• Economic and Environmental Geology
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• v.26 no.3
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• pp.337-347
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• 1993

Mineralogical and geochemical studies on some pyrophyllite deposits in Milyang area, Kyeongnam Province (Milyang and Sungjin mine) were carried out in order to investigate dispersion patterns of chemical elements in altered volcanic wallrocks, and to interpret genetic environments of the pyrophyllite deposits. Cretaceous andesitic and tuffaceous rocks, and pyrophyllite ore specimens were collected from the dumps and drilling cores. Andesitic wallrocks were grouped as unaltered and altered rocks in the order of pyrophyllitization. Vertical dispersion patterns and relative mobilities of chemical elements in volcanic wallrocks were discussed. Geochemical environment in the Milyang area is characterized by the occurrence of boron minerals such as dumortierite coexisting with pyrophyllite ores, and tourmaline in granitic rocks. Unaltered andesitic rocks are mainly composed of plagioclase, pyroxene and hornblende, and were propylitized and saussuritized. Altered andesitic rocks are bleached and consist of quartz, sericite, pyrophyllite, kaolinite, chlorite and disseminated pyrite. Pyrophyllite ores are mainly composed of quartz, pyrophyllite, dumortierite, dissemianted pyrite and some diaspore. Enrichment of $SiO_2$, $Al_2O_3$, LOI (loss on ignition), As and Cr, and depletion of $K_2O$, $Na_2O$, CaO, MgO and total Fe are characteristic during alteration process. The REE patterns show that the pyrophyllite deposits could be originated from the continental margin volcanics. The $(La/Lu)_{cn}$ ratios of the pyrophyllite ores increase from 4.2~23.2 to 2.67~128.8 owing to strong acidic hydrothermal alteration. Vertical dispersion patterns of $Al_2O_3$, $K_2O$, $Na_2O$, CaO, MgO, $Fe_2O_3$ (total Fe), As, Au, Sb, Cr and Sr in the wallrocks show the location of orebodies. Particularly dispersion patterns of $Al_2O_3$ and Cr indicate the extension of orebodies. Anomalous distribution of Au, As and Sb in wallrocks shows potential for gold occurrence below the pyrophyllite deposits. Judging from the relative mobilities of elements in wallrocks, $Al_2O_3$ could be added from hydrothermal solution, and the silicified rone be formed from the excess of $SiO_2$.

• Current Optics and Photonics
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• v.4 no.6
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• pp.477-482
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• 2020

Recently, one of the authors has been reported an optically tunable fiber Bragg grating (FBG) with a photomechanical polymer. It was based on a typical FBG with a downsized diameter of 60 ㎛, coated with azobenzene-containing polymer material. Azobenzene is a well-known reversibly photomechanical stretchable material under ultraviolet (UV) light. The small part of the functional-coating region on the FBG absorbed UV light, which pulled the UV-exposed part of the grating. It was selectable as tunable FBG or tunable chirped FBG, by adjusting the position of UV exposure on the grating. As proof of concept for the tunable FBG device, the characteristics just including UV-induced center-wavelength shift and spectral-width changes of the device were reported. In this paper, we report for the first time that the microactuator makes it possible to control the spectral shape of the FBG reflection, according to the specifications (shape and intensity) of the UV beam that reaches the FBG coated with the azobenzene polymer. In addition, we provide the group-delay profiles for the chirped FBG, so that the sign of its dispersion (normal or anomalous) can be tailored by simply selecting the moving direction of the UV light's displacement in the experiment.

• Korean Journal of Materials Research
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• v.34 no.5
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• pp.242-246
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• 2024

La modified lead zirconate titanate ceramics (Pb_0.92La_0.08)(Zr_0.95Ti_0.05)O₃ = PLZT-8/95/5 were prepared using the conventional solid state reaction method in order to investigate the complex impedance characteristics of the PLZT-8/95/5 ceramic according to temperature. The complex impedance in the PLZT-8/95/5 ceramic was measured over a temperature range of 30~550 ℃ at several frequencies. The complex dielectric constant anomaly of the phase transition was observed near T_U1 = 179 ℃ and T_U2 = 230 ℃. A remarkable diffuse dielectric constant anomalous behaviour of the complex dielectric constant was found between 100 ℃ and 550 ℃. The complex impedance spectra below and above T_U1 and T_U2 were fitted by the superposition of two Cole-Cole types of impedance relaxations. The fast component in the higher frequency region may be due to ion migration in the bulk, and the slow component in the lower frequency region is interpreted to be the formation and migration of ions at the grain boundary or electrode/crystal interfacial polarization.

• The Journal of Natural Sciences
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• v.8 no.1
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• pp.87-92
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• 1995

In the Vicinity of the Sindae-dong waste disposal site in Taejon, the average Cu, pb and Zn concentrations in soils are higher than those in other Korean soils but these are not high enough to cause any harmful effect to human and animal through the crop plants. Copper, Pb and Zn are not detected in the groundwater samples and F, Cl, $NO_2$, $NO_3$ and $SO_4$ concentrations in groundwater samples are lower than drinking water standards. However, the pH of groundwater sample in site D is 5.58 which is not suitable for the drinking water. With the electric resistivity method, the water-containg layers are found in contaminated soils and the resistivity values are considerably low because of the dispersion of plume by the leak of leachates. According to the results from the magnetic survey method, the anomalous values of the total geomagnetic fields and their gradients are found in the sampling site of low resistivity and high trace element concentrations.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.5
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• pp.9-15
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• 2000

The 3 ${\mu}{\textrm}{m}$-thick PVDF (polyvinylidene fluoride) thin film have been prepared using physical vapor deposition with electric field, and its FT-IR spectrum, dielectric property and electric conduction phenomenon have been investigated. Since the characteristic peaks are detected at 509.45 ［$cm^{-1}$ /］ and 1273.6 ［$cm^{-1}$ /］in the FT-IR spectrum, we are confirmed that the $\beta$ -phase is dominant in the PVDF thin film. In the results of dielectric properties, the PVDF thin film shows anomalous dispersion, i.e. gradual decrease of dielectric constant with increase of frequency, and also that the dielectric absorption point changes from 200 Hz to 7000 Hz with increasing temperature of thin film, which is consistent with the Debye's theory. The activation energy ( $\Delta$H) obtained from temperature dependence of dielectric loss is 21.64 ㎉/mole. We confirm that the electric conduction mechanism of PVDF thin film is dominated by ionic conduction by investigating the dependence of the leakage current of the thin film on the temperature and the electric field.