• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.2
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• pp.84-89
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• 2016

We present the results of a study of a piezoelectric generator that generates electricity by the application of tension to an element. A device is named "EYE-type generator". The EYE-type generator consists of a rectangular ceramic and two elastic body plates that are attached to upper and lower surfaces of a ceramic. If tension is applied to both ends of the elastic body, that tension is transformed to pressure on the ceramic through a change in the form of the elastic body, causing a piezoelectric effect whereby electricity is generated by the ceramic. This generator is relatively durable because a forces are not applied directly to the ceramic. We examined dependencies of the generator's output characteristics on the size of the ceramic and elastic body. A resonance and output characteristics were analyzed by using a finite element method. The generator was fabricated based on results of the analysis, and this was attached to a frequency-controllable vibrator to measure the output characteristics. The measured results were compared with results of the simulation, and the results pointed to the practicality of the design.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.11 s.114
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• pp.1021-1029
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• 2006

In this paper, we designed and implemented a dual wideband dipole type antenna for the reception of S-DMB (Satellite Digital Multimedia Broadcasting) and 2.4/5 GHz WLAN(Wireless Local Area Network) signals. The proposed antenna based on conventional monopole type dual band antenna was implemented as planar wideband dipole type antenna with the volume of $8{\times}33.8{\times}1.68mm^3$. The proposed antenna is printed type on FR4 substrate of 1.6 mm thick and composed of a dipole type antenna for low frequency band and two symmetric structured resonance elements for high frequency band. We confirmed antenna area with dense surface current for each frequency band with simulation. By varying the length of the antenna area with dense surface current, we could vary resonance frequency of each frequency band separately. Impedance bandwidths$(VSWR{\leq}2)$ are 362 MHz(14.23 %) for 2 GHz band and 1188 MHz(22.13, %) for 5 GHz band which show wideband characteristic. Measured maximum gains were 4.33 dBi for 2 GHz band and 5.48 dBi for 5 GHz band which showed improved performance. And the implemented antenna has a good omni-directional radiation pattern characteristic.

• Proceedings of the Acoustical Society of Korea Conference
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• 1984.12a
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• pp.96-99
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• 1984

In this study, the underwater acoustic images were obtained by ultrasonicwave. The experiment was performed in the anechoic watertank, using a passive sonar array for one and two sound source respectively by X-Y scanning technique. The receiving array was consist of 8 disc type transducers with 1.5cm diameter at 25KHz resonance frequency. The scanned data were processed by the FORTRAN IV algorithm for the reconstruction of image, and the image had some noise due to the surface reflected waves. As the result, it was found that the acoustic imaging by electrical deflection and dynamic focusing technique is applicable to SONAR with the suppression of surface reflected wave.

• Proceedings of the Acoustical Society of Korea Conference
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• 1984.12a
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• pp.78-82
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• 1984

The purposed of this paper is to realize two dimensional acoustic image using focusing method. In the experiment, it consists of phase delay part, 14 analog multiplexers, multi-amplifiers, A/D converter, DMA interfacing parts, two linear arrays(resonance frequency 25 KHz, radius 0.75 Cm diac type). Finally in this experimental result, both electrical deflection and dynamic focusing are realized and gets two dimensional acoustic image using focusing method.

• Proceedings of the KIEE Conference
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• 1988.11a
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• pp.21-23
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• 1988

Microstepping drive of 3 phase VR step motor with 2 phase exciting scheme is proposed. Considering the presence of harmonic components of inductance, the current reference is calculated. The experimental results show high accuracy of divided step position and resonance or instability in operating range.

• Proceedings of the KSMRM Conference
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• 2001.11a
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• pp.143-143
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• 2001

목적： 현재 3.0T MRI system은 세계적으로 개발이 진행되고 있는 가운데, 3.0T에서 사용할 수 있는 RF coil의 개발이 시급한 상황이다. 1.0T 및 1.5T MRI 와는 달리 3.0T에서 사용할 수 있는 Body coil 및 그에 따른 High power RF amplifier 제작에 많은 제약이 있다. 작은 용량의 RF amplifier를 이용하여 신체의 부분을 촬영 하고자 한다면, Tx/Rx 가능한 coil을 이용하면 가능할 것이다. 이러한 이유로 본 연구에서는 Tx/Rx 가능한 Quadrature type C-spine RF coil을 설계, 제작하여 3.0T 고자장 자기공명 영상장치에서의 임상진단 활용범위를 확대하였다.

• Journal of KSNVE
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• v.3 no.1
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• pp.29-37
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• 1993

This study is concerned about the impact type damper for effectively restraining the high vibration amplitude in the resonance regions. The theoretical analysis is based on the assumption that the impacts occur twice per cycle at an equal time interval. Simple but reasonable approximations have been derived for the optimum collision clearance and maximum amplitude ratio. Using the impact dampers which is rigidly attached to the primary vibration system, we have experimented for mass ratios and restitution coefficients. The experimental results are in good agreement with theoretical results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1280-1285
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• 2000

The paper deals with a theoretical study on the vibrational characteristics of piezoelectric torsional transducers. The differential equations of piezoelectric torsional motion have been derived in terms of the circumferential displacement and the electric potential. Applying mechanical and electrical boundary conditions has yielded the characteristic equations of natural vibration in several transducer types. Numerical results have clarified the effect of the piezoelectric phenomenon on the mechanical resonance and the effect of the elastic block of a Langevin-type transducer on the natural frequency.

• Journal of KSNVE
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• v.10 no.6
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• pp.955-962
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• 2000

The paper deals with a theoretical study on the vibrational characteristics of piezoelectric torsional transducers. The differential equations of piezoelectric torsional motion have been derived in terms of the circumferential displacement and the electric potential. Applying mechanical and electrical boundary conditions has yielded the characteristic equations of natural vibration in several transducer types. Numerical results have clarified the effect of the piezoelectric phenomenon on the mechanical resonance and the effect of the elastic block of a Langevin-type transducer on the natural frequency.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.192-194
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• 1994

High homogeneity and stability are required in superconducting magnet for Magnetic Resonance Imaging. In this paper, Magnetic Field theories for the design of high homogeneity magnet are introduced and multi-sections solenoid type coils are optimzed to produce highly homogeneous field.