• Journal of the Institute of Electronics Engineers of Korea SP
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• v.41 no.6
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• pp.209-220
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• 2004

The main feature of H.264 standard against conventional video standards is the high coding efficiency and the network friendliness. In spite of these outstanding features, it is not easy to implement H.264 codec as a real-time system due to its high requirement of memory bandwidth and intensive computation. Although the variable block size motion compensation using multiple reference frames is one of the key coding tools to bring about its main performance gain, it demands substantial computational complexity due to SAD (Sum of Absolute Difference) calculation among all possible combinations of coding modes to find the best motion vector. For speedup of motion estimation process, therefore, this paper proposes fast algorithms for both integer-pel and fractional-pel motion search. Since many conventional fast integer-pel motion estimation algorithms are not suitable for H.264 having variable motion block sizes, we propose the motion field adaptive search using the hierarchical block structure based on the diamond search applicable to variable motion block sizes. Besides, we also propose fast fractional-pel motion search using small diamond search centered by predictive motion vector based on statistical characteristic of motion vector.

• Journal of Digital Contents Society
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• v.19 no.8
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• pp.1603-1615
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• 2018

In order to achieve the low complexity and area, power in the design of Optical Image Stabilization (OIS) suitable for the smart phone, this paper presents the following design explorations, such as; optimization of gyroscope sampling rate, simple and accurate gyroscope filters, and reduced operating frequency of motion compensation, optimized bit width in ADC and DAC, evaluation of noise effects due to PWM driving. In experiments of gyroscope sampling frequencies, it is found that error values are unvaried in the frequency above 5KHz. The gyroscope filter is efficiently designed by combining the Fuzzy algorithm, to illustrate the reasonable compensation for the angle and phase errors. Further, in the PWM design, the power consumption of 2MHz driving is shown to decrease up to 50% with respect to the linear driving, and the imaging noises are reduced in the driving frequency above 2MHz driving frequency. The operating frequency could be reduced to 5KHz in controller and 10KHz in driver, respectively, in the motion compensation. For ADC and DAC, the optimized exploration experiments verify the minimum bit width of 11bits in ADC as well as 10bits in DAC without the performance degradation.

• 한국HCI학회:학술대회논문집
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• 2006.02b
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• pp.185-190
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• 2006

휴대폰 산업의 발전과 더불어 발전해온 휴대폰 서비스는 최근 단순한 정보 제공을 넘어 생활에 중요한 도구로 활용되는 모습을 보인다. 최근 등장하는 휴대폰 서비스는 종류가 다양하고 최신 휴대폰과 결합되어 복잡해져 사용자로 하여금 필요한 서비스를 선택하여 조작하는 것까지 전반적인 사용 과정의 어려움을 가져왔다. 더군다나 휴대폰 서비스는 무형의 상품이기 때문에 직접 조작해보지 못하고 사용해야 하며, 이것은 사람들로 하여금 불안감을 갖도록 한다. 따라서, 본 연구에서는 휴대폰 서비스에 대한 불안감을 줄이고 사용을 확장시키는 방법으로 서비스를 직접 만지고 조작해볼 수 있는 사전 체험을 제안하며, 이를 위한 도구로 웹사이트를 활용하는 방안을 제안한다. 웹사이트는 상호작용적인 매체로써 자연스럽게 사용자가 참여하고 개입하도록 유도하는 매체이며, 다양한 시각적, 청각적 미디어를 활용할 수 있어 감각적 체험을 제공하는데 유리하다. 또한 다른 매체와 비교해 웹사이트는 공간적, 시간적 제약이 적어 많은 사람들이 원하는 시간에 접근하도록 한다. 또한 이성과 감성적인 정보를 통합적으로 처리하는 인간의 특성을 고려해 볼 때, 정보와 재미를 함께 제공할 수 있는 웹사이트의 특성은 효과적이라 볼 수 있다. 마케팅 측면에서 보더라도 저렴한 비용으로 많은 사람들에게 정보를 전달할 수 있고, 사용자들의 행동을 측정해 데이터베이스화 한 후 후에 활용할 수 있다. 이러한 점들을 통합해보면 웹사이트는 휴대폰 서비스를 체험해보도록 하는 공간으로 적합하다고 볼 수 있다. 웹사이트에서 가상 체험을 효과적으로 활용하기 위해서 사용자들의 체험 과정에 어떠한 요인이 영향을 미치는지 알 필요가 있다. 이를 위해 본 연구에서는 현재 휴대폰 서비스 체험 사이트들의 체험 제공 방식을 분석해 유형을 나눈 후에 사용자 조사를 통해 사용자들에게 선호되는 방식과 체험 과정에 영향을 미친 요인을 고찰한다. 그리고 최종적으로 이러한 요인이 실제 휴대폰 서비스에 대한 호감과 어떤 관계를 갖는지 알아본다. 본 연구에서는 이를 위해 최근 가장 높은 이용률을 보이고 있는 20,30대 휴대폰 서비스 사용자 100명을 대상으로 2005년 10월 20일~30일에 설문조사와 간단한 인터뷰를 실시하여 선호 유형과 체험에 영향을 미치는 요인을 도출하였으며, 서비스 호감과의 관계를 알기 위해 이 중 가장 관여도가 높았던 17명을 대상으로 2005년 11월 10일~15일에 심층 인터뷰를 실시하였다. 사용자 조사 결과, 분류된 유형 중 체험방식에서는 개입의 정도가 클수록, 사용상황 안내방식에서는 가상공간과 메뉴로 제공하는 방식을, 사용방법 안내형식에서는 휴대폰 전체 이미지를, 마지막으로 표현형식에서는 일러스트레이션과 영상을 가장 선호하는 것으로 나타났다. 체험에 영향을 미치는 요인은 체험적 측면,정보제공 측면,웹사이트의 측면으로 구분되었으며 휴대폰 서비스의 호감과의 관계에서는 체험적 측면과 정보제공 측면은 서비스에 대한 호감과 깊은 관계를 갖고 있는 것으로 나타난 반면에 웹사이트의 측면은 서비스와 직접적인 관련을 짓지 않는 것으로 나타났다.

• Journal of Korea Multimedia Society
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• v.7 no.1
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• pp.132-144
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• 2004

With the rapid development of internet technology, the number of internet users and the amount of multimedia information on the internet is ever increasing. Recently, the web sites, such as e-business sites and shopping mall sites, deal with lots of image information. As a result, it is required to support content- based image retrieval efficiently on such image data. This paper proposes an intelligent image retrieval system, which adopts XML, technology. To support object-based col)tent retrieval on product catalog images containing multiple objects, we describe a multi -level metadata structure which represents the local features, global features, and semantics of image data. To enable semantic-based and content-based retrieval on such image data, we design a XML-Schema for the proposed metadata and show how to represent such metadata using XML- documents. We also describe how to automatically transform the retrieval results into the forms suitable for the various user environments, such as web browser or mobile browser, using XSLT The proposed scheme can be easily implemented on any commercial platforms supporting XML technology. It can be utilized to enable efficient image metadata sharing between systems, and it will contribute in improving the retrieval correctness and the user's satisfaction on content-based e-catalog image retrieval.

• Journal of Broadcast Engineering
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• v.18 no.2
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• pp.271-282
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• 2013

Recently, ITU-T/VCEG and ISO/IEC MPEG have started a new joint standardization activity on video coding, called High Efficiency Video Coding (HEVC). This new standard gives significant improvement in terms of picture quality for high resolution video. The main challenge in this upcoming standard is the time complexity. In this paper we have focused on CU splitting algorithm. We have proposed a novel algorithm which can terminate the CU splitting process early based on the RD cost of the parent and current level and the motion vector value of the current CU. Experimental result shows that our proposed algorithm gives on average more than about 10% decrement in time over ECU [8] with on average 1.78% of BD loss on the original.

• Journal of Korea Water Resources Association
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• v.51 no.6
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• pp.481-490
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• 2018

Recently, the spatiotemporal patterns of flood disasters have become more complex and unpredictable due to climate change. Flood hazard map including information on flood risk level has been widely used as an unstructured measure against flooding damages. In order to product a high-precision flood hazard map by combination of hydrologic and hydraulic modeling, huge digital information such as topography, geology, climate, landuse and various database related to social economic are required. However, in some areas, especially in developing countries, flood hazard mapping is difficult or impossible and its accuracy is insufficient because such data is lacking or inaccessible. Therefore, this study suggests a method to delineate large scale flood-prone area based on topographic factors produced by linear binary classifier and ROC (Receiver Operation Characteristics) using globally-available geographic data such as ASTER or SRTM. We applied the proposed methodology to five different countries: North Korea Bangladesh, Indonesia, Thailand and Myanmar. The results show that model performances on flood area detection ranges from 38% (Bangladesh) to 78% (Thailand). The flood-prone area detection based on the topographical factors has a great advantage in order to easily distinguish the large-scale inundation-potent area using only digital elevation model (DEM) for ungauged watersheds.

• Journal of the Korean Society of Radiology
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• v.9 no.2
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• pp.67-72
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• 2015

In diagnostic radiology, the use of automatic exposure control device is internationally recommended for diagnosis and optimization. However, if exposed to prolonged radiation is a complicated manufacturing process, there is a problem that occurs decrease of various performance overall brightness sensor, which is commercially available conventional. Therefore, in this study, absorption of X-ray is high, and I want to evaluate the AEC applicability of the sensor of the photoconductor-based production has an easy advantage. Experimental results confirms the possibility of fabrication of the sensor through an increase in the SNR, with the detection efficiency superior, accurate turn-off. In addition, it is confirmed that the experimental results of the transmittance and the latent image, Ghost effect by the light conductor does not appear, in the case of a photoconductor with the exception of the PbO, 80% - and it was confirmed good transmittance of 90%. Therefore, excellent mechanical stability and poor performance due to a change of the doping concentration than the existing products that have been put to practical use, the sensor easy photoconductor based, fabrication and can be applied as AEC sensor is expected.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.8
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• pp.597-609
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• 2020

These days, the coaxial rotor system is used for various purposes like UAVs, Mars exploration helicopters, and the next-generation high-speed rotorcraft. A number of research projects on aerodynamic performance of rotor systems, including the coaxial configuration have been made previously. On the contrary, research on rotor blade deformation has been mainly carried out regarding the single rotor system, where such effort has not been enough on the coaxial system. Nonetheless, in case of the coaxial system, blade deformation analysis is much more important because of the complex air flow around the rotors, and that the distance between the two rotors is a key factor affects aerodynamic performance of the entire system. For these reasons, an experimental study on rotor blade deformation of the coaxial system was conducted using the Stereo Pattern Recognition(SPR) technique, one of the state-of-the-art of photogrammetry method. In this research, a small-scale coaxial rotor test stand designed by Korea Aerospace Research Institute(KARI) was used. With the same test stand, performance of the coaxial configuration had been studied before the experimental study on blade deformation, in order to find the relation between performance and blade deformation of the rotor system. Results of the performance test and the deformation study are presented in this article.

• Korean Journal of Agricultural and Forest Meteorology
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• v.9 no.2
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• pp.140-148
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• 2007

The remote sensing observations of land surface properties are inevitably influenced by the landscape heterogeneity. In this paper, we introduce a geostatistical technique to provide a quantitative interpretation of landscape heterogeneity in terms of key land surface parameters. The study areas consist of the two KoFlux sites: (1) the Gwangneung site, covered with temperate mixed forests on a complex terrain, and (2) the Haenam site with mixed croplands on a relatively flat terrain. The semivariogram and fractal analyses were performed for both sites to characterize the spatial heterogeneity of two radiation parameters, i.e., land surface temperature (LST) and albedo. These parameters are the main factors affecting the reflected longwave and shortwave radiation components from the two study sites. We derived them from the high-resolution Landsat ETM+ satellite images collected on 23 Sep. 2001 and 14 Feb. 2002. The results of our analysis show that the characteristic scales of albedo was >1 km at the Gwangneung site and approximately 0.3 km at the Haenam site. For LST, the scale of heterogeneity was also >1 km at the Gwangneung site and >0.6 to 1.0 km at the Haenam site. At both sites, there was little change in the characteristic scales of the two parameters between the two different seasons.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.2
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• pp.335-342
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• 2016

This paper proposes efficient hardware structure of in-loop filter for a high-performance HEVC (High Efficiency Video Coding) encoder. HEVC uses in-loop filter consisting of deblocking filter and SAO (Sample Adaptive Offset) to improve the picture quality in a reconstructed image due to a quantization error. However, in-loop filter causes an increase in complexity due to the additional encoder and decoder operations. A proposed in-loop filter is implemented as a three-stage pipeline to perform the deblocking filtering and SAO operation with a reduced number of cycles. The proposed deblocking filter is also implemented as a six-stage pipeline to improve efficiency and performs a new filtering order for efficient memory architecture. The proposed SAO processes six pixels parallelly at a time to reduce execution cycles. The proposed in-loop filter encoder architecture is designed by Verilog HDL, and implemented by 131K logic gates in TSMC $0.13{\mu}m$ process. At 164MHz, the proposed in-loop filter encoder can support 4K Ultra HD video encoding at 60fps in real time.