Detection of hydrogen gas is a crucial task for establishing safety and reliability of fuel cells, a key technology for the environment and our society. However, hydrogen is difficult to detect and various hydrogen sensors have many drawbacks. Here we report a novel hydrogen gas sensor, the ball surface acoustic wave (SAW) sensor, using Pd or PdNi sensitive film. The ball SAW sensor is based on a novel phenomenon, diffraction-free propagation of collimated beam along an equator of sphere. The resultant ultra-multiple roundtrips of SAW makes it possible to achieve highest sensitivity among SAW sensors. Moreover, it enables to use a very thin sensitive film, and consequently the shortest response time (2 s) was realized. In terms of the sensing range, it has the widest range of 10 ppm to 100% among any hydrogen sensors including FET or resistivity sensors. The response time was less than 1 s for 3.0% hydrogen concentration in nitrogen gas, evaluated by using a newly developed digital quadrature detector.
We present a 300 MHz surface acoustic wave (SAW) oscillator for gas sensor application. As the oscillator element, SAW delay lines on an ST-X quartz substrate with low insertion loss and single-mode-selection capability were developed. And they were structured by Electrode Width Control Single Phase Unidirectional Transducer (EWC/SPUDT) configuration and comb transducer. The coupling of modes (COM) model was used to predict device performance prior to fabrication. The measured frequency response S12 showed a good agreement with simulated results; a low insertion loss of less than 9 dB and a linear phase in the 3 dB bandwidth were observed. The experimental results show that the baseline noise of the fabricated oscillators was typically up to ∼0.7×10−7 in a laboratory environment with temperature control. The oscillator was successfully applied to a gas sensor coated with fluoroalcoholpolysiloxane (SXFA) as the sensor material for O-isopropyl methyphosphonofluoridate (GB) detection, and a superior threshold detection limit was obtained (<<0.4 mg/m3).
China has various ecologically important sites that provide wonderful research opportunities. The biosonar behavior of Yangtze finless porpoises (Neophocaena phocaenoides asiaeorientalis) in the semi-natural reserve, Hubei, China has been extensively studied for the past five years by the Japan Fisheries Research Agency and Institute of Hydrobiology, Chinese Academy of Sciences. Careful scanning and acoustical autofocusing behavior in porpoises was firstly observed in free-ranging conditions. The biosonar model obtained in this study allowed us to recently develop a broadband high-resolution sonar system called the Dolphin Sonar Simulator. Frequent biosonar production by finless porpoises also allowed an effective passive acoustical survey to be conducted of the animal along the entire habitat of this species in 2006. Bilateral collaboration with cutting-edge acoustical technologies was proven to be highly productive for basic behavioral science, engineering applications, and the conservation of endangered species.
Distance to target is fundamental and very important information in many engineering fields. In some applications sound is often used to measure distances to targets. For this purpose, the time delay of reflected wave is typically used. This method, however, can not measure short distance because the transmitted wave, which has not attenuated enough as of reception of reflected waves, suppresses the reflected waves for short distance. Meanwhile, in the research field of microwave radar, to measure distances to multiple targets even if they are short, a novel method by using standing wave has been recently proposed. In this paper, we apply the fundamental principle of this method to measurement of short distance for multiple targets using sound wave. Specifically, we focus our attention on audible band-limited signal with random phases. To verify the validity and effectiveness of our method, we perform computer simulations and experiments. As a result, it has been confirmed that short distances to multiple targets, such as the distances of two targets located at 0.5 m and 1 m, can be measured by our method.
Currently, there is a constraint in the individual equalization of the differences in head-related transfer functions (HRTFs) between a dummy head and a listener for a binaural system. Therefore, the equalization function of a listener must be measured in the original sound field. To remove this constraint, we have developed a method that replaces the function measured in the original sound field with that measured in another sound field (an equalization sound field). The two functions’ profiles are similar. Therefore, the original function is approximated by adding reflected sound components to the transfer function measured in an equalization sound field. In the proposed method, the reflected sound components are extracted by applying the auto regressive moving-average (ARMA) model to the transfer function measured in the original sound field. An ear canal transfer function is introduced into the proposed method to calculate the transfer function measured at the entrance of the ear canal from that at the eardrum. A psychoacoustical experiment is carried out to evaluate the equalized sound with respect to four criteria and localization. The experimental results confirm that the proposed method is effective for all listeners.
The paper presents a prosody adaptation method which is able to adapt the prosody model of text to speech (TTS) to a new style with a small training corpus. Unlike the conventional prosody mapping between two parallel prosody features, the paper tries to integrate the prosody conversion into the prosody generation model of TTS. In the paper, we use a template-based prosody model which consists of two major parts: the prosody template library and the template parameter prediction trees for TTS system. With this model, the prosody adaptation is realized by the following two steps: converting the prosody template library to the target speaker’s prosody based on the mapping methods, re-training prosody prediction trees with the small target training set. In the model, some transformation algorithms, including linear regression, Gaussian Mixture Model (GMM) and Classification and Regression Tree (CART) are involved. Experimental results show that the prosody adaptation system can generate synthesized speech which is much similar with the target speaker.
Ultrasonic motor is one of the most promising candidates for arranging the joints of robot arms or fingers. In this paper, we design and fabricate a robot finger involving two joints with four degree-of-freedom (DOF) based on two hybrid multi-DOF piezoelectric ultrasonic motors. The motor’s stator consists of a multi-layered piezoelectric longitudinal vibrator and a sandwich bending vibrator. The multi-layered vibrator can produce large longitudinal vibration velocity in the z direction at low driving voltage. The sandwich vibrator is composed of two PZT rings and four-divided bronze electrodes, and is driven by phased voltages to excite the bending vibrations in two orthogonal directions. The synthesis of an elliptical motion with the longitudinal and bending vibrations can make a ball rotor rotate in three directions. Two multi-DOF motors are designed and installed in the prototype two-joint-finger. The frequency of the upper motor is 33 kHz and that for the lower motor is 22.8 kHz. In our model, a stainless steel layer is adhered on the stator’s surface to improve the rotation torque, and the maximum torque of 23.5 mNm was obtained for the lower motor. Holding mechanism using a bearing-Teflon disk is introduced to hold the ball rotor without preventing the multi-DOF motions of the robot finger joint. The motions of the finger are demonstrated and evaluated experimentally.