• Journal of the Institute of Electronics Engineers of Korea SC
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• v.40 no.5
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• pp.350-354
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• 2003

This study proposes a new self-driven active clamp forward converter eliminating the extra drive circuit for the active clamp switch. The converter used the auxiliary winding of the power transformer to drive the active clamp switch and a simple R-C circuit to get the dead time between the two switches. The operation principle was presented and experimental results were used to verify theoretical predictions. A 100-W (5V/20A) prototype converter built that only exhibited 1.5-turn winding number in the auxiliary winding was sufficient to drive the active clamp switch on the input of 50V. Finally, the measured efficiency of the converter was presented and the maximum efficiency of 91% was obtained.

• ETRI Journal
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• v.33 no.4
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• pp.621-628
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• 2011

The redactable signature scheme was introduced by Johnson and others in 2002 as a mechanism to support disclosing verifiable subdocuments of a signed document. In their paper, a redactable signature based on RSA was presented. In 2009, Nojima and others presented a redactable signature scheme based on RSA. Both schemes are very efficient in terms of storage. However, the schemes need mechanisms to share random prime numbers, which causes huge time consuming computation. Moreover, the public key in the scheme of Johnson and others is designed to be used only once. In this paper, we improve the computational efficiency of these schemes by eliminating the use of a random prime sharing mechanism while sustaining the storage efficiency of them. The size of our signature scheme is the same as that of the standard RSA signature scheme plus the size of the security parameter. In our scheme, the public key can be used multiple times, and more efficient key management than the scheme of Johnson and others is possible. We also prove that the security of our scheme is reduced to the security of the full domain RSA signature scheme.

• ETRI Journal
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• v.38 no.5
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• pp.818-828
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• 2016

This paper proposes a reusable design for the merging process used in three-dimensional High Efficiency Video Coding (3D-HEVC), which can significantly reduce the implementation complexity by eliminating duplicated module redundancies. The majority of inter-prediction coding tools used in 3D-HEVC are utilized through a merge mode, whose extended merging process is based on built-in integration to completely wrap around the HEVC merging process. Consequently, the implementation complexity is unavoidably very high. To facilitate easy market implementation, the design of a legacy codec should be reused in an extended codec if possible. The proposed 3D-HEVC merging process is divided into the base merging process of reusing HEVC modules and reprocessing process of refining the existing processes that have been newly introduced or modified for 3D-HEVC. To create a reusable design, the causal and mutual dependencies between the newly added modules for 3D-HEVC and the reused HEVC modules are eliminated, and the ineffective methods are simplified. In an application of the proposed reusable design, the duplicated reimplementation of HEVC modules, which account for 50.7% of the 3D-HEVC merging process, can be eliminated while maintaining the same coding efficiency. The proposed method has been adopted as a normative coding tool in the 3D-HEVC international standard.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.3
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• pp.623-638
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• 2017

Application fields of cloud technologies have been gradually expanded with development of technology development and diversification of services. Cloud technology is used for investment efficiency, operation efficiency and service competitive advantage in digital broadcasting platform. Recently, Cloud broadcasting platform commercialized for UI(User Interface) and data broadcasting in Korea, and broadcasting service competition becomes fierce. Cloud technology of broadcasting provides remove a service dependency hardware resource and software architecture on STB device, and unified operation of user interface and service using cloud server without legacy separating management of STB types. In this paper, we explain application effects in image based cloud broadcasting service platform.

• Journal of Power Electronics
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• v.15 no.4
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• pp.910-919
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• 2015

The use of a PV grid-connected inverter with non-isolated topology and without a transformer is good for improving conversion efficiency; however, this inverter has become increasingly complicated for eliminating leakage current. To simplify the complicated architecture of traditional three-level dual buck inverters, a new dual Buck three-level PV grid-connected inverter topology is proposed. In the proposed topology, the voltage on the grounding stray capacitor is clamped by large input capacitors and is equal to half of the bus voltage; thus, leakage current can be eliminated. Unlike in the traditional topology, the current in the proposed topology passes through few elements and does not flow through the body diodes of MOSFET switches, resulting in increased efficiency. Additionally, a multi-loop control method that includes voltage-balancing control is proposed and analyzed. Both simulation and experimental results are demonstrated to verify the proposed structure and control method.

• Particle and aerosol research
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• v.17 no.3
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• pp.71-79
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• 2021

Ultrafine dust, which is emitted from industrial factories or all kinds of vehicles, threatens the human's respiratory system and our environment. In this regard, separating airborne particles is essential to mitigate the severe problem. In this work, an axial cyclone for the effective technology of eliminating harmful dust is investigated by numerical simulation using Ansys 2020, Fluent R2. In addition, the optimized structure of the cyclone is constructed by means of multi objective optimization based on the response surface method which is a representative method to analyze the effect of design parameter on response variables. Among several design parameters, the modified length of the vortex finder and dust collector is a main point in promoting the performance of the axial cyclone. As a result, the optimized cyclone exhibits remarkable performance when compared to the original model, resulting in pressure drop of 307 Pa and separator efficiency of 98.5%.

• Journal of Broadcast Engineering
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• v.27 no.5
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• pp.773-793
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• 2022

The moving picture experts group (MPEG) immersive video (MIV) coding standard has been established to support six degrees of freedom (6DoF) in virtual reality (VR) by transmitting high-quality multiple immersive videos. The MIV exploits two approaches considering tradeoff between bandwidth and computational complexity: 1) eliminating correlation between multi-view videos or 2) selecting representative videos. This paper presents performance analysis on intermediate synthesized views on source view positions and synthesized pose traces using high-efficiency video coding (HEVC) and versatile video coding (VVC) for above-mentioned two approaches.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.9C
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• pp.869-875
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• 2006

Nowadays JPEG encoder uses block based DCT and quantization to compress the size of still image. JPEG encoding method performs better compression efficiency than the other still image encoding method. However, when encoding a still image at low bit-rate, high frequency coefficients could be lost because of the coarse quantization so the blocking artifacts occur. In this paper, we propose the method of eliminating the blocking artifacts which occur when the still image is encoded by JPEG at a high compression rate. The principle of proposed algorithm is that the eliminating the blocking artifacts, which occur in the boundary of blocks, in DCT domain with $4{\times}4$ block-based method. First of all, observe the blocking artifacts with $4{\times}4$ block in DCT domain. Then eliminate the blocking effects using effective filtering method that is $4{\times}4$ block-based. Experimental results have clearly shown that our algorithm presents substantially higher quality in subjective and objective point of view than the other algorithms.

• Journal of Korean Society for Geospatial Information Science
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• v.13 no.4 s.34
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• pp.27-32
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• 2005

DEM is needed for urban modeling, forecasting of floods and the analysis of slope and aspect. It has been generated using digital maps, aerial photos or satellite imageries. Recently, however, many studies on DEM generation from LiDAR data has been conducted because of its efficiency and accuracy. Filtering is said to be the process of making DEM by eliminating non-ground points from LiDAR data. In most researches, some input parameters such as the size of filter are required. The purpose of this investigation is to automatically obtain DEM by eliminating objects of various sizes without the knowledge of the objects' sizes. The experimental results show that most of objects on steep terrain are eliminated by the proposed method.

• 지역과문화
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• v.6 no.2
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• pp.77-104
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• 2019

This study examines the efficiency of using local cultural resources in local governments. The study does so by DEA(Data Envelope Analysis) using data from the year 2017 for 17 local governments in Korea. In addition, this study tries to estimate environmental efficiency of local cultural resources. For this, the 'Total Efficiency' including the output variables related to the local cultural resource environment was analyzed. After than It compared the 'Total Efficiency' with the 'Utilization Efficiency', to estimate the 'Environmental Efficiency' of local cultural resources. The followings are results which are significant statistically. Firstly, it was evaluated that five of the 17 local governments utilized the local cultural resources efficiently. Secondly, it was result that the inefficiency of the other local governments was relatively influenced by the economies of scale than PTE(Pure Technical Efficiency). Thirdly, It has been confirmed that environmental aspects such as cultural properties and cultural infrastructure have a considerable impact on the increase or decrease of efficiency in local governments. The difference in the efficiency of local governments are influenced by the population density. In order to improve the efficiency in the future, it is necessary to adjust the appropriate level of input according to the local population estimate, which is a major consumer of the local cultural resource utilization. In addition, the local festivals and village festivals held by local governments should be checked to improve in quality by eliminating inefficiencies. Also, it should be considered of environmental factors together, when analyzing the efficiency of the local cultural resource in local governments.