• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.3
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• pp.160-166
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• 2014

In this research, as a measure of reducing energy lost through external wall, we used Glass Hollow Micro Sphere (HMS) to improve insulation performance to structural concrete. The following is a result of experimenting concrete using HMS. As usage of HMS, decrease in slump arose and it is judged as a need of using superplasticizer. Replacement ratio increasing more and more, amount of air showed tendency to decrease and compressive strength decreased for interfacial adhesion had not been formed. as replacement ratio and unit volume decreased. It appears that thermal conductivity decreased about 30.0~46.5 percent as compared with normal weight concrete.

• Journal of Biomedical Engineering Research
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• v.25 no.1
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• pp.33-41
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• 2004

Accuracy of registration between images acquired from various medical image modalities is one of the critical issues in radiation treatment planing. In this study, a method of accuracy evaluation of image registration using a homemade brain phantom was investigated. Chamfer matching of CT-MR and CT-SPECT imaging was applied for the multimodal image registration. The accuracy of image correlation was evaluated by comparing the center points of the inserted targets of the phantom. The three dimensional root-mean-square translation deviations of the CT-MR and CT-SPECT registration were 2.1${\pm}$0.8 mm and 2.8${\pm}$1.4 mm, respectively. The rotational errors were ＜ 2$^{\circ}$ for the three orthogonal axes. These errors were within a reasonable margin compared with the previous phantom studies. A visual inspection of the superimposed CT-MR and CT- SPECT images also showed good matching results.

• Journal of the Korean GEO-environmental Society
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• v.23 no.11
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• pp.5-11
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• 2022

The objective of this study is to evaluate the mechanical properties of high-flowable retaining wall material (RWM) incorporated with ground granulated blast-furnace slag (SG) and steel fiber (SF) based on a comparison with those of ordinary portland cement (OPC). To produce the specimens of RWM, some chemical agents such as superplasticizer (SP), air-entrained agent (AEA) and viscosity modifying agent (VMA) are added in the fresh RWM. The compressive, split tensile and flexural strength measurements were performed on the hardened RWM specimens. Additionally, surface electric resistivity and absorption tests according to ASTM standards were carried out at predetermined periods after water curing. It was found that the mechanical properties of slag cement concrete (SGC) RWM mix are better than those ordinary portland cement concrete (OPC) RWM mix. The effect of SF is remarkable to improve the mechanical properties of RWM mixes. It is noted that the usage of SG shows a beneficial effect to resist water penetration as well as long-term strength development of RWM mixes.

• Journal of the Korean GEO-environmental Society
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• v.24 no.6
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• pp.13-20
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• 2023

This paper is aimed to evaluate the mechanical properties and durability of high-flowable retaining wall material (RWM) with different levels of steel fiber (SF) content. To produce the specimens of RWM, some chemical agents such as superplasticizer (SP), air-entrained agent (AEA) and viscosity modifying agent (VMA) were added in the fresh RWM. The compressive and split tensile strength measurements were performed on the hardened RWM specimens at the predetermined periods. Additionally, surface electric resistivity and absorption tests according to ASTM standards were carried out to examine mechanical properties of RWM mixes. The durable performances such as chloride ions penetrability and freezing-thawing resistance of RWM mixes were experimentally investigated. As resutls, it was found that the performance of RWM mix with SF were much better than that without SF, especially at the 2% addition of SF. Thus, it is noted that the proper addition of SF in the RWM mix may have a beneficial effect to improve mechanical properties and durability of RWM mixes.

• Journal of Broadcast Engineering
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• v.23 no.4
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• pp.526-535
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• 2018

Many steganography algorithms have been studied, and steganalysis for detecting stego images which steganography is applied to has also been studied in parallel. Especially, in the case of the image steganalysis, the features such as ALE, SPAM, and SRMQ are extracted from the statistical characteristics of the image, and stego images are classified by learning the classifier using various machine learning algorithms. However, these studies did not consider the effect of image size, aspect ratio, or message-embedding rate, and thus the features might not function normally for images with conditions different from those used in the their studies. In this paper, we analyze the classification rate of the SPAM-based image stegnalysis against variety image sizes aspect ratios and message-embedding rates and verify its versatility.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.477-477
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• 2018

하천의 제방은 하천수의 범람을 방지하기 위하여 인공적으로 만든 구조물로서, 유수의 흐름을 일정하게 하고 자연재해에 대하여 제내지를 보고하기 위한 목적도 있다. 제방은 제내지와 제외지의 수위차로 인해 발생하는 파이핑, 제방의 월류, 사면의 탈락 등으로 파괴가 발생되고, 제방의 파괴는 제내지의 인명, 토지, 건물 등에 많은 피해가 발생한다. 이러한 제방의 파괴를 방지하기 위하여 제방 사면의 호안, 차수벽, 수제 등을 설치하고 있으며, 구조물 외에도 제방 응급복구를 위한 모래주머니, 비탈면 보호 시설 등을 이용한 피해방지에 대한 대책을 세우고 있다. 제방 구조물의 대부분은 콘크리트를 이용한 고강도 재료를 사용하여 설치되고 있으며, 재료의 환경성에 대한 문제점이 대두되어 왔다. 이에 따라 코코넛껍질을 이용한 사면 보호공, 고강도 식생매트를 이용한 사면 보호 등 친환경 재료를 이용한 사면보호 공법에 대한 연구들이 다양하게 진행되어 왔다. 본 연구에서는 미생물을 이용하여 사면을 보호하기 위한 블록 및 피복기법에 대한 연구를 진행하고 있으며, 다양한 환경성 및 무독성 검증도 병행중에 있다. 그 중 본 연구에서는 신소재와 황토, 모래, 석고를 다양한 비율로 조합하여 블록으로 활용하기 위한 일축압축 강도 실험을 수행하였으며, 신소재의 소류력 저항능력을 실험하기 위하여 안동 하천실증연구센터의 급경사 수로에 신소재를 피복한 시험구를 조성하고 5m/s 이상의 유속에서 저항능력 실험을 수행하였다. 본 연구에서는 본 실험 결과를 기반으로 하여 추후 다양한 친환경 재료를 이용한 조합을 통해 기존 콘크리트 블록에 준하는 강도를 발현할 수 있는 신소재 블록의 개발을 목표로 하고 있다.

• Journal of Broadcast Engineering
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• v.24 no.2
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• pp.315-328
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• 2019

Image steganalysis is an algorithm that classifies input images into stego images with steganography methods and cover images without steganography methods. Previously, handcrafted feature-based steganalysis methods have been mainly studied. However, CNN-based objects recognition has achieved great successes and CNN-based steganalysis is actively studied recently. Unlike object recognition, CNN-based steganalysis requires preprocessing filters to discriminate the subtle difference between cover images from stego images. Therefore, CNN-based steganalysis studies have focused on developing effective preprocessing filters as well as network structures. In this paper, we compare previous studies in same experimental conditions, and based on the results, we analy ze the performance variation caused by the differences in preprocessing filter and network structure.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.3
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• pp.187-194
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• 2005

This paper deals with a waterproof and mechanical feature of concrete using an inorganic self waterproof agent. The waterproof agents having been used in our country were a membrane agent, penetration agent and an organic waterproof agent. However, these agents have a lot of problems such as losing the effect of waterproof in the environment of lots of water, the difficulty of dispersion. For the clear of problems of these water -proof agents, we used the inorganic waterproof agent. This agent was made from inorganic fluosilicate. Generally, a waterproof agent has been used only for the waterproof effect. In this paper, however through the some tests of concrete using the inorganic self waterproof agent, we recognized that the concrete using the agent is more excellent in some peculiar properties than general concrete's properties. In this paper, we performed compressive strength, permeability, pore volume test, etc. As a result, the concrete of using the agent is more excellent in economy, waterproof, compressive strength.

• Korean Chemical Engineering Research
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• v.47 no.5
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• pp.639-645
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• 2009

In this study, alkanolamine was used to achieve high absorption rates for $CO_2$ as suggested at several literatures. The absorption rates of aqueous AMP and MEA solutions with $CO_2$, $SO_2$, $NO_2$ were measured using a stirredcell reactor. The reaction rate constants were determined from the measured absorption rates. The performances were evaluated under various operating conditions. As a result, the reactions with $SO_2$, $NO_2$ into aqueous AMP and MEA solutions were classified as an instantaneous reaction respectively. The absorption rates increased with increase of the reaction temperature and the concentration of absorbents. The simultaneous absorption rate of $CO_2/SO_2/NO_2$ into 3, 5, 10 wt.% MEA at various pressure of $CO_2/SO_2/NO_2$, was more increased 14~20% than AMP solution. We investigated the effect of $SO_2$ and $NO_2$ on the simultaneous absorption of $CO_2/SO_2/NO_2$ from a flue gas. The performances were evaluated under various operating conditions in order to investigate the absorption characteristic.

• Journal of the Korean Wood Science and Technology
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• v.46 no.5
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• pp.449-470
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• 2018

A review of research trends on wood surface protection for exterior use obtained the following conclusions: It has been reported that inorganic compounds such as chrome and copper used as wood preservatives can protect wood from weathering. It has been shown that precoating with hydrophobic substances such as wax and oil, UV absorbers, and HALS (Hindered Amine Light Stabilizers) enhances weathering resistance on the surface of ACQ-treated wood. Opaque coatings of paint/stains and semitransparent stains on the surface of preservative treated wood can increase the synergistic effects on prevention of weathering deterioration. Also the need for repainting periodically for the protection of the preservative treated wood surface has also been suggested. ZnO or $TiO_2$ of fine particles, metal ions such as Co, Cr, Fe, Mn, Ni and Ti, and UV absorbers such as tris-resorcinol triazine derivatives, triazine and benzotriazole were introduced as additives for preventing UV in the transparent coating on wood. Several reports showed that chemical modification such as methylation, acetylation, or alkylations have made some increases the effects of preventing weathering with the increasing weight gain of chemical formulas. In heat-treated wood, there were various contradictory reports on the resistance of weathering, and there were some other reports emphasizing the necessity of painting with UV resistance, which leads to the necessity of more advanced studies.