• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.880-894
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• 1995

Magnetic properties of $Nd_{x}{(Fe_{0.9}Co_{0.1})}_{90-x}B_{6}Nb_{3}Cu_{1}(x=\;3,\;4,\;5)$ rrelt-spun alloys with 6 at% B content were studied aiming for finding out a new $\alpha$-Fe based Nd-Fe-B nanocrystalline alloy with good hard magnetic properties. $Nd_{x}{(Fe_{0.9}Co_{0.1})}_{90-x}B_{6}Nb_{3}Cu_{1}$ melt-spun alloys prepared by RSP crystallized to nanocrystalline phase. An optimally annealed $Nd_{3}{(Fe_{0.9}Co_{0.1})}_{87}B_{6}Nb_{3}Cu_{1}$ melt-spun alloys had larger volume ratio of $\alpha$-Fe(Co) than that of higher Nd content alloy and showed high remanence of about 1.6 T. On the contrary, the increase of Nd content in $Nd_{x}{(Fe_{0.9}Co_{0.1})}_{90-x}B_{6}Nb_{3}Cu_{1}$ alloys gave rise to gradual increase of an amount of $Nd_{2}{(Fe,\;Co)}_{14}B$ phase and improved coercivity. An optimally annealed $Nd_{5}{(Fe_{0.9}Co_{0.1})}_{85}B_{6}Nb_{3}Cu_{1}$ alloy showed the most improved hard mag¬netic properties. The remanence, coercivityand energy product of the alloy were 1.35 T, 219 kA/m (2.75 kOe), and $129\;kJ/m^{3}$ (16.2 MGOe), respectively.

• Bulletin of the Korean Chemical Society
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• v.6 no.6
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• pp.344-347
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• 1985

Perovskite type oxides of $SrTiO_3,SrZrO_3,and\;SrTi_{1-x}Zr_xO_3$ have been systematically synthesized at $1250^{\circ}C$and $1550^{\circ}C$ with specimens containing additions of up to x=0.9 of zirconium by solid state reactions and characterized by X-ray diffraction. X-ray diffraction studies showed that the compound $SrTi_{1-x}Zr_xO_3$ has cubic structure. The lattice paramters of $SrTi_{1-x}Zr_xO_3$ solid solutions obey the Vegard's law and fairly large increase in volume can acompany the formation of this solution with increasing Zr content(X). Assuming the lattice constants of perovskite type compounds $A(B_{1-x}B'_x)O_3$where $B_{1-x}B'_x$ is $Ti_{1-x}Zr_x$, to be a linear function of the ionic radii of B and B' ions, the disordered ion pair of $Ti^{4+}$and $Zr^{4+}$ was verified from the lattice constants of a series compounds varying x=0,0.05, 0.25, 0.5, 0.75, 0.9, and 1.0 with known isovalent pairs.

• Electrical & Electronic Materials
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• v.10 no.6
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• pp.533-540
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• 1997

The microwave dielectric properties of ((P $b_{1-x}$ C $a_{x}$)Zr $O_3$ and (P $b_{0.63}$,C $a_{0.37-x}$ $M_{x}$)Zr $O_3$(M=Mg,Sr) ceramics were investigated. In (P $b_{1-x}$ C $a_{x}$)Zr $O_3$ (X=0.33~0.40) ceramics, high quality factor and small temperature coefficient of resonant frequency were obtain in (P $b_{0.63}$C $a_{0.37}$)Zr $O_3$with perovskite structure. In the case of (P $b_{0.63}$C $a_{0.37-x}$M $g_{x}$)Zr $O_3$ dielectric constant temperature coefficient of resonant frequency increased and quality factor decreased due to increase of polarization of A-O bonding. When replacing Ca ion with Sr ion with large ion radius, polarization decreased with increased of bonding length and thus dielectric constant and temperature coefficient of resonant frequency decreased.decreased.creased.

• Journal of the Korean Magnetics Society
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• v.9 no.3
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• pp.154-158
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• 1999

Magnetic properties and microstructure of nanocrystalline $\alpha$-(Fe, Co)-based Nd-(Fe, Co)-B-Nb-Cu alloys have been investigated. $Nd_x(Fe_{0.9}Co_{0.1})_{90-x}B_6Nb_3Cu_1$(x=2, 3, 4, 5, 6) alloys prepared by rapid solidification process show amorphous phase except the one with x=2. By a proper annealing, the amorphous in the alloy is changed to a nanocrystalline phase. It is confirmed that the nanocrystalline alloys are composed of $\alpha$-(Fe, Co) and $Nd_2(Fe, Co)_{14}B_1$ phase. The optimally annealed $Nd_3(Fe_{0.9}Co_{0.1})_87B_6Nb_3Cu_1$ alloy shows the highest remanence of 1.55 T. The coercivity increases with the increase of Nd content The maximum coercivity of 4.6 kOe is obtained from an optimally annealed $Nd_6(Fe_{0.9}Co_{0.1})_84B_6Nb_3Cu_1$ alloy, resulting in the maximum energy product of 10.6 MGOe.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.427-431
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• 1995

The influence of Nd and B contents on the magnetic properties and structures of ${\alpha}-Fe$ based Nd-(Fe,Co)-B-Mo-Cu alloys was investigated. $Nd_{4}{(Fe_{0.9}Co_{0.1})}_{92-x}B_{x}Mo_{3}Cu_{1}$ and $Nd_{x}{(Fe_{0.9}Co_{0.1})}_{86-x}B_{10}Mo_{3}Cu_{1}$ amorphous alloys prepared by rapid solidification process were crystallized to form nanocrystalline structure. The increase of B content in $Nd_{4}{(Fe_{0.9}Co_{0.1})}_{92-x}B_{x}Mo_{3}Cu_{1}$ nanocrystalline resulted in the change of stucture of soft phase in the sequence of ${\alpha}-Fe$->${\alpha}-Fe+Fe_{3}B$->$Fe_{3}B$. The coercivitis of the alloys were increased with increasing B content and was 263 kA/m at x=18. On the contrary, the remanence has shown an opposite trends. The increase of Nd content in $Nd_{x}{(Fe_{0.9}Co_{0.1})}_{86-x}B_{10}Mo_{3}Cu_{1}$ nanocrystalline containing ${\alpha}-Fe$ as main phase had no effect on the structure and improved coercivity up to 256 kA/m. However, the remanence was decreased from 1.4 T to 1.15 T according to the increase of Nd content.

• Journal of Environmental Health Sciences
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• v.36 no.4
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• pp.313-322
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• 2010

The aim of this research was to apply experimental design methodology to optimization of conditions of electrochemical oxidation of Rhodamine B (RhB) and N, N-Dimethyl-4-nitrosoaniline (RNO, indicative of the OH radical). The reactions of electrochemical oxidation of RhB degradation were mathematically described as a function of the parameters of current ($X_1$), NaCl dosage ($X_2$) and pH ($X_3$) and modeled by the use of the central composite design. The application of response surface methodology (RSM) yielded the following regression equation, which is an empirical relationship between the removal efficiency of RhB and RNO and test variables in a coded unit: RhB removal efficiency (%) = $94.21+7.02X_1+10.94X_2-16.06X_3+3.70X_1X_3+9.05X_2X_3-{3.46X_1}^2-{4.67X_2}^2-{7.09X_3}^2$; RNO removal efficiency (%) = $54.78+13.33X_1+14.93X_2- 16.90X_3$. The model predictions agreed well with the experimentally observed result. Graphical response surface and contour plots were used to locate the optimum point. The estimated ridge of maximum response and optimal conditions for the RhB degradation using canonical analysis was 100.0%(current, 0.80 A; NaCl dosage, 2.97% and pH 6.37).

• Journal of the Korean Mathematical Society
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• v.44 no.4
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• pp.787-797
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• 2007

In this paper, the following fourth-order rational difference equation $$x_{n+1}=\frac{{x_n^b}+x_n-2x_{n-3}^b+a}{{x_n^bx_{n-2}+x_{n-3}^b+a}$$, n=0, 1, 2,..., where a, b ${\in}$ [0, ${\infty}$) and the initial values $X_{-3},\;X_{-2},\;X_{-1},\;X_0\;{\in}\;(0,\;{\infty})$, is considered and the rule of its trajectory structure is described clearly out. Mainly, the lengths of positive and negative semicycles of its nontrivial solutions are found to occur periodically with prime period 15. The rule is $1^+,\;1^-,\;1^+,\;4^-,\;3^+,\;1^-,\;2^+,\;2^-$ in a period, by which the positive equilibrium point of the equation is verified to be globally asymptotically stable.

• Bulletin of the Korean Chemical Society
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• v.32 no.6
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• pp.2045-2050
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• 2011

Using first principles density functional theory the formation energies of various binary compounds of lithium graphite and its homologues were calculated. Lithium and graphite react to form $Li_1C_6$ (+141 mV) but not form $LiC_4$ (-143 mV), $LiC_3$ (-247 mV) and $LiC_2$ (-529 mV) because they are less stable than lithium metal itself. Properties of structure and reaction potentials of $C_5B$, $C_5N$ and $B_3N_3$ materials as iso-structural graphite were studied. Boron and nitrogen substituted graphite and boron-nitrogen material as a iso-electronic structured graphitic material have longer graphene layer spacing than that of graphite. The layer spacing of $Li_xC_6$, $Li_xC_5B$, $Li_xC_5N$ materials increased until to x=1, and then decreased until to x=2 and 3. Nevertheless $Li_xB_3N_3$ has opposite tendency of layer spacing variation. Among various lithium compositions of $Li_xC_5B$, $Li_xC_5N$ and $Li_xB_3N_3$, reaction potentials of $Li_xC_5B$ (x=1-3) and $Li_xC_5$ (x=1) from total energy analyses have positive values against lithium deposition.

• Journal of the Korean Mathematical Society
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• v.45 no.4
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• pp.993-1005
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• 2008

Let {$X,\;X_n;n{\geq}1$} be a sequence of i.i.d. random variables. Set $S_n=X_1+X_2+{\cdots}+X_n,\;M_n=\max_{k{\leq}n}|S_k|,\;n{\geq}1$. Then we obtain that for any -1$\lim\limits_{{\varepsilon}{\searrow}0}\;{\varepsilon}^{2b+2}\sum\limits_{n=1}^\infty\;{\frac {(log\;n)^b}{n^{3/2}}\;E\{M_n-{\varepsilon}{\sigma}\sqrt{n\;log\;n\}+=\frac{2\sigma}{(b+1)(2b+3)}\;E|N|^{2b+3}\sum\limits_{k=0}^\infty\;{\frac{(-1)^k}{(2k+1)^{2b+3}$ if and only if EX=0 and $EX^2={\sigma}^2<{\infty}$.

• Proceedings of the Korean Ceranic Society Conference
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• 2000.04a
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• pp.117.2-117.2
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• 2000