• Journal of Broadcast Engineering
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• v.24 no.3
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• pp.452-462
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• 2019

A digital hologram, which is one of the next generation visual systems, can be generated and displayed in various formats, and a digital hologram is created in accordance with the characteristics of the system for display. Diffraction efficiency can be used as a measure of the characteristics of digital holograms generaged under various conditions in various display environments. In this paper, diffraction efficiency for computer-generated hologram (CGH) under various conditions was measured. This paper discusses the generation conditions that should be considered in hologram display. We compared each condition by measuring the intensity of the first order diffraction pattern of the fringe generated under the Fresnel condition for the phase hologram. Through this paper, we showed the tend about characteristics of the diffraction efficiency according to object point, reconstruction distance, laser and SLM.

• Journal of Conservation Science
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• v.37 no.6
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• pp.738-747
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• 2021

This study attempted to investigate the metallurgical characteristic through material scientific analysis of hammer scale produced as a direct smelting method restoration experiment for each raw material of iron. To this end, four hammer scale groups were set up, respectively, by experimenting with Gyeongju-Gampo Iron sand and Yangyang Iron ore. For the analysis, principal component analysis, compound analysis, microstructure observation, and chemical composition were confirmed. As a result of principal component analysis, as forging and refining progressed, the content of Fe increased and the content of non-metallic objects decreased. As a result of compound analysis, iron oxide-based compounds were identified. As a result of confirming microstructure and chemical composition, Wüstite and Fayalite were observed overall, and agglomerated Wüstite were observed in some. Magnetite on shape of polygon and pillar was observed. In addition, it was confirmed that internal defects, impurities, and non-metallic interventions gradually decreased. In the future, it is necessary to investigate the metallurgical characteristic through material scientific analysis of hammer scale produced through restoration experiments using various raw material of iron, and compare them with those excavated from Iron manufacture ruins.

• Journal of Conservation Science
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• v.26 no.1
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• pp.25-32
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• 2010

The yellowing is always occurred phenomena in epoxy restoration material of antic-ceramics. For re-restoration of remains with epoxy restoration material, the epoxy elimination step is the first one in all course of restoration In this paper, the chemically elimination treatments methods of epoxy in various antic-ceramics were discussed. We fabricated the epoxy elimination material for antic-ceramics restoration which were made up Dichloromethane and Dichlormethane based Dimethylformamide solution. Dichloromethane and Dichloromethane + Dimethylformamide mixture were applied to epoxy in various antic-ceramic sample. Particularly, Dichloromethane + Dimethylformamide solution had the best result in variation of color change, gloss, vending strength, weight, exfoliation time test after deposition in this solution. Dichloromrthane had the volume increase characteristics for epoxy material and Dimethylformamide had the mollification ones. So, Dichloromathane increased exfoliation in approximal surface of the epoxy material and antic ceramic, and Dimethylformamide decreased the surface hardness of epoxy. In this result, epoxy material even inside of ceramic that have very weak inside bonding is adaptable and stable eliminated. And in order to show the perfect elimination of this material, we successfully dissolve the epoxy restoration material in one antic pottery that is in one university museum's possession using this mixture. So, there is guarantee in the eternity and stabilization of restoration for antic-ceramics.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.40 no.4
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• pp.353-362
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• 2020

Korea was recognized as a relatively safe area for earthquake. However, due to considerable damage to facilities caused by the earthquake in Gyeongju and Pohang, interest in the maintenance and repair of structures is increasing. So interest in vibration damping technology applicable to existing structures is also increasing. However, vibration damping technology has a problem in that its usability is reduced due to damage of the damping device when a strong earthquake occurs. Recently, in order to solve such a problem, study is being conducted to apply a superelastic shape memory alloys (SSMA) capable of recentering bracing. Therefore, in this study, nonlinear dynamic analysis is performed to evaluate the seismic performance of the buckling-restrained braced frame (BRBF) applied SSMA to bracing.

• Composites Research
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• v.15 no.5
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• pp.7-13
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• 2002

The piezoelectric thin film sensor has good characteristics to observe the impact responses of composite structures. The capabilities for monitoring impact behavior of Gr/Ep laminates subjected to damage-induced impact using the PVDF(polyvinylidene fluoride) film sensor were examined. For a series of low-velocity impact tests from low energy to damage-induced energy, simulated sensor signals were compared with measured signals and the PVDF film sensor. Local impact damages(matrix cracking and delamination) were found at three impact tests, but the measured signals agreed well with the simulated sensor signals based on the linear relationship between the impact forces and the PVDF film sensor signals. And the inverse technique was applied to reconstruct the impact forces using the PVDF film sensor signals. Most of reconstructed impact forces had good agreement with the measured forces. The comparison results showed that the local damage due. to low-velocity impact didn't disturb the global impact responses of composite laminates and the reconstruction of impact forces from PVDF sensor signals wasn't affected by the local damage.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.633-637
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• 2007

하천환경 복원사업이나 자연형하천 정비사업의 근본 목표는 그 하천 고유의 하천경관이나 생태계 등 특성을 회복(Rehabilitation)시키거나 복원(Restoration)하는 것이다. 현재 이 치수기능 확보를 위한 댐 보의 건설, 하천정비 및 골재채취 등 하천의 인공화가 계속되고 있으며, 이에 따른 하천 및 하도의 물리, 화학, 생물에 미치는 영향은 심각한 수준이다. 이러한 하천의 인위적 교란은 요인, 규모, 빈도 및 강도는 다르지만 하천생태 서식처의 물리적, 화학적 특성이 변형, 변질되어 하천생태계가 변화, 단절, 절멸되는 심각한 상태가 빈발하고 있다. 하천교란(River disturbance)은 요인에 따라 유량 및 유사량 변화, 하상변동, 하도준설, 인공호안, 생태통로 차단 등 하천의 물리적 환경 변화를 초래하고, 그에 따른 영향으로 생물종의 감소 및 단순화, 개체수 감소 등과 같이 하천 생태계가 변화하게 된다. 그러나 하천의 교란평가에 대한 연구가 미흡하고, 또한 표준화된 평가체제가 구축되어 있지 않을 뿐 만 아니라 하천환경의 복원에 대한 의식 보급도 부족한 것이 현실이다. 따라서, 본 연구에서는 하천의 교란정도를 파악하기 위한 하천교란평가기법 개발을 위한 전단계로서 일본의 하천수변 국세조사, 영국의 River Habitat Survey, 호주의 River Assessment System, 미국의 Stream Corridor Restoration 등에서 제시하는 하천모니터링 및 평가체제를 비교, 분석하였다. 외국사례 분석 결과를 토대로 하천교란 요인을 하천정비, 댐건설, 골재채취로 유형화하고 교란요인별 조사해야 할 물리적 인자로서 유량, 유사량, 하도 제원, 특징적 내용, 하도형상, 여울과 소, 점사주, 인공구조물, 제방 호안의 재료 및 특징 등으로 선정, 검토하였으며, 생태계 인자로서는 제방 마루의 토지이용 및 식생구조, 하도의 식생유형, 하도주변 토지이용, 하안(bank) 형상 및 구조, 수종 및 구조, 하도 및 하안 특징 및 구조 등으로 선정, 검토하였다. 이상의 하천교란과 관계되는 지표를 선정하여 물리적, 생태적 조사 및 교란평가기법(안)을 개발, 제시하였다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.6
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• pp.459-468
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• 2023

In this study, an experiment on pullout capacity was conducted of rock bolts using grouting materials such as cement mortar and resin, which are widely used, and a newly proposed steel pipe friction type rock bolt using elastic restoring force, and the results were compared and analyzed. The experimental results showed that the pullout capacity on the rock bolts with cement mortar under a dry condition (no ground water) was relatively larger than the rock bolts with resin and the steel pipe. Nevertheless, the friction type steel pipe rock bolt to use elastic restoring force is expected to be useful in the field particularly where groundwater exists and it affects the loss and curing of grouting materials such as cement mortar or resin. In addition, it was found to have the advantage of being easy and quick to install.

• Conservation Science in Museum
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• v.15
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• pp.122-137
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• 2014

The National Museum of Korea own a historical document box ^K976 that was once used to store Joseon Wangjo Sillok ^{Annals of the Joseon Dynasty} of the Joseon Dynasty. The rectangular box has a lid, and the entire surface is varnished with black lacquer. The wood of the box had become warped and the upper part of the wooden frame had been damaged. In some areas, the paint was flaking off, exposing the underlying wood, and an iron ring that connected the lid to the body of the box was missing. Thus, in 2013, Conservation Science Department in National Museum of Korea began to repair and restore the Joseon document box. Before the treatment, analyses were conducted to examine the box's structure, damaged parts, species of wood, and lacquering techniques. The wood was found to be that of a linden tree. As for the lacquering technique, the surface of the box was first coated with a layer of lacquer and bone ash, and then covered with Korean traditional paper. Next, the box was painted with a layer of mud and ashes, followed by a layer of black pigment mixed with soot, and then varnished again with lacquer.

• Journal of Conservation Science
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• v.33 no.6
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• pp.443-456
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• 2017

The Geumran-gasa (Kasaya) and Jangsam of the monk Samyeong are historical relics and were designated as object No.29, a Buddhist costume of the Joseon Dynasty, by the National Folklore Cultural Heritage, in 1973. In 1984, after being treated for the purposes of washing and preserving the shape of the garments, the object was kept in the Temple Museum of Pyochungsa, as their holding institution. However, regular inspection conducted by the Cultural Heritage Administration in 2013 determined the need for a re-treatment. The Geumran-gasa had been originally made with 25 strips, but it had been separated into two parts and many pieces were lost. A part of the collar in the Jangsam was lost as well. Therefore, both relics needed to be restored. The re-treatment process involved pre-investigation, washing, reinforcement fabric dyeing, restoration, and fumigation. In particular, we focused on reinforcing the damaged parts and restoring the missing parts by applying advanced materials and methods in order to restore the original form as much as possible. This conservation is the result of the re-treatment of the cultural properties by replacing the old material used in past treatments and applying advanced methods under the basic principle of reversibility in conservation treatment.

• Journal of Conservation Science
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• v.31 no.4
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• pp.373-386
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• 2015

This study identified degradation properties by temperature stress with Araldite$^{(R)}$ AY103-1/HY956 used for ceramics. Tensile and compressive strength of durability increased for 6,480 hours at temperature of $34{\sim}45^{\circ}C$. In stability of external stress and temperature, compressive strength is superior to tensile strength, it requires conservation plans considering strength properties and stress of restoration materials. The tensile shear strength of adhesion properties decreased for 4,320 hours at temperature of $40{\sim}60^{\circ}C$. In ceramics with porosity, environments under isothermal-isohumidity are important because interfacial properties of adherend are concerned with performance variation. Glossiness decreased for 6,480 hours at temperature of $34{\sim}45^{\circ}C$ and color difference increased. Gloss stability was superior and color stability was weak, which requires improvement of optical properties. In artifacts on display in museums, there is concern about temperature rise on restoration materials by lighting therefore, it needs to minimize change in physical properties by exposure environments.