• Journal of the Korean Ceramic Society
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• v.47 no.2
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• pp.99-105
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• 2010

The electrical transport properties of mayenite ($Ca_{12}Al_{14}O_{33}$ or $12CaO{\cdot}7Al_2O_3$; mostly abbreviated as $C_{12}A_7$) can be controlled in a wide range by varying the oxygen deficiency: At high temperatures mayenite becomes either an oxygen solid electrolyte, a mixed ionic/electronic conductor or an inorganic electride with metal-like properties upon chemical reduction (removing oxygen). The underlying defect chemistry can be understood on the basis of a relatively simple model-despite the complex cage structure: A point defect model based on the assumption that the framework $[Ca_{12}Al_{14}O_{32}]^{2+}$ acts as a pseudo-donor describes well the high temperature transport properties. It accounts for the observed conductivity plateau at higher oxygen activities and also describes the experimentally observed oxygen activity dependence of the electronic conductivity with -1/4 slope at temperatures between 800 and $1000^{\circ}C$. Doping effects in mayenite are still not well explored, and we review briefly the existing data on doping by different elements. Hydration of mayenite plays a crucial role, as Mayenite is hygroscopic, which may be a major obstacle for technical applications.

• Structural Engineering and Mechanics
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• v.45 no.4
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• pp.423-437
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• 2013

Complex structures are usually assembled from several substructures with joints connecting them together. These joints have significant effects on the dynamic behavior of the assembled structure and must be accurately modeled. In structural analysis, these joints are often simplified by assuming ideal boundary conditions. However, the dynamic behavior predicted on the basis of the simplified model may have significant errors. This has prompted the researchers to include the effect of joint stiffness in the structural model and to estimate the stiffness parameters using inverse dynamics. In the present work, structural joints have been modeled as a pair of translational and rotational springs and frequency equation of the overall system has been developed using sub-structure synthesis. It is shown that using first few natural frequencies of the system, one can obtain a set of over-determined system of equations involving the unknown stiffness parameters. Method of multi-linear regression is then applied to obtain the best estimate of the unknown stiffness parameters. The estimation procedure has been developed for a two parameter joint stiffness matrix.

• Journal of the Korean Ceramic Society
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• v.40 no.9
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• pp.849-854
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• 2003

Temperature dependent thermoelectric power (TEP) of La$_{2.1}$ Sr$_{1.9}$ Mn$_3$O$_{10}$ system has been studied in the temperature range 80-373 K. In the low temperature ferromagnetic regime, TEP (S) follows an expression of formS＝S$_{0}$ ＋S$_{1.5}$ T$^{1.5}$ ＋S$_4$T$^4$ over the wide range of temperature. The broad peak below the ferromagnetic transition and complicated temperature dependence of S may be understood on the basis of electron-magnon scattering as predicted for an itinerant ferromagnet. High temperature TEP data can be well fitted with Mott's small polaron hopping model.

• Journal of Power Electronics
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• v.15 no.3
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• pp.712-720
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• 2015

A model predictive current control (MPCC) method that does not employ a cost function is proposed. The MPCC method can decrease common-mode voltages in loads fed by three-phase voltage-source inverters. Only non-zero-voltage vectors are considered as finite control elements to regulate load currents and decrease common-mode voltages. Furthermore, the three-phase future reference voltage vector is calculated on the basis of an inverse dynamics model, and the location of the one-step future voltage vector is determined at every sampling period. Given this location, a non-zero optimal future voltage vector is directly determined without repeatedly calculating the cost values obtained by each voltage vector through a cost function. Without utilizing the zero-voltage vectors, the proposed MPCC method can restrict the common-mode voltage within ± V_dc/6, whereas the common-mode voltages of the conventional MPCC method vary within ± V_dc/2. The performance of the proposed method with the reduced common-mode voltage and no cost function is evaluated in terms of the total harmonic distortions and current errors of the load currents. Simulation and experimental results are presented to verify the effectiveness of the proposed method operated without a cost function, which can reduce the common-mode voltage.

• Journal of The Korean Astronomical Society
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• v.48 no.3
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• pp.165-175
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• 2015

We investigate physical properties of the nearby (∼ 7.5 pc) astrometric binary μ Cas in the context of standard evolutionary theory. Based on the spectroscopically determined relative abundances ([α/Fe] ≳ +0.4 dex, [Fe/H] ∼ −0.7 dex), all physical inputs such as opacities and equation of state are consistently generated. By combining recent spectroscopic analyses with the astrometric observations from the HIPPARCOS parallaxes and the CHARA array, the evolutionary model grids have been constructed. Through the statistical evaluation of the χ²-minimization among alternative models, we find a reliable evolutionary solution (M_A, M_B, t_age) = (0.74 M_⊙, 0.19 M_⊙, 11 Gyr) which excellently satisfies observational constraints. In particular, we find that the helium abundance of μ Cas is comparable with the primordial helium contents (Y_p ∼ 0.245). On the basis of the well-defined stellar parameters of the primary star, the internal structure and the p-mode frequencies have been estimated. From our seismic computation, μ Cas is expected to have a first order spacing ∆ν ∼ 169 μHz. The ultimate goal of this study is to describe physical processes inside a low-mass star through a complete modelling from the spectroscopic observation to the evolutionary computation.

• Bulletin of the Korean Chemical Society
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• v.29 no.5
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• pp.979-984
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• 2008

In this study, 8 solutes (aniline, caffeine, p-cresol, ethyl benzene, methylparaben, phenol, pyridine, and toluene) have been tested in terms of linear solvation energy relationships (LSER). Several micellar liquid chromatography (MLC) systems using cationic surfactant cetyltrimethylammonium bromide (CTAB) and a mixture of water with (methanol, n-propanol, and n-butanol) modifiers were characterized using the LSER solvation parameter model. The effects of the surfactant and modifier concentration on the retention in MLC were discussed. LSER model had demonstrated high potential to predict retention factors with high squared correlation coefficients ($r^2$ > 0.99). A comparison of predicted and experimental retention factors suggests that LSER formalism is able to reproduce adequately the experimental retention factors of the solutes studied in the different experimental conditions investigated. This model is a helpful tool to understand the solute-surfactant interactions and evaluate the retention characteristic of micellar liquid chromatography.

• Molecules and Cells
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• v.47 no.1
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• pp.100005.1-100005.15
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• 2024

Amyotrophic lateral sclerosis is a devastating neurodegenerative disease with a complex genetic basis, presenting both in familial and sporadic forms. The hexanucleotide (G₄C₂) repeat expansion in the C9orf72 gene, which triggers distinct pathogenic mechanisms, has been identified as a major contributor to familial and sporadic Amyotrophic lateral sclerosis cases. Animal models have proven pivotal in understanding these mechanisms; however, discrepancies between models due to variable transgene sequence, expression levels, and toxicity profiles complicate the translation of findings. Herein, we provide a systematic comparison of 7 publicly available Drosophila transgenes modeling the G₄C₂ expansion under uniform conditions, evaluating variations in their toxicity profiles. Further, we tested 3 previously characterized disease-modifying drugs in selected lines to uncover discrepancies among the tested strains. Our study not only deepens our understanding of the C9orf72 G₄C₂ mutations but also presents a framework for comparing constructs with minute structural differences. This work may be used to inform experimental designs to better model disease mechanisms and help guide the development of targeted interventions for neurodegenerative diseases, thus bridging the gap between model-based research and therapeutic application.

• Transactions of the Korean hydrogen and new energy society
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• v.2 no.1
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• pp.1-6
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• 1990

The desorption kinetics of $Mg_2Cu$ hydride were studied by thermal analysis technique in order to study desorption behavior and to relate thermal desorpton spectra to occuption site of hydrogen. It is suggested that a continuous ${\alpha}/{\beta}$ interface boundary is formed at the initial absorption stage. And the desorption kinetics were analysed by the theoretical equation which was derived on the basis of continous moving boundary model. The number of thermal desorption peak corresponds to the occupation sites of hydrogen. The apparent activation energy for the desorption of $Mg_2Cu$ hydride is 91 KJ/mol.

• International Journal of Contents
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• v.6 no.1
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• pp.26-34
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• 2010

This paper is on the premise that we need objective and measurable researches on quality evaluation of serious game for users' correct selection of games fitting for their purposes, for development of competitive high-quality game, and for stable growth of game industry. At first, we looked into various characteristics of serious game, read the present situation of game market, and proposed the necessity of quality evaluating model for serious game. To guarantee the objectivity of the proposed models, we compared and analyzed various proposals of standard model on the basis of international standard quality-evaluating model, ISO/IEC 9126 S/W. And so we extracted quality-evaluating items for serious game that composed of 8 evaluating areas and 25 sub-attributes, and presented quality-evaluating indices of each area. The proposed quality-evaluating model was added 2 areas and 8 sub-attributes to the international standard model, and the validity of the extracted items' was verified by expert group's questionnaire. Accordingly, we expect that this paper will increase game users' satisfaction, promote the development of high-quality games, and contribute to continuous growth in serious game market.

• Bulletin of the Korean Chemical Society
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• v.29 no.1
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• pp.122-126
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• 2008

The magnetic properties of the organic/inorganic hybrid copper-methylenediphosphonate, Cu2(O3PCH2PO3) were examined by performing the spin dimer analysis based on the extended Hckel tight binding method. In Cu2(O3PCH2PO3) the CuO3 chains made up of edge-sharing CuO5 square pyramidal units are inter-linked by O-P-O bridges. The Cu-O-Cu superexchange interactions of the CuO3 chains are negligibly weak compared with the Cu-O…O-Cu super-superexchange interactions that occur between the CuO3 chains. The spin exchange interactions of Cu2(O3PCH2PO3) are dominated by three super-superexchange interactions, which leads to a three-dimensional antiferromagnetic spin lattice. The strongest spin exchange interactions form isolated spin dimers, which suggests that, to a first approximation, the magnetic properties can be described in terms of an isolated spin dimer model.