• The Korean Journal of Ceramics
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• v.3 no.2
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• pp.92-95
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• 1997

Because of the novel characteristics such as chemical stability, hardness, electrical resistivity and thermal conductivity, diamond-like carbon (DLC) film is a suitable material for the passivation layers. For this purpose, using the PECVD, DLC films were synthesized at room temperature. The adhesion and the hardness of the DLC films deposited on Si an SiO2 substrate were measured. The resistivity of 5.3$\times$$10^8$$\Omega$.cm was measured by automatic spreading resistance probe analysis method. The thermal conductivities of different DLC films were measured and compared with that of phospho silicate glass (PSG) film which is commonly used as passivation layers. The thermal conductivity of DLC film was improved by increasing hydrogen flow rate up to 90 sccm and was better than that of PSG film. The patterning techniques of the DLC film developed using the RIE and the lift-off method to form 5$\mu\textrm{m}$ line. Finally, the thermal characteristics of the power transistor with the DLC film as passiviation layer was analyzed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.9
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• pp.1914-1922
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• 2002

Operating test of power-transmission plastic spur gears were performed inspecting both characteristics of friction-wear and endurance, and suggesting endurance improvement method that either drills internal holes of tooth or inserts metallic pin in the internal hole of tooth and verifying this newly-provided method. In case of acetal gears, amount of friction-wear is observed to increase by development of plastic deformation and increase of tooth stiffness due to brittle material property of acetal. To the contrary, in case of nylon gears, suggested method is shown to drop down the tooth temperature for about 3∼10$^{\circ}C$ than original gear, thus amount of wear is reduced by over 30% and operating lift prolonged by more than 200%. Hence, suggested method is proved to be practically applicable to the plastic gears made by soft polymers such as Nylon.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.10a
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• pp.59-65
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• 2003

Four kinds of $Si_3N_4$-based ceramic cutting tools with different sintering time were fabricated to investigante the effect of sintering time on the microstructure, mechanical properties, grain sizes and the cutting performance. An endeavor was also made to determine the relation among mechanical property, Brain size and tool life. $Si_3N_4$ home made cutting tool sintered for 1 hour under $1760^{\circ}$ temperature and 25MPa pressure showed the best cutting performance among selected ceramic tools during machining both Bray cast iron and heat treated SCM440. Multiple linear regression model was used to estimate the tool lift from mechanical property, grain size and showed good result. It was also shown that hardness imposed the biggest offect on tool life.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.6
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• pp.1669-1678
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• 1990

The annular and coaxial swirl flows between which LPG is supplied was selected to study the swirling flames in double co-swirl flows. The objective of this study is to research into the effects of double co-swirl flow conditions on the stability limit, the reverse flow boundary, and the time mean temperature distributions of the swirling flames. The increase of swirl intensity of axial flow makes the stability limit decrease, but the annular swirl flow (SM>0.5) makes stability and swirl intensity of axial flow increase, And the existence of axial swirl flow makes flame intensive and small in size, and this may be applicable to the design of high power compact combustor.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.273-274
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• 2006

The sea is origin of all lift, and 90% of the all living organisms are in the sea. The biosynthesis is very different. Many organisms are kept on a lower or developed to another evolutionary level than on shore. Our society is increasing demand and need for marine food and this food has to product at onshore or offshore fish farming sites. Ocean fish farms have a special operation properties such as a good quality water, net cage, sheltered locations and feeding system. The farming site is controlled and monitored for fish welfare as ammonia($NH_3$), temperature, the speed of a running fluid. Specially, the fish farm is seriously influenced by ammonia. In this paper, $NH_3$ monitoring system for ocean fish farm is researched for the suitable fish farming sites, and test equipment is designed for achieving practical data. The equipment wit monitoring algorithm is expected to the useful system for ocean fish farm.

• The KSFM Journal of Fluid Machinery
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• v.11 no.2
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• pp.20-28
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• 2008

Recently, butterfly valves are used as control valves for industrial process. However, there are not so many reports on cryogenic butterfly valves in spite of broad application in LNG storage station and LNG carriers. Present study is focused on the investigation of the detailed hydrodynamic and aerodynamic characteristics of cryogenic butterfly valves to contribute to the operation during the handling on LNG transportation system, and to the practical utilization in design of butterfly valves and actuators. The results show that large recirculation vortices in the region downstream of the valve are founded and the cavitation flows are intensively generated on the surface of valve disc at the relatively small opening angle. The aerodynamic characteristics, lift, drag and torque, acting on the valve disc are calculated. The pressure distribution and the pressure loss coefficient of the cryogenic butterfly valve show almost similar pattern with those of the butterfly valve which is used on the normal temperature.

• Journal of the Korean Society of Combustion
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• v.21 no.3
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• pp.7-15
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• 2016

The fuel in conventional liquid fuel combustor is atomized by spray method for high efficiency and low emissions. To improve the overall fuel efficiency and lower pollutant emissions in liquid fuel combustion systems, the effective spatial and temporal separation of droplet evaporation from normal spray process is needed. In this paper, the recuperation of high temperature burnt gas for fuel evaporation was proposed to develop a cylindrical premixed combustor. The recuperation process using U shaped tube is effective to evaporate the liquid fuel. The results show that the flame mode is changed into red radiation flame, blue flame and lift off flame with decreasing equivalence ratio as gas fuel combustion mode. In particular, the blue flame is found to be very stable at heating load 9.2 kW and equivalence ratio 0.731. NOx was measured blow 105 ppm ($O_2$ zero base) from equivalence ratio 0.705 to 0.835. CO which is a very important emission index in liquid fuel combustor was observed below 5 ppm ($O_2$ zero base) under the same equivalence region.

• Journal of the korean Society of Automotive Engineers
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• v.10 no.6
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• pp.72-84
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• 1988

Engine performance is one of the main objectives specified at the beginning of a new engine design project. The cycle simulation for SI engine is based on the zero-dimensional gas exchange model and a heat release expression by Viebe. This program also requires minimum input data and takes only a short time to run. Heat transfer from cylinder transfer formula. The flow coefficient (effective area) is calculated from valve lift using the standard flow coefficient curve and engine friction is calculated from the Millington and Hartles' engine friction formula. The chemical species considered in burned gas are 6 species CO, CO, H$_{2}$, H$_{2}$O, $O_{2}$, N$_{2}$ and the cylinder pressure, homogeneous cylinder temperature, gas composition and burned fraction are calculated at each crank angle through the cycle. To check the validity and accuracy, experimental study was done with 3 engines for measuring cylinder pressure, indicated mean effective pressure, brake mean effective pressure and air flow rate, etc. Despite its simple assumptions, cycle simulation showes excellent breathing and performance correlation when compared with data of tested engines, and have been proved useful in engine design.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.8
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• pp.319-324
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• 2003

AIN thin films are deposited on Si (100) and $SiO_2$/Si substrates by using an RF magnetron sputtering method and by changing the conditions of deposition variables, such as RF power, $N_2$/Ar flow ratio, and substrate temperature ($T_sub$). For all the deposited AIN films, XRD Peak patterns are monitored to examine the effect of deposition condition on the crystal orientation. Highly (002)-oriented AIN films are obtained at following nominal deposition conditions; RF Power : 350W, $N_2$/Ar ratio = 10/20, T$_{sub}$ : $250^{\circ}C$, and working pressure = 5mTorr, respectively. AIN-based SAW devices are fabricated using a lift-off method by varying the thickness of AIN layer. Insertion losses and side-lobe rejection levels of fabricated SAW devices are extracted from their frequency response characteristics, which are also compared in terms of AIN thickness and substrate. Relationships between the film properties of AIN films and the frequency responses of SAW devices are discussed. It is concluded from the experimental results that the (002)-preferred orientation as well as the surface roughness of AIN film may play a crucial role of determining the device performances of AIN-SAW devices.s.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.2
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• pp.9-17
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• 2007

The performance test of recirculation line in propellant feeding system was carried out. Liquid oxygen was used as cryogenic propellant and helium was used as recirculation promotion gas. Tests were done in cases at atmospheric pressure and at pressure of 4 barg in the ullage space of propellant tank. Liquid oxygen recirculation flowrate with helium injection flowrate and temperature distribution along the line were measured. There was appropriate helium injection flowrate for gas-lift recirculation system. Test data were used to make calculation program by test data correlation method. In this paper the procedure of calculation was presented and the results were compared to test data.