• 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.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권7호
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• pp.2879-2890
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• 2020

In this paper, we study the estimation of angle, range and polarization parameters of a bistatic polarization sensitive frequency diverse array multiple-input multiple-output (PSFDA-MIMO) radar system. The application of polarization sensitive array in receiver is explored. A signal model of bistatic PSFDA-MIMO radar system is established. In order to utilize the multi-dimensional structure of array signals, the matched filtering radar data can be represented by a third-order tensor model. A joint estimation of the direction-of-departure (DOD), direction-of-arrival (DOA), range and polarization parameters based on parallel factor (PARAFAC) algorithm is proposed. The proposed algorithm does not need to search spectral peaks and singular value decomposition, and can obtain automatic pairing estimation. The method was compared with the existing methods, and the results show that the performance of the method is better. Therefore, the accuracy of the parameter estimation is further improved.

• Advances in Energy Research
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• 제1권1호
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• pp.35-52
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• 2013

A model for DMFC anode performance is developed. The model takes into account potential--independent methanol adsorption on the catalyst surface, finite rate of proton transport through the anode catalyst layer (ACL), and a potential loss due to methanol transport in the anode backing layer. An approximate analytical half--cell polarization curve is derived and equations for the anode limiting current density are obtained. The polarization curve is fitted to the curves measured by Nordlund and Lindbergh and parameters resulted from the fitting are discussed.

• 한국전자파학회논문지
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• 제14권2호
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• pp.133-138
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• 2003

본 논문에서는 비가시거리(NLOS) 전파환경에서 원형편파를 송신하고 수직, 수평편파 안테나로 수신하는 원형편파 다이버시티(CV-CH)방식에 대하여 이론적 모델을 제시하고 이의 우수성을 확인하였다. 원형편파 다이버 시티에 대한 간단한 이론적 모델을 통하여 XPD에 대한 상관계수 평가식을 유도하였으며, 비가시거리 전파환경에서 원형편파다이버시티 경우 직선편파다이버시티(VV-VH) 경우보다 교차편파분리도(XPD)가 약 6~7 dB 정도 낮게 됨을 알 수 있었다. 그 결과 원형편파 다이버시티 경우의 상관계수는 기존의 직선 편파다이버시티보다 더 낮은 상관계수 값을 나타내는 이론적 모델을 제시하였고 측정된 결과로부터 이의 성능을 확인하였다.

• Current Optics and Photonics
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• 제6권1호
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• pp.23-31
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• 2022

Heterodyne efficiency is an indicator to evaluate the performance of space coherent laser communication systems. It is affected by signal light and local oscillator (LO) light amplitude, phase and polarization state. In this paper, based on the common heterodyne efficiency, a heterodyne efficiency model that can reflect polarization aberration of optical system is proposed. The heterodyne efficiency is analyzed when the signal light and the LO light are linearly polarized or circularly polarized. For a coherent communication optical system, when the incident signal light is right-circularly polarized light and the incident LO light is 45° linear polarized light. Based on the three-dimensional ray tracing theory and the heterodyne efficiency proposed in this paper, the change of polarization states and the distribution of heterodyne efficiency of the signal light and LO light influenced by the optical system's polarization aberration are analyzed. Analysis shows that the heterodyne efficiency model proposed in this paper can be used to evaluate coherent communication systems and reflect the influence of optical system polarization aberration.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 I
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• pp.609-612
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• 2003

For combating multipath fading in wireless radio environment, diversity schemes is useful. In this paper, for performance improvement of polarization diversity system, we analyzed a two-branch polarization diversity at the receiving end of a mobile link when the transmitter emits a circularly polarized wave. And In order to calculate the correlation coefficient considering the XPD(cross polarization discrimination) between the received signals for the two diversity branches, a simple theoretical model of circular polarization diversity is adopted and calculate correlation coefficient. From the analysis results, it is seen that the correlation coefficient of circular polarization diversity evaluated by the XPD is less than that of vertical polarization diversity. And also, we designed and fabricated circular polarization diversity system with microstrip antenna. we analyzed data measured in indoor NLOS environment using fabricated circular polarization diversity system. From the measurement results, it is clearly seen that the diversity effect of circular polarization diversity system is higher 3dB than vertical polarization diversity system.

• 한국수자원학회논문집
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• 제47권9호
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• pp.801-812
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• 2014

본 연구에서는 합천댐, 회천 유역에 대하여 비슬산 이중편파 레이더를 이용하여 유역평균강우량을 각각 추정하여 지상 우량계의 강우량과 비교한 후 분포형 유출모형인 Vflo 모형을 사용하여 유출을 모의하였다. 유역평균 강우량 분석 결과 이중편파 레이더 변수를 사용한 결과 첨두우량 및 전체 강우량 값이 지상우량계 값과 근접하게 산정되었고, Vflo 분포형 모형을 사용한 유출모의 분석 결과 또한 이중편파 레이더 변수를 사용한 유출모의가 실제 유출량에 근접하였다. 이는 이중편파 레이더를 사용한 강우추정 및 유출모의가 기존의 수평반사도만을 사용한 단일편파 레이더보다 정확성을 높일 수 있는 방법이라고 판단된다.

• 한국표면공학회지
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• 제53권6호
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• pp.330-342
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• 2020

Since the original report on ferroelectricity in Si-doped HfO2 in 2011, fluorite-structured ferroelectrics have attracted increasing interest due to their scalability, established deposition techniques including atomic layer deposition, and compatibility with the complementary-metal-oxide-semiconductor technology. Especially, the emerging fluorite-structured ferroelectrics are considered promising for the next-generation semiconductor devices such as storage class memories, memory-logic hybrid devices, and neuromorphic computing devices. For achieving the practical semiconductor devices, understanding polarization switching kinetics in fluorite-structured ferroelectrics is an urgent task. To understand the polarization switching kinetics and domain dynamics in this emerging ferroelectric materials, various classical models such as Kolmogorov-Avrami-Ishibashi model, nucleation limited switching model, inhomogeneous field mechanism model, and Du-Chen model have been applied to the fluorite-structured ferroelectrics. However, the polarization switching kinetics of fluorite-structured ferroelectrics are reported to be strongly affected by various nonideal factors such as nanoscale polymorphism, strong effect of defects such as oxygen vacancies and residual impurities, and polycrystallinity with a weak texture. Moreover, some important parameters for polarization switching kinetics and domain dynamics including activation field, domain wall velocity, and switching time distribution have been reported quantitatively different from conventional ferroelectrics such as perovskite-structured ferroelectrics. In this focused review, therefore, the polarization switching kinetics of fluorite-structured ferroelectrics are comprehensively reviewed based on the available literature.

• 한국전자파학회논문지
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• 제10권5호
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• pp.766-776
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• 1999

본 논문에서는 실내 전파 환경에서의 편파 다이버시티와 공간 다이버시티의 성능을 분석하기 위하여 영상 법을 기본으로 한 3차원 광선 추적법을 이용하였다. 본 모텔링은 선호강도 뿐만 아니라 채널의 페이딩 특성 을 예측할 수 있기 때문에 편파 및 공간 다이버시티 기법의 성능을 분석하는데 이용될 수 있다. 측정과 시율 레이션 결과로부터 편파 및 공간 다이버시티가 실내 무선 통선 채널의 성능을 향상시킬 수 있음을 확인하였 고, 특히 지향성 안테나를 이용한 편파 다이버시티를 제안하여 기존의 다이폴 안테나를 이용하는 다이버시티 기볍보다 우수한 성능을 가짐을 보였다.

• 천문학회보
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• 제43권1호
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• pp.36.2-36.2
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• 2018

Radiative transfer models were developed to understand the optical polarizations in edge-on galaxies, which are observed to occur even outside the geometrically thin dust disk, with a scale height of ~0.2 kpc. In order to reproduce the vertically extended polarization structure, we find it is essential to include a geometrically thick dust layer in the radiative transfer model, in addition to the commonly-known thin dust layer. The models include polarizations due to both dust scattering and dichroic extinction which is responsible for the observed interstellar polarization in the Milky Way. It is found that the magnetic fields in edge-on galaxies are in general vertical (or poloidal) except the central part, where the magnetic fields are mainly toroidal. We also find that the polarization level is enhanced if the clumpiness of the interstellar medium, and the dichroic extinction by vertical magnetic fields in the outer regions of the dust lane are included in the radiative transfer model. The predicted degree of polarization outside the dust lane was found to be consistent with that (ranging from 1% to 4%) observed in NGC 891.