Efficient model reduction in non-linear dynamics using the Karhunen-Loève expansion and dual-weighted-residual methods

 We look at the task of computing the time-evolution of a non-linear system for a long time, in our case under random external influences. Our specific example is the fatigue evaluation of a wind turbine. To facilitate such a computation, we look at a reduction of the computational effort by projecting everything on a low-dimensional basis. In this case we take the Karhunen-Loève basis generated from running the model a little while under the random loading. It is important that the error which is caused by this reduction process can be controlled. We estimate the error by dual or adjoint methods. This in turn allows the process of model reduction to be performed adaptively. Dedicated to the memory of Prof. Mike Crisfield, for his cheerfulness and cooperation as a colleague and friend over many years.     

Validation of a Three-Dimensional Computational Fluid Dynamics Model of a Contact Tank

A three-dimensional (3D) computational fluid dynamics (CFD) model of a contact tank is presented in this paper. The model results are compared against 3D velocities and flow through curve (FTC) data, representing a tracer concentration profile, from a 1:8 scale physical model. The objective is to demonstrate that CFD models can simulate both the FTC and the 3D velocity field quite well. Simultaneous validation of velocities and FTC is important in ascertaining the predictive capabilities of CFD models, as physical model studies indicate that different baffle arrangements can lead to similar FTCs. Therefore, a good prediction of only FTC, as presented in previous 3D CFD model studies, does not necessarily imply a correct simulation of the flow field.     

Heat transfer and flow of He II in narrow channels

Heat transfer and fluid flow of He II in a long, narrow channel connected to a bath that supplies a constant supply of heat have been investigated by numerical simulations by using the simplified model of Kitamura et al. [Cryogenics 37 (1) (1997) 1]. Such channels are used to cool compact, stable, low-temperature magnets. The fluid flow is driven by natural convection and the mutual friction between the normal fluid and the superfluid.In this model, the thermomechanical effect and the Goter-Mellink mutual friction balance each other. A consequence of this balance is that the velocity and temperature distributions of He II can be characterized by a dimensionless, dependent parameter equal to the ratio of the fluid speeds of internal convection to the total fluid flow. After a sudden application of heat flux, the internal convection dominates over the total fluid flow until the establishment of steady-state temperature gradients. This predicts that the time required to set up the steady-state total fluid flow is proportional to the total heat capacity in the channel.     

Thin film deposition on a corrugated surface: A molecular dynamics approach

This paper presents the use of molecular dynamics (MD) simulation in the investigation of the surface topography of early-stage film growth on a GMR (giant-magnetoresistance) corrugated structure. The size of the simulated system is limited in order to reduce the computational workload. The numerical model adopts the Morse potential and the Verlet-leapfrog time evolution scheme [R.W. Hockney, 1970; D. Potter, 1972 (Chapter 5). [1]] to describe the atomic interactions which take place between the atoms. The impact energy transferred from the incident atoms to the substrate is modeled by rescaling the atoms within the upper substrate layers. It is found that the important properties of the film-substrate system may be obtained after the deposition of just several atomic layers. The influence of the impact velocity upon the coating parameters is investigated by varying the incident energy of the deposited atoms. The current results indicate that the surface coverage is poor, when atoms are deposited at low incident energies upon a low temperature substrate. At a higher incident energy, the deposited film tends to exhibit a quasi-layer-by-layer growth mechanism, which results in an improved surface coverage. Finally, it is demonstrated that a distinct quasi-fluid behavior is evident on the substrate when the atoms are deposited at high incident energies.     

Evaporation induced self-assembly of zeolite A micropatterns due to the stick-slip dynamics of contact line

In this study, a new surfactant-solvent system was described for the preparation of periodic stripe patterns of zeolite A on solid substrates. The evaporation induced self-assembly of zeolite A particles was due to the stick-slip dynamics of the three-phase contact line of the colloid solutions in acetone containing 10% (v/v) poly(dimethylsiloxane) (PDMS) fluid (2 cst.). In order to investigate the possible effects of particle size and the particle concentration on the stick-slip dynamics, three types of zeolite A samples with different particle sizes (zeolite A-I: 250-500 nm, zeolite A-II: 100-250 nm and zeolite A-III: 0-100 nm) were utilized to prepare 0.007-0.06% (w/v) colloidal dispersions. Zeolite A micropatterns were self-assembled on the surface of glass, high density polyethylene (HDPE) and poly(tetrafluoroethylene) (PTFE) substrates, which were placed vertically inside the colloid solutions and held against the wall of the cylindrical vial during the evaporation of acetone. The stripe patterns of zeolite A particles were analyzed with field emission scanning electron microscope (FE-SEM) and optical microscope. The widths of microstripes and the distance between the stripes were found as 2-20 μm and 40-60 μm respectively depending on the particle concentration. By using the stick-slip dynamics of colloids, the linear micropatterns of zeolite A nanocrystals were prepared with low cost and low energy.     

Lesbian homoerotic transference in dialectic with developmental mourning: On the way to symbolism from the protosymbolic.

This clinical study illustrates the developmental nature of homoerotic transference, when the psychoanalyst is attuned to the evolving dynamics of the mourning process, in this case with a lesbian analysand. The analysand's psychic fantasies of the female analyst as a muse and a demon lover figure are seen to transform into discrete mother and father transferences, as split off feminine and aggressive parts of the self are reintegrated along with heterosexual desires and oedipal desires. Protosymbolic enactments in terms of romantic gift giving and other seductive overtures transform into symbolic expressions of love, concern, regret, and tenderness. A lesbian marriage is preserved, and the loss of intimacy with men is mourned so that desires for intimacy with men can be sublimated. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A probabilistic simulator for population dynamics of quasispecies

We constructed a probabilistic simulator that allows all the events in population dynamics such as death, birth, mutation, and suppression/stimulation to be described by probabilistic rules. The simulator also facilitates a lattice used for expressing distribution and diversity (number of distinct strains) of quasispecies. The simulator is used to investigate the diversity threshold in HIV and T-cell interaction. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Prediction of the effects on dynamic response due to distributed structural modification with additional degrees of freedom

The aim of this study is to investigate means of efficiently assessing the effects of distributed structural modification on the dynamic properties of a complex structure. The dynamic properties of the modified structure can be determined by experimental testing or numerical simulation, both of which are complex, expensive and time-consuming. Assuming that the original dynamic characteristics are already established and that the modification is a relatively simple attachment, the modified dynamic properties may be determined numerically without solving the equations of motion of the full-modified structure. The frequency response functions (FRFs) of the modified structure can be computed by coupling the original FRFs and a delta dynamic stiffness matrix for the modification introduced. The validity of this approach is investigated by applying it to a cantilever beam to which a smaller beam is attached as modification. The original FRFs were obtained experimentally as well as numerically. The delta dynamic stiffness matrix was determined numerically by modeling the attachment and part of the original structure including the attachment points. The FRFs of the modified beam were then computed. Good agreement is obtained by comparing the results to the FRFs of the modified beam determined experimentally as well as by numerical modeling of the complete modified structure.     

利用Love波特性计算地基动力响应

本文利用Love波弥散特性在频域上对地基出平面振动及扭振问题进行了研究。在计算区域内结构将采用有限单元划分,而在边界上则根据Love 面波特性使用传递边界有限单元。本文同时讨论了不同模态波对结构动力响应的贡献。本文方法也适合于静力分析。