• Korean Journal of Materials Research
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• v.27 no.10
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• pp.557-562
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• 2017

The microstructural evolution and modulation of mechanical properties were investigated for a $Ti_{65}Fe_{35}$ hypereutectic alloy by addition of $Bi_{53}In_{47}$ eutectic alloys. The microstructure of these alloys changed with the additional BiIn elements from a typical dendrite-eutectic composite to a bimodal eutectic structure with primary dendrite phases. In particular, the primary dendrite phase changed from a TiFe intermetallic compound into a ${\beta}$-Ti solid solution despite their higher Fe content. Compressive tests at room temperature demonstrated that the yield strength slightly decreased but the plasticity evidently increased with an increasing Bi-In content, which led to the formation of a bimodal eutectic structure (${\beta}$-Ti/TiFe + ${\beta}$-Ti/BiIn containing phase). Furthermore, the (Ti65Fe35)95(Bi53In47)5 alloy exhibited optimized mechanical properties with high strength (1319MPa) and reasonable plasticity (14.2 %). The results of this study indicate that the transition of the eutectic structure, the type of primary phases and the supersaturation in the ${\beta}$-Ti phase are crucial factors for controlling the mechanical properties of the ultrafine dendrite-eutectic composites.

• Korean Journal of Materials Research
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• v.5 no.6
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• pp.748-753
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• 1995

Solid solution of NaNb $O_3$70 mol% and SrTi $O_3$30 mol% was single phase. A broad dielectric peak was found at about l00K. Crystal structure was analysed at room temperature and 12K using Rietveld analysis. The unit cell was assigned to have a a doubled lattice parameter of simple perovskite sturcture at room temperatue, the structure was orthorombic with space group Pmmn. At 12K, the structure was also orthorombic with space group Pnma. This structure change with temperature was due to the distortion of oxygen octahedron. This distortion of oxygen octahedron was made by the decrease of (Ti, Nb)-O bounds length with no variation of (Ti, Nb)-O-(Ti, Nb) bound angle. Therefore the broad dielectirc peak about l00K was attributed to the structural change casued by oxygen octahedron distortion.

• Journal of Sensor Science and Technology
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• v.11 no.6
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• pp.319-326
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• 2002

$SrCl_2:Eu^{2+}$ phosphors were prepared by the solid phase reaction method, and their photostimulated luminescence(PSL) and photoluminescence(PL) characteristics were investigated. The PSL and PL peak of the $SrCl_2:Eu^{2+}$ phosphors are due to the $5d{\rightarrow}4f$ transition of $Eu^{2+}$ ions in phosphors. The PSL and PL spectrum obtained by the 355nm excitation was observed in $380{\sim}440\;nm$ region with the peak at 407 nm. The dose response of the PSL phosphors were linear within $2.5\;mGy{\sim}200\;mGy$ of 100 kV X-ray. The fading of the phosphors at room temperature was approximately 60% after 20 min.

• Korean Journal of Animal Reproduction
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• v.7 no.2
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• pp.57-71
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• 1983

1. Diluted chicken semen can be preserved at 2 to 5$^{\circ}C$ for 24 to 48 hr with resultant fertility of greater than 90% of that of fresh semen. Turkey semen can be preserved at 10 to 15$^{\circ}C$ for 6 to 24 hr and provide economical fertility. 2. Frozen chicken semen has given variable results; a 21 to 93% fertility ranges as compared to 92 to 94% expected with fresh semen. Highest fertility levels obtained with frozen turkey semen intravaginally inseminated have been 61 and 63% using DMSO and glycerol, respectively, as cryoprotectants. 3. The use of glycerol as a cryoprotectant reauires that its concentration in semen be reduced to less than 2% either by dialysis or centrifugation after thawing and before intravaginal insemination if optimal fertility is to be obtained. 4. The temperature at which cryoprotectants are added to semen and the time allowed for equilibration are important for subsequent fertility pre- and post-freezing. 5. The type of container used for packaging the semen, freeze or cooling rates, thaw rates and level of cryoprotectant all interact in affecting cell survival. 6. Plastic freeze straws as a packaging device for semen offers the following advantages: easy to handle, require minimal storage space, offer a wide range of freeze and thaw rates, and insemination can be made directly from them upon thawing. 7. Controlled slow cooling rates of 1 to 8$^{\circ}C$/min have thus far provided the best results for cooling chicken semen throught the transition phase change (liquid to solid) or critical temperature range of ＋5 to -20 or -35$^{\circ}C$. 8. Highest fertilities have been achieved with frozen chicken semen where a slow thaw rate (2。 to 5$^{\circ}C$) has been used regardless of the freeze rate. 9. To maintain a constant high level of fertility throughout a breeding season with frozen semen, a higher absolute number of spermatozoa must be inseminated (2 to 3 times as many) as compared to fresh semen since a, pp.oximately 50% are destroyed during processing and freezing. 10. The quality of semen may vary with season and age of the male. Such changes in sperm quality could be accentuated by storage effects. Thus, the correct number of spermatozoa may very well vary during the course of a breeding period. 11. As to time of insemination, it is best to avoid inseminating chicken hens within 1-2 hr after or 3-5 hr before oviposition; and turkey hens during or 7-10 hr before oviposition. 12. The physiological receptiveness of the oviduct at the time of insemination is a very important biological factor influencing fertility levels throughout the breeding season.

• Elastomers and Composites
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• v.39 no.3
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• pp.217-227
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• 2004

A new thermotropic liquid crystalline polymer(TLCP) containing a triad aromatic ester type mesogenic unit and butylene terephthalate unit(BT) in the main chain was synthesized by polycondensation reaction. The TLCP synthesized showed nematic mesophasic behavior and its transition temperature from solid to mesophase was $260^{\circ}C$. The TLCP/PBT blends were prepared by in-situ polymerization in PBT solution and characterized by differential scanning calorimeter(DSC), thermogavimetric analyzer(TGA), scanning electron microscope(SEM), x-ray diffractometer(XRD), and dynamic mechanical thermal analyze, (DMTA). The blends showed well dispersed TLCP phases with domain sizes $0.05{\sim}0.2{\mu}m$ in the PBT matrix. As the increasing TLCP content from 5 to 20 wt%, ${\Delta}Hm$ values of pure PBT in the blend were increased because TLCP acts as a nucleating agent in the PBT matrix. The mechanical properties of the blends depended on the TLCP contents because the TLCP acted effectively as a reinforcing material in the PBT matrix. The blends showed good interfacial adhesion between the TLCP phase and PBT matrix.The blends prepared by in-situ polymerization showed higher mechanical properties and well dispersed TLCP domains than those of the blends prepared by melt blending.

• Journal of the Korean Society of Radiology
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• v.15 no.3
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• pp.391-399
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• 2021

Eu²⁺ doped polyphosphate NaSr(PO₃)₃ blue-emitting phosphors were synthesized by the conventional solid state method in a reductive atmosphere. The phase formation of NaSr(PO₃)₃ phosphors were characterized by using the X-ray powder diffraction (XRD) measurement. The photoluminescence emission and excitation spectra of the NaSr(PO₃)₃:Eu²⁺ phosphor, and decay curves were measured. Under the near-UV excitation, the phosphor exhibits a band emission around 420 nm assigned to the 4f⁶5d→f7(8S^7/2) transition of Eu²⁺. The temperature dependent emission spectra and decay curves were measured to elevate the thermal properties of the Eu²⁺ doped phosphors. The as-prepared NaSr(PO₃)₃:Eu²⁺ phosphors show a strong temperature dependent performance, which can serve as a promising temperature sensor.