• 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.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.2
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• pp.269-276
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• 2017

In order to study ultimate flexure behavior of FRP-concrete composite structures which can replace reinforced concrete structures, ABAQUS, a general purpose analysis program, was utilized for numerical nonlinear analysis of structural performance and behavior characteristics of FRP-concrete composite beams. Explicit nonlinear finite element analysis was conducted and the numerical results were compared with previous experiments. Concrete damaged plasticity model was adopted as material properties of concrete and Euro code was used as compressive stress state. Nonlinear analysis was performed for four different types of FRP-concrete composite beams, and ultimate load and cracking pattern was compared and analyzed. The model suggested in this research was able to simulate ultimate load and cracking pattern properly, it is expected to be utilized in study of precise structural and behavioral characteristics of various FRP-concrete composite structures.

• Journal of the Korea Furniture Society
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• v.21 no.6
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• pp.449-458
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• 2010

This study attempted to investigate the effect of panel thickness on the horizontal density distribution (HDD) of medium density fiberboard (MDF) in a destructive way. Full size MDF panels with five different thicknesses such as 2 mm, 4.5 mm, 9 mm, 18 mm and 30 mm were cut into two different specimen sizes, i.e., $500{\times}500\;mm$ and $120{\times}120\;mm$ to measure the HDD. In general, the overall density of MDF panel diminished as the thickness increased, showing the highest density for the thinnest MDF panels. The HDD variation was significant for the samples of smaller specimen size ($120{\times}120\;mm$). MDF panel thickness significantly influenced to the HDD, which increased as the thickness decreased. In addition, the thinner panels showed much wider range in the HDD than those of thicker panels. The coefficient of variation (COV) of HDD also followed a similar trend to the panel density as the thickness increased. In summary, MDF panel thickness had a significant impact on the HDD within a panel. The sample size also showed a considerable effect to the HDD of MDF panels.

• Journal of Korean Society of Steel Construction
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• v.27 no.4
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• pp.359-370
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• 2015

This paper presents the experimental results for the interfacial bond behaviour between AFRP strip and steel members. The objective of this paper is to examine the interfacial behavior and to evaluate the interfacial bond stress between Aramid FRP strips and steel plates. The test variables were bond length and AFRP thickness. 18 specimens were fabricated and one-face shear type bond tests were conducted in this study. There were two types of failure mode which were debonding and delamination between AFRP strip and steel plates. From the test, the load was increased with the increasing of bond length and AFRP thickness, which was observed that maximum increase of 63 and 86% were also achieved in load with the increasing of bond length and AFRP thickness, respectively. Finally, bond and slip characteristics had the elastic bond-slip model and it was observed that bond strength and fracture energy were not affected by bond length and AFRP thickness.

• Journal of the Korean Wood Science and Technology
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• v.44 no.3
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• pp.424-429
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• 2016

In this study, the carbonized boards were manufactured from different types of wood-based panel and then their moisture absorption/desorption properties were investigated and compared. The carbonization temperature was maximum $600^{\circ}C$ with 2 h maintains. Test results showed higher absorption/desorption capacity on carbonized plywood than carbonized MDF, PB, and OSB, respectively. However, carbonized MDF, OSB, and plywood had similar absorption/desorption rate per hour. It means carbonized OSB and plywood can transfer moisture into deeper side and then possibly hold more amount of water. Based on SEM images, carbonized OSB and plywood showed more like wood structure, while carbonized MDF and PB had only wood fiber or/and chunk of wood fragments. Therefore, original wood structure may affect moisture absorption/desorption capacity. In order to manufacture high moisture absorbing/desorbing carbonized board, wood structure should be considered and then carbonized.

• Journal of the Korean Wood Science and Technology
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• v.41 no.1
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• pp.58-63
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• 2013

This study is a basic research for practical applications of carbonized boards, which measured thermal conductivity and electrical properties of carbonized boards manufactured at different carbonization temperature ($400{\sim}1,100^{\circ}C$) using a medium density fiberboard, particleboard, plywood and wood (Fraxinus rhynchophylla). The highest value of thermal conductivity was 0.1326 m/k at carbonization temperature of $900^{\circ}C$ in the carbonized particleboard. Overall, the higher density of carbonized board, thermal conductivity was faster. As the electrical resistivity decreased with increased carbonization temperature, it was almost close to conductor after carbonization temperature of $1,000^{\circ}C$. When electricity has worked on the carbonized board by high voltage, the current and the electric power increased and surface temperature of carbonized board was high.

• Journal of the Korean Wood Science and Technology
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• v.46 no.1
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• pp.60-66
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• 2018

For new use development of carbonized board, we investigated the effect of carbonization temperature on the surface temperature of carbonized board manufactured from a plywood, particle board, MDF, and wood of Fraxinus rhynchophylla at different carbonization temperature ($400^{\circ}C{\sim}1100^{\circ}C$). The surface temperature of carbonized board precipitously increased until 12 minutes elapsed, after smoothly increased and thereafter which were stable after 20 minutes. The higher carbonization temperature increased density of carbonized board and surface temperature of carbonized board so that density is considered to influence surface temperature change. Moreover, carbonized boards kept heat for a long time because the descent velocity of carbonized boards' surface temperature was slower than that of heater's.

• Progress in Medical Physics
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• v.22 no.3
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• pp.117-123
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• 2011

Synchrotron radiation (SR) imaging enables us to observe internal structures of biologic samples without staining. In this study, we obtained X-ray microscopic images of human breast tissues with 11.1 KeV hard X-ray microscope of the Pohang light source and used zone plates and phase-contrast technique to get high resolution X-ray images. Hard X-ray microscopic images of fibrocystic change and breast cancer tissues with a spatial resolution of 60 nm were obtained and from these images, we could observe the micro-structures of human breast tissue. Also we analyzed and compared these images, which revealed distinct features of each condition. In conclusion, SR imaging with phase-contrast hard X-ray microscope for medical application, especially in breast disease can give some useful information for clinical research.

• Journal of Chest Surgery
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• v.30 no.12
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• pp.1247-1250
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• 1997

A 13-year-old boy presented with anterior chest wall depression and dyspnea on exertion(NYHA II). He underwent Ravitch operation for pectus excavatum 7 years ago. A preoperative echocardiographic study revealed secundum atrial septal defect. He had no other abnormality of laboratory test, except FVC and FEVI were decreased into 2.03 L(7 %) and 1.82 L(71 %). He underwent repair of secondary anterior chest wall deformity and secundum atrial septal defect. We used unique method, raising sternum at right angle to secure good operative field for open heart surgery. Acute respiratory insufficiency was developed on postoperative day 1. Mechanical ventilation was applied which could be weaned on postoperative day 6 and thereafter hospital course was uneventful without any other sequale. He was discharged on postoperative day 19.