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Reduced System (reduced + system)

Distribution by Scientific Domains

Engineering	50%

Selected Abstracts

A reduced-order modeling technique for tall buildings with active tuned mass damper

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 3 2001
Zu-Qing Qu
Abstract It is impractical to install sensors on every floor of a tall building to measure the full state vector because of the large number of degrees of freedom. This makes it necessary to introduce reduced-order control. A kind of system reduction scheme (dynamic condensation method) is proposed in this paper. This method is iterative and Guyan condensation is looked upon as an initial approximation of the iteration. Since the reduced-order system is updated repeatedly until a desired one is obtained, the accuracy of the reduced-order system resulting from the proposed method is much higher than that obtained from the Guyan condensation method. Another advantage of the method is that the reduced-order system is defined in the subspace of the original physical space, which makes the state vectors have physical meaning. An eigenvalue shifting technique is applied to accelerate the convergence of iteration and to make the reduced system retain all the dynamic characteristics of the full system within a given frequency range. Two schemes to establish the reduced-order system by using the proposed method are also presented and discussed in this paper. The results for a tall building with active tuned mass damper show that the proposed method is efficient for the reduced-order modelling and the accuracy is very close to exact only after two iterations. Copyright © 2001 John Wiley & Sons, Ltd. [source]

A combined freeze-and-cut strategy for the description of large molecular systems using a localized orbitals approach

JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 10 2005
Stefano Borini
Abstract A technique to reduce the computational effort in calculating ab initio energies using a localized orbitals approach is presented. By exploiting freeze strategy at the self-consistent field (SCF) level and a cut of the unneeded atomic orbitals, it is possible to perform a localized complete active space (CAS-SCF) calculation on a reduced system. This will open the possibility to perform ab initio treatments on very large molecular systems, provided that the chemically important phenomena happen in a localized zone of the molecule. Two test cases are discussed, to illustrate the performance of the method: the cis,trans interconversion curves for the (7Z)-13 ammoniotridec-7-enoate, which demonstrates the ability of the method to reproduce the interactions between charged groups; and the cisoid,transoid energy barrier for the aldehydic group in the C13 polyenal molecule. © 2005 Wiley Periodicals, Inc. J Comput Chem 26: 1042,1051, 2005 [source]

Projected Schur complement method for solving non-symmetric systems arising from a smooth fictitious domain approach

NUMERICAL LINEAR ALGEBRA WITH APPLICATIONS, Issue 9 2007
J. Haslinger
Abstract This paper deals with a fast method for solving large-scale algebraic saddle-point systems arising from fictitious domain formulations of elliptic boundary value problems. A new variant of the fictitious domain approach is analyzed. Boundary conditions are enforced by control variables introduced on an auxiliary boundary located outside the original domain. This approach has a significantly higher convergence rate; however, the algebraic systems resulting from finite element discretizations are typically non-symmetric. The presented method is based on the Schur complement reduction. If the stiffness matrix is singular, the reduced system can be formulated again as another saddle-point problem. Its modification by orthogonal projectors leads to an equation that can be efficiently solved using a projected Krylov subspace method for non-symmetric operators. For this purpose, the projected variant of the BiCGSTAB algorithm is derived from the non-projected one. The behavior of the method is illustrated by examples, in which the BiCGSTAB iterations are accelerated by a multigrid strategy. Copyright © 2007 John Wiley & Sons, Ltd. [source]

SLIDING VECTOR DESIGN BASED ON THE POLE-ASSIGNMENT METHOD

ASIAN JOURNAL OF CONTROL, Issue 1 2000
Jeang-Lin Chang
ABSTRACT This paper mainly focuses on the sliding vector design based on the poleassignment method. Unlike the general sliding vector design, the poleassignment method is applied to the overall system, not to a reduced system in sliding mode. Funrthermore, because four important conditions are considered, this sliding vector design is much simpler and more straightforward. Finally, a numeric example is included to demonstrate the validity of the proposed technique. [source]