• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.8
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• pp.1129-1136
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• 2010

Damper springs in a drive-line absorb the impulsive torque generated when a lock-up clutch is connected directly, instead of via a fluid coupling. Design optimization and finite element analysis were performed to improve the shock- and vibration-absorption capacity of the lock-up clutch. For this purpose, a multi-body dynamics model was developed by including the main parts of a vehicle, such as an engine with a clutch, a transmission, drive shafts and wheels, and a whole mass of a vehicle. The spring constants were selected so that resonance of a system could be avoided. Damper springs were optimized on the basis of the spring constants, impulsive torques, compressed angles, spring counts, fatigue constraints, etc. Topology optimization was performed for three plates with the damper springs. The compliance was set up as an objective function, and volume fraction was fixed below 0.3. A new shape for the plates was proposed on the basis of the topology result.

• The KIPS Transactions:PartB
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• v.17B no.1
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• pp.31-36
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• 2010

After the launch of MPEG-2, it is widely used in multimedia applications like a Digital-TV or a DVD. Then, After the launch of H.264 at 2004, it has been expected to replace MPEG-2 and services IPTV and DMB. As we have been used to MPEG-2 devices by this time, we can not access H.264 Broadcast with MPEG-2 device. So We propose a new approach to transcode H.264 video into MPEG-2 form which can facilitate to display H.264 video with MPEG-2 device. To reduce the quality loss by transcoding, we use CPDT(Cascaded Pixel Domain Transcoder) structure. And to minimize processing time, SKIP block, INTRA block and motion vectors obtain from decoding process is employed for transcoding. we use BMA(Boundary Matching Algorithm) to select only one from candidate motion vectors. Experimental results show a considerable improved PSNR with reduction in processing time compared with existing methods.

• Journal of Broadcast Engineering
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• v.25 no.2
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• pp.252-264
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• 2020

Korea has launched the world-wide first terrestrial UHD broadcast services on May 31, 2017. While the existing HDTV broadcast services use MPEG-2 TS (Tranport Stream) standard for multiplexing and delivering compressed media with additional data, the terrestrial UHD broadcast services use MMT (MPEG Media Transport) standard, which is the next-generation standard beyond MPEG-2 TS. However, the production cost of UHD contents is so high that only a part of the total broadcast time is filled with UHD contents and the UHD time portion is planned to be gradually increased. On the other hand, the ATSC 3.0 standard that uses MMT is not yet used in full-fledged broadcast services in North America. Hence MMT broadcast equipment is still at an early stage with high prices. In this paper we implemented a multi-thread software running on an ordinary PC that can be utilized to realize a low-cost converter that converts the output of an existing MPEG-2 TS multiplexer to an MMTP (MMT Protocol) packet stream. We also verified the functionality of the software through experiments.

• The Transactions of the Korea Information Processing Society
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• v.4 no.12
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• pp.3185-3199
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• 1997

This paper suggests techniques to reduce coding time which is a problem in traditional fractal compression and to improve fidelity of reconstructed images by determining fractal coefficient through adaptive selection of block approximation formula. First, to reduce coding time, we construct a linear list of domain blocks of which characteristics is given by their luminance and variance and then we control block searching time according to the first permissible threshold value. Next, when employing three-level block partition, if a range block of minimum partition level cannot find a domain block which has a satisfying approximation error, we choose new approximation coefficients using a non-linear approximation of luminance term. This boosts the fidelity. Our experiment employing the above methods shows enhancement in the coding time more than two times over traditional coding methods and shows improvement in PSNR value by about 1-3dB at the same com- pression rate.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.5
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• pp.42-47
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• 2017

In the distribution of digital image, the median filtering is used for a forgery. This paper proposed the algorithm of a image forensics detection for the classification of median filtering. For the solution of this grave problem, the feature vector is composed of 42-Dim. The detected quantity 32, 64 and 128 of forgery image edges, respectively, which are processed by the Hough transform, then it extracted from the start-end point coordinates of the Hough Lines. Also, the Hough Peaks of the Angle-Distance plane are extracted. Subsequently, both of the feature vectors are composed of the proposed scheme. The defined 42-Dim. feature vector is trained in SVM (Support Vector Machine) classifier for the MF classification of the forged images. The experimental results of the proposed MF detection algorithm is compared between the 10-Dim. MFR and the 686-Dim. SPAM. It confirmed that the MF forensic classification ratio of the evaluated performance is 99% above with the whole test image types: the unaltered, the average filtering ($3{\times}3$), the JPEG (QF=90 and 70)) compression, the Gaussian filtered ($3{\times}3$ and $5{\times}5$) images, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.9C
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• pp.697-703
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• 2008

The H.264/AVC video coding standard provides higher coding efnciency compared to the conventional MPEG-2 standard. Since a lot of videos have been encoded using MPEG-2, the format conversion from MPEG-2 to H.264 is essential. In this paper, we propose an efficient method for the conversion of DCT coefficients to H.264/AVC transform coefficients. This conversion is essential, since $8{\times}8$ DCT and $4{\times}4$ integer transform are used in MPEG-2 and H.264/AVC, respectively. The mathematical analysis and computer simulation show that the computational complexity of the proposed algorithm is reduced compared to the conventional algorithm, while the loss caused by the conversion is negligible.

• Journal of the Institute of Convergence Signal Processing
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• v.9 no.1
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• pp.10-17
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• 2008

The purpose of this thesis is to reduce of error for source location through acoustic emission(AE) signal, generated elastic wave from crack growth to leak for facility diagnosis. Especially, in order to overcome noise from original signal, this paper proposed enhancement of source location by using noise reduction based on wavelet transform. To evaluate actual performance in experiments, Pencil Lead Break is used crack signal source on the aluminum plate and drain valve of air compressor is used as substitute pressure vessel to generate leak signal. In signal processing, wavelet shrinkage and soft threshold are used to discriminate signal source and then source location techniques have been effectively used with group velocity using material property and time difference between sensor using cross correlation. Source location for crack and leak test have some difference, but the result show that improved 30% with a average length within 10.46mm in crack test and improved 2% compare with average filter in leak test when we applied wavelet transform.

• 한국신재생에너지학회:학술대회논문집
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• 2005.11a
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• pp.363-372
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• 2005

최근 고유가상황 및 에너지소비가 증대되는 사회적 분위기와 환경적 변화에 힘입어 대체에너지기술개발에 대한 절실한 대책마련이 중요시 되고있다. 기후변화협약의 발효로 환경에너지에 대한 새로운 인식의 필요로 에너지체제의 변환이 촉구되어지고 있으며 이에 따른 환경친화적 에너지자원을 이용한 신 재생에너지개발에 대한 연구개발기술이 관심을 받고 있다. 현재 사용중인 화석연료는 환경오염 및 지구의 온난화 현상 등 심각한 공해문제를 야기시키고 있는 반면에 태양에너지와 같은 청정에너지의 개발은 환경오염방지와 친환경에너지자원의 활용이라는 점에서 관심이 대상이 되고 있고 특히, 우리나라의 경우 에너지수입 의존율이 97%로 높은 상황에서 국가에너지대책을 수립하고 해외수입에너지 의존율을 최소화시키기 위하여 가히 필수적인 상황이다. 따라서, 본 실증연구사업(태양열 이용 Hybrid냉난방시스템 실증연구)은 태양열 집열기에서 생산된 저온의 $20\sim30^{\circ}C$의 승온된 양질의 열원을 히트펌프 증발기 열원으로 이용 히트펌프의 압축동력이 상대적으로 작아져 기존 히트펌프 시스템에서의 성적계수(COP)를 높여 주는 효과를 기대할 수 있고, 특히 하절기 복사량이 많은 시기에는 $50\sim60^{\circ}C$ 정도로 승온되어진 중 고온수를 직접 온수탱크로 이동시켜 필요수요처에 공급함으로써 이에 따른 에너지절감효과를 기대할 수 있다. 구축된 태양열 이용 하이브리드(Hybrid)냉난방시스템은 계절별, 설비별 특성을 적절히 활용하여 연평균 집열기 효율은 70%수준으로 유지하면서, 계절별 성적계수는 '4'수준을 목표로 하여 추진되었으며, 그간, 태양열 이용 보급분야의 실용화는 주로 건물의 급탕용 온수생산의 수준에 머물렀으나 이 단계를 극복한 건물의 냉 난방 및 급탕을 위한 태양열 및 공기열원을 활용한 하이브리드(Hybrid)냉난방 시스템 구축하였다. 아울러, 태양열 이용 하이브리드 냉난방 히트펌프 시스템 실증 실험은 유가상승과 신재생에너지에 대한 국가적 분위기 고취로 어느때 보다도 개발기술의 상용화 및 실용화적 측면의 염두와 태양열 이용 Hybrid냉난방 시스템의 효율향상과 저가화를 통해 기술의 경제성과 신뢰성을 확보하여 태양열 이용 시스템의 보급활성화를 목표로 하고 있다.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.6
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• pp.109-118
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• 1998

This paper presents an ASIC implementation of video encoder which converts either digital RGB or YCbCr to S-video(Y/C) and composite video signal. The video timing signal of this encoder includes horizontal sync., vertical sync. signal and blanking, and this encoder supports field identification signal which is convenient for video editing. The encoder has been designed in the 4 stages pipeline structure to assure the stable operation of each submodule. The proposed encoder requires only 20K gates ,which is a 40% reduction in hardware compared with [13]. The designed encoder was fabricated in $0.65{\mu}m$ SOG triple metal CMOS technology. Chip size is $3.7478mm {\times} 4.4678mm$ including PAD, gate counts is 19,468 and dissipated power is 0.9W.

• Journal of the Korea Society of Computer and Information
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• v.10 no.3 s.35
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• pp.151-159
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• 2005

Traditional watermarking technologies are symmetric method which embedding and detection keys are same. Although the symmetric watermarking method is easy to detect the watermark, this method has weakness against to malicious attacks to remove or modify the watermark information when the symmetric key is disclosure. Recently, the asymmetric watermarking method that has different keys to embed and detect is watched several researchers as a next generation watermarking technology. In this paper, we have expanded search space of secret key using the solution set of linear simultaneous equations. Secret key is generated by secure linear transformation method to prevent of guessing secret key from public key, and the correlation value between secret key and public key is high. At theresults, the multi bits information can be embedded and high correlation value was detected after JPEG compression.