• 대한전자공학회논문지SD
• /
• 제42권12호
• /
• pp.19-26
• /
• 2005

모드별 광출력-전류-전압 특성, RIN (relative intensity noise) 스펙트럼, 계단 전류입력에 대한 과도응답의 측정을 통하여 다중 횡모드 VCSEL의 모드 거동과 동특성 사이의 관계에 대하여 살펴보았다. RIN 스펙트럼의 공진 주파수는 모드별 광출력 특성 곡선으로 잘 설명할 수 있었다. 그리고, 활성영역이 넓은 VCSEL은 각각의 횡모드가 문턱전류가 서로 다른 독립적인 레이저로 동작하여 turn-on 지연시간이 달라 다단계 turn-on 특성을 보인다. 고차 모드가 발진하면서 이렇게 펄스의 파형이 찌그러지고 상승시간이 급격히 증가하기 때문에 단일 모드로 동작하도록 전류입력을 조절하지 않으면 고속 광통신용 광원으로서는 적합하지 않게 된다.

• 한국초전도학회:학술대회논문집
• /
• 한국초전도학회 2007년도 High Temperature Superconductivity Vol.XVII
• /
• pp.91-91
• /
• 2007

• 한국전자파학회논문지
• /
• 제19권3호
• /
• pp.343-351
• /
• 2008

본 논문에서는 FPC(Flexible Printed Circuit) 케이블에 적층된 나선형 인덕터를 내장하여 다기능 케이블을 위한 공통 모드 필터를 제안하였다. 공통 모드 필터가 내장된 FPC 케이블은 별도의 SMD(Surface Mounted Device) 필터 없이 연성 케이블과 공통 모드 차단 특성을 가짐으로서, 다기능 케이블이라는 새로운 개념을 제시한다. 내장된 공통 모드 필터는 광대역의 공통 모드 차단 대역을 가지고 손실이 큰 페라이트와 같은 자성 물질을 사용하지 않아 차동 모드 삽입 손실 및 반사 손실이 향상되었다. 3-turn 인덕터를 가진 공통 모드 필터는 공통 모드차단 대역이 $0.4{\sim}3.12GHz$이며, 페라이트를 적용한 상용 LTCC(Low Temperature Co-fire Ceramic) 공통 모드 필터에 비해 3 GHz에서 1.95 dB, 8 GHz에서 6.97 dB의 향상된 차동 모드 삽입 손실을 갖는다.

• East Asian Economic Review
• /
• 제19권2호
• /
• pp.189-220
• /
• 2015

Multi-scale representations are effective in characterising the time-frequency characteristics of financial return series. They have the capability to reveal the properties not evident with typical time domain analysis. Given the aforesaid, this study derives crucial insights from multi scale analysis to investigate the co-movements between Indian and emerging Asian equity markets using wavelet correlation and wavelet coherence measures. It is reported that the Indian equity market is strongly integrated with Asian equity markets at lower frequency scales and relatively less blended at higher frequencies. On the other hand the results from cross correlations suggest that the lead-lag relationship becomes substantial as we turn to lower frequency scales and finally, wavelet coherence demonstrates that this correlation eventually grows strong in the interim of the crises period at lower frequency scales. Overall the findings are relevant and have strong policy and practical implications.

• 한국유체기계학회 논문집
• /
• 제7권5호
• /
• pp.7-12
• /
• 2004

Multi-path ultrasonic flowrate measuring technology is being received much attentions from a variety of industrial fields to exactly measure the flowrate. Multi-path ultrasonic flowmeter has much advantage since it has no moving parts and little pressure loss. It offers good accuracy, repeatability, linearity and turn-down ratio can be over 1:50. The present study investigates flowrate integration errors using weighting factors. A theoretical flow model uses power law to describe a fully developed velocity profiles and wall roughness is changed. Gaussian, Chebyshev, and Tailor methods are used to integrate line-average velocities. The obtained results show that Chebyshev method in 2, 4-path arrangement and Gaussian method in 3, 5-path arrangement are not affected for wall roughness changes.

• 한국초전도ㆍ저온공학회논문지
• /
• 제15권4호
• /
• pp.10-14
• /
• 2013

We have clearly investigated with respect to the survival of the insulator at cryogenic temperature under the electrical stress. The breakdown and voltage-time characteristics of turn-to-turn models for point contact geometry and surface contact geometry using copper multi wrapped with polyimide film for an HTS transformer were investigated under AC and impulse voltage at 77 K. Polyimide film (Kapton) 0.025 mm thick is used for multi wrapping of the electrode. As expected, the breakdown voltages for the surface contact geometry are lower than that of the point contact geometry, because the contact area of the surface contact geometry is lager than that of the point contact geometry. The time to breakdown t50 decreases as the applied voltage is increased, and the lifetime indices increase slightly as the number of layers is increased. The electric field amplitude at the position where breakdown occurs is about 80 % of the maximum electric field value. The relationship between survival probability and the electrical stress at cryogenic temperature was evident.

• KIEE International Transactions on Electrophysics and Applications
• /
• 제3C권4호
• /
• pp.155-160
• /
• 2003

In this study, an Alexandrite laser system for hair removal adopting a multi-discharge method in which three flash lamps are turned on consecutively was designed and fabricated to examine the pulse width and the pulse shape of the laser beams depending upon the changes in the lamp turn-on time. Specifically, this study demonstrates a technology that makes it possible to formulate various pulse shapes by turning on three flashlamps consecutively on a real-time basis with the aid of a PIC (program integrated circuit) one-chip microprocessor. With this technique, the lamp turn-on delay time can be varied more diversely from 0 to 10 ms and real-time control is possible with an external keyboard, enabling an assortment of pulse shapes. In addition, longer pulses can be more widely used for industrial processing as well as for numerous medical purposes.

• 전력전자학회논문지
• /
• 제11권6호
• /
• pp.570-576
• /
• 2006

본 논문에서는 이산 웨이브렛 변환을 이용하여 원통형 동기발전기 회전자 권선의 층간단락을 진단하는 방법에 대해 기술하였다. 제안하는 방법에서는 회전자 권선의 층간단락 진단을 위해 다중해상도 분석을 이용하여 회전자 전류를 여러 스케일 영역으로 분할한 후, 각 영역에서의 신호의 에너지 값을 비교하였다. 실험적인 결과는 특정 회전자 슬롯 내에 25%, 42%, 67%, 83%, 99%단락이 발생한 경우와 정상적인 경우를 비교한 것으로, 그 편차는 층간단락 비율에 반비례하여 나타났다. 이러한 실험적인 결과는 제안한 이산 웨이브렛 변환을 이용한 방법이 원통형 동기발전기 회전자 권선의 충간단락 진단에 적절함을 보여준다.

• 한국전기전자재료학회논문지
• /
• 제13권5호
• /
• pp.371-375
• /
• 2000

In this paper a new conductivity modulated power transistor called the Lateral Insulated Gated Bipolar Transistor which included n+ ring and p-channel gate is presented. A new lateral IGBT structure is proposed to suppress latch-up and to improve turn off time by imploying n+ ring and p-channel gate and verified by MEDICI. The simulated I-V characteristics at $V_{G}$=15V show that the latch up occurs at $V_{A}$=18V and 6.9$\times$10$^{-5}$ A/${\mu}{\textrm}{m}$ for the proposed LIGBT while the conventional LIGBT latches at $V_{A}$=1.3V and 1.96${\mu}{\textrm}{m}$10$^{-5A}$${\mu}{\textrm}{m}$. It is shown that turn off characteristic of new LIGBT is 8 times than that of conventional LIGBT. And noble LIGBT is not n+ buffer layer because that It includes p channel gate and n+ ring. Therefore Mask for the buffer layer isn’t needed. The concentration of n+ ring is and the numbers of n+ ring and p channel gate are three for the optimal design.n.n.n.n.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1997년도 추계학술대회 논문집 학회본부
• /
• pp.500-504
• /
• 1997

Current source inverter drives of auto sequentially commutated type are very popular in high power applications, because of simple power circuit configuration with four quadrant operation. But the six-step current output create harmonic problems and the input power factor of such a drive is not always good. In this respect pulse width modulated drives using gate turn off thyristors ( GTO ) are finding application, especially in traction drives. However the switching and snubber loses of a GTO do not permit the inverter switching frequency go beyond a few hundred hertz.This will again introduce low frequency harmonic problems. Multi level inverters of the 3-level and 5-level can be considered as an alternative to overcome the low switching frequency harmonic problem of the 2-level GTO inverters. But with multi level inverters the complexity of the power circuit increases. In this paper a combination of multi level ( 2-level and 3-level ) inverters and multi phase induction motor ( 3-phase and 6-phase) configurations are presented for high power VSI drives for traction applications with reduced inverter switching frequency requirements coupled with reduced voltage rating for the power switch.