Equivalent Linearization for Continuous Dynamical Systems

1983 ◽  
Vol 50 (2) ◽  
pp. 415-420 ◽  
Author(s):  
W. D. Iwan ◽  
C. M. Krousgrill
Keyword(s):  
Time Domain ◽  
Spatial Domain ◽  
Equivalent Linearization ◽  
Dynamical Response ◽  
System Equation ◽  
Comparison Functions ◽  
Complex Boundary ◽  
The Time Domain ◽  
Transverse Response ◽  
Selection Of

An approximate method is presented for determining the dynamical response of certain continuous nonlinear systems. In the proposed method, the system equation is linearized in the time domain prior to generation of a solution in the spatial domain. The approach is particularly suited to problems with complex boundary conditions which make selection of realistic global, spatial, domain comparison functions difficult. The approach is ideally suited to problems where discretization using finite elements is appropriate. The transverse response of a nonlinear rectangular plate is examined by way of the application of the proposed method.

Analysis of Brief Tension Loss in TLP Tethers

1988 ◽  
Vol 110 (1) ◽  
pp. 43-47 ◽  
Author(s):  
J. N. Brekke ◽  
T. N. Gardner
Keyword(s):  
Time Domain ◽  
Large Diameter ◽  
Nonlinear Effects ◽  
Response Analysis ◽  
Bending Stress ◽  
Large Wave ◽  
Wave Trough ◽  
Design Selection ◽  
The Time Domain ◽  
Selection Of

The avoidance of “slack” tethers is one of the factors which may establish the required tether pretension in a tension leg platform (TLP) design. Selection of an appropriate safety factor on loss of tension depends on how severe the consequences may be. It is sometimes argued that if tethers go slack, the result may be excessive platform pitch or roll motions, tether buckling, or “snap” or “snatch” loading of the tether. The results reported here show that a four-legged TLP would not be susceptible to larger angular motions until two adjacent legs lose tension simultaneously. Even then, this analysis shows that a brief period of tether tension loss (during the passage of a large wave trough) does not lead to excessive platform motion. Similarly, momentary tension loss does not cause large bending stress in the tether or significant tension amplification as the tether undergoes retensioning. This paper presents TLP platform and tether response analysis results for a representative deepwater Gulf of Mexico TLP with large-diameter, self-buoyant tethers. The time-domain, dynamic computer analysis included nonlinear effects and platform/tether coupling.

scholarly journals Multiple Spatiotemporal Characteristics-Based Zonal Voltage Control for High Penetrated PVs in Active Distribution Networks

Energies ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 249 ◽  
Author(s):  
Chuanliang Xiao ◽  
Lei Sun ◽  
Ming Ding
Keyword(s):  
Time Domain ◽  
Reactive Power ◽  
Voltage Control ◽  
Distribution Networks ◽  
Spatial Domain ◽  
Active Power ◽  
Short Term ◽  
Control Scheme ◽  
The Time Domain ◽  
Active Distribution Networks

The penetration of photovoltaic (PV) outputs brings great challenges to optimal operation of active distribution networks (ADNs), especially leading to more serious overvoltage problems. This study proposes a zonal voltage control scheme based on multiple spatiotemporal characteristics for highly penetrated PVs in ADNs. In the spatial domain, a community detection algorithm using a reactive/ active power quality function was introduced to partition an ADN into sub-networks. In the time domain, short-term zonal scheduling (SZS) with 1 h granularity was drawn up based on a cluster. The objective was to minimize the supported reactive power and the curtailed active power in reactive and active power sub-networks. Additionally, a real-time zonal voltage control scheme (RZVC) with 1 min granularity was proposed to correct the SZS rapidly by choosing and controlling the key PV inverter to regulate the supported reactive power and the curtailed active power of the inverters to prevent the overvoltage in each sub-network. With the time domain cooperation, the proposed method could achieve economic control and avoid overvoltage caused by errors in the forecast data of the PVs. For the spatial domain, zonal scheduling and zonal voltage control were carried out in each cluster, and the short-term scheduling and voltage controlling problem of the ADN could then be decomposed into several sub-problems. This could simplify the optimization and control which can reduce the computing time. Finally, an actual 10kV, 103-node network in Zhejiang Province of China is employed to verify the effectiveness and feasibility of the proposed approach.

scholarly journals Random analysis of coupled vehicle-bridge systems with local nonlinearity based on explicit time-domain method

2021 ◽  
Author(s):  
Huan Huang ◽  
Hengbin Zheng ◽  
Jianliang Deng ◽  
Wenxiong Li ◽  
Yuyu Li
Keyword(s):  
Time Domain ◽  
Vibration Analysis ◽  
Time Instant ◽  
Time Domain Method ◽  
Equivalent Linearization ◽  
Linearization Technique ◽  
Suspension Spring ◽  
Domain Method ◽  
The Time Domain ◽  
Bridge System

Abstract Based on the explicit time-domain method in conjunction with the equivalent linearization technique, an efficient analysis algorithm is developed for the random vibration analysis of the coupled vehicle-bridge system with local nonlinear components under the random irregular excitation from a bridge deck. With the coupled vehicle-bridge system divided into two subsystems, the equivalent linearized subsystem for the vehicle subsystem with the hysteretic suspension spring is constructed for the given time instant using the equivalent linearization technique. Then the dimension-reduction vibration analysis for the equivalent linearized coupled vehicle-bridge system can be carried out based on the time-domain explicit method, which has been proven to be highly efficient. The numerical example indicates that the proposed approach is of feasibility.

Modeling Dynamic Response of Hydraulic Fluid Within Tapered Transmission Lines

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Jeremy W. ven der Buhs ◽  
Travis K. Wiens
Keyword(s):  
Transmission Lines ◽  
Time Domain ◽  
Pipe Wall ◽  
High Frequencies ◽  
Enhanced Transmission ◽  
Transmission Line Method ◽  
The Time Domain ◽  
High Frequency Harmonic ◽  
Selection Of ◽  
Frequency Harmonic

This paper examines modeling of the laminar dynamic fluid responses within hydraulic transmission lines that have a tapered shape between the inlet and the outlet. There are excellent models available for fast simulation of pressure and flow dynamics within uniform lines; however, the established models for tapered lines either cannot be implemented in the time domain, are complex to implement, or have long simulation times. The enhanced transmission line method (TLM) structure is applied in this paper since it can be computed quickly in the time domain and has shown to accurately model the effects of frequency-dependent friction. This paper presents a method of optimizing the TLM weighting functions, minimizing the error between the TLM transmission matrix terms and a numerical ordinary differential equation (ODE) solution calculated using a boundary value solver. Optimizations have shown that using the TLM to model tapered lines can provide a fair approximation when compared in the frequency domain. Two-dimensional (2D) interpolation of a look-up table is possible allowing for quick selection of the optimized parameters. Further investigation into the effects of pipe wall elasticity and its inclusion into the TLM is also performed. Also, an experiment was performed to validate high frequency harmonic peaks present in the frequency response, which yielded acceptable results when compared to the theory, and the proposed tapered TLM. This model can be used in numerous applications where line dynamic effects must be accounted for, especially with digital hydraulic switched inertance converters where high frequencies are present.

Flexible Modelling of the Activated Sludge System – Theoretical and Practical Aspects

1985 ◽  
Vol 17 (2-3) ◽  
pp. 247-258 ◽  
Author(s):  
M. S. Sheffer ◽  
M. Hiraoka ◽  
K. Tsumura
Keyword(s):  
Model Selection ◽  
Computer Program ◽  
Time Domain ◽  
Mechanistic Models ◽  
Parameter Fitting ◽  
Modelling Method ◽  
Using Data ◽  
The Time Domain ◽  
Fitting In ◽  
Selection Of

For the purpose of optimal modelling, a “Flexible Modelling” method was developed. A flexible set of models consisting of hierarchical mechanistic models derived from a highly detailed structured model by mechanistic simplification was obtained. The performance of a computer program with an algorithm for parameter fitting in the time domain was evaluated by use of simulation. The program was able to estimate the models' parameters, even when using data with different degrees of inaccuracy. A computer program for model selection was developed, whereby the model was selected according to the information required. It was found that for prediction of the dynamic behavior of the MLVSS, the simplest model can supply all the necessary information. For prediction of effluent substrate concentration, the differences between the models' predictions depend on the characteristics of the disturbances and on the values of the models' parameters. The selection of the proper model and updating its parameters can be done by a computer which uses the presented program for model selection and parameter fitting.

Deconvolving the ghost effect of the water surface in marine seismics

Geophysics ◽  
2000 ◽  
Vol 65 (6) ◽  
pp. 1831-1836 ◽  
Author(s):  
Santi Kumar Ghosh
Keyword(s):  
Least Squares ◽  
Time Domain ◽  
Water Surface ◽  
Inverse Filtering ◽  
Autocorrelation Matrix ◽  
Common Time ◽  
Unit Impulse ◽  
The Time Domain ◽  
Sampling Instant ◽  
Selection Of

The ghost filters arising from the effect of the water surface on both source and receiver sides have a common time domain representation that consists of a unit impulse followed by its ghost, which is a delayed, negative unit impulse. The origin of the difficulties of deghosting lies in the zeroes in the spectrum of the ghost filter, which render incorrect any deghosting through least‐squares inverse filtering in the time domain. Another shortcoming of the time domain approach is that the digital description of the ghost filter is inexact when a sampling instant does not coincide with the instant of the onset of the ghost impulse. A frequency domain approach, on the other hand, is straightforward and accurate because it can avoid the zeroes of the filter either by explicitly choosing a recording band that excludes the zeroes or by recording at two depths. These two depths should be selected according to the criterion that their highest common measure is small enough to prevent zeroes at a common frequency of the two recordings. As the source‐side and the receiver‐side ghost filters have the same form, the criterion derived for the selection of the depths of the receivers would also hold for the selection of the depths of two sources whose aggregate signature is desired to have no zeroes in the spectrum, within the operative band. An important ramification of the analysis consists of the disproof of a prevalent conjecture that the zeroes in the spectrum of a wavelet make its autocorrelation matrix singular; actually, the zeroes cause an inexact and unacceptable least‐squares inverse, although the matrix itself is well conditioned.

scholarly journals Minimizing the Computational Effort to Optimize Solar Concentrators with the Open-Source Tools SunPATH and Tonatiuh++

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4412
Author(s):  
Manuel J. Blanco ◽  
Victor Grigoriev ◽  
Kypros Milidonis ◽  
George Tsouloupas ◽  
Miguel Larrañeta ◽  
...  
Keyword(s):  
Open Source ◽  
Time Domain ◽  
High Performance ◽  
Software Tool ◽  
Spatial Domain ◽  
Computational Effort ◽  
Test Case ◽  
Optical Efficiency ◽  
The Time Domain

Integrals that are of interest in the analysis, design, and optimization of concentrating solar thermal systems (CST), such as the annual optical efficiency of the light collection and concentration (LCC) subsystem, can be accurately computed or estimated in two distinct ways: on the time domain and on the spatial domain. This article explores these two ways, using a case study that is highly representative of the commercial CST systems being deployed worldwide. In the time domain, the computation of these integrals are explored using 1-min, 10-min, and 1-h solar DNI input data and using The Cyprus Institute (CyI)’s High-Performance Computing (HPC) system and an open-source ray tracer, Tonatiuh++, being actively developed at CyI. In the spatial domain, the computation of these integrals is explored using SunPATH, another open-source software tool being actively developed at CyI, in tandem with Tonatiuh++. The comparison between the time and spatial domain approach clearly indicate that the spatial domain approach using SunPATH is dramatically more computationally efficient than the time domain approach. According to the results obtained, at least for the case study analyzed in this article, to compute the annual energy delivered by the LCC subsystem with a relative error less than 0.1%, it is enough to provide SunPATH with 1-h DNI data as input, request from SunPATH the sun position and weights of just 30 points in the celestial sphere, and run Tonatiuh++ to simulate these 30 points using 15 million rays per run. As the test case is highly representative, it is expected that this approach will yield similar results for most CST systems of interest.

EEG-Based Motor Imagery Feature Extraction

2013 ◽  
Vol 846-847 ◽  
pp. 944-947
Author(s):  
Yang Liu ◽  
Nian Qiang Li ◽  
Yong Xiang Li
Keyword(s):  
Feature Extraction ◽  
Motor Imagery ◽  
Time Domain ◽  
Classification Accuracy ◽  
Power Spectrum Density ◽  
Continuous Wavelet ◽  
Spectrum Density ◽  
Energy Feature ◽  
The Time Domain ◽  
Selection Of

In this study, we proposed a simple and effective approach for feature extraction of motor imagery (MI) data. Aside from the original use of continuous wavelet transform (CWT), the Blackman filter is proposed to further refine the selection of active segments. In the time domain we compute the energy feature by squared-amplitude of EEG; in the frequency domain BT method power spectrum density (PSD) is used to get energy feature. The method is simple and the classification accuracy is satisfactory, especially for classification 2.

The Application of CRFSD Algorithm on Data Fusion of WSN

2013 ◽  
Vol 389 ◽  
pp. 823-827
Author(s):  
Yang Chen ◽  
Qi Dong Yong ◽  
Shi Long Yang ◽  
Ze Zhong Ding
Keyword(s):  
Data Fusion ◽  
Time Domain ◽  
Simulation Experiment ◽  
Spatial Domain ◽  
Previous Method ◽  
Information Support ◽  
Data Redundancy ◽  
Temporal And Spatial ◽  
The Time Domain

The data redundancy will produce in the procedure of gather of graphics and video or the data in the WSN, and then the data fusion is needed. On the basis of the previous method of data fusion, the data method based on information support (that is CRFSD) is provided, and through the simulation experiment, which is held in the time domain, spatial domain, temporal and spatial domain, the data fusion is realized.

Dynamic Analysis of the Axially Moving String Based on Wave Propagation

1995 ◽  
Author(s):  
S. Ying ◽  
C. A. Tan
Keyword(s):  
Wave Propagation ◽  
Boundary Conditions ◽  
Time Domain ◽  
General Boundary Conditions ◽  
Axially Moving String ◽  
Convolution Integrals ◽  
Axially Moving ◽  
The Time Domain ◽  
Transverse Response ◽  
Physical Boundary

Abstract This paper presents an exact solution for the transverse response of an axially moving string under general boundary conditions. The response solution is derived in the frequency domain and interpreted in terms of wave propagation functions. The response in the time domain involves only several convolution integrals which can easily be obtained for many physical boundary conditions. The transient response of the translating string with a spring or a dashpot at a boundary is presented.

Sign in / Sign up

Export Citation Format

Share Document