• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.06a
• /
• pp.164-164
• /
• 2009

A multilayer piezoelectric transformer(MPT) for step-down voltage was made by ceramic stack process. And then, the characteristics of piezoelectric transformer, such as resonance frequency, matching impedance, electro-mechanical coupling coefficient, voltage gain, heat generation and efficiency, are analyzed. The piezoelectric transformer consists of a lead zirconate titanate ceramic with a high electromechanical quality factor. The piezoelectric transformer, with a multilayered construction in the thickness direction, was formed with dimensions 15mm long, 15mm wide and 5mm thick.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.40 no.10
• /
• pp.833-839
• /
• 2012

In this paper, we analyze the reconstruction error in the modeling of flow field on BFS(Backward Facing Step). In order for the mathematical modelling of a density on the field, the spatial and temporal modes are extracted by POD(Proper Orthogonal Decomposition) method. After formulating the modeling error, we summarize the relationship between the energy strength and the reconstruction errors. Moreover the allowable modeling error limits in the flow control point of view are confined by analysing in the frequency domain as well as time domain of the reconstructed data.

• Structural Engineering and Mechanics
• /
• v.45 no.4
• /
• pp.521-542
• /
• 2013

In this study a truss model is used for the geometrically nonlinear static and dynamic analysis of a thin shallow arch subject to snap-through. Thanks to the very simple geometry of a truss, the equilibrium conditions can be easily written and the global stiffness matrix can be easily updated with respect to the deformed structure, within each step of the analysis. A very coarse discretization is applied; so, in a very simple way, the high frequency modes are suppressed from the beginning and there is no need to develop a complicated reduced-order technique. Two short computer programs have been developed for the geometrically nonlinear static analysis by displacement control of a plane truss model of a structure as well as for its dynamic analysis by the step-by-step time integration algorithm of trapezoidal rule, combined with a predictor-corrector technique. These two short, fully documented computer programs are applied on the geometrically nonlinear static and dynamic analysis of a specific thin shallow arch subject to snap-through.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2006.11a
• /
• pp.225-227
• /
• 2006

Multilayer step down piezoelectric transformers were manufactured using PZN-PMN-PZT and PMN-PNN-PZT ceramics respectively. Sintering temperature of the ceramics was $940^{\circ}C$. And then. their electrical properties were investigated according to the variations of frequency and load resistance. The voltage step-up ratio of multilayer piezoelectric transformer showed the maximum values in the vicinity of 69 and 71kHz, respectively. At the load resistance of $100{\Omega}$, the piezoelectric transformers showed the temperature rises of about 21 and $18^{\circ}C$ at the output power of 15W and 18W, respectively. At the transformer with high effective electromechanical coupling factor($k_{eff}$), lower temperature increase was appeared.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2006.11a
• /
• pp.223-224
• /
• 2006

This paper present a new disk-type piezoelectric transformer. The input side of the transformer has a crescent-shaped electrode and the output side has a focused poling direction. This transformer has multi-layered structure. The piezoelectric transformers operated m each transformer's resonance vibration mode. The electrodes and poling directions on commercialy available piezoelectric ceramic disks were designed so that the planar or shear mode coupling factor ($k_p,\;k_{15}$) becomes effective rather than the transverse mode coupling factor ($k_{31}$). The Resonance frequency is 65.22[kHz] and maximum voltage step-up ratio is 149. Multi-layered transformer has better efficiency and step-up ratio than the single-layered transformer.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.18 no.6
• /
• pp.261-269
• /
• 2014

In order to increase the seismic safety of nuclear power plant (NPP) structures in high seismicity regions, seismic isolation techniques can be adapted to NPP structures. In this paper, the applicability of multi-step analysis of seismically isolated NPP containment structures with lead-rubber bearings (LRB) is evaluated. The floor response spectrum of NPP containment structures with equivalent linear LRB and nonlinear LRB are compared. In addition, the force-displacement relationships for equivalent linear LRB and nonlinear LRB are compared.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.07a
• /
• pp.143-146
• /
• 2002

The characteristics of a multilayer piezoelectric transformer were investigated using 0.05Pb(A $l_{0.5}$N $b_{0.5}$) $O_3$-0.95Pb(Z $r_{0.52}$ $Ti_{0.48}$) $O_3$+0.9wt%N $b_2$ $O_{5}$+0.5wt%Mn $O_2$+0.04wt% $V_2$ $O_{5}$ ceramics. The multilayer piezoelectric trans formers were developed for voltage step-up. The multilayer ceramic technology was applied in piezoelectric transformer. The electrical characteristics of the piezoelectric transformer (33x8.5x1mm) has the efficiency of above 85%, step-up ratio of 70 under the 130 kΩ load, and driving frequency of 93.5kHz, respectively.ctively.y.y.

• Proceedings of the KIEE Conference
• /
• 2000.11a
• /
• pp.152-155
• /
• 2000

This paper deals with the PSS modelling of Ulchin N/P Unit #1 by utilizing the recorded data from AVR step test. In addition to it, the recorded results obtained from the AVR step test with PSS running and without PSS running are not only compared each other on the time domain but they are also analyzed with FFT on the frequency domain; the desirable effect of running PSS in Ulchin N/P Unit #1 is examined. Finally, the derived PSS model parameters lead to good matches between simulation results and recorded data.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.07b
• /
• pp.595-598
• /
• 2004

We have explained Process and electrical characteristics of a step-down Rosen type piezoelectric transformer for AC-adapter. When the electric voltage is applied to the driving piezoelectric vibrator notarized in the thickness direction, then output voltage is generated at the generating piezoelectric vibrator polarized in the thickness direction due to the piezoelectric effects. Output voltage and current from a single-layered piezoelectric transformer were measured under the various condition of loads and frequencies It was shown from experiments that output voltage has increased and resonance frequency has changed according to various resistor loads. Output current has decreased inversely proportional to the loads

• Proceedings of the KIEE Conference
• /
• 1997.11a
• /
• pp.618-620
• /
• 1997

A $50{\times}50{\mu}m^2$ aluminum micromirror array is fabricated using shadow evaporation process. The fabrication process is very simple with use of shadow evaporation process, and the micromirror array has a high fill-factor. The static and dynamic characteristics such as deflection angle vs. applied voltage, step response, and frequency response are measured using a contact free optical measurement technique. The downward threshold voltage was 8 V, step response time was $13.5{\mu}s$ when 32 V step voltage applied, and a resonance observed at 11kHz. The lifetime of micromirror with anti-stiction coating was tested and micromirror operated successfully over 200 million cycles of touch-down operations.