• Progress in Superconductivity and Cryogenics
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• v.15 no.2
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• pp.16-19
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• 2013

The magneto-resistivity and electric field-current density (E-J) curves were investigated up to a magnetic field 9 T in the optimally doped $BaFe_{1.8}Co_{0.2}As_2$ single crystal with a superconducting temperature ($T_c$) of 24.6 K. The E-J Scaling behaviors below and above vortex glass transition temperature ($T_g$) were found, confirming the existence of the vortex glass phase transition. The critical exponents for the diverging spatial and time correlations at $T_g$, were obtained as v = $1.1{\pm}0.1$ and z = $4.5{\pm}0.3$, respectively. The obtained critical exponents are in good agreement with the predicted values of v ~ 1 - 2 and z > 4 within the 3D vortex glass theory.

• Current Applied Physics
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• v.18 no.11
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• pp.1393-1398
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• 2018

We have investigated Bernal-stacked tetralayer graphene as a function of interlayer distance and perpendicular electric field by using density functional theory calculations. The low-energy band structure was found to be very sensitive to the interlayer distance, undergoing a metal-insulator transition. It can be attributed to the nearest-layer coupling that is more sensitive to the interlayer distance than are the next-nearest-layer couplings. Under a perpendicular electric field above a critical field, six electric-field-induced Dirac cones with mass gaps predicted in tight-binding models were confirmed, however, our density functional theory calculations demonstrate a phase transition to a quantum valley Hall insulator, contrasting to the tight-binding model prediction of an ordinary insulator.

• Applied Microscopy
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• v.47 no.3
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• pp.187-202
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• 2017

The classical electron band theory is a powerful tool to describe the electronic structures of solids. However, the band theory and corresponding density functional theory become inappropriate if a system comprises localized electrons in a scenario wherein strong electron correlations cannot be neglected. $SrRuO_3$ is one such system, and the partially localized d-band electrons exhibit some interesting behaviors such as enhanced effective mass, spectral incoherency, and oppression of ferromagnetism and itinerancy. In particular, a Metal-Insulator transition occurs when the thickness of $SrRuO_3$ approaches approximately four unit cells. In the computational studies, irrespective of the inclusion of on-site Hubbard repulsion and Hund's coupling parameters, correctly depicting the correlation effects is difficult. Because the oxygen atoms and the symmetry of octahedra are known to play important roles in the system, scrutinizing both the electronic band structure and the lattice system of $SrRuO_3$ is required to find the origin of the correlated behaviors. Transmission electron microscopy is a promising solution to this problem because of its integrated functionalities, which include atomic-resolution imaging and electron energy loss spectroscopy.

• New & Renewable Energy
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• v.17 no.1
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• pp.7-18
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• 2021

This study analyzes the role of market actors in the energy transition process and the interaction between them and ordinary citizens, primarily focusing on the mini-PV project in Seoul. The study also proposes measures to harness market actors' activities and successfully implement the distribution of mini-PV systems in Seoul. In this study, practice theory is used as a theoretical resource to analyze the interaction between market actors and civil society actors and to help understand how market actors influence the decisions of regular citizens in installing mini-PV at their properties. After conducting surveys and hosting in-depth interviews with ordinary citizens and market actors, it was found that to further promote the role of market actors, the Seoul Metropolitan Government should actively support and monitor the public relations activities of market actors, while concurrently managing selected companies and establishing relevant administrative systems for continued effective use post-installation of mini-PV systems. In future studies of the energy transition process, market actors should also be recognized as key players, along with government and civil society actors, and their roles should be studied in a balanced way.

• East Asian Economic Review
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• v.21 no.4
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• pp.385-432
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• 2017

This paper investigates how firm age, size and ownership are related with job creation and destruction, and how these patterns differ across transition and non-transition economies. The analysis finds that age is inversely related with gross job creation and net job creation in the two samples. This finding is consistent with the theory of the learning effect. The relationship between age and job destruction is indifferent in non-transition economies. On the contrary, old firms in transition economies destroy more jobs than young ones. The paper further establishes an inverse relationship between size and gross job creation in the two groups. However, there is divergence between the two samples; small firms in non-transition economies also exhibit a higher gross job destruction rate. Consequently large firms have a higher net job creation rate. In transition economies, small and large firms exhibit similar rates of job destruction. But small firms retain a higher net job creation rate. A more intriguing finding is that state owned firms do not underperform domestic private ones. This means these countries may be using soft budget constraint which allows state owned firms to overstaff. Finally, crowding out of SMEs by foreign owned firms is not evident in transition economies.

• Journal of the Korean Chemical Society
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• v.56 no.1
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• pp.14-19
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• 2012

We investigate the doublet and quartet potential energy surfaces associated with the gas-phase reaction between $Ti^+$ and $CF_3COCH_3$ for two plausible reaction pathways, $TiF_2^+$ and $TiO^+$ formation pathways by using the density functional theory (DFT) method. The molecular structures of intermediates and transition states involved in these reaction pathways are optimized at the DFT level by using the PBE0 functional. All transition states are identified by using the intrinsic reaction coordinate (IRC) method, and the resulting reaction coordinates describe how $Ti^+$ activates $CF_3COCH_3$ and produces $TiF_2^+$ and $TiO^+$ as products. On the basis of presented results, we propose the most favorable reaction pathway in the reaction between $Ti^+$ and $CF_3COCH_3$.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.10a
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• pp.37-44
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• 2003

In this proposed work, computational, finite element model far multi-delaminated plates will be developed. In the current analysis procedures of multi-delaminated plates, different elements are used at delaminated and undelaminated region separately. In the undelaminated region, plate element based on Mindlin plate theory is used in order to obtain accurate results of out-of-plane displacement of thick plate. And for delaminated region, plate element based on Kirchhoff plate theory is considered. To satisfy the displacement continuity conditions, displacement vector based on Kirchhoff theory is transformed to displacement of transition element. Element mass and stiffness matrices of each region (delaminated, undelaminated and transition region) will be assembled for global matrix.

• Bulletin of the Korean Chemical Society
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• v.31 no.12
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• pp.3718-3722
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• 2010

Theoretical investigations are carried out on the title reaction by means of ab-initio and DFT methods. The optimized geometries, frequencies and minimum energy path are obtained at UB3LYP/6-311G(d,p) level. Single point energy calculations are performed at MP2 and MP4 levels of theory. Energetics are further refined by calculating the energy of the species with a modified Gaussian-2 method, G2M(CC,MP2). The rate constant of the reaction is calculated using Canonical Transition State Theory (CTST) utilizing the ab-initio data obtained during the present study and is found to be $5.47{\times}10^{-12}\;cm^3\;molecule^{-1}s^{-1}$ at 298 K and 1 atm.

• Bulletin of the Korean Chemical Society
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• v.25 no.11
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• pp.1657-1660
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• 2004

Several critical geometries associated with the rearrangement of $CH_3SNO_2\;to\;CH_3SONO$ are calculated with the density functional theory (DFT) method and compared with those of the ab initio molecular orbital methods. There are two probable pathways for this rearrangement, one involving the transition state of an oxygen migration and the other through the homolytic decomposition to radicals. The reaction barrier via the transition state is about 60 kcal/mol and the decomposition energy into radicals about 35 kcal/mol, suggesting that the reaction pathway via the homolytic cleavage to radical species is energetically favorable. Since even the homolytic cleavage requires large energies, the rearrangement reaction is unlikely without the aid of catalysts.

• Journal of the Korean Chemical Society
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• v.57 no.2
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• pp.216-220
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• 2013

The hydroalumination of cyclopropane has been investigated using the B3LYP density functional method employing several split-valence basis sets. It is shown that the reaction proceeds via an intermediate weakly bound complex and a four-centered transition state. Calculations at higher levels of theory were also performed at the geometries optimized at the B3LYP level, but only slight changes in the barriers were observed. Structural parameters for the transition state are also reported.