• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.52.2-52.2
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• 2021

우리는 quiescent state magnetar의 물리적 특성을 연구하기 위해 복사특성이 잘 알려진 24개의 대상을 선정하였고 가장 어두운 시기(quiescent state)의 Chandra와 XMM-Newton의 X-ray 관측 데이터를 분석하여 복사특성과 시간 특성을 측정하였다. 이 측정을 이용하여 복사특성과 시간 특성 사이의 여러 경우에 대해 상관관계를 분석하였다. 그 결과 기존에 높은 상관관계를 갖는 것으로 알려진 표면 자기장(B_s)과 흑체복사 광도(L_BB), B_s와 X-ray photon index (Γ_X) 관계를 더 많은 magnetar에 대하여 재확인하였으며, spin-down rate (Ṗ)와 L_BB, characteristic age (𝜏_c)와 L_BB의 새로운 유의미한 관계를 찾았다. 또한 magnetar의 pulsed fraction (PF)과 흑체복사 반경(R_BB), PF와 Γ_X, 그리고 Ṗ과 Γ_X가 서로 상관되어 있다는 단서를 확인하였다.

• Proceedings of the Optical Society of Korea Conference
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• 2002.07a
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• pp.60-61
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• 2002

Laser-induced incandescence (LII) 측정법은 조사된 레이저에 의하여 입자가 가열됨에 따라서, 그 온도에 상응하는 흑체복사의 시간적 감소추이가 입자의 크기에 따라서 달리 나타나는 것을 이용하여 입자의 크기를 측정하는 방법이다. LII 감쇄법은 레이저에 의하여 가열된 입자의 에너지 균형 상관식에서 입자의 크기가 클수록 신호의 감쇄속도가 느리고, LII 신호의 감쇄비가 실험적으로 입자의 크기에 비례한다는 사실을 이용하여 연소진단에 응용되어 왔다. (중략)

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1282-1287
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• 2004

The bubble behavior and the radiation mechanism from a laser-induced collapsing bubble were investigated theoretically using the Keller-Miksis equation for the bubble wall motion and analytical solutions for the vapor inside bubble. The calculated time dependent bubble radius is in good agreement with observed ones. The half-width of the luminescence pulse at the collapse point, which was calculated under assumption that the light emission mechanism is black body radiation from the vapor bubble agreed well with observed value of several nanoseconds. The gas content inside the vapor bubble was too small to produce the light emission due to bremsstrahlung.

• Journal of the Korean Vacuum Society
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• v.12 no.1
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• pp.64-69
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• 2003

Using a high fewer electron beam gun (max. power 20 kW), Gadolinium (Gd, atomic number 64) metal was melted and the temperature distribution of melted surface was measured. With proper optical filters and the adjustment of aperture of lens, the radiation of melted surface was received by a ccd camera and its signal transferred to a computer. The real time monitoring of melted surface with a variation of electron beam Power was Possible and stable operation of electron beam was achieved. It was found that the max. temperature measured by a ccd camera with an assumption of blackbody radiation of melted Gd surface and adaption of Planet's law was above 100~$200^{\circ}C$ compared to that measured by a pyrometer in the same e-beam power.

• Journal of the Institute of Convergence Signal Processing
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• v.18 no.1
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• pp.21-24
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• 2017

Passive millimeter wave (MMW) imaging penetrates clothing to detect concealed objects. The distances extraction to the concealed objects is critical for the security and defense. In this paper, we address a passive stereo 3 mm MMW imaging system to extract the longitudinal distance to the concealed object. The concealed object area is segmented and extracted by the k-means clustering algorithm with splitting initialization. The distance to the concealed object is estimated by the corresponding centers of the segmented objects. In the experimental two pairs (each pair for horizontal and vertical polarization) of stereo MMW images are obtained to estimate distances to concealed objects.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.6
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• pp.466-473
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• 2016

In a shipbuilding process, thermal damage to the ship structure at the rear end results from an excessive heat input and conduction during welding process. To prevent such damage, appropriate control of the heat input, based on welding temperature measurement, is required. For temperature measurement, contact and non-contact methods are available; the thermography system is a popular non-contact temperature measurement. When the intensity of radiation from a high-temperature object is excessive, however, detecting the sensors of ordinary thermography systems leads to an inability in measuring the temperature due to saturation. Hence, this study suggests use of a neutral density filter that prevents an excessive amount of radiation from being accumulated in a thermography system, and thus makes it possible to quantitatively measure an object's temperature as high as $3000^{\circ}C$.

• Journal of the Korean Vacuum Society
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• v.18 no.2
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• pp.108-115
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• 2009

The superlattice infrared photodetector (SLIP) with an active layer of 8/8-ML InAs/GaSb type-II strained-layer superlattice (SLS) of 150 periods was grown by MBE technique, and the proto-type discrete device was defined with an aperture of $200-{\mu}m$ diameter. The contrast profile of the transmission electron microscope (TEM) image and the satellite peak in the x-ray diffraction (XRD) rocking curve show that the SLS active layer keeps abrupt interfaces with a uniform thickness and a periodic strain. The wavelength and the bias-voltage dependences of responsivity (R) and detectivity ($D^*$) measured by a blackbody radiation source give that the cutoff wavelength is ${\sim}5{\mu}m$, and the maximum Rand $D^*$ ($\lambda=3.25{\mu}m$) are ${\sim}10^3mA/W$ (-0.6 V/13 K) and ${\sim}10^9cm.Hz^{1/2}/W$ (0 V/13 K), respectively. The activation energy of 275 meV analyzed from the temperature dependent responsivity is in good agreement with the energy difference between two SLS subblevels of conduction and valence bands (HH1-C) involving in the photoresponse process.

• Journal of the Korean Vacuum Society
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• v.22 no.6
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• pp.327-334
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• 2013

Long-wave infrared detectors using the type-II InAs/GaSb strained superlattice (T2SL) material system with the nBn structure were designed and fabricated. The band gap energy of the T2SL material was calculated as a function of the thickness of the InAs and GaSb layers by the Kronig-Penney model. Growth of the barrier material ($Al_{0.2}Ga_{0.8}Sb$) incorporated Te doping to reduce the dark current. The full width at half maximum (FWHM) of the $1^{st}$ satellite superlattice peak from the X-ray diffraction was around 45 arcsec. The cutoff wavelength of the fabricated device was ${\sim}10.2{\mu}m$ (0.12 eV) at 80 K while under an applied bias of -1.4 V. The measured activation energy of the device was ~0.128 eV. The dark current density was shown to be $1.0{\times}10^{-2}A/cm^2$ at 80 K and with a bias -1.5 V. The responsivity was 0.58 A/W at $7.5{\mu}m$ at 80 K and with a bias of -1.5 V.