• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.391-392
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• 2010

• Journal of Sensor Science and Technology
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• v.26 no.2
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• pp.107-113
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• 2017

Energy source of a piezo-electric harvester is vibration. Sources of vibration are machineries operated with high frequencies, constructions and people operated with low frequencies and etc. In this study, we tried to figure out power generation properties over vibrations upon angles of a piezo-cantilever for applying them to movements of the construction and/or people, which are vibration sources at low frequencies. A uni-morph cantilever with a $59mm{\times}29mm{\times}0.2mm$ piezo-electric element attached on a $71mm{\times}46mm{\times}0.25mm$ copperplate was used. A spring was attached to the lower side of the cantilever and a mass was attached on the opposite side. Also, a structure with a specific angle which is an angle in between the ground and the cantilever was prepared and then, connected to a spring or the cantilever. Then, this structure was divided into the A-type and B-type and excited in the direction of z- axis. After that, the angle between the ground and the cantilever was changed and excited by 1 to 10 Hz upon the existence of a spring and/or a mass to compare power generation properties.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.671-674
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• 2004

This paper presents design and analysis of multi-layered ring-dot type piezoelectric transformer. These transformers are useful for step up and step down. The transformers consist of disk type multi-layered piezoelectric ceramic plates. The finite element method(FEM) was used for analysis transformer. Vibration mode, electric field and equivalent elastic strain of piezoelectric transformer were simulated by changing frequency. As results, the strain was distributed in isolation part entirely. We can get the operated in step up transformer when the inner side electrode using by input parts. Also we can get the step down transformers using by input Part as outer side electrode. The step up ratio and step down ratio was increased by decreasing inner side electrode. The resonance frequency was increased by increasing inner side electrode when the transformer was operated in step down transformer. But the step up one was decreased. From these results, we can expect to multi-layered ring-dot type piezo transformers as step up and step down transformers.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.8
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• pp.1112-1118
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• 2000

The objective of this study is to increase lift and decrease drag of an airfoil at high angles of attack by delaying flow separation with piezo-ceramic actuators. The airfoil used is NACA 0012 and its chord length is 0.3m. An experiment is performed at the freestream velocity of 15m/s at which the Reynolds number based on the chord length is $2{\times}10^5$. Seven rectangular actuators are attached to the airfoil surface and move up and down based on the electric signal. Drag and lift are measured using an in-house two-dimensional force-balance and the surface pressures are also measured. At the attack angle of $16^{\circ}$, the separation point is delayed downstream due to momentum addition induced by the movement of the actuators. Lift is increased by 10%, drag is reduced by 37%, and the efficiency is increased up to 170%. The flow fields with and without control are visualized using the smoke-wire and tuft techniques.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.414-417
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• 2001

Recently, developments of device using characteristics of ceramics as a new technical material is in progress. While doing so, Ultrasonic motor which is a part of research & development of piezo-actuator by piezo-effects is being used in the various applications. So, we fabricated a flat-type $L_{1}-B_{8}$ mode Ultrasonic motor and measured the operation characteristics of its. The size of USM is 80*20*1.5[$mm^{3}$](length*width*thickness) and is constructed with stator by piezo-ceramics and stainless elastic body and rotator by bearings. As results of experiments, the fastest speed of revolution(v), the maximum torque(T) and the efficiency( $\eta$ ) were 37.5[cm/sec], 5.0[ $mN{\cdot}m$ ] and 1.17[%] respectively when 27.9[kHz], 150[gf], 50[V] were applied. So, we think this $flat-type_{1}-B_{8}$ mode Ultrasonic motor is able to be used for applications in forwarding device of a paper or electric card and so on.

• Journal of the Korean earth science society
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• v.23 no.1
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• pp.112-118
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• 2002

The anomalous behaviour of animals prior to a large earthquake has been frequently reported from many places throughout the world since ancient times. This study is to experimentally testify what relations exist between the anomalous animal behavior and electric field effect, which is reported due to the piezo-electric effects in a basement rock before earthquake occurrences. We investigated the electric field effects on behaviors of two kinds of rats and birds. Rats show more sensitive anomalous behavior than birds. Even though the current applied to the experimental birds and rats is just a few ${\mu}$A, they show various abnormal behaviors. The anomalous animal behaviors under the small ground electric field may have some relations to the actual phenomena before great earthquake.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.507-512
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• 2001

In this work, tool holder system has been designed and builted to measure cutting forces in diamond turning. This system design includes a 3-component piezo-electric tranducer. Initial experiments with tool holder system included verification of its predicted dynamic characteristics as well as a detailed study of cutting parameters. Tool holder system is modeled by considering the element dividing, material properties, and boundary conditions using MSC/PATRAN. Mode and frequency analysis of structure is simulated by MSC/NASTRAN, for the purpose of developing the effective design. Many cutting experiments have been conducted on 6061-T6 aluminum. Tests have involved investigation of velocity effects, and the effects of depth and feedrate on tool force. Forces generally increase with increasing depth of cut. Increasing feedrate does not necessarily lead to higher forces.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.10a
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• pp.286-289
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• 2004

This paper presents the fatigue characteristics of LIPCA (LIghtweight Piezo-Composite Actuator) device system. The LIPCA device system is composed of a piezoelectric ceramic layer and fiber reinforced lightweight composite layers. Typically a PZT ceramic layer is sandwiched by a top fiber layer with low CTE (coefficient of thermal expansion) and base layers with high CTE. The advantages of the LIPCA design are weight reduction by using the lightweight fiber reinforced plastic layers without compromising the generation of high force and large displacement and design flexibility by selecting the fiber direction and the size of prepreg layers. To predict the degradation of actuation performance of LIPCA due to fatigue, the cyclic electric loading tests using PZT specimens were performed and the strain for a given excitation voltage was measured during the test. The results from the PZT fatigue test were implemented into CLPT (Classical Laminated Plate Theory) model to predict the degradation of LIPCA's actuation displacement. The fatigue characteristic of PZT was measured using a test system composed of a supporting jig, a high voltage power supplier, data acquisition board, PC, and evaluated.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.938-941
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• 2001

A tool holder system has been designed and builted to measure cutting forces in diamond turning. This system design includes a 3-component piezo-electric tranducer. Initial experiments with tool holder system included verification of its predicted dynamic characteristics as well as a detailed study of cutting parameters. In this research, tool holder system is modeled by considering the element dividing, material properties, and boundary conditions using MSC/PATRAN. Mode and frequency analysis of structure is simulated by MSC/NASTRAN, for the purpose of developing the effective design. In addition, tool holder system is verified by vibration test using accelerometer. Many cutting experiments have been conducted on 6061-T6 aluminum. Tests have involved investigation of velocity effects, and the effects of depth and feedrate on tool force. Cutting velocity has been determined to have negligible effects between 4 and 21㎧.(6) Forces generally increase with increasing depth of cut. Increasing feedrate does not necessarily lead to higher forces. Results suggest that a sample model may not be sufficient to describe the forces produced in the diamond turning process.

• Korean Journal of Optics and Photonics
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• v.10 no.6
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• pp.473-481
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• 1999

We propose a new scheme of hologram multiplexing that can improve the crosstalk noise in the conventional phase-code multiplexing. Our method is based on the idea that the separate holograms to be stored in a certain region of the photorefractve material should have relative phase other than $180^{\circ}$. To demonstrate the new idea we fabricate a phase spatial light modulator using piezo-electric material. The experimental result shows that the crosstalk noise in the restored holograms is reduced much in our method. We also computer simulate the hologram multiplexing and compare the result with the experimental data.l data.