• Kyungpook Mathematical Journal
• /
• 제43권4호
• /
• pp.503-512
• /
• 2003

In this paper, we first give an alternative description of the fundamental orthodox semigroup $\bar{A}$(1, 2). We then use this to represent the double four-spiral semigroup $DSp_4$ as a regular Rees matrix semigroup over $\bar{A}$(1, 2).

• 한국수학교육학회지시리즈B:순수및응용수학
• /
• 제20권1호
• /
• pp.25-35
• /
• 2013

In this paper, we study lightlike hypersurfaces of an indefinite Sasakian manifold $\bar{M}$. First, we construct a type of lightlike hypersurface according to the form of the structure vector field of $\bar{M}$, named by ascreen lightlike hypersurface. Next, we characterize the geometry of such ascreen lightlike hypersurfaces.

• 대한수학회보
• /
• 제51권6호
• /
• pp.1711-1726
• /
• 2014

In this paper, we study the geometry of indefinite generalized Sasakian space form $\bar{M}(f_1,f_2,f_3)$ admitting a generic lightlike submanifold M subject such that the structure vector field of $\bar{M}(f_1,f_2,f_3)$ is tangent to M. The purpose of this paper is to prove a classification theorem of such an indefinite generalized Sasakian space form.

• Kyungpook Mathematical Journal
• /
• 제55권4호
• /
• pp.1097-1104
• /
• 2015

In this paper, we study the geometry of indefinite generalized Sasakian space form $\bar{M}(f_1,f_2,f_3)$ admitting a lightlike hypersurface M subject such that the almost contact structure vector field ${\zeta}$ of $\bar{M}(f_1,f_2,f_3)$ is tangent to M. We prove a classification theorem of such an indefinite generalized Sasakian space form.

• 대한수학회논문집
• /
• 제32권4호
• /
• pp.1047-1065
• /
• 2017

The notion of a non-metric ${\phi}$-symmetric connection on semi-Riemannian manifolds was introduced by Jin [6, 7]. The object of study in this paper is generic lightlike submanifolds of an indefinite Kaehler manifold ${\bar{M}}$ with a non-metric ${\phi}$-symmetric connection. First, we provide several new results for such generic lightlike submanifolds. Next, we investigate generic lightlike submanifolds of an indefinite complex space form ${\bar{M}}(c)$ with a non-metric ${\phi}$-symmetric connection.

• East Asian mathematical journal
• /
• 제31권3호
• /
• pp.337-344
• /
• 2015

We study screen quasi-conformal irrotational half lightlike submanifolds M of a semi-Riemannian space form $\bar{M}$ (c) equipped with a semi-symmetric non-metric connection subject such that the structure vector field of $\bar{M}$ (c) belongs to the screen distribution S(TM). The main result is a non-existence theorem for such half lightlike submanifolds.

• East Asian mathematical journal
• /
• 제30권3호
• /
• pp.371-383
• /
• 2014

We study the geometry of lightlike submanifolds of a semi-Riemannian manifold. The purpose of this paper is to prove two singular theorems for irrotational lightlike submanifolds M of a semi-Riemannian space form $\bar{M}(c)$ admitting a semi-symmetric non-metric connection such that the structure vector field of $\bar{M}(c)$ is tangent to M.

• 한국추진공학회지
• /
• 제14권6호
• /
• pp.17-24
• /
• 2010

비충돌형 인젝터로부터 발생하는 액체추진제 분무의 준3차원 구조를 규명하기 위한 연구를 수행하였다. 인젝터 출구 근처에서의 분무 형상을 고속카메라를 사용하여 촬영하였고, 인젝터 분무에서 주기적 흘림현상이 관찰되었다. 또, 이중모드 위상도플러속도계(Dual-mode Phase Doppler Anemometry, DPDA)로 분무특성 매개변수(속도, 직경, 부피유속 등)를 측정하여 인젝터 분무의 공간분포 특성을 파악하였다. 본 실험은 분사압력 17.2~27.6 bar의 조건에서 분사축방향 및 확산방향 거리를 변화시키며 수행하였다.

• 한국구조물진단유지관리공학회 논문집
• /
• 제15권6호
• /
• pp.201-211
• /
• 2011

우리나라는 삼면이 바다로 이루어져 있으며 많은 철근콘크리트 구조물이 위치해 있다. 만약 철근콘크리트 구조물이 염해의 노출이 장기화 된다면 철근의 부식으로 인하여 철근-콘크리트 부착성능이 감소될 뿐만 아니라, RC 구조물의 성능저하가 우려되고 있다. 따라서 본 연구에서는 부착성능이 상실된 RC 보-기둥 접합부에 대한 기초자료를 확보하기 위해 연구를 수행하였다. 철근-콘크리트 부착이 상실된 보-기둥 접합부를 제작하여 부착 및 비부착 특성 여부에 따라 반복 횡하중 실험 및 해석적 연구를 수행하여 접합부의 성능을 평가 및 고찰하였다.

• East Asian mathematical journal
• /
• 제40권1호
• /
• pp.1-23
• /
• 2024

Let M be a semi-invariant submanifold of codimension 3 with almost contact metric structure (𝜙, 𝜉, 𝜂, g) in a complex space form M_n+1(c). We denote by A, K and L the second fundamental forms with respect to the unit normal vector C, D and E respectively, where C is the distinguished normal vector, and by R_𝜉 = R(𝜉, ·)𝜉 the structure Jacobi operator. Suppose that the third fundamental form t satisfies dt(X, Y) = 2𝜃g(𝜙X, Y) for a scalar 𝜃(≠ 2c) and any vector fields X and Y , and at the same time R_𝜉K = KR_𝜉 and ∇_{𝜙∇𝜉𝜉}R_𝜉 = 0. In this paper, we prove that if it satisfies ∇_𝜉R_𝜉 = 0 on M, then M is a real hypersurface of type (A) in M_n(c) provided that the scalar curvature $\bar{r}$ of M holds $\bar{r}-2(n-1)c{\leq}0$.