bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonradiative Transition Processes Observed from Photoacoustic Spectra of ZnO Thin Films Fabricated by Pulsed Laser Deposition
Authors: Inoue Yoshihiro , Okamoto Masaki , Kawahara Toshio , Morimoto Jun
Published: July 2005

Photoacoustic (PA) spectroscopy is a powerful tool for evaluating nonradiative transition processes in semiconductors. By this technique, we evaluated the nonradiative transition process (NRTP) in ZnO thin films that were fabricated by pulsed laser deposition on R-sapphire and C-sapphire substrates in vacuum and in oxygen ambient. The samples each exhibited a specific PA spectrum reflecting the characteristics based on different crystalline orientations and qualities. The relationships between a NRTP and a radiative transition process (RTP) were studied using photoluminescence and PA spectroscopy to investigate the effect of oxygen vacancy (V
O) compensation in films. (1120) ZnO/R-sapphire indicated that the NRTP in the UV region and the RTP in the green-yellow region dominate strongly over transition processes. On the other hand, (0001) ZnO/C-sapphire had opposite domination relationships in the RTP and the NRTP to those of (1120) ZnO/R-sapphire. We concluded that the decrease of the NRTP that originated from the compensation of V
O strongly affected the RTP in (0001) ZnO/C-sapphire and the NRTP in (1120) ZnO/R-sapphire.
Quasi-Monochromatic X-Ray Generator Utilizing Graphite Cathode Diode with Transmission-Type Molybdenum Target
Authors: Sagae Michiaki , Sato Eiichi , Tanaka Etsuro , Hayasi Yasuomi , Mori Hidezo , Kawai Toshiaki , Ichimaru Toshio , Sato Shigehiro , Takayama Kazuyoshi , Ido Hideaki
Published: July 2005

An X-ray generator consists of a negative high-voltage power supply and a field-emission-type cold-cathode X-ray tube. The tube is a glass-enclosed diode utilizing a transmission-type molybdenum target with a thickness of 20 µm, a needle graphite (carbon) cathode, a glass tube body, and a 0.5-mm-thick beryllium window. The tube current decreases gradually with time. After aging for 30 minutes, the tube current was approximately 0.2 mA with a tube voltage of 25 kV, and the focal-spot dimensions were 2.2×1.6 mm. Characteristic X-rays of molybdenum K-series were obtained after penetrating the molybdenum target and the beryllium window, and the K-absorption edge was observed clearly. The generator produced number of K photons was approximately 4×106 photons/cm2·s at 1.0 m from the source. The average photon energies of Kα and Kβ lines were 17.4 and 19.6 keV, respectively, and quasi-monochromatic radiography was performed using a computed radiography system.
Photoacoustic Spectra of Heavily Co-Doped ZnO Powders
Authors: Okamoto Masaki , Inoue Yoshihiro , Kawahara Toshio , Morimoto Jun
Published: July 2005

Photoacoustic (PA) spectra were measured for heavily Co-doped ZnO powders using a microphone at room temperature. In PA spectra, the PA signal peaks of Co2+ and Co3+ can be observed with the ZnO band-gap signals. The two PA peaks related to Co ions show the Co valency change induced by the sintering, and depend on the sintering temperature and the Co concentration. For the heavily Co-doped samples, the Co valency conversion occurred at a low sintering temperature. PA spectroscopy has potential for estimating the inner ion state change during the sintering process.
Synthesis and Photoacoustic Spectra of Sm6Ga3.33S14
Authors: Hasegawa Tomoya , Aruga Atsushi , Okamoto Youichi
Published: July 2005

Photoacoustic spectra of ternary compounds, which involved Sm, Ga and S, were measured using powder samples. A chemical reaction in an evacuated silica tube was adopted as synthesis process. Obtained powder samples were identified using Sm6Ga3.33S14 by X-ray diffraction (XRD). Single crystals could be obtained from the samples, which were gradually cooled from 1100°C to 900°C for 4 d. These crystals, which are hexagonal and transparent yellow, could be identified using the superstructure of Sm6Ga3.33S14 by single-crystal X-ray diffraction. However, the samples with a short firing time at the temperature range from 1100°C to 900°C, included another red cluster. The red cluster could be estimated using SmGa2S4 or SmGa4S7 by scanning electron microscopy-energy-dispersive X-ray spectrometry (SEM-EDX). These two phases, indicated different photoacoustic signals corresponding to yellow crystals and red clusters in the wavelength region between 300 nm and 680 nm. Additionally, photoacoustic spectrum intensity decreased by extending firing time at the temperature range from 1100°C to 900°C. We considered the relationship between synthesis regime and photoacoustic spectra.
Terahertz Ultrasonic Generation and Detection in GaAs/AlGaAs Quantum Wells
Authors: Tachizaki Takehiro , Matsuda Osamu , Fukui Takashi , Baumberg Jeremy J. , Wright Oliver B.
Published: July 2005

High frequency ultrasonic pulse generation and detection are investigated in a sample with three embedded GaAs/Al0.3Ga0.7As quantum wells by means of ultrashort optical pulses. The experimental results, showing that ultrasonic frequencies up to 0.5 THz are detected, are compared with numerical simulations of the ultrasonic pulse generation, propagation and attenuation, and of the optical detection process. The effective optical extinction coefficients of the embedded quantum wells and the ultrasonic attenuation coefficient of Al0.3Ga0.7As are determined from the analysis.
LiNbO3 Ultrasonic Transducers with an Inverted-Domain Layer for Radiation to Solid Media
Authors: Nakamura Kiyoshi , Koyama Hirokatsu , Odakura Satoshi , Yamada Ken , Saito Shigemi
Published: July 2005

Heat treatment of lithium niobate (LiNbO3) plates induces domain inversion, thereby yielding a ferroelectric inversion layer. In such a piezoelectric plate with an inversion layer, even-order thickness-extensional modes, as well as odd-order modes, can be excited piezoelectrically. Therefore, ultrasonic transducers using such a piezoelectric plate are expected to operate over a wide frequency range. In this paper, it is shown both theoretically and experimentally that broadband ultrasonic transducers for radiation to solid media can be obtained when the inversion layer is on the side of the acoustic load medium and the inversion layer-to-plate thickness ratio is around 0.3. A 50–110 MHz ultrasonic transducer was fabricated using 36°-rotated Y-cut LiNbO3 plates with an inversion layer. The conversion loss characteristic was evaluated when the transducer was bonded to an acoustic medium of fused silica by a low-temperature Au diffusion bonding technique. The 3 dB specific bandwidth was as large as 74% and the minimum conversion loss was as low as 2 dB.
Development of High-Sensitivity Ultrasonic Transducer in Air with Nanofoam Material
Authors: Nagahara Hidetomo , Hashida Takashi , Suzuki Masa-aki , Hashimoto Masahiko
Published: July 2005

For a high-sensitivity ultrasonic transducer in air, it was considered that nanofoam be applied to its acoustic matching layer. Nanofoam is a porous material that is made by the sol-gel process. Since nanofoam has an extremely low acoustic impedance, it is effective for the acoustic matching layer of an ultrasonic transducer in air. In this study, we have fabricated an ultrasonic transducer that had two acoustic matching layers and estimated its acoustic properties. The two matching layers were made of silica nanofoam and porous ceramic. The sensitivity of the developed ultrasonic transducer was about twenty times higher than that of a conventional ultrasonic transducer in air.
Resonance Behavior of a Four-Terminal Quartz Resonator with Two Modes
Authors: Hirama Koichi , Nakagawa Yasuhiko , Yanagisawa Takeshi
Published: July 2005

Connecting a load capacitor to a quartz resonator in series is, for practical purposes, the only method of changing the resonance frequency of the resonator. However, some unavoidable restrictions are posed in relation to the range over which the frequency may be changed and other aspects. Consequently, we propose a mode-shape-ratio-controlled quartz resonator. While exciting two different eigenmodes of vibration on one crystal plate of a quartz resonator, the associated antiresonance frequency is controllable by changing the ratio of amplitudes of the two different eigenmodes. The ratio is controllable externally on four terminals. Results of experiments utilizing a 9.72 MHz AT-cut fundamental mode quartz resonator show that the antiresonance frequency changes continuously in the range of 500 ppm and 35% of the frequency width between these two eigenfrequencies.
Edge Mode Vibrator Using Piezoelectric Ceramic Bar with Stepped End and Its Application in Sensor for Detecting Hardness
Authors: Watanabe Hiroshi , Ishida Takanori , Katayose Yuichi
Published: July 2005

A miniaturized edge mode vibrator using a piezoelectric ceramic bar with stepped end is proposed and the characteristics of the vibrator are determined by finite element method and experiments. In addition, the application of the vibrator in a tactile sensor is experimentally investigated. The result shows that a new sensor for detecting hardness with a high contact sensitivity and easy mechanical support can be obtained using the edge mode vibrator.
Refraction-Contrast Articular Cartilage Image: Comparison of Depiction Abilities between In-Line Holographic Method and a Laue Type Analyzer Method
Authors: Shimao Daisuke , Mori Koichi , Sugiyama Hiroshi , Hyodo Kazuyuki
Published: July 2005

Two kinds of refraction-contrast image, one obtained using the in-line holographic method and the other obtained using an analyzer crystal in the Laue geometry, from a specimen of a human articular cartilage were investigated using synchrotron X-rays at 30 keV. The former image was superior in spatial resolution and the latter image was superior in contrast regarding the delineation of the articular cartilage, which is invisible by the absorption contrast.
Vibration Characteristics of Trident-Type Tuning-Fork Resonator in the Second Flexural Mode for Application to Tactile Sensors
Authors: Kudo Subaru
Published: July 2005

Tactile sensors are used for measuring the softness and hardness of an object. This paper presents a new tactile sensor with a trident-type tuning-fork resonator using the second flexural vibration mode. The vibration modes and displacements are calculated using the finite element method. The dimensions of the resonator, which are not influenced by supporting conditions, are determined. The calculated results are experimentally confirmed with the trident-type tuning-fork resonators fabricated for various trials. The experimental characteristics of the tactile sensor are shown by measuring the softness and hardness of test pieces. This trident-type tuning-fork resonator is expected to be a highly stable tactile sensor with a high quality factor.
Surface Acoustic Wave Properties of Atomically Flat-Surface Aluminum Nitride Epitaxial Film on Sapphire
Authors: Uehara Kensei , Aota Yuji , Shibata Tomohiko , Kameda Suguru , Nakase Hiroyuki , Isota Yoji , Tsubouchi Kazuo
Published: July 2005

We have investigated the surface acoustic wave (SAW) properties of atomically flat-surface (0001)aluminum nitride on a (0001)sapphire (AlN/α-Al2O3) combination. SAW propagated along [1210]AlN/[1100]α-Al2O3 and [1010]AlN/[1120]α-Al2O3. SAW velocity was measured to be approximately 1.0% higher than that of a conventionally calculated curve. The dispersion of SAW velocity as a function of normalized thickness (kH) was as low as 1.3%. The measured temperature coefficient of delay was 9 ppm/°C at kH values of 5.9 and 9.9. The propagation loss in the case of using an atomically flat-surface AlN film was lower by one order of magnitude than that using a conventional AlN film. The propagation loss at 5.172 GHz was measured to be 0.0053 dB/λ.
Synthesis of CdSe Quantum Dots Using Micro-Flow Reactor and Their Optical Properties
Authors: Omata Takahisa , Nose Katsuhiro , Otsuka-Yao-Matsuo Shinya , Nakamura Hiroyuki , Maeda Hideaki
Published: July 2005

CdSe quantum dots (QDs) have been synthesized continuously at 200–320°C using a micro-flow reactor. Instead of the usual tri-n-octylphosphineoxide (TOPO)-tri-n-octylphosphine (TOP) solvent, octadecene (ODE)-oleic acid-TOP mixed solvent was used in the present study. Because the ODE-oleic acid-TOP solvent is in liquid form at room temperature, it enabled us to handle the reaction solution at room temperature. The particle size of the QDs synthesized at 250°C was controlled between 3.4 to 4.2 nm by changing the reaction time from 3 to 300 s. Clear photoluminescence was observed at 509 nm for 3.4 nm particles and at 578 nm for 4.2 nm particles. In comparison with the QDs synthesized using a small batch reactor, the particle size distribution of the QDs synthesized using the micro-flow reactor was distinctly sharp. The sharp particle distribution came from the accurate controllability of reaction temperature and time due to the short representative length of the micro-flow reactor.
Study of Electrostatic Discharge Durability for Surface Acoustic Wave Module
Authors: Shiba Takashi , Hikino Osamu , Okajima Daini , Kamogawa Naoko
Published: July 2005

The electrostatic discharge (ESD) characteristics of surface acoustic wave (SAW) antenna duplexer modules are studied. We have researched the main spectrum of ESD at first. Using the result showing that the main ESD response has a 200 to 250 MHz spectrum, three new techniques for an improved circuit and one new technique for an improved SAW package are developed to achieve the desired ESD durability in this study. A high-pass filter (Q) circuit is proposed in order to suppress the 200 to 250 MHz spectrum. A large capacitance voltage control (Cv) circuit is proposed for suppressing the minus pulse ESD signal. A low impedance transmitter (Tx) port circuit (L) near 200 to 250 MHz is proposed for suppressing the plus pulse ESD signal. A high-pressure-sealing SAW package is proposed to improve SAW device ESD durability. The obtained circuits and methods are applied to an extended global system for mobile communication/digital cellular system/personal communication system (EGSM/DCS/PCS) triple-band SAW antenna duplexer modules. A sufficiently high ESD durability is obtained consequently.
Surface Acoustic Wave Duplexer for US Personal Communication Services with Good Temperature Characteristics
Authors: Kadota Michio , Nakao Takeshi , Taniguchi Norio , Takata Eiichi , Mimura Masakazu , Nishiyama Kenji , Hada Takuo , Komura Tomohisa
Published: July 2005

The transmission (Tx) and receiving (Rx) passbands of the Personal Communication Services (PCS) mobile phone system in the US are 1850–1910 MHz and 1930–1990 MHz, respectively. The transition bandwidth between Tx and Rx is very narrow, 20 MHz. A duplexer for the US-PCS employing surface acoustic waves (SAWs) requires a substrate which has good temperature stability, an optimum electromechanical coupling factor, a large reflection coefficient, and a good resonant mechanical Q value. Previously, there did not exist any substrate suitable for the US-PCS SAW duplexer. In this paper, we describe a new substrate that is suitable for the US-PCS SAW duplexer and a US-PCS SAW duplexer constructed with this new substrate.
Ultra Low-Insertion-Loss Surface Acoustic Wave Filters Using Unidirectional Interdigital Transducers with Grating SAW Substrates
Authors: Yamanouchi Kazuhiko , Satoh Yusuke
Published: July 2005

Surface acoustic wave (SAW) filters employing unidirectional interdigital transducers (UIDT) exhibit low-loss properties. We propose a new single-phase unidirectional transducer (SPUIDT) with an electrode width of approximately λ/4 of the best transducer efficiency. The new UDTs are obtained by fabricating an IDT on a very thin dielectric grating with λ/8 shifts. The electromechanical couplings (k2) of electrodes on SiO2 films decrease rapidly with film thickness. Therefore, good UIDT properties are obtained for a very thin SiO2 grating (about 0.03 µm at 2 GHz with an Al electrode thickness of 0.07 µm).
In this paper we describe the experimental results of wide-band and very low-loss filters with an insertion loss of less than 1 dB in the 2 GHz-range.
Propagation Characteristics of Surface Acoustic Waves on K3Li2Nb5O15
Authors: Hasegawa Koji , Ikeda Yuki , Okano Hiroshi
Published: July 2005

The contour maps of the phase velocity v
f, the temperature coefficient of delay (TCD), the electromechanical coupling coefficient K2, and the power flow angle (PFA) of surface acoustic waves (SAWs) on K3Li2Nb5O15 are presented for Euler angles (φ, θ, ψ) with φ=0, 10°, 20°, 30°, and 40°, and -180° ≤φ, θ< 180°. These maps computed by Campbell and Jonnes' method reveal that SAWs on K3Li2Nb5O15 with Euler angles (4°, 49°, 92°), (33°, 76°, 126°), and (30°, 86°, 151°) have v
f of 3255 m/s, 3383 m/s, and 3728 m/s, K2 of 0.0115, 0.0147, and 0.0045, the values of first-order TCD of 0.02 ppm/°C, 0.05 ppm/°C, and 0.04 ppm/°C, and PFAs of 0.005°, 4.7°, and 5.1°, respectively.
Propagation Characteristics of Shear-Horizontal-Type Surface Acoustic Wave on Langasite with Au or Ta2O5 Thin Film
Authors: Kakio Shoji , Nozawa Masaya , Nakagawa Yasuhiko
Published: July 2005

The propagation characteristics, mainly the propagation loss and bulk wave radiation loss, of a pure shear-horizontal-type surface acoustic wave on (0°, θ, 90°)-cut langasite with a high-density thin film such as a gold (Au) film or a tantalum pentoxide (Ta2O5) dielectric film were investigated experimentally. The cut angles θ of 0°, 10° and 20° were chosen because a coupling factor of 1.0% and a zero temperature coefficient of delay (TCD) can both be expected at approximately these cut angles. For the Au film, the propagation loss and bulk wave radiation loss were small at θ=10°.
Nanoparticles with Multiple Perfluorocarbons for Controllable Ultrasonically Induced Phase Shifting
Authors: Kawabata Ken-ichi , Sugita Nami , Yoshikawa Hideki , Azuma Takashi , Umemura Shin-ichiro
Published: July 2005

In studying the feasibility of developing tissue-targeted contrast media that can be administered as liquids and vaporized by an external stimulus such as ultrasound, we have investigated the properties of emulsions of nanometer-size particles containing perfluoropentane and 2H,3H-perfluoropentane. We found that the ultrasound intensity required to induce echographically significant vaporization can be controlled by changing the ratio of 2H,3H-perfluoropentane to perfluoropentane and that the intensity threshold increases as this ratio increases. Significant azeotropic phenomena were not observed when the perfluorocarbon mixtures were heated, which indicates that mechanisms other than azotropy are involved in the threshold change. The vaporization of 2H,3H-perfluoropentane may have been due not only to ultrasound energy but also to the energy deposited by ultrasonically induced bubbles of perfluoropentane. Our results might lead to a phase-shift contrast agent with controllable ultrasound energy for phase shifting.
Improvement of Dispersibility of Nanosize Diamond by Sonochemical Reaction–Relationships among Acoustic Intensity, Disaggregation, and Surface Modification–
Authors: Uchida Takeyoshi , Hamano Akiko , Kawashima Norimichi , Takeuchi Shinichi
Published: July 2005

Aggregated nanosize diamond particles were disaggregated and had their surfaces modified by ultrasound exposure. A standing wave sound field was formed in a water tank using a Langevin-type transducer. Acoustic cavitation was generated in the water tank. Aggregated nanosize diamond particles with sizes of about 5 µm were disaggregated in particles with sizes of 40 nm by ultrasound exposure for 20 min. The magnitude of the zeta potential on nanosize diamond particles was increased by more than twice by ultrasound exposure. The sound field in the water tank was measured using a hydrophone. The average acoustic intensity was calculated from measured values of sound pressure. The zeta potential began to increase with increasing average acoustic intensity of more than 800 W/m2.
Effects of Metal Particle Dopant on Acoustic Attenuation Properties of Silicone Rubber Lens for Medical Echo Array Probe
Authors: Hosono Yohachi , Itsumi Kazuhiro
Published: July 2005

A low-acoustic-attenuation silicone rubber lens was developed by using a nanometer-size fine metal powder as a dopant for silicone rubber. Ten-nanometer-platinum (Pt)-powder-doped silicone rubber material showed not only a low sound velocity of 0.858 km/s, but also low acoustic attenuation properties, 0.84 dB/mmMHz with an acoustic impedance of 1.37 MRalys. By virtue of its low sound velocity and low attenuation, the Pt-doped silicone rubber provides a better figure of merit (attenuation x sound velocity) for the acoustic lens material of medical array probes than does silicone-rubber doped with conventional inorganic powders, namely, SiO2, TiO2, or Al2O3. The Pt-doped silicone lens material provides increased sensitivity for the high-frequency, 5 to 10-MHz-probe application because it can be used to realize a thinner lens than conventionally used.
Three-Dimensional Tracking Method of Tissue Motion with Biplane Images
Authors: Yoshikawa Hideki , Azuma Takashi , Kawabata Ken-ichi , Taniguchi Yo , Umemura Shin-ichiro
Published: July 2005

For real-time three-dimensional tissue motion detection using biplane ultrasound images, we investigated the efficiency of a correlation method in which each region of interest (ROI) is divided into sub-regions so small that the deformation in each subregion can be ignored when estimating its motion in and perpendicular to the image planes. The allowed range of displacement perpendicular to the image planes in sensitively estimating tissue motion by cross-correlation was analyzed. In vitro results with a phantom revealed that the velocity component in the image plane could be detected when the perpendicular displacement between two consecutive frames was as small as 0.4 mm. Moreover it was also revealed that the subregion size must be larger than the speckle size. We also performed in vivo experiments on human liver and found that the tissue motion induced by systole was detectable by our cross-correlation method. The obtained results demonstrated the potential usefulness of the proposed method in medical applications, such as an image guide for minimally invasive therapy.
Growth of Single-Walled Carbon Nanotubes Rooted from Fe/Al Nanoparticle Array
Authors: Wongwiriyapan Winadda , Katayama Mitsuhiro , Ikuno Takashi , Yamauchi Norihiro , Mizuta Tomoaki , Murakami Toshiya , Honda Shin-ichi , Oura Kenjiro , Kisoda Kenji , Harima Hiroshi
Published: July 2005

We explored the growth of single-walled carbon nanotubes (SWNTs) from nanoparticle array made of an Fe/Al multilayer catalyst by thermal chemical vapor deposition. Fe nanoparticles with a high number density and a narrow size distribution (1–5 nm) were efficiently formed by annealing the Fe/Al thin layer, resulting in the high-yield growth of SWNTs. Moreover, it was found that isolated SWNTs are rooted from patterned Fe/Al islands. The SWNTs bridged between electrodes exhibited semiconducting and metallic properties.
Quantitative Estimation of Bone Density and Bone Quality Using Acoustic Parameters of Cancellous Bone for Fast and Slow Waves
Authors: Otani Takahiko
Published: July 2005

In previous studies, two longitudinal waves, the fast and slow waves, were observed in cancellous bone. The propagation speed of the fast wave increases with bone density and that of the slow wave remains almost constant. The attenuation constant of the fast wave is much higher than that of the slow wave and is independent of bone density, but the attenuation constant of the slow wave increases with bone density. In the present study, experimental results on ultrasonic waves transmitted through cancellous bone show that the fast wave amplitude increases proportionally and the slow wave amplitude decreases inversely with bone density. The dependence of the fast wave amplitude on bone density cannot be explained by the attenuation constant. The ultrasonic wave propagation path through cancellous bone is modeled to specify the causality between ultrasonic wave parameters and bone density. Then bone density and bone elasticity are quantitatively formulated.
Cross-Sectional Elasticity Imaging of Arterial Wall by Comparing Measured Change in Thickness with Model Waveform
Authors: Tang Jiang , Hasegawa Hideyuki , Kanai Hiroshi
Published: July 2005

For the assessment of the elasticity of the arterial wall, we have developed the phased tracking method [H. Kanai et al.: IEEE Trans. Ultrason. Ferroelectr. Freq. Control 43 (1996) 791] for measuring the minute change in thickness due to heartbeats and the elasticity of the arterial wall with transcutaneous ultrasound. For various reasons, for example, an extremely small deformation of the wall, the minute change in wall thickness during one heartbeat is largely influenced by noise in these cases and the reliability of the elasticity distribution obtained from the maximum change in thickness deteriorates because the maximum value estimation is largely influenced by noise. To obtain a more reliable cross-sectional image of the elasticity of the arterial wall, in this paper, a matching method is proposed to evaluate the waveform of the measured change in wall thickness by comparing the measured waveform with a template waveform. The maximum deformation, which is used in the calculation of elasticity, was determined from the amplitude of the matched model waveform to reduce the influence of noise. The matched model waveform was obtained by minimizing the difference between the measured and template waveforms. Furthermore, a random error, which was obtained from the reproducibility among the heartbeats of the measured waveform, was considered useful for the evaluation of the reliability of the measured waveform.
Development of Ultrasonic Propagation Analysis Method for Estimation of Inner State of Bone Phantom
Authors: Endoh Nobuyuki , Tsuchiya Takenobu , Saito Yoshikazu
Published: July 2005

The preliminary study on the ultrasonic pulse propagation in the bone is described in this paper. The proposed method concerns about not only longitudinal waves but also shear waves in the bone. A simple phantom composed of three materials is also proposed, because the cancellous bone has the trabecular bone and the bone marrow. Calculated results show that the characteristics of received pulse waveforms are affected by the contents of the trabecular bone. The experimental results agree with the calculated results
Ultrasonic Measurement of Fluid Viscosity for Blood Characterization
Authors: Nitta Naotaka , Homma Kazuhiro
Published: July 2005

Although plaque rupture in arteriosclerosis is affected by not only its strength but also by hemodynamic factors, such as blood pressure and shear stress, in particular, the viscous coefficient which directly controls the magnitude of shear stress might be a risk factor in plaque rupture. Therefore, if the viscous coefficient can be assessed noninvasively, it can be a useful index for prediction of a plaque rupture and assessment of various diseases. In this work, an ultrasonic methodology to estimate the viscous coefficient was investigated by numerical simulation and flow-phantom experiment as the fundamental investigation for noninvasively assessing the viscous characteristics of blood. These results show that the proposed method is useful for estimating the kinematic viscosity coefficient in the viscous evaluation of blood.
Frequency Analysis of Strain of Cylindrical Shell for Assessment of Viscosity
Authors: Hasegawa Hideyuki , Kanai Hiroshi
Published: July 2005

For tissue characterization of atherosclerotic plaque, we have developed a method, namely, the phased tracking method, [H. Kanai et al.: IEEE Trans. Ultrason. Ferroelectr. Freq. Control 43 (1996) 791] to measure the regional strain (change in wall thickness) and elasticity of the arterial wall. In addition to the regional elasticity, we are attempting to measure the regional viscosity for a more precise tissue characterization. Previously, we showed that the viscosity can be obtained by measuring the frequency dependence of the elastic modulus using remote actuation [H. Hasegawa et al.: Jpn. J. Appl. Phys. 43 (2004) 3197]. However, in this method, we need to apply external actuation to the subject. To simplify the measurement, we instead to obtain the frequency dependence of the elastic modulus from the change in arterial wall thickness spontaneously caused by the heartbeat because this change in thickness consists of frequency components up to 20–30 Hz. In this paper, the frequency dependence of the elastic modulus of a silicone rubber tube was investigated by applying frequency analysis to the change in wall thickness caused by the change in internal pressure simulating the actual arterial blood pressure.
Evaluation of Ultrasonic Fiber Structure Extraction Technique Using Autopsy Specimens of Liver
Authors: Yamaguchi Tadashi , Hirai Kazuki , Yamada Hiroyuki , Ebara Masaaki , Hachiya Hiroyuki
Published: July 2005

It is very important to diagnose liver cirrhosis noninvasively and correctly. In our previous studies, we proposed a processing technique to detect changes in liver tissue in vivo. In this paper, we propose the evaluation of the relationship between liver disease and echo information using autopsy specimens of a human liver in vitro. It is possible to verify the function of a processing parameter clearly and to compare the processing result and the actual human liver tissue structure by in vitro experiment. In the results of our processing technique, information that did not obey a Rayleigh distribution from the echo signal of the autopsy liver specimens was extracted depending on changes in a particular processing parameter. The fiber tissue structure of the same specimen was extracted from a number of histological images of stained tissue. We constructed 3D structures using the information extracted from the echo signal and the fiber structure of the stained tissue and compared the two. By comparing the 3D structures, it is possible to evaluate the relationship between the information that does not obey a Rayleigh distribution of the echo signal and the fibrosis structure.
Distribution of Longitudinal Wave Velocities in Bovine Cortical Bone in vitro
Authors: Yamato Yu , Kataoka Hideo , Matsukawa Mami , Yamazaki Kaoru , Otani Takahiko , Nagano Akira
Published: July 2005

The distribution of longitudinal wave velocities and longitudinal moduli in a bovine femoral cortical bone was experimentally investigated. In all parts of the long cylindrical bone, the velocities and longitudinal moduli in the axial direction were the highest. In the anterior (A) part, the velocities in the axial direction were high and almost constant, whereas the velocities in the proximal postero medial (PM) and distal postero lateral (PL) parts markedly decreased. Classifying the cortical bone into three structures (plexiform, Haversian, and porotic), we clarify the velocity distributions in the bone with discussion from an anatomical point of view.
Bubble Generation by Standing Wave in Water Surrounded by Cranium with Transcranial Ultrasonic Beam
Authors: Azuma Takashi , Kawabata Ken-ichi , Umemura Shin-ichiro , Ogihara Makoto , Kubota Jun , Sasaki Akira , Furuhata Hiroshi
Published: July 2005

Low-frequency ultrasound, typically less than 1 MHz, is suitable for enhancing thrombolysis because it penetrates the cranium effectively. However, intracerebral hemorrhages after transcranial insonation in clinical trials at 300 Hz have been reported. In this study, acoustic bubble formation in a standing wave with a 617 kHz ultrasonic beam in water surrounded by a contoured piece of a human cranium was detected by ultrasound B-mode imaging. This bubble formation was indirect evidence that standing-wave formation led to cavitational adverse effects in brain tissue at the place of reflection by transcranial insonation at a relatively low ultrasonic frequency. A way of suppressing cavitation after bubble formation was also investigated. The efficiency of nucleation of bubbles was highly dependent on pulse duration at a constant total acoustic power. The obtained result suggests that inertial cavitation can be suppressed while preserving the efficiency of thrombolysis by temporally changing the acoustic condition before resonant bubble formation.
Speckle Noise Reduction by Superposing Many Higher Harmonic Images
Authors: Akiyama Iwaki , Ohya Akihisa , Saito Shigemi
Published: July 2005

A novel ultrasonic imaging method offering high resolution and high-quality images for clinical diagnosis has been developed. This method produces an image using many higher harmonic components contained in the echoes from the inside of a human body, generated due to ultrasonic nonlinear propagation through biological tissues. A new ultrasonic probe has been designed to detect higher harmonic components efficiently over a broad band produced by nonlinear propagation through biological tissues. This probe has a bilayer structure consisting of a lead zirconate titanate (PZT) transmitter and a polyvinylidene fluoride (PVDF) receiver. Experiments employing the new probe show that the receiving transducer easily detects higher harmonics from the fundamental through the tenth in the spectrum of reflected sound from an agar-gel phantom submerged in water. By scanning the probe, the harmonic images of the fundamental through the ninth harmonic component are successfully obtained. In addition, it is demonstrated that speckle noise can be reduced by averaging many harmonic images.
Measurement and Visualization of Three-Dimensional Vertebra Shape by Freehand Ultrasound Scanning
Authors: Kohyama Kazuhiro , Yasumuro Yoshihiro , Imura Masataka , Manabe Yoshitsugu , Oshiro Osamu , Moroi Keishichiro , Chihara Kunihiro
Published: July 2005

Paracentesis is a common operation for pain clinics and spinal anesthetics administration and requires empirical training and flexible skills to cope with the various cases of individual patients. We propose a method of measuring and visualizing three-dimensional vertebra shapes for assisting anesthesiologists, by an ultrasound imaging technique that is prevalent in many hospitals and has no harmful risks to the human body. The proposed system enables anesthesiologists to investigate vertebra shapes by freehand probing. Three-dimensional reconstruction and graphical rendering can be performed by monitoring the motion of the ultrasound probe and registering the scanned echography into the identical three-dimensional space. Considering the echography imaging features, volume rendering of hard tissue surfaces is achieved and interactive measurement is possible. This paper describes the practicability of the proposed method based on experimental measurement of both phantom and real lumbar vertebre and sacra.
Microwave Irradiation for Chemical Modification of Carbon Nanotubes for Better Dispersion
Authors: Kubota Kazuhiro , Sano Masahito , Masuko Toru
Published: July 2005

A mixture of single-walled carbon nanotubes (SWCNTs) and alkylamines was irradiated using microwave at various powers and for various durations. The amount of the resulting SWCNTs dispersed in chloroform was monitored as a function of time. We showed that irradiating a 100 W microwave for 20 min is sufficient to stably disperse SWCNTs. Moreover, nearly all SWCNTs irradiated using the microwave remained dispersed over a period of one month. In comparison, the same reaction conducted by ordinary oil heating required a few days of refluxing and gave a 60% yield at best. These results indicate that microwave irradiation is a powerful method of enhancing the dispersibility of SWCNTs by chemical modification.
Temperature Distributions in Welding Specimens for Ultrasonic Plastic Welding Systems Using Various Frequencies
Authors: Hongoh Misugi , Yoshikuni Masafumi , Miura Hiroyuki , Koike Yuji , Ueoka Tetsugi , Tsujino Jiromaru
Published: July 2005

Welding characteristics and temperature increases of plastic welding parts over a frequency range of 27 kHz to 94 kHz are studied. Using 27 kHz, 40 kHz, 67 kHz and 94 kHz ultrasonic plastic welding systems, temperature increase at welded surfaces of 1.0-mm-thick polypropylene plates and polymethyl methacrylate plates is measured using thermocouples inserted between plates, and temperature distributions at cross-sections of lapped plate specimens are measured using a thermotracer. The 94 kHz vibration system used for ultrasonic plastic welding consists of a bolt-clamped Langevin type longitudinal vibration source using four 30-mm-diameter piezoelectric ceramic (PZT) rings, a stepped horn (vibration velocity transform ratio N=3.0) and a catenoidal horn (N=3.13) with an 8-mm-diameter welding tip. The other vibration systems have similar configurations. Using a higher frequency system, increases in temperature measured at the welding parts are higher. The maximum temperature increase measured using thermocouples and a thermotracer was over 330°C.
A Low-Profile Design for the Noncontact Ultrasonically Levitated Stage
Authors: Ide Takeshi , Friend James Robert , Nakamura Kentaro , Ueha Sadayuki
Published: July 2005

In this paper, we propose a new low-profile design for a linear bearing based on Near-Field Acoustic Levitation (NFAL). Two flat beams at a 45° angle are used as a guide rail, and a slider is levitated by ultrasonic bending vibrations excited along the beams. The beams are excited by a pair of Langevin transducers with “+”-shaped vibration direction converters (L-L converters) to install the transducers in the same plane of the beam and to lower the total height of the setup. First, the design of the vibration converter is described. Then, a two-phase driving system to excite a traveling wave is investigated theoretically and experimentally. The levitation characteristics and the sliding performance of the prototype stage are measured and discussed.
Resonant Mode Design for Noncontact Ultrasonic Motor with Levitated Rotor
Authors: Saito Junichi , Friend James Robert , Nakamura Kentaro , Ueha Sadayuki
Published: July 2005

An noncontact ultrasonic motor, which is composed of two metal disks for a low-profile configuration and 30 mm in diameter, is proposed. To enhance rotation characteristics, the resonant mode of the air gap between the stator and rotor is chosen to coincide with the resonance of stator vibration both in frequency and mode shape. The motor rotated at 1,260 rpm with the (1,1) flexural vibration mode of the disk stator, driven at about 25 kHz.
Experimental Investigation of Deflection of High-Speed Water Current with Aerial Ultrasonic Waves
Authors: Ito Youichi
Published: July 2005

Inside a simulated standing wave sound field that was formed with high intensity aerial ultrasonic waves with a frequency of 20 kHz and a rigid plate, we passed a high-speed current of water with a diameter of approximately 0.6 mm and a speed of 5–30 m/s and deflected the current using primarily the force of the field's sound radiation pressure. Together with the acoustic radiation force, acoustic streaming, produced from convergent ultrasonic waves and moving in a direction away from the rigid plate, generated a force that acted on a small object placed inside the standing wave sound field. The water current was deflected almost proportionally to the magnitude of this compound force. The current's angle of deflection depended on the electric power supplied to the sound source that produced the convergent ultrasonic waves and on the speed of the current.
Ultrasonic Heat Transfer Enhancement with Obstacle in Front of Heating Surface
Authors: Nomura Shinfuku , Nakagawa Masafumi , Mukasa Shinobu , Toyota Hiromichi , Murakami Koichi , Kobayashi Ryousuke
Published: July 2005

Heat transfer enhancement using a horn-type transducer was carried out in the natural convection region while a flat plate was used as a wall-like obstacle in front of the heating surface. Three types of plate were used as obstacles: acrylic, aluminum, and Styrofoam. A horn tip of 6 mm diameter and 60.7 kHz was used as the ultrasonic transducer. The acoustic cavitation jet induced by the ultrasonic vibration exhibited the same tendency as the axisymmetric free jet. The acoustic jet from the horn tip was shut out by the flat plate; however, the ultrasound passed through the flat plate and transferred the flow effect and agitation effect to the area behind the plate. By applying ultrasonic vibration, the heat transfer coefficient of the heating surface behind the flat plate was increased by up to threefold. The heat transfer coefficient decreased as the thickness of the flat plate increased. The heat transfer coefficient was the highest for the acrylic plate, then the aluminum plate, and lowest for the Styrofoam plate.
Basic Study on Sludge Concentration and Dehydration with Ultrasonic Exposure
Authors: Sawada Yuta , Nagashima Satoshi , Uchida Takeyoshi , Kawashima Norimichi , Takeuchi Shinichi , Akita Masashi , Nagaoka Hiroshi
Published: July 2005

We study the condensation of sludge and the improvement of the dehydration efficiency of sludge by acoustic cavitation for efficiency improvement and cost reduction in water treatment. An ultrasound wave was irradiated into activated sludge in the water tank of our ultrasound exposure system and a standing wave acoustic field was formed using a vibrating disk driven by a Langevin-type transducer. The vibrating disk was mounted on the bottom of the water tank. Acoustic cavitation was generated in the activated sludge suspension and the sludge was floated to the water surface by ultrasound exposure with this system. We observed B-mode ultrasound images of the activated sludge suspension before ultrasound exposure and that of the floated sludge and treated water after ultrasound exposure. The ultrasound diagnostic equipment was used for the observation of the B-mode ultrasound images of the sludge. It was found that the sludge floated to the water surface because of adhesion of microbubbles generated by acoustic cavitation to the sludge particles, which decreased the sludge density. It can be expected that the drifting sludge in water can be recovered by the flotation thickening method of sludge as an application of the results of this study. It is difficult to recover the drifting sludge in water by the conventional gravity thickening method.
Convergence of Sound Waves Radiated from Aerial Ultrasonic Source Using Square Transverse Vibrating Plate with Several Reflective Boards
Authors: Onishi Yuu , Miura Hikaru
Published: July 2005

An ultrasonic source using a metal square vibrating plate radiates extremely intense ultrasonic waves into the air. The plate experiences transverse vibration when a longitudinal vibration is applied to the central point of the plate. In the lattice mode, the nodal positions of the plate take the form of straight lines, creating a lattice-like pattern. The source radiates four directional sound waves in the far field. The aim of our study is to obtain high sound pressure by converging the sound waves radiating from a source of this shape in the near field. We studied the construction of an ultrasonic field converged by using several flat boards plus four parabolic reflective boards placed near the source. The results of the measurements of sound pressure and phase distributions show that these boards can create the convergence of sound waves.
Basic Study of Underwater Acoustic Communication Using 32-Quadrature Amplitude Modulation
Authors: Ochi Hiroshi , Watanabe Yoshitaka , Shimura Takuya
Published: July 2005

In order to realize a high-speed acoustic digital communication to control an ROV remotely, a basic experiment on a method using 32-quadrature amplitude modulation (QAM) was carried out. Using a two-channel decision feedback equalizer (DFE) demodulator, good demodulation results were obtained in a tank test at a range of 2 m. In spite of a channel with a wide time spread, transmission rates of 62.5 k bit per second (bps) and 100 kbps were achieved. Even in the case of a transmission rate of 125 kbps, a symbol error rate on the order of 10-4 was achieved, which is sufficient performance to transmit an image.
Tunable Field-Effect Transistor Device with Metallofullerene Nanopeapods
Authors: Shimada Takashi , Ohno Yutaka , Suenaga Kazutomo , Okazaki Toshiya , Kishimoto Shigeru , Mizutani Takashi , Taniguchi Risa , Kato Haruhito , Cao Baopeng , Sugai Toshiki , Shinohara Hisanori
Published: July 2005

A fine tuning of the band gap of single-wall carbon nanotubes (SWNTs) has been achieved by filling various types of endohedral metallofullerenes into the SWNTs, the so-called nanopeapods. We report various electronic transport properties of fullerene peapods used as the channels of field-effect transistors (FETs) and demonstrate that the metallofullerene peapods can provide the tunable band gaps of the FET channels depending on the type of metallofullerene inserted in the SWNTs. All of the metallofullerene peapods FETs exhibit p- and n-type, the so-called ambipolar carrier transportation by variable gate bias. The ranges of the off state regions of the FET fabricated highly sensitivity with respect to the amount of charge transfer in metallofullerenes, which results in band-gap engineering. Metallofullerene peapods can be used to manipulate the electronic structure of SWNTs in nanometer scale. In such a highly functionalized SWNT, metallofullerene peapods, might be a key material for fabricating and developing sophisticated electronic devices in the future.
Impulsive Ultrasonic Measurement for Underwater Shockwave Detection
Authors: Hasegawa Daiki , Inoue Hiroshi , Murata Kenji
Published: July 2005

A polyvinylidenefluoride (PVDF) film transducer is proposed as a new sensor for the detection of underwater shockwaves from an explosion. The basic characteristics of the reception of the underwater shockwave by the developed PVDF transducer, such as the rise time of the received pulse, distance characteristics of the underwater shockwave, and reception of the explosion generated by a detonator, are described. It was shown that the developed transducer is capable of detecting an underwater shockwave generated by a low-energy exploding detonator.
3-D FDTD Analysis of Sound Field Focused by Biconcave Acoustic Lens for Normal Incidence
Authors: Mori Kazuyoshi , Nakamura Toshiaki , Yokoyama Tomoki , Hasegawa Akio
Published: July 2005

Recently, the finite difference time domain (FDTD) method has been frequently used for the analysis of underwater sound propagation. There are demonstrated advantages of this FDTD method in terms of obtaining data regarding snapshots of sound pressure distribution and a series of waveforms at any point. In addition, the method facilitates the modeling of factors, such as the sound source and media into the analysis domain. In this study, a three-dimensional FDTD analysis was carried out in order to obtain the sound field focused by a biconcave acoustic lens specialized to measure the normal incidence of the spherical wave. Additionally, the results of the analysis were compared with experimental results obtained in a water tank. When the frequency of the sound source was 500 kHz, the range between the acoustic lens and the sound source was 1.78 m, and the attenuation constant was 0.5–1.0 dB/λ, the experimental results regarding the position of the focal point, the on-axis characteristics and the beam pattern were all found to agree well with the simulation results obtained by FDTD method.
Phase Modulation of Wave Radiated from Time Reversal Array
Authors: Kikuchi Toshiaki , Saito Hideaki , Tsuchiya Toshio , Hiyoshi Yoshihisa
Published: July 2005

In shallow water, since the propagation path of an acoustic wave exists in multiplex, the transfer of information is usually difficult. On the other hand, phase conjugate wave has the property converged on a sound source location even in shallow water and an inhomogeneous medium. A communication simulation of the information that utilized the phase conjugate wave was then performed. Phase modulation was added to the probe wave sent from the sound source, and the signal was reradiated from the array. This not only converged the emitted acoustic wave on the sound source location, but the phase of the converging wave changed in proportion to the modulation phase.