• Journal of Positioning, Navigation, and Timing
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• v.10 no.4
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• pp.315-333
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• 2021

Due to the Global Navigation Satellite System (GNSS) modernization, recently launched GNSS satellites transmit signals at various frequency bands such as L1, L2 and L5. Considering the Korean Positioning System (KPS) signal and other GNSS augmentation signals in the future, there is a high probability of applying more complex communication techniques to the new GNSS signals. For the reason, GNSS receivers based on flexible Software Defined Radio (SDR) concept needs to be developed to evaluate various experimental communication techniques by accessing each signal processing module in detail. This paper proposes a novel SDR-based A-GNSS receiver capable of processing multi-GNSS/RNSS signals at multi-frequency bands. Due to the modular structure, the proposed receiver has high flexibility and expandability. For real-time implementation, A-GNSS server software is designed to provide immediate delivery of satellite ephemeris data on demand. Due to the sampling bandwidth limitation of RF front-ends, multiple SDRs are considered to process the multi-GNSS/RNSS multi-frequency signals simultaneously. To avoid the overflow problem of sampled RF data, an efficient memory buffer management strategy was considered. To collect and process the multi-GNSS/RNSS multi-frequency signals in real-time, the proposed SDR A-GNSS receiver utilizes multiple threads implemented on a CPU and multiple NVIDIA CUDA GPGPUs for parallel processing. To evaluate the performance of the proposed SDR A-GNSS receiver, several experiments were performed with field collected data. By the experiments, it was shown that A-GNSS requirements can be satisfied sufficiently utilizing only milliseconds samples. The continuous signal tracking performance was also confirmed with the hundreds of milliseconds data for multi-GNSS/RNSS multi-frequency signals and with the ten-seconds data for multi-GNSS/RNSS single-frequency signals.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.3
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• pp.340-347
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• 2004

Ultra-small size, high-performance, solenoid-type RF chip inductors utilizing low-loss A1$_2$O$_3$ core materials were investigated. The dimensions of the RF chip inductors fabricated were 1.0mm${\times}$0.5mm${\times}$0.5mm and copper coils were used. The materials (96％ A1$_2$O$_3$) and shape (I-type) of the core, the diameters (40${\mu}{\textrm}{m}$) and position (middle) of the coil, and the lengths (0.35mm) of solenoid were determined by a high-frequency structure simulator (HFSS) to maximize the performance of the inductors. The high-frequency characteristics of the inductance (L) and quality-factor (Q) of the developed inductors were measured using a RF impedance/material analyzer (E4991A with E16197A test fixture). The developed inductors exhibit an inductance of 11 to 11.3nH and a qualify factor of 22.3 to 65.7 over the frequency ranges of 250 MHz to 1.7 GHz, and show results comparable to those measured for the inductors prepared by Coilcraft$^{TM}$. The simulated data described the high-frequency data of the L and Q of the fabricated inductors well.

• Journal of the Korean Geographical Society
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• v.46 no.1
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• pp.36-49
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• 2011

This paper aims to investigate the frequency and intensity variations of Okhotsk high pressure system focused on the Korean Peninsula. Weather chart (00UTC), daily weather data and reanalysis data were used. The first occurrence date of Okhotsk high pressure system tends to be earlier in those years that surrounding land air temperature in April is high. The frequency of Okhotsk high has recently decreased, and its intensity tends to be stronger when the difference between sea surface temperature and surrounding land air temperature is big. The frequency of Okhotsk high in April, May, June and July increases when surrounding land air temperature is high, and its intensity grows when the difference between surrounding land air temperature and sea surface temperature is big. The frequency of Okhotsk high may increase and its intensity may increase when the first occurrence date comes earlier. In June, however, the reverse may apply.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.1454-1462
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• 2008

This paper is focused on the analysis of the noise and vibration measured near the wheelset of the high-speed trains using a time-varying frequency transform as a preliminary research of running monitoring. Due to the non-stationary characteristics, it is necessary to examine noise and vibration of the train with time-varying frequency transforms. In this paper, the short-time Fourier transform method is utilized - the stored data is localized by modulating with a window function, and Fourier transform is taken to each localized data. For the examination, the non-stationary noise and vibration of the high-speed train's wheelset are measured by using some microphones and accelerometers, and those signals are stored in a on-board data acquisition system. The non-stationary random signal analyses with the short-time Fourier transform are performed, and the result are classified as follows; auto-spectral density, cross-spectral density, frequency response, and coherence functions. From those functions, it is possible to observe the frequency characteristics of sleepers, switchers, tunnels, and steel bridges. Also, some distinct peaks, which are not dependent upon the train's speed, are identified from the results.

• Korean Institute of Interior Design Journal
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• v.22 no.5
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• pp.152-161
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• 2013

This study is about the visual appreciation by sex with the analysis of time range of observing data which was got through observation experiment with the space of lobby in hospitals. The observation data of the subjects who observed the space include the frequency and time, through which the process of visual appreciation could be evaluated with the definition of the frequency and the time of observation. First, the fact that men had higher frequency of observation than women means the former had more movement than the latter, and another fact of their fewer times can be understood as the time of their staying was shorter. That is, even though the men had more movements of sight, they showed the feature of staying shorter. Second, the rate high and low of observation frequency and times made it possible for observation characteristics to be defined as 'intensive search' 'active search' 'fixed concentration' and 'search wandering.' The definition of understanding this process of visual appreciation can be available for a frame of effective analysis of observation characteristics according to the passage of time. Third, the intense search is the case of 'high frequency' having the feature of high visual appreciation owing to the active visual actions for acquiring information. Men were found to have more intense search which decreased gradually as time passed, while women showed the feature of many times of intense search. Fourth, it was found that with many observation data in a certain range of time the subjects had fixed concentration, where women were found to have repetitive fixed concentration along with the change of observation time while men were seen to have more observation tendency for fixed concentration. Fifth, at the cross tabulation of frequency and times, men had the feature of dispersed visual appreciation while women had more distinction between fixation and movement, which revealed that there is surely the difference between men and women in the process of visual appreciation.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.209-210
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• 2006

Digital technology has been applied to marine seismic survey to develop data processing technology and multi-channel marine seismic survey. In result, high-resolution marine seismic survey ended in a success. Surveys are conducted for various purposes using various frequencies of acoustic sources. A low frequency source is used for deeper penetration and a high frequency source is used for higher resolution survey. In this study, a multi-source system was used for multi-channel marine seismic survey to acquire seismic sections of both low and high frequencies. Variations of depth of penetration and resolution would be used to achieve more accurate analysis of formations. In this study, the multi-source system consists of Bubble Pulser(400 Hz) for low frequency source and Sparker(1.5 kHz) for high frequency source.

• Geophysics and Geophysical Exploration
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• v.14 no.3
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• pp.254-260
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• 2011

We studied magnitude determination method using high-frequency energy radiation duration to calculate rapidly magnitude of large earthquakes that occurred around Japan. Fourteen earthquakes were analyzed using Korea Meteorological Administration (KMA) data. We calculated duration of high-frequency energy radiation with 2~4 Hz band pass filter at each data and estimated magnitude. As a result, duration becomes longer as magnitude becomes larger and the magnitude estimated using regional earthquake data are similar to that using teleseismic data. Therefore when an earthquake occurs around Japan we will be able to estimate the magnitude in a relatively short time using KMA data and it may be possible to determine if the earthquake is large enough to produce tsunami.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2004.10a
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• pp.582-586
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• 2004

The purpose of this study is to examine the lead-lag relationship between volatility and returns in high frequency stock market data to see the validity of two hypotheses that explain volatility asymmetry. Specifically, wavelet analysis is applied to decompose the volatility process into permanent and transitory components and then each component is investigated in conjunction with returns. The results from cross-correlation analysis between volatility and returns support the leverage effect hypothesis rather than the volatility feedback hypothesis in all cases.

• Journal of The Korean Society of Integrative Medicine
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• v.4 no.3
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• pp.27-30
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• 2016

PURPOSE : The effect of the vestibular caloric stimulation with ice water on the autonomic nervous system was investigated using pulse oximetry. METHOD : Thirty-four healthy men and women were subject to a 2-minute vestibular caloric stimulation with ice water, and autonomic nervous activities (low frequency, high frequency, and total power) were measured before and after the vestibular caloric stimulation. Data were analyzed separately for men and women. RESULT : Low frequency, high frequency, and total power in the men and low frequency in the women were statistically significantly higher after vestibular caloric stimulation. High frequency and total power in the women were higher but not significantly different after vestibular caloric stimulation. CONCLUSION : Vestibular caloric stimulation with ice water increases autonomic nervous activities, with the variation being within the normal range. The test can be considered safe for use.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.509-510
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• 2006

FLL (Frequency Locked Loop) is the core block for high-speed transceiver. It incorporates a PLL for fine locking action, and a coarse controller for coarse locking action. A coarse controller compares frequencies coarsely and is applied to detected frequency difference directly. Compare to conventional FLL, frequency is applied to proposed FLL. Proposed FLL in this paper achieves only 5 cycles for coarse lock and total frequency locking time is 5 times faster than conventional FLL. Thus, proposed FLL is more useful to Ethernet transceiver application that requires high-speed data transfer than conventional FLL. Proposed FLL is based on $0.18{\mu}m$ process.