• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.60.3-61
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• 2020

We perform disk-halo decomposition of the Large Magellanic Cloud (LMC) using a novel HI velocity field extraction method, aimed at better deriving its HI kinematics and thus the dark matter density profile. For this, we use two newly developed galaxy kinematic analysis tools, BAYGAUD and 2DBAT which have been used for the kinematic analysis of resolved galaxies from Australian Square Kilometre Array (ASKAP) observations like WALLABY which is an all-sky HI galaxy survey in southern sky. By applying BAYGAUD to the combined HI data cube of the LMC taken with the Australia Telescope Compact Array (ATCA) and Parkes radio telescopes, we decompose all the line-of-sight velocity profiles into an optimal number of Gaussian components based on Bayesian MCMC techniques. From this, we disentangle turbulent non-circular gas motions from the overall rotation of the galaxy. We then derive the rotation curve of the LMC by applying 2DBAT to the separated circular motions. The rotation curve reflecting the total kinematics of the LMC, dark and baryonic matters is then be combined with the mass models of baryons, mainly stellar and gaseous components in order to examine the dark matter distribution. Here, we present the analysis of the extracted HI gas maps, rotation curve, and J, H and K-band surface photometry of the LMC.

• Journal of IKEEE
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• v.27 no.4
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• pp.411-417
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• 2023

Unmanned aerial vehicle (UAV)-assisted relay has the advantages of ease of deployment, good communication channels, and mobility over traditional terrestrial relay, which greatly improves wireless connectivity. In this paper, we design a UAV-enabled relay network that can utilize radio frequency bands to harvest energy from sources and utilize terahertz (THz) bands to transmit information between secondary transmitters and receivers. Next, we solve the optimal position of the UAV that maximizes the relay channel capacity, and propose an algorithm to design two trajectories of UAV (a straight and an elliptical trajectory) using the derived solution. Numerical results show that the straight trajectory is better in terms of harvested energy and channel capacity.

• ETRI Journal
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• v.46 no.3
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• pp.404-412
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• 2024

We propose a method for increasing the bandwidth of a substrate-integrated-waveguide (SIW) cavity-backed antenna with taper-based micro-strip SIW transition feeding. For radio transmission, a circular slot is etched on top of the SIW cavity. For optimal antenna design, the slot is etched slightly away from the cavity center to generate circularly polarized waves. Simulations show a wide axial ratio bandwidth of 7.860% between 11.02 GHz and 11.806 GHz. Experimental results confirm a similar wide axial ratio bandwidth of 4.9% between 10.8 GHz and 11.35 GHz. An SIW feed from an inductive window excites the radiating circular slot, resulting in a simulated wide impedance range of 1.548 GHz (10.338 GHz-11.886 GHz) and bandwidth of 13.93%. Experimental results show a wide impedance of 2.08 GHz (10.2 GHz-12.08 GHz) and bandwidth of 18.84%. The SIW cavity-backed antenna creates a unidirectional pattern, leading to gains of 6.61 dBi and 7.594 dBi in simulations and experiments, respectively. The proposed antenna was fabricated on a Rogers RT/Duroid 5880 substrate, and the reflection coefficient, radiation patterns, and gains were tested and compared using a computer simulator. The developed broadband antenna seems suitable for X-band applications.

• Journal of Surface Science and Engineering
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• v.57 no.3
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• pp.179-191
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• 2024

This study focuses on improving the photocatalytic degradation efficiency by synthesizing a TiO₂/WO₃ composite. Given the environmental significance of photocatalysis and the limitations posed by TiO₂'s large bandgap and high electron recombination rate, we explored doping, surface modification, and synthesis strategies. The composite was created using a ball mill process and heat treatment, analyzed with field emission scanning electron microscope, high resolution X-ray diffraction, Raman microscope, and UV-Vis/NIR spectrometer to examine its morphology, composition and absorbance. We found that incorporating WO₃ into the TiO₂ lattice forms a W_x-Ti_1-x-O₂ solution, with optimal WO₃ content reducing the band gap and enhancing sterilization efficiency by inhibiting the anatasese to rutile transition. This contributes to the field by offering a way to overcome TiO₂'s limitations and improve photocatalytic performance.

• Journal of the Korean Association of Geographic Information Studies
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• v.5 no.2
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• pp.16-24
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• 2002

Classification of the land cover characteristics is a major application of remote sensing. The goal of this study is to propose an optimal classification process for electro-optical camera(EOC) of Korea Multi-Purpose Satellite(KOMPSAT). The study was carried out on Landsat TM, high spectral resolution image and KOMPSAT EOC, high spatial resolution image of Miho river basin, Korea. The study was conducted in two stages: one was image fusion of TM and EOC to gain high spectral and spatial resolution image, the other was land cover classification on fused image. Four fusion techniques were applied and compared for its topographic interpretation such as IHS, HPF, CN and wavelet transform. The fused images were classified by radial basis function neural network(RBF-NN) and artificial neural network(ANN) classification model. The proposed RBF-NN was validated for the study area and the optimal model structure and parameter were respectively identified for different input band combinations. The results of the study propose an optimal classification process of KOMPSAT EOC to improve the thematic mapping and extraction of environmental information.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.5
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• pp.61-69
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• 2017

The study on interference channel is very important information theoretically and many studies have been done on it. However, even in the simplest case, even in the case of two user interfering channels, the channel capacity is not yet known except in special cases. Recently, research on the multiplexing gain that shows the tendency of the transmission rate in the high signal to noise ratio (SNR) band has been actively carried out, instead of accurately grasping the channel capacity. Obtaining optimal multiplexing gain can reveal trends in channel capacity at high signal-to-noise ratio bands. In an interfering channel with two users, the best multiplexing gain can be obtained by eliminating the interference. However, recent research shows that when the number of users is more than three, the optimal multiplexing gain can not be obtained only by zero forcing and a new technique called interference sorting is needed. There are two types of interference sorting techniques. Beamforming A method of effectively separating signals and interference by properly selecting matrices and constructing structured codes using rational numbers and irrational numbers. The interference alignment technique can achieve optimal multiplexing gain in various environments such as interference channel, X channel, compound broadcast channel, and multi hop network for multi source multi destination. In recent years, it has also been applied to distributed storage. Lee et al., "Lattice Code Interference Alignment in Cooperative Multipoint Transmission (COMP) for Interference Channels of Three Users", Journal of the Institute of Electronics Engineers, vol.49-TC,no.6,2012. In this paper, the DoF of delayed channel information is obtained.

• Korean Journal of Remote Sensing
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• v.33 no.5_1
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• pp.559-570
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• 2017

A partial least squares regression (PLSR) model was developed to map the internal soluble solids content (SSC) of apples using a ground-based hyperspectral scanner that could simultaneously acquire outdoor data and capture images of large quantities of apples. We evaluated the applicability of various preprocessing techniques to construct an optimal prediction model and calculated the optimal band through a variable importance in projection (VIP)score. From the 515 bands of hyperspectral images extracted at wavelengths of 360-1019 nm, 70 reflectance spectra of apples were extracted, and the SSC ($^{\circ}Brix$) was measured using a digital photometer. The optimal prediction model wasselected considering the root-mean-square error of cross-validation (RMSECV), root-mean-square error of prediction (RMSEP) and coefficient of determination of prediction $r_p^2$. As a result, multiplicative scatter correction (MSC)-based preprocessing methods were better than others. For example, when a combination of MSC and standard normal variate (SNV) was used, RMSECV and RMSEP were the lowest at 0.8551 and 0.8561 and $r_c^2$ and $r_p^2$ were the highest at 0.8533 and 0.6546; wavelength ranges of 360-380, 546-690, 760, 915, 931-939, 942, 953, 971, 978, 981, 988, and 992-1019 nm were most influential for SSC determination. The PLSR model with the spectral value of the corresponding region confirmed that the RMSEP decreased to 0.6841 and $r_p^2$ increased to 0.7795 as compared to the values of the entire wavelength band. In this study, we confirmed the feasibility of using a hyperspectral scanner image obtained from outdoors for the SSC measurement of apples. These results indicate that the application of field data and sensors could possibly expand in the future.

• Journal of Applied Biological Chemistry
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• v.60 no.1
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• pp.79-86
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• 2017

Microbes in forest are very important due to not only to enhance soil fertility but also maintain a healthy ecosystem by supplying the energy available to living organisms by producing various kinds of enzymes related to degradation of lignocellulosic biomass. In order to isolate a lignocellulosic biomass degrading bacterial strain from the Jurassic park located in Gyeongnam National University of Science and Technology, We used the Luria-Bertani-Carboxymethyl cellulose (CMC) agar trypan blue method containing 0.4 % carboxymethyl cellulose and 0.01 % trypan blue. As a result, we isolated a bacterial strain showing both activity on the CMC and xylan. To identify the isolated strain, 16S rRNA sequencing and API kit analysis were used. The isolated strain turned out to belong to Bacillus species and then named Bacillus sp. GJY. In the CMC zymogram analysis, it showed that one active band of about 28kDa in size is present. Xylan zymogram analysis also showed to have one active band of about 25kDa in size. The optimal growth temperature of Bacillus sp. GJY was $37^{\circ}C$. The maximal activities of CMCase and xylanase were 12 hour after incubation. The optimal pH and temperature for CMCase were 5.0 and $40^{\circ}C$, respectively, whereas the optimal pH and temperature for xylanase was 4.0 and $40^{\circ}C$. Both activities for CMCase and xylanase showed to be thermally stable at 40and $50^{\circ}C$, while both activities rapidly decreased at over $60^{\circ}C$.

• Journal of the Korean Association of Geographic Information Studies
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• v.21 no.1
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• pp.35-45
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• 2018

Image data collected by an airborne hyperspectral camera system have a great usability in coastal line mapping, detection of facilities composed of specific materials, detailed land use analysis, change monitoring and so forh in a complex coastal area because the system provides almost complete spectral and spatial information for each image pixel of tens to hundreds of spectral bands. A few approaches after classifying by a few approaches based on SAM(Spectral Angle Mapper) supervised classification were applied for extracting optimal land cover information from hyperspectral images acquired by CASI-1500 airborne hyperspectral camera on the object of a coastal area which includes both land and sea water areas. We applied three different approaches, that is to say firstly the classification approach of combined land and sea areas, secondly the reclassification approach after decompostion of land and sea areas from classification result of combined land and sea areas, and thirdly the land area-only classification approach using atmospheric correction images and compared classification results and accuracies. Land cover classification was conducted respectively by selecting not only four band images with the same wavelength range as IKONOS, QuickBird, KOMPSAT and GeoEye satelllite images but also eight band images with the same wavelength range as WorldView-2 from 48 band hyperspectral images and then compared with the classification result conducted with all of 48 band images. As a result, the reclassification approach after decompostion of land and sea areas from classification result of combined land and sea areas is more effective than classification approach of combined land and sea areas. It is showed the bigger the number of bands, the higher accuracy and reliability in the reclassification approach referred above. The results of higher spectral resolution showed asphalt or concrete roads was able to be classified more accurately.

• Korean Journal of Agricultural and Forest Meteorology
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• v.23 no.4
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• pp.316-328
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• 2021

In this study, the leaf Na content prediction model for spring potato was established using 400-1000 nm hyperspectral sensor to develop the multispectral sensor for the salinity monitoring in reclaimed land. The irrigation conditions were standard, drought, and salinity (2, 4, 8 dS/m), and the irrigation amount was calculated based on the amount of evaporation. The leaves' Na contents were measured 1st and 2nd weeks after starting irrigation in the vegetative, tuber formative, and tuber growing periods, respectively. The reflectance of the leaves was converted from 5 nm to 10 nm, 25 nm, and 50 nm of FWHM (full width at half maximum) based on the 10 nm wavelength intervals. Using the variance importance in projections of partial least square regression(PLSR-VIP), ten band ratios were selected as the variables to predict salinity damage levels with Na content of spring potato leaves. The MLR(Multiple linear regression) models were estimated by removing the band ratios one by one in the order of the lowest weight among the ten band ratios. The performance of models was compared by not only R2, MAPE but also the number of band ratios, optimal FWHM to develop the compact multispectral sensor. It was an advantage to use 25 nm of FWHM to predict the amount of Na in leaves for spring potatoes during the 1st and 2nd weeks vegetative and tuber formative periods and 2 weeks tuber growing periods. The selected bandpass filters were 15 bands and mainly in red and red-edge regions such as 430/440, 490/500, 500/510, 550/560, 570/580, 590/600, 640/650, 650/660, 670/680, 680/690, 690/700, 700/710, 710/720, 720/730, 730/740 nm.