• Economic and Environmental Geology
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• v.28 no.6
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• pp.587-597
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• 1995

Two distinct precious-metal mineralizations actively occur at central and southeastern Korea which display consistent relationships among geologic, geochemical and genetic environments. A large number of preciousmetal vein deposits in the central Korea occur in or near Mesozoic granite batholiths elongated in a NE-SW direction. Whereas, gold and/or silver deposits in the southeastern Korea occur within Cretaceous volcanic and sedimentary rocks. However, most of the precious-metal deposits in the southeastern Korea show characteristics of the silver-rich deposits than the gold-rich deposits in the central Korea. Two epochs of main igneous activities are recognized: a) Jurassic Daebo igneous activity between 121 and 183 Ma, and b) Cretaceous Bulgugsa igneous activity between 60 and 110 Ma. Precious-metal mineralization took place between 158 and 71 Ma, coinciding with portions of the two magmatic activities. Contrasts in the style of mineralization, together with radiometric age data and differences in geologic settings reflect the genetically variable natures of hydrothermal activities from middle Jurassic to late Cretaceous time. The compilation and re-evaluation of these data suggest that the genetic types of hydrothermal precious-metal vein deposits in the central and southeastern Korea varied with time. The Jurassic and early Cretaceous mineralizations are characterized by the Au-dominant type, but tend to change to the Au-Ag and/or Ag-dominant types at late Cretaceous. The Jurassic Au-dominant deposits commonly show several characteristics; prominent associations with pegmatites, simple massive vein morphologies, high fmeness values in ore-concentrating parts, and a distinctively simple ore mineralogy such as Fe-rich sphalerite, galena, chalcopyrite, Au-rich electrum, pyrrhotite and/or pyrite. The Cretaceous precious-metal deposits are generally characterized by some- features such as complex vein morphologies, low to medium fmeness values in the ore concentrates, and abundance of ore minerals including Ag sulfosalts, Ag sulfides, Ag tellurides and native silver. Mineralogical and fluid inclusion studies indicate that the Jurassic Au-dominant deposits in the central area were formed at the high temperature (about $300^{\circ}$ to $500^{\circ}C$) and pressure (about 4 to 5 kbars), whereas mineralizations of the Cretaceous Au-Ag and Ag-dominant deposits were occurred at the low temperature (about $200^{\circ}$ to $350^{\circ}C$) and pressure (<0.5 kbars) from the ore fluids containing more amounts of less-evolved meteoric waters.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.218-218
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• 2003

21세기 정보기반사회에서는 정보처리량의 증가로 인한 대용량 정보 교환을 위하여 신호처리의 고속화/광대역화가 요구되어진다. 완전 광통신망의 구축에 의한 대용량의 광통신을 위해서는 고속이며, 집적화가 가능한 저가의 광전자 소자 개발이 필요하다. 광전자 소자 중 전기-광학 변조 효과를 이용한 광소자의 구현을 위한 소재로서 극성 배향된 비선형 광학 유기고분자 소재는 가공성이 뛰어나 원하는 형태의 광도파로로 제조할 수 있다는 장점에 많은 연구가 진행되고 있다. 그러나 아직 전기광학계수의 향상과 더불어 유기고분자가 가지고 있는 열 및 광화학적 안정성이 낮은 기본적인 문제점과 폴링(poling)에 의해 배향된 극성이 시간에 따라 완화되는 문제의 해결이 요구되고 있다. 이러한 문제점 해결을 위한 기초 연구로 유기물을 졸-겔 매트릭스에 나노 사이즈로 분산하는 방법으로 유기물의 내화학적 안정성을 향상하고자 시도하였다. 잘 알려져 있는 바와 같이 유/무기 하이브리드 졸-겔 재료는 광 투광성이 우수하고 저온에서의 재료 합성과 저가 공정이 가능하여 광기능성 유기물의 호스트(host) 재료로 많이 연구되고 있다. 본 연구에서는 MTMS(methyltrimethoxysilane)과 TEOS (tetra-ethoxyorthosilicate)를 0-100 mol%로 혼합하고 가수분해하는 방법으로 친수성/친유성 특성을 제어하여, 분산되는 유기물의 사이즈를 조정하였다. 각 실험 조건에 따른 유기물 분산체의 크기를 SEM 및 TEM으로 관찰하였으며, 나노 사이즈로 분산된 유/무기 졸-겔 코팅막의 광학적 특성을 프리즘 커플러를 이용하여 조사하였다.

• Journal of Energy Engineering
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• v.15 no.2 s.46
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• pp.96-106
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• 2006

Among several different hydrogen production technologies, solar hydrogen system for water splitting is the only clean and sustainable energy supplier. Hydrogen production by water-splitting utilizing solar energy has attracted considerable interest since the pioneering work of Honda and Fujishima in 1979, who discovered that water can be photo-electrochemically decomposed into hydrogen and oxygen using a semiconductor ($TiO_2$) electrode under UV irradiation. Most efforts to utilize solar ray lead to explore visible responding photocatalysts, PEC cells and other fusion technology like bio-photocatalytic conversion. In this paper, photon utilization technologies for water splitting have been briefly reviewed except solar thermal utilization technology.

• Economic and Environmental Geology
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• v.51 no.3
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• pp.213-222
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• 2018

Metasediment-hosted Pb-Zn mineralized zone has been found in Dyusembay of Kazakhstan. Its petrological properties, metal index, alteration index and redox-sensitivity are compared with those of SEDEX type deposit. Mineralization is developed along foliation of host rock (graphitic phyllite) and controlled by folds and faults; major ore minerals including pyrite, pyrrhotite, sphalerite, and galena are disseminated or interlayered with fine-grained quartz. The margin of the mineralized zone is metamorphosed accompanying sericite and chlorite. Hydrothermal brecciation and Pb-Zn mineralization formed in quartz-calcite stockworks are confirmed at the around of Maytyubin granitoid intrusions. The mineralization is classified into three types according to those of occurrence, paragenesis, chemical composition and isotopic characteristics. Type 1 whose fine-grained pyrite, pyrrhotite and sphalerite are formed in parallel yet discontinuous to well-developed foliations of the host rock; its geochemistry is similar to those of the earlier stage in SEDEX-type mineralization. In case of type 2, the ore minerals of which are concentrated being parallel to a foliation by regional metamorphism, and most of them associated with quartz and muscovite (${\pm}$ biotite) paragenetically. Type 3 is formed in the hydrothermal breccia zone whose ore minerals are controlled by foliation and breccia and developed in quartz ${\pm}$ calcite veins having a form such as stratification, stockwork or veinlets. Host rocks in the mineralized zone indicate homogeneous metamorphic grade and there is no specific alteration zonation. Also, all types (type 1, type 2, and type 3) represent similar REEs patterns, it can be interpreted that these are originated from a same source. Sulphides occurred in mineralized zone indicate a limited range of sulphur isotope values (type 2, ${\delta}^{34}S=-13.3{\sim}-11.7$‰; type 3, ${\delta}^{34}S=-13.9{\sim}-8.2$‰), and a result of geothermometry presents different temperature ranges: type 2($251{\pm}38^{\circ}C{\sim}277{\pm}40^{\circ}C$); type 3($360{\pm}2^{\circ}C$ to $537{\pm}29^{\circ}C$). It is estimated to be due to the effect of metamorphism and Maytyubin granitoid intrusions, respectively. In addition, ternary chart of thorium, scandium, and zircon for discrimination of tectonic setting and redox sensitivity using V/Mo values indicate that hydrothermal sediments put on reduction environment after precipitation, before being affected by metamorphism and intrusion activity. Geochemical data are plotted on a distal trend of SEDEX-type with discrimination plot using SEDEX index. As a result, petrological-geochemical properties demonstrate that Dyusembay Pb-Zn mineralized zone is comparable to distal-type of SEDEX deposit.

• Journal of the Korean Chemical Society
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• v.20 no.3
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• pp.212-220
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• 1976

The photocyclization of 1,1'-dicycloalkenyls (1,1'-dicyclohexenyl, 1,1'-dicyclopentenyl, 1,1'-dicycloheptenyl and 1,1'-dicyclooctenyl) is studied. Irradiation at liquid nitrogen temperature does not show trans double bond band in IR spectra. Even though naphthalene and pyrene fluorescence are quenched very efficiently by 1, 1'-dicycloalkenyls, no or trace amount of cyclobutenes are accompanied. When acetophenone or benzophenone is used, cyclobutene is obtained only from 1,1'-dicyclohexenyls, 1,1'-dicycloheptenyl giving some adducts. Naphthalene and pyrene sensitizes adduct formation but not cyclization. From above observations, it is concluded that photocyclization occurs from the planar s-cis triplet state rather than twisted triplet, singlet excited state or vibrationally excited ground state in sensitized photocyclization of 1,1'-dicycloalkenyls.

• Journal of the Korean Chemical Society
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• v.20 no.3
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• pp.229-235
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• 1976

Phenylacetic acid is chlorinated photochemically in carbon disulfide and carbon tetrachloride solvents to obtain ${\alpha}$-chlorophenylacetic acid in $43{\%}$ yield (after separation and purification). The amination of ${\alpha}$-chlorophenylacetic acid yielded the desired dl-phenylglycine in $16\sim27{\%}$ yield depending on the solvent used. Sensitized photophenylation of glycine is also attempted utilizing benzoylperoxide as a phenyl radical source in benzene or acetone solvent.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2003.05b
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• pp.209-210
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• 2003

최근 동북아시아지역의 급속한 산업발달과 더불어 많은 양의 오염물질을 대기로 배출하고 있다. 특히 중국의 급속한 산업화와 문화수준의 향상 등으로 인해 배출되는 막대한 양의 대기오염물질이 동북아시아지역에서 주기적으로 발생하는 황사와 함께 장거리 이동현상에 의해 우리나라 및 일본 등의 대기 에어로졸 질량 농도 및 화학적 조성에도 많은 변화를 가져올 정도로 직접적인 영향을 끼친다. 그 중에서도 입자 크기가 2.5~10$\mu\textrm{m}$사이에 있는 조대입자(coarse particle)의 광화학적 특성에 많은 변화를 야기시키는 것으로 알려져 있다. (중략)

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2003.05b
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• pp.377-378
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• 2003

휘발성유기화합물(volatile organic compounds, 이하 'VOCs')은 대기 중에서 태양광선에 의해 질소산화물과 광화학적 산화반응을 일으켜 그 결과 지표면의 오존농도를 증가시켜 스모그(Smog) 현상을 초래시키는 모든 유기화합물을 일컫는다. 이러한 VOCs를 제거하기 위하여 여러 방법이 제시되고 있는데, 촉매를 이용하여 VOCs를 산화시켜 제거하는 촉매 산화법은 촉매사용으로 인하여 소각법에 비하여 조업온도를 많이 떨어뜨릴 수 있으므로, 에너지 소비의 절감과 이에 따른 제2의 오염물질의 배출이 거의 없다는 점에서 유리한 면을 갖고 있어 VOCs 제거에 가장 적합한 방법이라고 할 수 있다. (중략)

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2003.05b
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• pp.231-232
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• 2003

과산화수소(hydrogen peroxide, $H_2O$$_2$)는 광화학적 2차 생성물이며, 대기의 산화상태를 알려주는 지시자의 역할을 한다. 과산화수소는 HO$_2$ radical의 self-reaction 으로 생성된다. HO$_2$+ HO$_2$+ M $H_2O$$_2$ + M (1) OH나 HO$_2$ radical은 NOx나 hydrocarbon 과 같은 대표적인 오존 전구물질들을 산화시킨다. 대기 내 수명이 불과 1초 이내인 OH나 HO$_2$ radical을 직접 측정하기란 어려우므로 수명이 1~2 일 정도인 $H_2O$$_2$를 측정하여 이들 radical의 대기 내 농도를 추정할 수 있다. (중략)

• Analytical Science and Technology
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• v.25 no.6
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• pp.339-344
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• 2012

In this research, hydride generation in HPLC-ICPMS for the selenium speciation was investigated. Chemical and photochemical vapor generation techniques were compared for the effective generation of selenium vapour. $HBr/KBrO_3$ was used for the chemical reduction and a UV lamp was used for the photochemical reduction. It was found out that the photochemical reduction was more effective than the chemical reduction in all of selenium species studied. The optimum conditions for the generation of vapour are 0.4% KI, 2.5% $NaBH_4$, and 1.0 M HCl. The enhancement factor using a photochemical hydride generation was from 6.3 to 16.7 times for inorganic and organic selenium species.