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Multifarious defects are introduced in SnTe by CuSbSe2 alloying to induce full-scale phonon scattering, which leads to an ultra-low lattice thermal conductivity, reaching the amorphous limit, and achieves prominent thermoelectric performance.

For the open perfect electric conductor (PEC)-dielectric objects, a novel type of volume surface integral equation (VSIE) is proposed to solve the current distribution on both sides of the open PEC surfaces, which cannot be obtained by using the traditional VSIE. In the proposed method, both the electric and magnetic field integral equations are established on both sides of the PEC surfaces, while the basis functions are also defined at the borders of PEC surfaces to consider the current flowing over the edges of PEC surfaces. Compared with the traditional VSIE, due to the asynchronous solution processes of the surface current, the added CPU time for the proposed method is quite limited, while the memory usage is the same. Numerical results verify the validity and efficiency of the proposed method.

Seeking new strategies to tune the intrinsic defect and optimize the thermoelectric performance via no or less use of external doped elements (i.e., plain optimization) is an important method to realize the sustainable development of thermoelectric materials. Meanwhile, creating dislocation defects in oxide systems is quite challenging because the rigid and stiff ionic/covalent bonds can hardly tolerate the large strain energy associated with dislocations. Herein, taking BiCuSeO oxide as an example, the present work reports a successful construction of dense lattice dislocations in BiCuSeO by self-doping of Se at the O site (i.e., Se O self-substitution), and achieves plain optimization of the thermoelectric properties with only external Pb doping. Owing to the self-substitution-induced large lattice distortion and the potential reinforcement effect by Pb doping, high-density (about 3.0 × 10 14 m −2 ) dislocations form in the grains, which enhances the scattering strength of mid-frequency phonon and results in a substantial low lattice thermal conductivity of 0.38 W m −1 K −1 at 823 K in Pb-doped BiCuSeO. Meanwhile, Pb Bi doping and Cu vacancy markedly improve the electrical conductivity while maintaining a competitively high Seebeck coefficient, thereby contributing to a highest power factor of 942 μW m −1 K −2 . Finally, a remarkably enhanced zT value of 1.32 is obtained at 823 K in Bi 0.94 Pb 0.06 Cu 0.97 Se 1.05 O 0.95 with almost compositional plainification. The high-density dislocation structure reported in this work will also provide a good inspiration for the design and construction of dislocations in other oxide systems.

We develop a method to model the microwave transmissivity of row crops that explicitly accounts for their periodic nature as well as multiple scattering. We hypothesize that this method could eventually be used to improve satellite retrieval of soil moisture and vegetation optical depth in agricultural regions. The method is characterized by unit cells terminated by periodic boundary conditions and Floquet port excitations solved using commercial software. Individual plants are represented by vertically oriented dielectric cylinders. We calculate canopy transmissivity, reflectivity, and loss in terms of S-parameters. We validate the model with analytical solutions and illustrate the effect of canopy scattering. Our simulation results are consistent with both simulated and measured data published in the literature.

To effectively solve the electromagnetic scattering or radiation properties from the perfect electric conductor objects containing closed–open surface junctions, how to establish the hybrid combined field integral equation–electric field integral equation (CFIE–EFIE) is studied, which is different from the existing scheme for the objects, where the closed and open parts are separate. Furthermore, it is found that when the integral equation is solved using the method of moments, if the widely used RWG basis functions are employed to expand the induced surface current, the CFIE–EFIE may give inaccurate numerical results for the objects containing fine structures. The numerical accuracy can be improved by introducing the linear–linear (LL) basis functions. Moreover, to pursue a high computational efficiency, the LL and RWG basis functions are simultaneously used to expand the current on the fine structures and other relatively smooth surfaces, respectively, whose validity is verified by the numerical results.

Model assisted probability of detection (MAPoD) is crucial for quantifying the inspection capability of a nondestructive testing (NDT) system which uses the coil or probe to sense the size and location of the cracks. Unfortunately, it may be computationally intensive for the simulation models. To improve the efficiency of the MAPoD, in this article, an efficient 3D eddy current nondestructive evaluation (ECNDE) forward solver is proposed to make estimations for PoD study. It is the first time that singular value decomposition (SVD) is used as the recompression technique to improve the overall performance of the adaptive cross approximation (ACA) algorithm-based boundary element method (BEM) ECNDE forward solver for implementation of PoD. Both the robustness and efficiency of the proposed solver are demonstrated and testified by comparing the predicted impedance variations of the coil with analytical, semi-analytical and experimental benchmarks. Calculation of PoD curves assisted by the proposed simulation model is performed on a finite thickness plate with a rectangular surface flaw. The features, which are the maximum impedance variations of the coil for various flaw lengths, are obtained entirely by the proposed model with selection of the liftoff distance as the uncertain parameter in a Gaussian distribution. The results show that the proposed ACA-SVD based BEM fast ECNDE forward solver is an excellent simulation model to make estimations for MAPoD study.

The Arabidopsis thaliana ASYMMETRIC LEAVES2 (AS2) gene is responsible for the development of flat, symmetric, and extended leaf laminae and their veins. The AS2 gene belongs to the plant-specific AS2-LIKE/LATERAL ORGAN BOUNDARIES (LOB)-domain (ASL/LBD), which consists of 42 proteins in Arabidopsis with a conserved amino-terminal domain known as the AS2/LOB domain, and a variable carboxyl-terminal region. AS2/LOB domain consists of an amino-terminal (N-terminal) that contains a cysteine repeat (the C-motif), a conserved glycine residue, and a leucine-zipper-like. AS2/LOB domain has been characterised in plants such as A. thaliana, Zea mays, and Oryza sativum. Nevertheless, it remains uncharacterised in cassava (Manihot esculenta). Characterisation and identification of cassava ASL/LBD genes using the computational algorithms, hidden Markov model profiles (PF03195), determined 55 ASL/LBD genes (MeASLBD1 to MeASLBD55). The gene structure and motif composition were conserved in MeASLBDs, while the expression profiles of these genes were highly diverse, implying that they are associated with diverse functions. Weighted gene co-expression network analysis (WGCNA) of target genes and promoter analysis suggest that these MeASLBDs may be involved in hormone and stress responses. Furthermore, the analysis of cis-regulatory elements in promoter regions suggested that MeASLBDs may be involved in the plant phytohormone signal response. The transcriptome data of cassava under biotic and abiotic stresses revealed that MeASLBD46 and MeASLBD47 greatly respond to disease and drought. The MeASLBD47 gene was selected for functional analysis. The result indicated that MeASLBD47 significantly mitigated the virulence of cassava bacterial blight (XamCHN11) through Real-Time Quantitative Reverse Transcription PCR (qRT-PCR) and Virus-induced gene silencing (VIGS). These findings provided a comprehensive analysis of ASL/LBD genes and laid the groundwork for future research to understand ASL/LBD genes.

A well‐conditioned volume‐surface integral equation, called the volume integral equation‐combined field integral equation, is applied to analyse electromagnetic (EM) scattering from arbitrarily shaped three‐dimensional composite objects comprising both inhomogeneous bi‐anisotropic material and closed perfect electric conductors (PECs). The equivalent surface and volume currents are respectively expanded using the commonly used RWG and SWG basis functions, while a matrix equation is derived by the method of moments. Because the magnetic field integral equation is involved in modelling the surface electric current, and the constitutive parameters are all tensors, some new kinds of singularities are encountered and properly handled in the filling process of the impedance matrix. Several numerical results of EM scattering from composite bi‐anisotropy and closed PEC objects are shown to illustrate the accuracy and efficiency of the proposed scheme. The validity of the continuity condition of electric flux enforced on the bi‐anisotropy‐PEC interfaces, which can be used to eliminate the volumetric electric unknowns, is also verified.

Electromagnetic metasurfaces are structured surfaces consisting of a thin array of subwavelength elements with engineered scattering properties, thus providing a promising means of holographic display by controlling the field distributions. However, the existing metasurface holography has limited capabilities in achieving 3-D fields with simultaneous features of high spatial resolution and energy efficiency due to the design methods. In this work, we present a transmissive metasurface to achieve polarization-dependent field distributions in 3-D space with both high resolution and efficiency. In the design, a new method that utilizes dyadic Green’s function (DGF) as the rigorous propagator is used. Using the method, the sources and fields are linked directly and can be located on arbitrary 3-D points with the intermediate spaces being equal or unequal. The design is successfully validated by full-wave simulations and experimental measurements. The broadband simulation results indicate that the design has a bandwidth of 0.8 GHz. This work demonstrates a feasible and simple route of field synthesis for real-world applications that require high resolution, high efficiency, and 3-D scenarios.

A dual-polarization frequency-selective rasorber (FSR) with two absorptive bands at both sides of a passband is presented. Based on the characteristic mode analysis, a circuit analog absorber is designed using a lossy frequency-selective surface (FSS) that consists of miniaturized meander lines and lumped resistors. The positions and values of resistors are determined according to the analysis of modal significances and modal current. After that, the presented rasorber is designed by cascading of the lossy FSS and a lossless bandpass FSS. Equivalent circuits of the FSR are modeled, and surface current distributions of both FSSs are illustrated to explain the operation mechanism. Measurement results show that, under the normal incidence, a minimum insertion loss of 0.27 dB is achieved at a passband around 6 GHz, and the absorption bands with an absorption rate higher than 80% are 2.5–4.6 GHz in the lower band and 7.7–12 GHz in the higher band, respectively. Our results exhibit good agreements between measurements and simulations.

The interpolation errors of bivariate Lagrange polynomial and triangular interpolations are studied for the plane waves. The maximum and root-mean-square (rms) errors on the right triangular, equilateral triangular, and rectangular (bivariate Lagrange polynomial) interpolations are analyzed. It is found that the maximum and rms errors are directly proportional to the ( p + 1)th power of kh for both 1-D and (2-D, bivariate) interpolations, where k is the wavenumber and h is the mesh size. The interpolation regions for the right triangular, equilateral triangular, and rectangular interpolations are selected based on the regions with smallest errors. The triangular and rectangular interpolations are applied to evaluate the 2-D singly periodic Green's function. The numerical results show that the equilateral triangular interpolation is the most accurate interpolation method, whereas the right triangular interpolation is the most efficient interpolation method.

A prismatic conformal metasurface, based on optimized multielement phase cancellation, is proposed for wideband radar cross-sectional (RCS) reduction. The metasurface is composed of 35 lattices located in seven zones of a prismatic structure. The lattices in different zones are simulated under corresponding incident angles and taken into account the difference of wave path caused by the bending of the conformal structure. The interactions between multiple backscattered waves produced by the lattices are manipulated and optimized simultaneously by the hybrid array pattern synthesis and particle swarm optimization to achieve wideband destructive interference. The proposed metasurface can realize a 10 dB reduction in backscattered RCS under normal incidence for HH polarization from 9.6 to 10.6 GHz and 11.7 to 17.7 GHz with the fractional bandwidths of 9.9% and 40.8%, respectively. The theoretical analysis, simulated, and measured results are in a good agreement. The proposed approach verifies the innovation and effectiveness in achieving wideband RCS reduction for conformal metasurface.

Ultra-high voltage (UHV) power grid is a new transmission and transformation technology, which has the advantages of large transmission capacity, long transmission distance, low line loss, saving land resources and obvious economic benefits. Taking the Zhangbei-xiongan 1000kv AC high voltage power transmission and transformation project as an example, this paper constructs the eco-environmental index system of the UHV transmission and transformation project by using the pressure-state-response model, and constructs a set of 18 indexes eco-environmental index system, it mainly includes three aspects: the eco-environmental pressure index caused by the construction behavior in different construction stages of power transmission and transformation projects, and the eco-environmental state index given by on-the-spot investigation and study of projects, based on the construction unit on the ecological environment impact management response measures given indicators. The index system provides a basis for comprehensive and systematic evaluation of the impact of power transmission and distribution projects on the ecological environment, and finally draws the corresponding project construction evaluation conclusions. In this paper, the eco-environmental impact assessment index system of power transmission and transformation engineering has certain universality, and it has certain reference and guiding significance for the ecological environment evaluation of power transmission and transformation engineering.

In this work, an ultrawideband and high-efficient polarization conversion metasurface (PCM) is proposed, which can efficiently convert linearly polarized waves into cross-polarized waves in an ultra-wide frequency range. The unit cell of the proposed PCM is composed of two pairs of L-shaped metallic patches covered by a dielectric superstrate and an air-based substrate attached with a metallic ground. The PCM has an operating band from 3.37 to 22.07 GHz with the polarization conversion ratio (PCR) over 90% under the normal incidence, which the ratio bandwidth (fH/fL) is 6.5:1. The PCR can achieve 100% at seven resonant frequencies. The equivalent circuit model is analyzed to explain the fundamental cause of the PCM’s multi-resonance and polarization conversion behaviors. In addition, all possible near-field interactions among the resonator, the superstrate, and the ground sheet can be accurately calculated using interference theory, which reveals the underlying physical mechanisms of the multi-resonance metasurface. The theoretical calculated, numerically simulated, and measured results are in good agreement. Compared to other PCMs, the proposed PCM has a simple geometry structure but an ultrawideband and high PCR property.

The boundary element method (BEM) is an efficient way to compute solutions of eddy current nondestructive evaluation (NDE) problems. However, in boundary element analysis of eddy currents, the computational accuracy and efficiency depend on the element discretization employed and are very sensitive to the liftoff distance and the relative geometry size between the detecting coil and object under evaluation or test. In this paper, the skin depth parameter is applied to study the element discretization effects on boundary element analysis for 3D eddy current NDE problems. The element discretization rules are concluded by conducting numerical experiments for different liftoff distances and relative probe sizes so that they can be adjusted to account for variations in these parameters, and validated against the analytical method, semi-analytical method, and experiments of some benchmark problems. With the help of the rules, the overall computational accuracy is improved while the cost is reduced for the BEM modeling of eddy current NDE problems.

The efficiency of the multilevel fast multipole algorithm (MFLMA) is improved by using the triangular interpolation instead of the commonly used Lagrange interpolation. For pth-degree interpolation, the data points used for the triangular interpolation are only $(p+2)/(2p + 2)$ of the Lagrange interpolation, while the interpolation accuracy is in the same order. Numerical results of electromagnetic scattering from conducting sphere are shown to illustrate the accuracy and efficiency of the proposed method.

The Stratton-Chu (SC) formulation has been applied to model the low frequency problems. With quasi-static limit, the low frequency approximation is made to the Stratton-Chu formulation which results in the decrease of the dimensions for the discretized impedance matrix. In this paper, the robustness of the approximation is well studied and analyzed with a practical nondestructive evaluation testing case. For the common conductor, we show that the approximated SC formulation works up to 50 MHz.

The interpolation accuracy of isosceles triangular interpolation for the linear and quadratic interpolations are analyzed. The isosceles triangular grids are generated by shifting every other row of pre-calculation points by $h/2$ , where $h$ is sampling interval. Compared with the two-dimensional Lagrange interpolation, the isosceles triangular interpolation has higher interpolation accuracy and does not need additional precalculation points.

In this article, the multilevel adaptive cross approximation (MLACA) algorithm is presented to accelerate the boundary element method (BEM) for eddy current nondestructive evaluation (NDE) 3D problems involving arbitrary shapes. The Stratton-Chu formula, which does not have the low frequency breakdown issue, has been selected for modeling. The equivalent electric and magnetic surface currents are expanded with Rao-Wilton-Glisson (RWG) vector basis functions while the normal component of the magnetic field is expanded with pulse basis functions. The MLACA compresses the rank deficient matrices with the ACA and the butterfly algorithm. We improve the efficiency of MLACA by truncating the integral kernels after a certain distance and applying the multi-stage (level) algorithm adaptively based on the criteria for different operators to further decrease the memory and CPU time requirements while keeping almost the same accuracy comparing with the traditional MLACA. The proposed method is especially helpful to deal with the large solution domain issue of the BEM for eddy current problems. Numerical predictions are compared with the analytical, the semi-analytical predictions and the experimental results for 3D eddy current NDE problems of practical interest to demonstrate the robustness and efficiency of the proposed method.

This letter presents an absorptive/transmissive frequency selective surface (ATFSS) with wide absorption bands at both sides of a passband. A double-layer structure consisting of a lossy FSS and a lossless FSS was employed. The lossy and lossless FSSs were designed based on tripole loops and tripole slots, respectively. The tripole loops and slots were constructed as a hexagonal periodic structure. The tripole loops equated to a series-parallel circuit and exhibited lossy feature after they were loaded with lumped resistors, which were used to absorb the incident wave at lower and upper absorption bands. Surface current distributions were illustrated to explain the operation mechanism. A prototype of the proposed ATFSS was fabricated and measured. Our results showed good agreement between measurements and simulations. Measurement results showed that a passband with a center frequency of 5 GHz and a minimum insertion loss of 0.35 dB was obtained. Out of the passband, absorption rates higher than 80% were obtained at a lower absorption band, from 2.66 to 4.5 GHz, and at a higher absorption band, from 5.66 to 8.56 GHz.

Photocatalytic hydrogen generation from water splitting has become a favorable route for the utilization of solar energy. An effective strategy, the combination of C-doping with nanocomposite semiconductors, is presented in this work. C-doped g-C3N4 (CCN) was prepared by supramolecular self-assembly and subsequently a number of CdIn2S4/CCN composite photocatalysts were designed and fabricated though in situ decoration of CdIn2S4 crystals on the surface of CCN nanosheets via a hydrothermal method. This unique architecture was able to efficiently promote the transfer and separation of photon-generated charges, enhance light absorption, and significantly increase photocatalytic H2 production. Detailed characterization was performed to analyze the crystal structure, morphology, elementary composition, optical properties and catalytic mechanism. The CdIn2S4/CCN nanocomposites with optimal CdIn2S4 content exhibited a maximum H2 production rate of 2985 μmol h−1 g−1, almost 15 times more than that obtained using pure g-C3N4 (205 μmol h−1 g−1). In addition, the hybrid photocatalysts display good recycling stability under visible-light irradiation. This research may provide promising information for the preparation of more efficient multifunctional hybrid photocatalysts with excellent stability in fine chemical engineering.

A highly selective DNA-based electrochemiluminescence (ECL) based biosensor is described for the detection of human IgG. It is exploiting the effect of steric hindrance that affects the strength of the ECL signal in the presence of IgG. Digoxin-linked signaling DNA was specifically bound to IgG, and this causes steric hindrance which limits the ability of DNA to hybridize with capturing DNA attached to a gold electrode. Europium (II) doped CdSe quantum dots were covalently linked to the DNA in order to generate the ECL signal. Using this steric hindrance hybridization method, the ECL signal of the biosensor were proportional to the concentration of IgG with a wide linear range and a 14 pM detection limit. Conceivably, the method can be expanded to the detection of a wide range of proteins for which homologous recognition elements are available.

A new generalized volume-surface integral equation, volume integral equation-combined field integral equation (VIE-CFIE), is proposed to analyze the electromagnetic (EM) scattering from composite objects comprised of both perfect electric conductor (PEC) and inhomogeneous bi-isotropic material. By discretizing the objects using triangular and tetrahedral cells on which the commonly used Rao-Wilton-Glisson (RWG) and Schaubert-Wilton-Glisson (SWG) basis functions are respectively defined, the matrix equation is derived using the method of moments (MoM) and the Galerkin's testing. Furthermore, the continuity condition (CC) of electric flux is explicitly enforced on the PEC and bi-isotropy interfaces. In this way, the number of volumetric unknowns is reduced based on the same set of meshes, particularly for the thin coated PEC objects. A convenient way to embed the CC into the context of MoM solution is provided in detail. Several numerical results of EM scattering from coated PEC objects are shown to illustrate the accuracy and efficiency of the proposed method.

This paper presents an active frequency selective surface (AFSS) with a wide reconfigurable passband. The tuning mechanism was investigated with an equivalent circuit which consists of a parallel L-C resonant circuit and a series L-C resonant circuit. A cross-loop slot was selected as a unit cell, and varactor diodes were added across the slot to tune the passband. The effects of various bias configurations on the transmission coefficients were studied. The simulation results showed that a reconfigurable passband ranged from 2.92 to 5.74 GHz was obtained with a variable capacitance from 0.8 to 0.1 pF. A prototype of the proposed AFSS was fabricated and measured. The measurement results showed that the passband was altered from 2.94 to 5.66 GHz if the biasing voltage of varactor diodes was increased from 4 to 18V. The measurement and simulation results agree well with each other.

An absorptive/transmissive frequency selective surface (ATFSS) with absorption bands at both sides of a passband is presented. Equivalent circuits of the ATFSS that consists of a lossy frequency selective surface (FSS) and a lossless FSS were modeled. To improve the rejection at an undesired band, a transmission zero was introduced and controlled by loading the lossless FSS with four-legged loaded slots. The parasitic passband was suppressed when the cross structure in the lossless FSS was loaded with resistance. In order to expand the absorption band, loaded dipoles were utilized for the lossy FSS design. An ATFSS with wide absorption bands was realized after three ATFSSs with different performances were investigated. The proposed ATFSS was fabricated and measured. The measurement results showed that a passband at around 5 GHz with a minimum insertion loss of 0.92 dB was obtained. Within an ultrawide band from 2.8 to 11.4 GHz with |S11

MnO2 possesses multiple crystal phases and various geometrical morphologies, so there remains a big challenge to simultaneously control the crystal phases and geometrical morphologies of MnO2 by a facile process. Indeed, these controllable syntheses will provide material bases to investigate their effects on the specific capacitance. Herein, benefiting from the first attempt of using Co2+ as a phase transformation-inducing agent and a doping ion, we present an interesting report on controllable phase transformation from δ- to α-MnO2 and their morphology evolution from nanosheets to nanowires. These transformations need the synergistic effect between MnCO3 and Co2+. Furthermore, three dimensional hierarchical α-MnO2@δ-MnO2 core–shell heterophase nanostructures were fabricated to improve capacitance performance. Impressively, the specific capacitance of α-MnO2@δ-MnO2 reaches up to 206 F g−1, which is higher than those of the corresponding single components. An asymmetric supercapacitor device based on the α-MnO2@δ-MnO2 cathode exhibits a good energy density of 12.9 W h kg−1 at a power density of 230 W kg−1 and excellent cycle lives with a decrease of 26% capacitance after 10 000 charge/discharge cycles.

Here, we report the complete chloroplast genome of Pittosporum brevicalyx. The genome is 153,388 bp in size, which is comprised of a large single-copy (LSC) region of 84,724 bp, a small single-copy (SSC) region of 18,716 bp, and two inverted repeat (IR) regions of 24,974 bp. The overall GC content of the plastome was 38.3%. The new sequence comprised 127 unique genes, including 82 protein-coding genes, 8 rRNA genes, and 37 tRNA genes. Phylogenetic analysis showed that P.brevicalyx was close to Pittosporum kerrii and Pittosporum eugenioides. These data may providing useful information for phyletic evolution of P.brevicalyx within the Pittosporaceae family.

An important advantage of guided waves is their ability to propagate large distances and yield more information about flaws than bulk waves. Unfortunately, the multi-modal, dispersive nature of guided waves makes them difficult to use for locating flaws. In this work, we present a method and experimental data for removing the deleterious effects of multi-mode dispersion allowing for source localization at frequencies comparable to those of bulk waves. Time domain signals are obtained using a novel 64-element phased array and processed to extract wave number and frequency spectra. By an application of Auld’s electro-mechanical reciprocity relation, mode contributions are extracted approximately using a variational method. Once mode contributions have been obtained, the dispersion for each mode is removed via back-propagation techniques. Excepting the presence of a small artifact at high frequency-thicknesses, experimental data successfully demonstrate the robustness and viability of this approach to guided wave source location.

The eddy current non-destructive evaluation (NDE) modelling using Stratton-Chu formulation-based fast algorithm is analysed. Stratton-Chu formulations, which have no low frequency breakdown issue, are selected for modelling electromagnetic NDE problems with low frequency and high conductivity approximations. As the main contribution of this article, the robustness and efficiency of the approximations, which result in big savings in both memory and CPU time, are validated and analysed using examples from practical EC testing. The boundary element method (BEM) is used to discretize the integral equations into a linear system of equations: the first order Rao-Wilton-Glisson (RWG) vector basis functions with the flat triangle meshes of the object and pulse basis functions are selected to expand the equivalent surface currents and the normal component of magnetic fields, respectively. Then the multilevel adaptive cross approximation (MLACA) algorithm is applied to accelerate the iterative solution process. The performance and efficiency of adaptively applying a multi-stage (level) algorithm based on the criteria concluded for the operators are shown.This article is part of the theme issue ‘Advanced electromagnetic non-destructive evaluation and smart monitoring’.