• 한국전기전자재료학회논문지
• /
• 제18권2호
• /
• pp.148-152
• /
• 2005

Atmospheric low-temperature plasma was produced using dielectric barrier discharge (DBD) plate-type plasma reactor and high frequency of 13.56 Hz. The surfaces of polyimide films for insulating and packaging materials were treated by the atmospheric low-temperature plasma. The contact angle of 67$^{\circ}$ was observed before the plasma treatment. The contact angle was decreased with deceasing the velocity of plasma treatment. In case of oxygen content of 0.2 %, electrode gap of 2 mm, the velocity of plasma treatment of 20 mm/sec, and input power of 400 W, the minimum contact angle of 13$^{\circ}$ was observed. The chemical characteristics of polyimide film after the plama treatment were investigated using X-ray photoelectron spectroscopy (XPS), and new carboxyl group bond was observed. The surfaces of polyimide films were changed into hydrophilic by the atmospheric low-temperature plasma. The polyimide films having hydrophilic surface will be very useful as a packaging and insulating materials in electronic devices.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2007년도 춘계학술대회B
• /
• pp.2228-2231
• /
• 2007

Water gas shift reactor in fuel processing is an important part that converts carbon monoxide into hydrogen. Fuel processing system for PEMFC usually has two stages of WGS reactors, which are high temperature and low temperature shifter. In this study we prepared noble metal catalysts and compared their performances with that of a commercial iron chromium oxide catalyst. Noble metal catalysts and the commercial catalyst showed quite different temperature dependence of carbon monoxide conversion. The conversion of carbon monoxide at the commercial catalyst was very low at medium temperature(${\sim}300^{\circ}C$) and increased rapidly as temperature increased while the conversion at noble metal catalysts was high in the medium temperature range and decreased as temperature increased, which is thermodynamically expected. Their characteristics agreed well with the literature published, and we are accomplishing further study for improvement of the noble metal catalysts.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1999년도 하계학술대회 논문집 D
• /
• pp.1818-1820
• /
• 1999

This paper presents direct ${\mu}c$-Si:H thin film growth on the glass substrates using RPCVD system (remote plasma chemical vapor deposition) in low temperature. Hydrogenated micro-crystalline silicon deposited by RPCVD system in low temperature is very useful material for photovoltaic devices, sensor applications, and TFTs (thin film transistors). Varying the deposition conditions such as substrate temperature, gas flow rate, reactive gas ratio $(SiH_4/H_2)$, total chamber pressure, and rf power, we deposited ${\mu}c$-Si:H thin films on the glass substrates (Corning glass 1737). And then we measured the structural and electrical properties of the films.

• 전기학회논문지
• /
• 제65권10호
• /
• pp.1694-1696
• /
• 2016

Present thin film solar cells with hydrogenated amorphous silicon oxide (a-SiO:H) as an absorber suffer from low fill factor(FF) of 61~64 [%] in spite of its benefits related to high open circuit voltage ($V_{oc}$). Since degraded quality of a-SiO:H absorber by alloying with oxygen can affect the FF, we aimed to achieve high photosensitivity by minimizing $CO_2$ gas addition. Improving optical gap($E_{opt}$) has been attained by strong hydrogen dilution combined with lowering substrate temperature down to 100 [$^{\circ}C$]. Small amount of the $CO_2$ was added in order to disturb microcrystalline formation by high hydrogen dilution. The developed a-SiO:H has high photosensitivity (${\sim}2{\times}10^5$) and high $E_{opt}$ of 1.85 [eV], which contributed to attain remarkable FF of 74 [%] and high $V_{oc}$ (>1 [V]). As a result, high power conversion efficiency of 7.18 [%] was demonstrated by using very thin absorber layer of only 100 [nm], even though we processed all experiment at extremely low temperature of 100 [$^{\circ}C$].

• 소성∙가공
• /
• 제14권3호
• /
• pp.277-281
• /
• 2005

LTCC(Low temperature co-fired ceramic) is being recognized as a significant packaging material of electrical devices for the advantages such as relatively low temperature being needed for process, low conductor resistance and high printing resolution. In the process of LTCC electrical devices, the punched via-hole quality is one of the most important factors on the performance of the device. However, its mechanism is very complicated and optimization of the process seems difficult. In this paper, to clarify the process, via-hole punching experiments were carried out and the punched holes were examined in terms of their burr formation. The effects of thickness of PET sheet, ceramic sheet and punch-to- die clearance on via-hole quality were also discussed. Optimum process conditions are proposed and a factor $\kappa$ is introduced to express effect of the process variables.

• 한국유체기계학회 논문집
• /
• 제14권1호
• /
• pp.42-47
• /
• 2011

Measurement uncertainty analysis of fuel flow using turbine flowmeter was performed for the case of altitude engine test. SAE ARP4990 was used as the fuel flow calculation procedure, as well as the mathematical model for the measurement uncertainty assessment. The assessment was performed using Sensitivity Coefficient Method. 11 parameters involved in the calculation of the flow rate were considered. For the given equipment setup, the measurement uncertainty of fuel flow was assessed in the range of 1.19~1.86 % for high flow rate case, and 1.47~3.31 % for low flow rate case. Fluctuation in frequency signal from the flowmeter had the largest influence on the fuel flow measurement uncertainty for most cases. Fuel temperature measurement had the largest for the case of low temperature and low flow rate. Calibration of K-factor and the interpolation of the calibration data also had large influence, especially for the case of very low temperature. Reference temperature, at which the reference viscosity of the sample fuel was measured, had relatively small contribution, but it became larger when the operating fuel temperature was far from reference temperature. Measurement of reference density had small contribution on the flow rate uncertainty. Fuel pressure and atmospheric pressure measurement had virtually no contribution on the flow rate uncertainty.

• 한국작물학회지
• /
• 제29권2호
• /
• pp.152-156
• /
• 1984

본시험은 저온 조건에서 우리 나라 보리 주요 품종의 발아력과 출현력의 품종간 차이를 구명하고자 실시하였던 바 그 결과를 요약하면 다음과 같다. 1. 발아세는 온도가 $4^\{\circ}C$에서 $3^{\circ}C$씩 상승할수록 70에서 10~45 정도 증가되었고 $7^{\circ}C$에서 변이가 가장 컸으며, 저온(4$^{\circ}C$)에서 백동, 남해보리, 강보리, 부흥 등의 발아력이 좋았다. 2. 출현률은 온도가 $4^{\circ}C$에서 $7^{\circ}C$로 상승할 때 84%에서 92%로 증가하였으며 출현력(ERI)은 영산보리, 광성, 백동이 불량하였으며 부호보리, 남해보리, 오월보리, 알보리, 사천 6호 등이 양호하였다. 3. 저온에서 발아력과 출현력 및 기타 형질과는 관련성이 없었으나, $4^{\circ}C$ 와 $7^{\circ}C$구간에 출현력과 건물중은 서로 상관이 높았다. 4. 따라서 저온 조건에서 보리 종자의 발아력과 출현력은 품종간 변이가 컸으며 발아력으로 출현역을 추정할 수는 없었다. 또한 저온 출현력을 검정하는데 ERI와 건물중을 같이 이용하면 좀더 정확할 것으로 생각된다.

• 한국섬유공학회:학술대회논문집
• /
• 한국섬유공학회 2003년도 봄 학술발표회 논문집
• /
• pp.434-435
• /
• 2003

Physicochemical properties of a polymer surface significantly affect adhesion, wetting, and dyeing properties. In recent years, low temperature plasma technology has been widely used for surface modification of polymers. Surface fluorination by low temperature plasma treatment has been employed to improve the water and oily repellency of textile fabrics. However, very few results have been reported on soil release properties of the oxygen plasma treated textile fabrics. (omitted)

• 한국도로학회논문집
• /
• 제14권5호
• /
• pp.75-83
• /
• 2012

PURPOSES: Suggestion of asphalt binder constitutive model based on time-temperature superposition principle and overstress concept in order to describe behavior of asphalt binders. METHODS: A series of temperature sweep tests and multiple stress creep and recovery(MSCR) tests are performed to verify the applicability of time-temperature superposition principle(t-Ts) and to develop viscoelastoplastic constitutive equation based on overstress concept. For the tests, temperature sweep tests at various high temperature and various frequency and MSCR test at $58^{\circ}C$, $64^{\circ}C$ $70^{\circ}C$, $76^{\circ}C$, and $82^{\circ}C$ are performed. From the temperature sweep tests, dynamic shear modulus mastercurve and time-temperature shift function are built and the shift function and MSCR at $58^{\circ}C$ are utilized to determine model coefficients of VBO model. RESULTS: It is observed that the time-temperature shift function built at low strain level of 0.1% is applicable not only to 1.0% strain level temperature sweep test but also maximum 500,00% strain level of MSCR test. As well, the modified VBO model shows perfect prediction on MSCR measured strain at the other temperatures. CONCLUSIONS: The Time-temperature superposition principle stands hold from very low strain level to very high strain level and that the modified VBO model can be applicable for various range of strain and temperature region to predict elastic, viscoelastic, and viscoplastic strain of asphalt binders.

• 한국정밀공학회지
• /
• 제16권8호
• /
• pp.162-169
• /
• 1999

Fourier heat conduction law becomes invalid for the situations involving extremely short time heating, very low temperatures and fast moving heat source(or crack), since the wave nature of heat propagation becomes dominant. For these conditions, the modified heat conduction equation with the finite propagation speed of heat in the medium could be applied to predict heat flux and temperature distributions. In this study, temperature distributions at the vicinity of a very fast moving heat source are investigated numerically. Thermal fields are characterized by thermal Mach numbers(M) defined as the ratio of moving heat source speed to heat propagation speed in the solid. In the transonic and supersonic ranges($M{\ge}1$), thermal shocks are shown, which separate the heat affected zone from the thermally undisturbed zone.