The middle ear transmits sound signals from the external auditory meatus to the cochlea through the mechanical linkage of the tympanic membrane and the ossicular chain. However, the dynamic behavior of the middle ear has not been well analyzed. Therefore, in order to clarify its dynamic behavior, the velocity amplitudes of the tympanic membrane and ossicles of guinea pigs are measured before and after the manipulation of the middle and inner ear using a laser doppler vibrometer coupled to a compound microscope.

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A few investigations of the applicability of the finite-element method (FEM) to middle car analysis have already been reported. However, in the models used in these studies, the effects of ossicles, external auditory meatus and middle ear cavities on the dynamic behavior of the middle ear have been neglected. In this study, first, a three-dimensional FEM model of human auditory periphery was established by applying a FEM program devoloped by US. Then, vibration patterns of the tympanic membrane and ossicles at several frequencies were obtained, and the effects of middle ear cavities on the middle ear dynamic behavior were analyzed. The following conclusions were drawn. (1) The tympanic membrane vibration pattern is relatively simple at low frequencies. However, it becomes more complex at about 4 kHz. (2) The axis of rotation of the ossicular chain shifts to the upper part of the ossicles with increasing frequency. (3) The middle ear cavities suppress the tympanic membrane displacement at low frequencieS.

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We have developed a cardiovascular system to analyze the origin of Korotkoff sounds. Using the cardiovascular system, the sound field of an artificial blood vessel (silicone tube) was measured under normal vascular conditions of blood pressure and flow. We determined that the sounds emanating from the vessel wall were due to turbulent flow and shock wave. Furthermore, considering the tube law of an artery occluded by a cuff, it is clear that a shock wave could not occur at or in the vicinity of the measuring point of systolic pressure. Consequently, this shows that in the area of the measuring point, the eddy caused by turbulence induces the sounds. On the other hand, the sounds near the diastolic pressure measuring point are concluded to be caused by a shock wave. These two points were investigated experimentally through the measurement of arterial pressure using the cadiovascular system. Our experimental studies produced results which were in agreement with theoretical assumptions and clinical experiments. It was found that (1) the times required for Korotkoff sounds to occur changed in accordance with gradual decrease in cuff pressure, (2) the Korotkoff sounds during Swan I to II had a lower frequency than that detected during Swan II to III; the two sounds were different. After that point, the sounds exhibited a single spectral peak whose frequency was higher than that before, (3) the point of appearance of the shock wave was largely influenced by the silicone tube and the blood flow in the artery. Therefore it should be possible to estimate the change in these parameters from detection of Korotkoff sounds.

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The local velocity field in a self-excited oscillating flow through a collapsible tube has been precisely measured using a fiber optic laser Doppler velocimeter. Velocity distributions along the tube axis and across the tube cross section were measured. Time-varying flow rate at downstream end of the tube and pressure drop in the tube were also measured simultaneously. The following results were obtained: In the vicinity of the most strongly collapsed portion fluid is pushed to the downstream and upstream sides and then sucked back into the distending portion as the tube wall collapses and then recovers during the oscillation, and therefore superposition of this back-and-forth fluid motion to the gently varying flow gives rise to a sharp dent at the peak of the velocity waveform at upstream and a very sharp peak of the velocity waveform at downstream. Sufficiently far upstream from the collapsed portion, flow velocity is not influenced by the wall motion.

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The purpose of this experiment is to clarify the mechanism of drag reduction in the natural swimming of fish, whales and dolphins. It is well known that the change in their shape and the local deformation of their skin contribute to drag reduction, especially in the case of dolphins. Therefore, in order to understand the interaction between a deformable surface and the local flow pattern, RFFRC (rigid front flexible rear cylinder) models of a simplified marine animal were studied in a water tunnel. The laser light sheet method was used to visualize the flow field around the models. The vortex pair shedding period from the models, the deformation of the models' cross-sectional form and models' drag were measured simultaneously. The following results were obtained. For some types of RFFRC which could be deformed easily in response to a change in the local flow pattern with vortex shedding, the increase in flow velocity in the wake was observed. In the case the St number was about 20% higher than that of a rigid cylinder. Although, the drag that some types of RFFRC had was higher than that of the rigid one. However, the other types of RFFRC which could not quickly deform show no difference in St number, whereas the mean drag of this type was about 20% lower and the time variation of the drag became smaller than that of the rigid cylinder.

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Artificial valves are used in most artificial hearts to pump up blood against high aortic pressure. However, they cause serious damage to blood by inducing hemolysis and thrombus formation. To solve these problems, we have devised a prototype model of a valveless blood pump which can produce pulsatile flow by periodically compressing from one end to the other a lunar-shaped polyurethane-made blood chamber with an oscillating disk. The pumping characteristics of the blood pump were studied by setting up a mock circulatory system. It was found that the pump could generate flow and pressure waves which were similar to those generated by a natural heart in vivo. The amount of hemolysis caused by this blood pump was comparable to that caused by an ordinary roller pump and a centrifugal pump. These results indicate that the new apparatus could serve as a blood pump in clinical practice.

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High-frequency oscillation (HFO) is an artificial respiratory system based on small tidal volume and high frequency. Axial gas dispersion in an oscillatory flow occurs due to the interaction between radial mixing and radially nonuniform axial velocity profile. Furthermore, the dispersion can be improved by intermittent oscillatory flow. Most previous studies employ the insulating trachea wall model. However, an actual airway wall has conductivity and absorptivity of flowing gaS. In the present study, numerical simulation of CO₂ gas transport in an oscillatory flow through an infinitely long straight airway was carried out to reveal the effect of wall conductivity on axial CO₂ gas transport in oscillatory flow. The ratio of resultant effective diffusivity to the effective diffusivity of the insulating wall was markedly enhanced if β<1, due to the gas exchange on the wall. The maximum ratio was more than 200 in this computation. Furthermore, by employing intermittent oscillatory flow, CO₂ gas transport resistance was improved in all airway regions, because of radial diffusion during stationary period in thick airways and wall gas exchange in thin airways.

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To simulate heavy voice, we propose a new two-dimensional vocal cord model. The vocal cord model is composed of distributed springs and dampers covered with a massive elastic membrane. To simulate the effect of three-dimensional collision of the vocal cords using the two-dimensional model, we introduce two threshold values for the width between the two-dimensional vocal cords at which viscoelasticity changes. The two values divide the state of the three-dimensional vocal cord motion into three, i.e., the vocal cords are separated, contact partially, or contact completely. The vocal cord model is coupled with the fluid dynamic force based on the one-dimensional unsteady separable and reattachable flow theory which we previously presented. The numerical results show that the spectra of the sound pressure of heavy voice have high frequency components because of the inclusion of the high frequency components of the source sound which are induced by the collision of the vocal cords.

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Considering the human upper limb from the viewpoint of mechanics, every degree of freedom of motion is actuated and controlled by more than two muscles. In this paper we describe a method of numerical analysis of muscle force in a human upper limb during pronation-supination of the forearm joint. Because no muscle force can be calculated from only the equilibrium equations of force moment, the optimization method using Lagrange multipliers, which was proposed by Raikova, was applied to this analysis. Muscles were modeled by a straight line from the origin to the insertion. The analytical results were mostly affected by musculoskeletal geometry, in particular, the results for the short muscles of the forearm exhibited such an effect. Therefore, the muscle paths were determined by using a plastic three-dimensional human upper limb prototype. Parameters in the object function of the optimization method were selected to express the muscle properties acting only in the direction of the contraction. Therefore, the synergist and the antagonist could be separated analytically. The results obtained from this analysis were confirmed by experiments using electromyography.

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Not only handicapped people, but also elderly people living in Hokkaido, the northern most island in Japan, desire to participate in outdoor activities during the winter season which is characterized by heavy snow and low temperatures. Most of these people are required to venture outdoors to go shopping or to hospitals, even under severe conditions. Wheelchairs are generally used for outdoor transport. There are, however, many problems with wheelchair use during the winter; roads covered by snow and ice are very slippery, casters are easily buried in the snow, and handrims are too cold to handle. Therefore, wheelchair appropriate for outdoor use during the winter season is strongly desired. We have developed an electric wheelchair with front-wheel drive which will be effective for outdoor use during winter. In this work, three types of wheelchairs with electric motors (of front-wheel drive, rear-wheel drive with free casters and rear-wheel drive with mechanically controlled casters) were tested for the driving ability on iced roads, snow-covered roads, and on indoor floors. In addition, computer simulations were carried out for driving under snowy conditions for these three types of wheelchairs with electric motors.

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We discuss the incidence of consciousness disturbance, by converting the centripetal theory proposed by Ommaya and Gennarelli (1974) into a circular mechanical model, and comparing it with the finite element model. The centripetal theory assumes that the consciousness disturbance becomes more severe as the sequential disruption of a nerve track caused by a given shear strain becomes deeper from the periphery of the brain to the diencephalon and to the mesencephalon. By assuming that the sagittal section of the brain is circular in the mechanical model, it is possible to that the angular acceleration of the brain is a cause of traumatic unconsciousness. However, a finite element brain model has been used to reproduce the shape of a brain more precisely, since the shape of a brain is not circular. The concentration of shear stress is analyzed, where both rotational and translational impacts are applied to the model. As a result, the stress concentration is found to occur on the rostral brain stem acting as the mesencephalon, as well as on the surface of the brain, where a rotational impact is applied. This does not agree with the mechanical model representing the stress gradient from the periphery of the brain to the core of the brain. It is thus clarified that the type of impact - whether it is rotational or translational - is not related to the stress concentration in the core of the brain, as the stress concentration occurs in both rotational and translational impacts, according to the results of the analysis performed with the finite element model. It is well known among those engaged in impact biomechanics and/or neurosurgery that the angular acceleration contributes to the consciousness disturbance caused by an impact loading, and such a disturbance occurs as a result of an extensive injury of the cerebrum. The results of analysis of the impact shear stress concentration by means of the finite element model have reproduced the conditions under which the brain stem region in the core of the brain was injured primarily by external forces of rotational and translational impacts. According to the medical information that brain stem reticular formation and the ascending projectional system play important roles in maintaining consciousness, it can be deduced that the disturbance of consciousness under a given impact loading is caused by the concentration of shear stress at the core of the brain consisting of the brain stem and the diencephalon, which is caused by the complex head structure.

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Elucidation of the vibration mechanism of winged insect from the viewpoint of bionic design might aid in development and design of the driving systems for small- or micro-size actuators, because some flying insects easily overcome scale effects through use of wing vibration and achieve flight with high robustness and speed under conditions of large air viscosity. The aim of this report is to describe a theoretical model of the dynamics of relatively large-size insect wings powered by the direct-flight-muscle and of the dynamics of small-size insect wings powered by the indirect-flight-muscle. Based on morphological consideration of these two types of insect wing dynamics, the equations of motion for the wings are formulated. In the model, the dry friction-type and van der Pol-type forces are employed to power the wings of direct-flight-muscle-type insects, and the periodic impulsive force is assumed to power the wings of indirect-flight-muscle-type insects. Applying the equations of motion to the wings of insects such as dragonflies and flies, the wing vibration is analyzed under various conditions. From the numerical results, the vibration mechanism of two types of flying insects' wings is clarified.

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Although the amplitude of tympanic membrane vibrations is only a few nanometers when we speak in a low voice, we can understand clearly what is being said. This is speculated to be due to the cochlear amplification which is based on outer hair cell (OHC) motility. However, the mechanism of OHC motility in the cochlea is unclear. In order to understand this mechanism, motility of an isolated OHC in response to step voltage stimuli is measured using a high-speed video system. Results indicate that the generation force of the short OHC taken from the basal region of the cochlea was larger than that of the long OHC taken from its apical region.

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The application of dynamics in organisms to the field of engineering is very instructive. To make an artificial micro propulsion mechanism in liquid, a simulation study of a propulsion mechanism, modeled on the sliding mechanism of microtubules in flagella was carried out. In the simulation, a bending wave was formed by three regions of sliding condition between two microtubules. Both the movement and the thrust force of the propulsion mechanism were calculated. The characteristics of thrust force with change in microtubule distance and sliding length were discussed.

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The spontaneous alignment of arterial endothelial cells under flow conditions was simulated using a three dimensional computational fluid mechanical model of cultured endothelial cells. Endothelial cells were simulated using a 2D Gaussian distribution function. The nearly round model cells were randomly placed on a flat plate with random orientation. Navier-Stokes equations of a Newtonian fluid were solved using a finite volume method, and the absolute wall shear stress (WSS) at the summit of cells was calculated. Model cells were assumed to change their shape and orientation randomly and only the deformation of cells, which reduces the WSS, was assumed to be conserved under steady flow conditions. The model cells eventually demonstrated alignment during the simulation, which closely resembled that of real cells. This deformation and alignment was thought to simulate the flow induced self reorganization of the endothelial cells observed in vivo.

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The viscous property of synovial fluids and sodium hyaluronate (HA) solutions with and without proteins was measured by a cone/plate viscometer. The influences of molecular weight and concentration of HA, solvents and addition of proteins on viscosity were examined. It was shown that at low shear rates, the higher the molecular weight and concentration of HA are, the higher the viscosity of HA solution is. It is noted that addition of albumin alone to HA solution decreases the viscosity, which is subsequently returned to the original level by the addition of γ-globulin. Next, the effect of lubricant viscosity on frictional behavior in natural synovial joints was investigated by pendulum tests of pig shoulder joints under both high- and low-load conditions, The dependence of friction on viscosity, which was changed by HA concentration or addition of proteins, was clearly demonstrated under the low-load condition.

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During walking motion, the tibial axis load and flexion-extension patterns in the knee joint are complex and these patterns may contribute to the formation of lubricating film. In order to evaluate tribological behavior of knee prostheses, the load and motion patterns were approximated using combinations of sinusoidal curves. The frictional behavior and lubricating film formation were examined under cyclic load and velocity conditions in a knee joint simulator. Fluid film formation in knee prostheses composed of metallic fernoral and conductive silicone rubber tibial components was examined using the electric resistance method. The tribological severity was evaluated using the friction coefficient and degree of separation. The importance of the walking pattern in fluid film formation was demonstrated.

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Increased friction in animal joints with duration under compressire load was measured using a robotic system. Force control of a robotic arm was used to survey the geometry of a sliding surface. Compressive load of 10 N was added between the femoral condyle and the tibial plateau at a flat and horizontal point before friction started. Six canine stifles were used. The starting frictional coefficient was 0.006 S.D. 0.003 immediately after loading. This value increased to 0.183 S.D. 0.054 after 1800 s under load. Furthermore, the friction between the femoral condyle and the glass plate increased in a similar manner. We concluded that the ploughing effect was slight in friction occurring in animal joints.

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The antagonistic pairs of mono- and bi-articular muscles of the upper extremity demonstrated perfectly coordinated muscular functions during arm push and pull movements with maximal effort in all round directions (360°) in the horizontal plane, which has been already observed in the sagittal plane through our experiments. Analysis of a proposed neural network suggested that the tightly coordinated functional patterns could be induced using only force direction information via the spinal level, and also that the tight coordination can be applied in mechanical engineering and robotics.

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To investigate mechanical remodeling of cancellous bone from the viewpoint of trabecular surface remodeling due to trabecular level mechanical stimuli, first, a rate equation for trabecular surface remodeling is proposed based on the uniform stress hypothesis, which suggests that the nonuniformity of the local stress distribution on the trabecular surface is the driving force for remodeling. The proposed local rate equation for trabecular surface remodeling is applied to a computational simulation of morphological changes, in which the trabeculae are modeled as an assemblage of two-dimensional boxel elements and their morphological changes are simulated by removal/addition of the elements from/to the trabecular surface. The basic features of the proposed rate equation and simulation method are investigated through the remodeling simulations applied to the basic trabecular element, cancellous bone structure and the proximal femur. In all cases, the trabecular orientation, thickness, and connectivity are adapted to the mechanical environment, which demonstrates the capability of the proposed rate equation for computational prediction of the adaptation phenomenon and supports the hypothesis regarding the optimality of trabecular architecture as a mechanical load bearing structure.

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Hydroxyapatite (HAp) is one of the most effective biomaterials used in artificial bone and dental design implant. It is important to investigate in detail the mechanical characteristics of HAp for the improvement of mechanical reliability of those. HAp implant is usually made by sintering HAp powder. In general, it has been considered that the thermal stress caused by heating and cooling processes in sintering disappears and does not remain in the material, because such sintered material does not reach an actual density of 100% which is the perfectly solid state. However, if residual stress occurs in sintering, it will exert a profound influence on the mechanical strength and biocompatibility of HAp implant in vivo. Therefore, we present a method for measuring residual stress in sintered HAp using polychromatic X-rays, and investigate the effect of preforming pressure, sintering temperature and sintering pressure on the residual stress. As a result, large tensile residual stress on the surface of implant and steep stress gradient were confirmed by this method, and the relationship between the magnitude of residual stress and several conditions of HAp sintering was clarified.

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Neck injury by rear-end collision occurs frequently in automobile accidents, yet its pathomechanical process has not been investigated. For the purpose of developing a better seat and head restraint to reduce whiplash injuries in rear-end collisions, we performed impact analyses using finite element models of the human head and neck, and a new neck model in rear-end collisions. A pseudo 3D FEM model using a rear-end collision of 5.7 km/h was prepared. The FEM results showed a higher tensile stress localized in anterior longitudinal ligaments during impact. Compressire stresses localized in soft tissues, reached its maximum value at 140 ms after collision. We also compared the results displacements of head relative to chest with and without headrestraint and head angles on sled test of the new neck model, the dummy and volunteer. It is clear that the new neck model in rear-end collision behaves closer to that of human neck than the conventional dummy neck.

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Two-dimensional deformation of human left ventricles (Subjects were four normal volunteers and a patient with hypertrophic obstructive cardiomyopathy) during the ejection period was investigated using MRI with the tagging technique. The regional displacements and strains in the myocardial wall were analyzed from the motions of intersections of tagging stripes formed in the short-axis images. The results for normal volunteers showed that the magnitudes of displacement differed among regions (anterior, septal, posterior and lateral) of the left ventricle, but the magnitudes and the directions of the minimum principal strain were almost uniform over all regions. The magnitude of the minimum principal strain (cardiac contractility) in the anterior wall of the patient with hypertrophic obstructive cardiomyopathy clearly decreased compared with that of normal volunteers.

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A three-dimensional transversely isotropic constitutive model of cardiac muscle is formulated by taking account of the mechanism of excitation-contraction coupling. For this purpose, stress in cardiac muscle is assumed to be the sum of passive and active parts. The passive part is represented by a nonlinear elastic material expressed by a strain energy density function of exponential type. The active part, on the other hand, is modeled by a series of evolution equations that represents the process of excitation-contraction coupling. Comparison of simulation results with experimental results in the literature shows that this model can describe the behavior of isotonic contraction as well as isometric contraction. The model can also represent inotropic effects because it includes the evolution equations describing the change in the concentration of intracellular calcium ions. The model can be incorporated into finite element codes in order to simulate a left ventricle.

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Changes in the morphology and mechanical properties of the patellar tendon with maturation were studied in rabbits aged 1, 2, and 6 months. The length, cross-sectional area, tensile strength, and tangent modulus of the tendon significantly increased with age. The rate of increase in the maximum load which was estimated by multiplying tensile strength by the cross-sectional area was similar to that in body weight. Tension in the patellar tendon was measured in vivo with a buckle transducer. The rate of age-related increase in the peak tension measured during normal locomotion was almost equal to that in body weight. These results indicate that the pateliar tendon responds well to increases of in vivo tension which occurs as part of the maturation process and exhibits corresponding increases in mechanical strength.

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Ankle foot orthosis (AFO) assists the gait motion of persons with disability such as of hemiplegia, and the biomechanical function is the primary concern of AFO. In conventional prescription of AFO, the attention has been mainly focused on the ankle joint support at a secure position against the stumbling due to toe contact with floor during the swing phase of gait cycle, but little attention has been paid for its function during the stance phase. In this study, the mechanical characteristics of shoehorn-type AFO is examined in the context of the gait motion analysis during the stance phase of normal subjects, and by experimental analysis of the ankle joint stiffness in sagittal plane on a universal testing machine. Deformation of AFO is characterized by the relative angle between the shank and foot planes, and it is found that the stiffness of AFO depends strongly on the foot angle. The joint moment during the stance phase is evaluated for slow-speed gait with and without AFO. It is found that the knee extension moment of the gait with AFO is significantly larger than that without AFO. It is expected that the ankle joint constraint imposed by AFO results in a gait pattern different from the normal, although the resisting moment of AFO is not so significant in the joint moment.

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The vascular endothelial cell vesicles are attached to both luminal and abluminal surfaces of the endothelium and contribute to the transport of specific macromolecules between the exterior environment and the cell. The vesicles mostly have flask-like or chained bead-like shapes, while they appear free within the cytoplasm and are essentially spherical. The existence of transendothelial channel, which is considered to be involved in specific transportation system, is also reported. In this study, generation mechanism of vascular endothelial chained vesicles and transendothelial channel is theoretically investigated based on a method proposed by J. C. Luke (1982). A system of nonlinear differential equations is derived according to the variational principle and is reduced to a two point boundary value problem. The equations are solved through the shooting method along with Newton-Raphson and Runge-Kutta method. The computed shape of the vesicle suggests that the chained vesicles and the cylindrical transendothelial channel are the most dynamically stable shape which can be formed in the vascular endothelial cell.

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The purpose of this study is to investigate a method of thawing a milliscale biological cell used for cryopreservation. The rewarming system was equipped with a heater and copper block immersed in liquid nitrogen (-196°C), and regulated the warming rate of the test section from 0.1 to 100°C/min over the temperature range -196 to 0°C. A killifish embryo was placed at the tip of the test section (a truncated cone) with a drop of 15% dimethylsulfoxide-water and cooled to -196°C. To avoid recrystallization, it was rewarmed at a rate of 100°C/min to -7°C and at various rates from -7 to 6°C. After thawing, the morphology of the embryo was observed. As a result, a warming rate of 0.3°C/min was found to be optimum for morphological preservation. The warming rate should be rapid up to the extracellular melting point and slow during thawing.

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The morphological responses of cultured bovine aortic endothelial cells to fluid-imposed shear stress under sparse and colony conditions were studied. Applied shear stress was controlled to 2 Pa and the exposure time was set to be between 1 and 24 hours. Before and after flow exposure, the shape index and the angle of cell orientation to flow direction of each individual cell were measured. In the experiment under sparse conditions, the shape index was 0.33±0.13 (mean±SD) and cells almost randomly distributed under the no-flow condition. This randomness continued following application of shear stress for 24 hours, and a morphological difference between the cells under no-flow conditions and after exposure to shear stress was not observed. In the experiment under colony conditions, the ceils in the center portion of the colony were round and were randomly oriented under no-flow conditions. After exposure to shear stress for 24 hours, the cells in the center portion were elongated and aligned with the flow direction, although the cells on the periphery were randomly oriented. From these results, we conclude that the degree of cell to cell contact may affect the morphological response of endothelial cells to fluid-imposed shear stress.

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The permeability and endothelial cell morphology in rat aortae were measured. FITC-albumin was used as a tracer. The permeability was measured on the lateral side of ascending (immediately before brachiocephalic artery, A), descending (immediately after left subclavian artery, C) and thoracic segments, and on the medial side of ascending (B), descending (D) and thoracic segments. Endothelial cell morphology was observed in the same portions in which the permeability was measured. The permeabilities in A and B were higher than those of the descending and thoracic segments. The cell morphology in A and B was almost the same as in the other portions. However, the deviation values of the cell orientation to the axis of the blood vessel in A and B were higher than those of the other portions. These results indicate that endothelial cells in the ascending aorta reflect a complex blood flow pattern and that the permeable function of endothelial cells is affected by the complex blood flow.

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The effect of smooth muscle contraction on strain distribution in the arterial wall was investigated. The opening angle of short, ring-shaped specimens obtained at various longitudinal positions of rat thoracic aortas was measured in an aerated Krebs-Ringer solution (37°C) under smooth muscle contraction induced with norepinephrine and under relaxation induced with sodium nitroprusside. The angle was significantly greater under smooth muscle contraction than relaxation at all positions except the branching site in the aortic arch. There was significant variation of the angle along the aortic tree under both conditions, being highest at the aortic root and generally low in the descending aorta. The angle reached a local minimum at the branching site. In spite of the large angle variation, the amount of increase in the residual strain due to smooth muscle contraction was very similar among the sites investigated except for the branching site, where smooth muscle alignment differed from that of the other sites. These results suggest that the effect of smooth muscle contraction on residual strain is significant and quantitatively similar among the sites in the thoracic aorta with ordinal histology.

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Residual strain in a systolic heart was measured in equatorial ring like slices of canine left ventricles arrested in systole with barium. Global and two-dimensional local strains were computed from the deformation of each slice following its radial cutting. Global circumferential strain in the epicardial surface was 1.033±0.037 (mean±SD) and was significantly larger than that in the endocardial surface (0.985±0.052), corresponding to opening-up of the ring like slice after the radial cutting. Local strain distribution through out the wall thickness differed from position to position and from specimen to specimen, although cumulative data showed that local circumferential strain was distributed similarly to the global strain. Histological observation showed that large tensile strain appeared preferentially in the area where myocardial fibers run in the circumferential direction and that the strain was generally compressire in other areas. The residual strain in the systolic heart may be closely correlated with the orientation of myocardial fibers.

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A pipette aspiration technique has been developed to clarify the local anisotropic stiffness of soft biological tissues. This technique provides a simple and practical method of measuring an initial elastic modulus by comparing the slope of the pressure-deformation curve obtained from a finite element analysis with that obtained by experiment using a pipette to aspirate the tissue surface. In previous studies, linear numerical simulations were performed for circular cross-sectional pipettes using an axisymmetric model that is assumed to be isotropic and homogeneous. In this paper, the use of rectangular cross-sectional pipettes was proposed to parametrically evaluate the effects of anisotropic properties of living tissues on the measurement of their stiffness. The calculated results indicated that rectangular pipettes eliminated the effect of the modulus parallel to the pipette major axis. The aspiration technique with a rectangular cross-sectional pipette should be effective for clarifying the anisotropy of biological tissues. Experimental verification of this technique was performed for the canine ligamentum nuchae.

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When patellar dislocation occurs in the knee joint, surgical treatment is needed as soon as possible. The mechanism of patellar dislocation must be elucidated to ensure optimum surgical treatment of each patient. We studied proximal patellar movement in the standing position. The 3-D geometry of the articular surface of the femur and the patella and the attachment point of the tibial tuberosity were constructed from successive cross-sectional plane MRI images. 3-D patellar movement was constructed from front and side images of the knee joint taken by X-ray video imaging. The force exerted on the patella can be determined from these data. As a result, it was found that the direction of the quadriceps force is parallel to the Mikulitz line on the front view of the knee joint, and the magnitude increases monotonically to 800 Newtons and remains constant thereafter.

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There are several tactile receptors at specific locations in the tissue of human fingers. In this study we calculate in detail the deformation of finger tissue when a finger comes into contact with a rigid plate using a FE (finite element) model in order to clarify the reason for the precise location of the receptors. The FE model is constructed using the measured geometry and properties. As a result, we found that the strain energy is concentrated at tactile receptor locations. When a frictional force is applied, the stress/strain is concentrated near the edge of the contact area. By calculating using models with/without epidermal ridges/papillae, we found that the shape of the epidermal ridges/papillae influences the stress/strain distribution near the tactile receptors.

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Noninvasive diagnosis by near-infrared light is widely used because it can provide physiological information about biological tissues. For quantitative measurement, however, estimation of the optical properties of biological tissues is necessary with respect to understanding of photon migration in media which scatter light strongly. The purpose of this study is to fabricate stable, solid phantoms which optically simulate biological tissues, and to measure their optical properties using an integrating sphere and a Monte Carlo simulation. The solid phantoms were fabricated using either polyester or epoxy resin as the base material, and small titanium oxide particles were mixed to provide appropriate scattering of light. Their optical properties were measured by means of spectroscopy using an integrating sphere and numerical simulation using a Monte Carlo method. The reduced scattering coefficients were measured within an uncertainty of approximately 4% and ranged from 0.3 to 1.5 mm^-1, which are typical values of biological tissues in the near-infrared wavelength range. The measured absorption coefficients of the phantoms were below 0.0034 mm^-1, which are satisfactorily small values.

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Light pulses have found increasing use in medicine and biology. Biological tissues, however, scatter light very strongly, and the modeling of light pulse propagation in biological tissues has not been established because of scattering. We compare the results of three modeling methods, the photon diffusion approximation, the diffusive wave approximation, and the two-flux method with those of the discrete ordinate method which provides the exact solution of the transient equation of radiative transfer for the case of 1 picosecond pulse incidence on scattering and absorbing slab or semi-infinite media simulating biological tissues. The early behavior of the light pulses predicted by the photon diffusion approximation is quite different from that by the diffusive wave approximation. In the later period both the photon diffusion and diffusive wave approximations are able to give reasonable results, but the two-flux method is not. Because of much shorter computation time, the diffusive wave approximation is advantageous to the photon diffusion approximation.

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A numerical approach for analyzing the forced vibration problem of an unsymmetrically laminated FRP (fiber reinforced plastic) composite plate has already been proposed by us. The purpose of this study was to apply the numerical approach to a clamped antisymmetrically laminated rectangular plate and to compare numerical results with experimental ones. First, we attempted to estimate numerically the steady-state response of a rectangular plate, and discussed the convergence of the results. Next, the accelerances of the clamped antisymmetrically laminated square and rectangular plates made of CFRP were obtained experimentally. These experimental accelerances were compared with and found to agree well with the numerical results computed using the measured structural damping factors of the lamina.

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A tower of a major suspension bridge under construction is subjected to vortex-induced vibration. Our purpose in this study is to suppress this vibration to an allowable level by active vibration control using μ synthesis. We use the bridge tower model with height of 4.6 m and weight of 370 kg as an example of this problem. When we design a μ controller, considering that the tower is complex in structure and under construction, we assume that the system has two types of uncertainty. One is the higher vibration mode uncertainty, and the other is the parametrized uncertainty which represents the variations of the system due to progress in construction. From the dosed loop properties and simulation results, compared to our previous μ controller which considers only the higher vibration modes uncertainty, our new μ controller is proved to maintain the stability and the performance against the progress in construction.

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Kane's method and algebraic vector representation are utilized to construct a new equation of motion for constrained multirigid-body systems. This new equation is called "matrix equation of motion for constrained multirigid-body systems" and can be used conveniently to derive the equations of motion for each application model. It can also be used as a basic equation for creating new methods of simulation, as well as design or control problems. A simple example is given to illustrate how this equation is used.

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This paper presents modeling and control of an overhead travelling crane at three-dimensional complex transfer trajectory with and without hoisting motion of the straight and curved trajectories. First, the proposed model of an overhead travelling crane with respect to the sway of a suspended object is given as two models with mutual coupling projected on the travelling-vertical plane and the transverse-vertical plane. Second, in order to achieve practical control of the tracking of a reference trajectory, the suppression of sway of an object suspended by a wire and the time variation of a crane system during hoisting motion, two optimal regulator control systems with gain schedule are independently designed along the X and Y directions. Finally, the usefulness of the present approach is demonstrated through control simulations and experiments.

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This study deals with the hybrid control of response of pressure pulsation of gas in piping excited by a compressor. That is, the response of pressure pulsation of gas in piping is controlled passively by the branch pipe for the tuned mode and actively by a control device installed at the end of the branch pipe for other modes. The mathematical model of the system is formulated and Den Hartog's theory of the optimal dynamic absorber is applied to optimize the parameters of the branch pipe. Next, the state space equation of the system is formulated to determine the optimal feedback gain. Finally, the efficiency of the presented method is verified by the numerical simulation.

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In this paper we study the performance of contact tasks by a robot manipulator on flexible objects. The flexible object's distributed parameter model is approximated as a lumped "position state-varying" model. By using nonlinear feedback compensation, the robot's control space is decomposed into the position control subspace and the object's force control subspace. An optimal state feedback is designed for the position loop, and the robot's contact force is controlled using model-reference simple adaptive control. Experiments using a PUMA robot interacting with an aluminum plate show the effectiveness of this control approach.

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In this work, a grip force dynamometer composed of pressure-sensitive conductive rubber was used to study the sensibility characteristics for grasping of a solid cylinder. The mechanical and physical parameters for ten normal male subjects (aged between 22 and 26) were measured at various cylinder diameters and weights. In addition, a direct linear transformation technique employing a video camera system was developed to determine the finger joint motion used to grasp the cylinder. The experimental results showed that the frictional coefficien of a palm is significantly dependent upon the deform ability of the soft tissue of the palm. It was found that the optimum cylinder diameter for easy grasping is nearly equal to the inner grip diameter formed by the fingers.

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This paper deals with a multiple mobile working robot, which has a six-legged locomotion function and a vertically articulated manipulator. The walking mechanism consists of a parallel link mechanism connecting two frames with three linear actuators and six extendable legs fixed to the frames. The manipulation function has 4 degrees of freedom and locomotion function has 6 degrees of freedom, thus this working robot is a redundant mechanism with 10 degrees of freedom. We propose a trajectory following control method by switching the normalizing matrix according to the freedom. The simulation results and the experimental results leads to the availability of the method.

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The present research concerns a compensation method for dynamic measurement error using the laser beacon measuring system (LBMS), which is necessary for highly accurate positioning control and trajectory tracking control of a wheeled mobile robot (WMR). The LBMS uses particular laser beacons, each of which emits two symmetrical laser beams traveling in opposite directions around the beacon. The beacons are placed at two reference positions. Receiving beams from these beacons, a photosensor carried on a sensor unit of WMR yields four time intervals which are necessary to calculate the position of WMR. The position of a standing WMR can be measured with high accuracy by LBMS. However, the position of a moving WMR can not be measured as accurately, because the above-mentioned four time intervals change slightly owing to motion of WMR and consequently, dynamic measurement error arises. The proposed method is the one which compensates the position of a moving WMR measured by LBMS, making use of the dynamic measurement error calculated from four different time intervals. In this paper, we report on this compensation method which has been found to yield satisfactory results concerning its accuracy and repeatability after various simulations and experiments.

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Research on labor saving and automation of housework by robots is proceeding rapidly due to the increasing population of aged persons and improved electronics in houses. The special problems concerning housework robots are the enormous complexity of the working environment and huge number and variety of objects in a house. Therefore the recognition function of the robot is desired to be highly independent of the working environment. Moreover, the robot should be able to treat various kinds of "nonsolid-form objects" in a house. The object of this research is to develop the technology by which a robot can handle nonsolid-form objects, particularly clothes. The final goal of the research is the creation of a housekeeping robot which can put unarranged clothes into order at a specified place. Some of the concrete subtasks of this job are taking out one form of clothes and expanding, classifying, folding and putting it in the specified place. In this paper we propose a planning strategy for the task of the unfolding clothes.

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Non stationary signals must be represented in a time-frequency plane, because the frequency of those signals evolve with time. For the time-frequency analysis, some representative methods such as spectrogram, Wigner distribution (WD) and wavelet transform (WT) have been investigated. When a certain kind of data processing is applied to the time-frequency two-dimensionally analyzed signals and the effects of the processing are examined, those signals must be inversely transformed to the time domain. Time-frequency two-dimensionally analyzed signals derived from WT can be easily reconstructed into the time domain. In this study, the inverse transform algorithm of WD (IWD) is developed. In the inverse transform algorithms of RID and BLMSWD, both of which are proposed to reduce interference terms of WD, the reconstruted results closely agree with original simulated signals. For the analysis of a measured phonetic signal, inverse transform algorithms of RID and BLMSWD are applied and results are compared with those calculated from the inverse wavelet transform (IWT). Close agreement is obtained between the measured signal and that calculated using IWT. It is clarified that reconstructions from the inverse transform of RID and BLMSWD give satisfactory results.

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