• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.109-110
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• 2002

The purpose of a superconductive DC/SFQ circuit is to produce a controlled number of picosecond single flux quantum pulses at the output when a slowly changing DC current is applied to the input. In this work, we have designed and simulated a DC/SFQ circuit based on Nb/Al$O_{x}$/Nb Josephson junction technology. From the simulation, we could obtain the margins for various circuit parameters. And also we have successfully operated a DC/SFQ circuit which was fabricated with the same design. The margin for the input bias current of the circuit was observed to be of $\pm$60%, which was very close to the simulated value.

• Transactions on Electrical and Electronic Materials
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• v.17 no.5
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• pp.270-274
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• 2016

This article investigates the use of the Gaussian-channel doping profile for the control of the short-channel effects in the double-gate MOSFET whereby a two-dimensional (2D) quantum simulation was used. The simulations were completed through a self-consistent solving of the 2D Poisson equation and the Schrodinger equation within the non-equilibrium Green’s function (NEGF) formalism. The impacts of the p-type-channel Gaussian-doping profile parameters such as the peak doping concentration and the straggle parameter were studied in terms of the drain current, on-current, off-current, sub-threshold swing (SS), and drain-induced barrier lowering (DIBL). The simulation results show that the short-channel effects were improved in correspondence with incremental changes of the straggle parameter and the peak doping concentration.

• Journal of the Korean Magnetic Resonance Society
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• v.9 no.1
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• pp.67-73
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• 2005

$^{27}AI$ triple quantum magic angle spinning (3QMAS) NMR spectra of several mordenite (MOR) sample were simulated with the point charge model method and compared with experimental 3QMAS spectra. Signal positions from different tetrahedral (T) sites in 3QMAS spectra are mainly governed by local structures of T sites such as T-O-T angles and T-O bond lengths. When preparation methods, cations in addition to Si/Al rations vary, the local structures of T sites in MOR change enough to alter signal patterns in 3QMAS of MOR. This inhibits to study the of Al distribution variation over 4 different T sites in mordenite during process such as dealumination by 3QMAS spectra.

• Electrical & Electronic Materials
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• v.9 no.5
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• pp.498-505
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• 1996

In the present work, we have developed the simulator to optimize the process conditions of the AR(antireflection) and HR(high-reflection) coatings for the high power laser diode. The simulator can run on the PC. After making the simple optical model, we establish the Maxwell equations for the model by the operator conversion. By using the Mathematica, we derive a matrix for the multilayer system by applying the equations to the model and optimize the AR and HR coating process conditions by obtaining the reflection rate from the matrix. We also prove the validity of the simulator by comparing the simulation with the characteristics of the laser diode which is AR and HR coated according to the optimized conditions.

• Progress in Superconductivity
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• v.4 no.1
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• pp.37-41
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• 2002

In this work. we have designed two different kinds of Rapid Single Flux Quantum (RSFQ) OR-gates. One was based on the already developed RSFQ cells and the other was aimed to develop a more compact version. In the first circuit, we used a combination of two D Flip-Flops and a merger and in the other circuit we used a combination of RS Flip-Flops and Confluence Buffer. We tested the circuit performance by using the simulation tools, Xic and Wrspice. We obtained the operation margins of the circuit elements by a margin calculation program, and we obtained the minimum operation margins of $\pm$30%. The circuits were laid out, aimed to fabricate by using the existing KRISS Nb process. KRISS Nb process includes the $Nb／Al_2$$O_3$／Nb trilayer fabricated by DC magnetron sputtering and the reactive ion etching technique for the definition of the features. The major tools used in the layouts were Xic and L-meter.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.393-393
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• 2011

오늘 날 태양전지 산업에서 가장 많은 생산을 하고 있는 분야는 결정질 태양전지분야이다. 현재는 이러한 시대적 요구에 따라 많은 연구가 진행되고 있는데 특히 junction을 이루는 n layer의 doping profile을 선택적으로 형성하여 개방전압 및 단락전류를 향상시키는 연구가 활발히 진행되고 있다. 본 연구는 이러한 n type layer의 doping profile을 선택적으로 형성하는 selective emitter solar cell에 관한 연구로써 SILVACO simulation을 이용하여 low Rs 영역은 고정하고 high Rs 영역의 doping depth를 가변 함으로써 high Rs 영역을 달리 형성하는 방법으로 selective emitter solar cell의 high Rs영역의 최적화에 관한 전산모사를 실시하였다. 각각의 가변조건에 따라 quantum efficiency를 통한 광학적 분석과 I-V를 통한 전기적 분석을 하여 high Rs영역을 최적화 하였다.

• Proceeding of EDISON Challenge
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• 2015.03a
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• pp.91-98
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• 2015

Formamide의 중성가수분해 mechanism은 QM/MM (quantum mecahnics/molecular mechanics) molecular dynamics simulations 및 CPMD과 같은 방법으로 연구되어왔다. 본 연구에서는. Umbrella sampling을 이용한 QM/MM-MD simulation을 사용하여 4가지 반응의 free energy surface를 도출해냈다. 전체적으로, 가장 선호되는 메커니즘은 two step으로 구성된 water assisted stepwise mechanism이었으며 모든 mechanism은 ab-initio calculation과 QM/MM-MD simulation이 수행되었다. water assisted stepwise mechanism을 살펴보면, 첫 번째 step에서 formamide의 carbonyl group이 hydrate되면서 gem-diol intermediate를 형성한다. 다음 step에서, intermediate의 hydroxyl group으로부터 amino group으로 water-assisted proton transfer이 일어난다. 두 반응 모두에서 물이 proton transfer를 직접적으로 도와주는 것을 관찰할 수 있었다. 특히, ab-initio calculation과는 다르게 QM/MM-MD에서는 gem-diol intermediate가 안정화되는 것으로 solvent effect를 잘 보여준다.

• Korean Journal of Optics and Photonics
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• v.32 no.1
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• pp.29-33
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• 2021

We have experimentally simulated the violation of the Leggett-Garg inequality (LGI) using a heralded-single-photon source via spontaneous parametric down-conversion (SPDC) in a periodically poled potassium titanyl phosphate (PPKTP) crystal. We measured the polarization fringe as a function of the angle of the linear polarization of the photons, and analyzed the LGI according to n measurement. Simulation results for LGI based on the polarization of the heralded single photon were in good agreement with theoretical calculations.

• Nuclear Engineering and Technology
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• v.56 no.4
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• pp.1267-1276
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• 2024

The emerging technologies at the industrial level have deployed rapidly within the energy transition process innovations. The nuclear industry incorporates several technologies like Artificial Intelligence (AI), Machine Learning (ML), Digital Twins, High-Performance-Computing (HPC) and Quantum Computing (QC), among others. Factors identifications are explained to set up a regulatory framework in the digitalization era, providing new capabilities paths for nuclear technologies in the forthcoming years. The Analytical Network Process (ANP) integrates the quantitative-qualitative decision-making analysis to assess the implementation of different aspects in the digital transformation for the New-Energy Transition Era (NETE) with a Nuclear Power Infrastructure Development (NPID).

• Korean Journal of Materials Research
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• v.18 no.11
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• pp.571-576
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• 2008

The simulation program for solar cells, PC1D, was briefly reviewed and the device modeling of a multicrystalline Si solar cell using the program was carried out to understand the internal operating principles. The effects of design parameters on the light absorption and the quantum efficiency were investigated and strategies to reduce carrier recombination, such as back surface field and surface passivation, were also characterized with the numerical simulation. In every step of the process, efficiency improvements for the key performance characteristics of the model device were determined and compared with the properties of the solar cell, whose efficiency (20.3%) has been confirmed as the highest in multicrystalline Si devices. In this simulation work, it was found that the conversion efficiency of the prototype model (13.6%) can be increased up to 20.7% after the optimization of design parameters.