Development of a reliable method to determine the "softness" of materials or objects will provide us some meaningful mechanical information. In this study, a novel method of sensing is specifically developed to detect softness of sponge-like soft and cell-like small objects by using dynamic response of piezoelectric vibrator. The bending mode of vibration of a small beam type vibrator is excited by using piezoelectric ceramics. Once the vibrating end of this vibrator is contacted on the soft object, the natural frequency of the vibrator could be changed according to degrees of its dynamic constraints at the end boundary. This frequency change has a certain kind of relationships with the mechanical properties of the object and is considered to give us useful indicator as the softness of that object. In order to demonstrate the capability of this sensing system, experimental studies have been carried out to detect softness of silicone rubber blocks and fertilized living egg cells of killifish.

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Intracellular stress distributions in cultured endothelial cells exposed to fluid shear stress were Studied using finite-element analysis, in which cell surface geometries were measured by atomic force microscopy. After applying shear stress, the endothelial cells showed marked elongation and orientation in the now direction. Finite-element analysis indicated that wan shear stress in the central region around the nucleus was significantly higher than those in the upstream and downstream sides for both control, statically cultured cells, and sheared cells, but the intracellular stress concentrations between the central regions and the other two sides reduced with fluid now. Fluorescent images showed that stress fibers of F-actin bundles were mainly formed in the central portion of the cells. These results indicate that endothelial cells may charlie their cytoskeletal structures to increase their stiffness and reduce stress concentrations in the cells.

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We have developed a method to construct bite element models of the whole thoracic aortas from Tl-weighted MRl images. Intraluminal shape of the aorta perpendicular to its axis was assumed to be circular. We constructed a normal aortic model from a healthy male. Aneurysm models were made by adding a fusiform bulge to the ascending, arch, or descending regions of the normal model. In the analysis, aortic walls were assumed to be linearly elastic and the inner surface were pressurized at the pulse pressure of the subject. In all models, high stress appeared in the inner and lateral regions of the arch where aneurysm is prone to form. Peak stress in the wall was highest in the model with aneurysm at aortic arch. Eccentricity increased the peak stress. Aneurysms at the arch or with eccentricity have higher risk of rupture. Stress analysis may provide important information on aneurysm treatment.

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It is well known that bone has the capability to adapt to a normal mechanical environment and to reconstruct functionally its structure and geometry. This phenomenon is called "adaptive bone remodeling". One of the most important mechanical factors of remodeling is stress. To induce bone remodeling, some stress should be present to stimulate the osteocyte over a relatively long period. Thus, this stress is a type of residual stress. To verify this assumption, it is necessary to measure residual stress in intact bone tissue. Bone has an extremely anisotropic structure which consists of hydroxyapatite crystals. In this work, the polychromatic X-ray diffraction method is used to measure anisotropic residual stress in compact bone. The interplanar spacing of hydroxyapatite in bone Can be measured by this method. The ratio of atomic interplanar distance of a strained specimen to that of a nonstrained one is defined as lattice strain. Biaxial residual stress is calculated from the lattice strains measured in three directions. The compact bone of bovine diaphysis is used as the specimen. To observe the difference of residual stress dependent on the region, the specimen is taken from the middle part of the diaphysis that was divided into four parts : anterior, posterior, medial and lateral, for each bone in the axial and circumferential directions. As a result, it was confirmed that residual stress in the bone could be measured nondestructively by this method. Tensile residual stress was found in the axial direction of bovine femoral bone.

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Total knee replacement changes the shape of articular surfaces and the condition of cruciate ligaments depending on the type of artificial knee joint used. This affects the contact conditions between femur and tibia. In order to evaluate and improve the performance of artificial knee joints, it is necessary to determine the variation of contact conditions to which the components are subjected. In this study, contact conditions during gait were calculated using motion analysis, inverse dynamics and non-linear optimization methods for a two-dimensional lower limb model, and stress analysis of the fixation interfaces of tibial components was performed. Results indicated that differences in the shape of articular surfaces and the condition of cruciate ligaments led to marked differences in the contact conditions and the stress distributions at the interface. It is generally considered that these differences would affect the loosening of the components and the life of the joints.

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The formation of syringomyelia is caused by some mechanical factors. In Chiari type I malformation, it is observed that the flow of cerebrospinal fluid is blocked by a herniated cerebellar tonsil. However, the influence of the blockade by the hernia on the spinal cord is not clarified. In this study, we examine the stress state in the spinal cord when it is deformed in certain bending modes:one state is that caused by a certain load and the other state is that of free vibration. Through numerical examples by FEM (finite element method), we consider the relationship among the impediment in the flaw of cerebrospinal fluid, the stress distribution and the location of syringomyelia.

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The cardiac contractility in human hearts was investigated by analyzing the deformations of the left ventricular myocardial walls during systole using a magnetic resonance tagging technique. Subjects were ten normal humans, eight patients with a hypertrophic cardiomyopathy (HCM) and seven patients with a hypertensive heart disease (HHD). The minimum principal strain, which describes the maximum contraction, was employed as an index for an evaluation of the cardiac contractility. The obtained results showed that the minimum principal strains in local regions of the patients with a HCM were significantly smaller compared with those in corresponding regions of the normal humans, while the minimum principal strains in whole regions of the patients with a HHD were similar to those in corresponding regions of the normal humans. This study suggests that to evaluate the cardiac contractility from a mechanical point of view is useful for a quantitative evaluation of heart diseases.

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An ultra-microindenter was utilized for the evaluation of the local mechanical properties of bone tissue. The tangents of loading and unloading curve, A and D, were adopted as the parameters for the hardness and stiffness, respectively. An anisotropy due to the orientation of collagen fibers between sagittal and transverse planes of rabbit tibia was observed under the loading condition of 19.6 mN. When the indentation load was lowed, fragile properties of the hydroxyapatite could be evaluated. This technique was further used for the rat caudal vertebrae during mechanical adaptation in order to investigate in-plane distribution of the local mechanical property. Decrease of A and increase of 1/D were observed near the periosteum in the cortex, indicating that immature bone was formed and mineralized progressively. Additionally, higher A and lower 1/D under articular cartilage of the loaded rat suggested that the subchondral bone stiffened for it to adapt to the mechanical stimulation.

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This paper is concerned with the formulation of a mathematical model to describe mechanical bone remodeling process. Firstly, mechanical stimulus is defined as a function of the rate-of-deformation power per unit mass. Physiological signal transmission processes of remodeling from the mechanical stimulus to change of bone density are described by n+1 sequential evolution equations with n+1 macroscopic internal state variables. The evolution equations are established on the basis of the experimental results in a literature. The value of the internal variable in the last step specifies the balance level of bone density, which is the target of the current bone density. The comparison of the predicted results with the corresponding experimental ones shows that this model can quantitatively describe a time-dependent process of bone remodeling.

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As a model of the now through the coronary artery, the laminar flow through a two-dimensional channel that oscillates toward a transverse direction has been studied numerically. In this calculation, the moving boundary problem was transformed into the fixed boundary problem using the coordinate transformation method, and the fully implicit bite difference method was used to solve the mass and momentum conservation equations. The calculated results are summarized as follows. (i) The particle trap extended over a long time is not generated by the transverse oscillation of the channel. (ii) The transverse oscillation of the channel has an effect of Battening the distribution of shear rate in the downstream side of the oscillating region. (iii) This numerical calculation method is effective to understand the now pattern through the oscillating channel.

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The application of the dynamics in organisms to the field of engineering is very instructive. We noted the utility of eukaryotic flagellar motion for the propulsion of micromachines in liquid, and proposed a micropropulsion mechanism modeled on the active Sliding of microtubules in eukaryotic flagella. The bending movement and the thrust force of the mechanism were simulated. For the modeling in the simulation, we took account of the elasticity of the micropropulsion mechanism. The influences of elasticity, maximum sliding length and viscosity of liquid on the bending movement and the thrust force were discussed.

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This paper describes the improvement of accuracy for prediction of index of hemolysis in shear blood flow by computational fluid dynamics(CFD) with modiaed turbulence model, applying to orifice-pipe blood now, which is simple model of turbulent shear stress induced hemolysis in the high speed rotary blood pump. Using CFD with partially patched modified κ-ε model (Launder-Kato partially patched model;LK-Zonal), results of the now field in the orifice-pipe flow are compared with standard low Reynolds number κ-ε model at whole region (STD), and it is found that the shear stress by LK-Zonal model is predicted more precisely than that by STD model near the impinging flow region. As for hemolysis, from the computational data of orifice-pipe now, the index of hemolysis is estimated in the same way as our previous paper⁽1), and it is found that the accuracy for prediction of index of hemolysis is also improved using LK-Zonal model in comparison with STD model, particularly in case of the orificel pipe now with large and long contracted part. From these results, the design method using CFD for the rotary blood pumps, that have impinging flow region to the wall, for suppressing the hemolysis can be proposed.

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Recent research has shown that the centerline of the human aortic arch does not lie in a plane, but has a three-dimensional (3-D) distortion. This distortion is thought to be a risk factor in the development of aneurysms. In the present study, the aorta was numerically modeled using a computational fluid dynamics method. The flow geometry consisted of a circular tube with a centerline approximated by an ordinary helix. A region with a high component of longitudinal wall shear stress was found distributed along the direction of the torsion. The localizadon of the wad shear stress distribution is due to complex centrifugal forces, and is discussed with respect to the development of vascular diseases including aneurysms and atherosclerosis.

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Tensile properties of rat aortic smooth muscle cells (RASMs) freshly isolated by enzymatic digestion were obtained under a physiological salt solution at 37°C and compared with those of cultured bovine aortic smooth muscle cells (BASMs, P6-7). Overall elastic modulus of RASMs and BASMs were 9.3±2.8 kPa (mean±SEM, n=8) and 1.5±0.2 kPa (n=6), respectively under the strain rate of 0.2-4%/s. Due to the difference in the cell preparation method, RASMs and BASMs are considered to show contractile and synthetic phenotype, respectively. Contractile cells are much more abundant in myofilaments than synthetic cells. Myofilament bundles may be stiffer than other cellular components and extends throughout the cytoplasm. Contractile cells may thus be stiffer than synthetic cells. The difference in the mechanical properties of these cells may be due to the difference in the phenotype of the two cell specimens.

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The swimming motion of a bacterium model consisting of a spherical cell body and a rotating helical flagellum is discussed. In order to calculate the speed and efficiency, we adopt the slender body theory (SBT) developed by Higdon. The effect of flagellar dimensions on the swimming motion is elucidated. The results are compared with those of the boundary element method (BEM), which is expected to provide more accurate results. The agreement is excellent, and the computational time of the SBT is about 1/400 of the time of the BEM. From the viewpoint of fluid dynamics, the optimal flagella for speed and effciency are both illustrated. The difference between the two shapes is apparent in the radius of the flagellar helix. The reason for this is explained taking into account the roles of the force and torque produced by the flagellar motion. In addition, the two flagella are compared to the flagellum in the real world. The bacterial flagellum resembles in shape the most efficient flagellum rather than the fastest one.

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In this study, an experiment was performed to investigate the dynamic character. istics of flow in a collapsible tube. The effect of initial axial strain of the tube on selfexcited oscillation was studied by changing the initial stretch of a silicone rubber tube at various values of the Row rate. The frequency of oscillation and the time-dependent pressure and flow rate were measured at the upstream and the downstream location of the tube. The characteristics of the self-excited oscillation were strongly affected by the initial strain in a range of smaller flow rate and smaller initial tube stretch. Three different types of oscillation were observed in the present condition. The type of oscillation changes due to variation of the initial axial strain or the supply now rate.

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By using the tube law, which describes the relationship between the cross-sectional area of a collapsible tube and the transmural pressure, which is the difference between inside pressure and outside pressure, a coupled problem between flow in the tube and wall deformation is formulated. In this paper, a numerical method for calculating two-dimensional deformation of the tube is presented and the results are compared with experimental results. The calculation results are compared with those of Ref. (6) to show the validity of our calculation method in which tube wall thickness is taken into account in determining the contact behavior of the tube wall. In the experiment, we use a silicone rubber tube as the collapsible tube. The tube's cross-sectional shape is visualized by using the laser light sheet method. It is shown experimentally that the tube law calculated by dividing the inner volume of the tube by its length has a large error in the wall contact region. In the calculation in Ref.(6), tube wall thickness is not treated rigorously in the wall contact region. However, according to our results, the effect of wall thickness on the tube law is not negligible in the wall contact region.

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This paper describes detailed wing morphology of some kinds of insects. The structural properties of dragonfly, fly, and mosquito wings were studied. Microscopic observations on the insect wings were examined with a scanning electron microscope. The surface roughness of the insect wings was measured by a three-dimensional, optical shape measuring system. The roughness distribution on the wing surface was presented for some kinds of insects. Some functional principles underlying insect wing design were revealed by the measurements of surface roughness and microscopic observations.

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Tactile wear (or "tezure" in Japanese) is the phenomenon generated by the touch of the human hand and skin over a period of one to several hundreds of years. Tactile wear can be observed in objects of daily use, but particularly in statues of Buddha that are frequently touched by people. The phenomenon of tactile wear was not discussed in the recent tribology conference, though human hand and friction coefficients between various materials were measured and have been recently reported. However, to our knowledge, there has been no research on the wear phenomenon and friction coeffcient. Some examples of tactile wear on wood, metal, and stone are presented in this study. In the example of the 286-year-old Buddha statue (Pindola Bharadvaja in Sinsyu-Zenkoji), the wear volume of the nose is 15 cm³, and the wear rate is of 10^-8 (mm²/N) order. In addition, we also describe a simple experiment that can verify tactile wear phenomenon.

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An on-line learning based EMG to motion classifier can manage learning data set by manual appending and automatic elimination compared with conventional off-line learning based classifiers. It is designed to track the alteration of an operator's characteristics through time. The automatic elimination is based on the continuity of human motion. Moreover, in this study we quantify the attainment of motor skin using the classifier. By classifying up to eight forearm motions from two channels of EMG, we investigate the effectiveness of the automatic elimination process, the validity of the attainment of motor skill by seven trials on an unskilled subject, as well as the relationship among the number of electrodes, the classification performance, and the subject's motor skill. Results show that the proposed approaches can simplify decision boundaries, the attainment of motor skill can be used for judging completion of the training by external observers, and bottlenecks in this classifier can be detected.

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We aimed for permanently supplying the electrical energy to an apparatus for in vivo use such as a cardiac pacemaker and proposed and developed an electrostatic (ES) generator that harnesses the motion of the living body. The generating system consists of a battery as an initial charge supply (ICS), a variable capacitor (VC) ill which mechanical energy is converted to electrical energy, a capacitor for energy storage and two rectifiers. In this study, an ES generator which does not consume electrical energy of the lCS was used. Since high frequency driving of the VC leads to large power generation, it is effective to introduce a resonant phenomenon. A honeycomb-type variable capacitor whose capacitance varies from approximately 32 to 200 [nF] was used as the VC. The resonator (resonant frequency 4.76 [Hz]) which consists of a honeycomb-type VC, tension coil springs and mass was made. It was possible to generate electrical power of 58 [μW] in case of the ICS with constant voltage of 24 [V] and a load with resistance of 1.0 [MΩ]. We found that use of resonant phenomenon was effective to increase generated power.

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There are many kinds of action plants like Mimosa pudica in the world. It is very interesting and important to investigate the mechanism of their motion with the viewpoint to develop a new micro-machine or to use them as bio-machines. In this paper we have investigated the mechanism of the main pulvinus movement of Mimosa pudica by measuring in detail the torque generated during the deflection of the pulvinus. After a petiole was attached to a load cell to measure the deflecting torque, a thermal stimulation was given by ice. The experiments were carried out under controlled illumination. Furthermore a new model of the deflection has been proposed using the concept of ion channel and ion pump.

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In this paper we describe the distributed controls for an ultra-multilink bending propulsion mechanism in water. Functions of the neural oscillator of an organism were programmed into each unit that consists of a controller and an actuator. The bending movement was generated by the cooperation of each unit. As an experiment of robustness, we assumed the case of a locked joint (no rotation). The bending movement was recovered using the cooperation of other joints. We discussed the influence of movement of the mechanism on thrust force.

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This paper presents a phase plane analysis of the motion of the CG (center of gravity) of the human body during the sit-to-stand movement. The time history of the joint angles of the ankle, knee and hip were measured by optical position sensors during the motion. The experimental data when combined with human morphology, such as mass and length of each part of the body, allows the tracking of the CG position. Experiments were done on four healthy young men. Analysis shows that the motion of the CG can be clearly recognized as three motion modes:an acceleration mode and two convergent modes to an origin of the phase plane and to an equilibrium state of the standing state. Furthermore, it is suggested that the elderly usually use a spiral trajectory to the equilibrium state in the sit-to-stand movement, which is observed when a system is close to an unstable state.

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Magnetic bearings have been widely used to support rotors without physical contact. Since a power motor has a configuration similar to that of the magnetic bearing, a self-bearing motor is investigated in this study, which has functions of both a rotary motor and a magnetic bearing. In this paper we introduce an application of this selfbearing motor to an artificial blood pump. The thin Permanent Magnet(PM)-type self-bearing motor has the capability of controlling x and y directions and of giving a rotating torque actively. Other three degrees of freedom are passively stable. In this study, electromagnetic field analysis is applied to clarify the passive stability problem of the PM rotor using the bite element method. An experimental setup is made and tested to confirm the applicability of the proposed thin PM-type self-bearing motor. The results show a high feasibility of using this motor in the fabrication of a nonpulsatile-type artificial heart.

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We are developing basic technology for a walking-support system. As part of this technology, we have determined the best support-arm path for assisted standing-up and sitting-down motion of an elderly person who can sit but cannot stand up. We developed a program for analyzing the load acting on lower-limb joints during the motion. Experimentally measured joint positions and floor-reaction force enabled us to calculate joint torque during motion along several paths by using the Newton-Euler formulation. And we evaluated the supporting performance of the paths of a machine arm. These calculations indicate that a linear interpolating path minimizes the necessary joint torque for assisting standing-up or sitting-down motion. A sensory evaluation test showed that users tend to feel comfortable when the path shape is similar to that of unassisted motion and when hip trajectory is smooth.

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This paper describes a new structurally-motivated phenomenological approach. Such assumption was made that the ACL can be idealized as being composed of a homogeneous matrix in which two non-interacting families of densely distributed extensible fibers are embedded. Then a constitutive equation for the ACL composite was formulated. Using the finite element method, the visual simulations were performed in terms of three-dimensional change in shape, stress distribution and intraligaments' stresses, as a function of knee angle. Variations in stress due to tibial anterior-posterior displacements were also introduced. All the results were compared and discussed with the previous studies, thereby verifying the validity and usefulness of our model.

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The development of machines for assisting the elderly society during walking is becoming increasingly important these days. Some assisting machines of a cart type have been developed. However, it has not been clarified how the machines an effect the generated muscle tensions and energy consumption of human users. In this study, we have evaluated human walk using a cart developed for this research. We have estimated the energy consumption based on the musculo-skeletal model. It is shown that the energy consumption using the cart decreased by 15% from that of the normal gait. Our evaluation method will be useful for developing practical assisting machines for walking.

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