• Polymer(Korea)
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• v.30 no.2
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• pp.182-186
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• 2006

Due to their periodic helical structure, cholesteric liquid crystals (CLC) have a unique ability to selectively reflect light. CLC films reflecting a broad wavelength band were prepared by inducing a pitch gradient in CLC layer through a phase separation. The reflection bandwidth of the CLC cell was broaden as irradiation light intensity decreased and as the amount of the UV absorbing dye increased. Initial reflection bandwidth of 50 nm was broaden to 300 nm Various pitch distributions in the CLC cell was observed using SEM and ATR-IR technique was used to prove that the pitch distributions are induced through the phase separation.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.4
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• pp.375-387
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• 2015

This study investigates an economic and highly efficient power-converter topology and its modulation scheme for 60 kW rapid EV charger system. The target system is a three-phase three-switch buck-type rectifier topology. A new carrier-based PWM scheme, which is characterized by simple implementation using logic gates, is introduced in this paper. This PWM scheme replaces the diode rectifier equivalent switching state with an active switching state to produce the same effective current flowing path. As a result, the distortion of input current during the polarity reversal of capacitor line voltage can be mitigated. The proposed modulation technique is confirmed through simulation verification. The proposed modulation technique and its implementation scheme can expand the operation range of the three-phase three-switch buck-type rectifier with high-quality AC input and capacitor ripple current.

• Annual Conference of KIPS
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• 2023.05a
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• pp.8-10
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• 2023

삼킴장애는 음식물이 입에서 식도로 가지않고 걸리거나 기도(Trachea)로 흡입되는 문제를 갖는 상태이다. 특히 노인이나 신경계 질환을 앓는 환자의 경우 기도로 흡입된 음식덩이가 폐렴을 일으키고 결국에는 사망으로 이어지기에 적절한 치료와 관리가 요구된다. 보통 영상으로 판단할 수 있는 삼킴단계는 구강준비단계(Oral Preparatory Phase), 구강단계(Oral Phase), 인두단계(Pharyngeal Phase), 식도단계(Esophageal Phase) 4가지로 분류하고 삼킴장애는 침습(Penetration)과 흡인(Aspiration)으로 크게 2가지로 분류한다. 본 논문에서는 이러한 6가지 클래스를 가지는 삼킴장애 환자 비디오 파일을 라벨링하기 위한 웹 애플리케이션을 제안한다. 이를 구현하기 위해서 대용량 멀티프레임 이미지를 수신해서 분리하여 저장하도록 개발하였다. 또한 음식덩이를 정교하게 분할할 수 있도록 GrabCut 알고리즘을 적용하여 라벨링할 수 있도록 하였다. 차후 라벨러와 전문의 간의 협업이 가능하도록 라벨링 데이터의 상태를 관리할 수 있도록 개발하고자 한다.

• Transactions of the Society of Information Storage Systems
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• v.8 no.2
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• pp.44-49
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• 2012

We measured the surface flatness of both sides for refractive media using the transmitted digital holography method. To enhance the accuracy of the result, phase-shifting system was used. With two different phase modulation of reference beam, the phase profile of object can be easily obtained. Thus, we proposed the surface measurement method which can measure large area fast, compared with conventional methods. To guarantee the reliability of obtained result, we compared with Zygo measurement system. With the proposed method, the surface flatness of $3.45{\mu}m$ resolution could be obtained.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.277-281
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• 2004

The following paper proposes the new design of digital sine wave generator which allows users to define the phase shift of the out put sinewave according to user's demands. This new sinewave generator will have 2 outputs, cos(${\omega}_0n$) and cos(${\omega}_0n$+${\phi}$) The design of the new system starts from the construction of discrete time system with impulse response as cos(${\omega}_0n$) in a pair of conjugate complex poles and a pair of zeros at the origin and the real axis. If users want to make a phase shift of sign wave, users can change the position of zero at the real axis. The results of the experiment have shown that the new design of sign wave generator has generated sine wave with the correct phase shift according to the theory.

• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.547-550
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• 2001

Through matched filtering synthetic aperture radar (SAR) produces high-resolution imagery from data collected by a relative small antenna. While the impulse response obtained by the matched filter approach produces the best achievable signal-to-noise ratio, large sidelobes must be reduced to obtain higher-resolution SAR images. So, many enhancement methods of SAR imagery have been proposed. As a deconvolution method, the phase-extension inverse filtering is based on the characteristics of the matched filtering used in SAR imaging. It improves spatial resolution as well as effectively suppresses the sidelobes with low computational complexity. In the phase-extension inverse filtering, the impulse response is obtained from simulation with a point target. But in a real SAR environment, for example ERS-1, the impulse response is distorted by many non-ideal factors. So, in the phase-extension inverse filtering for a real SAR processing, the magnitudes of the frequency transfer function have to be compensated to produce more desirable results. In this paper, an estimation method to obtain a more accurate impulse response from a real SAR image is studied. And a compensation scheme to produce better performance of the phase-extension inverse filtering is also introduced.

• Journal of Korean Society on Water Environment
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• v.26 no.5
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• pp.834-840
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• 2010

To find out the toxin production characteristics of Korean harmful cyanobacteria, we isolated 14 cyanobacterial strains from Korean lakes and rivers and analyzed the kinds and cellular content of microcystins (MCYSTs) of cyanobacterial isolates using cultured biomass. And we measured the MCYSTs production by growth phase of two representative toxic strains, Microcystis aeruginosa (HG-015) and Anabaena planktonica (HG-012). Among seven cyanobacteral species, Microcystis wesenbergii showed the highest cellular MCYSTs content. MCYST-RR was the most dominant toxin reaching more than 85% of MCYSTs produced by isolated cyanbacterial strains. During the mass culture, Microcystis aeruginosa (HG-015) showed the highest yield and accumulation of MCYSTs in the exponential growth phase. However the cellular content of chlorophyll a and MCYSTs of Anabaena planktonica (HG-012) showed higher value in the stationary and early death phase than in the exponential growth phase. Our results suggest that control and removal of harmful cyanobacterial bloom before exponential growth phase may be effective to prevent health risk of cyanobacterial toxins in the drinking water sources.

• Journal of Information Display
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• v.12 no.3
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• pp.115-119
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• 2011

Optically isotropic liquid crystal (LC) mixture such as blue-phase LC and nanostructured LC composites exhibit the advantages of fast response time, high contrast ratio and wide-viewing angle due to the induced birefringence along the horizontal electric field. Utilizing this mixture, a novel single cell gap in-plane switching-type polymer-stabilized blue-phase transflective liquid crystal display by embedding the nanowire grid polarizer as a polarization-dependent reflective polarizer in the R region is proposed. This device can be used as a normal black mode without any quarter-wave plate or patterned in-cell phase retarder. Moreover, the transmittance is identical to the reflectance so that it will be suitable for single gamma driving. Detailed electro-optic performances, such as voltage-dependent light efficiency and viewing angle of the proposed device configuration, are investigated.

• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2701-2703
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• 1999

A new mode of parallel operation of a modular 3-phase AC-DC Flyback converter for high power factor correction along with tight regulation is presented in this thesis. The converter offers input/output transformer isolation for safety, a unity input power factor for minimum reactive power, high efficiency and high power density for minimum weight and volume. Compared with previously developed 3-phase two-stage power converter, the advantage of the proposed converter does not require expensive high voltage and high current devices that are normally needed in popular boost type 3-phase converter. In this paper, a detailed small signal analysis of the modular 3-phase AC-DC flyback converter is provided for control purposes and also experimental results are included to confirm the validity of the analysis.

• Journal of Korea Foundry Society
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• v.27 no.4
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• pp.167-172
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• 2007

In the present study, the microstructural evolution and mechanical properties of $Al_{71.6}Ge_{28.4}$ eutectic alloy have been investigated. Stable (fcc ${\alpha}$-Al and diamond cubic ${\beta}$-Ge) and various metastable crystalline (monoclinic, rhombohedral) phases were produced by competitive phase selection during non-equilibrium processing methods i.e. melt spinning and injection casting. The as-injection casted samples containing metastable-equilibrium eutectic (${\alpha}$-Al + monoclinic) structure showed much higher strength than samples with equilibrium eutectic (${\alpha}-Al+{\beta}-Ge$) structure but plasticity disappointingly diminished. In order to endow the enhanced ductility without significant strength drop, the alloys was heat-treated at transition temperature from metastable phase to stable phase. The annealed specimen displayed the phase transformed microstructural evolution and enhanced macroscopic plasticity.