• Magazine of the Korean Society of Agricultural Engineers
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• v.34 no.E
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• pp.60-69
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• 1992

The research significance of the paper is to identify the major properties of synthetic lightweight concrete that are affected by ASR expansion and to determine the extent and magnitude of the loss in these properties. Emphasis is also given to the use of non-destructive testing techniques ; Such as dynamic modulus of elasticity and ultrasonic pulse velocity, to examine whether these methods could be used to identify the initiation of expansion and the internal structural damage caused by ASR.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1997.04a
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• pp.45-52
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• 1997

The elastic deflection of thin ice sheets due In bending and shear deformation is considered. The in-plane Young's modulus and the transverse shear modulus are calculated by least squres fit of transverse plate deflection data. Results show that thin ice plates behave predominantly in shear. Previously, the Young's moduli were calaulated based on bending theory alone. The Young's moduli of thin model ice sheets, estimated using the bending and shear theory, are more than an order of magnitude greater than calculated previously, and hence are more realistic. Further, the previous ambiguity in the Young's modulus, arising from fitting the data at various distances from the point of loading, is removed by considering shear and bending deformation.

• Journal of The Korean Astronomical Society
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• v.44 no.1
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• pp.33-38
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• 2011

We study near-infrared properties of the old open cluster King 11, based on the 2MASS photometric data. We determine the location of the red giant clump(RGC) in the (K, J - K) colo-magnitude diagram and derive the distance modulus of King 11 to be $(m-M)_0$ = $12.50{\pm}0.10$ using the mean K magnitude of RGC. From the red giant branch slope - [Fe/H] relation we obtain the metallicity of this cluster, [Fe/H]=$-0.17{\pm}0.07$. The age and interstellar reddening of this cluster are estimated to be log t = $9.48{\pm}0.05$, E(B-V)=$0.90{\pm}0.03$, by applying Padova isochrone fits to the data.

• Journal of Astronomy and Space Sciences
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• v.23 no.2
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• pp.91-96
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• 2006

We use near-infrared observations of eight selected Galactic globular clusters to estimate their distances by comparing the observed and theoretically predicted K magnitudes of the red giant branch bumps and tips. The K magnitude levels of the RGB bump and tip have been measured from the luminosity function of the selected RGB stars in the clusters. Theoretical absolute $M_k$ magnitudes of the RGB bump and tip are taken from the Yonsei-Yale isochrones. Comparing the observed apparent K magnitude with the derived absolute $M_k$ magnitude, we calculate the distance moduli of the clusters. We discuss the dependency of the derived distance modulus on the cluster age and the uncertainty of the distance measurement from the near-infrared photometry of the RGB bump and tip.

• Journal of Astronomy and Space Sciences
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• v.23 no.2
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• pp.97-104
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• 2006

From the BV images of the metal-poor globular cluster NGC 1904 obtained with the 2K CCD camera equipped on the BOAO 1.8m telescope, we construct (B - V, V) color-magnitude diagram of the cluster. The apparent V magnitudes of the RGB bump and tip have been measured from the luminosity function of the iteratively selected RGB stars in NGC 1904. Theoretical absolute $M_v$ magnitudes of the RGB bump and tip are estimated using the Yonsei-Yale isochrones. The distance modulus of NGC 1904 has been derived by comparing the observed apparent V magnitude with the estimated absolute $M_v$ magnitude of the RGB bump and tip.

• Korea-Australia Rheology Journal
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• v.16 no.1
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• pp.17-26
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• 2004

We examine rigorous computations on microstructural as well as rheological properties of concentrated dispersions of bidisperse colloids. The NVT Monte Carlo simulation is applied to obtain the radial distribution function for the concentrated system. The long-range electrostatic interactions between dissimilar spherical colloids are determined using the singularity method, which provides explicit solutions to the linearized electrostatic field. The increasing trend of osmotic pressure with increasing total particle concentration is reduced as the concentration ratio between large and small particles is increased. From the estimation of total structure factor, we observe the strong correlations developed between dissimilar spheres. As the particle concentration increases at a given ionic strength, the magnitude of the first peak in structure factors increases and also moves to higher wave number values. The increase of electrostatic interaction between same charged particles caused by the Debye screening effect provides an increase in both the osmotic pressure and the shear modulus. The higher volume fraction ratio providing larger interparticle spacing yields decreasing high frequency limit of the shear modulus, due to decreasing the particle interaction energy.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.1
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• pp.145-150
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• 2008

One of the unresolved questions in articular cartilage biomechanics is the magnitude of the dynamic modulus and tissue compressive strains under physiological loading conditions. The objective of this study was to characterize the dynamic modulus and compressive strain magnitudes of bovine articular cartilage at physiological compressive stress level and loading frequency. Four bovine calf shoulder joints (ages 2-4 months) were loaded in Instron testing system under load control, with a load amplitude up to 800 N and loading frequency of 1 Hz, resulting in peak engineering stress amplitude of ${\sim}5.8\;MPa$. The corresponding peak deformation of the articular layer reached ${\sim}27%$ of its thickness. The effective dynamic modulus determined from the slope of stress versus strain curve was ${\sim}23\;MPa$, and the phase angle difference between the applied stress and measured strain which is equivalent to the area of the hystresis loop in the stress-strain response was ${\sim}8.3^{\circ}$. These results are representative of the functional properties of articular cartilage in a physiological loading environment. This study provides novel experimental findings on the physiological strain magnitudes and dynamic modulus achieved in intact articular layers under cyclical loading conditions.

• Tunnel and Underground Space
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• v.13 no.1
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• pp.44-51
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• 2003

Changes of the hydraulic conductivity resulting from the redistribution of stresses by underground excavation are examined using the strain-dependent hydraulic conductivity modification relation, where the modulus reduction ratio and induced strain are the major parameters. The modulus reduction ratio is defined in terms of RMR(Rock Mass Rating) to represent the full gamut of rock mass condition. Though shear dilation has the effect on the modification of hydraulic conductivity, the extent of it depends on RMR When the extensional strain is applied to a fracture, the hydraulic conductivity increases with the decrease of RMR Loading configuration has the effect on the modification of hydraulic conductivity, where the differential stress mode with a magnitude of the minimum principal stress $($\sigma$_x)$ fixed and a magnitude of the maximum principal stress $($\sigma$_y)$ varied is found to exert the greatest effect on the change of hydraulic conductivity.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.1
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• pp.133-143
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• 1996

The constant modulus algorithm (CMA), one of the widely used blind equalization algorithms, equalizes channels using the second-order statistic of equalizer outputs. The performance of the CMA for multi-level signals such as the quadrature amplitude modulation (QAM) signal degrades because the CMA maps all signal power onto a single modulus. in this paper, to improve the equalization performance of a QAM system, we propose a shell partitioning method based on error magnitude. We assume the probability distribution of an equalizer output as Gaussian, and obtain decision boundaries by maximum likelihood estimation based on the fact that the distribution of the equalizer output power is noncentral $x^2$. The proposed CMA constructs a multi-moduli equlization system based on the fact that each shell separated by decision boundaries employs a single modulus. Computer simulation results for 32-QAM and 64-QAM show the effectiveness of the proposed algorithm.

• Structural Engineering and Mechanics
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• v.64 no.1
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• pp.71-79
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• 2017

In this study, interaction of several interface cracks located between a functionally graded material (FGM) layer and an elastic layer under anti-plane deformation based on the distributed dislocation technique (DDT) is analyzed. The variation of the shear modulus of the functionally graded coating is modeled by an exponential and linear function along the thickness of the layer. The complex Fourier transform is applied to governing equation to derive a system of singular integral equations with Cauchy type kernel. These equations are solved by a numerical method to obtain the stress intensity factors (SIFs) at the crack tips. The effects of non-homogeneity parameters for exponentially and linearly form of shear modulus, the thickness of the layers and the length of crack on the SIFs for several interface cracks are investigated. The results reveal that the magnitude of SIFs decrease with increasing of FG parameter and thickness of FGM layer. The values of SIFs for FGM layer with exponential form is less than the linear form.