• Journal of the Korean Ceramic Society
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• v.38 no.11
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• pp.1030-1036
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• 2001

Hydroxyapatite[COL] nanocomposite was prepared through coprecipitation process. The chemical bond formation between HAP and COL was confirmed by diffusive reflectance FT-IR and TEM observation. Higher concentration of COL in the preparation induced tiny nanocrystalline composite particles, but lower concentration of COL contributed to form the well developed HAP particles. From TEM observation and ED(Electron Diffraction) pattern the embedded HAP nanoparticles were oriented along the c-axis of COL fiber. In an aqueous system of constant [Ca$\^$2+/] and [PO$_4$$\^$3-/], quantity of soluble COL matrix was doing an important role of controlling the heterogeneous nucleation site for the formation of HAP nanocrystals. Higher concentration of COL will provide more nucleation sites for Ca$\^$2+/ and so the concentration of calcium ions for the total number of active nucleation sites will be getting relatively dilute.

• Applied Microscopy
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• v.28 no.2
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• pp.193-205
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• 1998

The Urechis unicinctus sperm and spermatogenic cells prepared from the testis are investigated to identify $\alpha-tubulin$ of axoneme microtubules using mouse monoclonal $anti-\alpha-tubulin$ as the first Ab and Gold(10nm) conjugated goat anti-mouse IgG as the Ab marker. The Ag-Ab reaction analyzed excellently the localization of $\alpha-tubulin$ and the gold particles incorporated with the proximal and distal centrioles, manchette microtubules, and flagellum. The gold particles can be also observed in the spermatogenic cells while the cells are still in sperm ball which is composed of a somatic cell and spermatogenic cells. The sperm ball is the functional unit of sperm production in U unicinctus testis. The spermatids are developed from the spermatogenic cells in the sperm ball and released into the testis cavity through a cortical cytoplasmic opening. The spermatid architectures are similar with the mature sperm of the testis cavity in aspects of shape of discoid acrosome, degree of nuclear condensation and ring type of mitochondrion. However, the distal centriole connecting with the flagella can be observed from the mature sperm while the both proximal and distal centrioles reveal only in the spermatids. The proximal centriole is directly connected with nuclear outer membrane during the stage of nuclear condensation and oriented perpendicularly to the distal centriole whose axis coinciding with the longitudinal axis of the spermatozoon. There are indications that the distal centriole is intimately associated with the polymerization of the flagellum. The manchette microtubules appear during spermatid development but the mature sperm have round head and no conspicuous middle piece.

• Journal of the Korean Wood Science and Technology
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• v.14 no.1
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• pp.3-44
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• 1986

In order to obtain the basic physical and mechanical properties of steel wire reinforced particleboard, particleboards were formed with large particles through 2.11 mm (12 meshes) and retained on 1.27mm (20 meshes) sieves and small particles through 1.27mm (20 meshes) and retained on 0.42mm (60 meshes) sieves from the plywood mill wastes of meranti (Shorea spp.) in the form of pallmanchips, applying urea-formaldehyde resin as an adhesive on the particle surface in 10 percent on the oven dried weight of particles, and arranging steel wires of 1mm in diameter 5,10,15,20, and 25mm in longitudinal and transverse direction with crossing in the mid of the board depth in single layer boards, 10mm in longitudinal or transverse direction without crossing in two layers and 10mm in longitudinal and transverse directions with and without crossing in three steel wire layers boards. The stepwise 9-minutes-multi-pressing schedule in 5 minutes at 35 kgf/$cm^2$, 2.5 minutes at 25 kgf/$cm^2$. and 1.5 minutes at 15 kgf/$cm^2$ was applied for $300{\times}200{\times}13$mm board at the temperature of 160$^{\circ}C$ in a hot press. Specific gravity, thickness swelling, bending properties of modulus of rupture (MOR), modulus of elasticity(MOE), work to proportional limit, and work to ultimate load, internal bond (IB), and screw holding power(SHP) of the reinforced boards were analyzed on the wire openings and wire layers. The results obtained are summarized as follows; 1) In specific gravity, particleboards with large particles and small particles had higher value with more steel wire placements and more steel layers composition, 2) Particleboards with large particles in accordance with more steel wire liners composition gave very poor thickness swelling. 3) The mechanical properties of particleboards formed with large or small particles were reinforced with more steel wire layers. Therefore, bending strength was improved in modulus of rupture, modulus of elasticity, and work to ultimate load. Especiallv, particleboards with two or three steel wire layers showed the tension lamination effect when the steels in lower steel wire layer were oriented parallel to the board length. 4) The modulus of rupture, modulus of elasticity, and work to ultimate load in bending varied with opening area, distance of lengthwise wires multipled by distance of transverse wires. Particleboards formed with large particles resulted in higher value in modulus of rupture with 1.5-3 $cm^2$ opening area, 1-2cm distance between transverse wires, and 1.5-2.5cm distance between lengthwise wires. Particle boards formed with small particles showed higher value with 0.5-1.5$cm^2$ or 3.75-6.25 $cm^2$ opening area, 0.5 or 2.5cm distance between transverse wires. 5) In modulus of elasticity, particleboards formed with large particles with one steel wire layer suggested higher value with 5-3$cm^2$ opening area, 1-2.5cm distance between transverse wires and also 1-2.5 cm distance between lengthwise wires. Particleboards formed with small particles showed higher value with 0.75-1.25$cm^2$ or 3-6.25$cm^2$ opening area and 0.5 or 2.5cm distance between transverse wires. 6) Particleboards formed with large particles gaved higher value in work to ultimate load with 1-3$cm^2$ opening area. Particleboards formed with small particles showed increasing tendancy with decreasing opening area. 7) In internal bond and screw holding power, particleboards formed with large particles had increasing value in two and three steel wire layers compositions, but particleboards formed with small particles showed no difference. Particleboards formed with large particles containing one steel wire layer showed no difference in internal bond and screw holding power, and particleboards formed with small panicles containing one steel wire layer resulted in increasing value in internal bond and decreasing value in screw holding power in accordance with increase in opening area.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.469-474
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• 2003

Talus topography is that rock clasts that is weathered is accumulated dropping in steep slope to action of gravity. Rock fall talus is formed by the accumulation of rock debris falling as individual particles from a cliff. If the collapse is produced in talus slope, it will be possible the loss of manpower and country. Despite correct access about talus is required, domestic research was scientific access about talus short. The aim of the present study is to review and compare fabric data derived from rock fall talus about orientation, distribution and morphology in Sukam area. These deposits tend to have approximately equal amounts of clasts oriented parallel and perpendicular to the dip direction of the slope. And, platy-shaped clasts dominate the proximal and intermediate parts of the talus, whereas blocky-shaped clasts is more common in the distal part.

• Journal of the Korean Ceramic Society
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• v.34 no.3
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• pp.296-302
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• 1997

The effect of cold cyclic compaction on densification of SiC whisker/Al2O3 composite was investigated. Re-lative density of the compact increased as the number of cycle and the compaction pressure increased and the bias pressure decreased. The rate of loading and unloading and the frequency of cold cyclic compaction did not affect much on sliding and rearrangement of the particles. Fracture of SiC whisker was hardly ob-served during cold cyclic compaction and the direction of whisker was randomly oriented throughout the compact regardless of the direction of compaction. Thus, cold cyclic compaction may be an efficient method to densify SiC whisker/Al2O3 composite.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.12
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• pp.2550-2555
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• 2002

Hybrid composites usually are defined as composites having different types of reinforcements such as fibers and particles. The major advantage of hybrid composites is able to control the material properties such as optical, electrical, and mechanical properties. For this reason, hybrid composites are widely used in automotive, marine, household, and electrical industries. The objective of this work was to investigate processing characteristics in the compression molding of hybrid thermoplastic composites. The mechanical properties of composites manufactured in various forming conditions were monitored. The composites contained randomly oriented long carbon fiber and carbon black in polypropylene(PP) matrix were used. The carbon fiber contents of composites were 5%, 10%, 15%, and 20%, and carbon black contents were 5%, 10%, 15%, 20%, and 25% by weight. Compression molding was conducted at various mold temperatures. Crstallinity was also measured by using X-RD. The tensile modulus of the composites increased with increasing the mold temperature. However, the impact strength of the composites decreased as the mold temperature increased.

• Proceedings of the Korean Magnestics Society Conference
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• 2003.06a
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• pp.21-21
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• 2003

Microstructure and magnetic transport phenomina in rf sputtered AlN/Co type ten-layered discontinuous films of nanoscaled [AlN (3 nm)/Co (t nm)]...$\sub$10/ with t$\sub$Co/=1.0∼2.0 nm have been investigated. The microstructure and tunneling magnetic resistance of the samples are strongly dependent on the thickness of Co layer. Negative tunneling magneto-resistance due to the spin-dependent transport has been observed along the current-in-plane configuration in the samples having the Co layers below 1.6 nm thick. When the thickness of Co layer was less than 1,2 nm, randomly oriented granular Co particles were completely isolated and embedded in amorphous AlN matrix, and the films showed the superparamagnetic behavior with a high MR value of Δ$\rho$/$\rho$$\sub$0/=1.8 %. As t$\sub$Co/ increases, a transition from the regime of co-existence of superparamagnetic and ferromagnetic behaviors to ferromagnetic behavior was observed. Tunneling barrier called "decay length for tunneling" for the films having the thickness of Co layer from 1.4 to 1.6 nm was measured to be ranged from 0.004 to 0.021 ${\AA}$$\^$-1/.

• Journal of the Korean Applied Science and Technology
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• v.26 no.3
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• pp.288-296
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• 2009

In this study, the silica-based hybrid material with high barrier property was prepared by incorporating ethylene-vinyl alcohol (EVOH) copolymer, which has been utilized as packaging materials due to its superior gas permeation resistance, during sol-gel process. In preparation of this EVOH/$SiO_2$ hybrid coating materials, the (3-glycidoxy-propyl)-trimethoxysilane (GPTMS) as a silane coupling agent was employed to promote interfacial adhesion between organic and inorganic phases. As confirmed from FT-IR analysis, the physical interaction between two phases was improved due to the increased hydrogen bonding, resulting in homogeneous microstructure with dispersion of nano-sized silica particles. However, depending on the range of content of added silane coupling agent (GPTMS), micro-phase separated microstructure in the hybrid could be observed due to insufficient interfacial attraction or possibility of polymerization reaction of epoxide ring in GPTMS. The oxygen barrier property of the mono-layer coated BOPP (biaxially oriented polypropylene) film was examined for the hybrids containing various GPTMS contents. Consequently, it is revealed that GPTMS should be used in an optimum level of content to produce the high barrier EVOH/$SiO_2$ hybrid material with an improved optical transparency and homogeneous phase morphology.

• Journal of Magnetics
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• v.8 no.2
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• pp.98-102
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• 2003

Microstructure and magnetic transport phenomina in rf sputtered AIN/CO type ten- layered discontinuous films of nanoscaled [AIN(3 nm)/Co(t nm)]…$_10$ with t$_Co$=1.0∼2.0 nm have been investigated. The microstructure and tunneling magnetic resistance of the samples are strongly dependent on the thickness of Co layer, Negative tunneling magneto-resistance due to the spin-dependent transport has been observed along the current-in-plane configuration in the samples having the Co layers below 1.6 nm thick. When the thickness of Co layer was less than 1.2 nm, randomly oriented granular Co particles were completely isolated and embedded in amorphous AIN matrix, and the films showed the superparamagnetic behavior with a high MR value of ${\Delta}p/p_0$=1.8%. As t$_Co$ increases, a transition from the regime of co-existence of superparamagnetic and ferromagnetic behaviors to ferromagnetic behavior was observed. funneling barrier called “decay length far tunneling” fur the films haying the thickness of Co layer from 1.4 to 1.6 nm was measured to be ranged from 0.004 to 0.021 ${\AA}$$^{-1}$.

• Journal of Magnetics
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• v.1 no.1
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• pp.46-50
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• 1996

Highly oriented ${BaFe_{12}{O_{19}$ films were obtained by a KrF excimer laser ablation technique using (110)$(012){Al_2}{O_3}$(001)$(012){Al_2}{O_3}$ and $(012){Al_2}{O_3}$ substrates, respectively.The degree of alignment of more than 95% were achieved for (100) on (110)$(012){Al_2}{O_3}$ and (001)$(001){Al_2}{O_3}$ planes, and heteroepitaxial films of (114) on (012)$(012){Al_2}{O_3}$were possible to be grown with a lasing energy density of 6.67 J/$cm^2$ at an oxygen partial pressure ${PO_2}$ of 900 mTorr. The best magnetic properties were obtained from the as-deposited films at the substrate temperature of $700^{\circ}C$, and post annealing treatment was not needed to enhance the magnetic properties. Experimentally saturated magnetization ($4_pi M_S$) of 3600~3800 Gauss and coercivities $(H_c)$ of 3050~3080 Oe, which approach 85% of those of Ba-ferrite bulk composed of single domain particles, were obtained in this study.