• 한국정보전자통신기술학회논문지
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• 제2권1호
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• pp.65-72
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• 2009

기지국 배열안테나의 근역장 프로빙을 통해 원역장 성능을 평가하기 위해 반사판을 갖는 다이폴 배열 안테나와 프로브 사이 높이에 따른 상호 간의 영향을 분석하였다. 기본 개념은 기지국 배열 안테나의 입력단들과 프로브의 입력 port P 에 대한 근역장에서의 상호 높이를 변화시키며 S 파라미터 측정값을 분석하여 상호결합 효과가 가장 적으면서 프로빙 효율이 높은 위치를 결정하는 것이다. 그리고 여기서 얻어진 높이는 기지국 배열안테나의 정밀한 원역장 성능을 구하기 위한 근역장 프로빙 시스템 설계에 적용 가능할 것이다.

• 한국광학회지
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• 제3권2호
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• pp.123-132
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• 1992

반도체 레이저로써 세슘원자의 상태를 선택하는 방식인 광펌핑 세슘원자시계를 개발하기 위해 Ramsey공진기, 정자장 형성전극, 형광 측정장치 등을 설계, 제작하였으며, 세슘원자빔 튜브를 구성하였다. 세슘원자빔 튜브의 Ramsey 공진기로 주입되는 마이크로파를 시계전이 주파수인 9192.6MHz 부근에서 주사시킬때 검출용 레이저에 의해 발생하는 형광을 측정함으로써 원자시계에서 기준 주파수로 사용되는 Ramsey 신호를 관측하였다. Ramsey 신호의 선폭은 200Hz이었고, 정자장의 세기는 정자장 형성전극에 전류가 0.8A가 흐를때 $8.61\muT$이었으며, 이 자장에 의해 시계전이 주파수는 약3.17Hz만큼 주파수가 높은 쪽으로 편이되었음을 알았다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.515-516
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• 2006

A THz near-field microscope(THz NFM) is developed by a combination of THz time-domain spectroscopy and AFM(Atomic Force Microscopy). We have observed 80nm lateral resolution, demonstrating that the THz NFM technique has a great potential as a important probing tool for the analysis of the biological and semiconductor nanostructures.

• 천문학회보
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• 제40권2호
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• pp.31.1-31.1
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• 2015

For probing magnetic fields in the universe, rotation measure (RM) have been often used. RM allows us to obtain the information of integrated (or averaged) magnetic fields along a line of sight (LOS). On the other hand, the new technique so-called Faraday tomography will be used in practical in the near future thanks to the wide-band polarimetry by Square kilometre Array and/or its precursors. The technique allows us to obtain so-called Faraday dispersion function (FDF). FDF is the distribution function of magnetic fields and polarized sources along a LOS. Because of this fact, it is expected that the studies of magnetic fields associated with various astronomical objects will progress dramatically. Since FDF also includes information of cosmic-rays and thermal electrons, the investigation of FDF may advance the studies of dynamics of external galaxies and/or the star formation activities. We have studied the potentials of Faraday tomography such as a tool to probe the intergalactic magnetic field associated with filaments of galaxies in the large scale structure. We have also studied the realistic FDFs of galaxies for understanding global magnetic field, cosmic-ray and thermal electrons of external galaxies. In the talk, we briefly introduce the Faraday tomography technique and report the results related to the Faraday tomography.

• 천문학회보
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• 제38권1호
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• pp.34.1-34.1
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• 2013

The first generation stars in the universe are not observed as discrete objects by using current observational facilities, but their contributions are redshifted to the near infrared wavelength bands at present universe. Therefore, investigation of background radiation at near infrared is important for the study of the first stars. In this study, we present new observations of spatial fluctuations in sky brightness toward the north ecliptic pole using data from AKARI. Among pointed observation program of AKARI, we used two pointing surveys named Monitor field and NEP wide field at three wavelength bands 2.4, 3.2, and 4.1 ${\mu}m$. To obtain spatial fluctuations from observed images, first of all, we exclude pixels affected by resolved foreground objects and then obtain diffuse map which consists of diffused radiation only. Because the diffuse map contains not only cosmological components but also various foreground components, in order to detect cosmological components, we estimate the contributions of foreground components separately. The results of this study show that there remains excess spatial fluctuation that cannot be explained by known foreground sources. This work is based on observations with AKARI, a JAXA project with the participation of ESA.

• 천문학회보
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• 제38권1호
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• pp.35.1-35.1
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• 2013

The first generation stars in the universe are not observed as discrete objects by using current observational facilities, but their contributions are redshifted to the near infrared wavelength bands at present universe. Therefore, investigation of background radiation at near infrared is important for the study of the first stars. In this study, we present new observations of spatial fluctuations in sky brightness toward the north ecliptic pole using data from AKARI. Among pointed observation program of AKARI, we used two pointing surveys named Monitor field and NEP wide field at three wavelength bands 2.4, 3.2, and 4.1 ${\mu}$. To obtain spatial fluctuations from observed images, first of all, we exclude pixels affected by resolved foreground objects and then obtain diffuse map which consists of diffused radiation only. Because the diffuse map contains not only cosmological components but also various foreground components, in order to detect cosmological components, we estimate the contributions of foreground components separately. The results of this study show that there remains excess spatial fluctuation that cannot be explained by known foreground sources. This work is based on observations with AKARI, a JAXA project with the participation of ESA.

• 한국정보통신학회논문지
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• 제16권5호
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• pp.1023-1028
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• 2012

본 논문에서는 비접촉 마이크로웨이브 프루브 시스템의 I/Q demodulator를 위한 MMIC (Monolithic Microwave Integrated Circuit) mixer chip을 GaAs p-HEMT 공정의 Schottky 다이오드를 이용하여 설계 및 제작하였다. 프루브 시스템의 I/Q demodulator 구조를 단순화하기 위해 single balanced 구조의 mixer를 채택하였다. Single balanced mixer에서 $90^{\circ}$hybrid coupler와 ${\lambda}/4$ 전송선로를 이용하여 $180^{\circ}$hybrid를 설계하였으며 이를 MIM 커패시터와 spiral 인덕터를 이용하여 구현함으로써 mixer chip의 크기를 줄일 수 있었다. On-wafer 측정 결과, 본 논문의 MMIC mixer는 1650MHz ~ 2050MHz의 RF 및 LO 주파수 대역을 포함하고 있으며, 응용 주파수 대역 내에서 RF 및 LO의 변화에 대해 약 12dB 이하의 평탄한 변환손실(conversion loss) 특성을 나타내었다. 또한, MMIC mixer chip은 $2.5mm{\times}1.7mm$의 초소형 크기를 가지며 LO-IF 및 RF-IF의 격리도는 각각 43dB 및 23dB 이상의 특성을 나타내었다.

• Bulletin of the Korean Chemical Society
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• 제35권3호
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• pp.891-894
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• 2014

The ultrashort electron pulse, laser-emitted from the metal tip apex has been characterized and used as a probing source for a new electron microscope to visualize the morphology of the gold-mesh in the nanometric resolution. As the gap between the tungsten tip and Au-surface is approached within a few nm, the large electromagnetic field enhancement for the incident P-polarized laser pulse with respect to the tip-sample axis is strongly observed. Here, we demonstrate that the time-resolved tip-enhanced electron emission microscope (TEEM) can be implemented on the laboratory table top to give the two-dimensional image, opening lots of challenges and opportunities in the near future.

• Bulletin of the Korean Chemical Society
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• 제26권1호
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• pp.151-156
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• 2005

The conformational dynamics of heme pocket, a small vacant site near the binding site of heme proteins -myoglobin (Mb) and hemoglobin (Hb), was investigated after photolysis of carbon monoxide from MbCO and HbCO in D$_2$O solution at 283 K by probing time-resolved vibrational spectra of photolyzed CO. Two absorption bands, arising from CO in the heme pocket, evolve nonexponentially in time. The band at higher energy side blue shifts and broadens with time and the one at lower energy side narrows significantly with a negligible shift. These spectral evolutions are induced by protein conformational changes following photolysis that modify structure and electric field of heme pocket, and ligand dynamics in it. The conformational changes affecting the spectrum of photolyzed CO in heme pocket likely modulates ligand-binding activity.

• 천문학회보
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• 제44권1호
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• pp.83.1-83.1
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• 2019

Identifying asteroid families, which are groups of asteroids with similar orbital properties, is important for understanding the formation and evolution of the solar system, and probing the origins of Near-Earth Objects (NEOs). Although asteroid taxonomy can be used to identify and refine asteroid families, there are numerous asteroids which are not taxonomically classified yet. Korea Microlensing Telescope Network (KMTNet) can be useful to investigate types of that asteroids, because the telescope can observe a number of asteroids at once by its large field of view. Using KMTNet data, we confirmed that the taxonomic classification of the asteroids is possible by plotting color-color diagram. There is a clear division between C-type and S-type, but ambiguous division between C-type and X-type. In the future, we will observe and classify asteroids which are not classified yet and utilize the data to identify and refine asteroid families.