Parallel Slots Research Articles

A Complete Quasi-3-D Analytical Model of No-Load Magnetic Field of Double-Sided Slotted AFPMMs Considering End Effect

This paper presents a complete quasi-3-D analytical model combining the solution of Maxwell’s equations and the magnetic equivalent circuit for the determination of no-load magnetic field distributions of slotted axial flux permanent magnet machines (AFPMMs) considering the end effect without using 3-D finite element method (FEM). The effect of end effect on the air gap magnetic field distributions along the radial direction of AFPMMs is considered by introducing the end function. Moreover, based on the proposed analytical model, the method of adjusting the pole-arc ratio along the radial direction is adopted to solve the local saturation problem of the stator teeth at the inner radius when adopting the parallel slot structure. The relationship between the inner pole-arc ratio and the outer pole-arc ratio is obtained when the tooth flux densities are consistent along the radial direction. Finally, taking two AFPMM prototypes as examples, the analytical calculation results, 3-D FEM analyses and experiment results are compared to validate the accuracy of the analytical model.

Slotted rotatable target assembly and systematic error analysis for a search for long range spin dependent interactions from exotic vector boson exchange using neutron spin rotation

We discuss the design and construction of a novel target array of nonmagnetic test masses used in a neutron polarimetry measurement made in search for new possible exotic spin dependent neutron–atominteractions of Nature at sub-mm length scales. This target was designed to accept and efficiently transmit a transversely polarized slow neutron beam through a series of long open parallel slots bounded by flat rectangular plates. These openings possessed equal atom density gradients normal to the slots from the flat test masses with dimensions optimized to achieve maximum sensitivity to an exotic spin-dependent interaction from vector boson exchanges with ranges in the mm - μm regime. The parallel slots were oriented differently in four quadrants that can be rotated about the neutron beam axis in discrete 90°increments using a Geneva drive. The spin rotation signals from the 4 quadrants were measured using a segmented neutron ion chamber to suppress possible systematic errors from stray magnetic fields in the target region. We discuss the per-neutron sensitivity of the target to the exotic interaction, the design constraints, the potential sources of systematic errors which could be present in this design, and our estimate of the achievable sensitivity using this method.

Control of a three-dimensional turbulent shear layer by means of oblique vortices

The effect of local forcing on the separated, three-dimensional shear layer downstream of a backward-facing step is investigated by means of large-eddy simulation for a Reynolds number based on the step height of 10,700. The step edge is either oriented normal to the approaching turbulent boundary layer or swept at an angle of $$40^\circ $$ . Oblique vortices with different orientation and spacing are generated by wavelike suction and blowing of fluid through an edge parallel slot. The vortices exhibit a complex three-dimensional structure, but they can be characterized by a wavevector in a horizontal section plane. In order to determine the step-normal component of the wavevector, a method is developed based on phase averages. The dependence of the wavevector on the forcing parameters can be described in terms of a dispersion relation, the structure of which indicates that the disturbances are mainly convected through the fluid. The introduced vortices reduce the size of the recirculation region by up to 38%. In both the planar and the swept case, the most efficient of the studied forcings consists of vortices which propagate in a direction that deviates by more than $$50^\circ $$ from the step normal. These vortices exhibit a spacing in the order of 2.5 step heights. The upstream shift of the reattachment line can be explained by increased mixing and momentum transport inside the shear layer which is reflected in high levels of the Reynolds shear stress $$-\rho \overline{u'v'}$$ . The position of the maximum of the coherent shear stress is found to depend linearly on the wavelength, similar to two-dimensional free shear layers.

Spreadsheet calculations of jets injected normal to a crossflow in a rectangular duct from opposed rows of slots slanted at 45°

The purpose of this study was to show expected results for cases of opposed rows of jets entering the mainstream from 45° slanted slots and round holes. The results in this paper were obtained using the spreadsheet version of the NASA JIC empirical model posted with NASA/TM—2011-215980. This version incorporates two significant changes that only affect slanted slots: 1) the translation function was corrected so distributions for round holes (as L/W=1 slanted slots) do not translate and 2) the capability was added to allow 45° slots to slant in either direction so “crossed” slot configurations can be calculated.The primary conclusion in this paper is that the best mixing configuration for opposed rows of slanted slots, at any downstream distance, is a parallel staggered configuration. Although distributions from “crossed” slanted slots are similar to those from parallel configurations at particular locations, results for crossed slots are highly dependent on downstream distance and are no better than parallel slots at locations where they are similar and are worse than parallel ones at other distances.

Field Reconstruction Method in Axial Flux Permanent Magnet Motor With Overhang Structure

This paper employs an overhang structure for axial flux permanent magnet motor to enhance the torque density. However, the overhang structure requires a computationally expensive 3-D finite-element method (FEM) for analysis, because a quasi-3-D FEM cannot be applied to such a geometry. Thus, in order to reduce the computational cost of above-mentioned topology, this paper adopts a field reconstruction method (FRM). The conventional FRM is applicable only in the case, where the slot pitch to teeth length ratio is the same along radial direction. To address this problem, we introduce a virtual air gap concept so that it can take into account parallel slot effect as well as overhang effect. In this paper, the effectiveness of the proposed method is verified by the 3-D FEM and experimental results.

Massively parallel anisotropic mesh adaptation

Mesh adaptation has proven to be very efficient for simulating transient multiphase computational fluid dynamics applications. In this work, we present a new parallel anisotropic mesh adaptation technique relying on an edge based error estimator. It provides a high level of accuracy while substantially reducing the computational effort. This technique enables a good capture of physical phenomena, boundary layers, interfaces, free surfaces and even multiphase turbulent flows, and has a great potential to simulate a large variety of applications. Current investigations explore the performance of the new algorithm on massively parallel resources. In this paper, we show that the developed adaptive meshing works very well in a parallel environment involving topological mesh modifications and dynamic repartitioning of parallel slots. It is also shown that the proposed methodology provides an additional gain in terms of computational cost due the production of a non-uniform mesh size distribution. Runs performed on national and European supercomputers will show the scalability and pertinence of our developments.

Miniaturization of Microstrip Patch Antenna by Using Two L-shaped Slots for UHF RFID Reader

A novel design for miniaturization of microstrip patch antenna for the RFID reader is proposed. The proposed antenna design consists of two L-shaped slots on the patch and two parallel slots on the ground plane. The patch and the ground are shorted through a shorting probe. The area of the proposed antenna is reduced around 51% compared with the slot less one. The validity and feasibility of the proposed antenna has been simulated and analyzed by HFSS. The simulation results show that the proposed antenna has relatively good gain of 8.05dBi and radiation characteristics and it covers the required bandwidth, 902-928MHz. The measured results are compared with the simulated results, and good agreement is obtained.

A printed wide-beamwidth circularly polarized antenna via two pairs of radiating slots placed in a square contour

A low-profile circularly polarized (CP) slot antenna to achieve a wide axial-ratio (AR) beamwidth is proposed in this paper. The radiating patch consists of two orthogonal pairs of parallel slots etched symmetrically onto a ground plane. Firstly, our theoretical study demonstrates that the CP radiation can be satisfactorily achieved at the broadside, when the vertical and horizontal paired-slots are excited in the same amplitude with 90° phase difference. Secondly, the principle of CP radiation of the proposed antenna on an infinite ground plane is described. Through analyzing the spacing between two parallel slots, the |Eθ| and |Eφ| radiation patterns can be made approximately identical with each other over a large angle range. As such, the slot antenna achieves a wide AR beamwidth. After that, the 3 dB AR beamwidth with respect to the size of a finite ground plane is investigated to constitute a practical CP antenna on a finite ground plane. In final, the proposed CP antenna with a 1–4 probe-to-microstrip feeding network is designed and fabricated on a finite ground plane of a dielectric substrate. Measured results are shown to be in good agreement with the simulated ones about the gain, reflection coefficient, AR bandwidth, and radiation patterns. Most importantly, a wide 3 dB AR beamwidth of 126° and low-profile property with the height of 0.036λ0 are achieved.

Metamaterial loaded vivaldi antenna with high gain and equal beamwidths at KA band

ABSTRACTA high gain and broadband Vivaldi antenna with end‐fire and equal beamwidth radiation pattern at Ka band is presented in this paper. The Vivaldi slot is fed by the microstrip line‐to‐substrate integrated waveguide (SIW) transformer. The SIW transmission performance is enhanced by another row of metal vias beside the original one. On both sides of the Vivaldi conductor planes, 8 parallel slots with gradually increasing length are etched to improve the front‐to‐back ratios. Under the microstrip feed line, three pairs of split ring resonators (SRRs) are etched on the ground to suppress the secondary harmonic. In order to improve the antenna gain and obtain the equal E‐ and H‐plane beamwidths, the special designed zero‐epsilon metamaterial (ZEM) units are loaded on the Vivaldi slot with a maximum gain increment of 3.4dB being obtained. The antenna exhibits a broad bandwidth of 38.5% at 35GHz ranging from 26.5GHz to 40GHz with the reflection coefficient less than −10dB, and the gain varying between 9.7dBi and 12.2dBi. The proposed antenna is fabricated and measured to validate the design. The measured results are in good agreement with the simulated ones. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2337–2341, 2016

Scheduling Algorithm to Select Optimal Programme Slots in Television Channels: A Graph Theoretic Approach

In this paper, it is shown that all programmes of all television channels can be modelled as an interval graph. The programme slots are taken as the vertices of the graph and if the time duration of two programme slots have non-empty intersection, the corresponding vertices are considered to be connected by an edge. The number of viewers of a programme is taken as the weight of the vertex. A set of programmes that are mutually exclusive in respect of time scheduling is called a session. We assume that a company sets the objective of selecting the popular programmes in k parallel sessions among different channels so as to make its commercial advertisement reach the maximum number of viewers, that is, a company selects k suitable programme slots simultaneously for advertisement. The aim of the paper is, therefore, to help the companies to select the programme slots, which are mutually exclusive with respect to the time schedule of telecasting time, in such a way that the total number of viewers of the selected programme in k parallel slots rises to the optimum level. It is shown that the solution of this problem is obtained by solving the maximum weight k-colouring problem on an interval graph. An algorithm is designed to solve this just-in-time optimization problem using \(O(kMn^2)\) time, where n and M represent the total number of programmes of all channels and the upper bound of the viewers of all programmes of all channels respectively. The problem considered in this paper is a daily life problem which is modeled by k-colouring problem on interval graph.

Low‐profile wide‐beamwidth circularly‐polarised patch antenna on a suspended substrate

A low-profile circularly-polarised (CP) patch antenna with wide axial-ratio (AR) beamwidth is proposed. Based on the transmission-line model, the radiation patterns of a CP patch antenna are calculated by modelling the entire patch as two pairs of equivalent parallel slots. Initially, the mechanism of wide-beamwidth CP radiation pattern is investigated. The results show that the | E θ | and | E φ | radiation patterns can be made nearly equalized over a large angular range, if the spacing L between two parallel slots is selected as 0.45 λ 0 (Condition I). For a square patch, the length of each slot must be equal to the spacing L , and it needs to be maintained as one half wavelength at resonance for radiation (Condition II). By using a suspended dielectric substrate, the two above conditions is simultaneously satisfied, resulting to achieve a wide AR beamwidth. After that, the effect of the finite ground size on the 3-dB AR beamwidth is analysed to constitute a practical CP antenna. Finally, the proposed CP antenna is designed and fabricated. Experimental results are in good agreement with the simulated ones in terms of radiation beamwidth, reflection coefficient and AR bandwidth. Practically, the antenna achieves a wide 3-dB AR beamwidth of 120°.

Heat transfer enhancement to an array of synthetic air jets by an induced crossflow

Jet vectoring and crossflow enhanced heat transfer to a modular synthetic air jet array consisting of six individually controllable parallel slot jets is investigated. When applied in a multi-jet array, jet vectoring can be implemented to operate as an adaptive, modular heat exchanger capable of dynamically targeting hot spots and enhancing local cooling. Time averaged surface heat transfer distributions are presented for varying Reynolds number, stroke length and axial spacing. It is shown that crossflow is achievable for an array of jets; however vectoring performance is dictated by inter-jet phase delay and limited by axial spacing and stroke length. All operating parameters showed increased levels of heat transfer are produced by operating the array out of phase. In particular, at small axial spacings this is attributed to crossflow generated by the out of phase jet pulsation.

Lock-Free and Wait-Free Slot Scheduling Algorithms

In this paper, we consider the design space of parallel non-blocking slot scheduling algorithms. Slot schedulers divide time into discrete quanta called slots , and schedule resources at the granularity of slots. They are typically used in high throughput I/O systems, data centers, video servers, and network drivers. We propose a family of parallel slot scheduling problems of increasing complexity, and then propose parallel lock-free and wait-free algorithms to solve them. In specific, we propose problems that can reserve, as well as free a set of contiguous slots in a non-blocking manner. We show that in a system with 64 threads, it is possible to get speedups of 10X by using lock-free algorithms as compared to a baseline implementation that uses locks. We additionally propose wait-free algorithms, whose mean performance is roughly the same as the version with locks. However, they suffer from significantly lower jitter and ensure a high degree of fairness among threads.

Small Square Reconfigurable Antenna with Switchable Single/Tri-Band Functions

A novel frequency reconfigurable slot antenna for suitable switchable radiations at WLAN and a tri-band at Bluetooth, WiMAX and upper WLAN applications is designed and fabricated. Switchable frequency responses are achieved by implementation of a PIN diode within the antenna ground plane. The antenna structure consists of a square radiation patch with an E-shaped slot, a modified ground plane with an inverted T-shaped strip that acts as a parasitic stub and two parallel slots and a protruded strip which is connected to the parasitic stub with a PIN diode. The presented antenna has a compact size of 20 × 20 mm 2 while providing switchable radiations at 2.36-2.5 GHz Bluetooth, 3.51-3.79 GHz WiMAX, and 5.47-5.98 GHz WLAN when the diode is ON and 5.04-6.13 GHz WLAN when the diode is OFF.

Broadband RCS reduction and gain enhancement microstrip antenna using shared aperture artificial composite material based on quasi‐fractal tree

A shared aperture artificial composite material (SA-ACM) with broadband absorption and partial reflection feature is proposed. The SA-ACM is composed of artificial composite material absorber (ACMA) and partial reflection surface (PRS), where the ACMA and PRS share the same aperture in the vertical dimensionality. The ACMA consists of quasi-three-dimensional fractal tree loaded with lumped resistances and metallic pattern on the bottom side of a dielectric slab, and the PRS consists of etched parallel slots in a metallic plane. The SA-ACM as the role of superstrate is applied to the mircrostrip antenna. The Fabry–Perot resonator cavity constructed by the PRS and the metallic ground of the mircrostrip antenna can achieve high gain, while the ACMA can obtain the low radar cross section (RCS) characteristic by absorbing the incident wave. Simulation and experiment results demonstrate that the gain of the antenna with SA-ACM is enhanced over 3 dB in the operation frequency band, and the backscattering RCS is obviously reduced by 10 dB in a wide frequency range.

Third Harmonic Generation With the Effect of Nonlinear Loss

We demonstrate an efficient third harmonic generation (THG) with the effect of nonlinear loss based on a proposed double-hybrid plasmonic slot waveguide structure. Silicon nanocrystal is integrated into the two parallel slots acting as the main interactive nonlinear material. To achieve phase matching condition, we analyze the relation between the guided mode dispersions and the waveguide geometrical parameters. The effect of nonlinear loss, which is contributed by the two-photon-absorption (TPA) effect, on the THG conversion efficiency is investigated numerically. The simulation results reveal that the THG conversion efficiency can be significantly enhanced by the field confinement and enhancement, whereas it is greatly impeded in the presence of the TPA effect (a decrement of 17.6% on the THG conversion efficiency with a pump power of 4 W). According to our calculation, the THG conversion efficiency of 0.91% without the consideration of the TPA effect and 0.75% with the TPA effect under a 4-W input pump power condition is achieved.

A Polarization-Rotating SIW Reflective Surface With Two Sharp Band Edges

A single-layer polarization-rotating reflective surface with two sharp band edges is proposed in this letter using the substrate integrated waveguide (SIW) technology. The linearly polarized incident electromagnetic wave can be reflected back with its polarization rotated orthogonally, and two sharp band edges of the cross-polarized reflection coefficient can be achieved using the proposed reflective surface. The periodic element of the proposed reflective surface is a square SIW cavity resonator with two parallel L-shaped slots etched on its front side. The operating principle is investigated with the mode analysis and parametric study performed. A more accurate analysis on the structure with one L-shaped slot is presented. Moreover, the leaky mode and coplanar waveguide (CPW) mode of parallel slots are introduced to explain the operating principle of the modified structure with two parallel L-shaped slots. A prototype is designed and fabricated with its frequency centered at 34.5 GHz to validate the proposed structure. The simulated and experimental results are consistent well, with two zeros of copolarized reflection coefficient in the passband and two zeros of cross-polarized reflection coefficient in the stopband observed. The fractional bandwidth (FBW) is around 3%, and the mode conversion loss is around 0.6 dB with the copolarized reflection coefficient under -10 dB. Oblique incident cases are also investigated, and stable frequency responses can be achieved.

宽带近红外表面等离激元逻辑与门器件的设计

A nanostructure of broadband surface plasmons logic AND gate was presented. The two input ports were composed of broadband infrared directional couplers which were a pair of two parallel slot nano-antennas milled into gold film. An array of couplers arranged on an arc-shaped circle was capable of focusing the surface plasmons to the circular center when it was illuminated with radially polarized beam. The same two focused surface plasmons spots were coupled into two groove-shaped waveguides, respectively, and then interfered each other at the cross point. The intensity was four times that of intensity produced by a single arc-shaped nanostructure when two arc-shaped nanostructures produced the surface plasmons in the center with the same amplitude, polarization direction and zero phase difference. The nanostructure and device principle were theoretically analyzed. The relation between input ports and output port along with broadband property were simulated with the finite difference in time domain method.

Tri-Band Parallel Slots Loaded Circular Disk Patch Antenna for C and X-Band Applications

This paper presents the tri-band slot loaded patch antenna for mobile communication. The antenna consists of parallel slots loaded circular disk with defected ground structure antenna (DGS). The antenna without DGS, acts like wide band antenna and bandwidth is 34.45% (3.47 - 4.92 GHz) with maximum gain of 4.97 dBi, which can be used in WiMax application. This structure has the following advantages: 1) co-axial feeding technique, which is very simple as compared to other feeding technique, 2) simple and cost effective and 3) it is more efficient than the antenna without DGS. This antenna has been analyzed using IE3D simulation software.

Triple U-slot loaded defected ground plane antenna for multiband operations

In this letter, a three U-shaped slot loaded rectangular patch with defected ground plane antenna has been analyzed. The antenna shows multiresonance. The resonance frequencies of single layer patch are found to be 9.75 GHz, 11.55 GHz, 12.15 GHz, 13.49 GHz, and 14.3 GHz and its frequency ratio are found to be f2/f1 = 1.18%, f3/f2 = 1.05%, f4/f3 = 1.11%, and f5/f4 = 1.06%, respectively. The bandwidths of this proposed antenna are found to be 2.88%, 0.0%, 5.59%, 4.96%, and 1.53% and the respective gains are 0.46 dB, 4.02 dB, 4.28 dB, 4.85 dB, and 3.78 dB, respectively. Introducing three U-slots in the rectangular patch with three parallel slots loaded on the ground plane, near about 30% of size reduction has been achieved. All the simulation results obtained from IE3D which are in good condition. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:124–128, 2016