• Proceedings of the Korean Vacuum Society Conference
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• 1995.06a
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• pp.158-158
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• 1995

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.1
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• pp.456-461
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• 2012

The glycerol carbonate was synthesized by glycerol and urea using metal oxide catalysts. The physical properties of the prepared metal oxide catalysts were investigated by X-ray diffraction (XRD), specific surface area analysis (BET), field emission scanning electron microscopy (FE-SEM) and temperature programmed desorption (TPD). In addition, we confirmed the conversion of the glycerol and the yield of the glycerol carbonate according to characteristics of metal oxide catalysts. From XRD and FE-SEM analysis, the crystallite size and crystallinity of metal oxide catalysts decrease with addition of Al. In addition, the Zn-Al mixed metal oxide had higher catalytic activity than the pure ZnO due to decreased side reaction in the synthesis of glycerol carbonate.

• Journal of Powder Materials
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• v.10 no.1
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• pp.6-14
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• 2003

The purpose of the present study is to investigate the method decreasing debinding time as well as lowering operation condition than pure supercritical $CO_2$ debinding by using cosolvent or binary mixture of propane + $CO_2$. First method is to add cosolvent, such as n-hexane, DCM, methanol, 1-butanol, in supercritical $CO_2$. In case of adding cosolvent, we were found the addition of non-polar cosolvent (n-hexane) improves dramatically the binder removal rate (more than 2 times) compared with pure supercritical $CO_2$ debinding, second method is to use mixture of supercritical propane + $CO_2$, as solvent. In case of using mixture of supercritical propane + $CO_2$, the rate of debinding speeded up with increasing of pressure and concentration of propane at 348.15 K. It was found that addition of cosolvent (e.g., n-hexane, DCM) and binary mixture propane + $CO_2$ for supercritical solvent remarkably improved binder removal rate for the paraffin wax-based binder system, in comparison with using pure supercritical $CO_2$.

• Journal of Soil and Groundwater Environment
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• v.18 no.4
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• pp.32-39
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• 2013

This research focused on the effects of heavy metals on the biomonitoring activity of genetically engineered bioluminescent bacteria, Pseudomonas putida mt-2 KG1206. KG1206 was exposed to single or binary mixtures of different heavy metals as well as soils contaminated with heavy metals. In case of single exposure with different inducer pollutant, the toxicity order was as followings : As(III) > Cd, As(V) >> Cu, Cr(VI). The toxic effects of the binary mixtures was compared to the expected effect based on a simple theory of probabilities. The interactive effects were mostly additive, while in few cases antgonistic and synergistic mode of action was observed for some concentration combinations. No considerable correlation was found between the total metal contents in soils and the bioluminescence activity of each sample. However, statistically significant differences (p = 0.0102) were observed between two groups, classified based on arsenite contamination. These results demonstrate the usage of recombinant bioluminescent microorganism in biomonitoring and the complex interactive effects of metals.

• Journal of the Korean Vacuum Society
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• v.4 no.S2
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• pp.148-155
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• 1995

(1) The metastable crystalline(MX) phases formed by ion mixing are classified into 5 types, i.e. the super-saturated solid solutions and the enlarged HCP-I phases reported earlier, and the newly observed FCC-I phases in hcp-based alloys, The FCC-ll and HCP-ll phases in bcc-based alloys. The growth kinetics of the MX phases is discussed. (2) The interfacial free energy in the multilayered films was found to play an important role in ion beam mixing(IM) induced amorphization. By adding sufficient interfaces, amorphous alloys were obtained even in the systems with rather positive heat of formation. (3) Gibbs free energy diagrams of some representative systems were constructed, by calculating the free energy curves of all the competing phases. Steady-state thermal annealing was conducted and the results confirmed the relevance of the constructed diagrams, which were inturn employed to interpret the MX phase formation as well as the glass forming ability upon IM in the binary metal systems.

• Journal of Welding and Joining
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• v.23 no.6
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• pp.43-48
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• 2005

This work was carried out to obtain sound welds and to select a most suitable binary metal joint among three different dissimilar binary metal combinations such as Zr-4/Ta, Mo/Ta and Ti/Ta(seal tube/sensor sheath) joints fur the instrumented nuclear fuel irradiation test. To do this, Taguchi experimental method was employed to optimize the experimental data. In addition, metallography, micro-focus x-ray radiography and hardness test were conducted to examine the welds. From the weld bead appearance, penetration depth and bead width as well as weld defects standpoint, Zr-4/Ta joint is suggested for the circumferential joining between a seal tube and a sensor sheath. The optimized welding parameters based on Zr-4/Ta joint are suggested as well.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.9
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• pp.685-691
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• 2003

This work describes a 3 V 12b 100 MS/s CMOS digital-to-analog converter (DAC) for high-speed communication system applications. The proposed DAC is composed of a unit current-cell matrix for 8 MSBs and a binary-weighted array for 4 LSBs, considering linearity, power consumption, chip area, and glitch energy. The low-glitch switch driving circuit is employed to improve the linearity and the dynamic performance. Current sources of the DAC are laid out separately from the current-cell switch matrix core. The prototype DAC is implemented in a 0.35 urn n-well single-poly quad-metal CMOS technology. The measured DNL and INL of the prototype DAC are within $\pm$0.75 LSB and $\pm$1.73 LSB, respectively, and the spurious-free dynamic range (SFDR) is 64 dB at 100 MS/s with a 10 MHz input sinewave. The DAC dissipates 91 mW at 3 V and occupies the active die area of 2.2 mm ${\times}$ 2.0 mm.

• Journal of Welding and Joining
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• v.17 no.4
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• pp.60-68
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• 1999

The previously developed two dimensional model was modified in order to predict more accurately the degree of microsegregation and eutectic fraction on in weld metal whose solidification rate is very fast. The model employed the same assumptions with previous model but considered of a tip undercooling. The previously predicted microsegregation and eutectic fraction has the discrepancies between simulated and examined results in the weld metal solidification. The experiments for the weld metal solidification of 2024 A1 and Fe-Ni alloy were carried out in order to examine the reasonability and feasibility of this modified model. The concentration profile of the solute and eutectic fraction predicted by the simulation agreed well with those found from experimental works. According to the results, it was believed that the dendrite tip undercooling considered in the modified model be reasonable for predicting the degree of microsegregation more accurately in weld metla solidification. In the GTA welds, degree of dendrite-tip undercooling increases with increasing solidification rage(welding speed). This serves to increase the concentration of dendrite core and thus result in reducing the degree of segregation. And solid state diffusion(back diffusion) during solidification is very low in the weld metal solidification so that little additional homogenization of solute occurs during solidification. With consideration of tip undercooling this modified model can predict exactly degree of microsegregation and eutectic fraction from slow solidification(casting) to fast solidification(welding).

• Journal of Soil and Groundwater Environment
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• v.13 no.1
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• pp.101-109
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• 2008

The adsorption characteristics of cationic metals such as copper, cadmium, and lead onto the amorphous aluminum oxide, AMA-L, which was mineralized from raw sanding powder at $550^{\circ}C$ were investigated. Additionally, surface complexation reaction of cationic heavy metals onto AMA-L was simulated with MINEQL + software employing a diffuse layer model. From the batch adsorption tests in a single element system, the adsorption affinity of each metal ion onto AMA-L was following order: lead > copper > cadmium. In a binary system composed with copper and cadmium, quite a similar adsorption affinity was observed in each metal ion compared to the single element system. When the surface complexation constants obtained in the single system were used in the prediction of experimental adsorption results, model predictions were well fitted with experimental results of both single and binary systems.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.4
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• pp.552-560
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• 1997

Analysis is performed to determine the optimal lengths or cross-sectional areas of refrigerator-cooled current leads that can be applied to the conduction-cooled superconducting systems. The binary current lead is composed of the series combination of a normal metal at the upper(warm) part and a high $T_c$ superconductor(HTS) at the lower(cold) part. The heat conduction toward the cold end of HTS part constitutes a major refrigeration load. In addition, the joint between the parts should be cooled by a refrigerator in order to reduce the load at the low end and maintain the HTS part in a superconducting state. The sum of the work inputs required for the two refrigeration loads needs to be minimized for an optimal operation. In this design, three simple models that depict the refrigeration performance as functions of cooling temperature are developed based on some of the existing refrigerators. By solving one-dimensional conduction equation that take into account the temperature-dependent properties of the materials, the refrigeration works are numerically calculated for various values of the joint temperature and the sizes of two parts. The results show that for given size of HTS, there exist the optimal values for the joint temperature and the size of the normal metal. It is also found that the refrigeration work decreases as the length of HTS increases and that the optimal size of normal metal is quite independent of the size of HTS. For a given length of HTS, there is an optimal cross-sectional area and it increases as the length increases. The dependence of the optimal sizes on the refrigerator models employed are presented for 1kA leads.