• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.2
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• pp.181-191
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• 2014

This study aims to evaluate cutter acting forces as well as axial stresses and torques in the shaft of two kinds of disc cutters including a single disc cutter and a double disc cutter with the same cutter ring geometry in a series of linear cutting tests. From the tests, the mean values of normal forces and rolling forces acting on the double disc cutter were approximately twice as high as those from the single disc cutter. Similarly, the mean values of axial stresses in the shaft of the double disc cutter were also twice as high as those from the single disc cutter even though the comparisons of torques from two kinds of disc cutters were insignificant since they showed very low values. However, it is necessary to take the durability of a tapered roller bearing used for the double disc cutter into high consideration since the average normal force from the double disc cutter exceeds the allowable force for a disc cutter with the diameter of 432 mm (17 inches). Finally, there is no practical problem in terms of axial stresses in the shaft of the double disc cutter since they are much lower than the yielding stress of the cutter shaft material, even though the axial stresses in the shaft of the double disc cutter are approximately twice as high as those from the single disc cutter.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.9
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• pp.914-923
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• 2009

Helix antennas have been widely applied to satellite TT&C, data communication and GPS receiver systems onboard military, remote sensing and communication purpose satellites. The helix antennas are known to be convenient to control impedance and radiation coverage characteristics with a maximum directivity in satellite z-axis. Waveguide horn is commonly used for radar system that needs ultra-wideband pulse for exploration ground radar and electromagnetic disability measurement etc. It has high efficiency and low reflection characteristics provided by the low-profile shape and suppressed radiation distortion. In this paper, a waveguide horn structure incorporated with helix antenna design is proposed for satellite applications that require ultra-wideband pulse radar and high rate RF data communication link to ground station over wide coverage area. The main design concern is to synthesize variable beam forming pattern based on modified horn-helix combination helicone structure such that multi-mission antenna is implemented applicable for TT&C, earth observation, high data rate transmission. Waveguide horn helps to reduce the overall antenna structure size by introduction fold type reflector connected to the tapered helix antenna. The next generation KOMPSAT satellite currently under development requires high-performance precision attitude control system. We present an initial design of a hybrid hern-helix antenna structure suitable for efficient RF communication module design of multi-purpose satellite systems.