Search results for "Modeling and simulation"
showing 10 items of 1561 documents
Strain gradient plasticity, strengthening effects and plastic limit analysis
2010
Abstract Within the framework of isotropic strain gradient plasticity, a rate-independent constitutive model exhibiting size dependent hardening is formulated and discussed with particular concern to its strengthening behavior. The latter is modelled as a (fictitious) isotropic hardening featured by a potential which is a positively degree-one homogeneous function of the effective plastic strain and its gradient. This potential leads to a strengthening law in which the strengthening stress, i.e. the increase of the plastically undeformed material initial yield stress, is related to the effective plastic strain through a second order PDE and related higher order boundary conditions. The plas…
Attosecond magnetization dynamics in non-magnetic materials driven by intense femtosecond lasers
2023
Irradiating solids with ultrashort laser pulses is known to initiate femtosecond timescale magnetization dynamics. However, sub-femtosecond spin dynamics have not yet been observed or predicted. Here, we explore ultrafast light-driven spin dynamics in a highly non-resonant strong-field regime. Through state-of-the-art ab-initio calculations, we predict that a non-magnetic material can be transiently transformed into a magnetic one via dynamical extremely nonlinear spin-flipping processes, which occur on attosecond timescales and are mediated by a combination of multi-photon and spin-orbit interactions. These are non-perturbative non-resonant analogues to the inverse Faraday effect that buil…
Towards an Assessment of Public Library Value
2010
PurposeThis paper aims to present a methodology, early findings, possible applications of results and lessons learned from the research study “Public libraries: value, trust and satisfaction”, which has been conducted within the public library development project ‘Father's Third Son’ in Latvia.Design/methodology/approachA combination of quantitative and qualitative methods was used (although the findings reported here are largely drawn from the quantitative study) drawing on various theories of information behaviour and use‐oriented information service evaluation.FindingsThe study gives a good picture of user information needs in Latvia, the sources they use to fulfil them and the role of p…
Modeling and simulation of a High Pressure Roller Crusher for silicon carbide production
2011
Author's version of a chapter published in the book: 11th International Conference on Electrical Power Quality and Utilisation. Also available from the publisher at: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6128963&tag=1 This paper describes the modeling and simulation of High Pressure Roller Crusher (HPRC) for the production of silicon cabide grains. The study is to make a model for simulation of a High Pressure Roller Crusher. A High Pressure Roller Crusher (HPRC) is an important part in the production of silicon carbide, where the grains are crushed into powder form and then sieved into specified sizes based on its usage. This paper will present a model based on Johanson's…
Bond graph modeling and simulation of wind turbine systems
2013
Published version of an article in the journal: Journal of Mechanical Science and Technology. Also available from the publisher at: http://dx.doi.org/10.1007/s12206-013-0435-x This paper addresses the problem of bond graph methodology as a graphical approach for the modeling of wind turbine generating systems. The purpose of this paper is to show some of the benefits the bond graph approach has, in contributing a model for wind turbine systems. We will present a nonlinear model of a wind turbine generating system, containing blade pitch, drive train, tower motion and generator. All which will be modeled by means of bond graph. We will especially focus on the drive train, and show the differ…
ean-Square Filtering for Polynomial System States Confused with Poisson Noises over Polynomial Observations
2011
Published version of an article in the journal: Modeling, Identification and Control. Also available from the publisher at: http://dx.doi.org/10.4173/mic.2011.2.1 In this paper, the mean-square filtering problem for polynomial system states confused with white Poisson noises over polynomial observations is studied proceeding from the general expression for the stochastic Ito differentials of the mean-square estimate and the error variance. In contrast to the previously obtained results, the paper deals with the general case of nonlinear polynomial states and observations with white Poisson noises. As a result, the Ito differentials for the mean-square estimate and error variance corre- spon…
Adaptive H ∞ synchronization of master-slave systems with mixed time-varying delays and nonlinear perturbations: An LMI approach
2011
Published version of an article in the journal: International Journal of Automation and Computing. Also available from the publisher on SpringerLink: http://dx.doi.org/10.1007/s11633-011-0595-z This paper proposes an adaptive synchronization problem for the master and slave structure of linear systems with nonlinear perturbations and mixed time-varying delays comprising different discrete and distributed time delays. Using an appropriate Lyapunov-Krasovskii functional, some delay-dependent sufficient conditions and an adaptation law including the master-slave parameters are established for designing a delayed synchronization law in terms of linear matrix inequalities(LMIs). The time-varying…
Semi-decentralized strategies in structural vibration control
2011
Published version of an article published in the journal: Modeling, Identification and Control. Also available from the publisher at: http://dx.doi.org/10.4173/mic.2011.2.2 In this work, the main ideas involved in the design of overlapping and multi-overlapping controllers via the Inclusion Principle are discussed and illustrated in the context of the Structural Vibration Control of tall buildings under seismic excitation. A detailed theoretical background on the Inclusion Principle and the design of overlapping controllers is provided. Overlapping and multi-overlapping LQR controllers are designed for a simplied five-story building model. Numerical simulations are conducted to asses the pe…
Automatic defect localization in VLSI circuits: A fusion approach based on the Dempster-Shafer theory
2017
Defect localization in Very Large Integration Cir-cuits (VLSI) requires to use multi-sensor information such aselectrical waveforms, emission microscopy images and frequencymapping in order to detect, localize and identify the failure. Eachsensor provides a specific kind of feature modeling the evidence.Thus, the defect localization in VLSI can be summarized asa problem of data fusion with heterogeneous and impreciseinformation. This study illustrates how to reproduce the humandecision for modeling and fusing the different multi-sensorfeatures by using the Demspter-Shafer theory. We propose notonly an automatic decision rule for mass functions computingbut also confidence intervals to quantif…
A second strain gradient elasticity theory with second velocity gradient inertia – Part I: Constitutive equations and quasi-static behavior
2013
Abstract A multi-cell homogenization procedure with four geometrically different groups of cell elements (respectively for the bulk, the boundary surface, the edge lines and the corner points of a body) is envisioned, which is able not only to extract the effective constitutive properties of a material, but also to assess the “surface effects” produced by the boundary surface on the near bulk material. Applied to an unbounded material in combination with the thermodynamics energy balance principles, this procedure leads to an equivalent continuum constitutively characterized by (ordinary, double and triple) generalized stresses and momenta. Also, applying this procedure to a (finite) body s…