Hasil untuk "Electricity and magnetism"

Zibo ZHUANG, Jun CHEN, Peilin HE et al.

To address the issue of LiDAR’s low turbulence recognition rate at airports in low-altitude areas, a clear air turbulence recognition method based on an improved Squeeze-and-Excitation Residual Network with 50 layers (SE-ResNet50) is proposed. By introducing the squeeze-and-excitation module and improving the network structure, the model’s excessive sensitivity to feature location is reduced, thereby enabling the network to selectively highlight useful information features during the learning process. A sample dataset was established using measured data from Lanzhou Zhongchuan International Airport; for model training, a balanced dataset was created by extracting an equal amount of weak, moderate, and strong turbulence data based on the turbulence classification level. Under the same experimental conditions, the recognition accuracy of the improved SE-ResNet50 was increased by 7.44%, 6.52%, and 4.11% compared with the convolutional neural network, MobileNetV2, and ShuffleNetV1 networks, respectively. A comparison of the confusion matrices generated by each model showed that the accuracy of the proposed method reached 95%, verifying the feasibility of the proposed method.

Yangkun Zhu, Wenyu Ma, Chuang Wang et al.

Abstract Conventionally, both electrically larger (EL) arrays and sparse arrays offer the advantage of element number reduction but disadvantage of high sidelobe levels. A new scheme of planar EL sparse array antenna based on a genetic algorithm (GA) to achieve low sidelobe with element number reduction is proposed. To begin with, EL sparse array antenna optimisation models based on GA for both linear and planar arrays are analysed. Then, an EL slot antenna element based on a 3 × 3 substrate integrated waveguide cavity is designed. An 8‐element linear EL sparse array antenna is designed and compared with a uniform array antenna, demonstrating a reduction in the maximum sidelobe level (MSLL) by nearly 4.6 dB. After that, a 4 × 8 element planar EL sparse array antenna is fabricated and measured. Compared to an 8 × 16 element planar EL uniform array antenna, the number of antenna elements is reduced by 75%, while the MSLL is reduced by approximately 3 dB. The measured −10 dB impedance bandwidth ranges from 25.3 to 27.8 GHz. At the central frequency, the radiation pattern achieves a peak gain of 29.6 dBi, exhibiting low sidelobe levels below −15.0 dB.

Yanmiao HE, Yin HUANG, Xianglian YAN et al.

In order to support the "dual carbon" goals, adapt to the requirements of limiting the use of SF6 gas, and enhance the environmental friendliness of power grid equipment, research on the standardization of SF6 mixed gas and eco-friendly alternative gas equipment is conducted. Based on the current status of eco-friendly gas equipment research and application, the technical standards of SF6/N2 mixed gas equipment were reviewed. A standardization framework was established covering equipment materials, operation and maintenance, test and detection, instruments and meters. For eco-friendly alternative gas C4F7N equipment replacing SF6, a standardization framework was constructed, including gas performance detection technology and method, equipment operation and maintenance, test and detection, and recycling. Based on this, a standard system of SF6 mixed gas and eco-friendly alternative gas equipment was preliminarily proposed, consisting of six sub-branches consistent with the standard system of GIS equipment in power industry, reflecting the research direction of eco-friendly gas equipment standardization.

Shifang Yang, Zexuan Zhang, Qianpeng Hou et al.

Abstract The authors explore the limitations of silicone rubber (SR) in tropical environments due to its lack of antimicrobial activity. The use of a 2‐methylisothiazol‐3(2H)‐one compound with 5‐chloro‐2‐methylisothiazol‐3(2H)‐one is proposed as an efficient and environmentally friendly antimicrobial agent to enhance the fungistatic properties of SR. The fungicide added specimen was obtained by directly adding a quantitative amount of isothiazolinone to the polymer system. Through an in‐depth analysis of the material properties of MCMSR, the form in which 2‐methyl‐4‐isothiazolin‐3‐one/5‐chloro‐2‐methyl‐4‐isothiazolin‐3‐one (MIT/CMIT) exists in the molecular structure of the SR crosslink system was carefully explored. The accelerated hydrolysis process of polysiloxane, which caused fungi secretion, was proven to be suppressed due to the effects of MIT/CMIT. The antimicrobial mechanism of isothiazolinone in preventing microbial growth was interpreted as the apoptosis and necrosis procedures of Aspergillus niger cells, which were verified by flow cytometry results. By choosing the appropriate concentration of isothiazolinone, the original properties of the SR were successfully maintained while effectively preventing the aggregation of isothiazolinone. This opens up a new research direction and application prospect for the antimicrobial modification of SR.

Tinghua Zhang, Sishen Yuan, Chao Xu et al.

Miniature rotation actuators have been extensively developed and utilized in optical coherence tomography (OCT) endoscopy, enabling distortion-free OCT imaging in complex and tortuous environments. However, the use of electrical-driven rotation actuators raises safety concerns. Although magnetic-driven rotation actuators have been reported in OCT endoscopy, their use can potentially interfere with other medical devices in clinical settings. Here, we propose a pneumatic miniature rotation actuator that eliminates the electricity and magnetism concerns in circumferential imaging for OCT endoscopy. The rotor of the actuator is designed as a windmill, enabling it to convert air energy into rotation energy. In addition, to maintain the stable rotation, both a sliding bearing with two supporting points and a glass spindle with a half-ball end surface are developed. The rotation speed of our pneumatic actuator can be controlled from 66 to 97 revolutions per second by adjusting the airflow rate from 3.25 to 4.00 liters per minute. By OCT imaging of the human fingers, we demonstrate the feasibility of the pneumatic actuator in electricity-free distal scanning OCT endoscopy. Our pneumatic rotation actuator has wide-ranging potential in various fiber-imaging modalities, including not only OCT but also ultrasound imaging that requires similar rotation capabilities.

N. Husna, Sahyar

This study analyzes the integration of green energy concepts, energy efficiency, and sustainable development in high school physics teaching materials on electricity and magnetism. This study involves 10 physics teachers from high schools in Medan, consisting of 5 government high school teachers and 5 private high school teachers who have professional certification. The sampling technique used is a mixed method that combines qualitative and quantitative data. The research was conducted in Medan, Indonesia. For data analysis, descriptive statistical techniques were used for quantitative data, while qualitative data were analyzed using the Miles and Huberman approach. This study assesses the relevance and effectiveness of the current teaching materials. The research results show that the highest score of 73.25% in respondents’ perceptions is on the relevance of teaching materials to basic physics concepts, while the lowest score of 49.75% is on the effectiveness of the materials in enhancing students’ understanding of green energy and energy efficiency. This study recommends the development of more integrated and contextually relevant teaching materials to enhance students’ understanding and engagement with global sustainability issues. The implications of this study indicate that integrating green energy and sustainability into physics education not only enhances the relevance of the curriculum but also increases students’ awareness of their roles in addressing global issues such as the energy crisis and climate change. This approach supports the Sustainable Development Goals (SDG 7 and SDG 13) and prepares students for future contributions to sustainable energy solutions.

M. E. Capoulat, M. E. Capoulat, M. E. Capoulat et al.

The global effort to establish Accelerator-Based Boron Neutron Capture Therapy (AB-BNCT) facilities involves various accelerator technologies and neutron-producing targets, each characterized by different properties of the primary beam and neutron spectra they generate. With an emphasis on long-term sustainability, it is essential to minimize the production of residual radioactivity to the lowest possible level, particularly given their intended use in a hospital environment. This paper aims to quantitatively assess the residual radioactivity in these facilities, taking into account both primary and secondary activation. Primary activation primarily arises from the interaction of the proton or deuteron beam and the neutron-producing target. Secondary activation results from neutron-induced reactions on the elements exposed to the neutron flux, with the Beam Shaping Assembly (BSA) being the most exposed one. To assess activation, we evaluated a representative group of target-BSA configurations. Primary activation was calculated based on cross-sectional data and the corresponding target materials. Neutron activation was assessed using Monte Carlo simulations with the MCNP 6.1 code. Regarding target activation, our findings indicate that 9Be targets working with protons of less than 10 MeV represent the cleanest option, while 7Li targets working with protons lead to the highest activation levels. As for BSA activation, the neutron energy is a crucial factor. In the case of standard BSA materials, higher neutron energy results in an increased number of potential reactions that produce radioactive products. Additionally, our findings suggest that radioactivity induced by impurities and minor components in alloyed materials cannot be disregarded and must be taken into account in radioactivity calculations. In summary, this research provides a comprehensive analysis of activation of the commonly used targets and BSA materials, aimed at contributing to the optimization of AB-BNCT facilities from a radiological perspective.

James Clerk Maxwell

Arguably the most influential nineteenth-century scientist for twentieth-century physics, James Clerk Maxwell (1831–1879) demonstrated that electricity, magnetism and light are all manifestations of the same phenomenon: the electromagnetic field. A fellow of Trinity College Cambridge, Maxwell became, in 1871, the first Cavendish Professor of Physics at Cambridge. His famous equations - a set of four partial differential equations that relate the electric and magnetic fields to their sources, charge density and current density - first appeared in fully developed form in his 1873 Treatise on Electricity and Magnetism. This two-volume textbook brought together all the experimental and theoretical advances in the field of electricity and magnetism known at the time, and provided a methodical and graduated introduction to electromagnetism. Volume 1 covers the first elements of Maxwell's electromagnetic theory: electrostatics, and electrokinematics, including detailed analyses of electrolysis, conduction in three dimensions, and conduction through heterogeneous media.

Guanghui Cheng, Mohammad Mushfiqur Rahman, Andres Llacsahuanga Allcca et al.

Moiré superlattices in van der Waals structures can be used to control the electronic properties of the material and lead to emergent correlated and topological phenomena. Its first demonstration in van der Waals magnets exhibited noncollinear states and domain structures with, however, limited manipulation. Here we report electrically tunable moiré magnetism in twisted double bilayers - that is, a bilayer plus a bilayer with a twist angle between them - of layered antiferromagnet CrI3. Using magneto-optical Kerr effect microscopy, we observe the coexistence of antiferromagnetic and ferromagnetic order with nonzero net magnetization - a hallmark of moiré magnetism. Such magnetic state extends over a wide range of twist angles (with transitions at around 0° and above 20°) and exhibits a nonmonotonic temperature dependence. We further demonstrate voltage-assisted magnetic switching. The observed nontrivial magnetic states and unprecedented control by twist angle, temperature and electrical gating are supported by the simulated phase diagram of the moiré magnetism.

Karunakaran M, Rudra Banerjee

The ferromagnetic Heusler alloy $Ni_2MnGa$ had been of major interest in the past few years because of its magnetic properties which can be easily tuned. The $Ni_2MnGa$ Heusler alloys are intermetallic alloy with $L2_1$ structure. Here we report a detailed investigation of the effect of doping of Co and Mn in Ni2MnGa. Magnetic properties and electronic structure of $Ni_{2-x}Co_xMnGa_{1-y}Mn_y$ Heusler alloys have been studied by using Green's function-based KKR-CPA method based DFT calculations. We will show the magnetization can be tuned depending on the Co and Mn occumencies. We will also discuss the critical temperature, magnetic interactions and magnetic stability of the systems.

László F. Kiss, László Bujdosó, Dénes Kaptás

Evidence for the suppression of collective magnetic behavior of dipolarly interacting Fe nanoparticles is found in Fe-Ag granular multilayers. Interaction of Fe particles located in neighboring Fe layers is studied as a function of the nominal thickness of the Ag layer in between only two Fe layers. The surprisingly increasing interaction with increasing Ag-layer thickness, verified by memory-effect measurements, is explained by the formation of pinholes in the Ag layer at small Ag thicknesses, allowing direct ferromagnetic coupling between Fe particles in neighboring Fe layers which may hinder the frustration of superspins favored by dipolar interactions. At larger Ag thicknesses, the Ag layer is continuous without pinholes and frustration leads to the appearance of the superspin-glass state. The effect of increasing interactions correlates well with the growing deviation at low temperatures of the measured field-cooled (FC) magnetization from the interaction-free FC curve calculated by a model based on the relaxation of two-level systems. Similar phenomenon is reported in a recently published paper (Sánchez et al., Small 2022, 18, 2106762) where a dense nanoparticle system is studied. The collective magnetic behavior of the particles due to dipolar interactions is suppressed when the anisotropy energy of the individual particles exceeds a certain threshold.

Vittorio Basso, Carlo P. Sasso, Martino LoBue et al.

We investigate the magnetocaloric effect obtained by the rotation of a magnetic field applied to an exchange-coupled multilayer system composed of two different ferromagnetic (FM) materials. We specifically consider a system in which the two FMs have perpendicular uniaxial anisotropy axes and utilise conditions which yield a reorientation of the total magnetization when compensation between the anisotropies of the two layers occurs. We calculate the consequent entropy change associated with the "artificial" reorientation. By using known parameters from MnBi and Co we predict an entropy change of $Δs = 0.34$ Jkg$^{-1}$K$^{-1}$ for perfect coupling. Lastly, we study the behavior of the multilayer under a rotating magnetic field via a micromagnetic model. When the layer thicknesses are of the order of the local domain wall width, the magnetic field-induced entropy change can be obtained with magnetic fields one order of magnitude lower than in the uncoupled case.

Brandon Wilfong, Vaibhav Sharma, Omar Bishop et al.

Fe$_{3}$Ga$_{4}$ displays a complex magnetic phase diagram that is sensitive and tunable with both electronic and crystallographic structure changes. In order to explore this tunability, vanadium-doped (Fe$_{1-x}$V$_{x}$)$_{3}$Ga$_{4}$ has been synthesized and characterized. High-resolution synchrotron X-ray diffraction and Rietveld refinement show that samples up to 20\% V-doping remain isostructural to Fe$_{3}$Ga$_{4}$ and display a linear increase in unit cell volume as doping is increased. Magnetic measurements reveal a suppression of the antiferromagnetic helical spin-density wave (SDW) with V-doping, revealed by changes in both the low-temperature ferromagnetic-antiferromagentic (FM-AFM) transition (T$_{1}$) and high-temperature AFM-FM transition (T$_{2}$). At 7.5\% V-doping, the metamagnetic behavior of the helical AFM SDW phase is no longer observed. These results offer an avenue to effective tuning of the magnetic order in Fe$_{3}$Ga$_{4}$ for devices, as well as increased understanding of the magnetism in this system.

Anjun ZHAO, Pengzhu WANG, Jing JING et al.

For optimal configuration of the rural household new energy system with photovoltaic power generation as main source, a new life cycle optimization configuration method is proposed for rural household new energy system from the perspective of user economic benefits, which uses electric vehicles (EVs) as energy storage facilities and considers the travel demands of users. Firstly, an optimal configuration model is established with the objective of minimum annual system energy cost and maximum self-generation and self-use rate. And a new energy system integrated operation model is formulated based on the electricity price and the demand for electric vehicles. And then the particle swarm optimization (PSO) algorithm is applied to solve the optimal configuration capacity of distributed power in the household new energy system. Finally, simulation experiments are carried out based on actual electricity load data and meteorological parameters for typical rural households in Shijiazhuang, Hebei. Results show that the combination of electric vehicles and photovoltaic power can effectively improve the system energy efficiency and reduce the energy cost.

Guizhou WU, Yuan ZHANG, Wenjun ZHANG et al.

Signal Direct Position Determination (DPD) is a novel passive localization technology, which shows superior performance in terms of low signal noise rate adaptability and no parameter association necessity. To adapt to the complex electromagnetic environment, this study proposes a coprime array-based DPD method with single moving observation. Considering narrowband signals as an example, this study first formulates the intercepted signal model, then derives its equivalent model related to the corresponding difference co-array, and finally builds the DPD cost function via spatial spectrum technology. Simulation results show that the proposed method can greatly improve the degree of freedom compared to the traditional DPD with a minor loss of resolution and accuracy when an identical coprime array is used. Meanwhile, compared to the uniform linear array-based DPD, the proposed method shows superior performance in terms of the degree of freedom, resolution, and accuracy of localization.

Sui PENG, Xianfu GONG, Xinmiao LIU et al.

With the increasing installed capacity of wind power, stronger demand for flexible adjustment resources such as energy storage occurs in the power system, and the AC/DC hybrid power grid is the basis for the grid connection, transmission, and accommodation of large-scale wind power. Given the above background, an energy storage configuration scheme is proposed for the wind power integrated system considering the DC regulation capacity to promote the accommodation of renewable energy and reduce the investment cost of energy storage. First, a scenario analysis method is adopted to deal with the randomness of wind power and loads. Then, a DC line model with adjustable transmission power is constructed. Furthermore, combined with the constraints including energy storage configuration, energy storage operation, and AC power grid, a configuration model of energy storage based on multi-scenario stochastic optimization is built considering DC regulation capacity to minimize the total daily operating cost of the power system. Finally, a comparative analysis of multiple energy storage configuration schemes is simulated in the modified IEEE 14-bus system. The results show that the proposed scheme can promote the accommodation of wind power while lessening the demand for energy storage. As a result, the economic operation of the wind power integrated system is guaranteed.

Gerrit Wulf, Bernd Mayer, Uwe Lommatzsch

Plasma co-polymers (co-p) were deposited with an atmospheric pressure plasma jet (APPJ) using a precursor mixture containing hexamethyldisiloxane (HMDSO) and limonene. A coating with fragments from both precursors and with siloxane, carbonyl and nitrogen functional groups was deposited. The flow rate of limonene was found to be an important parameter for plasma co-polymerization to tune the formation and structure of the functional groups. The FTIR and XPS analysis indicates that with increasing flow rate of limonene a higher proportion of carbon is bound to silicon. This is related to a stronger incorporation of fragments from limonene into the siloxane network and a weaker fragmentation of HMDSO. The formation mechanism of the nitroxide and carboxyl groups can be mainly differentiated into in-plasma and post-plasma reactions, respectively.

Hongyuan XU, Taicong LONG, Qidao ZHAO et al.

Aiming at the surplus water problem caused by insufficient regulation capacity of power system and uncertainty on the load side, a multi-energy coordinated low-carbon robust scheduling model of hydro-electricity-natural gas system was proposed and solved in this paper. The nonlinear constraint in the proposed model is transformed into a mixed-integer linear model based on piecewise linearization method and Taylor series expansion method. For the uncertain parameters in the model, the column and constraint generation method are used to further transform it into a master-subproblem framework, consequently solved by GUROBI solver. Numerical results of an improved 6-bus electricity/7-node gas system show that the proposed model can make full use of the complementary characteristics of different energy systems to improve the regulation capacity of the power system and promote the consumption of hydro power, as well as reduce the operation cost and achieve low-carbon operation of power system.

Wen FAN, Baoguo YU, Jing CHEN et al.

In this study, under the Peak-to-Average Power Ratio (PAPR), energy, and binary (for antenna position selection) constraints, we proposed an antenna position selection and beam scanning method for colocated Multiple-Input Multiple-Output (MIMO) radar system using the min-max beampattern amplitude matching criterion. In our design, antenna positions and a set of probing waveforms were jointly determined to match a set of beampattern masks, and hence realize the beam scan. The resultant problem was large-scale, nonconvex, nonsmooth, and typical nondeterministic hard, because of the PAPR and nonconvex binary constraints, and the max and modulus operations in the objective function. To address these issues, we first transformed the min-max problem into the Iterative weighted Least Squares (ILS) problem using the Lawson algorithm, replaced the nonsmooth nonconvex objective function with the convex majorization function, and finally applied the alternating direction method of multipliers to solve the majorized ILS problem. Finally, several numerical examples were given to show the effectiveness of the proposed algorithms.

Gang ZHU, Yanhe LI, Zhen ZHANG et al.

Electricity plays an important role in energy transformation. The future energy transformation will show the trend of clean, low carbon and electrification. This paper mainly introduces the operation control technology and application of all-clean energy supply in provincial power grid. Firstly, this paper introduces the technical problems faced by the power grid to achieve all-clean energy supply; secondly, the power and electricity balance equation of the power grid under the condition of all-clean energy supply is analyzed; thirdly, based on the output constraints of the power grid and Hydropower units, dispatching generation scheduling optimization function is analyzed. Finally, taking the clean energy power supply successfully realized in Qinghai Province in recent three years as an example, this paper analyzes the feasibility and main implementation process of the clean energy in the provincial power grid from the perspective of engineering practice, and discusses the innovative connotation of the three clean energy power supply in technology and transaction mode. The practice and exploration of all-clean energy power supply can provide practical experience for improving the multi-energy complementary coordination control and new energy absorption capacity of power grid, promoting the development of clean energy, and providing meaningful reference for the power grid to carry the new energy revolution.