Uniform Field Distribution Research Articles

Research on energy utilization of electron beam melting for silicon purification

As a key material for solar photovoltaic power generation, the purity of silicon plays a crucial role in the photovoltaic conversion efficiency and performance. The electron beam melting (EBM), which is irreplaceable metallurgical methods, has been widely used for silicon purification. However, high energy consumption result in relatively high cost, which limits its widespread application in melting industry. This study was centered on the energy distribution that proposes a new approach to reducing energy consumption during EBM. The scanning form of electron beam is most important factor concerning energy consumption. Different scanning forms can affect the characteristics of molten pool which is closely correlated with the purification process. In this study, efficient and energy-saving preparation processes of EBM are being explored through the numerical model and experimental. The relationship of energy distribution form and purification efficiency is studied. The research results indicate that electron beam scanning under uniform distribution can achieve more uniform temperature and flow field distribution in the molten pool, which has a higher energy utilization rate during silicon purification by EBM. The mathematical model established in this study can effectively predict the energy consumption level under different melting parameters, providing important reference for the optimization and energy conservation of EBM process for other materials. In addition, evaporation characteristics of volatile impurity, migration of the second phase particles in the melt, controlling of melt pool characteristics and the crystal growth control all can be conducted based on this study.

Effect of horizontal cartridges on the uniformity of flow field distribution inside a cartridge filter

Cartridge filters are widely utilized in industrial dust removal due to their advantages of high dust removal efficiency, compact size relative to bag filters, and the capacity to reuse collected dust. However, the conventional upright installation of the cartridges' front row directly faces the air inlet, which is directly impacted by the high-velocity dirt airflow and is often broken. This setup also disrupts airflow distribution, leading to uneven mass flow distribution and localized high velocity. To address these challenges, this study proposes horizontally installing the cartridges, by utilizing the bottom cone to buffer the airflow. This not only resolves issues of localized cartridge breakage but also promotes uniform airflow distribution, thereby prolonging filter service life. Computational Fluid Dynamics (CFD) is employed to simulate the changes in the flow field within the physical model, using finite element iterative calculations. This approach reduces experimental costs while providing precise data. Therefore, numerical simulation is used to verify the effectiveness of horizontal cartridges in improving the uniformity of the flow field distribution in the cartridge filter. The results showed that the horizontal cartridge filter improved the mass flow distribution uniformity by 54.9%, the peak velocity difference was reduced by 69.63%, and the maximum velocity was reduced by 68.42% compared to the upright cartridge filter. Horizontal cartridges have a more uniform flow field distribution, effectively avoiding problems such as abrasion and rupture of the filter media caused by excessive local air velocity.

Simulation of electrostatic particulate matter sensor regeneration based on the particulate deposition patterns

Purpose This study aims to establish a multi-physics-coupled model for an electrostatic particulate matter (PM) sensor. The focus lies on investigating the deposition patterns of particles within the sensor and the variation in the regeneration temperature field. Design/methodology/approach Computational simulations were initially conducted to analyse the distribution of particles under different temperature and airflow conditions. The study investigates how particles deposit within the sensor and explores methods to expedite the combustion of deposited particles for subsequent measurements. Findings The results indicate that a significant portion of the particles, approximately 61.8% of the total deposited particles, accumulates on the inside of the protective cover. To facilitate rapid combustion of these deposited particles, a ceramic heater was embedded within the metal shielding layer and tightly integrated with the high-voltage electrode. Silicon nitride ceramic, selected for its high strength, elevated temperature stability and excellent thermal conductivity, enables a relatively fast heating rate, ensuring a uniform temperature field distribution. Applying 27 W power to the silicon nitride heater rapidly raises the gas flow region's temperature within the sensor head to achieve a high-temperature regeneration state. Computational results demonstrate that within 200 s of heater operation, the sensor's internal temperature can exceed 600 °C, effectively ensuring thorough combustion of the deposited particles. Originality/value This study presents a novel approach to address the challenges associated with particle deposition in electrostatic PM sensors. By integrating a ceramic heater with specific material properties, the study proposes an effective method to expedite particle combustion for enhanced sensor performance.

Spatial-Dependent Spectral Response of Acousto-Optic Tunable Filters with Inhomogeneous Acoustic Distribution.

The spectral response of an acousto-optic tunable filter (AOTF) is crucial for an AOTF based spectral imaging system. The acousto-optic (AO) interaction within the spatial-distributed area of the acoustic field determines the spectral response of the light incidence. Assuming an ideally uniform acoustic field distribution, phase-matching geometries can be applied to calculate the anisotropic Bragg diffraction in AO interactions, determining the wavelength and direction of the diffracted light. In this ideal scenario, the wavelength of the diffracted light depends solely on the direction of the incident light. However, due to the non-ideal nature of the acoustic field, the wavelength of the diffracted light exhibits slight variations with incident position. In this paper, an analytical model is proposed to calculate the spatial-dependent spectral response of the diffracted light under non-uniform acoustic field distribution. The study computes the variation pattern of the diffracted light amplitude caused by the inhomogeneous acoustic distribution. The theoretical considerations and computational model are confirmed by AOTF frequency scanning experiments. The study demonstrates that the distribution of the acoustic field leads to non-uniform spatial-spectral response in the AOTF, and the spatial AO interaction computational model can provide data support for calibrating AOTF systems in imaging applications.

Coupled stack-up volume RF coils for low-field open MR imaging.

Low-field open magnetic resonance imaging (MRI) systems, typically operating at magnetic field strengths below 1 Tesla, has greatly expanded the accessibility of MRI technology to meet a wide range of patient needs. However, the inherent challenges of low-field MRI, such as limited signal-to-noise ratios and limited availability of dedicated radiofrequency (RF) coils, have prompted the need for innovative coil designs that can improve imaging quality and diagnostic capabilities. In response to these challenges, we introduce the coupled stack-up volume coil, a novel RF coil design that addresses the shortcomings of conventional birdcage in the context of low-field open MRI. The proposed coupled stack-up volume coil design utilizes a unique architecture that optimizes both transmit/receive efficiency and RF field homogeneity and offers the advantage of a simple design and construction, making it a practical and feasible solution for low-field MRI applications. This paper presents a comprehensive exploration of the theoretical framework, design considerations, and experimental validation of this innovative coil design. We demonstrate the superior performance of the coupled stack-up volume coil in achieving 47.7% higher transmit/receive efficiency and 68% more uniform magnetic field distribution compared to traditional birdcage coils in electromagnetic simulations. Bench tests results show that the B1 field efficiency of coupled stack-up volume coil is 57.3% higher compared with that of conventional birdcage coil. The proposed coupled stack-up volume coil outperforms the conventional birdcage coil in terms of B1 efficiency, imaging coverage, and low-frequency operation capability. This design provides a robust and simple solution to low-field MR RF coil design.

One-way valley-locked waveguide with a large channel achieved by all-dielectric photonic crystals

One-way transmission of light constitutes the cornerstone of modern photonic circuits. In the realm of photonic devices, it has been widely utilized in isolators, circulators, etc. Recent topology in artificial materials, an unprecedented degree of freedom, has been proposed to solve the effect of impurities on one-way transmission. However, in view of the bulk-edge correspondence, the spatial width of the transmission channel with uniform field distribution is quite narrow and needs further exploration. In this paper, we proposed a one-way valley-locked waveguide with a large channel in an all-dielectric reciprocal photonic crystal. Quite different from the topological edge states, our waveguide is topologically trivial; the unidirectional property comes from the bulk modes with valley-lock in the vicinity of Dirac points, which can naturally fully utilize the whole dimension of the structure. Additionally, such one-way bulk modes keep single mode regardless of the channel width increasing, along with uniform electrical field distribution across the entire channel, which opens a new avenue for large channel optical devices.

Probabilistic design and optimization of thermal protection system with variable thickness based on non-uniform aerodynamic heating

Thermal Protection System (TPS) is a critical component of space vehicles to protect them from damage by extreme aerothermal heating conditions. The uncertainty of the aerothermal heating conditions, including approaching velocities, atmospheric density, pressure, etc., significantly affects the aerothermal heating imposed on the TPS, vastly changing the initial design conditions. In this study, we developed a new uncertainty quantitative (UQ) analysis method to comprehensively consider all the uncertainty of TPS materials, structures, and aerothermal heating conditions. To address the challenges of a massive amount of input and determined optimization parameters, we first induced the response surface method and Monte Carlo algorithm to produce a large number of analysis samples for Probabilistic Design. Then, the key affecting factors, not all the input design parameters, were chosen for optimization with sequential optimization and reliability assessment (SORA) strategy by a sensitivity analysis. With such improvements, the optimization for UQ analysis becomes practical. We used this new UQ method to analyze the effects of uncertainty of the aerothermal heating conditions on the thermal protection layer. A variable thickness design is proposed to adapt the non-uniform aerothermal heating conditions for the TPS. The results show that significant light-weighting can be achieved without the reliability penalty. The optimized structure also reduces internal temperature gradients and facilitates a more uniform temperature field distribution for the TPS. This study provides a new UQ engineering design approach for the system with many designed parameters.

Design and optimization of a long-range surface plasmon resonance-based plasmonic SERS biosensor

In this paper, we designed and studied a novel type of hybrid chip based on long-range surface plasmon resonance (LRSPR) and surface-enhanced Raman scattering (SERS). The substrate has periodic arrangement gold nanoring cavity arrays structure, which can obtain a uniform and stable electromagnetic field distribution. In addition, due to the clever design of the long-range configuration (a “sandwich” structure with symmetric refractive index), the chip has a significant extended electromagnetic field enhancement ability. In numerous existing studies focusing on SERS performance, the consideration of plasmonic structure is limited to its shape and size, while neglecting the significance of spacer layer parameters. Thus, we use the Finite Difference Time Domain (FDTD) software to design and optimize the chip substrate configuration by investigating the impact of various parameters such as refractive index, spacer layer thickness, plasmonic structure's inner and outer radius, and period of array on the long-range effect. The presented geometrically-tunable long-range plasmonic chip provides a way to identify the governing factors for SERS and presents a design principle for optimizing SERS substrates.

Study on the Flow Field Distribution in Microfluidic Cells for Surface Plasmon Resonance Array Detection.

This research is dedicated to optimizing the design of microfluidic cells to minimize mass transfer effects and ensure a uniform flow field distribution, which is essential for accurate SPR array detection. Employing finite element simulations, this study methodically explored the internal flow dynamics within various microfluidic cell designs to assess the impact of different contact angles on flow uniformity. The cells, constructed from Polydimethylsiloxane (PDMS), were subjected to micro-particle image velocimetry to measure flow velocities in targeted sections. The results demonstrate that a contact angle of 135° achieves the most uniform flow distribution, significantly enhancing the capability for high-throughput array detection. While the experimental results generally corroborated the simulations, minor deviations were observed, likely due to fabrication inaccuracies. The microfluidic cells, evaluated using a custom-built SPR system, showed consistent repeatability.

ИЗЛУЧАТЕЛИ ДЛЯ СВЕРХВЫСОКОЧАСТОТНЫХ КОНВЕКТИВНЫХ УСТАНОВОК. РЕЗУЛЬТАТЫ МОДЕЛИРОВАНИЯ

The studies were carried out to simulate the distribution of the electromagnetic field to assess the efficiency of three types of emitters according to the following parameters: standing wave coefficient, which makes it possible to compare the consistency of emitters; radiation efficiency, showing the amount of energy transferred to the grain layer; microwave field radiation pattern, which allows one to evaluate the uniformity of the field distribution in the grain layer. For evaluation and comparison, three types of waveguides were considered: horn, rectangular with slot emitters; semicircular with slot emitters. The distribution of the electromagnetic field was modeled using the CST Microwave Studio program. The use of horn waveguides in ultra-high-frequency convective installations makes it possible to produce fairly simple devices for grain processing. The standing wave coefficient for the operating frequency in this case is 1.3, with a radiation efficiency of 78 dB. However, they do not ensure uniform distribution of the ultrahigh frequency field at the exit from the waveguide, which affects the efficiency of grain processing. The use of rectangular waveguides 55 mm × 110 mm with slot emitters ensures more uniform radiation of the electromagnetic field across the entire spectrum of wave types. The standing wave ratio is 1.0 and the radiation efficiency is 94.43 dB. However, their use requires additional design developments to ensure the supply of coolant to the processing zone. Semicircular waveguides with slot emitters provide a standing wave ratio of 1.0 over the entire frequency range from 2 to 3 GHz. Radiation efficiency is 94.28 dB. The uniformity of the electromagnetic field distribution along a semicircular waveguide is better than along a rectangular one.

Design and Parameter Optimization of Double-Mosquito Combination Coils for Enhanced Anti-Misalignment Capability in Inductive Wireless Power Transfer Systems

This paper proposes a novel double-mosquito combination (DMC) coil for inductive wireless power transfer (IPT) systems to improve their anti-misalignment capability. The DMC coil consists of a mosquito coil with single-turn spacing and a tightly wound close-wound coil. By superimposing the magnetic fields generated by both coils, a relatively uniform magnetic field distribution is achieved on the receiving coil plane. This approach addresses the challenges of significant output voltage fluctuations and reduced transmission efficiencies caused by coupling coil misalignments in conventional IPT systems. To further optimize the DMC coil, an interaction law between its parameters and the mutual inductance is established, setting the coil mutual inductance fluctuation rate as the optimization objective, and using the coil turn spacing, number of turns, and outer diameter as constraint conditions. The beetle antennae search algorithm (BAS) is employed to enhance the whale optimization algorithm (WOA), facilitating the adaptive optimization of the coil parameters. An experimental IPT system platform with a 50 mm transmission distance is developed to validate the robust anti-misalignment capability of the proposed coil. The results demonstrate that within a horizontal misalignment range of 50 mm, the system’s output voltage fluctuation rate stays below 7.4%, and the transmission efficiency remains above 83%.

Treatment Temperature and Magnetic Field Distribution for Magnetic Hyperthermia Using Magnetic Nanoparticles

A minimally invasive cancer treatment method utilizing magnetic nanoparticles (MNPs) and magnetic coils, magnetic hyperthermia, generates heat locally inside the body to degenerate cancer cells. The uniformity of the coil's magnetic field is a crucial factor in enhancing the therapeutic effect. In this study, we evaluated the temperature distribution of MNPs on induction heating experiments at various distances using two types of coils. We found that the 2‐turn coil with a larger outer diameter and higher magnetic field uniformity resulted in a treatment temperature region approximately twice as wide as the 4‐turn coil, indicating the enhancement of the treatment effect under the uniform magnetic field distributions. © 2024 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

High-permittivity ceramics enabled highly homogeneous zero-index metamaterials for high-directivity antennas and beyond

Zero-index metamaterials (ZIMs) can support uniform electromagnetic field distributions at any frequency, but their applications are hampered by the ZIM’s homogenization level—only 3 unit cells per free-space wavelength, which is fundamentally limited by the low-permittivity inclusions (εr ≈ 12) and background matrix (εr ≈ 1). Here, by filling high-permittivity SrTiO3 ceramic (εr ≈ 294) pillars in BaTiO3 (εr ≈ 25) background matrix, we demonstrate a highly homogeneous microwave ZIM with an over threefold increase in the homogenization level. Leveraging such a ZIM, we achieve not only an antenna, approaching the fundamental limit in the directivity with outstanding scalability, but also a concave lens with a focal length of as short as 1λ0. Our highly homogeneous ZIM has profound implications in ceramics, ZIM-based waveguides and cavities, free-space wavefront manipulation, and microwave quantum optics, and opens up enormous possibilities in wireless communications, remote sensing, global positioning satellites, etc.

基于深度学习的线性偏振均匀聚焦的超构透镜逆向设计

基于深度学习的线性偏振均匀聚焦的超构透镜逆向设计

A review of electromagnetic stirring on solidification characteristics of molten metal in continuous casting

The solidification of molten metal represents a pivotal phase in the preparation and shaping of metallic materials. Continuous casting, as a crucial juncture in the solidification of molten metal, occupies a position of paramount significance. Nevertheless, during the process of continuous casting, challenges emerge, including uneven temperature field distribution, non-uniform solidification microstructures, and the presence of impurities, leading to defects such as segregation and shrinkage in the castings. Researchers have devoted decades to addressing these issues, culminating in the discovery that the application of electromagnetic stirring during continuous casting can expedite the flow of molten metal, enhance solute diffusion, thereby achieving uniform temperature and flow field distributions, refining solidification microstructures, and ameliorating macrosegregation, among other benefits. This article provides an overview of the recent research achievements and advancements in the utilization of electromagnetic stirring during the continuous casting process. It primarily elucidates various stirring devices commonly employed in continuous casting and expounds upon the influence of electromagnetic stirring on solidification characteristics. And the current problems and future development trends in the application of electromagnetic stirring were discussed.

Deep learning-based field-guided optimization method

TEAM Problem 35, a benchmark problem in the optimization of electrical equipment, is a multi-objective, multi-variable optimization problem involving uniform field optimization. This paper proposes a novel guided optimization algorithm to address this problem and achieve optimal magnetic field regulation. First, the deep learning method is used to predict the magnetic field of the solenoid; second, the generated magnetic field cloud map is screened to extract the magnetic field information of the more optimal solution with uniform magnetic field distribution by calculating the variance of the generated magnetic field map; finally, the magnetic field features are combined with the particle swarm optimization algorithm; specifically, the variance of the calculated magnetic field map is added to the objective function of the optimization algorithm to strengthen the optimization process. This integration improves the convergence speed of the optimization process and ensures the continuity and stability of the obtained Pareto solutions. To optimize the solenoid, this paper considers the uniformity of magnetic field distribution and power loss as the primary optimization objectives. The radius of the coil is chosen as the design variable. The optimization results are compared with those obtained by conventional optimization algorithms, demonstrating superior optimization performance.

Three-dimensional ionospheric conductivity associated with pulsating auroral patches: reconstruction from ground-based optical observations

Abstract. Pulsating auroras (PsAs) appear over a wide area within the aurora oval in the midnight–morning–noon sector. In previous studies, observations by magnetometers on board satellites have reported the presence of field-aligned currents (FACs) near the edges and interiors of pulsating aurora patches. PsAs are thus a key research target for understanding the magnetosphere–ionosphere coupling process. However, the three-dimensional (3-D) structure of the electric currents has yet to be clarified, since each satellite observation is limited to a single dimension along its orbit. This study's aim was a reconstruction of the 3-D structure of ionospheric conductivity, which is necessary to elucidate the 3-D ionospheric current. Tomographic analysis was used to estimate the 3-D ionospheric conductivity for rapidly changing auroral phenomena such as PsAs. The reconstructed Hall conductivity reached its maximum value of 1.4 × 10−3 S m−1 at 94 km altitude, while the Pedersen conductivity reached its maximum value of 2.6 × 10−4 S m−1 at 116 km altitude. A secondary peak in the Pedersen conductivity, due to electron motion, at 9.9 × 10−5 S m−1 appears at 86 km altitude. The electron Pedersen conductivity maximum value in the D region was approximately 38 % of the ion Pedersen conductivity maximum value in the E region. The FAC, derived under the assumption of a uniform ionospheric electric field, was approximately 70 µA m−2 near the edge of the PsA patch. This FAC value was approximately 10 times that observed by satellites in previous studies. If the conductivity around the patch is underestimated or the assumption of a uniform field distribution is incorrect, the FAC could be overestimated. By contrast, due to sharper boundary structures, the FAC could actually have had such a large FAC.

Numerical evaluation of heat-triggered drug release via thermo-sensitive liposomes: A comparison between image-based vascularized tumor and volume-averaged porous media models

In this study, two numerical models for controlled drug delivery through thermo-sensitive liposomes under mild microwave hyperthermia are compared. The first model simulates blood flow directly in a realistic tumor vascular network. The second one, at the volume-averaged macro scale, employs the porous media model. Using the vascular-scale approach is helpful for these kind of applications since the porous media assumption does not allow to account for local vascular blood flow, which is a crucial variable to quantify outputs like local drug accumulations. In the present study, the vascularized tumor model is obtained from a photo-acoustic scan and used as computational domain. The vascular-scale model considers heat and drug transfer in vascular and intracellular spaces, employing energy equations for heat transfer and a three-compartment convection-diffusion model for drug diffusion. Blood flow is simulated using the momentum equation for non-Newtonian fluids. The volume-averaged model shows good agreement with the vascular-scale model even if provides less precise information about temperature field distribution and drug localization within the tumor tissue. Also, the volume-averaged model underestimates Fraction of Killed Cells by 3 % post-treatment, presenting a more uniform temperature field and drug distribution compared to the vascular-scale one. Despite these small limitations, the porous media model is reliable for obtaining average results, while the vascular-scale model is suitable when more accurate results are needed. This study's findings aid those who aim to predict hyperthermia-driven drug delivery, suggesting the vascular-scale approach for precision and accuracy and the volume-averaged approach for average outcomes.

All-dielectric scale invariant waveguide

Total internal reflection (TIR) governs the guiding mechanisms of almost all dielectric waveguides and therefore constrains most of the light in the material with the highest refractive index. The few options available to access the properties of lower-index materials include designs that are either lossy, periodic, exhibit limited optical bandwidth or are restricted to subwavelength modal volumes. Here, we propose and demonstrate a guiding mechanism that leverages symmetry in multilayer dielectric waveguides as well as evanescent fields to strongly confine light in low-index materials. The proposed waveguide structures exhibit unusual light properties, such as uniform field distribution with a non-Gaussian spatial profile and scale invariance of the optical mode. This guiding mechanism is general and can be further extended to various optical structures, employed for different polarizations, and in different spectral regions. Therefore, our results can have huge implications for integrated photonics and related technologies.

Strain-induced self-rolled-up microtubes for multifunctional on-chip microfluidic applications.

On-chip microfluidics are characterized as miniaturized devices that can be either integrated with other components on-chip or can individually serve as a standalone lab-on-a-chip system for a variety of applications ranging from biochemical sensing to macromolecular manipulation. Heterogenous integration with various materials and form factors is, therefore, key to enhancing the performance of such microfluidic systems. The fabrication of complex three-dimensional (3D) microfluidic components that can be easily integrated with other material systems and existing state-of-the-art microfluidics is of rising importance. Research on producing self-assembled 3D architectures by the emerging self-rolled-up membrane (S-RuM) technology may hold the key to such integration. S-RuM technology relies on a strain-induced deformation mechanism to spontaneously transform stacked thin-film materials into 3D cylindrical hollow structures virtually on any kind of substrate. Besides serving as a compact microfluidic chamber, the S-RuM-based on-chip microtubular architecture exhibits several other advantages for microfluidic applications including customizable geometry, biocompatibility, chemical stability, ease of integration, uniform field distributions, and increased surface area to volume ratio. In this Review, we will highlight some of the applications related to molecule/particle sensing, particle delivery, and manipulation that utilized S-RuM technology to their advantage.