• Journal of Magnetics
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• v.7 no.4
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• pp.138-142
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• 2002

Magnetic properties, microstructure and texture of NdFeB magnets fabricated by a modified hot working process from commercial melt-spun powders (Magnequench; MQPA, MQPB and MQPB＋) have been investigated. The hot-pressed isotropic magnet made from MQPA powder, which contains higher Nd content than that of MQPB or MQPB＋, shows higher coercivity. The magnet also shows homogenous and fine grains with higher coercivity for higher consolidation pressure. The hot-deformed MQPA magnet shows a strong anisotropy along the press direction with homogeneous platelet Nd$_2$Fe$_{14}$B grains of 50∼100nm in thickness and 200∼500nm in length. The hot-deformed MQPB＋ magnet, however, shows low remanence and low coercivity. The microstructure of the magnet consists of two areas; undeformed Nd$_2$Fe$_{14}$B grains and well-aligned but large grains with 3∼4 $\mu$m in length. Low Nd content attributes to the formation of the two different area.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.130-131
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• 2005

In the era of submicron devices, super ultra thin gate oxide characteristics are required. Titanium silicide process has studied gate oxide reliability and dielectric strength characteristics as the composition of gate electrode. In this study the author observed process characteristics on MOS structure. In view point of the process characteristics of MOS capacitor, the oxygen & Ti, Si2 was analyzed by SIMS analysis on before and after annealing with 1,2 step silicidation, the Ti contents[Count/sec]of $9.5{\times}1018$ & $6.5{\times}1018$ on before and after 2'nd anneal. The oxygen contents[Count/sec] of $4.3{\times}104$ & $3.65{\times}104$, the Si contents[Count/sec] of $4.2{\times}104$ & $3.7{\times}104$ on before and after 2'nd anneal. The rms value[A] was 4.98, & 4.03 on before and after 2'nd anneal.

• Korean Chemical Engineering Research
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• v.60 no.2
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• pp.175-183
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• 2022

With the expansion of the automobile market, the demand for Nd as an essential rare earth material for automobile motors is rapidly increasing. Research on the calcio-thermic reduction process between Nd₂O₃ and calcium-based alloys has been extensively studied in order to manufacture Nd. In this study, Ca-Cu, as a reducing for Nd₂O₃, was prepared by electrolysis in CaCl₂ molten salt. Cu wire and graphite were employed as a working electrode and a counter electrode for electrolysis reaction, respectively. The reference electrode was manufactured by putting Ag wire in a mixture of AgCl and CaCl₂ at a ratio of 1:99 mol%. The cyclic voltammetry results showed that the deposition of Ca²⁺ on the surface of working electrode was observed from a potential of -1.8 V, and the reduction potential of Ca²⁺ decreased as the reaction temperature increased. The diffusion coefficient of Ca²⁺ calculated by the chronoamperometry experiment was found to be 5.4(±6.8)×10^-6 cm²/s. In addition, Ca-Cu liquid alloy was prepared by applying a constant potential to Cu electrodes. The element ratio of Ca-Cu alloy formed by applying a potential of -2.0 V was found to Ca:Cu=1:4.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1741-1744
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• 2005

The electron beam machining provides very high resolution up to nanometer scale, hence the E-Beam writing technology is rapidly growing in MEMS and nano-engineering areas. For E-Beam machining, $2^{nd}$ electron detector is required to see a machined sample at the stage. The $2^{nd}$ electron detector is composed of scintillator and photomultiplier with signal amplifier and high voltage power supplier. Since a photomultiplier tube is an extremely high-sensitivity photodetector, the signal light level to be detected is very low and therefore particular care must be exercised in shielding external light. In this paper, the design methodology of $2^{nd}$ electron detector and the image noise removal method are introduced.

• Journal of Welding and Joining
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• v.11 no.2
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• pp.42-52
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• 1993

The corrosion fatigue fracture behaviour of dual phase steel was investigated in 3% NaCl solution at 302MPa and 137MPa. Fatigue test was conducted by cantilever type of self-made rotary bending fatigue testing machine. The fatigue strength increased with increasing the hardness of 2nd phase. Corrosion pit originated at the boundary of the 2nd phase. The size and number of corrosion pits were influenced by the 2nd phase hardness, and pits remained constant in size just after they were transited into cracks. The life of crack initiation was effected by stress level. The shape of relation of .DELTA. K and da/dN has smaller scattering in it in 3% NaCl solution than that in air. The higher the 2nd phase hardness is, the greater the corrosion fatigue life becomes. Corrosion fatigue fracture behaviour was primarily effected by mechanical factor in case of high stress(302MPa), but by electro-chemical reaction in a lower stress(137MPa). As stress level got lower and hardness of the 2nd phase got higher, the roughness of fracture surface increased.

• Journal of Magnetics
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• v.9 no.2
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• pp.27-33
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• 2004

Magnetic properties of $Nd_4Fe_{77.5}B_{18.5}$ compound in term of exchange coupling between $Nd_2Fe_{14}B$ and $Fe_3B$ magnetic nano crystals in melt spun powders were characterized by varying the quenching speed in mass production line. The exchange coupled phenomenon was characterized as functions of nano crystal size and volume fraction of each magnetic phase which was possible by employing Henkel plot (${\delta}M$) and refined Mossbauer spectroscopy. The optimized magnetic properties obtained from the present volume production line were: $B_r= 11.73 kG,{_i}H_c/ = 3.082 kOe$, and $(BH)_{max} = 12.28 MGOe.$ The volume fraction of each magnetic phase for those conditions giving the grain size of 10 nm were ${\alpha}-Fe; 4.2%, Fe_3B; 60.1 %$, and $Nd_2Fe_{14}B; 35.7%$. The superior magnetic properties in the $Nd_2Fe_{14}Fe_3B$ based nanocomposites were confirmed to be dependant on the volume fraction of $Fe_3B$.

• Journal of The Korean Society of Grassland and Forage Science
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• v.9 no.1
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• pp.15-19
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• 1989

This experiment was carried out in order to know the changes in dry matter production of the 2nd cutting by the times of established pasture and its relation with morphological and structural characters of orchardgrass sward. Experimental pasture was established by the times of year, from 1 year to 7 year, 1986 through 1980, alternately. The results were summarizedas follows: 1. The population density of the 2nd cutting was extremely decreased by the times of established year. 2. The dry weight of $plantsW)$ was positively significant correlations with plant length(PL), number of tillers per plant (NT/pl.) and the dry weight of plant(DW/pl.). 3. The highest value of the dry weight of plants(DW) was obtained at 7 year old pasture. 4. The pasture productivity of 7 year old pasture was resulted by the increases of regrowth capacity, yield components and structural characters of the 2nd cutting. 5 . Relationship between morphological and structural characters concerned vegetational structure of the 2nd cutting were changeable year by year.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.312-316
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• 1999

I-V characteristics of Praseodymium-based ZnO varistor doped with $Nd_2O_3$ in the range 0.0-2.0mol% sintered at 130$0^{\circ}C$ and 135$0^{\circ}C$ were investigated. In the all sides, ZnO varistors sintered at $1300^{\circ}C$ exhibited much better varistor characteristics than that at 135$0^{\circ}C$. All ZnO varistors doped with $Nd_2O_3$ sintered at $1300^{\circ}C$ exhibited good varistor characteristics but particularly ZnO varistor doped with l.Omol% $Nd_2O_3$ exhibited the best characteristics, which the nonlinear is 65.2 and the leakage current is 4.5pA. It is estimated that ZnO varistor doped with l.Omol% $Nd_2O_3$ will begin to be sufficiently used as basic composition to fabricate a good varistor.

• Animal cells and systems
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• v.4 no.1
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• pp.31-37
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• 2000

The genetic variations among six species of Rana from Korea (R. nigro-maculata, R. piancyi, R. dybowskii, R. sp, R. rugosa type A, B and R. amurensis) were investigated using 499 bases of mitochondrial DNA sequences for ND2 (NADH dehydrogenase subunit 2) gene and $tRNA^{Trp}$ gene. Partial sequences of ND2 gene (427 bp) and full sequences of $tRNA^{Trp}$ gene (73 bp) were identified. The level of sequence divergences ranged from 0.2 to 5.2% within species and 4.9-28.0% among 6 species of the genus Rana. The $tRNA^{Trp}$ gene of the genus Rana was composed of 77 nucleotides which showed a two dimensional "cloverleaf" structure. The secondary structure of $tRNA^{Trp}$ was not found compensatory changes which could potentially confound phylogenetic inference. In the neighborjoining tree, brown frogs were clustered first with the level of sequence divergence of 13.20% between R. amurensis and R. dybowskii, and 9% between R. dybowskii and R. sp. supported by 99% bootstrap iterations, respectively. R. nigromaculata and R. plancyi were clustered into another group with 5.1% divergence supported by 100% bootstrap iteration. R. rugosa A 8nd B types were grouped by 4.9% divergence and clustered into the last group with other two groups with 100% bootstrap iterations.

• Journal of Animal Science and Technology
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• v.46 no.6
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• pp.903-908
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• 2004

Alternative initiation codon(AlC) has been reported in the mitochondrial genes in various mammalian species. We investigated the AlC of mitochondrial NADH dehydrogenase 2 gene(rntDNA ND2) in five pig breeds. Two kinds of initiation codons(ATA/ATf) showing different frequencies among tested pig breeds were used. While all Large White pigs had ATA as an initiator methionine codon, all Landrace pigs had ATf. The other breeds(Berkshire, Duroc and Hampshire) had both initiation codons with the ATA frequencies, 91.9, 21.3 and 60.00/0, respectively. In the previous reports, all Chinese indigenous pig breeds were identified to have unique initiation codon ATA. Although the effect of Ale on the translation of mtDNA ND2 has not been studied in this study, AlC patterns in mtDNA ND2 will contribute to the maternity test using molecular markers in pig breeding.