• 에너지공학
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• 제2권2호
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• pp.187-193
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• 1993

인산형 연료전시에서의 인산 전해질을 지지하기 위한 다공성 메트릭스의 제조는 결합제인 PTFE와 각종입자의 크기를 갖는 SiC분말 또는 whisker를 혼합 사용하여 제작하였다. 메트릭스로서 갖추어야 될 기본조건중에 bubble pressure와 인산 전해질의 함침량은 전지운영시 전극성능에 가장 큰 영향을 미칠것이라 보아 다공성 전극의 pore size보다 작은 pore size를 가지는 메트릭스를 제작하였다. 각종 SiC입자 크기와 PTFE함량에 따라 제작된 matrix의 bubble pressure와 함침량을 측정하였으며 porosimeter를 이용하여 측정된 메트릭스의 다공도와 비교하여 인산형 연료전지에 사용할 수 있는 최적의 메트릭스 조건을 결정하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 춘계학술대회 논문집
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• pp.167-170
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• 2005

This paper briefly reviews various existing methods to account for the effect of particle size on mechanical properties of particulate metal matrix composites. A simple and easy method is to use a size-dependent constitutive equation for the matrix. The suggested method does not require the development of a new computational algorithm and is compatible with any standard finite element software. Finite element analyses have been carried out to show how the deformation behavior of a metal matrix composite changes as the particle size and volume fraction are varied.

• 한국재료학회지
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• 제28권12호
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• pp.691-695
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• 2018

In this study, we investigate the recycling of aluminum-based metal matrix composites(AMCs) embedded with SiC particulates. The microstructure of the AMCs is characterized by X-ray diffraction and scanning electron microscopy. The possibility of recycling the composite scrap is attempted from the melted alloy and SiC particulates by re-melting, holding and solidification in crucibles. The recovery percentage of the matrix alloy is calculated after a number of holding times, 0, 5, 10, 15, 20, 25 and 30 minutes and for different particulate sizes and weight fractions in the Al matrix. The results show that the recovery percentage of the matrix alloy, as well as the time required for maximum recovery of the matrix, is dependent on the size and weight fraction of SiC particulates. In addition, the percentage recovery increases with particulate size but drops with the particulate fraction in the matrix. The time to reach maximum recovery falls rapidly with an increase in particulate size and fraction.

• 한국전기전자재료학회논문지
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• 제11권5호
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• pp.384-393
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• 1998

A mixed powder of electrolyte and matrix support materials with a proper proportion was used for the fabrication of an electrolyte matrix sheet. The purpose of this study is to reduce the large change in MCFC cell thickness occurring in the initial start-up period when separate sheets of electrolyte and support are used. A focus was put on how small the carbonate particles could be made. The particle size of the carbonate powder was controlled by ball milling and the distribution was measured using a particle size analyser. The thickness change was reduced to 20% by this approach, which could be compared to 27% observed in a conventional cell. The thickness changes of electrolyte matrix have linear relation sizes of carbonate powders.

• 대한수학회논문집
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• 제35권2호
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• pp.487-497
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• 2020

In this paper, we establish a complex matrix representation of the Clifford algebra Cℓ_p,q. The size of our representation is significantly smaller than the size of the elements in L_p,q(ℝ). Additionally, we give detailed information about the spectrum of the constructed matrix representation.

• 핵의학기술
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• 제24권1호
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• pp.27-32
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• 2020

사구체 여과율은 신 기능의 평가와 신 질환의 경과 관찰에 중요한 지표다. 현재 임상에서 사구체 여과율을 측정하는 방법은 크게 혈청 크레아티닌 수치와 ^99mTc-DTPA을 이용해서 계산하는 검사가 유용하게 이용되고 있다. Gates 공식이 발표된 이후, ^99mTc-DTPA Renal Dynamic Scan 검사시 이를 적용해 GFR을 감마카메라 장비를 이용하여 측정하고 있다. 본 논문의 목적은 Gates 공식을 적용해 사구체 여과율을 측정할 때 동위원소의 용량 변화, Matrix Size 변경에 따른 사구체 여과율을 분석해 보고자 한다. 본원에서 ^99mTc-DTPA Renal Dynamic Scan 검사를 받은 성인 환자 5명 (환자나이 = 62 ± 5, 남자 3명, 여자 2명)의 결과를 분석하였다. ^99mTc-DTPA 15 mCi를 환자의 정맥에 순간 주사 후 21분간 동적 영상을 획득하였다. Activity, Matrix Size 변화에 따라 사구체 여과율을 평가하기 위해 2-3분 구간의 양쪽 신장과 조직에 관심 영역을 설정 후 총 계수를 측정하였다. Detector와 Table 간의 거리는 30cm로 유지하였고, 동위원소의 용량 변화 평가를 위해 Pre Syringe(PR)의 용량을 15, 20, 25, 30 mCi로 설정하였고, Post Syringe(PO)의 용량을 1, 5, 10, 15 mCi로 각각 설정하였다. 그리고 각각의 Matrix size를 32 × 32, 64 × 64, 128 × 128, 256 × 256, 512 × 512, 1024 × 1024로 변경하여 값을 비교 평가하였다. Matrix Size에서 동위원소의 용량이 증가할수록 사구체 여과율의 차이는 최대 52.95%에서 최소 16.67%로 점차 감소하였다. Matrix size 변화에 따른 사구체 여과율 값은 128에서 256, 256에서 512, 512에서 1024로 변경 시 2.4%, 0.2%, 0.2%로 유사하게 나타났으나, 32에서 64, 64에서 128로 변경 시 54.3 %, 39.43%로 GFR 값의 차이가 발생하였다. 마지막으로, 현재 사용 중인 256 Matrix, Pre syringe 15 mCi의 GFR 값을 기준으로 32 Matrix, Pre Syringe 15 mCi, Post Syringe 1 mCi 조건에서 82%로 가장 큰 차이가 발생하였고, 64 Matrix, Pre Syringe 30 mCi, Post Syringe 15 mCi의 조건에서 0.2%로 유사한 결과 값을 나타내었다. 본 논문을 통해 ^99mTc-DTPA Renal Dynamic Scan에서 Gates 공식을 이용해 사구체 여과율을 측정할 때, 동위원소의 용량과 Matrix Size 변화에 따라 사구체 여과율 측정에 영향이 있음을 확인하였다. 그러므로 각 병원에서 이를 적용해 GFR을 측정할 때 적절한 Parameter를 적용해서 검사의 유용성을 높아야 한다고 생각한다.

• 대한수학회보
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• 제60권4호
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• pp.873-893
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• 2023

In 2017, Nikiforov proposed the A_𝛼-matrix of a graph G. This novel matrix is defined as A_𝛼(G) = 𝛼D(G) + (1 - 𝛼)A(G), 𝛼 ∈ [0, 1], where D(G) and A(G) are the degree diagonal matrix and adjacency matrix of G, respectively. Recently, Zhai, Xue and Liu [39] considered the Brualdi-Hoffman-type problem for Q-spectra of graphs with given matching number. As a continuance of it, in this contribution we consider the Brualdi-Hoffman-type problem for A_𝛼-spectra of graphs with given matching number. We identify the graphs with given size and matching number having the largest A_𝛼-spectral radius for ${\alpha}{\in}[{\frac{1}{2}},1)$.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권10호
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• pp.3482-3497
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• 2021

Artificial intelligence has emerged as the core of the 4th industrial revolution, and large amounts of data processing, such as big data technology and rapid data analysis, are inevitable. The most fundamental and universal data interpretation technique is an analysis of information through regression, which is also the basis of machine learning. Ridge regression is a technique of regression that decreases sensitivity to unique or outlier information. The time-consuming calculation portion of the matrix computation, however, basically includes the introduction of an inverse matrix. As the size of the matrix expands, the matrix solution method becomes a major challenge. In this paper, a new algorithm is introduced to enhance the speed of ridge regression estimator calculation through series expansion and computation recycle without adopting an inverse matrix in the calculation process or other factorization methods. In addition, the performances of the proposed algorithm and the existing algorithm were compared according to the matrix size. Overall, excellent speed-up of the proposed algorithm with good accuracy was demonstrated.

• Geomechanics and Engineering
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• 제28권2호
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• pp.135-143
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• 2022

Soils are natural granular materials whose mechanical properties differ according to the size and composition of the particles, so soils exhibit an obvious scale effect. Traditional soil mechanics is based on continuum mechanics, which can not reflect the impact of particle size on soil mechanics. On that basis, a matrix-reinforcing-particle cell model is established in which the reinforcing particles are larger-diameter sand particles and the matrix comprises smaller-diameter bentonite particles. Since these two types of particles deform differently under shear stress, a new shear-strength theory under direct shear that considers the stress concentration and bypass phenomena of the matrix is established. In order to verify the rationality of this theory, a series of direct shear tests with different reinforcing particle diameter and volume fraction ratio are carried out. Theoretical analysis and experimental results showed that the interaction among particles of differing size and composition is the basic reason for the size effect of soils. Furthermore, the stress concentration and bypass phenomena of the matrix enhance the shear strength of a soil, and the volume ratio of reinforcing particles has an obvious impact on the shear strength. In addition, the newly proposed shear-strength theory agrees well with experimental values.

• 대한화장품학회지
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• 제22권2호
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• pp.182-192
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• 1996

In this study, the relationship between wax matrix in lipstick and sweating was investigated by observing the change of size and shape of wax matrix with sweating by Scanning Electron Microscopy (SEM). For observation by SEM, a lipstick sample was frozen in liquid nitrogen, then the oil in the lipstick was extracted out in cold isopropanol($-70^{\circ}C$) for 1-3days. After isopropanol was evaporated, the sample was sputtered with gold, and examined by SEM. When examined the sweated sample by SEM, the change of wax matrix underneath the surface from fine, uniform structure to coarse, nonuniform structure was observed, which was resulted from the caking of surrounding wax matrix. That is, the oil underneath the surface was migrated to the surface of lipstick with sweating, consequently the wax matrix at that region was rearranged into the coarse matrix. In case of flamed lipstick, sweating was delayed and the wax matrix was much coarser than that of unflamed one. Its larger wax matrix at surface region was good for including oil. The effect of molding temperature on sweating was also studied. As the molding temperature was increased, sweating was greatly reduced and the size of wax matrix was increased. It was also found that sweating was influenced with the compatinility of wax and oil. A formula consisting of wax and oil which have good compatibility has a tendency of reduced sweating and increased size of wax matrix. When pigment was added to wax and oil. It was also found that sweating was influenced with the passage of time by observing a thick membrane of wax on surface of lipstick after a month from molding. In case of some lipsticks, the size of wax matrix was altered to bigger or smaller. In conclusion, the structure of wax matrix at the surface region of lipstick was changed with the process of foaming, molding temperature, compatibility of wax and oil, addition of pigment, and the passage of time. In most cases, as the size of wax matrix was increased, sweating was reduced and delayed.