The article reviews the know-why and the know-how of an invention based on the patented dissipative granular high-pressure technology. It was found that by proper selection of damping material and hydrostatic pressure to which material is exposed during the loading, one can match material maximum damping properties with the frequency or rate of the applied loading. In this way one, can fully utilize damping characteristics of the selected material and maximize the energy absorption properties of a damper. Using this unique potential of the dissipative granular high-pressure technology, one can build ultimate damping elements that surpass the existing damping elements for sever orders of magnitude. Applications of such damping elements include for instance supports for industrial machines to damp vibrations, fundamentals in building constructions to reduce susceptibility to earthquake damage and resonance, as well as trains and railway tracks to reduce vibration during travel, and to improve passive car safety in road transportation. This article reviews phenomenological description of the time-dependent response of polymeric material when excited by impact- or vibrational loading needed in development of the new generation impact- and vibration isolation.

In this study effectiveness of microbubbles as tracer of PIV measurement is investigated. Test case is turbulent separated flow over a backward-facing step (Re=3700,110000). In the present experiment microbubbles (mean diameter is 42 μm) are uniformly suspended in the water. Mean velocity and Reynolds stresses in the separated shear layer are measured by PIV using these microbubbles as tracer particles. Results are compared with those measured by PIV using conventionalsolid particles as tracer in the same experimental conditions. Distributions of mean velocity, Reynolds normal and shear stresses measured by PIV with microbubbles are in good agreement with those measured by PIV with conventional solid particles. It is suggested that microbubbles can be used as tracer of PIV for the measurement of turbulent separated flow in this Re range.

Microbubbles have various properties such as low rising velocity and large surface area per unit volume. Owing to these favorable properties, there has been a recent increase in the application of microbubbles in the agricultural and medical fields, including the development of a microbubble generator, which employs a hollow cylindrical ultrasonic horn. In this device, gas is supplied through a path in the horn to create a gas-liquid interface in water. Thereafter, ultrasonic oscillation is irradiated to the surface to generate microbubbles. However, to realize practical applications of microbubbles, a higher yield is required. This study aims to increase the microbubble yield by modifying the shape of the orifice at the horn end and evaluating the resulting microbubble yield by measuring the concentration of oxygen dissolved in water. The horn end contains side orifices and releases bubbles between walls; it achieved an increase of up to 60% in the generation of microbubbles. This increase is likely because this modified design enables better reception of strong ultrasonic oscillations, as compared to conventional straight orifices. The effect of ultrasonic amplifications were also evaluated.

The purpose of this study is to investigate the influence of the frequency ratio on the thrust and the vortex street in a periodic flow. The periodic flow is the model of an unsteady freestream velocity, and the frequency ratio is defined as the frequency of pitching wing divided by that of the periodic flow. The thrust and the vortex street are measured by a load cell and particle image velocimetry (PIV), respectively. In this study, the pitching wing is modeled as a NACA 0012 airfoil pitching sinusoidally at a Reynolds number of 4000. We compare a steady with the periodic flow to find the difference in the thrust and the vortex street at frequency ratios of 1, 2, and 3. Furthermore, FFT analysis of the thrust is conducted to investigate the difference in more detail. It is found that the thrust and vortex street are more affected by periodic flow at the low-frequency ratio than at the high-frequency ratio.

The present paper discusses the wind-induced vibration of a long-span flat roof based on a wind tunnel experiment and a fluid-structure interaction (FSI) simulation with the free-vibration technique. The experiment and simulation were carried out in a smooth uniform flow and a turbulent boundary layer to evaluate the effect of turbulence on the dynamic response. The variation of mean and standard deviation of the roof displacement with wind velocity was obtained. In the experiment, the similarity between the practical membrane structure at full scale and the model used in the wind tunnel experiment was not satisfied because of the limitation of experimental conditions, such as the model material. Subsequently, an FSI simulation that couples a computational fluid dynamics (CFD) analysis for fluid with a finite element method analysis for structure was carried out to examine the practical behavior of a long-span flat roof in strong winds. In addition, the modes and natural frequencies of vibration at each wind velocity are detected by using a proper orthogonal decomposition analysis. The results indicate that the aerodynamically unstable vibration does not occur under the condition proposed by Matsumoto (1983). It is found that the mean deformation is one of the most important factors for assessing the vibration mechanism of long-span flat roofs.

In this study, the pressure distribution around a circular cylinder rotating on the ground is estimated from velocity data measured by particle image velocimetry (PIV) using a virtual flux method. The method enables the estimation of the pressure distribution of the flow around an object of arbitrary shape from velocity data on a Cartesian grid measured by PIV.

This method is first validated with synthetic velocity data obtained by computational fluid dynamics. Then, this method is applied to the flow around a circular cylinder rotating on the ground at a Reynolds number of 1000, which has a boundary that cannot be represented on the Cartesian grid. Furthermore, the flows around a stationary circular cylinder and a circular cylinder without ground contact are investigated to understand the effect of rotation and ground contact on the flow. It is found that rotation produces a high pressure in the stagnation region between the cylinder and the ground and clearance from the ground generates an extremely low pressure region between the cylinder and the ground.

In this study, a cleaning device to remove micron-sized particles on a solid surface device has a special nozzle containing a triangular cavity to add high intensity turbuimpinges on the solid surface removing the particles. Assuming the removal of a spheriwe performed numerical simulation of the flow field in the cleaning device and estimatdrag force from the numerical results. As the results of the numerical analysis for modified nothe minimization of slit length reduced pressure loss in the slit and increased the velenhanced the removal moment and improved removal performance.

A detailed experimental investigation was made on the droplet evaporation of an azeotropic mixture, ethanol solution of 1-heptane. The solution was a pressure-maximum azeotropic mixture and had a minimum boiling point in the azeotropic composition. The mixture droplet of 10 mm³ volume was slowly dripped on to heated brass surface, which was smoothly burnished and thinly gold plated to prevent oxidization. The evaporating behavior and the lifetime of the droplets were examined within a temperature range of the wall from 100 to 300℃. The results were compared with those of a non- azeotropic mixture, ethanol solution of 1-butanol. There were clear differences on the variations of Leidenfrost point and the variations of droplet-lifetime at Leidenfrost point with an increase in the concentration of the mixture, although the evaporating behavior of the azeotropic mixture droplets did not differ much from that of the non-azeotropic mixture droplets.

MT type blade configuration, which is exclusively designed for vertical axis wind turbine, has been proposed by authors. It has been discovered that performance of this MT blade is better than those of conventional blades such as Savonius turbine or NACA0018 airfoil. In this paper it is attempted to improve the performance of the MT blade by changing its configuration. To this end, genetic algorithm is employed. By changing blade configuration, it is attempted to increase lift force of the MT blade. Two-dimensional panel method, numerical analysis of inviscid potential flow, is employed to evaluate the lift force. Obtained improved new MT blade are provided for experiments to confirm its lift force. This experiment is conducted in Hele-Shaw cell. In this Hele-Shaw cell streamlines of potential flow around a blade are visualized. The lift force of the new MT blade is calculated from streamline intervals visualized in the Hele-Shaw cell. Results of the experiments show that the lift force of the new MT blade has similar trend to that predicted by two-dimensional panel method. Lift and drag forces of the blades in viscous flow condition are also measured by wind tunnel experiments. From the results obtained by these inviscid and viscid investigation it is suggested that the new MT blade may increase the performance of actual VAWT.

The purpose of this study is to investigate the relationship between unsteady fluid forces and airfoil profiles. It is necessary to know the unsteady properties determined from the vortex dynamics, as unsteadiness is known to increase the lift force. In this study, by using a rectangular airfoil and a discoid airfoil, the angle of attack of the airfoil was impulsively changed from 0^° to an angle set beyond the static stall angle. When the airfoil was raised to form a large angle of attack, a delay of the stall was observed, and a high C_Lmax was attained. Also, C_L gradually decreased after the airfoil stopped, and the value of C_L asymptotically came to that of the static condition. For the discoid airfoil, the decrement of C_L, just after the airfoil stopped, was suppressed in contrast to the rectangular airfoil.

Fuel debris retrieval and contaminated water analysis are some of the most important issues of post-Fukushima NPS accident. The information about the fuel debris and contaminated water properties is needed before starting the decommissioning. Due to the high radiation environment, remote analysis is required. In this study, the preliminary study on the development of elemental analysis in order to obtain the chemical element information of the liquid around the debris is presented. Also, the possibility of a combination with the existing flow measurement technique (Ultrasonic Velocity Profiler- UVP) for fuel debris retrieval is presented. The elemental analysis deploys the specific light emission from low-frequency ultrasonic sonication in aqueous solution. The external transducer was chosen to perform the sonication as it enables the remote analysis. The experiments were performed under a stagnant and flowing condition. The visualization of NaCl, KCl, LiCl aqueous solution in stagnant condition showed a different color for each element. The combination experiment under a flowing condition showed a possibility of combining the abovementioned method with the measurement gap at 13 cm between transducers.

Microbubbles are tiny bubbles with a 1–100 µm diameter. Their chemical and physical properties are different from those of normal bubbles. One important characteristic of microbubbles is that they are electrically charged at the gas–water interface (ʽζ-potential). Microbubble bathing is believed to decrease sympathetic nervous system activity and stimulate the parasympathetic nervous system via bioactive effects. The parasympathetic nervous system is stimulated when we feel relaxed, and relaxation is important for improving depression. Therefore, recovery of energy via microbubbles can be used as antidepression treatment. In this study, the bioactive effects of microbubbles produced by two types of microbubble generators (slit type and pressurized dissolution type) is investigated. Furthermore, the relationship between ζ-potential and restoring vitality is evaluated. We estimated the stress-coping effect on the basis of the serum globopentaosylceramide (GPC) levels. GPC is a biochemical marker of vitality. Microbubbles generated by the slit-type microbubble generator showed a higher ζ- potential at the gas–water interface compared to those generated by the pressurized-dissolution-type microbubble generator. The shrinkage rate of microbubbles generated by the slit-type microbubble generator was less compared to the pressurized- dissolution-type microbubble generator, indicating that self-shrinkage is affected by the ζ-potential. Restoration of vitality significantly increased via microbubbles generated by the slit-type microbubble generator. In addition, microbubble bathing increased serum GPC levels; also, using the slit-type microbubble generator significantly increased serum GPC levels.

In order to develop an automatic driving system, it needs to examine the effect of cars in a line on the flow around a car. In the study, the drag force acting on car models was studied where the two car models were arranged linearly at a certain interval in a wind tunnel. Drag force reduction of the leading car model was observed. The slip stream effect was clear only for a very short inter-vehicle distance under Re=1.0x10⁶ and the effect disappeared for the middle distance between car models.

The mechanical properties of steels are known to be improved by grain refinement and by smaller and more finely dispersed cementite particles. Super-rapid induction tempering can achieve smaller and more finely dispersed cementite particles, and super-rapid induction quenching can improve grain refinement. In this study, we investigated the fatigue properties of carbon steel treated by induction quenching and tempering using a super-rapid induction heating technique. Hollow test specimens were fabricated to observe the mechanical properties of the structure obtained by induction heating. Based on our observations, in the finite-life region, no difference was found between tempering conditions for each hardness value, but a transition to longer life due to differences in quenching conditions was observed. In addition, no clear grain refining effect was found in the fatigue limit of induction-quenched steel in the range of the quenching conditions of this study. However, a delay effect due to grain refinement was recognized at the initial stage of crack growth from the consideration of the crack growth rate of induction-tempered steel.

The torsion test of 6061-T6 Al alloy friction-welded butt joints was carried out using a self-developed torsion test device. Digital images near the joint interface during torsional loading were captured and displacement distributions were measured by a digital image correlation method (or a DIC method). Local shear strain distributions around the joint were determined and relatively compared with micro-hardness distributions. The test results showed that a sufficient upset pressure was needed for increasing the torsional strength of the friction-welded butt joints. Larger shear strains were generated in a softened region near the joint interface. EBSD analysis revealed that grain sizes at the joint interface were distinctly different from those of the base material. The global shear strains along the gauge length were determined by superimposing respective local shear strains using “the inverse rule of mixtures” for composites and compared with those obtained from a goniometer.

This study is focused on the expansion properties of CFRTP plate in thickness direction when it is heated at a temperature near the melting point of matrix resin. The purpose of this study is to investigate the usefulness of homo- and hetero-junctions with pins utilizing these expansion properties. In the study, two steel plates with a straight or tapered hole were heated to an appropriate temperature, and a cylindrical pin made of a laminated CFRTP was inserted into the hole on the plates stacked each other so as to align the positions of each hole. By heating the pin through the heated steel plates so as to generate volumetric expansion force against the wall of each hole, we have developed a new joining method of metal pieces with CFRTP pin. Experiments were performed on the new joining method. Moreover shear strength and tensile strength were evaluated. In this evaluation, it was confirmed that there is a relationship between volumetric expansion of CFRTP by heating and joint strength. It was further found that high joint strength was obtained by application of tapered hole on the steel plates.

The purpose of this research was to investigate the effect of ultrasonic needle punching on interlaminar strength and fracture toughness of unidirectional carbon fiber reinforced thermo-plastics. The ultrasonic needle punching process was conducted with four stabbing speeds and three stabbing densities. The results of the interlaminar tensile test showed slight improvement in interlaminar tensile strength when the needle was stabbed at higher speed. In addition, when the direction of the fiber on the bonding surfaces facing each other was the same, the interlaminar tensile strength was improved compared with the case where the fiber directions were different. The results of the double cantilever beam test showed that the Mode I interlaminar fracture toughness improved when the stabbing density was low or the needle was stabbed at high speed. In addition, the amount of load decreasing at the time of crack propagation decreased when the needle was stabbed at high speed.

In recent years, the relationship between the durability and the corrosion of reinforced concrete structures has been discussed as a technical problem. In this study, the evaluation method of concrete's damages is proposed by acoustic emission (AE) energy under a process of compressive fracture. Concrete-core samples were the taken from a canal structure in Hokkaido, Japan, which freeze-thawed damages developed heavily. The samples were tested by the compression test with AE system. Prior to the compression test, micro-cracks of the samples were estimated by helical X-ray CT. Thus, Initial AE energy characteristics depended on the degree of damage. AE energy is an effective parameter for evaluating the degree of damage that is not fully understood by compressive strength. The damage parameter from X-ray CT images was correlated with the dynamic Young's modulus. This result suggests that the damage of concrete can be evaluated by non-destructive inspection method, such as dynamic Young's modulus.

A stent is a small medical device that is used to open the stenosed artery for securing blood flow. Since the stent has higher rigidity than the blood vessel, the stent deployment may induce stress concentration and damage on the vessel wall and may cause restenosis or thrombosis. In order to reduce the risk, it is important to understand the mechanical response occurring in the artery by the stent placement. In the present study, we performed the axisymmetric finite element analysis, in which the stent was modeled as rigid struts while the three-layered coronary artery was modeled according to the mechanical properties reported by Holzapfel et al., and then, the influences of the strut cross-sectional shape, the strut width, and the distance between struts on the deformation and the stress in the artery were investigated. The results revealed that the large stress was generated in the intima in the vicinity of the intima-media interface by the movement of the strut. It was found that the deformation and the maximum stress were more influenced by the distance between the struts than the cross-section shape and the strut width. The findings will be utilized to optimize the strut shape as well as the strut arrangement on designing the stent.

This study proposes a method for computing stresses from measured values of in-plane strains in viscoelastic body under plane stress condition. Since Poisson's ratio depends on time and temperature, it is difficult to calculate stresses from in-plane strains unless Poisson's ratio is treated as a constant. This research focuses on pseudoelasticity in the linear viscoelasticity and the stresses are computed using a numerical Laplace transformation. Since the relation between a through-thickness strain and in-plane strains is expressed in Laplace domain, Poisson's ratio can be treated as time-and temperature-dependence. The Laplace transformation is performed numerically using a fast Fourier transformation. Therefore, the computational nature of FFT affects the process of calculating the stress of the viscoelastic body. Appropriate values can be calculated by increasing the number of input data using the numerical Laplace transformation. The effectiveness of the proposed method is demonstrated by computing stresses from strains. Results show that stresses can be evaluated from in-plane strains even if Poisson's ratio exhibits time-and temperature-dependence.

Diamond-like carbon (DLC) films have excellent properties such as high hardness, wear resistance and low friction coefficient. Therefore, DLC is used for surface treatment in the fields of cutting tools, molds, automobile industry, medical care, nanotechnology, etc. Since the reliability of the DLC films are evaluated by their adhesion to the substrate, a quantitative evaluation method for it is desired. The adhesion can be evaluated by the residual stress of the film, but the optimum nondestructive measurement method for it has not been established. Therefore, we propose a residual stress measurement method using the photoelastic method. This paper describes the method and results for obtaining the photoelastic constant of DLC. In this study, DLC films were formed on a glass substrate by plasma enhanced chemical vapor deposition. Then, from the warpage of the substrate due to the residual stress of DLC, the residual stress was calculated using the Stoney equation. On the other hand, the retardation of the DLC film was measured by the photoelastic experiment. The photoelastic constant of the DLC, 5.13 x 10-11 Pa-1, was obtained from the obtained relation between the residual stress and retardation.

Hollow particles contain a void structure and exhibit unique properties, such as greater thermal and acoustic insulation properties, a lower dielectric constant, and distinct optical properties. Among various hollow particles, those in which the shell material is silica are called hollow silica particles. In this study, we fabricated silica hollow particles by generating microbubbles with an ultrasonic generator. A silica shell was formed at the gas—liquid interface of microbubbles because of hydrolysis and condensation of methyltrimethoxysilane (MTMS), resulting in the formation of hollow silica particles. In addition, we examined the effect of changing the concentration of MTMS vapor in the dry air and the type of carrier gas on the hollow particle formation. As a result, it has been revealed that the adjustment of the MTMS vapor concentration leads to an increase in the yield of hollow silica particles. It has also been shown that the yield of hollow particles is improved by changing the carrier gas to one with low solubility in the liquid.

In this study, tensile tests of single layer and multi-layer specimens were conducted based on Al or MgAg alloy as metal electrode and tris (8-hydroxyquinolinato) aluminum or 4,4'-Bis(N-carbazolyl)-1,1'-biphenyl as lower organic layer and polyethylene naphthalate as substrate with measuring electric resistance change, then the surface and cross section were observed to investigate the occurrence of cracking and the location of delamination, finally the damage phenomenon was discussed. For cross-sectional observation, the specimens were embedded in a resin, cut with a microtome, and observed with a scanning electron microscope. As a result, the following conclusions were obtained. Further, the delamination was observed at the interfaces between the metal electrode layer and the lower organic semiconductor layer in both of the specimens. The cracks were observed in both the metal electrode layer and the lower organic semiconductor layer, but the number of cracks is larger in the electrode layer, and it has been suggested that the metal electrode layers are dominant in crack generation.

We investigated the effects of mechanical milling of the raw powders on the reaction sequence of thermite combustion synthesis (TCS) to produce fluid tri-nickel aluminide. The TCS reaction combines the ordinary combustion synthesis reaction and a modified thermite reaction which is more exothermic than the former reaction. The pre-milled mixture of nickel (Ni) and nickel oxide (NiO) was blended with aluminum powder manually in a mortar. The mixed powder with no NiO agglomerates was cold-pressed into a cylindrical precursor and then preheated to ignite the TCS reaction. The critical ratio of the modified thermite reaction for fluid product formation was 0.20 which was lower than the value (0.23) in the previous study in which all the raw powders were mixed in a mortar. On the other hand, additional mechanical milling of the pre-milled Ni+NiO mixture and aluminum powder suppressed the fluidized product formation. The reaction sequence of the pre-milled Ni+NiO mixture and aluminum powder was well explained by considering two competing mechanisms: reactive diffusion which is to produce relatively large liquid pools and reactive infiltration to produce composite material regions having fine alumina networks which support the shape of the specimen.

Tire cavity resonance is one source of noise inside cars. In the case of a deformed tire, this resonance splits into horizontal and vertical modes around the fundamental mode in the range of 180-280 Hz. The frequency difference between these two modes is derived theoretically using Thompson theory and modeling the tire cavity as a stepped tube. However, theoretical and experimental results do not agree in cases of substantial deformation. In this study, we expand the theory by using a multiple-stepped-tube model. The model geometrical parameters and the difference between the two modes are measured using a multi-microphone system. For the tire conditions of the tire load of 5 kN and the internal pressure of 200 kPa, the result of the expanded theory agrees with the experimental results comparing to other theories.

In this study, a broad band frequency tunable dynamic absorber was designed and fabricated based on the primary design principle of a mass damper. A magneto-rheological elastomer (MRE) that can change the relative stiffness when an external magnetic field is applied was used to control the natural frequency of the movable mass of the absorber. A coil to generate the magnetic field was also used as a movable mass to decrease the total weight and to create a constant closed loop of the magnetic force. The hammer impact test results showed that the present absorber could change its natural frequency and had an almost constant damping ratio. In addition, the natural frequency and damping ratio of the absorber could be changed by adjusting the mixing ratio of materials to prepare MRE. Further, experimental results of vibration absorbing of a flat plate and a vibrating part of the commercial vehicle showed that the vibrational acceleration could be reduced automatically in the frequency range from 50 to 150 Hz with simple techniques to determine the strength of the magnetic field to be applied to the MRE by controlling the electric current applied to the coil.

In this study, an actuator made of polyvinylidene fluoride (PVDF) was designed and fabricated to investigate its effectiveness in the active vibration control of light-weight structures which generally have low internal damping. The actuator was composed of two acrylic films, two film electrodes, and PVDF. PVDF was installed between the two acrylic films, with the film electrodes glued onto both sides of PVDF. The thickness and electrostatic capacity of PVDF were 28 μm and 11 nF, respectively. The length, width, thickness, and weight of the actuator were 171 mm, 22 mm, 40 μm, and 3 g, respectively. The electrodes of the actuator were connected to an AC power supply with a voltage amplifier. AC power was supplied within the frequency range 100-2,000 Hz. Active vibration control was achieved using a simple feed-forward control technique. The results showed that the vibrational acceleration of the vibrating flat plate in the range 2-12 m/s² could be decreased by up to 50% using the actuator as intended in one-frequency vibration control. Further, it also could be decreased by up to 40% using the actuator in two-frequency vibration control.

Magnetic compound fluid (MCF) rubber can be used to construct a self-sensing smart sensor because it has a self- induced voltage that is changed by normal and shear forces. MCF rubber is flexible and elastic, and can thus be incorporated into a wide variety of devices, such as haptic sensors, capacitors, and solar cells. We thus plan to install MCF rubber on a robot to examine a radiation environment such as a nuclear power plant. Here, we conduct a fundamental study of a sensing technique that utilizes MCF rubber in a radiation environment. We clarify the irradiation effect on an MCF rubber sensor at an irradiation facility. The results show that MCF rubber installed on a robot can effectively sense radiation.