• Transactions of the Korean hydrogen and new energy society
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• v.19 no.1
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• pp.49-55
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• 2008

The feasibility of ionic liquid as a novel absorbent of $SO_2$ for the separation of $SO_2$ from $SO_2/O_2$ mixture in the thermochemical IS(Iodine-Sulfur) cycle was investigated. 1,3-dimethylimidazolium methylsulfate ([DMIm]$MeSO_4$) had shown twenty five times higher solubility of $SO_2$ than that of $O_2$. The dependence of $SO_2$ solubility by [DMIm]$MeSO_4$ on temperature and $SO_2$ partial pressure was examined, which confirmed the possibility of temperature and pressure swing for the separation process. Through cyclic absorption and desorption with temperature swing the stability of [DMIm]$MeSO_4$ in the separation process was also demonstrated. As a result of the experiments carried out, $SO_2$ separation from $SO_2/O_2$ mixture with ionic liquid([DMIm]$MeSO_4$) can be applied to the thermochemical IS cycle.

• Economic and Environmental Geology
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• v.40 no.1 s.182
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• pp.29-45
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• 2007

Biogeochemical characteristics involving redox processes in groundwater from a riverine alluvial aquifer was investigated using multi-level monitoring wells (up to 30m in depth). Anaerobic conditions were predominant and high Fe ($14{\sim}37mg/L$) and Mn ($1{\sim}4mg/L$) concentrations were observed at 10 to 20 m in depth. Below 20 m depth, dissolved sulfide was detected. Presumably, these high Fe and Mn concentrations were derived from the reduction of Fe- and Mn-oxides because dissolved oxygen and nitrate were nearly absent and Fe and Mn contents were considerable in the sediments. The depth range of high Mn concentration is wider than that of high Fe concentration. Dissolved organics may be derived from the upper layers. Sulfate reduction is more active than Fe and Mn reduction below 20 m in depth. Disparity of calculated redox potential from the various redox couples indicates that redox states are in disequilibrium condition in groundwater. Carbonate minerals such as siderite and rhodochrosite may control the dissolved concentrations of Fe(II) and Mn(II), and iron sulfide minerals control for Fe(II) where sulfide is detected because these minerals are near saturation from the calculation of solubility equilibria.

• Membrane Journal
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• v.24 no.4
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• pp.325-331
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• 2014

We synthesized novel polyimides with high gas permeability and selectivity for application of on board inert gas generation system (OBIGGS). 2,2-bis(3,4-carboxylphenyl) hexafluoropropane dianhydride (6FDA) and two kinds of amines with high permeability and solubility were used to prepare the novel polymide. 2,3,5,6-Tetramethyl-1,4-phenylenediamine (TMPD) was used to improve gas permeability and various kinds of diamines were used to improve the gas selectivity respectively. The polyimide copolymers were synthesized by commercial chemical imidization method and their average molecular weights were over 100,000g/mol. The glass temperature ($T_g$) and the thermal degradation temperature were characterized using differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA). The synthesized copolymers showed high $T_g$ over $300^{\circ}C$ and high thermal degradation temperature over $500^{\circ}C$. The gas permeation properties were measured by time-lag equipment. Although general polyimides showed very low gas permeability, synthesized polyimide copolymer showed high $O_2$ permeability of 36.21 barrer with high $O_2/N_2$ selectivity around 4.1. From this result, we confirm that these membranes have possibility to apply to OBIGGS.

• Applied Chemistry for Engineering
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• v.26 no.1
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• pp.35-39
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• 2015

Polyvinylchloride (PVC) thin films having a microporous structure could be prepared by using the solubility difference in solvents. PVC thin film with a water contact angle of $150^{\circ}$ or more was obtained from the PVC solution consisting of the mixture of tetrahydrofuran as a solvent and propanol as a non-solvent. In the drying process of dip-coated PVC film, the increase of drying temperature reduced the tendency of roughened surface, which led the decrease of surface hydrophobicity. As the addition of propanol in the solution with 1 wt% PVC increased, the uniformity of surface roughness was improved. In the case of oxygen plasma treatments, even though the surface structure of PVC thin film was not notably changed, the surface property of the film was changed from the super-hydrophobicity to hydrophilicity as a function of the plasma exposing time.

• Applied Chemistry for Engineering
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• v.10 no.4
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• pp.502-508
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• 1999

We prepared non-porous membrane on the $Al_2O_3$ substrate with the different pore by the size by the plasma polymerization of $CHF_3$. We studied the permeability characteristics of membrane by Ar treatment and the effect of substrate pore size on gas permeation mechanism. The selectivity was increased with Ar plasma treatment time and rf-power near the substrate to the cathode while the permeability was decreased. It was observed that the solution-diffusion model would be applied to non-porous layers while it is applied Knudsen diffusion model to the substrate. From the experimental observation, it could be concluded that the pore size of $Al_2O_3$ membrane influenced on the permeability and the selectivity.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.7
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• pp.1563-1568
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• 2003

The introduction of invasive marine species of living things into new environments by ship's ballast water, attached to ships' hulls and via other vectors has been identified as one of the four greatest threats to the world's oceans by Global Environment Facility(GEF). Making use of the new technology of alpha-AL$_2$O$_3$ dielectric barrier layer, the strong electric-field gas discharge was introduced and obtained between micro-gap electrodes at high pressure (∼105㎩) of $O_2$ in air and $H_2O$ in seawater. The mixed air with $H_2O$ could be ionized and dissociated into large numbers of activated particles of OH, $O_2$＋, O(1D), HO$_2$ and so on, and then dissolved into the ballast water to form dissolved hydroxyl radical with the concentration of ∼20mg/L. Therefore, the invasive marine species was treated effectively through the hydroxyl radical dissolved pipeline of ballast water by strong electric -field discharge.

• Journal of the Korean Society of Marine Environment & Safety
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• v.18 no.6
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• pp.569-576
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• 2012

In general, aluminum alloys forms the passive film($Al_2O_3$, $Al_2O_3{\cdot}3H_2O$) in neutral solution. However, the passive film created on the surface will be destroyed by chloride ions contained in sea water so the corrosion will occur. In this study, in order to solve the problem of corrosion under a seawater environment, potentiostatic protection techniques were applied to Al-4.5%Mg-0.6%Mn aluminum alloy in seawater. At polarization experiments, active state were observed at anodic polarization and concentration polarization by reduction of dissolves oxygen and activation polarization were found at anodic polarization. As a results of potentiostatic experiment, calcareous deposit were created much more as applying time increase from the turning point of the concentration polarization and activation polarization and crevice corrosion was partially observed between calcareous deposit and surface of base metal. Overall potentiostatic anodic polarization experiment was difficult to apply potentiostatic corrosion protection technology by occurrence of active state, whereas potentiostatic cathodic polarization experiment examined optimum corrosion protection condition of -1.1 V~-0.75 V within the range of concentration polarization considered various applying time.

• Clean Technology
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• v.18 no.1
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• pp.57-62
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• 2012

Aqueous poly (vinyl alcohol) (PVA) solution was modified by using hydrophobic vinyltriethoxysilane (VTEOS) and then adding different amounts of poly (acrylic acid) (PAA) to the resulting solution. Thermal and mechanical properties, contact angle, water vapor transmission rate (MVTR) and oxygen gas transmission rate ($O_2TR$) of the film samples fabricated by these solutions were investigated. The glass transition temperature (Tg) of the VTEOS-modified films was sightly increased and the value remained unchanged according to the amount of PAA. The tensile strength of the VTEOS-modified films was found to be 9.48~10.72 $kg/mm^2$ which showed no significant difference compared with that of PVA. The film prepared with VTEOS-modified PVA/PAA (= 90/10), of which the swelling and solubility were measured to be 198% and 0%, respectively, showed improved water-resistance. The MVTR and $O_2TR$ for the PET film (thickness 50 ${\mu}m$) coated with VTEOS-modified PVA/PAA (= 90/10) film (thickness 2.5 ${\mu}m$) were measured to be 11.04 $g/m^2/day$ and 3.1 $cc/m^2/day$, respectively.

• Korean Journal of Food Science and Technology
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• v.28 no.1
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• pp.1-7
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• 1996

Three formulations were used to prepare the cellulose-based edible films consisting of hydrocolloid and lipids; film A made by coating method, films B and C by emulsion method, which were formed in a thin layer glass plate and then dried. Films A, B and C were all approximately 0.03 mm thick with 1-3% moisture, 59-68% lipid, and almost whitish color. Film A was better in tensile strength, and lipids affected water vapor permeability on three films, in which films A and B did not differ significantly. Water vapor permeability of film A did not change but those of films B and C decreased significantly after storage for 8 weeks at $-15^{\circ}C$. Oxygen transmission rate and oxygen permeability of films A and C did not differ and changed significantly after 8-week storage at $-15^{\circ}C$. Under scanning electron microscope (SEM) observation on the structural characteristics of each film, film A indicated relatively uniform and smooth surface coatings of beeswax, while films B and C had individual lipid crystals and could be discerned. As a result, film A was better than films B and C in respect of physical properties, but the selection of useful film depended upon which physical property was more functional. Moreover, it was desirable in some cases for using films B and C because of their easiness of preparation and cold storage durability. It will be further needed to investigate how to formulate films B and C to have more unique surface characteristics, and to reduce water vapor and oxygen transmission rates.

• Journal of Advanced Marine Engineering and Technology
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• v.41 no.3
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• pp.230-237
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• 2017

In this study, electrochemical methods were used to determine the optimum protection potential of S355ML steel for the cathodic protection of offshore wind-turbine-tower substructures. The results of potentiodynamic polarization experiments indicated that the anodic polarization curve did not represent a passivation behavior, while under the cathodic polarization concentration, polarization was observed due to the reduction of dissolved oxygen, followed by activation polarization by hydrogen evolution as the potential shifted towards the active direction. The concentration polarization region was found to be located between approximately -0.72 V and -1.0 V, and this potential range is considered to be the potential range for cathodic protection using the impressed current cathodic protection method. The results of the potentiostatic experiments at various potentials revealed that varying current density tended to become stable with time. Surface characterization after the potentiostatic experiment for 1200 s, by using a scanning electron microscope and a 3D analysis microscope confirmed that corrosion damage occurred as a result of anodic dissolution under an anodic polarization potential range of 0 to -0.50 V, which corresponds to anodic polarization. Under potentials corresponding to cathodic polarization, however, a relatively intact surface was observed with the formation of calcareous deposits. As a result, the potential range between -0.8 V and -1.0 V, which corresponds to the concentration polarization region, was determined to be the optimum potential region for impressed current cathodic protection of S355ML steel.