Electromagnetic energy is being utilized over multiple frequency bands to sustain high speed wireless communication systems around the globe. As a consequence, living bodies such as humans, animals, plants, and fruits continuously get exposed to electromagnetic radiation. To safeguard human health, a number of diversified international and national electromagnetic regulatory standards have been prescribed across geographical boundaries for limiting electromagnetic radiation - specific absorption rate and reference power density limits have been prescribed by the international organizations to protect humans from immediate thermal effects. However, reference power density limits differ by ten to hundred times across geographical boundaries depending upon the electromagnetic standards in effect. Moreover, prescribed reference power density limit also varies with frequency of irradiation. On the other hand, plants and fruits possess reasonably high permittivity and electrical conductivity that contribute to considerable electromagnetic energy absorption rates inside typical plant and fruit models. In addition, plants and fruits are primarily asymmetric in nature, and therefore direction of arrival and polarization of incident electromagnetic field are two additional factors that significantly influence the amplitude and spatial distribution of specific absorption rate. Therefore, prescribing only the maximum permissible power density limit in far field seems inadequate. To address these issues, specific absorption rates inside a typical multilayer mango fruits model have been estimated at five different frequencies in accordance with four different international and national electromagnetic regulatory standards (with contrasting reference power density limits) - the magnitudes and spatial distributions of specific absorption rates have been quantified and reported at different frequencies as well as for distinct averaging techniques. Moreover, the impact of direction of arrival and polarization of incident electromagnetic field on the magnitude and spatial distribution of specific absorption rate has also been investigated. A total of one hundred and twenty rigorous simulations has been performed, and as a consequence, four hundred and eighty specific absorption rate data points have been analyzed. Wide disagreement in specific absorption rate data is observed due to variations in four factors mentioned above, i.e. reference power density, frequency, direction of arrival, and polarization of incident electromagnetic field. Moreover keeping all the other factors unaltered, specific absorption rate cannot be directly correlated with the reference power density limit primarily due to non-identical and asymmetric structures of bunch of fruits and plants in most practical scenarios. Thus, observations indicate the necessity of adopting globally harmonized electromagnetic regulatory standards and direct adoption of specific absorption rate limit for plants and fruits instead of only the reference power density limits in far field exposure scenario.

In this study, a novel vehicle-mounted flywheel battery system is proposed, which can effectively balance the load capacity with margin, strong anti-interference, uncoupled magnetic circuit and low energy consumption. The proposed new flywheel battery adopts multiple magnetic circuits, reducing the number of permanent magnets and the complexity of the magnetic circuit. It is worth mentioning that the proposed ``side branch'' radial/tilting shared magnetic circuit can realize the main bearing function of the flywheel weight, and the axial biased magnetic field is used to suspend the near ``zero weight'' flywheel, so that the flywheel can withstand a certain interference margin in the axial direction, and then improve the active disturbance rejection and effectively reduce the control loss. After optimization, the unique overall structure of the flywheel battery can significantly improve the overall performance of the flywheel battery. Finally, the stiffness, decoupling, and anti-interference experiments are carried out, and the experimental results show that the proposed flywheel battery has good performance.

A broadband artificial magnetic conductor (AMC) metasurface for radar cross section reduction is proposed. Modified Jerusalem cross unit and quasi-circular unit can achieve effective reflection phase difference of 180˚ (±37˚) within a wide frequency range from 8.95-17.3 GHz. The broadband metasurface consists of chessboard-arranged 3 × 3 block arrays, and each block arrays is composed of 4 × 4 AMC units. The proposed AMC metasurface is applied to a microstrip antenna for reducing RCS. The measurement results show that the low RCS antenna can obtain 10 dB RCS reduction from 7.93-17.5 GHz. The relative bandwidth is 75.2%, and the maximum reduction value is 30.2 dB. Also, radiation performance of the antenna is well maintained.

Permanent magnet assisted synchronous reluctance motor (PMaSynRM) has been widely concerned, but the research on the vibration and noise of this kind of motor is relatively limited. In addressing the problem of significant vibration noise caused by radial electromagnetic force waves in PMaSynRM. The research explores a motor vibration and noise suppression solution involving stator slotting and rotor magnetic isolation hole opening. The study analyzed the impact of different slotting parameters on the radial electromagnetic force and air gap magnetic flux density of the motor and compared it with the solution involving slotting of the stator teeth only and magnetic isolation hole opening of the rotor only. Finally, the modal, vibration response and noise response of the motor after slotting are analyzed and verified. The results show that the amplitude of radial electromagnetic force and the total harmonic distortion rate of the air gap magnetic flux density of the motor are significantly reduced by opening the stator auxiliary slot and the rotor magnetic isolation hole. The maximum vibration acceleration of the motor is reduced by 33.44 mm/s², and the peak A-weighted sound pressure level of the motor decreases by 5.49 dBA.

The measurement and decoupling of currents in multi-core power cables is a significant concern for power operators and holds immense potential for optimizing the monitoring and control of urban distribution networks. This paper aims to provide a widely applicable method for reconstructing current measurements. The YJLV22-3 * 300 power cable is taken as an example, specifically focusing on the effect of steel armor on the measurement of the magnetic field generated by the current. Sample tests and field experiments are conducted to verify the spatial distribution of the magnetic flux density. Then the inverse problem of calculating current from the magnetic field is discussed. The defects of the existing methods are shown, and a new method for the inverse problem with the measured waveform of the tangential component of the magnetic flux density is proposed. The feasibility of the new method has been verified. The least-squares method is introduced to obtain the generalized inverse of the position coefficient matrix by maximum rank decomposition to extrapolate the conductor current matrix. A query method is proven to efficiently generate this matrix. Finally, the inverse problem is modeled as a stochastic search problem to compare the efficiency and stability of different algorithms, and CAM-ES performs best. The future research direction is oward developing and testing hardware measurement systems.

Dispersion error analysis can help to assess the performance of finite-element discretizations of the wave equation. Although less general than the convergence estimates offered by standard finite-element error analysis, it can provide more detailed insight as well as practical guidelines in terms of the number of elements per wavelength needed for acceptable results. We present eigenvalue and eigenvector error estimates for cubic Hermite elements on an equidistant 1-D mesh and on a regular structured 2-D triangular mesh consisting of squares cut in half. The results show that in 1D, the spectrum consists of 2 modes. If these are unwrapped, the spectrum is effectively doubled. The eigenvalue or dispersion error stays below 7% across the entire spectrum. The error in the corresponding eigenvectors, however, increases rapidly once the number of elements per wavelength decreases to one. In terms of element size, the dispersion error is of order 6 and the eigenvector error of order 4. The latter is consistent with the classic finite-element error estimate. In 2D, we provide eigenvalue and eigenvector errors as a series expansion in the element size and obtain the same orders. 2-D numerical tests in the timeand frequency-domain are included.

In this paper, the design and validation of an implantable antenna which is applicable to biotelemetry services is presented. This proposed antenna operates in the wireless medical telemetry service (WMTS) frequency band of 1.39-1.4 GHz. As compared to other contemporary antennas, this design provides better gain of -31 dB and reflection coefficient of -20.2 dB with better safe limit of specific absorption rate (SAR). At the resonating frequency of 1.4 GHz, the intended antenna provides good radiation and gain characteristics. The VSWR parameter for this designed antenna has been obtained as 1.25 which promises for proper impedance match. The designed antenna has been fabricated and validated with tissue mimic liquid-phantom to make sure the suitability for implantation. The simulated measurements have a close agreement with the experimentally measured results.

Gap-coupled designs of Sectoral microstrip antenna for 90˚ and 45˚ sectoral angle are proposed for wideband and circularly polarized response. On total substrate thickness of ~0.1 g, proximity fed design of 90˚ Sectoral patch yields simulated bandwidth of 827 MHz (50.41%) with a peak gain of 8.1 dBi, whereas its gap-coupled configuration with parasitic 45˚ Sectoral patches yields simulated bandwidth of 1336 MHz (69.11%) with a peak gain of 8.0 dBi. A gap-coupled design of two 90˚ Sectoral patches is presented in which orthogonal directions of the fundamental mode currents over the aperture are maintained. This yields circularly polarized response with axial ratio bandwidth of 709 MHz (34.88%), which lies inside the impedance bandwidth of 1103 MHz (60.09%). It offers a peak gain of larger than 7 dBi across the axial ratio bandwidth. To achieve all these operational features using a single patch, a reconfigurable design of Sectoral patches is proposed that yields similar wideband and circularly polarized characteristics. Thus, present study provides a wideband and circularly polarized design that offers either impedance bandwidth of more than 65% or axial ratio bandwidth of nearly 35%. For achieved antenna response, the proposed designs fulfill the requirements of LTE (band 65, 66, and 70) and various aeronautical service mobile satellite bands (1610-2300 MHz). Experimental validation for the obtained results is carried out that shows close matching.

In order to solve the problem that the recognition accuracy of human motion is not high when a single feature is used, a feature fusion human motion recognition method based on Frequency Modulated Continuous Wave (FMCW) radar is proposed. By preprocessing the FMCW radar echo data, the range and Doppler parameters of human motions are obtained, and the range-time feature map and Doppler-time feature map datasets are constructed. In order to fully extract and accurately identify the human motion features, the two features are fused, and then the two features maps and feature fusion spectrograms are put into the VGG16 network model based on transfer learning for identification and classification. Experimental results show that this method can effectively solve the problem of lack of information and recognition rate of single feature motion recognition, and the recognition accuracy is more than 1{\%} higher than that of the single feature recognition method.

For orbital angular momentum (OAM) based practical applications in radio frequency, inherent puzzles of traditional OAM carrying waves will be encountered inevitably, such as the inherent dark zone in the beam center and severe beam divergence. To solve the problem, some specific beams which are directional beams with high gain, and retain the vorticity and orthogonality of conventional OAM carrying beams have been put forward. They are termed as composite-orbital angular momentum (c-OAM) beam for the first time in this paper. Continuous arc source model (CASM) and discrete arc source model (DASM) are proposed to generate c-OAM beams which are composed of several OAM waves with different weights. Mathematical models of CASM and DASM are demonstrated, and the field expressions are derived. Numerical simulations are conducted to analyze the characteristics of the c-OAM beams, including directivity, vorticity, orthogonality, etc., and certify validity of the proposed model. In all, CASM and DASM are capable of generating c-OAM beams which are more suitable for OAM property based practical applications. Since beamforming is one of the key technologies in 5G systems, c-OAM beams are beneficial to be applied in current communication systems.

Double Parallel Rotor Permanent Magnet Synchronous Motors exhibit superior performance and compact size, but the growing trend of electrification imposes higher demands on them. This study proposes a predictive fault-tolerant control integrating a closed-loop identification model and conducts experiments on Double Parallel Rotor Permanent Magnet Synchronous Motors. Results indicated that the proposed closed-loop identification model, along with its fractional-order lead-lag compensator module, effectively optimized motor performance, reducing average tracking error by 78.36%. Additionally, with demagnetization faults, the predictive fault-tolerant control outperformed traditional fault-tolerant control in speed, current, and torque fault-tolerant control, demonstrating superior performance. Through 10 weeks of practical application records, Double Parallel Rotor Permanent Magnet Synchronous Motors achieved a working accuracy of 95%-99% under the closed-loop identification model, with recall rates reaching 92%-96% in fault-tolerant scenarios. In both natural and simulated demagnetization fault situations, 97.69% of Double Parallel Rotor Permanent Magnet Synchronous Motors could continue normal operation. This research holds positive significance for the development of motor systems and enhancing their adaptability in the trend of electrification.

In the past, copper served as the material for conductive patches in antennas, but its use was limited due to high costs, susceptibility to fading, bulkiness, environmental sensitivity, and manufacturing challenges. The emergence of graphene nanotechnology has positioned graphene as a viable alternative, offering outstanding electrical conductivity, strength, and adaptability. In this investigation, graphene is employed to fabricate conductive silver nanocomposites. The silver-graphene (Ag/GO) sample exhibits an electrical conductivity of approximately 21.386 S/cm as determined by the four-point probe method. The proposed flexible antenna, characterized by four carefully selected cylindrical shapes were used to construct the antenna patch. for enhanced bandwidth, resonates at 2.45 GHz. It achieves amazing performance characteristics, with a high gain of 11.78 dBi and a return loss greater than -20 dB. Safety considerations are addressed by evaluating the Specific Absorption Rate (SAR). For an input power of 0.5 W, the SAR is calculated to be 1.2 W/kg per 10 g of tissue, affirming the safety of integrating the suggested graphene flexible antenna into flexible devices. In this study, the bending of the antenna was assessed by subjecting the structure to bending at various radii and angles along both the X and Y axes. These findings underscore the promising utility of Ag/GO nanocomposites in the development of flexible antennas for wireless systems.

This letter describes the design of a third-order, compact, wideband waveguide filtering antenna with a transmission zero (TZ) in the upper stopband. A novel frequency-variant coupling (FVC) network that provides a TZ in addition to the pole is used to achieve compactness and higher selectivity. The position of the TZ can be changed in the upper stopband by altering the physical parameters of the proposed FVC. The radiating waveguide aperture is matched to the real admittance of the generator over a wide bandwidth by utilizing coupled-resonator theory. This leads to a wide fractional bandwidth of 23%, along with a TZ at the upper stopband. The filtering antenna has been manufactured using metal 3-D printing to achieve low manufacturing costs and light weight. The measured results are in good agreement with the simulated ones, which shows the feasibility of the proposed FVC structure for the design of the waveguide filtering antenna with a TZ.

Optical direct current (DC) transformer has become a hot spot of research with its high accuracy, wide bandwidth, and high voltage isolation characteristics, but has the technical difficulties of low signal-to-noise ratio of ODCT signal and poor temperature stability. For this reason, the study proposes a new type of optical DC transformer integrating material science and signal processing. The study introduces an improved terbium gallium garnet crystal sensing unit material and a signal processing algorithm with a plus-window dual correlation detection algorithm, and constructs an optical DC transformer model. Simulation results show that the temperature compensation method can effectively weaken the influence of temperature change on the measurement accuracy under both warming and cooling conditions, and higher accuracy can be obtained by using the whole period window for measurement. The system applying terbium gallium garnet crystals helps to enhance the measuring system's output signal-to-noise ratio and sensitivity. Terbium gallium garnet crystals as a sensing material can further decrease the measuring error compared with other magneto-optical glasses. Taken together, DC measurement system using terbium gallium garnet crystals and dual correlation detecting algorithm can control the error to about 0.3 s. Simulation experiments verify the validity and feasibility of the research methodology, which can guide the research and application of optical DC transformers in the future.

In order to improve the classification performance of Polarimetric Synthetic Aperture Radar (PolSAR) image by synthesizing various polarimetric features, a supervised manifold learning method is proposed in this paper for PolSAR feature extraction and classification. Under the umbrella of tensor algebra, the proposed method characterizes each pixel with a feature tensor by combining the high-dimensional feature information of all the pixels within its local neighborhood. The tensor representation mode integrates the polarimetric information and spatial information, which is beneficial for alleviating the influence of speckle noise. Then, the tensor discriminative locality alignment (TDLA) method is introduced to seek the multilinear transformation from the original polarimetric-spatial feature tensor to the low-dimensional feature. The label information of training samples is utilized during feature transformation and feature mapping; therefore, the discriminability of different classes can be well preserved. Based on the extracted features in the low-dimensional space, the SVM classifier is applied to achieve the final classification result. The experiments implemented on two real PolSAR data sets verify that the proposed method can extract the features with better stability and separability, and obtain superior classification results compared to several state-of-the-art methods.

In this work, a low-profile and flexible antenna operating in the ISM (2.4-2.4835) GHz band for bio-telemetry applications is presented. This antenna is designed on two flexible substrate materials: Roger RO3003 with a thickness of 0.254 mm and jeans fabric material with a thickness of 0.7 mm, of an overall foot print of 20 × 30 mm². The deformation bending of the designed antenna in two different cases is studied. The designed antenna is backed by a 3 × 3 artificial magnetic conductor (AMC) array structure, which resulted in the final design configuration. The antenna is backed by an AMC array structure to achieve a lower specific absorption rate (SAR) as well as high gain when it is mounted on biological tissue. For validation, the antenna is fabricated on two flexible substrate materials and then measured in free space as well as on four different parts of the realistic human (chest, back, arm, and leg) body with and without AMC structure. Furthermore, the SAR is measured on cSAR3D flat. Finally, for reliable communication, the link margin is calculated.

The process of smart antenna synthesis involves the automatic selection of the optimal antenna type and geometry in order to enhance antenna performance. A model for intelligent antenna selection employs an optimizable K-nearest neighbors (KNN) classifier to determine the optimal antenna choice. To optimize the utilization of different learner types, the geometric parameters of the antenna are presented as the final step prior to the construction of the ANFIS model, which involves the integration of five distinct primary learners. The classification of three distinct types of antennas, namely helical antenna, pyramidal horn antenna, and rectangular patch antenna, is performed using an optimizable K-nearest neighbors (KNN) classifier. Additionally, an ANFIS approach is employed to determine the optimal size parameters for each antenna. The accuracy is used to evaluate the performance of an Optimizable KNN classifier, whereas Mean Squared Error and Mean Absolute Percentage Error are used to evaluate the performance of an ANFIS. The proposed technique demonstrates high performance in parameter prediction and antenna categorization, achieving a Mean Absolute Percentage Error of less than 3% and an accuracy exceeding 99.16%. The recommended methodology holds significant potential for widespread application in the development of practical smart antennas.

An optimal blend of relatively high frequency and effective atmospheric penetration renders the X-band a versatile selection for a wide range of applications. Hence, metamaterial absorber and frequency selective surface (FSS) as a band-stop filter and shielding element play a significant role in X-band. This article proposes a cost-effective, wide oblique and polarization-insensitive metamaterial, whose applications as an absorber and FSS having band-stop characteristics for X-band are explained. The isotropic unit cell of the proposed metamaterial is designed by an array of two subunit cells, where one is the 90˚ rotated version of the other with diagonal symmetry. Equivalent circuits of both subunit cells and array structure are systematically designed and analyzed, which provides scope for future modification according to the required frequencies. The proposed absorber provides three absorption peaks and absorptivity of more than 90% up to 60˚ oblique incidence angle. A good agreement between experimentally measured and simulated results is observed. For the use of the structure as FSS, it has been optimized to provide band-stop characteristics precisely for the X-band up to a wide oblique incidence angle. The proposed design can be used as an absorber, band-stop filter, reflector, and shielding element for the X-band.

The application scenarios of near-field focusing metasurfaces usually require scanning the target area. Passive metasurface requires a turntable to complete scanning due to its limited functionality. The active metasurface typically has a high cost because it needs to load PIN diodes. To address this issue, the article introduces a 1-bit reconfigurable metasurface that can achieve multi-focus tunability under fixed polarization through a rotating array. The 1-bit polarization-independent metasurface unit consists of three layers of metal. The top layer of the unit consists of three rectangular patches in the X-direction, the middle layer is a cross-shaped patch structure, and the bottom layer is a metal ground. The cross-shaped structure in the middle layer can easily provide the 1-bit reflection phase required for two orthogonal polarizations independently. Using a vertically polarized horn to illuminate the metasurface, the top layer's X-direction rectangular patches do not provide phase for vertical polarization. By rotating the array where the cross-shaped patches are located by 90°, the phase shift provided can achieve two focal points. On this basis, rotate the upper array by 90°, making the rectangular patches change from the X-direction to the Y-direction. Meanwhile, the current of the cross-shaped patches is blocked under vertical polarization illumination. By changing the upper rectangular patches, a third independent phase can be provided. After size optimization, a third focus can be formed. The proposed 1-bit focusing-adjustable metasurface array has a simple structure, low cost, and enhanced utilization rate of the metasurface array. It has a high application prospect in projects such as microwave imaging.

The Stochastic Reduced-Order Models (SROM) is a non-embedded uncertainty analysis method that has the advantages of high computational efficiency, easy implementation, and no dimensional disasters. Recently, it has been widely used in the field of EMC simulation. In the process of optimizing electromagnetic protection design, the worst-case estimation value is an extremely important uncertainty quantification simulation result. However, the SROM has a large error in providing this result, which limits its application in the field of EMC simulation prediction. An improved SROM based on the Radial Basis Function (RBF) neural network algorithm is proposed in this paper, which improves the fitness function in the genetic algorithm center clustering process and constructs an RBF neural network model to obtain accurate worst-case estimation results. The accuracy improvement effect of the algorithm proposed in this paper in worst-case estimation is quantitatively verified by using a parallel cable crosstalk prediction example from published literature.