Dosimetry of Various Human Bodies Exposed to Microwave Broadband Electromagnetic Pulses

In this paper, human exposures to ultra-wideband (UWB) electromagnetic (EM) pulses in the microwave region are assessed using a frequency-dependent FDTD scheme previously proposed by the authors. Complex permittivity functions of all biological tissues used in the numerical analyses are accurately expressed by the four-term Cole–Cole model. In our method, we apply the fast inverse Laplace transform to determine the time-domain impulse response, utilize the Prony method to find the Z-domain representation, and extract residues and poles for use in the FDTD formulation. Update equations for the electric field are then derived via the Z-transformation. Firstly, we perform reflection and transmission analyses of a multilayer composed of six different biological tissues and then confirm the validity of the proposed method by comparison with analytical results. Finally, numerical dosimetry of various human bodies exposed to EM pulses from the front in the microwave frequency range is performed, and the specific energy absorption is evaluated and compared with that prescribed in international guidelines.

Impedance eduction for uniform and multizone acoustic liners

This paper presents results for five uniform and two multizone liners based on data acquired in the NASA Langley Grazing Flow Impedance Tube. Two methods, Prony and CHE, are used to educe the impedance spectra for each of these liners for many test conditions. The Prony method is efficient and generally provides accurate results for uniform liners, but is not well suited for multizone liners. The CHE method supports assessment of both uniform and multizone liners, but is much more computationally expensive. The results from these liners demonstrate the efficacy of both eduction methods, but also clearly demonstrate that sufficient attenuation is required to support accurate impedance eduction. For the liners considered in this study, the data indicate approximately 3 dB attenuation is needed for each zone of a multizone liner in order to ensure quality impedance eduction results. This study was conducted in response to two acoustic liner research challenges in support of a collaboration of multiple national laboratories under the International Forum for Aviation Research.

Control loop oscillation detection and quantification using PRONY method of IIR filter design and deep neural network

Generally, the process industry is affected by unwanted fluctuations in control loops arising due to external interference, components with inherent nonlinearities or aggressively tuned controllers. These oscillations lead to production of substandard products and thus affect the overall profitability of a plant. Hence, timely detection of oscillations is desired for ensuring safety and profitability of the plant. In order to achieve this, a control loop oscillation detection and quantification algorithm using Prony method of infinite impulse response (IIR) filter design and deep neural network (DNN) has been presented in this work. Denominator polynomial coefficients of the obtained IIR filter using Prony method were used as the feature vector for DNN. Further, DNN is used to confirm the existence of oscillations in the process control loop data. Furthermore, amplitude and frequency of oscillations are also estimated with the help of cross-correlation values, computed between the original signal and estimated error signal. Experimental results confirm that the presented algorithm is capable of detecting the presence of single or multiple oscillations in the control loop data. The proposed algorithm is also able to estimate the frequency and amplitude of detected oscillations with high accuracy. The Proposed method is also compared with support vector machine (SVM) and empirical mode decomposition (EMD) based approach and it is found that proposed method is faster and more accurate than the later.

Properties of the Inter-area Modes of the U.S. Eastern Interconnection System

<div>With an increase in the oscillation events observed in the U.S. Eastern Interconnection (EI), it has become increasingly important to have a good understanding of the EI system oscillatory behavior. However, as compared to the Western Interconnection system (WI), not much work has been done in this regard for the EI system. Therefore, in this paper, a thorough analysis is carried out to identify inter-area modes and their properties for the EI system using a 80000+ bus real EI model. Multi-channel Prony method is used in this paper for estimating system modes and mode-shapes. </div>

Properties of the Inter-area Modes of the U.S. Eastern Interconnection System

<div>With an increase in the oscillation events observed in the U.S. Eastern Interconnection (EI), it has become increasingly important to have a good understanding of the EI system oscillatory behavior. However, as compared to the Western Interconnection system (WI), not much work has been done in this regard for the EI system. Therefore, in this paper, a thorough analysis is carried out to identify inter-area modes and their properties for the EI system using a 80000+ bus real EI model. Multi-channel Prony method is used in this paper for estimating system modes and mode-shapes. </div>

On quasinormal frequencies of black hole perturbations with an external source

In the study of perturbations around black hole configurations, whether an external source can influence the perturbation behavior is an interesting topic to investigate. When the source acts as an initial pulse, it is intuitively acceptable that the existing quasinormal frequencies will remain unchanged. However, the confirmation of such an intuition is not trivial for the rotating black hole, since the eigenvalues in the radial and angular parts of the master equations are coupled. We show that for the rotating black holes, a moderate source term in the master equation in the Laplace s-domain does not modify the quasinormal modes. Furthermore, we generalize our discussions to the case where the external source serves as a driving force. Different from an initial pulse, an external source may further drive the system to experience new perturbation modes. To be specific, novel dissipative singularities might be brought into existence and enrich the pole structure. This is a physically relevant scenario, due to its possible implication in modified gravity. Our arguments are based on exploring the pole structure of the solution in the Laplace s-domain with the presence of the external source. The analytical analyses are verified numerically by solving the inhomogeneous differential equation and extracting the dominant complex frequencies by employing the Prony method.

On the generalised eigenvalue method and its relation to Prony and generalised pencil of function methods

We discuss the relation of a variety of different methods to determine energy levels in lattice QCD simulations: the generalised eigenvalue, the Prony, the generalised pencil of function and the Gardner methods. All three former methods can be understood as special cases of a generalised eigenvalue problem. We show analytically that the leading corrections to an energy $$E_l$$ E l in all three methods due to unresolved states decay asymptotically exponentially like $$\exp (-(E_{n}-E_l)t)$$ exp ( - ( E n - E l ) t ) . Using synthetic data we show that these corrections behave as expected also in practice. We propose a novel combination of the generalised eigenvalue and the Prony method, denoted as GEVM/PGEVM, which helps to increase the energy gap $$E_{n}-E_l$$ E n - E l . We illustrate its usage and performance using lattice QCD examples. The Gardner method on the other hand is found less applicable to realistic noisy data.