• Economic and Environmental Geology
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• v.35 no.3
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• pp.191-201
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• 2002

The Gubong gold-silver deposits if gold-silver-bearing hydrothermal massive quartz veins which were filled the fractures along fault shear (NE, NW) zones within Precambrian banded or granitic gneiss of Gyeonggi massif. Ore mineralization of this deposits is contained within a single stage of quartz vein which was formed by multiple episodes of fracturing and healing. Ore minerals are comported mainly of arsenopyrite, pyrite, sphalerite, chalcopyrite, galena with minor amounts of pyrrhotite, marcasite and electrum. The frequency and volume percentages of electrum associated with ore minerals from this deposits are recognized as follows; 44.5% and 54.3% with arsenopyrite, 24.3% and 33.8% with quartz, 12.6% and 0.1% with pyrite, 11.0% and 4.8% with galena, 5.0% and 7.0% with sphalerite and 2.5% and 0.02% with chalcopyrite, respectively. They show irregular (41.6%), subround (34.7%), elongate (17.0%) and granular (6.6%) shapes, respectively. Their grain size ranges from 2 to 150 um, but 90.9 percent of the grains are below 30 um. The chemical composition of electrums ranges from 26.39 to 72.51 Au atomic %. These composition (Au atomic %) on the basis of associated minerals are from 44.97 to 71.75 with arsenopyrite, pyrite, sphalerite and quartz, from 44.37 to 72.51 with quartz, from 35.40 to 41.01 with sphalerite and chalcopyrite, from 26.39 to 54.84 with pyrite, chalcopyrite, quartz and galena, from 28.49 to 53.28 with galena, respectively. We suggest that optimum recovery of gold would be obtained with reference to these results.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.15 no.2
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• pp.97-110
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• 2020

This paper is on the policy proposal for venture ecosystem. First, one of the three secrets of the US venture ecosystem is the law of 50:50. Angel capital investment is as important as venture capital investment. Although professional angel investors and accelerators account for as much as VC in the venture ecosystem, they are ignored from policy considerations. We argue that the revision of related law is urgent. Second, large US firms invest more in M&As than in internal R&D. Therefore, accelerators and professional angel investors could make effective investment recovery after investing in a startup company. In other words, angel capital does not come in without secondary market development. Angel capital and secondary markets are the two pillars of the venture ecosystem. The government alone is difficult to develop a secondary market. This is why the private sector should come in and introduce corporate venture capital (CVC). Third, we believe the policy direction for national economic growth should be extended from the startup to scale-up. This is because the startup's sales and job creation will start in five years. While the previous study focused on funding (venture financing), this paper aims to balance all three stages of a venture: startup, growth, and recovery, which are the life cycle of a venture company or venture investment. In particular, we propose specific policies in each chapter to improve practical application.

• Journal of the Korean earth science society
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• v.35 no.4
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• pp.259-266
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• 2014

This study was carried out to find an environmental friendly and effective way to leach Au and Ag from scrap of Printed Circuit Boards (PCBs) using sodium-hypochlorite solution. In an EDS analysis, valuable metals such as Cu, Sn, Sb, Al, Ni, Pb and Au were all found in PCBs. The highest leaching rates obtained were 1% of pulp density with a chlorine:hypochlorite of 2:1 and a concentration of NaCl at 2M. The highest Au recovery was observed with the addition of sodium metabisulfite to make a 3M solution. It is confirmed that the leaching agent (chlorine-hypochlorite) could effectively leach Au and Ag from Printed Circuit Boards (scrap parts) and the additive reagent sodium metabisulfite could easily precipitate Au from the chlorine-hypochlorite solution.

• Journal of the Korean Chemical Society
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• v.7 no.2
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• pp.165-169
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• 1963

12 samples from an assay process chain were submitted to qualitative and quantitative neutron activation analysis for the determination of gold. Gold was detected and quantitatively determined in three samples after a chemical separation consisting of solvent extraction and precipitation steps. Recoveries ranged between 81.0 and 93.6% and results of duplicated determinations were reproducible. Quantitative data were obtained from gamma-spectrometric photopeak-area counting. Interference from fast neutron reactions was negligible.

• 한국연소학회:학술대회논문집
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• 2015.12a
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• pp.201-204
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• 2015

Recently, energy excessive consumption and environmental pollution are the social issued. The most efficient way to solve both energy excessive consumption and environmental pollution is existing combustion system improved. This study was part of the assume and commercial used existing waste heat recovery condensing boiler to low emission performance for exhaust gas recirculation(EGR) and thermal efficiency rise by applying the condensed water recirculation(CWR) conducted. The researchers applied the EGR and CWR develop a new concept for the condensed water recirculation waste heat recovery condensing boiler. Waste heat recovery condensing boiler applied to the condensed water recirculation thermal efficiency of the same conditions was increased by about 4.8~5.5% and pollution emission also decreased.

• Resources Recycling
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• v.5 no.3
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• pp.31-36
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• 1996

The metallic copper was recovered from sludge of the copper electro-plating plant by pyrometallurgical process. The reducing agent was Pyrolysized from waste tires and the flux was a mixture $Na_2CO_3$, $NaB_4O_7$, and glass. The green sludge contained 87.5% moisture and 12.5% solid with 56.5% Cu and 1.59% Fe. The sludge dried at $100^{\circ}C$ was analyized to be $Cu_4SO_4(OH)_6{\cdot}2H_2O$ and CuO by XRD analysis. The former was 84% and the latter 16%, However, the calcined sludge at $500^{\circ}C$ was 49% $Cu_2O(SO_4)$ and 51% CuO. The sludge could by smelted at $1100^{\circ}C$ for two hours with 6 to 8 moles carbon with respect to copper to produce metallic copper (>90%) with recovery of 9% above.

• Journal of Digital Convergence
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• v.10 no.10
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• pp.19-29
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• 2012

We made a regression analysis on the early IPO of venture capital investments in Korean IPO market. First, we found that it was likely to shorten the period to IPO in companies which were fast growing with a good operating cash flow, but these companies had a higher possibility of the earning management. Second, companies with more assets and larger size of the board of directors did not take companies public any earlier. Third, a better corporate governance also had no impact on the time period to IPO in the newly public firms. The findings above clearly show that venture-backed companies in Korea pursue the tendency of an early IPO. This phenomenon was much clearer when the companies were invested in by multiple venture capital firms than by a single investor. In general, venture capital firms invest in companies which are fast growing and which have a good operating cash flow. On the other side, venture capitals make investee companies go public earlier by manipulating operating earnings, so that they themselves may exit early. In conclusion, this research has shown that venture capitals in Korea do not play a positive role in the corporate transparency. This is the paradox of venture capital investment and this also shows the current status of Korean venture capital firms.

• Resources Recycling
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• v.21 no.5
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• pp.31-37
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• 2012

As a recovery of elemental silicon from the sludge of Si wafer process, a process of mechanical separation-chlorine roasting-electrolysis has been suggested. The silicon sludge consisted of Si, SiC, machine oil, and metallic impurities. The oil and metal impurities was removed by mechanical separation. The Si-SiC mixture was converted to silicon chloride by chlorine roasting at $1000^{\circ}C$ for 1 hr and the silicon chloride was dissolved into an ionic liquid of $[Bmpy]Tf_2N$ as an electrolyte. Cyclic voltammetry results showed an wide voltage window of pure $[Bmpy]Tf_2N$ and a reduction peak of elemental Si from $[Bmpy]Tf_2N$ dissolved $SiCl_4$ on Au electrode, respectively. The silicon deposits could be prepared on the Au electrode by the potentiostatic electrolysis of -1.9 V vs. Pt-QRE. The elemental silicon uniformly electrodeposited was confirmed by various analytical techniques including XRD, FE-SEM with EDS, and XPS. Any impurity was not detected except trace oxygen contaminated during handling for analysis.

• Membrane Journal
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• v.13 no.1
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• pp.9-19
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• 2003

Membrane process was investigated to recover process water and valuable gold from washing water of electroless PCB plating processes. The filtration experiments were carried out using not only a RO membrane test cell to determine suitable membrane for washing water but also spiral wound membrane modules of nanofiltration and reverse osmosis for scale-up. At first, RO-TL(tap water, low pressure), RO-BL(brackish water, low pressure) and RO-normal(for water purifier) sheet membranes made by Saehan Co. were tested, and the performance of RO-TL membrane showed most suitable f3r recovery of soft etching, catalyst and Ni washing waters. As a result of RO test cell, the experiments for scale-up were carried out using RO-TL modules far water purifier at 7bar and $25^{\circ}C $The permeate flux fur Au washing water was about 30 LMH, but Au rejection was less than 80%. The permeate fluxes for Pd, Ni and soft etching washing water were about 22, 17 and 10 LMH, respectively. The Pd, Ni and Cu rejections showed more than 85, 97 and 98% respectively. The nanofiltration module for water purifier was introduced to recover Au selectively from Au, Ni and Cu ions in Au washing water. Most of Ni and Cu ions in the feed washing water were removed, and only Au ion was existed 81.9% in the permeate. Furthermore, Au ion in the permeate was concentrated and recovered by RO-TL membrane module. Finally, Au was also able to recover effectively by using 4 inch diameter spiral wound modules of NF and RO-TL membranes, in series.

• Environmental and Resource Economics Review
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• v.17 no.3
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• pp.91-134
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• 2008

Korean district heating companies levy comprehensive construction fee on consumers in the beginning of construction period and the consumers' burden is much higher than those in any other network industries in Korea. It has also many problems such as inappropriate fee calculation method, cross subsidization, property right dispute, etc.. I show that the cut of construction fee by 30% and at the same time, the upward adjustment of tariff rates by 4~6% for 20 years on average will maintain current profitability based on the standard model simulation, I also suggest that fixed charge part of double tariff should be increased to 25% of total tariff and the cut of construction fee should be levied on fixed charge, directly to improve efficiency.