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PMMA particle synthesis was performed from MMA (methyl methacrylate) and water mixtures, exposed to different ultrasonic systems and frequencies. The sonication sequence was 20kHz→580kHz→858kHz→1138kHz, and the solution was sampled after each irradiation step for polymerization. Effects of sonication parameters (time, power), polymerization method (thermo-initiated or photo-initiated), use of small amounts of surfactant (Triton X-100™ or Tween® 20) and initial MMA quantity were investigated on particle size and synthesis yields. Particle size and size distribution were measured by DLS (Dynamic Light Scattering), and confirmed via SEM (Scanning Electron Microscopy) images. Synthesis yield was calculated using the dry weight method. Particle composition was estimated using FTIR (Fourier Transform Infra-Red) spectroscopy. PMMA (polymethylmethacrylate) monodispersed particles were successfully synthesized, with a possibility of control in the 78-310nm size range. These sized-controlled particles were synthesized with a 7.5-85% synthesis yield (corresponding to 7.5-40g/L particle solid content), depending on operational parameters. Furthermore, a trade-off between particle size and synthesis yield can be proposed: 20kHz→10min waiting time→580kHz→858kHz leading to 90nm particles diameter with 72% yield in less than 40min for the whole sequence. Thus, the synthesis under ultrasound can be found easy to implement and time efficient, ensuring the success of the scale-up approach and opening up industrial applications for this type of polymeric particles.

In a first part of the study, we shall give a description of the mathematical model of the two kinds of metallurgic furnaces of reheating, that is : - the impelling furnace where the thermic exchanges are unidirectional (continuous sheet). - the furnace with stringers into which a given space is kept between two products. . The numerical methods analyzing the thermic process by a solution of the equations of the model are then described. The second part of the study is devoted to the identification of the parameters of the model (thermal conductivity and heat capacity of the metal) from a punctual observation of the phenomena (two measures on the surface and in the middle of the metal. For this purpose, some methods of non-linear p ogramming are used and then analyzed critically. The last part deals with “the optimization” of the furnaces operating under steady-state conditions (homogeneous filling), in the case of the two criterion of optimality (energizing one or that of the quality of the metal) and constraints of “rolling” of the metal.