complex mode
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2021 ◽  
Author(s):  
Eisuke Higuchi ◽  
Hiroshi Yabuno ◽  
Kiyotaka Yamashita

Abstract The dynamics of a flexible cantilevered pipe conveying fluid have been researched for several decades. It is known that the flexible pipe undergoes self-excited vibration when the flow speed exceeds a critical speed. This instability phenomenon is caused by nonconservative forces. From a mathematical point of view, the system has a characteristic of non-selfadjointness and the linear eigenmodes can be complex and non-orthogonal to each other. As a result, such a mathematical feature of the system is directly related to the instability phenomenon. In this study, we propose a method of experimentally identifying the complex mode from experimentally obtained time histories and decomposing the linear mode into real and imaginary components. In nonlinear analysis, we show that the nonlinear effects of practical systems on the mode in the steady-state selfexcited oscillation are small. The real and imaginary components identified using the proposed method for experimental steady-state self-excited oscillations are compared with those obtained in the theoretical analysis, thus validating the proposed identification method.


2021 ◽  
Author(s):  
Masaru Kitahara ◽  
Takeshi Ishihara

Abstract. In this study, the seismic soil-structure interaction (SSI) of wind turbine support structures is investigated using response spectrum method (RSM) based on the complex eigenmodes. Seismic loadings on wind turbine support structures are newly derived by complex mode superposition RSM. To improve the prediction accuracy of the shear force acting on footings, this method is augmented by introducing the upper limit of modal damping ratios of 10 %. In addition, the bending moment at the hub height due to the mass moment of inertia of rotor and nacelle assembly is considered as an additional loading. The proposed method is validated by comparison with time history analysis (THA) accounting for different types of foundations and different tower geometries. Seismic loadings acting on the towers and footings by the proposed method show favourable agreement with the mean results by THA of several input acceleration time histories, while the original complex mode superposition RSM strongly underestimates shear forces acting on footings.


Author(s):  
Cristina Valdés

This study on the translation of television commercials explores several aspects of this very specific audiovisual translation subtype. Firstly, it looks into dubbing and the language policies on Spanish television, which are issues affecting the decisions on the translation of television advertisements. Secondly, it approaches the notion of a TV ‘spot’ as an audiovisual text whose main components, image and sound, form a cohesive unity that is meant to trigger a persuasive effect, but may vary in translation. Finally, it analyses an example of a television spot, in English and in Spanish, focusing on the manipulation of the text when it is translated for Spanish television channels.


2021 ◽  
Vol 152 ◽  
pp. 107436
Author(s):  
Szymon Greś ◽  
Michael Döhler ◽  
Palle Andersen ◽  
Laurent Mevel

ACS Photonics ◽  
2021 ◽  
Author(s):  
Niccolò Caselli ◽  
Tong Wu ◽  
Guillermo Arregui ◽  
Nicoletta Granchi ◽  
Francesca Intonti ◽  
...  

2021 ◽  
Vol 8 (4) ◽  
Author(s):  
R. S. MacKay

For dynamical systems that can be modelled as asymptotically stable linear systems forced by Gaussian noise, this paper develops methods to infer (estimate) their dominant modes from observations in real time. The modes can be real or complex. For a real mode (monotone decay), the goal is to infer its damping rate and mode shape. For a complex mode (oscillatory decay), the goal is to infer its frequency, damping rate and (complex) mode shape. Their amplitudes and correlations are encoded in a mode covariance matrix that is also to be inferred. The work is motivated and illustrated by the problem of detection of oscillations in power flow in AC electrical networks. Suggestions of some other applications are given.


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