• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.4
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• pp.191-195
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• 2017

The microstructures of nonwoven fabric with and without nanofibers used as a filter for air purification type mask were investigated using scanning electron microscope. Moreover, we proposed a new mask design which is effective in the improvement of the fine dust blocking property. When comparing to nonwoven fabrics of which an average diameter was $25{\mu}m$, the nanofibers formed by the electrospinning process had a tight mesh structure arranged irregularly with a relatively large specific surface area, which could be associated with their much smaller diameter ranging from 25 to 120 nm. Such a prominent structural feature at nanofibers led to mechanical adsorption of fine particles, resulting in enhancement of filtering behavior maintaining high permeability. In addition to the excellent performance of the mask filter, wearing the mask properly is expected to maximize the blocking property of fine dust. To meet such a requirement, a new mask design that can be closely attached to the face in order to effectively block fine dust entering the gap between the face and the mask.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.1
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• pp.38-44
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• 2010

In this paper, the higher order FDTD(Finite-Difference Time-Domain) method is used to obtain the frequency response characteristics of the cylindrical metamaterial slab. FDTD method is one of strongest electromagnetic numerical method which is widely used to analyze the metamaterial structure because of its simplicity and the dispersive FDTD equation which has the dispersive effective dielectric constant and permeability are derived to analyze the metamaterials. This derived dispersive FDTD equation has no errors in analyzing the dielectric materials but there are some time and frequency errors in case of analyzing the metamaterials. We used the higher order FDTD method to obtain the accurate frequency response of the metamaterials. Comparisons between the dispersive FDTD method and the higher order FDTD method are performed in this paper also. From the results, we concluded that more accurate frequency response for various metamaterials applications can be obtained using the proposed method in this paper.

• Journal of the Korean GEO-environmental Society
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• v.19 no.10
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• pp.5-11
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• 2018

The PBD (Plastic Board Drain) method is one of effective ground improvement methods on the soft dredging reclamation ground. This method has outstanding economic efficiency and constructability, and it is widely used for the soft ground improvement. However, the PBD method reduces permeability and drainage capacity of the ground due to the long construction period. Therefore, the nano coated Plastic drain board (PDB) was developed to solve problems. It is the non-metallic electrode and improves the weakness of the PBD method by using electric force of the electro-osmosis method. Various researches have been conducted to apply the nano coated PDB, but these researches were limited to model tests in laboratory. In this study, model and field tests were conducted to assess field applicability of the nano coated PDB. The result showed that the nano coated PDB had the better effect on the ground improvement compared to the normal PDB.

• Journal of the Korea Concrete Institute
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• v.26 no.5
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• pp.607-614
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• 2014

The purpose of this dissertation was to investigate the effect of mineral admixtures, such as fly ash, blast furnace slag powder, meta kaolin and silica fume, on the basic properties and durability of crushed sand shotcrete, selecting a series of shotcrete mixtures with a variable admixture. Compressive strength increased as the content of mineral admixtures increased, specially it was the most effective when using meta kaolin both at sample specimen and core after shotcreting. Rapid chloride ion permeability test and sulfuric acid resistance test showed that both durability increased as the substitute rate of mineral admixture increased. In air void analysis with image analysis, the targeted the spacing factor and specific surface were not satisfied because air-entrained agent was not used.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.9
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• pp.919-925
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• 2011

In this paper, we designed and analyzed a 3D isotropic bulk structure consisting of thin wires and SRR's(Split Ring Resonator) with which the permittivity and permeability can be controlled at the same time. For the 3D isotropic bulk structure, first of all, the geometry seen by three main axes must look alike. Thus, we adopted the orthogonal thin wires and symmetrical SRR's. As a result, we constructed metamaterial bulk structures of which effective relative permittivity and permiability are about -0.6 and -1.5, respectively. Its refractive index is about -0.95 in each direction(x, y and z direction). The computed Brillouin dispersion diagram also showed that the proposed structure is almost near isotropic.

• The Korean Journal of Community Living Science
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• v.23 no.3
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• pp.317-328
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• 2012

In this study, printing was introduced to the common dip-dyeing method of persimmon juice dyeing so as to develop two different colored persimmon juice dyed fabrics with printings of 'jorangmal' patterns (a national monument) instead of producing a plain textile. Following are the results of a comparative study between the persimmon dyed fabric and undyed fabric, both with printings, in terms of its properties, and hand values. Cotton and rayon were chosen as samples and were compared separately. Firstly, the samples showed differences in terms of clarity and visual sensation depending on the presence of persimmon dye, even if the same pattern and color was used. Secondly, the air permeability of two samples improved after persimmon dyeing even though their thickness increased, and their moisture regain increased as well in all humidity conditions. Thirdly, protectiveness against UV increased in dyed samples, and sweat, sunlight, and compound colorfastness improved in printed dye-fabrics compared to plain dyed ones. Therefore, printing proved to be effective in preventing discoloration. Fourthly, tensile linearity and resilience, bending rigidity, compressive linearity and resilience, and shearing stiffness increased more in the dyed samples compared to undyed ones. However, shearing recovery decreased in both dyed fabrics. Fifthly, the result of its hand value showed that Koshi value increased in all samples than undyed ones, whereas Fukurami, Numeri, and Softosa values decreased. Incorporating printing in persimmon dyeing process could expect creative outcomes not only in today's diverse fashion but in areas of arts or crafts as well.

• Membrane and Water Treatment
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• v.1 no.2
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• pp.121-137
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• 2010

This work presents inexpensive inorganic precursor formulations to yield submicron range symmetric ceramic microfiltration (MF) membranes whose average pore sizes were between 0.1 and $0.4{\mu}m$. Incidentally, the sintering temperature used in this work was about 800 to $950^{\circ}C$ instead of higher sintering temperatures ($1100^{\circ}C$) that are usually deployed for membrane fabrication. Thermogravimetric (TGA) and X-Ray diffraction (XRD) analysis were carried out to evaluate the effect of temperature on various phase transformations during sintering process. The effect of sintering temperature on structural integrity of the membrane as well as pore size distribution and average pore size were evaluated using scanning electron microscopy (SEM) analysis. The average pore sizes of the membranes were increased from 0.185 to $0.332{\mu}m$ with an increase in sintering temperature from 800 to $950^{\circ}C$. However, a subsequent reduction in membrane porosity (from 34.4 to 19.6%) was observed for these membranes. Permeation experiments with both water and air were carried out to evaluate various membrane morphological parameters such as hydraulic pore diameter, hydraulic permeability, air permeance and effective porosity. Later, the membrane prepared with a sintering temperature of $950^{\circ}C$ was tested for the treatment of synthetic oily waste water to verify its real time applicability. The membrane exhibited 98.8% oil rejection efficiency and $5.36{\times}10^{-6}\;m^3/m^2.s$ permeate flux after 60 minutes of experimental run at 68.95 kPa trans-membrane pressure and 250 mg/L oil concentration. Based on retail and bulk prices of the inorganic precursors, the membrane cost was estimated to be $220 /$m^2$ and $1.53 /$m^2$, respectively.

• Korean Journal of Crystallography
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• v.12 no.3
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• pp.182-187
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• 2001

The purpose of this study is to investigate the degradation of soft magnetic properties of Fe-Hf-N thin films after annealing in vacuum. They were annealed at 450℃∼650℃. The microstructure and crystal phase of the selected area of the thin films were analyzed by TEM and SAD. After annealing at 450℃-600℃, the coercivity of the films increased by 0.2 Oe and the effective permeability decreased by 1500 as compared with them before annealing due to the growth of α-Fe crystallites. The saturation magnetic flux density of the films increased by 0.5 KG after annealing under 600℃. However, the soft magnetic properties of the film annealed at 650℃ degraded abruptly, which was attributed to the destruction of nano-crystalline microstructure of the film due to the rapid growth of α-Fe crystallites with the segregation of N sited in the α-Fe lattice into HfN.

• Applied Chemistry for Engineering
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• v.28 no.6
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• pp.679-684
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• 2017

Hydrated liquid crystalline vesicles incorporating a edge activator, which confers flexibility to the vesicle membranes, were prepared and niacinamide was encapsulated in them. The formation of liquid crystalline phases and their thermal phase transitions were investigated by polarized optical microscopy and differential scanning calorimetry (DSC), respectively. Droplet sizes of the vesicles were reduced to several tens of nanometers by incorporating edge activators, such as sodium deoxycholate, lysolecithin, or polysorbate 80. The amount of niacinamide permeated into a pig skin increased greatly using the hydrated liquid crystalline vesicles compared to the case where niacinamide was applied in an aqueous solution state. The vesicles incorporating 10% sodium deoxycholate increased the amount of niacinamide permeated nearly four times. These results suggest that edge activators are effective in improving the skin permeability of vesicles.

• Research in Plant Disease
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• v.12 no.3
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• pp.164-167
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• 2006

Potential factors favoring black stains during fruit development in Pyrus serotina was investigated. Black stain occurred from young fruit till harvest. The color of the affected fruits in early stage was black or light reddish brown, but turned to light brown over time. Fruit bags with lower light transmission and inner bags with poor aeration stimulated the symptoms, and high water permeability of the bags increased the black stain. Much rain and/or poor light transmission and aeration within the canopies also favored the occurrence of black stain. Diminution of pathogenic fungi density by lime sulfur was more effective than the canopy spray of fungicide for the prevention of black stain.