• Korean Journal of Materials Research
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• v.26 no.11
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• pp.583-589
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• 2016

In this study, recrystallization behaviors in the two-phase (${\alpha}+{\gamma}$) region of micro-alloyed steels such as Base, Nb, TiNbV and CAlN were investigated in terms of flow stress, microstructure and associated grain boundary characteristics. The flow stress of all specimens reached peak stress and gradually decreased, which means that recrystallization or recovery of proeutectoid deformed ferrite and recovery or transformation to ferrite of deformed austenite occurred by thermal activation. The precipitation of carbide or nitride via the addition of micro-alloying elements, because it reduced prior austenite grain size upon austenitization, promoted transformation of austenite to ferrite and increased flow stress. The strain-induced precipitation under deformation in the two-phase region, on the other hand, increased the flow stress when the micro-alloying elements were dissolved during austenitization. The recrystallization of the Nb specimen was more effectively retarded than that of the TiNbV specimen during deformation in the two-phase region.

• Communications for Statistical Applications and Methods
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• v.19 no.6
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• pp.837-847
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• 2012

Inverse Gaussian distribution is widely used in applications to analyze and model right-skewed data. To assess the appropriateness of the distribution prior to data analysis, Mudholkar and Tian (2002) proposed an entropy-based test of fit. The test is based on the entropy power fraction(EPF) index suggested by Gokhale (1983). The simulation results report that the power of the entropy-based test is superior compared to other goodness-of-fit tests; however, this observation is based on the small-scale simulation results on the standard exponential, Weibull W(1; 2) and lognormal LN(0:5; 1) distributions. A large-scale simulation should be performed against various alternative distributions to evaluate the power of the entropy-based test; however, the use of a theoretical method is more effective to investigate the powers. In this paper, utilizing the information discrimination(ID) index defined by Ehsan et al. (1995) as a mathematical tool, we scrutinize the power of the entropy-based test. The selected alternative distributions are the gamma, Weibull and lognormal distributions, which are widely used in data analysis as an alternative to inverse Gaussian distribution. The study results are provided and an illustrative example is analyzed.

• Journal of Physiology & Pathology in Korean Medicine
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• v.24 no.3
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• pp.439-445
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• 2010

Pretreatment with Taraxacum Mongolicum H(TMH) prior to the administration of on $CCl_4$ significantly prevented the increased serum enzymatic activity of aminotransferase(ALT, AST), gamma-glutamyl transpeptidase(GGT) and bilirubin concentration in dose-dependent manner. In addition, pretreatment with TMH also significantly restored the elevation of hepatic malondialdehyde formation and the depletion of reduced glutathione content in the liver $CCl_4$-intoxicated rats. The restoration of microsomal aniline hydroxylase and aminopyrine N-demethylase activities indicated the improvement in functional status of endoplasmic reticulum. $CCl_4$-induced hepatotoxicity was also essentially prevented, as indicated by a liver histopathologic study. TMH showed antioxidant effects in $FeCl_2$-ascorbate-induced lipid peroxidation in rat liver homogenate and in superoxide radical scavenging activity. Our results suggest that the protective effect of TMH against $CCl_4$-induced hepatotoxicity possibly involve mechanisms related to its ability to block p450-mediated $CCl_4$ bioactivation and free radical scavenging effects.

• Journal of Applied Biological Chemistry
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• v.42 no.2
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• pp.66-70
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• 1999

Effects of the enhanced level of L-ascorbic acid (AA) on the water deficit-induced oxidative damage were studied in rice (Oryza sativa L.) seedlings. The seedlings sprayed with 20 to 80 mM L-galactono-${\gamma}$-lactone (GL), a putative precursor of AA, showed 2 to 5-fold higher levels of AA compared with controls. Pretreatment of the seedlings with GL prior to water stress imposition caused virtually no effect on dehydration of tissues during water deficit but substantially mitigated oxidative injury, as accessed by 2-thiobarbituric acid-reactive substances, ${\alpha}$-tocopherol, chlorophylls and ${\beta}$-carotene. Proline accumulation during water stress was also significantly lowered in the treated seedlings. In a complementary experiment, AA retarded photodegradation of ${\alpha}$-tocopherol in isolated thylakoids far more efficiently than glutathione. GL in itself did not show any noticeable reactivity toward ${\alpha}$-tocopheroxyl radical. The results demonstrate the antioxidative function of AA in rice seedlings encountering water-limited environments, suggesting a critical role of AA as a defense against oxidative stress in plants.

• Korean Journal of Veterinary Pathology
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• v.2 no.1
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• pp.37-46
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• 1998

It has been known that $\gamma$-irradiation usually induces cell death in regenerating stem cell in normal tissues like skin, intestine and hematopoietic organ. The experiment were carried out to evaluate the early response of radiation injury in radiosensitive and intermediate radiosensitive tissues in feeding and starving rats with the doses of 3.5 and 7.0 Gy. The results of the study showed that the histological phenomenon was apoptosis in the doses of the radiation as the early response of tissue injury. Apoptosis were showed organ-specific and cellular specific responses suggesting that the selection of apoptosis be exactly focused on highly renewal organs and cells. It was interesting that the rats starved for 72 hours prior to irradiation induced less apoptosis in liver than fed rats. As for cellular responses it appeared that apoptotic cells were mostly distributed in ductal or periportal cells in liver of feeding rats unlikely in liver of Starving rots which showed no difference in zonal distribution. In salivary gland apoptotic cells in fed rats were highly induced in intercalating and ductal cell population than in acinar cell population although unlikely in starved rats. This study showed the value of apoptosis using the detection system of TUNEL for evaluating cellular damage after radiation injury and the diminished effect of starvation on cell damage after ionizing irradiation.

• Journal of Korea Foundry Society
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• v.9 no.6
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• pp.463-473
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• 1989

This study is aimed to investigate the effect of cyclic heat treatment which is special heat treatment on the strength and toughness in Multi-phase(Ferrite-Bainite-Martensite) Ductile cast Irons. Spceimens were austenitized at eutectoid transformation temperature range(${\alpha}+{\gamma}$) for 30min and austempered at $300^{\circ}C$ and $400^{\circ}C$ for different holding times, and then quenched in ice water to obtain the multi-phase(Ferrite-Bainite-Martensite) structure from various prior structures, which was obtained by various cyclic heat treatments. As the number of cycle in cyclic heat treatment increased, volume fraction of pearlite increased and the its morphology was refined. As the number of cycle in cyclic heat treatment increased, the multi-phase(Ferrite-Bainite-Martensite) was dispersed in whole matrix as refined island phase. Particularly, martensite among the multi-phase gradually became a spherical shape. Good combination in impact energy and tensile strength was detained in $840^{\circ}C-300^{\circ}C-15min$ condition after 10 cycles in cyclic heat treatment, and its multi-phase volume fraction is Ferrite(50%)-Martensite(l3%)-Bainite(37%).

• Structural Engineering and Mechanics
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• v.81 no.1
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• pp.103-115
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• 2022

The prediction error variances for frequencies are usually considered as unknown in the Bayesian system identification process. However, the error variances for mode shapes are taken as known to reduce the dimension of an identification problem. The present study attempts to explore the effectiveness of Bayesian approach of model parameters updating using Markov Chain Monte Carlo (MCMC) technique considering the prediction error variances for both the frequencies and mode shapes. To remove the ergodicity of Markov Chain, the posterior distribution is obtained by Gaussian Random walk over the proposal distribution. The prior distributions of prediction error variances of modal evidences are implemented through inverse gamma distribution to assess the effectiveness of estimation of posterior values of model parameters. The issue of incomplete data that makes the problem ill-conditioned and the associated singularity problem is prudently dealt in by adopting a regularization technique. The proposed approach is demonstrated numerically by considering an eight-storey frame model with both complete and incomplete modal data sets. Further, to study the effectiveness of the proposed approach, a comparative study with regard to accuracy and computational efficacy of the proposed approach is made with the Sequential Monte Carlo approach of model parameter updating.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.19 no.1
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• pp.20-26
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• 2023

The defected baffle former bolts of Kori unit 1 were withdrawn to analyze the cause of damage and gamma-ray measurement is being scheduled. Prior to that, in order to calculate the specific radioactivity value of the baffle former bolt, a radioactivity calculation method considering the actual operation history of the nuclear power plant is introduced and the calculation results are shown. In particular, the radioactivity calculation method considering the operation history is obtained by defining the monthly contribution factor from the actual monthly operation history. As a result, the results considering operation history are 16-28% lower than the general radioactivity calculation results. These results can contribute to establish a reasonable but economical strategy when planning nuclear power plant decommissioning.

• Radiation Oncology Journal
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• v.12 no.1
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• pp.1-8
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• 1994

When cells are exposed to low doses of a mutagenic or clastogenic agents. they often become less sensitive to the effects of a higher dose administered subsequently. Such adaptive responses were first described in Escherichia coli and mammalian cells to low doses of an alkylating agent. Since most of the studies have been carried out with human lymphocytes, it is urgently necessary to study this effect in different cellular systems. Its relation with inherent cellular radiosensitivity and underlying mechanism also remain to be answered. In this study, adaptive response by 1 cGy of gamma rays was investigated in three human lymphoblastoid cell lines which were derived from ataxia telangiectasia homozygote, ataxia telangiectasia heterozygote, and normal individual. Experiments were carried out by delivering 1 cGy followed by 50 cGy of gamma radiation and chromatid breaks were scored as an endpoint. The results indicate that prior exposure to 1 cGy of gamma rays reduces the number of chromatid breaks induced by subsequent higher dose (50 cGy), The expression of this adaptive response was similar among three cell lines despite of their different radiosensitivity. When 3-aminobenzamide, an inhibitor of poly (ADP-ribose) polymerase, was added after 50 cGy, adaptive responses were abolished in all the tested cell lines. Therefore it is suggested that the adaptive response can be observed in human lymphoblastoid cell lines, which was first documented through this study. The expression of adaptive response was similar among the cell lines regardless of their radiosensitivity. The elimination of the adaptive response by 3-aminobenzamide is consistent with the proposal that this adaptive response is the result of the induction of a certain chromosomal repair mechanism.

• Korean Journal of Food Science and Technology
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• v.44 no.5
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• pp.532-539
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• 2012

Electron spin resonance (ESR) spectroscopy of gamma-irradiated fresh broccoli and kimchi cabbage was conducted to identify their irradiation history. Different pretreatments, such as freeze-drying (FD), oven-drying (OD), alcoholic-drying (ALD), and water-washing and alcoholic-drying (WAD) were used to lower the moisture contents of the samples prior to ESR analysis. The non-irradiated samples exhibited a single central signal ($g_0$=2.0007) with clear effect of $Mn^{2+}$, especially in kimchi cabbage. Upon irradiation, there was an increase in the intensity of the central signal, and two side peaks, mutually spaced at 6 mT, were also observed. These side peaks with $g_1$ (left)=2.023 and $g_2$ (right)=1.985 were attributed to radiation-induced cellulose radicals. Leaf and stem in broccoli, and root and stem in kimchi cabbage provided good ESR signal responses upon irradiation. The signal noise was reduced in case of ALD and WAD pretreatments, particularly due to $Mn^{2+}$ signals. The ALD treatment was found most feasible to detect the improved ESR spectra in the irradiated samples.