• 한국초전도학회:학술대회논문집
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• v.9
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• pp.48-53
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• 1999

We demonstrate small-scale high-T$_c$ superconductor RSFQ(Rapid Single Flux Quantum) circuits using multilayer bicrystal technology. An RSFQ balanced comparator is demonstrated with good current resolution, and its operating conditions are discussed in some detail. A single-loop delta-sigma modulator is realized adding a feedback loop to the comparator. The effect of the feedback is confirmed by dc measurement and simulation. A design of an RSFQ toggle flip-flop with the same multilayer bicrystal technology is suggested.

• Progress in Superconductivity and Cryogenics
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• v.7 no.1
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• pp.17-20
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• 2005

We has designed, fabricated, and measured a Single flux quantum (SFQ) toggle flip-flop (TFF). The TFF is widely used in superconductive digital electronics circuits. Many digital devices, such as frequency counter, counting ADC and program counter be used TFF Specially, a program counter may be constructed based on TFF We have designed the newly TFF and obtained high bias margins on test. In this work, we used two circuit simulation tools, WRspice and Julia, as circuit optimization tools. We used XIC for a layout tool. Newly designed TFF had minimum bias margins of +/- $37\%$ and maximum bias margins of +/-$37\%$(enhanced from +/- $37\%$). The designed circuits were fabricated by using Nb technology The test results showed that the re-optimized TFF operated correctly on 100kHz and had a very wide bias margins of +/- $53\%$.

• Journal of the Optical Society of Korea
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• v.10 no.2
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• pp.86-90
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• 2006

The external feedback effect on the relative intensity noise (RIN) characteristics of blue InAlGaN laser diode has been analyzed taking into account the spontaneous emission noise and the injection current for the high frequency modulation. A Langevin diffusion model was exploited to characterize its relative intensity noise. The simulation parameters were quantitatively evaluated from the optical gain properties of the InAlGaN multiple quantum well active regions by using the multiband Hamiltonian for the strained wurtzite crystals. The extracted parameters were then applied to the rate equations taking into account the external feedback and the high frequency modulation current. The RIN characteristics were investigated to optimize the low frequency laser diode noise characteristics.

• Journal of Astronomy and Space Sciences
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• v.14 no.1
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• pp.117-125
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• 1997

A Fabry-Perot interferometer has a very high (~1,000,000) resolution, so recently this has been widely used for many fields of space science. To understand the working principle of this a mathematical modeling is needed, and to analyze the interferogram it is essential to know the precise instrument function. The spectrum from the interferometer is mixed with a true signal from the light source and the instrument function through convolution. The true signal has the information about the quantum state of mo lecules, temperature and bulk motion of the gas. Therefore if we model the signal and convolve this with the theoretical instrument function we can predict the spectrum for the real case.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.10a
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• pp.76-78
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• 2003

We have designed and tested an RSFQ (Rapid Single Flux Quantum) NDRO (Non Destructive Read Out) circuit for the development of a high speed superconducting ALU (Arithmetic Logic Unit). When designing the NDRO circuit, we used Julia, XIC and Lmeter for the circuit simulations and layouts. We obtained the simulation margins of larger than $\pm$25％. For the tests of NDRO operations, we attached the three DC/SFQ circuits and two SFQ/DC circuits to the NDRO circuit. In tests, we used an input frequency of 1 KHz to generate SFQ Pulses from DC/SFQ circuit. We measured the operation bias margin of NDRO to be $\pm$15％. The circuit was measured at the liquid helium temperature.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.10a
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• pp.113-116
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• 2003

Confluence buffers and single flux quantum (SFQ) switches are essential components in constructing a high speed superconductive Arithmetic Logic Unit (ALU). In this work, we developed a SFQ confluence buffer and an SFQ switch. It is very important to optimize the circuit parameters of a confluence buffer and an SFQ switch to implement them into an ALU. The confluence buffer that we are currently using has a small bias margin of $\pm$11％. By optimizing it with a Josephson circuit simulator, we improved the design of confluence buffer. Our simulation study showed that we improved bias global margin of 10％ more than the existent confluence buffer. In simulations, the minimal bias margin was $\pm$33％. We also designed, fabricated, and tested an SFQ switch operating in a DC mode. The mask layout used to fabricate the SFQ switch was obtained after circuit optimization. The test results of our SFQ switch showed that it operated correctly and had a reasonably wide margin of $\pm$15％.

• Bulletin of the Korean Chemical Society
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• v.25 no.1
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• pp.69-72
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• 2004

The N-alkylation of 4-aminopyrimidine with a tetrahydro-3-aza-cyclopropa[c]inden-5-one, which is a model reaction of the pharmacophore of duocarmycins, was studied with a quantum chemical method. We consider two factors for the acceleration of the N-alkylation; distortion and protonation of the model pharmacophores. The distortion of the spirocyclopropyl moiety in the model spirocyclopropylcyclohexadienone could induce an intrinsic energy of 3-4 kcal/mol, but the protonation on the carbonyl oxygen of the model cyclohexadienone lowers the transition energy of the N-alkylation of 4-aminopyrimidine dramatically (~46 kcal/mol) and is considered to play a major role in the enzyme reaction. The distorted and protonated spirocyclohexadienone is exothermally relieved to a phenol with the heat of reaction of -37 kcal/mol. The protonation process is proposed to be the mode of action of duocarmycins in the DNA alkylation.

• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.357-361
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• 2016

Si와 InAs 두 가지 채널 물질을 가지고 3가지 수송 방향 <100>, <110>, <111>으로 변화시키며 각각의 Nanowire nMOSFETs을 가지고 ballistic quantum transport simulation을 진행하였다. 각각의 경우에 대해 E-k curve를 구한 다음에 band curvature로 캐리어의 유효질량을 계산하고, 이를 통해 MOSFET의 전류 세기를 결정짓는 DOS와 carrier injection velocity를 구하여 어떤 경우에 가장 높은 ON-current를 흐르게 하는지 확인해 보았다. 하지만 예상과 달리 나노와이어의 직경이 1.4nm으로 매우 작기 때문에 valley-splitting이 일어나 Si<110>의 경우에 가장 작은 캐리어 유효 질량을 갖고 있는 사실을 확인할 수 있었다. 결론적으로 Si<100>의 경우에 trade-off 관계에 있는 DOS와 carrier injection velocity가 6가지 경우 중 최적의 조합을 가짐으로써 가장 높은 ON-current를 흐르게 하였다.

• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.368-372
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• 2016

In this paper, the physics-based analytical model of transition metal dichalcogenide (TMD)-based double-gate (DG) tunneling field-effect transistors (TFETs) is proposed. The proposed model is derived by using the two-dimensional (2-D) Landauer formula and the Wentzel-Kramers-Brillouin (WKB) approximation. For improving the accuracy, nonlinear and continuous lateral energy band profile is applied to the model. 2-D density of states (DOS) and two-band effective Hamiltonian for TMD materials are also used in order to consider the 2-D nature of TMD-based TFETs. The model is validated by using the tight-binding non-equilibrium Green's function (NEGF)-based quantum transport simulation in the case of monolayer molybdenum disulfide ($MoS_2$)-based TFETs.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.10
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• pp.3256-3274
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• 2022

With the rapid development of information and communications technology, the construction of efficient, reliable, and safe Internet of Things (IoT) is an inevitable trend in order to meet high-quality demands for the forthcoming 6G communications. In this paper, we study a secure intelligent reflecting surface (IRS)-assisted IoT system where malicious eavesdropper trying to sniff out the desired information from the transmission links between the IRS and legitimate IoT devices. We discuss the system overall performance and propose a hybrid resource allocation scheme for maximizing the secrecy capacity and secrecy energy efficiency. In order to achieve the trade-off between transmission reliability, communication security, and energy efficiency, we develop a quantum-inspired marine predator algorithm (QMPA) for realizing rational configuration of system resources and prevent from eavesdropping. Simulation results demonstrate the superiority of the QMPA over other strategies. It is also indicated that proper IRS deployment and power allocation are beneficial for the enhancement of system overall capacity.