We prepared the computational domain, which 9 dimples of golf ball are linearly distributed on a flat plane. The Reynolds number based on dimple diameter is 22000 and a time step is 1×10^-5s. We found out that the momentum thickness on a first dimple was also same value for different depth models and the momentum of the flow over 9 dimples didn’t change significantly after a fourth dimple. We think turbulence doesn’t develop after the fourth dimple. Observing the vortex structure visualized by lamda2-criterion (λ²=-6×10⁸ /s²), there was no vortex on first dimple. Span axis vortices was generated on second dimple and it transformed to hairpin and streamwise vortices. After third dimple, there are almost only streamwise vortices except around dimple edges. These vortices help to transport a momentum from main flow to a turbulent boundary layer. Then, we measured vorticities for each directions ω_x, ω_y, ω_z. The maximal value of ω_x didn’t change after the fourth dimple, so that the momentum hardly change. As these results, we revealed that the vortex structure is completed over there dimples.

Air permeability is one of the important functions of footwear to control microclimate inside a shoe for keeping comfort. Focusing on running motion, swing phase should significantly affect ventilation of a shoe due to large velocity of foot. During the swing phase, foot posture and angle of attack (AoA) change at every moment. In this study, the relationships between AoA and ventilation in a footwear were investigated. To imitate the swing phase of running, a new experimental apparatus was built with a combination of a simple wind tunnel and a posture-changeable artificial foot. Ventilation in a footwear was obtained by tracer gas method. In the AoA range between 0 to 135 degree, ventilation in toe and instep area took minimum value at about 45 degree of AoA. Judging from extra Particle Image Velocimetry (PIV) measurement, ventilations in toe and instep area have positive correlation to wind velocity and gauge pressure near the measurement point.

We have spent to walk the majority of the activities of daily living. We can reduce the burden on the foot by putting insoles in the shoes. In addition, insoles are used as part of rehabilitation. It can be proposed for the maintenance of a healthy life by studying the effect on the body due to the shape of the insole. This study focused on the thickness of the insoles and aimed to clarify the influence on the body when to use different insoles of the toe portion and the heel portion. Experimental subjects were opened with resting stance posture, both feet standing position and one-foot standing position. The condition of the insole was 5.5 ㎜ and 7.5 ㎜ in the thickness of the toes, and the heels were 5.0 ㎜ and 7.5 ㎜ in thickness. The experimental participants were four men in their twenties. The measuring device was a force plate. The sampling rate was 1000 Hz. From the result of the total trajectory length, it was confirmed that the center of gravity fluctuation becomes smaller by the insole.

In ball game sports, swing velocity is one of crucial importance to improve performance. There are several study reported on the relationship between swing velocity and upper/lower limbs. However, influence of shoes on swing motion has not been clarified yet. The purpose of this study was to investigate mechanical factors to achieve the swing velocity. One male subject having tennis experience participated and was performed swing motion with different stance width and hitting position. Upper limb was fixed to keep the repeatability of the swing motion. The motion was measured using a motion capture system and two force plates. As a result, it was confirmed that pelvic rotation angular velocity has positive correlation to swing velocity. Furthermore, the maximum value of the pelvic maximum rotational angular velocity was increased with shifting resultant center of pressure (CoP) to the pivot foot side at the end of the preparatory motion. In the acceleration phase, increase of the maximum value of the resultant free moment obtained from both feet was effective to achieve the swing velocity.

American football (AF) is characterized as a collision sport and it has been reported that there are a lot of injuries including catastrophic injuries. Many reports state that head injury has occurred in about 10% of the whole, and especially the incidence of a brain concussion is very high. Biomechanics research to analyze a mechanism of the brain concussion by video analysis has been done since the 1960s. Then, several collision experiments to investigate the linear and rotational accelerations acting in the head during a collision in the actual field have been conducted since 2003. However, it is unclear how much the impact force is acting on a head itself by using an acceleration sensor. Thus, we have constructed a digital filter estimating the head action force with a new method using a strain gauge although the digital filter was obtained from only one location of the head. In addition, we should consider the force on an outer shell of the helmet and the force buffered by the inner pads separately because the head action force at the time of collision is attenuated by inner pads inside the helmet. For this reason, when considering the head acting force, it is necessary to consider the force acting on the outer shell of the helmet and the force buffered by the inner pad. The purpose of this study was to verify the measurement method of constructing a digital filter by using strain gauges attached to the front and back surfaces of an acrylic board.

In football of recent years, the shape of the panel of the ball has changed greatly with each year, and the types of balls used by the professional leagues and international conventions of each country are not unified. Changes in panel shape greatly influence aerodynamic characteristics, and characteristics, characteristics, and performances change as balls are different, so the game affects the game in a professional world where delicate play is required. In our experiment, we measured the impact point of a soccer ball using an injection machine. Capture the influence of different panel shape on the trajectory of a soccer ball. As a result, it was found that if the number of panels is small, it tends to be aimed at, and even if the number of panels is the same, the landing characteristics are different.

The purpose at this study is to clarify the influence of aerodynamic characteristics for various groove shape of soccer balls by a wind tunnel experiments. The width and the depth of the groove of ball surface were changed. Drag coefficient was measured in the range of Reynolds number 0.6×10⁵~3.6×10⁵. As a result of experiment, it was revealed that a critical region changed to the low Reynolds number and the drag coefficient in the super critical region increase as a groove depth is deep. The drag coefficient in the super critical region increase as the groove volume increases.

In recent years, soccer balls of various designs have been developed, but depending on the design of the "panel" on the ball surface, there is a case that a "Knuckle ball" in which the trajectory changes irregularly during flight may occur. Knuckle ball is an element that audiences enjoy in games, but it is an obstacle in fostering players. In this research, we aim to clarify the influence of the panel on the surface of the soccer ball on " Knuckle ball" by wind tunnel experiment and to grasp the relationship between the panel shape of the ball and aerodynamic characteristics.

This paper describes the initial conditions of a kick for goal in rugby with respect to the ball attitude on the kicking tee. The initial conditions are defined by the initial velocity vector and the angular velocity vector. The initial conditions were obtained by the Vicon motion capture system. A rugby ball with seven markers on the surface was kicked by the kicker in university level. The experimental parameter was how to place the ball on the kick tee. Two ways of placing the ball was examined. One is the vertical type, in which the longitudinal axis of the rugby ball lies in the vertical direction. The other is the rocket type, in which the longitudinal axis is tilted forward. It was found that the initial velocity of rocket type is greater than that of vertical type. The initial velocity and the angular velocity are related to negative correlation.

A cracking rate was calculated from the video by the video camera with the road surface property of the Tamagawa cycling course by the machine learning method. The cracking rate measurement distance accounted for 26.4% of 18.2km in total length of the Tamagawa cycling course at 4.8km.

Cr = 100% were mixed with cracking rate Cr = 60% at width 2.0m with crazing rate Cr = 0% at width 3.0m.

Right-side gap rate RGr of a bicycle run and the walker was measured by the video measurement of the traffic state.

Right-side gap rate RGr was 70%±5% without depending on width in the case of an independent bicycle run, walk.

On the other hand, a right-side gap rate decreased so that cracking rate Cr increased in width 2.0m by the two-way traffic and was RGr25% - 38%.

right side gap rate RGr was 35% - 50% at width 3.0m.

In addition, the acceleration of the Z-axis direction increased so that cracking rate Cr increased, and the maximum of the Z-axis acceleration was 75.5m/s2 in 25km/h per an hour, crazing rate Cr = 100%.

In Japan, the amount of purchases of sports-type bicycle and electric-powered bicycle have become large annually because of health consciousness and awareness of energy saving. For these bicycles, traveling speed gets higher. This makes brake systems more important for bicycle to stop the bicycle safely and reliably even in rainy weather, and to be able to easily control the traveling speed. In this study, we developed a rubber brake shoe filled with rice bran ceramics (RBC) particles, and evaluated the braking performances under simulated rain conditions using the apparatus simulated actual bicycle, comparing a commercially available brake shoe. One test cycle was conducted from 60 km/h to stop; the number of test repetition was 50 cycles to obtain the effect of duration. In the initial test cycles, the commercial shoe showed high friction coefficient but then the friction coefficient decreased. The shoe had high aggression to the aluminum alloy rim. In contrast, the RBC-filled shoe exhibited high and stable friction coefficient due to low aggression to the rim, regardless of the test repetition even at high traveling speed, and also showed low specific wear rate compared to the other samples. Therefore, the RBC-filled shoe can be said as a promising shoe with high controllability and high wear resistance under rain conditions.

Pedaling techniques of road bikes play an important role in competitions. Pull-up action using the binding pedals is widely known as one of the essential pedaling one techniques to win the race. The previous research demonstrated that this skill will improve the efficiency of road bike pedaling. Meanwhile, there is a little research into learning method of the pull-up action. Therefore, this study developed an equipment to train pull up action by using local braking. A training method using the change of the environment, providing braking force to crank, during pull-up action was devised. This equipment consists of a braking disc and brake pads, and could be easily attached to road bike instead of a rear wheel by using quick release mechanism. Moreover, Breaking blocks are attached to the disc, and disc's rotation angle is synchronized with crank angle. The braking force will be provided by touching the blocks on the disc with the brake pads during the pull up action. The pedaling efficiency was calculated by measuring leg-power during the pull up action. This result indicated that providing local brake would lead to improvement of pedaling efficiency.

Road bicycle racing is the cycle sport discipline of road cycling, held on paved public roads. The riders travel a long course including flatlands and mountains. In order to improve a record, not only physical abilities but also skill for riding downhill safely as fast as possible (faster cornering skill) are required. The faster cornering skill is composed of three factors, situational analysis, postural control and speed control. Due to the difficulty of considering three factors in a short time and the risk of serious accident, it is difficult to train this skill. Therefore, this study will investigate a method of developing faster cornering skill on downhill. A method of training situational analysis and postural control while speed control automated is contrived. Authors develop a caliper brake with speed keeping function using a servo motor and the parameter of speed control is based on the opinions from a cyclist. Running test on downhill is held and it is suggested that this method will help acquiring faster cornering skill on downhills.

It is a common desire that people make the live comfortable. One of the method for it in severe environments is to utilize clothing effectively. Since the clothing microclimate greatly influence the clothing comfort, we investigated the air filed in clothing microclimate. The clothing microclimate is a small gap space between the human body and clothing. Experimental parameters of the clothing microclimate is the air temperature, humidity and air flow. Among them, air flow is the most important. Therefore, we investigated the condition of air field in clothing microclimate at simulated human body by particle image velocimetry (PIV) analysis. In this study, the results of PIV analysis showed that the air flows upward in the gap because of the natural convection due to human body temperature. The air velocity and angle in the gap was influenced by the air gap size and the amount of human heat generation. We finally clarify a mechanism of air field formation in clothing microclimate.

This paper proposes the estimation method of friction coefficients using the high sensitivity force plate. This force plate can measure 3-axis force, 3-axis moment and COP (center of pressure). The proposed method estimates coulomb and viscous friction coefficients by using the shear force, the normal force and the velocity of force plate data. The velocity is calculated by differentiating the COP information. The friction coefficients are modeled as the values proportioning to the normal force. The estimation method conducted by the Kalman filter. We conducted the measurement experiment using the force plate and the 5 type clothes, and we estimated the coulomb and viscous friction coefficients between the finger and clothes. The analytical results showed the difference by clothes, the change of friction coefficients was indicated.

This paper proposes the method for estimating seating face geometry in dynamic condition using belt-shaped inertial sensors system. This method estimates the posture information in relative coordinate system, and the method compensates the accumulated error by using the adaptive Kalman filter. The sensor fusion estimates the Roll and Pitch angles using gyro sensor and acceleration sensor outputs, and the effect of drift error is reduced. The shape is estimated by applying forward kinematics analysis and the posture information calculated by the sensor fusion. The correction is performed using an adaptive Kalman filter. We conducted the measurement experiments using belt-shaped inertial sensors system and 3D motion capture system in dynamic condition. The results indicated that this method can estimate the face geometry in static and dynamic conditions. This system can be used to represent the face geometry in dynamic condition.

In recent years, the number of patients with low back pain has increased, and it is a problem in various aspects such as health and economics. It is caused by a mechanical load acting on the muscles and the spine in the lumbar part. To reduce the risk of back pain, a support wear that reduces the load on the lumbar spine during flexion has been suggested by our group. This paper presents a dynamic model to calculate the load on the lumbar vertebrae. Especially, ligament tension considering Flexion Relaxation Phenomenon (FRP) which has not been considered so far and intra-abdominal pressure using two dimensional image information were modeled. First, the degree of FRP was measured from the myoelectric potential information of the back muscle in different bending postures. Next, we modeled the ligament tension using the results. Finally, the intra-abdominal pressure was incorporated into the model to calculate the compression force of the lumbar spine, and the experiment to estimate the lumbar load was performed. As a result, the experiment show that the load of the lumbar spine increases markedly due to FRP and this model is effective in calculation of the lumbar load compared to results of actual measurements of internal pressure.

The purpose of this study was to investigate the functional roles of the joint torques of the outer-side support leg considering deforming characteristics of foot segment during cutting motion. Three male participants performed cutting motions under bared and shod conditions. The three-dimensional coordinated data of markers attached to the body and foot were measured with a motion capture system, and the ground reaction forces exerted by fore and rear side of foot, which is modelled as two-segment model separated at the navicular bone, were measured with 3 force plates. Bending and torsional stiffness of axes at virtual joint, set at the boundary part of the foot segments, were calculated from static equilibrium equation with respect to the moments exerted about the two axes. The functional roles of the leg joints were quantified from a dynamic force equation derived from multi-body dynamics. The results obtained in this study show that 1) the bending stiffness differ between subjects, 2) braking and accelerating forces were manly caused by ankle plantar flexion and knee flexion torques, and 3) the stiffness of the bending maybe relates to the contribution of ankle plantar flexion torque to the braking force during the braking phase.

The purpose of this study was to clarify relationship between foot arch deformation characteristics and balance maintenance mechanism during support phase in running. The functional roles of support leg joints were analyzed by quantifying dynamic contributions of the joint torques to the generation of ground reaction force (GRF) and ankle angular acceleration vectors normal to the frontal plane using the equation of whole-body motion. Seven male runners participated in this research and ran at the speed of 5.5m/s. The trajectories of 47 markers attached to the body and the ground reaction force of the support leg were measured with VICON-MX system with a force plate. In addition, the stiffness of the arch was identified during a support phase of a gait for one step. From the magnitude of the arch stiffness, the participants were divided into two groups such as Type L (low arch stiffness) and Type H (high arch stiffness). The results of analyses indicate that 1) the contributions of individual joint axial torques to the horizontal medial-lateral components of the GRF were canceled so as to reduce the component regardless of the type of groups, 2) the contributions of individual joint axial torques to the ankle angular acceleration, whose axis is normal to the frontal plane, were canceled so as to reduce the angular acceleration, 3) the GRF and the angular acceleration were induced by joint torques whose axes are not only normal to frontal plane but also along other directions, and 4) the difference of balance maintenance mechanisms between the groups in the frontal plane maybe due to differences in arch stiffness as well as running forms and COP locations.

In this paper, we propose a supporting device using the gyro-moment for sprinter's movements. Since previous studies have already proven the effect of the device on femur movement, we have applied the device to the upper limb motion. Experimental results show that running time is shortened by assistive devices on the brachium.

The purpose of this research was to investigate a kinematic and kinetic change at approach to curved path in sprinting. Curved sprinting acquire centripetal force. In order to produce centripetal force in the curved sprinting, leaning trunk is necessary at the approach phase. Obviously, the centripetal force acting on the runner must be the lateral component of the ground reaction force. The authors conducted the experiment to obtain the ground reaction force and three-dimensional coordinates of the body segments’ markers by the motion capture system on two athletes at the approach phase on the curved path (radius:38.2m). The lateral component of the ground reaction force was changing three steps before entering curved path. Once the body leaned, posture changed due to the lateral direction component of the ground reaction force.

This paper proposes the compensation method of vibration noise in the treadmill installing force plate. The treadmill can measure force and moment in walking and running. However, the vibration noise is included the force plate outputs by the belt drive, and the dynamic characteristics of treadmill is increased the effect. The compensation method estimates the error by using the accelerometers installing to force plate in the treadmill. The error is estimated by applying the disturbance observer. We conducted the measurement experiment by no load and belt drive, we obtained the accelerations, and we estimated the inverse models of dynamic characteristics representing by using the pulse transfer function. The error force components were estimated by the models and the accelerations. The compensated forces were calculated by using the force plate outputs and the error force components. The compensated force indicated the results reducing the effect of vibration noises and dynamic characteristics. The proposed method can be used to performance improvement of the treadmill installing force plate.

In order to evaluate the balance ability and diagnose the disease, it is necessary to measure the standing motion easily and accurately. The purpose of this study is to estimate small motion of human body from force plates during standing on swaying support surface. This paper discusses a posture estimation method for the frontal plane. Accurate posture estimation method from the force plates requires an appropriate kinematic chain representing the lower body. We defined a three-link chain as a mechanical model of lower body and single-link as a model of upper body. Assuming that subjects stand with their stance parallel and movement of upper body synchronizes with lower body, we can simplified the mechanical chain to an single-degree of freedom system. Based on the equation of motion, the present method can estimate the posture angle and the angular acceleration of the body from shearing force and center of pressure measured by force plate and acceleration of support surface. To verify the validity of the estimation method, we conducted sway test using an electric board equipped with two force plates. Comparing the posture estimated from the force plates by the present method with that from motion capture system, it was found that sufficient estimation accuracy can be obtained by the proposed method.

The goal of this work is to identify a controller of a human who steps and brakes. The loci of the center of mass (COM) of the motion of interest were measured and plotted in the state space. It was seen in them that the motion gradually converged to a regulatory behavior after the landing, which was supported by overlaying the loci of regulatory motions on them. Two hypotheses were made to model the behavior: (1) the delay in ground force manipulation (or the center of pressure (ZMP)) causes the smooth transition, or (2) a control which can produce both a stepping motion and a regulatory motion by adjusting the references of COM and ZMP works. (1) was rejected since a negative feedback gain was identified together with the delay. In order to verify (2), a stepping controller developed for biped robots was employed as a model of the human's control scheme. The identified controller showed qualitative similarity to the measured behavior, though it still has some points of discussion.

In this study, the relation between a behavior of a neural oscillator with a feedback signal and the coefficient parameters were analyzed numerically. Especially, regular sin waves were used as a feedback signal. Under this condition, the period T_N and amplitude A_N of the output signal from the neural oscillator were evaluated for a_ij and T_a /T_r as coefficient parameters, f_b as feedback parameter and T as the period of the sin wave. As a result, the period T_N got longer, when a_ij was increased or T_a /T_r was decreased. Also, when the feedback parameter f_b was increased, the output signal from the neural oscillator tended to be stable. The distribution of the period T_N related to a_ij and T_a /T_r was divided into three areas; similar, twice and unstable period areas compared to the period T of the feedback sin wave. The boundaries of the three areas were separated clearly. For the amplitude A_N of the output signal from the neural oscillator, although the distribution of the amplitude A_N showed a similar tendency to the period T_N, the boundaries were varied continuously. Based on our results, the feedback coefficient f_b could be decided to be larger in order to spread the stable areas. Then, the coefficient parameters a_ij and T_a /T_r could be decided to satisfy the required period T_N and amplitude A_N with avoiding the boundaries the areas.

The aerodynamic behavior of tennis balls is very complex by the surface structures (felt length, material). We carried out the flight experiment to analyze the performance of tennis balls by air pressure ejection machine. Two video cameras were used to measure the aerodynamics of flight tennis balls at two positions separated horizontally by about 7.5 m. We proposed a new estimation method uniquely obtained from the position coordinates of the ball using the least squares method The balls were ejected at 42 m/s, 30 m/s, then the spin rate was about 2500 rpm. when ejected at 42 m/s, the average of C_D of entire balls is about 0.6, the average of C_L is about 0.2, when ejected at 30 m/s, the average of C_D is about 0.58 and the average of C_L is about 0.25. The drag coefficient was increased along with increasing flight speed, the lift coefficient was decreased along with increasing flight speed.

Fluid analysis is indispensable in recent ball game. Even in soft tennis balls are flying while rotating, so that various ballistic changes can be seen. Basically ballistic is as expected by the batter, but sometimes balls that take long-time trajectory (unique flight) to emerge will emerge. Therefore, in this study, we aimed to observe and examine the force occurring in the unique flight behavior and its occurrence range aerodynamically, and usually we analyzed the difference of trajectory of unique flight by high speed photographing. As a result, it was confirmed that a negative Magnus force was generated in the case of unique flight.

Spinning serve or shot exist as a technique in tennis. For a correct competition to hit across the net. The batted ball of the high spin is shot by friction with the gut. Due to wear, tennis balls will have a difference in performance between new and worn. So It is necessary to measure the fluid force of new and used spinning tennis balls. In addition, it is necessary to compare various tennis balls. In this research, not only the fluid force measurement is carried out, but also the experimental apparatus is improved more than the previous research, and more accurate fluid force measurement was carried out.

This paper examined the influence of the racket on tennis strokes motion. In the experiments, 13 male subjects hit the balls with four kinds of rackets, and the tennis stroke was recorded and digitized by twelve motion capture cameras. After that, using three-dimensional coordinate value of the body, the contribution of the segments to the velocity of racket head was calculated to derive the distinctive marker of the body in the tennis strokes. The position in the vertical direction of the marker was analyzed, and the changes of the stroke motion using each rackets were examined. As a result, an index of tennis stroke motion was derived.

In this study, numrical simulation of string-bed of tennis rackets were conducted to evaluate the effect of string pattern on the mechanical characteristics of tennis rackets. Kinematical data including main and cross strings of seven tennis rackets were measured and FEM models of the string beds were prepared for the numerical simulation . The out-of-plane stiffness and in-plane stiffness of the string beds of the seven rackets were compared to investigate the relationships between the mechanical properties and the string pattern.

In ski jumping competition, there are many regulations to ensure fairness. In the international ski jumping competition rules, suit fabric must show the air permeability of a minimum of 40 liters per m2/sec under 10 mm water pressure. However, the effect of air permeability of suit fabric on aerodynamic characteristics has not been completely clarified yet. The purpose of this study is to investigate the effect of air permeability of suit fabric on aerodynamic characteristics. The fabrics with different air permeability are used and the wind tunnel experiments were carried out using the fabric clothed elliptic cylinder. The experimental results show that the stall characteristics are greatly affected by the air permeability. Furthermore, the flow around the fabric-clothed elliptic cylinder also varies, depending on the position of the fabric's air permeability on the upper surface of the elliptic cylinder. It is presumed that the aerodynamic performance of ski jumpers during a flight can be improved by adjusting the air permeability of the suit fabric.

Recently the sport using flying disc is enjoyed in the world. Flying disc has the peculiar aerodynamic characteristic different from other throw things. Therefore the flight mechanism of Flying disc wasn’t understood still unclear. Elucidation of a flight principle of flying discs leads, ideal throw form of the disc and development of good Flying discs of the flight performance. In this research, CFD analysis was performed on three kinds of flying discs (for flight stability, flight distance, duration). By the CFD analysis, fluid force of the disc was calculated and the flow around the disc was visualized. From the calculation result, we have grasped the aerodynamic characteristics of each flying disc. And the factor of fluctuation of fluid force were mentioned by visualizing a flow around the disc.

The purpose of this research is to propose a stream line that can do swimming at a certain depth and can combine less drag. Acquiring a low resistance streamline in swimming competition is very important for performance and efficient swimming. Also, in the diving competition, there is a competition competing for distances where you can stop breathing and swim horizontally in the water, breathing is stopped. It is important to promote a certain depth to earn swimming distance. Because when it swims in the position close to the water surface, the wave-making resistance works. It is necessary to balance both the forward tilted posture and the small drag. Therefore, in this research, using various 3DCAD software, various streamline forms were created and flow analysis around the streamline model was performed with general-purpose thermal fluid analysis software STAR-CCM+. Buoyancy and lift force are balanced, I found a streamline with less drag

The drafting is a main strategy to reduce aerodynamics drag in bicycle race, and the effect of the drafting is drastically affected by a positioning of the cyclists in the running group. We perform aerodynamics simulations to study a bicycle configuration for group race. The simulations adopt locally mesh-refined lattice Boltzmann method (LBM) with coherent-structure Smagorinsky model (CSM) to calculate the turbulent flow around the bicycles as a large eddy simulation (LES). Each calculation took 1 or 2 day(s) to get a result of 4 seconds in physical duration. First, we calculate an isolated cyclist test for a validation. The results of drag area show good agreements with experiments in both of the cyclist with the upright and the drop posture. Second, we evaluate the drafting effect in a group 4 cyclists. We revealed that the drafting effect on the trailing cyclist is enough gained when the longitudinal distance from the leading 3 cyclists to the trailing cyclist is less than 1 meter. We also found that the drafting effect on the trailing cyclist is strictly affected by the lateral distance rather than the longitudinal distance in such small gap. Finally, we execute a large-scale simulation of the group of 72 cyclists.

We prepared 7 cavity-backed disk plates which were same to baseline calibration plate used in COR test. Their membrane thickness increased by 0.2mm from 1.8mm to 3.0mm. CT(Characteristic Time)s were tested by a pendulum test instrument and CORs were measured through COR test using an air gun. The relation between CT and COR agreed with their linear characteristic described in "Technical Description of the Pendulum Test" by R&A and USGA for the thickness of 2.6mm or more. On the other hand, COR was constant and CT only increased for 2.4mm or less. Finally estimation of CT of the plates was simulated. As a result, we show that it is possible.

Various materials, such as natural wood, plywood, and wood laminate, have been studied for application in table tennis rackets. The performance of each the rackets is evaluated independently by every manufacturing company; however, their performance criterion is unclear owing to their qualitative evaluation. The correlation between the natural frequencies and the coefficient of restitution has already been studied for metal baseball bats. However, this correlation has been barely studied for table tennis rackets. This study conducted natural frequency measurements for several kinds of rackets and investigated the impact of a ball against a racket at different speeds. First, the correlations among the impact velocity, coefficient of restitution, and damage to a ball were investigated by means of colliding the ball against a rigid wall to estimate the characteristics of the ball. Furthermore, the natural frequencies and coefficients of restitution of the rackets were measured using rackets with and without rubber in cantilever state by fixing grip part of the racket. Finally, the effect of natural frequency on the racket's coefficient of restitution was investigated.

In table tennis games, players receive the ball served from the opponent and return it to the opponent's table by striking the bounced ball using a racket with two rubber sheets. The ball speed and spin influence the flight trajectory of the ball notably, which is related to the game scores. Since that the diameter of the ball adopted in the table tennis games was changed from 38 mm to 40 mm in 2000, the difference of the receiving performance with respect to the ball diameter has been studied by some researchers. However, there are only a few works focusing on the performance evaluation of the rubber sheets on the table tennis rackets. In this study, in order to evaluate the rebound performance of the rubber sheets, ball speed and spin rate are measured according to the collision experiments using the four-roller table tennis launching machine. Then, the performance of four kinds of rubber sheets according to the catalogue specifications made by two companies are investigated and compared. We perform the collision experiments with ball speed from 20 to 70 km/h and spin rate from 0 to 4300 rpm by adjusting the launching machine. From the experiment results, we find that the coefficients of restitution in all rubber sheets decrease as the launching ball speed increase. Also, the coefficient of restitution is also influenced by the racket angle (i.e., incidence angle). Among the four kinds of rubber sheets, the ball speed and spin rate in two kinds of rubber sheets have the same rebound performance values, whereas the other two kinds of rubber sheets are different from those in the catalogue.

The objective of this study was to measure rebound characteristics for running-specific prostheses by quantifying their dynamic behavior using an impact testing apparatus which was developed to produce a typical ground foot strike contact. Impact tests were conducted with different types and categories of blades to obtain the impact load and the deformation of blades. A motion of the impactor and blade was taken by two synchronized high-speed video cameras. The deformation of blade was obtained from the positional coordinate of the blade, by tracking markers attached on the surface using the digital image correlation method. The impact load was also calculated using the time history of the acceleration which was measured by an accelerometer affixed on the impactor. The energy absorption rate was defined to evaluate the rebound characteristics using the load and deformation histories. As a result, energy absorption is likely to represent the differences between kinds of blades. On the other hand, at this stage, it has limited applicability to the evaluation of difference between categories in the same blade.

A badminton shuttlecock is an airborne projectile with a unique shape. The shuttlecock creates much higher drag, causing it to decelerate more rapidly than a ball. In the previous study, high aerodynamic characteristics of a badminton shuttlecock was examined in a wind tunnel, and it was confirmed that the gaps of shuttlecock were strongly related to high aerodynamic drag. However, it is difficult to investigate the flow through the gaps experimentally. In the present study, the numerical analysis on the flow behavior through the gaps of the shuttlecock with and without gaps is performed by using OpenFOAM method. The calculated drag is in good agreement with the experimental results. For the shuttlecock with gaps, the air flowed through the gaps in the shuttlecock skirt, and flow through the gaps behave like a jet. This flow causes a high drag because the pressure inside of the shuttlecock with gaps becomes lower than that of the shuttlecock with no gaps.

In this research, we developed two numerical models to determine flight trajectories of badminton shuttle during “spin-net shot” and tested validity of the models. One was a model made of two spheres introduced in a previous study (model I) and the other was a model made of a truncated cone and a sphere (model II). The simulation outcomes of these two models were compared with experimental values. The results showed that flight trajectories of “spin-net-shots” were predicted more accurately with model II than model I. Rotational motion of the shuttle was not predicted accurately with either models. We suggest that the effects of “added mass” should be included in the model to improve the accuracy of predicting both translational and rotational motions of the shuttle.

The badminton shuttlecock is an airborne projectile with a unique shape. It is known that the shuttlecock has high deceleration characteristics and aerodynamic stability. The purpose of this study is to investigate the aerodynamic stability (turnover stability) of shuttlecocks during the flip phenomenon between feather and synthetic shuttlecock. Wind tunnel experiments were carried out on two kinds of shuttlecocks (feather and synthetic shuttlecocks) to measure the fluid forces, and to analyze the flip phenomenon. The oscillating period during the flip movement for the feather shuttlecock was found to be shorter than that for the synthetic shuttlecock. As results of the static fluid force measurement, it was found that the pitching moment coefficient near zero-angle-of-attack for feather shuttlecock is larger than that for synthetic shuttlecock. The results indicate that the feather shuttlecock demonstrates high stability in response to the flip phenomenon.

Various sports are enjoyed in the world. A unique type of ball, which is called a shuttlecock, is used in badminton. It is known that the shuttlecock is the fastest in compared to balls used in the other sports. Furthermore, shuttlecock has high air-friction properties and therefore slows quickly due to its special shapes. In sports, the fluid dynamics in ball movement are very important in the development of sports. Thus, many studies on the aerodynamic characteristics of these balls have been carried out. However, the effects of badminton shuttlecock with rotation on aerodynamic characteristics are still unknown. In this paper, the effects of a feather shuttlecock and a nylon shuttlecock with rotation on the aerodynamic characteristics are investigated by using a wind tunnel. The pressure at the shuttlecock cork tip and slip stream is measured. Flow visualization are carried out by using smoke wire method. From results of the pressure measurement, the shuttlecock pressure coefficient at slip stream of a standard shuttlecock is higher than that of a shuttlecock without slots. From the smoke wire method, the slip stream of the "standard shuttlecock" confirmed that a slip stream domain is big as compared with “without slots”.

In this paper, an anisotropic hyperelastic modeling for leather materials was conducted. Natural leather is widely used for sports equipment. However, from the performance instability and the ethical point of view, artificial leather and synthetic leather have been expected as the substitutes. They have reinforcing fibers in the body. So, the mechanical properties show non-linear elastic characteristics, and they depend on the deformation directions and the dispersion of fiber orientation angles. A hyperelastic modeling for arterial layers was conducted by Holzapfel & Gasser (1). Holzapfel model was able to reproduce the mechanical characteristics of arterial layers. In this research, an anisotropic hyperelastic model based on the Holzapfel model was proposed. From the analysis results, the proposed model could reproduce anisotropic mechanical behaviors well and take into account of the dispersion of fiber orientation angles.

In order to develop magnesium (Mg) alloys showing good absorption properties, the effect of alloying elements on mechanical properties was investigated using several kinds of Mg binary alloys and pure Mg. These materials, which were produced by hot extrusion, had a fine-grained structure, i.e., an average grain size of ~ 3 μm. As compared to that of pure Mg, most of the binary alloys showed higher yield strength due to solid solution strengthening effect, but the specific alloying element addition played a role in enhancing elongation-to-failure in both tension and compression testing. This specific binary alloy, namely the Mg-Mn alloy, exhibited an accordion-like deformation without any fractures, which has never been observed in the other/common Mg alloys. The absorption energy against fracture of this alloy was more than several times superior to that of the conventional wrought processed Mg alloy.

In this study, strain distributions of sports compression tights were observed based on image correlation method. An artificial leg jig made of polymer foam was prepared. The artificial leg jig reproduced the shape of the leg of the 3-dimensional computer graphic model of the human body. The strain distributions of the sports compression tights worn by the leg jig were measured by the image correlation method. From the experimental results, strain was measured on the front surface of knee joint. The experimental results were compared with strain calculated by 3-dimensional computer graphic model of human body.

Compression garment is widely said to improve performance and shorten recovery time, however, there seem to be a few scientific evidences how it all actually works. The aim of this study is to clarify the effect of compression garment on body and mind during high intensity exercise. A long distance (10 km) running and a weight training (three sets of leg presses) was conducted on 14 subjects, measuring the change of heart rate, autonomic nerve, body surface temperature, hip joint angle, salivary amylase, hemoglobin concentration and oxygen saturation of lateral broad muscle. The measurements mentioned above were conducted on subjects wearing and not wearing compression garment. Obtained results show that the compression garment markedly increases the hemoglobin concentration in comparison to that of the subjects not wearing compression garment. Furthermore, it should be noted that the change in hip joint angle of subjects in compression garment is smaller than that of subjects without compression garment during traveling over long distances. On the other hand, there was no significant difference in autonomic nervous system and salivary amylase between subjects with/without compression garment. Consequently, compression garment has a physical effect from a viewpoint of hemoglobin concentration, but it does not have an outstanding mental effect. Moreover, a subsidiary effect of compression garment is found, i.e. compression garment decreases the flexibility of the hip joint movement resulting in the stability of the running form.

The wheelchair for Single-Hand-Operation takes a heavy load on operation. Even though it has much advantages for people who can use both hands, it can’t be said that it is widespread in daily life of disabled people who are not athletes. The purpose of this study is to reduce the driving load of users during Single-Hand-Operation Wheelchair. In this research, we clarify that the load on driving to passengers is reduced by setting the seat angle in the roll direction. On the Single-Hand-Operation Wheelchair, which only the driving wheel side is operated, the operation is performed in the left-right direction. Thus, the Single-Hand-Operation Wheelchair was hypothesized that seating angle in the roll direction affects the operation load. In this experiment, myoelectric potential and body movement were used as indices. Subjects used the one-handed wheelchair with respective angled (0°,10°) seats drove and to measure EMG and body movements. We discuss whether the bearing surface angle in the roll direction is effective with reducing the driving load of the passenger.

The objective of this study was to construct a musculoskeletal model which can estimate biomechanical parameters by simulating a forward liner operation of a competition wheelchair based on an experimental data for motion and to investigate the relationship between an angle and moment of joint and biomechanical parameters. The simulation model was represented by restraining the contact area between the body model and the frame and seat of the wheelchair. The operation of the wheelchair was represented by inputting a subject data which was measured using a motion capture system. A torque around the axis of the wheelchair was also measured to estimate the force at the contact area between the hand and the frame in the simulation. The body model was constructed as the target for the most player numbers class 2.0. As a result of the simulation, the push operation is mainly performed during the shoulder joint flexion operation. The elbow joint extension is also likely to contribute strongly to the pushing of the wheel.

Wheelchair is known to have a risk of hindering other daily operations if the operation burden is large. Furthermore, it is also known that the secondary risk such as neck pain and tenosynovitis increases. Therefore, development of a wheelchair that can reduce the burden on passengers is required. Many proposals and reports on the quantification of physical and mental loads on wheelchair passengers and methods for alleviating them are made, there is, however, not much enough with respect to hand rims that controls the most of the operation of wheelchairs. In this study, we focused on grasping the hand rim, objectively evaluated the physical load by heart rate, which is a physiological index, and subjective sensibility evaluation by SD method. In this study, we used hand rims for wheelchairs with different surface processing methods, we examined the operability of the wheelchair by driving experiments. Experimental results showed that sandblasting treatment and “pla-soft” painting treatment were more effective for use of routine wheelchairs such as hospital facilities and home than those coated with polyvinyl chloride resin to reduce the load on passengers was suggested.

The purpose of this research is to provide a control interface with less body movement than joysticks, which have been used to control electric wheelchairs. The force applied to the wheelchair armrest by the user was used for controlling the wheelchair. We used tactile sensors that measured three axis force, which is normal force and shear forces in two directions. The user placed his arm on the armrest, on which four tactile sensors were fixed, and shear forces were measured by the tactile sensors. The averaged shear forces in the anteroposterior and lateral directions were used as the input of translational and turning speed of the wheelchair, respectively.