• 제목/요약/키워드: Mid-Infrared

검색결과 275건 처리시간 0.032초

A SIGNATURE OF CHROMOSPHERIC ACTIVITY IN BROWN DWARFS: A RECENT RESULT FROM NIRLT MISSION PROGRAM

  • Sorahana, Satoko;Suzuki, Takeru K.;Yamamura, Issei
    • 천문학논총
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    • 제32권1호
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    • pp.131-133
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    • 2017
  • We present the latest results from the Mission Program NIRLT (PI: I.Yamamura), the near-infrared spectroscopy of brown dwarfs using the AKARI/IRC grism mode with the spectral resolution of ~ 120. The near-infrared spectra in the wavelength range between 2.5 and $5.0{\mu}m$ are especially important to study the brown dwarf atmospheres because of the presence of major molecular bands, including $CH_4$ at $3.3{\mu}m$, $CO_2$ at $4.2{\mu}m$, CO at $4.6{\mu}m$, and $H_2O$ around $2.7{\mu}m$. We observed 27 sources, and obtained 16 good spectra. Our model fitting reveals deviations between theoretical model and observed spectra in this wavelength range, which may be attributed to the physical condition of the upper atmosphere. The deviations indicate additional heating, which we hypothesize to be due to chromospheric activity. We test this effect by modifying the brown dwarf atmosphere model to artificially increase the temperature of the upper atmosphere, and compare the revised model with observed spectra of early- to mid-L type objects with $H{\alpha}$ emission. We find that the chemical structure of the atmosphere changes dramatically, and the heating model spectra of early-type brown dwarfs can be considerably improved to match the observed spectra. Our result suggests that chromospheric activity is essential to understand early-type brown dwarf atmospheres.

보배광산에서 산출하는 열수변질 기원 녹염석의 분광학적 특성: 적외선 및 뫼스바우어 연구 (FTIR and M ssbauer Spectroscopic Studies on the Hydrothermal Epidote from the Bobae Clay Deposit, Pusan, Korea)

  • 추창오;김수진
    • 한국광물학회지
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    • 제9권2호
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    • pp.55-63
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    • 1996
  • Epidote occurs as veinlets in the propylitic alteration zone of the Bobae clay deposit, Pusan, Korea. Its cell parameters apparently decrease with the contents of Al, Fe, and Ca. Fourier transform infrared (FTIR) spectra show one hydrosyl environment related to AlM2 at 3357-3358 cm-1. In the mid-infrared region, the peaks at 950 and 1030 cm-1 sharper with increasing Al shifting to higher energy region. The peak at 885 cm-1 shifts slightly to a lower energy region with a decreasing intensity as the Fe content increases. In the far-IR region, epidote exhibits absorption bands at 120 and 140 cm-1, which are related to the Ca-O bonds in A-sites.M ssbauer spectra of epidote show that the isomer shifts of Fe3+ range from 0.36-0.37 at the M3 site and from 0.35-0.44 at M1 site. Fe2+ shows the isomer shift ranging from 1.11 to 1.13. Quadrupole splitting is 2.04 for Fe3+M3, 0.52-0.70 for Fe3+M1, and 2.61-2.70 for Fe2+M3. Calculation shows Fe3+M386-90.7%, Fe3+M12.5-3.6%, and Fe2+M35.8-11.4% of total iron, showing preferential distribution of Fe3+ in the M3 site. The Fe3+M3 content is between 0.486 and 0.513 per formula unit. in the Fe-rich epidote, less Fe3+ and more Fe2+ are accommodated in the M1 and M3 sites. Hence, the overall disorder increases as total Fe content increase. The ordering parameter of the Bobae epidote is 0.93-0.95, suggesting a disequilibrium state below 200$^{\circ}C$. The constant temperature over a long period may be essential for the transition from disordered state to equilibrium state, despite the possible variation in flux and composition of the hydrothermal fluid.

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SEJONG OPEN CLUSTER SURVEY (SOS) - V. THE ACTIVE STAR FORMING REGION SH 2-255 - 257

  • LIM, BEOMDU;SUNG, HWANKYUNG;HUR, HYEONOH;LEE, BYEONG-CHEOL;BESSELL, MICHAEL S.;KIM, JINYOUNG S.;LEE, KANG HWAN;PARK, BYEONG-GON;JEONG, GWANGHUI
    • 천문학회지
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    • 제48권6호
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    • pp.343-355
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    • 2015
  • There is much observational evidence that active star formation is taking place in the Hii regions Sh 2-255 – 257. We present a photometric study of this star forming region (SFR) using imaging data obtained in passbands from the optical to the mid-infrared, in order to study the star formation process. A total of 218 members were identified using various selection criteria based on their observational properties. The SFR is reddened by at least E(B −V ) = 0.8 mag, and the reddening law toward the region is normal (RV = 3.1). From the zero-age main sequence fitting method it is confirmed that the SFR is 2.1 ± 0.3 kpc from the Sun. The median age of the identified members is estimated to be about 1.3 Myr from a comparison of the Hertzsprung-Russell diagram (HRD) with stellar evolutionary models. The initial mass function (IMF) is derived from the HRD and the near-infrared (J, J −H) color-magnitude diagram. The slope of the IMF is about Γ = −1.6 ± 0.1, which is slightly steeper than that of the Salpeter/Kroupa IMF. It implies that low-mass star formation is dominant in the SFR. The sum of the masses of all the identified members provides the lower limit of the cluster mass (169M). We also analyzed the spectral energy distribution (SED) of pre-main sequence stars using the SED fitting tool of Robitaille et al., and confirm that there is a significant discrepancy between stellar mass and age obtained from two different methods based on the SED fitting tool and the HRD.

A Polarimetric Study of Long-Period Comet C/2013 US10 (Catalina) and Estimation of Its Gas Contamination in Optical and Near-Infrared Wavelengths

  • Kwon, Yuna Grace;Ishiguro, Masateru;Kuroda, Daisuke;Hanayama, Hidekazu;Kawabata, Koji S.;Akitaya, Hiroshi;Itoh, Ryosuke;Nakaoka, Tatsuya
    • 천문학회보
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    • 제41권1호
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    • pp.48.1-48.1
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    • 2016
  • Polarimetric study of light scattering from cometary dust particles can provide us opportunity to decipher their characteristics, such as sizes, structures, compositions of dust grains, etc. Herein, we present the results of our polarimetric study of long-period comet, C/2013 US10 (Catalina), in optical and near-infrared wavelengths which appeared at large phase angle (52.7 degrees) around the mid-December, 2015. We performed polarimetric and spectroscopic observations with HONIR, attached to the 1.5-m telescope at Higashi-Hiroshima Observatory, on UT 2015 December 17-18 and also obtained optical imaging data sets by the Ishigakijima Astronomical Observatory (IAO) and Okayama Astrophysical Observatory (OAO) taken between 2014-2015. By measuring the intensities of gas emission lines with respect to dust continuum and considering transmittance of each filter, we estimated that the percentages of gas contamination are approximately 10 percents in $R_C$-band and 3 percents in $I_C$-band. With these results, we derive the degree of linear polarization scattered solely from dust components in the coma. At this presentation, we will compare the phase-angle dependence of the degree of linear polarization with those of previous archive data in a wide coverage of wavelengths from $R_C$-band to $K_S$-band. Finally, we are supposed to discuss the spatial variations in polarization within the coma.

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섬광의 복사온도 측정 장치의 설계 및 제작 (Design and Implementation of a Radiative Temperature Measurement System for a Flash Light)

  • 진정호;한승오;양희원;박승만
    • 한국광학회지
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    • 제26권1호
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    • pp.30-37
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    • 2015
  • 섬광의 복사온도를 측정 할 수 있는 장치를 설계하고 제작하였다. 본 논문에서는 중 원적외선 영역에서 광원의 스펙트럼 복사휘도(spectral radiance)를 측정하여 두 영역의 복사휘도 비로부터 섬광의 복사온도를 구할 수 있는 장치를 설계 및 제작하였다. 중 원적외선 영역에서 파장에 따른 복사휘도를 측정하기 위하여 광학적 대역 투과필터로 입사광을 파장에 따라 분할하고 각각의 파장으로 분할된 광을 동시에 적외선 검출기로 검출하여 입력광의 파장에 따른 복사휘도를 측정하였다. 제작된 장비로 섬광의 온도를 측정한 결과 1393K와 1455K의 온도를 얻었다. 제작된 복사온도 측정 장치는 섬광의 광원 정보를 파악하는데 중요하게 활용될 수 있으며, 섬광의 효과를 위한 M&S에 활용될 수 있다.

Near-elliptic Core Triangular-lattice and Square-lattice PCFs: A Comparison of Birefringence, Cut-off and GVD Characteristics Towards Fiber Device Application

  • Maji, Partha Sona;Chaudhuri, Partha Roy
    • Journal of the Optical Society of Korea
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    • 제18권3호
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    • pp.207-216
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    • 2014
  • In this work, we report detailed numerical analysis of the near-elliptic core index-guiding triangular-lattice and square-lattice photonic crystal fiber (PCFs); where we numerically characterize the birefringence, single mode, cut-off behavior and group velocity dispersion and effective area properties. By varying geometry and examining the modal field profile we find that for the same relative values of $d/{\Lambda}$, triangular-lattice PCFs show higher birefringence whereas the square-lattice PCFs show a wider range of single-mode operation. Square-lattice PCF was found to be endlessly single-mode for higher air-filling fraction ($d/{\Lambda}$). Dispersion comparison between the two structures reveal that we need smaller lengths of triangular-lattice PCF for dispersion compensation whereas PCFs with square-lattice with nearer relative dispersion slope (RDS) can better compensate the broadband dispersion. Square-lattice PCFs show zero dispersion wavelength (ZDW) red-shifted, making it preferable for mid-IR supercontinuum generation (SCG) with highly non-linear chalcogenide material. Square-lattice PCFs show higher dispersion slope that leads to compression of the broadband, thus accumulating more power in the pulse. On the other hand, triangular-lattice PCF with flat dispersion profile can generate broader SCG. Square-lattice PCF with low Group Velocity Dispersion (GVD) at the anomalous dispersion corresponds to higher dispersion length ($L_D$) and higher degree of solitonic interaction. The effective area of square-lattice PCF is always greater than its triangular-lattice counterpart making it better suited for high power applications. We have also performed a comparison of the dispersion properties of between the symmetric-core and asymmetric-core triangular-lattice PCF. While we need smaller length of symmetric-core PCF for dispersion compensation, broadband dispersion compensation can be performed with asymmetric-core PCF. Mid-Infrared (IR) SCG can be better performed with asymmetric core PCF with compressed and high power pulse, while wider range of SCG can be performed with symmetric core PCF. Thus, this study will be extremely useful for designing/realizing fiber towards a custom application around these characteristics.

ADVANTAGES OF USING ARTIFICIAL NEURAL NETWORKS CALIBRATION TECHNIQUES TO NEAR-INFRARED AGRICULTURAL DATA

  • Buchmann, Nils-Bo;Ian A.Cowe
    • 한국근적외분광분석학회:학술대회논문집
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    • 한국근적외분광분석학회 2001년도 NIR-2001
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    • pp.1032-1032
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    • 2001
  • Artificial Neural Network (ANN) calibration techniques have been used commercially for agricultural applications since the mid-nineties. Global models, based on transmission data from 850 to 1050 nm, are used routinely to measure protein and moisture in wheat and barley and also moisture in triticale, rye, and oats. These models are currently used commercially in approx. 15 countries throughout the world. Results concerning earlier European ANN models are being published elsewhere. Some of the findings from that study will be discussed here. ANN models have also been developed for coarsely ground samples of compound feed and feed ingredients, again measured in transmission mode from 850 to 1050 nm. The performance of models for pig- and poultry feed will be discussed briefly. These models were developed from a very large data set (more than 20,000 records), and cover a very broad range of finished products. The prediction curves are linear over the entire range for protein, fat moisture, fibre, and starch (measured only on poultry feed), and accuracy is in line with the performance of smaller models based on Partial Least Squares (PLS). A simple bias adjustment is sufficient for calibration transfer across instruments. Recently, we have investigated the possible use of ANN for a different type of NIR spectrometer, based on reflectance data from 1100 to 2500 nm. In one study, based on data for protein, fat, and moisture measured on unground compound feed samples, dedicated ANN models for specific product classes (cattle feed, pig feed, broiler feed, and layers feed) gave moderately better Standard Errors of Prediction (SEP) compared to modified PLS (MPLS). However, if the four product classes were combined into one general calibration model, the performance of the ANN model deteriorated only slightly compared to the class-specific models, while the SEP values for the MPLS predictions doubled. Brix value in molasses is a measure of sugar content. Even with a huge dataset, PLS models were not sufficiently accurate for commercial use. In contrast an ANN model based on the same data improved the accuracy considerably and straightened out non-linearity in the prediction plot. The work of Mr. David Funk (GIPSA, U. S. Department of Agriculture) who has studied the influence of various types of spectral distortions on ANN- and PLS models, thereby providing comparative information on the robustness of these models towards instrument differences, will be discussed. This study was based on data from different classes of North American wheat measured in transmission from 850 to 1050 nm. The distortions studied included the effect of absorbance offset pathlength variation, presence of stray light bandwidth, and wavelength stretch and offset (either individually or combined). It was shown that a global ANN model was much less sensitive to most perturbations than class-specific GIPSA PLS calibrations. It is concluded that ANN models based on large data sets offer substantial advantages over PLS models with respect to accuracy, range of materials that can be handled by a single calibration, stability, transferability, and sensitivity to perturbations.

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LANDSAT 영상을 이용한 세종특별자치시의 도시화와 열섬현상 분석 (Urbanization and Urban Heat Island Analysis Using LANDSAT Imagery: Sejong City As a Case Study)

  • 김미경;김상필;김남훈;손홍규
    • 대한토목학회논문집
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    • 제34권3호
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    • pp.1033-1041
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    • 2014
  • 우리나라는 세계적으로 유례없이 도시화가 급속하게 이루어졌으며 그 결과, 국토 면적의 10%인 수도권에 인구의 50%가 밀집하여 국토 개발의 불균형 및 열섬현상을 비롯한 각종 도시 문제가 수도권을 중심으로 발생하고 있다. 이에 수도권의 과잉 밀집을 해소하고 국토의 균형개발을 위해 2012년 7월 세종특별자치시가 출범하였으며, 세종시는 2000년대 후반부터 실질적인 개발이 진행되어 급격한 도시화를 겪고 있는 곳으로 급격한 개발에 따른 도시 문제를 수반할 것으로 예상된다. 도시화로 인한 지표면 특성의 변화는 도시열섬의 주요인이며 도시열섬현상은 결과적으로 도시지역의 기후변화 및 자연환경에 영향을 끼칠 수 있다. 본 논문은 급속한 도시화를 겪고 있는 세종시를 대상으로 도시화의 정도와 도시열섬효과를 파악하였고 도시화와 지표면온도와의 상관관계를 분석하였다. 이를 위하여 LANDSAT 영상을 사용하였으며, 2001년부터 2013년까지의 LANDSAT의 $0.63{\mu}m-1.75{\mu}m$에 해당하는 적색, 근적외선, 중적외선 영역 영상으로 NDVI, NDBI, UI를 산출하였고, $10.4{\mu}m-12.5{\mu}m$에 해당하는 열적외선 영역대의 영상을 통하여 세종시의 지표온도를 추정하였다. 산출된 각 지수와 지표면 온도를 바탕으로 세종시의 NDVI의 변화, UI의 변화를 파악하였고, TVI를 통해 도시열섬을 분석하였다. TVI를 통해 새로 건설된 행정중심복합도시 지역 일대를 중심으로 도시열섬현상이 두드러지게 증가한 것을 확인할 수 있었고 각 지수와 지표온도와의 상관관계 분석 결과 NDVI가 높을수록 온도는 낮아지는 음의 상관 관계를, NDBI와 UI는 증가할수록 온도가 높아지는 양의 상관관계를 갖는 것으로 나타났으며 이 중에서도 UI는 지표면 온도와 가장 강한 양의 상관관계를 보였다.

InAs 및 GaAs 웨이퍼를 이용한 Type-II InSb 나노 구조 형성

  • 이은혜;송진동;김수연;배민환;한일기;장수경;이정일
    • 한국진공학회:학술대회논문집
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    • 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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    • pp.305-305
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    • 2011
  • Type-II 반도체 나노 구조는 그것의 band alignment 특성으로 인해 광학 소자에 다양한 응용성을 가진다. 특히, 대표적인 Type-II 반도체 나노 구조인 InSb/InAs 양자점의 경우, 약 3~5 ${\mu}m$의 mid-infrared 영역의 spectral range를 가지므로, 장파장을 요하는 소자에 유용하게 적용될 수 있다. 또한, Type-II 반도체 나노 구조의 밴드 구조를 staggered gap 혹은 broken gap 구조로 조절함으로써 infrared 영역 광소자의 전자 구조를 유용하게 바꾸어 적용할 수 있다. 최근, GaSb wafer 위에 InSb/InAsSb 양자점을 이용하여 cutoff wavelength를 6 ${\mu}m$까지 연장한 IR photodetector의 연구도 보고되고 있다. 하지만, GaSb wafer의 경우 그것의 비용 문제로 인해 산업적 적용이 쉽지 않다는 문제가 있다. 이러한 문제를 해결하기 위해 GaAs wafer와 같은 비용 효율이 높은 wafer를 사용한 연구가 필요할 것이다. 본 연구에서는 Molecular Beam Epitaxy(MBE)를 이용하여 undoped InAs wafer 와 semi-insulating GaAs wafer 상에 InSb 양자 구조를 형성한 결과를 보고한다. InSb 양자 구조는 20층 이상의 다층으로 형성되었고, 두 가지 경우 모두 400${\AA}$ spacer를 사용하였다. 단, InAs wafer 위에 형성한 InSb 양자 구조의 경우 InAs spacer를, GaAs wafer 위에 형성한 양자 구조의 경우 InAsSb spacer를 사용하였다. GaAs wafer 위에 양자 구조를 형성한 경우, InSb 물질과의 큰 lattice mismatch 차이 완화 뿐 아니라, type-II 밴드 구조 형성을 위해 1 ${\mu}m$ AlSb 층과 1 ${\mu}m$ InAsSb 층을 GaAs wafer 위에 미리 형성해 주었다. 양자 구조 형성 방법도 두 종류 wafer 상에서 다르게 적용되었다. InAs wafer 상에는 주로 일반적인 S-K 형성 방식이 적용된 것에 반해, GaAs wafer 상에는 migration enhanced 방식에 의해 양자 구조가 형성되었다. 이처럼 각 웨이퍼에 대해 다른 성장 방식이 적용된 이유는 InAsSb matrix와 InSb 물질 간의 lattice mismatch 차이가 6%를 넘지 못하여 InAs matrix에 비해 원하는 양자 구조 형성이 쉽지 않기 때문이다. 두 가지 경우에 대해 AFM과 TEM 측정으로 그 구조적 특성이 관찰되었다. 또한 infrared 영역의 소자 적용 가능성을 보기 위해 광학적 특성 측정이 요구된다.

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Characterization of intrinsic molecular structure spectral profiles of feedstocks and co-products from canola bio-oil processing: impacted by source origin

  • Alessandra M.R.C.B., de Oliveira;Peiqiang, Yu
    • Animal Bioscience
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    • 제36권2호
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    • pp.256-263
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    • 2023
  • Objective: Feed molecular structures can affect its availability to gastrointestinal enzymes which impact its digestibility and absorption. The molecular spectroscopy-attenuated total reflectance Fourier transform infrared vibrational spectroscopy (ATR-FTIR) is an advanced technique that measures the absorbance of chemical functional groups on the infrared region so that we can identify and quantify molecules and functional groups in a feed. The program aimed to reveal the association of intrinsic molecular structure with nutrient supply to animals from canola feedstocks and co-products from bio-oil processing. The objective of this study was to characterize special intrinsic carbohydrate and protein-related molecular structure spectral profiles of feedstock and co-products (meal and pellets) from bio-oil processing from two source origins: Canada (CA) and China (CH). Methods: The samples of feedstock and co-products were obtained from five different companies in each country arranged by the Canola Council of Canada (CCC). The molecular structure spectral features were analyzed using advanced vibrational molecular spectroscopy-ATR-FTIR. The spectral features that accessed included: i) protein-related spectral features (Amide I, Amide II, α-helix, β-sheet, and their spectral intensity ratios), ii) carbohydrate-related spectral features (TC1, TC2, TC3, TC4, CEC, STC1, STC2, STC3, STC4, TC, and their spectral intensity ratios). Results: The results showed that significant differences were observed on all vibrationally spectral features related to total carbohydrates, structural carbohydrates, and cellulosic compounds (p<0.05), except spectral features of TC2 and STC1 (p>0.05) of co-products, where CH meals presented higher peaks of these structures than CA. Similarly, it was for the carbohydrate-related molecular structure of canola seeds where the difference between CA and CH occurred except for STC3 height, CEC and STC areas (p>0.05). The protein-related molecular structures were similar for the canola seeds from both countries. However, CH meals presented higher peaks of amide I, α-helix, and β-sheet heights, α-helix:β-sheet ratio, total amide and amide I areas (p<0.05). Conclusion: The principal component analysis was able to explain over 90% of the variabilities in the carbohydrate and protein structures although it was not able to separate the samples from the two countries, indicating feedstock and coproducts interrelationship between CH and CA.