Transverse Oscillations of a Vertical Pile in Waves

1982 ◽  
Vol 104 (1) ◽  
pp. 46-52 ◽  
Author(s):  
F. Angrilli ◽  
V. Cossalter
Keyword(s):  
Mathematical Model ◽  
Natural Frequency ◽  
Transverse Direction ◽  
Wave Action ◽  
Simple Mathematical Model ◽  
Transverse Vibrations ◽  
Lock In Effect ◽  
Lock In ◽  
Transverse Oscillations

A cantilevered pile, flexible only in the transverse direction, has been submitted to wave action. It has been found that resonance transverse vibrations, with natural frequency fn, are induced by eddies shedding in waves having frequency fw = 1, 1/2, 1/3, 1/4 fn. A lock-in effect has been observed within the range of 0.9 fn ≤ fw ≤ 1.1 fn. Results of a simple mathematical model find reasonable support in the experiments.

A Nonlinear and Non-Ideal Wind Generator Supporting Structure

2006 ◽  
Vol 5-6 ◽  
pp. 433-442 ◽  
Author(s):  
Reyolando Manoel Lopes Rabelo da Fonseca Brasil ◽  
L.C.S. Feitosa ◽  
José Manoel Balthazar
Keyword(s):  
Mathematical Model ◽  
Energy Supply ◽  
Degrees Of Freedom ◽  
Transverse Direction ◽  
Equations Of Motion ◽  
Power Source ◽  
Sommerfeld Effect ◽  
Simple Mathematical Model ◽  
Supporting Structure ◽  
Tower Vibration

We present a simple mathematical model of a wind turbine supporting tower. Here, the wind excitation is considered to be a non-ideal power source. In such a consideration, there is interaction between the energy supply and the motion of the supporting structure. If power is not enough, the rotation of the generator may get stuck at a resonance frequency of the structure. This is a manifestation of the so-called Sommerfeld Effect. In this model, at first, only two degrees of freedom are considered, the horizontal motion of the upper tip of the tower, in the transverse direction to the wind, and the generator rotation. Next, we add another degree of freedom, the motion of a free rolling mass inside a chamber. Its impact with the walls of the chamber provides control of both the amplitude of the tower vibration and the width of the band of frequencies in which the Sommerfeld effect occur. Some numerical simulations are performed using the equations of motion of the models obtained via a Lagrangian approach.

The Capital Gains Lock-In Effect and Earnings Quality

2019 ◽  
Author(s):  
Stephen G. Dimmock ◽  
Fan Feng ◽  
Huai Zhang
Keyword(s):  
Earnings Quality ◽  
Capital Gains ◽  
Lock In Effect ◽  
Lock In

scholarly journals Informal Reform of the United Nations Security Council

2018 ◽  
Vol 40 (1) ◽  
pp. 97-115
Author(s):  
Mariana Pimenta Oliveira Baccarini
Keyword(s):  
Cold War ◽  
United Nations ◽  
Security Council ◽  
United Nations Security Council ◽  
Decision Making Process ◽  
Institutional Perspective ◽  
The United Nations ◽  
Lock In Effect ◽  
The Cold War ◽  
Lock In

Abstract This article analyses attempts to reform the United Nations Security Council from a historical-institutional perspective. It argues that the possibilities for reform have suffered from a ‘lock-in’ effect that has rendered the UN resistant to change. On the other hand, the UN decision-making process has evolved since its establishment, especially since the end of the Cold War, in response to new power aspirations, making it more representative and legitimate. The Security Council has also undergone continuous informal reform that has allowed it to adapt to new times.

Preliminary Investigations of Machine Frame Vibration Damping Using Eddy Current Principle

2016 ◽  
Vol 821 ◽  
pp. 288-294 ◽  
Author(s):  
George Juraj Stein ◽  
Peter Tobolka ◽  
Rudolf Chmúrny
Keyword(s):  
Mathematical Model ◽  
Natural Frequency ◽  
Eddy Current ◽  
Asynchronous Motor ◽  
Oscillatory System ◽  
Vibration Damping ◽  
Combined Effects ◽  
Magnetic Forces ◽  
Novel Approach ◽  
Vibration Attenuation

A novel approach to vibration attenuation, based on the eddy current principle, is described. The combined effects of all magnetic forces acting in the oscillatory system attenuate frame vibrations and, concurrently, decrease the damped natural frequency. A mathematical model of the forces balance in the oscillatory system was derived before. Some experimental results from a mock-up machine frame excited by an asynchronous motor are presented.

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