• 천문학회보
• /
• 제36권1호
• /
• pp.50.1-50.1
• /
• 2011

We report the results of the monitoring of a flaring gamma-ray blazar, 3C454.3 in total flux density at 22 and 43GHz and in polarization at 22GHz with KVN Ulsan 21-m radio telescope every 3-4 days from 19 November 2010 to 31 January 2011. After an extraordinary 5-day gamma-ray outburst in November 2010, the radio total flux density at 22/43GHz and the linear polarization at 22GHz has been decreased with a variation of a short time scale. In this paper, we also discuss a spectral change of 3C454.3 at 22 and 43GHz after the extraordinary gamma-ray outburst.

• 한국정보통신학회:학술대회논문집
• /
• 한국해양정보통신학회 1999년도 추계종합학술대회
• /
• pp.120-123
• /
• 1999

This paper presents the design method of EMC(Electromagnetic Coupling) microstrip array antenna for CS(Communication Satellite) system. Microstrip dipole antennas are attractive elements owing to the desirable properties such as simplicity, small size and linear polarization. From the optimum simulation results by the FDTD method[1], design parameters such as EMC dipole length, width, height and offset are discussed at 12CHz. The array characteristics of 5-elements and 10-elements array are also presented. By adjusting geometry of model antenna, we can design dual polarization EMC microstrip dipole antenna for CS system. Direction of nam beam is easily tilted by the control of distance between dipole elements.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1987년도 전기.전자공학 학술대회 논문집(I)
• /
• pp.82-85
• /
• 1987

Electromagnetic waves from the satellite may be utilized to direct the tracking antenna toward the satellite. We design and fabricate the feed appropriate to the monopulse tracking technique which derive angle-error information on the basis of a single pulse. The feed consists of five cavity-backed turnstile elements mounted on a common ground plane. The turnstile dipole are connected to a set of five quadrature hybrids which convert the dual linear polarization into dual circular polarization. The five feed outputs are then processed in the monopulse comparator which is constructed in microstrip for compactness.

• 멤브레인
• /
• 제7권2호
• /
• pp.84-94
• /
• 1997

Hollow fiber의 diameter와 curvature 및 turn수 등의 변화에 따른 첫번째 모듈 set와 두번째 모듈 set 사이의 성능비교가 이루어졌다. 모든 실험들은 같은 transmembrane pressure와 막면적당 에너지 소모하에서 수행되었다. 첫번째 모듈 set에 대해서 Dean vortices에 의한 농도분극과 막오염현상의 감소시키는 효과가 매우 작음을 알 수 있었다. 두번째 모듈 set에 대해서 115%의 투과 flux 향상값 (투과 flux 증분 ${\times}100$/선형 모듈의 투과 flux)을 보였다. 이로부터 두번째 모듈 set가 yeast suspension에 의한 농도분극과 막오염현상의 감소에 훨씬 효과적임을 알 수 있었다.

• Journal of Electrochemical Science and Technology
• /
• 제10권1호
• /
• pp.37-54
• /
• 2019

A new organic Schiff base compound N-benzylidene-2,5-dichloroaniline (BDC) was synthesized and the structure of the Schiff base is illuminated by some spectroscopic techniques. In addition, whether it is an applicable inhibitor in the industrial field was examined by conventional methods such as linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization for different concentrations. The BDC concentration and temperature effects were surveyed for elucidating the inhibitive mechanism. The BDC molecules are adsorbed to surface of mild steel via the Langmuir isotherm. Atomic force (AFM) and scanning electron microscope (SEM) techniques were utilized to give insight into surface characterization.

• Current Optics and Photonics
• /
• 제5권3호
• /
• pp.329-335
• /
• 2021

The problem of polarized light scattering by a cylinder on or close to a planar substrate is analytically solved. The light is assumed to be normally incident to the axis of the cylinder. Transverse magnetic (TM) and transverse electric (TE) polarizations are treated separately. The solution for each polarization is composed of a coupled set of linear equations which couples the scattering characteristics of the cylinder and the planar substrate. The coupling comes from the scattering by the planar substrate and by the cylinder. The solution of the coupled set of equations obtained by iterative substitution consists of infinite series, where each term represents the contribution of single and multiple scatterings of all orders.

• Journal of the Optical Society of Korea
• /
• 제15권3호
• /
• pp.232-236
• /
• 2011

We analyze the linear equalizers used in optically amplified on-off-keyed (OOK) systems to combat chromatic dispersion (CD) and polarization mode dispersion (PMD), and we derive the mathematical minimum mean squared error (MMSE) performance of these equalizers. Currently, the MMSE linear equalizer for optical OOK systems is obtained by simulations using adaptive approaches such as least mean squared (LMS) or constant modulus algorithm (CMA), but no theoretical studies on the optimal solutions for these equalizers have been performed. We model the optical OOK systems as square-law nonlinear channels and compute the MMSE equalizer coefficients directly from the estimated optical channel, signal power, and optical noise variance. The accuracy of the calculated MMSE equalizer coefficients and MMSE performance has been verified by simulations using adaptive algorithms.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2006년도 하계종합학술대회
• /
• pp.215-216
• /
• 2006

In this paper, the antenna the with linear active phased array of $1{\times}16$ operated in DBS band was designed. The antenna was composed of sixteen radiating elements, sixteen active channels and five Wilkinson power combiners with 4-channel inputs, a digital control board and a stabilizing DC bias board. The radiating element of the array has the structure of a microstrip stack patch with a left-hand circular polarization. And, each active channel consists of a low noise ampilifier, a 3-bit digital phase shifter and a variable analog attenuator. The breadboard of linear active phased array antenna was also fabricated to test the electrical performances. The radiation patterns of the antenna were measured after correcting initial phases of each active channel in aechoic chamber. And also, the beam scanning chracteristcs of $10^{\circ}$, $20^{\circ}$, $30^{\circ}$ were measured.

• 한국전자파학회논문지
• /
• 제22권1호
• /
• pp.81-88
• /
• 2011

본 논문은 비선형 소자 탐지기용 광대역 스파이럴 안테나의 설계를 제안한 것이다. 방사면 위의 스파이럴 소자뿐만 아니라 방사면 중심부에 위치한 방사 소자인 타원형 패치가 스파이럴 안테나의 광대역화를 위하여 설계되었다. 또한, 그라운드면 위에 스파이럴 슬릿을 삽입함으로써 다중 공진을 일으키는 안테나 그라운드 구조가 제안되었다. 제안된 안테나의 높은 지향성과 고이득을 실현하기 위해, Fr4-epoxy로 만든 캐비티 벽과 금속캡이 설계에 고려되었다. 그 결과, 금속 캡을 가진 안테나의 계산된 이득은 금속 캡이 없는 안테나의 이득과 비교하여 약 3 dBi 개선되었으며, -z축 방향으로의 측정된 주 빔 지향성도 계산 결과와 잘 일치하였다. 설계 주파수 대역에서 측정된 축비도 -z축을 기준으로 ${\pm}45^{\circ}$의 범위에서 원편파를 만족하였으며, 예상과 잘 일치하였다.

• 한국전자파학회논문지
• /
• 제19권11호
• /
• pp.1294-1302
• /
• 2008

이중 편파 특성을 갖는 위상 배열 안테나에 사용될 수 있는 도파관형 방사 소자의 설계 방법을 제시하였다. 소형화를 위하여 리지 형태의 도파관을 사용하였고, 이중 편파를 위해서는 도파관 내에 인쇄된 다이폴 구조의 마이크로스트립 형태를 부가적으로 추가하는 형태를 취하였다. 설계 방법의 타당성 검증을 위하여 $1{\times}4$ 배열 안테나를 제작하여 반사 손실, 인접 채널간 동일 편파 상호 간섭 및 복사 패턴을 측정하여 이론치와 비교하여 잘 일치함을 확인하였다. 본 논문에서 제시한 구조는 이중 편파 특성을 갖는 위상 배 열 안테나의 단위 소자로서 유용한 구조로 사용될 수 있을 것으로 생각된다.