With the advance of computing capability, many studies have attempted to understand the mechanics of sports through numerical simulations. This study focuses on baseball pitching, in which a player can throw various types of breaking balls. Because every pitcher's hand has different mechanical characteristics, the trajectory of the thrown ball varies among pitchers even if baseball pitching grips are identical. Therefore, a pitching simulation system that reflects the mechanical characteristics of individual pitchers should include not only the fluid dynamics around the ball but also the hand model by taking into account ball grip and shape, elasticity, and friction of the pitcher's hand. This study explains the modeling of the flexion motion of the finger by the flexor digitorum profundus muscle. In the hand model, the flexor digitorum profundus muscle contracts and transmits a contraction force to the finger, generating a joint torque through the flexor tendon pulleys that results in the movement of the finger. Based on this model, the acting force from the finger to the ball is calculated. Held within the hand, the ball moves toward the fingertip and is perpendicularly directed to the finger pulp. After the ball is released, its trajectory is calculated by analyzing the airflow around the ball. In the airflow analysis, the equations of the finite element method are solved by streamline upwind/pressure stabilizing Petrov-Galerkin (SUPG/PSPG) methods, which enable the stability analysis of the aerodynamic coefficients corresponding to the ball's seam position. This experiment showed that the ball's angular velocity and position at the moment of its release increased with the increasing force generated by the flexor digitorum profundus muscle and altered the subsequent trajectory of the ball.
Because of simplicity, subjective evaluation methods with questionnaires have been used conventionally to assess biological effects of viewing visual images. However, these methods have low objectivity and low reproducibility, and it is difficult to evaluate the effects as a time series. On the other hand, physiological indices based on such as electrocardiography, photoplethysmography, and electroencephalography have commonly been used to evaluate the effects objectively and continuously. However, physiological indices may include psychological effects as well as physiological effects, which have been considered little in the conventional studies. In this study, therefore, in order to remove the psychological effects from the physiological indices as much as possible and to extract the physiological effects such as eye strain or visually induced motion sickness, we performed the experiment in which the same video was shown multiple times to subjects with an expectation of attenuation of the psychological effects by adapting to the experiment. From the experimental result, a physiological index related to correlativity of the baroreflex system was increased significantly with the repeat count of the experiment. The comparison between the physiological index and the questionnaire on psychological state has suggested that this fact was caused by a decrease in not only stress or anxiety to the experiment but also a decrease in concentration or a reduction of interests in the video image.
Monitoring heart rate has possibility to detect signs of cardiovascular diseases such as hypertension because these diseases are related to abnormal autonomic nervous function that has a relationship with heart rate variability (HRV). Some previous studies have been proposed estimate methods of HRV based on signals from non-contact measurements, however, there is few techniques to predict the reliability of the estimated value without the true heart rate signal. This paper proposes a new method to estimate HRV of a person in a chair using signals from sheet-shaped microdisplacement sensors attached on the chair. In addition, a technique to predict the reliability of the estimated HRV is introduced to know whether the estimated value is reliable or not even under conditions difficult to obtain information of real HRV. An experiment 27 subjects participated in was carried out to evaluate the performance of the proposed method. Experimental results showed that the estimate accuracy, which is defined as a correlation coefficient between true and estimated HRVs, is 0.87. The accuracy of the proposed method is higher than that of a previous study.
It is well known that “Secondary Bjerknes Force” works attractive and repulsive force between microbubbles by acoustic radiation. But it has not cleared that effective way to trap microbubbles aggregations. Hence, in this report, we aimed to design an acoustic field that is capable of trapped large microbubbles per unit acoustic power by aligning the acoustic power passing through the flow channel. First, we examined the relation between the total trapped area of microbubbles and the elevation angle of the transducer in an opposite direction to the suspension flow, so that we can minimize the influence caused by irradiating acoustic beam angle deviating from the centralaxis of the transducer. Next, we designed 19 kinds of acoustic field using a 2D-array transducer, and examined the acoustic pattern's capability of the amount of trapped microbubbles per unit acoustic power. Through these experiments, we found that the trapped amount of microbubbles was stable according to the variation of the irradiation angle of ultrasound with the condition of flow rate of 20 mm/s and elevation angle of 40 deg. Furthermore, we have succeeded to form an acoustic field which has been able to trap 1.87 times greater microbubbles than a conventional focused acoustic field.
This study describes a new approach to provide detailed quantification of the impact of surgical intervention on bilateral nasal airflow using voxel-based simulation. Computed tomography and magnetic resonance imaging scans were used to reconstruct 3D realistic models of both the pre- and post-operative nasal airways. Voxel-based simulation of quiet restful inspiratory flow was then performed using meshes of varying refinement to determine the level of mesh refinement required to adequately resolve the flow and heat transfer. For meshes with voxel pitches of 0.10 mm, the voxel model successfully simulated the overall pressure drop and airflow temperatures.
Intradialytic hypotension occurred in about 20 to 30% of treatments. Therefore, it is important to observe the variation of intravascular volume and blood pressure to prevent intradialytic hypotension during hemodialysis (HD). In this study, we constructed a mathematical model to understand the variation of intravascular volume in HD patients. Then, we examined the validity of the model. By applying this model, we proposed a method for identifying patients in need of pharmacotherapy to prevent intradialytic hypotension during HD. In 14 patients with end-stage renal disease (ESRD), we measured the variation of intravascular volume through blood volume monitoring (BVM) during HD. Then, we estimated the water movement rate, r, and the maximum excess volume in extravascular, VO. max, using nonlinear least-squares method. The relation of the mathematical model and the BVM value showed a high correlation. The correlation coefficient R (=0.95) could be used to detect patients in need of observation. Further, the relation of the maximum excess volume in extravascular, VO. max, and difference between body weight and dry weight showed also a high correlation. The model expressed correctly the variation of the intravascular volume. The correlation coefficient R of the mathematical model and the BVM value and the maximum excess volume in extravascular, VO. max were important parameters to manage HD. We proposed the mathematical model and new index to control HD efficiently.