• Economic and Environmental Geology
• /
• v.32 no.5
• /
• pp.445-454
• /
• 1999

The Sanjeon Au-Ag deposit consists of three subparallel hydrothermal quartz-calcite veins which filled fault-related fractures (generally $N20^{\circ}$ to 35"W-trending and $70^{\circ}$ to $80^{\circ}$ SW-dipping) within quartz porphyry. The vein mineralization shows an apparent variation of mineral assemblages with paragenetic time: (1) early, white quartz + pyrite + arsenopyrite + brown sphalerite, (2) middle, white (vein) to clear quartz (vug) + base-metal sulfides + electrum + argentite, (3) late, calcite + pyrite + native silver. Mineralogic and fluid inclusion data indicate that gold-silver minerals were deposited at temperatures from 2l $0^{\circ}$ to $250^{\circ}$ with salinities of 4 to 5 wt. % equiv. NaCl and log fS2 values from -14.0 to -12.2 atm. The linear relationship between homogenization temperature and salinity data indicates that gold-silver deposition was a result of meteoric water mixing. Ore mineralization occurred at pressure conditions of about 70 bars, which corresponds to the mineralization depths of about 260 m to 700 m. There is a remarkable decrease of the calculated 1)180 values of water from 1.3 to -9.7%0 in hydrothermal fluid with increasing paragenetic time. This indicates a progressive increase of meteoric water influx in the hydrothermal system at the Sanjeon deposit. Oxygen-hydrogen, sulfur, and carbon isotope values of hydrothermal fluids indicate that the ore mineralization was formed largely from meteoric waters with the contribution of sulfur and carbon from a deep igneous source.

• Journal of the Korean Geographical Society
• /
• v.46 no.4
• /
• pp.396-412
• /
• 2011

Multi-proxy analysis was used to produce a high-resolution paleoclimatic record from a thick section of the Holocene alluvial fan deposit in Gatap-ri, Buyeo. According to ${\delta}^{13}C$ analyses, five minor climate fluctuations can be determined. From the stage I to stage VI, climate changes are as follows: cool-dry, warm-humid, cool-dry, warm humid, drier than stage IV, and finally more humid environment than stage V. According to magnetic susceptibility records, four different stages can be identified, among which stage ii shows the highest susceptibility. Stage-i deposit is derived from sediments of back marsh-type wetland. Stage-ii and stage-iii deposits, however, show higher magnetic susceptibility because magnetite-enriched soil from weathered upland was transported to the area to form an alluvial fan deposits. Stage-iv deposit is comparable to the modern plow horizon.

• Journal of the korean society of oceanography
• /
• v.36 no.4
• /
• pp.109-123
• /
• 2001

The importance of phytoplankton, benthic vegetation, vascular marsh plants (primarly Phragmites communis and Salix gracilstyla) and riverine particulates inputs to the coastal bay food web was studied in Kwangyang Bay, Korea using stable carbon isotope ratios. Vascular marsh plants (${\delta}^{13}$C=-27.4${\pm}$0.8%o) and riverine particulates (-26.0${\pm}$0.8%o) were isotopically distinct from phytoplankton (-20.7${\pm}$0.8%o), microphytobenthos (-14.2${\pm}$0.6%o) and seagrass (8.8%o). The ${\delta}^{13}$C values of consumers in the study site ranged from -20.2 to -11.3olo suggesting the assimilation of carbon derived from both phytoplankton and benthic vegetation (including algae and seagrass), The relative importance of both pelagic and benthic origins of food sources was likely to vary depending on feeding habit of the consumers. The isotopic difference between pelagic and benthic consumers indicated that plankton-derived carbon was used mostly by pelagic consumers, but the carbon derived from intertidal benthic vegetation was incorporated into food webs through benthic consumers. The ${\delta}^{13}$C values of consumers in the present study differed noticeably from published values of the phytoplankton-based ecosystem, particularly in the $^{13}$C enrichment of benthic grazers, deposit-feeders and demersal feeders of fishes. This tendency of the $^{13}$C enrichment was also found in suspension-feeding bivalves. Taking the biomasses of benthic vegetation into consideration, benthic microalgae was likely to account for the consumer $^{13}$C enrichment. Role of terrestrially derived riverine carbon was limited to the riverine system and was not evident within the bay systems. Phragmites, despite their important biomass, appeared to be of little importance as consumer diet.

• Journal of the Korean institute of surface engineering
• /
• v.36 no.1
• /
• pp.27-33
• /
• 2003

Pulsed magnetron sputtering of graphite target was employed for deposition of diamond-like carbon (DLC) films. Time-resolved probe measurements of magnetron discharge plasma have been performed. It was shown that the pulsed magnetron discharge plasma density ($∼10^{17}$ $m^{-3}$ ) is close to that of vacuum arc cathode sputtering of graphite. Raman spectroscopy was sed to examine DLC films produced at low ( $U_{sub}$ / < 1 kV) pulsed bias voltages applied to the substrate. It has been shown that maximum content of diamond-like carbon in the coating (50-60%) is achieved at energy per deposited carbon atom of $E_{c}$ =100 eV. In spite of rather high percentage of $sp^3$-bonded carbon atoms and good scratch-resistance, the films showed poor adhesion because of absence of ion mixing between the film and the substrates. Electric breakdowns occurring during the deposition of the insulating DLC film also thought to decrease its adhesion.

• Journal of the Korean institute of surface engineering
• /
• v.43 no.2
• /
• pp.105-110
• /
• 2010

Electroless nickel plating on porous carbon substrate for the application of MCFC electrodes was investigated. Acidic and alkaline bath were used for the electroless nickel plating. The pore sizes of carbon substrates were 16-20 ${\mu}m$ and over 20 ${\mu}m$. The carbon surface was changed from hydrophobic to hydrophilic after immersing the substrate in an ammonia solution for 40 min at $60^{\circ}C$. The contact angle of water was decreased from $85^{\circ}C$ to less than $20^{\circ}$ after ammonia pretreatment. The deposition rate in the alkaline bath was higher than that in the acidic bath. The deposition rate was increased with increasing pH in both acidic and alkaline bath. The content of phosphorous in nickel deposit was decreased with increasing pH in both acidic and alkaline bath. The contents of phosphorous is low in alkaline bath. The minimum concentration of $PdCl_2$ for the electroless nickel plating was 10 ppm in alkaline bath and 5 ppm in acidic bath. The thickness of nickel was not affected by the concentration of $PdCl_2$.

• Journal of the Mineralogical Society of Korea
• /
• v.19 no.4 s.50
• /
• pp.337-346
• /
• 2006

The Jinwon Pb-Zn deposit is located within the Precambrian Youngnam Massif. Ore mineralization at the Jinwon deposit occurred in quartz veins that filled fractures in the Hongjesa granite. Mineral paragenesis can be divided into two stages(stage I and II). Stage I, at which the precipitation of major ore minerals occurred, is further divided into two substages with paragenetic time based on minor fractures and discernible mineral assemblages: substage la is characterized by pyrite, arsenopyrite ($28.4{\sim}30.3$ atomic % As), pyrrhotite, magnetite, chalcopyrite, sphalerite ($13.1{\sim}16.0$ mole % FeS) assemblages; substage $I_a$ is represented by main precipitation of Zn, Pb minerals and is characterized by sphalerite ($15.1{\sim}19.0$ mole % FeS), galena, miargyrite, argentile assemblages. Stage II is economically barren quartz veins. Thermodynamics study is used to estimate changes in chemical conditions of the hydrothermal fluids during stage I mineralization, the main ore deposition period at the Jinwon hydrothermal system. The range of estimated sulfur fugacity ($fs_2$) was from $10^{-7}\;to\;10^{-16}$ atm and oxygen fugacity ($fo_2$) was in the range of $10^{-32.8}{\sim}10^{-38.5} atm$. Carbon dioxide fugacity ($fco_2$) was $<10^{-0.6} atm$.

• Journal of the Mineralogical Society of Korea
• /
• v.28 no.2
• /
• pp.83-93
• /
• 2015

This study investigated genetic, mineralogical and spectral characteristics of oil shale and coal samples in Dundgobi area, Mongolia. Based the Rock/Eval and Total organic carbon (TOC) analysis, kerogen type, hydrogen quantity, thermal maturity and depositional environment were confirmed. Moreover, the mineral composition of oil shale and coal samples were analyzed by XRD and spectroscopy. The result of Rock Eval/TOC analysis revealed that the samples of Eedemt deposit are immature to mature source rocks with sufficient hydrocarbon potential, and the kerogen types were classified as Type I, Type II and Type III kerogen. On the other hand, the samples from Shine Us Khudag deposit were mature with good to very good hydrocarbon potential rocks where kengen types are defined as Type I, Type II/III and Type III kerogen. According to the carbon and sulfur contents, the depositional environment of the both sites were defined as a freshwater depositional environment. The XRD analysis revealed that the mineral composition of oil shale and coal samples were quartz, calcite, dolomite, illite, kaolinite, montmorillonite, anorthoclase, albite, microcline, orthoclase and analcime. The absorption features of oil shale samples were at 1412 nm and 1907 nm by clay minerals and water, 2206 nm by clay minerals of kaolinite and montmorillonite and 2306 nm by dolomite. It is considered that spectral characteristics on organic matter content test must be tested for oil shale exploration using remote sensing techniques.

• Proceedings of the Korea Association of Crystal Growth Conference
• /
• 1996.06a
• /
• pp.75-87
• /
• 1996

This review is presented under the following headings: 1.Introduction 1.1 Brief review of the properties of AlN 1.2 Historical survey of work on ceramic and single crystal AlN 2.Thermochemical background 3.Crystal growth 4.Doping 5.Potential applications and future work The known properties of AlN which make it of interest for various are discussed briefly. The properties include chemical stability, crystal structure and lattice constants, refractive indices and other optical properties, dielectric constant, surface acoustic wave velocity and thermal conductivity. The history of work in single crystals, thin films and ceramics are outlined and the thermochemistry of AlN reviewed together with some of the relevant properties of aluminium and nitrogen; the problems encountered in growing crystals of AlN are shown to arise directly from these thermochemical relationships. Methods have been reported in the literature for growing AlN crystals from melts, solution and vapour and these methods are compared critically. It is proposed that the only practicable approach to the growth of AlN is by vapour phase methods. All vapour based procedures share the share the same problems: $.$the difficulty of preventing contamination by oxygen & carbon $.$the high bond energy of molecular nitrogen $.$the refractory nature of AlN (melting point~3073K at 100ats.) $.$the high reactivity of Al at high temperatures It is shown that the growth of epitactic layers and polycrystalline layers present additional problems: $.$chemical incompatibility of substrates $.$crystallographic mismatch of substrates $.$thermal mismatch of substrates The result of all these problems is that there is no good substrate material for the growth of AlN layers. Organometallic precursors which contain an Al-N bond have been used recently to deposit AlN layers but organometallic precursors gave the disadvantage of giving significant carbon contamination. Organometallic precursors which contain an Al-N bound have been used recently to deposit AlN layers but organometallic precursors have the disadvantage of giving significant carbon contamination. It is conclude that progress in the application of AlN to optical and electronic devices will be made only if considerable effort is devoted to the growth of larges, pure (and particularly, oxygen-free) crystals. Progress in applications of epi-layers and ceramic AlN would almost certainly be assisted also by the availability of more reliable data on the pure material. The essential features of any stategy for the growth of AlN from the vapour are outlined and discussed.

• Journal of Korean Society of Forest Science
• /
• v.98 no.1
• /
• pp.33-48
• /
• 2009

Forests store carbon dioxide ($CO_2$), one of the major factors of global warming, in vegetation and soils through photosynthesis process. In addition, woods deposit $CO_2$ for a long term until the harvested wood is decomposed or burned, and deforested areas could be expanded the carbon sinks through reforestation. Forests are a lso able to decrease temperature through transpiration and contribute to control the micro climate in global climate systems. Consequently, forests are considered as one of major sinks of greenhouse gases for mitigating global warming. It is very important to develop a Korea specific forest carbon flux model for preparing adaptation measures to climate change. In this study, we compared the climate change impact models in forests developed in foreign countries and analyzed the applicability of the models to Korean forest. Also we selected models applicable to Korean forest and suggested approaches for developing Korean specific model.

• Journal of the Korean Society for Precision Engineering
• /
• v.14 no.4
• /
• pp.30-37
• /
• 1997

This thesis is concerned with the study on the characteristics of the tool failure occuring at the beginning of cutting in finish machining of hardened steels such as carbon tool steel and alloy tool steel by a ceramic tool (Al$_{2}$O$_{3}$+TiC) with nose radius. In the machining of hardened carbon steel STC3, the wear mechanism on the flank face of the ceramic tool is abrasion wear. The mode of tool failure is developed into catastropic fracture with flaking. It is thought that the fracture caused by FeO and TiO$_{2}$ results from the oxidation of Fe in the workpice and TiC in the ceramic tool and the deposit of Fe formed on the surface of the ceramic tool. In the machining of hardened alloy steel STD11, the wear mechanism on the flank face of the ceramic tool is that abrasion and adhesion wear exist simultaneously. The mode of tool failure at the beginning of cutting features is DOC notch wear. It is thought that the DOC notch wear caused by FeO and TiO$_{2}$results from the oxidation of Fe and TiC in the workpiece and ceramic tool, respectively.