• 한국정밀공학회지
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• 제31권5호
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• pp.417-422
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• 2014

A guitar pickup is a transducer that converts string vibration to an electrical signal. The magnetic and piezo pickups are the most commonly used for the respective electric and electroacoustic guitars. The magnetic pickups are prone to magnetic interference between the steel strings and permanent magnets, while the piezo ones are not free from signal inference between the strings. Thus, this paper presents the development of an optical pickup for the electroacoustic guitar. The proposed optical pickup has the top-to-bottom structure. It uses two of Infrared (IR) Light Emitting Diode (LED) and one photodetector. The developed optical pickup is subjected to the evaluation with commonly used piezoelectric pickup. It becomes obvious that SNR with the optical pickup is increased by 45 percent in average, compared with the piezoelectric pickup. It can be concluded that the developed optical pickup has a potential to be applied to the acoustic guitar.

• 한국음향학회지
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• 제20권5호
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• pp.76-82
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• 2001

음향특성이 균일하지 않는 생체조직은 특정의 형태 유지가 어렵기 때문에 종래의 극소형 수중청음기의 스캐닝 방법에 의한 초음파 음장 전파특성 측정이 곤란하다. 본 연구에서는 PVDF (Polyvinylidene fluoride) 압전막을 사용하여 2차원 배열 수중청음기를 제작하고, 그것에 의한 음장 측정 시스템을 구축한 후, 생체조직에 적용하였다. 중심주파수 2.25 ㎒이고 직경이 13㎜인 원형평면 트랜스듀서에 의한 실험 결과, 구축한 시스템에 의해 비교적 정밀한 음장 측정이 가능한 것을 알았으며, 그 주파수에 대해 소와 돼지의 간에서는 각각 0.7∼l.3dB/cm (평균; 1.0 dB/cm), 1.0∼l.8 dB/cm (평균; 1.6 dB/cm), 근육에서는 각각 0.9∼2.9 dB/cm (평균; 2.1dB/cm), 1.7∼3.3 dB/cm (평균: 2.5 dB/cm)의 값을 갖는 감쇠계수의 공간적 분포를 측정할 수 있었다.

• Advances in nano research
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• 제8권1호
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• pp.69-82
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• 2020

In this study, the free and forced vibration analysis of micro sandwich plate with porous core layer and magneto-electric face sheets based on modified couple stress theory and first order shear deformation theory under simply supported boundary conditions is illustrated. It is noted that the core layer is composed from balsa wood and also piezo magneto-electric facesheets are made of BiTiO₃-CoFe₂O₄. Using Hamilton's principle, the equations of motion for micro sandwich plate are obtained. Also, the Navier's method for simply support boundary condition is used to solve these equations. The effects of applied voltage, magnetic field, length to width ratio, thickness of porous to micro plate thickness ratio, type of porous, coefficient of porous on the frequency ratio are investigated. The numerical results indicate that with increasing of the porous coefficient, the non-dimensional frequency increases. Also, with an increase in the electric potential, the non-dimensional frequency decreases, while and with increasing of the magnetic potential is vice versa.

• Smart Structures and Systems
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• 제25권5호
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• pp.619-630
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• 2020

This paper studies nonlinear free vibration characteristics of nonlocal magneto-electro-elastic (MEE) nanobeams resting on nonlinear elastic substrate having geometrical imperfection by considering piezoelectric reinforcement scheme. The piezoelectric reinforcement can cause an enhanced vibration behavior of smart nanobeams under magnetic field. All of previously reported studies on MEE nanobeams ignore the influences of geometric imperfections which are very substantial due to the reason that a nanobeam cannot be always perfect. Nonlinear governing equations of a smart nanobeam are derived based on classical beam theory and an analytical trend is provided to obtained nonlinear vibration frequency. This research shows that changing the volume fraction of piezoelectric constituent in the material has a great influence on vibration behavior of smart nanobeam under electric and magnetic fields. Also, it can be seen that nonlinear vibration behaviors of smart nanobeam are dependent on the magnitude of exerted electric voltage, magnetic potential, hardening elastic foundation and geometrical imperfection.

• Structural Engineering and Mechanics
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• 제69권2호
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• pp.145-153
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• 2019

Modified couple stress formulation and first order shear deformation theory are used for magneto-electro-elastic bending analysis of three-layered curved size-dependent beam subjected to mechanical, magnetic and electrical loads. The governing equations are derived using a displacement field including radial and transverse displacements of middle surface and a rotation component. Size dependency is accounted based on modified couple stress theory by employing a small scale parameter. The numerical results are presented to study the influence of small scale parameter, initial electric and magnetic potentials and opening angle on the magneto-electro-elastic bending results of curved micro beam.

• Structural Engineering and Mechanics
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• 제85권6호
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• pp.743-753
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• 2023

Piezoelectricity is defined as the ability of certain materials to produce electric signals when mechanically stressed or to deform when an electrical potential is applied. Piezo technology is becoming increasingly crucial as intelligent devices use vibration sensors to detect vibrations in consumer electronics, the automotive industry, architectural design, and other applications. A wide range of applications is now possible with piezoelectric sensors, such as skin-attachable devices that monitor health and detect diseases. In this article, copper nanoparticles are used in the piezoelectric sensor as the driving agent of the magnetic field. Magnetic nanocatalysts containing copper nanoparticles are used due to their cheapness and availability. Considering that the increase of the electric field acting on the piezoelectric increases the damping (As a result, damping materials reduce radiation noise and increase material transfer losses by altering the natural vibration frequency of the vibrating surface). Among the advantages of this method are depreciating a significant amount of input energy using high energy absorption capacity and controlling slight vibrations in the sensors.

• 한국전기전자재료학회논문지
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• 제11권3호
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• pp.221-228
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• 1998

In this study, the $\beta$-Polyvinylidene fluoride(PVDF) thin films were fabricated by physical vapor deposition method. Also, the properties of dielectric relaxation were studied to understand carrier's behavior of PVDF thin films, to be regarded as the excellent piezo and pyroelectricity. In the process of vapor deposition, the $\beta$-PVDF thin films have been fabricated under the condition of the substrate temperature at 3$0^{\circ}C$, the applied electric field at 142.8kV/cm and the pressure at 2.0${\times}10^{-5}$torr. The dielectric properties of PVDF have been studied in the frequency range 10Hz to 1MHz at temperature from 30 to $100^{\circ}C$. The relative dielectric constant of $\alpha$ and $\beta$-PVDF were 6.8 and 9.8, respectively, under a frequency of 1kHz. Such a phenomenon was caused by the decrease in intermolecular forces originated by the phase-transition from the TGTG' molecular conformation to the TT planar zig-zag conformation. And the relative dielectric constant is increased as a measuring temperature increases, because of the reduction of relaxation time caused by the decrease of intermolecular force.

• Advances in Computational Design
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• 제5권1호
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• pp.55-89
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• 2020

For the first time, an accurate analytical solution, based on coupled three-dimensional (3D) piezoelasticity equations, is presented for free vibration analysis of the angle-ply elastic and piezoelectric flat laminated panels under arbitrary boundary conditions. The present analytical solution is applicable to composite, sandwich and hybrid panels having arbitrary angle-ply lay-up, material properties, and boundary conditions. The modified Hamiltons principle approach has been applied to derive the weak form of governing equations where stresses, displacements, electric potential, and electric displacement field variables are considered as primary variables. Thereafter, multi-term multi-field extended Kantorovich approach (MMEKM) is employed to transform the governing equation into two sets of algebraic-ordinary differential equations (ODEs), one along in-plane (x) and other along the thickness (z) direction, respectively. These ODEs are solved in closed-form manner, which ensures the same order of accuracy for all the variables (stresses, displacements, and electric variables) by satisfying the boundary and continuity equations in exact manners. A robust algorithm is developed for extracting the natural frequencies and mode shapes. The numerical results are reported for various configurations such as elastic panels, sandwich panels and piezoelectric panels under different sets of boundary conditions. The effect of ply-angle and thickness to span ratio (s) on the dynamic behavior of the panels are also investigated. The presented 3D analytical solution will be helpful in the assessment of various 1D theories and numerical methods.

• 한국지반환경공학회 논문집
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• 제15권1호
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• pp.5-12
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• 2014

본 논문은 심층연약지반 개량용 전기가열장치를 개발하여 경기도 화성시 인근 연약지반에 적용한 것이다. m당 1 kW의 전기를 소비하는 니켈-크롬선으로 구성된 길이 4.0 m의 전기가열장치를 지표하 3.5~6.5 m 사이에 설치하여 48시간의 지반가열을 2회, 총 96시간 실시하였으며, 온도계와 압력계를 지표하 5.0 m 지점에 매설하여 지반가열에 의한 온도 및 증기압 변화를 측정하였다. 실험결과 가열원으로부터 횡방향 거리의 온도분포 및 선단지지력의 변화는 이차함수를 나타내었으며, 둘 다 R2값은 1로 산정되었다. 또한, 전기가열로 인해 수증기가 배출됨에 따라, 함수비 및 간극수압이 감소함을 관찰할 수 있었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 D
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• pp.2165-2166
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• 2006

Estrangement hierarchical by bipolarization is deepened and time space that social welfare by graying corresponds great so. Specially, is real condition that indifference by patient's increase which is solitary life string is come to involve by social problem.Together, Jaetaek bone fracture patient's ratio is zooming. Domestic BT technology, medical treatment solution technology offer more important role than role assistance enemy of modern technology and utilize by creative technology can. Specially, if apply supersonic waves in bone fracture treatment, there is treatise data that can reduce bone fracture treatment period of bone that bone does not stick well about 40%. Supersonic waves operation frequency used on both end because do 1m Hz, 1.3mHz, supersonic waves origination that have 1.5mHz's Piezo-ceramic crystal tranducer material each 4 premature senilitys in this research, and outside diameter according to impedance and Phase d used Gakgak4mm, 5.4mm, Dukke0.5mm, transformer deuce of length 70mm. Manufactured, and investigated supersonic waves distribution chart by capacity 50m W. Supersonic waves used by diagnosis mainly but is seen to become convenient medical treatment mounting in bone fracture patient's treatment if supplement clinically.If supplement system furthermore, is going to apply to osteoporosis patient, and this research tried to design poetic theme width directly and study rain standardization special quality and approach basic form because do modelling.