Hasil untuk "Electricity and magnetism"

MENG Jingxin, WANG Yuanjun

In recent years, significant progress has been made in tractography of superficial white matter in the brain based on diffusion magnetic resonance imaging. Superficial white matter fiber tracts serve as critical pathways connecting cortical and subcortical structures, playing a vital role in the construction of complete human connectome and neuropathological studies. This paper first summarizes the development of superficial white matter tractography techniques. Subsequently, it evaluates the strengths and weaknesses of different methods employed in superficial white matter fiber tract segmentation. Afterwards, the construction process of superficial white matter fiber tract atlas is discussed. Finally, this review concludes with an outlook on future research direction of superficial white matter tractography technology and segmentation methods.

Pengfei LV, Yutao QIU, Sheng JIN et al.

To address the problems of complex testing, long construction period, and insufficient diagnostic testing results for numerous secondary devices in smart substations, this paper introduces the forward maximum matching (FMM) algorithm to achieve automatic protection testing, and improves the support vector machines (SVM) model based on the frog leaping algorithm (FLA) to complete the verification and diagnosis of test results. For the protection configuration and information relationship of intelligent stations, propose an architecture for protecting automatic testing and diagnosis systems; By analyzing different protection principles and the relationship between applied voltage/current and setpoints, establish protection testing requirements, construct a set of testing templates, compare similarity using hash and edit distance algorithms, and FMM algorithm was used to achieve automatic testing of the device under test. The effectiveness of the proposed technology was verified through case analysis and engineering examples.

Kaifa ZHAO, Hu SONG, Rong LIU et al.

To address the ineffectiveness of single-base radar in suppressing adjoint main-lobe interference, an equivalent large-aperture array can be designed by deploying sparse auxiliary arrays to separate main-lobe interference from targets in the spatial domain. However, this method is prone to generating spatial grating lobes. To overcome this problem, this study proposes a dual-parameter iterative optimization framework comprising two parts: array configuration optimization and subarray element number optimization. Array configuration optimization caters to the number of subarray elements and creates nulls in the main-lobe interference direction on the basis of the minimum variance distortionless response criterion. To suppress grating lobes of the beam an improved adaptive genetic particle swarm algorithm is used to optimize the array configuration under constraints, such as aperture size, minimum subarray spacing, and null depth in the main-lobe interference direction. Subarray element number optimization uses the above-mentioned algorithm to optimize the number of subarray elements under constraints, such as a limited number of subarray elements and null depth in the main-lobe interference direction, further suppressing beam grating lobes. Finally, numerical simulations confirmed the effectiveness of the dual-parameter iterative optimization framework for array configuration and element number under the same parameter conditions. Additionally, this study explores the performance boundaries of main-lobe interference suppression and grating lobe suppression for typical distributed mobile platform cooperative detection scenarios.

Hai QIN, Sheng CHEN, Honglue ZHANG et al.

The existing equivalent methods for reactive power regulation capacity of grid-connected photovoltaic(PV) plant do not take into account the voltage security constraints in the plant and the impacts of random fluctuations of grid-connected voltage and photovoltaic output, which makes it hard to meet the requirements of actual engineering. For this reason, a time-based equivalent method for reactive power regulation capacity of grid-connected PV plant is proposed, which can provide an effective decision-making basis for actual engineering management. Firstly, under the given gate voltage and PV output, and with consideration of the static var generator within the PV plant, the reactive power regulation capacity of the PV unit and the upper & lower limits of the reactive power regulation range, an optimal equivalent method for maximum gate reactive power regulation capacity of PV plant is proposed to determine the relationship between the gate reactive power regulation capacity of the PV plant and its active output and gate voltage. Secondly, considering the time period characteristics of the gate voltage and PV output fluctuations, the time-based equivalent scheme for reactive power regulation capacity of PV station is realized through the time period fusion strategy for fluctuation thresholds of similar days. Finally, the simulation analysis of an actual PV plant verified the effectiveness of the proposed method.

Yong Heng Zhao, Yin Li, Li Jun Jiang et al.

Abstract A novel broadband dual‐polarised transmitarray antenna (TA) utilising tightly coupled cross dipole cells is proposed in this work. The transmitarray cell using the tightly coupling wideband principle comprises two radiation patches designed as two orthogonal planar dipoles with four interdigital capacitors, two meandered parallel plate transmission lines, and a ground. Each cell has a square shape and a dimension of approximately 0.28 λc where λc is the wavelength at central frequency 5.5 GHz. The transmitarray cell can achieve 475° phase shift at central frequency and transmission magnitude better than −2.5 dB within the working band. To verify the feasibility of this design, a tightly coupled dual‐polarised transmitarray antenna (TCDPTA) is modelled and manufactured. The transmitarray aperture size is approximately 4.1 λc × 4.1 λc. The simulation and measurement illustrate that the TCDPTA has stable and distortion‐free main beams whose side lobe levels are generally below −10 dB in the band of 3.0–8.0 GHz. The measured gain at central frequency is 16.2 dBi and peak gain is 19 dBi at 7.5 GHz. The working bandwidth is 90.9% and 3 dB gain bandwidth is 66.7%. The measured cross‐polarisation levels are below −15 dB at axial direction. This TA has potential applications for high‐date‐rate communication and high‐revolution radar imaging systems at C‐band.

Li FENG, Lianmei ZHANG, Jiajia WEI et al.

At present, the research on economic evaluation of offshore wind power (OWP) is poor, while OWP urgently needs economic evaluation as the basis for its large-scale application. Based on the economy of OWP projects, this article firstly reviews the composition and development of offshore wind farms and analyzes 3 types and 6 development models of current OWP projects. Then the whole life cycle of OWP projects are divided into 3 stages, including initial investment, operation maintenance and retirement recovery, and the cost of each stage is analyzed and its respective mathematical model is established. Then, 6 economic indicators such as NPV are introduced to evaluate an OWP project for case study. Finally, the current progress and research deficiencies of OWP projects are summed up, which can provide a direction for future research and a support and reference for the more economical development of OWP.

Yanru WANG, Xiyang YIN, Qinghai OU et al.

With the rapid development of 5G technology, the large-scale application of 5G base stations with high energy consumption increases the operation costs of base stations and exacerbates problems such as the supply-demand imbalance in the distribution network. To this end, this paper analyzes the regulation potential of 5G base stations based on their energy consumption characteristics and constructs the energy sharing model among base stations and the energy trading model between base stations and distribution network by combining the dynamic changes of energy consumption and photovoltaic output of 5G base stations. Then, with the optimization objectives of promoting energy sharing of 5G base stations, improving operation efficiency of base stations, and participating in peak shaving and valley filling, the optimization problem of energy storage regulation of base stations in a 5G integrated distribution network is constructed, and an energy storage regulation algorithm of 5G base stations based on energy sharing and trading coordination is proposed. Finally, simulation results show that the proposed algorithm can improve the operation efficiency of base stations, promote peak shaving and valley filling in the distribution network, and effectively consume photovoltaic output.

S. A. Mohassieb, E. G. Ouf, K. F. A. Hussein et al.

In this work, a super wide band antenna is proposed to operate in the frequency band 2.3-23 GHz. The antenna has two planar arms with a modified diamond shape printed on the opposite faces of three-layer dielectric substrate. Each arm of the antenna is capacitively coupled to circular sector near its end to increase the impedance matching bandwidth. The dielectric substrate is customized to fit the shape of the antenna arms and the parasitic elements to reduce the dielectric loss. The substrate material is composed of three layers. The upper and lower layers are Rogers RO3003TM of 0.13 mm thickness and the middle layer is made of paper of 2.3 dielectric constant and 2.7 mm thickness. The antenna is fed through a wide band impedance matching balun. The antenna design stages are performed through electromagnetic simulations concerned with the parametric study to get the optimum antenna dimensions to numerically investigate the role of the parasitic element to enhance the antenna performance. A prototype of the proposed antenna is fabricated to validate the simulation results. The experimental measurements come in good agreement with the simulation results and both of them show that the antenna operates efficiently over the frequency band 2.3-23 GHz with minimum radiation efficiency of 97% and maximum gain of 5.2 dBi. The antenna has bandwidth to dimension ratio (BDR) of 1360.

Yingchun Xiao, Yang Yang, Feng Zhu

To separate electromagnetic interference sources with an unknown source number, a new separation method is proposed, which includes five key steps: spatial spectrum estimation, source number and direction-of-arrival estimation, mixed matrix estimation, separation matrix estimation, and source signal recovery. A pseudospatial spectrum estimation network based on a convolutional neural network is proposed to estimate the number of electromagnetic radiation sources, their direction of arrival, and the mixing matrix. A new loss function is designed as an optimization criterion for estimating the separation matrix. To ensure generalization, both simulated and measured datasets are used to train the proposed network. Experimental results demonstrate that the proposed separation method outperforms existing source separation techniques in terms of correlation coefficient, root mean square error, and running time. Importantly, it exhibits strong performance in underdetermined cases, as well as in overdetermined or determined cases.

Sungsik Wang, Doyoung Jang, Youngwan Kim et al.

This article proposes the S/X band dual-loop shared-aperture 2 × 2 array antenna, which is constructed using a unit-cell having one S-band element stacked on 3 × 3 X-band elements. The unit-cell employs a coupled-fed dual-loop structure with a direct-feed pin on the upper loop to obtain the broadband matching characteristics and low manufacturing error. This radar configuration has the advantages of easy installation and low cost. In addition, the thin loop structure of the upper layer S-band element is optimized so that the S-band element has electromagnetic (EM) transparent characteristics in the X-band. The extended via cavity wall is also applied outside the nine X-band elements to block the mutual coupling effect among the X-band elements. To confirm the feasibility of the proposed array antenna, the beamforming performance and active reflection coefficient (ARC) characteristics of the fabricated array are examined in the S/X band.

Guiting Dong, Jianlin Huang, Simin Lin et al.

In this paper, a dual-band multiple-input-multiple-output (MIMO) antenna is proposed for fifth-generation (5G) wireless communication terminals. The measured −10 dB impedance bandwidths of 380 MHz (3.34–3.72 GHz) and 560 MHz (4.57–5.13 GHz) can cover the 3.4–3.6 GHz and 4.8–5 GHz 5G bands. The single antenna element of this proposed MIMO is composed of an F-shaped feed strip and an inverted L-shaped radiation strip. A defected ground structure is employed to obtain a good isolation performance, whereby the measured isolation between the antenna elements is observed to be larger than 23 dB. The measured total radiation efficiencies at 3.5 GHz and 4.9 GHz are 76.65% and 71.93%, respectively. Besides, the calculated envelope correlation coefficients (ECC) are less than 0.00125 and 0.01164 at the low-frequency and high-frequency bands, respectively. Furthermore, the specific absorption ratio (SAR) analysis of the antenna verifies that it qualifies for 5G terminals.

Meng QI, Lijia HUANG, Xiaolan QIU et al.

To a certain extent, SAR images are affected by range ambiguity due to antenna sidelobe characteristics and pulse operating system. The work of range ambiguity suppression focuses on SAR system design and signal processing. One type of idea tries to modify the way of transmitting and receiving to block the receiving of the ambiguous energy, such as multiple elevation beams and azimuth phase coding. The other ideas are algorithms that use signal processing technology to reduce the distance ambiguity energy in echo and image domains. This paper proposes a range ambiguity suppression method that combines sparse reconstruction and matched filtering. The method performs the sparse reconstruction of the ambiguity area, estimates the ambiguity area signal using the ambiguity area image and reconstruction matrix, separates it from the echo signal to obtain the primary image signal after range ambiguity suppression, and uses matched filtering to obtain the main area image. In this method, sparse reconstruction ensures the accuracy of fuzzy signal estimation, and matched filtering ensures the efficiency of imaging processing. Simulation results show that the proposed method can effectively suppress range ambiguity, with a suppression effect of 10 dB or higher, and it has a good ability to maintain the weak targets and the details of the main image.

Chaoxian Qi, David R. Jackson, Yong Wei et al.

Abstract A near‐field planar sensor fabricated from a substrate integrated waveguide (SIW) cavity resonator is presented. The SIW cavity resonator is a modification of a rectangular microstrip antenna. The rectangular microstrip antenna radiates from two radiating edges that produce far‐field radiation, which is undesired for near‐field sensing. To suppress the radiation from the edges, the microstrip antenna is modified to have conducting vias that short all four edges of the patch to the ground plane. A circular hole is placed on the patch surface in the middle of the patch to form a sensing aperture. The field is thus confined inside the cavity with leakage only allowed through a small aperture, which is used for sensing surrounding objects in the vicinity of the aperture. This cavity resonator operates in the TM21 mode of the SIW cavity. Full‐wave simulations are performed and the results are consistent with the theoretical analysis as well as CAD formulas that are derived. The performance of the sensor as a near‐field sensing device and as a near‐field imager is explored.

Eder Hernandez, Esmeralda Campos, Pablo Barniol et al.

The research in electricity and magnetism has commonly focused on problem-solving abilities and the application of physical principles. Several studies have found that some concepts represent a challenge for undergraduate students, such as Gauss's and Ampere's laws. The inability to identify and analyze the symmetry of field and field source distributions and focus on the surface features of these electricity and magnetism systems are two of the main difficulties associated with these laws. We present this study with a different perspective of observing 322 introductory electricity and magnetism students' understanding of these laws with unconventional shapes for the field sources' enclosing objects. We use a phenomenographic approach to detect difficulties and compare the two contexts. Our main findings suggest that some students make an incomplete or incorrect analysis of the situation when referring to its surface features. The confusions between flux and field in the electric context or between circulation and field in the magnetic context persist. Finally, we present recommendations for teachers to approach these difficulties.

Maricel G. Dayaday, Jordan-James S. Olivo

This paper presents the potential of an electromagnetic transducer device in a form of audio speaker that is used to capture sound waves to be converted into electricity. It is an interesting concept but less explored by researchers. The objective of the study is to measure the potential of electromagnetic transducer as a way to generate electricity. It deals with the creation of electricity through movement and magnetism. Sound waves can induce movement on the surface which in turn moves the transducer thus creating electricity. The source of sound was coming from an 8-inch subwoofer speaker with a frequency of 80 Hz that was held constant throughout the experiment. Furthermore, using simple linear regression analysis, the study showed that for every linear increase of sound intensity level and distance of the source, there is an exponential increase and an exponential decrease in the voltage root mean square (RMS) respectively. The functionality assessment of the device was statistically analyzed using completely randomized design. It was found that the energy level significantly increased as the sound intensity level increases given a fixed distance of 15 mm from the source. The device could generate enough energy to power small electronics such as light emitting diodes (LED), transistor and resistor.

Qing Liu, Qikun Liu, Jianbin Li et al.

Abstract This paper proposes three balanced multiple‐layer dual‐mode substrate integrated waveguide (SIW) bandpass filters. The first balanced filter has two substrate layers, and two pairs of balanced feeding ports are located on the upper substrate layer. The lower and upper dual‐mode SIW cavities are coupled by two crossed slots in the middle metal layer. The second balanced filter has two substrate layers, and two pairs of balanced feeding ports locate parallelly on the upper and lower substrate layers, respectively. The third balanced filter has three substrate layers, and two pairs of balanced feeding ports locate vertically on the upper and lower substrate layers, respectively. The proposed three balanced filters can produce three, two and one finite‐transmission zeros (FTZs), respectively. Characteristics of the proposed multiple‐layer SIW filters with controllable FTZs' locations are analysed in detail. For the demonstration, some design examples with the centre frequency of 7.5 GHz and bandwidth of 240 MHz are presented, and three design examples are fabricated to verify the performance of the proposed balanced filters. The measured results agree well with simulated ones.

Yongchul Jung, Seunghyeok Lee, Seongjoo Lee et al.

A pre-processing technique is proposed to reduce the complexity of two-dimensional multiple signal classification (2D-MUSIC) for the joint range and angle estimation of frequency-modulated continuous-wave (FMCW) radar systems. By using the central symmetry of the angle steering vector from a uniform linear array (ULA) antenna and the linearity of the beat signal in the FMCW radar, this pre-processing technique transforms 2D-MUSIC from complex values into real values. To compare the computational complexity of the proposed algorithm with the conventional 2D-MUSIC, we measured the CPU processing time for various numbers of snapshots, and the evaluation results indicated that the 2D-MUSIC with the proposed pre-processing technique is approximately three times faster than the conventional 2D-MUSIC.

Jared Carpendale, A. Hume

A global shortage of qualified physics teachers requires some teachers to teach physics out-of-field (OOF). A concern for OOF physics teaching is that without appropriate physics content knowledge (CK), these teachers tend to focus on rote learning and may find it difficult to support students who require additional assistance or extension; they tend to teach in ways that do not foster conceptual understanding. This paper reports on research that investigated how content representations (CoRes) could be used to support OOF physics teachers’ knowledge for teaching electricity and magnetism. CoRes were used to elicit discussions between OOF and in-field physics teachers about important teaching and learning considerations (e.g. appropriate CK for students and appropriate instructional strategies for promoting conceptual understanding). Prior to engaging with CoRes, three OOF teachers were interviewed about teaching electricity and magnetism and their lessons during this topic were video recorded. Later, as these OOF teachers worked with their in-field colleagues using the CoRe framework, all discussions were audio recorded. To explore changes to the OOF teachers’ knowledge and practice from the CoRe process, they were interviewed and their follow-up electricity and magnetism lessons (for a different class) were video recorded. Findings showed that the CoRe processstimulated important discussions about teaching electricity and magnetism and considerations for students learning this topic. As a result, the OOF teachers developed their professional knowledge, including refinement of their CK, acquirement of new topic-specific instructional strategies, and more awareness of students’ understanding during lessons. This study concludes that CoRes are an effective strategy for supporting the professional learning of OOF physics teachers.

M. Cruz, A. Tolentino, L. Roleda

This study aimed at exploring the effects of gamification on the motivation of freshmen engineering students in Physics. Physics for Engineers 2, a course focused on the fundamentals of electricity and magnetism, was gamified by incorporating elements like experience (XP) points, badges, leaderboards and replayable quests. To determine if gamification has significant effect on students' motivation, the responses of the students in the Physics Motivation Questionnaire administered before and after the implementation were analyzed using the Wilcoxon Signed Rank test. Results showed that gamified instruction brought about a significant increase in all the five components of student motivation in Physics, namely: intrinsic motivation, self-efficacy, grade motivation, career motivation and self-determination. For corroboration, the qualitative data gathered from students' weekly journal entries and interview transcripts were coded to determine their perspectives and feedback on their experience of gamified instruction. Analysis of the themes revealed that students find gamified instruction to be enjoyable and exciting, highly-motivating and challenging. The replayability feature prompted them to think critically and persevere in pursuit of achieving perfect scores in the quest and make it weekly on the leaderboard. Since the structure allows them to be constantly aware of their standing in class, they can monitor their progress, identify their weaknesses and do the necessary actions to improve their performance. In summary, the freshmen engineering students had a positive experience in gamified Physics instruction.

Changhao WANG, Yang LIU, Lixiong XU

Considering the influence of uncertainties of wind power outputs and load on the operation of microgrid, a two-stage robust stochastic scheduling model is established for CCHP microgrid with multi-type distributed generations after distinguishing the characteristics of uncertain sources and loads. Although the current accuracy of wind power prediction is low, its fluctuation range is easy to measure, so a robust optimization method is applied; the load forecasting accuracy is high and has certain regularity, and then a stochastic optimization method is applied. Firstly, multiple load scenarios are formed by random sampling, then several typical load scenarios are obtained by reducing them. Next a day-ahead scheduling scheme is formulated with the goal of minimizing the weighted average of the scheduling cost of each scenario, in which a two-stage robust optimization method is used to solve the scheme. Considering the phenomenon of wind abandonment in actual production, penalty cost is introduced to increase wind power absorption. Simulation results show the rationality and economy of the proposed scheduling method.