Flux Phase Research Articles

Modification of Majorana leakage effect due to the presence of quantum interference

This study delves into the Majorana leakage effect modified by the quantum interference, by coupling one Majorana zero mode (MZM) simultaneously to two dots in a double-quantum-dot Aharonov-Bohm interferometer device. Our findings reveal that the Majorana leakage effect significantly diverges from the single-dot case, predominantly influenced by the symmetry properties of the arms of the interferometer. Remarkably, with identical arms, the Majorana leakage effect halves the low-bias conductance magnitude for magnetic flux phase factor ϕ≠2nπ (n∈Integer). In contrast, when inter-arm symmetry is disrupted, this halving phenomenon is restricted to instances where ϕ=2nπ, accompanied by a 4π-periodic variation in low-bias conductances. Consequently, the Majorana leakage effect is intricately tied to the quantum interference patterns, offering insights into the quantum coherence and transport in hybrid superconducting systems.

Influence of mass flux ratio and phase difference on impingement heat transfer characteristics of coaxial synthetic jet

The aim of the present study is to introduce and investigate the performance of a novel independently controlled coaxial synthetic jet (CSJ) designed for enhancing impinging heat transfer applications. The CSJ features a unique configuration with two coaxial cavities, each featuring inner and annular orifices of the same hydraulic diameter, all aligned at 0∘ The independently controlled CSJ allows precise manipulation of jet conditions and phase differences between its inner and outer cavities, offering a versatile platform for optimizing heat transfer performance under varying operational scenarios. This capability not only enhances our understanding of the heat transfer characteristics of the CSJ but also underscores its potential as an innovative tool for advancing thermal management in engineering systems. Here, the actuators are operated at a Reynolds number (Re) of 1260 to perform the jet impingement experiment. The study explores mass flux ratios, including 0.5, 1, and 2, to understand how these ratios affect impinging heat transfer characteristics. The investigation also explores the influence of different phase differences (∅) between the inner and outer diaphragms, ranging from 0∘ to 180∘ for different mass flux ratios. It has been observed that the percentage enhancement of the peak stagnation Nusselt number (Nustag) for Mr=0.5 is approximately 30.36░% and 53.68░% compared to Mr=1 and Mr=2, respectively. The peak Nustag enhancement of CSJ operated at Mr=0.5 is approximately 63.9░% and 58.6░% compared to the inner jet and annular jet operated separately. In the far field, when a phase difference of ∅=135∘ is provided, the peak Nustag is enhanced by approximately 17.29░% compared to ∅=0∘ for Mr=0.5. Based on the present study, it is recommended to operate the CSJ at a lower mass flux ratio (Mr=0.5) and a higher phase difference between the actuators (∅=135∘) to achieve maximum cooling effect from the heated plate.

Flux phases in the extended Hubbard model on the triangular lattice

Flux phases in the extended Hubbard model on the triangular lattice

Optical manipulation of the charge-density-wave state in RbV3Sb5.

Broken time-reversal symmetry in the absence of spin order indicates the presence of unusual phases such as orbital magnetism and loop currents1-4. The recently discovered kagome superconductors AV3Sb5 (where A is K, Rb or Cs)5,6 display an exotic charge-density-wave (CDW) state andhave emerged as astrong candidate for materialshosting a loop currentphase. The idea that the CDW breaks time-reversal symmetry7-14 is, however, being intensely debated due to conflicting experimental data15-17. Here we use laser-coupled scanning tunnelling microscopy to study RbV3Sb5. By applying linearly polarized light along high-symmetry directions, we show that the relative intensities of the CDW peaks can be reversibly switched, implying a substantial electro-striction response, indicative of strong nonlinear electron-phonon coupling. A similar CDW intensity switching is observed with perpendicular magnetic fields, which implies an unusual piezo-magnetic response that, in turn, requires time-reversal symmetry breaking. We show that the simplest CDW that satisfies these constraints is an out-of-phase combination of bond charge order and loop currents that we dub a congruent CDW flux phase. Our laser scanning tunnelling microscopy data open the door to the possibility of dynamic optical control of complex quantum phenomenon in correlated materials.

Numerical investigation of jet impingement on flat/concave cooling of CO2 with different phase states under high heat flux

The thermal load and high temperature brought by the increase in power of electronic devices or the increase in speed of supersonic aircraft limit the respective development. In this paper, a numerical model of CO2 jet impingement cooling of a constant heat flux plate/concave surface in different phase states was established. Secondly, the non-equilibrium phase transition and the real-thermophysical properties of CO2 was considered. The effects of different wall heat flux (0.7 MW/m2 ∼ 6.5 MW/m2) and initial phase states on the impact cooling performance of CO2 jet were studied.It is found that for SCO2 jet impingement, when the inlet temperature is lower than the pseudo-critical temperature, the heat transfer coefficient increases with the increase of inlet pressure, and the maximum increase is 24.7 %. For near-critical liquid CO2 (LCO2) jet impingement, low latent heat prevents temperature overshoot in the heat flux range studied. With the increase of the proportion of dry ice in the inlet, the heat transfer coefficient also increases. When q > 3 MW/m2, the heat transfer coefficient of dry ice jet impact is 2.5 ∼ 3 times and 1 ∼ 1.4 times of that of SCO2 and near-critical LCO2 jet impingement for the flat plate model, respectively. For concave surface with high heat flux, near-critical LCO2 jet impingement cooling effect is relatively good. In addition, concave surface will aggravate the uneven cooling surface temperature.The results can provide more references for the CO2 jet impingement technology in the design of stagnation cooling system of supersonic aircraft and thermal management of high-power electronic devices.

A dynamical measure of the black hole mass in a quasar 11 billion years ago

Tight relationships exist in the local Universe between the central stellar properties of galaxies and the mass of their supermassive black hole (SMBH)1–3. These suggest that galaxies and black holes co-evolve, with the main regulation mechanism being energetic feedback from accretion onto the black hole during its quasar phase4–6. A crucial question is how the relationship between black holes and galaxies evolves with time; a key epoch to examine this relationship is at the peaks of star formation and black hole growth 8–12 billion years ago (redshifts 1–3)7. Here we report a dynamical measurement of the mass of the black hole in a luminous quasar at a redshift of 2, with a look back in time of 11 billion years, by spatially resolving the broad-line region (BLR). We detect a 40-μas (0.31-pc) spatial offset between the red and blue photocentres of the Hα line that traces the velocity gradient of a rotating BLR. The flux and differential phase spectra are well reproduced by a thick, moderately inclined disk of gas clouds within the sphere of influence of a central black hole with a mass of 3.2 × 108 solar masses. Molecular gas data reveal a dynamical mass for the host galaxy of 6 × 1011 solar masses, which indicates an undermassive black hole accreting at a super-Eddington rate. This suggests a host galaxy that grew faster than the SMBH, indicating a delay between galaxy and black hole formation for some systems.

Створення активних оптичних метаповерхонь на плівках халькогенідних напівпровідників зі зміною фазового стану

The development of meta-optics is due to human aspirations for the maximum miniaturization of optical elements, the design and control of light fluxes, as well as the improvement of visualization and image processing. Metasurfaces, i.e. arrays with subwavelength distances (smaller than the wavelength of light), and optically thin elements trigger new physical mechanism and phenomena that are very different from those observed in three-dimensional bulk materials. Thus, meta-devices perform complete control and management of the characteristics of the light flux (phase, amplitude, polarization) with the help of one flat layer. Compared to traditional bulky lenses, metasurface lenses have advantages such as flatness, light weight, and compatibility with semiconductor manufacturing technology. The use of active (reconfigurable) metasurfaces, the characteristics of which can be dynamically rearranged after manufacturing, makes it possible to significantly expand the capabilities of meta-optics. The paper presents the results of the analysis of the properties and technologies of creating optically active metasurfaces for optical image processing and transformation systems. Generalized methods of forming metasurfaces are described: self-organization, selective chemical etching, holographic and lithographic. To implement the work of active (reconfigured) metasurfaces based on materials with a change in phase state (amorphous/crystalline), heating technologies with electric current pulses of various amplitudes and durations and the action of direct optical radiation are used. The analysis of materials for the formation of optically active metasurfaces and devices based on them that simulate the front of a light wave and work on reflection and transmission is presented. Special attention is paid to the use of photosensitive chalcogenide semiconductors as metamaterials with a phase change. Examples of materials such as Ge2Sb2Te5 (GST) and AgxInSb2Te (AIST), which have been used for decades in optical data storage and electronic memory devices, are given. A series of novel compositions of optical phase change materials such as Ge2Sb2Se4Te (GSST), Sb2S3, Sb2Se3, Ge2Sb2Te3S2 and In3SbTe2 for optical and photonic applications are also proposed. Direct laser recording on photosensitive films of chalcogenide semiconductors with the use of technological equipment for laser recording of master disks is proposed as a promising method of forming arrays with submicron distances and realizing the work of active metasurfaces.

Estimation of the sensitivity of optical measurements using a holographic interferometer

Various interferometers used for high-precision spectroscopic measurements are considered, and the choice of a holographic interferometer based on the spatial-spectral method of holographic interferometry is justified, with the help of which the movements of the phase center of a coherent light flux in a wide dynamic range are measured in real time and measurement information is recorded digitally. On the basis of mathematical relations proposed by the authors in previous publications and based on the results of experimental studies, the sensitivity of a holographic interferometer to spatial displacements of phase centers (focus points) of light streams – point light sources forming a holographic interferogram is numerically estimated. The dependence of the level of the normalized intensity of the luminous flux in the central region of the holographic interferogram on the movement of the actual point light source along the normal to the plane of the Fourier hologram is established. Based on the results of mathematical modeling, it is shown that the sensitivity of the holographic interferometer to the movements of a real point light source along the normal to the plane of the Fourier hologram depends on the parameters of the optical scheme of the holographic interferometer when exposing the hologram and during measurements. At the same time, the sensitivity of the holographic interferometer to the indicated displacements of a real point light source can only be evaluated experimentally. It is proposed to increase the sensitivity of the holographic interferometer by using a thin collecting lens in its optical scheme. For the first time, a mathematical relation was obtained and investigated for the gain coefficient of the light flux phase with a spherical wavefront, which makes it possible to numerically estimate the increase in sensitivity of a holographic interferometer implementing the spatial-spectral method of holographic interferometry with known parameters of a thin collecting lens in an optical scheme. It is shown that the sensitivity of a holographic interferometer to the movements of an imaginary point light source along the normal to the plane of the Fourier hologram is 2.86 times greater than its sensitivity to the same movements of a real point light source. It is established that the sensitivity of a holographic interferometer with a volumetric Fourier hologram and a thin collecting lens in its design can be increased by at least an order of magnitude compared to the sensitivity of known optical interferometers. The results of assessing the sensitivity of a holographic interferometer implementing the spatial-spectral method of holographic interferometry to the movements of point sources of real and imaginary light fluxes, as well as the obtained ratio for the gain of the light flux phase gain by a thin collecting lens will be useful for high-precision measurements of linear and angular displacements of objects, as well as for the construction of photonic device designs. Based on the results of the study, an experimental sample of an acousto-electric converter was developed and manufactured on the basis of a holographic interferometer, which has high sensitivity in wide dynamic and frequency ranges and is intended for use in acoustic location of unmanned aerial vehicles.

A novel route to fibers with volatile crystalline semiconductor cores part 2: Selenides and phosphides

The flux assisted molten core method, previously employed to fabricate glass-clad crystalline GaAs core fiber, is applied here to realize crystalline selenide and phosphide cores. These semiconductor families show great promise in photonics, optoelectronics, and thermoelectrics, although their volatility has previously prohibited successful fabrication utilizing the conventional molten core method. Through the introduction of a flux, the alloy melt temperature and associated vapor pressure can be sufficiently reduced to permit thermal drawing of the melt inside a glass cladding into fiber. Reported here are demonstrations of crystalline selenide and phosphide cores. Also reported is the CO2 laser post processing of a ZnSe core fluxed with Cu8GeSe6, which resulted in lateral segregation of the ZnSe phase from the flux. X-ray diffraction and electron microscopy were deployed to determine the resulting ZnSe, InP and flux alloy phases and elemental distributions in the fiber core. X-ray diffraction of the InP: flux and most of the ZnSe: flux systems showed intermetallic flux phases that were not present on the phase diagrams reported in the literature. Formation enthalpy and phase diagrams of the intermetallic phases at room temperature were used to determine which observed phases were thermodynamically stable or meta-stable. The results indicate that the influences at play are primarily thermodynamic, but in some cases, kinetics plays a role during the fabrication of these fibers, forming metastable phases. Lastly, a review and discussion of the new demands on cladding glasses is presented for laser post-processing such fibers. This work demonstrates an approach to incorporating volatile and incongruently melting phases, that are not compatible with the standard molten core method, to realize novel in-fiber optoelectronic compositions.

Bulk defect-induced phase transition assisting high-flux magnesium ions intercalation in manganese tetroxide

The industry consensus is that finding appropriate electrode materials is a major obstacle to the widespread use of magnesium ion (Mg2+) energy storage devices due to challenges like high charge density, intense polarization, and strong interaction with the surrounding matrix of Mg2+. Manganese tetroxide electrodes for magnesium ion energy storage suffer from the limited capacity resulting by pseudocapacitance reaction on the subsurface. Herein, manganese tetroxide with bulk cation-anion dual defects (CADDs-Mn3O4) is constructed for the first time by a facile hydrothermal reduction method. The as-prepared bulk CADDs-Mn3O4 electrode in the three-electrode system exhibits a high discharge capacity of 320.93 mAh g−1 contributing by the intercalation of high flux Mg2+, which achieves capacity breakthrough that ever reported. Coupled with the activated carbon anodes in a full-cell configuration, aqueous magnesium ion capacitors display an energy density of 128.39 Wh/kg with an ultra-long cycling capability, giving 85 % capacitance retention after 6000 cycles. This outstanding performance can be attributed to the metastable region created by unique bulk cation-anion dual defects. The transition of Mn3O4 to layered MnO2 is promoted, achieving the quick migration of magnesium ions in the bulk phase in a large flux, thus breaking the constraint of the spinel structure on the insertion of divalent magnesium ions. Moreover, the manganese cation defects reduce the band gap and increase the electrical conductivity of the electrodes, and the oxygen anion defects change the spin state of the electron and weaken the bonding energy of Mg-O. This work provides a detailed understanding of the structure-function relationship based on the introduction of cation-anion dual defects, and thus opens up new pathways for modifying energy storage materials.

Effect of non-uniform heating on conjugate heat transfer and entropy generation characteristics within a partially filled porous corrugated channel

The persistence of the present numerical investigation is to evaluate the thermal and total entropy generation characteristics of flow within a partially filled porous wavy channel with finite wall thickness subjected to non-uniform wall heat flux. The average Nusselt number and the total entropy generation increase with the permeability value of the porous medium (Da) irrespective of asymmetric wall heat flux amplitude and wavelength as well as with the variation in thickness ratio and thermal conductivity value of the solid substrate. However, the total irreversibility decreases for a high Darcy number value when the phase angle between the applied heat fluxes is varied. Moreover, the average Nusselt number decreases up to a critical value of phase angle followed by a gradual increment for Da = 10−5 and 10−3, respectively. On the contrary, the reverse trend can be seen for Da = 10−1. The optimal choice of nonuniform heat flux amplitude, wavelength, and phase angle for a high heat transfer rate with minimum irreversibility generation is found to be 10 W/cm2, 5 mm, and 180°, respectively for a thickness ratio of 0.5 and thermal conductivity value of 646.07 W/m·K independent of Darcy number.

Chiral-Flux-Phase-Based Topological Superconductivity in Kagome Systems with Mixed Edge Chiralities.

Recent studies have attracted intense attention on the quasi-2D kagome superconductors AV_{3}Sb_{5} (A=K, Rb, and Cs) where the unexpected chiral flux phase (CFP) associates with the spontaneous time-reversal symmetry breaking in charge density wave states. Here, commencing from the 2-by-2 charge density wave phases, we bridge the gap between topological superconductivity and time-reversal asymmetric CFP in kagome systems. Several chiral topological superconductor (TSC) states featuring distinct Chern numbers emerge for an s-wave or a d-wave superconducting pairing symmetry. Importantly, these CFP-based TSC phases possess unique gapless edge modes with mixed chiralities (i.e., both positive and negative chiralities), but with the net chiralities consistent with the Bogoliubov-de Gennes Chern numbers. We further study the transport properties of a two-terminal junction, using Chern insulator or normal metal leads via atomic Green's function method with Landauer-Büttiker formalism. In both cases, the normal electron tunneling and the crossed Andreev reflection oscillate as the chemical potential changes, but together contribute to plateau transmissions (1 and 3/2, respectively) that exhibit robustness against disorder. These behaviors can be regarded as the signature of a TSC hosting edge states with mixed chiralities.

Mass spectrum in a six-dimensional SU(n) gauge theory on a magnetized torus

We examine six-dimensional SU(n) gauge theories compactified on a two-dimensional torus with a constant magnetic flux background to obtain a comprehensive low-energy mass spectrum. We introduce general background configurations including the magnetic flux and continuous Wilson line phases, consistent with classical equations of motion. Under the standard gauge fixing procedure, the complete mass spectrum in low-energy effective theory for the SU(n) case is newly presented without imposing restrictions on the gauge fixing parameter. Our analysis confirms the inevitable existence of tachyonic modes, which neither depend on the background configurations of Wilson line phases nor are affected by the gauge fixing parameter. Masses for some low-energy modes exhibit dependence on the gauge fixing parameter, and these modes are identified as would-be Goldstone bosons that are absorbed by massive four-dimensional vector fields. We discuss the phenomenological implications associated with stabilization or condensation of the tachyonic states. Various mass spectra and symmetry-breaking patterns are expected with flux backgrounds in the SU(n) case. They are helpful for constructing phenomenologically viable models beyond the standard model, such as gauge-Higgs unification and grand unified theories.

The Detection of Possible Transient Quasiperiodic Oscillations in the γ-Ray Light Curve of PKS 0244-470 and 4C+38.41

The continuous monitoring capability of Fermi-LAT has enabled the exploration of quasiperiodic oscillations (QPOs) in the γ-ray light curve of blazars that has given a new perspective to probe these sources over a wide range of timescales. We report the presence of transient QPOs in the long-term γ-ray light curve of blazars PKS 0244-470 and 4C +38.41. We first identified different flux states using the Bayesian block algorithm and then explored the possible transient QPOs in the segments of each flux phase where the flux level changes over fairly regular intervals. Combining this with the source’s intrinsic variance, we identified two flux phases for PKS 0244-470: one activity (AP-1) and one quiescent phase (QP-1). For 4C+38.41, we similarly identified four activity (AP-1, AP-2, AP-3, and AP-4) and two quiescent (QP-1 and QP-2) phases. The AP-1 phase of PKS 0244-470 shows QPO of ∼225 days persisting for eight cycles (∼4.1σ). In 4C+38.41, AP-1 and AP-2 phases show QPO-like behavior of ∼110 days and ∼60 days, respectively, persisting for five cycles. In AP-3, we identified three subphases, and all show a ∼7 day scale possible recurrent rise with five complete cycles, while in QP-1, we could identify two subphases (Q1 and Q2). The Q1 phase shows a period of ∼104 days with six complete cycles. The Q2 phase also shows QPO but with only ∼3.7 cycles. We discuss the possible origin and argue that the current-driven kink instability and curved jet model seem to be the most likely causes for shorter and longer QPOs.

Comparative analysis of thermal damage to laser-irradiated breast tumor based on Fourier conduction and non-Fourier heat conduction models: A numerical study

In recent decades, laser technology has been widely used in surgeries and thermal therapies. To ensure patient safety and enhance therapeutic effectiveness in laser applications, it is crucial to accurately analyze burn injuries during the treatment process. In this study, a bioheat transfer model that includes the effects of metabolic heat generation, capillary blood vessels, and relaxation times of heat flux and temperature gradient was developed to study the non-Fourier heat conduction behavior in 2-D spherical breast tumor during the laser hyperthermia process. By employing different heat conduction models and the Arrhenius burn integration, the temperature distribution and laser-induced thermal damage to tumors were obtained. The progression of burn injury in time and the effect of various parameters on it were investigated. It was observed that the DPL model provides more reliable results in comparison with the CV model in predicting thermal damage to bio-tissue when non-Fourier effects are taken into consideration. The results showed that increasing heat flux phase lag leads to severe thermal damage, earlier onset of empyrosis, and wider and deeper burn injury. However, a greater phase lag of temperature gradient results in lower and superficial thermal damage, milder burn, later onset of empyrosis, and smaller burned area. The effect of laser power density on the onset time of different degrees of burn and their sensitivity to input power were investigated, and the results were represented graphically. Finally, investigation of wave propagation in various tissues revealed that the wave propagation speed is not constant and reduces as time increases.

Spin current and internal Zeeman field in spin-orbit coupled rings

We investigate the one-dimensional quantum ring constructed by the spin-orbit coupled material, in which the quantum spin-Hall Bernevig-Zhang (BZ) Hamiltonian and Rashba-Dirac (RD) type spin-orbit coupling are taken into account (called RD-BZ Hamiltonian in this paper). It is known that the curvature of the ring generates an out-of-plane effective magnetic field, acting as an internal Zeeman field. We find that only the BZ coupling can change the strength of the internal Zeeman field, which enables us to detect the effect of the internal Zeeman field. Furthermore, we find that the total angular momentum is conserved in the RD-BZ Hamiltonian, and the energy eigenvalue and wave function must be modified to fit the conserved quantity, which are ignored in the previous studies. The conductance without leads is discussed. Different from the previous results, we find that the conductance behaves like a beat phenomenon resulting from the interplay between the magnetic flux and Aharonov-Casher (AC) phase, and thus, it can oscillate without passing through the insulating state in some regimes of magnetic flux or AC phase. Importantly, we find that the conductance with integer and half-integer magnetic flux provides us a method to measure the AC phase. The cancellation of the internal Zeeman field due to the BZ coupling can be detected by using specific fractional magnetic flux. In the ring with nonvanishing RD and BZ couplings, the conductance can exhibit a quasiplateau near the small RD coupling. The increase in the strength of BZ coupling would result in wider quasiplateau in conductance, which implies that the ring could remain insulating state (or conducting state) regardless of the small change in RD coupling. The thermal average of spin and charge currents are calculated at low temperatures without impurities. Importantly, we find that the persistent spin and charge currents as a function of the magnetic flux exhibit nodelike lines, which amazingly are perpendicular to each other. As a consequence, the persistent spin current could be nonzero even when the charge current vanishes at nonzero magnetic flux. The result suggests a pure spin current in quantum rings, and its direction can be reversed by changing the magnetic flux. The increase in the BZ coupling would exhibit the plateaulike pure spin current.

Improved phase fraction measurement via non-intrusive optical sensing for vertical upward gas -liquid flow

This paper presents the design and application of a non-intrusive optical sensor for the accurate measurement of phase fractions under a vertical upward gas-liquid flow. The sensor was made of two pairs of emitter and photo receivers operated at a wavelength of 1480 nm. The measurement principle of the sensor is based on the disparity in refractive indexes of gas and liquid that provides a proportional relationship between the phase fraction and light intensity. A flow regime dependent calibration model was then developed which corrects for structural scattering derived from the calibrated sensor responses. The model was able to measure local and average phase fractions under varied flow regimes with errors of ± 1.25% and ± 2% relative to photography and swell level methods respectively with a combined uncertainty of ± 2.3%. Comparisons of the non-intrusive optical sensor with the homogenous, Drift flux and Armard phase fraction correlations showed reasonable agreements. The concept of slip as a dominant effect for flow regime in the slug, churn and annular flow regimes accounted for these disparities. The work demonstrates the efficacy of a low cost, non-intrusive method to determine phase fraction in two phase flow over a wide range of flow conditions.

Gamma-ray flares and broad-band spectral study of PKS 0402-362

ABSTRACTWe study the long-term behaviour of the bright gamma-ray blazar PKS 0402-362. We collected approximately 13 yr of Fermi-LAT data between August 2008 to January 2021 and identified three bright γ-ray activity epochs. The second was found to be the brightest epoch ever seen in this source. We observed most of the γ-ray flare peaks to be asymmetric in profile suggesting a slow cooling time of particles or the varying Doppler factor as the main cause of these flares. The γ-ray spectrum is fitted with PL and LP spectral models, and in both cases, the spectral index is very steep. The γ-ray spectrum does not extend beyond 10 GeV energy suggesting the emission is produced within the BLR. The absence of time lags between optical-IR and γ-ray suggest one zone emission model. Using the above information, we have modelled the broad-band SED with a simple one-zone emission model using the publicly available code ‘GAMERA’. The particle distribution index is found to be the same as expected in diffusive shock acceleration suggesting it as the main mechanism of particle acceleration to very high energy up to 4–6 GeV. Throughout the various flux phases, we noticed that the optical emission is dominated by the thermal disc, suggesting it to be a good source to examine the disc-jet coupling. We postulate that the observed broad-band flares could be linked with perturbation produced in the disc, which propagates to the jet and interacts with the standing shock. However, a more detailed examination is required.

Gravitational wave from extreme mass-ratio inspirals as a probe of extra dimensions

The field of gravitational waves is rapidly progressing due to the noticeable advancements in the sensitivity of gravitational-wave detectors that has enabled the detection prospects of binary black hole mergers. Extreme mass-ratio inspiral (EMRI) is one of the most compelling and captivating binary systems in this direction, with the detection possibility by the future space-based gravitational wave detector. In this article, we consider an EMRI system where the primary or the central object is a spherically symmetric static braneworld black hole that carries a tidal charge Q. We estimate the effect of the tidal charge on total gravitational wave flux and orbital phase due to a non-spinning secondary inspiralling the primary. We further highlight the observational implications of the tidal charge in EMRI waveforms. We show that LISA (Laser Interferometer Space Antenna) observations can put a much stronger constraint on this parameter than black hole shadow and ground-based gravitational wave observations, which can potentially probe the existence of extra dimensions.

An Inrush Current Suppression Strategy for UHV Converter Transformer Based on Simulation of Magnetic Bias

The Ultra High Voltage (UHV) converter transformer may generate serious inrush current during closing. It will cause commutation voltage distortion and easily result in commutation failure of converters on the same commutation bus. Due to the change of flux amplitude and phase caused by closing resistance in the Ultra High Voltage Direct Current (UHVDC) system, it is difficult to determine the closing time of the converter transformer when considering the influence of residual flux. Therefore, this paper first analyses the existing closing resistance strategy, and constructs the magnetic bias function according to the influence characteristics of closing resistance on the flux and phase. Then an inrush current suppression strategy based on magnetic bias simulation is proposed for star connection and delta connection of UHV converter transformers, which can accurately calculate the ideal closing time of mutual cancellation between the residual flux and bias flux during closing. Finally, the no-load closing model of the UHV converter transformer is established by PSCAD/EMTDC for simulation analysis of the feasibility, real-time verification is carried out using the RTDS closed-loop experimental platform. The results show that the proposed inrush current suppression strategy can effectively suppress the inrush current under different residual flux conditions.