• Restorative Dentistry and Endodontics
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• 제29권3호
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• pp.249-266
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• 2004

The purpose of this study was to determine whether pH and time has any influence on the degradation behavior of composite restoration by analyzing the leached monomers of dental composites qualitatively and quantitatively after storage in acetate buffer solution as a function of time using high performance liquid chromatography (HPLC) / mass spectrometer. Materials and Methods：Three commercial composite restorative resin materials (Z-250, Heliomolar and Aeliteflo) with different matrix structure and filler composition were studied. Thirty specimens (7mm $diameter{\times}2mm$ thick) of each material were prepared. The cured materials were stored in acetate buffer solution at different pH (4, 7) for 1, 7 and 45days. As a reference, samples of unpolymerized composite materials of each product were treated with methanol (10mg/ml). Identification of the various compounds was achieved by comparison of their mass spectra with those of reference compound, with literature data. and by their fragmentation patterns. Data were analysed statistically using ANOVA and Duncan's test. Results：1. Amounts of leached TEGDMA in Aeliteflo were significantly larger than those of UDMA in Z-250 and Heliomolar at experimental conditions of different storage time and pH variation (p<0.001). 2. As to comparison of the amounts of leached monomers per sorage time, amounts of leached TEGDMA in Aeliteflo and UDMA in Z-250 and Heliomolar were increased in the pH 4 solution more significantly than in the pH 7 solution after 1day, 7days and 45days, respectively (p<0.001). 3. In total amounts of all the leached monomers with storage times, the overall amounts of pH 4 extracts were larger than those of pH 7 extracts for all resin groups, but there was no significant difference (p>0.05).

• Bulletin of the Korean Chemical Society
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• 제28권5호
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• pp.745-750
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• 2007

An isotope dilution-liquid chromatography/tandem mass spectrometric method was developed as a candidate reference method for the accurate determination of folic acid in infant milk formula. Sample was spiked with 13C5-folic acid and then extracted with phosphate buffer (pH 6) solution. The extract was further cleaned up by deproteinization followed by a C18 solid-phase extraction cartridge. The extract was analyzed by using LC/ ESI/MS/MS with selectively monitoring the collisionally induced dissociation channels of m/z 442 → m/z 295 and m/z 447 → m/z 295, which are the neutral glutamyl loss from the [M+H]+ ions of folic acid and 13C5-folic acid, respectively. LC/MS/MS chromatograms showed substantially reduced background from chemical noises compared to LC/MS chromatograms. Repeatability and reproducibility studies showed that the LC/MS/ MS method is a reliable and reproducible method which can provide less than 1.5 relative percentage of method precision.

• 한국전자파학회논문지
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• 제11권7호
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• pp.1211-1217
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• 2000

The three-dimensional finite-difference time-domain (FDTD) method and the two-dimensional quasi-static formulation have been used to calculate the characteristic impedance and the microwave effective index of coplanar waveguide structures on Lithium Niobate ($LiNBO_3$) single crystal substrates with a yttria-stabilized zirconia (YSZ) or $SiO_2$ buffer layer. The results shown can be a good source to predict the modulator characteristics. The effects of the thin buffer layer and anisotropy of the $LiNBO_3$ crystal (x-cut and z-cut) are discussed. The comparison between the FDTD and quasi-static results shows good agreement. In this paper, the efficient modeling technique of the FDTD method for the coplanar waveguide (CPW) structures based on an anisotropic substrate with a thin buffer layer is developed.

• 한국전기전자재료학회논문지
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• 제13권12호
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• pp.1051-1057
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• 2000

A traveling-wave CPW(coplanar waveguide) electrode with abruptly broken input/output-taper for LiNbO$_3$optical modulator was designed and fabricated. The electrical characteristics of traveling-wave electrode on z-cut LiNbO$_3$crystal with SiO$_2$buffer layers were measured by network analyzer. To confirm the possibility of the electro-optic modulator electrode, detailed calculations of the impedance, microwave effective index and attenuation constants are presented as a function of the microwave electrode thickness, but the buffer layer thickness is fixed as 1${\mu}{\textrm}{m}$. These characteristics are discussed from the viewpoint of the device optimization and are expected to be design guides for the LiNbO$_3$modulator’s electrodes.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 하계종합학술대회 논문집
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• pp.319-322
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• 1999

In this paper, we report characteristics of a internal chip of LiNbO$_3$ modulator with low-driving-voltage at 150nm wavelength. A Ti diffusion method for LiNbO$_3$ optical waveguide and a buffer layer for improving phase velocity mismatch between optical and microwave waves were employed. The traveling-wave coplanar waveguide electrode of 35mm is used for reducing the driving voltage. From this work, wideband modulation of 10㎓ and low-driving voltage of 3.9volts are realized.

• JSTS:Journal of Semiconductor Technology and Science
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• 제3권4호
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• pp.175-180
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• 2003

In this paper, we present a new method for early depth test for a 3D rendering engine. We add a filter stage to the rasterizer in the 3D rendering engine, in an attempt to identify and avoid the occluded pixels. This filtering block determines if a pixel is hidden by a certain plane. If a pixel is hidden by the plane, it can be removed. The simulation results show that the filter reduces the number of pixels to the next stage up to 71.7%. As a result, 67% of memory bandwidth is saved with simple extra hardware.

• 한국해양공학회지
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• 제9권2호
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• pp.83-88
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• 1995

In this paper, the solid modeller suitable for PC was developed for Top-down 3-D representation and analysis of fixed offshore structures. Also solid modelling and hidden line removal were conducted in order to visualize the offshore structures based on the scan line z-buffer algorithm.

• 미생물학회지
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• 제24권3호
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• pp.228-235
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• 1986

Zymomonas mobilis의 spheroplast 형성과 새생조건의 새량과 초|소배시에서의 새생에 대해서 연구하였다. Tris-maleate buffer (pH 5~6), $Ca^{++}$ ions 그러고 EDTA등은 out야 membrane의 투과성 변화를 야기시 켰다 Zymommonas의 세포벽은 lysozyme, mutanolysin같은 세포벽 분해효소에 의해 분해가 되지 않은 것처럼 보였고 sphe-roplast 생성에 glycine 처리는 필수적이었다. 그러나 lysozyme 처리에 의해서 spheroplast 형성이 촉진되는 것을 확인하였다. 따라서 ly sozyme과 glycine을 함께 처리함으로서 spheroplasting배지에서의 처리시간을 4시간으로 단축 할 수 있었고 재생율이 7-10% 증가되었다.

• 한국정보과학회논문지:시스템및이론
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• 제30권10호
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• pp.579-585
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• 2003

최근 대부분의 3차원 그래픽 렌더링 프로세서는 메모리 접근 지연 및 대역폭을 줄이기 위해 깊이 데이타와 색상 데이타를 가지고 있는 픽셀 캐쉬(pixel cache)를 사용한다. 본 논문에서는 렌더링 프로세서의 성능을 향상시키기 위한 효과적인 픽셀 캐쉬 구조를 제시한다. 제안하는 픽셀 캐쉬 시스템은 기본적으로 3차원 렌더링 프로세서에서 수행되는 깊이 검사(Z-test) 결과에 의해 선택적으로 깊이 데이터를 캐쉬에 저장하며, 색상 데이타는 별도의 버퍼에 저장한다. 시뮬레이션 결과에 의하면 16K바이트의 제안하는 캐쉬 시스템이 32K바이트의 일반적인 캐쉬보다 더 나은 성능을 보인다.

• 농약과학회지
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• 제3권2호
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• pp.37-46
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• 1999

침투성 살충제 carbofuran의 작물체중 잔류성과 그 안전성을 평가하기 위하여 carbofuran을 살포했을 것으로 간주되는 감자와 땅콩 및 마늘 시료를 주산지 부근의 대규모 시장에서 수집한 후 carbofuran과 carbofuran의 식물체중의 주 대사산물로 보고된 3-hydroxycarbofuran의 잔류량을 조사하고 carbofuran의 각 작물체내 대사 양상을 구명하기 위하여 각 작물의 phesphate buffer 추출액중 carbofuran의 분해실험을 수행하였다. 여러 지역의 시장으로부터 수집한 총 20 점의 완숙마늘 시료중 2점 (M-12와 M-16)의 시료에서 0.13과 0.07mg/kg의 carbofuran이 검출되어 10%의 검출빈도를 보였으나, 그 잔류량은 잔류허용기준인 0.5 mg/kg 보다 훨씬 작았다. 3-Hydroxycarbofuran은 총 20점의 시료중 1점 (M-12)의 시료에서 0.13 mg/kg이 검출되어 5%의 검출빈도를 보였으며, 풋마늘과 감자 및 땅콩 시료중 carbofuran과 3-hyoxycarbofuran의 잔류량은 분석결과 모든 시료에서 검출한계 미만이었다. 완숙마늘의 1일 섭취량에 근거한 carbofuran의 최대 섭취추정량은 0.0013mg으로 1일 최대섭취허용량인 0.55 mg의 0.24%이었으며, 마늘과 감자 및 땅콩시료에서 carbofuran이 검출되지 않아 마늘과 감자 및 땅콩 경작시 carbofuran을 사용하여도 생산물은 안전한 것으로 평가되었다. Carbofuran은 각 작물의 phosphate buffer 추출액중에서 주로 가수분해에 의하여 주 대사산물인 carbofuran phenol (m/z 164)을 생성하였으며, 그 양은 배양기간에 비례하여 증가하였다.