Key Engineering Materials Vols. 326-328

Abstract: Our new constructed LCM system with a near field fiber probe heated the thermoplastic polymer film which placed above the tissue section by focusing laser beam (810 nm), and this method improved the resolution of the dissection capture. In this study, we designed a new cap with a hole, which made the fiber probe exert close melting, and the optimal conditions of making the thermoplastic film adhere on the cap were also studied. We used a copolymer with ethylene vinyl acetate (EVA) as the main material of the film and 0.001 M infrared naphthalocyanine dye dissolved in toluene were added and mixed for spin coating. The thermoplastic film was coated on a release agent sprayed substrate, and the new cap was placed on the substrate then put into the oven at 80
for one hour. After cooling to the room temperature, we got the thermoplastic film on the cap, and we investigated the effect of different thickness of the thermoplastic film. By using the LCM system with near-field fiber probe, the melted spots have successfully formed on the films, and the results showed that the melted size is related to the thickness of the film. According to the results of this study, the fiber probe was workable on the hollow cap with thermoplastic film, and these provided the further development of the new LCM system in nano-captures.

Abstract: In this study, we developed a fuzzy-logic-controlled PGO (Power Gait Othosis) that controls the flexion and extension of each PGO joint using bio-signals and an FSR sensor. The PGO driving system works to couple the right and left sides of the orthosis by specially-designed hip joints and pelvic section. This driving system consists of the orthosis, sensor, and control system. An air supply system for muscle action is composed of an air compressor, 2-way solenoid valve (MAC, USA), accumulator and pressure sensor. The role of this system is to provide constant “air muscle” with compressed air at the hip joint. With the output signal of the EMG and foot sensors, air muscles assist the flexion of the hip joint during the PGO gait.

Abstract: Human postural responses appeared to have stereotyped modality, such as ankle mode, knee mode, and hip mode in response to various levels of postural challenges. We examined whether human postural control gain of full-state feedback could be decoupled along with the eigenvectors. To verify the model, postural responses subjected to fast backward perturbation were used. Upright posture was modeled as 3-segment inverted pendulum incorporated with linear feedback control, and joint torques were calculated using inverse dynamics. Postural modalities, such as ankle, knee and hip mode, were obtained from eigenvectors of biomechanics model. As oppose to the full-state feedback control, independent modal control assumes that modal control input is determined by the linear combinations of corresponding modality. We used linear regression to obtain and compare the feedback gains for both eigenvector control gain and full-state feedback. As a result, we found that both feedback gains of two control models that fit the joint torque data are reasonably closed each other especially at the joint angle feedback gains. This implies that the simple parameterization using eigenvectors may be used to correlate the feedback gains of full-state feedback control.

Abstract: A finite element simulation model was developed for the performance optimization of a closed type air-cell mattress used for the ulcer prevention. An H-model with material properties of human flesh and kinematic joints were used for the calculation of the body contact pressure. The material property of rubber air-cell was evaluated by tensile test of standard specimen. We evaluated the body contact pressure distribution after laying human model on the inflated air-cell mattress. It was found that the body contact pressure was dependent on cell height, but hardly affected by the cell thickness.

Abstract: In this paper, non-linear interactions between a stent and an artery are analyzed using the finite element method [ANSYS (Ver 10.0)]. The material property of the artery is assumed to be hyper-elastic. The loading conditions were applied in three steps, according to the pressure level (pressure increase, constant load pressure, and pressure decrease). From the results, the maximum von Mises stresses were measured in the area of contact of the stent and the artery. The maximum von Mises stresses of the stent and artery were obtained and the increase in the maximum pressure showed a decrease in the von Mises stress of the stent. The simulated results show that the distal end of the stent, which tilted after the expansion behavior in the artery, may damage the artery wall. The finite element model used in this study may help in designing the stent.

Abstract: In this study, we investigated the relationship between the finger force and the neural command in multi-finger force production tasks in order to characterize the neural enslaving effect and the force-deficit effect among fingers. Seven healthy male subjects were instructed to press one, two, three and four fingers on the finger sensors as hard as possible acting in parallel in all possible combinations. Then, the finger forces in each task were recorded and analyzed to represent the neural enslaving effect and the force-deficit effect. The results confirmed that individual finger forces were smaller in multi-finger maximal voluntary contraction tasks than in single-finger tasks. The force deficit effect increased with the number of fingers involved. A mathematical model proposed in this paper based on the experimental results could explicitly describe the two effects of finger interaction by representing the relationship between the neural commands and finger forces. The present results could be useful information to understand the basic neuro-muscular mechanism in hand biomechanics and the fundamentals of intelligent hand robots.

Abstract: In this study, we determined joint moments and muscle forces in the lower extremity during walking with different heel-height shoes using the 3D motion analysis and the corresponding musculoskeletal modeling. Totally fifteen healthy women participated in the 3D motion analysis for various walking with barefoot, flat shoe, 3cm, 6cm and 9cm high heels. Inverse dynamic simulations were also performed using a musculoskeletal model in order to calculate joint moments and muscle forces in the lower extremity. As for the hip, joint angles, joint moments and corresponding muscle forces did not show significant differences. Rectus femoris, a biarticular muscle for hip flexor and knee extensor, revealed stronger effect on the knee than the hip. Soleus, playing the most important role for ankle plantarflexor, showed decreases in the maximum muscle force at pre-swing, as heel height increased. Tibialis anterior produced larger dorsiflexion moments for foot clearance with higher-heeled shoes.

Abstract:
Conventional limb rehabilitation requires a person-to-person meeting in a same physical place within a fixed setting. The virtual reality (VR) aid for rehabilitation therapy eliminates such limitations by utilizing computer generated virtual environment and off-the-shelf haptic devices. In the proposed upper limb rehabilitation system, two identical VR systems, placed one in the expert (therapist) location and the other in the learner (patient), are connected via communication network, enabling interactive rehabilitation training in separate places. For the effective training and evaluation, the expert and learner’s haptic devices are synchronized in real-time with slight active correction by human’s active visual feedback. To verify the feasibility and usability, example tests are presented for the developed laboratory test system.

Abstract: A material testing methodology is investigated in line with non-invasive manner using XRay CT images for characterizing biological tissues. Three-dimensional digital image volumes are generated for initial and loaded states. Tentative displacement field is represented by basis function of B-spline. Unknown parameters included in the functions are identified through an inverse problem minimizing error in terms of pixel intensity between actual deformed image volume and virtual one according to the tentative displacement field of B-spline. A constraint of incompressibility affects well for stable and prompt solution search. The proposed methodology is demonstrated in identification problem of three-dimensional displacement field by using an experimental data of compressive specimen.

Abstract: In this study, we introduced a virtual model and experimental simulator applicable to kinematics and kinetics analyses of the human cervical spine. The geometry of cervical vertebrae was created from computer tomography images. The disc joints were modeled as load-based joints having non-linear viscoelastic properties defined by data from in vitro experiments. The facet joints were modeled to rotate freely and translate along facet planes. Ligaments were modeled as nonlinear spring-damper elements. Simulated testing of the virtual model was conducted and the global stiffness response passed all of the statistical comparison tests. The model provided realistic visualization of in vitro experimental protocol.