• Journal of ILASS-Korea
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• v.5 no.4
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• pp.33-39
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• 2000

The behavior of the 2-stage spray was studied by using the schlieren method with the high pressure common-rail injection system. The spray injected 2 times with the interval of $0.3ms{\sim}1.5ms$ between the 1st and the 2nd spray in a modeled combustion chamber of constant volume bomb. In this case, the quantity of injected fuel of 1st and 2nd also changed. The schlieren photograph shows that the 2nd spray goes further away than the 1st spray when the quantity of the 1st spray is less than that of the 2nd spray. The dispersion of the vapour to the combustion chamber is not affect in a 10% of 1st spray quantity. When the 1st spray quantity is more than the 2nd spray, the vapour scattering of spray is good.

• Journal of the Korean Ceramic Society
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• v.30 no.5
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• pp.339-346
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• 1993

Inproving laser efficiency, optimum content of Nd3+ which is active ion and effect of Cr3+ as a sensitizer are investigated in 60SiO2.30Li2O.10CaO host glass. The glasses are fabricated with the addition of Nd3+, Cr3+ and then optical properties such as absorption spectrum, fluorescence spectrum and fluorescence lifetime were studied. Finally, lasing efficiency was measured. From this study, optimum content of Nd2O3 appeared to be 3.5wt% and it was observed that the energy absorbed by optical exicitation of the Cr3+ is transfered to the Nd3+. Addition of Cr2O3 tend to improve characteristic of laser oscillation for the laser glass.

• Korean Journal of Optics and Photonics
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• v.16 no.5
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• pp.456-461
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• 2005

We numerically investigate the characteristic of single Nd:YAG rod laser with the convex-plane resonator configuration in order to get the best condition for high efficient intra-cavity second harmonic generation(SHG). The beam quality is analyzed with ABCD matrixes including the thermal lensing characteristic of Nd:YAG rod. The analysis is focused on stability, M2, beam waist and mode-volume of laser beam inside the resonator. The best conditions for SHG is obtained when a laser rod is set near the curved laser mirror.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.4
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• pp.655-659
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• 1998

The effect of quenching speed of melt-spinning on intrinsic coercivity ($_iH_c$$) of annealed ribbons and the crystallization behavior from amorphous $Nd_{14.73}Fe_{78.67}B_{6.60}$ alloy have been studied. We have found that the intrinsic coecivity for annealed melt-spun ribbon is reduced with increasing of quenching rate. $\alpha$-Fe and $Fe_3B$ were formed as intermediate phases prior to the formation of $Nd_2Fe_{14}B$ phase during crystallization. The $Fe_3B$ is disappeared with crystallization of $Nd_2Fe_{14}B$ phase. But the $\alpha$-Fe phase is retained in fully crystallized ribbon by annealing. The intrinsic coercivity loss of annealed ribbon with increasing of quenching speed is believed to be due to existence of soft magnetic phase $\alpha$-Fe in annealed ribbons.

• Korean Journal of Crystallography
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• v.9 no.1
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• pp.48-52
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• 1998

The new Nd3Ba5Co4O15 phase was synthesized with Nd2O3, BaCO3, and Co3O4 by solid state reaction at 1200℃ with intermittent grinding. The crystal structure of Nd3Ba5Co4O15 has been refined on X-ray diffraction powder data by means of Rietveld method. The starting model was based on the Nd3.43Ba4.42Co2.23Al1.77O15 structure. The crystal system was hexagonal, space group P63mc(186), a=11.629(3) Å, c=6.842(2) Å. Final R values were Rwp=0.097 and Rp=0.068. The structure consists of clusters of CoVICoIV3O15 in which a CoVI octahedron shares corners with 3CoIV tetrahedra.

• Korean Journal of Optics and Photonics
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• v.10 no.4
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• pp.318-322
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• 1999

Perdeuterated hexaflouroacetylacetonato-neodymium [$Nd(HFA-D)_3$] complexes were synthesized by the keto-enol tautomerism reaction of $Nd(HFA-D)_3$ in methanol-d$_4$ in order to reduce the radiationless transition to the ligands. The emission properties of $Nd(HFA-D)_3$ complex were measured in the following anhydrous deuterated organic solvents; $Methanol-d_4$, $Aceton-d_6$, $THE-d_8$ and $DMSO-d_6$, and these properties depended on the coordination ability of solvent molecules. The intensity and lifetime of the emission in dimethysulfoxide (DMSO-$d_6$) were superior to those in other in other deuterated solvents. It was suggested that the anhydrous $DMSO-d_6$might be the most appropriate solvent for the liquid laser material of $Nd(HFA-D)_3$ complex.

• KOREAN POULTRY JOURNAL
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• v.38 no.2 s.436
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• pp.84-87
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• 2006

최근 문제가 되고 있는 ND가 현재의 양상으로 발생하기 시작한 것은 벌써 8년여가 된다. 필자가 양계전문병원을 시작할 무렵이 ND가 서서히 전국적으로 확산되던 시기이니, 대략 그 정도가 지난 것으로 보인다. 물론 지역별로 분석을 해보면 서해안쪽과 호남지역은 부분적으로 5~6년 정도 ND로 인한 피해를 경험한 지역도 있다. ND가 본격적으로 발병하기 시작할 무렵에는 많은 사람들이 유행적인 발병, 다시 말하면 일정기간 폭발적으로 발병하다가 없어질 질병으로 예상하였지만, 예상은 여지없이 빗나가고 오랜기간을 농가에 지속적으로 피해를 입히는 질병으로 남아 있다. 본소에서 질병관리를 하는 농장들에 대해 2000년도부터 ND를 혈청학적으로 집중 모니터링하기 시작했다. 본소가 출입하는 모든 농장들의 전 계군에 대해 일정간격으로 질병발생 여부에 상관없이 혈청모니터링을 실시하다보니 농장별 ND발생의 특징과 매년 ND가 발생하는 동향에 약간의 변화들을 감지할수 있었다. 그 대표적인 발생 동향으로 첫째 산란을 시작하기 전 높은 면역을 부여해주지못한 계군에서 산란급상승 기간 중에 ND발생으로 인한 피해를 들 수 있으며, 둘째는 주로 동절기에만 발생하던 ND가 이제는 1년 내내 발생하는 양상으로 바뀌어 온 것 등 두 가지 동향에 대해 분석을 해보기로 한다. ND의 발생동향 분석이 ND예방에 어떻게 참고가 될 것인지는 그것을 정확히 인식하기 위한노력을 기울이는 농장들과 발생동향에 따른 대책을 적극 수행하는 농장들에 달려있다. ND발생시 피해의 정도를 결정하는 것은 여러가지이다. 계군의 면역상태와 고른 면역 정도, 영양상태, 환경조건, ND바이러스의 병원성 정도 등 여러 조건에 따라 ND에 의한 피해 정도가 결정된다. 이러한 조건 중 어느 하나도 중요하지 않은 것은 없으며 이것들은 ND로 인한 피해정도를 결정하는 중요한 요소들이다.

• Journal of the Korean Ceramic Society
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• v.33 no.12
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• pp.1311-1318
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• 1996

• Journal of Powder Materials
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• v.18 no.1
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• pp.18-23
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• 2011

Sintered Nd-Fe-B magnets are widely used in many fields such as motors, generators, actuators, microwaves and so on due to their excellent magnetic properties. Many researchers have shown that the Nd-rich phase was essentially important for high magnet properties. In this study, we focused on controlling of the Nd-rich phase to enhance magnetic properties by the cyclic sintering process. Nd-Fe-B based sintered magnets were prepared by isothermal sintering and cyclic sintering processes. Magnetic properties and microstructure of the magnets were investigated. The coercivity was enhanced from 21.2 kOe to 23.27 kOe after 10 cycles of the sintering. The Nd-rich phase was effectively penetrated into the grain boundary between the $Nd_2Fe_{14}B$ grains by the cyclic sintering.

• Journal of Magnetics
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• v.7 no.4
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• pp.143-146
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• 2002

Mechanical milling technique is considered to be a useful way of processing the fine Nd-Fe-B-type powder with high coercivity. In the present study, phase evolution of the $Nd_{15}(Fe_{1-x}Co_{x})_{77}B_{8}$ (x=0-0.6) alloys during the high energy mechanical milling and annealing was investigated. The effect of Co-substitution on the crystallization of the mechanically milled $Nd_{15}(Fe_{1-x}Co_{x})_{77}B_{8}$ amorphous material was examined. The Nd-Fe-B-type alloys can be amorphized completely by a high-energy mechanical milling. On annealing of the amorphous material, fine $\alpha$-Fe crystallites form first from the amorphous. These fine $\alpha$-Fe crystallites reacts with the remaining amorphous afterwards, leading to crystallization to $Nd_2Fe_{14}$B phase. The Co-substitution for Fe in $Nd_{15}(Fe_{1-x}Co_{x})_{77}B_{8}$ ($\mu$x=0∼0.6) alloys lower significantly the crystallization temperature of the amorphous phase to the $Nd_2Fe_{14}$B phase. The mechanically milled and annealed $Nd_{15}Fe_{77}B_8$ alloy without Co-substitution exhibits consistently better magnetic properties with respect to the alloys with Co-substitution.