• The Journal of the Korea institute of electronic communication sciences
• /
• v.5 no.6
• /
• pp.581-587
• /
• 2010

In this study, we investigated the effect of the simplification for low frequency region in Head-Related Transfer Function(HRTF) on the sound localization. For this purpose, HRTF was measured and analyzed. The result in the standard deviation of HRTF showed that the directional dependence of low frequency was smaller than that of high frequency region, which means the possibility of simplification in the low frequency region. Simplification was performed by flattening of the low frequency amplitude characteristics with the insertion of the high-pass filter, whose cutoff frequency is given by boundary frequency. Auditory experiments were performed to evaluate the simplified HRTF. The result showed that direction perception was not influenced by the simplification of the frequency characteristics of HRTF for the error of sound localization. The rate of confusion for the front and back was not affected by the simplification of the frequency characteristics within 1kHz of HRTF. Finally, we made it clear that the sound localization was not affected by the simplification of frequency characteristics of HRTF within 1kHz. The result is expected to be utilized to reduce the size of speech information with no deterioration of the directional characteristics of the speech signal.

• The Journal of Korean Medicine
• /
• v.29 no.2
• /
• pp.107-115
• /
• 2008

Objectives: The objective of this study was to assess the effects of acupuncture applied at PC6 and SP4 points on heart rate variability (HRV) in normal subjects under mental stress Methods: 24 healthy male subjects were recruited and randomized to a treatment group (12 subjects) or a control group (12 subjects). Both groups performed a mental arithmetic stress test and then acupuncture needles were inserted on PC6 and SP4 for the study group. In the control group, they took sham acupuncture as a control. Heart rate variability (HRV) was measured during the whole study period by FM-150 (digital Holter ECG recorder). Results: In the both groups, low frequency (LF) power and ratio of low frequency to high frequency (LF/HF) was significantly increased after mental stress. Acupuncture induced significant decrease in low frequency (LF) power and ratio of low frequency to high frequency (LF/HF) which were increased after mental stress test. But sham acupuncture induced no changes. Results: In both groups, low frequency (LF) power and ratio of low frequency to high frequency (LF/HF) significantly increased after mental stress. Acupuncture induced significant decrease in low frequency (LF) power and ratio of low frequency to high frequency (LF/HF) which increased after mental stress test. In contrast, sham acupuncture induced no changes. Conclusions: Acupuncture on PC6 and SP4 could be useful to decrease sympathetic activity and balance autonomic nervous system for those who are under stress.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.27 no.2
• /
• pp.69-76
• /
• 2013

In this paper, electronic ballast using resonant inverter for HID lamp is designed and implemented. The proposed electronic ballast is used the soft switching technology ZVS(Zero Voltage Switching) to reduce turn-on and turn-off loss. The ignition of proposed electronic ballast is achieved by controlling a full bridge inverter which is consisted of LC filter for resonance. After ignition the ballast operates as a low frequency square wave inverter by controlling a full bridge inverter as a buck converter. After ignition at resonant frequency of $f_o$=160kHz, the switching frequency of a buck converter is consisted of 50kHz of high frequency and 170Hz of low frequency. This is for attenuating high frequency harmonics and avoiding acoustic resonance. The experimental results show that electronic ballast using resonant inverter is operated stably.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.17 no.5
• /
• pp.193-197
• /
• 2017

In this paper, we present a low-power delta-sigma based digital frequency synthesizer with high frequency resolution for bio sensor networks. Biomedical radio-frequency (RF) transceivers require miniaturized forms with a long battery life and low power consumption. For the technology scaling, digital circuits have become preferable compared to analog circuits because of the aggressive cost, size, flexibility, and repeatability. Therefore, the digital circuits based on standard-cell library are used to reduce a power consumption. Additionally, a delta-sigma is used for making fractional frequency tuning range. From the simulation, we confirmed that proposed scheme has good performance in accordance with power and frequency resolution.

• Structural Engineering and Mechanics
• /
• v.66 no.2
• /
• pp.185-193
• /
• 2018

In this study, low- and high-frequency structure behaviors were identified and a systematic analysis procedure was proposed using noisy GPS data from a 165-m-high tower in ${\dot{I}}stanbul$, Turkey. The raw GPS data contained long- and short-periodic position changes and noisy signals at different frequencies. To extract the significant results from this complex dataset, the general structure and components of the GPS signal were modeled and analyzed in the time and frequency domains. Uncontrolled jumps and deviations involving the signal in the time domain were pre-filtered. Then, the signal was converted to the frequency domain after applying low- and high-pass filters, and the frequency and periodic component values were calculated. The spectrum of the tower motion obtained from the filtered GPS data had dominant peaks at a low frequency of $1.15572{\times}10-4Hz$ and a high frequency of 0.16624 Hz, consistent with two equivalent GPS datasets. Then, the signal was reconstructed using inverse Fourier transform with the dominant low frequency values to obtain filtered and interpretable clean signals. With the proposed sequence, processing of noisy data collected from the GPS receivers mounted very close to the structure is effective in revealing the basic behaviors and features of buildings.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.50 no.12
• /
• pp.287-291
• /
• 2013

The low- frequency hydrophone sensor, using the recently developed FBG has an excellent merits which the existing fiber-optic sensor has and also it has an excellent signal sensing effect in the environment of low-frequency(30Hz-300Hz), not to be detected by the PZT sensor. we have the detection of frequency 19KHz right signals when was using more Hopper lenz WDM than $1{\times}3$ optical coupler. furthermore, we can expect the uitilization of low-frequency signal detection to be used for the military purpose and also it can be developed as the high-sensibility multiplexing through the sensor array system.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.15 no.5
• /
• pp.394-400
• /
• 2010

In this paper, We proposed electronic ballast that applys Buck Converter operation principle to Full-Bridge inverter. The proposed ballast consists of an EMI Filter, a full-bridge rectifier, a passive power factor correction (PFC) circuit and a full-bridge inverter. The passive PFC is used and a Full-Bridge inverter operation by two frequency. High Side and Low Side switch was driven by high frequency and low frequency and realized buck Converter's operation. The lamp is driven by Low Frequency square wave to avoid Acoustic Resonance. Also, bulk of inductor is reduced by high frequency switching. Performance of the proposed ballast was validated through computer simulation using Pspice, experimentation and by applying it to an electronic ballast for a prototype 700W MHL.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2009.10a
• /
• pp.167-168
• /
• 2009

The noise sources in ship and offshore structure have an influence on adjacent receiving area through a partition between noise sources and receiving area. The partition in ship is usually made of stiffened plate. Sound transmission loss (STL) of the partition at high frequency could be improved by additional installation of insulation or wall panel. At low frequency, however, it is very difficult and needs an increase of plate thickness which causes a considerable weight increase of ship. In this paper, we have investigated the effect of the bulkhead boundary condition. From measurement result, we found that the bulkhead boundary condition can affect a lot in STL, especially at low frequency range. Finally, we get the 5dB increase in STL through the modification of boundary condition.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
• /
• 1992.11a
• /
• pp.11-15
• /
• 1992

Currently-using low-pressure lamps are usually drivel by the AC power supply. There are good and bad points according to high or low frequency in AC power driving type. For the low-pressure lamps, its efficiency increases and flicker decreases when it ignites at high frequency. So we already use the high-frequency electronic ballast of the low-pressure discharge lamps broadly. But there are EMI interference in high-frequency driving type because of giving the fluorescent lamp the high- frequency current. So recently, we have a tendency to compensate for that defects by DC driving method. As follows, we suggest pseudo DC discharging electronic bar lasts for fluorescent lamps which have the characteristics of high efficiency and no flicker by driving constant current boosted square wave.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.05a
• /
• pp.127-131
• /
• 2007

A laboratory study on low frequency noise assessment was carried out to determine the acceptability limits in the frequency range between 20 and 200 Hz. The acceptability limits were tested in the anechoic chamber to minimize the background noise. A total of 30 test subjects, who were aged between 19 to 33 years, participated in this study. They were exposed to various stimuli for about 1 hour by supra-aural earphone. The experiment consisted of two listening sessions; hearing threshold and the acceptability limits session. The results showed that the trend of the acceptability limits curve was approximately equal to C-weighting curve which had been found to be superior to A-weighting curve in low frequency noise assessment.