An equibiaxial thermal fatigue test of die-attach materials that reproduces the same stress state as the power cycle was proposed, and the fatigue fracture behavior of Ag sintered die-attach materials under equibiaxial thermal stress was investigated. Thermal fatigue tests under equibiaxial stress showed that vertical cracks were observed throughout the sintered Ag nanoparticles. Thermal fatigue fracture was out-of-phase type, in which crack initiation and opening were driven by equibiaxial tensile stress during temperature drop. It is suggested that the fatigue crack growth in the die-attach joint during power cycling can be predicted by the fatigue crack growth law at high temperatures obtained by mechanical fatigue tests.

In this study, fatigue crack growth rate at Si/UF interface was evaluated by four-point bending fatigue crack growth tests. At the bottom of the Si die, the fatigue crack growth behavior was similar to that of the UF bulk, in which the transition from the threshold to steady-state crack growth was observed. The power exponent of the Paris law in the steady-state region was similar to that of the UF bulk, and the fatigue crack growth rate was different between the side and bottom of the Si die. These results suggest that the fatigue crack growth behavior at the interface strongly depends on the surface roughness of the Si die and the manufacturing process of underfilling.

This paper presents a structure model construction for statistical energy analysis (SEA) using FEM. Identifying SEA parameter regardless of the excitation method is demanded effectively. The proposed method is based on a combination of SEA and vibration response by base excitation like forced displacement vibration analysis, random vibration analysis, and large mass method. These methods are effective on an analytical cost performance compared with the conventional force excitation method that is called rain-on-the-roof-excitation. In this study, the proposal method is validated through the two types of model, (i) simple flat plate consisting of one subsystem, and (ii) an L plate consisting of two subsystems. As a result, the method is shown to work quantitatively well to the coupling loss factors.

In recent years, a variety of microscopes using heat sources, such as photoacoustic microscopes, have been developed. In this observation principle, reflection and diffraction phenomena of two waves with different properties, namely thermal wave and elastic wave, are utilized. However, the thermal wave cannot be reproduced using the classical Fourier-type heat conduction equation. In order to overcome this mathematical difficulty, we had derived a coupled nonlinear partial differential equation consisting of the heat conduction with a delay time and the dynamic thermoelastic equation, and had simulated numerically the propagation process of thermal and elastic waves for one-dimensional problem. In this study, thermal and elastic waves were simulated for a two-dimensional plane problem with and without defect using the finite-difference time-domain method. The results showed that the reflection and interference phenomena of two waves can employ for detecting small internal defects existing near the surface of target sample.

In FBR plants the head plate constitutes a part of the boundary of the containment vessel (CV), therefore, it is a very important issue if the function as the boundary is maintained or not in the case of severe accident (SA). Buckling and post-buckling behaviors due to pressure loading must be affected by the thickness distribution of the head plate during press forming process. In this paper non-linear finite element simulation analyses assuming press forming process of a head plate are improved after the previous paper and the discussion is made comparing the analysis results with the measured results of thickness distribution of the head plate specimen used for the pressure endurance test. And also, the modelling for finite element analyses of head plates is discussed. In this study, axisymmetric analyses are implemented focused on the thickness distribution along the meridional direction of the head plate.

For the structural components which constitute a part of the boundary of the containment vessel (CV) in FBR plants, it is a very important issue if the function as the boundary is maintained or not in the case of severe accident (SA). In this case, the criteria of boundary penetration are matters beyond the design criteria. One of the authors has paid his attention to FLD (Forming Limit Diagram) which is broadly used in the field of press-forming of sheet metal. In this study the experiments for FLD and their simulation analyses are implemented focusing on the austenitic stainless steel which is one of the main materials used for the equipment of nuclear plants for the discussion on the adoptability of FLD to the criteria of boundary penetration.

In this study, we present a 3D shape optimization method for designing micro- and macro-structures concurrently. We assume the macrostructure consists of several arbitrary subdomains, which have different periodic microstructures. The macro- and microstructures are bridged by the homogenized elastic tensors, which are calculated by applying the homogenization method to the unit cells of the microstructures. Defining the boundary shapes of the macro-, microstructures and the interface shapes between the subdomains as design variable, the compliance of the macrostructure is minimized. The volume of the macrostructure considering the whole holes in the microstructures is used as the constraint. The homogenization equations for the microstructures and the equilibrium equation for the macrostructure are also used as the constraint. This design problem is formulated as a distributed-parameter optimization problem, and the shape sensitivity functions are theoretically derived. The optimum boundaries of the macro- and microstructures are determined by the H¹ gradient method. The proposed method is applied to a numerical example to confirm the effectiveness of the proposed method.

In this paper, we propose a solution to a shape optimization problem for the strength design of periodic microstructures in multiscale structures. Two maximum stress minimization problems are addressed; minimization of the maximum stress of the microstructure and minimization of the maximum stress of the macrostructure. The homogenization method is used to bridge the macrostructure and the microstructures, and also to calculate the local stress in the microstructures. By replacing the maximum value of the stress with a Kreisselmeier-Steinhauser function, the difficulty of non-differentiability on the maximum stress is avoided. Each strength design problem is formulated as a distributed parameter optimization problem with the area constraint including the whole microstructures. The shape gradient functions for both problems are derived using Lagrange's undetermined multiplier method, the material derivative method, and the adjoint variable method. The H¹ gradient method is used to determine the unit cell shapes of the microstructures, while reducing the objective function and maintaining the smooth design boundaries. In the numerical examples, the optimal shapes obtained for the maximum local stress minimization of the microstructure and the macrostructure are compared and discussed. The results confirm the effectiveness of the microstructure shape optimization method for the two strength design problems of multiscale structures.

Dampers are often used for vibration suppression of a civil or mechanical structure. It is considered that vibration can be further suppressed by optimizing the shape of the structure after the installation of dampers. In this paper, we proposed a shape optimization method for minimizing strain energy for a structure with a viscous damper. The shape gradient function was derived using the Lagrange multiplier method. Both the frequency response and adjoint variable were solved using the modal analysis. It is expected that these calculations will be simplified. To obtain a smooth shape of the solution, H¹ gradient method was used as the shape modification method. The numerical analysis was performed by combining the FEM software, HyperWorks, and a self-made program. A solid model excided by a load over a wide frequency range was used as a numerical example. From the analysis result, we confirmed the effectiveness of the shape optimization method considering the damper by H¹ gradient method.

It is an urgent problem to maintain the high-level urban function by evaluating the serious damage of the structure immediately after the disaster of typhoon and earthquake in Japan. However, it is difficult to find the evaluation of damage and a cumulative external force for a damaged structure immediately after a disaster. It is most important technology to measure the cumulative external force quickly, easily and immediately to evaluate the relationship between the energy applied to the structure and the damage. In this study, we propose a method for evaluating the degree of damage by simply and extensively measuring the cumulative external force of a structure by using a mechanoluminescent material (ML) that emits light from the stress concentration area by applying a mechanical external force.

Visualization and characterization of changes in equipment conditions over time based on precise Lissajous curves are discussed. Enhancing the performance of condition monitoring and diagnostic technology based on vibration measurement requires the use of vibration phase information. The commercialized 3-axis high-precision digital vibration sensor, M-A342, combined with the proposed algorithm that suppresses the effects of external interference, make it possible to draw accurate and high SNR Lissajous curves. The trajectories of precise Lissajous curves corresponding to equipment vibrations are observed to be distributed in certain planes in many cases. We propose that the vibration surface angle (θv, φv), which is a vector perpendicular to the vibration surface expressed as an angular component in polar coordinates, can be used as an indicator. The standard deviation of the variation of θv, φv and the fluctuation of θv, φv well reflect changes in the equipment operating conditions over time, indicating the possibility of detecting changes in the operating conditions earlier than conventional methods such as using RMS values. Since these indicators are dimensionless quantities and can be calculated independently of the type and size of the equipment, direct and absolute value comparisons may be performed even if the equipment and measurement location are different.

The number of development man-hours is also rapidly increasing to respond to CASE, which includes automated driving and electric vehicles. To reduce this rapid increase in development man-hours, we are rushing to introduce a full-scale model-based development method that focuses on simulation, but we believe that this is a tough solution. This is because the "calibration process" during the development process is relied on to deal with hardware components and real-world phenomena, and the number of man-hours required for calibration in simulation or on the actual device is enormous. Therefore, we propose a control system that applies autonomous decentralized control as an approach to suppress the explosion of man-hours in the "calibration process" caused by the increasing complexity of electronic control. In this study, we present the system architecture of the autonomous decentralized control and discuss the calculation method and results of "behavior prediction," which is one of the core functions.

Elastomeric gels are soft-elastic materials consisting of a three-dimensional crosslinked polymer network and liquid filling the space among such network. To take advantage of the swelling-deformation behavior of elastomeric gel and explore its possibility for applications in engineering as a structural member, investigations on the swelling-deformation behavior under various loading conditions are indispensable. Therefore, in this study, we at first proposed a nonaffine model for the elastomeric gel to account for the change of the entangling structure of polymer chains during the swelling-deformation process, in which the change of the number of polymer chains per unit volume N is depending on the first invariant of right Cauchy-Green deformation tensor I₁. And then, to investigate the effect of the nonaffine movement of the polymer chain on the mechanical behavior of the elastomeric gel, we performed a FEM simulation for a spherical gel under quasi-static compressive loading condition. The results show that the swelling-deformation behavior of the spherical gel is quite different at the positions such as the polar, the equator or the center of the sphere.

A multi-material structure that is composed of several different material properties is promising for achieving an ideal functionality that can outperform a single material structure. In particular, increasing the value of the fundamental eigenfrequency is important because it can increase dynamic stability. Since the beginning, Topology optimization (TO) to maximize the fundamental eigenfrequency of a single-material structure has been investigated. However, there are few research papers on multi-material topology optimization (MMTO) for the eigenfrequency maximization problem thus far. Therefore, we propose a novel framework for the MMTO of the eigenfrequency problem. From a theoretical standpoint, two key features are addressed: (i) multi-material level set (MMLS) method is developed. In this method, interfaces between different material phases are represented by iso-surfaces of multiple level set functions. Hence, the optimal solutions have a 1/0 binary structure and are free from greyscale elements; (ii) The proposed design methodology uses a reaction-diffusion equation (RDE) to update the level-set functions based on the topological derivative, allowing new holes to form during the optimization process. The effectiveness of our methodology is demonstrated by benchmark test cases.

Static mixers have been widely used in the biochemical industry because they are portable, reliable and low-energy. We construct a rection-diffusion equation-based (RDE) level-set method (LSM) to conduct topology optimization (TO) for a T-junction static mixer design. The RDE-based TO method combines the concept of the Ersatz material approach with the boundary variation level set-based method. In the context of a fluid-based TO problem, a fluid-solid system can be modeled by using either a monolithic formulation or a system of separate equations. In this paper, we present a comparative study and discuss their different features. After describing the numerical example model, we show the optimized flow path based on both flow modeling strategies. The generally optimized flow paths are quite similar, indicating the CPU time to calculate. Due to algorithmic differences, the use of a system of separate equations is more advantageous with respect to CPU time.

In hitting sports, the coefficient of restitution (COR) is one of the most important items in evaluating the performance of hitting. Many previous studies have shown that the COR has the relation to the natural vibrations of the impacting body and impacted body. However, it is still not clarified in the treatment of boundary condition for the calculation of natural frequencies, and the use of evaluation model. In this study, we created the models of an impacting body and an impacted body with simple 3D FEM models. By changing the shape of the impacting body consecutively, we investigated numerically the relationship between the natural frequencies and COR. The correlation of each eigenmode to the deformation of impacting body during impact was calculated and used to evaluate the contribution of the eigenmode to the COR. From the analysis results, we found that: 1) in the case of a dominant eigenmode existing at the impact, COR can reach to a peak value by adjusting the natural frequency of the impact body to that of the impacted body; 2) in the case of no dominant eigenmode existing, multiple eigenmodes have the contribution to the COR.

In this study, we propose a multiscale shape optimization method for designing micropores in porous laminated shell structures. The shapes of the unit cells of the periodic micropores distributed in each layer of the laminated shell structure are optimized. The homogenization method is used to bridge the macrostructure and the periodic microstructures. A squared error norm is minimized for controlling the displacements at arbitrary points of the laminated shell structure to the target values under the total volume constraint including the microstructures. The equilibrium equation of the macrostructure and the homogenization equations of the unit cells are also used as the constraints. The shape optimization problem is formulated as a distributed-parameter optimization problem, and the shape gradient function is theoretically derived. The H¹ gradient method is used for shape optimization of the unit cells of the micropores. The validity of the proposed method is confirmed by a numerical example for designing the optimal shapes of the micropores distributed in a laminated shell structure. With the proposed method, arbitrary stiff and compliant porous laminated shell structures can be created.

Turbopumps are generally operated close to the design specifications, but diffuser pumps such as for the liquid natural gas in particular can be required in a wide range of flow rates. If the flow rate is lower than the design specifications, an unstable phenomenon called diffuser rotating stall(DRS) will occur, which will interfere with the operation of the pump. However, it is difficult to predict the flow rate onset DRS. Unsteady state analysis by computational fluid dynamics is commonly used to investigate the internal flow of DRS to pumps in detail, but the computational cost is huge and the design process is inefficient. In this study, authors investigated the effectiveness of the design method and the optimaized inlet angle of the target pump using the DRS simple prediction method using steady-state analysis of computational fluid dynamics. Then, it was confirmed that the DRS simple prediction method can be used qualitatively in the target pump. It was also confirmed that the optimaized inlet angle of the diffuser vane for the target pump was in the range of 6 degree to 7 degree.

This paper describes abut hydrogen dispersion in the partially open space with hanging wall. Hydrogen flow collide the hanging wall and get over the hanging wall. This flow makes forward and also backward of hanging wall, hydrogen concentration a little higher than without hanging wall. But no significant differences are appeared between hydrogen dispersion with and without hanging wall.

The authors have previously shown that a numerical simulation using the Fire Dynamics Simulator (FDS) can accurately reproduce hydrogen leakage experiments using the Hallway model. In this report, investigate the feasibility of using FDS to reproduce the experiment and simulation about a study of the diffusion behavior of hydrogen leaking due to damage to buried conduits. In this report, the spread of leaked hydrogen in a soil is simulated with assuming a soil as a porous media. The results of this simulation show that the hydrogen leaked in a soil is spreading in almost concentric circles as in the comparison target, but the hydrogen concentration is lower and the speed of spreading is faster than the experimental and simulation results that are used for comparison. Further detailed investigation is needed to determine the cause of the discrepancy between the past research of experimental and simulation results and the calculation results of this study.

Hydrogen is expected to leak in a variety of situations, from production to consumption. In order to realize a hydrogen sensing system that is more flexible and quicker than conventional systems, we have proposed a new drone-based system for hydrogen sensing with a small thermal conductivity type hydrogen sensor. Initially, quad-rotor drones were thought to be unsuitable for hydrogen leak detection because hydrogen is pushed away from the drone by propeller downwash. However, recent CFD (Computational Fluid Dynamics) analysis and smoke experiments have shown that hydrogen leak detection is possible even under the propeller downwash. In this study, we experimentally investigate the mechanism of hydrogen sensing by the quad-rotor drone. For this purpose, hydrogen leakage experiments were conducted and the path of hydrogen dispersion around the drone is measured by twenty hydrogen sensors installed on a lattice constructed around the drone. It became clear that the actual hydrogen was also pushed down by the descending airflow once, and then passed outside on the circulating airflow to reach the drone. With this result, drone sensing can be achieved more reliably.

Advanced hydrogen safety technology is essential for the realization of a hydrogen energy society. In this context, the role of hydrogen sensors are very important. Therefore, we have been developing a novel thermal conductivity gas sensor using a MEMS (Micro Electro Mechanical Systems) micro heater. This sensor is a low power, extremely robust device especially suited to detect hydrogen as hydrogen possesses the highest thermal conductivity of all known gases. The use of a MEMS heater to reduce the element size has resulted in a faster thermal response, resulting in a faster response to hydrogen compared to conventional sensors.

It is the great interest for detecting hydrogen for safety in the hydrogen society. The sensitivity of detecting hydrogen by Raman scattering was improved about 35 times by using multiple reflections of excite laser beam compared to a single laser beam. 355 nm semiconductor laser beam was reflected about 30 to 40 times between the two concave mirrors. The detection limit of hydrogen was 0.1% and Raman intensity showed linear relation with the hydrogen concentration.

In future space transportation system, concept of fault tolerant is important. Propellant leakage is one of fault modes that should be considered in the system. The space transportation vehicles could have flight environment with very little or without oxygen. Therefore, for the propellant leakage detection, gas sensors that can work without oxygen are needed. The authors have developed the gas sensor that can work without oxygen and of which output depends on the ratio of hydrogen to oxygen concentration. The present sensors were installed on a hydrogen-fueled reusable rocket experimental vehicle so that the characteristics of the sensor’s behavior was measured and evaluated though ground firing test operation of the rocket engines. Comparison of the present sensor’s behavior to that of reference sensors shows validity of the present sensor.

In order to analyze the macroscopic characteristics of a gas jet or liquid fuel spray based on the visualized image, it is necessary to separate the jet region from the background to grasp the outline. In this study, we proposed a method to determine the outline of jet based on the difference in the probability density functions (PDF) of brightness in a test section. The difference in PDFs between jet region and background was quantified with KL divergence (Kullback-Leibler divergence). As the result of analysis into Schlieren image of hydrogen jet, we can obtain reasonable penetration length and jet volume by selecting an appropriate test section size for PDF calculation and a threshold level of KL divergence.

This research group has developed an intelligent ankle foot orthosis. A motor linked to the ankle joint implements a semiactive variable damper in the ankle joint of the ankle foot orthosis. The damping coefficient of the motor is varied according to the gait condition, preventing foot drop due to paralysis and enabling a smooth gait. In this study, an active assist function is added during the kicking motion on the paralyzed side for further gait improvement. Here, the kicking motion on the healthy side is recorded, and the motion is reproduced at the ankle joint on the paralyzed side one step later. In this report, first, the angle sensor attached to the ankle joint on the healthy side acquires the time change of the angle, which is transmitted to a PC by a wireless microcomputer, and recorded. Then, we developed a system that extracts only the kicking motion from the recorded angle changes of the healthy side and transmits it to the motor controller mounted on the paralyzed side. The operation of the developed data communication system was verified using a simple experimental model. As a result, data was successfully transmitted, but a large delay was observed before the motor controller received the data transmitted by the PC.

It is very important to quantitatively calculate muscle strength and evaluate exercise in daily training and functional recovery training in the rehabilitation field. The value of joint torque at each joint of the limb is generally used for motion evaluation. However, bi-articular muscles in the limb might act antagonistically on one joint while acting cooperatively on the other joint. This bi-articular muscle action is known to cause lower power output than the power calculated from individual joint torque. Therefore, this study focused on the motion of the upper limb in the horizontal plane, and attempted to determine the relationship between the distribution of tip output and joint torque of each joint, and to simply estimate the muscle strength of bi-articular muscles from the commonly used joint torques.

Recently, telework or online education due to digitalization acceleration is increased, but reported that many employees such as over 80% feel their faulty posture. Poor posture has effects on productivity, physical disorders, and other body risks. The LaLaCo Chair can provide sitting posture improvement benefits relatively safely even for users. However, these effects are limited to the impressions of each user. In this study, we quantitatively analyzed the cervical vertebra angle using a flexible goniometer when using the LaLaCo Chair. Ten healthy subjects participated in this experiment, and these subjects were measured and analyzed sitting posture after watching a video at 5 minutes, and before and after exercise. The condition that exercise was set to 10, 20 and 30 times at this time. As a result, the posture improvement effect of the LaLaCo Chair on the cervical vertebra angle was over 70% on each exercise condition. Also, the improvement when 10 times of exercise is the highest at 86%. In the future, we plan to analyze the improvement of sitting posture in other working conditions such as using smartphones, personal computers and others.

In this paper, we propose a new air conditioning system that predicts the indoor comfort distribution by computational fluid dynamics (CFD) and the Internet of Things (IoT), and incorporates human behavior patterns to adjust to the appropriate indoor comfort level. In this air conditioning system, the temperature as well as the airflow distribution in the room needs to be predicted and then a solution is proposed based on the prediction results. In this paper, we present the experimental model we used and the related experiments for the analysis.

The authors have been developing a generator for NCPAP (hereinafter abbreviated as HNCPAP) using an air-curtain. This paper is reported that HNCPAP has characteristics as a fluidic device. The experiment was performed using the healthy breathing mode of the spontaneous breathing simulator for newborns (PT-2: manufactured by Atom Medical) equipped with HNCPAP, and the MAP was changed with constant tidal volume. The experimental conditions were that the respiratory rate and the tidal volume TV were constant at 50 times/minute and 7ml, respectively, and the experiment was performed by changing every 100 Pa within the MAP range (300 Pa to 900 Pa). The result obtained was that the prong flow developed into a forced vortex in the inhalation, and the inhalation flow was stable regardless of the increase in MAP. In the first half of exhalation, the sub-vortex developed into a forced vortex and sub-flow was stably discharged, so that the entrainment was stable regardless of the increase in MAP. By alternately repeating these inhalation and first-half exhalation flows, the characteristics as a fluidic device were clarified. Further NDPAP results revealed that abdominal distension was caused by the inhalation flow more than tidal volume due to Bernoulli’s effect.

The effect of feathering motion during flapping flight on aerodynamic characteristics is numerically studied for an enlarged model of a mosquito wing by using OpenFOAM together with immersed boundary method. It is shown that aerodynamic performance is improved because the separated region is reduced by feathering motion.

Hummingbirds can hover by flapping their wings composed of multiple flight feathers and wings consisting of multiple separate flight feathers are considered robust against collision. However, most of hummingbird-inspired wings developed so far were composed of one membrane and the feathers are not separate. Therefore, in-plane deformation of a hummingbird-inspired wing would be difficult, and the wing would not be easily twisted like a real hummingbird, causing large angle of attack and low efficacy. In this study, we propose a hummingbird-inspired wing composed of multiple separate flight feathers and discuss the difference from one composed of one membrane from the viewpoint of efficacy and angle of attack. First, we fabricated a wing with 8 flight feathers and one composed of one membrane for comparison. Then, we conducted flapping tests for the two wings and measured time-averaged efficacy and angle of attack at 57% wing chord. As a result, there was no difference of time-averaged efficacy between the two wings. However, angle of attack at 57% chord was different between the two wings. A wing with 8 flight feathers maintained lower angle of attack during first half of downstroke and upstroke because of wing twist. However, during last half of each stroke, the angle of attack for a wing with 8 flight feathers was larger. This may be caused by elevation of a wing. By preventing wing elevation, we would be able to realize a wing composed of multiple flight feathers more efficient than one composed of one membrane.

In this paper, a study of the flow behavior in a backward facing step in low Reynolds number range from 100 to 800 is conducted using COMSOL Multiphysics^®. The k-ε turbulence model is takne into account. The investigation starts from a standard mesh and then refine the standard mesh using an adaptive mesh refinement method. The horizontal and vertical velocity component profiles, pressures and the velocity quiver are shown on the refined meshes. The overall characteristics of separating shear layer, the flow behavior of the transverse vortices in the main flow and a reattachment length on a lower side wall is presented. The effectiveness of the adaptive mesh refinement method is verified and the method could be expected as a CAE analysis tool for industrial utilization.

Medical Images such as MRI and CT can reproduce in-vivo configuration of an artery not in zero-pressure state (ZPS) but in physiological blood pressure. To determine the geometry of a patient-specific artery in zero-pressure state is important for structural analyses of arterial wall. Thus, we propose a new method for ZPS estimation of patient specific artery. The local diameter of an arterial cross section in the zero-pressure state is estimated using our proposing ZPS estimation method by applying negative pressure. The reduction rate of the vessel diameter is obtained for various diameters. Based on the relation between in-vivo diameter and the reduction rate, a medical image-based geometry model is shrunk toward the axial center line of the artery. We found that the ZPS-estimated model could reconstruct the cross section area of the original medical image at the physiological pressure, but some difficulties on the estimation of the bifurcation geometry due to the non-circular cross sectional shape. For better estimation of a bifurcation, the interpolation function should be modified.

Penguins are propelled through the water by flapping their wings. During swimming, wing flapping causes bending deformation of the wings. The cross section of the wing forms a thick wing shape, and the wing skeleton consists of a humerus, a forearm, a manus, and digits. Previous anatomical studies have shown that penguin wings are mobile in the wing plane at each joint. However, the range of motion and stiffness of bending outside the wing plane have not been investigated. Furthermore, the range of motion and stiffness with respect to torsion is unknown. In this study, we measured the static flexural and torsional stiffness of wings collected from a gentoo penguin (Pygoscelis papua) cadaver. As a result, we found asymmetries in flexural stiffness with respect to the bending direction and torsional stiffness with respect to the torsional direction. Furthermore, assuming that each joint of the penguin wing is a torsional spring and the other parts are rigid, the spring stiffness of each joint during bending and torsional deformation was measured. The results showed that the asymmetry of wing flexural stiffness was strongly influenced by the wrist joint and the asymmetry of wing torsional stiffness was strongly influenced by the elbow joint.

It is well known that a high-speed submerged water jet generates a cloud of cavitation bubbles experiencing a collective unsteady behavior that repeats growth and collapse. In particular, it is considered that a high-pressure shock wave may be emitted associated with the collapse of the cloud. However, its mechanism has not been enough clarified and hence it is required to be explored both from the experimental and numerical analyses. In this study, we fist make an observation of such a unsteady behavior of the cloud cavitation that is generated by a pulsed Ho:YAG laser-induced liquid jet using a high-speed video camera. Then, a two-dimensional numerical analysis based on the SPH method is examined to simulate the unsteady behavior of the cloud, in which the mixture model of liquids and gas bubbles is employed. Finally, the validity of our numerical analysis is illustrated by showing that the unsteady behavior of the cloud from its inception, growth, shrink, collapse to rebound is realized in qualitative agreement with the experimental data.

Recently, the development of the supersonic transportation system is desired. For the development, the reduction of the wave drag and sonic boom is crucial problem. For the solution of the problem, the shock wave modulation technique by using the electro-magnetic power is one of the promising methods. This technique makes use of the baroclinic effect. For the application of this method to the other method of vortex generation method in the supersonic flow field, such as the scram jet engine inlet, the comprehension of the baroclinic effect is inevitable. In this study, for the comprehension of the baroclinic effect due to the electro-magnetic power, the three-dimensional numerical analysis code to simulate the interaction between the shock wave and the temperature modulated field was developed. The results were verified by comparing with the experimental visualization data.

It is important to enhance the safety to passenger even in a train accident. In order to grasp secondary impact risk to walkover seat occupant, the sled tests that assumed a level crossing accident were carried out. The results of the test made it clear that the severity of the leg injury to the passenger was higher than any other parts of body since the passenger's legs collided with the edge of a seating face of the front seat. To reduce such type of injury risk, the seating face which supported both ends of the aluminum pipe with the urethane elastomer was developed based on the impact test results. The sled tests were carried out to identify the injury risk reduction effect of the seating face with buffer. It was found that the leg injury risk of the seating face with buffer reduced for the conventional seating face more than 60%.

In this study, we discussed countermeasures using multibody simulations of vehicle-elderly cyclist accidents especially in helmet-use．Bicycle helmets was examined as safety measure for head injury risk in an elderly cyclist accident. Multibody simulation software MADYMO (TASS International) was used for the analysis. The material properties of the helmet model were determined by simulating an experiment using an actual soft-shell helmet and cycle helmet, and it were incorporated into the elderly model. The simulation focused on the presence or absence of a helmet and divided the pattern according to the vehicle's collision speed and the gender of the elderly. As a result, it was found that the risk of head injury was significantly reduced by using either helmet at the secondary impact to the road surface after the primary impact to the vehicle. Furthermore, it was found that the behavior of the cyclist changed depending on the mass and presence of the helmet after the collision with the vehicle. In the future, we plan to investigate the effects of helmet mass and behavioral changes.

Cerebral concussion caused by a contact in American football games is a serious problem today, since its mechanism remains unclear so far. From some prior researches head vibration would induce the cerebral concussion. In this study we had carried out a modal analysis for a human head model consisting of skull, falx cerebri, cerebellar tentorium, cerebrum, cerebral cortex, corpus callosum, cerebellum, brainstem, septum pellucidum, cervical cord, cervical vertebrae, and lateral ventricles (cerebrospinal fluid) with mechanical properties that we referred to some papers. The results show that the 1st, the 2nd and the 3rd modes are sagittal rotation (eigenfrequency: 7.29 Hz), coronal rotation (eigenfrequency: 7.65 Hz), and axial rotation (eigenfrequency: 11.24 Hz), respectively. The maximum of 1st principal stress, 3rd principal stress, equivalent stress and 1st shear stress for these three modes were located in the cervical cord, cervical vertebrae and skull, not inside the brain. On the other hand, the maximum and minimum principal strain were located inside the brain for these three modes. Nucleating higher strain inside the brain might be caused to occur cerebral concussion when the head vibrated due to the contact.

We conducted a literature review and determined the specifications of an ideal virtual accelerometer in order to design an economical and portable acceleration measurement system that can be used in amateur sports. As a result, the performance of the ideal and virtual accelerometer was determined to have a sampling frequency of 1000 Hz, an acceleration of 200 G (1962 m/s2), and duration of 40 ms. The rotation tests for comparing the ideal and virtual one were conducted on three existing sensors using a rotating impact test system. The results showed that the minimum requirements were a sampling frequency of 200 Hz, a maximum acceleration of 200 m/s² with a duration of 27 ms. If a sensor also holds，a Bluetooth® communication device, and is dimensions of 30 × 30 × 15 mm or less, it will be used in the storage system of our goal.

The autopsy is performed when a case is suspected, and the autopsy physician makes an educated guess as to the circumstances of the accident, which is the decisive factor in determining the case. Conversely, in head trauma cases, the injury situation can be inferred by simulation from the mechanical point of view. In this study, we estimated the behavior of the victim by whole-multi-body analysis, calculate the mechanical responses in the brain at the time of collision by head finite element analysis, and compared the calculated results with the location of the victim’s injury to verify the validity of accident reconstruction. In a hit-and-run case, we estimated the violations traffic regulations, the vehicle type, the vehicle speed, and the relative position of the victim and the vehicle. The results demonstrated the possibility of quantitative evaluation by adding mechanical information to the opinion findings of forensic experts.

Previous our study, in vivo impact test assuming human-personal care robot interaction was conducted using live porcine in order to evaluate soft tissue bruise injury tolerance. Subcutaneous hemorrhage was determined by observation of hematoxylin and eosin stained tissue. As a result, bleeding occurs at the part of adipose tissue and muscle. In this study, 3-dimentional finite element analysis were conducted on simple model consist of skin and soft tissue in order to clarify the occurrence mechanism of bruise injury. FE model imitated subcutaneous structure of porcine skin used in impact test. Analytical conditions were assumed to the experimental condition that bleeding occurs at the part of adipose tissue and muscle. As a results, the part of taking maximum first principal strain is good agreement with the bleeding point obtained by experiment. The experiments and analytical results show that possibility of bleeding will be occurred capillary failure at the part of local high strain.

An actuator is a mechanical element that converts an external input such as an external field or an electrical signal into a physical motion. Soft actuators are made of soft polymer materials such as gels and elastomers, and have various advantages such as lightweight and quietness. We have previously fabricated a channel structure with a re-entrant structure with a kind of auxetic structure, and developed it into a highly stretchable wearable sheet. However, the deformation of the cell structure was limited to two dimensions. In this study, we designed a soft actuator with a three-dimensional auxetic structure using a 3D printer, and aimed to drive it by pneumatic control.

Urolithiasis is a disease in which calcium oxalate crystallizes in the urinary tract, and has a high recurrence rate. It is necessary to consider the burden on the body by surgical treatment, therefore, treatment methods that effectively promote spontaneous stone passage are required. In this study, we investigated the effects of angular velocity on spontaneous stone passage and established the parameters needed to develop a working accelerated renal pelvis and calyx simulator. According to analysis from experiments, it was confirmed that the simulator using our established parameters is able to reproduce spontaneous stone passage similar to our experiment results. By establishing a spontaneous stone passage prediction simulator, it will be possible to devise a method to effectively promote spontaneous stone passage in patients. By reducing the morbidity of urinary lithiasis that requires surgery, it is expected to reduce the burden on patients and medical sites.

Proximal tubule plays an important role in reabsorption of nutrients and excretion of drugs. Such reabsorption and excretion processes are mediated by proteins known as transporters in the proximal tubule cells. To evaluate the transport of nutrients and xenobiotics in vitro, proximal tubule microphysiological systems (MPS) have been developed. However, conventional proximal tubule MPS employ cells derived from experimental animals or cells immortalized by genetic modification. Apparently, the expression levels of transporters are insufficient in these cells. In this study, we prepared MPS employing proximal tubular cells isolated from kidney organoids generated from iPS cells. In this MPS, we quantitatively evaluated the transport of SGLT2, which is responsible for glucose reabsorption, and P-gp, which is responsible for drug excretion. As a result, compared to MPS using immortalized cells, MPS using iPS cell-derived cells showed an approximately 1.6-fold improvement in the transport capacity. This indicates that we were able to produce an MPS that better reproduced reabsorption and excretion rates in vivo.

Recently, the interaction between graphene and biological membranes has been under intensive research because graphene and its related materials exhibit distinctive characteristics. For example, water-soluble graphene oxide (GO) is expected to be used as a carrier of drug delivery systems (DDS), but it is also known to have cytotoxicity. Thus, it is important to understand the interaction between lipid bilayers and graphene/GO in order to design molecular systems. Furthermore, these interactions have been studied mostly using small lipid vesicles (< 1 μm), although the size of biological cells is much greater. In this study, we studied the interaction between GO and cell-sized giant unilamellar vesicles (GUVs). We especially examined the effect of the lipid compositions, including neutral, negatively charged, and pyrene-grafted lipids. Pyrene is known to adhere to graphene with the non-covalent π-π stacking interaction. Microscope observations and flow cytometry measurement revealed that GUVs composed of lipids which have attractive interaction with GO rupture at a high probability.

Detection of nanoparticles (NPs) plays an important role in a wide variety of fields such as medical diagnostics and environmental monitoring. We have been developing a simple system for detecting NPs in small samples using vibration-induced flow (VIF), in which a mean flow is induced around a micropillar by applying small periodic vibrations. The system can evaluate the presence and concentration of specific NPs in a minute sample from the extent of aggregation of affinity capture beads agitated by VIF. This technique eliminates the use of fluorescent labeling or expensive image analysis equipment. In this study, we investigated the relationship between various flow patterns and capture bead aggregation. It was found that large vortex flows induced by circular and elliptical vibration produce large aggregations, whereas small vortex flows induced by rectilinear vibration produce a large number of small aggregations with relatively uniform sizes. This result indicates that the size of aggregations depends on the size of the vortices in the flow field and that can be readily controlled by the flow pattern tuned with vibration conditions.

Cryopreservation is widely used for the stable and long-term storage of cells in various fields. To inhibit ice crystal generation, at least one cryoprotective agent (CPA) must be added. We previously reported a CPA-free cryopreservation method based on inkjet technology. To achieve vitrification of cells, tiny droplets containing cells are deposited at intervals of 200 μm on the liquid nitrogen-cooled substrate, which confines the number of cells in a single operation. In this study, we aim to increase the number of droplets containing cells on the substrate by reducing the intervals between the droplets. To inhibit an influence on the cell viability, the temperature rise of formerly deposited droplets and the decrease in the cooling rate were analyzed and evaluated. The temperature of the neighboring droplet did not exceed the glass transition temperature, over which recrystallization ultrarapidly occurs, even when the droplet interval was 75 μm. On the other hand, the cooling rate at the intervals of 125 μm was slightly below the critical cooling rate of the cell. Therefore, the intervals between the droplets should be above 150 μm. We also experimentally confirmed that the cell viability at the intervals of 150 μm was the same and the viability at the intervals of 75 μm decreased by approximately 40% compared to the one at the intervals of 200 μm. Both the results suggest that CPA-free cryopreservation achieves by depositing 70pL droplets at intervals above 150 μm.

Active matter is a materials and objects that have autonomous motion mechanisms and interact with each other. For example, animals, living cells, and bacteria are classified as active matter. The dynamic performance of various animals and insects that walk and propel themselves on the water surface is mainly related to the surface tension.

In this study, the elastomeric film containing liquid metal was floated on the water surface, and the Marangoni propulsion induced by near-infrared light (NIR) irradiation was verified by kinetic analysis.