• Polymer(Korea)
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• v.33 no.2
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• pp.158-163
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• 2009

In this study, we synthesized a series of dendritic polystyrene-b-linear poly (t-butyl acrylate) copolymers with well-defined molecular architectures. The hydroxyl group located at the focal point of the second generation dendron bearing polystyrene ($M_n$ = 1000 g/mol) peripheries was converted into amine group via the following stepwise reactions: 1) tosylatoin, 2) azidation, and 3) reduction. On the other hand, the linear poly (t-butyl acrylate)s were prepared by an atom transfer radical polymerization (ATRP) of t-butyl acrylate where benzyl 2-bromopropanoate and Cu(I)Br/PMDETA were used as initiator and catalyst, respectively. To convert the end group of prepared poly (t-butyl acrylate) s into carboxylic acid, a debenzylation was performed using Pd/C catalyst under $H_2$ atmosphere. In the final step, dendritic-linear block copolymers were obtained through a simple amide coupling reaction mediated by 4-(dimethylamino) pyridine(DMAP) and N,N'-diisopropylcarbodiimide(DIPC). The resulting diblock copolymers were shown to have well-defined molecular weights and narrow molecular weight distributions as supported by $^1H$-NMR spectroscopy and gel permeation chromatography(GPC).

• Economic and Environmental Geology
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• v.29 no.2
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• pp.105-117
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• 1996

The Baegjeon Au-Ag and Sb deposits, small of disseminated-type gold deposits are formed as a result of epithermal processes associated a shallow-seated Cretaceous Yeogdun granitoids intrusion. The orebodies are formed by the replacement of carbonate minerals in thin-bedded oolitic limestone beds favorable for mineralization within the upper-most Cambrian Pungchon Limestone Formation. The mineralization can be recognized one stage, ore minerals composed of base metal sulfides, electrum, AgSb-S, Ag-Cu-S, and Sb-S minerals. Gold-bearing minerals consist of electrum and submicroscopic invisible gold in pyrite and arsenopyrite. The composition of electrums ranges from 33.58 to 63.48 atomic % Ag. Fluid inclusion studies reveal that ore fluids were low saline $NaCl-CO_2-H_2O$ system. Temporary fluid mixing and boiling occured in later stage. Fluid inclusion data indicates the homogenization temperatures and salinities of NaCl eqivalent wt% were 176 to $246^{\circ}C$ and from 0.0 to 4.8 wt%, respectively. And $-logfs_2$, of mineralization obtained by thermodynamic considerations as 12.4 to 13.8 atm. The ${\delta}^{34}S_{H_2S}$, values of hydrothermal sulfides were calculated to be 6.8 to 10.2‰ which was of sedimentary origin. The ${\delta}^{18}O_{H_2O}$ and ${\delta}^{13}C_{CO_2}$, range from -3.9 to 9.6‰, from -1.1 to -2.2‰, and ${\delta}D$ range from -89 to -118‰, respectively. The Au deposition during mineralization seems to have occurred as a result of decrease of temperature, $fs_2$, $fo_2$, and pH probably due to oxidation by meteoric water mixing, which destabilized original $Au(HS)^-{_2}$. The mineralization of the Baegjeon deposits is similar to the Carlin-type deposits characterized by sediments-hosted epithermal bedding replacement disseminated gold deposits.

• Journal of Welding and Joining
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• v.28 no.6
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• pp.63-69
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• 2010

The pre-heat free consumables for GMAW, SAW and FCAW processes that matche with the Cu-bearing PFS-700 steel which has yield strength over 700MPa were developed and evaluated to see the suitability in military such as submarine and battle ship. Explosion Bulge Test underwater was developed and applied to see the reliability of welded structure. All welding was conducted without pre-heat before welding, the interpass temperature was below $150^{\circ}C$ for all welding conditions. Tensile strength for the weld metal in GMAW, SAW and FCAW process is 887MPa, 875MPa and 813MPa, respectively, these values are similar to the base metal of PFS-700 steel of 838MPa. EBT results in GMAW, SAW and FCAW show 14.0%, 14.02% and 15.9% reduction of thickness without generation of crack, respectively and stand-off distance was set up properly to have over 14.0% reduction of thickness. Through EBT results, the developed new consumables are applicable to the weapon systems such as submarine and battle ship.

• Economic and Environmental Geology
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• v.11 no.4
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• pp.169-182
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• 1978

The Weolagsan area consists of four units; (1) Low grade meta-sediments of the upper members of Ogcheon age unknown group such as Changri (mainly black slate and phyllitic rock), Majeonri (mainly alternation of slate, limestone and chert) and Hwanggangri Formation (pebble bearing phyllitic sediments); (2) Samtaesan Formation of Chosun System of Ordovician; (3) So called meta-volcanics and (4) Weolagsan Granite and its associations which intruded above mentioned meta-sediments and meta-volcanics. This study was focused to know the Woelagsan granite and its metasomatic effects to the country rocks petrographically and petrochemically. According to the field survey, microscopic work and some chemical analysis, the granite is a "normal granite" based on the Streckeisen's classification and belongs to a mass of the Central-zone younger group in Ogcheon geosynclinal belt. The granite metasomatized the country rocks along its northern contact zone. Zone of calcareous and cherty rocks (Majeonri formation) was silicified partly and skarned locally at the contact with the granite. The chemical analysis of the zone show no difinite variations in contents of $SiO_2$ and CaO with the distance from the granite. It seems to be indicated that the silicification of this part was not so metasomatized by the granite body, but thermally affected as much as to be partially remelted in the specific parts of the formations. Meta-volcanic rock zone was slightly chloritized near contact with the granite. Limestone of Samtaesan Formation was silicified and skarned along the contact zone by the granite body. The chemical analysis of the zone show some noticiable changes in compositions of $SiO_2$ and CaO with distance from the granite boundary. It can be imagined that the silicification of this zone was metasomatically originated by Woelagsan Granite. According to chemical analysis on several trace elements, the ratio of Zn/Cr and Ni/Cr are relatively higher than that of Cu/Cr in the above mentioned silicified zones. Generally the variation of these metal elements in the zones tend to be regular with distance from the granite body.

• Proceedings of the KWS Conference
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• 2010.05a
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• pp.63-63
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• 2010

The pre-heat free consumables for GMAW, SAW and FCAW processes that matches the Cu-bearing PFS-700 steel which has yield strength over 700MPa were developed and evaluated to see the suitability in military such as submarine and battle ship. Explosion bulge test in underwater was developed and applied to see the reliability of welded structure. All welding was conducted without pre-heat before welding, the interpass temperature was below $150^{\circ}C$ for all welding conditions. Tensile strength for the weld metal in GMAW, SAW and FCAW process is 887MPa, 875MPa and 813MPa, respectively, these values are similar to the base metal of PFS-700 steel of 838MPa. EBT results in GMAW, SAW and FCAW show 14.0%, 14.02% and 15.9% reduction of thickness without generation of crack, respectively and stand-off distance was set up properly to have over 14.0% reduction of thickness. Through EBT results, the developed new consumables are applicable to the weapon systems such as submarine and battle ship.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.40-40
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• 2009

The Cu-bearing PFS-700 steel which has yield strength over 700 MPa was developed to replace the existing submarine structural material, HY-100. PFS-700 steel has good combination of mechanical properties and superior weldability which can be welded without pre-heating before welding. Application PFS-700 steel to submarine or battle ship will give a great reduction of cost by removing or lowing pre-heating. To develop pre-heat free welding consumables that matches and take advantage of PFS-700 steel, new welding consumables have been designed for the GMAW, SAW processes and explosion bulge test(EBT) were conducted to see the reliability of welded structure. All welding was conducted without pre-heating before welding, the inter-pass temperatures were below $50^{\circ}C$ for SAW50 and $150^{\circ}C$ for GMAW and SAW150. All EBT specimens show over 14% reduction of thickness without through-thickness crack or propagation of crack to the hole-down area. Tensile properties for all welding conditions show higher(GMAW) or similar values(SAW50, SAW150) to the base metal. Charpy impact values for the weld metal also show 163.5J(GMAW), 95.4J(SAW50) and 69.0J(SAW150), which meet the goal, 50J, of this project.

• Economic and Environmental Geology
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• v.24 no.1
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• pp.1-8
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• 1991

North ore deposits of the Dunjeon gold mine is disseminated-stockworks deposits emplaced in Ordovician Dongjeom quartzite. Six types of fluid inclusions are recongnized in the stage I quartz. Among them polyphase inclusions(type-IV-A, B) are predominent in the lower part of stage I quartz crystals whereas liquid and gas inclusions(type I, II) are abundant in the upper part of the same quartz crystals. Liquid $CO_2$-bearing inclusions(type III-A, B)occur as pseudosecondary inclusions. Solid phases in polyphase inclusions are identified by using scanning electron microscopy combined with energy dispersive x-ray spectroscopy. The solid phases are as follows; halite, sylvite, hydrophyllite, quartz, muscovite, calcite, ankerite, K-Mg-Fe-Al-Si mineral, Ca-Fe-Si mineral, Mg-Al-Si mineral, two kinds of Fe-mineral and Cu-Fe mineral. Results of freezing and heating experiments of fluid inclusions and identification of daughter minerals in polyphase inclusions in the stage I quartz reveal that ore fluids were high saline system NaCl-KCl-$CaCl_2$-$H_2O$ in the earier stage and then evolved to rather simple system NaCl-$H_2O$ in the later stage, and temporally fluid mixing occured with system $CO_2$-$H_2O$. Homogenization temperatures and salinity of fluid inclusions in the stage I range from 290 to $454^{\circ}C$ and from 0.2 to 54.2 wt. % equivalent to NaCl.

• Economic and Environmental Geology
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• v.24 no.2
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• pp.151-165
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• 1991

The Au-Ag deposits of the Euiseong area occurred in quartz veins which filled fissures in Cretaceous sedimentary and volcanic rocks. These ore veins can be classified in two types of deposits based on metallic mineral assemblages as follow: a pyrite type gold-silver deposit (Hoedong mine), characterized by Cu sulfides with Au-Ag alloy, and a Sb-rich silver deposit (Keumdongdo mine), characterized by base metal with Ag-bearing sulfosalts. Mineralogic and fluid inclusion evidences suggest that the ore minerals of these deposits was deposited from initial high temperatures (near $350^{\circ}C$) to later lower temperatures ($200^{\circ}C$) with moderate salinity fluids ranging from 5.8 to 3.8 eq. wt. % NaCl. The gold-silver mineralization of the Hoedong mine occurred at temperatures between 300 and $200^{\circ}C$ from fluids with log $f_{s_2}$ of -10 ~ -16 atm. The antimony - silver mineralization of the Keumdongdo mine were deposited at the higher temperatures (350 to $250^{\circ}C$) and $f_{S_2}$ (-10 ~ -13 atm) than gold mineralization of the Hoedong mine. The calculated log f02 of fluids at $250^{\circ}C$ in two deposits are -32 to -34 atm and -36.5 to -38.5 atm, respectively. Boiling evidences indicate that the ore mineralization of the Hoedong mine occurred at more shallow depth (0.5km) than that (1km) of the Keumdongdo mine. The above differences of depositional environments between two deposits caused the compositional changes of ore minerals such as electrum and sphalerite.

• Journal of Welding and Joining
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• v.27 no.6
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• pp.80-86
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• 2009

The Cu-bearing PFS-700 steel which has yield strength over 700 MPa was developed to replace the existing submarine structural material, HY-100. The PFS-700 steel has a combination of good mechanical properties and superior weldability. Becaus of that, it can be welded without pre-heating. The application of PFS-700 steel to submarine or battle ship will give a great reduction of cost by omitting pre-heating or lowering pre-heat temperature. To develop pre-heating free welding consumables that match and take advantage of PFS-700 steel, new welding consumables have been designed for the GMAW, SAW processes and explosion bulge test(EBT) was conducted to see the reliability of welded structure. All welds were made without pre-heating, and the inter-pass temperature was below $50^{\circ}C$ for SAW50 and $150^{\circ}C$ for GMAW and SAW150. All EBT specimens show over 14% thickness reduction without through-thickness crack or crack propagation to the hole-down area. Tensile properties for all welding conditions show higher(GMAW) or similar values(SAW50, SAW150) to the base metal. Charpy impact values for the weld metal also show 163.5J(GMAW), 95.4J(SAW50) and 69.0J(SAW150), which meet the goal(higher than 50J) of this project.

• Economic and Environmental Geology
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• v.21 no.3
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• pp.269-276
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• 1988

Ore deposits of Dadeok mine, the largest in the Bonghwa gold mining district, are composed of numerous gold and silver-bearing quartz veins emplaced in granite batholith. Mineralization of the Pungjeong vein, one of the representative vein in the mine was investigated. K-Ar age of sericite in the vein is $84{\pm}5$ Ma. Hypogene 6pen-space filling can be devided into four paragenetic stages; (1) fine grained quartz and carbonate; (2) quartz and carbonates with base metal sulfides, electrum, native silver, argentite, polybasite, freibergite, pyrargyrite, and Cu-Ag-Fe-S minerals; (3) quartz with base metal sulfides; (4) quartz and calcite with or without pyrite. Composition of electrum ranges from 44.17 to 56.50 atomic % Ag. Meanwhile FeS content of sphalerite coexisting with elctrum in stage II range from 0.01 to 1.67 mol. %. Homogenization temperatures for quartz and sphalerite of stage II ($239^{\circ}$ to $310^{\circ}C$), quartz of stage III ($206^{\circ}$ to $255^{\circ}C$) and quartz and calcite of stage IV ($232^{\circ}$ to $253^{\circ}C$) show little time-space variation during mineralization. Salinities of the fluid inclusions range from 5.5 to 12.8wt% NaCI in stage II, 7.3 to 12.3wt% in stage III and 4.5 to 8.0wt% in stage IV. Based on the homogenization temperatures, Fe content of sphalerite and Ag content of electrum, tempera ture and sulfur fugacity for stage II are estimated to be $208^{\circ}$ to $310^{\circ}C$ and $10^{-9.2}-10^{-12.8}$ bars, respectively.