RESPONSE OF LINEAR AND NONLINEAR CONTINUOUS STRUCTURES SUBJECT TO RANDOM EXCITATION AND THE PROBLEM OF HIGH-LEVEL EXCURSIONS

Author(s):  
Y.K. LIN
Sensors ◽  
2020 ◽  
Vol 20 (19) ◽  
pp. 5456
Author(s):  
Tra Nguyen Phan ◽  
Sebastian Bader ◽  
Bengt Oelmann

The introduction of nonlinearities into energy harvesting in order to improve the performance of linear harvesters has attracted a lot of research attention recently. The potential benefits of nonlinear harvesters have been evaluated under sinusoidal or random excitation. In this paper, the performances of electromagnetic energy harvesters with linear and nonlinear springs are investigated under real vibration data. Compared to previous studies, the parameters of linear and nonlinear harvesters used in this paper are more realistic and fair for comparison since they are extracted from existing devices and restricted to similar sizes and configurations. The simulation results showed that the nonlinear harvester did not generate higher power levels than its linear counterpart regardless of the excitation category. Additionally, the effects of nonlinearities were only available under a high level of acceleration. The paper also points out some design concerns when harvesters are subjected to real vibrations.


2014 ◽  
Vol 67 (3) ◽  
Author(s):  
Garba Aliyu ◽  
Saifulnizam Abd. Khalid ◽  
Jafaru Usman ◽  
Ahmad Fuad A. Aziz ◽  
Hussein Shareef

This paper present improved Walsh function (IWF) algorithm as an alternative approach for active and reactive power measurement in linear and nonlinear, balanced and unbalanced sinusoidal three phase load system. It takes advantage of Walsh function unified approach and its intrinsic high level accuracy as a result of coefficient characteristics and energy behaviour representation. The developed algorithm was modeled on the Matlab Simulink software; different types of load, linear and nonlinear were also modeled based on practical voltage and current waveforms and tested with the proposed improved Walsh algorithm. The IEEE standard 1459-2000 which is based on fast Fourier transform FFT approach was used as benchmark for the linear load system while a laboratory experiment using Fluke 435 power quality analyzer PQA which complies with IEC/EN61010-1-2001standards was used to validate the improved algorithm for nonlinear load measurement. The results showed that the algorithm has the potential to effectively measure three phase power components under different load conditions.


Author(s):  
M. R. Machado ◽  
L. Khalij ◽  
A. T. Fabro

AbstractThe application of the composite materials in the aeronautical and aerospace industries has been increasing over the last several decades. Compared to conventional metallic materials, they present better strength to weight and stiffness to weight ratio. However, they can also present a high level of uncertainty, mainly associated with the manufacturing processes. Besides the uncertainty in the composite material parameters, which can play a role in the structural dynamic response, randomness can also be associated with boundary condition and external excitation sources. This paper treats the dynamic analysis of a composite beam under random excitation and uncertainties in the boundary condition. The beam is modelled by the spectral element method, a wave propagation technique. Some numerical examples are used to study the influence of random source on the dynamic behaviour of the composite structure.


2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Saifulnizam Bin Abdul Khalid ◽  
Garba Aliyu ◽  
Mohd Wazir Mustafa ◽  
Hussein Shareef

This paper presents an improved Walsh function IWF algorithms as an alternative approach for active and reactive powers measurement in linear and nonlinear, balanced and unbalanced sinusoidal three-phase load system. It takes advantage of Walsh function unified approach, simple algorithm and its intrinsic high level of accuracy as a result of coefficient characteristics and energy behaviour representation. The developed algorithm was modeled on the Matlab Simulink software; different types of load, linear and nonlinear, were also modeled based on practical voltage and current waveforms and tested with the proposed improved Walsh algorithms. The IEEE standard 1459–2000 which is based on fast Fourier transform FFT approach was used as benchmark for the linear load system. The data obtained from laboratory experiment to determine power components in harmonic load systems using Fluke 435 power quality analyzer PQA which complies with IEC/EN61010-1-2001 standard was modeled and used to validate the improved algorithm for nonlinear load measurement. The results showed that the algorithm has the potential to effectively measure three-phase power components under different load conditions.


2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Swen Koerner ◽  
Mario S. Staller ◽  
André Kecke

PurposeThe study compares the impact of two different pedagogical approaches in police training by assessing the knife defense performance of German police recruits against different types of knife attacks. Linear or nonlinear – which pedagogical approach leads to more efficient knife defense performance?Design/methodology/approachA total of 20 German state police recruits (w = 5, m = 15) were assigned to linear and nonlinear groups. The linear and nonlinear groups' performance on knife defense was assessed in a pretest, after a three-week training intervention in a posttest and eight weeks thereafter in a retention test, utilizing a mixed-method design (Sendall et al., 2018).FindingsQuantitative data on knife defense performance suggest a lastingly better performance of the nonlinear group: in the retention test, participants of the nonlinear group were hit less (p = 0.029), solved the attack faster (p = 0.044) and more often (81.8%) than participants of the linear group (55.6%). In contrast, qualitative data reveal that, despite of evidence for a high level of perceived competence, the nonlinear teaching of knife defense skills has been accompanied by considerable uncertainties, affected by the lack of techniques and the focus on principles and operational parameters only.Originality/valueIt is the first study assessing the impact of different pedagogical approaches in police training. For the practice of police trainers, the results provide empirical orientations for an evidence-based planning of and reflection on pedagogical demands within their training (Mitchell and Lewis, 2017).


Author(s):  
C. A. Kitio Kwuimy ◽  
G. Litak ◽  
C. Nataraj

A bistable mechanical system having fractional order restoring force is considered for possible energy harvesting. The effects of the fractional order stiffness α on the crossing well dynamics (large amplitude motion) and the output electrical power are analyzed. The harvested electric power appears to be efficient for deterministic and random excitation, for small α ( α ≈ 2). High level noise intensity was found to reduce the output power in the region of resonance and surprisingly increases the outup in other region of α. For larger enough amplitude of harmonic excitation this effect is realized in a stochastic resonance.


2012 ◽  
Vol 20 (3) ◽  
pp. 293-310 ◽  
Author(s):  
Kevin Long ◽  
Paul T. Boggs ◽  
Bart G. van Bloemen Waanders

Sundance is a package in the Trilinos suite designed to provide high-level components for the development of high-performance PDE simulators with built-in capabilities for PDE-constrained optimization. We review the implications of PDE-constrained optimization on simulator design requirements, then survey the architecture of the Sundance problem specification components. These components allow immediate extension of a forward simulator for use in an optimization context. We show examples of the use of these components to develop full-space and reduced-space codes for linear and nonlinear PDE-constrained inverse problems.


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