• The Journal of Korean Institute of Communications and Information Sciences
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• v.13 no.4
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• pp.302-308
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• 1988

The paper describes a very simple algorithm for reducing the encoding complexity of vector quantization(VQ), exploiting the feature of a vector currently being encoded. A proposed VQ of 16(=4x4) vector dimension shows a slight performance degradation of about 0.1-1.9dB, however, with only 16-32 among 256 codeword searches, i.e., with just 1/16-1/8 search complexity compared to a full-search VQ. And the proposed VQ scheme is also compared to outperform tree-search VQ with regard to their SNR performance and memory requirement.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2022.06a
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• pp.1286-1289
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• 2022

최근 영상 군집화 분야는 딥러닝 모델에게 Self-supervision을 주거나 unlabeled 영상에 유사-레이블을 주는 방식으로 연구되고 있다. 또한, 고차원 컬러 자연 영상에 대해 잘 압축된 특징 벡터를 추출하는 것은 군집화에 있어 중요한 기준이 된다. 본 연구에서는 자연 영상에 대한 Convolutional Auto Encoder의 특징 추출 성능을 평가하기 위해 설계한 실험 방법을 소개한다. 특히 모델의 특징 추출 능력을 순수하게 확인하기 위하여 Self-supervision 및 유사-레이블을 제공하지 않은 채 Naive한 모델의 결과를 분석할 것이다. 먼저 실험을 위해 설계된 4가지 비지도학습 모델의 복원 결과를 통해 모델별 학습 정도를 확인한다. 그리고 비지도 모델이 다량의 unlabeled 영상으로 학습되어도 더 적은 labeled 데이터로 학습된 지도학습 모델의 특징 추출 성능에 못 미침을 특징 벡터의 군집화 및 분류 실험 결과를 통해 확인한다. 또한, 지도학습 모델에 데이터셋 간 교차 학습을 수행하여 출력된 특징 벡터의 군집화 및 분류 성능도 확인한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.9
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• pp.927-938
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• 1992

In 1-D subband coding system, a quadrature mirror filter (QMF) pair can be used to split a signal into two subbands and to reconstruct the original signal. In this paper, a pair of 1-D reconstruction filter for the subband coding system is introduced and a coding technique with classified vector quantization, based on energy distributions, for 16 subband images is presented. As computer simulation results show that the method can give similar perceptual quality with bit rate reduced by $20{\sim}30%$ of that of ordinary vector quantization.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.2
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• pp.162-170
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• 2015

Commute time embedding involves computing the spectral decomposition of the graph Laplacian. It requires the computational burden proportional to $o(n^3)$, not suitable for large scale dataset. Many methods have been proposed to accelerate the computational time, which usually employ the Nystr${\ddot{o}}$m methods to approximate the spectral decomposition of the reduced graph Laplacian. They suffer from the lost of information by dint of sampling process. This paper proposes to reduce the errors by approximating the spectral decomposition of the graph Laplacian using that of the affinity matrix. However, this can not be applied as the data size increases, because it also requires spectral decomposition. Another method called approximate commute time embedding is implemented, which does not require spectral decomposition. The performance of the proposed algorithms is analyzed by computing the commute time on the patch graph.

• Proceedings of the KIPE Conference
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• 2013.11a
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• pp.39-40
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• 2013

본 논문에서는 직접토크 제어에서 자속과 토크의 오차에 따라 결정된 전압벡터와 회전자 위치에 따른 실제 인가될 수 있는 d-q축 전압을 근사 전압함수로 근사화하여, 자속 및 토크오차와 전동기의 속도에 따라 듀티비를 결정하는 방식을 제안한다. 이러한 방식은 선택된 전압벡터가 일정한 상수 크기의 전압을 인가하는 것으로 가정된 기존의 직접토크 제어 방식에 비해 정밀한 전압 기준을 바탕으로 펄스폭의 듀티비를 결정함으로써, 동일한 스위칭 주파수 내에서 토크 및 자속오차의 크기를 감소 시킬 수 있는 장점이 있다.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.6
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• pp.525-537
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• 2001

In this paper a new space vector RPPWM(Random Position PWM) is proposed. In the propsed RPPWM each of three phase pulses is located randomly in each switching interval. Based on the Space vector modulation technique the duty ratio of the pulses is calculated Along with the randomization of the PWM pulses. we can obtain the effects of spread spectra of votlage, current as in the case of randomly changed switching frequency, To verify the validity of the proposed RPPWM simulation study was tried using Matlab/Simulink The main model described in Simulink block diagrams includes the space vector modulation block pulse position randomization block inverter block 3 phase induction motor block and so on By the simulation study, the harmonics of the output voltage and the current of inverter are predicted in different PWM methods- SVPWM, LLPWM proposed RPPWM.

• Journal of Internet Computing and Services
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• v.6 no.4
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• pp.103-114
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• 2005

In this paper, we propose a new trnascoding method for improving picture's visual quality when frames are skipped. the proposed method utilizes the relationships of motion vectors between successive frames, and 4 motion vectors a macroblock are considered in transcoding. Since the proposed method does not require any decoding process of encoded bit stream, the computational complexity for estimating motion vectors can be eliminated. Experimental results illustrated that as transcoded frames are getting far from I pictures and as the degree of motions in video sequences are getting higher, the picture quality by using our proposed method shows better performances than existing schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.4
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• pp.761-771
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• 1994

This paper focuses on how spectrum information can be represented efficiently in a very low bit rate CELP speech coder. To achieve the goal, an LPC cepstral coefficients VQ scheme representing the spectrum information in a CELP coder is proposed. To represent the spectrum information using LPC cepstrums, three different cepstral distance measures having different spectral meanings in the frequency domain are considered, and their performances are compared and analyzed. The experimental results show that spectrum information in low bit rate CELP coders can be represented very efficiently using the proposed LPC cepstral vector quantization scheme.

• 전기의세계
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• v.36 no.9
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• pp.658-664
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• 1987

최적이득을 구하는 해석적인 방식으로 안정여유에 의한 최적화방식과 공액경사법에 의한 최적화방식을 살펴보았으며, 두방식을 비교해 보면 몇몇 문제점이 존재하나 다음의 몇가지 점에서 공액경사법에 의한 최적화방식이 더 우수하다는 것을 알 수 있다. 1) 제어루우프내의 제어기 수에 관계없이 이 방식을 쉽게 적용할 수 있다. 2) 시스템을 수식으로 모델링할 때 거의 간략화함이 없이 표현하므로 실제 시스템과의 오차를 줄일 수 있다. 3) 평가함수 내의 가중치를 조정하여 원하는 과도응답을 가지는 최적이득으로 유도할 수 있다. 공액경사법에 의한 최적화방식은 벡터제어나 전류제어PWM등 보다 복잡한 제어루우프에도 쉽게 적용시킬 수 있으며 직류기 및 서보전동기의 속도 및 위치 제어시스템에도 적용이 가능하다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.11
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• pp.6838-6844
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• 2014

3GPP LTE-Advanced systems adopt multiple antennas for high speed data transmission. In general, the receiver complexity of a spatially mutiplexed (SM) multiple-input multiple-output (MIMO) system grows in proportion to the number of candidate vectors. A large number of candidate vectors increases the reliability of the soft output values. The maximum likelihood (ML) signal detection with a large number of candidate vectors achieves high performance. On the other hand, low complexity receiver techniques with a small number of candidate vectors provide soft output values, such as low reliability. This paper addresses the improving reliability of the soft output obtained from a small number of candidate vectors. The improved performance of the proposed technique with the aid of computer simulations is reported.