Variation Of Transfer Function Research Articles

Artificial Neural Network Accuracy Optimization Using Transfer Function Methods on Various Human Gait Walking Environments

A bionic leg with ergonomic functionality can increase the user’s independence. However, an ergonomic bionic leg can be challenged to be developed. One of its challenges is related to functionality, where the bionic leg motor can be rugged to adapt to the user. One of the solutions for the bionic leg challenge is the application of a motor driver controlled by the user’s muscle signal. EMG signal can be utilized as the user’s signal source. The EMG signal is then fed back into the motor device. EMG signals obtained during a natural walking environment can result in smooth and natural movement. This study classifies EMG signals into 8 classes: a controlled walking environment (treadmill walking with various speeds) and a natural walking environment (ground walking, upstairs and downstairs walking). This research aims to optimize the ANN method using transfer function variations. The best method will be used to train EMG-driven motors for future studies related to bionic legs. The best ANN parameter in this research using Levenberg-Marquardt backpropagation as a training algorithm with transfer function pairing of the exponential function: Hyperbolic tangent sigmoid transfer function and SoftMax transfer function with 98.8% accuracy and 0.036 MSE value. The best method from the experiment and ANN classification can be used as a training method for a bionic leg in future research.

Modulation transfer function variation through anisotropic turbulence in biological tissue

Analysis of the long-exposure modulation transfer function (MTF) is performed for optical imaging using plane and spherical waves through anisotropic turbulence in biological tissues. To obtain the MTF, the wave structure functions of plane and spherical waves are obtained in closed-form expressions. Results are presented depending on various parameters of the turbulent medium and optical beam. The positive effect of anisotropy on optical imaging is remarkable in turbulent biological tissues. Besides scattering and absorption, taking anisotropy into account as well as turbulence will lead to a more accurate description of the performance of the medical imaging systems that use optical spectrums in biological tissues.

Physical-virtual time reversing of nonlinear Lamb waves for fatigue crack detection and quantification

This article presents the investigation of a nonlinear Lamb wave time reversing technique for fatigue crack detection and quantification. A 2D analytical framework is initially presented, modeling Lamb wave generation, propagation, wave crack linear and nonlinear interaction, and reception. This study extends the Time Reversal (TR) techniques into the realm of nonlinear Lamb waves. Due to the structural transfer function variation between the forward and backward transmission process, the Virtual Time Reversal (VTR) algorithm reveals obvious deviation for predicting nonlinear Lamb waves, given that it replaces the backward TR procedure with the forward transfer function. However, this study demonstrates that the difference between the physical nonlinear TR method and the conventional VTR algorithm proves to be sensitive to detect and quantify fatigue cracks. Fatigue tests on a thin aluminum plate with a rivet hole are conducted to induce a fatigue crack. The experimental results further illuminate that the proposed physical-virtual nonlinear Lamb wave TR technique possesses remarkable sensitivity to the nucleation and growth of fatigue cracks. The paper finishes with discussion, concluding remarks, and suggestions for future work.

A compact printed ultra-wideband filtenna with low dispersion for WiMAX and WLAN interference cancellation

A printed monopole filtenna fed by a co-planar waveguide with U-shaped split slot on patch and circular split ring resonator pairs at the other side of feed is proposed in this letter. The compact filtenna of dimension 0.32λ × 0.215λ (λ denotes wavelength corresponding to 2.68 GHz) is capable of providing large bandwidth from 2.68 to 8.72 GHz with dual frequency notch bands over 3.28–3.84 and 4.95–6.02 GHz, primarily to eliminate the WiMAX and WLAN interferences. The dual notched antenna performances are evaluated by simulation and experimental measurement and compared to those of recently reported ultra-wideband (UWB) notched antennas. The proposed filtenna provides bidirectional E-plane and omni-directional H-plane radiation patterns with gain variation of 2–4.5 dBi and average radiation efficiency of 78% in its pass band. Also the filtenna offers minimal dispersion characteristic as stable group delay response, and linear variation of transfer function (S21) is achieved in its pass bandwidth.

Modeling of SAM Impedance Onto Gold and Silver Thin-Film Mass-Produced Electrodes and Their Use for Optimization of Lactic Acid Detection.

In this work, we demonstrate how an innovative, out-of-cleanroom customized CD/DVD fabrication process can be successfully used for mass production of biosensors with thin-film electrodes. We show that silver and gold electrodes can be used for impedimetric and voltammetric biosensing applications, both in presence and absence of a redox mediator. We modeled the redox/non-redox electrodes impedance through equivalent electrical circuits, and we evaluated their transfer function sensitivity with a one-factor-at-a-time approach. Using this approach, we introduced a new prediction method to find which equivalent electrical circuit elements contribute more to the transfer function variations, then we experimentally validated the predictions measuring the electrodes electrochemical impedance spectroscopy responses with relevant self-assembled monolayer molecules immobilized on them, i.e., MCH and DTSP. We also assess the silver electrodes long-term stability with impedance spectroscopy measurements over a period of 1200 hours, proving their possible use in point-of-care applications. Finally, we also prove that the sensors correctly perform in a practical case, i.e., as a lactic acid biosensor, by studying the optimization of the biosensor efficiency through different enzyme immobilization methods. By comparing lactate oxidase enzyme direct adsorption and covalent binding to DTSP self-assembling monolayers, we found that covalent binding to DTSP can boost the catalytic current of about 40% with respect to that obtained from the direct adsorption of the same enzyme concentration.

A Compact Planar UWB Antenna with Triple Controllable Band-Notched Characteristics

A modified compact planar ultrawideband (UWB) monopole antenna with triple controllable band-notched characteristics is presented in this paper. The proposed antenna consists of a modified stair cased V-shaped radiating element and partial ground plane. The triple band-notched characteristics are achieved by embedding two different vertical up C-shaped slots with a vertical down C-shaped slot in the radiating patch and in the ground plane, respectively. Besides, the bandwidth of each rejected band can be independently controlled by adjusting the dimensions of the corresponding band notched structure. The proposed antenna with rejected bands characteristics is successfully simulated, prototyped, and measured. The measured results show that the antenna operates until upper 11 GHz for voltage standing wave ratio (VSWR) is less than 2, and exhibits bands rejection of 1.6–2.66 GHz (49.76%), 3-4 GHz (28.57%), and 5.13–6.03 GHz (16.12%). Moreover, the proposed antenna shows a near omnidirectional radiation patterns, stable peak gain, and with small group delay and transfer function variation on the whole UWB frequency range except in the notched frequency bands, which makes it suitable for being used in the future UWB applications.

New feedback detection method for performance evaluation of hearing aids

New objective and accurate feedback detection method, transfer function variation criterion (TVC), has been developed for evaluating the performance of feedback cancellation techniques. The proposed method is able to classify stable, unstable, and sub-oscillatory stages of feedback in hearing aids. The sub-oscillatory stage is defined as a state where the hearing aid user may perceive distortion of sound quality without the occurrence of oscillation. This detection algorithm focuses on the transfer function variation of hearing aids and the relationship between system stability and feedback oscillation. The transfer functions are obtained using the FIR Wiener filtering algorithm off-line. An anechoic test box is used for the exact and reliable evaluation of different hearing aids. The results are listed and compared with the conventional power concentration ratio (PCR), which has been generally adopted as a feedback detection method for the performance evaluation of hearing aids. The possibility of real-time implementation is discussed in terms of a more convenient and exact performance evaluation of feedback cancellation techniques.

Error propagation in electromagnetic transfer functions: what role for the magnetotelluric method in detecting earthquake precursors?

SUMMARY Whether electromagnetic precursors exist is a contentious issue that should be considered in the context of the focal depth and epicentral distance at which earthquakes nucleate, and with due regard to externally driven changes in the electromagnetic fields recorded at the Earth’s surface. If high-frequency electromagnetic signals are generated by earthquakes, then these signals may not be detectable because of attenuation occurring between the focal depth of the earthquake and the Earth’s surface. This is particularly true in seismotectonic regions (e.g. subduction zones) where saline fluids (including seawater), raised heat flow and partial melts often lead to enhanced conductivities. A technique for examining temporal variations in magnetotelluric (MT) spectra is presented, which: (i) considers both non-inductive and inductive parts of the MT transfer function; (ii) allows electromagnetic skin depths and adjustment distances to be calculated; (iii) takes account of error propagation in the transfer functions and; and (iv) acknowledges possible nonearthquake sources of observed variations in transfer functions and their errors. Data processing tends to eliminate non-stationary electromagnetic disturbances of the source field. Hence the method is more suited to detecting hypothesized changes in subsurface conductivity than short-lived electromagnetic bursts. The technique is applied to MT data from seismotectonic regions in New Zealand (Mt. Ruapehu), the Andes (western Cordillera) and the Mediterranean (Montecristo island) and to a culturally quiet, control site situated on a stable craton in central Australia. We demonstrate that the MT method can resolve apparent conductivity changes of the order of a few percent over 48 hr time intervals and give thresholds for other interval lengths. Comparison of the results obtained from seismotectonic regions with those from central Australia, and consideration of external source field effects, highlight how temporal variations of electromagnetic fields might be speciously interpreted as earthquake precursors.

Analytic Estimation of Penalty Due to Filter Transfer Function Variation on WDM Systems

Analytic estimates of pulse broadening and system penalty caused by wavelength-division-multiplexing (WDM) filter amplitude variation is derived. We show that root mean square pulsewidth is not a reliable measure of system penalty and noise equivalent bandwidth plays a key role in determining system penalty.

Study on electric variations of media in epicentral area by geomagnetic transfer functions

Taking the graph of the apparent resistivityρ yx in Lanzhou area, its geomagnetic transfer function variations and the investigation of moderate-strong local earthquakes as example and from the viewpoint of seismomagnetic effect, the authors found that subterranean conductivity values might be applied to the division of Lanzhou area from the surface downward into four layers, i. e., the anomalous, the transitional, the non-anomalous and the anomalous layer. Only the transfer function modular |A| and |B|, magnetic azimuth α P with its variance Δα P , and the total varianceσ z in the anomalous layers showed obvious anomalies with time changes. Thus, it could be conjectured that the anomalous layer was closely associated with the anisotropic variations of conductivity of the subterranean media in the seismicity area. This phenomenon might provide a way to the further study of its mechanism. It is needed to study the inherent connotation deeply.

Nondestructive evaluation of crazes and microcracks on polymers by the elastic-wave transfer function method

The precise study of the relation between microdefects such as crazes or microcracks and the elastic-wave transfer function method (ETFuM) was conducted in acrylonitrile butadiene styrene and acetal homopolymer. The ETFuM is the method of comparing the input elastic wave and the output wave from the specimens, and separating and analysing only the information on the object condition in the specimen from the transfer function in the frequency domain. In order to investigate the formation of crazes or microcracks caused by tensile deformation, transmission electron microscopy and polarization microscopy was used. The variation of transfer function before/after annealing indicated the dependence on the nucleation and growth of crazes or microcracks. The results suggested that ETFuM has potential as a useful method for the analysis of the micromechanism of the deformation process during nondestructive tensile and fatigue tests on polymers.

正常聴力耳に於ける周波数分析機能のか電図的評価

Techniques for scaling human cochlear frequency selectivity were studied and validated. Twelve ears of normal adults were examined by means of compound action potential tuning curve (CAP-TC). CAP-TC was reduced from the pure-tone masking profile of CAP recorded by transtympanic electrocochleography. CAP was evoked by 2 or 4kHz tone pip with an intensity 20dB above threshold, then a pure-tone masker was presented at various frequencies and the amount of CAP amplitude suppression was plotted as to make a CAP-TC.Q10dB and half-power bandwidth were measured in CAP-TC as frequency selectivity parameters. These values corresponded well with the published results in animals and humans. However, some differences from animals were found: (1) Frequency of the CAP-TC tip was not necessarily equal to that of the tone pip, (2) Low- and high-frequency slope of CAP-TC showed no statistical difference at 4kHz. Measurements with an acoustic manikin suggested that the difference (1) was caused by the transfer function variation of the external canal.It was concluded that electrophysiological evaluation of human frequency selectivity by CAP-TC is reliable and deserves clinical application.

Compensation in pneumatically actuated servomechanisms

This paper describes the features of a pneumatically actuated servomechanism which has been designed for the point-to-point positioning of payloads. The servomechanism utilises low cost computer control and interface electronics to facilitate software compensations for system time delays and non-linearities. The compensation algorithms hve been designed and developed with reference to a linearised model of pneumatic servodrives, which allows for variation in transfer function with load position. Application of these algorithms has allowed a substantial improvement in static performance and dynamic characteristics to be realised for drives incorporating various forms of pneumatic servo valves, pneumatic actuators and load systems. This offers a significant opportunity for commercial exploitation of the pneumatic servodrive. The paper describes the method by which compensation is achieved and references experimental data, which have been obtained by using a standardised evaluation procedure.

Calcul des efforts de la houle sur une structure semi-immergée comparaison avec des essais sur maquettes

The development of offshore drilling has brought with it a demand for increasingly large floating rigs. One of the main problems in building such large rigs is how to reduce wave forces and the motion they cause to a minimum. The object of the investigation described was to test an overall mathematical model designed to calculate these wave forces, considering their application to a simple submerged horizontal element with vertical columns emerging above water. A description of the mathematical model was given at the Symposium on research on wave action held in Delft in March 1969(see Proceedings). The calculated results were compared with vertical forces measured on a wave flume model, which showed that the mathematical model accurately rendered wave/force transfer function variations with changing wave period. Some discrepancies occurred in the short period range, but it is hoped to clear these by closer consideration of the free surface. An overall mathematical model based on simple formulation and a few preliminary model tests also gave very satisfactory results in this connection. Thus, a whole range of research facilities are now available for the various design stages for this type of structure, by means of which both local and overall wave forces and motion can be determined.

Ambiguity of the Transfer Function with Partially Coherent Illumination

The one-dimensional case of the image of a sinusoidal transmittance distribution in partially coherent illumination (with the quasimonochromatic approximation) is described analytically, and shown generally to bear a nonlinear relation to the object. It is shown that the significant parameter is the ratio of coherence interval to the diameter of the Airy disk (or diffraction spot) of the imaging lens. It is further shown that since the spatial frequency of the object is related to coherence interval, typical nonlinear effects can take place at low frequencies. Since the transfer function is defined only for the incoherent limit without ambiguity, an apparent transfer function, dealing only with the image component which existed in the object, is used for comparison. The harmonics generated by the nonlinear behavior are ignored, and the variation of transfer function is observed to be a function of coherence and input modulation. It becomes apparent that the transfer function, as currently defined and measured, is inadequate to describe optical-system performance under all conditions of illumination.

Variation of Transfer Functions with the Modification of Pole Location

Variation of Transfer Functions with the Modification of Pole Location