Slot Shape Research Articles

Cyclic performance of flange-plate connection to box column with finger shaped plate

The objective of using the flange plate connection as one of the most popular indirect connections to the built-up box column is to avoid using long plates. In deep beams, the need to provide sufficient length to fillet welds necessitates using of long flange plates, which may cause brittle failure due to increasing the bending moments at the face of the column. In the present study, configuring the top flange plate with a finger slot shape type is proposed in order to diminish length of the flange plates. In the proposed configuration, the longitudinal fillet weld was used in flange plates in addition to the transverse fillet and slot weld in the top and bottom flange plates, respectively; in order to provide the required strength for welds. Two full-scale specimens fabricated based on the proposed design methodology were subjected to the cyclic loading. The study results indicated that the flange plate connection with a suggested modified configuration could be prequalified for use in the special moment frames. In a parametric analytical study, the best arrangement of the longitudinal as well as the transverse fillet weld in a top flange plate was proposed for flange plate connections.

Analysis of the proximity and skin effects on copper loss in a stator core

Abstract Accurate prediction of power loss distribution within an electrical device is highly desirable as it allows thermal behavior to be evaluated at the early design stage. Three-dimensional (3-D) and two-dimensional (2-D) finite element analysis (FEA) is applied to calculate dc and ac copper losses in the armature winding at high-frequency sinusoidal currents. The main goal of this paper is showing the end-winding effect on copper losses. Copper losses at high frequency are dominated by the skin and proximity effects. A time-varying current has a tendency to concentrate near the surfaces of conductors, and if the frequency is very high, the current is restricted to a very thin layer near the conductor surface. This phenomenon of nonuniform distribution of time-varying currents in conductors is known as the skin effect. The term proximity effect refers to the influence of alternating current in one conductor on the current distribution in another, nearby conductor. To evaluate the ac copper loss within the analyzed machine a simplified approach is adopted using one segment of stator core. To demonstrate an enhanced copper loss due to ac operation, the dc and ac resistances are calculated. The resistances ratio ac to dc is strongly dependent on frequency, temperature, shape of slot and size of slot opening.

Design of an Aperture-Coupled Frequency-Reconfigurable Microstrip Stacked Array Antenna for LTE and WiMAX Applications

The aim of this paper is to design a novel structure of a frequency-reconfigurable microstrip array antenna by using a combination of aperture-coupled and the stacked patch technology. The four sets of two different aperture slot shapes (I-shaped and H-shaped) are printed on the ground and are functional to transfer the wave and the signal to the selected radiating layers. Both aperture slot positions are based on the bottom patches (layer 2) and top patches (layer 1), respectively. To achieve the frequency reconfigurability, four PIN diode switches are integrated on the feed line layer positioned between both aperture slots on the ground. The activation of the selected patches will determine the current operating frequency of the proposed antenna. A 2.6 GHz or 3.5 GHz frequency is achieved by switching all the PIN diode switches to ON or OFF mode synchronously. The advantage of the proposed antenna is that it can minimize the usage of the antenna’s surface area, with different size of the patch having different operating frequencies, sorted in different layer. The measured results of the return losses, radiation patterns, and the practical indoor propagation measurement achieved good agreement with the simulated results.

Effects of Rotor Bar Shape for Squirrel Cage Induction Motor in Transient State Using Moving Band Technique

This paper presents a dynamics analysis algorithm and the effect of rotor bar shape in the transient characteristics of the squirrel cage induction motor, in which the aluminum, copper, and silicon-copper are used for the conductor bars. The electromagnetic field, stator, and rotor circuit equations are coupled to analyze the motor performance in time domain using finite element method. The generated torque is calculated using the relationship of input and output power. Also, motion equation is used to find the next position of the rotor. Moving band technique is used to move the rotor of the motor in irregular intervals. In order to know the starting characteristics, various rotor slot shapes are analyzed and the results are compared with experiments to evaluate its torque performance by using the proposed method.

An optimum design of rotor slot shape of induction motor for electric vehicles using numerical techniques

A rotor slot shape of induction motor for electric vehicle is optimized by FEM with the numerical techniques. To optimize the rotor slot shape, two objective function and 3 variables are defined, and the optimization algorithm is developed. To verify the program, 4 poles 44 kW induction motor is modeled, simulated and analyzed by the program. The optimized rotor slot shape result makes reasonably good improvement to increase torque and efficiency of the motor performance.

The acoustic properties of panels with rectangular apertures.

A model for the acoustic properties of a plate perforated with slots of rectangular shape is proposed. The model is based on known expressions for the complex density and compressibility of a pore of rectangular shape together with the radiation impedance of a rectangular shaped piston in a baffle. For the so-called end correction of a rectangular aperture in a plate, an approximate solution is shown to fit an exact solution for the imaginary part of the radiation impedance, the latter solution based on the work of Lindemann [J. Acoust. Soc. Am, 55, 708-717 (1974)]. Two different procedures are tested to calculate the mutual influence of the apertures on the end correction, the one calculating the mutual impedance of neighboring pistons in the plate, the other by calculating the end correction of a piston placed in the end of an infinitely long tube. The model is used calculating the input impedance and absorption coefficient of a Helmholtz resonator with such a plate, comparing with measurement results. The fit between predicted and measured results, using plates with narrow slits, is good, but it is believed that the model also cover a wider range of dimensions for such a slotted plate.

Miniaturized designs of circularly polarized slot antenna

ABSTRACTDesigns of reducing the overall antenna size for a circularly polarized slot antenna are studied. The miniaturized design is based on a square‐ring slot antenna fed with an L‐shaped coupling strip, and it is performed by varying the slot shape and simultaneously cutting the ground plane. Two compact prototypes are implemented and measured. For the first one prototype, both the ring slot and ground plane have a narrow rectangular shape, and experimental results demonstrate that it can provide monopole‐like radiation as well as broadband circular polarization operation. As for the second one, its overall antenna dimensions are further reduced to be less than 0.1 , and it has a 3‐dB‐axial‐ratio bandwidth of about 4%. For the two prototypes, processes of the miniaturized designs are shown, and details of the experimental results are given along with the simulated results carried out by HFSS. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1522–1526, 2014

Miniaturised printed slot antenna with multi‐ring technique for dual‐band and broadband operations

Miniaturised microstrip-line-fed slot antennas with ring-shaped metallic strips for dual-band and broadband operations are investigated and verified in this study. The proposed designs implemented on a 0.8-mm FR-4 substrate show that the ring-shaped metallic strips and the feeding structure yield multiple resonant modes, achieving 66.3% size reduction. The proposed dual-band design reveals two operating bandwidths (12.4 and 46.5%) at the central frequencies of 2445 and 4813 MHz, respectively. The broadband design indicates the maximum bandwidth of 2511 MHz (69.6%) at 3606 MHz. This large operating bandwidth is obtained by choosing suitable combinations of feeding structure and multi-ring slot shapes. Simulated and experimental investigations are clearly conducted to understand their behaviours and optimise them for dual-band and broadband operations.

Investigation of Additional Harmonic Losses in Induction Motors Driven by PWM Inverters: Variation with Slot Shapes and Load Conditions

Investigation of Additional Harmonic Losses in Induction Motors Driven by PWM Inverters: Variation with Slot Shapes and Load Conditions

RECONFIGURABLE MICROSTRIP STACKED ARRAY ANTENNA WITH FREQUENCY AND PATTERN CHARACTERISTICS

This paper presents a frequency and pattern reconflgurable stacked patch microstrip array antenna fed by aperture-coupled technique. The antenna consists of three substrate layers with radiating elements sorted at substrate layer 1 (top patches) and substrate layer 2 (bottom patches). The layers have difierent sizes to indicate difierent operating frequencies. On the ground plane, the four sets of two difierent aperture slot shapes (I-shaped and H-shaped) are used to transfer the wave and signal to particular radiating elements during the PIN diode switches conflgurations. The I-shaped slots are used to activate the bottom patches while the H-shaped slots are used to activate the top patches. Four PIN diode switches are placed at the feed line, positioned between the I- and H-shaped slots. Next, by changing the PIN diode switches conflguration to ten cases, the proposed antenna has capabilities to change the operating frequencies and the pattern characteristics itself. The measured results of return loss, gain and radiation patterns have slightly shifted compared to the simulated results.

Broadband Substrate Integrated Waveguide Cavity-Backed Bow-Tie Slot Antenna

A novel design technique for broadband substrate integrated waveguide cavity-backed slot antenna is demonstrated in this letter. Instead of using a conventional narrow rectangular slot, a bow-tie-shaped slot is implemented to get broader bandwidth performance. The modification of the slot shape helps to induce strong loading effect in the cavity and generates two closely spaced hybrid modes that help to get a broadband response. The slot antenna incorporates thin cavity backing (height <;0.03λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ) in a single substrate and thus retains low-profile planar configuration while showing unidirectional radiation characteristics with moderate gain. A fabricated prototype is also presented that shows a bandwidth of 1.03 GHz (9.4%), a gain of 3.7 dBi over the bandwidth, 15 dB front-to-back ratio, and cross-polarization level below -18 dB.

Development of a Semielliptical Partial Ground Plane Antenna for RFID and GSM-900

A novel compact broadband patch antenna for UHF (ultrahigh frequency), RFID (radio frequency identification), and GSM-900 (global system for mobile communications) band is shown in this paper. The antenna is composed of an ellipse shape annular ring at the patch. The ground plane of the planar antenna is modified with a semiellipse shape slot. The structure can generate substantial amount of current at the feed-line. The geometry of the antenna is evaluated by using HFSS simulation software and deliberated across the paper. Parametric study is exhibited to delineate the response change of the antenna. The antenna has a physical width of 0.24 λand length of 0.3 λ. It covers a frequency starting from 0.9 GHz to 1.08 GHz. A fractional bandwidth of 18.2% has been achieved from 0.9 GHz till 1.08 GHz. An average gain of 5.5 dBi is achieved at the resonance frequency. The simulated and measured results have good agreement.

PLANAR ULTRAWIDEBAND MONOPOLE ANTENNA WITH TRI-NOTCH BAND CHARACTERISTICS

In this article, a compact ultra-wideband (UWB) planar monopole antenna with the triple notched band is proposed. The antenna consists of a semicircular radiating patch and a modifled ground plane with two bevels at upper edge. By etching two round shape slots in radiating patch the notch characteristics are achieved at WiMax band (3.3{3.7GHz) and WLAN band (5.15{5.875GHz). In order to realize notch band at X-band downlink satellite communication band (7.1{7.76GHz) a pair of rotated V-shape slot are etched on the ground plane. The measured operating impedance bandwidth of proposed antenna ranges from 2.9 to 10.9GHz having return loss less than 10dB with triple notched bands. The proposed antenna exhibits a nearly omnidirectional radiation pattern in the H-plane, and a dipole-like radiation pattern in the E-plane for the ultra-wideband. The efiects of each individual slot on band-notch characteristics are also investigated. The measured gain of the proposed triple band notched antenna is relatively stable across the operating frequency band except notched bands and thereby making the proposed antenna suitable for practical UWB applications. Proposed antenna has a compact size of 27 £ 25mm 2 .

Compact equilateral triangular patch antenna with slot loading

ABSTRACTThis article presents a comparative study on the effects of different slot shapes on the size reduction of a microstrip patch antenna. The antenna investigated consists of a triangular shaped patch using air as substrate which is primarily used for cost effectiveness and ease of fabrication. At first, the effect of slot loading on the patch antenna for compactness is investigated using circular slots and then triangular, rectangular, star shaped, and folded rectangular slots are introduced on the microstrip patch and their effects are studied too. The simulated and measured results show that the size reduction is achieved by 18.86, 27.35, 27.77, 29.8, and 43.47%, respectively, for these cases compared to a conventional triangular patch antenna operating at the same center frequency. It is worth mentioning that this communication presents maximum reduction in size reported so far for equilateral triangular patch antennas, apart from overcoming some significant drawbacks of other compact equilateral triangular patch antennas reported earlier in literature. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:268–274, 2014

Using polygonal defect in ground structure to reduce mutual coupling in microstrip array antenna

The surface wave propagation is a significant problem in designing microstrip array antennas that causes the mutual coupling between array elements. There are several methods to suppress this effect and decrease the propagation of surface waves,such as using defected ground structures (DGS). Determining the shape of DGS is the main difficulty when using these structures. In this paper,a new method is proposed to be used in designing array antennas in which the slot shape of DGS in the ground plane of the antenna is assumed to be a polygon, and its shape is obtained by using the enhanced genetic algorithm (GA) and ant colony optimization (ACO). In this case, an array antenna with two elements is designed to work in 9.5 GHz and the gain, return loss and mutual coupling of this antenna is optimized. Finally, the design procedure is verified by simulation and measurement.

Parallel CFD–DEM modeling of the hydrodynamics in a lab-scale double slot-rectangular spouted bed with a partition plate

This paper presents a numerical modeling of the gas–solid motion in a 3-D lab-scale double slot-rectangular spouted bed with a partition plate under the parallel framework of CFD–DEM coupling approach. Solid motion is tracked with the discrete element method, while the gas motion is solved by the k–ε turbulence model. The bed has two uniform chambers with the diverging base and two parallel slots lying in the bottoms of these two chambers. A total of 2,590,000 glass particles have been tracked with 112 CPUs in a cluster. The distributions of the gas–solid hydrodynamics are investigated initially. Then, the interaction between the spout and the annulus is explored. Finally, the effect of the plate height on the gas–solid motion of the bed is discussed. The results show that the insertion of the partition plate leads to the formation of two parallel fountains without information exchanging and the enlargement of the pressure drop. A velocity peak of the fluid phase or solid phase appears in the central region of each individual chamber. Furthermore, large vertical solid flux appears in the central region of each chamber and shows a distribution strongly related to the slot shape. The slot shape influences the spout–annulus interaction boundary, whereas this effect diminishes obviously with increasing the bed height. Spout–annulus interaction intensity shows the strongest in the conical region of bed and reduces along the axial direction. Finally, the plate height exerts little effect on the solid velocity and voidage distributions.

Three-Dimensional Modeling of Gas–Solid Motion in a Slot-Rectangular Spouted Bed with the Parallel Framework of the Computational Fluid Dynamics–Discrete Element Method Coupling Approach

The gas–solid flow in a three-dimensional slot-rectangular spouted bed is numerically investigated under the parallel framework of the computational fluid dynamics–discrete element method coupling approach. The fluid phase is solved with the k–ε turbulence model at the computational grid level, while the solid phase is tracked individually with the discrete element method at the particle scale. Millions of particles are calculated using a total number of 112 CPUs in a cluster. The predicted pressure drop profiles and the minimum spouting velocities of the calculations under different bed heights agree well with the experimental data. The startup procedure and the solid flow pattern are identified. Then, wall effects on the distribution properties of the gas–solid hydrodynamics are explored. Moreover, the interaction between spout and annulus and the effects of the superficial velocity and bed height on the bed hydrodynamics are discussed. The results show that a larger pressure drop appears in the system with a higher bed height. A bubble with its shape influenced by the slot geometry is formed in the startup procedure. Moreover, the bed hydrodynamics show a strong 3-D behavior along the depth direction. Large vertical solid flux mainly concentrates in the central region of the spout. The spout–annulus interface is dramatically influenced by the slot shape and shows different evolutionary tendencies in the different directions, and this influence becomes weaker along the bed height. The larger the superficial velocity is, the higher the bed height and the larger the spouting height appear. Besides, solid flow patterns under different bed heights with the superficial velocity the same ratio to the corresponding minimum spouting velocity show a similar behavior.

UWB antenna with notched band at 5.5 GHz

A slot antenna with a notched band at 5.5 GHz is proposed for UWB applications. The basic UWB antenna comprises of a rectangular radiating patch and a ground plane with a tapered shape slot and printed on 1.6 mm-thick FR4 dielectric substrate. To realise a notch band, two symmetrical slits are etched on the slot of the ground plane. Experimental results show that the proposed antenna exhibits wideband performance from 3.08 to more than 11 GHz with a notched frequency band centred at 5.5 GHz which can effectively mitigate the interference between the WLAN and UWB systems. It is also confirmed from the measurements that the insertion of slits does not affect the antenna performance, except at the notched frequency band.

Design of Miniaturized Dual-Band Artificial Magnetic Conductor with Easy Control of Second/First Resonant Frequency Ratio

A novel miniaturized artificial magnetic conductor (AMC) is proposed for dual-band operation. An AMC unit cell that employs four slots in the metallic patch is used to achieve miniaturization as well as easy control of the second/first resonant frequency ratio, which can be varied from 1.5 to 3.26 by simply changing the slot shape for a given metallic patch size. A dual-band antenna composed of a wideband monopole suspended over the proposed AMC surface is designed and tested to validate this approach. The measurements result in a satisfactory and good matching condition for the dual-band antenna.

Design of ultra wideband trapezoidal shape slot antenna with circular polarization

A CPW-feed printed slot antenna with circular polarization characteristics is presented in this paper. The basic structure of the antenna is a rectangular slot excited by a 50Ω CPW line terminated on a trapezoidal shaped tuning stub. Perturbations in the form of circular stubs are applied in the slot to realize circular polarization. The measured impedance bandwidth (S11<−10dB) for the initial design is 4.4GHz (from 2.2GHz to 6.6GHz) while the 3-dB axial ratio bandwidth is 1.77GHz (from 4GHz to 5.77GHz) which is 36.23% at the center frequency of 4.88GHz. The basic structure of the antenna was further modified to enhance the impedance bandwidth to reach well beyond 12GHz while increasing the ARBW to 44.3% (from 4.3GHz to 6.75GHz). The proposed antenna in its final version has a measured peak gain of about 5dB throughout the useful band and nearly stable radiation pattern.