• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.9
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• pp.770-781
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• 2008

In nuclear power plants, ferritic low alloy steel components were connected with austenitic stainless steel piping system through alloy 82/182 butt weld. There have been incidents recently where cracking has been observed in the dissimilar metal weld. Alloy 82/182 is susceptible to primary water stress corrosion cracking. Weld-induced residual stress is main factor for crack growth. Therefore exact estimation of residual stress is important for reliable operating. This paper presents residual stress computation performed by 6" safety & relief nozzle. Based on 2 dimensional and 3 dimensional finite element analyses, effect of welding variables on residual stress variation is estimated for sensitivity analysis.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2003.10a
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• pp.90.1-90
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• 2003

Colonization of Pseudomonas chlororaphis O6, a nonpathogenic rhizobacterium, on the roots induced systemic resistance in cucumber plants against tai-get leaf spot, a foliar disease caused by Corynespora cassiicola. A cDNA library was constructed using mRNA extracted from the cucumber leaves 12 h after inoculation with C. cassiicola, which roots had been previously treated with O6. To identify the genes involved in the O6-mediated induced systemic resistance (ISR), we employed a subtractive hybridization method using mRNAs extracted from C cassiicola-inoculated cucumber leaves with and without previous O6 treatment on the plant roots. Differential screening of the cDNA library led to the isolation of 5 distinct genesencoding a GTP-binding protein, a putative senescence-associated protein, a galactinol synthase, a hypersensitive-induced reaction protein, and a putative aquaporin. Expressions of these genes are not induced by O6 colonization alone. Before challenge inoculation, no increase in the gene transcriptions could be detected in previously O6-treated and untreated plants but, upon subsequent inoculation with the pathogenic fungus, transcription levels in O6-treated plants rose significantly faster and stronger than in untreated plants. Therefore, the O6-mediated ISR may be associated with an enhanced capacity for the rapid and effective activation of cellular defense responses which becomes apparent only after challenge inoculation on the distal, untreated plant parts, as suggested by Conrath et al. (2002). This work was supported by a grant R11-2001-092-02006-0 from the Korea Science and Engineering Foundation through the Agricultural Plant Stress Research Center at Chonnam National University.

• Korean Journal of Acupuncture
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• v.25 no.3
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• pp.65-80
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• 2008

Objective : In recent years, many investigators have questioned whether the analgesic effect of acupuncture is simply related to the stress-induced analgesia (SIA). However, there has been lack of studies on this issue. In this study, the stress levels induced by manual acupunctures are compared with the stress in animal experiment models. The experiments have been carried out with Sprague Dawley (SD) rats. Method : For stress level evaluation, Hot plate test has been used. Maximum Possible Effect (MPE) has been measured by checking the pre-test time and post-test time. Cortisol and corticosterone concentrations in serum were measured by enzyme-linked immunosorbent assay (ELISA). Results : In the hot plate test, MPE values of post-test time were significantly decreased after 10 minutes than after 5 minutes. Therefore, optimal time interval was chosen as 10 minutes. There was significant difference of MPE values between Suspension group and all other treatment groups. However, there were no significant differences of MPE values between Sham group and all other treatment groups. However, MPE values showed tendency to decrease when acupuncture needle diameter increased. MPE values of ST040, ST040(lido), NAP040(lido) groups were markedly decreased than that of Suspension group, while that of NAP040 group was substantially increased than that of Sham group increased in acupoint and nonacupoint models. Serum cortisol concentrations of treatment groups were not significantly different from that of Suspension and Sham groups. Serum corticosterone concentration of 0.25 mm group was substantially increased than that of compared with Sham group. Serum cortisol and corticosterone concentrations of treatment groups were not significantly different from those of Suspension and Sham groups in acupoint and nonacupoint models. Conclusion : From hot plate test and serum stress hormones concentrations, it is found that manual acupuncture treatment induces negligible stress or SIA on ST36. And the stress induced by manual acupuncture is more closely related to acupuncture point needlings than diameters of acupuncture needles.

• Journal of Oriental Neuropsychiatry
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• v.12 no.1
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• pp.123-135
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• 2001

Objective: This study was designed to assess antidepressant effects of Quibitang on an Animal Model of Depression induced by Chronic Mild Stress. Method: The consumption of 1% sucrose solution and active avoidance learning test were used to evaluate antidepressant effect of Quibitang. The consumption of 1% sucrose solution was measured every week for 8 weeks, and active avoidance learning test was executed after 4 weeks treatment of saline or Quibitang. Result: 1. The consumption of 1% sucrose solution was significantly reversed in test group (Quibitang-treated group) at 5th, 7th, 8th weeks, but there was no significant change in control group. 2. Chronic Mild Stress was found to suppress the increase of body weight at 5th, 6th, 7th, 8th weeks. Treatment of Quibitang did not enhanced the body weigt, but it enhanced the consumption of sucrose solution. 3. In order to measure the learning ability of rat which drived to be depressed, we executed active avoidance test. The result revealed that depressed rat showed impaired acquisition than control group, and the treatment of Quibitang restored the learning activity. Conclusion: These results suggest that Quibitang may have antidepressant effects on depression induced by chronic mild stress.

• Geomechanics and Engineering
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• v.9 no.5
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• pp.645-667
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• 2015

Single treatment and staged treatments in vertical wells are widely applied in sandstone and mudstone thin interbedded (SMTI) reservoir to stimulate the reservoir. The keys and difficulties of stimulating this category of formations are to avoid hydraulic fracture propagating through the interface between shale and sand as well as control the fracture height. In this paper, the cohesive zone method was utilized to build the 3-dimensional fracture dynamic propagation model in shale and sand interbedded formation based on the cohesive damage element. Staged treatments and single treatment were simulated by single fracture propagation model and double fractures propagation model respectively. Study on the changes of fracture vicinity stress field during propagation is to compare and analyze the parameters which influence the interfacial induced stresses between two different fracturing methods. As a result, we can prejudge how difficult it is that the fracture propagates along its height direction. The induced stress increases as the pumping rate increasing and it changes as a parabolic function of the fluid viscosity. The optimized pump rate is $4.8m^3/min$ and fluid viscosity is $0.1Pa{\cdot}s$ to avoid the over extending of hydraulic fracture in height direction. The simulation outcomes were applied in the field to optimize the treatment parameters and the staged treatments was suggested to get a better production than single treatment.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.5
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• pp.69-78
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• 2009

Since the blast vibration induced by explosives of the powder possibly provide damage of the nearby structures adjacent to the tunnel, the stability of the nearby structures should be estimated. In this study, the stability of the tunnel based on the allowable peak particle velocity of the structures as well as allowable stress of the structures presented in the concrete structural design standard was estimated with respect to the stress of the concrete lining and axial force of the rockbolt during the blasting operation at the ground surface of the pre-existing tunnel. The analyses were carried out by using $FLAC^{2D}$ which is one of the programs developed based on the finite difference method. The bending compressive stress and shear stress of the concrete lining and axial force of the rockbolt were rapidly increased when the blasting operation was conducted near the tunnel.

• Structural Engineering and Mechanics
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• v.7 no.6
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• pp.575-588
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• 1999

A boundary element method is applied to the analysis of crack trajectory in materials with complex microstructure, such as discontinuously reinforced composite materials, and systems subjected to complex loading, such as indentation. The path followed by the crack(s) has non-trivial geometry. A study of the stress intensity factors and fracture toughness of such systems must therefore be accompanied by an analysis of crack trajectory. The simulation is achieved using a dual boundary integral method in planar problems, and a single boundary integral method coupled with substructuring in axisymmetric problems. The direction of crack propagation is determined using the maximum mechanical energy release rate criterion. The method is demonstrated by application to (i) a composite material composed of components having the elastic properties of aluminium (matrix) and silicon carbide (reinforcement), and (ii) analysis of contact damage induced by the action of an indenter on brittle materials. The chief advantage of the method is the ease with which problems having complex geometry or loading (giving rise to complex crack trajectories) can be treated.

• Plant Biotechnology Reports
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• v.3 no.1
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• pp.57-65
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• 2009

Cultured Cupressus lusitanica cells induced by various stresses are thought to produce different complexes of defense chemicals to optimize defense. To compare the induced products of two stimulations, we investigated the emission of monoterpenes, biosynthesis of ${\beta}-thujaplicin$, and accumulation of lignin in mechanically stressed and fungal elicited cultured C. lusitanica cells. Both mechanical stress and fungal elicitor caused emission of qualitatively similar monoterpene blends indicating de novo biosynthesis of these compounds after stimulation, while mechanical stress alone is sufficient to induce fungal elicitor-related monoterpene emission. Sabinene and limonene were the dominant compounds over the time course in both volatile blends. Although the emitted volatile blends were qualitatively similar, the time course and the relative ratios of the constituents of the volatile blends differed with the type of stimulation. While fungal elicited cells produced significant amounts of ${\beta}-thujaplicin$ over the 5-day time course, no ${\beta}-thujaplicin$ was observed in the mechanically stressed cells. The production of ${\beta}-thujaplicin$ was the main dissimilarity of the induced products of these two treatments, suggesting that synthesis of ${\beta}-thujaplicin$ is not a general response to all types of stresses, but is a specific response and serves as a strong toxic compound against already invaded fungus. Significantly higher amounts of lignin accumulations were observed in the fungal elicited and mechanically stressed cells on the 5th day after induction. Based on these results, we suggest the composition of induced products was dependent on the method of stimulation.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.8
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• pp.188-195
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• 2004

In this paper we analyzed the mechanical behavior with respect to the thickness variation of elastic foundation(fatty tissue) in end-to-end anastomosis. This study considered the preliminary deformed shape induced by suturing in the anastomosis of coronary artery and PTFE with different diameters using simplified suturing model and the fatty tissue surrounding heart and coronary artery for more accurate result using finite element method. Area compliance(CA) was used to analyze the final deformed shape of the anastomotic part with respect to the thickness variation of fatty tissue under mean blood pressure, 100mmHg(13.3㎪). And Equivalent and circumferential stresses in the anastomosis were also analyzed with respect to the change of initial diameter ratio( $R_1$) and fatty tissue thickness( $T_{F}$). The results obtained were as follows : 1 When the elastic foundation, assumed to be incompressive material, surrounded the grafts in anastomosis, the compliance mismatch of artery and PTFE was reduced by 47 -72%. 2. As the initial diameter ratio( $R_1$) became larger, the higher difference of compliance was induced in spite of elastic foundation surrounding grafts. 3. The maximum nondimensional circumferential stress is twice or three times as high as the maximum nondimensional equivalent stress in the anastomotic part.t.

• Journal of Industrial Technology
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• v.18
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• pp.187-193
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• 1998

In this study, about the fatigue life of welded structure material under fluctuation loading, the prediction life which is produced by using the Histogram Recorder System was compared with the experimental life which is produced by the RMC model which is imported by conception of equivalent stress. In this result, this is represented few difference by comparing prediction life which is produced by damage analysis depended on Miner's rule, by using the Histogram Recorder System, with experimental life which is produced by the RMC load model which is imported by conception of equivalent of stress, therefore fatigue life is easily predicted by using Histogram Recorder System, and result of prediction has equivalent accuracy with other method which is more complex than the Histogram Recorder System. Besides the damage which is produced by stress which is high thirty percentage rank in the stress range of damage inducing, is nearly equal to the damage which is induced the rest of seventy percentage, there fore we can see that damage accumulation which is induced few time overload which is effected welded structure material is great.