Annular Ring Structure Research Articles

Annular Ring UWB Wearable Textile Antenna for Telemetry and Healthcare Applications

A wearable microstrip UWB antenna employing jeans textile material as a substrate is proposed and analyzed. Two variants of conducting material comprising copper tape and copper wire of thickness of 0.1mm are utilized as patch and ground. The overall antenna volume is 50 × 50 × 1 mm3 with an impedance bandwidth of 24.13 GHz (0.87 to 25 GHz) and a peak gain of 10.93 dB at 14.80 GHz. The design comprising an annular ring structure with connecting feed at the optimized location has been analyzed and optimized using FEM based ANSYS High-Frequency Structural Simulator. The low values of Specific Absorption Rate (SAR) 1.23W/kg, 1.26W/kg, and 0.64W/kg averaged over 1-g of tissue for arm, leg, and head respectively at 2.45 GHz validate the antenna design for wearable telemetry applications. The proposed design is also analyzed under different bent radii for wearable applications. Measured results for both prototypes agree well with the simulated results.

Design and Fabrication of Wideband Air-Coupled Capacitive Micromachined Ultrasonic Transducers With Varying Width Annular-Ring and Spiral Cell Structures.

Air-coupled transducers with broad bandwidth are desired for many airborne applications, such as obstacle detection, haptic feedback, and flow metering. In this article, we present a design strategy and demonstrate a fabrication process for developing improved concentric annular- and novel spiral-shaped capacitive micromachined ultrasonic transducers (CMUTs) that can generate high output pressure and provide wide bandwidth in air. We explore the ability to implement complex geometries by photolithographic definition to improve the bandwidth of air-coupled CMUTs. The ring widths in the annular design were varied so that the device can be improved in terms of bandwidth when these rings resonate in parallel. Using the same ring width parameters for the spiral-shaped design but with a smoother transition between the ring widths along the spiral, the bandwidth of the spiral-shaped device is improved. With the reduced process complexity associated with the anodic-bonding-based fabrication process, a 25- [Formula: see text] vibrating silicon plate was bonded to a borosilicate glass wafer with up to 15- [Formula: see text] deep cavities. The fabricated devices show an atmospheric deflection profile that is in agreement with the FEM results to verify the vacuum sealing of the devices. The devices show a 3-dB fractional bandwidth (FBW) of 12% and 15% for spiral- and annular-shaped CMUTs, respectively. We measured a 127-dB sound pressure level at the surface of the transducers. The angular response of the fabricated CMUTs was also characterized. The results demonstrated in this article show the possibility of improving the bandwidth of air-coupled devices by exploring the flexibility in the design process associated with CMUT technology.

ОПРЕДЕЛЕНИЕ КОМПОНЕНТОВ, РАСТВОРЕННЫХ ОРГАНИЧЕСКИХ И НЕОРГАНИЧЕСКИХ ВЕЩЕСТВ В ПРИРОДНЫХ ВОДАХ

Introduction. Large urban agglomerations have to deal with issues related to the high-quality drinking water supply. These issues are mainly due to water quality deterioration, poor condition and severe wear of water supply infrastructure facilities. Materials and methods. In our study, we analyze the composition of drinking water in the water supply system of St. Petersburg for SiO2 and Al2O3 nanoparticles and organic substances, including soluble proteins, protein components, and salts. For this purpose, we estimated the concentration and distribution of nanoparticles and organic impurities in the sediment formed after water evaporation from a sample in the form of a droplet. During the process, the following methods were used: the method for dehydration of water droplets with the formation of a solid phase, the methods for optical analysis of the sediment structure based on image analysis and recognition (photo and video recording of microscopic images), mathematical modeling of sediment structures’ formation, and statistical analysis of the results. Results. The presence of impurities in water was determined by the formation of periodic annular ring structures in sediments of aqueous solutions. The analysis of the structures obtained made it possible to determine the composition of the mixture and percentage content of individual fractions by the type of structural elements and their periodicity. We also developed a mathematical model simulating the processes of particle settling out of a solution. The calculations were carried out using model liquids and made it possible to obtain dependencies for the distribution of various dissolved particles in the structure of the solid phase, as well as to describe the staged mechanism in settling during its formation.

Compact Multiband Microstrip Printed Slot Antenna Design for Wireless Communication Applications

In this paper, a compact multiband printed antenna is proposed to cover four resonant bands in the range of 1-6 GHz. The antenna structure is inspired from that of the classical multi-cavity magnetron resonator. The antenna comprises a slot annular ring structure in the ground plane of an Isola FR4 substrate having Ԑr = 3.5 and thickness h=1.5 mm. The outer circle of the annular ring is loaded with radial arranged small circular slots. On the opposite side of the substrate, the antenna is fed with a 50-Ohm microstrip line. To investigate the effect of different antenna elements on the antenna performance, a parametric study is conducted. The antenna is simulated, fabricated, and measured. The simulated 10 dB return loss bandwidths for the four resonant bands are 35% (1.53–2.11GHz), 14% (2.9–3.34GHz), 12% (4.2–4.75GHz), and 9% (4.94–5.39GHz), respectively. Thus, the antenna is a proper candidate for many in use bands of wireless systems (1.65, 3.14, 4.44, 5.24 GHz), including LTE-FDD, GNSS, GSM-450, W-CDMA/HSPA/k, 802.11a, and IEEE 802.11ac WLAN. The results indicate that the designed antenna has quad-band resonant responses with substantial frequency ratios of f4/f3, f3/f2 and f2/f1. Besides, the antenna offers reasonable radiation characteristics with a gain of 2.5, 4.0, 6.2, and 4.2 dBi, throughout the four resonant bands.

Improving Radiation Pattern Roundness of a Monopole Antenna Placed Off-Center Above a Circular Ground Plane Using Characteristic Mode Analysis

The radiation pattern of a quarter-wavelength monopole antenna placed off-center above a circular ground plane is seriously distorted due to the noncircular symmetric discontinuity encountered at the edge of the ground plane. An annular ring structure surrounding the monopole antenna is proposed to localize most currents for omnidirectional radiation with an enforced circular symmetric discontinuity. The characteristic mode analysis (CMA) shows that two modes with desired radiation patterns contribute most to the radiation of the proposed ring-loaded monopole. With the information of the calculated modal significances (MSs) and characteristic currents in CMA, the size of the loading ring is optimized. The simulated and experimental study shows that after introducing the ring structure, the maximum unroundness of the off-center monopole is reduced by 66%, which is improved from 3.5 to 1.2 dB.

GAG content, fiber stiffness, and fiber angle affect swelling-based residual stress in the intact annulus fibrosus.

Biological tissues with a high glycosaminoglycan (GAG) content have an excellent ability to swell by absorbing water molecules from the surrounding environment. Our recent work showed that anisotropy in tissue swelling depends on the fiber-network architecture, including fiber angle, fiber stiffness, and lamellae structure. However, that work did not evaluate the effect of in situ boundary conditions, such as the kidney-bean shape of the annulus fibrosus (AF), on swelling behavior. The biochemical composition of intact AF is inhomogeneous with respect to GAG composition, collagen fiber angle, and fiber stiffness. Moreover, the GAG content in the inner AF decreases significantly with degeneration. In this study, we investigated the role of GAG content, fiber angle, and fiber stiffness in AF swelling and residual strain development using a finite element model based on a human lumbar disk. Our results showed that the annular ring structure had a great impact on swelling by developing region-dependent compressive stress/stretch in the inner layers and tensile stress/stretch in the outer AF. Swelling-based residual stretch was comparable to experimentally measured values, suggesting an important role of tissue swelling in maintaining residual stresses. Moreover, GAG loss in the inner AF, as observed with degeneration, decreased circumferential-direction stress by over 65%. Homogeneous distributions of fiber angle and stiffness overestimated or underestimated AF swelling behavior, such as swelling ratio, circumferential/axial stretch, and fiber stretch/reorientation. These findings demonstrate the need to include native fiber architecture in finite element models, to accurately predict tissue failure, as well as to cultivate engineered disks.

Design of a Multimode UWB Antenna Using Characteristic Mode Analysis

In this communication, a low-profile ultrawide band (UWB) antenna is designed, fabricated, and measured for TV white space devices (TVWSDs). Starting from a simple annular ring, the proposed design procedure is guided by the characteristic mode analysis. First, a closed-form estimation to the resonant frequencies of the first two characteristic modes for the annular ring structure is provided. Then, the annular ring is modified to introduce more characteristic modes resonating within the interested spectrum. To excite these modes and to achieve a wideband antenna covering the whole ultrahigh frequency (UHF) TV spectrum, the feeding structure is also carefully designed and refined. Finally, a prototype is fabricated and measured to verify its UWB performance, and radiation patterns at different frequencies are presented to prove the switching of dominating resonating modes. The analyses and performance evaluation show that the proposed antenna is a strong contender to be used for TVWSDs. Furthermore, thanks to the simplicity of tuning and controlling modal resonant frequencies, this procedure can be flexibly applied to various antenna designs.

Refined shear deformation theories for laminated composite arches and beams with variable thickness: Natural frequency analysis

A higher-order mathematical formulation with applications is presented in this paper for the free vibration analysis of arches and beams made of composite materials. Higher-order shear deformation theories are required to capture accurately the three-dimensional behavior of these structures through a one-dimensional scheme. Several orders of kinematic expansion are investigated and compared. In addition, the so-called zig–zag theories obtained through the use of the well-known Murakami's function are employed. Their effectiveness is extremely clear when laminates with inner-soft cores are analyzed. A set of numerical applications is presented to prove the accuracy of the current methodology. In particular, the comparison with exact solutions and results available in the literature or obtained through three-dimensional finite element commercial codes justifies the use of higher-order models, in which the displacement field is defined through the arbitrary choice of the maximum order of kinematic expansion. The in-plane vibrational modes of arches and beams, as well as annular ring structures, are computed and presented, discussing also the Poisson effect on the solutions.

Design and analysis of annular ring-based RIS and its use in dual-band patch antenna miniaturization for wireless applications

This paper proposes the design of a Reactive Impedance Surface (RIS) which comprises a 5 × 5 array of grounded unit cells. The unit cells have annular ring structures on their top surfaces. A detailed analysis of the unit cell leading to its impedance characteristic is presented and validated with simulated results. The RIS exhibits inductive impedance below 4.92 GHz. Next, the RIS is used as the ground of a dual-band patch antenna instead of a metallic ground for the purpose of miniaturization. As a result, the lower resonant frequency of the antenna is lowered from 3.36 to 2.4 GHz exhibiting 28.6% miniaturization. The higher resonant frequency is decreased from 4.77 to 3.43 GHz exhibiting 28.1% miniaturization. The theory of antenna miniaturization using RIS is also discussed. The lower and higher resonant frequencies of the miniaturized antenna correspond to the WiFi and WiMAX frequencies, respectively. The gain and efficiency at these two frequencies are significant and radiation patterns are stable with low cross- polarization level. Hence, the proposed structure can be used for practical wireless applications.

A Novel Six-Band Dual CP Rectenna Using Improved Impedance Matching Technique for Ambient RF Energy Harvesting

A novel six-band dual circular polarization (CP) rectenna for ambient radio frequency (RF) energy harvesting is presented. Due to the nonlinearity and complex input impedance of the rectifying circuit, the design of a multiband and/or broadband rectenna is always challenging and its performance can be easily affected by variation in the input power level and load. Therefore, an improved impedance matching technique is introduced, which is aimed to improve the performance of the rectifier with a varying condition. A broadband dual CP receiving antenna is proposed, which has a very wide bandwidth (from 550 to 2.5 GHz) and a compact size. An annular ring structure and a novel feeding technique are employed in order to reduce the size and improve the antenna performance. As a result, the proposed rectenna is the first design that covers six frequency bands, including part of the digital TV and most cellular mobile and WLAN bands in the U.K., while the optimal load range for a constant conversion efficiency is from 10 to 75 $\text{k}\Omega $ . The measured results show that the maximum harvested dc power of the rectenna in typical outdoor and indoor environments are 26 and 8 $\mu \text{W}$ , respectively; it can therefore be applied to a range of low-power wireless applications.

Gap Plasmon Enhanced Metasurface Third-Harmonic Generation in Transmission Geometry

The influence of gap plasmons in the third-harmonic generation of annular and H-shaped aperture arrays has been investigated. Surprisingly, the maximum third harmonic in the annular ring structures is not from the smallest gap, but rather appears for a gap of 14 nm. We interpret this result in terms of resonant plasmonic antenna design to match scattering and absorption cross sections. Unlike the annular aperture, continuous gold apertures, like the H-structure, achieve 0.45% conversion efficiency for 2 mW/μm2 CW pump power of a 100 fs pulse, which is 9 times larger than rectangular apertures we have reported in the past. Nonlinear scattering theory has been used to estimate the transmitted third-harmonic signal and is in generally good agreement with the experimental results.

Suppression of Radiative Damping and Enhancement of Second Harmonic Generation in Bull's Eye Nanoresonators.

We report a drastic increase of the damping time of plasmonic eigenmodes in resonant bull's eye (BE) nanoresonators to more than 35 fs. This is achieved by tailoring the groove depth of the resonator and by coupling the confined plasmonic field in the aperture to an extended resonator mode such that spatial coherence is preserved over distances of more than 10 μm. Experimentally, this is demonstrated by probing the plasmon dynamics at the field level using broadband spectral interferometry. The nanoresonator allows us to efficiently concentrate the incident field inside the central aperture of the BE and to tailor its local optical nonlinearity by varying the aperture geometry. By replacing the central circular hole with an annular ring structure, we obtain 50-times higher second harmonic generation efficiency, allowing us to demonstrate the efficient concentration of long-lived plasmonic modes inside nanoapertures by interferometric frequency-resolved autocorrelation. Such a light concentration in a nanoresonator with high quality factor has high potential for sensing and coherent control of light-matter interactions on the nanoscale.

High-power test of annular-ring coupled structures for the J-PARC linac energy upgrade

Annular-ring coupled structures (ACSs) will increase the beam energy of the Japan proton accelerator research complex (J-PARC) linac from 181 to 400 MeV to achieve a beam power of 1 MW for a materials and life science experimental facility. The mass production of the ACS cavities commenced in March 2009. Before the installation, all cavities require power testing. High-power testing is essential not only for confirming the cavity’s design performance but also for preventing delays in cavity conditioning schedule. However, the 2011 Tohoku earthquake damaged J-PARC facilities, including the ACS power-test area, and cavity conditioning was interrupted for two years. After the facility’s restoration, two ACS cavities (M01 and M11) were conditioned. They performed 15–20% above the designed accelerating field of 4.2 MV/m. As M01 was initially conditioned six years ago, the most recent conditioning time required for M01 was drastically reduced. From this result, we confirmed that long-term stored ACS cavities purged with nitrogen gas do not produce critical cavity performance issues. During high-power operation of M11, which is a unique cavity equipped with a capacitive iris in a waveguide, no significant increases in the temperature and the discharge rate around the capacitive iris were observed. Even considering beam loss due to residual gas scattering, the vacuum pressure was sufficiently low (4 × 10−6 Pa). More stable operation can be expected following a month-long conditioning process before the beam is commissioned. M11’s conditioning successfully demonstrated an auto-conditioning program, and we established the conditioning scheme using this auto-conditioning program for all ACS cavities in a limited time and with limited manpower.

Phase-only shaping algorithm for Gaussian-apodized Bessel beams

Gaussian-apodized Bessel beams can be used to create a Bessel-like axial line focus at a distance from the focusing lens. For many applications it is desirable to create an axial intensity profile that is uniform along the Bessel zone. In this article, we show that this can be accomplished through phase-only shaping of the wavefront in the far field where the beam has an annular ring structure with a Gaussian cross section. We use a one-dimensional transform to map the radial input field to the axial Bessel field and then optimized the axial intensity with a Gerchberg-Saxton algorithm. By separating out the quadratic portion of the shaping phase the algorithm converges more rapidly.

Light focusing at metallic annular slit structure coated with dielectric layers

We report the focusing of a normally incident plane wave of 405 nm through a Ag/dielectric annular ring structure, using finite-difference time domain analysis. We first study the dependency of the focusing efficiency on slit width when the incident wave is transmitted through a single ring whose slit is filled with a dielectric. Then, light focusing by the multiple-ring structure is investigated as a function of the dielectric thickness. It is observed that the focusing is tunable between near-field and quasi-far-field regimes in the Ag/dielectric layered annular ring structure. Also, the focal intensities are remarkably enhanced by the addition of the dielectric layer, showing a Fabry-Perot-like resonance with respect to the thickness of the dielectric layer. The controllable near-field and far-field focusing offers more flexibility for applications of future nano-optic devices.

Plasmonic near-field probe using the combination of concentric rings and conical tip underradial polarization illumination

We numerically study a plasmonic near-field probe design that integrates a sharp metallicconical tip at the center of a multiple concentric ring plasmonic lens under radiallypolarized illumination. Due to the symmetry match between the plasmonic structure andthe illumination polarization, surface plasmon waves can be efficiently excited and focusedby the annular ring structure towards the conical tip at the center. The metallictip further localizes and enhances the plasmonic field at the tip apex. With a5 µm tip height and 5 nm tip radius, spatial resolution with the full widthat half-maximum of 5.97 nm and electric energy enhancement of7.29 × 104 can be achieved with 632.8 nm optical excitation. The enhancement factor of this probedesign does not strongly depend on the tip cone angle and the excitation wavelength. Thestrong local field enhancement at the end of the tip and its less stringent fabricationrequirements make this probe design very attractive for a broad range of applications innear-field optical imaging.

Spinoptics: Spin-Based Plasmonics in Nanostructures

T interaction between light and metallic subwavelength structures results in various anomalous effects, such as extraordinary optical transmission1 and beaming.2 These effects have been elegantly explained by a mechanism that involves the coupling of light to collective surface-confined electronic oscillations known as surface plasmon-polaritons (SPPs). Extensive research has been carried out in the field of electromagnetic surface waves, which has rich technological potential. Apparently, the handedness of the light’s polarization (spin of photons) may provide an additional degree of freedom in nanoscale photonics. Here, we demonstrate the spin-dependent behavior of SPPs, which results from a geometric Berry phase that we found experimentally while exploring the interaction of light with metallic anisotropic and inhomogeneous nanoscale structures.3,4 The proposed anisotropic inhomogeneous plasmonic structure was produced on top of a thin metal film evaporated onto a glass plate. The element consisted of a spiral Bragg grating with a central defect surrounded by a coupling grating, as shown in part (a) of the figure. The structure was illuminated by circularly polarized light (R=right-handed, L=left handed). The intensity in the plasmonic cavity was measured by a near-field scanning optical microscope (NSOM). The measured intensity distribution exhibits a strong dependence on the incident spin. An annular ring structure with a dark spot in the center for R illumination and with a bright spot for L illumination indicates coupling to different spiral plasmonic modes (plasmonic vortices). The origin of the spin-dependent change in the near-field intensity distributions is in the geometric phase of the excited plasmonic mode. In the most general case, when a wave carrying an arbitrary intrinsic angular momentum (spin) changes its direction of propagation and polarization state, the geometric phase is given by a simple expression stemming from the Coriolis effect,3 which appears due to rotation of the reference frame represented by the local direction of the grating grooves. Accordingly, a spiral geometric phase with spin-dependent helicity arises in a circular grating.4 In the spiral structure, such as that shown in (a), an additional dynamic phase arises as a result of a space-variant path difference. The overall phase in the spiral cavity is the sum of the geometric and dynamic phases, which is manifested by different spiral modes that are obtained in the cavity for different polarizations. One of the possible technological implementations of the plasmonic geometric phase could be a spin-dependent plasmonic focusing lens. The proposed structure is presented in (b). We illumi(a) The scanning electron microscope (SEM) image of the spiral nanostructure and the scheme of the optical setup. Intensity distribution in the cavity measured by an NSOM for R and L illumination. The blue dashed line represents the spiral phasefront obtained in the cavity. (b) Spin-dependent plasmonic lens based on a plasmonic spin Hall effect. The intensity distributions measured by an NSOM for R and L illumination and the corresponding transverse cross-sections in the focal plane of the lens (measured: R=blue squares, L=red circles; calculated: R=solid blue line, L=dashed red line). The SEM picture of the element is depicted in the inset.

Compact concentric annular-ring patch antenna for triple-frequency operation

A novel single-layer, single-feed concentric annular-ring microstrip patch antenna providing triple-frequency operation is proposed and experimentally studied. This is achieved by embedding a small circular patch into a dual stub-loaded concentric annular-ring structure and by employing a cross-slot in the ground plane. The proposed technique can provide triple-band operation and reduce the antenna size by over 50% compared to the conventional annular-ring patch antenna for a given frequency. Experimental results show the proposed antenna to have impedance bandwidths of 6.38, 6.30 and 35% for the three bands, at 1.17, 1.428 and 1.9 GHz, respectively. The proposed structure is capable of realising a dramatically small frequency ratio. The measured radiation patterns for each band are presented

Intercalation and Surface Modification of Smectite by Two Non-Ionic Surfactants

AbstractNon-ionic surfactants Brij 56 and Igepal CO 720, containing hydrophilic poly(ethylene oxide) (PEO) segments, expanded smectite from 1.5 nm to 1.7 nm at room temperature. The surfactant-smectite composites had larger layer spacings than Ca-smectite after heat treatment. The surfactant-smectite composites were solvated and expanded to 1.8–1.9 nm by polar solvents, glycerol and water, but were not affected by the non-polar or weakly polar solvents, toluene, hexane or octanol. The hydrophilic PEO segments of non-ionic surfactants would logically access the interlayer spaces of smectite whereas the hydrophobic segments extend away from the mineral. The molecular structure and solvation properties suggest that the surfactant molecules are probably concentrated in the margin area of the interlayer galleries forming an annular ring structure between two neighboring silicate sheets. Only two layers or less of the surfactants could access the interlayer galleries of smectite and layer spacings did not exceed 1.8 nm even where excess surfactant was introduced into the composites. The layer spacings of the surfactant-smectite composites were well preserved during water or electrolyte solution washings, indicating stability of most non-ionic surfactant molecules in the interlayer galleries even though ∼30% of the adsorbed Igepal CO 720 was desorbed by exhaustive washing. The non-ionic surfactant treatment preserved >80% of the CEC of the smectite. The interlayer cations of the resulting surfactant-smectite were exchangeable as in the untreated smectite. Therefore, the non-ionic surfactant-smectite was much more efficient at removing heavy metal ions than activated carbon or cationic surfactant-treated smectite. The surfactant-smectite composites effectively removed aromatic chlorophenols from a pH 4.9 acetate buffer solution while untreated smectite did not adsorb these molecules. The enhanced adsorption of the aromatic compounds is attributed to the aliphatic segments of the two surfactants.

Microstrip lines on annular‐ring photonic bandgap structures

AbstractWith the advent of planar photonic bandgap (PBG) materials, different topologies of PBG structures have been proposed to improve the bandgap performances of microwave signals. Conventional circular‐patterned PBGs have constraints in the broadband stopband performance due to the high ripple heights in S‐parameters. In this paper, we suggest a novel annular‐ring‐patterned PBG to improve the stopband bandwidth and the ripples. The aspect ratio of the annular‐ring‐patterned PBG plays an important role in controlling the bandwidth of the rejection band, as well as the ripple heights in the S‐parameters of the PBG‐engineered transmission lines. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 32: 431–433, 2002.