Uniform Field Distribution Research Articles

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.

Experimental study and characteristic analysis of vacuum arc between cup-type axial magnetic contacts under different diameter-to-gap ratios

Since vacuum circuit breakers gradually advanced to higher voltage levels, axial magnetic field (AMF) contacts have drawn a great deal of attention due to their excellent breaking ability. The cup-type AMF contact is a common kind of AMF contact, which has much potential in contact design and application of high voltage grade systems due to the advantages of strong structural strength, uniform magnetic field distribution, lower resistance, etc. This study analyzes the arcing characteristics of a cup-type AMF contact with a large slotted rotation angle at various diameter-to-gap ratios (DGRs). The arcing process is divided into five stages as follows: initial diffusion, contracting, fully constricted, re-diffusion, and extinguished. Arc self-rotation and anode separation phenomena in the re-diffusion stage appear when the DGR is 58/24. The reasons for these occurrences were discussed and explained with regard to the magnetic field vector's spatial distribution. The duration of each stage and the current threshold of a fully constricted arc will both differ with the change of the DGR. The structural parameters of the fully constricted arc were computed through the method of imaging the luminous intensity distribution after the arc was fully constricted. The source of the change in the arc voltage can be seen in the variation of arc structural parameters, which also reflect anode activity intensity to a certain extent. The transient magnetic field simulation method was used to explain why the arc under the same instantaneous current shows variable morphology at the extinguished stage and contracting stage in one arcing process. The research results presented in the article can be used as a reference for developing high-voltage cup-type AMF contacts.

The magnetic field design of a solenoid for the cold-cathode Penning ion source of a miniature neutron tube

A high-yield and beam-stable neutron tube can be applied in many fields. It is of great significance to the optimal external magnetic field intensity of the cold-cathode Penning ion source (PIS) and precisely controls the movement of deuterium (D), tritium (T) ions and electrons in the source of the neutron tubes. A cold-cathode PIS is designed based on the solenoidal magnetic field to obtain better uniformity of the magnetic field and higher yield of the neutron tube. The degree of magnetic field uniformity among the magnetic block, double magnetic rings and solenoidal ion sources is compared using finite element simulation methods. Using drift diffusion approximation and a magnetic field coupling method, the plasma distribution of hydrogen and the relationship between plasma density and magnetic field intensity at 0.06 Pa pressure and a solenoid magnetic field are obtained. The results show that the solenoidal ion source has the most uniform magnetic field distribution. The optimum magnetic field strength of about 0.1 T is obtained in the ion source at an excitation voltage of 1 V. The maximum average number density of monatomic hydrogen ions (H+) is 1 × 108 m−3, and an ion-beam current of about 14.51 μA is formed under the −5000 V extraction field. The study of the solenoidal magnetic field contributes to the understanding of the particle dynamics within the PIS and provides a reference for the further improvement of the source performance of the neutron tube in the future.

Triple-Mode Resonant Backfire Feed Antenna With Nearly Equal E-/H-Plane and Inverse Taper Patterns

A design approach to triple-mode resonant feed antenna is advanced for parabolic reflector antenna system. The antenna is composed of a slit-loaded 1.5-wavelength sectorial dipole, a primary corner reflector, and an auxiliary circular reflector. The corner angle of the primary reflector can be employed to properly narrow down the H-plane half-power beam width (HPBW), while with the E-plane one rarely affected, such that equal E-/H-plane characteristic can be yielded accordingly. Unlike traditional backfire antennas, high-order resonant modes are employed to generate inverse taper radiation pattern at the high frequency band. As is numerically demonstrated and experimentally validated, the corner angle of the primary reflector can be eventually determined as 45∘. The antenna exhibits an impedance bandwidth of up to about 79.7%, and a nearly equal E-/H-plane bandwidth of up to about 29.4%. Average HPBW of about 65∘, gain up to about 8.9 dBi with fluctuation of less than 1 dB can be achieved within the equal E-/H-plane bandwidth. The inverse taper radiation pattern at the high frequency band can provide effective edge illumination and uniform aperture field distribution in parabolic reflector antenna systems.

Experimental investigation of metasurface-based resonator for one-to-many wireless power transfer systems in the presence of foreign objects

The wireless charging of multiple devices simultaneously is on a high demand. Metasurface-based resonators with a uniform magnetic field distribution over a large area have been recently proposed as a transmitting resonator for one-to-many WPT systems. However, the problem of the influence of foreign objects on a one-to-many WPT system characteristics has not been deeply studied. Herein, we explore the influence of different foreign objects such as a metal screen, ferrites, coins, and a smartphone on the input impedance of the WPT system utilizing a metasurface-based resonator. We experimentally investigate the impact of foreign objects on the WPT system parameters and define the most destructive foreign objects. To avoid this parasitic impact, we modify the metasurface-based resonator design by shielding the magnetic field. We numerically demonstrate that the modified design does not provide any magnetic field beneath the metasurface-based resonator.

Electric activation curing behaviour of reinforced concrete beam under severely-cold environment: Breakthrough of rapid concrete manufacturing at cold region

Rapid on-site fabrication of concrete structure in severely-cold environment is a tough problem. Electric activation (EA) curing exhibited significant advantage on preparing laboratory-scale cement mortar at negative temperature, however, the feasibility of this curing method on manufacturing full-size concrete structure needs to be investigated. In this work, EA curing was proposed to rapidly manufacture on-site reinforced concrete (RC) beam in practical cold environment. The specific development regularity of the electrical resistance for EA cured RC beam was theoretically predicted and experimentally verified, and the electrical resistance of EA cured beam kept in a stable increasing trend during the whole curing process, regardless the harsh environment. Moreover, the temperature field distribution inside the structure was also clarified, it was found that EA curing could maintain a uniform temperature field distribution of RC beam at around 45 ℃ during the whole EA curing process. Further, mechanical property results revealed that EA curing could rapidly promote the strength formation of RC beam under severely-cold environment with the 2-day compressive strength of 28.4 MPa, reaching C30 concrete strength grade. In addition, this work firstly revealed the structural performance of EA manufactured RC beam, which exhibited higher ultimate flexural bearing capacity (233 kN) comparing with standard curing manufactured beam of 215 kN. This work gives a thorough investigation over the performance development of RC beam subjected to EA curing under extremely-harsh environment, making a breakthrough towards rapid fabrication of high-quality concrete structure at winter in cold regions.

Reconciling Mass Loading and Gravimetric Performance of MnO2 Cathodes by 3D‐Printed Carbon Structures for Zinc‐Ion Batteries

AbstractTo promote the real application of zinc‐ion batteries (ZIBs), reconciling the high mass loading and gravimetric performance of MnO2 electrodes is of paramount importance. Herein, the rational regulation of 3D‐printed carbon microlattices (3DP CMs) enabling an ultrathick MnO2 electrode with well‐maintained gravimetric capacities is demonstrated. The 3DP CMs made of graphene and carbon nanotubes (CNTs) are fabricated by direct ink 3D printing and subsequent high‐temperature annealing. 3D printing enables a periodic structure of 3DP CMs, while the thermal annealing contributes to high conductivity and defective surfaces. Due to these structural merits, uniform electrical field distribution and facilitated MnO2 deposition over the 3DP CMs are permitted. The optimal electrode with MnO2 loaded on the 3DP CMs can achieve a record‐high specific capacity of 282.8 mAh g−1 even at a high mass loading of 28.4 mg cm−2 and high ion transfer dynamics, which reconciles the loading mass and gravimetric performance. As a result, the aqueous ZIBs based on the 3DP CMs loaded MnO2 afford an outstanding performance superior to most of the previous reports. This study reveals the essential role of interaction between active materials and current collectors, providing an alternative strategy for designing high‐performance energy storage devices.

Study of Electromagnetic Characteristics of Brushless Reverse Claw-Pole Electrically Excited Generators for Automobiles

A new type of brushless reverse claw-pole electrically excited generator is proposed for the problems of the low sine degree of the induced electromotive force waveform and the high harmonic content of the output voltage of the conventional electrically excited claw-pole generator. The design uses the equivalent magnetic network method to establish the equivalent magnetic circuit model of the motor and determines the equation for calculating the magnetoresistance of the isosceles trapezoidal variable section claw-pole structure. It derives the mathematical model of the no-load induced electric potential of the generator and completes to optimize the motor parameters with the no-load induced electric potential as the target. This study shows that the brushless reverse claw-pole electrically excited generator has the advantages of uniform magnetic field distribution, high harmonic fundamental amplitude of induced electromotive force and low harmonic content. It can better meet the application requirements compared with the conventional electrically excited claw-pole generator.

A nanocellulose-mediated, multiscale ion-sieving separator with selective Zn2+ channels for durable aqueous zinc-based batteries

A heterostructure engineered, multiscale ion-sieving separator with desired macro‑meso-molecular pores that can render selective Zn2+ permeability and homogeneous Zn2+ distribution at the separator-electrode interface is designed to achieve durable aqueous Zn-ion batteries. The proposed separator is fabricated by stacking an intermediate nanocellulose layer and a poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) upper layer on a glass fiber substrate, wherein the nanocellulose layer contains uniform mesopores favoring a homogeneous Zn2+ flux and endowing the attainment of a PEDOT:PSS layer. While the PEDOT:PSS layer features intrinsic ionic/electronic conductivity and rich sulfonate groups enabling uniform electrical field distribution and inhibiting anions migration. The combination of mesoporous nanocellulose and cation-permeable PEDOT:PSS used in the heterostructure separator yields a high ionic transference number and fast Zn2+ desolvation kinetics. This unique separator enables highly compact and dendrite-free Zn deposition at 4 mA cm−2/8 mAh cm−2, and sustains the symmetric Zn||Zn cell over 400 h at 10 mA cm−2/4 mAh cm−2. Such advantages bring remarkable reversibility to full AZBs with high I2 mass loading cathodes of 13.0 mg cm−2, delivering a discharge capacity of 172.1 mAh g−1 after 1000 cycles. This multiscale ion-sieving design principle provides new insight into separator engineering for ultra-stable Zn metal batteries.

A universal UHF near‐field RFID reader antenna with wide bandwidth and adjustable reading area

AbstractA universal ultrahigh‐frequency (UHF) near‐field radio‐frequency identification (RFID) reader antenna with wide bandwidth and adjustable reading area is proposed in this letter. The antenna consists of an inverting power splitter base on double‐sided parallel stripline and adjustable traveling‐wave near‐field radiation units, which consists of two symmetrical meander microstrips and a complementary open resonant ring loaded on the ground plane. A design example with three radiation units is simulated, fabricated, and tested for verification. The result indicates that the proposed antenna has the 10‐dB impedance bandwidth of 128%, which completely covers the universal UHF RFID band from 840 to 960 MHz. The 100% read–write rate is achieved within the read–write distance of 10 mm according to the reading test. The reading area of 731 × 120 mm2 can be obtained for increasing the number of radiation units to 10. Moreover, the antenna features low far‐field gain, low‐cost, strong and uniform magnetic field distribution. Therefore, the proposed antenna and design method have good application prospects in the Internet of Things.

3D Multiphysics simulation of microwave heating of bulk metals with parametric variations

Microwave processing of metal base material is a novel and energy-efficient technique. Microwave heating of bulk metal is an emerging method with cost, time, and energy savings over conventional heating methods. This numerical study uses the finite element method-based COMSOL Multiphysics tool to analyse the microwave heating properties of a bulk metal sample. Further in this study, the effects of tooling design assembly and microwave power parameters have been analysed for temperature profile and electric field distribution. The outcome of parametric variations has been analysed in terms of electric field distribution, heating uniformity, temperature gradient, and energy requirement. Experimental results coincided with simulated results in terms of time-temperature characteristics within ±5% error. The heating uniformity of bulk metal can be achieved at low power with small-size component whereas high power creates thermal heterogeneity with high energy consumption. The cylindrical casket geometry shows uniform field distribution with rapid heating of the specimen compared to prismatic geometry. Susceptor's dielectric properties have a significant effect on the homogeneity of the process, and the heating efficiency of the irradiated specimen. The present simulation model can be used to control the heating rate of bulk metal considering various dynamic parametric properties for a complex microwave hybrid heating process.

Thermal field control in heated concrete mixture

Direct electric preheating of concrete mixture (DEPC), which significantly improves the energy efficiency of thermal curing stage, is mostly used in winter concreting and is promising for application in precast concrete production. However, to date, DEPC is not fully utilized. One of its limitations is the temperature difference in the heated volume. The paper proposes methods and means of achieving the uniform temperature field distribution in the heated concrete mixture. The proposed method includes the replacement of plate electrodes by a group of independently controlled electrodes of a smaller size, that makes the system flexible and capable of controlling the electric and, consequently, thermal field. The paper describes the equipment, principles of constructing the algorithm for the heating process control program.

Thermal system for a new flexible composite tank

A flexible thermal insulation system is proposed in this study, which considers the application and promotion of flexible composite materials in the field of marine engineering. This system is designed to provide a cost-effective and convenient thermal insulation solution for avoiding impurity precipitation and formation of wax plugs caused by extremely low temperature during mining, transportation, and storage of oil. The thermal insulation system includes two main parts: the insulation layer and the heating source. In accordance with the laws of thermodynamics and the primary characteristics of the flexible structure, two different insulation systems were designed and model tests were performed to compare performance in heating efficiency, thermal insulation, and temperature field distribution under identical environmental conditions. Compared with the plan 1 thermal insulation system, the plan 2 system has lower requirements for heating power, more uniform temperature field distribution inside the flexible structure, and a difference of only 7.18°C between the highest and lowest temperatures.

Compact High Gain Omnidirectional Horizontally Polarized Antenna Array Utilizing an Aperture With Uniform Field Distribution

A compact high gain omnidirectional horizontally polarized (OHP) antenna array is proposed in this communication. The theoretical calculations prove that a slender aperture with uniform field distribution can achieve OHP radiation with high directivity. The rectangular patch antenna operating in TM10 mode is employed to obtain an element with the specific field distribution. To extend the electrical length of the aperture, the element is elongated, and four collinear elements are integrated as an array without any redundant structures. Benefitted from the reasonable electric field distribution and concise configuration, the aperture efficiency is significantly improved. Therefore, the proposed antenna can achieve high gain OHP radiation in a compact size. The overall dimension of the antenna array is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4.62\lambda \times 0.22\lambda \times 0.07\lambda $ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda $ </tex-math></inline-formula> is the free space wavelength at the center frequency). Measured results verify that the impedance bandwidth of the array covers 5.46–6.13 GHz with a relative bandwidth of 11.6%, a maximum realized gain of 11 dBi, and good omnidirectional characteristics with a gain variation of less than 3 dB in the entire operating bandwidth.

Research progress on heteromorphic structure parts fabricated by additive manufacturing based on inside-laser coaxial powder feeding

Inside-laser material feeding laser cladding deposition (IMF-LCD) is a directed energy deposition technology featuring “hollow beam, annular spot, centered powder, and coaxial powder feeding.” IMF-LCD offers distinct advantages over traditional outside laser material feeding laser cladding deposition (OMF-LCD), such as a good laser-powder coupling effect, high powder utilization, high forming flexibility, uniform thermal field distribution in molten pools, and excellent forming surface quality. IMF-LCD would significantly improve forming efficiency and surface quality while it was applied to rapid direct manufacturing and repair of complex metallic parts compared to OMF-LCD. In this manuscript, the working principle of IMF-LCD technology is briefly introduced. Mostly, the research progress on heteromorphic structure parts fabricated by IMF-LCD was summarized, focusing on layered design, posture change, forming strategy optimization, and process parameter adjustment. The heteromorphic structure included a twisted thin-walled structure, variant height/width structure, overhanging structure, and closed structure. Based on the excellent characteristics of this technology, the exploration of high forming quality heteromorphic structural parts is carried out by changing the process parameters and forming processes such as the variable attitude stacking method, the conformal discrete layering method and the normal layering method, and the surface roughness is as low as 1.323 μm, the dimensional accuracy is as high as 1.6%. Simultaneously, the powder utilization rate of IMF-LCD reached 60%–80% on average, in accordance with the advantages of the laser-powder coupling effect. Finally, the remarkable research and application of IMF-LCD technology in high flexibility, high precision, high surface quality, and high material utilization would further promote the development of additive manufacturing with higher performance, higher quality, and lower cost in the future.

Dynamic Induction Heating Temperature Field Analysis of Spiral Bevel Gears

Combining tooth surface induction heating and shot peening is an efficient method to improve tooth surface performance. Reasonable designs of the induction coil structure and parameters are essential for achieving uniform and efficient tooth surface heating. In this work, to precisely control the tooth surface temperature field and improve the heat uniformity across the tooth surface, a transverse coil (TC) and a longitudinal coil (LC) were designed, and the gear was set to rotate at a constant speed of 20 r/min, dividing the tooth surface is into a shot-peening area and heating area. Further, dynamic numerical simulations were performed using COMSOL Multiphysics in combination with the uniform rotation of gears to investigate the effect of the coil structure on the temperature field of the outer surface of gears. The results of the analyses combining the effects of different electrical parameters revealed that the gear surface temperature under LC heating was more uniformly distributed in the axial and circumferential directions, the tooth surface temperature fluctuations were smaller, the temperature difference between the root and top of the tooth was smaller, an coil heating was more efficient. Thus, the LC was deemed suitable for use as the spiral bevel gear induction heating coil. Finally, heating experiments were conducted using the LC to validate the simulation model. The results show that the use of LC heating can achieve the research goals of uniform temperature field distribution on the tooth surface and efficient temperature rise, providing the prerequisite for shot peening.

A Design Method for a Leaky-Wave System With Uniform Field Coverage and Broadside Radiation for a Vacuum-Tube Ultra-High-Speed Train

The communication system for vacuum-tube ultrahigh-speed trains faces great challenges from unstable signal coverage and severe Doppler effects as a result of long running distances and ultrahigh speeds. This communication presents a possible solution for a communication system in a vacuum-tube high-speed train system that operates using a leaky waveguide. The design method for the leaky waveguide is demonstrated in detail. The developed leaky waveguide consists of periodic metal posts and longitudinal slots in a staggered arrangement, and it can achieve the properties of uniform field coverage and broadside radiation. Therefore, the performance of long-distance transmission with stable signal quality can be realized, and the Doppler effect in the scenario of ultrahigh-speed rail can be mitigated. Leaky waveguides with lengths of 5, 10, and 20 m are designed as verifications of the method. A 5 m leaky waveguide is fabricated and measured. The measured results are consistent with the simulated results, demonstrating that a uniform field distribution and broadside radiation can be achieved using the developed leaky waveguide.

Design of Electrically Large UHF RFID Near-Field Bidirectional Antenna With AMC-Based Unidirectional Improvement

Two novel multisegment loops coupled ultrahigh-frequency (UHF) radio frequency identification near-field (NF) antenna with a uniform and strong magnetic field distribution over an electrically large interrogation zone are designed. Each proposed antenna is composed of eight loops, and the current distribution along the loop is kept in-phase using a segmented line. To further achieve a more uniform magnetic field, the last four loops of the two proposed antennas (ANT 1 and ANT 2) are loaded with parasitic structures. Here, a 100% detection rate is achieved by ANT 1 within an interrogation area of 370×560×105 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> for the bidirectional operation setup. As for ANT2, it is backed by an artificial magnetic conductor to enhance the magnetic field strength and reduce the profile with respect to a configuration with a PEC reflector plane, and it has yielded a 100% detection rate within the interrogation area of 370×560×185 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> for the unidirectional operation setup. The proposed ANT2 can cover the UHF band of China, the Federal Communications Commission band of North America, and European Telecommunication Standards Institute band of Europe.

Design and optimization of a modular wireless power system based on multiple transmitters and multiple receivers architecture

Wireless Power Transfer (WPT) technology has been applied to electric vehicles (EVs), for its convenience, safety, and high reliability. However, for the traditional single-transmitter-single-receiver WPT system, due to its uneven electromagnetic field distribution, the power transfer capability and the anti-offset performance are always insufficient. The multi-transmitter-multi-receiver (MTMR) WPT system based on modular inverters with coils can not only improve the transmission power of the system but also boost the system’s anti-offset ability due to its more uniform magnetic field distribution. In this study, the topology and transmission characteristics of the MTMR WPT system are discussed accordingly: 1) A decoupling method of transmitting coil based on capacitance compensation is proposed, and the particle swarm optimization algorithm is used to derive the optimal design scheme of magnetic coupling coil. 2) A phase-shifting control strategy is proposed to realize the phase synchronization and current sharing control of coil current at each transmitter. Finally, the simulation and experimental results show that the modular wireless power transfer system with multiple transmitters and multiple receivers has strong power transmission capability and anti-offset performance.

FDTD Analysis on WPT Efficiency Between Circuit-Shape Leaky Waveguide and 𝝀/2 Dipole Antenna for Snow Melting Application

The wireless transfer characteristics between a circuit-shape leaky waveguide and a /2 dipole antenna were analyzed with scattering parameters obtained with the FDTD method. The circuit-shaped leaky waveguide was composed of two pairs of straight slotted waveguides and two semicircular waveguides. The circuit-shape leaky waveguide was designed to achieve uniform electromagnetic field distribution with a source for snow melting with microwave radiations by microwave heating. The electromagnetic field of the circuit-shape leaky waveguide was firstly simulated with the FDTD method. Although the electromagnetic distribution exhibited the point symmetry with an off-set feeding point and a slot spacing 𝝀𝒈, it was nearly uniform. The wireless transfer efficiency and the maximum transfer efficiency for four locations at 2.45 GHz revealed that the farthest location from the feeding point had the largest WPT efficiency among four locations. This ensures the circuit-shape leaky waveguide’s uniqueness. The circuit-shape leaky waveguide has favorable characteristics to provide WPT energy at any location above it.