• Safety and Health at Work
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• v.12 no.4
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• pp.544-545
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• 2021

The article by Tae-Gu Kim et al. conducted elastic FE modeling, which was inappropriate for fracture of elastic-plastic chain material (11.3% of elongation). FE analysis results and the findings in the fracto-graphic analysis did not tally but contradicted each other. The article identified "incorrect installation"/bending forces as the root cause while FE results of the chain under bending forces showed very low stresses at fracture locations but the highest stress in the middle of shank of the chain. The article's "step-like topographies indicating the fracture due to bending moment rather than uniaxial tension" lacked scientific support. The load value carried by each chain section under bending/incorrect installation was only half of that under tension, thus the article using same load value in FE simulation comparison for bending and tension was incorrect. The real cause of the chain fracture was likely improper checking the lifted load or/and using the wrong chain with much lower safety working load.

• Nuclear Engineering and Technology
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• v.26 no.4
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• pp.453-460
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• 1994

The migration equation is modified for a three-member decay chain in the fracture and porous matrix Analytical solutions are obtained by utilizing Laplace transform the initial conditions of Delta function and Bateman equation. The concentrations for each nuclide of Np$^{237}$ -U$^{233}$ -Th$^{229}$ and U$^{234}$ -Th$^{230}$ -Ra$^{226}$ chains selected from the 4n＋1 and 4n＋2 chains are plotted by utilizing analytical solutions in the fracture. Retardation coefficient of the nuclides are obtained using those of the granite. The results indicate that the daughter nuclides such as U$^{233}$ , Th$^{229}$ , Th$^{230}$ and Ra$^{226}$ become important at the far field from the repository though there is very small initial inventory in the waste solid or spent fuel, for they are produced by the mother nuclides decayed in the fracture and porous matrix.

• Proceedings of the Korean Society For Composite Materials Conference
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• 1999.04a
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• pp.1.1-4
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• 1999

The toughening mechanism and fracture behavior of rubber/polymer composites were investigated with respect to two factors; (1) the composition ratio of polymers(PPO and PS which have a different chain flexibility) and (ii) the rubber particle size in PPO/PS blend system Izod impact test and fractographic observation of the fracture surface using scanning electron microscope were conducted, Finite element analysis were carried out to gain understanding of plastic deformation(shear yielding and crazing) of these materials.

• Journal of the Korean Ceramic Society
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• v.23 no.5
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• pp.75-80
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• 1986

The mechanical properties were measured for magnesium phosphate glasses containing small amounts of water. The decrease in hardness with increasing water content was resulted from a looser chain structure caused by water. The fracture of these glasses was changed from brittle fracture to plastic deformation as a results of the increased viscous flow with increasing water contents. The extent of any viscous flow or deformation initiating from the crack tips in these glasses could be considered as quite small.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.9
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• pp.52-57
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• 2010

The analysis of a crack in a bone-like material is performed numerically. The bone-like material is hierarchically structured and each hierarchy is structured by mineral platelets and protein matrix through staggered arrangement. Mechanical behavior of the composite can be analyzed using tension shear chain model. The Dugdale model is adopted to evaluate the fracture energy of Bone-like material. The fracture energy dissipation is assumed to concentrate within a strip near the crack tip along the prospective crack path. Fracture criterion of the bone-like material is estimated by using J integral. Effects of hierarchical level, ratio of elastic modulus of mineral to protein, aspect ratio of mineral platelet and volume fraction on J integral are investigated. It is found that the J integral decreases as elastic modulus ratio and hierarchy level increase. It is also shown that the J integral increases as the volume fraction and aspect ratio decrease.

• Journal of Korean Medicine Rehabilitation
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• v.30 no.4
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• pp.17-30
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• 2020

Objectives The purpose of this study is to evaluate the healing effect of Yukmijihwang-tang (YM) on femur fractured mice. Methods Mice were randomly divided into 6 groups: normal, control, positive control, YM with low, medium, high dosage each. All groups were prepared with femur fracture and treated diffrently. In order to measure bone regeneration effects, we analysed the levels of cyclooxygenase-2 (COX2), bone morphogenetic protein-2 (BMP2), collagen type II alpha 1 chain (Col2a1), Sox9, runt-related transcription factor 2 (Runx2), and osterix genes expressed in bone. For morphological analysis, muscles were removed and femur was observed with naked eye. Results COX2 gene expression in bone marrow significantly decreased. BMP2 gene expression significantly increased. Col2a1 gene expression significantly increased. Sox9 gene expression increased as well. Runx2 gene expression in bone marrow increased, but there was no statistical significance. Osterix gene expression significantly increased. Union of the fracture site progressed more in YM group compared to the control group. The fracture union score was significantly decreased in YM group compared to the control group. Conclusions YM showed anti-inflammatory effect, promoted bone regeneration by stimulating the bone regeneration factor. In conclusion, YM can help fracture healing and it well be applied clinically to patients with fracture.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.2
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• pp.228-240
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• 1991

Many experimental data of fatigue crack propagation show that the fatigue crack propagation process is stochastic. Therefore, the study on the crack propagation must be based on the probabilistic approach. In the present paper, fatigue crack propagation process is assumed to be a discrete Markov process and the method is developed, which can evaluate the reliability of the structural component by using Markov chain model(Unit step B-model) suggested by Bogdanoff. In this method, leak failure, plastic collapse and brittle fracture of the critical component are taken as failure modes, and the effects of initial crack distribution, periodic and non-periodic inspection on the probability of failure are considered. In this method, an equivalent load value for random loading such as wave load is used to facilitate the analysis. Finally some calculations are carried out in order to show the usefulness and the applicability of this method. And then some remarks on this method are mentioned.

• Nuclear Engineering and Technology
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• v.34 no.3
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• pp.218-231
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• 2002

Using a three-dimensional numerical code, B3R developed for nuclide transport of an arbitrary length of decay chain in the buffer between the canister and adjacent rock in a high- level radioactive waste repository by adopting a finite difference method utilizing the control- volume scheme, some illustrative calculations have been done. A linear sorption isotherm, nuclide transport due to diffusion in the buffer and the rock matrix, and advection and dispersion along thin rigid parallel fractures existing in a saturated porous rock matrix as well as diffusion through the fracture wall into the matrix is assumed. In such kind of repository, buffer and rock matrix are known to be important physico-chemical harriers in nuclide retardation. To show effects of buffer and rock matrix on nuclide transport in HLW repository and also to demonstrate usefulness of B3R, several cases of breakthrough curves as well as three- dimensional plots of concentration isopleths associated with these two barriers are introduced for a typical case of decay chain of $^{234}$ Ulongrightarrow$^{230}$ Thlongrightarrow$^{226}$ Ra, which is the most important chain as far as the human environment is concerned.

• Journal of Korean Medicine Rehabilitation
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• v.30 no.4
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• pp.1-16
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• 2020

Objectives The main purpose of this study was to evaluate the bone healing effect of Pahyeolsandong-tang (PHT)(Poxiesanteng-tang) extract in tibia fracture-induced mice. Methods PHT was extracted using a solution of 35% ethanol in 60℃ for 8 hours. Mice were randomly divided into 4 groups (normal, control, PHT 50 and PHT 100). Mice of experimental groups were medicated with PHT 50 or 100 mg/kg for 7 to 21 days. To clarify the effect of bone fracture healing, relative messenger RNA (mRNA) expressions of osteocalcin (OCN), runt-related transcription factor 2 (Runx2), osterix (OSX), Sox9, collagen type II alpha 1 chain (Col2a1), receptor activator of nuclear factor kappa-B ligand (RANKL), osteoprotegerin (OPG) were examined. Results In in vitro experiment, relative mRNA expression of OCN, Runx2, Col2a1 was significantly increased in PHT treated group to compare with control differentiation group. In in vivo experiment, relative mRNA expression of OCN, Runx2, OSX, Sox9, Col2a1, RANKL, OPG was significantly increased in PHT treated group. Conclusions This study showed that PHT accelerates bone fracture healing through the activation of osteoclasts and osteoblasts. It was showed that PHT significantly promotes osteoblasts differentiation by osteoblast differentiation markers such as OCN, Runx2, Col1a2. Also it was investigated that PHT had stimulatory effect on osteoblasts function through enhancing OCN, Runx2, OSX, Sox9, Col2a1 and, osteoclasts function through enhancing RANKL and OPG markers. PHT effectively promotes bone fracture healing process through activation of osteoblasts and osteoclasts.

• Journal of Korean Medicine Rehabilitation
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• v.31 no.1
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• pp.1-16
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• 2021

Objectives This study was designed to evaluate the effects of Danggwisu-san (Dangguixu-san, DG) on bone repair from femur fracture in mice. Methods Mice were randomly divided into 4 groups (normal, control, positive control and DG 300 mg/kg-treated group). In order to investigate the effects of DG on gene expressions in experimental animals with fracture, we measured the levels of bone morphogenetic protein-2 (BMP2), cyclooxygenase-2 (COX2), Sox9, collagen type II alpha 1 chain (Col2a1), runt-related transcription factor 2 (Runx2), osterix genes. After the cytotoxicity test, we analyzed the levels of expression of osteocalcin and Runx2, and tumor necrosis factor-α (TNF-α), a pro-inflammatory cytokine. The process of fusion in the fracture was also investigated by gross examination. Results Through in vivo BMP2, COX2 gene expression significantly decreased. Sox9 significantly increased. Col2a1, Runx2, osterix gene expression also increased as well, but there was no statistical significance. The degree of unilateral fracture fusion investigated by gross examination was significantly faster than those of the other groups. Through in vitro the level of TNF-α in macrophages was increased by DG in a dose-dependent mannerand and 250 and 500 ㎍/mL showed statistical significance. Osteocalcin and Runx2 genes expressions increased when DG was treated in osteoblasts. Conclusions DG promotes the healing of the fracture through the expression of bone repair-related genes and TNF-α production. This study may set the foundation for the clinical application of DG to the patients with bone fractures.