Neutrophils must flow through the pulmonary capillary network in a deformed shape because pulmonary capillaries are closely interconnected, and deformed neutrophils take about 15 s to 1 min to return to their resting spherical shape. In this paper, flow of a neutrophil through two moderate constrictions in a pipeline is numerically investigated, focusing on the effect of cell deformation on the cell's transit time through the constrictions. Changing sizes and positions of the constrictions, we found that the maximum cell radius at the entrance of the constriction and the throat radius of the constriction are the dominant factors in predicting the cell's transit time through the constriction. When the difference between these two radii is relatively large, steeper constriction (smaller radius of curvature) increases the transit time, but this tendency is reversed when the difference is small. Cells traverse the constriction without delay when the maximum cell radius and throat radius are comparable. Finally, we present a simple mathematical model for the transit time.

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Evanescent wave-excited fluorescence microscopy, which selectively probes the ventral membranes of cells adhered to glass substrate, was utilized to observe the change in the topography of the ventral plasma membranes of Swiss 3T3 fibroblasts during spreading. In the initial stage of the spreading (up to 2 hours after seeding), the ventral membrane was close (<100nm) to the substrate in the peripheral and the central regions. About 4 hrs after seeding, the ventral surface assumed a flat topography for a short period and then gradually became uneven, displaying streak pattern of cell-to-substrate contact (6-8 hours after seeding). By 24 hours after seeding, cells gained polygonal shape and most regions except for the focal adhesions were separated from the substrate. Within these well-spread cells actin stress fibers were found to emanate obliquely from the focal adhesions, as previously reported. When cells were grown in the presence of 2, 3-butanedione monoxime (BDM), an inhibitor of actomyosin-based contraction of stress fibers and the cell, the ventral membranes in majority of the cells displayed flat topography, and the tilt of the stress fibers decreased. Cells grown in the presence of colchicine, a microtubule-depolymerizing agent also possessed flat ventral membrane and less tilted stress fibers. These results suggest that the contraction of stress fibers and integrity of microtubules are important in the formation of the uneven topography of ventral membrane and the tilt of stress fibers.

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There are several experimental observations which give evidence for the presence of transendothelial cell channels such as chained vesicular channels and infundibular channels, which are membrane patent channels across the endothelial cells. These channels are considered to be involved in specific transport mechanisms of macromolecules, and also there should be some specific mechanisms which lead to their formation. In this study, generalized governing equations were formulated for the transendothelial cell channels. The shapes of axisymmetric transendothelial chained vesicular channel and infundibular channel were computed based on minimization of bending strain energy of the membrane to investigate their forming conditions and morphological characteristics. Simulated transendothelial channel changes its shape dramatically from chained vesicular channel to infundibular channel depending on lower opening radius. Among the channels, the lowest energy equilibrium shape is chained vesicular channel, while radius of the infundibular channel is about half compared to that of adjacent single vesicle or the chained vesicular channel. Simulated shapes are generally in good agreement with experimentally observed shapes. These results provide insights into forming mechanism of membrane patent channels across the endothelial cells.

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Endothelial cells (ECs) that line the inner surface of blood vessels are continuously exposed to shear stress induced by blood flow, in vivo, and shear stress affects the intracellular calcium ([Ca²⁺]_i), which initiates cellular responses. Although shear-stress induced [Ca²⁺]_i responses shortly (within 10min) after initiation of flow have been studied, the effects of long-term exposure (24hr) of shear stress on [Ca²⁺]_i responses have not. Here, we studied the effect of long-term exposure of shear stress on [Ca²⁺]_i responses in cultured ECs by using a confocal laser microscope and calcium indicator (Calcium Green-1/AM). At the initiation of shear stress of 2Pa (0hr), 27% of the cells exhibited [Ca²⁺]_i responses. This percentage gradually decreased with increasing exposure time, reaching about 4% after 24hr of exposure. These data indicate that long-term shear-stress exposure affects [Ca²⁺]_i responses in cultured ECs.

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Formulations are conducted to numerically analyze the effect of flexible flagellum of swimming bacteria. In the present model, a single-flagellate bacterium is assumed to consist of a rigid cell body of the prolate spheroidal shape and a flexible flagellum of the helical form. The resistive force theory is applied to estimate the force exerted on the flagellum. The torsional as well as the bending moments determine the curvature and the torsion of the deformed flagellum according to the Kirchhoff model for an elastic rod. The unit tangential vector along the deformed flagellum is calculated by applying evolution equations for space curves, and also a deformed shape of the flagellum is obtained.

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The deformation of a flagellum of Vibrio alginolyticus, single-flagellate bacteria, is analyzed theoretically assuming the shape of the flagellum to be a circular helix. The viscous force exerted on the flagellum in aqueous fluid is estimated applying the resistive-force theory based on the Stokes flow. The moment of force in the flagellum are described in analytical expressions and also the curvature and the torsion of the deformed flagellum are expressed analytically according to the Kirchhoff rod model. The deformation of the flagellum is obtained numerically solving evolution equations which determine a space curve from the curvature and the torsion. Comparing variations of the pitch of helical flagella between the numerical solutions and the results of measurement, the flexural rigidity or the elastic bending coefficient for the flagellum of Vibrio alginolyticus is estimated.

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Morphological responses of cultured bovine endothelial cells (ECs) exposed to hydrostatic pressure were investigated. ECs were exposed to physiological blood pressure under a hydrostatic head of culture medium for 24 hours. Pressured ECs exhibited marked elongation and orientation with the random direction, together with development of centrally located, thick stress fibers. Pressured ECs also exhibited multilayered structure unlike under control conditions. The area and the shape index value significantly decreased after exposure to hydrostatic pressure, which were in good agreement with the results from conventional flow-imposed experiments. In contrast, a tortuosity index, which was newly introduced to represent cell shape tortuosity, significantly increased for pressured ECs, while sheared ECs had no difference in turtuosity index from control. In addition, pressured ECs aligned with no predominant direction, while sheared ECs aligned in the flow direction. These results indicate that ECs can respond very specifically to the type of imposed mechanical stimuli such as hydrostatic pressure and fluid shear stress.

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The force generated by the outer hair cell (OHC) motility greatly contributes to the high sensitivity and sharp tuning of the cochlea. However, the dynamic characteristics of this force in vivo have not yet been clarified. In this study, a finite-element model of the organ of Corti including OHCs was constructed, and the magnitude of the force generated by the OHC motility and its phase relative to the deflection of the OHC's hair bundle were obtained by comparing the numerically obtained gain of the basilar membrane vibration with experimental data. Consequently, it was found that the phase delay of the force is within the range between 45deg. and 180deg. and that the magnitude of the force is nearly 1.8nN/nm. Moreover, it was suggested that the electric potential which drives the OHC is likely to be the extracellular potential rather than the receptor potential.

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Mammalian hearing sensitivity relies on a mechanical amplification mechanism involving the outer hair cells (OHCs), which rapidly alter their longitudinal length in response to changes in their membrane potential. The molecular basis of this mechanism is thought to be a motor protein embedded in the lateral membrane of the OHCs. Recently, this motor protein was identified and termed prestin. Since then, prestin has been researched intensively to elucidate the behavior of the OHCs. However, little progress in the study of prestin at the molecular level has been made because no method of obtaining an adequate amount of prestin has been established. In this study, therefore, an attempt was made to construct a stable expression system of prestin using Chinese hamster ovary (CHO) cells. The expression of prestin in the transfected CHO cells and the activity of prestin on CHO cells were confirmed by immunofluorescence and whole-cell patch-clamp measurements, respectively.

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Morphological remodeling of endothelial cells that was induced by blood flow is considered an adaptive response to a mechanical stimulus. To determine the mechanisms of the response, we examined how shear stress on the surface of the same group of cells changed. The surface geometry of the cells was measured by confocal laser scanning microscopy, and the shear stress distribution on the measured cell surface was determined using the flow field simulated by computational fluid dynamics. When the cells, which were polygonal without alignment at the beginning of the flow exposure, elongated and aligned in the flow direction, the mean shear stress of the cells decreased with time. However, there were some cells whose mean shear stress was increased, and the morphological change of each cell was not always adaptive. The results show the importance of interaction with surrounding cells to the adaptive response as demonstrated in the endothelial layer.

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The wear debris caused by joint prosthesis is well known to induce an inflammation in the peripheral tissue. The authors carried out two kinds of experiments, to clarify the phagocytable size of wear particles and the cytotoxicity of macrophage related to the size and materials. The test materials were Al₂O₃, SiO₂, TiO₂ fine particles and Ti-6Al-4V, Co-28Cr-6Mo wear particles. The results showed that the phagocytable particle size was less than 11.9±11.2µm. It appears that the cytotoxicity did not depend on the particle size, even if the particles were phagocytable size. In the relationship between material type and inflammation, damage levels were found to be different between SiO₂ and TiO₂ particles, even if neither material released metal ions. The cells were damaged more severely by SiO₂ particles than by Co-28Cr-6Mo for which the eluted ion could not be ignored (damage levels; SiO₂>Co-28Cr-6Mo>Ti-6Al-4V>Al₂O₃≧TiO₂). For these reasons, it was confirmed that there was a factor in addition to the toxicity of the eluted metal ion (i. e., the implant material's corrosion resistance ability), which influenced the inflammation.

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It is expected to be clinically useful to know the mechanical properties of human aortic aneurysms in assessing the potential for aneurysm rupture. For this purpose, a newly designed experimental setup was fabricated to measure the rupture properties of blood vessel walls. A square specimen of porcine thoracic aortas is inflated by air pressure at a rate of 10mmHg/s (≈1.3MPa/s) until rupture occurs. Mean breaking stress was 1.8±0.4 MPa (mean±SD) for the specimens proximal to the heart and 2.3±0.8MPa for the distal specimens, which are not significantly different to those values obtained longitudinally from conventional tensile tests. Moreover, the local breaking stretch ratio in the longitudinal direction was significantly higher at the ruptured site (2.7±0.5) than at the unruptured site (2.2±0.4). This testing system for studying the rupture properties of aortic walls is expected to be applicable to aortic aneurysms. Experimental verification of the present technique for the homogeneous, isotropic material is also presented.

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Ultra high molecular weight polyethylene (UHMWPE) has been used as a bearing material for artificial joints since the 1960's, and experience has shown that its wear is one of the limiting factors for long term use in such prosthetic implants. For improving wear resistance, we studied the influence of uniaxial compression on molecule orientation obtained by processing UHMWPE above (Sample A) and below (Sample B) its melting point, respectively. We then compared the wear properties of both UHMWPE samples. Using a slightly cross-linked UHMWPE, sample A was compressed during the molten state. Sample B UHMWPE was compressed at a temperature below the melting point. X-ray refraction tests revealed the (200) crystalline plane of Sample A and B to be oriented parallel to the compression surface. Further tests showed the heat of fusion and the density of Sample A to be higher than Sample B. The storage modulus of Sample A was always higher than in the original untreated UHMWPE (Sample C), while in Sample B it rapidly collapsed with increasing temperature. The α_c-peak of Sample A was shifted to about 5°C higher, while the α_c-peak of Sample B was shifted to the lower temperature side and the β-peak disappeared, compared with Sample C. Reciprocating wear tests carried out over 2×10⁶ cycles, showed that the wear resistance of the sample A was enhanced by a factor of 10 when compared to Sample C. UHMWPE compressed during the molten state exhibits superior wear characteristics and has the potential to improve implant technology for artificial joints, potentially providing a longer lifetime.

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Simplified two-dimensional flow analysis is performed in order to simulate frictional characteristics measurement of red blood cells moving on a glass plate in a medium with an inclined centrifuge microscope. Computation under various conditions reveals the influences of parameters on lift, drag, and moment acting on a red blood cell. Among these forces, lift appears only when the cell is longitudinally asymmetric. By considering the balance of forces, the frictional characteristics of the red blood cell are modeled as the sum of Coulomb friction and viscous drag. The model describes the possibility that the red blood cell deforms to expand in the front side in response to the inclined centrifugal force. When velocity exceeds some critical value, the lift overcomes the normal centrifugal force component, and the thickness of the plasma layer between the cell and the glass plate increases from the initial value of the plasma protein thickness.

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This study was done to know the effects of aging on arterial mechanics from the viewpoint of tissue remodeling. Rats at growing (8 and 16weeks), maturated (32weeks) and middle (64weeks) ages were used. After blood pressure and blood flow were measured in the abdominal aorta and common carotid artery, respectively, the carotid artery was excised to obtain pressure-diameter relations and wall dimensions. Although blood pressure increased during growth and blood flow gradually increased with age, wall hoop stress and wall shear stress showed no significant changes except for a decrease in wall shear stress during growth, which was attributable to morphological changes of wall. Wall stiffness and elastic properties at in vivo pressure did not significantly change until maturation; however, they increased by middle age.

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A computational model combined ultrasonographic data and computational fluid dynamics (CFD) was developed and applied to an anatomically realistic model of the human left ventricle. The proposed methodology employs but not limited to ultrasonographic scans of a human left ventricle to obtain a set of time-varying images of morphology and dynamics of the left ventricle, which are utilized in generating a dynamic geometrical model for blood flow simulation. A so-called Two-Chamber-View modeling method has been proposed to obtain digitized anatomical images on two mutually orthogonal planes that cut through the left ventricle chamber along the long axis from base to apex, and from which two endocardial borderlines in the two planes are extracted for each time frame. Endocardial contours in the short-axis plane is approximated as an ellipse with two radii determined from the extracted endocardial borderlines in the two long-axis planes and stacked up from base to apex to generate a fully three-dimensional geometric model. Physiological conditions of inflow/outflow at orifices notionally representing the mitral and aortic vales are obtained also based on the ultrasonographic images by deriving flow rates at the orifices directly through calculating time-variation-rate of the left ventricle volume. Computational modeling of left ventricle hemodynamics is accomplished by using an in-house NS solver with specific modification for blood flow in heart chamber. The reconstructed CFD model well captures the three-dimensional dynamics of endocardial wall in terms of contraction and expansion phases in the left ventricle; and the dominant fluid dynamics involving vortices and swirls are simulated reasonably. Our computed results indicate that realistic modeling of both geometry and physiological conditions of left ventricle is of great importance in correctly predicting the behavior of the dominant vortex flow and their influence on the heart function.

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In this study, a 3D finite element based simulation program incorporating the propagation of excitation and excitation-contraction coupling mechanisms developed by us was modified to reproduce the more realistic ventricular wall structure. FE model of LV consists of six layers of muscle bundles and the fiber direction of the inner-most layer was longitudinal. Although the detailed modeling did not influence the global pump function of the LV appreciably, we could successfully identify the functional significance of longitudinal fibers as pointed out by clinical observations. Furthermore, we also changed the heart structure drastically to elucidate the functional significance of the fiber structure. The results suggest that the double-helical structure the heart has developed through the evolutionary process can be an optimal design for a blood pump.

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The application of dynamics observed in organisms is very instructive in the field of engineering. We noted the utility of ciliary movement for propulsion in fluid, and developed an enlarged propulsion mechanism modeled on ciliary movement. To realize the effective stroke and recovery stroke of ciliary movement, the mechanism was equipped with a motor on its base and a variable-bending-stiffness fin. The variable-bending-stiffness fin consists of two flexible sheets and electromagnets. Electromagnets control the frictional force between the two flexible sheets. Bending stiffness is controlled dynamically by changing the frictional force between the two flexible sheets. We discussed the thrust force characteristics of the mechanism in water and highly viscous liquid paraffin.

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In this paper we solve the energy-efficient periodic gaits for a biped mechanism walking in the sagittal plane. The biped locomotion mechanism that has thighs, shanks and small feet is modeled as a four-degree-of-freedom (DOF) link system composed of a two-DOF stance leg and a two-DOF swing leg that are connected directly at the hip joint. Using the optimal trajectory planning method based on function approximation, we obtained minimum square input torque trajectories of cyclic walking gaits with flexed knee stance leg for both full-actuated and under-actuated models that are similar to those of the human walking. Also, the validity of this gait generating method is confirmed by forward dynamic simulation.

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This paper describes the use of a mechanical pectoral fin as a new device for maneuvering and stabilizing an underwater vehicle. The mechanical pectoral fin consists of three servo-motors, which respectively generate a rowing motion, a feathering motion, and a flapping motion. We focused on the comparison of load characteristics of the mechanical pectoral fin between the drag-based swimming mode and the lift-based swimming mode, undertaken under the conditions of uniform flow and still water, respectively. Optimization of the parameters of fin motion so as to generate maximum propulsive force in terms of flow condition and motion pattern revealed that the lift-based rather than the drag-based swimming mode is suitable for generation of propulsive force in uniform flow, whereas the drag-based rather than the lift-based swimming mode is suitable for generation of propulsive force in still water within the range of motion of the mechanical pectoral fin.

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Penguins are sea birds that swim using lift and drag forces by flapping their wings like other birds. Although diving data can be obtained using a micro-data logger which has improved in recent years, all the necessary diving conditions for analysis cannot be acquired. In order to determine all these hard-to-get conditions, the posture and lift and drag forces of penguins were theoretically calculated by the technique used in the analysis of the optimal flight path of aircrafts. In this calculation, the actual depth and speed of the dive of an Adélie penguin (Pygoscelis adeliae) were utilized. Then, the calculation result and experimental data were compared, and found to be in good agreement. Thus, it is fully possible to determine the actual conditions of dive by this calculation, even those that cannot be acquired using a data logger.

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In this paper, the measurement of 3D motion from 2D perspective projections of knee prosthesis is described. The technique reported by Banks and Hodge was further developed in this study. The estimation was performed in two steps. The first-step estimation was performed on the assumption of orthogonal projection. Then, the second-step estimation was subsequently carried out based upon the perspective projection to accomplish more accurate estimation. The simulation results have demonstrated that the technique archived sufficient accuracies of position/orientation estimation for prosthetic kinematics. Then we applied our algorithm to the CCD images, thereby examining the influences of various artifacts, possibly incorporated through an imaging process, on the estimation accuracies. We found that accuracies in the experiment were influenced mainly by the geometric discrepancies between the prosthesis component and computer generated model and by the spacial inconsistencies between the coordinate axes of the positioner and that of the computer model. However, we verified that our algorithm could achieve proper and consistent estimation even for the CCD images.

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This paper describes a method, inspired by voiceprints, to visualize dynamical features of the counter-rolling: rotational eye movements being made when our bodies are tilted. We identify the experimental time series with a discrete time-varying model by means of Kalman filters and visualize magnitudes of the internal model parameters. The obtained images visualize the time-varying impulse response (TVIR) of the counter-rolling system. An irregular eye movement with small jumps can be characterized as clear borders in the TVIR image. The method is expected to provide a useful tool for various diagnostic purposes. It may also be worth noting that many theoretical tools for complex dynamical systems have also been inspired by visual images called strange attractors.

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A hypothesis that idiopathic scoliosis is a buckling phenomenon of the fourth or sixth mode, which is the second or third lateral bending mode, induced by the growth of vertebral bodies was presented in a previous paper by the authors using numerical simulations with a finite-element model of the spine. This paper presents experimental proof of the buckling phenomenon using mechanical spine models constructed with the geometrical data of the finite-element model used in a previous work. Using three spine mechanical models with different materials at intervertebral joints, the change in the natural vibration eigenvalue of the second lateral bending mode with the growth of vertebral bodies was measured by experimental modal analysis. From the result, it was observed that natural vibration eigenvalue decreased with the growth of vertebral bodies. Since the increase in primary factor inducing the buckling phenomenon decreases natural vibration eigenvalue, the obtained result confirms the buckling hypothesis.

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In the present study, the effects of brain-skull boundary conditions on the responses of a simplified three-dimensional finite element model of a thin sagittal slice of the human head were investigated. The model was excited using a time-dependent angular velocity with a maximum of 16 rad/s (maximum angular acceleration, around 5000 rad/s²). The present study was conducted using the non-linear explicit finite element code LS-DYNA. Three methods for simulation of the brain-skull boundary conditions were investigated: 1) with brain rigidly attached to the skull; 2) using frictionless sliding contact allowing no separation between the brain and skull; and 3) direct simulation of cerebrospinal fluid CSF using a layer of eight-noded solid elements with fluid-like properties. Varying the method for simulation of the brain-skull boundary conditions appreciably affected the brain responses. However, varying parameters of a given method, such as viscosity of cerebrospinal fluid CSF and CSF-skull friction coefficient, exerted only minor effects on these responses. The present results suggest that accurate simulation of brain-skull boundary conditions requires direct representation of the subarachnoidal space/CSF as a fluid-like medium.

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Temporomandibular joint (TMJ) disorder relates to the biomechanical irregularity of the structual joint components, and the behavior of soft tissue components is considered as a key to understand the biomechanical condition in the TMJ. The configuration of joint components, however, closely depends on individual patients. In this study, attention has been focused on the stress and displacement of irregular TMJs with anterior disc displacement. Using biplane magnetic resonance (MR) images, typical anterior-disc-displaced (ADD) TMJ of a patient with temporomandibular disorder has been modeled individually. The stress distribution in ADD TMJs has been compared with that in normal TMJs. Parameter studies with the elastic modulus have been carried out and it revealed that the stress distribution in the TMJ is highly dependent on the connective tissue modulus as well as disc modulus in the case of ADD TMJ, and that the disc displacement due to mouth opening movement depends on disc modulus in normal TMJ but depends on retrodiscal connective tissue in ADD TMJ.

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Guided Bone Regeneration (GBR) is a method for bone tissue regeneration. In this method, membranes are used to cover bone defects and to block the invasion of the surrounding soft tissues. It would provide sufficient time for the osteogenic cells from bone marrow to proliferate and form new bony tissues. In spite of the potential usefulness of this method, no appropriate materials for the GBR membrane have been developed. Here we design the ideal mechanical properties of the GBR membranes and created novel materials, which is the composite of β-tricalcium phosphate and block copolymer of L-lactide, glycolide and ε-caplolactone. In the animal experiments with the use of the trial products, we observed significant enhancement in the bone regeneration and proved the effectiveness of the materials.

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Tensile tests were performed on bone-ligament-bone (BLB) units, sections of ligament, and individual collagen fascicles all from the knees of swine hind legs. A universal testing machine was used for the tensile tests of the BLB units. A specially designed test apparatus was used for the tensile tests of ligament sections and fascicles. The strain values were calculated from the elongation values recorded by a video camera. The results showed that the BLB's stiffness was greatest, followed by the fascicles and the ligament sections. The results are contrary to the popular notion that because the ligament is composed of collagen fascicles in a matrix whose stiffness is almost negligible, the ligament should not be stiffer than the fascicles that compose it. The stiffness might have been caused by mechano-chemical interactions between fascicles and matrix, or contributions from the membranous septum that combines fascicles.

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The purpose of this study is to establish a method of measuring precisely the seismocardiogram (SCG) of a patient who lying in an open magnetic resonance imaging (openMRI) machine for myocardial ischemia monitoring during surgery. Vibration isolation was examined by analyzing the gantry vibration during MRI scanning and the SCG of a healthy volunteer. The MRI gantry vibration had maximum amplitude of 2.5m/s², which are several peaks more than 100Hz up to 500Hz. Up to 94% reduction in amplitude was observed in the patient bed vibration under both T1-weighted and T2-weighted sequences. The power spectrum center of the patient bed vibration was more than 30Hz. The maximum amplitude of SCG was 0.92m/s² and a FFT analysis revealed that the SCG was not higher than 25Hz. The signal-to-noise ratio between the SCG and the patient bed vibration was calculated to be from 4 to 7. These results demonstrate that the peak acceleration of the SCG can be monitored during openMRI scanning. In conclusion, vibration analysis showed the feasibility of using the piezoelectric acceleration sensor for seismocardiogram measurement in the openMRI-guided operating theater.

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In this study, the tympanic membrane (TM) of the guinea pig was exposed to a blast wave generated by micro-explosion of 10mg silver azide, and the time history of TM rupture was recorded using a high-speed video camera. The relationship between the process of TM rupture and the peak pressure of the blast wave was then examined. The critical value which caused the TM rupture was found to be 192dB SPL (79.6kPa), and when this level of pressure was applied to the TM, tears were immediately caused in the radial direction, although they did not subsequently expand. When pressures above 195dB SPL (112kPa) were applied to the TM, it suffered a perforation, and this perforation continued to expand for several milliseconds, even after disappearance of the pressure change caused by the blast wave.

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This paper presents an integrated simulation of the circulatory system in physiological movement. The large circulatory system model includes principal organs and functional units in modules in which comprehensive physiological changes such as nerve reflexes, temperature regulation, acid/base balance, O₂/CO₂ balance, and exercise are simulated. A beat-by-beat heart model, in which the corresponding electrical circuit problems are solved by a numerical analytic method, enables calculation of pulsatile blood flow to the major organs. The integration of different perspectives on physiological changes makes this simulation model applicable for the microscopic evaluation of blood flow under various conditions in the human body.

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This study presents the control design and tests of an intra-oral hydraulic system for quantitatively loading of a dental implant. The computer-controlled system was developed and employed for better pressure error compensation by PID (proportional-integral-derivative) control and point-to-point iterative learning algorithm. In vitro experiments showed that implant loading is precisely controlled (error 3%) for 0.5Hz loading without air inclusion, and reasonably performed (error<10%) with air inclusion up to 20% of the total hydraulic volume. The PID controller maintains forces at the desired level while the learning controller eliminates overshoot/undershoot at the onset of each loading cycle. The system can be potentially used for in vivo animal studies for better understanding of how bone responds to implant loading. Quantitative information derived from this biomechanical model will add to improved designs of dental implants.

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In this paper, we propose a method for obtaining the strict solution of a steady response and the periodic solution by which only the impact time of the impact oscillator system was assumed to be a parameter for which no sticking occurred. First, the response conversion which is the derivation operation of a steady response is defined. Two methods are shown to exist for the deriving process of a steady response, depending on the order of application of the response conversion and the “reference value expansion”. By these methods, a general form of the periodic solution can be obtained from a steady response. In addition, the results obtained by these two methods show good agreement on the most fundamental periodic solution. Finally, the validity of the proposed method is confirmed using a numerical simulation example.

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This paper describes the structure and development strategy for integrity evaluation system for nuclear power plants called NPP-KINS/SAFE. NPP-KINS/SAFE consists of three different programs covering the integrity assessment of reactor pressure vessel, pipings, and pressure tubes, respectively. The system has been developed based on currently available codes and standards, and includes a number of databases, expert systems, and numerical analysis schemes. NPP-KINS/SAFE is applicable for various types of nuclear power plants constructed in Korea with the aid of attached database systems including plant specific data. Case studies for the developed system are also provided.

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A two-degree-of-freedom (DOF) global sliding-mode control (GSMC) scheme with adjustable performance robustness is proposed for motor drives with bounded control and system uncertainty. Through introducing an auxiliary process and eliminating the reaching phase, the sliding dynamics is equivalent to the overall closed-loop system dynamics, and can be adjusted to yield the desired performance robustness. By fully utilizing the tolerance in performance specifications, the chatter phenomenon is alleviated while the performance specifications are satisfied. In dealing with the problem of bounded control, an estimation process is proposed for estimating the maximum control input required by the uncertain system with external disturbance. The estimation process can be utilized in two ways. For specific output command, the estimation result reveals the maximum control input that the actuator must deliver in order to maintain performance robustness. On the other hand, given bounds on control input, the estimation process can be applied to find the range of allowable output command, within which the performance robustness is guaranteed. Simulation results show the feasibility of the control scheme and the estimation process.

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This paper considers the stability of time delay systems with both parameter uncertainties and nonlinear perturbations. A nonlinear type of robust controller is proposed based on a variable structure control technique. A Delay-dependent controller can eliminate the effect of the nonlinear uncertainties in the system and guarantee the stability of the closed-loop when the time delay is less than a given bound. Examples illustrate the effectiveness of the proposed method.

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Growing complexity of artificial systems arises reliability and flexibility issues of large system design. Robots are not exception of this, and many attempts have been made to realize reliable and flexible robot systems. Distributed modular composition of robot is one of the most effective approaches to attain such abilities and has a potential to adapt to its surroundings by changing its configuration autonomously according to information of surroundings. In this paper, we propose a novel three-dimensional self-reconfigurable robotic module. Each module has a very simple structure that consists of two semi-cylindrical parts connected by a link. The modular system is capable of not only building static structure but also generating dynamic robotic motion. We present details of the mechanical/electrical design of the developed module and its control system architecture. Experiments using ten modules with centralized control demonstrate robotic configuration change, crawling locomotion and three types of quadruped locomotion.

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There is growing in interest in the modeling and simulation of the dynamic behavior of advanced vehicles, including maglev-type systems. This paper demonstrates the application of DADS, a program especially suited for the analysis of multibody mechanical systems, to the dynamic modeling and simulation of a maglev system. A brief description is made of the modeling requirements of magnetically levitated systems along with a summary of some of the related capabilities of DADS. As a case study, an analysis of a vehicle based on the UTM01 system is presented. This paper shows that the presented modeling technique is applicable to the dynamic characteristics evaluation and control-law design of maglev-type vehicles.

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An approach to study of the tip dynamic response (displacement and velocity) of elastic joint manipulators subjected to a vertical stochastic excitation of the base is presented. The crossing analysis of maximum displacement of the manipulator tip along a determined path is also investigated. The dynamic equations of motion of an n-link articulated elastic joint manipulator subjected to a vertical stochastic base excitation are derived by using the Euler-Lagrange equations and then extended by Taylor series expansion. The result dynamic equations are linearized with respect to links vibration. The power spectral density representation is used to compute the second moment matrix of angular displacement and velocity of the links and also to compute the second moment matrix of manipulator tip dynamic response. Then the crossing analysis and also the probability that any maximum peak displacement values of manipulator tip exceed from a determined level along a path are investigated. Finally, some of simulation results for a two-link planar robot manipulator subjected to a vertical stochastic excitation of the base are presented.

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In this paper a new disk type of the variable torque slipping clutch with skewed rollers (VTSCSR) is presented and investigated both theoretically and experimentally. It is comprised of two flat disks, a number of skewed cylindrical rollers, and a cage. The slipping torque is produced by the skewed rollers rolling and slipping between the two disks. Based on the integral equation of the Boussinesq solution, the contact pressures are numerically calculated under the condition that the nonlinear equilibrium equations of the clutch elements are satisfied. By considering both pressure and friction, the components of subsurface stress are calculated from the integration of the Mindlin's subsurface stress equations of concentrated force. A numerical solver is then successfully developed by which the characteristics of the disk-type VTSCSR, including the torque capacity, angular velocities of the roller and cage, contact pressure and von Mises stress, etc, are calculated and illustrated for the typical designs. The influences on the distribution of the von Mises stress by applying various types of profiled rollers to the disk-type VTSCSR are also discussed. It has been found that the full crown with two arcs profiled roller can approximately give rise to the axially uniform distribution of the von Mises stress and therefore satisfies the design principle of the average damage of materials. In addition, the preliminary experiment was done in order to show the feasibility of this design idea and to verify the theoretical torque capacity.

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This paper presents a comparison of three s-shaped curves for parallel parking a car subject to nonholonomic constraints. The comparison is based on the rate at which the car approaches the curb (the parking criterion). The curves (two circular arcs, a cosine curve and a quintic) are shown to accommodate an initial and final position, but only the quintic accommodates initial and final curvature. The time penalty in straightening out the wheels at the maneuver end-points (or midpoint) causes the other curves to be suboptimal. Representative examples of the curves are shown. Also illustrated is the effect of the turning radius of the car on the time required to park it.

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This paper presents a new scanning multi-probe arrangement for precision measurement of surface profiles of cylinders. Analysis of the influence of error motions associated with the scanning on the probe output showed that the minimum number of the displacement probes is five for separating the surface profile of the cylinder from error motions of scanning. The surface of the cylinder was sampled by the five probes in a scanning system where the rotation of the cylinder spindle and the movement of the probe carriage were synchronized. The five probes were arranged in such a way that the sampling points of the all the probes were located on the same spiral line over the surface of the cylinder. This probe-arrangement and sampling strategy makes the scanning over the entire cylinder surface effective. It also makes it possible to make use of the inverse filtering method for data processing of the probe outputs, which has been well-developed in straightness measurement of using multi-probes. A prototype instrument based on the proposed multi-probe method was constructed for measurement experiments. Comparison between the results of the prototype instrument and a commercially available roundness measuring machine has indicated the feasibility of the proposed method for roundness measurement.

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Recently, Otsubo and Edamura have reported that dielectric fluids show a striking viscosity increase in an electric field when the electrode surface is planted with hair-like short fibers. Due to this phenomenon, the electro-rheological (ER) effect is obtained without any costly ER fluids. In this study, we aim to develop a fluid control valve with the above-described new ER effect. In this paper, first, a fiber-planted ER valve is proposed with a fiber-planted high-voltage electrode and a normally-surfaced ground electrode. Second, a two-port fiber-planted ER valve is fabricated, and its static and dynamic characteristics are examined. Finally, as further application of this technology, a four-port fiber-planted ER valve is proposed and fabricated, and then its ability to control a piston cylinder is demonstrated.

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We describe the folding/wrapping methods of thin flat circular membranes using folding patterns prescribed by combining two groups of spirals. By using both folding conditions at nodes and continuous conditions of equiangular spiral fold lines in the membranes, two kinds of folding patterns have been analytically designed: (1) folding patterns consisting of pseudo-equiangular spirals (zigzag spirals) and equiangular spirals, and (2) folding patterns consisting of two groups of equiangular spirals. The applicability of the present folding/wrapping methods to circular membranes has been verified by manufacturing paper and very thin metal sheet samples.

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The concept of relating the physical characteristics of a multi-component composite with its component proportions involves the determination of a mathematical equation that adequately represents the response surface. The objective of this paper is to describe the shape of the response surface of elastic modulus of epoxy concrete over the simplex factor space (experimental region) with the help of the simplex-centroid design and the associated polynomial model and to determine the roles played by individual components. Epoxy concrete is a synthetic composite material specially developed for precision machine tool structures. The proposed model to which observations were fitted is the Scheffe's special cubic model for the simplex-centriod design. The adequacy of the fitted model was tested by both check points and F-test to ensure that it predicts a value at each point in the experimental region which is as close as possible to the true value of the response.

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This paper presents a model for calculating the equivalent misalignment of gears due to deformations of shafts, bearings and gears in gear box. This modeling consists of calculating the bending and torsional deflections of gear shaft considering the bearing stiffnesses (radial and moment stiffnesses) and gear body, and a method for calculating the equivalent misalignment of gears was obtained. The calculation program was developed using MS Visual Basic and the validity of the calculation program developed was examined by comparing the results of this program with those presented by United States, Germany and France to the ISO TC60 WG6. This program enables Japan to catch up with these countries in terms of usage of ISO 6336 standard for load carrying capacity of cylindrical involute gears in practice of international technical/industrial affairs.

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The alignment condition of automotive gears changes considerably during operation due to the deformation of shafts, bearings, and gear box by transmission of load. Under such conditions, the gears are required to satisfy not only reliability in strength and durability under maximum loading conditions, but also low vibrational characteristics under light loading conditions during the cruising of a car. In this report, the characteristics of the optimum tooth flank form of gears in terms of both vibration and load carrying capacity are clarified. The local optimum tooth flank form appears in each excitation valley, where the vibrational excitation is low and the actual contact ratio takes a specific value. The influence of the choice of different local optimum solutions on the vibrational performance of the optimized gears is investigated. The practical design algorithm for the optimum tooth flank form of a gear set in terms of both vibration and load carrying capacity is then proposed and its result is evaluated by field experience.

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In this paper, an optimum design of a two-stage spur gear system is performed. The optimization is based on a multicriterion technique consisting of a Min-Max method combined with a direct search technique. The optimum design includes the minimization of seven objective functions. They are the volume of gears, the center distance and five dynamic factors in the input shaft, first-teeth meshing, intermediate shaft, second meshing and the output shaft. The dynamic factors are estimated using a dynamic model of twelve degrees of freedom. The objective functions are governed by eleven design variables, chosen to be the number of teeth and face width of the pinion of each stage, stiffness of the input, intermediate, and output shafts and the inertia of the four gears of the mechanism. The developed optimum design is found to give compact-gear system with quiet running (minimum dynamic factors) compared with the classical design. The angle between the power transmitting directions is found to have an important role on the objective functions and the optimum design. A value of 180° for this angle is found to be the optimal for all functions.

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Ceramics are being increasingly used in industry due to their outstanding physical and chemical properties. But these materials are difficult to machine by traditional machining processes because they are hard and brittle. Recently, as one of the various alternative processes, laser-beam machining is widely used in the cutting of ceramics. Although the use of lasers presents a number of advantages over other methods, one of the problems associated with this process is the uncertain formation of cracks that result from the thermal stresses. This paper presents a Bayesian probabilistic modeling of crack formation over thin alumina plates during laser cutting. The proposed model can predict the critical cutting front angle which is directly related to the initiation of crack formation.

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In this research, the manufacturing processes of aspherical refraction microlens array by gray-scale mask if investigated. In the first part of this research, we emphasize on the gray-scale mask based microlens array fabrication processes through the UV-LIGA approach. Furthermore, a two-stage process-modeling scheme is proposed to reduce the time-consuming trail-and-error parameters tuning labor works. Experimental results demonstrate that the proposed approach can well model the fabrication process and is capable of providing effective fabrication parameters once the diameter and height of a certain microlens is provided.

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