• Proceedings of the KIEE Conference
• /
• 2005.07b
• /
• pp.1364-1367
• /
• 2005

In this paper, a novel prototype topology of soft switching PWM controlled high frequency AC power conversion circuit without DC voltage smoothing chemical capacitor filter link from the voltage grid of utility frequency AC power supply source with 60Hz-100V or 60Hz-200V is proposed and introduced for innovative consumer induction heating(IH) boiler applications as hot water producer, steamer and super heated vapor steamer.

• Speech Sciences
• /
• v.15 no.3
• /
• pp.95-102
• /
• 2008

Multiple physical changes of the larynx and its components occur with age. Vocal pitch, commonly expressed through measures of fundamental frequency (Fo) relate to physical conditions of the larynx. Available data is lacking for the senescent voice, and should be applied to the of changes of elderly speakers' Fo characteristics. The purpose of this study was to investigate the Fo of normal elderly speaker's voice. A total of 406 normal elderly speakers (207 males and 199 females) participated in this experiment. Age ranged from 60 years to 89 years. The subjects were asked to produce sustained corner vowels (/a/ /i/ /u/) three times each and the data were analyzed using the MDVP of CSL. According to the results of this study, the mean Fo from the ages of 60's to 80's shows 143.95Hz(SD 13.94) for men and 185.42Hz (SD 15.29) for women. For men, a significant change is found as a function of age in the Fo (F=16.181, p<.05). A post-hoc Scheffe test revealed significant differences between the Fo data of subjects aged 60's and 70's, 60's and 80's. For women, a significant change is found as a function of age in the Fo (F=49.013, p<.05). A post-hoc $Scheff'{e}$ test revealed significant differences between the Fo data of subjects in their 60's and 70's, 70's and 80's, 60's and 80's. The Fo of men goes up from their 60's to 80's gradually, whereas the Fo of women goes down gradually until their 70's, and after their 70's it again increases. It has been known that diminishing estrogen levels in women in old age may be a factor in lowering Fo, whereas diminishing testosterone levels in men may contribute to a rising Fo. This result may be used as some meaningful guideline and lead the basic data to differentiate between normal aged voice and aged voice disorders.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
• /
• 1999.07a
• /
• pp.147-155
• /
• 1999

• Electric Engineers Magazine
• /
• v.229 no.9
• /
• pp.27-36
• /
• 2001

기존의 HID 램프용 안정기는 대부분이 인덕터와 콘덴서를 사용한 수동소자 회로이며 사용 전원 60HZ에서는 그 부피가 커짐은 물론 중량이 무거워 설치에 제약조건이 많고 효율이 나쁘기 때문에 전자식 안정기를 사용하여 단점을 보완할 필요가 있다.

• Railway Journal
• /
• v.16 no.1
• /
• pp.8-11
• /
• 2013

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.4
• /
• pp.446-451
• /
• 2020

Flow induced vibration in a heat exchanger may cause damage to piping. The purpose of this study was to compare the characteristics of vortex shedding behavior through the circular tube banks at several tube locations, No.1, No. 10, and No. 19, with respect to time when the flow velocity of the inlet is constantly and periodically fluctuating.(60) The time characteristics of lift and the PSD characteristics were also investigated. In the case of periodic inlet flow velocity, strong vortex occurred at some time and after that time, a weak vortex was generated through the tube banks simultaneously. In the case of constant inlet flow velocity, the lift fluctuating frequency was 37.25Hz and that at the No. 19 tube was 18.63Hz and near 50Hz. In the case of periodic inlet flow velocity, the lift fluctuating frequency was 37.25Hz and 18.63Hz. The lift fluctuating frequency at No. 19 tube was observed broadly from 20Hz and 50Hz.

• Journal of IKEEE
• /
• v.14 no.2
• /
• pp.16-23
• /
• 2010

Since the interest of a brain science research is increased recently, various devices using brain waves have been developed in the field of brain training game, education application and brain computer interface. In this paper, we have developed a portable EEG measurement and a bluetooth based wireless transmission device measuring brain waves from the frontal lob simply and conveniently. The low brain signals about 10~100${\mu}V$ was amplified into several volts and low pass, high pass and notch filter were designed for eliminating unwanted noise and 60Hz power noise. Also, PIC24F192 microcontroller has been used to convert analog brain signal into digital signal and transmit the signal into personal computer wirelessly. The sampling rate of 1KHz and bluetooth based wireless transmission with 38,400bps were used. The LabVIEW programing was used to receive and monitor the brain signals. The power spectrum of commercial biopac MP100 and that of a developed EEG system was compared for performance verification after the simulation signals of sine waves of $1{\mu}V$, 0~200Hz was inputed and processed by FFT transformation. As a result of comparison, the developed system showed good performance because frequency response of a developed system was similar to that of a commercial biopac MP100 inside the range of 30Hz specially.

• Journal of Bio-Environment Control
• /
• v.21 no.4
• /
• pp.437-444
• /
• 2012

This study was aimed to minimized the impact force and vibration transmitted to transporting agricultural product from the power tiller trailer by installing vibration absorption device. The vibration absorbable trailer (I) mounted with leaf spring suspension and shock absorber was developed and compared on vibration absorption performance with the existing trailer (E) equipped no vibration absorption device. In order to identify the vibration absorption effect of the trailer developed in this study, the vibration accelerations, occurred during driving on paved road with loading 360 kg of pear, were measured and analyzed using FFT analyzer. The magnitude of average vibration acceleration was decreased highly for the improved trailer mounted with vibration absorption device in comparing with existing trailer in the frequency range under 60 Hz and under 80 Hz. And similar vibration absorption effect was represented for the improved trailer in all frequency range. Especially, in the frequency range between 40 Hz and 80 Hz, the magnitude of vibration acceleration for the improved trailer was decreased with 1/3 times in comparing with existing trailer. So, the transporting loss including damage of agricultural product could be decreased highly by using the improved vibration absorbable trailer mounted with leaf spring suspension and shock absorber simultaneously, designed in this study.

• Geophysics and Geophysical Exploration
• /
• v.8 no.2
• /
• pp.145-155
• /
• 2005

A two-dimensional (2-D) interpretation of MT data has been performed for the purpose of fracture detection for geothermal development. Remote stations have been operated in Kyushu, Japan (480 km apart) as well as in Korea (60 km and 165 km apart in 2002 and 2003 data set, respectively). Apparent resistivity and phase curves calculated by remote processing with the Japan remote data showed enough quality for 2-D inversion for the whole frequency range. Remote reference processing with Korea remote reference data also showed quite good continuity in apparent resistivity and phase curves except some noisy frequency bands; around the power frequency, 60 Hz, and around the dead band $10^{-1}Hz\;Hz\;\~1\;Hz$, where the natural EM signal is known to be very weak. Even though the subsurface showed severe three-dimensional (3-D) characteristics in the survey area so that 2-D inversion by itself could not give enough information for deep geological structures, the 2-D inversion for the 5 survey lines showed several common features. The conductive semi-consolidate mudstone layer is dipping from north to south (about 500 m depth on the south and 200 m on the north most part of the survey area). The boundary between the low (L-2) and high (H-2) resistivity anomalies can be thought as a major fault with strike $N15^{\circ}E$, passing through the sites 206, 112 and 414. The shallow (< 1 km) conductive anomalies (L-4) seem to be fracture zones having strike E-W (at site 105) and $N60^{\circ}W$ (at site 434). And there exists a conductive layer in the western and west-southern part of the survey area in the depth below $2\~3\;km$, for which further investigation is to be needed.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.20 no.3
• /
• pp.371-377
• /
• 2007

In this paper, acceleration threshold of perception for the horizontal vibration of tall buildings was estimated. Excessive vibration of tall buildings by wind can give displeasure, such as giddiness and visual insecurity. To provide comfortable environment to residents of tall buildings, acceleration needs to be limited. For tall buildings the first mode of vibration is dominant. To reproduce the first mode of vibration, experiments were performed by generating sine waves by a shaking table. A nitration house was made and forty persons were employed for experiments. The forty persons were organized into five experimental groups, each of which was composed of eight persons, and the threshold of perception for horizontal vibration was measured by increasing acceleration in the range of 0.2Hz through 1.2Hz of frequency, Performance curves were obtained by dividing the distribution of perception for horizontal vibration into the range of $0{\sim}20%,\;21{\sim}40%,\;41{\sim}60%,\;61{\sim}80%\;and\;81{\sim}100%$ and by fitting curves.