http://hdl.handle.net/123456789/3 Mon, 03 Aug 2026 17:58:09 GMT 2026-08-03T17:58:09Z http://hdl.handle.net/123456789/620231 A systematic parameters study from analytic calculations to optimize ozone concentration in an oxygen-fed wire-to-cylinder ozonizer A systematic parameter study from analytic calculations is presented to optimize ozone concentration in an oxygen-fed wire-to-cylinder ozonizer. Using experimental results, an analytic temperature law is deduced and included in a previously published analytical model [1]. From this latter a systematic parameters study shows that optimum conditions for ozone generation depend on electric power, gas flow and ozonizer geometry. A general relationship is given to calculate the best working conditions. The Mayn physical functions for ozone production (formation and destruction overall coefficients, ozone concentration, specific energy and economical criterion) are studied and commented. These results are finally compared with experiments for a wide range of parameters and a good agreement is found. http://hdl.handle.net/123456789/620231 http://hdl.handle.net/123456789/620230 Ion-acoustic wakefields and molecular ions in dense plasmas It is shown, both analytically and through one-dimensional numerical computations, that highly charged ions propagating through a plasma with thermal or faster than thermal velocities, drive significant ion-acoustic wakefields. By a mechanism similar to electron pairing in superconductors, such wakefields may contribute to the formation of transient molecular ions. Comparison is made with the results of experiments in which dense high temperature plasmas are created by laser irradiated colliding foils. http://hdl.handle.net/123456789/620230 http://hdl.handle.net/123456789/620232 Current and electric field measurements in coaxial system during the positive DC corona in humid air A stable positive corona discharge in coaxial electrode system with varying humidity is analysed using a model which separates the corona in two distinct regions. A careful choice of boundary conditions in the drift region, particularly at the cathode surface, is needed. A new method of current and electric field measurements with a linear biased probe, incorporated in the outer cylinder, is used. The corona current, at a given voltage, decreases with humidity but the electric field at the outer cylinder is independent of humidity. The fields at the surfaces of the cathode and the anode vary linearly with the applied voltage between electrodes. The exact value of the average mobility of positive ions in the drift region is deduced from current and field measurements. This mobility increases when the potential difference across the drift region increases and it decreases slightly as the air is made more humid. Other parameters of the positive corona are successively determined by the current and field measurements, in particular, the total field distribution between electrodes. http://hdl.handle.net/123456789/620232 http://hdl.handle.net/123456789/620228 Modelling of the steady state thermal behaviour of a permanent magnet direct current motor with commutator. 3D finite elements study The aim of this work concerns the development and the validation of a thermal steady state model applied to a permanent magnet direct current motor with commutator. The rated power of the machine is 120 W. Design has been realized thanks to the thermal modulus of the computation software with the finite element method Flux3D. It is shown in this work how it is possible to use only the heat equation to simulate the thermal behaviour of the motor. It implies calculating of new fluid conductivities (considering also all thermal modes) by comparison of calculated and experimental temperatures. To realize these 3D modelizations, it is necessary to know and to locate all the losses of the motor which are considered as thermal sources. The experimental temperatures are given by 40 chromel-alumel thermocouples of 100 μm diameter located in the rotor and the stator of the machine. Numerical computations use Dirichlet boundary layer conditions given by an IR camera. http://hdl.handle.net/123456789/620228