Vertical Field Research Articles

Three-dimensional Atmospheric Dynamics of Jupiter from Ground-based Doppler Imaging Spectroscopy in the Visible

We present three-dimensional (3D) maps of Jupiter’s atmospheric circulation at cloud-top level from Doppler-imaging data obtained in the visible domain with JIVE, the second node of the JOVIAL network, which is mounted on the Dunn Solar Telescope at Sunspot, New Mexico. We report on 12 nights of observations between 2018 May 4 and May 30, representing a total of about 80 hr. First, the average zonal wind profile derived from our data is compatible with that derived from cloud-tracking measurements performed on Hubble Space Telescope images obtained in 2018 April from the Outer Planet Atmospheres Legacy program. Second, we present the first ever 2D maps of Jupiter’s atmospheric circulation from Doppler measurements. The zonal velocity map highlights well-known atmospheric features, such as the equatorial hot spots and the Great Red Spot (GRS). In addition to zonal winds, we derive meridional and vertical velocity fields from the Doppler data. The motions attributed to vertical flows are mainly located at the boundary between the equatorial belts and tropical zones, which could indicate active motion in theses regions. Qualitatively, these results compare well to recent Juno data that have unveiled the 3D structure of Jupiter’s wind field. To the contrary, the motions attributed to meridional circulation are very different from what is obtained by cloud tracking, except at the GRS. Because of limitations with data resolution and processing techniques, we acknowledge that our measurements of the vertical or meridional flows of Jupiter are still to be confirmed.

Coherence analysis of geophysical wakes in flow past a three-dimensional hill

Wakes generated by topographies are ubiquitous in nature. The formation and evolution mechanism of wake-generated eddies is essential to understanding the effect of topography on oceanic bottom flow. In this study, we analyze the temporally resolved numerical database [1] of stratified wakes past an isolated three-dimensional hill, via proper orthogonal decomposition (POD) of the vertical vorticity field. We study the dynamics of the near wake (x/D < 3) and the far wake (x/D ≥ 3) separately, where x is the downstream distance from the center of the hill. The aim is to understand how rotation influences the change of coherence from the near to the far wake and also the coherence across heights.

Magnetically driven winds from accretion disks in post-asymptotic giant branch binaries

Context. Jets are commonly detected in post-asymptotic giant branch (post-AGB) binaries and originate from an accretion process onto the companion of the post-AGB primary. These jets are revealed by high-resolution spectral time series. Aims. This paper is part of a series. In this work, we move away from our previous parametric modelling and include a self-similar wind model that allows the physical properties of post-AGB binaries to be characterised. This model describes magnetically driven jets from a thin accretion disk threaded by a large-scale, near equipartition vertical field. Methods. We expanded our methodology in order to simulate the high-resolution dynamic spectra coming from the obscuration of the primary by the jets launched by the companion. We present the framework to exploit the self-similar jet models for post-AGB binaries. We performed a parameter study to investigate the impact of different parameters (inclination, accretion rate, inner and outer launching radius) on the synthetic spectra. Results. We successfully included the physical jet models into our framework. The synthetic spectra have a very similar orbital phase coverage and absorption strengths as the observational data. The magnetohydrodynamic (MHD) jet models provide a good representation of the actual jet creation process in these evolved binaries. Challenges remain, however, as the needed high-accretion rate would induce accretion disks that are too hot in comparison to the data. Moreover, the rotational signature of the models is not detected in the observations. In future research, we will explore models with a higher disk ejection efficiency and even lower magnetisation in order to solve some of the remaining discrepancies between the observed and synthetic dynamic spectra.

Electric Field-Assisted Molecularly Imprinted Polymer-Modified QCM Sensor for Enhanced Detection of Immunoglobulin.

In this study, an electric-field-assisted molecularly imprinted polymer (EFAMIP) as an enhanced form of MIP was developed to improve the MIP-modified quartz crystal microbalance (QCM) biosensors. While exerting a vertical electric field, polymerization of methacrylic acid in the presence of immunoglobulin G (IgG) as the template was initiated, and later, after the template removal process, the EFAMIPs were obtained. The polymer surface characterization was conducted by using a scanning electron microscope. The impact of electric field direction on IgG binding sites, forming either EFAMIP-Fab or EFAMIP-Fc, was assessed. Next, the static measurement results in liquid for EFAMIP-modified QCM and MIP-modified QCM were compared. While encompassing IgG, EFAMIP-modified QCMs exhibited up to a 113.5% higher frequency shift than typical MIP in time-limited detection. The final frequency shift of EFAMIP, which determines the detection limit of IgG, was improved up to 12.5% compared to typical MIP. Moreover, the EFAMIP-Fab performance was promising for the selective detection of IgG in a solution containing different types of immunoglobulins.

External electric field assisted energy band gap modulation and optical properties of SiGe/AsSb heterobilayers

In this work, first-principle calculations within Density Functional Theory (DFT) were performed to study the structural, electronic, and optical properties of eight different bilayer van der Waals (vdW) heterostructures composed of SiGe and AsSb monolayers. These heterobilayers exhibit large energy bandgap (90 meV–459 meV) with linear energy–momentum relationship, implying high charge carrier mobility. Application of external vertical electric field can effectively modulate the energy bandgap of these heterobilayers from 64 meV to 459 meV, depending on stacking orders. Our study shows that a moderate amount of electric field can almost linearly tune the energy bandgap, however, semiconductor to metal transition occurs beyond a certain limit. The mechanism of energy bandgap tuning by the external electric field was examined by studying differential charge density. The optical properties such as complex dielectric function, electron energy loss function, complex refractive index, reflectivity, absorption coefficient, and optical conductivity of these SiGe/AsSb heterobilayers are studied for parallelly and perpendicularly polarized incident light. Our research demonstrates that these heterostructures exhibit variable plasma frequency depending on the stacking order of the heterostructures, anisotropic reflectivity i.e., birefringence properties in response to the incident light's polarization. Also, they exhibit high refractive indices (∼3) and absorption coefficients (∼105 cm−1) from visible to ultraviolet incident light frequencies. Our study proposes several SiGe/AsSb heterobilayers with unique electronic and optical properties which may have potential applications in nanoscale electronic and optoelectronic applications.

On statistical submersions from 3-Sasakian statistical manifolds

In this paper, we define and characterize 3-Sasakian statistical manifolds and then investigate statistical submersions from 3-Sasakian statistical manifolds. We prove that invariant statistical submersions from 3-Sasakian statistical manifolds with vertical structure vector fields have 3-Sasakian statistical totally geodesic fibers. Moreover, the base space admits a quaternionic Kähler statistical structure. We construct non-trivial examples to illustrate some results of the paper.

Expanding Sparse Radar Depth Based on Joint Bilateral Filter for Radar-Guided Monocular Depth Estimation.

Radar data can provide additional depth information for monocular depth estimation. It provides a cost-effective solution and is robust in various weather conditions, particularly when compared with lidar. Given the sparse and limited vertical field of view of radar signals, existing methods employ either a vertical extension of radar points or the training of a preprocessing neural network to extend sparse radar points under lidar supervision. In this work, we present a novel radar expansion technique inspired by the joint bilateral filter, tailored for radar-guided monocular depth estimation. Our approach is motivated by the synergy of spatial and range kernels within the joint bilateral filter. Unlike traditional methods that assign a weighted average of nearby pixels to the current pixel, we expand sparse radar points by calculating a confidence score based on the values of spatial and range kernels. Additionally, we propose the use of a range-aware window size for radar expansion instead of a fixed window size in the image plane. Our proposed method effectively increases the number of radar points from an average of 39 points in a raw radar frame to an average of 100 K points. Notably, the expanded radar exhibits fewer intrinsic errors when compared with raw radar and previous methodologies. To validate our approach, we assess our proposed depth estimation model on the nuScenes dataset. Comparative evaluations with existing radar-guided depth estimation models demonstrate its state-of-the-art performance.

Dependence of Positive Bias Stress Instability on Threshold Voltage and Its Origin in Solution-Processed Aluminum-Doped Indium Oxide Thin-Film Transistors.

The initial electrical characteristics and bias stabilities of thin-film transistors (TFTs) are vital factors regarding the practical use of electronic devices. In this study, the dependence of positive bias stress (PBS) instability on an initial threshold voltage (VTH) and its origin were analyzed by understanding the roles of slow and fast traps in solution-processed oxide TFTs. To control the initial VTH of oxide TFTs, the indium oxide (InOx) semiconductor was doped with aluminum (Al), which functioned as a carrier suppressor. The concentration of oxygen vacancies decreased as the Al doping concentration increased, causing a positive VTH shift in the InOx TFTs. The VTH shift (∆VTH) caused by PBS increased exponentially when VTH was increased, and a distinct tendency was observed as the gate bias stress increased due to a high vertical electric field in the oxide dielectric. In addition, the recovery behavior was analyzed to reveal the influence of fast and slow traps on ∆VTH by PBS. Results revealed that the effect of the slow trap increased as the VTH moved in the positive direction; this occured because the main electron trap location moved away from the interface as the Fermi level approached the conduction band minimum. Understanding the correlation between VTH and PBS instability can contribute to optimizing the fabrication of oxide TFT-based circuits for electronic applications.

Analysis of the Effects of Temperature and Vertical Electric Field on the Propagation of Transverse Electric Waves in Silicene Monolayer

Analysis of the Effects of Temperature and Vertical Electric Field on the Propagation of Transverse Electric Waves in Silicene Monolayer

Terminator effect in the model Schumann resonance signals

We model Schumann resonance (SR) amplitude variations driven by the diurnal and seasonal motion of the day–night interface in the Earth – ionosphere cavity that is regarded as the terminator effect. The current moment of the equatorial source is a constant. The observer occupies the middle, the high latitudes, or the South Pole. Vertical electric field is calculated at the frequencies 8, 14, and 20 Hz. The following results were obtained. Amplitude modulations relevant to the day-night interface acquire ubiquitous patterns in the local time of the observer. The date–time changes have a convex lens-like structure at the mid-latitude observatory. The simultaneous displacement of the source and observer along the longitude causes an appropriate shift of the date–time pattern plotted in the universal time (UT). Relocation of the observer from the Northern to the Southern Hemisphere shifts the pattern by 6 months. These changes might totally alter the outline of the observed “12 months - 24 h” pattern. The shape of date–time variation alters from the convex lens-like to the cross-like when the observer is located in the high latitudes owing to the polar day and the polar night periods. When the observatory occupies a geographic pole, the season-diurnal variations resemble a ‘chessboard’. The Wentzel – Kramers – Brillouin (WKB) approximation allows obtaining the general outline of the date–time variations. The data obtained might be interpreted as a combination of two effects. The first one forms the general outline of temporal changes; and it is linked to the height of the Earth-ionosphere cavity above the source and the observer. The second one is related to "reflections" of ELF radio waves from the day–night interface, and it drives oscillations with the period equivalent to the wavelength at the particular frequency. All effects are related to the position of the day–night interface and occur in the observer's local time. The range of amplitude modulations in a non-uniform cavity is of ± (10–15)% relative to the average amplitude.

Tuning the Bandgap and Topological Phase Transition in Bilayer Van der Waals Stanane by Electric Field

For very few special 2D materials, electric field can be used to realize the topological phase transition from normal insulator (NI) into topological insulator (TI). To design the low‐power electronic devices based on 2DTIs, tunable and practical 2DTIs may be necessary. Herein, a model of electric field‐tunable 2DTIs based on bilayer van der Waals semiconductors is proposed. The bilayer semiconductors can be tuned by electric field from NIs into TIs. As a good candidate of the predicted 2DTIs, the possible topological phase transition of bilayer stanane (SnH) under electric field using first‐principles calculations is studied. The calculations suggest that bilayer stanane can be converted from NI into TI by vertical electric field. The topological bandgap can be up to about 22.8 meV, which is giant for the electric field‐tunable 2DTIs. It can be further enlarged by vertical pressure. This discovery provides new possibilities for converting NIs into TIs by electric field and creating multifunctional topological field‐effect transistors by tunable 2DTIs.

Symmetry-selective quasiparticle scattering and electric field tunability of the ZrSiS surface electronic structure

Three-dimensional Dirac semimetals with square-net non-symmorphic symmetry, such as ternary ZrXY (X = Si, Ge; Y = S, Se, Te) compounds, have attracted significant attention owing to the presence of topological nodal lines, loops, or networks in their bulk. Orbital symmetry plays a profound role in such materials as the different branches of the nodal dispersion can be distinguished by their distinct orbital symmetry eigenvalues. The presence of different eigenvalues suggests that scattering between states of different orbital symmetry may be strongly suppressed. Indeed, in ZrSiS, there has been no clear experimental evidence of quasiparticle scattering reported between states of different symmetry eigenvalues at small wave vector q⃗. Here we show, using quasiparticle interference, that atomic step-edges in the ZrSiS surface facilitate quasiparticle scattering between states of different symmetry eigenvalues. This symmetry eigenvalue mixing quasiparticle scattering is the first to be reported for ZrSiS and contrasts quasiparticle scattering with no mixing of symmetry eigenvalues, where the latter occurs with scatterers preserving the glide mirror symmetry of the crystal lattice, e.g. native point defects in ZrSiS. Finally, we show that the electronic structure of the ZrSiS surface, including its unique floating band surface state, can be tuned by a vertical electric field locally applied by the tip of a scanning tunneling microscope (STM), enabling control of a spin–orbit induced avoided crossing near the Fermi level by as much as 300%.

Global rotation of skyrmion bags under vertical microwave fields

Magnetic skyrmion bags are composite topological spin textures with arbitrary topological charges. Here, we computationally study the transient rotational motion of skyrmion bags, which is characterized by a global rotation of inner skyrmions around the central point. Distinct from conventional rotational modes found in skyrmions, the observed rotation is a forced motion associated with the breathing mode induced solely by vertical microwave fields. The driving force behind this rotation originates from the interactions between outer and inner skyrmions, with the angular velocity determined by the phase difference resulting from their asynchronous breathing behaviors. It is also found that skyrmion bags with larger skyrmion numbers are more conducive to the occurrence of the rotation. Our results are useful for understanding the cluster dynamics of complex topological spin textures driven by dynamic fields.

Orbital Torus Imaging: Acceleration, Density, and Dark Matter in the Galactic Disk Measured with Element Abundance Gradients

Under the assumption of a simple and time-invariant gravitational potential, many Galactic dynamics techniques infer the milky Way’s mass and dark matter distributions from stellar kinematic observations. These methods typically rely on parameterized potential models of the Galaxy and must take into account nontrivial survey selection effects, because they make use of the density of stars in phase space. Large-scale spectroscopic surveys now supply information beyond kinematics in the form of precise stellar label measurements (especially element abundances). These element abundances are known to correlate with orbital actions or other dynamical invariants. Here, we use the Orbital Torus Imaging framework that uses abundance gradients in phase space to map orbits. In many cases these gradients can be measured without detailed knowledge of the selection function. We use stellar surface abundances from the Apache Point Observatory Galactic Evolution Experiment survey combined with kinematic data from the Gaia mission. Our method reveals the vertical (z-direction) orbital structure in the Galaxy and enables empirical measurements of the vertical acceleration field and orbital frequencies in the disk. From these measurements, we infer the total surface mass density, Σ, and midplane volume density, ρ 0, as a function of Galactocentric radius and height. Around the Sun, we find Σ⊙(z=1.1kpc)=72−9+6M⊙pc−2 and ρ⊙(z=0)=0.081−0.009+0.015M⊙pc−3 using the most constraining abundance ratio, [Mg/Fe]. This corresponds to a dark matter contribution in surface density of Σ⊙,DM(z = 1.1 kpc) = 24 ± 4 M ⊙ pc−2, and in total volume mass density of ρ ⊙,DM(z = 0) = 0.011 ± 0.002 M ⊙ pc−3. Moreover, using these mass density values we estimate the scale length of the low-α disk to be h R = 2.24 ± 0.06 kpc.

MTD-YOLOv5: Enhancing marine target detection with multi-scale feature fusion in YOLOv5 model

Underwater light attenuation leads to decreased image contrast. This reduction in contrast subsequently decreases target visibility. Additionally, marine target detection is challenging due to multi-scale problems from varying target-to-device distances, complex target clustering, and noise from waterborne particulates.To address these issues, we propose MTD-YOLOv5.Initially, we enhance image contrast with grayscale equalization and mitigate color shift issues through color space transformation.We then introduce a novel feature extraction module, PCBR, combining max pooling and convolution layers for more effective target feature extraction from the background.Furthermore, we present the Multi-Scale Perceptual Hybrid Pooling (MHP) module.This module integrates horizontal and vertical receptive fields to establish long-range dependencies, thereby capturing hidden target information in deep network feature maps. In the Labeled Fishes in the Wild test datasets, MTD-YOLOv5 achieves a precision of 88.1% and a mean Average Precision (mAP[0.5:.95]) of 49.6%.These results represent improvements of 2.6% in precision and 0.4% in mAP over the original YOLOv5.

Magnetic Relaxation Seen in a Rapidly Evolving Light Bridge in a Sunspot

We report a magnetic relaxation process inside a sunspot associated with the evolution of a transient light bridge (LB). From high-resolution imaging and spectro-polarimetric data taken by the 1.6 m Goode Solar Telescope installed at Big Bear Solar Observatory, we observe the evolutionary process of a rapidly evolving LB. The LB is formed as a result of the strong intrusion of filamentary structures with relatively horizontal fields into the vertical umbral field region. A strong current density is detected along a localized region where the magnetic field topology changes rapidly in the sunspot, especially in the boundary region between the LB and the umbra, and bright jets are observed intermittently and repeatedly in the chromosphere along this region through magnetic reconnection. In the second half of our observation, the horizontal component of the magnetic field diminishes within the LB, and the typical convection structure within the sunspot, which manifests itself as umbral dots, is restored. Our findings provide a comprehensive perspective not only on the evolution of an LB itself but also on its impacts in the neighboring regions, including the chromospheric activity and the change of magnetic energy of a sunspot.

Spatio-temporal electric field distributions in an atmospheric plasma jet impinging on a microchannel array surface

The electric field distribution in the ionization waves (IWs) propagating over a microchannel array dielectric surface, with the channels either empty or filled with distilled water, is measured by ps electric field induced second harmonic generation. The surface IW is initiated by the atmospheric pressure N2–Ar plasma jet impinging on the surface vertically and powered by ns pulse discharge bursts. The results show that the electric field inside the microchannels, specifically its horizontal component, is enhanced by up to a factor of 2. The field enhancement region is localized within the channels. The vertical electric field inside the channels lags in time compared to the field measured at the ridges, indicating the transient reversal of the IW propagation direction across the channels (toward the jet). This is consistent with the phase-locked plasma emission images and confirmed by the kinetic modeling predictions, which show that the IW ‘jumps’ over the empty channels and propagates into the channels only after the jump between the adjacent ridges. When the channels are filled with water, the wave speed increases by up to 50%, due to the higher effective dielectric constant of the surface. No evidence of a significant electric field enhancement near the dielectric surface (ceramic or water) has been detected, within the spatial resolution of the present diagnostic, ∼100 μm.

Tunable electronic and optical properties of WSe2/Si2H heterojunction via electric field

Van der Waals heterojunctions based on two-dimensional (2D) materials hold great potential applications in photodetectors. Using the density functional theory (DFT) method, the structures, electronic and optical properties of van der Waals WSe2/Si2H heterojunction are investigated. 1.32 eV of indirect bandgap is calculated from the WSe2/Si2H heterojunction, which is 0.3 eV and 0.1 eV smaller than those of its monolayer WSe2 and Si2H. This contributes to the photocarrier generations, and the Type-II heterojunction also benefits to the separation of the photogenerated electron and hole pairs. A significant hole mobility 1.05 × 104 cm2 V−1 s−1 of the heterojunction along the y-direction is obtained. Moreover, a high Ultraviolet light (UV) absorption coefficient is presented in the heterojunction. The heterojunction transforms to Type-I under a vertical electric field, with the bandgap, orientation and amount of transfer electrons modulated sufficiently. As a result, the optical absorption coefficient of the heterojunction is also improved significantly, leading to the red-shift of the absorption spectrum. These excellent properties address the WSe2/Si2H heterojunction one of the good candidates for UV detectors.

Wall-attached convection under strong inclined magnetic fields

We employ a linear stability analysis and direct numerical simulations to study the characteristics of wall modes in thermal convection in a rectangular box under strong and inclined magnetic fields. The walls of the convection cell are electrically insulated. The stability analysis assumes periodicity in the spanwise direction perpendicular to the plane of a homogeneous magnetic field. Our study shows that for a fixed vertical magnetic field, the imposition of horizontal magnetic fields results in an increase of the critical Rayleigh number along with a decrease in the wavelength of the wall modes. The wall modes become tilted along the direction of the resulting magnetic fields and therefore extend further into the bulk as the horizontal magnetic field is increased. Once the modes localized on the opposite walls interact, the critical Rayleigh number decreases again and eventually drops below the value for onset with a purely vertical field. We find that for sufficiently strong horizontal magnetic fields, the steady wall modes occupy the entire bulk and therefore convection is no longer restricted to the sidewalls. The aforementioned results are confirmed by direct numerical simulations of the nonlinear evolution of magnetoconvection. The direct numerical simulation results also reveal that at least for large values of horizontal magnetic field, the wall-mode structures and the resulting heat transfer are dependent on the initial conditions.

Wind tunnel tests applied to wind energy management: comparison of measurements in closed-circuit and open-circuit wind tunnels

Power loss, damages overestimation and environmental impacts are the main problems related to wind energy and its planning and management. One of the tools used to analyse and manage this problem is the aerodynamic wind tunnel. In this work wind tunnel tests were performed in two different facilities, an open-circuit wind tunnel and a close-circuit wind tunnel, in order to study the suitability of these features to optimize wind farms layout and power quality and its dependence of the type of tests facility. Experimental results in this work are reported as wind speed and turbulence intensity vertical profiles and flow fields with a simulated ABL with and without the presence of a three-bladed wind turbine model. Results show that mean wind velocity is similar in both tunnels, but turbulence intensity is higher for the open-circuit wind tunnel.