• Journal of Energy Engineering
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• v.9 no.2
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• pp.138-145
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• 2000

고체재료의 열확산계수나 열전도계수와 같은 열물성을 비접촉식 방법으로 측정하기 위하여 광열변위법에 대한 이론적인 해석을 수행하였다. 가열빔의 파형을 코사인파, 삼각파 그리고 사각파로 가정하여 2차원 열전도 방정식과 열탄성 방정식의 엄밀해를 구하였고, 이를 가열빔으로부터 직접 구한 실제파의 결과와 비교하였다. 코사인파의 결과가 다른 파형에 비하여 실제파와 가장 유사한 것으로 보아 비교적 해석이 복잡한 실제파를 코사인파로 가정하여도 무방하다.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.1251-1254
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• 1998

본 논문에서는 최근들어 널리 연구되고 있는 다해상도 신호해석 방법인 웨이브렛 변환, 웨이브렛 패킷, 그리고 코사인 패킷 알고리듬을 음성개선에 이용하여 각각의 성능을 비교하였으며, 또한 이를 기존의 스펙트럼차감법의 성능과 비교 분석 하였다. 성능비교의 척도로는 SNR과 ㅋ스트랄 거리를 이용하였다. 실험결과 SNR면에서는 코사인 패킷이 가장 좋은 결과를 보였다. 그리고 ㅋ스트랄 거리의 경우 코사인 패킷과 웨이브렛 패켓이 훨씬 나은 결과를 보였으며 주관적인 청취결과 역시 코사인 패킷이 가장 좋은 결과를 보였고, 기존의 스펙트럼 차감법은 musical noise의 영향으로 인해 상대적으로 다른 방식에 비해 합성음의 음질이 많이 떨어짐을 확인할 수 있었다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.5
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• pp.409-415
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• 2013

In this paper, we propose a correlation function using newly designed local signals for cosine-phased binary offset carrier (BOC) signal tracking. First, we divide a sub-carrier pulse over one pseudo random noise code period into multiple rectangular pulses, and subsequently, design novel local signals. Then, we obtain a correlation function with no side-peak based on a combination of correlations between the newly generated local signals and received cosine-phased BOC signal. From numerical results, it is confirmed that the proposed correlation function provides a tracking performance improvement over the conventional correlation functions in terms of the tracking error standard deviation.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.45 no.6
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• pp.88-94
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• 2008

A DCT-based energy-ratio measure for autofocus in digital camera is proposed in this paper. This measure, namely AC2DC1 and AC5DC1, determines the sharpness of an image using a ratio between AC and DC energy in the DCT domain. This method is derived from energy analysis of DCT coefficients. Autofocus score calculation method is used to assess the performance of the proposed measure and to compare it with other measures. Experimental results under various conditions verify the robustness of the proposed focus measure for the Gaussian as well as impulsive noises.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.05c
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• pp.2073-2076
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• 2003

본 논문에서는 이산코사인변환의 선형성을 이용하여 정지화상의 위변조를 방지하기 위한 semi-fragile 워터마킹 방법을 제안하였다. 제안한 방법에서는 이산코사인변환의 선형특성을 이용하여 공간영역에서 임의의 DCT 계수를 변형시킬 수 있으므로 이산코사인변환을 행하지 않고도 워터마킹 정보를 삽입할 수 있으므로 빠른 워터마킹 삽입이 가능하다 또한 정해진 DCT 계수에만 워터마킹 정보를 삽입할 수 있으므로 비가시성의 향상을 가져올 수 있다. 제안한 방법이 압축에 강인함을 실험을 통하여 입증하였다.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.7
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• pp.134-135
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• 1999

This paper presents a speech enhancement method with spectral subtraction using wavelet, wavelet packet and cosine packet transforms which are known as multiresolutional signal analysis method. The performance of each method is compared with the conventional spectral subtraction method. Performance assessments based on average SNR, cepstral distance and informal subjective listening test are carried out. Experimental result demonstrate that cosine packet shows the best result in objective performance measure as well as subjective shows less musical noise than the conventional spectral subtraction method after removing the noise components.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.10 no.3
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• pp.130-134
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• 1985

In two-dimensional discrete cosine transform(DCT) coding, the measurements of the distributions of the transform coefficients are important because a better approximation yields a smaller mean square distorition. This paper presents the results of distribution tests which indicate that the statistics of the AC coefficients are well approximated to a generalized Gaussian distribution whose shape parameter is 0.6. Furthermore, from a simulation of the DCT coding, it was shown that the above approximation yields a higher experimental SNR and a better agreement between theory and simulation than the Gaussian or Laplacian assumptions.

• Proceedings of the Korea Information Processing Society Conference
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• 2020.05a
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• pp.165-168
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• 2020

사용자 행위 기반 인증 기술은 다른 인증 기술들에 비해서 인증의 인식률을 높이는데 많은 데이터의 장기간 추출이 필요하다. 본 논문은 터치 센서와 자이로스코프를 이용하여 그동안의 행위 기반 인증 연구에서 사용 되었던 행위 특정 데이터들 중에서 핵심적인 최소한의 데이터들만을 사용하였다. 측정한 데이터들의 검증에는 그간 사용자 행위 기반 인증 연구에서 이용되지 않고 문서 검색의 유사도 측정에 사용되었던 코사인 유사도를 사용하였다. 이를 통해 최소한의 특정 데이터와 기준이 되는 데이터의 코사인 유사도 비교 검증만을 통해서도 인증 범위에 적용되는 임계값을 조절하는 방식을 동해서 최초 EER 37.637%에서 최종 EER 1.897%의 높은 검증 성능을 증명하는데 성공하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.4
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• pp.727-736
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• 2009

In this paper, the $arccos(cos^{-1})$ arithmetic unit for mobile graphics accelerator is designed. The mobile vector graphics applications need tight area, execution time, power dissipation, and accuracy constraints compared to desktop PC applications. The designed processor adopts 2nd-order polynomial approximation scheme based on IEEE floating point data format to satisfy speed and accuracy conditions and reduces area via hardware sharing structure. The arccosine processor consists of 15,280 gates and its estimated operating frequency is about 125Mhz at operating condition of $0.35{\mu}m$ CMOS technology. Because the processor can execute arccosine function within 7 clock cycles, it has about 17 MOPS(million arccos operations per second) execution rate and can be applicable to mobile OpenVG processor. And because of its flexible architecture, it can be applicable to the various transcendental functions such as exponential, trigonometric and logarithmic functions via replacement of ROM and minor hardware modification.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.4
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• pp.17-22
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• 2020

Behavior-based authentication technology, which is currently being researched a lot, requires a long extraction of a lot of data to increase the recognition rate of authentication compared to other authentication technologies. This paper uses the touch sensor and the gyroscope embedded in the smartphone in the Android environment to measure five times to the user to use only the minimum data that is essential among the behavior feature data used in the behavior-based authentication study. By requesting, a total of six behavior feature data were collected by touching the five touch screen, and the mean value was calculated from the changes in data during the next touch measurement to measure the cosine similarity between the value and the measured value. After generating the allowable range of cosine similarity by performing, we propose a user behavior based authentication method that compares the cosine similarity value of the authentication attempt data. Through this paper, we succeeded in demonstrating high performance from the first EER of 37.6% to the final EER of 1.9% by adjusting the threshold applied to the cosine similarity authentication range even in a small number of feature data and experimenter environments.