• Korean Chemical Engineering Research
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• v.50 no.2
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• pp.282-291
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• 2012

The PGLE and PGLE3 nonionic surfactants were synthesized from the reaction between glycidol and lauryl acid and their structures were confirmed by $^1H$ and $^{13}C$ NMR analysis. The CMCs of PGLE and PGLE3 surfactants were found to be $3.59{\times}10^{-2}$ mol/L and $8.80{\times}10^{-2}$ mol/L respectively and the surface tensions at their CMC conditions were 26.09 mN/m and 28.68 mN/m respectively. Dynamic surface tension measurement has shown that the adsorption rate of surfactant molecules at the interface between air and surfactant solution was found to be relatively fast in both surfactant systems, presumably due to high mobility of surfactant molecules. The contact angles of PGLE and PGLE3 nonionic surfactants were $25.5^{\circ}$ and $9.5^{\circ}$ respectively. Dynamic interfacial tension measurement showed that both surfactant systems reached equilibrium in 20 minutes and the interfacial tensions at equilibrium condition in both systems were 0.42 mN/m and 0.53 mN/m respectively. The PGLE surfactant system has indicated higher foam stability than the PGLE3 surfactant system, which is consistent with surface tension measurement. The phase behavior experiments performed at $25{\sim}60^{\circ}C$ in systems containing nonionic surfactant, water, n-hydrocarbon oil and cosurfactant showed a lower phase or oil in water microemulsion in equilibrium with excess oil phase at all conditions investigated during this study.

• Tuberculosis and Respiratory Diseases
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• v.82 no.3
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• pp.251-260
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• 2019

Background: Beyond its current function as a rescue therapy in acute respiratory distress syndrome (ARDS), extracorporeal membrane oxygenation (ECMO) may be applied in ARDS patients with less severe hypoxemia to facilitate lung protective ventilation. The purpose of this study was to evaluate the efficacy of extended ECMO use in ARDS patients. Methods: This study reviewed 223 adult patients who had been admitted to the intensive care units of 11 hospitals in Korea and subsequently treated using ECMO. Among them, the 62 who required ECMO for ARDS were analyzed. The patients were divided into two groups according to pre-ECMO arterial blood gas: an extended group (n=14) and a conventional group (n=48). Results: Baseline characteristics were not different between the groups. The median arterial carbon dioxide tension/fraction of inspired oxygen ($FiO_2$) ratio was higher (97 vs. 61, p<0.001) while the median $FiO_2$ was lower (0.8 vs. 1.0, p<0.001) in the extended compared to the conventional group. The 60-day mortality was 21% in the extended group and 54% in the conventional group (p=0.03). Multivariate analysis indicated that the extended use of ECMO was independently associated with reduced 60-day mortality (odds ratio, 0.10; 95% confidence interval, 0.02-0.64; p=0.02). Lower median peak inspiratory pressure and median dynamic driving pressure were observed in the extended group 24 hours after ECMO support. Conclusion: Extended indications of ECMO implementation coupled with protective ventilator settings may improve the clinical outcome of patients with ARDS.

• Journal of the Korean Applied Science and Technology
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• v.35 no.3
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• pp.579-586
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• 2018

In this study, surfactants were synthesized using fatty alcohols of 8, 10, 12 and 14 carbon chains length. The structures of the synthesized surfactants was confirmed by FT-IR and $^1H$-NMR analysis. The surface tension of the diluted surfactant was measured as 26~32 mN/m depending on the carbon length and the critical micelle concentration was measured as $10^{-3}{\sim}10^{-5}mol/L$.The minimum value per molecule of the synthesized sulfonic acid surfactant is 1.68 to $1.30nm^2$. The physical properties of the synthesized surfactants were determined by measuring the critical micelle concentration, foaming power, emulsifying stability, and contact angle.

• 연구논문집
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• s.23
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• pp.127-140
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• 1993

The drive pulley, which is employed for loading and unloading raw materials in a steel mill, is usually manufactured by use of various welding processes. In this study the weldment in the pulley, in which TIG and $CO_2$ welding processes are used, has been analyzed from view point of fracture mechanics. Fracture toughness tests have been performed according to ASTM E813. A servo-hydraulic testing machine (10kN) has been employed. Also the crack propagation tests (Mode I) have been performed with compact tension specimen in compliance with ASTM E647. To predict the critical crack size in the weldment, finite element stress analysis for the drive pulley under real operating conditions have been performed. In addition, the residual stresses at the weldment and in heat-affected zone have been obtained by hole drilling method. The planar critical crack size have been predicted for the drive pulley by considering the stress analysis results and the residual stresses due to welding process. For the drive pulley considered in this study, it has been concluded that the most important factor in determining the critical crack size is the welding residual stress in the transverse direction. Also the effect of stress concentration at the root of the weldment have been noticeable. For the planar crack, the fatigue crack growth life from an initial crack size of 2mm to the critical crack size obtained as in the above have been predicted. The predicted lives were between 55, 900 and 72, 000 cycles depending on the shape of the elliptical crack. The predicted lives were in fairly good agreement for the drive pulley considered in this study.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.380-387
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• 2004

Recently the geosynthetics reinforced retaining wall has been widely used instead of the steel reinforced retaining wall. The geosynthetics reinforced retaining wall is a very dangerous structure if the geosynthetics lose their strength about tension or if it lose their pullout resistence, but it was known that the geosynthetics reinforced wall had a great resistence and was a very safe structure against a earthquake or a dynamic load. It can be said that most important factors in the stability of the geosynthetics reinforced wall are the horizontal length of reinforcement and the vertical distance between two reinforcements. That is to say, as the length of reinforcement is longer, the structure is more stable and as the vertical distance between two reinforcements is shorter, it is more stable. In this study, in order to get the critical condition with a safety rate of 1, various kinds of model tests about geosynthetics reinforced wall has been performed. Photos by B-shutter method has been taken during tests and from photos, which show us the failure state, the critical condition about failure has been conformed. Accordingly the equation, which says the limit of stability in geosynthetics reinforced wall., has been proposed.

• Applied Chemistry for Engineering
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• v.30 no.1
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• pp.102-107
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• 2019

Anionic surfactants were synthesized by using an sarcosine, taurine and fatty alcohol with varying the carbon chain length. The structure of synthesized surfactants was confirmed by $^1H$ NMR analysis. The critical micelle concentration of the synthetic anionic surfactant was $10^{-2}{\sim}10^{-4}mol/L$ and the surface tension value at the critical micelle concentration was between 21 and 39 mN/m. It was confirmed by the Ross-Miles method that the synthetic surfactant with the carbon chain of 12 showed a good foaming power and stability. In addition, the surfactant using the sacosine was found to have a good affinity in soybean oil while that using taurine in benzene. The physical properties of synthesized surfactants were determined by measuring the critical micelle concentration, foaming power and emulsifying stability.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.850-853
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• 2008

In the motorized retractor of the smart seat belt system, anti-overload clutch is a very important element to prevent the excessive belt tensional force. Anti-overload clutch is the essential device to protect drivers from chest damage by the excessive belt tension. It generates slipping motion under excessive webbing moment and the belt tensional force is limited below critical value. In this study, slipping mechanism in the antioverload clutch is investigated by analysis and experiment. On the prototype model, finite element analysis is performed to identify the slipping condition and to determine the critical load. Analysis result is compared with the experimental result and the validity of the analysis model is verified. The purpose of the study is to provide the analytical background for the systematic design of the anti-overload clutch mechanism.

• Applied Chemistry for Engineering
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• v.3 no.2
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• pp.224-229
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• 1992

Sodium acyl isethionate, one of the anionic surfactants, was synthesized and purified from the fatty acid and the sodium isethionate. To investigate the tendency of the surface active properties of acyl group, surface tension, foaming power, foam stability, lime soap dispersing power, detergency, and critical micelle concentration were determinded. The results exhibited that sodium acyl isethionates had exellent surface active properties and critical micelle concentrations were measured between $1.1{\times}10^{-4}mol/l$ and $4.8{\times}10^{-3}mol/l$. In this case, surface tensions were indicated between 26.8dyn/cm and 36.7dyn/cm.

• Progress in Superconductivity and Cryogenics
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• v.16 no.4
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• pp.7-16
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• 2014

Rare-earth barium copper oxide (REBCO) coated conductor (CC) tapes have already been commercialized but still possess some issues in terms of manufacturing cost, anisotropic in-field performance, $I_c$ response to mechanical loads such as delamination, homogeneity of current transport property, and production length. Development on improving its performance properties to meet the needs in practical device applications is underway and simplification of the tape's architecture and manufacturing process are also being considered to enhance the performance-cost ratio. As compared to low temperature superconductors (LTS), high temperature superconductor (HTS) REBCO CC tapes provide a much wider range of operating temperature and a higher critical current density at 4.2 K making it more attractive in magnet and coil applications. The superior properties of the REBCO CC tapes under magnetic field have led to the development of superconducting magnets capable of producing field way above 23.5 T. In order to achieve its optimum performance, the electromechanical properties under different deformation modes and magnetic field should be evaluated for practical device design. This paper gives an overview of the effects of mechanical stress/strain on $I_c$ in HTS CC tapes due to uniaxial tension, bending deformation, transverse load, and including the electrical performance of a CC tape joint which were performed by our group at ANU in the last decade.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.4
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• pp.174-181
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• 2005

In order to investigate the behavior of fatigue crack growth of SiC-particulate- reinforced Al-Si alloy composites, fatigue tests using single edge notched tension(SENT) specimens were performed. Composite materials were manufactured by using both permanent die casting and extrusion processes with different volume fractions of $10\%\;and\;20\%$. $SiC_p-reinfurced$ Al-Si composites showed the increased levels of threshold stress intensity factor range, ${\Delta}K_{th}$, for the increased volume fractions of SiC particles, which implies the increased fatigue crack growth resistance at the threshold or low ${\Delta}K$ levels, compared to the unreinforced Al-Si alloy. In the Paris region, however, the composites showed the increased rate of crack growth resulting in the unfavorable effects on the fatigue crack growth resistance. Critical stress intensity factor range at unstable crack growth leading to final fracture decreased as the volume fraction of SiC particle increased, because of the reduced fracture toughness of the composites. Extruded materials showed higher threshold and critical values than the cast materials.