The known multiferroics (MFs)-ternary oxides with perovskite-type structure [Formula: see text] that undergo successive phase transitions (PTs), ferroelectric (FE) or antiferroelectric (AFE) — at the Curie temperature, [Formula: see text], and ferromagnetic (FM), antiferromagnetic (AFM) or ferrimagnetic at the Néel temperature, [Formula: see text] —and classical FEs and AFEs are considered. The dependences of the [Formula: see text], [Formula: see text] on the interatomic bond A–O strains in their perovskite structures have been constructed. On constructed dependencies, some ternary MFs are discovered, which have comparatively high temperatures of first FE or AFE and second magnetic PTs but their difference [Formula: see text]–[Formula: see text] values are high comparatively with the binary MFs.
This paper presents a CMOS low-noise amplifier (LNA) for wideband applications that require high linearity. A frequency staggering technique is employed to achieve a flat gain response over a wide frequency band. In the first stage, the LNA uses a common-source topology with resistive feedback to achieve wideband input matching, while inductive series peaking is adopted at the output to attain gain peaking at a high frequency. In the second stage, an inductive load with high inductance is employed to ensure low-frequency gain and high linearity. Furthermore, the bias condition of the transistors is optimized by considering the trade-off between linearity and DC power consumption. The proposed LNA achieved a measured peak gain of 10.5 dB at 18 GHz and a wide 3-dB bandwidth ranging from 6.1 to 41.5 GHz. The third-order intercept point exceeded 1.3 dBm, and the input matching remained below −8 dB over the entire 3-dB bandwidth. Furthermore, the noise figure ranged from 4.7 to 7.3 dB up to 26.5 GHz.
Electrical engineering. Electronics. Nuclear engineering, Electricity and magnetism
Brain age has become an important analysis object in the diagnosis and mechanism research of neurodegenerative diseases. There is no consistent conclusion on whether major depression increases the brain age of patients, and few studies in this direction have been conducted in the Chinese population. In this paper, a REST-meta-MDD (resting-state functional magnetic resonance imaging dataset of major depressive disorder) dataset collected from 25 hospitals in China was used to construct a convolutional neural network model based on high-resolution T1-weighted three-dimensional magnetic resonance images of brain structures to predict the brain age of patients and calculate the difference from the actual age. The mean absolute error and correlation coefficients of the final results were 3.16 and 0.93, and the mean brain age of the patients with major depression increased by 3.94 years compared with the healthy group, further confirming that major depression accelerates brain aging, and the severity of the disease is related to the gender, age, and education of the patients. Compared with the traditional machine learning algorithms, the average absolute error of the results obtained by this model is smaller and the correlation coefficient is higher.
Abstract The authors investigated the ingredient detection technique of silicone rubber based on the Terahertz spectrum. For this purpose, 18 diverse high‐temperature vulcanised silicone rubber (HTVSR) formulations were customised, 8 of which are used as calibration set while the rest 10 as prediction set. Based on the Beer‐Lambert Law, the partial‐least‐square (PLS) regression model and the least‐squares support‐vector machines (LS‐SVM) regression model were used to yield the relationships between the absorption spectrums and the content percentages of polydimethylsiloxane (PDMS), alumina trihydrate (ATH), and silica in HTVSR. The results showed that for the formulations tested, the prediction accuracy of all three main ingredients by the PLS regression model could be improved by changing the spectrum range from 0.2–4 to 0.5–2 THz. If the data were pre‐processed by the Savitzky–Golay smoothing method or multiplicative scatter correction method, the prediction accuracy of PDMS could be further enhanced. However, this would lead to a slight decrease in the prediction accuracy of ATH. For the LS‐SVM regression model, the radial basis function (RBF) kernel and the linear kernel were studied. It was found that the prediction accuracy of both kernels was better than that of the PLS regression model. With the LS‐SVM regression model using the RBF kernel, the correlated coefficients of PDMS and ATH in the prediction set could be up to 0.9915 and 0.9742, respectively.
Piezoelectric materials are commonly used in transducers to convert electromechanical signals due to their energy conversion characteristics. We designed a PIMNT/epoxy 2–2 composite to take full advantage of the excellent beam-mode piezoelectric and acoustic features of PIMNT single crystals. Following the approach used for piezoelectric ceramic composites, we selected PIMNT piezoelectric single crystal and EPO-TEK301-2 epoxy resin for the composite, and combined finite element analysis with experimental preparation. We prepared, tested and analyzed 2–2 piezoelectric single crystal composites with varying volume fractions, which showed high electromechanical coupling properties ([Formula: see text]%) and low acoustic impedance ([Formula: see text][Formula: see text]MRayl). These encouraging findings suggest the possibility of devising high-performance ultrasonic transducers utilizing the PIMNT/epoxy 2–2 composite.
Ruize Ma, Nikita V. Tepliakov, Arash A. Mostofi
et al.
Atomically thin crystals hosting flat electronic bands have been recently identified as a rich playground for exploring and engineering strongly correlated phases. Yet, their variety remains limited, primarily to two-dimensional moiré superlattices. Here, we predict the formation of reversible, electrically-induced ultra-flat bands and $π$-electron magnetism in one-dimensional chevron graphene nanoribbons. Our $ab$ $initio$ calculations show that the application of a transverse electric field to these nanoribbons generates a pair of isolated, nearly perfectly flat bands with widths of approximately 1 meV around the Fermi level. Upon charge doping, these flat bands undergo a Stoner-like electronic instability, resulting in the spontaneous emergence of local magnetic moments at the edges of the otherwise non-magnetic nanoribbon, akin to a one-dimensional spin-$\frac{1}{2}$ chain. Our findings expand the class of carbon-based nanostructures exhibiting flat bands and establish a novel route for inducing correlated electronic phases in chevron graphene nanoribbons.
This paper presents the transformation of four Maxwell’s equation into relativistic electromagnetism via the partial differential equation of electric and magnetic field with respect to spatial and temporal coordinates. The relativistic form of magnetic field is developed based on Gauss’s law for magnetism and Ampere’s law while the relativistic form of electric field is developed based on Gauss’s law for electricity and Faraday’s law, where and are rest magnetic and electric field. We can easily explain theoretically about the various properties of electromagnetic waves (EM waves) with help of this relativistic formula such as; 1) Why EM waves are not deflected by electric and magnetic field as they have both oscillating electric and magnetic field? ;2) why can’t light travel faster than the speed of light? In this highly interesting topic, the particular purpose is not to enter into the merits of existing theory of relativistic electromagnetism, but rather to present a succinct and carefully reasoned account of new aspect of Maxwell’s equation which properly describe the relativistic nature of magnetic and electric Field.
Abstract A broadband dual‐polarised reconfigurable frequency selective surface (RFSS) based on general dual‐branch parallel circuit model is proposed by the authors. The specific circuit model is constructed to feature the switchable functions of transmission and reflection characteristics by introducing a parallel branch. It is beneficial to clarify the operating mechanism and provide an effective guidance to satisfy the switching bandwidth requirements of the desired RFSS. In order to validate the proposed concept of the dual‐branch parallel circuit model, a broadband dual‐polarised RFSS prototype has been designed, fabricated and measured. A satisfactory agreement can be reached between the synthesis, simulation and measurement. The experimental results exhibit the merits of low insertion loss, broad switching bandwidth and good angular stability for different polarisation and different incident angles.
Researchers have expressed concern about the state of STEM education. To improve this situation, new pedagogies, such as blended learning, have been proposed and tested. The last decade has seen an increase in the use of blended learning to support learning; however, the effect of blended learning on learning remains unclear and often mixed. The two studies in this paper draw on data from pre-university science students in the following courses: (1) Electricity and Magnetism (E&M) and (2) Waves, Optics & Modern Physics (Waves). In study 1, the treatment group (blended learning coupled with two-stage quizzes & peer formative feedback) performed significantly higher than the control group (lecture format with online homework & instant feedback) in the standardized final exam. In contrast, in study 2, there was a non-significant main effect of groups, indicating that the treatment group (blended learning with online homework & instant feedback) and the control group (lecture format with online homework & instant feedback) performed similarly in the standardized final exam. The finding of study 1 suggests that the effect of an instructional pedagogical framework embedded in a blended learning context improves performance in STEM education. Whereas the finding of study 2 suggests that a blended learning context without incorporating any instructional framework or support for cognition other than the lecture is comparable to a traditional face-to-face course.
The interplay among magnetization and deformation of solids has long been an important issue in magnetism, the elucidation of which has made great progress in material physics. Controlling volume and shapes of matter is now indispensable to realizing various actuators for precision machinery and nanotechnology. Here, we show that the volume of a solid can be manipulated by injecting a spin current: a spin current volume effect (SVE). By using a magnet Tb0.3Dy0.7Fe2 exhibiting strong spin-lattice coupling, we demonstrate that the sample volume changes in response to a spin current injected by spin Hall effects. Theoretical calculation reflecting spin-current induced modulation of magnetization fluctuation well reproduces the experimental results. The SVE expands the scope of spintronics into making mechanical drivers. Manipulation of sample volume by spin current could lead to spintronics-based mechanical devices, such as actuators operating without electricity. Here, the authors report that the thickness of thin films of the ferromagnetic material Tb0.3Dy0.7Fe2 changes in response to a spin current injected by means of spin Hall effects.
In order to improve the energy efficiency level of park customers, it is necessary to evaluate the energy efficiency level of customers to find out the weak links of energy consumption before energy efficiency optimization. Considering the logical dynamic relationship between energy efficiency indicators, the dynamic energy efficiency index system is constructed by selecting evaluation indexes from three dimensions based on PSR model. Combining principal component analysis and correlation analysis, the index system is optimized and redundant indexes are eliminated. An improved Grey TOPSIS energy efficiency evaluation model is constructed where entropy weight method is introduced to calculate the objective weight of indexes. The weighted grey correlation degree is used to replace the Euclidean distance as the distance measurement to evaluate the customers energy efficiency level, and the energy consumption status is analyzed from three dimensions. Finally, the energy efficiency level of 10 typical park customers is evaluated. The result shows that the comprehensive energy efficiency evaluation results of customers with good response performance are higher, which verifies the feasibility of PSR index system. Compared with the results of other methods, the effectiveness of the evaluation model is verified.
Electricity, Production of electric energy or power. Powerplants. Central stations
Different types of oriented silicon steels exhibit different magnetic properties in complicated power electronic equipment operating conditions. For the sake of accurate selection of oriented silicon steel type, the magnetic characteristics of 0.10 mm ultra-thin oriented silicon steel and 0.23 mm ordinary thickness oriented silicon steel were measured under different operating conditions based on the medium frequency Epstein Frame. The magnetic characteristics of two types of oriented silicon steels are revealed. According to the performance under different frequency sinusoidal magnetization, PWM pulse magnetization and special pulse magnetization conditions, the selection suggestions of oriented silicon steel under different operating conditions are given, which provides data support for the design of power electronic equipment.
Electricity, Production of electric energy or power. Powerplants. Central stations
In this paper, different arrangements of infinite arrays of nonlinearly loaded antennas are analyzed in the frequency domain by an efficient approximate method and compared with the exact one which are respectively based on the nonlinear current and harmonic balance techniques. In one hand, although the exact method is suitable for strongly nonlinear load, it is suffering from gradient operation and initial guess in the iteration process especially under multi-tone excitations. On the other hand, although the approximate method is very efficient, it is limited to weakly nonlinear loads and low-valued incident waves. Finally, acceptable ranges for application of the approximate method versus different parameters such as nonlinearity effect of the load and the magnitude of incident wave are extracted.
This study focuses on the use of Partnership Comprehensive Literacy (PCL) as a reading strategy to support reading in science and to explore the level of students’ Scientific argument. Partnership Comprehensive Literacy consist of 4 components that address the topic of the reading activity: the statements of the content, what I think, what the texts say, and evidence of the text. This study uses a mix method to identify and improve students’ scientific argumentation skills. The instrument used is a set of questions about electricity and magnetism. In addition, the argument level rubric instrument that contains argument components is used to analyse the level of students’ scientific arguments. The participants of this study were 40 college students consisting of 25 females and 15 males in the department of physics education taking a course in the fundamental of physics. The findings revealed that the students’ level argument was dominated by the use of Claim-Reasoning-Evidence (CRE). In addition, students evaluated that the use of PCL in reading activity as being challenging but an interesting process because they have to find the evidence in the texts to support their statements of what I think.
Mahmoud Al Ahmad, Saifudeen Kabeer, Ala Abu Sanad
et al.
Abstract A single‐varactor frequency‐reconfigurable microstrip patch antenna is presented. The antenna comprises a symmetrical arrangement of four metallised patches coupled and interconnected via slots and metallic bars, respectively. The antenna structure is excited through a single feed probe connected to one of the patches. To achieve a compact size of 22 × 21 × 1.57 mm, a shorting pin is placed close to the feed point to pull down the antenna's resonant frequency. By adding a varactor diode at the centre of the patch, frequency reconfigurability is introduced. Variation in the varactor's DC reverse bias voltage from 0 to 7.5 V results in a corresponding resonant frequency shift from 1000 to 1150 MHz, thus providing a tuning range of 15%. The proposed design is compact and achieves frequency reconfiguration with a single‐varactor diode and a low bias voltage requirement compared with the design characteristics reported in existing works. The antenna can find application in various existing and emerging communication systems.
A feature of the "modern theory" is that electric polarization is not well-defined in a metallic ground state. A different approach invokes the general existence of a complete set of exponentially localized Wannier functions, with respect to which general definitions of microscopic electronic polarization and magnetization fields, and free charge and current densities are always admitted. These definitions assume no particular initial electronic state of the crystal, and the set of microscopic fields satisfy the usual relations of classical electrodynamics. Notably, when applied to a trivial insulator initially occupying its $T=0$ ground state, the expressions for the unperturbed polarization and orbital magnetization, and for the orbital magnetoelectric polarizability tensor obtained from these different approaches can agree. However, the "modern theory of magnetization" has been extended via thermodynamic arguments to include metals and Chern insulators. We here compare with that generalization and find disagreement; the manner in which the expressions differ elucidates the distinct philosophies of these approaches. Our approach leads to the usual electrical conductivity tensor in the long-wavelength limit; in the absence of any scattering mechanisms, the dc divergence of that tensor is due to the free current density and the finite-frequency generalization of the anomalous Hall contribution arises from a combination of bound and free current densities. As well, in the limit that the electronic ground state is that of a trivial insulator, our expressions reduce to those expected for the unperturbed polarization and magnetization, and the electric susceptibility.
Arduino microcontrollers are becoming increasingly popular in the physics/astronomy community. These devices can provide more in-depth labs on mechanics, electricity and magnetism, light and optics, etc., in addition to programming. These devices can be readily utilized to reach more non-physics/astronomy majors and underrepresented STEM students. The hands-on approach facilitates the learning of physics concepts and their applications in everyday life. This paper describes how Arduino Uno microcontrollers were used as an extra credit exercise to create interest in physics and to understand some basic physics concepts. The idea was experimented in an algebra-based undergraduate physics course at a four-year college. In the various phases of this exercise, students moved from replication of known projects to simple yet interesting applications. The activity was kept optional due to resource limitations, namely instructor time, availability of a sufficiently large lab to accommodate all students of a class at the same time or more than one time, and lack of enough support staff. For the same reasons, this was the only extra credit activity offered to students. The results presented in this paper reflect the activity spread over a few semesters. An anonymous survey was conducted at the end of the activity for student feedback. The survey and comments of some students are included at the end.
This study explored teachers’ experiences in the teaching of electricity and magnetism during a Lesson Study intervention. Using a case study research design, a sample of 4 physical sciences teachers was conveniently selected from schools in rural and suburban areas. Due to logistical challenges, the 4 participants were grouped into 2 separately functioning lesson study pairs. Data were collected through multiple sources including semi-structured interviews, observations of classroom teaching and Lesson Study meetings, field notes, participants’ initial lesson plans and reflective writings. It was found that collaboration through Lesson Study enhanced teachers’ professional teaching strategies, networking skills, lesson plan writing, classroom management, self-efficacy and positive attitudes towards teaching. However, challenges such as lack of time, lack of institutional support and insufficient instructional materials pose a threat to teachers’ participation in Lesson Study. It is therefore recommended that policy makers develop strategic plans to promote the use of Lesson Study as a school-based professional development initiative. Further research on Lesson Study in pre-service science teacher education may pave the way towards professional collaboration as a sustainable practice amongst science teachers. This may ultimately improve the performance levels of science learners in South Africa. Keywords: electricity and magnetism; lesson study; physical sciences; professional development; science teaching
Computation is becoming an increasingly important part of physics education. However, there are currently few theories of learning that can be used to help explain and predict the unique challenges and affordances associated with computation in physics. In this study, we adapt the existing theory of computational literacy, which posits that computational learning can be divided into material, cognitive, and social aspects, to the context of undergraduate physics. Based on an exploratory study of undergraduate physics computational literacy, using a newly-developed teaching tool known as a computational essay, we have identified a variety of student practices, knowledge, and beliefs across these three aspects of computational literacy. We illustrate these categories with data collected from students who engaged in an initial implementation of computational essays in an introductory electricity and magnetism class. We conclude by arguing that this framework can be used to theoretically diagnose student difficulties with computation, distinguish educational approaches that focus on material vs. cognitive aspects of computational literacy, and highlight the benefits and limitations of open-ended projects like computational essays to student learning.