Octagonal Ring Research Articles

Hair transplantation Follicular Unit Excision (FUE): Introducing the multipurpose octagonal ring punch.

The technique of follicular unit excision for harvesting grafts for hair transplantation procedures has become very popular. This technique relies on the use of small punches to remove viable grafts. Many different punch shapes have been developed to accommodate the varying nature of skin and hair characteristics, resulting in hair transplant surgeons requiring a variety of punches to suit a wide range of patients, which can be overwhelming to the beginner when trying to decide on the optimal choice of a punch to suit a particular skin characteristic. We describe a novel multipurpose ring punch that can be used on patients with a variety of skin and hair characteristics, as well as for shaved and long hair FUE. Features of this punch include an octagonal ring that protrudes from the outer wall of the punch and functions to control the punch's trajectory into the deeper dermis during incision. Additionally, this punch has a dull, notched edge which allows for use in long hair and shaved FUE without sacrificing ease of incision through the epidermis. This punch is the first of its kind to have this breadth of versatility with a one-size-fits-all design.

An octagonal split ring resonator-based double negative metamaterial for S-, X- and Ku-band applications

This study aimed to produce a miniaturised double negative metamaterial with a lower resonance frequency. Therefore, a new combination of a multi-circular ring connected with octagonal shape ring metamaterial was developed on a 9 × 9 mm2 dielectric substrate material with a thickness of 1.6 mm, named the Flame Retardant 4 (FR-4). While the selected frequency ranged between 0 and 18 GHz for the unit and array metamaterial design. Numerical simulation was used for the design and analysis of the proposed metamaterial. A few analysis were performed to validate the performance of the new design including the analyses of the different dimensions of the substrate and varying widths of the split gaps. The proposed design structure manifested resonance frequencies at S, X and Ku-bands. The resonance frequency at S-band (3.31 GHz) and X-band (8.60 GHz) presented double-negative (DNG) metamaterial behaviour while X-band (11.93 GHz) and Ku-band (12.99 GHz) presented single-negative (SNG) medium characteristics. The simulation and measured results almost coincided with each other. The compactness of the proposed design was proven by the effective medium ratio (EMR) of 10.07. In conclusion, the miniaturised structure can be accredited for satellite communication and radar applications.

An instrumentation system to measure the loads acting on the tractor PTO bearing during rotary tillage

Application of rotary tillage has been increased due to less tillage passes required, reduced draft, and greater efficiency through reduction in wheel slippage. Early failure of the bearing of tractor power take-off (PTO) shaft was observed in tractors of power range 30–35 horsepower during rotary tillage. An instrumentation setup involving an extended octagonal ring transducer (EORT) was developed and installed at the bottom of the bearing to measure the axial load and the vertical component of the radial load. The horizontal component of radial load was measured by strain gauges. Based on measured loads, the bearing life was assessed. Independent variables were: operating depth, number of blades, gear setting, engine speed, and tyre size. The average axial and radial loads varied from 786–3869 N, and 134–430 N, respectively. However, bearing experienced very high peak loads during each trial. The peak axial and radial loads was recorded between 1081–7534 N and 566–1794 N, respectively. The estimated bearing life based on peak loads was 171.98–28341.39 h. Based on the findings, it may be concluded that the average loads were not sufficient to cause quick failure of PTO bearing, rather sudden peak loads might be the root cause of early failure.

Design of a Low-profile Chipless RFID tag Using a Grounded Wall

ABSTRACT An 8-bit chipless radio-frequency identification (RFID) tag with a compact structure is proposed in this paper. Designing a RFID tag with a compact size is highly demanded in RFID technology. The original RFID tag is composed of 8 octagonal rings. In order to minimize its dimensions, the tag is divided in two equal parts. One part is completely omitted with its substrate. A grounded wall is placed in front of the remaining part to compensate the effects of the removed part and generate an image of it. Comparing a radar cross-section (RCS) of the compact and normal structure implies that by minimizing the tag, the RCS response of the structure is approximately similar with that of the normal tag. An equivalent circuit model for the RFID tag is presented, which shows a reasonable agreement with its full-wave result. The presented tag exhibits an RCS of σ = −26 dBsm from 2 to 7 GHz with an overall size of 15 × 30 mm2. Through using the aforementioned method, a 50% reduction in the overall area of the structure is observed.

Doxorubicin Encapsulation in Carbon Nanotubes Having Haeckelite or Stone-Wales Defects as Drug Carriers: A Molecular Dynamics Approach.

Doxorubicin (DOX), a recognized anticancer drug, forms stable associations with carbon nanotubes (CNTs). CNTs when properly functionalized have the ability to anchor directly in cancerous tumors where the release of the drug occurs thanks to the tumor slightly acidic pH. Herein, we study the armchair and zigzag CNTs with Stone–Wales (SW) defects to rank their ability to encapsulate DOX by determining the DOX-CNT binding free energies using the MM/PBSA and MM/GBSA methods implemented in AMBER16. We investigate also the chiral CNTs with haeckelite defects. Each haeckelite defect consists of a pair of square and octagonal rings. The armchair and zigzag CNT with SW defects and chiral nanotubes with haeckelite defects predict DOX-CNT interactions that depend on the length of the nanotube, the number of present defects and nitrogen doping. Chiral nanotubes having two haeckelite defects reveal a clear dependence on the nitrogen content with DOX-CNT interaction forces decreasing in the order 0N > 4N > 8N. These results contribute to a further understanding of drug-nanotube interactions and to the design of new drug delivery systems based on CNTs.

Ab initio study of lithium decoration of popgraphene and hydrogen storage capacity of the hybrid nanostructure

The successful realization of extended ‘5-5-8’ line defects in graphene in a controlled way has suggested the possible formation of a new 2D carbon allotrope consisting in pentagonal-octagonal-pentagonal carbon rings. The mechanical and thermal stability of this nanostructure, called popgraphene, has recently been confirmed on the basis of first-principles calculations. Moreover, it has been proposed as a promising anode material for use in Li-ion batteries with fast charge/discharge rates. In the present paper we perform density functional theory calculations to investigate the hydrogen storage ability of popgraphene. Our calculations show that popgraphene can be decorated in a very stable way by placing Li atoms on the pentagonal carbon rings of both sides of the sheet, leaving free the octagonal carbon rings. In that condition, the Li-decorated popgraphene sheet can bind up to four H2 molecules per unit cell, with an average adsorption energy in a range between physisorption and atomic chemisorption, which would allow for reversible hydrogen storage at moderate temperatures and pressures. Moreover, the gravimetric density of the Li-decorated popgraphene is 4.24 wt%, which is almost equal to the threshold specified by the U.S. Department of Energy for novel hydrogen-storage materials. All these results show that Li-decorated popgraphene nanostructures could be good materials for hydrogen storage.

A Broadband Polarized Metamaterial Absorber Driven by Strong Insensitivity and Proximity Effects

Artificial electromagnetic metamaterial produces exotic resonance, extra ordinary characteristics not available in nature, but engineers can inherit the characteristics by controlling and manipulating their structure. This research primarily the design and realization of dual-band, polarization, and incident angle insensitive metamaterial absorber (MA) is presented. By controlling and manipulating the electromagnetic design shape, artificial structure, periodic array pattern, and dielectric layer thickness a significant way to realize high absorption. In order to achieve high absorption a new shape of an octagonal ring (OR), cross-wires (CWs), and cut-off circle (CC) artificial structure have been sensibly selected. The special characteristics of this structure produce a dual resonance and its bandwidth rises compared that of classical absorber. The proposed artificial structure operation suits the Ku-band application, but possible to enhance in $C$ -band. The numerical and experimental results display a dual-band 99.8% at 12.2 GHz and 99.9% at 15.5 GHz resonance is an excellent agreement in theory and numerical analysis. The effects of the constitutive property parameters: dielectric constant ( $\varepsilon $ ), magnetic permeability ( $\mu$ ), and negative refractive index ( $n$ ) are also investigated. The investigation of symmetric design structure shows the polarization-insensitivity and high absorption initiated even in changing the incident angle. Numerical and experimental results confirmed the destructive interference of multiple penetrations are responsible for the near-unity absorption. An excellent agreement in the absorptivity rates that touches near perfection which is prominent for solar cells, detection, and imaging applications.

A New Frame-Based Calibration Method for Extended Octagonal Ring Transducers

HighlightsA simple frame was built to hold and apply uniaxial and biaxial loads to octagonal ring transducers for calibration.Similar results were obtained with the frame as with a universal tensile testing machine.The transducer outputs exhibited low cross-sensitivities and hysteresis (=0.4%), and R2 = 0.9998.The frame is portable and safe, and its concept can be adapted to take a wide range of non-gravitational loads.Abstract. An extended octagonal ring transducer (EORT) is a simple, single, and compact biaxial force measuring transducer, which is ideal for soil force measurement in tillage tool research. Calibration of EORTs is needed to ascertain their sensitivities and to determine an accurate calibration equation to convert voltage output to force measurement. Typically, calibration of EORTs involves the use of universal tensile testing machines, hydraulic systems and large gravitational loads (hanging weights) to apply loads. In this study, a simple calibration frame that enables application of non-gravitational loads was evaluated and used to hold and calibrate an EORT through both uniaxial and biaxial loading. The frame was suitable for both uniaxial and biaxial application of offset coincident force up to 3000 N and centered perpendicular force up to 1500 N. The EORT exhibited a strong linear relationship (R2 = 0.9998) between applied forces and voltage outputs, low hysteresis errors (=0.4%), and low cross-sensitivities (3.61% and 1.6% for coincident and perpendicular forces, respectively). Calibration equations developed from the primary bridge output data or from the biaxial loading data using the frame produced good force predictions, which also improved when taking into account the impacts of cross-sensitivity. The results confirmed that this calibration approach can integrate the interactions of output cross-sensitivity to deliver more accurate force prediction. Coefficients of determination of the relationships between applied and predicted forces were 0.9993 to 0.9996 and 0.9877 to 0.9984 for coincident and perpendicular forces, respectively. This calibration frame presents potential for safely applying large, non-gravitational loads in a contained and portable manner and its concept can easily be adapted to suit the scale of the transducer. Keywords: Biaxial loading, Cross-sensitivity, EORT calibration, Offset coincident force, Uniaxial loading.

Designing of Triple Band Octagonal Ring Antenna for Flexible and Wearable Application

Designing of Triple Band Octagonal Ring Antenna for Flexible and Wearable Application

Simulation study of microstrip antenna for 2.45 GHz applications based on octagon shaped

In late years, microstrip patch antennas have been widely used in various communication systems due to their lightness in weight, smallness in size, low manufacturing cost and, reasonable gain. Therefore, various figures and dimensions of microstrip patch antennas are available. This paper presents an octagonal ring-shaped multi-slot patch antenna with a single resonant frequency at 2.45 GHz of the Industrial Scientific and Medical (ISM) band with an omnidirectional pattern based on the Tikrit university logo. The unique structure of the octagon figure is demonstrated by adding trigonal patches on the sides and top of the rectangular microstrip patch antenna to achieve the eight-pointed star figure. The Octagon ring shape is achieved by inserting a single octagon slot and multi slots of a rectangular, square, triangle to maintain the operating frequency. The reduction in the size of the antenna is carried out by adding an octagon/rectangular patch to the partial ground plane. The suggested antenna is plotted and simulated on a substrate board FR-4 of dimensions 60 × 46 × 1.6 mm3 using CST Microwave Studio 2017. The results show compact size, 2.9 dBi gain, improved S11 response of −23.18 dB at 2.45 GHz, size reduction of 10.44%, and omnidirectional radiation pattern that can be utilized to harvest radio frequency (RF) energy from Wi-Fi and bluetooth (2.4–2.5 GHz).

On development of a ring type mechanical force transducer: Shape optimization, modification and characterization with different optimization codes

This research paper focuses on the design and optimization of a ring type mechanical force transducer known as a proving ring. Three different optimization codes were used and compared to develop a universal ring design with optimum stress and enhanced ring sensitivity. In the optimization section, minimum ring thickness was found between 45 and 60° with maximum thickness at point of load application across all three optimization codes. Generalized reduced gradient code (GRG) yielded the largest decrease in maximum stress at 98% with a ring sensitivity increased by 19.5%. Bidirectional evolutionary structural optimization code (BESO) sees a slight reduction of stress at horizontal location at 8.3% but sensitivity was increased by 8%. ABAQUS shape optimization codes saw significant decrease in stress at horizontal location with reduction of 66.5% with ring sensitivity having the largest increase by 48.7%. From the optimization results, a simple geometric modification of the circular ring was made. Using finite element analysis, the modified ring design showed increased sensitivity as well as better stress levels compared to the conventional circular and octagonal ring shapes. With respect to the stress and deflection characteristics of the modified ring, the design can be said to be universal due to no minimal change in those factors when ring size increases. A last design modification was made to the modified ring by implementing a double ring design with two curved sections. It was found that the double ring design had lower stress levels compared to the modified ring with a slight increase in ring sensitivity.

Computational Prediction for Stable Structures of Graphene Van Der Waals Heterostructures Composed of Group-III-V Compounds

Two-dimensional (2D) materials with honeycomb structure such as graphene have attracted much attention due to their potential applications in nanoelectronics devices. [1] Furthermore, 2D van der Waals (vdW) heterostructures can be formed by stacking different types of 2D layered materials through the weak interlayer vdW interaction, and have attracted interest due to unique functionalities which are impossible in homogeneous bulk materials. [2,3] For instance, various graphene and hexagonal boron nitride (h-BN) related vdW heterostructures have been demonstrated and their physical properties have been discussed. On the other hand, a new class of 2D materials composed of traditional group III–V materials have been recently proposed. Lucking et al. predicted that the double-layer honeycomb (DLHC) structure where pair of single layer honeycomb structure forms interlayer bonds can be realized in various group III-V, II–VI, and I–VII materials, and some of these 2D materials exhibit exotic topological properties. [4] It has also been reported that most of group III–V and II–VI thin films are stabilized by forming the DLHC structure when the thickness deceases toward the 2D limit whereas a structure with alternating octagonal and square rings called a haeckelite structure is favorable beyond 3–15 monolayers depending on the constituent elements. [5] These findings suggest the realization of a new class of vdW heterostructures consisting of conventional 2D materials (such as graphene, h-BN, and transition-metal dichalcogenides) and DLHC structure. In this study, we explore new stable structures of vdW heterostructures composed of group III-V compounds on the basis of density functional calculations taking account of vdW interaction.The calculations for superlattices consisting of MoS2/AlAs heterostructure reveal that covalent Al-S bonds are formed between Al atoms of AlAs with zinc blende structure and S atoms of MoS2, which stabilizes zinc blende phase over the DLHC structure. This indicates that the combination of transition-metal dichalcogenides and group III-V compounds such as MoS2/AlAs hardly forms vdW heterostructures. On the other hand, we find that vdW heterostructures can be formed for the superlattices consisting of graphene and group III-V compounds (AlAs, AlSb, GaAs, GaSb, InP, InAs, InSb) when its thickness is two monolayers. Furthermore, the vdW heterostructure with DLHC structure in group III-V compounds is more stable than that with conventional zinc blende structure. Therefore, a stable structure whose atomic configurations are different from those of bulk phase is newly found for the combination of graphene and DLHC structure. The calculated biding energies are ranging from 0.22 to 0.30 eV/unit cell, indicating that this vdW heterostructures can be stabilized even at room temperature. The calculations of phonon dispersion also reveal that no imaginary frequencies are present for graphene/InAs with DLHC structure, suggesting its dynamical stability. This is due to nearly coherent in-plane lattice matching (misfit of ~0.1 %) between InAs with DLHC structure and graphene, as demonstrated in InAs nanowire growth by vdW epitaxy. [6] These calculated results suggest that diverse combinations and exotic electronic properties could be discovered in the vdW heterostructures consisting of graphene and group III-V compounds. Acknowledgements: This work was supported in part by the Grant-in-Aid for Scientific Research Grant (JP20K05324, JP19K05268, and JP16H06418) from the JSPS, and KIOXIA Corporation (former Toshiba Memory Corporation).

Design of Reconfigurable Patch Antenna in Frequency, Pattern, and Switchable Polarization

In this paper, a circularly polarized frequency, pattern, and polarization switching antenna is proposed. The antenna consists of an octagonal patch, a narrow octagonal ring and four diamond-shaped parasitic patches on the top layer. Two feed points of the radiating patch are connected to a Wilkinson power divider loaded with the phase reconfigurable transmission lines on the bottom layer. Reconfiguration of the polarization and pattern is realized by using PIN diodes as switching components. By controlling the bias voltage across the varactors, various narrow frequency bands can be achieved. The proposed antenna operates at a frequency tuning range from 1.96 to 2.03 GHz. The radiation pattern can be switched among five cases in yoz-plane and xoz-plane, with the switchable polarization between left- and right-hand circular polarization. In addition, these three types of reconfiguration can be controlled independently.

A new two-dimensional semiconducting carbon allotrope with direct band gap: a first-principles prediction

Two-dimensional (2D) carbon materials with an appropriate band gap play important roles in the various electronics fields. Here, based on first-principles calculations, we predict a new 2D carbon allotrope containing 32 atoms, consists of pentagonal, hexagonal, octagonal and decagonal rings. This new allotrope is named as Po-C32, which possesses P4/MMM symmetry with a tetragonal lattice and has a vertical distance of 2.22 Å between the uppermost and undermost atoms. The cohesive energy, phonon band structure, ab initio molecular dynamics simulations and elastic constants fitting confirm Po-C32 has high stabilities. The fitted in-plane Young’s modulus and Poisson’s ratio along a and b directions are Y a = Y b = 244 N m−1 and v a = v b = 0.14, respectively, exhibiting the same mechanical properties along a and b directions. Interestingly, Po-C32 is a semiconductor with a direct band gap of 2.05 eV, comparable to that of phosphorene, exhibiting great potential in nanoelectronics. Moreover, two stable derivative allotropes are also predicted based on Po-C32. Po-C24-3D is an indirect narrow band gap (1.02 eV) semiconductor, while Po-C32-3D possesses a wider indirect band gap of 3.90 eV, which can be also applied in optoelectronic device.

The selectivity of the transition metal encapsulated in fullerene-like B36 clusters

The transition metal encapsulated in fullerene-like B36 cages have been investigated by using the PBE functional. The Os and Ir atoms severely distort the B36 clusters, which cause a pentagonal ring, a heptagonal ring and an octagonal ring occurring. The Ti@B36, Zr@B36 and Hf@B36 clusters display more structural stabilities. Sc, Y, Lu and Os atoms prefer to encapsulate in the B36 clusters. All the TM-B bonds of the TM@B36 clusters display covalent bond attributes. The d and p orbitals of the TM atoms in the TM@B36 clusters acquire electrons while the s orbital loses electrons.

A robust effect of the defect on the switching behavior in carbon-based molecular device.

In this paper, we investigate the effects of spin-dependent electron and defect in the carbon-based molecular device. Our proposed molecular device is designed by two carbon chains, which is bonded to a defect. The defect topology includes pentagonal and octagonal carbon rings, which is put between two zigzag-edged graphene nanoribbon (ZGNR). The spin effect and switching symbiosis are shown in this carbon-based device. By switching of the orientation of the defect in two states (S1/S2 states) relative to the two electrodes, the full spin effect is shown. Also, we report the obvious negative differential resistance (NDR) behavior in our proposed molecular device. The results suggest that the proposed composition significantly affects the ratio of current and voltage, which the maximum peak of current (S2 state) is lower than 0.0022μA and could have a potential application in the next generation of molecular circuits.

Double-Layer Microstrip Band Stop Filters Etching Periodic Ring Electromagnetic Band Gap Structures

The electromagnetic band gap structure (EBGs) is widely used in microwave engineering, such as amplifiers, waveguides, microstrip filters, due to the fact of its excellent band stop characteristics. In this paper, three kinds of microstrip band stop filters were proposed which were etched with a hexagonal ring EBGs, octagonal ring EBGs and elliptical ring EBGs. Firstly, the etching coefficient of a band stop filter is proposed, and the performance of filters with different etching coefficient was analyzed. Secondly, the equivalent circuit of an EBGs band stop filter is proposed. By comparing the simulation results using advanced design system (ADS) and high frequency structure simulator (HFSS), it was found that the simulation results had the same −10 dB stopband width which verifies the correctness of the equivalent circuit model. Finally, three kinds of microstrip stopband filters were fabricated and measured. The experimental results of the −10 dB stopband width and resonant frequency were in good agreement with the simulation results. The −10 dB stopband fractional bandwidth of the three kinds of microstrip stopband filters was more than 63%. The proposed microstrip band stop filters can be widely used in microwave devices with a wide stopband.

Design, Development, and Calibration of Octagonal Ring Type Dynamometer with FEA for Measurement of Drilling Thrust and Torque

Abstract In this study, the design, development, and calibration of a strain-gauge–based octagonal ring type tool dynamometer was carried out. This dynamometer has the capacity to simultaneously measure thrust and torque during drilling operation. The thin strain ring theory was used for finalizing the dimensions of strain rings. Finite element analysis was carried out to compare theoretical strains with the experimental values and to finalize the location of strain gauges. The thrust force and torque were measured by eight strain gauges, each forming a Wheatstone bridge circuit, converting the deflections of elastic strain rings to proportional electrical signals. A suitable data acquisition system was used for recording the thrust and torque in a computer system. Calibration curves were plotted by applying known thrust and torque repeatedly. It was observed that the designed tool dynamometer is capable of measuring the cutting forces satisfactorily.

Design, development, calibration, and testing of indigenously developed strain gauge based dynamometer for cutting force measurement in the milling process

In this work, a milling dynamometer based on strain gauge with an octagonal and square ring was designed and tested. Strain gauges were attached with the mechanical rings to detect the deformation, during the machining process. Wheatstone bridge circuit was equipped with gauges to acquire the strain as voltage owing to the deformation of mechanical rings when machining takes place. The finite element analysis (FEA) was used to identify the location of maximum deformation and stress. The direction of rings and location of gauges were decided to increase the sensitivity and decrease the cross-sensitivity. Then, the cutting force was acquired through NI 6221 M series data acquisition (DAQ) card. The dynamometer had undergone a cycle of tests to verify its static and dynamic characteristics. The metrological characterization was performed according to the calibration procedure based on ISO 376 – 2011 standard. The cutting force was measured with both the dynamometers through milling experiments based on Taguchi’s L9 orthogonal array and the results were recorded. The measured cutting force varied from 300 N to 550 N. The obtained results depicted that low-cost milling dynamometer was reliable to measure the three component machining force. Overall, the square ring based dynamometer provides the better static and dynamic characteristics in terms of linearity, cross-sensitivity (4%), uncertainty (0.054%), and natural frequency (362.41 rev/s).

Low‐loss ultra‐wideband beam switching metasurface antenna in X‐band

This study proposes an ultra-wideband (UWB) metasurface-based beam-switching antenna system. A coplanar (CP) waveguide fed slot antenna (with 49% operating bandwidth) is coupled with a hexagonal metallic aperture to generate CP beam in the 10.2–10.8 GHz band. An octagonal split ring inclusion-based meta-element is designed to achieve 2π transmission phase variation with near-unity magnitude. The principle of the Pancharatnam–Berry metasurface is used to design an offset metasurface superstrate for tilting the main beam of the UWB antenna for the CP band. Measured results (S11, axial ratio, and radiation pattern) agree well with full-wave simulations. The fabricated X-band UWB aperture coupled antenna system uses the metasurface superstrate to achieve a broadside beam for the lower band and tilted beam for the upper band. This antenna system holds promise for next-generation vehicular and satellite communication applications.