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The purpose of this paper is to present a time domain discontinuous Galerkin (DG) approach for modeling wideband frequency dependent surface impedance boundary conditions.

The paper solves the Maxwellian initial value problem in a computational domain, which is spatially discretized by the higher order DG method. On the boundary of the computational domain the paper applies a suitable impedance boundary condition (IBC). The frequency dependency of the impedance function is modeled by auxiliary differential equations (ADE).

The authors will study the resonance frequency and the Q factor of different types of cavity resonators including lossy materials. The lossy materials are modeled by means of IBCs. The authors will compare the results with analytical results, as well as numerical results obtained by direct calculations where lossy materials are included explicitly into the numerical model. Several convergence studies are performed which demonstrate the accuracy of the approach.

Modeling of frequency dependent boundary conditions in time domain with finite difference time domain method (FDTD) method is considered in numerous papers, as well as in frequency domain finite element method (FEM), and in a few papers also time domain FEM. However, FDTD method is only first order accurate and fails in modeling of complicated surfaces. FEM allows for high order accuracy, but time domain modeling is numerically extremely expensive. In frequency domain, broadband modeling of frequency dependent boundary conditions requires several simulations as opposed to the time domain, where a single simulation is needed. The time domain DG method proposed in this paper allows to overcome the difficulties. The authors introduce a broadband surface impedance formulation based on the ADE approach for the higher order DG method.

The purpose of this paper is to focus on the frequency-dependent non-linear magnetization behaviour of the soft magnetic material, which influences both the energy loss and the performance of the electrical machine. The applied approach is based on measured material characteristics for various frequencies and magnetic flux densities. These are varied during the simulation according to the operational conditions of the rotating electrical machine. Therewith, the fault being committed neglecting the frequency-dependent magnetization behaviour of the magnetic material is examined in detail.

The influence of non-linear frequency-dependent material properties is studied by variation of the frequency-dependent magnetization characteristics. Two different non-oriented electrical steel grades having the same nominal losses at 1.5 T and 50 Hz, but different thickness, classified as M330-35A and M330-50A are studied in detail. Both have slightly different magnetization and loss behaviour.

This analysis corroborates that it is important to consider the frequency-dependency and saturation behaviour of the ferromagnetic material as well as its magnetic utilization when simulating electrical machines, i.e., its performance. The necessity to change the magnetization curve according to the applied frequency for the calculation of operating points depends on the applied material and the frequency range. Using materials, whose magnetization behaviour is marginally affected by frequency, causes a deviation in the flux-linkage and the electromagnetic torque in a small frequency range. However, analysing larger frequency ranges, the frequency behaviour of the material cannot be neglected. For instance, a poorer magnetizability requires a higher quadrature current to keep the same torque leading to increased copper losses. In addition, the applied iron-loss model plays a central role, since changes in magnetization behaviour with frequency lead to changes in the iron losses. In order to study the impact, the iron-loss model has to be capable to incorporate the harmonic content, because particularly the field harmonics are influenced by the shape of the magnetization curve.

This paper gives a close insight on the way the frequency-dependent non-linear magnetization behaviour affects the energy loss and the performance of electrical machines. Therewith measures to tackle this could be derived.

This paper aims to investigate the interrelations between purchasing power parity (PPP) and uncovered interest parity (UIP) in BRICS economies, namely, Brazil, Russia, India, China and South Africa, by checking the validity of the capital-enhanced equilibrium exchange rate (CHEER) approach. Further, this study tests whether the CHEER results are data frequency-dependent.

The present study uses monthly data ranging from 1997M01 to 2016M12 and considers the US economy as the representative foreign country. The study uses structural break unit root test and structural break cointegration technique to test the presence of economic relationships between nominal exchange rates and each of the price and interest rate differentials. Then, the study examines the validity of the CHEER approach by testing the appropriate theoretical restrictions.

The cointegration results suggest the existence of two cointegrating vectors representing UIP and PPP conditions. For all countries, the data appear to support the hypothesis that the system contains UIP and PPP relations. However, each of the international parity hypotheses is strongly rejected when formulated in isolation and jointly, leading to repudiation of the CHEER validity. Further, it is found that the results are data frequency-dependent and suggest that higher frequencies should be used as they provide additional information.

First, the literature on equilibrium exchange rates in BRICS economies is scanty. BRICS economies are large-emerging economies and one of the fastest growing economies and thus entail an empirical enquiry on their exchange rates. Second, the empirical application has mainly used monthly data to test the validity of the CHEER approach. However, data frequencies could affect the results. To the best of the authors’ knowledge, this study is the first to check data frequency-dependency in examination of the CHEER approach.

The purpose of this paper is to introduce a new method to model a stranded wire efficiently in 3D finite element simulations.

In this method, the stranded wires are numerically approximated with the Cauer ladder network (CLN) model order reduction method in 2D. This approximates the eddy current effect such as the skin and proximity effect for the whole wire. This is then projected to a mesh which does not include each strand. The 3D fields are efficiently calculated with the CLN method and are projected in the 3D geometry to be used in simulations of electrical components with a current vector potential and a homogenized conductivity at each time step.

In applications where the stranded wire geometry is known and does not change, this homogenization approach is an efficient and accurate method, which can be used with any stranded wire configuration, homogenized stranded wire mesh and any input signal dependent on time steps or frequencies.

In comparison to other methods, this method has no direct frequency dependency, which makes the method usable in the time domain for an arbitrary input signal. The CLN can also be used to interconnected stranded cables arbitrarily in electrical components.

The purpose of this paper is to numerically investigate time-harmonic elastic wave propagation with the analysis of effective wave velocities and attenuation coefficients in a three-dimensional elastic composite consisting of infinite matrix and uniformly distributed soft, low-contrast and absolutely rigid disc-shaped micro-inclusions.

Within the assumptions of longitudinal mode of a propagating wave as well as dilute concentration and parallel orientation of inclusions in an infinite elastic matrix, Foldy’s dispersion relation is applied for introducing a complex and frequency-dependent wavenumber of homogenized structure. Then, the effective wave velocities and attenuation coefficients are directly defined from the real and imaginary parts of wavenumber, respectively. Included there a far-field forward scattering amplitude by a single low-contrast inclusion given in an analytical form, while for the other types of single scatterers it is determined from the numerical solution of boundary integral equations relative to the displacement jumps across the surfaces of soft inclusion and the stress jumps across the surfaces of rigid inclusion.

On the frequency dependencies, characteristic extremes of the effective wave velocities and attenuation coefficients are revealed and analyzed for different combinations of the filling ratios of involved types of inclusions. Anisotropic dynamic behavior of composite is demonstrated by the consideration of wave propagation in perpendicular and tangential directions relatively to the plane of inclusions. Specific frequencies are revealed for the first case of wave propagation, at which inclusion rigidities do not affect the effective wave parameters.

This paper develops a micromechanical study that provides a deeper understanding of the effect of thin-walled inclusions of diversified rigidities on elastic wave propagation in a three-dimensional composite. Described wave dispersion and attenuation regularities are important for the non-destructive testing of composite materials by ultrasonics.

The paper aims to give the reader a consolidated state of art in the full‐wave modeling of passive interconnection systems using equivalent circuits and presents several advantageous techniques developed by the authors.

The paper presents the theory of generalized partial element equivalent circuit (PEEC) modeling in the frequency domain (FD) and time domain (TD) developed by the authors. The widely spread simplified approaches are derived from this general formulation and the most important issues (e.g. stability in the TD) are considered. The theoretical part is completed by a simulation example, which shows the efficiency of studied methods.

Novel approaches for co‐simulation of passive interconnections in their circuit environment.

The PEEC method is widely used in the practice of computational electromagnetics, e.g. by the authors in the practical electromagnetic compatibility simulation.

The paper is based on the original work of authors carried through over many years.

The purpose of this paper is to present an analysis of common mode oscillations of several kilohertz in electrical drive systems. The analysed oscillations occur especially in electrical drive systems with active front end (AFE), common DC link and long motor cables and are independent of the well‐known reflection phenomenon. Owing to the resulting overvoltages, the motor isolation lifetime may be significantly reduced.

For the analysis of the described problem, all parts of the common mode system of an electrical drive system are carefully modelled. This leads to an analysis of the frequency behaviour of the common mode system. The excitation mechanisms are also analysed and simulation in the time domain is performed to show the resulting overvoltages. Finally, measurements confirm the findings.

The investigations identified the reasons for the oscillations: the common mode system behaviour, including the common mode resonant behaviour of some special kinds of motor. Furthermore, the excitation mechanism is found to be dependent on the modulation schemes of the AFE and the inverters. Accordingly, a special remedy concerning the modulation is derived and compared to other known remedies. The results of the simulations show the good efficiency of the proposed remedy.

The presented results describe important basics for the development of electrical drive systems. By taking these issues into consideration, many unpredictable failures can be avoided.

The purpose of this paper is to offer a fast and accurate simulation method for printed spiral radio frequency identification coils and to extract the parameters of an equivalent resonance circuit.

The frequency‐dependent port impedance of a rectangular spiral multi‐turn antenna is simulated with the non‐retarded partial element equivalent circuit (PEEC) method. The discretization settings needed for an accurate modeling of skin and proximity effects at medium frequencies as well as parasitic capacitances are discussed. Two different PEEC approaches are used, a magneto‐quasi‐static (resistive and inductive cells) model and a non‐retarded (capacitive cells included) model in order to extract a reduced equivalent resonance circuit which is beneficial to describe the inductive coupling to further inductors via the transformer concept.

With optimized mesh settings, the extremely fast simulation can be carried out just in seconds whereas the results compared to a computationally much more expensive CST Microwave Studio^® reference solution as well as an analytical direct current solution show errors of only about a few percent.

The methodology is limited to frequencies up to the first self‐resonant frequency of the coil. In addition, piecewise‐homogeneous materials are implied.

Specialized mesh settings allow for a very fast and accurate simulation of rectangular spiral inductors. A method for the parameter extraction of a resonance circuit is proposed by evaluating two different PEEC models.

Efficient calculations of the transient behaviour after disturbances of large-scale power systems are complex because of, among other things, the non-linearity and the stiffness of the overall state equation system (SES). Because of the rising amount of flexible transmission system elements, there is an increasing need for reduced order models with a negligible loss of accuracy. With the Extended Nodal Approach and the application of the singular perturbation method, it is possible to reduce the order of the SES adapted to the respective setting of the desired tasks and accuracy requirements.

Based on a differential-algebraic equation for the electric power system which is formulated with the Extended Nodal Approach, the automatic decomposition into reduced order models is shown in this paper. The paper investigates the effects of different coordinate systems for an automatic order reduction with the singular perturbation method, as well as a comparison of results calculated with the full and reduced order models.

The eigenvalues of the full system are approximated sufficiently by the three subsystems. A simulation example demonstrates the good agreement between the reduced order models and the full model independent of the choice of the coordinate system. The decomposed subsystems in rotating coordinates have benefits as compared to those in static coordinates.

The paper presents a systematic decomposition based only on a differential-algebraic equation system of the electric power system into three subsystems.