• Journal of the Chungcheong Mathematical Society
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• v.21 no.1
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• pp.29-48
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• 2008

We deal with the classification problem of real hypersurfaces in a complex hyperbolic space. In order to classify real hypersurfaces in a complex hyperbolic space we characterize a real hypersurface M in $H_n(\mathbb{C})$ whose structure vector field is not principal. We also construct extrinsically homogeneous real hypersurfaces with four distinct curvatures and their structure vector fields are not principal.

• Bulletin of the Korean Mathematical Society
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• v.33 no.1
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• pp.45-55
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• 1996

Recently, Giannessi [1] introduced a vector variational inequalityy for vector-valued functions in an Euclidean space. Since then, Chen et al. [2-6], Lee et al. [7], and Yang [8] have intensively studied vector variational inequalities for vector-valued functions in abstract spaces.

• Journal of Digital Contents Society
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• v.16 no.6
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• pp.909-916
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• 2015

This paper presents a method to display the 3D vector fields by analyzing phase space. This method is based on the connections between ordinary differential equations and the topology of vector fields. The phase space analysis should be geometric interpolation of an autonomous system of equation in the form of the phase space. Every solution of it system of equations corresponds not to a curve in a space, but the motion of a point along the curve. This analysis is the basis of this paper. This new method is required to decompose the hexahedral cell into five or six tetrahedral cells for 3D vector fields. The critical points can be easily found by solving a simple linear system for each tetrahedron. The tangent curves can be integrated by finding the intersection points of an integral curve traced out by the general solution of each tetrahedron and plane containing a face of the tetrahedron.

• Communications of the Korean Mathematical Society
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• v.21 no.3
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• pp.429-432
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• 2006

We use Cauchy's functional equation to construct a new non-measurable set which is a (vector) subspace of \mathbb{R}$ and is of a codimensiion 1, considering \mathbb{R}$, the set of real numbers, as a vector space over a field \mathbb{Q}$ of rational numbers. Moreover, we show that \mathbb{R}$ can be partitioned into a countable family of disjoint non-measurable subsets.

• Bulletin of the Korean Mathematical Society
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• v.42 no.2
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• pp.279-294
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• 2005

We study a real hypersurface M satisfying $L_{\xi}S=0\;and\;R_{\xi}S=SR_{\xi}$ in a complex hyperbolic space $H_n\mathbb{C}$, where S is the Ricci tensor of type (1,1) on M, $L_{\xi}\;and\;R_{\xi}$ denotes the operator of the Lie derivative and the Jacobi operator with respect to the structure vector field e respectively.

• Korean Journal of Mathematics
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• v.30 no.4
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• pp.561-569
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• 2022

In this paper, we study the generalization of the Banach contraction principle in the vector space, involving four rational square terms in the inequality, by using the notation of bilinear functional. We also present an extension of Selberg's inequality to vector space.

• Journal of Power Electronics
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• v.13 no.4
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• pp.647-655
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• 2013

In this paper, an approach to reduce the common-mode voltage and to eliminate narrow pulse for implemented AC-DC matrix converters is presented. An improved space vector modulation (SVM) strategy is developed by replacing the zero space vectors with suitable pairs of active ones. Further, while considering the commutation time, the probability of narrow pulse in the conventional and proposed SVM methods are derived and compared. The advantages of the proposed scheme include: a 50% reduction in the peak value of the common-mode voltage; improved input and output performances; a reduction in the switching loss by a reduced number of switching commutations and a simplified implementation via software. Experimental results are presented to demonstrate the correctness of the theoretical analysis, as well as the feasibility of the proposed strategy.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.337-341
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• 1994

This paper describes an effort to develop a simulator of Active Power Filter (APF) by three dimentional(3-D) space current co-ordinate. System current is represented by 3-D vector composed of three current components - active, reactive and distorted. %THD (%Total Harmonics Distortion) can be converted to height-angle of system current vector and power factor can be defined on 3-D space current co-ordinate without loss of generality. Current of APF and power system can be analyzed by 3-D visualization of current vector trajectory. So, the computer simulation results show that the proposed method by 3-D space current co-ordinate make up for disadvantages of performance evaluation on time / frequency domain.

• Journal of Power Electronics
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• v.15 no.2
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• pp.497-503
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• 2015

This paper analyses the harmonic pollution to power grids caused by several high-power rectifiers, summarizes the requirements for rectifiers in suppressing grid-side current harmonics and optimizes a new-type of current source PWM rectifier with a hybrid switch. The rectifier with a hybrid switch boasts significant current characteristics and cost advantages in the high-power area. To further enhance the working frequency of the current source rectifier with a hybrid switch for suppressing grid-side harmonics and reducing the inductance size, this paper proposes an optimal control strategy based on space vector. It also verifies that the optimal control strategy based on space vector can reduce the total harmonic distortion of the grid-side current of the rectifier with a hybrid switch via circuit simulation and experimental results.

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.368-371
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• 2003

In this paper, we present a way that can implement the vector control Algorithm of induction motor and PWM signal generation on the condition Matlab/Simulink. The overall system model is designed by Simulink toolbox for vector control in induction motor. and then implement experiment with the DS1103 board of dSPACE. Although we are not coding the system, it is capable of doing simulation and experiment simultaneously. That is why Matlab and dSPACE board compiler can generate the "*.c" and "*.obj" files on the designed system automatically. After considering about hardware structure and driving system in DS1103 board. we verify the availability of proposed method through making a comparison/analysis between simulation and experiment.