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Metal object detection (MOD) and living object detection (LOD) are essential for ensuring the safe operation of the electric vehicle (EV) wireless charging system. Since most MOD or LOD single-type systems protect the EV wireless charging system incomprehensively, the existing MOD and LOD shared system has problems such as difficulty in acquiring detection signal, and low accuracy for small-sized living objects (LOs). Thus, this article proposes a planar double-winding foreign object detection (FOD) system based on the time-division multiplexing control strategy. First, the planar double-winding FOD system structure is given, and the time-division multiplexing FOD mode switching as well as FOD judgement principle are analyzed. Second, the phase variation of bandpass filter output voltage in the planar double-winding FOD system is analyzed. Third, the sensing coil structure and detecting circuit parameters are optimized. Finally, an experimental platform is built to verify the feasibility. The results show that when MOD and LOD phase thresholds are set to 3$^{\circ }$ and 20$^{\circ }$, respectively, the phase variation is −21.3$^{\circ }$, −27.9$^{\circ }$, −7$^{\circ }$, and 48.3$^{\circ }$ for a copper plate, aluminum plate, iron plate of 40 × 40 mm2 and one hand. Therefore, the phase variation is larger than the phase threshold, which can effectively detect MO and LO.

Due to the complexity of current variation of the multifrequency and multiload (MFML) wireless power transfer (WPT) system based on hysteresis current (HC) control, resulting in a wide range of switching frequency variation, high frequency, and high switching losses of the inverter. This article proposes a blocking delay switching frequency control strategy. Based on the design of blocking delay module, the time division blocking delay and full-time fixed frequency blocking delay control modes are investigated, which can reduce the inverter switching frequency fluctuation range and fix the inverter switching frequency respectively. First, the structure and working principle of the MFML WPT system based on HC control containing passive compensation network are analyzed. Second, the system switching frequency characteristics are analyzed. Third, for different system switching frequency limitation requirements, time division blocking delay control mode and full-time fixed-frequency blocking delay control mode are proposed. Finally, an experimental platform is built to verify the proposed control strategy, the experimental results show that the system switching frequency of different parameters is reduced to within 200 kHz and 180 kHz in the time division blocking delay control, and the system switching frequency is fixed to 150 kHz and 250 kHz in the full-time fixed-frequency blocking delay control.

Wireless power transfer technology is widely used for wireless electric vehicle chargers (WEVC) due to its safety, flexibility, and convenience. However, there is an inevitable misalignment between the transmitter and receiver of WEVC, which reduces the efficiency and stability of power transfer significantly. To this end, this article proposes a receiver position detection (PD) system based on the novel active beacon structure to improve the transfer performance of WEVCs. First, the novel beacons are activated to detect the receiver misalignment accurately before power transfer, which are placed on the vehicle side. Meanwhile, the PD coil matrix is employed on the ground side to achieve large-area and precise misalignment detection. Then, the parameters of PD circuits are optimized to reduce the sampled voltage errors correspondingly. In addition, with the aid of the proposed system structure, a weighted centroid PD algorithm is given to calculate the position of the receiver. Finally, the feasibility of the proposed PD system is verified by using an experimental prototype. The experimental results achieve an offset detection accuracy of 3 mm in the area of 600 mm×480 mm and a yaw angle detection accuracy of 2$^{\circ }$ in the area of 120 mm×480 mm.

• CSMA offers excellent electromagnetic stealth performance for a variety of complex applications. • The dual structures synergistically drive the formation of current vector vortices to enhance the loss of electromagnetic wave energy. • CSMA has an effective absorption bandwidth of 6.07–18 GHz and a thickness of 4 mm. The amount of absorbent used is half that of a slab coating of equivalent thickness. The performance breakthroughs of some stealth materials have benefited from incorporating biomimetic concepts, and the design ideas of wave-absorbing metamaterials have been greatly broadened. However, stealth materials developed based on a single biological structure still have limitations regarding overall performance and design freedom. Herein, a dual-structure element combination model with a butterfly-wing porous structure and moth-eye raised structure arranged in an orderly manner is established. Carbonyl iron and polyurethane are mixed as wave absorbents, and the model is utilized to make a biomimetic metamaterial (CSMA), which has an absorption rate of more than 90 % at 6.07–18 GHz, achieving broadband effective absorption. It has been verified that the two biostructures designed after an ordered arrangement show synergistic effects in the combined model, and the cooperation between the structures induces the formation of current vector vortices, which are able to induce microwave losses to broaden the effective absorbing bandwidth. Further, the model has the combined application performance of polarization insensitivity, strong stability of oblique incidence, and low bistatic RCS. Such a thought based on the combination of multiple components provides an effective strategy for the design of broadband-absorbing metamaterials. [Display omitted] [ABSTRACT FROM AUTHOR]

For underwater wireless power transfer (UWPT) systems, one of the most difficult problems is how to accurately identify the mutual inductance, load resistance, and parasitic parameters of the system. That is because these parameters will be influenced by the electromagnetic properties of seawater, the wave disturbance, and the charging process. And the system performance will be impacted correspondingly. Therefore, this article presents a new parameter identification and frequency regulation strategy for the UWPT systems. First, an improved mathematical model of the UWPT system is established by considering the eddy current effect in the primary, secondary, and mutual inductance branches. Then, the parameter identification strategy of mutual inductance, load resistance, and parasitic parameters is proposed by a simple frequency regulation method based on the proposed UWPT system model. Subsequently, with the identified results, the frequency splitting phenomenon and frequency regulation strategy are studied to further improve the system's performance. Finally, a 600 W UWPT setup is built up to verify the theoretical analysis, and the experimental results show that the average identification accuracy can reach 97.3%, and the maximum output power can be realized with nearly constant system efficiency.

Aiming at the problems that existing multifrequency and multiload (MFML) magnetic coupling resonant wireless power transfer (MCR-WPT) systems either the output power frequencies are limited or a large amount of reactive power in them leads to decreased power factor (PF). This article proposes an MFML MCR-WPT system based on hysteresis current control, which controls multifrequency current superposition output and has equivalent current source characteristics. The system outputs multifrequency current by tracking the command current, which consists of subcommand currents designed according to load frequency and power requirements and raises PF without affecting power transfer quality by adding power compensating capacitor (CP) with lower cost and design complexity than existing technologies. First, the system structure and working principle are introduced. Then, the criterion of equivalent current source is deduced, based on which the system model is established, and its characteristics are analyzed. After that, the system parameter design methods are given. Finally, an experimental platform is built to verify the proposed theory. The simulation and experimental results show that the proposed system can output multifrequency power, switch the frequency freely, and raise PF by adding Cp without affecting power transfer.

Different kinds of compensation topologies are widely used in wireless power transfer (WPT) systems, resulting in loads with different compensation topologies hardly obtaining the same power from the same power transmitter. In addition, the load power and system efficiency are hard to hold constant when the mutual inductance or load resistance varies, and these two variation parameters are both hard to be accurately identified. These severely limit the practical popularization of the WPT technology. Therefore, a new strategy to improve the compatibility and performance of the WPT system based on the Q-learning algorithm and switch-controlled-capacitor (SCC) is proposed in this article. The Q-learning algorithm is used to train an intelligent offline database by monitoring the voltage and current in the primary side of the system to obtain an optimized compensation capacitor on the primary side without knowing the mutual inductance and load resistance. A 1-kW prototype is established and the experimental results demonstrate that the load side can receive desired power when the load changes from one kind of compensation topology to another, or the load resistance and mutual inductance vary together. Meanwhile, the coil-to-coil efficiency can also be effectively maintained.

It is practically challenging for the output power in the magnetic field energy harvesting systems around high-voltage transmission lines. Consequently, a system of isolated orthogonal magnetic energy harvesting is proposed, which is consisted of two mutually orthogonal magnetic field energy harvesting modules and subsequent rectification circuits. According to the magnetic field distribution around the power transmission lines based on the catenary model at an existing 500 kV double circuit transmission tower, an H-type magnetic field energy harvesting module is designed based on the isolated magnetic field energy harvesting principle. Through two H-type magnetic energy harvesters, the energy is harvested and converted into voltage. The corresponding voltage is connected in series to power the load after being rectified respectively by the Cockcroft–Walton voltage multiplier circuit. Compared with the existing harvesting modules, the output power of the H-type magnetic field energy harvesting module is significantly improved in the condition of the same external magnetic flux density. The system proposed is modeled and analyzed, then a prototype was designed. The experimental results show that the DC output power of the system can reach up to 13 mW in an environment with an external magnetic flux density of 18 μT. And the correctness and feasibility of the system of isolated orthogonal magnetic field energy harvesting are verified.

One of the most difficult problems of the three-coil wireless power transfer (WPT) systems is that the receiving coil is hardly fully aligned with the transmitting and relay coils, which affects the efficiency of the practical system seriously as the coupling exists among the transmitting, relay and receiving coils simultaneously. Therefore, this article presents a new mutual inductance identification and efficiency optimization method for the three-coil WPT system with a switchable relay coil. First, the mathematical model of the three-coil WPT system with and without the relay coil is constructed. Second, the mutual inductance identification method is proposed to analyze the mutual inductances among the three coils by the switchable relay coil, which does not need complicated mathematical calculation strategies and the operating frequency of the system can be held constant. Then the coil-to-coil efficiency of the system is compared with and without the relay coil when the load resistance or position varies. Finally, a coil-to-coil efficiency improvement method is proposed to ensure that the system can always operate under high-efficiency conditions according to the identified mutual inductances of the three-coil WPT system.

Mid-range wireless power transfer (WPT) system for consumer electronics has been hamstrung by modest energy efficiencies and low misalignment tolerance. As the increase in transfer distance, the increasing leakage magnetic flux between transmitting coil and receiving will deteriorate the system performance. In this article, a novel optimization-based design method of passive array coils (PACs) is presented in order to maximize the power transfer efficiency (PTE) and improve the misalignment tolerance in WPT system. A modified multiobjective genetic algorithm is implemented to optimize parameters of PACs in consideration of PTE, displacement flexibility and volume of PACs. Moreover, a parameter design scheme for compensation network, namely Series-Seriess-Series topology for co-planar multiple coils is investigated, which can achieve zero phase angle in primary side and enhance power factor. Finally, the reasonable prototype of the proposed WPT system with PACs is designed, fabricated and tested. The experimental results show that the proposed structure can increase the efficiency by almost 50% over the system without PACs at 400 mm distance and deliver almost 40 W of output power. Moreover, the PTE and output power can still remain stable under large lateral misalignment with PACs.

Metal object detection (MOD) technology can effectively improve the safety of wireless charging systems for electric vehicles. To solve the problem of disunity in sensitivity evaluation methods and the lack of parameters design rules in the research field of MOD technology, a sensitivity evaluation model for MOD systems based on sensing coils is constructed and three system parameters design rules are proposed based on this model. First, a sensitivity evaluation factor is defined and different types of detection blind spot generation mechanisms are distinguished. Second, three parameters design rules are obtained: parameters design rules for high sensitivity, parameters design rules for low detection voltage errors, and parameters design rules for reducing Rx coil impact. Third, the parameters design rules are verified and modified by electromagnetic field simulation. Three engineering parameters design rules for the bipolar checkerboard MOD system are obtained. Finally, a bipolar checkerboard MOD system is built to test different materials and sizes of metal objects (MOs). The eddy current dividing MOs capability and the advantage of high sensitivity of the bipolar checkerboard MOD system are verified.

In order to reduce the reactive power of the existing hybrid modulation pulsewidth modulation (HM-PWM)-controlled multifrequency and multiload wireless power transfer (MFML WPT) system without a resonant network, a design idea of a variable resonant network is proposed, accordingly, an HM-PWM-controlled MFML WPT system based on a variable resonant network is studied. According to the variation in load frequency, the output frequency of the inverter and the frequency of the variable resonant network can change accordingly. First, the structure and working principle of the MFML WPT system based on a variable resonant network are introduced. Second, taking a dual-frequency variable resonant network as an example, the control method and range of frequency adjustment are studied by modeling. Third, the MFML WPT system based on a variable resonant network is mathematically modeled, the output power and efficiency are analyzed. Finally, the feasibility of the design idea of the variable resonant network is proved by experiments. The results show that in the range of 20–90 kHz, the variable resonant network can realize stable switching of any two frequencies, and the power factor of the system can reach 0.99. So, the MFML WPT system can realize high-efficiency WPT for loads with different frequencies.

In this article, electromagnetic metamaterials with mu-near-zero (MNZ-MM) have been presented to explain the shielding effect in the wireless power transfer systems. First, the optimized design of the metamaterials unit cell has been carried on to achieve the near-zero permeability at the working frequency of 13.56 MHz. The equivalent circuit model of the MNZ-MM unit cell has been derived, which illustrates metamaterials with near-zero permeability have the great electromagnetic field (EMF) shielding effect. Additionally, the self- and mutual inductances associated with the resonance coils and MNZ-MM unit cells are deduced in detail. Moreover, the simplified human head model is established to investigate the magnetic field cancellation by MNZ-MM on the coil side. To evaluate the performance of the proposed MNZ-MM, the magnetic field strengths of the receiving terminal with different shielding materials have been compared in simulation. Finally, a series of experiments in real-environment are implemented to discuss the shielding effect of the MNZ-MM. The measurement results show the MNZ-MM has better performance in the swine brain sample than the ferrite and aluminum plate on the whole. With the proposed MNZ-MM, we demonstrate a maximum reduction of 17.52 dB in the leakage EMF and basically no effect on transfer efficiency.

Metal object detection (MOD) technology provides a guarantee for the safe operation of electric vehicle (EV) wireless charging system. To solve the problem of detection blind zone caused by excitation magnetic field in the existing MOD technology, a bipolar checkerboard MOD technology is proposed. By adding an excitation source, not only the blind zone is eliminated but also it makes the EV wireless charging system and the MOD system work independently. First, the positions and causes of the blind spot caused by the excitation magnetic field of the Tx coil in the EV wireless charging system are analyzed. Second, the structure and principle of the bipolar checkerboard MOD system are analyzed. Third, a definition of the detection sensitivity of MOD is given, and the relationship between sensitivity and the size parameters of bipolar checkerboard sensing coil sets is analyzed. Moreover, the parameter optimization method of the sensing coil sets and detection circuit is analyzed. Finally, a MOD system experimental setup is built to verify its feasibility. The results show that the highest sensitivity can reach 20% for a square aluminum plate of 80 × 80 × 1 mm3 without a blind zone and the two systems can work independently with each other.

This paper tracks trends in COVID-19 case, death, and vaccination rate disparities by race and ethnicity in Virginia during the COVID-19 pandemic. COVID-19 case, death, and vaccination rates were obtained from electronic state health department records from March 2020 to February 2022. Rate ratios were then utilized to quantify racial and ethnic disparities for several time periods during the pandemic. The Hispanic population had the highest COVID-19 case and age-adjusted death rates, and the lowest vaccination rates at the beginning of the pandemic in Virginia. These disparities resolved later in the pandemic. COVID-19 case and death rates among the Black population were also higher than those of the White population and these disparities remained throughout the pandemic. Racial and ethnic disparities changed over time in Virginia as vaccination coverage and public health policies evolved. Year 2 of the analysis saw lower case and death rates, and higher vaccination rates for non-White populations in Virginia. Public health strategies need to be addressed during the pandemic and developed before the next pandemic to ensure that large racial and ethnic disparities are not again present at the outset.

It is the key to realize the precise control of power transfer direction and energy to ensure the synchronous phase shift of the bilateral converters in bidirectional inductive power transfer (BD-IPT) system. In order to solve the problem that wireless communication is adopted in bidirectional inductive power transfer system, and the delay caused by the power oscillation affects power transfer. A method for synchronizing the control signals of the bilateral converters that track the extreme value of the output DC current is proposed in this paper, and dual phase-shift control is adopted to make the system efficient when it operates in a wide output power range. First, the power and efficiency characteristics of the BD-IPT system are analyzed in the paper. Next, a method to track the extreme value of the output DC current is designed for synchronization. Then, in order to ensure that the system maintains high-efficiency operation in a wide power range, a bilateral phase shift control is proposed. Finally, the validity of the scheme is verified through simulation and experiment.

Ticks are specialized ectoparasites that feed on blood, causing physical harm to the host and facilitating pathogen transmission. The genus Haemaphysaliscontains vectors for numerous infectious agents. These agents cause various diseases in humans and animals. Mitochondrial genome sequences serve as reliable molecular markers, forming a crucial basis for evolutionary analyses, studying species origins, and exploring molecular phylogeny. We extracted mitochondrial genome from the enriched mitochondria of Haemaphysalis tibetensisand obtained a 14,714-bp sequence. The mitochondrial genome consists of 13 protein-coding genes (PCGs), two ribosomal RNA, 22 transfer RNAs (tRNAs), and two control regions. The nucleotide composition of H. tibetensismitochondrial genome was 38.38 % for A, 9.61 % for G, 39.32 % for T, and 12.69 % for C. The A + T content of H. tibetensismitochondrial genome was 77.7 %, significantly higher than the G + C content. The repeat units of H. tibetensisexhibited two identical repeat units of 33 bp in length, positioned downstream of nad1and rrnLgenes. Furthermore, phylogenetic analyses based on the 13 PCGs indicated that Haemaphysalis tibetensis(subgenus Allophysalis) formed a monophyletic clade with Haemaphysalis nepalensis(subgenus Herpetobia) and Haemaphysalis danieli(subgenus Allophysalis). Although the species Haemaphysalis inermis, Haemaphysalis kitaokai, Haemaphysalis kolonini, and Haemaphysalis colasbelcouribelong to the subgenus Alloceraea, which were morphologically primitive hemaphysalines just like H. tibetensis, these four tick species cannot form a single clade with H. tibetensis. In this study, the whole mitochondrial genome sequence of H. tibetensisfrom Tibet was obtained, which enriched the mitochondrial genome data of ticks and provided genetic markers to study the population heredity and molecular evolution of the genus Haemaphysalis.

A design methodology for making magnetic coupling wireless power transfer (MC-WPT) systems resonate at given frequencies is proposed in this paper. Proposing such a method not only can improve the energy efficiency against frequency splitting, but also can satisfy the requirement of frequency standards and then promote its industrial application. The method is based on eigenvalues configuration and comprehensively considers all electric parameters. The quantitative relationship between the performance indexes and electric parameters is derived, based on which the expected electric parameters can be quickly and accurately determined. The design theory and design flow are provided, and practical systems are designed, simulated and measured to show the effectiveness of the proposed method. The results show that the proposed method can: 1) eliminate frequency splitting to make MC-WPT systems resonate at a given frequency; 2) utilize frequency splitting to make MC-WPT systems resonate at two given frequencies. [ABSTRACT FROM AUTHOR]

Traditional polar codes are constructed based on a size-2 kernel and the code length is thus restricted to an integer power of 2. To achieve flexible code lengths, punctured and shortened schemes are used in the existing 5G standard. Recently, an alternative approach for flexible code lengths, multi-kernel (MK) polar code, has been proposed, which is constructed based on both size-2 and other larges kernels. However, the error-correction performance is not as good as that of the punctured and shortened schemes. In this letter, an MK polar code construction method based on a kernel substitution scheme is proposed, which is a practical scheme to construct the codes using two types of large kernels with the same size so that the error-correction performance can be improved. Compared with the existing MK polar codes, simulation results show that 0.15 - 0.25dB performance gain can be achieved by SC decoding for most code settings at a block error rate of 10−4 without complexity overhead.