• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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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.

• Analytical Science and Technology
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• v.16 no.5
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• pp.391-398
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• 2003

Basic research for the determination of boron content in biological sample has been carried out using the PGAA facility of the 24MW research reactor(HANARO). For investigation of characteristics for the measurement condition, neutron flux and its homogeneity were measured at irradiating geometry. The size of thermal neutron beam collimated from beam guide is $2{\times}2cm^2$ at the sample position. The neutron flux measured was the range of $1.0{\sim}6.5{\times}10^7n{\cdot}cm^{-2}{\cdot}s^{-1}$, and flux distribution from center within the radius of 4.5 mm and 9.0 mm was $5.77{\pm}0.71{\times}10^7n{\cdot}cm^{-2}{\cdot}s^{-1}$ and $4.68{\pm}1.64{\times}10^7n{\cdot}cm^{-2}{\cdot}s^{-1}$, respectively. Accordingly, sample size is adjusted within 10 mm for a homogeneous irradiation of high quality. Measurement system is designed to reduce the background source by Compton scattering and to improve the analytical sensitivity. To investigate the energy calibration and Compton suppression effect of gamma-ray counting system, the background conditions on both of Compton and single-mode were measured using NaCl standard. On the other hand, degree of spectral interference for sodium 472 keV peak as a matrix effect in the sample is established for an accurate boron analysis, and then boron content in three certified reference materials (NIST SRM 1570a, 1547, 1573a) was measured by using two modes and the results were compared with each other.

• Economic and Environmental Geology
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• v.18 no.4
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• pp.309-320
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• 1985

The crustal structure of the southern part of the Korean peninsula has been investigated based on the results of processing and anlaysis of gravity data. The processing techniques involve i) seperation of regional and residual anomalies by polynomial fittings, ii) power spectral analyses to determine the mean depth to the crustal base, iii) a filtering operation called "high-cut filtering and resampling," and iv) downward continuation to determine the undulation of the crustal base. The Bouguer anomalies show a lineation in the NE-SW direction which is the same as that of most mountains and tectonic lines of this area. The mean crustal depth is found to be 34km. The depth of the crustal base is varying in the estimated range of 26km to 36km with a thinner crust below the east coast than that of the west coast. The relief of the crustal base is appeared to be correlated with the regional surface topography. The linear regression relations computed between elevations and gravity anomalies indicate that the crust of this area seems to be not in perfect isostatic equilibrium but a little undercompensated state.

• Journal of Sensor Science and Technology
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• v.9 no.5
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• pp.341-349
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• 2000

CsI(Br) single crystals doped with 1, 3, 5 or 10 mole% $Br^-$ ions, as an activator, were grown by Czochralski method. The lattice structure of grown CsI(Br) single crystal was bcc and its lattice constant was $4.568\;{\AA}$. The absorption edge of the CsI(Br) single crystals was observed at 243 nm. The spectral range of the luminescence excited by 243 nm of wavelength was $300{\sim}600\;nm$, and its peak emission appeared at 440 nm. The luminescence intensity was maximum when CsI(Br) was doped with 3 mole % $Br^-$ ions. The energy resolutions of the CsI(Br) scintillator doped with 3 mole % $Br^-$ ions were 15.0% for $^{137}Cs$(662 keV), 13.1% for $^{54}Mn$(835 keV), and 18.0% and 6.3% for $^{22}Na$(511 keV and 1275 keV), respectively. The decay curves had fast and slow components, and the fast component was about 41 ns independent on the concentration of the $Br^-$ ions. The time resolution of CsI(Br) scintillators decreased with increasing of the concentration of $Br^-$ ions.

• Journal of The Korean Society of Grassland and Forage Science
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• v.35 no.3
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• pp.257-263
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• 2015

This study was conducted to assess the potential of using NIRS to accurately determine the chemical composition and fermentation parameters in fresh coarse sorghum and sudangrass silage. Near Infrared Spectroscopy (NIRS) has been increasingly used as a rapid and accurate method to analyze the quality of cereals and dried animal forage. However, silage analysis by NIRS has a limitation in analyzing dried and ground samples in farm-scale applications because the fermentative products are lost during the drying process. Fresh coarse silage samples were scanned at 1 nm intervals over the wavelength range of 680~2500 nm, and the optical data were obtained as log 1/Reflectance (log 1/R). The spectral data were regressed, using partial least squares (PLS) multivariate analysis in conjunction with first and second order derivatization, with a scatter correction procedure (standard normal variate and detrend (SNV&D)) to reduce the effect of extraneous noise. The optimum calibrations were selected on the basis of minimizing the standard error of cross validation (SECV). The results of this study showed that NIRS predicted the chemical constituents with a high degree of accuracy (i.e. the correlation coefficient of cross validation ($R^2{_{cv}}$) ranged from 0.86~0.96), except for crude ash which had an $R^2{_{cv}}$ of 0.68. Comparison of the mathematical treatments for raw spectra showed that the second-order derivatization procedure produced the best result for all the treatments, except for neutral detergent fiber (NDF). The best mathematical treatment for moisture, acid detergent fiber (ADF), crude protein (CP) and pH was 2,16,16 respectively while the best mathematical treatment for crude ash, lactic acid and total acid was 2,8,8 respectively. The calibrations of fermentation products produced poorer calibrations (RPD < 2.5) with acetic and butyric acid. The pH, lactic acid and total acids were predicted with considerable accuracy at $R^2{_{cv}}$ 0.72~0.77. This study indicated that NIRS calibrations based on fresh coarse sorghum and sudangrass silage spectra have the capability of assessing the forage quality control

• Journal of The Korean Society of Grassland and Forage Science
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• v.37 no.2
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• pp.154-160
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• 2017

This study was conducted to find out an alternative way of rapid and accurate analysis of chemical composition of permanent pastures in hilly grazing area. Near reflectance infrared spectroscopy (NIRS) was used to evaluate the potential for predicting proximate analysis of permanent pastures in a vegetative stage. 386 pasture samples obtained from hilly grazing area in 2015 and 2016 were scanned for their visible-NIR spectra from 400~2,400nm. 163 samples with different spectral characteristics were selected and analysed for moisture, crude protein (CP), crude ash (CA), acid detergent fiber (ADF) and neutral detergent fiber (NDF). Multiple linear regression was used with wet analysis data and spectra for developing the calibration and validation mode1. Wavelength of 400 to 2500nm and near infrared range with different critical T outlier value 2.5 and 1.5 were used for developing the most suitable equation. The important index in this experiment was SEC and SEP. The $R^2$ value for moisture, CP, CA, CF, Ash, ADF, NDF in calibration set was 0.86, 0.94, 0.91, 0.88, 0.48 and 0.93, respectively. The value in validation set was 0.66, 0.86, 0.83, 0.71, 0.35 and 0.88, respectively. The results of this experiment indicate that NIRS is a reliable analytical method to assess forage quality for CP, CF, NDF except ADF and moisture in permanent pastures when proper samples incorporated into the equation development.

• Journal of The Korean Society of Grassland and Forage Science
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• v.37 no.4
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• pp.350-357
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• 2017

Near infrared spectroscopy (NIRS) is a rapid and accurate method for analyzing the quality of cereals, and dried animal forage. However, one limitation of this method is its inability to measure fermentation parameters in dried and ground samples because they are volatile, and therefore, respectively lost during the drying process. In order to overcome this limitation, in this study, fresh coarse haylage was used to test the potential of NIRS to accurately determine chemical composition and fermentation parameters. Fresh coarse Italian ryegrass haylage samples were scanned at 1 nm intervals over a wavelength range of 680 to 2500 nm, and optical data were recorded as log 1/reflectance. Spectral data, together with first- and second-order derivatives, were analyzed using partial least squares (PLS) multivariate regressions; scatter correction procedures (standard normal variate and detrend) were used in order to reduce the effect of extraneous noise. Optimum calibrations were selected based on their low standard error of cross validation (SECV) values. Further, ratio of performance deviation, obtained by dividing the standard deviation of reference values by SECV values, was used to evaluate the reliability of predictive models. Our results showed that the NIRS method can predict chemical constituents accurately (correlation coefficient of cross validation, $R_{cv}^2$, ranged from 0.76 to 0.97); the exception to this result was crude ash ($R_{cv}^2=0.49$ and RPD = 2.09). Comparison of mathematical treatments for raw spectra showed that second-order derivatives yielded better predictions than first-order derivatives. The best mathematical treatment for DM, ADF, and NDF, respectively was 2, 16, 16, whereas the best mathematical treatment for CP and crude ash, respectively was 2, 8, 8. The calibration models for fermentation parameters had low predictive accuracy for acetic, propionic, and butyric acids (RPD < 2.5). However, pH, and lactic and total acids were predicted with considerable accuracy ($R_{cv}^2$ 0.73 to 0.78; RPD values exceeded 2.5), and the best mathematical treatment for them was 1, 8, 8. Our findings show that, when fresh haylage is used, NIRS-based calibrations are reliable for the prediction of haylage characteristics, and therefore useful for the assessment of the forage quality.

• Journal of Korean Society for Geospatial Information Science
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• v.17 no.1
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• pp.21-35
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• 2009

KOMPSAT-2 is the seventh high-resolution image satellite in the world that provides both 1m-grade panchromatic images of the GSD and 4m-grade multispectral images of the GSD. It's anticipated to be used across many different areas including mapping, territory monitoring and environmental watch. However, due to the complexity and security concern involved with the use of the MSC, the use of KOMPSAT-2 images are limited in terms of geometric images, such as satellite orbits and detailed mapping information. Therefore, this study aims to produce DEM and orthoimage by using the stereo images of KOMPSAT-2, and to explore the applicability of geo-spatial information with KOMPSAT -2. Orientation interpretations were essential for the production of DEM and orthoimage using KOMPSAT-2 images. In the study, they are performed by utilizing both RPC and GCP. In this study, the orientation interpretations are followed by the generation of DEM and orthoimage, and the analysis of their accuracy based on a 1:5,000 digital map. The accuracy analysis of DEM is performed and the results indicate that their altitudes are, in general, higher than those obtained from the digital map. The altitude discrepancies on plains, hills and mountains are calculated as 1.8m, 7.2m, and 11.9m, respectively. In this study, the mean differences between horizontal position between the orthoimage data and the digital map data are found to be ${\pm}3.081m$, which is in the range of ${\pm}3.5m$, within the permitted limit of a 1:5,000 digital map. KOMPSAT-2 images are used to produce DEM and orthoimage in this research. The results suggest that DEM can be adequately used to produce digital maps under 1:5,000 scale.

• Korean Chemical Engineering Research
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• v.50 no.1
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• pp.106-111
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• 2012

Drying characteristic of high moisture coal using a 5 kg/hr bench scale flash dryer was investigated. Moisture content and heating value of raw coal as received basis were 29.74 wt% and 4,270 kcal/kg, respectively. Gas inlet temperature and gas inlet flow rate were $400{\sim}600^{\circ}C$ and 10~20 m/sec, respectively. The raw coal was ground and classified to the particle size range of $100{\sim}2,000{\mu}m$. The moisture removal rate of raw coal was dramatically increased with increasing gas inlet temperature and decreasing gas inlet flow rate. The heating value of dried coal was increased to 5,100~5,900 kcal/kg. To examine the chemical change on the surface of high moisture coal during flash drying process, FT-IR spectral analysis was carried out. As a result, major changes in hydroxyl, carboxyl and carbonyl peak was confirmed.

• Korean Journal of Optics and Photonics
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• v.8 no.6
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• pp.445-449
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• 1997

The complex refractive indices of $Ge_2Se_2Te_5$ which show reversible phase change between the crystalline phase and an amorphous one depending upon the annealing process have been determined in the spectral range of 0.7-4.5 eV. The $Ge_2Se_2Te_5$ films were DC sputter deposited on the crystalline silicon substrate. The spectro-ellipsometry data of a thick film were analyzed following the modelling procedure where the quantum mechanical dispersion relation were used for the complex refractive indices of both the cryastalline phase $Ge_2Se_2Te_5$ and and amorphous phase $Ge_2Se_2Te_5$, respectively. On the other hand, with the surface micro-roughness layer whose effective thickness was determined from AFM analysis, the spectro-ellipsometry data were numerically inverted to yield the complex refractive index of $Ge_2Se_2Te_5$ at each wavelength. With these set of complex refractive indices, the reflectance spectra were calculated and those spectra obtained from the numerical inversion showed better agreement with the experimental reflection spectra for both the cryastalline phase and an amorphous phase. Finally, the thin $Ge_2Se_2Te_5$ film which has the optimum thickness of 26 nm as the medium for optical recording was also analyzed and the quantitative result of the film thickness and the surface microroughness has been reported.