• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.264-264
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• 2007

$B_2Mg_{2/3}/Nb_{4/3}O_7\;(B_2MN)$ thin films and $Bi_{3/2}MgNb_{3/2}O_7\;(B_{1.5}MN)$ thin films were deposited as a function of various deposition temperatures on Pt/$TiO_2/SiO_2$/Si substrates by radio frequency magnetron sputtering system. Both of their thin films are shown to crystalline phase at $500^{\circ}C$, deposition temperature, using 100W RF power. The composition of them and structural micro properties are investigated by RBS spectrum and SEM, AFM. 200 nm-thick $B_2MN$ thin films were deposited at room temperature had capacitance density of $151nF/cm^2$ at 100kHz, dissipation factor of 0.003 and had capacitance density of $584nF/cm^2$ at 100kHz, dissipation factor of 0.0045 at $500^{\circ}C$ deposition temperature. Both of their dielectric constant deposited at room temperature and at $500^{\circ}C$ were each approximately 40 and 100.

• Journal of information and communication convergence engineering
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• v.16 no.1
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• pp.12-16
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• 2018

In this work, a voltage controlled oscillator (VCO) monolithic microwave integrated circuit (MMIC) was demonstrated for 10-GHz band motion detecting sensors. The VCO MMIC was fabricated using a $2-{\mu}m$ InGap/GaAs HBT process, and the tuning of the oscillation frequency is achieved by changing the internal capacitance in the HBT, instead of using extra varactor diodes. The implemented VCO MMIC has a micro size of $500{\mu}m{\times}500{\mu}m$, and demonstrates the value of inserting the VCO into a single chip transceiver. The experimental results showed that the frequency tuning characteristic was above 30 MHz, with the excellent output flatness characteristic of ${\pm}0.2dBm$ over the tuning bandwidth. And, the VCO MMIC exhibited a phase noise characteristic of -92.64 dBc/Hz and -118.28 dBc/Hz at the 100 kHz and 1 MHz offset frequencies from the carrier, respectively. The measured values were consistent with the design values, and exhibited good performance.

• Journal of Korean Ophthalmic Optics Society
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• v.14 no.3
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• pp.89-93
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• 2009

Purpose: To purpose of this study was the pure-tone audimetry changes to compare pre and post fogging after visual correction in normally hearing adults. Methods: The estimated that no ocular and audiolar disesases, we selected (male: 30, female: 20) in corrected visual acuity over the 1.0 eye. Pre and post fogging were measured using the pure-tone audimetry. Results: To compared fre and post fogging, fre fogging was higher than fre fogging. The take value were just about every kind of Hz but 200 Hz, respectively which were statistically significant (p<.05). Low Hz area in 250 and 500 Hz were 6.8${\pm}$8.4dBHL, 4.3${\pm}$6.6dBHL, there is not all the difference between any other area, 2000 Hz in the middle Hz area was 0.8${\pm}$4.5dBHL. Conclusions: The study presents different results of measurements in within normal limits. we thought that pure-tone thresholds to the pre and post fogging after refractive correction in normal adults and would be used basic data.

• The Journal of the Acoustical Society of Korea
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• v.37 no.5
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• pp.323-330
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• 2018

This study investigated effects of absorbent gypsum board in the ceiling on low-frequency heavyweight floor impact sound through sound absorption coefficient and floor impact sound measurement. The sound absorption coefficients were measured with sound absorbent gypsum board, glass wool on gypsum board, and a double panel absorbent gypsum board (absorbent gypsum board + glass wool + absorbent gypsum board). Result showed that the absorbent gypsum board had sound absorption coefficient of 0.1 ~ 0.7 from 200 and 630 Hz octave band. The sound absorption coefficient was increased in all frequency range by adding glass wool. Additional absorbent gypsum board increased sound absorption coefficient up to 250 Hz octave band, but decreased over 250 Hz. Heavyweight floor impact sounds were measured in test building for three materials above, gypsum board, and bare slab. Result showed that glass wool on gypsum board and a double panel absorbent gypsum board reduced by 3 dB ~ 4 dB (single number quantity) heavyweight floor impact sound. Comparing with bare slab condition, floor impact sound reduction was mainly found from 125 Hz to 500 Hz octave band, and the maximum reduction was shown in the 250 Hz octave band.

• Journal of Broadcast Engineering
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• v.16 no.3
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• pp.490-500
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• 2011

The channels of domestic FM broadcast are needed to provide various kinds of new broadcasting services. However, available channels are limited and saturated. The channel interval of FM broadcast is changed from 200 kHz to 100 kHz to maximize utilization efficiency of scarce broadcast spectrum at all over the world. Also, there are many researches such as IBOC(In Band On Channel) and DRM+(Digital Radio Mondial+) that is to allocate the digital signal beside analog bandwidth. But output power is decrease to avoid interference between adjacent radio stations. In this paper, we analyzes the problems of the protection ratio which is decided in 1986 and we propose method to improve about 7~10dB significantly the protection ratio according to the recent DSP(Digital Signal Processing) techniques without loss of both transmission power and broadcast quality. In addition, we examined the possibility of securing two times available channels by reducing minimum frequency interval from 800 kHz to 400 kHz or 600 kHz in the equal site.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.5
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• pp.1068-1073
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• 2004

5 V/500 mA transless type power module was designed by using a semiconductor switching technique for a small-sized electric power source. It used voltage drop type chopper method, and is composed of switching circuit, control circuit, voltage detect circuit, and constant voltage circuit. The switching power module which is designed in this study, showed load regulation of 0.2 V, line regulation of 0.1 V, output ripple of 85 mVp-p, switching frequency of 64.7 kHz, maximum power efficiency of 58 %, and satisfied its reliability and EMC test.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.6
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• pp.581-584
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• 2000

In order to obtain the fundamental data about method of luring fish schools by underwater audible sound, the auditory threshold of black rockfish Sebastes inermis on the coast of Cheju Island was investigated by heartbeat conditioning technique using pure tones coupled with a delayed electric shock, The audible range of black rockfish extended from 80 Hz to 800 Hz with a peak sensitivity at 300 Hz. The mean auditory thresholds of black rockfish at the frequencies of 80 Hz, 100 Hz, 200 Hz, 300 Hz, 500 Hz and 800 Hz were 102 dB, 103 dB, 99 dB, 96 dB, 116 dB and 122 dB, respectively, As the frequency became higher than 300 Hz, the auditory threshold increased rapidly.

• Journal of Biomedical Engineering Research
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• v.19 no.6
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• pp.595-602
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• 1998

Among the apex locators, the frequency dependent type is more accurate and convenient to use than others, But the accuracy of the apex locator is still influenced by the presence of various electrolytes used in root canal treatments. In this study, we have developed a frequency dependent electronic apex locator minimizing the influence of the electrolytes on the measurement of root canal lengths. It was also confirmed that two frequencies of 500Hz and 100kHz are optimal for the measuring impedance compare with commercial product used(400Hz and 8kHz)a and there were no differences in accuracy among the three different types of the waveforms; sinusoidal, triangular, and rectangular waves(p>0.05). Impedance ratio of the two different frequencies represents the position of the file in root canal, and the voltage difference of two signals represents the status of the fluid in the root canal. As a result of compensation using the voltage differences, the errors were decreased on the average from +0.54mm to +0.18mm in $H_2O_2$ solution (p<0.01), and from -0.33mm to -0.01mm in NaOCl solution(p<0.01). The accuracies based on ${\pm}$0.5mm, in $H_2O_2$ and NaOCl solutions were improved with the automatic compensation from 71.1% and 91.1% to 82.2% and 100% respectively.

• Proceedings of the KIEE Conference
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• 2005.11a
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• pp.33-35
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• 2005

In this paper, a two-mass system for SiOG (Silicon on Glass) vibratory gyroscope with the need of frequency tuning was proposed to increase the stability of the device with wide bandwidth. Air damping and bandwidth were analyzed using MATLAB. The measured resonance frequency is 5.2 kHz, which is 7 kHz in the design. But the measured bandwidth is 450 Hz, similar to the designed bandwidth with 500 Hz. Also the frequency difference (210 Hz) between the driving and sensing part is smaller than the wide bandwidth of two mass system.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.12
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• pp.1310-1315
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• 2006

This study examines algae removal and reduction using ultrasonic. Experiments were carried out on frequency: 28 kHz single-wave, 40 kHz multi-wave; intensity: 10, 15, 20, 25, 30 W/L; algae concentration: 500, 1000, 1700/ml; exposure time: 1, 3, 5, 7, 10, 15, 20 min. Also, We investigated algae removal and reduction in single cistern where raw water including algae was directly exposed to ultrasonic and in the double cisterns located in 4 cm from ultrasonic vibrator. The algae type used in this study was Melosira genus of Bacillariophceae. The Bacillariophceae is the representative algae which causes blockage of filter basin. Because of its resistance against oxidizers, it flows into the filter basin after sterilization. As a result of this study, the form of Bacillariophceae was completely destroyed and dissolved after the application of ultrasonic waves unlike the sterilization using oxidizers. Removal efficiency of algae using ultrasonic waves increased in proportion to intensity and exposure time of ultrasonic waves, and in double cisterns is better than single cistern.