• Journal of the Optical Society of Korea
• /
• 제7권3호
• /
• pp.139-144
• /
• 2003

We have characterized the optical parametric chirped-pulse amplification of femtosecond Ti:sapphire laser pulses by using a BBO crystal. It is numerically verified that a high gain and a broad gain bandwidth can be obtained with a 532-nm pump laser. The dependence of the gain profile of OPA on phase matching angles, pump intensity, and crystal length is numerically investigated. Experimental results shows that the temporal fluctuation of a pump laser causes the modulation of an amplified spectrum in OPCPA.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2002년도 하계학술대회 논문집 B
• /
• pp.1169-1171
• /
• 2002

In this paper, RFRPP(Random Frequency Randomized Pulse Position ) PWM for three-phase voltage-controlled inverters is proposed. The LLPWM(Lead-Lag PWM) techinquc is that three switching pulses are located randomly back and forth in each switching interval. But with the restriction of random distribution, the harmonic spectrum cannot be dispersedly and continuously distributed. This paper calculates the duty ratio of the switching pulse firstly. Second, the switching pulses are located randomly in the switching interval. Third, the fixed switching frequency of the space vector modulation is randomly varied. To verify the validity of the proposed technique, simulation study is tried using Matlab/Simulink. When a proposed techniquc is employed, the harmonic spectrum of the inverter output voltagc varies from one cycle to the next and the EMI(Electromagnetic Interference) and resonant vibration are greatly alleviated.

• 한국광학회지
• /
• 제11권6호
• /
• pp.400-404
• /
• 2000

능동 모드 잠김 8자형 레이저를 이용하여 10Gb/s RZ 신호로부터 클럭을 추출하고 이 클럭 성분의 품질을 평가하였다. 10ps의 펄스폭을 갖는 광원을 $2^{23}-1$ PRBS로 외부 변조하였으며 이를 클럭 추출회로에 인가함으로써 12ps의 펄스폭을 갖는 클럭을 얻었다. 이렇게 얻어진 펄스를 다시 같은 외부 변조기에 입력하여 BER을 측정한 결과 $10_{11}$의 BER에서 패널티가 거의 나타나지 않았다.

• Transactions on Electrical and Electronic Materials
• /
• 제7권5호
• /
• pp.252-256
• /
• 2006

When a partial discharge takes place at the stator of a generator, the electrical pulse will propagate along the stator bars and the capacitor chains formed by the end part of the stator winds. On the first path, the pulse propagates as a travel wave at slow speed. On the second path, the pulse propagates at quick speed. Based on the data of the experiments on a real 50 MW steam generator, the author has found the pulses can propagate by magnetic field of the stator winding. It was studied that how to locating the partial discharge by signals coming from the different paths, including the features of signals on the two paths at time domain and frequency domain, the measurement frequency rang of the signals, the blind area, the advantage and disadvantage of this method.

• ETRI Journal
• /
• 제18권1호
• /
• pp.1-14
• /
• 1996

We have experimentally observed and theoretically analyzed the gain dependent optimum repetition rates of a hybrid-type active and passive mode locked laser pulses in an erbium-doped fiber laser of the figure-of-eight geometry by utilizing a nonlinear amplifier loop mirror (NALM) as a saturable absorber and a directional-coupler type electro-optic modulator as an active mode locker. Transform-limited mode-locked pulses of about 10 ps width were obtained at repetition rates which correspond to harmonics of the cavity fundamental frequency and depend on the optical amplifier gain in the NALM.

• 대한전자공학회논문지
• /
• 제12권1호
• /
• pp.12-17
• /
• 1975

광대역의 계수율을 선택 스윗치 없이 계측하기 위한 대수계수율회로에 관한 해석을 하였고 그에 의한 다데케이드 계수율회로의 구성방법과 실험결과를 지시하였다. 이 대수계수율회로는 주기적인 입력 펄스 뿐만 아니라, Poisson분포를 갖는 random한 펄스에 대하여도 대수적인 응답특성을 가지며 계수율 1pps로 부터 $10^5$pps까지 데케이드의 영역에 걸쳐 좋은 대수특성을 가지며 또한 낮은 영역과 높은 영역에서의 특성저하의 원인을 규명하여 양단에서의 특성을 효과적으로 보상하였다.

• 전기전자학회논문지
• /
• 제12권4호
• /
• pp.234-238
• /
• 2008

We demonstrate a simple method to generate a stable 40 GHz pulse train at 1550 nm by spectral filtering of a 10 GHz mode.locked pulse source using a fiber Fabry-Perot interferometer (FFPI). A high finesse FFPI with a 40 GHz free spectral range blocks successfully unwanted spectral components of a 10 GHz pulse source and passes only 40 GHz spaced spectral lines ensuring pulse repetition-frequency quadruplication of the input pulses.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
• /
• pp.9-11
• /
• 2004

The vocal folds play an important role to produce glottal pulse which is an essential factor of phonation. There have been some models which implement the vocal folds' dynamics, such as one-mass model, two-mass model, multi-mass model and ribbon model. Among them, this paper uses nonlinear two-mass model, which is simple structure and produces similarly real glottal pulses and vocal folds' vibration, to realize vocal folds digital model. The pattern of movements in vocal folds will be shown in this paper by using vocal folds digital model. It will be verified how initial position of vocal folds. variation of tension and change of lung pressure influences vibration and glottal pulses.

• 대한전기학회논문지
• /
• 제32권7호
• /
• pp.227-233
• /
• 1983

Noticing that action of gaseous phase in insulating oil concerns to the discharging characteristics, I investigated the smalness pressure effects on quantity of the partial discharge and discharging pulse frequency. Tests are carried out between the niddle points in insulating oil at pressure being changed by gradual charge of inert gas Ar. At pressure as low as of 0.1-0.5 torr pulse frequency and maximum partial discharge reach peak while at pressure haigher than 20 torr no pulse is observed. The fact that pulse frequency has peak value at certain presure, which is changed either by charging Ar or by adding oil, implies that the action of gaseous phase depends on pressure. Test results are that partial discharge pulse are governed by pressure of Ar-charged oil, and less partial discharge pulses correspond to smaller bubbles whereas more partial descharge pulses correspond to larger bubbles.

• Journal of Chest Surgery
• /
• 제18권3호
• /
• pp.466-469
• /
• 1985

The patient was 17 years old female who complained of coldness of right arm and occasional dizziness, since 4 months prior to admission. On physical examination, the right radial, brachial and common carotid arterial pulses were not palpable. Aortography revealed narrowing of innominate and right common carotid arteries, and complete obstruction of right subclavian artery. The right axillary artery was faintly visualized on the delayed film. Axillo-axillar bypass was done using Gore-Tex graft of 8 mm I.D.. By bilateral subclavicular incision, both side axillary arteries was exposed. End to side anastomosis was made between graft and right axillary artery and the graft was brought out to the left side, subcutaneously, over the sternum, and the anastomosis was made between graft and left axillary artery. Postoperatively, both radial pulses were equally palpable. On follow-up visiting, there were no subjective symptoms and blood pressure in both arms was equal.