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Principles Of Optics Electromagnetic Theory Of Propagation Interference And Diffraction Of Light

This review provides a detailed overview of the energy harvesting technologies associated with piezoelectric materials along with the closely related sub-classes of pyroelectrics and ferroelectrics. These properties are, in many cases, present in the same material, providing the intriguing prospect of a material that can harvest energy from multiple sources including vibration, thermal fluctuations and light. Piezoelectric materials are initially discussed in the context of harvesting mechanical energy from vibrations using inertial energy harvesting, which relies on the resistance of a mass to acceleration, and kinematic energy harvesting which directly couples the energy harvester to the relative movement of different parts of a source. Issues related to mode of operation, loss mechanisms and using non-linearity to enhance the operating frequency range are described along with the potential materials that could be employed for harvesting vibrations at elevated temperatures. In addition to inorganic piezoelectric materials, compliant piezoelectric materials are also discussed. Piezoelectric energy harvesting devices are complex multi-physics systems requiring advanced methodologies to maximise their performance. The research effort to develop optimisation methods for complex piezoelectric energy harvesters is then reviewed. The use of ferroelectric or multi-ferroic materials to convert light into chemical or electrical energy is then described in applications where the internal electric field can prevent electron–hole recombination or enhance chemical reactions at the ferroelectric surface. Finally, pyroelectric harvesting generates power from temperature fluctuations and this review covers the modes of pyroelectric harvesting such as simple resistive loading and Olsen cycles. Nano-scale pyroelectric systems and novel micro-electro-mechanical-systems designed to increase the operating frequency are discussed.

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Piezoelectric and ferroelectric materials and structures for energy harvesting applications

An ultrasonic array is a single transducer that contains a number of individually connected elements. Recent years have seen a dramatic increase in the use of ultrasonic arrays for non-destructive evaluation. Arrays offer great potential to increase inspection quality and reduce inspection time. Their main advantages are their increased flexibility over traditional single element transducer methods, meaning that one array can be used to perform a number of different inspections, and their ability to produce immediate images of the test structure. These advantages have led to the rapid uptake of arrays by the engineering industry. These industrial applications are underpinned by a wide range of published research which describes new piezoelectric materials, array geometries, modelling methods and inspection modalities. The aim of this paper is to bring together the most relevant published work on arrays for non-destructive evaluation applications, comment on the state-of the art and discuss future directions. There is also a significant body of published literature referring to use of arrays in the medical and sonar fields and the most relevant papers from these related areas are also reviewed. However, although there is much common ground, the use of arrays in non-destructive evaluation offers some distinctly different challenges to these other disciplines.

Ultrasonic arrays for non-destructive evaluation: A review

Electromagnetic forming—A review

https://www.aeromech.usyd.edu.au/wwwcomp/pzferev.pdf

Advances in piezoelectric finite element modeling of adaptive structural elements: a survey

A method for the analysis of piezoelectric media based on finite-element calculations is presented in which the fundamental electroelastic equations governing piezoelectric media are solved numerically The results obtained by this finite-element calculation scheme agree with theoretical and experimental data given in the literature The method is applied to the vibrational analysis of piezoelectric sensors and actuators with arbitrary structure Natural frequencies with related eigenmodes of those devices as well as their responses to various time-dependent mechanical or electrical excitations are computed The theoretically calculated mode shapes of piezoelectric transducers and their electrical impedances agree quantitatively with interferometric and electric measurements The simulations are used to optimize piezoelectric devices such as ultrasonic transducers for medical imaging The method also provides deeper insight into the physical mechanisms of acoustic wave propagation in piezoelectric media >

Simulation of piezoelectric devices by two- and three-dimensional finite elements

An ultrasound transducer for diagnostic and therapeutic generates ultrasound waves of different wavelengths in diagnostics mode or therapy mode. The ultrasound transducer has an n×λ/4 matching layer for a propagation medium adjoining the ultrasound transducer, and a piezoelectric ultrasound transducer element with a first electrode located between the matching layer and the ultrasound transducer element, a second electrode attached at the opposite side of the ultrasound transducer element, and a third electrode that divides the ultrasound transducer element into two regions. Ultrasound waves can be generated for the diagnostics mode and for the therapy mode dependent on the division of the ultrasound transducer element. The n×λ/4 matching layer is effective for the wavelength of the ultrasound waves in diagnostics mode as well as in therapy mode.

Ultrasound transducer for diagnostic and therapeutic use

Many surface acoustic wave (SAW) devices consist of quasiperiodic structures that are designed by successive repetition of a base cell. The precise numerical simulation of such devices, including all physical effects, is currently beyond the capacity of high-end computation. Therefore, we have to restrict the numerical analysis to the periodic substructure. By using the finite-element method (FEM), this can be done by introducing periodic boundary conditions (PBCs) at special artificial boundaries. To be able to describe the complete dispersion behavior of waves, including damping effects, the PBC has to be able to model each mode that can be excited within the periodic structure. Therefore, the condition used for the PBCs must hold for each phase and amplitude difference existing at periodic boundaries. Based on the Floquet theorem, our two newly developed PBC algorithms allow the calculation of both, the phase and the amplitude coefficients of the wave. In the first part of this paper we describe the basic theory of the PBCs. Based on the FEM, we develop two different methods that deliver the same results but have totally different numerical properties and, therefore, allow the use of problem-adapted solvers. Further on, we show how to compute the charge distribution of periodic SAW structures with the aid of the new PBCs. In the second part, we compare the measured and simulated dispersion behavior of waves propagating on periodic SAW structures for two different piezoelectric substrates. Then we compare measured and simulated input admittances of structures similar to SAW resonators.

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Finite-element simulation of wave propagation in periodic piezoelectric SAW structures

A novel Inverse Method for the determination of material parameters characterizing discoidal piezoceramic actuators is presented. In contrast to the common identification method, no specially shaped test samples are required. The Inverse Method is based on a finite element simulation. Both the measured mechanical and the electrical behavior of the actuator serve as input quantities of the new procedure. The presented results show the efficiency and correctness of the developed Inverse Method.

Inverse Method to estimate material parameters for piezoceramic disc actuators

A finite element technique for modeling the vibrational behavior of arbitrarily shaped piezoelectric transducers immersed in an acoustic fluid is presented. The elastic and electrical responses of the piezoelectric structure are computed by piezoelectric finite elements, and the wave propagation in the ambient acoustic medium is computed by acoustic finite elements. The acoustic feedback of the surrounding acoustic fluid to the piezoelectric solid is considered. This method makes it possible to analyze piezoelectric devices with respect to their mechanical strains and stresses, electrical fields and displacements, and various integral properties, such as the electric input impedance and the electromechanical coupling coefficient. The application of this method to ultrasonic transducers, especially those used in array antennas, is reported. >

Reinhard Lerch

Papers

Simulation of piezoelectric devices by two- and three-dimensional finite elements

Ultrasound transducer for diagnostic and therapeutic use

Finite-element simulation of wave propagation in periodic piezoelectric SAW structures

Inverse Method to estimate material parameters for piezoceramic disc actuators

Finite element analysis of piezoelectric transducers