Electromagnetic Sources Research Articles

Energy Efficient, Highly Precise Cascade Dryness Control for Fibrous Tape by Induction-Based Surface Heating of a Rotating Steel Cylinder with Moving Inductors

Drying various materials constitutes an essential component of several industrial processes, e.g., paper production. Typically, rotating cylinders heated internally by water steam are used for drying tape-shaped material in paper-making machines. Such an approach remains very energy-consuming, while the whole process is expensive and in conflict with the global policy of reducing energy consumption in heavy industry. One promising alternative method of drying fibrous tapes is the induction heating of drying cylinders. In this paper, we propose a drying system based on a set of inductors (electromagnetic field sources) that generate energy in the mantle of the cylinder and dry the running tape. By enabling the movement of the inductors, the system provides a high level of flexibility in terms of reacting to the varying humidity of the tape. Additionally, imaging the temperature field on the cylinder surface provides a supplementary source of information, enabling the temperature profile to be controlled. Two types of humidity control systems, a one-loop feedback control and a cascade control, were designed and analyzed. Simulation analysis and experimental verification performed using a semi-industrial setup proves that using the proposed cascade control ensures more than 30% faster response of the whole dryness control system.

Monostatic microwave ellipsometry for material characterization

We propose Microwave ellipsometry based on monostatic measurements in which the transmitter and receiver are located in the same location. The traditional ellipsometry technique is based on bi-static measurements in which the polarization state of the reflected wave from a sample is analyzed to estimate its electromagnetic properties. Initially, the ellipsometric methods had been applied in the optical spectrum since the wavelengths and the constituent atomic structure are comparable leading to the strong matter-wave interaction and polarization changes. Thanks to the recent advancements in metasurfaces, chiral sensing can now be potentially applied to characterize materials at the microwave frequencies in a compact laboratory environment. In this paper, we lay down the fundamentals of microwave monostatic elliposmetry method. We demonstrate the permittivity detection by a numerically simulated monostatic sensing set-up composed of L-shaped unit chiral unit cells etched on the dielectric sample and illuminated by a monochromatic linearly polarized electromagnetic source. We construct the Jones matrix to extract the polarization states from the reflection coefficients. The determination of the reflection coefficients is greatly simplified by using a cross-dipole antenna receiver which provides the ratio of the two corresponding orthogonal complex currents.

수직 배열된 원전 케이블 트레이 내부 누설전류에 의한 전자파 장해 분석

An analytical interpretation of the electromagnetic interference between open cable trays vertically placed in a nuclear power plant is presented using a mode-matching method. The cable trays were modeled by considering the various structural parameters. Subsequently, the electric and magnetic fields and the electromagnetic sources were derived using the Helmholtz equation in conjunction with the superposition principle. After dividing the overall analyzed space into multiple sub-regions, the continuities of the electric and magnetic fields were applied to the interfaces between the sub-regions to compute the modal coefficients included in the electric field expressions. The proposed mode-matching method was verified by checking the convergence of the electric field at certain interesting points and comparing the electric field derived from the mode-matching method with that calculated from a commercial electromagnetic simulator. Furthermore, the electromagnetic interference caused by the type and number of electromagnetic sources, and the distances between the later walls and cable trays were investigated. The results of this study provide valuable information to alleviate the electromagnetic interference between the open cable trays in a nuclear power plant.

Analytical Model to Calculate Radial Forces in Permanent-Magnet Synchronous Machines

There are three principal sources of noise and vibration in electrical machines: electromagnetic sources, mechanical sources, and aerodynamic sources. Nowadays, one of the major advantages of permanent-magnet synchronous machines is their torque density. This density is achieved through a high magnetic flux density in the air gap, which is achieved through hard magnets. Unfortunately, in these machines, electromagnetic forces have been identified as the main source of vibration and noise, and high magnetic flux densities make these vibrations and noises more significant. With the aim of better understanding the relationship between electromagnetic forces and design variables, this article, which is the continuation of previous work, firstly describes a study of the sources of magnetic forces in permanent-magnet synchronous machines. Subsequently, an analytical model for the computation of the radial forces originating from electromagnetic sources in permanent-magnet synchronous machines is stated. This model analyzes the forces on both the rotor surface and the base of the stator tooth. The analytical results were corroborated through simulations using the finite element method (FEM) and also by experimental tests performed over two prototypes. The results achieved by the analytical model show good agreement with both FEM results and experimental measurements.

Conversion of a donut-shaped pattern to a directive one using a wide frequency band hive-shaped pattern director antenna

ABSTRACT In this paper, a pattern director antenna (PDA) with 4 GHz bandwidth was designed, simulated, and measured. In the past, to convert a donut-shaped pattern into a directive, mode converters have been used. But their losses, weight, size, and cost additions had a negative impact on the total system performance. Furthermore, the very low bandwidth of the mode converters prevented their use in a broadband source. When testing an electromagnetic diode, the operating frequency may change dramatically. PDA is best used to change the output mode of electromagnetic sources which their frequency is a function of the size of the electromagnetic source and voltage applied. To solve this problem, we propose the pattern directors. The PDA accepts directly (without the need for mode conversion) an azimuthally symmetric generated mode of an electromagnetic source and radiates a directive and pencil-beam pattern. 3D printer technology has been used to reduce manufacturing costs. The gain is from 17 to 22 dB in the frequency band. The S11, main lobe deviation (MLD), and sidelobe level (SLL) are less than −15 dB, 2°, −6 dB in all frequency band, respectively. Also, the 3 dB beamwidths are 4 to 8 and 11 to 15 in the E and H plates, respectively. The pattern was measured at three frequencies in the frequency band. The simulation results are a good agreement with the measurement.

Event Distortion-Based Clustering Algorithm for Energy Harvesting Wireless Sensor Networks

Wireless sensor networks (WSNs) consist of compact deployed sensor nodes which collectively report their sensed readings about an event to the Base Station (BS). In WSNs, due to the dense deployment, sensor readings can be spatially correlated and it is nonessential to transmit all their readings to the BS. Therefore, for more energy efficient, it is vital to choose which sensor node should report their sensed readings to the BS. In this paper, the event distortion-based clustering (EDC) algorithm is proposed for the spatially correlated sensor nodes. Here, the sensor nodes are assumed to harvest energy from ambient electromagnetic radiation source. The EDC algorithm allows the energy-harvesting sensor nodes to select and eliminate nonessential nodes while maintain an acceptable level of distortion at the BS. To measure the reliability, a theoretical framework of the distortion function is first derived for both single-hop and two-hop communication scenarios. Then, based on the derived theoretical framework, the EDC algorithm is introduced. Through extensive simulations, the performance of the EDC algorithm is evaluated in terms of achievable distortion level, number of alive nodes and harvested energy levels. As a result, EDC algorithm can successfully exploit both the spatial correlation and energy harvesting to improve the energy efficiency while preserving an acceptable level of distortion. Furthermore, the performance comparisons reveal that the two-hop communication model outperforms the single-hop model in terms of the distortion and energy-efficiency.

Optimization of the Microwave-Assisted Carbothermical Reduction Process for Metals from Electric Arc Furnace Dust with Biochar

The main purpose of this work was to extract valuable metals from EAF dust with the addition of biochar, using microwaves to control and optimize the carbothermical reduction process. To achieve better microwave penetration and the most homogeneous electromagnetic heat source distribution possible in a sample, the content of EAF dust and biochar in centimeter-size spherical particles prepared by the pelletization process was considered to be radially heterogeneous. The content of EAF dust was determined experimentally and the effective permittivity, permeability, and thermal conductivity of the EAF dust as well as biochar–EAF powder mixture were determined using effective medium approximation. The microwave heating of a multilayered pellet of biochar-containing EAF dust was simulated and investigated. The influence of the distribution of the components within the pellet on the effectiveness of the microwave heating was investigated, as was the influence of the biochar conductivity. The interaction of the pellet with both plane waves in free space and with H10 mode waves in a single-mode waveguide was considered. The most optimal distribution of EAF dust and biochar within the pellet for the reduction process was determined.

A new transient electromagnetic prospecting method in TBM tunnel environment

Tunnel boring machine (TBM) construction is a safe and efficient tunnel construction method at this stage, which contributes to the essential role of ahead prospecting methods, an essential prerequisite for ensuring the safety of TBM construction. Due to the high interference in the TBM tunnel environment, it is difficult to effectively apply multiple ahead prospecting methods. The existing geophysical methods are restricted because of the extremely small prospecting space in the TBM tunnel environment. Also, the TBM tunnel environment is required to introduce high-resolution detection methods. This paper proposes an ahead prospecting method suitable for TBM tunnel, using the simulation of three-dimensional vector finite element. Specifically, this prospecting method uses transient electromagnetic electrical radiation sources to emit and receives the Ex. Besides, the full field apparent resistivity imaging method is used to perform imaging interpretation of the adverse geological structures in front of the tunnel face in a semi-quantitative manner, to obtain the prospecting results required for the ahead prospecting in TBM tunnel.

Wide-band conversion of donut-shaped pattern to directive one by square-shaped pattern director antenna

AbstractIn this paper, an antenna with 8 GHz (7–15 GHz) bandwidth is designed, simulated, fabricated, and measured. Commonly, for the effective use of electromagnetic sources, mode converters are used to transform donut-shaped patterns to directive patterns. This paper introduces a novel antenna called the pattern director antenna (PDA) that solves most problems associated with the azimuthally symmetric output modes of high-power microwave sources. The PDA accepts directly (without the need for mode conversion) an azimuthally symmetric generated mode of an electromagnetic source and converts it to radiate a directive pattern. For the proof of concept and validation of the design by simulations, the 3D printing technology [using polylactic acid (PLA)] is used to fabricate the PDA and measure its radiation patterns and return loss. The selected material is cheap and also environmentally friendly. The antenna was coated with aluminum to become a conductor. The gain is from 16.8 to 21.8 dB in the frequency range. The S11, main lobe deviation (MLD), and sidelobe level (SLL) are less than −15 dB, 2°, and −7 dB, in all frequency range, respectively. The simulation results are in good agreement with the measurement.

Investigation of the Polycrystalline Silicon PV Cell Efficiency in 3D Approximation versus Electromagnetic Field under Monochromatic Illumination

This manuscript is about the electric output of the silicon (Si) photovoltaic (PV) cell versus the electromagnetic field of a radio wave and a monochromatic illumination in three-dimensional (3D) assumptions. The polarisation direction of the electromagnetic wave and power density are fixed. The electromagnetic wave is provided by electromagnetic emission sources such as the telecommunication, radio, or TV antennas. A PV system is installed in the vicinity of an electromagnetic emission source. The current produced by the PV cell is sensitive to electromagnetic field increase more than the electric voltage. The electromagnetic field causes the decomposition of the current into two components which are a transferred current and a leakage current. The transferred component provides the transmitted current to the external load while the leakage component gives the loss of the carrier charge into the junction. Consequently, this decomposition of the current shares the electric power in transferred electric power and leakage electric power. The transferred electric power is obtained only in the intermediate circuit, and the maximum power point (MPP) shifts to the short circuit situation as the junction dynamic velocity becomes the greatest. However, the leakage electric power corresponds to a loss of the minority carrier’s charge in the junction during the crossing of the junction. This loss causes a Joule heating effect of the junction. The heating of the junction causes the quality degradation of the PV cell mainly due to the electric component. The solar illumination wavelength is presenting the inversion phenomenon with the maximum of the electrical outputs of the silicon PV cell of around 0.70 μm which provides the greatest conversion efficiency. This value has been chosen for the modelling of the radio wave influence. Hence, the conversion efficiency increases when the PV system is far away from the electromagnetic emission source. PV system installation in the vicinity of an electromagnetic emission source is not advised.

Cross-Modal Cortical Activity in the Brain Can Predict Cochlear Implantation Outcome in Adults: A Machine Learning Study.

Objectives: Prediction of cochlear implantation (CI) outcome is often difficult because outcomes vary among patients. Though the brain plasticity across modalities during deafness is associated with individual CI outcomes, longitudinal observations in multiple patients are scarce. Therefore, we sought a prediction system based on cross-modal plasticity in a longitudinal study with multiple patients.METHODS: Classification of CI outcomes between excellent or poor was tested based on the features of brain cross-modal plasticity, measured using event-related responses and their corresponding electromagnetic sources. A machine learning estimation model was applied to 13 datasets from 3 patients based on linear supervised training. Classification efficiency was evaluated comparing prediction accuracy, sensitivity/specificity, total mis-classification cost, and training time among feature set conditions.Results:Combined feature sets with the sensor and source levels dramatically improved classification accuracy between excellent and poor outcomes. Specifically, the tactile feature set best explained CI outcome (accuracy, 98.83 ± 2.57%; sensitivity, 98.00 ± 0.01%; specificity, 98.15 ± 4.26%; total misclassification cost, 0.17 ± 0.38; training time, 0.51 ± 0.09 sec), followed by the visual feature (accuracy, 93.50 ± 4.89%; sensitivity, 89.17 ± 8.16%; specificity, 98.00 ± 0.01%; total misclassification cost, 0.65 ± 0.49; training time, 0.38 ± 0.50 sec).Conclusion:Individual tactile and visual processing in the brain best classified the current status when classified by combined sensor–source level features. Our results suggest that cross-modal brain plasticity due to deafness may provide a basis for classifying the status. We expect this novel method to contribute to the evaluation and prediction of CI outcomes.

A sliced-3D approach to finite-difference time-domain modeling by optimizing perfectly matched layers

Finite-difference time-domain forward modeling is often used to gain a more quantitative understanding of the interactions between electromagnetic fields and targets. To undertake full 3D simulations, the computational demands are challenging, so simulations are often undertaken in two dimensions, in which assumptions in the propagation of electromagnetic fields and source type can result in errors. We have developed the concept of a sliced-3D simulation, wherein a thin slice of a 3D domain with strictly 2D geometry is used to minimize computational demands while obtaining synthetic waveforms that contain full 3D propagation effects. This approach requires optimization of perfectly matched layer (PML) boundary condition parameters so as to minimize the errors associated with the source being located close to the boundary, and as a result of grazing-incident angle wave conversion to evanescent energy. We explore the frequency dependence of PML parameters, and we establish a relationship between complex frequency stretching parameters and effective wavelength. The resultant parameter choice is shown to minimize propagation errors in the context of a simple radioglaciological model, in which 3D domains may be prohibitively large, and for a near-surface cross-borehole survey configuration, a case in which full-waveform inversion may typically be used.

Twisted Electromagnetic Multi-Gaussian Schell-Model Pulsed Source and Its Propagation

Here, a novel family of random electromagnetic sources (twisted electromagnetic multi-Gaussian Schell-model pulsed beams) exhibiting transverse orbital angular momentum is proposed. The physically realizable conditions for these sources are established, and the analytical formulas of the cross-spectral density matrix elements of the beam propagating through an ABCD optical system are derived within the framework of the extended Collins formula. The behaviors of the spectral density, and the spectral degree of coherence of the beam during transmission are investigated numerically. This work enriches the classical theory of stochastic electromagnetic beams propagation, and may benefit applications requiring a specified degree of beam coherence with transverse orbital angular momentum.

Collapse and revival of spatial coherence on free-space propagation

We demonstrate analytically and numerically that the transverse spatial coherence (the spectral degree of coherence) of the field radiated by two partially correlated electromagnetic sources oscillates as a function of propagation distance in free space. In particular, it is possible for its magnitude to completely collapse to zero on propagation, and then return again to unity at a further distance. Our results are a direct demonstration of the wave character of the optical correlation functions. A similar oscillatory effect occurs for the degree of polarization.

Electromagnetic stimulation increases mitochondrial function in osteogenic cells and promotes bone fracture repair

Bone fracture is a growing public health burden and there is a clinical need for non-invasive therapies to aid in the fracture healing process. Previous studies have demonstrated the utility of electromagnetic (EM) fields in promoting bone repair; however, its underlying mechanism of action is unclear. Interestingly, there is a growing body of literature describing positive effects of an EM field on mitochondria. In our own work, we have previously demonstrated that differentiation of osteoprogenitors into osteoblasts involves activation of mitochondrial oxidative phosphorylation (OxPhos). Therefore, it was reasonable to propose that EM field therapy exerts bone anabolic effects via stimulation of mitochondrial OxPhos. In this study, we show that application of a low intensity constant EM field source on osteogenic cells in vitro resulted in increased mitochondrial membrane potential and respiratory complex I activity and induced osteogenic differentiation. In the presence of mitochondrial inhibitor antimycin A, the osteoinductive effect was reversed, confirming that this effect was mediated via increased OxPhos activity. Using a mouse tibial bone fracture model in vivo, we show that application of a low intensity constant EM field source enhanced fracture repair via improved biomechanical properties and increased callus bone mineralization. Overall, this study provides supporting evidence that EM field therapy promotes bone fracture repair through mitochondrial OxPhos activation.

Three-Dimensional Inversion of Borehole-Surface Resistivity Method Based on the Unstructured Finite Element

The electromagnetic wave signal from the electromagnetic field source generates induction signals after reaching the target geological body through the underground medium. The time and spatial distribution rules of the artificial or the natural electromagnetic fields are obtained for the exploration of mineral resources of the subsurface and determining the geological structure of the subsurface to solve the geological problems. The goal of electromagnetic data processing is to suppress the noise and improve the signal-to-noise ratio and the inversion of resistivity data. Inversion has always been the focus of research in the field of electromagnetic methods. In this paper, the three-dimensional borehole-surface resistivity method is explored based on the principle of geometric sounding, and the three-dimensional inversion algorithm of the borehole-surface resistivity method in arbitrary surface topography is proposed. The forward simulation and calculation start from the partial differential equation and the boundary conditions of the total potential of the three-dimensional point current source field are satisfied. Then the unstructured tetrahedral grids are used to discretely subdivide the calculation area that can well fit the complex structure of subsurface and undulating surface topography. The accuracy of the numerical solution is low due to the rapid attenuation of the electric field at the point current source and the nearby positions and sharply varying potential gradients. Therefore, the mesh density is defined at the local area, that is, the vicinity of the source electrode and the measuring electrode. The mesh refinement can effectively reduce the influence of the source point and its vicinity and improve the accuracy of the numerical solution. The stiffness matrix is stored with Compressed Row Storage (CSR) format, and the final large linear equations are solved using the Super Symmetric Over Relaxation Preconditioned Conjugate Gradient (SSOR-PCG) method. The quasi-Newton method with limited memory (L_BFGS) is used to optimize the objective function in the inversion calculation, and a double-loop recursive method is used to solve the normal equation obtained at each iteration in order to avoid computing and storing the sensitivity matrix explicitly and reduce the amount of calculation. The comprehensive application of the above methods makes the 3D inversion algorithm efficient, accurate, and stable. The three-dimensional inversion test is performed on the synthetic data of multiple theoretical geoelectric models with topography (a single anomaly model under valley and a single anomaly model under mountain) to verify the effectiveness of the proposed algorithm.

Radiation of arions by electromagnetic field of rotating magnetic dipole

The electromagnetic source of arions, as well as axions, is a scalar product of the magnetic field induction and the electric field intensity. For electromagnetic waves, this product can be nonzero only in the near zone. Pulsars and magnetars are natural sources of this type. Based on these considerations, we calculate the generation of arions by coherent electromagnetic field of rotating magnetic dipole of pulsars and magnetars. It is shown that the radiation of arion waves occurs at the frequency of magnetic dipole rotation. This radiation has a maximum when the angle between the rotation axis and the magnetic dipole moment of the neutron star is $\ensuremath{\pi}/4$ and it is completely absent, when the magnetic dipole moment is perpendicular or parallel to this axis. A formula for the angular distribution of arion radiation is constructed; and on its basis, it is shown that the radiation is maximal in the plane which is perpendicular to the axis of rotation.

A Correlation-Based Electromagnetic Time Reversal Technique to Locate Indoor Transient Radiation Sources

To overcome the multipath interference in locating transient electromagnetic (EM) radiation sources in an indoor environment, we propose a criterion that calculates the correlation between back-propagated signals from observation points, to be used in EM time reversal (EMTR) algorithms. The method introduced in this article has three main advantages with respect to classical methods that use full-wave simulations and other criteria, such as maximum field strength. First, compared with full-wave techniques in the back-propagation phase, the proposed correlation-based method utilizes approximated transfer functions from the ray-tracing technique, which can improve the computation efficiency. Second, an inverted-loss model is used for the back-propagation, which could reduce the localization error caused by multipath effects due to signal attenuation and time delay. Third, the proposed correlation criterion has weak correlation with the source characteristics, which makes it applicable to the localization in indoor reflective environments with only two observation points. Several numerical simulations are carried out to assess the performance of the proposed method. The results indicate that the proposed correlation-based EMTR technique is able to locate radiation sources accurately and efficiently in indoor reflective environments.

Anapole Meta-Atoms: Nonradiating Electric and Magnetic Sources.

The existence of classical nonradiating electromagnetic sources is one of the puzzling questions to date. Here, we investigate radiation properties of physical systems composed of a single ultrahigh permittivity dielectric hollow disk excited by electric or magnetic pointlike dipole antennas, placed inside the inner bore. Using analytical and numerical methods, we demonstrate that such systems can support anapole states with total suppression of far-field radiation and thereby exhibit the properties of electric or magnetic nonradiating sources. It is shown that the suppression of the far-field radiated power is a result of the destructive interference between radiative contributions of the pointlike dipole antennas and the corresponding induced dipole moments of the hollow disk. The experimental investigation of the nonradiating electric source has been performed to confirm our theoretical predictions. Our results pave the way to create and realize compact nonradiative sources for applications in modern wireless power transfer systems, sensors, RFID tags, and medical technologies.

Optimal template banks

When searching for new gravitational-wave or electromagnetic sources, the $n$ signal parameters (masses, sky location, frequencies,...) are unknown. In practice, one hunts for signals at a discrete set of points in parameter space, with a computational cost that is proportional to the number of these points. If that is fixed, the question arises, where should the points be placed in parameter space? The current literature advocates selecting the set of points (called a "template bank") whose Wigner-Seitz (also called Vorono\"i) cells have the smallest covering radius ($\equiv$ smallest maximal mismatch). Mathematically, such a template bank is said to have "minimum thickness". Here, for realistic populations of signal sources, we compute the fraction of potential detections which are "lost" because the template bank is discrete. We show that at fixed computational cost, the minimum thickness template bank does not maximize the expected number of detections. Instead, the most detections are obtained for a bank which minimizes a particular functional of the mismatch. For closely spaced templates, the fraction of lost detections is proportional to a scale-invariant "quantizer constant" G, which measures the average squared distance from the nearest template, i.e., the average expected mismatch. This provides a straightforward way to characterize and compare the effectiveness of different template banks. The template bank which minimizes G is mathematically called the "optimal quantizer", and maximizes the expected number of detections. We review optimal quantizer and minimum thickness template banks that are built as n-dimensional lattices, showing that even the best of these offer only a marginal advantage over template banks based on the humble cubic lattice.