• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1995년도 추계학술대회 논문집
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• pp.205-208
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• 1995

PZT powders were prepared by the molten salt synthesis method. The porous PZT specimens were prepared from a mixture of PZT and Polyvinylalcohol(PVA) powders by BURPS(Burnout Plastic Sphere) technique. The pulse-echo response of PZT-polymer 3-3 type composite transducer with various PVA wt.% were studied, The fall time of pulse-echo response of PZT-polymer 3-3 type composite transducer was shorten to that of solid PZT-maded transducer. Therefore, a good transmitting and receiving properties could be obtained. The distance between transducer and reflector was in good agreement both solid PZT and PZT-polymer 3-3 type composite fabricated transducer.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 추계학술대회 논문집 학회본부
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• pp.358-360
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• 1995

PZT powders were prepared by the molten salt synthesis method. The porous PZT specimens were prepared from a mixture of PZT and polyvinylalcohol(PVA) powders by BURPS(Burnout Plastic Sphere) technique. The pulse-echo response of porous PZT transducer with various PVA wt.% were studied. The fall time of pulse-echo response of porous PZT transducer was shorten to that of solid PZT-maded transducer. Therefore, a good transmitting and receiving properties could be obtained. The distance between transducer and reflector was in good agreement both solid PZT and porous PZT fabricated transducer.

• E2M - 전기 전자와 첨단 소재
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• 제8권2호
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• pp.211-216
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• 1995

In this study, the piezoelectric ceramics/polymer composite transducers with 1-3 connectivity have been studied. A piezoelectric ceramics PZT prepared by Wet-Dry Combination method was used as a filler in polymer matrix Eccogel. We've got the pulse-echo response for 1-3 type piezc-electric composite transducers in water. It was shown that the transmitting and receiving sensitivity of 1-3 type piezoelectric composite transducers could be improved in comparison with that- of solid PZT transducers. The reason is for that 1-3 type Piezoelectric composites have low dielectric constant and density. There was in a good agreement between the resonant frequencies calculated from one period and observed results on the Ultrasonic Transducer Analyzer. According to these results we could be figured out the distance in water by virture of the pulse-echo response.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 C
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• pp.1403-1405
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• 1994

In this study, the piezoelectric transducers with 1-3 connectivity have maded. A piezoelectric ceramic PZT prepared by Wet-Dry Combination method is used as a filler in Eccogel polymer matrix. The pulse-echo response for 1-3 type composite transducers were carried out in water. It was observed that the transmitting and receiving sensitivity of 1-3 type composite transducers were improved in comparison with that or solid PZT transducer. The reason is for that 1-3 composites have a hish piezoelectric voltage coefficients, The period of pulse-echo response for the transducer is in a good agreement with the resonant frequency of self-maded composite transducer.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 춘계합동학술대회 논문집
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• pp.224-228
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• 2002

In this study, the piezoelectric ceramics PZT powder was synthesized by the Wet-Dry combination method. Flexible 1-3 type composite specimens were fabricated with the piezoceramics PZT filler phase and Eccogel polymer matrix phase. This paper represents the pulse-echo response of the 1-3 type composite transducer to check it out to investigate a basic property regarding a level limit switch. The acoustic impedance of 1-3 type composite was improved than that of single phase PZT ceramics. The pulse-echo response of transducer fabricated with the self-made 1-3 type composites resonator was better than that of the solid PZT transducer.

• 한국기계가공학회지
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• 제16권5호
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• pp.141-149
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• 2017

Due to the inaccuracy of micro-machining, various special processing methods have been investigated recently. Among them, pulse electrochemical machining is a promising machining method with the advantage of no residual stress and thermal deformation. Because the cross section of the wire electrode used in this study is circular, wire-pulse electrochemical machining is suitable for micro-hole machining. By applying the response surface methodology, the experimental plan was made of three factors and three levels: machining time, duty factor, and voltage. The regression equation was obtained through experiments. Then, by referring to the main effect diagram, we fixed the duty factor and machining time with little relevance, and solved the equation for the target 900 microns to obtain the voltage value. The results obtained from the response surface methodology were approximately those of the target value when the actual experiment was carried out. Therefore, it is concluded that the optimal conditions for hole processing can be obtained by the response surface methodology.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 춘계학술대회 논문집 디스플레이 광소자 분야
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• pp.152-154
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• 2000

Electro_optical characteristics in AC-PDP are confined by a lots of parameters. especially driving pulse shape is very important to improve AC-PDP's luminosity and efficiency. In that experiment measure the luminosity, IR(Infra Red) peak value and response time as the increase of 1st, 2rd sustain pulse width. The VDS(Versatile Driving Simulator -developed by kwangwoon university-) was used to make driving pulse shape. It is found that IR response time after displacement current, Luminosity and IR peak value are changed on account of 1st,2rd sustain pulse width.

• Smart Structures and Systems
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• 제18권6호
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• pp.1111-1123
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• 2016

The present study aims at proposing an analytical method for semi-active structural control by using block pulse functions. The performance of the resulting controlled system and the requirements of the control devices are highly dependent on the control algorithm employed. In control problems, it is important to devise an accurate analytical method with less computational expenses. Block pulse functions (BPFs) set proved to be the most fundamental and it enjoyed immense popularity in different applications in the area of numerical analysis in systems science and control. This work focused on the application of BPFs in the control algorithm concerning decrease the computational expenses. Variable orifice dampers (VODs) are one of the common semi-active devices that can be used to control the response of civil Structures during seismic loads. To prove the efficiency of the proposed method, numerical simulations for a 10-story shear building frame equipped with VODs are presented. The controlled response of the frame was compared with results obtained by controlling the frame by the classical clipped-optimal control method based on linear quadratic regulator theory. The simulation results of this investigation indicated the proposed method had an acceptable accuracy with minor computational expenses and it can be advantageous in reducing seismic responses.

• E2M - 전기 전자와 첨단 소재
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• 제9권10호
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• pp.1053-1059
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• 1996

The pulse-echo response of the piezoceramics PZT-polymer 3-3 type composite transducers with various PVA additions were investigated. The PZT powder was prepared by the molten salt synthesis method. The porous PZT specimens will be used as a filler to make 3-3 type comosite were prepared from a mixture of PZT and polyvinylalcohol(PVA) sphere by utilizing BURPS(Bumout Plastic Sphere) technique. It was shown that the transmitting and receiving sensitivity of 3-3 type piezoelectric composite transducers could be improved than that of solid PZT transducers. The reason is that 3-3 type piezoelectric composite have low dielectric constant, density and acoustic impedance. The distance between transducer and reflector was in good agreement with the distance calculated from the longitudinal velocity of the specimens and receiving time observed pulse-echo responses on the ultrasonic transducer analyzer.

• The Korean Journal of Physiology and Pharmacology
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• 제13권6호
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• pp.443-448
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• 2009

For successful visual perception by visual prosthesis using electrical stimulation, it is essential to develop an effective stimulation strategy based on understanding of retinal ganglion cell (RGC) responses to electrical stimulation. We studied RGC responses to repetitive electrical stimulation pulses to develop a stimulation strategy using stimulation pulse frequency modulation. Retinal patches of photoreceptor-degenerated retinas from rd1 mice were attached to a planar multi-electrode array (MEA) and RGC spike trains responding to electrical stimulation pulse trains with various pulse frequencies were observed. RGC responses were strongly dependent on inter-pulse interval when it was varied from 500 to 10 ms. Although the evoked spikes were suppressed with increasing pulse rate, the number of evoked spikes were >60% of the maximal responses when the inter-pulse intervals exceeded 100 ms. Based on this, we investigated the modulation of evoked RGC firing rates while increasing the pulse frequency from 1 to 10 pulses per second (or Hz) to deduce the optimal pulse frequency range for modulation of RGC response strength. RGC response strength monotonically and linearly increased within the stimulation frequency of 1~9 Hz. The results suggest that the evoked neural activities of RGCs in degenerated retina can be reliably controlled by pulse frequency modulation, and may be used as a stimulation strategy for visual neural prosthesis.