• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2023.11a
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• pp.149-151
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• 2023

MX-S2X(선박중심직접통신)은 선박을 중심으로 한 D2D 통신을 통해 육상·선박·시설의 유기적 연결을 제공함으로써, 해양 분야의 4차 산업혁명에서 해상 통신 기술 인프라로서의 핵심 역할이 가능할 것으로 기대 된다. '초고속해상무선통신망 무설설비 다각화 및 통신연계 기술개발 '의 1단계 3차년도에서는 2차년도에 제작한 MX-S2X 1차 시제품에 대한 기능을 보완하고 ISM 대역의 소출력 요구사항을 만족하기 위한 DSSS을 적용하여 2차 시제품을 구현/제작하고 실제 해상환경에서 성능을 검증한다. 본 논문에서는 MX-S2X 2차 시제품에 대한 1, 2차 실해역 시험결과 및 향후 계획에 대해 공유한다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2022.11a
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• pp.96-98
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• 2022

MX-S2X(선박중심직접통신)은 디지털 통신 연계기술 개발 및 실증을 통한 육상·선박·시설의 유기적 연결을 제공함으로써, 향후 도래할 해상 통신 기술 인프라로서의 효과적 활용이 가능할 것으로 기대된다. 본 논문은 '초고속해상무선통신망 무설설비 다각화 및 통신연계 기술개발 '의 1차년도에 수행한 MX-S2X 시스템의 물리계층 설계에 대한 보완 및 해상통신을 위한 최적화를 통해 상세설계를 확정하고, 이를 구현/제작한 HW의 성능을 검증한다. 제작한 HW의 검증을 위해 시험환경을 구성하여 PER 성능을 측정하고 M&S 결과와 비교 분석함으로써 MX-S2X HW의 기능 및 성능을 검증하였다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2021.11a
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• pp.121-123
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• 2021

선박중심직접통신(MX-S2X)은 디지털 통신 연계기술 개발 및 실증을 통한 육상·선박·시설의 유기적 연결을 제공함으로써, 해양사고 저감 및 자율운항선박을 위한 인프라로 활용될 수 있다. 본 논문은 MX-S2X 기술개발에 대한 소개, MX-S2X 개발을 위한 운용 및 설계 요구사항에 대해 기술하고 있으며, 더 나아가 해상 통신 환경이 통신성능에 영향을 끼칠수 있는 경우에 대해 살펴보고 이를 극복하기 위한 MX-S2X 시스템의 물리계층 설계에 대해 기술하였다.

• Journal of Navigation and Port Research
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• v.45 no.6
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• pp.352-359
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• 2021

This paper presents the definition and importance of ship-centric direct communication concerning ship safety of maritime autonomous and unmanned ships. It also proposes the concept of MX-S2X communication based on high frequency for wide-bandwidth technology and describes the design and simulation result for the physical layer of MX-S2X. It considered high-speed communication as well as overcoming maritime multi-path fading required to be resolved in the marine environment. The physical layer of MX-S2X communication was designed to overcome the occurrence of error-floor caused by multi-path fading even with receiving sufficient signal strength. To this purpose, a performance analysis was conducted on the physical layer by applying the channel model of the actual maritime communication environment. As a result of the performance analysis of the MX-S2X physical layer, it was confirmed that the BER error-floor observed in the VDE physical layer test was overcome, and it operated within the SNR 2dB degradation range compared to the AWGN channel. It is expected that this will show enough performance suitable for short-distance ship-centered direct communication and can be used for direct communication of maritime autonomous ships, unmanned ships, and group navigation of themshortly.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2022.11a
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• pp.99-100
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• 2022

자율운항 및 무인선 등 새로운 선박의 도입을 위한 기술개발과 함께 선박중심직접통신(M-S2X)의 필요성이 확대되고 있으며, 고용량, 고속의 서비스 구현을 위해 광대역 기반의 선박중심직접통신(Mx-S2X) 기술개발이 진행되고 있다. Mx-S2X의 안정적 서비스 구현을 위해 활용 가능한 주파수를 탐색하고 적정 주파수를 식별하고자 한다.

• Journal of Navigation and Port Research
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• v.46 no.6
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• pp.570-575
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• 2022

The MX-S2X, utilizing high-frequency broadband communication technology, provides a reliable connection between land, ship, and facilities. This technology is expected to be effectively utilized as a future maritime communication infrastructure in the upcoming mixed navigational situation among autonomous and manned and/or unmanned ships. Following the physical layer design and M&S-based performance analysis of the MX-S2X system to overcome maritime multipath fading, this paper confirms the optimized and detailed design of physical layer hardware and implemented it to verify the performance. The PER(Packet Error Rate) performance was then measured by configuring a test environment to verify the implemented hardware. The results showed that the performance degradation was 0.2 dB in the AWGN environment and 1.2 dB in the Multi-path Fading on Sea Environment, thus confirming the successful implementation of the physical layer.

• Proceeding of EDISON Challenge
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• 2017.03a
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• pp.441-447
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• 2017

본 논문에서는 다양한 원소 조합을 통한 다양한 특성과 2D 구조의 형성이 가능한 물질로서 최근 많은 응용에 활용되고 있는 TMD물질에 대하여 strain 엔지니어링 방법을 탐색하고자 하였다. 에디슨 나노물리의 LCAO 기반 DFT 전자구조계산 SW를 이용해 4, 5, 6족의 TMD물질($MX_2$, M = Zr, Nb, Mo; X = S, Se, Te)의 monolayer, bulk 상태에 strain을 가했을 때 전자 구조의 변화를 계산하였다. Band gap 크기, 전자의 effective mass의 변화, direct-indirect gap transition 등을 전이금속의 종류에 따라 분류하여 분석할 수 있었다.

• Journal of the Korean Mathematical Society
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• v.55 no.6
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• pp.1485-1498
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• 2018

We disprove a conjecture of Bombieri regarding univalent functions in the unit disk in some previously unknown cases. The key step in the argument is showing that the global minimum of the real function (n sin x - sin(nx))/(m sin x - sin(mx)) is attained at x = 0 for integers m > $n{\geq}2$ when m is odd and n is even, m is sufficiently big and $0.5{\leq}n/m{\leq}0.8194$.

• Journal of the Korean Vacuum Society
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• v.4 no.S2
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• pp.148-155
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• 1995

(1) The metastable crystalline(MX) phases formed by ion mixing are classified into 5 types, i.e. the super-saturated solid solutions and the enlarged HCP-I phases reported earlier, and the newly observed FCC-I phases in hcp-based alloys, The FCC-ll and HCP-ll phases in bcc-based alloys. The growth kinetics of the MX phases is discussed. (2) The interfacial free energy in the multilayered films was found to play an important role in ion beam mixing(IM) induced amorphization. By adding sufficient interfaces, amorphous alloys were obtained even in the systems with rather positive heat of formation. (3) Gibbs free energy diagrams of some representative systems were constructed, by calculating the free energy curves of all the competing phases. Steady-state thermal annealing was conducted and the results confirmed the relevance of the constructed diagrams, which were inturn employed to interpret the MX phase formation as well as the glass forming ability upon IM in the binary metal systems.

• Journal of the Korea Society of Computer and Information
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• v.20 no.8
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• pp.29-33
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• 2015

This paper proposes a discrete logarithm algorithm that remarkably reduces the execution time of Pollard's Rho algorithm. Pollard's Rho algorithm computes congruence or collision of ${\alpha}^a{\beta}^b{\equiv}{\alpha}^A{\beta}^B$ (modp) from the initial value a = b = 0, only to derive ${\gamma}$ from $(a+b{\gamma})=(A+B{\gamma})$, ${\gamma}(B-b)=(a-A)$. The basic Pollard's Rho algorithm computes $x_i=(x_{i-1})^2,{\alpha}x_{i-1},{\beta}x_{i-1}$ given ${\alpha}^a{\beta}^b{\equiv}x$(modp), and the general algorithm computes $x_i=(x_{i-1})^2$, $Mx_{i-1}$, $Nx_{i-1}$ for randomly selected $M={\alpha}^m$, $N={\beta}^n$. This paper proposes 4-model Pollard Rho algorithm that seeks ${\beta}_{\gamma}={\alpha}^{\gamma},{\beta}_{\gamma}={\alpha}^{(p-1)/2+{\gamma}}$, and ${\beta}_{{\gamma}^{-1}}={\alpha}^{(p-1)-{\gamma}}$) from $m=n={\lceil}{\sqrt{n}{\rceil}$, (a,b) = (0,0), (1,1). The proposed algorithm has proven to improve the performance of the (0,0)-basic Pollard's Rho algorithm by 71.70%.