• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.2
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• pp.207-213
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• 1997

Measurements of the RF(Radio Frequency) noise spectrum from 30 MHz to 18 GHz have been conducted at 21 urban areas in Korea in 1994 and 1995. Statistical analysis of the data measured seasonally, day and night, at each different point has been performed. The results of the computer analysis on APD, NAD, and ACR[1] using GUI(Graphical User Interface) program show that the radio noise environments vary little in spring, summer, and winter, while the noise level increases a little in fall. In addition, the noise level of the night time shows a little higher than that of the day time.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.51.3-51.3
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• 2019

Its ability to measure the polarization of light at four frequencies makes the KVN a "plasma physics observatory" that can probe the internal physics (e.g., magnetic fields, outflow geometries) of AGN radio jets and cores. We initiated a Key Science Program, the Plasma-physics of Active Galactic Nuclei (PAGaN) project, dedicated to polarimetric monitoring of 14 radio-bright AGN. We have been able to measure the Faraday rotation measure of the cores of our targets as function of frequency; the observed scaling relation is in good agreement with conically expanding outflows to first order. We are further probing a polarized hotspot in the jet of 3C84 and possible systematic differences in the Faraday rotation in BL Lacertae objects and flat spectrum radio quasars.

• Journal of The Korean Astronomical Society
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• v.38 no.2
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• pp.125-128
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• 2005

In this paper, we argue that the gigahertz peaked spectrum (GPS) quasars are special blazars, blazars in dense and dusty gas enviornment. The ROSAT detection rate of GPS quasars is similar to that of flat spectrum radio quasars (FSRQs), suggesting that the relativistic jets in GPS quasars are oriented at small angle to the line of sight. Due to strong inverse Compton scattering off infrared photons from dense and dusty nuclear interstellar media in GPS quasars, most of them may have significant soft gamma-ray and X-ray emission, which is consistent with ASCA X-ray observations. Because Compton cooling in GPS quasars is stronger than that in FSRQs, synchrotron emission in GPS quasars may less dominate over thermal emission of the accretion disk and hot dust, hence most GPS quasars show low optical polarization and small variability, consistent with observations. We suggest that it is the significant radio emission of electron/positron pairs produced by the interaction of gamma-rays with the dense gas and dust grains in GPS quasars that makes GPS quasars show steep radio spectra, low radio polarization, and relatively faint VLBI/VLBA cores. Whether GPS quasars are special blazars can be tested by gamma-ray observations with GLAST in the near future, with the detection rate of GPS quasars being similar to that of FSRQs.

• Journal of electromagnetic engineering and science
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• v.15 no.3
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• pp.181-184
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• 2015

Evaluation of radiating radiofrequency fields from hand-held and body-mounted wireless communication devices to human bodies are conducted by measuring the specific absorption rate (SAR). The uncertainty of system validation and probe calibration in SAR measurement depend on the variation of RF power used for the validation and calibration. RF input power for system validation or probe calibration is controlled manually during the test process of the existing systems in the laboratories. Consequently, a long time is required to reach the stable power needed for testing that will cause less uncertainty. The standard uncertainty due to this power drift is typically 2.89%, which can be obtained by applying IEC 62209 in a normal operating condition. The principle of the Automatic Input Power Level Control System (AIPLC), which controls the equipment by a program that maintains a stable input power level, is suggested in this paper. The power drift is reduced to less than ${\pm}1.16dB$ by AIPLC, which reduces the standard uncertainty of power drift to 0.67%.

• Journal of The Korean Astronomical Society
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• v.29 no.spc1
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• pp.395-396
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• 1996

We developed a telescope control system called ASTROS for the VST1 and VST2, which are specially designed radio telescopes to make a survey and have a 60-cm main dish. ASTROS is designed on the distributed intelligence concept and structurized programming. The hardware of the system is composed of several intelligent devices connected with de facto standard interfaces and main control unit is PC. The program is coded in the C language and its structure is object oriented in order to make easy to replace the component devices. ASTROS is now running on two twin telescopes, VST1 and VST2. VST1 is installed at Nobeyama in Japan and VST2 is installed at La Silla in Chile. They are making a galactic plane survey in CO (J=2-1) with 9 arcmin beam semi-automatically.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.35.3-36
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• 2020

The Time Domain Field is one of the future GTO program fields of JWST(JWST/GTO TDS), surveying about 14' diameter field at the North Eliptical Pole(NEP) with NIRCam/NIRISS. As a part of the multi-wavelength study of the field, we have obtained SCUBA-2 850㎛ mapping which reaches a depth of σrms = 0.9mJy/beam and detect 93 sources at S/N > 3.5 ― which are expected to be highly star-forming (SFR>400M◉/yr) galaxies at z ≳ 1.5-4 and pinpoint the location at <0. " 1 accuracy of 68 sub-mm sources by identifying VLA 3GHz radio counterparts. In this talk, we will introduce the SCUBA-2 JWST/GTO TDS project and the newly discovered sub-mm sources in this field.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.2
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• pp.380-385
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• 2006

In this paper, a program that can be utilized to measure and analyze radio propagation characteristics is developed. This program is able to control the measurement instruments including spectrum analyzer through GPIB interface and analyze the measured data to yield mean excess delay and RMS delay spread. The measured path loss can be compared with theoretical value in free space or inside a tunnel. The measured and analyzed results can also be presented in the forms of graphs. As these tasks can be conducted on the spot of the measurements, this program is very helpful in performing and verifying the measurements immediately. In this thesis radio propagation characteristics with frequency bands of 2.45 and 5.8GHz in subway tunnels are measured by using the program. Path loss and delay spread in subway tunnel is measured and compared according to the form of antenna beam and LOS(Line of Sight) and N-LOS(Non-Line of Sight).

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2007.04a
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• pp.175-181
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• 2007

• Journal of The Korean Astronomical Society
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• v.47 no.5
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• pp.179-185
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• 2014

We study the physical and chemical properties of the molecular clump hosting a young stellar cluster, IRAS 20160+3636, which is believed to have formed via the "collect and collapse" process. Physical parameters of the UC H II region associated with the embedded cluster are measured from the radio continuum observations. This source is found to be a typical Galactic UC H II region, with a B0.5 type exciting star, if it is ionized by a single star. We derive a CN/HCN abundance ratio larger than 1 over this region, which may suggest that this clump is being affected by the UV radiation from the H II region.

• Journal of Astronomy and Space Sciences
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• v.21 no.2
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• pp.121-128
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• 2004

As the first step of the real time monitoring system of the solar radio disturbance, we constructed the control system of the solar radio telescope. An 1.8m antenna built by Korean Astronomy Observatory has been used, and the observed radio flux is transformed to the digital signal by the powermeter. We have also developed a computer program CBNUART in order to control the telescope system and the powermeter. As the sun rises, the telescope begins to observe the sun, and ends the observation automatically at sunset. The CBNUART enables the telescope automatically to go to the position of the sunrise for the beginning the observation and come back to the setposition after the ending the observation at the sunset. An active tracking routine is adopted in order to improve the tracking accuracy of the control system, and we used an optical telescope equipped in front of the antenna for control test. The tracking test shows that our control system can track with the accuracy of arc seconds, and the 50 minute pointing test shows that the pointing accuracy of right ascension and declination are 1.12 and 0.08 arc minutes respectively.