Spiral Elements Research Articles

Thermal Vacuum Synthesis: Physical Processes in Nanomaterial Production

The thermovacuum process offers an efficient and cost-effective method for producing nanomaterials by ensuring the continuous flow of dispersed material inside a spiral heating element. This is achieved by introducing the material into the heating element's cavity along with air, forming a two-phase gas-solid particle system. The material moves upward through the heated space, where pressure gradually decreases. Experimental studies on materials like carbon, brown coal, and zirconium dioxide indicate specific conditions are necessary for the system's continuous operation. One key requirement is that the mass of solid particles should not exceed 1.0 to 1.2 grams per liter of air entering the heating element. This limit ensures that nanodispersed and finely dispersed particles can move freely, avoiding collisions and allowing faster-moving particles to overtake slower ones. These particles increase in velocity and temperature as they pass through the heating element, with changes in heat capacity and particle motion contributing to wave motion and pulsed heat loads. The velocity at which the material particles travel depends on the thermal radiation from the heater walls and the energy generated by local pulse steam explosions, which create shock waves. Higher explosion energy results in increased particle velocity, greater impact angles against the heater walls, and higher environmental temperatures. These conditions lead to accelerated electron, proton, and other charged particle flows, forming plasma clots and neutrino clouds. The nanoparticles take various forms, including nanotubes, fullerenes, thin films, and crystals, reaching velocities up to a thousand kilometers per second and heating temperatures of up to 17 million degrees during pulses. This process consistently subjects the material to force, heat, deformation, and ionization, expediting the creation of nanodispersed materials with enhanced physicochemical and mechanical properties. The thermovacuum process not only improves the efficiency of thermotechnological equipment but also reduces energy consumption, production time, and costs. The research findings support its use in the continuous and effective production of high-quality nanomaterials.

Effects of introducing astigmatism aberration to spiral elements of diverse geometrical shapes

Effects of introducing astigmatism aberration to spiral elements of diverse geometrical shapes

Solving an internal problem for finite regular two-dimensional lattice spiral elements, excitable plate electromagnetic wave

Background. The work is aimed at developing and researching rigorous methods for solving internal problem of electrodynamics for multi-element structures (metastructures) consisting from the final number of elements, as well as to study the physical processes occurring in them. A special case of such structures are two-dimensional lattices with a fixed interelement distance, consisting of identical elements having the same spatial orientation (regular lattices). Aim. In this work, based on an iterative approach, the internal solution is solved. problems of electrodynamics for a finite regular two-dimensional lattice of spiral elements. In order to obtain a priori information about the electrodynamic characteristics of elements lattice and justification for the choice of projection function systems are analyzed spectral characteristics of the integral operator of the internal problem for a single spiral element. Then the currents on the structure elements are calculated, their spectral characteristics are determined. The results of spectral analysis allow increase the efficiency of solving an internal problem. Methods. The research is based on a strict electrodynamic approach, within the framework of which, for the specified structure in the thin-wire approximation, an integral representation of the electromagnetic field is formed, which, when considered on the surface of conductors together with boundary conditions, is reduced to a system of Fredholm integral equations of the second kind, written relative to unknown current distributions on conductors (internal task). The solution of the internal problem within the framework of the method of moments is reduced to solving a SLAE with a block matrix. Results. A mathematical model of a finite two-dimensional lattice of spiral elements is proposed radiating structure. For the specified structure, in the case of its excitation by a flat electromagnetic wave, based on the iterative approach, the internal problem of electrodynamics was solved. The following were carried out in a wide frequency range: analysis of the convergence of the iterative process, spectral analysis of the integral operator of the internal problem for a single spiral element, as well as spectral analysis of external field and current functions functions on lattice elements. Conclusion. The feasibility of determining the spectral characteristics of integral operators is shown internal task for the elements forming the metastructure. A relationship has been identified between the frequency dependence eigenvalues of the integral operator of the internal problem of single elements, forming a metastructure, with resonance phenomena arising in the metastructure, the influence of resonances on the convergence of the iterative process was confirmed. The feasibility of considering averaged amplitude current spectra is shown. It was revealed that the averaged spectrum of current functions is close to degenerate, especially near resonant frequencies. This allows for use as projection functions a compact set of eigenfunctions that have significant amplitudes in the vicinity of the frequency under study, which significantly simplifies the solution of the internal problem.

Hybrid rotational cavity optomechanics using an atomic superfluid in a ring

We introduce a hybrid optomechanical system containing an annularly trapped Bose-Einstein condensate (BEC) inside an optical cavity driven by Lauguerre-Gaussian (LG) modes. Spiral phase elements serve as the end mirrors of the cavity such that the rear mirror oscillates torsionally about the cavity axis through a clamped support. As described earlier in a related system [P. Kumar , ], the condensate atoms interact with the optical cavity modes carrying orbital angular momentum which create two atomic side modes. We observe three peaks in the output noise spectrum corresponding to the atomic side modes and rotating mirror frequencies, respectively. We find that the trapped BEC's rotation reduces quantum fluctuations at the mirror's resonance frequency. We also find that the atomic side modes-cavity coupling and the optorotational coupling can produce bipartite and tripartite entanglements between various constituents of our hybrid system. We reduce the frequency difference between the side modes and the mirror by tuning the drive field's topological charge and the condensate atoms' rotation. When the atomic side modes become degenerate with the mirror, the stationary entanglement between the cavity and the mirror mode diminishes due to the suppression of cooling. Our proposal, which combines atomic superfluid circulation with mechanical rotation, provides a versatile platform for reducing quantum fluctuations and producing macroscopic entanglement with experimentally realizable parameters. Published by the American Physical Society 2024

Insights into the fluid dynamics of the Bach impeller

The Bach impeller is a novel impeller that was purposefully designed to reduce power consumption as well as shear stress levels in stirred bioreactors. Contrary to conventional impellers where stirring is achieved by the pushing action of the blades, the Bach impeller relies on a central spiral element which induces an up-pumping central vortex and discharges the flow in the tangential direction through vanes. This feature is new and relevant to the field of biochemical engineering where cell culture and microbial fermentation often make use of shear-sensitive, living organisms to produce biopharmaceuticals and medicines. This article offers a thorough characterisation of the fluid mechanics of this impeller by means of 2D phased- and time-resolved particle image velocimetry (PIV) experiments. Key flow dynamics parameters including velocity magnitudes, kinetic energy, and shear stresses were estimated for different combinations of impeller size, clearance, and speed. The standard impeller size, D/T=0.52, performed most promisingly in combination with an off-bottom clearance of C=0.6 T, as the elevated impeller height allowed to pull high momentum fluid to the upper part of the tank and therefore improved overall transport phenomena in the entire reactor volume. For this impeller diameter-clearance combination peak ensemble-averaged shear stresses at the vessel base were lower due to the impeller greater distance from the bottom. A distinctive feature of the Bach impeller was its "smooth operation" mode, where velocity fluctuations due to the vane passages are nearly negligible (∼5 % of ensemble-averaged kinetic energy). These aspects make of the Bach impeller an appealing option in the context of stem cell bioprocess applications.

Industrial Scale Manufacturing Sub‐10 nm Reverse Osmotic Desalination Membrane on Metallic Single‐Walled Carbon Nanotubes Network

AbstractDifferent from extensively reported carbon nanotubes‐polyamide (PA) composite membranes, this work reports the scalable, low‐cost manufacturing of metallic single‐walled carbon nanotubes network supported PA reverse osmotic desalination membranes. Metallic single‐walled carbon nanotubes (SWCNTs) separated from high‐pressure carbon monoxide conversion (HiPCO) SWCNTs with a diameter ranging from 0.6 to 1.2 nm are deposited on polyethersulfone (PES) films by replacing surfactants around SWCNTs dispersed in aqueous solution, for supporting uniform and smooth sub‐10 nm PA nanofilm formed through aqueous‐organic bilayer interfacial polymerization. The industrial scale manufactured PA/SWCNTs/PES desalination membranes (508 mm × 915 mm) are rolled into spiral wound elements without damage through cutting, gluing, and rolling. The desalination tests on flat PA/SWCNTs/PES membranes exhibits 30 l m−2 h−1 (LMH) under 17.2 bar with 98.45% salt injection when fed with 2000 ppm NaCl at pH = 9. The normalized permeate flux of PA/SWCNTs/PES spiral wound elements is ≈17 LMH under 13.8 bar with 90% salt injection underfed with 2000 ppm MgSO4 at pH = 9–11 condition. The high‐performance sub‐10 nm smooth PA/SWCNTs/PES desalination membranes are fabricated with materials savings and can promote low operation costs compared to conventional 50–100 nm crumpled PA films on any supporting substrates.

Effect of spacer on mass transfer coefficient and calcium sulfate scaling phenomena in reverse osmosis desalination

Inorganic material (scale) precipitation on reverse osmosis (RO) membranes is a serious issue in plants because performance recovery via cleaning is challenging, and the replacement expenses are enormous. This study investigated the calcium sulfate scaling phenomena on membranes using a flat membrane cell with a spacer to model a spiral wound-type RO element. Subsequently, the mass transfer coefficient of the flat membrane cell with the spacer and the convergent value of permeate flux due to solute precipitation were determined. The dimensionless equation for the mass transfer coefficient of the cell with the spacer could be expressed using the dimensionless equation for the mass transfer coefficient of a flat membrane cell without a spacer. The behavior in permeate flux due to the precipitation of calcium sulfate on the RO membrane of the cell with the spacer was analyzed based on the scaling-based critical flux and scaling index, which discriminate scale precipitation. Finally, scale precipitation experiments were conducted by varying spacers and the operating conditions of pressure, solute concentration, temperature, and Reynolds number; the permeate flux was confirmed to converge to the scaling-based critical flux, and the scaling index could discriminate the operating condition area of scale precipitation.

A clear view of biofouling in spacer filled membrane filtration channels: Integrating OCT and CT for improved visualization and localization

Spiral wound membrane elements for reverse osmosis (RO) seawater desalination are increasingly important to produce clean water to cope with the rising global freshwater scarcity. Spiral wound elements are prone to biofouling development which can be monitored in-situ using optical coherence tomography (OCT). Although OCT has emerged as a dominant technology for nondestructive monitoring of membrane fouling, the application of OCT to study fouling on feed spacers has been limited because image processing of spacers is complex. In this study, an automated image processing algorithm was developed for visualization and quantification of fouling in spacer filled channels. The spacer shadow was used to estimate the location of the spacer in the OCT image. Subsequently, a computed tomography (CT) scan of the same spacer type was overlaid, providing a clear indicator of the spacer position. The spacer position was used to i) correct the distortion below the spacer, ii) visualize fouling in 3D with reference to the membrane and spacer, and iii) reproducibly and precisely locate images to make time series and compare parallel experiments. The results showed that the addition of a spacer geometry as a solid object in a 3D representation of an OCT-scan greatly improves visualization, because fouling and the spacer can be distinguished and the position of fouling relative to the spacer and membrane can be clearly seen. Moreover, the ability to select a dataset relative to the orientation of the spacer will enable objective and automated quantitative analysis in future work.

CALCULATION OF SPECIFIC SURFACE AREA AND POROSITY OF PACKING OF MASS-EXCHANGE COLUMN WITH MODIFIED RASHIG RINGS

New modified Rashig rings are proposed for mass transfer packing columns. Inside these rings, plate elements are attached to rods or springs in the form of rolled spirals with spiral gaps to increase the contact surface area of the phases. A formula linking the porosity and specific surface area of the packing through its geometric dimensions is obtained, allowing for the theoretical determination of one of these parameters based on the known value of the other. An example calculation of specific surface area using the derived formula for a standard Rashig ring is provided. It is demonstrated that the calculation results coincide with reference tabular values. The use of the derived formula in technological calculations of mass transfer columns allows for the theoretical determination of initial parameters (porosity or specific surface area of the packing) without the need for reference or experimental data. An analytical formula for determining the specific surface area of the proposed modified packing is derived. The ordered arrangement of this packing on the support grids of the mass transfer column apparatus is considered, with the spiral element of the modified packing having three turns with uniform spiral gap and made of thin plates. An example calculation of the specific surface area of the proposed modified Rashig ring is given for the considered packing arrangement in the column apparatus. The porosity of the modified packing is calculated using the proposed formula. A comparative analysis of the porosity and specific surface area of the proposed modified Rashig ring with a plate rolled in a spiral inside it and the standard Rashig ring is performed. The results show an increase in specific surface area of the packing in the modified ring by 1.5 times or more, from 65 to 102.7 m2/m3, with a slight decrease in porosity from 0.6 to 0.55 m3/m3. This reduces the calculated height of the packing layer in the mass transfer column apparatus and, consequently, the height and volume of the apparatus itself. The use of the new modified Rashig rings allows for a significant reduction in the total volume of packing in packing columns during extraction, absorption, desorption, and rectification processes.

Sequentially rotated loop and spiral antenna arrays with a coplanar C‐figured feedline

AbstractUsing the moment method, two array antennas are investigated to reveal the effects of different radiation elements on the array characteristics. Each array comprises four elements sequentially rotated by 90° and excited by a coplanar C‐figured feedline above the ground plane. It is found that a loop element array has a 3 dB axial ratio bandwidth of 30%, 3.3 times as wide as that of an isolated loop without an array environment. In contrast, a spiral element array shows a 3 dB gain drop bandwidth of 62% (72% for the axial ratio bandwidth, wider than that of an isolated spiral by a factor of 3.0). Almost the same factors of 3.0 and 3.3 for the spiral and loop element arrays are then compared with those in similar studies. It is found that factors are classified into three groups by feedline types. The simulated results are verified by experimental work.

Application potential of combining strain hardening cementitious composites and helical reinforcement for 3D concrete printed structures: Case study of a spiral staircase

Despite 3D Concrete Printing having the potential to advance the construction industry through material savings, design flexibility, and a more efficient workflow from design to construction, the challenge of reinforcing the layers of created structures remains unresolved. Recent developments within reinforcement techniques for 3D concrete printing, such as helical reinforcement and strain-hardening cementitious composites, have shown promise to work as potential solutions. To demonstrate the effectiveness of these techniques on a load-bearing structure, an automated production of spiral staircase elements is presented combining automated placement of helical reinforcement and strain-hardening cementitious composites. A design study is presented and different staircase elements were produced, experimentally tested in bending and compared to analytical results. The findings of the study reveal that the strengths and weaknesses of each reinforcement concept are evident when examined individually. However, when integrated together, these concepts complement each other, resulting in a successful and efficient reinforcement method for printed concrete.

Spiral-phase-objective for a compact spiral-phase-contrast microscopy.

Spiral-phase-contrast imaging, which utilizes a spiral phase optical element, has proven to be effective in enhancing various aspects of imaging, such as edge contrast and shadow imaging. Typically, the implementation of spiral-phase-contrast imaging requires the formation of a Fourier plane through a 4f optical configuration in addition to an existing optical microscope. In this study, we present what we believe to be a novel single spiral-phase-objective, integrating a spiral phase plate, which can be easily and simply applied to a standard microscope, such as a conventional objective. Using a new hybrid design approach that combines ray-tracing and field-tracing simulations, we theoretically realized a well-defined and high-quality vortex beam through the spiral-phase-objective. The spiral-phase-objective was designed to have conditions that are practically manufacturable while providing predictable performance. To evaluate its capabilities, we utilized the designed spiral-phase-objective to investigate isotropic spiral phase contrast and anisotropic shadow imaging through field-tracing simulations, and explored the variation of edge contrast caused by changes in the thickness of the imaging object.

Mathematical Model of Conformal Radiating Structures with Chiral Filling Based on Spiral Elements Taking into Account the Macroscopic Parameters Frequency Dispersion

Mathematical Model of Conformal Radiating Structures with Chiral Filling Based on Spiral Elements Taking into Account the Macroscopic Parameters Frequency Dispersion

Low-profile closed cavity backed spiral antennas with circular AMC reflector for V/UHF bands

In this study, two low-profile wideband spiral antennas that are backed by Circular Artificial Magnetic Conductors (C-AMC) are proposed for V/UHF bands. Rather than using a C-AMC design that has single resonance frequency, different C-AMC structures that have different resonance frequencies are used beneath corresponding active regions of spiral antenna, such that frequency independent radiation characteristics are achieved. The C-AMC surface is designed to aim of covering the entire frequency band of antenna so that frequency regions where reflection phase of C-AMC rings are between +90° and −90° will follow each other. It is observed that using frequency-independent C-AMC and a thin absorber between C-AMC and outer region of spiral antenna element provides wideband antenna characteristics and improves axial ratio of antennas. Proposed Antenna 1 in this paper has low-profile (0.47λ0×0.47λ0×0.055λ0) at 300 MHz and high gain at frequencies between 300 MHz and 950 MHz. An absorbing material is used at the inner wall of the closed cavity to improve performance of Proposed Antenna 2 at lower frequencies. In this manner, 0 dBi realized gain transition point is achieved at 235 MHz. Proposed Antenna 2 has also low-profile (0.37λ0×0.37λ0×0.043λ0) at 235 MHz.

Multiscale static and dynamic mechanical study of the Turritella terebra and Turritellinella tricarinata seashells.

Marine shells are designed by nature to ensure mechanical protection from predators and shelter for molluscs living inside them. A large amount of work has been done to study the multiscale mechanical properties of their complex microstructure and to draw inspiration for the design of impact-resistant biomimetic materials. Less is known regarding the dynamic behaviour related to their structure at multiple scales. Here, we present a combined experimental and numerical study of the shells of two different species of gastropod sea snail belonging to the Turritellidae family, featuring a peculiar helicoconic shape with hierarchical spiral elements. The proposed procedure involves the use of micro-computed tomography scans for the accurate determination of geometry, atomic force microscopy and nanoindentation to evaluate local mechanical properties, surface morphology and heterogeneity, as well as resonant ultrasound spectroscopy coupled with finite element analysis simulations to determine global modal behaviour. Results indicate that the specific features of the considered shells, in particular their helicoconic and hierarchical structure, can also be linked to their vibration attenuation behaviour. Moreover, the proposed investigation method can be extended to the study of other natural systems, to determine their structure-related dynamic properties, ultimately aiding the design of bioinspired metamaterials and of structures with advanced vibration control.

Algorithm for calculation of wave numbers in a chiral metamaterial based on composite spiral elements

Materials with various exotic electromagnetic characteristics have been extensively studied in recent decades to satisfy the growing interest in various fields, including visualization, telecommunications, energy use, and so on. As a particularly promising candidate, electromagnetic metamaterials exhibit electromagnetic properties that are inaccessible to natural materials. Due to the fact that the chiral medium (metamaterial) is a set of uniformly distributed conductive mirror-asymmetric (chiral) elements in an isotropic dielectric medium. In addition to the material from which the chiral element is made, its shape also plays an important role. That is why it is so important to study new types of chiral elements, as well as to determine the electrodynamic properties of chiral metamaterials based on them. The paper considers the solution of the problem of determining the reflection and transmission coefficients when a plane electromagnetic wave falls on a planar layer of a chiral metamaterial based on multi-pass conducting elements of the spiral type, taking into account the structural parameters of the metamaterial, which is a matrix of thin-wire ideally conducting elements in the form of N mutually orthogonal spirals. To determine the parameters of a chiral metamaterial based on composite spiral elements, the construction of a particular mathematical model of a composite element based on an arbitrary number of spiral elements in a spatial configuration, as well as a metamaterial based on a matrix of such elements, is considered. An algorithm for calculating the propagation constants of waves with circular polarizations in the specified metamaterial is proposed. From the calculations presented, it can be noted that the metastructure under study at one frequency can act as a frequency-selective protective shield that is not transparent to radiation near the main resonant frequency.

Powder Microscopy, Fluorescence, Qualitative Phytochemistry, and GC- MS analysis of a Neglected Ethnomedicinal Weed - Ruellia brittoniana Leonard

Ruellia brittoniana is a common wild ethnomedicinal plant belonging to the Acanthaceae family. The plant was claimed ethnically wound-healing properties, use as an antidote against snake bites and to cure bone fractures. However, these claims are not been validated. The present study deals with powder microscopy, fluorescence, and qualitative phytochemical analysis of the leaves, stem, and root of this plant. The powdered microscopy showed the presence of both types of trichomes and spiral elements. The Fluorescence analysis under visible and ultra-violet light for leaves, stems and root powder treated with various chemical reagents revealed different patterns of fluorescence effect. The qualitative phytochemical study showed that the plant is rich in phytochemicals and possesses significant levels of Glycosides, alkaloids, flavonoids, terpenoids, steroids, and saponins. The availability of these groups of Phyto- components indicates that the plant could prove an alternative remedy to cure asthma, fever, bronchitis, high blood pressure, eczema, and diabetes. Further, the GC-MS analysis revealed the 10 phytochemical compounds have significant medicinal potential. The major objective of this study is to endorse this plant as a step toward commercial drug developments after confirming and standardizing its microscopic features and fluorescence behavior to identify adulteration in market-available crude drug powder and screening for possible drug molecules.

A Compact Modified Two-Arm Rectangular Spiral Implantable Antenna Design for ISM Band Biosensing Applications

This paper presents a new microstrip implantable antenna (MIA) design based on the two-arm rectangular spiral (TARS) element for ISM band (Industrial, Scientific, and Medical 2.4–2.48 GHz) biotelemetric sensing applications. In the antenna design, the radiating element consists of a two-arm rectangular spiral placed on a ground-supported dielectric layer with a permittivity of ϵr = 10.2 and a metallic line surrounding this spiral. Considering the practical implementation, in the proposed TARS-MIA, a superstrate of the same material is used to prevent contact between the tissue and the metallic radiator element. The TARS-MIA has a compact size of 10 × 10 × 2.56 mm3 and is excited by a 50 Ω coaxial feed line. The impedance bandwidth of the TARS-MIA is from 2.39 to 2.51 GHz considering a 50 Ω system, and has a directional radiation pattern with directivity of 3.18 dBi. Numerical analysis of the proposed microstrip antenna design is carried out in an environment with dielectric properties of rat skin (Cole–Cole model ϵf (ω), ρ = 1050 kg/m3) via CST Microwave Studio. The proposed TARS-MIA is fabricated using Rogers 3210 laminate with dielectric permittivity of ϵr = 10.2. The in vitro input reflection coefficient measurements are realized in a rat skin-mimicking liquid reported in the literature. It is observed that the in vitro measurement and simulation results are compatible, except for some inconsistencies due to manufacturing and material tolerances. The novelty of this paper is that the proposed antenna has a unique two-armed square spiral geometry along with a compact size. Moreover, an important contribution of the paper is the consideration of the radiation performance of the proposed antenna design in a realistic homogeneous 3D rat model. Ultimately, the proposed TARS-MIA may be a good alternative for ISM-band biosensing operations with its miniature size and acceptable radiation performance compared to its counterparts.

Single-layer frequency selective dual-band reflectarray operating at 28 GHz and 39 GHz

We report a single-layer frequency selective dual band reflectarray operated at 28 and 39GHz simultaneously. The reflectarray consists of cross dipole and spiral elements aligned on the surface of a substrate and dual band frequency selective surfaces aligned on the rear side. We aligned the cross dipole and spiral elements that can control the reflection direction at 28 and 39GHz aligned on the same plane of the substrate, resulting in a simultaneous dual-band control of the reflection direction up to ±30° independently. Furthermore, the dual band reflectarray showed higher transmittance at frequencies except for the target frequencies, indicating the reflectarray function only at 28 and 39GHz and does not interfere with the other communication bands.

Cosine-type apodized spiral zone plate to handle the topological charge of a vortex beam

By taking advantage of spiral petal-like zone plates, we have recently demonstrated that a spiral element’s geometric shape impacts its charge. Keeping it in mind, we aim to control the topological charge of a vortex using phase modification of a spiral zone plate without transforming its geometrical shape. This is achieved by apodizing a spiral zone plate having p spiral zones with a radial grating with spatial frequency m. Having implemented some gratings with different m, we realized that an optical vortex is produced whose topological charge and its handedness depend on p and m. Consequently, a constant phase replaces on-axis screw dislocation under the situation that p takes odd multiples of m. Studies are carried out for large and small pairs of (p, m) and various gaps between the couple.