• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.11
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• pp.2429-2435
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• 2002

The aim of this paper is to investigate the problem of strip down method, which is usually used to evaluate the engine friction level. The validity of strip down method was investigated by theoretical analysis of friction in crank and piston assembly. The friction of cylinder and piston assembly was analyzed under the various test conditions. The measured cylinder pressure was used as boundary conditions of friction torque and loss calculation. The friction loss of crank and piston assembly was influenced by test conditions that resulted from the variation of load condition. From the results, we have known that the strip down method could be possible to distort the friction loss of engine moving components.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.7
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• pp.81-88
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• 2004

In case of mechanical down tilting, a horizontal pattern is distorted and beam width widens whenincreasing tilt angle, which causes an expansion of hand off region and burden base station equipment. In contrast, electrical down tilting has advantage that horizontal HPBW is kept constant with down tilting. In this paper, based on a phased array technology, dual polarized base station antenna with electrical down tilting was developed at 800MHz band. The antenna has down tilting range of 0$^{\circ}$ to 14$^{\circ}$, and 15㏈i gain. We use stacked microstrip patch as a radiated element and apply balanced feed technique to improve isolation between ports and discrimination of cross polarization. The effect of electrical down tilting was verified by field test.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.10
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• pp.2159-2164
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• 2002

This paper reports on the effects of additional factors on the engine friction characteristics. The total friction loss of engine is composed of pumping and mechanical friction loss. The pumping loss was calculated from the cylinder pressure, and the mechanical friction loss was measured by strip-down method under the motoring condition. The various parameters were tested. The engine friction loss was much affected by oil and coolant temperature. The low viscosity oil was very effective to reduce the friction loss, and friction modifier was very useful to reduce the friction loss at lower engine speed. The engine friction loss was varied with engine running time because of surface roughness decreasing and oil degradation. To prevent oil-churning effect, it was very important to maintain the proper oil level. The presented results will be very useful to understand friction characteristics of engine.

• Journal of Advanced Navigation Technology
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• v.21 no.5
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• pp.466-471
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• 2017

SOTM is a device for the satellite communication on the move. Many studies are conducted on microstrip, waveguide and array antenna for the low profile of the SOTM's antenna. But those antennas have a problem that is difficult to adjust the polarization, and for that reason we have studied the parabolic antenna structure. The general form of parabolic reflector structure is circular, but we used cut-off shape reflector by cutting the upper and lower reflector for low profile antenna. Accordingly, this results in the decrease of reflector area which causes reduced gain and G/T ratio. In order to solve this problem, we have transformed and designed the sub reflector for improving the efficiency and gain of the cut- off shape parabolic antenna.