• 대한수학회지
• /
• 제53권5호
• /
• pp.1077-1100
• /
• 2016

We develop an invariant local theory of Lorentz surfaces in pseudo-Euclidean 4-space by use of a linear map of Weingarten type. We find a geometrically determined moving frame field at each point of the surface and obtain a system of geometric functions. We prove a fundamental existence and uniqueness theorem in terms of these functions. On any Lorentz surface with parallel normalized mean curvature vector field we introduce special geometric (canonical) parameters and prove that any such surface is determined up to a rigid motion by three invariant functions satisfying three natural partial differential equations. In this way we minimize the number of functions and the number of partial differential equations determining the surface, which solves the Lund-Regge problem for this class of surfaces.

• 대한수학회보
• /
• 제56권5호
• /
• pp.1315-1325
• /
• 2019

The purpose of this article is to study the Ricci solitons and Ricci almost solitons on para-Kenmotsu manifold. First, we prove that if a para-Kenmotsu metric represents a Ricci soliton with the soliton vector field V is contact, then it is Einstein and the soliton is shrinking. Next, we prove that if a ${\eta}$-Einstein para-Kenmotsu metric represents a Ricci soliton, then it is Einstein with constant scalar curvature and the soliton is shrinking. Further, we prove that if a para-Kenmotsu metric represents a gradient Ricci almost soliton, then it is ${\eta}$-Einstein. This result is also hold for Ricci almost soliton if the potential vector field V is pointwise collinear with the Reeb vector field ${\xi}$.

• Korean Journal of Mathematics
• /
• 제29권2호
• /
• pp.445-453
• /
• 2021

The purpose of the paper is to study of Para-Kenmotsu metric as a 𝜂-Ricci soliton. The paper is organized as follows: • If an 𝜂-Einstein para-Kenmotsu metric represents an 𝜂-Ricci soliton with flow vector field V, then it is Einstein with constant scalar curvature r = -2n(2n + 1). • If a para-Kenmotsu metric g represents an 𝜂-Ricci soliton with the flow vector field V being an infinitesimal paracontact transformation, then V is strict and the manifold is an Einstein manifold with constant scalar curvature r = -2n(2n + 1). • If a para-Kenmotsu metric g represents an 𝜂-Ricci soliton with non-zero flow vector field V being collinear with 𝜉, then the manifold is an Einstein manifold with constant scalar curvature r = -2n(2n + 1). Finally, we cited few examples to illustrate the results obtained.

• 대한수학회논문집
• /
• 제38권3호
• /
• pp.865-880
• /
• 2023

The main intention of the current paper is to characterize certain properties of *-conformal Ricci solitons on non-coKähler (𝜅, 𝜇)-almost coKähler manifolds. At first, we find that there does not exist *-conformal Ricci soliton if the potential vector field is the Reeb vector field θ. We also prove that the non-coKähler (𝜅, 𝜇)-almost coKähler manifolds admit *-conformal Ricci solitons if the potential vector field is the infinitesimal contact transformation. It is also studied that there does not exist *-conformal gradient Ricci solitons on the said manifolds. An example has been constructed to verify the obtained results.

• Journal of Magnetics
• /
• 제8권4호
• /
• pp.164-168
• /
• 2003

In high density recording system, the recording head field on a medium should be focused in small bit area and should have a sufficient value to overcome the medium coercivity, which resulted in head saturation. In this paper, an efficient method to access the head field and field gradient considering head saturation is presented. The magnetic vector potential on the head surface is pre-calculated considering head saturation in several cases and accumulated into database. The head field on the recording media is easily produced solving Laplace equation using accessed magnetic vector potential boundaries. The computed head field is compared with a quantified magnetic force microscopy measurement.

• 한국멀티미디어학회논문지
• /
• 제11권10호
• /
• pp.1460-1470
• /
• 2008

최근 휴대용 기기의 성능이 향상되면서 다양한 형태의 메뉴 구성과, 메일 및 이차원 지도 등의 표현에 벡터 그래픽을 많이 도입하고 있다. 본 논문은 모바일 기기에서 많이 사용되고 여는 이차원 벡터의 처리 기술인 OpenVG (Open Vector Graphics)의 하드웨어 가속기를 제안했다. 제안된 하드웨어 가속기는 그래픽에서 처리가 빈번한 렌더링(rendering)의 각 기능을 분석하여 하드웨어 구현에 적합하도록 나누고, 그 알고리즘을 설계 및 검증하여 HDL (Hardware Description Language)로 FPGA (Field Programmable Gate Array)에 이식하여 구현되었으며, 알렉스 처리기에 비하여 약 4배의 빠른 처리속도를 보였다.

• Bulletin of the Korean Chemical Society
• /
• 제14권1호
• /
• pp.21-29
• /
• 1993

For the study of relaxation processes in complex spin system, a general master equation, which can be used to simulate a vast range of pulse experiments, has been formulated using the Liouville representation of quantum mechanics. The state of a nonequilibrium spin system in magnetic field is described by a density vector in Liouville space and the time evolution of the system is followed by the application of a linear master operator to the density vector in this Liouville space. In this master equation the nuclear spin relaxation due to intramolecular dipolar interaction or randomly fluctuating field interaction is explicitly implemented as a relaxation supermatrix for a strong coupled two-spin (1/2) system. The whole dynamic information inherent in the spin system is thus contained in the density vector and the master operator. The radiofrequency pulses are applied in the same space by corresponding unitary rotational supertransformations of the density vector. If the resulting FID is analytically Fourier transformed, it is possible to represent the final nonstationary spectrum using a frequency dependent spectral vector and intensity determining shape vector. The overall algorithm including relaxation interactions is then translated into an ANSIFORTRAN computer program, which can simulate a variety of two dimensional spectra. Furthermore a new strategy is tested by simulation of multiple quantum signals to differentiate the two relaxation interaction types.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2004년도 학술대회지
• /
• pp.503-508
• /
• 2004

This paper proposes an efficient computation method for fixed and mixed polarity Reed -Muller function vector over Galois field GF(p). Function vectors of fixed polarity Heed Muller function with single variable can be generated by proposed method. The n-variable function vectors can be calculated by means of the Kronecker product of a single variable function vector corresponding to each variable. Thus, all fixed and mixed polarity Reed-Muller function vectors are calculated directly without using a polarity function vector table or polarity coefficient matrix.

• 대한기계학회논문집A
• /
• 제20권6호
• /
• pp.1819-1826
• /
• 1996

This paper present the claculating method of optimum correction mass within permissible vibration linits for ratating machinery in two-plane field balancing. Basic technique of this method is based on influence coefficient method, and grphic vector composition that the resultant of two influence vectors obtained by trial mass have to be equilibrium with initial vibration vector in the each correction plane. Genetic algorithm which is a search algorithm based on the mechanism of natural selection and natural genetics is sued for vector composition, and SUMT method is used to objective function which seeks optimum correction mass for balancing a rotor.

• 한국정밀공학회지
• /
• 제22권2호
• /
• pp.70-78
• /
• 2005

In this paper, a novel rotor flux estimation method of an induction motor using support vector regression(SVR) is presented. Two well-known different flux models with respect to voltage and current are necessary to estimate the rotor flux of an induction motor. Training of SVR which the theory of the SVR algorithm leads to a quadratic programming(QP) problem. The proposed SVR rotor flux estimator guarantees the improvement of performance in the transient and steady state in spite of parameter variation circumstance. The validity and the usefulness of proposed algorithm are throughly verified through numerical simulation.