• 제목/요약/키워드: Wave Distortion

검색결과 184건 처리시간 0.024초

초음파 영상 시스템에서 합성 집속을 위한 새로운 구면파 발생 방법 (New Circular Wave Generation Method for Synthetic Focusing in Ultrasonic Imaging Systems)

  • 안영복
    • 대한의용생체공학회:의공학회지
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    • 제28권6호
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    • pp.798-802
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    • 2007
  • The synthetic focusing in the ultrasonic imaging systems has been formed in the way that one element transmits a circular wave and receives an echo signal. The amplitude of the signal transmitted from one element is too small to propagate a long distance so that the SNR(Signal to Noise Ratio) is very low in an image obtained by the synthetic focusing. To solve this problem, a defocusing method which uses several elements has been proposed. In this method, the SNR is improved due to using several elements to transmit the circular wave. But if the number of transmitting elements increases, the phase distortion is severe in the defocusing method. In this paper, we propose a new method that can generate a circular wave using a lot of elements without phase distortion. At first, we generate limited plane waves with different propagation angles and then superpose them to make a circular wave. We show that the circular wave can be used to improve SNR in the real-time 3D ultrasonic imaging as well as the synthetic focusing through computer simulation and experiments.

데이퍼형 마이크로 스트립 선로에서 분산과 반사가 펄스의 왜곡에 미치는 영향 (An effects of the Pulse Distortion due to Dispersion and Reflection on Tapered Microstrip Line)

  • 김기래
    • 대한전자공학회:학술대회논문집
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    • 대한전자공학회 2000년도 하계종합학술대회 논문집(1)
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    • pp.271-274
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    • 2000
  • In this paper, the distortion of an electrical pulse with rise/fall time resulting from dispersion and reflection as it propagates along a tapered microstrip line is investigated, and the delay time and distortion rate with respect to input and load impedances are analyzed on triangular and exponential tapered lines and analyzed the influence of the reflection and frequency dispersion on the distorted voltage wave in the tapered lines. The observed overshoot in front of the distorted wave is caused due to the frequency dispersion and the sustained tail of that comes from the reflection in the tapered line.

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Distortion Compensation of Reconstructed Hologram Image in Digital Holographic Display Based on Viewing Window

  • Park, Minsik;Kim, Hyun-Eui;Choo, Hyon-Gon;Kim, Jinwoong;Park, Cheong Hee
    • ETRI Journal
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    • 제39권4호
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    • pp.480-492
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    • 2017
  • A holographic display based on a viewing window enables the converging of a reconstruction wave into a viewing window by means of an optical system. Accordingly, a user can observe a reconstructed hologram image, even with a small diffraction angle. It is very difficult to manufacture an optical system with no aberrations; thus, it is inevitable that a certain amount of wave aberrations will exist. A viewing-window-based holographic display, therefore, always includes distortions in an image reconstructed from a hologram pattern. Compensating the distortions of a reconstructed image is a very important technical issue because it can dramatically improve the performance when reconstructing a digital three-dimensional content image from a hologram pattern. We therefore propose a method for suppressing image distortion by measuring and compensating the wave aberration calculated from a Zernike polynomial, which can represent arbitrary wave aberrations. Through our experimental configuration using only numerical calculations, our proposed method decreased the reconstructed image distortion by more than 28%.

전자현미경의 이미지 향상을 위한 주사시스템의 안정성 (Scanning System Stability for Improving SEM Image)

  • 김승재;김동환
    • 한국생산제조학회지
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    • 제18권5호
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    • pp.455-461
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    • 2009
  • In a scanning electron microscopy, image distortion is a critical issue and it is needed to be eliminated by some kinds of schemes. In this work, scanning frequency and scanning wave form are adjusted to have an improved image. The relationship between scan coil and its driver is investigated and appropriate frequency and wave form are suggested. It is proved that the selected frequency and wave form showed an enhanced image with less distortion, which were done by experiments. In addition, a noise elimination is addressed, providing improved image with a GROUND signal integration with the amplifier and the scan driver.

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연료액적의 Air-Assisted Breakup에 대한 수치해석적 연구 (A Numerical Study on Air-Assisted Breakup of Fuel Droplets)

  • 황상순
    • 한국분무공학회지
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    • 제1권2호
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    • pp.57-65
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    • 1996
  • Breakup models are evaluated using the experimental drop trajectory ill this study. The experimental conditions corespond to Weber # 56, 260, 463. Computations are carried out using a modified KIVA-II program with 2 different breakup submodel(TAB and Wave breakup model) and dynamic drag model which the drag coefficient changes dynamically with distortion parameter. Results show that computation with wave breakup model represents the experimental drop trajectory better than that with TAB submodel. And result with wave breakup model shows similar breakup pattern to experimental breakup process. It is thought that in wave breakup model the small drops are shed from the parent drop throughout parcel lifetime such thai this modelling represents the real breakup process well.

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환경조건의 변화에 따른 EPDM 애자의 표면 오손정도의 진단기술 (Diagnosis Technique of Surface Contamination Degree for EPDM Insulator according to Variation of Environment Condition)

  • 박재준;최인혁;김정부
    • 한국전기전자재료학회논문지
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    • 제17권10호
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    • pp.1132-1141
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    • 2004
  • The waveforms of the leakage currents for the surface discharge according to the degree of salt contamination and the variation of environmental condition on the EPDM polymer insulators, were shown in this paper. The variation phenomena of fundamental wave, 3rd and 5th harmonic waveforms were also shown from the beginning of the applied voltage and to the flashover voltage. To develop the technique of percentage contamination degree of EPDM polymer insulator according to the variation of environmental condition, the distortion degree of 3rd and 5th harmonic wave to the fundamental wave was utilized through the spectrum analysis for the waveforms of leakage current in the simulation of salt and fog test. The fact that distortion degree % of 3rd and 5th harmonics for fundamental wave is a necessary indicator for the assessment of contamination degree for the polymer insulators, was known.

Discrimination of Arcing Faults from Normal Distribution Disturbances by Wave form Distortion Analysis

  • Kim, C. J.
    • Journal of Electrical Engineering and information Science
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    • 제1권2호
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    • pp.52-57
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    • 1996
  • Detection of arcing high impedance faults has been a perplexing in the power distribution protection. Transient analysis of distribution disturbances for fault discrimination from other normal events is important for a secure protection of the power system. A simple parameter of wave form distortion quantification is used to analyze the behaviors of arcing faults and normal distribution disturbances. Theoretical perspectives of the transients were studied and actual disturbances were examined. From this investigation, a discrimination guideline based on the revised crest factor is developed. The discrimination method has a high potential to enhance the reliability and security for the distribution system protection.

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비선형 왜곡법을 이용한 악기음의 합성 (Musical Tone Synthesis using Nonlinear Distortion Method)

  • 이덕수;성굉모
    • 한국음향학회지
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    • 제8권5호
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    • pp.33-50
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    • 1989
  • 본 논문에서는 비선헝 왜곡법을 사용하여 악기음을 합성하였다. 비선형 왜곡법은 기본적으로 하나의 정현파 발생기와 이에 의해 발생된 정현파에 인위적인 왜곡을 일으키는 증폭기로 구성된다. 출력파는 비선형 증폭기의 전달함수, 즉 파형 형성 항수를 변화시킴으로써 제어되는 배음을 갖는다. 파형 형성 함수는 녹음된 악기음을 분석하여 얻어진 각 부분음 크기를 바탕으로 체비세프 다항식을 이용하여 얻어진다. 합성 시스템은 IBM-PC에서 수행되는 프로그램이며, 합성 결과는 파형과 스펙트럼 분석기에 의한 스펙트럼으로 보였다. 또한 합성 결과의 검증을 위해 전문가를 대상으로 시청 테스트를 수행하여, 합성음의 만족도를 평가하였다.

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직관내를 전파하는 압축파의 감쇠와 변형에 관한 수치해석적 연구 (Numerical study on attenuation and distortion of compression wave propagation into a straight tube)

  • 김희동
    • 대한기계학회논문집B
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    • 제20권7호
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    • pp.2315-2325
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    • 1996
  • A compression wave is attenuated or distorted as it propagates in a tube. The present study investigated the propagation characteristics of the compression waves which are generated by a train in a high-speed railway tunnel. A Total Variation Diminishing (TVD) difference scheme was applied to one-dimensional, unsteady viscous compressible flow. The numerical calculation involved the effects of wall friction, heat transfer and energy loss due to the friction heat in the boundary layer behind the propagating compression wave, and compared with the measurement results of a shock tube and a real tunnel. The present results show that attenuation of the compression wave in turbulent boundary layer is stronger than in laminar boundary layer, but nonlinear effect of the compression wave is greater in the laminar boundary layer. The energy loss due to the frictional heat had not influence on attenuation and distortion of the propagating compression waves.

공중교환전화망 (PSTN)에 의한 데이터 전송에 있어서의 군지정 #곡에 관한 연구 (Study on Group Delay Distortion in Data transmission by Means of Public Switching Telephone Network (PSTN))

  • 조규심;박규태
    • 대한전자공학회논문지
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    • 제21권4호
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    • pp.24-30
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    • 1984
  • 군지연왜곡(상위왜곡)은 음성전송의 입장에서는 그다지 문제가 되지 않는 특성이다. 그러나 기존의 공중교환전화망(음성대역전송)을 통하여 데이터, FAX 등의 파형전송을 하는 경우에는 데이터 신호를 왜곡시키는 최대의 요인이 되므로 이를 철저하게 검토하여야 한다. 본고는 기존의 공중교환전화망을 데이터전송에 개방하기 위하여 군지연왜곡에 관한 해석을 하고, 실험 및 측정결과를 기술하고 또 이 왜곡의 개선에 대해서도 언급한 것이다.

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