• Bulletin of the Korean Mathematical Society
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• v.38 no.1
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• pp.175-182
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• 2001

In this paper we prove the existence and uniqueness of a mild solution of a functional differential equation with nonlocal condition using the semigroup theory and the Banach fixed point principle.

• Journal of the Korean Mathematical Society
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• v.42 no.4
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• pp.749-759
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• 2005

We apply a cone theoretic fixed point theorem and obtain conditions for the existence of positive periodic solutions of the system of functional differential equations $$x'(t)\;=\;A(t)x(t)+{\lambda}f(t,\;x(t-\tau(t))$$.

• Bulletin of the Korean Chemical Society
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• v.25 no.12
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• pp.1855-1858
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• 2004

Molecular geometries for the cationic and neutral species of OXO (X=Cl, Br, and I) are optimized using the Hartree-Fock (HF) theory, the second order Moller-Plesset perturbation theory (MP2), the density functional theory with the B3LYP hybrid functional (B3LYP), and the coupled cluster theory using single and double excitation with a perturbational treatment of triplet excitation (CCSD[T]) methods, with two basis sets of triple zeta plus polarization quality. The single point calculations for these species are performed at the CCSD(T,Full) level. The harmonic vibrational frequencies for these species are calculated at the HF, MP2, B3LYP and CCSD(T) levels. The adiabatic ionization potential for OIO is calculated to be 936.7 kJ/mol at the CCSD(T,Full) level and the correct value is estimated to be around 945.4 kJ/mol.

• Journal of the Korean Physical Society
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• v.73 no.9
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• pp.1315-1323
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• 2018

The classical-fluids density functional theory has been developed for studying the structural and the electrical properties of electrolyte solutions containing uniformly charged hard-spherical ions. The modified fundamental-measure theory has been used to evaluate the hard-sphere contribution. The mean-field approximation has been employed to calculate the cross correlation between the hard sphere contribution and the Coulomb interaction. The Poisson equation for ions carrying charges that are spatially separated has been solved. The present theory shows reasonably good agreement with the corresponding Monte Carlo simulation results. The calculated results show that the attraction between like-charged planar surfaces is the result of the intra-ionic correlation and depends strongly on the ion size, valence, mole fraction, and charge distribution of electrolytes.

• Journal of the Korean Mathematical Society
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• v.54 no.3
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• pp.821-833
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• 2017

We get a result that shows the existence of infinitely many solutions for a class of the elliptic systems involving subcritical Sobolev exponents nonlinear terms with even functionals on the bounded domain with smooth boundary. We get this result by variational method and critical point theory induced from invariant subspaces and invariant functional.

• Journal of the Korean Mathematical Society
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• v.48 no.2
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• pp.223-240
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• 2011

In this paper, the problem on periodic solutions of the bidirectional associative memory neural networks with both periodic coefficients and periodic time-varying delays is discussed. By using degree theory, inequality technique and Lyapunov functional, we establish the existence, uniqueness, and global asymptotic stability of a periodic solution. The obtained results of stability are less restrictive than previously known criteria, and the hypotheses for the boundedness and monotonicity on the activation functions are removed.

• Bulletin of the Korean Chemical Society
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• v.34 no.3
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• pp.943-945
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• 2013

• Korean Journal of Mathematics
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• v.21 no.1
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• pp.81-90
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• 2013

We investigate the bounded weak solutions for the Hamiltonian system with bounded nonlinearity decaying at the origin and periodic condition. We get a theorem which shows the existence of the bounded weak periodic solution for this system. We obtain this result by using variational method, critical point theory for indefinite functional.

• Proceeding of EDISON Challenge
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• 2014.03a
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• pp.459-463
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• 2014

$MoS_2$ bulk에 Lithium을 intercalate했을 때 가장 안정한 위치와 그 위치에서의 결합에너지에 대한 분석을 진행하였다. 이를 위해 Density Functional Theory를 기반으로 한 계산을 실행하였으며 MoS2 bulk 내의 여러 위치에서의 에너지를 구하여 Li이 가장 안정하게 흡착되는 비율과 Li 원자가 안정한 흡착 위치를 계산했다. 그 결과 Li 원자가 1/4 monolayer을 형성할 때 가장 안정하며 그 때 Li 원자는 Hollow site에 결합한다는 결론을 얻었다.

• Proceeding of EDISON Challenge
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• 2017.03a
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• pp.11-15
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• 2017

We present a study of transition metal compounds using density functional theory (DFT), and density-corrected density functional theory(DC-DFT). By replacing the self-consistent density with that obtained from Hartree-Fock calculation, i.e., HF-DFT, the abnormality driven by self-interaction error is removed in several important cases. We discuss when and how HF-DFT works by examining 3d orbital dimers using approximate functionals and by comparing the results from self-consistent-DFT and HF-DFT with experimental values.