• Transactions of Materials Processing
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• v.20 no.7
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• pp.479-484
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• 2011

Dry sliding wear behavior of AISI 52100 steel that has a pearlite or bainite microstructure was characterized to explore the effect of microstructure on the wear of the steel. Isothermal heat treatments were employed to obtain the different microstructures. Pin-on-disk type wear tests of the steel disk were performed at loads of 25~125N in air against an alumina ball. Sliding speed and wear distance used were 0.1m/sec and 300m, respectively. Worn surfaces, wear debris and cross-sections of the worn surfaces were examined with SEM to investigate the wear mechanism of the steel. Hardness of the steel was also evaluated. Wear rate of the steel was correlated with the hardness and the microstructure. On the whole, wear resistance increased with an increase in hardness. However, the pearlite microstructure showed superior wear resistance as compared to the bainite microstructure with a similar hardness. The effect of the microstructure on the wear rate was attributed to the morphological differences of the carbide in the microstructure, which was found to have a significant effect on strain hardening during the wear.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.2
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• pp.51-58
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• 2006

Laser welding of dissimilar metals has been widely used to improve a wear resistance and a corrosion resistance of the industrial parts. The objective of this research works is to investigate the influence of the process parameters, such as the welding for SM45C and STS304 with CW Nd:YAG lasers. The bead-on-plate welding tests are carried out for several combinations of the experimental conditions. In order to quantitatively examine the characteristics of the dissimilar welding, the welding quality of the cut section, stain-stress behavior and the hardness of the welded part are investigated. From the results of the investigation, it has been shown that the optimal welding condition without defects in the vicinity of the welded area and with a good welding qualify is 1600W of the laser power, 0.85m/min of welding speed and $4{\ell}/min$ of pressure for shielding gas.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.17-18
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• 2006

Laser welding of metals has been widely used to improve a wear resistance and a corrosion resistance of the industrial parts. The objective of this research works is to investigate the influence of the process parameters, such as the welding for metals with CW Nd:YAG lasers. The bead-on-plate welding tests are carried out for several combinations of the experimental conditions. In order to quantitatively examine the characteristics of the butt welding, the welding quality of the cut section, stain-stress behavior and the hardness of the welded part are investigated. From the results of the investigation, it has been shown that the optimal welding condition without defects in the vicinity of the welded area and with a good welding quality is 1400W of the laser power, 0.8m/min, 0.9m/min of welding speed and $4{\ell}$ in of pressure for shielding gas.

• Journal of Life Science
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• v.11 no.3
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• pp.266-272
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• 2001

A total of 79 Salmonella spp. were isolated from Pusan area in 2000. The serotypes of 79 Salmonella isolates were classified as 42 strains of S. typhi(53.1%), 24 strains of S. enteritidis(30.4%), 9 strains of S. montevideo(11.4%), 2 strains of S. typhimurium(2.5%), 1 strain of S. infantis(1.3%) and 1 strain of S. indiana(1.3%) strains(16.5%) of Salmonella sp. were isolated at May July, respectively. The isolates of S. typhi were sensitive to most sntibiotics except streptomycin. All isolates of S. typhi were especially sensitive to tobramycin, gentamicin, colistin, kanamycin, samikacin, sulfamethozazole/ trimethoprim, cefriaxone, ceftazdime, cifrofloxacin, cefoxitin and cefotaxime. Isolates of S. enteritidis wer presented higher resistance than isolates of S. typhi. Twenty-four strains of S. enteritidis were sensitive to kanamycin, amikacin cifrofloxacin, cefoxitin and cefotaxime, however 13 strains(54.2%) of S. enteritidis were resistant to carbenicillin, ampicillin and ticarcillin. Nine strains of S. montevideo were sensitive to most antibiotics except carbenicillin and streptomycin. Each 1 stain of S. indiana and S. infantis was sensitive to most antibiotics used in this study except streptomycin. Three kinds of resistant pattern (CB, SM, TE, AM, TC). In the case of S. enteritidis isolates, 9 kinds resistant pattern were detected. Most frequent resistant pattern of S. enteritidis isolates was CB, AM, TC type(16.7%)

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.997-1003
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• 2005

Laser welding of dissimilar metals has been widely used to improve a wear resistance and a corrosion resistance of the industrial parts. The objective of this research works is to investigate the influence of the process parameters, such as the welding for SM45C and STS304 with CW Nd:YAG lasers. The bead-on-plate welding tests are carried out for several combinations of the experimental conditions. In order to quantitatively examine the characteristics of the dissimilar welding, the welding qualify of the cut section, stain-stress behavior and the hardness of the welded part are investigated. From the results of the investigation, it has been shown that the optimal welding condition without defects in the vicinity of the welded area and with a good welding quality is 1600W of the laser power, 0.85m/min of welding speed and 4m/min of pressure for shielding gas.

• The Plant Pathology Journal
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• v.37 no.1
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• pp.72-78
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• 2021

Various management systems are being broadly employed to minimize crop yield loss resulting from abiotic and biotic stresses. Here we introduce a Bacillus zanthoxyli HS1 strain as a potent candidate for managing manifold stresses on vegetable plants. Considering 16S rDNA sequence and biochemical characteristics, the strain is closely related to B. zanthoxyli. The B. zanthoxyli HS1's soil-drench confers disease resistance on tomato and paprika plants against infection with Ralstonia solanacearum and Phytophthora capsici, respectively. Root and shoot growths are also increased in B. zanthoxyli HS1-treated cabbage, cucumber, and tomato plants, compared with those in mock-treated plants, after application of high salinity solution. Moreover, the pretreatment of B. zanthoxyli HS1 on cabbage plants inhibits the degradation of chloroplast pigments caused by high salinity stresses, whereas the inhibitory effect is not observed in cucumber plants. These findings suggest that B. zanthoxyli HS1 stain inhibits disease development and confers tolerance to salinity stress on vegetable plants.

• Elastomers and Composites
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• v.34 no.2
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• pp.177-182
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• 1999

SBS thermoplastic elastomers offer an inexpensive alternative to vulcanised rubbers for many undemanding applications. They are, however, particularly susceptible to attack from atmospheric ozone leading to cracking as soon as any strain is applied. In most rubber applications some strain is unavoidable. In this paper a compounding approach to protecting SBS thermoplastic rubbers against ozone is described. An explanation is offered for why a protective effect Is observed only when certain combinations of additive are used. SBS elastomers are the most affordable class of thermoplastic rubbers. To achieve finished products resistant to ozone and without compromising the light colours often demanded, recourse must be made to blending with other saturated elastomers or replacement by hydrogenated (SEBS) types. The latter is a significantly more expensive alternative. Under laboratory conditions where the rate of ozone attack is increased by several decades, unprotected SBS begins to crack within a few hours. Several different protective agents are examined here, the best of which, a cyclic enol ether, $Vulkazon^{(R)}$ AFD, can extend the resistance to any cracking to several weeks by the use of a few percent by weight of additive. The systems reported neither discolour the polymer nor stain other materials with which it may be in contact. Use of the protective systems described here could enable SBS elastomers to compete in many applications with the more expensive SEBS polymers.

• Earthquakes and Structures
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• v.19 no.4
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• pp.273-286
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• 2020

The pile group foundation is widely used for gravity pier of high-speed railway bridges in China. If a moderate or strong earthquake occurs, the pile-surrounding soil will exhibit obvious nonlinearity and significant pile group effect. In this study, an improved pushover analysis model for the pile group foundation with consideration of pile group effect is presented and validated by the quasi-static test. The improved model uses simplified springs to simulate the soil lateral resistance, side friction and tip resistance. PM (axial load-bending moment) plastic hinge model is introduced to simulate the impact of the axial force changing of pile group on their elastic-plastic characteristics. The pile group effect is considered in stress-stain relations of the lateral soil resistance with a reduction factor. The influence factors on nonlinear characteristics and plastic hinge distribution of the pile group foundation are discussed, including the pier height, longitudinal reinforcement ratio and stirrup ratio of the pile, and soil mechanical parameters. Furthermore, the displacement ductility factor, resistance increase factor and yielding stiffness ratio are provided to evaluate the seismic performance of soil-pile system. A case study for the pile group foundation of a railway simply supported beam bridge with a 32 m-span is conducted by numerical analysis. It is shown that the ultimate lateral force of pile group is not determined by the yielding force of the single one in these piles. Therefore, the pile group effect is essential for the seismic performance evaluation of the railway bridge with pile group foundation.

• Journal of Conservation Science
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• v.31 no.1
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• pp.13-20
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• 2015

Surface of the wooden cultural heritage has been protected from moisture by natural oils (such as perilla oil and tung oil), which accelerated degradation. But we can find seldom the research on the processes and performances of oil coatings. In this study, the water resistant performances by wood direction were compared to 3 types of natural oil and 2 types of oil stain, and the effect of additional indoor conditioning and temperature of oil were appraised in longitudinal direction. The natural oils block moisture about 79.2% comparing to the control in longitudinal direction. Especially the tung oil showed the outstanding water resistance about 90.5%. The water resistant performances decreased about 8.8% by additional indoor conditioning for 2 years. Heated oil improved the water resistance about average 5.0%.(Max. 9.6% with linseed oil).

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.4
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• pp.54-61
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• 2002

Inconel 690 alloy has widely been used in power plant and high temperature facilities because it has high thermal resistance and toughness. But we have little design data about the creep behaviors of the alloy. Therefore, in this study, an apparatus has been designed and built for conducting creep tests under constant load conditions. A series of creep tests on Inconel 690 alloy have been performed to get the basic design data and life prediction of inconel products and we have gotten the following results. First, the stress exponents decrease as the test temperatures increase. Secondly, the creep activation energy gradually decreases as the stresses become bigger. thirdly, the constant of Larson-Miller Parameters on this alloy is estimated about 10. And last the fractographs at the creep rupture show both the ductile and the brittle fracture according to the creep conditions.