Several training methods have been developed to obtain motion information during real-time walking and feed it back to trainees who adjust their gait to ensure that the measured gait parameters approach target value, which may not always be suitable for every trainee owing to physical differences between individuals. This paper proposes a method of setting this target value considering these physical differences and discusses the usefulness of the gait training method, wherein a multichannel deep convolutional neural network (MC-DCNN) gait classification model constructed by learning ideal or non-ideal gait features beforehand is used for trainee gait classification. Activation maximization is applied to the MC-DCNN model; data wherein the ideal walking features are activated are generated based on trainee gait data. However, the amounts of features to be activated to generate a possible and natural gait are restricted. The original trainee gait, beyond individual physical differences, and gait data generated based on the original gait data seem to yield the target value considering the physical differences among individuals. This study focused on gait related to stumbling. To verify its usefulness, a multivariate gait dataset consisting of kinematic and kinetic indices labeled as "gait rarely associated with stumbling" or "gait frequently associated with stumbling" was divided into a training set, validation set, and test set. The MC-DCNN model learned gait features for multivariate gait data classification in the training set. It classified the gait with 96.04±0.12% accuracy against the validation set. Finally, by applying the proposed method to the multivariate gait data contained in the test set, we generated multivariate gait data classified as "gait rarely associated with stumbling" based on the input data. In addition, the generated multivariate gait data include motion that increases the thumb-to-ground distance and describe possible and natural gait considering the physical differences among individuals.

Keywords

Healthcare, Gait training, Motion analysis, Walking factor, Neural network, Activation maximization

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Carbon fiber running-specific prostheses (RSPs) are widely used among lower-limb amputee runners. However, which prosthesis provides the best performance for runners remains unknown. For this purpose, a computational model of the human body with a prosthesis was created and the effect of the prosthetic parameters on performance was investigated. First, motion capture systems were used to collect motion data from amputees. Furthermore, marker and force plate data were obtained to create a digital human model. Kinematic data such as limb lengths and joint angles were calculated using marker data. Afterward, the inertial properties were estimated to conduct inverse dynamic analyses. After building a computational model of amputee sprinting, the joint positions and ground reaction forces (GRFs) were compared with the experimental results. The design parameters of the prosthesis were introduced to understand the effects of the prosthesis on motion and performance. The response surface method was used to express motion adaption regarding the geometry and stiffness of the prosthesis. Hip and knee sagittal joint angles were updated based on the response surface method to simulate joint motion adaptations of the worn prosthesis. Additionally, average horizontal velocity, horizontal velocity change over one gait cycle, vertical and horizontal impulses were considered as performance functions. An evaluation parameter was proposed to generalize the idea of performance. The moment of the prosthetic knee and the closest point of the prosthesis to the ground during the swing phase were defined as design constraints to consider knee buckling and prosthetic leg tripping, respectively. The effect of the design parameters on the performance and constraint functions was also investigated and a method to determine and design a suitable prosthesis for an individual was proposed. It was revealed that proper selection and design of prostheses represent an important way to increase performance.

Keywords

Amputee running, Running-specific prosthesis, Prosthetic parameters, Running performance, Multilink model, Motion capture

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This paper discussed if a powered attendant propelled wheelchairs (PAPW) with assist-as-needed control reduces energy consumption and maximise attendant's physical activity in powered system use. This study introduced a PAPW with force velocity assist control (FVAC) based on individual capability of pushing force velocity relationship. This PAPW assists attendant pushing when more pushing force is needed over usual range of individual physical capabilities of pushing. With the PAPW, we investigated the performance of the FVAC and compared it with proportional assist control (PAC) on a flat level surface and a longitudinal slope (6.5%) with three participants. The experimental results showed that the PAPW with the FVAC reduced 50% of pushing force on the slope and this was similar performance of the PAC in terms of assisting. The FVAC also reduced 79% of mean mechanical assisting power on the flat against the PAC. These results support that the PAPW with the FVAC has flexibilities to adapt to individual physical capabilities and provides certain level of physical activities with sufficient assisting when needed, and low energy consumption for long time and distance operations for attendants.

Keywords

Assist-as-needed control, Assistive device, Attendant-propelled wheelchair, Force-velocity relationship, Iindividual physical capability

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Various effects have been observed when a slimy fluid is held in palmar skin. The observed effects include friction control of the skin and cleansing and moisturizing of the skin. However, few reports exist regarding the changes in the emotional state of persons when a slimy fluid is held in their palmar skin, even though the viscosity properties of the fluid affect emotional changes. Thus, this study investigates the emotional changes due to holding slimy fluid in the palmar skin by evaluating heart rate variability (HRV) and sensibility. Newtonian and non-Newtonian fluids, with viscosities ranging from 0.01 to 100 Pa·s, were prepared. Eight male subjects in their 20s soaked their palms in the slimy fluid without seeing it. At the room temperature of 25 °C, the subjects moved their palms freely for 1 min. They were allowed to rub their palms together. During the experiments, the HRV was recorded. A frequency analysis was performed for estimating autonomic nerve activity. After holding the fluid, the subjects were asked to provide feedback through the semantic differential method. Significant changes in autonomic nerve activations were observed when the subjects soaked their palms in the slimy fluid. The high viscosity Newtonian fluid reduced the parasympathetic nervous system activity. These changes in the psychophysiological indexes influenced the feelings of the subjects ascertained according to the semantic differential method. A relationship between the characteristic of the slimy fluid and a psychophysiological index can improve the efficiency when developing products exposed to human skin.

Keywords

Slimy liquid, Newtonian fluid, Non Newtonian fluid, Skin, Emotions, R-R interval, Sympathetic nerve, Parasympathetic nerve

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Fruit tree branches are deflected with large deformation under bending loads applied owing to fruit weight and environmental burdens such as wind and snow. Stress and strain analyses in large bending deformations of tree branches can prevent tree failure. An extensive deformation analysis method for a fruit tree branch subjected to fruit weight applied as concentrated and distributed type loads is proposed herein. The method is based on actual loading tests for identifying the material properties of an apple tree branch and numerical simulation for deformation analysis. The estimated branch geometry at significant bending is obtained via iterative calculations and is consistent with the actual loading case; hence, it identifies the local bending stiffness. The effects of both the base angles of a cantilever-modeled tree branch with different bending stiffness distributions and initial curvatures and the load distribution patterns simulating the fruit arrangement on the branch on the maximum bending strain are investigated via numerical deformation analysis. The method provides critical loading conditions for fruit cultivation, focusing on the maximum strain on the branch. The information gained can be applied for generating fruit cultivation plans, where reduction in load applied on the fruit branch is emphasized.

Keywords

Large deformation, Fruit tree branch, Numerical simulation, Bending load, Bending stiffness, Fruit cultivation

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This study describes a new calibration procedure that provides a simple and accurate method to place and align an inertial measurement unit (IMU) sensor with the relative clinical bone frame on a developed lower limb skeletal model. The calibration can be easily replicated without the need for additional tools and, more importantly, it is independent of the joint attachment position. The proposed method was validated under realistic gait tests using eight healthy subjects in a motion capture system environment. Calculated results showed that the joint angles were correctly measured after applying the calibration method. Therefore, the proposed calibration procedure is an interesting alternative to solve the alignment problem when using IMU sensors for gait analysis.

Keywords

IMU sensor, Static calibration, Tibiofemoral rotation, Clinical bone coordinate system, Skeletal model

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To ensure safe coil embolization for cerebral aneurysms, it is important to investigate the contact force between a coil and an aneurysm wall. Therefore, in our previous study, we developed an experimental system for measuring the contact force between a coil and an aneurysm biomodel. However, because the aneurysm model was made of silicone rubber, its physical properties, such as the friction coefficient, differed from those of aneurysms in vivo. Therefore, in this study, we made an aneurysm model using poly (vinyl alcohol) hydrogel (PVA-H) and evaluated the effect of the model material on the contact force. In addition, we acquired images during the experiment and evaluated the behavior of the coil and catheter and the relationship between the catheter movement and the contact force. A commercially available coil was inserted through a catheter into two types of aneurysm models (silicone rubber and PVA-H), and the effects of the model material and the catheter tip position (near dome, at the center, and near neck) were evaluated. The contact force and the total movement of the catheter tip for the PVA-H model were smaller than those for the silicone rubber model. The contact force (total catheter movement) was greater (smaller) when the catheter tip was inserted deeper into the silicone rubber model. These results suggest that the state of contact between the aneurysm and the coil affects the contact force and the catheter movement and that these two values are related.

Keywords

Endovascular treatment, Cerebral aneurysm, Coil embolization, Contact force, Catheter, Phantom, First coil

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Erythrocytes swell owing to the osmotic shock caused by hypotonic liquids, and when the membrane tension exceeds a certain limit, hemolysis occurs. The base tension in the membrane of a spherically shaped erythrocyte is usually ignored in the mechanical evaluation of hemolysis. However, the base tension cannot be ignored when the rigidity of the erythrocyte membrane increases owing to lesions, oxidative stress, and other phenomena. Therefore, it is necessary to re-evaluate the tension level at which hemolysis occurs by considering the increased base tension, which is caused by a combined increase in the bending and shear rigidity of the membrane. To achieve this, we calculated the effect of increases in the combined rigidity on the increases in the internal pressure and membrane tension of the erythrocyte. In this study, assuming the surface area to be constant, the swelling process of erythrocytes was evaluated under the condition that hemolysis does not occur. Evaluation was performed by minimizing strain energy, which is the sum of bending strain and shear strain. When the erythrocyte was spherical, the membrane base tension increased linearly with combined rigidity. Even when the bending rigidity was increased to 100 times that of normal erythrocytes, the effect of the base tension on the hemolysis tension level (15 mN/m) was negligible. However, when shear rigidity was increased to 50-100 times that of normal erythrocytes, it became necessary to decrease the hemolysis tension level by 10% and 20%, respectively, because the base tensions were approximately 1.5 and 3.0 mN/m, respectively.

Keywords

Erythrocyte, Hypotonic osmotic shock, Hemolysis, Bending rigidity, Shear rigidity, Strain energy minimization, Membrane tension

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This paper presents a formulation to identify muscle activities from the variation in shapes of organs during swallowing. We assume that each organ consists of a three-dimensional hyperelastic body, and the contraction movement of the muscle is caused by a contractive inelastic stress in the organ. A function distributed in the organ domain to control the magnitude of the inelastic stress is chosen as a design variable in the same manner as the density in the topology optimization problem of density variation type. The identification problem is formulated as a problem of determining the design variable that minimizes an objective cost function defined by the squared L² norm of the reaction force in the normal direction on the boundary when an enforced displacement to fit the varied boundary of the organ and the inelastic stress modeling the muscle activity are applied. The finite deformation problem of the hyperelastic body is analyzed using the finite element method. The direction of the muscle fiber is assumed to be the direction of the minimum principal stress obtained as the solution to the finite deformation problem. The solution to the identification problem is presented based on a scheme using the H¹ gradient method for the topology optimization problem of density variation type. A numerical example using a previously developed model of the tongue is introduced to demonstrate the effectiveness of the proposed approach.

Keywords

Muscle activity, Identification problem, Hyperelastic body, Initial stress, Finite element method, Topology optimization of density type, H1 gradient method

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