• Analytical Science and Technology
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• v.8 no.1
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• pp.1-7
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• 1995

Spectrophotometric determination of U(VI) and Th(IV) by Flow injection method is described. Chrome Azurol S forms water soluble complexes with U(VI) and Th(IV) in the presence of cethyltrimethylammonium bromide. The maximum adsorption of U(VI) and Th(IV) complexes are at 600nm with molar absorptivity of $2.3{\times}10^5Lmol^{-1}cm^{-1}$ and 611nm with molar absorptivity of $3.8{\times}10^5Lmol^{-1}cm^{-1}$ in acetate buffer medium having pH 5.0 and 5.5. The calibration curves of U(VI) and Th(IV) are linear over the range of 0.1~0.8ppm and the correlation coefficients are ca. 0.9960 and 0.9930 respectively. The detection limits(S/N) are 20ppb for U(VI) and 15ppb for Th(IV). The relative standard deviation are ${\pm}1.8%$ for U(VI) and ${\pm}2.1%$ for Th(IV). The sample throughput was ca. $50hr^{-1}$.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.108-108
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• 2009

Precipitation hardening nickel base alloys strengthened by intermetallic compounds are extensively used to manufacture on the components of the hot section of gas turbine engines. To ensure structural stability and maintenance of strength properties for a long time, nickel alloys are normally subjected to complex alloying with elements to form ${\gamma}'$(gamma prime). Such alloys have a limited weldability, are normally welded in high temperature. However, laser welding have a merit that applies in room temperature as easy control of welding parameter and heat input. In this study, $CO_2$ laser welding is applied on STS304 plate with good ductility and precipitation hardening nickel base alloy (GTD111DS) used blade material. Also, several welding parameters are applied on powder, power and travel speed. There are no cracks in Rene 80 and IN 625 powder when STS304 plate is used. But IN 625 powder has no cracks and Rene 80 have some cracks in welds with GTD111DS substrate. Adjusting of welding parameter is tried to apply Rene 80 having a good strength compare to IN 625. In the result of adjusted welding parameter, optimized welding parameters are set with low power, low feed rate and high welding speed. Tensile strength of GTD111DS substrate with Rene 80 powder is same and over than the one of base metal in room temp and high temp($760^{\circ}C$).

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.2
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• pp.144-154
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• 1999

Masan Bay is highly polluted by the discharge of large quantities of effluents from the industrial complex and domestic sewage of Masan City, Southeast Korea. Surface sediments from 9 stations were used for geochemical and foraminiferal analyses in order to investigate foraminiferal response to sedimentary pollution in the Bay. The heavy metal concentrations in sediments are relatively higher than those in Kyeonggi Bay and Daesan area, west coastal region of Korea. Zn, Cd, Pb, and As are more concentrated than in world average shale, indicating that the municipal and industrial effluents cause sediment contamination. Responses of benthic foraminifera to the sedimentary pollution effect document a degree of pollution in Masan Bay. The species number and diversity in Masan Bay had lower values than those in Gadeog Channel. In Masan Bay, agglutinated foraminifera are abundant and calcareous foraminiferal tests were frequently pyritized. Eggerella advena and Trochammina pacifica dominated at levels of pollution and could be opportunistic species. These data will provide a baseline for future assessments of environmental quality in Masan Bay.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.72-72
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• 2012

Lithium rechargeable batteries have been widely used as key power sources for portable devices for the last couple of decades. Their high energy density and power have allowed the proliferation of ever more complex portable devices such as cellular phones, laptops and PDA's. For larger scale applications, such as batteries in plug-in hybrid electric vehicles (PHEV) or power tools, higher standards of the battery, especially in term of the rate (power) capability and energy density, are required. In PHEV, the materials in the rechargeable battery must be able to charge and discharge (power capability) with sufficient speed to take advantage of regenerative braking and give the desirable power to accelerate the car. The driving mileage of the electric car is simply a function of the energy density of the batteries. Since the successful launch of recent Ni-MH (Nickel Metal Hydride)-based HEVs (Hybrid Electric Vehicles) in the market, there has been intense demand for the high power-capable Li battery with higher energy density and reduced cost to make HEV vehicles more efficient and reduce emissions. However, current Li rechargeable battery technology has to improve significantly to meet the requirements for HEV applications not to mention PHEV. In an effort to design and develop an advanced electrode material with high power and energy for Li rechargeable batteries, we approached to this in two different length scales - Atomic and Nano engineering of materials. In the atomic design of electrode materials, we have combined theoretical investigation using ab initio calculations with experimental realization. Based on fundamental understanding on Li diffusion, polaronic conduction, operating potential, electronic structure and atomic bonding nature of electrode materials by theoretical calculations, we could identify and define the problems of existing electrode materials, suggest possible strategy and experimentally improve the electrochemical property. This approach often leads to a design of completely new compounds with new crystal structures. In this seminar, I will talk about two examples of electrode material study under this approach; $LiNi_{0.5}Mn_{0.5}O_2$ based layered materials and olivine based multi-component systems. In the other scale of approach; nano engineering; the morphology of electrode materials are controlled in nano scales to explore new electrochemical properties arising from the limited length scales and nano scale electrode architecture. Power, energy and cycle stability are demonstrated to be sensitively affected by electrode architecture in nano scales. This part of story will be only given summarized in the talk.

• Applied Biological Chemistry
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• v.34 no.1
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• pp.54-60
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• 1991

Serratia marcescens CK-3, decomposing chitin which is a mar component of cell wall in phyitopathogenic fungi, was isolated from the continuous cropping rhizosphere of pepper and cucumber and its enzymatic property was examined. S. marcescens CK-3 was found tn have an tagonistic effects against, Fusarium axysporum and Rhizoctonia solani and to have complex enzyme system such as chitinase, laminarinase, and proteinase. The preferable composition of the medium for production of chitinase was fond and was as follows : colloidal chitin 1.5%, tryptone 0.5%, glucose 1.0%, peptone 0.2%, $MgSO_4{\cdot}7H_2O\;0.1%,\;K_2HPO_4\;0.1%,\;and\;NaCl\;0.1%$(w/v), pH 6.8. The maximum enzyme production was observed after culture of 72 hours at $30^{\circ}C$ using a medium containing the above chemical composition. The optimal pH and temperature for in vitro activity of chitinase from S. marcescens CK-3 were pH 7.5 and $50^{\circ}C$, respectively. The enzyme activity in-creased by metal ions such as$Ag^+$ and $Mn^{++}$.

• Journal of the Korean Chemical Society
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• v.33 no.5
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• pp.516-521
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• 1989

Reaction between the $N_2O_2-type$ tetradentate ligand, ethylenediamine-N,N'-di-S-${\alpha}$-isobutylacetic acid (SS-emiba) and $RhCl_3{\cdot}3H_2O$ has yielded ${\Delta}-s-cis-\;and\;{\wedge}-uns-cis-[Rh(SS-eniba)Cl_2]-$. ${\Delta}-s-cis-[Rh(SS-eniba)Cl_2]^-$ has been utilized to react with S-methyl-L-cystcine(Smc) to give ${\Delta}-s-cis-[Rh(SS-eniba(Smc)]^+$. The oxidation of ${\Delta}-s-cis-[Rh(SS-eniba(Smc)]^+$ using $H_2O_2$ has produced ${\Delta}-s-cis-[Rh(SS-eniba)(Smc-o)]^+$, in which the coordinated sulfur has been converted into the sulfoxide group. In a separate series of experiments the S-methyl-L-cysteine is oxidized by $H_2O_2$ to give S-methyl-L-cysteine sulfoxide, which is then coordinated to ${\Delta}-s-cis-[Rh(SS-eniba)Cl2]^-$ to make the standard complet of ${\Delta}-s-cis-[Rh(SS-eniba)(Sme-o)]+$ for comparison with the complex obtained from the oxidation of ${\Delta}-s-cis-[Rh(SS-eniba)(Smc)]^+\;by\;H_2O_2.$

• Journal of the Korean Chemical Society
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• v.36 no.4
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• pp.540-545
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• 1992

Kinetics and mechanism on the solvent extraction of nickel(Ⅱ) with 8-hydroxyquinoline (HOx) was studied spectrophotometrically. Absorbance variation was measured by changing the 8-hydroxyquinoline concentration in the chloroform organic phase and the pH values in the aquous phase. By analyzing absorbance data the reaction rate was found to be the first order for 8-hydroxyquinoline concentration and the inverse first one for [H$^+$]. Therefore the rate determining step of the extraction reaction is the formation of the one-to-one metal chelate NiOx$^+$ and the rate equation is as follows; -d[Ni$^{2+}$]/dt = k[Ni$^{2+}$][Ox$^-$] = k'[Ni$^{2+}$][HOx]$_0$/[H$^+$]. The value of k' was evaluated from the slope of plot of log [Ni$^{2+}$]$_0$/[Ni$^{2+}$]$_t$ versus time and the rate constant k was calculated according to the equation k' = k ${\times}$ K$_{HOx}$ / K$_{D,HOx}$. From the temperature dependence of the extraction rate, the activation energy E$_a$ = 6.26 kcal/mol is calculated, and activation parameters, ${\Delta}$G$^{\neq}_{298}$ = 6.59 kcal/mol, ${\Delta}$H$^{\neq}_{298}$ = 5.68 kcal/mol, ${\Delta}$S$^{\neq}_{298}$ = -3.09 eu/mol are estimated.

• Journal of the Korean Chemical Society
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• v.27 no.2
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• pp.83-94
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• 1983

The effects of cis and trans configurations of ligands for $[M(II)O_3N_3]$ and $[Ni(II) O_2N_4]$ type complexes [M(II) = Co(III), Ni(II) and Cu(II)] on the calculated dipole moments have been investigated, adpoting the eigenvectors of EHT calculation. The calculated dipole moments for cis complexes are higher than those of trans complexes. The calculated dipole moments for the octahedral trans $[Co(III)O_3N_3]$ type complex fall in the range of experimental values. However the calculated dipole moments for cis $[Ni(II) O_2N_4]$ type complexes fall in the range of the experimental values. These results predicts the trans structure for $[Co(III)O_3N_3]$ and $[Ni(II) O_2N_4]$ type complexes. Those structures are in agreement with the experimental one (Three bidentate (O-N) ligands in $[M(II)O_3N_3]$ type complexes coordinate to the metal ion and two tridentate (O-N-N) ligands in [Ni(II)O2N4] type complexes coordinate to Ni(II) ion).

• Journal of Conservation Science
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• v.28 no.1
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• pp.53-62
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• 2012

The archival objects are tangible evidence related to the public service. They are unique and offer information representing the specific events, time or person. The archival objects as modern cultural heritage do not have the guideline to classify, manage and conserve them. Especially, it is difficult to apply general conservation process for burial artifacts, because there are few study example of conservation for metal archival objects and they have complex administrative value. We tried to find suitable material and application method for consolidation of copper alloy archival object. We choose three kinds of wax and acrylic resin for burial artifacts and had done comparative analysis of their characterizations following kinds and coating methods. As a result of evaluation by several surface analysis such as optical microscope, measuring film thickness, adhesive strength, contact angle and yellowing test, acrylic resin can use to archival objects of copper alloy, effectively but the method of heating after dip-coating with Wax B used before can get best effect of consolidation.

• Journal of Conservation Science
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• v.32 no.4
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• pp.491-500
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• 2016

Fog is atmospheric in which tiny drops of water vapor are suspended in the air near the ground. Its form, occurrence, etc., change according to the temperature, relative humidity, wind and geographical features of the space around it. In particular, fog tends to occur near a source of water because of temperature and relative humidity difference. These days, climate change is increasingly affecting the occurrence of fog. Therefore the purpose of this study was to investigate how fog affects materials that are part of our cultural properties through outdoor exposure tests and artificial degradation. The degradation evaluation of materials as a function of fog occurrence frequency, showed that the color of metals changed noticeably, whereas dyed silk and Dancheong showed degradation on the surface and color differences but no particular tendencies. Therefore, damage prediction by color differences as a function of fog occurrence frequency was based on metal samples, which showed constant color differences. Through a comparison of the predictive value and color difference by outdoor exposure, the accuracy and applicability of the damage prediction formula was confirmed. If a more complex damage prediction formula is created, it is expected that prediction of the degree of material damage in the field would be possible.