• Journal of the Korean Ceramic Society
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• v.43 no.12 s.295
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• pp.865-871
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• 2006

In order to examine and compare the characteristics of two vitrified forms (AG8W1 and DG2) simulated for the operation of a commercial vitrification facility being constructed in Ulchin nuclear power plant, the vitrified forms were cooled by the natural cooling and annealing methods respectively. And the Product Consistency Test (PCT), compressive strength, thermal conductivity, specific heat, phase stability, softening point and Coefficient of Thermal Expansion (CTE) of the vitrified farms were experimented. Consequently, it was shown that there were no significant differences on the physiochemical properties of the vitrified forms performed the natural cooling and annealing.

• Electrical & Electronic Materials
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• v.9 no.10
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• pp.1047-1052
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• 1996

In this study, the thermal and optical proper-ties of multicomponent oxide glass fiber for IR sensor by adding heavy metal oxide Ga$_{2}$O$_{3}$ were investigated. The fiber samples were made by rod-in tube method. The optical loss of fiber was measured in 0.3-1.8/M wavelength region. As Ga$_{2}$O$_{3}$ increased up to 12wt%, the transition and softening temperature of bulk glass were increased from 495.deg. C to 564.deg. C and from 548.deg. C to 612.deg. C respectively. Whereas the thermal expansion coefficient was decreased from 102 to 88.2*10$^{-7}$ /.deg. C. The refractive index was increased from 1.621 to 1.662, and IR cut-off wavelength was enlarged from 4.64.mu.m to 5.22.mu.m. The optical loss of fiber was decreased and more remarkably decreased in 1.146.mu.m-1.8.mu.m wavelength region.

• Nuclear Engineering and Technology
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• v.53 no.11
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• pp.3816-3823
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• 2021

The mechanical features evaluated theoretically using Makishima-Mackenzie's model for glasses xBaO-(50-x) PbO-50P₂O₅ where x = 0, 5, 10, 15, 20, 30, 40, and 50 mol%. Wherefore, the elastic characteristics; Young's, bulk, shear, and longitudinal modulus calculated. The obtained result showed an increase in the calculated values of elastic moduli with the replacement of the PbO by BaO contents. Moreover, the Poisson ratio, micro-hardness, and the softening temperature calculated for the investigated glasses. Besides, gamma and neutron shielding ability evaluated for the barium doped lead phosphate glasses. Monte Caro code (MCNP-5) and the Phy-X/PSD program applied to estimate the mass attenuation coefficient of the studied glasses. The decrease in the PbO ratio has a negative effect on the MAC. The highest MAC decreased from 65.896 cm²/g to 32.711 cm²/g at 0.015 MeV for BPP0 and BPP7, respectively. The calculated values of EBF and EABF showed that replacement of PbO with BaO contents in the studied BPP glasses helps to reduce the number of photons accumulated inside the studied BPP glasses.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.1
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• pp.7-14
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• 2023

Forty Viscosity data of glass bottles fabricated in a glass bottle manufacturing plant for 4 years were calculated using Lakatos model. The relationship between the glass bottle compositions and viscosities at log η of 3, 6.6, 10 and 12.3 Pa·s was analyzed. MgO that was a component of the glass bottle showed the maximum coefficient of variation of 0.89, but it gave a very small change in the viscosity. CaO that was another component of the glass bottle lowered the isokom temperature because it tended to reduce the number of non-bridging oxygen at temperature below a softening point.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.4
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• pp.180-188
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• 2013

The glass of E-glass fiber composition was fabricated by using refused coal ore which is obtained as by-product from Dogye coal mine in Samcheok. We used silica-alumina refused coal ore which has low carbon content relatively, and the amount of refused coal ore has been changed from 0 to 35 % in batch composition. E-glass was fabricated by the melting of mixed batch materials at $1550^{\circ}C$ for 2 hrs with different refused coal ore composition of 0~35 %. We obtained a transparent and clear glass with high visible light transmittance value of 81~84%, thermal expansion coefficient of $5.39{\sim}5.61{\times}10^{-6}/^{\circ}C$ and softening point of $851{\sim}860^{\circ}C$. The glass fiber samples were also obtained through fiberizing equipment at $1150^{\circ}C$, and tested chemical resistance and tensile strength to evaluate the mechanical property as a reinforced glass fiber of composite material. As the result, we identified the properties of E-glass fiber by using refused coal ore are plenty good enough compare to that of normal E-glass without refused coal ore, and confirmed the possibility of refused coal ore as for the raw material of E-glass fiber.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.2A
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• pp.281-288
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• 2008

The Prestressed Concrete (hereinafter PSC) box girder bridges with corrugated steel webs have been drawing an attention as a new structure type of PSC bridge fully utilizing the feature of concrete and steel. However, the previous study focused on the shear buckling of the corrugated steel web and development of connection between concrete flange and steel web. Therefore, it needs to perform a study on the torsional behavior and develop the rational torsional analysis model for PSC box girder with corrugated steel web. In this study, torsional analysis model is developed using Rausch's equation based on space truss model, equilibrium equation considering softening effect of reinforced concrete element and compatibility equation. Validation studies are performed on developed model through the comparison with the experimental results of loading test for PSC box girder with corrugated steel webs. Parametric studies are also performed to investigate the effect of prestressing force and concrete strength in torsional behavior of PSC box girder with corrugated steel web. The modified correction factor is also derived for the torsional coefficient of PSC box girder with corrugated steel web through the parametric study using the proposed anlaytical model.

• Korean Journal of Materials Research
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• v.18 no.12
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• pp.678-682
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• 2008

This study investigates $Bi_2O_3$-$B_2O_3$-BaO-ZnO glass with variations of the $Co_3O_4$ content (0.25, 0.5, 1, and 2 wt%) and the interaction between transparent dielectric and Ag electrodes heat-treated at $500-560^{\circ}C$ for 30 min. The glass transition temperature, softening temperature and thermal expansion coefficient were $432^{\circ}C$, $460^{\circ}C$ and $81.4{\times}10^{-7}/^{\circ}C$, respectively. The transmittance of 0.25 wt% $Co_3O_4$ to which dielectric was added was highest and was decreased due to coloration with the addition of more than 0.25 wt%. However, without $Co_3O_4$, the transmittance of the transparent layer was decreased due to the formation of $Ba_5Bi_3$; however, the occurrence of the crystal phase decreased as a result of the addition of $Co_3O_4$. The amount of $Co^{2+}$ ions increased as the $Co_3O_4$ increased. With a maximum of $Co^{3+}$ ions, the highest transmittance was observed.

• Journal of the Korean Ceramic Society
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• v.50 no.1
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• pp.75-81
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• 2013

We fabricated translucent opal glass to replace the polycarbonate diffuser in LED lighting systems in order to solve the durability problem. Batch materials of opal glass with a composition of calcium phosphate were created and melted at $1550^{\circ}C$, and the effect of opaqueness was identified by an addition of 1~7% calcium phosphate as an opacifier raw material. As a result, translucent opal glass was obtained by the melting of the mixed batch materials with a composition of more than 5% calcium phosphate glass at $1550^{\circ}C$ for 2 hrs, which had excellent optical properties for the diffuser of a LED lighting system with no dazzling from direct light by a high haze value exceeding 90% and a low parallel transmittance value of about 5%. For the thermal properties, the thermal expansion coefficient was found to be $5.6{\sim}5.9{\times}10^{-6}/^{\circ}C$ and the softening point was $874{\sim}884^{\circ}C$. In addition, good thermal properties such as good thermal shock resistance and feasibility for use with a general manufacturing process during the forming of glass tubes and bulbs were noted. Therefore, it is concluded that this translucent opal glass can be used as a glass diffuser material for LED lighting due to its high heat resistance and high durability as a replacement for a polycarbonate diffuser.

• Korean Journal of Materials Research
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• v.22 no.12
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• pp.650-657
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• 2012

For the purpose of improving the durability problem, translucent opal glass was fabricated as a substitute for the polycarbonate diffuser of LED lighting. Calcium phosphate was used as an opacifier of opal glass and melted in an electric furnace. The opaque effect was identified according to the change of the cooling procedure. As results, translucent opal glass was obtained by the melting of a batch with a composition of 3.8% calcium phosphate at $1550^{\circ}C$ for 2 hrs and then the cooling of the material in the furnace. For the cooling condition of the glass sample, HTCG (High Temperature Cooled Glass) was found to have better optical properties than LTAG (Low Temperature Annealed Glass). It had excellent optical properties for a diffuser of LED lighting, with no dazzling from direct light due to its high haze value of over 99% and low parallel transmittance value of under 1%. For the thermal properties, it had an expressed thermal expansion coefficient of $5.7{\times}10^{-6}/^{\circ}C$ and a softening point of $876^{\circ}C$; it also had good thermal properties such as good thermal shock resistance and was easy to apply to the general manufacturing process in the forming of glass tubes and bulbs. Therefore, it is concluded that this translucent opal glass can be used as a glass diffuser material for LED lighting with high heat resistance and high durability; this material is suitable as a substitute for polycarbonate diffusers.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.3
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• pp.576-585
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• 2002

A three-dimensional Lagrangian explicit time-integration finite element code for analyzing the dynamic impact phenomena was developed. It uses four node tetrahedral elements. In order to consider the effects of strain rate hardening, strain hardening and thermal softening, which are frequently observed in high-velocity deformation phenomena, Johnson-Cook model is used as constitutive model. For more accurate and robust contact force computation, the defense node contact algorithm was adopted and implemented. In order to evaluate the performance of the newly developed three-dimensional hydrocode NET3D, numerical simulations of the oblique impact of mild steel plate by mild steel sphere were carried out. Ballistic limit about various oblique angle between 0 degree and 80 degree was estimated through a series of simulations with different initial velocities of sphere. Element eroding by equivalent plastic strain was applied to mild steel spheres and targets. Ballistic limits and fracture characteristics obtained from simulation were compared with experimental results conducted by Finnegan et al. From numerical studies, the following conclusions were reached. (1) Simulations could successfully reproduce the key features observed in experiment such as tensile failure termed "disking"at normal impacts and outwards bending of partially formed plus segments termed "hinge-mode"at oblique impacts. (2) Simulation results fur 60 degrees oblique impact at 0.70 km/s and 0.91 km/s were compared with experimental results and Eulerian hydrocode CTH simulation results. The Lagrangian code NET3D is superior to Eulerian code CTH in the computational accuracy. Agreement with the experimentally obtained final deformed cross-sections of the projectile is excellent. (3) Agreement with the experimental ballistic limit data, particularly at the high-obliquity impacts, is reasonably good. (4) The simulation result is not very sensitive to eroding condition but slightly influenced by friction coefficient.