Chinese cabbage are steadily decreasing recently. Because meteorological changes destabilize the balance of Chinese cabbage, we need to study on meteorological factors affecting estimation of Chinese cabbage yield. So we conducted a panel analysis using mean temperature, maximum temperature, minimum temperature, precipitation and sunshine's duration from August to November for estimation of Chinese cabbage yield. As the results, we found that if the mean temperature of September increase by $1^{\circ}C$ the amount of production of Chinese cabbage per unit area was increased by 348.6 kg/10a. We also found that the mean temperature of October increased by 174.8 kg/10a, that of November 148 kg/10a, the difference between the maxium temperature and the minimum temperature of October equals 443.3 kg/10a. However, we found that the difference between the maximum temperature and the minimum temperature of November decreased 274.1 kg/10a.