Analysis Of Transfer Functions Research Articles

Investigation of Conducted Noise Impact on Conducted Susceptibility Testing for a Wireless Power Transfer System with Bifurcation Phenomena

This paper presents the modeling of bifurcation phenomena in a wireless power transfer (WPT) system along with its application in the testing of conducted susceptibility (CS). The presented model represents an analytic transfer function based on the equivalent circuit models of strongly coupled coils, and its validation was performed using a simple WPT system designed and fabricated as equipment under test (EUT). Additionally, experimental verification of effectiveness of the presented model was performed via transfer-function measurement. The presented model was applied to estimate the impact of conducted noise on measurement-based CS testing of WPT systems demonstrating bifurcation phenomena. Results obtained in this investigation demonstrate that the impact of conducted noise with bifurcation phenomena can be successfully estimated using the presented model.

Accelerating silicon photonic parameter extraction using artificial neural networks

We present a novel silicon photonic parameter extraction tool that uses artificial neural networks. While other parameter extraction methods are restricted to relatively simple devices whose responses are easily modeled by analytic transfer functions, this method is capable of extracting parameters for any device with a discrete number of design parameters. To validate the method, we design and fabricate integrated chirped Bragg gratings. We then estimate the actual device parameters by iteratively fitting the simultaneously measured group delay and reflection profiles to the artificial neural network output. The method is fast, accurate, and capable of modeling the complicated chirping and index contrast.

Further observations on a principal components analysis of head-related transfer functions

Humans can externalise and localise sound-sources in three-dimensional (3D) space because approaching sound waves interact with the head and external ears, adding auditory cues by (de-)emphasising the level in different frequency bands depending on the direction of arrival. While virtual audio systems reproduce these acoustic filtering effects with signal processing, huge memory-storage capacity would be needed to cater for many listeners because the filters are as unique as the shape of each person’s head and ears. Here we use a combination of physiological imaging and acoustic simulation methods to confirm and extend previous studies that represented these filters by a linear combination of a small number of eigenmodes. Based on previous psychoacoustic results we infer that more than 10, and as many as 24, eigenmodes would be needed in a virtual audio system suitable for many listeners. Furthermore, the frequency profiles of the top five eigenmodes are robust across different populations and experimental methods, and the top three eigenmodes encode familiar 3D spatial contrasts: along the left-right, top-down, and a tilted front-back axis, respectively. These findings have implications for virtual 3D-audio systems, especially those requiring high energy-efficiency and low memory-usage such as on personal mobile devices.

Analytic Calculation of Jitter Induced by Power and Ground Noise Based on IBIS I/V Curve

Supply fluctuation is one of the most significant factors that cause jitter in high-speed I/O links. The traditional SPICE simulation or measuring method for power supply induced jitter is quite time-consuming and draining on resources. The I/O buffer information specification (IBIS) model is a popular standard for electronic behavioral specifications of digital integrated circuit I/O characteristics. Analytic jitter transfer functions for supply fluctuations are derived by solving two-order differential equations based on IBIS current versus voltage characteristics and pin package parameters. Then, the total time interval error induced by power and ground noise is obtained in both frequency domain and time domain. The method is validated by comparing the analytic calculation results with HSPICE simulated results for a DDR4 output buffer.

Performance Analysis of Artificial Neural Networks Training Algorithms and Transfer Functions for Medium-Term Water Consumption Forecasting

Artificial Neural Network (ANN) is a widely used machine learning pattern recognition technique in predicting water resources based on historical data. ANN has the ability to forecast close to accurate prediction given the appropriate training algorithm and transfer function along with the model’s learning rate and momentum. In this study, using the Neuroph Studio platform, six models having different combination of training algorithms, namely, Backpropagation, Backpropagation with Momentum and Resilient Propagation and transfer functions, namely, Sigmoid and Gaussian were compared. After determining the ANN model’s input, hidden and output neurons from its respective layers, this study compared data normalization techniques and showed that Min-Max normalization yielded better results in terms of Mean Square Error (MSE) compared to Max normalization. Out of the six models tested, Model 1 which was composed of Backpropagation training algorithm and Sigmoid transfer function yielded the lowest MSE. Moreover, learning rate and momentum value for the models of 0.2 and 0.9 respectively resulted to very minimal error in terms of MSE. The results obtained in this research clearly suggest that ANN can be a viable forecasting technique for medium-term water consumption forecasting.

Combination of Data-driven Feature Selection Methods with Domain Knowledge for Diagnosis of Railway Vehicles

Railway vehicles are generally maintained preventively within certain time periods. Condition based predictive maintenance strategies have a great economic potential so that modern trains are equipped with many sensors in order to perform diagnostics and prognostics of components.Methods for fault detection need appropriate feature subsets in order to achieve small in-sample and out-sample errors. In our case the typical feature selection approach using pure data-driven methods is difficult, as the number of possible feature sets is very large. On the other hand there exists rich domain knowledge and detailed physical models of the mechanical system. The aim is to combine this knowledge with the often used mathematical methods for feature selection for improving classification of cases when a faulty damper is present. Based on the dynamic equations of motion, this paper presents heuristic feature selection via the analysis of transfer functions. We describe several wellknown methods of automated feature selection and a workflow which combines domain knowledge with automated methods. Results show that it is difficult to definefeatures based only on domain-knowledge, but in combination with data-driven techniques good classification performance can be achieved.

Electromagnetic signals on active volcanoes: Analysis of electrical resistivity and transfer functions at Taal volcano (Philippines) related to the 2010 seismovolcanic crisis

Electromagnetic (EM) methods are powerful for imaging lithology, geological discontinuities, and hydrothermal and plumbing systems of volcanoes. These methods can also be efficiently used for monitoring temporal changes related to the time evolution of volcanic activity. However, the magnetotelluric (MT) technique has not been yet investigated on many volcanoes. In this study, we take advantage of simultaneous magnetic and electric records made on Taal volcano in The Philippines to prospect if resistivity changes were related to the 2010–2011 seismovolcanic crisis. The seismicity began on April 19, 2010 and abruptly raised up on April 29. The crisis vanished nine months later on March 2011, and was characterized by the appearance of a source of deformation at 5km depth which gave birth to a secondary deformation source located in the hydrothermal system at about 2.5km depth some weeks later. Two stations, DAK and MCL, located respectively on the northern flank and inside the summit crater, were simultaneously recording the horizontal North-South and East-West components of both magnetic and electric fields from March 11 to June 13, 2010. 1D inversion modeling shows that resistivity at the depth of 5km where dikes and deformation sources are positioned, is estimated smaller a ten of Ωm. Temporal changes of the apparent resistivity and power spectra of the components of the EM field are analyzed using both a single station approach at the two DAK and MCL stations, and a remote reference technique with a far (~3000km) and a near station (~1.1km). Local noises due to radio transmitters at stations prevent studying signals below 10s of period. The day-to-day time-lapse analysis with the single station method shows several clear decreases of the apparent resistivity at the station inside the crater, and high fluctuations at the station outside of it, both in relation to the crisis for periods less than few hundred seconds . Application of the remote reference technique with far and close remote stations leads to assume that there was no clear change at the station located in the crater, while some fluctuating resistivity changes could have occurred at the second station DAK. Furthermore, the MT responses undoubtedly show that other local EM signals have taken place on the volcano before and during the crisis. In particular, electric signals linked to the reactivation of fissures and disturbances of ground fluids are present.

Geomagnetic coast effect at two Croatian repeat stations

<p>Knowledge of inductive effects is important for the reliability of geomagnetic surveys as well as reduction of measurements, and hence for the accuracy of models and maps of the Earth’s magnetic field. Detection of anomalous induced fields, due to the geomagnetic coast effect, was carried out by the transfer function method to estimate the induction arrows indicating areas of anomalous induced currents. To determine the transfer function at the two coastal Croatian repeat stations used in this study, the so-called geomagnetic plane-wave events from July 2010 were used. Analysis of transfer functions for Krbavsko polje and Sinjsko polje first order repeat stations, using observatories Grocka and Tihany as references, revealed the existence of the Adriatic coastal effect on periods of 10-65 minutes.</p>

Some investigations on properties of spatial principal components analysis of individual head-related transfer functions

Analysis for compact representation of spatial change of Head-Related Transfer Functions (HRTFs) based on principal components analysis (PCA), called Spatial PCA (SPCA), is investigated in this report. Although the SPCA of HRTFs has been researched for about 30 years, there exist some questions left unclear. In this report, the author tries to answer the following two questions: (1) how much amount of data (number of subjects and/or directions) is enough for generation of principal components, and (2) which domain (impulse response, frequency spectrum, etc.) is the best for compact representation of individual HRTFs based on the SPCA. As for (1), the amount of data may be relatively small as a result of the preliminary investigation, meaning that the HRTFs of a certain subject can be reconstructed by using the SPCA with the HRTFs of the other subjects of relatively small numbers. As for (2), the author concluded that the complex frequency spectrum brings about the most compact representation as the result...

Sound field interpolation in the spatial domain with a rigid spherical microphone array

Sound field interpolation aims to calculate sound fields at arbitrary points from original measurements at discrete points. Rigid spherical microphone arrays are effective for interpolation because they can capture sound from several directions with uniform resolution. Interpolation from spherical array measurements is typically based on the spherical Fourier transform and assumes no prior knowledge concerning the source positions. The spherical Fourier transform, however, yields results whose accuracy strongly depends on microphone positioning and the inversion method used for its computation. When knowledge of the source positions is available, the pressure generated at any point on the rigid spherical baffle can be estimated with an existing physical model. This model was used in this study to define an analytic transfer function that relates the pressure at two arbitrary points on a rigid sphere. Based on this analytic function, an interpolation method in the spatial domain is presented as an alternative to transformed domain methods. Numerical experiments with a rigid sphere showed that accurate interpolation of magnitude and phase, over the full range of frequencies, is possible on the side of the array ipsilateral to the sound sources. However, on the contralateral side, accuracy systematically decreased as frequency increased.

Analysis of Channel Transfer Functions in Power Line Communication System for Smart Metering and Home Area Network

The paper deals with simulations of power line channel transfer functions in Network Simulator version 3. Firstly, an empirical model and calculation of the channel transfer function a ...

Three‐dimensional modelling of magnetotelluric data to image Sehqanat hydrocarbon reservoir in southwestern Iran

ABSTRACTA detailed magnetotelluric survey was conducted in 2013 in the Sehqanat oil field, southwestern Iran to map the geoelectrical structures of the sedimentary Zagros zone, particularly the boundary between the Gachsaran Formation acting as cap rock and the Asmari Formation as the reservoir. According to the electrical well logs, a large resistivity contrast exists between the two formations. The Gachsaran Formation is formed by tens to hundreds of metres of evaporites and it is highly conductive (ca. 1 Ωm–10 Ωm), and the Asmari Formation consists of dense carbonates, which are considerably more resistive (more than 100 Ωm). Broadband magnetotelluric data were collected along five southwest–northeast directed parallel lines with more than 600 stations crossing the main geological trend. Although dimensionality and strike analysis of the magnetotelluric transfer functions showed that overall they satisfied local 2D conditions, there were also strong 3D conditions found in some of the sites. Therefore, in order to obtain a more reliable image of the resistivity distribution in the Sehqanat oil field, in addition to standard 2D inversion, we investigated to what extent 3D inversion of the data was feasible and what improvements in the resistivity image could be obtained. The 2D inversion models using the determinant average of the impedance tensor depict the main resistivity structures well, whereas the estimated 3D model shows significantly more details although problems were encountered in fitting the data with the latter. Both approaches resolved the Gachsaran–Asmari transition from high conductivity to moderate conductivity. The well‐known Sehqanat anticline could also be delineated throughout the 2D and 3D resistivity models as a resistive dome‐shaped body in the middle parts of the magnetotelluric profiles.

Analytic Transfer Functions for the Dynamics & Control of Flexible Rotating Spacecraft Performing Large Angle Maneuvers

A symmetric flexible rotating spacecraft can be modeled as a distributed parameter system of a rigid hub attached to two flexible appendages with tip masses. First, Hamilton’s extended principle is utilized to establish a general treatment for deriving the dynamics of multi-body dynamical systems to establish a hybrid system of integro-partial differential equations that model the evolution of the system in space and time. A Generalized State Space (GSS) system of equations is constructed in the frequency domain to obtain analytic transfer functions for the rotating spacecraft. This model does not include spatial discretization. The frequency response of the generally modeled spacecraft and a special case with no tip masses are presented. Numerical results for the system frequency response obtained from the analytic transfer functions are presented and compared against the classical assumed modes numerical method with two choices of admissible functions. The truncation-error-free analytic results are used to validate the numerical approximations and to agree well with the classical widely used finite dimensional numerical solutions. Fundamentally, we show that the rigorous transfer function, without introduction of spatial discretization, can be directly used in control law design with a guarantee of Lyapunov stable closed loop dynamics. The frequency response of the system is used in a classical control problem where the Lyapunov stable controller is derived and tested for gain selection. The correlation between the controller design in the frequency domain utilizing the analytic transfer functions and the system response is analyzed and verified. The derived analytic transfer functions provide a powerful tool to test various control schemes in the frequency domain and a validation platform for existing numerical methods for distributed parameters models. The same platform has been used to obtain the frequency response of more complex beam models following Timoshenko beam theory and the control problem for such models can be pursued in future works.

Acoustic transfer functions and speech intelligibility in permanent wearing headsets

A detailed analysis of the acoustic transfer functions has been investigated for different locations of the headset microphones in the area of human head. Amplitude-frequency and phase-frequency characteristics of acoustic signals are discussed in the report. The signals have been recorded with the micro-mechanical-electrical-system (MEMS) microphones located on a mannequin, simulating the acoustic properties of the human torso. The the source of the signals is an emitter built in the mouth of the manikin's head. Analysis of the characteristics has shown that the acoustic signals undergo significant phase and amplitude changes associated with the interference and diffraction processes. These changes result in significant nonlinearity phase characteristics, and this nonlinearity depends on the installation location of the MEMS microphone. Also quality of speech intelligibility has been estimated by the method of expert evaluation and the speech has been recorded for different positions of the microphones and speaker head. A comparative analysis of the results has shown the optimal location of the microphones in the ear and on the breast of man.

Effect of Control Method on Impedance-Based Interactions in a Buck Converter

All the interconnected regulated systems are prone to impedance-based interactions making them sensitive to instability and transient-performance degradation. The applied control method affects significantly the characteristics of the converter in terms of sensitivity to different impedance interactions. This paper provides for the first time the whole set of impedance-type internal parameters and the formulas according to which the interaction sensitivity can be fully explained and analyzed. The formulation given in this paper can be utilized equally either based on measured frequency responses or on predicted analytic transfer functions. Usually, the distributed dc–dc systems are constructed by using ready-made power modules without having thorough knowledge on the actual power-stage and control-system designs. As a consequence, the interaction characterization has to be based on the frequency responses measureable via the input and output terminals. A buck converter with four different control methods is experimentally characterized in frequency domain to demonstrate the effect of control method on the interaction sensitivity. The presented analytical models are used to explain the phenomena behind the changes in the interaction sensitivity.

Processing of Ultrahigh-Resolution Spaceborne Sliding Spotlight SAR Data on Curved Orbit

In high-resolution spaceborne synthetic aperture radars (SARs), with increasing synthetic aperture length on curved orbits, the hyperbolic range history (HRH) assumption deteriorates, and simple analytic transfer functions in the Doppler domain used in SAR processing do not exist. A subsection HRH model is proposed. Ultra- high-resolution sliding spotlight SAR data can be handled satisfactorily, and simple analytic transform functions are used all the same. The proposed range history model is also applicable to bistatic SARs.

Analytical Transfer Functions Relating Power and Ground Voltage Fluctuations to Jitter at a Single-Ended Full-Swing Buffer

The transfer functions relating supply voltage fluctuations to jitter are analytically derived in closed form expressions for a single-ended buffer. The analytic transfer functions are derived from a linear differential equation obtained from asymptotic linear inverter I-V curves. The transfer functions are validated by comparison with HSPICE simulations. The estimated jitter is compared with the simulated jitter using eye diagrams with single-frequency and multitone supply voltage fluctuations.

One year stored corneas: is it possible?

AbstractPurpose To evaluate the endothelial characteristics after very long term organ culture (OC) of human corneas.Methods Human corneas with initial endothelial cell density (ECD) >2000 cells/mm2 were stored at 31°C in sealed flasks containing 100mL of a commercial medium with 2% foetal calf serum (CorneaMax, Eurobio, France): 6 for 3‐6 months (M), 7 for 6‐12 M and 5 for more than 12 M. The medium was renewed every 2 M. Transparency was quantified by analysis of modulation and contrast transfer functions. On one half of each cornea, ECD and EC morphology were analysed by image analysis (CellP‐Olympus, and SambaCornea‐TribVn) after alizarin red staining and flat mounting. On the other half of the cornea, EC differentiation status (NaK ATPase, ZO‐1, JAM‐1) and proliferative capacity (Ki67, Click‐it EdU) were studied by immunostaining in flat mounted corneas (He, MolVis2011;17:3494 and He, StemCells2012 in press). Epithelial cells and stroma were observed by histology on cross sections stained with Hematein/Eosin/Safran and by transmission electron microscopyResults Corneal transparency and ECD decreased after very long‐term OC, but were partially preserved. ECD was about 1200, 800 and 400 cell/mm2 after respectively 3, 6 and 12 months. Morphology and differentiation of residual EC remained nevertheless almost preserved. The epithelium lost its multilayered organizationConclusion Corneal cells, particularly EC, can survive for a very long time in the rustic environment of OC, suggesting that they are well equipped against environmental stress and cell death. The improvement of storage process and/or storage medium could potentially allow very long term storage without significant attrition of graft quality and therefore provide corneas suitable for graft

Comparison of decellularization methods for human corneal lenticules

AbstractPurpose Human or animal thin corneal lenticules (L) have been used as biological carrier to experimentally reconstitute tissue‐engineered grafts. Decellularization of the stroma proved to reduce immune rejection after allografts in animals. Aim: to assess different decellularization methods of human corneal L.Methods Stromal L were prepared with a Moria microkeratome on human organ cultured corneas mounted on an artificial anterior chamber. After desepithelialization, an anterior L was obtained with a 90 μm head and a posterior one with a 110 μm head. Four physical methods (sonification at 37 kHz for 45 minutes (min), 3 freeze/thaw cycles in liquid nitrogen, heating at 50°C for 60 min, and hypoxia) and four chemical methods (75% ethanol for 2x10 min, 0,1% sodium Dodecyl sulphate for 24 hours (h), 4M urea for 4h, and 29% NaCl for 24h) were tested. Efficiency and safety were assessed by determining: 1/mortality of the keratocytes using the Hoechst‐Ethidium‐Calcein triple labelling (Pipparelli, IOVS2011;52:6018), 2/alteration of the stroma using transparency measurement (analysis of modulation and contrast transfer functions), and collagen fibres analysis by transmitted electron microscopy (TEM), and 3/elimination of the cell debris using a staining of cell cytoplasm (Dioc 6) and TEM.Results 75% ethanol and hypoxia triggered complete keratocytes mortality with minimal alterations of the stroma. None of the methods eliminated dead cells debris. Combination with the sonification helped fragmenting cellsConclusion Two simple and rapid methods allow complete decellularization of human corneal L. The ability of these Lt to promote endothelial cells adhesion and proliferation is under investigation.

Rabbit, rat and pig corneas: main characteristics and storage in organ culture

AbstractPurpose Except for primates, animal models of corneal are far from human. Animal models of corneal storage are virtually non‐existent. Aim: to update the main characteristics (especially for endothelial cells (EC)) of the cornea of 3 easily available animals, as well as their ability to be stored in organ culture (OC)Methods 30 corneas of 6 month‐old Large White pig, 20 of 10 week‐old California rabbits and 10 of 8 week‐old Lewis rats were investigated. Macroscopic data: 1/horizontal and vertical diameters (digital calliper), 2/transparency (analysis of modulation and contrast transfer functions), 3/ corneal thickness (CT) (ultrasound pachymetry). Microscopic data: 1/ histology on Hematein‐Eosin‐Safran stained cross sections and ultrastructure, 2/ EC density (ECD) and morphometry, 3/ EC proliferative status (Ki67 and 5‐Ethynyl‐2’‐Deoxyuridine incorporation (Clik‐it EdU)), differentiation status (Na+/K+ ATPase, ZO‐1, JAM‐1), and existence of stem cells (Nestin, ABCG2, Telomerase). Fresh corneas were organ cultured in 2 commercially available media. CT was measured every 2h during 6h, then every 12h. Transparency and EC survival was determined after 2, 3 and 4 days of OCResults We constituted a complete database of ex vivo corneal characteristics of the 3 species. ECD, polymorphism and polymegathism were higher than in human. CT increased rapidly (up to 3 times) in both OC media, resulting in biconvex tissues with almost complete loss of transparency and significant endothelial folding. EC survival decreased especially in foldsConclusion Corneas of the 3 animals cannot be stored more than 2 to 3 days in OC media designed for human. Specific media should be developed to obtain reliable models of animal corneal OC