• Journal of Electrical Engineering and Technology
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• v.9 no.5
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• pp.1670-1676
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• 2014

This paper presents the modeling of Single Electron Transistor (SET) based on Physical model of a device and its equivalent circuit. The physical model is derived from Schrodinger equation. The wave function of the electrode is calculated using Hartree-Fock method and the quantum dot calculation is obtained from WKB approximation. The resulting wave functions are used to compute tunneling rates. From the tunneling rate the current is calculated. The equivalent circuit model discuss about the effect of capacitance on tunneling probability and free energy change. The parameters of equivalent circuit are extracted and optimized using genetic algorithm. The effect of tunneling probability, temperature variation effect on tunneling rate, coulomb blockade effect and current voltage characteristics are discussed.

• Coupled systems mechanics
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• v.6 no.1
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• pp.17-28
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• 2017

In this work, we extend the previously developed split kinetic energy (dubbed KEP) method by Mineo and Chao (2012) by modifying the mass parameter to include the negative mass. We first show how to separate the total system into the subsystems with 3 attractive delta potentials by using the KEP method. For repulsive delta potentials, we introduce "negative" mass terms. Two cases are demonstrated using the "negative" mass terms for repulsive delta potential problems in quantum mechanics. Our work shows that the KEP solution scheme can be used to obtain not only the exact energies but also the exact wavefunctions very precisely.

• Bulletin of the Korean Chemical Society
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• v.14 no.1
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• pp.47-52
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• 1993

The vibrational relaxation rate constants of NO(v = 1-7) by $O_2\;and\;N_2$ have been calculated in the temperature range of 300-1000 K using the solution of the time-dependent Schrodinger equation. The calculated relaxation rate constants by $O_2$ increase monotonically with the vibrational energy level v, which is compatible with the experimental data, while those by $N_2$ are nearly independent of v in the range of $3.40 {\pm}1.60{\times}10_{-16} cm^3$/molecule-sec at 300 K. Those for NO(v) + $N_2$ are about 2-3 orders of magnitude smaller than those for NO(v) + $O_2$, because the latter is an exothermic processes while the former an endothermic. Relaxation processes can be interpreted by single-quantum V-V transition. The contributions of V-T/R transition and double-quantum V-V transition to the relaxation are negligible over the entire temperature range.

• Bulletin of the Korean Chemical Society
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• v.8 no.6
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• pp.449-453
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• 1987

The temperature dependence of the vibrational relaxation of NO(= 2) by NO(v = 0) has been investigated over the temperature range 100-3000 K. We have assumed that the deexcitation of NO(2) by NO(0) undergoes vibration-to-vibration (VV) energy exchange with the transfer of the energy mismatch ${\Delta}$E through rotation (R) and translation(T). The relaxation rate constants are calculated by solving the time-dependent Schrodinger equation. The sum of V-V, T, and V-V, R contributions shows very weak temperature dependence and is in reasonable agreement with observed data over the temperature range 300-3000 K.

• Bulletin of the Korean Chemical Society
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• v.7 no.3
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• pp.241-245
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• 1986

The vibration-vibration energy exchange of $N_2(v=1)+O_2(v=0){\to}N_2(v=0)+O_2(v=1)$ has been investigated, in particular, at low temperatures. The energy exchange rate constants are calculated by use of the solution of the time-dependent Schrodinger equation with the interaction potential of the colliding molecule as a perturbation term. The predicted rate constants are significantly agree with a experimental values in the range of 295∼$90^{\circ}K$. The consideration of the VV-VT coupling decreases the predicted pure VV energy exchange value by a factor of ∼2. When the collision frequency correction is introduced, the VV-VT rate constant is consistent with the observed value in the liquid phase. The consideration of the population of the rotational energy level increases the VV-VT value significantly.

• Journal of the Korean Vacuum Society
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• v.16 no.4
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• pp.273-278
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• 2007

For the simulation of active region in the quantum cascade lasers (QCL), we solved Schrodinger equation utilizing Runge-Kutta method and Shotting method. Wavelength, phonon resonant energy, and dipole matrix element were simulated with the variation of active region thickness. As a result of such simulation, it was suggested the tolerance range of epi-layer thickness error when 3-quantum well QCL structures are grown.

• Coupled systems mechanics
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• v.3 no.4
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• pp.329-344
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• 2014

In this work, quantum molecular dynamics simulations (QMD) are preformed to study the hydrogen molecules in three types of carbon nanostructures, $C_{60}$ fullerene, (5,5) and (9,0) carbon nanotubes and graphene layers. Interactions between hydrogen and the nanostructures is of importance to understand hydrogen storage for the development of hydrogen economy. The QMD method overcomes the difficulties with empirical interatomic potentials to model the interaction among hydrogen and carbon atoms in the confined geometry. In QMD, the interatomic forces are calculated by solving the Schrodinger's equation with the density functional theory (DFT) formulation, and the positions of the atomic nucleus are calculated with the Newton's second law in accordance with the Born-Oppenheimer approximation. It is found that the number of hydrogen atoms that is less than 58 can be stored in the $C_{60}$ fullerene. With larger carbon fullerenes, more hydrogen may be stored. For hydrogen molecules passing though the fullerene, a particular orientation is required to obtain least energy barrier. For carbon nanotubes and graphene, adsorption may adhere hydrogen atoms to carbon atoms. In addition, hydrogen molecules can also be stored inside the nanotubes or between the adjacent layers in graphite, multi-layer graphene.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.7 s.337
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• pp.5-12
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• 2005

The device performance of nano-scale center-channel (CC) double-gate (DG) MOSFET structure was investigated by numerically solving coupled Schr$\"{o}$dinger-Poisson and current continuity equations in a self-consistent manner. The CC operation and corresponding enhancement of current drive and transconductance of CC-NMOS are confirmed by comparing with the results of DG-NMOS which are performed under the condition of 10-80 nm gate length. Device optimization was theoretically performed in order to minimize the short-channel effects in terms of subthreshold swing, threshold voltage roll-off, and drain-induced barrier lowering. The simulation results indicate that DG-MOSFET structure including CC-NMOS is a promising candidates and quantum-mechanical modeling and simulation calculating the coupled Schr$\"{o}$dinger-Poisson and current continuity equations self-consistently are necessary for the application to sub-40 nm MOSFET technology.

• Korean Journal of Optics and Photonics
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• v.13 no.5
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• pp.400-407
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• 2002

Two dimensional solitary waves are stably propagated in a saturable medium which has a saturable nonlinear index as input intensity. However, in the case of low intensity. a negative fifth-order nonlinear medium has properties of a saturable medium. So a Gaussian beam travels stably. The propagation process into the fifth order nonlinear medium of the Gaussian beam with a weak intensity is investigated by using the computer simulation of the two-dimensional nonlinear Schrodinger equation. As a result, it is confirmed that the two-dimensional spatial solitary waves are stably propagated in this medium when the incident powers are self-trapping powers. In the condition of the phase difference and collisional angle between two input beams of 180 degree and 0.05 degree, respectively, we can confirm that all optical switching is as simple as controlling the incident power of one input beam.

• Korean Journal of Optics and Photonics
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• v.9 no.5
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• pp.333-341
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• 1998

The novel integrated device, 1.55 ${\mu}{\textrm}{m}$ DR-LD(distrbuted reflector laser diode) integrated EA-MOD (electro-absorption modulator) as light source, is proposed to improve the device yield and its operational performances. This device can be easily fabricated by the selective MOVPE technique and its fabrication processes are almost the same as the reported 1.55 ${\mu}{\textrm}{m}$ DFB-LD(distributed feedback laser diode) integrated EA-MOD except the asymmetric gratings. The static and dynamic properties are investigated simultaneously by solving the transfer matrix method for light propagation, the time-dependent rate equation for carrier change and schr$\"{o}$dinger equation for QCSE (Quantum-Confined Stark Effect). The performances of the proposed device such as output power, chirp, and extinction ratio are compared with those of DFB-LD integrated EA-MOD. Under 10Gb/s NRZ modulation, we obtain that DR-LD integrated EA-MOD. is 30% higher in output power on the on-state, about 50% lower in chirp, and slightly larger in extinction ratio than DFB-LD integrated EA-MOD.-MOD.