• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 2011.07a
• /
• pp.177-179
• /
• 2011

최근 표준화가 진행되고 있는 HEVC는 H.264/AVC의 기본 구조를 유지하면서 각 부호화기의 성능을 향상시키는 방향으로 진행되고 있다. 기존의 H.264/AVC는 화면 간 예측에서 예측 정보를 보내지 않고 복호화가 가능한 SKIP 모드와 예측 정보를 보내주는 화면 간 예측 모드들을 사용한다. 그런데 SKIP 모드는 율-왜곡 측면에서 극단적인 특성을 갖기 때문에 SKIP 모드와 다른 화면 간 예측 모드들 사이에 넓은 율-왜곡 파라미터 간격이 존재하며, 이는 화질 저하의 원인이 된다. 본 논문에서는 HEVC에서도 동일한 문제점이 존재하는지 분석하기 위해 SKIP 모드와 화면 간 예측 모드들의 율-왜곡 파라미터에 대한 분석을 수행하였다. 분석 결과를 바탕으로 HEVC에서도 부호화 효율을 향상시키기 위하여 새로운 화면 간 예측 모드가 필요함을 보였다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 2011.07a
• /
• pp.475-478
• /
• 2011

율-왜곡 최적화 기법을 통한 화면내 예측 모드 결정 방법은 부호화 효율이 높지만 복잡도가 크다. 본 논문에서는 H.264/AVC의 율-왜곡 값의 특성을 분석하여 율-왜곡 최적화 기법에 사용되는 예측 모드의 후보를 줄임으로써 보다 빠른 휘도 화면내 $4{\times}4$ 예측 모드 결정 방법을 제안한다. 제안된 방법은 균일한 차분 블록값을 가지는 예측 모드와 균일하지 않은 차분 블록값을 가지는 예측 모드의 통계적 분석을 통해 부호화 속도를 향상시킨다. H.264/AVC의 참조 소프트웨어 JM 14.2와 비교하여 0.04[dB]라는 무시할 수 있는 PSNR의 손실을 가지면서도 0.3[%]의 비트율 절약과 19.6[%]의 부호화 속도 향상을 가져왔다.

• Journal of the Korean Magnetics Society
• /
• v.12 no.5
• /
• pp.163-167
• /
• 2002

In order to study the temperature dependence of the magnetostatic wave modes for an YIG thin film, grown by a liquid phase epitaxy method, The ferromagnetic resonance was performed by an FMR spectrometer in the temperature range -140$\^{C}$∼200$\^{C}$. The magnetostatic surface wave and backward volume wave modes show periodic excitations in parallel configuration. The resonance fields of all modes and intensities decreased with decreasing the temperature. All magnetostatic modes can be well explained by the Walker and Damon-Eshbach theory. The calculated saturation magnetization Ms of the YIG thin film was increased with decreasing the temperature. The line widths of magnetostatic modes changed in various trends with decreasing the temperature.

• Information Display
• /
• v.5 no.5
• /
• pp.10-12
• /
• 2004

우수한 화질특성을 나타내는 새로운 반투과형 액정모드를 개발했다. 단일 셀캡 구조에서 감마(Gamma) 보정없이 투과모드와 반사모드를 동시에 구동하기 위해 유기막을 이용하여 반사모드 영역의 액정 Cap을 두 가지로 분리하는 새로운 설계구조를 도입했다. 반사모드 영역의 액정 Cap을 순수한 액정 $Cap(C_{LC})$과 유기막 $Cap(C_{OL})$으로 분리함으로써 액정에 걸리는 실제 전압을 조절하게 되어 단일 셀캡 구조에서도 감마 보정없이 우수한 특성을 나타내는 반투과형 VA 액정모드를 개발하였다. 이러한 Cap-Divided 방식의 신규 VA 액정모드는 높은 콘트라스트, 광시야각 특성 및 공정 단순화의 장점이 있기 때문에 향후 반투과형 LCD에 적극적인 채용이 기대되어진다.

• Proceedings of the KIPE Conference
• /
• 2016.11a
• /
• pp.147-148
• /
• 2016

토템폴 구조는 브리지리스 부스트 역률보상회로 중에서도 저손실, 고효율, 저비용 그리고 낮은 전도 EMI의 특징으로 인해 많이 사용된다. 토템폴 구조의 역률보상 회로는 내부 다이오드의 역회복 문제로 인해 Si MOSFET을 이용한 전류연속모드 구동할 수 없어 전류 불연속 모드 혹은 임계 도통 모드로 동작시키는 것이 통상적이다. 본 논문에서는 역회복 문제를 해결해 전류연속모드 구동하기 위해 기존 Si MOSFET보다 낮은 역회복 전하(Qrr)와 역회복 시간(Trr)를 가지는 SiC MOSFET을 이용하여 토템폴 역률 보상 회로를 구현하고 이를 시뮬레이션과 실험을 통해 검증했다.

• Journal of IKEEE
• /
• v.13 no.2
• /
• pp.101-107
• /
• 2009

Growth in the VLSI process and design technology is resulting into a continuous increase in the number of IPs on a chip to form a system. Because of many IPs on a single chip, efficient communication between IPs is essential. We propose a dynamically reconfigurable 3-layer bus structure which can adapt to the pattern of data transmission to achieve an efficient data communication between various IPs. The proposed 3-layer bus can be reconfigured to multi-single bus mode, and single-multi bus mode, thus providing the benefits of both single-bus and multi-bus modes. Experimental results show that the flexibility of the proposed bus structure can reduce data transmission time compared to the conventional fixed bus structure. We incorporated the proposed bus structure in a JPEG system and verified that the proposed structure achieved an average of 22% improvement in time over the conventional fixed bus structure.

• Geophysics and Geophysical Exploration
• /
• v.12 no.1
• /
• pp.143-153
• /
• 2009

Using a discrete wavenumber method, we examine the effects on Logging-While-Drilling (LWD) logs when a mismatch exists between the amplitudes or generating times of the signals from individual monopoles in a LWD multipole source. An amplitude-mismatched LWD dipole/quadrupole source produces non-dipole/non-quadrupole modes as well as flexural and screw modes. The strongest of non-dipole/non-quadrupole modes is the Stoneley mode, whose amplitude increases with increasing mismatch. However, we can recover the flexural mode signals by A-C processing, and the screw mode by A-B+C-D processing, respectively. The Stoneley mode, which has the same amplitude at the same radial distance from the borehole axis, is cancelled out by A-C and A-B+C-D processing as long as the tool is placed at the centre of the borehole. The responses from a time-mismatched LWD multipole source look like the summation of responses by two or four monopole sources off the borehole axis. However, we can avoid the misinterpretation of the formation velocities by referring to the computed dispersion curves, which are independent of the arrival times of the modes, on the frequency semblance plot.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.37 no.12
• /
• pp.1184-1191
• /
• 2009

In order to reduce the download around the Smart UAV(SUAV) at Transition mode, flow control using synthetic jet has been performed. Many of the complex tilt rotor flow features are captured including the leading and trailing edge separation, and the large region of separated flow beneath the wing. Based on the results of part 1 of the present work, synthetic jet is located at 0.01c, $0.95c_{flap}$ and it is operated with the non-dimensional frequency of 0.5, 5 to control the leading edge and trailing edge separation. Consequently, download is substantially reduced compared to with no control case at transition mode using leading edge jet only. The present results show that the overall flight performance and stability of the SUAV can be remarkably improved by applying the active flow control strategy based on synthetic jet.

• Korean Journal of Optics and Photonics
• /
• v.14 no.5
• /
• pp.565-569
• /
• 2003

We designed a transflective-type LCD using a twisted VA mode. Generally, a VA mode had a blue shift due to intrinsic properties. We solved this problem using spectroscopic compensation film. We used the front scattering film and negative C-plate to improve characteristics of the viewing angle and contrast ratio. As a result, we found that proposed the transflective-type TVA mode had a contrast ratio of about 80:1, a response time of 22 ms, and a reflectance of 25% in comparison with the standard MgO reflector.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.19 no.9
• /
• pp.1702-1709
• /
• 1994

In the postprocessing of Hangul recognition system, the storage structure of contextual information is an important matter for the recognition rate and speed of the entire system. Trie in general is used to represent the context as word dictionary, but the memory space efficiency of the structure is low. Therefore we propose a new structure for word dictionary that has better space efficiency and the equivalent merits of trie. Because Hangul is a compound language, the language can be represented by phonemes or by characters. In the representation by phonemes(P-mode) the retrieval is fast, but the space efficiency is low. In the representation by characters(C-mode) the space efficiency is high, but the retrieval is slow. In this paper the two representation methods are combined to form a hybrid representation(H-mode). At first an optimal level for the combination is selected by two characteristic curves of node utilization and dispersion. Then the input words are represented with trie structure by P-mode from the first to the optimal level, and the rest are represented with sequentially linked list structure by C-mode. The experimental results for the six kinds of word set show that the proposed structure is more efficient. This result is based on the fact that the retrieval for H-mode is as fast as P-mode and the space efficiency is as good as C-mode.