• Journal for History of Mathematics
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• v.14 no.2
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• pp.77-92
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• 2001

P. Dirac's contribution to the advent of the modern quantum mechanics is undeniable. His main research guideline is the principle of mathematical beauty. What is this principle on the earth\ulcorner Are there distinctive features between pure mathematician's mind and theoretical physicist' mind about the mathematical beauty\ulcorner These problems will be analyzed with respect to Dirac's case which can reflect a historical interrelationship between science and philosophy.

• The Journal of the Korea Contents Association
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• v.9 no.11
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• pp.309-315
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• 2009

Image reconstruction of Inverse Fourier Transform after Frequency Domain Data is filtered applies to Image signal acquired from MR. There are various kinds of image processing techniques; image preprocessing, image reconstruction, image compression, image restoration image mixture, noise and artifact elimination, and image quality improvement. In this paper, optimum filter applicable to diagnosis in clinic by comparing and analyzing the characteristics of the filter will be explained. Fermi-Dirac filter will improve the image quality better than the previous MR image.

• Bulletin of the Korean Mathematical Society
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• v.50 no.2
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• pp.431-440
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• 2013

Let ($M^3$, $g$) be a 3-dimensional closed Sasakian spin manifold. Let $S_{min}$ denote the minimum of the scalar curvature of ($M^3$, $g$). Let ${\lambda}^+_1$ > 0 be the first positive eigenvalue of the Dirac operator of ($M^3$, $g$). We proved in [13] that if ${\lambda}^+_1$ belongs to the interval ${\lambda}^+_1{\in}({\frac{1}{2}},\;{\frac{5}{2}})$, then ${\lambda}^+_1$ satisfies ${\lambda}^+_1{\geq}{\frac{S_{min}+6}{8}}$. In this paper, we remove the restriction "if ${\lambda}^+_1$ belongs to the interval ${\lambda}^+_1{\in}({\frac{1}{2}},\;{\frac{5}{2}})$" and prove $${\lambda}^+_1{\geq}\;\{\frac{S_{min}+6}{8}\;for\;-\frac{3}{2}<S_{min}{\leq}30, \\{\frac{1+\sqrt{2S_{min}}+4}{2}}\;for\;S_{min}{\geq}30$$.

• Bulletin of the Korean Chemical Society
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• v.24 no.6
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• pp.809-811
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• 2003

This brief review contains surveys of both four-component and two-component relativistic molecular theories. First the four-component relativistic approach is reviewed. Emphasis is placed on efficient computational schemes for the four-component Dirac-Hartree-Fock and Dirac-Kohn-Sham methods. Next, in the twocomponent relativistic framework, two relativistic Hamiltonians, RESC and higher-order Douglas-Kroll (DK), are introduced. An illustrative application is shown for the relativistic study on valence photoelectron spectrum of OsO₄. The developing four-component relativistic and approximate quasi-relativistic methods have been packed in a program suite named REL4D.

• Journal of the Korean Mathematical Society
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• v.42 no.6
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• pp.1169-1186
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• 2005

We study the properties of the transversal Killing and twistor spinors for a Riemannian foliation with a transverse spin structure. And we investigate the relations between them. As an application, we give a new lower bound for the eigenvalues of the basic Dirac operator by using the transversal twistor operator.

• Proceeding of EDISON Challenge
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• 2017.03a
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• pp.463-467
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• 2017

본 연구에서는 위상적 Dirac nodal line 준금속으로 알려진 fcc 구조의 Ca과 hcp 구조의 Be에 대하여 LCPAO (Linear Combination of Pseudo Atomic Orbital) 방법을 이용하는 코드인 OpenMX를 통해 제일원리 전자 구조 계산을 수행하였다. 그 결과로 두 물질에서 밴드의 교차가 일어남을 확인하였으며, 준금속적인 성질이 있음을 확인하였다. 끝으로 EDISON의 사이언스 앱을 이용한 물질의 위상적 특성에 대한 연구의 가능성을 살펴보았다.

• Journal of IKEEE
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• v.6 no.2 s.11
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• pp.119-127
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• 2002

An algorithm for analyzing the characteristics of the power BJT using numerical analysis method is proposed. The Fermi-Dirac statistics is used to calculate the carrier concentration in highly doped region. Philips Unified mobility model, SRH model and Auger model is used to calculate the recombination current of base region. To verify the accuracy of the proposed method, the collector current of BANDIS is compared with the measured data in the condition of the base current increased from $1.0[{\mu}A]\;to\;3.5[{\mu}A]$. The collector current of BANDIS show a maximum relative error within 8.9% compared with the measured data.

• Honam Mathematical Journal
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• v.24 no.1
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• pp.43-65
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• 2002

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.367-367
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• 2012

We investigate Landau level spectra of twisted bilayer graphene under a perpendicular magnetic field, showing that the layers provide rich electronic structure depending on misoriented angle. New types of excitations with Landau level sequences due to the reflection of interlayer coupling level are matter of interest in the present work. We calculate the electronic structure of bilayer systems with a relative small angle rotation of the two graphene layers. Calculated Landau level spectra for twisted bilayer graphene using a continuum formulation are in good agreement with existing experimental and theoretical studies. Twist angle dependent numerical simulations provide significant insights for the nature of the Landau level spectra in bilayer graphene, combining signals from both massive and massless Dirac fermions. We finally discuss the influence of the graphene layers in the experimental sample that related to the magneto-transport measurements including quantum Hall conductance.

• Bulletin of the Korean Chemical Society
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• v.33 no.3
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• pp.803-808
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• 2012

We have implemented two-component spin-orbit relativistic effective core potential (SOREP) methods in an all-electron relativistic program DIRAC. This extends the capacity of the two-component SOREP method to many ground and excited state calculations in a single program. As the test cases, geometries and energies of the small halogen molecules were studied. Several two-component methods are compared by using spin-orbit and scalar relativistic effective core potentials. For the $I_2$ molecule, excitation energies of low-lying excited states agree well with those from corresponding all-electron methods. Efficiencies in SOREP calculations enhanced by using symmetries are also discussed briefly.