Mirror Effect Research Articles

Manipulation of optical bound states in the continuum in a metal-dielectric hybrid nanostructure

Optical bound states in the continuum (BICs) are spatially localized states with vanishing radiation, despite their energy embedded in the continuum spectrum of the environment. They are expected to greatly enhance light–matter interaction due to their long lifetime and high quality factor. However, the BICs in all-dielectric structures generally exhibit large mode volumes and their properties are difficult to manipulate. In this paper, we propose a metal–dielectric hybrid nanostructure where a silver film is inserted into the silicon (Si) substrate under the Si nanopillar array. We show that symmetry-protected BIC in this system can couple with surface plasmon polaritons (SPPs) to form a hybridized mode. Compared with previous symmetry-protected BICs in all-dielectric structures, the SPP-coupled BIC has a significantly decreased mode volume, and its corresponding electric field is strongly localized below the Si nanopillars. We also show that the SPP mode makes the original polarization-independent symmetry-protected BIC become polarization-dependent. In addition, we demonstrate that the silver film in the considered structure can induce a metal mirror effect. The destructive interference between the magnetic dipole inside the Si nanopillars and the mirror magnetic dipole in the silver film can lead to the formation of accidental BICs. Our hybrid structure provides a versatile platform for the manipulation of light–matter interaction in the nanoscale.

High harmonic generation by co-rotating bi-circular laser fields interaction with relativistic plasmas

We present an investigation of high harmonic generation (HHG) from relativistic plasmas driven by two-color co-rotating circularly polarized (CP) laser fields at various frequency ratios ω2/ω1. The theoretical analysis and the particle-in-cell simulation results reveal that when ω2/ω1≥4, CP harmonics with opposite helicities can appear simultaneously due to the relativistic mirror effect and the related conservation laws. Meanwhile, the harmonic spectra features (including the HHG efficiency, the allowed harmonic orders, and their polarization states) can be tuned through adjusting the frequency and intensity ratio of the two driving field components. This finding might be helpful for a consummate understanding of the bi-circular HHG technique.

Stimulus-based mirror effects in associative recognition revisited.

The mirror effect, the finding that a manipulation which increases the hit rate in recognition tests also decreases the false alarm rate, is held to be a regularity of memory. Neath et al. (in press) took advantage of the recent increase in the number of linguistic databases to create sets of stimuli that differed on one dimension but were more fully equated on other dimensions known to affect memory. Using these highly controlled stimulus sets, no mirror effects were observed; in contrast, using stimulus sets that had confounds resulted in mirror effects. In this article, we use their stimulus sets to examine associative recognition. Using confounded stimuli, Experiment 2 found a lower false alarm rate for high- compared to low-frequency words, replicating previous results, and Experiment 4 found a mirror effect when manipulating concreteness, also replicating previous results. Using highly controlled stimuli, Experiment 1 found no evidence that frequency affected associative recognition, and Experiment 3 found concreteness affected only the hit rate, not the false alarm rate. When highly controlled stimuli are used, frequency affects only the false alarm rate in item recognition and has no effect in associative recognition, whereas concreteness affects hit rates in both item and associative recognition. Implications for theoretical accounts are discussed. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Magnetic field deflection in a 100 W Hall thruster with permanent magnets

The compact structure restrains the application of magnetic shielding in low-power Hall thrusters (LpHTs), leading to an asymmetric magnetic field or partial magnetic shielding of the channel wall. This study employs a trim coil to implement an asymmetric magnetic configuration in a 100 W laboratory Hall thruster. The locations of the maximum curvature of magnetic lines are deflected toward the inner and outer channel wall corresponding to the inward and outward deflected magnetic field configurations. Effects of the magnetic field deflection on the position of the ionization zone, efficiency of the thruster, discharge oscillations, and wall erosion are studied. Optical imaging and electrostatic probes are employed to monitor and scan the plasma beam. Experimental results show that the outward deflection induces a change in the magnetic mirror effect and alters the location of the ionization zone. The radial movement of the ionization zone away from the inner channel wall decreases the near-wall conductivity, reducing the electron current by 13.5% and promoting the current efficiency. Discharge oscillations are suppressed, and the propellant utilization efficiency is improved by 8.2%. Erosion of the channel wall shows an improvement of 40%. Generally, an outward deflected magnetic configuration can significantly improve the performance of LpHTs.

Analysing wrinkle interaction behaviour with Z-fold crease pattern in thin-film planar membrane reflector

Limited stowage volume of launch vehicles demands compact packaging of large deployable membrane structures. Employment of different folding approaches led to the unavoidable fold-lines(creases). Moreover, wrinkle reduction is essential in such thin-film solar sail and inflatable antenna structures. This article analyzes the combined effect of multiple creases and wrinkles on deployed thin Kapton’s surface accuracy. Authors have introduced a novel approach for employing membrane length shortening because of multiple creases and fold characteristics. Real-world logarithmic behaviour of crease relaxation and fold-region properties help in computing the crease curvature. A rhombus-shaped shell model with Z-folding is introduced and explored for the effect of the number of creases and their orientation. Stress concentration and wrinkle contours for applied edge tensile loading state that the fold lines affect the stress transfer path. Non-linear post-buckling analyses for the Kapton® membrane express higher wrinkle evolution in the central region over the loading edge. Besides, a discrepancy in wrinkle amplitude and wavelength reveals the effect of fold-line orientation on wrinkling. Sighting actual conditions for antenna structure, creasing profile normal to the loading direction was found preferable for maintaining reflector surface-effectiveness. Additionally, double creased membranes achieve maximum surface correctness for any angular position, as the mirror effect fold shapes reduce wrinkles the most. Results are validated by comparing with experimental outcomes.

A Theoretical Proposal for an Ultrabroadband Metamaterial Absorber for the Circular Polarization Waves Based on Anapole Mode in the Near‐Infrared Region

AbstractThe absorber excited by anapole response is in the spotlight owing to its non‐radiating merits, whereas the existing designs suffer from poor bandwidth and absorption. Furthermore, the circular polarization (CP) wave promises numerous application scenarios; thus, the absorbers aimed at it are sorely called for. An ultrabroadband metamaterial absorber (MMA) for the CP waves based on anapole mode is proposed in this paper. In this structure, the symmetrical split‐ring resonators (SRRs) are acted as the resonant unit to excite the toroidal dipole (TP) and electric dipole (EP) moments in the near‐infrared region. By applying the perfect electric conductor mirror effect, the enhanced field energy results in the absorption peak in the given band. Aimed at optimizing the absorption performance of the designed MMA, the SRRs are rotated, introduce the cavity resonance, and add the nickel patch to excite more electromagnetic resonance. The final optimized MMA can achieve an absorption exceeding 90% in an ultrabroadband of 1228–2156.7 nm, whose relative absorption bandwidth is 54.9%. Meanwhile, on account of its highly symmetrical structure, the MMA is insensitive to the polarization state of the CP waves. These splendid properties make the MMA a good candidate for potential applications.

Local Binary Pattern Regrouping for Rotation Invariant Texture Classification

This paper represent a deep study of the Local Binary Pattern (LBP) method and its variants of patterns regrouping , which is largely used in texture classification as well in other domain. The analysis of LBP’s two hundred fifty-six patterns has led us to propose a new organization of uniform and no uniform patterns into twenty-eight groups; each group assembled a number of patterns varied according to specific terms. The principal idea is to preserve the low complexity of LBP and simultaneously increase the method robustness against quality degradation caused by image operations like rotation, grey level changes, illumination and mirror effects. The experiments are done with the two texture databases Outex and Brodatz; the tests are proving the robustness of Local Binary Pattern Regrouping (LBPG) under circumstances.

Plasma diagnosis of an unclosed E × B drift thruster with a visible ionization zone

The traditional annular closed-loop E × B drifting Hall thruster is limited by its compact structure. Two-dimensional (2D) distribution of the plasma parameters inside the discharge channel cannot be accurately measured, thus directly hindering further understanding of the discharge process. In this paper, we propose to employ an unclosed E × B drift thruster with a visible (UDTv) ionization zone to conduct research into the effects of the crossed electric field and magnetic field on the plasma distribution inside the discharge channel. Experiments showed that the UDTv presented discharge similar to a Hall thruster, especially the low-frequency oscillation related to the discharge voltage. A 2D symmetrically crescent-shaped distribution of plasma inside the channel with a hollow zone located near the maximum of the magnetic field was clearly captured by optical imaging and an emission spectrometer. Correlation between the location of the maximal magnetic gradient and the 2D ionization zone configuration was verified. A decreased magnetic mirror effect at the location of the maximum magnetic field enhanced the electron–wall interaction, inducing near-wall conduction and secondary electron emission. The electron temperature presented a canyon distribution, resulting in a bimodal configuration of the plasma density. Increased flowrate lowered the ionization inside the channel and transformed the plasma distribution into a unimodal structure because of enhanced electron conduction and the lower electron temperature. Generally, the ability to capture the correlation between 2D plasma distribution and the magnetic field inside the discharge channel was successfully demonstrated, thus proposing new ideas for further research into the internal plasma of Hall thrusters.

Investigation of the Effect of Side Mirror Forms on Ahmed Body with CFD Method

The purpose of this study is to investigate the air resistance effect of different side mir-ror models on automobiles. The Ahmed Body model with 250 slant angle is taken as ref-erence for use as automobile geometry. Ahmed body is a simplified geometry model used for aerodynamic analysis of land vehicles. Side mirror models with the same front projection area were modeled using Solidworks. CFD simulation was performed with ANSYS Fluent 19.2. Realizable k-ε model is used as turbulence model and pressure-based type is used as solver type. In this study, the mesh quality was checked in terms of skewness and showed conformity. CD value obtained by numerical analysis is compati-ble with experimental data. Then, a comparison was made by adding side mirrors to the Ahmed Body model. As a result of the analysis, the display of the velocity and pressure distribution caused by the change of form around the mirror models and total CD values were determined.

Ground Effect of a Two-Dimensional Flapping Wing Hovering in Inclined Stroke Plane

Abstract The ground effect aerodynamics and flow physics of a 2D dragonfly wing hovering (the Reynolds number is 157) in an inclined stroke plane are investigated via solving 2D unsteady incompressible laminar flow Navier–Stokes equations. An analysis road map is proposed to explain the influence of the ground on the flow field, pressure distribution on the wing surface, and the aerodynamic force. In the analysis road map, the flow relative to the wing surface induced by the wing motion and vortex is classified into vertical and parallel wing surface flows. The vertical flow impinges on the wing surface to form a positive pressure zone. In contrast, the parallel flow generates the boundary layer and further concentrated vortex and secondary vortex, which induce negative pressure on the wing surface. The ground impacts the flow relative to the wing in three ways: changing the trajectory of the shed vortex by the mirror effect, promoting the deformation and fusion of the vortices, and causing the cushion effect at extremely small ground clearance.

The “Mirror Effect Plus Protocol” for acute Bell's palsy: A randomized controlled trial with 1-year follow-up

Objective To study the effects of the “Mirror Effect Plus Protocol” (MEPP) on global facial function in acute and severe Bell's Palsy. Design Single blind and randomized controlled trial to compare the effects of basic counseling (control group) versus MEPP (experimental group) over one year. Setting Outpatient clinic following referrals from Emergency or Otorhinolaryngology Departments. Subjects 40 patients (n = 20 per group) with moderately severe to total palsy who received standard medication were recruited within 14 days of onset. Baseline characteristics were comparable between the groups. Interventions The experimental group received the MEPP program (motor imagery + manipulations + facial mirror therapy) while the control group received basic counseling. Both groups met the clinician monthly until 6 months and at one-year post-onset for assessments. Outcome measures Facial symmetry, synkinesis, and quality of life were measured using standardized scales. Perceived speech intelligibility was rated before and after therapy by naïve judges. Results Descriptive statistics demonstrated improvements in favor of the MEPP for each measured variable. Significant differences were found for one facial symmetry score (House-Brackmann 2.0 mean (SD) = 7.40 (3.15) for controls versus 5.1 (1.44) for MEPP), for synkinesis measures (p = 0.008) and for quality-of-life ratings (mean (SD) score = 83.17% (17.383) for controls versus 98.36% (3.608) for MEPP (p = 0.002)). No group difference was found for perceived speech intelligibility. Conclusion The MEPP demonstrates promising long-term results when started during the acute phase of moderately severe to total Bell's Palsy.

Topological imbalanced phononic crystal with semi-enclosed defect for high-performance acoustic energy confinement and harvesting

Phononic crystals (PnCs) attract attentions in acoustic energy conversion and harvesting due to their excellent properties in regulating elastic and acoustic waves. Topological imbalance and semi-enclosed defect has been proposed in this work to systematically broaden the band gap of PnCs and improve the localization of elastic wave in defect. Parametric equations are introduced to generate nine square lattice unit cells with four-fold rotationally symmetric shapes. The imbalance between the long and short branches is utilized to describe the topological evolution of the perfect PnCs. With the increase of topological imbalance, the jump of the Bloch mode appears and thus leads to the band gap opening and expansion. The defect supercell with the highest topological imbalance has the best energy confinement effect. The 2D and 3D transient numerical simulations for the PnC of the highest topological imbalance indicate that the energy confinement effect of the semi-enclosed line defect is more intensive than the semi-enclosed arrow or bottle defect, which is confirmed by piezoelectric energy harvesting experiments. Under the excitation of 50 kHz, the period-2 nonlinear phenomena of the output voltage by piezoelectric disk are experimentally noticed in the PnC with the semi-enclosed line defect. The peak-to-peak power is 3.08 mW at the optimal resistance. Compared with the traditional point defect case, the voltage of the semi-enclosed line defect case is increased by 12.0 times and its power is increased by 75.1 times due to combination of perfect mirror effect and nonlinear defect state mechanism. This study provides a new avenue in design of high-frequency nonlinear acoustic devices and self-powered acoustic sensors.

Tunable bilayer dielectric metasurface via stacking magnetic mirrors.

Functional tunability, environmental adaptability, and easy fabrication are highly desired properties in metasurfaces. Here we provide a tunable bilayer metasurface composed of two stacked identical dielectric magnetic mirrors. The magnetic mirrors are excited by the interaction between the interference of multipoles of each cylinder and the lattice resonance of the periodic array, which exhibits nonlocal electric field enhancement near the interface and high reflection. We achieve the reversible conversion between high reflection and high transmission by manipulating the interlayer coupling near the interface between the two magnetic mirrors. Controlling the interlayer spacing leads to the controllable interlayer coupling and scattering of meta-atom. The magnetic mirror effect boosts the interlayer coupling when the interlayer spacing is small. Furthermore, the high transmission of the bilayer metasurface has good robustness due to the meta-atom with interlayer coupling can maintain scattering suppression against positional perturbation. This work provides a straightforward method to design tunable metasurface and sheds new light on high-performance optical switches applied in communication and sensing.

Influence of Imperfect Faraday Rotation Mirror on All-Fiber Optic Current Sensor

The effects of the Faraday rotation mirror on the all-fiber optic current sensor (AFOCS) are studied in this paper. The reflectivity degradation of FRM with the long-term operation, the misalignment of the optical axis between FRM and the sensing fiber, and the influence of temperature fluctuation on FRM are modeled and simulated in this paper. The effect of temperature is the biggest obstacle to the application of the Faraday rotation mirror, while other factors can be easy to overcome by the data processing method. The experiments are designed and realized for verification. The temperature fluctuation range is related to the measured electric current to satisfy the required accuracy for IEC 60044-8 class 0.2S.

The mirror effect: influence of national governance on environmental disclosure in coordinated economies

PurposeBased on the approach of the varieties of capitalism, this paper aims to investigate the influence of national governance characteristics on environmental disclosure.Design/methodology/approachThis research analyzed companies based in coordinated economies, i.e. 1,815 companies from Austria, Belgium, Denmark, Finland, France, Germany, Italy, Japan, The Netherlands, Norway, Portugal, Spain and Sweden were investigated for the period 2009–2018. The authors created an index to measure environmental disclosure, and national governance was measured using the United Nations governance indicators.FindingsThe findings show that countries with greater transparency, democracy, citizen participation and government effectiveness tend to have companies with a greater environmental concern. The results allow us to conclude that the responsible behavior of companies is a mirror of the governance environment of the country where they operate. The findings have managerial implications.Practical implicationsFirms must be aware that institutional factors can influence their business. In institutional structures with low government effectiveness, little confidence in social rules and high levels of corruption, corporations tend to be less ethical.Originality/valueThis research used the varieties of capitalism approach to explain companies’ environmental disclosure. This is a recent approach to the institutional theory, and little explored in previous studies. Institutional level variables, such as governance indicators, can be used in other studies that analyze the relationship between institutional environment and corporate disclosure.

Screening: From tornado diagrams to effective dimensions

Popular sensitivity analysis techniques such as Tornado Diagrams or the Morris method are based on one-at-a-time input variations (local main effects, henceforth). We evidence a link between local main effects of screening methods and global sensitivity measures. The link allows analysts to obtain insights on interactions on the local and global scales simultaneously. We evidence a mirroring effect according to which a local main effect calculated from the base case to the sensitivity case is equal in magnitude to the local total effect in the opposite direction, and their difference yields an overall local interaction index. We then obtain the exact relationship between Morris sensitivity measures and Sobol’ total indices and discuss its implications on the choice of the sampling scheme. We show that the non-diagonal elements of the variance-covariance matrix of main effects computed at randomized locations yield Liu and Owen’s global interaction indices. Asymptotic results are derived with particular reference to confidence intervals for the mean dimension. We illustrate findings and insights through numerical experiments on two well known simulators.

P397. Genomic Deletions and Duplications Show Mirror Effects on Cognitive Ability According to Spatial Patterns of Gene Expression in the Human Brain

Genomic deletions or duplications, which increase risk for neurodevelopmental-psychiatric-disorders, can contain several genes and decrease or increase gene-expression respectively. Studies have estimated that 50% of coding genes show measurable effects on cognitive-ability when deleted or duplicated. Genes with large effect-sizes show enrichment in molecular/cellular functions. However, these functions only apply to small groups of genes. We hypothesize that spatial patterns of gene-expression reflect macroscale brain functions and will shed light on the effects of large groups of genes.

Cross-coupling effects in common-source current mirrors composed by UTBB transistors

This work performs an analysis of the cross-coupling effects influence on the performance of current mirrors composed by advanced UTBB SOI MOSFETs through 3D numerical simulations validated to experimental data of single devices. It is shown the presence of a capacitive coupling acting in the system, which can be demonstrated through the threshold voltage reduction at small distances between devices. Additionally, the temperature rise in the system due to the thermal coupling provokes a decrease in the input current as the devices become closer to each other. This is responsible for an increase of 3 % on ID2/ID1 ratio when the devices are biased at the same time and when the distance between them is lowered to 100 nm.

Study on the Correlation between Magnetic Field Structure and Cold Electron Transport in Negative Hydrogen Ion Sources

In most negative hydrogen ion sources, an external magnet is installed near the extraction region to reduce the electron temperature. In this paper, the self-developed CHIPIC code is used to simulate the mechanism of a magnetic filter system, in the expansion region of the negative hydrogen ion source, on “hot” electrons. The reflection and the filtering processes of “hot” electrons are analyzed in depth and the energy distribution of electrons on the extraction surface is calculated. Moreover, the effects of different collision types on the density distribution of “cold” electrons along the X-axis and the spatial distribution of “cold” electrons on the X−Z plane are discussed. The numerical results show that the electron reflection is caused by the magnetic mirror effect. The filtering of “hot” electrons is due to the fact that the magnetic field constrains most of the electrons from reaching the vicinity of the extraction surface, being that collisions cause a decay in electron energy. Excitation collision is the main decay mechanism for electron energy in the chamber. The numerical results help to explain the formation process of “cold” electrons at the extraction surface, thus providing a reference for reducing the loss probability of H−.

Investigation of trapped charges profile for an irradiated insulated material.

The process of examining and analysing insulating materials using a scanning electron microscope usually accompanied by an important phenomenon called the mirror effect or charging effects. Such effects arise due to the ability of insulators to trapping charges at the sample surface for a period. The accumulation of charges leads to creating an electric potential that may be strong enough to deflect incident electrons in the same way a convex mirror scatters light. The created potential depends mainly on the charge amount, charges accumulation profile and the way by which the charges arranging themselves. Present work aims at exploring the influences of the charges distribution profile and their arrangements. In order to achieve such a goal, the sample-surface potential has theoretically formulated to include various shapes of the accumulated charges. Thereafter, the correspondence expression of the mirror plot curve is defined to link thegeometrical distribution of charges.The resultant formula for the surface potential and mirror plot showed that the point charge approximation is a special case of the presented model. The formulaof mirror-plot curve hasput forward to be a detection tool for the actual build-up form that the electrons accumulating might take on the insulator surface.Simulation results have shown that the presented procedurecould be adopted to search for the optimum distribution profile that may meet an experimental data. It is found that the most probable profile that accumulated electrons might form is the semi-hemispheric one. The surface of this profile is generally an ellipsoid of a variant axis rather a flat one. Results also reveal that, all the multipole-moment typescould be formed for any shape of accumulation, but their weightiness progressively decreases whenever the pole-number increases. Furthermore, the configurations that trapped electrons arrange themselves within each distribution profile can be traced with the variation of scanning potential.