• Journal of the Korean Mathematical Society
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• v.57 no.1
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• pp.195-213
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• 2020

We define two types of null hypersurfaces as; isoparametric and quasi isoparametric null hypersurfaces of Lorentzian space forms, based on the two shape operators associated with a null hypersurface. We prove that; on any screen conformal isoparametric null hypersurface, the screen geodesics lie on circles in the ambient space. Furthermore, we prove that the screen distributions of isoparametric (or quasi isoparametric) null hypersurfaces with at most two principal curvatures are generally Riemannian products. Several examples are also given to illustrate the main concepts.

• Kyungpook Mathematical Journal
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• v.49 no.4
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• pp.789-799
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• 2009

In this study we consider ${\varphi}$-conformally flat, ${\varphi}$-conharmonically flat, ${\varphi}$-projectively at and ${\varphi}$-concircularly flat Lorentzian ${\alpha}$-Sasakian manifolds. In all cases, we get the manifold will be an ${\eta}$-Einstein manifold.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.3
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• pp.267-273
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• 1992

An advanced on-resistance model of VDMOS devices in the low voltage regimes is proposed and verified by 2-D device simulations. The model considers the lateral gaussian doping profiles in the channel region and exact current spreading angles in the epitaxial layer for both linear and cellular geometries by employing the conformal mapping, It is found out that the on-resistance of low voltage VDMOS may be overestimated considerably if it is analyzed by the conventional method. The 2-D device simulation results show that the proposed model is valid for the VDMOS devices in the low voltage regimes.

• Proceedings of the Korean Biophysical Society Conference
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• 2002.06b
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• pp.25-26
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• 2002

The goal of radiation therapy is to maximize the tumor dose and to minimize the dose of normal tissue. In order to achieve this goal, the new radiation therapy techniques such as three dimensional conformal therapy or intensity modulated radiation therapy has been developed and tried to clinical application. The relationship between radiation dose and normal tissue response is an interesting subject in the radiation therapy field.(omitted)

• Honam Mathematical Journal
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• v.26 no.3
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• pp.341-353
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• 2004

We denote by ${{\mathcal{Q}}(A)}$ the set of all matrices with the same sign pattern as A. A matrix A has signed null-space provided there exists a set ${\mathcal{S}}$ of sign patterns such that the set of sign patterns of vectors in the null-space of ${\tilde{A}}$ is ${\mathcal{S}}$, for each ${\tilde{A}}{\in}{{\mathcal{Q}}(A)}$. Some properties of matrices with signed null-spaces are investigated.

• Honam Mathematical Journal
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• v.28 no.3
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• pp.333-342
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• 2006

We denote by Q(A) the set of all matrices with the same sign pattern as A. A matrix A is an SN-matrix provided there exists a set S of sign patterns such that the set of sign patterns of vectors in the null-space of A is S, for each A ${\in}$ Q(A). We have a characterization of an SN-matrix related with L-matrix and we analyze the structure of an SN-matrix.

• Honam Mathematical Journal
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• v.40 no.2
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• pp.367-376
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• 2018

The object of the present paper is to study the Kenmotsu manifolds which metric tensor is ${\eta}$-Ricci soliton. We bring out curvature conditions for which Ricci solitons in Kenmotsu manifolds are sometimes shrinking or expanding and some other times steady.

• 한국전산유체공학회:학술대회논문집
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• 2002.10a
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• pp.88-94
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• 2002

Curved intakes are commonly used from commercial aircraft to military missile. Sound radiation from the intake of air vehicle affects cabin noise, community noise and military detection. In this paper, Sound radiation from curved intake is computed using the high order, high resolution scheme. The generalized characteristic boundary conditions, adaptive nonlinear artificial dissipation model and conformal mapping for high order, high resolution scheme are used. The geometric change of curved intake and the frequency of acoustic source are considered. Two dimensional Euler equations are solved for theses analyses.

• Honam Mathematical Journal
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• v.30 no.3
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• pp.487-504
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• 2008

In this paper we study the geometry of codimension 2 screen conformal Einstein half lightiike submanifolds M of a semi-Riemannian manifold $(\={M}(c),\={g})$ of constant curvature c, with a Killing co-screen distribution on $\={M}$. The main result is a classification theorem for screen homothetic Einstein half lightlike submanifold of Lorentzian space forms.

• Journal of Industrial Technology
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• v.9
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• pp.119-125
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• 1989

Lennard-Jones 유체 혹은 거의 구형에 가까운 분자들의 혼합물의 열역학적 성질을 예측하기 위한 용액이론이 유도되었다. 이 이론에는 에너지와 분자직경에 대한 두 개의 변수가 존재하며, 강구(hard sphere)를 중심으로 하여 동경함수(pair distribution function)를 확장시키는 교반이론(perturbation theory)에서 1/kT에 대한 일차와 이차계수의 관계로부터 얻어지는 혼합법칙을 이용하는 HSE이론과 달리 Orstein-Zernike결과와 일치되는 분자직경 변수를 먼저 구한 다음, 일차계수와 함께 얻어진 혼합법칙이 유도되었다. 이 방법으로 위 유체들의 혼합물에 적용시켰을 때, 원래의 HSE나 vdW-1의 방법보다 좋은 결과의 열역학적 성질을 예측할 수 있었다.