• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.2
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• pp.17-24
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• 2004

In end milling process, undeformed chip thickness and cutting forces vary periodically with phase change of the tool. Recently, a model has been proposed to simulate the shear and friction characteristics of an up-end milling process in terms of the equivalent oblique cutting to this. In the current study, a down-end milling process has been replaced with the equivalent oblique cutting process. And shear and tool-chip friction characteristics variation of SM45C steel has been studied using the end-mills of different helix angles. The specific shear and friction energy consumed with helix angle of $50^{\circ}$ is somewhat larger than those of$30^{\circ}$ and $40^{\circ}$. The specific shear energy consumed is about 76-77% of the specific cutting energy regardless the helix angles.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.6
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• pp.1419-1424
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• 1998

In phased array antennas that scan elevation, the number of radiator rows is one of the important factors to minimizing both cost and weitht. Therefore, the antenna tilt angles having relation with element spacing are among the improtant design parameters. The exact optimum tilt angles for several types of uniformly and nonuniformly excited arrays are obtained theoretically. Four types of uniform linear arrays and Chebyshev array factors as a nonuniformly excited arrav are considered.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.2
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• pp.141-146
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• 2019

Non-emissive LCDs need a backlight, and have difficulty implementing wide viewing angles due to differences in phase retardation depending on the behavior of the liquid crystals. Although wide viewing angles are good characteristics for devices such as TVs, they are not good for mobile devices. In this paper, we propose ways to design diffusers with ELC lenses to achieve wide and narrow viewing angles depending on the circumstances. A study was conducted on optimizing the design of a liquid lens diffuser with the same light as that for an OLED, by extracting design factors that affect the performance of the diffuser and applying the Taguchi method to them.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.53 no.2
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• pp.58-64
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• 2004

Most of the loads in industrial power distribution systems are balanced and connected to three power systems. However, in the user power distribution systems, most of the loads are single & three phase and unbalanced, generating voltage unbalance. Voltage unbalance is a condition in a polyphase system in which the rms values of the line-to-line voltages or the phase angles between consecutive line-to-line voltages, are not all equal. Slight voltage unbalance generates a disproportionately high current unbalance at the motor stator winding. This paper presents a scheme on operation states of a three-phase induction motor under unbalanced voltages. The three-phase voltages applied to the stator winding of the studied induction motor are controlled by respectively adjusting the magnitude and phase angle of each phase. The voltage unbalanced factor(VUF) of the three-phase source voltages can then be varied to examine the different values of VUF on machine's operation characteristics.

• Journal of Ocean Engineering and Technology
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• v.32 no.2
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• pp.77-83
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• 2018

In this study, a series of experiments were performed to investigate the variations in the behavior of green water generation and the flow kinematics of bubbly flow on deck with various flare angles. The experiments were conducted in a 2-D wave flume using a simplified model of a BW Pioneer FPSO operating in the Gulf of Mexico, with a 100-year return period wave condition. The green water phenomena were captured with a high speed CCD camera. The variations in the behavior of the green water generation were investigated with various flare angles, and the horizontal mean velocity profiles of bubbly flow on deck obtained using bubble image velocimetry (BIV) were provided. The differences in flow kinematics of bubbly flow on deck were analyzed with various flare angles.

• Korean Journal of Applied Biomechanics
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• v.16 no.4
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• pp.83-94
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• 2006

The purpose of this study is to elucidate how walking speed influences on change of angles of lower extremity and ground reaction force in normal and obese people. One group with normal body weight who were experimented at a standard speed of 1.5m/s and the other obese group were experimented at two different walking speeds (standard speed of 1.5m/s and self-selected speed of 1.3m/s). We calculated angles of lower extremity and ground reaction force during stance phase through video recording and platform force measuring. When the obese group walked at the standard speed, dorsi-flexion angle of ankle got bigger and plantar-flexion angle of ankle got smaller, which were not statistically significant. There was no significant difference of knee joint angles between normal and obese group at the same speed walking but significant post hoc only for the first flexion of knee joint in obese group. $F_z1$ was bigger than $F_z3$ in vertical axis for ground reaction force in both groups at the standard speed walking and the same force value at self-selected speed in obese group. $F_y3$ was always bigger than $F_y1$ in anterior-posterior axis in both groups.

• Korean Journal of Applied Biomechanics
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• v.17 no.1
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• pp.145-153
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• 2007

The purpose of this study is to compare and analyze the phase-by-phase elapsed time, the COG, the body joint angle changes and the angular velocities of each phase of Handspring Salto Forward Piked performed by 4 college gymnasts through 3D movement analysis program. 1. The average elapsed time for each phase was .13sec for Phase 1, .18sec for Phase 2, .4sec for Phase 3, and .3sec for Phase 5. The elapsed time for Phase 1 to Phase 3 handspring was .35sec on average and the elapsed time for Phase 4 to Phase 5 handspring salto forward piked was .7sec on average. And so it showed that the whole elapsed time was 1.44sec. 2. The average horizontal changes of COG were 93.2 cm at E1, 138. 5 cm at E2, 215.7 cm at E3, 369.2 cm at E4, 450.7 cm at E5, and 553.1 cm at E6. The average vertical changes of COG were 83.1 cm at E1, 71.3 cm at E2, 78.9 cm at E3, 93.7 cm at E4, 150.8 cm at E5, and 97.2 cm at E6. 3. The average shoulder joint angles at each phase were 131.6 deg at E1, 153.5 deg at E2, 135.4 deg at E3, 113.4 deg at E4, 39.6 deg at E5, and 67.5 deg at E6. And the average hip joint angles at each phase were 82.2 deg at E1, 60 deg at E2, 101.9 deg at E3, 161.2 deg at E4, 97.7 deg at E5, and 167 deg at E6. 4. The average shoulder joint angular velocities at each phase were 130.9deg/s E1, 73.1 deg/s at E2, -133.9 deg/s at E3, -194.4 deg/s at E4, 29.4 deg/s at E5, and -50.1 deg/s at E6. And the average hip joint angular velocities at each phase were -154.7 deg/s E1, -96.5 deg/s at E2, 495.9 deg/s at E3, 281.5 deg/s at E4, 90.3 deg/s at E5, and 181.7 deg/s at E6. The results shows that, as for the performance of handspring salto forward piked, it is important to move in short time and horizontally from the hop step to the point to place the hands on the floor and jump, and to stretch the hip joints as much as possible after the displacement of the hands and to keep the hip joints stretched and high in the vertical position at the takeoff. And it is also important to bend the shoulder joints and the hip joints fast and spin as much as possible after the takeoff, and to decrease the speed of spinning by bending he shoulder joints and the hip joints quickly after the highest point of COG and make a stable landing.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1304-1306
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• 1995

In this study, a neural network algorithm through a data standardization method was developed to discriminate the phase-shifted partial discharge(PD) patterns such as a $\phi$-q-n pattern. Considering the PD measurement in the field, it is not so easy to acquire absolute phase angles of PD pulses. As a consequence, one of the significant problems to be solved in applying the neural network algorithm to practical systems is to develop a method that can discriminate phase-shifted $\phi$-q-n patterns. Therefore, authors established a new method which could convert phase-shifted $\phi$-q-n patterns to a standardized $\phi$-q-n pattern which was not influenced by phase shifting. This new standardization method improved the recognition performance of a neural network for the phase-shifted $\phi$-q-n patterns considerably.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.243-249
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• 2003

The characteristics of harmonic phase angles and phase angle differences contained in earthquake ground motions such as El Centre 1530 NS, Taftl 1952 NS, Hachinohe 1968 NS and Mexico 1985 are figured, which have been mostly overlooked in contrast with the importance placed on harmonic amplitudes. And, energy input spectrum of structures excited by such an earthquake motion is expressed with smoothed Fourier amplitude spectrum. In dynamic response analysis, there must be earthquake ground accelerations which contain the phase angle, the phase angle difference and energy input spectrum characteristics of the zone considered to be constructed building structures. To make clear the importance of phase angle differences, 4-earthquake ground motions are normalized by 200 gal and energy input spectrum characteristics of normalized 4-earthquake ground motions are compared.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.497-504
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• 2002

The characteristics of harmonic phase angles and phase angle differences contained in earthquake ground motions such as El Centre 1940 NS, Taft1 1952 NS, Hachinohe 1968 NS and Mexico 1985 are figured, which have been mostly overlooked in contrast with the importance placed on harmonic amplitudes. Recently, performance based design method is used for seismic design and seismic retrofitting, which needs nonlinear response analysis, there must be earthquake ground accelerations which contain the phase angle and the phase angle difference characteristics of the zone considered to be constructed building structures. To make clear the importance of phase angle differences, 4-earthquake ground motions are normalized by 200 gal and nonlinear response characteristics of normalized 4-earthquake ground motions are compared.