• Journal of Institute of Convergence Technology
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• v.7 no.2
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• pp.25-30
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• 2017

This paper presents the effects of a virtual mass with a low-pass filter on the stability boundary of a virtual spring in the haptic system. In general, a haptic system consists of a haptic device, a sampler, a virtual impedance model and zero-order-hold. The virtual impedance is modeled as a virtual spring and a virtual mass. However the high-frequency noise due to the sampling time and the quantization error of sampled data may be generated when an acceleration is measured to compute the inertia force of the virtual mass. So a low-pass filter is needed to prevent the unstable behavior due to the high-frequency noise. A finite impulse response (FIR) filter is added to the measurement process of the acceleration and the effects on the haptic stability are simulated. According to the virtual mass with the FIR filter and the sampling time, the stability boundary of the virtual spring is analyzed through the simulation. The maximum available stiffness to guarantee the stable behavior is reduced, but simulation results still show that the stability boundary of the haptic system with the virtual mass is larger than that of the haptic system without the virtual mass.

• Journal of Institute of Convergence Technology
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• v.13 no.1
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• pp.29-34
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• 2023

This paper presents the effects of a virtual mass with a low-pass filter on stability boundaries of a virtual spring in the haptic system with first-order hold. A virtual mass is required to improve the realism of a virtual environment. However the second derivative of a displacement of a haptic device is needed while the inertia forces are computed, which causes the reflective force to change quickly and then makes the haptic system unstable. A low pass filter is added to resolve this problem and the stability region of a haptic system depends on the characteristics of the filter. In this paper the finite impulse response filter (FIR filter) is applied as one of low pass filters and the effect of the FIR filter on the stable region of a haptic system with first order hold is analyzed. When compared to stable region of the system without the FIR filter, the region of available virtual mass is increased by 20% and the maximum of the stable virtual spring is reduced by 32%, irrespective of the sampling time. Besides it is shown that the stable region of a virtual spring is proportional to the inverse square of the sampling period.

• Proceedings of the KIPE Conference
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• 2004.07a
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• pp.101-104
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• 2004

대체에너지 시스템에서 필수적인 계통연계형 인버터는 LC필터를 거친 정현전압 출력에 계통과 연계용 인덕터를 연결하여 사용하여 왔으나, 최근 들어 인버터와 계통을 LC필터 없이 인덕터로만 계통과 연결하여 직접 전류를 제어하는 형태가 적용되고 있다. 또한 출력에 절연 변압기를 사용하던 기존방식과 달리 변압기가 없는 비절연형 인버터는 전류제어를 통해 계통과 직접연결하고, 부피감소와 원가절감을 이룰 수 있다. 본 논문에서는 저주파 절연변압기가 없는 3kW급의 태양광 발전시스템 시제품을 소개하고 단상계통과 연계한 전류제어 알고리즘의 실험결과를 통해 순시전류제어의 타당성을 확인한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.603-606
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• 2001

의료영상 이미지에서 이상유무 등 진단능력을 향상시키기 위해 2D 웨이블릿 변환을 이용하여 그레이 이미지를 의사컬러로 향상하기 위한 연구이다. 웨이블릿 필터설계는 변환된 영상데이터의 블록킹을 줄이기 위해 차수가 높은 다우비치 8차 웨이블렛 함수을 사용하여 필터함수를 구성하였고, 저주파 성분과 고주파 성덕, 대역통과 성분으로 각각 분리하여 R, G, B 이미지의 성분으로 매핑하여 의사 컬러 이미지로 향상하였다. 의사컬러로 향상된 이미지는 그레이 이미지에 비해 결함 유무를 빠르게 구분할 수 있어 신속한 진단이 가능하고,. 웨이블릿 변환을 이용함으로서 기존의 주파수변환 기법에 비하여 변환과정을 간소화 할 수 있다.

• Journal of KIISE:Software and Applications
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• v.31 no.7
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• pp.901-910
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• 2004

In this paper, we propose a content-based MPEG transcoding method using a discontinuity feature in the Discrete Cosine Transform (DCT) domain. A DCT block is transcoded differently depending on the height of dominant discontinuity within a block. In the experiment, we show the result that the video quality of content-based transcoding is better than that of a constant cut-off method and the processing time of the adaptive method is much faster compared with the pixel domain methods in the same bandwidth.

• Journal of Biomedical Engineering Research
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• v.21 no.5
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• pp.495-503
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• 2000

스트레스 심전계에서 발생되는 근잡음을 제거하기 위하여 wavelet interpolation filter(WIF)를 설계하였다. WIF는 크게 웨이브렛 변환부와 보간법 적용부로 구성되어 있다. 웨이브렛 변환부는 Haar 웨이브렛을 이용하였으며 심전도 저주파 영역과 고주파 영역으로 분할하는 과정이다. 보간법 적용부에서는 분할되어진 신호 중 A3을 선택하여 신호의 재생 성능을 향상시키기 위하여 보간법을 적용하였다. WIF의 성능을 평가하기 위해서 신호대 잡음비, 재생신호 자승오차 및 표준편차의 파라미터를 이용하였다. 본 실험에서는 MIT/BIH 부정맥 데이터베이스, European ST-T 데이터베이스 및 삼각파형을 이용하여 성능 파라미터를 측정하였다. 결과적으로 WIF는 성능 파라미터에서 기존에 많이 사용되고 있는 평균값 필터, 중간값 필터 및 hard thresholding 방법에 비해 우수함을 알 수 있었다.

• Journal of IKEEE
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• v.3 no.2 s.5
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• pp.168-177
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• 1999

In this paper, we present a new interpolation scheme for image enhancement using fuzzy inference. In general, interpolation techniques are based on linear operators which are essentially lowpass filters, hence, they tend to blur fine details in the original image. In our approach, the operator itself balances the strength of its sharpening and noise suppressing components according to the Properties of the input image data.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.305-307
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• 2005

본 연구는 순수 국내기술로 개발된 국산화 전동차 광주도시철도 1호선의 추진제어 장치의 본선시운전에 관한 것으로, 외국기술에 의존해온 추진 제어장치를 국내기술로 설계하고 본선시운전을 통하여 추진제어장치의 신뢰성 및 안정성에 관하여 실험을 실시하였다. 그리고 추진제어 장치에 적용한 알고리즘은 필터 사이즈를 감소하기위하여 기존의 패턴에 의한 PWM방식을 사용치 않고, 출력전류의 고조파 리플이 적은 저주파 동기 공간벡터 PWM 알고리즘을 제안하고, 가선전압의 변동에 강인한 댐핑 제어 및 과전압 제한 제어 알고리즘을 제시하고, 제안된 알고리즘은 본선시운전을 통하여 타당함을 확인하였다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.78-81
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• 2004

As a society has Progressed rapidly toward a highly advanced digital information age, a multimedia communication service for acquisition, transmission and storage of image data as well as voice has being commercialized externally and internally. However, in the process of digitalization or transmission of data, noise is generated by several causes, and researches for eliminating those noises have been continued until now. The mean filter is useful method to remove AWGN (additive white gaussian noise) from degraded image and has excellent low-frequency properties. However, it brings about degradation of high-frequency properties in image. So in this paper we removed noise with mean filters added directional information and minimized degradation of high-frequency properties.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.1B
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• pp.89-98
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• 2000

This paper presents an active noise cancelling model using wavelet transform and subband filter banks based on adaptive filter. The analysis filter banks decompose input and error signals into QMF filter banks of lowpass and highpass bands. Each filter bank uses wavelet filter with dyadic tree structure. The decomposed input and error signals are iterated by adaptive filter coefficients of each subband using filtered-X LMS algorithm. The synthesis filter banks make output signal of wideband with perfect reconstruction to prepare adaptive filter output signals of each subband. The analysis and synthesis niter hants use conjugate quadrature filters for Pefect reconstruction. Also, The delayed LMS algorithm model for on-line identification of error path transfer characteristics is used gain and acoustic time delay factors. The proposed adaptive active noise cancelling modelis suggested by system retaining the computational and convergence speed advantage using wavelet subband filter banks.