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Objective: The current distribution of the matrix gradient coil can be optimized via matrix gradient coil modeling to reduce the Lorentz force on individual coil elements. Two different modeling approaches are adopted, and their respective characteristics are summarized.
Methods: The magnetic field at each coil element is calculated. Then, the Lorentz force, torque, and deformation of the energized coil element in the magnetic field are derived. Two modeling approaches for matrix gradient coil, namely, optimizing coil element current (OCEC) modeling and optimizing coil element Lorentz force (OCEF) modeling, are proposed to reduce the Lorentz force on individual coil elements. The characteristics of different modeling approaches are compared by analyzing the influence of the weighting factor on the performance of the coil system. The current, Lorentz force, torque, and deformation results calculated via different modeling approaches are also compared.
Results: Coil element magnetic fields are much weaker than the main magnetic field, and their effect can be ignored. Matrix gradient coil modeling with different regularization terms can help to decrease the current and Lorentz force of coil elements. The performance of the coil system calculated via different modeling approaches is similar when suitable weighting factors are adopted. The two modeling approaches, OCEC and OCEF, can better reduce the maximum current and Lorentz force on individual coil elements compared with the traditional modeling approach.
Conclusions: Different modeling approaches can help to optimize the current distribution of coil elements and satisfy various requirements while maintaining the performance of the coil system.
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http://dx.doi.org/10.1007/s10334-022-01022-6 | DOI Listing |
Micromachines (Basel)
August 2025
Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China.
DC arcs are widely used in many fields such as shipbuilding, machinery manufacturing, and aerospace due to their advantages of high energy density, simple structure, and low price. However, there are few studies on the sensitivity of the arc pressure and temperature fields to current and protective gas flow rate. In order to solve this problem, this paper establishes a numerical model for the coupling of DC arc electric-thermal-flow multi-physical fields.
View Article and Find Full Text PDFSensors (Basel)
August 2025
School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China.
Accurate stress evaluation of structural components during manufacturing and operation is essential for ensuring the safety and reliability of advanced equipment in aerospace, defense, and other high-performance fields. However, existing electromagnetic ultrasonic stress detection methods are often limited by low signal amplitude and limited adaptability to complex environments, hindering their practical deployment for in situ testing. This study proposes a novel surface wave transducer structure for stress detection based on acoustoelastic theory combined with electromagnetic ultrasonic technology.
View Article and Find Full Text PDFACS Nano
September 2025
Beijing National Laboratory for Molecular Sciences, Center for Carbon Neutral Chemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
Electrochemical deposition is a facile and effective method for the in situ growth of metal electrocatalysts; however, it is difficult to optimize their morphology and performance due to the kinetics-controlled growth at high current density. Herein, we develop a new magneto-electrochemical deposition technique to prepare the faceted microcrystals of copper (Cu) catalysts for highly efficient electrocatalytic nitrate-to-ammonia conversion. The field generates a Lorentz force on the flow of Cu ions near the cathode surface, which retards the mass transport to predeposited Cu particles and increases the density of Cu nucleation sites due to the magnetohydrodynamics (MHD) effect.
View Article and Find Full Text PDFSci Rep
August 2025
School of Engineering Science, University of Chinese Academy of Sciences, Beijing, 100049, China.
This study investigates Marangoni convection in a liquid metal-filled cubic cavity, relevant to fusion reactor plasma-facing components, using three-dimensional direct numerical simulations with a self-developed magnetohydrodynamic (MHD) code. The effects of magnetic field strength (Hartmann number, Ha = 0-200) and orientation (x, y, z directions) are analyzed at a fixed Reynolds number (Re = 100,000). Strong magnetic fields suppress convection, with the x and y directions exhibiting greater suppression than the z direction.
View Article and Find Full Text PDFACS Photonics
August 2025
Department of Chemical Physics and Optics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, Prague CZ-12116, Czech Republic.
Ultrafast electron microscopy aims for imaging transient phenomena occurring on nanoscale. One of its goals is to visualize localized optical and plasmonic modes generated by coherent excitation in the vicinity of various types of nanostructures. Such imaging capability was enabled by photon-induced near-field optical microscopy, which is based on spectral filtering of electrons inelastically scattered due to the stimulated interaction with the near-field.
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