• Journal of the Society of Naval Architects of Korea
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• v.58 no.4
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• pp.262-270
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• 2021

Consumption of Liquefied Natural Gas (LNG) has increased due to environmental pollution; therefore, the need for LNG carriers can efficiently transport large quantities of LNG, is increased. In various types of LNG Cargo Containment System (CCS), Membrane-type MARK-III composed of composite materials is generally employed in the construction of an LNG carrier. Among composite materials in a Mark-III system, glass-fiber composites act as a secondary barrier to prevent the inner hull structure from leakage of LNG when the primary barrier is damaged. Nevertheless, several cases of damage to the secondary barriers have been reported and if damage occurs, LNG can flow into the inner hull structure, causing a brittle fracture. To prevent those problems, this study conducted the applicability assessment of composite material manufactured by bonding glass-fiber and aluminum with epoxy resin and increasing layer from three-ply (triplex) to five-ply (pentaplex). Tensile tests were performed in five temperature points (25, -20, -70, -120, and -170℃) considering temperature gradient in CCS. Scanning Electron Microscopy (SEM) and Coefficient of Thermal Expansion (CTE) analyses were carried out to evaluate the microstructure and thermos-mechanical properties of the pentaplex. The results showed epoxy resin and increasing layer number contributed to improving the mechanical properties over the whole temperature range.

• Clean Technology
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• v.28 no.2
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• pp.123-130
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• 2022

Nanoparticles are used in various fields such as chemistry, medicine, the environment, and information and communication. With the increasing use of engineered nanomaterials, exposure to nanoparticles is expected to increase in the workplace and the environmental media. However, while nanotechnology industries are expanding, research on the exposure assessment of nanomaterials to humans and the environment is only at a beginning stage. Especially, if nanoparticles with a size of 100 nm or less that are contained in nano-products are released unintentionally, they may pose potential risks to the human body through breathing or skin exposure. Therefore, in this work, the possibility of potential exposure of nanoparticles moving from the laboratory to the office was confirmed, and nanoparticle safety guidelines are proposed. A nano-collector was used to detect nanoparticles in the atmosphere, and through use of a scanning mobility particle sizer it was found that nanoparticle concentrations in the laboratory and the office tended to be similar. On the assumption that nanoparticles attached to a lab-coat move out of the laboratory, a lab-coat to which nanocarbon black was attached was shaken and the concentration of the remaining particles on the lab-coat determined. The results confirmed that sufficient amounts of nanoparticles attached to the lab-coat could move from the laboratory to the office along the path of a researcher; thus, safety guidelines for the handling of lab-coat nanoparticles are required.

• Research in Plant Disease
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• v.12 no.1
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• pp.15-19
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• 2006

This study was carried out to know pathogenicity of the pathogen isolated in several location of Korea and penetration mechanism of the Pseudocercospora vitis ($(L\acute{e}v)$.) Speg. Inoculation tests at room temperature were performed on both sides of leaves with different isolates of the fungus. The typical symptoms appeared on the abaxial leaf surface, but no symptom was observed on the adaxial leaf surface with all isolates. The average incubation period was nine days, since all symptoms appeared from 8 to 10 days after inoculation. In order to know the mechanism of invasion of P. vitis to grapevine, the behavior of penetration hyphae through stomata were compared in two cultivars having different level of resistance. In order to know the mechanism of resistance of grape vine to P.vitis, two cultivars having different level of resistance were compared by counting the numbers and measuring size of the stomata per leaf. In a susceptible cultivar Campbell Early, the number of stomata was more than that of a resistance cultivar 'Kyoho'. In a susceptible cultivar 'Campbell Early', the fungus entered readily into stomata after inoculation. However, in a resistant cultivar 'Kyoho', the fungus seemed to pass over or surrounded only the guard cells. In comparison of height of guard cells of stomata between the two cultivars, significant differences were observed by scanning electron microscopy and light microscopy. The height of guard cells of 'Campbell Early' showed a little higher than those of 'Kyoho' known to be resistant to the fungus.

• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.4
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• pp.261-283
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• 2023

This study aimed to review the performance stability of PET (Polyethylene terephthalate) fiber reinforcing materials among the synthetic fiber types for which the application of performance reinforcing materials to fiber-reinforced concrete is being reviewed by examining short-term and long-term performance changes. To this end, the residual performance was analyzed after exposing the PET fiber to an acid/alkali environment, and the flexural strength and equivalent flexural strength of the PET fiber-reinforced concrete mixture by age were analyzed, and the surface of the PET fiber collected from the concrete specimen was examined using a scanning microscope (SEM). The changes in were analyzed. As a result of the acid/alkali environment exposure test of PET fiber, the strength retention rate was 83.4~96.4% in acidic environment and 42.4~97.9% in alkaline environment. It was confirmed that the strength retention rate of the fiber itself significantly decreased when exposed to high-temperature strong alkali conditions, and the strength retention rate increased in the finished yarn coated with epoxy. In the test results of the flexural strength and equivalent flexural strength of the PET fiber-reinforced concrete mixture, no reduction in flexural strength was found, and the equivalent flexural strength result also did not show any degradation in performance as a fiber reinforcement. Even in the SEM analysis results, no surface damage or cross-sectional change of the PET reinforcing fibers was observed. These results mean that no damage or cross-section reduction of PET reinforcing fibers occurs in cement concrete environments even when fiber-reinforced concrete is exposed to high temperatures in the early stage or depending on age, and the strength of PET fibers decreases in cement concrete environments. The impact is judged to be of no concern. As the flexural strength and equivalent flexural strength according to age were also stably expressed, it could be seen that performance degradation due to hydrolysis, which is a concern due to the use of PET fiber reinforcing materials, did not occur, and it was confirmed that stable residual strength retention characteristics were exhibited.

• Journal of the Korean Magnetics Society
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• v.17 no.1
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• pp.18-21
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• 2007

The hexagonal $HoMn_{1-x}-Fe_xO_3$(x=0.00, 0.05) thin films were prepared using pulsed laser deposition(PLD) method on $Pt/Ti/SiO_2/Si$ substrate. The microstructure and magnetic properties have been studied by x-ray diffraction(XRD), atomic force microscopy (AFH), scanning electron microscope(SEM:), x-ray photoelectron spectroscopy(XPS), and conversion electron $M\"{o}ssbauer$ spectroscopy(CEMS). From the analysis of the x-ray diffraction patterns, the crystal structure for all films was found to be a hexagonal($P6_3cm$), which was preferentially grown along(110) direction. The lattice constant $c_0$ of the film with x=0.05 was close to that of single crystal, whereas lattice constant $a_0$ with respect to single crystal shows a slight decrease. This difference of lattice parameters between film and single crystal was caused by the lattice mismatch between the film and $Pt/Ti/SiO_2/Si$ substrate. Conversion electron $M\"{o}ssbauer$ spectrum of $HoMn_{0.95}Fe_{0.05}O_3$ thin film shows an asymmetry doublet absorption ratio at room temperature, which is due to the oriented direction of crystallographic domains. This is corresponding with analysis of x-ray diffraction. The quadrupole splitting(${\Delta}E_Q$) at room temperature is found to be $1.62{\pm}0.01mm/s$. This large ${\Delta}E_Q$ was caused by asymmetry environment surrounding Fe ion.

• Korean Journal of Heritage: History & Science
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• v.55 no.1
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• pp.175-198
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• 2022

With the development of technology, the methods of digitally converting various forms of analog information have become common. As a result, the concept of recording, building, and reproducing data in a virtual space, such as digital heritage and digital reconstruction, has been actively used in the preservation and research of various cultural heritages. However, there are few existing research results that suggest optimal scanners for small and medium-sized relics. In addition, scanner prices are not cheap for researchers to use, so there are not many related studies. The 3D scanner specifications have a great influence on the quality of the 3D model. In particular, since the state of light reflected on the surface of the object varies depending on the type of light source used in the scanner, using a scanner suitable for the characteristics of the object is the way to increase the efficiency of the work. Therefore, this paper conducted a study on nine small and medium-sized buried cultural properties of various materials, including earthenware and porcelain, by period, to examine the differences in quality of the four types of 3D scanners. As a result of the study, optical scanners and small and medium-sized object scanners were the most suitable digital records of the small and medium-sized relics. Optical scanners are excellent in both mesh and texture but have the disadvantage of being very expensive and not portable. The handheld method had the advantage of excellent portability and speed. When considering the results compared to the price, the small and medium-sized object scanner was the best. It was the photo room measurement that was able to obtain the 3D model at the lowest cost. 3D scanning technology can be largely used to produce digital drawings of relics, restore and duplicate cultural properties, and build databases. This study is meaningful in that it contributed to the use of scanners most suitable for buried cultural properties by material and period for the active use of 3D scanning technology in cultural heritage.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.222-222
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• 2012

Metal oxide gas sensors based on semiconductor type have attracted a great deal of attention due to their low cost, flexible production and simple usability. However, most works have been focused on n-type oxides, while the characteristics of p-type oxide gas sensors have been barely studied. An investigation on p-type oxides is very important in that the use of them makes possible the novel sensors such as p-n diode and tandem devices. Monoclinic cupric oxide (CuO) is p-type semiconductor with narrow band gap (~1.2 eV). This is composed of abundant, nontoxic elements on earth, and thus low-cost, environment-friendly devices can be realized. However, gas sensing properties of neat CuO were rarely explored and the mechanism still remains unclear. In this work, the neat CuO layers with highly ordered mesoporous structures were prepared by a template-free, one-pot solution-based method using novel ink solutions, formulated with copper formate tetrahydrate, hexylamine and ethyl cellulose. The shear viscosity of the formulated solutions was 5.79 Pa s at a shear rate of 1 s-1. The solutions were coated on SiO2/Si substrates by spin-coating (ink) and calcined for 1 h at the temperature of $200{\sim}600^{\circ}C$ in air. The surface and cross-sectional morphologies of the formed CuO layers were observed by a focused ion beam scanning electron microscopy (FIB-SEM) and porosity was determined by image analysis using simple computer-programming. XRD analysis showed phase evolutions of the layers, depending on the calcination temperature, and thermal decompositions of the neat precursor and the formulated ink were investigated by TGA and DSC. As a result, the formation of the porous structures was attributed to the vaporization of ethyl cellulose contained in the solutions. Mesoporous CuO, formed with the ink solution, consisted of grains and pores with nano-meter size. All of them were strongly dependent on calcination temperature. Sensing properties toward H2 and C2H5OH gases were examined as a function of operating temperature. High and fast responses toward H2 and C2H5OH gases were discussed in terms of crystallinity, nonstoichiometry and morphological factors such as porosity, grain size and surface-to-volume ratio. To our knowledge, the responses toward H2 and C2H5OH gases of these CuO gas sensors are comparable to previously reported values.

• Journal of the Mineralogical Society of Korea
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• v.29 no.1
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• pp.23-34
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• 2016

Tsogttsetsii area, an intrusive complex associated with Cu porphyry mineralization, is located in the Gurvansaikhan island arc terrane of the Central Asian Orogenic belt, Southern Mongolia. We performed a reconnaissance survey in Tsogttsetsii area. Cu mineralization in Tsogttsetsii area is porphyry Cu type related with alkali granite intruded in Permian. Mineralogical and textural properties of the ores and associated minerals were analyzed using X-ray diffraction, thin section petrography, and Scanning electron microscopy-Energy dispersive spectroscopy (SEM-EDS). Ore minerals identified in polarizing microscope are magnetite, pyrite and bornite. Propylitic alteration zone occurs broadly in the area where malachite occurrences are shown to be spread intensively in alkali granite area. Quartz, sericite, chlorite and epidote were observed in the alteration zone samples. As results of XRD and SEM-EDS analysis, samples of copper oxides were composed mainly of malachite, cuprite and small amounts of quartz. Average and maximum Cu contents of samples collected from malachite occurrences area are 759 ppm and 6190 ppm, respectively. The characteristics of mineralization in Tsogttsetsii area is similar to Oyu Tolgoi Cu-Au (Mo) deposit and Tsagaan Suvarga Cu-Mo deposit which are 56 km south and 120 km northeast from Tsogttsetsii area, respectively. Characteristics of the study area, such as the geology, tectonic environment, lithology, mineralization, and alterations of the rocks within the survey area, resemble the characteristics of other porphyry deposits. Therefore further exploration including Induced Polarization (IP) survey for identifying subsurface orebody is required.

• Journal of the Korean Applied Science and Technology
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• v.34 no.1
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• pp.50-57
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• 2017

Zinc oxide is, one of metal oxide semiconductor, harmless to human and environment-friendly. It has excellent chemical and thermal stability properties. Wurtzite-zinc oxide is a large band gap energy of 3.37 eV and high exciton binding energy of 60 meV. It can be applied to various fields, such as solar cells, degradation of the dye waste, the gas sensor. The photocatalytic activity of zinc oxide is varied according to the particle shape and change of crystallinity. Therefore, It is very important to specify the additives and the experimental variables. In this study, the zinc oxide were synthesized by using a microwave assisted hydrothermal synthesis. The precursor was used as the zinc nitrate, the pH value was controlled as 11 by NaOH. Surfactants are the ethanolamine, cetyltrimethylammonium bromide, sodium dodecyl sulfate, sorbitan monooleate was added by changing the concentration. The composite particles had the shape of a star-like, curcular cone, seed shape, flake-sphere. Physical and chemical properties of the obtained zinc oxide was characterized using x-ray diffractometer, field emission scanning electron microscopy, thermogravimetric analysis and optical properties was characterized using UV-visible spectroscopy, photoluminescence and raman spectroscopy.

• Korean Journal of Clinical Pharmacy
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• v.21 no.3
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• pp.256-269
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• 2011

Omega-3 fatty acids are a specific type of unsaturated fat that the body cannot manufacture on its own, so they must be obtained from food which is essential fatty acids (EFAs). Omega-3 fatty acids consist of three types which are a-Linolenic Acid (ALA), Eicosapentaenoic (ELA), and Docosahexaenoic Acid (DHA). Especially, EFAs help to prevent skin and hair drying, acne, eczema, prevention from allergies, brittle nails, rashes, and tiny lumps. The aim of this study is to investigate improvement and protection for hair damaged by chemical treatment with omega-3 formulated shampoo. We selected virgin hair sample and divided into two groups for bleaching once and three times and then damaged hair by changing the number of hair bleaching (twice with interval of 15 minutes). Each bleached hair was treated by five different kinds of shampoo (Control, Horse shampoo, DHA shampoo, EPA shampoo, Omega-3 shampoo mixture). Apart from this, EPA/DHA 2, 5, 8, 10 and 12% shampoo were prepared and treated to hair for comparing rate of progress in damaged hair. To quantify improved condition of damaged hair, we performed Scanning Electron Microscope (SEM) for ultrastructure of damaged hair fraction, measurement of thickness change and BCA Protein Assay for recovery rate of damaged hair. The moisture in hair was measured by Thermal analysis machine. In results, we observed the particle of hair surface damaged by bleaching treatment were well improved with treatment with EPA and DHA shampoo. Also, quantity of protein was lowered with higher concentration of EPA & DHA i.e., 8 and 12 % then compared with horse oil shampoo in three times treatment group. It shows that bleached hair have been recovered by treating rapidly and get protective coat. In conclusion, EPA and DHA shampoo improved damaged hair, especially with EPA / DHA 12% shampoo. Also, EPA shampoo could protect the damaged hair depending on increasing concentration of EPA. Therefore, we conclude omega-3 shampoo could make damaged hair protect and get healthy hair environment.