• The Journal of the Acoustical Society of Korea
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• v.19 no.2
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• pp.13-18
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• 2000

This paper presents the result of a technique to enhance TDAC in the AC-3 algorithm. To reduce block boundary noise without decreasing the performance of transform coding, We propose new special windows which improve the defect of the AC-3 algorithm that could not properly cancel aliasing in the transient period. In addition, a fast MDCT calculation algorithm based on a fast Fourier transform, is adopted.

• Proceedings of the IEEK Conference
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• 2003.11a
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• pp.497-500
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• 2003

In this paper, a new filter structure to improve frequency response characteristics in CIC(Cascaded Integrator-Comb) decimation filters is proposed. Conventional filters improve passband characteristics, but they make worse slinging band characteristics. In this paper, we propose a new filter which is called IFOP(Interpolated Fourth-Order Polynomials). By using this proposed filter, passband droop and aliasing band attenuation are simultaneously improved. Since proposed filter needs only one multiplication computation is not much. And overall linear phase characteristics are maintained since the proposed filter is also linear phase. Finally, implementation cost of the proposed filter is compared with those of conventional filters.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.7
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• pp.984-994
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• 2003

The suitability of high-order accurate, centered and upwind-biased compact difference schemes for large eddy simulation is evaluated by a spectral, static error analysis. To investigate the effect of numerical dissipation on LES solutions, power spectra of discretization errors are evaluated for isotropic turbulence models in both continuous and discrete wavevector spaces. Contrary to the common belief, the aliasing errors from upwind-biased schemes are larger than those from comparable non-dissipative schemes. However, this result is the direct consequence of the definition of the power spectral density of the aliasing error, which poses the limitation of the static error analysis for upwind schemes.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.7
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• pp.973-983
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• 2003

The suitability of high-order accurate, centered and upwind-biased compact difference schemes is evaluated for large eddy simulation of turbulent flow. Two turbulent flows are considered: turbulent channel flow at Re = 23000 and flow over a circular cylinder at Re = 3900. The effects of numerical dissipation on the finite differencing and aliasing errors and the subgrid-scale stress are investigated. It is shown through the simulations that compact upwind schemes are not suitable for LES, whereas the fourth order-compact centered scheme is a good candidate for LES provided that proper dealiasing of nonlinear terms is performed. The classical issue on the aliasing error and the treatment of nonlinear terms is revisited with compact difference schemes.

• Proceedings of the KOSOMBE Conference
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• v.1998 no.11
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• pp.213-214
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• 1998

The important role of the ultrasonic Doppler system in the modem clinical medicine is to provide the clinical information of the vascular system. The ultrasonic pulsed wave(PW) Doppler system, a kind of the ultrasound Doppler system, is more available than the ultrasonic continuous wave(CW) Doppler system because it can evaluate the velocity and the direction of blood flow as well as the depth of vessel. However, the ultrasonic PW Doppler system has the disadvantage that the range of evaluating velocity of blood flow is limited(Nyquist limit). In order to solve this limit, we propose the algorithm for eliminating this aliasing in this paper. In addition, we propose the efficient signal processing algorithm.

• Proceedings of the KIEE Conference
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• 1990.07a
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• pp.529-531
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• 1990

Because Filters do both the sampling or Sampled-and-Hold(S/H) operations, it result in the replication of the spectrum of input signal and (unless Nyquist's criterion is satisfied) induce aliasing distortion. In this paper, therefore, we designed AAF(Analog Anti-aliasing Filers) so as to remove high-frequency components from input signal for aliasing distortion prevention before input signal had been processed frequency seletion by filters. and then, researched characteristics of it.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.104-105
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• 2017

본 논문에서는 전동기를 구동하는 인버터 출력단에 있는 LC필터의 공진현상을 피하기 위한 능동감쇠 방법을 제안하였다. 기존의 방법들은 추가적인 센서 혹은 복잡한 신호처리를 필요로 한다. 이에 비해 제안된 방법은 기존의 방법과 달리 샘플링 주파수를 변경하여 추가적인 제어 없이 공진 문제를 해결한다. 제어 시스템이 특정한 조건을 만족하는 경우, 샘플링 주파수를 공진 주파수와 일치시켜 공진 전류를 Aliasing된 형태의 저주파수 성분으로 계측한 후, 이를 통해 시스템의 안정성을 확보하여 공진현상을 억제한다. 이산 시간(discrete-time)에서의 모델링을 통해 제안된 방법의 안정성 여부를 확인하였고, 최종적으로 실험을 통해 제안된 능동감쇠 방법의 유효성을 검증하였다.

• Journal of Broadcast Engineering
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• v.14 no.5
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• pp.638-649
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• 2009

Image resizing (or scaling) is one of the most essential issues for the success of visual service because image data has to be adapted to the variety of display features. For 2D imaging, the image scaling is generally accomplished by 2D image re-sampling (i.e., up-/down-sampling). However, when it comes to stereoscopic 3D images, 2D re-sampling methods are inadequate because additional consideration on the third dimension of depth is not incorporated. Practically, stereoscopic 3D image scaling is process with left/right images, not stereoscopic 3D image itself, because the left/right Images are only tangible data. In this paper, we analyze stereoscopic 3D image scaling from two aspects: geometrical deformation and frequency-domain aliasing. A number of 3D displays are available in the market and they have various screen dimensions. As we have more varieties of the displays, efficient stereoscopic 3D image scaling is becoming more emphasized. We present the recommendations for the 3D scaling from the geometric analysis and propose a disparity-adaptive filter for anti-aliasing which could occur during the image scaling process.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.12
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• pp.98-105
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• 1997

Image transformation ahs been widely used in compuater graphics, computer vision, robot vision, and image processing. Image rotation is one of important part of image transformation. In image rotation, a two-pass algorithm has many advantages over a one-pass algorithm in high speed computation. This paper presents a new two-pass algorithm that overcomes the limitations of previously reported effect of interpolation. A brief comparison of existent techniques and the twp-pass algorithm newly suggeste is presented. This paper also present the hardware structure for the two-pass algorithm suggested.

• Journal of the Korea Convergence Society
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• v.11 no.11
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• pp.89-94
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• 2020

This paper proposes a better shielding method to over sampling technique. The new method uses aluminum foil for RF shielding. As a result of the phantom test, when the over-sampling technique was applied, the aliasing artifact was reduced by about 94% compared to before the application, and the case where the aluminum shielding band was applied was also reduced by about 92% compared to before application. In addition, the scan time also increased by more than 3 times in the case of the over-sampling technique, while it was found that there was no change from before the application of the aluminum shielding band Therefore, it was confirmed that the shielding band using aluminum foil can effectively remove aliasing artifacts without increasing the scan time..