• Journal of Korean Society of Disaster and Security
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• v.14 no.4
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• pp.47-60
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• 2021

Recently, as the occurrence frequency of sudden floods due to climate variability increased, the damage of aging chuteway slabs of spillway are on the rise. Accordingly, a wide array of field survey, hydraulic experiment and numerical simulation have been conducted to find the cause of damage on chuteway slabs. However, these studies generally reviewed the flow characteristics and distribution of pressure on chuteway slabs. Therefore the derivation of damage on chuteway slabs was relatively insufficient in the literature. In this study, the cavitation erosion and hydraulic jacking were assumed to be the causes of damage on chuteway slabs, and the phenomena were reproduced using 3D numerical models, FLOW-3D and COMSOL Multiphysics. In addition, the cavitation index was calculated and the von Mises stress by uplift pressure distribution was compared with tensile and bending strength of concrete to evaluate the possibility of cavitation erosion and hydraulic jacking. As a result of numerical simulation on cavitation erosion and hydraulic jacking under various flow conditions with complete opening gate, the cavitation index in the downstream of spillway was less than 0.3, and the von Mises stress on concrete was 4.6 to 5.0 MPa. When von Mises stress was compared with tensile and bending strength of concrete, the fatigue failure caused by continuous pressure fluctuation occurred on chuteway slabs. Therefore, the cavitation erosion and hydraulic jacking caused by high speed flow were one of the main causes of damage to the chuteway slabs in spillway. However, this study has limitations in that the various shape conditions of damage(cavity and crack) and flow conditions were not considered and Fluid-Structure Interaction (FSI) was not simulated. If these limitations are supplemented and reviewed, it is expected to derive more efficient utilization of the maintenance plan on spillway in the future.

• Journal of the Korea Concrete Institute
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• v.24 no.6
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• pp.737-744
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• 2012

Hysteretic steel damper has been applied mainly to steel buildings. However, the usage in RC buildings is rapidly increasing recently. In order to apply the steel hysteretic damper in RC buildings, supporting elements of the damper should have sufficient strength and stiffness suitable for transferring damper forces to beams and walls. But due to the inevitable damage in reinforced concrete elements due to cracking, identification of the load transfer mechanism from damper to supporting element and hysteretic characteristics of the supporting element are extremely important in evaluating the damper behavior. Experiments were carried out on connection details between RC walls and supporting elements of the steel plate typed damper such as EaSy damper. The test results showed that fracture patterns of all specimens were almost identical except in the crack number and pattern associated with shear loading condition. Among the specimens, HD-3 shoed a well distributed cracks patterns along with good performance with respect to energy dissipation capacity, stiffness deterioration, and strength degradation.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.1
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• pp.39-47
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• 2004

In this paper, the defects of two-dimensional anisotropic elastic bodies are identified by using the boundary element method. The use of numerical models that contain only boundary integral terns reduces the dimensionality of the problem by one. This advantage is particularly important in problems such as crack mechanics. Avoiding domain meshing is also particularly advantageous in the solution of inverse problems since it overcomes mesh perturbations and simplifies the procedure. In this paper, nondestructive approaches for the existing isotropic materials are extended to analyze the elastic bodies made of anisotropic materials such as composites. After verifying that the proposing boundary element model is in good agreement with numerical results reported by other investigators, the effect of noise in the measurements on the identifiability is studied with respect to different design parameters of layered composites. Sample studies are carried out for various layup configurations and loading conditions. The effects of the layup sequences in detecting flaw of composites is explored in this paper.

• Journal of Conservation Science
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• v.19
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• pp.85-98
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• 2006

Rock property of the Seosan Maaesamjonbulsang is composed of biotite granite with medium grained texture. The triad Buddha is highly deteriorated by the joint, fracture, break-out, exfoliation, dew condensation of the surface and discoloration of the secondary pollutant. Host rock of the triad Buddha is divided dozens of rock blocks with various shape, and developed irregular discontinuity planes. Besides, the host rock is promoted biological pollution due to the surrounding crowded vegetation and high humidity environment. As the results of structural stability, it is confirmed that developed discontinuity system in the host rock is exposed instability sloping environment. Therefore, the host rock and surroundings are required maintenance, and required preservation by continuance monitoring for understand behavior of discontinuity system.

• Journal of the Korean Society for Advanced Composite Structures
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• v.1 no.2
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• pp.51-58
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• 2010

This work examines the identification of stiffness reduction in damaged reinforced concrete bridges under moving loads, and carries out the performance assessment after repairing using advanced composite materials. In particular, the change of stiffness in each element before and after repairing, based on the Microgenetic algorithm as an advanced inverse analysis, is described and discussed by using a modified bivariate Gaussian distribution function. The proposed method in the study is more feasible than the conventional element-based method from computation efficiency point of view. The validity of the technique is numerically verified using a set of dynamic data obtained from a simulation of the actual bridge modeled with a three-dimensional solid element. The numerical examples show that the proposed technique is a feasible and practical method which can inspect the complex distribution of deteriorated stiffness although there is a difference between actual bridge and numerical model as well as uncertain noise occurred in the measured data.

• Applied Microscopy
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• v.38 no.3
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• pp.265-273
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• 2008

We investigated the morphological differences of the ethnic hairs using scanning electron microscopy and transmission electron microscopy, sampled from African, Asian and Caucasian women. Transverse section of African hair had a highly elliptical type whereas those of Asian and Caucasian hairs had circular and elliptical types, respectively. The diameter of African hair showed wide variations from 90 to 115 ${\mu}m$. The diameter of Asian hair was 100 ${\mu}m$ and Caucasian hair had a lesser diameter of 80 ${\mu}m$ on average. African hair were much more damaged in cuticle layer compared with Asian or Caucasian hairs. In particular, endocuticle of cuticle cell had a lot of holes in it, which resulted that it tends to be easily broken. Phaeomelanin in the cortex of Caucasian hair had a concentrically helical structure in it.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.29-32
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• 2008

The renewal of existing buildings rather than new construction has increased due to it's cost effective characteristics. Remodeling is also an environmentally-friendly approach that reduces the amount of waste in construction site. Remodeling can sometimes include partial destruction of the structural members of a building. In addition it is important that the buildings under going remodeling retrofitted to make themselves stable and meet up with the future demands for better structural performance. The objective of this paper is to present the test results and structural behavior of RC walls that are perforated and to introduce effective retrofitting methods by evaluating efficacy of passive retrofit and active retrofit. Passive retrofit and Active retrofit using carbon fiber sheets, steel plates and wire that are widely used for strengthening the main members of existing buildings. The test results showed that the failed specimens had shear fractures and that two different types of retrofit method had different effects on the strengths of each specimen.

• Tuberculosis and Respiratory Diseases
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• v.42 no.4
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• pp.522-534
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• 1995

Background: In the pathogenesis of acute lung injury induced by lipopolysaccharide(LPS), oxygen radiclls are known to be involved in one part. Superoxide dismutase(SOD) protects oxygen radical-induced tissue damage by dismutating superoxide to hydrogen peroxide. In eukaryotic cells, two forms of SOD exist intracellularly as a cytosolic, dimeric copper/zinc-containing SOD(CuZnSOD) and a mitochondrial, tetrameric manganese-containing SOD(MnSOD). But there has been little information about SOD gene expression and its regulation in pulmonary alveolar macrophages(PAMs). The objective of this study is to evaluate the SOD gene expression induced by LPS and its regulation in PAMs of rat. Method: In Sprague-Dawley rats, PAMs obtained by broncholaveolar lavage were purified by adherence to plastic plate. To study the effect of LPS on the SOD gene expression of PAMs, they were stimulated with different doses of LPS($0.01{\mu}g/ml{\sim}10{\mu}g/ml$) and for different intervals(0, 2, 4, 8, 24hrs). Also for evaluating the level of SOD gene regulation actinomycin D(AD) or cycloheximide(CHX) were added respectively. To assess whether LPS altered SOD mRNA stability, the rate of mRNA decay was determined in control group and LPS-treated group. Total cellular RNA extraction by guanidinium thiocyanate/phenolfchlorofonn method and Northern blot analysis by using a $^{32}P$-labelled rat MnSOD and CuZnSOD cDNAs were performed. Results: The expression of mRNA in MnSOD increased dose-dependently, but not in CuZnSOD. MnSOD mRNA expression peaked at 8 hours after LPS treatment. Upregulation of MnSOD mRNA expression induced by LPS was suppressed by adding AD or CHX respectively. MnSOD mRNA stability was not altered by LPS. Conclusion: These findings show that PAMs of rat could be an important source of SOD in response to LPS, and suggest that their MnSOD mRNA expression may be regulated transcriptionally and require de novo protein synthesis without affecting mRNA stability.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.44 no.2
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• pp.151-159
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• 2018

In this study, we investigated the anti-oxidative activities and cell protective effects of the constituents isolated from S. aqueum branches. DPPH and $ABTS^+$ radical scavenging activities were screened for the ethanol extract and solvent fractions, ethyl acetate (EtOAc) and butanol (BuOH) fractions showed potent activities. When HaCaT cells were treated with $H_2O_2$, the ethanol extract and EtOAc fractions ($20{\mu}g/mL$) protected the cells against oxidative damage. Two constituents were isolated from the EtOAc fraction of S. aqueum branches; pinocembrin (1), desmethoxymatteucinol (2). The chemical structures of the isolated compounds were elucidated based on the spectroscopic data including $^1H$ and $^{13}C$ NMR spectra, as well as comparison of the data to the literature values. Anti-oxidative activities and cell protective effects were studied for the isolated compounds. For the anti-oxidative activities, all of the compounds 1 and 2 showed DPPH and $ABTS^+$ radical scavenging activities. Also, from the cell protective effect test, the compounds 1 and 2 protected the cell against oxidative stress by $H_2O_2$. Based on these results, S. aqueum branches extract could be potentially applicable as anti-oxidant ingredients in cosmetic industries.

• Tuberculosis and Respiratory Diseases
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• v.48 no.2
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• pp.246-259
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• 2000

Background: As one of the etiologies of acute respiratory distress syndrome(ARDS), sepsis is one of the morbid causes of this cryptogenic malady. Even though many documents on the role of endotoxin(ETX) in the pathogenesis of ARDS have been issued, still the underlying mechanism associated with oxidative stress and activation of $PLA_2$ has been controversial. In the present study, the role of phospholipase $A_2(PLA_2)$ in the neutrophilic respiratory burst, which is presumed to cause acute lung injury during sepsis, was probed. Method: In glutathione-depleted Sprague-Dawley rats, lung leak, infiltration of neutrophils, $PLA_2$ activity and lipid peroxidation in the lung were measured after intratracheal instillation of endotoxin(delete). In addition, gamma glutamyl transferase(GGT) activity and the amount of pulmonary surfactant were measured. Morphologically, the changes in ultrastructure and cytochemical demonstration of oxidants were presented to confirm the neutrophilic oxidative stress and to elucidate the effects of $PLA_2$ activation on(delete) oxidative stress. Results: Instillation of ETX to glutathione-depleted rats intensified lung leak and lipid peroxidation when compared with non-glutathione depleted rats treated with the endotoxin. Moreover, oxidative stress was confirmed by the assay of GGT and malondialdehyde. Functionally, the depletion of glutathione altered the secretion of pulmonary surfactant from alveolar type II cells. Ultrastructurally and cytochemicaliy, oxidative stress was also confirmed after treatment of with ETX and diethylmaleate(DEM). Conclusion: The endotoxin-induced acute lung injury was mediated by oxidative stress, which in turn was provoked by the neutrophilic respiratory burst. The activation of $PLA_2$ in the lung seems to playa pivotal role in the oxidative stress of the lung.