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We studied the characteristics of coupled-core four-core fibers (CC-4CFs) with different core pitches both theoretically and experimentally. The spatial mode dispersions of different fibers were analyzed, and the result agrees well with theoretical ones. In the experiment, we achieved a spatial mode dispersion as low as 3.72 ps/km1/2 for a 4 km-long CC-4CF with core pitch of 19 μm at a bending radius of 8 cm. The impulse response matrices of four core fibers with different core pitches was investigated using swept-wavelength interferometry over 100 nm bandwidth. The impulse responses were Gaussian-shaped and consistent between different inputs and outputs for CC-4CFs. Our results show that the CC-4CFs with core pitches of 17 and 19 μm exhibit narrower pulse broadening. In addition, the mode-dependent losses of different fibers were analyzed. For the fibers with core pitch of 19 μm, the estimated mode-dependent loss was lower than 3 dB for the entire 100 nm bandwidth. Our results are especially helpful for developing coupled-core multicore fibers for long-haul transmission applications.

This study is focused on energy harvesting. The goal was to develop a new energy-harvesting system using a pressure regulator and establish an efficient energy flow model within it. The harvested electrical energy can be used as a power source for devices around the regulator, such as primary battery-powered gas meters, thereby enabling battery-free operation. Here, we focus on pressure regulators for LP and city gases, which are used by a vast number of consumers. We systematically modeled complicated energy-conversion processes using the transfer matrix method to maximize the recovered electrical energy. Under normal gas usage conditions, the gas flow is low, and the harvested energy is limited. However, it surpasses the energy supplied by the primary batteries. The results obtained under the actual operational conditions were compared with those calculated using a theoretical model. Within the system, a DC motor and an AC motor were used as generators, and the results were compared. When a DC motor was used as the generator under 0.05 MPa, 0.8 L/m, and maximum power-harvesting load conditions, the harvested power was 0.237 W, which is sufficient to drive the meters. Additionally, the error between the experimental and theoretical results ranged from 2.6% to 4.6%. When an AC motor was used as a generator, the harvested energy was 0.015 W and the error was −14.7%. Utilizing this theoretical model allows for the calculation of the optimal conditions for energy harvesting from various pressure regulators, thereby offering design guidelines for energy-harvesting systems.

We present a novel numerical analysis method called 1D full-vectorial finite element bidirectional beam propagation method (BiBPM) for the efficient design of nonradiative dielectric (NRD) waveguide components. The BiBPM is a field-based propagation operator method that does not require computing eigenpairs or diagonalizing characteristic matrixes. The dimension of the problem can be reduced in the case that the structure of the NRD guide does not vary in the perpendicular direction to its parallel perfect conductor plates. Moreover, since propagation operator methods eliminate the need to discretize in a homogeneous direction, a 3D problem can be converted into a 1D problem in specific situations. First, we analyze NRD guides with an offset and an air gap to verify the applicability of the transfer-matrix-based BiBPM to NRD guides. Given the instability of transfer matrix formulation, we also introduce the scattering-matrix-based BiBPM. Its validity is confirmed using numerical examples of an electromagnetic bandgap filter and a square resonator.

In this work, we theoretically investigate the superluminal and subluminal reflected group delay in an air-Weyl semimetal film-Weyl semimetal substrate layered structure by using the $4\times $ 4 transfer matrix method. We show a tunable transition between positive and negative group delays of reflection pulse in this layered structure by controlling the properties of the Weyl Semimetal layer, and we also reveal its mechanism to modify the propagation properties of the light pulse reflected from this structure. It is demonstrated that the reflected group delays are tunable from positive to negative values and vice versa, which are adjusted by tuning the incident angle, thickness of Weyl semimetal film, tilt parameter, and Fermi energy. The control of the magnitude and the sign of the reflected group delay of light propagation represent a key point in slow and fast light technologies. Our results are helpful in controlling pulse propagations and are useful for the design of Weyl semimetal-based delay devices. [ABSTRACT FROM AUTHOR]

Electrocardiographic Imaging (ECGI) aims to estimate the intracardiac potentials noninvasively, hence allowing the clinicians to better visualize and understand many arrhythmia mechanisms. Most of the estimators of epicardial potentials use a signal model based on an estimated spatial transfer matrix together with Tikhonov regularization techniques, which works well specially in simulations, but it can give limited accuracy in some real data. Based on the quasielectrostatic potential superposition principle, we propose a simple signal model that supports the implementation of principled out-of-sample algorithms for several of the most widely used regularization criteria in ECGI problems, hence improving the generalization capabilities of several of the current estimation methods. Experiments on simple cases (cylindrical and Gaussian shapes scrutinizing fast and slow changes, respectively) and on real data (examples of torso tank measurements available from Utah University, and an animal torso and epicardium measurements available from Maastricht University, both in the EDGAR public repository) show that the superposition-based out-of-sample tuning of regularization parameters promotes stabilized estimation errors of the unknown source potentials, while slightly increasing the re-estimation error on the measured data, as natural in non-overfitted solutions. The superposition signal model can be used for designing adequate out-of-sample tuning of Tikhonov regularization techniques, and it can be taken into account when using other regularization techniques in current commercial systems and research toolboxes on ECGI. [ABSTRACT FROM AUTHOR]

It is essential to perform end-to-end performance testing of multiple-input–multiple-output (MIMO) systems under realistic propagation channel conditions. However, due to the highly integrated and compact radio frequency (RF) system design, the traditional conducted cable testing method is getting more and more problematic. The wireless cable solution, which can achieve the equivalent functionality of the conducted cable testing without actual RF coaxial cables, has attracted huge attention from the industry and standardization for over-the-air (OTA) testing in recent years. However, the state-of-the-art solutions to achieve wireless cable testing necessitate at least reference signal received power (RSRP) reporting per device under test (DUT) antenna port for MIMO capable terminals, which is demanding and might not be accessible for commercial DUTs. In this work, a novel wireless cable solution based only on the maximum RSRP measurement of all DUT antenna ports is proposed, which can significantly alleviate the requirement of DUT RSRP reporting. To achieve the wireless cable testing, a novel calibration procedure is proposed to determine the transfer matrix between the probe antenna ports and the DUT antenna ports based on the DUT maximum reported RSRP measurement. The proposed algorithm is theoretically derived and experimentally validated for a $2\times 2$ MIMO system, where the isolation of above 25 dB is achieved for the measurement setup. The numerical simulation and experimental validation demonstrate the efficiency and robustness of the proposed algorithm. [ABSTRACT FROM AUTHOR]

Yield estimation and yield-driven design optimization play important roles in microwave design. Existing surrogate-based yield estimation/optimization methods need to develop separate surrogate models or a large surrogate model with high complexity to deal with multiport problems, which is computationally inefficient. This article proposes a novel surrogate-based method to expedite yield estimation/optimization of multiport microwave structures using combined quadratic mappings and matrix-valued transfer functions. For multiport structures, the responses of different transfer functions corresponding to different pairs of input–output ports are computed with separate residues, while the responses of transfer functions for all pairs of input–output ports are computed with a common set of poles. Taking advantage of this, we propose to formulate a set of quadratic functions to map the relationship between the separate residues and statistical/geometrical parameters while employing merely one quadratic function to map the relationship between the common poles and statistical/geometrical parameters. The resultant mappings together with the matrix-format transfer function form an efficient surrogate to expedite the yield estimation and optimization processes for microwave structures. Compared with existing surrogate-based methods, the proposed method can achieve similar yield estimation accuracy in a shorter time due to fewer electromagnetic (EM) simulations. Three microwave structures are used to demonstrate the advantages of the proposed method. Based on accurate yield estimations, we further perform yield-driven design optimization incorporating the proposed surrogate for all the three examples. [ABSTRACT FROM AUTHOR]

Differing from a two-level voltage source converter (TL-VSC), the internal dynamics of a modular multilevel converter (MMC) are much more complicated. Since the fluctuation of submodule capacitor voltage is unavoidable when transmitting power, the MMCs output voltages cannot track the references perfectly. The interaction between the time-varying capacitor dynamics and controllers may lead to self-instability of the MMCs. In order to address this self-instability issue, this paper first establishes the small-signal closed loop transfer function matrices (TFMs) of the external and internal control loop by the harmonic linearization method. Further, a novel design principle of MMC controllers is proposed. Then, the critical impact factors on the stability of circulating current controller and AC voltage controller are investigated based on the generalized Nyquist criterion(GNC). The proposed models and analysis methods are validated by time-domain simulations in PSCAD/EMTDC. [ABSTRACT FROM AUTHOR]

Time-of-flight measurements are key to study distributed mode coupling and differential mode group delay (DMDG) in multimode fibers (MMFs). However, current approaches using regular photodetectors with limited sensitivity preclude the detection of weak modal interactions in such fibers masking interesting physical effects. Here we demonstrate the use of high-sensitivity superconducting nanowire single-photon detectors (SNSPDs) to measure the mode transfer matrix of a commercial graded-index multimode fiber. Two high performance 45-mode multi-plane light conversion (MPLC) devices served as the mode multiplexer/demultiplexer. Distributed mode coupling and DMDG among different mode groups are accurately quantified from the impulse response measurement. We also observed cladding modes of the MMF as a pedestal of the pulse in the measurement. This work paves the way for applications such as quantum communications using many spatial modes of the fiber. [ABSTRACT FROM AUTHOR]

This work presents a broadband linear–cross polarizer for K- and Ka-band applications. The design consists of a simple asymmetric width-based meander-line metasurface printed on a thin FR-4 grounded dielectric substrate. Normal incidence demonstrates 90% polarization conversion ratio (PCR) bandwidth (BW) of 20.64 GHz from 18.31 to 38.95 GHz with 72.1% fractional BW (FBW). Due to the destructive interference involved at greater oblique angles, reflective polarizers experience severe degradation of 90% PCR BW response. The proposed polarizer’s performance is obliquely stable up to 43° for transverse electric (TE) and 45° for transverse magnetic (TM) incidence with minimal 90% PCR BW reduction of only 13.95% (TE) and 15.25% (TM) compared with normal incidence. For the first time, transfer matrix method (TMM)-based equivalent surface impedance technique is modeled for oblique incidence analytically, closely resembling the full-wave analysis. The design is compact with a periodicity of $\lambda \text{o}$ /5.98 and a thickness of $\lambda \text{o}$ /13.69. The surface current patterns at resonant frequencies illustrate the reason behind broadband behavior. Bistatic radar cross section (RCS) analysis of the proposed converter is studied with reference to PEC. To the best of the author’s knowledge, this structure demonstrates broadband response with wide angular stability with less than 90% PCR BW reduction at higher oblique angles reported so far. [ABSTRACT FROM AUTHOR]

A systematic and efficient multimodal transfer-matrix approach is proposed for the comprehensive Bloch analysis of general 1-D/2-D/3-D periodic structures. We provide a linearization procedure for transforming the original nonlinear eigenvalue problem associated with 2-D/3-D structures to a standard one that can easily be solved without the need of a zero-searching algorithm in the complex plane. The proposed approach has been validated with bounded/open structures with complex geometries and/or inhomogeneous lossless/lossy materials. It demonstrates a significantly reduced computational time and leverages the strengths of full-wave simulators to deal with general problems and ad hoc quasi-analytical methods to give a fundamental understanding of the behavior of the structure. Also, it allows for an accurate evaluation of the imaginary part of the wavenumber, which offers information of material dissipation, stopband rejection, leakage, and complex modes. [ABSTRACT FROM AUTHOR]

The aim of this article is to present a novel model-order reduction (MOR) algorithm for fast finite-element frequency-domain simulations of microwave two-port structures. The projection basis used to construct the reduced-order model (ROM) comprises two sets: singular vectors and regular vectors. The first set is composed of the eigenvectors associated with the poles of the finite-element method (FEM) state-space system, while the second one is made up from the eigenvectors corresponding to the zeros of the diagonal elements of the matrix-valued immittance transfer function. Importantly, just one LU factorization of the FEM system is required to construct the projection basis during the reduction process, due to the application of a new formulation based on the Schur complement. The sets of eigenvectors that are used in the basis are independent of one another, which makes the new technique better suited for parallel computing compared with previously developed methods, which are sequential in nature. The reliability and accuracy of the proposed scheme are compared with that of the standard MOR technique, namely, the reduced-basis method (RBM), and verified through the analysis of three microwave structures: an eighth-order dual-mode waveguide filter, a dielectric resonator filter, and a folded waveguide filter. [ABSTRACT FROM AUTHOR]

A scheme to characterize and model the dynamics of the electron beam–electromagnetic power exchange along a traveling-wave tube (TWT) is proposed. The method is based on defining a state vector at discrete periodic locations along the TWT and determining the transfer matrix of the unit cell of the “hot” (i.e., beam loaded) slow wave structure (SWS) that considers the small-signal interaction between the electromagnetic guided field and the electron beam via 3-D particle-in-cell (PIC) simulations. Once the estimate of the unit-cell transfer matrix is obtained, we show how to find the hot guided eigenmodes in the interactive system made of an electromagnetic wave in the SWS coupled to an electron beam by using Floquet theory. In particular, we show how to determine the complex-valued wavenumbers of the hot modes and the eigenvectors associated with them. We focus on finding the hot modes supported by a TWT amplifier with a serpentine SWS operating at millimeter waves. We show the dispersion relation of the modal complex-valued wavenumbers of the hot modes when varying frequency; near the synchronization point, the results are in agreement with the Pierce theory. Finally, we show how the proposed scheme is also useful to estimate the gain performance of a long TWT amplifier by cascading the transfer matrices estimated from PIC simulations of a shorter hot SWS. The results show that the gain calculated based on the proposed model very well matches the one calculated from 3-D PIC simulations of the whole structure. The technique is general and can be applied to any SWS geometry where electromagnetic modes interact with an electron beam. The model we proposed can be a very powerful tool to understand the physics of TWTs and can be used for optimization purposes. [ABSTRACT FROM AUTHOR]

Due to the nonlinear time-periodic nature, precise impedance modeling of power-converter-based single-phase ac systems is complex. Small-signal modeling for the systems with a fixed operating point is easy, but the extension of the same procedure to the systems with time-periodic trajectory is still challenging. In this article, a recursive single-input single-output (SISO) impedance modeling framework for single-phase rectifiers is presented, which can greatly simplify both the modeling procedure and the resulting impedance model. A general linear-time periodic modeling method is proposed by extending the linear-time invariant modeling method, where frequency-coupling effects are modeled by the transfer function vector rather than the transfer function matrix, so the modeling complexity is reduced. Furthermore, based on the idea of mathematical induction, an analytical and accurate recursive SISO impedance model is derived. The resulting recursive SISO impedance model can characterize the frequency-coupling dynamics of arbitrary order with a low computation burden. Experiments validate the accuracy of the recursive SISO impedance modeling method. [ABSTRACT FROM AUTHOR]

Interactions of identical inverters in weak grids have received wide attentions. However, in a practical wind farm, parameters of grid-side inverters and lengths of collecting lines are not completely the same. In this case, a multi-inverter system is not symmetric, and thus the interaction mechanism could be more complicated than that of identical inverters. To investigate the interaction mechanism of differently parameterized inverters, this paper proposes a clustering-based modeling method, in which inverters with identical parameters are classified as one group. The clustering-based model allows for efficient stability assessment using three low-order transfer function matrices, instead of a full-order dynamic model. The root locus analysis is applied in the clustering-based model for stability analysis. Results show that the interconnection of distinct groups of inverters deteriorates common current stability, but has no impact on interactive current stability. The simulation and rtlab-based experimental results validate the effectiveness of the proposed model and the interaction mechanism of differently parameterized inverters. [ABSTRACT FROM AUTHOR]

The accurate prediction of molten iron quality in blast furnace (BF) can effectively improve the smelting efficiency and operation stability, which plays an important role in energy saving, emission reduction, and economic benefits improving. With the improvement of BF information acquisition technology and data storage technology, some data-driven modeling methods for simultaneously predicting multiple molten iron quality indexes have been presented. However, these modeling processes do not explore the use of the correlation information among multiple molten iron quality indexes, resulting in the suboptimal models. In addition, they do not pay attention to the molten iron quality indexes missing issue, which may lead to a great decline in modeling accuracy. To avoiding the above disadvantage, this article presents a novel multiple-input–multiple-output random vector functional-link networks. An output space transfer matrix is exploited, which not only makes full use of the correlation among all the molten iron quality indexes, but also greatly reduces the impact of index missing. For the corresponding tricky optimization problem, an alternative optimization algorithm is given, the convergence of which is guaranteed. A simulation of an actual BF data illustrates the proposed method. [ABSTRACT FROM AUTHOR]

In this article, a novel nonlinear model is proposed to describe the permittivity of the plasma, and the nonlinear optical bistable phenomenon of the 1-D photonic crystals, which is composed of a nonlinear plasma defect layer, is theoretically investigated by the conventional transfer matrix method (TMM) under TM wave. It is figured out that the permittivity of nonlinear plasma exists in bistable state. Then, the tuning effects of the number of the photonic crystals’ (PCs) periodic layers, the incident frequency, the thicknesses of the nonlinear plasma layer, and the incident angle on the optical bistability (OB) have been emphatically studied. Additionally, the transmission and the reflectance under the influences of this bistable tuning are further proposed. The calculated results show that the adjustment of the OB can be achieved without changing the multi-layer material geometry. This multi-composite nonlinear plasma defect structure with the tunable bistable phenomenon can be applied to numerous valuable optical devices, such as novel optical power threshold devices, logic gates, and optical information memory. [ABSTRACT FROM AUTHOR]

In this article, the frequency coupling of weak grid-connected doubly fed induction generator (DFIG) based wind turbines (WT) during asymmetric faults have received little attention. To analyze the frequency coupling phenomenon of the system during asymmetric faults, this article established the complex transfer function model in αβ frame based on the transformation relationship between complex transfer function and transfer matrix. According to the complex transfer function, the frequency coupling mechanism of the DFIG system during asymmetric faults is revealed, and the transfer evolution law of coupling frequencies is described in detail. Finally, the correction of theoretical analysis and the validity of proposed complex transfer models are verified by the simulation and experiment. [ABSTRACT FROM AUTHOR]

In this article, we rapidly and accurately solve out reflection and transmission coefficients in the multilayered fully anisotropic media (MFAM) based on the transfer-matrix method (TMM) so that we could find out the energy transmission course (ETC) of plane waves that transmit through MFAM in the air background. Beginning with Maxwell’s equations, MFAM’s Helmholtz equation could be obtained by the known transverse- $k$ vectors of plane waves. Through a series of complicated manipulations applied to the derivation of Helmholtz equations, we can attain ordinary differential equation of electric fields that merely exist in a certain direction and then compute four different eigenvalues in different MFAM regions. Under 3-D cases, meanwhile, concrete expressions of other fields can be obtained by given electric fields in the fixed direction. The ETC of electromagnetic fields in the tangential continuity is mainly considered in the TMM, and hence, the transferring matrix of electromagnetic field between MFAM regions can be constructed to achieve reflection and transmission coefficients. With various plane-wave modes such as transverse electromagnetic (TEM), transverse electric (TE), and transverse magnetic (TM) field modes, respectively, computational results of MFAM models are solved and adopted to compare with those from the commercial software of COMSOL. Finally, to discuss deeply and efficiently achieve color images, we acquire those reflection and transmission coefficients of more complicated fully anisotropic materials under the different transverse- $k$ vectors. Our work can be an efficient and reliable solver for excavating prospective applications to predict ETC of models with single-layered/multilayered materials possessing fully anisotropy. [ABSTRACT FROM AUTHOR]

An $\alpha $ -power refractive index profile circular core fiber Bragg grating (FBG) sensor has been numerically and experimentally analyzed for the first time. In the experiment, 40% concentrated hydrofluoric acid (HF) has been used to fabricate an etched FBG (e-FBG) sensor with variable cladding thickness. The proposed study can also be demonstrating the marginal tuning capability of Bragg wavelength shift by deeply etched cladding process. The target of this article is to analyze the $\alpha $ -power refractive index profile e-FBG sensor. For this purpose, a transfer matrix method (TMM) has been devised to analyze the complicated double-clad waveguide structure, while grating is taken along the length of fiber core. In this article, three samples have been fabricated and analyzed with various etched cladding thicknesses, i.e., 6, 8, and $10~\mu \text{m}$ , which give significant change in the refractive index sensitivity. Experimental results of sensitivity analysis have been matched closely with the numerical one. The estimated maximum sensitivity of the developed $\alpha $ -power e-FBG sensor has been found $\approx 35$ nm/refractive index unit (RIU). Also, this value is equivalent to the minimum change in the refractive index of $\leq 10^{-5}$. It has been found that the Bragg wavelength can be tuned marginally as a result of reducing the cladding diameter. It has been noticed that the tuning range can be substantially improved by the deep etching process along with $\alpha $ -power refractive index profile FBG and found to be $4.5 \,\times \, 10^{-3}$ RIU at optimum cladding diameter. [ABSTRACT FROM AUTHOR]

It is valuable to improve the resolution and speed of acoustic beamforming in real-time measurement, especially fault location, noise mapping, and so on. However, multiplication of the power transfer matrix takes much time in the iteration of the deconvolution algorithm. This article proposes a novel method based on the convolution approximation and GPU platform to obtain acoustic imaging with a high resolution quickly. First, the power propagation matrix is approximated by a symmetric Toeplitz block Toeplitz (STBT) matrix, which can transform the product of matrix and vector into the convolution of two smaller patterns. Three different convolution kernels are derived for the convolution operation, including 2-D variant convolution kernel, 2-D invariant convolution kernel, and 1-D separable invariant convolution kernel. Then, the regularization deconvolution algorithm with the convolution kernel is derived. Besides, the relation between approximation error, time cost, and setting parameters is discussed. The results show that the separable invariant convolution kernel can obtain the fastest imaging and relatively accurate localization, while the time consumption of the variant kernel is the highest. Simulations and experiments are operated on the CPU and GPU to make a comparison, which validates that our proposed deconvolution-GPU implementation can significantly improve the computation speed for the matrix on a large scale. [ABSTRACT FROM AUTHOR]

Only one high-intensity focused ultrasound device has been clinically approved for transcranial brain surgery at the time of writing. The device operates within 650 and 720 kHz and corrects the phase distortions induced by the skull of each patient using a multielement phased array. Phase correction is estimated adaptively using a proprietary algorithm based on computed-tomography (CT) images of the patient’s skull. In this article, we assess the performance of the phase correction computed by the clinical device and compare it to: 1) the correction obtained with a previously validated full-wave simulation algorithm using an open-source pseudo-spectral toolbox and 2) a hydrophone-based correction performed invasively to measure the aberrations induced by the skull at 650 kHz. For the full-wave simulation, three different mappings between CT Hounsfield units and the longitudinal speed of sound inside the skull were tested. All methods are compared with the exact same setup due to transfer matrices acquired with the clinical system for ${N} = 5$ skulls and ${T} = 2$ different targets for each skull. We show that the clinical ray-tracing software and the full-wave simulation restore, respectively, 84% ± 5% and 86% ± 5% of the pressure obtained with hydrophone-based correction for targets located in central brain regions. On the second target (off-center), we also report that the performance of both algorithms degrades when the average incident angles of the acoustic beam at the skull surface increase. When incident angles are higher than 20°, the restored pressure drops below 75% of the pressure restored with hydrophone-based correction. [ABSTRACT FROM AUTHOR]

A d-q frame impedance model of modular multilevel converter (MMC), which is suitable for high-frequency resonance (HFR) analysis under the condition that the number of submodules in MMC reaches hundreds level, is presented in this work. A 10th-order dynamic phasor model for the MMC is linearized and combined with a control subsystem model. A modular modeling approach based on transfer matrix is applied to the overall linearized model to derive the impedance model. The validity and accuracy of the model are verified using a 501-level MMC aggregated model in SIMULINK. Results show that the impedance model has satisfactory accuracy in the frequency ranging from 1 to 3000 Hz. Then, the impedance model is used to analyze an HFR accident in a realistic MMC project. Therefore, a high time delay in controller is proved can provide negative resistance in high frequency and cause instability. [ABSTRACT FROM AUTHOR]

For complex and difficult-to-control blast furnace systems with hour-level delay, accurate prediction of molten iron quality plays a very important role in guaranteeing the stable and smooth operation. Recently, some data-driven multi-input multi-output (MIMO) modeling methods have been proposed to model multiple molten iron quality indicators including molten iron temperature, silicon content ([Si]), phosphorus content ([P]), and sulfur content ([S]). However, those data-driven MIMO models ignore the interindicator correlation, which leads to the suboptimal model for the estimation of multiple molten iron quality indicators. Moreover, the above methods do not pay attention to the molten iron quality indicators missing issue, which often occurs on blast furnace. To address the above two issues, this article proposed a novel MIMO Takagi–Sugeno (T–S) fuzzy model by utilizing an output transfer matrix. In the novel method, the interindicator correlation was explicitly modeled by a low-rank learning of the correlation matrix that overcame the great challenge of jointly determining the fuzzy rules of the MIMO T–S model and the interindicator correlation. Moreover, a new complete complementary matrix can be obtained by the output transfer from the original incomplete matrix resulting from molten iron quality indicators missing issues. For the corresponding optimization problem, an effective alternating optimization algorithm is presented, and the convergence of the optimization algorithm is also rigorously proved. The validity of the proposed method is verified by comparison with some related methods on real blast furnace data. [ABSTRACT FROM AUTHOR]

Starting from Boltzmann’s approximate equation, the Bhatnagar-Gross-Krook (BGK) collision model of inhomogeneous dusty plasma is derived. In the case of an external magnetic field, the expression of the dielectric coefficient of the dusty plasma under the collision condition of the fully ionized BGK is obtained by combining the collision effect and charging effect of the dusty plasma. By using the transfer matrix method, the reflection coefficient and transmission coefficient of electromagnetic (EM) waves under different external magnetic fields and dusty plasma parameters are calculated, and the propagation characteristics of dusty plasma under the nonuniform fully ionized BGK collision model are analyzed. Results show that the inelastic collision absorption effect between electrons and dust particles is the strongest when the incident frequency of EM waves is close to or equal to the charging frequency of dusty plasma. Meanwhile, the size and density of dust particles can affect the effective collision frequency of dusty plasma and strongly influence the EM wave propagation characteristics. By analyzing the propagation characteristics of different external magnetic fields to circularly polarized waves, changing the size and direction of the external magnetic field can artificially control the low coefficient band range and size of the EM wave transmission coefficient in dusty plasma. These results provide a theoretical basis for the study of EM wave propagation in weakly impacted fully ionized dusty plasma and communication problems in near space. [ABSTRACT FROM AUTHOR]

In this letter, a digital control strategy with a simple transfer matrix between three-phase ac input voltages and dc-link voltage is proposed for a three-phase buck rectifier (3ph-BR) under unbalanced ac input conditions. The proposed digital control strategy can eliminate both the odd harmonics of the ac input currents and the even harmonics of the output voltage ripple under unbalanced ac input conditions. Compared with the state-of-the-art control strategies, the proposed control strategy does not require the extraction of the positive sequence voltage and the negative sequence voltage, thus a three-phase lock loop and complex calculation are not required. The proposed control strategy is essentially an input voltage feedforward control, which is independent of the loop bandwidth of the feedback system. Therefore, the processing speed of the digital processor is no longer the critical factor for the 3ph-BR under the unbalanced ac input conditions. The proposed control strategy makes it possible to utilize low-cost and small-sized digital processors. An experimental prototype of a 1.5-kW 3ph-BR with the proposed control strategy is built to verify the analysis results. [ABSTRACT FROM AUTHOR]

In this article, the coupling between the inner conductor and the shield of a coaxial cable is summarized with different coupling directions and shielding grounding conditions. An internal and external transmission line (IETL) transfer matrix is proposed to validate this coupling relationship. The induced voltage and current of the IETLs can be more intuitively represented by the IETL transfer matrix and the port voltage and current. By introducing the three-conductor system and the surface transfer impedance into the transmission line theory, the IETL transfer matrix representation of the transmission line equation with coupling components is obtained. Moreover, when analyzing the problems of coupling between field and transmission line, the coaxial cable can be equivalent to a bare wire by using IETL transfer matrix. According to this idea, an improved approximation method based on Hertzian dipole and a numerical method based on the finite element method algorithm are proposed to calculate the radiation of a coaxial cable and the crosstalk between a coaxial cable and a bare wire. Then, the results of the two methods are compared with the electromagnetic calculation software. [ABSTRACT FROM AUTHOR]

It is of great significance to adjust bandgaps (BGs) of laminated Galfenol phononic crystal (PC) by using nonlinearity of Villari effect and shunt elements for effectively reducing vibration. Based on the modified constitutive equations, the effective elastic modulus, and transfer matrix method (TMM), a dynamic nonlinear model with tunable elastic modulus for the PC is established. Comparisons between the calculated and measured results show that the model can describe the changing laws of the Galfenol rod’s effective elastic modulus with frequency and shunt capacitance, and can predict nonlinearity of the rod. The effects of stress and bias field on the attenuation constant peak and cutoff frequency of Bragg BGs (BBGs) are analyzed, and the optimal and suboptimal operating points of BBGs are determined. The effects of shunt capacitance and stress on BBGs, resonant BGs (RBGs), and common BGs (CBGs) are analyzed, and it is found that larger magnetomechanical coupled factor and smaller shunt capacitance can effectively reduce vibration. [ABSTRACT FROM AUTHOR]

In this article, a simple periodic 1-D magnetized plasma photonic crystal (PPC) is proposed. The effects of plasma frequency and plasma cyclotron frequency on the absorption of such magnetized PPCs are investigated theoretically by the transfer matrix method. The simulated results show that, for the TM wave, a tunable absorption window in the transmission region (AWTR) can be achieved when the incident angle is 82°, and the absorption peak of AWTR shifts to the higher frequencies when the plasma frequency and plasma cyclotron frequency are increased. On this basis, a multistack structure is designed by splicing periodic PPC structures with different plasma cyclotron frequencies. The calculated results indicate that an ultrawideband absorption band can be achieved for the stacked structure, and the broadband transmission window in the absorption region (TWAR) can be obtained by changing the distribution of plasma cyclotron frequency. Besides, the ultrawideband absorption and TWAR can be realized in different frequency bands after optimization parameters. Those simulated results can provide ideas for designing the angle-dependent polarized splitters, tunable ultrawideband absorbers, radomes, or switchable absorption–transmission window signal modulators. [ABSTRACT FROM AUTHOR]

This article presents a new method for accurately designing and analyzing an antenna or array. The proposed technique operates solely on the transfer admittance matrix of a perfect electrically conducting antenna fabric that is obtained using a full-wave simulator only once. The desired antenna, which must be a subset of the fabric, is then synthesized by progressively loading the fabric and applying a computationally efficient iterative postprocessing technique that transforms the stored admittance matrix into one that corresponds to the desired antenna or array. Given that the admittance matrix of the fabric is used as the basis for all subsequent antennas that can be represented by the fabric, it contains the solutions to an entire class of antennas. The proposed method is demonstrated by applying it to the class of colinear antennas up to five wavelengths long, arranged along a single axis. The method is validated by comparing its results to those obtained using a conventional full-wave simulator. The proposed method is applied first to the case of multiple loads located at arbitrary port locations along the fabric. Then, open-circuited loads are used to decimate the tips of a linear antenna to demonstrate that the method accurately predicts the response of an electrically shorter antenna. Finally, decimation is used to transform the fabric into an array of smaller antennas, where it is shown that mutual coupling effects are accurately predicted. [ABSTRACT FROM AUTHOR]

The theory of electrostatic (or, more accurately, slow electric or quasi-electrostatic) waves propagation in 1-D magnetized plasma periodic structures, at frequencies below both the plasma and cyclotron frequencies, is presented using the transfer matrix method. It assumes that the applied static magnetic field is perpendicular to the surface of the plasma layers. The dispersion relation of the waves is obtained and it is shown to break up into bands of allowed and forbidden propagation, which are conspicuous in periodic structures. Furthermore, the transmittance behavior of the electrostatic waves as a function of frequency is studied. At a fixed value of the wavenumber, the frequency range of forbidden band gaps is found to become smaller by increasing the plasma width, while the forbidden band gaps become broader as external magnetic field increases. [ABSTRACT FROM AUTHOR]

Instrument transformers suffer from weak nonlinearities, which may have a significant impact on harmonic measurements. Therefore, their detailed characterization should be based on a nonlinear model instead of a mere measurement of the frequency response function. Starting from this assumption, this article compares different models that can be employed to represent the behavior of voltage transformers (VTs): simplified Volterra models, frequency transfer matrixes (FTMs), and spectral linearization approximation; an inductive VT has been considered as a case study. The results highlight that the FTM approach is significantly affected by the range of variation of the fundamental component, while remarkable accuracy can be reached with the spectral linearization approximation at the expense of complexity. On the other hand, simplified Volterra models allow obtaining an effective tradeoff between the achieved accuracy and the number of coefficients. [ABSTRACT FROM AUTHOR]

We propose a method that simultaneously identifies a sparse transfer matrix and a disturbance signal for a multizone building’s temperature dynamics from the measurements of inputs and outputs. The proposed method is based on solving a convex optimization problem whose cost function involves an $\ell _{1}$ -penalty to promote a sparse solution. The method ensures that the transfer matrix is sparse, so that only dominant interactions among zones are retained in the model. The disturbance, which is mostly occupant-induced, is assumed to be a piecewise-constant signal, which aids in identification, since the derivative of a piecewise-constant signal is a sparse signal. We test our method on data from a virtual building (a simulation model) and a real building. Results from the virtual building show that the proposed method can accurately identify a sparse network model and a transformed disturbance. Results from the real building data—that does not have a ground truth—show that the method produces sensible results. [ABSTRACT FROM AUTHOR]

The properties of the square array of coupled Microring Resonators (MRRs) with interstitial rings are studied. Dispersion behavior of the interstitial square coupled MRRs is obtained through the transfer matrix method with the Floquet-Bloch periodic condition. Analytical formulas of the eigen wave vectors, band gaps and eigen mode vectors are derived for the special cases of the interstitial square coupled MRRs array with identical couplers and the regular square coupled MRRs array without the interstitial rings. Then, the eigen modes’ field distribution are calculated for each of the four eigen wave vectors for a given frequency through the secular equation. Finally, numerical simulation is performed for an interstitial square coupled MRRs array with identical couplers and a regular square coupled MRRs array. The simulation result verifies the analytical analysis. Finally, the loaded quality factors of the interstitial 5-ring configuration, the regular 4-ring configuration and the 1-ring configuration are obtained. It is found that the loaded quality factor of the interstitial 5-ring configuration is >20 times and >8 times as high as those of the 1-ring configuration and the regular 4-ring configuration respectively, making it attractive in applications like selective filters, ultra-sensitive sensor and four-wave mixing quantum entangled photon pair sources. [ABSTRACT FROM AUTHOR]

Distance protection encounters some problems such as time coordination, protection of short lines, capacitive charging current and high impedance faults. Its shortcomings are extended in the case of protection of hybrid transmission lines, including overhead line and underground cable. To cope with the mentioned problems, in this paper, a novel approach is proposed for pilot protection of hybrid transmission lines. The proposed approach utilizes three phase voltage and current signals of both ends and transfer matrix of the hybrid line. Indeed, voltage and current angles of specific points on the line are calculated from both ends and the absolute values of the differences between the results obtained from the sending and receiving ends are computed for each point to detect the fault and identify its exact location and phase. The achieved results confirm the security, dependability, and efficiency of the algorithm in critical conditions of power system, i.e., high impedance fault occurrence, power swing, different strengths of equivalent sources at both ends, loss of time synchronization of remote end data, and different fault locations with various inception angles. Although the proposed method is very simple, its performance is surprisingly satisfactory and it is suitable for practical implementation in real-life applications. [ABSTRACT FROM AUTHOR]

In this article, we present the analysis of a special featured grating-assisted surface plasmon resonance (SPR) phenomena by multiple stacked metamaterial and silver layers as one grating structure. The bimetallic layer of gold (Au) and silver (Ag) has been used with stacked multiple negative refractive index (NRI) metamaterial layers to explore the special featured sensing capability. NRI grating with Ag layer supports better coupling to excite the multimode for the proposed structure at the same excitation condition. Hence, the alternating layer of NRI material along with Ag is used as a grating structure that is an excellent combination of the grating layer through which the proposed structure supports better coupling to the adjacent sensing region. The grating parameters have been optimized in such a way to enhance the number of resonance modes in the sensing region. It is found that SPR sensor sensitivity using negative diffraction order has a larger dip, while the resonant angle became wider for positive diffraction order. The transfer matrix method is used for the calculation of various parameters. The special featured structure with corresponding response graphs is described along with discussing what happens when the metamaterial layer thickness varies (and vice versa). Sensitivity tunability is demonstrated with variable metamaterial layer thickness. A sensitivity study is a significant parameter in the design of any high-sensitive sensor to enhance the performance. Hence, the sensitivity slope property has been explored further for each case. [ABSTRACT FROM AUTHOR]

This article presents an efficient electromagnetic (EM) characterization technique to extract the permeability and permittivity tensors of multilayer graphene-plasma formations. This method uses the scattering parameters of normally incident circularly polarized plane waves in free space, making use of the circular polarization to deal with the discontinuity ambiguities in the extracted tensorial permeabilities and permittivities. The proposed method directly determines the linear permeability and permittivity tensors from the combined parameters that are deduced from the circularly polarized wave components. This simple procedure succeeds in overcoming the limitation to usable terahertz and optical frequency bands suffered by existing extraction techniques for lossy and lossless anisotropic material behavior. The retrieved graphene-plasma tensor elements are validated by means of comparison with analytical parameters obtained by solving the original EM problem using the transfer matrix method extended for the circularly polarized fields. [ABSTRACT FROM AUTHOR]

This paper presents an active fault diagnosis (AFD) method with reduced excitation for detection and identification of sensor faults of vehicles in a platoon formation. By introducing a probing signal into the platooning, it will allow an active excitation of the system, reveling a residual component, with the same frequency, that can be explored to obtain a fault identification of specific system faults. A supervisor is introduced to monitor the platoon behavior and activate the auxiliary input whenever the system natural excitation is insufficient for a clear fault diagnosis. This solution will allow the fault diagnosis to behave as active or passive through the adaptive signal provided by the supervisor. A dual Youla-Jabr-Bongiorno-Kucera (YJBK) matrix transfer function, also known as fault signature matrix (FSM) is investigated to get a fault diagnosis. In order to obtain an online identification of specific faults in the system, a Taylor approximation of the FSM is pursued. Computational simulations with a high-fidelity full-vehicle model, provided by CarSim, are carried out to demonstrate the effectiveness of the proposed active approach. A direct comparison between an active and a passive behavior in the same scenario shows that the active fault diagnosis method outperforms the passive approach whenever the dynamic behavior does not provide sufficient excitation. Furthermore, the excitation supervisor is able to significantly reduce the amount of artificial excitation introduced into the system ensuring a more energy efficient active fault diagnosis. [ABSTRACT FROM AUTHOR]

The ray-series (RS) method, which is practically more tractable and feasible than the transfer matrix (TM) method for the time-domain analysis, is examined and applied for investigation of temporal reflection and transmission responses of an N-layer structure for a plane wave incidence. These responses are represented by reduced reflection and transmission coefficients associated with unit step functions with different effective time periods and weightings depending on electromagnetic properties of the layers constituting the N-layer structure. Numerical and simulation analyses in line with the residue theorem and Bromwich integral were performed to validate our formalism and practically demonstrate its applicability for temporal analysis. [ABSTRACT FROM AUTHOR]

The stability margin is an important attribute for the robustness analysis of the closed loop in a control system design, which indicates the tolerant-ability of the closed-loop stability to system uncertainty (or fault). Seeking to develop an advanced data-driven monitoring and management framework for control performance (especially for robust stability) of the closed-loop system, this paper presents a study on the data-driven realization of the closed-loop stability margin, and its application to control-performance-oriented process monitoring. Specifically, without identifying the system parameters, a data-driven realization of the stability margin is first determined based on the identified multiplication operator of the closed-loop transfer function matrices using time-domain closed-loop measurements. Second, a control-performance-oriented process monitoring approach is proposed based on the determined data-driven realization of the stability margin. The contributions of this paper will bridge the gap between the model-based robustness analysis/design and the data-driven techniques for the future research. The main results of this paper are verified and demonstrated through the case studies on a dc motor benchmark system. [ABSTRACT FROM AUTHOR]

An innovative effective medium model based on the transfer matrix method is proposed for the simulation of 1D-periodic subwavelength metal–dielectric laminated structures excited by TM- or TE-polarized plane wave with oblique incidence angles. The homogeneous medium of each period is characterized by TM or TE complex effective permeability and conductivity. The resulting effective single layer (ESL), having the same total thickness of the multilayer laminate, is represented by a transfer matrix given by the product of the transmission matrices of the periods composing the structure. Notice that this model allows the homogenization of n-layer periods, while the effective medium approximation method is formulated for only two-layer periods. The ESL is used to compute the transmission and reflection coefficients and the shielding effectiveness of 1D-periodic nanolayered transparent coatings made by alternating layers of silver, zinc oxide, or titanium dioxide films, in the frequency range from 100 MHz up to 10 THz. The propagating wave performances of the ESL are compared with the ones given by the rigorous multilayer model. Finally, two different screens made of transparent coatings over glass are proposed and analyzed. [ABSTRACT FROM AUTHOR]

This paper generalizes a propagation graph model to polarized indoor wireless channels. In the original contribution, the channel is modeled as a propagation graph in which vertices represent transmitters, receivers, and scatterers, while edges represent the propagation conditions between vertices. Each edge is characterized by an edge transfer function accounting for the attenuation, delay spread, and the phase shift on the edge. In this contribution, we extend this modeling formalism to polarized channels by incorporating depolarization effects into the edge transfer functions and hence, the channel transfer matrix. We derive closed form expressions for the polarimetric power delay spectrum and cross-polarization ratio of the indoor channel. The expressions are derived considering average signal propagation in a graph and relate these statistics to model parameters, thereby providing a useful approach to investigate the averaged effect of these parameters on the channel statistics. Furthermore, we present a procedure for calibrating the model based on method of moments. Simulations were performed to validate the proposed model and the derived approximate expressions using both synthetic data and channel measurements at 15 GHz and 60 GHz. We observe that the model and approximate expressions provide good fit to the measurement data. [ABSTRACT FROM AUTHOR]

This paper proposes a d–q cross-coupling current controller for permanent magnet synchronous motor (PMSM) drives. Slotting and cross-coupling effects in PMSMs cause the effective air-gap length to vary with the rotor angle and distort the distribution of the air-gap flux. Such distortions have a significant influence on the current control by changing the relationship between the stator currents and voltages. To investigate their effects, a d–q model is established in this paper, which is suitable for describing the voltage characteristics of the actual PMSMs. The model contains the angle-dependent parameters, the cross-coupling inductance between d–q axes, and the q-axis permanent magnet flux linkage, unlike the ideal d–q model. The transfer function matrix from the d–q currents to d–q voltages of PMSM is newly derived from the model. Based on that, the current controller with the feedback and feedforward terms of 2-by-2 matrix is proposed. It is designed so that the independent gains are in low-pass filter forms and the coupling control gains are zero with eliminating interference between d–q axes. The proposed controller contributes to providing the stable control performance by canceling the slotting and cross-coupling effects. The performance of the proposed current controller is verified by experimental results. [ABSTRACT FROM AUTHOR]