Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 162 for “"reduced-order model"”.
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Numerical Analysis for Data-Driven Reduced Order Model Closures
… both theoretical and numerical aspects of reduced order models (ROMs). In an under-resolved regime, the classical Galerkin reduced order model (G-ROM) fails to yield accurate approximations. Thus, we propose a new ROM, the data-driven variational multiscale ROM (DD-VMS-ROM) built by adding …
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Reduced-order model framework for thermochemical non-equilibrium hypersonic flows
… time-scales. As a result, work focused on modeling this type of flowfield has been hindered by inaccurate physical and chemical models. For example, the conventional approach to model chemical non-equilibrium, still widely used today, was developed nearly 40 years ago and relies heavily on …
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Reduced Order Model Study of Burgers' Equation using Proper Orthogonal Decomposition
… of the 1D viscous Burgers' equation and several Reduced Order Models (ROMs) over a range of parameter values. This study is motivated by the need for robust reduced order models that can be used both for design and control. Thus the model should first, allow for selection of optimal parameter …
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A Reduced-Order Model Bi-Modal Excitation of a Supersonic Planar Jet
… is applied to the flow components. A reduced order model is derived, turning the Navier-Stokes partial differential equations into a set of coupled ordinary differential equations, relating the momentum thickness and amplitudes of a fundamental and subharmonic mode to the streamwise …
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A Two-Level Galerkin Reduced Order Model for the Steady Navier-Stokes Equations
… numerically a novel two-level Galerkin reduced order model (2L-ROM) for the efficient and accurate numerical simulation of the steady Navier-Stokes equations. In the first step of the 2L-ROM, a relatively low-dimensional nonlinear system is solved. In the second step, the Navier-Stokes …
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Homotopy methods for solving the optimal projection equations for the reduced order model problem
The optimal projection approach to solving the reduced order model problem produces two coupled, highly nonlinear matrix equations with rank conditions as constraints. Due to the resemblance of these equations to standard matrix Lyapunov equations, they are called modified Lyapunov equations. The …
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Reduced-order model-reference adaptive system identification of large scale systems with discrete adaptation laws
Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1985.
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The Development of a Reduced Order Model for Prediction of Haemodynamic and Biochemical Changes in a Computational Cerebral Aneurysm Thrombosis Model
… A computational fluid dynamics (CFD) model that couples haemodynamics and biochemistry was developed to simulate cerebral aneurysm thrombosis. The blood was modelled as a Newtonian fluid and thrombin generation curves (TGCs) were used to model the release of thrombin from the injured …
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Near aggregation: a time and frequency domain analysis using state trajectories and transfer function residues
… basic idea of aggregation is that there exists a reduced order model such that, for an appropriate initial condition, the trajectories of the reduced-order model are linear combinations of the trajectories of the ful 1-order model. We study systems which do not aggregate exactly, but which "nearly …
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Study of reduced order models for vortex-induced vibration and comparison with CFD results
… behaves when trying to control vibrations; a reduced order model may be an effective way to study the system dynamics. Developing a data driven model from simulation and/or experimental results can be difficult, but there are existing phenomenological models that attempt to describe VIV, …
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Reduced-order modeling for ensemble real-time estimation and control
… complex probabilistic distributions of uncertain model parameters. To reduce the computational burden and make it feasible to apply the ensemble closed-loop control to large-scale problems, this thesis proposes a robust reduced-order model for subsurface solute transport that is sufficiently …
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A hierarchy of microgrid models with some applications
… dissertation proposes a hierarchy of microgrid models that can be utilized for power system analysis and control design purposes. The microgrid models are classified according to time resolution and, consequently, according to complexity and computational cost as well. Our approach involves …
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Iterative Rational Krylov Algorithm for Unstable Dynamical Systems and Genaralized Coprime Factorizations
… when applied in numerical simulations. In order to overcome these challenges we use several model reduction techniques. For stable linear models these techniques work very well and provide good approximations for the full model. However, large-scale unstable systems arise in many …
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Efficient reduced-basis approximation of scalar nonlinear time-dependent convection-diffusion problems, and extension to compressible flow problems
In this thesis, the reduced-basis method is applied to nonlinear time-dependent convection-diffusion parameterized partial differential equations (PDEs). A proper orthogonal decomposition (POD) procedure is used for the construction of reduced-basis approximation for the field variables. In the …
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Investigation of the Mechanical Behavior of Microbeam-Based MEMS Devices
… and resonant microsensors. Nonlinear models are developed to simulate the behavior of the microbeams in each device. The models account for mid-plane stretching, an applied axial load, a DC electrostatic force, and, for the case of resonant sensors, an AC harmonic force. Further, a …
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The design of suboptimal linear regulators using reduced order aggregated models
… Two techniques are proposed for obtaining a reduced order aggregated model for a constant coefficient dynamic system. This model is then used to determine a suboptimal control law to solve an output regulator problem. The research is developed by first examining the problems involved when the …
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An augmented basis method for reduced order models of turbulent flow
Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2024-05-01
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IGFEM-based reduced-order modeling and design of nonlinear composites
… is the computational cost associated with modeling the mechanical behavior of complex domains as optimization algorithms are usually iterative, requiring many evaluations of the domain response. For this reason, the majority of existing work on this subject focuses on linear theory. In this …
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Physical domain model reduction for design and control of engineering systems
There is an increasing need for obtaining low order approximations of high order models of physical systems. Low order models result in several advantages including the reduction of computational complexity and improved understanding of the original system structure. Although different methods have …
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