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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Design of operable reactive distillation columns

Schenk, Myrian Andrea January 1999 (has links)
Reactive distillation is an integrated process which considers simultaneous physical and chemical transformations. It is increasingly receiving attention both from industry and academia. Significant advances have been made in the area of modelling and simulation as well as the implementation of such units industrially. However, the area of control and optimisation of such units has not been explored thoroughly. The thesis presents a general framework for simulation and design, which can handle reactive and non-reactive systems. Various different aspects of the modelling and simulation of distillation have been described in order to understand the behaviour of the reactive distillation columns. In the framework both simulation modes, steady-state and dynamic, are considered and the process is described by equilibrium and non equilibrium-based models. In a rate-based (or non equilibrium) model, mass transfer rates between liquid and vapour phase are considered explicitly, based on the Maxwell-Stefan equations. Equilibrium is attained at the phase interface in the non-equilibrium model. A switching policy makes it possible to go from one model to the other, based on the knowledge gained, by following the Gibbs free energy as a function of time. Tray efficiency has also helped in determining the switch between the non-equilibrium and equilibrium models, and has been studied for various systems. The existence of multiple steady state has been verified through simulation with the hybrid model. Bifurcation diagrams also confirmed the existence of output multiplicity obtained in the simulations. Analysis of process controllability at the design stage has been shown to provide guidance for improving process operation. In the thesis controllability measures for the reactive systems studied are presented as a first step towards control structure selection. A method for obtaining the design of reactive separation columns at minimum total annualised cost (investment and operating costs) and which will be able to maintain stable operation in the presence of variability is also presented.

Conditions de bifurcation dans les solides /

Hachich, Mohamed. January 1994 (has links)
Th. doct.--Mécanique des solides et des structures--Paris 6, 1994. / Bibliogr. p. 89-92. Résumé en français et en anglais.

Continuation methods applied to non linear flight dynamics and control

Richardson, Thomas Stuart January 2002 (has links)
No description available.

Characterisation and suppression of chattering in impacting structures

Lee, June-Yule January 1997 (has links)
No description available.

Existence of periodic travelling waves to reaction-diffusion equations with excitable-oscillatory kinetics

Haaf, Hermann January 1993 (has links)
No description available.

Fundamental flow phenomena in a sudden symmetric expansion

Fearn, R. M. January 1988 (has links)
No description available.

Forced convection in curved ducts multiplicity and stability /

Liu, Fang, January 2006 (has links)
Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Nonlinear aeroelastic analysis of high aspect-ratio wings using the method of numerical continuation

Nichkawde, Chetan 16 August 2006 (has links)
This research explores the impact of kinematic structural nonlinearities on the dynamics of a highly deformable cantilevered wing. Two different theoretical formulations are presented and analysed for nonlinear behavior. The first formulation, which is more conventional, assumes zero equilibrias and structural nonlinearities occur as terms up to third order in the Taylor series expansion of structural nonlinearities. In the second approach, no prior assumption about equilibria states of the wing is made. Kinematic nonlinearities due to curvature and inertia were retained in their exact form. Thus, the former becomes a special case of the latter. This nonlinear formulation permits the analysis of dynamics about nonzero trims. Nonzero trim states are computed as a system parameter is varied using a continuation software tool. The stability characteristics of these trim states are also ascertained. Various bifurcation points of the system are determined. Limit-cycle oscillations are also investigated for and are characterized in terms of amplitude of vibration. The research in particular examines the impact of in-plane degree of freedom on the stability of nonzero trim states. The effect of variation of system parameters such as stiffness ratio, aspect ratio and root angle of attack is also studied. The method of direct eigenanalysis of nonzero equilibria is novel and new for an aeroelastic system.

Hypersurfaces à courbure moyenne constante

Jleli, Mohamed Boussaïri Pacard, Franck. January 2004 (has links)
Thèse de doctorat : Mathématiques : Paris 12 : 2004. / Titre provenant de l'écran-titre.

Stability and bifurcation in flow induced vibration

徐善強, Chui, Sin-keung. January 1997 (has links)
published_or_final_version / Civil and Structural Engineering / Doctoral / Doctor of Philosophy

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