• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.06a
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• pp.51-60
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• 2000

High-speed milling machine is being sold mainly in the market of die and mold industries, because it reduces machining time greatly as proportion to the spindle speed of machine tool. From the experimental milling tests, it has been cleared that the ball end mill is quite suitable for high speed milling and also tool wear reduces in higher speed milling condition. And a new milling concept with ultra high speed over 100, 000 rpm is proposed for solving the various problems such as NC cutter path generation and NC feed conformity etc.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.1
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• pp.97-104
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• 2015

This study is a part of the high pressure injection system development on the Turbo GDI engine in order to reduce smoke emission in case of using the low volatile(high DI) fuel which is used as normal gasoline fuel in the US market. Firstly, theoretical approach was done regarding gasoline fuel property, performance, definition of particle matters and its creation as well as problems of the high DI fuel. In this experimental study, 2L Turbo GDI engine was selected and optimized system parameter was inspected by changing fuel, fuel injection mode (single/multiple), fuel pressure, distance between injector tip and combustion chamber, start of injection, intake valve timing in engine dyno at all engine speed range with full load. In case of normal gasoline fuel, opacity was contained within 2% in all conditions. On the other hands, in case of low volatile fuel (high DI fuel), it was confirmed that the opacity was rapidly increased above 5,000 rpm at 14.5 ~ 20 MPa of fuel pressure and there were almost no differences on the opacity(smoke) between 17 MPa and 20 MPa fuel pressure. According to the SOI retard, smoke decrease tendency was observed but intake valve close timing change has almost no impact on the smoke level in this area. Consequently, smoke decrease was observed and 16% at 6000rpm respectively with injector washer ring installed. By removing injector washer to make injector tip closer to the combustion chamber, smoke decrease was observed by 46% at 5,500 rpm, 42% at 6,000 rpm. It is assumed that the fuel injection interaction with cylinder head, piston head, intake and exhaust valve is reduced so that impingement is reduced in local area.

• Journal of Korea Foundry Society
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• v.41 no.2
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• pp.127-131
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• 2021

Based on its good compatibility with high-temperature environments, the Ti-48Al-2Cr-2Nb alloy is used for high-temperature materials of industrial equipment. In this study, a Ti-48Al-2Cr-2Nb alloy turbocharger turbine wheel was fabricated by a vacuum centrifugal casting method. The conditions that prevent misrun defects of the turbocharger turbine wheel blade from centrifugal casting using alumina molds were investigated. The microstructure of the alloy prepared by vacuum centrifugal casting was studied by means of optical microscopy (OM), with a micro-Vickers hardness analyzer (HV), by X-ray diffraction (XRD) and by SEM-EDS. The HV and SEM-EDS examinations of the as-cast Ti-48Al-2Cr-2Nb alloy showed that the thickness of the oxide layer (α-case) was typically less than 50 ㎛. At a high preheating temperature of 1,100℃, a moderate RPM of 260, and with an alumina mold with a large gate size, there were almost no misrun defects. Therefore, it was confirmed that a Ti-48Al-2Cr-2Nb alloy turbocharger turbine wheel with fewer misrun defects could be achieved through a high preheating temperature, a moderate RPM, a large gate size and an alumina mold to suppress the formation of alpha-case components.

• Journal of Navigation and Port Research
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• v.36 no.1
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• pp.35-41
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• 2012

In this paper, we analyze the current submarine cooling system and study control algorithms for cooling system. Cooling system are installed in the submarine propulsion motor to protect the motor from high-temperature by iron loss and copper loss. The cooling system control the sea water and fresh water pump RPM to keep the motor temperature stable by external environment and motor RPM holding time. The cooling system simulation program is made for checking the cooling performance, and simulation is performed with various control strategy. The results with proposed cooling algorithm is shown to improve the thermal stability and efficiency of cooling system.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.6
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• pp.685-691
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• 2005

In this study, high performance waste heat recovery heat exchanger was developed using the bayonet tube with spiral serrated fins. Especially, heat exchanger of the bayonet tube type was operated well because of double water passes mechanism and characteristics. A cooling water Passes down inner tubes to thimble-form tubes, then flows back up as it boils. The heat exchanger of bayonet tube type was composed of steel tube with 7channels$(I.D_1\;14mm.\;I.D_2\;31.6mm)$ and spiral serrated fins. The performance tests were conducted under the following conditions A cooling water flow rate was 273kg/h and engine l·pm was varied from 750rpm to 3500 rpm. From the experimental result. waste heat recovery was 9.21kW when engine rpm was 3500. and pressure drop was $15\~260mmHg/m^3$ The effectiveness of heat exchanger was about /$0.7\~0.9$. The performance of heat exchanger was evaluated by using the $\varepsilon-NTU$ method. In the study the NTU of the heat exchanger was $1.57\~2.33$.

• Journal of Advanced Marine Engineering and Technology
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• v.8 no.2
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• pp.25-38
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• 1984

Since the energy shock in 1973, there have been wide studies for the developments of the alternative energy source, the rationalization of the energy utilization and the energy economy because of the recognition of the limitation of energy source all over the world. This study is experimentally examined in and compared with the engine performance of output, torque and fuel consumption rate, and the exhaust emissions with the change of engine rmp in the cases of using water-gashol blends, gashol and gasoline as a fuel in a conventional 4 cycle 4 cylinder gasoline engine. In the case of using water-gashol blends, it is installed by the exhaust manifold pipe into the intake manifold, and water is injected from nozzle fitted up the air horn of the carburetor. The results are obtained as follows; 1. In the case of an addition with water, the engine output and the torque are little difference with the case of gasoline. 2. The fuel consumption rate is decreased as compared with the case of gasoline. Especially, the decrease in quantity is remarkable at the low rpm. 3. The exhaust emissions are remarkably decreased as compared with the case of gasoline. Especially, decreases of CO and HC in quantity are remarkable at the low rpm, and a decrease of No/sub x/ in quantity is remarkable at the high rpm. 4. There is a moderate condition of operation because the producing factors of NO/sub x/ and CO, HC are contrary to each other.

• Journal of Biosystems Engineering
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• v.32 no.2 s.121
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• pp.77-83
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• 2007

The purpose of this study is to find optimal conditions for various outlet clearances of prototype garlic clove separator with a rotating cone in the constant inlet clearance and cone height. Optimal outlet clearance from medium to small size garlics was 25 mm at the $200{\sim}400rpm$. For large garlic, optimal outlet clearances of Namdo and Uiseong garlic were 34 mm and 37 mm, respectively, in the range of $300{\sim}400rpm$. The proportion of garlic separation was over 95% for all quality of garlics. The proportions of damaged garlics at 25 mm and 28 mm outlet clearances were below 5% and below 10%, respectively. Therefore, in order to maintain high performance of garlic separation for the various varieties and qualities, the rotating cone type separator should be designed with cone speed ranges of $200{\sim}400rpm$ and the outlet clearance ranges of $25{\sim}37 mm$. The outlet clearance of the separator should be easily controlled within those ranges.

• Food Science of Animal Resources
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• v.32 no.3
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• pp.369-375
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• 2012

The current study was carried out to investigate the impact of extraction conditions on the free amino acid level and type in beef longissimus muscle. The sample blocks were chiller aged for 1 d and 7 d at $4^{\circ}C$. There are three homogenization speeds (11,000, 19,000 and 24,000 rpm) for bigger and two speeds (11,000 and 13,000 rpm) for smaller homogenizer's dispersing tools were used for evaluation. Results showed that chiller ageing greatly (p<0.05) increased extractable free amino acids, except cystine. Homogenization with the bigger dispersing tool at 24,000 rpm resulted in the highest free amino acid levels for both 1 and 7 d samples. Significant differences (p<0.05) in the mean values of most amino acids due to the effect of speed and interactions between ageing times. However, the speed effect and interaction between ageing with homogenization speed were not significant (p>0.05) for most of the amino acids except valine and isoleucine when using the smaller dispensing tools. The current data indicated that a standardized method for free amino acid types and levels of aged beef samples. In addition, the results also suggested that utilization of a big dispensing tool at high homogenization speed is a better condition for releasing free amino acid contents in beef samples.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.4
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• pp.32-40
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• 2005

The purpose of this study is to investigate variation of spark plug protrusion and PDA valve on the exhaust emission in a gasoline engine. Swirl is one of the important parameters that affects the characteristics of combustion. PDA valve has been developed to satisfy requirements of sufficient swirl generation for improving the combustion and reducing of emission level. Also, especially, the variation of spark plug protrusion have an important effect to the early flame propagative process. This is largely due to the high flame speed by short of flame propagation distance. So, this is forced that injection timing, spark timing and intake air motion govern the stable combustion. As a result, using two combustion chamber, without charge of engine specification and the variable spark plug location and PDA valve could be reduced exhaust gas at a part load engine conditions(1500rpm imep 3.9bar, 2000rpm imep 3.2bar, 2400rpm imep 3.9bar).

• Journal of Power System Engineering
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• v.6 no.4
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• pp.30-35
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• 2002

This study represents the effects of the material of the air cleaner on the performance in a 4-stroke spark-ignition engine for motorcycles. This study is mainly focused on the possibility of the adopting the STS wire mesh air cleaner of a S.I engine. For investigating the possibility of that, the engine power, the fuel consumption and the exhaust gas analysis were carried out for the synthetic fiber air cleaner and the different size of 200 mesh, 250 mesh, 300 mesh of STS wire mash air cleaner. As the results of this study, the performance of STS wire air cleaner was similar to the fiber air cleaner at 9000 rpm but 300 mesh of STS air cleaner had a high engine power and torque at 9500 rpm. In the case of the synthetic fiber air cleaner the concentration of CO was low at 6500 rpm and in the case of the 300 mesh in STS wire mesh air cleaner the concentration of HC was lowest at all experimental regions.