Wyniki wyszukiwania - BazTech

1

Resonance phenomena in micro/nanoelectromechanical systems

Foryś A., Foryś A. S.

Czasopismo Techniczne. Nauki Podstawowe

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2013

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R. 110, z. 1-NP

3--10

EN

In the paper, some aspects of nonlinearity of micro/nanoelectromechanical systems (MEMS/ NEMS) are presented. Because of great values of strains of micro/nanobeams the nonlinear description is necessary. Particularly, the nonlinear inertia term is added to equation relating to motion of the beam. Numerical calculations of resonance curves and instability regions are given. Results are presented on graphs.

PL

W artykule przedstawiono pewne aspekty nieliniowości w mikro/nanoukładach elektromechanicznych (MEMS/NEMS). Ze względu na duże odkształcenia mikro/nanobelek nieliniowy opis jest konieczny. W szczególności do równania ruchu belki wprowadzono wyraz opisujący nieliniową bezwładność. Podano wyniki obliczeń numerycznych dla krzywych rezonansowych oraz obszarów niestateczności. Rezultaty przedstawiono na wykresach.

2

Oil Paintings and Mechanics : How To Save Art Treasures Using Knowledge from Dynamics

Kracht K., Wagner U. v.

Machine Dynamics Research

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2011

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Vol. 35, No. 4

49-61

EN

Oil paintings of the old masters are valuable not only for education and social life but also from an economical point of view. These artworks undergo vibrations due to multiple reasons. During exposition there is excitation by public or external traffic load. Higher excitation levels are reached during transports. Consequences may be the emergence of cracks or loss of paint slabs. For protecting an oil painting from damage it is essential to be aware of its condition.Conventional techniques applied by conservators are based on visual detection. In contrastto this, our work is based on knowledge from dynamics applied to this new field. Test objects were prepared by a docent of old painting techniques of Berlin Universityof Arts. They were aged at different levels by a research institution for paint and varnish atMagdeburg. After aging the dummies are investigated for their dynamical behavior usingdifferent excitations (harmonic, broad-band) and measuring dynamic responses. Speciallaser equipment and the experimental set up were developed for measurements on thesurface of painted canvas. Strong influences of the alteration of the dummies andcharacteristic nonlinearities could be observed during these measurements. Cracks wereinitiated during dynamic fatigue tests and correlated with dynamic responses. Acorresponding modeling is based on a Kirchhoff plate with non-constant pre-stress. The presented work should finally lead to condition monitoring of oil paintings and techniques for the prevention of artworks from vibrations.

3

Ranking of the Nonlinearities of Electrodynamic Loudspeakers

Ravaund R., Lemarquand G., Lemarquand V., Roussel T.

Archives of Acoustics

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2010

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Vol. 35, No. 1

49-66

EN

The aim of this paper is to present a way of ranking the nonlinearities of electrodynamic loudspeakers. For this purpose, we have constructed a nonlinear analytic model which takes into account the variations of the small signal parameters. The determination of these variations is based on a very precise measurement of the electrical impedance of the electrodynamic loudspeaker. First, we present the experimental method to identify the variations of these parameters, then we propose to study theoretically the importance of these nonlinearities according to the input level or the input frequency. We show that the parameter which creates most of the distortions is not always the same and depends mainly on both the input level and the input frequency. Such results can be very useful for optimization of electrodynamic loudspeakers.

4

SOI Technology: An Opportunity for RF Designers?

Raskin J.-P.

Journal of Telecommunications and Information Technology

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2009

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nr 4

3-17

EN

This last decade silicon-on-insulator (SOI) MOS-FET technology has demonstrated its potentialities for high frequency (reaching cutoff frequencies close to 500 GHz for n-MOSFETs) and for harsh environments (high temperature, radiation) commercial applications. For RF and system-onchip applications, SOI also presents the major advantage of providing high resistivity substrate capabilities, leading to substantially reduced substrate losses. Substrate resistivity values higher than 1 k? cm can easily be achieved and high resistivity silicon (HRS) is commonly foreseen as a promising substrate for radio frequency integrated circuits (RFIC) and mixed signal applications. In this paper, based on several experimental and simulation results the interest, limitations but also possible future improvements of the SOI MOS technology are presented.

5

Harmonic domain modelling of transformer core nonlinearities using the DIgSILENT powerfactory software

Wiechowski W., Bak-Jensen B., Bak C. L., Lykkegaard J.

Electrical Power Quality and Utilisation. Journal

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2008

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Vol. 14, iss. 1

3-11

EN

This paper demonstrates the results of implementation and verification of an already existing algorithm that allows for calculating saturation characteristics of singlephase power transformers. The algorithm was described for the first time in 1993. Now this algorithm has been implemented using the DIgSILENT Programming Language (DPL) as an external script in the harmonic domain calculations of a power system analysis tool PowerFactory [10]. The algorithm is verified by harmonic measurements on a single-phase power transformer. A theoretical analysis of the core nonlinearities phenomena in single and three-phase transformers is also presented. This analysis leads to the conclusion that the method can be applied for modelling nonlinearities of three-phase autotransformers.

6

On linking of two approaches which lead to the power behaviour: the privilege concept and we non-linear models

Czechowski Z.

Acta Geophysica Polonica

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2002

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Vol. 50, nr 3

321-335

EN

In this contribution it is assumed that nature is purely random in its deep structure. However, many geophysical phenomena manifest power behaviour. Two approaches for explanation of the behaviour were previously proposed. The influence of non-linearities of the stochastic model onto output distributions was analyzed in the first approach and the concept of the physical privilege was introduced in the second. The links between these two models show how the privilege is described by non-linear functions and how the non-linearities in many models may gain physical description related to the privilege. However, for boundary conditions of the source type the power solutions are obtained even for a linear (or weaker) privilege. The role of the boundary condition in the first (initial problem) approach is investigated. We show how the initial function in linear models should be modified in order to obtain the power output after sufficiently long time.