• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.1
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• pp.73-84
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• 2014

The present paper includes recent research works on the estimation of physical properties like equivalence ratio and heat release rate of flame through chemiluminescence measurement. Modern combustion devices require a precise control to increase combustion stability as well as to suppress pollutant emissions. The determination of combustion characteristics from chemiluminescence provides practical advantages over other techniques. However, the technique is dependent on equivalence ratio, combustion pressure, inlet temperature, turbulent intensity and fuel type. The intensity ratio of $OH^*$ and $CH^*$ has a strong relation with an equivalence ratio for methane/air premixed flames. The global measurement of chemiluminescence is accepted as a good indicator for a global heat release rate.

• Journal of Korean Society for Atmospheric Environment
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• v.34 no.3
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• pp.493-507
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• 2018

Due to high spatio-temporal variability of amount and optical/microphysical properties of atmospheric aerosols, satellite-based observations have been demanded for spatiotemporal monitoring the major aerosols. Observations of the heavy aerosol episodes and determination on the dominant aerosol types from a geostationary satellite can provide a chance to prepare in advance for harmful aerosol episodes as it can repeatedly monitor the temporal evolution. A new geostationary observation sensor, namely the Advanced Himawari Imager (AHI), onboard the Himawari-8 platform, has been observing high spatial and temporal images at sixteen wavelengths from 2016. Using observed spectral visible reflectance and infrared brightness temperature (BT), the algorithm to find major aerosol type such as volcanic ash (VA), desert dust (DD), polluted aerosol (PA), and clean aerosol (CA), was developed. RGB color composite image shows dusty, hazy, and cloudy area then it can be applied for comparing aerosol detection product (ADP). The CALIPSO level 2 vertical feature mask (VFM) data and MODIS level 2 aerosol product are used to be compared with the Himawari-8/AHI ADP. The VFM products can deliver nearly coincident dataset, but not many match-ups can be returned due to presence of clouds and very narrow swath. From the case study, the percent correct (PC) values acquired from this comparisons are 0.76 for DD, 0.99 for PA, 0.87 for CA, respectively. The MODIS L2 Aerosol products can deliver nearly coincident dataset with many collocated locations over ocean and land. Increased accuracy values were acquired in Asian region as POD=0.96 over land and 0.69 over ocean, which were comparable to full disc region as POD=0.93 over land and 0.48 over ocean. The Himawari-8/AHI ADP algorithm is going to be improved continuously as well as the validation efforts will be processed by comparing the larger number of collocation data with another satellite or ground based observation data.

• Journal of Sensor Science and Technology
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• v.15 no.6
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• pp.397-405
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• 2006

Single crystal $AgGaSe_{2}$ layers were grown on thoroughly etched semi-insulating GaAs(100) substrate at $420^{\circ}C$ with hot wall epitaxy (HWE) system by evaporating $AgGaSe_{2}$ source at $630^{\circ}C$. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of single crystal $AgGaSe_{2}$ thin films measured with Hall effect by van der Pauw method are $4.05{\times}10^{16}/cm^{3}$, $139cm^{2}/V{\cdot}s$ at 293 K, respectively. The temperature dependence of the energy band gap of the $AgGaSe_{2}$ obtained from the absorption spectra was well described by the Varshni's relation, $E_{g}(T)$=1.9501 eV-($8.79{\times}10^{-4}{\;}eV/K)T^{2}$/(T+250 K). The crystal field and the spin-orbit splitting energies for the valence band of the $AgGaSe_{2}$ have been estimated to be 0.3132 eV and 0.3725 eV at 10 K, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the ${\Delta}So$ definitely exists in the ${\Gamma}_{5}$ states of the valence band of the $AgGaSe_{2}$. The three photocurrent peaks observed at 10 K are ascribed to the $A_{1}-$, $B_{1}-$, and $C_{1}-$exciton peaks for n=1.

• Proceedings of the National Institute of Ecology of the Republic of Korea
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• v.1 no.1
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• pp.31-40
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• 2020

The rapid development of technologies in unmanned aerial vehicles (UAVs) has led to their use in various areas. UAVs are mainly used for commercial purposes, but their utilization is increasingly important in other areas because their operation cost is less than satellites and aerial imaging. The utilization of UAVs in the environment/ecology area is relatively new. Therefore, identifying the trends of UAV-related spatial information is significant in basic research for UAV utilization. This study quantitatively identified domestic and international research trends related to UAV utilization and analyzed research areas. An attempt was also made to identify upcoming UAV-related topics in the environment/ecology research field using text mining to analyze the bibliographic information of global research literature. Domestic UAV-related studies were classified into seven clusters where basic research on "UAV technology/industry trends" was abundant, and studies on data collection and analysis through UAV remote sensing technology have increased since 2015. Eight clusters were identified for international studies where the most active research area international was "remote sensing technology/data analysis". In addition, Canopy, Classification, Forest, Leaf Area Index, Normalized Difference Vegetation Index, Temperature, Tree, and Atmosphere appeared as the main keywords related to environment and ecology. The appearance frequencies and association strengths were high because the advancement in UAV optical sensor technology and the rapid development of image processing technology enabled the acquisition of data that could not be obtained from existing spatial information. They are recognized as future research topics as related domestic studies have begun corresponding to international research.

• Journal of Sensor Science and Technology
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• v.17 no.6
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• pp.437-446
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• 2008

Single crystalline ${ZnIn_2}{Se_4}$ layers were grown on thoroughly etched semi-insulating GaAs (100) substrate at $400^{\circ}C$ with hot wall epitaxy (HWE) system by evaporating ${ZnIn_2}{Se_4}$ source at $630^{\circ}C$. The crystalline structure of the single crystalline thick films was investigated by the photoluminescence (PL) and Double crystalline X-ray rocking curve (DCRC). The carrier density and mobility of ${ZnIn_2}{Se_4}$ single crystalline thick films measured from Hall effect by van der Pauw method are $9.41{\times}10^{16}cm^{-3}$ and $292cm^2/V{\cdot}s$ at 293 K, respectively. The temperature dependence of the energy band gap of the ${ZnIn_2}{Se_4}$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)$=1.8622 eV-$(5.23{\times}10^{-4}eV/K)T^2$/(T+775.5 K). After the as-grown ${ZnIn_2}{Se_4}$ single crystalline thick films was annealed in Zn-, Se-, and In-atmospheres, the origin of point defects of ${ZnIn_2}{Se_4}$ single crystalline thick films has been investigated by the photoluminescence (PL) at 10 K. The native defects of $V_{Zn}$, $V_{Se}$, $Zn_{int}$, and $Se_{int}$ obtained by PL measurements were classified as a donors or acceptors type. And we concluded that the heat-treatment in the Se-atmosphere converted ${ZnIn_2}{Se_4}$ single crystalline thick films to an optical p-type. Also, we confirmed that In in ${ZnIn_2}{Se_4}$/GaAs did not form the native defects because In in ${ZnIn_2}{Se_4}$ single crystalline thick films existed in the form of stable bonds.

• Journal of Biomedical Engineering Research
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• v.40 no.6
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• pp.250-259
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• 2019

Ophthalmic Laser System is widely used in Selective Laser Trabeculoplasty of Open Angle Glaucoma and Ocular Hypertension. Versatile ophthalmic laser system is a medical device with technology that checks the condition of the treatment area by irradiating a continuous laser pulse on the treatment area, and monitoring the microbubble reaction caused by the temperature increase of the melanosome through the ultrasonic signal and the optical signal sensor. It performs selective laser treatment without damaging the photoreceptor by controlling the wavelength of the laser when microbubbles are detected. This study aims to suggest a guideline for evaluating safety, performance and clinical effectiveness of Versatile Ophthalmic Laser System in accordance with the growing technology. International Standards, Regulations, and Clinical Trial Protocols were investigated and analyzed for this study. As a result of this study, the safety, performance and clinical effectiveness test guideline for Versatile Ophthalmic Laser System were proposed. This guideline will ensure the safety and efficacy of Medical device, and furthermore it is expected to be able to promote the development of technology development by supporting a clinical trial plan.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.1
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• pp.6-12
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• 2010

Fiber optic sensor using fiber Bragg grating(FBG) probes is used for monitoring strain and temperature distributed on the wide surfaces of large structures. In this paper, in order to use many FBG probes in one optical fiber line, we propose a complex multiplexing technology which is composed of two techniques, one is time division multiplexing and another is wavelength division multiplexing. However, we only investigate the characteristics of time division multiplexing because FBG sensors basically can be operated by wavelength division multiplexing. We calculate the optimal reflectivities and the lengthwise location of five FBG probes in serial connection in order to obtain the unique reflected intensities from the FBG probes. We fabricate five FBG probes with the reflectivities of 13%, 16%, 25%, 40% and 80%, which are determined by the theoretical calculation, and observe the signal reflected from each FBG in the time domain from the experiment. There are differences between experimental and theoretical results caused by the signal noise and the differences of reflectivities of FBG probes. But the experimental results shows the reflected signals of five FBG probes which prove the availability of complex multiplexing.

• Composites Research
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• v.36 no.3
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• pp.186-192
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• 2023

Recently, in the field of railway vehicles, interest in the use of composite materials for weight reduction and transportation efficiency is increasing. Accordingly, research and commercialization development to apply composite materials to various vehicle parts are being actively conducted, and evaluation is conducted centering on post-measurement such as mechanical performance evaluation of finished products to verify quality when composite materials are applied. However, the analysis of heat and stress generated during the molding process of composite materials, which are factors that greatly affect manufacturing quality, is insufficient. Therefore, in this study, in order to verify the molding quality of composite parts for railway vehicles, the molding quality analysis was conducted for the two types of composite interior panels (laminate panel and sandwich panel) that are most actively used. To this end, temperature and strain changes were monitored during the molding process by using an FBG fiber optic sensor, which is easy to apply to the inside of the composite, and the residual strain value generated after molding was completed was measured. As a result, it was confirmed that overheating and excessive residual stress did not occur, thereby verifying the excellent molding quality of the composite interior panel for railway vehicles.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.102-102
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• 2014

The NISS (Near-infrared Imaging Spectrometer for Star formation history) onboard NEXTSat-1 is the near-infrared instrument onboard NEXTSat-1 which is being developed by KASI. The main scientific targets are nearby galaxies, galaxy clusters, star-forming regions and low background regions in order to study the cosmic star formation history in local and distant universe. After the Preliminary Design Review, we have fixed major specifications of the NISS. The off-axis optical design with 15cm apertureis optimized to obtain a wide field of view ($2deg.{\times}2deg.$), while minimizing the sensitivity loss. The opto-mechanical structure of the NISS was designed to be safe enough to endure in the launching condition as well as the space environment. The tolerance analysis was performed to cover the wide wavelength range from 0.95 to $3.8{\mu}m$ and to reduce the degradation of optical performance due to thermal variation at the target temperature, 200K. The $1k{\times}1k$ infrared sensor is operated in the dewar at 80K stage. We confirmed that the NISS can be cooled down to below 200K in the nominal orbit through a radiative cooling. Here, we report the preliminary design of the NISS.

• Korean Journal of Remote Sensing
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• v.40 no.4
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• pp.319-341
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• 2024

The utilization of multispectral imaging systems (MIS) in remote sensing has become crucial for large-scale agricultural operations, particularly for diagnosing plant health, monitoring crop growth, and estimating plant phenotypic traits through vegetation indices (VIs). However, environmental factors can significantly affect the accuracy of multispectral reflectance data, leading to potential errors in VIs and crop status assessments. This paper reviewed the complex interactions between environmental conditions and multispectral sensors emphasizing the importance of accounting for these factors to enhance the reliability of reflectance data in agricultural applications.An overview of the fundamentals of multispectral sensors and the operational principles behind vegetation index (VI) computation was reviewed. The review highlights the impact of environmental conditions, particularly solar zenith angle (SZA), on reflectance data quality. Higher SZA values increase cloud optical thickness and droplet concentration by 40-70%, affecting reflectance in the red (-0.01 to 0.02) and near-infrared (NIR) bands (-0.03 to 0.06), crucial for VI accuracy. An SZA of 45° is optimal for data collection, while atmospheric conditions, such as water vapor and aerosols, greatly influence reflectance data, affecting forest biomass estimates and agricultural assessments. During the COVID-19 lockdown,reduced atmospheric interference improved the accuracy of satellite image reflectance consistency. The NIR/Red edge ratio and water index emerged as the most stable indices, providing consistent measurements across different lighting conditions. Additionally, a simulated environment demonstrated that MIS surface reflectance can vary 10-20% with changes in aerosol optical thickness, 15-30% with water vapor levels, and up to 25% in NIR reflectance due to high wind speeds. Seasonal factors like temperature and humidity can cause up to a 15% change, highlighting the complexity of environmental impacts on remote sensing data. This review indicated the importance of precisely managing environmental factors to maintain the integrity of VIs calculations. Explaining the relationship between environmental variables and multispectral sensors offers valuable insights for optimizing the accuracy and reliability of remote sensing data in various agricultural applications.