• Korean Journal of Mathematics
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• 제27권4호
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• pp.949-968
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• 2019

In this work, we characterize some matrix classes concerning the Binomial sequence spaces b^r,s_∞ and b^r,s_p, where 1 ≤ p < ∞. Moreover, by using the notion of Hausdorff measure of noncompactness, we characterize the class of compact matrix operators from b^r,s₀, b^r,s_c and b^r,s_∞ into c₀, c and ℓ_∞, respectively.

• 대한수학회보
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• 제48권5호
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• pp.1093-1103
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• 2011

We give the characterizations of the classes of matrix trans-formations ($m(\phi),{\ell}_p$), ($n(\phi),{\ell}_p$) ([5, Theorem 2]), (${\ell}_p,m(\phi)$) ([5, Theorem 1]) and (${\ell}_p,n(\phi)$) for $1{\leq}p{\leq}{\infty}$, establish estimates for the norms of the bounded linear operators defined by those matrix transformations and characterize the corresponding subclasses of compact matrix operators.

• 한국재료학회지
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• 제30권3호
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• pp.149-154
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• 2020

A powder-in-sheath rolling method is applied to the fabrication of a carbon nano tube (CNT) reinforced copper composite. A copper tube with outer diameter of 30 mm and wall thickness of 2 mm is used as sheath material. A mixture of pure copper powder and CNTs with a volume content of 3 % is filled in a tube by tap filling and then processed to an 93.3 % reduction using multi-pass rolling after heating for 0.5 h at 400 ℃. The specimen is then sintered for 1h at 500 ℃. The relative density of the 3 vol%CNT/Cu composite fabricated using powder in sheath rolling is 98 %, while that of the Cu powder compact is 99 %. The microstructure is somewhat heterogeneous in width direction in the composite, but is relatively homogeneous in the Cu powder compact. The hardness distribution is also ununiform in the width direction for the composite. The average hardness of the composites is higher by 8Hv than that of Cu powder compact. The tensile strength of the composite is 280 MPa, which is 20 MPa higher than that of the Cu powder compact. It is concluded that the powder in sheath rolling method is an effective process for fabrication of sound CNT reinforced Cu matrix composites.

• 한국전자파학회논문지
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• 제12권2호
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• pp.299-307
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• 2001

이 논문에서는 MP(Matrix Pencil) 방법을 이용한 ISAR(Inverse Synthetic Aperture Radar) 영상에 대한 실험적 연구결과를 기술하였다. 측정은 CR(Compact Range) RCS 측정시설을 이용하였으며 두 가지 종류의 표적이 사용되었다. 첫 번째 표적은 MP의 성능을 확인하기 위하여 길이가 짧고 반경이 작은 원통형 표적이고 두 번째 표적은 실제 비행기 형상과 같이 복잡한 구조를 가진 무인항공기 모형이다. ISAR 영상을 얻기 위하여 MP와 FFT(Fast Fouier Transform)를 이용하였으며 실험결과를 비교해 보면 MP 방법을 사용하는 것이 기존의 FFT를 사용하는 것보다 더 좋은 영상을 얻을 수 있다는 것을 입증하였다.

• 대한수학회보
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• 제40권4호
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• pp.641-648
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• 2003

In this paper, we characterize the compact sets full-invariant properties, dual invariant properties and quasi full invariant properties in a class of infinite matrix algebras.

• 한국생산제조학회지
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• 제22권2호
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• pp.337-341
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• 2013

In this study, fatigue crack propagation in composite material under fatigue is investigated by simulation result. When another material on the specimen exists vertically to the crack line, the phenomena that crack may go straight or propagate along the boundary face according to the elastic modulus ratio of another material to matrix are investigated with compact tension specimen by compliance method. Crack propagation direction is evaluated by compliance method. By arranging this study result systematically about the crack propagation behavior due to the stiffness of inhomogeneous material, high-tech material (automobile, aircraft and steel industry) can be improved. The estimation of safety design and life (construction & nuclear power station, etc.) will be of great value industrially.

• 한국수학교육학회지시리즈B:순수및응용수학
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• 제25권2호
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• pp.171-180
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• 2018

In this paper, the necessary and sufficient conditions are considered for biprojectivity of Banach algebras $E_p(I)$. As an application, we investigate biprojectivity of convolution Banach algebras A(G) and $L^2(G)$ on a compact group G.

• Nuclear Engineering and Technology
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• 제55권2호
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• pp.749-755
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• 2023

A new approximation method was proposed for treating the non-resonant spatial self-shielding effects of double heterogeneous region such as the double heterogeneous effect of VHTR fuel compact in the thermal energy range and that of BP compact with BISO. The method was developed based on the effective homogenization method and a spherical unit cell model with explicit coated layers and a matrix layer. The self-shielding factor was derived from the relation between the collision probabilities for a double heterogeneous compact and the effective cross section for the homogenized compact. First, the collision probabilities and transmission probabilities for all layers of the spherical model were calculated using conventional collision probability solver. Then, the effective cross section for the homogenized sphere cell representing the homogenized compact was obtained from the transmission probability calculated using the probability density function of a chord length. The verification calculations revealed that the proposed method can predict the self-shielding factor with a maximum error of 2.3% and the double heterogeneous effect with a maximum error of 200 pcm in the typical VHTR problems with various packing fractions and BP compact sizes.

• 한국정밀공학회지
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• 제5권1호
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• pp.50-62
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• 1988

An experimental investigation of the machining characteristics of compact vermicular cast iron whose matrix were formulated under two kinds of annealing conditions has been conducted. The various characteristics of the machinability of CA cast iron depending upon its matrix and cutting condition have been obtained from the experiment. The results are as follow. As depth of cut increases, the shear stress slightly decreases in order $P_1, \P_2, \P_3$ which are classified by ferrite matrix of CV cast iron. As depth of cut increases, the normal stress increases, and annealing effect in heavy cutting is smaller than that in light cutting. The cutting energy slightly decreases, as depth of cut increases and the effect of annealing on cutting energy in light cutting is higher than that in heavy cutting. The cutting equation in this study are as follow. $P_1\:\2{\phi}\ + \1.49({\beta} - {\alpha} )=84^{\circ}$ $P_2\:\2{\phi}\ + \1.36({\beta} - {\alpha} )=82^{\circ}$ $P_3\:\2{\phi}\ + \1.34({\beta} - {\alpha} )=79^{\circ}$ Machining constants in this study for $P_1, P_2, P_3$give $74^{\circ} , 66^{\circ}, 61^{\circ}$ Tool wear increases as depth of cut increases, and decreases as ferrit matrix increases.

• 대한수학회지
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• 제57권4호
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• pp.973-986
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• 2020

In this paper, we compute the Hankel matrix representation of the Hankel operator on the Hardy space of a general bounded domain with respect to special orthonormal bases for the Hardy space and its orthogonal complement. Moreover we obtain the compact form of the Hankel matrix for the unit disc case with respect to these bases. One can see that the Hankel matrix generated by this computation turns out to be a generalization of the case of the unit disc from the single simply connected domain to multiply connected domains with much diversities of bases.