Some problems in model order reduction using frequency-domain methods

2005 ◽  
pp. 639-656 ◽  
Author(s):  
Antonio Lepschy ◽  
Umberto Viaro
Keyword(s):  
Frequency Domain ◽  
Model Order Reduction ◽  
Order Reduction ◽  
Model Order ◽  
Frequency Domain Methods

Investigation of Transient Thermal Analysis Computational Efficiency Improvements via Frequency Domain Methods

2012 ◽  
Author(s):  
Gregory A. Banyay ◽  
John C. Brigham ◽  
Evgenii Rudnyi
Keyword(s):  
Thermal Analysis ◽  
Frequency Domain ◽  
Time Domain ◽  
Model Order Reduction ◽  
Order Reduction ◽  
Model Order ◽  
Frequency Domain Methods ◽  
Thermal Transient ◽  
The Time Domain ◽  
Transient Thermal

During the operation of a Nuclear Steam Supply System (NSSS), the possibility exists for certain thermal transients to occur in the Reactor Coolant System (RCS). These transients exhibit some amount of periodicity in terms of temperature versus time. The current method of solving for temperature or thermal-mechanical stress states in the nuclear pressure vessel industry is by solving the governing equations in the time domain. For some analytical situations, significant computational savings could be realized by solving the thermal transient problem in the frequency domain. That is, the time, memory, and disk space required to solve the analysis is much less in the frequency domain than in the time domain. Two frequency domain methods are discussed in this paper. First, a Laplace-based model order reduction approach is applied to a reactor vessel component subjected to a representative thermal transient. Second, the feasibility of a Fourier-based spectral approach is discussed. For transient thermal analysis, it is shown that by employing model order reduction, significant computational savings can be realized with insignificant compromise in the accuracy of results.

scholarly journals Rational Approximations of Arbitrary Order: A Survey

2021 ◽  
Vol 5 (4) ◽  
pp. 267
Author(s):  
José Daniel Colín-Cervantes ◽  
Carlos Sánchez-López ◽  
Rocío Ochoa-Montiel ◽  
Delia Torres-Muñoz ◽  
Carlos Manuel Hernández-Mejía ◽  
...  
Keyword(s):  
Frequency Domain ◽  
Approximation Method ◽  
Model Order Reduction ◽  
Reduction Method ◽  
Arbitrary Order ◽  
Order Reduction ◽  
Synthesis Process ◽  
Rational Approximations ◽  
Model Order ◽  
Advantages And Disadvantages

This paper deals with the study and analysis of several rational approximations to approach the behavior of arbitrary-order differentiators and integrators in the frequency domain. From the Riemann–Liouville, Grünwald–Letnikov and Caputo basic definitions of arbitrary-order calculus until the reviewed approximation methods, each of them is coded in a Maple 18 environment and their behaviors are compared. For each approximation method, an application example is explained in detail. The advantages and disadvantages of each approximation method are discussed. Afterwards, two model order reduction methods are applied to each rational approximation and assist a posteriori during the synthesis process using analog electronic design or reconfigurable hardware. Examples for each reduction method are discussed, showing the drawbacks and benefits. To wrap up, this survey is very useful for beginners to get started quickly and learn arbitrary-order calculus and then to select and tune the best approximation method for a specific application in the frequency domain. Once the approximation method is selected and the rational transfer function is generated, the order can be reduced by applying a model order reduction method, with the target of facilitating the electronic synthesis.

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