• Journal of Korean Society of Steel Construction
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• v.14 no.6
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• pp.823-834
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• 2002

Maximum-strength concrete-filled steel square tubular columns were tested under concentric and biaxial eccentric load. Buckling length-section depth ratio $L_k/D$, magnitude of eccentricity e, and angle of eccentric load ${\theta}$ were selected as experimental parameters. Strength and behavior were also examined. Test results showed that the maximum strength of columns under biaxial eccentric load could be predicted using the previously proposed strength formula of columns undr uniaxia eccentric load. Likewise, the behavior and maximum strength of columns could be predicted using the analysis.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.700-703
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• 2004

A reliability analysis and design procedure based on the design of experiment (DOE) is combined with the response surface method (RSM) for numerical efficiency. The procedure established is based on a 3$^n$ full factorial DOE for numerical quadrature using explicit formula of optimum levels and weights derived for general distributions. The full factorial moment method (FFMM) shows good performance in terms of accuracy and ability to treat non-normally distributed random variables. But, the FFMM becomes very inefficient because the number of function evaluation required increases exponentially as the number of random variables considered increases. To enhance the efficiency, the response surface moment method (RSMM) is proposed. In RSMM, experiments only with high probability are conducted and the rest of data are complemented by a quadratic response surface approximation without mixed terms. The response surface is updated by conducting experiments one by one until the value of failure probability is converged. It is calculated using the Pearson system and the four statistical moments obtained from the experimental data. A measure for checking the relative importance of an experimental point is proposed and named as influence index. During the update of response surface, mixed terms can be added into the formulation.

• Journal of electromagnetic engineering and science
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• v.18 no.1
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• pp.13-19
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• 2018

Wireless power transfer (WPT) based on magnetic resonant coupling is a promising technology in many industrial applications. Efficiency of the WPT system usually depends on the tilt angle of the transmitter or the receiver coil. This work analyzes the effect of the tilt angle on the efficiency of the WPT system with horizontal misalignment. The mutual inductance between two coils located at arbitrary positions with tilt angles is calculated using a numerical analysis based on the Neumann formula. The efficiency of the WPT system with a tilted coil is extracted using an equivalent circuit model with extracted mutual inductance. By analyzing the results, we propose an optimal tilt angle to maximize the efficiency of the WPT system. The best angle to maximize the efficiency depends on the radii of the two coils and their relative position. The calculated efficiencies versus the tilt angle for various WPT cases, which change the radius of RX ($r_2=0.075m$, 0.1 m, 0.15 m) and the horizontal distance (y=0 m, 0.05 m, 0.1 m), are compared with the experimental results. The analytically extracted efficiencies and the extracted optimal tilt angles agree well with those of the experimental results.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.7
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• pp.615-619
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• 2008

A molecular memory device which has a structure of Al/$Al_2O_3$/ASA-15 LB monolayer/Ti/Al device, was fabricated. To study a charge transfer mechanism of molecular memory devices, current density-voltage (J-V) characteristics were measured at an increasing temperature range from 10 K to 300 K with an interval of 30 K. Strong temperature-dependent electrical property and tunneling through organic monolayer at low bias (below 0.5 V) were appeared. These experimental data were fitted by using a theoretical formula such as the Simmons model. In comparison between the theoretical and the experimental results, it was verified that the fitting results using the Simmons model about direct tunneling was fairly fitted below 0.5 V at both 300 K and 10 K. Hopping conduction was also dominant at all voltage range above 200 K due to charges trapped by defects located within the dielectric stack, including the $Al_2O_3$, organic monolayer and Ti interfaces.

• Journal of KSNVE
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• v.6 no.5
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• pp.607-616
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• 1996

A combined computational fluid dynamics(CFD)-Kirchhoff method is presented for predicting high-speed impulsive noise generated by a hovering blade. Two types of Kirchhoff integral formula are used; one for the classical linear Kirchhoff formulation and the other for the nonlinear Kirchhoff formulation. An Euler finite difference solver is solved first to obtain the flow field close to the blade, and then this flow field is used as an input to a Kirchhoff formulation to predict the acoustic far-field. These formulas are used at Mach numbers of 0.90 and 0.95 to investigate the effectiveness of the linear and nonlinear Kirchhoff formulas for delocalized flow. During these calculiations, the retarded time equation is also carefully examined, in particular, for the cases of the control surface located outside of the sonic cylinder, where multiple roots are obtained. Predicted results of acoustic far-field pressure with the linear Kirchhoff formulation agree well with experimental data when the control surface is at the certain location(R=1.46), but the correlation is getting worse before or after this specific location of the control surface due to the delocalized nonlinear aerodynamic flow field. Calculations based on the nonlinear Kirchhoff equation using a linear sonic cylinder as a control surface show a reasonable agreement with experimental data in negative amplitudes for both tip Mach numbers of 0.90 and 0.95, except some computational integration problems over a shock. This concliudes that a nonlinear formulation is necessary if the control surface is close to the blade and the flow is delocalized.

• Steel and Composite Structures
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• v.22 no.2
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• pp.217-234
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• 2016

In order to investigate mechanical properties and load-bearing capacity of T-shaped Concrete-Filled Square Steel Tubular (TCFST) composite columns under eccentric axial load, three T-shaped composite columns were tested under eccentric compression. Experimental results show that failure mode of the columns under eccentric compression was bending buckling of the whole specimen, and mono column performs flexural buckling. Specimens behaved good ductility and load-bearing capacity. Nonlinear finite element analysis was also employed in this investigation. The failure mode, the load-displacement curve and the ultimate bearing capacity of the finite element analysis are in good agreement with the experimental ones. Based on eccentric compression test and parametric finite element analysis, the calculation formula for the equivalent slenderness ratio was proposed and the bearing capacity of TCFST composite columns under eccentric compression was calculated. Results of theoretical calculation, parametric finite element analysis and eccentric compression experiment accord well with each other, which indicates that the theoretical calculation method of the bearing capacity is advisable.

• Journal of Pharmaceutical Investigation
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• v.40 no.1
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• pp.1-7
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• 2010

K-$BEtest^{(R)}$ is a well known program for bioequivalence test using a $2{\times}2$ design. Lee et al.(1998) and Park et al.(1999) suggested a $3{\times}3$ and $3{\times}2$ design, and also discussed their benefits. We developed a computer program, called BioEquiv, which can analyze some complex experimental designs such as, $3{\times}3$ design and $3{\times}2$ design including a standard $2{\times}2$ design. This program is a user-friendly one and overcomes the disadvantages of K-$BEtest^{(R)}$. The detailed statistical formula and structure of BioEquiv are presented with some examples. The comparison between K-$BEtest^{(R)}$ and BioEquiv are given with actual data analysis. BioEquiv is able to present a table of ANOVA test over some complex experimental designs. Moreover K-$BEtest^{(R)}$ and BioEquiv draw the same result when data consists of $2{\times}2$ design.

• Transactions on Electrical and Electronic Materials
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• v.17 no.2
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• pp.79-85
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• 2016

In this study, we proposed a new single-stage small power MH lamp electronic ballast and power-factor correction circuit with improved circuit by the current of passive power factor correction. Main circuit integrates traditional DC/DC and DC/AC circuits into one-stage DC/AC inverter. Moreover, we described the working principle and control strategy of the new circuit; it's soft switching principle; and resonant element parameter design formula. An experimental prototype of HID lamp electronic ballast with output power of 70 W was built to verify the feasibility of the analysis and design. The simulation and experimental results proved that the power factor of this circuit could reach 94%, with efficiency of 90%. The input current harmonics conform to IEC 61000-3-2 standards and its cost is low. These superior performances of the new circuit indicate certain practical values.

• Journal of Korean Society of Steel Construction
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• v.20 no.2
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• pp.347-354
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• 2008

Steel plate-concrete (SC) structure has recently been used in nuclear power structure because of its construction efficiency. In this study, experimental and analytical study to investigate the behavior of the SC structure's wall slab connection was carried out. Experiments were performed for typical SC and RC connections in order to examine the basic difference between each structure. Finite element analysis was performed and the result of the analysis was found to closely reflect the experimental result. By varying the thickness of the shear plate and friction coefficients and the distance of applied load from the wall, the influence of the parameters on the joint strength and failure modes were examined. Finally, it was confirmed that the joint strength formula proposed in th this research gives conservative results.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.7
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• pp.21-29
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• 1989

Using Fresnel diffraction theory a formula is drived for signal intensity variation caused by finite strip obstacles. Signal intensity according to parameter variation of the obstacle is theoretically calculated by a computer and compared with experimental results. For the experiment, an acryl board 3 mm thick was used on which a special material was painted to prevent some reflections and transmissions of the incident wave. 10-element Yagi antennas were used for transmitting and receiving antenna and the frequency was 820 MHz. Finally a tree model was made as a combination of many different finite strip obstacles. Signal attenuation calculated from numerical analysis agree reasonably with experimental data.