• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.1
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• pp.237-242
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• 2017

This paper presents development of the transponder system which provides an accurate train position, especially for supporting 400km/h high speed train. Here, we analyzed an operating frequency band of the transponder system which can be interoperable with the Eurobalise system already installed in Korea railroad as to be used for the automatic train protection (ATP). By investigating the power frequency band and its data frequency band of the transponder system, we presents the adoptable frequency band for the developed transponder system. Additionally, through the real testbed using HEMU-430X, we evaluate its performance requirement and shows interoperable operation with the Eurobalise system.

• Korean Journal of Optics and Photonics
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• v.13 no.4
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• pp.336-339
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• 2002

For the improvement of the lock-in frequency of a ring laser gyro, a low-scattering mirror was employed in the laser resonator. A super-polishing technique produced fine mirror substrates of less than 1-A-rms-roughness. The mirror coating using an ionbeam sputtering technique reduced the scattering loss to less than 30 ppm. As a result of the mirror scattering enhancement of the ring laser, the lock-in frequency of the gyro was improved up to about 0.1 deg/sec.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.527-532
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• 2014

Generator is the main equipment of a power plant that generates electric power. The line frequency is 60Hz, since that is operated at 3600rpm in fossil power plant. Therefore, the specific frequency 120Hz by the electromagnetic excitation force is generated inherently. If the looseness of stator at generator happens, abnormal sound that has 120Hz and the harmonic frequency is emitted from generator frame. In that case, binding of end-winding or re-wedging is needed for the reduction of sound level. In case of severe level of sound, belly band can be additionally installed at core. In this paper, the characteristics of generator sound is described and modal data is analyzed after installation of belly band.

• The Journal of the Acoustical Society of Korea
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• v.26 no.1E
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• pp.8-13
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• 2007

It has long been known that high-frequency sensorineural hearing loss (HFHL) can contribute to difficulty in speech understanding by elderly listeners. This study evaluated the relative contribution of HFHL and age to speech understanding. Subjects included adult middle-aged and old groups with normal hearing or with limited HFHL. The Hearing-in-Noise-Test (HINT) was used to measure speech perception performance in quiet and in noise. The middle-aged groups showed significant effects of HFHL for speech intelligibility in quiet and in noise, but the old groups showed the difference in quiet only due to high frequency hearing. The results suggest that HFHL may affect speech intelligibility differently with age and therefore hearing aid selection needs to take into account the influence of age.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1836-1840
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• 2003

This paper, we propose a new phase-locked loop (PLL) system with the controllable output phase, independent from the output frequency, and lock-up time. This PLL system has a dual control loop is described, the inner loop greatly improved VCO characteristic such as faster speed response as well as higher operation bandwidth, to minimize the effect of the VCO noise and the power supply variation and also get better linearity of VCO output. The main loop is the heart of this PLL which greatly improved the output frequency instability due to the external high frequency noise coupling to the input reference frequency also the main loop can control the output phase, independent from the output frequency, and reduce the lock-up time of the step frequency response. The experimental results confirm the validity of the proposed strategy.

• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1984-1987
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• 2002

This paper describes the design and implementation of a single-chip digitally synthesized 0-35MHz agile function generator. The chip comprises an integrated direct digital synthesizer (DDS) with a 10-bit on- chip digital-to-analog converter (DAC) using an n-well single-poly triple-metal 0.5-$\mu\textrm{m}$ CMOS technology. The main features of the chip include maximum clock frequency of 100 MHz at 3.3-V supply voltage, 32-bit frequency tuning word resolution, 12-bit phase tuning word resolution, and an on-chip 10-bit DAC. The chip provides sinusoidal, ramp, saw-tooth, and random waveforms with phase and frequency modulation, and power-down function. At 100-MHz clock frequency, the chip covers a bandwidth from dc to 35 MHz in 0.0233-Hz frequency steps with 190-ns frequency switching speed. The complete chip occupies 12-mm$^2$die area and dissipates 0.4 W at 100-MHz clock frequency.

• Korean Journal of Clinical Laboratory Science
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• v.45 no.4
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• pp.164-169
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• 2013

Red cell alloantibodies other than naturally occurring anti-A or anti-B are called unexpected red cell antibodies, and can be detected by performing an antibody screening. The frequency and distribution of unexpected antibody identified in Asan Medical Center were analyzed. We investigated a total of 135,238 cases of antibody screening test in AMC for 3 years from 2010 to 2012. Using column agglutination techniques, antibody identification tests were performed for the cases with positive antibody screening. Among 135,238 cases, 854 (0.6%) cases showed positive results of antibody screening test. In the order of frequency, 284 (33.3%) anti-Rh, 89 (10.4%) anti-MNS, 62 (7.3%) anti-Lewis, 34 (4.0%) anti-Kidd, 10 (1.2%) anti-Duffy, and 9 (1.1%) anti-P were identified. Multiple antibodies were detected in 199 (23.3%) cases. Among 381 subjects investigated for transfusion history, 299 (78.5%) had history of transfusion while 82 (21.5%) had unknown history. Thus the incidence of unexpected antibody was higher in the group with history of transfusion than the group without (p<0.001). Also, among 435 subjects investigated for the history of pregnancy, 46 (10.6%) had no history while 389 (89.4%) had history of pregnancy, showing higher incidence of unexpected antibody in the group with history of pregnancy than the group without pregnancy (p<0.001). Evaluated amounts and frequency of antigen exposure due to transfusion and pregnancy is suggested to increase the frequency of identification of unexpected antibody.

• Atmosphere
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• v.30 no.1
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• pp.47-57
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• 2020

In this study, the climatological spatio-temporal variation of strong wind and gust wind in Korea during the period from 1993 to 2018 was analyzed using daily maximum wind speed and daily maximum instantaneous wind speed data recorded at 61 observations. Strong wind and gust wind were defined as 14 m s^-1 and 20 m s^-1, which are the same as the KMA's criteria of special weather report. The frequency of strong wind and gust wind occurrence was divided into regions with the higher 25 percent (Group A) and the lower 75 percent (Group B). The annual frequency of strong wind and gust wind occurrence tended to be decreased in most parts of the Korean peninsula. In Group A with stations located at coastal region, strong wind and gust wind occurred most frequently in winter with higher frequency at 1200~1600 LST and 2300~2400 LST due to influence of East Asian winter monsoon. In addition, a marked decreasing trend throughout the four seasons was shown at Daegwallyeong, Gunsan and Wando observations. In contrast, it can be found in Group B that the monthly frequency of strong wind and wind gust occurrence was higher in August and September by effect of typhoon and hourly frequency was higher from 1200 LST to 1800 LST.

• Journal of Environmental Health Sciences
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• v.45 no.6
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• pp.583-593
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• 2019

Objectives: The purpose of this study was to evaluate the relationship between the frequency score of wearing personal protective equipment (PPE) and concentration of urinary organophosphorus pesticide metabolites in farmers. Methods: The study was conducted in Chungcheongnam-do Province of South Korea. We collected urine samples from 308 farmers from September to December 2017 and May to July 2018. Among them, 17 farmers with urinary creatinine levels outside the normal range were excluded. Information on the frequency of wearing PPE was obtained from the farmers through face-to-face survey. Each frequency of wearing for seven types of PPE was converted into a score and expressed as a total score, which was divided into quartiles. Four types of urinary organophosphorus pesticide metabolites were analyzed using a gas chromatography mass selective detector. Multiple linear regression analysis was used to identify concentrations of urinary organophosphorus pesticide metabolites affected by the frequency of wearing PPE. Results: The average frequency score of wearing PPE was 8.0. The quartiles of frequency score of wearing PPE were divided as follows: 1st quartile (≤1), 2nd quartile (1-6), 3rd quartile (6-12), and 4th quartile (>12). Compared with subjects with a low frequency score of wearing PPE (reference), subjects with a high frequency score of wearing PPE (4th quartile) had lower concentrations of urinary diethyl phosphate (DEP) (p<0.01) and dialkyl phosphate (ΣDAP) (p<0.05), which is the sum of dimethyl phosphate (DMP), DEP, dimethyl thiophosphate (DMTP), and diethyl thiophosphate (DETP). Conclusion: Concentrations of urinary organophosphorus pesticide metabolites were associated with frequency score of wearing PPE. Particularly as the frequency score of wearing PPE increased, concentrations of urinary DMP, DEP, DETP, and ΣDAP significantly decreased. The findings of this study can contribute to the management of health effects among farmers working with pesticides.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.5
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• pp.682-686
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• 2016

A fully differential RC calibrator for accurate cut-off frequency of a programmable channel selection filter is proposed. The proposed RC calibrator consists of an RC timer, clock generator, synchronous counter, digital comparator, and control block. To verify the proposed RC calibrator, a six-order Chebyshev programmable low-pass filter with adjustable 3 dB cut-off frequency, which is controlled by the proposed RC calibrator, was implemented in a $0.18-{\mu}m$ CMOS technology. The channel selection filter with the proposed RC calibrator draws 1.8 mA from a 1.8 V supply voltage and the measured 3 dB cut-off frequencies of the channel selection LPF is controlled accurately by the RC calibrator.