• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• v.28 no.4
• /
• pp.256-263
• /
• 2002

Using the rat's skull, the study on the biodegradability and guided bone regeneration of the chitosan membrane was performed. The results are as follows: 1. The biodegradability of the chitosan membrane could not be confirmed, but after 12 weeks, this membrane did not yet break into small pieces and there was no specific local tissue reaction. 2. It was not certain whether the pore size of this membrane was affected on osteoblastic activity. 3. After 6 weeks, the bony defect area of rat's skull was not completely filled, but on high magnification it showed that the osteoclasts and the osteoblasts were observed in the regenerating area. In conclusion, the chitosan membrane developed in this study was fit for guided bone regeneration.

• Korean Journal of Veterinary Research
• /
• v.50 no.1
• /
• pp.71-74
• /
• 2010

A trematode species belonging to the genus Prosthogonimus (family: Prosthogonimidae) was collected in August, 2004 from the bursa of Fabricius of a single Little Grebe, Tachybaptus ruficollis, caught in Chuncheon, Korea. Five specimens were collected in total and fluke morphology was examined under using a light microscope. The average parasite size was 5.6 ${\times}$ 3.2 mm (length ${\times}$ width; based on 4 specimens). The genital pore was located on the anterior right margin of the oral sucker. The cirrus sac was strongly sinuous and extended beyond the intestinal bifurcation to the ventral sucker. The prepharynx was extremely short and the pharynx was small. The vitellaria consisted of 6 follicle bunches and extended from the ventral sucker to the posterior of the testes. Finally, the uterus filled the body cavity posterior to the testes. In addition, there were no heavy slings occurred anterior to the testes. Based on these morphological characteristics, the parasites were identified as P. cuneatus. The discovery of P. cuneatus within a Little Grebe constitutes a new host identification and a new geographical record. This is the first reported case of Prosthogonimus infection within wild birds in Korea.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.40 no.5
• /
• pp.43-51
• /
• 1998

In design and management of sea0dikes, engineers need to study various transient seepage conditions through dikes not only for the sea water infiltration into dikes due to cyclic rises of sea water level also for the seepage flow out from dikes toward the sea due to cyclic drawdown of sea water level. Characteristics of seepage flow toward the sea from dikes are more complicated than as known and remained unclearly. The case of such seepage flow may be explained by figuring out seepage characteristics in filter as a part of sea-dikes. Filters in most sea-dikes in Korea are inevitably placed with reversely inclined shape due to field construction conditions. Most computer programs for seepage analysis based on the various numerical methods give practically acceptable results, but for the case of reversely inclined section of filters any verification to apply them might be needed. In this study, large scaled model tests were executed to verify and understand seepage flow through earth-filled sea-dikes. The results from numerical analysis and model tests show some remarkable differences in pore pressure distribution under cyclic changes of see level, and some of the results need to be considered in design and construction practices with further study.

• Journal of Korea Foundry Society
• /
• v.23 no.5
• /
• pp.244-250
• /
• 2003

The aim of this study is fabricating of composite filler metal (CFM) by a combination of selective laser sintering (SLS) of stainless steel powders (RapidSteel $2.0^{TM}$ and liquid phase infiltration of Ag-28 wt.%Cu alloy. Porous stainless steel body with inter-connected pore channels was fabricated by SLS, binder decomposing and densification processes. By the direct contact infiltration, the narrow inter-particle channels of the porous body were completely filled with the Ag-28 wt.%Cu alloy infiltrant. During infiltration, the dissolved elements of Fe, Ni and Cr from the porous body were solved into copper solid solution phases, which consist of eutectic structure of composite metal matrix. The S10C/CFM/S10C joints, which have narrow clearance gaps between them up to 10 micrometers, were joined successfully by self-feeding of filler metal from the matrix of CFM. The CFM kept its original thickness and microstructure after brazing. The tensile strength of brazed specimen was higher than 30 kgf/$mm^2$ and showed a typical ductile fracture mode in the CFM.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2009.03a
• /
• pp.819-835
• /
• 2009

In order to investigate the field application of selected stabilization methods(cover soil method, surface and total interval treatment of embankment method) on rice paddies contaminated by heavy metals, column test was carried out with heavy metal-contaminated soils collected from rice paddies around abandoned mine site. Columns were made by acrylic and filled with untreated soil, treated soil mixed with amendments(lime stone and steel refining slag) and uncontaminated cover soil according to the design report. Distilled water was discharged into the columns with the velocity of 1 pore volume/day. During test, pH, EC, and heavy metal concentration were measured in the regular term. The column test result showed that the selected stabilization methods were effective remediation method to stabilize heavy metals in paddy soils, but it was also expected that application of surface treatment methods was required the careful observation on pH variation due to the lowest increment.

• Polymer(Korea)
• /
• v.31 no.5
• /
• pp.379-384
• /
• 2007

The nanocomposites with inorganic nano powder, improved thermal stability, were prepared by urethane polymerization. The structure and surface properties of the nanocomposites were determined by X-ray diffraction and FT-IR, respectively. The thermal stabilities were studied using TGA and DSC. Their morphologies and mechanical properties were observed by SEM and UTM. As a result, the nanocomposites with MMT led to the increase of the silicate layers. The distance between layers of the nanacomposites with MMT was increased by $7.5{\AA}$ and the new peaks at $1038cm^{-1}$ were shown in the presence of the Si-O groups on the silica. The thermal stabilities of the nanocomposites were higher than those of pore polyurethane matrix. The nanocomposites had higher in mechanical properties than the pure polyurethane matrix.

• Journal of the Korean Ceramic Society
• /
• v.43 no.8 s.291
• /
• pp.472-478
• /
• 2006

The effect of compositional and processing variables on a nitriding reaction of silicon powder compact and subsequent post sintering of RBSN (Reaction-Bonded Silicon Nitride) was investigated. The addition of a nitriding agent enhanced nitridation rate substantially at low temperatures, while the formation of a liquid phase between the nitriding agent and the sintering additives at a high temperature caused a negative catalyst effect resulting in a decreased nitridation rate. A liquid phase formed by solely an additive, however, was found to have no effect on nitridation for the additive amount used in this research. The original site of a decomposing pore former was loosely filled by a reaction product ($Si_3N_4$), which provided a specimen with nitriding gas passage. For SRBSN (Sintered RBSN) specimens of high porosity, only a marginal dimensional change was measured after post sintering. Its engineering implication for near-net shaping ability is discussed.

• Journal of the Korean Geotechnical Society
• /
• v.15 no.2
• /
• pp.81-93
• /
• 1999

This paper investigated the negative skin friction acting on the model piles driven in the cylindrical chamber filled with remolded marine clay. In model tests, three load cells were installed on the model piles consisting of three parts to measure the negative skin friction forces independently. Pore pressures and ground movements were monitored throughout the period of investigation. Finite element analysis was used to simulate the behavior of a model pile. This paper describes the comparison of the behavior of negative skin friction on the single model pile with a numerical analysis by CRISP.

• Journal of the Korean Applied Science and Technology
• /
• v.31 no.3
• /
• pp.394-401
• /
• 2014

In order to minimize a building energy consumption with ventilation, a development of smart ventilation system is very important. In this study, a dry adsorbent that is main element of smart ventilation system was developed for removing indoor $CO_2$, and evaluate the adsorption performance. Specific surface area, pore characteristic and crystal structure of the modified sorbent was measured to analyze physical properties. From this analysis, it was found that the developed absorbent has a low specific surface area, due to mesopores of substrate was filled with metal contained raw material. Additionally, through analysis of the adsorption properties, the developed adsorbent was shown a adsorption form of mesopore (type IV), which means adsorption amount was rapidly increased at the part of high-pressure. Order to applying for the field, chamber test was performed. Continuous column tests (2,500 ppm) and batch chamber tests ($4m^3$, 5,000 ppm) showed $CO_2$ removal efficiency of 95% and 88% within 1 hour, respectively.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2022.04a
• /
• pp.109-110
• /
• 2022

Recently, it tend to increase the high-rise and large-scale of buildings and the developtment of construction technology can to be applied reinforced concrete structures to high-rise buildings. However, when a high-rise buildings is constructed with reinforced concrete, it has a disadvantage that buildings weight increases. In order to resolve the weight of reinforced concrete structures, various types of lightweight aggregates become development and research. Although lightweight aggregates can be reduced the weight of concrete, the strength of ITZ(Interfacial Transition Zone) is lowered due to its less strength than natural aggregates. In this study, an experimental study was conducted to coat the surface of lightweight aggregates with GGBFS(ground granulated blast furnace slag) to improve the strength of cement matrix mixed with lightweight aggregates. Result of this experimental study shows that the compressive strnegth of the surface coating lightweight aggregates was higher than general lightweight aggregates. Also, it was considered that this is because the pore at the ITZ of the surface-coated lightweight aggregates mixed cement matrix are filled with GGBFS fine particle.