DNA 단편 조합에서 쌍정렬 후보를 구하는 방법

학위논문(석사)--서울대학교 대학원 :전기·컴퓨터공학부,2003.Maste

(A) Global strategy of smartphone OS as a late entrant : focusing on Samsung`s smartphone platform

Thesis(masters) --서울대학교 경영전문대학원 :경영학과(SNU Global MBA),2010.8.Maste

First Principles Calculations on Effects of Crystal Structure on Electronic and Magnetic Properties

덩치 망간의 평형상태에서의 결정구조와 자성 구조는 아주 복잡한 것으로 알려져 있다. 본 연구에서는 자성 연구에서 가장 적합한 방법으로 알려져 있는 Full-potential Linearized Augmented Plane Wave(FLAPW) 방법을 사용하여 격자상수의 함수로 면심입방 Mn과 체심입방 Mn의 계산 가능한 자성 상태(상자성, 강자성, 반강자성 상태)의 총에너지를 계산하여 결정구조에 따른 Mn의 자성 변화를 연구하였다. 계산 결과, 면심입방 Mn은 반강자성 상태가 안정하고 체심입방 Mn은 강자성상태가 안정한 것으로 밝혀졌다. 면심입방 Mn과 체심입방 Mn의 평형상태의 격자상수는 각각 6.750, 5.314 a.u. 이었고 자기모멘트는 1.15 μ_B과 0.85 μ_B인 것으로 계산되었다. 면심입방의 경우는 강자성 상태가, 체심입방의 경우는 반강자성 상태가 전혀 안정되지 못하는 것으로 나타났다.Manganese is known to have a very complicated crystal structure due to its complex magnetism. In this study we investigated the magnetism of fee and bcc Mn as functions of lattice constants, using Full-potential Linearized Augmented Plane Wave(FLAPW) method and assuming para-, ferro-, and antifcrro-magnetic states. The anti ferromagnetic and ferromagnetic states were calculated to be energetically stable for fee Mn and bcc Mn, respectively. The lattice constants of fee and bcc Mn at equilibrium are 6.750 and 5.314 a.u. and the magnetic moments are 1.15 and 0.85 μ_B, respectively. The ferro- and antiferro-magnetic states are so unstable (not even metastable) that the states were converged to the other magnetic states in self-consistent calculations.Manganese is known to have a very complicated crystal structure due to its complex magnetism. In this study we investigated the magnetism of fee and bcc Mn as functions of lattice constants, using Full-potential Linearized Augmented Plane Wave(FLAPW) method and assuming para-, ferro-, and antifcrro-magnetic states. The anti ferromagnetic and ferromagnetic states were calculated to be energetically stable for fee Mn and bcc Mn, respectively. The lattice constants of fee and bcc Mn at equilibrium are 6.750 and 5.314 a.u. and the magnetic moments are 1.15 and 0.85 μ_B, respectively. The ferro- and antiferro-magnetic states are so unstable (not even metastable) that the states were converged to the other magnetic states in self-consistent calculations

Simultaneous tuning of the magnetic anisotropy and thermal stability of a′′-phase Fe16N2

Simultaneously enhancing the uniaxial magnetic anisotropy (Ku) and thermal stability of a"-phase Fe16N2 without inclusion of heavy-metal or rare-earth (RE) elements has been a challenge over the years. Herein, through first-principles calculations and rigid-band analysis, significant enhancement of Ku is proposed to be achievable through excess valence electrons in the Fe16N2 unit cell. We demonstrate a persistent increase in Ku up to 1.8 MJ m -3 , a value three times that of 0.6 MJ m -3 in a"-Fe16N2 , by simply replacing Fe with metal elements with more valence electrons (Co to Ga in the periodic table). A similar rigid-band argument is further adopted to reveal an extremely large Ku up to 2.4 MJ m -3 in (Fe0.5Co0.5)16N2 obtained by replacing Co with Ni to Ga. Such a strong Ku can also be achieved with the replacement by Al, which is isoelectronic to Ga, with simultaneous improvement of the phase stability. These results provide an instructive guideline for simultaneous manipulation of Ku and the thermal stability in 3d-only metals for RE-free permanent magnet applications

Enhancing magnetic anisotropy and stability of α′′-Fe16N2 phase by Co and V co-substitution

Employing first-principles density functional calculations, we investigate critical effects of V and Co co-substitution on the structural stability and intrinsic magnetic properties of α′′-phase Fe16N2. We demonstrate that only 1 or 2V substitutes per formula unit stabilize the α′′ phase and enhance uniaxial magnetic anisotropy (Ku) up to 1.1 MJ m?3, which is nearly 2 times that of 0.6 MJ m?3 in α′′-Fe16N2. It is further predicted that Ku can even reach up to 1.8 MJ m?3 in Fe12V2Co2N2 with good stability. These results provide an instructive guideline for simultaneous enhancement of the structural stability and energy product in 3d-only permanent magnets

매개하향변환과정에서 발생되는 광자쌍의 4차간섭현상

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First-principles prediction of rare-earth free permanent magnet: FeNi with enhanced magnetic anisotropy and stability through interstitial boron

Ab initio electronic structure calculations reveal that interstitial 2p elements (B, C, and N) have dramatic effects on the structural stability and intrinsic magnetic properties of L10-phase FeNi. Among the 3 possible interstitial impurities, only the B improves the L10-phase stability of FeNi and enhances its uniaxial magnetic anisotropy (0.7 MJ m?3) up to 2.6 MJ m?3. The underlying mechanism is elucidated in terms of single-particle energy spectra analyses along with atom- and orbital-resolved magnetocrystalline anisotropy energy, where both the Fe and Ni 3d level changes induced by charge rearrangement and 2p-3d hybridization are responsible. These findings point toward feasibility of enhancing the structural stability and energy product of 3d-only magnetic metals through the interstitial doping with 2p nonmetal elements

Fe-Ni-N based alloys as rare-earth free high-performance permanent magnet across α'' to L10 phase transition: A theoretical insight

Over the years, simultaneous enhancement of the energy density product and thermal stability of 3 d -only metals, without including heavy metals or rare-earth elements, has been a tremendous challenge in the field of permanent magnetism. In this study, we investigate the structural stability and intrinsic magnetic properties of (Fe 1 - x Ni x ) 16 N 2 ( x = 0 ?1 ) across the α to L 1 0 phase transition using the systematic density- functional theory and Monte Carlo simulations. We theoretically demonstrated an extremely large en- hancement in the uniaxial magnetic anisotropy ( K u ), up to 1.8 MJ ·m ?3 in the L 1 0 -type (Fe 0 . 5 Ni 0 . 5 ) 16 N 2 , a value roughly three times those of α -Fe 16 N 2 (0.6 MJ ·m - 3 ) and L 1 0 -FeNi (0.68 MJ ·m - 3 ). Simultaneously, it is predicted that the resulting L 1 0 -type (Fe 0 . 5 Ni 0 . 5 ) 16 N 2 phase is energeticallymore stable than the α - Fe 16 N 2 phase. Further calculations reveal that in L 1 0 -type (Fe 0 . 5 Ni 0 . 5 ) 16 N 2 , K u can increase up to nearly 3.9 MJ ·m - 3 with additional interstitial N atoms. In conclusion, we predict that the Fe 16 N 2 -based compounds can be effectively used as efficient rare-earth free permanent magnets by simultaneously enhancing their structural stability and energy product (BH) max