Authorship：Lead author,　Corresponding author  

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DOI： 10.1299/mej.20-00545

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DOI： 10.1299/mej.20-00476

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Authorship：Lead author,　Corresponding author  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：INT INST ACOUSTICS & VIBRATION  

A shock load occurred in a short time duration can lead to dangerous effect on the machine or structure. The use of conventional technique for shock vibration control by modifying the systems damping reduces the steady-state response of the system. However, this method fails to attenuate a large acceleration peak at the moment after the shock. An alternative method for reducing the maximum acceleration peak due to shock load using the principle of momentum exchange has been developed. When the shock excitation frequency is much larger in comparison with the main mass natural frequency, the passive momentum exchange impact damper(PMEID) produces good performance. However, the performance of PMEID decreases as the shock excitation frequency close to the main mass natural frequency. In this research, a simple technique to improve the performance of PMEID utilizing the pre-straining spring mechanism (PSMEID) is proposed. The dynamic model of the system with PSMEID is derived. Next, the simulation is conducted to evaluate the effectiveness of the proposed method.

DOI： 10.20855/ijav.2017.22.4487

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Authorship：Lead author,　Corresponding author   Language：English   Publisher：The Japan Society of Mechanical Engineers  

<p>This paper describes optimum values of an electrical circuit for energy harvesting using a beam and piezoelectric elements. Energy harvesting techniques recover energy from the environment. We target the energy harvesting methods that extract energy from mechanical vibration systems in this research. Vibration energy is usually extracted through electrical circuits using electromechanical transducers such as DC motors and piezoelectric elements. In order to extract energy effectively, these electrical circuits and additional vibration systems must be optimally tuned. The optimum values of an electrical circuit and additional vibration system can be derived based on impedance matching when a vibration source includes only a single excitation frequency; however, in certain cases, vibration sources include several excitation frequencies. The optimum values derived based on impedance matching are not optimum when the vibration source includes several excitation frequencies. Therefore, we additionally investigated the case of random excitation as a representative of such cases in this research. The optimum values for the case of random excitation are also effective for the cases of free vibration including impulse excitation. The governing equations were formulated using equivalent mechanical models in this research. The combination of a beam and a piezoelectric element was used as the piezoelectric energy harvester because the thorough formulation of the governing equations for this configuration was not found in the research literature. The optimum values of the electrical circuit and additional vibration system were derived using the governing equations. The effectiveness of the optimum values was verified through numerical calculations.</p>

DOI： 10.1299/mej.17-00023

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD  

This paper describes passive technique for suppressing vibration in flexible structures using a multi-layered piezoelectric element, an inductor, and a resistor. The objective of using a multi-layered piezoelectric element is to increase its capacitance. A piezoelectric element with a large capacitance value does not require an active electrical circuit to simulate an inductor with a large inductance value. The effect of multi-layering of piezoelectric elements was theoretically analyzed through an equivalent transformation of a multi-layered piezoelectric element into a single-layered piezoelectric element. The governing equations were derived using this equivalent transformation. The effect of the resistances of the inductor and piezoelectric elements were considered because the sum of these resistances may exceed the optimum resistance. The performance of the passive vibration suppression using an LR circuit was compared to that of the method where a resistive circuit is used assuming that the sum of the resistances of the inductor and piezoelectric elements exceeds the optimum resistance. The effectiveness of the proposed method and theoretical analysis was verified through simulations and experiments. (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jsv.2016.10.009

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD  

This paper describes a new method that enhances the efficiency of a piezoelectric element attached to a beam, based on mechanical impedance matching. The attached piezoelectric element is often used to suppress bending vibration passively or actively. This element can also be used as a sensor or an energy-harvesting source and placement optimization is often used for enhancing its efficiency. When the efficiency is insufficient despite using placement optimization, the size or number of piezoelectric elements is increased. Although these two methods improve the efficiency of the piezoelectric element qualitatively and quantitatively, respectively, the improvements are still insufficient for practical applications. We have proposed a method based on mechanical impedance matching for enhancing the efficiency of the attached piezoelectric element and found that the width and thickness of the element were independent of the maximum value of the modal equivalent stiffness ratio, the parameter that determines the performance of passive vibration suppression under the ideal condition. However, the maximum value of the modal equivalent stiffness ratio depends on the length of the piezoelectric element. In this paper, we propose yet another new method that does not require a piezoelectric element of large length. In this method, the modal equivalent stiffness ratio is independent of the length of the piezoelectric clement under the ideal condition. As this new method involves extending the region of the beam with respect to mechanical impedance matching using spacers extended in the longitudinal direction, the efficiency of the piezoelectric element is improved. Although the only difference between the new method and our previous methods is the extended parts of the spacers, the proposed method was theoretically investigated because of the need to additionally consider the effect of the extended parts. The optimum condition for the proposed method was theoretically formulated, and the effectiveness of the new method and the theoretical analysis was verified through simulations and experiments. (C) 2014 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jsv.2014.12.022

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD  

This paper describes a vibration suppression method based on passive vibration suppression using a piezoelectric element and an LR circuit. The proposed method applies a voltage that is proportional to the displacement or acceleration of the host structure to the LR circuit in series. Because the applied voltage equivalently increases the voltage generated by the piezoelectric effect in the piezoelectric element, the effect of the vibration suppression is increased with an increase in the applied voltage. The proposed method is categorized as a hybrid vibration suppression method that involves only an analog circuit. The governing equations were formulated, and the optimum values of the inductance and resistance were theoretically derived using the two fixed point method as well as the passive method. The characteristic features of the proposed method were theoretically investigated by comparing the added stiffness and damping, amount of the applied voltage, and time-averaged power of the applied voltage with those of the conventional methods. In addition, the stability of the proposed method was theoretically analyzed. The effectiveness of the proposed method and the theoretical analysis were verified through experiments. (C) 2013 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jsv.2013.10.001

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD  

This paper describes new methods that improve the efficiency of a piezoelectric element attached to a beam based on mechanical impedance matching. Piezoelectric elements are often used to suppress bending vibration. They are also used as sensors or energy-harvesting sources. In such cases, the piezoelectric element is usually bonded onto the host structure by an adhesive bond. The efficiency of the piezoelectric element depends on the bonding location. When the efficiency is insufficient despite a good location, the size or number of piezoelectric elements is increased. However, the efficiency of the piezoelectric element is usually insufficient even if these methods are applied. In order to enhance the efficiency of the piezoelectric elements without using active methods, this paper proposes a mechanical impedance matching method that uses spacers or tuning for the size of the piezoelectric element. Because the attached piezoelectric element and host structure in this region behave as springs in parallel to the bending deformation, the stored strain energy in the piezoelectric element is maximized under the condition that their spring constants match. The proposed methods were theoretically investigated with consideration for the effects of the bonding layer, spacers, and host structure. The optimum conditions for the proposed methods were theoretically formulated, and the effectiveness of the proposed methods and theoretical analysis was verified through simulations and experiments. (C) 2013 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jsv.2013.08.038

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Authorship：Lead author,　Corresponding author  

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Language：Japanese   Publishing type：Research paper (scientific journal)  

This paper discusses landing response control methods of planetary exploration spacecrafts on the basis of momentum exchange principles. Concretely, the methods adopt momentum exchange impact dampers (MEIDs) that absorb the controlled object's momentum with extra masses close to the object (damper masses). For example, this paper shows Upper-MEID (U-MEID) that launches the damper mass upward and Lower-MEID (L-MEID) that drops the damper mass downward. Moreover, Generalized-MEID (G-MEID) consisting of U-MEID and L-MEID is introduced. The optimal design parameters of the G-MEID mechanism in a single-axis case for the landing of a spacecraft are investigated. Simulation investigation verifies that the G-MEID mechanism is superior than any other MEID mechanisms from the point of view of reduction of the maximum rebound of the spacecraft. Moreover, the effectiveness of the G-MEID whose U-MEID adopts an active actuator (G-Hybrid MEID) is verified in the view of the rebound reduction performance and the robustness against the landing ground stiffness and spacecraft's mass variations. © 2012 The Japan Society of Mechanical Engineers.

DOI： 10.1299/kikaic.78.2781

Scopus

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST AERONAUTICS ASTRONAUTICS  

Upon landing of a spacecraft, a large shock load can lead to such undesirable responses as rebound, swing vibration, sideslip, and tripover of the spacecraft. This paper discusses the problem of controlling these shock responses by means of momentum exchange impact dampers, especially the active momentum exchange impact damper. The momentum exchange impact dampers are classified into two types: the passive momentum exchange impact damper composed of passive elements and the active momentum exchange impact damper that includes active actuators. The active momentum exchange impact damper can greatly reduce the effects of shock responses. First, landing systems consisting of momentum exchange impact dampers are designed to conduct simulations and model a two-legged system. The passive momentum exchange impact damper mechanism is a one-degree-of-freedom vibration system. The active momentum exchange impact damper mechanism employs electrical motors as actuators in addition to the passive momentum exchange impact damper components. To assess the effectiveness of the control system, three cases are simulated: without momentum exchange impact damper, with passive momentum exchange impact damper, and with active momentum exchange impact damper. The results of the simulations show that the active momentum exchange impact damper is most effective in controlling spacecraft landing responses.

DOI： 10.2514/1.53786

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Publisher：The Japan Society of Mechanical Engineers  

Blood pressure pulse wave is propagated from heart to peripheral blood vessels with changing its waveform according to characteristics of pass way. Dynamic characteristics of total arteries have been investigated by wave equation on multi-branched arterial model. Some diseases, such as an abdominal aortic aneurysm, can be predicted by using the relation between the pulse waveform and arterial stiffness. The aim of this research is to propose a new method to detect such diseases based on the pulse wave propagation model on an arterial tree. In this paper, influences of tissue surrounding an artery, model of peripheral arteries and elasticity of arteries are investigated to elaborate a multi-branched arterial model of human body.

DOI： 10.1299/kikaic.77.2695

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Publisher：The Japan Society of Mechanical Engineers  

Life style related diseases such as hypertension and diabetes promote arteriosclerosis which causes circulatory diseases. It is important to evaluate arterial condition for prevention of circulatory diseases. The pulse wave velocity method has become familiar as a vascular test because it is easy and non-invasively. However, the accuracy of the method seems not to be high because it just compares two points ignoring the frequency dependence and reflection waves from peripheral vessels. In this study theory of pulse wave propagation considering such effects was formulated. A new method to identify the reflection ratio from peripheral vessels and pulse wave velocity was proposed. This method was verified by experiment using a silicon tube and applied to measure the pulse wave propagation of human arm as a case study. The results showed that this method has possibility to apply to measure the pulse wave propagation of human pulse wave.

DOI： 10.1299/kikaic.77.989

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Authorship：Lead author,　Corresponding author  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SAGE PUBLICATIONS LTD  

In the authors&apos; previous study, we proposed a novel shock vibration control method using the active momentum exchange impact damper (AMEID). By using this method, the shock vibration of the vibratory system is greatly reduced by transferring part of its momentum to the damper mass. This feature is effective for suppressing the first large peak value of the acceleration response due to a shock load. However, the validity of AMEID for actual implementations has not yet been investigated. In this paper, the active control of shock vibration using AMEID under real conditions is evaluated by simulation and experiment. A one-degree-of-freedom vibratory system is used as the controlled object. The controller is designed using the linear quadratic regulator optimal control theory. Reductions in the acceleration response and transmitted force to the base are investigated using simulations. Experiments are carried out to verify the simulation results.

DOI： 10.1177/1077546309102675

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

Some arterial diseases, such as a peripheral arterial disease can be detected by blood pressures and pulse waves using non-invasive blood pressure monitoring devices. On the other hand, some diseases, like an abdominal aortic aneurysm, are hard to find in the same way though they also make influence to pulse waves. The aim of our research is to propose new method to detect such diseases. This paper shows two identification methods of pulse wave propagation characteristics in arteries under the assumption that arteries are viscoelastic tube. One method identifies material parameters, stiffness and density of a viscoelastic tube by measuring pressures at three points and flow volume at one point. The other method identifies them by measuring pressures at four points. Two proposed methods were verified by experiment using a silicon tube.

DOI： 10.1299/kikaib.76.766_961

Scopus

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

The authors' previous study proposed a novel shock vibration control using the active momentum exchange impact damper (AMEID) in simulations. By using this method, the shock vibration of the vibratory system is greatly reduced by transferring a part of its momentum to the damper mass. This feature is effective for suppressing the first large peak value of the acceleration response due to a shock load. In this paper, the active control of shock vibration using AMEID in actual conditions is evaluated by experiments. A one-degree-of-freedom vibratory system is used as the controlled object. The controller is designed by using the discrete-time LQR optimal control theory. The effectiveness of the AMEID approach is verified experimentally.

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Authorship：Lead author,　Corresponding author   Language：English   Publisher：Japan Society of Mechanical Engineers  

This paper describes a new hybrid vibration suppression technique for flexible structures like beams and plates using piezoelectric elements and analog circuits. There are two main methods to suppress vibration of flexible structures. One is active vibration control and the other is passive vibration suppression. The former is often effective but has a stability problem. While the latter avoids such instability, its controlling force is small. Hence, this paper is proposing a new hybrid vibration suppression method that is stable and effective. The optimum values of the circuit are determined by simple formulations derived by Two Fixed Points Method. The proposed method is verified by experiments that demonstrate that the hybrid method works better than conventional passive vibration suppression methods.

DOI： 10.1299/jee.3.424

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Other Link： https://jlc.jst.go.jp/DN/JALC/00323192970?from=CiNii

Language：English   Publisher：The Japan Society of Mechanical Engineers  

This paper proposes an active control type of momentum exchange impact damper (AMEID) and its application to reducing shock vibration of the floor. The floor is modeled as a one-degree-of-freedom system. The active component of AMEID is realized by using a linear motor. The controller design of AMEID is based on the LQR optimal control theory. The simulation results show that the performance of AMEID is not affected by the mass ratio. In addition, the performance of AMEID is compared with the conventional passive momentum exchange impact damper (PMEID), the active mass damper (AMD) and the conventional active control method in reducing the floor shock vibration. It is shown that the shock reduction performance obtained by AMEID is larger than that obtained by PMEID. The power consumption and the stroke of the actuator for AMEID are lower than those of AMD. Furthermore, the transmitted force obtained by AMEID is smaller than that of the conventional active control.

DOI： 10.1299/jsdd.2.930

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

The momentum exchange impact damper (MEID) has already proposed for reducing the shock vibration of the floor. In the MEID, the shock energy of the floor is suppressed by transferring a part of its kinetic energy to the damper mass during collision time. in this study, an active shock control using the momentum exchange impact damper (AMEID) and its application to reducing shock vibration of the floor is proposed. The floor is modeled as a one-degree-of-freedom system. The actuator is installed between the contact spring and the damper mass. A linear motor is assumed as the actuator. The LQR optimal control is applied to design the controller of AMEID. It is verified that the performance of AMEID is not affected by the mass ratio between the impact damper mass and the floor mass. In addition, the performance of AMEID is compared with the conventional passive momentum exchange impact damper (PMEID) and the conventional active control method in reducing the floor shock vibration. It is shown that the shock reduction performance obtained by AMEID is larger than that obtained by PMEID. Furthermore, the transmitted force obtained by AMEID is smaller than that of die conventional active control.

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Authorship：Lead author,　Corresponding author  

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

This paper proposes new methods which improve the robustness and the performance of the passive vibration suppression by a dual electrical absorber using piezoelectric elements and analog circuits. Two types of methods which use two inductances were proposed in this paper. Because the electrical systems of new methods have two resonance frequencies, those new methods could improve the performance and the robustness by choosing the inductances and resistances of the circuit. Optimum values of the circuit were derived for both cases with and without the variation of the stiffness of the main system. The effectiveness of new methods and the optimum values of the circuit were verified by calculation and experiment.

CiNii Books

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Authorship：Lead author,　Corresponding author  

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Authorship：Lead author,　Corresponding author  

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

This paper describes the precise measuring method of electromechanical coupling coefficient of piezoelectric element. The precise electromechanical coupling coefficient of a piezoelectric element is needed to know the performance of the active vibration control or the passive vibration suppression using piezoelectric elements. However, the coefficient could not be measured good enough to simulate the performance of the vibrating system by the conventional method because of the error of the measurement. In this study, a new method using the resonance frequencies when an inductance is connected to the piezoelectric element was proposed, and the effectiveness was investiated by experiments.

CiNii Books

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Authorship：Lead author,　Corresponding author  

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

The spacecraft needs to decrease falling velocity to protect its body against the landing impact. This paper proposes a new method using momentum exchanging to decrease falling velocity. The momentum exchange device is composed of a compressed spring and an auxiliary mass at the under part of the spacecraft. Just before the landing, the spring is released and the mass is discharged toward the landing surface, consequently a part of momentum of the body of spacecraft is moved to the mass, and velocity of the spacecraft is decreased. This phenomenon is investigated theoretically and experimentally. The results show that the velocity can be decreased remarkably.

CiNii Books

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Piezoelectric elements are often used as actuators and sensors. In the case that the target is flexible structure, a piezoelectric element should be attached to the position where the curvature is large because the electromechanical coupling coefficient of the piezoelectric element becomes large value. However, the improvement is usually insufficient. To improve the value drastically, a new technique of attachment of a piezoelectric element which uses spacers was proposed in this paper. The optimum height of the spacers was formulated, and the relationship between the value and the size of the piezoelectric element were investigated in the theoretical analysis. The effectiveness of the proposed method and the theoretical analysis were validated by calculation and experiment.

CiNii Books

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

CiNii Books

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

This paper shows two identification methods of propagation characteristics of pulse wave in viscoelastic duct. One method identifies material parameters of viscoelastic duct by measuring pressures at three points and flow volume at one point. The other method identifies them by measuring pressures at four points. Material parameters of the same silicon tube were calculated by two methods. And reasonability of two proposed method was confirmed by comparison of two calculated material parameters.

CiNii Books

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

This paper proposes one of hybrid vibration suppression methods based on the passive one using piezoelectric elements and a LR circuit. A lot of hybrid methods have been proposed; however, most of them merely use both the active and the passive methods together. In contrast, large controlling force is generated in this method by amplifying the sensed voltage in piezoelectric elements using a sensor and an amplifier. Because the governing equations of the proposed method are also similar to those of the passive method, the optimum values of the circuit can be determined by simple formulations derived by the Two Fixed Points Method. The characteristics of the proposed method were investigated by theoretical analysis, and its effectiveness was verified by the experiment.

CiNii Books

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

CiNii Books

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

This paper proposes a new method of the hybrid vibration suppression using piezoelectric elements and the displacement signal of the object. A lot of hybrid methods have been proposed; however, most of them merely use both the active method and the passive one together. In contrast, the controlling force of the proposed method is based on that of the passive method. Because the governing equations of the proposed method are also similar to those of the passive method, the optimum values of the circuit can be determined by simple formulations derived by the two fixed points method. The performance and the stability of the proposed method were verified by theoretical analysis and the experiment.

CiNii Books

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

This paper describes acoustic absorption property of a perforated panel and the availability as an acoustic absorbent. Improvement of absorption property of this panel under steady flow was verified and not only the normal incidence sound absorption property of this panel but the parallel incidence one were investigated. Furthermore, a method of acoustic analysis by boundary element method (BEM) which considers the acoustic damping on a rigid wall was proposed. Finally, high sound absorption property of this panel when it was applied to a duct and the effectiveness of acoustic analysis of a duct using this panel by BEM were confirmed.

CiNii Books

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

This paper proposes new methods which improve the robustness and the performance of the passive vibration suppression using piezoelectric elements applying the dual-inductance circuit. Two types of methods which use two inductances were proposed in this paper. Because the electrical systems of new methods have two resonances, they could solve the problems of the performance and the robustness which had not been done by previous methods. Optimum values of the circuit were derived both with and without considering the variation of the stiffness of the main system. The effectiveness of new methods and the optimum values of the circuit were verified by calculation and experiment.

CiNii Books

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

This paper describes a hybrid multi dynamic absorber using piezoelectric elements and an analogue circuit. There are some passive methods to suppress the vibration of flexible structures using piezoelectric elements, however, most of them can suppress only one vibrational mode although flexible structures have some vibrational modes even in low frequency domain. It is true that there are some methods to suppress some vibrational modes using multiple degree of freedom circuit, however, they have problems in the performance and it is complicated to design the circuit. Hence, this paper proposes a new method which solves those problems using an analogue circuit as in previous methods. The optimum values of each element of the circuit are determined by a simple formulation derived by the two fixed points method. Its performance and effectiveness are verified by the experiment.

CiNii Books

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Event date： 2016.7

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Event date： 2016.7

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Event date： 2015.7

Venue：Florence, Italy  

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Event date： 2014.11

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Event date： 2013.7

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