• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.331-332
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• 2008

Couplings between electric, magnetic, and structural order parameters result in the so-called multiferroic phenomena with two or more ferroic phenomena such as ferroelectricity, ferromagnetism, or ferroelasticity. The simultaneous ferroelectricity and ferromagnetism (magnetoelectricity) permits potential applications in information storage, spintronics, and magnetic or electric field sensors. The perovskite BiFeO3(BFO) is known to be antiferromagnetic below the Neel temperature of 647K and ferroelectric with a high Curie temperature of 1043K. It exhibits weak magnetism at room temperature due to the residual moment from a canted spin structure. It is likely that non-stoichiometry and second-phase formation are the factors responsible for leakage current in BFO. It has been suggested that oxygen non-stoichiometry leads to valence fluctuations of Fe ions in BFO, resulting in high conductivity. To reduce the large leakage current of BFO, one attempt is to make donor-doped BFO compounds and thin films. In this study, (Bi1-x,Ndx)(Fe1-y,Tiy)O3 thin films have been deposited on Pt(111)/TiO2/SiO2/Si substrates by pulsed laser deposition. The effect of dopants on the phase evolution and surface morphology are analyzed. Furthermore, electrical and magnetic properties are measured and their coupling characteristics are discussed.

• Korean Journal of Materials Research
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• v.4 no.6
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• pp.626-637
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• 1994

The relationship between microstructures and tensile properties depending on various solution treatment temperature and cooling rate of Ti-6A1-4V alloy have been investigated. The complex and random edge shaped $\alpha$ phases were formed after the 1st solution treatment at $\beta$ region and the 2nd solution treatment at $900^{\circ}C$, which was followed by furnace cooled. When the specimen was subjected to the 2nd solution treated at $950^{\circ}C$, and furnace cooled, $\alpha$ phase changed its morphology to equiaxed structure. The aspect ratio showing the appreciation basis of microstructual refinement decreases with the temperature of 1st and 2nd solution treatment. The slightly decrease in strength were observed in the Widmanstltten structures than in the bimodal structures. Also, ductility of the Widmanstatten structures was considerable lower than that of bimodal structures. The tensile-fractured surface of the Widmanstatten structures appears to be quasi-cleavage and dimple fracture, while that of the bimodal structures was the type of ductile fracture. The tensile fracture surface of the bimodal structures can easily be separated into cental crack areas lying generally perpendicular to the tensile axis and shear lip areas lying at angles of high shear(around 45 deg.) to the tensile axis.

• Korean Journal of Food Science and Technology
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• v.31 no.4
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• pp.945-951
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• 1999

A simple and practical method for the determination of gardenia yellow in foods was developed. In this method, analysis of gardenia yellow in food products has been carried out by the detection of crocetin and/or geniposide as indicator compounds. As a new analytical method for gardenia yellow, we adopted crocetin, which is produced from colored components of gardenia yellow by alkaline hydrolysis, as an indicator compound. The analysis of gardenia yellow was performed by reverse phase high performance liquid chromatography using a Capcell pak $C_{18}$ column at wave length 240 nm (geniposide) and 435 nm (crocetin). The recovery rates of geniposide and crocetin were found to be 93.4% and 87.8% for Dan Mu Ji, 90.2% and 85.9% for milk, 92.8% and 86.5% for snack, respectively. With this method, the range of crocetin and geniposide contents $({\mu}g/g)$ were as follows: $ND{\sim}1.7$ and $ND{\sim}14.1$ for Dan Mu Ji, $ND{\sim}0.2$ and $ND{\sim}13.6$ for milk, $ND{\sim}1.6$ and $ND{\sim}0.9$ for snack, respectively. The detection limits of crocetin and geniposide were 0.07 ${\mu}g/g$ and 0.05 ${\mu}g/g$, respectively.

• Resources Recycling
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• v.29 no.1
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• pp.17-24
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• 2020

In this study, rare earth elements (REE) leaching from a refractory REE ore containing goethite as a major gangue mineral was conducted, introducing a two-stage method of chemical decomposition-acid leaching. At the chemical decomposition step, using one of alkaline agent, NaOH, the ore was decomposed, changing NaOH concentration from 20 to 50 wt% at 10% (w/w) of pulp density and the maximum temperature achieved without boiling at each NaOH concentration. With increasing NaOH concentration, light REE (Ce, La and Nd) and iron were concentrated in the solid phase which is the decomposed product, while aluminum (Al) and phosphorus (P) were removed to the liquid phase, and their concentrations in the solid phase were down to 0.96 and 0.17%, respectively. In addition, through XRD analysis, it was found that the crystallinity of goethite was considerably decreased. At the acid leaching step, the product decomposed by 50 wt% NaOH was leached at 3.0 M HCl and 80 ℃ for 3 hr, then the REE leaching efficiency was above 94% (Ce 80%), and the leaching efficiencies of Al and P were decreased to 12 and 0%, respectively. Therefore, in terms of both REE leaching efficiency and impurity removal, those decomposition and leaching conditions were chosen as optimum processing methods of the investigated material. In terms of REE leaching mechanism, because REE and iron leaching efficiencies showed the positive correlation each other, so it can be concluded that decreasing crystallinity of goethite affect the improvement of REE leaching.

• Clean Technology
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• v.28 no.2
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• pp.103-109
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• 2022

Nd-Fe-B waste permanent magnet contains about 20~30% rare earth elements and about 60~70% iron elements, and the rare earth and iron components were recovered through sulfuric acid leaching and fractional crystallization. Oxidation roasting was not performed for separation and recover of the rare earth and iron elements. The leaching characteristics were confirmed by using as variables the sulfuric acid concentration and the mineral solution concentration ratio. Sulfuric acid leaching was carried out for 3 hours for each sulfuric acid concentration. The leached solid phase was characterized for its crystalline phase, composition, and quantitative components by XRD and XRF analysis, and the filtrate was analyzed for components by ICP analysis. With sulfuric acid leaching at 3M sulfuric acid concentration, neodymium compounds were formed, the iron content was the least, and the recovery rate was high. After the filtrate remaining after sulfuric acid leaching was subjected to fractional crystallization through evaporation and concentration, the neodymium component was found to be concentrated 7.0 times and the iron component 2.8 times. In this study, the recovery rate of waste permanent magnets through sulfuric acid leaching and a fractional crystallization method without an oxidation and roasting process was confirmed to be about 99.4%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1991.10a
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• pp.37-39
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• 1991

This paper is studies the effects of additives on the magnetic properties of Sr-ferrite. The specimens have been composed of SrO and Fe$_2$O$_3$with ratio of 1:5.9. As 1st additives, it is mixed to 0.2wt%, 0.7wt% and 1wt% of CaCo$_3$with 0.3wt% SiO$_2$. As 2nd addition, it is mixed to 0.5wt%, 1wt% of Na$_2$SiO$_3$, 0.5wt%, 1wt% of Cr$_2$O$_3$and 0.5wt%, 1wt% of Al$_2$O$_3$and sintering conditions was carried out at 1210$^{\circ}C$, 1230$^{\circ}C$ and 1250$^{\circ}C$. From experiments on the magnetic properties of specimen, the results were shown follows; (1) In case of additive SiO$_2$and CaO, it is stable magnetoplumbite structure for liquid phase grown, enhances mignetic propertics. (2) In case of basic compositions + 0.5wt% Al$_2$O$_3$, it is confirmed better properties by increasing of the coercivity than 0.5wt% Cr$_2$O$_3$additives. (3) In case of mixed additives of Cr$_2$O$_3$and Al$_2$O$_3$, magnetic propeties decrease with sintering density.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1616-1623
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• 2011

The concrete track was applied for Gyungbu 2nd phase high_speed railroad line as a basic track structure. Two track structures, ballasted track and non_ballasted concrete track, have a different train load transfer mechanisms. However, it's rare to see about research results related with it. So, to understand dynamic response characteristics of the concrete track and roadbed, we measured accelerations of carbody and bogie, vertical and lateral load, stress and displacement of rail, and earth pressures of subgrade at ${\bigcirc}{\bigcirc}{\bigcirc}$k930 station of Gyungbu high_speed line during speed up tests before opening it. Based on these measured results, we could evaluate the level of dynamic responses of the track quantitatively.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.870-873
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• 1991

In this paper, We present demodulation and synchronization method of phase shift keying signal using Double Frequency Vector Technique for Reference Vector. 2nd Harmonic Vector for Reference Vector is utilized in discriminating between noise and carrier signal, and in producting correlation value for data bit logical level. And we applied this demodulator to Automatic Meter Reading System being communicated with electric distribution power lines.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.8
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• pp.62-68
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• 1998

Optical broadband second harmonic genration (SHG) in thin film waveguide structure was investigated. The copolymer poly(MMA-co-DR1MA) which was consiste dof PMMA (polymethylmethacrylate) and DR 1 (disperse red 1) was spin coated on the pyrex substrate. The green and near UV SHG were observe dfrom the fundamental beam even though the poled polymer has the absorption in second harmonic wavelength range. It was able to genrate SHG by cerenkov type phase matching. Th epoled polymer film thickness was decided by theoretical analysis. The green (532nm) and near UV SHG (370nm) were observed from the Q-switched Nd-YAG laser (1064nm) and Ti-sapphire laser (740nm). It was in good agreement with the experimental results.

• Journal of the Korea Institute of Military Science and Technology
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• v.19 no.4
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• pp.492-499
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• 2016

Null pattern synthesis method using the Quantum-inspired Evolutionary Algorithm(QEA) is described in this study. A $12{\times}12$ planar array antenna is considered and each element of the array antenna is controlled by 6-bit phase shifter. The maximum number of iteration of 500 is used in simulation and the rotation angle for updating Q-bit individuals is determined to make the individual converge to the best solution and is summarized in a look-up table. In this study we showed that QEA can satisfactorily synthesize the null pattern using smaller number of individuals compared with the conventional Genetic Algorithm.