• Journal of Astronomy and Space Sciences
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• v.17 no.1
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• pp.77-86
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• 2000

There have been a few attempts to measure diffuse line emission between 900 $\AA$ and 1200 $\AA$, and only in a limited number of sight lines has it been detected. The main contributions to the equilibrium radiative cooling curve between $10^{4.5}K\;to\;10^6K$ are from the doublet of Ovi ${lambda}{lambda}1032;and;{lambda}{lambda}1038$ in the FUV spectral region. There are several bright airglow lines which could interfere with attempts to observe the OVI lines. The nearest lines HI 1025 $\AA$, OI 1027 $\AA$ have a combined intensity of about $10^{5.5}$ photons/s/$cm^2$/sr. In the present study, the detectability simulation of OVI doublet is performed using a Monte-Carlo technique and chi-square statistics. The analysis results are compared with the previous observations and with the predictions of several interstellar medium models, and are used to limit manufacturing and alignment errors of FIMS optical system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.9
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• pp.3194-3210
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• 2022

Wall obstruction is the main factor leading to the non-line of sight (NLoS) error of indoor localization based on received signal strength indicator (RSSI). Modeling and correcting the path loss of the signals through the wall will improve the accuracy of RSSI localization. Based on electromagnetic wave propagation theory, the reflection and transmission process of wireless signals propagation through the wall is analyzed. The path loss of signals through wall is deduced based on power loss and RSSI definition, and the theoretical model of path loss of signals through wall is proposed. In view of electromagnetic characteristic parameters of the theoretical model usually cannot be accurately obtained, the statistical model of NLoS error caused by the signals through the wall is presented based on the log-distance path loss model to solve the parameters. Combining the statistical model and theoretical model, a hybrid model of path loss of signals through wall is proposed. Based on the empirical values of electromagnetic characteristic parameters of the concrete wall, the effect of each electromagnetic characteristic parameters on path loss is analyzed, and the theoretical model of regional path loss of signals through the wall is established. The statistical model and hybrid model of regional path loss of signals through wall are established by RSSI observation experiments, respectively. The hybrid model can solve the problem of path loss when the material of wall is unknown. The results show that the hybrid model can better express the actual trend of the regional path loss and maintain the pass loss continuity of adjacent areas. The validity of the hybrid model is verified by inverse computation of the RSSI of the extended region, and the calculated RSSI is basically consistent with the measured RSSI. The hybrid model can be used to forecast regional path loss of signals through the wall.

• Journal of Aerospace System Engineering
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• v.9 no.2
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• pp.25-33
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• 2015

Global market of unmanned aircraft(UA) is rapidly expending based on the versatile and efficient utility of the UA. Domestically many industries, universities and research institutes are trying to do research and development of the UA in various angle of aspect. In spite of these effort, all the participants of research and development of the UA has been suffering the difficulty of acquiring the airspace around vicinity of Goheung airfield for the flight test of UA. Although the current procedure of execution of the flight test of UA is set after acquiring the airspace by applying the NOTAM(Notice To Air Man) to the Ministry of Land, Infrastructure and Transport(MLIT) at least 7 days before the flight test and commencing with the publication of the NOTAM by MLIT, if the flight test is carried out as planned, changing or reapplying the NOTAM expends mort time and makes difficulty often. Therefore it is needed that a restricted airspace for the flight test of UA is established and make all the executioner of flight test uses the exclusive airspace without limitation. This research proposes the restricted airspace with short term and long term establish requirement of airspace separately. The short term requirement has been established with the airspace of 10 nm radius and 8,000 ft altitude in which the requirements of flight test can be carried out more than 90% without needs of supplement of the additional airspace. The long term has been established within the airspace of 30 nm radius which is the maximum Radio Line Of Sight(RLOS) and 8,000 ft altitude with exclusion of current air way, airport control area, approaching corridor to the airport, existing restricted area(RA) and Military Operating Area(MOA) for the purpose of minimizing inconvenience of the other airspace user. Once establishing the exclusive airspace for the flight test of UA, research and development of industries, universities and research institutes will be more vigorous and contributes to the national economy.

• Korean Journal of Agricultural Science
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• v.2 no.1
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• pp.265-279
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• 1975

This study was conducted to investigate the development of Gab river-basin which was a part of the farm land enlargement to contribute to the increased production of food. The results were as follows; 1. Gab river has the upper stream which occupy 50 percent in moumtains and the mid-stream in the Daejeon city area, and the downstream in a field which is about 22.9 percent in which farming area per household is 0.82 ha., agricultural population is 76 percent except of Daejeon city. Also, urban enlargement of mid-stream basin and development of industrial area in the lower stream diminish farm land. Consequently, this area should be developed to farm land to increase farming size. 2. There is no possibility to develop farm land in mountains of which (64.9 percent) is forests and in midstream which was constructed river-improvement. But Weonjeong area and Yongcheon area will be effective area. 3. If river banks of Weonjeong area will make straight with cost of construction 195,000,000 won, bank length 6 km will be useless, water will flow smoothly, flood will be prevented, farm land will develop 21.66 ha in which rice will produce annually 81.698 M/T which is about 10,860,000 won. 4. This area has good conditions of development. that is, investment efficiency (B/C) is 1.47 more than 1.00. 5. This area is a multiple purpose development district. The reasons are that there are beautiful mountains and a reservoir to be expected to construct, so it will be a sight seeing district in the vicinity of Daejeon city. 6. If Honam railway double line and river straight construction had executed simultaneously, cost of construction 50,000,000 won would have saved.

• The Journal of the Korea Contents Association
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• v.12 no.7
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• pp.40-53
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• 2012

In the past, the elements that determine the movie performance were directors, movie stars, the number of opening screens, on-line ratings or distributing agencies. However, the word-of-mouth effect has changed this trends. So the influence of word of mouth grows more and more strong at this stage of the Internet and smart phones being widely prevalent. I fix my sight upon SNS which is one of the medium of arousing the word-of-mouth effect, and I have a purpose to cast light upon a real example of the influence of SNS on the movie performance. The way is to analyze SNS activities that accompany the process of production and showing of , which is said to have had an beneficial effect of SNS among the enormously successful movies last year. It is relevant to provide a new milestone regarding the movie performance through the successful case of SNS activities by examining the word-of-mouth activities through SNS in the manner of the period division of the pre-release, the early stage of release and the maturity.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.70.2-71
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• 2021

We examine gas kinematics and star formation activities of NGC 6822, a gas-rich dwarf irregular galaxy in the Local Group at a distance of ~490 kpc. We perform profile decomposition of all the line-of-sight (LOS) HI velocity profiles of the high-resolution (42.4" × 12" spatial; 1.6 km/s spectral) HI data cube of the galaxy, taken with the Australian Telescope Compact Array (ATCA). To this end, we use a novel tool based on Bayesian Markov Chain Monte Carlo (MCMC) techniques, the so-called BAYGAUD, which allows us to decompose a velocity profile into an optimal number of Gaussian components in a quantitative manner. We group all the decomposed components into bulk-narrow, bulk-broad, and non-bulk gas components classified with respect to their velocity dispersions and the amounts of velocity offset from the global kinematics, respectively. Using the surface densities and velocity dispersions of the kinematically decomposed HI gas maps together with the rotation curve of NGC 6822, we derive Toomre-Q parameters for individual regions of the galaxy which quantify the level of local gravitational instability of the gaseous disk. We also measure the local star formation rate (SFR) of the corresponding regions in the galaxy by combining GALEX Far-ultraviolet (FUV) and WISE 22㎛ images. We then relate the gas and SFR surface densities in order to investigate the local Kennicutt-Schmidt (K-S) law of gravitationally unstable regions which are selected from the Toomre Q analysis. Of the three groups, the bulk-narrow, bulk-broad and non-bulk gas components, we find that the lower Toomre-Q values the bulk-narrow gas components have, the more consistent with the linear extension of the K-S law derived from molecular hydrogen (H2) observations.

• Journal of The Korean Astronomical Society
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• v.48 no.5
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• pp.299-311
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• 2015

We report first results from KVN and VERA Array (KaVA) VLBI observations obtained in the frame of our Plasma-physics of Active Galactic Nuclei (PAGaN) project. We observed eight selected AGN at 22 and 43 GHz in single polarization (LCP) between March 2014 and April 2015. Each source was observed for 6 to 8 hours per observing run to maximize the uv coverage. We obtained a total of 15 deep high-resolution images permitting the identification of individual circular Gaussian jet components and three spectral index maps of BL Lac, 3C 111 and 3C 345 from simultaneous dual-frequency observations. The spectral index maps show trends in agreement with general expectations – flat core and steep jets – while the actual value of the spectral index for jets shows indications for a dependence on AGN type. We analyzed the kinematics of jet components of BL Lac and 3C 111, detecting superluminal proper motions with maximum apparent speeds of about 5c. This constrains the lower limits of the intrinsic component velocities to ~ 0.98c and the upper limits of the angle between jet and line of sight to ~20°. In agreement with global jet expansion, jet components show systematically larger diameters d at larger core distances r, following the global relation d ≈ 0.2r, albeit within substantial scatter.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.70.1-70.1
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• 2021

We examine the HI gas kinematics and distributions of galaxy pairs in group or cluster environments from high-resolution Australian Square Kilometer Array Pathfinder (ASKAP) WALLABY pilot observations. We use 32 well-resolved close pair galaxies from the Hydra, Norma, and NGC 4636, two clusters and a group of which are identified by their spectroscopy information and additional visual inspection. We perform profile decomposition of HI velocity profiles of the galaxies using a new tool, BAYGAUD which allows us to separate a line-of-sight velocity profile into an optimal number of Gaussian components based on Bayesian MCMC techniques. Then, we construct super profiles via stacking of individual HI velocity profiles after aligning their central velocities. We fit a model which consists of double Gaussian components to the super profiles, and classify them as kinematically cold and warm HI gas components with respect to their velocity dispersions, narrower or wider 𝜎, respectively. The kinematically cold HI gas reservoir (M_cold/M_HI) of the paired galaxies is found to be relatively higher than that of unpaired control samples in the clusters and the group, showing a positive correlation with the HI mass in general. Additionally, we quantify the gravitational instability of the HI gas disk of the sample galaxies using their Toomre Q parameters and HI morphological disturbances. While no significant difference is found for the Q parameter values between the paired and unpaired galaxies, the paired galaxies tend to have larger HI asymmetry values which are derived using their moment0 map compared to those of the non-paired control sample galaxies in the distribution.

• Journal of The Korean Astronomical Society
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• v.48 no.5
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• pp.285-298
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• 2015

Active Galactic Nuclei (AGN) with bright radio jets offer the opportunity to study the structure of and physical conditions in relativistic outflows. For such studies, multi-frequency polarimetric very long baseline interferometric (VLBI) observations are important as they directly probe particle densities, magnetic field geometries, and several other parameters. We present results from first-epoch data obtained by the Korean VLBI Network (KVN) within the frame of the Plasma Physics of Active Galactic Nuclei (PAGaN) project. We observed seven radio-bright nearby AGN at frequencies of 22, 43, 86, and 129 GHz in dual polarization mode. Our observations constrain apparent brightness temperatures of jet components and radio cores in our sample to > 10^8.01 K and > 10^9.86 K, respectively. Degrees of linear polarization m_L are relatively low overall: less than 10%. This indicates suppression of polarization by strong turbulence in the jets. We found an exceptionally high degree of polarization in a jet component of BL Lac at 43 GHz, with m_L ~ 40%. Assuming a transverse shock front propagating downstream along the jet, the shock front being almost parallel to the line of sight can explain the high degree of polarization.

• Korean Journal of Remote Sensing
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• v.35 no.1
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• pp.29-37
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• 2019

Synthetic Aperture Radar (SAR) observations are powerful tools to monitor surface's displacement very accurately, induced by earthquake, volcano, ground subsidence, glacier movement, etc. Especially, radar interferometry (InSAR) which utilizes phase information related to distance from sensor to target, can generate displacement map in line-of-sight direction with accuracy of a few cm or mm. Due to decorrelation effect, however, degradation of coherence in the InSAR application often prohibit from construction of differential interferogram. Offset tracking method is an alternative approach to make a two-dimensional displacement map using intensity information instead of the phase. However, there is limitation in that the offset tracking requires very intensive computation power and time. In this paper, efficiency of parallel computing has been investigated using high performance computer for estimation of glacier velocity. Two TanDEM-X SAR observations which were acquired on September 15, 2013 and September 26, 2013 over the Narsap Sermia in Southwestern Greenland were collected. Atotal of 56 of 2.4 GHz Intel Xeon processors(28 physical processors with hyperthreading) by operating with linux environment were utilized. The Gamma software was used for application of offset tracking by adjustment of the number of processors for the OpenMP parallel computing. The processing times of the offset tracking at the 256 by 256 pixels of window patch size at single and 56 cores are; 26,344 sec and 2,055 sec, respectively. It is impressive that the processing time could be reduced significantly about thirteen times (12.81) at the 56 cores usage. However, the parallel computing using all the processors prevent other background operations or functions. Except the offset tracking processing, optimum number of processors need to be evaluated for computing efficiency.