scholarly journals TIME AND FREQUENCY LOADING ANALYSIS OF SUBMARINE PIPELINES

1984 ◽  
Vol 1 (19) ◽  
pp. 183
Author(s):  
H.C. Alexander ◽  
P.L. Allen ◽  
J.L. Warner
Keyword(s):  
Spectral Analysis ◽  
Frequency Domain ◽  
Fatigue Damage ◽  
Time Domain ◽  
Time Domain Analysis ◽  
Wave Force ◽  
Domain Analysis ◽  
Wave Spectra ◽  
Frequency Domain Methods ◽  
Wave Conditions

Fatigue damage to marine pipelines subjected to wave forces is evaluated using time-domain and frequency-domain methods. Spectral techniques are applied to North Sea, Gulf of Mexico and offshore Atlantic Canada wave conditions. Time-domain analysis is applied to wave conditions in the Canadian North Atlantic Ocean. The frequency-domain analysis is performed using spectral and probabilistic techniques suggested by L. Borgman {?.). The pipeline dynamic characteristics are described by classical analytical descriptions. The time-domain analysis computes time histories of wave force loading on the submerged pipeline from actual wave records. The traditional Morison wave force equation is used to obtain the time history of the loading on the pipeline. Empirically determined wave spectra are shown not to produce as good a correlation with the deterministic results as the actual wave spectra. Free spanning submarine pipelines subjected to cyclic surface wave loading accumulate strength reductions leading to failure from material fatigue. The Palmgren-Miner rule for the linear accumulation of fatigue damage is applied to evaluate the time to failure. The American Welding Society X-X stress accumulation curve is applied. The results of the deterministic analysis were compared with those of the more efficient spectral analysis. It is shown that comparable results can be obtained from the spectral analysis provided the actual spectra of the water surface elevation is employed in the spectral analysis.

Spectral Analysis: A Tool for Study of Neonatal Sympathetic Systems

Physiology ◽  
1994 ◽  
Vol 9 (5) ◽  
pp. 233-236
Author(s):  
PM Gootman ◽  
AL Sica
Keyword(s):  
Spectral Analysis ◽  
Frequency Domain ◽  
Time Domain ◽  
Spectral Methods ◽  
Sympathetic Activity ◽  
Time Domain Analysis ◽  
Domain Analysis ◽  
Statistical Information ◽  
Neural Signals ◽  
Power Spectral

Preference for statistical information from frequency domain rather than time domain analysis becomes apparent when applied to complex neural signals. Further, we demonstrate how power spectral methods reveal significant changes in neonatal sympathetic activity.

scholarly journals Analysis of Three-Phase Wye-Delta Connected LLC

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3606
Author(s):  
Jing-Yuan Lin ◽  
Chuan-Ting Chen ◽  
Kuan-Hung Chen ◽  
Yi-Feng Lin
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Operation Time ◽  
Time Domain Analysis ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Complete Analysis ◽  
Plane Analysis ◽  
Analysis Methods ◽  
Three Phase

Three-phase wye–delta LLC topology is suitable for voltage step down and high output current, and has been used in the industry for some time, e.g., for server power and EV charger. However, no comprehensive circuit analysis has been performed for three-phase wye–delta LLC. This paper provides complete analysis methods for three-phase wye–delta LLC. The analysis methods include circuit operation, time domain analysis, frequency domain analysis, and state–plane analysis. Circuit operation helps determine the circuit composition and operation sequence. Time domain analysis helps understand the detail operation, equivalent circuit model, and circuit equation. Frequency domain analysis helps obtain the curve of the transfer function and assists in circuit design. State–plane analysis is used for optimal trajectory control (OTC). These analyses not only can calculate the voltage/current stress, but can also help design three-phase wye-delta connected LLC and provide the OTC control reference. In addition, this paper uses PSIM simulation to verify the correctness of analysis. At the end, a 5-kW three-phase wye–delta LLC prototype is realized. The specification of the prototype is a DC input voltage of 380 V and output voltage/current of 48 V/105 A. The peak efficiency is 96.57%.

Drilling Riser VIV Analysis Using Time Domain Code SimVIV

2013 ◽  
Author(s):  
Djoni E. Sidarta
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Time Domain Analysis ◽  
Domain Analysis ◽  
Ocean Currents

Drilling risers are often subjected to VIV from ocean currents, which may vary in directions over depth. VIV of drilling riser has commonly been analyzed using frequency domain code. This paper presents an alternative tool of analyzing VIV of drilling riser using time domain code SimVIV. With this tool it is possible to apply currents in varying directions over depth. Measured currents and VIV responses of a drilling riser available in the literature are used in this study. The results of time domain analysis using SimVIV are compared against measured responses. The effect of current directionality over depth on drilling riser VIV response is also analyzed.

A Frequency Domain Analysis of Learning Control

1994 ◽  
Vol 116 (4) ◽  
pp. 781-786 ◽  
Author(s):  
C. J. Goh
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Linear Time ◽  
Planning Horizon ◽  
Time Domain Analysis ◽  
Learning Control ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Convergence Criterion ◽  
The Time Domain

The convergence of learning control is traditionally analyzed in the time domain. This is because a finite planning horizon is often assumed and the analysis in time domain can be extended to time-varying and nonlinear systems. For linear time-invariant (LTI) systems with infinite planning horizon, however, we show that simple frequency domain techniques can be used to quickly derive several interesting results not amenable to time-domain analysis, such as predicting the rate of convergence or the design of optimum learning control law. We explain a paradox arising from applying the finite time convergence criterion to the infinite time learning control problem, and propose the use of current error feedback for controlling possibly unstable systems.

Efficient Dynamic Analysis of a Combined Spar System via a Frequency Domain Approach

2005 ◽  
Author(s):  
Pol D. Spanos ◽  
Rupak Ghosh ◽  
Lyle D. Finn ◽  
Fikry Botros ◽  
John Halkyard
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Time Domain Analysis ◽  
Domain Analysis ◽  
Alternative Methods ◽  
Design Parameters ◽  
Combined System ◽  
Frequency Dependent ◽  
Equivalent Linear ◽  
Frequency Domain Approach

The response of a combined Spar/ risers/mooring lines system is conventionally determined by conducting nonlinear time domain analysis. The system nonlinearity is introduced by the mooring nonlinear force, the friction between the buoyancy-can and the preloaded compliant guide, and the quadratic model of the fluid related damping. Obviously, during the design process, it is important to understand the sensitivity of the Spar responses to various parameters. To a great extent, these objectives cannot be readily achieved by using time domain analysis since, in this context, elements with frequency dependent representation such as the added masses and supplementary damping must be incorporated in the analysis; this may require the use of elaborate convolution techniques. This attribute of the time domain solution combined with the necessity of running a significant number of simulations makes it desirable to develop alternative methods of analysis. In the present paper, a frequency domain approach based on the method of the statistical linearization is used for conducting readily a parametric study of the combined Spar system. This method allows one to account by an equivalent linear damping and an equivalent linear stiffness for the mooring nonlinearity, friction nonlinearity, and the damping nonlinearity of the system. Further, frequency dependent inertia and radiation damping terms in the equations of motion are accommodated. This formulation leads to a mathematical model for the combined system, which involves five-by-five mass, damping and stiffness matrices. In the solution procedure, the equivalent parameters of the linear system are refined in an iterative manner, and by relying on an optimization criterion. This procedure is used to assess the sensitivity of representative Spar system responses to various design parameters. Further, the effect of various design parameters on the combined system response is examined. The environmental loadings considered are of the JONSWAP format of a 100-yr hurricane in the Gulf of Mexico.

scholarly journals EFFICIENT TIME-DOMAIN ANALYSIS OF WAVEGUIDE DISCONTINUITIES USING HIGHER ORDER FEM IN FREQUENCY DOMAIN

2011 ◽  
Vol 120 ◽  
pp. 215-234 ◽  
Author(s):  
Eve M. Klopf ◽  
Sanja B. Manić ◽  
Milan M. Ilic ◽  
Branislav M. Notaroš
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Time Domain Analysis ◽  
Domain Analysis ◽  
Higher Order ◽  
Waveguide Discontinuities
Sign in / Sign up

Export Citation Format

Share Document