Predicted Transfer Functions Research Articles

Simplified prediction models for acoustic installation effects of train-mounted equipment

Acoustic models of railway vehicles in standstill and pass-by conditions can be used as part of a virtual certification process for new trains. For each piece of auxiliary equipment, the sound power measured on a test bench is combined with measured or predicted transfer functions. It is important, however, to allow for installation effects due to shielding by fairings or the train body. In the current work, fast-running analytical models are developed to determine these installation effects. The model for roof-mounted sources takes account of diffraction at the corner of the train body or fairing, using a barrier model. For equipment mounted under the train, the acoustic propagation from the sides of the source is based on free-field Green’s functions. The bottom surfaces are assumed to radiate initially into a cavity under the train, which is modelled with a simple diffuse field approach. The sound emitted from the gaps at the side of the cavity is then assumed to propagate to the receivers according to free-field Green’s functions. Results show good agreement with a 2.5D boundary element model and with measurements. Modelling uncertainty and parametric uncertainty are evaluated. The largest variability occurs due to the height and impedance of the ground, especially for a low receiver. This leads to standard deviations of up to 4 dB at low frequencies. For the roof-mounted sources, uncertainty over the location of the corner used in the equivalent barrier model can also lead to large standard deviations.

Improvement of predictive control algorithm based on fuzzy fractional order PID

Abstract The existing predictive control strategy has comprehensive prior knowledge of the controlled process, requires weak continuity of the search space for parameter optimization, and its application is limited to some extent. Therefore, improved research on the fuzzy fractional proportional integral differential (PID) predictive control algorithm is proposed. First, the control principle of PID predictive control equipment is proposed. According to this principle, the structure of the PID predictive control equipment adaptive fuzzy PID energy-saving controller is constructed. Through the PID energy-saving control parameter setting principle and fuzzy control rules, the adaptive fuzzy PID energy-saving control of PID predictive control equipment is realized. Finally, the fractional order PID predictive transfer function model is constructed to improve the predictive control algorithm based on PID optimization technology. The experimental results show that the accuracy and efficiency of the designed algorithm can get the best performance index, and its stability, overshoot, time, and control accuracy are basically unchanged. In the small area temperature control, the disturbance interference is small, the anti-disturbance ability is good, and it has strong robustness.

Artificial Neural Network Modeling for Airline Disruption Management

Since the 1970s, most airlines have incorporated computerized support for managing disruptions during flight schedule execution. However, existing platforms for airline disruption management (ADM) employ monolithic system design methods that rely on the creation of specific rules and requirements through explicit optimization routines, before a system that meets the specifications is designed. Thus, current platforms for ADM are unable to readily accommodate additional system complexities resulting from the introduction of new capabilities, such as the introduction of unmanned aerial systems, operations, and infrastructure, to the system. To this end, historical data on airline scheduling and operations recovery are used to develop a system of artificial neural networks (ANNs), which describe a predictive transfer function model (PTFM) for promptly estimating the recovery impact of disruption resolutions at separate phases of flight schedule execution during ADM. Furthermore, this paper provides a modular approach for assessing and executing the PTFM by employing a parallel ensemble method to develop generative routines that amalgamate the system of ANNs. Our modular approach ensures that current industry standards for tardiness in flight schedule execution during ADM are satisfied, while accurately estimating appropriate time-based performance metrics for the separate phases of flight schedule execution.

Transfer function replacement of phenomenological single-mode equations in semiconductor microcavity modeling.

Semiconductor microcavities are frequently studied in the context of semiconductor lasers and in application-oriented fundamental research on topics such as linear and nonlinear polariton systems, polariton lasers, polariton pattern formation, and polaritonic Bose-Einstein condensates. A commonly used approach to describe theoretical properties includes a phenomenological single-mode equation that complements the equation for the nonlinear optical response (interband polarization) of the semiconductor. Here, we show how to replace the single-mode equation by a fully predictive transfer function method that, in contrast to the single-mode equation, accounts for propagation, retardation, and pulse-filtering effects of the incident light field traversing the distributed Bragg reflector (DBR) mirrors, without substantially increasing the numerical complexity of the solution. As examples, we use cavities containing GaAs quantum wells and transition-metal dichalcogenides (TMDs).

Determination of the transfer function between the injected flow-rate and high-pressure time histories for improved control of common rail diesel engines

Theoretical and experimental methodologies have been proposed and illustrated to determine the transfer function between the injected flow-rate and the rail pressure for common rail injection systems. An analytical transfer function has been calculated in the frequency domain, utilizing a previously developed lumped parameter model of the overall hydraulic layout of a common rail system. The predicted transfer function has been compared, in a Bode diagram, with an experimental estimation of the transfer function, based on the measured rail pressure and injected flow-rate time histories that were acquired at the hydraulic rig for different working conditions. The experimental estimation of the transfer function has been worked out by applying a selective spectral technique in order to reduce the effects of measurement noise on the rail pressure and injected flow-rate time histories. The accuracy of the model-derived transfer function has been improved significantly by integrating a pressure control system sub-model, which includes the action of the electronic control unit on the rail pressure time history through the pressure regulator, in the hydraulic model of the common rail circuit. Finally, the time histories of the rail pressure, predicted by means of the complete injection apparatus model, have been compared with the corresponding experimental traces at different working conditions and a very satisfactory agreement has in general been found. The methodologies proposed for the accurate evaluation of the transfer function between the injected flow-rate and the rail pressure time histories can be applied to diesel engines in order to implement innovative closed-loop strategies for the injected mass control.

Impact of water saturation on seismoelectric transfer functions: a laboratory study of coseismic phenomenon

Seismic waves propagating in a porous medium, under favourable conditions, generate measurable electromagnetic fields due to electrokinetic effects. It has been proposed, following experimental and numerical studies, that these so-called ‘seismoelectromagnetic’ couplings depend on pore fluid properties. The theoretical frame describing these phenomena are based on the original Biot's theory, assuming that pores are fluid-filled. We study here the impact of a partially saturated medium on amplitudes of those seismoelectric couplings by comparing experimental data to an effective fluid model. We have built a 1-m-length-scale experiment designed for imbibition and drainage of an homogeneous silica sand; the experimental set-up includes a seismic source, accelerometers, electric dipoles and capacitance probes in order to monitor seismic and seismoelectric fields during water saturation. Apparent velocities and frequency spectra (in the kiloHertz range) are derived from seismic and electrical measurements during experiments in varying saturation conditions. Amplitudes of seismic and seismoelectric waves and their ratios (i.e. transfer functions) are discussed using a spectral analysis performed by continuous wavelet transform. The experiments reveal that amplitude ratios of seismic to coseismic electric signals remain rather constant as a function of the water saturation in the Sw = [0.2–0.9] range, consistently with theoretically predicted transfer functions.

Comparison Between the Theoretical and Experimental Performance of a Differential Mobility Analyzer with Three Monodisperse-Particle Outlets

Differential mobility analyzers (DMAs) with more than one monodisperse-particle outlet can offer a number of advantages compared to conventional single monodisperse-particle outlet designs. A generalized theoretical model and experimental measurements describing the performance of a DMA with 3 monodisperse-particle outlets have been independently reported in the literature. The objective of this article is to compare the theoretical predictions with the measurements. Resolutions determined by the theoretically predicted transfer functions for the three monodisperse-particle outlets are compared with measurements when the DMA was operated under different operating conditions. Predictions and measurements show good agreement when the DMA is operated at low sheath flow rates and for aerosol outlets relatively far from the aerosol inlet. For aerosol outlets relatively near the inlet there is evidence that the discrepancy between theoretical predictions and measurements may disappear at higher sheath flow rate...

Acoustic noise synthesis for duct systems

Studies on acoustical noise from duct systems are important in their design and performance. A methodology is presented for simulation of acoustical noise from a duct system which can be modeled in terms of source, duct element and termination. In this methodology first the transfer function of the given duct system is evaluated using the four pole parameters of the duct system, source strength, source acoustic and termination acoustic impedances. Then the impulse response of the predicted transfer function is convolved with source signal to obtain the acoustic noise output of the duct system in frequency domain. In order to verify this methodology, the simulated noise is compared with experimentally measured noise for two types of duct systems namely a straight pipe and a simple expansion chamber. The results show good agreement between the simulated and measured noise spectra. The methodology presented in this work provides the capability of simulating the noise of a duct system from its design before it is actually built. Also sound quality studies can be based on design that would assist in reaching the final design to be fabricated

System for configuring audio system

A system is provided for configuring an audio system for a given space. The system may statistically analyze potential configurations of the audio system to configure the audio system. The potential configurations may include positions of the loudspeakers, numbers of loudspeakers, types of loudspeakers, listening positions, correction factors, or any combination thereof. The statistical analysis may indicate at least one metric of the potential configuration including indicating consistency of predicted transfer functions, flatness of the predicted transfer functions, differences in overall sound pressure level from seat to seat for the predicted transfer functions, efficiency of the predicted transfer functions, or the output of predicted transfer functions. The system also provides a methodology for selecting loudspeaker locations, the number of loudspeakers, the types of loudspeakers, correction factors, listening positions, or a combination of these schemes in an audio system that has a single listening position or multiple listening positions.

Optimal Deterministic Transfer Function Modelling in the Presence of Serially Correlated Noise

This article addresses the development of predictive transfer function models for nonlinear dynamic processes under serially correlated model error. This work is presented in the context of the block-oriented exact solution technique (BEST) for multiple input, multiple output (MIMO) processes proposed by Bhandari and Rollins (2003) for continuous-time modelling and Rollins and Bhandari (2004) for constrained discrete-time modelling. This work proposes a model building methodology that is able to separately determine the steady state, dynamic and noise model structures. It includes a pre-whitening procedure that is affective for the general class of discrete ARMA(p, q) noise (Box and Jenkins, 1976). The proposed method is demonstrated using a simulated physical system and a real physical system.

Site effects in Parkway Basin: comparison between observations and 3-D modelling

This paper is a contribution towards filling the large gap that currently exists between theoretical and observational studies of site effects. We present results of numerical modelling of ground motion in Parkway Valley, a small alluvial valley in New Zealand. We use a 3-D, finite-difference code, and compute ground motion for the vertical incidence of plane waves,P andS. The results are compared with a thorough analysis of site effects in this basin presented previously, based on the records obtained using a dense temporary seismic array. The results of the simulations confirm the observation that ground motion in Parkway Basin is dominated by locally generated surface waves. Diffracted surface waves are generated mainly towards the south. This direction does not depend on the polarization of the incident waves. We obtain a very good agreement between observed and predicted transfer functions for the two horizontal components of stations located towards the centre of the valley. Our model clearly performs less well towards the edges of the basin, where the details of the real structure are missing in our model. Our results suggest that the 3-D shape of the basin may be more important than a detailed knowledge of the subsoil mechanical properties in predicting ground response. A correct estimate of the absolute amplification level, however, requires a correct estimate of the impedance contrast, but this also applies to any modelling of site response.

Contemporary foraminiferal distributions of a mangrove environment, Great Barrier Reef coastline, Australia: implications for sea-level reconstructions

Contemporary foraminiferal samples and associated environmental information were collected from Cocoa Creek, a mesotidal fringing mangrove environment on the Great Barrier Reef (GBR) coastline, Australia, to elucidate the relationship of the foraminiferal assemblages with elevation and environment. There is a strong and highly significant relationship between elevation and the foraminiferal assemblages, supporting the intertidal vertical zonation concept, which suggests that the distribution of foraminifera in the intertidal zone is usually a direct function of elevation, with the most important controlling factors being the duration and frequency of subaerial exposure. Multivariate analyses separate the intertidal foraminiferal assemblages into three elevational zones, with Zone I the highest and Zone III the lowest: Zones I and II are dominated by agglutinated species Trochammina inflata and Miliammina fusca, respectively; and Zone III is dominated by calcareous species, notably Ammonia tepida and Elphidium discoidale multiloculum. These assemblage zones are similar to those found in both tropical and temperate intertidal environments. A predictive transfer function has been developed to allow reconstruction of former sea levels for tropical environments, based upon the relationship between foraminiferal assemblage and elevation. Results suggest that a precision of ±0.07 m should be attainable, superior to most similar studies from temperate, mid latitude environments. Our work has produced the first foraminifera-based transfer function for environmental interpretations for tropical Australia, and allows the potential development of a new generation of high-resolution sea-level reconstructions for the post-glacial sequences of the GBR shelf.

The motion of a deep-sea remotely operated vehicle system: Part 2: Analytical model

We developed a continuous linear-elastic one-dimensional analytic model that should accurately represent a vertically tethered system subject to surface excitation. Our model accurately predicts: (a) the transfer function between the motion of the ship and cage, (b) the transfer function between ship motion and tension in the tether and (c) the natural frequency and its harmonics of the ROPOS deep-sea ROV system for depths between 0 and 1765 m up to moderately rough sea conditions. By solving the ship–cage motion transfer function for the onset of zero tension in the tether, we were able to predict the amplitude of ship motion that triggers a snap load. The solution to our model requires only two non-dimensional parameters representing the mass ratio of the cage and tether and the force ratio of drag to tension. The predicted transfer function and natural frequency are not excessively sensitive to the value of these parameters for the ROPOS ROV system.

A FORAMINIFERAL-BASED TRANSFER FUNCTION: IMPLICATIONS FOR SEA-LEVEL STUDIES

A dataset consisting of 165 contemporary foraminiferal samples and associated tide level information was compiled by combining data from ten intertidal study areas situated on the east, south and west coasts of the UK. The relationship between the foraminiferal data and a series of environmental variables (elevation, pH, salinity, substrate and vegetation cover) are examined using canonical correspondence analysis (CCA) and partial CCA. To facilitate comparisons between study areas with different tidal ranges, the elevational data are expressed as a standardised water level index (SWLI). The foraminiferal distributions show a strong and highly statistically significant relationship with SWLI. A predictive transfer function has been developed for SWLIs using weighted averaging calibration with inverse and classical deshrinking regression (inverse r 2 jack = 0.74; classical r 2 jack = 0.75). Statistical measures assessing the performance of this model suggest that reliable reconstructions of former sea levels are possible. The transfer function has important implications for establishing continuous records of relative sea-level change or sedimentation.

Two‐microphone measurements of the acoustical properties of plane asphalt surfaces in the presence of wind and temperature gradients.

When performing two‐microphone measurements of surface properties, an algorithm is used to find the properties that give the best fit between measured and predicted transfer functions between the two microphones. Recently it was found necessary to adjust certain geometrical parameters, e.g., the separation between the source and microphones, to obtain an acceptable fit between measured and predicted data measured over asphalt surfaces. It was hypothesized that it was necessary to allow that variation to account for the effects of wind and temperature gradients. That hypothesis has been confirmed by using ray tracing techniques to simulate the effect of wind and temperature gradients on two‐microphone measurements. It has been found that near‐surface gradients have significant effects on both the angle of specular reflection and the path length difference between the direct and reflected arrivals. These effects are particularly important when estimating the properties of high impedance surfaces owing to the rapid change of the reflection coefficient at near‐grazing angles in that case. Nevertheless, it will be shown that the impedance of asphalt can be estimated accurately if the effect of ray curvature is accounted for when fitting measured and theoretical transfer functions.

Ultrasonic measurement of the thickness, phase velocity, density or attenuation of a thin-viscoelastic plate. Part II: the inverse problem

Abstract Part II of this two-part paper is concerned with the inverse problem: given the measured transfer function, deduce any one of the four acoustical properties of a thin, linear-viscoelastic plate (thickness, wave-speed, density or attenuation) given the remaining three, through a comparison with the theoretically predicted transfer function. A systematic and detailed analysis of the sensitivity of the through-transmission transfer function to the four acoustical parameters is presented. An inverse algorithm, which utilizes the well-known secant method in conjunction with the method of least squares, is used to deduce the acoustical parameters. The technique is fully automated and computer controlled and can be easily adapted for in situ NDE applications. The technique is used to measure the acoustical properties of plates made up of aluminium (thickness = 100 μm to 2 mm), steel (25 μm–500 μm), brass (1.625 mm), glass (1 mm), Plexiglas (500 μm–2 mm) and bulk epoxy (1.54mm), using commercially available, low frequency transducers (0.5–10 MHz). The errors are frequency dependent and become progressively worse as frequency decreases. In the case of thickness, where the sensitivity is relatively large, excellent results were obtained down to ( h gl ) = O(10 −2 ) , where h is the layer thickness and λ is the wavelength.

Line profile and variability data to probe the broad-line region geometry - Of disks and nests

A simplified, bidimensional method to test the gas distribution in the broad-line regions of AGNs is proposed. Assuming the geometry of the distribution, the transfer function is derived by inverting the observed line profile. The predicted transfer function can be compared with the one derived independently from variability data. As an example this method have been applied to NGC 5548 assuming two different geometries: a disk, and a «nest.» The former can reproduce very easily the line profile, but the two estimates of the transfer function are largely discrepant. The latter gives a transfer function which agrees with the observed one, at the expenses of a poorer fit to the line shape

The error in a narrow-band transfer function model prediction

The error in narrow-band analytical or physical model predictions is estimated for the example of a harmonic force-driven rectangular plate. It is shown that a 5% uncertainty in input parameters defining structural dimensions, material properties, and source location may account for errors in a predicted transfer function exceeding 10 dB over a reasonably broad bandwidth. It is also shown that this error increases 6 dB per doubling of the (percent) uncertainty. These results imply that in the absence of incoherent averaging, either temporal, spatial, or ensemble, expectations for favorable comparisons of structural acoustic predictions among models, or between model and prototype, may often be unrealistic.

Identification of human lower extremity dynamics in torsion

A four degrees of freedom, damped, linear oscillator model of the lower extremity in torsion was identified through laboratory frequency response tests. The foot was rotated sinusoidally in the mediallateral plane through the 1–20 Hz frequency band at the constant amplitudes 2, 4 and 6 degrees. Weight bearing on the foot, muscle-induced bias torsion and knee flexion were also test variables. Identification was undertaken by minimizing the squared difference between the measured and predicted transfer functions of the pelvis and foot. The model specification and the laboratory identification procedures were the focus of this work. Variations greater than 30% in the identification stiffness, damping and inertia values were predicted over the test variable ranges. The transfer functions recorded in these tests indicated the lower extremity can be modeled as a compliance between a foot inertia and the pelvis-torso inertia. Joint compression, induced by weight bearing, and muscle contraction, measured by the bias torsional moment at the foot, increased the torsional stiffness of the knee, ankle and pelvis model elements, and they had an indeterminate influence on the hip stiffness. The model knee and hip stiffnesses and the model pelvis-torso inertia were maximized, and the model ankle stiffness was minimized at the maximum foot rotation amplitude.