• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.583-584
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• 2015

In this paper, the numerical results concerning different orbits of a 3D axisymmetric non-rotating galactic potential are presented. We use $Paczy{\acute{n}}ski^{\prime}s$ gravitational potential with different birth velocity distributions for the isolated old Neutron Star (NS) population. We note some smooth non-constant segments corresponding to regular orbits as well as the characterization of their chaoticity. This is strongly related to the effect of different kick velocities due to supernovae mass-loss and natal kicks to the newly-formed NS. We further confirm that the dynamical motion of the isolated old NSs in the gravitational field becomes obvious, with some significant diffraction in the symmetry of their orbital characteristics.

• Journal of Powder Materials
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• v.10 no.4
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• pp.288-293
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• 2003

Mechanical alloying (MA) by high energy ball mill of Pure chromium Powders was carried out under the nitrogen gas atmosphere. Cr-N amorphous alloy powders have been produced through the solid-gas reaction subjected to MA. The atomic structure during amorphization process was observed by X-ray and neutron diffractions. An advantage of the neutron diffraction technique allows us to observe the local atomic structure surrounding a nitrogen atom. The coordination number of metal atoms around a N atom turns out to be 5.5 atoms. This implies that a nitrogen atom is located at both of centers of the tetrahedron and octahedron formed by metal atoms to stabilize an amorphous Cr-N structure. Also, we have revealed that a Cr-N amorphous alloy may produced from a mixture of pure Cr and Cr nitrides powders by solid-solid reaction during mechanical alloying.

• Journal of the Korean earth science society
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• v.18 no.6
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• pp.553-558
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• 1997

Colorless and transparent cubic zirconia($Zr_{0.73}Y_{0.27}O_{1.87}$) crystal has been synthesized by the Bridgman-Stock-bager method(also called Skull melting method). $Y_2O_3$ is used as stabilizer. The crystal shows a vitreous luster with a slight oily appearance. Under a polarizing microscope, it shows isotropic nature with no appreciable anisotropism. Mohs hardness value is measured to be $8{\sim}8\frac{1}{2}$ and specific gravity 5.85. Under ultraviolet light it shows a faint white glow. The crystal structure of yttria stabilized zirconia was determined, using single crystal X-ray diffraction techniques to be a cubic symmetry, space group $Fm\overline{3}m({O^5}_h)$ with $a=5.1552(5){\AA}$, $V=136.99(5){\AA}^3$, Z=4, and R=0.0488 for 29 unique reflections. Each zirconium atom is at the center of eight oxygen atoms situated at the corners of a surrounding cube and each oxygen atom is at the center of a tetrahedron of zirconium atoms. So a coordination of 8:4 holds in the structure.

• Journal of the Mineralogical Society of Korea
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• v.16 no.3
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• pp.215-222
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• 2003

The Rietveld structure refinement for the natural trioctahedral mica, phlogopite-1M (Parker Mine, Quebec, Canada) has been done by high resolution neutron powder diffraction at $25^{\circ}C$ and -263$^{\circ}C$. The structural formula of phlogopite determined by electron probe microanalysis is $K_2$(M $g_{4.46}$F $e_{0.83}$A $l_{0.34}$ $Ti_{0.22}$)(S $i_{5.51}$A $l_{2.49}$) $O_{20}$(O $H_{3.59}$ $F_{0.41}$). Cell parameters are a=5.30∼5.31 $\AA$, b=9.18∼9.20 $\AA$, c=10.18∼10.21 $\AA$, $\beta$=100.06∼100.08$^{\circ}$. Refinements converged to R values in the range of $R_{p}$=2.35%, $R_{wp}$=3.01%, respectively. In this study, the OH bond length is calculated to 0.93 $\AA$ at room temperature and 1.03 $\AA$ at -263$^{\circ}C$, and the angles between OH vector and (001) plane are obtained 93.4$^{\circ}$∼93.6$^{\circ}$. The decrease in the length of OH with the increase in temperature should be due to the hydrogen bonding in the structure of phogopite.e.e.f phogopite.e.e.

• Journal of the Korean Magnetics Society
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• v.16 no.6
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• pp.287-292
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• 2006

Al substituted $CoAl_{0.5}Fe_{1.5}O_{4}$ has been studied with x-ray and neutron diffraction, $M\"{o}ssbauer$ spectroscopy and magnetization measurements. $CoAl_{0.5}Fe_{1.5}O_{4}$ revealed a cubic spinel structure of ferrinmagnetic long range ordering at room temperature, with magnetic moments of $Fe^{3+}(A)(-2.29{\mu}_{B}),\;Fe^{3+}(B)(3.81\;{\mu}_{B}),\;Co^{2+}(B)(2.66{\mu}_{B})$, respectively. The temperature dependence of the magnetic hyperfine field in $^{57}Fe$ nuclei at the tetrahedral (A) and octahedral (B) sites was analyzed based on the $N\'{e}el$ theory of magnetism. In the sample of $CoAl_{0.5}Fe_{1.5}O_{4}$, the interaction A-B interaction and intrasublattice A-A superexchange interaction were antiferromagnetic with strengths of $J_{A-B}=-19.3{\pm}0.2k_{B}\;and\;J_{A-A}=-21.6{\pm}0.2k_{B}$, respectively, while the intrasublattice B-B superexchange interaction was found to be ferromagnetic with a strength of $J_{B-B}=3.8{\pm}0.2k_{B}$.

• Nuclear Engineering and Technology
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• v.6 no.4
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• pp.219-230
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• 1974

The previous expression for the diffracted neutron intensity by a highly oriented polycrystalline is modified using the Kunitomi's formula of the crystal reflectivity The method of studying the preferred orientation in metals with white neutron is proposed utilizing the above formula and the fact that the real position of the diffraction of certain grain in the sample can be found by the comparison of the smaller angle part of the maxwellian curve of the calculated intensity of neutrons diffracted and the experimenal curves. The most probable wavelength of thermal neutrons from the reactor is found by the measurement of the neutron spectrum with the correction for the crystal about the multiple reflection and the absorption of neutrons and turned out to be 1.025 $\pm$ 0.001$\AA$. The preferred orientations of some electric steel sheets, mostly with the cube-on-face orientations, are investigated by the present method. The orientations of most grains relative to the rolling directions are found to be within 5 degrees. It is found the most of theories for large crystals may be extended to highly oriented polycrystalline materials without extensive modification.

• Proceedings of the Korean Magnestics Society Conference
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• 2012.11a
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• pp.100-100
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• 2012

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2003.10a
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• pp.73-73
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• 2003

• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.106-107
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• 2002

상온 거대자기저항 물질로 많은 연구가 이루어지고 있는 double perovskite (A$_2$BB'O$_{6}$) 계 물질은 B-site의 전이금속 윈자 종류에 따라 다양한 특성이 나타나는 것으로 보고되고 있다$^{[1]-[4]}$ . 그 중 Sr$_2$FeMoO$_{6}$ 시료가 MR 특성 및 전자기적 특성이 가장 우수한 것으로 알려져 있으나, Figure 1에 보이는 것과 같이, Sr$_2$CrMoO$_{6}$ 시료가 가장 높은 전이온도를 갖음으로 훌륭한 소자로의 응용 가능성을 보이고 있다. (중략)

• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.110-111
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• 2002

최근 Y. Masumoto[1]등에 의하여 Co가 도핑된 anatase 구조의 TiO$_2$ 물질에서 상온 강자성 현상이 보고된 이후, 이에 대한 관심이 고조되면서 다른 연구 그룹들에 의해 실험적으로 상온 강자성을 성공하였다는 보고[2,3]가 있으나 현재 그 메커니즘에 대하여 명확한 해석이 되어있지 않고 있기 때문에 이것이 정말 자성반도체의 성질인지 아니면 clustering에 의한 것인지 아직 확실히 밝혀져 있지는 않다. (중략)