241 research outputs found
Multimodal electromechanical model of piezoelectric transformers by Hamilton's principle
This work deals with a general energetic approach
to establish an accurate electromechanical model of a
piezoelectric transformer (PT). Hamiltonâs principle is used to obtain the equations of motion for free vibrations. The modal characteristics (mass, stiffness, primary and secondary electromechanical conversion factors) are also deduced. Then, to illustrate this general electromechanical method, the variational principle is applied to both homogeneous and nonhomogeneous Rosen-type PT models. A comparison of modal parameters, mechanical displacements, and electrical potentials are presented for both models.
Finally, the validity of the electrodynamical
model of nonhomogeneous Rosen-type PT is confirmed
by a numerical comparison based on a finite elements
method and an experimental identification
First Approach for the Modelling of the Electric Field Surrounding a Piezoelectric Transformer in View of Plasma Generation
This paper is about an open multi-physics modelling problem resulting from recent investigations into plasma generation by piezoelectric transformers. In this first approach, the electric field distribution surrounding the transformer is studied according to a weak coupling formulation. Electric potential distribution views obtained numerically are compared to real views of plasma generation observed experimentally
Identification Methodology of Electrical Equivalent Circuit of the Piezoelectric Transformers by FEM
Methodology using Ansys analyses for the identification of Electrical Equivalent Circuit of piezoelectric transformer. The demonstration is done with typical multilayered Rosen transformer but the method is relevant for any kind of transformer structures
Modeling of a Ring Rosen-Type Piezoelectric Transformer by Hamiltonâs Principle
This paper deals with the analytical modeling of a ring Rosen-type piezoelectric transformer. The developed model is based on a Hamiltonian approach, enabling to obtain main parameters and performance evaluation for the first radial vibratory modes. Methodology is detailed, and final results, both the input admittance and the electric potential distribution on the surface of the secondary part, are compared with numerical and experimental ones for discussion and validation
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Control of pool boiling incipience in confined space: dynamic morphing of the wall effect
This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.A new active heat transfer enhancement and control technique is proposed in this work. One of the major aims of the technique is to decrease pool boiling incipience temperature by dynamic morphing imposed to confinement wall. Dynamic deformation generates variation of pressure which increases the fluid metastability level. An experimental device was built to evaluate boiling incipience temperature. Experimental results were compared with hydrodynamic and nucleation models.CNRS Energie CITAMPE PR09-3.1.3-2 and FNRAE SYRTIP
Low voltage plasma jet with piezoelectric generator : preliminary evaluation of decontamination capabilities
This paper deals with the proof of concept and the preliminary evaluation of decontamination performances obtained with a plasma jet generated by a piezoelectric transformer. This low voltage supply solution (<10V) is investigated as a plasma jet device, compact and safe solution for the decontamination of medical thermo-sensitive devices. The principle of the piezoelectric generator is presented, followed by the optical spectroscopy of the plasma jet, the protocol conditions for the bactericidal effect observations and finally the reduction rates obtained on Pseudomonas aeruginosa and Staphylococcus aureus bacteria strains with an argon plasma jet at atmospheric pressure about 2.5W electrical input power
Compact Electron Gun Based on Secondary Emission Through Ionic Bombardment
We present a new compact electron gun based on the secondary emission through ionic bombardment principle. The driving parameters to develop such a gun are to obtain a quite small electron gun for an in-flight instrument performing Electron Beam Fluorescence measurements (EBF) on board of a reentry vehicle in the upper atmosphere. These measurements are useful to characterize the gas flow around the vehicle in terms of gas chemical composition, temperatures and velocity of the flow which usually presents thermo-chemical non-equilibrium. Such an instrument can also be employed to characterize the upper atmosphere if placed on another carrier like a balloon. In ground facilities, it appears as a more practical tool to characterize flows in wind tunnel studies or as an alternative to complex electron guns in industrial processes requiring an electron beam. We describe in this paper the gun which has been developed as well as its different features which have been characterized in the laboratory
Pumping and heat transfer enhancement by wall's morphing
In a previous study, heat transfer enhancement using a deformable
wall in a heat exchanger was demonstrated numerically
using CFD calculations in liquid single-phase situation.
This configuration allows the pumping function to be integrated
within the heat exchanger itself. Based on these results, a prototype
has been developed (but with different dimensions than in
the numerical study) in which one of the walls constituting the
channel is subjected to dynamic deformations in the form of a
traveling wave. Electric heaters on the other wall heat the channel.
Actuation is achieved by means of piezoelectric actuators.
Experimentally, the pumping function is observed, for all frequencies
of deformations and for two different fluids (water and
HFE 7000). The heat transfer intensification is also shown, and
this in two experimental configurations:
- a pressure difference (which may be zero) between the inlet and
outlet of the channel is imposed: in this configuration, the traveling
wave imposes the flow-rate. The heat transfer enhancement
is then due both to the increase of the flow-rate and the disruption
of the thermal boundary layers generated by the wave;
- a flow-rate is imposed with a mechanical pump: in this case
actuation has no effect on the pumping, and the measured heat
transfer enhancement is then due only to the effects of the imposed
dynamic deformations.
First experiments with the presence of boiling were also performed.
It was found that boiling can occur even if the fluid
does not reach the saturation temperature within the channel. A
100% increase in the mean heat transfer coefficient was found
when actuating the channel wall.Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016
Solution structure and dynamics of DNA duplexes containing the universal base analogues 5-nitroindole and 5-nitroindole 3-carboxamide
Universal bases hybridize with all other natural DNA or RNA bases, and have applications in PCR and sequencing. We have analysed by nuclear magnetic resonance spectroscopy the structure and dynamics of three DNA oligonucleotides containing the universal base analogues 5-nitroindole and 5-nitroindole-3-carboxamide. In all systems studied, both the 5-nitroindole nucleotide and the opposing nucleotide adopt a standard anti conformation and are fully stacked within the DNA duplex. The 5-nitroindole bases do not base pair with the nucleotide opposite them, but intercalate between this base and an adjacent WatsonâCrick pair. In spite of their smooth accommodation within the DNA double-helix, the 5-nitroindole-containing duplexes exist as a dynamic mixture of two different stacking configurations exchanging fast on the chemical shift timescale. These configurations depend on the relative intercalating positions of the universal base and the opposing base, and their exchange implies nucleotide opening motions on the millisecond time range. The structure of these nitroindole-containing duplexes explains the mechanism by which these artificial moieties behave as universal bases
Ătude des marqueurs gĂ©nĂ©tiques sanguins dans deux races de poneys de pologne
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