• 대한수학회보
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• 제39권1호
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• pp.133-140
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• 2002

On compact complex hyperbolic manifolds of complex dimension two, we show that the dimension of the space of infinitesimal deformations of self-dual conformal structures is smaller than that of the deformation obstruction space and that every self-dual metric with covariantly constant Ricci tensor must be a standard one upto rescalings and diffeomorphisms.

• 대한수학회지
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• 제37권5호
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• pp.687-705
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• 2000

The main purpose of this paper is to study differentiable one-parameter groups and cosine families of operators acting on white noise functions and their associated infinitesimal generators. In particular, we prove the heredity of differentiable one-parameter group and cosine family of operators under the second quantization of the Cuchy problems for the first and second or der differential equations.

• 대한수학회지
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• 제40권4호
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• pp.695-708
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• 2003

We study the existence of solutions for overdetermined PDE systems that admit prolongation to a complete system. We reduce the problem to a Pfaffian system on a submanifold of the jet space of unknown functions and then express the integrability conditions in terms of the coefficients of the original system. As possible applications we present some local problems in CR geometry: determining the CR embeddibility into spheres and the existence of infinitesimal CR automorphisms.

• Journal of applied mathematics & informatics
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• 제24권1_2호
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• pp.541-545
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• 2007

In this paper, we study the infinitesimal transformation on the fibred Riemannian space. The conharmonic curvature tensor is invariant under the conharmonic transformation. We have proved that the conharmonically flat fibred Riemannian space with totally geodesic fibre is locally the Riemannian product of the base space and a fibre.

• Korean Journal of Mathematics
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• 제29권3호
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• pp.547-554
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• 2021

The object of the present paper is to characterize Sasakian 3-manifolds admitting a gradient Ricci-Yamabe soliton. It is shown that a Sasakian 3-manifold M with constant scalar curvature admitting a proper gradient Ricci-Yamabe soliton is Einstein and locally isometric to a unit sphere. Also, the potential vector field is an infinitesimal automorphism of the contact metric structure. In addition, if M is complete, then it is compact.

• 충청수학회지
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• 제33권3호
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• pp.365-374
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• 2020

Given a noncompact semisimple Lie group G and its maximal compact Lie subgroup K such that the right multiplication of each element in K gives an isometry on G, consider a principal bundle G → G/K, which is a Riemannian submersion. We study the infinitesimal holonomy isometries. Given a closed curve at eK in the base space G/K, consider the holonomy displacement of e by the horizontal lifting of the curve. We prove that the correspondence is continuous.

• Kyungpook Mathematical Journal
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• 제63권1호
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• pp.97-104
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• 2023

In the present paper, we characterize, for a class of almost Kenmotsu manifolds, those that admit quasi Yamabe solitons. We show that if a (k, 𝜇)'-almost Kenmotsu manifold admits a quasi Yamabe soliton (g, V, 𝜆, 𝛼) where V is pointwise collinear with 𝜉, then (1) V is a constant multiple of 𝜉, (2) V is a strict infinitesimal contact transformation, and (3) (£_Vh')X = 0 holds for any vector field X. We present an illustrative example to support the result.

• Kyungpook Mathematical Journal
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• 제18권1호
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• pp.109-117
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• 1978

• 전자공학회논문지
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• 제49권9호
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• pp.287-292
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• 2012

본 논문에서는 액체의 전기 전도도를 저잡음으로 검출하기 위하여 동기복조를 이용하는 전도도 검출기를 설계한다. 이를 위하여 검출기는 반송파 발생기, 전도도 검출 셀, 전류-전압 변환기 및 동기 복조기로 구성하며, 복조기의 대역폭을 조정하여 검출기의 신호 대 잡음비(SNR)를 개선함으로써, 액체의 극미한 전도도도 용이하게 측정할 수 있도록 한다. 이의 응용 예로써, 반도체 공정의 공기감시용 전도도 검출기를 동기복조를 이용하여 설계하며, 실험을 통하여 설계의 타당성을 확인한다. 실험 결과, 검출기는 설계 성능에 부합하는 특성을 나타내므로, 동기복조를 이용한 전도도 검출기는 액체의 극미한 전도도 측정에 유용하게 사용될 수 있음을 입증하였다.

• 한국공작기계학회논문집
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• 제12권2호
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• pp.44-52
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• 2003

This research suggests a cutting force model for the ball end milling processes. This model includes the effect of tool run out and tool deflection. In the proposed model, the flutes of ball end mills are considered as series of infinitesimal elements and each cutting edge is assumed to be straight for the analysis of the oblique cutting process, in which the small cutting edge element has been analyzed as an orthogonal cutting process n the plane including the cutting velocity and the chip-flow vector. Therefor, the cutting forces can be calculated through the model using the orthogonal cutting data obtained from the orthogonal cutting test. In order to enhance the performance of the model, the flutes of ball end mill are defined to keep geometric consistency at the peak of the ball part and the junction with the end mill part. The divided infinitesimal cutting edges are regulated to be even lengths. Some experiments show the validity of the developed model in the various cutting coalitions.