• Proceedings of the KACD Conference
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• 2008.05a
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• pp.235-245
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• 2008

The aim of this study was to develop a method for measuring the slumping resistance of resin composites and to relate it to the rheological characteristics. Five commercial hybrid composites (Z100. Z250. DenFil, Tetric Ceram. ClearFil) and a nanofill composite (Z350) were used to make disc-shaped specimens of 2 mm thickness. An aluminum mold with square shaped cutting surface was pressed onto the composite discs to make standardized imprints. The imprints were light-cured either immediately (non-slumped) or after waiting for 3 minutes at $25^{\circ}C$ (slumped). White stone replicas were made and then scanned for topography using a laser 3-D profilometer. Slumping resistance index (SRI) was defined as the ratio of the groove depth of the slumped specimen to that of the non-slumped specimen. The pre-cure viscoelasticity of each composite was evaluated by an oscillatory shear test and normal stress was measured by a squeeze test using a rheometer. Flow test was also performed using a flow tester. Correlation analysis was performed to investigate the relationship between the viscoelastic properties and the SRI. SRI varied between the six materials (Z100 < DenFil < Z250 < ClearFil < Tetric Ceram < Z350). The SRI was strongly correlated with the viscous (loss) shear modulus G' but not with the loss tangent. Also. slumping resistance was more closely related to the resistance to shear flow than to the normal stress. Slumping tendency could be quantified using the imprint method and SRI. The index may be applicable to evaluate the clinical handling characteristics of composites.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.4
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• pp.25-33
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• 2012

In electric power transmission tower structures on offshore, implementation of life management using the event data of regular safety inspections for structural and material damages is strongly recommended. In this study, six tower structures in Sihwa Lake around Yeoungheung island were target bodies for the safety inspections. safety inspections for deterioration about each of six towers were performed about three items for steel member, five items for concrete foundation, and four items for steel-pipe pile in seawater and seawater itself. Safety inspections for steel members included the visual observations of surface appearances, the measurements of member thicknesses, and the checks of painting states. Also safety inspections for concrete foundations comprised the estimation of crack features, the evaluation of non-destructive compression strengths, and the measurements of neutralization depths and chlorides contents. For steel-pipe piles in seawater the inspections comprised the surveys of corrosion states in accordance with potential levels tests and anode tests, the analyses of photos taken on surfaces of the piles as well as the evaluation of seawater quality. A set of deterioration inspections was performed at the same positions around october of each year for three consecutive years. As a result in this study, Newly developed deterioration indexes have been applied profitably to maintain structural safety for electric power transmission towers by utilizing these event data systematically.

• Restorative Dentistry and Endodontics
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• v.33 no.3
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• pp.235-245
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• 2008

The aim of this study was to develop a method for measuring the slumping resistance of resin composites and to relate it to the rheological characteristics. Five commercial hybrid composites (Z100, Z250, DenFil, Tetric Ceram, ClearFil) and a nanofill composite (Z350) were used to make disc-shaped specimens of 2 mm thickness. An aluminum mold with square shaped cutting surface was pressed onto the composite discs to make standardized imprints. The imprints were light-cured either immediately (non-slumped) or after waiting for 3 minutes at $25{\circ}C$ (slumped). White stone replicas were made and then scanned for topography using a laser 3-D profilometer. Slumping resistance index (SRI) was defined as the ratio of the groove depth of the slumped specimen to that of the nonslumped specimen. The pre-cure viscoelasticity of each composite was evaluated by an oscillatory shear test and normal stress was measured by a squeeze test using a rheometer. Flow test was also performed using a flow tester. Correlation analysis was performed to investigate the relationship between the viscoelastic properties and the SRI. SRI varied between the six materials (Z100 < DenFil < Z250 < ClearFil < Tetric Ceram < Z350). The SRI was strongly correlated with the viscous (loss) shear modulus G' but not with the loss tangent. Also, slumping resistance was more closely related to the resistance to shear flow than to the normal stress. Slumping tendency could be quantified using the imprint method and SRI. The index may be applicable to evaluate the clinical handling characteristics of composites.

• Journal of Biomedical Engineering Research
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• v.19 no.4
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• pp.379-384
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• 1998

To measure precisely the blood velocity in the skin microcirculation, we have used time domain correlation (called Cross-Correlation) based on the processing of the backscattered RF signal obtained with a wideband echographic imaging transducer, although it is difficulties of adaptation of the pulsed wave system, because of the data processing in real time and the hardware problem. This dedicated technology based on a 20MHz echographic imaging system has been developed. We present how the experimental data, i.e. the backscattered RF signal, have to be analyzed. After RF lines realignment, stationary echo canceling procedure and correlation level control, a velocity profile has been obtained. In-vitro result show that velocity measurements as low as 0.1mm/sec attainable with a 80${\mu}m$ in axial resolution. We have also validated with in-vivo experimentation on the external ear of a rabbit using B-mode sector scanning image and M-mode image of a custom made 20MHz skin image system. The flow of the "auriculares caudales" vein, a microvessel of 600 m diameter, has been detected and studied. This technique will allow a more precise exploration of circulatory troubles in cutaneous pathologies.

• Science of Emotion and Sensibility
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• v.15 no.1
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• pp.17-28
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• 2012

Recent development of 3D technologies made it possible that observers perceive 3D depth from two dimensional images. Despite this kind of technological development, when observers watch 3D display they experience 3D visual fatigue that they do not usually experience in real life. It is critical to measure visual fatigue in order to overcome the problem of 3D visual fatigue. The purpose of the present study was to develop a protocol to measure 3D visual fatigue based on an EEG signal and to examine its validity. The first experiment explored the possible ERP components that reflected visual fatigue in 2D and 3D conditions. The second experiment examined whether the feature of the component found in the first experiment was affected by the amount of binocular disparity. Both in Cz and Pz channels, the peak amplitude of P3 component was much lower in 3D rather than in 2D conditions, and it decreased as the amount of binocular disparity increased. The subjective 3D visual fatigue also increased with the amount of binocular disparity. These results imply that the peak amplitude of P3 component at Cz and Pz channels can be used as an index of 3D visual fatigue.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.8
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• pp.2043-2050
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• 2014

As most the scanning systems developed until now provide radiation scan plane images of the inspected objects, there has been a limitation in judging exactly the shape of the objects inside a logistics container exactly with only 2-D radiation image information. As a radiation image is just the density information of the scanned object, the direct application of general stereo image processing techniques is inefficient. So we propose that a new volume-based 3-D reconstruction algorithm. Experimental results show the proposed new volume based reconstruction technique can provide more efficient visualization for X-ray inspection. For validation of the proposed shape reconstruction algorithm using volume, 15 samples were scanned and reconstructed to restore the shape using an X-ray stereo inspection system. Reconstruction results of the objects show a high degree of accuracy compared to the width (2.56%), height (6.15%) and depth (7.12%) of the measured value for a real object respectively. In addition, using a K-Mean clustering algorithm a detection efficiency of 97% is achieved. The results of the reconstructed shape information using the volume based shape reconstruction algorithm provide the depth information of the inspected object with stereo X-ray inspection. Depth information used as an identifier for an automated search is possible and additional studies will proceed to retrieve an X-ray inspection system that can greatly improve the efficiency of an inspection.

• Journal of the Korean Society of Radiology
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• v.15 no.4
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• pp.401-408
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• 2021

Proton therapy using the Bragg peak is one of the radiation therapies and can deliver its maximum energy to the tumor with giving least energy for normal tissue. A cross-sectional image of the human body taken with the computed tomography (CT) has been used for radiation therapy planning. The HU values change according to the tube voltage, which lead to the change in the boundary and thickness of the anatomical structure on the CT image. This study examined the changes in the Bragg peak of the brain region according to the thickness variation in the head phantom composed of several materials using the Geant4. In the phantom composed of a single material, the Bragg peak according to the type of media and the incident energy of the proton beams were calculated, and the reliability of Geant4 code was verified by the Bragg peak. The variation of the peak in the brain region was examined when each thickness of the head phantom was changed. When the thickness of the soft tissue was changed, there was no change in the peak position, and for the skin the change in the peak was small. The change of the peak position was mainly changed when the bone thickness. In particular, when the bone was changed only or the bone was changed together with other tissues, the amount of change in the peak position was the same. It is considered that measurement of the accurate bone thickness in CT images is one of the key factors in depth-dose distribution of the radiation therapy planning.

• Journal of Broadcast Engineering
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• v.27 no.2
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• pp.216-227
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• 2022

The MPEG-I (Immersive) group is working on a standardization project for immersive video that provides 6 degrees of freedom (6DoF). The MPEG Immersion Video (MIV) standard technology is intended to provide limited 6DoF based on depth map-based image rendering (DIBR) technique. Many efficient coding methods have been suggested for MIV, but efficient transmission strategies have received little attention in MPEG-I. This paper proposes group-based adaptive rendering method for immersive video streaming. Each group can be transmitted independently using group-based encoding, enabling adaptive transmission depending on the user's viewport. In the rendering process, the proposed method derives weights of group for view synthesis and allocate high quality bitstream according to a given viewport. The proposed method is implemented through the Test Model for Immersive Video (TMIV) test model. The proposed method demonstrates 17.0% Bjontegaard-delta rate (BD-rate) savings on the peak signalto-noise ratio (PSNR) and 14.6% on the Immersive Video PSNR(IV-PSNR) in terms of various end-to-end evaluation metrics in the experiment.

• Journal of Korea Entertainment Industry Association
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• v.14 no.8
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• pp.103-116
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• 2020

This paper starts with the recognition of the problem of the need for a link between text-centered acting and body-centered acting. This study is focused on Brecht's theory of acting to overcome loss of presence by repetition which have been discussed many times by not only actors, but also acting educators. Brecht's acting theory has already been mentioned by many researchers as an alternative to conventional actor training. However, not many studies have been conducted on practical applicable methods. The purpose of this study is to provide the basis for the actual practice of Brecht acting and possibility that his acting theory can serve as a link between text and body-centered acting theory. As a research method, we first conduct theoretical considerations on the concepts and limitations of text-centered representational acting and body-centered post-drama acting. Then distinguish between text and body-centered acting tools among Brecht's epic theatre, to summarize the terms and concepts he uses and to identify the existing effects he reaches while acting. Finally, this paper proposes an teaching model that transforms and develops Brecht's acting theory through the writer's teaching experience. However, there are limitations in generalizing its effectiveness because this study is based on the writer's experience. We hope that further research will help the diversity of acting education by developing in-depth insights on Brecht acting theory and various models of acting teaching methods.

• 지역과문화
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• v.7 no.1
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• pp.99-126
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• 2020

This study aimed to investigate the effects of multicultural complexes on activating local culture. Prior studies that discuss activating local culture through multicultural complexes focus on literature reviews or quantitative research methods, which do not incorporate the detailed and practical opinions of the users of the location. Therefore, this study collected detailed information through in-depth interviews with users, and investigated the future development methods of multicultural complexes based on the obtained information. It focused on the Asia Culture Center (ACC) in Gwangju, which is considered a prime example of a multicultural complex, and conducted in-depth interviews with citizens who have lived in Gwangju for at least five years as well as visited the ACC to investigate the research question from a detailed perspective. The results revealed that although the citizens of Gwangju have a positive perception of the functions of ACC as a cultural space representing the city that activates the local culture, they perceive it as partially insufficient to be considered a multicultural complex. Major findings included the following: the contents of the ACC do not have a mass appeal, its inflexible hours of operation inconvenience visitors, and the contents available for visitors lack in quantity and quality. Therefore, in order for the ACC to appeal as a successful multicultural complex, it is necessary to cooperate with the members of the community to investigate their needs with respect to the contents and location, and prepare strategic plans to satisfy those needs.