Search

This study's focus was to ascertain how teaching strategies and teacher motivation affected students' performance in integrated science in Ghana's Upper East. The researcher employed a survey design. Heads of senior high schools and teachers of integrated science constitute the study's population. Purposeful and straightforward random samplings were utilised to choose the respondents. 84 respondents made up the sample, comprising 80 integrated science teachers and 4 school heads. A structured questionnaire served as the primary tool, and the Statistical Package for Social Sciences was used to analyse the data (SPSS). The data analysis revealed that a large percentage of integrated science instructors (52.5%) thought that teacher motivation led them to perform in-depth study in order to teach effectively. Additionally, it was found that every integrated science instructor stated that skilled teachers employ effective teaching strategies to raise student achievement.

Purpose Acoustic noise is a crucial performance index in the design of electrical machines. Due to the challenges associated with modelling a complete motor, the stator is often used to estimate the sound power in the prototyping stage. While this approach greatly reduces lengthy simulations, the actual sound power of the motor may not be known. But, from the acoustic noise standpoint, not much is known about the correlation between the stator and complete motor. This paper, therefore, aims to use the sound pressure levels of the stator and the full motor to investigate the existence of correlations in the interior permanent magnet synchronous motor. Design/methodology/approach A multiphysics simulation framework is proposed to evaluate the sound pressure levels of multiple motor geometries in a given design space. Then, a statistical analysis is performed on the calculated sound pressure levels of each geometry over a selected speed range to compare the correlation strength between the stator and the full model. Findings It was established that the stator and the complete motor model are moderately correlated. As such, a reliance on the stator sound power for design and optimization routines could yield inaccurate results. Originality/value The main contribution involves the use of statistical tools to study the relationship between sound pressure levels associated with the stator geometry and the complete electric motor by increasing the motor sample size to capture subtle acoustic correlation trends in the design space of the interior permanent magnet synchronous motor.

The need for wideband metamaterial absorbers (WBMA) for applications other than sensing and filtering has demanded modifications to the conventional three-layer metal-insulator-metal (MIM) absorber configuration. This modification often results in complex geometries and an increased number of layers requiring complex lithographic processes for fabrication. Here, we show that a metamaterial absorber with rectangular geometry in the simple MIM configuration can provide wideband absorption covering the ultraviolet and near-infrared spectral range. Due to its asymmetric nature, the WBMA is sensitive to the polarization of the incident light and independent of the angle of incidence up to about 45° depending on the polarization of the incident light. The characteristics of the WBMA presented here may be useful for applications such as detectors for wide spectral band applications. publishedVersion

Design and optimization problems typically require running thousands of motor simulations which can take several hours, if not days. To overcome this bottleneck, surrogate models are often used in engineering design to expedite the process. When inverter-fed motor drives are involved, the cost of generating a finite element (FE) database from a pulsewidth modulated (PWM) current simulations to fit such models can be prohibitive. This article compares an ensemble of surrogate models of synchronous motors generated with sinusoidal and PWM stator excitations, in terms of computational burden and performance. The main contribution resides in showing whether computational resources can be saved with sinusoidal excitation models without compromising the optimization results of a real inverter-fed permanent magnet synchronous motor design.

Supplementary material

Additional file 1: Table S1. Ambient and rearing water conditions for each temperature regime. Table S2. Mortality in An. gambiae s.l. mosquitoes exposed to pyrethroids. Table S3. Median levels of metabolic enzymes in An. gambiae s.l. mosquitoes reared at different temperature regimes. Table S4. Pairwise comparisons of enzyme levels in An. gambiae s.l. mosquitoes reared at different temperature regimes. Table S5. Mann–Whitney U-test between mosquitoes that were not exposed and those exposed to pyrethroids.

Design and optimization problems typically require running thousands of motor simulations, which could take several hours if not days. Finding alternative means of reducing the solution time has recently gained research interest. Surrogate models can emulate the outputs of computer simulations with less computational effort. This article proposes the use of surrogate models to predict the acoustic noise, applied to an interior permanent-magnet synchronous motor (IPMSM). The simulation procedure involves using finite element analysis (FEA) to evaluate the acoustic performance across a design space of stator and rotor geometric variations. Then, four different classes of surrogate models are used to learn a portion of the design space before attempting to generalize and make predictions in a much larger space with relatively less computational burden. It is demonstrated that the trained models can be considered as appropriate replacements of the time-consuming FEA for future design and optimization problems of the same motor case study.

Purpose The design of electromagnetic systems for a variety of applications such as induction heating, electrical machines, actuators and transformers requires the solution of a multi-physics problem often involving thermal, structural and mechanical coupling to the electromagnetic system. This results in a complex analysis system embedded within an optimization process. The appearance of high-performance computing systems over the past few years has made coupled simulations feasible for the design engineer. When coupled with surrogate modelling techniques, it is possible to significantly reduce the wall clock time for generating a complete design while including the impact of the multi-physics performance on the device. Design/methodology/approach An architecture is proposed for linking multiple singe physics analysis tools through the material models and a controller which schedules the execution of the various software tools. The combination of tools is implemented on a series of computational nodes operating in parallel and creating a “super node” cluster within a collection of interconnected processors. Findings The proposed architecture and job scheduling system can allow a parallel exploration of the design space for a device. Originality/value The originality of the work derives from the organization of the parallel computing system into a series of “super nodes” and the creation of a materials database suitable for multi-physics interactions.

This paper investigates acoustic noise when an electric motor is fed with three-phase pulsewidth-modulated (PWM) currents with varying modulation indices. The procedure involves using a data-driven process to create a design space for different geometries of an interior permanent magnet synchronous motor. The motor structures are then analyzed using a finite-element analysis package to extract knowledge related to the sound pressure levels from the PWM excitation. It is demonstrated that sampling the air-gap space at a single time instant, which is a routine procedure in acoustic noise calculations, can result in an inaccurate estimation of the sound pressure levels, especially when the noise source is PWM motivated. Multiple-time sampling over the electrical period is proposed as a better approach for analyzing the sound pressure levels, irrespective of the type of supply current quality.

This paper investigates the effect of stator laminations on the acoustic noise field around the interior permanent magnet synchronous motor. The procedure involves filling the design space of a 4 pole 12 slot interior permanent magnet synchronous motor with multiple motor samples that are partitioned into two sets: the first set represents electric motors with laminated stator cores, while the other set comprises electric motors with non-laminated stator cores. Then, the sound pressure levels for both sets of designs are studied using finite element simulations and statistical analysis to better understand the effect of modeling the electrical steel laminations from the acoustic noise perspective.

This paper investigates the effects of temperature changes and the switching strategy of the inverter on the acoustic noise performance of the interior permanent magnet synchronous motor drive system. The proposed approach uses the finite element method to extract a library of knowledge related to the acoustic field of the electric motor under different operating conditions. The paper is sectionalized as follows: Section one introduces the importance of incorporating thermal models in acoustic noise studies by drawing motivation from the paucity of thermo-acoustic materials in the literature; Section two briefly describes how the CAD model is built and how the geometric database is generated from the parameterized model. It also points the reader to the design and simulation assumptions that have been formulated to support the proposed methodology; Section three discusses how the excitation currents are generated and applied to the finite element models to evaluate the multiphysics objectives for the study; finally, Section four presents the simulated results for all the investigated motor designs and provides a detailed discussion of the emerging trends associated with varying the operating temperature and the switching frequency of the inverter circuit.