• Nuclear Engineering and Technology
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• v.53 no.3
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• pp.879-887
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• 2021

The nuclear supply chain attack surface is a large, complex network of interconnected stakeholders and activities. The global economy has widened and deepened the supply chain, resulting in larger numbers of geographically dispersed locations and increased difficulty ensuring the authenticity and security of critical digital assets. Although the nuclear industry has made significant strides in securing facilities from cyber-attacks, the supply chain remains vulnerable. This paper discusses supply chain threats and vulnerabilities that are often overlooked in nuclear cyber supply chain risk analysis. A novel supply chain cyber-attack surface diagram is provided to assist with enumeration of risks and to examine the complex issues surrounding the requirements for securing hardware, firmware, software, and system information throughout the entire supply chain lifecycle. This supply chain cyber-attack surface diagram provides a dashboard that security practitioners and researchers can use to identify gaps in current cyber supply chain practices and develop new risk-informed, cyber supply chain tools and processes.

• Proceedings of the KIEE Conference
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• 2004.11b
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• pp.36-38
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• 2004

In many countries, including Korea, in order to transmit the more electric power, the higher transmission line voltage is inevitable. So, a rapid reclosing scheme is important for UHV transmission lines to ensure requirements for high reliability of main lines. But, because of the high voltage and long span of UHV lines, the secondary arc current flows across the fault point even after the interruption of the fault current. i.e. A critical aspect of reclosing operation is the extinction of the secondary arc since it must extinguish before successful reclosure can occur. In Korea transmission lines, it is scheduled to energize 765kV single transmission line(79km) between Sin-Ansung S/S and Sin-Gapyeong S/S at June 2006. Therefore this paper analyzes characteristics of the secondary arc extinction on 765kV single transmission line using EMTP. Simulation results shows that the average value of the secondary arc is $30A_{rms}$ and the auto-extinction time of it is longer at closer point to Sin-Gapyeong S/S.

• Korean Journal of Metals and Materials
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• v.47 no.11
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• pp.728-733
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• 2009

Cu based amorphous ($Cu_{54}Zr_{22}Ti_{18}Ni_{6}$) powders were deposited onto Al 6061 substrates by cold spray process with different powder preheating temperatures (below glass transition temperature: $350^{\circ}C$, near glass transition temperature: $430^{\circ}C$ and near crystallization temperature: $500^{\circ}C$). The microstructure and macroscopic properties (hardness, wear and corrosion) of Cu based amorphous coating layers were also investigated. X-ray diffraction results showed that cold sprayed Cu based amorphous coating layers of $300{\sim}350{\mu}m$ thickness could be well manufactured regardless of powder preheating temperature. Porosity measurements revealed that the coating layers of $430^{\circ}C$ and $500^{\circ}C$ preheating temperature conditions had lower porosity contents (0.88%, 0.93%) than that of the $350^{\circ}C$ preheating condition (4.87%). Hardness was measured as 374.8 Hv ($350^{\circ}C$), 436.3 Hv ($430^{\circ}C$) and 455.4 Hv ($500^{\circ}C$) for the Cu based amorphous coating layers, respectively. The results of the suga test for the wear resistance property also corresponded well to the hardness results. The critical anodic current density ($i_{c}$) according to powder preheating temperature conditions of $430^{\circ}C$, $500^{\circ}C$ was lower than that of the sample preheated at $350^{\circ}C$, respectively. The higher hardness, wear and corrosion resistances of the preheating conditions of near $T_{g}$ and $T_{x}$, compared to the properties of below $T_{g}$, could be well explained by the lower porosity of coating layer.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.933-934
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• 2007

We fabricated and tested a resistive type superconducting fault current limiter (SFCL) based on BSCCO-2212 bulk coils. Each bulk coils of the SFCL was designed to have the rated voltage of 220 $V_{rms}$ and the critical current($I_C$) of 320$\sim$340 A at 77K. Ten components in series, make the SFCL having the rated voltage of 2.2 $kV_{rms}$ for equal quench test. The fault test was conducted at an input voltage of 2.2 $kV_{rms}$ and fault current of 25 $kA_{rms}$. In addition, we examined the endurance characteristics for all bulk coils through repeat fault test. Test results shows that the SFCL successfully limited the fault current of 25$kA_{rms}$ to below $7{\sim}8kA_{p}$ within minimum 1.1msec after fault occurred. All bulk coils quenched together upon faults and shared the rated voltage evenly. The endurance test results show an equivalent among repeat fault test. During the quench process, average temperature of all bulk coils did not exceed 250 K, and the SFCL was totally safe during the whole operation.

• Progress in Superconductivity
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• v.6 no.2
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• pp.142-145
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• 2005

YBCO coated conductors have been fabricated with a newly developed oxide-precursor-based MOD process. The precursor solution was synthesized with low cost YBCO powders as starting materials and YBCO coated conductors have been deposited on IBAD substrate ($CeO_2$/IBAD-YSZ/SS). YBCO coated conductor prepared by dip coating shows transport $I_c$ of 15A/cm-w at 77 K. Microstructural and crystallographic analyses indicate that YBCO layer was grown in epitaxy with substrate and exhibited well-developed dense microstructure. Also discussed are processing and analysis of YBCO coated conductor by slot-die web coating method. It was shown that this oxide-based MOD process provides a low cost route to coated conductor with high $J_c$.

• Current Applied Physics
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• v.18 no.11
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• pp.1294-1299
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• 2018

In this paper, we demonstrate the feasibility of constructing DNA nanostructures (i.e. DNA rings and double-crossover (DX) DNA lattices) with appropriate doxorubicin hydrochloride (DOX) concentration and reveal significant characteristics for specific applications, especially in the fields of biophysics, biochemistry and medicine. DOX-intercalated DNA rings and DX DNA lattices are fabricated on a given substrate using the substrateassisted growth method. For both DNA rings and DX DNA lattices, phase transitions from crystalline to amorphous, observed using atomic force microscopy (AFM) occurred above a certain concentration of DOX (at a critical concentration of DOX, $30{\mu}M$ of $[DOX]_C$) at a fixed DNA concentration. Additionally, the coverage percentage of DNA nanostructures on a given substrate is discussed in order to understand the crystal growth mechanism during the course of annealing. Lastly, we address the significance of optical absorption and photoluminescence characteristics for determining the appropriate DOX binding to DNA molecules and the energy transfer between DOX and DNA, respectively. Both measurements provide evidence of DOX doping and $[DOX]_C$ in DNA nanostructures.

• Progress in Superconductivity
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• v.8 no.1
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• pp.87-92
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• 2006

The effects of Ba and Ce addition has been investigated in YBCO prepared by trifluoroacetate(TFA) metalorganic depostition(MOD) method. Precursor solutions with cation ratios of Y:Ba:Cu:Ce=1:2+x:3:x(x=0, 0.05, 0.1 and 1.5) have been prepared by adding an excess amount of cerium and barium. Coated film was calcined at lower temperature under a moisture-containing oxygen atmosphere. Superconducting YBCO films have been obtained by performing conversion heat treatment at temperature of $780{\sim}810^{\circ}C$ under a moisture-containing Ar(1,000 ppm oxygen) atmosphere. It has been shown that the critical current($I_c$) of YBCO film was degraded by doping of Ba and Ce atoms. But $I_c$ was increased as the amount of doped Ba and Ce content increased from 5% to 15 %. It was observed that there was little increase of a flux pinning force with Ba and Ce addition in YBCO film prepared by TFA-MOD process.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.3
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• pp.283-289
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• 2016

In this study, electrochemical characterizations of PdCu/C catalysts that are synthesized by modified polyol method are investigated. Most of all, amount of ethylene glycol (EG) that is used as main component for catalyst synthesis is mainly modulated to optimize synthetic condition of the PdCu/C catalyst, For evaluations about catalytic activity and performance of direct formic acid fuel cell (DFAFC), half cell and full cell tests are implemented. As a result, when amount of EG is 4M, catalytic activities of the PdCu/C catalyst such as peak current of formic acid oxidation and active surface area are best, while maximum power density of DFAFC using the optimized PdCu/C catalyst is better than that using commercial Pd/C (30 wt%) by 6%. Based on that, PdCu/C catalyst synthesized by modified polyol method plays a critical role in improving (i) catalytic activity for formic acid oxidation and (ii) DFAFC performance by employing as anodic catalyst.

• Progress in Superconductivity
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• v.5 no.1
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• pp.75-79
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• 2003

YBCO films were deposited with various thicknesses from 100nm to 1.6$\mu\textrm{m}$ on single crystal $SrTiO_3$ substrates by pulsed laser deposition (PLD). The effects of different deposition conditions, especially different deposition rates by means of changing the pulsed laser frequency up to 200Hz, on the J$_{c}$ value were studied. For YBCO film with the thickness of 200nm, the $J_{c}$ value of $2.1MA/\textrm{cm}^2$ has been achieved under the high deposition rate of 3.2nm/s (190nm/min). The $J_{c}$ can be maintained greater than $1M/\textrm{cm}^2$ with the thickness less than 1$\mu\textrm{m}$. The X-ray analysis was used to examine the texture, crystallization and surface quality. The SEM was employed to analyze the surface of YBCO, and it was shown the surface of YBCO film became rougher with increasing the thickness. There were many large singular outgrowths and networks of outgrowths on the surface of YBCO films which lowered the density of thick YBCO film. The outgrowth network was probably the a-axis YBCO corresponding to XRD $\theta$-2$\theta$scan and $\chi$-scan which were used to characterize a-axis orientation of YBCO film. The reason for J$_{c}$ declining with increasing the thickness was studied and discussed.sed.

• Progress in Superconductivity and Cryogenics
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• v.15 no.4
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• pp.15-20
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• 2013

We investigated the flux pinning properties of both 10 mol% Zr-and Sn-doped $YBa_2Cu_3O_{7-{\delta}}$ (YBCO) films with the same thickness of ~350 nm for a comparative purpose. The films were prepared on the $SrTiO_3$ (STO) single crystal substrate by the metal-organic deposition (MOD) process. Compared with Sn-doped YBCO film, Zr-doped one exhibited a significant enhancement in the critical current density ($J_c$) and pinning force density ($F_p$). The anisotropic $J_{c,min}/J_{c,max}$ ratio in the field-angle dependence of $J_c$ at 77 K for 1 T was also improved from 0.23 for Sn-doped YBCO to 0.39 for Zr-doped YBCO. Thus, the highest magnetic $J_c$ values of 9.0 and $2.9MA/cm^2$ with the maximum $F_p$ ($F_{p,max}$) values of 19 and $5GN/m^3$ at 65 and 77 K for H // c, respectively, could be achieved from Zr-doped YBCO film. The stronger pinning effect in Zr-doped YBCO film is attributable to smaller $BaZrO_3$ (BZO) nanoparticles (the average size ${\approx}28.4$ nm) than $YBa_2SnO_{5.5}$ (YBSO) nanoparticles (the average size ${\approx}45.0$ nm) incorporated in Sn-doped YBCO film since smaller nanoparticles can generate more defects acting as effective flux pinning sites due to larger incoherent interfacial area for the same doping concentration.