• Journal of Korea Society of Digital Industry and Information Management
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• v.12 no.3
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• pp.25-31
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• 2016

Mechanical properties of Y2O3-containing tetragonal ZrO2 polycrystals(Y-TZP) were investigated. Several additives were used to modify the hardness and fracture toughness of Y-TZP. The effects of these individual additives were discussed and their interactions were also analysed. Each additive, such as CoO, Fe2O3, MnO2 was found to deteriorate the mechanical properties of Y-TZP when it was used singly. But the fracture toughness of Y-TZP was significantly improved when these additives and Al2O3 were added in combination at a certain ratio. The addition of CoO, Fe2O3 and MnO2 into Y-TZP resulted in the more complex behavior of fracture toughness and hardness. The specimen with 1.5 wt%-Fe2O3, 3.0 wt% -Al2O3 and 1.5 wt%-CoO showed the monoclinic to tetragonal phase ratio of 18% and the highest toughness of $10.8MPa{\cdot}m1/2$ with Vickers hardness of 1201 kgf/mm2. However, the toughness decreased as the ratio increased and macrocracks developed beyond the ratio of 25%. Sample No. 16 is improved high Physical and Mechanical Properties.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.311-314
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• 1998

The effects of the additions of transition metal oxides on ZrO$_2$ - Y$_2$O$_3$ (Y$_2$O$_3$ - containing tetragonal zirconia polycrystals : Y-TZP) system has been studied by investigating fracture toughness and phase stability of the sintered specimens. In the specimens sintered at 1450$^{\circ}C$ for 2hrs in air the phase transformation from tetragonal to monoclinic was observed. The ratios of monoclinic phase to tetragonal phase were changed with the additions of CoO, Fe$_2$O$_3$ and MnO$_2$, respectively, from 0.00 to 8.00wt%. The fracture toughness was increased with increasing the monoclinic to tetragonal phase ratio and was maximum at the ratio of about 18%. However, the hardness was decreased with increasing the ratio. The additions of CoO, Fe$_2$O$_3$ and MnO$_2$ together into Y-TZP resulted in more complex behaviors of fracture toughness and hardness. The specimen with the additions of 1.5wt% Fe$_2$O$_3$, 3.0wt% Al$_2$O$_3$ and 1.5wt% CoO showed the monoclinic to tetragonal phase ratio of 18% and the highest toughness of 10.8 MPa.m$\^$$\frac{1}{2}$/ and Vickers hardness of 1201kgf/mm$^2$.

• Journal of the Korean Institute of Educational Facilities
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• v.19 no.2
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• pp.3-12
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• 2012

This study is carried out to analyze transition about educational facilities of elementary schools with the change of policy and to find out a developmental direction for qualitative improvement. An analysis of blueprints is done to 34 elementary schools representing periodic characteristics after the 1960's. As a result, various cases were shown in arrangement type, unit space, block planning and plane planning of the schools after a abolition of law about the standardization of educational facilities on 1997, however, they were showing a tendency to simplify after the introduction of BTL on 2005. Spatial composition factors were very various in the schools planned from the middle of 1990's to the early of 2000's. Meanwhile, nearly fifty percent of occupying ratio about learning space in the schools of standard type was gradually decreased by modernization planning on 1990's. However, it was increased a little again after the BTL. In case of living area, the occupying ratio was comparatively high in the schools having characteristics of 1990's and it also tends to increase after the introduction of BTL.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2005.10a
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• pp.97-101
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• 2005

High strength concretes utilizing EVA with micro particles were prepared by varying polymer/binder mass ratio and curing conditions with a constant water/binder mass ratio of 0.3. The EVA modified concretes on the compressive and flexural strength, microstructure, ultrapulse modulus in curing condition(dry and water curing) were studied. Also, scanning electron microscope analysis(SEM) was performed to reveal the presence of polymer film and cement hydrates in the concrete. The compressive strength of the EVA modified concretes cured at water conditions ere higher than that of the EVA modified concretes cured at dry conditions. But, the flexural strength of the specimens cured at dry conditions were higher than that of the specimens cured at water conditions. Due to the interaction of the cement hydrates and polymer film, an interpenetrating network originated in which the aggregates were embedded. The curing of the polymer modified concrete involves two step of cement hydrates and polymer modification, and cement hydrates was promoted in water conditions and polymer film formation take place when water evaporates and was thereby was favored in dry conditions. By SEM analysis, influences of polymer modification was strengthening of the transition zone between the aggregate and the paste, and the porosity of transition zone decreases. By spring analysis, it could known that polymer film affects in porosity decrease and strengthening of transition zone.

• Journal of Korea Planning Association
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• v.54 no.1
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• pp.40-51
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• 2019

The ultimate aim of this study is to diagnose the process stage and look at the step change of transition process to see how the step changes. Therefore, in this study, cluster analysis was conducted by examining four types of commercial characteristics such as Retail Homogeneity, Share of Neighbourhood store, Share of chain store, and Share of cafe & Western food store. Through the cluster analysis, three types have been identified. Type1 is the first step which can explain the time before gentrification occurs and when the ratio of neighborhood facilities is the highest. Type2 is the second step that can explain boutique stage where the gentrification occurs. At this time, the ratio of Cafes & Western food restaurant increased and the proportion of neighborhood shops decreased. And Type3, third step is when the mature gentrification occurs. In the analysis of the transition period, it is necessary to monitor the change of the industry in the period from the first stage to the second stage. In the transition period from the second stage to the third stage, It is necessary to constantly monitor such factors as the increase of shops.

• Bulletin of the Korean Chemical Society
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• v.19 no.1
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• pp.83-86
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• 1998

The luminescence spectra of Eu(Ⅲ) complexes have been measured as a function of molar metal-to-ligand ratio and pH. The ligands used in this study are tridentate iminodiacetate (IDA) and methyliminodiacetate (MIDA). The 620 nm emission band, attributed to the $^5D_0{\to}^7F_2$ transition, is monitored to investigate the optimum condition for $EuL_3^{3-}$ complex formation in aqueous state. In addition, the sensitivity of the 465 nm absorption band, attributed to the $^7F_0{\to}^5D_2$ transition, to the ligand environment has been also investigated.

• Proceedings of the KSR Conference
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• 2009.05b
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• pp.379-384
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• 2009

It is of great importance to assure the running safety and ride comfort in designing the floating slab track for the mitigation of train-induced vibration. In this paper, for this, analyzed are the system requirements for the running safety and ride comfort, and then, the behavior of train and track at the transition zone between the floating slab track and the conventional concrete slab track according to several main design variables such as spring constant, damping coefficient, spacing and arrangement of isolators and slab length, using the dynamic analysis technique considering the train-track interaction. The results of numerical analysis demonstrate that the discontinuity of the support stiffness at the transition results in a drastic increase of the vertical vibration acceleration of the train body, wheel-rail interaction force, rail bending stress and uplift force. The increase becomes higher with the decrease of the spring constant of isolators and the increase of the isolator spacing, but the damping ratio does not significantly affect the behavior of train and track at the transition. Therefore, to assure the running safety and ride comfort, simultaneously increasing the effectiveness of vibration isolation, it is effective to minimize the relative vertical offset between the floating slab and the conventional track slab by adjusting the spring constant and spacing of isolators at the transition.

• The Journal of the Acoustical Society of Korea
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• v.37 no.1
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• pp.1-11
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• 2018

Sound propagation in shallow water changes from spherical spreading to cylindrical spreading, depending on boundary conditions, and this point is defined as a transition point of the sound propagation condition. Theoretically, the transition point can be estimated using the transmission loss as a function of source-receiver range. In this paper, the transmission loss curve in a Pekeris waveguide is predicted using a parabolic-equation based acoustic propagation model and using this transmission loss curve, the range from the source of the transition point is estimated, which is compared to the critical distance calculated using the sound speed ratio of water to sediment. In addition, the effects of the sound speed profile and source depth change on the transition point are investigated. Finally, the transition point is estimated using the transmission loss data measured during the period of the SAVEX15 (Shallow Water Acoustic Variability EXperiment 2015) conducted 65 km southwest of Jeju Island in May 2015, and it is compared to the ocean environmental parameters to understand the properties of sound propagation in the experimental area.

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.59-62
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• 2004

The performance of turbo code is improved by updating extrinsic information. The bit patterns are categorized by the transition characteristics of extrinsic information in this paper. And the distribution of these patterns is surveyed according to signal-to-noise ratio. Based on the results, the dominant error pattern is determined at high signal-to-noise ratio range. Thus, it is expected to improve the error performance in the error floor region by correcting the dominant error pattern which is found in this paper.

• Journal of computational fluids engineering
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• v.17 no.2
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• pp.107-112
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• 2012

We explored the dynamic motions and the lateral equilibrium positions of an elastic capsule in channel flow at moderate Reynolds number varying Re, aspect ratio, size ratio, membrane stretching and bending coefficient. The transition of tank-treading/swinging to tumbling motion was observed in the simulations and the transition of dynamic motions for capsules resulted in different trend of the variation in the lateral equilibrium positions. Though other conditions were similar, the capsule with tumbling motion migrated closer to the wall than that with tank-treading motion.