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A wideband differentially fed circularly polarized (CP) antenna featuring a slotted patch design with a large beamwidth is presented. The final design of the differentially fed CP antenna, aimed at achieving high gain and a wide axial ratio (AR) bandwidth, involves coupling a differential bending dipole antenna to the slotted patch in the same plane. The presented differentially fed CP antenna demonstrates characteristics of a large AR beamwidth, as verified by simulation and experiment. The measured AR beamwidths of 132.3° in the xoz plane (phi = 0°) and 116.2° in the yoz plane (phi = 90°) are realized at 5.5 GHz. The measured result exhibits broadband performance with a −10-dB impedance bandwidth of 78.8% (3.81–8.76 GHz), a 3-dB AR bandwidth of 36.7% (4.78–6.93 GHz), and a maximum gain of 10.2 dBic.

In this article, a three-element circularly polarized multiple-input-multiple-output (CP-MIMO) antenna array with self-decoupled probing method is introduced. Three unidirectional radiated Guo-shaped patch antennas were arranged in a triangular lattice and excited by L-shaped feeding probes at different locations with respect to the patch center. Meanwhile, the patches themselves remained artistic and were placed in the upward position. Namely, the main motivation is to generate CP directional beams without requiring orthogonal placement. The contributions of this work account for (i) spatial diversity, (ii) pattern diversity, (iii) polarization diversity, and (iv) enhanced isolations (25 dB) between patch elements without inserting any external decoupling structures. As such, the antenna efficiency of Guo-patch elements can be raised in an order of 90 % within the band of interest at IEEE 802.11n/g/ac, viz., 2.4–2.5 GHz. The CP-MIMO prototype was fabricated and validated with experimental tests. Outstanding performance metrics such as an envelope correlation coefficient (ECC) of 0.005, mean effective gain (MEG) of −3.5 dB, channel capacity loss (CCL) of 0.18b/s/Hz, and a total active reflection coefficient (TRAC) of better than −15 dB were obtained. The measured results, which agreed with theoretical simulations, confirmed that the multi-element MIMO antenna with the spatial-, pattern- and polarization-diversity is a good candidate for the multi-user B5G-V2X.

The rapid development of modern communication systems propels the demand of high performance and miniaturization of RF/microwave components. Power dividers and filters are indispensable circuit components in amplifiers and antenna feed-networks which occupy large footprint of circuit broads, particularly at low frequency. The purpose of this study is to initiate a new type of planar transmission line with unique dual signal-path characteristics and ultimately achieve circuit miniaturization. In this paper, a novel technique of consolidating microstrip lines (MLs) and coplanar waveguide (CPW) lines on a single dielectric substrate, designated as the composite microstrip/CPW line (CM/CPW line), is proposed. With reference to the average line length of ML and CPW, it warrants a physical length reduction of 48.3% and further achieves a reduction of 80.8% after zigzagging CM/CPW line. The proof-of-concept design example of a two-way Wilkinson power divider (WPD) has demonstrated the effectiveness of the miniaturization technique. The simulation, in combination with the experimental results, validates that a size reduction factor of 86.9% when compared to conventional one has been achieved while maintaining a fractional bandwidth of 57.7% for the WPD.

Traditional methods for flexible capacity allocation do not take into account the actual operation status of resources, and this can lead to redundancy of allocation results in a high renewable penetration power system. Using collaborative optimization during the flexibility resource planning stage can significantly improve the overall economics and flexibility. Therefore, a bilevel operation-planning joint optimization model for flexible capacity allocation is proposed in this paper. The aim is to optimize the annual total cost and flexibility of the system. The upper planning level introduces the economic costs, flexibility resource capacity, and flexibility index which are used as the evaluation index of system flexibility, while in the lower operation level, a morphological clustering algorithm based on the multiscale and entropy weight method is proposed for obtaining typical scenarios of flexibility demand. On this basis, the lower level simulates production to estimate daily operating costs. In addition, the model is solved iteratively using the nondominated sorting genetic algorithm-II (NSGA-II) and the linear programming method to obtain the Pareto solutions. Case studies are carried out based on a practical town area, and the results verify the validity and rationality of the proposed bilevel capacity allocation model.

In view of the known problems of parameter sensitivity, local optimum, and slow convergence in the ant colony optimization (ACO), we aim to improve the performance of the ACO. To solve the traveling salesman problem (TSP) quickly with accurate results, we propose a fully parallel ACO (FP-ACO). Based on the max–min ant system (MMAS), we initiate a compensation mechanism for pheromone to constrain its value, guarantee the correctness of results and avoid a local optimum, and further enhance the convergence ability of ACO. Moreover, based on the compute unified device architecture (CUDA), the ACO is implemented as a kernel function on a graphics processing unit (GPU), which shortens the running time of massive iterations. Combined with the roulette wheel selection mechanism, FP-ACO has powerful search capabilities and is committed to obtaining better solutions. The experimental results show that, compared with the effective strategies ACO (ESACO) that runs on CPU, the speed-up ratio of the proposed algorithm reaches 35, and the running time is less than that of the max–min ant system-roulette wheel method-bitmask tabu (MMAS-RWM-BT) that runs on GPU. Furthermore, our algorithm outperforms the other two algorithms in the speed-up ratio and less runtime, proving that the proposed FP-ACO is more suitable for solving TSP.

Abstract In this study, a novel frequency beam‐scanning (FBS) antenna based on composite substrate integrated waveguide/spoof surface plasmon polariton (SIW/SSPP) waveguide is proposed. The composite SIW/SSPP slow‐wave waveguide is designed by embedding a series of periodic subwavelength H‐shaped grooves on the top surface of the SIW. Its transmission characteristics own both the features from SIW and SSPP, and can be flexibly mansplained by tuning the key structural parameters. To convert the propagating composite slow‐wave mode into the radiation mode effectively, a new flexible digital modulation method with staggered metallic vias is proposed and used. The presented beam‐scanning antenna has a simple feeding structure, a single dielectric layer, and a compact volume of 0.75 × 8.55 × 0.015 λ03. A prototype of the antenna is fabricated and tested to verify its performance. The experimental results demonstrate that the proposed antenna can realise a continuous beam‐scanning angle of 49° in an operating bandwidth of 8.7–9.2 GHz with a high frequency‐scanning sensitivity (FSS) of 9.8 °/100 MHz−1. Moreover, the measured results indicate that the antenna has high peak gain with an average level of 12.7 dBi, high radiation efficiency with an average level of 87%, and stable unidirectional radiation pattern in the working band.

A passive wireless strain-sensing system for strain monitoring of metallic structures is presented in this paper, wherein single-feed (SF) patch antenna with near orthogonal fundamental modes is initiated as the sensing element. A new approach is proposed by using input admittance of the orthogonal modes as the strain measurand. Strain sensing proof-of-concept of the SF patch-sensor was first established through electromagnetic simulation, then a cantilever beam strain measurement system was designed and employed to quantify the changes of input admittance while directional strain was arising. The simulated results reinforced with mathematical derivation and verified by experimental results to demonstrate that there is a linear relationship between normalized admittance and micro-strain with a high sensitivity factor of 97 ppm/με from simulation. Experimental results also verified that the single patch sensor can monitor the bidirectional (tensile and compressive) strain in multi-directions. An implementation example of the wireless passive sensing system is also presented in a proof-of-concept case. The change of minimum admittance that is linked with the applied strain was realized and interrogated using a monostatic radar system where the maximum radar cross section (RCS) and frequency differences were used as strain measurands. The interrogation method shows the RCS variations and the frequency shifts of the orthogonal modes in correspondence to the directional strains induced at the sensor in four uniaxial scenarios with a high sensitivity factor of 176 ppm/με.

A dual linearly-polarized (LP) high-order-mode antenna with high gain and high isolation is proposed for 5G millimeter-wave (mm-wave) applications. To obtain high gain and wide bandwidth, a 2 × 2 slot-fed magneto-electric (ME)-dipole antenna elements are excited by a high-order-mode TM430 cavity. Two substrate integrated waveguide (SIW) feeding networks that are vertically arranged in the bottom layers are employed to feed the high-order-mode cavity antenna for a double capacity, high isolation and low transmission loss. Moreover, an 8 × 8 antenna array is fed by a pair of compact modified H-shaped full-corporate SIW networks. Measurement results show that an overlapped frequency bandwidth of 14.6% (36.8-42.6 GHz) with a peak gain of 25.8 dBi and an isolation of greater than 45 dB for the 8 × 8 dual LP antenna array are achieved, which guarantee reliable high-speed data transmission and anti-interference capacity for 5G communications.

This contribution presents a novel 3-D circular conformal MIMO antenna system composed of three magneto-electric dipoles (MED) antennas. The single MED element was delicately designed to include one main (lower-band) dipole and two auxiliaries (upper-band) dipoles in order to achieve the dual-band radiation. The proposed MED owns a low-profile conformal geometry but features a wide H-plane beamwidth (minimum 103°). By embedding the metamaterial of the broadside-coupled E-shaped unit cells into the magnetic dipole, the height of MED can be dramatically reduced by 37.2% as compared with the conventional ones. Meanwhile, the two U-shaped notches together with a rectangular notch were included onto the E-dipole to create a band-notch, which offers the anti-interference capability to the ubiquitous 2.4-GHz signal of the wireless local area network. According to the measurement results, the MED element exhibits an impedance bandwidth of 54.2% (1.68-2.93 GHz) with a stable gain of 6.05± 1.15 dBi in the lower band and 9.2% (3.32-3.64 GHz) with 5.71 ± 0.7 dBi in the upper band, respectively. Moreover, the three-element MIMO system provides quasi-omnidirectional coverage in the H-plane from 1.68 to 3.64 GHz. The outstanding performance metrics validate the proposed ME dipole antenna that is well suited for the future sub-6-GHz fifth-generation MIMO mobile base stations.

We present a cross-disciplinary approach applied to the strength prediction and correlation of cement composites in this paper. The empirical models for predicting flexural and compressive strengths of a kind of fiber reinforced cement composites, known as engineered cementitious composites (ECCs), were first developed. Nonlinear regressions were applied to the measurement data of a destructive compression test and four-point bending test. Each of these tests was conducted on 36 specimens at growing ages (3, 7, 14, and 28 days), wherein three mixes of ECC (PE1, PE2, and PE3) were prepared for each test. Each mix had different water-to-binder (w/b) ratios of 0.20, 0.255, and 0.30 whereas the total volume of each mix remained the same. The correlations among flexural strength, compressive strength, and electrical conductance of ECCs were then developed based on the early-age measurement using the microwave non-destructive test (mDNT). The primary objective of this research is to study the relations between flexural strength and compressive strength of ECC specimens under the influence of small deviations in w/b ratio. The secondary objective is to predict the strength growth of ECCs with the microwave effective conductance. The correlation results show that the flexural strength behaves as a quasi-linear function with increasing compressive strength, which has been verified by using direct measurement data. This cross-disciplinary approach highlights the effectiveness of the mDNT in predicting the mature strengths of ECCs at early ages.

In this paper, we introduce a reconfigurable artistic patch antenna with unidirectional circular-polarization (CP) radiation. The novel geometry composed of a Chinese character Meng shaped patch and dual L-shaped feeding probes that are connected to a PIN-diode-based switching circuit. The simulated and experimental results show that the proposed antenna achieves the operating bandwidth from 2.4 to 2.5 GHz that covers dynamically the 14 channels of IEEE 802.11/b/g/b/ax. By switching the L-probes, either left-handed CP or right-handed CP can be generated to cover different seven-channel blocks in order to enhance the channel efficiency. A broadside realized gain varying between 5-6 dBic and an efficiency of -0.5dB were recorded. The proposed antenna holds an overall dimension of 0.72λ0 × 0.72λ0 × 0.12λ0 with an aperture efficiency of 59% at 2.45 GHz.

In this paper, the improved design of a small automatic-identification-system (AIS) based man overboard (MOB) device is described. The device is one of the state-of-the-art maritime vehicular technologies and has been widely used in marine vehicles for search and rescue (SAR) purposes. Similar devices have been available in the market for years; however, the design methodology and hardware circuitries have never been exposed in literature. This paper first reviews the basic principles of Gaussian minimum-shift keying modulation and the direct digital frequency synthesis technique. Second, the design methodology and hardware implementation of subsystems of the device with design objectives in effective SAR are presented. Finally, a prototype of the AIS MOB was fabricated and fully tested. The experimental results demonstrate that the emitted signal spectrum meets the AIS standards. The fabricated prototype has a minimum effective range of five nautical miles with a battery life of 36 h under continuous operation. This AIS MOB device is a multidisciplinary design product. The described work comprises of active antenna design, the microcontroller-based AIS control circuit design, the global positioning system circuit design, and the implementation of Gaussian minimum-shift keying modulation.

A novel linearly dual-polarized antenna array with triple elements is proposed for beamwidth reconfigurable base-station communications. By cutting off the arc-shaped corners on the radiated patches, the single dual-polarized antenna unit can obtain a wide bandwidth of 78.4% for SWR ≤ 2, ranging from 1.63 to 3.73 GHz for 2G/3G/LTE and 3.5-GHz C-band (3.4-3.6 GHz) applications. In addition, with the box-shaped reflector and the inherent characteristic of the ME dipole antenna, the average gain of the dual-polarized antenna element is about 11.5 dBi. Finally, by employing a two-stage circuit with several power dividers, a three-element antenna array with a widely adjustable beamwidth in both the E-plane and H-plane is investigated, which could meet the demand of the future smart applications.

A substrate integrated magneto-electric (ME) dipole antenna with metasurface is proposed for the 5G/WiMAX/WLAN/X-band MIMO applications. In order to provide a low profile, the radiated electric dipoles integrated with shorted wall are used in the multi-layer substrates at different heights. Owing to the coordination of the metasurface and the ME dipole, dual wideband and high gain have been obtained. As a result of the 3-D hexagonal structure, good envelope correlation coefficient and mean effective gain performance can be achieved by the MIMO antenna system. The antenna element can provide an impedance bandwidth of 66.7% (3.1 - 6.2 GHz) with a stable gain of 7.6 ± 1.5 dBi and an impedance bandwidth of 20.3% (7.1 - 8.7 GHz) with a gain of 7.4 ± 1.8 dBi for the lower and upper bands, respectively. The overall size of the element is 60 × 60 × 7.92 mm3. Hence, it is well-suited for the future 5G/WiMAX/WLAN/X-band MIMO communications.

Pleomorphic xanthoastrocytoma (PXA) is a rare primary CNS tumor. Recent advances in the molecular characterization are helping to define subtypes of tumor. The discovery of BRAF mutations within a substantial percentage of PXA fosters a clearer understanding of the pathophysiology of these tumors with clear prognostic and therapeutic implications. These findings are expected to provide insight into the spectrum of clinical behavior observed in PXA, ranging from cure with surgery to diffuse dissemination throughout the neuraxis. This review details the clinical presentation including radiographic appearance of PXA. Pathology, including molecular pathology is discussed. Therapeutic management including surgical resection, radiotherapy and systemic therapies are reviewed.

In bearing diagnostics using a data-driven modeling approach, a concern is the need for data from all possible scenarios to build a practical model for all operating conditions. This paper is a study on bearing diagnostics with the concurrent occurrence of multiple defect types. The authors are not aware of any work in the literature that studies this practical problem. A strategy based on one-versus-all (OVA) class binarization is proposed to improve fault diagnostics accuracy while reducing the number of scenarios for data collection, by predicting concurrent defects from training data of normal and single defects. The proposed OVA diagnostic approach is evaluated with empirical analysis using support vector machine (SVM) and C4.5 decision tree, two popular classification algorithms frequently applied to system health diagnostics and prognostics. Statistical features are extracted from the time domain and the frequency domain. Prediction performance of the proposed strategy is compared with that of a simple multi-class classification, as well as that of random guess and worst-case classification. We have verified the potential of the proposed OVA diagnostic strategy in performance improvements for single-defect diagnosis and predictions of BPFO plus BPFI concurrent defects using two laboratory-collected vibration data sets.

The battery management system (BMS) is a critical component of electric and hybrid electric vehicles. The purpose of the BMS is to guarantee safe and reliable battery operation. To maintain the safety and reliability of the battery, state monitoring and evaluation, charge control, and cell balancing are functionalities that have been implemented in BMS. As an electrochemical product, a battery acts differently under different operational and environmental conditions. The uncertainty of a battery’s performance poses a challenge to the implementation of these functions. This paper addresses concerns for current BMSs. State evaluation of a battery, including state of charge, state of health, and state of life, is a critical task for a BMS. Through reviewing the latest methodologies for the state evaluation of batteries, the future challenges for BMSs are presented and possible solutions are proposed as well.

Lead-zirconate-titanate (PZT) nanoscale powder was first synthesized by the sol-gel method, then PZT and 0–3 type PZT/chrysotile fiber (CSF)/cement composite (PZTCC) wafers were fabricated after grind-mixing PZT powder with strontium carbonate and/or cement, ductile CSF in tandem with press-sintered process, respectively. The crystal structure (XRD), microstructure (SEM), piezoelectric properties after surface silver penetration, and polarization of the PZT and PZTCC wafer were investigated. Furthermore, self-sensing responses under either impulse or cyclic loading and micro-hardness toughness of PZTCC were also investigated. Results show that the incorporation of CSF and cement admixture weakens the perovskite crystalline peak of PZTCC; reduces the corresponding piezoelectric coefficient from 119.2 pC/N to 32.5 pC/N; but effectively bridges the gap on the toughness between PZTCC and concrete since the corresponding microhardness with 202.7 MPa of PZTCC is close to that of concrete. A good linear and fast electrical response against either impulse or cyclic loading of the PZTCC is achieved with their respective sensitivity, linearity, and repeatability to 1.505 mV/N, 2.42%, and 2.11%. The sensing responses and toughness of PZTCC is encouraging as an intrinsic piezoelectric sensor for real-time health monitoring of ductile concrete structures.

This research article presents dual-frequency correlation models for predicting the growth of elasticity and flexural strength of engineered cementitious composites (ECCs) using microwave nondestructive inspection technique. Parallel measurements of microwave properties and mechanical properties of ECC specimens were firstly undertaken in the sense of cross-disciplinary experiments. Regression models were developed via means of nonlinear regression to the measured data. The purpose of the study is: (i) to monitor the flexural strength and elasticity growth; and (ii) to predict their mature values under the influence of different initial water contents, via microwave effective conductance at early ages. It has been demonstrated that both the modulus of rupture (MOR) and modulus of elasticity (MOE) can be accurately modeled and correlated by microwave conductance using exponential functions. The moduli developed as a function of conductance whereas the regression coefficient exhibited a linear relation with water-to-binder ratio. These findings have highlighted the effectiveness of the microwave non-destructive technique in inspecting the variation of liquid phase morphology of ECCs. The dual-frequency correlation can be used for structural health monitoring, which is not only for prediction but also provides a means of verification.

The health conditions of complicated concrete structures require intrinsic cement-based sensors with a fast sensing response and high accuracy. In this paper, static, modal, harmonic, and transient dynamic analyses for the 0–3 type piezoelectric cement-based material with interdigitated electrodes (IEPCM) wafer were investigated using the ANSYS finite element numerical approach. Optimal design of the IEPCM was further implemented with electrode distance (P), electrode width (W), and wafer density (H) as the main parameters. Analysis results show that the maximum stress and strain in the x-polarization direction of the IEPCM are 2.6 and 3.19 times higher than that in the y-direction, respectively; there exists no repetition frequency phenomenon for the IEPCM. These indicate 0–3 type IEPCM possesses good orthotropic features, and lateral driving capacity notwithstanding, a hysteresis effect exists. Allowing for the wafer width (Wp) of 1 mm, the optimal design of the IEPCM wafer arrives at the best physical values of H, W and P are 6.2, 0.73 and 1.02 mm respectively, whereas the corresponding optimal volume is 10.9 mm3.

The conventional isolation structure with rubber bearings exhibits large deformation characteristics when subjected to infrequent earthquakes, which may lead to failure of the isolation layer. Although passive dampers can be used to reduce the layer displacement, the layer deformation and superstructure acceleration responses will increase in cases of fortification earthquakes or frequently occurring earthquakes. In addition to secondary damages and loss of life, such excessive displacement results in damages to the facilities in the structure. In order to overcome these shortcomings, this paper presents a structural vibration control system where the base isolation system is composed of rubber bearings with magnetorheological (MR) damper and are regulated using the innovative control strategy. The high-order single-step algorithm with continuity and switch control strategies are applied to the control system. Shaking table test results under various earthquake conditions indicate that the proposed isolation method, compared with passive isolation technique, can effectively suppress earthquake responses for acceleration of superstructure and deformation within the isolation layer. As a result, this structural control method exhibits excellent performance, such as fast computation, generic real-time control, acceleration reduction and high seismic energy dissipation etc. The relative merits of the continuity and switch control strategies are also compared and discussed.

Dielectric characterization of concrete is essential for the wireless structural health monitoring (SHM) of concrete structures. Guo Biao (GB) concrete refers to the concrete mixed and cast in accordance with the Chinese standard. Currently, China is the largest producer and consumer of concrete in the world. However, minimal attention has been paid to the dielectric properties of GB concrete. This paper presents the results of the dielectric constant of GB concrete, where three regression models have been used to present the measurement data from 10 MHz to 6 GHz. The objective is to provide a data set of nominal values of the dielectric constant for ordinary GB concrete. The final goal is to facilitate a compressive strength evaluation via the measured dielectric constant. Measurements of the dielectric constant and compressive strength for five types of ordinary concrete have been undertaken, after 28 days of curing. As the main contribution in this work, the correlation model between the compressive strength and dielectric constant of GB concrete is realized.

This paper presents the results of microwave and mechanical measurements of engineered cementitious composites (ECCs) using a nondestructive microwave near-field detecting technique. The objective of this research is to investigate the correlations between effective conductance and compressive strength of ECCs at various curing ages under the influence of different initial water contents. Parallel measurements and regression analysis on compressive strength and microwave conductance were undertaken. It is shown that the strength evolution of ECCs can be accurately modeled and predicted by using microwave conductance at the early ages using bi-exponential functions. Compressive strength grows as a function of decreasing effective conductance, whereas the regression coefficients of the correlation models have a linear variation with water-to-binder ratios. These findings have highlighted the effectiveness of the microwave technique in detecting the variation of liquid phase morphology and pore structure.

Because of their low cost, photovoltaic (PV) cells made from upgraded metallurgical grade silicon (UMG-Si) are a promising alternative to conventional solar grade silicon-based PV cells. This study investigates the outdoor performance of a 1.26 kW grid-connected UMG-Si PV system over five years, reporting the energy yields and performance ratio and estimating the long-term performance degradation rate. To make this investigation more meaningful, the performance of a mono-Si PV system installed at the same place and studied during the same period of time is presented for reference. Furthermore, this study systematizes and rationalizes the necessity of a data selection and filtering process to improve the accuracy of degradation rate estimation. The impact of plane-of-array irradiation threshold for data filtering on performance ratio and degradation rate is also studied. The UMG-Si PV system’s monthly performance ratio after data filtering ranged from 84% to 93% over the observation period. The annual degradation rate was 0.44% derived from time series of monthly performance ratio using the classical decomposition method. A comparison of performance ratio and degradation rate to conventional crystalline silicon-based PV systems suggests that performance of the UMG-Si PV system is comparable to that of conventional systems.