Table of contents

This work discusses the effects of temperature, force, and acceleration on the frequency of quartz thickness shear mode resonators. Historically, workers in the frequency control industry have tried to reduce these effects. Some of the physical principles will be discussed. Turning the problem around, sensitivity to these effects can be maximized to develop sensors for temperature and pressure. Advantages of such sensors include inherently digital format, high resolution, high accuracy, and long-term stability. This work reviews the physical principles involved in the operation of some devices used down-hole in the oil and gas service industry.

The author reviews the interaction of micro bubbles with ultrasound. First, the action of acoustic radiation pressure on bubbles is discussed in contrast with that on small particles noting the concept of Bjerknes force, resonant bubbles and nonlinear oscillation of bubbles. In the past decade, sonoluminescence, light emission from a single oscillating bubble, attracted attention of researchers because of its strange characteristics. A short history of sonoluminescence and its characteristics are summarized based on bubble motion in a sound field. Lastly, industrial and medical applications of extreme environment generated by collapsing micro bubbles are discussed as promising technology in the new century.

The novel properties of a "sonic crystal" are investigated and its application to a new acoustic waveguide are discussed by developing the finite-difference time-domain (FDTD) method for acoustic wave propagation in a finite-size periodic structure. A sonic crystal is formally an acoustic version of a "photonic crystal." It is not an actual crystal but an artificial one composed of a periodic array of acoustic scatterers imbedded in the host material, and expected to have acoustical band gaps where the acoustic wave cannot penetrate the crystal. These properties are numerically investigated, and sonic crystals are shown not to be acoustic replicas of photonic crystals. Interesting artificial crystals which can be realizable as sonic crystals but not as photonic crystals are realized by clarifying the correspondence relationship between the transverse-electric and transverse-magnetic waves and the longitudinal acoustic wave in the two-dimensional space. Full band-gap characteristics versus wavelength and wave propagation in acoustic waveguides are shown.

The frequency dependence of the hydroxyl radical yield produced by 47 kHz and 400 kHz ultrasound in the presence of rare gases was studied by electron paramagnetic resonance-spin trapping. 5,5-Dimethyl-1-pyrroline-N-oxide was used to detect hydroxyl radicals. Here, we show that the amount of hydroxyl radical yield produced by 400 kHz ultrasound was less inversely proportional to the thermal conductivity than those induced by 47 kHz ultrasound.

To study the behavior of divacancy and impurity, the diffusion process of InCl₃ doped on the surface of a AgCl single crystal was measured by the internal friction and dielectric loss. All of the In³⁺ ions move to the dislocation core with a rate proportional to t^1/6 and the migration energy is 0.060 eV. The concentration in the dipole of In³⁺ ion and cation vacancy rapidly becomes zero at the critical temperature 566 K. Reorientation of the dipole and ionic conductivity gives an identical migration energy of 0.33 eV. The binding energy between the vacancy and the trivalent impurity E_b is 0.10 eV.

Molecular dynamics simulation was performed for three-dimensional (3D) cubic mass-spring model crystals. Anharmonic potential up to the fourth order was taken into account, and central forces between the nearest neighbor (nn) and the next nearest neighbor (nnn) atoms were considered. The ratio of the potential between the nnn atoms to the potential between the nn atoms was varied. An input pulse displacement was given to central atomic planes in the crystal or to the end atomic plane of the crystal, and induced displacements and velocities of all atoms were computed. As the nnn interaction was enhanced, the soliton velocity increased and the soliton energy decreased. The results were compared with those of 1D and 2D crystals obtained previously. The increase of soliton velocity due to the enhanced nnn interaction was largest for 1D crystals, and the decrease of soliton energy was smallest for 2D crystals. Discussions and remarks were presented for these results.

Mode coupling in two-dimensional bulk waves confined in a two-dimensional rectangular resonator is discussed using a 4 ×4 unitary matrix and Neumann series; this differs from the conventional methods which involve a coupling between N resonance systems solved as an eigenvalue problem of an N ×N matrix, which becomes complicated when the loss phenomenon is included or when the value of N increases. The coupling is dealt with by considering the energy distribution between the two modes with unitarity or energy conservation. The 4 ×4 unitary matrix is adopted to distinguish between self-coupling and mutual coupling, and the confinement of wave energy due to the multiple reflection is represented by the Neumann series. Simple and unified matrix algebra gives the resonance characteristics when the mode coupling occurs in an infinite number of degrees of freedom.

The effect of tensile stress on the hypersonic wave velocities of polymer films was investigated using a Brillouin scattering method. From the real-time measurements during the tensile test, an interesting behavior of the longitudinal wave velocity has been observed. By comparing the velocity profile with the stress-strain curve, velocity changes indicate that the small scale deformation of the film propagates from the edge to the center and gradually spreads. These results point out the possibility of the Brillouin scattering method as a useful tool for nondestructive and real-time measurement of the stress and deformation in the sample.

Compressional and shear wave velocities and attenuation in sintered magnetite were accurately measured to investigate the Verwey transition by the pulse transmission method using a dual acoustic path across the temperature range between 78 K and 300 K. The temperature dependence of the compressional and shear wave velocities of the sintered magnetite exhibited a steep depression at ∼ 90 K. The low transition temperature suggests nonstoichiometry of the present sintered sample. Using the measured ultrasonic data, the elastic properties of sintered magnetite are discussed.

Ultrasonic relaxation measurement was employed for confirmation of the interaction between dimyristoylphosphatidylcholine (DMPC) membrane and a soluble protein, carbonic anhydrase II (CA II). The enhancement of the fluctuation of DMPC membrane structure was observed in the presence of CA II under acidic condition, pH 3.6–4, indicating the interaction between DMPC and CA II. The pyrene fluorescence spectrum of CA II solution clearly showed that this protein adopted an unfolding intermediate called the molten globule state under the low pH condition, in which CA II interacted with DMPC. However, CA II in the molten globule state did not cause membrane lysis in contrast to the high lytic activity of α-lactalbumin on DMPC liposomes.

We have demonstrated the existence of shear waves which were predicted to radiate from the pseudocapillary surface mode propagating on agarose gel. The technique of stroboscopic photoelasticity imaging was used to visualize the shear waves propagating in the bulk of the gel. The shear-wave velocity was obtained from the wavefront image, and was found to agree with that obtained from the surface-wave measurements previously reported.

Propagation characteristics of a shear horizontal (SH) wave in a cell structure containing a nematic liquid crystal layer are described on the basis of numerical analysis and experimental results. The SH wave propagation is described by the numerical analysis result for the nematic liquid crystal as an anisotropic liquid, considering the director angle of the liquid crystal. The temperature dependence of effective viscosities of a typical nematic liquid crystal N-(p-methoxybenzylidene)-p'butylaniline)] (MBBA) is evaluated from the measurement of the phase velocity change of the SH wave in the liquid crystal cell.

Scanning nonlinear dielectric microscopy (SNDM) is the first successful purely electrical method for observing the ferroelectric domain distributions. At present its resolution is of the sub-nanometer order. As another method for measuring the ferroelectric domains, the piezoelectric response imaging method is often used. In this study, we compare the resolution of SNDM with that of piezoelectric response imaging and confirm that SNDM gives a much higher resolution than that obtained by piezoelectric imaging. A fundamental study to apply the SNDM system to the ferroelectric reading and writing system is also performed.

A characterization technique for homogeneity of piezoelectric wafers utilizing bulk-wave measurement was established, and measurements were carried out on langasite (LGS: La₃Ga₅SiO₁₄) wafers fabricated in our laboratory. The technique is capable of predicting the homogeneity of the phase velocity of a surface acoustic wave (SAW), which determines the deviation of the central frequencies of SAW devices, by measuring the distribution of the frequency constant of thickness-shear mode resonance. The frequency constant, measured by a combination of resonance frequency measurement and thickness measurement in a single wafer, yields a relative accuracy of about ±55 ppm. The distribution of the frequency constant is consistent with that of the phase velocity of SAW obtained by fabricating and measuring SAW devices. The method is both rapid and nondestructive, thus is suitable for routine characterization in the production of piezoelectric wafers. Characterization of langasite wafers using this technique correlated inhomogeneity to the growth conditions of the crystal.

We investigated new features (functions) of scanning nonlinear dielectric microscopy (SNDM), namely, higher-order nonlinear dielectric imaging and the very high vertical resolution. The resolution of the higher-order nonlinear dielectric imaging is higher than that of the conventional nonlinear dielectric imaging which detects the lowest order of the nonlinear dielectric constant. The very high vertical resolution of SNDM is also reported. These features of the SNDM enable us to obtain a new microscopy for measuring the topography or a new displacement sensor with extremely high sensitivity.

It has long been known that the mechanical quality factor at resonance for multilayer piezoelectric transducers decreases as the number of ceramic layers is increased. We investigated this phenomenon using multilayer transducers, which are driven in a longitudinal mode of the piezoelectric transverse-effect. In this report, we express equivalent circuits for the transducers with resistance for electrode layers. We concluded that the mechanical quality factor at resonance for the transducers decreases because the ratio of resistance for electrode layers to the total equivalent resistance increases with the number of ceramic layers.

Precise correction for γ ray attenuation in the skull bone is essential when obtaining quantitative single-photon emission computed tomography (SPECT) images of the brain. Correction for γ ray attenuation is approximately proportional to the density and thickness of the bone under investigation. Therefore, if the acoustic impedance and speed of sound in the bone are measurable using ultrasonic techniques, then the density and thickness of the bone sample can be calculated. We propose a method for determining simultaneously the thickness of and speed of sound in the skull bone through in vivo measurements; the principle being that the time delay between two discrete transmission paths will yield the desired information. Thus, it is necessary to distinguish between the responses of these two transmission paths. The proposed method incorporates the pulse compression method to measure the time delay between detected transmission paths and reduce dispersion in the transmission line, thus increasing the signal-to-noise (S/N) ratio and significantly improving measurement accuracy. Using the proposed pulse compression method, the speed of sound in a number of materials was obtained, with the following results: 5 mm-thick poly methyl methacrylate(PMMA) plate, 2620±130 m/s; compact bone, 3820±250 m/s; spongy bone, 1930±90 m/s. The errors in thickness indicated by these measurements were 5.6%, 7.2% and 12% for the PMMA plate, compact bone and spongy bone, respectively. Thus, using a thin transmission line, the proposed method makes it possible to determine the thickness of a bone sample with sufficient accuracy. It is anticipated that this method, which is based on ultrasonic measurements, will be useful for application in brain SPECT.

We are in the process of developing a doppler borehole televiewer (DBHTV) which quantitatively evaluates the permeability of independent subsurface fractures in a borehole. The system employs an ultrasonic pulsed Doppler method, and is compatible with the conventional acoustic borehole imaging system called borehole televiewer (BHTV). Using the DBHTV, back-scattered waves from fine particles in the borehole fluid such as drill mud or cuttings in a water filled borehole are detected along with the reflected waves from the borehole wall, and the Doppler shift of the back-scattered waves is used to estimate the fluid velocity. A method to estimate the distribution of Doppler shift was examined using a laboratory experimental model. An attempt to locate the sampling volume and a method to quantitatively estimate the flow velocity by scanning the transducer are examined. This study shows that the location of permeable fractures, the distribution of fluid velocity and the fluid volume can be visualized using the DBHTV.

Acoustic holography has attained a high lateral resolution but a poor axial resolution. In this study, to achieve the high axial resolution, time slice is applied to an imaging system using acoustic holography. The time slice can select the reflected signals from objects at different distances. In this method, the sampling interval of detected signal decides the axial resolution, and the aperture of the transducer decides the lateral resolution. The result of a simulation shows good axial and lateral resolutions. The method uses only one specified frequency which matches with narrow-band transducers.

In this paper, we propose a new simple ultrasonic technique for measuring the concentration of solutions by a phase difference method with temperature compensation. This technique relies on sound velocity changes due to variations in solution concentration. An empirical equation of the sound velocity for both the sugar and NaCl solutions, which covered a concentration range of 0.0–20.0% and a temperature range of 15–45°C, was obtained by analyzing the measurements of various sound velocities through the least squares method. It became evident that a similar temperature-compensation factor can be used for both the solutions in terms of dependence on temperature in their equations. An empirical equation was applied to design a temperature compensation circuit. The measuring system with temperature compensation was shown to yield a 0.01% accuracy of concentration determination, independent of the temperature variation of ±0.9°C around 25.2°C for the sugar solution and of ±1.0°C around 25.4°C for the NaCl solution.

Experimental performance of a newly developed diffusive hydrophone (DHP) is evaluated with respect to its sensitivity and spatial resolution. Although conventional hydrophones such as a polyvinylidene fluoride (PVDF) needle type hydrophone have been widely used in measurements of sound pressure, they have often failed to show sufficient sensitivity when their active elements are as small as 0.2 mm in diameter or below. The DHP allows precise use in sound field measurements with sufficient sensitivity. The basic operation of the DHP is discussed below, taking into account the spatial averaging effect that inevitably occurs over the hydrophone aperture.

An image processing technique for measuring the mode shapes of piezoelectric resonators is described. Laser speckle interference, a periodic resonator excitation and charge coupled device (CCD) image captures are effectively combined in this method. The experimental results for three kinds of AT-cut quartz resonators demonstrate the applicability of the proposed method.

An angular dispersion-type Fabry-Perot interferometer is a powerful tool for measuring the Brillouin spectra of glass-forming materials, particularly of low-molecular-weight molecules which require a high cooling rate to avoid crystallization. A solid-state etalon, a highly sensitive charge-coupled-device (CCD) detector and a small-aperture iris were used to obtain a high finesse above 100. The Brillouin spectra of ethanol were measured using a Brillouin system in the temperature range from 350 K to 220 K. Relaxation times obtained from the analysis using a simple viscoelastic theory shows an Arrhenius behavior with an activation energy of 2.7 kcal/mol and a pre-exponential factor of 5.8×10^-14 s in the high-temperature range above 220 K, which is consistent with the newly observed β process by dielectric spectroscopy [R. Brand et al.., Phys. Rev. B 62 (2000) 8878].

A finite element method (FEM) simulation of wave propagation is performed for a model plate which includes minute cracks nucleated by spallation. The minute cracks are modeled by singular elements which express nonlinear stress-strain at the crack surfaces. The transmitted wave through these cracks is simulated and the 2nd harmonic amplitude is processed by fast fourier transform (FFT). The ratio of the 2nd harmonic component to the fundamental one increases with an increase in the incident wave of amplitude for the incident wave of amplitude 5–20 nm. The simulated results qualitatively confirm the measured nonlinear acoustic response on spalled samples.

We report the effect of voltage on a concentrated KCl electrolyte applied to a highly porous TiO₂ electrode during its final preparation process on the photoelectrochemical current (PEC) spectra. Optical absorption measurements were monitored by a photoacoustic (PA) method. The PA spectrum of the TiO₂ electrode with the voltage treatment is similar to that without the treatment above the band-gap region. Below the band-gap region, the intensities of the PA spectrum of the TiO₂ electrode with the voltage treatment are higher than those without the treatment, suggesting an increase of carrier concentration by the voltage treatment. The PEC spectra without the voltage treatment show a monotonic increase with the photon energy above the band-gap region. The PEC intensity with the voltage treatment increases rapidly immediately above the band-gap region and shows saturated values. The PEC intensity of the TiO₂ electrode with the voltage treatment is approximately twice that without the treatment above the band-gap region. The increase of the PEC intensity implies an increase of carrier concentration due to partially reduced Ti ions. The modulation frequency dependence of the PEC intensity of TiO₂ electrodes with and without the voltage treatment shows two types of exponential decay. The decay rate in the TiO₂ electrode with the voltage treatment is slower than that without the treatment below the modulation frequency of 100 Hz. The decay rate with the voltage treatment agrees with that without the treatment above the modulation frequency of 100 Hz.

We have measured the optical absorption of mixed TiO₂ ultrafine powders with rutile and tanatase structures by photoacoustic (PA) spectroscopy, which is a powerful technique for detecting small amounts of strongly scattered materials. The values of band-gap energies, E_g, of the TiO₂ ultrafine powders with different rutile contents were determined by the theory of interband transition in semiconductors. The values of E_g of rutile and anatase structures of TiO₂ ultrafine powders are 3.00 eV and 3.20 eV, respectively, obtained from PA intensity and PA phase spectra, indicating the usefulness of PA spectroscopy. Mixed TiO₂ ultrafine powders with rutile and anatase structures (20–140 nm diameters) were obtained by thermal oxidation of TiCl₄. Rutile structure contents depend on the thermal oxidation temperature. The value of E_g of a mixed TiO₂ ultrafine powder with rutile and anatase structures decreases continuously with the increase of the rutile content. This indicates that the apparent E_g can be controlled by mixing the nanometer-sized TiO₂ powders with rutile and anatase structures, hence, we can control and obtain TiO₂ materials with an arbitrary apparent E_g between rutile and anatase structures.

A photothermal deflection microscope using linear-motor-driven slide stages for scanning was designed and fabricated. The photothermal microscope achieved high-resolution scanning (0.1 µm step), fast scanning (40 mm/s) and random access. It operates in a conventional operating software environment as a photoacoustic microscope and is capable of operating in an open-air environment. It was applied to the imaging of semiconductor microdevices such as integrated circuits. Resolution up to 8–12 µm was achieved.

Morphology and sound velocity of plasticized polyvinylchloride were studied using scanning acoustic microscope. Pseudonetwork and well-dispersed domains were observed as acoustic images. The sound velocity of leaky surface skimming compressional waves in the two domains and the intermediate domain were evaluated by analysis of the V(z) curves. The sound velocity in the well-dispersed domains was faster than that in the pseudonetwork domains.

Multimode Lamb waves in a 1.0-mm-thick aluminum plate were excited by a line-focused Q-switched neodymium yttrium aluminum garnet (Nd:YAG) laser and the waves were received at two different positions by a laser interferometer. Using the phase spectrum method and moving average, we measured the dispersion curves of the group velocities of various modes of the Lamb waves and compared the measured results with the theoretical dispersion curves. The measured dispersion curves of the modes (S₀, S₁, A₁, A₂, and A₃) of the Lamb waves agree well with the theoretical dispersion curves in the velocity range of 2000–4000 m/s and frequency x thickness range of 0.2–8.5 MHz mm. This method may be effective for material characterization of thin plates and pipes.

We succeeded in generating and detecting high-frequency surface acoustic waves (SAWs) up to 400 MHz by improving an apparatus for the scanning interference fringes (SIF) approach of the phase velocity scanning method using an optical knife-edge technique with a single lens. Using the new SIF apparatus, we confirmed that we are able to measure the SAW velocity anisotropy of a single-crystal Si(001) wafer within 0.1% relative error. We also measured the velocity anisotropy of Sezawa waves on a Si(001) wafer with a 1430-nm-thick Cu film and estimated Young's modulus and thickness of the Cu film by an inverse analysis. The estimated Young's modulus was close to that of bulk Cu (129.8 GPa). On a single-crystal Si(001) wafer with thinner Cu films (270–700 nm), we measured the SAW velocity along the [110] direction of the Si substrate by the time-of-flight method. The measured velocities decreased with increasing film thickness. The measured velocity for the thicker sample approximated the group velocity calculated from the estimated value for 1430-nm-thick Cu film by the inverse analysis.

In this study, the imaging of simulated branched complicated defects using a photoacoustic microscope has been demonstrated. A surface vertical defect is fabricated on a metal specimen surface by mechanical processing. The subsurface defect was made perpendicular to the surface defect by drilling. The surface defect and the subsurface defect were relevantly distinguishable in the photoacoustic amplitude image obtained using the photoacoustic microscope. The size of the subsurface defect and information on the undersurface structure were obtained.

ZnO varistors degraded under various conditions were evaluated by photoacoustic spectroscopy (PAS). The degradation where the grain boundary is damaged by DC bias stress is more than that by AC bias stress. PAS, however, reveals that the interior of the grains of the sample degraded by AC bias stress is much more damaged than that by the DC bias stress. The PA signal intensity at a wavelength of more than 500 nm increases and the dispersion of the spectrum decreases throughout the wide wavelength range considered with the degradation time. In particular, the decrease of the spectral dispersion below 500 nm is caused by the change of the electronic states at the interface, that is, the increase of the recombination center of the space charge. The annealing effect on the degradation of ZnO varistors was also studied. The PA spectrum of the sample annealed in N₂ gas corresponds to those of the sample degraded by DC and AC bias stress for a long time. This suggests that the degradation of ZnO varistors is closely related to the release of oxygen from both ZnO grain interior and grain boundaries.

Photoacoustic (PA) spectra are measured for porous Si (PS) using piezoelectric detectors (PPT) and compared with the microphone PA (MPA) spectra to examine the nonradiative properties of PS that has complicated nanostructures. Three peaks (peaks 1 and 2, and a small peak at 600 nm) are observed in samples 2 and 3 with porosities p=60 and 70%, respectively, while only a single peak (peak 1) is observed in sample 1 with p=30%. Peak 2 is related to the band gap of the Si substrate. In contrast, peak 1 seems to be due to the absorption change at the band gap unique to the PS. This band gap shifts to higher energy for PS samples with higher porosity. We propose that this band gap is defined by the largest size nanocrystals, where PS has nanocrystallite size distribution. The small peak at 600 nm is related to the PL peak and it is observed only in PPT spectra. These results suggest that different mechanisms are operating in PPT spectra and MPA ones for the enhancement of the PA spectra.

Photoacoustic spectra (PA) of Zn_1-xCo_xO alloy semiconductors sintered as powdered samples were measured to estimate the optical absorption. Photoacoustic spectroscopy (PAS) is insensitive to the light scattering effects on the samples. CoO molecular percentages in the alloy were changed from 0 to 20 mol%. The samples were sintered at 600 or 950°C for 24 h in a quartz glass tube. From the PA spectra in the short wavelength region, we plotted (ρh ν)² vs h ν and estimated the band-gap energy (E_g) of the alloy semiconductors, where ρ is the PA signal intensity and h ν is the excitation light photon energy. E_g of ZnO-CoO alloy decreases as the CoO content increase and reaches to 2.19 eV in the 20 mol% CoO sample. Although the band-gap variation in the lower-CoO-content samples (CoO content below 10 mol%) is large, it becomes small in the high CoO concentration samples. This result concurred with the result of dissolving CoO in ZnO as obtained by X-ray diffraction measurement.

An optical method for measuring information of sound fields using the Mach-Zehnder interferometer is described. The Mach-Zehnder interferometer is advantageous for obtaining quantitative measurements of phase values in comparison to other visualization methods. In this study, we simultaneously investigate a two-dimensional data acquisition system for the projection image of an optical phase deviation in proportion to sound fields below the frequency of 2.16 MHz. In the experiment, the charge-coupled device (CCD) camera is used as a function of a mean value detector. The experimental results of the optical phase deviation along the ultrasound axis are useful as primary data for estimating the sound pressure. The two-dimensional measurement system using a CCD camera proposed in this paper has the advantages of acquiring the data in a short time when used in an environment where the measurement conditions change.

We have been studying an underground imaging method using shear-horizontal (SH) waves to detect buried relics and ruins at shallow depths. To improve the underground image, a deconvolution method has been introduced. An exploration experiment was conducted at a test site to confirm the validity of the method. As a result, we confirmed that the processing technique is effective for improvement of underground imaging at extremely shallow subsurfaces within a depth of 10 m.

Using the laser ultrasonic method, we investigated the distribution of surface acoustic waves (SAWs) on a sphere excited by a line source. Experimental results revealed that the SAWs were confined within a narrow path due to the balance of the diffraction and convergence effects. Moreover, the distribution had unique divergent, collimating and focussing forms, which had been predicted theoretically. These results were generally in good agreement with the results calculated using the approximate Green's function. It was shown that the distribution of SAWs is well defined by the half-aperture angle of the source and by the product of the wavenumber and the radius of the sphere.

In this study we deal with a flexural vibrating resonator for flatly supported vibratory gyro-sensors in parallel with the rotating plane. This type of gyro-sensor uses two vibration modes in only one plane of single crystal quartz, and therefore can be constructed to be very stable under operating conditions. The double-T type vibrator that has two T-type resonating arms and two resonant arms is designed for improving the quality factor Q of both driving and detecting vibration modes for this vibratory gyro-sensor. The result of finite element analysis of the double-T type vibrators shows the small influence of its vibration mode with the support at the center of gravity of the vibrator.

The operation of an optical fiber vibration sensor using two fiber Bragg gratings (FBGs) and incoherent light has been demonstrated, based on the intensity-modulation method. One FBG is used to make a narrow-band incoherent light source from a broad-band light source and the other is used for sensing the vibration of a solid. Stable and linear operation of the sensor is realized without optical isolators and fusion splicing. The developed sensor is expected to be temperature insensitive if the temperatures of the two FBGs are kept same during the operation.

In this paper, a new piezoelectric transformer for AC-DC converters is presented. This piezoelectric transformer, with a multilayered construction in the thickness direction, operates in a fundamental contour-extensional vibration mode. Output impedance is designed to be low, approximately several tens of ohms. First, we simulated the design of the transformer using equivalent circuit method and finite element method (FEM) analyses. We calculated that the transformer could work with an eficiency higher than 95% and a gain of 0.4 at a resonant frequency of 140 kHz. Second, we fabricated a transformer of 14 mm length, 14 mm width and 5.8 mm thickness and examined it. It was found that the transformer exhibited a 0.4 gain and 96.3% efficiency at 135 kHz, when the temperature increase was 30°C. We applied the transformer to the fabrication of an AC-DC converter using a half-bridge zero voltage switching circuit, and examined the converter. It was found to achieve good line and load regulation, and the highest efficiency of 90% was obtained for V_in=80–120 V_ac, V_out=13 V_dc, and I_out= 0.8–1.5 A.

The energy trapping of thickness-shear vibrations that are excited by parallel electric field in a partially polarized piezoelectric-ceramic plate is analyzed by the finite element method (FEM), and characteristics of the thickness-shear-mode trapped-energy resonators for vibratory gyroscopes are theoretically revealed. The calculated results obtained by FEM agree well with the measured results with respect to the displacement and vibration energy distributions. It is shown from the results that the vibrational energy of trapped-energy modes is almost confined to the central region of a partially polarized piezoelectric-ceramic plate and the displacement distribution of the mode can be varied by adjusting electrode dimensions.

In this paper, the evaluation of the sensitivity, resolution, and contact force of a touch probe sensor device for higher sensitivity and low contact force is reported. Our goal in designing our touch probe sensor was to realize high-resolution, low-contact-force, wide-scanning-area up to mm scale square, and quick-scanning surface profile measurement. The sensitivity and resolution of our touch probe sensor were 2.0×10^-2 mV/nm and 2.4 nm, respectively. Although this resolution depends on the noise level, the noise level of the pre-amplifier circuit was much larger than that of the vibrator. By minimizing the noise of the circuit by using low-noise-type operational amplifiers, higher resolution up to 0.2 nm can be obtained. Although the contact force was estimated to be 25 µN under a 0.3 V_p-p driving voltage, it will be 300 nN when using a low-noise circuit.

In this paper, we propose and design a new ultrasonic probe that can effectively measure both the fundamental and the second-harmonic waves simultaneously. The transducer consists of two bonded Pb(Zr, Ti)O₃ (PZT) disks with the same properties and the same polarization, and a variable capacitor is connected to the electric terminals of one of the PZT disks for the simulation and experiment. It is shown that the second harmonic as well as the fundamental component can be efficiently received by controlling the capacitance. The result of the nonlinearity parameter B/A for ethanol measured using the double ultrasonic transducer shows good agreement with the reference value, and the B/A value for soybean is obtained.

Transversal effects of a piezoceramic disk-type Pb(Zr,Ti)O₃ (PZT) transducer are newly introduced in the measurement of dynamic viscosity of liquid. The fundamental resonance (75 kHz) and the higher harmonic resonant frequencies (195, 310, 424 kHz) of the transducer are used in the experiments. The resonant resistance R_r and the resonant frequency shift Δf_r of transducer are measured with a water-glycerin mixtures (viscosity η_L:3∼490 mPa·s) and silicone oil (η_L:10 ∼1000 mPa·s) as the sample liquids. From the experimental results, it is gathered that 1) the resonant resistance R_r has a linear relationship to η_L^1/2, 2) the resonant frequency shift Δf_r does not show a linearity in the high viscosity range larger than 100 mPa·s. The viscosity measurement in the frequency range of 75∼424 kHz, which has not been explored previously, was successfully accomplished by our method.

We describe the static and dynamic characteristics of a giant magnetostrictive material under high pre-stress, using the pre-stress given to the giant magnetostrictive material as a parameter, and also evaluate material constants. Seven evaluation units, each having an optimum magnetic bias applied to vary the pre-stress given to the material from 15 MPa to 54 MPa, were used to measure the static and dynamic characteristics. As a result, the trends of equivalent circuit constants such as stiffness, internal resistance, and force factor in response to the increase in pre-stress for enhancing the output, were clarified. Furthermore, considering the linearity to the input level, the necessity of examining the optimum pre-stress region, in addition to the simple increase in pre-stress, was suggested.

A focusing source to concurrently detect the nonlinearly generated second harmonic sound contained in the reflected wave has been produced. A 36° rotated Y-cut LiNbO₃ plate of 20 MHz fundamental resonance frequency with a reversed polarization layer formed by heat treatment is bonded to a plane surface of a solid acoustic lens whose thickness is set at a small value so as to avoid the influences of nonlinear distortion and multiple reflection within the lens. One of the electrodes on the piezoelectric plate is fabricated to a 20-point-star shape. The formation of a 20 MHz focused Gaussian beam and the capability of receiving the 40 MHz second harmonic sound are confirmed through experiments.

This paper describes suppression of inharmonic modes in a trapped-energy AT-cut resonator operating in a very high frequency (VHF) fundamental mode. This resonator has an elliptical excitation electrode conforming to the anisotropy in the AT-cut quartz plate. Moreover, the new resonator has a mesa to control the plateback and a second electrode with an elliptical opening to decrease the plateback. Resonators operating at 155 MHz are manufactured. In these resonators, the length of the excitation electrode is 53 times the thickness of the crystal substrate. Nevertheless, all of the inharmonic modes can be suppressed by employing the above electrode structure. The ratio of the impedance at the most strongly excited inharmonic mode to the impedance at the main mode in the new resonator is four times that in a conventional resonator with a rectangular excitation electrode.

This paper describes the development process for acceleration sensors used on automobiles and an acceleration evaluation system designed specifically for acceleration at super-low-range frequencies. The features of the newly developed sensor are as follows. 1) Original piezo-bimorph design based on a disc-center-fixed structure achieves pyroeffect cancelling and stabilization of sensor characteristics and enables the detection of the acceleration of 0.0009 G at the super-low-range-frequency of 0.03 Hz. 2) The addition of a self-diagnostic function utilizing the characteristics of piezoceramics enables constant monitoring of sensor failure. The frequency range of acceleration for accurate vehicle motion control is considered to be from DC to about 50 Hz. However, the measurement of acceleration in the super-low-range frequency near DC has been difficult because of mechanical and electrical noise interruption. This has delayed the development of the acceleration sensor for automotive use. We have succeeded in the development of an acceleration evaluation system for super-low-range frequencies from 0.015 Hz to 2 Hz with detection of the acceleration range from 0.0002 G (0.2 gal) to 1 G, as well as the development of a piezoelectric-type acceleration sensor for automotive use.

The strip-type resonator that uses 2nd-harmonic thickness-extensional (TE2-mode) vibration in a two-layered monolithic piezoelectric plate was developed for a ceramic oscillator. By using the TE2-mode vibration, piezoelectric ceramic materials that have better temperature characteristics and higher Q_m could be utilized. Furthermore, TE2-mode vibration has no problems such as spurious responses often found in the 3rd-harmonic thickness extensional (TE3-mode) vibration in a single-layered piezoelectric plate. By shaping the resonator into a strip, the resonator was miniaturized. By means of the finite element method, the displacement distribution and the relationship between resonator width and spurious responses were analyzed. From the results, it was clarified that the resonator could be miniaturized and had good frequency characteristics. Those superior characteristics were demonstrated in an experiment. It was recognized that there was no spurious response that disturbed stable oscillation and that the volume of the resonator was less than 1/10 of that of conventional trapped-energy resonators using the TE3-mode vibration in a single-layered piezoelectric plate.

The equivalent circuit for a flexurally vibrating thick bar with axial force is represented by impedance analogy. The effect of axial force is not represented as terminal pairs on the circuit, but is included in its matrix elements. It is shown that the resonant frequency equations under various end conditions can be easily obtained from the circuit. As an example, the resonant frequency change of the slender bar with both clamped ends by axial force was analyzed, and confirmed experimentally. The relationship between the change rate of the resonant frequency and axial force is linear. The value of the change rate for the first mode is larger than that for the second mode, and decreases as the thickness and width become larger. Moreover, the value increases with the length. These results will be utilized for the development and design of a force sensor based on the principle of the resonant frequency change by axial force.

In this paper, charge sensitivity has been considered as a figure of merit of piezoelectric vibratory gyroscope. First, an approximate equation for charge sensitivity is derived based on an equivalent circuit of the gyroscope. Second, the charge sensitivity characteristics have been discussed in terms of the effects of frequency deviation and load capacitance. The difference between charge sensitivity and voltage sensitivity is quantitatively clarified. Charge sensitivity is effective as a figure of merit for applying a piezoelectric single crystal to the gyroscope.

We have previously proposed a piezoelectric sensor configuration determined using an optical-access method and reported the simulation results. Two issues have to be resolved for fabricating such a sensor; one is to develop a suitable optical-to-electrical conversion technique, and the other is to develop an optical measurement method for piezoelectric resonance. We examined the use of a Schottky-barrier photodiode (SBPD) for photoelectric conversion to excite piezoelectric vibration in the very high frequency (VHF) region. We found that the photoelectric output of SBPD corresponds to the intensity of the modulated light. The excitation power of piezoelectric vibration is between 10 µW (at 70 MHz) and 32 µW (at 50 MHz). However, optical detection of piezoelectric vibration is difficult. In this paper, we propose a waveguide-type light circuit using a pair of Y-branch elements based on the Mach-Zender interferometer. An analysis on the sensitivity of the circuit for vibration detection was carried out and relatively higher sensitivity was predicted. Furthermore, the photoelastic constant p₆₆^' for AT-cut quartz was measured.

For obtaining greater accuracy and stability of piezoelectric gyroscopes, the authors have advanced the research on H-type LiTaO₃ single-crystal piezoelectric gyroscopes, which combine the tuning fork vibration with H-type vibration. In this paper, the H-type LiNbO₃ gyroscope of an oppositely polarized single crystal plate is reported. The electromechanical coupling factor of LiNbO₃ is larger than that of LiTaO₃ for the flexural vibration mode. Using an oppositely polarized plate, the electrode construction without a side electrode becomes possible. Therefore, the possibility of miniaturizing the H-type single-crystal piezoelectric gyroscope is examined to obtain the same sensitivity level. In the trial experiment, the dimensions of the LiNbO₃ gyroscope were reduced to be 1/8 that of the LiTaO₃ gyroscope.

The edge mode, whose vibrational energy is confined to the edge region of a piezoelectric-ceramic bar, is analyzed by the finite element method (FEM) and characteristics of the mode are clarified. A new tactile sensor using the edge mode in a piezoelectric-ceramic bar is proposed and its experimental results are presented. The results show that piezoelectric tactile sensors with very high sensitibity and supporting ease can be realized by the use of the edge mode.

To simulate the electromechanical characteristics of a piezoelectric transverse mode vibrator with negative impedance converter (NIC) circuit, we propose a new simulation model for Pspice implementation, which is coupled to the distributed constant equivalent circuit for a piezoelectric vibrator with divided electrodes and the NIC circuit including an active device, such as operational amplifier. The usefulness of the model is demonstrated by comparing the simulation results with experimental ones.

We developed a method for analyzing the effect of a supporting wire on the frequency of a quartz-crystal tuning fork independent of the finite element method (FEM). In order to estimate the influence of the supporting wire of the tuning fork, we approximated the right half of the tuning fork as an L-shaped bar in which the bars at both the base and the arm undergo bending vibration. Furthermore, we approximated the supporting wire as an elastic foundation with a spring constant K. A comparison was made between frequency changes calculated by this method and those calculated by FEM, and the influences of spring constant K and the length of the supporting wire on the frequency change calculated by this method are discussed.

A shear horizontal surface acoustic wave (SH–SAW) can function as a liquid-phase sensor. In this paper, we describe the simultaneous measurement methods for liquid density and viscosity. For this purpose, a textured (or sagittally corrugated) propagation surface is designed to trap the liquid in dented structures. Although a smooth surface is affected by the density and viscosity products, the textured surface is influenced by both the density and viscosity products, and also the density due to trapping of liquid in the dented structures. Therefore, by detecting the differential signals between the textured and the smooth surfaces we can determine the liquid density and viscosity separately.

By composing interdigital transducers (IDTs) and reflectors consisting of films made of a heavy metal such as Au, Ta or W on an ST cut 90°X propagation (direction perpendicular to X-axis) quartz substrate, the authors realized a new type of shear horizontal (SH) wave. This wave has an excellent temperature characteristic, a large electromechanical coupling factor (k), and a large reflection coefficient at reflector electrodes. The square of this electromechanical coupling factor (k²=0.28∼0.34%) and the reflection coefficient at reflector electrodes are 2.2∼2.6 times and 30∼35 times, respectively, as large as those of a Rayleigh wave on an ST cut X propagation quartz substrate. The authors applied this technology to filters for the first intermediate frequency (first IF) stage of a global system for mobile communications (GSM) in the nominal center frequency from 200 to 400 MHz. As a result, we succeeded in developing the first IF filter having a low insertion loss, an excellent temperature characteristic (frequency shift: 1 ppm/°C) and a small package size (3×3 mm²), which is as small as a radio frequency (RF) surface acoustic wave (SAW) filter, for the first time.

A conventional surface acoustic wave (SAW) resonator filter requires reflectors with many grating fingers at both sides of the interdigital transducers (IDTs). On the other hand, a small-sized low-loss resonator filter without grating fingers can be realized by utilizing the reflection of a Bleustein-Gulyaev-Shimizu (BGS) wave or a shear horizontal (SH) wave at the edge of a substrate. As a result, the authors have developed longitudinally coupled resonator filters using the reflection of BGS and SH waves at the edges of a substrate. Longitudinally coupled resonator filters on piezoelectric ceramic substrates for the first intermediate frequency (IF) stage have been realized to be low-loss, small-sized and extremely wide bandwidth (fractional bandwidth of 15%) filters as compared to the ordinary resonator filters, and they can have various kinds of bandwidths (2 to 15%) by employing ceramic substrates with various electromechanical coupling factors. On the other hand, the edge-reflection-type resonator filters on LiTaO₃ single crystal for various first IF stages have also been realized to be low-loss and small-sized filters. In spite of being a wire-bonding type of IF filter, the package size of this filter is the same as that of the radio frequency (RF) SAW filter.

The properties of surface acoustic wave (SAW) devices mainly depend on the choice of piezoelectric substrate materials. The important properties required for SAW substrates are a large electromechanical coupling coefficient (k²), small temperature coefficient of delay (TCD), and low propagation loss, etc. Especially, super-high coupling substrates are very important for obtaining wide-band SAW filters, wide-band voltage controll oscilater (VCO) and delay lines with small insertion loss. KNbO₃ single crystal has an extremely large electromechanical coupling coefficient (k²=53%) and zero TCD at approximately room temperature. Large-scale single-crystal growth technologies are now under investigation. In this study, the propagation characteristics of SAW in PZNT and KTP substrates are investigated experimentally in order to obtain higher coupling substrates than those of KNbO₃. The experimental results show that the substrates have large k². Also, theoretical SAW propagation characteristics with a k² of about 100% are analyzed and their physical phenomena are discussed.

In this work, we studied a fabrication process of the surface acoustic wave (SAW)-semiconductor coupled device with a Si/LiNbO₃ structure by a film bonding process. The aim of this process is to realize a coupled device with a high performance and mass productivity for cost reduction. In order to realize bonding silicon films on a LiNbO₃ substrate, we proposed the process of releasing a Si thin film from a silicon-on-insulator (SOI) wafer and examined the etching conditions of a SiO₂ (box) layer. We also tried to apply local heating treatment using a microwave and an infrared laser to enhance the bonding force between the Si film and LiNbO₃ substrate, and successfully bonded Si films released from a SOI wafer onto the LiNbO₃ substrate. Based on these results, a test device with a Si/LiNbO₃ structure was fabricated and the interaction between SAW and the optically induced carrier in the Si film semiconductor was discussed.

In this paper, we report the results of a study on the basic problems of the mass production of epitaxial liftoff (ELO) film bonding technology. We propose a new releasing method for a large number of semiconductor films using polyimide to protect the semiconductor films. We investigated the basic process conditions and successfully released a large number of stripe shaped GaAs films. We also studied the heating method for enhancing the bonding strength between a small-sized semiconductor film and a piezoelectric substrate. We investigated the effect of migration of water molecules from the bonding interfaces using microwave and laser irradiation. We estimated the crystallinity of semiconductor films by X-ray diffraction. The results clarified that these processes were effective in improving mass productivity on the fabrication technology of surface acoustic wave (SAW)-semiconductor coupled devices.

This paper presents results of simulation study on a semiconductor coupled surface acoustic wave (SAW) convolver, in which the propagating SAW on a highly coupling coefficient piezoelectric substrate, couples with a bonded semiconductor diodes through multi-strip electrodes. We focus our study on a relatively wide band device which is the main feature of a highly efficiency device. By using a simple analysis and circuit simulator, based on the simulation program with integrated circuit emphasis (SPICE), we clarified the effect of device parameters, such as the shape of multi-strip tapping electrodes, characteristics of diode, impedance matching condition, kinds of transmission code and electro-mechanical coupling coefficient of SAW, on the device performances. We discussed the phenomenon, which cause the degradation, focusing on the frequency domain. We also clarified the essential problems of second order effect on the wide bandwidth device, which should be solved.

The parameters included in coupling-of-modes equations such as coupling coefficients, transduction coefficients and electrostatic capacitances are theoretically determined for an electrode-width-difference-reversal-of-directivity transducer (EWD-RDT) on a La₃Ga_5.5Nb_0.5O₁₄ substrate with Euler angles of (108°, 148°, 144°). In the hybrid finite-element method (HFEM), used for determining these parameters, all the effects of anisotropy of the substrate, piezoelectric perturbation, mechanical perturbation and energy storage are taken into account. Numerical results for the frequency characteristics of insertion loss and for the directivity are compared to the experimental data, and the validity and usefulness of the present method are demonstrated. Furthermore, the electrode height dependence of the parameters and the directivity of EWD-RDT are investigated in detail.

Computed results of all the coefficients of coupled-mode equations are presented for a transduction center-shift-reversal-of-directivity transducer (TCS-RDT) and an electrode-width-controlled-reversal-of-directivity transducer (EWC-RDT) on a 50°Y-25°X La₃Ga₅-SiO₁₄ substrate. To the best of our knowledge, an EWC-RDT is being reported for the first time. The aluminum electrode thickness and width dependences of the coefficients are investigated in detail. Numerical results show that we can choose pairs of width and height of the electrodes for a distance of λ/8 with λ being the surface acoustic wave (SAW) wavelength at the center frequency between the reflection center and the transduction one. Our results of the insertion loss for a filter composed of a TCS-RDT and two split-electrode interdigital transducers (IDTs) agree well with those of the earlier experiments.

The propagation characteristics of the longitudinal leaky surface wave propagating on a La₃Ga₅SiO₁₄ substrate were theoretically investigated for all cuts and propagation directions. The results of temperature coefficient of delay (TCD), electro-mechanical coupling constant (K²) and phase velocity were displayed on contour maps. Cuts with zero TCD were obtained at Euler's angle's of (20°,θ,ψ) and (30°,θ,ψ). Temperature dependence of fractional time delay (Δτ/τ) on (90°,90°,0°)-cut changes only by 18.5 ppm from -30°C to 110°C. This cut has very good temperature characteristics.

This paper describes surface acoustic wave (SAW) propagation under a periodic metallic grating structure overlaid with an SiO₂ film. An analysis was made by modifying the software FEMSDA, in which the finite element method is applied to both the grating electrodes and SiO₂ overlay. For Rayleigh-type SAW propagating on 128°YX-LiNbO₃, changes in the reflection coefficient and effective velocity are calculated as a function of the SiO₂ film thickness overlaying an Al grating structure. It is shown that the SiO₂ film overlaying the top surface of the grating electrodes affects both the SAW reflection coefficient and effective SAW velocity more significantly than the film overlaying the electrode gaps.

Photonic switching systems in wavelength-division-multiplexed (WDM) networks are discussed. By employing collinear acoustooptic (AO) devices as wavelength selective functional devices, the system structure can be simplified with flexibility in wavelength assignment. As the AO devices, collinear AO wavelength separators and switches consisting of an optical directional coupler are investigated in integrated structures. Integrated optic devices such as WDM demultiplexers/multiplexers, wavelength-selective matrix-switches, and routers for delay time selection in buffer memories are described. Wavelength selective characteristics are theoretically estimated for a material combination of TiO₂/Ta₂O₅/proton-exchanged layers on LiNbO₃ substrates. The switching capacity in the switching system consisting of AO devices is evaluated. Issues for employing AO switching devices in WDM networks are also discussed.

Interaction between optical guided waves and magnetostatic waves (MSW) has great potential for wideband optical signal processing directly at microwave signal frequencies. However, till now, all theoretical and experimental investigation has focused on optical mode conversion involving a change in polarization induced by magnetostatic waves. So far, the efficiency of this mode conversion has been low. Here, we propose and analyze, for the first time, the feasibility of obtaining an optical phase shift induced by magnetostatic surface waves in thin film waveguides. We show that with proper selection of the waveguide parameters, it is possible to obtain a phase shift which is sufficient for design of efficient optical-MSW signal processing devices. Further, we propose and analyze a device structure for an optical switch based upon this phase shift and demonstrate the design feasibilty through a numerical example.

A hybrid transducer type ultrasonic linear motor using the 1st longitudinal and the 2nd bending vibration modes of a bolt-clamped Langevin type transducer has been proposed and studied for accomplishing high mechanical output. The longitudinal vibration generates the mechanical driving force and the bending vibration controls the frictional force. To obtain large vibration amplitude and large mechanical output, a method of tuning the longitudinal resonance frequency to the bending one was investigated using finite element simulations, and demonstrated experimentally. To avoid magnetic interaction, we employed phosphor bronze for the bolt of the transducer. The prototype motor achieved the no-load velocity of 0.47 m/s and the maximum output mechanical force of 92 N.

A deep-sea unmanned vehicle "Kaiko," which can be used under water to a depth of 11,000 m, is equipped with a side scan sonar newly developed for underwater topographic survey and searching for lost objects. The side scan sonar features a tilted arrangement transducer array for suppressing grating lobes. The driving frequency on the port side is 38 kHz, and that on the starboard side is 42 kHz. The source beam width in the longitudinal direction is 2° and that in the transverse direction is 50°. In 1999, objects lost underwater were located using the side scan sonar, and fallen rocket parts as large as several meters could be found in a range of about 1 km.

Acoustic scattering and reflection phenomena at the surface of marine sediment models were visualized by the shadowgraph method with an impulse source realized by a small spark gap. Water saturated glass beads were used as a sediment model. Lateral wave was clearly observed for fine sediments (small grain size compared with wavelength). Scattered waves and multiple reflected waves were observed for coarse sediments (larger or equivalent grain size compared with wavelength).

Utilizing a high-intensity ultrasonic cavitation, a processing experiment was conducted with the aim of performing volumetric flow adjustment of a fuel jet nozzle to be used for a small engine, which cannot be carried out by a method such as machining. At the bottom of the nozzle used for the experiment, which is in the shape of a cup, a nozzle hole with a diameter of 0.15 mm is drilled. In this experiment, we make adjustments in the volumetric flow by grinding and removing the machining burr with the aid of the processing power of ultrasonic cavitation. The processing effect is highly dependent on the ultrasonic cavitation intensity. In the experiment, the processing reservoir was filled with pressurized highly deaerated water to increase the processing force by allowing cavitation with high intensity to be generated. The processing principle is to utilize the effect of a cavitation jet flow passing through the nozzle hole. To restrain the intake of the bubbles into the flow circuits during the pressure reduction cycle of the vibrator, the water flow was discharged into a pressure reduction reservoir. By allowing the horn tip with a diameter of 6 mm at a frequency of 28 kHz to approach the sample, followed by high-intensity ultrasonic irradiation, powerful cavitation was generated. As a result of the evaluation of the processing efficiency made based on the volumetric flow increase and microscopic observation of the nozzle, burrs smaller than 10 µm were almost entirely removed within 15 min of initial irradiation, resulting in a volumetric flow increase of more than 0.4%/min. However, in the case of burrs of more than 10 µm, no force that could remove the burrs was found. It was surprising for the burrs to generate deformation rather than to be removed.

Copper is a useful metal widely used for electric materials, etc. In order to raise the copper purity, electrolytic refining is used. Since the long time is needed for the purification of this method, to shorten this time is desirable. In this study, ultrasonic irradiation was attempted to shorten this time. It was found that to shorten the refining time was possible by ultrasonic irradiation.

In recent years, we have attempted ultrasonic ceramic joining for the purpose of extending the application field of ultrasonic joining. By devising a vibration system, the authors have attempted ceramic ultrasonic joining by which a metal becomes an intermediate material. In this method, however, the high temperature resistance and strength of the joint are dependent on the melting point and strength of the metallic material. Therefore, in this study, we attempted ultrasonic joining of silicon nitride (Si₃N₄) plates without using any intermediate material. The experimental result showed that ultrasonic joining was possible without using the intermediate material. The maximum joint strength was 33 MPa and the joining time required was about 10 s.

An experimental study has been carried out on the atomization of a water jet by aerially radiating it with high-intensity ultrasonic waves. A sound source that enables the linear generation of high-intensity aerial ultrasonic waves (frequency: approximately 20 kHz) is combined with a cylindrical reflection plate in order to create a standing-wave sound field. An attempt has been made to atomize a water jet of 1 mm diameter by passing it through the above sound field at a velocity of approximately 30 m/s. It has been clarified that nodes of sound pressure in the standing-wave sound field are effective for the atomization of a water jet. In addition, the atomizing phenomenon of a water jet has been observed precisely. The relation between the intensity of sound waves required for atomization and the radiation duration has also been clarified. Even the radiation of sound waves for only 2 ms atomizes water. This suggests that a very fast water jet at 300–500 m/s might be atomized.

This paper deals with the influence of ultrasound energy in high-pressure glow discharge. A discharging unit was set inside an acoustic tube and glow discharge was produced between a positive needle electrode and a negative disk electrode. A high-intensity standing wave field was produced in the tube at the resonance frequency and sound pressure level was increased to 163 dB. As a result, the sound energy was affected by the glow discharge at the loop of particle velocity distribution, which means that the glow discharge was controlled by the sound energy only in terms of particle velocity.

Generally, a lead zirconate titanate ceramic is utilized for a high-power transducer such as an ultrasonic motor drive. However, it is difficult to realize an ultrasonic motor that can withstand a high temperature, above 500°C. We focused on lithium niobate because it has a high Curie temperature (1210°C) and high quality factor. The electromechanical coupling factor of lithium niobate is large, although the permittivity is one hundred times smaller compared to that of hard-type lead zirconate titanate (PZT)-8. Hence a stacked structure is required to generate high output power. Dimensions of the fabricated actuator were 10 mm square and 18.5 mm long. The number of lithium niobate layers was 18. The calculated force factor of this transducer was 0.28 N/V, a value comparable to that of the bolted Langevin transducer using PZT, though the vibration velocity was saturated at 0.12 m/s. To realize improved transducer performance, we are attempting to fabricate a new transducer that can generate high vibration velocity.

In ocean acoustic tomography, unexpected changes in the travel time of acoustic pulses can sometimes be observed. It is considered that the possible causes are internal waves, layered sound speed microstructures and surface ducts. In this paper, we analyze the effect of a surface duct on a pulse that is propagating in a sound channel in the ocean by using the parabolic equation (PE) method. The received pulses change sensitively when a surface duct exists above the sound source or the receiver that is located around the axis of the sound channel. It has little effect on the pulses when it is located in the area between the source and the receiver. Consequently, one should pay attention to the sound speed profile near the surface above the source and the receiver in ocean acoustic tomography.

We present the stability estimation results of the data collected during the sound transmission experiment performed by Japan Marine Science and Technology Center (JAMSTEC) in 1996 in the western equatorial Pacific Ocean. The combined information of the amplitude and the phase was effective for identifying a ray and observing the ocean-structure change. The phases of correlated signals were very stable within 50 s not only for the paths propagated near the sound fixing and ranging (SOFAR) axis but for ones turning at about 2500 m depth. The travel time could be estimated within an error of less than 0.3 ms.

In this paper, by defining a vibrating surface to be a set of small point sources, a new calculation method for the rectangular vibrating surface with a finite baffle is suggested by considering the effect of the finite baffle on the source strength of each point source. As an example, the variation in self-radiation impedance for a rectangular vibrating surface is calculated based on the size of the baffle.

A circular six-receiver array centered around the transmitter and a compensation method are proposed in order to improve the discrimination ratio of underwater materials located on a declined seabed. The signal intensity reflected from the seabed is employed as data for neural network processing. Compared to the distribution of the intensities of the original data acquired from the declined seabed, the compensated values approach those acquired from a planar seabed, which are employed as the standard learning data for neural network discrimination. A comparison of the results of discrimination of the underwater materials with and without compensation verifies the efficiency of the method. However, the intensity of the echo signal decreases with increasing angle of decline, and the discrimination ratio is reduced accordingly. The valid limitation of the angle of decline for the compensation method is about 9°, according to the discrimination results obtained under the conditions of different angles of decline.

The decomposition of the time reversal operator (DORT) method is a selective detection and focusing technique for the pulse-echo mode that uses an array of transmit-receive transducers. Because it is an application of the acoustic time reversal mirror, the irregular shape of the array and the aberration of the propagation medium are compensated and the selective focusing on targets is made possible. In this paper, we examined the application of this method to the underwater acoustics and the application to active sonar and communication are made possible. To clarify the relationship between the focusing effect of the DORT method and the sound propagation property in shallow water, we examined the selective focusing effect with respect to the propagation distance by using the cylindrical spread model without the sea surface and bottom and the Pekeris model, which is typical of shallow water models. There are few influences of the propagation distance on the focusing effect in shallow water model as a result, and it is shown that the focusing effect improves with the increase of the sound velocity of the bottom.

We have been studying a radiation field prediction system for an acoustic source that has an arbitrary shape. First, the nearfield sound pressure distribution around the source is measured and the normal velocity distribution over the surface of the source is predicted using the equivalent phased array method (EPAM). Then, radiation characteristics of the source, such as the pressure field, are predicted using the combined Helmholtz integral equation formulation(CHIEF). First in this paper, EPAM based on solutions for the exterior steady-state acoustic radiation problem is described. This method is applicable for predicting the normal surface velocity for sources that have an arbitrary shape. Then, an experimental example using a cylindrical source is presented. The predicted result of the pressure field is shown, and then the validity of this radiation field prediction system is confirmed by comparing the predicted pressure field with the actual field. The influence of the aperture restriction for the measurement contour on the surface of normal velocity predicted by EPAM is discussed. It is found that the error between the predicted and the ideal velocity distribution becomes smaller as the measurement contour covers the cylinder.

A data assimilation scheme for ocean acoustic tomography (OAT) data is developed and evaluated by an identical twin experiment to understand the dynamical processes and the evolution of flow pattern in the Kuroshio extension region. The scheme consists of three components, i.e., the two-layer quasi-geostrophic (QG) oceanic numerical model, the travel time data obtained from OAT, and the data assimilation technique which consists of the Kalman filter and observation equations relating the model variables (stream function and interface displacement) to the OAT-derived reciprocal travel time. The identical twin experiment using two different model fields made from the same model demonstrates both the stability and the availability of the scheme developed in the present study.

The velocities of particle falling in a standing wave field through a vertical pipes filled with a stagnant liquid in are analyzed numerically for Reynolds number (Re)<1, for a wide range of pipe diameters. The equations of motion of a spherical particle in a viscous fluid are solved based on the Basset-Boussinesq-Ossen (BBO) equation to clarify the falling velocities in an infinite stagnant fluid, and two-dimensional hydrodynamic equations based on the cubic-interpolated pseudo-particle (CIP)-combined and unified procedure (C-CUP) method to clarify the effects of the walls of pipes. The velocity of a particle is periodically changed due to the influence of the radiation force of the standing wave. The average terminal velocity in a standing wave field is lower than that for which there is no ultrasonic field. As the particle diameter approaches the pipe diameter, the velocity of the particle approaches zero due to the influence of the pipe wall. The C-CUP method effectively simulates the behavior of a particle falling through a liquid-filled pipe in the standing wave field.

An Eulerian numerical scheme for the direct simulation of bubble dynamics in an acoustic field is proposed. The compressible Navier-Stokes equation with a surface tension term is used as a governing equation. The convection terms in the equation are solved using the hybrid interpolation-extrapolation scheme which stably provides a nonsmoothed solution of density interface between bubbles and a surrounding material. The acoustic terms in the equation are solved by the generalized Crank-Nicholson method which is an implicit method and has a temporally second-order accuracy under the low-Courant-number condition and is applicable to high-Courant-number computation. Using this scheme, some typical results of single- and multibubble phenomena are given.

When gas-filled microbubbles flow into an ultrasonic wavefield, the microbubbles interact with the ultrasonic waves and aggregate into large masses of bubbles. Those bubbles are trapped against the surrounding liquid flow by ultrasonic waves. In this paper, the microbubble trapping by an ultrasonic wavefield are discussed both from theoretical and experimental viewpoints. Both, the microbubble aggregation by ultrasonic-wave secondary Bjerknes force and the microbubble trapping by ultrasonic-wave primary Bjerknes force are considered. The dynamics of microbubbles inside an ultrasonic wavefield are observed using two different types of gas-filled microbubbles with corresponding mean diameters of 20 µm and 1.3 µm.

Decrease in luminous intensity of multibubble sonoluminescence (MBSL) at excessive ultrasonic intensity is studied in connection with the behavior of cavitation bubbles. The intensity of MBSL from aerated distilled water in a rectangular vessel with six transducers, in which a standing wave field was established, was measured while the voltage applied to the transducers was increased. The corresponding change in the distribution of cavitation bubbles in the field was observed. The distributions of bubbles were compared with those of MBSL using an intesified charge-coupled device (ICCD) camera, and the bubble motion was observed with a high-speed camera. It is clarified that the expulsion of bubbles from the pressure antinode in the field is responsible for the decrease in MBSL intensity at high ultrasonic intensity. The expulsion is caused by the primary Bjerknes force which changes from an attractive force to a repulsive one depending on pressure amplitude and bubble radius, assisted by coalescence of bubbles due to the secondary Bjerknes force.

Microbubbles strongly affect the sound field in a medium and various phenomena are caused by this sound field. In particular, in this study, the influence of microbubbles on acoustic streaming in water is quantitatively investigated by an experimental method. In order to ensure a constant distribution of microbubbles in water with time, and to appreciate the quantity of the microbubbles, water containing a certain amount of microcapsules packed in a cell is prepared. The streaming velocities are measured using a laser Doppler velocimeter (LDV). The observed results evidently show that the acoustic streaming velocity in water increases due to the microcapsules, and fluid-dynamic nonlinearity affects both velocities with and without microcapsules at a high sound pressure. This nonlinearity controls the velocity with microcapsules at a low sound pressure and also causes the dependence of the ratio between the streaming velocities of the medium with microcapsules and that without microcapsules on the sound pressure.

Using ultrasonic, we propose here a novel method of transmitting power and information to implanted medical equipment. The proposed system is composed of two piezo oscillators and has the following functions: transmission of power and control information to an implanted device, and transmission of the information acquired by an implanted device to the outside of a living body. With amplitude shift keying (ASK), 9.5 Kbps is obtained for the proposed information transmission system.

In ultrasonic diagnostic equipment, I/Q signals are usually used for the construction of B-mode images, displays in the M-mode, and the acquisition of Doppler information. On the other hand, the number of ultrasonic diagnostic equipment in which the digital technique is applied has continuously increased. Accordingly, it is important to understand how I/Q signals are digitized and compressed. In this study, the compression of I/Q signals by wavelet transform is attempted. First, the results are compared with those of a typical compression method by discrete cosine transform (DCT). The proposed method achieved a higher compression ratio than DCT under the same quality of the restored signal. Then, several types of mother wavelets (MWs) are tested. The MW can control the efficiency of compression. The result suggests that the most appropriate MW for I/Q signals compression exists.

We previously proposed the combined autocorrelation (CA) method to estimate the strain distribution in tissue. This method is based on the conventional Doppler method but overcomes the problem of aliasing, which is a weakness of the Doppler method. The ability of the CA method has been demonstrated with phantom experiments and in vitro measurements. However, we have to maintain the tissue displacement in the axial direction because the CA method is based on 1-D processing, and this is difficult to perform with the conventional compression system. Therefore, in this paper, we propose an extended CA method that is robust against sideslip. We also demonstrate the ability of this method with computer simulations.

In this paper, we propose a new framework of ultrasonic (US) three-dimensional (3D) imaging, introducing laser-induced breakdown (LIB) as an acoustic source. LIB is a phenomenon in which a substance is transformed to a plasma by a pulsed laser beam. LIB explosively emits a variety of energies such as heat, light and sound which also includes pulsed ultrasound. Emitted US waves have suitable characteristics for US 3D imaging in terms of low directivity, enabling a wide view and sharply pulsed waves. Utilizing these characteristics, we attempt to apply the synthetic aperture method for frontal 3D imaging in a real-time process. Experimental results show that even sparsely arrayed sensors allow a wider frontal view than that allowed in the case using existing transducers.

Power spectral analysis is extensively used to interpret ultrasound data. However, the technique is useful only when the data can be treated as stationary. Ultrasound data are mostly nonstationary. Thus, a short time Fourier transform (STFT or spectrogram) is widely used to analyze spectral components which change with time. However, the STFT has a low accuracy in both time and frequency domains. Currently, Cohen's class time-frequency (TF) analysis is popular for analyzing nonstationary signals. The authors recently proposed a new kernel (named a figure eight kernel). In order to apply the TF analysis with the new kernel to a blood flow signal, experimental data were obtained from the carotid artery by an ultrasound Doppler monitor (Toitsu, Japan). To analyze the data, three kernels were used: (1) a Wigner kernel, (2) a Choi-Williams kernel, and (3) a figure eight kernel. Using our new figure eight kernel, the demodulation accuracy was improved and blood flow components were observed.

In this paper, the authors present the experimental results of using a quantitative ultrasonic diagnosis technique for human liver diseases using the fractal dimension (FD) of the shape of the power spectra (PS) of RF signals. We have developed an experimental system based on a conventional ultrasonic diagnostic system. As a result, we show that normal livers, fatty livers and liver cirrhosis can be identified using the FD values.

Transmission-type inverse scattering computed tomography for reconstructing both sound speed and attenuation images using the observation data along circular arc points was explored. To date, there has been difficulty in reconstructing the attenuation image, but not the sound speed image, since the attenuation contrast of tissue is very low compared to that of sound speed. Hence, a high-precision data observation, being tolerant to measurement noise and avoidable of spurious edge wave interference, is inevitable to realize stable attenuation image reconstruction. To this end, the present study revealed that circular arc observation method was highly superior to the conventional straight line observation. The optimum determination of circular-observation distance and angular-observation aperture was investigated through numerical examination of the attenuation image. Furthermore, an experimental phantom examination assuming actual parameters in tissues was performed. As a result, the validity of the present method was demonstrated.

We have developed an imaging system that applies FM-chirp pulse compression technology for use in intraductal ultrasonography, or intravascular ultrasonography. The pulse compression technique attempts to raise resolving power by using average power effectively under peak power restriction. This paper describes a method that use pulse compression technology in intravascular ultrasonography. In this paper, the following are reported: 1) A method to use the FM-chirp pulse compression technique in an imaging system is proposed. 2) A transmission line suited for intravascular ultrasonography is constructed using the L(0, 1) mode of the Pochhmmer-Chree wave propagating in a fused quartz rod coated with carbon. 3) A receiving signal from a target is compressed to give a shot pulse.

To realize quantitative diagnosis of liver cirrhosis, we have been analyzing the probability density function (PDF) of echo amplitude using B-mode images. However, the B-mode image is affected by the various signal and image processing techniques used in the diagnosis equipment, so a detailed and quantitative analysis is very difficult. In this paper, we analyze the PDF of echo amplitude using RF echo signal and B-mode images of normal and cirrhotic livers, and compare both results to examine the validity of the RF echo signal.

Because of the success of the ultrasonic method for diagnosing osteoporosis, the challenge to obtain ultrasonic images of the inner part of bone has begun. Since ultrasonic imaging of the inner part of bone is very difficult, further research is necessary. The goal of this study is to develop a bone-mimicking phantom for use in the visualization of bone by ultrasound. The developed phantom using apatite and polyvinyl alcohol (PVA) as materials with consideration of the periosteum showed fairly good agreement with real bone.

Acoustic properties of living tissues are an important parameter for quantitative estimation of the tissue structure. It is very important to determine the relationship between the physical and the chemical change of tissue structure and the change of acoustic properties. In this paper, using a new system with high density measuring points, we present the relationship diagram between the speed of sound and attenuation of human heart and liver tissues at 25 MHz. To compare normal and diseased tissues, we investigate the relationship between the sound speed and the attenuation of tissue. A characteristic relationship of the tissue is found in cirrhotic liver and aortic regurgitation tissue.

The inverse scattering imaging method based on reflection and transmission observation data, which was previously developed by the present author, is anticipated for its practical advantage in which the necessary range of observation view can be reduced to half compared to the conventional full observation view. In this report, we propose a modified method, which involves data observation carried out while rotating an object under the fixed condition of a transmitter/receiver pair, and a reflector. The inverse scattering reconstruction procedure is developed by applying the mirror-image theory. A special feature of the present method which is stressed is its superiority for the limitation of the observation view range much smaller than 180 deg. The validity of the method is tested using simulation and experimental data from the triangular specimen. It is shown that the quantitative precision of the reconstructed sound speed images is fairly good even when the limited viewing range is less than 120 deg.

We have previously developed a method for measurement of a small change in thickness of the arterial wall during a single cardiac cycle [H. Kanai, M. Sato, Y. Koiwa and N. Chubachi: IEEE Trans. UFFC 43 (1996) 791]. The resultant change in thickness is shown to be useful for the in vivo assessment of the regional elasticity of the arterial wall. Although the accuracy of the measurement of the change in thickness is found to be within 1 µm, it is affected by the interference of ultrasonic pulses. In this study, we simulate the propagation of ultrasonic pulses transmitted and received by a linear probe. In the simulation experiments, the ultrasonic pulses generated by a computer are reflected by a tube, which has a small change in wall thickness of 10 µm. The optimum focal position of the ultrasonic beam is determined by evaluating the root-mean-square (rms) error in the measured change in thickness.

In contrast with tissue elasticity imaging, a nonquantitative but high-resolution and real-time image of abdominal tissue strain could be a promising diagnostic tool for ultrasonic visualized palpation using a conventional array transducer. In order to realize the 2D strain imaging, accurate estimation of the lateral displacement perpendicular to the beam axis is required, which overcomes the limitation of the 2D cross-correlation method affected by the data window which determines the spatial resolution and computing efficiency of the estimation. The hierarchical 2D wavelet coefficients of successive complex-valued echo frames were applied to realize the excellent performance of the 2D motion estimate in accuracy, variance, spatial resolution and computational cost. The resultant total performance of this algorithm is evaluated on the basis of physiological free motion to obtain clinical data of hepatocellular carcinoma.

We present a theory of circular-scanning ultrasonic diffraction tomography along with simple preliminary experimental results. Images of cross-sectional structures of objects achieved by diffraction tomography have a high resolution, which is finer than a wavelength of the probing wave, in the presence of diffraction, reflection, and refraction phenomena. We investigate the spatial resolution and quantitative reconstruction of the object function, focusing on the role of the low-frequency component of the scattered wave, and show a simple method of extrapolation to determine the lacking low-frequency component. Additionally, we present numerical investigations on the quantitative accuracy of the reconstruction of a complex object function, introducing new numerical phantoms for the circular scanning diffraction tomography like Shepp and Logan's phantoms which are utilized in the numerical investigations of X-ray CT and MRI.

This report describes the three-dimensional (3D) visualization of skin and an eye using high-frequency ultrasound. A high-frequency ultrasound image has high resolution of the order of 10 µm and demonstrates the detailed internal structure of an organ. Therefore it is suitable for visualizing the structure of organs such as skin and the eye. The method of 3D visualization of skin and an eye we used is as follows. Initially, a high-frequency ultrasound image was obtained by using a transducer made of lead zirconate titanate (PZT) ceramics with a central frequency of 32 MHz. The spatial resolution of the image is 25 µm. Next, we applied a binarization procedure to the image and reconstructed a 3D image using a volume-rendering technique. From the results, we were able to separately image each layer of the skin and recognize the stratum corneum, epidermis and dermis. Moreover, we obtained images of the structure of the eye, that is, cornea and iris.