Articulos(INTEC)
http://hdl.handle.net/11336/300
Articulos de INST.DE DES.TECNOL.PARA LA IND.QUIMICA (I)Sat, 20 Jul 2019 02:56:23 GMT2019-07-20T02:56:23ZA probabilistic approach to radiant field modeling in dense particulate systems
http://hdl.handle.net/11336/76437
A probabilistic approach to radiant field modeling in dense particulate systems
Busciglio, A.; Alfano, Orlando Mario; Scargiali, F.; Brucato, A.
Radiant field distribution is an important modeling issue in many systems of practical interest, such as photo-bioreactors for algae growth and heterogeneous photo-catalytic reactors for water detoxification.In this work, a simple radiant field model suitable for dispersed systems showing particle size distributions, is proposed for both dilute and dense two-phase systems. Its main features are: (i) only physical, independently assessable parameters are involved and (ii) its simplicity allows a closed form solution, which makes it suitable for inclusion in a complete photo-reactor model, where also kinetic and fluid dynamic sub-models play a role. A similar model can be derived by making use of concepts developed in the realm of stereology. The resulting equation is similar, yet not identical, to that obtained with the probabilistic approach, due to the fact that in stereology the front plane, or the focus plane, may well cut through particles, a circumstance excluded both in the probabilistic model and in actual photoreactors.The two models are compared with pseudo-experimental data obtained by means of Monte Carlo simulations, and the probabilistic model is found to give rise to the best agreement.
Tue, 01 Mar 2016 00:00:00 GMThttp://hdl.handle.net/11336/764372016-03-01T00:00:00ZSuboptimal Control Strategies for Finite-Time Nonlinear Processes with Input Constraints
http://hdl.handle.net/11336/76434
Suboptimal Control Strategies for Finite-Time Nonlinear Processes with Input Constraints
Rivadeneira Paz, Pablo Santiago; Adam, Eduardo Jose
Novel techniques for the optimization and control of finite-time processes in real-time are pursued. These are developed in the framework of the Hamiltonian optimal control. Two methods are designed. The first one constructs the reference control trajectory as an approximation of the optimal control via the Riccati equations in an adaptive fashion based on the solutions of a set of partial differential equations called the $alpha$ and $eta$ matrices. These allow calculating the Riccati gain for a range of the duration of the process $T$ and the final penalization $S$. The second method introduces input constraints to the general optimization formulation. The notions of linear matrix inequalities allow us to recuperate the Riccati gain as in the first method, but using an infinite horizon optimization method. Finally, the performance of the proposed strategies is illustrated through numerical simulations applied to a batch reactor and a penicillin fed-batch reactor.
Sun, 01 Sep 2013 00:00:00 GMThttp://hdl.handle.net/11336/764342013-09-01T00:00:00ZElectronic and Magnetic Changes in a Finite-Sized Single-Walled Zigzag Carbon Nanotube Embedded in Water
http://hdl.handle.net/11336/76432
Electronic and Magnetic Changes in a Finite-Sized Single-Walled Zigzag Carbon Nanotube Embedded in Water
Ruiz Tobon, Carlos Mario; Dalosto, Sergio Daniel
In vacuum an open-ended finite-sized zigzag and hydrogen atom terminated carbon nanotube (FS-CNT) has a ground state with antiferromagnetic configuration, and the α and β gaps are degenerated with a magnitude inversely proportional to the nanotube length. However, when a FS-CNT is embedded in a box of water molecules, a single-file hydrogen bonded chain of water molecules (confined water inside) flows through it from one side to the other, while a spatially varying density profile occurs for the bulk water molecules (unconfined water outside). As a consequence, we have observed for an embedded FS-CNT(11,0,L) with L < 2.0 nm important changes in its electronic and magnetic properties. The electronic gap degeneracy is broken, and the gap value for each spin state fluctuates around a mean value which depends on the CNT length. We rationalized these changes by decomposing the fluctuating electric field produced by the water molecules as due to molecules of unconfined water outside and confined water inside the FS-CNT. The confined water inside produces an electric field nearly constant in magnitude and pointing almost along the axial axis of the tube, equivalent to an external uniform electric field with a mean value of 0.56 ± 0.05 V/nm. Meanwhile, the unconfined water outside produces an electric field that fluctuates randomly in direction and magnitude, and it is equivalent to an external uniform electric field with a mean value of 0.7 ± 0.4 V/nm. The maximum electric field observed was 1.7 ± 0.2 V/nm which occurs when both confined water inside and unconfined water outside the electric fields have the same direction. The maximum electric field is three times smaller than the one necessary to change the CNT from semiconductor to half-metallic. The findings are important in devices where solvent molecules change the electronic properties of the CNT.
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/11336/764322013-01-01T00:00:00ZFinite-element modelling of heat transfer in shaped metal deposition and experimental validation
http://hdl.handle.net/11336/76428
Finite-element modelling of heat transfer in shaped metal deposition and experimental validation
Fachinotti, Victor Daniel; Cardona, Alberto; Baufeld, Bernd; Van Der Biest, Omer
Shaped metal deposition (SMD) is a novel technology for building near-net-shaped components by successive layer deposition using a welding machine. The SMD rig consists of a robot with a tungsten inert gas welding torch and manipulator, both of which are housed inside a sealed chamber. A series of walls were made from Ti-6Al-4V alloy by SMD and the heat transfer problem during layer deposition was analysed in all cases. The specimens were built using a wide range of process parameters (number of layers, layer height, wire feed rate, travel speed, heat input, etc.) and wall dimensions. During the fabrication process, the SMD built part is subjected repeatedly to high temperature gradients and high heating and cooling rates, resulting in a unique morphology and microstructures usually not observed in conventional fabrication techniques. A finite-element model for the thermal analysis of this deposition process was constructed. The aims of this study are, firstly, to correlate the predicted temperature field to experimental observations to validate the numerical model of this complex process; and secondly, to explain on the basis of the computed temperature and temperature rate the appearance of characteristic microstructures on the top of the walls, and in the substrate and intermediate region.
Thu, 01 Nov 2012 00:00:00 GMThttp://hdl.handle.net/11336/764282012-11-01T00:00:00Z