Slot Geometry Research Articles

Ultra-Wide Band MIMO Antennas with Notched-Band Characteristics of Various Slot Geometries for Wireless Applications

Abstract: Ultra-Wide Band (UWB) technology has experienced rapid growth over the last few years due to its various applications. Antennas developed for UWB applications are desired to have notch characteristics for avoiding interference from other existing radio communication systems. Different techniques related to the design and development of band-notched antennas is utilized to improve the antenna performance. This paper presents a comprehensive study of UWB antennas with band-notch characteristics and the effect of taking different slot geometry for multiple-input multiple-output (MIMO) applications.

Analytical Modeling of Magnetic Air-Gap Field Distribution Due to Armature Reaction

The following paper presents an analytical study of the air-gap magnetic field distribution produced by the armature reaction of a linear machine. Based on the method of images, the magnetic field generated by a current carrying conductor inside the air-gap between two smooth infinitely permeable iron surfaces is modeled as a complex 2D function. The conductor model then becomes a current sheet model and horizontally oriented current sheets are used to model the magnetic field produced by the armature reaction for smooth ferromagnetic surfaces. Focus will be given to the study of the slot opening function in front of energized slots in comparison to the not energized ones of the classical theory pointing out some remarkable differences. Later, the model is extended to slotted geometries using a complex slotting function adapted for energized slots. At last, the Maxwell tensor expressed in complex formulation will be integrated to obtain the force components acting on the machine tooth tips, quantities that will be compared with FEM simulations in order to validate the proposed analytical model.

Analytical Modeling of Magnetic Field Distribution at No Load for Surface Mounted Permanent Magnet Machines

This paper presents an analytical study of the air-gap magnetic field of a Surface Permanent Magnet (SPM) linear machine under no load. By means of the method of images, the complex expression of the magnetic field of a conductor, inside the air gap between two smooth iron surfaces, is retrieved. Then, integrating the conductor expression, the formulation of the magnetic field of a current sheet and thus the one of a SPM, using two vertical current sheets, is obtained. At last, the no-load magnetic field expression, for a generic time instant, of a slotless machine is retrieved. The novelty of the proposed approach is the availability, due to a different calculation approach, of a unique closed-form formulation for the slotless machine air-gap field, a quantity that, in literature, is usually present in Fourier series formulation. Additionally, as a means to calculate integral quantities and show the goodness of the method a complex slotting function is introduced to account for the slotted geometry. Finally, starting from Lorenz’s force formulation, the expression of the Maxwell tensor in complex form is retrieved and the contribution of forces, integral of the complex stress tensor quantity, will be calculated and compared with FEM simulations, showing a good agreement also with the analytical slotted model.

Mechanical and energy absorption behavior of an innovative high-performance auxetic structure

Auxetic structures possess high energy absorption, especially under impact loads that are influenced by their negative Poisson’s ratio (NPR). This negative ratio is due to their specific microstructural designs. In this article, newly modified designs for an existing chiral auxetic structure have been proposed and their mechanical and energy absorption performances have been investigated. In the proposed designs, the geometry of slots in an available peanut-shaped auxetic structure has been modified and some extra masses have been removed to introduce innovative auxetic structures with higher NPRs, higher energy absorption, and lower structural weight. By performing finite element simulations in ABAQUS software, it has been found that the proposed modifications in the design of the available auxetic structure result in up to 7.3% and 76.6% increases in Poisson’s ratio and energy absorption respectively. The accuracy of simulations has also been confirmed by performing a comparison study with some available results of experimental tests.

A model volcanic fissure with adjustable geometry and wall temperature

Fissure eruptions initiate with magma ascending and spreading through cracks in the ground that can extend for kilometres at the surface. Eruptions eventually localise to form one or a few persistent conduits and ultimately an array of discrete cones or craters. We built a new experimental apparatus to investigate the influences of fissure shape and wall-rock temperature on localisation within a volcanic fissure, and the thermal feedbacks associated with variability of these parameters. Our artificial fissure, or “Artfish,” has a slot geometry with adjustable shape and wall temperature. We can simulate both starting variability in fissure geometry and wall temperature, as well as changes in these parameters during an experiment to replicate, for example, blockage by wall-rock collapse, widening by wall-rock erosion, and warming by adjacent intrusions. We use polyethylene glycol (PEG 600) for our analogue fluid. A variable-speed pump allows for a range of fluid injection and ascent rates. Initial tests showcase the capabilities of the model and the types of data that may be acquired. Additional key features achieved include a stable and planar injection system, fluid recycling, and the use of particle tracers for monitoring flow patterns and velocities. The thermal evolution of the fluid-wall interface is quantitatively measured with thermal sensors, and the change in state of the PEG provides a clear visual indication of flow behaviour and solidification progress recorded on video. The potential experiments that can be conducted with this highly versatile model are numerous and will be used to gain a better understanding of the thermal controls on flow localisation and conduit development. This will assist hazard modellers to assess controls on eruption evolution and potentially to forecast sites where an initial fissure eruption may focus.

Investigation of the Pressure Fluctuation of Piston Chambers with Variable Slot Geometry

High-pressure fluctuation and flow ripple may cause unexpected vibration and noise when the piston pump works under severe conditions, and eventually lead to hydraulic transmission failure. The geometry of the valve plate has a great influence on the pressure fluctuation of the piston chamber. In order to optimize the structure of the valve plate, a mathematical model considering the slot geometry and the flow leakage of the lubricating interfaces was established in this paper. The model was used to investigate the pressure of the piston chamber, and then the accuracy of the model was validated by comparing simulation and experimental results. Further simulation results show that the pressure fluctuation in the piston chamber can be effectively suppressed by optimizing the triangular slots parameter of the valve plate, and a good design of the slot geometry could reduce the undershoot and overshoot of the pressure in piston chamber at the starting moment.

Experimental Investigation of Surface Roughness and Material Removal Rate in Wire EDM of Stainless Steel 304.

Its unexcelled mechanical and physical properties, in addition to its biocompatibility, have made stainless steel 304 a prime candidate for a wide range of applications. Among different manufacturing techniques, electrical discharge machining (EDM) has shown high potential in processing stainless steel 304 in a controllable manner. This paper reports the results of an experimental investigation into the effect of the process parameters on the obtainable surface roughness and material removal rate of stainless steel 304, when slotted using wire EDM. A full factorial design of the experiment was followed when conducting experimental trials in which the effects of the different levels of the five process parameters; applied voltage, traverse feed, pulse-on time, pulse-off time, and current intensity were investigated. The geometry of the cut slots was characterized using the MATLAB image processing toolbox to detect the edge and precise width of the cut slot along its entire length to determine the material removal rate. In addition, the surface roughness of the side walls of the slots were characterized, and the roughness average was evaluated for the range of the process parameters being examined. The effect of the five process parameters on both responses were studied, and the results revealed that the material removal rate is significantly influenced by feed (p-value = 9.72 × 10-29), followed by current tension (p-value = 6.02 × 10-7), and voltage (p-value = 3.77 × 10-5), while the most significant parameters affecting the surface roughness are current tension (p-value = 1.89 × 10-7), followed by pulse-on time (1.602 × 10-5), and pulse-off time (0.0204). The developed regression models and associated prediction plots offer a reliable tool to predict the effect of the process parameters, and thus enable the optimizing of their effects on both responses; surface roughness and material removal rate. The results also reveal the trade-off between the effect of significant process parameters on the material removal rate and surface roughness. This points out the need for a robust multi-objective optimization technique to identify the process window for obtaining high quality surfaces while keeping the material removal rate as high as possible.

Design and Analysis of 15 MW SPM Vernier Generator for Direct-Drive Wind Turbine Applications

This paper presents the design and an analysis of a surface PM vernier generator (SPMVG) for MW-scale direct-drive (DD) wind turbine application. An SPMVG has the advantage of higher torque density; however, especially at higher power ratings with increased electrical loadings, the power factor worsens and there are some serious concerns including magnetic saturation of cores and PM demagnetization. These issues are directly related to machine design parameters such as PM dimensions, applied electrical loading, slot geometry and the choice of slot–pole combination. It is determined that depending on the PM thickness and a few other design variables, each slot–pole combination has an optimal value of specific electrical loading. The use of the optimal value of specific electrical loading ensures that the machine is not saturated, the performance is optimum and the power factor is not unnecessarily degraded. Moreover, under certain design constraints, design criteria are developed that ensure the proper choice of various entailed design variables. By using the developed design criteria, the trends of various electromagnetic performances with variation in the slot–pole combination are discussed. The obtained trends clearly show that each slot–pole combination offers a certain torque density and power factor; thus, it serves as a guide for the selection of the slot–pole combination considering the required torque density and/or certain power factor limit. Finally, by using the developed design approach, an SPMVG for rated power of 15 MW is designed; the design objectives are to maximize torque per volume with a power factor limit of 0.4. Moreover, the various aspects of the performances of the designed SPMVG are comprehensively compared against a conventional PM DD 15 MW generator.

Strong Er3+ radiative emission enhancement by quasi-BIC modes coupling in all-dielectric slot nanoantenna arrays

We have designed and realized all-dielectric lossless nanoantennas, in which a thin SiO2 layer doped with erbium ions is placed inside slotted silicon nanopillars arranged in a square array. The modal analysis has evi-denced that the slotted nanopillar array supports optical quasi-BIC resonances with ultra-high Q-factors (up to Q∼109), able to boost the electromagnetic local density of optical states in the optically active layer. Up to 3 orders of magnitude photoluminescence intensity increment and 2 orders of magnitude decay rate enhancement have been measured at room temperature when the Er3+ emission at about λ=1540 nm couples with the quasi-BIC resonances. Furthermore, by tailoring the nanopillar aspect ratio, the slot geometry has been exploited to obtain selective enhancements of the electric or magnetic dipole contribution to Er3+ radiative transitions in the NIR, keeping the emitter quantum efficiency almost unitary. Finally, by computing the angularly resolved elec-tromagnetic field enhancement inside the nanoslot, the nanoantenna directivity has been designed, proving that strong beaming effects can be obtained. Our findings have a direct impact on the development of bright and effi-cient photon sources operating at telecom wavelength that are of primary importance for quantum nanophotonic applications.

Review on design of hybrid longitudinal-torsional ultrasonic vibration horn for rotary ultrasonic machining (RUM) processes

Longitudinal-torsional (L-T) vibration machining process in rotary ultrasonic machining (RUM) technologies has been considered one of the most promising method in order to cope the machining problems of various difficult-to-machine materials (composites, metallic alloys, abrasives, ceramics and glass). However, design complexity of the L-T machining systems keeps it limited for commercial applications. Hybrid L-T horn is the key component to achieve the efficient performance of RUM systems. Design of hybrid L-T horn is highly intricate due to slots geometry, position, and number of slots. At present, there is no study available in the literature specifically focused on the design and implementation of hybrid L-T horn. Therefore, this study systematically describes literature review on the design, simulations and implementation of hybrid L-T vibration horn in RUM applications of difficult-to-machine materials. Furthermore, the present research reveals the critical design parameters of hybrid L-T horn such as incident angle 47.6° gives better surface quality of the machined hole compared to 67.2° at designed resonant frequency 35 kHz.

Evaluating orthodontic bracket slot dimensions and morphology: A narrative review.

The current article aims to review the previous studies that measure the orthodontic bracket slot dimensions and geometry. Searches in different databases, including PubMed Central, Science Direct, Wiley Online Library, the Cochrane Library, Textbooks, Google Scholar, and Research Gate, in addition to a manual search, were performed about the methods of assessing orthodontic bracket slot dimension up to March 2023. The irrelevant and duplicate studies were eliminated, leaving 35 studies for this narrative review. The findings indicate that the slots are oversized with diverging walls in most studies. Manufacturers must respect the standards during manufacturing brackets and adhere to the actual dimensions and tolerance values.

Heat dissipation optimization of ventilated brake disc recirculation zone based on NSGA-II algorithm

The Brakes contact surface temperature rises sharply when vehicle braking by friction, so vehicles are generally equipped with ventilated brake discs for cooling. However, the recirculation zone in the ventilated brake disc passage severely blocks fluid flow. In order to improve the convective and heat dissipation performance of the ventilated brake disc, this paper aims to introduce an optimized slotted vane geometry to improve the heat dissipation performance of ventilated brake discs. Therefore, three structural parameters of slot width, slot inclination and number of vanes were selected as optimization variables, and the optimization objective was to maximize the mass flow rate and convection heat transfer coefficient. And then, combined with the RSM and NSGA-II for optimization. The results showed that the optimized slotted vanes effectively suppressed the recirculation zone in the flow passage and made the airflow distribution more uniform. The optimal characteristic parameters after optimization are N = 36,θ = 56.38°, H = 12.7 mm. The CFD calculation results are consistent with the experimental results, and the Nu error obtained is about 2.6%. Within the given speed range, compared with experimental data of the straight vane brake disc, the total heat dissipation rate of the optimized brake disc is increased by 9%, the heat dissipation rate in the channel was increased by 5.6%, and the pumping capacity is increased by 12%.

Integrated large‐frequency‐ratio dual‐band tapered slot with monopole antenna for 4G/5G/B5G

AbstractWith the advanced communications systems, the integration of 5G bands, including sub‐6‐GHz and millimeter‐wave (mm‐wave) bands with the existing lower bands of 3G/4G has become an essential need for the future mobile handsets. This article proposes an integration between a large‐frequency‐ratio dual‐band tapered slot antenna with a multisection meander monopole antenna on a handset board. The tapered slot Vivaldi antenna (TSVA) functions as a resonant open‐ended slot at low frequencies (sub‐6 GHz) while also acting as a high‐gain Vivaldi antenna at higher frequencies (mm‐wave 28 GHz). The modification of the slot geometry, that is, generating multisections within the slot, is shown to improve the impedance bandwidth. Furthermore, the meander‐line monopole antenna covers the bands of the existing mobile generation (3G/4G) at 0.8, 1.8, 2.1, and 2.3 GHz. Most importantly, the compact size of the proposed antenna is realized by utilizing the side wall of a mobile board.

Trapezium backed dual circularly polarised hepta-band monopole antenna

ABSTRACT This paper presents a hepta-band planar monopole antenna which exhibits circular polarization (CP) at two bands and linear polarization at other five bands. Combination of rectangular slots to form a single E-shaped structure has been introduced in half ground to excite hepta-band operations. Asymmetric trapezoidal parasitic element is also placed under the monopole radiator positioned at upper half ground plane of antenna. Due to asymmetric effect attained by the placement of trapezium, CP is achieved at 4.2 GHz and 10 GHz with 3-dB axial ratio bandwidth of 4.21–4.29 GHz and 9.92–10.01 GHz, respectively. The antenna acquires remaining five resonant modes at 2.4 GHz, 5.4 GHz, 7.2 GHz, 8.86 GHz and 11.8 GHz with 10-dB impedance bandwidth of 90 MHz, 160 MHz, 100 MHz, 200 MHz and 410 MHz, respectively. Sensitive study of the E slot and trapezoidal structured geometry is conducted. The proposed antenna is designed on low cost FR4 (εr = 4.4, tanδ = 0.02). To ensure the practicability, the proposed antenna design is fabricated and measured. A good agreement of simulation and measurement validates the proposed designed. The antenna has potential to cover frequency bands of IEEE802.11, Bluetooth, WLAN, WiMAX, Satellite Communication, Short Range RADARs and Radio band applications.

Steady flow of power-law fluids past a slotted circular cylinder at low Reynolds number

Steady laminar flow past a slotted circular cylinder was investigated for non-Newtonian power-law fluids at the low Reynolds number (Re) range (5 ⩽ Re ⩽ 40). Flow simulation was carried out for shear-thinning fluids with their power-law indices (n) varying from 0.2 to 1 (n = 0.2, 0.4, 0.6, 0.8, and 1). The normal (case A) and the slotted (case B) circular cylindrical geometries were considered, where the slit was placed between the front and the base pressure stagnation points. A finite volume method was used to calculate the flow field. The flow characteristics, such as flow separation angles, wake size, coefficients of pressure (Cp), and drag (CD), were studied for different Re and n values. For all n values, the slotted cylinder effectively delayed the flow separation. It showed much better pressure recovery than the normal cylinder due to the interaction between the self-bleed from the slit exit to the cylinder wake. The vorticity of this bleed influenced the wake's vorticity, and an increase of 3%–26.4% in higher maximum surface vorticity was reported for the slotted cylinder. An increase of 0.7%–6.5% in the bubble length was observed for the normal cylinder due to early flow separation. An enhanced pressure recovery across the slotted cylinder resulted in a significant drop in the pressure drag with 0.2%–4.56% reduction in the overall drag coefficient.

A wide inter-absorption dual-transmission dual-polarized frequency selective rasorber based on SRRs

ABSTRACT In this letter, a dual-polarized dual-transmission frequency selective rasorber (FSR) geometry is demonstrated. The top layer of the FSR is built of a cross-dipole design loaded with chip resistors for obtaining a wideband absorption. In addition, two different split ring resonator patterns are printed at each side of the substrate connected by metallized vias to achieve two in-band transmission responses. The bottom layer is designed from a slot geometry to exhibit two transmission bands similar to that of the top layer. The overall FSR structure exhibits a −10 dB reflection response ranging from 2.0 GHz to 8.15 GHz (having a fractional bandwidth of 121%), with transmission peaks appearing at 4.2 GHz and 6.2 GHz having insertion losses of 2.3 dB and 2.9 dB, respectively. The unit cell topology is miniaturized with dimensions of 0.1λL×0.1λL, λL being the free space wavelength at the lowest operating frequency. The proposed FSR also satisfies polarization-insensitive characteristic and angular stability behavior for differentmodes. The working principle behind such wideband absorption and in-band transmission phenomena are analyzed and an equivalent circuit model is presented. A prototype of the proposed FSR is manufactured and measured, confirming the simulated responses.

Computational Investigation of Effects of Side-Injection Geometry on Thrust-Vectoring Performance in a Fuel-Injected Dual Throat Nozzle

Dual-throat Nozzle (DTN) is known as one of the most effective approaches of fluidic thrust-vectoring. It is gradually flourishing into a promising technology to implement supersonic and hypersonic thrust-vector control in aircrafts. The main objective of the present study is numerical investigation of the effects of secondary injection geometry on the performance of a fuel-injected planar dual throat thrust-vectoring nozzle. The main contributions of the study is to consider slot and circular geometries as injector cross-sections for injecting four different fuels; moreover, the impact of center-to-center distance of injection holes for circular injector is examined. Three-dimensional compressible reacting simulations have been conducted in order to resolve the flowfield in a dual throat nozzle with pressure ratio of 4.0. Favre-averaged momentum, energy and species equations are solved along with the standard k- ε model for the turbulence closure, and the eddy dissipation model (EDM) for the combustion modelling. Second-order upwind numerical scheme is employed to discretize and solve governing equations. Different assessment parameters such as discharge coefficient, thrust ratio, thrust-vector angle and thrust-vectoring efficiency are invoked to analyze the nozzle performance. Computationally predicted data are agreed well with experimental measurements of previous studies. Results reveal that a maximum vector angle of 17.1 degrees is achieved via slot injection of methane fuel at a secondary injection rate equal to 9% of primary flow rate. Slot injection is performing better in terms of discharge coefficient, thrust-vector angle and thrust-vectoring efficiency, whereas circular injection provides higher thrust ratio. At 2% secondary injection for methane fuel, vector angle and vectoring efficiency obtained by slot injector is 8% and 34% higher than the circular injector, respectively. Findings suggest that light fuels offer higher thrust ratio, vector angle and vectoring efficiency, while heavy fuels have better discharge coefficient. Increasing center-to-center distance of injector holes improves thrust ratio, while having a negative effect on discharge coefficient, vector angle and vectoring efficiency. A comparison between fuel injectant of current study and inert injectant in the previous studies indicates that fuel reaction could exhibit substantial positive effects on vectoring performance. Secondary-to-primary momentum flux ratio is found to play a crucial role in nozzle performance.

Effects of air-suction guide structures on the condensing zone of pneumatic compact spinning with perforated drum

PurposeThe purpose of this study is to investigate the effects of air-suction slots geometry on the condensing zone of pneumatic compact spinning.Design/methodology/approachThis paper investigated the condensing zone of pneumatic compact spinning with perforated drum for different structures of air-inlet slot geometry with computational fluid dynamics. For this purpose, three air-suction guides with different air-slots were designed. To create the condensing zone for the numerical simulation, a suction insert and the perforated drum were also designed. Flow velocity components on the X, Y, and Z axes, static pressure distribution and the streamline diagram were used for comparative analysis. Designed air-suction guides were produced with a 3D printer and used for yarn production.FindingsNumerical simulation results showed that condensing effects were provided for all three types of air-suction guides and approaching air-slots on the suction guides resulted in greater flow components but may cause fluctuations. Experimental results also showed that actual flow velocity components (Z-axis) are effective on hairiness (H) properties of the yarn while assisting flow-velocity components are more effective on the evenness and tenacity properties of the yarn.Originality/valueThis paper presents the numerical flow field simulation of compact spinning for different structures of air-suction guides with detailed measurements. To know the effects of air-suction guides on the condensing zone may be helpful to improve yarn properties. In addition, a 3D printer was used for the production of designed parts.

Effects of Slotted Impeller Configurations on the Hydraulic Performance of Double-Suction Pump

A double-suction centrifugal pump is widely used in various industrial fields due to its stable and durable operability. There are many studies to improve pump performance, but in most cases changes in blade angle and thickness have been considered. In this paper, the optimal design was performed to improve the hydraulic performance of the double-suction centrifugal pump by applying slotted blade geometry. The shape of the slotted impeller is defined by angle, clearance, and location. A range of values, for each parameter, were selected and used in the design of experiments (DOE). An optimized space-filling design sampling technique (OSFD) was used to select 25 points for optimization through the response surface method. Response surfaces effectively analyze the correlation between the design variables and performance variables. The objective of the optimization is to increase efficiency. The numerical results of the optimized model are graphically depicted and compared with the coefficients using the ANSYS CFX. Through comparison with the results from the reference model, it is shown that the optimized slotted impeller decreased the turbulence kinetic energy and stabilized the flow.

Rotor Slot Design of Squirrel Cage Induction Motors With Improved Rated Efficiency and Starting Capability

Among the electro-mechanical devices transforming energy from electrical to mechanical, the squirrel cage induction motor can be surely considered a workhorse of the industry due to its robustness, low cost and good performance when directly fed by the a.c. grid. Being the most influencing motor topology in terms of energy consumption, optimizing the efficiency of squirrel cage induction motors could lead to a great impact towards the reduction of the human environmental footprint. The induction motor design aided by finite element analysis presents significant challenges because an accurate performance prediction requires a considerable computational burden. This paper makes use of an innovative fast and accurate performance evaluation method embedded into an automatic design procedure to optimize different rotor slot geometries. After introducing the performance estimation approach, its advantages and limits are discussed comparing its prediction with the experimental tests carried out on an off-the-shelf induction motor. Different rotor cage structures with increasing geometrical complexity are then optimized in terms of starting and rated performance adopting the same design optimization process, the same stator geometry and constituent materials. The analysis of the optimal solutions shows how it is possible to improve the rated efficiency without compromising other performance indexes. The presented results can be used as general design guidelines of squirrel cage induction motors for industrial applications.