• Journal of Powder Materials
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• v.21 no.2
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• pp.119-123
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• 2014

Pt has been widely used as catalyst for fuel cell and exhausted gas clean systems due to its high catalytic activity. Recently, there have been researches on fabricating composite materials of Pt as a method of reducing the amount of Pt due to its high price. One of the approaches for saving Pt used as catalyst is a core shell structure consisting of Pt layer on the core of the non-noble metal. In this study, the synthesis of Pt shell was conducted on the surface of $TiO_2$ particle, a non-noble material, by applying ultraviolet (UV) irradiation. Anatase $TiO_2$ particles with the average size of 20~30 nm were immersed in the ethanol dissolved with Pt precursor of $H_2PtCl_6{\cdot}6H_2O$ and exposed to UV irradiation with the wavelength of 365 nm. It was confirmed that Pt nano-particles were formed on the surface of $TiO_2$ particles by photochemical reduction of Pt ion from the solution. The morphology of the synthesized Pt@$TiO_2$ nano-composite was examined by TEM (Transmission Electron Microscopy).

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6A
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• pp.379-387
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• 2012

This study investigates free vibration characteristics of new energy harvesting multi-layer block structures with different geometrical shapes using solid and shell finite elements and evaluate their piezoelectric effect on experiments. The two and three-dimensional finite element (FE) delamination models for block structures described in this paper is attractive not only because it shows excellent accuracy in analysis but also it shows the entire vibration mode shape. The FE model using ABAQUS is used for studying free vibrations of multi-layer block structures for various tip mass and PZT. In particular, new results reported in this paper are focused on the significant effects of the global and local vibration modes for various parameters, such as size of block shape, existence of tip mass and hole, and location of tip mass and PZT. In addition, we evaluate the power generation capacity of developed energy block structures through a laboratory-scale experiment.

• 한국해양학회지
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• v.30 no.1
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• pp.1-12
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• 1995

The modal analysis was carried out for the total of 216 subface sediments of southern continental shelf of Korean peninsula. Sandy mud or muddy sand distributed in the range of 70∼100 m water depth revealed the bimodal type (sand and mud components). The relations of textural parameters obtained from every modal were consistent with those of shallow marine sediments. The characteristics of sand component between bimodal were as follows: (1) the distributions of mean grain size, sorting, shell content were repeatedly distributed like the directions of depth contour lines. (2) Sand component was composed of medium to fine sand (Mz, 1-3$\psi$) containing many shell fragments, a few pebbles, and iron-stained quartz. (3) The surface of quartz revealed the concordial breakage and V-shaped features formed at high energy environment. (4) In CM-pattern, sand component was plotted in rolling and bottom suspension area. These characteristics imply that sand component probably derives from shoreface sediments deposited at the beach environment.

• Journal of Aquaculture
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• v.10 no.3
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• pp.227-237
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• 1997

Five species of intertidal clams including Ruditapes philippinarum, Tegillarca granosa, Solen strictus, Heteromacoma irus, and Coecella chinensis were tested for the presence of the protozoan parasite, Perkinsus sp. using fluid thioglycollate medium (FTM) fortified with antibiotics and histological techniques. Each individual clam was placed in a test tube filled with 10ml FTM, placed in totally dark place, and incubated over a week. After incubation the clam tissues were stained with Lugol's iodine solution and examined under a light microscope to find out any hypnospores of Perkensus sp. in the tissues. Cross-sections of the clams were also embedded in paraffin, sliced to 3um, and stained with Harry's hematoxylene and Picro eosine to observe the presence of tomont or trophozoites. Perkinsus sp. were found in the presence of tomont or trophozoites. Perkinsus sp. were found in the tissues of R. philippinarum collected from Kangjin and Wando, along the south coast of Korea. However, Perkinsus sp. was not found in four other species of clams nor R. philippinaurm collected from Kimnyong and Waido in Cheju. A size-dependent Perkinsus sp. infection was found in R. philippinarum collected rom Kangjin and Wando the clams smaller than 15mm in shell width do not exhibit and Perkinsus sp. while other clams greater than 20mm in shell width exhibit almost 100% infection. To determine the number of Perkinsus sp. in the clams, FTM cultured clam tissues were digested with 2M NaOH solution and the number of hypnospores in the tube were counted. The number of hypnospores counted from the tissues indicated that each Manila clam contains 100,000 to 3,500,000 Perkinsus cells or 20,000 to 1,000,000 cells per gram tissue wet weight. The results of cell counts also suggests that such a high occurrence of Perkinsus sp. in the clam may cause mortality, as already reported from other studies of Perkinsus spp.

• Wind and Structures
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• v.25 no.2
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• pp.131-156
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• 2017

This paper deals with the dynamic stability of embedded functionally graded (FG)-carbon nanotubes (CNTs)-reinforced micro cylindrical shells. The structure is subjected to harmonic non-uniform temperature distribution and 2D magnetic field. The CNT reinforcement is either uniformly distributed or FG along the thickness direction where the effective properties of nano-composite structure are estimated through Mixture low. The viscoelastic properties of structure are captured based on the Kelvin-Voigt theory. The surrounding viscoelastic medium is considered nonhomogeneous with the spring, orthotropic shear and damper constants. The material properties of cylindrical shell and the viscoelastic medium constants are assumed temperature-dependent. The first order shear deformation theory (FSDT) or Mindlin theory in conjunction with Hamilton's principle is utilized for deriving the motion equations where the size effects are considered based on Eringen's nonlocal theory. Based on differential quadrature (DQ) and Bolotin methods, the dynamic instability region (DIR) of structure is obtained for different boundary conditions. The effects of different parameters such as volume percent and distribution type of CNTs, mode number, viscoelastic medium type, temperature, boundary conditions, magnetic field, nonlocal parameter and structural damping constant are shown on the DIR of system. Numerical results indicate that the FGX distribution of CNTs is better than other considered cases. In addition, considering structural damping of system reduces the resonance frequency.

• Polymer(Korea)
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• v.28 no.2
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• pp.154-161
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• 2004

Modified poly(4-vinylpyridine) was obtained by partial quarternization of nitrogen atoms in pyridine rings of poly(4-vinylpyridine) with methyl group. By means of laser light scattering and fluorescence, it was found that this modified polymer chains were aggregated in the aqueous solution and its structure was core-shell type. The hydrophobic parts of the chains were densely condensed in core part and the hydrophilic part of quarternized amino with positive charge formed the shell part. In the mixed system of modified poly(4-vinylpyridine) and anionic surfactant, sodium dodecyl sulfate, it was observed that a critical aggregation concentration existed and that this critical concentration was suddenly decreased above 0.1 M NaCl. The size change of aggregates was also investigated by dynamic light scattering while sodium dodecyl sulfate was added into polymer solution upto the critical aggregation concentration.

• Journal of the Korean Society of Clothing and Textiles
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• v.40 no.1
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• pp.97-113
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• 2016

This study develops pant patterns using body shape, measurement and shell mesh data to decide optimal women's pants according to styles with excellent size, fit and shape for different individuals and silhouettes. Standard landmarks, lines, triangles and structures were set on a 3D scanned lower body shell to represent women in their twenties and flattened as a 2D pattern. Patterns were created and analyzed according to culotte, formal, slacks and tight type considering crotch shape, location of the crotch point, and adjusting waist darts. Flattened patterns were rotated to compare existing methods. The crease lines were then set through the hip protrusion point and compared. The main factor of the pant pattern were extracted, total rise, crotch depth, crotch width, angle of center line, shape of the center line curve, the thigh width, the amount of waist dart, and crease line position. With going tight style from the culotte, the fits are closer to the figure with minimized thigh circumference, the dart amount decreases, the crotch depth increases, the crotch extensions were shorter, and the angle of the center back increased. The total rise is U shape for culotte and is closer to V shape as the silhouette tightens. T-test of appearance evaluation of the developed pant pattern were conducted after analyzing measurements and shapes of each styles. The results of the developed patterns were superior to existing patterns in accordance to hip line between body and pants as well as appearance evaluation. We found systematic mechanisms among pattern factors that create various pant silhouettes. Evidence on classification of the silhouettes of traditional types of pants were explained objectively through the process of playing out 3D forms.

• Korean Journal of Materials Research
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• v.9 no.9
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• pp.865-871
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• 1999

Effect of sintering condition in mechanical properties of ZrSiO\ulcorner shell molds was investigated. Number of microcrack in primary layer of the mold was maximized after preheating at $1000^{\circ}C$ for 1.5 hours. Yield strength and specific surface area of the mold were inversely proportion to sintering temperature and time. After hot deformation test at $1500^{\circ}C$ for 4 hours, molds were deformed opposite to the loading direction and backup layers were cracked along the interface between stucco and zircon slurry. Reverse deformation of the molds during hot deformation test was considered to be resulted from the difference of thermal expansion coefficient between alumina stucco and zircon slurry in primary coat, and size difference between zircon stucco and zircon slurry in backup coat.

• Journal of Powder Materials
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• v.22 no.6
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• pp.385-390
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• 2015

We report a synthesis of non-toxic InP nanocrystals using non-pyrolytic precursors instead of pyrolytic and unstable tris(trimethylsilyl)phosphine, a popular precursor for synthesis of InP nanocrystals. In this study, InP nanocrystals are successfully synthesized using hexaethyl phosphorous triamide (HPT) and the synthesized InP nanocrystals showed a broad and weak photoluminescence (PL) spectrum. As synthesized InP nanocrystals are subjected to further surface modification process to enhance their stability and photoluminescence. Surface modification of InP nanocrystals is done at $230^{\circ}C$ using 1-dodecanethiol, zinc acetate and fatty acid as sources of ZnS shell. After surface modification, the synthesized InP/ZnS nanocrystals show intense PL spectra centered at the emission wavelength 612 nm through 633 nm. The synthesized InP/ZnS core/shell structure is confirmed with X-ray diffraction (XRD) and Inductively Coupled Plasma - Atomic Emission Spectrometer (ICP-AES). After surface modification, InP/ZnS nanocrystals having narrow particle size distribution are observed by Field Emission Transmission Electron Microscope (FE-TEM). In contrast to uncapped InP nanocrystals, InP/ZnS nanocrystals treated with a newly developed surface modified procedure show highly enhanced PL spectra with quantum yield of 47%.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.55 no.4
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• pp.310-319
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• 2019

Although mud shrimp (Upogebia Major) provides benefits on the tidal flat ecosystem, it is causing the mass mortality of Manila clam (Tapes philippinarum) and large economic loss to the aquaculture farmer due to spreading in the entire coastal clam farm area of the West Sea of Korea. In this study, a mud shrimp blocking box for cultivating clam was tested to prevent the mud shrimp from invading the habitat of the clam. To determine the effect of the blocking box, the growth characteristics of the clams under various culture conditions were investigated. The shell length, total weight, condition index, the presence of mud shrimp in the box, and the soil decay in the box were examined according to whether the clams were raised in the box or in natural state, whether the box is covered with a net or not and the gap size of the box. As a result, no significant differences in shell length, total weight, and condition index were found between the clam grown in the box and the natural state (P>0.05) without any evidence of invading of mud shrimp to the box. In addition, the soil inside the box was in good condition, not decayed. Therefore, using the mud shrimp blocking box, mud shrimp can be prevented from propagating to the habitat of the clam, thereby contributing to the normal production of the clam and thus to restoring the clam farming.