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Magnetic-Field-Induced Partial-to-Full Penetration Evolution and Its Mechanism During Laser Welding
摘要： The geometry and tensile strength of magnetic-?eld-assisted laser-welded Ti-6Al-4V joints have been studied. Due to the effects of the magnetic ?eld on the melt ?ow behavior during welding, the weld penetration depth increased from 4.27 mm (partial penetration) to 5.00 mm (full penetration) and the curvature of the weld cross-section decreased, improving the weld tensile strength. The fusion zone was enlarged, showing a maximum increase of 53.4% in area when the magnetic ?eld intensity was 90 mT. The increased penetration depth and fusion zone area suggest that application of a magnetic ?eld can improve the energy utilization of the laser during laser butt welding. The mechanism of the magnetic-?eld-induced penetration depth evolution is discussed. This study provides a new energy-saving method to obtain a full-penetration weld using laser welding at lower power.
关键词： Magnetic-field-assisted laser welding,Tensile strength,Energy utilization,Ti-6Al-4V,Weld geometry
更新于2025-11-28 14:24:20
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Influence of the position dependent effective mass on the nonlinear optical properties in semiparabolic and parabolic quantum well with applied magnetic field
摘要： In the current work, the nonlinear optical properties in GaAs/Ga1?xAlxAs semiparabolic and parabolic quantum well(QW) with constant effective mass(CEM) and position dependent effective mass(PDEM) are estimated for different applied magnetic field. In this regard, we have obtained the analytical expressions of the nonlinear rectification(OR), second harmonic generation(SHG), third harmonic generation(THG), optical absorption coefficients(OACs), and refractive index changes(RICs) by using the compact density matrix formalism. Simultaneously, we obtain the reliable energy eigenvalues and their corresponding eigenfunctions via the finite difference method. According to the obtained results, it is found that: (1)the correct inclusion of PDEM is the cause of a noticeable difference in nonlinear optical properties with respect to the use of CEM. (2)the applied magnetic field bear substantial technological importance in the process of nonlinear optical properties modulation.
关键词： Quantum well,Magnetic field,Position dependent effective mass,Optical properties
更新于2025-09-23 15:23:52
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Magneto-optical imaging characteristics of weld defects under alternating and rotating magnetic field excitation
摘要： This paper mainly examines the characteristics of magneto-optical (MO) images of weld defects under alternating and rotating magnetic field excitation. Weld defects including surface and subsurface defects were subjected to magneto-optical imaging (MOI) nondestructive testing (NDT) experiments. The MO images of different weld defects under alternating magnetic field excitation and rotating magnetic field excitation have been compared to determine the best effect of nondestructive testing, and a cruciform welding seam was used to verify the detection effect of rotating magnetic field. Besides, the values of standard deviation and maximum difference have been determined to analyze the difference in the effects of two magnetic fields, and image processing methods were applied to extract defect information, such as histogram equalization. Experimental results show that the optimal excitation voltage and lift-off value of rotating magnetic field are 120 V and 20 mm, respectively; image histogram equalization can significantly improve the contrast of MO images, and there is a distinct difference in the detection effect of two magnetic fields. Under the same excitation conditions, the detection effect of rotating magnetic fields is always better than the effect of alternating magnetic fields, and rotating magnetic field excitation has obvious advantages in detecting multidirection and subsurface defects in that the detection depth can reach about 8 mm.
关键词： Magneto-optical imaging,Electromagnetic optics,Nondestructive testing,Rotating magnetic field
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE PELS Workshop on Emerging Technologies: Wireless Power Transfer (WoW) - Montréal, QC, Canada (2018.6.3-2018.6.7)] 2018 IEEE PELS Workshop on Emerging Technologies: Wireless Power Transfer (Wow) - An Elliptical Magnetic Field-Orientated Control for Interoperability and Misalignment Tolerance in Inductive Power Transfer
摘要： To improve the interoperability and misalignment tolerance of the inductive power transfer (IPT) system, the concepts of circular rotating magnetic field control and elliptical rotating field orientated control(FOC) are proposed in this paper. The method of analogy analysis between LIM (liner inductive motor) and IPT is adopted to improve the magnetic field distribution characteristics. Detailed output voltage derivation of circular pads and DD pads under misalignment are given. An approximate calculation model is built to study the influence of end effect and gap variation on magnetic field distribution. Experimental results verify the laws of circular magnetic field and elliptical magnetic field.
关键词： misalignment,magnetic field-orientated control,analogy analysis,wireless power transfer,interoperability,inductive power transfer(IPT)
更新于2025-09-23 15:23:52
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Ultrasensitive and simultaneous detection of two cytokines secreted by single cell in microfluidic droplets via magnetic-field amplified SERS
摘要： A surface-enhanced Raman scattering (SERS)-microfluidic droplet platform for the rapid, ultrasensitive and simultaneous detection of vascular endothelial growth factor (VEGF) and interleukin-8 (IL-8) secreted by a single cell is presented. The high throughput water-in-oil droplets containing individual cell along with four kinds of immune-particles (antibody-conjugated silver nanoparticles or magnetic beads, AgNPs@Ab1 and MNs@Ab2) in each were achieved by a cross-typed microfluidic chip, and then they were captured by a collection channel array for SERS measurements. In the appearance of cytokines secreted by one cell, AgNPs@Ab1 can be linked onto the surface of MNs@Ab2 through the immune-recognition to form an immune-sandwich, which makes the 'turn on' SERS signal of the Raman reporters previously laid on the surface of MNs due to the adjacent AgNPs. Furthermore, the second SERS signal amplification is from the magnetic field-induced spontaneous collection effect, which brings 75 times enhancement for SERS signal. Additionally, the encapsulation of cytokines in an isolated droplet permits an accumulation effect of targets with time. Owing to the dual signal enhancement and the accumulation effect, such few cytokines secreted by single cell become detectable and a limit of detection is achieved as 1.0 fg/mL in one droplet. By using this ultrasensitive SERS-microdroplet method, the VEGF and IL-8 secretions from several cells in one droplet were explored and the data show that the cell–cell interactions may promote angiogenesis of cancer cells through the up-regulation of VEGF and IL-8.
关键词： surface-enhanced Raman scattering,VEGF,magnetic field amplification,single-cell analysis,IL-8,cytokines,microfluidic droplets
更新于2025-09-23 15:23:52
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Focused Ion Beam
摘要： Hybrid superconducting-spin systems offer the potential to combine highly coherent atomic quantum systems with the scalability of superconducting circuits. To fully exploit this potential requires a high-quality-factor microwave resonator, tunable in frequency and able to operate at magnetic fields optimal for the spin system. Such magnetic fields typically rule out conventional Al-based Josephson-junction devices that have previously been used for tunable high-Q microwave resonators. The larger critical field of Nb allows microwave resonators with large field resilience to be fabricated. Here we demonstrate how constriction-type weak links, patterned in parallel into the central conductor of a Nb coplanar resonator with a neon focused ion beam, can be used to implement a frequency-tunable resonator. We study transmission through two such devices and show how they realize high-quality-factor, tunable, field-resilient devices that hold promise for future applications coupling to spin systems.
关键词： magnetic field resilience,focused ion beam,superconducting,tunable resonator,Nb,nano-SQUID
更新于2025-09-23 15:23:52
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Resonant Enhancement of THz Radiation Through Vertically Aligned Carbon Nanotubes Array by Applying Wiggler Magnetic Field
摘要： The present analysis develops a novel theory of terahertz radiation generation by beating of two laser beams, incident obliquely on the array of vertically aligned carbon nanotubes (CNTs) in the presence of an external wiggler magnetic field. The array of CNTs behaves as nanoantenna to generate THz radiations. The incident lasers exert a ponderomotive force on the electrons of the CNTs to produce nonlinear oscillatory velocity, which beats with the applied wiggler magnetic field. This beating produces a nonlinear current at (ω2 ? ω1, k2 ? k1 + k0) which acts as an antenna to produce the THz radiation. We observe that when the beat frequency (ω2 ? ω1) lies near the effective plasmon frequency of the CNTs, strong THz radiation is produced due to a resonant interaction of the laser with CNT electrons. The externally applied wiggler magnetic field enhances the efficiency of THz radiation of nanoantenna by providing the necessary momentum to the generated THz radiation. We explore the impact of radius and length of nanotubes on the efficiency of THz generation. The generated THz power is enhanced at an optimum angle of incidence of lasers with an array of CNTs.
关键词： THz radiation,Carbon nanotubes,Antenna theory,Wiggler magnetic field,Plasma,Nanotechnology
更新于2025-09-23 15:23:52
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General condition for realizing a collinear spin-orbit effective magnetic field in two-dimensional electron systems and its application to zinc-blende and wurtzite quantum wells
摘要： In this paper, we have studied two-dimensional (2D) electron systems described by the effective Hamiltonians containing spin-orbit coupling (SOC) terms up to an arbitrary odd order in wave vector k. The general condition for realizing a SOC-induced effective magnetic field (SOF) in such systems, formulated only in terms of the SOC parameters, is derived. When this condition is satisfied, the projection of the electron spin on the direction of the collinear SOF is a conserved quantity. The complete set of the k-linear and k-cubic Dresselhaus SOC contributions to the effective 2D Hamiltonian of an arbitrarily oriented zinc-blende quantum well is computed by a proper averaging of the corresponding tight-binding bulk SOC Hamiltonian. We investigate possibilities for realization of the collinear SOF in zinc-blende quantum wells of different orientation and obtain some interesting findings, which supplement the results of earlier works. Application of the developed formalism to wurtzite semiconductor 2D systems shows that the collinear SOF can be also realized in a wide class of such quantum wells.
关键词： effective magnetic field,spin-orbit coupling,quantum wells,wurtzite,zinc-blende
更新于2025-09-23 15:23:52
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Monolayer transition metal dichalcogenides in strong magnetic fields: Validating the Wannier model using a microscopic calculation
摘要： Using an equation of motion (EOM) approach, we calculate excitonic properties of monolayer transition metal dichalcogenides perturbed by an external magnetic field. We compare our findings to the widely used Wannier model for excitons in two-dimensional materials and to recent experimental results. We find good agreement between the calculated excitonic transition energies and the experimental results. In addition, we find that the exciton energies calculated using the EOM approach are slightly lower than the ones calculated using the Wannier model. Finally, we also show that the effect of the dielectric environment on the magnetoexciton transition energy is minimal due to counteracting changes in the exciton energy and the exchange self-energy correction.
关键词： monolayer transition metal dichalcogenides,magnetic field,Wannier model,excitons,magnetoexcitons,equation of motion
更新于2025-09-23 15:23:52
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[IEEE 2018 19th International Conference of Young Specialists on Micro/Nanotechnologies and Electron Devices (EDM) - Erlagol (Altai Republic), Russia (2018.6.29-2018.7.3)] 2018 19th International Conference of Young Specialists on Micro/Nanotechnologies and Electron Devices (EDM) - Evaluation of Hall Effective Masses in Callium Arsenide Monocrystal in Quantizing Magnetic Field
摘要： Results of calculation of the holes effective masses values in a 3D GaAs monocrystal in a quantizing magnetic field are presented, the masses were evaluated using perturbation theory in the proximity of the point for the magnetic field oriented along [001] crystallographic direction. The masses were calculated for the Landau levels n = 0,1. The condition for application of the considered holes effective mass spectrum for thin monocrystalline films is formulated.
关键词： magnetic field,holes spectrum,holes masses
更新于2025-09-23 15:23:52