Hasil untuk "Electricity and magnetism"

Xi Zhang, Xiao Li, Jun Yin et al.

Yttrium oxide–magnesium oxide (Y2O3–MgO) composite nanopowders were synthesized via three distinct methods: sol–gel, co-precipitation and glycine–nitrate process. The synthesized powders were calcined at various temperatures, and their microstructure, specific surface area and particle size were characterized. A comparative study was conducted to assess the impact of the synthesis method on the microstructure and transparency of the resulting ceramic sintering. Notably, the powder synthesized by the sol–gel technique exhibited the highest specific surface area and superior light transmittance, reaching a maximum of 85.33% at a wavelength of 5.31[Formula: see text]m.

Yani Wang, Ruobing Xu, Pinshun Ren et al.

Abstract The space charge accumulation in the heterogeneous insulation composed of cross‐linked polyethylene (XLPE) cable and silicone rubber (SiR) accessory poses a serious threat to the safe operation of the high voltage direct current (HVDC) cable. When the cable is in heavy load, the charge transport behaviour in XLPE/SiR becomes more complicated due to the high temperature. In order to investigate the charge transport characteristics of XLPE/SiR under heavy load condition, the simultaneous measurement of space charge and relaxation current is performed on XLPE/SiR at both 70°C and 30°C with different polarities. The results show that the polarity of the interface charges in XLPE/SiR is always consistent with that of the SiR side electrode, and the influence of high temperature (70°C) caused by heavy load on the interface charge accumulation of XLPE/SiR is reversed at different polarities. The interface trap depth of XLPE/SiR is consistently greater than the bulk trap depths in both XLPE and SiR. When at high temperature of 70°C, the depth and density of interface traps increase, and the bulk traps in XLPE and SiR also exhibit increased depth. The component of polarisation relaxation current associated with space charge activity increases and exhibits longer decay time at 70°C, indicating more active and complex charge trapping‐detrapping activities under heavy load condition. In this paper, an advanced simultaneous measurement is used to correlate the internal charge distribution with the external current for analysis, and the charge transport characteristics of XLPE/SiR under heavy load condition is revealed. The results can provide reference for the operation and maintenance of HVDC cable, and can also provide a basis for the space charge regulation of heterogeneous insulation at HVDC cable accessories.

Valérie Paul-Boncour, Véronique Charbonnier, Nicolas Madern et al.

In this study, the crystal structure and magnetic properties of La$_{2-x} A'_{x}$Ni$_{7}$ compounds with magnetic rare earth elements ($A$' = Sm, Gd) have been investigated combining X-ray powder diffraction and magnetic measurements. These intergrowth compounds crystallize in a mixture of 2$H$ hexagonal (Ce$_{2}$Ni$_{7}$-type) and 3$R$ rhombohedral (Gd$_{2}$Co$_{7}$-type) polymorphic structures which are related to the stacking of [$AB_{5}$] and [$A_{2}B_{4}$] subunits along the $c$-axis.The average cell volume decreases linearly versus $A$' content, whereas the $c/a$ ratio reaches a minimum at $x$ = 1, due to geometric constraints upon $A$' for La substitution between the two different subunits. The magnetic properties strongly depend on the structure type and the $A$' content. Hexagonal La$_{2}$Ni$_{7}$ is a weak antiferromagnet (wAFM) at low field and temperature and undergoes metamagnetic transitions towards weak ferromagnetic state (wFM) under applied field. Under an applied field of 0.1 T, La$_{2-x}A'_{x}$Ni$_{7}$ intermetallic compounds display two different transition temperatures $T_{1}$ and $T_{2}$ that both increase with $x$. $T_{1}$ is associated with a wFM-wAFM transition in the 2$H$ phase for $A$'= Sm, whereas $T_{2}$ is related to the Curie temperature of both 2$H$ and 3$R$ phases. A metamagnetic behaviour is observed between $T_{1}$ and $T_{2}$ with transition field $μ_{0}H_{Trans}$ between 2 and 3.5 T for compounds with $A$' = Sm. The La$_{2-x}Sm_{x}$Ni$_{7}$ compounds ($x$ > 0} behave as hard magnets with a large coercive field $μ_{0}H_{C}$ at low temperature ($μ_{0}H_{C}$ > 9 T at 5 K for $x$ = 2), whereas the La$_{2-x} Gd_{x}$Ni$_{7}$ compounds ($x$ > 0) are soft ferrimagnets with a linear increase of the saturation magnetization versus Gd content.

E. M. Salah, H. A. Atallah, A. Abdelaziz et al.

This paper describes the design and analysis of a reconfigurable radiation pattern dual-band antenna for Wi-Fi and WLAN applications. The antenna patch comprises two parts: the upper part, which consists of three symmetrical oval rings, and the lower part, which is shaped like a lotus flower. By controlling the ON and OFF states of lumped p-i-n switches to control the direction of the radiation beams, the proposed pattern reconfigurable antenna achieves three reconfigurable states. The beam's direction change is performed by two switches that are connected in the gap between the feedline and the arch. The proposed antenna operates at 2.4 and 5.5 GHz, covering the bands from 2.1882 to 2.55 GHz and from 5.31 to 5.96 GHz, respectively. Additionally, the directivity over the working bands is about 1.92 to 4 dBi while the gain lies in the range of 1.66 to 3.5 dB. Moreover, the voltage standing wave ratio (VSWR) varies from 1 to 1.20. The size of the antenna is 47×59.5 mm2 which is printed on a 1.6 mm thickness FR-4 substrate of 4.4 relative permittivity. Computer simulation technology Microwave Studio is used to design and study the recommended constructions. The proposed design achieves an acceptable value of VSWR, stable gain, and good directivity, which makes it a suitable choice for future radiation pattern reconfiguration applications. The proposed antenna is distinguished by a simple shape, compact size, respectable return loss, good radiation characteristics, and high efficiency. The obtained results from measurements are quite close to the simulations.

Salim Adolfo Giha Yidi, Vladimir Sousa Santos, Kelly Berdugo Sarmiento et al.

This paper compares concentrated and distributed reactive power compensation to improve the power factor at the point of common connection (PCC) of an industrial electrical system (IES) with harmonics. The electrical system under study has a low power factor, voltage variation, and harmonics caused by motors operating at low loads and powered by variable-speed drives. The designed compensation system mitigates harmonics and reduces electrical losses with the shortest payback period. Four solutions were compared, considering concentrated and distributed compensation with capacitor banks and harmonic filters. Although the cost of investment in concentrated compensation is lower than that of distributed compensation, a higher reduction in electrical losses and a lower payback period are obtained with distributed compensation. Although the lowest payback period was obtained with distributed compensation with capacitor banks (0.4 years), it is not recommended in the presence of harmonics because the effects of current harmonics significantly reduce the useful life of these elements. For this reason, distributed compensation with harmonic filters obtained a payback period of 0.6 years, and it was proposed as the best solution. These results should be considered in projects aimed at power factor compensation in IESs with harmonics. The concentrated compensation of the capacitor bank at the PCC is proposed because of the lower investment cost and ease of installation. However, the advantages of distributed compensation with harmonic filters have not been evaluated. An energy efficiency approach is used to analyze the impact of the location methods of the power factor compensation equipment on the electrical losses of the IES.

Giulia Polverini, Jakob Melin, Elias Onerud et al.

Artificial intelligence-based chatbots are increasingly influencing physics education due to their ability to interpret and respond to textual and visual inputs. This study evaluates the performance of two large multimodal model-based chatbots, ChatGPT-4 and ChatGPT-4o on the Brief Electricity and Magnetism Assessment (BEMA), a conceptual physics inventory rich in visual representations such as vector fields, circuit diagrams, and graphs. Quantitative analysis shows that ChatGPT-4o outperforms both ChatGPT-4 and a large sample of university students, and demonstrates improvements in ChatGPT-4o's vision interpretation ability over its predecessor ChatGPT-4. However, qualitative analysis of ChatGPT-4o's responses reveals persistent challenges. We identified three types of difficulties in the chatbot's responses to tasks on BEMA: (1) difficulties with visual interpretation, (2) difficulties in providing correct physics laws or rules, and (3) difficulties with spatial coordination and application of physics representations. Spatial reasoning tasks, particularly those requiring the use of the right-hand rule, proved especially problematic. These findings highlight that the most broadly used large multimodal model-based chatbot, ChatGPT-4o, still exhibits significant difficulties in engaging with physics tasks involving visual representations. While the chatbot shows potential for educational applications, including personalized tutoring and accessibility support for students who are blind or have low vision, its limitations necessitate caution. On the other hand, our findings can also be leveraged to design assessments that are difficult for chatbots to solve.

Timur Seidov, Maxim Gorlach

We investigate the electromagnetic fields produced by the oscillating point electric or magnetic dipole placed in a spherical volume with nonzero time-independent effective axion field. Our analytical solution shows that the fields outside the volume are a superposition of electric and magnetic dipole fields. Such multipole time-dependent generalization of the Witten effect can be realized in magneto-electrics, topological insulators or metamaterials providing a flexible probe of P- and T-symmetry breaking phenomena in different electromagnetic structures.

Nanse Esaki, Yutaka Akagi, Hosho Katsura

We theoretically propose the electric field induced thermal Hall effect of triplons in the quantum dimer magnets $X$CuCl$_{3}$ ($X =$ Tl, K), which exhibit ferroelectricity in the Bose-Einstein condensation phase of triplons. The interplay between ferroelectricity and magnetism in these materials leads to the magnetoelectric effect, i.e., an electric-field induced Dzyaloshinskii-Moriya (DM) interaction between spins on the same dimer. We argue that this intradimer DM interaction breaks the symmetry of the system in the absence of an electric field and gives rise to the thermal Hall effect, which can be detected in experimentally accessible electric and magnetic fields. We also show that the thermal Hall effect can be controlled by changing the strength or direction of the electric field.

O. Mattei, G. Milton, M. Putinar

A body $\Theta$ containing two phases, which may form a periodic composite with microstructure much smaller that the body, or which may have structure on a length scale comparable to the body, is subjected to slowly time varying boundary conditions that would produce an approximate uniform field in $\Theta$ were it filled with homogeneous material. Here slowly time varying means that the wavelengths and attenuation lengths of waves at the frequencies associated with the time variation are much larger than the size of $\Theta$, so that we can make a quasistatic approximation. At least one of the two phase does not have an instantaneous response but rather depends on fields at prior times. The fields may be those associated with electricity, magnetism, fluid flow in porous media, or antiplane elasticity. We find, subject to these approximations, that the time variation of the boundary conditions can be designed so boundary measurements at a specific time $t=t_0$ exactly yield the volume fractions of the phases, independent of the detailed geometric configuration of the phases. Moreover, for specially tailored time variations, the volume fraction can be exactly determined frommeasurements at any time $t$, not just at the specific time $t=t_0$. We also show how time varying boundary conditions, not oscillating at the single frequency $\omega_0$, can be designed to exactly retrieve the response at $\omega_0$.

N. Yu, Bin An, J. Ding et al.

Susmita Bala, P. Soni Reddy, Rahul Mondal et al.

A novel design for the planar monopole antenna presented in this article consists of a patch resembling a tree and a modified ground plane resembling a flower vase. The proposed antenna is planned, designed, and made by utilizing FR4 substrate. The proposed antenna contributes to a computer simulation and tested S11 bandwidth of 9.4 GHz (144.62%) and 9.3 GHz (136.76%), respectively. A peak tested gain of 6.5 dBi and peak efficiency of 77.51% have been achieved. The measured results of the fabricated antenna are compared with the simulated results and are found to be in good agreement. The proposed antenna has a low general volume of 38 × 20 × 1.6 mm3. The antenna can be used in C-band and X-band application.

M. B. Perotoni, M. S. Vieira, K. M. Santos

This article presents a system to generate transient signals for EMC testing purposes. It is based on a low-cost commercial Software-Defined Radio (SDR) whose output contains the desired transient signal modulated by a higher-frequency sinusoidal. An envelope detector board removes the carrier so that the slow-varying curve is amplified to be used in the test setup. Due to the SDR nature, it is completely controlled by software, which enables a quick and easy operation able to synthesize different waveforms. An open-source software tool is used to control the SDR to generate the signal and set the carrier frequency. Here, the article focuses on double-exponential curves, very common in different EMC tests, but its application is not limited to them. A 5.9 s risetime waveform is generated and tested against a real prototype representing a shielded cable over a ground plane. Individual building blocks are presented and the signal is analyzed as it goes through the cascade.

Yuanbing ZHOU, Fang YANG, Xiaoxiao YU et al.

Based on the actual national conditions of China’s economic and social, energy and power development, this paper analyzes China’s carbon neutralization mechanism framework and puts forward the mitigation solutions for carbon emissions with China energy interconnection. With the target of optimal cost for achieving carbon neutrality for the whole society, the MESSAGE integrated assessment model (IAM) is used to study the overall pathways for China's whole society carbon neutralization and the transition pathways for energy and power system based on the China energy interconnection. The results show that the carbon neutrality pathways before 2060 for China can be advanced in view of three stages of early peaking, rapid mitigation and overall neutrality. The carbon emissions will reach the peak around 2028; 90% of the energy demand will be met by clean energy in 2060, and the electricity will account for two-thirds in the whole society end-use energy consumption, achieving the total transition of energy use system. Besides, some key issues for achieving carbon neutralization are analyzed, including emission reduction speed and pace, power system balance and adjustment, and transition cost and allocation.

Xuechao Zhai, Yaroslav M. Blanter

Compared to monolayer graphene, electrons in Bernal-stacked bilayer graphene (BLG) have an additional layer degree of freedom, offering a platform for developing {\it layered spintronics} with the help of proximity-induced magnetism. Based on an effective phenomenological model, we systematically study the effect of this magnetism on the spin-dependent band structure near the Fermi energy and identify the magnetic phases induced in BLG by proximity with magnets. We show that spin polarization can develop in BLG due to this proximity effect. This spin polarization depends strongly on the layer distribution of magnetism, and can always be controlled by gate voltage which shifts spin-dependent band edges and modifies the total band gap. We further show that the band spin polarization can be modified by the proximity-induced staggered sublattice potential. By taking full advantage of layer-dependent magnetism in BLG, we propose that spintronic devices such as a spin filter, a giant magnetoresistence device, and a spin diode can operate under fully electric control, which is easier than the common magnetic field control.

Anlli Teekarama

: Nanomaterials have brought an unprecedented revolution to the development of building materials with their unique properties of light, electricity, heat and magnetism. According to the future development trend of building materials and the development and application prospects of nanomaterials, this paper studies the application of nanomaterials in new building materials, providing a better development space for the future direction of new building materials. This research mainly conducted research from five aspects: the effect of modified carbon nanotubes on the bending performance and compressive strength of cement-based materials; the effect of composite materials on the effectiveness of cement-based materials in electromagnetic wave protection; the effectiveness of nano-carbon fiber cement materials Self-shrinking; Formaldehyde gas sensitivity of nanomaterials; The effect of surface modification of nano-TiO2 on the thermal stability of wheat straw fibers. The test results show that the results of improving the mechanical properties include: compressive strength increased by 132%, tensile strength increased by 34.28%, and flexural strength increased by 124.85%. When the silica fume content is 0, the electromagnetic shielding efficiency of different doped carbon nanometers are 22.1, 25.8, 27.6 and 31.4 respectively. As the silica fume content gradually increases, the ability to shield electromagnetic waves is stronger. When the water-cement ratio is 0.25 and 0.3, the autogenous shrinkage value of the nano-carbon fiber cement paste specimens shows a trend of first decreasing

Martin J. N. Sibley

James Clerk Maxwell (1831–1879) was one of the major contributors to physics in the nineteenth century (Figure \(\PageIndex{1}\)). Although he died young, he made major contributions to the development of the kinetic theory of gases, to the understanding of color vision, and to the nature of Saturn’s rings. He is probably best known for having combined existing knowledge of the laws of electricity and of magnetism with insights of his own into a complete overarching electromagnetic theory, represented by Maxwell’s equations.

M. Rezaei, M. Baharian, K. Mohammadpour‐Aghdam

Electromagnetic (EM) field is one of the Nature’s fundamental phenomena produced by electric charges. Maxwell’s equations describe how electricity and magnetism are related to each other, and how both are related to the properties of the source, i.e., charge’s density and velocity. Considering charge’s properties in space and time as a whole, electricity and magnetism will no longer be two separate mechanisms but only two different dimensional aspects of one single phenomenon. In this article, there is a short discussion on how the magnetic component of an EM field can be distinguished. We search for an ideal structure that responds exclusively to this aspect of the field. Mentioning the inevitable limits, some definitions for the figure of merit (FoM) and the efficiency factor of magnetic antennas (and probes) are suggested, the existing structures are investigated, and finally, by putting all the pieces together, a new structure is proposed. Along with higher FoM, the new structure has the advantage of being practically feasible with no need for active devices or balun transformers.

Tetsuya Furukawa, Yuta Watanabe, Naoki Ogasawara et al.

Chiral matter has a structure that lacks inversion, mirror, and rotoreflection symmetry; thus, a given chiral material has either a right- or left-handed structure. In chiral matter, electricity and magnetism can be coupled in an exotic manner beyond the classical electromagnetism (e.g., magneto chiral effect in chiral magnets). In this paper, we give a firm experimental proof of the linear electric-current-induced magnetization effect in bulk nonmagnetic chiral matter elemental trigonal tellurium. We measured a ^{125}Te nuclear magnetic resonance (NMR) spectral shift under a pulsed electric current for trigonal tellurium single crystals. We provide general symmetry considerations to discuss the electrically (electric-field- and electric-current-) induced magnetization and clarify that the NMR shift observed in trigonal tellurium is caused by the linear current-induced magnetization effect, not by a higher-order magnetoelectric effect. We also show that the current-induced NMR shift is reversed by a chirality reversal of the tellurium crystal structure. This result is direct evidence of crystal-chirality-induced spin polarization, which is an inorganic-bulk-crystal analog of the chirality-induced spin selectivity in chiral organic molecules. The present findings also show that nonmagnetic chiral crystals may be applied to spintronics and coil-free devices to generate magnetization beyond the classical electromagnetism.

Danyun Xu, Zhe Guo, Y. Tu et al.

Abstract Two-dimensional iron phosphorus trichalcogenide (FePS3) has attracted significant attention for its use in electricity, magnetism and optical fields due to its outstanding physical and chemical properties. Herein, FePS3 was prepared using the chemical vapor transportation (CVT) method and then exfoliated by using fast electrochemical exfoliation. After gradient centrifugation, FePS3 nanosheets with thicknesses ranging from 1.5 to 20 nm and lateral dimensions of 0.5–3 μm were obtained. By utilizing the spatial self-phase modulation (SSPM) effect, the relationships between the nonlinear refractive index and the size of the FePS3 nanosheets were investigated in detail which revealed that the nonlinear refractive index can be effectively controlled by the size of the FePS3 nanosheets. It is worth noting that the optimal FePS3 nanosheets (3–5 layers thick and ∼1 μm in lateral dimensions) displayed the highest nonlinear refractive index of ∼10−5 cm2 W−1. This work demonstrates the potential that FePS3 nanosheets have for use in nonlinear optics or nonlinear optical devices.