Single-layer Square Research Articles

A polarization conversion metasurface for broadband and high-efficiency bidirectional filtering

Here, we demonstrate a polarization conversion metasurface which is composed of a single layer square split-ring resonator and bi-layered slotted perfect electrical conductor (PEC) to realize broadband and high-efficiency bidirectional filtering. The numerical results indicate that y-polarized waves can be converted to x-polarized transmission waves in the frequency range of 6.6 GHz to 13.9 GHz, while prevent this polarized waves with frequency beyond this band, and purity x-polarized waves can be obtained as electromagnetic (EM) waves are incident along negative z-axis, meanwhile, x-polarized waves can be converted to y-polarized transmission waves and only y-polarized waves available when EM waves are incident along positive z-axis. This designed polarization conversion metasurface has the function of bidirectional filtering in a wideband frequency range. Furthermore, the broadband property can be maintained as the incident angle up to 30°. The Fabry–Pérot-like cavity model is established to clarify the interference and enhancement effect of polarization conversion, and the electrical field and surface current distributions are used to elucidate the physical mechanism of polarization conversion and filtering. The experimental results are coincident with the numerical simulations. This metasurface can be employed in controlling the filtering signal of the polarized devices and can be functional as a bandpass filter in communication systems.

Silicon nitride-based ultra-wideband ultra-long infrared metamaterial absorber with large angle and high absorption

In the study of mid-infrared band long wavelength infrared (LWIR) has attracted the attention of domestic and foreign researchers due to its great role in medical diagnosis and detection. Broadband absorption is also a key index for metamaterial absorption applications. In this paper, a design of a highly absorbing, large-angle ultra-wideband ultra-long infrared metamaterial absorber based on a single-layer square Si3N4 cavity array and an intermediate layer of Si3N4 thin film, as well as metal Ti as the substrate, is proposed. The ultra-long infrared metamaterial absorber has polarization insensitivity under the condition of positive incidence. Numerical simulations show that the effective absorption bandwidth with more than 90% absorption is 11.12 μm in the band range of 7.65–18.77 μm, in which the average absorption reaches 96.54%. Diffraction and impedance matching induced strong absorption and wide bandwidth. We can adjust the absorption performance by changing the structural size of the absorber. In addition, our design has a very wide operating range of incidence angles, and the TM and TE modes maintain ultra-high average absorption levels under 0°-60° incidence angles, it is worth mentioning that the absorption of the absorber can reach 95.08% at an incident angle of 60°. The absorber design proposed in this paper has a simple structure, the material is easily available and inexpensive, and the fabrication process is very simple, which makes it suitable for infrared imaging, medical detection, and thermoselectronic devices.

Designing and experimental validation of single-layer mixed foil resonator acoustic membrane to enhance sound transmission loss (STL) within low to medium frequency range

This study presents a novel design for an acoustic membrane structure that employs a parallel-arrangement of mixed foil sound resonators to improve sound absorption and insulation capabilities in the low to medium frequency range. The structure is composed of a single layer of parallel-arranged mixed foil wedge-shaped coffers and a bottom flat panel separated by an air cavity. The mixed thickness-based foil resonators are treated as a combination of independent resonators with unique resonance frequency, resulting in improved sound insulation with broadband efficacy. A comprehensive parametric analysis was carried out using the Finite Element Method (FEM) based COMSOL Multiphysics, yielding the anticipated outcomes. The study revealed that the broadband Sound Transmission Loss (STL) can be tailored by varying the thickness of the top and side walls, the bottom plate thickness, and the depth of the rear air cavity. The findings suggest that existing acoustic membrane design can be highly efficient, achieving, and average STL of over 40 dB ∼ 45 dB across the low to medium frequency range of 500 Hz to 3000 Hz. The experimental validation was conducted in an anechoic chamber, and the results were found to be in close agreement with the FEM simulation results. In comparison to conventional uniform foil sound resonator based acoustic membrane structure, this mixed single-layer square wedge-shaped foil resonator based acoustic membrane exhibits outstanding sound insulation performances in the low to medium frequency range, owing to its lightweight structure and availability of conventional manufacturing techniques. This advanced version of the foil sound resonator based acoustic membrane holds immense promise for the use in acoustics and noise control applications across domestic, commercial, and industrial environments.

Equation of State and Thermometry of the 2D SU(N) Fermi-Hubbard Model.

We characterize the equation of state (EoS) of the SU(N>2) Fermi-Hubbard Model (FHM) in a two-dimensional single-layer square optical lattice. We probe the density and the site occupation probabilities as functions of interaction strength and temperature for N=3, 4, and 6. Our measurements are used as a benchmark for state-of-the-art numerical methods including determinantal quantum MonteCarlo and numerical linked cluster expansion. By probing the density fluctuations, we compare temperatures determined in a model-independent way by fitting measurements to numerically calculated EoS results, making this a particularly interesting new step in the exploration and characterization of the SU(N) FHM.

Design and analysis of terahertz multifunctional tunable metasurfaces based on single-layer square split ring

Aiming at the problems of single function, limited application range and complex structure of most metasurfaces, we propose a terahertz multifunctional tunable metasurface based on VO2-metal hybrid structure. The metasurface consists of three layers, from top to bottom, VO2-metal resonance layer, Topas dielectric layer and bottom gold film reflective layer. When circularly polarized light is incident, the metasurface can achieve broadband circular dichroism (CD) function, and the CD intensity generated at 3.19–6.24 THz is greater than 0.8, and the relative bandwidth is as high as 64.69%. When linearly polarized light is incident, the dual-band reversible linear dichroism (LD) function, broadband linear-to-circular polarized conversion function, and high-efficiency linear cross-polarization conversion function can be achieved by adjusting the polarization state of the incident light. Moreover, by adjusting the conductivity of VO2 and the state of the incident light, the adjustment of each functional intensity can be achieved. Finally, we believe that the proposed multifunctional metasurface has significant reference value in the terahertz range for constructing chiral photodetectors, CD metamirrors, intelligent switches, and polarization digital imaging systems.

Effect of Knitting Pattern of PP Mesh on the Flexural Properties of Heat-cured PMMA Denture Base Resin

Heat-cured polymethyl methacrylate is (PMMA) is the most common denture base material and some mechanical properties such as flexural strength and impact resistance etc. may lead to fail, besides its excellent properties. Polypropylene (PP) hernia mesh is a commercially available medical textile used in surgical repair of different types of hernia. It was aimed to investigate the effect of two different knitting patterns of PP meshes on the flexural properties of the PMMA denture base resin when they are used as reinforcement and compare with glass fiber mesh reinforced and no mesh used resins. Knitting patterns of the PP mesh structures were hexagonal honeycomb pattern and square pattern and these were used as single or double layer as reinforcement. 6 groups were established in the study: control group with no mesh and 5 reinforced groups with meshes (glass fiber mesh, single layer honeycomb patterned PP mesh, double layer honeycomb patterned PP mesh, single layer square patterned PP mesh, double layer square patterned PP mesh). A total of 60 samples with the dimensions of 65x10x3 mm, n=10 in each group were fabricated. The flexural strength, maximum deformation, and flexural modulus were determined by three-point bending test. Fracture surfaces were evaluated by scanning electron microscopy. The obtained data were statistically analyzed by two-way ANOVA test with Bonferroni corrections. The single layer square patterned PP mesh group exhibited the highest (76.67 ± 7.64 MPa), and the control group showed the lowest (63.49 ± 7.18 MPa) flexural strength values. The single layer glass fiber mesh group showed the highest (7.13 ± 0.55 mm) and the control group showed the lowest (4.72 ± 0.81 mm) maximum deformation values. The single layer glass fiber mesh group exhibited the highest (2131.87 ± 205.76 MPa), and the control group exhibited the lowest (1582.26 ± 98.63 MPa) flexural modulus values. Significant increase in flexural strength was observed in all polypropylene mesh-reinforced groups compared to the control group except double layer honeycomb patterned PP mesh group (p < 0.05). Using PP fiber mesh for reinforcement provide a very favorable aesthetic view and PP fiber mesh is concluded to be a promising material for reinforcement of heat-cured PMMA denture base resins.

Ultra-broadband and polarization-insensitive terahertz metamaterial absorber based on undoped silicon

Terahertz (THz) absorbers with high absorptivity across a wide frequency band have attracted considerable interest. In this paper, we present the design of an ultra-broadband THz metamaterial absorber with high absorptivity based on a single-layer square silicon array and a silicon film backed with metallic gold. It is numerically demonstrated that the absorption exceeds 90% covering the frequency range of 0.62–8.75 THz (with an effective absorption bandwidth of 8.13 THz) when the conductivity of semiconductor (undoped silicon) is 600 S/m. Diffraction and impedance-matched induce strong absorption and the corresponding broad bandwidth. The proposed ultra-broadband THz absorber is polarization-insensitive at normal incidence. It can operate over a rather wide range of incidence angle up to 60 degrees for transverse magnetic (TM) terahertz wave. This work provides a way to achieving ultra-broadband terahertz absorption, which is very useful in the development of terahertz imaging, high sensitivity sensors and detection.

A Polarization and Frequency Reconfigurable Microstrip Antenna for Vehicular Communication System Application

To face a complex wireless communication scenario, a flexible and tunable multi-functional antenna system should be employed to guarantee system quality. This paper presents a polarization and frequency reconfigurable microstrip patch antenna with a wide 3-dB axial ratio beam-width for vehicle communication systems. By controlling the p-i-n diodes, the proposed design can achieve four operating states: linear polarization (LP) in lower frequency bands between 1.45 and 1.47 GHz, and LP, left-hand circular polarization (LHCP), and right-hand circular polarization (RHCP) in higher frequency bands between 1.50 and 1.53 GHz. The proposed antenna has an exceptionally low profile (0.02 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda _{0}$</tex-math></inline-formula> at 1.5 GHz) and a simple structure, consisting of a single-layer square patch with two annular ring slots and four switches placed at appropriate locations in the slots. P-i-n diodes, as the switchs, change the current distribution on the radiating patch to achieve the antenna's polarization and frequency reconfigurability. The proposed antenna was fabricated and tested, and the observed results are identical to those predicted by the simulation. The antenna has outstanding reconfigurable capabilities independent of frequency or polarization in the operational frequency range. Therefore, it can be well used for vehicular communication systems because of its multi-reconfigurability and stable mechanical property.

Tunable broadband terahertz absorber using a single-layer square graphene patch with fourfold rotationally symmetric groove

We present a broadband and tunable graphene-based absorber in the terahertz (THz) region, which is composed of a monolayer of graphene square-shaped patch with fourfold rotationally symmetric groove and a metallic ground film separated by a silicon dioxide (SiO2) spacer layer. The bandwidth of 90% absorbance for the structure reaches up to 1.66 THz with a central frequency of 2.53 THz under normal incidence, and the broadband absorption still remains 80% over a wide incident angles up to 50° for both transverse electric (TE) and transverse magnetic (TM) modes. Furthermore, the peak absorption of the proposed absorber can be tuned from 15% to near 100% by varying the graphene's Fermi energy from 0 to 1.0 eV via adjusting the bias voltage of the graphene layer or chemical doping. Due to the geometrical symmetry, the proposed structure is insensitive to the polarization state of incidence wave. Benefits from these outstanding performances, we believe that our proposed absorber may have great applications in tunable THz filtering, imaging, and cloaking.

Sublaminate variable kinematics shell models for functionally graded sandwich panels: Bending and free vibration response

An advanced kinematic formulation is applied to multilayered cylindrical sandwich panels with continuously graded layers. Free vibration and bending problems are considered. The mean mechanical properties of the composite material are estimated by means of the extended rule of mixture or the Eshelby-Mori-Tanaka method. The displacement field is postulated by means of variable-kinematics sublaminate models, therefore the applicability is not restricted to monolithic panels, on the contrary, the approach is well suited for sandwich panels with marked thickness-wise heterogeneity. Due to the efficiency of the formulation, the effect of various design parameters, either geometrical or mechanical, can be easily explored. The validation is performed against benchmarks of increasing complexities, namely a single-layer square plate, a shell reinforced by randomly oriented nanotubes, sandwich panels with three distinct configurations. The importance of allowing kinematic descriptions of tunable accuracy within a unique framework is well demonstrated by the proposed assessments.

Tunable multi-band terahertz absorber using a single-layer square graphene ring structure with T-shaped graphene strips.

We numerically demonstrate a tunable dual-band terahertz metamaterial absorber (MA) with near-unity absorption using single-layer square graphene ring structure with T-shaped graphene strips. By periodically loading four T-shaped graphene strips to the square graphene ring periodic array without additionally increasing the size of MA device, the pre-existing resonant frequency will have a red shift and simultaneously a new resonance will be generated at higher frequency for achieving a dual-band MA. The two absorption peaks can be tuned to the resonant frequencies of interest by varying the parameters of the square graphene ring and T-shaped graphene strips. The operating frequency of the absorption spectrum can be also manipulated by adjusting the chemical potential of graphene, without changing their geometric parameters. Additionally, numerical results show that the proposed MA possesses polarization-independent and incident-angle-insensitive properties. To further extend the proposed structure's application with more absorption peaks, a tri-band MA is investigated through adding four more T-shaped graphene strips based on the dual-band absorber configuration. Therefore, our research work will be a good candidate for the design of various graphene-based tunable multi-band absorbers at different frequency regions with potential applications in optoelectronic devices and systems.

Modeling and Analysis of GPS–GLONASS Navigation for Car Like Mobile Robot

An idea to amalgamate GPS and GLONASS to form the best part of GNSS tracking system for mobile robot navigation. The introduction of GNSS made additional satellites visible to localize Mobile robot accurately in both indoor and outdoor application; hence the localization accuracy will be increased in the non-line of sight areas of GPS satellites. This paper explains about an antenna which operates in GPS-1.575 GHz and GLONASS-1.602 GHz system frequency bands. A single layer square patch antenna with size of 45 mm * 45 mm is designed and simulated using Computer Simulation Technology Algorithmic model of the proposed antenna is derived and RLC values of equivalent circuit are identified using MATLAB program. The prototype antenna is fabricated and tested using network analyser for observing the experimental results. The Proposed antenna parameters are compared with simulation, theoretical and existing antenna results. Thus, the findings support that the proposed antenna system could be useful for the localization of car like mobile robot in indoor and outdoor environments.

Evolutionary Games in Two-Layer Networks with the Introduction of Dominant Strategy**Supported by the National Natural Science Foundation of China under Grant Nos 11575036, 71301012, and 11505016.

We study evolutionary games in two-layer networks by introducing the correlation between two layers through the C-dominance or the D-dominance. We assume that individuals play prisoner’s dilemma game (PDG) in one layer and snowdrift game (SDG) in the other. We explore the dependences of the fraction of the strategy cooperation in different layers on the game parameter and initial conditions. The results on two-layer square lattices show that, when cooperation is the dominant strategy, initial conditions strongly influence cooperation in the PDG layer while have no impact in the SDG layer. Moreover, in contrast to the result for PDG in single-layer square lattices, the parameter regime where cooperation could be maintained expands significantly in the PDG layer. We also investigate the effects of mutation and network topology. We find that different mutation rates do not change the cooperation behaviors. Moreover, similar behaviors on cooperation could be found in two-layer random networks.

Staging Entrapment in Mexico City

Five actors move around an almost empty theater stage carrying ubiquitous gray building bricks; they are costumed in jeans, skirts, shirts, and blouses that have been dyed to produce a whitish mottled coloring, as if covered in brick dust from construction work. Gradually, at center-front stage, they collectively construct a single-layer square platform of bricks—a stage on a stage. Standing side by side behind the square of bricks, the actors leap into the air in unison, gesturing upward. Together they take a step onto the brick stage, facing the audience square on. > —It was the day of the fiesta of our lord Huitzilopochtli. We were celebrating in the temple…. The plaza was full of people … > —There were snipers on the roofs. > —Those who were going to kill us covered one hand with a white glove. > —Suddenly there was a gunshot in the distance. We didn’t know where it came from. > —“Get down!” someone shouted. “They’re going to kill us!” > — They closed the eagle entrance in the smaller palace … and when it was closed, they all took their positions. > —The plaza was a mousetrap. The actors gaze out into the darkness of the auditorium, staring directly at the audience, as intensive bright lights shine in their faces, illuminating expressions of fear and terror. Pressed together they form a tight cluster of bodies. Standing huddled, the bodies push, touch, crouch, and lean sideways, falling … falling as one body, in slow motion, bodies contorted, awkward, one on top of the other, heads falling slowly down to the ground. > —I remember perfectly the blood running down the forehead of someone who was by my side. > —I had blood in the sides of my shoes, in the hem of my dress. > —“Everyone against the wall! Everyone on the ground, and whoever …

ANALYSIS AND DESIGN OF DUAL BAND HIGH DIRECTIVE EBG RESONATOR ANTENNA USING SQUARE LOOP FSS AS SUPERSTRATE LAYER

A superstrate layer is used to enhance the directivity of the small radiation sources such as Microstrip Patch Antennas. In this paper, we use square loop frequency selective surface (SLFSS) configuration to design the superstrate layer. To compact the structure, we propose a new single layer square loop FSS configuration that operates in two frequency bands such as multi-layer SL-FSS. Simulation results are shown to have good agreement with experimental results.

Quantum Criticality and Percolation in Dimer-Diluted Two-Dimensional Antiferromagnets

The S = 1/2 Heisenberg model is considered on bilayer and single-layer square lattices with couplings J1, J2, with each spin belonging to one J2-coupled dimer. A transition from a Néel to disordered ground state occurs at a critical value of g = J2/J1. The systems are here studied at their dimer-dilution percolation points p*. The multicritical point (g*,p*) previously found for the bilayer is not reproduced for the single layer. Instead, there is a line of critical points (g < g*, p*) with continuously varying exponents. The uniform magnetic susceptibility diverges as T(-alpha) with alpha element of [1/2,1]. This unusual behavior is attributed to an effective free-moment density approximately T(1-alpha). The susceptibility of the bilayer is not divergent but exhibits remarkably robust quantum-critical scaling.

Tow-Dimensional Micro-grating Formed by Polystyrene Spheres

We report a simple method to make two-dimensional plane gratings thatcan be used as splitters. In the self-assembly process, the colloidalspheres can form single layer square or triangular lattice on a flatsurface and in our experiments the triangular lattice is a more commonstructure. As an incident beam passes through the triangular lattice,it can be split into seven sub-beams, among which six beams have thesame density and scattering angle. This grating is not sensitive to thepolarization direction of the incident light.

Single-patch and single-layer square microstrip antenna with 67.5% bandwidth

A square microstrip patch antenna with broadband operation is demonstrated. With an air-filled substrate of thickness around 0.1/spl lambda//sub 0/ and one patch edge shorted by three symmetrical shorting pins, the antenna achieves an impedance bandwidth (return loss /spl les/-10 dB) of 67.5%. The broadband feature of the antenna is mainly realised by exciting three resonant modes in a single patch and making them sufficiently close to one another. Details of the antenna design, equivalent circuit, and typical characteristics are presented and discussed both theoretically and experimentally.

The effect of shaking on magnetic shields

The increase of the shielding factor due to shaking was measured in a scale model for a magnetically shielded room. The increase was found to be 7 dB for a single-layer square cylinder biased by the Earth's magnetic field. The shielding factor of a large-volume three-layer Mumetal <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">®</sup> room was estimated to increase by a factor of 30, thus confirming the feasibility of shaking in magnetic shields. The shaking parameters, amplitude, and frequency are not critical according to the experiments. Winding the shaking coils along the edges of the cubic shield leads to minimum disturbances inside the cube, and the winding can also be applied to demagnetize the shield by an alternating field of 25 A/m, 50 Hz. The relative incremental permeability of Mumetal was studied as a function of the shaking and biasing fields. The permeability was found to increase considerably by shaking and by decreasing the biasing field. With zero biasing and with shaking field of H <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</inf> = 5 A/m root mean square (rms), 50 Hz, the permeability reached its maximum value of 89 000, which is sevenfold the value without shaking.