Reliability of parameter estimates from models applied to respiratory impedance data

1987 ◽  
Vol 62 (2) ◽  
pp. 403-413 ◽  
Author(s):  
K. R. Lutchen ◽  
A. C. Jackson
Keyword(s):  
Random Noise ◽  
Element Model ◽  
Parameter Estimates ◽  
Frequency Range ◽  
High Frequencies ◽  
Estimated Parameters ◽  
Impedance Data ◽  
Lumped Parameter ◽  
Lumped Parameter Models ◽  
Very High Frequencies

Many previous studies have fit lumped parameter models to respiratory input (Zin) and transfer (Ztr) impedance data. For frequency ranges higher than 4–32 Hz, a six-element model may be required in which an airway branch (with a resistance and inertance) is separated from a tissue branch (with a resistance, inertance, and compliance) by a shunt compliance. A sensitivity analysis is applied to predict the effects of frequency range on the accuracy of parameter estimates in this model obtained from Zin or Ztr data. Using a parameter set estimated from experimental data between 4 and 64 Hz in dogs, both Zin and Ztr were simulated from 4 to 200 Hz. Impedance sensitivity to each parameter was also calculated over this frequency range. The simulation predicted that for Zin a second resonance occurs near 80 Hz and that the impedance is considerably more sensitive to several of the parameters at frequencies surrounding this resonance than at any other frequencies. Also, unless data is obtained at very high frequencies (where the model is suspect), Zin data provides more accurate estimates than Ztr data. After adding random noise to the simulated Zin data, we attempted to extract the original parameters by using a nonlinear regression applied to three frequency ranges: 4–32, 4–64, and 4–110 Hz. Estimated parameters were substantially incorrect when using only 4- to 32-Hz or 4- to 64-Hz data, but nearly correct when fitting 4- to 110-Hz data. These results indicate that respiratory system parameters can be more accurately extracted from Zin than Ztr, and to make physiological inferences from parameter estimates based on Zin impedance data in dogs, the data must include frequencies surrounding the second resonance.

Modeling of respiratory system impedances in dogs

1987 ◽  
Vol 62 (2) ◽  
pp. 414-420 ◽  
Author(s):  
A. C. Jackson ◽  
K. R. Lutchen
Keyword(s):  
Respiratory System ◽  
Element Model ◽  
Parameter Estimates ◽  
Frequency Range ◽  
Nonlinear Regression Analysis ◽  
Entire Frequency Range ◽  
Frequency Dependent ◽  
Impedance Data ◽  
Parameter Values ◽  
Gas Compressibility

Mechanical impedances between 4 and 64 Hz of the respiratory system in dogs have been reported (A.C. Jackson et al. J. Appl. Physiol. 57: 34–39, 1984) previously by this laboratory. It was observed that resistance (the real part of impedance) decreased slightly with frequency between 4 and 22 Hz then increased considerably with frequency above 22 Hz. In the current study, these impedance data were analyzed using nonlinear regression analysis incorporating several different lumped linear element models. The five-element model of Eyles and Pimmel (IEEE Trans. Biomed. Eng. 28: 313–317, 1981) could only fit data where resistance decreased with frequency. However, when the model was applied to these data the returned parameter estimates were not physiologically realistic. Over the entire frequency range, a significantly improved fit was obtained with the six-element model of DuBois et al. (J. Appl. Physiol. 8: 587–594, 1956), since it could follow the predominate frequency-dependent characteristic that was the increase in resistance. The resulting parameter estimates suggested that the shunt compliance represents alveolar gas compressibility, the central branch represents airways, and the peripheral branch represents lung and chest wall tissues. This six-element model could not fit, with the same set of parameter values, both the frequency-dependent decrease in Rrs and the frequency-dependent increase in resistance. A nine-element model recently proposed by Peslin et al. (J. Appl. Physiol. 39: 523–534, 1975) was capable of fitting both the frequency-dependent decrease and the frequency-dependent increase in resistance. However, the data only between 4 and 64 Hz was not sufficient to consistently determine unique values for all nine parameters.

scholarly journals Estimation of Optimal Values for Lumped Elements in a Finite Element — Lumped Parameter Model of a Loudspeaker

2020 ◽  
Vol 28 (02) ◽  
pp. 2050012
Author(s):  
Daniel Gert Nielsen ◽  
Peter Risby Andersen ◽  
Jakob Søndergaard Jensen ◽  
Finn Thomas Agerkvist
Keyword(s):  
Finite Element ◽  
Element Model ◽  
Lumped Parameter Model ◽  
Model Complexity ◽  
Fe Model ◽  
High Frequencies ◽  
Lumped Parameter ◽  
Lumped Elements ◽  
Optimal Values ◽  
Very High Frequencies

Finite element methods are progressively being utilized to assist in the continuous development of loudspeakers. The core of this paper is the method of lumping certain parts of the finite element model, creating a significant reduction in the model complexity that allows for e.g. faster structural optimization. This is illustrated in the paper with a loudspeaker example where the electromagnetic parts are lumped as well as the spider. It is shown that the simplified model still matches the complex response of the full FE model at very high frequencies.

scholarly journals Influence of Metal?Glass Contact on the Dynamic Response of 0.40Ag2O:0.60P2O5 Glass

1994 ◽  
Vol 47 (4) ◽  
pp. 487 ◽  
Author(s):  
NU Haque ◽  
RA Hashmi ◽  
MK Anis
Keyword(s):  
Contact Resistance ◽  
Complex Impedance ◽  
Peak Frequency ◽  
Barrier Effect ◽  
Loss Peak ◽  
Frequency Range ◽  
High Frequencies ◽  
Impedance Data ◽  
Complex Capacitance ◽  
Temperature Dependences

The results of impedance measurements on a low-conducting 0�40Ag20: 060P20S glass are reported in the frequency range 10-3 to 105 Hz and the temperature range 250 to 400 K. The observed dispersions in the complex impedance data are attributed to a barrier effect in the region of the electrodes and are shown to follow simple power law behaviour for low and high frequencies with respect to the loss peak frequency. Using the complex impedance and complex capacitance data, the contact resistance and the corresponding contact capacitance have been worked out. The temperature dependences of the contact resistance R. and the contact capacitance C. are also reported. The activation energy for this glass is found to be 0�50�O�02 eV.

The Treatment of Systematic Errors in Model Updating

1995 ◽  
Author(s):  
Michael I. Friswell ◽  
John E. Mottershead ◽  
Youhe Zhang
Keyword(s):  
Finite Element ◽  
Model Updating ◽  
Element Model ◽  
Systematic Errors ◽  
Measured Data ◽  
Parameter Estimates ◽  
Finite Element Model Updating ◽  
Finite Element Models ◽  
Frequency Range ◽  
Discretisation Error

Abstract In the standard methods, accurate parameter estimates in finite element model updating rely on the model being fully converged in the frequency range of interest. In this paper a method is presented for the estimation of natural frequency discretisation errors in finite element models. The discretisation error is added to the measured data and is shown to reduce the bias in the resulting parameters estimates. The method is demonstrated using a bar and a beam example.

A hybrid model to study the effect of tooth lead modifications on the dynamic behavior of double helical planetary gears

2019 ◽  
Vol 233 (21-22) ◽  
pp. 7224-7235
Author(s):  
Stéphane Portron ◽  
Philippe Velex ◽  
Vincent Abousleiman
Keyword(s):  
Dynamic Behavior ◽  
Hybrid Model ◽  
Load Distribution ◽  
Element Model ◽  
Ring Gear ◽  
Planetary Gears ◽  
Lumped Parameter ◽  
Lumped Parameter Models ◽  
Lumped Parameters ◽  
Planet Carrier

In this paper, a hybrid model is used to investigate the dynamic behavior of planetary gears. Sun-gear, planets, and ring-gear are modeled using lumped parameters elements, while planet carrier is integrated via a condensed finite element model. This approach intends to be more precise than the traditional lumped parameter models while keeping acceptable computational times. In some aeronautical applications, tooth lead modifications can be necessary to counterbalance the effect of planet carrier deflections on tooth load distribution. This study focuses on the influence of various lead modifications on the dynamic behavior of double helical planetary gears over a broad range of loads.

High-frequency electromagnetic impedance method for subsurface imaging

Geophysics ◽  
2002 ◽  
Vol 67 (2) ◽  
pp. 501-510 ◽  
Author(s):  
Yoonho Song ◽  
Hee Joon Kim ◽  
Ki Ha Lee
Keyword(s):  
Electrical Properties ◽  
High Frequency ◽  
Plane Waves ◽  
Impedance Method ◽  
Distinct Advantage ◽  
Angle Of Incidence ◽  
Frequency Range ◽  
High Frequencies ◽  
Shallow Subsurface ◽  
Impedance Data

This paper presents a high-frequency electromagnetic (EM) impedance method that extends the utility of conventional controlled-source audio-frequency magnetotelluric (CSAMT) method to the frequency range from 100 kHz to 100 MHz. In this frequency range diffusion and wave propagation must be considered together. In principle, both the electrical conductivity and the permittivity of the shallow subsurface can be imaged using impedance data gathered on the surface of the earth. The impedance approach has a distinct advantage in that coupling with the source is unnecessary, provided that the source can be positioned far enough away to yield plane waves at the receiver positions. At high frequencies the EM impedance is a function of the angle of incidence or the horizontal wavenumber, so the electrical properties cannot be readily extracted without eliminating the effect of horizontal wavenumber on the impedance. For this purpose, this paper considers two independent methods for accurately determining the horizontal wavenumber, which in turn is used to correct the impedance data. The apparent electrical properties derived from the corrected impedance data correlate poorly to the real structure, especially for the model with a resistive overburden. However, the impedance data along with the incidence angles thus estimated can be successfully inverted to yield an accurate subsurface layering through the simulated annealing inversion scheme.

scholarly journals A computationally efficient hybrid 2D–3D subwoofer model

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ahmad H. Bokhari ◽  
Martin Berggren ◽  
Daniel Noreland ◽  
Eddie Wadbro
Keyword(s):  
Hybrid Model ◽  
3D Model ◽  
Element Model ◽  
Acoustic Properties ◽  
Computational Time ◽  
Average Response ◽  
Frequency Range ◽  
Computationally Efficient ◽  
Lumped Element ◽  
Lumped Element Model

AbstractA subwoofer generates the lowest frequency range in loudspeaker systems. Subwoofers are used in audio systems for live concerts, movie theatres, home theatres, gaming consoles, cars, etc. During the last decades, numerical simulations have emerged as a cost- and time-efficient complement to traditional experiments in the design process of different products. The aim of this study is to reduce the computational time of simulating the average response for a given subwoofer design. To this end, we propose a hybrid 2D–3D model that reduces the computational time significantly compared to a full 3D model. The hybrid model describes the interaction between different subwoofer components as interacting modules whose acoustic properties can partly be pre-computed. This allows us to efficiently compute the performance of different subwoofer design layouts. The results of the hybrid model are validated against both a lumped element model and a full 3D model over a frequency band of interest. The hybrid model is found to be both accurate and computationally efficient.

scholarly journals A New Concept for Deeper Integration of Converters and Drives in Electrical Machines: Simulation and Experimental Investigations

Open Physics ◽  
2019 ◽  
Vol 17 (1) ◽  
pp. 809-815
Author(s):  
Hossam Al Ghossini ◽  
Thu Thuy Dang ◽  
Stéphane Duchesne
Keyword(s):  
Motor Drives ◽  
Electrical Machines ◽  
Experimental Investigations ◽  
Power Switching ◽  
Switched Reluctance ◽  
High Frequencies ◽  
Reluctance Motor ◽  
Switching Structure ◽  
Very High Frequencies

AbstractThis paper introduces a new concept for integrated electrical motor drives (IEMD) with the aim of minimizing the number of inverter’s power switching components. The latter is switched reluctance motor (SRM) based. The control strategy is jointly designed, inspired by Flyback power supplies operating at very high frequencies. A simple case study on an 8/6 SRM has been carried out. The study enables to highlight most challenging problems that have to be overcome in future works: overvoltages during switching due to the flux leakage, and the efficiency of the magnetic material constituting the machine at high switching frequencies. This concept turns out to be an interesting basis for a very advanced integration of the switching structure within electrical machines.

scholarly journals EXTENSION OF THE FREQUENCY-RANGE OF INTERFEROMETERS FOR THE "MAGNETIC" COMPONENTS OF GRAVITATIONAL WAVES?

2007 ◽  
Vol 22 (13) ◽  
pp. 2361-2381 ◽  
Author(s):  
CHRISTIAN CORDA
Keyword(s):  
Data Analysis ◽  
Frequency Dependence ◽  
Gravitational Waves ◽  
Response Functions ◽  
Frequency Range ◽  
Total Response ◽  
High Frequencies ◽  
Magnetic Components ◽  
Linear Dimensions ◽  
Dominant Part

Recently, with an enlightening treatment, Baskaran and Grishchuk have shown the presence and importance of the so-called "magnetic" components of gravitational waves (GW's), which have to be taken into account in the context of the total response functions of interferometers for GW's propagating from arbitrary directions. In this paper the analysis of the response functions for the magnetic components is generalized in its full frequency dependence, while in the work of Baskaran and Grishchuk the response functions were computed only in the approximation of wavelength much larger than the linear dimensions of the interferometer. It is also shown that the response functions to the magnetic components grow at high frequencies, differently from the values of the response functions to the well-known ordinary components that decrease at high frequencies. Thus the magnetic components could in principle become the dominant part of the signal at high frequencies. This is important for a potential detection of the signal at high frequencies and confirms that the magnetic contributions must be taken into account in the data analysis. More, the fact that the response functions of the magnetic components grow at high frequencies shows that, in principle, the frequency-range of Earth-based interferometers could extend to frequencies over 10000 Hz.

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