Slab curvature compensation in a hot rolling mill by means of fuzzy control
In the flat products steel industry, the hot rolling mill transforms the incoming slabs in a thin coil which then can be processed to obtain the final products. Thickness is reduced by pulling the plate between two parallel rolls while moving the upper work roll. The effect of uneven thickness at both sides can produce deviations in the longitudinal direction of the slab, which have to be manually compensated for an human operator. In this paper a multivariable control system and a fuzzy control system are described and compared. Results are illustrated with real data from ACERALIA STEEL CORPORATION.
Modeling and Control of Plate Mill Processes
In this thesis two processes have been modeled and controlled, namely the plate thickness control and the slab temperature control. The classical solution for the thickness control problem can't handle asymmetric hardness variations and the estimation of the controlled output introduces stability problems. A nonlinear multivariable model for the thickness control system is derived. The parameters of the model for the rolling mill are identified using data from The Danish Steel Works Ltd. and the model is used for designing a nonlinear multivariable thickness control algorithm. The algorithm is evaluated using computer simulations and the new controller is able to handle the asymmetric case and gives a more accurate thickness control compared to the existing control system. The new control strategy is also found to be stable. The task of the slab temperature controller is to ensure a high furnace throughput, and a proper heating quality while minimizing the energy consumption. Models for the slab and furnace temperatures are identified using data collected during normal production at The Danish Steel Works Ltd. A new way of obtaining parameters for the existing slab temperature control system is described. Furthermore, a nonlinear controller is designed which it is shown to be is globally asymptotically stable. The performance of the linear and nonlinear controller are compared using computer simulations which show that the performance of the nonlinear controller is superior to the performance of the linear controller. The linear slab temperature controller design has been implemented in the slab temperature control system at The Danish Steel Works Ltd. The experimental results indicate that the new controller parameters have lead to a 10% increase in furnace capacity, with unchanged heating quality. Data from the reheat furnace no. 2 indicate that the energy consumption has not been increased by the adjustments. (Less)
Single step formation of biocompatible bimetallic alloy nanoparticles of gold and silver using isonicotinylhydrazide.
Manufacturing nanoparticles with controlled physicochemical properties using environment-friendly routes have potential to open new prospects for a variety of applications. Accordingly, several approaches have been established for manufacturing metal nanoparticles. Many of these approaches entail the use of hazardous chemicals and could be toxic to the environment, and cannot be used readily for biomedical applications. In the present work, we report a single step bio-friendly approach to formulate gold (Au), silver (Ag), and Au-Ag alloy nanoparticles with desired surface corona and composition using isonicotinylhydrazide (INH) as a reducing agent. INH also functioned as a stabilizing agent by enabling a surface corona around the nanoparticles. Remarkably, within a single step INH could also provide a handle in regulating the composition of Au and Ag in bimetallic systems without any additional chemical modification. The physicochemical and surface properties of the different nanoparticles thus obtained have been examined by analytical, spectroscopic and microscopic techniques. Cell cytotoxicity (release of lactate dehydrogenase), cell viability and intracellular reactive oxygen species (ROS) assays confirmed that the Au, Ag, and Au-Ag bimetallic nanoparticles prepared with INH are biocompatible. Finally, the presence of organic surface corona of INH on the nanoparticles was found to impart nanozyme activity and antimycobacterial sensitivity to the nanoparticles.