Monopole Structures Research Articles

Eddy-induced sea surface salinity changes in the South China Sea

Eddy-induced sea surface salinity (SSS) changes are systematically studied in the South China Sea (SCS) by using Soil Moisture Active Passive (SMAP) satellite salinity data from 2015 to 2021 for the first time. All eddies in the SCS during this period are analysed, and two normalized eddy composites are reconstructed under the long-term basin mean. In general, anticyclonic eddies (AEs) tend to result in lower salinity than cyclonic eddies (CEs) in the upper ocean. The salinity anomalies of the AE and CE composites are dominated by dipole and monopole structures, respectively. The different patterns in eddy-induced salinity anomalies are generally controlled by horizontal and vertical advections, which is further confirmed by their seasonal evolutions. A spatiotemporal decomposition of these salinity anomaly patterns suggests that the dipole and monopole patterns account for more than 70% of the salinity variability. All the eddies in the SCS are monopole-dominated and dipole-supplemented overall. This finding infers a relatively uniform eddy-induced salinity structure across the SCS and provides an observational-based metric for future model studies.

Improving the Directionality of Low-Frequency Acoustic Radiation by a Finite Array of Quadrupolar Sources with Acoustic Metamaterials

Manipulating radiation patterns is challenging, especially at low frequencies. In this paper, we demonstrate that acoustic metamaterials arranged as an array of quadrupoles remarkably improve the directionality of acoustic radiation at low frequencies, compared with previous metamaterials arranged as monopole and dipole structures. The directivity of the acoustic radiation can be adjusted by changing the characteristic parameter and the symmetry of the structure, which provides a flexible method of adjusting radiation directions. The directionality can be further improved by constructing a linear array. Our work establishes acoustic radiation control via quadrupolar metamaterials.

Far-Field Radiation Characteristics of Folded Monopole Antennas over a Conducting Ground Plane

Folded monopole structures have been used for many applications, including low-frequency electromagnetic wave transmission and reception. However, the literature on these antenna types is quite limited. Folded monopole antennas are mathematically complex compared to conventional monopole or dipole antennas since every fold introduces a new set of design parameters. This work studied the far-field radiation characteristics of multi-folded monopole antennas operating at 75 MHz in terms of their radiated power concerning the frequency, the far-field directivity of the electric field, and the effect of each design parameter on the far-field radiation power. According to the results, folding a monopole antenna multiple times increases its effective length, making this antenna a suitable candidate for applications where the antenna height is restricted. Additionally, the ground-to-wire separation has the biggest effect on radiated power. In both single-fold and two-fold cases, doubling the ground-to-wire separation increased the radiated power by 0.2 W compared to the other models with the same number of folds. As for the challenges, the impedance mismatch between the source and antenna causes a significant amount of power reflection; hence, suitable impedance matching is required to reduce reflected power.

Performance of Steel Monopole Transmission Line Supporting Structure in Various Wind Zones of India

The design of every new transmission line can address the solutions to fresh engineering problem. Therefore, the selection of the monopole structures in place of conventional lattice towers summarized the obligatory design parameters. The reliability climatic wind loads and the security longitudinal broken wire load combinations influence the internal parameter assessment of the steel pole structures. To assess them, a 60m high double circuit (DC) 220kV line with 305 m basic span is selected. All the Six wind zones (33, 39, 44, 47, 50, and 55 m/s) of India are selected to compute the transverse wind loads on the tower. Secondly broken wire security load in the longitudinal direction is adopted for the load combination for the monopole transmission tower design. With the above data, this paper presented the variation of the internal parameters in the wind zones. It is found that even though the basic wind speed from 33 m/s to 55 m/s is increased to 66.66%, top deflection is increased by 1.6%, a bending moment is enhanced by 6.3 % and shear force is increased by 12.6% only. The results show the change of wind speed has a little effect on the monopole tower. However, the variations of internal parameters in the wind zone are strongly depending on the Longitudinal loading only. The ASCE 48-19 steel monopole code is adopted to design the monopole since the Indian standard design code for monopole was not found. However, when comparing with the Indian Standard general Steel code IS 800-2007(Limit state) design guidelines, the Indian steel code contributes 10% more weight.

Ambient vibration testing and operational modal analysis of monopole telecoms structures

A structural health monitoring (SHM) system was developed to study the ambient response of monopole communication structures in the UK operated by Arqiva Ltd. The exercise had several purposes that included the evaluation of the SHM system itself and the system identification procedures applied to the data, followed by analysis of the evaluated modal properties to validate the current analytical models, structural assessments and standardised design procedures advising on dynamics actions. This paper describes the instrumentation and procedures used during monitoring of a lightweight flexible 14.5 m tubular tapered monopole supporting an array of mobile telecoms antennas. A Bayesian OMA (BAYOMA) approach is implemented to identify structural modal properties under different time windows as comparison for further assessments. Results from stochastic subspace identification are also obtained and compared. The correlation between modal properties and monitoring wind-response data reveals specific tendencies such as nonlinear stiffness behaviour, the existence of aerodynamic damping and typical directionality of the mode shapes with future implications for reformulation of current methods of assessing dynamics on monopole.

A neurocomputational model for estimating the triple‐frequency of T‐shaped patch antennas

AbstractThis article deals with the analysis of T‐shaped patch antennas (TPAs) that operates between 1 and 7 GHz at triple‐band characteristics. A TPA is composed of three monopole structures so that it has triple‐resonant frequency. Neurocomputational (NC) models eliminate the complex procedures for the analysis of patch antennas with irregular shapes. In this study, a NC model based on artificial neural network (ANN) is constructed for analyzing the triple‐frequency of TPAs. One hundred TPAs with different electrical and geometric parameters are simulated with a full‐wave electromagnetic simulator, and a data matrix is obtained for the training and testing the NC model. The model is trained through the simulated data vector of 80 TPAs and is tested with the remainders 20 TPAs and a fabricated TPA. Therefore, the computed results by the NC model which estimates simply and fast the operating triple‐frequency of TPA agree well with the simulated and measured ones.

Experimental validation of lift and drag forces on an asymmetrical hydrofoil for seafloor anchoring applications

Tidal power can be described as harnessing the kinetic energy of the in and out flows known as tides created by the changing gravitational pull of the moon and the sun on the oceans of the world. As the relative positions of the sun and moon can be accurately predicted, so can the resultant tidal movements, making tidal energy such a valuable resource and an attractive option for renewable power generation. However, the high costs and difficulties associated with the deployment of underwater turbines, which includes anchoring, are prohibitive factors in the widespread utilisation of tidal power technology. Existing turbine fixation methods are primarily based on the use of large gravity anchors or monopole structures to secure the turbine to the seabed. In an effort to reduce size, environmental impact on the seafloor and installation cost, a hydrofoil-based anchor could be considered. The objective of this study is to experimentally test the lift and drag force behaviour of a finite-span hydrofoil with endplates, whose profile was selected based on simplified two-dimensional (2D) numerical simulations using the vortex panel method. A customised lift and drag force measurement system for this prototype hydrofoil was designed, fabricated and calibrated, and subsequently installed and tested in the Dutch Tidal Testing Centre (TTC) in Den Oever, the Netherlands. A series of tests with force and flow velocity measurements are described for different angles-of-attack under realistic tidal flow conditions. Results for the lift and drag coefficients as a function of angle-of-attack are compared to numerical simulation data and revealed that the real-world lift force is predicted well, whereas the drag force is underpredicted by the numerical predictions. These findings provide useful information for the design of anchoring systems based of hydrofoil profiles.

АНАЛИЗ ХАРАКТЕРИСТИК ПЛАНАРНОЙ ШИРОКОПОЛОСНОЙ ДВУХКОЛЬЦЕВОЙ АНТЕННЫ

The topology is presented and the electrodynamic characteristics of the linear polarization antenna in the form of two planar partially intersecting circular disks are considered. Each of these discs has a hole in the centre, and in the area of their intersection there is a narrow longitudinal rectangular slot whose axis is oriented in the direction of the centres of the holes. Results of numerical simulation of the characteristics of such an antenna are presented, discussed and compared. Broadband properties of this antenna are explained by the presence in its design of two broad partially crossed planar rings and a relatively short narrow slot, which is excited in the region of their intersection. This feature provides a sufficiently wide band of operating frequencies, both in directivity characteristics and in input impedance. In this case, the antenna has an input resistance about 50 ... 60 Ohm, which can be adjusted by changing the width of the slot and rings. For comparison, similar characteristics of small-size low-directional antennas, such as vertical monopole, slot half-wave antennas and a zigzag antenna (the Kharchenko antenna or the "Z-antenna") are also considered in this paper. It is shown that the antenna under consideration possesses, in comparison with them, improved frequency properties, both in matching at the input and in the directivity. Along with broadband, the advantages of such an antenna are: an increased value of the directivity as compared to the monopole and dipole wire structures, and also a simple manufacturing technology that gives a certain benefit in mass production.

The Unusual Surface Chlorophyll Signatures of Southern Ocean Eddies

AbstractSouthern Ocean mesoscale eddies play an important role in ocean circulation and biogeochemical cycling, but their biological characteristics have not been well quantified at the basin scale. To address this, we combined a 15‐year tracked eddy data set with satellite observations of ocean color, sea surface temperature, and autonomous profiling floats to quantify the surface and subsurface properties of eddies. Anomalies of surface temperature and chlorophyll were examined in eddy‐centric composite averages constructed from thousands of eddies. Normalized surface chlorophyll anomalies (chlnorm) vary seasonally and geographically. Cyclones typically show positive chlnorm, while anticyclones have negative chlnorm. The sign of chlnorm reverses during late summer and autumn for eddies between the Subtropical and Polar Fronts. The reversal is most obvious in the Indian sector, and we attribute this to a combination of eddy stirring (deformation of surface gradients by the rotational velocity of an eddy) and deeper winter mixing in anticyclones. Both chlnorm and sea surface temperature anomalies transition from dipole structures north of the Subtropical Front to monopole structures south of the Subantarctic Front. Sea surface temperature and chlnorm composites provide evidence for eddy trapping (transporting of anomalies) and eddy stirring. This research provides a basin‐scale study of surface chlorophyll in Southern Ocean eddies and reveals counterintuitive biogeochemical signals.

A dual‐band MIMO antenna decoupled by a meandering line resonator for WLAN applications

AbstractIn this article, a couple of dual‐band MIMO antenna operating in 2.4–2.48 GHz and 5.15‐5.825 GHz bands for WLAN applications is presented. The WLAN MIMO antenna system comprised double dual‐band monopole structures and a meandering line decoupling resonator connected to the ground. The two antenna elements have a distance of 15.3 mm which is about 1/8 wavelength at 2.4 GHz. The coupling between two ports at 2.4 GHz is decreased from −9 dB to −25 dB by involving the meandering‐line resonator. Since the return loss becomes worse after the meandering line resonator is involved for decoupling, the parasitic elements are used to improve the matching performance in the working frequency band. The simulation model is designed and manufactured. The measurement results show the antenna system is an eligible candidate in MIMO WLAN applications.

Design and Implementation of Compact Coax Fed Multi Band MIMO Antenna for 4G Applications

Background/Objectives: In multimedia data communication environment a trade-off shall be opted between power, spectrum needs and wireless channel capacity in Global System for Mobile, Long Term Evaluation, and Wireless Local Area Networks applications. Multi-Input Multi-Output antenna elements display a high degree of similarity and it leads to efficacy reduction in multi user milieu. Methods: This paper investigates and presents a condensed 2-port coax fed multiband MIMO antenna for 4G applications. The proposed MIMO antenna possesses dimensions of 45mm×50mm×0.4mm 3 and comprises two layers, a rectangular patch, a pair of small-N shaped strips, two G-shaped monopole structures and L-shaped slots. An array of three resonant frequencies is opted for exciting the proposed design with the values of 1.8GHz, 2.5GHz and 5GHz. The methodology exhibits an adaptable frequency selecting with the ability to neutralize the impact of the other frequency. Findings: The implemented design accomplishes a high efficiency rates for LTE-Advanced, WiMAX and Wi-Fi applications 71.80%, 72.28% and 85.74%. Applications/Improvements: Fabrication with a suitable FR4 substrate material is used in the design of the coax fed multiband MIMO antenna. For future enhancements, the radiation pattern and reflection coefficient of an antenna shall be assessed.

Optimal Design of the Monopole Structures Using the CBO and ECBO Algorithms

Tubular steel monopole structure is widely used for supporting antennas in telecommunication industries. This research presents two recently developed meta-heuristic algorithms, which are called Colliding Bodies Optimization (CBO) and Enhanced Colliding Bodies Optimization (ECBO), for size optimization of monopole steel structures. The design procedure aims to obtain minimum weight of monopole structures subjected to the TIA-EIA222F specification. Two monopole structure examples are examined to verify the suitability of the design procedure and to demonstrate the effectiveness and robustness of the CBO and ECBO in creating optimal design for this problem. The outcomes of the enhanced colliding bodies optimization (ECBO) are also compared to those of the standard colliding bodies optimization (CBO) to illustrate the importance of the enhancement of the CBO algorithm.

Sub- and super-luminar propagation of structures satisfying Poynting-like theorem for incompressible generalized hydrodynamic fluid model depicting strongly coupled dusty plasma medium

The strongly coupled dusty plasma has often been modelled by the Generalized Hydrodynamic (GHD) model used for representing visco-elastic fluid systems. The incompressible limit of the model which supports transverse shear wave mode is studied in detail. In particular, dipole structures are observed to emit transverse shear waves in both the limits of sub- and super-luminar propagation, where the structures move slower and faster than the phase velocity of the shear waves, respectively. In the sub-luminar limit the dipole gets engulfed within the shear waves emitted by itself, which then backreacts on it and ultimately the identity of the structure is lost. However, in the super-luminar limit the emission appears like a wake from the tail region of the dipole. The dipole, however, keeps propagating forward with little damping but minimal distortion in its form. A Poynting-like conservation law with radiative, convective, and dissipative terms being responsible for the evolution of W, which is similar to “enstrophy” like quantity in normal hydrodynamic fluid systems, has also been constructed for the incompressible GHD equations. The conservation law is shown to be satisfied in all the cases of evolution and collision amidst the nonlinear structures to a great accuracy. It is shown that monopole structures which do not move at all but merely radiate shear waves, the radiative term, and dissipative losses solely contribute to the evolution of W. The dipolar structures, on the other hand, propagate in the medium and hence convection also plays an important role in the evolution of W.

CPW-Fed 8-Shaped Monopole Antenna for Ultra Wideband Applications

AbstractA CPW-fed 8-shaped monopole antenna for ultra wideband applications is presented. It consists of a 8-shaped monopole and two quarter elliptical coplanar waveguide ground planes. An impedance bandwidth from 5.4 GHz to 23.83 GHz is achieved. The radiation patterns are observed to be omnidirectional and bidirectional in E-and H-plane respectively at lower resonances. At higher frequencies, the radiation patterns are found to be nearly omnidirectional in both planes. The group delay variation is also observed to be constant in the operating frequency range. A good agreement is found between the simulation and experimental results. The designed antenna structure has miniaturized dimensions and wider bandwidth as compared to other already reported monopole structures.

Highly Omnidirectional and Frequency Controllable Carbon/Polyaniline-based 2D and 3D Monopole Antenna.

Highly omnidirectional and frequency controllable carbon/polyaniline (C/PANI)-based, two- (2D) and three-dimensional (3D) monopole antennas were fabricated using screen-printing and a one-step, dimensionally confined hydrothermal strategy, respectively. Solvated C/PANI was synthesized by low-temperature interfacial polymerization, during which strong π–π interactions between graphene and the quinoid rings of PANI resulted in an expanded PANI conformation with enhanced crystallinity and improved mechanical and electrical properties. Compared to antennas composed of pristine carbon or PANI-based 2D monopole structures, 2D monopole antennas composed of this enhanced hybrid material were highly efficient and amenable to high-frequency, omnidirectional electromagnetic waves. The mean frequency of C/PANI fiber-based 3D monopole antennas could be controlled by simply cutting and stretching the antenna. These antennas attained high peak gain (3.60 dBi), high directivity (3.91 dBi) and radiation efficiency (92.12%) relative to 2D monopole antenna. These improvements were attributed the high packing density and aspect ratios of C/PANI fibers and the removal of the flexible substrate. This approach offers a valuable and promising tool for producing highly omnidirectional and frequency-controllable, carbon-based monopole antennas for use in wireless networking communications on industrial, scientific, and medical (ISM) bands.

The ray tracing analytical solution within the RAMOD framework. The case of a Gaia-like observer

This paper presents the analytical solution of the inverse ray tracing problem for photons emitted by a star and collected by an observer located in the gravitational field of the Solar System. This solution has been conceived to suit the accuracy achievable by the ESA Gaia satellite (launched on 19 December 2013) consistently with the measurement protocol in General Relativity adopted within the RAMOD framework. The aim of this study is to provide a general relativistic tool for the science exploitation of such a revolutionary mission, whose main goal is to trace back star directions from within our local curved space-time, therefore providing a three-dimensional map of our Galaxy. The calculations are performed assuming that the massive bodies of the Solar System move uniformly and have monopole and quadrupole structures. The results are useful for a thorough comparison and cross-checking validation of what already exists in the field of relativistic astrometry. Moreover, the analytical solutions presented here can be extended to model other measurements that require the same order of accuracy as that expected for Gaia.

Modified theta‐shaped monopole antenna with defected ground structure for UWB applications

ABSTRACTA compact modified theta‐shaped monopole antenna for ultrawideband communication is presented. It consists of a modified theta‐shaped radiator fed with a modified microstrip feedline and rectangular notch‐loaded quarter elliptical coplanar waveguide ground plane. An impedance bandwidth of 4.35–20.75 GHz (131%) below −10 dB reflection coefficient line is achieved. The designed antenna structure has nearly omnidirectional radiation pattern in H‐plane and bidirectional pattern in E‐plane. The cross polarization level is also 20 dB lesser than copolarization level in every direction at lower frequencies. The performance of the designed antenna structure for three substrate materials, that is, FR‐4 epoxy, carbon nanotubes, and Ni0.2Co0.2Zn0.6Fe2O4, are also studied. The experimental and simulation results are found to be in good agreement. The designed antenna structure has advantage of wider bandwidth along with smaller dimensions as compared to previously reported monopole structures. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1625–1632, 2015

Wideband Unidirectional Antenna of Folded Structure in Microwave System for Early Detection of Congestive Heart Failure

A three-dimensional antenna based on a combination of loop and dual monopole structures with parasitic elements is presented. The antenna is specifically designed for a microwave system aimed at the early detection of congestive heart failure. The antenna is first designed as a planar structure and then folded over optimally defined folding lines to properly alter the path and phase of the surface currents for a unidirectional radiation and compact size as needed for the detection system. A prototype antenna of size 0.29λ × 0.08λ × 0.08λ (where, λ is the wavelength of the lowest resonant frequency) is developed to cover the band required in the targeted application. The measured results indicate 53% fractional bandwidth (580 - 1000 MHz), 6-8 dB front to back ratio, and 3-5 dBi gain. The antenna is then used to build a heart failure detection system, which also includes a compact microwave transceiver, a processing and image reconstruction algorithm based on the synthetic aperture focusing technique, and a display unit. The system is used to successfully detect an early case of congestive heart failure in an artificial torso phantom that includes the main torso organs (lungs, heart, ribs, and fat).

Charge structure in volcanic plumes: a comparison of plume properties predicted by an integral plume model to observations of volcanic lightning during the 2010 eruption of Eyjafjallajökull, Iceland.

Observations of volcanic lightning made using a lightning mapping array during the 2010 eruption of Eyjafjallajökull allow the trajectory and growth of the volcanic plume to be determined. The lightning observations are compared with predictions of an integral model of volcanic plumes that includes descriptions of the interaction with wind and the effects of moisture. We show that the trajectory predicted by the integral model closely matches the observational data and the model well describes the growth of the plume downwind of the vent. Analysis of the lightning signals reveals information on the dominant charge structure within the volcanic plume. During the Eyjafjallajökull eruption both monopole and dipole charge structures were observed in the plume. By using the integral plume model, we propose the varying charge structure is connected to the availability of condensed water and low temperatures at high altitudes in the plume, suggesting ice formation may have contributed to the generation of a dipole charge structure via thunderstorm-style ice-based charging mechanisms, though overall this charging mechanism is believed to have had only a weak influence on the production of lightning.

A MICROSTRIP-FED MULTIBAND SPIRAL RING MONOPOLE ANTENNA WITH IMPROVED RADIATION CHARACTERISTICS AT HIGHER RESONANT FREQUENCIES

A novel approach for the design of a compact multiband monopole antenna for improving radiation characteristics at higher resonant frequencies is presented. The proposed structure consists of a conventional printed monopole loaded with spiral ring resonators and fed by microstrip. When at higher resonant frequency, the electrical length of the conventional monopole antennas is relatively large and the surface currents distribute on the patch periodically which will degrade the omnidirectional property. To achieve good radiation characteristics at the upper bands, two spiral ring strips are inserted into the microstrip line on the difierent layer and connected through via hole. Thus, the direction of surface currents on the spiral ring strips changes with the alteration of spiral structure and their efiects on the radiation pattern are reduced. The radiation pattern is mainly contributed by the surface current on the microstrip line and very good stable radiation pattern can be obtained within all the operating bands. In comparison to the previous printed strip monopole structures, the miniaturized Antenna dimension is only about 28 mm£20 mm£1mm. The experimental results show that the proposed antenna can provide operating bands which meet the required bandwidths speciflcation of 2.4/5.2GHz WLAN and 3.5GHz WiMAX standard. Detailed design considerations of the proposed Antenna are described, and both the simulated and measured results of the proposed Antenna are also presented and discussed.