Circular Strip Research Articles

Enhancing Sensing Performance of Capacitive Sensors Using Kirigami Structures

Capacitive sensors have widespread applications in human-machine interaction, Internet of Things, and smart home systems due to their low cost, high sensitivity, and ease of integration. However, improving the sensitivity and sensing distance of capacitive sensors remains a challenging issue. This study proposes a novel capacitive sensor design method based on Kirigami structures, which enhances sensor performance by introducing specific cutting patterns into the conductive layer to leverage edge effects. Through experimental testing and statistical analysis, we systematically investigated the influence of Kirigami geometric parameters on sensor sensitivity and sensing distance. We designed and fabricated 12 different Kirigami structures, including circular flower patterns, array patterns, layered pointed flower patterns, and circular strip structures, and compared them with traditional non-cut structures. The results show that Kirigami structures significantly improved sensor performance. Compared to traditional sensors without Kirigami structures, optimally designed Kirigami capacitive sensors demonstrated approximately a 3-fold increase in sensitivity and up to 170 percent extension in sensing distance. Multivariate regression analysis and nonlinear models revealed complex relationships between Kirigami structural parameters and sensor performance. Notably, the circular strip (three-layer) structure exhibited the best performance, possibly due to its maximization of edge effects and optimization of electric field distribution. This study provides new design insights for developing high-performance capacitive sensors, with potential applications in improving smart home systems and indoor activity monitoring for solitary elderly individuals.

Design of UWB Wearable Conformal Antenna for Body Area Networks

In this paper, a wearable ultra-wideband (UWB) micro-strip antenna is designed to meet the demand for Wireless Body Area Network (WBAN). This is a wearable textile antenna, which was formed on a jeans fabric substrate to reduce surface-wave losses. The single-fed circular strip monopole antenna provides good impedance matching over the entire UWB frequency range of 2.9∼10.6 GHz. The dielectric constant εr 2.2, and the loss tangent tan δ 0.04 of the jean substrates are measured by using the coaxial ring method. The proposed antenna consists of an improved circular radiation patch with the defective ground structure to expand the frequency band of the antenna and improve the radiation characteristics of the antenna with small dimensions of 20 × 30 × 1.4 mm3. In addition, structural deformation of the proposed antenna is performed to analyze the flexibility of the proposed antenna. The simulated SAR values follow the FCC limit, making it most suitable for wearable applications. Key Words: Antenna, S-Parameters, Far Field Directivity, Applications of Antenna, HFSS.

Design and analysis of X-band metamaterial absorber

This study introduces a novel metamaterial absorber operating in X-band frequency range, characterized by two resonating peaks. The proposed structure consist of four circular sectors connected by two cross resonators enclosed by a circular strip with the dielectric between them. FR4 is used as a substrate backed by a copper ground plane. Simulation results reveal that the reflection co-efficient remains consistently below -10dB across the entire X-band, ensuring effective absorption of incident electromagnetic waves. Moreover, the absorber achieves 100% absorptivity with the gain of -25dB under normal incidence. The validity of absorber performance is confirmed through impedance plot and Voltage Stand Waving Ration (VSWR) analysis, verifying the accuracy of S11 parameter. Furthermore, the proposed structure has a compact size of 0.1666 λ. The absorber’s robust performance validated through numerical analysis, positions it as a compelling candidate for various X-band applications, including radar systems, communication devices, and stealth technology. This research establishes the proposed metamaterial absorber as a promising solution for X-band electromagnetic wave attenuation needs, offering both superior performance and compact design.

Electromagnetic scattering of H‐polarised cylindrical wave by a double‐sided impedance circular strip

AbstractThe authors investigate electromagnetic scattering by a circular strip with impedance boundary conditions in detail. The excitation is obtained by the H‐polarised line source and the impedance boundary condition with different impedance values on each surface of the circular strip is imposed. Electromagnetic scattering from circular strips is formulated employing an integral equation approach including the orthogonal polynomials while expressing the current densities on inner and outer surfaces. To consider the edge condition, the current density on the scatterer is expressed in terms of Gegenbauer polynomials with the weighting function. Unlike the previous studies, the authors investigate the behaviour of the EM field regarding the location of the cylinder source, the size of the aperture and the different impedance values. The convergence of the proposed approach, which is one of the analytical–numerical methods, is investigated for different impedance values; considering the results, resonators with impedance surfaces of certain complex values and certain locations of the cylinder source perform better than the known PEC and PMC resonators for some specific resonance cases. An effective analytical–numerical approach is proposed for such geometry with the impedance boundary condition. An extensive analysis and comparison with other methods are provided. The limit cases of the impedance boundary condition (Dirichlet and Neumann boundary conditions) are validated.

A Dual-Band Composite Frequency Selective Rasorber With Broadband Absorption Performance

In this paper, a dual-band frequency selective rasorber(FSR) is proposed based on a composite absorption structure. The FSR is a three-tier structure composed of lossy layer I, lossy layer II and a dual-band frequency selective surface (FSS). The lossy layer I is composed of a lossy cross-shaped structure in which, dual-passband resonators are added and constructed by parallel interdigital capacitors and meandering strip inductors(PLC). The lossy layer II is composed of a hybrid circular strip resonator loaded with lossy elements. FSS is implemented in two Jerusalem slots. By combining the lossy layers I and II as a composite lossy structure, the absorption bands of lossy layers I and II are successfully connected in the frequency response, and the bandwidth of S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> under -10dB is extended from 3.1 to 20.6GHz. The proposed FSR integrate dual-band, dual-polarized, and broadband absorption performance simultaneously. Finally, a prototype of the composite FSR is fabricated to validate the simulated results.

Deployable strip structures

We introduce the new concept of C-mesh to capture kinetic structures that can be deployed from a collapsed state. Quadrilateral C-meshes enjoy rich geometry and surprising relations with differential geometry: A structure that collapses onto a flat and straight strip corresponds to a Chebyshev net of curves on a surface of constant Gaussian curvature, while structures collapsing onto a circular strip follow surfaces which enjoy the linear-Weingarten property. Interestingly, allowing more general collapses actually leads to a smaller class of shapes. Hexagonal C-meshes have more degrees of freedom, but a local analysis suggests that there is no such direct relation to smooth surfaces. Besides theory, this paper provides tools for exploring the shape space of C-meshes and for their design. We also present an application for freeform architectural skins, namely paneling with spherical panels of constant radius, which is an important fabrication-related constraint.

Design and Analysis of CPW Fed Antenna with Triangular Separated Stub for Wireless Applications

One of the most active areas of research in the field of communication systems today is wireless technology, and a study of communication systems would be lacking without a grasp of how antennas work and are constructed. We offer a straightforward and small printed ultra-wideband antenna with dual-band notched properties. A redesigned ground plane and a rectangular patch make up the proposed antenna. The lossy FR4 substrate is etched with the rectangular patch. The rectangular patch that a U-shaped slot has embedded in it is parasitized by a circular ring strip. A rectangular slit, two inverted-L slits, and a slit are imbedded into the ground plane. The antenna structure uses some bandwidth improvement and bandnotched techniques to widen the bandwidth and create notches. With dual-notched bands of 3.30-4.20 and 5.10-5.85 GHz, the proposed antenna covers the 3.3/3.7 GHz WiMAX, 3.7/4.2 GHz C-band, and 5.2/5.8 GHz wireless local area network systems. This is demonstrated by the simulated and measured results, which indicate that the proposed antenna offers a very wider bandwidth ranging from 3.04 to 17.30 GHz, defined by the return loss less than 10 dB.

Numerical study of rotating convection with bi-directional temperature gradients

In this work, we report results from three-dimensional numerical simulations of convection in a rotating cylindrical annulus with mean temperature gradients present along the radial and vertical directions. The simulations have been performed in OpenFOAM (Open-source Field Operation And Manipulation). The bi-directional temperature gradient is achieved by imposing uniform heat flux in a thin circular strip at the outer periphery of the bottom surface, and a uniform temperature at the entire inner cylindrical surface. The study has been carried out for a particular Rayleigh number, Ra = 4.76×108, and a range of Taylor numbers, Ta = 6.5×108–2.7×109. The Ra value is chosen so that some qualitative comparison could be done with available experimental data. A laminar flow solver has been used to perform the computations in a rotating frame of reference. Complex empirical orthogonal function analysis has been carried out for the velocity and temperature fields. The contour maps of the radial velocity field in the r−θ plane clearly show the existence of mode 4 and 4 AV (amplitude vacillation) baroclinic waves at low values of Ta, which break down into eddies as Ta increases. The mean temperature field in the r–z plane supports the existence of Convective Columnar Plumes (CCP) on the outer edge, which interacts with the baroclinic waves, aiding in the transport of heat in the system. The fluctuations in CCP disintegrate into smaller-scale structures at the highest Ta. Quantification of turbulent fluxes shows the effectiveness of the heat transport at Ta∼O(108), as compared to Ta∼O(109). Our results clearly demonstrate the role of waves, plumes, and eddies on heat transport in the presence of bi-directional temperature gradients.

Soil health responses of circular grass buffer strips in center‐pivot irrigated agriculture

AbstractDecline in water table in the Ogallala Aquifer, along with soil degradation, has threatened the sustainability of agriculture in the US High Plains region. Circular grass buffers in center pivot irrigated cropping systems could support sustainable crop production by providing multiple ecosystem services. This study evaluated soil organic matter (SOM), nutrients, and other selected soil health indicators under circular buffer strip grasses (BSG), adjacent buffer strip corn (Zea mays L.) (BSC), and continuous conventional corn (CCC) in the 0–80 cm soil profile. Soil samples were collected from the center of corn and grass strips for 5 years (2017–2021) and analyzed for nitrate N (NO3−‐N), soil pH, electrical conductivity, cation exchange capacity, SOM, and soil nutrients. The NO3−‐N under CCC in 0–20 cm (18.4 mg kg−1) and 60–80 cm (4.97 mg kg−1) were 1.56 and 1.96 times higher than BSC. The NO3−‐N was significantly lower under BSG than other treatments in 0–20 cm, 20–40, and 40–60 cm depths. The SOM was similar among all treatments. Response of other nutrients varied among treatments and inter‐annually. Soil pH in 0–20 cm depth was 0.1 and 0.3 units lower in CCC (pH = 7.7) than in BSC and BSG. Soil electrical conductivity was 37.5% and 25% greater in CCC than BSG (0.24 and 0.24 dS m−1) in 0–20 and 20–40 cm depths, respectively. Grass buffer strips maintaining SOM despite no irrigation, less residual N under corn with grass buffer, and less rapid changes in soil pH suggest the potential of grass buffer to maintain soil health in semi‐arid cropping systems facing the transition to dryland.

Design of miniaturize flexible wideband frequency selective surface for electromagnetic shielding application

In this paper, a flexible, ultra-thin, miniaturized broadband frequency selective surface (FSS) is demonstrated for wideband electromagnetic shielding application. The unit cell of the proposed FSS structure consists of cross dipoles loaded with the metallic circular strip. The proposed miniaturized FSS structure has an extremely low profile with a thickness of and a unit cell size of . This FSS structure provides wideband shielding of more than 20 dB from 1.1 to 2.6 GHz frequency region. Besides this wide stopband, the FSS structure acts as a transparent window in the frequency band which can be used for the 5G communication purpose. Moreover, by comprehending the interaction between the incident electromagnetic wave and unit cell, a conceptual equivalent circuit model is developed that helps to interpret the mechanism of the miniaturization as well as the broadband response of FSS structure. We also compared the proposed FSS with other recently reported structures and observed more than 55% improvement in size reduction with several other miniaturized flexible FSS structure. Furthermore, this FSS structure exhibits 20 dB attenuation over a wide frequency region with a fractional bandwidth of 111%. Moreover, excellent resonant stability is achieved in regards to different polarization and incident angle up to .

Design of UWB Wearable Conformal Antenna Based on Jean Material

In this paper, a wearable ultra-wideband (UWB) microstrip antenna is designed to meet the demand for Wireless Body Area Network (WBAN). This is a wearable textile antenna, which was formed on a jeans fabric substrate to reduce surface-wave losses. The single-fed circular strip monopole antenna provides good impedance matching over the entire UWB frequency range of 2.9∼10.6 GHz. The dielectric constant ε r = 2.2, and the loss tangent tan δ = 0.04 of the jean substrates are measured by using the coaxial ring method. The proposed antenna consists of an improved circular radiation patch with the defective ground structure to expand the frequency band of the antenna and improve the radiation characteristics of the antenna with small dimensions of 20 × 30 × 1.4 mm 3 . In addition, structural deformation of the proposed antenna is performed to analyze the flexibility of the proposed antenna. The simulated SAR values follow the FCC limit, making it most suitable for wearable applications.

Investigation of the enhancing thermal performance of phase change material in a double-tube heat exchanger using grid annular fins

In the present paper, the enhancement of the thermal performance of the phase change material (PCM) in a double-tube heat exchanger using new grid annular fins is investigated. The grid annular fins, which consist of straight and circular strip components, are placed on the inner tube. To examine the thermal performance of the grid annular fins, a comparison with the conventional annular fins is conducted. To make the results comparable, the same volume of the conventional annular fins is converted to the grid annular fins. Moreover, the impact of fin spacing (longitudinal pitch) on the melting process time and the amount of energy storage of the PCM are studied and compared for the grids and conventional annular fins. According to the obtained results, the conversion of the annular fins to the new grid fins for the same fins volume at the longitudinal pitches of 125, 62.5, 31.25, and 15.625 mm reduces the melting time by 27, 37.5, 53.5, and 69.5%, respectively. Also, the comparison of the thermal performance of the new grid fins at different longitudinal pitches with the fins volume of 0.5% shows that the best thermal performance of the new grid fins occurs at fins spacing of 31.25 mm. The study demonstrates the importance of the arrangement of the grid annular fins components. In the longitudinal pitch 31.25 mm, the best-case scenario, the complete melting time of the PCM is improved 40% compared to the state with the 125 mm longitudinal pitch. Finally, the non-uniform distribution of grids for the annular grid fins also is considered in this study. The results show 16% improvement in full melting time compared to the best annular grid fins with uniform distribution of grids.

Effect of metritis on in-vitro uterine contractility in cows during the puerperium

Aim of this study was to determine the effect of metritis on in-vitro uterine contractility. Uteri obtained from 16 euthanized Holstein-Friesian cows were divided into two groups depending on whether metritis was absent (M-, n = 6) or present (M+, n = 10). Four longitudinal and four circular myometrial strips of all uteri were incubated in an organ bath. Spontaneous contractility was recorded in five consecutive 30-minute periods (T1-T5). This was followed by stimulation of one longitudinal and one circular strip with increasing concentrations of oxytocin, prostaglandinF2α (PGF2α), and calcium chloride (each during four 30-minute periods [T6-T9]). Strips in group M+ had higher minimum amplitude (minA) values at T1 and higher minA, mean amplitude (meanA), and area under the curve (AUC) values at T2 than strips in group M- (P ≤ 0.05). In the M+ group, the maximum amplitude (maxA), meanA, and AUC values of circular strips were higher than those of longitudinal strips during spontaneous contractility (T1, T4, and T5; P ≤ 0.05). The minA, meanA, and AUC values for strips in group M+ were higher than those in group M- when exposed to the highest concentration of PGF2α (P ≤ 0.05). During stimulation with PGF2α (T9), longitudinal strips had higher maxA values than the circular strips in group M+ (P ≤ 0.05). Spontaneous and stimulated contractility were temporarily increased in uteri with metritis compared to healthy uteri. Both myometrial layers, especially in uteri with metritis, reacted differently during spontaneous contractility and to stimulation with PGF2α.

The Thermal Dissipation Characteristics Analysis of the Rotatable Circular Pantograph–Catenary System

As the unique power entrance of high-speed trains, the pantograph–catenary system (PCS) plays the critical role of power transmission for high-speed trains. The pantograph achieves the electrical power based on the sliding electrical contact between the pantograph strip and the high-voltage contact line. However, when the environmental temperature is relatively low especially during the winter, the contact line is covered by ice or snow easily. The ice or snow adhering on the surface of contact line may lead to poor electrical contact between the pantograph strip and the contact line, which may trigger the pantograph–catenary arc appearing. Accompanying with mechanic shock and friction heat, the off-line arc may deteriorate the quality of power transmission and meanwhile erode the contacting surface of the pantograph strip and the contact line to some extent. In order to solve this technique bottleneck, a novel rotatable circular-shape pantograph strip is proposed to improve the overall performance of the traditional pantograph strip. Compared with the traditional strip, the circular pantograph strip owns many advantages, such as less friction, better thermal dissipation, and better shock resistance. The thermal dissipation performance of both the traditional and circular pantograph strip is evaluated in this article, with the consideration of suffering off-line arc under the icing conditions.

General approach to the line source electromagnetic scattering by a circular strip: Both E‐ and H‐polarisation cases

This study presents a new approach to line-source diffraction by a circular strip. The investigation is obtained by employing both electric and magnetic line sources where the corresponding field components satisfy the Dirichlet and Neumann boundary conditions. The position of the line source in the problem resulted in a very different radiation mechanism. Regarding the boundary condition and the aperture size, the total field characteristics change noticeably. The current density on the circular strip is expressed by Fourier series expansion, and then, orthogonal polynomials including edge condition are utilised to obtain the scattered field. The investigation is done throughout the far-field radiation pattern, near-field distributions, and the total radar cross-section. Then, the results are compared with the analytical and numerical outcomes. For the comparison, the method of moments and the method of auxiliary sources are employed as the numerical tools.

Opportunistic control of fractal‐based MIMO antenna for sub‐6‐GHz 5G applications

SummaryThe proposed research work is on fractal MIMO antenna with microstrip feeding for lower sub‐6 GHz. The design construct's goal is to improve the isolation among the patches and is constructed with a combination of circular strip and rectangular strip slots, and rectangular slots are introduced on the ground plane. The fractal‐shaped MIMO structure composes of FR‐4 material and compact size of 25 × 35 mm2. The current 2 × 1 fractal MIMO radiator resonates at a frequency 3.5 GHz for lower sub‐6‐GHz applications with directional radiation patterns. In this structure, the performance characteristics of design antenna parameters like S‐parameters, surface current distributions, and radiation pattern of the fractal MIMO radiator are investigated. In addition to antenna parameters, MIMO parameters like diversity gain (DG), mean effective gain (MEG), channel capacity loss (CCL), total active reflection coefficient (TARC), and time‐domain analysis parameters are also evaluated. It has been observed that the MIMO parameters of the antenna are in the acceptable range. Fractal‐based prototype MIMO structures are fabricated as well as tested for effective radiation and impedance. The improvised MIMO design that's been installed on a printed circuit board with connector, device housing, compact size, and various types of housing shows better performance compared to the conventionally designed antennas.

Novel Compact Dual Band Notched Ultra Wide Band Print-ed Antenna

Wireless technology is one of the main areas of research in the world of communication systems today and a study of communication systems is incomplete without an understanding of the operation and fabrication of antennas. A simple and compact printed ultra-wideband antenna with dual-band-notched characteristics is presented. The proposed antenna is composed of a rectangular patch and a modified ground plane. The rectangular patch is etched onto a lossy FR4 substrate. A circular ring strip parasitizes the rectangular patch embedded by a U-shaped slot. Two Inverted-L slits and a rectangular slit are embedded onto the ground plane. Some bandwidth enhancement and band notched techniques are applied in the antenna structure for broadening the bandwidth and generating notches. The simulated and measured results show that the proposed antenna offers a very wider bandwidth ranging from 3.04 to 17.30 GHz, defined by the return loss less than −10 dB, with dual-notched bands of 3.30–4.20 and 5.10–5.85 GHz covering the 3.3/3.7 GHz WiMAX, 3.7/4.2 GHz C-band, and 5.2/5.8 GHz wireless local area network systems.

Performance Analysis of Circular Shape Microstrip Antenna for Wireless Communication System

In this paper proposes a broad band circular strip antenna based on numerical techniques. For the operating frequencies, a circular patch antenna is installed on FR-4 substrate material 4.2. The proposed antenna uses the finite element method to design an operating frequency from 2GHz to 10GHz. Substrate height is 1.6mm. The circular patch has a circumference of 8.82mm. The antenna displays good output below -16dB is the return loss value and the antenna gain is obtained in the range from 2.4dBi to 10.02dBi. The proposed circular patch antenna is designed and analysed the various parameters like VSWR, Gain, Return Loss, Directivity and Radiation pattern.

Brownian flights over a circle.

The stationary radial distribution, P(ρ), of a random walk with the diffusion coefficient D, which winds at the tangential velocity V around an impenetrable disk of radius R for R≫D/V converges to the distribution involving the Airy function. Typical trajectories are localized in the circular strip [R,R+δR^{1/3}], where δ is a constant which depends on the parameters D and V and is independent of R.

Advanced Models of Personal Protective Equipment for Ground Forces Against Chemical and Biological Weapons Effects

Modern personal protective equipment for military personnel against the damaging factors of chemical and biological weapons (CBW) does not always allow to achieve an acceptable combination of body armor, protective helmet, respiratory and skin protective equipment from vapors and aerosols of toxic substances (TS) and biological agents (BA) in one set of equipment. The purpose of the work is to propose a promising form of personal protective equipment for Ground Forces servicemen against the damaging factors of chemical and biological weapons. The main characteristic feature of the existing gas masks is the invariable level of protection against the damaging factors of CBW. However, they do not provide protection for the head of servicemen from bullets and shrapnel. Based on the fact that danger levels for military personnel in case of a CBW attack differ and depend on the type of agent and on the time elapsed after the attack, the authors propose to combine a gas mask and a helmet in one product and to install disk filtering and sorbing elements (PSE) in the temporal region of the protective helmet with an air-duct, connected with an elastic half mask. The first universal PSE (sorbing-filtering) has the characteristics of a gas mask (shortness of breath) for protection from poisonous substances and biological agents in conditions of uncertainty of their use. It is transferred to the firing position simultaneously with the lowering of the visor. The second PSE possesses the parameters of a respirator (sorbing-filtering for easier breathing) for protection against TS. The second PSE should be used after the establishment of the fact of chemical, biological or radioactive contamination within an hour after the use of weapons of mass destruction. Thus, the main part of the soldier's head will be protected against bullets and shrapnel, as well as against TS and BA. To protect the lower part of the soldier's face (the chin, jaws and neck), it is proposed to use a circular elastic strip with a nasolabial device (screen) in the form of a half mask.