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In this work, we study the photoproduction of ρ$$ \rho $$ mesons considering the proton and the nucleus as the target. Utilizing the dipole picture and the wave functions obtained via AdS/QCD, we were able to describe the HERA γp$$ \gamma p $$ data and extend the formalism to the nuclear case considering the Glauber–Gribov model. The preliminary results obtained in the nuclear regime are compared to the recent LHC PbPb→ρPbPb$$ PbPb\to \rho PbPb $$ data and suggest the presence of a nuclear effect called shadowing. [ABSTRACT FROM AUTHOR]

Cortical stimulation via electrocorticography (ECoG) may be an effective method for inducing artificial sensation in bi-directional brain-computer interfaces (BD-BCIs). However, strong electrical artifacts caused by electrostimulation may significantly degrade or obscure neural information. A detailed understanding of stimulation artifact propagation through relevant tissues may improve existing artifact suppression techniques or inspire the development of novel artifact mitigation strategies. Our work thus seeks to comprehensively characterize and model the propagation of artifacts in subdural ECoG stimulation. To this end, we collected and analyzed data from eloquent cortex mapping procedures of four subjects with epilepsy who were implanted with subdural ECoG electrodes. From this data, we observed that artifacts exhibited phase-locking and ratcheting characteristics in the time domain across all subjects. In the frequency domain, stimulation caused broadband power increases, as well as power bursts at the fundamental stimulation frequency and its super-harmonics. The spatial distribution of artifacts followed the potential distribution of an electric dipole with a median goodness-of-fit of R 2 = 0.80 across all subjects and stimulation channels. Artifacts as large as ±1,100 μV appeared anywhere from 4.43 to 38.34 mm from the stimulation channel. These temporal, spectral and spatial characteristics can be utilized to improve existing artifact suppression techniques, inspire new strategies for artifact mitigation, and aid in the development of novel cortical stimulation protocols. Taken together, these findings deepen our understanding of cortical electrostimulation and provide critical design specifications for future BD-BCI systems.

Urban power transmission and distribution rely on safe operation of vast network of power cables. Majority cable insulation defects can result in partial discharge (PD), which is therefore a degradation mechanism as well as a good indicator of cable insulation condition. Previously published PD models, however, failed to help quantitatively evaluate the insulation condition, or they fail to help differentiate those in between the conditions which are safe to operate from those which may need urgent testing or inspection. PD mechanisms in power cables are reviewed first in this paper. Then a novel model which is based on F distribution is proposed aiming to classify the PD activities which may be associated with different level of degradation. This is based on previous reports that PD activities manifests differently when the levels of degradation of the defect site(s) progress. After that, the features and effects of the model are presented with a case study, and the model is verified by analyzing the waveform similarities. Finally, the nature of the model is compared with the abc-model and the dipole model, demonstrating that proposed model can uniquely recognize the three stages of PD defect development.

We review a broad range of phenomena in diffraction in the context of hadronâ€"hadron, hadronâ€"nucleus collisions and deep inelastic leptonâ€"proton/nucleus scattering focusing on the interplay between the perturbative QCD and non-perturbative models. We discuss inclusive diffraction in DIS, phenomenology of dipole models, resummation and parton saturation at low x, hard diffractive production of vector mesons, inelastic diffraction in hadronâ€"hadron scattering, formalism of color fluctuations, inclusive coherent and incoherent diffraction as well as soft and hard diffraction phenomena in hadronâ€"hadron/nucleus and photonâ€"nucleus collisions. For each topic we review key results from the past and present experiments including HERA and the LHC. Finally, we identify the remaining open questions, which could be addressed in the continuing experiments, in particular in photon-induced reactions at the LHC and the future electronâ€"ion collider in the US, large hadron electron collider and future circular collider at CERN. [ABSTRACT FROM AUTHOR]

Cortical stimulation via electrocorticography (ECoG) may be an effective method for inducing artificial sensation in bi-directional brain-computer interfaces (BD-BCIs). However, strong electrical artifacts caused by electrostimulation may significantly degrade or obscure neural information. A detailed understanding of stimulation artifact propagation through relevant tissues may improve existing artifact suppression techniques or inspire the development of novel artifact mitigation strategies. Our work thus seeks to comprehensively characterize and model the propagation of artifacts in subdural ECoG stimulation. To this end, we collected and analyzed data from eloquent cortex mapping procedures of four subjects with epilepsy who were implanted with subdural ECoG electrodes. From this data, we observed that artifacts exhibited phase-locking and ratcheting characteristics in the time domain across all subjects. In the frequency domain, stimulation caused broadband power increases, as well as power bursts at the fundamental stimulation frequency and its super-harmonics. The spatial distribution of artifacts followed the potential distribution of an electric dipole with a median goodness-of-fit of R2 = 0.80 across all subjects and stimulation channels. Artifacts as large as ±1,100 μV appeared anywhere from 4.43 to 38.34 mm from the stimulation channel. These temporal, spectral and spatial characteristics can be utilized to improve existing artifact suppression techniques, inspire new strategies for artifact mitigation, and aid in the development of novel cortical stimulation protocols. Taken together, these findings deepen our understanding of cortical electrostimulation and provide critical design specifications for future BD-BCI systems.

The effects of photon self‐absorption and recycling on the efficiency of light generation and out‐coupling in perovskite light emitting diodes are assessed using a novel detailed‐balance compatible dipole emission model coupled to a full‐fledged drift‐diffusion simulation of charge transport in complex device stacks. This enables an in‐depth analysis of the impact on device performance of both, the optical modes and the electrical stack configuration. [ABSTRACT FROM AUTHOR]

[Display omitted] Calculating the magnetic interaction between magnetic particles that are positioned in close proximity to one another is a surprisingly challenging task. Exact solutions for this interaction exist either through numerical expansion of multipolar interactions or through solving Maxwell's equations with a finite element solver. These approaches can take hours for simple configurations of three particles. Meanwhile, across a range of scientific and engineering problems, machine learning approaches have been developed as fast computational platforms for solving complex systems of interest when large data sets are available. In this paper, we bring the touted benefits of recent advances in science-based machine learning algorithms to bear on the problem of modeling the magnetic interaction between three particles. We investigate this approach using diverse machine learning systems including physics informed neural networks. We find that once the training data has been collected and the model has been initiated, simulation times are reduced from hours to mere seconds while maintaining remarkable accuracy. Despite this promise, we also try to lay bare the current challenges of applying machine learning to these and more complex colloidal systems. [ABSTRACT FROM AUTHOR]

Location and characterization of a buried target from its electromagnetic induction response is a key problem for unexploded ordnance (UXO) detection. This article focuses on the influence of target size, depth, and orientation on its location and characterization on the basis of single dipole model with differential evolution (DE) algorithm against data collected by a portable transient electromagnetic (TEM) system. The sensor of the portable TEM system is composed of a single-layer transmitting coil and five three-component receiving coils. The diameter and current of transmitting coil are 0.5 m and 5 A. The length and resonant frequency of receiving coil are 5.6 cm and 180 kHz. The results of test-stand experiment show that the errors in location and characterization an underground target depend not only on the signal-to-noise ratio of the response, but also on the orientation of the target. For large target vertically (tail down) oriented, the estimated depth and characteristic response only represent the part of target close to the sensor, which are smaller than the real ones. For target flat-lying oriented, the algorithm overestimates both the depth and the characteristic response for the nonuniform primary field throughout the target. Finally, field experiment has been conducted. In general, the target can be located and characterized well even if the response of two targets is superimposed. The errors in estimated positions of about 5–7 cm support the conclusions from our test-stand experiment. These errors are especially critical when excavating targets.

Expressions for the rotational barrier height parameters K1 and K2 have been derived for dilute OH-impurity in KCl, KBr and KI lattices. These values are derived using an ab initio calculations using point charge point dipole model, which appears to be suited for the present systems. The obtained values are close to what is observed generally for such systems. The results explains the the energy orientational configuration direction for each system. The value of potential parameters K1 and K2 also describes the energy eigen values for the rotor. [ABSTRACT FROM AUTHOR]

This article presents a new analytical model for a permanent magnet that is particularly useful for calculating the magnetic force between two permanent magnets in a magnetic spring. The new model treats a single magnet as a pair of parallel magnetically charged surfaces, which we call dual-charged surfaces (DCSs). With the model, the force between two magnets is treated as the interaction of four charged surfaces, which can be calculated analytically as a function of magnets’ geometry and magnetization. This new model overcomes a major problem of other commonly used analytical models (dipole and point charge models) that predict infinitely large repulsive force when the separation distance between two magnets approaches zero and allows accurate calculation of the repulsive force in both near and far fields. The model is verified with experiments and finite element method (FEM) simulations through demonstrating correct prediction on the magnetic force versus separation over a wide range of the separation distance. With the root-mean-square deviation (RMSD) as a measure of the model accuracy, the DCS model is shown to have better accuracy over the Gilbert model (based on a pair of point charges), the Ampere model (based on a pair of dipoles), and the fitted polynomial method. [ABSTRACT FROM AUTHOR]

Using the charmonium light-front wavefunctions obtained by diagonalizing an effective Hamiltonian with the one-gluon exchange interaction and a confining potential inspired by light-front holography in the basis light-front quantization formalism, we compute production of charmonium states in diffractive deep inelastic scattering and ultra-peripheral heavy ion collisions within the dipole picture. Our method allows us to predict yields of all vector charmonium states below the open flavor thresholds in high-energy deep inelastic scattering, proton–nucleus and ultra-peripheral heavy ion collisions, without introducing any new parameters in the light-front wavefunctions. The obtained charmonium cross section is in reasonable agreement with experimental data at HERA, RHIC and LHC. We observe that the cross-section ratio σΨ(2s)/σJ/Ψ reveals significant independence of model parameters.

In this paper, hysteresis of magnetorheological (MR) fluids is identified from experimental tests following the mechanism of rate-independence and further studied to explore the hysteresis mechanism. The theoretical analysis based on the dipole model is provided to reveal the hysteresis mechanism of MR fluids. Specifically, the performance tests of a self-developed double-rod MR damper under different excitations show that instead of the typical force-velocity plot, the relationship between the force and displacement meets the requirements of rate-independence of the hysteresis well. A critical concept of “yield displacement” is defined and analyzed in the force-displacement plot to illustrate the hysteresis characteristics. In addition, the relationship of the normalized restoring force vs. strain is derived for a single chain from the dipole model. Then a stress-strain curve is developed for the multi-chain structure with an assumption of the dynamic equilibrium between the rupture and reconstruction of the chains. Sequentially, the hysteresis mechanism is established based on the force-displacement characteristics under reciprocating excitations. The consistency between the yield displacement in experiment and yield strain in theory verifies the effectiveness of the hypothetical hysteresis mechanism. The analysis results provide a guideline for the structural design of MR devices to enhance/reduce the hysteresis effect. The hysteresis mechanism-based further extension for the stress-strain properties of MR elastomers and the response time of MR fluids are provided as well.

The previously developed volume-surface integral equation-based domain decomposition method (VSIE-DDM) generally requires huge matrix filling time. To alleviate this issue, the equivalent dipole-moment (EDM) method is applied to the VSIE-DDM for complex electricallylarge planar thin-layer composite objects. Therefore, an efficient hybrid VSIE-DDM-EDM method is developed, in which the EDM technique remarkably saves the calculation time of the VSIE-DDM matrix. In this hybrid method, a new simplified prism vector basis-based dipole model is proposed. Compared with the Schaubert–Wilton–Glisson basis-based dipole model, the proposed model significantly reduces the number of numerical integrations within the threshold for planar thin dielectrics. Furthermore, to ensure the flexibility of the solution for a variety of electromagnetic problems, two strategies for solving equations (inner–outer iteration scheme and direct-iterative hybrid method) are, respectively, adopted. Finally, the multilevel fast multipole algorithm (MLFMA) is utilized for iteration procedure. Numerical examples are shown to validate the accuracy and efficiency of the proposed method. [ABSTRACT FROM AUTHOR]

An elementary magnetic emitter is considered as an approximation for the variable magnetic field of an electrically small radiating loop antenna. The frequency limits for applicability of the stationary dipole model are studied. Approximate formulas are obtained for characterizing the difference between the magnetic field of a circular loop antenna and the magnetic field of the equivalent point source. [ABSTRACT FROM AUTHOR]

One of the most common methods for performing non-destructive testing in steel tank floors is DC magnetic flux leakage (MFL). The magnetic dipole method is the most widely used mathematical technique to predict the MFL from defects in such structures. However, due to the complexity of an exact analytical description of an MFL system, researchers often make coarse approximations for the profile of the magnetic surface charge density $\sigma _{m}$ , orientation of the magnetic field H, and variation of relative permeability $\mu _{r}$. In this paper, the validity of these approximations is evaluated for 2-D rectangular defects in a steel plate, by comparing model predications with finite element results. The primary sources of deviation between the approximate solutions and true MFL profiles were found to be caused by assumptions that 1) $\sigma _{m}$ on the specimen surface adjacent to a flaw is zero. This assumption is equivalent to treating the orientation of H to be parallel to the specimen surface, even at locations in close proximity to a flaw and 2) local variation in permeability around the defect can be ignored. This approximation was found to cause an underestimation of $\sigma _{m}$ and, consequently, the predicted MFL. In contrast, approximating $\sigma _{m}$ to be zero at the bottom of a flaw, and approximating uniform distribution for $\sigma _{\mathbf {m}}$ on the vertical defect sides of a slot defect was found to generate only minor errors in an estimate of flux leakage. [ABSTRACT FROM AUTHOR]

Purpose. The application in electrostatic analogy of magnetostatics for inhomogeneous magnetized media of two known magnetization models. Methodology. A comparison of basic equations and formulas of electrostatic and magnetostatic field in immoveable isotropic inhomogeneous polarized medium for dipole model and the magnetization model by molecular currents is made. The value-analogues for dipole model of magnetization are established. Results. We have shown that the using of dipole model of magnetization is correct. There is not even formal analogy with electrostatic field in the case of using the magnetization model by molecular currents. The relation between the magnetizations for various models is obtained. It allows us to justify the using magnetization by molecular currents in electrostatic analogy. Originality. The magnetization for dipole model is introduced and the possibility of using magnetization by molecular currents in the formulas for calculating potential magnetostatic field in magnetized medium is substantiated. Practical value. The results allow to obtain correct formulation and solution of the problem of magnetostatic field calculation in inhomogeneous magnetized medium.

It has been shown theoretically and experimentally that locally magnetizing rebar through a protective layer of concrete makes it possible to determine both the depth of the protective layer of concrete and the diameter of rebar based on stray magnetic fields regardless of the magnetic properties of steel that rebar is made of. [ABSTRACT FROM AUTHOR]

In the present work, an investigation of wavelength-dependent absorption spectrum of spherical nanoparticles with different arrangements in organic medium using discrete dipole approximation (DDA) has been performed. Specifically, we study the impact of different arrangements such as monomer, dimer (compositionally symmetric and asymmetric), 1D array of spherical nanoparticle on surface plasmon resonance (SPR) peak position, and its spectral broadening in distinct regimes of the electromagnetic spectrum. Three different organic materials such as P3HT:PCBM blend (Poly(3-hexyl thiophene))-(phenyl-C61-buryricacid methyl ester), P3HT(poly (3-hexyl thiophene)), and PEOPT ((4’-(1”, 4”, 7”-trioaoctyl) phenyl) theophany) have been chosen in the present work to study the absorption and scattering spectrum of MNP. Further, near-field pattern of homo-dimer nanogeometry is also shown in the present study. We also observed that on increasing the interacting number of particles in 1D array, the corresponding FWHM (full width at half maxima) value increases as well, which covers the large spectral region of the electromagnetic spectrum. The comparison between dipole model and numerical model has been performed to analyze the extinction behavior of smaller size (d << λ) metal nano dimer which shows a good agreement in 400-600nm wavelength range. [ABSTRACT FROM AUTHOR]

Photoproduction of vector mesons is computed with dipole model in proton–proton ultraperipheral collisions (UPCs) at the CERN Large Hadron Collider (LHC). The dipole model framework is employed in the calculations of vector mesons production in diffractive processes. Parameters of the bCGC model are refitted with the latest inclusive deep inelastic scattering experimental data. Employing the bCGC model and boosted Gaussian light-cone wave function for vector mesons, we obtain the prediction of rapidity distributions of J/ψ and ψ(2s) mesons in proton–proton ultraperipheral collisions at the LHC. The predictions give a good description of the experimental data of LHCb. Predictions of ϕ and ω mesons are also evaluated in this paper. [ABSTRACT FROM AUTHOR]

AdS/QCD is implemented to calculate the basis light-front quantization (BLFQ) wave function for J/ψ meson. Exclusive J/ψ photoproduction is computed in the dipole picture using this holographic wave function. The bCGC model is employed in the calculation of J/ψ production for dipole amplitude. The differential cross-sections and total cross-sections of J/ψ meson are computed and compared with the experimental data. We fi nd that the AdS/QCD holographic wave function in BLFQ can be employed as a new candidate for the light-front wave function of J/ψ meson in diffractive process. [ABSTRACT FROM AUTHOR]

Four geomagnetic field models are discussed: IGRF, inclined, direct and simplified dipoles. Geomagnetic induction vector expressions are provided in different reference frames. Induction vector behavior is compared for different models. Models applicability for the analysis of satellite motion is studied from theoretical and engineering perspectives. Relevant satellite dynamics analysis cases using analytical and numerical techniques are provided. These cases demonstrate the benefit of a certain model for a specific dynamics study. Recommendations for models usage are summarized in the end. [ABSTRACT FROM AUTHOR]

In the present work, we report our observations drawn from the numerical simulation of absorption and scattering efficiencies of spheroid shape nanostructures using discrete dipole approximation technique. The absorption and scattering spectra are discussed in terms of shell thickness, composition of core and shell material, aspect ratio and size of the spheroidal nanoparticle (NP). The normalized electric field intensity around the sphere and spheroidal core@shell geometry has been studied in the present work. The characteristics of surface plasmon resonance (SPR) depend upon the symmetry of NP. For core@shell spherical nanogeometry, only one plasmon mode is found while for asymmetric nanogeometry (such as oblate and prolate), more distinct plasmonic modes are found. It was accounted that for oblate shape T i O @ A u spheroid of effective core radius 80 nm with 0.1 aspect ratio, two SPR peaks have been found, one is in visible range (725 nm) corresponding to transverse mode (TM) and the other is in an infrared region (1099 nm) corresponding to longitudinal mode (LM). In this paper, two cases of core-shell oblate shape nanogeometry are considered to study the optical properties; one is nanospheroid of metal (Au, Ag) shell with an oxide ( T i O ) core, and the other is metal core with an oxide shell. Numerical results illustrate that the behaviour of SPR of these two core@shell structures are quite different from each other. On increasing the shell thickness of metal@dielectric nanogeometry, SPR peak is red shifted while blue shifted for dielectric@metal nanogeometry. The comparison has been done between analytical (electrostatic approach) and numerical (DDA) approaches for ellipsoidal nanogeometries. It was observed that numerical results are in good agreement with analytical predictions for very small sized NP ( d < < λ). [ABSTRACT FROM AUTHOR]

The accuracy of a method for noninvasive localization of the origin of premature ventricular complex (PVC) was tested on simulated data. The method is based on inverse solution in terms of a single dipole that uses integrals of body surface potentials (BSPs) and a model of the torso volume conductor. ECGSIM software was used to simulate ectopic activation in a realistic ventricular model and BSPs on an inhomogeneous torso. Ectopic activation origins were simulated in 120 positions located in anterior, lateral, posterior, and septal segments of the right and left ventricle (RV, LV). In both septal segments 15 endocardial positions were specified, in all other segments 5 epicardial, 5 endocardial, and 5 in the valvular region were defined. Corresponding BSPs for initial 5 ms interval of the ectopic activity were simulated in 300 torso nodes as well as in 192 points representing BSP mapping leads. Simulated BSPs and the torso model with lungs and heart cavities were then used for the inverse localization of each PVC origin. The localization error (LE) was defined as the distance between the simulated and inversely estimated PVC origin position. All simulated PVC origins were localized in the correct ventricular segment. There was no significant difference between the LEs in the RV and LV, except the septal segments where the LE was significantly smaller in the RV (p<0.05). There were no significant differences between the LEs obtained using BSP maps from 300 torso nodes or 192 mapping leads (mean values LE300=5.2±4.4 mm and LE192=5.3±4.5 mm). [ABSTRACT FROM AUTHOR]

Wideband electromagnetic induction (WEMI) sensors are used to detect, classify, and locate obscured targets. WEMI sensors can be designed to measure the magnetic fields either in the time domain or frequency domain. They also capture multiple location measurements from a target by either a physical sensor array, a synthetic sensor array created by scanning the sensor, or a combination of the two. This letter uses a physical model for the sensor to develop a low-rank model for WEMI data. The data are organized into a matrix where the rows contain the time/frequency measurements and the columns contain the multiple locations so all of the data can be exploited jointly. It is shown that this data matrix can be processed directly with singular value decomposition (SVD) to extract three independent terms—one for target signature, one related to location, and one for tensors that define the orientation. The low-rank model predicts a maximum rank for WEMI measurements and is exploited to provide a relationship between the rank of the measurements and the number of linearly independent tensors for the target. Results are presented from the laboratory data to validate the low-rank model and demonstrate the connection between the data’s rank and the physical target. The low-rank model leads to a new “filterless” processing paradigm for exploiting WEMI data by using the SVD to perform sensor calibration, hardware debugging, as well as target detection. [ABSTRACT FROM PUBLISHER]

An investigation of the wavelength dependent extinction spectra of coated sphere with different core@shell compositions based on discrete dipole approximation technique has been presented in this paper. We have used combinations of A g, A u, and S i O for this analysis. Specifically, we study the impact of spherical core-shell thickness on its surface plasmon resonance (SPR) peak positions and corresponding spectral widening in distinct regimes of the spectrum. We observe that SPR peak of core-shell nanoparticle( CSNP) can be tuned over the visible to near-infrared spectrum region by manipulating the core/shell ratio and composition of core and shell. Specifically, for dielectric@metal (core@shell) nanoparticle, SPR peak position shifted towards lower wavelength as we increase the shell thickness, which is opposite to the SPR behavior of metal@dielectric. The extinction spectrum shows linear relation between SPR position and thickness of the shell. Further, we observed two resonant peaks for the case of metal@metal CSNP. The SPR peak of Au@Ag ( a 100 nm with shell thickness 8 nm) reveals two resonant peak corresponding to Au (594 nm) in red domain, while the peak in blue domain corresponds to Ag (402 nm). We also observe that optical resonance of CSNP can be tuned across the near-infrared region by changing the surrounding medium of higher refractive index. Further, near field pattern of core@shell geometry at resonance wavelength is also shown in the present study. We have also compared the numerical and analyticalmethod for smaller size CSNP with varying thickness and the results show good agreement. [ABSTRACT FROM AUTHOR]

Using the charmonium light-front wavefunctions obtained by diagonalizing an effective Hamiltonian with the one-gluon exchange interaction and a confining potential inspired by light-front holography in the basis light-front quantization formalism, we compute production of charmonium states in diffractive deep inelastic scattering and ultra-peripheral heavy ion collisions within the dipole picture. Our method allows us to predict yields of all vector charmonium states below the open flavor thresholds in high-energy deep inelastic scattering, proton–nucleus and ultra-peripheral heavy ion collisions, without introducing any new parameters in the light-front wavefunctions. The obtained charmonium cross section is in reasonable agreement with experimental data at HERA, RHIC and LHC. We observe that the cross-section ratio σ Ψ ( 2 s ) / σ J / Ψ reveals significant independence of model parameters. [ABSTRACT FROM AUTHOR]

The incoherent rapidity distributions of vector mesons are computed in dipole model in PbPb ultraperipheral collisions at the CERN Large Hadron Collider (LHC). The IIM model fitted from newer data is employed in the dipole amplitude. The Boosted Gaussian and Gaus-LC wave functions for vector mesons are implemented in the calculations as well. Predictions for the J / ψ , ψ ( 2 s ) , ρ and ϕ incoherent rapidity distributions are evaluated and compared with experimental data and other theoretical predictions in this paper. We obtain closer predictions of the incoherent rapidity distributions for J / ψ than previous calculations in the IIM model. [ABSTRACT FROM AUTHOR]

We calculate the coherent and incoherent production of J / ψ in PbPb ultraperipheral collisions (UPCs). The rapidity distributions of J / ψ in UPCs is the product of the photon flux distribution and the photon–nucleus cross section. The equivalent photon flux is computed in light-cone perturbation theory. The photon–nucleus cross section is calculated in the dipole model. We assume that two-gluon exchange contribution is coherent photonproduction cross section and the large- N c contribution provides an additional contribution to incoherent photonproduction cross section in photon–nucleus scattering. Our numerical results for the rapidity distributions of J / ψ production in PbPb UPCs at s N N = 2.76 TeV are compared to the experimental data measured by the ALICE Collaboration. [ABSTRACT FROM AUTHOR]

Modern fighter aircrafts, ships, missiles etc need to be very low Radar Cross Section (RCS) designs, to avoid detection by hostile radars. Hence accurate prediction of RCS of complex objects like aircrafts is essential to meet this requirement. A simple and efficient numerical procedure for treating problems of wide band RCS prediction Perfect Electric Conductor (PEC) objects is developed using Method of Moment (MoM). Implementation of MoM for prediction of RCS involves solving Electric Field Integral Equation (EFIE) for electric current using the vector and scalar potential solutions, which satisfy the boundary condition that the tangential electric field at the boundary of the PEC body is zero. For numerical purposes, the objects are modeled using planar triangular surfaces patches. Set of special sub-domain type basis functions are defined on pairs of adjacent triangular patches. These basis functions yield a current representation free of line or point charges at sub-domain boundaries. Once the current distribution is obtained, dipole model is used to find Scattering field in free space. RCS can be calculated from the scattered and incident fields. Numerical results for a square plate, a cube, and a sphere are presented over a bandwidth.

Simultaneous measurements of EEG-functional magnetic resonance imaging (fMRI) combine the high temporal resolution of EEG with the distinctive spatial resolution of fMRI. The purpose of this EEG-fMRI study was to search for hemodynamic responses (blood oxygen level-dependent - BOLD responses) associated with interictal activity in a case of right mesial temporal lobe epilepsy before and after a successful selective amygdalohippocampectomy. Therefore, the study found the epileptogenic source by this noninvasive imaging technique and compared the results after removing the atrophied hippocampus. Additionally, the present study investigated the effectiveness of two different ways of localizing epileptiform spike sources, i.e., BOLD contrast and independent component analysis dipole model, by comparing their respective outcomes to the resected epileptogenic region. Our findings suggested a right hippocampus induction of the large interictal activity in the left hemisphere. Although almost a quarter of the dipoles were found near the right hippocampus region, dipole modeling resulted in a widespread distribution, making EEG analysis too weak to precisely determine by itself the source localization even by a sophisticated method of analysis such as independent component analysis. On the other hand, the combined EEG-fMRI technique made it possible to highlight the epileptogenic foci quite efficiently.

In this paper, we present an improved analytical 3-D magnetic flux leakage (MFL) model of the field due to the occurrence of a surface-breaking defect in a ferromagnetic specimen. This model is based on our recent magnetic dipole model (MDM) of the MFL field, which was derived from the first principles of Maxwell’s equations. The MDM assumes a ferromagnetic specimen with a small defect exposed to a uniform external magnetic field, which is strong enough to saturate the specimen locally and causes uniform magnetization around the defect. Under this assumption, the MFL field can be mathematically described as if it is caused by magnetic charges on the surface of the defect. The magnitude and the sign of these magnetic charges are given by the magnetization vector and the local unit vector normal to the surface of the defect. Our original MDM uses only one parameter to describe the normal vector, and can only be used to analyze simple defect shapes, such as cylinders and cuboids. Our improved model in this paper uses two parameters to describe the normal vector, and can be used to analyze a wider range of defects, such as cones, ellipsoids, and real defect shapes. We illustrate our improved model by comparing its solution to that of the original MDM and validating it with the finite-element method simulations for different defect shapes. Our analysis shows that the improved model gives a good approximation of the MFL fields for a much wider range of defect shapes than the original MDM does. [ABSTRACT FROM PUBLISHER]

Despite evoked potentials' (EP) ubiquity in research and clinical medicine, insights are limited to gross brain dynamics as it remains challenging to map surface potentials to their sources in specific cortical regions. Multiple sources cancellation due to cortical folding and cross-talk obscures close sources, e.g. between visual areas V1 and V2. Recently retinotopic functional magnetic resonance imaging (fMRI) responses were used to constrain source locations to assist separating close sources and to determine cortical current generators. However, an fMRI is largely infeasible for routine EP investigation. We developed a novel method that replaces the fMRI derived retinotopic layout (RL) by an approach where the retinotopy and current estimates are generated from EEG or MEG signals and a standard clinical T1-weighted anatomical MRI. Using the EEG-RL, sources were localized to within 2 mm of the fMRI-RL constrained localized sources. The EEG-RL also produced V1 and V2 current waveforms that closely matched the fMRI-RL's ( n = 2) r(1,198) = 0.99, P < 0.0001. Applying the method to subjects without fMRI ( n = 4) demonstrates it generates waveforms that agree closely with the literature. Our advance allows investigators with their current EEG or MEG systems to create a library of brain models tuned to individual subjects' cortical folding in retinotopic maps, and should be applicable to auditory and somatosensory maps. The novel method developed expands EP's ability to study specific brain areas, revitalizing this well-worn technique. Hum Brain Mapp 37:1696-1709, 2016. © 2016 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The transformation of recorded electrocardiographic leads (source leads) into leads that are wanted but were not recorded (target leads) has many practical applications. In general, two transformation methods are put to use, a purely statistical one and a model-based one. They are briefly reviewed and compared. Lead transformations were first used in the early nineteen-sixties to transform the component leads of one vectorcardiographic lead system into those of another. Since then, the use of lead transformations has proliferated and they are currently applied for a variety of purposes. Lead transformations can be grouped according to the source and target leads that are involved. A few applications of lead transformations from the different groups are presented, with a focus on the practicality of the application. The validity and value of the dipole approximation in relation to lead transformations is discussed. [ABSTRACT FROM AUTHOR]

We consider inelastic proton-proton interactions at high energies in transverse spatial coordinates. Colliding hadrons are represented as ensembles of color dipoles. We use prescriptions of the M¨uller dipole cascade model for the elementary interaction probability. Multiparton interactions are taken into account in the framework of the eikonal approach. We consider two variants of the model, namely, with and without confinement taken into account. We obtain the asymptotic form of the collision profile function for large impact parameters. We use the considered approach to find the slope of the diffraction cone in elastic pp scattering at high energies and compare our results with other models describing profile functions and with the experimental data. [ABSTRACT FROM AUTHOR]

This paper presents the application of a bio-inspired method for optimizing a lifelike vectorcardiographic (VCG) model. During the model estimation, a Particle Swarm Optimization (PSO) seeks the optimal combination of all parameters that maximize the correlation coefficient ( r ) and minimize the Mean Squared Error (MSE) between the synthetic and directly measured VCG leads. The proposed method was tested on 52 different VCG records annotated as a healthy control (HC) from PTB database. 156 models were individualized without any previous analysis of the waves of the original records. The PSO method automatically provides very realistic models with a correlation coefficient r > 0.995 and MSE < 0.0005 mV 2 for 152 of the 156 VCG signals. [ABSTRACT FROM AUTHOR]

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This study proposes a method for the fast simulation of the distribution of alternating magnetic fields around internal cracks as well as cracks on the inner and outer diameter surfaces of a pipe. This method, which uses a bobbin-type magnetic camera to inspect cracks in small-bore piping systems, is based on a dipole model, allowing for the rapid calculation and storage of data on the distribution of alternating magnetic fields around cracks from a sensor moving inside a pipe. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The Pedemis sensor is a newly designed electromagnetic induction sensor that exhibits the unique characteristics of: 1) being able to physically decouple its transmitter and receiver modules and 2) offering the possibility of dynamically selecting various data acquisition modes (individual selection of transmitters and selection of data acquisition time for shallow/deep target interrogation). Such flexibility is expected to be instrumental in non-trivial terrains exhibiting either an abundant vegetation or being highly contaminated by large or dense clutter. Before validating the sensor in such challenging configurations, however, the Pedemis was taken to Aberdeen Proving Ground, MD, for its first test site validation. This letter presents the protocol adopted for data acquisition as well as inversion results on typical targets, including inversion of semi-synthetic data with up to five simultaneous targets. [ABSTRACT FROM PUBLISHER]

Cortical stimulation via electrocorticography (ECoG) may be an effective method for inducing artificial sensation in bi-directional brain-computer interfaces (BD-BCIs). However, strong electrical artifacts caused by electrostimulation may significantly degrade or obscure neural information. A detailed understanding of stimulation artifact propagation through relevant tissues may improve existing artifact suppression techniques or inspire the development of novel artifact mitigation strategies. Our work thus seeks to comprehensively characterize and model the propagation of artifacts in subdural ECoG stimulation. To this end, we collected and analyzed data from eloquent cortex mapping procedures of four subjects with epilepsy who were implanted with subdural ECoG electrodes. From this data, we observed that artifacts exhibited phase-locking and ratcheting characteristics in the time domain across all subjects. In the frequency domain, stimulation caused broadband power increases, as well as power bursts at the fundamental stimulation frequency and its super-harmonics. The spatial distribution of artifacts followed the potential distribution of an electric dipole with a median goodness-of-fit of R 2 = 0.80 across all subjects and stimulation channels. Artifacts as large as ±1,100 μV appeared anywhere from 4.43 to 38.34 mm from the stimulation channel. These temporal, spectral and spatial characteristics can be utilized to improve existing artifact suppression techniques, inspire new strategies for artifact mitigation, and aid in the development of novel cortical stimulation protocols. Taken together, these findings deepen our understanding of cortical electrostimulation and provide critical design specifications for future BD-BCI systems., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Lim, Wang, Shaw, Gong, Armacost, Liu, Do, Heydari and Nenadic.)

Abstract: The dipole model method (DMM) for simulating an alternating magnetic field around a hole-type crack in a small-bore pipe as a nondestructive evaluation method is proposed in the present paper. Simulation results were compared with those of the finite element method (FEM) and experimental results obtained using a bobbin-type magnetic camera, and they were found to be in good agreement; thus validating the DMM. The DMM was also found to be faster and easier to implement compared to the FEM. Furthermore, the crack volume could be estimated by linear approximations with a good correlation among the three methods. [Copyright &y& Elsevier]

Abstract: Two inverse methods using dipole models for noninvasive assessment of local repolarization changes were investigated and compared in the simulation study. Lesions with changed repolarization were modeled by shortening of the action potential durations in ventricular regions typically influenced by occlusion of coronary arteries. Corresponding body surface potentials were computed using a multiple dipole model of the cardiac generator and an inhomogeneous torso model. Position of each lesion was then estimated by an inverse solution to a single dipole and to a group of five neighbouring dipoles. For both methods the lesion localization error was evaluated and its dependence on the lesion size and the noise in input data was studied. When no noise was present in the input data, the use of the inverse method to a group of dipoles instead of a single dipole resulted in an unsubstantial reduction of the mean localization error of small lesions from 0.6 to 0.5cm. For medium and especially for large lesions the mean localization errors decreased significantly from 1.1 to 0.6cm and from 2.3 to 1.0cm, respectively. The inverse solution to a group of five dipoles was more sensitive to noise. However, for large lesions it still gave better results than the solution to a single dipole if the signal to noise ratio was higher than 30dB. [Copyright &y& Elsevier]

Abstract: Nondestructive evaluation (NDE) is an important methodology for quantifying cracks in engineering structures. In this paper, we propose a dipole model method (DMM) for NDE. The method is used to simulate an alternating magnetic field around a crack on a paramagnetic metal specimen and to estimate the shape and volume of the crack. This method enables faster and simpler evaluation of crack size than the traditional analytical methods. The DMM performance was verified by comparing the simulation results with the experimental results obtained using an AC-type magnetic camera. [Copyright &y& Elsevier]

Two modified versions of the dipole model with a pair of mediating fields are considered. In the first version, the modification affects the Yukawa term in the Lagrangian. In the second version a non-linear self-action term is added. By constructing exact solutions of the field equations with the use of a covariant Green function we derive a Lagrangian with many-point time-nonlocal interaction terms. For the linear dipole model the two-particle interaction, in the non-relativistic limit, is shown to be a sum of Coulomb and linear confinement terms. For the nonlinear φ3-model the interactions are shown to include pairwise potentials and also three-particle cluster potentials with a logarithmic confinement. The approaches towards a consistent relativistic treatment of the models are proposed, and the problem of divergences is discussed. [ABSTRACT FROM AUTHOR]

The radiative transfer framework that underlies all current rendering of volumes is limited to scattering media whose properties are invariant to rotation. Many systems allow for "anisotropic scattering," in the sense that scattered intensity depends on the scattering angle, but the standard equation assumes that the structure of the medium is isotropic. This limitation impedes physics-based rendering of volume models of cloth, hair, skin, and other important volumetric or translucent materials that do have anisotropic structure. This paper presents an end-to-end formulation of physics-based volume rendering of anisotropic scattering structures, allowing these materials to become full participants in global illumination simulations. We begin with a generalized radiative transfer equation, derived from scattering by oriented non-spherical particles. Within this framework, we propose a new volume scattering model analogous to the well known family of microfacet surface reflection models; we derive an anisotropic diffusion approximation, including the weak form required for finite element solution and a way to compute the diffusion matrix from the parameters of the scattering model; and we also derive a new anisotropic dipole BSSRDF for anisotropic translucent materials. We demonstrate results from Monte Carlo, finite clement, and dipole simulations. All these contributions are readily implemented in existing rendering systems for volumes and translucent materials, and they all reduce to the standard practice in the isotropic case. [ABSTRACT FROM AUTHOR]

Abstract: In this study, we proposed and evaluated the use of Independent Component Analysis (ICA) combining the EEG dipole model to automatically remove eye movement artifacts from the EEG without needing EOG as a reference. We separated the EEG data into independent components using the ICA method, and determined the source localization of these independent components with a single dipole model. The EEG signal was reconstructed by automatically excluding those components localized within a preset eye model. EEGs from 12 patients were analyzed. The experimental results indicate that ICA with the dipole model is very efficient at automatically subtracting the eye movement artifacts, while retaining the EEG slow waves and making their interpretation easier. [Copyright &y& Elsevier]

We are presenting an unusual set microcoaxial for RF field, associated with a submicron position sensor. The near field is determined experimentally and calculated theoretically with comparative experiments. The measurements are interpreted as an electric model of the probe for applications on the submicron components. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1765–1769, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24448 [ABSTRACT FROM AUTHOR]

Although the head is more closely represented as an ellipsoid than a sphere, calculation in ellipsoidal coordinates is difficult. This paper presents a four shell ellipsoidal model, employing multipole expansion in ellipsoidal coordinates, for EEG, MEG, and evoked potential applications. Computational detail and insight into efficient calculation of the Lamé functions of the first and second kind are provided to demonstrate feasibilty. The Lamé function of the second kind, derived from the Lamé function of the first kind, can be computed at higher degrees by means of partial fraction expansion. [ABSTRACT FROM AUTHOR]

Design and control of multi-degree-of-freedom (DOF) electromagnetic actuators require a good understanding of the magnetic fields, and involve real-time calculation of magnetic forces. This paper presents a method to derive distributed multipole (DMP) models for characterizing the magnetic field and torque of permanent magnet (PM) based devices. The DMP method, which offers magnetic-field solutions in closed form, inherits many advantages of the dipole model originally conceptualized in the context of physics, but provides an effective means to account for the shape and magnetization of the physical magnet. Three practical applications are given to demonstrate the DMP models for design of PM-based actuators and sensing systems. The magnetic fields and forces calculated using DMP models have been validated by comparing against numerical and experimental results which show excellent agreement. [ABSTRACT FROM PUBLISHER]