Yukio Kagawa

A tubular piezoelectric vibrator gyroscope

This paper proposes a vibrator gyroscope made of a piezoelectric tube, which has the same configuration as that used for the tri-axial sensors and actuators developed in our previous paper. The gyroscopic operation is the same as a circular rod, but the polarization (in thickness direction of the shell) and, accordingly, the electrode arrangement are much simpler. Wireless LAN arrangement is devised for remote data access with which the measurement is possible for the gyroscope under rotation. The experimental results are compared with the numerical simulation with three-dimensional finite-element calculation. The discrepancy between the measured and the experimental is found to depend on the asymmetrical deformation of the structure, and the cause is clearly demonstrated via simulation. This shows the usefulness of the numerical modeling to investigate the cause, in which the parameters of dimensions and boundary conditions can easily change.

Digital Equivalent Circuits for Acoustic Field Based on Discrete Huygens' Modeling

A digital equivalent circuit for a three-dimensional acoustic field is developed on the basis of the discrete Huygens model (DHM) in which the propagation and scattering of waves are simulated as the sequences of impulses scattering as Huygens principle states. The scattering matrix of a DHM element for propagation velocity variation is first derived. Applying the z transformation to the scattering matrix, the transfer function in the z-domain is then derived. The transmission characteristic is numerically discussed in comparison with the analog equivalent circuit model.

Tri-axial sensors and actuators made of a single piezoelectric cylindrical shell

Electromechanical transducers for sensing and actuating disturbances or vibrations have been used in many fields of applications. There have been transducers of different configuration developed for the unidirectional transduction. This paper demonstrates a single element transducer for tri-axial components made of a piezoelectric cylindrical shell. The separation of the tri-axial transductions is achieved by devising a proper electrode arrangement. The structure and the fundamental idea are first presented, and then the numerical analysis by means of the finite element modeling follows, and their characteristics and behaviors are then experimentally verified.

Finite element simulation of non-linear acoustic generation in a horn loudspeaker

The loudspeaker is an electro-acoustic device for sound reproduction which requires the distortion as small as possible. The distortion may arise from the magnetic non-linearity of the york, the uneven magnetic field distribution, the mechanical non-linearity at the diaphragm suspension and the acoustic non-linearity due to the high sound pressure and velocity in the duct-radiation system. A horn is sometimes provided in front of the vibrating diaphragm radiator, which plays an important role to increase the efficiency by matching the acoustic impedance between the radiator and the ambient medium. The horn is in many cases folded twice or three times to shorten the length, which further degrades the reproduction quality. The sound intensity and velocity are apt to attain very high in the small cross-sectional area in the throat and in the folded regions, which may cause the distortion due to the non-linear effect of the medium. The present paper is to investigate the frequency characteristics of the loudspeaker numerically evaluating the generation of the harmonics and sub-harmonics. An axisymmetric folded horn is considered for which the wave equation with the non-linear term retained is solved by the finite element method. The solution is made in time domain in which the sound pressure calculated at the opening end of the horn is Fourier-transformed to the frequency domain to evaluate the distortion, while the wave marching in the horn is visualized.

3D direct inversion algorithm for electrical impedance underground anomaly detection with dual reciprocity boundary element modeling

Anomaly detection is a technique to visualize the interior from the data measured on the ground surface for geophysical applications. The application can be used from oil field prospecting to land mine searching. We have developed the direct inversion algorithm for electrical impedance tomography based on dual reciprocity boundary element modeling, first for the two-dimensional field, which is here extended to three-dimensional field cases. The validation has been made for cases when impedance data are available for electrical current emanation diagonally injected to the surface surrounding the field of interest [Kagawa, Y., Sun, Y. and Zhao, Y., 1997, Direct inversion algorithm for electrical impedance tomography using dual reciprocity boundary element models. Inverse Problems in Engineering, 15, 217–237; Horikane, T., Hataya, T., Xu, W., Zhao, Y. and Kagawa, Y., 2002, 3D electrical impedance prospecting simulation based on dual reciprocity boundary element modelling. In: M. Tanaka and G.S. Dulikravich (Eds) Inverse Problems in Engineering Mechanics III (Amsterdam: Elsevier Science), pp. 411–418.] In practical prospecting, however, this is not always the case, as data are not always available for all surfaces. The present simulation includes the case of anomaly detection when the data are only available on the ground surface.

FIR-type and IIR-type neural networks, and their application to shape optimization of a magnetic pole

This article presents two types of neural network (NNs), Finite Impulse Response (FIR) and Infinite Impulse Response (IIR) and their application to a magnetic pole shape optimization problem. To begin with, the architecture and the learning algorithm of the two types of the NN are provided, and then their application to the magnetic pole shape optimization problem is presented. The feature of the two networks is that they have delay elements within the network, which act as a memory function that stabilizes the back propagation learning process calculation. The conclusions obtained showed that these NNs could reduce the iteration process when compared to the conventional feed forward type NN, and the learning iteration for the convergence of the IIR network is less than that of the FIR network.

Discrete huygens' modelling and simulation for wave propagation

With the advent of digital computers, wave field problems are best solved by computers. Present paper introduces a physical model for wave propagation, which is traced on the computer based on the mechanism equivalent to the Huygens principle. The approach does not require the numerical solution of the differential equation or wave equation which is the mathematical model of the wave propagation phenomena. It only requires the manipulation tracing the sequence of the impulse scattering at the discretized nodes due to the Huygens principle. The paper describes the discrete Huygens modelling for the acoustic field and demonstrates the some applied examples.

Determination of the Mass Density of the Layer Deposited on the Surface of the Resonator in QCM (Quartz Crystal Microbalance)

ABSTRACT The quartz crystal microbalance (QCM) is a quartz crystal resonator vibrating in thickness-shear mode, in which a minute mass is measured in terms of the resonant frequency change as an mass loading on the resonator surface decreases the resonant frequency [1]. In most applications, however, an adsorbing film layer is formed on the surface, which adsorbs the micro-mass material. The presence of the thin film affects not only the resonance but also its damping, which can not simply be ignored in most QCM applications [2]. That is, the film should be considered as a viscoelastic layer, which must be included in the modeling. In the present paper, the viscoelastic layer is characterized from the measurement of the multiple resonant frequencies and the corresponding resonant resistance by virtue of the overtone operation of the quartz crystal plate.

On the passive vibration damping by piezoelectric transducers with inductive loading

The increase of the effectiveness of the passive damping in mechanical vibrations is discussed with piezoelectric transducers. An electrical resistor with shunt inductor is connected between the electrodes of the piezoelectric transducers, which transformed the vibrating energy into the electrical energy by means of the electromechanical coupling. The electrical equivalent circuit modeling has been developed for an electromechanical coupling system. The circuit parameters are determined by the modal analysis based on the finite element model. Some examinations are demonstrated for a thin plate. It is found that the introduction of the electrical shunt inductor is more effective than the simple electrical resistor termination because the electrical inductance cancels the equivalent shunt capacitance or damped capacitance between the electrodes.

Identification of Speech Source wave by Inverse-Filtering of Vocal Tract Transfer Characteristics

Here is presented a way that identifies the shape of source wave from speech signals by inverse-filtering of the vocal tract transfer characteristics that are reconstructed from formant frequencies and band widths obtained by peak picking method. First the experiment is conducted using artificial voices. Then it is applied to the real speech signals. Some comparison with the results from Linear Prediction residue method is also presented.