• Korean Journal of Metals and Materials
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• v.49 no.1
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• pp.32-39
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• 2011

The present investigation was performed on the die compaction and sintering behavior of Fe micro-nano mixed powder with a mixed binder for powder injection molding. Warm die compaction of the feedstock for simulation of the static injection molding process was conducted using a cylindrical mold of 10 mm diameter at $100^{\circ}C$ under 4MPa. The die compaction of the micro-nanopowder feedstock underwent a uniform molding behavior showing a homogeneous distribution of nanopowders among the micropowders without porosity and distortion. After debinding, the powder compact maintained a uniform structure without crack and distortion, leading to a high green density of 64.2% corresponding to the initial powder loading of 65%. The sintering experiment showed that the micro-nanopowder compact underwent a near full and isotropic densification process during sintering. It was observed that the nanopowders effectively suppressed the growth of micropowder grains during densification process. Conclusively, the use of nanopowder for PIM feedstock might provide a new concept for processing a full density PIM parts with fine microstructure.

• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.1-7
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• 2015

The industry has rapidly growth and energy supply technology advanced are become main factor which to contribute of the harmonic losses. This problem is one aspect that may affect the capability of the transmission line and also to the efficiency of electricity. This paper proposes a new scheme to allocate the cost pertaining to transmission loss due to harmonics. The proposed method, called as Generalized Harmonic Distribution Factor, uses the principle of proportional sharing method to allocate the losses among the transmission users especially for industry consumers. The IEEE 14- and 30 bus test system is used to compare the proposed method with existing method. The results showed that the proposed method provided a scheme better in allocating the cost of transmission loss, which could encourage the users to minimize the losses.

• Transactions of Materials Processing
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• v.3 no.1
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• pp.120-132
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• 1994

Strip drawing of strain-hardening, viscoplastic materials with damage is analyzed by a rigid plastic finite element method. A process model is formulated using two state variables, one for strain hardening from slip dominated plastic distortion and the other for damage from growth of microvoids. Application of the model to aluminum strip drawing is given via implementation in a consistent penalty finite element formulation. The predicted density changes as a result of void growth are compared to those from experiments reported in the literature. The effects of drawing conditions such as drawing speed and die angle on the mechanical property chages are studied.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1994.03a
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• pp.71-79
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• 1994

Strip drawing of strain-hardening, viscoplastic materials with damage is analyzed by a rigid plastic finite element method. A process model is formulated using two state variables, one for strain hardening from slip dominated plastic distortion and the other for damage from growth of microvoids. Application of the model to steady state drawing is given via implementation in a consistent penalty finite element formulation. The predicted density changes as a result of void growth are compared to those from experiments reported in the literature. The effects of drawing conditions such as drawing speed and die angle on the mechanical property changes are studied.

• Journal of the Semiconductor & Display Technology
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• v.3 no.3
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• pp.23-25
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• 2004

The defect formation energy of boron nitride (BN) nanotubes is investigated using molecular-dynamics simulation. Although the defect with tetragon-octagon pairs (4-88-4) is favored in the flat cap of BN nanotubes, BN clusters, and the growth of BN nanotubes, the formation energy of the 4-88-4 defect is significantly higher than that of the pentagon-heptagon pairs (5-77-5) defect in BN nanotubes. The 5-77-5 defect reduces the effect of the structural distortion caused by the 4-88-4 defect, in spite of homoelemental bonds.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2004.05a
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• pp.59-62
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• 2004

The defect formation energy of boron nitride (BN) nanotubes is investigated using molecular-dynamics simulation. Although the defect with tetragon-octagon pairs (4-88-4) is favored in the flat cap of BN nanotubes, BN clusters, and the growth of BN nanotubes, the formation energy of the 4-88-4 defect is significantly higher than that of the pentagon-heptagon pairs (5-77-5) defect in BN nanotubes. The 5-77-5 defect reduces the effect of the structural distortion caused by the 4-88-4 defect, in spite of homoelemental bonds. The instability of the 4-88-4 defect generates the structural transformation into BNNTs with no defect at about 1500 K.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.52.2-53
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• 2017

We develop a methodology to use the redshift dependence of the galaxy 2-point correlation function (2pCF) as a probe of cosmological parameters. The positions of galaxies in comoving Cartesian space varies under different cosmological parameter choices, inducing a redshift-dependent scaling in the galaxy distribution. This geometrical distortion can be observed as a redshift-dependent rescaling in the measured 2pCF. The shape of the 2pCF exhibits a significant redshift evolution when the galaxy sample is analyzed under a cosmology differing from the true, simulated one. Other contributions, including the gravitational growth of structure, galaxy bias, and the redshift space distortions, do not produce large redshift evolution in the shape. We show that one can make use of this geometrical distortion to constrain the values of cosmological parameters governing the expansion history of the universe. This method could be applicable to future large scale structure surveys, especially photometric surveys such as DES, LSST, to derive tight cosmological constraints. This work is a continuation of our previous works as a strategy to constrain cosmological parameters using redshift-invariant physical quantities.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.1
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• pp.107-112
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• 1999

The ZnSe/GaAs epilayers were grown by RF reactive sputtering. In order to obtain the optimum condition of the growth, we have studied the dependence of Ar pressure, input power of sputter, temperature of substrate, and the distande between substrate and target. Through the observation of the grown epilayer via electronic microscope, we confirmed that the layer's surface was uniform and the boundary of the substrate and the layer was well defined. The defotmation of lattice distortion and the distortion ratio were obtained by DCRC measurements. From mrasurements of photoluminescence, in the ZnSe/GaAs sample without injection of $N_2$gas, we found that the intensity of bound exciton $I_2$is stronger than that of $I_1$and the bound exiton $I_1$represents the deep acceptor level, $I_1\;^d$. On the other hand, in the ZnSe/GaAs sample with injection of$N_2$gas, the peak of$I_1$ was much higher than that of the $I_2$and the half width appeared to be narrow. We concluded that the p-type of ZnSe/GaAs epilayer was grown successfully, because of stronger peak of the bound exciton $I_1$due to the $N_2$dopping.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.10C
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• pp.991-999
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• 2006

This paper shows that the support growth of an optimum (minimum mean square-error) scalar quantizer for a Laplacian density is logarithmic with the number of quantization points. Specifically, it is shown that, for a unit-variance Laplacian density, the ratio of the support-determining threshold of an optimum quantizer to $\frac 3{\sqrt{2}}1n\frac N 2$ converges to 1, as the number of quantization points grows. Also derived is a limiting upper bound that says that the optimum support cannot exceed the logarithmic growth by more than a constant. These results confirm the logarithmic growth of the optimum support that has previously been derived heuristically.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.4
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• pp.132-138
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• 2023

Doped and undoped-BiVO₄ samples with different elements (Li, Mg) and amounts were synthesized with a hydrothermal method. The synthesized samples were characterized using various techniques including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-Vis diffusion reflectance spectroscopy (UV-Vis DRS), and photoluminescence (PL) spectroscopy. Photocatalytic activity of the samples was evaluated by measuring the degradation of methyl blue (MB) under visible light irradiation. The results indicated that the incorporation of Mg and Li into BiVO₄ caused lattice distortion, the presence of surface hydroxyl groups, a narrower band gap, and a reduced recombination ratio of photo-induced electron-hole pairs. Notably, the photocatalytic activity of Mg5%-Li5% co-doped BiVO₄ sample exhibited a significant improvement compared to that of undoped BiVO₄ sample.