• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.5
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• pp.1083-1091
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• 1988

Vacuum brazing is the most modern brazing process and is at present, far from being completely understood. By brazing under high vacuum, in an atmosphere free of oxidizing gases, a superior product with greater strength, ductility and uniformity can be obtained. In this study, the influence of brazing parameters such as base metal characteristics, joint clearance and brazing time were described in relation to the metallurgical phenomena and shear strength of vacuum-brazed joints between carbon steels and 304 stainless steel (SUS 304) brazed by copper filler metal. In copper brazing of SUS 304 to a medium carbon steel(M.C.S) the columnar Fe-Cr-Ni-Cu-C alloy structure was formed and grew from the M.C.S side and at the same time, the surface of M.C.S. was decarbonized. The driving force for the formation and growth of columnar structure was the difference of carbon content between base metals. As the joint clearance is narrower and brazing time is longer, the formation and growth of columnar phase and decarburization of carbon steels were more noticeable. Because of decarburization of carbon steels, the shear strength of brazed joints were reduced as the formation of columnar structure was increased.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.2
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• pp.68-76
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• 2022

This study was performed to investigate the mechanism of the change in compressive strength of autoclave cured geopolymers. Specimens were immerged in distilled water, 2M, 8M, and 14M alkaline solutions for 3, 7, and 21 days. The change in the specimens immersed in a short period of time was not significant, but the compressive strength of the specimens immersed in the distilled water and 8M alkali solution) for 21 days increased more than twice as much as before immersion because of additional geopolymerization. However, compressive strength decreased due to the alkaline aggregate reaction when alkaline solution was supplied more than a certain level of concentration. Therefore, immersing the specimens for more than 21 days in the distilled water or 8M alkaline solution would be desirable for the improvement of compressive strength of autoclave cured specimens.

• Clinical Nutrition Research
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• v.12 no.4
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• pp.293-303
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• 2023

Patients with chronic renal failure, many of which treated with hemodialysis, present a high prevalence of impaired muscle strength which suggest that muscle mass parameters may be used as markers for changes in muscle in these patients. Measurement of handgrip strength (HGS) is a common, simple, and quick measure of muscle function an indicator of overall muscle strength which has been associated with physical activity and several anthropometric traits. Intercellular adhesion molecule-1 (ICAM-1) and insulin-like growth factor-1 (IGF-1) are biochemical markers associated with inflammatory processes which are a common consequence of dialysis. Additionally, hemodialysis patients frequently present signs of malnutrition and depression. This cross-sectional study aimed to evaluate if muscle and biochemical markers could be used to predict the risk of depression in hemodialysis patients. Several anthropometric parameters, nutrient intake, depression state and the serum levels of ICAM-1 and IGF-1 were determined and Pearson's correlation coefficient and/or Spearman's correlation coefficient were used to test the correlation between them. Our results do not show a correlation between HGF, IGF-1 and ICAM-1 with the depression status of the patients, but mid-arm muscle circumference (MAMC) was statistically and positively correlated with depression. Additionally, ICAM-1 levels were negatively correlated with HGS, MAMC, and IGF-1. Overall, the results of the present study suggest that HGS may be used as an indicator of cardiovascular diseases and MAMC may be a good predictor of the level of depression in hemodialysis patients, although further studies are required.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1997.10a
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• pp.187-187
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• 1997

Silicon nitride is the most excellent materials among structural ceramics. It has been reported that fracture toughness was improved with adding second phase particles, whisker, fiber etc. However, containing of second phase particles enhanced fracture toughness, however flexural strength was degraded. As adding nanosize SiC particles into silicon nitride, the physical properties of fluxural strength, fracture toughness, the modulus of elasticity. In this study, 2wt% $Al_2$O$_3$ and 4 wt% $Y_2$O$_3$ were added into UBE E-10 and 0, 10, 20, 30, 40, 50 vol% nano-SiC powder (Sumitomo T1 powder) were added, respectively. It is hot pressed at 185$0^{\circ}C$ for 1 hour. Most of structural ceramics for engineering application are wear resistance. In this study, wear behaviors (in water) of silicon nitride with varying the amount of nano-size silicon carbide were investigated, and was compared to physical properties. Simultaneously wear mechanism will be found out.

• Journal of the Korean Society for Heat Treatment
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• v.12 no.1
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• pp.40-46
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• 1999

Rotary bending fatigue tests were carried out to investigate the improvement of fatigue limit in annealed and austempered spheroidal graphite cast iron. Main results obtained are as follows. (1) The tensile strength(hardness) of Series C is higher than that of Series B, and fatigue limits are 245MPa in Series C, 230MPa in Series B and 195MPa in Series A, respectively. (2) The fatigue limits of Series B and Series A are mainly governed by the resistance to fatigue crack initiation. Whereas, the fatigue limit of Series C is governed by the resistance to fatigue crack initiation and growth. The defect size and the resistance to crack initiation and growth should be considered to clarify the fatigue properties in spheroidal graphite cast iron. (3) Improvement of fatigue limit by half-austempering is more reasonable than that of full-austempering treatment in multi defective materials as spheroidal graphite cast iron.

• Journal of Korean Society for Quality Management
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• v.38 no.1
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• pp.52-63
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• 2010

The purpose of this study is to investigate whether or not belt's jobs represent a source of job enrichment that translates into positive job characteristics and satisfaction. Hackman and Oldham's 5 job characteristics, 3 critical psychological states and MPS are utilized for analyzing results of the study. The results indicate that Black and Master Black Belt's jobs have positive effects on all five job characteristics, 3 psychological states, and MPS score. However, the findings indicate that Black and Master Black Belt's jobs are no direct effect on job satisfaction suggesting that growth need strength controls on job satisfaction. The result shows that there is a support for the prediction that growth needs strength controls the effect of belt's jobs on job satisfaction.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1997.04a
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• pp.143-149
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• 1997

the horizontal corrosion fatigue tester has been developed for investigating environmental strength. Using this tester, we investigated about corrosion fatigue caracteristic for A106 GrB steel weldments in 3.5% synthetic seawater and room temperature. Considered parameter is only frequency of 1,3 and 5Hz. and Corrosion fatigue crack length was measured by DC potential difference method. From the results, we could find that the horizontal corrosion fatiued tester could be well applied to estimation of fatigue strength. and In case of 5Hz, corrosion fatigue crack growth path of A106 GrB steel weldment was transgranular, and of 1 and 3Hz showed that transgranular and intergranular was mixed. Also, Corrosion fatigue crack growth caracteristic values estimated in each frequency were C=9.33 x 10-9 and m=2.93 in 1Hz, C=9.77x10-10 and m=3.47 in 3Hz, C=1.02x10-10 and m=4.05 in 1Hz

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.1
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• pp.142-149
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• 1999

A machine frame has been manufactured by casting. However, due to the development of the industrial society, 3-D duties was refused. Especially, the declination of the casting industry makes it difficult to produce the frame. Many companies still manufacture the small casting products. The large casting products are extremely limited and manufactured for their own use. Therefore, it is difficult to keep the term of order. In this study, the characteristics of steel structure which is produced by welding were identified in the view of mechanical strength of steel structure which is produced by welding were identified in the view of mechanical strength to substitute steel structure for casting frame. But welding structure has the residual stress, HAZ and welding deformation. Residual stress and HAZ especially cause crack growth. The proposed steel structure, based on the simulation and experiment(tensile curve and S-N curve), can reduce not only the producting term but also the weight of the frame.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1998.06a
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• pp.81-86
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• 1998

The light aggregates were fabricated by sintering green bodies made form the fly ash-clay alip. The content of fly ashes in the slip could be increased up to 70wt.% due to controlled rheological behavior of the slip, and the green body of uniform microstructure could be obtained by DCC(Direct Coagulation Casting)method. The apparent density, microstructure and compressive strength for sintered bodies fired at 1100∼1200$^{\circ}C$ were evaluated. The properties of light aggregates fabricated depend on slip density, particle behavior in the slip and sintering conditions. The sintered body prepared by firing a green body made from slip of density 1.60 at 1150$^{\circ}C$/2hr satisfied conditions of a light aggregate as apparent density of 1.49${\pm}$0.02 and compressive strength of 584${\pm}$62kg/$\textrm{cm}^2$.

• Journal of the Korean Ceramic Society
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• v.28 no.7
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• pp.541-548
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• 1991

Sinterability and stability of TZP ceramics co-stabilized by 12 mol% CeO2 and divalent or trivalent oxides less than 1 mol% were investigated. Divalent and trivalent oxides increased stability of tetragonal ZrO2. 100% tetragonal ZrO2 phase was obtained by doping 12 mol% CeO2 and 0.2 mol% CaO and MgO respectively when sintering was carried out at 1500$^{\circ}C$ for 2 hours. Divalent and trivalent oxides improved sinterability and inhibit grain growth of ZrO2. And it was found that CaO was the most effective sintering aid and grain growth inhibitor for ZrO2 in this study. Incorporation of divalent and trivalent oxides into 12Ce-TZP increased the strength of 12Ce-TZP and particulary 12Ce, 0.4Ca-TZP exhibited a flexural strength of about twofold greater than 12Ce-TZP.