• Journal of the Korea Concrete Institute
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• v.25 no.4
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• pp.381-388
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• 2013

This study presents that effect of anchor plate on concrete breakout strength was evaluated. The addition of the anchor plate is to improve the concrete breakout capacity for a single anchor system in a thin-walled concrete panel (Insulated concrete sandwich wall panel). In this study, an elasticity-based simplified model was developed and used to predict effect on the anchor plate. Flexural stresses of the plate with respect to the concrete breakout strength obtained from CCD (Capacity Concrete Design) approach were compared with the test results. Through the test results, while the concrete breakout strength was improved due to increment of the width and thickness of the anchor plate, improvement of the strength was steadily declined. In addition, the It was observed that the analytical and experimental flexure of the anchor plate was comparatively in good agreement using the simplified elastic analysis model.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.4
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• pp.83-89
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• 2015

In this paper, we propose a fabrication technique for enhanced electrical properties of piezoelectric thick films with excellent patterning property using sol-infiltration and a direct-patterning process. To achieve the needs of high-density and direct-patterning at a low sintering temperature (< $850^{\circ}C$), a photosensitive lead zirconate titanate (PZT) solution was infiltrated into a screen-printed thick film. The direct-patterned PZT films were clearly formed on a locally screen-printed thick film, using a photomask and UV light. Because UV light is scattered in the screen-printed thick film of a porous powder-based structure, there are needs to optimize the photosensitive PZT sol infiltration process for obtaining the enhanced properties of PZT thick film. By optimizing the concentration of the photosensitive PZT sol, UV irradiation time, and solvent developing time, the hybrid films prepared with 0.35 M of PZT sol, 4 min of UV irradiation and 15 sec solvent developing time, showed a very dense with a large grain size at a low sintering temperature of $800^{\circ}C$. It also illustrated enhanced electrical properties (remnant polarization, $P_r$, and coercive field, $E_c$). The $P_r$ value was over four times higher than those of the screen-printed films. These films integrated on silicon wafer substrate could give a potential of applications in micro-sensors and -actuators.

• Journal of the Korea Concrete Institute
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• v.23 no.4
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• pp.413-420
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• 2011

The test results of high-strength concrete beam specimens, which have various combinations of different types of flexural reinforcement and short fibers, were compared with the prediction results of codes, guidelines and models proposed by researchers. The theoretical calculation based on the ultimate strength method of the KCI and ACI Code underestimated the ultimate moments of FRP bar-reinforced beams without fibers. The models proposed by ACI 544.4R and Campione predicted the ultimate moment capacities inaccurately for the FRP bar-reinforced beam with steel fibers, because these models do not consider the increased ultimate compressive strain of fiber reinforced concrete. Bischoff's deflection model predicted the service load deflections reasonably well, while the deflection model of ACI Committee 440 underestimated the deflection of FRP bar-reinforced beams. Because the ACI 440 expression, used to predict member deflection, cannot directly apply to the beams reinforced with different types of reinforcing bars, an alternative method to estimate the deflections of beams with different types of reinforcing bars using the ACI 440 expression was proposed. In addition, Bischoff's approach for computing deflection was extended to include deflection after yielding of the steel reinforcement in the beams reinforced with steel and FRP bars simultaneously.

• Journal of the Korean Ceramic Society
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• v.39 no.3
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• pp.286-293
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• 2002

Microstructure and the electrical porperties of a ZnO-based multilayered chip-type varistor(abbreviated as MLV) with Ag/Pd(7:3) inner electrode have been studied as a function of firing of temperature. At 1100$^{\circ}$C, inner electrode layers began to show nonuniform thickness and small voids, which resulted in significant disappearance of the electrode pattern and delamination at 1100$^{\circ}$C. MLVs fired at 950$^{\circ}$C showed large degradation in leakage current, probably due to incomplete redistribution of liquid and transition metal elements in pyrochlore phase decomposition. Those fired at 1100$^{\circ}$C and above, on the other hand, revealed poor varistor characteristics and their reproductibility, which are though to stem from the deformation of inner electrode pattern, the reaction between electrode materials and ZnO-based ceramics, and the volatilization of $Bi_2O_3$. Throughout the firing temperature range of 950∼1100$^{\circ}$C, capacitance and leakage current increased while breakdown voltage and peak current decreased with the increase of firing temperature, but nonlinear coefficient and clamping ratio kept almost constant at ∼30 and 1.4, respectively. In particular, those fired between 1000$^{\circ}$C and 1050$^{\circ}$C showed stable varistor characteristics with high reproducibility. It seems that Ag/Pd(7:3) alloy is one of the electrode materials applicable to most ZnO-based MLVs incorporating with $Bi_2O_3$ when cofired up to 1050$^{\circ}$C.

• Journal of the Korean Society of Food Science and Nutrition
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• v.45 no.10
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• pp.1525-1531
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• 2016

The objective of the present study was to investigate the rheological properties of potato starch cross-linked with different concentrations (0, 0.125, 0.25, and 0.5%, w/v) of cross-linking agents (10 g of adipic acid and 40 g of acetic anhydride). Cross-linked potato starch dispersions showed shear-thinning behaviors (n=0.43~0.63) at $25^{\circ}C$. Apparent viscosity (${\eta}_{a,100}$), consistency index (K), and yield stress (${\sigma}_{oc}$) significantly increased with an increase in the concentrations of cross-linking agents from 0.125 to 0.5% (w/v). Storage modulus (G') and loss modulus (G'') increased, whereas complex viscosity (${\eta}^*$) was reduced with increasing frequency (${\omega}$) from 0.63 to 62.8 rad/s. Magnitudes of G' and G'' for cross-linked potato starch were significantly increased with an elevation in the concentrations of cross-linking agents. G' values of cross-linked potato starches were significantly higher than G'', indicating that the starches had more elastic properties than viscous properties. Cox-Merz rule was not applicable to potato starch dispersions.

• Journal of the Korean Institute of Gas
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• v.18 no.6
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• pp.27-31
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• 2014

This paper presents a study on the strength safety of the weak parts at Part 1, Part 2 and Part 3 in the valve structure for LPG cylinder by using the finite element method. The maximum Von Mises stress of 27.5MPa was occurred at the corner edge of a valve Part 1 for the valve thickness of 1.5mm and LPG pressure of 3.5MPa. And the maximum Von Mises stresses for the valve thickness of 1.5mm and LPG pressure of 3.5MPa were 41.5MPa at Part 2 and 46.5MPa at Part 3. The FEM computed results show that the maximum Von Mises stresses at Part 1, Part 2 and Part 3 are very low value of 9.2~15.5% compared with the yield strength of a copper alloy, C3604. This means that the valve thickness for LPG cylinder is so over designed for the conventional valve. Thus, this paper recommends that the thickness at Part 1 and Part 2 is reduced for a light weight of a copper valve. But, the thickness at Part 3 may be better for a thick valve as a conventional valve for high torque strength.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.661-671
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• 2018

Domestic studies on steel plate concrete structures have focused on nuclear structures with high strength. In this study, the SC structure was applied to the general structure, and the SC structure that is advantageous in terms of safety and construction was limited to a special structure. As a basic study for applying SC, this paper proposes basic design information of a SC structure applying cement concrete to plan the structure, which is suitable for eco - friendliness by replacing concrete cement, an important factor in a SC structure, with blast furnace slag. This study examined the compression characteristics and the effective length factor under central compression load. To calculate the effective length factor, the Euler column theory was applied without applying plate theory. The effective length factor was calculated from the yield strength of the steel plate, buckling of the steel plate, and the point at which the concrete was broken. In addition, this study examined whether the maximum compressive strength meets the national and international reference equations with the slenderness ratio (B/t) as a parameter. By analyzing the buckling of the specimen by applying the column theory and selecting the strain of the measured steel plate, the effective length factor was analyzed and compared with the value presented in the reference equation.

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.2
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• pp.181-191
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• 2014

This study aims to evaluate cutter acting forces as well as axial stresses and torques in the shaft of two kinds of disc cutters including a single disc cutter and a double disc cutter with the same cutter ring geometry in a series of linear cutting tests. From the tests, the mean values of normal forces and rolling forces acting on the double disc cutter were approximately twice as high as those from the single disc cutter. Similarly, the mean values of axial stresses in the shaft of the double disc cutter were also twice as high as those from the single disc cutter even though the comparisons of torques from two kinds of disc cutters were insignificant since they showed very low values. However, it is necessary to take the durability of a tapered roller bearing used for the double disc cutter into high consideration since the average normal force from the double disc cutter exceeds the allowable force for a disc cutter with the diameter of 432 mm (17 inches). Finally, there is no practical problem in terms of axial stresses in the shaft of the double disc cutter since they are much lower than the yielding stress of the cutter shaft material, even though the axial stresses in the shaft of the double disc cutter are approximately twice as high as those from the single disc cutter.

• Journal of the Korea Concrete Institute
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• v.21 no.6
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• pp.719-727
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• 2009

The requirements of the maximum shear reinforcement in the EC2-02 and CSA-04, which are developed based on the truss model, are quite different to those in the ACI-08 code and AIJ-99 code, which are empirical equations. The ACI 318-08, CSA-04, and EC2-02 codes provide an expression for the maximum amount of shear reinforcement ratio as a function of the concrete compressive strength, but Japanese code does not take the influence of the concrete compressive strength into account. For high strength concrete, the maximum amount of shear reinforcement calculated by the EC2-02 and CSA-04 is much greater than that calculated by the ACI 318-08. Ten RC beams having various shear reinforcement ratios were tested and their corresponding shear stress-shear strain curves and failure modes were compared to the predicted ones obtained by the current design codes.

• Journal of the Korea Concrete Institute
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• v.28 no.3
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• pp.365-373
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• 2016

Ultra-High-Performance Steel Fiber-Reinforced Concrete (SUPER Concrete) exhibits improved compressive and tensile strengths far superior to those of conventional concrete. These characteristics can significantly reduce the cross sectional area of the member and the anchorage strength of a headed bar is expected to be improved. In this study, the anchorage strengths of headed bars with $4d_b$ or $6d_b$ embedment length were evaluated by simulated exterior beam-column joint tests where the headed bars were used as beam bars and the joints were cast of 120 or 180 MPa SUPER Concrete. In all specimens, the actual yield strengths of the headed bars over 600 MPa were developed. Some headed bars were fractured due to the high anchorage capacity in SUPER Concrete. Therefore, the headed bar with only $4d_b$ embedment length in 120 MPa SUPER Concrete can develop a yield strength of 600 MPa which is the highest design yield strength permitted by the KCI design code. The previous model derived from tests with normal concrete and the current design code underestimate the anchorage capacity of the headed bar anchored in SUPER Concrete. Because the previous model and the current design code do not consider the effects of the high tensile strength of SUPER Concrete. From a regression analysis assuming that the anchorage strength is proportional to $(f_{ck})^{\alpha}$, the model for predicting anchorage strength of headed bars in SUPER Concrete is developed. The average and coefficient of variation of the test-to-prediction values are 1.01 and 5%, respectively.