• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.10a
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• pp.108-113
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• 2004

The compressive axial collapse tests were performed to investigate energy absorption characteristics of Al/CFRP compound tubes which are aluminum tubes wrapped with CFRP (Carbon Fiber Reinforced Plastics) outside the aluminum circular and square tubes. Based on collapse characteristics of aluminum tubes and CFRP tubes respectively, the axial collapse tests were performed for Al/CFRP compound tubes which have different fiber orientation angles. Test results showed that Al/CFRP compound tubes supplemented the unstable brittle failure of CFRP tubes due to ductile nature of inner aluminum tubes. In the light-weight aspect, specific energy absorption were the highest for Al/CFRP, CFRP in the middle, and aluminum the lowest. Also, specific energy absorption of circular tubes was higher than square tubes'. It turned out that fiber orientation angle of Al/CFRP compound tubes influence specific energy absorption together with the collapse modes of the tubes.

• International Journal of Automotive Technology
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• v.6 no.5
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• pp.501-506
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• 2005

With the respective collapse characteristics of aluminum and CFRP (Carbon Fiber Reinforced Plastics) tubes in mind, axial collapse tests were performed for aluminum/CFRP compound tubes, which are composed of square or circular shaped aluminum tubes wrapped with CFRP outside. In this study, the collapse modes and the energy absorption characteristics were analyzed for aluminum/CFRP compound tubes which have different fiber orientation angle of CFRP. Fracture modes in the aluminum/CFRP compound tubes were rather stable than those in the CFRP tubes alone, probably due to the ductile nature of the inner aluminum tubes. The absorbed energy per unit volume of the aluminum or the aluminum/CFRP compound tubes was higher than that of CFRP tubes. Meanwhile, the absorbed energy per unit mass, for the light-weight design aspect was higher in the aluminum/CFRP compound tubes than in the aluminum tubes or the CFRP tubes. The energy absorption turned out to be higher in circular tubes than in square tubes. Beside the collapse modes and the energy absorption characteristics were influenced by the orientation angle, and the compound tubes took the most effective energy absorption when the fiber orientation angle of CFRP was 90 degrees.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.11
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• pp.1768-1775
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• 2004

The compressive axial collapse tests were performed to investigate collapse modes and energy absorption characteristics of Al/CFRP compound tubes which are aluminum tubes wrapped with CFRP(Carbon Fiber Reinforced Plastics) outside the aluminum circular and square tubes. Based on collapse characteristics of aluminum tubes and CFRP tubes respectively, the axial collapse tests were performed for Al/CFRP compound tubes which have different CFRP orientation angles. Test results showed that Al/CFRP compound tubes supplemented the unstable brittle failure of CFRP tubes due to ductile nature of inner aluminum tubes. In the light-weight aspect, specific energy absorption were the highest for Al/CFRP, CFRP in the middle, and aluminum the lowest. Also, specific energy absorption of circular tubes was higher than square tubes'. It turned out that CFRP orientation angle of Al/CFRP compound tubes influence specific energy absorption together with the collapse modes of the tubes.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.6
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• pp.699-705
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• 1985

Heat transfer characteristics in terms of the tube wall-temperature and the enthalpy have been investigated utilizing ribbed (rifled) tubes in order to enhance heat transfer performance. Considerations were given for the cases of smooth tubes in order to compare with the case of ribbed tubes. The tilt angle of the experimental tubes are from 0.deg. to 90.deg. , in order to simulate the boiler water tubes having 15.deg.-90.deg. inclined angle in boiler nose and studded tubes (burner zones), Natural convection and forced convection (Re=1810) conditions were considered in the experiments. The experimental results for the effect for the tube inclination through a natural convection and forced convection are presented and it is shown that ribbed tubes permit an appreciable increase in heat transfer coefficients and consequently it means substantial reductions in boiler water wall tubes and heat exchanger surface areas.

• Nuclear Engineering and Technology
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• v.29 no.2
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• pp.138-147
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• 1997

Korean-made alloys 600 and 690 tubes were evaluated by flare tests according to ASTM standards, and acting stresses during the test ore analyzed. All the tubes, including alloys 600 and 690 tubes with various heat treatment conditions, satisfied the requirement with 30 or 35750.D expansion. Axial stresses in alloy 690 tubes were higher than those in alloy 600 ones and the gap increased gradually with flaring percentage(F.P, %). Assuming the tubes as the rigid-perfectly plastic body, a stress equation was obtained using modified Tresca's yield criterion. Also microstructural change of the flared tubes was discussed with the acting stresses.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1235-1238
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• 2006

One-Drop-Filling (ODF) process is an advanced vacuum filling process in LCoS manufacture line. The merits not only increase the throughput of liquid crystal filling process but also reduce the number of equipments. Studying application of ODF process in LCoS panel manufacturing is the purpose of is this article. The accuracy of liquid crystal drop size, the stability of seal dispensing and the nozzle size etc. In the tiny panel manufacture are more important than those factors in normal panel manufacture.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1398-1401
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• 2006

Silver paste curing process is very important in LCoS panel manufacture because incomplete curing process will cause poor bonding strength and increase resistance. The imperfection situation results in poor reliability and the variation of the common voltage, respectively. The change of the common voltage causes image flicker. According to Kinetics, we acquire activation energy by using dynamic DSC and compare two kinds of silver paste. From the result of isothermal DSC, we get optimum curing parameters to solve the flicker problem caused of incomplete curing of the silver paste.

• Journal of the Korean Professional Engineers Association
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• v.30 no.3
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• pp.43-51
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• 1997

Vacuum tubes are electron tubes in which the motion of electrons are utilized. There are many kinds of vacuum tubes, e.g. diode tubes, triode tubes, pentodes. muti-tubes and etc. Generally accommodated in glass tube, its eletrodes can be seen easily from outside and it easy to understand. In 1884 Edison discovered a current flow in the vacuum tube. He could not, however, explain this phenomenon. This is called Edison effect. In 1904 Fleming developed the backup for the practical diode theory. The most important milestone in this early history of electronics came in 1906 when De Forest put a third electrode (a grid) into the above, and thus invented the triode tube. It is 90 years since the triode was invented by De Forest (as of 1996) and 100 years (centennial also as of 1996) since the specific electric change e/mo$_0$ ≒ 1.7589 ${\times}$ 1011 (C/kg) was confirmed by the English scientist Thomson in 1896. On the occasion of the 90th and 100th anniversary of these inventions and discovery, E would like to describe the rise and 1111 of the vacuum tubes and the current status of these tubes.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.12
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• pp.1676-1683
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• 2001

An experimental study on condensation heat transfer characteristics of helically coiled spiral tubes was performed. The refrigerant is R-113. A refrigerant loop was established to measure the condensation heat transfer coefficients. Experiments were carried out uniform heat flux of 15 kw/m$^2$, refrigerant quality of 0.1∼0.9, curvature ratio of 0.016, 0.025 and 0.045. The curvature of a coil was defined as the ratio of the inside diameter of the tube to the diameter of the bending circle. To compare the condensation heat transfer coefficients of coiled spiral tubes, the previous results on coiled plain tubes and straight plain tubes were used. The results shows that the condensation heat transfer coefficients of coiled spiral tubes largely increase, as increasing Re and quality, compared to those of coiled plain tubes and straight plain tubes. As increasing degree of subcooling, however, the condensation heat transfer coefficients on coiled spiral tubes decrease. It is found that the heat transfer enhancement is more better than coiled plain tubes and straight plain tubes, as increasing curvature ratio.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.3
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• pp.224-234
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• 2007

Large diameter tubes have been used until comparatively lately. However, small diameter tubes are largely used because of their high efficiency in heat transfer and low cost, recently. This study focuses on the experimental research of the heat transfer coefficients during evaporation process of R-22 and R-134a in small diameter tubes. The evaporation heat transfer coefficients were measured in smooth horizontal copper tubes with ID 1.77, 3.36 and 5.35 mm. The evaporation heat transfer coefficients in the small diameter tubes (ID <7 mm) were observed to be strongly affected by the size of tube diameters and to differ from those of general predictions in the large diameter tubes. The heat transfer coefficients of ID 1.77 mm copper tube were higher by 20 and 30 % than those of ID 3.36 mm, ID 5.35 mm copper tubes respectively. Also, it was found that it was very difficult to apply some well-known previous predictions (Shah's, Jung's. Kandlikar's and Oh-Katsuda's correlation) to small diameter tubes. Based on the data, the new correlation is proposed to predict the evaporation heat transfer coefficients of R-22 and R-134a in small diameter tubes.