• Journal of the Korean Vacuum Society
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• v.13 no.4
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• pp.150-156
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• 2004

Boron nitride thin films were deposited on Si(100) substrate by RF (Radio-frequency) UBM (Unbalanced Magnetron) sputtering system. The effect of working pressure and substrate bias voltage on microstructure and compressive stress of boron nitride thin films has been investigated. In high working pressure, the alignment of hBN laminates increased with substrate bias voltage, in low working pressure, however, it was high in low substrate bias voltage. Compressive stress evolution and surface morphology of deposited BN films are closely related with the alignment of hBN laminates. The cBN phase without high compressive stress could be nucleated on hBN thin film by controlling the alignment of hBN laminates.

• Journal of Powder Materials
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• v.17 no.3
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• pp.190-196
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• 2010

In this paper, rapid solidified Mg-4.3Zn-0.7Y (at.%) alloy powders were prepared using an inert gas atomizer, followed by a severe plastic deformation technique of high pressure torsion (HPT) for consolidation of the powders. The gas atomized powders were almost spherical in shape, and grain size was as fine as less than $5\;{\mu}m$ due to rapid solidification. Plastic deformation responses during HPT were simulated using the finite element method, which shows in good agreement with the analytical solutions of a strain expression in torsion. Varying the HPT processing temperature from ambient to 473 K, the behavior of powder consolidation, matrix microstructural evolution and mechanical properties of the compacts was investigated. The gas atomized powders were deformed plastically as well as fully densified, resulting in effective grain size refinements and enhanced microhardness values.

• The Journal of the Petrological Society of Korea
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• v.5 no.2
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• pp.168-187
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• 1996

In the study area Uanggunbong-Samgunri area), Precambrian metamorphic complex, (Taebacksan gneiss complex, Hyundong gneiss complex, and Taebacksan schist complex) had undergone three different regional metamorphisms at least before Paleozoic. The Paleozoic sediments in the study area also had undergone three different metamorphisms at least. The first is low pressure type regional metamorphism, the second is low pressure type contact metamorphism due to the intrusion of Chunyang granite, and the last is medium pressure type metamorphism caused by thrust in south of Janggunbong area. The first metamorphism formed the prevailing metamorphic zones in the Paleozoic metasediments and the metamorphic grade of the first regional metamorphism increases from the chloritoid zone, through the staurolite zone, garnet zone, staurolite+biotite zone, and to the andalusite+biotite zone. The second metamorphism affected both Pre-Cambrian and Paleozoic metasediments located close to the Chunyang granite. The effect of the contact metamorphism is restricted to the very narrow zone around the granite. The third metamorphism that produced kyanite, is restricted to the very narrow region near the thrust fault in the south of Janggunbong with an E-W trend.

• Journal of Plant Biotechnology
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• v.49 no.1
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• pp.46-60
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• 2022

The genetic variability and population structure of apple mosaic virus (ApMV) have been studied; however, synonymous codon usage patterns influencing the survival rates and fitness of ApMV have not been reported. Based on phylogenetic analyses of 52 ApMV coat protein (CP) sequences obtained from apple, pear, and hazelnut, ApMV isolates were clustered into two groups. High molecular diversity in GII may indicate their recent expansion. A constant and conserved genomic composition of the CP sequences was inferred from the low codon usage bias. Nucleotide composition and relative synonymous codon usage (RSCU) analysis indicated that the ApMV CP gene is AU-rich, but G- and U-ending codons are favored while coding amino acids. This unequal use of nucleotides together with parity rule 2 and the effective number of codon (ENC) plots indicate that mutation pressure together with natural selection drives codon usage patterns in the CP gene. However, in this combination, selection pressure plays a more crucial role. Based on principal component analysis plots, ApMV seems to have originated from apple trees in Europe. However, according to the relative codon deoptimization index and codon adaptation index (CAI) analyses, ApMV exhibited the greatest fitness to hazelnut. As inferred from the results of the similarity index analysis, hazelnut has a major role in shaping ApMV RSCU patterns, which is consistent with the CAI analysis results. This study contributes to the understanding of plant virus evolution, reveals novel information about ApMV evolutionary fitness, and helps find better ApMV management strategies.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.62-65
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• 2008

Extrusion characteristics of Mg alloys were studied experimentally. The Al-Zn-Mg alloys, AZ31, AZ6l, AZ80, and AZ91 were extruded with hot hydrostatic extrusion process. The hydrostatic process was efficient to reduce surface friction and extend steady state region in extrusion which made it more convenient to examine deformation behavior of the alloys avoiding the disturbance caused by temporary contact state between billet and die, and billet and container. High pressure was cooperative to expand forming limit of the alloys which were applied on the billet during the extrusion process. Extrusion limits were traced in temperature and extrusion speed domain with changing composition of the alloying elements. Effects of process parameters on extrusion load and microstructure evolution were investigated also.

• Corrosion Science and Technology
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• v.7 no.2
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• pp.85-91
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• 2008

By operation in aqueous environment at high temperature and pressure, the structural materials from Primary Heat Transport System (PHTS) cover with protective oxide films, which maintain the corrosion rate in admissible limits. A lot of potential factors exist, which conduct to degradation of the protective films and consequently to intensification of the corrosion processes. The existing experience of different nuclear reactors shows that the water chemistry has an important role in integrity maintaining of the protective oxide films. To investigate the influence of water chemistry (pH, O2 dissolved, $Cl^-$, $F^-$) on corrosion of some structural materials (carbon and martensitic steel, Zr and Ni alloys) and to establish the maximum permissible values, corrosion experiments by static autoclaving and electrochemical methods were performed. The experimental results allowed us to establish the contribution of the water chemistry in initiation and evolution of some accelerated corrosion processes.

• Journal of the Korean Chemical Society
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• v.24 no.6
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• pp.463-468
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• 1980

Tris(hydroxyethyl) phosphate, ethylphosphoramidic dichloride, N,N-diethylphosphoramidic dichloride, bis(hydroxyethyl) N-ethylphosphoramidate and bis(hydroxyethyl) N,N-diethylphosphoramidate were synthesized and characterized. Phosphate and phosphoramidates were polymerized with the elimination of ethylene glycol when heated under reduced pressure and they gave no molecular ion peaks in their mass spectra. And also ethylphosphoramidic dichloride gave polymeric products at 180$^{\circ}C$ with the evolution of HCl. IR spectra showed characteristic P=O streching bands in the range of 1,300 to$ 1,200 cm^{-1}.$

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.207-210
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• 2002

Metal matrix composites(MMCs) are increasingly attractive for high technology components such as aerospace applications and transportations due to their high strength, stiffness, and toughness. Many processes for fabricating MMCs have been developed, and relatively simple Foil-Fiber-Foil method is usually employed in solid state consolidation processes. During the consolidation processes at high temperature, densification occurs by the inelastic flow of the matrix materials, and the process is coupled with the conditions of pressure, temperature and volume fraction of fiber and matrix materials. This is particularly important in titanium matrix composites, and thus a generic model based on micro-mechanical approaches enabling the evolution of density over time to be predicted has been developed. The mode developed is then implemented into FEM so that practical process simulation has been carried out. Further the experimental investigation of the consolidation behavior of SiC/Ti-6Al-4V composites using vacuum hot pressing has been performed, and the results obtained are compared with the model predictions.

• Journal of the Korean Ceramic Society
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• v.29 no.11
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• pp.877-887
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• 1992

Tetragonal zirconia powder with 3 mol% Y2O3 mas mixed with up to 30 vol% of ${\beta}$-SiC powders, and the mixtures were hot-pressed at 1500$^{\circ}C$ for 60 min under a pressure of 30 MPa in Ar atmosphere. Flexural strength and fracture toughness were measured at room-and high-temperature (1000$^{\circ}C$). Evolution of microstructure was also conducted to investigate the effects of SiC addition on the properties of 3Y-TZP ceramics. Average grain size of the composites was about 0.5 $\mu\textrm{m}$, and decreased with SiC addition. Both room- and high-temperature mechanical properties of the composites were improved with SiC content. Particularly, high-temperature strength and fracture toughness of 3Y-TZP/30v/o SiC composite were twice as high as those of 3Y-TZP. The hardness of the composites also increased with SiC content and reached maximum value at 3Y-TZP/30v/o SiC composite.

• Journal of the Korean Ceramic Society
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• v.41 no.8
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• pp.582-587
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• 2004

Biphasic Calcium Phosphate (BCP) consisted of hydroxyapatite (HAp) and $\beta$-tricalcium phosphate (P-TCP) has been prepared by solid state reaction. The size reduction of the resultant BCP agglomerate was carried out by reaction with hot water under atmospheric condition uld also under high pressure using an autoclave. The influence of processing conditions on the change of crystalline phase and composition, relative amount of constituent, specific surface area, and microstructure was investigated by means of XRD, FT-IR, BET method using a nitrogen adsorption and SEM.