• The Journal of the Acoustical Society of Korea
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• v.43 no.3
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• pp.261-269
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• 2024

In this paper, the acoustic performance of an absorptive silencer was enhanced by optimizing an arrangement of multi-layered absorbing materials. The acoustic performance of the silencer was evaluated through transmission loss, and finite element method-based numerical analysis program was employed to calculate the transmission loss. Polyurethane, a porous elastic material frequently used in absorptive silencers, was employed as the absorbing material. The Biot-Allard model was applied, assuming that air is filled inside the polyurethane. By setting the frequency range of interest up to the 2 kHz and the acoustic performance affecting properties of the absorbing materials were investigated when it was composed as a single layer. And the acoustic performance of the silencers with the single and multi-layered absorbing materials was compared with each other based on polyurethane material properties. Subsequently, the arrangement of the absorbing materials was optimized by applying the Nelder-Mead method. The results demonstrated that the average transmission loss improved compared to the single-layered absorptive silencer.

• The Journal of Korean Academy of Prosthodontics
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• v.30 no.3
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• pp.361-378
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• 1992

The purpose of this investigation was to evaluate the effect of the porous hydroxyapatite particles (Interpore $200^{(R)}$) and guided tissue regeneration membrane ($Gore-Tex^{TM}$ augmentation material) on amount and shape of generating new bone adjacent to implant. Implants were placed immediately after extraction in the bilateral 3rd, 4th premolars of the mandible of the adult dogs. In all experimental groups, artificial bony defects were formed at the buccal cortex area, 3.3mm in width and 3.0mm in depth. In the control group : sutured without HA particles & membranes after placing implants, the experimental group 1 : membrane was place over the artificial bony defect, the experimental group 2 : bony defect was filled with HA particles and covered with membrane. The examination of bone-implant interfaces using light microscope and fluorescent microscope concluded as follows. 1. In all three experimental groups, osseointegration was observed without epithelial migration. 2. In the healing degree of bony defect area, the experimental group 1, 2 showed more prominent healing than control group, and the experimental group 1 showed the most excellent bone formation. 3. In fluorescent microscopic finding, bone remodeling was observed in regenerated bone tissue at defect area of experimental group 1, but in experimental group 2, irregular, discontinuous linear fluorescence was observed at the lower portion of defect area and sign of bone remodeling was weak.

• Journal of Biomedical Engineering Research
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• v.25 no.1
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• pp.1-4
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• 2004

On the background of general idea and technique of bioscience, medicine and engineering, tissue engineering aim at maintenance, improvement and repair of human body function through manufacturing and transplantation of artificial tissue and organ exchangeable human body. Basic material used in the area is scaffold that aid tissue and organ formation. Making scaffold, solvent-casting and particulate leaching technique is widely used in manufacturing of porous polymer scaffold. There are many types of particle including salt and gelatin. Salt is a most commonly used particulate because it is easily available and very easy to handle and gelatin particle is another candidate for this method because it is known as a material, which enhances cell attachment and proliferation. But there is no comparative study of two kinds of materials. In this study we compared the biocompatibility of the two scaffolds made from salt(salt scaffold) and gelatin particle (gelatin scaffold). These results demonstrated that gelatin scaffold showed better attachment of cells at the initial stage and better proliferation of cells. The better performance of gelatin scaffold is contributed to the better connection of pores in the same porosity.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.10 no.1
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• pp.72-81
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• 2007

This study mainly aims at suggesting plans applicable to the outdoor of environment-friendly communities in Korea by leveraging more natural conditions and materials when creating an outdoor biotop for an environment-friendly community and generating material types and development techniques enabling a natural circulation system. To this end, materials used in the outdoor of environment-friendly communities and traditional residential areas in Korea and biotop materials found in natural areas were examined. First, when the case examples of environment-friendly communities were reviewed, biotop spaces and materials that may function as habitats were hardly found. Materials used in biotop were mainly man-made structures made of artificial or processed materials, such as concrete, stones, bricks, woods and steels. Meanwhile, the outdoor space of traditional Korean villages had stone walls, soil walls, rock piles and composite piles, which composed of natural materials such as rocks, soil and plants, that naturally formed porous spaces along with the introduction of plants and provided habitats for a variety of insects. In natural areas, naturally created biotop spaces, such as rock piles, log piles, old tree deployment, branch piles, hay stacks and defoliated leaves, were found. Meanwhile, when spaces and materials available for biotop creation were reviewed to create an environment-friendly residential complex, they were divided into fences and hedges, green spaces between parks and residential buildings, ponds and waterscape spaces, zones separating pedestrian walks and roadways, breast walls and slope boundary, plant box and pergola. For each space, materials used for creating biotops and that were found in traditional Korean residential areas and natural areas were applied and suggested.

• Ecology and Resilient Infrastructure
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• v.11 no.1
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• pp.11-22
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• 2024

A fishway is an artificial waterway or device used to resolve difficulties in the movement of fish in a river. Most existing fishways are made of concrete and emit toxic substances, which has a negative impact on the river environment. Accordingly, there is a need to develop fishway construction technology that is eco-friendly and can increase movement efficiency. The technology presented in this study is an integrated porous structure that combines the aggregate with a biopolymer material extracted from castor oil, a non-toxic material. It is a fishway construction technology using eco-friendly materials that can allow vegetation to grow on the surface. In this study, an eco-friendly fishway mixed with biopolymer and aggregate was built on a real scale and the fish movement efficiency was tested and analyzed. As a result of the experiment, a total of 201 fish of 14 species were released with tags inserted, and the detection rate of released fish was confirmed to be 82.6% on average. A total of 40 fish of 6 species were transported upstream through the fishway, and the average passage rate was confirmed to be 21.7%. As a result of checking the circadian migration pattern, it was found that all fish mainly migrate during the day. It was confirmed that there was no significant functional difference between a fishway using biopolymer and a concrete fishway. It is believed that a fishway using biopolymer can be used as a replacement for a concrete fishway.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1B
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• pp.51-60
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• 2006

Water quality improvement in mattress/filter system using porous material like slag from industrial activity and zeolite that has been studied for environment improvement and pollution abatement is very useful in polluted stagnant stream channel. Slag is consisted of CaO, $SiO_2$, $Al_2O_3$ and $Fe_2O_3$. Slag with large specific surface area of porosity has been used such as sludge settling and adsorptive materials. Because slag is porous, it can be used for purification filter. As slag is used as filled materials of mattress/filter system and the system has good advantages for the waste water treatment, water recycling, and the improvement of water quality at the same time and so on. Because zeolite has much advantage of cation exchange, adsorption, catalyst and dehydration characteristics, It is used for environment improvement of livestock farms, treatment of artificial sewage and waste water, improvement of drinking water quality, radioactive waste disposal and radioactive material pollution control. In this study, according to verifying effects of water quality improvement of fill materials by porosity that 38.6%, 45.8% and 49.8% respectively in the stagnant stream channel, water quality monitoring of inflow and outflow was conducted on pH, DO, BOD, COD, SS, T-N and T-P. Mattress/filter system was able to accelerate water quality improvement by biofilter as waste water flows through gap of mattress/filter fill materials and by contact catalysis, absorption, catabolism by biofilm. Mattress/filter system used slag and zeolite forms biofilm easily and accelerates adsorption of organic matter. As a result, mattress/filter system increases water self-purification and accelerates water quality improvement available for stream water clean-up.

• Journal of Chest Surgery
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• v.30 no.8
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• pp.739-746
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• 1997

A variety of experiments concerning the development of ideal prosthetic grafts for correcting circumferential tracheal defects have been performed. The requirements for an ideal tracheal prosthesis are impermeability to air, consistency to prevent collapse, and acceptance by the host tissue causing a minimum inflammatory reaction, allowing fibroblastic infiltration and epithelialization. The synthetic material, polyurethane(PU), is known as a biocompatible polymer with an inert component. In this study, the tracheal prosthesis was made from microporous PU(30 micrometer in diameter) coated with gelatin and reinforced with isoplastic rings. This procedure provides the prosthesis with a compression strength. The out side diame er of the prosthesis was 20 mm with a length of 30 mm. The gelatin used in the study was obtained from pig skin and immobilized and cross-linked by irradiation(60 Co gamma ray) to promote host tissue incorporation and render the prosthesis epithelization after implantation. Animal experiments using 10 mongrel dogs were performed to compare three kinds of prosthesis; gelatin coated polyurethane graft, uncoated polyurethane graft, and prosthesisf pericadium complex graft. After 6 weeks of implantation, the epithelialization of implants was seen on the gelatin-coated and prosthesisfpericadium complex grafts. Implanted prosthesis were complicated by airway obstruction due to anastomosis granuloma. Early tracheal stenosis was found in the uncoated graft group. Two kind of anastomosis techniques were tested on the gelatin-coated prosthesis. Everted anastomosis resulted severe granuloma than the inverted anastomosis. In the prosthesislpericadium complex graft, bacteria and inflammation at a anastomotic site was found. Based on these results, gelatin coated porous polyurethane trachea prosthesis is biocompatible and may be useful in clinical application with further investigation.

• Applied Chemistry for Engineering
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• v.16 no.4
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• pp.527-532
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• 2005

Ionic polymer metal composites (IPMC) are soft polymeric smart materials having large displacement at low voltage in air and water. The polymeric electrolyte actuator consists of a thin and porous membrane and metal electrodes plated on both faces, in impregnation electro-plating method. The response and actuation of actuator are governed. Among many factors governing the activation and response of IPMC actuator, the surface electrode plays an important role. In this study, the well-designed modification of electrode surface was carried out in order to improve the chemical stability well as electromechanical characteristics of the IPMC actuator. We employed Ion Beam Assisted Deposition (IBAD) method to prepare the topologically homogeneous thin surface electrode. After roughing the surface of Nafion membrane in order to get a larger surface area, the IPMC was prepared by impregnation for electro-plating and re- coating on the surface through traditional chemical deposition, followed by an additional surface treatment with high conductive metals with IBAD. It was observed that our IPMC specimen shows the enhanced surface electrical properties as well as the improved actuation and response characteristics under applied electric field.

• Korean Journal of Heritage: History & Science
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• v.56 no.2
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• pp.148-169
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• 2023

Hayeob pigment is known as one of the traditional dark green pigments, but the color, raw material, and manufacturing method have not been clearly identified. However, comparing the analysis results of the particle shape and constituent minerals of Hayeob pigments revealed through pigment analysis studies of colored cultural properties such as Dancheong, Gwaebul, and paintings, Hayeob pigments appear to be the same as Dongrok pigments produced by salt corrosion. Therefore, in order to restore Hayeob pigment, the manufacturing method of Dongrok pigment was studied based on the records of old literature. The Dongrok pigment manufacturing method confirmed in the old literature records is a natural corrosion method in which copper powder and a caustic are mixed and then left in a humid condition to corrode. Based on this, artificial corrosion using a corrosion tester was adopted to corrode the copper powder more efficiently, and an appropriate mixing ratio was selected by analyzing the state of corrosion products according to the mixing ratio of the caustic agent. In addition, the manufacturing method of Dongrok pigment was established by adding a salt removal process to remove residual caustic agents and a purification process to increase chroma during pigment coloring. The prepared Dongrok pigments have a bluish green or green color, show an elliptical particle shape and a form in which small particles are aggregated, and a porous surface is observed. The main constituent elements are copper(Cu) and chlorine(Cl), and the main constituent mineral is identified as atacamite [Cu₂Cl(OH)₃]. As a result of an accelerated weathering test to evaluate the stability of the prepared Dongrok pigments, it was found that the greenness partially decreased and the yellowness significantly increased as deterioration progressed. Before deterioration, the Dongrok pigments had lower yellowness compared to the Hayeob pigments of the old Dancheong, but after deterioration, yellowness increased significantly, and it was found to have a similar chromaticity range as Dancheong's Hayeob pigments. As a result, the prepared Dongrok pigments were confirmed to be similar to Dancheong's Hayeob pigments in terms of color as well as particle shape and constituent minerals.