• Journal of the Korea Institute of Military Science and Technology
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• v.1 no.1
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• pp.154-165
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• 1998

In this paper, the mongrel singular element with 6 node triangle and 8 node quadrilateral element with J-integral are developed and applied to the various plane crack problems for the isotropic material. The convergence nature is excellent for various crack size with even coarse mesh using the direct method. But the results of the mongrel element with J-integral are worse than the former's ones. Fracture tests were conducted on precracked CT specimens. Results show that, for 7075-T6 aluminum wing spar materials, the fracture toughness is 31.06 ksi.inch $\frac{1}{2}$ in the L-T direction.

• Journal of IKEEE
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• v.20 no.2
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• pp.152-162
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• 2016

Electrical resistivity tomography (ERT) is a technique to reconstruct the internal resistivity distribution using the measured voltages on the surface electrodes. ERT inverse problem suffers from ill-posedness nature, so regularization methods are used to mitigate ill-posedness. The reconstruction performance varies depending on the type of regularization method. In this paper, an interacting dual-mode regularization method is proposed with two different regularization methods, L1-norm regularization and total variation (TV) regularization, to achieve robust reconstruction performance. The interacting dual-mode regularization method selects the suitable regularization method and combines the regularization methods based on computed mode probabilities depending on the actual conditions. The proposed method is tested with numerical simulations and the results demonstrate an improved reconstruction performance.

• The Journal of the Korea Contents Association
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• v.7 no.1
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• pp.124-130
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• 2007

A rectangular coaxial line is mainly utilized as a transition structure from a coaxial line to a rectangular waveguide. A TEM cell is also widely used to measure the EMC characteristics of a DUT. In order to understand the operations of a rectangular coaxial line and a TEM cell, it is essential to analyze the dispersion relations of a rectangular coaxial line and a TEM cell. In this paper, we present simple yet accurate dispersion relations of the TE and TM higher modes based on the TEM mode. Manipulating a mode-matching technique and a Green's function approach allows us to obtain the analytic dispersion equations of a rectangular coaxial line and a TEM cell. In our approach, a rectangular coaxial line is divided into four L-blocks and its electromagnetic fields representations are easily obtained with a superposition. To verify the convergence of our dispersion relations, we perform numerical computations and compare our results with those of FDTD.

• Transactions of the KSME C: Technology and Education
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• v.2 no.1
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• pp.39-46
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• 2014

This study presents computational analysis of aerodynamic characteristics of two-dimensional airfoil sections with elastic flap attached at the trailing edge. EDISON_CFD was utilized to simulate the incompressible turbulent flow around the foil and MIDAS_IT was employed to estimate the deflection of the flap under the pressure loading. Using iterative procedure, the terminal deflection was estimated and the resulting lift-drag ratio indicates that the favorable effect of the flap is expected within certain amount of angle of attack.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.7
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• pp.731-738
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• 2012

In this study, the evaluation of the aerodynamic characteristics of the NREL Phase VI Rotor System has been performed, for the 7 m/s upwind case using commercial FEA and CFD tools which are ANSYS Mechanical 12.1 and CFX 12.1. The initial operating conditions of the rotor blade include a $3^{\circ}$ tip pitch angle. A numerical simulation was carried out on only the rotor parts, excluding the tower structure based on the equivalent stiffness model, to consider the aeroelastic effect for the numerical simulation using the loosely coupled 2-way fluid-structure interaction method. The blade root bending moment was monitored in real time to obtain reasonable results. To verify the analysis results, the numerical simulation results were compared with the measurements in the form of the root bending moment and the pressure distributions of the NREL/NASA Ames wind tunnel test.

• Journal of the Korean Society of Food Science and Nutrition
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• v.41 no.9
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• pp.1211-1219
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• 2012

In this study, extracts from Caragana sinica flowers and leaves were tested for antioxidant and angiotensin converting enzyme inhibitory activities, along with xanthine oxidase, tyrosinase, elastase, and astringent effects. Total phenolic compounds of acetone extracts from Caragana sinica flowers and leaves were the highest at 3.42 and 2.98 mg/g, respectively, when various extraction solvents were used. Optimal conditions for extraction of phenolic compounds from Caragana sinica leaves and flowers were 70% ethanol for 18 hr. DPPH scavenging activities were the highest in 70% ethanol extracts of Caragana sinica. ABTS radical cation decolorization values of 70% ethanol extracts were higher than those 60% ethanol extracts at 74%. Antioxidant protection factor was 1.2 PF in 70% ethanol extracts from Caragana sinica flowers and leaves. TBARS was lower than that of control (0.54 ${\mu}M$) in all sections. Angiotensin converting enzyme inhibitory activity of Caragana sinica flower extract was 80~90% at a phenolic concentration of 0.2~1.0 mg/mL, whereas xanthin oxidase inhibitory activity of Caragana sinica leaf extract was higher than that of flower extract. Tyrosinase inhibitory activity, which is related to skin-whitening, was above 20%, whereas elastase inhibitory activity related to anti-wrinkle effect was above 50% at a phenolic concentration of 0.8 mg/mL. Astringent effects of Caragana sinica flower and leaf extracts were higher than tannic acid as a control at an equivalent concentration. This result suggests that extracts from Caragana sinica flowers and leaves are suitable as functional foods having anti-hypertension, anti-gout, and medicinal cosmetic activities, including whitening and anti-wrinkle effects.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.4
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• pp.209-216
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• 2020

In this paper, parametric structural analysis is presented utilizing the co-rotational(CR) shell analysis utilizing EDISON. CR shell analysis shows faster convergence than the commercial software, NASTRAN, does. The 1st natural frequency of the rear frame is obtained, which is close to that of the engine during high speed cruise. Three cases under two design variables are presented and analyzed. Gusset is shown to be more effective among those which feature the same weight change. The results presented in this paper will be applicable for further researches to improve the durability of a motorcycle rear frame.

• The Journal of the Petrological Society of Korea
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• v.26 no.1
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• pp.45-54
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• 2017

The characteristics of the rock cleavage in Jurassic Geochang granite were analysed using the distribution of microcrack lengths and spacings. The phases of distribution of the above lengths and spacings were derived from the enlarged photomicrographs(${\times}6.7$) of the thin section. First, the length and spacing-cumulative diagrams for the six directions of rock cleavages were arranged in increasing order($H2{\rightarrow}R1$) on the density(${\rho}$) of microcrack length. The various parameters were extracted through the combination of the above two types of diagrams. The discrimination factors representing the three quarrying planes and three rock cleavages were acquired through the mutual contrast between the values of parameters. The analysis results of the research are summarized as follows. The evaluation for the six directions of rock cleavages was performed using the parameters such as (1) intersection angle(${\alpha}-{\beta}$) and (2) exponent difference(${\lambda}_S-{\lambda}_L$) between two exponential straight lines related to spacing(${\alpha}$, ${\lambda}_S$) and length(${\beta}$, ${\lambda}_L$). The values of parameters(1 and 2) are in order of H(hardway, (H1 + H2)/2) < G(grain, (G1 + G2)/2) < R(rift, (R1 + R2)/2). On the contrary, the values of the above two parameters for three planes are in order of R < G < H. Meanwhile, the direction of convergence between two exponential straight lines was derived. The above direction is compliant to arrangement of the line os' centering around the line ol. The above two lines converge in the direction of the Y-axis when the line ol and line os' occupy the upper region on the left and the lower region on the right, respectively(R-type). On the contrary, the above two lines converge in the direction of the X-axis when the order of arrangement between line ol and line os' is reversed(H-type). Especially, the positive(+) or negative(-) value of intersection angle(${\alpha}-{\beta}$) is determined by the arrangement of two vertical lines. This type of correlation analysis is useful for evaluating the relative strength of rock cleavage and discriminating three quarrying planes.

• The Journal of the Acoustical Society of Korea
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• v.18 no.6
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• pp.31-37
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• 1999

This paper describes the far-field estimation using the near-field measurement data. Measurement in far-field region gives us the acoustical characteristics of the source but in general measurement is made in near-field such as acoustic water tank or anechoic chamber, so far-field acoustical characteristics of the source should be predicted from near-field data. In this case, the number of measurement points in the near field which relates to the accuracy of the predicted field and the amount of data processing, should be optimized. Existing papers say that measurement points is proportional to kL and depends on geometry and directivity of the source. But they do not give us any definite criterion for the required number of measurement points. Boundary Collocation Method which is one of the far-field prediction methods, is analyzed based on Helmholtz integral equation and Green function and it has been found that the number of measurement points is optimized as 0.54kL which is about one half of the existing results.

• Journal of the Korea Convergence Society
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• v.10 no.5
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• pp.149-156
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• 2019

This study adopts 'intersectionality' as a key concept of Sheila Levrant de Bretteville's design works. As a method of research, this research suggests the definition of intersectionality, from the idea of black feminism. Analysis of the features are such as 1) Typography of speech, 2) Collection of narrative, and 3) site specific installation. The inclusion of the various situations of the individuals reflected in the design throughout de Bretteville's works has made it possible to guarantee the intersectionality. De Bretteville overthrows the context of the power in which the design is placed, embracing forgotten or less illuminated positions. As a result, this research could derive three implications such as 1) visualization of invisibility, 2) subjectification of object, and 3) demarginalization of marginality. The perspective of the intersectionality are in line with the values of contemporary Korean society and might be an insight for researchers who want to establish a design philosophy.