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  • Title/Summary/Keyword: 펄스열

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An Analysis of Photoacoustic Signals Excited by Excimer Pulsed Laser (엑시며 레이저 펄스에 의해 여기된 광음향신호 분석)

  • Yi, Chong-Ho;Jun, Kye-Suk
    • The Journal of the Acoustical Society of Korea
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    • v.16 no.1
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    • pp.39-46
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    • 1997
  • In this paper, the PA(PhotoAcoustic) signals excited in metals by Xef, KrF excimer laser pulse were detected by a PZT transducer, and its transforming machanism and directivity patterns were analysed. The laser energy density in irradiation spot divides the PA trasnsorming machanism to be classified into thermoelastic and plasma regime, and the transforming machanisms in two regimes are different from each other. Based on theoretical model, it is predicted that shear wave is greater than longitudinal in the thermoelastic regime and longitudinal is greater than shear wave by reaction force in plasma regime. These predictions were verified through experiments by using of the XeF excimer pulsed laser of 480nm center-wavelength and the KrF excimer pulsed laser of 248nm. Also, for its directivity pattern, an arrival angle of the maximum longitudinal energy was around 60 and maximum shear energy was around 30 in the thermoelastic regime, and an arrival angle of maximum longitudinal energy was shown on nomal to the surface and maximum shear energy was represented in about 30 in plasma regime.

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Design and Performance Analysis of Current Source for 3.0T MREIT System (3.0T MREIT 시스템을 위한 정전류원의 설계 및 성능검증)

  • 김규식;오동인;백상민;오석훈;우응제;이수열;이정한
    • Journal of Biomedical Engineering Research
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    • v.25 no.3
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    • pp.165-169
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    • 2004
  • In Magnetic Resonance Electrical Impedance Tomography (MREIT), we inject current through electrodes placed on the surface of a subject and measure the induced magnetic flux density distribution using an MRI scanner. This requires a constant current source whose output pulses are synchronized with MR pulse sequences. In this paper, we present a design and performance analysis of a current source used in a 3.0T MREIT system. The developed current source was tested using a saline phantom. We found that its performance is satisfactory for the current MREIT system. We suggest future improvements for better SNR(signal-to-noise ratio).

Performance of PN Code Based Time Hopping Sequences in M-ary Ultra Wide Band Multiple Access Systems Using Equicorrelated Signal Sets (동일 상관 신호군을 이용하는 M-ary UWB 다원 접속 시스템에서 PN 부호 기반 시간 도약 시퀀스의 성능)

  • 양석철;신요안
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.28 no.10A
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    • pp.816-829
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    • 2003
  • In this paper, we evaluate the performance of PN (Pseudo Noise) code based time hopping sequences for M-ary UWB (Ultra Wide Band) multiple access systems using the equicorrelated signal sets. In particular, we consider two different types of M-ary UWB systems in UWB indoor wireless multipath channels: The first type of the systems (System #1) has identical symbol transmission rate regardless of the number of symbols M since the length of signal pulse train is fixed while M increases, and the second type of the systems (System #2) has the same bit transmission rate regardless of M since the length of signal pulse train is extended according to the increase of M. We compare the proposed systems with those using the ideal random time hopping sequence in terms of the symbol error rate performance. Simulation results show that the PN code based time hopping sequence achieves quite good performance which is favorably comparable to that of the ideal random sequence. Moreover, as M increases, we observe that System #2 shows better robustness against multiple access interference than System # 1.

유기박막트랜지스터를 위한 극초단 펄스 레이저 마이크로-나노 패터닝

  • Jo, Jeong-Hyeong;Chae, Sang-Min;Kim, Yong-Hwi;Lee, A-Ra;Lee, Hyeon-Hwi;Choe, Ji-Yeon;Kim, Hyo-Jeong
    • Proceedings of the Korean Vacuum Society Conference
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    • 2016.02a
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    • pp.271-271
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    • 2016
  • highly doped N-type 실리콘 기판 위에 극초단 펄스 레이저를 이용하여 LIPSS (Laser-Induced Periodic Surface Structure) 패턴을 형성하였다. 형성된 LIPSS 구조는 15μm와 500 nm 주기를 가지는 ripple로 형성이 되었고 이 구조를 형성하기 위해서 사용된 레이저는 Satsuma HP2, Amplitude syst?mes 이다. LIPSS 패턴을 가지는 기판 위에는 유기반도체 물질인 pentacene을 50 nm로 열 증착방법을 통해 박막을 형성하여 유기박막트랜지스터를 제작하였고, hole mobility를 측정하였다. LIPSS 패턴을 가지는 실리콘 기판과 pristine 실리콘 기판 위의 pentacene의 morphology를 AFM으로 관찰하고 유도된 구조를 연구하였다.

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Manufacturing and Testing of a DDT Tube for a Pulse Detonation Engine (펄스데토네이션엔진(PDE)용 DDT 튜브의 제작 및 시험)

  • Kim, Do-Hun;Lee, In-Chul;Choi, Yong-Joon;Gong, Joo-Yeol;Koo, Ja-Ye
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2011.11a
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    • pp.624-628
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    • 2011
  • To develop a pulse detonation engine, it needs to understand the mechanism of a detonation initiation, and establish the methods for measuring and analyzing the detonation phenomenon. In this study, DDT tube, which use oxygen-acetylene propellant mixture, were designed and manufactured, and the effect of equivalent ratio and Schelkin spiral on the characteristics of the detonation initiation were discussed.

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A Study on the Passive Modelocking of Ring Type Er-doped Fiber laser (고리형 어븀첨가 광섬유 레이저의 수동형 모드로킹에 관한 연구)

  • 한두희
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.1 no.2
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    • pp.63-68
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    • 2000
  • A passively mode-locked ring type fiber laser had been installed in order to get the short pulses The single and the double mode-locking were appeared, and the shortest pulse length of 65 fs was obtained with a 110 m long dispersion shifted fiber(DSF) in a local cavity of 139.8 m. Also high order harmonic modelocking of 17th and Q-switched high order harmonic modelocking were obtained.

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Reactive Power Compensator for Pulsed Power Electric Network of International Thermonuclear Experimental Reactor (국제 열핵융합실험로 펄스전원계통의 무효전력보상기 검증)

  • Jo, Hyunsik;Bae, Sanghoon;Oh, Jong-Seok;Cha, Hanju
    • Proceedings of the KIPE Conference
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    • 2014.11a
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    • pp.72-73
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    • 2014
  • 본 논문에서는 ITER 펄스전원계통의 무효전력보상기(Reactive Power Compensator)의 해석 및 검증에 대하여 기술하였다. ITER 펄스전원계통은 66kV에 흐르는 무효전력량을 250MVar이하로 제한하기 위하여 정지형 무효전력보상기(Static Var Compensator)의 대표적인 장치인 싸이리스터 제어 리액터(TCR)와 고조파 필터(HF)로 구성된 무효전력보상기(RPC)를 사용한다. RPC에 적용되어 여러 ITER 초전도 코일 전원장치에서 발생하는 무효전력의 크기를 예측하여 보상하는 무효전력 보상기법을 해석한다. 본 논문에서는 RPC의 무효전력 보상동작을 실제 제어기와 RTDS를 연동하여 실험하여 검증하였고, RPC의 유무에 따라서 66kV 계통의 무효전력 최대값이 120MVar에서 40MVar로 감소하는 것을 확인하였다.

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An Algorithm for Estimating Pulse Repetition Intervals of Stagger PRI Pulse Train Using 2D-TDOA Histogram (2차원 TDOA 히스토그램을 이용한 스태거 PRI 펄스열의 펄스반복주기 탐지 알고리즘)

  • Kim, Yong-Woo;Yang, Hai-Won
    • Journal of Institute of Control, Robotics and Systems
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    • v.8 no.8
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    • pp.673-681
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    • 2002
  • This paper presents a new algorithm for estimating pulse repetition intervals (PRIs) of stagger PRI pulse trains using a 2 dimensional TDOA histogram. The PRI transform algorithm can remove harmonics of stable and jitter PRI pulse trains in a TDOA histogram. But, it is impossible for the algorithm to detect stagger PRI pulse trains because it regards frame PRIs of stagger Pulse trains as harmonics of stable PRI pulse trains. A new algorithm of this paper has an ability to distinguish stagger pulse trains from harmonics of other pulse trains and to estimate frame PRIs of detected pulse trains.

A CELP Speech Coder Using Secondary Long Term Prediction with Multi-Band Pass Filtered Multi-Pulses (다중 펄스와 다중 대역 이차 장구간 예측을 이용한 CELP 음성 부호화기)

  • 서정태;최용수;강홍구;윤대희
    • The Journal of the Acoustical Society of Korea
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    • v.17 no.1
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    • pp.9-16
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    • 1998
  • 본 논문에서는 낮은 비트율 CELP 음성 부호화기의 장구간 예측기의 성능 향상 방 법을 제안한다. 비트율을 낮추기 위해서는 분석 구간의 길이가 길어져야하며 이에 따라 장 구간 예측기의 성능이 저하되어 장구간 예측 후에도 준 주기성 성분이 상당량 존재하므로 백색 잡음으로 구성된 통계 코드북만으로는 이를 모델링하기 어려워진다. 제안 방법에서는 다중 대역 필터와 다중 펄스열을 이용하여 한 번 더 필터링(이차 장구간 예측)함으로써 장 구간 예측 후의 신호가 통계 코드북에 적합한 백색 잡음 형태로 되도록 모델링한다. 제안된 방법의 성능을 평가하기 위해 4.8kbps 비트율로 양자화한 후, 기존에 제안된 같은 전송률의 MBCELP와 DoD-CELP와 비교하였다. 실험 결과 제안된 방법이 기존 부호화기들에 비해 주/객관적인 음질에서 우수한 성능을 보여준다.

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