• Smart Structures and Systems
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• 제23권4호
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• pp.347-357
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• 2019

A new methodology for mitigation of the wheel squealing is proposed and investigated based on the dithering control. The idea can be applied in railway lines particularly in urban areas. The idea is clearly presented, and applied to a validated model. A full-scale model including the vehicle, curved track and wheel/rail contact is developed in the time domain to analyze the possibility and level of wheel squeal noise. Comparing the numerical results with a field test, the model is validated in different levels namely i) occurrence, ii) squealing frequency and iii) noise level. Two different approaches are proposed a) dithering of the wheel with piezoelectric patches and b) dithering of the rail with piezoelectric stacks. The noise level as well as the wheel responses is compared after applying the control strategy. A parametric study is carried out and effect of the dithering voltage and frequency on the squealing noise is investigated. It is found that both the strategies perform quite effectively within the saturating threshold of piezoelectric actuators.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 하계종합학술대회 논문집
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• pp.569-574
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• 1999

New methods for both color palette design and dithering based on human visual system (HVS) characteristics are proposed. Color quantization for palette design uses the relative visual sensitivity and spatial masking effect of HVS. The dithering operation for printing uses nonlinear quantization, which considers the overlapping phenomena among neighbor printing dots, and then a modified dot-diffusion algorithm is followed to compensate the degradation produced in the quantization process. The proposed techniques can produce high quality image in the low-bit color devices.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.559-559
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• 2012

We developed a new scheme for the highly sensitive near-field scanning optical microscope (NSOM) by using a dithering sample stage rather than a dithering probe. In the proposed scheme, the sample is directly loaded on one prong surface of a dithering bare tuning fork. Gap control between probe and sample is performed by detecting the shear force between an immobile fiber probe and the dithering sample. In a conventional NSOM, the Q factor drastically decreases from 7783 to 1000 or even to 100 by attaching a probe to the tuning fork. In our proposed NSOM, on the contrary, the Q factor does not change significantly, 7783 to 7480, when the sample is loaded directly to the tuning fork instead of attaching a probe. Consequently, the graphene sheets that cannot be observed by a conventional NSOM were clearly observed by the proposed method with sub-nanometer vertical resolution due to the extremely high Q factor.

• Journal of the Optical Society of Korea
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• 제15권4호
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• pp.362-367
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• 2011

Organic ($Alq_3$) film, which was coated on a donor plate, was transferred to an organic light emitting diode (OLED) substrate with help of heat generated by a dithering laser beam. The laser beam was diffracted in an acousto-optic modulator (AOM), then focused on the laser-to-heat converting layer of the donor plate; the focused spot followed trajectories guided by rotation of a Galvano-mirror. Three different functional waveforms, sine wave, square wave, and saw tooth wave were applied to the AOM as modulation signal to generate the dithering beam. The fluorescence microscope images of the donor plate showed that the patterns of removed $Alq_3$ film were affected considerably by the modulation waveforms and the phase difference between adjacent dithering beams. Further, the printed images of Alq3 film on the OLED substrate were different from the patterns of removed Alq3 film. Atomic force microscope images indicated that not only direct transfer but also deposition by sublimated vapor of Alq3 contributed to the pattern formation. Printed patterns affected considerably the electricity-to-light conversion characteristics of OLEDs. For uniform transfer, not only the phase relation of dithering beam lines but also adequate waveform were important.

• 한국광학회지
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• 제34권2호
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• pp.76-83
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• 2023

본 논문에서는 랜덤 디더링을 이용한 링레이저 자이로 주파수 잠김 깨짐 특성을 수치적 실험을 통해 분석한 결과를 나타내었다. 디더링 진폭잡음 크기에 따른 링레이저 자이로 주파수 잠김 특성 변화 관찰을 통해 주파수 잠김 깨짐을 유발하는 최소 진폭 잡음 크기를 분석할 수 있었다. 해당 결과는 평균 디더링 진폭에 상응하는 동적 주파수 잠김 크기 및 회전 각속도 입력에 대응하여 사냑 효과에 의해 발생하는 주파수 사이의 상대적인 차이와 밀접한 관련이 있음을 확인하였다.

• 한국정밀공학회지
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• 제26권8호
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• pp.7-13
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• 2009

• 대한전자공학회논문지SP
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• 제39권3호
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• pp.1-10
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• 2002

플라즈마 디스플레이에서는 역감마 보정으로 인한 표현 계조수의 감소 때문에 어두운 영역에서 의사윤곽이 발생하게 된다. 기존에는 이와 같은 문제를 해결하기 위해 주로 오차확산 방법이 사용되었다. 하지만, 오차확산 방법은 계산량이 많고, 많은 메모리 용량을 필요로 한다. 본 논문에서는 적은 계산량으로 어두운 영역에서의 계조 표현 성능을 향상시키기 위한 디더링 방법을 제안한다. 제안하는 방법에서는 표현 가능한 계조수 증가를 위하여 복수개의 디더링 마스크들을 프레임마다 번갈아 적용한다. 또한, 디더링 방법에서 발생하는 규칙적인 패턴을 감소시키기 위해 프레임별로 사용되는 디더링 마스크내의 문턱치의 위치를 변화시키도록 한다. 제안하는 방법은 기존의 오차확산 방법과 비교하여 상대적으로 적은 계산량과 메모리를 사용하면서도 시각적으로 유사한 계조 재현 성능을 나타낸다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(1)
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• pp.415-419
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• 2003

This paper focuses on a simple technique to reduced torque ripple in the direct torque control inverter for PMSM drive. It is actually impossible to raise the inverter switching frequency in the conventional system, although the hysterisis bandwidths for the stator flux and torque control are sufficiently diminished, because of the sampling Interval and the delay in estimating the flux and the torque In order to overcome the problem, the proposed method introduces a dithering technique into the conventional system by superposing triangular waves with high frequency and minute amplitude on the torque error. And the programable 3- stage lowpass filter is added instead of pure Integrator. Simulation results prove the feasibility of proposed strategy compared with conventional method.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 합동 추계학술대회 논문집 정보 및 제어부문
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• pp.581-584
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• 2002

In this study, an algorithm for dithering true color image to 8-bit indexded color image using Artificial Neural Network was proposed. An adaptive vector quantization algorithm based on Artificial neural network was proposed for dithering color images. To evaluate the proposed algorithm, Mean Square Error(MSE) and quality between original image and dithered image was compared to those of other algorithm. As a results, MSE of proposed algorithm was lower than that of other algorithm used in commercial application and quality of dithered image was also highly improved.

• 한국정보처리학회논문지
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• 제4권7호
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• pp.1893-1899
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• 1997

디더링이란 두가지의 밝기 해상도만을 이용하여 더 많은 밝기 해상도를 가진 영상을 표현하는 기술이다. 본 논문에서는 인접 화소에 오차를 대칭적으로 확산시키는 새로운 디더링 알고리듬을 제안하였다. 본 방법은 그래픽 영상에 대해서 오차 확산 디더링에서 발생하는 아티펙트 문제와 순서 디더링에서 특정 밝기의 재생이 어려운 문제점을 개선하였다. 본 방법을 그래픽 영상에 적용한 결과 기존 디더링 방법의 취약점을 개선함을 볼 수 있었다.