• 한국근적외분광분석학회:학술대회논문집
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• 한국근적외분광분석학회 2001년도 NIR-2001
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• pp.1182-1182
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• 2001

In this study, the newly constructed optical measurement system, which was mainly composed of a parametric tunable laser and a near infrared photoelectric multiplier, was introduced to clarify the optical characteristics of wood as discontinuous body with anisotropic cellular structure from the viewpoint of the time-of-flight near infrared spectroscopy (TOF-NIRS). The combined effects of the cellular structure of wood sample, the wavelength of the laser beam λ, and the detection position of transmitted light on the time resolved profiles were investigated in detail. The variation of the attenuance of peak maxima At, the time delay of peak maxima Δt and the variation of full width at half maximum Δw were strongly dependent on the feature of cellular structure of a sample and the wavelength of the laser beam. The substantial optical path length became about 30 to 35 times as long as sample thickness except the absorption band of water. Δt ${\times}$ Δw representing the light scattering condition increased exponentially with the sample thickness or the distance between the irradiation point and the end of sample. Around the λ=900-950 nm, there may be considerable light scattering in the lumen of tracheid, which is multiple specular reflection and easy to propagate along the length of wood fiber. Such tendency was remarkable for soft wood with the aggregate of thin layers of cell walls. When we apply TOF-NIRS to the cellular structural materials like wood, it is very important to give attention to the difference in the light scattering within cell wall and the multiple specular-like reflections between cell walls. We tried to express the characteristics of the time resolved profile on the basis of the optical parameters for light propagation determined by the previous studies, which were absorption coefficient K and scattering coefficient S from Kubelka-Munk theory and n from nth power cosine model of radiant intensity. The wavelength dependency of the product of K/S and n, which expressed the light-absorbing and -scattering condition and the degree of anisotropy, respectively, was similar to that of the time delay of peak maxima Δt. The variation of the time resolved profile is governed by the combination of these parameters. So, we can easily find the set of parameters for light propagation synthetically from Δt.

• 천문학회지
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• 제29권2호
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• pp.245-253
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• 1996

We have analyzed infrared (IR) images of Jupiter which was observed at the McDonald Observatory, Texas, U.S.A., during the P/SHoemaker-LEvy 9 (SL9) impact period and about one week after the last impact. The IR images were obtained on the 2.7m telescope using a NICMOS array with filters to isolate the $1.5{\mu}m\;NH_3\; band,\;the\;2.3{\mu}m\;CH_4\;band,\;the\;2.12{\mu}m\;H_2\;S(0)$ pressure-induced absorption, and the continua at $1.58{\mu}m\;and\;2.0{\mu}m$ (short K-band). All images except those with the $1.58{\mu}m$ continuum filter show bright impact sites against the relatively dark Jovian disk near the impact latitude of about $45^{\circ}$ S. This implies that dusts originated from the impacts reflect the solar radiation at high altitudes before absorbed by stratospheric $CH_4,\;NH_3 \;or\;H_2$. The impact sites observed with the $2.3{\mu}m$ filter are conspicuously bright against a very dark background. The morphology of impact sites, G, L, and H at 2.3 and $2.12{\mu}m$ filters shows clearly an asymmetric structure toward the incident direction of the comet fragments, in agreement with the studies of visible impact images obtained with the Hubble Space Telescope. Comparisons of reflectances of G, L, and H sites with simple radiative transfer models suggest that optically thick dust layers were formed at high altitudes at which methane absorption attenuates incoming sunlight only by about $1\%$. The dust layers in these sites seem to form at about the same altitude regardless of the magnitude of the impacts, but they appear to descend gradually after the impacts. The dust layers have optical depths of 2-5, according to the models.

• 천문학회지
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• 제33권3호
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• pp.143-149
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• 2000

We present the results of near-IR band (JHK) photometric study for the old open cluster To 2. Combined with existing optical data, our IR photometry is used to derive the reddening E(B- V)=0.24$\pm$0.12 and the distance (m-M)o=14.6$\pm$0.42. Comparison with theoretical isochrones suggests the age and metallicity of To 2 are log t$\~$9.3 and [Fe/H]$\~$-0.3, respectively.

• Journal of Biosystems Engineering
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• 제42권4호
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• pp.301-313
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• 2017

Purpose: This study was conducted to discriminate between normal hulled barley and Fusarium (Fusarium asiaticum and Fusarium graminearum) infected hulled barley by using the near-infrared spectroscopy (NIRS) technique. Methods: Fusarium asiaticum and Fusarium graminearum were artificially inoculated in hulled barley and the reflectance spectrum of the barley spike was obtained by using a near-infrared spectral sensor with wavelength band in the range 1,175-2,170 nm. After obtaining the spectrum of the specimen, the hulled barley was cultivated in a greenhouse and visually inspected for infections. Results: From a partial least squares discriminant analysis (PLS-DA) prediction model developed from the raw spectrum data of the hulled barley, the discrimination accuracy for the normal and infected hulled barley was 99.82% (563/564) and 100% (672/672), respectively. Conclusions: NIRS is effective as a quick and nondestructive method to detect whether hulled barley has been infected with Fusarium. Further, it expected that NIRS will be able to detect Fusarium infections in other grains as well.

• 천문학회보
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• 제36권2호
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• pp.152.1-152.1
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• 2011

We report preliminary results of long-slit near-infrared (NIR) spectroscopy of Luminous Blue Variables (LBVs) with moderate resolution of R ~ 2400. We obtained Jshort (1.04-1.26 micron) and Ks (2.02-2.31 micron) band spectra of 4 LBVs and 3 LBV candidates in Southern hemisphere using IRIS2, infrared imager and spectrograph, mounted on the 4-m Anglo-Australian Telescope. All targets are fairly bright in NIR so that we can obtain high signal-to-noise ratio for clear line detection and modeling. They are also widely distributed in the HR diagram so that we can compare the spectral properties of LBVs in different temperature and luminosity ranges. Among them, we present the results of two well-known LBVs AG Car and HR Car. Their spectra show similar properties with hydrogen, He I, and metallic lines such as Fe II and Mg II, most of them in emission. We discuss, in particular, the He I 1.083 micron lines formed in stellar wind because these two LBVs show large variation in their He I line intensities, compared to previous studies. Since the He I 1.083 line is known to be anticorrelated with the photometric variation of LBVs, strong line intensities with P-Cygni profiles in both stars indicate that they are now near the visual minimum phase. We model the obtained spectra using non-LTE atmosphere code CMFGEN of Hillier (1998) to derive stellar parameters such as wind velocity and mass loss rate, and discuss the long-term variability of stellar parameters of these LBVs. deduced from our otometric solution.

• 천문학논총
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• 제22권4호
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• pp.169-175
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• 2007

The international cooperation project CIBER (Cosmic Infrared Background ExpeRiment) is a rocket-borne instrument, of which the scientific goal is to measure the cosmic near-infrared extra-galactic background to search for signatures of primordial galaxy formation. CIBER consists of a wide-field two-color camera, a low-resolution absolute spectrometer, and a high-resolution narrow-band imaging spectrometer. Currently, all the subsystems have been built, and the integration, testing, and calibration of the CIBER system are on process for the scheduled launch in June 2008.

• 천문학회보
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• 제44권1호
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• pp.69.1-69.1
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• 2019

We present the ALMA observations of the infrared dark cloud (IRDC) core MSXDC G053.11+00.05 MM1 at the distance of 1.7 kpc. While the core was first identified at 1.2 mm with a mass of 124 Msun, recent near- and mid-infrared observations have revealed a parsec-scale molecular hydrogen (H2 1-0 S(1) at 2.12 micron) outflow and two early class young stellar objects (YSOs) at the center of the core, one of which is likely massive (M > 8 Msun). From the ALMA Band 7 observations with a resolution of 0.5", we have found a dust filament of < 0.1 pc in which five dense cores are embedded in the 870 micron continuum. The brightest core is consistent with one of the two previously-detected YSOs, but the other four are newly discovered implying their very deeply embedded status. We have also detected several molecular line emission including H13CO+ and C17O as well as 13CO outflow with complicated morphology. At the brightest core, the methanol line (CH3OH) shows velocity gradients, which may support the existence of a circumstellar disk around a high-mass protostar. Based on the derived properties of the dense cores, we discuss their association with the two YSOs and H2 outflow detected in infrared and high-mass star-formation process occurring in IRDC cores.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2011년도 한국우주과학회보 제20권1호
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• pp.30.4-31
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• 2011

The Korea Astronomy and Space Science Institute (KASI) and the Department of Astronomy at the University of Texas at Austin (UT) are developing a near infrared wide-band high resolution spectrograph, IGRINS (Immersion Grating Infrared Spectrograph). The white-pupil design of the instrument optics uses 7 cryogenic mirrors including 3 aspherical off-axis collimators and 4 flat fold mirrors. Two of the 3 collimators are H- and K-band pupil transfer mirrors and they are designed as compensators for the system alignment in each channel. Therefore, their mount design will be one of the most sensitive parts in the IGRINS optomechanical system. The design work will include the computer-aided 3D modeling and finite element analysis (FEA) to optimize the structural stability of the mount models. The mount body will also include a tip-tilt and translation adjustment mechanism to be used as the alignment compensators.

• 천문학회보
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• 제38권1호
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• pp.55.1-55.1
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• 2013

We analyze the behaviors of reddening vectors in the Spitzer/IRAC photometric system for young stellar objects (YSOs) of different evolutionary stages, masses, and inclinations using the model spectral energy distributions (SED) by Robitaille et al. As reported in visible and near-infrared photometric systems, the magnitudes and colors of YSOs show strong SED dependence and non-linearity. In the [8.0] band where the 9.7 ${\mu}m$ interstellar silicate feature plays a significant role in extinction, the effective wavelength shifts "bluewards", not "redwards" as in most, if not all, optical and infrared bands including the other three IRAC bands, as the extinction in Ks increases up to ~2 mag, and then asymptotically reaches a constant value as the extinction further increases. This "bluening" is seen when the YSO is in later evolutionary stage and/or has a stellar mass of ~2 $M_{\odot}$ or greater. In many cases, the reddening vectors in the IRAC color-color diagrams are prominently curved, and in some extreme cases, the colors involving the [8.0] band becomes bluer in the beginning and then becomes redder later as the amount of extinction increases. We also present our "suggested" extinction laws employing the combination of a broken-power law and the 9.7 ${\mu}m$ silicate feature, which well reproduce the extinction behaviors observed in the IRAC bands.

• 천문학회보
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• 제38권1호
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• pp.73.2-73.2
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• 2013

An autoguiding system for astronomical observations should be accurate and stable for efficient data taking. IGRINS (Immersion Grating Infrared Spectrograph) is a high resolution near-IR spectrograph which is now developed by Korea Astronomy and Space Science Institute and the University of Texas. We plan to attach this instrument on the 2.7m telescope at the McDonald observatory in 2013. IGRINS consists on three detector modules, i. e., H and K band spectrograph modules and a K band slit camera module. We use the slit camera for autoguiding of the telescope. In this poster, we describe the system architecture of the hardware and software of the autoguiding system, and the algorithm which would effectively find centers of stellar images on or outside of the slit of the infrared array.