Hasil untuk "Electricity and magnetism"

P. Scharbach

D. MacGorman, W. D. Rust, E. Williams

Xinyuan SU, Sinong QUAN, Zhihao CAI et al.

Adversarial sample generation is a key research direction for uncovering the vulnerabilities of deep neural networks and improving the robustness of Synthetic Aperture Radar Automatic Target Recognition (SAR ATR) systems. This study proposes an optimal adversarial sample generation method for SAR ATR that jointly optimizes misleading effectiveness and fidelity, aiming to resolve the core contradiction between adversarial effectiveness and visual concealment. The generation process is modeled as a joint optimization problem with the goals of balancing “misleading” and “fidelity”. First, an integrated composite transform attack strategy is designed to enhance attack effectiveness, and a joint measurement model is developed that combines the classification accuracy of the target model with the Learned Perceptual Image Patch Similarity (LPIPS) to quantify the two optimization goals. Next, an improved uniformity-guided multiobjective RIME algorithm is proposed. By integrating the Tent chaotic map, hybrid dynamic weighting, and golden sine guidance, the model is efficiently solved, yielding a set of Pareto-optimal solutions that represent various tradeoff degrees. Finally, the YOLOv10 object detection network is employed to identify perturbations in the samples within the solution set, thereby locating the critical points where disturbances occur and enabling the quantification of optimal parameters. Experiments on MSTAR and MiniSAR datasets show that the proposed ensemble compound transform attack method achieves an average target model recognition accuracy of 8.96% across different ensemble models and classification networks, improving the overall misleading effect by an average of 2.25% compared to other methods. Among them, the complex model increases by an average of 5.56%, while the proposed uniformity-guided multiobjective RIME algorithm improves the solution set diversity and convergence speed by over 25% compared with the comparison method. Using this method, the learned perceptual image patch similarity is maintained at 0.407 and the perturbation factor at 0.031, while classification accuracy decreases to 28.81%, demonstrating a tradeoff between misleading effectiveness and visual fidelity. This parameter maintains effective misleading performance under six different defense strategies, demonstrating strong robustness and providing a new approach and quantitative benchmark for adversarial attack research in SAR ATR.

Pema Gyelpo

This action research examined the effectiveness of multiple representations (MRs) in enhancing students' science learning achievement in grade 6. The study was done using a convergent parallel mixed-method design for a period of 6 weeks. A quantitative methodology was administered through a pre-test and post-test and a student perception survey (N = 23), and qualitative data were collected through focus group interviews. The findings from the quantitative methodology include a significantly positive outcome in the scores obtained after the intervention (mean difference = 4, P < .001). Qualitative findings show that various forms of representation, like models, video presentations, demonstrations, diagrams, out-of-class performances, and hands-on procedures on vastly different topics like the solar system, electricity, magnetism, environment, and living things, helped the respondents perform well by improving their understanding, making the learning process more enjoyable. Nonetheless, the challenges faced by the scholars often led to their confusion owing to the various representations. This study concludes that the integration of MRs plays a significant role for both achievement and enjoyment aspects, considering that an effective strategy for MRs is necessary to improve the learning process and enhance understanding.

Bin Zhang, Xiaobing Zhang, Bayu Dharmaputra et al.

ABSTRACT The thermal effect and hydrodynamic perturbation within a high‐frequency pulse‐periodic nanosecond coplanar surface dielectric barrier discharge (ncSDBD), are studied experimentally and numerically. The discharge is initiated in a coplanar open electrodes arrangement with 10 mm inter‐electrode gap for pulse repetition frequencies (PRF) between 10 and 100 kHz. The discharge morphology, heat release, ozone distribution and refractive index perturbation with different repetition frequency are measured by intensified charge‐coupled device (ICCD) imaging, spatially resolved emission spectroscopy, optical absorption methods and the background‐oriented schlieren technique, respectively. With the increase of frequency and number of pulses, the discharge morphology changes from quasi‐uniform structure at 10 kHz to filamentary mode, and a higher gas temperature is observed near the grounded electrode. In turn, the gas heating largely determines the dynamics of ozone. The discharge characteristics and hydrodynamic perturbation are modelled and analysed numerically. The existence of the exposed grounded electrode facilitates the connection between the positive and negative discharges. During the afterglow phase, a large amount of positive charge accumulates near the two exposed electrodes due to charge separation, resulting in a strong body force, which triggers the blowing up of the flow.

Mustafa M. Jaafar, Anwar I. Habeeb, Hassan I. Asker et al.

Nan Tang, Stephan Glamsch, Aisha Aqeel et al.

Magnetic monopoles, elusive in high-energy physics, have been realised as emergent quasiparticles in solid-state systems, where their unique properties hold promise for novel spintronic applications. Magnetic monopoles have been invoked in diverse platforms, including skyrmion lattices, chiral magnets, soft ferromagnets, aritifical nanomagnets. Yet, a demonstration of their role in magnetic transport has remained elusive. Here, we report such an observation via the spin Seebeck effect in the bulk insulating pyrochlore oxide, spin ice $\mathrm{Dy_2Ti_2O_7}$. By applying a thermal gradient perpendicular to a $[111]$-oriented magnetic field, we detect a transverse spin Seebeck voltage marked by a dominant peak at the onset of monopole proliferation, accompanied by a secondary feature and frequency-dependent behavior. Our findings establish a direct link between monopole dynamics and magnetic transport in an insulating medium, establishing a new pathway for probing fractionalized excitations and advancing towards novel spintronic applications.

Sen Chen, Hongzhang Wang, Tianying Liu et al.

Unlike conventional rigid machines, soft robots generally have unique operation styles that rely heavily on soft matter engineering and smart material systems. Owing to the superior merits of both metals and fluids, liquid metal smart materials are increasingly being innovatively used as soft actuators and sensors to construct soft robots. To promote further development and prosperity in this field, this review organizes and summarizes the typical progress in liquid metal smart materials, with a special focus on their robotic response behaviors. In particular, the article emphasizes the concept of smart composite systems consisting of liquid metals and synergistic substances (e.g., solutions, particles, and polymers). The response behaviors of liquid metal smart materials under the actions of external factors (electricity, magnetism, ultrasound, light, heat, etc.) are examined and the smart properties occurring during these responses, such as motion, transformation, self‐organization, adaptive healing, and autonomous sensing, are identified. Furthermore, soft actuators, control systems, and robots based on liquid metal smart materials are summarized and elaborated upon. Finally, the potential directions worth pursuing and challenges are outlined. It is expected that this review will stimulate further investigations into liquid metal smart materials with the aim of building a new generation of soft robots.

Somayeh Vatanparast, A. Boschetto, L. Bottini et al.

In a variety of industries, Additive Manufacturing has revolutionized the whole design–fabrication cycle. Traditional 3D printing is typically employed to produce static components, which are not able to fulfill dynamic structural requirements and are inappropriate for applications such as soft grippers, self-assembly systems, and smart actuators. To address this limitation, an innovative technology has emerged, known as “4D printing”. It processes smart materials by using 3D printing for fabricating smart structures that can be reconfigured by applying different inputs, such as heat, humidity, magnetism, electricity, light, etc. At present, 4D printing is still a growing technology, and it presents numerous challenges regarding materials, design, simulation, fabrication processes, applied strategies, and reversibility. In this work a critical review of 4D printing technologies, materials, and applications is provided.

Zhixue Liu, Wenjing Lin, Y. Liu

ConspectusHyaluronic acid (HA), which contains multiple carboxyl, hydroxyl, and acetylamino groups and is an agent that targets tumors, has drawn great attention in supramolecular diagnosis and treatment research. It can not only assemble directly with macrocyclic host-guest complexes through hydrogen bonding and electrostatic interactions but also can be modified with macrocyclic compounds or functional guest molecules by an amidation reaction and used for further assembly. Macrocycles play a main role in the construction of supramolecular drug carriers, targeted imaging agents, and hydrogels, such as cyclodextrins and cucurbit[n]urils, which can encapsulate photosensitizers, drugs, or other functional guest molecules via host-guest interactions. Therefore, the formed supramolecular assemblies can respond to various stimuli, such as enzymes, light, electricity, and magnetism for controlled drug delivery, enhance the luminescence intensity of the assembly, and improve drug loading capacity. In addition, the nanosupramolecular assembly formed with HA can also improve the biocompatibility of drugs, reduce drug toxicity and side effects, and enhance cell permeability; thus, the assembly has extensive application value in biomedical research. This Account mainly focuses on macrocyclic supramolecular assemblies based on HA, especially their biological applications and progress in the field, and these assemblies include (i) guest-modified HA, such as pyridinium-, adamantane-, peptide-, and other functional-group-modified HA, along with their cyclodextrin and cucurbit[n]uril assemblies; (ii) macrocycle-modified HA, such as HA modified with cyclodextrins and cucurbit[n]uril derivatives and their assembly with various guests; (iii) direct assembly between unmodified HA and cyclodextrin- or cucurbit[n]uril-based host-guest complexes. Particularly, we discussed the important role of macrocyclic host-guest complexes in HA-based supramolecular assembly, and the roles included improving the water solubility and efficacy of hydrophobic drugs, enhancing the luminescent intensity of assemblies, inducing room temperature phosphorescence and providing energy transfer systems, constructing multi-stimulus-responsive supramolecular assemblies, and in situ formation of hydrogels. Additionally, we believe that obtaining in-depth knowledge of these HA-based macrocyclic supramolecular assemblies and their biological applications encompasses many challenges regarding drug carriers, targeted imaging agents, wound healing, and biomedical soft materials and would certainly contribute to the rapid development of supramolecular diagnosis and treatment.

Harun Faridi, Neha Tuli, A. Mantri et al.

Physics is a branch of science that deals with different properties of energy and matter. Most of the principles of Physics are based on Mathematics, Mechanics, Optics, Electricity, Magnetism, and Thermodynamics. It is often difficult for students to grasp concepts as they cannot visualize the phenomena, resulting in compounding the problem of lack of interest in STEM subjects. Augmented reality (AR) can be effective in providing better visualization and interaction with real‐like three‐dimensional virtual objects that can ease the learning experience. In this paper, an AR‐based learning environment is developed to help students understand concepts of the magnetic field, electric current, electromagnetic waves, Maxwell's equations, and Fleming's rules for electromagnetism. An experimental study was conducted to determine the impact of AR intervention on student's learning and critical thinking capabilities. The study was conducted among 80 engineering students, who were distributed into two different groups: the AR teaching group (N = 40) and the conventional teaching group (N = 40). The AR teaching group was instructed through the AR‐based learning environment while the conventional teaching group students were taught using a conventional teaching approach. The experimental results indicate that the AR‐based learning environment has a significant positive impact on the critical thinking and learning gain of the students. The AR experience helped the students in visualizing the abstract concepts of Physics and enhanced their understanding.

Zhe Li, Yijia Gao, Xingyu Chen et al.

The World Health Organization (WHO) reports that by 2050, nearly 2.5 billion people are expected to have some degree of hearing loss (HL) and at least 700 million will need hearing rehabilitation. Therefore, there is an urgent need to develop treatment strategies for HL. At present, the main treatment strategies for HL are hearing aids and cochlear implants (CIs), which cannot achieve a radical cure for HL. Relevant studies have shown that the most fundamental treatment strategy for sensorineural hearing loss (SNHL) is to regenerate hair cells and spiral ganglion neurons (SGNs) through stem cells to repair the structure and function of cochlea. In addition, physical stimulation strategies, such as electricity, light, and magnetism have also been used to promote SGN regeneration. This review systematically introduces the classification, principle and latest progress of the existing hearing treatment strategies and summarizes the advantages and disadvantages of each strategy. The research progress of physical regulation mechanism is discussed in detail. Finally, the problems in HL repair strategies are summarized and the future development direction is prospected, which could provide new ideas and technologies for the optimization of hearing treatment strategies and the research of SGN repair and regeneration through physical regulation.

Xing Wang, Pingping Yao, Haibin Zhou et al.

Electromagnetic rail launch technology has attracted increasing attention owing to its advantages in terms of range, firepower, and speed. However, due to electricity-magnetism-heat-force coupling, the surface of the armature–rail friction pair becomes severely damaged, which restricts the development of this technology. A series of studies have been conducted to reduce the damage of the armature–rail friction pair, including an analysis of the damage mechanism and protection strategies. In this study, various types of surface damage were classified into mechanical, electrical, and coupling damages according to their causes. This damage is caused by factors such as mechanical friction, mechanical impact, and electric erosion, either individually or in combination. Then, a detailed investigation of protection strategies for reducing damage is introduced, including material improvement through the use of novel combined deformation and heat treatment processes to achieve high strength and high conductivity, as well as surface treatment technologies such as structural coatings for wear resistance and functional coatings for ablation and melting resistance. Finally, future development prospects of armature–rail friction pair materials are discussed. This study provides a theoretical basis and directions for the development of high-performance materials for the armature–rail friction pair.

Zeming Liu, Xiang Yu, Jing Huang et al.

Nerve stimulation technology utilizing electricity, magnetism, light, and ultrasound has found extensive applications in biotechnology and medical fields. Neurostimulation devices serve as the crucial interface between biological tissue and the external environment, posing a bottleneck in the advancement of neurostimulation technology. Ensuring safety and stability is essential for their future applications. Traditional rigid devices often elicit significant immune responses due to the mechanical mismatch between their materials and biological tissues. Consequently, there is a growing demand for flexible nerve stimulation devices that offer enhanced treatment efficacy while minimizing irritation to the human body. This review provides a comprehensive summary of the historical development and recent advancements in flexible devices utilizing four neurostimulation techniques: electrical stimulation, magnetic stimulation, optic stimulation, and ultrasonic stimulation. It highlights their potential for high biocompatibility, low power consumption, wireless operation, and superior stability. The aim is to offer valuable insights and guidance for the future development and application of flexible neurostimulation devices.

Yan Wang, Pengyu Zang, Dan Yang et al.

Malignant tumors are one of the main diseases leading to death, and the vigorous development of nanotechnology has opened up new frontiers for antitumor therapy. Currently, researchers are focused on solving the biomedical challenges associated with traditional anti-tumor medical methods, promoting the research and development of nano-drug carriers and new nano-drugs, which brings great hope for improving the curative effect and reducing toxic and side effects. Among the new systems being investigated, piezoelectric nano biomaterials, including ferroelectrics, piezoelectric and pyroelectric materials, have recently received extensive attention for antitumor applications. By coupling force, light, magnetism or heat and electricity, polarized charges are generated in these materials microscopically, forming a piezo-potential and establishing a built-in electric field. Polarized charges can directly act on the materials in the tumor micro-environment and also assist in the separation of carriers and inhibit recombination based on piezoelectric theory and piezoelectric optoelectronic theory. Based on this, piezoelectric materials convert various forms of primary energy (such as light energy, mechanical energy, thermal energy and magnetic energy) from the surrounding environment into secondary energy (such as electrical energy and chemical energy). Herein, we review the basic theory and principles of piezoelectric materials, pyroelectric materials and ferroelectric materials as nanomedicine. Then, we summarize the types of piezoelectric materials reported to date and their wide applications in treatment, imaging, device construction and probe detection in various tumor treatment fields. Based on this, we discuss the relevant characteristics and post-processing strategies of nano piezoelectric biomaterials to obtain the maximum piezoelectric response. Finally, we present the key challenges and future prospects for the development of ferroelectric, piezoelectric and pyroelectric nanomaterial-based nanoagents for efficient energy harvesting and conversion for desirable therapeutic outcomes.

Lei Han, Jiawei Si, Miaomiao Guo et al.

Soft robots based on flexible materials have attracted the attention due to high flexibility and great environmental adaptability. Among the common driving modes, electricity, light, and magnetism have the limitations of wiring, poor penetration capability, and sophisticated equipment, respectively. Here, an emerging wireless driving mode is proposed for the soft crawling robot based on wireless power transfer (WPT) technology. The receiving coil at the robot's tail, as an energy transfer station, receives energy from the transmitting coil and supplies the electrothermal responsiveness to drive the robot's crawling. By regulating the WPT's duration to control the friction between the robot and the ground, bidirectional crawling is realized. Furthermore, the receiving coil is also employed as a sensory organ to equip the robot with localization, ID recognition, and sensing capabilities based on electromagnetic coupling. This work provides an innovative and promising strategy for the design and integration of soft crawling robots, exhibiting great potential in the field of intelligent robots.

Xinyue Chen, Yun Wu, Zhu Long et al.

Stiffness change materials have been widely used in soft robots, intelligent adhesives and biomedical minimally invasive devices which can respond to specific stimuli. Compared with stimuli such as light, electricity, magnetism, temperature, and pressure, moisture is a non-toxic, readily available, and inexhaustible triggered source in the atmosphere. However, it is challenging to achieve a stiffness variable material with a large stiffness change using moisture. Traditional sensitive materials usually swell to expand the volume or dissolve to a liquid-like state when absorbing moisture, which is unfavorable for real applications. Herein, we demonstrate a polyvinylamine (PVAm)/polyethylenimine (PEI) composite film with variable stiffness change by moisture absorption and release. PVAm is a semicrystalline polymer with high stiffness and PEI forms intermolecular hydrogen bonding with primary amine groups on PVAm. The synergistic effect of hydrogen bonding and crystallization was maximized when 15 wt % PEI was added to the composite system, resulting in a large stiffness change of up to 7.1 × 104 (0.022 MPa versus 1560.85 MPa) of PVAm/PEI composite film under 25 °C, 95% RH. The crystallinity structure and hydrogen bonding can be broken and reformed by adjusting humidity. As promising variable stiffness polymers, the developed PVAm/PEI composite film is demonstrated as a reconfigurable multitool for shape memory and locking on demand.

Jianhui Zhu, Jie Xie, Shuqi Liu et al.

Minghe Chi, Xue Sun, Xiaorui Zhang et al.

Abstract Oil‐paper insulation material is an essential component for oil‐filled transformers, and polyimide (PI) insulation paper is a novel material in the field of electricity. The improvement of insulation class for insulation paper has gained significant attention in recent years. In this study, SiO2 nanoparticles were modified with a silane coupling agent (KH550), and the KH550‐SiO2 was added to the fibre membrane through in situ polymerisation. The chemical composition and microcosmic characteristics of the PI porous fibre membrane were characterised using FT‐IR and SEM FT‐IR and SEM. Consequently, the dielectric constant of the composite paper was reduced to 2.3 upon adding 3 wt% of KH550‐SiO2, and the dielectric strength reached its maximum value of 85 kV/mm. The results demonstrate that the insulation performance of the KH550‐SiO2/PI composite was significantly improved due to the incorporation of nano‐SiO2. This establishes an efficient approach for achieving excellent electrical and thermal properties in practical applications using the KH550‐SiO2/PI fibre membrane.

Liming Chen, Jie Feng, Wenchao Yan et al.

Ultra-intense laser-plasma wakefield accelerator possess several superior properties compared with the traditional radio-frequency accelerators. These characteristics include femtosecond duration, micro-source size, and ultra-dense beam density, result in highly advantageous for various important applications. In this paper, we reviewed the generation of ultra-intense and high charge electron beam based on laser-plasma acceleration and its nuclear applications in Shanghai Jiao Tong University, including the production of 10 s nC charge beams, the generation of ultra-high flux neutron source on the order of 1019 n/cm2/s, and the excitation of nuclear isomers with the peak efficiency on the order of 1015 particle/s. This laser driving ultra-dense electron source, in conjunction with the plasma environment, presents immense potential in addressing critical problems in astrophysics, and facilitating various nuclear applications. Based on above progress in nuclear astrophysics, a new research plateform about laboratory astrophysics with a 2.5 PW laser will be constructed in TDLI institute.