• ETRI Journal
• /
• 제39권3호
• /
• pp.390-397
• /
• 2017

In this paper, we propose a scheme for designing a tunable pixel layer based on a $Ge_2Sb_2Te_5$ (GST) alloy thin film. We show that the phase change of GST can significantly affect the reflection characteristic when the GST film is embedded into a dielectric encapsulation layer. We investigate the appropriate positions of the GST film within the dielectric layer for high diffraction efficiency, and we prove that they are antinodes of Fabry-Perot resonance inside the dielectric layer. Using the proposed scheme, we can increase the diffraction efficiency by about ten times compared to a bare GST film pixel, and 80 times for the first-to-zeroth-order diffraction power ratio. We show that the proposed scheme can be designed alternatively for a broadband or wavelength-selective type by tuning the dielectric thickness, and we discuss a multi-phase example with a double-stack structure.

• 조명전기설비학회논문지
• /
• 제29권12호
• /
• pp.83-87
• /
• 2015

This paper presents a simple notch filter, which is so suitable for three-phase unbalanced and distorted power line. In the d-q synchronous transformation, three-phase unbalanced and distorted voltages generate lots of ripple voltages on d-q axes. The ripples make disturbances on controllers such as PLL of phase tracking. Unbalanced state makes ripple of double the frequency of power line. Odd harmonics 5th and 7th on the line make even 4th and 6th ripples on d-q axes due to the rotating reference frame, respectively. Cascaded two comb filters, delay lines 1/4T and 1/8T, are adopted for the ripple rejection. The filter rejects harmonics 2nd, 4th, 6th, 10th and so on. They are very effective to remove the ripples of both unbalance and distortion. The filter, implemented by two FIFOs on an experimental system, is adopted on a PLL controller of power line phase tracking. Through the simulation and experimental results, performance of the proposed comb filter has been validated.

• 농업생명과학연구
• /
• 제44권3호
• /
• pp.7-14
• /
• 2010

Alternative subirrigation way, capillary wick system (CWS) was tested to reduce labor cost, waste water, contamination of ground water, and use of fungicide compared to overhead irrigation system (OIS). CWS helped reduce remarkably the working hours for watering from 4 hours in OSI to just 5 minutes. Labor cost was saved 98% in CWS compared to OIS. By the physical characteristics of various growing media, 1 coconut coir+2 perlite (v/v) mixture was selected because it had an ideal distribution of three phase, e.g. 1 solid: 1 liquid: 2 gas phase. Medium mixture containing scoria had so high bulk and particle density to hurt root. In bark-containing medium, the liquid phase and the percent saturation of liquid phase with time elapsed was lower than that of other mixture. It meant that the mixture contained very low level of water. Application of CWS for cyclamen pot production played an important role in reducing the incident of fusarium wilt symptom from 18% in conventional over watering system to 4%. Cyclamen pot irrigated by capillary wick had shorter petiole and more leaves than those by overhead watering. As a result, this system was highly beneficial to get uniform pot products with high quality. It improved water and nutrient solution efficiency relative to conventional overhead irrigation system (OIS).

• 한국자기학회지
• /
• 제10권3호
• /
• pp.133-138
• /
• 2000

최초의 상온 초거대 자기저항(colossal magnetoresistance)효과 물질인 망간 산화물$La_{1-x}Ba_{x}MnO_3(0\leq\chi\leq$1) 에 대한 결정학적, 자기적, 전기적 성질들을 온도 및 자기장의 함수$5\;K\leqT\leq360\;K,\;-7\;T\leqH\leq7\;T)$로 정밀 조사하였다. $La_{1-x}Ba_{x}MnO_3$는 x<1/2 일 때는 x에 의존하는 구조를 가진 단일상(single phase)의 강자성, $x\geq1/2$ 일 때는 화학적, 자기적 상분리에 의한 강자성과 비강자성 복합상(multi phase)을 가지는 것으로 나타났다. 강자성 전이 온도(Tc)는 x=1/3이 될 때까지 꾸준히 증가하였고 x＞1/3 일 때 일정한 값 Tc(340 K)을 가졌다. 또 포화 자화값(Ms)은 x=1/8이 될 때까지 증가하였고 $1/8\leqx<1/2$에서는 이론적인 최대값을 가지고$x\geq1/2$ 에서는 자기적 상분리에 의해 감소하였다. 또 $La_{1-x}Ba_{x}MnO_3$는 $1/4\leqx<1/2$에서 금속성을 가졌다. 특히 $x\geq1/2$인 시료는 화학적, 자기적 상분리로 인하여 스미기 형태(percolation type)의 저항 온도 의존성 및 큰 저자기장 자기 저항 효과를 보였다.

• 한국해양공학회지
• /
• 제23권4호
• /
• pp.52-57
• /
• 2009

The effect of aging treatment on the microstructure and mechanical properties of super duplex stainless steel with W was investigated. The phase was precipitated mainly at the early stage of aging and a lower aging temperature under $750^{\circ}C$, but the phase was formed after long-term aging treatment between $600^{\circ}C$ and $900^{\circ}C$. The volume fraction of the phase increased with aging temperature up to $750^{\circ}C$ and then decreased up to $900^{\circ}C$. With an increase in the aging time, the volume fraction phase at the early stage of aging increased slightly, and then increased rapidly beyond a certain time. The rapid increase in the tensile strength and hardness and decrease in the elongation and impact toughness were measured with aging temperatures up to $750^{\circ}C$. On the other hand, the tensile strength and hardness decreased slightly, and the elongation and Charpy impact toughness were unchanged with aging temperatures over $750^{\circ}C$. The tensile strength and hardness increased rapidly at the early stage of aging, and then increased slowly beyond a certain time. The elongation and Charpy impact toughness decreased rapidly at the early stage of aging, and then remained unchanged beyond a certain time. The phase that formed at the early stage of aging and the lower aging temperature had a considerable effect on the elongation and Charpy impact toughness of the super duplex stainless steel with W.

• Korea-Australia Rheology Journal
• /
• 제21권1호
• /
• pp.59-69
• /
• 2009

The prediction of pressure drop for a droplet flow in a confined micro channel is presented using FE-FTM (Finite Element - Front Tracking Method). A single droplet is passing through 5:1:5 contraction - straight narrow channel - expansion flow domain. The pressure drop is investigated especially when the droplet flows in the straight narrow channel. We explore the effects of droplet size, capillary number (Ca), viscosity ratio ($\chi$) between droplet and medium, and fluid elasticity represented by the Oldroyd-B constitutive model on the excess pressure drop (${\Delta}p^+$) against single phase flow. The tightly fitted droplets in the narrow channel are mainly considered in the range of $0.001{\leq}Ca{\leq}1$ and $0.01{\leq}{\chi}{\leq}100$. In Newtonian droplet/Newtonian medium, two characteristic features are observed. First, an approximate relation ${\Delta}p^+{\sim}{\chi}$ observed for ${\chi}{\geq}1$. The excess pressure drop necessary for droplet flow is roughly proportional to $\chi$. Second, ${\Delta}p^+$ seems inversely proportional to Ca, which is represented as ${\Delta}p^+{\sim}Ca^m$ with negative m irrespective of $\chi$. In addition, we observe that the film thickness (${\delta}_f$) between droplet interface and channel wall decreases with decreasing Ca, showing ${\delta}_f{\sim}Ca^n$ Can with positive n independent of $\chi$. Consequently, the excess pressure drop (${\Delta}p^+$) is strongly dependent on the film thickness (${\delta}_f$). The droplets larger than the channel width show enhancement of ${\Delta}p^+$, whereas the smaller droplets show no significant change in ${\Delta}p^+$. Also, the droplet deformation in the narrow channel is affected by the flow history of the contraction flow at the entrance region, but rather surprisingly ${\Delta}p^+$ is not affected by this flow history. Instead, ${\Delta}p^+$ is more dependent on ${\delta}_f$ irrespective of the droplet shape. As for the effect of fluid elasticity, an increase in ${\delta}_f$ induced by the normal stress difference in viscoelastic medium results in a drastic reduction of ${\Delta}p^+$.

• Korea-Australia Rheology Journal
• /
• 제18권2호
• /
• pp.99-102
• /
• 2006

Primitive chain network model for block copolymers is used here to simulate molecular dynamics in the entangled state with acceptable computational cost. It was found that i) the hooking procedure rearranging the topology of the entangled network is critical for the equilibrium structure of the system, and ii) simulations accounting for the different chemistry, i.e., with a biased hooking probability based on interaction parameter ${\chi}$ for selection of the hooked partner, generates a reasonable phase diagram.

• 한국통계학회:학술대회논문집
• /
• 한국통계학회 2002년도 추계 학술발표회 논문집
• /
• pp.79-83
• /
• 2002

A phase III clinical trial of a new drug for neutropenia induced by chemotherapy is presented and consider adding random effects in crossover design which was used in the clinical study. The diagnostics for its heteroscedasticity based on score statistic is derived for detecting homoscedasticity of errors in crossover design. A small simulation study is peformed to investigate the finite sample behaviour of the test statistic which is known to have an asymptotic chi-square distribution under the null hypothesis.

• 한국세라믹학회지
• /
• 제22권5호
• /
• pp.66-70
• /
• 1985

This study was to investigate physical properties of the system $Ca(Mg_{1-x}Al_x) (Si_{2-x}Al_x)O_6$ by quenching method. This system $\chi$=0.1 to 0.3 had same crystal phase microstructure and similar properties. Bulk density microhardness thermal expansion coefficient and modulus of rupture of these solid solutions were 2.87~2.95g/cm3 850~900kg/$mm^2$, $7.5~7.8{\times}10^{-6}$/$^{\circ}C$ and 1950~1980kg/$cm^2$ respectively.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.I
• /
• pp.314-316
• /
• 2005

Light flicker is a notorious phenomenon influencing light quality. The flicker of the light flux outputs from the light sources perceived by human eyes depends upon the lamp brightness fluctuations for projector display. This paper describes a ballast ignition control system, which makes the lamp strike frequency phase lock the blanking time period to minimize the flicker effect