• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.434-437
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• 2007

Cold forging technology of a gear product is being interested in the dimensional accuracy, high stiffness and reduction of stress concentration. Especially it is needed to avoid the damage due to extremely high local pressure. Therefore it is important to ensure high pressure in die design. In this study, single die insert type and splitted die insert type are considered to recognize the notch effects in the die of sprocket forming. The stress concentration has been released at the notch area by the cushion effect in the splitted die insert.

• The Journal of Korean Medicine
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• v.34 no.1
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• pp.29-34
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• 2013

Objectives: This report aimed to demonstrate effect of human placental extract (HPE) pharmacopuncture in students suffering fatigue due to hard work and mental stress. Methods: Thirty-four college students, preparing for the final-term exam, received pharmacopuncture of HPE into Kwanwon (CV4) subcutaneously twice a week for 7 weeks. After every pharmacopuncture of HPE, degree of fatigue was surveyed by questionnaire including physical condition, physical endurance, concentration and memory. Results: Pharmacopuncture of HPE into CV4 gently improved physical condition, physical endurance, concentration and memory. Improvement of physical condition was especially positively correlated with the increasing number of pharmacopuncture of HPE into CV4 as confirmed by calculation of Pearson coefficient. Conclusions: Pharmacopuncture of HPE into CV4 alleviated fatigue in the students from hard work and mental stress.

• Journal of the Korean Graphic Arts Communication Society
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• v.21 no.1
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• pp.1-10
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• 2003

Printing ink is faced various shear stress situation until it transfer to the printed substrate through the press. And in each shear stress condition the ink is needed to keep the appropriate viscosity according to the condition. The change of printing ink viscosity has been explained by well-known through the viscosity profile curve. But actually, the quality of printed paper depends on the ink behavior after transfer the substrates. Like this, to look into the behaviour of the ink on the printed substrate, it is needed the experiment of the ink structure recovering by rheology study. In this study, by controling the $CaCO_3$ content in the ink, after investigating the effect of the ink's structure recovery of the pigment concentration, we intend to predict the printing quality of the ink behvior on the substrate depending on pigment content.

• Transactions of Materials Processing
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• v.16 no.6
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• pp.452-456
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• 2007

Cold forging technology of a gear product is being interested in the dimensional accuracy, high stiffness and reduction of stress concentration. Especially it is needed to avoid the damage due to extremely high local pressure. Therefore it is important to reduce the high pressure in die design of cold forging. In this study, single die insert type and splitted die insert type are considered to recognize the notch effects in the die of sprocket forming. The stress concentration has been released at the notch area by the cushion effect in the splitted die insert.

• Journal of Surface Science and Engineering
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• v.43 no.5
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• pp.243-247
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• 2010

The micro Vickers hardness and internal stress of Ni-Fe metal thin film synthesized by electrodeposition method at $25^{\circ}C$ were studied as a function of bath composition, and surface microstructure and atomic compositions of thin films were investigated by SEM and EDS. And the shape change of $200\;{\AA}$ Ni-Fe nanowires made using anodic aluminum oxide(AAO) templates by electrodeposition method were observed by SEM as a function of ultrasonic treatment time and bath composition. The Fe deposition contents on the substrate non-linearly increased with Fe ion concentration over total metal ion concentration. In case of low Fe contents film, the grain size is smaller and denser than high Fe contents deposited films, and the micro Vickers hardness increased with Fe contents of electrodeposited films. These results affected the shape change of nanowire after ultrasonic treatments.

• Safety and Health at Work
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• v.10 no.1
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• pp.109-113
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• 2019

Background: In both developed and developing countries, noise is regarded as the most common occupational hazard in various industries. The present study aimed to examine the effect of sound pressure level (SPL) on serum cortisol concentration in three different times during the night shift. Methods: This case-control study was conducted among 75 workers of an industrial and mining firm in 2017. The participants were assigned to one of the three groups (one control and two case groups), with an equal number of workers (25 participants) in each group. Following the ISO 9612 standard, dosimetry was adopted to evaluate equivalent SPL using a TES-1345 dosimeter. The influence of SPL on serum cortisol concentration was measured during the night shift. The serum cortisol concentration was measured using a radioimmunoassay (RIA) test in the laboratory. Repeated measure analysis of variance and linear mixed models were used with ${\alpha}=0.05$. Results: The results indicated a downward trend in the serum cortisol concentration of the three groups during the night shift. Both SPL and exposure time significantly affected cortisol concentration (p < 0.0001, p < 0.0001). Conversely, age and body mass index had no significant influence on cortisol concentration (p = 0.360, p = 0.62). Conclusion: Based on the obtained results, increasing SPL will lead to enhancement of serum cortisol concentration. Given that cortisol concentration varies while workers are exposed to different SPLs, this hormone can be used as a biomarker to study the effect of noise-induced stress.

• Proceedings of the Korean Society of Crop Science Conference
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• 2020.06a
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• pp.32-32
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• 2020

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.585-590
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• 2003

It analyzed the reinforcement effect according to reinforced period for FREP. It found that reinforcement effect of P-Type that was reinforced during the usage decreased compared to I-Type that was reinforced before the usage. So when reinforcing a existing structure that is being used, it should consider the stress that is produced due to the fixed load. It evaluated bending and shear of RC reinforcing beam based on the test and analytical conditions of this study. It found that stress concentration was concentrated due to rapid change of bending rigidity in reinforced cutting part as a result of excessive reinforcement thickness of FREP. It resulted in rip-off failure. It means that it should evaluate the shear when designing reinforcement.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.21 no.4
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• pp.245-275
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• 2017

The present investigation deals, Dufour and heat source effects on radiative MHD slip flow of a viscous fluid in a parallel porous plate channel in presence of chemical reaction. The non-linear coupled partial differential equations are solved by using two term perturbation technique subject to physically appropriate boundary conditions. The numerical values of the fluid velocity, temperature and concentration are displayed graphically whereas those of shear stress, rate of heat transfer and rate of mass transfer at the plate are presented in tabular form for various values of pertinent flow parameters. By increasing the slip parameter at the cold wall the velocity increases whereas the effect is totally reversed in the case of shear stress at the cold wall. It is observed that the effect of Dufour and heat source parameters decreases the velocity and temperature profiles.

• Proceedings of the Korean Society of Crop Science Conference
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• 2022.10a
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• pp.284-284
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• 2022

The overall effects of gibberellic acid (GA3) with NaCl on different rice genotypes are inadequately understood. The present study determines the effect of different GA3 concentrations on the morphophysiological, molecular and biochemical effects of 120 mM NaCl salt stress in rice seedlings. Salt stress reduced germination percentages and seedling growth and decreased bioactive GA content. It also downregulated the relative expression of a-amylase-related genes - OsAmy1A, OsAmy1C, and OsAmy3C in the salt-sensitive IR28 cultivar. Salt stress differentially regulated the expression of GA biosynthetic genes. Salt stress increased antioxidant activity in all rice genotypes tested, except in IR28. GA3 (50 and 100 µM) mitigates the effect of salt stress, rescuing seed germination and growth attributes. GA3 significantly increased bioactive GA content in Nagdong and pokkali (50 µM) and Cheongcheong and IR28 (100 µM) cultivars. The a-amylase genes were also significantly upregulated by GA3. Similarly, GA3 upregulated OsGA2oxl and OsGA2ox9 expression in the Cheongcheong and salt-sensitive IR28 cultivars. The present study demonstrated that salt stress inactivates bioactive GA - inhibiting germination and seedlings growth - and decreases bioactive GA content and GSH activity in IR28 and Pokkali cultivars. Further, GA3 significantly reversed the effects of 120 mM NaCl salt stress in different rice genotypes. The current study also suggests if we know the coastal area water NaCl concentration we can apply the exogenous GA3 accordingly. Thus, we would be able to grow rice cultivars near the coastal area and reduce the rice damage by salinity.