• 세라미스트
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• 제21권2호
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• pp.29-37
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• 2018

In order to overcome the problems of existing low-dimensional materials (carbon nanotubes, graphene, transition metal dichalcogenides, etc) researches on new 1D materials have been studied. In the case of $LiMo_3Se_3$ and $Mo_6S_{9-x}I_x$, continuous researches have been carried out for 3D bulk synthesis and atomic scale dispersion. Recently, quantum confinement effect of $LiMo_3Se_3$ and bio-stability of $Mo_6S_{9-x}I_x$ have been proven and various applications have started to be studied. In addition, device application results using new 1D materials such as $Sb_2Se_3$ (optoelectronic devices using the property of effectively reducing exciton decay due to no dangling bond) and $VS_4$ (electrochemical energy storage using the space between 1-D nanostructures) have been reported very importantly. Therefore, it can be claimed that it has reached a very important time to find and synthesize new 1D materials and to report various characteristics not existing.

• 한국전기전자재료학회논문지
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• 제16권9호
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• pp.795-800
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• 2003

The dielectric and piezoelectric properties of the xPb(A $l_{0.5}$N $b_{0.5}$) $O_3$-(1-x)Pb(Z $r_{0.52}$ $Ti_{0.48}$) $O_3$ [xPAN-(1-x)PZT] thin films by pulsed laser deposition (PLD) were investigated as a function of PAN contents. The effect of texture on dielectric and piezoelectric properties of the 0.05PAN-0.95PZT thin films having the highest piezoelectric constant( $d_{33}$) was studied more precisely. For 0$\leq$x$\leq$0.15 compositions in xPAN-(1-x)PZT thin films, the well-developed perovskite phase with (111) preferred orientation was obtained at the deposition temperature of 50$0^{\circ}C$. With increasing PAN content, remanent polarization and coercive field decreased. The dielectric constant increased with an increase of PAN content until it reached 1450 at $\chi$= 0.05, and then decreased for higher PAN content. The maximum points of dielectric constant coincides with the maximum points of the piezoelectric constant $d_{33}$.33/.33/././.

• Bulletin of the Korean Chemical Society
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• 제5권4호
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• pp.135-140
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• 1984

The reduction of vacuum-dehydrated $Na_xAg_{12-x}-A, 0 {\le} x {\le} 9.2$, and its reoxidation by O$_2$, have been studied by X-ray powder diffraction. Also, the structure of $Na_6Na_6-A$ treated with hydrogen at room temperature has been studied by single crystal methods in the cubic space group Pm3m at $24{\circ}C (a = 12.221(2) {\AA})$. The diffraction pattern of dehydrated Ag$_{12}$-A reduced by H$_2$ contains only the (111) and (200) reflections of silver metal, indicationg that the zeolite structure has been lost, but the zeolite's diffraction pattern and structural integrity can be fully restored by oxidation with O$_2$ at 100 or 200${\circ}C$. In contrast, the structures of $Na_xAg_{12-x}-A$, x = 4.5 and 9.2, were not destroyed by treatment with hydrogen. Dehydrated Na$_6Ag_6$-A treated with 50 Torr of hydrogen gas at 24${\circ}C$ for 30 minutes has $6\; Na^+\;and\;1.27\;Ag^+$ ions at 6-ring sites. These $Ag^+ ions are associated with 2.54 Ag${\circ}$ atoms to form 1.27 $Ag_3^+$ clusters per unit cell. Also found were 0.7 $Ag_3^{2+}$ clusters per unit cell near the 8-rings. The structure was refined to the final error indices R$_1$ = 0.134 and R$_2$ (weighted) = 0.147, using 168 independent reflections for which $I_0 >3{\sigma}(I_0)$.

• 한국세라믹학회지
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• 제52권3호
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• pp.215-220
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• 2015

Phase evolution, microstructure, and microwave dielectric properties of $Li_2O$ and $Al_2O_3$ doped $Zn_{1.9}Si_{1.05}O_4$, i.e., $Zn_{1.9-2x}Li_xAl_x-Si_{1.05}O_4$, ceramics (x = 0.02 ~ 0.10) were investigated. The ceramics were densified by $SiO_2$-rich liquid phase composed of the Li-Al-Si-O system, indicating that doped Li and Al contributed to the formation of the liquid. As the secondary phase, ${\beta}$-spodumene solid solution with the composition of $LiAlSi_3O_8$ was precipitated from the liquid during the cooling process. The dense ceramics were obtained for the specimens of $$x{\geq_-}0.06$$ showing the rapid densification above $1000^{\circ}C$, implying that a certain amount of liquid is necessary to densify. The specimen of x = 0.06 sintered at $1050^{\circ}C$ exhibited good microwave dielectric properties; the dielectric constant and the quality factor ($Q{\times}f_0$) were 6.4 and 11,213 GHz, respectively.

• 한국세라믹학회지
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• 제41권10호
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• pp.735-741
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• 2004

단순화한 연소법에 의해 합성한 $LiMn_{1.92}Co_{0.08}O_4$와 $LiNi_{0.7}Co_{0.3}O_2$의 혼합물의 전기화학적 성질을 알아보기 위하여, 30분 동안 milling하여 $LiMn_{1.92}Co_{0.08}O_4$-x wt$\%$ $LiNi_{0.7}Co_{0.3}O_2$ (x=9, 23, 33, 41, and 47) 조성의 혼합물을 제조하였다. x=9 조성의 전극이 비교적 큰 초기방전용량(109.9mAh/g at 0.1C)과 좋은 싸이클 성능을 가지고 있었다. 싸이클링에 따른 혼합물 전극의 방전용량 감소는 주로 $LiNi_{0.7}Co_{0.3}O_2$의 퇴화에 기인한다고 생각된다. $LiNi_{0.7}Co_{0.3}O_2$의 퇴화는 $LiMn_{1.92}Co_{0.08}O_4$로부터 용해된 Mn이 $LiNi_{0.7}Co_{0.3}O_2$ 입자를 둘러싸서(coating) 일어나는 것으로 판단된다.

• 한국결정학회지
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• 제8권2호
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• pp.138-143
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• 1997

Isoimperatorin, 4-[3-methyl-2-butenly)oxy]=7H-furo[3,2-g][1] benzopyran-7-one의 분자 및 결정구조를 X-선 회절법으로 연구하였다. 이 결정의 분자식은 C16H14O4, 결정계는 단사정계이고 공간군은 P21/c이다. 단위세포상수는 a=8.865(1) Å, b=9.331(1) Å, c=16.156(1) Å이며 β=98.12(1)', V=1322.9(2) Å3, T=293(2)K, z=4이다. 구조해석에 사용한 X-선은 Cu Kα선(λ=1.5418 Å)이다. 구조는 직접법으로 풀었으며, 최소자승법으로 정밀화하였다. 최종 신뢰도 R값은 Fo>4o(F0)인 1922개의 독립회절데이타에 대해 5.72% 이다.

• 대한수학회논문집
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• 제9권3호
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• pp.753-765
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• 1994

The linearly constrained quadratic programming(QP) considered is : $$ min f(x) = c^T x + \frac{1}{2}x^T Hx $$ $$ (1) subject to A^T x \geq b,$$ where $c,x \in R^n, b \in R^m, H \in R^{n \times n)}$, symmetric, and $A \in R^{n \times n}$. If there are bounds on x, these are included in the matrix $A^T$. The Hessian matrix H may be positive definite or negative semi-difinite. For large problems H and the constraint matrix A are assumed to be sparse.

• Bulletin of the Korean Chemical Society
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• 제9권3호
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• pp.121-126
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• 1988

The molecular interaction of $Mo_2(OR)_4({\mu}-OR)_2$$ unit has been studied for carbonyl and acetylene ligands by means of extended Huckel calculations. We have extended the extended Hckel calculations to unknown apex bridged $Mo_2(OR)_6({\mu}-X)$ complexes (X = $SO_2$H, and Cl) in order to compare the stability of the complexes. In the $C_2H_2$and H apex bridged complexes, one finds a relatively small HOMO-LUMO gap. However, both complexes are stabilized due to Jahn-Teller distortion. The stability of both complexes is comparable to that of $Mo_2(OR)_6(CO)$ complex. The comparisons and predictions in the stability of known and unknown complexes are the subject of this study.

• 한국전기전자재료학회논문지
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• 제13권12호
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• pp.1017-1024
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• 2000

Effect of the microwave dielectric properties and the microstructure on a mole fraction(x=0.1~0.9) of (1-x)Mg$_2$SiO$_4$-xZnAl$_2$O$_4$ ceramics was investigated. When (1-x)Mg$_2$SiO$_4$-xZnAl$_2$O$_4$(x=0.1~0.9) ceramics were sintered at 130$0^{\circ}C$, 135$0^{\circ}C$ and 140$0^{\circ}C$ for 2hr, the microwave dielectric properties were obtained $\varepsilon$r=6.8~8.3, Q.f$_{0}$=36000~77600. On the other hand, the temperature coefficients of resonant frequency($\tau$$_{f}$) were obtained in the properties of -62ppm/$^{\circ}C$ to -49ppm/$^{\circ}C$. In order to adjust the temperature coefficient of resonant frequency($\tau$$_{f}$), CaTiO$_3$was added in (1-x)Mg$_2$SiO$_4$-xZnAl$_2$O$_4$ceramics. 0.7Mg$_2$SiO$_4$-0.2ZnAl$_2$O$_4$-0.1CaTiO$_3$ceramics sintered at 135$0^{\circ}C$ for 2hr showed the excellent microwave dielectric properties of $\varepsilon$r=7.7, Q.f$_{0}$=32000, and $\tau$$_{f}$=-7.9 ppm/$^{\circ}C$.EX>.>.EX>.

• 대한수학회보
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• 제21권1호
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• pp.1-5
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• 1984

The notion of linear 2-normed spaces was introduced by S. Gahler ([8,9,10,11]), and these space have been extensively studied by C. Diminnie, R. Ehret, S. Gahler, K. Iseki, A. White, Jr, and others. For nonzero vectors x,y in X, let V(x,y) denote the subspace of X generated by x and y. A linear 2-normed space (X,v) is said to be strictly convex ([3]) if v(x+y,z)=v(x,z)+v(y+z) and z not.mem.V(x,y) imply that y=ax for some a>0. Some characterizations of strict convexity for linear 2-normed spaces are given in [1,3,4,5,12]. Also, a linear 2-normed space (X,v) is said to be strictly 2-convex ([6]) if v(x,y)=v(x,z)=v(y,z)=1/3v(x+z, y+z)=1 implies that z=x+y. These space have been studied in [2,4,6,13]. It is easy to see that every strictly convex linear 2-normed space is always strictly 2-convex but the converse is not necessarily true. Throughout this paper, let (X,v) denote a linear 2-normed space.