• The Journal of Korean Medicine
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• v.37 no.2
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• pp.76-84
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• 2016

Objectives: We evaluated the anti-fatigue effects of Rh2-enriched Korean ginseng (Ginseng Rh2+) using a forced exercise-induced chronic fatigue mouse model. Methods: ICR male mice were subjected to running wheel for 1 h, 5 days/week during 4 weeks, and running velocity was gradually increased. Each running session was followed by oral administration of distilled water, Ginseng Rh2+ (150 or 300 mg/kg), or N-acetyl-L-cysteine (NAC, 100 mg/kg) 1 h later. The exercise tolerance and forced swimming test were performed to evaluate the fatigue condition. Results: Chronic forced exercise reduced the physical activity, as evidenced by the behavioral tests, which were notably ameliorated by Ginseng Rh2+ treatment. Ginseng Rh2+ treatment also attenuated the alterations of energy metabolism and oxidative stress in skeletal muscle tissues and/or sera, including malondialdehyde (MDA), lactate concentration and its related factors (lactate dehydrogenase, blood urea nitrogen, and glucose levels). Conclusion: These findings strongly suggest that Ginseng Rh2+ exerts a potent anti-fatigue effect through modulation of energy metabolism and oxidative response.

• Corrosion Science and Technology
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• v.16 no.2
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• pp.64-68
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• 2017

The interactions between corrosion pits on stainless steel under loading conditions are studied by using a cellular automata model coupled with finite element method at a mesoscopic scale. The cellular automata model focuses on a metal/film/electrolyte system, including anodic dissolution, passivation, diffusion of hydrogen ions and salt film hydrolysis. The Chopard block algorithm is used to improve the diffusion simulation efficiency. The finite element method is used to calculate the stress concentration on the pit surface during pit growth, and the effect of local stress and strain on anodic current is obtained by using the Gutman model, which is used as the boundary conditions of the cellular automata model. The transient current characteristics of the interactions between corrosion pits under different simulation factors including the breakdown of the passive film at the pit mouth and the diffusion of hydrogen ions are analyzed. The analysis of the pit stability product shows that the simulation results are close to the experimental conclusions.

• Development and Reproduction
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• v.23 no.3
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• pp.239-253
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• 2019

We investigated the physiological responses of the river puffer, Takifugu obscurus, the tiger puffer, T. rubripes, a hybrids of the two (river puffer${\times}$tiger puffer) and a hybrid triploids to acute changes of salinity from 30 psu to 0 psu and from 0 psu to 30 psu. The blood and plasma factors of each species were elevated for 48, 72, or 96 hrs, and thereafter decreased due to hyper-osmoregulation and hypo-osmoregulation. In hyper-osmoregulation and hypo-osmoregulation, the cortisol concentration of river puffer, hybrids, hybrid triploids and tiger puffer increased for 12 or 48 hrs, and decreased thereafter. Chloride cells in the gill filaments of each species increased with increasing salinity, and melano-macrophages in the kidney tissue of each species increased with decreasing salinity. In conclusion, the hematological and stress responses of the hybrids were between those of the river puffer and tiger puffer, and the hematological responses of the hybrid triploids were higher than those of the other groups. The stress response of the hybrids was more sensitive than that of the hybrid triploids. In all groups, the histological responses of kidney in hyper-osmoregulation were more sensitive than those in hypo-osmoregulation.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.1
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• pp.178-201
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• 2019

The appropriate design of a mooring system to maintain the position of an offshore structure in deep sea under various environmental loads is important. Fatigue design of the mooring line considering OPB/IPB(out-of-plane bending/in-plane bending) became an essential factor after the incident of premature fatigue failure of the mooring chain due to OPB/IPB in the Girassol region in West Africa. In this study, mooring line fatigue analysis was performed considering the OPB/IPB of a spread moored FPSO in deep sea. The tension of the mooring line was derived by hydrodynamic analysis using the de-coupled analysis method. The floater motion time histories were calculated under the assumption that the mooring line behaves in quasi-static manner. Additional time domain analysis was carried out by prescribing the obtained motions on top of the selected critical mooring line, which was determined based on spectral fatigue analysis. In addition, nonlinear finite element analysis was performed considering the material nonlinearities, and both the interlink stiffness and stress concentration factors were derived. The fatigue damage to the chain surface was estimated by combining both the hydrodynamic and stress analysis results.

• Journal of Power System Engineering
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• v.13 no.6
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• pp.95-101
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• 2009

The generator for gas turbine power generation consists of the rotor which generates magnetic field, the winding coil which is the path for the field current and the wedge and retaining ring which prevents the radial movement of the coil. Relatively severe deformation was observed at the coil end section during the inspection of the generator for peaking-load operation, and the thermal-electricity and the centrifugal force were evaluated by the simple modeling of the windings to find the cause. But the simulation stress was not sufficient to induce the coil plastic deformation. The analysis result seems to be applicable to the base-load generators which runs continuously without shut down up to a year, but there had been more deformation than simulated for the generator which is started up and shut down frequently. The cause of the coil deformation was the restriction of the expansion and shrinkage. The restriction occurs when the winding coil shrinks, and the stress overwhelms the yield stress and cause the plastic deformation. The deformation is accumulated during the start-ups and shut-downs and the thermal growth occurs. The factors which induce the coil restriction during the expansion and shrinkage should be reduced to prevent the unallowable deformation. The resolutions are cutting off the field current earlier during the generator shut-down, modifying the coil end section to remove the stress concentration and making the insulation plate inserted between the coil end section and the retaining ring have the constant thickness.

• Journal of the Korean Society for Railway
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• v.9 no.4 s.35
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• pp.371-378
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• 2006

This study investigates the effects of the material properties and the fatigue behaviors in the SM490A material butt weld specimens due to the heat-treatment and the grinding. In the fatigue behavior, the heat-treatment affects the fatigue life. The S-N curves of both matrix specimen and butt weld specimen are reversed at some cycle by the existence or nonexistence of heat-treatment. The grinding on the bead makes the fatigue limit decrease in the all specimens. But the reinforcement removed, the fatigue limit increases at the high cycle. Also, this study investigates the fatigue life estimation by examining butt weld bead profiles. The butt weld beads, which are welded by semi-robot method, have non-uniform bead profiles described by $\theta,\;\rho$ and h. The stress concentration factors $K_t$, are changed by each different $\theta,\;\rho$ and h from 1.395 to 2.863. Hence, the sensitivity of $K_t$ is changed by each $\theta,\;\rho$ and h. As $\theta$ becomes lower and $\rho$ and h become higher, $K_t$ increases. The fatigue life can he estimated very closely for the AAY specimens without residual stress using only butt weld bead profiles. But, fur the AAN specimens with residual stress, the fatigue life must be estimated by considering both the weld bead profiles and the residual stress data.

• Journal of the Korean Applied Science and Technology
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• v.35 no.4
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• pp.1369-1378
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• 2018

The purpose of this study was to investigate the effect of skate skin collagen peptide (SCP) according to its molecular weight (<1,000 Da or >1,000 Da) which was divided using the ultrafilatration method. The 200 mg/kg collagen peptide was administrated to obesity-induced db/db mice for 8 weeks. As the results, in collagen peptide-treated groups, body weight gain was decreased, the plasma and hepatic concentration of reactive oxygen species decreased and oxidative stress was alleviated. In addition, SCP-treated group showed the significant reduction of the protein expressions of nuclear transcription factors($NF-{\kappa}B$), enzymes(COX2, iNOS), and inflammatory cytokine(IL-6) in hepatic tissue, compared with those of the obese control group. There was a slight difference depending on the molecular weight of collagen peptide, but overall it was not significant. Therefore, SCP effectively inhibited the obesity-induced inflammatory response through attenuation of oxidative stress in the liver.

• Journal of Korean Tunnelling and Underground Space Association
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• v.4 no.1
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• pp.71-78
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• 2002

In this study, the influence of the presence of discontinuity planes on the load transfer mechanism and the pattern of loosening zone was studied based on the laboratory test. The trap-door and the reaction plates are installed as the bottom plane of the model box. The vertical discontinuity plane is installed in the dry sand. Various overburden heights and locations of discontinuity planes are applied as major factors in this study. The results show that at higher overburden heights over about 1.5 times the excavation width, the ratio of the transferred stress to the insitu stress converges to a certain value even if the overburden height increases further. The results also show that the discontinuity plane gives relatively larger influence on the load transfer mechanism, that produces the unsymmetrical load concentration, when the discontinuity plane locates within the tunnel width. When the discontinuity plane locates outside the tunnel width, the unsymmetrical load concentration is reduced considerably.

• Journal of the Society of Disaster Information
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• v.5 no.1
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• pp.48-62
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• 2009

Bodyguards always perform their duty with psychological burdens in their mind, not only because security situations are developed in various forms dependent on the surrounding environments or circumstances, but because bodyguards only take follow-up actions while the criminal decides time, place, and style of every attack. Thus, in the security situation, it is not uncommon for bodyguards to experience muscle rigidity, uncontrollable emotional elevation, difficulty in concentration, negative perception, frustration and enervation, which are caused by continuous physical/mental burdens, stimulations by various interpersonal behaviors or minute environmental stimulants. In conclusion, the result of performing security duties is related in the first place with the degree of the bodyguard's potential, in the second place with the degree of training and efficiency. And the result can also be changed by the way they control their negative psychological state of the moment when they carry out the skills they acquired. Maximizing the performance of the bodyguards by helping them overcome these psychological factors may be facilitated by detecting their psychological factors, understanding the causes, and training them in applying appropriate measures for overcoming these factors. When these measures are applied, the positive perception is indispensable that duties of protecting clients can be carried out successfully. No single measure can be declared to be more effective than the other because the effect of each measure is expressed differently by the individual characteristics of the bodyguards. However, it is important to select and apply the measures most appropriate to the bodyguard. Besides, they should devote themselves to the training with persistence because efficient implement of the measures for overcoming psychological factors takes a lot of time.

• Korean Journal of Environment and Ecology
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• v.30 no.5
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• pp.810-820
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• 2016

This study is focused on the investigation of the genes which are induced by various stresses of the halophyte Salicornia herbacea. One of the factors influencing in the germination of Salicornia herbacea is salt stress. The highest germination rate was found in the condition without NaCl, and the upper limit of the NaCl concentration for the germination of Salicornia herbacea was 7%. The optimal temperature of $20^{\circ}C$showed a germination rate of 98%. Among genes induced by stress the 2CysPrx gene was cloned and analyzed for this study. The 2CysPrx gene has two cysteine conserved residues and is composed of 275 amino acids with molecular weight of 30.1kDa. The 2CysPrx gene appeared to be one copy in the genome and consists of 6 introns and 7 exons. Quantitative real-time PCR revealed that the highest transcription rate induced by NaCl and $H_2O_2$ appeared to be at the concentration of 3.5% NaCl and 40mM $H_2O_2$, respectively. The amount of transcript induced by high temperature($40^{\circ}C$) and $75{\mu}M$ of ABA was respectively highest. The gene at low temperature ($4^{\circ}C$) appeared not to be expressed. We are conducting to clone other peroxyredoxin genes induced by various environmental stresses.