• Proceedings of the KIPE Conference
• /
• 2000.07a
• /
• pp.330-334
• /
• 2000

This paper proposes a new double-connected 3-phase voltage source inverter with improved output voltage waveform. An auxiliary single-phase inverter injects a ripple voltage into the double- connected inverter to convert 12-step operation to 36-step operation. The KVA rating of the output phase-shifting transformer is reduced by employing a harmonic canceling reactor. The whole rectifier-inverter system including the proposed technique is introduced and the experimental results are provided.

• The Journal of Korean Academy of Prosthodontics
• /
• v.37 no.6
• /
• pp.800-808
• /
• 1999

To compare several porcelains made by various manufacturers in shrinkage after firing and investigate the effect of condensation on shrinkage, specimens were prepared and the volume of each body was measured by the phase-shifting profilometry. Baseplate wax was cut by $2.5cm{\times}2cm$ and cast in nonprecious metal(Verabond, U.S.A.), then any surfaces of specimens were abrased and polished on the SiC abrasing papers, preparing 120 specimens. Specimens were divided into six groups according to the porcelain used, and the porcelain used in each group were as follows. Group I : Ceramco dentin porcelain Group B : Creation dentin porcelain Group III : Creation margin porcelain Group IV : Vintage margin porcelain Group V : Vita dentin porcelain Group VI : Vintage dentin porcelain Porcelain was built up on the metal plates using a small spoon and then solution matching to each porcelain was added. The six groups are subdivided into a and b. In subgroup a, only excessive solution was absorbed with tissue and in subgroup b, porcelain was condensed sufficiently. When build-up was completed, the shape was measured using the phase-shifting profilometry. After that, specimens were fired in the furnace programed for each porcelain and then their changed shape were measured again. Using the difference between the two above measurements, the ratio of shrinkage was calculated. Obtained results were as follows ; 1. Regardless of condensation, the volume of fired specimens were not different significantly between the two subgroups a and b in the same group. 2. The ratios of shrinkage were significantly higher in the groups porcelain built-up was condensed than in the groups not condensed 3. The ratios of shrinkage were in the range of 36.81-27.19% in the groups porcelain built up was condensed and 44.52-37.54% in the other groups not condensed.

• Proceedings of the Optical Society of Korea Conference
• /
• 2007.07a
• /
• pp.69-70
• /
• 2007

• Journal of the Korean Society for Precision Engineering
• /
• v.20 no.10
• /
• pp.12-21
• /
• 2003

• Proceedings of the Optical Society of Korea Conference
• /
• 2006.07a
• /
• pp.415-416
• /
• 2006

• Current Optics and Photonics
• /
• v.3 no.4
• /
• pp.350-350
• /
• 2019

• The Transactions of the Korean Institute of Power Electronics
• /
• v.13 no.3
• /
• pp.229-236
• /
• 2008

Recently, multilevel H-bridge inverters have become popular in medium to high power ac drive applications. One of significant advantages of them is low harmonic contents in their input line currents thanks to the transformer with multiple phase-shifted secondary windings. This paper attempts to provide basic guidelines for the design of the phase shifting transformer windings and theoretical analysis of input line current harmonics of H-bridge inverters. The part I provides the derivation of basic relationships between input and output current of the transformer and the relationship between the phase shifting characteristics and design aspects of the transformer.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.25 no.3
• /
• pp.171-177
• /
• 2005

Phase-shifting method using Fourier transform (PSM/FT) has been applied to measurement of in-plane displacement of a specimen. Thirty-two interference fringe patterns each of which has different phase of ${\pi}/16$ radian have been gathered from a specimen with in-plane displacement. Low-pass filtering by 2-D Fourier transform is used to suppress spatial noise of the fringe patterns. ${\alpha}-directional$ Fourier transform for PSM/FT is performed by use of the low-pass filtered 32 fringe patterns. Two kinds of specimens are used for experiment. One is a rectangular steel plate and the other one is a rectangular steel plate containing a circular hole at the center. In-plane displacement of each specimen is measured by PSM/FT, and calculated by finite element method (ANSYS) for comparison. The results are quite comparable, so that PSM/FT can be applied to measurement of in-plane displacement.

• Journal of the Optical Society of Korea
• /
• v.17 no.5
• /
• pp.384-391
• /
• 2013

We propose a split-encryption scheme on converting original images to multiple ciphertexts. This conversion introduces one random phase-only function (POF) to influence phase distribution of the preliminary ciphertexts. In the encryption process, the original image is mathematically split into two POFs. Then, they are modulated on a spatial light modulator one after another. And subsequently two final ciphertexts are generated by utilizing two-step phase-shifting interferometry. In the decryption process, a high-quality reconstructed image with relative error $RE=7.6061{\times}10^{-31}$ can be achieved only when the summation of the two ciphertexts is Fresnel-transformed to the reconstructed plane. During the verification process, any silhouette information was invisible in the two reconstructed images from different single ciphertexts. Both of the two single REs are more than 0.6, which is better than in previous research. Moreover, this proposed scheme works well with gray images.

• Journal of the Optical Society of Korea
• /
• v.9 no.4
• /
• pp.145-150
• /
• 2005

The method to obtain four speckle patterns with relative phase shift of $\pi$/2 by passive devices such as two waveplates and a linear polarizer, and to calculate the phase at each point of the speckle pattern in shearography with a Wollaston prism is described. In this paper, we analyze its potential error sources caused by wave plates.