• Journal of Astronomy and Space Sciences
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• 제21권1호
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• pp.29-38
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• 2004

VLBI(Very Long Baseline Interferometer)에서 요구되는 고위상 안정도를 갖는 국부발진기를 사용하여 초저잡음 Q-band우주 전파 수신기를 개발하였다. 냉각용 HEMT 중폭기를 사용하여, 관측 주파수 범위인 420㎓에서 44㎓까지의 대역폭에서는 65K정도의 수신기 잡음 온도를 얻었으며, 390㎓ -46㎓의 대역폭에서는 l00k 이하의 잡음 온도를 얻었다. SiO분자선 관측이 주된 목적이며, 이 대역에서 얻어진 수신기 잡음온도는 독일$.$일본 전파천문대에서 개발된 수신기보다 우수한 성능을 나타낸다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 추계학술발표대회
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• pp.44.2-44.2
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• 2009

Polycrystalline materials suchas yttria and alumina have been applied as a plasma resisting material for the plasma processing chamber. However, polycrystal line material may easily generate particles and the particles are sources of contamination during the plasma enhanced process. Amorphous material can be suitable to prevent particle generation due to absence of grain-boundaries. We manufactured nitrogen-containing $SiO_2-Al_2O_3-Y_2O_3$ based glasses with various contents of silicon and fixed nitrogen content. The thermal properties, mechanical properties and plasma etching rate were evaluated and compared for the different composition samples. The plasma etching behavior was estimated using XPS with depth profiling. From the result, the plasma etching rate highly depends on the silicon content and it may results from very low volatile temperature of SiF4 generated during plasma etching. The silicon concentration at the plasma etched surface was very low besides the concentration of yttrium and aluminum was relatively high than that of silicon due to high volatile temperature of fluorine compounds which consisted with aluminum and yttrium. Therefore, we conclude that the samples having low silicon content should be considered to obtain low plasma etching rate for the plasma resisting material.

• Journal of Korean Vacuum Science & Technology
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• 제7권2호
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• pp.33-38
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• 2003

Fluorinated amorphous carbon thin films (a-C:F) for the use of low dielectric constant intermetallic layer dielectrics are deposited by plasma enhanced chemical vapor deposition with $C_4$F$_{8}$ and Si$_2$H$_{6}$/He gas mixture as precursors. To characterize and improve film properties, we changed various conditions such as deposition temperature, and RF power, and we measured the thickness and refractive indexes and FT-IR spectrum before and after annealing. At low temperatures the film properties were very poor although the growth rate was very high. On the other hand, the growth rate was low at high temperature. The growth rate increased in accordance with the deposition pressure. The dielectric constants of samples were in the range of 1.5∼5.5∼5.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.67-70
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• 2007

LTCC (Low Temperature Co-fired Ceramic) has been emerged as a promising technology in packaging industry. In this technology the lamination and the sintering process are very important because they change the permittivity of ceramics and the dimension of metal pattern which have influences on electric property. In this paper we studied on influence of the permittivity and the dimension change by lamination pressure and sintering temperature of LTCC process. As a results, permittivity increase along with increasing of lamination pressure and sintering temperature.

• 소성∙가공
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• 제16권5호통권95호
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• pp.396-400
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• 2007

LTCC(Low Temperature Co-fired Ceramic) which offers a good performance to produce multilayer structures with electronic circuits and components has emerged as an attractive technology in the electronic packaging industry. In LTCC module fabrication process, the lamination and the sintering are very important processes and affect the electrical characteristics of the final products because the processes change the permittivity of ceramics and the dimension of the circuit patterns which have influences on electronic properties. This paper discusses the influence of lamination pressure and sintering temperature on the permittivity and the dimensional change of LTCC products. In the present investigation, it is shown that the permittivity increases along with increasing of the lamination pressure and the sintering temperature.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.66-70
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• 2001

The combustion characteristics have been investigated to develop the low $NO_{x}$ gas turbine combustor. The lean premixed combustion technology was applied to reduce the $NO_{x}$ emission. Also, the conventional combustor was designed and tested for the baseline of low $NO_{x}$ combustor performance. The test was conducted at the condition of high temperature and ambient pressure. The combustion air which has the temperature of 500K were supplied to the combustor through the air preheater. The temperature and emissions of $NO_{x}$ and CO were measured at the exit of combustor. The premixing chamber can be operated very lean condition of equivalence ratio around 0.35. The $NO_{x}$ was decreased with decreasing the equivalence ration. The CO was decreased with decreasing the equivalence ratio, but the CO was increased with decreasing the equivalence ratio below 0.45. But, at the very lean condition of equivalence ratio below 0.35 both NOx and CO were increased because of the flame unstability. The $NO_{x}$ was decreased slightly and CO was increased with increasing inlet air flowrate. This results can be used to determine the size of combustor. The low $NO_{x}$ combustor has lower values of $NO_{x}$ and CO compared with conventional one. Consequently the performance of combustor shows the possibility of the application to the gas turbine system.

• 한국안전학회지
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• 제13권4호
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• pp.213-220
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• 1998

Welding structures will be occurred sudden crack or failure by reduced fracture toughness in case of low temperature. To protect these unstable fracture is very important. Because fracture of welding part come from welding faults or residual stress, critical stress intensity factors are acquired at temperatures between $22^{\circ}C$ and $-70^{\circ}C$ from base metal, welding metal and H.A.Z. It was studied effectiveness of annealing and affection of residual stress under low temperatures. In case of fracture toughness test, it showed that fracture toughness value decreased, according to the decrease of temperature. Expecially In case that compressive residual stress was existed, $K_C$ increased.

• JSTS:Journal of Semiconductor Technology and Science
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• 제15권2호
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• pp.249-254
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• 2015

Solution-derived amorphous indium-gallium-zinc oxide (a-IGZO) thin-film-transistor (TFTs) were developed using a microwave irradiation treatment at low process temperature below $300^{\circ}C$. Compared to conventional furnace-annealing, the a-IGZO TFTs annealed by microwave irradiation exhibited better electrical characteristics in terms of field effect mobility, SS, and on/off current ratio, although the annealing temperature of microwave irradiation is much lower than that of furnace annealing. The microwave irradiated TFTs showed a smaller $V_{th}$ shift under the positive gate bias stress (PGBS) and negative gate bias stress (NGBS) tests owing to a lower ratio of oxygen vacancies, surface absorbed oxygen molecules, and reduced interface trapping in a-IGZO. Therefore, microwave irradiation is very promising to low-temperature process.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.199-204
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• 2000

A low temperature differential model stirling engine is manufactured, and its operation characteristics are measured and analyzed by SIMPLE analysis model, in which heat transfer processes are simply considered. The heat transfer coefficients between working fluid and heat sources in the analysis are estimated by comparing the P-V diagrams by experiment and by analysis. This result may be very useful for further design and manufacture of model Stilting engines as well as real engines because it provides a comparatively correct predictions of the operation conditions and power output. It will be also conveniently used as an educational material for mechanical engineering students because it can be a nice example of optimal design process to decide the phase angle and compression ratio of engine design with a simple but realistic simulation.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1994년도 특별강연 및 춘계학술발표 개요집
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• pp.39-43
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• 1994

The effects of ageing treatment on the mechanical properties of two Cu-bearing HSLA(High Strength Low Alloy) steels, HSLA-A and HSLA-B ,were studied by means of SEM, TEM, tensile, charpy impact and hardness tests. These steels showed excellent combination in strength and toughness at an ageing of $650^{\circ}C$ by the precipitation of $\varepsilon$-Cu and low carbon alloying. The peak strength was achieved at an ageing of 50$0^{\circ}C$ in both steels, while the impact energy was very low in this peak strength. With ageing temperature above this temperature, strength was decreased whereas impact energy increased. A marked increase in hardness above 675$^{\circ}C$ was associated with the formation of “M-A constituents” which forms during cooling from austenite-ferrite two phase region. The impact transition temperature of HSLA-A and HSLA-B steels were -l$25^{\circ}C$ and -145$^{\circ}C$, respectively.