• Journal of Welding and Joining
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• 제30권6호
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• pp.68-73
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• 2012

Nowadays, car manufacturers tried to improve automotive fuel efficiency, and applied many high strength steels such as AHSS or UHSS to car bodies. Therefore, the number of steel combinations for the resistance spot welding are dramatically increased and the need for weldability evaluation of these combinations are also required. In this study, we suggest the lobe curve using FEM simulations for DP780 steel with 1.0t, 1.4t. The lobe curves which could expressed weldablity and optimal welding condition were obtained according to 6 steel combinations. There were two combinations for same steel sheet which were DP780 1.0t, DP780 1.4t. Dissimilar steel sheet combination with different thickness was 1.0t and 1.4t of DP780. Different steel combinations were DP780 1.0t and SPRC440 1.0t, and DP780 1.0t and DP590 1.0t. Finally dissimilar combinations was and DP780 1.0t and DP590 1.4t. The trend of low boundary and high boundary variation of lobe curve were analyzed with a viewpoint of the contact resistance and the heat input.

• 한국농공학회:학술대회논문집
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• 한국농공학회 1998년도 학술발표회 발표논문집
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• pp.438-443
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• 1998

In this study, compared the degree of consoildation of vertical drain considering variation of smear effect and well resistance with that of hyperbolic and curve fitting method. It applied Barren, Yoshikuni, Hansbo, Onoue's theory for the consolidation of vertical drain, and compared differences of theoretical curve by comparing with measured value, and finded out the extent of smear effect and well resistance.

• 대한기계학회논문집
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• 제7권4호
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• pp.441-450
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• 1983

A reasonable J-resistance curve determination procedure is suggested by correcting the amount of overestimation in J-value whose effect becomes significant when crack grows. Experiments using compact tension specimens of an alloy steel (SCM4, K.S. Designation) are performed. The value of J estimated according to this procedure is compared with that as obtained from the method by Merkle and Corten. The conditions for J controlled crack growth proposed by Hutchinson and Paris are examined for the material used here. It appears that J resistance curve, which is independent of crack ratio can be obtained for those specimens satisfying the conditions of J controlled crack growth.

• 한국해양공학회지
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• 제8권2호
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• pp.157-165
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• 1994

Effect of an accelerated iso-thermal aging (375 degree C x 66days, 375 degree C x 200days) on elastic-plastic fracture resistance curve were examined in SA533B low alloy steel. Fracture toughness test are conducted by unloading compliance method at room temperature. But the apparent negative crack growth phenomenon, usually arise in partial unloading compliance test. The phenomenon of negative crack growth may be eliminated by the offset technique. There is no effect of aging on J sub(IC) and dJ/da in iso-thermal aged (375 degree C x 66 days) specimen, but there is very little effect in iso-thermal aged (375 degree C x 200 days) specimen.

• 대한의생명과학회지
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• 제19권3호
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• pp.233-238
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• 2013

Aspirin is still the mainstay of antiplatelet therapy in the cardiovascular and cerebrovascular disease. However, some patients are not responsive to the antithrombotic action of aspirin. The aim of this study was to assess the prevalence and clinical characteristics of aspirin resistance in patients with cerebral infarction. We tested platelet function in 557 patients who had been treated with aspirin in J general hospital. Platelet function was tested using the multiple electrode platelet aggregometry (MEA). Platelet reactivity was expressed as area under the aggregation curve (AUC, U) and >30 AUC was defined as aspirin resistance. Aspirin resistance was detected in 16.2% patients. There was not any significant differences in age, gender between aspirin resistance and aspirin sensitive patients. WBC was significantly higher in patients with aspirin resistance (P < .05). HDL-cholesterol was significantly higher in patients with aspirin sensitive (P < .05). Aspirin resistance was positive correlation with platelet count (r =.314, P =.003). The prevalence of aspirin resistance in cerebral infarction was 16.2%, and platelet count were related with aspirin resistance.

• 한국화재소방학회논문지
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• 제1권1호
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• pp.19-26
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• 1987

In this study, fire resistance of steel fiber reinforced concrete was investigated Cylindrical and prismatic specimens made of Ordinary Portland Cement plain concrete and steel fiber reinforced concrete were exposed to heating in accordance with a standard time-temperature curve as specified in KS·F22 57, method of fire resistance test for structural parts of buildings, the period of heating was 1 hour and 2 hours. After the fire resistance test, mechanical properties of specimens such as compressive and bending strength, stress-strain curve, static and dynamic modulus of elasticity and bending toughness were investigated. Also the cracks and spallings of the specimens were observed. From the test results, it was confirmed that steel fiber reinforced concrete has a excellent fire resistance than plain concrete in the view of higher residual strength of concrete and smaller crackings because of steel fibers in concrete.

• 한국재료학회지
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• 제12권2호
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• pp.135-139
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• 2002

Carbon powders (CP) and carbon fiber (CF) were introduced info glass fiber reinforced plastics (FRP) composites to obtain fracture detection function. The composites were evaluated through the relation between a load-displacement curve and an electrical resistance change curve in three point bending test. CP containing FRP (CP-FRP) has a sensitivity of electrical resistance change at much lower load level than CF containing FRP (CF-FRP). In loading-unloading tests, CP-FRP showed a large amount of residual electrical resistance which enables the estimation of loading hysteresis.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회 논문집(II)
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• pp.1267-1272
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• 2000

When fresh concrete is exposed to low temperature, the concrete may suffer frost damage due to freezing at early ages and strength development may be delayed. These are problems on cold weather concrete. One of the solution methods for resolving these problems has been to reduce the freezing temperature of concrete by the use of chemical admixtures called Accelerators for freezing resistance. Therefore, in this study, we executed freezing temperature of mortar, setting and strength properties with using water reducing accelerator and accelerators for freezing resistance which are producted internationally. As a result of this experiment, the freezing temperature of mortar is lower and the setting property is promoted when the admixing content of accelerators for freezing resistance is increased. Moreover, the compressive strength of mortar used accelerators for freezing resistance represented the result which is similar with result of analysis of compressive strength increase with using logistic curve formula, but in the case of plain and using water reducing accelerator, there is no relation between logistic curve formula, maturity and compressive strength.

• 소성∙가공
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• 제28권2호
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• pp.77-82
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• 2019

Corrosion occurs well on surface of roll formed and Zn alloy subsequently electro-deposited on steel bolt under wet condition. In this study, variations in corrosion resistance were investigated through the measurement of polarization curves on steel bolts which were roll formed and subsequently coated with various types of coating methods. According to the measured polarization curve, Ni-P electroless deposits on roll formed steel increased the resistance to corrosion. The corrosion resistance of Zn alloy powder coated steel bolt was found to be better than that of Zn-Ni electro-deposited sample.

• Asian Pacific Journal of Cancer Prevention
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• 제16권12호
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• pp.5037-5041
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• 2015

Background: An hCG regression curve has been used to predict the natural history and response to chemotherapy in gestational trophoblastic disease. We constructed hCG regression curves in high-risk gestational trophoblastic neoplasia (GTN) treated with EMA/CO and identified an optimal hCG level to detect EMA/CO resistance in GTN. Materials and Methods: Eighty-one women with GTN treated with EMA/CO were classified as primary high-risk GTN (n = 65) and single agent-resistance GTN (n = 16). The hCG levels prior to each course of chemotherapy were plotted in the 10th, 50th, and 90th percentiles to construct the hCG regression curves. Diagnostic performance was evaluated for an optimal cut-off value. Results: The median hCG levels were 264,482 mIU/mL mIU/mL and 495.5 mIU/mL mIU/mL for primary high-risk GTN and single agent-resistance GTN, respectively. The 50th percentile of the hCG level in primary high-risk GTN and single agent-resistance turned to normal before the 4th and the 2nd course of chemotherapy, respectively. The 90th percentile of the hCG level in primary high-risk GTN and single agent-resistance turned to normal before the 9th and the 2nd course of chemotherapy, respectively. The hCG level of ${\geq}118.6mIU/mL$ mIU/mL at the 5thcourse of EMA/CO predicted the EMA/CO resistance in primary high-risk GTN patients with a sensitivity of 85.7% and a specificity of 100%. Conclusion: EMA/CO resistance in primary high-risk GTN can be predicted by using an hCG regression curve in combination with the cut-off value of 118.6 mIU/mL at the 5thcourse of chemotherapy.