• Journal of the Korean institute of surface engineering
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• v.39 no.5
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• pp.229-234
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• 2006

Diamonds have been widely employed as polishing media for precise machining and noble substrates for microelectronics. The recent development of the split sphere press has led to the enhancement of low quality natural diamonds. Synthesized and treated diamonds are sometimes traded deceptively as high quality natural diamonds because it is hard to distinguish among these diamonds with conventional gemological characterization method. Therefore, we need to develop a new identification method that is non-destructive, fast, and inexpensive. We proposed using new methods of UV fluorescence and X-ray Lang topography for checking the local HPHT stress field to distinguish these diamonds from natural ones. We observe unique differences in the local stress field images in treated diamonds using UV fluorescence and Lang topography characterization. Our result implies that our proposed methods may be appropriate for identification of the treated diamonds.

• Journal of Wetlands Research
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• v.24 no.1
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• pp.25-37
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• 2022

Climate change is becoming increasingly unpredictable. This has led to changes in various systems such as ecosystems, human life and hydrological cycles. In particular, the recent unpredictable climate change frequently causes extreme droughts and torrential rains, resulting in complex water resources disasters that cause water pollution due to inundation and retirement rather than primary disasters. SWAT was used as a watershed model to analyze future runoff and pollutant loads. The climate scenario analyzed the RCP4.5 climate scenario of the Meteorological Agency standard scenario (HadGEM3-RA) using the normal quantitative mapping method. Runoff and pollutant load analysis were performed by linkage simulation of climate scenario and watershed model. Finally, the results of application and verification of linkage model and analysis of future water quality change due to climate change were presented. In this study, we simulated climate change scenarios using artificial neural networks, analyzed changes in water temperature and turbidity, and compared the results of dams with artificial neural network results through W2 model, a reservoir water quality model. The results of this study suggest the possibility of applying the nonlinearity and simplicity of neural network model to Hapcheon dam water quality prediction using climate change.

• The Research Journal of the Costume Culture
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• v.20 no.5
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• pp.766-774
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• 2012

Ancient Chinese philosophy has had a profound influence on Chinese clothing culture. The researchers reviewed five ancient Chinese philosophical thoughts on Chinese clothing culture. The results show that they had different view of point. The Confucianism advocated "being elegant and refined in manner". Dong Zhongshu believed "Interaction between heaven and mankind is the center of Dress rules". Mohist insisted "Clothing should meet warm first, and then seek for beauty ". Taoism believed "Although a gentleman wears coarse clothes, he has gem in his chest". Legalism believed "Clothing should focus on quality rather than decoration". These philosophy thoughts all have had a profound influence on Chinese clothing culture.

• Journal of the Mineralogical Society of Korea
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• v.10 no.1
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• pp.50-59
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• 1997

the crystal structure of pale green gem-quality olivine from Bisbee mine,Arizona, (Mg1.83Fe0.18)Si0.99O4, a=4.7608(4)$\AA$, c=5.9903(6)$\AA$, c=5.9903(4)$\AA$, V=291.49(1)$\AA$, Pbnm, Z=4 has been refined by both single-crystal and Rietveld methods to R(%) indices of 2.20 and 9.07, respectively. Comparison of site occupancies, cell dimensions, atomic coordinations, and interatomic distances/angles obtained from both methods shows that the Rietveld method produces more accurate site scattering values, cell dimension, and atomic positions than the single-crystal method. This indicates that the Rietveld method is a useful technique for the structural characterization and crystal-chemical study of powdered samples of natural minerals and synthetic materials.

• Economic and Environmental Geology
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• v.47 no.6
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• pp.563-569
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• 2014

Ruby is one of the most favor colored gem, for beautiful red tone, be high in scarcity value. However, rubies with high quality are produced in restricted regions, such as in Thailand, Sri Lanka, Myanmar, and Tanzania etc., and they have been gradually exhausted by mining for a long period. Therefore, improving qualities of low level rubies with various treatments is arising an alternative way to obtain better rubies. Gemological and mineralogical properties of the natural ruby from Tanzanian were studied with heat treatments. Those characteristics were compared between only heat and adding flux materials under heating. Tanzanian raw rubies were applied a heat treatment ($1,600^{\circ}C$ for 6 hours). However, chromameter and UV-Vis analyses found that a simple heat treatment is inappropriated for the Tanzanian ruby. Although $Cr^{3+}$ containing for red color in the ruby increased with heat treatment, the ruby displays dark medium red because of Fe in the ruby as a form of $Fe_2O_3$. The low transparency after heat treatment is attributed to the recrystallization of $SiO_2$ which has a low melting point. Chromameter confirmed adding Pb-containing flux under heating greatly improves the clarity and color of Tanzanian rubies with micro-fractures and cavities on the surface. EMPA results show that Pb as an additive fills the cavities and cracks on raw Tanzanian rubies during the heat treatment. As a rewult of it, the quality of the Tanzanian ruby raw dramatically improved. These results indicate that the heat treatment with an additive (Pb in this study) is an effective way to obtain better quality of the Tanzanian ruby. Consequently, this study suggests a suitable method to improve the properties of the Tanzanina ruby. The result of this study would provide useful information to upgrade the qualities of similar gem stones such as corundum and sapphire.

• Journal of the Mineralogical Society of Korea
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• v.14 no.2
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• pp.99-110
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• 2001

A gem-quality yttria-stabilized zirconium oxide crystals were synthesized by the skull-melting method, using the RF electrical apparatus. Principal raw materials used were $ZrO_2$and 25 wt.% $Y_2O_3$as stabilizer and 0.03~0.05 wt.% $Nd_2O_3$decolorizing agent were added to it. The single crystals were approximately 20$\times$63 mm in size with chemical composition $Zr_{0.73}$ $Y_{0.27}$ $O_{1.87}$ . The crystals are isotropic with no appreciable anisotropism under a polarizing microscope. Their refractive indices are in the range of 2.15~2.18, specific gravity 5.85, Mohs' hardness 8~8.5, and reflectivity 13.47%. The zirconia crystals were confirmed to have cubic structure with Face-centered lattice(Z=4), space group Fm3m ($CaF_2$-type structure) and unit cell parameters are a=5.157 $\AA$. The optimal growing conditions for yttria-stabilized zirconia are 50 kW, 2.94 MHz in power and to use a crucible with 105 mm $\times$ 135 mm in size. When the lowering speed of the crucible was set 16mm/hr gave the best yield, 42%. Since the refractive index(2.15~2.18) of cubic zirconia is smaller than that of diamond, the angle between crown and pavilion should be fashioned to make it smaller than $40.5^{\circ}$ to show the maximum brilliancy and fire.

• Journal of Korea Water Resources Association
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• v.51 no.10
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• pp.863-874
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• 2018

The purpose of this study is to evaluate the future climate change impact on stream aquatic ecology health of Han River watershed ($34,148km^2$) using SWAT (Soil and Water Assessment Tool) and random forest. The 8 years (2008~2015) spring (April to June) Aquatic ecology Health Indices (AHI) such as Trophic Diatom Index (TDI), Benthic Macroinvertebrate Index (BMI) and Fish Assessment Index (FAI) scored (0~100) and graded (A~E) by NIER (National Institute of Environmental Research) were used. The 8 years NIER indices with the water quality (T-N, $NH_4$, $NO_3$, T-P, $PO_4$) showed that the deviation of AHI score is large when the concentration of water quality is low, and AHI score had negative correlation when the concentration is high. By using random forest, one of the Machine Learning techniques for classification analysis, the classification results for the 3 indices grade showed that all of precision, recall, and f1-score were above 0.81. The future SWAT hydrology and water quality results under HadGEM3-RA RCP 4.5 and 8.5 scenarios of Korea Meteorological Administration (KMA) showed that the future nitrogen-related water quality in watershed average increased up to 43.2% by the baseflow increase effect and the phosphorus-related water quality decreased up to 18.9% by the surface runoff decrease effect. The future FAI and BMI showed a little better Index grade while the future TDI showed a little worse index grade. We can infer that the future TDI is more sensitive to nitrogen-related water quality and the future FAI and BMI are responded to phosphorus-related water quality.

• Journal of The Korean Society of Agricultural Engineers
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• v.59 no.3
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• pp.41-50
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• 2017

The purpose of this study were to evaluate the effect of best management practices (BMPs) of Haean highland agricultural catchment ($62.8km^2$) under future climate change using SWAT (Soil and Water Assessment Tool). Before future evaluation, the SWAT was setup using 3 years (2009~2011) of observed daily streamflow, suspended solid (SS), total nitrogen (T-N), and total phosphorus (T-P) data at three locations of the catchment. The SWAT was calibrated with average 0.74 Nash and Sutcliffe model efficiency for streamflow, and 0.78, 0.63, and 0.79 determination coefficient ($R^2$) for SS, T-N, and T-P respectively. Under the HadGEM-RA RCP (Representative Concentration Pathway) 4.5 and 8.5 scenarios, the future precipitation and maximum temperature showed maximum increases of 8.3 % and $4.2^{\circ}C$ respectively based on the baseline (1981~2005). The future 2040s and 2080s hydrological components of evapotranspiration, soil moisture, and streamflow showed changes of +3.2~+17.2 %, -0.1~-0.7 %, and -9.1~+8.1 % respectively. The future stream water quality of suspended solid (SS), total nitrogen (T-N), and total phosphorus (T-P) showed changes of -5.8~+29.0 %, -4.5~+2.3 %, and +3.7~+17.4 % respectively. The future SS showed wide range according to streamflow from minus to plus range. We can infer that this was from the increase of long-term rainfall variability in 2040s less rainfalls and 2080s much rainfalls. However, the results showed that the T-P was the future target to manage stream water quality even in 2040s period.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.6
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• pp.272-276
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• 2007

The various colored cubic zirconia single crystals for jewelry were grown by skull melting method of excellent productivity. The cubic zirconia is similar to the character of diamond, which has high refractive index, large dispersion and high hardness. It is possible that the development of new colored cubic zirconia by doping 3d-transition elements or 4f-rare earth elements. The colored cubic zirconia is representative of synthetic gemstone which was grown up by mixing one or over two materials among $Pr_6O_{11},\;TiO_2,\;MnO_2\;and\;Er_2O_3$ as coloring agent. Subsequent heat treatment improves the quality of color and uniformity. This study is aimed the color reappearance of cubic zirconia such as natural peridot, smoky-quartz and red-tourmaline.

• Journal of the Korean earth science society
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• v.23 no.1
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• pp.52-58
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• 2002

A colorless and transparent zirconium oxide ($Zr_{0.73}Y_{0.27}O_{1.87}$) crystal has been synthesized by the Bridgman-Stockbager method. The gem-quality material is produced by adding 20${\sim}$25 wt.% $Y_2O_3$ (stabilizer) and 0.04 wt.% $Nd_2O_3$ (decolorising agent) to the $ZrO_2$ powder. It shows a vitreous luster with a slight oily appearance. Under a polarizing microscope, it shows isotropic nature with no appreciable anisotropism. Mohs hardness value and specific gravity is measured to be 8${\sim}$$8{\frac{1}{2}}$ and 5.85, respectively. Under ultraviolet light it shows a faint white glow. The crystal structure of yttria-stabilized zirconia with 0.27 at.% Y has been re-investigated, using single crystal X-ray diffraction, and confirmed to be a cubic symmetry, space group $Fm{\overline{3}}m$ ($O^5_h$) with a=5.1552(5) ${{\AA}}$, V=136.99(5) ${{\AA}}^3$, Z=4. The stabilizer atoms randomly occupy the zirconium sites and there are displacements of oxygen atoms with amplitudes of ${\Delta}/a{\sim}$0.033 and 0.11 along <110> and <111> from the ideal positions of the fluorite structure, respectively.