• Applied Chemistry for Engineering
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• v.7 no.2
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• pp.215-220
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• 1996

Nine kinds of amphoteric surfactants were derived from 1-(2-hydroxyethyl)-2-undecyl-2-imidazoline. Their surface activities including surface tension and isoelectric points were measured in aqueous solution and critical micelle concentration(cmc) was also evaluated by the measurement of surface tension. From the measurement of surface tension, carboxylated amides revealed to be 26~40dyne/cm at $4.0{\times}10^{-4}{\sim}1.0{\times}10^{-3}mol/{\ell}$, sulfonated or sulfated imidazolines, 30~35 dyne/cm at $1.5{\times}10^{-3}{\sim}2.5{\times}10^{-3}mol/{\ell}$ and sulfonated amides, 25~33 dyne/cm at $5.8{\times}10^{-4}{\sim}8.0{\times}10^{-4}mol/{\ell}$ concentration range. It was found that isoelectric points of carboxylated amides were pH 7.2~7.9 and those of sulfonated or sulfated imidazolines and sulfonated amides were pH 4.5~5.5.

• Journal of the Korean Applied Science and Technology
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• v.15 no.2
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• pp.11-24
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• 1998

All the surface activities including surface tension, foaming power, foam stability, emulsifying power, dispersion effect, and detergency were measured and critical micelle concentration(cmc) was evaluated in dilute aqueous solution. The cmc evaluated by the Ring method was $10^{-3}{\sim}10^{-4}mol/L$ in case of monoesters, and $10^{-3}{\sim}5.0{\times}10^{-5}mol/L$ in case of diesters, respectively. Surface tension of the aqueous solution was decreased to $45{\sim}50dyne/cm$, showing the tendency that the ability of lowering the surface tension was dependent on increasing of carbon atom number in alkyl chain. Foaming power of all the monoesters was better than that of diesters. while foam stability of diesters was to the contrary. Emulsifying power of soybean oil or benzene was specially expected to be good for emulsifiers in industrial application fields. HLB values of monoesters and diesters evaluated by Griffin's method were in the range of 8 to 12. Dispersion property of ferric oxide was stable in the range of $4.5{\times}10^{-5}{\sim}5.0{\times}^{-4}mol/L$ in case of monoesters, and $10^{-5}{\sim}10^{-4}mol/L$ in case of diesters.

• Journal of the Korean Applied Science and Technology
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• v.11 no.1
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• pp.79-85
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• 1994

All the activities and physical properties including surface tension' foaming power, foam stability, emulsifying power, dispersion effect of 3-(N, N-dimethyl N-alkylammonio)-2-hydroxyY-1-propane sulfonate (HSB)류와 3-CN-alkylamidopropyl-N,N-dimethylamm-onjo)-2-hydroxy-1-propane sulfonate (APSB) aquous solution were measured and critical micelle concentration was evaluated. Their cmc of hydroxy sulfobetaine derivatives evaluated by the surface tension method was $1.0{\times}10^{-3}{\sim}1.0{\times}10^{-4}$ mol/l, and surface tension of the aquous solution was decreased to $27{\sim}38dyne/cm$. The experimental results for foaming power, foam stability, emulsifying power in liquid paraffin showed a good surface active properties, especially, dispersion effect in ferric oxide exhibited some efficient surface active properties, and then it would be expected to application as detergent and dispersion agent.

• Nuclear Engineering and Technology
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• v.52 no.7
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• pp.1571-1578
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• 2020

As a critical material in very/high-temperature gas-cooled reactors, graphite material directly affects the safety of the reactor core structures. Owing to the complex structures of graphite material in reactors, the material typically undergoes complex stress states. It is, therefore, necessary to study its mechanical properties, failure modes, and strength criteria under complex stress states so as to provide guidance for the core structure design. In this study, compressive failure tests were performed for graphite material under the condition of different confining pressures, and the effects of confining pressure on the triaxial compressive strength and Young's modulus of graphite material were studied. More specifically, graphite material based on the fracture surfaces and fracture angles, the graphite specimens were found to exhibit four types of failure modes, i.e., tension failure, shear-tension failure, tension-shear failure and shear failure, with increasing confining pressure. In addition, the Mohr strength envelope of the graphite material was obtained, and different strength criteria were compared. It showed that the parabolic Mohr-Coulomb criterion is more suitable for the strength evaluation for the graphite material.

• Progress in Superconductivity and Cryogenics
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• v.18 no.4
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• pp.21-24
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• 2016

The mechanical properties of REBCO coated conductor (CC) wires under uniaxial tension are largely determined by the thick component layers in the architecture, namely, the substrate and the stabilizer or even the reinforcement layer. Depending on device applications of the CC tapes, it is necessary to reinforce thin metallic foils externally to one-side or both sides of the CC tapes. Due to the external reinforcement of brass foils, it was found that this could increase the reversible strain limit from the Cu-stabilized CC tapes. In this study, the effects of differently hardened brass foil laminate on the electromechanical property of CC tapes were investigated under uniaxial tension loading. The tensile strain dependence of the critical current ($I_c$) was measured at 77 K and self-field. Depending on whether the $I_c$ of CC tapes were measured during loading or after unloading, a reversible strain (or stress) limit could be determined, respectively. The both-sides of the Cu-stabilized CC tapes were laminated with brass foils with different hardness, namely 1/4H, 1H and EH. From the obtained results, it showed that the yield strength of the brass laminated CC tapes with EH brass foil laminate was comparable to the one of the Cu-stabilized CC tape due to its large yield strength even though its large volume fraction. It was found that the brass foil with different hardness was mainly sensitive on the stress dependence of $I_c$, but not on the strain sensitivity due to the residual strain induced in the laminated CC tapes during unloading.

• Journal of the Korean Society of Food Science and Nutrition
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• v.37 no.11
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• pp.1465-1471
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• 2008

This study was carried out to make water-soluble tocopherol emulsion which can be applicable directly in water. The molecular weight of tocopherol was 340 to 360 and tocopherol emulsion model was decided as O/O/W/W type. In correlation between stability of emulsion and surface tension, the stability in surface tension of emulsion was from 40 to 46 dyne/cm. In the case of lower than 40 dyne/cm of surface tension, the stability of the emulsion was lower. Lipophilic surfactants, especially for a polyglycerine polyricinoleate in 20%, 30% and 40% tocopherol emulsion, was the most effective in emulsion stability. A higher stability of the emulsion among hydrophilic surfactants in the tocopherol emulsion was obtained in the following order; polyglycerine monostearate> polyglycerine monooleate> polyoxyethylene (20) sorbitan monooleate$\geq$ polyoxyethylene (20) sorbitan monolaurate.

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.3
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• pp.193-199
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• 2002

Structral crack of RC structure generally occurs when the tension stress by applied load is larger than tension resistance of concrete, and it means deterioration of structure and the decrease of load resistance. Because structural crack of structure can occur critical damage to structure occasionally, the research on crack detection algorithm of RC structure is needed for assurance of structural safety and effective maintenance of structure. In this paper, we executed the laboratory test on measuring strain of RC beam's tension and compression zone, using strain gauge which is widely used on strain measurement of civil structure. By using measured strain, we analyzed strain change, elastic modulus change, and neutral axis change to detect crack of RC beam. As a result, we proposed the simple and effective crack detection algorithm using trends of neutral axis position change.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.9
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• pp.877-880
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• 2009

A curing process in post-printing section of R2R process is required for an electrical property of the printed pattern when devices such as RFID, Solar cell are printed. PEN as well as heat-stabilized PET which is used as a plastic substrate would be deformed at high temperature due to change of its elastic modulus. And crack in the printed pattern, which is on the plastic substrate is occurred due to the deformation of the substrate. The occurrence of crack causes electrical resistance to increase and the quality of the device to deteriorate. In case of RFID antenna, the range of reading distance is shortened as the electrical resistance of the antenna is increased. Therefore, the deformation of the plastic substrate, which causes the occurrence of crack, should be minimized by setting up low operating tension in R2R process. In low tension, slippage between a moving substrate and a roller would be generated when the operating speed is increased. And scratch would be occurred when slippage is generated due to an air entrainment, which is related to the thickness of the air film. The thickness of the air film is increased when operating speed is increased as shown by simulation based on mathematical model. The occurrence of scratch in conductive pattern printed by roll to roll process is a critical damage because it causes degradation or failure of electrical property of it.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.11
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• pp.2752-2761
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• 1993

The purpose of this study is to confirm the decreasing problems of residual bending strength, and the fracture machanism experimentally when CFRP composite laminates are subjected to Foreign Object Damage. Composite laminates used for this experiment are CFRP orthotropy laminated plates, which have two-interfaces [O/sub 6//sup o//90/sub 6//sup o/]sub sym/ and four-interfaces [O/sub 3//sup o//90/sub 6//sup o//O/sub 3//sup o]/sub sym/. When the specimen is subjected to transverse impact by a steel ball, the delamination area generated by impact damage is observed by using SAM(Scanning Acoustic Microscope). also, Thefracture surfaces obtained by three-point bending test were observed by using SEM (Scanning Electron Microscope). Then, fracture mechanism was investigated based on the observed delamination area and fracture surface. The results were summarized as follows; (1) It is found that for the specimen with more interface, the critical delamination energy is increased while delamination-development energy is decreased. (2) Residual bending strength of specimen A is greater than that of Specimen B within the impact range of impact energy 1. 65J (impacted-side compression) and 1. 45J (impacted-side tension). On the other hand, when the impact energy is beyond the above ranges, residual bending strength of specimen A is smaller than that of specimen B. (3) In specimen A and B, residual strength of CFRP plates subjected to impact damage is lower in the impacted-side compression than in the impacted-side tension. (4) In the case of impacted-side compression, fracture is propagated from the transverse crack generat-ed near impact point. On the other hand, fracture is developed toward the impact point from the edge of interface-B delamination in the case of impacted-side tension.

• Smart Structures and Systems
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• v.29 no.1
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• pp.41-51
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• 2022

Cables are critical components of cable-stayed bridges. A structural health monitoring system provides real-time cable tension recording for cable health monitoring. However, the measurement data involve multiple sources of variability, i.e., varying environmental and operational factors, which increase the complexity of cable condition monitoring. In this study, a one-class classification method is developed for cable condition assessment using Bayesian factor analysis (FA). The single-peaked vehicle-induced cable tension is assumed to be relevant to vehicle positions and weights. The Bayesian FA is adopted to establish the correlation model between cable tensions and vehicles. Vehicle weights are assumed to be latent variables and the influences of different transverse positions are quantified by coefficient parameters. The Bayesian theorem is employed to estimate the parameters and variables automatically, and the damage index is defined on the basis of the well-trained model. The proposed method is applied to one cable-stayed bridge for cable damage detection. Significant deviations of the damage indices of Cable SJS11 were observed, indicating a damaged condition in 2011. This study develops a novel method to evaluate the health condition of individual cable using the FA in the Bayesian framework. Only vehicle-induced cable tensions are used and there is no need to monitor the vehicles. The entire process, including the data pre-processing, model training and damage index calculation of one cable, takes only 35 s, which is highly efficient.