Objectives:
VO2max is globally considered as the gold standard to evaluate the cardiorespiratory fitness that is an essential component to judge one’s aerobic fitness level. The present study was ...aimed to enumerate the validity for application of Cooper’s 12 min run test (CRT) in predicting VO2max among Indian swimmers and volleyball players.
Materials and Methods:
Swimmers (male = 66, female = 70) and volleyball players (male = 88, female = 81) were recruited by simple random sampling from reputed clubs of Kolkata. They were segregated into study and confirmatory groups. VO2max was determined by graded incremental cycle ergometer test followed by expired gas analysis and indirect CRT method.
Results:
Predicted VO2max (PVO2max) showed significant difference with the directly measured VO2max (VO2max) in study groups of both sports. Limits of agreement between PVO2max and VO2max proved inapplicability of current CRT protocol in studied populations. Modified population specific equations were computed from significant correlation of VO2max with distance covered in Cooper run test. Application of these norms in confirmatory groups revealed insignificant difference between PVO2max and VO2max in both genders.
Conclusion:
Modified equations are validated for application of CRT in evaluating VO2max in swimmers and volleyball players of both genders of Kolkata, India.
•A novel magnetic helical swimmer is designed and fabricated.•Propulsion force and translational velocity of the novel swimmer are improved.•The motion of the novel swimmer is simulated.•The ...translational velocity of the novel swimmer is analyzed parametrically.
Magnetic helical swimmers are one type of robots that swim at low Reynolds number environments by rotating around the helix axis. Considering the importance and dramatic increase in the use of robots and microrobots in the near future, optimizing and increasing their efficiency is very important and noteworthy. Propulsion force and translational velocity are among the most important features of the magnetic helical swimmer, which improves the function of the swimmer as each of them increases. In this paper, a new design has been proposed for the magnetic helical swimmer by changing the geometry of the tail region, which has increased the propulsion force and improved its translational velocity. A suitable experimental setup has been designed and built in accordance with the required experiments to evaluate the translational velocity of the proposed swimmer. Using the experimental results, two models have been presented to express the translational velocity and propulsion force of the swimmer in terms of its angular velocity. The results of the experiments show that the propulsion force of the built swimmer is 698.89 % higher than that of the common magnetic helical swimmer with similar dimensions and the same environmental conditions in Newtonian fluid. At the end of the experiments, the motion of the proposed swimmer is simulated in the COMSOL software, and the results of the experiments are used to validate the simulation results. Finally, the effect of parameters such as the helix pitch and the number of turns of the helix on the translational velocity of the swimmer is investigated using the computer simulations.
Different training methods are used to improve children's swimming degrees and motor performance. There are a limited number of studies examining the effects of therabands, which are portable and ...available everywhere, on swimmers. The aim of this study was to investigate the effect of 8 weeks of theraband exercises on motor performance and 50 m freestyle swimming degree. 45 voluntary children (male = 27, female = 18) participated in the study. The children were divided into three groups; control group (CG), swimming group (SG) and theraband group (TG), each consisting of 15 people. SG did swimming training only three times a week for eight weeks. In addition to swimming exercises, TG did theraband exercises consisting of 8 movements to the lower and upper extremities. The motor performances of the swimmers were determined by the Dordel Koch Test (DKT), which consists of 7 subtests, and swimming degrees were determined by the stopwatch. Wilcoxon Signed Ranks Test was used to determine the difference between pre-tests and post-tests following 8-weeks of exercise. According to the results, it was determined that in SG, 50 m swimming degree and DKTsideward jump performances increased in the posttest, while in TG, 50 m swimming degree, DKTsideward jump, DKTflexibility, DKT standing long jump, DKTsit-up, DKTbalance and DKTpush-up performances improved significantly in the post-test (p lt;0.05). As a result, in addition to in-water training to improve swimming performance, it can be stated that land training has positive effects on swimming degrees and theraband exercises increase motor performance. It can be recommended that swimming coaches incorporate theraband exercises into the content of training programs to improve both swimming and motor performance of children.
An autonomous swimmer with the acoustic propulsion system is proposed and evaluated in novel area of acoustofluidic actuation. The ultrasonic transducer has the same or higher propulsion power with ...the nanometer/micrometer vibration amplitude and the MHz/kHz frequency, compared with the locomotion of jellyfish body. The sound pressure and flow velocity measurements demonstrate the higher-pressure gradient and fluid downstream to investigate the acoustic propulsion force generated by pushing the surrounding water rearward. The performance of acoustic propulsion system is thus evaluated based on the sound pressure and flow velocity measurements equivalently. The vibration distributions in the transducer surface exhibit a ripple effect and gradually decayed from the center to the edge. The radial distributions of the sound pressure and flow velocity in water match the surface vibration amplitudes for thickness-vibration-mode. Based on the investigation of two thickness-vibration-mode PZT disc transducers, the longitudinal sound pressure and flow velocity in the normal direction result in ZSP force. The power radiated by the longitudinal vibration on the surface of the transducer is shown to be the main cause of the propulsion power. The propulsion calculation with vibration velocity is studied to evaluate the propulsion force. For an input power, the acoustic propulsion system with a higher Q-factor transducer has better performance. Autonomous underwater acoustic propulsion systems have a small size, high power density, and a simple structure, making them suitable for pipeline robots, endovascular microrobots, and underwater drones.
Display omitted
•Mechanism of underwater acoustic propulsion system is illustrated in terms of the bio-inspired and biomimetic engineering.•The sound pressure and flow velocity measurements demonstrate the higher-pressure gradient and fluid downstream to investigate the acoustic propulsion force.•The power radiated by the longitudinal vibration on the surface of the transducer is shown to be the main cause of the propulsion power.
Neuromuscular actuation of biohybrid motile bots Aydin, Onur; Zhang, Xiaotian; Nuethong, Sittinon ...
Proceedings of the National Academy of Sciences,
10/2019, Letnik:
116, Številka:
40
Journal Article
Recenzirano
Odprti dostop
The integration of muscle cells with soft robotics in recent years has led to the development of biohybrid machines capable of untethered locomotion. A major frontier that currently remains ...unexplored is neuronal actuation and control of such muscle-powered biohybrid machines. As a step toward this goal, we present here a biohybrid swimmer driven by on-board neuromuscular units. The body of the swimmer consists of a free-standing soft scaffold, skeletal muscle tissue, and optogenetic stem cell-derived neural cluster containing motor neurons. Myoblasts embedded in extracellular matrix self-organize into a muscle tissue guided by the geometry of the scaffold, and the resulting muscle tissue is cocultured in situ with a neural cluster. Motor neurons then extend neurites selectively toward the muscle and innervate it, developing functional neuromuscular units. Based on this initial construct, we computationally designed, optimized, and implemented light-sensitive flagellar swimmers actuated by these neuromuscular units. Cyclic muscle contractions, induced by neural stimulation, drive time-irreversible flagellar dynamics, thereby providing thrust for untethered forward locomotion of the swimmer. Overall, this work demonstrates an example of a biohybrid robot implementing neuromuscular actuation and illustrates a path toward the forward design and control of neuron-enabled biohybrid machines.
This article presents a miniature magnetic swimmer and a control apparatus able to perform both 3-D path following and blood clot removal. The robots are 2.5 mm in diameter, 6 mm in length, contain ...an internal permanent magnet, and have cutting tips coated in diamond powder. The robots are magnetically propelled by an external magnetic system using three coil pairs arranged orthogonally. A range of robot tip designs were tested for abrading human blood clots in vitro . The best design removed a blood clot at a maximum rate of 20.13 mm<inline-formula><tex-math notation="LaTeX">^3</tex-math></inline-formula>/min. A controller for 3-D navigation is presented and tested. The best prototype was used in an experiment that combined both 3-D path following and blood clot removal.
Self-propelled swimmers using ultrasonic transducers have been proposed and studied. The screw and bionic propulsion systems have dominated underwater robots. However, the complex structures make ...miniaturization difficult. The swimmers with ultrasonic transducers have no moving parts such as fins or propellers and can be driven by the nanomechanical-vibration in the surface of the transducer. Simple structure and high driving frequency make it easy to miniaturize. A 36° Y-cut lithium niobate (LN) thickness-vibration-mode transducer is used to investigate an underwater acoustic propulsion system. LN transducers are manufactured to 10 × 10 mm, 7 × 7 mm, and 4 × 4 mm square plates. The zero-speed propulsion and no-load speed are investigated to evaluate the swimmer performance. A mm-order swimmer is studied with a 4 × 4 mm LN transducer. At last, the multi-degrees-of-freedom swimmer driven by three 7 × 7 mm LN transducers is demonstrated with the advance and sway locomotion. In the future, a small-scale and agile self-propelled swimmer with an acoustic propulsion system can be expected for narrow and complex environment tasks, such as seagrass-prone areas and narrow pipelines.
Display omitted
•At 10 W, the zero-speed propulsions of LN and PZT transducer are 7.8 mN and 4.9 mN. The zero-speed propulsion of LN transducer is 1.6 times greater.•A mm-order miniaturized swimmer with 4 × 4 × 0.35 mm LN transducer is realized.•A triangle multi-degree-of-freedom swimmer with three 7 × 7 mm LN transducers is designed and fabricated.
Emulsion droplets, composed of long linear molecules (e.g. n-alkanes) and stabilized by long chain surfactants, can spontaneously change their shape upon cooling and morph from spheres into regular ...polyhedra, polygonal platelets, rods and thin fibers. Until now, these dynamic shape changes have been studied upon continuous temperature decrease. Therefore, it had remained unclear whether the observed shapes were stable or they appeared as intermediate states during the transformation of the initial sphere into some final shape(s). In the current study, we performed dedicated experiments at fixed temperature to distinguish between the stable, metastable and unstable shapes and to define the factors which affect the kinetics of the observed transitions. The results showed that the stable shapes are equilateral triangular platelets (in all surfactant solutions) and the rod-like particles, when stabilized by surfactants with narrow compositional variations. The distorted octahedrons (seen as hexagonal platelets in transmitted light) were metastable and preserved their shape for many minutes. The other shapes, e.g. the flat hexagonal and tetragonal platelets, were unstable and continued to transform until they reached one of the stable states or alternatively – until they formed spheroidal droplets extruding thin fibers from their bodies. These experimental results are in general agreement with the theoretical model developed by Haas et al. (Phys. Rev. Lett. 2017, Phys. Rev. Res. 2019). The rate of shape transformations increased with the level of subcooling and/or with the decrease of drop size.
Display omitted
•Emulsion drops stabilized by long-chain surfactants can change shape upon cooling.•The stability of the non-spherical shapes at constant temperature is studied.•From all shapes observed, equilateral triangles only are stable in all systems.•The other shapes could be metastable or unstable depending on the conditions.•The cooling protocol can change the type of particles observed in given emulsion.
•The foil with undulating motion can obtain energy more easily in the karman vortex street.•Both leading-edge and secondary vortex can influence either thrust enhancement or lift of the foil.•The ...combined influence of lateral and longitudinal distances on an undulated foil is explored for the first time.•Unlike in the reverse kármán vortex street, the undulating foil always achieves an enhanced thrust effect in the kármán vortex street. However, the undulating foil has a distance limitation to decrease the vortex shedding frequency of a cylinder.
Aquatic animals have evolved diverse swimming techniques. They have demonstrated abilities to harness energy from vortices, particularly the Kármán vortex street, resulting in enhanced thrust. However, gaps remain in comprehensively understanding the factors influencing this increased thrust and the specific hydrodynamic characteristics involved. In this study, we studied an undulating foil downstream a circular cylinder to further understand the flow control mechanism involved in optimizing energy capture from hydrodynamic disturbances. We utilised numerical simulations with a moving adaptive mesh in laminar flow. We found that the leading vortex and secondary vortex at the foil's leading edge, originating from the Kármán vortex, played a crucial role in thrust enhancement. The undulating foil was more efficient in capturing energy from the Kármán vortex street than a stationary foil. When the foil was nearer to the cylinder, the energy capture was more evident, leading to intricate vortex patterns and easier leading vortex and secondary vortex generation. The foil's lift initially rose with closer proximity but decreased with increased distance. Our results showed that for minimal drag and optimal lift, the cylindrical body's position is closely tied to the interaction between the Kármán vortex street and the undulating foil. These insights can be applied in applications of designing efficient propulsion systems for underwater vehicles and optimising energy harnessing mechanisms in marine environments.
PDF
