Evaluation Of Transfer Function Research Articles

Comparison of Artificial Neural Networks and the Transfer Function Method for Force Reconstruction in Curved Composite Plates

This paper presents two of the most recent approaches for impact force reconstruction, applied to a curved composite panel. The first one is based on the development of an artificial neural network, while the other on the evaluation of transfer functions in the frequency domain. Both methods provide advantages and disadvantages so that a detailed study should be conducted in order to determine which one can be considered more suitable for impact identification purposes. The aim of this paper is to present a comparison between these two methods, in particular when impacts on different surfaces of the plate are present. The main contribution is the application of the two approaches on a curved composite panel. The radius of curvature plays an important role in the contact force due to impacts on the inner or outer surface of the panel, introducing one more parameter in the reconstruction problem.

RETRACTED: Evaluation of modulation transfer function of optical lens system by support vector regression methodologies – A comparative study

The quantitative assessment of image quality is an important consideration in any type of imaging system. The modulation transfer function (MTF) is a graphical description of the sharpness and contrast of an imaging system or of its individual components. The MTF is also known and spatial frequency response. The MTF curve has different meanings according to the corresponding frequency. The MTF of an optical system specifies the contrast transmitted by the system as a function of image size, and is determined by the inherent optical properties of the system. In this study, the polynomial and radial basis function (RBF) are applied as the kernel function of Support Vector Regression (SVR) to estimate and predict estimate MTF value of the actual optical system according to experimental tests. Instead of minimizing the observed training error, SVR_poly and SVR_rbf attempt to minimize the generalization error bound so as to achieve generalized performance. The experimental results show that an improvement in predictive accuracy and capability of generalization can be achieved by the SVR_rbf approach in compare to SVR_poly soft computing methodology.

Effects of the transfer function evaluation on the impact force reconstruction with application to composite panels

The determination of a reliable transfer function for force reconstruction of impacts on composite panels is addressed in the paper. The reconstruction of the impact force history requires the knowledge of the transfer function which relates the response to the contact force. In this paper, a new method to determine the transfer function of a composite plate, instrumented with surface bonded piezoelectric sensors, is proposed. Impact tests are carried out and the data are used to evaluate the transfer function. The force reconstruction results, obtained by using the new transfer function, are compared with the results obtained with the classic approach. Significant improvements are observed in predicting the force history, particularly when large deflections are present; these are quantifiable as an out of plane displacement of the same order of magnitude as the thickness of the plate. The influence of increasing the impact velocity, with the related increase in the contact force, is also studied. The proposed method provides good results over a range of impact velocities. Multiple impacts were also investigated and the method could correctly reconstruct force histories of consecutive impacts.

基于480×6阵列探测器的红外连续变焦光学系统设计

The design of an infrared zoom optical system based on 480×6focal plane array detector was introduced.The zoom theory,diffractive theory and aspheric design method were used in the aberration balance.The operating wavelength region was 7.7to 10.3μm,F-number was 2.62,and zoom ratio was 15to 1.The result indicates that the zoom optical system could obtain better optical performance in all zoom range,by the general analysis and evaluation of modulation transfer function,distortion curve, diffractive optical element,and zoom curve analysis.The overall length of optical system is 480 millimeter,back focal length is 28 millimeter,modulation transfer function is more than 0.3and distortion is less than 5percent.

Evaluation of the impact of light scatter from glistenings in pseudophakic eyes

To study the impact of light scatter from glistenings in pseudophakic eyes using ray tracing in a model eye Department of Research, Advanced Vision Science, Inc., Goleta, California, USA. Mathematical modeling and simulation. A pseudophakic eye model was constructed in Zemax using the Arizona eye model as the basis. The Mie scattering theory was used to describe the intensity and direction of light as it scatters for a spherical particle immersed in a given media (intraocular lens [IOL]). The modeling and evaluation of scatter and modulation transfer function (MTF) were performed for several biomaterials with various size and density of glistenings under scotopic, mesopic, and photopic conditions. As predicted by the Mie theory, the amount of scatter was a function of the relative difference in refractive index between the media and the scatterer, the size of the scatterer, and the volume fraction of the scatterer. The simulation demonstrated that an increase in density of glistenings can lead to a significant drop in the MTF of the IOL and the pseudophakic eye. This effect was more pronounced in IOLs with smaller cavitations, and the observation was consistent for all tested biomaterials. Mathematical modeling demonstrated that glistenings in IOLs will lead to reduction in the MTF of the IOL and the pseudophakic eye. The loss in MTF was more pronounced at high densities and small cavitation sizes across all biomaterials. Inconsistent and poor clinical quantification of glistenings in IOLs may explain some inconsistencies in the literature.

Nonlinear Parametric Inversion Using Interpolatory Model Reduction

Nonlinear parametric inverse problems appear in several prominent applications; one such application is Diffuse Optical Tomography (DOT) in medical image reconstruction. Such inverse problems present huge computational challenges, mostly due to the need for solving a sequence of large-scale discretized, parametrized, partial differential equations (PDEs) in the forward model. In this paper, we show how interpolatory parametric model reduction can significantly reduce the cost of the inversion process in DOT by drastically reducing the computational cost of solving the forward problems. The key observation is that function evaluations for the underlying optimization problem may be viewed as transfer function evaluations along the imaginary axis; a similar observation holds for Jacobian evaluations as well. This motivates the use of system-theoretic model order reduction methods. We discuss the construction and use of interpolatory parametric reduced models as surrogates for the full forward model. Within the DOT setting, these surrogate models can approximate both the cost functional and the associated Jacobian with very little loss of accuracy while significantly reducing the cost of the overall inversion process. Four numerical examples illustrate the efficiency of the proposed approach. Although we focus on DOT in this paper, we believe that our approach is applicable much more generally.

Evaluation of a collocation method for the analysis of multi-segmented waveguides at high-frequencies

A method for analyzing high-frequency signal propagation in rectilinear waveguides consisting of interconnected segments has been proposed [Ginsberg, POMA 19, 030104 (2013)]. The signal within each segment is represented as a series of modes that either propagate or evanesce in the forward and backward directions. The state variables are the modal amplitudes. Equations for these parameters are obtained by satisfying continuity and boundary conditions on pressure and axial particle velocity at preselected points on transitional cross-sections. This leads to a sequential evaluation of transfer functions for the modal amplitudes. The present work will examine the convergence and accuracy properties of the formulation by comparing its results to those obtained from a classical orthogonality analysis. The system consists of a pair of coaxial circular hard-walled cylinders axisymmetrically excited by a piston covering half the radius at one end, and the other end is rigidly closed. The frequency for the evaluation is slightly greater than the cutoff value for the sixth mode in the narrower segment. Aspects that are examined are computer code verification, metrics for comparing analyses, the influence of the number and placement of the collocation points, and the influence of evanescent modes.

Evaluation of Equivalent Circuit Diagrams and Transfer Functions for Modeling of Lithium-Ion Batteries

AbstractThe rapid developments in the field of electrochemistry, enabled lithium-ion batteries to achieve a very good position among all the other types of energy storage devices. Therefore they became an essential component in most of the modern portable and stationary energy storage applications, where the specific energy and the life time play an important role. In order to analyze and optimize lithium-ion batteries an accurate battery model for the dynamic behavior is required. At the beginning of this paper four different categories of electrical models for li-ion cells are presented. In the next step a comparison between equivalent circuit diagrams and fractional rational functions with the complex variable s is shown for lithium-ion battery modeling. It is described how to identify the parameters of the models in the time domain and also in frequency domain. The validation of the different models is made for high and low dynamic current profiles. In the first step the dependency of all model parameters on the temperature and on the battery age is neglected. These effects will be taken into account in the continuation of this work

Evaluation of Transfer Function and Dynamic Properties from Strain-Controlled Resonant Column Tests

Abstract Dynamic properties of soils can be inferred via curve fitting of the transfer function between the excitation and the induced strain using a resonant column device. The shape of the measured transfer function is distorted and differs from that of the theoretical transfer function because of different shear strain levels at different frequencies in the specimen. The difference becomes more pronounced with increasing shear strain levels. This study presents a new methodology for the evaluation of dynamic properties from an improved transfer function. In this methodology, the soil specimen is excited using a sinusoidal carrier excitation at the desired strain level coupled with simultaneous excitation of a very small strain random noise. The desired strain level induced by the fixed sine controls the resonant frequency of the specimen, whereas the small strain random noise (always kept small) determines the shape of the transfer function and thus the damping coefficient. The results indicate excellent matching of the transfer function obtained from the proposed method and the theoretical transfer function at all shear strain levels. The new methodology also shows good potential for the evaluation of dynamic properties of soils as a function of frequency in resonant column testing.

Application of unsteady flow rate evaluations to identify the dynamic transfer function of a cavitatingVenturi

This study concerns the simulation of the implementation of the Kinetic Differential Pressure (KDP) method used for the unsteady mass flow rate evaluation in order to identify the dynamic transfer matrix of a cavitatingVenturi. Firstly, the equations of the IZ code used for this simulation are introduced. Next, the methodology for evaluating unsteady pressures and mass flow rates at the inlet and the outlet of the cavitatingVenturi and for identifying the dynamic transfer matrix is presented. Later, the robustness of the method towards measurement uncertainties implemented as a Gaussian white noise is studied. The results of the numerical simulations let us estimate the system linearity domain and to perform the Empirical Transfer Function Evaluation on the inlet frequency per frequency signal and on the chirp signal tests. Then the pressure data obtained with the KDP method is taken and the identification procedure by ETFE and by the user-made Auto-Recursive Moving-Average eXogenous algorithms is performed and the obtained transfer matrix coefficients are compared with those obtained from the simulated input and output data.

An evaluation of site-specific, local and regional chironomid-water depth transfer functions using independent palaeohydrological data

An evaluation of site-specific, local and regional chironomid-water depth transfer functions using independent palaeohydrological data

Earthquake Induced Site Effect in the Algiers–Boumerdes Region: Relation Between Spectral Ratios Higher Peaks and Observed Damage During the May 21st M w 6.8 Boumerdes Earthquake (Algeria)

The Algiers–Boumerdes regions were hit by an M w 6.8 destructive earthquake on May 21, 2003. The accelerometric and seismometric networks successfully recorded the main shock and many aftershocks at some locations where the damage was most extensive. A microtremor measurement was performed in the same locations; some of them are localized on the Mitidja basin. In this paper, we propose to analyze earthquake-induced site effect derived from horizontal to vertical spectral ratio from ambient noise (noise horizontal to vertical—NHV), or from very weak, weak, moderate and strong ( peak ground acceleration—PGA >10 % g) seismic motions (EHV), and transfer function evaluation from soil velocity profile data at four sites. H/V spectral ratios are computed by using both Fourier and response spectra. Compared to the transfer function, the obtained results show that in the case of soft soils, NHV as well as EHV give a good estimation of the soil's fundamental frequency, whereas the NHV underestimate the H/V amplitude and the EHV amplitude increase with the seismic motion intensity. In the case of firm soils, whereas the NHV gives flat curves synonymous for a rock site or a bump, the EHV is more appropriate as seen by identifying clear peaks with non negligible amplitude. In the case of soft sites as well as in the case of firm sites, strong peaks at frequencies higher than the fundamental one are found from EHV curves. Those peaks would not be found when looking at NHV ratios alone, are evidenced by the computed transfer function as well as by an analytical formulation, and are in agreement with the observed distribution of damage during the M w 6.8 2003 Boumerdes earthquake. Finally, the same analysis is performed by using response spectra rather than Fourier spectra and leads to the same conclusions. Moreover, the calculation of the response spectra is more easily compared with the smoothing operation of the Fourier spectra.

Mask roughness impact on extreme UV and 193nm immersion lithography

The contribution of mask absorber line edge roughness on printed resist lines is studied for extreme UV and 193nm immersion lithography. Programmed roughness modules were designed for roughness transfer function evaluation on 88nm pitch line space patterns. The tested modules were designed applying variations of roughness amplitude and spatial frequency. Power spectral density analysis was performed on top-down SEM images. The effect of frequency roughness filtering by the lithographic optical system was studied with different illumination settings. It was found that, except for the degradation of the aerial image due to the filtering effect, less performing illuminations show an increased deterioration of the aerial image quality and thus contribute further to line edge roughness. A comparison with previous work was completed on different mask architectures and photoresist platforms. Resist performance can attenuate the roughness transfer from mask but at the cost of worse chemical gradient at the edges of the exposed regions.

Comparison of transfer functions using estimated rational functions to detect winding mechanical faults in transformers

Comparison of transfer functions using estimated rational functions to detect winding mechanical faults in transformers As it is found in the related published literatures, the transfer function (TF) evaluation method is the most feasible method for detection of winding mechanical faults in transformers. Therefore, investigation of an accurate method for evaluation of the TFs is very important. This paper presents three new indices to compare the transformer TFs and consequently to detect the winding mechanical faults. These indices are based on estimated rational functions. To develop the method, the necessary measurements are carried out on a 1.3 MVA transformer winding, under intact condition, as well as different fault conditions (axial displacement of winding). The obtained results demonstrate the high potential of proposed method in comparison with two other well-known indices. Additionally, two important methods for describing TFs by rational functions are studied and compared in this paper.

Effects of image resampling on modulation transfer function evaluation

Effects of image resampling on modulation transfer function evaluation

Development and evaluation of transfer functions for a variable speed compressor

In this study, transfer functions of electronic expansion valve and variable speed scroll compressor in a chiller system are developed based on an experimental analysis. Dynamic behaviours of water temperature at chiller output and refrigerant superheat at evaporator outlet have either the first- or the second-order linear models, respectively. Different from the existing modelling studies in literature novel models are presented for variable speed refrigeration system with scroll compressor and liquid type evaporator. The scroll compressor used in the current study is not produced for variable speed operation however it is operated with some limitations in the range of 30 to 50 Hz through an inverter. Similar restrictions are presented for the electronic expansion valve as 10 per cent to 35 per cent opening range because of operational limitations. To validate transfer functions of the variable speed scroll compressor and electronic expansion valve, mean square error values for all transfer functions are calculated. The mean square error values vary between 0.0126 and 0.3116. In addition, all transfer functions are designed and tested using corresponding proportional–integral–derivative controllers in order to see their applicability. The results indicate that energy savings are a consequence of operating the chiller at smaller frequencies than the basic 50 Hz while partial load occurred.

Power line communication channel modeling with Orthogonal Frequency Division Multiplexing signal modulation in LabView

The aim of this work is development of algorithm for evaluation of transfer function in power line communication (PLC) channel with narrowband orthogonal frequency division multiplexing (OFDM) signal modulation using convenient user interface. This algorithm can be used while planning PLC system. There were explored long line and parametric model of power line. Assuming similarity of wireless and power line communication the influence of multipath on line impedance was investigated. It was shown that signal amplitude is Ricean distributed. The coefficients for this variance distribution were derived from the attenuation parametric modeling. For simulation LabView program interface was chosen. The developed algorithm permits evaluation of maximal distance between receiver and transmitter that doesn’t require repeater installation.

A systematic method for designing depth-fused multi-focal plane three-dimensional displays

Lack of accurate focus cues in conventional stereoscopic displays has potentially significant effects on depth perception accuracy and visual fatigue. Recently several multi-focal plane display prototypes have been demonstrated with the promise of improving the accuracy of focus cue rendering in stereoscopic displays. In this paper, we present a systematic method to address two fundamental issues in designing a multi-focal plane display: (1) the appropriate dioptric spacing between adjacent focal planes; and (2) the depth-weighted fusing function to render a continuous three-dimensional (3-D) volume using a sparse number of focal planes placed in the space. By taking account of both ocular factors of the human visual system (HVS) and display factors of a multi-focal plane system, we determine that an appropriate spacing between two adjacent focal planes should be ~0.6 diopter (D) while a smaller spacing may be necessary for further improving retinal image quality. We further develop a set of nonlinear depth-weighted fusing function with the promise of balancing perceptual continuity of a 3-D scene and retinal image quality. Our method was based on quantitative evaluation of the modulation transfer functions (MTF) of depth-fused images formed on retina.

Modulation transfer function evaluation of cone beam computed tomography for dental use with the oversampling method

The aim was to investigate the possibility of evaluating the modulation transfer function (MTF) of cone beam CT (CBCT) for dental use using the oversampling method. The CBCT apparatus (3D Accuitomo) with an image intensifier was used with a 100 mum tungsten wire placed inside the scanner at a slight angle to the plane perpendicular to the plane of interest and scanned. 200 contiguous reconstructed images were used to obtain the oversampling line-spread function (LSF). The MTF curve was obtained by computing the Fourier transformation from the oversampled LSF. Line pair tests were also performed using Catphan(R). The oversampling method provided smooth and reproducible MTF curves. The MTF curves revealed that the spatial resolution in the z-axis direction was significantly higher than that in the axial direction. This result was also confirmed by the line pair test. MTF analysis was performed successfully using the oversampling method. In addition, this study clarified that the 3D Accuitomo had high spatial resolution, especially in the z-axis direction.

Composite modulation transfer function evaluation of a cone beam computed tomography breast imaging system

Several factors during the scanning process, image reconstruction and geometry of an imaging system, influence the spatial resolution of a computed tomography imaging system. In this work, the spatial resolution of a state of the art flat panel detector-based cone beam computed tomography breast imaging system is evaluated. First, scattering, exposure level, voltage, voxel size, pixel size, back-projection filter, reconstruction algorithm, and number of projections are varied to evaluate their effect on spatial resolution. Second, its uniformity throughout the whole field of view is evaluated as a function of radius along the x-y plane and as a function of z at the center of rotation. The results of the study suggest that the modulation transfer function is mainly influenced by the pixel, back-projection filter, and number of projections used. The evaluation of spatial resolution throughout the field of view also suggests that this imaging system does have a 3-D quasi-isotropic spatial resolution in a cylindrical region of radius equal to 40 mm centered at the axis of rotation. Overall, this study provides a useful tool to determine the optimal parameters for the best possible use of this cone beam computed tomography breast imaging system.