• Journal of electromagnetic engineering and science
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• v.15 no.3
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• pp.134-141
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• 2015

The effect of a 60 Hz time-varying electric field was studied using a facing-electrode device (FED) and a coplanar-electrode device (CED) for further investigation of the genotoxicity of 60 Hz time-varying magnetic field (MF) from preceding research. Neither a single 30-minute exposure to the CED or to the FED had any obvious biological effects such as DNA double strand break (DSB) and apoptosis in cancerous SCC25, and HeLa cells, normal primary fibroblast IMR90 cells, while exposures of 60 Hz time-varying MF led to DNA damage with induced electric fields much smaller than those used in this experiment. Nor did repetitive exposures of three days or a continuous exposure of up to 144 hours with the CED induce any DNA damage or apoptosis in either HeLa or IMR90 cells. These results imply that the solitary electric field produced by time-varying MF is not a major cause of DSBs or apoptosis in cancer or normal cells.

• Proceedings of the Korean Society of Applied Pharmacology
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• 2003.11a
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• pp.61-61
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• 2003

The ethanol extract of peony root (Paeonia Lactiflora Pall, Paeoniaceae) and its major active components including gallic acid and methyl gallate were evaluated for their protective effects against free radical generation and lipid peroxidation. And protective effects against hydrogen peroxide-induced oxidative DNA damage in a mammalian cell line were performed. The ethanol extract of peony root (PRE), gallic acid and methyl gallate were shown to possess the significant free radical scavenging effect against 1,1-diphenyl-2-picryl hydrazine (DPPH) radical generation and were revealed the inhibitory effect of lipid peroxidation as expressed by malondialdehyde (MDA) formation. They were also found to strongly inhibit hydrogen peroxide-induced DNA damage from NIH/3T3 fibroblasts, assessed by single cell gel electrophoresis. Furthermore, oral administration of 50% PRE (50% ethanol extract), gallic acid and methyl gallate potently inhibited micronucleated reticulocyte (MNRET) formation of mouse peripheral blood induced by KBrO3 treatment in vivo. Therefore, PRE containing gallic acid and methyl gallate may be a useful natural antioxidant by scavenging free radicals, inhibition of lipid peroxidation and protecting oxidative DNA damage.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.3 s.174
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• pp.634-644
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• 2000

Fatigue crack growth and life is estimated by various fracture mechanical parameters but affected by load, material and environment. Fatigue character of component without surface notch cannot be e valuated by above-mentioned parameters due to microstructure of in-service material. Single fracture mechanical parameter or nondestructive parameter cannot predict fatigue damage in arbitrary boundary condition but multiple fracture mechanical parameters or nondestructive parameters can Fatigue crack growth modelling with three point representation scheme uses this merit but has limit on real-time monitoring. Therefore, this study shows fatigue damage model using backpropagatior. neural networks on the basis of X-ray half breadth ratio B/$B_o$ fractal dimension $D_f$ and fracture mechanical parameters can predict fatigue crack growth rate da/dN and cycle ratioN/$N_f$ at the same time within engineering estimated mean error(5%).

• Structural Monitoring and Maintenance
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• v.3 no.2
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• pp.115-127
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• 2016

It is a challenging problem of assessing the location and extent of structural damages with vibration measurements. In this paper, an improved Extended Kalman filter (EKF) with Tikhonov regularization is proposed to identify structural damages. The state vector of EKF consists of the initial values of modal coordinates and damage parameters of structural elements, therefore the recursive formulas of EKF are simplified and modal truncation technique can be used to reduce the dimension of the state vector. Then Tikhonov regularization is introduced into EKF to restrain the effect of the measurement noise for improving the solution of ill-posed inverse problems. Numerical simulations of a seven-story shear-beam structure and a simply-supported beam show that the proposed method has good robustness and can identify the single or multiple damages accurately with the unknown initial structural state.

• Steel and Composite Structures
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• v.33 no.6
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• pp.777-792
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• 2019

This paper presents a new efficient approach to estimate the S-N type fatigue life assessment curve for S550 high strength steels under low-cycle actions at -60℃. The proposed approach combines a single set of monotonic tension test and one set of fatigue tests to determine the key material damage parameters in the continuum damage mechanics framework. The experimental program in this study examines both the material response under low-cycle actions. The microstructural mechanisms revealed by the Scanning Electron Microscopy (SEM) at the low temperature, furthermore, characterizes the effect due to different strain ratios and low temperature on the low-cycle fatigue life of S550 steels. Anchored on the experimental results, this study validates the S-N curve determined from the proposed approach. The S-N type curve determined from one set of fatigue tests and one set of monotonic tension tests estimates the fatigue life of all specimens under different strain ratios satisfactorily.

• Advances in concrete construction
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• v.8 no.4
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• pp.277-283
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• 2019

In evaluating explosion-protection capacity, safety distance is broadly accepted as the distance at which detonation of a given explosive causes acceptable structural damage. Safety distance can be calculated based on structural response under blast loading and damage criteria. For the applicability of the safety distance, the minimum required stand-off distance should be given when the explosive size is assumed. However, because of the nature of structures, structural details and material characteristics differ, which requires sensitivity analysis of the safety distance. This study examines the safety-distance sensitivity from structural and material property variations. For the safety-distance calculation, a blast analysis module based on the Kingery and Bulmash formula, a structural response module based on a Single Degree of Freedom model, and damage criteria based on a support rotation angle were prepared. Sensitivity analysis was conducted for the Reinforced Concrete one-way slab with different thicknesses, reinforcement ratios, reinforcement yield strengths, and concrete compressive strengths. It was shown that slab thickness has the most significant influence on both inertial force and flexure resistance, but the compressive strength of the concrete is not relevant.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.616-621
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• 2003

Fluid-elastic instability is believed to be a cause of the large-amplitude vibration and resulting rapid wear of heat exchanger tubes when the flow velocity exceeds a critical value. For sub-critical flow velocities, the random turbulence excitation is the main mechanism to be considered in predicting the long-term wear of steam generator tubes. Since flow-induced interactions of the tubes with tube supports in the sub-critical flow velocity can cause a localized tube wear, tube movement in the clearance between the tube and tube support as well as the normal contact force on the tubes by fluid should be maintained as low as possible. A simplified method is used for predicting fretting-wear damage of the double $90^{\circ}$U-bend tubes. The approach employed is based on the straight single-span tube analytical model proposed by Connors, the linear structural dynamic theory of Appendix N-1300 to ASME Section III and the Archard's equation for adhesive wear. Results from the presented method show a similar trend compared with the field data. This method can be utilized to predict the fretting-wear of the double $90^{\circ}$U-bend tubes in steam generators.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.39 no.spc1
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• pp.123-131
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• 2006

Immmune parameters of the Manila clam Ruditapes philippinarum collected from four tidal flats, Nudong, Gonam, Hwangdo and Bangpo on Anmyeon-do, Korea were optimized and evaluated at the single cell level using flow-cytometry Hemocytes were withdrawn from the sinus of each clam, and total hemocyte counts (THC), phagocytosis rate, hemocyte mortality (HM) and DNA damage of hemocyte were analyzed. The highest hemocyte counts was recorded from the clams collected from Gonam, followed by Hwangdo, Nudong and Bangpo (P<0.001). Phagocytosis rate and hemocyte mortality of Gonam and Nudong clams were significantly higher than those of clams from Hwangdo and Bangpo (P<0.001). DNA damage in the clams from Nudong was higher twice than that of clams from Gonam (P<0.05). We suggest that the flow-cytometry has a high potential for evaluation of immunity of marine bivalves.

• Biomolecules & Therapeutics
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• v.10 no.1
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• pp.12-18
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• 2002

Silymarin and curcumin have been used for supportive treatment of liver disease of difffrent etiology due to their hepatoprotective activities. The present study was carried out to investigate the hepatoprotective efffcts of silymarin and/or curcuma extract against hepatotoxins induced liver injury. To investigate hepatoprotective effects, the silymarin and/or curcuma extract were pre-treated orally to experimental animals. And thereafter a single dose of hepatotoxin, carbon tetrachloride ($CCl_4$) and acetaminophen were administered through oral or intraperitoneal route, respectively. Chronic liver damage was induced by subcutaneous injection of $CCl_4$ for 3 weeks (2 times/week). Hepatoprotective and therapeutic effects were monitored by estimating serurn ALT and AST levels and by measuring hepatic glutathione (GSH) and malondialdehyde (MDA)levels. Collagen type 1 was detected with irnrnunostaining to assess fibrosis. The results showed that the mix-ture of silymarin and curcuma extract significantly reduced serum biochemistry levels and MDA levels com-pared with those of control group in both acute and chronic animal models. In antifibrotic effect, the relative hepatic collagen content was significantly decreased by silymarin and/or curcuma extract treatment. It was concluded that the complex of silymarin and curcuma extract have a both hepatoprotective and therapeutic effect synergically in rat liver injury induced by heptotoxins.

• Journal of Food Hygiene and Safety
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• v.14 no.1
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• pp.60-66
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• 1999

Diethylnitrosamine (DEN) is known as a potential hepatic carcinogen by single administration. This study was designed to measure the effects of DEN-induced cell damage on the triglyceride and cholesterol concentration in the liver, excluding dietary effects. Fertilized chicken eggs, 10 days before hatching, were randomly divided into three groups (n=20) and each egg was injected 10 ${mu}ell$ of corn oil (vehicle control), 5 $\mu\textrm{g}$ of DEN/10 ${mu}ell$ of DEN/10 ${mu}ell$ into yolk via air sac. After 48 hr and 96 hr incubation, the damage of the chick-embryo liver cell was investigated by electron microscopy and by measuring the concentration of lipid components (total cholesterol, free cholesterol, phospholipid and triglyceride). For eggs administered 10 $\mu\textrm{g}$ of DEN and incuvated 96 hr, in hepatocyte, the nucleus membrane was roughed, the size of nucleolus was apparently increased and euchromatin was accumulated. Mitochondria were condensed and cristae, located mitochondiral inner membrane, were obscured. Additionally, the leaves of triglyceride and cholesterol classes were significantly increased depend on the amount treated with 10 $\mu\textrm{g}$ DEN at 96 hr, but phospholipids component of cell membrane, were decreased with significance. As a conclusion, carcinogen induced hepatic lesion was correlated with the changes in lipid component of liver.