• Archives of Plastic Surgery
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• v.32 no.5
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• pp.599-606
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• 2005

Clinical application of the cartilage formed by tissue engineering is of no practical use due to the failure of long-term structural integrity maintenance. One of the important factors for integrity maintenance is the biomaterial for a scaffold. The purpose of this study is to evaluate the difference between polylactic-co-glycolic acids (PLGA) and chitosan as scaffolds. Human auricular chondrocytes were isolated, cultured, and seeded on the scaffolds, which were implanted in the back of nude mice. Eight animals were sacrificed at 4, 8, 12, 16, and 24 weeks after implantation respectively. In gross examination and histological findings, the volume of chondrocyte-PLGA complexes was decreased rapidly. The volume of chondrocyte-chitosan complexes was well maintained with a slow decrease rate. The expression of type II collagen protein detected by immunohistochemistry and western blots became weaker with time in the chondrocyte-PLGA complexes. However, the expression in the chondrocyte-chitosan complexes was strong for the whole period. Collagen type II gene expressions using RT-PCR showed a similar pattern. In conclusion, these results suggest that chitosan is a superior scaffold in cartilage tissue engineering in terms of structural integrity maintenance. It is expected that chitosan scaffold may become one of the most useful scaffolds for cartilage tissue engineering.

• Archives of Plastic Surgery
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• v.40 no.2
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• pp.89-90
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• 2013

• Archives of Plastic Surgery
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• v.47 no.5
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• pp.392-403
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• 2020

Severe cartilage defects and congenital anomalies affect millions of people and involve considerable medical expenses. Tissue engineering offers many advantages over conventional treatments, as therapy can be tailored to specific defects using abundant bioengineered resources. This article introduces the basic concepts of cartilage tissue engineering and reviews recent progress in the field, with a focus on craniofacial reconstruction and facial aesthetics. The basic concepts of tissue engineering consist of cells, scaffolds, and stimuli. Generally, the cartilage tissue engineering process includes the following steps: harvesting autologous chondrogenic cells, cell expansion, redifferentiation, in vitro incubation with a scaffold, and transfer to patients. Despite the promising prospects of cartilage tissue engineering, problems and challenges still exist due to certain limitations. The limited proliferation of chondrocytes and their tendency to dedifferentiate necessitate further developments in stem cell technology and chondrocyte molecular biology. Progress should be made in designing fully biocompatible scaffolds with a minimal immune response to regenerate tissue effectively

• Journal of the Korean Society of Safety
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• v.17 no.4
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• pp.146-152
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• 2002

The steel shows plastic deformation after the yield point exceeds. Because of overloads, the plastic deformation occurs at the interior support of a continuous bridge. The plastic deformation is concentrated at the interior support, and the permanence deformation at the interior support remains after loads pass. Because local yielding causes the positive moment at the interior support, it is called "auto moment". Auto moment redistributes the elastic moment. Because of redistribution, auto moment decreases the negative moment at the interior support of a continuous bridge. In this paper, the moment-rotation curve from Schalling is used. The Plastic rotation is computed by using Beam-line method, and auto moment is calculated based on the experiment curve. The design example is presented using limit state criterion.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.9
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• pp.475-483
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• 2015

In Korea, a typically hot and humid summer means that air-conditioners consume a large quantity of electricity; accordingly, the simultaneous usage of an indirect evaporative cooler may reduce the sensible-heat level and save the amount of electricity that is consumed. In this study, the heat-transfer and pressure-drop characteristics of an indirect evaporative cooler made of paper/plastic film were investigated under both dry and wet conditions; for the purpose of comparison, an indirect evaporative cooler made of plastic film was also tested. Our results show that the indirect evaporative efficiencies under a wet condition are greater than those under a dry condition, and the efficiencies of the paper/plastic sample (109% to 138%) are greater than those (67% to 89%) of the plastic sample; in addition, the wet-surface, indirect evaporative efficiencies of the paper/plastic sample are 32% to 36% greater than those of the plastic sample. Further, the wet-surface pressure drops of the paper/plastic sample are 13% to 23% larger than those of the plastic sample, and this might have been caused by the surface roughness of the samples. A rigorous heat-transfer analysis revealed that, for the plastic sample, 30% to 37% of the wet channels remained dry, whereas all of the channels were wet for the paper/plastic sample.

• Advances in materials Research
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• v.13 no.2
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• pp.115-128
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• 2024

Concrete is the most significant material in the construction industry which is required to construct several facilities like roads, buildings, and bridges etc. which leads to the economic development of a country. But now days, in view of sustainable development and environmental problems, plastic waste management is one of the major environmental issues due to its non-biodegradable nature which allows it to stay in the landfills until they are cleaned up. To overcome all these concerns, plastic waste may be used as a substitute of natural fine and coarse aggregate in concrete and a valuable solution to utilize the plastic items which causes several problems. In order to, present study is focused on the affecting properties of concrete as workability, compressive strength, and tensile strength of concrete with using plastic waste and without using plastic waste. Based on the detailed literature, it was observed that the plastic waste is not affecting the quality and consistency of concrete. However, as the number of PVC particles in the mixture increased, the drying shrinkage values decreased and the inclusion of plastic flakes can mitigate drying shrinkage cracking which leads the higher durability of concrete. Based on the comprehensive literature, it was also observed that the plastic aggregate found to be suitable for low and medium strength concrete. However, the investigation on the application of plastic aggregate in the high strength concrete is found limited. It was concluded that the optimum percentage of the plastic aggregate was found about 20%.

• Design & Manufacturing
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• v.8 no.1
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• pp.40-44
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• 2014

As a rotating machine element, plastic gears are more and more widely used in such as industrial machine element, since plastic gear is lighter, higher wear-resistance, and higher vibration absorbing ability than metal gears. When operating plastic parts, tooth breakage and fatigue life shortened due to increasing number of applying load and tooth flank temperature rising, such that accuracy of plastic gears is divided from allowable range to cause vibration and noise. On this study, a internal plastic gears are developed which improved the filling balance molding process by a new injection mold structure. The new mold structure called HR3P(hot runner type 3plate mold). As the result from this studies, we obtained a very accurate roundness internal gears by using design of experiment.

• Geomechanics and Engineering
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• v.8 no.6
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• pp.783-799
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• 2015

In this study, effect of horizontal in situ stress on failure mechanism around underground openings excavated in isotropic, elastic rock zones is investigated. For estimating the plastic zone occurrence, an induced stress influence area approach (Bray Equations) was modified to define critical stress ratio according to the Mohr-Coulomb failure criterion. Results obtained from modified calculations were compared with results of some other analytical solutions for plastic zone thickness estimation and the numerical modelling (finite difference method software, FLAC2D) study. Plastic zone and its geometry around tunnels were analyzed for different in situ stress conditions. The modified equations gave similar results with those obtained from the other approaches. However, safer results were calculated using the modified equations for high in situ stress conditions and excessive ratio of horizontal to vertical in situ stresses. As the outcome of this study, the modified equations are suggested to use for estimating the plastic zone occurrence and its thickness around the tunnels with circular cross-section.

• Computers and Concrete
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• v.10 no.6
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• pp.663-681
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• 2012

This paper presents a parametric study of the plastic hinge length of circular reinforced concrete columns using a three-dimensional finite element analysis method, and using the Taguchi robust design method to reduce computational cost. Parameters examined include the longitudinal reinforcing ratio, the shear span-to-depth ratio, the axial force ratio and the concrete compressive strength. The study considers longitudinal reinforcement with yield strengths of 414 MPa and 685 MPa, and proposes simplified formulas for the plastic hinge length of circular reinforced concrete columns, showing that increases in plastic hinge length correlate to increases in the axial load, longitudinal reinforcing and shear span-to-depth ratios. As concrete strength increases, the plastic hinge length decreases for the 414 MPa case but increases for the 685 MPa case.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1450-1453
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• 2003

Safety-shoes are developed for heavy industry. Nowadays with the development of industry, it is increase on all of industry field. Safety-shoes are to be classfied into using intention. And it's developed not only protect from danger but also more comfort wearing. When wear a safety shoes, in cold weather, serious disease could be occur such as frostbitten and so on. In the study replacees steel toe-cap by polymer. When it replace by polymer, Moreover add keeping warm, light weighting, chemicals-proof. Nowadays plastic material can exchanged from metal, because of rapid growth in engineering plastic and FRP. Prodcts of engineering plastic and FRP goods are equal. So we develop plastic Toe-Cap using plastic technology.