Terms Of Transfer Function Research Articles

A borehole array data–based approach for conducting 1D site response analyses II: Accounting for modeling errors

Site response estimates from one-dimensional (1D) site response analyses (SRAs) carry inaccuracies due to modeling and parametric errors. Modeling errors are due to the condensation of the three-dimensional (3D) wave propagation phenomenon to the vertical propagation of a horizontally polarized wave through a soil column, and parametric errors are due to the incomplete knowledge of the distributions of soil parameters, leading to the selection of nonoptimal input parameters for a site of interest. While parametric errors are traditionally handled using different soil parameters (e.g. alternative shear-wave velocity profiles), modeling errors are generally neglected. This paper proposes an approach for conducting linear elastic 1D SRAs to improve site response predictions and account for modeling errors. First, ground-motion data from borehole array sites are collected, processed, and screened for appropriateness (e.g. expected shear strains lower than 0.01%, signal-to-noise ratio higher than 3). Second, 1D SRA predictions in terms of transfer functions and amplification factors are compared against observations, and the discrepancies are quantified as residuals. Finally, the residuals are partitioned into a model bias term [Formula: see text], a site term [Formula: see text] with standard deviation [Formula: see text], and a event- and site-specific remaining residual [Formula: see text] with standard deviation [Formula: see text]. Values for [Formula: see text] and [Formula: see text] for forward predictions are recommended. The sensitivity of the site response residuals to region, site type (1D- or 3D-like), and the applicability of findings to outcropping applications are discussed, and an example application for a hypothetical project site is presented.

A 2.5D automatic FEM-SBM method for the evaluation of free-field vibrations induced by underground railway infrastructures

This paper presents an efficient method to predict underground railway-induced vibrations. The method uses the finite element method (FEM) to model the railway tunnel structure and the singular boundary method (SBM) to model the wave propagation in the surrounding soil. The FEM mesh and the distribution of SBM collocation points at the tunnel/soil interface are generated using an automatic meshing strategy. The presented method is one of the main components of VIBWAY, a user-friendly prediction tool to address railway-induced vibration problems. This paper presents three calculation examples in which the soil response due to forces applied on the tunnel structure are computed in terms of transfer functions. The results obtained for each one of the calculation examples are compared with those computed using a model based on a 2.5D FEM-BEM approach. The presented comparisons show that the proposed approach is a suitable strategy for predicting underground railway-induced vibrations, both in terms of accuracy and computational efficiency. Moreover, the use of an automatic meshing strategy and the SBM formulation not only eases the implementation of the approach but it also makes it easier to use, which is one of the key features of the VIBWAY tool.

Spectral analysis for GARCH processes through a bilinear representation

In this paper, we deal with the frequency domain approach to describe some probabilistic properties of the processes using the associated transfer functions which seem more informative. So, in the first part, we propose an appropriate bilinear representation of model governed by a second-order Hermite polynomial with leading coefficient 1, and we give a necessary and sufficient condition for the causal and second-order stationary solution. In a second part, we establish the autocovariance and the associated spectral density function of such a representation, and for its squared version in terms of transfer functions. As a consequence, it is observed that the second-order properties are similar to an ARMA process with uncorrelated innovations and hence the resort to higher-order properties however becomes inevitable. Therefore, the explicit expressions of bispectral densities of the process and its squared version are given and several illustrative examples are emphasized. Our results are related to the work of Terdik (2000, §3) for the GARCH(1, 1) model.

Gain-Scheduled Level Controller for FESTO MPS PA Station Tank

In this article, a Gain Scheduling (GS) approach is proposed to control the FESTO MPS PA Station Tank level by controlling the centrifugal pump. The open loop transfer function for each operating condition is experimentally obtained. The data from the open-loop system is imported to MATLAB in order to get the transfer function for each condition. The data shows that each operating point has a different transfer function in terms of gain and time constant. Based on this, a gain-scheduling controller is proposed to handle the variations of process model parameters. The proposed controller parameters are adapted based on the operating conditions of the system. These parameters include the tank capacitance and the flow pipe resistance and/or the valve resistance to the flow. Two different controller techniques for FESTO MPS PA Station Tank level control are applied, verified and compared. The first controller is based on classical Proportional Integral (PI) controller, while the second one is based on the proposed gain scheduling controller. Experimental results show that the proposed gain-scheduling controller can manipulate the process at different operating conditions with parameters variations in order to give uniform performance. The classical PI controller has failed to achieve this requirement at different operation conditions.

Semianalytical modeling of the mass transfer in microfluidic electrochemical chips.

This paper reports a mass transfer model of a reactant flowing in a large aspect ratio microfluidic chip made of a channel with electrodes on the side walls. A semianalytical solution to the two-dimensional Fickian diffusion of a reactant in a microchannel, including the electrochemical reaction at the electrode interface and the velocity profile obtained from the Navier-Stokes equations in a fully developed laminar regime, is found. The solution is written in the Laplace domain in terms of transfer functions. The proposed solution is an extension of the Lévêque approximation describing the reactant diffusion from the electrode to the middle of the microfluidic channel. The main applications of this work are the use of the obtained transfer functions for the measurement of the Faradic current density or the chemical concentration at the electrode interface. The study can also be extended to the heat transfer in microfluidic electrochemical chips (temperature or heat flux measurements at the electrode interface).

Nonlinear dynamics of a floating offshore wind turbine platform via statistical quadratization — Mooring, wave and current interaction

This paper applies the method of statistical quadratization to investigate the first and second-order responses of a floating offshore wind turbine platform due to forces from a catenary mooring system, and wave–current coupled interaction. The hydrodynamics are based on the generalized Morison’s equation, while the catenary mooring system is based on a quasi-static approach. The method of statistical quadratization replaces the nonlinearities using equivalent linear and quadratic terms by minimizing the difference between the nonlinear model and the approximated model in a mean-square sense. In this regard, an iterative scheme is applied, in which the equivalent polynomial coefficients are calculated based on the non-Gaussian distribution generated by means of Gram–Charlier expansions. The dynamics are solved using the Volterra theory, and described in terms of transfer functions, which can be directly integrated into the central moments of the distribution. The results demonstrate an excellent agreement with nonlinear time-domain simulations in terms of spectral response and probability distribution. Sensitivity studies are performed to show the contribution of the second-order motion over several environmental conditions. Despite the excellent accuracy, the main advantage of the statistical quadratization is the low computational cost, which is approximately two orders of magnitude faster than nonlinear time-domain simulations.

Strain Transfer Function of Distributed Optical Fiber Sensors and Back-Calculation of the Base Strain Field.

Distributed optical fiber sensors are a promising technology for monitoring the structural health of large-scale structures. The fiber sensors are usually coated with nonfragile materials to protect the sensor and are bonded onto the structure using adhesive materials. However, local deformation of the relatively soft coating and adhesive layers hinders strain transfer from the base structure to the optical fiber sensor, which reduces and distorts its strain distribution. In this study, we analytically derive a strain transfer function in terms of strain periods, which enables us to understand how the strain reduces and is distorted in the optical fiber depending on the variation of the strain field. We also propose a method for back-calculating the base structure’s strain field using the reduced and distorted strain distribution in the optical fiber sensor. We numerically demonstrate the back-calculation of the base strain using a composite beam model with an open hole and an attached distributed optical fiber sensor. The new strain transfer function and the proposed back-calculation method can enhance the strain field estimation accuracy in using a distributed optical fiber sensor. This enables us to use a highly durable distributed optical fiber sensor with thick protective layers in precision measurement.

Methodology of determining of the transfer function of engagement kinematics of accelerations of an aircraft and its elliptic coordinates used for thr guidance based on time difference of arrival

This paper discusses the problem of determining a kinematics (in terms of transfer function, as far as possible) of parameters of the motion of an aircraft expressed in the curvilinear coordinate system and control accelerations expressed in a rectangular coordinate system. Examples of curvilinear coordinate systems using in practice can be polar, biangular, two-center bipolar, elliptic, parabolic cylindrical, spherical, ellipsoidal, coordinate systems. A technique for obtaining a kinematic link for the control problem of an unmanned aerial vehicle in the elliptic coordinate system was described. It allowed to obtain simpler view of the kinematic link which could provide navigation an aircraft along the hyperbola deriving from the time difference of arrival navigation system. It can. As a result, it is possible to reduce the number of the navigation radio beacons.

An experimental assessment of nonlinear effects of vertical motions of Naples systematic series planing hulls in regular waves

A comprehensive experimental assessment of vertical motions and accelerations of two Naples warped hard chine hulls systematic series (NSS) hulls in regular waves is presented. The seakeeping performance in regular waves are investigated, in particular nonlinear motion responses in terms of transfer functions and higher harmonic response as a function of wave frequency, steepness, hull slenderness and speed. In order to highlight the effects of wave properties on motion responses, transfer functions of both motion harmonics and phases are presented via iso-frequency and iso-steepness plots. Slenderness ratio is found to have a notable effect on motion transfer functions only at higher speeds. The presence of a higher harmonics in motion and acceleration response is also observed and the proposed analysis shows that increasing wave steepness and speed lead to increased higher harmonics responses of both vertical motions and accelerations. The effect of slenderness ratio on the second harmonic response of heave and pitch is only noticeable at higher speed. Phase difference between wave and motions shows that higher second harmonic content is generally associated with a higher phase lead. The main novelty of the present work is represented by the extensive analysis of NSS planing hulls in regular waves. In particular the aspects concerning higher harmonics and their trends with respect to speed, wave and hull geometrical characteristics.

Study of the Valuation of Multimode Optical Fibers by Translation of Transmission Techniques of Optical Fiber and High Speed Mimo Radio Frequency in Local Area Network.

— In this paper, we focused on making a study of the valuation of multimode optical fiber which is used a lot in local networks and yet that we talk less in this last decade which knows an increase of new technologies using an enormous speed. To do so, we made a translation between radio frequency MIMO and optical MIMO; a study which has already been carried out in a framework of comparison of two technologies and in the literature, this convergence is already possible. Note that this is done in terms of transfer functions and of which we have made a very explicit analytical study compared to other studies already carried out in the literature for an educational and didactic objective for future studies in this context. Then we focused on doing our valuation study of multimode optical fiber, through optical MIMO technology, and our thinking was based on the quality of the signal at reception, for this, a study of modulation formats was made, because with the rise of technologies, this of course leads to an increase in speeds, so that certain formats tend to almost total disappearance. During this study, the RZ (Return to zero) format is much better in a larger local network, in terms of its Q factor and NRZ (None Return to Zero), for a smaller network, depending on its bit error rate (BER) and their eye diagrams which have a very large aperture and this is extended for the RZ format.

Simulation/Experiment Confrontation, an Efficient Approach for Sensitive SAW Sensors Design.

Sensitivity is one of the most important parameters to put in the foreground in all sensing applications. Its increase is therefore an ongoing challenge, particularly for surface acoustic wave (SAW) sensors. Herein, finite element method (FEM) simulation using COMSOL Multiphysics software is first used to simulate the physical and electrical properties of SAW delay line. Results indicate that 2D configuration permits to accurately obtain all pertinent parameters, as in 3D simulation, with very substantial time saving. A good agreement between calculation and experiment, in terms of transfer functions (S21 spectra), was also shown to evaluate the dependence of the SAW sensors sensitivity on the operating frequency; 2D simulations have been conducted on 104 MHz and 208 MHz delay lines, coated with a polyisobutylene (PIB) as sensitive layer to dichloromethane (DCM). A fourfold increase in sensitivity was obtained by doubling frequency. Both sensors were then realized and tested as chem-sensors to detect zinc ions in liquid media. 9-{[4-({[4-(9anthrylmethoxy)phenyl]sulfanyl} methyl)]methyl] anthracene (TDP-AN) was selected as the sensing layer. Results show a comparable response curves for both designed sensors, in terms of limit of detection and dissociation constants Kd values. On the other hand, experimental sensitivity values were of the order of [7.0 ± 2.8] × 108 [°/M] and [16.0 ± 7.6] × 108 [°/M] for 104 MHz and 208 MHz sensors, respectively, confirming that the sensitivity increases with frequency.

АЛГОРИТМЫ УПРАВЛЕНИЯ УГЛОВЫМ ДВИЖЕНИЕМ КОРОМЫСЛА С ВИНТОВЫМИ ЭЛЕКТРОПРИВОДАМИ

The subject of study in the article is the process of forming algorithms for controlling the angular motion of the rocker with a screw electric actuator. The purpose is to develop approaches to the formation of algorithms for controlling the angular motion of the rocker with a screw electric actuator as the automatic control object. Tasks: to specify the synthesis process of the state control algorithm for a linear mathematical description of the automatic control object in the state space according to the minimum criterion of the integral from the weighted error module. To form the block diagram of the automatic control system by the state. To improve the approach to the development of algorithms for controlling automatic control objects by output for mathematical description in the frequency domain. To illustrate the features of the approach on the specific example of automatic control object represented by transfer functions in terms of references and disturbances. To develop the simulation scheme in Simulink and study the reactions to stepwise references and disturbances. To develop the approach to the formation of control algorithms for the diagnosis of the rocker as the automatic control object. To describe the procedure and means of deep diagnosis of emergency situations of the automatic control object. To develop means of recovery the automatic control object. The methods used are the state space method, transfer function method, integral optimality criteria, methods of diagnosing, and recovering. The following results were obtained: approaches to the formation of algorithms for controlling the angular motion of the rocker with a screw electric actuator using linear mathematical descriptions in time and frequency domains were formed. Conclusions. The scientific novelty lies in the formation of approaches to the development of algorithms for controlling the angular position of the rocker with a screw electric actuator which differs from the known accounting the structural and functional features of the automatic control object.

Spectral Graph Based Vertex-Frequency Wiener Filtering for Image and Graph Signal Denoising

In this article, we propose and develop a spectral graph based vertex varying Wiener filtering framework in the joint vertex-frequency domain for denoising of graph signals defined on weighted, undirected and connected graphs. To this end, we first extend the Zadeh time-frequency filter concept to graph signals and obtain vertex-frequency transfer function of the proposed Wiener filter by transforming its vertex varying impulse response that minimizes the mean square error between original and recovered signals. To facilitate the derived Wiener filter, we present a detailed derivation of a recently proposed graph Rihaczek vertex-frequency signal distribution (GRD) so as to match the structure of the proposed graph Zadeh filter, based on a graph translation operator defined by generalized convolution with a delta signal. We express the filter transfer function in terms of this graph transform of the original, noiseless signal. The form of the obtained Wiener filter is, interestingly, different than those of time-frequency Wiener filters prevalent in the classical signal processing. We also investigate the invertibility of the employed GRD. Assuming that the original graph signal of interest can be viewed as deterministic, we propose two algorithms to implement the proposed vertex-frequency Wiener filter from a single realization of a noisy, input signal. We derive mean and variance of the GRD of the noisy signal, since they are required in one of these algorithms. We apply proposed Wiener filter algorithms to denoise a standard set of images and three irregularly structured graph signals, and demonstrate their competitiveness with compared high performance denoising methods.

Effects on the OTF of MSF structures with random variations.

In diamond-machined freeform manufacturing processes, a tool-tip often leaves behind characteristic mid-spatial frequency (MSF) structures on the optical surface. Unwanted movement between the tool-tip and the part results in MSF structures with random variations. Here, we analyze the effects of these MSF structures on the system's optical performance and derive simple analytic estimates for the optical transfer function in terms of the parameters of these structures. These expressions are expected to aid in MSF tolerancing.

Car-following model based delay feedback control method with the gyroidal road

Connected vehicles are expected to become commercially available by the next decade. In this work, we propose a delay feedback control method for car-following model on a gyroidal road. By using the Hurwitz criteria and the condition for transfer function in terms of [Formula: see text]-norm, the impact of controller gain coefficient and the delay time on the performance of traffic flow is investigated. Based on the bode curve, we verify that the designed delay feedback controller is effective in suppressing traffic congestion and reducing energy consumption. The enhanced traffic flow model is more sensitive to the controller gain coefficient and delay time at downhill situation compared to the uphill situation. The conclusion obtained from the simulation example is consistent with the theoretical analysis.

Magnetic Measurements on the Prototype Magnets of the High-Order Correctors for HL-LHC

The National Institute for Nuclear Physics (INFN) is developing, at the Laboratory of Accelerators and Applied Superconductivity (LASA Milan, Italy), five families of corrector magnets, from skew quadrupole up to dodecapole order, which will be installed in the interaction regions of the High-Luminosity Large Hadron Collider (LHC). These magnets are based on a superferric design, which allows a relatively simple, compact and easy-to-construct magnets. This activity takes place within the framework of a collaboration agreement between CERN and INFN. The magnets have been designed and prototype units have been built and tested for the sextupole, octupole, and decapole orders. Magnetic measurements have been performed in order to characterize the field quality, and to validate the design and construction. This paper presents the instruments and the approach for the magnetic measurements on the prototype magnets. Moreover, the results of measurements at cryogenic temperature, up to the nominal field level, are reported. The magnetic field quality, in terms of transfer function and field multipoles, is analysed as function of the excitation level. The iron saturation effects, which are a major concern of the selected design, are compared with the 3-D magnetic calculations and discussed in view of the construction of the series magnets to be integrated in the corrector package assembly.

The Importance of Transfer Function in Solving Set-Union Knapsack Problem Based on Discrete Moth Search Algorithm

Moth search (MS) algorithm, originally proposed to solve continuous optimization problems, is a novel bio-inspired metaheuristic algorithm. At present, there seems to be little concern about using MS to solve discrete optimization problems. One of the most common and efficient ways to discretize MS is to use a transfer function, which is in charge of mapping a continuous search space to a discrete search space. In this paper, twelve transfer functions divided into three families, S-shaped (named S1, S2, S3, and S4), V-shaped (named V1, V2, V3, and V4), and other shapes (named O1, O2, O3, and O4), are combined with MS, and then twelve discrete versions MS algorithms are proposed for solving set-union knapsack problem (SUKP). Three groups of fifteen SUKP instances are employed to evaluate the importance of these transfer functions. The results show that O4 is the best transfer function when combined with MS to solve SUKP. Meanwhile, the importance of the transfer function in terms of improving the quality of solutions and convergence rate is demonstrated as well.

Impact of Line and Control Parameters on Droop Stability in Inverters for Distributed Generation

This paper analyzes stability conditions and design requirements for the control parameters in droop-controlled inverters. The analysis focusses on a single inverter unit with ac (output) filters and interface transformer, as this may be regarded as the elementary component of a distributed generation system. Through a process of thought simplifications and manipulations, the linearized full state-space model is transformed into a unique single-input, single-output system comprising several nested loops. The resulting analytical model in terms of transfer functions has enough “structure” to represent interactions between the different actors of the overall control, such as droop linear and derivative terms, virtual impedance, and voltage controllers. Stability conditions for the corresponding parameters are then derived analytically. Experimental tests are carried out on the complete system to check the reliability of the proposed model.

Horizontal-to-vertical spectral ratio of S-waves and SH-wave transfer functions at the vertical seismic and strong-motion arrays in the Central United States

Spectral analyses were performed on S-waves of earthquake recordings from two vertical seismic and strong-motion arrays in the central United States to obtain horizontal-to-vertical spectral ratios (HVSR) and transfer functions. Spectral analyses were also performed on ambient noises to obtain HVSRs at both sites. Theoretical SH-wave transfer functions were obtained using Thomson-Haskell propagation matrices and soil profiles at both sites. The results demonstrate that the S-wave HVSR is similar to the observed and theoretical SH-wave transfer functions in terms of peak frequencies up to the fifth mode. In other words, the S-wave HVSR could be used as an empirical SH-wave transfer function and provide in situ constraints on the shear-wave velocity structure of soils at these sites. The results also demonstrate that the ambient-noise HVSR is different from the S-wave HVSR and SH-wave transfer functions of the soils. Thus, the ambient-noise HVSR is not applicable for characterizing earthquake ground-motion site-effect, as well as determining the shear-wave velocity structure.

Minimum variance control for mitigation of vibrations in adaptive optics systems.

In this paper, we address the design of a minimum variance controller (MVC) for the mitigation of vibrations in modern telescope adaptive optics (AO) systems. It is widely accepted that a main source of non-turbulent perturbations is the mechanical resonance induced by the wind or the instrumentation systems, such as fans and cooling pumps. To adequately mitigate vibrations, the application of frequency-based controllers has been considered in the past decade. In this work, we express the system model in terms of the tracking of a zero-input signal via the MVC. We show that the MVC is an equivalent representation of the linear quadratic Gaussian (LQG) controller for the AO system. We also show that by developing the MVC, we can obtain different expressions, in terms of transfer functions, that offer insights into the behavior and expected performance of the controller in the frequency domain. In addition, we analyze the impact of the accuracy of the system and perturbations model on the mitigation of vibrations.