Search

Abstract The improved hybrid discretisation of volume integral equation (VIE) combined with the characteristic basis function method is proposed to analyse the scattering from complex dielectric objects in this study. To mitigate the excessive number of discrete elements which arise from the conformal discretisation on the complex dielectric objects, the hybrid discretisation is developed. For the conventional hybrid discretisation, the conformal Schaubert–Wilton–Glisson (SWG) basis functions are used to discretise the homogeneous regions, meanwhile, the non‐conformal half‐SWG basis functions are employed to discretise the boundary regions which separate different materials or multiscale structures. The hybrid discretisation takes advantage of the merits of both conformal and non‐conformal basis functions and improves the computational efficiency for solving the VIE. In our study, a kind of edge basis function defined within boundary tetrahedral elements substitutes for the SWG basis functions to model the boundary regions, leading to the further reduction on the number of basis functions. Moreover, the characteristic basis functions extracted from the low‐level basis functions are employed to construct the reduced matrix of which the size is considerably smaller than that of the system matrix derived from the VIE. Several numerical results are presented to demonstrate the accuracy and efficiency of the proposed method.

Wastewater and sewage sludge treatment plants are known to be important entrance routes for microplastics (MPs) into the aquatic environment. Although traditional wastewater treatment plants with primary and secondary purification processes can remove over 99 % of MPs, the majority of these are believed to be deposited into the sewage sludge. This provides a route into the environment, especially if the treated sludge is used as a fertilizer on agricultural land. Although methods do exist for the removal of MPs from water, there are limited studies with sludge. The possibility of using electron beam treatment for the removal of microplastics from wastewater and sewage sludge has been investigated in the laboratory using both tap water and actual sewage sludge. Microplastics were created from six types of plastics in daily use,

IntroductionThe SARS-CoV-2 Omicron variant has become the dominant SARS-CoV-2 variant and exhibits immune escape to current COVID-19 vaccines, the further boosting strategies are required.MethodsWe have conducted a non-randomized, open-label and parallel-controlled phase 4 trial to evaluate the magnitude and longevity of immune responses to booster vaccination with intramuscular adenovirus vectored vaccine (Ad5-nCoV), aerosolized Ad5-nCoV, a recombinant protein subunit vaccine (ZF2001) or homologous inactivated vaccine (CoronaVac) in those who received two doses of inactivated COVID-19 vaccines. ResultsThe aerosolized Ad5-nCoV induced the most robust and long-lasting neutralizing activity against Omicron variant and IFNg T-cell response among all the boosters, with a distinct mucosal immune response. SARS-CoV-2-specific mucosal IgA response was substantially generated in subjects boosted with the aerosolized Ad5-nCoV at day 14 post-vaccination. At month 6, participants boosted with the aerosolized Ad5-nCoV had remarkably higher median titer and seroconversion of the Omicron BA.4/5-specific neutralizing antibody than those who received other boosters. DiscussionOur findings suggest that aerosolized Ad5-nCoV may provide an efficient alternative in response to the spread of the Omicron BA.4/5 variant.Clinical trial registrationhttps://www.chictr.org.cn/showproj.html?proj=152729, identifier ChiCTR2200057278.

Abstract This letter develops a fast spectral peak estimation method, which is inspired by the theory of compressed sensing (CS). In this work, the measurement procedure of the CS is employed to construct an underdetermined equation, and then a low complexity spectral peak search method is established by using a priori knowledge of signal amplitude. Compared with other frequency estimation methods, the proposed method requires only 10% inner products demanded to obtain the spectral peak positions, and this method can be introduced into any existing discrete Fourier transform (DFT)‐based interpolation methods. Experimental results show that the proposed method yields nearly the same accuracy as other interpolation methods, but with lower computational demands.

In this paper, an improved genetic algorithm (GA) for automatically optimizing electromagnetic bandgap (EBG) structure with good power integrity performance is presented. The traditional GA is improved in several ways including Hamming Distance initialization, elite selection and non-repeating crossover, which can generate initial population charactering solution space in detail, increase crossover efficiency, and accelerate convergence. Furthermore, an EBG structure for power distribution network is optimized with the presented GA method to improve the performances of power integrity. The simultaneous switching noise propagation can be prohibited from 0.38 GHz to 20 GHz with a suppression level of -60 dB. Good agreements between the measured results and the simulation ones are observed.

Spectral peak search is an essential part of the frequency domain parametric method. In this paper, a spectral peak search algorithm employing the principle of compressed sensing (CS) is proposed to rapidly estimate the spectral peaks. The algorithm adopts fast Fourier transform (FFT) with a few points to obtain the coarsely estimated spectral peak positions, and then only three small-scale inner products are iteratively calculated by increasing the input sequence length to rapidly refine the estimated positions. Compared with the conventional methods, this algorithm can directly capture the exact locations of spectral peaks without acquiring the entire spectrum. In addition, the proposed algorithm can be easily integrated into the existing frequency domain interpolation methods to accurately determine the spectral peak positions, and if so, only 30% of inner product operations of the original algorithms are required. Theoretical analysis and numerical results show that this algorithm yields accurate results with low complexity for analyzing both one-dimensional and two-dimensional signals.

The characteristic basis function method (CBFM) based on large-size blocks with multilevel subdivision is proposed to improve the analysis of electromagnetic scattering from dielectric objects. The small-size blocks' strategy is widely used to alleviate the computational burden on generating the characteristic basis functions (CBFs) in the perfectly electrical conducting (PEC) object problems. However, when transplanted into the dielectric objects, this strategy performs poorly according to our empirical results. For adapting the CBFM to dielectric objects, the large-size blocks' strategy is proposed for the first time. Primarily, it remarkably reduces the number of CBFs required for the reduced matrix. Furthermore, the multilevel subdivision on the blocks is adopted to convert the full-rank impedance matrices of the blocks into hierarchical matrices, leading to great advantage in two aspects. In the CBFs' generation, the self-impedance matrices with hierarchical structure can be easily inversed by a recursive inversion algorithm based on the Sherman-Morrison-Woodbury (SMW) formula, which significantly cuts down the consumption in terms of CPU time and memory requirement. In addition, the hierarchical structure is taken advantage of by the multiscale adaptive cross approximation (MS-ACA) to accelerate the filling of the mutual-impedance matrices of the adjacent blocks. The numerical results of several dielectric objects are presented to demonstrate the accuracy and efficiency of the proposed method.

In immune system, B cells are classically positive modulators that regulate inflammation and immune responses. Regulatory B cells (Bregs) are a subset of B cells which play crucial roles in various conditions, including infection, allergies, autoimmune diseases, transplantation, and tumors. Until now, unequivocal surface markers for Bregs still lack consensus, although numerous Breg subsets have been identified. Generally, Bregs exert their immunoregulatory functions mainly through cytokine secretion and intercellular contact. In the tumor microenvironment, Bregs suppress effector T cells, induce regulatory T cells and target other tumor-infiltrating immune cells, such as myeloid-derived suppressor cells, natural killer cells and macrophages, to hamper anti-tumor immunity. Meanwhile, the cross-regulations between Bregs and tumor cells often result in tumor escape from immunosurveillance. In addition, accumulating evidence suggests that Bregs are closely associated with many clinicopathological factors of cancer patients and might be potential biomarkers for accessing patient survival. Thus, Bregs are potential therapeutic targets for future immunotherapy in cancer patients. In this review, we will discuss the phenotypes, functions, and clinical relevance of Bregs in cancer.

A compact wideband printed antenna with deca-band 4G/5G/WLAN for mobile phone devices is proposed in this paper. The complete structure is composed of a monopole antenna and a coupling strip, occupying a small C-shape PCB area of 27 × 10.8 mm2. This antenna, which is printed on FR4 substrate with 0.8 mm thickness and fed by a coaxial cable, can provide three wide operating bandwidths that cover 685–1012 MHz, 1596–2837 MHz, and 3288–3613 MHz for 4G/5G/WLAN communication systems. The gains and total radiation efficiencies of the antenna in the low, middle, and high bands are 1.4 dBi–2.5 dBi and 38%–47%, respectively. Besides, the measured results are in good agreement with the simulated results. Further experiments demonstrate that the proposed antenna exhibits a good performance for mobile phones.

A broadband radar cross section (RCS) calculation approach is proposed based on the characteristic basis function method (CBFM). In the proposed approach, the desired arbitrary frequency band is adaptively divided into multiple subband in consideration of the characteristic basis functions (CBFs) number, which can reduce the universal characteristic basis functions (UCBFs) numbers after singular value decomposition (SVD) procedure at lower subfrequency band. Then, the desired RCS data can be obtained by splicing the RCS data in each subfrequency band. Numerical results demonstrate that the proposed method achieve a high accuracy and efficiency over a wide frequency range.

In this paper, a novel measurement matrix construction method based on adaptive cross-approximation (ACA) is proposed to improve the performance of the compressive sensing-based method of moments (CS-MoM) for analyzing electromagnetic scattering problems. ACA is based on a weight scheme and is able to recognize the rows and columns that contribute significantly to the matrix. Thus, the object is divided into multiple blocks, and the impedance matrix is partitioned into near-field and far-field groups to establish the condition for applying ACA. Then, the row indexes are extracted from the group with the highest number of ACA recognized rows in the far-field groups of each block. Finally, by combining all row indexes to extract the impedance matrix, a lower-dimensional and deterministic measurement matrix is constructed, thereby improving computational efficiency. Numerical simulation results validate the accuracy and effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

According to the characteristic mode basis function method (CMBFM) in analyzing electrically large problems, blocking and extending lead to the problem of slow convergence in the iterative solution of a reduced matrix equation, and the characteristic mode basis function method combined with principal component analysis (CMBFM-PCA) is proposed in this study. The characteristic modes (CMs), calculated from each extended block, are subjected to PCA to enhance the orthogonality between them and improve the reduced matrix's condition number to facilitate its quick convergence through an iterative solution. The corresponding numerical calculations demonstrate that significant efficiency and accuracy are achieved by the proposed method. [ABSTRACT FROM AUTHOR]

While analyzing wideband electromagnetic scattering problems using ultra-wideband characteristic basis function method (UCBFM), the reconstruction of a reduced matrix and the recalculation of an impedance matrix at each frequency point cost a large amount of time. To overcome this issue, a novel method that combines UCBFM with compressive sensing (CS) is proposed in this paper to rapidly analyse the wideband RCS. The proposed method makes the ultra-wideband characteristic basis functions (UCBFs) generated at the highest frequency as the sparse basis, introduces the CS theory, randomly extracts several rows from the original matrix as the measurement matrix, utilizes the corresponding excitation vector as the measurement value, and then employs the recovery algorithm, through which the solution of target induced current can be obtained. Due to partial filling of impedance matrix and efficient recovery algorithm, the wideband RCS computation time of the object is significantly reduced using the proposed method. Furthermore, the numerical simulation results show that the computation efficiency for the target wideband RCS can be further enhanced compared with that of the stand-alone UCBFM. [ABSTRACT FROM AUTHOR]

A compact sub-6 GHz multiple-input multiple-output (MIMO) antenna based on a complementary split-ring resonator (CSRR) and electromagnetic bandgap (EBG) is proposed in this paper. The antenna has an interesting structure and a compact size of 38 x 38mm². Four identical antenna elements are deposited orthogonally to each other, using polarization diversity and adding decoupling structures, so that good isolation and miniaturized size can be obtained. The isolation is less than -17:5 dB in the operating bandwidth of 3.28{3.62 GHz and -19:5 dB in 4.78{5.04 GHz. The simulation results are consistent with the measured ones, indicating that the antenna is suitable for Sub-6 GHz communication equipment. [ABSTRACT FROM AUTHOR]

A CPW-fed compact multiband planar printed monopole antenna for WLAN/WiMAX/XBand applications is presented in this paper. The structure size of antenna is 0.144 0×0.176 0×0.008 0. The proposed antenna is composed of three monopole radiators, a microstrip feed line, and the ground with chamfer. With these structures employed, the antenna can generate four different resonances to cover the desired bands while maintaining low profile. The antenna simulation results show four distinct bands from 2.24 to 2.85 GHz, from 3.29 to 4.12 GHz, from 5.13 to 6.24 GHz, and from 6.58 to 8.57 GHz, which cover the entire WLAN bands (2.4-2.484, 5.15-5.35, and 5.725-5.825 GHz), WiMAX bands (2.5-2.69, 3.4-3.69, and 5.25-5.85 GHz), and X-band satellite communication systems (7.25- 7.75 and 7.9-8.4GHz). For verification of simulation results, a prototype of quad-band antenna is designed, fabricated, and tested. The simulated and measured return losses, radiation patterns, and gains are presented. The proposed antenna possesses compact size, simple structure, high gain, and omnidirectional radiation pattern, which make it a suitable candidate used in small/portable WLAN/WiMAX/X-Band devices. [ABSTRACT FROM AUTHOR]

A novel hierarchical characteristic basis function method (HCBFM) is proposed to calculate monostatic radar cross section based on singular value decomposition characteristic basis function method. In order to reduce the number of incident plane waves and accelerate the generation of characteristic basis functions (CBFs), an improved CBFs construction method is studied in this paper. Firstly, the target is partitioned with hierarchical approach, and at each incident plane wave, the highlevel CBFs defined in large blocks are expressed as a linear combination of the previously generated low-level CBFs defined in the corresponding small blocks. Finally, the high-level CBFs in large blocks are orthogonalized by using singular value decomposition at multiple excitations, and a set of linearly independent CBFs can be obtained. Numerical results are given to demonstrate the accuracy and high efficiency of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, a novel wideband dual-band dual-polarized magneto-electric (ME) dipole antenna is proposed. The proposed antenna consists of a folded double-layer magneto-electric dipole, a stair-shaped feeding line with a balun structure and a rectangular box-shaped re ector. The folded double-layer magneto-electric dipole is able to generate two resonant frequencies. The polygon balun structure can better match the antenna impedance. The rectangular box-shaped re ector not only can suppress antenna's back radiation but also can realize high gain over the operating frequencies. Both simulated and measured results show that the antenna can obtain two wide impedance bandwidths of 60% (1.54-2.87 GHz) in lower frequency band and 27% (4.62-6.10 GHz) in higher frequency band with the re ection coefficients lower than 10 dB for both input ports. The isolation between ports is greater than 25 dB in the corresponding frequency band. The gains of the measured antenna were 8.5-9.7 dBi in the low frequency band and 8.5-11.5 dBi in the high frequency band, respectively. [ABSTRACT FROM AUTHOR]

In this paper, an enhanced characteristic basis function method (ECBFM) is proposed to calculate the monostatic radar cross section (RCS) of electrical large targets efficiently. The enhanced characteristic basis functions (ECBFs) are defined by combining improved primary-characteristic basis functions (IP-CBFs) with the first level improved secondary-characteristic basis functions (IS-CBFs) for each block. IS-CBFs are obtained by substituting IP-CBFs for PCBFs in Foldy-Lax multiple scattering equation in which mutual coupling effects among all blocks can be included systematically. As a result, a small number of incident plane waves (PWs) is sufficient when dealing with large scale targets. The numerical results demonstrate that the computational efficiency in this paper is much higher than that of the improved primary-characteristic basis function method (IP-CBFM) without losing any accuracy. [ABSTRACT FROM AUTHOR]

In this paper, a dual-band antenna in orthogonal polarization with stacked configuration is proposed. The proposed antenna introduces two layers of radiating patches to realize the dual frequency characteristic. A pair of novel 180° broadband microstrip baluns, printed on the backside of the bottom substrate, are utilized to feed the antenna. By employing wideband feeding mechanisms for the two input ports, high input port isolation and wide impedance bandwidth are successfully realized. The proposed antenna is fabricated and measured. It exhibits a characteristic of two resonant frequencies. The lower band f1 is from 2.75 to 4.01 GHz with a relative bandwidth of 37.3% and over 8.1 dBi gain at two ports, and the upper band f1 is from 4.4 to 5.21GHz with a relative bandwidth of 16.9% and over 5.8 dBi gain at two ports. The port isolation is below -35 dB, and the cross-polarization level is below -20 dB at broadside across the whole band. [ABSTRACT FROM AUTHOR]

In this paper, a merged characteristic basis function method (MCBFM) is proposed to analyze the electromagnetic scattering characteristics from conducting targets. A merged characteristic basis function (M-CBF) is newly defined in the MCBFM. Considering the mutual interaction of surrounding blocks, the M-CBF is generated by merging the conventional secondary characteristic basis functions (SCBFs) and the high order characteristic basis functions (HO-CBFs) of each block in the conventional primary characteristic basis function (PCBF). Thus, the true current distribution of the targets is approached by using a single M-CBF reducing the number of CBFs when the incident plane waves (PWs) are certain. The numerical results of a PEC hexahedron demonstrate that the proposed MCBFM improves the accuracy without increasing the number of PWs and the CBFs compared to the improved primary CBFM (IP-CBFM). The results also demonstrate that the MCBFM is capable of effectively reducing the CPU time by 63.38% without losing any accuracy compared to the conventional characteristic basis function method (CBFM). Other results of a PEC cylinder demonstrate that when a considerable computational accuracy is required, the efficiency of the proposed MCBFM is the highest among these three methods. [ABSTRACT FROM AUTHOR]

A novel broadband dual-polarized magneto-electric (ME) dipole antenna is proposed for 2G/3G/LTE/WiMAX applications. The proposed antenna has stair-shaped feeding strips to impart a wide impedance bandwidth to it and a rectangular box-shaped reflector to enhance its stability in radiation patterns and high gain over the operating frequencies. The measured results show that a common impedance bandwidth is 80% with standing-wave ratio (SWR) ≤ 1.5 from 1.68 to 3.92GHz, and port-to-port isolation larger than 25 dB within the bandwidth. The measured antenna gains vary from 9.2 to 12 dBi and from 9.2 to 11.8 dBi for port 1 and port 2, respectively. The antenna has nearly symmetrical radiation patterns with low back-lobe radiation both in horizontal and vertical planes, and broadside radiation patterns with narrow beam can also be obtained. [ABSTRACT FROM AUTHOR]

A new structure of coupled-fed loop antenna connected with two branch radiators for eight-band LTE/WWAN (LTE700/GSM850/900/1800/1900/UMTS/LTE2300/2500) operation in the ultra-thin laptop computer is presented. The two branch strips of the antenna are efficient radiators and contributing multi-resonant modes to greatly enhance the bandwidth of the antenna. The proposed antenna on the top shielding metal wall of the laptop display, with a planar and compact size of 12.5 x 70 x 0.8mm³, is suitable to be embedded inside the casing of the laptop computer. The proposed antenna is fabricated and tested, and good radiation performances are obtained. Compared with the existing published antennas, the volume of the planar antenna is quite small. [ABSTRACT FROM AUTHOR]