• Advances in nano research
• /
• v.15 no.5
• /
• pp.385-399
• /
• 2023

Hexagonal boron nitride (h-BN), commonly referred to as Boron Nitride Nanoribbons (BNNRs), is an electrical insulator characterized by high thermal stability and a wide bandgap semiconductor property. This study delves into the electronic properties of two BNNR configurations: Armchair BNNRs (ABNNRs) and Zigzag BNNRs (ZBNNRs). Utilizing the nearest-neighbour tight-binding approach and numerical methods, the electronic properties of BNNRs were simulated. A simplifying assumption, the Hamiltonian matrix is used to compute the electronic properties by considering the self-interaction energy of a unit cell and the interaction energy between the unit cells. The edge perturbation is applied to the selected atoms of ABNNRs and ZBNNRs to simulate the electronic properties changes. This simulation work is done by generating a custom script using numerical computational methods in MATLAB software. When benchmarked against a reference study, our results aligned closely in terms of band structure and bandgap energy for ABNNRs. However, variations were observed in the peak values of the continuous curves for the local density of states. This discrepancy can be attributed to the use of numerical methods in our study, in contrast to the semi-analytical approach adopted in the reference work.

• Management Science and Financial Engineering
• /
• v.20 no.1
• /
• pp.17-19
• /
• 2014

In this paper, we consider an interesting variant of the inverse minimum traveling salesman problem. Given an instance (G, w) of the minimum traveling salesman problem defined on a metric space, we fix a specified Hamiltonian cycle $HC_0$. The task is then to adjust the edge cost vector w to w' so that the new cost vector w' satisfies the triangle inequality condition and $HC_0$ can be returned by the minimum spanning tree algorithm in the TSP-instance defined with w'. The objective is to minimize the total deviation between the original and the new cost vectors with respect to the $L_1$-norm. We call this problem the inverse metric traveling salesman problem against the minimum spanning tree algorithm and show that it is closely related to the inverse metric spanning tree problem.

• Bulletin of the Korean Chemical Society
• /
• v.33 no.3
• /
• pp.885-892
• /
• 2012

Energy transfer dynamics of excited vibrational energy of OH stretching bonds in liquid water is theoretically studied. With time-dependent vibrational Hamiltonian obtained from a mixed quantum/classical calculation, we construct a master equation describing the energy transfer dynamics. Survival probability predicted by the master equation is compared with numerically exact one and we found that incoherent picture of energy transfer is reasonably valid for long-time population dynamics. Within the incoherent picture, we assess the validity of independent pair approximation (IPA) often introduced in the theoretical models utilized in the analysis of experimental data. Our results support that the IPA is almost perfectly valid as applied for the vibrational energy transfer in liquid water. However, proper incorporation of radial and orientational correlations between two OH bonds is found to be critical for a theory to be quantitatively valid. Consequently, it is suggested that the Forster model should be generalized by including the effects of the pair correlations in order to be applied for vibrational energy transfer in liquid water.

• Bulletin of the Korean Chemical Society
• /
• v.24 no.8
• /
• pp.1091-1096
• /
• 2003

The effects of different polarization conditions on vibrational echo signals are systematically explored for the rigid cyclic dipeptide 2,5-diazabicyclo[2,2,2]octane-3,6-dione. An anharmonic vibrational Hamiltonian is constructed by computing energy derivatives to fourth order using density functional theory. Molecular frame transition dipole orientations are then used to calculate polarization dependent orientational factors corresponding to various Liouville space pathways. Enhancement and elimination of specific peaks in twodimensional correlation plots is accomplished by identifying appropriate pulse configurations.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.25 no.12
• /
• pp.1919-1925
• /
• 2001

Overhead cranes consist of trolley, girder, rope, objects, trolley motor, girder motor, and hoist motor. If objects are regarded as mass point, and the acceleration of hoisting motion for objects is neglected, analytical model of overhead cranes becomes a nonlinear model because the length of a rope changes. Equations of motion this model is derived of simultaneous differential equations fur motors and object. Positions of the model are controlled by optimal inputs which obtain from a nonlinear optimal control method. From the results of computer simulation, even if initial states of objects suing, it is founded that position of overhead cranes is controlled, and that swing of objects is suppressed.

• Bulletin of the Korean Space Science Society
• /
• 2011.04a
• /
• pp.24.3-24.3
• /
• 2011

우주발사체를 이용하여 인공위성을 궤도에 올리는 문제에서 가장 중요시해야 할 부분은 임무의 성공, 즉 정밀한 궤도 진입이다. 이것이 만족되어졌을 때, 비용의 최소화 또한 설계 시 중요한 고려사항이 된다. 이 두 가지 문제를 동시에 해결하기 위해선 최적 제어 전략이 필요한데, 통상적으로 이 과정은 발사 전에 최적화 기법 등을 이용하여 계산되고 검증된다. 그러나 기존의 최적화 기법은 대부분 선형 시스템에 적합한 기법들 이고, 우주발사체와 같이 매우 복잡하고 강한 비선형을 가진 운동방정식을 최적화 하려면 많은 계산이 소요된다. 계산 소모 시간을 줄이기 위해서는 선형화 등의 기법이 사용되는데, 그러한 경우 최적 해에 대한 신뢰도가 낮아질 수밖에 없다. 이 논문에서는 그러한 문제를 해결하기 위해 최근 활발히 연구되고 있는 비선형 최적화 기법인 상태 의존 Riccati 방정식 기법 (SDRE)을 이용하여 인공위성을 주어진 궤도에 진입시키는 우주발사체의 최적궤도를 계산하였다. 또한 Hamiltonian 을 이용하여 산출된 궤도의 최적성을 보이고, 목표한 궤도와의 비교를 통해 제어기의 정밀성을 확인하였다.

• Journal of the Korean Magnetic Resonance Society
• /
• v.12 no.2
• /
• pp.103-110
• /
• 2008

Spin Hamiltonian for the paramagnetic center with a three-fold symmetry and high spin ($S{\geq}2$) multiplicity should contain the fourth order zero-field splitting (ZFS) terms. Electron magnetic resonance transition lines of the center with S = 5/2 are expected to split in a pair when the magnetic field is applied off the principal axes of ZFS, while they are superimposed when the magnetic field is applied parallel to the principal axes of ZFS. In this study we report that the transition lines of $Mn^{2+}$ centers at the three-fold symmetric sites in $LiNbO_3$, chemically equivalent but physically different, split in two due to the nonzero fourth order ZFS term.

• Journal of Ocean Engineering and Technology
• /
• v.10 no.3
• /
• pp.96-104
• /
• 1996

Hamilton's principle is used to derive Euler-Lagrange equations for free surface flow problems of incompressible ideal fluid. The velocity field is chosen to satisfy the continuity equation a priori. This approach results in a hierarchial set of governing equations consist of two evolution equations with respect to two canonical variables and corresponding boundary value problems. The free surface elevation and the Lagrange's multiplier are the canonical variables in Hamilton's sense. This Lagrange's multiplier is a velocity potential defined on the free surface. Energy is conserved as a consequence of the Hamiltonian structure. These equations can be applied to waves in water of finite depth including generalization of Hamilton's equations given by Miles and Salmon.

• Journal of the Korean Mathematical Society
• /
• v.36 no.2
• /
• pp.403-419
• /
• 1999

We introduce a Hamiltonian system which consists of two balls in the vertical line colliding elastically with each other and the floor. Wojtkowski proved that for the system of two linear balls with a linear potential (with gravity), there is a periodic orbit which becomes linearly stable if m1

• Proceedings of the KSME Conference
• /
• 2007.05a
• /
• pp.332-336
• /
• 2007

Temperature is an essential process variable in nanoimprint lithography(NIL) where the temperature varies between room temperature and above the glass transition temperature. To simulate NIL process, we employ both the Nose-Poincare method for temperature controlled molecular dynamics(MD) and force field for polymer material i.e. polymethyl methacrylate(PMMA), which is most widely selected as NIL resist. Nose-Poincare method, which convinces the conservation of Hamiltonian structure and time-reversal symmetry, overcomes the drawbacks inherent in the conventional methods such as Nose thermostat and Nose-Hoover thermostat. Thus, this method exhibits enhanced numerical stability even when the temperature fluctuation is large. To describe PMMA, we adopt the force field which account for bond stretch, bending, torsion, inversion, partial charge, and van der Waals energy.