• 한국토양비료학회지
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• 제47권2호
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• pp.85-91
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• 2014

Ground-based polarimetric scatterometers have been effective tools to monitor the growth of crop with multi-polarization and frequencies and various incident angles. An important advantage of these systems that can be exploited is temporal observation of a specific crop target. Polarimetric backscatter data at L-, C- and X-bands were acquired every 10 minutes. We analyzed the relationships between L-, C- and X-band signatures, biophysical measurements over the whole corn growth period. The Vertical transmit and Vertical receive polarization (VV) backscattering coefficients for all bands were greater than those of the Horizontal transmit and Horizontal receive polarization (HH) until early-July, and then thereafter HH-polarization was greater than VV-polarization or Horizontal transmit and Vertical receive polarization (HV) until the harvesting stage (Day Of Year, DOY 240). The results of correlation analysis between the backscattering coefficients for all bands and corn growth data showed that L-band HH-polarization (L-HH) was the most suited for monitoring the fresh weight ($r=0.95^{***}$), dry weight ($r=0.95^{***}$), leaf area index ($r=0.86^{**}$), and vegetation water content ($r=0.93^{***}$). Retrieval equations were developed for estimating corn growth parameters using L-HH. The results indicated that L-HH could be used for estimating the vegetation biophysical parameters considered here with high accuracy. Those results can be useful in determining frequency and polarization of satellite Synthetic Aperture Radar stem and in designing a future ground-based microwave system for a long-term monitoring of corn.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 춘계학술대회 논문집 유기절연재료 전자세라믹 방전플라즈마 일렉트렛트 및 응용기술
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• pp.122-126
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• 2002

A diagnostic test of 15.4kV cross-linked polyethylene(XLPE) ultra high voltage power cables from generator in the Soyanggang hydro electric power plant was conducted over 3 months, beginning April 2001. According to the results, in the case of the power cables from generator 1, there was little possibility of proceeding rapid1y to failure or defect because the data from diagnosis doesn't indicate any failure, deterioration or partial discharge. However, in the case of the power cables from generator 2, the. polarization index show a slight abnormal condition of the insulator that is not severe, and the deterioration was also identified as not severe. However, the partial discharge had an abnormal condition which was severe.

• Current Optics and Photonics
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• 제7권5호
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• pp.574-581
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• 2023

A scheme is proposed to generate triangular waveforms with alterable symmetry. The key component is a cascaded single-drive Mach-Zehnder modulator (SD-MZM) and optical polarization beam splitter-combiner architecture. In this triangular waveform generator, the bias-induced phase shift, modulation index and controllable delay difference are changeable. To generate triangular waveform signals with different symmetry indexes, different combinations of these variables are selected. Compared with the previous schemes, this generator just contains one SD-MZM and the balanced photodetector (BPD) is not needed, which means the costs and energy consumption are significantly reduced. The operation principle of this triangular waveform generator has been theoretically analyzed, and the corresponding simulation is conducted. Based on the theoretical and simulated results, some experiments are demonstrated to prove the validity of the scheme. The triangular waveform signals with a symmetry factor range of 20-80% are generated. Both experiment and theory prove the feasibility of this method.

• 한국광학회:학술대회논문집
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• 한국광학회 2009년도 창립 20주년기념 특별학술발표회
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• pp.361-362
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• 2009

• 한국진공학회지
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• 제18권6호
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• pp.453-458
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• 2009

SiOC 박막을 BTMSM과 산소의 혼합가스를 사용하여 CVD 방법으로 증착하였다. 박막의 특성은 가스 유량비에 따라서 변하였다. 유전상수는 MIS 구조를 이용하여 C-V 측정법에 의하여 얻었다. 결합의 말단을 구성하는 Si-$CH_3$ 결합 사이의 공간효과에 의해서 기공이 만들어지며, 기공의 형성에 의해서 박막의 두께가 증가하였다. 그러나 분극의 감소에 의해서 만들어지는 SiOC 박막은 두께가 감소하면서 유전상수도 감소되었다. 열처리 후 유전상수는 수산기의 기화에 의해서 감소되었다. 박막의 두께는 분극의 감소에 의한 유전상수의 감소와 연관이 있었다. 굴절률은 박막의 두께에 반비례하는 경향성이 있으며, 박막의 두께와 굴절률의 경향성은 열처리 후에도 변하지 않았다.

• Journal of the Optical Society of Korea
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• 제19권4호
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• pp.376-381
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• 2015

Transmission characteristics of long-period fiber gratings (LPFGs) fabricated by periodically etching a conventional single-mode fiber (SMF) are investigated. After coating the SMF with photoresist, the cladding of the SMF is symmetrically and periodically removed by using a wet etching technique resulting in the formation of the LPFG. Tensile strain reinforces the coupling strength between the core and the cladding mode based on the photoelastic effect. The extinction ratio of the SMF-based LPFG at a wavelength of 1550.8 nm is measured to be -15.1 dB when the applied strain is $600{\mu}{\varepsilon}$. The ascent of ambient index shifts the resonant wavelength to shorter wavelength because of the increase of the effective refractive index of the cladding mode. The extinction ratio is diminished by increase in the ambient index because of the induction of the optical attenuation of the cladding mode. The transmission characteristics of the proposed LPFG with variations in torsion are also measured. The photoelastic effect based on torsion changes the extinction ratio and the resonant wavelength of the proposed SMF-based LPFG. The polarization-dependent loss of the LPFG is also increased by torsion because of the torsion-induced birefringence. The polarization-dependent loss of the LPFG at torsion of 8.5 rad/m is measured to be 3.9 dB.

• 대한의용생체공학회:의공학회지
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• 제28권2호
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• pp.195-198
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• 2007

In this paper, we introduce a digital cross-polarization and fluorescent color imaging system for quantitative evaluation of skin lesions. We describe the characterization of the imaging systems and the quantitative image analysis methods to show the feasibility for quantitative evaluation of skin lesions. The polarization color image was used to compute erythema and melanin index image which are useful for quantitative evaluation of pigmentation and vascular skin lesions, respectively. The fluorescent color image was used to quantitatively evaluate "sebum" and "vitiligo". In quantitative evaluation of various skin lesions, we confirmed the clinical efficacy of the imaging systems for dermatological applications. Finally, we sure that the imaging systems can be utilized as important assistant tools for the evaluation of skin lesions by providing reproducible quantitative result for widely distributed skin lesions.

• 한국광학회지
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• 제13권2호
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• pp.134-139
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• 2002

금속-클래드 평면 도파로와 접합된 측면 연마된 광섬유의 파장 및 편광 선택성에 관한 실험 결과를 보고한다. 금속의 두께와 최상부층의 굴절률을 포함한 평면 도파로의 구조가 소자의 광전송 특성에 미치는 영향을 측정하였고 그 결과를 설명하였다. 높은 파장 선택성과 편광 선택성을 가지는 조건을 예측하였고 실험으로 검증하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 E
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• pp.2456-2458
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• 1999

The polarization mode dispersion (PMD) that restricts the transmission bandwidth was investigated in standard long single mode fiber which optimized at 1.3${\mu}m$. Although fiber has perfect circular symmetry, each optical fiber has different refractive index profiles. The investigation of PMD with random mode couplings were conducted in three kinds of fiber by the time-domain interferometric method. By using two manufacturing methods, MCVD(Modified Chemical Vapor Deposition) method and VAD(Vapor Phase Axial Deposition) method, the property of mechanical asymmetric lateral pressure, bending and twisting induced polarization mode dispersion were measured. The concatenated optical fibers were compared with other types.

• Journal of the Optical Society of Korea
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• 제10권2호
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• pp.63-66
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• 2006

In microband-induced fiber gratings, polarization properties and birefringence are investigated as a function of an applied line force. With the transmission curves associated with the maximum and minimum resonant wavelengths, the polarization-dependent behaviors are analyzed. By increasing the transverse line force, the resonance wavelength for an incident light polarized to the same direction of the force is blue-shifted as much as 0.69 nm/(N/cm) while that for the other polarization is insensitive. Using the resonant wavelength separation corresponding to the force variation, the transverse effective index change or modal birefringence variation is obtained. The ratio of modal birefringence versus applied line force is ${\Delta}B/{\Delta}f_x={\sim}8.38{\times}10^{-7}$.