1,721,017 research outputs found
Characterization of a digital Image Correlation system for small biological tissues dynamic strain measurements
No full textDigital image correlation (DIC) is an optical technique for contactless displacement and strain measurement recently applied to biological tissues. We characterized a DIC system for small biological specimens based on a high speed camera, a stereomicroscope, and an original image correlation algorithm. Optical features have been evaluated calculating the optical distortion and the modulation transfer function. The accuracy of the DIC algorithm used here has been assessed employing an elastic specimen subjected to known amount of strains, and has been compared with accuracies obtained in the same way using two other algorithms. For strain values up to 25%, that is within the typical strain range for biological tissues, and for magnifications up to 6.3×, our DIC algorithm was able to compute strains with a relative error lower than 1%. The accuracies obtained with the elastic specimen were then confirmed performing DIC analysis on mouse skin samples subjected to controlled strains
Using an ankle robotic device for motor performance and motor learning evaluation
No full textBiomedical engineering; Rehabilitation; Biomechanics; Biomechanical engineering; pediAnklebot; Motor learning; Kinematic indices; Ankle; Learning index.; Goal directed task
An experimental analysis of accuracy and precision of a high speed strain gage system based on the direct resistance method”,
No full textMilwaukee WI (U.S.A.
Battery energy storage. an automated system for the simulation of real cycles in domestic renewable applications
No full textIn the last decades, the use of renewable energy solutions (RES) has considerably increased in various fields, including the industrial, commercial, and public sectors as well as the domestic ones. Since the RES relies on natural resources for energy generation, which are generally unpredictable and strongly dependent on weather, season and year, the choice of the more effective energy storage system (ESS) plays a significant role in the application of domestic renewable energy technologies. On this basis, the impact of the ESS on the optimal use of domestic RES is widely studied in the literature in terms of technologies, mathematical models and energy markets, aiming to find the optimal battery size and chemical composition and the more efficient home energy management (HEM). The lithium-ion (Li-ion) batteries are considered one of the most promising electrochemical energy storage approaches. In this context, we have developed an automated system for the characterization of lithium-ion cells, simulating versatile protocols for cell cycle usage, with a real-time acquisition and elaboration of the battery voltage and current. In this study, we focused on the metrological characterization of the system in terms of the accuracy of the more critical parameters mostly involved in the charge and discharge basic characterization tests. Then, we conducted an experimental test to simulate a real scenario of home solar-based storage in 24h. Results showed that our system was able to achieve the desired critical parameters during both charging and discharging cycles, with relative errors between the measured and imposed parameters always lower than 0.21%
A laboratory investigation of the flow in the left ventricle of the human heart with prosthetic, tilting-disk valves
No full textThe understanding of the phenomena involved in ventricular flow is becoming more and more important because of two main reasons: the continuous improvements in the field of diagnostic techniques and the increasing popularity of prosthetic devices. On one hand, more accurate investigation techniques gives the chance to better diagnose diseases before they become dangerous to the health of the patient. On the other hand, the diffusion of prosthetic devices requires very detailed assessment of the modifications that they introduce in the functioning of the heart. The present work is focussed on the experimental investigation of the flow in the left ventricle of the human heart with the presence of a tilting-disk valve in the mitral position, as this kind of valve is known to change deeply the structure of such a flow. A laboratory model has been built up, which consists of a cavity able to change its volume, representing the ventricle, on which two prosthetic valves are mounted. The facility is designed to be able to reproduce any arbitrarily assigned law of variation of the ventricular volume with time. In the present experiment, a physiologically shaped curve has been used. Velocity was measured using a feature-tracking (FT) algorithm; as a consequence, the particle trajectories are known. The flow has been studied by changing both the beat rate and the stroke volume. The flow was studied both kinematically, examining velocity and vorticity fields, and dynamically, evaluating turbulent and viscous shear stresses, and inertial forces exerted on fluid elements. The analysis of the results allows the identification of the main features of the ventricular flow, generated by a mitral, tilting-disk valve, during the whole cardiac cycle and its dependence on the frequency and the stroke volume
On the reliability and repeatability of surface electromyography factorization by muscle synergies in daily life activities
Full text linkMuscle synergy theory is a new appealing approach for different research fields. This study is aimed at evaluating the robustness of EMG reconstruction via muscle synergies and the repeatability of muscle synergy parameters as potential neurophysiological indices. Eight healthy subjects performed walking, stepping, running, and ascending and descending stairs' trials for five repetitions in three sessions. Twelve muscles of the dominant leg were analyzed. The “nonnegative matrix factorization” and “variability account for” were used to extract muscle synergies and to assess EMG goodness reconstruction, respectively. Intraclass correlation was used to quantify methodology reliability. Cosine similarity and coefficient of determination assessed the repeatability of the muscle synergy vectors and the temporal activity patterns, respectively. A 4-synergy model was selected for EMG signal factorization. Intraclass correlation was excellent for the overall reconstruction, while it ranged from fair to excellent for single muscles. The EMG reconstruction was found repeatable across sessions and subjects. Considering the selection of neurophysiological indices, the number of synergies was not repeatable neither within nor between subjects. Conversely, the cosine similarity and coefficient of determination values allow considering the muscle synergy vectors and the temporal activity patterns as potential neurophysiological indices due to their similarity both within and between subjects. More specifically, some synergies in the 4-synergy model reveal themselves as more repeatable than others, suggesting focusing on them when seeking at the neurophysiological index identification
Ammonia decomposition over commercial Ru/Al2O3 catalyst: An experimental evaluation at different operative pressures and temperatures
No full textThe ammonia decomposition process for hydrogen production was studied experimentally in a fixed bed tubular micro-reactor (I.D. = 1 cm and h = 20 cm) filled with 15 ml of ACTA Hypermec 10010 Ru catalyst. With the aim of pointing out the best process conditions, experiments were carried out varying the reaction temperature between 400 and 500 C, the feeding gas pressure between 1 and 10 bar and the GHSV (Gas Hourly Space Velocity) between 300 and 2400 h -1. To maintain the temperature as uniform as possible along the reactor axis, a 3 zone heater was used and each zone was controlled independently. An acid H2SO4 trap was used downstream the reactor to remove by neutralization the residual ammonia from the product gas. Moreover, the residual ammonia amount in the gas and thus the NH3 dissociation were evaluated for the catalyst in different operative conditions by measuring the PH of the trap and its changing rate over time. Dissociations close to the chemical equilibrium were obtained for every GHSV and temperature we tested with a pressures of 1 and 5 bar in the reactor. In particular, the dissociation was always higher than 99% at 1 bar, while at 5 bar it varied from 96% at 400 °C to 99% at 500 °C. At 10 bar the chemical equilibrium was reached for all GHSVs only at 450 °C and 500 °C with dissociations equal to 95.5% and 97.2%. At 400 °C a dissociation close to the chemical equilibrium (92%) was reached only for a GHSV of 300 h-1 while for the remaining GHSVs the dissociation was always lower, down to 80.8% for a GHSV equal to 2400 h-1. The kinetic parameters of the Temkin-Pyzhev model were evaluated for the ACTA Hypermec 10010 catalyst starting from the literature data on Ru catalyst. The results of this analysis showed that a pre-exponential factor of 1.5 × 10-9 mol m-3 s-1, an activation energy of 117 kJ mol-1 and a reaction order of 0.27 can be adopted for numerical simulations. Copyright © 2013, Hydrogen Energy Publications, LLC
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