• 한국가시화정보학회:학술대회논문집
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• 2002.11a
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• pp.39-42
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• 2002

In the current study, characteristics of the laser-induced plasma were investigated in a gas filled chamber or in a gas jet by using a relatively low intensity laser $(I\;\leq\;5\;\times\;10^{12}\;W/cm^2)$. Temporal evolutions of the produced plasma were measured using the shadow visualization and the shock wave propagation as well as the electron density profiles in the plasma channel was measured using the Mach-Zehnder interferometry. Experimental results such as the structure of the produced plasma, shock propagation speed $(V_s)$, electron density profiles $(n_e)$, and the electron temperature $(T_e)$ are discussed in this study. Since the diagnostic laser pulse occurs over short time intervals compared to the hydrodynamic time scales of expanding plasma or a gas jet, all the transient motion occurring during the measurement is assumed to be essentially frozen. Therefore, temporally well-resolved quantitative measurements were possible in this study.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.54.3-54.3
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• 2019

During the formation of large-scale structures in the universe, shocks with the sonic Mach number Ms <~ 5 are naturally induced by supersonic flow motions of baryonic matter in the intracluster medium (ICM). Cosmic rays (CRs) are expected to be accelerated via diffusive shock acceleration (DSA) at these ICM shocks, although the existence of CR protons in the ICM remains to be confirmed through gamma-ray observations. Based on the results obtained from kinetic plasma simulations, we build an analytic DSA model for weak, quasi-parallel shocks in the test-particle regime. With our DSA model, the CR acceleration efficiency ranges ~ 0.001 - 0.02 in supercritical quasi-parallel shocks with sonic Mach number Ms ~ 2.25 - 5, and the acceleration would be negligible in subcritical shocks wth Ms <~ 2.25. Adopting our DSA model, we estimate gamma-ray and neutrino emissions from clusters of galaxies by performing cosmological hydrodynamic simulations. The estimated gamma-ray flux is below the Fermi-LAT upper limit. In addition, the possible neutrino emission due to the decay of charged pions in galaxy clusters would be about <~ 1% of the atmospheric neutrino intensity in the energy range of <~ 100 GeV. In this talk, we will discuss the implication of our results.

• Asian-Australasian Journal of Animal Sciences
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• v.32 no.6
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• pp.904-911
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• 2019

Objective: The study was conducted to evaluate the effects of night light regimen on growth performance, antioxidant status and health of Lingnan Yellow broiler chickens from 1 to 21 days of age. Methods: A completely randomized factorial design involved 2 photoperiods (constant lighting [CL], 24 L:0 D and intermittent lighting [INL], 17 L:3 D:1 L:3 D)${\times}2$ light intensities (10 lx and 30 lx). A total of one thousand six hundred and eighty 1-d-old Lingnan Yellow broiler chicks were randomly divided into 4 treatments with 6 replicates (70 birds per replicate). The experiment lasted for 21 d. Results: Photoperiods and light intensities had no effect on average daily gain, feed conversion ratio, and mortality of the broiler chickens (p>0.05). The INL had a significant effect on average daily feed intake (p<0.05) of broiler chickens compared with CL. Photoperiod and light intensity had an interactive effect on melatonin (MT) concentration (p<0.05). At CL, reducing light intensity increased MT concentration; INL birds had higher MT but MT concentration was not affected by light intensity. There was an interactive effect on glutathione peroxidase (GPx) and catalase (CAT) in serum and total antioxidant capability (T-AOC) in liver between photoperiod and light intensity. With the decrease of light intensity, the activities of GPx and CAT in serum and T-AOC in liver increased in CL group (p<0.05). Broiler chickens reared under INL had better antioxidant status and 10 lx treatments had higher activities of CAT in serum than 30 lx (p<0.05). Different photoperiods and light intensities had no effect on malondialdehyde. There was an interaction between photoperiod and light intensity on serum creatine kinase (CK) concentration (p<0.05). At CL, the elevated light intensity resulted in an increase in CK content; INL birds had lower CK concentration especially in low light intensity group. Besides, INL and low light intensity significantly reduced the concentration of serum corticosterone and heat shock protein 70 (p<0.05). Serum immunoglobulin M contents were increased in broiler chickens reared under the INL compared with CL group (p<0.05). Conclusion: Results above suggest that the night light regimen of INL and 10 lx could be beneficial to the broiler chickens from 1 to 21 days of age due to the better health status and electricity savings.

• Journal of the Korea Concrete Institute
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• v.13 no.5
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• pp.491-498
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• 2001

The failure phenomenon of overlaid concrete structures, such as surface crack and peel-off failure in the contact zone, was investigated due to temperature shock(rainfall). To investigate this failure phenomenon, the surface tensile stress, and the shear stress, the vertical tensile stress in the contact zone were analysed using the non-linear stress-strain relationship of material such as strain-hardening- and strain-softening diagrams. Rainfall intensity, overlay thickness and overlay material were the main variables in the analyses. It is assumed that the initial temperature of overlaid concrete structures was heated up to 55$\^{C}$ by the solar heat. With a rain temperature 10$\^{C}$ and the rainfall intensity of nR=1/a, tR=10min, 60min, the stress states of overlaid concrete structures were calculated. The result shows that only fictitious cracks occurred in the overlay surface and no shear bond failure occurred in the contact zone. The vortical tensile stress increasing with overlay thickness was proved to be the cause of peel-off failure in the contact zone. The formulae for relationship between the vertical tensile stress and overlay thickness, material properties were derived. Using this formulae, it is possible to select proper material and overlay thickness to prevent failure in the contact zone due to temperature shock caused by rainfall.

• Proceedings of the Korea Society of Environmental Toocicology Conference
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• 1997.12a
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• pp.101-101
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• 1997

Comet assay, single cell gel electrophoresis has been known as useful, rapid, simple, visual, and sensitive technique for measuring the DNA breakage in mammalian ce1ls. For evaluation of DNA damage using comet assay, early studies reported a change in comet length and intensity with DNA damage using simple visual technique, such as fluorescence microscopy with eyespiece. In recent, some workers are observing and analyzing nucleotide of comets using quantitative fluorescence image analysis system to estimate 'tail moment', which is defined as the product of the tail length and the fraction of total DNA in tail. Our laboratory also adopted the image analysis software for qualification. In addition, many of the practical features of comet assay render it potentially attractive as useful tool for molecular toxicology and carcinogenesis, because the system is already showing considerable promise as rapid predictor in both in vitro and in vivo experimental designs. Recently, the comet assay becomes a attractive technique to study of apoptosis, because apoptotic fragmentation of nuclear DNA into nucleosomal sizes can be evaluated by the comet assay. So, we attempted to apply the comet assay to studying the effect of various stress on the apoptosis-sensitive cell lines. Particularly, focusing on the hyperthermic apoptosis, we could find that heat shock(44˚C for 60 minutes) was sufficient to induced apoptosis in these cell lines. But using the highly sensitive comet assay, we could not detect DNA breaks immediately after heat shock.

• Journal of Mechanical Science and Technology
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• v.19 no.2
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• pp.634-648
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• 2005

Performed here is a comparative assessment study for the probabilistic fracture mechanics approach of the pressurized thermal shock of the reactor pressure vessel. A round robin consisting of one prerequisite deterministic study and five cases for probabilistic approaches is proposed, and all organizations interested are invited. The problems are solved by the participants and their results are compared to issue some recommendation of best practices and to assure an understanding of the key parameters in this type of approach, like transient description and frequency, material properties, defect type and distribution, fracture mechanics methodology etc., which will be useful in the justification through a probabilistic approach for the case of a plant over-passing the screening criteria. Six participants from 3 organizations responded to the problem and their results are compiled and analyzed in this study.

• Asian-Australasian Journal of Animal Sciences
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• v.19 no.7
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• pp.1033-1039
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• 2006

The metabolic response of Labeo rohita to thermal acclimation was assessed. Advanced fingerlings of L. rohita (average weight $31{\pm}1.4g$) were acclimated to 31, 33 and $36^{\circ}C$ compared with ambient temperatures ($26^{\circ}C$) for 30 days and different enzymes associated with stress response were estimated. Glycolytic enzyme-Lactate dehydrogenase, (LDH, E.C.1.1.1.27), TCA cycle enzyme-Malate dehydrogenase (MDH, E.C.1.1.1.37), Protein metabolizing enzymes-Aspartate amino transferase (AST, E.C.2.6.1.1) and Alanine amino transferase (ALT, E.C.2.6.1.2) of liver, gill and muscle, Gluconeogenic enzymes-Fructose 1,6 Bi phosphatase (FBPase, E.C. 3.1.3.11) and Glucose 6 phosphatase (G6Pase, E.C. 3.1.3.9) of liver and kidney were significantly (p<0.05) different with increasing acclimation temperatures. Heat Shock Protein-70 (HSP-70) was expressed in increasing intensity at 31, 33 and $36^{\circ}C$ but was not expressed at $26^{\circ}C$. Results suggest that higher acclimation temperatures enhance metabolism and L. rohita maintains homeostasis between $26-36^{\circ}C$ via an acclimation episode. Such adaptation appears to be facilitated by resorting to gluconeogenic and glycogenolytic pathways for energy mobilization and induction of HSPs.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.7
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• pp.1139-1146
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• 2001

The reactor pressure vessel(RPV) is usually cladded with stainless steel to prevent corrosion and radiation embrittlement, and a number of subclad cracks have been found during an in-service-inspection. These subclad cracks should be assured for a safe operation under normal conditions and faulted conditions such as pressurized thermal shock(PTS). Currently available integrity assessment procedure for an RPV, ASME Code Sec. XI, are built on the basis of linear fracture mechanics (LEFM). In PTS condition, however, thermal stress and mechanical stress give rise to high tensile stress at the cladding and elastic-plastic behavior is expected in this area. Therfore, ASME Code Sec. XI is overly conservative in assessing the structural integrity under PTS condition. In this paper, the fracture parameter (stress intensity factor, K, and RT(sub)NDT) from elastic analysis using ASME Sec. XI and finite element method were validated against 3-D elastic-plastic finite element analyses. The difference between elastic and elastic-plastic analysis became significant with increasing crack depth. Therfore, it is recommended to perform elastic-plastic analysis for the accurate assessment of subclad cracks under TPS which causes plastic deformation at the cladding.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.1
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• pp.118-131
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• 1995

The shock fracture analysis for the structures of navy vessels subject to underwater explosions or of high speed vessels frequently subject to impact loads has been carried out in two steps such as the global or macro analysis and the fine or micro analysis. In the macro analysis, Doubly Asymptotic Approximation(DAA) has been applied. The three main failure modes of structure members subject to strong shock loading are late time fracture mode such as plastic large deformation mainly due to dynamic plastic buckling, and the early time fracture mode such as tensile tearing failure or transverse shear failure. In this paper, the tensile tearing failure mode is numerically analyzed for the micro analysis by calculating the dynamic stress intensity factor $K_I(t)$, which shows the relation between stress wave and crack propagation on the longitudinal stiffener of the model. Especially, in calculating this factor, the numerical caustic method developed from shadow optical method of caustic well known as experimental method is used. The fully submerged vessel is adopted for the macro analysis at first, of which the longitudinal stiffener, subject to early shock pressure time history calculated in macro analysis, is adopted for the micro analysis.

• Journal of the Korea Convergence Society
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• v.12 no.11
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• pp.135-142
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• 2021

The purpose of this study was to determine the effect of extracorporeal shock wave therapy for the neck-shouler muscles of complex pain scales of the 20s adults with VDT Syndrome to prolonged smartphone use. Twenty subjects with neck pain due to VDT syndrome participated in the experiment. They were randomly divided into 10 experimental groups and 10 control groups. Experimental subjects were conducted for 4 weeks, 5 days a week. The experimental group was subjected to extracorporeal shock wave therapy 2000 times at an intensity of 5 Hz and 2.0 bar once, and the control group performed self-stretching exercise for 30 minutes once. Subjects measured and compared neck-shoulder pain with VAS and PPT before and after the experiment. Data analysis was performed with SPSS win 18.0, and correspondence comparison was performed to analyze the results of the experimental group and the control group before and after the experiment. After the experiment, the experimental group decreased more in VAS and PPT of the neck-shoulder muscle. but the control group was no difference. Though these results, extracorporeal shock wave therapy was showed a reduction in pain after treatment than before treatment but there are no difference in the pain reduction after self-stretching exercise. Thus, extracorporeal shock wave therapy is expected to be used as a variety of treatments to reduce neck-shoulder pain as a cause of VDT syndrome.