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Yokohama-shi, Japan

Fang Y.,Nanjing Agricultural University | Fang Y.,Zhejiang University | Lu Z.,Nanjing Agricultural University | Lin L.,Zhejiang University | And 2 more authors.

Air-coupled ultrasound has shown excellent sensitivity and specificity for the nondestructive imaging of wood-based material. However, it is time-consuming, due to the high scanning density limited by the Nyquist law. This study investigated the feasibility of applying compressed sensing techniques to air-coupled ultrasound imaging, aiming to reduce the number of scanning lines and then accelerate the imaging. Firstly, an undersampled scanning strategy specified by a random binary matrix was proposed to address the limitation of the compressed sensing framework. The undersampled scanning can be easily implemented, while only minor modification was required for the existing imaging system. Then, discrete cosine transform was selected experimentally as the representation basis. Finally, orthogonal matching pursuit algorithm was utilized to reconstruct the wood images. Experiments on three real air-coupled ultrasound images indicated the potential of the present method to accelerate air-coupled ultrasound imaging of wood. The same quality of ACU images can be obtained with scanning time cut in half. Source

Thornton B.,University of Tokyo | Asada A.,University of Tokyo | Ura T.,University of Tokyo | Ohira K.,Japan Probe Co. | Kirimura D.,Link Laboratory Inc.

This paper describes the development of an acoustic probe designed to perform in-situ measurements of ferro-manganese crust thickness at depths of up to 3000m. It is planned that this device will operate at low altitudes off the seafloor, mounted onboard an underwater vehicle, and continuously map the crust thickness of regions extending over several kilometres. A prototype probe has been developed together with an algorithm that automatically detects the reflections from the top and bottom surfaces of a layer of crust and measures its thickness. The performance of the system is demonstrated through a series of laboratory experiments carried out using crust samples obtained during the NT09-02 Leg2 of the R/V Natsushima. First, the ability of the system to measure crust thickness at various ranges to the target is assessed. Next, the effects of pressure are investigated in an experiment where the thicknesses of several crust samples are measured at pressures between 0.1 and 30MPa. Finally, the sub-bottom profiles of a number of crust samples, with and without substrates attached are measured. © 2010 IEEE. Source

Tanaka Y.,Ritsumeikan University | Tanaka K.,Ritsumeikan University | Sugiyama S.,Ritsumeikan University | Kurumi Y.,Shiga University of Medical Science | And 3 more authors.
Japanese Journal of Applied Physics

A small ultrasonic probe capable of precise control of needle position is required for biopsies taken in abdominal surgery and laparoscopic surgery. We fabricated a small size ring-shaped probe with a through hole to insert the needle. The probe simultaneously detects the object in front of it, e.g., a lesion, and the tip of the needle. The error of the insertion depth measured by this detection was estimated to be less than 10.1% at a depth of more than 5mm when the inner diameter of the probe was 1.1mm and the outer diameter of the needle was 0.6 mm. The results of an experiment using a stomach wall specimen indicate that the position of the needle can be precisely controlled because the needle is directly below the probe. © 2011 The Japan Society of Applied Physics. Source

Chang J.,Nanchang Hangkong University | Chang J.,Japan Probe Co. | Lu C.,Nanchang Hangkong University | Kawashima K.,Ultrasonic Material Diagnosis Laboratory
FENDT 2013 - Proceedings of 2013 Far East Forum on Nondestructive Evaluation/Testing: New Technology and Application

We have developed the V transmission system using for online scanning, insitu-defects testing and automatic detection by Non-contact Air Coupled Ultrasonic Testing (NAUT), NAUT with the ultra-high power square burst wave pulser & receiver. Square burst waves transmit and receive more powerful ultrasonic than pulse wave. It is easy to obtain the optimum detective condition by changing of frequency & numbers of waves. Therefore it is suitable for NAUT to require the powerful transmission and receiving. This paper mainly discusses the non-contact air-coupled ultrasonic testing method (abbr. V transmission method), which is based on the transmission mode but receives the reflected signals from the same side. Firstly, the basic principle of the air-coupled ultrasonic testing and the V transmission method was described. Then, it was focused on the velocity measurement by using the non-contact air-coupled ultrasonic method and detection of internal defects. The measured results for some application examples were shown, such as detection and imaging of the defects in the acrylic block with/without hole, which is very difficult by using traditional methods. Last, the propagation velocity in concrete and the imaging in reinforced concrete were measured. © 2013 IEEE. Source

Nishino H.,Tokushima University | Asano T.,Tokushima University | Taniguchi Y.,Tokushima University | Yoshida K.,Tokushima University | And 3 more authors.
Japanese Journal of Applied Physics

In this paper, we present a novel method of accurately estimating pipe wall thickness by detecting the minute difference in the angular wave number of a circumferential (C-) Lamb wave. A C-Lamb wave circling along a circumference of a pipe is transmitted and received by a pair of noncontact air-coupled ultrasonic transducers. For the accurate detection of the angular wave number, a large number of tone-burst cycles are used so as to superpose the C-Lamb wave on itself along its circumferential orbit. In this setting, the amplitude of the superposed region changes considerably with the angular wave number, from which the wall thickness can be estimated. This method is very useful to monitor the integrity of piping in high-temperature environments because of its noncontact nature. The principle of the method and experimental verification are shown. © 2011 The Japan Society of Applied Physics. Source

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