• Smart Structures and Systems
• /
• 제22권1호
• /
• pp.57-70
• /
• 2018

For the long-term structural health monitoring of civil structures, the effect of ambient temperature variation has been regarded as one of the critical issues. In this study, a principal component analysis (PCA)-based algorithm is proposed to filter out temperature effects on electromechanical impedance (EMI) monitoring of prestressed tendon anchorages. Firstly, the EMI monitoring via a piezoelectric interface device is described for prestress-loss detection in the tendon anchorage system. Secondly, the PCA-based temperature filtering algorithm tailored to the EMI monitoring of the prestressed tendon anchorage is outlined. The proposed algorithm utilizes the damage-sensitive features obtained from sub-ranges of the EMI data to establish the PCA-based filter model. Finally, the feasibility of the PCA-based algorithm is experimentally evaluated by distinguishing temperature changes from prestress-loss events in a prestressed concrete girder. The accuracy of the prestress-loss detection results is discussed with respect to the EMI features before and after the temperature filtering.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2001년도 하계학술대회 논문집
• /
• pp.806-808
• /
• 2001

In this thesis, specimens was manufactured in general method annexing PMB-PZT system ceramic, and the following conclusion has been deduced. In XRD, the crystal structure of ceramic has the tetragonal structure which is close to rombohedral structure, and consequently the specimen characterized by MPB was manufactured. According to dopping with xPMB, electromechanical factor(kp) little is changed. kp was maximum value 23.37[%] at xPMB 0.03[mol%]. mechanical quality factor(Qm) was maximum value 237.04 at xPMB 0.03[mo1%].

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2002년도 하계학술대회 논문집 Vol.3 No.2
• /
• pp.578-580
• /
• 2002

In this thesis, specimens was manufactured in general method annexing PMB-PZT system ceramic, and the following conclusion has been deduced. In XRD, the crystal structure of ceramic has the tetragonal structure which is close to rombohedral structure, and consequently the specimen characterized by MPB was manufactured. According to dopping with xPMB, electromechanical factor(kp) little is changed. kp was maximum value 23.37[%] at xPMB 0.03[mol%]. mechanical quality factor(Qm) was maximum value 237,04 at xPMB 0.03[mol%].

• International Journal of Control, Automation, and Systems
• /
• 제4권4호
• /
• pp.466-479
• /
• 2006

This paper addresses a formation navigation issue for a group of mobile robots passing through an environment with either static or moving obstacles meanwhile keeping a fixed formation shape. Based on Lyapunov function and graph theory, a NN formation control is proposed, which guarantees to maintain a formation if the formation pattern is $C^k,\;k\geq1$. In the process of navigation, the leader can generate a proper trajectory to lead formation and avoid moving obstacles according to the obtained information. An evolutionary computational technique using particle swarm optimization (PSO) is proposed for motion planning so that the formation is kept as $C^1$ function. The simulation results demonstrate that this algorithm is effective and the experimental studies validate the formation ability of the multiple mobile robots system.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2009년도 제33회 추계학술대회논문집
• /
• pp.282-285
• /
• 2009

MEMS를 적용한 추진기관용 점화안전장치를 설계하고 제작하였다. MEMS는 일반적인 기계요소 설계 방식을 따라 설계하였다. 제작된 시료에 대한 검사 결과와 설계 데이터를 비교해 본 결과 스프링의 비선형 요소에 의한 영향과 가공오차 등으로 인하여 설계된 성능 값과 근사한 차이를 나타냈다. MEMS가 결합된 점화안전장치의 성능 시험을 실시함으로써 MEMS 적용 가능성을 입증하였다.

• 한국전기전자재료학회논문지
• /
• 제19권12호
• /
• pp.1118-1122
• /
• 2006

In this study, in order to develop the low temperature sintering multilayer piezoelectric actuator, PMN-PNN-PZT system ceramics were manufactured and their microstructure, ferroelectric and piezoelectric properties were investigated. By increasing sintering temperature, remanent polarization$(P_r)$ was increased due to the increase of sinterability and grain size. However, coercive $field(E_c)$ showed an opposite tendency to remanent polarization owing to the feasibility of domain wall motion. At the sintering temperature of $900^{\circ}C$, dielectric $constant({\varepsilon}_r)$, electromechanical coupling $factor(k_p)$, piezoelectric $constant(d_{33})$ and mechanical quality $factor(Q_m)$ showed the optimal value of 1095, 0.60, 363 and 1055, respectively, for multilayer piezoelectric actuator application.

• Journal of Mechanical Science and Technology
• /
• 제20권11호
• /
• pp.1781-1789
• /
• 2006

Fourier methods are not generally an appropriate approach in the investigation of faults signals with transient components. This work presents the application of a new signal processing technique, the Hilbert-Huang transform and its marginal spectrum, in analysis of vibration signals and faults diagnosis of gear. The Empirical mode decomposition (EMD), Hilbert-Huang transform (HHT) and marginal spectrum are introduced. Firstly, the vibration signals are separated into several intrinsic mode functions (IMFs) using EMD. Then the marginal spectrum of each IMF can be obtained. According to the marginal spectrum, the wear fault of the gear can be detected and faults patterns can be identified. The results show that the proposed method may provide not only an increase in the spectral resolution but also reliability for the faults diagnosis of the gear.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
• /
• pp.429-429
• /
• 2013

We present a systematic study of the electrical, optical and electromechanical properties of flexible graphene/metal grid hybrid transparent conductive electrodes using 4-point prove method, ultraviolet/visible spectrometer and inner/outer bending test system. The hybrid electrodes were synthesized by depositing a silver grid on a graphene surface. The sheet resistance of hybrid electrodes was as low as 30 Ω/square, while the transmittance was 90%. The electromechanical properties as a function of the change of bending radius were evaluated by measuring the change in resistance. The result will be presented in detail. We believe that these results will provide useful information for the flexible optoelectronic devices based on graphene transparent electrodes.

• 대한전기학회논문지
• /
• 제41권1호
• /
• pp.50-55
• /
• 1992

Piezoelectric Buzzer which has been generally used requires about 30kV/cm poling process and has the aging effects. In this study, 0.85 PZN - 0.10 BT - 0.05 PT system ceramics with additives of 0 - 2 wt% YS12TOS13T were fabricated and investigated on electromechanical coupling coefficient(kS1pT), electric field induced charge coefficient(dS131T), and sound level. As the results, in the 0.4 wt% YS12TOS13T added composition ceramics compared with the basic, kS1pT was increased from 0.355 to 0.39 and induced piezoelectric d constant increased from 204 to 220 x 10S0-12T (C/N) and sound level of electrostrictive Buzzer has the highest value of 71.5 dB under 8kV/cm bias electric field.

• 반도체디스플레이기술학회지
• /
• 제12권2호
• /
• pp.63-66
• /
• 2013

Carbon Nanotube have been proposed for use in various applications for electromechanical systems. Nano-electromechanical resonators which provide high frequency resolution and long energy storage time, play an important role in wide area fields of science and engineering. Using the control of tension in carbon nanotube, can be made the tunable resonator. In the study, we analysis the tunable frequency change of resonator by tension changes due to the rotation angles of the single-walled carbon nanotube resonator. The frequency characteristics of a resonator as a function of the rotation angle. The tension was found to decrease with increasing rotation angle, and therefore the resonance frequencies could be changed by controlling the single-walled carbon nanotube rotation angle. The resonance frequencies decreased with increasing angle, and when the rotation angle was greater than $60^{\circ}$, these changes were marked.