Direct optimization determination of auxiliary test signals for linear problems with model uncertainty

2011 ◽  
Author(s):  
Ivan Andjelkovic ◽  
Stephen L. Campbell
Keyword(s):  
Model Uncertainty ◽  
Direct Optimization ◽  
Linear Problems ◽  
Auxiliary Test

Model Uncertainties of FEM Nonlinear Analyses of Concrete Structures

2016 ◽  
Vol 249 ◽  
pp. 197-202 ◽  
Author(s):  
Lukáš Kadlec ◽  
Vladimir Červenka
Keyword(s):  
Numerical Simulations ◽  
Model Uncertainty ◽  
Structural Reliability ◽  
Constitutive Relations ◽  
Nonlinear Analyses ◽  
Model Uncertainties ◽  
Flexural Failure ◽  
Literary Sources ◽  
Near Future

Advanced numerical simulations are more often used due to the increasing possibilities of computer technology. For material descriptions, generally nonlinear constitutive relations are employed. It is expected that in the near future the reliability of structures will be assessed by use of these sophisticated calculations. For this purpose, it is firstly necessary to evaluate the model uncertainty of the numerical model, because the structural reliability is directly affected by the model uncertainty. Recommended values of model uncertainties differ in individual scientific literary sources. In standard codes the partial safety factor for model uncertainty is set by relatively low value. This value was assessed by empirical way and it seems that such value is valid only for flexural failure. Contemporary numerical simulations indicate larger model uncertainties. Moreover, the value of model uncertainty should be related to particular failure mode. This paper presents a comprehensive procedure for the determination of model uncertainties of nonlinear analyses. In the second part, the value of model uncertainties is derived for punching of slabs.

Determination of state-space model uncertainty using bootstrap techniques

2006 ◽  
Vol 16 (7) ◽  
pp. 685-692 ◽  
Author(s):  
Vitor V. Lopes ◽  
Carla C. Pinheiro ◽  
Jose C. Menezes
Keyword(s):  
State Space ◽  
Model Uncertainty ◽  
State Space Model ◽  
Space Model ◽  
Bootstrap Techniques

scholarly journals On the effect of model uncertainty on the Hopf bifurcation of aeroelastic systems

2021 ◽  
Author(s):  
Andrea Iannelli ◽  
Mark Lowenberg ◽  
Andrés Marcos
Keyword(s):  
Nonlinear Dynamics ◽  
Hopf Bifurcation ◽  
Model Uncertainty ◽  
Relevant Information ◽  
Systematic Investigation ◽  
Aeroelastic System ◽  
Physical Mechanisms ◽  
Analysis Technique ◽  
Numerical Approaches

AbstractThis paper investigates the effect of model uncertainty on the nonlinear dynamics of a generic aeroelastic system. Among the most dangerous phenomena to which these systems are prone, Limit Cycle Oscillations are periodic isolated responses triggered by the nonlinear interactions among elastic deformations, inertial forces, and aerodynamic actions. In a dynamical systems setting, these responses typically emanate from Hopf bifurcation points, and thus a recently proposed framework, which address the problem of robustness from a nonlinear dynamics viewpoint, is employed. Briefly, the notion of robust bifurcation margin extends the concept of $$\mu $$ μ analysis technique from the robust control theory. The main contribution of this article is a systematic investigation of the numerous scenarios arising in the study of nonlinear flutter when uncertainties in the model are accounted for in the analyses. The advantages of adopting this framework include the possibility to: quantify relevant information for the determination of the nonlinear stability envelope; gain a more in-depth understanding of the physical mechanisms triggering subcritical and supercritical Hopf bifurcations; and reveal properties of the nominal system by identifying isolated branches not straightforward to detect with conventional numerical approaches.

scholarly journals Knowledge work difficulty factors: An empirical study based on different groups of knowledge workers

2012 ◽  
Vol 15 (1) ◽  
pp. 1-15 ◽  
Author(s):  
Jalil Heidary Dahooie ◽  
Abbas Afrazeh ◽  
Seyed Mohammad Hosseini ◽  
Mohamad Reza Ghezel Arsalan
Keyword(s):  
Empirical Study ◽  
Model Uncertainty ◽  
Regression Models ◽  
Knowledge Workers ◽  
Knowledge Work ◽  
The Other ◽  
Influential Factor ◽  
Knowledge Based ◽  
Information Amount

The determination of the difficulty factor in knowledge work can be important for improving the performance of knowledge workers. In this article a regression model for investigating the difficulty of knowledge based activities (KBAs) is proposed. Four factors are considered in the model: Uncertainty, Variability of information, Amount of information and Level of skill and expertise. An empirical study based on 119 jobs from three different groups of knowledge workers (i.e. managerial, professional and clerical) shows that there are significant differences between the difficulty of the KBAs in managerial, clerical and professional jobs, and that managerial KBAs are more difficult than the KBAs of the other two groups.  Furthermore, regression models indicate that Level of skill and expertise is the most influential factor in the difficulty of the KBAs in each of the three groups.

Galactic orbits of stars

1966 ◽  
Vol 25 ◽  
pp. 93-97
Author(s):  
Richard Woolley
Keyword(s):  
Globular Cluster ◽  
Potential Field ◽  
High Velocity ◽  
Velocity Vector ◽  
Variable Stars ◽  
The Sun ◽  
Proper Motions ◽  
Rr Lyrae ◽  
The Galaxy

It is now possible to determine proper motions of high-velocity objects in such a way as to obtain with some accuracy the velocity vector relevant to the Sun. If a potential field of the Galaxy is assumed, one can compute an actual orbit. A determination of the velocity of the globular clusterωCentauri has recently been completed at Greenwich, and it is found that the orbit is strongly retrograde in the Galaxy. Similar calculations may be made, though with less certainty, in the case of RR Lyrae variable stars.

Distance to SN 1987A and the LMC

1999 ◽  
Vol 190 ◽  
pp. 549-554
Author(s):  
Nino Panagia
Keyword(s):  
Angular Size ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Light Curves ◽  
Distance Modulus ◽  
Absolute Size ◽  
Sn 1987A

Using the new reductions of the IUE light curves by Sonneborn et al. (1997) and an extensive set of HST images of SN 1987A we have repeated and improved Panagia et al. (1991) analysis to obtain a better determination of the distance to the supernova. In this way we have derived an absolute size of the ringRabs= (6.23 ± 0.08) x 1017cm and an angular sizeR″ = 808 ± 17 mas, which give a distance to the supernovad(SN1987A) = 51.4 ± 1.2 kpc and a distance modulusm–M(SN1987A) = 18.55 ± 0.05. Allowing for a displacement of SN 1987A position relative to the LMC center, the distance to the barycenter of the Large Magellanic Cloud is also estimated to bed(LMC) = 52.0±1.3 kpc, which corresponds to a distance modulus ofm–M(LMC) = 18.58±0.05.

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