• Title/Summary/Keyword: Near infrared

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A Test of a Far Infrared Camera for Development of New Surface Image Velocimeter for Day and Night Measurement (주야간 겸용 표면영상유속계 개발을 위한 원적외선 카메라의 적용성 검토)

  • Yu, Kwonkyu;Kim, Seojun;Yoo, Byeongnam;Bae, Inhyuk
    • Journal of Korea Water Resources Association
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    • v.48 no.8
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    • pp.659-672
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    • 2015
  • In flow velocity measurement of natural rivers, taking images with proper image quality is the fundamental and the most important step. Since flood peaks generally occur in night time, it is very difficult to capture proper images in that time. The present study aims to test a far infra-red camera as a adequate alternative to resolve the various problems in measuring flood discharges. The far infra-red cameras are able to capture images in night time without help of any extra illuminations. Futhermore they are not affected by fog nor smoke, hence they can be adapted for a fixed-type surface image velocimeters. For comparison, a commercial camcorder and a near infra-red cameras were used together. The test images were taken at a day time and a night time, and the image acquisition work were performed at an artificial flow channel of the Andong River Experiment Station. The analyzed results showed that the far infra-red camera would be a good instrument for surface image velocimeters, since they were able to capture regardless light condition. There are, however, a few minor problems in their accuracy of the analyzed results. About their accuracy a more study would be required.

Design for Access Control System based on Voice Recognition for Infectious Disease Prevention (전염성 확산 차단을 위한 음성인식 기반의 출입통제시스템 설계)

  • Mun, Hyung-Jin;Han, Kun-Hee
    • Journal of the Korea Convergence Society
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    • v.11 no.7
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    • pp.19-24
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    • 2020
  • WHO declared a global pandemic on March 11th for Corona 19. However, there is a situation where you have to go to building for face-to-face education or seminars for economic and social activities. The first check method of COVID-19 infection is to measure body temperature, so the primary entrance and exit is blocked for near-field body temperature measurement. However, since it is troublesome to check directly, thermal camera is installed at the entrance of the building, and body temperature is measured indirectly using the infrared camera to control access. In case of middle and high schools, universities, and lifelong education center, we need a system that is possible to interoperate with attendance checks and automatically recognizes whether to wear masks and can authenticate students. We proposed the system that is to confirm whether to wear a mask with a camera that is embedded in a smart mirror, and that authenticates the user through voice recognition of the user who wants to enter the building by using voice recognition technology and determines whether to enter them or not. The proposed system can check attendance if it is linked with near-field temperature measurement and attendance check APP of student's smart phone.

Optical Characteristics of Near-monolayer InAs Quantum Dots

  • Kim, Yeong-Ho;Kim, Seong-Jun;No, Sam-Gyu;Park, Dong-U;Kim, Jin-Su;Im, In-Sik;Kim, Jong-Su
    • Proceedings of the Korean Vacuum Society Conference
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    • 2011.08a
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    • pp.293-294
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    • 2011
  • It is known that semiconductor quantum-dot (QD) heterostructures have superior zero-dimensional quantum confinement, and they have been successfully applied to semiconductor laser diodes (QDLDs) for optical communication and infrared photodetectors (QDIPs) for thermal images [1]. The self-assembled QDs are normally formed at Stranski-Krastanov (S-K) growth mode utilizing the accumulated strain due to lattice-mismatch existing at heterointerfaces between QDs and cap layers. In order to increase the areal density and the number of stacks of QDs, recently, sub-monolayer (SML)-thick QDs (SQDs) with reduced strain were tried by equivalent thicknesses thinner than a wetting layer (WL) existing in conventional QDs (CQDs) by S-K mode. Despite that it is very different from CQDs with a well-defined WL, the SQD structure has been successfully applied to QDIP[2]. In this study, optical characteristics are investigated by using photoluminescence (PL) spectra taken from self-assembled InAs/GaAs QDs whose coverage are changing from submonolayer to a few monolayers. The QD structures were grown by using molecular beam epitaxy (MBE) on semi-insulating GaAs (100) substrates, and formed at a substrate temperature of 480$^{\circ}C$ followed by covering GaAs cap layer at 590$^{\circ}C$. We prepared six 10-period-stacked QD samples with different InAs coverages and thicknesses of GaAs spacer layers. In the QD coverage below WL thickness (~1.7 ML), the majority of SQDs with no WL coexisted with a small amount of CQDs with a WL, and multi-peak spectra changed to a single peak profile. A transition from SQDs to CQDs was found before and after a WL formation, and the sublevel of SQDs peaking at (1.32${\pm}$0.1) eV was much closer to the GaAs bandedge than that of CQDs (~1.2 eV). These revealed that QDs with no WL could be formed by near-ML coverage in InAs/GaAs system, and single-mode SQDs could be achieved by 1.5 ML just below WL that a strain field was entirely uniform.

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Generation of Femtosecond Pulses in a Passively Mode-Locked 100 MHz Cr4+:YAG Laser (수동 모드 잠금된 100 MHz Cr4+:YAG 레이저에서의 펨토초 펄스 발생)

  • Cho, Won-Bae;Rotermund Fabian;Kim, Jong-Doo;Jeon, Min-Yong;Suh, Ho-Suhng
    • Korean Journal of Optics and Photonics
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    • v.16 no.6
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    • pp.535-541
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    • 2005
  • We report on the development of a passively mode-locked near-infrared femtosecond laser with Cr:YAG crystal that operates near room temperature. The laser wavelength could easily be tuned by using only the internal prism pair over 110 nm from 1400 nm to 1510 nm in cw and over about 30 nm in mode-locked operation, respectively Maximum cw output powers of 810 mW were obtained with $1.5 \%$ output coupler for absorbed pump powers of 7.6 W. For compensation of the internal group velocity dispersion, an IR graded prism pair was used. The Cr:YAG laser delivered nearly Fourier-transform limited pulses with a pulse duration as short as 64 fs at 100 MHz repetition rate. In the mode-locked regime, the laser was operating at 1510 nm with a spectral bandwidth of 44 nm. In order to avoid unstable mode-locking and power instabilities, self-built tubes were inserted into the beam path in the resonator and purged with N2 gas. Finally, output powers of the Cr:YAG laser were optimized to 250 mW fer long time stable mode-locked operation.

IMPLICATION OF STELLAR PROPER MOTION OBSERVATIONS ON RADIO EMISSION OF SAGITTARIUS A

  • CHANG HEON-YOUNG;CHOI CHUL-SUNG
    • Journal of The Korean Astronomical Society
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    • v.36 no.3
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    • pp.81-87
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    • 2003
  • It is suggested that a flying-by star in a hot accretion disk may cool the hot accretion disk by the Comptonization of the stellar emission. Such a stellar cooling can be observed in the radio frequency regime since synchrotron luminosity depends strongly on the electron temperature of the accretion flow. If a bright star orbiting around the supermassive black hole cools the hot disk, one should expect a quasi-periodic modulation in radio, or even possible an anti-correlation of luminosities in radio and X-rays. Recently, the unprecedentedly accurate infrared imaging of the Sagittarius A$\ast$ for about ten years enables us to resolve stars around it and thus determine orbital parameters of the currently closest star S2. We explore the possibility of using such kind of observation to distinguish two quite different physical models for the central engine of the Sagittarius A$\ast$, that is, a hot accretion disk model and a jet model. We have attempted to estimate the observables using the observed parameters of the star S2. The relative difference in the electron temperature is a few parts of a thousand at the epoch when the star S2 is near at the pericenter. The relative radio luminosity difference with and without the stellar cooling is also small of order $10^{-4}$, particularly even when the star S2 is near at the pericenter. On the basis of our findings we tentatively conclude that even the currently closest pass of the star S2 is insufficiently close enough to meaningfully constrain the nature of the Sagittarius A$\ast$ and distinguish two competing models. This implies that even though Bower et al. (2002)have found no periodic radio flux variations in their data set from 1981 to 1998, which is naturally expected from the presence of a hot disk, a hot disk model cannot be conclusively ruled out. This is simply because the energy bands they have studied are too high to observe the effect of the star S2 even if it indeed interacts with the hot disk. In other words, even if there is a hot accretion disk the star like S2 has imprints in the frequency range at v $\le$ 100 MHz.

The Measurements of Biomass Burning Aerosols from GLI Data (GLI 자료를 이용한 생체 소각 에어러솔 측정에 대한 연구)

  • Lee Hyun Jin;Fukushima Hajime;Ha Kyung-Ja;Kim Jae Hwan
    • Korean Journal of Remote Sensing
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    • v.21 no.4
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    • pp.273-285
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    • 2005
  • This study has investigated the suitable wavelength for detecting biomass burning aerosols. We have performed the analysis of the wavelength at 380nm in near-UV, 400nm, 412nm, 460nm, and 490nm in visible, and 2100nm in shortwave infrared regions from the Global Imager measurements. It is well known that the UV bands have the advantage of the aerosols retrieval due to the low surface reflectance and a weak effect of Bidirectional Reflectivity Distribution Function. However, the pure surface reflectances of shortwave visible bands, except 412nm, are as low as that of 380nm in near-UV over northeast Asia. In order to detect the aerosol signal, we have retrieved the aerosol reflectance as a function of wavelength based on the surface reflectivity contrast method for the period of May 2003. It is interesting that the retrieved aerosol reflectance with 460nm is slightly more sensitive than that with 380nm. Additionally, we have applied the TOMS aerosol index method to determine the best pair for biomass burning aerosols and found that the pair of 380 and 460nm results in the best signal for retrieving aerosols.

Magnetic and Magneto-Optical Properties of $Mn_{1-x}Cr_xPt_3$ Ordered Alloy Films ($Mn_{1-x}Cr_xPt_3$ 박막의 자기 및 자기광학 특성)

  • 박문기;조재경
    • Journal of the Korean Magnetics Society
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    • v.8 no.6
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    • pp.374-379
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    • 1998
  • $Mn_1-xCr_xPt_3$ alloy films have been prepared by depositing (Mn, Cr)/Pt multilayers using a rf magnetron sputterer followed by heat treatment. Small and wide angle x-ray diffractometry, magnetic hysteresis loops and Kerr rotation angle spectra of the films have been measured and used to investigate structural, magnetic and magneto-optic properties of the films. The films had a crystal structure of ordered AuCu$_3$ type and the strong preferred orientation of a (111)plane parallel to the film surface. The saturation magnetization of the films was decreased with Cr content reaching almost zero near x=0.58 and then increased for further increasement of Cr content up to x=0.77 over that stayed almost constant. This indicated that Cr atoms were antiferromagnetically coupled with Mn atoms. The magnetic easy axis of MnPt$_3$(x=0) film was parallel to the film surface but those of the films with x$\geq$0.58 increased as Cr content increased reaching about 4 kOe at x=1(CrPt$_3$). The dependence of the Kerr rotation angle on the Cr content was similar to that of the saturation magnetization on the Cr content. The films with x=0.77 and x=1 showed the larger Kerr rotation angle at the wavelengths of near infrared compared to the magneto-optic recording medium, TbFeCo, currently being used.

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Preprocessing and Calibration of Optical Diffuse Reflectance Signal for Estimation of Soil Physical and Chemical Properties in the Central USA (미국 중부 토양의 이화학적 특성 추정을 위한 광 확산 반사 신호 전처리 및 캘리브레이션)

  • La, Woo-Jung;Sudduth, Kenneth A.;Chung, Sun-Ok;Kim, Hak-Jin
    • Journal of Biosystems Engineering
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    • v.33 no.6
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    • pp.430-437
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    • 2008
  • Optical diffuse reflectance sensing in visible and near-infrared wavelength ranges is one approach to rapidly quantify soil properties for site-specific management. The objectives of this study were to investigate effects of preprocessing of reflectance data and determine the accuracy of the reflectance approach for estimating physical and chemical properties of selected Missouri and Illinois, USA surface soils encompassing a wide range of soil types and textures. Diffuse reflectance spectra of air-dried, sieved samples were obtained in the laboratory. Calibrations relating spectra to soil properties determined by standard methods were developed using partial least squares (PLS) regression. The best data preprocessing, consisting of absorbance transformation and mean centering, reduced estimation errors by up to 20% compared to raw reflectance data. Good estimates ($R^2=0.83$ to 0.92) were obtained using spectral data for soil texture fractions, organic matter, and CEC. Estimates of pH, P, and K were not good ($R^2$ < 0.7), and other approaches to estimating these soil chemical properties should be investigated. Overall, the ability of diffuse reflectance spectroscopy to accurately estimate multiple soil properties across a wide range of soils makes it a good candidate technology for providing at least a portion of the data needed in site-specific management of agriculture.

Automatic Mosaicing of Airborne Multispectral Images using GPS/INS Data and Unsupervised Classification (GPS/INS자료와 무감독 분류를 이용한 항공영상 자동 모자이킹)

  • Jang, Jae-Dong
    • Journal of the Korean Association of Geographic Information Studies
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    • v.9 no.1
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    • pp.46-55
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    • 2006
  • The purpose of this study is a development of an automatic mosaicing for applying to large number of airborne multispectral images, which reduces manual operation by human. 2436 airborne multispectral images were acquired from DuncanTech MS4100 camera with three bands; green, red and near infrared. LIDAR(LIght Detection And Ranging) data and GPS/INS(global positioning system/inertial navigation system) data were collected with the multispectral images. First, the multispectral images were converted to image patterns by unsupervised classification. Their patterns were compared with those of adjacent images to derive relative spatial position between images. Relative spatial positions were derived for 80% of the whole images. Second, it accomplished an automatic mosaicing using GPS/INS data and unsupervised classification. Since the time of GPS/INS data did not synchronized the time of readout images, synchronized GPS/INS data with the time of readout image were selected in consecutive data by comparing unsupervised classified images. This method realized mosaicing automatically for 96% images and RMSE (root mean square error) for the spatial precision of mosaiced images was only 1.44 m by validation with LIDAR data.

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Research on Real-Time Portable Quality Evaluation System for Raw Milk

  • Lee, Dae Hyun;Kim, Yong Joo;Min, Kyu Ho;Choi, Chang Hyun
    • Agribusiness and Information Management
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    • v.6 no.2
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    • pp.32-39
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    • 2014
  • The goal of this research was to develop a portable system that could be used to evaluate the quality of milk in real time at a raw milk production site. A real-time portable quality evaluation system for raw milk was developed to enable non-destructive quality evaluation of somatic cell count (SCC), fat, protein, lactose, and total solid (TS) in milk samples. A prediction model of SCC, fat, protein, lactose, and TS was constructed using partial least squares (PLS) and 200 milk samples were used to evaluate the prediction performance of the portable quality evaluation system and high performance spectroscopy. Through prediction model development and verification, it was found that the accuracy of high performance spectroscopy was 90% for SSC, 96% for fat, 96% for protein, 91% for lactose, and 97% for TS. In comparison, the accuracy of the portable quality evaluation system was relatively low, at 90% for SSC, 95% for fat, 92% for protein, 89% for lactose, 92% for TS. However, the measurement time for high performance spectroscopy was 10 minutes for 1 sample, while for the portable quality evaluation system it was 6 minutes. This means that the high performance spectroscopy system can measure 48 samples per day (8 hours), while the portable quality evaluation system can measure 80 (8 hours). Therefore, it was found that the portable quality evaluation system enables quick on-site quality evaluation of milk samples.