Branching airway network models for analyzing high-frequency lung input impedance

1993 ◽  
Vol 75 (1) ◽  
pp. 217-227 ◽  
Author(s):  
A. C. Jackson ◽  
B. Suki ◽  
M. Ucar ◽  
R. Habib
Keyword(s):  
Input Impedance ◽  
Structural Model ◽  
Complex Function ◽  
Low Frequency ◽  
Network Models ◽  
Scaling Factor ◽  
Forced Oscillation Technique ◽  
Geometrical Factors ◽  
Airway Walls ◽  
Parameter Values

The input impedance of the lung (Zin) at high frequencies (> 100 Hz) is a complex function of the airway geometry and the mechanical properties of the airway walls. To investigate how the purely geometrical factors influence Zin, we measured Zin between 16 and 1,520 Hz in six dried dog lungs with the forced oscillation technique. In each of the lungs we found three resonances, at 36 +/- 5, 648 +/- 100, and 1,289 +/- 150 Hz, and at least two antiresonances (relative maxima in the real part of Zin), at 372 +/- 60 and 1,105 +/- 110 Hz. These data were fit with models featuring a detailed asymmetric branching network of the airways obtained from morphometric data published by Horsfield et al. (J. Appl. Physiol. 52: 21–26, 1982). On the basis of low-frequency (< 100 Hz) data alone, we first established a model of the acini, which was then attached to the end of the airway branching model. With a single scaling factor for the radius and length of the airways, the fit was unsatisfactory. Using sensitivity analysis techniques we determined which candidate variables of the structural model could influence Zin in a manner to improve the fit. We found that a two-parameter model accounting for separate central and peripheral airway diameter scaling provided a reasonable fit to Zin. On average the model required central diameter scaling close to unity (0.94 +/- 0.09), and the peripheral diameter scaling factor was 0.87 +/- 0.38. Over a range of parameter values that we believed were physiologically reasonable (i.e., scaling factors between 0.5 and 1.5), a single set of parameter values was found in all lungs. These results suggest that structurally based inverse models of Zin that include multiple antiresonances may provide information about airway geometry.

scholarly journals An enhanced set of displacement parameter restraints in CRYSTALS

2018 ◽  
Vol 51 (4) ◽  
pp. 1059-1068 ◽  
Author(s):  
Pascal Parois ◽  
James Arnold ◽  
Richard Cooper
Keyword(s):  
Structural Model ◽  
Rigid Bodies ◽  
Model Parameters ◽  
Coordinate Systems ◽  
Principal Axes ◽  
Anisotropic Displacement Parameters ◽  
Set Up ◽  
Meaningful Relationships ◽  
Parameter Values ◽  
Total Model

Crystallographic restraints are widely used during refinement of small-molecule and macromolecular crystal structures. They can be especially useful for introducing additional observations and information into structure refinements against low-quality or low-resolution data (e.g. data obtained at high pressure) or to retain physically meaningful parameter values in disordered or unstable refinements. However, despite the fact that the anisotropic displacement parameters (ADPs) often constitute more than half of the total model parameters determined in a structure analysis, there are relatively few useful restraints for them, examples being Hirshfeld rigid-bond restraints, direct equivalence of parameters and SHELXL RIGU-type restraints. Conversely, geometric parameters can be subject to a multitude of restraints (e.g. absolute or relative distance, angle, planarity, chiral volume, and geometric similarity). This article presents a series of new ADP restraints implemented in CRYSTALS [Parois, Cooper & Thompson (2015), Chem. Cent. J. 9, 30] to give more control over ADPs by restraining, in a variety of ways, the directions and magnitudes of the principal axes of the ellipsoids in locally defined coordinate systems. The use of these new ADPs results in more realistic models, as well as a better user experience, through restraints that are more efficient and faster to set up. The use of these restraints is recommended to preserve physically meaningful relationships between displacement parameters in a structural model for rigid bodies, rotationally disordered groups and low-completeness data.

Preamplifier With Ultra Low Frequency Cutoff for Infrasonic Condenser Microphone

2012 ◽  
Author(s):  
Rasmus Trock Kinnerup ◽  
Arnold Knott ◽  
Ole Cornelius Thomsen ◽  
Kresten Marbjerg ◽  
Per Rasmussen
Keyword(s):  
Input Impedance ◽  
Dynamic Range ◽  
Cutoff Frequency ◽  
Low Frequency ◽  
Input Resistance ◽  
Bias Current ◽  
Microphone Signal ◽  
Low Frequencies ◽  
Pass Filter ◽  
Condenser Microphone

Measuring infrasonic sound sets high requirements on the instruments used. Typically the measurement chain consists of a microphone and a preamplifier. As the input resistance of the preamplifier forms a high pass filter with the capacitance of the microphone in the picofarad range, measuring ultra low frequencies becomes a challenge. The electric preamplifier presented in this paper together with a prepolarized condenser microphone form a measurement system. The developed preamplifier connects the microphone signal directly to the input of an operational amplifier with ultra high input impedance. The bias current for the preamplifier further complicates the signal amplification. A configuration of two diode-connected FETs provide the input bias current. The resulting input impedance of nearly 1 TΩ yields a total lower limiting −3 dB cutoff frequency of 8 mHz and a dynamic range of 95 dB. Being able to measure down to ultra low frequencies in the infrasonic frequency range will aid actors in the debate on wind turbine noise. Sonic booms from supersonic flights include frequencies down to 10 mHz and the preamplifier proposed in this paper will aid scientists trying to modify the N-shaped shock wave at high level which prohibits flights in land zones.

1/f Noise Behavior in Pentacene Organic Thin Film Transistors

1999 ◽  
Vol 598 ◽  
Author(s):  
P. V. Necliudov ◽  
D. J. Gundlach ◽  
T. N. Jackson ◽  
S. L. Rumyantsev ◽  
M. S. Shur
Keyword(s):  
Thin Film ◽  
Conducting Polymers ◽  
Thin Film Transistors ◽  
Low Frequency ◽  
Drain Current ◽  
Frequency Noise ◽  
Organic Thin Film ◽  
Amorphous Si ◽  
Parameter Values ◽  
Device Noise

ABSTRACTWe studied the low frequency noise in top-contact pentacene Thin Film Transistors (TFTs). The relative spectral noise density of the drain current fluctuations SI/I2 had a form of 1/f noise in the measured frequency range 1Hz - 3.5kHz.Our studies of the noise dependencies on the gate-source VGS and drain-source VDS voltages showed that the dependencies differed from those observed for conducting polymers and resembled those reported for crystalline Si n-MOSFETs.To compare the device noise level with those of other devices and materials, we extracted the Hooge parameter α. In order to calculate the total number of carriers we used a model simulating the device DC characteristics, similar to that for amorphous Si TFTs. The extracted Hooge parameter was 0.04. For an organic material this is an extremely small value, which is three orders of magnitude smaller that the Hooge parameter values reported for conducting polymers and only several times higher than the values for amorphous Si TFTs.

Laryngeal resistance immediately after panting in control and constricted airways

1985 ◽  
Vol 58 (4) ◽  
pp. 1164-1169 ◽  
Author(s):  
K. Sekizawa ◽  
H. Sasaki ◽  
T. Takishima
Keyword(s):  
Forced Oscillation ◽  
Low Frequency ◽  
Normal Subjects ◽  
Forced Oscillation Technique ◽  
Respiratory Resistance ◽  
Frequency Sound ◽  
Laryngeal Resistance ◽  
Control State

Laryngeal resistance (Rla) in the postpanting interval (PPRla) was examined in five normal subjects in the control state and with methacholine- and histamine-induced bronchoconstriction. Respiratory resistance (Rrs) was measured by the forced oscillation technique at 10 Hz, and Rla was measured by the low-frequency sound method (Sekizawa, K., C. Shindoh, W. Hida, S. Suzuki, et al. J. Appl. Physiol. 55:591–597, 1983). Inspiratory Rrs (IRrs) was lower than expiratory Rrs (ERrs), and Rrs immediately after panting (PPRrs) was not significantly different from IRrs in the three airway conditions. Rla increased with bronchoconstriction and inspiratory Rla (IRla) was lower than expiratory Rla (ERla). PPRla was lower than IRla (P less than 0.01) by an amount corresponding to the decrease in Rrs in the control airway. However, in constricted airways, PPRla was higher than IRla and about the same as ERla. We suggest that the panting maneuver is suitable for minimizing the effect of laryngeal artifact in the control airway, but in the constricted airway the panting maneuver may fail to cause widening of the laryngeal orifice.

Impedance of intrathoracic airway models during low-frequency periodic flow

1979 ◽  
Vol 47 (2) ◽  
pp. 347-351 ◽  
Author(s):  
J. J. Fredberg ◽  
J. Mead
Keyword(s):  
Low Frequency ◽  
Velocity Profiles ◽  
Tracheobronchial Tree ◽  
Lower Airway ◽  
Distributed Parameter ◽  
Viscous Effects ◽  
Distributed Parameter Model ◽  
Wall Compliance ◽  
Airway Walls ◽  
Distribution Of Flow

The total pulmonary and lower airway impedances of the normal adult lung were simulated from 0.5 to 10 Hz using a distributed parameter model of the complete tracheobronchial tree. The model includes branching asymmetry; distributed representation of gas compliance, inertance, viscous effects, and inertial distortion of velocity profiles; and nonrigid airway walls. The model predicts closely similar resistance and frequency dependence of resistance but substantially greater reactances than observed by Finucane et al. (J. Appl. Physiol. 38: 517--530, 1975). Increases in resistance with frequency could be explained by changes in the distribution of flow among parallel inhomogeneities (47%), inertial distortion of velocity profiles (35%), changes in the serial distribution of flow due to gas compliance (11%), and airway wall compliance (7%). The disparity between measured and simulated reactance is attirbutable to artifact in the previously reported reactance measurement.

scholarly journals Simplified Building Thermal Model Development and Parameters Evaluation Using a Stochastic Approach

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2899
Author(s):  
Abhinandana Boodi ◽  
Karim Beddiar ◽  
Yassine Amirat ◽  
Mohamed Benbouzid
Keyword(s):  
Reference Model ◽  
Model Development ◽  
Network Models ◽  
Real Data ◽  
Stochastic Approach ◽  
Simplified Model ◽  
Model Parameters ◽  
Order Model ◽  
Parameter Values ◽  
Low Order

This paper proposes an approach to develop building dynamic thermal models that are of paramount importance for controller application. In this context, controller requires a low-order, computationally efficient, and accurate models to achieve higher performance. An efficient building model is developed by having proper structural knowledge of low-order model and identifying its parameter values. Simplified low-order systems can be developed using thermal network models using thermal resistances and capacitances. In order to determine the low-order model parameter values, a specific approach is proposed using a stochastic particle swarm optimization. This method provides a significant approximation of the parameters when compared to the reference model whilst allowing low-order model to achieve 40% to 50% computational efficiency than the reference one. Additionally, extensive simulations are carried to evaluate the proposed simplified model with solar radiation and identified model parameters. The developed simplified model is afterward validated with real data from a case study building where the achieved results clearly show a high degree of accuracy compared to the actual data.

Effect of different mask design for measuring respiratory input impedance in pre-school children by forced oscillation technique (FOT)

2017 ◽  
Author(s):  
Pasquale Pio Pompilio ◽  
Delcourt Caroline ◽  
Alessandro Gobbi ◽  
Roberto Perissin ◽  
Raffaele Dellacà ◽  
...  
Keyword(s):  
School Children ◽  
Input Impedance ◽  
Forced Oscillation ◽  
Forced Oscillation Technique ◽  
Mask Design

Beyond Description in Interpersonal Construct Validation

Assessment ◽  
2016 ◽  
Vol 24 (1) ◽  
pp. 3-23 ◽  
Author(s):  
Johannes Zimmermann ◽  
Aidan G. C. Wright
Keyword(s):  
Structural Model ◽  
Dimensional Space ◽  
Construct Validation ◽  
Theory Building ◽  
Interpersonal Circumplex ◽  
Real World Data ◽  
Or Groups ◽  
Wide Range ◽  
Parameter Values ◽  
Structural Summary

The interpersonal circumplex is a well-established structural model that organizes interpersonal functioning within the two-dimensional space marked by dominance and affiliation. The structural summary method (SSM) was developed to evaluate the interpersonal nature of other constructs and measures outside the interpersonal circumplex. To date, this method has been primarily descriptive, providing no way to draw inferences when comparing SSM parameters across constructs or groups. We describe a newly developed resampling-based method for deriving confidence intervals, which allows for SSM parameter comparisons. In a series of five studies, we evaluated the accuracy of the approach across a wide range of possible sample sizes and parameter values, and demonstrated its utility for posing theoretical questions on the interpersonal nature of relevant constructs (e.g., personality disorders) using real-world data. As a result, the SSM is strengthened for its intended purpose of construct evaluation and theory building.

scholarly journals Analyses of a Dipole Antenna Loaded by a Cylindrical Shell of Double Negative (DNG) Metamaterial

2007 ◽  
Vol 2007 ◽  
pp. 1-10 ◽  
Author(s):  
Khan M. Z. Shams ◽  
Mohammod Ali
Keyword(s):  
Cylindrical Shell ◽  
Input Impedance ◽  
Dipole Antenna ◽  
Double Negative ◽  
Beam Splitting ◽  
Thin Cylindrical Shell ◽  
Half Wavelength ◽  
Antenna Length ◽  
Galerkin Formulation ◽  
Parameter Values

The current distribution, input impedance, and radiation pattern of a cylindrical dipole antenna enclosed by a thin cylindrical shell of double negative (DNG) metamaterial are computed using the piecewise sinusoidal Galerkin formulation. In the presence of the DNG shell, the dipole antenna exhibits three interesting characteristics. The input impedance shows potentials for wide bandwidth due to the relative insensitivity of the impedance with frequency. Within specific ranges of DNG material parameter values, the dipole shows resonance at much lower frequencies than its resonant frequency in free space. The dipole does not show change in the direction of the principal beam nor does it show signs of beam splitting and side lobes even when the antenna length approaches one and a half wavelength.

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