Accurate equivalent circuits for unloaded piezoelectric resonators

Skeleton-based hand gesture recognition has achieved great success in recent years. However, most of the existing methods cannot extract spatiotemporal features well due to the skeleton noise. In real applications, some large models also suffer from a huge number of parameters and low execution speed. This paper presents a lightweight skeleton-based hand gesture recognition network by using multi-input fusion to address those issues. We convey two joint-oriented features: Center Joint Distances (CJD) feature and Center Joint Angles (CJA) feature as the static branch. Besides, the motion branch consists of Global Linear Velocities (GLV) feature and Local Angular Velocities (LAV) feature. Fusing static and motion branches, a robust input can be generated and fed into a lightweight CNN-based network to recognize hand gestures. Our method achieves 95.8% and 92.5% hand gesture recognition accuracy with only 2.24M parameters on the 14 gestures and 28 gestures of the SHREC’17 dataset. Experimental results show that the proposed method outperforms state-of-the-art (SOAT) methods.KeywordsSkeleton-based hand gesture recognitionMulti-input fusionJoint-oriented feature Second Keyword

The dissipative properties of electromechanical systems based on structure with elements made of piezomaterial can be controlled by attaching external electric circuits to the piezoelements. One can change electric circuit parameters in such a way as to ensure the greatest possible energy dissipation on an external electric circuit and, thereby, the best damping of the system’s specified oscillation frequency. Since the external electric circuits are a collection of elements with lumped parameters attached to a system with distributed parameters, the solution for such a system of electro-viscoelasticity problems in the complete formulation by the finite element method leads to a large solving system of algebraic equations. The solution of this system requires considerable time and computational resources. There are known approaches in mechanics that make it possible to represent mechanical systems with distributed parameters in the form of discrete systems with lumped parameters, such as a spring–mass–damper. In this article, it is proposed to model electromechanical systems with external electric circuits based on their electrical analogue in the form of equivalent electric substitution circuits, which are discrete electrical systems with lumped parameters. These discrete systems are analogues of the initial electromechanical systems in terms of frequency characteristics and the electrical processes that take place in them. The equivalent substitution circuit is based on the Van Dyke model and allows one to obtain the required number of complex eigenfrequencies of the electromechanical system under consideration.

As an ultra-sensitivity sensor, a quartz crystal microbalance (QCM) could be used to quantitatively characterize the relation between QCM parameters and the characteristics of viscoelastic films. When a QCM coated with a viscoelastic thin film is in the gas phase, based on the constructive equation of the quartz crystal and ignoring the capacitance effect, the equivalent Butterworth–Van Dyke (BVD) model of the QCM and the explicit expression for its frequency shift are derived. The “extra mass effect” deduced by the complex modulus is also obtained. It is found that the tendency of the BVD model in this work agrees well with that of Voinova’s model, although both are derived in different ways. Meanwhile, it can be seen that the two above-mentioned models exhibit different characteristics when compared with Sauerbrey’s model and Arnau’s model. The BVD model will help analyze the properties of viscoelastic films in the gas phase.

In this article, we study magnetic field sensors based on the delta-E effect occurring in a magnetostrictive layer coupled to a piezoelectric resonator. The sensors consist in suspended beams that essentially vary in the bounded conditions at the edges. We examine a clamped-free and a double-clamped sensor. A finite-element model (FEM) is implemented and validated versus published experimental measurements. The latter are considered as reference results. A Butterworth–Van Dyke (BVD) model is also given in each case. The performances of these two types of resonators are pointed out and compared, especially in terms of sensitivity and equivalent magnetic noise level. The given approach gives the way of sensor optimization.

This research presents the analysis of the influence of design parameters on the performance of film bilk acoustic wave resonator (FBAR) working from 15 GHz to 19 GHz. The analysis is done by implementing one-dimensional (1-D) modellings, which are 1-D Mason model and Butterworth Van Dyke (BVD) model. The physical parameters such as piezoelectric materials and its thickness, and size of area affecting the characteristics of the FBAR are analyzed in detail. Zinc oxide (ZnO) and aluminum nitride (AlN) are chosen as the piezoelectric materials. From the analysis, it is found that as the frequency increases, the thickness of the piezoelectric material decreases. Meanwhile, the static capacitance increases as the frequency increases. It is also found that as the area increases, the electrical impedance and static capacitance also increases.

Determination of Impurities in Sintered Electronic Ceramics by Inductively Coupled Plasma Atomic Emission Spectrometry Following Acid Decomposition

Smart aggregate (SA), as a piezoceramic-based multi-functional device, is formed by sandwiching two lead zirconate titanate (PZT) patches with copper shielding between a pair of solid-machined cylindrical marble blocks with epoxy. Previous researches have successfully demonstrated the capability and reliability of versatile SAs to monitor the structural health of concrete structures. However, the previous works concentrated mainly on the applications of SAs in structural health monitoring; no reasonable theoretical model of SAs was proposed. In this paper, electromechanical properties of SAs were investigated using a proposed theoretical model. Based on one dimensional linear theory of piezo-elasticity, the dynamic solutions of a SA subjected to an external harmonic voltage were solved. Further, the electric impedance of the SA was computed, and the resonance and anti-resonance frequencies were calculated based on derived equations. Numerical analysis was conducted to discuss the effects of the thickness of epoxy layer and the dimension of PZT patch on the fundamental resonance and anti-resonance frequencies as well as the corresponding electromechanical coupling factor. The dynamic solutions based on the proposed theoretical model were further experimentally verified with two SA samples. The fundamental resonance and anti-resonance frequencies of SAs show good agreements in both theoretical and experimental results. The presented analysis and results contribute to the overall understanding of SA properties and help to optimize the working frequencies of SAs in structural health monitoring of civil structures.

This paper reports on our determination of the small signal properties of Motorola 3203 HD, including the effects of losses and dispersion, and it shows the limitations imposed by assuming that the material is loss-less. A set of PZT 3203 HD unloaded resonators manufactured by Motorola was cut to specifications outlined in the IEEE Standard on Piezoelectricity Std 176-1987 to ensure the appropriate boundary conditions of each resonance mode. Impedance spectra of the thickness, thickness shear, length and length thickness extensional modes were analyzed at the fundamental and second resonances using Smits' method while the analysis of the radial mode resonators was accomplished using a method that we had developed earlier. Using the results from the above analysis we have determined the 10 independent complex constants (S<SUB>11</SUB><SUP>E</SUP>, S<SUB>12</SUB><SUP>E</SUP>, S<SUB>13</SUB><SUP>E</SUP>, S<SUB>33</SUB><SUP>E</SUP>, S<SUB>55</SUB><SUP>E</SUP>, d<SUB>13</SUB>, d<SUB>33</SUB>, d<SUB>15</SUB>, (epsilon) <SUB>11</SUB><SUP>T</SUP>, and (epsilon) <SUB>33</SUB><SUP>T</SUP>) that define the reduced matrix for a C<SUB>(infinity</SUB> ) piezoelectric material at the fundamental resonance frequency of the resonator. The use of complex material constants to account for the loss of linear systems is discussed and the relationship between the mechanical Q, dielectric tan(delta) , piezoelectric loss and the complex material constants are presented. The dispersion in the martial constants, except for S<SUB>12</SUB><SUP>E</SUP> and S<SUB>13</SUB><SUP>E</SUP>, was studied by evaluating the constants at the second resonance. The source of the major components of the dispersion has been determined to be due to external effects such as mode coupling for high impedance resonators and electrode sheet resistance for low impedance resonators. The size of loss components and the dispersion are shown to be significant and it is suggested that ignoring these effects will reduce the accuracy and predictive capabilities of transducer models.

Piezoelectric Lead ZirconateTitanate (PZT) ceramics based acoustic transducers are widely used in a multitude of applications as sensors and actuators. Different modeling techniques are used by transducer designers to test the original designs without building costly prototypes. The equivalent circuit of piezoelectric vibrator represented by Van Dykemodel is used to plot the resonant curve. Based on the application, piezoelectric materials in the acoustic transducers are subjected to a variety of environmental conditions. This results in the shift in the resonant frequency. This paper reports the effect of change in temperature and pressure on the thickness mode response of equivalent circuit of piezoelectric Lead ZirconateTitanate (PZT) ceramic. The ranges considered are suitable for under water applications. With varying conditions of temperature and pressure, the changes in resonant and anti-resonant frequencies of the piezoelectric material are noted. Using these practically obtained values, parameters of the model are computed and the shift in the resonance curve is observed for the conditions considered. The values of resonant and anti-resonant frequencies obtained from the model response match with those obtained experimentally for the given conditions. Other material constants required for building realistic Finite Element Analysis models can be computed using these practically obtained values of resonant and anti-resonant frequencies.

The effects of internal mechanical losses and external mechanical loading on the characteristic frequencies of thickness extensional piezoelectric resonators and transducers are investigated around the fundamental resonance. The exact one-dimensional model is used for the computation of the electrical input impedance. A complex elastic constant (c33 D)* = c33 D (1 + j tan δm) is used for the representation of mechanical losses. A constant Q model, with an attenuation linearly increasing with frequency, has been assumed for the piezoelectric material. External mechanical loads, represented by means of the characteristic impedances of the backing material and the irradiated media are normalized with respect to the characteristic impedance of the piezoelectric material.

In recent years, battery chargers are not only capable of charging a battery, but also can measure the internal impedance spectrum of a battery in real-time. Measured battery impedance represents electrochemical characteristics, which are used to analyze the internal conditions of a battery and can be represented by a circuit model. This paper presents an equivalent circuit parameter extraction algorithm based on the impedance spectrum measurement of a battery. The proposed algorithm is designed using the Nyquist theory and is applicable to lithium ion batteries specifically. The circuit simulation, ac perturbation, and parameter extraction are processed with the measured circuit parameters, which are obtained from electrochemical impedance spectroscopy (EIS) test of a 1000mAh Li-ion battery. It shows 0.0216mΩ difference for Ohmic resistance extraction based on the proposed simulation results and the selected parameters from experiment. The presented algorithm could be applicable to the battery charger, which is capable of obtaining on-line electrochemical impedance spectrum. The algorithm could be useful for a battery management system as well.

The intra-layer no-insulation (LNI) coil, which has the advantages of self-protection and high magnetic field homogeneity, is of great potential in HTS NMR and MRI applications. Compared to the more commonly-used double-pancake coils, the transient characteristics are more complex due to additional axial current. While the present circuit model cannot accurately describe the geometry of the LNI coil and the internal characteristics of each turn of the coil, a helical grid equivalent circuit model with consideration of types of mutual inductances is proposed in this paper. In the circuit model, details of the coil are characterized with subdivided helical surface elements in each turn, and each helical surface element can be equivalent to corresponding circuit parameters. The circuit model is verified by a comparison experiment with an intra-layer insulation coil. And elaborate current distributions in each turn of the LNI coil can be obtained with this circuit model. Analysis results demonstrate that the azimuthal current and the axial current are always symmetrically distributed about the middle plane, and the radial current is always anti-symmetrically distributed about the midplane. The circuit model can be used to simulate the quench electromagnetic characteristics of the LNI coil in the future.

A methodology was developed to analyze the uniformity properties of amorphous silicon (a-Si) based triple-junction thin-film solar module for power stations or for building-integrated photovoltaic using circuit model parameters. First, a-Si-based triple-junction thin-film solar module with a size of 5G was fabricated via the mass production method. The module was divided into small modules with ten solar cells. A total of nine samples were selected and the dark I–V characteristics for each sample were measured. A circuit model for a triple-junction solar module was proposed. One sample that could represent the triple-junction properties was selected and the circuit parameters were extracted. The circuit model with the extracted parameters was simulated using H-spice and showed good agreement between experimental and simulation results. Ideality factors and reverse saturation currents from the selected samples were extracted from the dark IV curve and resistance parameters by using the numerical method with the circuit model. The distribution of each parameter for the samples and the uniformity of the large-size module were analyzed.

In inductive power transfer (IPT) systems, it is usually desirable to have an adjustable output voltage. This paper proposes a pulsewidth modulation scheme for active class-E rectifier based IPT systems. The output voltage is regulated by the duty cycle of the active rectifier. Utilizing the proposed modulation scheme, the active MOSFET is turned on at the zero crossing point of its drain-source voltage. Thus, the power MOSFET of the rectifier is achieved with zero-voltage-switching (ZVS) condition over a wide output range. Detailed circuit analysis, modeling and parameters design are presented. The experimental results match well with the circuit modeling and validate the soft-switching operation and the output voltage regulation capabilities. The efficiencies of overall system and rectifier reach 90.22 % and 95.45 % at 120 W output respectively.

The piezoelectric effect occurs in materials for which an externally applied elastic strain causes a change in electric polarization which produces a charge and a voltage across the material. The converse piezoelectric effect is produced by an externally applied electric field, which changes the electric polarization, which in turn produces an elastic strain. The most known piezoelectric material is quartz crystal. Many other natural crystalline solids, as Rochelle salt, ammonium dihydrogen phosphate, lithium sulfate, and tourmaline as well as some man-made crystal as gallium orthophosphate, aluminium nitride (AlN), and langasite exhibit piezoelectric properties. A lot of artificial ceramics as barium titanate, lead titanate, lead zirconate titanate (PZT), potassium niobate, lithium niobate, and lithium tantalite have similar properties. The most known technical application is the piezoelectric transducer. In the last years electromechanical AlN resonators emerged as a very efficient solution for mobile communications filters due to the possibility to be integrated at a relatively low cost together with CMOS circuits in systems on a chip and systems in a package. In most applications the piezoelectric devices have a linear behaviour. In Section 2 the linear and nonlinear equations of the piezoelectric effect are described, a new iterative procedure for solving the nonlinear equations is given, and some aspects of the Finite Element solution are discussed. An electromechanical field analysis of a displacement transducer is presented in Section 3. Sections 4 and 5 show some recent applications in the mobile communication technology. The field analysis of a bulk acoustic wave (BAW) resonator using 3D linear models is presented in Section 4. Some nonlinear effects in power BAW resonators together with their circuit models are discussed in Section 5.