• KCID journal
• /
• v.10 no.1
• /
• pp.112-120
• /
• 2003

• Proceedings of the Korean Society of Agricultural Engineers Conference
• /
• 2004.11a
• /
• pp.81-81
• /
• 2004

• Management Science and Financial Engineering
• /
• v.9 no.1
• /
• pp.1-10
• /
• 2003

We introduce a new estimator of the uncertainty of a jackknife estimate of standard error: the jack-knife-after-jackknife (JAJ). Using Monte Carlo simulation, we assess the accuracy of the JAJ in a variety of settings defined by statistic of interest, data distribution, and sample size. For comparison, we also assess the accuracy of the jackknife-after-bootstrap (JAB) estimate of the uncertainty of a bootstrap standard error. We conclude that the JAJ provides a useful new supplement to Tukey's jackknife, and the combination of jackknife and JAJ provides a useful alternative to the combination of bootstrap and JAB.

• Proceedings of the KIPE Conference
• /
• 2013.07a
• /
• pp.246-247
• /
• 2013

This paper investigates control algorithms for a doubly fed induction generator with a back-to-back three-level neutral-point clamped voltage source converter in medium voltage wind power system under unbalanced grid conditions. Control algorithms to compensate for unbalanced conditions have been investigated with respect to four performance factors; fault ride-through capability, instantaneous active power pulsation, harmonic distortions, and torque pulsation. The control algorithm having zero amplitude of torque ripple shows the most cost-effective performance concerning torque pulsation. The least active power pulsation is produced by control algorithm that nullifies the oscillating component of the instantaneous stator active and reactive power. Combination of these two control algorithms depending on the operating requirements and depth of grid unbalance presents most optimized performance factors under the generalized unbalanced operating conditions leading to high performance DFIG wind turbine system. The proposed control algorithms are verified through transient response in the simulation.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2005.05a
• /
• pp.35-39
• /
• 2005

This paper presents a method to reduce hysteresis in multilayer ceramic actuator by connecting the actuator with a capacitor in a series circuit. The change in hysteresis with respect to the capacitor was examined. $0.2Pb(Mg_{1/3}Nb_{2/3})O_3-0.8Pb(Zr_{0.475}Ti_{0.525})O_3$ ceramic material was used as a piezoelectric material for the actuator. Displacement of the actuator was measured in a capacitive gap sensor measuring system. In case of inserting a capacitor in a total circuit, hysteresis became dramatically decreased, and then finally the hysteresis value can be reduced below $0.2\%$. It was found in this present study that reducing the hysteresis in the actuator is dependent upon the characteristics of the capacitor in total circuit and also operating frequency.

• Proceedings of the KIPE Conference
• /
• 2014.07a
• /
• pp.213-214
• /
• 2014

This paper compares two instantaneous reactive power definitions in DFIG wind turbine with a back-to-back three-level neutral-point clamped voltage source converter under unbalanced grid conditions. In general, conventional definition of instantaneous reactive power is obtained by taking an imaginary component of complex power. The other definition of instantaneous reactive power can be developed based on a set of voltages lagging the grid input voltages by 90 degree. A complex quantity referred as a quadrature complex power is defined. Proposed definition of instantaneous reactive power is derived by taking a real component of quadrature complex power. The characteristics of two instantaneous reactive power definitions are compared using the ripple-free stator active power control algorithm in DFIG. Instantaneous reactive power definition based on quadrature complex power has a simpler current reference calculation control block. Ripple of instantaneous active and reactive power has the same magnitude unlike in conventional definition under grid unbalance. Comparison results of two instantaneous reactive power definitions are verified through simulation.

• Proceedings of the KIPE Conference
• /
• 2015.07a
• /
• pp.355-356
• /
• 2015

This paper proposes a control strategy of total output power ripple cancellation for both of Machine-Side Converter (MSC) and Grid-Side Converter (GSC) in a DFIG under unbalanced grid conditions. The proposed control strategy for the MSC is the zero torque ripple control algorithm with an enhanced LVRT capability. The control algorithm for the MSC exhibits reduced torque pulsation in steady-state unbalanced grid conditions. In addition, this control algorithm also minimizes a peak value of rotor current in transient unbalanced grid conditions. The total output power ripple cancellation control algorithm is adopted in the GSC. The total output power ripple cancellation is achieved by nullifying the oscillating component of the total output active and reactive power at the summing point of stator and rotor of DFIG. The proposed control strategy for the GSC reduces the output power oscillation leading to the improved quality of wind farms output.

• Journal of the Korean Society of Costume
• /
• v.60 no.7
• /
• pp.74-87
• /
• 2010

Jeokgwan(翟冠, crown decorated with pheasant motifs) is a queen's ceremonial headdress during the early Joseon dynasty. It originated from Bong-gwan(鳳冠, crown decorated with phoenix motifs) worn by the Chinese empress. Bong-gwan(鳳冠) was originally various types of hairpins worn with the topknot hair style, such as Bongchae(鳳釵) Hwasu(花樹) Bakbin(博鬢), but during the Sung dynasty(宋, 960-1279) these ornamental hairpins were combined with the crown worn by the empress. Bong-gwan(鳳冠) worn during the Ming dynasty(明, 1368-1644) varied according to the wearer's social status and it was worn both by the empress and other court ladies. Jeokgwan(翟冠), one type of Bong-gwan(鳳冠) worn by the queens and princesses of Ming dynasty, was given to those of the Joseon dynasty as a gift until the early 17th century. According to the portraits and remains of China, when women wore the Jeokgwan(翟冠), they were supposed to place the crown onto the hair, and then, fix the crown to the hair by putting on gorgeous hairpins. The lower edge of the crown was wrapped around with Gu-gwon(口圈), which was decorated with kingfisher's feathers. There are several flowery decorations on Gu-gwon(口圈), and this style is similar to Daeyobanja(大腰斑子), a queen's ceremonial hairband during the late Joseon dynasty.

• Journal of the Korean Society for Precision Engineering
• /
• v.33 no.6
• /
• pp.459-467
• /
• 2016

Using a line scan camera and a Galvano mirror, we constructed a high-speed line-scanning microscope that can generate 2D images ($8000{\times}8000pixels$) without any moving parts. The line scanner consists of a Galvano mirror and a cylindrical lens, which creates a line focus that sweeps over the sample. The measured resolutions in the x (perpendicular to line focus) and y (parallel to line focus) directions are both $2{\mu}m$, with a 2X scan lens and a 3X relay lens. This optical system is useful for measuring defects, such as spalling, chipping, delamination, etc., on the surface of carbon fiber reinforced plastic (CFRP) holes after machining in conjunction with adjustments in the angle of LED lighting. Defects on the inner wall of holes are measured by line confocal laser scanning. This confocal method will be useful for analyzing defects after CFRP machining and for fast 3D image reconstruction.

• Fashion & Textile Research Journal
• /
• v.6 no.5
• /
• pp.565-574
• /
• 2004

The purpose of this study is to investigate the historical background and basic composition of costume of the Baekje period. Main official hats of Baekje include the transformed hat, jougwan and daeryun-style ipsikgwan. Daeryun-style ipsikgwan employed chowha shape in most cases, symbolizing good auspice under the harmony of the male and female principles. Main types of costume of the Baekje period are po, yu, go and sang. The king, governmental officials and the common people all put on po of jikryeong gyoim style. Yu' is classified into two styles, chaksu with the narrow sleeve and daesu with the broad one. 'Go' has two styles, gunggo and gwango. The former is narrow in the breadth of the trouser and the latter, wide. 'Sang' is classified into various style according to whether it contains stripes of many colors, thin wrinkles or thick wrinkles. For the decoration of official hat used in the period of the Three Kingdoms, Baekje employed chowha in shape, Kokuryo, chowha and joik and Shilla, joik. In Baekje, rhythmic patterns of flame were applied to official hats, presenting brilliance. In Shilla, shaking geumyeongrak was used for official hats to show movement. In Kokuryo, such hats used flapping feathers, symbolizing dynamic power. Most necklaces and bracelets of the Baekje period were simple and plain.