• Journal of the Korean Applied Science and Technology
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• v.31 no.4
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• pp.642-652
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• 2014

The synthesis of octenyl succinyl ${\beta}$-gucan (OSA-${\beta}$-glucan) was carried out and its interfacial properties at the oil-water interface and in emulsion systems were investigated. An aqueous ethanol system as a reaction media was used to facilitate the synthesis process; 10% (w/w) ethanol found to be the best as it showed a maximum degree of substitution (DS: 0.0132). FT-IR showed a characteristic absorption spectrum at $1736cm^{-1}$, indicating the esterification of octenyl succinyl groups to ${\beta}$-glucan backbone. As for interfacial tension measurements, it was decreased with increasing concentration of OSA-${\beta}$-glucan in the aqueous phase and when NaCl was added to aqueous OSA-${\beta}$-glucan solution in the range of 0.01 M to 0.1 M and also when pH was raised (pH 3 ~ pH 9). In systems of emulsion stabilized with OSA-${\beta}$-glucan, fat globule size found to decrease with increasing concentration of OSA-${\beta}$-glucan, showing a critical value of about $0.32{\mu}m$ at 0.5 wt%. When the OSA-${\beta}$-glucan emulsions were stored, it was found that fat globule size was increased with storage time and particularly pronounced increase was observed in emulsion with 1% OSA-${\beta}$-glucan, possibly due to depletion flocculation. Results of creaming stability evaluated by light scattering technique showed that it was more stable in emulsions containing smaller fat globule size. Surface load of OSA-${\beta}$-glucan in emulsions increased with increasing concentration of OSA-${\beta}$-glucan, suggesting a multilayer adsorption.

• Korean Chemical Engineering Research
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• v.50 no.3
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• pp.455-463
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• 2012

In this study, the measurement of physical properties of ethylene oxide-propylene oxide adducted zwitterionic surfactants were measured such as critical micelle concentration, surface tension, interfacial tension, contact angle, viscosity and foam stability. Also, the dual function characteristics of a zwitterionic surfactant were investigated by determining an isoelectric point, which were obtained using zeta potential measurement and QCM (quartz crystal microbalance) experiments. The isoelectric point of DEP-OSA82-AO zwitterionic surfactant determined by zeta potential measurement was close to that obtained by QCM experiment and both results have shown almost the same trend as that determined by the frictional property measured using an automated mildness tester. In particular, it has been observed that DEP32-OSA82-AO and DEP34-OSA82-AO surfactants provide better softening effect at a pH of acidic or neutral condition than at an alkaline condition. This result indicates that both surfactants act as a cationic surfactant at a pH of acidic or neutral condition and thus provide good softening effect during a rinsing cycle in the detergency process.

• Applied Chemistry for Engineering
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• v.23 no.6
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• pp.521-528
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• 2012

In this study, we analyzed the physical properties of an ethylene oxide adducted amphoteric surfactant such as critical micelle concentration, surface tension, interfacial tension, contact angle, viscosity and phase behavior. The dual function characteristics of an amphoteric surfactant were investigated by determining an isoelectric point, which were attained using zeta potential measurements and quartz crystal microbalance (QCM) experiments. The isoelectric points of DE3-OSA82-AO, DE5-OSA82-AO and DE9-OSA82-AO surfactant systems determined by zeta potential measurements were 6.97, 6.93 and 7.10 respectively and they are in good agreement with the isoelectric point values measured by QCM experiments. The frictional property measured using an automated mildness tester showed that the DE-OSA82-AO surfactant could provide a good softening effect at neutral condition.

• Progress in Superconductivity and Cryogenics
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• v.17 no.3
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• pp.13-17
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• 2015

In superconducting coil applications particularly in wet wound coils, coated conductor (CC) tapes are subjected to different type of stresses. These include hoop stress acting along the length of the CC tape and the Lorentz force acting perpendicular to the CC tape's surface. Since the latter is commonly associated with delamination problem of multi-layered CC tapes, more understanding and attention on the delamination phenomena induced in the case of coil applications are needed. Difference on the coefficient of thermal expansion (CTE) of each constituent layer of the CC tape, the bobbin, and the impregnating materials is the main causes of delamination in CC tapes when subjected to thermal cycling. The CC tape might also experience cyclic loading due to the energizing scheme (on - off) during operation. In the design of degradation-free superconducting coils, therefore, characterization of the delamination behaviors including mechanism and strength in REBCO CC tapes becomes critical. In this study, transverse tensile tests were conducted under different loading conditions using different size of upper anvils on the GdBCO CC tapes. The mechanical and electromechanical delamination strength behaviors of the CC tapes under transverse tensile loading were examined and a two-parameter Weibull distribution analysis was conducted in statistical aspects. As a result, the CC tape showed similar range of mechanical delamination strength regardless of cross-head speed adopted. On the other hand, cyclic loading might have affected the CC tape in both upper anvil sizes adopted.

• Bulletin of the Korean Chemical Society
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• v.32 no.1
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• pp.59-64
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• 2011

Degree of unsaturation in fatty acid molecules plays an important role in the formation of vesicles. Vesicle formation from C18 fatty acids with different amount of double bonds such as oleic acid, linoleic acid and linolenic acid with the incorporation of 1,2-dipalmitoyl-sn-glycerol-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] (DPPE-PEG2000) have been examined by TEM. Critical vesicular concentrations (CVC) of the vesicle suspension are determined by turbidity and surface tension methods. The CVC of fatty acids increases when the amount of unsaturation in the alkyl chain increases. On the other hand, stability of vesicle suspension has been examined by using particle size and zeta potential at $30^{\circ}C$. There was a dramatic decrease in particle size measurement from mono-unsaturation to tri-unsaturation which could be due to the effect of fluidity in the membrane bilayer caused by different degree of unsaturation. The values of zeta potential for vesicles that were formed without the incorporation of DPPE-PEG2000 were in the range of -70 mV to -100 mV. It has been observed that the incorporation of DPPEPEG2000 to the vesicle reduces the magnitude of zeta potential. However, this phenomenon does not obviously seen in fatty acid vesicles formed by linoleate-linoleic acid and linolenate-linolenic acid. We therefore conclude that the addition of DPPE-PEG2000 does not effectively improve the stability of the linoleate-linoleic acid and linolenatelinolenic acid vesicle at pH 9.0 after the evaluation of their particle size and zeta potential over a period of 30 days. Although the vesicles formed were not stable for more than 10 days, they have displayed the potential in encapsulating the active ingredients such as vitamin E and calcein. The results show that the loading efficiencies of vitamin E are of encouraging value.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.7
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• pp.573-580
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• 2021

Paraffin wax is attracting many attentions for promising solid fuel of hybrid rocket because of its higher regression than other fuels. However, even with paraffin fuel combustion, unsteady low-frequency oscillation of combustion pressure is still observed. And, this is related to the formation of liquid layer and the entrainment of fuel droplets entering the axial combustion gas flow. This study investigates the effect of additional combustion of fuel droplets on the occurrence of low-frequency combustion instability. On the other hand, the formation of fuel droplets depends on Weber Number (the ratio of the inertial force to the surface tension of the liquid) and Reynolds Number of the oxidizer flow. Therefore, a laboratory-scale hybrid rocket was used to monitor the occurrence of combustion instability while changing We number. A series of combustion tests were conducted to control We number by changing the oxidizer flow rate or adding LDPE (low density polyethylene) to base fuel. In the results, it was confirmed that there is a critical We number above which the low-frequency combustion instability occurs.

• Journal of English Language & Literature
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• v.57 no.3
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• pp.473-493
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• 2011

This paper aims, first, to trace the trajectory of Sebastian Barry's dramatic works in terms of retrieving the hidden (hi)stories of his family members, and second, to analyze his most successful play to date in both critical and commercial senses, The Steward of Christendom, in terms of the tension or even rupture between Irish national history and the dramatic representation of it. If contemporary Irish drama as a whole can be seen as an act of mirroring up to nation, Barry's is a refracting than reflecting act. Whereas modern Irish drama tends to have helped, however inadvertently, consolidate the nation-state by imagining Ireland through its other (either in the form of the British empire or the Protestant Unionist north), Barry's drama aims at cracking the surface homogeneity of Irish identity by re-imagining "ourselves" (a forgotten part of which is a community of southern Catholic loyalists). Furthermore, the "ourselves" re-imagined in Barry's drama is more fractured than unified, irreducible in its multiplicity than acquiescent in its singularity. The playwright's foremost concern is to retrieve the lives of "history's leftovers, men and women defeated and discarded by their times" and re-member those men and women who have been expunged from the imagined community of the Irish nation. This he does by endowing "every life" with "an after-life" and "every demon" with "a fairy tale." The Steward of Christendom is Barry's dramatic attempt to bestow upon the historically demonized Thomas Dunne, an Irish policeman in the British Empire, his fairy-tale redemption.

• Journal of the Korean Applied Science and Technology
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• v.30 no.4
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• pp.635-648
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• 2013

This study was carried out to investigate the emulsifying properties of surface-active substances from defatted rapeseed cake by supercritical $CO_2$ extraction. Based on the interfacial tension data, a supercritical fluid extract (SFE) with the lowest value of 14.16 mN/m was chosen for evaluation which was obtained from No. 2 extraction condition (150 bar, $65^{\circ}C$, 250 g). For emulsions with SFE, some physicochemical properties (i.e., fat globule size, creaming stability, zeta potential etc) were investigated according to changes in SFE concentration, pH, and NaCl addition in an emulsion. It was found that fat globule size was decreased with increasing SFE concentration in emulsion, with showing a critical value at 0.5 wt%, thereby resulting in less susceptibility to creaming behavior. The SFE emulsion also showed instability at acidic conditions (pH<7.0) as well as by NaCl addition. This was coincided with zeta potential data of emulsion. In addition, SSL (sodium stearoyl lactylate) found to be suitable as a co-surfactant, as it helped considerably in decreasing fat globule size in emulsions and its optimum concentration to be over 0.03 wt%, based on 0.1 wt% SFE in emulsion.

• Membrane Journal
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• v.32 no.4
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• pp.253-263
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• 2022

This study suggests a guideline for designing unit process of wastewater reuse in terms of a maintenance of the process based on critical parameters to draw a high quality performance of RO unit. Defining the parameters was done by applying membrane integrity test (MIT) in pretreatment process utilizing lab-scale MF. SDI is utilized for judging whether permeate is suitable to RO unit. However, result said TOC concentration matching with particle count analysis is better for judging the permeate condition. When membrane test pressure (P_test) was measured to derive log removal value in PDT, virgin state of membrane fiber was used to measure dynamic contact angle utilizing surface tension of the membrane fiber. Actually, foulant affects to the state of membrane surface, and it decreases the P_test value along with time elapsed. Consequently, LRV_DIT is also affected by P_test value. Thus, sensitivity of direct integrity test descends with result of P_test value change, so P_test value should be considered not the virgin state of the membrane but its current state. Overall, this study focuses on defining design parameters suitable to MF pretreatment for RO process in wastewater reuse by assessing its impact. Therefore, utilities can acknowledge that the membrane surface condition must be considered when users conduct the direct integrity test so that P_test and other relative parameter used to calculate LRV_DIT are adequately measured.

• Korean Journal of Materials Research
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• v.22 no.9
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• pp.476-481
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• 2012

Among the various roll-to-roll printing technologies such as gravure, gravure-offset, and reverse offset printing, reverse offset printing has the advantage of fine patterning, with less than 5 ${\mu}m$ line width. However, it involves complex processes, consisting of 1) the coating process, 2) the off process, 3) the patterning process, and 4) the set process of the ink. Each process demands various ink properties, including viscosity, surface tension, stickiness, and adhesion with substrate or clich$\acute{e}$; these properties are critical factors for the printing quality of fine patterning. In this study, Ag nano ink was developed for reverse offset printing and the effect of polyvinylpyrrolidone(PVP), used as a capping agent of Ag nano particles, on the printing quality was investigated. Ag nano particles with a diameter of ~60 nm were synthesized using the conventional polyol synthesis process. Ethanol and ethylene glycol monopropyl ether(EGPE) were used together as the main solvent in order to control the drying and absorption of the solvents during the printing process. The rheological behavior, especially ink adhesion and stickiness, was controlled with washing processes that have an effect on the offset process and that played a critical role in the fine patterning. The electrical and thermal behaviors were analyzed according to the content of PVP in the Ag ink. Finally, an Ag mesh pattern with a line width of 10 ${\mu}m$ was printed using reverse offset printing; this printing showed an electrical resistivity of 36 ${\mu}{\Omega}{\cdot}cm$ after sintering at $200^{\circ}C$.