• Bulletin of the Korean Chemical Society
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• v.5 no.3
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• pp.108-112
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• 1984

Interactions between metal ions and chitosan in solution were studied by spectroscopic and viscometric measurements. $Cu^{++}$-chitosan complex exhibited an absorption band at 265 nm, whereas D-glucosamine complex showed one at 245 nm. The difference in ${\lambda}_{max}$ was attributed to the different amine to $Cu^{2+}$ ratios of the complexes, that is, 2 : 1 for chitosan and 1 : 1 for D-glucosamine. The molar absorptivities and binding constants of the complexes were evaluatatled. The binding of $Cu^{2+}$ to chitosan was cooperative near pH 5, and both intra- and intermolecular chelations depending on chitosan and $Cu^{2+}$concentrations were observed, The intermolecular chelation was stabilized by addition of salts. The cooperative intermolecular chelation of $Ni^{++}$ was also observed at pH 6.2. No significant binding of other divalent ions was observed. The reported high adsorption abilities of chitosan particles for these ions were attributed to the deposition of metal hydroxide aggregates in pores of chitosan particles rather than chelation to amine groups.

• Journal of Conservation Science
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• v.32 no.3
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• pp.313-320
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• 2016

The aim of this study was to obtain information on the ancient material of cast bronze through an investigation of the microstructure and impurity characteristics of the casting. Three Koryo bronze coins were analyzed using an optical microscope, scanning electron microscope, and electron dispersive X-ray analyses were used to determine the composition of the specimens. The three coins had 4 phases: ${\alpha}phase$, ${\delta}phase$, Pb, and impurities ($Cu_2S$). $Cu_2S$ was found to exist near Pb or in ${\delta}phase$. $Cu_2S$ is the inter mediate product of copper ore refining. Therefore, the copper ore was not completely refined. To find out the characteristic of $Cu_2S$, we melt 1)Koryo bronze coin and 2)$Cu_2S$ and Pb powder at 1273 K. The reaction between $Cu_2S$ and Pb at 1273 K yielded fine Cu and black gas, which was identified to be PbS and is presented below: $Cu_2S+Pb{\rightarrow}PbS{\uparrow}+2Cu$.

• Journal of Technologic Dentistry
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• v.34 no.4
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• pp.345-352
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• 2012

Purpose: The age-hardening mechanism of an Au-Ag-Cu-Pt-Zn alloy for crown and bridge fabrication was investigated by means of hardness test, X-ray diffraction study and field emission scanning electron microscopic observation. Methods: Before hardness testing, the specimens were solution treated and then were rapidly quenched into ice brine, and were subsequently aged isothermally at $400-450^{\circ}C$ for various periods of time in a molten salt bath and then quenched into ice brain. Hardness measurements were made using a Vickers microhardness tester. The specimens were examined at 15 kV using a field emission scanning electron microscope. Results: By the isothermal aging of the solution-treated specimen at $450^{\circ}C$, the hardness increased rapidly in the early stage of aging process and reached a maximum hardness value. After that, the hardness decreased slowly with prolonged aging. However, the relatively high hardness value was obtained even with 20,000 min aging. By aging the solution-treated specimen, the f.c.c. Au-Ag-rich ${\alpha}_0$ phase was transformed into the Au-Ag-rich ${\alpha}_1$ phase and the AuCu I ordered phase. Conclusion: The hardness increase in the early stage of aging process was attributed to the formation of lattice strains by the precipitation of the Cu-rich phase and then subsequent ordering into the AuCu I-type phase. The decrease in hardness in the later stage of aging process was due to the release of coherency strains by the coarsening of tweed structure in the grain interior and by the growth and coarsening of the lamellar structure in the grain boundary. The increase of inter-lamellar space contributed slightly to the softening compared to the growth of lamellar structure toward the grain interior.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.229-229
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• 2010

With the scaling down of ultra large integrated circuits (ULSI) to the sub-50 nm technology node, the need for an ultra-thin, continuous and conformal diffusion barrier and Cu seed layer is increasing. However, diffusion barrier and Cu seed layer formation with a physical vapor deposition (PVD) method has become difficult as the technology node is reduced to 30 nm and beyond. Recent work on self-forming barrier processes using PVD Cu alloys have attracted great attention due to the capability of conformal ultra-thin barrier formation using a simple technique. However, as in the case of the conventional barrier and Cu seed layer, PVD of the Cu alloy seed layer will eventually encounter the difficulty in conformal deposition in narrow line trenches and via holes. Atomic layer deposition (ALD) has been known for its good step coverage and precise thickness control, and is a candidate technique for the formation of a thin conformal barrier layer and Cu seed layer. Conformal Cu-Mn seed layers were deposited by plasma enhanced atomic layer deposition (PEALD) at low temperature ($120^{\circ}C$), and the Mn content in the Cu-Mn alloys were controlled form 0 to approximately 10 atomic percent with various Mn precursor feeding times. Resistivity of the Cu-Mn alloy films decreased by annealing due to out-diffusion of Mn atoms. Out-diffused Mn atoms were segregated to the surface of the film and interface between a Cu-Mn alloy and $SiO_2$, resulting in self-formed $MnO_x$ and $MnSi_xO_y$, respectively. No inter-diffusion was observed between Cu and $SiO_2$ after annealing at $500^{\circ}C$ for 12 h, indicating an excellent diffusion barrier property of the $MnSi_xO_y$. The adhesion between Cu and $SiO_2$ was enhanced by the formation of $MnSi_xO_y$. Continuous and conductive Cu-Mn seed layers were deposited with PEALD into 32 nm $SiO_2$ trench, enabling a low temperature process, and the trench was perfectly filled using electrochemical plating (ECD) under conventional conditions. Thus, it is the resultant self-forming barrier process with PEALD Cu-Mn alloy film as a seed layer for plating Cu that has further potential to meet the requirement of the smaller than 30 nm node.

• Journal of Broadcast Engineering
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• v.20 no.2
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• pp.340-347
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• 2015

HEVC (High Efficiency Video Coding) achieves high coding efficiency by employing a quadtree-based coding unit (CU) block partitioning structure and various prediction units (PUs), and the determination of the best CU partition structure and the best PU mode based on rate-distortion (R-D) cost. However, the computation complexity of encoding also dramatically increases. In this paper, to reduce such encoding computational complexity, we propose three fast PU mode decision methods based on encoding information of upper depth as follows. In the first method, the search of PU mode of the current CU is early terminated based on the sub-CBF (Coded Block Flag) of upper depth. In the second method, the search of intra prediction modes of PU in the current CU is skipped based on the sub-Intra R-D cost of upper depth. In the last method, the search of intra prediction modes of PU in the lower depth's CUs is skipped based on the sub-CBF of the current depth's CU. Experimental results show that the three proposed methods reduce the computational complexity of HM 14.0 to 31.4%, 2.5%, and 23.4% with BD-rate increase of 1.2%, 0.11%, and 0.9%, respectively. The three methods can be applied in a combined way to be applied to both of inter prediction and intra prediction, which results in the complexity reduction of 34.2% with 1.9% BD-rate increase.

• Journal of IKEEE
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• v.18 no.3
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• pp.356-361
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• 2014

This paper proposes hardware architecture of HEVC (high efficiency video coding) CABAC (context-based adaptive binary arithmetic coding) binarizer. The proposed binarizer was designed and implemented as an independent module that can be integrated into HEVC CABAC encoder. It generates each bin string of each syntax element in a single cycle. It consists of controller module, TU (truncated unary binarization) module, TR (truncated Rice binarization) module, FL (fixed length binarization) module, EGK (k-th order exp-Golomb coding) module, CALR (coeff_abs_level_remaining) module, QP Delta (cu_qp_delta_abs) module, Intra Pred (intra_chroma_pred_mode) module, Inter Pred (inter_pred_idc) module, and Part Mode (part_mode) module. The proposed binarizer was designed in Verilog HDL, and it was implemented in 45 nm technology. Its operating speed, gate count, and power consumption are 200 MHz, 1,678 gates, and 50 uW, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1270-1273
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• 2004

The combination of methane-chemical activation and Self-propagating High-temperature synthesis (SHS) has widened the possibilities for both methods. For YBCO systems the investigation showed that a short-term mechano-chemical activation of initial powders before SHS leads to single-phase and ultra-fine products. A new technique for preparation ultra-fine high-temperature superconductors of YBCO composition with a grain size d < $1{\mu}m$ is developed. The specific feature of the technique is formation of the $YBa_2Cu_3O_{7-x}$ crystalline lattice directly from an X-ray amorphous state arising as a result of mechanical activation of the original oxide mixture. The technique allows the stage of formation of any intermediate reaction products to be ruled out. X-ray and magnetic studies of ultra-fine high temperature superconductors (HTS) are carried out. Dimension effects associated with the microstructure peculiarities are revealed. A considerable enhancement of inter-grain critical currents is found to take place in the ultra-fine samples investigated.

• Journal of the Korean Magnetics Society
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• v.16 no.1
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• pp.75-78
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• 2006

In case of contacts between semiconductor and metal in semiconductor circuits, they become unstable because of thermal budget. To prevent these problems, we use diffusion barrier that has a good thermal stability between metal and semiconductor. So we consider the diffusion barrier to prevent the increase of contact resistance between the interfaces of metals and semiconductors, and the increase of resistance and the reaction between the interfaces. In this paper we deposited tungsten boron carbon nitride (W-B-C-N) thin film on silicon substrate. The impurities of the $1000\;{\AA}-thick$ W-B-C-N thin films provide stuffing effect for preventing the inter-diffusion between metal thin films $(Cu-2000\;{\AA})$ and silicon during the high temperature $(700\~1000^{\circ}C)$ annealing process.

• Journal of Powder Materials
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• v.11 no.4
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• pp.341-347
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• 2004

In the study, a hybrid constitutive model for densification of metallic powders was applied to cold isostatic pressing. The model is based on a pressure-dependent plasticity model for porous materials combined with a dislocation density-based viscoplastic constitutive model considering microstructural features such as grain size and inter-particle spacing. Comparison of experiment and calculated results of microscale and nanoscale Cu powders was made. This theoretical approach is useful for powder densification analysis of various powder sizes, deformation routes and powder processing methods.

• Bulletin of the Korean Chemical Society
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• v.11 no.6
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• pp.560-563
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• 1990

A.c. susceptibility for $Bi_{1.4}Pb_{0.6}Sr_2Ca_2Cu_{3.6}O_x$ superconductor is measured as a function of temperature at different value of a.c. magnetic field amplitude. Two transition steps are attributed to the intergranular and intragranular properties. Based on Bean's critical state model, intergranular critical current density, $J_c^{gb}$ (11 $A/cm^2$ at 77 K) and intragranular critical current density, $J_c^g (7{\times}10^3\;A/cm^2$ at 100 K) are estimated. The low values of $J_c^{gb}$and $J_c^g$ reflect a poor nature of coupling between grains and the low pinning force density of intragrain in $Bi_{1.4}Pb_{0.6}Sr_2Ca_2Cu_{3.6}O_x$ superconductor.