• Journal of the Korean Ceramic Society
• /
• v.22 no.4
• /
• pp.3-8
• /
• 1985

The layer charge densities and interlayer C. E. C(cation exchange capacity) of ten mica-type aluminosilicates from Yong-il Pohang-prefacture were determined by n-alkylammonium method which is based on the mo-nolayer-doubelelayer structural transition of ni-alkylammonium ion in interlayer space of the layered silcates. The upper and lower limits of layer charge and interlyer C, E, C estimated were about 0.25~0.36 eq/(Si, $Al)_4$ O10 and 69~99meq/100g, respectively.

• Vacuum Magazine
• /
• v.5 no.2
• /
• pp.10-17
• /
• 2018

Chalcogenide and oxide heterostructures have been studied as a next-generation electronic materials, due to their interesting electronic properties, such as direct bandgap semiconductor, ferroelectricity, ferromagnetism, superconductivity, charge-density waves, and metal-insulator transition, and their modification near heterointerfaces, so called, electronic reconstruction. An angle-resolved photoemission spectroscopy (ARPES) is a powerful technique to unveil such novel electronic phases in detail, especially combined with high quality thin film preparation methods, such as, molecular beam epitaxy and pulsed laser deposition. In this article, the recent ARPES results in chalcogenide and oxide thin films will be introduced.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.22 no.7
• /
• pp.1559-1565
• /
• 1997

A new multitrack RLL codes with immunity to intertrack interference (ITI) is proposed. This code takes aim at a high density storage channels by reducing the track width and/or guard bands between tracks since it prevents transition in neighboring tracks at the same time epoch. The capacities of the codes are found for each maximum and minimum constraint pair.

• The Bulletin of The Korean Astronomical Society
• /
• v.37 no.2
• /
• pp.79.1-79.1
• /
• 2012

Due to the quantum interference of many atomic levels, the exact scattering cross section around a given resonance transition deviates from the Lorentz function when the frequency of the incident radiation is quite far from the resonance frequency. This atomic effect is quite significant in the case of damped Ly alpha systems, where HI column density is in excess of 10^20 cm^-2. In this poster, we present the deviation quantitatively taking into consideration of the Rayleigh and Raman scattering around Lyman alpha and Lyman beta.

• Bulletin of the Korean Mathematical Society
• /
• v.59 no.2
• /
• pp.507-528
• /
• 2022

We propose a path integral method to construct a time stepwise local volatility for the stock index market under Dupire's model. Our method is focused on the pricing with the Monte Carlo Method (MCM). We solve the problem of randomness of MCM by applying numerical integration. We reconstruct this task as a matrix equation. Our method provides the analytic Jacobian and Hessian required by the nonlinear optimization solver, resulting in stable and fast calculations.

• Publications of The Korean Astronomical Society
• /
• v.27 no.4
• /
• pp.331-334
• /
• 2012

We investigate the role of galaxy environment in the evolution of individual galaxies through the AKARI observations of the merging galaxy cluster A2255. MIR diagnostics using N3-S11 colors are adopted to select star-forming galaxies and galaxies in transition between star-forming galaxies and quiescent galaxies. We do not find particular enhancement of star formation rates as a function of galaxy environment, reflected in cluster-centric distance and local surface density of galaxies. Instead, the locations of intermediate MIR-excess galaxies (-1.2 < N3 - S11 < 0.2) show that star-forming galaxies are transformed into passive galaxies in the substructures of A2255, where the local surface density of galaxies is relatively high.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.142.2-142.2
• /
• 2016

The metal intercalation to an organic semiconductor is of importance since the charge transfer between a metal and an organic semiconductor can induce the highly enhanced conductivity for achieving efficient organic electronic devices. In this regard, the changes of the electronic structure of copper phthalocyanine (CuPc) caused by the intercalation of potassium are studied by ultraviolet photoemission spectroscopy (UPS) and density functional theory (DFT) calculations. Potassium intercalation leads to the appearance of an intercalation-induced peak between the highest molecular occupied orbital (HOMO) and the lowest molecular unoccupied orbital (LUMO) in the valence-band spectra obtained using UPS. The DFT calculations show that the new gap state is attributed to filling the LUMO+1, unlike a common belief of filling the LUMO. However, the LUMO+1 is not conductive because the ${\pi}$-conjugated macrocyclic isoindole rings on the molecule do not make a contribution to the LUMO+1. This is the origin of a metal-insulator transition through heavily potassium doped CuPc.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2015.08a
• /
• pp.133-133
• /
• 2015

Recently, it has been shown that the ${\omega}B97X-D/aVTZ$ method is strongly recommended as the best practical density functional theory(DFT) for rigorous and extensive studies of saturated or unsaturated $C_4F_8$ species because of its high performance and reliability especially for van der Waals interactions. All the feasible isomerization and dissociation paths of $C_4F_8$ molecules were investigated at this theoretical level and rate constants of their chemical reactions were computed by using variational transition-state theory for a deep insight into $C_4F_8$ reaction mechanisms. Fates and roles of C4F8 molecules and their fragments in plasma phases could be clearly explained based on our computational results.

• Journal of Welding and Joining
• /
• v.23 no.1
• /
• pp.48-54
• /
• 2005

Laser keyhole welding is investigated using a three-dimensional Gaussian heat source, and the heat source parameters such as the keyhole depth, welding efficiency and power density distribution factor are determined in a systematic way. For partial penetration, the keyhole depth is same as the penetration and is predicted using the experimental data. The welding efficiency is calculated using the ray-tracing method and the power density distribution factor is determined from the bead shape. Full penetration is classified into the transition, normal and excessive modes depending on the degree of keyhole opening. Thermal analysis of the bead-on-plate welds is conducted using the Gaussian heat source, and the calculated weld geometries show reasonably good agreements with the experimental results.

• Proceedings of the Korea Society of Information Technology Applications Conference
• /
• 2005.11a
• /
• pp.237-241
• /
• 2005

We present a device model for organic light emitting diodes(OLEDs) which includes charge injection, transport, recombination, and space charge effects in the organic materials. The model can describe both injection limited and space charge limited current flow and the transition between them. Calculated device current, light output, and quantum and power efficiency are presented for different cases of material and device parameters and demonstrate the improvements in device performance in bilayer devices. These results are interpreted using the calculated spatial variation of the electric field, charge density and recombination rate density in the device. We find that efficient OLEDs are possible for a proper choice of organic materials and contact parameters.