Resonance Line Research Articles

Automatic detection of field line resonance frequencies in the Earth’s plasmasphere

Automatic detection of field line resonance frequencies in the Earth’s plasmasphere

Fault-Location Accuracy of Natural Frequencies Using Incomplete HVDC Station Models

This paper investigates how the accuracy of fault location estimated from a transmission line's natural frequencies is affected by imperfect modeling of HVDC power-converter sta- tions. These systems include a large number of devices each with specific frequency-dependent characteristics, as filters, reactors and surge protection systems. While it is well-known that location errors may ensue from inaccurate termination models, it is not clear to what extent location accuracy is affected when neglecting one or more of these devices. Results show significant differences depending on the kind of transmission line and the reactor inductance. Including reactors is found not to completely avoid errors, proving the need to take into account the reactive behavior of the converter, which strongly varies according to the HVDC technology. A notable source of errors is level repulsion between station and line resonances, a phenomenon observed when the converter station presents self resonances, e.g., due to DC filters and stray capacitances in reactors. Significant loss of sensitivity to the fault position is found in these cases, impairing fault-location resolution. The first, or dominant, natural frequency of the line is more strongly affected by all these phenomena, suggesting that the standard choice of using the dominant resonance may not be an optimal strategy. Higher-order resonances are instead found to be more robust against inaccurate converter models, and appear to be more suitable for accurate fault location in case of uncertainties about the converter model.

Capacitorless Synchronous Reluctance Motor Drives for Pump Applications With Resonance Damping and Line Current Harmonics Reduction

Capacitorless Synchronous Reluctance Motor Drives for Pump Applications With Resonance Damping and Line Current Harmonics Reduction

Tunable Diode Lasers for Analytics and Diagnostics

Continuous-wave diode lasers (DLs) with tunable emission wavelengths have become extensively used in various fields of analytical spectroscopy and diagnostics. Working in the near and mid-IR spectral region, tunable diode lasers are particularly effective in detecting simple molecules, making them invaluable for environmental monitoring, industrial process control, and diagnostics of subsonic and supersonic gas flows. However, the lack of commercial diode lasers operating in the spectral region shorter than 400 nm has restricted their applicability to elemental analysis, as many resonance lines of free atoms of elements lie in the region 250–400 nm. This review aims to highlight various applications of continuous diode lasers, which are lesser-known to analytical chemists. We briefly overview their main characteristics and discuss their advantages, enabling their successful implementation in traditional analytical spectroscopy tasks, as well as for diagnosing parameters of remote gas objects, including combustion processes in mixing gas flows.

Tunable Diode Lasers for Analytics and Diagnostics

Continuous-wave diode lasers (DLs) with tunable emission wavelengths have become extensively used in various fields of analytical spectroscopy and diagnostics. Working in the near and mid-IR spectral region, tunable diode lasers are particularly effective in detecting simple molecules, making them invaluable for environmental monitoring, industrial process control, and diagnostics of subsonic and supersonic gas flows. However, the lack of commercial diode lasers operating in the spectral region shorter than 400 nm has restricted their applicability to elemental analysis, as many resonance lines of free atoms of elements lie in the region 250–400 nm. This review aims to highlight various applications of continuous diode lasers, which are lesser-known to analytical chemists. We briefly overview their main characteristics and discuss their advantages, enabling their successful implementation in traditional analytical spectroscopy tasks, as well as for diagnosing parameters of remote gas objects, including combustion processes in mixing gas flows.

Characterization of harmonic modes and parasitic resonances in multi-mode superconducting coplanar resonators

Planar superconducting microwave transmission line resonators can be operated at multiple harmonic resonance frequencies. This allows covering wide spectral regimes with high sensitivity, as it is desired, e.g., for cryogenic microwave spectroscopy. A common complication of such experiments is the presence of undesired “spurious” additional resonances, which are due to standing waves within the resonator substrate or housing box. Identifying the nature of individual resonances (“designed” vs “spurious”) can become challenging for higher frequencies or if elements with unknown material properties are included, as is common for microwave spectroscopy. Here, we discuss various experimental strategies to distinguish designed and spurious modes in coplanar superconducting resonators that are operated in a broad frequency range up to 20 GHz. These strategies include tracking resonance evolution as a function of temperature, magnetic field, and microwave power. We also demonstrate that local modification of the resonator, by applying minute amounts of dielectric or electron spin resonance-active materials, leads to characteristic signatures in the various resonance modes, depending on the local strength of the electric or magnetic microwave fields.

Review of scientific instruments: Evaluation of adulteration in honey using a microwave planar resonator sensor.

A microwave microstrip line resonator sensor is developed as an alternative tool for detecting adulteration in honey. A honey-filled tube is placed at the position with the maximum electric field intensity. When the honey is adulterated, its permittivity is changed, leading to a distinct resonance frequency shift and enabling detection. Compared with the existing microwave sensors, this sensor offers the advantages of low cost, compact size, and easy fabrication. Moreover, quantitative analysis of the adulteration could be achieved. Electromagnetic simulation is performed using a co-simulation with CST and MATLAB. The simulation results reveal that the resonance frequency of the resonator decreases as the added water content increases, following a quadratic polynomial relationship. In the experiments, the results demonstrate a successive decrease in the resonance frequency from the empty tube, honey-filled tube to water-filled tube cases. Furthermore, honey samples with varying water contents (up to 70%) are tested, and the resonance frequency decreases with increasing added water content, which agrees well with the simulation results. In addition, there is a quadratic relationship between the two parameters. Principal component analysis is conducted on the transmission coefficients, and the first principal component decreases with increasing water content. With the addition of the second principal component, the cases of different water contents in honey can be well classified.

A Radial Standing Pc5‐6 Wave and Its Energy Coupling With Field Line Resonance Within the Dusk‐Sector Magnetosphere

AbstractGlobal ultra‐low frequency (ULF) oscillations are believed to play a significant role in the mass, energy, and momentum transport within the Earth's magnetosphere. In this letter, we observe a ∼1.2 mHz radial standing wave in the dusk‐sector magnetosphere accompanied by the field line resonance (FLR) on 16 July 2017. The frequency estimation from the simple box model also confirms the radial standing wave. The essential characteristics of FLR are concurrently identified at the dusk‐sector magnetosphere and the conjugated ground location. Further, the radial standing wave dissipates energy into upper atmosphere to enhance the local aurora by coupling itself to the FLR. The magnetospheric dominant 1.2/1.1 mHz ULF waves plausibly correspond well with the discrete ∼1 mHz magnetosheath ion dynamic pressure/velocity oscillation, suggesting this radial standing wave and FLR in the flank magnetosphere may be triggered by the solar‐wind and/or magnetosheath dynamic pressure/velocity fluctuations.

Switchable optical differentiator using Fano resonance metasurface

Optical differentiation plays a pivotal role in analog computing and image processing, owing to its faster operating speeds and lower power consumption. However, the conventional differentiator encounters a common issue of single and fixed functions due to the lack of effective dynamic modulation means. Here, we proposed a polarization-sensitive differentiator based on a Fano resonance metasurface. The interference between transmitted light and a quasi-guided mode induces Fano resonance, resulting in the leakage of high-frequency component of the p-wave. By adjusting the asymmetry and line width of the Fano resonance line shape, the metasurface can function as a Fourier spatial filter to achieve the differential of an incident beam. Additionally, the direction of the s- and p-wave can be controlled to realize multiple differential functions. We demonstrate the simulation of switchable differential between arbitrary one-dimensional (1D) direction and two-dimensional (2D) directions, with a numerical aperture up to 0.26. It is expected that this switchable optical differentiator will have broad applications in areas such as bioimaging and computer vision.

Electron-beam synthesis of thin magneto-dielectric coatings with mixed nickel-iron and upper alumina layers

We have synthesized magneto-dielectric coatings with thicknesses 290, 550, 5460 and 6063 nm with an upper protective and electrically insulating layer of alumina ceramic and a lower magnetic iron-nickel layer. The coatings were formed in a helium atmosphere at forevacuum pressures (from 1.5 to 15 Pa) by electron-beam evaporation of a mixture of iron and nickel fragments, and of a solid alumina ceramic target placed in a separate crucible. Magnetic properties of the coatings have been studied by a ferromagnetic resonance technique with estimation of the effective saturation magnetization together with evaluation of the signal-to-noise ratio and relative broadening of the resonance lines. Owing to the layer of alumina ceramic, the values of relative dielectric permittivity (5.6) and electrical conductivity (0.78–3.00 mS/m) remain typical for thin-film dielectrics.

Dynamics of γ-aminobutyric acid concentration in the human brain in response to short visual stimulation.

To find a possible quantitative relation between activation-induced fast (< 10s) changes in the γ-aminobutyric acid (GABA) level and the amplitude of a blood oxygen level-dependent contrast (BOLD) response (according to magnetic resonance spectroscopy [MRS] and functional magnetic resonance imaging [fMRI]). fMRI data and MEGA-PRESS magnetic resonance spectra [echo time (TE)/repetition time (TR) = 68ms/1500ms] of an activated area in the visual cortex of 33 subjects were acquired using a 3T MR scanner. Stimulation was performed by presenting an image of a flickering checkerboard for 3s, repeated with an interval of 13.5s. The time course of GABA and creatine (Cr) concentrations and the width and height of resonance lines were obtained with a nominal time resolution of 1.5s. Changes in the linewidth and height of n-acetylaspartate (NAA) and Cr signals were used to determine the BOLD effect. In response to the activation, the BOLD-corrected GABA + /Cr ratio increased by 5.0% (q = 0.027) and 3.8% (q = 0.048) at 1.6 and 3.1s, respectively, after the start of the stimulus. Time courses of Cr and NAA signal width and height reached a maximum change at the 6th second (~ 1.2-1.5%, q < 0.05). The quick response of the observed GABA concentration to the short stimulus is most likely due to a release of GABA from vesicles followed by its packaging back into vesicles.

Exploring Partial Structural Disorder in Anhydrous Paraxanthine through Combined Experiment, Solid-State Computational Modelling, and Molecular Docking

Paraxanthine (PX), a major metabolite of caffeine, a protective agent against Alzheimer’s and Parkinson’s disease, and a promising drug for the treatment of post-COVID 2019 anosmia and ageusia, has been studied in the solid state and protein–ligand complex. Partial disorder in PX, caused by the methyl group at the N(7) position, has been modelled and discussed. The relationship between the unusual structural disorder and the propensity to form a specific system of non-covalent bonds was analyzed. Three 1H-14N NMR-NQR (nuclear magnetic resonance–nuclear quadrupole resonance) experimental techniques were used, namely multiple frequency sweeps, Larmor frequency scanning, and the two-frequency irradiation, followed by solid-state computational modelling (density functional theory, supplemented by quantum theory of atoms in molecules, 3D Hirshfeld surfaces, and reduced density gradient), and molecular docking approaches. New quantitative methods for estimating changes in the global pattern of interactions under the influence of rotation of the methyl group in N(7) based on the Pompeiu–Hausdorff and Bhattacharayya metrics and the Wasserstein distance have been proposed and applied. A spectrum consisting of 12 lines, indicating the presence of 4 chemically inequivalent nitrogen sites in the PX molecule, was recorded, and the lines’ assignment to particular sites was made. The influence of the methyl rotation on the eigenvalues and eigenvectors of the electric field gradient tensor, NQR parameters, and resonance line positions was modelled in the solid (GGA/RPBE, m-GGA/RSCAN) and cluster (Minnesota M062X hybrid). Three factors have been found to determine structural disorder in PX: larger crystal voids near the methyl at N(7) than at N(1) (opening the path for the disorder), hyperconjugation strongly affecting the density distribution in the five-membered ring, and the involvement of the methyl group at N(7) in many non-covalent bonds that intercept (capture) subsequent jumping protons. The Pompeiu–Hausdorff and Bhattacharayya metrics and the Wasserstein distance confirmed the changes in the distribution and strength of non-covalent interactions throughout the molecule as a result of methyl rotation. This effect is clearly visible regardless of the type of metric, and its order of magnitude is consistent with the modulation effect of the NQR spectra (experimental and calculated). Through molecular docking, it was discovered that the PX moiety in protein–ligand complexes adopt the same methyl group conformation at N(7) as in the solid state. It was found that the cooperation–competition between the C-H⋯O hydrogen bonds and C-H⋯H-C dispersion interactions is the crucial factor that impedes methyl rotation and induces structural disorder, as well as being an important factor in the formation of the protein–ligand complexes.

III–V microdisk lasers coupled to planar waveguides

We report on InGaAs/GaAs quantum dot injection microdisk lasers laterally connected with a bus waveguide fabricated by planar technology from the same epi-structure. Various coupling schemes of microlaser with waveguide are studied including a microlaser attached to a waveguide (zero gap), a 100 nm gap for evanescence light outcoupling, and with a waveguide surrounding the resonator. The modes outcoupling and microlaser's loss (Q-factor) are analyzed by simulation of the lasers. A strong decrease in the number of the microdisk resonance lines associated with an increase in loss in the resonator due to the coupling with waveguide is observed in modeling and experimentally. We study the spectral and lasing parameters of the microdisk lasers, as well as characteristics of the outcoupled emission, and demonstrate efficient light outcoupling for 30 and 40 μm diameter continuous wave operating microdisk laser up to 96 °C.

Magnetic Field Information in the Near-ultraviolet Fe ii Lines of the CLASP2 Space Experiment

We investigate theoretically the circular polarization signals induced by the Zeeman effect in the Fe ii lines of the 279.3–280.7 nm spectral range of the CLASP2 space experiment and their suitability to infer solar magnetic fields. To this end, we use a comprehensive Fe ii atomic model to solve the problem of the generation and transfer of polarized radiation in semiempirical models of the solar atmosphere, comparing the region of formation of the Fe ii spectral lines with those of the Mg ii h and k and the Mn i resonance lines. These are present in the same near-ultraviolet (near-UV) spectral region and allowed the mapping of the longitudinal component of the magnetic field (B L) through several layers of the solar chromosphere in an active region plage. We compare our synthetic intensity profiles with observations from the IRIS and CLASP2 missions, proving the suitability of our model atom to characterize these Fe ii spectral lines. The CLASP2 observations show two Fe ii spectral lines at 279.79 and 280.66 nm with significant circular polarization signals. We demonstrate the suitability of the weak-field approximation applied to the Stokes I and V profiles of these Fe ii lines to infer B L in the plage atmosphere. We conclude that the near-UV spectral region of CLASP2 allows us to determine B L from the upper photosphere to the top of the chromosphere of active region plages.

Multi‐Band Periodic Poleward‐Moving Auroral Arcs at the Postdawn Sector: A Case Study

AbstractPoleward‐moving auroral arcs (PMAAs) with recurrence periods on the order of minutes have been established as a distinct form of auroral activities. Their origin and characteristics, especially those on the dayside, are less understood due to the paucity of observations. Here, we investigate a periodic PMAA event at the postdawn sector based on optical measurements from the high‐latitude Yellow River Station and magnetic measurements from multiple ground‐based stations. The optical observations demonstrate a long duration (∼2.5 hr) of the periodic auroral arcs at not only the well‐established red‐line but also the green‐ and the blue‐lines. This multi‐band feature, together with images at far‐ultraviolet wavelengths, demonstrates a wide energy range of precipitating electrons from hundreds of eV to several keV, with a characteristic energy of ∼2 keV. The auroral luminosity variations at different wavebands show a consistent periodicity within 1.67–3 mHz, which is also shown in the ground‐based magnetic pulsations. The auroral arc and magnetic field observations display signatures of field line resonance, which are likely driven by perturbations at the magnetopause boundary layer. These results complement our knowledge of the dayside periodic PMAAs and improve our understanding of their relationship with ultra‐low frequency waves.

Magnetic confinement less microwave discharge gridded ion thruster

A watt-level microwave discharge is induced without magnetic confinement for a high-precision gridded ion thruster, making use of a coaxial transmission line resonator. The thruster is characterized by performance measurements and plasma diagnosis, and a description of the operating mechanism of this thruster is given in this paper. A Faraday probe and a retarding potential analyzer are employed for the diagnosis. The results show that the plume divergence increases due to the electric field formed between the plume and the ion-induced electron emission cathode. A discharge mode transition is found during the increase of the microwave power, in which the bulk heating mode is converted to the surface heating mode. The magnetic-less microwave discharge gridded ion thruster performs a continuously adjustable thrust range of 5–115 μN and a highest total efficiency of 17.2%. Compared to the common ECR ion thruster, this thruster is free from magneto-static interference on the instruments and the additional magnetic momentum on the spacecraft.

Polarization of Magnetospheric ULF Waves Excited by an Interplanetary Shock on 27 February 2014

AbstractMany previous studies have reported that magnetospheric ultralow frequency waves excited by interplanetary shocks exhibit a strong toroidal component, corresponding to azimuthal displacement of magnetic field lines. However, the toroidal oscillations excited by an interplanetary shock on 27 February 2014 and observed on the dayside by multiple spacecraft were accompanied by a strong poloidal component (radial field line displacement). The frequency of the toroidal oscillations changed with the radial distance of the spacecraft as expected for standing Alfvén waves. We run a 3D linear numerical simulation of this wave event using a model magnetosphere with a realistic radial variation of the Alfvén velocity. The simulated wave fields, when sampled at a radial distance comparable to those of the observations in the real magnetosphere, exhibit polarization similar to the observations. In the simulation, the poloidal component comes from radially standing fast mode waves and the toroidal component results from a field line resonance driven by the fast mode waves. As a consequence, the relative amplitude and phase of the toroidal and poloidal components change with radial distance.

Development of Iron-Silicate Composites by Waste Glass and Iron or Steel Powders.

There is growing interest in the opportunities regarding construction and demolition wastes, such as glass and metal powders, for developing a circular economy and their transformation into new materials. This management and recycling of construction and demolition waste offers environmental benefits and conservation of natural resources. In this paper, new magnetic composite materials were prepared by wet chemical synthesis methods using crushed glasses and iron and steel waste powders as raw materials. The prepared iron-silicate composites were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis, infrared (IR), ultraviolet-visible, and electron paramagnetic resonance (EPR) spectroscopy, and magnetic measurements. The XRD data confirm the formation of varied crystalline phases of the iron ions. The presence of the Fe3O4 crystalline phase was detected in the composites containing the iron waste powders. The inspection of the SEM micrographs revealed slightly better homogeneity for the composite material containing larger amounts of iron waste and heterogeneous morphology with cracks and random crystallinity for the composite doped with steel waste. By doping with different contents of iron or steel waste powder, structural modifications in the silicate network and the formation of new bands in the IR spectra were evidenced. The UV-Vis spectra were characterized by the absorption peaks for both the tetrahedral and octahedral geometries of the Fe3+ ions and the octahedral coordination of the Fe2+ ions with oxygen anions. The EPR data show resonance lines with g ~2, 4.3, and 6.4, corresponding to the Fe3+ ions. Using hysteresis curves, the superparamagnetic properties of the iron-silicate composites were evidenced.

Structural, thermal and physical properties of cesium doped molybdenum-copper-lead glass

The influence of Cs2O content on MoO3CuO-PbO2 vitreous system has been investigated. The obtained samples labeled as: S1, S2, S3, and S4 respectively, with respect to Cs2O content were synthesized by the melt-quenching method. The Cs2O addition up to S3 sample increases the hardness, density and LAC values from 3.23 to 3.52 GPa, 6.553 to 6.906 g/cm3 and 588.50 to 610.39 cm−1 respectively, and decrease the Vm, HVL and MFP values. For S4 sample, reverse trends were observed. X-ray diffraction pattern reveals the presence of amorphous structure in the S1-S3 samples but further Cs2O addition, S4 sample leading to the formation of multiple crystalline phases. The FTIR spectra indicated that the structural unit distributions of the glasses network: [PbOn], [CuOn], and molybdate species [MoO6], [MoO4]2− and [Mo2O7]2− depends on the Cs2O content. The resonance line intensity of the Cu2+ ions gradually diminishes by addition of Cs2O.

Vacuum-ultraviolet laser source for spectroscopy of trapped thorium ions

A tunable vacuum-ultraviolet (VUV) laser source based on four-wave frequency mixing in xenon is presented. Using seed radiation from two continuous-wave lasers, the system allows for precise control of the VUV frequency and is developed for the resonant laser excitation of the Th-229 nucleus to its low-energy isomeric state. The system is prepared to operate in a wide scanning range from 148 nm to 155 nm. The source produces pulses of 6–10 ns duration with up to 40 µJ energy and is coupled via a vacuum beamline to a linear radiofrequency ion trap. In a first implementation of VUV laser spectroscopy of trapped Th+ ions we excite three previously unknown resonance lines near 149 nm wavelength to electronic levels that are close to the Th-229 isomer energy. The resonances are detected and analyzed via fluorescence of the excited Th+ ions. An analysis of the lineshape is used to estimate the linewidth of the VUV radiation to be in the range of 6 GHz, dominated by phase noise that is enhanced in harmonic generation and in the four-wave mixing process. The prospects for the use of the system in nuclear laser spectroscopy of Th-229 are discussed.