• 제목/요약/키워드: high-temperature stability

검색결과 1,938건 처리시간 0.027초

엔진 윤활특성과 연비 상관성에 대한 연구 (Correlation between Lubrication Characteristics of Engine and Fuel Economy)

  • 오정준;차상엽;정도곤;이종주
    • Tribology and Lubricants
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    • 제30권3호
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    • pp.189-198
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    • 2014
  • This paper presents the results of an experimental investigation of the correlation between the lubrication characteristics of an engine and its fuel economy. Improving the lubrication characteristics of the engine oil is one of the most efficient ways to improve a car's fuel economy. The methods to accomplish this include lowering the viscosity, adding a friction modifier and optimizing the shear stability index of a viscosity index improver. In addition, it is necessary to use different methods to reduce the friction to individual lubrication areas, because different lubrication regimes are used for different engine parts. The experimental investigation in this study is based on design of experiments ; this paper presents the results of a modified Sequence VID test, which is an ASTM standard test used to measure the effects of automotive engine oils on the fuel economy of passenger cars. The results demonstrate the effects of the following lubrication factors on the fuel economy : the low temperature cranking viscosity, high-temperature high shear (HTHS) viscosity, friction modifier, polymer type and shear stability index of the viscosity index improver. Moreover, this study involves an analysis of variance based on design of experiments. The test results show that the HTHS viscosity, friction modifier and shear stability index of the viscosity index improver are more effective than the other factors. Therefore, lowering the viscosity, adding a friction modifier and optimizing the shear stability index of a viscosity index improver should be considered to improve fuel economy.

스퍼터 공정을 이용한 SiZnSnO 산화물 반도체 박막 트랜지스터의 증착 온도에 따른 특성 (Effect of Deposition Temperature on the Electrical Performance of SiZnSnO Thin Film Transistors Fabricated by RF Magnetron Sputtering)

  • 고경민;이상렬
    • 한국전기전자재료학회논문지
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    • 제27권5호
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    • pp.282-285
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    • 2014
  • We have investigated the structural and electrical properties of Si-Zn-Sn-O (SZTO) thin films deposited by RF magnetron sputtering at various deposition temperatures from RT to $350^{\circ}C$. All the SZTO thin fims are amorphous structure. The mobility of SZTO thin film has been changed depending on the deposition temperature. SZTO thin film transistor shows mobility of 8.715 $cm^2/Vs$ at room temperature. We performed the electrical stress test by applying gate and drain voltage. SZTO thin film transistor shows good stability deposited at room temperature while showing poor stability deposited at $350^{\circ}C$. As a result, the electrical performance and stability have been changed depending on deposition temperature mainly because high deposition temperature loosened the amorphous structure generating more oxygen vacancies.

Changes of Emulsifying and Foaming Properties of Soy Protein with an Calcium , HCI and Microbial IJ-3 Strain Enzyme

  • Park, Yang-Won;Kim, Young-Jeon
    • Preventive Nutrition and Food Science
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    • 제1권1호
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    • pp.53-58
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    • 1996
  • The characterstics of the soy protein curd(eczyme-, HCI- and Ca-surd) were shown by scanning electron micrographs and gel electrophoreis. The emulsion stability of enzyme-curd showed high value in the range of pH 2~10and wide range of temperature(20~8$0^{\circ}C$). While at the isoelectric point(pH5.0), the emulsion stability of the HCI-and Ca-curd was decreased remarkably, and the emulsion stability of temperature was reduced quickly to the 60% and 40% at the 4$0^{\circ}C$. The foam stability of enzyme-curd was slightly higher than that HCI-and CA-curd in all ranges of pH and temperature. The feature of SEM of enzyme-cured produced degradation products faster than that of the HCI- and Ca-curd.

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TiAl 합금의 CaO 도가니 유도용융 및 정밀주조 (CaO Crucible Induction Melting and Investment Casting of TiAl Alloys)

  • 김명균;성시영;김영직
    • 한국주조공학회지
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    • 제22권2호
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    • pp.75-81
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    • 2002
  • The main objectives were to investigate the suitability of CaO crucible for melting TiAl alloys and to develop investment mold for investment casting of TiAl alloys. TiAl alloy specimen were prepared by plasma arc furnace under argon atmosphere. After melting of TiAl alloy using CaO crucible, the results showed that there is little contamination of oxygen in the TiAl bulk. Conventional vacuum induction furnaces can be readily adaptable to produce cast parts of TiAl without high skilled techniques. The determination of optical metallography and microhardness profiles in investment cast TiAl alloy rods has allowed the gradation of the relative thermal stability of the oxides examined. The molds used for the present study were $ZrO_2$, $Al_2O_3$, CaO stabilized $ZrO_2$ and $ZrSiO_4$. Even although high temperature of mold preheating, $Al_2O_3$ mold is a promising mold material for investment casting of TiAl alloys in terms of thermal stability, cost and handling strength. It is important to take thermal stability and preheating temperature of mold into consideration for investment casting of TiAl alloys.

Advanced Lubricants for Heat Engines

  • Hsu, S.M.;Li, H.;Perez, J.M.;Ku, C.S.;Wang, J.
    • Tribology and Lubricants
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    • 제11권5호
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    • pp.47-54
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    • 1995
  • An advanced liquid lubricants for heat engines has been developed and tested successfully in a prototype engine. The lubricant possesses superior oxidation stability and high temperature stability and is capable of surviving for a minimum of three minutes at 425$^{\circ}$C (800$^{\circ}$C) at the ring zone and maintains stability at an oil sump temperature of 171$^{\circ}$C. The lubricant has been evaluated by the Cummins Engine Co. Out of a field of several dozens of lubricant, six lubricant was selected for a prototype 200 hours endurance testing. The NIST lubricant was one of the two lubricants that successfully finished the endurance testing. This paper describes the key lubricant considerations including oxidation and thermal stability, volatility, deposit control. The engine test conditions and the results will be presented.

고온고압조건하에서의 핵연료 피복관 지지스프링의 하중-변위 특성 분석 (Analysis of Grid Spring Characteristic of Fuel Assembly in High Temperature and High Pressure Environment)

  • 이영호;김형규;정연호
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2004년도 춘계학술대회
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    • pp.2146-2150
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    • 2004
  • To evaluate the variation of spring stiffness in nuclear plant operating condition, load-displacement tests ($P-{\delta}$ test) were performed using two kinds of space grid springs in high temperature and high pressure water. With increasing temperature, stiffness of each spring gradually decreased except $100{\sim}150^{\circ}C$. It is apparently showed that spring with convex shape had a relatively high stability of spring stiffness at high temperature compared with I-shaped spring. It is suggested that the variation of spring stiffness with temperature and spring shape should be considered as an important variable in the design and analysis of the fuel assembly.

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디지털 온도보상 수정 발진기에 관한 연구 (A Study on Digital Temperature Compensated Crystal Oscillator)

  • 이창석;박영철;차균현
    • 한국통신학회논문지
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    • 제18권5호
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    • pp.739-745
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    • 1993
  • 이동통신 기기에서 온도에 대해서 고안정의 주파수 합성기를 구현함은 중요하다. 그런데, 고안정의 주파수 합성기를 구현하기 위해서는 기준 주파수를 제공하는 발진기가 온도에 대해서 안정해야만 한다. 본 논문에서는 이러한 필요성에 따라서 디지털 방식을 이용한 TCXO가 구현된다. DTCXO는 온도 감지부, 제어부, VCXO로 나뉜다. 구현된 DTCXO의 주파수 안정도는 평균 0.94ppm이다. 이는 아나로그 방식을 이용한 TCXO의 안정도인 2.5ppm과 비교해볼 때, 향상된 결과이다.

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Fabrication of Micromachined Ceramic Thin-Film Pressure Sensors for High Overpressure Tolerance

  • Chung, Gwiy-Sang
    • 한국반도체및디스플레이장비학회:학술대회논문집
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    • 한국반도체및디스플레이장비학회 2002년도 추계학술대회 발표 논문집
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    • pp.59-63
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    • 2002
  • This paper reports on the fabrication process and characteristics of a ceramic thin-film pressure sensor based on Ta-N strain-gauges for harsh environment applications. The Ta-N thin-film strain-gauges are sputter-deposited on a thermally oxidized micromachined Si diaphragms with buried cavities for overpressure tolerance. The proposed device takes advantage of the good mechanical properties of single-crystalline Si as a diaphragm fabricated by SDB and electrochemical etch-stop technology, and in order to extend the temperature range, it has relatively higher resistance, stability and gauge factor of Ta-N thin-films more than other gauges. The fabricated pressure sensor presents a low temperature coefficient of resistance, high-sensitivity, low non-linearity and excellent temperature stability. The sensitivity is 1.21 ~ 1.097 mV/V.kgf/$\textrm{cm}^2$ in temperature ranges of 25~ $200^{\circ}C$ and a maximum non-linearity is 0.43 %FS.

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실리사이드 복합 공정합금의 미세조직 및 고온 압축특성 (A Study on Microstructure and High Temperature Compression Characteristics of Silicide Eutectics)

  • 이재현;조용성;강수현;박장식;김상식
    • 한국주조공학회지
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    • 제17권1호
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    • pp.85-92
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    • 1997
  • There has been a considerable interest to develop the silicide alloys as high temperature structural materials because of their excellent high temperature stability and strength, however, their lack of room temperature ductility and toughness was a main obstacle for the application. In order to improve ductility while maintaining good high temperature properties, possible refractory metal-silicide eutectic alloys composed of fine two phases were prepared by VAR(Vacuum Arc Remelting). Three silicide alloys, $Nb-Nb_3Si$, $Ti-Ti_5Si_3$, $V-V_3Si$, were selected as prospecting silicide eutectics and those high temperature characteristics were evaluated by high temperature compression test.

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CaCl2-CaF2-CaO 용융염에서 YSZ 세라믹의 고온 안정성에 미치는 성형공정의 영향 (Effect of Pressing Process on the High-Temperature Stability of Yttria-Stabilized Zirconia Ceramic Material in Molten Salt of CaCl2-CaF2-CaO)

  • 김완배;권숙철;조수행;이종현
    • 한국재료학회지
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    • 제30권4호
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    • pp.176-183
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    • 2020
  • The high-temperature stability of YSZ specimens fabricated by die pressure and cold isostatic press (CIP) is investigated in CaCl2-CaF2-CaO molten salt at 1,150 ℃. The experimental results are as follows: green density 46.7 % and 50.9 %; sintering density 93.3 % and 99.3 % for die press and CIP, respectively. YSZ foremd by CIP exhibits higher stability than YSZ formed by die press due to denseness dependency after high-temperature stability test. YSZ shows peaks mainly attributed to CaZrO3, with a small t-ZrO2 peak, unlike the high-intensity tetragonal-ZrO2 (t-ZrO2) peak observed for the asreceived specimen. The t-ZrO2 phase of YSZ is likely stabilized by Y2O3, and the leaching of Y2O3 results in phase transformation from t-ZrO2 to m-ZrO2. CaZrO3 likely forms from the reaction between CaO and m-ZrO2. As the exposure time increases, more CaZrO3 is observed in the internal region of YSZ, which could be attributed to the inward diffusion of molten salt and outward diffusion of the stabilizer (Y2O3) through the pores. This results in greater susceptibility to phase transformation and CaZrO3 formation. To use SOM anodes for the electroreduction of various metals, YSZ stability must be improved by adjusting the high-density in the forming process.