Ring-shaped Geometry Research Articles

Koch Curves and Hexagonal Ring-Shaped Geometry Based Ultra-Wideband Fractal Antenna

Koch Curves and Hexagonal Ring-Shaped Geometry Based Ultra-Wideband Fractal Antenna

Assessment of the pineapple drying with a forced convection solar-electrohydrodynamic dryer

Drying assumes a pivotal role in the preservation of high-moisture products over extended durations. Despite the widespread utilization of solar dryers owing to their energy-efficient nature, they are often plagued by prolonged drying durations, subsequently impacting the quantity of dried products. This investigation endeavors to introduce an innovative technique aimed at augmenting the efficacy of solar drying processes. Specifically, the study integrates forced convection solar drying with electrohydrodynamic (EHD) drying. The experimentation entails the drying of pineapple slices conducted between December 2023 and January 2024 in Nakorn Pathom, Thailand. The pineapple slices, featuring a ring-shaped geometry, are subjected to varying corona voltages ranging from 7 to 10 kV. The findings reveal a direct correlation between the corona voltage and the diffusion coefficient of the pineapple slices, wherein an escalation in corona voltage leads to an elevation in the diffusion coefficient, consequently resulting in a reduction of moisture ratio during the drying process. Consequently, the novel drying approach exhibits superior efficiency compared to traditional solar drying techniques, particularly as corona voltages increase. Moreover, the study employs Buckingham-Pi terms to predict the fluctuations in the diffusion coefficient, yielding a diffusion coefficient function with an R2 value of 0.996. Subsequently, a novel kinetics model for the drying process is proposed, boasting an average R2 value of 0.98. This model is envisioned to serve as a vital tool for enhancing and advancing forced convection solar-EHD dryers in forthcoming industrial applications.

The Aharonov–Bohm effect in quadratic Gauss quantum rings

We outline a theory for the Aharonov–Bohm effect in a novel type of quantum ring, namely the quadratic Gauss quantum ring, here for brevity called the Gauss ring. A Gauss ring is a one-dimensional nonperiodic lattice with sites at z = z j = j n d with j ∈ {0, 1, 2, ⋯ , s + 1} (), n ≥ 2 (), and d the underlying period wrapped into a ring-shaped geometry. Here we discuss the electronic spectrum of quadratic Gauss rings (n = 2, s ∈ {0, 1, 2, ⋯ , 5, 6, 7}), and show that the spectrum can be described using theoretical tools recently devised to provide an understanding of the Gauss chain [D S Citrin (2023) Phys. Rev. B 107, 235 144]. We then consider the effect on the electronic states of a magnetic flux Φ threading the Gauss ring and show that the effect of the flux is to select specific electronic states from a periodic chain whose supercells are finite-length Gauss chains thus relating the states in the Gauss quantum ring with those in a periodic Gauss chain.

Periodicities in a multiply connected geometry from quenched dynamics

Exploring the lowest energy configurations of a quantum system is consistent with the counting statistics of the frequently appeared states from quenching dynamics. By studying the Little-Parks periodicities in a multiply-connected ring-shaped geometry from the holographic technique, it is found that the frequently appeared states from dynamics incline to have lower free energies. In particular, the resulting winding numbers from quenched dynamics are constrained in a normal distribution for a fixed magnetic flux threading the ring. Varying the magnetic fluxes, Little-Parks periodicities will take place with periods identical to the flux quantum $\Phi_0$. Favorable solutions with lowest free energies perform first order phase transitions which transform between distinct winding numbers as the magnetic flux equals half-integers multiplying $\Phi_0$.

Design of antenna by amalgamating staircase and hexagonal ring-shaped structures with the modified ground plane for multi-standard wireless applications

In this article, an antenna has been designed by amalgamating staircase structure on hexagonal ring-shaped geometry using the modified ground plane for multi-standard wireless applications. The proposed antenna is compact in size with volumetric dimension of 24 × 30 × 1.6 mm3 and designed on a low-cost FR4 glass epoxy substrate. Initially, the partial ground plane is being used, and antenna reports an impedance bandwidth of 2.64, 0.96, 0.59 and 1.24 GHz at the respective frequency ranges. Furthermore, the ground plane of the proposed antenna is modified by introducing stubs and parasitic elements to improve the performance parameters such as bandwidth and reflection coefficient. The final geometry of antenna reveals the enhanced bandwidth of 3.04 GHz (1.55–4.59 GHz), 930 MHz (5.19–6.12 GHz) and 3.92 GHz (7.0–10.92 GHz). Also, the proposed antenna resonates at four frequency bands of 3.0, 5.7, 8.5 and 10.1 GHz with the corresponding reflection coefficient of −32.17, −38.37, −46.0 and −28.61 dB. Thus, the final optimized structure is also being fabricated for the authentication of simulated results. Both the results are compared and found in agreement with each other. The rest of the parameters such as gain, radiation efficiency and radiation patterns are analyzed and found satisfactory for the wireless operations. Due to the wider bandwidth and proper impedance matching in the desired frequency ranges, the proposed antenna can be considered as a proficient candidate for distinct wireless applications.

Symmetry-controlled singlet-triplet transition in a double-barrier quantum ring

We engineer a system of two strongly confined quantum dots to gain reproducible electrostatic control of the spin at zero magnetic field. Coupling the dots in a tight ring-shaped potential with two tunnel barriers, we demonstrate that an electric field can switch the electron ground state between a singlet and a triplet configuration. Comparing our experimental co-tunneling spectroscopy data to a full many-body treatment of interacting electrons in a double-barrier quantum ring, we find excellent agreement in the evolution of many-body states with electric and magnetic fields. The calculations show that the singlet-triplet energy crossover, not found in conventionally coupled quantum dots, is made possible by the ring-shaped geometry of the confining potential.

Nonexponential Tunneling due to Mean-Field-Induced Swallowtails.

Typically, energy levels change without bifurcating in response to a change of a control parameter. Bifurcations can lead to loops or swallowtails in the energy spectrum. The simplest quantum Hamiltonian that supports swallowtails is a nonlinear 2×2 Hamiltonian with nonzero off-diagonal elements and diagonal elements that depend on the population difference of the two states. This work implements such a Hamiltonian experimentally using ultracold atoms in a moving one-dimensional optical lattice. Self-trapping and nonexponential tunneling probabilities, a hallmark signature of band structures that support swallowtails, are observed. The good agreement between theory and experiment validates the optical lattice system as a powerful platform to study, e.g., Josephson junction physics and superfluidity in ring-shaped geometries.

METHOD FOR MEASURING THE PRESSURE OF A SHOCK-ACOUSTIC WAVE OF AN ELECTRIC EXPLOSION OF A CONDUCTOR IN A DISCHARGE CHAMBER WITH A CONDENSED ENVIRONMENT

An electric explosion of conductors, as well as an electric discharge as a whole, is a poorly studied unique phenomenon that is widely used both in basic scientific research and in various technological processes, which determines the relevance of further studies of ongoing processes. In this paper, we consider the methods and carry out calibration procedures to determine the value of the conversion coefficient for a piezoelectric pressure transducer with a reactive acoustic waveguide made of non-Newtonian fluid material. Designs of calibration plants are shown, the principle of which is based on the method of falling load and the interaction of parallel currents. The results of recording and measuring the pressure of a shock acoustic wave (SAW) generated by an electric explosion of a metal conductor of a ring-shaped geometry in a closed space of conical geometry with a condensed (aqueous) medium are presented. The discharge current and the voltage drop across the exploding flat ring foil (EEFRF) were recorded by the Rogowski belt and voltage divider, respectively. The pressure pulse of the acoustic shock wave was recorded by a piezoelectric pressure transducer. The electrical signals were recorded with a GDS-810 S digital two-beam storage oscilloscope. The amplitude value of pressure was estimated by plastic deformation of the plate sensor in the form of a round thin plate with clamped edges.

Fracture assessment of seam and seamless steel pipes by application of the ring-shaped bending specimens

The topic of this work is analysis of fracture behaviour and resistance of the thin-walled seamless and seam steel pipes, through application of the recently proposed ring-shaped specimen (PRNB - Pipe Ring Notched Bend). The main loading of these pipes in exploitation is internal pressure, which is why axial defects present a significant threat to their integrity and work safety. The ring-shaped specimen geometry is fairly simple to fabricate from a new or exploited pipeline and the specimens have the same thermo-mechanical treatment, assembly conditions, etc. as the actual structure. Experimental-numerical procedure is applied for prediction of the fracture behaviour; this included material characterisation, testing of ring specimens by bending, as well as micromechanical analysis of ductile fracture. In experimental testing, the deformation of the specimens is monitored by using the stereometric measurement system. Numerical analysis is performed in software package Simulia Abaqus, including the application of the micromechanical Complete Gurson model (CGM). The results obtained in this study, along with some previously published results, lead to conclusion that PRNB specimen is a good option for testing of fracture resistance of cylindrical elements such as pipes.

Analogues of Josephson junctions and black hole event horizons in atomic Bose-Einstein condensates

We study dynamical processes in coherently coupled atomic Bose-Einstein condensates. Josephson effects in ring-shaped and dumbbell geometries are theoretically investigated. Conditions for observation of the Josephson effect are revealed. We found that multicharged persistent current in toroidal condensate can be robust even for supersonic atomic flow. In numerical simulations the acoustic analogues of event horizon in quantized superflow were observed. These theoretical finding open perspectives for investigation of Bose Josephson junctions and quantum aspects of acoustic analogue of Hawking radiation in existing experimental setups.

Interaction-enhanced flow of a polariton superfluid current in a ring

We study the quantum hydrodynamical features of exciton-polaritons flowing circularly in a ring-shaped geometry. We consider a resonant-excitation scheme in which the spinor polariton fluid is set into motion in both components by spin-to-orbital angular momentum conversion. We show that this scheme allows to control the winding number of the fluid, and to create two circulating states differing by two units of the angular momentum. We then consider the effect of a disorder potential, which is always present in realistic nanostructures. We show that a smooth disorder is efficiently screened by the polariton-polariton interactions, yielding a signature of polariton superfluidity. This effect is reminiscent of supercurrent in a superconducting loop.

Laser-writing of ring-shaped waveguides in BGO crystal for telecommunication band.

We report on the fabrication of ring-shaped waveguides operating at the telecommunication band in a cubic Bi4Ge3O12 (BGO) crystal by using technique of femtosecond laser writing. In the regions of laser written tracks in BGO crystal, positive refractive index is induced, resulting in so-called Type I configuration. The modal profiles are within the designed track cladding with ring-shaped geometries, which are analogous to circular optical lattices. The homogenous guidance along both TE and TM polarizations has been obtained at telecommunication wavelength of 1.55 μm. Both straight and S-curved waveguiding structures have been produced with ring-shaped configurations. This work paves the way to fabricate complex photonic networks for telecommunications by using ring-shaped waveguides in compact chips.

Increasing the sensitivity of electrical impedance to piezoelectric material parameters with non-uniform electrical excitation

Abstract. To increase the robustness and functionality of piezoceramic ultrasonic sensors, e.g. for flow, material concentration or non-destructive testing, their development is often supported by computer simulations. The results of such finite-element-based simulations are dependent on correct simulation parameters, especially the material data set of the modelled piezoceramic. In recent years several well-known methods for estimation of such parameters have been developed that require knowledge of the sensitivity of a measured behaviour of the material with respect to the parameter set. One such measurable quantity is the electrical impedance of the ceramic. Previous studies for radially symmetric sensors with holohedral electrode setups have shown that the impedance shows little or no sensitivity to certain parameters and simulations reflect this behaviour making parameter estimation difficult. In this paper we have used simulations with special ring-shaped electrode geometry and non-uniform electrical excitation in order to find electrode geometries, with which the computed impedance displays a higher sensitivity to the changes in the parameter set. We find that many such electrode geometries exist in simulations and formulate an optimisation problem to find the local maxima of the sensitivities. Such configurations can be used to conduct experiments and solve the parameter estimation problem more efficiently.

Improved two-dimensional responsivity physical model of a CMOS UV and blue-extended photodiode

A CMOS UV and blue-extended photodiode is presented and fabricated for light detection in the ultraviolet/blue spectral range. An octagon homocentric ring-shaped geometry is used to improve the ultraviolet responsivity and suppress edge breakdown. This paper has established a two-dimensional responsivity physical model for the presented photodiode and given some numerical analyses. The dead layer effect, which is caused by the high-doping effects and boron redistribution, is considered when analyzing the distribution of the current of the proposed UV and blue-extended photodiode. In the dead layer, the boron doping profile decreases towards the surface. Simulated results illustrate that the responsivity in the UV range is obviously decreased by the effect of the dead layer, while it is not affected in the visible and near-infrared part of the spectrum. The presented photodiode is fabricated and the silicon tested results are given, which agree well with the simulated ones.

Stability of persistent currents in spinor Bose-Einstein condensates

Motivated by a recent experiment [S. Beattie, S. Moulder, R. J. Fletcher, and Z. Hadzibabic, PRL 110, 025301 (2013)] we study the superflow of atomic spinor Bose-Einstein condensates optically trapped in a ring-shaped geometry. Within a dissipative mean-field approach we simulate a two-component condensate in conditions adapted to the experiment. In qualitative agreement with the experimental findings, we observe persistent currents, if the spin-population imbalance is above some well-defined `critical' value. The triply charged vortices decay in quantized steps. The vortex lines escape from the center of the ring through dynamically created regions in the condensate annulus with reduced density of one component filled by atoms of the other component. The vortices then leave the ring-shaped high density region of the condensate and finally decay into elementary excitations.

Planar Hall Effect Ring Sensors for High Field-Sensitivity

Planar Hall effect sensor has been explored using multi-layer cross-shaped and bridge geometry. We present planar Hall effect in a ring-shaped geometry experimentally that shows progress of sensor sensitivity as well as output signals. Sensitivity improves about 170 times compare to cross-shaped geometry and about 1.4 times to bridge geometry in conventional measurement system. These values become 2.5 times larger at 20o measurement system. The presented ring geometry may take great potential in Planar Hall effect sensor applications.

Phase fluctuations in anisotropic Bose-Einstein condensates: From cigars to rings

We study the phase-fluctuating condensate regime of ultra-cold atoms trapped in a ring-shaped trap geometry, which has been realized in recent experiments. We first consider a simplified box geometry, in which we identify the conditions to create a state that is dominated by thermal phase-fluctuations, and then explore the experimental ring geometry. In both cases we demonstrate that the requirement for strong phase fluctuations can be expressed in terms of the total number of atoms and the geometric length scales of the trap only. For the ring-shaped trap we discuss the zero temperature limit in which a condensate is realized where the phase is fluctuating due to interactions and quantum fluctuations. We also address possible ways of detecting the phase fluctuating regime in ring condensates.

Characterization of optical microring ultrasound detector by using a high frequency focused photoacoustic transmitter

We characterize a response of optical microring resonator to high frequency focused ultrasound. To properly evaluate the response over high frequency and broadband spectrum, we use a photoacoustic concave transmitter generating and subsequently focusing the ultrasound. A detected focused profile reveals two types of spatial peaks due to the special ring-shaped detector geometry interacting with the high frequency focused ultrasound. Spectral analysis shows that those peaks are contributed by the main and the side lobes of focused ultrasound, respectively. Experimental focal widths agree with theoretical values within +/-2 mum error, which can be attributed to the narrow width of waveguide.

Clockwise-directional circle swimmer moves counter-clockwise in Petri dish- and ring-like confinements

A self-propelled rod which is driven by a constant internal force and torque performs circular motion in two spatial dimensions with an “internal” radius governed by the torque-to-force ratio and is referred to as a circle swimmer. Using analytical methods and computer simulations, we study the Brownian dynamics of a circle swimmer in a confining Petri dish- or ring-shaped geometry and compute the mean of the swimmer's position, its steady-state properties and its orientational motion. For small torque-to-force ratios, the confinement inverts the orientational sense of the motion: a clockwise-directional circle swimmer moves counter-clockwise in the confinement. Our results are verifiable for self-propelled colloidal rods, for vibrated granular rods and for motile bacteria in cylindrical confinements.

A planar functional processor of complex signals based on the effect of domain-acoustic echo

The paper presents results of investigation of a domain-acoustic correlation processor, equipped with a long-term memory, for processing complex radio pulses. The basic functional materials of the processor represented a set of specimens of polycrystalline yttrium iron garnet, and epitaxial films in the shape of plates and rings. The specimens were excited by piezoelectric transducers with different polarization of ultrasonic oscillations, and the largest amplitude of the self-correlation function was recorded for shear waves with longitudinal polarization and in specimens with ring-shaped geometry.