• Journal of the Korean Society of Industry Convergence
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• v.22 no.6
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• pp.681-688
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• 2019

SM45C steel, which is widely used for mechanical structure, was carburized at 870℃ for 4 hours and tempered at 300℃ and 400℃ for 1, 3 and 6 hours. The tempered materials were evaluated for tensile test, hardness test and impact test. In particular, the hardness and the absorption energy were evaluate the reliability by the Weibull statistical analysis. 300℃-1h specimen is considered to be the best heat treatment condition in the tensile stress and the observation of fracture surface. 300℃-1h specimen showed larger shape and scale parameter than the other specimens, and Rockwell hardness variance was small and showed the best characteristics. 400℃-3h specimen showed larger shape and scale parameter than the other specimens, the dispersion of impact absorption energy is small, and showed excellent characteristics.

• Transactions of the Korean Society of Automotive Engineers
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• v.25 no.1
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• pp.35-41
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• 2017

The use of engineering plastics in automotive components is increasing with the trend towards improving the car strength and reducing weight. Among the different choices of materials, engineering plastic emerged as the necessary material for achieving lower costs, reduced weight and improved production efficiency. To produce the automotive parts, it is important to predict defect and validation of injection molding prior to design. Injection molding analysis and structural analysis are widely applied as a part of the design process when developing automotive parts. Injection molding analysis, in particular, involves a highly complicated mechanism that requires deep knowledge of polymer properties as well as an analytic approach different from that used for a general isotropic material when the molded material is used as a structural material. This is because the parts made of polymer have pre-stress factors such as intrinsic deformation and residual stress. The most important factors for injection molded plastic products are injection molding condition and cavity design, taking into account ease of molding, mass production and application. Despite optimal injection molding conditions and cavity design, however, glass fiber orientation is critically linked to strength reduction. The application of injection molding and structural coupled analysis provides a low-cost solution for product molding and structural validation, all prior to the actual molding. The purpose of this study involves the validation, pre-study, and solution of defect in injection-molded polymer automotive parts using the simulation software for injection molding and structural coupled analysis. Finally, this thesis provides validation of an injection molding and structural coupled analytic mechanism that can demonstrate the effect of glass fiber orientation on mechanical strength. Design improvement ideas for the injection molded product of PPS (Poly Phenylene Sulfide)+40% glass fiber are also suggested.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.12
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• pp.1521-1528
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• 2012

The present paper provides the elastic stress intensity factors (SIFs) and the crack opening displacements (CODs) of a thick-walled pipe with a slanted axial through-wall crack. For estimating these elastic fracture mechanics parameters, systematic three-dimensional elastic finite element (FE) analyses were performed by considering geometric variables, i.e., thickness of pipe, reference crack length, and crack length ratio, affecting the SIFs and CODs. As for loading condition, the internal pressure was considered. Based on the FE results, the SIFs and CODs of slanted axial through-wall cracks in a thickwalled pipe along the crack front and the wall thickness were calculated. In particular, to calculate the SIFs of a thick-walled pipe with a slanted axial through-wall crack from those of a thick-walled pipe with an idealized axial through-wall crack, a slant correction factor representing the effect of the slant crack on the SIFs was proposed.

• Korean Journal of Environmental Agriculture
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• v.25 no.2
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• pp.109-117
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• 2006

Photoinhibition and photoprotection of PSII in the leaves of hot pepper (Capsicum annuum L.) grown in Hoagland solution and Tap water were compared. Though changes in the rates of $O_2$ evolution as a function of photon fluence rate (PFR) were comparable, the rates of respiration in the dark was 3 times higher in the Hoagland solution grown leaves than in the Tap-water grown ones. Compared to Hoagland solution grown plane, PSIIs of Tap water grown pepper leaves were more susceptible to photoinhibitory light treatment. In order to inactivate functional PSII to the same extents, Hoagland solution grown plants required almost 2-fold high light $(1600{\mu}molm^{-2}s^-)$ treatment than those of Tap water $(900{\mu}molm^{-2}s^-)$. Interestingly, the remaining fraction of PSII in Hoagland grown pepper was able to survive under prolonged illumination in the presence of lincomycin, which probably means that the growth condition of plant seemed to have an effect on the recovery of PSII from light stress. When PSII was severly photoinactivated at a chilling temperature, recovery was observed only if the residual functional PSII were not inhibited with DCMU, Nigericin and MV during recovery. In conclusion, PSIIs grown in the Hoagland solution was more resistant to excess light than in the Tap water grown one and the recovery of PSII from photodamage was more efficient in Hoagland grown pepper leaves than Tap water grown one, which means that the increased dark respiration may play a important role in the protection of PSII from photoinhibition by helping repair photosynthetic proteins (in particular, the D1 protein of PSII) degraded by photoinhibition.

• Safety and Health at Work
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• v.9 no.1
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• pp.42-52
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• 2018

Background: Maintenance operations on-board ships are highly demanding. Maintenance operations are intensive activities requiring high man-machine interactions in challenging and evolving conditions. The evolving conditions are weather conditions, workplace temperature, ship motion, noise and vibration, and workload and stress. For example, extreme weather condition affects seafarers' performance, increasing the chances of error, and, consequently, can cause injuries or fatalities to personnel. An effective human error probability model is required to better manage maintenance on-board ships. The developed model would assist in developing and maintaining effective risk management protocols. Thus, the objective of this study is to develop a human error probability model considering various internal and external factors affecting seafarers' performance. Methods: The human error probability model is developed using probability theory applied to Bayesian network. The model is tested using the data received through the developed questionnaire survey of >200 experienced seafarers with >5 years of experience. The model developed in this study is used to find out the reliability of human performance on particular maintenance activities. Results: The developed methodology is tested on the maintenance of marine engine's cooling water pump for engine department and anchor windlass for deck department. In the considered case studies, human error probabilities are estimated in various scenarios and the results are compared between the scenarios and the different seafarer categories. The results of the case studies for both departments are also compared. Conclusion: The developed model is effective in assessing human error probabilities. These probabilities would get dynamically updated as and when new information is available on changes in either internal (i.e., training, experience, and fatigue) or external (i.e., environmental and operational conditions such as weather conditions, workplace temperature, ship motion, noise and vibration, and workload and stress) factors.

• Journal of the Korea Concrete Institute
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• v.22 no.5
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• pp.641-650
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• 2010

The concrete cracking from the restrained stress caused by the shrinkage may play significant cause of deterioration of concrete structures by allowing the permeation of sulphate and chloride ions which in turn triggers corrosion of steel reinforcement. In particular, the cracking becomes more critical as water binder ratio (W/B) is reduced and concrete strength increases. Therefore, it needs to evaluate correctly the comprehensive shrinkage behavior of concrete with high strength: high-strength concrete (HSC), ultra-highstrength concrete (UHSC). The unrestrained shrinkage tests, however, cannot estimate the net shrinkage effectively which affects cracking after full development of strength and stiffness because it does not consider the degree of restraint, strength development, stress relaxation, and so on. Therefore, in this study, both free and restrained shrinkage tests with variables of W/B (W/B of 30, 25 and 16%) and admixtures (fly ash (FA) and granulated blast-furnace slag (BFS)) for HSC, very-high-strength concrete (VHSC) and UHSC were performed. The test results indicated that the autogenous shrinkage and total shrinkage at drying condition were reduced as W/B increased and FA, BFS were added, and the cracking behavior was suppressed as W/B increased and FA was added.

• IMMUNE NETWORK
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• v.13 no.4
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• pp.141-147
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• 2013

Hypoxia has been shown to promote inflammation, including the release of proinflammatory cytokines, but it is poorly investigated how hypoxia directly affects inflammasome signaling pathways. To explore whether hypoxic stress modulates inflammasome activity, we examined the effect of cobalt chloride ($CoCl_2$)-induced hypoxia on caspase-1 activation in primary mixed glial cultures of the neonatal mouse brain. Unexpectedly, hypoxia induced by oxygen-glucose deprivation or $CoCl_2$ treatment failed to activate caspase-1 in microglial BV-2 cells and primary mixed glial cultures. Of particular interest, $CoCl_2$-induced hypoxic condition considerably inhibited NLRP3-dependent caspase-1 activation in mixed glial cells, but not in bone marrow-derived macrophages. $CoCl_2$-mediated inhibition of NLRP3 inflammasome activity was also observed in the isolated brain microglial cells, but $CoCl_2$ did not affect poly dA:dT-triggered AIM2 inflammasome activity in mixed glial cells. Our results collectively demonstrate that $CoCl_2$-induced hypoxia may negatively regulate NLRP3 inflammasome signaling in brain glial cells, but its physiological significance remains to be determined.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.65 no.4
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• pp.339-345
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• 2020

Recently, abnormal weather conditions, such as extreme high temperatures and droughts, have increased in frequency due to climate change, there has accordingly been growing concern regarding the detrimental effects on field crop, including soybean. Therefore, this study was conducted to examine the effects of increased temperatures on soybean growth and yield using a temperature gradient chamber (TGC). Two major types of soybean cultivar, a medium- seed cultivar such as Daepung-2 and a large-seed cultivar such as Daechan, were used and four temperature treatments, aT+1℃ (ambient temperature+1℃), aT+2℃ (ambient temperature+2℃), aT+3℃ (ambient temperature+3℃) and aT+4℃ (ambient temperature+4℃) were established to examine the growth response and seed yield of each cultivar. Seed yield showed a higher correlation with seed weight (r=0.713***) and an increase in temperature affected seed yield by reducing the single seed weight. In particular, the seed growth rate of the large-seed cultivar (Daechan) increased at high temperature, resulting in a reduction in the number of days for full maturity. Our results accordingly indicate that large-seed cultivar, such as Daechan, is potentially vulnerable to high temperature stress. The results of this study can be used as basic data in the development of cultivation technology to reduce the damage caused by elevated temperatures. Also, further research is required to evaluate the response of each process contributing to seed yield production under high temperatures.

• Speech Sciences
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• v.15 no.3
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• pp.159-173
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• 2008

The purpose of this study was to use fiber-optic nasolaryngoscope to find out differences in laryngeal behavior between persons who stutter(PS) and those who do not stutter(NS) upon their utterance. To meet the goal above, this study took 5 NS and 5 PS respectively as a part of sampling, so that they were all asked to join an experiment hereof. As a result, this study came to the following findings: First, there was not any significant difference in laryngeal behavior of uttering spoken languages between stuttering group and control. Second, there were some differences in laryngeal behavior of repetition and prolongation, which were a sort of disfluency revealed in the utterance of nonfluent spoken languages between stuttering group and control. Third, as reported by prior studies, it was found that there were differences in laryngeal abehavior of stutterer group's nonfluent spoken languages depending upon stuttering types. In this study, a variety of laryngeal behavior unreported in prior studies could be found. In addition, it was notable that stutterers showed different laryngeal behavior depending on their personal stuttering types. On block condition, Subject 1 showed laryngeal behavior of fAB, INT and fAD; Subject 2 showed laryngeal behavior of fAB, fAD and rAD; Subject 3 showed laryngeal behavior of fAD and rAD; Subject 4 showed only laryngeal behavior of fAD; and Subejct 5 showed laryngeal behavior of fAB, fAD and rAD. Summing up, these findings imply that when stutterers utter nonfluent words, they may reveal a variety of laryngeal behavior depending on their personal stuttering types. Moreover, it is found that there are more or less differences in the utterance of nonfluent spoken languages between NS and stuttering ones. In particular, it is interesting that one common trait of nonfluent spoken languages uttered by PS is evidently excessive laryngeal stress, no matter which type of stuttering they reveal.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.13 no.6
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• pp.309-314
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• 2003

A spark plasma sintering technique has been used for the fabrication of $Al_2O_3$-SiC nanocomposites at the low temperature of $1100^{\circ}C$∼$1500^{\circ}C$. The sintered $Al_2O_3$-SiC composites shows very homogeneous microstructure without any particular abnormal grain growth, indicating that the addition of nano-sized SiC particles is very effective to control grain growth and to induce the residual stress in the $Al_2O_3$ matrix, resulting in the intragranular fracture. These SiC particles are present in the grain boundaries and also intragrain, depending on the sintering condition, and improve remarkably the mechanical properties of $Al_2O_3$-SiC composite through the mechanisms of strengthening and toughening induced by crack diffraction and crack bridging.