This paper describes sound quality changes caused by a sound aerodynamic failure in a micro-axial fan when applying acoustic diagnostic methods at a cooling fan motor assembly line. The aerodynamic failure sound was focused to a rotational fan blade tone and a blade passing noise with a change in the fan blade run-out. Experimentally obtained results clarified the correlation between the sound quality metrics (Sharpness, Roughness, Fluctuation strength, Tone-to-noise ratio) and the blade run-out. Furthermore, an acoustic diagnosis technique for fan blade run-out is proposed using an adaptive spectrum enhancer. This proposed acoustic diagnosis technique is used for an adaptive feedback algorithm using an internal model control architecture to extract an abnormal periodic signal including aerodynamic sound generated by a rotating micro-axial fan. The experimentally obtained results show that the blade passing sound signal with the blade run-out change was improved by about 10 dB using this adaptive feedback algorithm.

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In this paper, several diameter of solid glass spherical grain was dealt. Each diameter grain has the each characteristic impedance and the complex wave constant. At first, the characteristic impedance and the complex wave constant for each grain diameters were measured. Then, the normal incidence absorption coefficient of each grain diameters for arbitrary layer thickness can be calculated. Likewise, the normal incidence absorption coefficient for multilayer with different grain diameters and arbitrary thicknesses can be calculated. This calculation process is comparatively lengthy, so the experiments for real multilayer and the calculations were compared. Result of the calculations coincided to the experiments. Consequently, calculation result of normal incidence absorption coefficient for multilayer with different grain diameters is useful.

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In this paper, we experimentally investigated detection of cavitation states using microphones placed outside a pipe at positions upstream and downstream from an orifice. From the visualization of cavitation bubbles and the characteristics of accelerometer outputs, the cavitation states from the orifice could be classified into 4 states; (A) no cavitation, (B) bubble collapse in the orifice, (C) bubble collapse at the center of the pipe and (D) bubble collapse near the pipe wall. The signal treatment technique for microphones was examined to improve detection sensitivity and the frequency characteristics were evaluated to detect a weak cavitation state. As the results, the ratios of (L_eq-L₅₀) (L_eq: equivalent sound level, L₅₀: 50 % percentile level) were selected to improve the detection sensitivity for the strong cavitation state (D). We proposed the evaluation of the power spectrum ratios (PSRs) between downstream and upstream from an orifice at each frequency band and their counts to detect the weak cavitation states (B) and (C). From the combination of the ratios of (L_eq-L₅₀), PSRs and their counts, the cavitation states (B), (C) and (D) were successfully detected and classified. Finally we discussed applicability of the proposed cavitation detection methods to components in plant piping systems.

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This paper describes the overspeed control of a vertical-axis wind turbine (VAWT) without an electric control system or mechanical brakes. To improve its performance with straight blades, a VAWT with a variable-pitch mechanism consisting of a four-bar linkage was designed. This wind turbine exhibits directivity to the wind, which is able to make use of rotational speed control in a VAWT. This wind turbine can achieve passive yaw control by means of tail vanes, which are installed on the eccentric link lever. The yaw angle characteristics of the tail vanes were measured in an open-circuit wind tunnel and in field tests. The yaw angle variations from the numerical analysis are in good agreement with the experimental data from the wind tunnel tests. It was found that overspeed prevention by means of tail vanes is useful in protecting a VAWT from strong winds without using mechanical brakes.

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This paper proposes a technique for modeling the dynamic behavior of the hysteresis in pneumatic muscle actuators (PMAs) and controlling the motion of PMAs with the hysteresis model. PMAs contract according to the internal pressure level; however, the relationship between the contraction and the internal pressure is subject to hysteresis, and the hysteresis distorts depending on the acting speed of PMAs. To describe such hysteresis, the proposed technique uses the dynamic Preisach model and adaptively tunes the parameters of the model by recursive parameter estimation if the distortion occurs due to speed variations. The hysteresis model with the on-line adjusted parameters was incorporated into a PMA control system as the adaptive hysteresis compensator for the purpose of reducing undesirable effects caused by the hysteresis on the control accuracy. Additionally, as introducing a fast inversion algorithm enabled the real-time calculation of hysteresis compensator outputs, the hysteresis compensator could cope with the reference-input changes while the system was in operation. Experimental results showed that the proposed technique achieved higher tracking performance than the technique developed in our previous work, both for a single PMA and for a parallel manipulator driven by three PMAs.

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In order to reduce Shinkansen noise, it is important to develop appropriate countermeasures for pantograph noise and the noise generated from the lower part of cars. The noise generated from the lower part of cars mainly consists of aerodynamic noise and rolling noise. In this paper, firstly, the contribution of rolling noise is quantitatively examined by using measured data of rail vibration and the TWINS (Track-Wheel Interaction Noise Software) model. Next, the contribution of aerodynamic noise to the noise generated from the lower part of cars is determined by a comparison of measured noise and predicted rolling noise. It is apparent that, through this study, the aerodynamic noise has a much greater contribution to the noise generated from the lower part of cars above 335km/h.

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Active acoustic shielding (AAS) is the system that can attenuate a sound passing through an open window. AAS is constructed from a number of AAS cells set in an array with having an approximately collocated microphone and speaker. Each AAS cell is individually controlled by a single-channel feedforward method. The concept of AAS was proposed by the authors and its feasibility was demonstrated in the previous report by performing some simple simulations and experiments. In this study, an AAS window with four AAS cells in a small open window was manufactured and installed in the door of a test room. Its noise-reducing performances were measured for noise from outside. The effects of multiple noise sources, moving noise sources and reflected sound in the room were also examined. As the results, the AAS window is demonstrated to be able to attenuate not only normal incident sound but also oblique incident sound in the frequency range from 500Hz to 1.5 or 2kHz. Moreover, noise reduction is obtained over a wide area in the room. Additionally the AAS window is also effective for multiple sound sources and moving sound sources.

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This paper presents an innovative design of a three-bed two-stage silica gel-water based adsorption cycle aiming to minimize the overall size of four-bed two-stage cycle. One heat exchanger bed was removed from former four-bed two-stage system and operational strategy was taken to increase the adsorption time compare to desorption time in the proposed design. A simulation model for the proposed cycle was developed in order to analyze the influence of cycle time on the performance of the system in terms of specific cooling power (SCP) and coefficient of performance (COP). The cycle time was optimized to obtain the maximum SCP for different heat source temperatures using the particle swarm optimization (PSO) method. Sensitivity analysis of the cycle time was conducted using contour plot of SCP and chilled water outlet temperature for driving heat source temperature at 55°C. Optimize results were compared with the results of four-bed two-stage cycle. It was found that the SCP was increased for the proposed cycle over the whole range of regeneration temperature. The proposed cycle seems advantageous from the economic viewpoint due to its improved performance and reduced volume.

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