• Journal of Conservation Science
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• v.26 no.1
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• pp.25-32
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• 2010

The yellowing is always occurred phenomena in epoxy restoration material of antic-ceramics. For re-restoration of remains with epoxy restoration material, the epoxy elimination step is the first one in all course of restoration In this paper, the chemically elimination treatments methods of epoxy in various antic-ceramics were discussed. We fabricated the epoxy elimination material for antic-ceramics restoration which were made up Dichloromethane and Dichlormethane based Dimethylformamide solution. Dichloromethane and Dichloromethane + Dimethylformamide mixture were applied to epoxy in various antic-ceramic sample. Particularly, Dichloromethane + Dimethylformamide solution had the best result in variation of color change, gloss, vending strength, weight, exfoliation time test after deposition in this solution. Dichloromrthane had the volume increase characteristics for epoxy material and Dimethylformamide had the mollification ones. So, Dichloromathane increased exfoliation in approximal surface of the epoxy material and antic ceramic, and Dimethylformamide decreased the surface hardness of epoxy. In this result, epoxy material even inside of ceramic that have very weak inside bonding is adaptable and stable eliminated. And in order to show the perfect elimination of this material, we successfully dissolve the epoxy restoration material in one antic pottery that is in one university museum's possession using this mixture. So, there is guarantee in the eternity and stabilization of restoration for antic-ceramics.

• Proceedings of the Korean Magnestics Society Conference
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• 2011.06a
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• pp.7-8
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• 2011

Basically, the lattice mismatch between film and substrate can make those BiFeO3(BFO) films distorted with strain structure. BFO phase can be stabilized on LaAlO3(LAO) represents the example of a multiferroic with giant axial ratio. Its crystal structure is not strictly tetragonal, but tetragonal with a slight monoclinic distortion and related to the rotation of the oxygen octahedra. In this study, we show that phases with a tetragonal-like epitaxial BFO films can indeed be ferroelectric and also can be stabilized via epitaxial growth onto LAO. Recent reports on epitaxial BFO films show that the crystal structure changes from nearly rhombohedral ("R-like") to nearly tetragonal("T-like") at strains exceeding approximately -4.5%, with the "T-like" structure being characterized by a highly enhanced c/a ratio. While both the "R-like" and the "T-like" phases are monoclinic, our detailed x-ray diffraction results reveal asymmetry change from MA and MC type, respectively. By applying additional strain or by modifying the unit cell volume of the film by substituting Ba for Bi, the monoclinic distortion in the "T-like" MC phase is reduced, i.e. the system approaches a true tetragonal symmetry. There are two different M-H loops for $Bi_{1-x}Ba_xFeO_{3-{\delta}}$(BBFO) and BFO films on SrTiO3(STO) & LAO substrates. Along with the ferroelectric characterization, these magnetic data indicate that the BFO phase stabilized on LAO represents the first example of a multiferroic with giant axial ratio. However, there is a significant difference between this phase and other predicted ferroelectrics with a giant axial ratio: its crystal structure is not strictly tetragonal, but tetragonal with a slight monoclinic distortion. Therefore, in going from bulk to highly-strained films, a phase sequence of rhombohedral(R)-to-monoclinic ["R-like" MA-to-monoclinic, "T-like" MC-to-tetragonal (T)] is observed. This sequence is otherwise seen only near morphotropic phase boundaries in lead-based solid-solution perovskites (i.e. near a compositionally induced phase instability), where it can be controlled by electric field, temperature, or composition. Our results show that this evolution can occur in a lead-free, stoichiometric material and can be induced by stress alone. Those major results are summarized as follows ; 1) Ba-doping increases the unit cell volume, 2) BBFO on LAO can be fully strained up to x=0.08 as a strain limit (Fig. 1), 3) P(E) & M(H) properties can be tuned by the variation of composition, strain, and film thickness.

• Korean Chemical Engineering Research
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• v.54 no.6
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• pp.786-791
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• 2016

Spherical graphene balls were fabricated by an aerosol spray drying process after reduced graphene oxide was prepared by the liquid phase reaction using glucose as an environment-friendly reducing agent. Spherical morphology of the as-fabricated particles was observed by FE-SEM analysis. Diffraction patterns of spherical particles were found as graphene by XRD analysis. Sphericity of GB was controlled by the variation of operating temperature, amount of glucose, and addition of $NH_4OH$. Higher sphericity of GB was prepared at higher operating temperature in the presence of $NH_4OH$. As the amount of glucose in the liquid phase reaction increased in the presence of $NH_4OH$, sphericity of GB increased. The highest sphericity of GB was 1.1. GB of higher sphericity showed lower aggregation property than that of lower sphericity. Furthermore, as-prepared GBs were found as a potential electrode material for capacitor.

• Journal of the Korea Concrete Institute
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• v.27 no.1
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• pp.21-28
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• 2015

Recent studies on concrete floating structure development focused on connection system of concrete modules. Precast concrete modules are designed to be attached by prestressing in the water, exposing the structure to the loads from water and making the construction difficult. Therefore, a development of bond material became a key issue in successful connection of floating concrete modules. In this study, micro-silica mixed aqua epoxy (MSAE) is developed for the task. Existing primer aqua epoxy, originally used as a bond material for the retrofit of concrete structures using fiber reinforced polymers, is evaluated to find the optimum micro-silica added mix proportion. Micro-silica of 0~4 volume % was mixed in standard mixture of aqua epoxy. Then, the material property tests were performed to study the effect of micro-silica in aqua epoxy by controlling the epoxy silane proportion by 0, ${\pm}5$, ${\pm}10%$. The optimum mix design of MSAE was derived based on the test results. The MSAE was used to connect concrete module specimens with the epoxy thickness variation of 5, 10, and 20mm. Then, 3-point loading test was performed to verify the bond capacity of MSAE. The results show that MSAE improves the bond capacity of concrete module.

• MALSORI
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• no.19_20
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• pp.58-87
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• 1990

According to Government Phonology, at 1 phonological positions save the domain's head must be licensed in order to appear in the syllable structure. A non-nuclear head is licensed by the following nucleus, and the nuclei with phonetic content are licensed through government by the nuclear head of the domain at the level of the nuclear projection. Therefore, in the theory of Government Phonology it is claimed that words always end with a nucleus. With regard to the licensing of empty nuclei, Kaye(1990a) proposes the 'Empty Category Principle' and its sub-theory of 'Projection Government'. Government Phonology claims that a nucleus which dominates a vowel that regularly undergoes elision in certain contexts is underlyingly empty. This underlying empty nucleus is not manifested phonetically when it is properly governed by an unlicensed(i, e, a nucleus filled with a full vowel). It is when proper government fails to apply, that the empty nucleus is phonetically Interpreted. The purpose of this paper is to present a principled account of the process of $[i]{\Leftrightarrow}{\emptyset}$ alternation in Korean. Following Kaye's proposal, we assume that [i] of Korean is underlyingly empty. This position is pronounced as [i] if it is unlicensed, and is not phonetically realized if is licensed. Empty nuclei ape devided into two categories: domain-internal and domain-final. Firstly, we consider the question why Korean has little word ending with [i]. As for this, ECP states that domain-final empty nuclei are not pronounced if the language licenses domain-final empty nuclei. Whether a final empty nucleus may occur in the structure is parametric variation. This property is seen from the fact that words may appear to end in consonants in this language. Since Korean abounds with words ending in a consonant, it licenses domain-final empty nuclei. Therefore, it is quite natural that Korean has little word ending with [i]. Secondly, word-internal empty nuclei of Korean respect proper government and inter-onset government. That is, an empty nucleus in word-internal position will be pronounced with the vowel [i] if either proper government or inter-onset government fail to apply. Inter-onset government refers to the government established between two onsets across an empty nucleus. Thirdly, we consider words ending with [i], which seems to be exceptional to the final licensing. Host of them are. either mono-syllabic verbs(for instance, [s'i-] 'to write') or derived adjectives ending with [p'i] (for instance, [kip'i-] 'be happy'). As for the former, the 'inaccessibility for proper government' is applied because the empty nucleus appears in the first syllable. In latter case, domain-final empty nuclei are pronounced as [i] because of government-licensing. That is, final empty nucleus is pronounced to license the preceding onset dominating negatively charmed segments which empty nucleus of Korean cannot license.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.5
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• pp.15-20
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• 2007

We fabricated ZnO thin films on quartz substrate using pulsed laser deposition method and investigated structural and optical properties of ZnO thin films with various substrate temperatures. Regardless of the substrate temperature variation, all ZnO thin films had grown to (002) and the thin film deposited at 400 $^{\circ}C$ exhibited an excellent crystallinity having 0.24$^{\circ}$ of Full-Width-Half-Maximum (FWHM). In the result of photoluminescence property, UV and deep-level emission peaks were observed in all ZnO films and the emission peaks were changed with various substrate temperatures. An highest UV emission was exhibited on the specimen deposited at 400 $^{\circ}C$ and the FWHM of UV peak was 14 nm. The optical transmittance was about 85 % in visible region regardless of the substrate temperature. The comparison result of the bandgap energies obtained from optical transmittance and UV emission centers, the two values were about the same. From these results, it is found that UV emission center has close relationship with near band edge emission of ZnO thin film.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.5
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• pp.663-676
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• 1996

Physical properties and textural parameters of thirty-five piston tore samples recovered from the southeastern coast of Korea (Korea Strait), were investigated using the autopycnometer. The physical properties (porosity, water content, wet bulk density, dry bulk density, gram density, and void ratio) were measured at rather uniform intervals along each core. Sediment texture (grain size, sand, silt, and clay contents) was also measured at the same subbottom depth. The measured and calculated results are; mean grain size $0.57\~8.09\phi(average:3.67\phi)$, porosity $26\~81\%\;(average:\;55\%)$, water content $16.7\~61.4\%(average:\;31.6\%)$, wet bulk density $1.37\~2.18g/cm^3\;(average:\;1.85g/cm^3)$, dry bulk density $2.55\~3.11g/cm^3\;(average:\;2.35g/cm^3)$, grain density $2.40\~3.10g/cm^3\;(average:\;2.85g/cm^3)$, and void ratio $0.56\~2.54$ (average: 0.94). The sediment texture generally coincides well with the bathymetry indicating the influence of Pleistocene-Holocene sea level changes. Also the contours of physical properties are closely related to the sediment texture. Fluctuation of physical properties are similar to the textural variation. It seems that sediment texture is a significant factor in determining physical property in this study area.

• Journal of Korea Water Resources Association
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• v.41 no.8
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• pp.761-772
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• 2008

The object of this study is to develop the model that solves the numerically difficult problems in hydraulic engineering and to demonstrate the applicability of this model by means of various test examples, such as, verification in the gradually varied unsteady condition, three steady flow problems with the change of bottom slope with exact solution, and frictional bed with analytical solution. The governing equation of this model is the integral form of the Saint-Venant equation satisfying the conservation laws, and finite volume method with the Riemann solver is used. The evaluation of the mass and momentum flux with the HLL Riemann approximate solver is executed. MUSCL-Hancock scheme is used to achieve the second order accuracy in space and time. This study introduce the new and simple technique to discretize the source terms of gravity and hydrostatic pressure force due to longitudinal width variation for the balance of quantity between nonlinear flux and source terms. The results show that the developed model's implementation is accurate, robust and highly stable in various flow conditions with source terms, and this model is reliable for one-dimensional applications in hydraulic engineering.

• Applied Microscopy
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• v.40 no.3
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• pp.155-162
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• 2010

Bone is a hierarchically structured composite material which has been well studied by the materials engineering community because of its unique structure and mechanical properties. Bone is a laminated organic-inorganic composite composed of primarily hydroxyapatite, collagen and water. The main mineral that gives bone's hardness is calcium phosphate, which is also known as hydroxyapatite. Light microscopy (LM) and transmission electron microscopy (TEM) were used to study the structure of femurs from chicken and rabbit. The elemental analysis was used to search variation in the distribution of calcium, potassium and oxygen in the femur. Current investigation focused on two structural scales: micro scale (arrangement of compact bone) and nano scale (collagen fibril and apatite crystals). At micro scale, distinct difference was found in microstructures of chicken femur and rabbit femur. At nano scale, we analyzed the shape and size of apatite crystals and the arrangement of collagen fibril. Consequently, femurs of chicken and rabbit had very similar chemical property and structures at nano scale despite of their different species.

• Korean Journal of Materials Research
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• v.23 no.12
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• pp.672-679
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• 2013

$Fe_4[Fe(CN)_6]_3$ coated on a mica or $TiO_2$/mica surface as infrared reflective blue pigment was prepared by a hydrothermal method. $Fe_4[Fe(CN)_6]_3$, used as coloring agent, was uniformly coated on mica or $TiO_2$/mica under the optimized condition of a 1.2 : 1 weight ratio between iron(III) chloride hexahydrate and potassium ferrocyanidetrihydrate at the initial pH level of 4.5 at $70^{\circ}C$. The infrared (IR)-reflective pigments were characterized by SEM, Zeta-potenial, FT-IR, and UV-VIS NIR spectrophotometry. Especially the CIE color coordinate and total solar reflectance(TSR) properties of the pigments were investigated in relation to variation of the coating and coated substrate thicknesses. Isolation-heat paint was prepared with 20 wt% blue pigments fully dispersed in acryl-urethane resin and several additives to coat the film uniformly. The films were also measured with CIE color coordinate, TSR, and the surface temperature was recorded by an isolation-heat measuring system. The pigments and films of $Fe_4[Fe(CN)_6]_3$ coated on mica and $TiO_2$/mica showed high TSR values compared with the TSR value of $Fe_4[Fe(CN)_6]_3$ itself. According to the increase of TSR value, the property of isolation-heat is effective. To realize the optimal blue color, we applied the the pigment to $TiO_2$ coated mica(TM(b)) which has blueish interference color. The pigment of $Fe_4[Fe(CN)_6]_3$ coated on TM(b) shows a strong blue color compared with that of $Fe_4[Fe(CN)_6]_3$ coated on $TiO_2$/Mmca(TM(w)), which has a whitish interference color.