• The Journal of the Petrological Society of Korea
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• v.23 no.3
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• pp.279-292
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• 2014

Nd isotopic compositions analyzed from the Phanerozoic granitoids of Korea are integrated and discussed. Variations in Nd isotopic compositions can be explained either by temporal trend or by regional differences. Among the three active periods, first two periods during the Permian-Triassic and Jurassic seem to show variations from rather high ${\varepsilon}_{Nd}(t)$ values at the beginning to lower ${\varepsilon}_{Nd}(t)$ values during the later stages. Such trends probably reflect melting of the subducting oceanic crust and producing magma with higher proportion of depleted mantle derived materials during the early stage of subduction process, and subsequent magmas with greater proportion of old continental crust with progress of subduction. However, the Cretaceous-Paleogene period of active magmatism displays higher ${\varepsilon}_{Nd}(t)$ values during the advanced stage of the igneous activities, which is opposite to the previous active periods. The other explanation is that such differences in ${\varepsilon}_{Nd}(t)$ reflect regional differences, based on the observations that such high-${\varepsilon}_{Nd}(t)$ granitoids distribute in the northeastern Gyeongbuk Province and Gyeongsang Basin. If this is the case, the regions with highr ${\varepsilon}_{Nd}(t)$ values may have distinct crustal evolution histories, e.g. younger average age. The choice between the two hypothesis could be made through further studies.

• Korean Journal of Food Science and Technology
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• v.37 no.1
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• pp.1-5
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• 2005

Contents of heavy metals [mercury (Hg), lead (Pb), cadmium (Cd), and arsenic (As)] in 218 samples including soybean curds (n = 138), processed bean curds (n = 37), starch jellies (n = 33), and mixed starch jellies (n = 10) were determined using mercury analyzer, atomic absorption spectrophotometer (AAS) or inductively coupled plasma spectrometer (ICP). Ranges and means of heavy metals in soybean curds and starch jellies were as follows [min-max (mean) values]: soybean curds -Hg $0.1-8.2(0.3)$, Pb not detectable (ND)-203.9(23.3),\ Cd ND-46.0 (8.1), and As ND-61.3 (0.7)${\mu}g/kg$, starch jellies-Hg 0.1-1.3(0.3)${\mu}g/kg$, Pb ND-90.2(22.4)${\mu}g/kg$, Cd ND-31.0(3.7) and As ND-23.6(1.1)${\mu}g/kg$. Daily intakes of Hg, Pb, and Cd from soybean curds and starch jellies were 0.001-0.3% of Provisional tolerable weekly intake established by FAO/WHO.

• Korean Journal of Optics and Photonics
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• v.15 no.3
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• pp.263-267
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• 2004

We have investigated the characteristics of a Nd:YAG laser pumped by a cw Ti:sapphire laser. When the pumping power of the Ti:sapphire laser was 850 ㎽, the maximum output power of the Nd:YAG laser was 450 ㎽. As a result, the slope efficiency for the output power of the Nd:YAG laser was measured to be 56%. We have also investigated the characteristics of a passively Q-switched Nd:YAG laser by using a Cr$^{4+}$:YAG as saturable absorber with initial transmission of 90%. The maximum average output power of 200 ㎽ was obtained with repetition rate of 23.8 KHz and pulse width of 17.0 ns.

• Resources Recycling
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• v.14 no.2
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• pp.33-42
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• 2005

Solvent extraction experiments have been performed to separate Nd and Sm from chloride solution with PC88A. The effect of the saponification of PC88A on the extraction and separation of the two metals were studied. In the experimental ranges conducted in this study, the distribution coefficients of Sm were higher than those of Nd and separation factor between them increased with the equilibrium pH of aqueous solution. Saponification of PC88A enhanced the distribution coefficients of Sm and Nd and the separation factor. A chemical model was developed to predict the distribution coefficients of metals and separation factor from the initial extraction conditions. The measured distribution coefficients of Nd and Sm with PC88A and saponified PC88A agreed well with those calculated in this study.

• Korean Journal of Materials Research
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• v.11 no.7
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• pp.609-614
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• 2001

This study was carried out to obtain a basic data on the production of the Nd-Fe-B system rare earth anisotropic bonded magnet by R-D & HDDR process. The reduction reaction of Nd$_2$O$_3$by metallic Ca and the diffusion reaction of Nd into Fe-B alloy powder were investigated for the production the Nd-Fe-B alloy powder. We concluded that a proper quantity of metallic Ca was about 1.3 times of theoretical equivalent from the yields of Nd and B after the R-D reaction at 100$0^{\circ}C$ for 1h. In the XRD analysis the diffusion reaction of Nd into the center of Fe-B alloy powder for the completed homogenization was required through about 45min at 110$0^{\circ}C$ for the R-D reaction, and also the maximum efficiency on the yield of Nd was obtained with such a condition. Residual Ca and oxygen contents of the final powder sample after washing were detected in 0.17wt% and 0.42wt% by ICP and oxygen analyzer, respectively.

• Proceedings of the Korean Ceranic Society Conference
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• 2000.10a
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• pp.70.2-70
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• 2000

• Journal of the Korean Magnetics Society
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• v.6 no.2
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• pp.80-85
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• 1996

An externally applied magnetic field during annealing the $Nd_{2}Fe_{14}B/Fe_{3}B$ based spring magnet was found to enhance the exchange coupling between the hard and soft magnetic grains. More than 30 % increase in remanence values for melt-spun $Nd_{4}Fe_{73.5}Co_{3}(Hf_{1-x}-Ga_{x})B_{18.5}$(x=0, 0.5, 1.0) alloys was resulted from uniform distribution of $Fe_{3}B$, $\alpha$-Fe as well as $(Nd_{2}Fe_{14}B)$, and also from reduced grain size of those phases by 20 %. The result also showed that there is an optimum grain size exhibiting a high coercivity value which will be discussed in terms of previously simulated exchange coupling parameter.

• Bulletin of the Korean Chemical Society
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• v.27 no.12
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• pp.2011-2018
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• 2006

We have investigated the solvent effects on $\Delta log\;K_s $(the difference of stability constant of binding) and the different free energies of binding of $Nd^{3+}$ and $Eu^{3+}$ ions to 18-crown-6, i.e., the selectivity of $Nd^{3+}$ and $Eu^{3+}$ ions to 18-crown-6 using a Monte Carlo simulation of statistical perturbation theory (SPT) in diverse solvents. The stability constant ($\Delta log\;K_s $) of binding of $Nd^{3+}$ and $Eu^{3+}$ ions to 18-crown-6, in $CH_3OH$ was calculated in this study as -1.06 agrees well with the different experimental results of -0.44~-0.6, respectively. We have reported here the quantitative solvent-polarity relationships (QSPR) studied on the solvent effects the relative free energies of binding of $Nd^{3+}$ and $Eu^{3+}$ ions to 18-crown-6. From the calculated coefficients of QSPR, we have noted that solvent polarity (ET) and Kamlet -Tafts solvatochromic parameters (b ) dominate the differences in relative solvation Gibbs free energies of $Nd^{3+}$ and $Eu^{3+}$ ions but basicity (Bj) dominates the negative values in differences in the stability constant ($\Delta log\;K_s $) as well as the relative free energies of binding of $Nd^{3+}$ and $Eu^{3+}$ ions to 18-crown-6 and acidity (Aj) dominates the positive values in differences in the stability constant ($\Delta log\;K_s $) as well as the relative free energies of binding of $Nd^{3+}$ and $Eu^{3+}$ ions to 18-crown-6.

• Proceedings of the Korean Magnestics Society Conference
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• 1993.11a
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• pp.54-55
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• 1993

• Proceedings of the Korean Ceranic Society Conference
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• 2003.04a
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• pp.115.2-115
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• 2003