• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.1
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• pp.62-67
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• 2005

Recently, polymer insulators that are used for high voltage applications have some advantages such as light weight, small size, vandalism resistance, hydrophobicity and easy making process. During outdoor service of polymer insulators, the surface of the insulating material is frequently subjected to moisture and contamination that lead to dry band arcing. Their tracking resistance, erosion resistance, end sealing and shed design are very important because dry band arcing causes degradation of polymer surface. Aging test to estimate life property of polymer insulator is executed through several international standard such as IEC 61109 and CEA tracking wheel test, but is not getting clear conclusion yet. There are two methods in the diagnosis method of polymer insulator such as off-line and on-line. The diagnosis methods in off-line are external condition analysis by the eye, contaminant analysis on surface, surface analysis, pollution withstand voltage test, power frequency flashover voltage test, lightning impulse flashover test, tensile fracture load test and flexural load test. Polymer material is also investigated it's tracking resistance by adding surface active agent in IEC 587. In this paper, the tracking performance of polymer insulator with salt solution which is added surface active agent. The diagnosis of insulator sample has been analyzed by leakage current and visual examination, STRI guide and thermal image camera.

• The Journal of the Korea Contents Association
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• v.8 no.5
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• pp.29-37
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• 2008

To transmit video bit stream over low bandwidth such as wireless channel, high compression algorithm like H.264 codec is exploited. In transmitting high compressed video bit-stream over low bandwidth, packet loss causes severe degradation in image quality. In this paper, a new algorithm for recovery of missing or erroneous motion vector is proposed. Considering that the missing or erroneous motion vectors in blocks are closely correlated with those of neighboring blocks. Motion vector of neighboring blocks are clustered according to average linkage algorithm clustering and a representative value for each cluster is determined to obtain the candidate motion vector sets. As a result, simulation results show that the proposed method dramatically improves processing time compared to existing H.264/AVC. Also the proposed method is similar to existing H.264/AVC in terms of visual quality.

• Journal of Radiation Protection and Research
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• v.29 no.4
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• pp.257-261
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• 2004

A coded-aperture gamma camera was developed to increase the sensitivity of a pin hole camera made with a pixellated CsI(Tl) scintillator and a position-sensitive photomultiplier tube. The modified round-hole uniformly redundant array of pixel size $13{\times}11$ was chosen as a coded mask considering the detector spatial resolution. The performance of the coded-aperture camera was compared with the pin hole camera using various forms of Tc-99m source to see the improvement of signal-to-noise ratio or the improvement of the sensitivity. The image quality is much improved despite of a slight degradation of the spatial resolution. Though the camera and the test were made for low energy case, but the concept of the coded-aperture gamma camera could be effectively used for the radioactive environmental monitoring and other applications.

• Journal of Digital Contents Society
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• v.16 no.3
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• pp.365-371
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• 2015

In wireless network, the amount of video streaming packet information in receiver replay buffer can be varied according tothe wireless network condition. By the effect, unforeseeable delay and jitter are generated and then busty video traffics can be made. If the amount of buffer information coming in receiver replay buffer is larger than the amount of a specific buffer information, buffer overflow is generated. Such a problem makes the image skip effect and packet loss, and then causes the quality degradation and replay discontinuity of the video streaming service in destination receiver. To solve the buffer overflow problem, this paper applies the token bucket for the busty traffic to the receiver terminal and analyzes the effect of the token bucket. The simulation result using NS-2 and JSVM shows that the proposed scheme with the token bucket has significantly better performance than the conventional scheme without the token bucket in terms of overflow generation number, packet loss rate and PSNR.

• Journal of the Optical Society of Korea
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• v.19 no.6
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• pp.687-694
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• 2015

A photoluminescence (PL) imaging method using a vision camera was employed to inspect InGaN/GaN quantum-well light-emitting diode (LED) epi-wafers. The PL image revealed dark spot defective regions (DSDRs) as well as a spatial map of integrated PL intensity of the epi-wafer. The Shockley-Read-Hall (SRH) nonradiative recombination coefficient increased with the size of the DSDRs. The high nonradiative recombination rates of the DSDRs resulted in degradation of the optical properties of the LED chips fabricated at the defective regions. Abnormal current-voltage characteristics with large forward leakages were also observed for LED chips with DSDRs, which could be due to parallel resistances bypassing the junction and/or tunneling through defects in the active region. It was found that the SRH nonradiative recombination process was dominant in the voltage range where the forward leakage by tunneling was observed. The results indicated that the DSDRs observed by PL imaging of LED epi-wafers were high density SRH nonradiative recombination centers which could affect the optical and electrical properties of the LED chips, and PL imaging can be an inspection method for evaluation of the epi-wafers and estimation of properties of the LED chips before fabrication.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.48 no.1
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• pp.64-70
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• 2011

In an H.264/AVC video encoder, the motion estimation at fractional pixel accuracy improves a coding efficiency and image quality. However, it requires additional computation overheads for fractional search and interpolation, and thus, reducing the computation complexity of fractional search becomes more important. This paper proposes a Pixel Re-composition Fractional Motion Estimation (PRFME) algorithm for an H.264/AVC video encoder. Fractional Motion Estimation performs interpolation for the overlapped pixels which increases the computational complexity. PRFME can reduce the computational complexity by eliminating the overlapped pixel interpolation. Compared with the fast full search, the proposed algorithm can reduce 18.1% of computational complexity, meanwhile, the maximum PSNR degradation is less than 0.067dB. Therefore, the proposed PRFME algorithm is quite suitable for mobile applications requiring low power and complexity.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.6
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• pp.78-87
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• 2009

In this paper, we propose a new method of blocky artifacts measurement for IP based video service. In order to assess the quality of IP based video service, we classify degradation into blocking artifacts by network error or by transmission error. in order to assess blocking artifacts based on No-reference, we estimate blocky artifacts from network errors and image compression by calculating amount of difference between target block and neighbor blocks and error concealment algorithm in a video receiver. To ensure accuracy of proposed method, we compare our result to MOS data using SSCQE method. Experimental results show that the proposed algorithm is better than a conventional method by around 1.3.

• Journal of the Korea Society of Computer and Information
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• v.10 no.4 s.36
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• pp.47-56
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• 2005

With the development of wearable(ubiquitous) computers, those traditional interfaces between human and computers gradually become uncomfortable to use, which directly leads to a requirement for new one. In this paper, we study on a new interface in which computers try to recognize the gesture of human through a digital camera. Because the method of recognizing hand gesture through camera is affected by the surrounding environment such as lighting and so on, the detector should be a little sensitive. Recently, Viola's detector shows a favorable result in face detection. where Adaboost learning algorithm is used with the Haar features from the integral image. We apply this method to hand area detection and carry out comparative experiments with the classic method using skin color. Experimental results show Viola's detector is more robust than the detection method using skin color in the environment that degradation may occur by surroundings like effect of lighting.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.39 no.2
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• pp.11-21
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• 2002

Although the matching Pursuit is effective for video coding at low bit rate, it has a Problem since it needs much more calculation than the conventional block-based video coding method. The proposed fast matching pursuit method reduces inner product calculation that takes the most part of entire calculation by utilizing the symmetry of the absolute values of the one-dimensional Gator dictionary bases, the modified dictionary which allows faster matching without causing image quality degradation, and a Property of the two-dimensional Gabor dictionary that can be grouped in advance to four classes according to its frequency characteristics. Proposed method needs only about 1/8 of multiplications compared to the well-known separability-based fast method proposed by Neff.

• Convergence Security Journal
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• v.12 no.2
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• pp.107-113
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• 2012

Recently, according to the establishment of personal information protection Act, the public and private organizations are taking a step to protect personal information rights and interests by employing the technical methods such as the access control mechanism, cryptography, etc. The result of the personal information leakage causes a serious damage for the organization image and also has to face with the responsibility by law. However, applying access control and cryptographic approach on the personal information item for every connection to large database system causes significant performance degradation in a large database system. In this paper, we designed and implemented the light weight system using JVM (Java Virtual Machine) for the Oracle DBMS environment which the concurrent transaction occurs many, thereby the proposed system provides the minimum impact on the system performance and meets the need of personal information protection. The proposed system was validated on the personal information protection system which sits on a 'A' public organization's portal site and personnel information management system.