• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.6
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• pp.241-248
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• 2003

$Bi_{1.84}Pb_{0.34}Sr_{1.91}Ca_{2.03}Cu_{3.06}O_{10+\delta}$ high $T_{c}$ superconductors containing Ag as an additive were fabricated by a solid-state reaction method. The superconducting properties, such as the structural characteristics, the critical temperatures, the grain size and the image of mapping on the surface were investigated. Samples with Ag and Au of 50 wt% each were sintered at various temperature(820~$850^{\circ}C$). The structural characteristics, the microstructure of surface and the critical temperature with respect to the each samples were analyzed by XRD and SEM, EDS and four-prove methode respectively. The critical temperature showed the result which the Ag additive samples are higher than Au additive samples. The microstructure of the surface showed the tendency which the Ag additive samples become more minuteness than Au additive samples.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.10
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• pp.1177-1186
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• 2009

High temperature steam pipes of thermal power plant are subject to a severe thermal range and usually operates well into the creep range. Cyclic operation of the plant subjects the piping system to mechanical and thermal fatigue damages. Also, poor or malfunctional supports can impose massive loads or stress onto the piping system. In order to prevent the serious damage and failure of the critical piping system, various inspection methods such as visual inspection, computational analysis and on-line piping displacement monitoring were developed. 3-dimensional piping displacement monitoring system was developed with using the aluminum alloy rod and rotary encoder sensors, this system was installed and operated on the high temperature steam piping of "Y" thermal power plant successfully. It is expected that this study will contribute to the safety of piping system, which could minimize stress and extend the actual life of critical piping.

• Fisheries and Aquatic Sciences
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• v.6 no.2
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• pp.59-65
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• 2003

The critical thermal maximum (CTM) of black rockfish, Sebastes schlegeli, was evaluated. Black rockfish were acclimated at $24^{\circ}C$, and then exposed to temperatures from 24 to $33^{\circ}C$. Black rockfish were kept in constant darkness and subjected to a gradual temperature increase $(1 ^{\circ}C\;12^{-1})$. The oxygen consumption rate (OCR) was measured using an automatic intermittent­flow-respirometer (AIFR) during the exposure period (from 119.3 to 143.5 h). The OCR increased from 94.5 to 214.2mL $O_2 kg^{-1}\;ww\;h^{-1}$ as the temperature rose from 24 to $29.4-30.9^{\circ}C$. Subsequently, the OCR increased abruptly, reaching 245.8-412.7mL $O_2 kg^{-1}\;ww\;h^{-1}$ at $32^{\circ}C$. This study suggests that the CTM for black rockfish is $29.4-30.9^{\circ}C$ when temperature is increased at $1^{\circ}C\;12h^{-1}$ following acclimation at $24^{\circ}C$.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.4 no.1
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• pp.43-50
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• 2000

In this study, experiments were carried out to measure the variations in the corrosion potential and current density of polarization curves using polycarbonate. The results were particularly examined to identify the influences affecting the corrosion potential including various conditions such as temperature, pH, catalytic enzyme, and salt. The lines representing the active anodic dissolution were only slightly shifted in the potential direction by temperature, pH, enzyme, and salt. The tafel slope for the anodic dissolution was determined based on the polarization effect with various conditions. The slope of the polarization curves describing the active-to-passive transition region were noticeably shifted in direction. Also, from the variation in the conditions, the optimum conditions were established for the most rapid transformation, including temperature, pH, corrosion rate, and resistance of corrosion potential. The second anodic current density peak and maximum passive current density were designated as the critical corrosion sensitivity(Ir/If). The value of Ir/If was then used in measuring the extent of the critical corrosion sensitivity of the polycarbonate. The potentiodynamic parameters of the corrosion were obtained using a Tafel plot.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.5
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• pp.467-472
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• 2007

In this study the penetration distance of liquid phase fuel(i.e. liquid phsae length) was investigated in evaporative field. An exciplex fluorescence method was applied to the evaporative fuel spray to measure and investigate both the liquid and the vapor phase of the injected spray. For accurate investigation, images of the liquid and vapor phase regions were recorded using a 35mm still camera and CCD camera, respectively. Liquid fuel was injected from a single-hole nozzle (l/d=1.0mm/0.2mm) into a constant-volume chamber under high pressure and temperature in order to visualize the spray phenomena. Experimental results indicate that the liquid phase length decreased down to a certain constant value in accordance with increase in the ambient gas density and temperature. The constant value, about 40mm in this study the, is reached when the ambient density and temperature of the used fuel exceed critical condition.

• Journal of Powder Materials
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• v.6 no.2
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• pp.145-151
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• 1999

Nickel silicides ($Ni_5$Si$_2$, Ni$_2$Si and NiSi) have been synthesized by mechanical alloying (MA) of Ni-27.9at.9at%Si, Ni-33.3at% and Ni-50.0at% powder mixtures, respectively. From in situ thermal analysis, eash citical milling period for the formation of the three phases was observed to be 40.2, 34.9 and 57.5 min, at which there was a rapid increase in temperature. This indicates that rapid, self-propagating high-temperature synthesis (SHS) reactions were observed to produce the three phases during room-temperature high-energy ball milling of elemental powders. Each Ni silicide, Ni and Si, however, coexisted for an extended milling time even after the critical milling period. The powders mechanically alloyed after the critical period showed the rapid increase in microhardness. The Hv values were found to be higher than 1000kgf/mm$^2$. The formation of nickel silicides by mechanical alloying and the relevant reaction rates appeared to be influenced by the critical milling period and the heat of formation of the products involved ($Ni_5$Si$_2$$\rightarrow$-43.1kJ/mol.at., Ni$_2$Si$\rightarrow$-47.6kJ/mol.at., NiSi$\rightarrow$-42.4kJ/mol.at).

• Nuclear Engineering and Technology
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• v.47 no.5
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• pp.559-566
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• 2015

The thermalehydraulic characteristics for the CANadian Deuterium Uranium Flexible (CANFLEX)-burnable poison (BP) fuel channel, which is loaded with a BP at the center ring based on the CANFLEX-RU (recycled uranium) fuel channel, are evaluated and compared with that of standard 37-element and CANFLEX-NU (natural uranium) fuel channels. The distributions of fuel temperature and critical channel power for the CANFLEX-BP fuel channel are calculated using the NUclear Heat Transport CIRcuit Thermohydraulics Analysis Code (NUCIRC) code for various creep rate and burnup. CANFLEX-BP fuel channel has been revealed to have a lower fuel temperature compared with that of a standard 37-element fuel channel, especially for high power channels. The critical channel power of CANFLEX-BP fuel channel has increased by about 10%, relative to that of a standard 37-element fuel channel for 380 channels in a core, and has higher value relative to that of the CANFLEX-NU fuel channel except the channels in the outer core. This study has shown that the use of a BP is feasible to enhance the thermal performance by the axial heat flux distribution, as well as the improvement of the reactor physical safety characteristics, and thus the reactor safety can be improved by the use of BP in a CANDU reactor.

• Nuclear Engineering and Technology
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• v.40 no.2
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• pp.133-138
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• 2008

The use of Supercritical Fluids(SCF) has been proposed for numerous power cycle designs as part of the Generation IV advanced reactor designs, and can provide for higher thermal efficiency. One particular area of interest involves the behavior of SCF during a blowdown or depressurization process. Currently, no data are available in the open literature at supercritical conditions to characterize this phenomenon. A preliminary computational analysis, using a homogeneous equilibrium model when a second phase appears in the process, has shown the complexity of behavior that can occur. Depending on the initial thermodynamic state of the SCF, critical flow phenomena can be characterized in three different ways; the flow can remain in single phase(high temperature), a second phase can appear through vaporization(high pressure low temperature) or condensation(high pressure, intermediate temperature). An experimental facility has been built at the University of Wisconsin to study SCF depressurization through several diameter breaks. The preliminary results obtained show that the experimental data can be predicted with good agreement by the model for all the different initial conditions.

• Advances in nano research
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• v.7 no.2
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• pp.89-98
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• 2019

In this work, the thermal buckling characteristics of zigzag single-walled boron nitride (SWBNNT) embedded in a one-parameter elastic medium modeled as Winkler-type foundation are investigated using a nonlocal first-order shear deformation theory (NFSDT). This model can take into account the small scale effect as well as the transverse shear deformation effects of nanotubes. A closed-form solution for nondimensional critical buckling temperature is obtained in this investigation. Further the effect of nonlocal parameter, Winkler elastic foundation modulus, the ratio of the length to the diameter, the transverse shear deformation and rotary inertia on the critical buckling temperature are being investigated and discussed. The results presented in this paper can provide useful guidance for the study and design of the next generation of nanodevices that make use of the thermal buckling properties of boron nitride nanotubes.

• Korean Journal of Metals and Materials
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• v.47 no.10
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• pp.635-643
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• 2009

The resistance to pitting corrosion of Fe-Cr alloys was evaluated by performing potentiodynamic polarization and critical pitting temperature (CPT) tests. For the potentiodynamic polarization tests, various standards were applied, i.e., KS D 0238 (wet, dry), ASTM G 61, and ISO 17475, showing different potentiodynamic polarization results including pitting potentials. ASTM G 61 and ISO 17475 standards presented relatively higher pitting potential while KS D 0238 (dry) indicated lower values than the others. Effects of surface roughness, scan rates, and exposure time to air before tests were also investigated. CPT tests were performed under two different applied potentials, 300 m$V_{SCE}$ and 200 m$V_{SCE}$ in deaerated 1 M NaCl aqueous solution. CPT values and the polarization test results showed a linear relationship.