• Korean Journal of Remote Sensing
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• v.29 no.2
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• pp.173-182
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• 2013

The early Sea-viewing Wide Field-of-view Sensor(SeaWiFS) atmospheric correction algorithm which is the basis of the atmospheric correction algorithm for Geostationary Ocean Color Imager(GOCI) assumes that water-leaving radiances is negligible at near-infrared(NIR) wavelengths. For this reason, all of the satellite measured radiances at the NIR wavelengths are assigned to aerosol radiances. However that assumption would cause underestimation of water-leaving radiances if it were applied to turbid Case-2 waters. To overcome this problem, Management Unit of the North Sea Mathematical Models(MUMM) atmospheric correction algorithm has been developed for turbid waters. This MUMM algorithm introduces new parameter ${\alpha}$, representing the ratio of water-leaving reflectance at the NIR wavelengths. ${\alpha}$ is calculated by statistical method and is assumed to be constant throughout the study area. Using this algorithm, we can obtain comparatively accurate water-leaving radiances in the moderately turbid waters where the NIR water-leaving reflectance is less than approximately 0.01. However, this algorithm still underestimates the water-leaving radiances at the extremely turbid water since the ratio of water-leaving radiance at two NIR wavelengths, ${\alpha}$ is changed with concentration of suspended particles. In this study, we modified the MUMM algorithm to calculate appropriate value for ${\alpha}$ using an iterative technique. As a result, the accuracy of water-leaving reflectance has been significantly improved. Specifically, the results show that the Root Mean Square Error(RMSE) of the modified MUMM algorithm was 0.002 while that of the MUMM algorithm was 0.0048.

• Korean Journal of Metals and Materials
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• v.50 no.1
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• pp.64-70
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• 2012

Samples of pure Mg, 76.5 wt%Mg-23.5 wt%Ni, and 71.5 wt%Mg-23.5 wt%Ni-5 wt%$Fe_2O_3$ were prepared by reactive mechanical grinding and their hydriding and dehydriding properties were then investigated. The reactive mechanical grinding of Mg with Ni is considered to facilitate nucleation and to shorten diffusion distances of hydrogen atoms. After hydriding-dehydriding cycling, the 76.5 wt%Mg-23.5 wt%Ni and 71.5 wt%Mg-23.5 wt%Ni-5 wt%$Fe_2O_3$ samples contained $Mg_2Ni$ phase. In addition to the effects of the creation of defects and the decrease in particle size, the addition of Ni increases the hydriding and dehydriding rates by the formation of $Mg_2Ni$. Expansion and contraction of the hydride-forming materials (Mg and $Mg_2Ni$) with the hydriding and dehydriding reactions are also considered to increase the hydriding and dehydriding rates of the mixture by forming defects and cracks leading to the fragmentation of particles. The reactive mechanical grinding of Mg-Ni alloy with $Fe_2O_3$ is considered to decrease the particle size.

• Journal of Nutrition and Health
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• v.35 no.4
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• pp.439-445
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• 2002

This study was undertaken to investigate the inhibitory effect of prunus fume extracts on the growth of Hep G2 and HeLa cells. Prunus mums was extracted using the following solvents hexane, chloroform, ethylacetate, methanol, and hot water. The effect on the growth of each cancer cell line was examined by MTT (3-[4, 5-dimethylthiaeol-2-yl)-2,5-diphenyl tetrazolium bromide) assay, cytotoxicity testing, and microscopic observation. The ethylacetate extracts of Prunus muse at the concentration of 250 $\mu\textrm{g}$/ml exhibited the greatest inhibitory effect on the growth of Hep G2 in the MW assay. In cytotoxicity testing, the treatment of the Hep G2 cells with ethylacetate extracts (1000 $\mu\textrm{g}$/ml for 72 hrs) destroyed 75% of the cells, and morphological changes were also observed. futhermore, the hexane extracts of Prunes muse at the concentration of 250 $\mu\textrm{g}$/ml exhibited the greatest inhibitory effect on the growth of HeLa cells in the MTT assay. The treatment of the HeLa cells with the hexane extracts (1000 $\mu\textrm{g}$/ml for 72 hrs) resulted in the destruction of 68% of the cells. Fibroblasts were not affected by either ethylacetate or hexane extracts of prunus muse.

• Korean Journal of Materials Research
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• v.23 no.10
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• pp.562-567
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• 2013

A 90 wt% Mg-10 wt% $NbF_5$ sample was prepared by mechanical milling under $H_2$ (reactive mechanical grinding). Its hydriding and dehydriding properties were then examined. Activation of the 90 wt% Mg-10 wt% $NbF_5$ sample was not required. At n=1, the sample absorbed 3.11 wt% H for 2.5 min, 3.55 wt% H for 5 min, 3.86 wt% H for 10 min, and 4.23 wt% H for 30 min at 593K under 12 bar $H_2$. At n=1, the sample desorbed 0.17 wt% H for 5 min, 0.74 wt% H for 10 min, 2.03 wt% H for 30 min, and 2.81 wt% H for 60 min at 593K under 1.0 bar $H_2$. The XRD pattern of the 90 wt% Mg-10 wt% $NbF_5$ after reactive mechanical grinding showed Mg, ${\beta}-MgH_2$ and small amounts of ${\gamma}-MgH_2$, $NbH_2$, $MgF_2$ and $NbF_3$. The XRD pattern of the 90 wt% Mg-10 wt% $NbF_5$ dehydrided at n=3 revealed Mg, ${\beta}-MgH_2$, a small amount of MgO and very small amounts of $MgH_2$ and $NbH_2$. The 90 wt% Mg-10 wt% $NbF_5$ had a higher initial hydriding rate and a larger quantity of hydrogen absorbed for 60 min than the 90 wt% Mg-10 wt% MnO and the 90 wt% Mg-10 wt% $Fe_2O_3$, which were reported to have quite high hydriding rates and/or dehydriding rates. The 90 wt% Mg-10 wt% $NbF_5$ had a higher initial dehydriding rate (after an incubation period) and a larger quantity of hydrogen desorbed for 60 min than the 90 wt% Mg-10 wt% MnO and the 90 wt% Mg-10 wt% $Fe_2O_3$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.6
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• pp.1634-1647
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• 2007

"To invest or not to invest?" Most business leaders are frequently faced with this question on new and ongoing projects. The challenge lies in deciding what projects to choose, expand, contract, defer, or abandon. The project valuation tools used in this process are vital to making the right decisions. Traditional tools such as discounted cash flow (DCF)/net present value (NPV) assume a "fixed" path ahead, but real world projects face uncertainties, forcing us to change the path often. Comparing to other traditional valuation methods, the real options approach captures the flexibility inherent to investment decisions. The use of real options has gained wide acceptance among practitioners in a number of several industries during the last few decades. Even though the options are present in all types of business decisions, it is still not considered as a proper method of valuation in some industries. Mining has been comparably slow to adopt new valuation techniques over the years. The reason fur this is not entirely clear. One possible reason is the level and types of risks in mining. Not only are these risks high, but they are also more numerous and involve natural risks compared with other industries. That is why the purpose of this study is to deal with a more practical approach to project valuation, known as real options analysis in mining industry. This paper provides a case study approach to the copper mining industry using a real options analysis. It shows how companies can minimize investment risks, exercise flexibility in decision making and maximize returns.