Experimental Comparison of Speed-Dependent Rolling Coefficients in Small Cycling Tires

ABSTRACT In this article, the methodology and results of an experimental campaign on small and slick bicycle tires are presented. The test was developed to compare the rolling resistance of tires to be used in high-speed competitions for streamlined human-powered vehicles. After an explanation of the theoretical background for the measurement, the test-rig and the adopted procedure to measure and subtract aerodynamic effects are presented. The obtained data show that the rolling resistance coefficient has a nonlinear dependency from the speed between 45 and 145 km/h. The data comparison points out a decrease in rolling losses up to 54% by switching from a butyl to latex inner tube on the same tire, whereas no significant difference is detected between the latex tube and tubeless configuration. An estimation of the impact on racing performance is provided, showing that selecting the best option could save up to 19% of the overall effort energetic cost, which means a higher final speed can be achieved with the same rider effort. Finally, a speculative analysis is proposed that considers different functions to fit the obtained data, pointing out the need for experimental measurements on the very-low-speed region to achieve a better understanding of the entire rolling resistance behavior with respect to speed.

Soft robot development: Air muscle for rehabilitation robotic application

Physiotherapy is a science which acts in the area of biomechanical and functional disorder, establishing diagnostics and supporting the locomotor system rehabilitation. These procedures require assistance of a physiotherapist, however they are insufficient for the country´s demand. Usually such procedures use devices with the newest technology, in order to enable recovery and avoid possible permanent trauma. In order to face this reality, we have committed to develop an air muscle, based on the McKibben´s model, with the purpose of proposing a new low-cost parallel robot to physiotherapy (Soft Robot) for the rehabilitation of patients with ankle injuries. This robot is responsible for moving three degrees of freedom platform, therefore acting directly in the rehabilitation of the patient through the execution of soft and accurate therapeutic movements that stimulate the recovery of operated tissues. First, it is build an air muscle that will be used as actuator in parallel platform. Then is raised a curve of behavior to shift versus pressure on proposed muscle. In conjunction with these data to actuator behavior is modelled and simulated the new parallel robot. This air muscle was build using a latex tube covered by a braided fibred mesh and fuelled by a pneumatic tire valve, therefore obtaining a nonlinear behavior of contraction to each pressure value admitted on muscle. By means of this prototype building purpose, we obtained satisfactory results, such as a contraction of 25% of the nominal length for pressures up to six bars. Considering such a result and the low cost involved building actuator as this one, the advantage in using this model is perceptible.

Stable Rat Model of Mechanical Allodynia in Diabetic Peripheral Neuropathy: The Role of Nerve Compression

Background Preclinical studies involving animal models are essential for understanding the underlying mechanisms of diabetic neuropathic pain. Methods Rats were divided into four groups: two controls and two experimental. Diabetes mellitus was induced by streptozotocin (STZ) injection in two experimental groups. The first group involved one sham operation. The second group involved one latex tube encircling the sciatic nerve. The vehicle-injection rats were used as two corresponding control groups: sham operation and encircled nerves. By the third week, STZ-injected rats with encircled nerves were further divided into three subgroups: one involving continuing observation and the other two involving decompression (removal of the latex tube) at different time points (third week and fifth week). Weight and blood glucose were monitored, and behavioral analysis, including paw withdrawal threshold (PWT) and latency, was performed every week during the experimental period (7 weeks). Results Hyperglycemia was induced in all STZ-injected rats. A significant increase in weight was observed in the control groups when compared with the experimental groups. By the third week, more STZ-injected rats with encircled nerves developed mechanical allodynia than those without (P < 0.05), while no significant difference was noted (P > 0.05) on the incidence of thermal hyperalgesia. Mechanical allodynia, but not thermal hyperalgesia, could be ameliorated by the removal of the latex tube at an early stage (third week). Conclusion With the combined use of a latex tube and STZ injection, a stable rat model of painful diabetic peripheral neuropathy (DPN) manifesting both thermal hyperalgesia and mechanical allodynia has been established.

Quantification of Arterial Stiffness Reduced Effect of Vessel Geometry

Arteriosclerosis is such as phenomena hardening of arteries, with thickening and loss of elasticity. Previous indexes include effect of geometric and mechanical factors as the radius, the wall thickness and mechanical properties of arteries. In this study, we proposed viscoelasticity indexes formulated by thin cylindrical shell theory estimated dynamic strain, and this index was independent of wall thickness and radius of arterial vessels. To confirm the validity of these indexes, we evaluated the parameters of viscoelasticity using the latex tube with different wall thickness of blood vessel model. We measured a radius of the latex tube and an inner pressure maintained by a pulsatile pump in a mock circuit filled with the water. Estimating the parameters of elasticity using these measured values, we concluded that a proposal index was independent of the wall thickness of the artery.

Resonance of Rubber Tubes Generated by Air Force Ultrasound Transducers

In paper, we report our recent results of using the air force ultrasound transducer to study the resonance of rubber tubes. Experiments were carried out on a rubber latex tube. Seven resonant frequencies were measured between 50 Hz and 200 Hz. Theoretical calculation of the resonant frequency on the tube was done with the wave propagation approach. The relative differences of the seven resonant frequencies between the experiment and the theory are less than 6 %. This research shows that the air force ultrasound transducer can be used for tube resonance measurement.