Slot Opening Research Articles

Wideband antenna pair and its applications for 5G metal frame mobile phones

A wideband antenna pair used for 5G mobile phones is proposed in this paper. Both elements of the antenna pair consisting of an open slot and a coupled feeding line can cover the band of 3.3–6 GHz, and the isolation is larger than 10 dB. The ground clearance and the total size are 1.5 mm and 30 mm × 1.5 mm × 7 mm, respectively. Using the antenna pair, four- and eight-element multiple-input–multiple-output (MIMO) antennas are constructed. The simulated results show that the proposed antenna pair can be used to construct MIMO antennas for 5G metal frame mobile phones. As an example, the four-element MIMO antenna is manufactured and tested. The measured results show that the four elements can cover the band of 3.3–6 GHz, and the n77, n78, n79, and 5 GHz WLAN bands are covered. At the working bands, the measured efficiencies and isolations are bigger than 46% and 11.4 dB, respectively.

Optimization of double stator PMSM with different slot number in inner and outer stators using genetic algorithm

<span lang="EN-US">This paper describes the performance enhancement of double stator permanent magnet synchronous machines (DS-PMSM) based on genetic algorithm optimization (GAO). Generally, throughout the development stage, an analytical calculation is implemented to build the initial model of the DS-PMSM since the analytical calculation can provide the initial parameters based on the types and materials used in the machine design. For further improvement, GAO might potentially be applied to provide the optimization technique in searching the optimal motor parameters iteratively and intelligently with specific objective functions. For this aim, a three-phase, DS-PMSM with different number of slots between the outer and inner stators is first designed by using analytical parameter estimation and then later optimized by GAO. The outer and inner stators have 12-slots and 9-slots respectively, while, the rotor carries 10 magnetic poles. Four main input motor parameters, i.e. outer stator slot opening, outer magnet pole arc, inner stator slot opening and inner magnet pole arc are varied and optimized to achieve the design objective functions, i.e. high output torque, low torque ripple, low cogging torque and low total harmonic distortion (THDv). The results from the optimized GAO are compared with the initial motor model and further validated by finite element method (FEM). The results show a good agreement between GAO and FEM. GAO has achieved very significant improvements in enhancing the machine performance.</span>

Slim RFID Tag Antenna for Metallic Tools With Narrow Footprint

A slim and semi-flexible UHF RFID tag antenna, which has a compact dimension of 40 mm × 5 mm × 3.2 mm ( 0.1221λ×0.0153λ×0.0098λ), is proposed for tagging on metallic industrial tools with a narrow footprint. For a metal-mountable tag antenna, the unwanted electromagnetic antenna-metal interaction can deteriorate the tag read performances and it is particularly pronounced when the tag is attached to a narrow industrial tool. To achieve a size-reduction, the proposed tag is made of an inlay comprising a very compact 3-layer structure with two radiating patches. The currents on the top and middle patches can be made in phase for enhancing the radiated fields. Digital serrations, inductive stubs, and open slots loading have been studied for optimizing the antenna resonant frequency efficiently. With the use of the tuning mechanisms, when being tested on a narrow-body metal tool, the antenna impedance can be fully matched with the RFID microchip impedance, resulting in a good power transmission coefficient of ~ 1. Despite its compactness, the proposed tag antenna is readable from 11.0 m with an EIRP of 4W. To the best of our knowledge, the proposed tag antenna has a much better aspect ratio between its read distance and tag volume than most of the commercially available on-metal tags and it can be used for tagging on narrow metallic surfaces.

Flux maximization in wind turbine permanent magnet synchronous generator made of NdFeB permanent magnets

The permanent magnets of the Permanent Magnet Synchronous Generator (PMSG) machine are made up of NdFeB alloy. The Neodymium-iron-boron (NdFeB) permanent magnets’ overall magnetic energy or energy product limits the maximum magnetic flux density value that can be achieved in the PMSG configuration. The generator shaft is made of stainless steel and has an electrical conductivity σ = 1.35 MS/m and relative permeability μr = 1. The flux is not well concentrated without optimizing the geometry of the NdFeB permanent magnets and rotoric slot opening. Therefore, optimization of NdFeB permanent magnet geometry and rotoric slot opening will maximize the linkage flux and mutual flux components and minimize leakage flux components of Permanent magnet synchronous generator. In this current research work, the goal is to maximize mutual flux and linkage flux while minimizing PMSG's leakage flux components at the same time by optimization of geometrical parameters of Permanent magnet synchronous generator using different optimization algorithms. In this work, finite element method is mapped by Radial Basis Function (RBF) neural network so that for any value of NdFeB permanent magnet length or rotoric slot opening, magnetic flux could be estimated immediately. In this present research work, an attempt has been made to determine the optimal values of geometric parameters, length of the NdFeB permanent magnet bm and slot opening of rotor bo for which the linkage flux and mutual flux are maximized and leakage flux is minimized. The values of permanent magnet length bm obtained using dynamic particle swarm optimization (DYPSO) and self-adaptive particle swarm optimization (ADPSO) are 28.5523 mm and 28.5524 mm respectively. The values of rotoric slot opening bo obtained using dynamic PSO and self-adaptive PSO are 18.587 mm and 18.587 mm respectively.

Fast Computation Method for Stator Winding Skin-Effect Additional Losses in Synchronous Machines With Open Slots and Arbitrary Rotor Geometry

Large medium-voltage electric machine stators are usually equipped with form wound coils made of flat conductors (strands) and embedded in open (rectangular) slots. Air-gap magnetic flux lines can enter the slot and, sweeping the strands placed nearest the slot opening, induce eddy currents in them. Such eddy currents cause additional losses which can be much higher than usual skin-effect and proximity losses. In order to avoid dangerous overheating and hot spots, the additional losses in question need to be carefully predicted in the design stage. Time-stepping finite-element analysis (TSFEA) can be used for the purpose, which however implies a large computational burden and requires the machine geometry to be modeled in detail. This article proposes alternative methods based on time-harmonic finite-element analysis (THFEA) simulations performed on highly simplified machine models and with no need to take rotor motion into account. The proposed methods are shown to produce very accurate results, compared to TSFEA, but with very significant time and computational savings.

Slot-PM-Assisted Hybrid Reluctance Generator With Self-Excited DC Source for Stand-Alone Wind Power Generation

This article proposed a new slot-permanent-magnet (PM)-assisted hybrid reluctance generator (SPMa-HRG) with self-excited dc source for stand-alone wind power generation system. By introducing PM excitation in stator slot openings, enhanced torque density due to flux modulation effect can be achieved compared with the original reluctance topology. Moreover, the introduced PMs make it feasible to build a self-excited dc source to fed dc field winding without using extra power supply. In particular, a simple design of ac supply winding is proposed, by splitting a small portion of ac armature winding to provide electrical power to dc field winding through a diode rectifier and small-capacity H-bridge converter. Compared with using separate dc source, the device cost is reduced, and the system reliability is improved. In this article, the generator structure and operation principle are introduced. PM usage is optimized to obtain the optimal torque. The feasibility of the optimal design with self-excited dc source is verified by field-circuit coupled finite element analysis.

Novel DC-Saturation-Relieving Hybrid Reluctance Machine With Skewed Permanent Magnets for Electric Vehicle Propulsion

Reluctance machines with dc excitation coils have become a promising solution for electric vehicle propulsion system because of its robust rotor structure and good field-weakening ability. However, these machines usually suffer from relatively low torque density and efficiency. To solve this problem, this article proposes a novel hybrid reluctance machine with improved torque density and efficiency. The key novelty is to introduce skewed permanent magnets (PMs) in slot openings. The tangential component of skewed PMs can be used to relieve the dc saturation in the stator iron core, so that the <inline-formula> <tex-math notation="LaTeX">$B-H$ </tex-math></inline-formula> working range can be extended and relatively high dc excitation can be applied in the proposed machine. Besides, the radial component of skewed PM provides extra torque component under flux modulation effect. Therefore, the proposed skewed PMs can achieve torque boost and core utilization improvement simultaneously. In this article, the dc-saturation-relieving effect of the proposed design is thoroughly investigated and verified by finite element analysis.

An empirical approach for predicting burden velocities in rock blasting

An analytical relation between burden velocity and ratio of burden to blasthole diameter is developed in this paper. This relation is found to be consistent with the measured burden velocities of all 37 full-scale blasts found from published articles. These blasts include single-hole blasts, multi-hole blasts, and simultaneously-initiated blasts with various borehole diameters such as 64 mm, 76 mm, 92 mm, 115 mm, 142 mm and 310 mm. All boreholes were fully charged. The agreement between measured and calculated burden velocities demonstrates that this relation can be used to predict the burden velocity of a wide range of full-scale blast with fully-coupled explosive charge and help to determine a correct delay time between adjacent holes or rows in various full-scale blasts involved in tunnelling (or drifting), surface and underground mining production blasts and underground opening slot blasts. In addition, this theoretical relation is found to agree with the measured burden velocities of 9 laboratory small-scale blasts to a certain extent. To predict the burden velocity of a small-scale blast, a further study or modification to the relation is necessary by using more small-scale blasts in the future.

Coplanar Dual-Band Base Station Antenna Array Using Concept of Cavity-Backed Antennas

In this article, we propose a novel reflector-back cavity-low-band (LB)/high-band (HB) configuration for the dual-band dual-polarized base station antenna array design. The HB antennas are embedded in the opening sections of the loop radiating arms of the LB antennas. Clear and independent radiating environments are fulfilled by using two different types of reflectors (large planar reflector and back cavity). The mutual effects between the LB and HB antennas help to acquire good impedance matching and stable radiation patterns. Loop-like LB radiators work as directors in the HB, thereby effectively suppressing the side and back radiations of the HB antennas. Dual-function open slots are loaded on the ground stubs of the LB baluns, serving as impedance transformer in the LB but filtering structures in the HB. The experimental results validate that the proposed antenna array successfully covers bandwidths of 0.69–0.96 and 3.3–3.8 GHz (VSWR < 1.5) for 4G/5G applications. The port isolations are higher than 38 and 25 dB in the LB and HB, respectively. With the two independent radiating environments formed in the two bands, both LB and HB antennas exhibit stable unidirectional radiation patterns. The antenna gains and HPBWs are also satisfactory in both bands.

Design of Broadband Dual-Polarized Rectenna Array for WPT Applications

A broadband dual-polarized microstrip array antenna designed is proposed. To achieve wide 10 dB bandwidth for broadband operation, the technique of applying a ladder-shaped monopole antenna type with a rectangular slot insertion in the ground plane is implemented. The proposed design showed wide impedance bandwidth of the 1702-2755 MHz (47.2%). In addition, adding an open slot into the rectangular radiating element with an asymmetric ground plane was used and resulted in a slightly displacement of the radiation pattern. The 1 × 2 array type for two ladder-shaped patch array elements are arranged in symmetric feed network. By meticulously arrangement the two array antennas’ positions to achieved good ports isolation, with 10 dB bandwidth for the operating bands in free-space can be achieved. This antenna is used as a rectenna (rectifying antenna), which receives the RF energy of vertical and horizontal polarization wave in free space for 2.4 GHz wireless power transmission. The rectifier circuit setup using two zero biased rectifier and voltage doubler circuit. A matching network designed with small size chip components have a significant improvement in impedance matching and eliminate high order harmonics between the antenna and rectifying circuit. The proposed dual-polarized rectenna provided the RF-to-DC conversion efficiency as high as 78.8% when 14 dBm microwave power was received at 2.4 GHz with a 1 KΩ load.

Service Coordination to Address Maternal Mental Health, Partner Violence, and Substance Use: Findings from a National Survey of Home Visiting Programs.

Maternal risks such as poor mental health, partner violence, and substance misuse can undermine child health and development. Maternal and early childhood home visiting programs address these risks primarily through referral and coordination with community-based services, yet effects on these outcomes have been small. This study assessed the strengths of local home visiting sites' systems to support coordination of mental health, partner violence, and substance use services. Investigators recruited home visiting sites (N = 88) representing diverse models from a national practice-based research network, the Home Visiting Applied Research Collaborative (HARC). Web-based surveys assessed five implementation system supports for coordination and nine coordination activities drawn from the Measurement Framework for Coordination developed earlier in the project. Surveys also assessed seven coordination barriers identified in previous research. Sites varied in their implementation supports and coordination activities; on average, sites had stronger systems in place to support screening and referring families than to support linkage and follow-up. Implementation supports and activity scores were higher for mental health and partner violence than for substance use. Across all service needs, scores were highest for offering a referral and documenting the caregiver's agreement for exchange of information between providers. Scores were lowest for offering a warm handoff. Lack of open slots and lack of transportation were major barriers to successful coordination for all three services. Results suggest that home visiting coordination could be strengthened by focusing on infrastructure for linkage and follow-up with services in the broader system of care.

Analysis of Dual-Armature Flux Reversal Permanent Magnet Machines With Halbach Array Magnets

In this paper, a novel dual-armature (DA) flux reversal permanent magnet (PM) machine with halbach array magnets in the stator slot opening is proposed, which is abbreviated as DA-Halbach machine. Besides the stator armature windings, another set of windings is added in the rotor slots to further enhance torque performance via fully utilizing the rotor space. The influences of major geometric parameters on torque performance are investigated. Both DA-Halbach machine and conventional Halbach machine are optimized with the goal of maximum torque under the same copper loss using finite element (FE) method. The electromagnetic performance of two optimized machines are compared, the results show that the proposed DA-Halbach has larger torque and smaller torque ripple than conventional Halbach machine. When compared with surface-mounted PM machines, the proposed DA-Halbach machine still show better torque performance.

Partitioned Stator Hybrid Excitation Doubly Salient Machine With Slot Halbach PM Arrays

A new partitioned stator (PS) hybrid excitation (HE) machine with slot Halbach permanent magnet (PM) arrays is proposed in this paper. Due to the adoption of PS structure, its armature winding (AW) is located in the outer stator, and the PMs and the field winding (FW) are housed in the inner stator, thus the space utilization is significantly enhanced. The key difference of proposed machine is that Halbach PM arrays are employed in the inner stator slot openings, so that the parallel magnetic circuit between PM field and wound field is performed and the ratio of PM field short-circuited in the inner stator is effectively reduced. Thus a wider speed regulation region and a higher torque/power density can be achieved. Firstly, the configuration of proposed machine is described, based on which its operating principle is discussed. Then the electromagnetic performances are calculated and compared based on 2-dimensional finite element analysis (FEA). The results show that the torque can be improved by 76% with a similar magnetic field regulation ratio compared with an existing PS-HE machine with slot PMs. Finally, a prototype machine is built and tested to verify the analysis and FEA results.

Investigation into the Thermal Behavior and Loadability Characteristic of a YASA-AFPM Generator via an Improved 3-D Coupled Electromagnetic-Thermal Approach

The objective of this paper is to investigate the thermal behaviour and loadability characteristic of a yokeless and segmented armature axial-flux permanent-magnet (YASA-AFPM) generator, which uses an improved 3-D coupled electromagnetic-thermal approach. Firstly, a 1-kW YASA-AFPM generator is modelled and analysed by using the proposed approach; the transient and steady-state temperatures of different parts of the generator are determined. To improve the modelling accuracy, the information is exchanged between the thermal and electromagnetic models at each step of the co-simulation, considering both the accurate calculation of losses and the impacts of temperature rise on the temperature-dependent characteristics of the materials. Then, by using the proposed approach, the impact of the slot opening width and the turn number of stator segments on the generator loadability are investigated. After that, the experimental tests are performed. The results reveal the effectiveness and accuracy of the approach to predict the machine loadability and thermal behavior.

Optimal Design of A 12-Slot/10-Pole Six-Phase SPM Machine with Different Winding Layouts for Integrated On-Board EV Battery Charging

The transition to electric vehicles (EVs) has received global support as initiatives and legislation are introduced in support of a zero-emissions future envisaged for transportation. Integrated on-board battery chargers (OBCs), which exploit the EV drivetrain elements into the charging process, are considered an elegant solution to achieve this widespread adoption of EVs. Surface-mounted permanent-magnet (SPM) machines have emerged as plausible candidates for EV traction due to their nonsalient characteristics and ease of manufacturing. From an electric machine design perspective, parasitic torque ripple and core losses need to be minimized in integrated OBCs during both propulsion and charging modes. The optimal design of EV propulsion motors has been extensively presented in the literature; however, the performance of the optimal traction machine under the charging mode of operation for integrated OBCs has not received much attention in the literature thus far. This paper investigates the optimal design of a six-phase SPM machine employed in an integrated OBC with two possible winding layouts, namely, dual three-phase or asymmetrical six-phase winding arrangements. First, the sizing equation and optimized geometrical parameters of a six-phase 12-slot/10-pole fractional slot concentrated winding (FSCW)-based SPM machine are introduced. Then, variations in the output average torque, parasitic torque ripple, and parasitic core losses with the slot opening width and the PM width-to-pole pitch ratio are further investigated for the two proposed winding layouts under various operation modes. Eventually, the optimally designed machine is simulated using analytical magnetic equivalent circuit (MEC) models. The obtained results are validated using 2D finite element (FE) analysis.

Modulation behaviours and interchangeability of modulators for electrical machines

The authors aimed to investigate the modulation behaviours and the interchangeability of three kinds of modulators in electrical machines, which are short circuited coil, salient pole reluctance and flux barriers, to understand the evolution of the modulator and reveal their individual action mechanism based on the general airgap field modulation theory. The modulation behaviours are systematically analysed and compared, including the modulation principles of the improved short circuited coil, the relationship between salient pole reluctance and pole arc together with slot opening depth etc., based on which the key rule of interchangeable modulators is summarised. Although different modulators possess different magnetic field modulation principles and magnetic conversion capabilities, they share the similar asynchronous behaviours and modulated harmonics distribution. In addition, the detailed topological analysis of traditional brushless doubly fed machine with interchangeable and combined modulators is presented to show the effectiveness of the theoretical investigation. Electromagnetic performances comparison, such as airgap flux density distribution, cross coupling ability, general torque performances and inductance characteristics, of a brushless doubly fed machine with different modulators are provided to reveal the relation between the machine performances and magnetic field conversion capability. Theoretical predictions are verified by 2-D finite element analysis and experimental measurements.

Implementation of Embedded Magnetic Encoder for Rotor Position Detection Based on Arbitrary Phase-Shift Phase-Lock Loop

Rotor position is essential in control of permanent magnet synchronous motors (PMSMs). In terms of resolution, structural complexity, occupied volume, anti-interference ability, environmental adaptability, and cost, embedded magnetic encoder based on linear Halls owns strong competitiveness. When linear Hall sensors are selectively installed at stator slot openings in extremely compact scenario, signal phase-shift asymmetry between two or three Hall sensors is inevitable. Conventionally, prefilter synchronous reference frame-phase-locked loops exhibit excellent phase-lock ability at fixed frequency (50/60Hz), but become ill when frequency changes especially at zero frequency. In this article, a novel transformation matrix is derived to map the asymmetric phase-shift signals onto two-phase stationary coordinate system. Then, an arbitrary phase shift-phase-locked loop is formed by replacing <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Clark</i> transformation with the proposed transformation matrix, which can accurately extract rotor position and speed information in a simple and effective way, avoiding the utilization of complex notch filter. Simulations in continuous domain based on MATLAB and experiments in discrete domain based on an 18-slot/20-pole prototyped PMSM both confirm the effectiveness of the proposed method.

Leaving No Stone Unturned: Flexible Retrieval of Idiomatic Expressions from a Large Text Corpus

Idioms are multi-word expressions whose meaning cannot always be deduced from the literal meaning of constituent words. A key feature of idioms that is central to this paper is their peculiar mixture of fixedness and variability, which poses challenges for their retrieval from large corpora using traditional search approaches. These challenges hinder insights into idiom usage, affecting users who are conducting linguistic research as well as those involved in language education. To facilitate access to idiom examples taken from real-world contexts, we introduce an information retrieval system designed specifically for idioms. Given a search query that represents an idiom, typically in its canonical form, the system expands it automatically to account for the most common types of idiom variation including inflection, open slots, adjectival or adverbial modification and passivisation. As a by-product of query expansion, other types of idiom variation captured include derivation, compounding, negation, distribution across multiple clauses as well as other unforeseen types of variation. The system was implemented on top of Elasticsearch, an open-source, distributed, scalable, real-time search engine. Flexible retrieval of idioms is supported by a combination of linguistic pre-processing of the search queries, their translation into a set of query clauses written in a query language called Query DSL, and analysis, an indexing process that involves tokenisation and normalisation. Our system outperformed the phrase search in terms of recall and outperformed the keyword search in terms of precision. Out of the three, our approach was found to provide the best balance between precision and recall. By providing a fast and easy way of finding idioms in large corpora, our approach can facilitate further developments in fields such as linguistics, language education and natural language processing.

Affective stance in constructional idioms: A usage-based constructionist approach to Mandarin [yòu X yòu Y

The Mandarin Chinese [yòu X yòu Y] is a semi-formulaic construction with two open slots X and Y, which admit a range of lexical input. Existing studies of this constructional idiom are incomplete due to the lack of a theoretical commitment to construction-level form-function pairing on the one hand and limitations in empirical data to support putative structural constraints on the other hand. This study takes a usage-based constructionist approach and offers quantitative and qualitative analyses of both naturally occurring corpus data and elicited native speaker response data. Our corpus-based findings demonstrate that [yòu X yòu Y] as a constructional idiom is highly productive, admitting all three major lexical classes in its open slots with a preponderance of adjectives. Structural constraints on X and Y are subject to frequency of use and idiosyncrasies of lexical input. The compositional semantics of X and Y concentrates in the perceptual and evaluative domains of experience. Results from the response data demonstrate that [yòu X yòu Y] expresses personal affective stance (i.e. personal liking or disliking) toward the perceptual information specified in the X and Y slots. Native speakers are not only aware of, but are able to employ, this constructional meaning in affectively appropriate contexts when given options that differed in constructional pattern but not in core lexical input. Together, our findings point to the expression of personal affective stance as the constructional pragmatic function of [yòu X yòu Y] that is larger than the sum of the meanings of the components.

Analytical calculations of electromagnetic quantities for wound rotor salient-pole synchronous machines

PurposeThis paper aims to present an analytical electromagnetic model for wound rotor synchronous machines with a salient-pole rotor structure based on the two-dimensional subdomain technique.Design/methodology/approachThe machine is divided into five active sub-regions: stator slots, stator slot openings, air gap, rotor slots and rotor slot openings. For each sub-region, the governing partial differential equations are derived and solved analytically.FindingsThe magnetic flux density distributions in all active sub-regions are analytically computed and other quantities such as back-emf, inductances, electromagnetic torque and unbalanced magnetic forces are also analytically calculated. The results of the analytical model are compared to those obtained from the finite element analysis to show the accuracy of the proposed model.Originality/valueThe two-dimensional analytical model of a wound rotor salient-pole synchronous machine using the sub-domain technique is the main contribution of the research.