• Macromolecular Research
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• v.17 no.2
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• pp.128-132
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• 2009

Fucoidan, a sulfated polysaccharide derived from brown seaweed, is an important material valued for its various biological functions, including anti-coagulation, anti-aging, and immune system support. In this study, we examined the potential of fucoidan as a novel emulsifying agent in BSA (bovine serum albumin)-stabilized emulsion at a neutral pH. We measured the dispersed oil-droplet size, surface zeta-potential and creaming formation of 0.5 wt% BSA emulsion (20 wt% oil traction) in the absence and presence of fucoidan. The average particle size and zeta-potential value were 625.4 nm and -30.91 mV in only BSA-stabilized emulsion and 745.2 nm and -44.2 mV in 1.0 wt% fucoidan-added BSA emulsion, respectively. This result suggested that some positive charges of the BSA molecules interacted with the negative charges of fucoidan to inhibit the flocculation among the oil droplets. The creaming rate calculated from the backscattering data measured by Turbiscan dramatically decreased in 1.0 wt% fucoidan-added BSA emulsion during storage. Accordingly, the repulsion forces induced among the oil particles coated with 1.0 wt% fucoidan in emulsion solution resulted in significantly increased emulsion stability. The turbidity of the BSA-stabilized emulsion at 500 nm decreased during five days of storage. However, the fucoidan-added BSA emulsion exhibited a higher value of turbidity than the BSA-stabilized emulsion did. In conclusion, an anionic sulfated fucoidan lowered the surface zeta-potential of BSA-coated oil droplets via the electrostatic interaction, and subsequently inhibited the flocculation among the oil droplets, thereby clearly minimizing the creaming and phase separation of the emulsion.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.631-631
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• 2013

Battery has major drawbacks including its size and life expectancy, and environmental problem. As an alternative, energy harvesting is emerging as a potential solution to replace battery along with more energy-efficient IT devices. The idea of harnessing energy from our living environment is sustainable, semi-permanent, and eco-friendly. Also, unlike battery, energy harvester does not require much space to store energy. Therefore, energy harvesting can provide a better source of power for small, portable, and wireless devices. Among various ways of harvesting energy from our surroundings, triboelectricity is chosen due to its potential to be miniaturized, and efficient. Triboelectric effect occurs as two different materials with different polarity of charge separation come into contact through friction, and then become separated so that electric potential difference is achieved. In this research, such characteristic of triboelectricity is used as a way to convert ambient mechanical energy into electric energy.Series of recent researches have shown promising results that the triboelectric energy harvester can be simple and cost effective. However, sufficient electricity level required to operate mobile devices has not yet been achieved.In this research, our group focuses on the design and optimization of triboelectric energy harvesting device to enhance its output. By using maskless lithography to pattern Kapton film and silicon substrate, which is used as a mold for PDMS thin layer, and sputtering metal electrodes on each side, we fabricate and demonstrate different designs of triboelectric energy harvester that utilizes the contact electrification between a polymer thin film and a metal thin foil. In order to achieve optimized result, the output voltage and current are measured under diverse conditions, which include different surface structure and pattern, material, and the gap between layers.

• Membrane Journal
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• v.25 no.2
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• pp.162-170
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• 2015

In this study, gas permeability of polyimide materials having a various amine group was measured and molecular dynamics was used to analyze the dynamic characteristics of the gas molecules in the polyimide by calculating the position and velocity of the gas molecules with change of the time. The gas permeability of polyimide membrane having substitution site which increase free volume in the polymer was increased. However, polyimide with rigid structure showed decreased gas permeability. As a result of analyzing the change in the gas permeation behavior using molecular dynamics simulations, we confirmed that the results show the same tendency with actual measurements of the gas permeability.

• Bulletin of the Korean Chemical Society
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• v.33 no.11
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• pp.3727-3734
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• 2012

An analytical method has been developed for the rapid determination of perfluorinated compounds (PFCs) in human serum samples. The extraction and purification of PFCs from human serum were performed by the modified method of previous report. Ten PFCs were rapidly separated within 3.3 min by C18-monolithic column liquid chromatography (LC) and detected by electrospray ionization (ESI) tandem mass spectrometry (MS/MS) in negative ion mode. The runtime of PFCs on monolithic column LC was up to 4-fold faster than that on conventional column LC. The effect of triethylamine (TEA) to the mobile phase has investigated on the overall MS detection sensitivity of PFCs in ESI ionization. Quantification was performed by LC-MS/MS in multiple-ion reaction monitoring (MRM) mode, using $^{13}C$-labeled internal standards. Method validation was performed to determine recovery, linearity, precision, and limits of quantification, followed by, the analysis of a standard reference material (SRM 1957 from NIST). The overall recoveries ranged between 81.5 and 106.3% with RSDs of 3.4 to 16.2% for the entire procedure. The calibration range extended from 0.33 to 50 $ng\;mL^{-1}$, with a correlation coefficient ($R^2$) greater than 0.995 and the limits of quantification with 0.08 to 0.46 $ng\;mL^{-1}$. This approach can be used for rapid and sensitive quantitative analysis of 10 PFCs in human serum with high performance and accuracy.

• Journal of the Korea Concrete Institute
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• v.17 no.6 s.90
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• pp.939-946
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• 2005

The stiffness properties of heterogeneous concrete materials and their degradation were investigated at different-levels of observations with aids of the opportunities and limitations of multi-resolution wavelet analysis. The successive Haw transformations lead to a recursive separation of the stiffness properties and the response into coarse-and fine-scale features. In the limit, this recursive process results in a homogenization parameter which is an average measure of stiffness and strain energy capacity at the coarse scale. The basic concept of multi-resolution analysis is illustrated with one and two-dimensional model problems of a two-phase particulate composite representative of the morphology of concrete materials. The computational studies include the meso-structural features of concrete in the form of a hi-material system of aggregate particles which are immersed in a hardened cement paste taking due to account of the mismatch of the two elastic constituents.

• Journal of Electrochemical Science and Technology
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• v.2 no.1
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• pp.1-7
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• 2011

Nanocomposites of reduced graphene oxide and manganese (II,III) oxide can be synthesized by the freeze-drying process of the mixed colloidal suspension of graphene oxide and manganese oxide, and the subsequent heat-treatment. The calcined reduced graphene oxide-manganese (II,III) oxide nanocomposites are X-ray amorphous, suggesting the formation of homogeneous and disordered mixture without any phase separation. The reduction of graphene oxide to reduced graphene oxide upon the heat-treatment is evidenced by Fourier-transformed infrared spectroscopy. Field emission-scanning electronic microscopy and energy dispersive spectrometry clearly demonstrate the formation of porous structure by the house-of-cards type stacking of reduced graphene oxide nanosheets and the homogeneous distribution of manganese ions in the nanocomposites. According to Mn K-edge X-ray absorption spectroscopy, manganese ions in the calcined nanocomposites are stabilized in octahedral symmetry with mixed Mn oxidation state of Mn(II)/Mn(III). The present reduced graphene oxide-manganese oxide nanocomposites show characteristic pseudocapacitance behavior superior to the pristine manganese oxide, suggesting their applicability as electrode material for supercapacitors.

• Korean Institute of Interior Design Journal
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• v.21 no.6
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• pp.271-279
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• 2012

Among the community-based cultural facilities, public libraries are places for social and educational purpose that improve the education of the resident, the expansion of the basic cultural education, communication between the members of society, and the accumulations and preservations of the culture. Public libraries should be a local cultural facility that expresses the value of a community. This study aims to analyze the design expression of publicness in a public branch library as a community-based cultural space through the study of branch library in the U.S. This study focused on the most future-oriented and innovative Ten New Landmark Libraries in the United States selected by Library Journal magazine in 2011. Among the selected libraries, three branch libraries which belongs Arizona Maricopa County were included in the study. The results of this study are as follows. First, the sites of the branch libraries vary geographically, but the libraries increase accessibility are caused by unique appearances and design concept of intellectual interest. Second, the floor plan shows the separation of meeting rooms and faculty space from the public space and has visual and spatial open space by high ceiling of the reading room. Third, multi-functional public space for residents are meeting rooms, the external patios for reading, galleries, cafes, libraries-shops which provides a variety of cultural programs, activities, and the opportunity to socialize neighbors. Fourth, branch Libraries have unique designs that harmonizes with nearby places to reflect locality, giving the locals a sense of pride in their community. Fifth, concrete brick and metal panel were used as finishing material for the practicality of maintenance. In particular, transparent glass envelope allows the locals to stay for long time due to openness and brightness of space.

• Resources Recycling
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• v.24 no.4
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• pp.50-55
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• 2015

In this study, we have investigated solvent extraction of Ga and recovery of high pure Ga solution from MOCVD dust for manufacturing of LED chip. Effect of extractan, concentration of extractant were examined for choosing the more effective extractant and high pure Ga solution was fabricated by multi-stage extraction/stripping process. For extraction/separation of Ga based on the analysis of raw-material in previous study, 3 different extractants PC 99A, DP-8R, Cyanex 272 has been investigated and the extraction efficiency of 1.5 M Cyanex 272 was 43.8%. It was conformed that extraction efficiency of Ga was 83% in multi-stage extraction and 5N high purity Ga stripping solution without impurities also obtained.

• Clean Technology
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• v.20 no.4
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• pp.367-374
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• 2014

Several experiments have been done to investigate the removal of hydrogen sulfide ($H_2S$) synthetic gas from biogas streams by means of chemical absorption and chemical reaction with 0.1-1 M Fe/EDTA solution. The roles of Fe/EDTA were studied to enhance the removal efficiency of hydrogen sulfide because of oxidizing by chelate. The motivation of this investigation is first to explore the feasibility of enhancing the toxic gas treatment in the biogas facility. The biogas purification strategy affords many advantages. For instance, the process can be performed under mild environmental conditions and at low temperature, and it removes hydrogen sulfide selectively. The end product of separation is elemental sulfur, which is a stable material that can be easily disposed with minor potential for further pollution. As the Fe-EDTA concentration increased, the conversion rate of hydrogen sulfide increased because of the high stability of Fe-EDTA complex. pH as an important environmental factor was 9.0 for the stability of chemical complex in the oxidation of hydrogen sulfide.

• Journal of Convergence for Information Technology
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• v.7 no.5
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• pp.103-109
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• 2017

A pressure vessel is a cylindrical container that accommodates a pressurized fluid. In real life, there are propane canisters and butane canisters. According to data from the Korea Gas Safety Corporation, The number of domestic gas accidents is average 33 cases of domestic gas accidents occurred per year and 20.8 for mobile butane gases. The purpose of this study was to investigate a method to prevent this kind of explosion. Common studies include forced drain through safe holes, forced separation of butane canisters, and manufacturing of high-strength steel. This paper uses a concept that reduces stress inside the cylinder using prestressed method that precede compression. In other words, install a long liner in both ends of the pressure vessel. I want to develop a safety device that acts like a gas intermediate valve.