• Proceedings of the Korea Information Processing Society Conference
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• 2001.10a
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• pp.175-178
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• 2001

동영상 정보는 압축율을 높이기 위해 서로 연관성이 깊고, 정확한 의미 전달을 위해 지연 민감한 데이터로 구성된다. 이와 같은 동영상 데이터를 다양한 대역폭 변화율, 전송중의 높은 패킷 손실율의 특성을 갖는 인터넷을 통해서 전송하기 위해서는 대역폭 적응적이고 에러강인성(Error Resilience)이 높은 시스템이 필요하다. ISO/IEC 의 MPEG-4 에서는 FGS(Fine Grannular scalability)를 표준으로 채택하여 이러한 문제점의 해결방안으로 삼고 있다. FGS 는 기존의 적응적 비디오 코딩의 개념을 적응적 비디오 컨텐츠로 바꾸면서 낮은 복잡도로 대역폭에 적응이 용이하여 다수의 다양한 망 사용자를 모두 만족시킬 수 있어 VoD 나 화상회의 등의 응용에 적합한 기술이라 할 수 있다. 또 인터넷에서 예측하기 어렵게 자주 발생하는 패킷 손실에 대한 오류전파(Error Propagation)가 없는 장점을 가지고 있다. 고용량의 영상 데이터를 다수의 사용자가 동시에 요구하게 되는 상황에서 네트워크 자원을 절약하는 멀티캐스트(Multicast)는 필수적이다. 그리고 비디오와 같은 정보는 그 중요도가 다른 데이터로 구성되므로 특정 상황에서 중요도에 따라 지능적인 처리를 필요로 하는데 차세대 망 기술로 연구되는 Active Network 를 고려 할 수 있다. 영상 정보를 효율적이고 안정적으로 활용하기 위한 이러한 신기술의 효율적인 적용방안을 제안하였다.

• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.319-322
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• 2001

최근 몇 년간 멀티미디어의 응용이 활발해지면서 H.261, H263을 이용한 영상회의 MPEG-1, MPEG-2등을 이용한 디지털 저장 미디어와 방송이 주요 관심분야로 발전해왔다. 이러한 기술을 바탕으로 이제는 무선망을 이용한 3세대 이동 통신이 새로운 이슈로 등장하고 있다. 그러나 무선 환경에서는 채널 상에서 데이터를 전송할 때 에러가 많이 발생하기 때문에 에러에 강인한 방법이 반드시 필요하게 된다. 본 논문에서는 특히 향후 많은 응용분야에 쓰일 MPEG-4 데이터를 무선망으로 전송함에 있어 MPEG-4 표준에서 규정하는 에러 내성 방법과 여기에 채널 코딩 기법을 도입하여 오류에 강인한 특성을 지니도록 하는 방법을 제안한다. 실험결과는 단순히 기존의 에러 내성 기법을 활용할 때 보다 에러에 대한 강인성과 에러 검출에 있어 향상된 성능을 보여준다.

• Proceedings of the IEEK Conference
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• 2003.07e
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• pp.2363-2366
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• 2003

With the increasing use of multimedia technologies, image compression requires higher performance as well as new features such as embedded Tossy to lossless coding, various progressive order, error resilience and region-of-interest coding. In the specific area of still image encoding, a new standard, the JPEG2000, has been currently developed. This paper presents a new compression scheme based on JPEG2000. In the proposed scheme, gray coding is applied to the wavelet coefficient. Since gray coding produces an image whose bit plane is will clustered. The proposed method improves compression efficiency of the JPEG2000.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11b
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• pp.637-639
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• 2005

최근 들어 유비쿼터스 관련 연구 개발을 통해 문맥 정보를 받아들여 이를 해석하고 분석한 후, 상황에 맞는 적절한 대응을 해주는 미들웨어의 연구가 많이 이루어지고 있다. 하지만, 미들웨어 입장에서 센서를 감싸는 위젯(widget)을 효과적으로 관리하는 연구가 부족하다. 이런 이유로, 우리는 이러한 위젯의 효과적인 유지 관리를 통해 미들웨어에서 가질 수 있는 장정을 알아보고 이를 지원하기 위한 위젯 통합 프레임워크를 제안하였다. 위젯 통합 프레임워크는 다양한 위젯을 통합하고 문맥 정보를 관리하기 위하여 위젯의 Runtime Binding, Error Resilience, Common Interface over Widget을 지원한다. 또한 서비스를 관리하는 서비스 매니저와 위젯 사이의 상호작용을 효율적으로 지원함으로써 상위 계층으로 보다 적당한 문맥 정보를 제공할 수 있다. 그리고 위젯 기반의 프레임워크를 구성함으로써 다른 미들웨어에서 제공하지 못한 위젯 중심의 기능들을 제공한다.

• Journal of Broadcast Engineering
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• v.10 no.3
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• pp.340-347
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• 2005

This paper presents a polyphase down sampling based multiple description coding applied to H.264 video coding standard. For a given macroblock, a residual macroblock is calculated by motion estimation, and before applying DCT, quantization and entrophy coding of the H.264 coding process, the polyphase down sampling is applied to the residual macroblock to code in four separate descriptions. Experiments were performed for all the 9 test sequences of JVT SVC standardization in various packet loss patterns. Experimental results show that the proposed one gives 0.5 to 5 dB enhancement over an error-concealment based on the slice group map technolgoy.

• The KIPS Transactions:PartB
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• v.9B no.5
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• pp.571-578
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• 2002

In this paper, we propose a video sequence coding scheme called AMV (Auxiliary Motion Vector) to minimize error propagation caused by transmission errors over the Internet. Unlike the conventional coding schemes the AMY coder, for a macroblock in a frame, selects two best matching blocks among several preceding frames. The best matching block, called a primary block, is used for motion compensation of the destination macroblock. The other block, called an auxiliary block, replaces the primary block in case of its loss at the decoder. When a primary block is corrupted or lost during transmission, the decoder can efficiently and simply suppress error propagation to the subsequent frames by replacing the block with an auxiliary block. This scheme has an advantage of reducing both the number and the impact of error propagations. We implemented the proposed coder by modifying H.263 standard coding and evaluated the performance of our proposed scheme in the simulation. The simulation results show that AMV coder is more efficient than the H.263 baseline coder at the high packet loss rate.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.11
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• pp.5465-5470
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• 2012

FPGA(Field Programmable Gate Array) devices are widely used due to their merits in circuit development time, and development cost. Among various FPGA technologies, SRAM-based FPGAs have large cell capacity so that they are attractive for complex circuit design and their reconfigurability. However, they are weak in space environment where radiation energy particles cause Single Event Upset(SEU). In this paper, we designed a controller supervising SRAM-based FPGA to protect configuration memory inside. The controller is implemented on an Anti-Fusing FPGA. Radiation test was performed on the implemented computer board and the result show that our controller provides better SEU-resilience than TMR-only system.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.39 no.4
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• pp.90-96
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• 2016

Incremental sheet forming (ISF) is a highly versatile and flexible process for rapid manufacturing of complex sheet metal parts. Compared to conventional sheet forming processes, ISF is of a clear advantage in manufacturing small batch or customized parts. ISF needs die-less machine alone, while conventional sheet forming requires highly expensive facilities like dies, molds, and presses. This equipment takes long time to get preparation for manufacturing. However, ISF does not need the full facilities nor much cost and time. Because of the facts, ISF is continuously being used for small batch or prototyping manufacturing in current industries. However, spring-back induced in the process of incremental forming becomes a critical drawback on precision manufacturing. Since sheet metal, being a raw material for ISF, has property to resilience, spring-back would come in the case. It is the research objective to investigate how geometrical shaping parameters make effect on shape dimensional errors. In order to analyze the spring-back occurred in the process, this study experimented on Al 1015 material in the ISF. The statistical tool employed experimental design with factors. The table of orthogonal arrays of $L_8(2^7)$ are used to design the experiments and ANOVA method are employed to statistically analyze the collected data. The results of the analysis from this study shows that the type of shape and the slope of bottom are the significant, whereas the shape size, the shape height, and the side angle are not significant factors on dimensional errors. More error incurred on the pyramid than on the circular type in the experiments. The sloped bottom showed higher errors than the flat one.

• Journal of Navigation and Port Research
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• v.41 no.3
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• pp.87-92
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• 2017

To enhance the reliability and/or resilience of the PNT service included in the e-Navigation strategy of the IMO, the evaluation of the AIS-TWR method for the asynchronous R-mode for maritime service, which is available even in the absence of the GNSS, is described. For the AIS-TWR, which is capable of ranging through message exchange even without high precision synchronization, the operation scenario and the error factors according to the AIS system specifications are proposed and analyzed. Cramer-Rao Lower Bound is presented for the performance evaluation of the AIS-TWR algorithm. A simulation by AIS-TWR method of two AIS systems in a 3 km static environment shows estimation error of about 41m compared to the real value..

• Journal of Broadcast Engineering
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• v.7 no.4
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• pp.317-326
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• 2002

The adaptive coding schemes in H.264 standardization provide a significant ceding efficiency and some additional features like error resilience and network friendliness. The variable block size motion compensation using multiple reference frames is one of the key H.264 coding elements to provide main performance gain, but also the main culprit that increases the overall computational complexity. For this reason, this paper proposes a selective motion estimation algorithm based on variable block size for fast motion estimation in H.264. After we find the SAD(Sum of Absolute Difference) at initial points using diamond search, we decide whether to perform additional motion search in each block. Simulation results show that the proposed method is five times faster than the conventional full search in case of search range $\pm$32.