Current Issue : July - September Volume : 2019 Issue Number : 3 Articles : 5 Articles
The aim of the research was to determine the optimal threadâ??s shape to be used in implants for direct skeletal attachment of limb\nprosthesis. In addition, by testing appropriate parametersâ?? modification of the suitable thread, an attempt was made to maximise its\neffectiveness. The analyses included three thread types described in the ISO standards: shallow, symmetrical, and asymmetrical. The\nobtained results suggest that shallow thread ensures the lowest equivalent and directional stress peaks generated in the bone as well\nas favourable stress patterns and profiles during implant loading in relation to symmetrical and asymmetrical threads. Moreover,\nshallow thread ensured the generation of single equivalent and directional stress peaks, while symmetrical and asymmetrical\nthreads provided additional stress peak for equivalent as well as for each of directional peaks. Subsequently, optimisation of the\nshallow threadâ??s shape was conducted by changing two relevant threadâ??s parameters (flank angle and rounding arc) which\ninfluence the generated stress distribution. The highest reduction of stress peaks was obtained while reducing the rounding arc\nby 0.2 mm. Therefore, it can be stated that the proposed modification of the HA thread can lead to obtaining a higher\nbiomechanical effectiveness of implants for direct skeletal attachment of limb prosthesis....
Objective. Gait asymmetry is a common adaptation observed in lower-extremity amputees, but the underlying mechanisms\nthat explain this gait behavior remain unclear for amputees that use above-knee prostheses. Our objective was to develop\na working hypothesis to explain chronic stepping asymmetry in otherwise healthy amputees that use above-knee\nprostheses. Methods. Two amputees (both through-knee; one with microprocessor knee, one with hydraulic knee) and\nfourteen control subjects participated. 3D kinematics and kinetics were acquired at normal, fast, and slow walking speeds.\nData were analyzed for the push-off and collision limbs during a double support phase. We examined gait parameters to\nidentify the stepping asymmetry then examined the external work rate (centre of mass) and internal (joint) power profiles\nto formulate a working hypothesis to mechanistically explain the observed stepping asymmetry. Results. Stepping\nasymmetry at all three gait speeds in amputees was characterized by increased stance phase duration of the intact limb\nversus relatively normal stance phase duration for the prosthesis limb. The prosthesis limb contributed very little to\npositive and negative work during the double support phase of gait. To compensate, the intact leg at heel strike first\nprovided aid to the deficient prosthetic ankle/foot during its push-off by doing positive work with the intact knee, which\ncaused a delayed stance phase pattern. The resulting delay in toe-off of the intact limb then facilitated the energy transfer\nfrom the more robust intact push-off limb to the weaker colliding prosthesis side. This strategy was observed for both\namputees. Conclusions. There is a sound scientific rationale for a mechanistic hypothesis that stepping asymmetry in\namputee participants is a result of a motor adaptation that is both facilitating the lower-leg trajectory enforced by the\nprosthesis while compensating for the lack of work done by the prosthesis, the cost of which is increased energy\nexpenditure of the intact knee and both hips....
Background. It has been stated that long-term participation in sport training can influence the motor asymmetry of the arms\nwith a decreased interlimb difference. However, whether this pattern is observable in different sports and with different\nvariables, like perceptual performance, still needs to be tested. Therefore, we investigated if long-term sports participation\nmight modify the motor and perceptual performance asymmetries of arms in water polo players. It was hypothesized that\nwater polo players would perform with less interlimb asymmetry in comparison to nonathletes. Methods. Right-handed water\npolo players and nonathletes were tested on motor performance for both arms during a reaching task. Thirteen water polo\nplayers and thirteen nonathletes performed reaching movements under two experimental conditions: (a) right arm and (b)\nleft arm. Velocity, accuracy, hand path deviation from linearity, and reaction time were calculated for each trial and for both\narms. The potential interlimb differences in movement performance could be assessed by testing. Results. Consistent with the\nhypothesis, our findings showed that water polo players displayed substantially less asymmetry in the performance of\naccuracy and reaction time. Conclusions. These findings suggest that performance asymmetries of arms can be altered via\nintense long-term practice....
An air suspension platform uses air pressure to realize the suspension function during the suspension process, and it has the\ndisadvantage of large air pressure and a small suspension force. In this study, an air suspension platform was built using bionic\ndesign to reduce the required air pressure and increase the suspension force. A suspension structure mapping model was\nestablished according to the physiological structure characteristics of albatross wings. A bionic model was established by using\nthe theoretical calculation formula and structural size parameters of the structural design. A 3D printer was used to manufacture\nthe physical prototype of the suspended workpiece. Based on this, a suspension test rig was built. Six sets of contrast\nexperiments were designed. The experimental results of the suspension test bench were compared with the theoretical\ncalculation results. The results show that the buoyancy of the suspended workpiece with a V-shaped surface at a 15-degree\nattack angle was optimal for the same air pressure as the other workpieces. The surface structure of the suspended workpiece\nwas applied to the air static pressure guide rail. By comparing the experimental data, the air pressure of the original air\nsuspension guide rail was reduced by 37%, and the validity of the theory and design method was verified....
Graphene nano-walls (GNWs) are promising materials that can be used as an electrode in\nelectrochemical devices. We have grown GNWs by inductively-coupled plasma-enhanced chemical\nvapor deposition on stainless steel (AISI304) substrate. In order to enhance the super-capacitive\nproperties of the electrodes, we have deposited a thin layer of MnO2 by electrodeposition method.\nWe studied the effect of annealing temperature on the electrochemical properties of the samples\nbetween 70 Degree C and 600 Degree C. Best performance for supercapacitor applications was obtained after\nannealing at 70 Degree C with a specific capacitance of 104 F g^-1 at 150 mV s^-1 and a cycling stability of\nmore than 14k cycles with excellent coulombic efficiency and 73% capacitance retention.\nElectrochemical impedance spectroscopy, cyclic voltammetry, and galvanostatic charge/discharge\nmeasurements reveal fast proton diffusion (1.3 * 10^-13 cm2â?¢s^-1) and surface redox reaction after\nannealing at 70 Degree C....
Loading....