scholarly journals Analysis and simulations of a frequency synthesizer with internal and external noise sources

2006 ◽  
Vol 4 ◽  
pp. 175-178
Author(s):  
G. S. Sangha ◽  
M. H. W. Hoffmann
Keyword(s):  
Output Signal ◽  
Phase Plane ◽  
Frequency Synthesizer ◽  
External Noise ◽  
Second Order ◽  
Noise Sources ◽  
Novel Technique ◽  
Non Linear ◽  
Linear Behaviour

Abstract. In this paper, a novel technique to analyse the noise behaviour of a second-order-PLL based synthesizer is demonstrated. Its non-linear behaviour is analyzed with independent noise-sources introduced at different points of the circuit. Phase plane trajectories will be used to demonstrate that noise sources at different locations in the loop produce qualitatively different contributions to the output signal of the synthesizer.

A second-order output spectrum based method for detecting bolt-loosening fault in a satellite-like structure

2019 ◽  
Vol 26 (4) ◽  
pp. 157-165
Author(s):  
Quankun Li ◽  
Xingjian Jing
Keyword(s):  
Second Order ◽  
Bolted Joint ◽  
Output Spectrum ◽  
Engineering Structures ◽  
Local Tuning ◽  
Damage Indicator ◽  
Non Linear ◽  
Linear Behaviour ◽  
Novel Method ◽  
Bolt Loosening

Bolt-loosening faults frequently exist in industrial engineering structures since these bolted structures are often subjected to vibrations or the like in their service process. In this paper, a novel method based on the second-order output spectrum (SOOS) is proposed to detect potential bolt-loosening faults in a complex satellite-like structure. In this method, a general multi-degree-of-freedom (MDOF) model simulating bolt-loosening faults induced non-linearities and inherent boundary or material non-linearities by non-linear forces is built to describe the non-linear behaviour of the structure, and then a local damage indicator is derived for bolt-loosening fault detection through a local tuning approach (LTA) which tunes local structural properties. Results of experimental cases demonstrate that the state of bolted joint in the satellite-like structure with inherent non-linearities can be estimated by this novel SOOS based method effectively and reliably.

First and Second Order Elastoplastic Analyses of Thin-Walled Metal Members using Generalized Beam Theory

2018 ◽  
Author(s):  
Miguel Abambres
Keyword(s):  
Finite Element ◽  
Stainless Steel ◽  
Cross Section ◽  
Beam Theory ◽  
Second Order ◽  
Flow Rule ◽  
Non Linear ◽  
Thin Walled ◽  
Shell Finite Element ◽  
Generalized Beam Theory

Original Generalized Beam Theory (GBT) formulations for elastoplastic first and second order (postbuckling) analyses of thin-walled members are proposed, based on the J2 theory with associated flow rule, and valid for (i) arbitrary residual stress and geometric imperfection distributions, (ii) non-linear isotropic materials (e.g., carbon/stainless steel), and (iii) arbitrary deformation patterns (e.g., global, local, distortional, shear). The cross-section analysis is based on the formulation by Silva (2013), but adopts five types of nodal degrees of freedom (d.o.f.) – one of them (warping rotation) is an innovation of present work and allows the use of cubic polynomials (instead of linear functions) to approximate the warping profiles in each sub-plate. The formulations are validated by presenting various illustrative examples involving beams and columns characterized by several cross-section types (open, closed, (un) branched), materials (bi-linear or non-linear – e.g., stainless steel) and boundary conditions. The GBT results (equilibrium paths, stress/displacement distributions and collapse mechanisms) are validated by comparison with those obtained from shell finite element analyses. It is observed that the results are globally very similar with only 9% and 21% (1st and 2nd order) of the d.o.f. numbers required by the shell finite element models. Moreover, the GBT unique modal nature is highlighted by means of modal participation diagrams and amplitude functions, as well as analyses based on different deformation mode sets, providing an in-depth insight on the member behavioural mechanics in both elastic and inelastic regimes.

scholarly journals Duplicate Detection of Spike Events: A Relevant Problem in Human Single-Unit Recordings

2021 ◽  
Vol 11 (6) ◽  
pp. 761
Author(s):  
Gert Dehnen ◽  
Marcel S. Kehl ◽  
Alana Darcher ◽  
Tamara T. Müller ◽  
Jakob H. Macke ◽  
...  
Keyword(s):  
Data Quality ◽  
Single Unit ◽  
Human Subjects ◽  
External Noise ◽  
Hospital Environment ◽  
Noise Sources ◽  
Recording Channels ◽  
Waveform Similarity ◽  
Therapeutic Procedures ◽  
Single Unit Recordings

Single-unit recordings in the brain of behaving human subjects provide a unique opportunity to advance our understanding of neural mechanisms of cognition. These recordings are exclusively performed in medical centers during diagnostic or therapeutic procedures. The presence of medical instruments along with other aspects of the hospital environment limit the control of electrical noise compared to animal laboratory environments. Here, we highlight the problem of an increased occurrence of simultaneous spike events on different recording channels in human single-unit recordings. Most of these simultaneous events were detected in clusters previously labeled as artifacts and showed similar waveforms. These events may result from common external noise sources or from different micro-electrodes recording activity from the same neuron. To address the problem of duplicate recorded events, we introduce an open-source algorithm to identify these artificial spike events based on their synchronicity and waveform similarity. Applying our method to a comprehensive dataset of human single-unit recordings, we demonstrate that our algorithm can substantially increase the data quality of these recordings. Given our findings, we argue that future studies of single-unit activity recorded under noisy conditions should employ algorithms of this kind to improve data quality.

scholarly journals Non-Linear Neutral Differential Equations with Damping: Oscillation of Solutions

Symmetry ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 285
Author(s):  
Saad Althobati ◽  
Jehad Alzabut ◽  
Omar Bazighifan
Keyword(s):  
Differential Equations ◽  
Oscillatory Behavior ◽  
Order Equation ◽  
Second Order ◽  
Riccati Technique ◽  
Neutral Equations ◽  
Neutral Differential Equations ◽  
Main Equation ◽  
Non Linear ◽  
Even Order

The oscillation of non-linear neutral equations contributes to many applications, such as torsional oscillations, which have been observed during earthquakes. These oscillations are generally caused by the asymmetry of the structures. The objective of this work is to establish new oscillation criteria for a class of nonlinear even-order differential equations with damping. We employ different approach based on using Riccati technique to reduce the main equation into a second order equation and then comparing with a second order equation whose oscillatory behavior is known. The new conditions complement several results in the literature. Furthermore, examining the validity of the proposed criteria has been demonstrated via particular examples.

Non-linear behaviour and failure mechanism of bamboo poles in bending

2021 ◽  
Vol 305 ◽  
pp. 124747
Author(s):  
Rodolfo Lorenzo ◽  
Leonel Mimendi ◽  
Dong Yang ◽  
Haitao Li ◽  
Theodora Mouka ◽  
...  
Keyword(s):  
Failure Mechanism ◽  
Non Linear ◽  
Linear Behaviour

Synthesis, Electronic Characterisation and Significant Second-Order Non-Linear Optical Responses ofmeso-Tetraphenylporphyrins and Their ZnII Complexes Carrying a Push or Pull Group in the β Pyrrolic Position

2005 ◽  
Vol 2005 (19) ◽  
pp. 3857-3874 ◽  
Author(s):  
Elisabetta Annoni ◽  
Maddalena Pizzotti ◽  
Renato Ugo ◽  
Silvio Quici ◽  
Tamara Morotti ◽  
...  
Keyword(s):  
Second Order ◽  
Optical Responses ◽  
Non Linear ◽  
Linear Optical
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