• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.8
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• pp.1309-1316
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• 2003

The general dicing process cuts a semiconductor wafer to lengthwise and crosswise direction by using a rotating circular diamond blade. But products with inferior quality are produced under the influence of several parameters in dicing process such as blade, wafer, cutting water and cutting conditions. Moreover we can not apply this dicing method to GaN wafer, because the GaN wafer is harder than the other wafer such as SiO2, GaAs, GaAsP, and AlGaAs. In order to overcome this problem, development of a new dicing process and determination of dicing parameters are necessary. This paper describes a new wafer dicing method using fixed diamond scriber and precision servo mechanism and determination of several parameters - scribing depth, scribing force, scriber inclined angle, scribing speed, and factor for scriber replacement - for a new dicing machine using scriber.

• Proceedings of the KIPE Conference
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• 1998.07a
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• pp.352-356
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• 1998

This paper is a study about Ac servo motor position and speed control characteristics which depend on feedforward control, the acceleration / deceleration time constant after the interpolation, and PI control, automatic deceleration at corner in order to shape cutting control of feed drive system of the machine tool. The shape error caused by delay of the servo system in the direction of radius at the time of circular cutting is reduced by feedforward control. The shape error generated by the position command delay is minimized by using the acceleration / deceleration time constant after the interpolation. The results were verified to optical machining center experimentation of the machine tool.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.234-235
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• 2005

This paper present a new disk-type piezoelectric transformer. The input side of the transformer has a crescent-shaped electrode and the output side has a focused poling direction. The piezoelectric transformers operated in each transformer's resonance vibration mode. The electrodes and poling directions on commercially available piezoelectric ceramic disks were designed so that the planar or shear mode coupling factor ($k_p,\;k_{15}$) becomes effective rather than the transverse mode coupling factor ($k_{31}$).

• Journal of the Korean Society for Precision Engineering
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• v.20 no.2
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• pp.218-225
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• 2003

The general dicing process cuts a semiconductor wafer to lengthwise and crosswise direction by using a rotating circular diamond blade. However, inferior goods may be made under the influence of several parameters in dicing process such as blade, wafer, cutting water and cutting conditions. Moreover we can not apply this dicing method to a GaN wafer, because the GaN wafer is harder than other wafers such as SiO$_2$, GaAs, GaAsP, and AlGaAs. In order to overcome this problem, development of a new dicing process and determination of dicing parameters are necessary. This paper describes determination of several parameters - scribing depth, scribing force, scriber inclined angle, scribing speed, and factor for scriber replacement - for a new dicing machine using a scriber.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.11
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• pp.912-917
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• 2007

Regionally averaged heat transfer distributions and friction factors in square channels with twisted tape inserts and with twisted tape inserts plus interrupted ribs are experimentally investigated. The effects of surface heating condition on heat transfer enhancement are also investigated. Each wall of the square channel is composed of isolated aluminum plates. The interrupted square ribs are arranged along the axial flow direction on the bottom wall only. Experimental tests are performed for Reynolds numbers ranging from 8,900 to 29,000. The results are compared with those of previous investigations for circular tube with axial interrupted ribs and twisted tape inserts.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.530-532
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• 2002

This paper presents an optimum design of herringbone grooved journal bearing for spindle motor of hard disk drive (HDD) system. In addition to the conventional “rectangular” groove, various groove profiles are designed. The stiffness and damping coefficients of the oil film and frictional torque are calculated and compared for tile various groove profiles. The “circular”, “valley”, and “reversed saw tooth” grooves do not produce high direct stiffness, since they partly increase the groove depths in the direction of lubricant flow, causing to reduce the pumping action of the bearing. The maximum direct stiffness can be obtained by the “rectangular”, “saw tooth”, and “step” grooves. With the same cross sectional area of the grooves, these three grooves have the same maximum stiffness, damping coefficients, and frictional torque. Among these recommendable grooves, the saw tooth groove may keep its original profile for long, enduring metal-to-metal contact during startup and shutdown.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.164-167
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• 2002

The general dicing process cuts a semiconductor wafer to lengthwise and crosswise direction by using a rotating circular diamond blade. But inferior goods are made under the influence of several parameters in dicing process such as blade, wafer, cutting water and cutting conditions. Moreover we can not applicable this dicing method to GaN wafer, because the GaN wafer is harder than the other wafer such as SiO$_2$, GaAs, CaAsP, and AlCaAs. In order to overcome this problem, development of a new dicing process and determination of dicing parameters are necessary. This paper describes determination of several parameters - scribing depth, scribing force, scriber inclined angle, scribing speed, and factor for scriber replacement - for a new dicing machine using scriber.

• Tribology and Lubricants
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• v.12 no.2
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• pp.8-19
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• 1996

Scroll compressor using a slide bushing type radial compliant crank mechanism is modelled, and it's dynamic behaviour characteristics are analyzed. Sealing forces generated in the flank surfaces of the orbiting scroll depending on the distance, e, from slide bushing center to crank pin center are calculated. From the stable condition of orbiting scroll for the moment equilibrium in tangential direction, the range of e is determined as 0$r_o$. Transient response of a crankshaft supported by two journal bearings is investigated, considering applied load, moment, and unbalance force by eccentric mass. As a result, conical whirl mode with circular orbits are obtained. The characteristics of journal orbits and frictional losses are calculated with a variation of viscosity and bearing clearance.

• Laser Solutions
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• v.12 no.1
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• pp.14-18
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• 2009

Ripple formation of femtosecond laser in stainless steel is investigated using 184 fs pulses with a center wavelength of 785 nm. The effect of the laser polarization relative to the translation direction is observed. For drilling with a certain aspect ratio, reflections at the hole walls take place, leading to a non-uniform intensity distribution deep inside the formed hole. Finally, it is shown that a circular polarization during the drilling process significantly improves the quality of the produced holes.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.04a
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• pp.11-13
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• 2002

The performance of DC current sensor based on giant magnetoimpedance (GMI) effect in amorphous ribbon has been tested. The ribbon after field annealing shows the maximum GMI ratio of 30 % at 100 kHz measuring frequency. In the sensor element of sample wound the circular form, GMI ratio and sensitivity are decreased due to internal stress. The sensor voltage output increases with applied DC current up to 1 A with a good linearity, of which direction can be known due to asymmetric characteristics.