• 한국자기학회지
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• 제5권1호
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• pp.34-37
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• 1995

단롤법 급속응고장치를 이용하여 비정질 $Nd_{x}Fe_{77}B_{23-x}(x=4,\;6,\;8,\;11,\;13)$ 합금을 제작하고 $650^{\circ}C$ 이상에서 결정화 시키어 자기적 특성을 조사하였다. 열처리 후의 결정상을 조사한 결 과 x=8 조성에서 준안정상 $Nd_{2}Fe_{23}B_{3}$가 단일상에 가깝게 생성되며 연자기특성을 나타냄 을 알았다. 자기특성 조사결과 $8{\leq}x{\leq}13$ 조성범위에서 Nd 함유량이 증가할수록 보자력은 증가하나 잔류자속밀도는 감소함을 알았다. 그러나, $4{\leq}x{\leq}6$ 합금의 경우 Nd 함유량이 감소할수록 보자 력과 잔류자속밀도가 함께 증가하였다. x=4 합금의 경우 연자성:경자성=70:30의 혼합조직이 얻어지며 $96kJ/m^{3}(12MGOe)$의 높은 에너지적을 나타냈다.

• 대한방사선기술학회지:방사선기술과학
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• 제22권2호
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• pp.33-39
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• 1999

This paper included a data analysis of the unit of medical devices using mainternance recording card that had medical devices of unit failure mode, hospital of failure mode and MTBF. The results of the analysis were as follows : 1. Medical devices of unit failure mode was the highest in QC/PM such A hospital as 33.9%, B hospital 30.9%, C hospital 30.3%, second degree was the Electrical and Electronic failure such A hospital as 23.5%, B hospital 25.3%, C hospital 28%, third degree was mechanical failure such A hospital as 19.5%, B hospital 22.5%, C hospital 25.4%. 2. Hospital of failure mode was the highest in Mobile X-ray device(A hospital 62.5%, B hospital 69.5%, C hospital 37.4%), and was the lowest in Sono devices(A hospital 16.76%, B hospital 8.4%, C hospital 7%). 3. Mean time between failures(MTBT) was the highest in SONO devices and was the lowest in Mobile X-ray devices which have 200 - 400 failure hours. 4. Anverage failure ratio was the highest in Mobile X-ray devices(A hospital 31.3%, B hospital 34.8%, C hospital 18.7%), and was the lowest in Sono(Ultrasound) devices (A hospital 8.4%, B hospital 4.2%, C hospital 3.5%). 5. Failure ratio results of medical devices according to QC/PM part of unit failure mode were as follows ; A hospital was the highest part of QC/PM (50%) in Mamo X-ray device and was the lowest part of QC/PM(26.4%) in Castro X-ray. B hospital was the highest part of QC/PM(56%) in Mobile X-ray device, and the lowest part of QC/PM(12%) in Gastro X-ray. C hospital was the highest part of QC/PM(60%) in R/F X-ray device, and the lowest a part of QC/PM(21%) in Universal X-ray. It was found that the units responsible for most failure decreased by systematic management. We made the preventive maintenance schedule focusing on adjustement of operating and dust removal.

• 한국세라믹학회지
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• 제31권3호
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• pp.249-256
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• 1994

By surface structure and X-ray topographic observation, growth mechanism of NAB single crystal grown by TSSG technique using a BaB4O7 flux was studied. Surface structure of grown crystals were investigated by optical microscope. Growth history and crystal defects included within grown crystal were investigated using X-ray topography. The {001} faces were grown by 2-D nucleation growth. As decreasing cooling rate, growth mechanism of {111} and {11} was changed from 2-D nucleation growth to the growth by screw dislocation. Only surface striations developed parallel to a-axis were observed on {010} faces. Growth sector of NAB crystals were divided into {001}, {111}, {010}, {021}, {11}. The inclusion which was usually trapped between {001} faces was investigated.

• 대한수학회논문집
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• 제9권3호
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• pp.701-710
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• 1994

Suppose ${X_n}$ is a Markov process taking values in some arbitrary space $(S, \varphi)$ with n-stemp transition probability $$ P^{(n)}(x, B) = Prob(X_n \in B$\mid$X_0 = x), x \in X, B \in \varphi.$$ We shall call a Markov process with transition probabilities $P{(n)}(x, B)$ $\phi$-irreducible for some non-trivial $\sigma$-finite measure $\phi$ on $\varphi$ if whenever $\phi(B) > 0$, $$ \sum^{\infty}_{n=1}{2^{-n}P^{(n)}}(x, B) > 0, for every x \in S.$$ A non-trivial $\sigma$-finite measure $\pi$ on $\varphi$ is called invariant for ${X_n}$ if $$ \int{P(x, B)\pi(dx) = \pi(B)}, B \in \varphi $$.

• 전기화학회지
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• 제15권2호
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• pp.67-73
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• 2012

본 연구에서는 습식분쇄, 구형화 분무건조 및 열처리 공정을 통해 구형의 $LiMn_{2-x}M_xO_4$(M = Al, Mg, B) 스피넬계 양극소재를 합성하고, 이의 전기화학적 성능을 평가하였다. $MnO_2$ (Tosoh, 91.94%), $Li_2CO_3$ (SQM, 97%), $MgCO_3$ (Aldrich, 99%), $Al(OH)_3$ (Aldrich, 99%) 및 $B_2O_3$ (Aldrich, 99%)를 원료로 사용하였으며, 분무건조공정에서 전구체의 구형화도 증가를 위해 PAAH 바인더를 첨가하였다. 200~500 nm 크기로 분쇄된 혼합 슬러리 용액으로부터 분무건조법을 통해 구형의 전구체를 제조하고, 이를 다양한 조건에서 열처리하여 최종 스피넬계 $LiMn_{2-x}M_xO_4$ (M = Al, Mg, B) 양극소재를 제조하였다. 제조된 구형의 $LiMn_{2-x}M_xO_4$ (M = Al, Mg, B) 양극재료는 이종원소 치환량, 특히 Boron 치환량에 따라 입자 표면 및 내부의 치밀도가 변화하는 것을 확인할 수 있었으며, 치밀도가 증가함에 따라 소재의 출력특성이 향상되었으며, 최적 조성의 양극소재는 상온 5 C 용량이 0.2 C 용량 대비 90% 이상이 됨을 확인하였다. 또한 표면의 치밀도도 증가함에 따라 $60^{\circ}C$ 고온 충방전 조건에서 수명특성이 향상되어 500회 사이클 이후에도 초기용량의 80% 이상을 유지하였다.

• Journal of Magnetics
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• 제16권3호
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• pp.229-233
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• 2011

Phase evolution during the hydrogen-assisted disproportionation of $Nd_{12.5}Fe_{80.6}B_{6.4}Ga_{0.3}Nb_{0.2}$ alloy was investigated mainly by using a magnetic balance-type thermomagnetic analyser (TMA). In order to avoid any undesirable phase change in the course of heating for TMA, a swift TMA technique with very high heating rate (around 2 min to reach $800^{\circ}C$ from room temperature) was adopted. The hydrided $Nd_{12.5}Fe_{80.6}B_{6.4}Ga_{0.3}Nb_{0.2}$ alloy started to be disproportionated in hydrogen from around $600^{\circ}C$, and the alloy after the early disproportionation (from 600 to $660^{\circ}C$) has been partially disproportionated. The partially disproportionated alloy consisted of a mixture of $NdH_x$, $Fe_3B$, ${\alpha}$-Fe, and the remaining undisproportionated $Nd_2Fe_{14}BH_x$-phase. During the subsequent heating to $800^{\circ}C$ in hydrogen, two additional phases of $Fe_{23}B_6$ and $Fe_2B$ were formed, and the material consisted of a mixture of $NdH_x$, $Fe_{23}B_6$, $Fe_3B$, $Fe_2B$, and ${\alpha}$-Fe phases. During the subsequent isothermal holding at $800^{\circ}C$ for 1 hour, the phase constitution was further changed, and one additional unknown magnetic phase was formed. Eventually, the fully disproportionated $Nd_{12.5}Fe_{80.6}B_{6.4}Ga_{0.3}Nb_{0.2}$ alloy consisted of $NdH_x$, $Fe_{23}B_6$, $Fe_3B$, $Fe_2B$, ${\alpha}$-Fe, and one additional unknown magnetic phase.

• 호남수학학술지
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• 제31권3호
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• pp.437-449
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• 2009

In this paper, we calculate the number of points on elliptic curves $E^{a^3}_0:y^2=x^3+a^3$ over ${\mathbb{F}}_p$ mod 24 and $E^b_0:y^2=x^3+b$ over ${\mathbb{F}}_p$ mod 6, where b is cubic non-residue in ${\mathbb{F}}^*_p$. For example, if p ${\equiv}$ 1 (mod 12) is a prime, and a and a(2t - 3) are quadratic residues modulo p with $3t^2{\equiv}1$ (mod p), then the number of points in $E^{a^3}_0:y^2=x^3+a^3$ is congruent to 0 modulo 24.

• Kyungpook Mathematical Journal
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• 제48권4호
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• pp.529-543
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• 2008

It is shown that every almost linear mapping h : $A{\rightarrow}B$ of a unital PoissonC*-algebra A to a unital Poisson C*-algebra B is a Poisson C*-algebra homomorph when $h(2^nuy)\;=\;h(2^nu)h(y)$ or $h(3^nuy)\;=\;h(3^nu)h(y)$ for all $y\;\in\;A$, all unitary elements $u\;\in\;A$ and n = 0, 1, 2,$\codts$, and that every almost linear almost multiplicative mapping h : $A{\rightarrow}B$ is a Poisson C*-algebra homomorphism when h(2x) = 2h(x) or h(3x) = 3h(x for all $x\;\in\;A$. Here the numbers 2, 3 depend on the functional equations given in the almost linear mappings or in the almost linear almost multiplicative mappings. We prove the Cauchy-Rassias stability of Poisson C*-algebra homomorphisms in unital Poisson C*-algebras, and of homomorphisms in Poisson Banach modules over a unital Poisson C*-algebra.

• 한국재료학회지
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• 제5권7호
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• pp.880-887
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• 1995

융체방사법으로 제작한 YB $a_2$C $u_3$A $g_{15}$과 YbB $a_2$C $u_3$A $g_{x}$(x=5, 16 and 53) 예비 합금 리본(precursor alloy ribbon)을 263~322$^{\circ}C$에서 산화시키고, 산소 1기압 온도 872~89$0^{\circ}C$에서 열처리하였다. 또한 약 10개의 리본을 층으로 쌓아 프레스로 압축.접착시켜 다층 시편(multilayered specimen)을 제작하였다. 이 다충 시편도 위의 리본과 같은 조건에서 열처리하였다. YB $a_2$C $u_3$ $O_{7-{\delta}}$ 혹은 YbB $a_2$C $u_3$ $O_{7-{\delta}}$상이 모든 리본과 모든 다층 시편에서 형성되었다. 이 1-2-3상들은 모든 리본에서 집합조직(texture)을 나타내지 않았으나, 다층 시편들에서는 약간의 집합조직을 나타내었다. 모든 리본은 0 자장 77K에서 임계 전류 밀도 $J_{c}$가 0을 나타내었다. 다층 시편 중에서 YB $a_2$C $u_3$A $g_{15}$과 YbB $a_2$C $u_3$A $g_{16}$시편이 각각 260, 180A/$\textrm{cm}^2$의 임계 전류 밀도를 나타내었다. 여러 리본들 중에서 YB $a_2$C $u_3$A $g_{15}$ 과 YbB $a_2$C $u_3$A $g_{16}$ 리본이, 프레스 변형으로 집합조직을 가지게 함으로써 향상된 $J_{c}$를 가진 초전도 산화물을 만들 수 있는 적절한 조성을 가지고 있다. 다층 YB $a_2$C $u_3$A $g_{15}$ 시편의 개시 임계 온도 ( $T_{on}$ )는 92K 이었으며, 다층 YbB $a_2$C $u_3$A $g_{x}$(x=5, 16 and 53)의 $T_{on}$ 은 88~90K이었다.

• 한국세라믹학회지
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• 제41권2호
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• pp.170-175
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• 2004

Y-acetate, Yb-acetate와 Mn-acetate를 출발물질로 사용하여 sol-gel 법으로 강유전성 (Y $b_{x}$ $Y_{1-x}$)Mn $O_3$ 박막을 제조하였다. Acetylaceton을 촉매로 사용하고 Reflux 법을 이용하여 안정한 (Y $b_{x}$ $Y_{1-x}$)Mn $O_3$ 전구체 용액을 얻었으며, 박막은 스핀 코팅방법으로 Si(100) 기판 위에 제조하였다 열처리 온도, 코팅용액의 Rw($H_2O$/alkoxide moi ratio)변화 등을 실험변수로 하여 박막의 결정상 변화를 연구하였다. X-선 회절분석 결과 YbMn $O_3$의 결정상을 얻기 위한 최저 열처리온도는 7$50^{\circ}C$이었으며, 최적 열처리 조건은 80$0^{\circ}C$였다 Rw를 1∼6 범위 내에서 조절하여 첨가한 결과, Rw=1의 조건에서 c-축 배향이 잘 발달된 hexagonal YbMn $O_3$ 단일 결정상을 얻었다. Si(100)기판 위에 제조된 (Y $b_{x}$ $Y_{1-x}$)Mn $O_3$ 박막은 x=0 또는 1인 경우 잔류분극(Pr)값이 약 200 nC/$ extrm{cm}^2$을 나타내었으나 0