• Korean Journal of Microbiology
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• v.30 no.3
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• pp.225-231
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• 1992

l o identil) ;~nclc li~iracterize; In iiscorhate oxiililinp enzyme in ('/rItrn~i~rlon~ir~c~t~itr~~lr.o\ r(1rii. we studicil ;is li)llows. Ascorh;ric oxiiliring cn/;jme activit) f ~ o ~thne crude extract 01' ( ' / ~ l o n ~ ~ . c l o t ~1~~oit~rl~1oin~/.t\ii W;I\ dctccietl by 5pecific active 5ta1ning through nati\e gel cletrophorcsi\ and ~iltra\~iolestp eciroscopy. Ascorb~ttco xidizing c n ~ y m ew i15 partilly 1~1rilieJ by \;~riousp roccclurcs inclucli~lga rnmoniu~ns uIl';~tcp recipit;iion. aJ\orption ~111-om;~togrophy on Iiy~lroxyapaiitca nd Scphailcx <;-I50 gel lillration chrornatogral>liy. Plie ~nolecularw eight 01' the nativc cnrytiic was ahour 88.000 tlalton hy nativc gel elcciroplloresis anci subunit niolecul;ir ~rciglit 55,000 ol' this cnrymc w;~c determined hy SIIS-P.ASI!. The optimum tcmper~tture ii)r the cnrymc nos ahout 5j$^{\circ}$C and pH 4.6 was the optimum. Moreover. ascorhaie oxi~losc in C: reinhardtii was confirmet1 by Ll1e\tcrn blotting technique.

• The Journal of the Acoustical Society of Korea
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• v.17 no.8
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• pp.41-47
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• 1998

이중 통신(Duplexer) 필터를 설계 및 개발하기 위한 최적조건을 구하기 위해 36° LiTaO3 기판 표면에 빗살무늬 변환기를 사용한 모의 실험을 수행하였으며, 전극 재료로는 Cu-Al(W3%)합금을 이용하였다. 제작한 듀플렉스 필터의 사다리(Lader)형 구조로서 직렬 공진기와 병렬 공진기의 결합으로 필터를 구성하였다. 적절한 통과대역과 저지대역을 형성 하기 위하여 직렬 공진기와 병렬 공지기의 주파수 차이를 30MHz로 했으며, 낮은 저지대역 을 형성하기 위하여 두 공진기의 전기용량의 비는 1로 하였고, 전극의 두께는 2,500Å으로 하였을 때 설계 조건과 일치하는 주파수 응답을 얻었다. 제작한 듀플렉서 필터의 주파수 특 성은 중심 주파수는 836.5MHz와 881.5MHz, 통과대역 폭은 25MHz, 삽입손실은 2.5dB 이하 및 저지대역은 -35dB이하로 나타났다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.184-184
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• 2009

Lead-free Piezoelectric $[Li_{0.04}(Na_{0.44}K_{0.56})](Nb_{0.88}Ta_{0.1}Sb_{0.02})$ (abbreviated as NKNLTS) has been synthsized by conventional mixed oxide method traditional ceramics process without cold-isostatic pressing. Effect of $Bi_2O_3$ addition on NKNLTS ceramics was investigated. Piezoelectric properties of the ceramic were varied with the amount of $Bi_2O_3$ addition and showed the maximum Kp value at 0.4wt% $Bi_2O_3$ addition. The results show that the optimum poling condition for NKNLTS ceramics of 3.5kV/mm, poling temperature of $120^{\circ}C$ and poling time of 30min. At the sintering temperature of $1100^{\circ}C$ and the calcination temperature $800^{\circ}C$, the optimal values of density=$4.7g/cm^2$, Kp=0.44, $\varepsilon_r$=1309 were obtained. Consequently, lead free piezoelectric ceramics with the excellent piezoelectric could be fabricated using a conventional mixed oxide process and the optimal manuacturing condition of those was obtained.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.319-322
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• 2004

본 연구에서는 DNA의 상보적인 결합을 이용하여 DNA 혼성화 반응을 감지할 수 있는 SH형 SAW 센서를 개발하였다. 측정에 사용된 DNA는 15개의 염기를 가진 올리고 뉴클레오티드를 사용하였으며 이에 대해 상보적 결합이 가능한 염기서열을 가진 것과 그렇지 않은 미스매치 형태의 DNA 올리고뉴클레오티드를 이용하여 DNA 혼성화 반응 특성을 측정하였다. SH형 SAW 센서는 압전 단결정 $LiTaO_{3}$를 사용하여 100 MHz 발진되는 형태로 제작하였으며, 센서의 지연선 위에 Ti/Au 층을 증착하여 SH기가 수식된 탐침 DNA의 고정화가 가능하게 하였다. 제작된 센서는 Au가 증착된 박막위에 탐침 DNA를 SAM 방법으로 고정화 시켰을 경우와 고정화된 탐침 DNA와 표적 DNA와의 혼성화 반응을 시키고 난 후의 센서의 주파수 변화를 각각 측정하였다. 개발된 DNA 혼성화 반응 측정용 SH형 SAW센서는 DNA 혼성화 특성에 기인한 질량하중 효과에 따른 안정적인 주파수 변화를 나타내었다.

• Proceedings of the IEEK Conference
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• 2001.06a
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• pp.245-248
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• 2001

In this paper, we have investigated the design technique and fabricated the surface acoustic wave (SAW) filter for duplexer, which consists of Tx. and Rx. filter, and antenna terminal. For Tx. and Rx. bandpass filters we used the one-port SAW resonators with n-section ladder structure. The structure is composed of couples of series-arm resonators and parallel-arm resonators. RF filter using ladder structure was designed and fabricated on 36$^{\circ}$Y-X LiTaO$_3$ substrates. Designed filters, insertion loss is less than 1.5dB, the bandwidth is more than 25MHz, rejection band level is less than -30dB and center frequency is 820MHz.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.201-204
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• 2001

Rosen형 또는 적층 Rosen형과 같은 압전세라믹 변압기는 고전압, 고효율의 출력특성과 소형이라는 장점을 가지는 반면에, 온도에 따른 압전 특성의 변화가 심하다는 단점을 가진다. 이러한 이유로 압전 단결정과 같은 온도특성이 안정적인 재료를 이용한 변압기의 개발이 진 행되고 있다. 따라서, 본 연구에서는 온도계수가 낮은 $LiTaO_3$ 단 결정$(X-112^\circ\;Y)$을 이용한 압전변압기를 제작 그 특성을 시뮬레이션 및 실험으로 해석하였다.

• Journal of the Korean Society for Nondestructive Testing
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• v.10 no.2
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• pp.56-62
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• 1990

Surface Acoustic Waves(SAW) are generated on silicon wafer and $YZ-LiTaO_3$ substrate and are detected by noncontact method. As wave sources two kinds of transducers are used : the wedge-type of 20.0 MHz and fabricated Interdigital Transducer(IDT) of 20.8 MHz. SAW are modulated by the optical chopper frequency and are syncronized with a laser beam. In signal processing, intensity variations of light due to the intensity of SAW are analyzed using lock- in amplifier. From the results, corresponding to the applied input power, the intensity variations of a deflected light by corrugations on the substrates are increased and saturation phenomenon is observed.

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.228-229
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• 2003

The quasi-phase matching (QPM) technique has dramatically changed the guidelines in developing nonlinear optical materials, which doesn't require birefringence and off-diagonal components for efficient wavelength conversion. Minimum requirement for QPM is the modulation of nonlinearity and ferroelectric materials with low coercive field has become fascinating in periodical poling. Stoichiometric lithium tantalate (SLT) has attractive advantages of low coercive field (∼l .5 KV/mm), high nonlinearity, high optical damage resistance and low thermo-optic coefficients, leading to a large aperture QPM devices for high power operation. (omitted)

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.597-598
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• 2006

This paper describes a development of a new $1.4{\times}1.1$ and $2.0{\times}1.4mm$ RF SAW filters made by PCB substrate instead of HTCC package, and this technology can reduce the cost of materials down to 40%. We have investigated the multi-layered PCB substrate structures and raw materials to find out the optimal flip-bonding condition between the $LiTaO_3$ wafer and PCB substrates. Also the optimal materials and processing conditions of epoxy laminating film were found out through the experiments which can reduce the bending moment caused by the difference of the thermal expansion between the PCB substrate and laminating film. The new PCB SAW filter shows good electrical and reliability performances with respect to the present SAW filters.

• Journal of the Korean Ceramic Society
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• v.40 no.11
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• pp.1047-1057
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• 2003

A sub-nanometer resolution Scanning Nonlinear Dielectric Microscope (SNDM) was developed for observing ferroelectric polarization. We also demonstrate that the resolution of SNDM is higher than that of a conventional piezo-response imaging. Secondly, we report new SNDM technique detecting higher nonlinear dielectric constants $\varepsilon$$\_$3333/ and $\varepsilon$$\_$33333/. Higher order nonlinear dielectric imaging provides higher lateral and depth resolution. Finally, the formation of artificial small inverted domain is reported to demonstrate that SNDM system is very useful as a nano-domain engineering tool. The nano-size domain dots were successfully formed in LiTaO$_3$ single crystal. This means that we can obtain a very high density ferroelectric data storage with the density above 1T-bits/inch$^2$.