• Current Optics and Photonics
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• 제7권1호
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• pp.33-37
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• 2023

Real-time adaptive control of laser output polarization is presented in a 10-W-level non-polarization-maintaining (non-PM) fiber amplifier. While the output polarization from a non-PM fiber amplifier tends to be irregular, depending on output power, time, and perturbation, closed-loop polarization control can maintain the polarization extinction ratio at higher than 20 dB. Real-time polarization control can attain the target linear polarization mostly within 1.4-25 ms and shows stability against external perturbations. This approach can satisfy both linear polarization and high output power in a non-PM amplifier, and facilitates optimization of laser performance and maintenance-free operation.

• Journal of Positioning, Navigation, and Timing
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• 제10권4호
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• pp.291-296
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• 2021

Recently, the dual-polarized antenna array has drawn attention due to the dependency of its signal processing gain on the signal polarization. Even though this polarization dependency makes it possible to mitigate a non-right-hand circularly polarized (non-RHCP) jamming signal from the same direction as a GPS signal, the dual-polarized antennas are not yet widely used for various applications. This study suggests a method that can acquire the polarization dependency of the signal-processing gain by intentionally misaligning antenna elements in a single-polarized antenna array. The simulation results show that the proposed method can successfully mitigate a non-RHCP jammer from the same direction as a GPS signal as if a dual-polarized antenna array does and provide comparable signal-to-jammer-plus-noise ratio (SJNR) performance with a completely aligned single-polarized antenna array and a dual-polarized antenna array.

• 한국정보통신학회논문지
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• 제16권7호
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• pp.1391-1396
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• 2012

본 연구에서는 해저의 반사면이나 흡음재와 같이 주파수에 따라 다른 특성을 가지는 매체를 수치적으로 모델링하였다. 기존의 흡음재 해석 등가회로 모델에 용량성 성분을 부가하기 위해 Debye polarization 기법을 적용하여 흡음재의 모델링을 하였다. 이 모델의 파라미터를 추정하기 위해 폴리우레탄이라는 흡음재의 흡음 주파수 특성을 이용하였다. 파라미터의 추정에는 non-linear least squares라는 비선형 최적화 기법을 사용하였다. 먼저 두께 25 mm의 폴리우레탄의 흡음재의 파라미터를 추정하였으며, 이 파라미터를 이용해 50 mm의 폴리우레탄의 특성을 모델링하는 것이 가능하였다. 이를 바탕으로 흡음재의 주파수에 따른 흡음 특성을 하나의 간단한 모델로 모델링하는 것이 가능함을 보였다.

• Journal of electromagnetic engineering and science
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• 제4권3호
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• pp.128-136
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• 2004

In this paper,. with the aim of achieving the expected performance improvement for a polarization diversity system, we analyzed two-branch polarization diversity at the receiving end of a mobile link which a transmitter emits circularly polarized wave. In this analysis, to calculate the correlation coefficient considered by XPD(cross polarization discrimination) between the two received signals, a simple theoretical model of circular polarization diversity is adopted. From the analysis results, it is clearly seen that the correlation coefficient of circular polarization diversity evaluated by the XPD is less than that of conventional linear polarization diversity. And also, we designed and implemented a circular polarization diversity system with micro-strip antenna. By using the circular polarization diversity system, we analyzed the measured data in indoor NLOS(Non-Line-Of-Sight) environments. From this analysis results, it is also clearly seen that the diversity effect of circular polarization diversity system shows better performance compared to the conventional linear diversity system by about 3 dB high.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.514-515
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• 2005

본 논문에서는 As-Ge-Se-S 박막에 (P:P) 편광빔을 이용하여 회절격자를 형성시키고 비편광 (Non-Polarization) 빔을 이용하여 생성된 격자를 소거시키고 그에 따른 회절효율을 조사 하였다. (P:P) 편광으로 기록된 회절 효율은 시간이 지나도 최대 회절효율의 변화가 없었으나 비편광 빔으로 기록된 회절효율은 시간이 지남에 따라 급격한 회절효율의 감소를 보인다. 따라서 (P:P) 편광으로 회절격자를 형성시키고 비편광빔으로 격자의 소거를 진행하여 약 83%의 회절격자의 소거가 이루어졌다.

• Journal of Advanced Marine Engineering and Technology
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• 제22권5호
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• pp.702-711
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• 1998

The characteristics of corrosion resistance for the surface of medium high carbon steels and low alloy steels utilizing as manufacturing the machinery structures and machining tools and treating by plasma/ion nitriding process have been studied in terms of electrochemical polarization behav-iors including corrosion potential(Ecorr) anodic polarization trends and polarization resistance(Rp) The seven base materials showed a clear passivation behavior for the polarization tests in the ASTM standard solution 1N ${H_2){SO_4}$ Although the treated surface by plasma nitriding for the seven test materials showed a significant increase in hardness the treatment gave a detri-mental effect in corrosion resistance. The various characteristics including corrosion potential polarization curves microstructures corrosion current polarization resistance among non-treat-ed nitriding and/or soft-nitriding treated specimens have been investigated and some of the mechanisms discussed.

• 동력기계공학회지
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• 제6권1호
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• pp.74-81
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• 2002

The characteristics of corrosion resistance for the surface of ductile cast iron(GCD40) by plasma nitriding process have been studied in terms of electrochemical polarization behaviors including corrosion potential($E_{corr}$), anodic polarization trends, polarization resistance($R_p$), and also have been studied microstructures, hardness and specific wear of nitrided layer Nitrided layer showed an enhanced hardness values in all the plasma nitriding condition investigated. In the result of wear test, specific wear of nitrided specimens were much decreased than that of non-treated specimens. In the results of XRD, ${\gamma}'phase\;and\;{\varepsilon}$ phase were detected in nitrided surface. And it was found that ${\varepsilon}$ phase was decreased and ${\gamma}'phase$ was increased respectively, as the nitriding time became longer. In the test of corrosion resistance, natural potentials in all the nitrided specimens were towards noble directions than in the case of non-treated specimens. The measurement of electrode potentials revealed that corrosion resistivity of plasma nitrided specimens were higher than in the case of the non-treated specimens.

• 도시과학
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• 제9권2호
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• pp.45-50
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• 2020

The formation characteristics of calcium carbonates are closely related to the durability and mechanical properties of cement-based materials. In this regard, a deep understanding of the reaction pathway of calcium carbonates is critical. Recently, non-classical nucleation theory was summarized and it was presumed that prenucleation clusters are present. The formation of the prenucleation cluster at undersaturated condition (≈ 0.1 ml) in the present study was investigated via electrical characteristics of an electrolytic solution. Calcium chloride dihydrate (CaCl2·2H2O) and sodium carbonate (Na2CO3) were used as starting materials to supply calcium and carbonate sources, respectively. Furthermore, the reaction pathway of calcium carbonates was investigated by time-resolved polarization and depolarization characteristics of the electrolytic solution. The time-resolved polarization and depolarization tests were conducted by switching polarity with an interval of 20 seconds for 1 hr and by measuring the variation of electrical resistance. It can be inferred from the results obtained in the present study that the reactive constituent for the formation of calcium carbonates was mostly consumed in the period possibly associated with the prenucleation and the reaction pathways may be governed by the monomer-addition mechanism.

• 한국전자파학회논문지
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• 제24권2호
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• pp.144-151
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• 2013

본 논문에서는 무선 인체 통신 중 off-body 채널에서 안테나 편파의 변화에 대한 영향을 알아보기 위한 실험을 수행하였다. 실험은 두 수신 안테나의 편파 조합에 따라 총 4가지로 나누었으며, Line-of-Sight(LOS)와 Non-LOS(NLOS)에 따른 영향도 조사하였다. 그리고 인체의 움직임으로 인하여 생기는 안테나 편파의 변화가 신호에 어떠한 영향을 미치는지 알아보기 위해, 인체를 정지한 상태와 움직이는 상태로 나누어 신호 세기를 측정하여 비교하였다. 본 논문의 결과를 통해 수신 안테나의 편파 및 두 수신 안테나의 편파 조합에 따른 성능을 확인하였다.

• 천문학회지
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• 제35권2호
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• pp.67-73
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• 2002

We have made a topological study of cosmic microwave background (CMB) polarization maps by simulating the AMiBA experiment results. A ACDM CMB sky is adopted to make mock interferometric observations designed for the AMiBA experiment. CMB polarization fields are reconstructed from the AMiBA mock visibility data using the maximum entropy method. We have also considered effects of Galactic foregrounds on the CMB polarization fields. The genus statistic is calculated from the simulated Q and U polarization maps, where Q and U are Stokes parameters. Our study shows that the Galactic foreground emission, even at low Galactic latitude, is expected to have small effects on the CMB polarization field. Increasing survey area and integration time is essential to detect non-Gaussian signals of cosmological origin through genus measurement.