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.

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.

Comparison of Model Selection Method Using Data from Classical Designed Experiment

2013 ◽  
Vol 677 ◽  
pp. 357-362
Author(s):  
Natthasurang Yasungnoen ◽  
Patchanok Srisuradetchai
Keyword(s):  
Model Selection ◽  
Quantitative Research ◽  
Selection Procedure ◽  
Information Criterion ◽  
P Value ◽  
Selection Procedures ◽  
Final Model ◽  
Designed Experiment ◽  
Using Data ◽  
Selection Of

Model selection procedures play important role in many researches especially quantitative research. . In several area of sciences, the analysis and model selection of experiments are often used and often contains two fundamental goals associated with the experimental response of interest which are to determine the best model. The way to address these goals is to implement a model selection procedure. Then, the objectives of this research are to determine whether or not the final models selected are in agreement or differ substantially across the three approaches to model selection: using Akaike’s Information Criterion, using a p-value criterion, and using a stepwise procedure.. Generally, results from these three models are usually compare to each other. All selected models are based on the heredity principle to design the possible model for each design. The actual data from literature, consisting of the 2x3 and 32 and 3x4 factorial designs are used to determine the final model. The results show that the P-Value WH and Stepwise methods give the highest percentage of matched model.

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.

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.

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.

FAST AND ACCURATE TIME-DOMAIN ANALYSIS OF PIECEWISE-LINEAR DYNAMICS CIRCUITS: THE COMPUTER PROGRAM PILA

1994 ◽  
Vol 04 (01) ◽  
pp. 71-92 ◽  
Author(s):  
MARIO BIEY ◽  
MARTIN HASLER ◽  
ROBERTO LOJACONO ◽  
AMEDEO PREMOLI
Keyword(s):  
Computer Program ◽  
Time Domain ◽  
Piecewise Linear ◽  
Time Domain Analysis ◽  
Domain Analysis ◽  
State Matrix ◽  
Linear Region ◽  
All Solutions ◽  
The Time Domain

The computer program PILA (piecewise-linear analysis) is described. It is specially designed for exploring complicated dynamics of moderately sized piecewise-linear circuits. The DC-analysis is performed either by an adapted version of Katzenelson’s algorithm or by an algorithm designed for solving the linear complementarity problem. If the user chooses the latter algorithm, he will get all solutions of the DC-problem, whereas with Katzenelson’s algorithm usually just one solution is found. The time-domain analysis proceeds by the calculation of eigenvalues of the state matrix in order to obtain a time-symbolic solution in each linear region. This method is particularly fast and accurate, as long as the order of the circuit is not too high. The main errors occur in the determination of the transition between two adjacent linear regions. Particular care has been taken to get maximum transition accuracy. Some examples illustrate the various features of PILA.

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.

Technique for Efficient Time-Domain Analysis of Complete Buoy-Cable Systems

1979 ◽  
Vol 101 (4) ◽  
pp. 416-420 ◽  
Author(s):  
H. T. Wang
Keyword(s):  
Elastic Modulus ◽  
Computer Program ◽  
Dynamic Behavior ◽  
Time Domain ◽  
Time Domain Analysis ◽  
Domain Analysis ◽  
Transient Phase ◽  
Two Dimensional ◽  
Cable Systems ◽  
The Time Domain

A brief description is given of a computer program for the time domain analysis of the two-dimensional dynamic behavior of general ocean buoy-cable-body systems. Several sample problems are given to illustrate the versatility of the program. The concept of using the results for a cable with reduced elastic modulus, adjusted so that the cable does not stretch, to predict the dynamic behavior of a nearly inextensible cable with much higher elastic modulus is discussed in detail. Except for the transient phase, it is shown that this technique generally predicts tensions and motions with errors of only a few percent for nearly inextensible cables which would otherwise require substantially longer computer times.

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