• 전기학회논문지
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• 제61권8호
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• pp.1199-1203
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• 2012

H.264 adopted many compression tools to increase image data compression efficiency such as B frame bi-directional predictions, the direct mode coding and so on. Despite its high compression efficiency, H.264 can suffer from its long coding time due to the complicated tools of H.264. To realize a high performance H.264, several fast algorithms were proposed. One of them is adaptive fast direct mode decision algorithm using mode and Lagrangian cost prediction for B frame in H.264/AVC (MLP) algorithm which can determine the direct coding mode for macroblocks without a complex mode decision process. However, in this algorithm, macroblocks not satisfying the conditions of the MLP algorithm are required to process the complex mode decision calculation, yet suffering a long coding time. To overcome the problem, this paper proposes a fast direct mode prediction algorithm. Simulation results show that the proposed algorithm can determine the direct mode coding without a complex mode decision process for 42% more macroblocks and, this algorithm can reduce coding time by up to 23%, compared with Jin's algorithm. This enables to encode B frames fast with a less quality degradation.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.626-631
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• 2007

MR(Magneto-rheological) fluid is smart material that can be changed viscosity by controlling the magnetic field. MR damper with MR fluid can control damping force. It can be used extensively many engineering structures for reducing the effect of dynamic external disturbances. There are three kinds of MR dampers, such as valve mode, direct-shear mode and squeeze mode. In this study, design process of direct-shear mode MR damper with the MR fluid gap was developed. The parameters that used in the direct-shear mode MR damper Informed from the experiment of valve mode MR damper of Lord company. Magnetic analysis with finite element method was performed to find the optimal annular gap.

• 방송공학회논문지
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• 제7권4호
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• pp.300-309
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• 2002

본 논문은 H.264 / MPEG-4 AVC 비디오 코덱에서 쌍예측 픽쳐의 시간적 다이렉트 모드의 모션벡터를 유포하는 방법을 소개한다. 우선, 다이렉트 모드의 list 1 레퍼런스 픽쳐에 있는 동일 위치 블록에서의 시간적 다이렉트 모드의 모션벡터 유포를 위해 사용될 모션벡터 결정 방법과 상기 결정된 모션벡터가 가리키는 레퍼런스 픽쳐를 다이렉트 모드의 list 0 레퍼런스 픽쳐로 결정하는 방법을 제시한다. 또한 동일 위치의 매크로블록이 인트라 모드를 예측모드로 가지고 있을 때, 코딩 효율을 높이기 위한 방법으로써 레퍼런스 픽쳐 인덱스 및 다이렉트 모드의 모션벡터를 공간적으로 예측하는 기법을 제시한다. 그리고, 쌍예측 픽쳐 매크로블록과 다이렉트 모드의 list 1 레퍼런스 픽쳐에 있는 동일 위치 블록은 프레임 모드 또는 피일드 모드로 코딩이 이루어질 수 있으므로 4가지 경우에 대한 다이렉트 모드의 모션벡터 연산 방법을 소개한다. 마지막으로, 실험을 통한 공간적 다이렉트 모드와의 성능평가 결과를 보임으로써, 본 논문이 제시한 기법이 H.264 / MPEG-4 AVC의 시간적 다이렉트 모드에 적용될 수 있음을 보여준다.

• Computers and Concrete
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• 제20권1호
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• pp.39-47
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• 2017

In this paper, mode I fracture toughness of rock was determined by direct and indirect methods using Particle Flow Code simulation. Direct methods are compaction tension (CT) test and hollow centre cracked quadratic sample (HCCQS). Indirect methods are notched Brazilian disk (NBD) specimen, the semi-circular bend (SCB) specimen, hollow centre cracked disc (HCCD), the single edge-notched round bar in bending (SENRBB) specimen and edge notched disk (END). It was determined that which one of indirect fracture toughness values is close to direct one. For this purpose, initially calibration of PFC was undertaken with respect to data obtained from Brazilian laboratory tests to ensure the conformity of the simulated numerical models response. Furthermore, the simulated models in five introduced indirect tests were cross checked with the results from direct tests. By using numerical testing, the failure process was visually observed. Discrete element simulations demonstrated that the macro fractures in models are caused by microscopic tensile breakages on large numbers of bonded discs. Mode I fracture toughness of rock in direct test was less than other tests results. Fracture toughness resulted from semi-circular bend specimen test was close to direct test results. Therefore semi-circular bend specimen can be a proper test for determination of Mode I fracture toughness of rock in absence of direct test.

• 방송공학회논문지
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• 제10권3호
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• pp.321-327
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• 2005

조명 변화에 적응적인 움직임 탐색 및 보상 방법과 2차원 다이렉트 모드 (2D Direct Mode)를 이용한 MVC (Multi-view Video Coding) 방법을 제안한다. 먼저, 공간적 및 시간적으로 인접한 영상으로부터 휘도 화소 값의 움직임 탐색 및 보상을 수행하기 위한 새로운 SAD (Sum of Absolute Difference) 측정 방법을 제안한다. 조명 변화에 적응적인 움직임 탐색 및 보상은 움직임 벡터의 정확도를 높이고, 비트의 절감을 위하여 새로운 SAD 계산식을 사용한다. 다음으로, 시점 간의 예측 시에 사용될 수 있는 2차원 다이렉트 모드는 MPEG-4 AVC의 시간적 다이렉트 모드 (Temporal Direct Mode)로부터 확장된 방식이다. 본 논문에서 제안된 MVC 방법은 MPEG-4 AVC의 Simulcast 부호화와 비교하여 약 0.8dB의 PSNR (Peak Signal-to-Noise Ratio) 향상을 보였다.

• 전력전자학회논문지
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• 제17권1호
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• pp.57-66
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• 2012

This paper proposes a performance improvement of grid-connected inverter system using sliding-mode based direct power control with a variable gain. The proposed control method determine variable gain of PI controller by using modeling at direct power control (DPC) applied to space vector modulation method. Also, this method use sliding-mode control to maintain excellent dynamic response of character of direct power control (DPC). The validity of the proposed algorithm are verified by simulations and experiments.

• 대한산업공학회지
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• 제33권2호
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• pp.237-245
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• 2007

In this paper, a modified PCF (Point Coordination Function) MAC (Medium Access Control) Protocol is proposed to support the multiple direct link communication between STAs (STAtions) in infrastructure mode IEEE 802.11 wireless LANs. By the proposed MAC protocol, the direct link communication between STAs, which are located within the communication range of each other, is allowed without the use of AP (Access Point) as a relay. Moreover, when multiple direct data communication between STAs can be simultaneously performed with a sufficiently small interference, multiple simultaneous direct link communication is allowed for the efficient use of radio bandwidth. AP polls STAs to grant the transmission opportunities using the direct link communication by transmitting the polling frames to STAs. An efficient polling method for granting the transmission opportunities to STAs is proposed to reduce the number of the polling frame transmissions and enhance the PCF MAC performance.

• 방송공학회논문지
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• 제9권3호
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• pp.214-224
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• 2004

본 논문에서는 차세대 실감형 3차원 영상 처리와 3차원 TV 3차원 화상회의 등과 같은 3차원 실감 미디어의 부호화에 적합한 H.264 기반의 적응적 시공간적 예측 부호화를 제안한다. 첫 번째로, 두 가지의 IPPP와 IBBP GOP(group of picture) 구조에서 기존의 동시방송(simulcast) 방식과 다르게 same-view와 inter-view 영상의 적응적 시공간적 예측 부호화를 제안한다. 두 번째로, GOP 구조가 IBBP에서 제안된 inter-view 방식의 예측 부호화시 B(hi-predictive) 화면이 MB(macroblock) 모드중 하나인 시간적 직접방식(temporal direct mode)을 수행하려고 할 때 참조 화면이 inter-view 영상을 참조하는 경우 현재의 시간적 직접 방식을 효율적으로 수행하기 위해서 2차원 inter-view 직접 방식을 제안한다. 제안된 방식은 실험결과에서 기존의 동시방송 방식과 비교되었으며 각각의 GOP 구조 모두 화질 면에서 우수한 결과를 확인할 수 있었다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.407-409
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• 1996

The Direct Arm(DDA) is a SCARA typed direct drive manipulator with three degree of freedom(DOF) using the direct motor of the NSK company. In the paper, we propose a convenient interface for the SCARA-type robot which is practical to use. The proposed Visual Robot Teaching Mode using 3D graphics replaces the current teaching box. And besides this graphical teaching software can be implemented on the PC which is company used as a robot controller. This program was developed for the Windows 95 OS.

• Structural Engineering and Mechanics
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• 제66권3호
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• pp.379-386
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• 2018

The present study addresses the direct and indirect methods of determining the mode-I fracture toughness of concrete using experimental tests and particle flow code. The direct method used is compaction tensile test and the indirect methods are notched Brazilian disc test, semi-circular bend specimen test, and hollow center cracked disc. The experiments were carried out to determine which indirect method yields the fracture toughness closer to the one obtained by the direct method. In the numerical analysis, the PFC model was first calibrated with respect to the data obtained from the Brazilian laboratory test. The crack paths observed in the simulated tests were in reasonable accordance with experimental results. The discrete element simulations demonstrated that the macro fractures in the models are caused by microscopic tensile breakages on large numbers of bonded particles. The mode-I fracture toughness in the direct tensile test was smaller than the indirect testing results. The fracture toughness obtained from the SCB test was closer to the direct test results. Hence, the semi-circular bend test is recommended as a proper experiment for determination of mode-I fracture toughness of concrete in the absence of direct tests.