Concentric Double Rings Research Articles

The outer ring of a circular structure in the Marche Region, Central Italy: Evidence of a non-extraterrestrial origin

Google Earth images in the Marche Region of Central Italy revealed a circular structure consisting of a ring system made up of concentric hills and valleys. Cartography, DEM, geological, and available geophysical data were used to constrain the possible origin of the structure. Located in the Messinian foredeep deposits of the Central Apennines, it has a rim diameter of 3.75 km and a central uplift connected to its southernmost part. As it was formed in the clays of the Lower Pliocene, and clays are believed to have emerged definitively after the Upper Pliocene, its age might be constrained to the Lower Pleistocene. Similar concentric structures are usually found in impact craters, sedimentary domes, and volcanic landforms. As salt domes and magmatic activity are not found in this region, this study seeks to validate the results of previous work that it was the result of an ancient impact crater, of hydrological, brachy anticline, or clayey diapiric origins. Specifically, an observed second ring portion, with a curvature radius about double the first in size, will be investigated in this work. This second ring portion appears to be concentric to the first one and is visible along the its northern and western parts. Although double concentric rings are usually due to impact craters, the absence of the ring portion in the other two directions, and the probable deviation of a river, deduced by studying hydrography, supports the hypothesis that it might be of a clay diapir origin.

A Complementary Frequency Selective Surface with Tri-Band Frequency Response for Applications in Wi-Fi and 5G

In this paper we proposed a novel tri-band complementary frequency selective surface (CFSS) with a traditional geometry composed of double concentric rings. The choice of this geometry is because of its very good angular stability. The proposed resonant frequencies were 2.5 GHz, 3.5 GHz, and 4.5 GHz. The CFSS is low profile and presents angular stability and polarization independence. Simulations were performed using HFSS software and they are compared with the experimental results for validation purposes. A very good agreement is observed between them.

Modelling of Wideband Concentric Ring Frequency Selective Surface for�G燚evices

Frequency selective surfaces (FSSs) play an important role in wireless systems as these can be used as filters, in isolating the unwanted radiation, in microstrip patch antennas for improving the performance of these antennas and in other 5G applications. The analysis and design of the double concentric ring frequency selective surface (DCRFSS) is presented in this research. In the sub-6 GHz 5G FR1 spectrum, a computational synthesis technique for creating DCRFSS based spatial filters is proposed. The analytical tools presented in this study can be used to gain a better understanding of filtering processes and for constructing the spatial filters. Variation of the loop sizes, angles of incidence, and polarization of the concentric rings are the factors which influence the transmission coefficient as per the thorough investigation performed in this paper. A novel synthesis approach based on mathematical equations that may be used to determine the physical parameters of DCRFSS-based spatial filters is presented. The proposed synthesis technique is validated by comparing results from high frequency structure simulator (HFSS), Ansys electronic desktop circuit editor, and an experimental setup. Furthermore, the findings acquired from a unit cell are expanded to a 2 × 2 array, which shows identical performance and therefore proves its stability.

Double Sided Wideband Concentric Ring Spatial Filters for Mid-Band 5G Devices

This paper presents the methodology, development, and implementation of the double concentric ring band-pass frequency selective surface (FSS) based spatial filters. The filters are designed to improve the active responses of the 5G antennas by incorporating them as superstrate or as substrates. A comparable circuit model is used to anticipate the resonant frequency bands required for predicting the FSS band-pass behavior. The designed spatial filter is composed of a combination of periodic circular loop structures engraved on both sides of a thin dielectric substrate. The proposed design of a double circular loop FSS exhibits band-pass characteristics for n77, n78, and n79 bands of the mid-band 5G spectrum (ranging from 3 GHz - 6 GHz) and provides insensitivity to polarization angles of the incident plane wave. The computed, simulated, and measured findings are all depicting a similar pattern that validates our structure.

Van der Waals epitaxy and defect-charge manipulation of InSb islands on graphene-covered SiC(0001)

Indium antimonide has attracted extensive interest due to its optical and electronic applications, and functions as a constituent block in exploring Majorana physics. Here, through molecular-beam epitaxy, we achieve van der Waals epitaxy of high-quality InSb islands on graphene-covered SiC(0001) substrate. As characterized with spectroscopic imaging scanning tunneling microscopy (STM), the islands have tens of nanometers in thickness and a 2 \ifmmode\times\else\texttimes\fi{} 2 surface reconstruction, exhibiting a narrow band gap of 0.315 \ifmmode\pm\else\textpm\fi{} 0.005 eV. Double concentric rings, whose diameters vary with the bias voltage of the STM tip, are observed in the spatially resolved conductance maps, which are explained as a charging process of solitary defects due to tip-induced band bending. Furthermore, high-temperature sample annealing induces a 3 \ifmmode\times\else\texttimes\fi{} 3 surface reconstruction, which possesses a larger gap of 0.40 \ifmmode\pm\else\textpm\fi{} 0.01 eV. Our work demonstrates the feasibility of van der Waals epitaxy of the InSb traditional semiconductor and enriches the understanding of charging process in single defects.

A tri‐band complementary frequency selective surface with very closely spaced resonances

This paper presents a tri-band complementary frequency selective surface (CFSS) with very closely spaced bands and angular stability. The proposed CFSS element geometry is composed of double concentric rings. The choice of this geometry is because of its very good angular stability. The gap between resonance frequencies is very close, only 404 MHz from the first to second band and 202 MHz from the third to second, which is only possible because of the use of CFSS. The CFSS simulation is performed using HFSS software and the design used the equivalent circuit method. The simulated results are compared with the experimental ones for validation purposes. A very good agreement is observed between the simulated and measured results.

Physical-Hydraulic Quality Indicators of soils with different years of management under Pinot Noir (Vitis vinifera L.)

The present study aimed to evaluate the physical-hydraulic quality of soils with different years of management after planting Vitis vinifera L. cv. Pinot Noir. Areas with 4, 9 and 16 years of cultivation were evaluated, at depths of 0.0-0.10, 0.10-0.20, 0.20-0.30, 0.30-0.40, 0.40-0.50 and 0.50-0.60 m, in three replicates, in the wheel track (WT), between wheel tracks (BWT) and in the planting row (PR), were analyzed. The physical quality indicators analyzed were bulk density, macroporosity, microporosity, total porosity. Soil water infiltration was also analyzed at these positions, by the method of double concentric rings, both with 30 cm height, and diameters of 50 cm in the outer ring and 25 cm in the inner ring, which were buried 15 cm deep into the soil and filled with water. Soil management in the different periods of planting resulted in a heterogenous soil compaction in the vine interrows. The position between wheel tracks (BWT) has a higher infiltration rate, regardless of the vineyard management time.

Influence of a split double concentric ring resonator elements axial rotation on the microwave transmission line frequency-selective characteristics

The work is dedicated toward studying the methods for correcting the frequency characteristics of a passive transmission path of a strip-line or coplanar microwave transmission line, equipped by a split double concentric ring resonator on the transmission section reverse side of the printed circuit board (plate). This correction is carried out by rotation around the center of the concentric rings (or an axis passing through this point and perpendicular to the plane of the substrate) of both constituent elements of the resonator separately and of the whole resonant structure.

Equivalent circuit model for analysis of frequency selective surfaces with ring and double concentric ring apertures

In this study, the authors present two new proposals for representation by the equivalent circuit model for aperture-type circular ring geometries, not yet studied in the literature. The study consists of the frequency response representation of frequency selective surfaces (FSSs) formed by circular ring aperture and concentric circular ring apertures. At first, the authors performed an equivalent circuit analysis for a single cell formed by a single circular ring. Then, they extend the analysis to concentric circular rings, which when used as FSS unit elements, present two passband responses. They compare results of the proposed method with results obtained with the commercial software ANSYS HFSS, showing a good agreement between the results. They built four prototypes and compared measured results with simulated results obtained with the suggested method and it completes the proposed equivalent circuit validation.

Angle insensitive broadband terahertz wave absorption based on molybdenum disulfide metamaterials

Abstract Two-dimensional semiconductor materials may be of importance in the field of nanophotonics. We design a broadband terahertz (THz) absorber based on molybdenum disulfide (MoS2) metamaterial, consisting of a monolayer MoS2 concentric double rings and a metal mirror separated by a thin SiO2 layer. The plasma hybridization between two MoS2 rings can effectively increase the operating bandwidth of the device under normal circumstances. The absorption rate of the structure and the absorption bandwidth can be also tuned by temperature or voltage-controlled carrier concentration. The special geometry makes our design exhibit properties that are insensitive to the angle of incidence and the polarization state of the pump source. We believe that our devices may pave the way for the design of tunable sensors in terahertz and other frequency bands.

Muti-band terahertz modulator based on double metamaterial/perovskite hybrid structure

We proposed a novel multi-frequency-band terahertz modulator working for free-space terahertz radiation. The unit cell of the metamaterial/perovskite hybrid structure, which consists of split-ring resonator, is patterned on silica with a dielectric constant of ε=3.75, a loss tangent of tan δ=0.01 and concentric double rings are fabricated on the bottom of the silica with the thickness of 200 nm. The split gaps of split-ring resonators are filled with perovskite quantum dots thin film. The terahertz wave modulation mechanism of our structure is numerically investigated by using CST Microwave Studio. We have also employed an equivalent circuit model (ECM) to validate our numerically simulated observations. The results exhibit four different frequency carrier wave signal modulation at 0.42THz, 0.83THz, 1.18THz and 1.62THz with modulation depth (>99%) and megahertz modulation speed. This work demonstrates a new approach for realizing multi-band terahertz amplitude shift keying (ASK) modulator for terahertz wavelength division multiplex (WDM) communication.

Tunable Graphene-Based Plasmon-Induced Transparency Based on Edge Mode in the Mid-Infrared Region.

A monolayer-graphene-based concentric-double-rings (CDR) structure is reported to achieve broadband plasmon-induced transparency (PIT) on the strength of edge mode in the mid-infrared regime. The theoretical analysis and simulation results reveal that the structure designed here has two plasmonic resonance peaks at 39.1 and 55.4 THz, and a transparency window with high transmission amplitude at the frequency of 44.1 THz. Based on the edge mode coupling between neighbor graphene ribbons, PIT phenomenon is produced through the interference between different (bright and dark) modes. The frequency and bandwidth of the transparency window and slow light time could be effectively adjusted and controlled via changing geometrical parameters of graphene or applying different gate voltages. Additionally, this structure is insensitive to the polarization and incident angle. This work has potential application on the optical switches and slow light modulators.

带有同心双圆环谐振腔的MIM波导的Fano谐振特性研究

带有同心双圆环谐振腔的MIM波导的Fano谐振特性研究

Hybridization-induced broadband terahertz wave absorption with graphene metasurfaces

Electromagnetic (EM) wave absorption plays a vital role in photonics. While metasurfaces are proposed to absorb EM waves efficiently, most of them exhibit limited bandwidth and fixed functionalities. Here, we propose a broadband and tunable terahertz (THz) absorber based on a graphene-based metasurface, which is constructed by a single layer of closely patterned graphene concentric double rings and a metallic mirror separated by an ultrathin SiO2 layer. Plasmonic hybridization between two graphene rings significantly enlarges the absorption bandwidth, which can be further tuned by gating the graphene. Moreover, the specific design also makes our device insensitive to the incident angle and polarization state of impinging EM waves. Our results may inspire certain wave-modulation-related applications, such as THz imaging, smart absorber, tunable sensor, etc.

Plasmonic Refractive Index Sensor with High Figure of Merit Based on Concentric-Rings Resonator.

A plasmonic refractive index (RI) sensor based on metal-insulator-metal (MIM) waveguide coupled with concentric double rings resonator (CDRR) is proposed and investigated numerically. Utilizing the novel supermodes of the CDRR, the FWHM of the resonant wavelength can be modulated, and a sensitivity of 1060 nm/RIU with high figure of merit (FOM) 203.8 is realized in the near-infrared region. The unordinary modes, as well as the influence of structure parameters on the sensing performance, are also discussed. Such plasmonic sensor with simple framework and high optical resolution could be applied to on-chip sensing systems and integrated optical circuits. Besides, the special cases of bio-sensing and triple rings are also discussed.

Unique double concentric ring organization of light harvesting complexes in Gemmatimonas phototrophica.

The majority of life on Earth depends directly or indirectly on the sun as a source of energy. The initial step of photosynthesis is facilitated by light-harvesting complexes, which capture and transfer light energy into the reaction centers (RCs). Here, we analyzed the organization of photosynthetic (PS) complexes in the bacterium G. phototrophica, which so far is the only phototrophic representative of the bacterial phylum Gemmatimonadetes. The isolated complex has a molecular weight of about 800 ± 100 kDa, which is approximately 2 times larger than the core complex of Rhodospirillum rubrum. The complex contains 62.4 ± 4.7 bacteriochlorophyll (BChl) a molecules absorbing in 2 distinct infrared absorption bands with maxima at 816 and 868 nm. Using femtosecond transient absorption spectroscopy, we determined the energy transfer time between these spectral bands as 2 ps. Single particle analyses of the purified complexes showed that they were circular structures with an outer diameter of approximately 18 nm and a thickness of 7 nm. Based on the obtained, we propose that the light-harvesting complexes in G. phototrophica form 2 concentric rings surrounding the type 2 RC. The inner ring (corresponding to the B868 absorption band) is composed of 15 subunits and is analogous to the inner light-harvesting complex 1 (LH1) in purple bacteria. The outer ring is composed of 15 more distant BChl dimers with no or slow energy transfer between them, resulting in the B816 absorption band. This completely unique and elegant organization offers good structural stability, as well as high efficiency of light harvesting. Our results reveal that while the PS apparatus of Gemmatimonadetes was acquired via horizontal gene transfer from purple bacteria, it later evolved along its own pathway, devising a new arrangement of its light harvesting complexes.

GHz frequency filtering source using hexagonal metamaterial splitting ring resonators

There are a number of characteristics that make metamaterial has wide applications and has been researched at present, such as negative phase, negative index of refraction, super resolution, and reverse of Doppler's effects. This paper investigates a hexagonal metamaterial structure with a split and a double concentric rings so-called split ring resonator hexagonal (SRR-H) for frequency filtering application. SRR-H is designed structurally and operated computationally for frequency range of 1 to 120 GHz. The simulation results showed that SRR-H size will affect the resonant frequency significantly. The resonant frequency tends to shift the lower frequency when the size of the structure is enlarged. The properties of the structure SRR-H, such as permeability, permittivity and the refractive index have a similarity because it is dominated by the properties of permeability. Metamaterial SRR-H successfully responded to double negative and agreed with Lorentz's model.

Monte Carlo simulation of the formation of AIIIBV nanostructures with the use of droplet epitaxy

A Monte Carlo lattice model is proposed to describe the formation of semiconductor nanostructures by the vapor–liquid–solid growth mechanism. This model is used to simulate the growth of GaAs nanostructures by the droplet epitaxy technique in the temperature range from 500 to 600 K in As2 fluxes with intensity of 0.005–0.04 ML/s. The morphology of the formed structures is demonstrated to depend on the growth parameters. Etching of the GaAs substrate by a gallium droplet is studied. The ranges of temperature and As flux rates necessary for the formation of GaAs nanorings are determined. The conditions of the formation of single and double concentric rings are analyzed.

An ultrasensitive optical label-free polymeric biosensor based on concentric triple microring resonators with a central microdisk resonator

In this paper we propose an optical label-free biosensor based on a polymeric platform. Label-free biosensors have not the drawbacks and stability problems of commercialized devices which are used for detection of labeled molecules. In addition, we choose polymeric platform, due to simple and low cost fabrication process and also high biocompatibility properties. The suggested structure consists of concentric triple ring resonators along with a disk resonator which offers deeper notches, higher sensitivity and vaster detection area with respect to other similar configurations such as single ring resonator, double concentric ring resonators, etc. Our numerical simulations based on the finite difference time domain (FDTD) method, show that in optimized structure, a transmission notch depth of −48.7dB for sensor at rest and a free spectral range of 56nm are achievable. In addition, resonance wavelength sensitivity and output power sensitivity of sensor are 1000nm/RIU and 1.8×104dB/RIU, respectively. The external radius of outer ring resonator is only 5μm, and detection area of the sensor is 40.37μm2. With this small size, to the best of our knowledge, the obtained notch depth and sensitivity parameters are one of the highest values in ring resonator-based biosensors reported to date.

Robustness Analysis Based on Optical Fiber Sensor Networks Topology

Although optical fiber sensor networks (OFSNs) attract more and more attentions, they are still facing the problem of lacking the methods for assessing network robustness quantitatively. This paper improves the recently presented OFSNs robustness evaluation model by proposing the robustness error assessment based on Monte Carlo method. Robustness simulations of several network topologies, including line, ring, star, bus, and double ring topologies, have been done with the model, proving that the concentric double ring topology proposed by Fernandez-Vallejo et al. is more robust than the other four topologies. Parameters required for robustness calculation in ring topology are listed in detail. Then, an experimental robustness assessment approach is established. According to it, eight-point fiber Bragg grating sensor networks with the four basic topologies are employed. Support vector machine is applied to process data. Both threshold and attenuation coefficient have been gotten from experiments. Comparison between experimental and simulative robustness verifies the practicability of the robustness evaluation method, and also proves that ring and star topologies are better than the others, whereas bus topology is unfit for improving robustness by adding sensors.