• Textile Coloration and Finishing
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• v.14 no.5
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• pp.268-276
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• 2002

Poly(trimethylene terephthalate)(PTT) and Poly(ethylene terephthalate)(PET) fibers were annealed at various temperatures ranging from $100^\circ{C}$ to $230^\circ{C}$ for 10 min under tension and tension free. Dyeing rates and absorption isotherms of both fibers were obtained with C.I. Disperse Red 60 at 100, 120 and $130^\circ{C}$ in water system. Also X-ray diffraction pattern, moisture regain and water absorption were investigated. The dyeing rate of PTT fiber is faster than PET fiber, and dyeing of PTT fiber begin at lower temperature compared to PET fiber. The absorption isotherms from both fibers with disperse dye we nearly linear up to the saturation dye uptake, which increase with dyeing temperature. Equilibrium dye uptake of PTT fiber annealed under tension above $180^\circ{C}$ was remarkably decreased because of a changes in the fine structure of fiber. The intensities of X-ray diffraction peaks of both annealed fibers were increased with increasing in annealed temperature. The reflections observed at $2\theta$=$15.8^\circ$, $24^\circ$ and $25.2^\circ$ were assigned reflection of crystal at the planes of (010), $(1\bar02,\;\bar112),\;and\;(\bar13,\; \bar113)$ respectively, and the peak became sharp with heat setting temperature.

• Journal of Biosystems Engineering
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• v.14 no.3
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• pp.196-206
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• 1989

와권(渦券) 노즐에 작용(作用)되는 힘은 분두(噴頭)의 도구(導溝) 및 와실(渦室)의 기능(機能)에 의하여 축방향력(軸方向力)과 반경방향력(半徑方向力)으로 분류(分類)되고, 이 두 개의 힘은 미립화(微粒化)의 과정(過程)에 각각(各各)의 특성(特性)을 주고 있다. 반경방향(半徑方向)의 힘은 분두(噴頭)에서 분사(噴射)되는 입자(粒子)에 전단력(剪斷力)으로서 작용(作用)하지만 이 힘의 크기는 물방울의 직경(直徑) $100{mu}m$을 기준(基準)하여 2.4m/s의 속도(速度) 이내(以內)의 범위(範圍)이었으며, 그 속도범위(速度範圍)는 다음 유도된 식(式)으로 산출(算出)할 수 있었다. $$V_{ot}=(\frac{8g{\sigma}}{d{\gamma}})^{1/2}$$ 축방향력(軸方向力)은 아래 유도된 식(式)과 같이 분사액류(噴射液流)의 굴절각에 매우 민감하게 영향을 미치었고, 그 크기는 반경방향력(半徑方向力)에 비교(比較)하여 큰 값을 나타내었다. $$V_{\ell}={\sigma}[\frac{1}{2}{\rho}_{a}sin2{\theta}_d-4({\mu}+{\eta})\frac{\ell}{r_o}]^{-1}$$.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.2
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• pp.379-385
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• 2004

Medical images are being managed more by PACS in general medical institutions. It is important to protect patients from being invaded their privacy related to the images. It is also necessary to confirm the ownership, the right of property of the medical images and notice whether the data are modified. In this paper, we propose a robust watermarking against RST attacks in medical images on the PACS. The proposed scheme modifies and improves Log-Polar Mapping and Fourier Mellin Transform in order to realize and recover serious image degradation and watermark data loss caused by the conversion between cartesian coordinate and log-polar coordinate. We used the radius and theta Look Up Table to solve the realization of the Fourier Mellin Transform, and inserted a watermark into 2D-DFT magnitudes using Spread Spectrum. Experimental results shows that this method are robust to rotation attack.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.99-100
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• 2007

ZnO films on $Al_2O_3$ substrates were grown using a pulsed laser deposition method. Through photoluminescence (PL) and X-ray diffraction (XRD) measurements, the optimum growth conditions for the ZnO growth were established. The results of the XRD measurements indicate that ZnO films were strongly oriented to the c-axis of the hexagonal structure and epitaxially crystallized under constraints created by the substrate. The full width half maximum for a theta curve of the (0002) peak was $0.201^{\circ}$. Also, from the PL measurements, the grown ZnO films were observed to give free exciton behaviour, which indicates a high quality of the epilayer. The Hall mobility and carrier density of the ZnO films at 293 K were estimated to be $299\;cm^2/V\;s$ and $8.27\;{\times}\;10^{16}\;cm^{-3}$, respectively. The absorption spectra revealed that the temperature dependance of the optical band gap on the ZnO films was $E_g(T)\;=\;3.439\;eV\;-\;(5.30\;{\times}\;10^{-4}\;ev/K)T^2(367\;+\;T)$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.490-491
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• 2007

We have investigated dielectric polarization in organic light-emitting diodes using 8-hydroxyquinoline aluminum$(Alq_3)$ as an electron transport and emissive material. We analyzed the dielectric polarization of organic light emitting diodes using impedance. Impedance characteristics was measured complex impedance Z and phase ${\theta}$ in the frequency range of 40Hz to $10^8Hz$. We obtained dielectric constant and loss tangent (tan ${\delta}$) of the device. From these analyses, we are able to interpret a dielectric dispersion and dielectric absorption contributed by an interfacial and orientational polarization.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.04a
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• pp.74-75
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• 2006

We have investigated dielectric properties depending on temperature in organic light-emitting diodes using 8-hydroxyquinoline aluminum ($Alq_3$) as an electron transport and emissive material. We analyzed the dielectric properties of organic light-emitting diodes using characteristics of impedance. he Impedance characteristics was measured complex impedance Z and phase $\theta$ in the temperature range of 10 K to 300 K. We obtained complex electrical conductivity, dielectric constant and loss tangent ($tan{\delta}$) of the device at room temperature. From these analyses, we are able to interpret a conduction mechanism and dielectric properties contributed by an interfacial and orientational polarization.

• Nuclear Engineering and Technology
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• v.28 no.3
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• pp.299-310
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• 1996

A two-step approach has been used to obtain a new criterion for the onset of slug formation : (1) In the first step, a more general expression than the existing models for the onset of slug flow criterion has been derived from the analysis of singular points and neutral stability conditions of the transient one-dimensional two-phase flow equations of two-fluid model. (2) In the second step, introducing simplifications and incorporating a parameter into the general expression obtained in the first step to satisfy a number of physical conditions a priori specified, a new simple criterion for the onset of slug flow has been derived. Comparisons of the present model with existing models and experimental data show that the present model agrees very closely with Taitel & Dukler's model and experimental data in horizontal pipes. In an inclined pipe ($\theta$ =50$^{\circ}$), however, the difference between the predictions of the present model and those of existing models is appreciably large and the present model gives the best agreement with Ohnuki et al.'s data.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.644-648
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• 2012

하천 내 설치하는 수제는 제방보호 및 유로변경의 목적으로 하천내 시공되는 구조물 중의 하나로서 하천복원과정에 있어 필수불가결한 구조물 중의 하나로 인식되고 있다. 수제는 대개 하나 이상의 일련의 군집형태로 수로 자체의 특성을 고려하여 설치가 되고 있다. 그러나 이러한 수제의 무분별한 설치는 주변 경관을 저해하거나 시공에 따른 비용 부담을 가중시키기 충분하다. 치수적 목적 이외에 경제적인 문제점을 해결하기 위해서는 실험을 통해 수제의 적절한 간격을 제시하는 것이 필요하다. 수제간격을 제시하기 위한 기초자료를 얻기 위해 본 연구에서는 기존 연직 및 하향군수제 하상변동실험과 동일한 조건으로 상향수제($\theta=45^{\circ}$)를 대상으로 수제간격에 대한 이동상 실험을 수행 하여 수제주변 및 수제역 내에서 발생하는 하상변동특성을 검토하였으며, 기존자료와 비교하였다. 실험결과 흐름집중 증가로 인해 국부세굴이 크게 발생하고 있으며 세굴폭은 수제길이의 3배 지점까지 영향을 미치고 있었으며, 퇴적고는 설치간격이 증가할수록 높게 형성되고 있었다. 연직 및 하향수제자료와 비교한 결과 상향수제는 수제끝단부에서 발생하는 국부적인 세굴에는 불리하나 수제역내 퇴적에는 유리한 것으로 나타났다.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.201-201
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• 2010

본 연구에서는 RF magnetron co-sputtering을 이용하여 Zn-O-Ga 구성비에 따른 광투과도 및 전기적 특성을 연구하였다. 타겟으로 ZnO 및 $Ga_2O_3$ 소결체를 이용하였으며, 두 개의 RF magnetron sputter의 RF power를 동시에 조절하여 타겟의 구성비를 조절하였으며, 기판과 타겟의 거리를 25 mm~75 mm 범위 내에 조절하여 거리에 따른 Zn-O-Ga 박막의 광투과 특성 및 전기적 특성을 관찰하였다. $Ga_2O_3$ 소결체의 magnetron sputter의 RF power를 30 watt에서 100 watt로 증가함에 따라 박막내의 Ga 성분은 0.5%에서 7.4%로 증가하였으며 Zn 성분은 46.3%에서 40.9%로 O성분은 53.2%에서 51.6%로 각각 줄어들었다. 이에 따라 ZnO의 우선방위 (002) 결정각($2{\theta}$)은 34.24에서 33.87로 줄어들었으며, 이동도 $5.5\;cm^2/Vs$ 에서 $1.99\;cm^2/Vs$ 정도로 감소하는 경향을 보였다. 광투과도는 가시광선 영역에서 85% 이상 보였으며, carrier 밀도는 $0.5\;{\sim}\;4.0^*10^{20}/cm^3$로 증가함에 따라 이동도는 $1.5{\sim}5.5\;cm^2/Vs$로 투명전도막의 특성을 보였다.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.67-70
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• 2008

This paper deals with the effect of radial parameters in cogging process such as reduction in height (Rh) and rotational angle ($\theta$) of a billet on a void closure for large forged products. Usually closing and consolidation of internal void defects in a ingot is a vital matter when utilized as large forged products, using a press with limited capacity and the sizes of the ingots becoming larger. Consequently, it is important to develop cogging process for improvement of internal soundness without a void defect and cost reduction by solid forging alone with limited press capacity. For experiments of cogging process, hydraulic press with a capacity of 800 ton was used together with a small manipulator which was made for rotation and overlapping of a billet. Size of a void was categorized into two types; $\emptyset$ 6.0 mm and $\emptyset$ 9.0 mm to investigate the change of closing and consolidation of void defects existed in the large ingot during the cogging process. Also open void and closed void in the ingot were tackled to show the differentiation of closing process of internal voids with respect to void sizes. In this paper systematic configuration for closing process of void defects were expressed based on this experiment results in the cogging process.