• Journal of Advanced Navigation Technology
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• v.11 no.4
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• pp.437-446
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• 2007

In this paper, we numerically induced the optimal values of optical phase conjugator (OPC) position and dispersion coefficients of fiber sections, which can improve the bit error rate (BER) and design the adaptive WDM transmission system, as a function of the extinction ratio (ER) of 10 dB and 20 dB in $16{\times}40$ Gb/s WDM transmission system. It is confirmed that these optimal parameter values for effectively compensating overall WDM channels are dependence on the extinction ratio of signals as well as modulation format, transmitted channel numbers, which were investigated in previous researches. It is also confirmed that ER of 20 dB has the advantage of designing flexible WDM systems using optimal parameters than ER of 10 dB.

• Journal of the Korean Chemical Society
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• v.26 no.3
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• pp.172-178
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• 1982

A psoralen-DNA monoadduct analogue, 4',5'-dihydropsoralen (DHP) is synthesized and its photophysical properties such as fluorescence quantum yield (0.08), phosphorescence quantum yield (0.013), fluorescence lifetime (0.95ns), and phosphorescence lifetime(0.039s) were measured in ether solution and in frozen matrix state at 77K. The photocycloaddition reaction of DHP with tetramethylethylene(TME) was carried out in solution and in the frozen state. The major photoadduct was isolated and characterized by elemental analysis and physical methods such as UV, IR, NMR, and mass spectrometry. The major DHP-TME photoadduct was proved to be an 1 : 1 $C_4$-cycloadduct formed through 2 + 2 cycloaddition of the pyrone double bond of DHP to TME.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.2
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• pp.1-8
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• 1999

We analyze the transmission performance of WDM system based on cascaded optical add/drop multiplexers. The considered factors degrading the performance in this paper include the intra-channel corosstalk caused from space switches and demultiplexers/multiplexers, the amplified spontaneous emission noise, and the extinction ratio. To ensure the power penalty within 1dB, the extinction ration more than 13dB, the switch corosstalk less than 39dB, and the demultiplexer/multiplexer crosstalk less than 20dB are required. Under the assumption of switch corosstalk less than 30dB, performance degradation due to the ASE noise is dominant compared to the crosstalk. With the fixed decision threshold in an optical receiver, the maximum number of cascaded nodes reduces to a half compared to the case of the optimum decision threshold.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.995-998
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• 2003

TiO$_2$ thin films have been grown by MOCVD. Envelope methods are applied to the analysis of the transmission spectra to obtain the optical constants such as refractive indices and extinction coefficients for the TiO$_2$ thin films. The envelope methods are proved to be accurate by simulating the transmission spectra. TiO$_2$ thin films start to crystallize at 35$0^{\circ}C$ and then crystallize fully into anatase phase at foot or higher temperatures. Activation energies are obtained by plotting the deposition rate with varying the substrate temperature. It is 17.8 kcal/mol for the reaction limited regions. The refractive infer and the extinction coefficient of the TiO$_2$ thin film at λ=632.8 nm increases from 2.19 to 2.32 and decreases from 0.021 to 0.007, respectively, as the substrate temperature increases from 400 to $600^{\circ}C$.

• 한국해양학회지
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• v.21 no.2
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• pp.101-109
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• 1986

To clarify the light condition which influence phytoplankton ecology in Kyeonggi Bay, light intensity, compensation depth, extinction coefficient, transparency and suspended substances are studied from May 1981 to September 1982.Light intensities lie within adequate values for the phytoplankton growth from spring to autumn. However, in the winter season the light intensities show less than 4.8mw/$\textrm{cm}^2$ on the surface resulting lower than optimum irradiance. Light intensity could be a limiting factor for phytoplankton growth in winter. Compensation depths seasonally varied over an annual period in this study. Especially, in winter, compensation depths are confined to only 1-2m below the surface. Extinction coefficient(K) values are relatively high over an year cycle. K values is highest in winter and lowest in summer. Transparency shows seasonal variation. Tansparency is high in summer and low in winter. Thus low light intensity, low compensation depth, low transparency and high extinction coefficient in winter are due to the high turbidity and high concentrations of suspended substances. High concentrations of S.S. in winter result from the sediments and detritus resuspended by the winter turbulence induced by the strong winter winds and the convectional mixing. In summer, good light condition and low turbidity may result from the thermal stability of water mass preventing the resuspension of sediment particles.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.80.2-80.2
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• 2012

홀로 고립되어 존재하는 은하는 주변 은하와 상호작용을 하지 않은 채 진화하므로 은하의 진화를 연구하기에 아주 좋은 대상이다. 은하의 정량적 연구를 위해 꼭 알아야 하는 중요한 물리량으로 거리와 성간소광량이 있다. 우리는 허블 우주망원경(HST) Advanced Camera for Surveys(ACS)/High Resolution Channel(HRC)로 관측한 고립된 왜소불규칙은하 NGC 1156 ($RA_{2000}$=02:59:42.19, $DEC_{2000}$=+25:14:14.2) 중심부($26^{\prime\prime}{\times}29^{\prime\prime}$)의 archive 자료를 분석하여 이 은하의 거리와 성간소광량을 새로 구했다. 이 은하의 거리를 측정한 과거 자료는 Tully(1988, Nearby Galaxies Catalog) 목록과 Special Astrophysical Observatory 6m 망원경/VI(각 300s) 영상자료의 가장 밝은 별로 거리를 구한 Karachentsev et al. (1996) 자료 뿐이다. 우리는 HST/ACS/HRC+UBVI 자료 중 U자료를 이용하여 아주 신뢰할 만한 소광량 값($E(B-V)=0.35{\pm}0.05$)을 얻었고, 가장 밝은 빨간 별과 파란 별 자료를 이용하여 새로운 거리지수($(m-M)_0=29.39{\pm}0.20$, $d=7.6{\pm}0.7$ Mpc)를 결정했다. 이 거리 값은 과거의 값들(Tully $6.4{\pm}1.2$ Mpc; Karachentsev et al. $7.8{\pm}0.5$ Mpc)과 크게 다르지 않으며, 기존의 거리 자료들 역시 신뢰할만함을 보여준다. ACS/Wide Field Channel과 달리 ACS/HRC의 경우 등급 표준화 방정식이 완벽하지 않은데, 우리의 경우 F550M자료를 표준화할 수 없었다. 그러나 우리는 여러 파장, 많은 관측자료가 존재하는 47 Tucanae (NGC 104) 구상성단의 관측자료와 Padova 등연령곡선을 이용하여 성공적인 등급변환을 수행할 수 있었다.

• Korean Journal of Optics and Photonics
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• v.35 no.1
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• pp.1-8
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• 2024

Explicit expressions for the transmission pseudo-ellipsometric constants and transmittance of a semi-transparent glass substrate coated with thin films are presented to determine the optical constants of a very weakly absorbing thin film coated on a glass substrate. The intensity of the multiply reflected light inside the semi-transparent substrate is superposed incoherently and the light absorption by the substrate is properly treated, so that modeling analysis of thin films coated on a semi-transparent substrate can be performed with increased accuracy. The extinction coefficient derived from transmittance analysis is compared to that from ellipsometric analysis in the weakly absorbing region, and the difference between the two extinction coefficients is discussed in relation to the sensitivities of the transmittance and ellipsometric constants. This transmittance analysis, together with ellipsometric analysis, is applied to a glass substrate coated with a SiN thin film, and it is shown that the thickness and complex refractive index of the SiN thin film can be determined accurately, even though the extinction coefficient is very small.

• Journal of the Korean Chemical Society
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• v.44 no.5
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• pp.453-459
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• 2000

FED has deserved an intensive attentioD as a new flat panel display. The present investigationaims at undemtanding the photoluminescence and cathodoluminescent properties of hGaO$_3$: $Eu^{3+}$ phosphor bytaking into account the possibility that this phosphor could be applied for FED. In onler to investigate on.sucha detailed behavior; 8everM experimental skil18 Je conducted to the LaGaO$_3$:$Eu^{3+}$ phosphoL The excimtion srectrum artd emission spectmn were rnezsured in the UV range and then decay curve of $^5D_0$+$^7F_j$transitions\vas examined. The decay behavior of $^5D_0$ emission was anMyzed by a newly Iuoposed cross-relaxation mech-ani8In in asswiation with inteFwnter di1ffision (or migration). The cross-mlaxation from $^5D_0$ to CTB (Cha'geTransfer Band) wuld be a quite retsonable by considering the excitation spectrum. It could be also found thatthe quenching type was changed from ditfrsion controlled process to the direct quenching process -s inJeasing $Eu^{3+}$ oncntration.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.9
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• pp.15-22
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• 2000

The effects of carrier transport and input power on the extinction ratio was theoretically analyzed in a 1.55${\mu}m$ InGaAsP/InGaAsP multiple-quantum-well(MQW) electroabsorption(EA) modulator. Poisson's equation, current continuity equations for electrons and holes, and optical field distribution were self-consistently solved by considering electric field dependent absorption coefficients. The field screening effect due to the carrier accumulation in heterointerface and the space-charge region occurred more seriously at the input side of modulator as input optical intensity increased. It was revealed that extinction ratio could be steeply degraded for modulator with the length of 200${\mu}m$ when an input power exceeds 10mW. A degradation of extinction ratio due to the field screening effect would be more significantly at high-performance devices such as a 1.55${\mu}m$DFB-LD/EA-modulator integrated source where optical coupling efficiency is almost complete or a very high-speed modulator with its length as short as a few tens ${\mu}m$.

• Proceedings of the Korean Magnestics Society Conference
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• 2009.05a
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• pp.133-134
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• 2009