• Journal of Microbiology and Biotechnology
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• v.6 no.2
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• pp.132-136
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• 1996

To investigate the characteristics of immobilized peppermint (Mentha piperita) cells, dry cell weight (DCW), change of cell viability, and oil productivity of the immobilized cells were determined. Peppermint cells were immobilized in polyurethane (PU) foams of $5{\times}5{\times}5$ mm and cultured in a shaking flask. The maximum DCW was 2.1 mg per foam piece after 20 days of cultivation and the cell density was approximately 420 mg per flask containing 200 foams in 200 ml medium. For the first five days of cultivation, the cell viability was about 80$%$ and decreased to 70$%$ during 5 to 20 days of cultivation. The maximum oil productivity, 148 mg/l was achieved after 40 days of cultivation. The immobilized cells were also cultivated in a bioreactor, equipped with a round spiral type impeller, containing 2, 400 PU foams. The cell viability after 30 days of cultivation with chitosan as an elicitor in the bioreactor was 67$%$ and DCW was 2.0 mg per foam piece. Though the cell viability was relatively high in the bioreactor system, the oil productivity was relatively lower than that of the flask system.

• Journal of the Korean Ceramic Society
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• v.50 no.2
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• pp.93-102
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• 2013

Macro porous ceramics possessing controlled microstructures and chemical compositions have increasingly proven useful in the industrial sphere. Their sintered structures have found application in both established and emerging, areas such as thermal insulation in buildings, filtration of liquids and molten materials, refractory insulation, bone scaffolds and tissue engineering. Stable ceramic foams can be formed by wet chemical methods using inorganic particles(e.g., $Al_2O_3$ or $SiO_2$). The wet foams are dried and sintered with improved porosity and mechanical properties. This review examines the different techniques used to prepare porous ceramics from ceramic foams, focusing on the explanation of this versatile method of direct foaming from the past to the present. Comparisons of the processes and the processing parameters are explained with the produced microstructures.

• Journal of the Korean Wood Science and Technology
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• v.48 no.6
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• pp.861-868
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• 2020

The use of polyphenol extracts from radiata pine (Pinus radiata) bark as raw materials for bio-foams was investigated along with the optimal NaOH extraction conditions. The targeted yield of alkaline extracts was 60%, and the targeted pH was 11 to 12. The radiata pine bark was composed of 70% of a 1% NaOH extract, which contained mainly polyphenols, such as proanthocyanidin (PA). As the particle size of the bark decreased, the yield of the 1% NaOH extracts increased from 57 to 87%. A range of NaOH concentrations, liquor ratios, and extraction times were explored to establish an economic polyphenol extraction method. More than 60% of the alkaline extract was extracted, and the pH of the extract was approximately 12 when the optimum extraction conditions were employed, i.e., a liquor to bark ratio of 5:1, a NaOH dosage of 17 to 18% based on the bark weight, and a 1 h extraction time. Following neutralization of the alkaline extract, structural analysis indicated severe structural changes in the PA during the alkaline extraction. Because the alkaline extract was barely soluble in the solvent used for the structural analyses, it is assumed that chemical modification is required to increase the solubility of the alkaline extract for the production of bio-foams.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.938-941
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• 2006

We present a new design method of one-dimensional multi-layered acoustic foams for transmission loss maximization by topology optimization. Multi-layered acoustic foam sequences consisting of acoustic air layers and poroelastic material layers are designed for target frequency values. For successful topology optimization design of multi-layered acoustic foams, the material interpolation concept of topology optimization is adopted. In doing so, an acoustic air layer is modeled as a limiting poroelastic material layer; acoustic air and poroelastic material are handled by a single set of governing equations based on Biot's theory. For efficient analysis of a specific multi-layered foam appearing during optimization, we do not solve the differential equations directly, but we use an efficient transfer matrix approach which can be derived from Biot's theory. Through some numerical case studies, the proposed design method for finding optimal multi-layer sequencing is validated.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.4
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• pp.118-125
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• 2009

Bumper is designed to protect the automotive frame without damage at low velocity. Expanded polypropylene (EPP) foam is used in the bumper as an energy absorbing material. In order to exactly predict the energy absorbing performance of the foam material under impact loading condition, it is important to use high strain rate material properties. In this study, a new apparatus for dynamic compression tests was developed to investigate the high strain rate behavior of EPP foams. Three kinds of EPP foams which have different expansion ratios were tested to investigate the quasi-static and dynamic compression behavior. Quasi-static compressions were performed at low strain rates of 0.001/s, 0.1/s and 1/s. The dynamic compressions were carried out at high strain rates of 50/s and 100/s with the developed apparatus. It was observed that the EPP foam has significant strain rate effect as compared to quasi-static behavior.

• Elastomers and Composites
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• v.35 no.4
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• pp.296-302
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• 2000

The surfaces of injection and pressure-molded sheets of poly(ethylene-covulylacetate)(EVA) foams used for shoe mid-sole were treated with low temperature plasma to improve adhesion with a water-based polyurethane adhesives. Several experimental variables were considered, such as radio frequency power, treating time, type of gas. gas flow, and distance between electrode and sample. The modificated surface by plasma treatment were characterized using contact angle meter, scanning electron microscopy(SEM), universal testing machine(UTM). Adhesion was tested by T-peel tests of treated EVA foams/polyurethane adhesive joints. The treatment in the low temperature plasma produced a noticeable decrease in contact angle. The peel strength of EVA foams treated with plasma was increased with plasma treating time, and gas flow.

• Journal of the Korean Ceramic Society
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• v.48 no.6
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• pp.600-603
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• 2011

The microstructure of particle stabilized wet foams can be tailored by using parameters including the amphiphile concentration, contact angle, and surface tension. The influence of these parameters on the porosity is satisfactorily described in terms of a combined influence of the contact angle and surface tension of the initial suspensions that are directly affected by the amphiphile concentration. The resulting macroporous structures exhibited a total porosity of 82%. The foam cells were predominantly closed due to the air bubbles of the original wet foams being completely covered.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.32 no.3
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• pp.25-31
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• 2000

It is required to use substantial amount of wet strength resin for producing multi-functional mulch papers since these paper products shold maintain its strength properties when they exposed to outdoor weather for several months. While producing mulch papers it is usual to observe significant amount of foam at white water silo. Thus it is imperative to use defoaming or antifoaming agents. In this study diverse defoaming and antifoaming agents have been tested for their effective-ness in eliminating foams that produced. It was shown that combined use of a silicone type defoamer and a fatty acid type anti-foaming agent was msot effective in eliminating foams. These chemicals were used in trial production of mulch papers and their influence on paper-making wet end system was examined including one pass retention cationic demand con-ductivity pH etc. It was found that the defoaming agents were very effective for removing foams in trial production. Tensile strengths of the mulch papers produced were significantly greater than commericial mulch papers produced in Japan.

• Journal of Korea Foundry Society
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• v.28 no.2
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• pp.79-84
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• 2008

Metal foam is one of the most interesting materials with various multi-functional properties such as light weight, energy absorption, high stiffness and damping capability. Among them, energy absorption property has keen interests in the field of automotives for passenger protection. Nowadays, researches about pore size and porosity control of the foam are increased to correspond them. However, though energy absorption properties are improved, these results are not cost-effective process. In present research, however, as a part of improving the energy absorption property of metallic foams, 606X aluminum alloy was used for cell wall material which has higher strength than pure aluminum. And its morphological features are characterized. As a results, porosity and pore size are uniformity distribution with increasing foaming temperature in the case of 6061 alloy foams. 6063 alloy foam specimens have opposite tendency because of the influence of alloying element and viscosity of the molten melt.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.1 s.232
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• pp.151-158
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• 2005

A characteristic of discharge for a foam spray nozzle with various parameters was investigated. The discharge patterns from a fire foam spray nozzle are important to evenly spray over a maximum possible floor area. Two parameters of a foam spray nozzle were chosen, and compared with those from the standard one. Also, in order to evaluate the performance of discharged foam agents used to protect structures from heat and fire damages, the thermal characteristics of fire-protection foams were experimentally investigated. A simple repeatable test for fire-protection foams subjected to fire radiation was developed. This test involves foam generation equipment, a fire source for heat generation, and data acquisition techniques. Results show that the bubble size of foam is increased by large inside diameter of orifice or closed air hole, but phenomenon of discharge angle and expansion ratio is opposite. For the case of the open air hole, liquid film of a circular cone discharges with formation, growth, split and fine grain. In case of the closed air hole, a pillar of foam solution discharges with that. Though the temperature gradient in the foam increases with increased foam expansion ratio. it is not change with increased intensity of heat flux.