• The Journal of Korean Institute of Next Generation Computing
• /
• v.15 no.3
• /
• pp.25-30
• /
• 2019

Magnetic sensors have the disadvantage that their vector values differ depending on the direction. In this paper, we propose a magnetic vector calibration method for geomagnetic-based indoor localization estimates. The fingerprinting technique used in geomagnetic-based indoor localization the position by matching the magnetic field map and the magnetic sensor value. However, since the moving direction of the current user may be different from the moving direction of the person who creates the magnetic field map at the collection time, the sampled magnetic vector may have different values from the vector values recorded in the field map. This may substantially lower the positioning accuracy. To avoid this problem, the existing studies use only the magnitude of magnetic vector, but this reduces the uniqueness of the fingerprint, which may also degrade the positioning accuracy. In this paper we propose a vector calibration algorithm which can adjust the sampled magnetic vector values to the vector direction of the magnetic field map by using the parametric equation of a circle. This can minimize the inaccuracy caused by the direction mismatch.

• Journal of Advanced Marine Engineering and Technology
• /
• v.28 no.2
• /
• pp.185-191
• /
• 2004

This study describes the scheme of vector drive system without speed sensor for AC servo motor using theory of a flux observer and based on the field oriented vector control. The new method of speed estimation is presented from operate with the position and magnitude of the secondary flux which obtain from the voltage reference and detected current. As the estimated speed is settled by the flux and the machine-specific parameters. this method don't need to adjust the gain of the parameter. Based on the derived theory for vector control. the scheme for sensorless vector drive of AC servo motor is designed and realized. And the experiment verifies it passable to realize the sensorless vector drive based on a field-oriented type.

• Bulletin of the Korean Mathematical Society
• /
• v.42 no.1
• /
• pp.1-4
• /
• 2005

In this paper, we will prove that in a compact almost Kahlerian manifold $M^n$, any conformal Killing vector field is Killing if n $\ge$ 4.

• Journal of KIISE:Computer Systems and Theory
• /
• v.33 no.4
• /
• pp.216-222
• /
• 2006

Vector field has been commonly used to visualize the data set which is invisible or is hard to explain. For instance, it could be used to visualize scientific data such as the direction and amount of wind and water field, transfer of heat through thermally conductive materials, and electromagnetic field. In this paper, we present a technique to enable intuitive recognition of the data though haptic feedback along with visual feedback. To add tactile information to graphical vector field, we model a haptic vector field and then apply it to the haptic map to guide a user to destination and haptic simulation of water field on 2D images whish can be used ill everyday life. These systems allow one to recognize vector information intuitively through haptic interface. We expect that the haptic rendering technique of vector field can be applied to various applications such as education, training, and entertainment.

• Communications of the Korean Mathematical Society
• /
• v.10 no.3
• /
• pp.661-679
• /
• 1995

The concept of the structure conformal vector field C on a Sasakian manifold M is defined. The existence of such a C on M is determined by an exterior differential system in involution. In this case M is a foliate manifold and the vector field C enjoys the property to be exterior concurrent. This allows to prove some interesting properties of the Ricci tensor and Obata's theorem concerning isometries to a sphere. Different properties of the conformal Lie algebra induced by C are also discussed.

• Communications of the Korean Mathematical Society
• /
• v.32 no.1
• /
• pp.107-118
• /
• 2017

In this paper we study CR-submanifolds of maximal CR-dimension by investigating extrinsic behaviors of integral curves of characteristic vector field on them. Also we consider the notion of ruled CR-submanifold of maximal CR-dimension which is a generalization of that of ruled real hypersurface and find some characterizations of ruled CR-submanifold of maximal CR-dimension concerning extrinsic shapes of integral curves of the characteristic vector field and those of CR-Frenet curves.

• Journal of the Korean Mathematical Society
• /
• v.60 no.5
• /
• pp.987-998
• /
• 2023

It is shown that every continuum-wise expansive C¹ generic vector field X on a compact connected smooth manifold M satisfies Axiom A and has no cycles, and every continuum-wise expansive homoclinic class of a C¹ generic vector field X on a compact connected smooth manifold M is hyperbolic. Moreover, every continuum-wise expansive C¹ generic divergence-free vector field X on a compact connected smooth manifold M is Anosov.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• v.18 no.4
• /
• pp.305-316
• /
• 2014

The Hodge-Helmholtz decomposition splits a vector field into the unique sum of a divergence-free vector field (solenoidal part) and a gradient field (irrotational part). In a bounded domain, a boundary condition needs to be supplied to the decomposition. The decomposition with the non-penetration boundary condition is equivalent to solving the Poisson equation with the Neumann boundary condition. The Gibou-Min method is an application of the Poisson solver by Purvis and Burkhalter to the decomposition. Using the $L^2$-orthogonality between the error vector and the consistency, the convergence for approximating the divergence-free vector field was recently proved to be $O(h^{1.5})$ with step size h. In this work, we analyze the convergence of the irrotattional in the decomposition. To the end, we introduce a discrete version of the Poincare inequality, which leads to a proof of the O(h) convergence for the scalar variable of the gradient field in a domain with general intersection property.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• v.2B no.4
• /
• pp.149-155
• /
• 2002

This paper presents magnetic field analysis technology that uses a vector magnetic characteristic. Recently the magnetic material was found to be measurable using the vector quantity technique. Therefore considering the anisotropy of the magnetic material in the vector field analysis is necessary. The magnetic field analysis method, which is considered the anisotropy by combining the finite element method with the E&$S^2$ (Enokizono, Soda, and Shimoji) modeling, is applied to a permanent magnet motor model.

• Communications of the Korean Mathematical Society
• /
• v.29 no.2
• /
• pp.319-329
• /
• 2014

In this paper we study the properties of conformally recurrent pseudo Riemannian manifolds admitting a proper conformal vector field with respect to the scalar field ${\sigma}$, focusing particularly on the 4-dimensional Lorentzian case. Some general properties already proven by one of the present authors for pseudo conformally symmetric manifolds endowed with a conformal vector field are proven also in the case, and some new others are stated. Moreover interesting results are pointed out; for example, it is proven that the Ricci tensor under certain conditions is Weyl compatible: this notion was recently introduced and investigated by one of the present authors. Further we study conformally recurrent 4-dimensional Lorentzian manifolds (space-times) admitting a conformal vector field: it is proven that the covector ${\sigma}_j$ is null and unique up to scaling; moreover it is shown that the same vector is an eigenvector of the Ricci tensor. Finally, it is stated that such space-time is of Petrov type N with respect to ${\sigma}_j$.