• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.123-128
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• 2001

The creep constants which are used to the reference stress equations of creep damage were obtained to type 316LN stainless steel, and their determining methods were described in detail. Typical Kachanov and Rabotnov(K-R) creep damage model was modified into the damage equations with reference stress concepts, and the modified equations were applied practically to type 316LN stainless steel. In order to determine the reference stress value, a series of high-temperature tensile tests and creep tests were accomplished at $550^{\circ}C$ and $600^{\circ}C$. By using the experimental creep data, the creep constants used in reference stress equations could be obtained to type 316LN stainless steel, and a creep curve on rupture strain was predicted. The reference stress concept on creep damage can be utilized easily as a design tool to predict creep life because the process, which is quantified by the measurement of voids or micro cracks during creep, is omitted.

• Toxicological Research
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• 제13권4호
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• pp.371-376
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• 1997

To compare the severe liver damage with the slight one on the bromobeazene metabolism in rats, the animal group described as B7 group was induced the stage of slight liver damage with 7 times bromobenzene injection every other day (400 mg/Kg body wt. i.p.), whereas B40 group was induced that of more severe liver damage with bromobeazene 40 times injection as identified with determination of serum levels of alanine aminotransferase(ALT) activity and the histopathological findings. In the present experimental animal model, the decreasing rate of glutathione(GSH) and the increasing rate of glutathione S-transferase activity to the control group were higher in B7 group than B40 group. Furthermore the single dose of bromobenzene was injected to the two groups and sacrificed at 8hr and the hepatic aniline hydroxylase(AH) activity, GSH content and GST activity were determined. The increasing rate of AH activity to the control was lower in B40 group than B7 group and the decreasing rate of GSH to the control was also lower in B40 than B7 group. Moreover, B7 group showed the increased activity of hepatic GST to the control whereas B40 group showed the decrease activity of the enzyme. And Vmax value in GST was more decreased in B40 group than B7 group.

• 한국소음진동공학회논문집
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• 제22권11호
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• pp.1144-1151
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• 2012

A damage in structure alters its dynamic characteristics. The change is characterized by changes in the modal parameter, i.e., modal frequencies, modal damping value and mode shape associated with each modal frequency. Changes also occur in some of the structural parameters; namely, the mass, damping, stiffness matrices of the structure. In this paper, evaluation of changes in stiffness matrix of a structure is presented as a method not only for identifying the presence of the damage but also locating the damage. It is shown that changed stiffness matrix can be accurately estimated a sensitivity coefficient matrix derived from modifying mode shapes, First, with 4 story shear structure models, the effect of presence of damage in a structure on its stiffness matrix is studied. By using these analytical model, the effectiveness of using change of stiffness matrix in detecting and locating damages is demonstrated. To validate the predicted changing stiffness and its location, the obtained results are compared to the reanalysis result which shows good agreement.

• 대한조선학회논문집
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• 제47권6호
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• pp.813-820
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• 2010

The spread mooring system for FPSO is developed to explore deep sea area, in which swell is dominant. It is known that the tension response of mooring lines in this sea area shows bimodal spectrum. Assuming normal distribution of tension profile and Rayleigh distribution of tension amplitude, the power spectral density function (PSD) of the mooring tension under the bimodal stationary random process is applied for the calculation of spectrum fatigue. Three popular methods, which are simple summation method, combined spectrum method and Jioa-Moan method, are used to combine fatigue damages from bimodal spectrum characteristics. Each damage value is compared with damage using Rainflow Cycle Counting (RCC) method which is believed to be close to exact solution. Vanmarcke' parameter and RMS(Root Mean Square) ratio are employed to assess relative damage variations between from RCC method and from three combination methods. Finally the most reliable fatigue damage combining method for spread mooring system is suggested.

• Geomechanics and Engineering
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• 제23권6호
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• pp.575-585
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• 2020

In this numerical study, the 2D dynamic behavior of a clayey basin and its effect on damage pattern over basin edge are investigated. To attain this goal, a fully nonlinear time domain analysis method has been applied. Then, the fragility curves of the considered two typical industrial structures for that certain point are estimated using the acceleration time histories recorded at each surface point. The results show that the use of the damage related parameters in site effect analyses, instead of amplification curves, can yield more realistic estimation of the basin dynamic response. In a distance about 150 m from outcrop at the basin edge, the differences between fragility curves increase when increasing the distance from outcrop with respect to the reference rock site. Outside this region and towards the basin center, they tend to occur in rather single curves. Furthermore, to connect the structural damage to the basin edge effect, the earthquake demand value at different points for two typical structures was evaluated. It was seen that the probability of occurrence of damage increases over 250 m from outcrop, while the effect of the basin edge was limited to 150 m in case of the basin edge evaluation by using fragility curves.

• 대한한방내과학회지
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• 제26권4호
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• pp.767-775
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• 2005

This study was carried out to investigate the preventive effect of Salviae Miltiorrhizae Radix, Rhei Rhizoma and Carthami Flos combined with Samgijiwhang-Tang(SJTSRC) on streptozotocin(STZ)-induced diabetic nephropathy. Rats were divided into a control group of rats with STZ-induced diabetic nephropathy, a sample group of those given SJTSRC, and a normal group. In the experiment diabetic nephropathy was induced by giving STZ(60mg/kg) to rats via the peritoneum, and effects were assessed with measures of serum creatinine, serum BUN, secretion content of albumin and glucose content of urine, malondialdehyde(MDA) and glutathione(GSH) content in cortex of kidney. When STZ was injected into sample rat, the value of creatinine and BUN increased validly and STZ did damage to the kidney. When applying SJTSRC to sample rats, the value of serum creatinine decreased validly but the value of serum BUN decreased invalidity. It was confirmed that SJTSRC had an effect on recovery after kidney damage and secretion content of albumin increasedafter administration of SJTSRC but there was no change in glucose content of urine compared with the control group. The decrease of secretion of albumin after injection of STZ was taken to mean progressive diabetic nephropathy, and that reversal of that trend after SJTSRC administration showed that kidney function had improved, not through decreasing blood sugar, but through other factors. Results suggest that diabetic nephropathy was induced by STZ, and SJTSRC was effective in restricting the extent of damage to the kidney and halting the progression of diabetic nephropathy with improvement in levels of serum creatinine and albumin secretion. More study is needed, particularity pertaining to anti-oxidative effects in the kidney cortex.

• Journal of Radiation Protection and Research
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• 제41권4호
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• pp.339-343
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• 2016

Background: Evaluation of deoxyribonucleic acid (DNA)-strand break is important to elucidate the biological effect of ionizing radiations. The conventional methods for DNA-strand break evaluation have been achieved by Agarose gel electrophoresis and others using an electrical property of DNAs. Such kinds of DNA-strand break evaluation systems can estimate DNA-strand break, according to a molecular weight of DNAs. However, the conventional method needs pretreatment of the sample and a relatively long period for analysis. They do not have enough sensitivity to detect the strand break products in the low-dose region. Materials and Methods: The sample is water, methanol and plasmid DNA solution. The plasmid DNA pUC118 was multiplied by using Escherichia coli JM109 competent cells. The resonance frequency and Q-value were measured by means of microwave dielectric absorption spectroscopy. When a sample is located at a center of the electric field, resonance curve of the frequency that existed as a standing wave is disturbed. As a result, the perturbation effect to perform a resonance with different frequency is adopted. Results and Discussion: The resonance frequency shifted to higher frequency with an increase in a concentration of methanol as the model of the biological material, and the Q-value decreased. The absorption peak in microwave power spectrum of the double-strand break plasmid DNA shifted from the non-damaged plasmid DNA. Moreover, the sharpness of absorption peak changed resulting in change in Q-value. We confirmed that a resonance frequency shifted to higher frequency with an increase in concentration of the plasmid DNA. Conclusion: We developed a new technique for an evaluation of DNA damage. In this paper, we report the evaluation method of DNA damage using microwave dielectric absorption spectroscopy.

• Journal of Korean Neurosurgical Society
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• 제39권4호
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• pp.271-276
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• 2006

Objective : Despite the recent progress that has been made in intracerebral monitoring, it is still difficult to quantify the exact extent of primary brain damage after severe head injury. In this work, we investigate the role of S-100B protein as a serum marker of brain damage after severe head injury. Methods : 21 patients with severe head injury [GCS score <9] were selected for this prospective study. A venous blood sample was taken as soon as possible after head injury and the serum concentration of S-100B protein was measured daily for five consecutive days. The serum level of S-100B protein was compared with the patients' outcome. The outcome was measured twice, at hospital discharge and after 6 months of follow-up using the Glasgow Outcome Scale[GOS]. Results : Those patients who died within two weeks [after head injury] had a significantly higher serum S-100B value than those who survived [median, 9.64ug/L versus 2.91ug/L]. Seven [78%] of the nine patients who died had a maximum S-100B value of 2ug/L or higher, while three [25%] of the twelve surviving patients showed a maximum S-100B protein value of more than 2ug/L [P<005]. Conclusion : These results indicate that S-100B protein appears to be the most reliable index for estimating the extent of brain damage.

• Journal of Nutrition and Health
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• 제36권1호
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• pp.24-31
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• 2003

The present study was attempted to investigate the antioxidant capacity of popular yellow-green vegetable juices (kale, Angelica keishei, carrot, small water dropwort) and to investigate the effect of vegetable juices on protecting oxidative damage to DNA in cultured Chinese hamster lung (CHL) cells. Antioxidant capacity was analyzed by TRAP assay (Total radical-trapping antioxidant potential). Cellular DNA dmamage was measured by SCGE (single-cell gel electrophoresis, also known as comet assay. Cells incubated in medium with PBS (negative control) or with various concentration of the freeze dried green juices (25, 50, 100, 250 $\mu\textrm{g}$/$m\ell$) resuspended in PBS were treated with $H_2O_2$ (200 ${\mu}{\textrm}{m}$) as an oxidative stimulus for 5 min at 4$^{\circ}C$. The physiological function of each vegetable juice on oxidative DNA damage was analyzed and expressed as tail moment (tail length X percentage migrated DNA in tail) . Kale juice had the highest TRAP value suggesting that kale has the highest antioxidant capacity followed by Angelica keishei, small water dropwort and carrot. Cells treated with $H_2O_2$ had extensive DNA damage compared with cells treated with PBS or pre-treated with vegetable juice extracts. All green juices inhibited $H_2O_2$-induced DNA damage with kale being the most effective juice among the tested juices. These results indicate that green juice supplementation to CHL cells followed by oxidative stimulus inhibited damage to cellular DNA, supporting a protective effect against oxidative damage induced by reactive oxygen species. (Korean J Nutrition 36(1) : 24-31, 2003)

• Structural Engineering and Mechanics
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• 제27권5호
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• pp.625-638
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• 2007

The damage detection process may appear difficult to be implemented for truss structures because not all degrees of freedom in the numerical model can be experimentally measured. In this context, the damage locating vector (DLV) method, introduced by Bernal (2002), is a useful approach because it is effective when operating with an arbitrary number of sensors, a truncated modal basis and multiple damage scenarios, while keeping the calculation in a low level. In addition, the present paper also evaluates the noise influence on the accuracy of the DLV method. In order to verify the DLV behavior under different damages intensities and, mainly, in presence of measurement noise, a parametric study had been carried out. Different excitations as well as damage scenarios are numerically tested in a continuous Warren truss structure subjected to five noise levels with a set of limited measurement sensors. Besides this, it is proposed another way to determine the damage locating vectors in the DLV procedure. The idea is to contribute with an alternative option to solve the problem with a more widespread algebraic method. The original formulation via singular value decomposition (SVD) is replaced by a common solution of an eigenvector-eigenvalue problem. The final results show that the DLV method, enhanced with the alternative solution proposed in this paper, was able to correctly locate the damaged bars, using an output-only system identification procedure, even considering small intensities of damage and moderate noise levels.