• Polymer(Korea)
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• v.37 no.6
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• pp.669-676
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• 2013

Demineralized bone particle (DBP) is a biomaterial used widely in the field of tissue engineering. In this study, in order to study the effect of DBP/poly(lactic-co-glycolic acid) (PLGA) scaffold on disc regeneration in vivo environment, we prepared the porous DBP/PLGA hybrid scaffold. Disc defect was induced by removing the nucleus pulposus tissue after incision the annulus fibrosus tissue in half and scaffolds were transplanted. After 1, 2 and 3 months later, the extracted discs were confirmed by collagen synthesis and glycosaminoglycan (sGAG). We conducted histology (H&E, Safranin-O, Alcian blue, Type I Collagen, Type II Collagen). From the results, it was confirmed that collagen and sGAG content were high in DBP/PLGA scaffold, and the regeneration of intervertebral disc was possible.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.1
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• pp.121-127
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• 2013

With the continuing demand for lightweight bicycles, carbon fiber composite materials have been widely used in manufacturing bicycle frames and components. Unlike general isotropic materials, the structural characteristics of composite materials are strongly influenced by the staking directions and sequences of composite laminates. Thus, to verify the design process of bicycles manufactured using composites, structural analysis is considered essential. In this study, a carbon-fiber-reinforced plastic (CFRP) bicycle frame was designed and its structural behavior was investigated using finite element analysis (FEA). By measuring the failure indices of the fiber and matrix under various stacking sequences and loading conditions, the effect of the stacking condition of composite laminates on the strength of the bicycle structure was examined. In addition, the structural safety of the bicycle frame can be enhanced by reinforcing weak regions prone to failure using additional composite laminates.

• Composites Research
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• v.35 no.4
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• pp.269-276
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• 2022

In this paper, a composite stiffened panel was fabricated using a three-dimensional weaving method that can reduce the risk of delamination, and mechanical properties such as buckling load and natural frequency were investigated. The preform of the stringer and skin of the stiffened panel were fabricated in one piece using T800 grade carbon fiber and then, resin (EP2400) was injected into the preform. The compression test and natural frequency measurement were performed for the stiffened panel, and the results were compared with the finite element analyses. In order to compare the performance of 3D weaving structures, the stiffened panels with the same configuration were fabricated using UD and 2D plain weave (fabric) prepregs. Compared to the tested buckling load of the 3D woven panel, the buckling loads of the stiffened panels of UD prepreg and 2D plain weave exhibited +20% and -3% differences, respectively. From this study, it was confirmed that the buckling load of the stiffened panel manufactured by 3D weaving method was lower than that of the UD prepreg panel, but showed a slightly higher value than that of the 2D plain weave panel.

• Journal of Korean Society of Forest Science
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• v.98 no.4
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• pp.417-425
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• 2009

This study analyzed core issues addressed in the tentative agreement of WTO ministerial meetings held to finish WTO/DDA negotiations in Geneva in July 2008. The objectives of this study are to analyze changes in tariff reduction on timber products, and their influence on demand and supply of the items according to the modality of Non-Agricultural Market Access (NAMA) and to provide basic information for strategy formulation of our country for further WTO/DDA negotiations. The results indicate that there will not be significant changes in the tariff on sawnwood and on veneer sheets, however, the tariff on plywood need to be cut by around 50% from the applicable tariff rates of 2008 on condition that our country is in the position of developed countries. Therefore, the item of plywood is expected to be influenced greatly according to the change in tariff reduction. From the analysis of influence of tariff reduction on the demand and supply of timber products including sawnwood and wood based panels, such as plywood, particleboard, and fiberboard, the import quantities of the items are expected to be changed from 0.8% to 13.3% if our country is in the position of developed countries, however, they are expected to decline by 0.8%~44.3%, if our country is in the position of developing countries (22, coefficient for developing members).

• Advances in pediatric surgery
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• v.1 no.1
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• pp.1-7
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• 1995

The acetylcholinesterase(ACHE) activity in 37 biopsies from the patients with Hirschsprung's disease was analyzed for histochemical patterns according to age, and its evolutional behavior was also assessed. The histochemical criterion used for the diagnosis of Hirschsprung's disease was that of Chow, i.e., "the presence of many coarse discrete cholinergic fibers in the muscularis mucosae and in the immediately subjacent submucosa regard less of an infiltration of cholinergic fibers in the lamina propria." The acetylcholinesterase activity in Hirschsprung's disease was further classified into 3 patterns, advocated by de Brito and Maksoud : Pattern I-many thick fibers exclusively in the muscularis mucosae and submucosa(newborn pattern). Pattern II-many thin fibers in the muscularis mucosae and submucosa with a clear infiltration of cholinergic fibers in the lamina propria(classical pattern). Pattern III-an intermediate pattern showing morphological characteristics of the two patterns with predominance of one or the other. Of 37 biopsies, Pattern 1 was seen exclusively in 16 biopsies taken from the neonates. Pattern III was 11 of 37 biopsies and it was mainly seen in children between 2 to 12 months of age. Pattern II was seen in all 3 biopsies of older than 1 year of age and in 6 ones of 3 to 12 months of age. In summary, this study reinforces the impression that there is an evolutional character of the distribution and morphology of the cholinergic ACHE positive fiber with age. In other words, ACHE activity in Hirschsprung's disease appears to evolve with age from the newborn pattern to the intermediate pattern finally to the classical pattern.

• Journal of Korean Society of Forest Science
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• v.97 no.4
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• pp.385-391
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• 2008

Republic of Korea (ROK) log import companies have clustered around In-cheon, Jeon-buk and Busan. This reason related to port for log import. This study analyzed the quantity of Whole imported log transported by port. As the result of analysis, In-cheon port accounted for 56.9% log import, which is the maximum log import port in ROK. Next Bu-san port 20.9%, Gun-san port 17.9%. However, these port have declined the quantity of imported log transported since 2000. Gun-san port and Dong-hae port increased narrow range. The reason of why In-cheon and Bu-san port declined log import and Gun-san and Dong-hae port increased is that a sudden rise in the price of log in 2003, and import of using a container ship increased. In the addition, log import from Far eastern Russia, Germany and America increased through a container ship, however, declined log import through a bulk ship. Most of imported log at In-cheon port are from New zealand and Russia, imported logs at Bu-san port are almost from US and New zealand.

• Polymer(Korea)
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• v.32 no.1
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• pp.26-30
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• 2008

This study was designed to investigate the effect of hybridization of synthetic/natural materials for annulus fibrosus (AF) tissue regeneration in vitro and in vivo. The synthetic/natural hybrid scaffolds were prepared using PLGA (poly (lactic-co-glycolic) acid), SIS (small intestinal submucosa) and DBP (demineralized bone particles). PLGA, PLGA/SIS(20%), PLGA/DBP(20%) and PLGA/SIS (10%)/DBP (10%) scaffold were manufactured by solvent casting/salt leaching method. Compressive strength was measured. Rabbit AF cells were isolated, cultured and seeded into experimental groups. Hydroxyproline production and DNA quantity of AP cells on each scaffold was measured at 2, 4 and 6 weeks after in vitro culture. Cell-scaffold composites were implanted subcutaneously into athymic mice. After 1,4 and 6 weeks postoperatively, specimens were taken and H&E, Safranin-O and type I collagen staining were carried out concerning formation of cartilagenous tissue. In vitro PLGA/SIS scaffold was evaluated for total collagen content (bydroryproline/DNA content) and PLGA scaffold was evaluated for compressive strength.

• The Journal of Korean Society for Radiation Therapy
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• v.30 no.1_2
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• pp.139-151
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• 2018

Objectives : A self-made "Tomotherapy couch device" capable of correcting the Yaw direction was fabricated and evaluated for its usefulness. Materials and Methods : "Tomotherapy couch device" capable of correcting the Yaw direction is made of rigid fibreboard with a flexural strength of $200kg/cm^2$. CBCT Image from Novalis Tx and Iso-Align Phantom from MED-TEC were used to evaluate the physical accuracy. The treatment plan was designed using Accuray $Precision^{TM}$ and In House Head and Phantom. Accuray $PrecisionART^{TM}$ and $Precision^{TM}$ was used to evaluate dose. Results : Evaluation results, the self-fabricated device accurately corrected the setup error, Target dose was within 95 %~107 % of all. In order to directly evaluate the OAR dose according to the Yaw change, the absolute dose was measured. As a result, when the error in the Yaw direction was $3^{\circ}$, the specific OAR showed a maximum difference of 18.4 %. Conclusion : "Tomotherapy couch device" capable of correcting the Yaw direction can be manufactured at a lower cost compared to the effect, and it can prevent the patient's MVCT image dose for re-imaging. Accurate radiation therapy without errors can be performed.

• Polymer(Korea)
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• v.39 no.1
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• pp.144-150
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• 2015

Gellan gum as a natural polysaccharide has good heat resistance, acid resistance and enzymes resistance. However, one of the drawbacks of gellan gum might be the lower mechanical strength. In this work, gellan gum scaffolds were mixed with poly(lactic-co-glycolic acid) (PLGA) microsphere in order to improve mechanical properties. The gellan gum scaffolds with various contents of PLGA microsphere were prepared for the regeneration of disc tissues. To evaluate the mechanical strength of hybrid structure of gellan gum and PLGA microsphere, compression strength of the fabricated scaffolds was measured. MTT analysis, SEM observation, histological evaluation and RT-PCR were performed to confirm the effect on the cell growth and extracellular matrix secretion. As a result, it showed the best cell proliferation and extracellular matrix secretion in gellan gum sponge containing 50% PLGA microspheres. In conclusion, this study confirmed that the hybrid structure of gellan gum and PLGA microspheres was found suitable in regeneration of the intervertebral disc.

• Journal of the Korean Society for Railway
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• v.15 no.6
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• pp.616-622
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• 2012

Earthquake damage of viaduct bridge of railroad may give rise to social loss due to transport restrictions greater than cost of structural recovery. Therefore, viaduct bridge of railroad should have ensure adequate seismic performance. But, results of seismic performance evaluation, many of seismic retrofit was required. In this study, five scale models of columns were made and four of them were reinforced by HT-A(HyperTex & perforate Aluminum) which is improved than existing method. Testing the columns by constant axial load and cyclic lateral displacements, seismic performance of columns has been verified from the result of evaluating the stiffness, ductility and energy dissipation capacity.