• Proceedings of the Korean Environmental Sciences Society Conference
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• 2020.10a
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• pp.146-146
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• 2020

• Korean Journal of Optics and Photonics
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• v.9 no.3
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• pp.186-190
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• 1998

We fabricated a diode-side pumped high power Nd:YAG laser with a gold coated flow tube(diameter of 10mm) and three sets of 140W diode bar. The diameter of Nd:YAG rod was 6mm and its length was 130mm. We obtained 130W cw power from a linear resonator with an 11% output coupler, which corresponds to the slope efficiency of 43% and the optical efficiency of 31%. The measured beam quality factor(M$^2$) reached about 85 which is fairly large due to the large size of the rod. Thermal lensing of the rod was measured to be 5.3-7.4D/$kW_{pump}$ when the laser was operating.

• Economic and Environmental Geology
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• v.53 no.2
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• pp.183-196
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• 2020

This study aimed to recover native gold from the concentrate using microwave-nitric acid leaching and magnetic/hydro separation experiments. The insoluble-residue was filtered from leaching solution through microwave-nitric acid leaching experiment. As a result of the atomic absorption spectrometer(AAS) analysis of the filtered leaching solution, it was discovered that Au content was not eluted at all and it was observed from the back scattered electron(BSE) image that native gold was liberated in the insoluble-residue. When magnetic/hydro separation experiments were applied for the insoluble-residue, magnetic and non magnetic minerals were separtated from insoluble-residue. Magnetite was recovered from the magnetic minerals and as a result of applying the hydro separation experiment again for the non-magnetic mineral, native gold was recovered. The native gold was identified through the X-ray diffraction(XRD) analysis and BSE image.

• Journal of the Mineralogical Society of Korea
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• v.32 no.3
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• pp.185-200
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• 2019

This study aimed to liberate gold from invisible gold concentrate (Au = 1,840.00 g/t) through microwave nitric acid leaching experiments. For the purpose, this study conducted microwave-nitric acid leaching experiments and examined nitric acid concentration effect, microwave leaching time effect and sample addition effect. The results of the experiments were as follows: Au (gold) contents were not detected in all of the microwave leaching conditions. In the insoluble-residue, weight loss rate tended to decrease as the nitric acid concentration, microwave leaching time and sample addition increased. In an XRD analysis with solid-residue, it was suggested that gypsum and anglesite were formed due to dissolution of calcite and galena by nitric acid solution. When a fire assay was carried out with insoluble-residue, it was discovered that gold contents of the solid-residue were 1.3 (Au = 2,464.70 g/t) and 28.8 (52,952.80 g/t) times more than those of concentrate. But in the gold contents recovered, a severe gold nugget effect appeared. It is expected that the gold nugget effect will decrease if a sampling method of concentrate is improved in the microwave-nitric acid leaching experiments and filtering paper with smaller pore size is used for leaching solution and burned filter paper is used for sampling in lead-fire assay.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.11 no.2
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• pp.75-87
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• 2016

This study examines the impact of government funds to venture capital on investment in early-stage firms. We provide novel explanations about this relationship focusing on mechanisms by which government funds influence the perceived uncertainty, decision about investment priority, scale economy of investment, information asymmetry in investment decision, and capital expense. We argue that venture capital's investment in early-stage firms increases as government funds increase and as government funds are explicitly directed for early-stage firms. However, we further claim that the impact of government funds on early-stage investment will be decreasing as their size increases and finally be reverted to negative impact beyond a certain amount of funds to show inverse-U relationship. Our empirical examination using data from 105 Korean venture firms active as of 2013 consistently supports the claims. This study contributes to the venture capital literature by providing novel arguments about mechanisms and effects of policy intervention in venture capital. In practice, we expect our results will provide an opportunity for relevant policy makers to review their venture support policy based on empirical evidences for policy effects.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2001.11a
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• pp.23-26
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• 2001

1879년 T. Edison이 백열전구(incandescent lamp)의 발명, 1920년대에는 형광램프(fluorescent lamp)의 개발에 이어 1990년대에는 무전극(electrodeless) 형광램프가 처음으로 실용화 되어진 비교적 새로운 광원(light source)으로 종래의 광원이 지니지 못하는 특징들이 있다. 본 보고는 그의 원리와 특징, 실용화, 제 문제점 등을 소개하고, 금후의 전망에 대하여 언급한다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.447-447
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• 2013

최근 전자산업의 발전으로 차세대 디스플레이 소자로 산화물반도체가 주목받고 있다. 산화물 반도체는 저온공정, 높은 이동도 및 투과율을 가지기 때문에 이러한 공정이나 물성 측면에 있어 기존의 a-Si, LTPS 등을 대채할 만한 소자로서 연구가 활발이 이루어지고 있다. 특히 고해상도 및 고속구동이 진행됨에 따라 높은 이동도의 필요성이 대두되고 있다. 본 연구에서는 IGZO 산화물 반도체 박막트랜지스터의 이동도 개선을 위해 나노입자를 사용하였다. 게이트전극으로 사용된 Heaviliy doped P-type Si 기판위에 200 nm의 SiO2 절연층을 성장시킨 후, 채널로 작동하기 위한 IGZO 박막을 증착하기 전에 10~20 nm 크기의 니켈, 금 나노입자를 부착시켰다. 열처리 온도는 $350^{\circ}C$, 90분동안 진행하였고, 100 nm의 알루미늄 전극을 증착시켜 TFT 소자를 제작하였다. TFT 소자가 동작할 시, IGZO 박막 내부의 전자들은 게이트 전압으로 인해 하부로 이동하여 채널을 형성, 동시에 드레인 전압으로 인한 캐리어들의 움직임으로 인해 소자가 동작하게 된다. 본 연구에서는 채널이 형성되는 계면 부근에 전도성이 높은 금속 나노입자를 부착시켜 다수 캐리어인 전자가 채널을 통과할 때 전류흐름에 금속 나노입자들이 기여하여 전기적 특성의 변화에 어떠한 영향을 주는지 연구하였다. 반응시간을 조절하여 기판에 붙는 나노입자의 밀도 변화에 따른 특성과 다양한 크기(5, 10, 20 nm)를 갖는 금, 니켈 나노입자를 포함한 IGZO TFTs 소자를 제작하여 전달특성, 출력특성의 변화를 비교하였고, 실질적인 채널길이의 감소효율과 캐리어 이동도의 변화를 비교분석 하였다.

• Korean journal of applied entomology
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• v.31 no.4
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• pp.371-378
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• 1992

The ecdysteroid titers of representive developmental stages of the blackblow fly, Phormia regina, were determined by radioimmunoassay and the effect of ecdysteroid on the oocyte maturation was investigated. Prior to every molts ecdysteroid levels began to increase sharply, suggesting ecdysteroid was the major component for egg-larval, larval-larval, and larval-pupal transformation. A difference in the levels of ecdysteroid between male and female was ob¬served during adult life span. Following the protein meal, ecdysteroid in the females increased rapidly to a maximum at 96 hr of age when terminal oocyte fully matured. Effect of ecdysteroid on oocyte development was determined for control and ecdysone-treated female flies after the liver-feeding. The growth of oocyte in the flies treated by $\mu$g of ecdysone, along with the control flies, was not facilitated. When the flies treated by 5 $\mu$g of ecdysone, however, duration of oocyte maturation was shorter than those of other two groups. This can be suggested that oocyte development in P. regina is due to the critical level of ecdysone.

• Economic and Environmental Geology
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• v.46 no.1
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• pp.21-28
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• 2013

In order to optimize gold leaching from refractory sulfide concentrate, a HCl-NaClO-$FeCl_3$ solution with varying attributes was applied to the roasted concentrate from Uil mine. The gold from Uil mine occurs in the form of invisible gold that is difficult to leach. The results of the gold leaching experiments showed that the best gold leaching parameters were $550^{\circ}C$ of roasting temperature, 2.0 M of concentration, 1.0% of pulp density, and $70^{\circ}C$ of leaching temperature. It is confirmed that the HCl-NaClO-$FeCl_3$ solution was an environmentally friendly method to leach gold and silver from the refractory sulfide concentrate as an alternative lixiviant to cyanide.

• Journal of the Korea Convergence Society
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• v.10 no.6
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• pp.203-218
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• 2019

Using the sample of 104 mutual savings banks inspected by the Financial Supervisory Service (FSS) on June 2011, this study examines if mutual savings banks manage BIS capital adequacy ratio using allowance for bad debts through comparison of BIS capital adequacy ratio before and after the 2011 when mutual savings banks experienced a large-scale restructuring by financial supervisory authorities. We find that mutual savings banks mainly use the allowance for bad debts to manage BIS capital adequacy ratio. It also shows that mutual savings banks with a business suspension order by FSS manage BIS capital adequacy ratio more than the others. Lastly, we find that Non Big4 auditors as well as Big 4 auditors don't effectively audit the use of the allowance for bad debts for mutual savings banks to manage their BIS capital adequacy ratio.