• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.10a
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• pp.7-15
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• 1995

Sound pressure and particle velocity are the most essential quantities prescribing a sound field; they correspond to voltage and electric current respectively, in electric system. As electric power is the product of voltage and electric current, sound intensity is the product of sound pressure and particle velocity and it means the acoustic power passing through a unit area in a sound field. Although the definition of sound intensity is very simple as mentioned above, the method of measuring this quantity has not been realized for a long time, because it has been very difficult to measure the particle velocity simultaneously with the sound pressure. Owing to the recent development of such technologies as transducer production and digital signal processing, it has finally been realized. According to the sound intensity(SI) method, the sound power flow in an arbitrary sound field can be directly measured as a vector quantify. In this paper, the principle of the SI method is briefly explained at first and some examples of its application made in the author's laboratory are introduced.

• Proceedings of the KIEE Conference
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• 2000.11b
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• pp.262-264
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• 2000

A numerical method for the analysis of 3D eddy current in conductors due to applied time varying field is suggested using the finite element method. In the approximation of the field quantifies, the edge element is used, because it reduce the required computer memory and the computing time compared with the nodal elements. With edge elements, furthermore, the field governing equations become simple because the electric scalar potential ${\phi}$ can be set to zero. The modified magnetic vector potential($A^*$) is used as a state variable. The analysed results are compared with the experimentally measured ones for the TEAM workshop problem3.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.10
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• pp.1639-1647
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• 2016

This paper deals with eddy current loss analysis of Slotless Double sided Cored type permanent magnet linear generator by using analytical method, space harmonic method. In order to calculate eddy current, this paper derives analytical solution by the Maxwell equation, magnetic vector potential, Faraday's law and a two-dimensional(2-D) cartesian coordinate system. First, we derived the armature reaction field distribution produced by armature wingding current. Second, by using derived armature reaction field solution, the analytical solution for eddy current density distribution are also obtained. Finally, the analytical solution for eddy current loss induced in permanent magnets(PMs) are derived by using equivalent, electrical resistance calculated from PMs volume and eddy current density distribution solution. The analytical result from space harmonic method are validated extensively by comparing with finite element method(FEM).

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.2
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• pp.127-134
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• 2006

This paper describes a fully hardware realization of vector controller for the permanent magnet synchronous motor (PMSM) using high density field programmable gate mays (FPGA). In the proposed system, the vector controller including vector transformation , PI regulator, position and speed measurement, current measurement, and space vector PWM blocks is implemented in a FPGA using a VHSIC hardware description language (VHDL). The experimental results using a 1.1kW PMSM are provided to show the validity of the proposed system.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1019-1020
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• 2011

This paper deals with torque analysis of axial flux permanent magnet (AFPM) type eddy current brake (ECB) based on analytical field computation. On the basis of a magnetic vector potential and a two-dimensional (2-D) polar coordinate system, analytical solutions for normal and tangential flux density due to permanent magnet (PM) considering eddy current effect are obtained. And then, using derived analytical field solutions, braking torque and normal force characteristics according to rotor speed are also predicted. A three-dimensional (3-D) finite element (FE) analysis is employed to confirm the validity of analyses.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.5 no.1
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• pp.88-93
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• 2005

Web usage mining is a research field for searching potentially useful and valuable information from web log file. Web log file is a simple list of pages that users refer. Therefore, it is not easy to analyze user's current interest field from web log file. This paper presents web usage mining method for finding users' current interest based on fuzzy categories. We consider not only how many times a user visits pages but also when he visits. We describe a user's current interest with a fuzzy interest degree to categories. Based on fuzzy categories and fuzzy interest degrees, we also propose a method to cluster users according to their interests for user modeling. For user clustering, we define a category vector space. Experiments show that our method properly reflects the time factor of users' web visiting as well as the users' visit number.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.12
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• pp.2135-2144
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• 2007

This paper presents system design of the slotless double-side Permanent Magnet Linear Synchronous Machine system (PMLSM) through magnetic field analysis and dynamic modeling. In our analysis, 2-D analytical treatments based on the magnetic vector potential were adopted to predict magnetic field with space harmonics by PM mover magnetization and stator winding current. From these, the design parameters such as inductance, Back-emf, and thrust are estimated. And, the electrical dynamic modeling including synchronous speed is completed by calculation of a DC link voltage in effort to obtain the accurate mechanical power from Space Vector Pulse Width Modulation(SVPWM). Therefore, the system design of PMLSM is performed from estimation of design parameters according to PM size and coil turns in magnetic field and from calculation of a DC link voltage to satisfy base speed and base thrust represented as the maximum output power in dynamic modeling. The estimated values from the analysis are verified by the finite element method and experimental results.

• Journal of Sensor Science and Technology
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• v.8 no.4
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• pp.308-313
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• 1999

This paper will present an anisotropic etching in TMAH technique used in the fabrication of three-dimensional magnetic field vector sensor based on angled Hall plate structure. This sensor design relies on simultaneously detecting all magnetic field vector components using Hall plates that are imbedded into the silicon [111] sloped-surface of bulk micromachined cavity by the anisotropic etching of [100] silicon. The fabricated Hall elements has relatively improved sensitivity compare to convensional Hall elements for three-dimensional magnetic field sensing. The product sensitivity of 547V/AT at the supply current of 1.0mA was achived. The corresponding limit in the detection of magnrtic field is 0.07G that calculated by measured power spectral density(PSD) in magnetic sensor output.

• Progress in Superconductivity
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• v.5 no.1
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• pp.38-44
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• 2003

The aim of this study is to confirm clinical usefulness of magnetocardiogram (MCG) by analyzing MCG data of health subjects and patients with Wolff-Parkinson-White (WPW) syndrome and dilated cardiomyopathy (DCM). Measurement of MCG signals was done with a home-made 40-channel SQUID system. MCG signals of 30 healthy subjects were measured as the reference of MCG signals. Among the DCM patients, 7 patients showed abnormal the direction of T wave vector. For a WPW syndrome patient, we measured the MCG signals before and after the surgery. and compared the difference. From the measured magnetic field distribution, current vector map was obtained to show the myocardium current activity. By comparing the MCG signals and current maps, we showed the differences in the analysis results between the healthy subjects and patients with heart diseases.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.1218-1220
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• 1992

This paper presents the three section sliding mode control algorithm based on variable structure current controller design in a synchronous frame and indirect field oriented control method, and applies it to the position control of induction motor. This control scheme solves the problem of robustness loss during the reaching phase that occurs in a conventional VSC strategy, and ensures the stable sliding mode and robustness enhancement throughout an entire response. As the performance of a VSI fed induction motor drives depends on the characteristics of inner loop current controller, it is desired that the current controller have the fast tracking and robust nature. Therefore, we introduced the voltage mapping table based on the concept of voltage space vector for variable structure current control, and implemented fully digital control system using 16-bit microcontroller with on-chip peripherals without additional processing circuits. Simulation and experimental results confirm the validity of this control scheme for robust AC servo drive system of VSI fed induction motor.