• 한국지구물리탐사학회:학술대회논문집
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• 2008.10a
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• pp.125-130
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• 2008

Electrical resistivity and seismic refraction surveys were conducted to investigate geologic structures and geotechnical characteristics of the subsurface in Dok-do island, along with rock physical properties. The resistivity results in Seo-do island show that the fault adjacent to the fisherman's shelter is a normal fault and extended towards the NW direction. Bedded Rapilli Tuff in the downstream was more severely influenced in depth by weathering and erosion than Trachy Andesite II in the upstream area. The physical properties of the rocks illustrate that Trachyte and Trachy Andesite are hardest, Massive Tuff Breccia is next, and Tuffs are the most soft rocks in Dok-do island.

• The Journal of the Acoustical Society of Korea
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• v.15 no.1
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• pp.71-80
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• 1996

Characteristics of sleeve-gun arrays installed on the R/V Onnuri were analyzed and compared with survey data. In the case of cluster array, the beam width in the frequency range up to 814Hz is constant as $179.5^{\circ}$, and rapidly narrows in the frequency range of 814-1631Hz. However, in the case of long and wide arrays, as the frequency increases, the beamwidth decreases. The optimal frequency is 69Hz. the main lobe of vertical inclination has its maximum amplitude at phase angle $0^{\circ}$. The optimal frequency of cluster array which produces little side lobe is less than 1631Hz, and those of long and wide arrays are less than 108Hz. As a result, the cluster array produces a good source for high-resolution seismic survey, while the long and wide arrays are suitable for the survey of deep structures. The final high-resolution seismic section with cluster array was compared with that of long and wide arrays.

• Geophysics and Geophysical Exploration
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• v.10 no.4
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• pp.345-352
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• 2007

Two-dimensional (2D) MT surveys near the Century mine in Australia have been performed with very far remote reference in Esashi, Japan (RR_ESS) as well as Gregory Downs (RR_GREG), which are roughly 6,400 km and 80 km apart from the survey area, respectively. Good quality of MT data could be obtained by remote reference processing with RR_GREG, while the coherency of magnetic fields between field sites and RR_ESS was not sufficient to be used as remote data. Both 2D and 3D inversion of 2D profile data represented the general geological structure beneath the survey area. The main target of the survey, Termite Range Fault, appeared as a boundary between a conductive block to the north and a resistive block to the south in the reconstructed resistivity section, and is inclined slightly to the north-east direction.

• Korean Journal of Clinical Laboratory Science
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• v.51 no.2
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• pp.265-269
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• 2019

Ebstein's anomaly is attached to the right ventricle with the tricuspid leaf attached to the lower right ventricle without any attachment to the tricuspid annulus. Most patients in their 20s are alive. Patients older than 25 years of age are similar in the incidence of heart failure and sudden death, and survive approximately 70% from 2 years, and 50% from 3 years, from 5% to over 50 years of age. Through this example, Ebstein's anomaly exists in various forms. A 22 year old case with WPW syndrome and those who survived to 77 years of age are reported. The normal heart structure in the apical four-chamber view should be observed on similar lines, even though the tricuspid annulus is slightly lower than the mitral annulus. If not, there will be some doubt regarding this anomaly. Furthermore, echocardiography plays an important role in the diagnosis and prognosis of congenital heart disease.

• Korean Journal of Materials Research
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• v.33 no.12
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• pp.558-564
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• 2023

In this study, we designed and manufactured a large angular contact ball bearing (LACBB) with low deformation using JIS-SUJ2 steel and analyzed changes in its structural characteristics and chemical composition upon heat treatment. The bearing was produced by hot forging and heat treatment including a quenching and tempering (Q/T) process, and its properties were analyzed using 4 mm thick specimens. A difference in the size distribution of the carbide in the outer and inner parts of the bearing was observed and it was confirmed that large and non-uniform carbide was distributed in the inner part of the bearing. After heat treatment, the hardness value of the outer part increased from 13.4 HRC to 61 HRC and the inner part increased from 8.0 HRC to 59.7 HRC. As a result of X-ray diffraction (XRD) measurements, the volume fraction of the retained austenite contained in the outer part was calculated to be 3.5~4.8 % and the inner part was calculated to be 3.6~5.0 %. The surface chemical composition and the content of chemical bonds were quantified through X-ray photoelectron spectroscopy (XPS), and a decrease in C=C bonds and an increase in Fe-C bonds were confirmed.

• The Journal of the Petrological Society of Korea
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• v.11 no.3_4
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• pp.259-270
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• 2002

A small granodiorite-quartz monzonitic stock containing sericitic and propylitic alteration assemblages hosts a Cu-W breccia-pipe deposit in the southeastern Cyeongsang basin. The mineralized breccia-pipe contains angular to subangular brecciated fragments of granitic rocks showing clast-supported textures. An assemblage of quartz, tourmalines, sulfide minerals (mainly chalcopyrite, arsenopyrite and pyrrhotite) and calcite was precipitated as a hydrothermal cement between the brecciated fragments. A tourmaline aureole surrounds the breccia pipe. Extensive tourmalinization of the granitic rocks near and within the pipe and no tourmalinization in the sedimentary and volcanic rocks. The tourmalines are marked by Fe-rich, black charcoal-like schorl (80 mol% schorl relative) nearer the schorl-dravite solid solution. The chemical changes in the hydrothermal fluid are reflected by variations in compositional Boning from cores to rims. They generally contain cores with low values of Fe/(Fe+Mg) and high values of Na/(Na+ca) relative to rims. This is because of an increase Fe and Ca contents toward rims. The main trend of these variations is a combination of the exchange vectors Ca(Fe, Mg) $(NaAl)_{- }$ $_1$ and $Fe^{3}^{+}$ $Al_{[-10]}$ $_1$ It is thought that boiling causes the loss of $H_2$ into the vapor phase resulting in the oxidation of Fe in the aqueous phase. pH of the melt would be one of important controlling factors for the tourmaline stability. The tourmalines could be precipitated when the system evolved to the acidic hydrothermal regime as most hydrothermal brines and acidic gases exsolved from the magma. The Ilgwang tourmaline crystallization is products of hypogene orthomagmatic hydrothermal processes that were strongly pipe-controlled.

• Economic and Environmental Geology
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• v.34 no.1
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• pp.25-38
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• 2001

Contrasts in the style of the gold-silver mineralization in geologic and tectonic settings in Korea, together with radiometric age data, reflect the genetically different nature of hydrothermal activities, coinciding with the emplacement age and depth of Mesozoic magmatic activities. It represents a clear distinction between the plutonic settings of the Jurassic Daebo orogeny and the subvolcanic environments of the Cretaceous Bulgugsa igneous activities. During the Daebo igneous activities (about 200-130 Ma) coincident with orogenic time, gold mineralization took place between 197 and 127 Ma. The Jurassic deposits commonly show several characteristics: prominent association with pegmatites, low Ag/Au ratios in the ore-concentrating parts, massive vein morphology and a distinctively simple mineralogy including Fe-rich sphalerite, galena, chalcopyrite, Au-rich eIectrum. pyrrhotite and/or pyrite. During the Bulgugsa igneous activities (120-60 Ma), the precious-metal deposits are generally characterized by such features as complex vein morphology, medium to high AgiAu ratios in the ore concentrates, and abundance of ore minerals including base-metal sulfides, Ag sulfides, native silver, Ag sulfosalts and Ag tellurides. Vein morphology, mineralogical, fluid inclusion and stable isotope results indicate the diverse genetic natures of hydrothermal systems. The Jurassic Au-dominant deposits were formed at the relatively high temperature (about 300 to 450$^{\circ}$C) and deep-crustal level (>3.0 kb) from the hydrothermal fluids containing more amounts of magmatic waters (3180; 5-10 %0). It can be explained by the dominant ore-depositing mechanisms as CO2 boiling and sulfidation, suggestive of hypo/mesothermal environments. In contrast, mineralization of the Cretaceous Au-Ag type (108-71 Ma) and Agdominant type (98-71 Ma) occurred at relatively low temperature (about 200 to 350$^{\circ}$C) and shallow-crustal level «1.0 kb) from the ore-fonning fluids containing more amounts of less-evolved meteoric waters (15180; -10-5%0). These characteristics of the Cretaceous precious-metal deposits can be attributed to the complexities in the ore-precipitating mechanisms (mixing, boiling, cooling), suggestive of epilmesothermal environments. Therefore, the differences of the emplacement depth between the Daebo and the Bulgugsa igneous activities directly influence the unique temporal and spatial association of the deposit type.

• Journal of the Mineralogical Society of Korea
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• v.24 no.4
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• pp.301-312
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• 2011

The study on the atomic structure of iron-bearing silicate glasses has significant geological implications for both diverse igneous processes on Earth surface and ultra-low velocity zones at the core-mantle boundary. Here, we report experimental results on the effect of iron content on the atomic structure in iron-bearing alkali silicate glasses ($Na_2O-Fe_2O_3-SiO_2$ glasses, up to 16.07 wt% $Fe_2O_3$) using $^{29}Si$ and $^{17}O$ solid-state NMR spectroscopy. $^{29}Si$ spin-lattice ($T_1$) relaxation time for the glasses decreases with increasing iron content due to an enhanced interaction between nuclear spin and unpaired electron in iron. $^{29}Si$ MAS NMR spectra for the glasses show a decrease in signal intensity and an increase in peak width with increasing iron content. However, the heterogeneous peak broa-dening in $^{29}Si$ MAS NMR spectra suggests the heterogeneous distribution of $Q^n$ species around iron in iron-bearing silicate glasses. While nonbridging oxygen ($Na-O-Si$) and bridging oxygen (Si-O-Si) peaks are partially resolved in $^{17}O$ MAS NMR spectrum for iron-free silicate glass, it is difficult to distinguish the oxygen clusters in iron-bearing silicate glass. The Lorentzian peak shape for $^{29}Si$ and $^{17}O$ MAS NMR spectra may reflect life-time broadening due to spin-electron interaction. These results demonstrate that solid-state NMR can be an effective probe of the detailed structure in iron-bearing silicate glasses.

• Economic and Environmental Geology
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• v.50 no.5
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• pp.375-387
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• 2017

Amphibolite-hosted Fe-Ti mineralization at the Soyeonpyeong Island, located in central western part of the Korean Peninsula is a typical orthomagmatic Fe-Ti oxide deposit in South Korea. The amphibolite intruded into NW-SE trending Precambrian metasedimentary rocks. Lower amphibolite is characterized by igneous layering, consisting of feldspar-dominant and amphibole-Fe-Ti oxide-dominant layers. The igneous layering shows complicated and/or sharp contact. In contrast, upper amphibolite has a more complicated lithofacies (garnet-bearing, coarser, and schistose), and massive Fe-Ti oxide ore alternates with schistose amphibolite. NS- and EW-trending fault systems lead to redistribute upper amphibolite-hosted Fe-Ti orebody and igneous layering of lower amphibolite, respectively. The whole-rock compositions of amphibolite and Fe-Ti oxide ore reflect their constituent minerals. Amphibolite shows significantly positive Eu anomalies whereas Fe-Ti oxide ore has weak negative Eu anomalies. Plagioclase (Andesine to oligoclase) and Fe-Ti oxide minerals have constant composition regardless of their distribution. Amphibole has a compositionally variable but it doesn't reflect the chemical evolution. Mineral compositions within individual layers and successive layers are relatively constant not showing any stratigraphic evolution. This suggests that there are no successive injections of Fe-rich magma or assimilation with Fe-rich country rocks. Contrasting Eu anomalies between amphibolite and Fe-Ti oxide ore also suggest that extensive plagioclase fractionation during early crystallization stage cause increase in $Fe_2O_3/FeO$ ratio and overall Fe contents in the residual magma. Thus, Fe-rich residual liquids may migrate at the upper amphibolite by filter pressing mechanism and then produce sheeted massive Fe-Ti mineralization during late fractional crystallization.

• Journal of the Korea Concrete Institute
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• v.18 no.2 s.92
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• pp.161-168
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• 2006

An experimental investigation was conducted to examine the hysteretic behaviors of ultra-high strength concrete tied columns. The purpose of this study is to investigate the safety of ultra-high strength concrete columns with 100 MPa compressive strength for the requirement of ACI provisions. Eight 1/3 scaled columns were fabricated to simulate an 1/2 story of actual structural members with the cross section $300{\times}300mm$ and the aspect ratio 4. The main variables are axial load ratio, configurations and volumetric ratios of transverse reinforcement. The results show that the deformability of columns are affected by the configurations and volumetric ratios of transverse reinforcement. Especially, it has been found that the behavior of columns are affected by axial load ratio rather than the amounts and the configurations of transverse reinforcement. Consequently, to secure the ductile behavior of 100 MPa ultra-high strength concrete columns, ACI provisions for the requirement of transverse steel may considered axial load level and the details of transverse reinforcement.