43 research outputs found
Experimental and numerical characterization of a gravitational electromagnetic energy harvester
No full textIn this paper, the dynamic experimental identification of an inductive energy harvester for the conversion of vibration energy into electric power is presented. Recent advances and requirements in structural monitoring and vehicle diagnostic allow defining Autonomous Internet of Things (AIoT) systems that combine wireless sensor nodes with energy harvester devices properly designed considering the specific duty cycle. The proposed generator was based on an asymmetrical magnetic suspension and was addressed to structural monitoring applications on vehicles. The design of the interfaces of the electric, magnetic, and structural coupled systems forming the harvester are described including dynamic modeling and simulation. Finally, the results of laboratory tests were compared with the harvester dynamic response calculated through numerical simulations, and a good correspondence was obtained
Inductive energy harvesters with magnetic suspensions: experimental identification of performances and efficiency
No full textThe design, fabrication and experimental identification of inductive energy harvesters for the conversion of vibrations into electricity are reported in this paper. The proposed generator is based on magnetically levitated suspensions and is addressed to structural monitoring applications on vehicles. The experimental tests have the goal to optimize the dynamic response of the harvester prototyp
Controls Over Particle Motion and Resting Times of Coarse Bed Load Transport in a Glacier-Fed Mountain Stream
No full textCoarse bed load transport is a crucial process in river morphodynamics but is difficult to monitor in mountain streams. Here we present a new sediment transport data set obtained from 2 years of field-based monitoring (2014–2015) at the Estero Morales, a high-gradient stream in the central Chilean Andes. This stream features step-pool bed geometry and a glacier-fed hydrologic regime characterized by abrupt daily fluctuations in discharge. Bed load was monitored directly using Bunte samplers and by surveying the mobility of passive integrated transponder (PIT) tags. We used the competence method to quantify the effective slope, which is the fraction of the topographical slope responsible for bed load transport. This accounts for only 10% of the topographical slope, confirming that most of the energy is dissipated on macroroughness elements. We used the displacement lengths of PIT tags to analyze displacement lengths and virtual velocity of a wide range of tracer sizes (38–415 mm). Bed load transport in the Estero Morales shown to be size-selective, and the distance between steps influences the displacement lengths of PIT tags. Displacement lengths were also used to derive the statistics of flight distances and resting times. Our results show that the average length of flight scales inversely to grain size. This contradicts Einstein's conjecture about the linear relationship between grain size and intervals between resting periods in a steep step-pool stream in ordinary flood conditions
Piezoelectric energy harvesting for autonomous sensors network on safety-improved railway vehicles
No full text Mechanical vibrations of railway vehicles were converted to electric power by means of a piezoelectric energy harvester, a rectification circuit, and a storage battery. The power harvested is used to supply one node of a sensor network for the structural monitoring and safety improvement on railway vehicles. The dynamic dimensioning of the piezoelectric generator is presented, for the mechanical and electric viewpoints; the resonance tuning is described and the experimental validation of the performances of the node is provided. The tests were conducted on a scaled railway bogie, which is able to simulate the real working conditions of a train. The efficiency and the duty cycle of the autonomous sensing platform are measured. </jats:p
Monocytes/macrophages prevent healing defects and left ventricular thrombus formation after myocardial infarction
No full textMyocardial infarction (MI) leads to rapid necrosis of cardiac myocytes. To achieve tissue integrity and function, inflammatory cells are activated, including monocytes/macrophages. However, the effect of monocyte/macrophage recruitment after MI remains poorly defined. After experimental MI, monocytes and macrophages were depleted through serial injections of clodronate-containing liposomes. Monocyte/macrophage infiltration was reduced in the myocardium after MI by active treatment. Mortality was increased due to thromboembolic events in monocyte-and macrophage-depleted animals (92 vs. 33%; P<0.01). Left ventricular thrombi were detectable as early as 24 h after MI; this was reproduced in a genetic model of monocyte/macrophage ablation. A general prothrombotic state, increased infarct expansion, and deficient neovascularization were not observed. Severely compromised extracellular matrix remodeling (collagen I, placebo liposome vs. clodronate liposome, 2.4 +/- 0.2 vs. 0.8 +/- 0.2 arbitrary units; P<0.001) and locally lost integrity of the endocardium after MI are potential mechanisms. Patients with a left ventricular thrombus had a relative decrease of CD14(+) CD16(+) monocyte/macrophage subsets in the peripheral blood after MI (no thrombus vs. thrombus, 14.2 +/- 0.9 vs. 7.80 +/- 0.4%; P<0.05). In summary, monocytes/macrophages are of central importance for healing after MI. Impaired monocyte/macrophage function appears to be an unrecognized new pathophysiological mechanism for left ventricular thrombus development after MI.-Frantz, S., Hofmann, U., Fraccarollo, D., Schafer, A., Kranepuhl, S., Hagedorn, I., Nieswandt, B., Nahrendorf, M., Wagner, H., Bayer, B., Pachel, C., Schon, M.P., Kneitz, S., Bobinger, T., Weidemann, F., Ertl, G., Bauersachs, J. Monocytes/macrophages prevent healing defects and left ventricular thrombus formation after myocardial infarction. FASEB J. 27, 871-881 (2013). www.fasebj.or
Impact of pressure guidewire on model-based FFR prediction
No full textIntroduction
Fractional Flow Reserve (FFR) is used to characterize the functional significance of coronary artery stenoses. FFR is assessed under hyperemic conditions by invasive measurements of trans-stenotic pressure thanks to the insertion of a pressure guidewire across the coronary stenosis during catheterization. In order to overcome the potential risk related to the invasive procedure and to reduce the associated high costs, three-dimensional blood flow simulations that incorporate clinical imaging and patient-specific characteristics have been proposed.
Purpose
Most CCTA-derived FFR models neglect the potential influence of the guidewire on computed flow and pressure. Here we aim to quantify the impact of taking into account the presence of the guidewire in model-based FFR prediction.
Methods
We adopt a CCTA-derived FFR model and perform simulations with and without the guidewire for 18 patients with suspected stable CAD.
Results
Presented results show that the presence of the guidewire leads to a tendency to predict a lower FFR value. The FFR reduction is prominent in cases of severe stenoses, while the influence of the guidewire is less pronounced in cases of moderate stenoses.
Conclusion
From a clinical decision-making point of view, including of the pressure guidewire is potentially relevant only for intermediate stenosis cases
