• Membrane and Water Treatment
• /
• v.6 no.5
• /
• pp.365-378
• /
• 2015

Herein, the preparation of anion exchange membrane (AEM) from brominated poly(2,6-dimethyl 1,6-phenylene oxide) BPPO and dimethylaniline (DMA) by phase-inversion process is reported. Anion exchange membranes (AEMs) are prepared by varying the DMA contents. Prepared AEMs show high thermal stability, water uptake (WR) around 202% to 226%, dimensional change ratios of 1.5% to 2.6% and ion exchange capacities (IECs) of 0.34 mmol/g to 0.82 mmol/g with contact angle of $59.18^{\circ}$ to $65.15^{\circ}$. These membranes are porous in nature as confirmed by SEM observation. The porous property of membranes are important as it could reduce the resistance of transportation of ions across the membranes. They have been used in diffusion dialysis (DD) process for recovery of hydrochloric acid (HCl) from the mixture of HCl and ferrous chloride ($FeCl_2$). Presence of $-N+(CH_3)_2C_6H_5Br^-$ as a functional group in membrane matrix facilitates its applications in DD process. The dialysis coefficients of hydrochloric acid ($U_H$) of the membranes are in range of 0.0016 m/h to 0.14 m/h and the separation factors (S) are in range of 2.09 to 7.32 in the $HCl/FeCl_2$ system at room temperature. The porous membrane structure and presence of amine functional group are responsible for the mechanism of diffusion dialysis (DD).

• Journal of the Institute of Electronics and Information Engineers
• /
• v.54 no.5
• /
• pp.24-32
• /
• 2017

In this paper, a low power 4th order delta-sigma modulator was designed with a high resolution of 12 bits or more for the biological signal processing. Using time-interleaving technique, 4th order delta-sigma modulator was designed with one operational amplifier. So power consumption can be reduced to 1/4 than a conventional structure. To operate stably in the big difference between the two capacitor for kT/C noise and chip size, the variable-stage amplifier was designed. In the first phase and second phase, the operational amplifier is operating in a 2-stage. In the third and fourth phase, the operational amplifier is operating in a 1-stage. This was significantly improved the stability of the modulator because the phase margin exists within 60~90deg. The proposed delta-sigma modulator is designed in a standard $0.18{\mu}m$ CMOS n-well 1 poly 6 Metal technology and dissipates the power of $354{\mu}W$ with supply voltage of 1.8V. The ENOB of 11.8bit and SNDR of 72.8dB at 250Hz input frequency and 256kHz sampling frequency. From measurement results FOM1 is calculated to 49.6pJ/step and FOM2 is calculated to 154.5dB.

• Journal of the Korean Chemical Society
• /
• v.58 no.6
• /
• pp.560-568
• /
• 2014

The contribution of electrostatic interactions to protein folding reaction was studied by using mutant ubiquitin with lysine to alanine mutation at residue position 29. Based on the three dimensional structure of ubiquitin, lysine 29 is located close to negatively charged glutamate 16 and aspartate 21 and considered to stabilize the native state of ubiquitin by electrostatic interactions between these residues. The equilibrium unfolding experiment showed that the native stability was decreased by about ~20% upon mutation. This observation indicates lysine 29 indeed forms electrostatic interactions with nearby residues. Folding kinetics measurements using stopped-flow device and quantitative analysis of kinetics data indicate that ubiquitin folds from unfolded state to native state via intermediate state as observed previously. This intermediate state was observed to form immediately after the initiation of folding reaction. The folding intermediate was shown to be destabilized considerably upon lysine to alanine mutation. These observations indicate that electrostatic interactions can form early stage of protein folding and hence lead the folding reaction.

• Journal of the Korean Solar Energy Society
• /
• v.34 no.4
• /
• pp.57-65
• /
• 2014

In order to reduce greenhouse gas emissions in recent agricultural energy and increase the energy self-sufficiency rate of each farmer, it is extremely important to expand the supply of solar energy using unused space of agricultural facilities, roof. This study surveyed and analyzed the environmental and administrative factors such as problems according to the structure, azimuth and latitude of broiler houses and stability of standard broiler houses required to use broiler house roof based on the poultry houses in Sangju-si. The results can be summarized as follows: 55.6% of the solar energy facilities of according to the classification of arable lands of broiler houses were available, and 31.7% of them were available by classifying according to the azimuth. However, 20.6% of them were available in the survey considering all the arable land and azimuth. In the roof inclination of the broiler houses, from 20 to $25^{\circ}$ was the most common, 30 broiler houses. The broiler houses with the roof inclination more than $20^{\circ}$ accounted for 63% of the total. It was considered that the inclination was generally proper. In the structural safety, only 3 broiler houses that were constructed as a standard broiler house were available. In practice, all but one broiler house was inappropriate to expand the solar energy project using roof. The solar thermal facility weighed $63.6kg/m^2$ in total: the frame and solar thermal collector weighed $27.8kg/m^2$ and $35.8kg/m^2$, respectively. The standard broiler house required to be internally reinforced. This study suggested a plan for internal reinforcement and a feasible plan because there were problems with structural safety when installing solar thermal and photovoltaic systems.

• Journal of the Society of Cosmetic Scientists of Korea
• /
• v.37 no.1
• /
• pp.1-21
• /
• 2011

This review describes several kinds of emulsification methods for nanoemulsions and the application of nanoemulsions. Nanoemulsion droplet sizes fall typically in the range of 20 ~200 nm and show narrow size distributions. Although most of the publications on either oil-in-water (O/W) or water-in-oil (W/O) nanoemulsions have reported their formation by dispersion or high-energy emulsification methods, an increased interest is observed in the study of nano-emulsion formation by condensation or low-energy emulsification methods based on the phase transitions that take place during the emulsification process. Phase behaviour studies have shown that the size of the droplets is governed by the surfactant phase structure (bicontinuous microemulsion or lamellar) at the inversion point induced by either temperature or composition. Studies on nanoemulsion formation by the phase inversion temperature (PIT) method have shown a relation between minimum droplet size and complete solubilization of the oil in a microemulsion bicontinuous phase independently of whether the initial phase equilibrium is single or multiphase. Due to their small droplet size nanoemulsions possess stability against sedimentation or creaming with Ostwald ripening forming the main mechanism of nanoemulsion breakdown. An application of nanoemulsions is the preparation of nanoparticles using a polymerizable monomer as the disperse phase where nanoemulsion droplets act as nanoreactors, cosmetics and controlled drug delivery. In this review, we mainly focus on the cosmetics.

• Geophysics and Geophysical Exploration
• /
• v.11 no.1
• /
• pp.68-77
• /
• 2008

We have developed an inversion algorithm for loop-loop electromagnetic (EM) data, based on the localised non-linear or extended Born approximation to the solution of the 2.5D integral equation describing an EM scattering problem. Source and receiver configuration may be horizontal co-planar (HCP) or vertical co-planar (VCP). Both multi-frequency and multi-separation data can be incorporated. Our inversion code runs on a PC platform without heavy computational load. For the sake of stable and high-resolution performance of the inversion, we implemented an algorithm determining an optimum spatially varying Lagrangian multiplier as a function of sensitivity distribution, through parameter resolution matrix and Backus-Gilbert spread function analysis. Considering that the different source-receiver orientation characteristics cause inconsistent sensitivities to the resistivity structure in simultaneous inversion of HCP and VCP data, which affects the stability and resolution of the inversion result, we adapted a weighting scheme based on the variances of misfits between the measured and calculated datasets. The accuracy of the modelling code that we have developed has been proven over the frequency, conductivity, and geometric ranges typically used in a loop-loop EM system through comparison with 2.5D finite-element modelling results. We first applied the inversion to synthetic data, from a model with resistive as well as conductive inhomogeneities embedded in a homogeneous half-space, to validate its performance. Applying the inversion to field data and comparing the result with that of dc resistivity data, we conclude that the newly developed algorithm provides a reasonable image of the subsurface.

• Applied Chemistry for Engineering
• /
• v.28 no.6
• /
• pp.720-725
• /
• 2017

M(10)-Ni(5)/SBA-15(M=Ce, Nd, Sm) catalysts were prepared for the partial oxidation of methane (POM) to syngas. The catalysts were characterized by BET, TEM, and XPS. The BET-specific surface area and average pore size for M(10)-Ni(5)/SBA-15(M=Ce, Nd, Sm) were 538.8, 504.3, and $447.3m^2/g$ and 6.4, 6.8, and 7.1 nm, respectively. TEM results showed that the mesoporous hexagonol structure was formed for SBA-15, while the homogeneous dispersion of Ni and Ce particles on the surface was formed for Ce(10)-Ni(5)/SBA-15 caused by the confinment effect of SBA-15. XPS data confirmed that $Ce^{4+}$ and $Ce^{3+}$ on the surface catalyst have two oxidation states due to the lattice oxygen species ($O^{2-}$, $O^-$). The yields of POM to syngas over Ce(10)-Ni(5)/SBA-15 were 52.9% $H_2$ and 21.7% CO at 1 atm, 973 K, $CH_4/O_2=2$, $GHSV=1.08{\times}10^5mL/g_{cat.}{\cdot}h$, and these values were kept constant even after 75 h on streams. The same tendency of syngas yields was observed for M(10)-Ni(5)/SBA-15(M=Ce, Nd, Sm). These results confirm that the redox reaction of promoters including Ce, Nd, and Sm enhanced the stability and yield of catalysts.

• Journal of Energy Engineering
• /
• v.25 no.4
• /
• pp.176-183
• /
• 2016

This study relates to a polymer electrolyte membrane for improved performance fuel cell, were researched with respect to properties required for driving a fuel cell. The bis(4-fluorophenyl)phenyl phosphine oxide was sulfonated using fuming sulfuric acid. Synthetic hydrophilic oligomer and the hydrophobic oligomer and the block copolymers were prepared via aromatic nucleophilic substitution polycondensation. A block copolymer structure and degree of sulfonation was analyzed by $^1H$-NMR and gel permeation chromatography(GPC) analysis. Thermal stability was confirmed by thermogravimetric analysis(TGA), block copolymer was stable at high temperature(>$200^{\circ}C$), The ion conductivity was measured in order to demonstrate the performance of fuel cell. Synthesis membrane was the increase of temperature was improved conductivity up to 58 mS/cm due to the influence of the developed ion clusters. The phase separation of the polymer was observed to make AFM analysis.

• Journal of Sericultural and Entomological Science
• /
• v.41 no.1
• /
• pp.41-47
• /
• 1999

Silk fibroin dissolved in highly concentrated calcium chloride and ethanol mixture aqueous solution turned into gel under suitable conditions. Preparation conditions and properties of gel were investigated as a function of parameters such as pH of solution, fibroin concentration, glycerol concentration and molecular weight. When pH of silk fibroin aqueous solution was near the isoelectronic point(pH 3.9~4.0), gelation occurred rapidly and strength of gel was stonger than that of pH-unadjusted due to electrostatic repulsion decrease between silk fibroin macromolecules. As concentration of silk fibroin and glycerol was higher, gelation occurred more rapid. FT Infra-red spectra of freeze-dried fibroin gel showed that gelation was derived by intermolecular anti-parallel ${\beta}$-sheet structure formation. In addition to, it was found that white-precipitate occurred instead of gelation when aqueous silk fibroin was treated by enzyme(flavouzyme), however, after flavouzyme-treated silk fibroin aqueous solution was centrifugated gelation occurred instantly. The results of differential scanning thermal analysis and infra-red spectroscopy showed that thermal stability and crystallinity of enzyme-hydrolyzed fibroin are superior to those of unhydrolyzed fibroin.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.29 no.6
• /
• pp.308-316
• /
• 2019

Electron beam physical vapor deposition (EBPVD) is a conventional method to fabricate thermal barrier coating (TBC) of high temperature airfoil engine parts, such as blade etc. for its high temperature structural stability from the nature of columnar growth behavior. For the high quality of TBC by EBPVD, the structural factors, such as growth behavior, thickness uniformity and so on, should be managed to obtain the coating which satisfied the required specifications of usable level of mechanical and thermal properties. In this study, the growth behavior and structure variations of 7YSZ (7 wt% yttria stabilized zirconia) coatings with different configurational deposition parameters for the specimens which have turbine blade shape mock-up were investigated. Growth behavior of coatings were studied by comparing computational modeling of evaporation behavior with actual deposition process using e-beam source.