• Geomechanics and Engineering
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• v.33 no.2
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• pp.133-140
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• 2023

Soil erosion can cause scouring and failures of underwater structures, therefore, various soil improvement techniques are used to increase the soil erosion resistance. The microbially induced calcium carbonate precipitation (MICP) method is proposed to increase the erosion resistance, however, there are only limited experimental and numerical studies on the use of MICP treatment for improvement of surface erosion resistance. Therefore, this study investigates the improvement in surface erosion resistance of sands by MICP through laboratory experiments and numerical modeling. The surface erosion behaviors of coarse sands with various calcium carbonate contents were first investigated via the erosion function apparatus (EFA). The test results showed that MICP treatment increased the overall erosion resistance, and the contribution of the precipitated calcium carbonate to the erosion resistance and critical shear stress was quantified in relation to the calcium carbonate contents. Further, these surface erosion processes occurring in the EFA test were simulated through the coupled computational fluid dynamics (CFD) and discrete element method (DEM) with the cohesion bonding model to reflect the mineral precipitation effect. The simulation results were compared with the experimental results, and the developed CFD-DEM model with the cohesion bonding model well predicted the critical shear stress of MICP-treated sand. This work demonstrates that the MICP treatment is effective in improving soil erosion resistance, and the coupled CFD-DEM with a bonding model is a useful and promising tool to analyze the soil erosion behavior for MICP-treated sand at a particle scale.

• Geomechanics and Engineering
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• v.37 no.6
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• pp.577-590
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• 2024

With increasing demand for nuclear power generation, nuclear structures are being planned and constructed worldwide. A grave safety concern is that these structures are sensitive to large-magnitude shaking, e.g., during earthquakes. Seismic response analysis, which requires P- and S-wave velocities, is a key element in nuclear structure design. Accordingly, it is important to determine the P- and S-wave velocities in the Gyeongju and Pohang regions of South Korea, which are home to nuclear power plants and have a history of seismic activity. P- and S-wave velocities can be obtained indirectly through a correlation with physical properties (e.g., N values, Young's modulus, and uniaxial compressive strength), and researchers worldwide have proposed regression equations. However, the Gyeongju and Pohang regions of Korea have not been considered in previous studies. Therefore, a database was constructed for these regions. The database includes physical properties such as N values and P- and S-wave velocities of the soil layer, as well as the uniaxial compressive strength, Young's modulus, and P- and S-wave velocities of the bedrock layer. Using the constructed database, the geological characteristics and distribution of physical properties of the study region were analyzed. Furthermore, models for predicting P- and S-wave velocities were developed for soil and bedrock layers in the Gyeongju and Pohang regions. In particular, the model for predicting the S-wave velocity for the soil layers was compared with models from previous studies, and the results indicated its effectiveness in predicting the S-wave velocity for the soil layers in the Gyeongju and Pohang regions using the N values. The proposed models for predicting P- and S-wave velocities will contribute to predicting the damage caused by earthquakes.

• Economic and Environmental Geology
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• v.34 no.6
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• pp.617-625
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• 2001

The Skaergaard intrusion is widely considered a type example of a strongly fractionated, layered intrusion that has undergone extensive in situ igneous differentiation. The Intrusion, therefore, should be a good locality for modeling trace element vriation in a closed system. Previous studios (Haskin and Haskin, 1968; Faster et al., 1974), however, have suggested thats the rare earth elements in whole rocks and mineeral separates from the Intrusion did not fellow the expected trend for closed system crystatllization. Trace element modeling using published distribution coefficients, modal abundances of the coexisting minerals, and the concentration of trace elements In whole rocks and mineral separates from the Skaergaard Intrusion, reveals that the rare earth elements were significantly Influenced by the crystallization of abundant apatite in the Layered Series suring the final stages of crystallization. The results of trace element modeling also suggcsts that apatite, which appears sporadically in the UBS, is not a primary liquidus phase in these samples as previously suggested (Naslund, 1984) but an interstitial phase that (lid not directly effect trace element abundances In the evolving magma As the Skaergaard magma coaled convection, or convected as small Isolated cells during the final stages of differentiation, an elebated $P_{H2O}$ Induced by accumulation of volatile elements near the roof of the magma chamber ingibited or delayed the precipitation of primary apatite in the UBS If the Skaergaard differentiation Is modeler assuming primary apatite crystallization In the upper par of the LS where abundant modal apatite is present, and only late stage crystallization of apatite In the UBS where apatite Is less abundant, rare earth elements abundances follow a closed system variation trend. These results rule but any differentiation model for the Skaergaard Intrusion that Includesvolumetrically significant injections or discharges of magma Into or out of the chamber during the final 20% of the crystallization history.

• Journal of the Mineralogical Society of Korea
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• v.26 no.4
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• pp.245-262
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• 2013

We analyzed 29 surface sediment samples in five submarine volcanoes (TA12, TA19, TA22, TA25, and TA26) located in the southern part of the Tonga arc for trace elements and rare earth elements to investigate characteristics of the hydrothermal alteration of surface sediments. Based on analytical results of trace element and rare earth element (REE), surface sediments of TA12, TA19, and TA22 submarine volcanoes, which are located in the northern part of the study area, were very little or not influenced by hydrothermal fluids. In contrast, some stations of TA25 and TA26 submarine volcanoes were strongly affected by hydrothermal fluids. However, these two submarine volcanoes showed different features in element concentration in the sediments. Some stations of TA25 submarine volcano showed enrichment of Ni, Cu, Sn, Zn, Pb, Cr, Cd, Sb, W, Ba, Ta, Rb, Sr, and As, however, those of TA26 submarine volcano showed enrichment of Sn, Zn, Pb, Cd, Sb, Ba, Rb, and Sr. Stations which enriched trace elements were observed, enriched REEs were also observed. Average upper continental crust (UCC)-normalized REE patterns of the surface sediments generally showed low light REE (LREE) abundances and increased heavy REE (HREE) abundances. Eu enrichment was identified at several stations of TA25 and TA26 submarine volcanoes. In addition, enrichment of Ce was found at some stations of TA26 submarine volcano and these enrichment patterns were similar with hydrothermal fluid of near stations. Furthermore, TA25 and TA26 submarine volcanoes showed different enrichment characteristics of trace elements and REE. Trace elements were concentrated at TA25 submarine volcano. TA26 submarine volcano, on the other hand, observed highly enrichment of REE especially, Eu and Ce. As a result of the investigation, the characteristics and concentrations of REEs and trace elements in the surface sediments of each submarine volcano can be applied to identify hydrothermal alteration of sediments during exploration for hydrothermal deposits.

• The Journal of the Petrological Society of Korea
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• v.19 no.3
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• pp.209-225
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• 2010

The Shinri area near the Yedang Lake, the eastern part of the Hongseong area in SW Gyeonggi Massif, consists of the Neoproterozoic Duckjeongri granodiorite-tonalite, mylonitized amphibole-bearing orthogneiss and impure marble with lens-shaped garnet-bearing metabasites. In this paper, we report mineralogical and geochemical data of Neoproterozoic lens-shaped garnet-bearing metabasites within marble of the Shinri area. The $SiO_2$ contents of garnet-bearing metabasites in marble vary between ~46.98 and 51.17 wt%, and the $Na_2O$ + $K_2O$ contents fall between ~1.95 and 2.85 wt%, similar to the tholeiitic sub-alkaline basaltic rocks. In the Zr/Y vs. Zr diagram, garnet-bearing metabasites also plot in the subalkaline basaltic rocks. The chondrite-normalized REE patterns for Shinri garnet-bearing metabasites show relatively flat patterns to that of chondrite. They show slight LREE-enriched and depleted patterns. The major and trace element data from lens-shaped garnet-bearing metabasites in marble of the Shinri area suggest that these rocks were formed in within plate. In contrast, previous major and trace element data of high pressure type garnet-bearing metabasites from the mafic-ultramafic complex in the Baekdong and Bibong areas suggest that these rocks were formed in a nascent arc to backarc spreading center within subduction zone setting. Based on mineral assemblage and mineral chemistry, P-T estimates for Shinri garnet-bearing metabasites are 9.6-12.7 kb, $695-840^{\circ}C$ for inclusions in the core, and 9.6-13.6 kb, $630-755^{\circ}C$ for those in the rim. These P-T estimates are distinct from those of the Baekdong and Bibong garnet-bearing metabasites with isothermal decompressional retrograde P-T path. In addition to Triassic tectonic activity previously reported in the Shinri area of Hongseong, the details of metamorphic history such as protolith age and Neo-Proterozoic metamorphic episode need to be solved.

• Korean journal of food and cookery science
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• v.32 no.5
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• pp.656-663
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• 2016

Purpose: This study was aimed to compare the nutritional content of the life stages of Tenebrio molitor. Methods: Nutritional element analysis comprised 12 minerals, 18 amino acids, 4 vitamins, and 12 fatty acids in larval, pupal, and adult stages. Nutritional element content was expressed as a percentage of 100 g of sample and determined in raw and freeze-dried samples to assess the food value of the insect. Results: Moisture, crude protein, and crude fat contents in raw samples were 63.5%, 23.19%, and 3.96%, respectively. Moisture content was significantly higher in the adult stage than in larval and pupal stages, whereas crude fat and crude ash contents were lower. Mineral composition of the mealworm showed K, P, and Mg in decreasing order of content, with no differences among life stages. Total amino acid content increased from adult, pupal to larval stages, in order with each stage's growth, without difference in amino acid composition. Seventy-six to 78% of total fatty acid corresponded to unsaturated fatty acids, with oleic acid as the most abundant. In addition, fatty acid content was high in the adult stage, and clear differences were observed between life stages. Finally, vitamins B1 and B3 showed similar content between life stages, whereas vitamin B2 showed a higher content the adult than larval and pupal stages. A higher folate content was observed in pupal and adult stages than in the larval stage. Although freeze-dried samples showed a higher nutritional content than raw samples, both samples were similar in composition and content between life stages, suggesting the suitability of freeze-dried samples for use as food materials. Conclusion: These results may provide a basis for more diversified industrial applications of the Tenebrio molitor.

• The Journal of Engineering Geology
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• v.22 no.2
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• pp.173-183
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• 2012

The nature of surface deformation of Tono granite was investigated using a confocal laser scanning microscope (CLSM) under water-saturated stress relaxation conditions. A new apparatus was developed for this experiment, enabling continuous measurements of stress-strain and simultaneous observations of surface deformation by CLSM. The amounts of grain contact deformation and intra-granular surface deformation were calculated using a finite element method. The results reveal that intense grain contact deformation and intra-granular surface deformation occurred during the period of stress relaxation, and that the intensity of this deformation increased with increasing applied stress. Finite element method (FEM) results show that the strain of grain boundary was greater than strain of inter-granular surface. Contour maps of these local strains were compiled for individual grains and their boundaries, revealing intense deformation at the boundaries between biotite and quartz under compressional stress. This result was a consequence of the mechano-chemical effect of biotite and quartz minerals. Biotite in granite has a layered structure of iron-magnesium-aluminum silicate sheets that are weakly bonded together by layers of potassium ions. In contrast, quartz occurs as stable spherical grains.

• Geophysics and Geophysical Exploration
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• v.11 no.2
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• pp.85-92
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• 2008

Magnetotelluric (MT) methods are widely applied as an effective exploration technique to geothermal surveys. Two-dimensional (2-D) analysis is frequently used to investigate a complicated subsurface structure in a geothermal region. A 2-D finite-element method (FEM) is usually applied to the MT analysis, but we must pay attention to the accuracy of so-called auxiliary fields. Rodi (1976) proposed an algorithm of improving the accuracy of auxiliary fields, and named it as the MOM method. Because it introduces zeros into the diagonal elements of coefficient matrix of the FEM total equation, a pivoting procedure applied to the symmetrical band matrix makes the numerical solution far less efficient. The MOM method was devised mainly for the inversion analysis, in which partial derivatives of both electric and magnetic fields with respect to model parameters are required. In the case of forward modeling, however, we do not have to resort to the MOM method; there is no need of modifying the coefficient matrix, and the auxiliary fields can be elicited from the regular FEM solution. The computational efficiency of the MOM method, however, can be greatly improved through a sophisticated rearrangement of the total equation.

• Resources Recycling
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• v.25 no.6
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• pp.50-57
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• 2016

This work was examined the extraction and stripping behavior of rare earths (La, Ce, Pr, Nd, Sm) from the hydrochloric acid solution by Cyanex 572 and compared to the results that of PC88A. Experimental parameters such as equilibrium pH, extractant & strip reagent concentration were observed and extraction percentage, distribution coefficient, stripping percentage and the separation factor of the adjacent element were analyzed. The $pH_{50}$ values was more higher using Cyanex 572 than that of PC88A. As the increase of the extractant concentration, the distribution coefficient of rare earth elements was increased. Stripping percentage of rare earth elementss from the Cyanex 572 was 85% to 95% and PC88A showed 80% to 87%. Separation factor of Ce/La, Ce/Pr, Pr/Nd, Nd/Sm was enhanced about 1.0-5.0 using Cyanex 572 as an extractant in mixture solution.

• The Journal of the Petrological Society of Korea
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• v.3 no.1
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• pp.76-93
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• 1994

The Precambrian Hongjesa granite is lithologically zoned from biotite granite in central part to biotite-muscovite granite towards the margin. The X_{Fe}$ (=Fe/(Fe+Mg)) value and the aluminum saturation index of biotite systematically vary as a function of mineral assemblage, and are positively related with those of bulk rock. This relationship as well as the lithological zoning are attributed to the fractional crystallization of the Hongjesa granitic magma. The trace element data corroborate that biotite-muscovite granite is more fractionated than biotite granite. The evolution of the Hongjesa granite is elucidated by using the AFM liquidus topology, where A=$Al_2O_3-CaO-Na_2O-K_2O$; F=FeO+MnO; and M=MgO. At an early magmatic stage where biotite is the only ferromagnesian mineral to crystallize, the X_{Fe}$ value and the alumina content of granitic magma continuously increase.. Muscovite subsequently crystallizes with biotite along the biotitemuscovite cotectic curve where biotite-muscovite granite forms. Local enrichments in Mn and B further crystallize garnet and tourmaline, respectively. The unique zonal pattern characterized by the occurrence of the evolved biotite-muscovite granite at the margin may be accounted for by the passive stoping during the emplacement of the Hongjesa granite. This emplacement may have occurred in continental collision environment, according to the tectonic discrimination diagram using major element chemistry.