• Journal of the korean society of oceanography
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• v.38 no.3
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• pp.135-142
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• 2003

Gas flux across the air-sea interface is often determined by the product of gas transfer velocity k) and the difference of concentrations in water and air. k is primarily controlled by wind stress on the air-sea interface, thus all parameterizations ofk involve wind speed, a rough indicator of wind stress, as one of the independent variables. We attempted to explore the spatial and temporal variations of k in the East (Japan) Sea using a database from Naet al. (1992). Three different parameterizations were employed: those of Liss and Merlivat (1986), Wanninkhof(1992), and Wanninkhofand McGillis (1999). The strong non-linear dependence of k on wind speed in all parameterizations leads us to examine the effect of time resolution, in which the binned wind speeds are averaged, on the estimation ofk. Two time resolutions of 12 hours (short-term) and one month (long-term) were chosen. The mean wind speeds were fed into the given parameterizations, resulting in six different transfer velocities of $CO_2$ ranging from 12 to 32 cm/h. In addition to the threefold difference depending on the choice of parameterization, the long-term average of wind speed results in a value ofk up to 20% higher than the short-term (12 hours) average of wind speed due to the non-Rayleigh wind distribution in the East (Japan) Sea. While it is not known which parameterization is more reliable, this study proposes that the time-averaged wind speed should not be used in areas where non-Ralyleigh wind distribution prevails such as the East (Japan) Sea. The net annual $CO_2$ flux was estimated using the value of k described above and the monthly ${\Delta}fCO_2$ of Oh et al. (1999); this ranges from 0.034 to 0.11 Gt-C/yr.

• 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.

• Journal of Surface Science and Engineering
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• v.32 no.2
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• pp.144-156
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• 1999

Thermal Barrier Coating with Functional Gradient Materials (FGM-TBC) can play an important role to protect the parts from harmful environments in high temperatures such as oxidation, corrosion, and wear and to improve the efficiency of aircraft engine by lowering the surface temperature on turbine blade. FGM-TBC can increase the life spans of product and improve the operating properties. Therfore, in this study the evaluations of mechanical and thermal properties of FGM-TBC such as fatigue, oxidation and wear-resistance at high temperatures have been conducted. The samples of both the TBC with 2, 3, 5 layers (YSZ/NiCrAlY) to be produced by Air Plasma Spray method (APS) and the bulk TBC with 6 layers to be produced by Plasma Assisted Sintering method (PAS) were used. Furthermore, residual stress, bond strength, and thermal conductivity were evaluated. The average thickness of the APS was 500$\mu\textrm{m}$ to 600$\mu\textrm{m}$ and the average thickness of the PAS was 3mm. The hardness number of the top layer of APS was 750 Hv to 810Hv and that of PAS was 950 Hv to 1440Hv. The $ZrO_2$ coating layer of APS was composed of tetragonal structure after spraying as the result of XRD analysis. As shown in the results of the high temperature wear test, the 3 layer coating of APS had the best wear resistance at $800^{\circ}C$ and the 5 layer coating of APS had the best wear resistance at $600^{\circ}C$. But, these coatings had the tendency of the low-temperature softening at $300^{\circ}C$. The main mechanism of wear was the adhesive wear and the friction coefficient of coatings was increased as increasing the test temperatures. A s results of thermal conductivity test, the ${\Delta}T$ of the APS coating was increased as number of layer and the range of thermal conductivity of the PAS was $800^{\circ}C$ to $1000^{\circ}C$.

• Nuclear Engineering and Technology
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• v.49 no.1
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• pp.178-188
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• 2017

To study the effects of zirconium (Zr) addition on the microstructure, hardness and the tensile properties of oxide dispersion strengthened (ODS) ferritic-martensitic steels, two kinds of 9Cr-ODS ferritic-martensitic steels with nominal compositions (wt.%) of $Fe-9Cr-2W-0.3Y_2O_3$ and $Fe-9Cr-2W-0.3Zr-0.3Y_2O_3$ were fabricated by the mechanical alloying (MA) of premixed powders and then consolidated by hot isostatic pressing (HIP) techniques. The experimental results showed that the average grain size decreases with Zr addition. The trigonal ${\delta}$-phase $Y_4Zr_3O_{12}$ oxides and body-centered cubic $Y_2O_3$ oxides are formed in the 9Cr-Zr-ODS steel and 9Cr non-Zr ODS steel, respectively, and the average size of $Y_4Zr_3O_{12}$ particles is much smaller than that of $Y_2O_3$. The dispersion morphology of the oxide particles in 9Cr-Zr-ODS steel is significantly improved and the number density is $1.1{\times}10^{23}/m^3$ with Zr addition. The 9Cr-Zr-ODS steel shows much higher tensile ductility, ultimate tensile strength and Vickers hardness at the same time.

• Journal of the Korean Ceramic Society
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• v.49 no.6
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• pp.485-492
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• 2012

Dense and single phase $BiFeO_3$ (BFO) ceramics were prepared using attrition milled calcined (coarse) powders of an average particle size of ${\approx}3{\mu}m$ by conventional sintering process. A relative density of ${\approx}96%$ with average grain size $7.3{\mu}m$ was obtained when the powder compacts were sintered at $850^{\circ}C$ even for a shorter duration of 10 min. In contrast, densification barely occurred at $800^{\circ}C$ for up to 12 h rather the microstruce showed the growth of abnormal grains. The grain growth behavior at different temperatures is discussed in terms of nonlinear growth rates with respect to the driving force. The sample sintered at $850^{\circ}C$ for 12 h showed enhanced electrical properties with leakage current density of $4{\times}10^{-7}A/cm^2$ at 1 kV/cm, remnant polarization $2P_r$ of $8{\mu}C/cm^2$ at 20 kV/cm, and minimal dissipation factor (tan ${\delta}$) of ~0.025 at $10^6$ Hz. These values are comparable to the previously reported values obtained using unconventional sintering techniques such as spark plasma sintering and rapid liquid phase sintering.

• Economic and Environmental Geology
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• v.45 no.2
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• pp.71-78
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• 2012

Illite-smectite mixed layers (I-S) occurring authigenically in diagenetic and hydrothermal environments reacts toward more illite-rich phases as temperature and potassium ion concentration increase. For that reason, I-S is often used as geothermometry and/or geochronometry at the field of hydrocarbons or ore minerals exploration. Generally, I-S shows X-ray powder diffraction (XRD) patterns of ultra-thin lamellar structures, which consist of restricted numbers of sillicate layers (normally, 5 ~ 15 layers) stacked in parallel to a-b planes. This ultra-thinness is known to decrease I-S expandability (%S) rather than theoretically expected one (short-stacking effect). We attempt here to quantify the short stacking effect of I-S using the difference of two types of expandability: one type is a maximum expandability ($%S_{Max}$) of infinite stacks of fundamental particles (physically inseparable smallest units), and the other type is an expandability of finite particle stacks normally measured using X-ray powder diffraction (XRD) ($%S_{XRD}$). Eleven I-S samples from the Geumseongsan volcanic complex, Uiseong, Gyeongbuk, have been analyzed for measuring $%S_{XRD}$ and average coherent scattering thickness (CST) after size separation under 1 ${\mu}m$. Average fundamental particle thickness ($N_f$) and $%S_{Max}$ have been determined from $%S_{XRD}$ and CST using inter-parameter relationships of I-S layer structures. The discrepancy between $%S_{Max}$ and $%S_{XRD}$ (${\Delta}%S$) suggests that the maximum short-stacking effect happens approximately at 20 $%S_{XRD}$, of which point represents I-S layer structures consisting of ca. average 3-layered fundamental particles ($N_f{\approx}3$). As a result of inferring the $%S_{XRD}$ range of each Reichweite using the $%S_{XRD}$ vs. $N_f$ diagram of Kang et al. (2002), we can confirms that the fundamental particle thickness is a determinant factor for I-S Reichweite, and also that the short-stacking effect shifts the $%S_{XRD}$ range of each Reichweite toward smaller $%S_{XRD}$ values than those that can be theoretically prospected using junction probability.

• Journal of information and communication convergence engineering
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• v.5 no.2
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• pp.140-143
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• 2007

Fingerprint Recognition System is made up of Off-line treatment and On-line treatment; the one is registering all the information of there trieving features which are retrieved in the digitalized fingerprint getting out of the analog fingerprint through the fingerprint acquisition device and the other is the treatment making the decision whether the users are approved to be accessed to the system or not with matching them with the fingerprint features which are retrieved and database from the input fingerprint when the users are approaching the system to use. In matching between On-line and Off-line treatment, the most important thing is which features we are going to use as the standard. Therefore, we have been using "Delta" and "Core" as this standard until now, but there might have been some deficits not to exist in every person when we set them up as the standards. In order to handle the users who do not have those features, we are still using the matching method which enables us to make up of the spanning tree or the triangulation with the relations of the spanned feature. However, there are some overheads of the time on these methods and it is not sure whether they make the correct matching or not. In this paper, introduces a new data structure, called Union and Division, representing binary fingerprint image. Minutiae detecting procedure using Union and Division takes, on the average, 32% of the consuming time taken by a minutiae detecting procedure without using Union and Division.