이재원 교수

There are many situations where investigators are not able to specify in advance the specific type of the survival differences that may exist between two groups. In this article, some versatile test procedures sensitive to a wide range of types of survival differences have been proposed. Either the maximum or a linear combination of selected members of the family of weighted log-rank statistics is considered. Simulation studies provide some insights into the properties of the proposed statistics

Abstract There are many clinical trials in which the patients enter sequentially, and a response variable is measured repeatedly over time for each patient. A group sequential procedure is proposed for comparing the rates of change between two treatment groups. Some existing procedures for testing the equality of means between two treatment groups with repeated measurements data, such as those proposed by Armitage, Stratton, and Worthington and by Geary, can be interpreted as special cases of th

The purpose of this paper is to study pointwise slant submersions from almost Hermitian manifolds which extends slant submersion in a natural way. Several basic results in this point of view are proven in this paper.

Most group sequential testing procedures assume that each patient has only one response. Thus interim test statistics have independent increments. In many clinical trials, however, a response variable is measured at each follow-up visit. In this article, I review some recently developed group sequential methods for repeated measures and for other types of multivariate responses. Six parametric methods and three non-parametric methods are included. My review focuses on the comparison of the assum

In this paper, we prove two optimal inequalities involving the intrinsic scalar curvature and extrinsic Casorati curvature of submanifolds of real space forms endowed with a semi-symmetric metric connection. Moreover, we show that in both cases, the equality at all points characterizes the invariantly quasi-umbilical submanifolds. MSC:53C40, 53B05.

Abstract For comparing responses in two groups of subjects observed repeatedly, we propose a group sequential procedure based on linear rank statistics. The asymptotic normality of the sequentially computed linear rank statistics is obtained, and construction of the group sequential boundaries is based on this distribution theory. By virtue of this asymptotic approximation, the proposed procedure can be applied to interim analyses with either continuous or discrete repeated measurements. Even fo

Abstract There are many clinical trials in which the patients enter sequentially, and a response variable is measured repeatedly over time for each patient. A group sequential procedure is proposed for comparing the rates of change between two treatment groups. Some existing procedures for testing the equality of means between two treatment groups with repeated measurements data, such as those proposed by Armitage, Stratton, and Worthington and by Geary, can be interpreted as special cases of th

In this paper we give a new proof for two sharp inequalities involving generalized normalized δ-Casorati curvatures of a slant submanifold in a quaternionic space form. These inequalities were recently obtained in Lee and Vîlcu (Taiwan. J. Math. 19(3):691-702, 2015) using an optimization procedure by showing that a quadratic polynomial in the components of the second fundamental form is parabolic. The new proof is obtained analyzing a suitable constrained extremum problem on submanifold.

We introduce anti-invariant ξ⊥ -Riemannian submersions from almostcontact manifolds onto Riemannian manifolds. We give an example,investigate the geometry of foliations which are arisen from the definition of a Riemannian submersion and check the harmonicity of suchsubmersions. We also find necessary and sufficient conditions for a special anti-invariant ξ⊥ -Riemannian submersion to be totally geodesic.Moreover, we obtain decomposition theorems for the total manifold ofsuch submersions.

Lightlike geometry has its applications in general relativity, particularly in black hole theory. Indeed, it is known that lightlike hypersurfaces are examples of physical models of Killing horizons in general relativity (Galloway, 2007). In this paper, we introduce the definition of generic lightlike submanifolds of an indefinite cosymplectic manifold. We investigate new results on a class of generic lightlike submanifolds M of an indefinite cosymplectic manifold .

유전적 정보와 관련한 연관성 연구에서 최근 많이 이용되고 있는 유전자는 단일염기서열다형성(single nucleotide polymorphism; SNP)이며, SNP에 의해서 추정되는 일배체형(haplotype) 정보에 대한 연구가 활발히 진행되고 있다. 이러한 연구는 한국인에서 질병과 관련하여 유용한 유전자의 구성을 찾아내고 질병 진단과 치료의 효과에 미치는 영향을 규명하고자 하는 것이다. 연관성 연구들에서 유전자들 간의 연관 불균형성(linkage disequilibrium, 유전자 간의 상관성)과, 질병과 유전자형 간의 오즈비(odds ratio; 유전자와 질병과의 연관성)는 중요한 변수가 되며, 최근에는 환경적 요인 또한 중요 변수가 되고 있다. 본 논문에서는 질병과 유전자에 대한 연관성 연구에서 연구 결과에 영향을 미칠 수 있는 상황들에 따른 모의실험을 통해 연관성 분석에서 유용한 접근 방법들을 살펴보았다.주요용어 : 단일염기서열다형성(SNP), 일배체형(haplotype

The goal of this paper is to prove new upper bounds for the first positive eigenvalue of the [Formula: see text]-Laplacian operator in terms of the mean curvature and constant sectional curvature on Riemannian manifolds. In particular, we provide various estimates of the first eigenvalue of the [Formula: see text]-Laplacian operator on closed orientate [Formula: see text]-dimensional Lagrangian submanifolds in a complex space form [Formula: see text] with constant holomorphic sectional curvature

In 1999, B. Y. Chen established a sharp inequality between the Ricci curvature and the squared mean curvature for an arbitrary Riemannian submanifold of a real space form. This inequality was extended in 2015 by M. E. Aydin et al. to the case of statistical submanifolds in a statistical manifold of constant curvature, obtaining a lower bound for the Ricci curvature of the dual connections. Also, the similar inequality for submanifolds in statistical manifolds of quasi-constant curvature studied