scholarly journals Diffusion Models to Construct a First Principles Multipole-Based Cable Braid Model for Conducting Wires in the Time Domain

2020 ◽  
Author(s):  
Salvatore Campione ◽  
Larry Warne
Keyword(s):  
Time Domain ◽  
First Principles ◽  
Diffusion Models ◽  
The Time Domain

Impact of FPSO Heading on Fatigue Design in Non-Collinear Environments

2002 ◽  
Author(s):  
Christina D. Nordstrom ◽  
Peter B. Lacey ◽  
Bob Grant ◽  
Derek D. Hee
Keyword(s):  
Time Domain ◽  
First Principles ◽  
Fatigue Cracks ◽  
Time History ◽  
Geographic Location ◽  
Analysis Procedure ◽  
Fatigue Design ◽  
Operational Life ◽  
Structural Details ◽  
The Time Domain

To achieve confidence in continuous 20+ year FPSO service without fatigue cracks leading to costly repair offshore or in dry-dock, ExxonMobil has developed a prescriptive Fatigue Methodology Specification (FMS, ref. 5) for new-build FPSOs. An important FMS requirement for turret-moored FPSOs is to determine relative wave headings in non-collinear wind, current and wave environments using a first-principles approach. Based on initial review with FPSO designers, this FMS requirement may pose a significant challenge because appropriately defined met-ocean criteria and efficient analytical design tools are not readily available. To date, FPSO designers typically account for weather-vaning in non-collinear environments by assuming a distribution of relative wave headings based on experience. For example, one assumption is to use 0 degrees (head seas) for 70% of the time and within ±30 degrees off the bow for the remaining 30%. In certain environments, this assumption can lead to a non-conservative fatigue design for hull structural details that are sensitive to beam seas, and an overly conservative fatigue design for details sensitive to head seas. ExxonMobil contracted Moffat & Nichol to develop a time-domain procedure to predict mean FPSO headings by considering wave, wind and current induced loads on the FPSO hull and topsides throughout the FPSO’s 20+ year operational life. A key element of this methodology is a directional representation of met-ocean data, including waves, winds and currents for every 3- or 6-hour sea-state. We have implemented our heading analysis procedure in robust software, which includes processing of the 20+ year met-ocean data in the time domain. Once the FPSO heading time history is known, fatigue lives at critical structural connections are predicted using the spectral fatigue method prescribed in the FMS. To demonstrate the heading methodology and assess its efficiency for project use, an example analysis was performed for an FPSO at a specific geographic location, where relatively strong currents exist. Comparison of predicted FPSO headings and fatigue lives with those using the existing industry practices confirmed the need for a first principles based heading methodology for FPSO fatigue design. The heading and fatigue analysis procedure described here can lead to more accurate, robust fatigue designs for FPSOs in non-collinear environments.

scholarly journals Sleep spindles comprise a subset of a broader class of electroencephalogram events

SLEEP ◽  
2021 ◽  
Author(s):  
Tanya Dimitrov ◽  
Mingjian He ◽  
Robert Stickgold ◽  
Michael J Prerau
Keyword(s):  
Time Domain ◽  
First Principles ◽  
Automated Detection ◽  
Detection Methods ◽  
Sleep Spindles ◽  
Complete Representation ◽  
Time Frequency ◽  
Multiple Datasets ◽  
Oscillatory Structure ◽  
The Time Domain

Abstract Study Objectives Sleep spindles are defined based on expert observations of waveform features in the electroencephalogram traces. This is a potentially limiting characterization, as transient oscillatory bursts like spindles are easily obscured in the time-domain by higher amplitude activity at other frequencies or by noise. It is therefore highly plausible that many relevant events are missed by current approaches based on traditionally-defined spindles. Given their oscillatory structure, we reexamine spindle activity from first principles, using time-frequency activity in comparison to scored spindles. Methods Using multitaper spectral analysis, we observe clear time-frequency peaks in the sigma (10-16 Hz) range (TFσ peaks). While nearly every scored spindle coincides with a TFσ peak, numerous similar TFσ peaks remain undetected. We therefore perform statistical analyses of spindles and TFσ peaks using manual and automated detection methods, comparing event co-occurrence, morphological similarities, and night-to-night consistency across multiple datasets. Results On average, TFσ peaks have more than 3 times the rate of spindles (mean rate: 9.8 vs. 3.1 events/min). Moreover, spindles subsample the most prominent TFσ peaks with otherwise identical spectral morphology. We further demonstrate that detected TFσ peaks have stronger night-to-night rate stability (rho = 0.98) than spindles (rho = 0.67), while covarying with spindle rates across subjects (rho = 0.72). Conclusions These results provide compelling evidence that traditionally-defined spindles constitute a subset of a more generalized class of electroencephalogram events. TFσ peaks are therefore a more complete representation of the underlying phenomenon, providing a more consistent and robust basis for future experiments and analyses.

Apodisation in the time domain

1992 ◽  
Vol 2 (4) ◽  
pp. 615-620
Author(s):  
G. W. Series
Keyword(s):  
Time Domain ◽  
The Time Domain

JOINT INTERPRETATION OF AIRBORNE ELECTROMAGNETIC DATA IN THE TIME DOMAIN AND FREQUENCY DOMAIN

2018 ◽  
Vol 12 (7-8) ◽  
pp. 76-83
Author(s):  
E. V. KARSHAKOV ◽  
J. MOILANEN
Keyword(s):  
Fourier Transform ◽  
Frequency Domain ◽  
Time Domain ◽  
Frequency Interval ◽  
Single Spectrum ◽  
Simultaneous Inversion ◽  
Homogeneous Half Space ◽  
Time Domain Data ◽  
The Time Domain

Тhe advantage of combine processing of frequency domain and time domain data provided by the EQUATOR system is discussed. The heliborne complex has a towed transmitter, and, raised above it on the same cable a towed receiver. The excitation signal contains both pulsed and harmonic components. In fact, there are two independent transmitters operate in the system: one of them is a normal pulsed domain transmitter, with a half-sinusoidal pulse and a small "cut" on the falling edge, and the other one is a classical frequency domain transmitter at several specially selected frequencies. The received signal is first processed to a direct Fourier transform with high Q-factor detection at all significant frequencies. After that, in the spectral region, operations of converting the spectra of two sounding signals to a single spectrum of an ideal transmitter are performed. Than we do an inverse Fourier transform and return to the time domain. The detection of spectral components is done at a frequency band of several Hz, the receiver has the ability to perfectly suppress all sorts of extra-band noise. The detection bandwidth is several dozen times less the frequency interval between the harmonics, it turns out thatto achieve the same measurement quality of ground response without using out-of-band suppression you need several dozen times higher moment of airborne transmitting system. The data obtained from the model of a homogeneous half-space, a two-layered model, and a model of a horizontally layered medium is considered. A time-domain data makes it easier to detect a conductor in a relative insulator at greater depths. The data in the frequency domain gives more detailed information about subsurface. These conclusions are illustrated by the example of processing the survey data of the Republic of Rwanda in 2017. The simultaneous inversion of data in frequency domain and time domain can significantly improve the quality of interpretation.

scholarly journals Broadband spectroscopy of astrophysical ice analogues

2019 ◽  
Vol 629 ◽  
pp. A112 ◽  
Author(s):  
B. M. Giuliano ◽  
A. A. Gavdush ◽  
B. Müller ◽  
K. I. Zaytsev ◽  
T. Grassi ◽  
...  
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Time Domain ◽  
Complex Refractive Index ◽  
Far Infrared ◽  
Infrared Region ◽  
Thz Radiation ◽  
The Real ◽  
Thz Range ◽  
The Time Domain

Context. Reliable, directly measured optical properties of astrophysical ice analogues in the infrared and terahertz (THz) range are missing from the literature. These parameters are of great importance to model the dust continuum radiative transfer in dense and cold regions, where thick ice mantles are present, and are necessary for the interpretation of future observations planned in the far-infrared region. Aims. Coherent THz radiation allows for direct measurement of the complex dielectric function (refractive index) of astrophysically relevant ice species in the THz range. Methods. We recorded the time-domain waveforms and the frequency-domain spectra of reference samples of CO ice, deposited at a temperature of 28.5 K and annealed to 33 K at different thicknesses. We developed a new algorithm to reconstruct the real and imaginary parts of the refractive index from the time-domain THz data. Results. The complex refractive index in the wavelength range 1 mm–150 μm (0.3–2.0 THz) was determined for the studied ice samples, and this index was compared with available data found in the literature. Conclusions. The developed algorithm of reconstructing the real and imaginary parts of the refractive index from the time-domain THz data enables us, for the first time, to determine the optical properties of astrophysical ice analogues without using the Kramers–Kronig relations. The obtained data provide a benchmark to interpret the observational data from current ground-based facilities as well as future space telescope missions, and we used these data to estimate the opacities of the dust grains in presence of CO ice mantles.

EPR light beams and non-Gaussian quantum distributions in the time domain

2009 ◽  
Vol 6 (7) ◽  
pp. 577-580
Author(s):  
N. H. Adamyan ◽  
H. H. Adamyan ◽  
G. Yu. Kryuchkyan
Keyword(s):  
Time Domain ◽  
Non Gaussian ◽  
The Time Domain ◽  
Light Beams ◽  
Quantum Distributions

Separating Multiple Moving Sources by Microphone Array Signals for Wayside Acoustic Fault Diagnosis

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Wei Xiong ◽  
Qingbo He ◽  
Zhike Peng
Keyword(s):  
Fault Diagnosis ◽  
Time Domain ◽  
Feature Matching ◽  
Matching Pursuit ◽  
Microphone Array ◽  
Time Frequency ◽  
Moving Sources ◽  
The Time Domain ◽  
Envelope Spectrum ◽  
Threshold Setting

Wayside acoustic defective bearing detector (ADBD) system is a potential technique in ensuring the safety of traveling vehicles. However, Doppler distortion and multiple moving sources aliasing in the acquired acoustic signals decrease the accuracy of defective bearing fault diagnosis. Currently, the method of constructing time-frequency (TF) masks for source separation was limited by an empirical threshold setting. To overcome this limitation, this study proposed a dynamic Doppler multisource separation model and constructed a time domain-separating matrix (TDSM) to realize multiple moving sources separation in the time domain. The TDSM was designed with two steps of (1) constructing separating curves and time domain remapping matrix (TDRM) and (2) remapping each element of separating curves to its corresponding time according to the TDRM. Both TDSM and TDRM were driven by geometrical and motion parameters, which would be estimated by Doppler feature matching pursuit (DFMP) algorithm. After gaining the source components from the observed signals, correlation operation was carried out to estimate source signals. Moreover, fault diagnosis could be carried out by envelope spectrum analysis. Compared with the method of constructing TF masks, the proposed strategy could avoid setting thresholds empirically. Finally, the effectiveness of the proposed technique was validated by simulation and experimental cases. Results indicated the potential of this method for improving the performance of the ADBD system.

scholarly journals Diagnostically Oriented Experiments and Modelling of Switched Reluctance Motor Dynamic Eccentricity

Sensors ◽  
2021 ◽  
Vol 21 (11) ◽  
pp. 3857
Author(s):  
Jakub Lorencki ◽  
Stanisław Radkowski ◽  
Szymon Gontarz
Keyword(s):  
Time Domain ◽  
Test Bench ◽  
Switched Reluctance Motor ◽  
Industrial Applications ◽  
Switched Reluctance ◽  
Static And Dynamic Analysis ◽  
Geometry Model ◽  
Reluctance Motor ◽  
Dynamic Eccentricity ◽  
The Time Domain

The article compares the results of experimental and modelling research of switched reluctance motor at two different operational states: one proper and one with mechanical fault, i.e., with dynamic eccentricity of the rotor. The experiments were carried out on a test bench and then the results were compared with mathematical modelling of quasi-static and dynamic analysis of 2D geometry model. Finally, it was examined how the operation with dynamic eccentricity fault of the motor affected its main physical parameter—the phase current. The analysis was presented in the frequency domain using the Fast Fourier Transform (FFT); however, individual current waveforms in the time domain are also shown for comparison. Applying results of the research could increase reliability of the maintenance of SRM and enhance its application in vehicles for special purposes as well as its military and industrial applications.

Sign in / Sign up

Export Citation Format

Share Document