• Journal of the Korean Society for Heat Treatment
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• v.4 no.1
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• pp.37-41
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• 1991

In this study, the effect of solution treatment temperature on the tensile property in intermediate thermo-mechanical treated Al-Li alloys are investigated. After the intermediate thermo-mechanical treated Al-Li, Al-Li-Mg and Al-Li-Mg-Zr alloys were solution treated at various temperatures (500, 520 and $540^{\circ}C$), these were aged at $190^{\circ}C$, $240^{\circ}C$ and tested tensile properties. The results obtained from the experiment are as follows ; 1) The optimum solution heat-treatment temperature is $540^{\circ}C$ for a Al-Li alloy, and the recrystallized grain size is about $70{\mu}m$. 2) The optimum solution heat-treatment temperature is $500^{\circ}C$ for a Al-Li-Mg alloy, and the recrystallized grain size is the most coarse in all alloys. 3) The tensile property is independent of the solution treatment temperature in a Al-Li-Mg-Zr alloy, and the recrystallized grain size is the finest owing to addition of Zr.

• Journal of applied mathematics & informatics
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• v.41 no.2
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• pp.273-286
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• 2023

In this paper we show that if T ∈ L(X) and S ∈ L(X) is a Riesz operator commuting with T and X_S(F) ∈ Lat(S), where F = {0} or F ⊆ ℂ ⧵ {0} is closed then T|X_S(F) and T|X_T(F) + S|X_S(F) share the local spectral properties such as SVEP, Dunford's property (C), Bishop's property (𝛽), decomopsition property (𝛿) and decomposability. As a corollary, if T ∈ L(X) and Q ∈ L(X) is a quasinilpotent operator commuting with T then T is Riesz if and only if T + Q is Riesz. We also study some spectral properties of Riesz operators acting on Banach spaces. We show that if T, S ∈ L(X) such that TS = ST, and Y ∈ Lat(S) is a hyperinvarinat subspace of X for which 𝜎(S|Y ) = {0} then 𝜎_*(T|Y + S|Y ) = 𝜎_*(T|Y ) for 𝜎_* ∈ {𝜎, 𝜎_loc, 𝜎_sur, 𝜎_ap}. Finally, we show that if T ∈ L(X) and S ∈ L(Y ) on the Banach spaces X and Y and T is similar to S then T is Riesz if and only if S is Riesz.

• Korean Journal of Metals and Materials
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• v.48 no.8
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• pp.780-789
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• 2010

The aim of this study is to evaluate the microstructure and tensile property of in-situ (TiB+TiC) particulate reinforced titanium matrix composites (TMCs) synthesized by the investment casting process. Boron carbide ($1,500{\mu}m$ and $150{\mu}m$) was added to the titanium matrix during vacuum induction melting, which can provide the in-situ reaction of $5Ti+B_4C{\rightarrow}4TiB+TiC$. 0.94, 1.88 and 3.76 wt% of $B_4C$ were added to the melt. The phases identification of the in-situ synthesized TMCs was examined using scanning electron microscopy, an X-ray diffractometer, an electron probe micro-analyzer and transmission electron microscopy. Tensile properties of TMCs were investigated in accordance with the reinforcement size and volume fraction. The improvement of tensile property of titanium matrix composites was caused by load transfer from the titanium matrix to the reinforcement and by grain refinement of titanium matrix and reinforcements.

• Journal of the Korean Mathematical Society
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• v.42 no.1
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• pp.101-110
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• 2005

Let (X, D; ${\Gamma}$) be a G-convex space and Y a Hausdorff space. Then $U^K_C$(X, Y) ${\subset}$ KD(X, Y), where $U^K_C$ is an admissible class (dup to Park) and KD denotes the class of multimaps having the KKM property for open-valued multimaps. This new result is used to obtain a KKM type theorem, matching theorems, a fixed point theorem, and a coincidence theorem.

• Journal of Powder Materials
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• v.21 no.6
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• pp.434-440
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• 2014

Silicon carbide(SiC) layer is particularly important tri-isotropic (TRISO) coating layers because it acts as a miniature pressure vessel and a diffusion barrier to gaseous and metallic fission products in the TRISO coated particle. The high temperature deposition of SiC layer normally performed at $1500-1650^{\circ}C$ has a negative effect on the property of IPyC layer by increasing its anisotropy. To investigate the feasibility of lower temperature SiC deposition, the influence of deposition temperature on the property of SiC layer are examined in this study. While the SiC layer coated at $1500^{\circ}C$ obtains nearly stoichiometric composition, the composition of the SiC layer coated at $1300-1400^{\circ}C$ shows discrepancy from stoichiometric ratio(1:1). $3-7{\mu}m$ grain size of SiC layer coated at $1500^{\circ}C$ is decreased to sub-micrometer (< $1{\mu}m$) $-2{\mu}m$ grain size when coated at $1400^{\circ}C$, and further decreased to nano grain size when coated at $1300-1350^{\circ}C$. Moreover, the high density of SiC layer (${\geq}3.19g/cm^3$) which is easily obtained at $1500^{\circ}C$ coating is difficult to achieve at lower temperature owing to nano size pores. the density is remarkably decreased with decreasing SiC deposition temperature.

• Journal of the Korean Wood Science and Technology
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• v.38 no.2
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• pp.101-107
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• 2010

Heat treatment was performed to improve sound absorption properties for four tree species; Tulip tree, Korean Paulownia, Red pine and Costata birch, at temperature of $175^{\circ}C$ and $200^{\circ}C$under vacuum condition. Sound absorption properties of two kinds of boards, which were in radial and tangential sections, were measured under a frequency range of 100 to 3200 Hz by the two microphone transfer function method. It was found that sound absorption properties were increased by heat treatment and the efficiency was higher at $200^{\circ}C$ than that at $175^{\circ}C$. Even Costata birch had a little effect on low temperature of $175^{\circ}C$, $200^{\circ}C$ heat treatment for sound absorption property, the efficiencies of sound absorption were 14, 19%, respectively. The efficiencies of sound absorption ranged 22 to 120% for heat-treated Tulip tree, Korean Paulownia.

• Communications of the Korean Mathematical Society
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• v.34 no.3
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• pp.981-989
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• 2019

In this paper we deal with some shadowing properties of discrete dynamical systems on a compact metric space via the density of subdynamical systems. Let $f:X{\rightarrow}X$ be a continuous map of a compact metric space X and A be an f-invariant dense subspace of X. We show that if $f{\mid}_A:A{\rightarrow}A$ has the periodic shadowing property, then f has the periodic shadowing property. Also, we show that f has the finite average shadowing property if and only if $f{\mid}_A$ has the finite average shadowing property.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.8
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• pp.670-677
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• 2012

In this paper, mechanical property of biomorphic C/SiC composite was calculated by unit cell analysis. The microstructural arrangements of carbonized pine and radiata pine which were impregnated with silicon, were idealized as square and hexagonal arrays. Unit cell was then defined and equivalent elastic constants were calculated. A single and double unit cell structures were considered. The effect of void distribution was also studied by monte carlo simulation.

• Bulletin of the Korean Mathematical Society
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• v.48 no.4
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• pp.673-688
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• 2011

Let $n{\geq}2$ be an even integer. We investigate that if an odd mapping f : X ${\rightarrow}$ Y satisfies the following equation $2_{n-2}C_{\frac{n}{2}-1}rf\(\sum\limits^n_{j=1}{\frac{x_j}{r}}\)\;+\;{\sum\limits_{i_k{\in}\{0,1\} \atop {{\sum}^n_{k=1}\;i_k={\frac{n}{2}}}}\;rf\(\sum\limits^n_{i=1}(-1)^{i_k}{\frac{x_i}{r}}\)=2_{n-2}C_{{\frac{n}{2}}-1}\sum\limits^n_{i=1}f(x_i),$ then f : X ${\rightarrow}$ Y is additive, where $r{\in}R$. We also prove the stability in normed group by using shadowing property and the Hyers-Ulam stability of the functional equation in Banach spaces and in Banach modules over unital C-algebras. As an application, we show that every almost linear bijection h : A ${\rightarrow}$ B of unital $C^*$-algebras A and B is a $C^*$-algebra isomorphism when $h(\frac{2^s}{r^s}uy)=h(\frac{2^s}{r^s}u)h(y)$ for all unitaries u ${\in}$ A, all y ${\in}$ A, and s = 0, 1, 2,....

• Bulletin of the Korean Mathematical Society
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• v.45 no.4
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• pp.645-650
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• 2008

Let M be a generalized homogeneous compact space, and let Z(M) denotes the space of homeomorphisms of M with the $C^0$ topology. In this paper, we show that if the interior of the set of weak stable homeomorphisms on M is not empty then for any open subset W of Z(M) containing only weak stable homeomorphisms the orbital shadowing property is generic in W.