• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2006년도 공동학술대회 논문집
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• pp.281-284
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• 2006

저항성 V 다이폴(RVD)은 V 안테나의 각 암(arm)에 연속적인 Wu-King 저항 프로파일을 실은 것이다. RVD는 매우 짧은 펄스를 한 방향으로 복사할 수 있고, 복사된 펄스는 입력 펄스의 미분 등으로 간단하게 연관되는 등 지표 및 지하 탐사를 위해 매우 좋은 특성을 가지고 있다. 또한 레이더 단면적이 적어 지표와 안테나 사이의 다중 반사를 줄일 수 있다. 단점으로는 높은 입력저항과 제작의 어려움을 들 수 있다. 본 연구에서는 저주파에서의 성능과 제작상의 문제를 개선하면서도 저항성 V 다이폴의 특성을 유지하기 위한 방법을 제시한다. 제작된 V 다이폴을 이용하여 간단한 바이스태틱 레이더를 구성하고 지하 구조물에 대하여 스캔하여 이미지로 나타내었다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2012년도 추계학술대회
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• pp.583-585
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• 2012

본 논문에서는 지상파 디지털방송 수신용 광대역 평면 야기 안테나의 설계방법에 대해 연구하였다. 다이폴을 급전하는 코프래너 스트립은 스트립에 내장된 마이크로스트립과 연결되고 종단은 단락되어 있다. 급전되는 다이폴에 근접한 영역에 폭이 넓은 스트립 도파기를 부가하여 광대역 임피던스 정합과 고주파 대역의 이득특성을 구현하였고, 접지면 반사기를 추가하여 저주파 대역의 이득특성을 개선하였다. 안테나를 소형화하기 위해 다이폴과 반사기의 모양을 반 보우타이(V)-형으로 변형하였으며, 여러 가지 파라미터들이 안테나 특성에 미치는 영향을 관찰하였다. 제안된 구조의 안테나를 지상파 DTV 방송 주파수대역인 470-806 MHz 대역에서 동작하도록 설계하였다. 최적화된 안테나를 FR4 기판 상에 제작한 후 특성 실험을 통하여 연구결과의 타당성을 검증하였다.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2005년도 종합학술발표회 논문집 Vol.15 No.1
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• pp.353-356
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• 2005

There have been many researches on the antenna performance degradation with the presence of the human body around the antenna structure to accomodate personal communication service [1][2]. To better understand the human body effects on the antenna resonance, radiation pattern, and input impedance, simulation was carried out with changing of the distance between antenna and lossy material. Effects on the antenna performance by the surrounding materials are also important in the case of the RFID system. It is desirable that the tag antennas for RFID system must reveal isotropic radiation pattern as well as attain the good impedance matching. In this paper, we investigated the antenna resonance and input impedance characteristic when there exist a lossy material sphere near various types of antenna at 900 MHz. In short antenna resonance was mostly affected by lossy material in the case of a rectangular loop antenna, and impedance variation was smallest in the case of a halfwave dipole.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.323-327
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• 2002

In order to control the railway noise, the radiation characteristic of the noise during the train passage should be analyzed. Generally, the major noise sources for Korean Train Express are the rolling noise and power unit noise up to 300km/h. In this paper, we describe on a train model that is considered to be a row of point sources to calculate the radiation characteristic. The calculation results are compared with short distance measurement. It is shown that the radiation characteristic of the rolling noise is dipole type. The noise generated by the power unit is radiated as the cosine type. The noise level at an observer is increased in the direction of motion and reduced in the direction opposite to the motion with increasing of the train speed. The calculation results including the moving effect of the noise source at 300km/h show in good agreement.

• 대한자기공명의과학회:학술대회논문집
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• 대한자기공명의과학회 2001년도 제6차 학술대회 초록집
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• pp.147-147
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• 2001

목적： RF 자기장이 존재하는 공간이 좁을수록 신호 대 잡음비가 증가한다. 이것을 이용하여, 기존의 표면 코일보다 RF 자기장의 공간을 좁혀서 코일 근방에서 신호 대 잡음비를 개선할 수 있는 표면 코일을 개발한다. 대상 및 방법： 기존의 표면 코일의 RF 자기장은 쌍극자(Dipole) 자기장 형태이다. 쌍극자 모드는 자기장의 세기가 1/r$^3$로 감소한다 하지만 자기장을 사중극자(Quadrupole) 형태도 발생시키면, 1/r$^{5}$ 로 감소하게 되어, 극자(pole)로부터 먼 곳에서는 자기장의 감소가 매우 급격히 일어난다. 극자 근방에서는 쌍극자와 사중극자 자기장의 세기 차이가 거의 없다. 이런 원리들을 이용하여 표면코일의 형태를 사중극자 자기장이 발생하도록 제작하여, 코일로부터 먼 곳의 신호는 코일에 검출되지 못하게 하였다. 그러므로 신호 대 잡음비에 큰 이득을 볼 수 있다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.337.1-337
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• 2002

In order to control the railway noise, the radiation characteristic of the noise during the train passage should be analyzed. Generally, the major noise sources for Korean Train Express are the rolling noise and power unit noise up to 300km/h. In this paper, we describe on a train model that is considered to be a row of point sources to calculate the radiation characteristic. The calculation results are compared with short distance measurement. (omitted)

• 대한기계학회논문집A
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• 제27권4호
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• pp.531-536
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• 2003

In order to control the railway noise. we should know the radiation characteristic of the noise during the train passage Generally, the railway noise sources for conventional trains are classified by the rolling noise and power unit noise in tangent track. In this Paper. we describe on a train model that is considered to be a row of point sources to calculate the radiation characteristic The calculation results are compared with short distance measurement of three kinds of trains (EMU, Mookungwha, Saemaul). It is shown that the radiation characteristic of the rolling noise that is major noise source of electric multiple unit is dipole type. We know that characteristic of the engine noise is radiated as the cosine type.

• Applied Science and Convergence Technology
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• 제25권6호
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• pp.128-132
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• 2016

We investigated the effect of Ar ion sputtering on the surface electronic structure of indium tin oxide (ITO) using X-ray and ultraviolet photoelectron spectroscopy (XPS and UPS) measurements with increasing Ar ion sputtering time. XPS measurements revealed that surface contamination on ITO was rapidly removed by Ar ion sputtering for 10 s. UPS measurements showed that the work function of ITO increased by 0.2 eV after Ar ion sputtering for 10 s. This increase in work function was attributed to the removal of surface contamination, which formed a positive interface dipole relative to the ITO substrate. However, further Ar ion sputtering did not change the work function of ITO although the surface stoichiometry of ITO did change. Therefore, removing the surface contamination is critical for increasing the work function of ITO, and Ar ion sputtering for a short time (about 10 s) can efficiently remove surface contamination.

• Journal of Magnetics
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• 제6권3호
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• pp.94-100
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• 2001

Fe-Co-Ni particles with an average size of 45 and 135 nm are characterized in terms of magnetic phase transformation and magnetic properties at room temperature. BCC structure of Fe-Co-Ni spherical particles can be synthesized from Fe-Co-Ni-Al-Cu precursor films by heating at 600-80$0^{\circ}C$ for the phase separation of Fe-Co rich Fe-Co-Ni particles, followed by a post heating at $600^{\circ}C$ for 5 hours. The average size of nanoparticles was directly determined by the thickness of precursor films. Exchange interactive hysteresis was observed for the nano-composite (Fe-Co-Ni)+(Fe-Ni-Al) films resulting from the short exchange interface between ferromagnetic Fe-Co-Ni particles surrounded by almost papramagnetic Ni-Al-Fe matrix. Arraying the isolated Fe-Co-Ni nano-particles in a random arrangement on $Al_2O_3$substrate the particle assembly showed a behavior of dipole interactive ferromagnetic clusters depending on their volume and inter-particle distance.

• Bulletin of the Korean Chemical Society
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• 제16권10호
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• pp.957-968
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• 1995

Generalized Multichannel Quantum Defect theory (MQDT) was implemented to the vibrational predissociation of triatomic van der Waals molecules in the previous paper [Bull. Korean Chem. Soc, 12, 228 (1991)]. Implementation was limited to the calculation of the scattering matrix. It is now extended to the calculation of the predissociation spectra and the final rotational distribution of the photofragment. The comparison of the results with those obtained by other methods, such as Golden-rule type calculation, infinite order sudden approximation (IOS), and close-coupling method, shows that the implementation is successful despite the fact that transition dipole moments show more energy dependence than other quantum defect parameters. Examination of the short-range channel basis functions shows that they resemble angle-like functions and provide the validity of the IOS approximation. Besides the validity of the latter, only a few angles are found to play the major role in photodissociation. In addition to the implementation of MQDT, more progress in MQDT itself is made and reported here.