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Electrovibrostimulation during the training of sportsmen, an experimental set-up
Get PDFIn this study the effects of electrovibrostimulation training are compared with classical powertraining, in a group of 18-24 years old healthy sportsmen, during the spring season of 2007. Former studies showed the effectiveness of electrovibrostimulation on the functional condition of muscles: increase of the strength in the active insufficiency zone and increase of the elasticity in the passive insufficiency zone, consequently improving joint strength and mobility. After four weeks of electrovibrostimulation, applied twice a week, significant increases of isometric strength and explosive strength were observed, whereas the flexibility remained the same. Some hypotheses are discussed concerning the possible working mechanisms of electrovibrostimulatio
The advanced structural materials for living beings implants
Get PDFThe paper deals with development of bioinert and bioactive biomaterials, different application of structural materials, including metallic materials, nanomaterials, nanostructured materials, biomaterials, ceramics, polymers, hybrid materials, functional graded materials, composites. Also are discussed multi-functional engineering materials with gradient properties, engineering materials for challenging application conditions, including aggressive environment and lightweight, multi-material (hybrid) systems where advanced materials are combined with more conventional / structural materials and materials production or joining technologies. Interdisciplinary approach to biomedicine materials research and production is very promising and horizontal cooperation of different national technology platforms is discusse
Representation of time averaged vibrating images in the operator format
Get PDFThe process of time averaging of greyscale images is expressed in the operator format. It is shown that the inverse problem of the reconstruction of the original image from its time averaged image is an ill-posed problem. Application of time averaging techniques is proposed for cryptographic applications especially when the density function of variable defining the dynamic deflection from the state of equilibrium is arcsine distributio
CFAR vibration signal change test and its applications to real-time recognition of developing cracks in jet engine rotors
Get PDFThis paper introduces a new technique for early identification of fatigue cracks, namely the constant false alarm rate (CFAR) test. This test works on the null hypotheses that a target vibration signal is statistically similar to a reference vibration signal. In effect, this is a time-domain signal processing technique that compares two signals, and returns the likelihood whether the two signals are similar or not. The system monitors the vibration signal of the rotor as it cycles, and compares that vibration signal with, say, the original vibration signal. The difference vector reflects the change in vibration over time. As a crack develops, the vector changes in a characteristic way. Thus, it is possible, during CFAR test, to determine whether the two signals are similar or not. Therefore, by comparing a given vibration signal to a number of reference vibration signals (for several crack scenarios) it is possible to state which is the most likely condition of the rotor under analysis. The CFAR test not only successfully identifies the presence of the fatigue cracks but also gives an indication related to the advancement of the crack. This test, despite its simplicity, is an extremely powerful method that effectively classifies different vibration signals, allowing for its safe use as another condition monitoring techniqu
Interaction of vibrating and translational motions
Get PDFThe mathematical model describing the interaction of a vibrating system and a system performing translational motion is proposed. Such motions take place in vibromotors. The main characteristics of the dynamic motion are defined. The model is investigated numerically and a number of graphical relationships are obtained. They are used in the process of design of systems with vibromotors like a walking inpipe robot
Computerized posturography for data analysis and mathematical modelling of postural sway during different two-legged and one-legged human stance
Get PDFMechanisms of balance control are investigated on computerized posturography data on vertical two-legged and uncomfortable one-legged stance measured on healthy subjects. Oscillations of the centre of mass in the course of 30 s standing and the corresponding trajectories for a step forward off the force platform have been computed. Spectral analysis of the time series revealed three main harmonics for the studied postures. When a volunteer was balancing standing on one leg, all the harmonics were shifted towards the high frequencies and the sway amplitude was twice increased in comparison with comfortable two-legged vertical stance. Decomposition of the sway trajectories into the rambling and trembling components has been carried out. It was shown that in the course of the one-legged stance the balance control strategy includes ‘scanning’ of the larger area with bigger sway amplitudes in the vicinity of the stable state as compared to two-legged stance. A mathematical model of the body as a multi-link system is considered. Mass and inertia of each body segment and torques in joints are taken into consideration. The calculated own and forced frequencies of the model correspond to the spectral analysis of the posturography data. One-legged stance is proposed as an excellent tool for revealing the balance problems. It is shown that investigation of the oscillations and trajectories of the centre of mass for the step forward off the force platform is perspective for medical diagnostics to distinguish between the spine and joint pathologie
Research of artificial heart ventricle based on the principle of travelling waves driven by piezoelectric actuation
Get PDFThe present article deals with the piezoelectrically-induced travelling wave that arises in periodically loaded tube and it drives blood through tube intended for application as an artificial heart ventricle. However, frequencies of piezoelectrically actuated running waves lie in ultrasonic frequency band and such big frequencies cannot be used for the blood transfer in an artificial heart. Using finite element method the forms of oscillations in the tube of the artificial heart ventricle, natural frequencies and the characteristics of blood flow through the tube (rate of flow-through, flow and pressure) were calculated. Blood pressure and flow dependencies on different tube characteristics such as tube diameter, wall thickness and frequency and magnitude of systolic driving force were studied. The calculation method allows estimating rational parameters of the artificial heart ventricle
Research of frequency characteristics of nonlinear biotronic subsystem of muscle
Get PDFPaper presents the research of muscle nonlinear stiffness characteristics dependence on the loading duration. The nonlinear differential equation of nonlinear biotronic subsystem of muscle has been derived. Analyzing mentioned expression by numerical methods it was determined that there are three main dominant frequencies in the frequentative characteristics of the muscle and values of them and amplitudes of oscillations decline as the load time becomes longer. Comparison of analytical research results to experimental ones has shown that their regularities are nearly related
Parametric and non parametric characterization of a shear mode magnetorheological damper
Get PDFMR (magnetorheological) dampers are versatile devices whose design is aimed to take the best of magnetorheological fluids: high yield strength, low power requirements, insensitivity to contaminants and hence, low cost. MR dampers have proven to be a good option for the mitigation of uncomfortable and hazardous vibrations in systems such as vehicles, buildings, bridges, etc. However, MR dampers are highly nonlinear devices that exhibit a hysteretic force-velocity loop. Their extensive applications in vibration control systems demand an accurate mathematical model. In this paper, two models for an MR damper operated in shear mode are presented: a parametric approach (Bouc-Wen model) and a non parametric one (neural network model
Development of threshold based EMG prosthetic hand
Get PDFThere is a real need of EMG (Electromyogram) based prosthetic hand for the amputee which should be economical as well as reliable. The cheap prosthetic hand available in market works passively. In those cases the patient does not feel the feeling of natural human hand. EMG based prosthetic hand provides the amputee feeling of natural human hand. The work that has been discussed here is to develop a prosthetic hand with one degree of freedom. The two motions developed were open and close. Most of the work is done at electronic level. The main work was to acquire the noiseless EMG signal and further to convert it into control signal for prosthetic hand, after suitable processing. For classification a threshold based technique has used rather than any classification technique like Artificial Neural Network (ANN), Fuzzy Logic and Genetic Algorithm (GA). It was tried to use the minimum hardware, without making any compromise with performance. It was done so, to achieve the target of developing a economical and reliable prosthetic hand. The threshold value used was variable and was controllable from outside by just varying the knob of potentiometer. This adds an additional dimension for tuning the device and scope to adjust the threshold according to muscle activity of subject. So the same prosthetic hand can be used by different amputees by just changing the threshold values only. The mechanical hand was having only two fingers to grasp the objects. The work was also extended to develop the frequency based Prosthetic hand. The scheme was to find out the frequency bands where the amplitude of open and close motions is different. The FFTs (Fast Fourier Transform) of EMG signal were calculated in MATLAB. The DSO (Digital Storage oscilloscope) was also having the facility of displaying the FFT of signal. It was found that there is certain possible frequency band which classifies the open and close motion of han