• Journal of Ocean Engineering and Technology
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• v.16 no.2
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• pp.60-66
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• 2002

The remote measurement system(RMS) as a new experimental method is limited in its application to crack measurement at elevated temperatures because of the oxide layer on the specimen surface. Since TiAIN and Cr coating layers have a high resistance to oxidation and wear, this paper proposed a TiAIN and Cr coating technique for specimens to facilitate the measurement of crack growth behavior using RMS. To investigate the effects of the coating layer, tension and fatigue tests were carried out at room temperature and at $538^{\circ}C$. The test material was 1Cr-1Mo-0.25V steel which is widely used as a turbine rotor material. From the experimental results, it was found that the mechanical properties of the TiAIN and Cr coated specimens were similar to those of the substrate. Accordingly, the TiAIN and Cr coated layer had hardly any influence on the fatigue crack propagation.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.337-337
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• 2002

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.05a
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• pp.365-366
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• 2010

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.416-417
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• 2011

• Magazine of the Korea Institute for Structural Maintenance and Inspection
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• v.18 no.2
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• pp.36-42
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• 2014

• Korean Chemical Engineering Research
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• v.47 no.1
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• pp.38-45
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• 2009

In this study, interfacial properties were measured for imidazoline type cationic surfactant system which has been widely used as a fabric softener, a dispersant, an anti-static agent, a bleach activator, and an emulsifier. The CMC of imidazoline surfactant was near $6{\times}10^{-5}mol/L$ and the surface tension at CMC was about 32 mN/m. It was found that surface tension was not affected by surfactant concentration but decreased with an increase in pH. The interfacial tension between 1 wt% aqueous solution and n-dodecane was shown to be about 0.01 mN/m and equilibration time was not affected by pH. Phase behavior experiment in a binary aqueous surfactant system showed that only micellar solution of $L_1$ phase was found under conditions of temperature and pH investigated during this study. Only a two-phase region consisting of lower-phase microemulsion in equilibrium with excess oil phase existed under the same conditions, when oil was added to the binary surfactant system. The foam stability measured with 1 wt% surfactant solution increased with pH, which is consistent with surface tension measurement result. QCM(quartz crystal microbalance) measurement showed that surfactant adsorption increased with surfactant concentration but decreased with pH. According to the friction measurement, best fabric softening effect by imidazoline surfactant system was found under alkali conditions.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.5
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• pp.120-129
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• 2023

Hanger cable tension is a major response that can determine the integrity and safety of suspension bridges. In general, the vibration method is used to estimate hanger cable tension on operational suspension bridges. It measures natural frequencies from hanger cables and indirectly estimates tension using the geometry conditions of the hanger cables. This study estimated the hanger cable tension of the Palyeong Bridge using a vision-based system. The vision-based system used digital camcorders and tripods considering the convenience and economic efficiency of measurement. Measuring the natural frequencies for high-order modes required for the vibration method is difficult because the hanger cable response measured using the vision-based system is displacement-based. Therefore, this study proposed a back analysis technique for estimating tension using the natural frequencies of low-order modes. Optimization for the back analysis technique was performed by defining the difference between the natural frequencies of hanger cables measured in the field and those calculated using finite element analysis as the objective function. The direct search method that does not require the partial derivatives of the objective function was applied as the optimization method. The reliability and accuracy of the back analysis technique were verified by comparing the tension calculated using the method with that estimated using the vibration method. Tension was accurately estimated using the natural frequencies of low-order modes by applying the back analysis technique.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.04a
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• pp.117-120
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• 2003

Electro-micromechanical techniques were applied using four-probe method for carbon nanotube (CNT) or nanofiber (CNF)/epoxy composites with their content. Carbon black (CB) was used to compare with CNT and CNF. The fracture of carbon fiber was detected by nondestructive acoustic emission (AE) relating to electrical resistivity for double-matrix composites test. Sensing for fiber tension was performed by electro-pullout test under uniform cyclic strain. The sensitivity for fiber damage such as fiber fracture and fiber tension was the highest for CNT/epoxy composites, and in CB case they were the lowest compared with CNT and CNF. Reinforcing effect of CNT obtained from apparent modulus measurement was the highest in the same content. The results obtained from sensing fiber damage were correlated with the morphological observation of nano-scale structure using FE-SEM. The information on fiber damage and matrix deformation and reinforcing effect of carbon nanocomposites could be obtained from electrical resistivity measurement as a new concept of nondestructive evaluation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.688-694
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• 2002

As a tool for strain measurement to work with screw driven or hydraulic material test systems, in which mechanical vibration is inherent, SSDG(Speckle Strain/Displacement Gage), ESP(Electronic Speckle Photography) and its 3-dimension version SDSP are investigated for the theory and practical appliance. Through tension test of steel strips, their validity and shortcomings are examined. As the results, it has been shown that, although SSDG and ESP provide direct measurement of in-plane strain in one direction, they are so sensitive to the out-plane displacement. On the other hand, SDSP which is aided with DIC (Digital Image Correlation) technique to trace the movement of the speckles provides not only in-plane 2-dimensional displacement field, but also out-of-plane displacement simultaneously. However, because the DIC is time-consuming, not automated yet and it needs post-processing to evaluate strain from the displacement field, SDSP appears to be not adequate as a real time sensor.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2000.04a
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• pp.164-169
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• 2000

The remote measurement system(RMS) as a new experimental method is limited in its application to crack measurements at elevated temperatures because of the oxide layer on the specimen surface. Since TiAlN and Cr coating layers have a high resistance to oxidation and wear, this paper proposed a TiAlN and Cr coating technique for specimens to facilitate the measurement of crack growth behavior using RMS. To investigate the effects of the coating layer, tension and fatigue tests were carried out at room temperature and at 538$^{\circ}C$, using specimens of 1Cr-1Mo-0.25V steel. From the experimental results, it was found that the mechanical properties of the TiAlN and Cr coated specimens were similar to those of the substrate. Accordingly, the TiAlN and Cr coated layer had hardly any influence on the fatigue crack propagation.