Search

Glide-symmetric (G-S) waveguides made of metallic metasurfaces are a wideband, low-loss, low-cost, and conformable alternative to dielectric materials for the design of antenna lenses at millimeter waves. However, computing the effective refractive index of glide-symmetric waveguides with existing full-wave analysis techniques results in cumbersome parametric studies for each new design. This article presents a new analytic homogenization technique for glide-symmetric holey parallel-plate waveguides (PPWs). The dispersion equation of these structures, found by way of mode-matching, is simplified at low frequency using the properties of the modes resonating within the holes, independently of the hole shape. This simplified equation yields a closed-form expression of the effective refractive index, relying on the eigenmodes of the hole cross section. This formula avoids solving a 3-D full-wave problem and is fully analytic in the case of canonical hole shapes. Although derived in the quasi-static regime, it characterizes propagation over an ultrawide band, due to the low dispersive properties of glide symmetric structures. It is a function of the angle of propagation within the waveguide and can thus be used to study anisotropic properties. Its efficiency is demonstrated with the example of glide-symmetric PPWs with rectangular and circular holes. [ABSTRACT FROM AUTHOR]

In recent years, metasurfaces have become a rapidly growing domain of research in several fields of engineering and applied physics due to their ability to manipulate both phase and amplitude of electromagnetic fields. These artificial 2D-materials, usually composed of metallic elements printed on dielectric substrates, have the advantages of being low profile, lightweight as well as easy to fabricate and integrate with standard circuit technologies. In this context, this paper reviews the latest progress in metasurface antenna design, where metasurfaces are used to miniaturize the profile, increase the bandwidth, and control the radiation pattern in the near- and far-field regions. [ABSTRACT FROM AUTHOR]

• Thermal energy recovery within a Sequencing Batch Biofilter Reactor (SBBGR) was performed for three months. • No evident fouling of the submerged thermal exchanger was observed. • Energy recovery did not affect SBBGR performance. • About 3 and 4 log 10 units of C. perfringens and E. coli were removed, respectively. • Effluent complied with standards for agricultural reuse in force in many countries. In the present study, the possibility of recovering both thermal energy and water for agricultural purposes from sewage is evaluated. A treatment plant, based on a sequencing batch biofilter granular reactor (SBBGR) followed by sand filtration and coupled with a solar wastewater source heat pump, was operated from September to November 2018 at a set-point temperature of 14 °C to verify the stability of heat recovery efficiency and the suitability of plant effluent to be reused for irrigation. Heat recovery did not influence the SBBGR treatment and disinfection efficiency, which removed about 90% of suspended solids, chemical and biochemical oxygen demand and ammonia, as well as 70% of total nitrogen, 3 log 10 units of Escherichia coli and more than 1 log 10 unit of Clostridium perfringens. Furthermore, after sand filtration, water quality complied with the standards for agricultural reuse currently in force in several countries. Energy extracted from SBBGR was mainly influenced by environmental conditions, affecting wastewater temperature, and also by wastewater composition, affecting the energy release due to bacterial metabolic activity for carbon and nitrogen removal. Notably, no evident deterioration of energy extraction efficiency from the SBBGR was observed, suggesting negligible fouling phenomena on the submerged thermal exchanger. [ABSTRACT FROM AUTHOR]

In this article, we propose the implementation of a triangular mesh along with Rao-Wilton-Glisson (RWG) basis functions to improve the performance and flexibility of a mixed mode-matching (MM)/method-of-moments (MoM) algorithm dedicated to substrate integrated waveguide (SIW) antennas analysis and optimization. These basis functions represent equivalent magnetic currents on either coupling or radiating apertures. In the initial implementation, the entire domain sine basis function was presented, providing fast and accurate simulations for electrically thin rectangular slots. In order to treat wider slots and other geometries, we add here RWG functions, present the theoretical framework of this approach, and highlight its potential through concrete examples. [ABSTRACT FROM AUTHOR]

We study the wave propagation between two glide-symmetric metallic plates drilled with periodic rectangular holes. A mode-matching method is proposed in order to derive efficiently the dispersive properties of these periodic structures. The method takes advantage of the higher symmetry of the structure reducing the computational cost by enforcing boundary conditions on the field on only one of the two surfaces. Physical insight on specific symmetry properties of Floquet harmonics in glide-symmetric structures is also gained. The code is validated with commercial software assessing its accuracy when varying the most influential/critical parameters. We confirm the potential of glide-symmetric structures to tune the effective refractive index. Specifically, we demonstrate that glide-symmetric structures with rectangular shapes can be employed to synthesize anisotropic refractive indexes with a large band of operation, which makes such metasurface structures applicable for the realization of ultrawideband planar lenses. [ABSTRACT FROM AUTHOR]

Abstract: In this work, we analyse the effect of mechanical stresses on graphene devices for application in flexible electronics. The possible Schottky contacts in the transistor are modeled through suitable transmission coefficients describing the tunnelling through the electrostatic potential along the graphene channel. The surface potential is determined by imposing an equality between the charges computed with a micromodel and a macromodel. All these computation tools are explicitly dependent on the choice of geometrical parameters, thus allowing the description of uniform geometrical deformations due to strains along a given direction. Numerical results are computed and discussed. [ABSTRACT FROM AUTHOR]

Protein heterologous production offers viable opportunities to tailor laccase properties to specific industrial needs. The high redox potential laccase POXA1b from Pleurotus ostreatus was chosen as case study of marketable enzyme, due to its desirable properties in terms of activity/stability profile, and already assessed applicability. POXA1b was heterologously produced in Pichia pastoris by investigating the effect of inducible and constitutive expression systems on both the yield and the cost of its production. System performances were first assessed in shaken-flasks and then scaled-up in bioreactor. The production level obtained in the inducible system is 42 U/mL, while the activity value achieved with the constitutive one is 60 U/mL, the highest obtained in constitutive systems so far. The economic feasibility of recombinant laccase production was simulated, describing the case of an Italian small-medium enterprise. Two scenarios were evaluated: Scenario (I) production based on methanol inducible system; Scenario (II) production based on the constitutive system, fed with glycerol. At all the scales the glycerol-based fermentation is more economic than the methanol-based one. The price forecast for rPOXA1b production is 0.34 € k U −1 for glycerol-based process, and is very competitive with the current price of commercial laccase. [ABSTRACT FROM AUTHOR]

Thin artificial surfaces that act as high frequency bandgap structures have been recently studied for the design of gap waveguides, hard surfaces, and planar lenses. Here, we propose a circuit-based method to analyze glide-symmetric corrugated metasurfaces that are embedded in a thin parallel plate waveguide. Our closed-form solution is based on rigorous analytical derivations. It achieves remarkable agreement with full-wave solvers, even when the waveguide thickness is extremely thin. In contrast, classical homogenization approaches are shown to be inaccurate for thin waveguides due to the interaction of higher order Floquet modes between the surfaces. Numerical results validate our theoretical analysis and show the utility of the proposed method. [ABSTRACT FROM PUBLISHER]

In this communication, it is shown that a nondiffracting vortex beam (i.e., a higher order Bessel beam with azimuthal phase variation) can be generated in the near field by synthesizing an inward cylindrical traveling-wave distribution over a finite aperture antenna. A radial line slot array (RLSA) is then designed to prove the concept. The collimated vortex beam is excited in the proximity of the RLSA, within a region properly defined by the nondiffracting range of the generated beam. The radial dependence of the longitudinal electric field of the vortex-beam magnitude follows a first-order Bessel function, and its phase presents a linear azimuthal variation. Full-wave results validate the generation of the nondiffractive higher order Bessel beam within the radiative near field of the launcher. [ABSTRACT FROM PUBLISHER]

In this paper, we present a method for the analysis of lossy substrate-integrated waveguide structures. The analysis is achieved through the cylindrical-wave mode expansion of the field and a mode matching technique to enforce boundary conditions on the post surfaces. We introduce an approximated formulation of the previous exact procedure, valid in the microwave regime, and numerically examine a number of microwave devices using both approximated and exact analyses. These devices include filters, couplers, phase shifter, and so on. Results are presented for the scattering parameters and compared with those obtained with the commercial software in terms of accuracy and computational time. [ABSTRACT FROM PUBLISHER]

The efficient computation of periodic Green’s functions is discussed here for an arbitrarily directed array of point sources in layered media. These Green’s functions are necessary to formulate boundary integral equations for arrays of scatterers inside a general layered medium, solved with the method of moments in the spatial domain. For this reason, mixed-potential Green’s functions—having a mild spatial singularity—are selected. The case of horizontally oriented dipoles is rather simple and has been previously solved. On the other hand, the case of vertically oriented dipoles (i.e., aligned perpendicular to the layers) is more intricate, since the extracted terms cannot be transformed into well-known Green’s functions. Previous works dealt with arrays of line and point sources, but did not address the critical task of computing the curl of the dyadic potentials, required to treat slot arrays and dielectric inclusions, whose available Floquet series expressions do not converge if the source and observation points lie in the same transverse plane. [ABSTRACT FROM AUTHOR]

We present a Bessel-beam launcher based on a leaky radial waveguide consisting of a capacitive sheet over a ground plane that supports higher-order leaky modes. A propagating Bessel beam is generated above the radiating waveguide. The Bessel beam is transverse-magnetic (TM) polarized with a vertical component of electric field that is a zeroth-order Bessel function of the first kind. A higher-order leaky-wave mode is used to reduce losses at millimeter waves and, at the same time, avoid the thin dielectric layers used in previously proposed lower order leaky-wave Bessel launchers. Closed-form design equations are provided for the proposed structure. In addition, the operating bandwidth of the launcher is defined using dispersion analysis. Near-field measurements of a prototype operating in the frequency range 38–39.5 GHz validate the concept. The measured launcher generates a Bessel beam with a stable spot size of about 4.3 mm ($0.57\,\lambda$) over a nondiffractive range of about 16.4 mm ($2.2\,\lambda$), within about a 4% fractional bandwidth. [ABSTRACT FROM PUBLISHER]

An efficient mixed-potential integral equation formulation is proposed for the analysis of one-dimensional (1-D) periodic leaky-wave antennas (LWAs) based on planar stratified configurations with inclusions of arbitrarily oriented metallic or dielectric perturbations. Both the transverse and vertical components of the mixed-potential Green’s functions due to a 1-D phased array of dipoles in a layered medium are accelerated using suitable homogeneous-medium asymptotic extractions from the standard spectral series of Floquet harmonics. A novel acceleration procedure is applied for the computation of the vertical potentials whose extracted terms can be expressed as potentials from a 1-D phased array of half-line sources in a homogeneous medium. Their numerical calculation requires a suitable modification of the Ewald method, thus resulting in new modified spectral and spatial series, having Gaussian convergence even in the case of complex modes and improper harmonics. Numerical comparisons for the 1-D periodic potentials, both in the case of bounded and unbounded (e.g., leaky) harmonics, validate the efficiency and accuracy of the proposed acceleration technique. The method is illustrated and verified by determining the dispersion behavior of both bound and leaky modes for several LWA test cases. [ABSTRACT FROM PUBLISHER]

A novel spectral formulation is proposed here for the coupling integral between a cylindrical wave with arbitrary radial wavenumber and azimuthal dependence, and a slot placed on a plane orthogonal to the wavefront. Such a kind of integral is massively encountered in electromagnetic modeling of stratified structures comprising slots and vertical pins or vias. The twofold spatial integral defining the coupling is transformed into an equivalent onefold spectral integral, the integration path of which is selected to obtain Gaussian decay of the integrand. Both propagating and evanescent cylindrical modes are considered. An arbitrary stratification orthogonal to the slot plane can be considered, as well as an arbitrary current on the slot. Numerical comparisons against the standard spatial approach are shown to validate the new formulation, and its advantage in terms of computation cost is investigated in depth. [ABSTRACT FROM PUBLISHER]

We propose a fast and accurate full-wave code capable of analyzing electrically large substrate integrated waveguides consisting of stacked parallel-plate waveguides hosting dielectric or metallic posts and coupling and/or radiating slots. Boundary conditions enforced on posts yield scattering amplitudes, while slots are modeled by equivalent magnetic currents, solved by a method of moments. Substantial accelerations are proposed to exploit various symmetries of the structures and to select the optimal number of modes according to the relevant geometrical and physical parameters. The formulation is validated by full-wave simulations with a commercial software and measurement results. [ABSTRACT FROM PUBLISHER]

The on-body propagation at 60 GHz is studied analytically, numerically and experimentally using a skin-equivalent phantom. First, to provide analytical-based fundamental models of path gain, the theory of propagating waves near a flat phantom is studied by considering vertical and horizontal elementary dipoles. The analytical models are in excellent agreement with full-wave simulations. For a vertically polarized wave, a minimum power decay exponent of 3.5 is found. Then, propagation on the body is investigated experimentally in vertical and horizontal polarizations using two linearly-polarized open-ended waveguides. The analytical models fit very well with the measurements. Furthermore, the effect of polarization on the antenna performance is studied numerically and experimentally. [ABSTRACT FROM AUTHOR]

An original acceleration procedure is proposed for the efficient calculation of the vertical components of the dyadic and scalar mixed-potential layered-media periodic Green's functions. The extraction of suitable asymptotic terms, i.e., quasi-static images, is performed in order to speed up the convergence of the relevant spectral series. This procedure, well known for planar Green's functions, is here generalized to treat the off-diagonal dyadic components and the corrective scalar potential arising from the vertical currents. The extracted terms are homogeneous-medium Green's functions due to a periodic phased array of half-plane currents, computed through a modified Ewald method, leading to a pair of Gaussian-convergent series. The highly improved convergence rate of the relevant series is shown, and the reduction of the computation time is numerically tested and discussed. The algorithm is implemented in EIGER, an open-source code based on the method of moments; several periodic structures are analyzed and fully validated through numerical comparisons. The proposed formulation has been proven very efficient, accurate, and stable. [ABSTRACT FROM PUBLISHER]

Abstract: In this work, the ability of Ground Penetrating Radar (GPR) to detect rocks buried in composite soil is studied in connection with the planned ExoMars mission, as GPR will be used during this mission to scan the Martian subsurface to help define feasible sites for shallow drilling. A realistic model of the operating environment is implemented through a full-wave electromagnetic simulator, taking into account the antenna system and the signal features. The flexibility and efficiency of this numerical approach has allowed for the analysis of a great variety of configurations. The regolith is modeled based on data from recent explorations, while various kinds of embedded rocks are considered that have different geometrical and physical characteristics. The simulated results are compared with ad hoc GPR measurements performed on basalts buried in a mixture of glass beads, as an analogue of a dry sandy Martian soil. A very good agreement between theoretical and experimental results is found, thus validating the proposed numerical approach. This research has defined useful and reliable information concerning the prediction of scattering effects from buried objects in the environment where the ExoMars rover will operate. [Copyright &y& Elsevier]

Closed-form expressions are derived for the number of surface waves propagating along a general multilayered structure with media having positive material parameters. The expressions shown here are also useful for the efficient numerical determination and ordering of the cutoff frequencies of surface waves on multilayered structures. The presented formulas are simple but exact. Validation is provided with full-wave dispersive analyses of several types of layered structures. [ABSTRACT FROM AUTHOR]

The input impedance of nonperiodic sources that excite a periodically loaded shielded microstrip line is studied numerically with a rigorous method-of-moments approach based on the array scanning method. Both a delta-gap voltage and an impressed vertical current sheet are considered to be idealized sources exhibiting different symmetry properties. Their input impedances, calculated according to either a power-voltage or a power-current definition, are compared with the Bloch impedance of the dominant mode excited along the structure in a wide frequency range encompassing different propagation regimes of the dominant and of the first higher order mode. Numerical results, validated also through independent full-wave codes, provide physical insight and quantitative information on the mode excitation efficiency and input-impedance features of finite sources in a periodic microstrip environment. [ABSTRACT FROM AUTHOR]

The problem of improving the computational efficiency in the numerical analysis of planar periodic structures is investigated here using the mixed-potential integral-equation (MPIE) approach. A new regularization of the periodic Green's functions (PGFs) that are involved in the analysis of multilayered structures is introduced, based on the effective-medium concept. This regularization involves extracting the singularities of the PGFs up to second-order terms. The resulting regularized PGF is very smooth and amenable to interpolation. Thus, optimized interpolation procedures for the PGFs can be applied, resulting in a considerable reduction of computation time without any significant effect on the accuracy. Another benefit of the regularization is that it significantly enhances the convergence of the series for both the vector- and scalar-potential PGFs. The theoretical formulation is fully validated with various numerical results for both two-dimensional (2-D) and one-dimensional (1-D) layered-media periodic structures. [ABSTRACT FROM AUTHOR]

The problem of accelerating the calculation of the periodic Green's function is addressed here for both 3-D and 2-D free-space configurations. In the 3-D case, periodicity is considered both along one axis and along two, generally skew, axes. A comprehensive review of the existing methods is first presented and some extensions are developed. The possibility of treating the case of complex phase shifts between unit cells, necessary for the study of complex modes in periodic structures, is also investigated. Comparisons among the various acceleration methods are performed, thus providing fundamental information on their actual efficiency in typical problems. [ABSTRACT FROM AUTHOR]

The effectiveness of an advanced treatment of wastewater generated by non-hazardous plastic solid waste (PSW) washing, based on the Sequencing Batch Biofilter Granular Reactor (SBBGR), was assessed in terms of gross parameters, removal efficiencies and sludge production. The proposed treatment was also compared with the conventional treatment, which was based on primary and secondary treatments, using the activated sludge process, performed by Recuperi Pugliesi, a leading company in the plastic recycling industry located in Bari, Italy. The company produces low-density polyethylene (LDPE) regenerated granules from PSW used in agricultural and floricultural greenhouse activities and industrial packaging after a washing stage in the aqueous phase. The latter generates large volumes of wastewater, the conventional treatment of which is characterised by large quantities of sludge and the associated disposal problems. Under steady-state conditions, the SBBGR provided impressive removal efficiencies regarding the main gross parameters (over 90% for COD and TKN, over 99% for BOD 5 , TSS, VSS and NH 3 , and over 80% for TN) with a statistically better effluent quality than that of the conventional treatment. The SBBGR effluent quality was modelled in terms of washing water characteristics by using generalized additive models (GAMs). The SBBGR treatment was characterised by a specific sludge production five times lower than that of the conventional treatment (0.21 kg TSS vs. 1.0 kg TSS per m3 of wastewater treated). Compared with the conventional treatment, the proposed process showed a five-fold reduction in the cost of sludge disposal, which saved 50% of the operating cost. • An advanced system was tested for treating and reusing plastic waste washing water. • The proposed system reduced sludge production from 1.00 to 0.21 kgTSS/m3. • The proposed system showed high efficiency and stability when operating at 3.1 d HRT. • Hydraulic residence time 38% lower than that of the conventional treatment was required. • Effluent quality better than that of conventional treatment was obtained. [ABSTRACT FROM AUTHOR]

In this work, we analyze the spatial and temporal features of electromagnetic X-waves propagating in free space and generated by planar radiating apertures. The performance of ideal X-waves is discussed and compared to practical cases where the important effects related to the finiteness of the radiating aperture and the wavenumber dispersion are taken into account. In particular, a practical device consisting of a radial waveguide loaded with radiating slots aligned along a spiral path is considered for the practical case in the millimeter-wave range. A common mathematical framework is defined for a precise comparison of the spatiotemporal properties and focusing capabilities of the generated X-wave. It is clearly shown that the fractional bandwidth of the radiating aperture has a key role in the longitudinal confinement of an X-wave in both ideal and practical cases. In addition, the finiteness of the radiating aperture as well as the wavenumber dispersion clearly affect both the transverse and the longitudinal profiles of the generated radiation as it travels beyond the depth-of-field of the generated X-wave. Nevertheless, the spatiotemporal properties of the X-wave are preserved even in this "dispersive-finite" case within a defined region and duration related to the nondiffractive range and fractional bandwidth of the spectral components of the generated X-wave. The proposed analysis may open new perspectives for the efficient generation of X-waves over finite radiating apertures at millimeter waves where the dispersive behavior of realistic devices is no longer negligible. [ABSTRACT FROM AUTHOR]

We discuss here under which conditions a periodic line with a twist-symmetric shape can be replaced by an equivalent non-twist symmetric structure having the same dispersive behavior. To this aim, we explain the effect of twist symmetry in terms of coupling among adjacent cells through higher-order waveguide modes. We use several waveguide modes to accurately derive the dispersion diagram of a line through a multimodal transmission matrix. With this method, we can calculate both the phase and attenuation constants of Bloch modes, both in shielded and open structures. In addition, we use the higher symmetry of these structures to further reduce the computational cost by restricting the analysis to a subunit cell of the structure instead of the entire unit cell. We confirm the validity of our analysis by comparing our results with those of a commercial software. [ABSTRACT FROM AUTHOR]

In this article, we demonstrate how twist symmetries can be employed in the design of flat lenses. A lens design is proposed, consisting of 13 perforated metallic sheets separated by an air gap. The perforation in the metal is a two-dimensional array of complementary split-ring resonators. In this specific design, the twist symmetry is local, as it is only applied to the unit cell of the array. Moreover, the twist symmetry is an approximation, as it is only applied to part of the unit cell. First, we demonstrate that, by varying the order of twist symmetry, the phase delay experienced by a wave propagating through the array can be accurately controlled. Secondly, a lens is designed by tailoring the unit cells throughout the aperture of the lens in order to obtain the desired phase delay. Simulation and measurement results demonstrate that the lens successfully transforms a spherical wave emanating from the focal point into a plane wave at the opposite side of the lens. The demonstrated concepts find application in future wireless communication networks where fully-metallic directive antennas are desired. [ABSTRACT FROM AUTHOR]

An anisotropic unit cell based on glide symmetry is proposed for tailoring a metasurface that engineers an optically transformed Luneburg lens. Thanks to the optical transformation, the size of the lens is reduced by 25%. The proposed lens is ultrawideband, and it covers multi-octave frequency bands. The required constitutive materials are achieved in an air gap bounded by top and bottom glide-symmetric metasurfaces; i.e., they are off-shifted by half the period. Each surface is implemented in standard printed-circuit-board technology, and its unit cell consists of a grounded substrate with an elliptical holey top cladding surrounded by metalized through-vias. This technology, known as substrate-integrated-holes (SIHs), mimics the operation of holes drilled in a parallel plate but provides the higher effective refractive index required for lens compression. The SIH is attractive for practical applications since most of the energy propagates in the air gap between the two surfaces and, therefore, it features low dielectric losses. Thanks to glide symmetry, the proposed metasurface demonstrates a further enhanced effective refractive index with lower dispersion over an ultra-wide bandwidth in comparison to its non-glide counterpart. A multimodal transfer-matrix approach is here employed to carry out the Bloch analysis of the proposed SIH. [ABSTRACT FROM AUTHOR]

In this article, we study the wave propagation in a metallic parallel-plate structure with glide-symmetric elliptical holes. To perform this study, we derived a mode-matching technique based on the generalized Floquet theorem for glide-symmetric structures. This mode-matching technique benefits from a lower computational cost since it takes advantage of the glide symmetry in the structure. It also provides physical insight into the specific properties of Floquet modes propagating in these specific structures. With our analysis, we demonstrate that glide-symmetric structures with periodic elliptical holes exhibit an anisotropic refractive index over a wide range of frequencies. The equivalent refractive index can be controlled by tuning the dimensions of the holes. Finally, by combining the anisotropy related to the elliptical holes and transformation optics, a Maxwell fish-eye (MFL) lens with a 33.33% size compression is designed. This lens operates in a wideband frequency range from 2.5 to 10 GHz. [ABSTRACT FROM AUTHOR]

Glide-symmetric structures have recently emerged as a smart choice to design planar lenses and electromagnetic bandgap materials. We discuss here the conditions under which a glide-symmetric structure is equivalent to a nonglide-symmetric structure with a reduced period. To this aim, we propose an analysis method based on network theory to efficiently derive the dispersive behavior of these periodic structures. Both phase and attenuation constants can be determined, with potential applications to both guiding and radiating structures. Retaining higher order modal interactions among cells helps to derive the dispersive behavior of periodic structures more accurately. Furthermore, we take advantage of the higher symmetry of these structures to decrease the computational cost by considering only one half or one-quarter of a unit cell instead of the entire cell. We study one and 2-D glide-symmetric structures and confirm the validity of our analysis with comparisons from commercial software. [ABSTRACT FROM AUTHOR]

A very efficient and accurate method is proposed to evaluate the lattice sums (LSs) for the analysis of leaky waves in 2-D periodic waveguides. The LSs are the series involving Hankel functions of arbitrary order, which are not convergent for complex wavenumbers. It is shown that by extending Ewald representations to higher order Hankel functions, the LSs can be expressed in terms of spatial and spectral series, granting Gaussian convergence even in the case of complex and leaky waves. The method allows for the appropriate choice of the spectral determination for each space harmonic of a given LS coefficient, thus permitting one to obtain modal solutions that may correspond to physical and nonphysical leaky-wave phenomena. First, the proposed LS calculation is exploited in the evaluation of the free-space 1-D periodic Green’s function for 2-D structures. Then, the same procedure for the LSs is implemented in a cylindrical harmonic expansion method, based on the transition-matrix and the generalized reflection-matrix approach, for the full-wave analysis of leaky modes in 2-D electromagnetic band-gap waveguides formed by layered arrays of cylindrical inclusions. The presented LS formalism is numerically slim, very fast, and thus well suited for the analysis of a significant class of lossy periodic waveguides and leaky-wave antennas. [ABSTRACT FROM AUTHOR]

Abstract: A strong trend toward using highly selective mass spectrometry technologies for screening of multiple mycotoxins has been observed in recent years. In the present study, the process of validation of a multimycotoxin screening method based on liquid chromatography–high‐resolution mass spectrometry method is presented. The method was intended for the simultaneous screening of the major Fusarium toxins (deoxynivalenol, 3‐ and 15‐acetyl deoxynivalenol, T‐2 and HT‐2 toxins, zearalenone, enniatins A, A1, B, and B1, and beauvericin) in wheat. The sample preparation protocol was based on a double extraction (methanol followed by acetonitrile/water mixture) and purification through solid‐phase extraction C18 column. To provide insights for full exploitation of the potential of the double‐stage high‐resolution mass spectrometry detection, a full‐scan acquisition event followed by a sequence of 5 fragmentation events (variable data‐independent acquisition) was set for mycotoxin detection, the latter to be exploited for confirmatory purposes. Method analytical performances were evaluated through in‐house validation and small‐scale interlaboratory study, designed according to Commission Regulation 519/2014/EU, setting performance requirements for screening methods for mycotoxins. Screening target concentrations were close to European Union maximum permitted or indicative levels. The in‐house validation provided the precision of the response under repeatability conditions and the intermediate precision (both resulting lower than 30%), the cutoff value, and the rate of false suspect results for negative (free of the mycotoxin of interest) samples, which resulted lower than 0.1% in all cases. The collaborative study provided reproducibility and laboratory independent cutoff values. Analysis of reference materials proved method trueness and suitability for screening of the major Fusarium mycotoxins in wheat. Finally, the applicability of the full‐scan/variable data‐independent acquisition detection approach was successfully tested on a set of naturally contaminated wheat samples, where 2 characteristic product ions could be detected for all identified mycotoxins even at levels in the low μg/kg range. [ABSTRACT FROM AUTHOR]

In this paper, the current–voltage characteristics of a graphene-based transistor in the presence of external strain are computed with different methods. A simplified semi-analytic method allows fast computation of the electric parameters by granting a good accuracy. A more complex matrix method based on second quantized version of Schrodinger equation by means of non-equilibrium Green’s function is used to validate the semi-analytic one. Both models are developed to evaluate the impact of mechanical stresses on this novel class of nano-transistors, where they are aimed for applications in the domain of flexible electronics. [ABSTRACT FROM AUTHOR]

Laccase-catalyzed synthesis of dye molecules represents a green choice to reduce the environmental footprint of conventional synthetic processes. Textile industry will benefit from this green technology since the synthesized dyes can be exploited to colour different fabrics. This work describes the application of the Pleurotus ostreatus POXA1b laccase in polymeric dye synthesis using resorcinol and 2,5-diaminobenzenesulfonic acid (2,5-DABSA) as substrates. The potential of the resorcinol/2,5-DABSA coupling route was transferred to a chemical industry, Setaş Colour Center, by introducing a greener synthesis step within the process routinely used for textile dyeing. Dye synthesis was performed at different precursor ratios (1:1 and 1:10 2,5-DABSA: resorcinol) and their dyeing properties were compared on different fibres. The two mixtures of synthesized dyes proved to be effective on nylon and wool, with 1:10 ratio displaying the best performances in terms of dyeing efficiency and colour strength. Good and comparable end quality and “performances during use” were observed for nylon and wool coloured with both synthesized dyes. [ABSTRACT FROM AUTHOR]

This article proposes a method to engineer degenerate band-edge conditions in periodic substrate-integrated waveguides (SIWs). A degenerate band edge (DBE) is a fourth-order exceptional point originating from the coupling of four Floquet–Bloch modes; it leads to a dispersion relation flatter than a regular band edge (RBE) and is suitable to design slow wave structures and high $Q$ -factor resonators. Design guidelines to achieve a DBE point are given based on Bloch analyses of unit cells. An oblique line of vias in SIW is proposed to form a suitable modal coupling between adjacent waveguides enabling a degenerate band-edge condition. The effect of losses and the robustness to parameter variations are discussed by means of rigorous Bloch analyses. A unit cell showing the best behavior concerning the losses and geometric tolerances is selected and prototypes of finite-length resonators are realized. Measurements validate simulated results and confirm the typical $N^{5}$ scaling of the loaded $Q$ -factor to the number of cells $N$ of the resonator. [ABSTRACT FROM AUTHOR]

We describe the design of a radial line slot array antenna with a shaped and focused near field. The antenna is designed in such a way to control the side lobe level and beamwidth of the normal component of the electric field with respect to the radiating aperture. The design procedure consists of two steps. In the first step, the requirements on the near-field pattern are provided over a focusing plane at a given distance from the radiating aperture. A set theoretic approach is then used to derive the aperture field distribution fitting the requirements over the near field. In the second step, the aperture field distribution is synthesized by accurately placing and sizing the slots of the antenna. The spillover efficiency is maximized during the design process. The antenna is centrally fed by a simple coaxial probe. The antenna design is validated by a prototype and measurements at 12.5 GHz. [ABSTRACT FROM PUBLISHER]

The effect of textiles on propagation along the body at 60 GHz is studied. A Green's function representation is used to investigate analytically the field excited by an infinitesimal dipole over a multilayer structure representing a flat skin model and clothing. The propagation between two rectangular open-ended waveguides is studied numerically and analytically in terms of path gain. Furthermore, the effect of an air gap between the textile and phantom is considered. Results show that the presence of a textile over a skin-equivalent phantom, as well as an air gap between them, induces a typical decrease of the path gain by 2–5 dB, but it doesn't significantly affect the path gain exponent. In all considered scenarios the power decay exponent is around 3.6. [ABSTRACT FROM PUBLISHER]

A new configuration of a self-polarizing Fabry–Perot (FP) antenna is presented to generate circular polarization with high gain levels using a simple linearly polarized feed. It consists of an FP resonator combined with a polarization-twisting ground plane. An analytical model is proposed to facilitate the antenna design, and the corresponding results are shown to be in very close agreement with full-wave simulations. The experimental prototype built in C-band exhibits a combined bandwidth (3 dB axial ratio, 3 dB gain drop, and -10 dB impedance matching) of 3% with a maximum realized gain of 18.0 dB. The antenna is completely shielded with an aperture size of 4.0\lambda0\times 4.0\lambda0 and a height of only \lambda0. Such antennas are attractive candidates for high-power space applications at low frequencies (L-to C-bands) where standard horns are very bulky. [ABSTRACT FROM PUBLISHER]

A novel low-cost element is proposed for S-band multifunction phased-array radars: a compact stacked-patch configuration is fed with a strip-line hybrid-ring network providing the dual polarizations for weather-surveillance applications.Full-wave simulations in a phased-periodic array environment show promising features, in terms of reduced cross-polarization, high isolation between the input ports, scanning capability, and regular radiation patterns. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:697-702, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26665 [ABSTRACT FROM AUTHOR]

Nowadays, sludge management represents one of the most critical challenges in the field of sewage treatment for economic and environmental impacts. Therefore, the reduction of sludge has become a major issue for the operators of municipal wastewater treatment plants. In the present paper, a new system, whose acronym is MULESL (MUch LEss SLudge), is proposed and tested at full scale for reducing the quantity of sludge in the water line of the sewage treatment plant. MULESL system takes the advantage of maintenance metabolism to significantly reduce the sludge production. The effectiveness of MULESL system in removing the typical pollutants and reducing sludge production was evaluated at full scale by using 3500 PE unit located in Putignano's WWTP (Puglia, Italy). This unit was obtained by retrofitting an existing activated sludge basin. The results obtained over 1-year period, during which MULESL unit treated the effluent of the preliminary treatment step, have indicated that it was characterized by a specific sludge production as low as 0.13 kg of dry sludge per kg of COD removed; 77% lower than that recorded for primary and secondary treatments of the conventional plant during the same period. This sludge reduction was obtained with a plant volume 27% smaller than that of the conventional water line. Furthermore, the organic matter of the sludge was already stabilized, thus allowing to save investment costs for digestion process facilities. Finally, MULESL unit guaranteed a mean removal efficiency higher than 95% for COD, BOD 5 , TSS, TKN, NH 3 and TN. • A new biological system was tested at full scale for reducing sludge production. • A sludge production 77% lower than that of the conventional plant was obtained. • An acceptable level of stabilization of excess sludge was obtained. • Plant volume 27% smaller than that of the conventional one was required. • The plant showed high and stable performances. [ABSTRACT FROM AUTHOR]

The green synthesis of highly conductive polyaniline by using two biological macromolecules, i.e laccase as biocatalyst, and DNA as template/dopant, was achieved in this work. Trametes versicolor laccase B (TvB) was found effective in oxidizing both aniline and its less toxic/mutagenic dimer N‐phenyl‐p‐phenylenediamine (DANI) to conductive polyaniline. Reaction conditions for synthesis of conductive polyanilines were set‐up, and structural and electrochemical properties of the two polymers were extensively investigated. When the less toxic aniline dimer was used as substrate, the polymerization reaction was faster and gave less‐branched polymer. DNA was proven to work as hard template for both enzymatically synthesized polymers, conferring them a semi‐ordered morphology. Moreover, DNA also acts as dopant leading to polymers with extraordinary conductive properties (∼6 S/cm). It can be envisaged that polymer properties are magnified by the concomitant action of DNA as template and dopant. Herein, the developed combination of laccase and DNA represents a breakthrough in the green synthesis of conductive materials. [ABSTRACT FROM AUTHOR]

In this study, a bound-constrained optimization algorithm is applied for estimating physiological data (pulse and breathing rate) of human body using 60 GHz Doppler radar, by detecting displacements induced by breathing and the heartbeat of a human subject. The influence of mutual phasing between the two movements is analyzed in a theoretical framework and the application of optimization algorithms is proved to be able to accurately detect both breathing and heartbeat rates, despite intermodulation effects between them. Different optimization procedures are compared and shown to be more robust to receiver noise and artifacts of random body motion than a direct spectrum analysis. In case of a large-scale constrained bound, a parallel optimization procedure executed in subranges is proposed to realize accurate detection in a reduced span of time. [ABSTRACT FROM AUTHOR]

The fluctuation in the number of people in tourist areas affects the wastewater quality and quantity. Constructed wetlands (CWs) aim to simulate physical, chemical, and biological processes occurring in natural environments for wastewater treatment and are considered a sustainable system. The current study aimed at evaluating the effectiveness of in-vessel CWs for supporting the wastewaters treatment plants in periods of overloading. Such approach can be quickly implementable, economic, and the CWs can be fast regenerated in the framework of sustainable good practices. Three pilot scale CWs were prepared in as many containers layering 10 cm of gravel, 60 cm of sand and 10 cm of gravel, and placing pieces of giant reed rhizomes in the upper layers. The bottom of each CW had a tap, and CWs were irrigated with a real municipal sewage three times a week. Before each new irrigation, the tap was opened, and the effluent collected for determining gross parameters, elemental composition, and contaminants of emerging concern (CECs). CWs significantly reduced almost all gross parameters considered and half the CECs, except for a couple of metabolites of corresponding parental compounds. With regards to the potentially toxic elements, all reduced their concentration from the influents to the effluents. The results of this study were promising and highlighted good efficiency of constructed wetlands as pre-treatment of real municipal sewage to reduce the overloading of the wastewater treatment plant. [Display omitted] • Containerized constructed wetlands were used to pre-treat real municipal sewage. • Almost all gross parameters significantly reduced in effluents. • Almost all potentially toxic elements significantly reduced in effluents. • Ten contaminants of emerging concern out of 20 significantly reduced in effluents. • Two metabolites increased their concentration in effluents. [ABSTRACT FROM AUTHOR]

The clarification step represents, in fruit juices industries, a bottleneck process because residual phenols cause severe haze formation affecting juice quality and impairing customers acceptance. An enzymatic step can be efficiently integrated in the process, and use of immobilized enzymes entails an economical advantage. In this work, covalent immobilization of recombinant POXA1b laccase from Pleurotus ostreatus on epoxy activated poly(methacrylate) beads was optimized thanks to a Response Surface Methodologies approach. Through regression analysis the process was well fitted by a quadratic polynomial equation ( R 2 = 0.9367, adjusted R 2 = 0.8226) under which laccase activity reached 2000 ± 100 U g −1 of beads, with an immobilization efficiency of 98%. The immobilized biocatalyst was characterized and then tested in fruit juice clarification reaching up to 45% phenol reduction, without affecting health-effective flavanones content. Furthermore, laccase treated juice displays an improved sensory profile, due to the reduction of vinyl guaiacol, a potent off-flavor possessing a peppery/spicy aroma. [ABSTRACT FROM AUTHOR]

An original architecture based on composite configurations of printed-circuit hybrid rings is developed for flexible signal-processing functionalities in advanced monopulse radar applications. The modularity of the proposed topology, together with proper design choices, strongly simplifies the structure of the beam forming network, reducing the relevant ohmic losses, and consequently improving the antenna gain. The circuit also allows us to manage only two radio frequency channels (instead of the conventional three), combining the delta- and omnidirectional channel functions. The principles of the structure are presented, and a specific layout is designed. Stripline prototypes are fabricated and tested for L-band applications. The compared results of simulations and measurements fully confirm the interesting performance of this device. The versatility of the architecture is illustrated further considering alternative circuit implementations. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1663-1670, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27647 [ABSTRACT FROM AUTHOR]

Abstract: In order to test the accuracy of Ground Penetrating Radar (GPR) in the detection of subsurface targets for planetary exploration, a laboratory scale experiment is performed based on a ‘sand box’ setup using two different bistatic GPR commercial instruments. Specific attention is paid to the challenging case of buried dielectric scatterers whose location and dimensions are of the same order of magnitude of the GPR antenna separation and signal wavelengths. The target depth is evaluated by using the wave propagation velocity measured with Time Domain Reflectometry (TDR). By means of a proper modeling of the different wave-propagation contributions to the gathered signal, the position of buried targets is correctly estimated with both GPRs even for rather shallow and small-size scatterers in near-field conditions. In this frame, relevant results for a basalt block buried in a silica soil are discussed. The experimental configuration is also simulated with an ad-hoc numerical code, whose synthetic radar sections fully confirm the measured results. The acquired information is of paramount importance for the analysis of various scenarios involving GPR on-site application in future space missions. [Copyright &y& Elsevier]

A simple and low-cost solution to reduce the height and weight of extended hemispherical lenses is proposed based on the introduction of a cylindrical air cavity above the primary feed. The presence of an additional air-dielectric interface enables one to shorten the focal length of the lens, which leads to antenna height and weight reductions of 13% and 27%, respectively. The communication describes the design principle and performance characteristics of the reduced-size integrated lens antenna, superimposed with a conventional synthesized elliptical one. Both prototypes are fabricated in Rexolite and measured in Ka band. A good agreement between the performance characteristics of the antennas is observed. The additional advantages of the proposed approach are explained, and its applicability for lens antennas made of high-k materials is discussed. [ABSTRACT FROM PUBLISHER]

This work studies the propagation characteristics of a rectangular waveguide with aligned/misaligned double-sided dielectric-filled metallic corrugations. Two modes are found to propagate in the proposed double-sided configuration below the hollow-waveguide cutoff frequency: a quasi-resonant mode and a backward mode. This is in contrast to the single-sided configuration, which only allows for backward propagation. Moreover, the double-sided configuration can be of interest for waveguide miniaturization on account of the broader band of its backward mode. The width of the stopband between the quasi-resonant and backward modes can be controlled by the misalignment of the top and bottom corrugations, being null for the glide-symmetric case. The previous study is complemented with numerical results showing the impact of the height of the corrugations, as well as the filling dielectric permittivity, on the bandwidth and location of the appearing negative-effective-permeability band. The multi-modal transmission-matrix method has also been employed to estimate the rejection level and material losses in the structure and to determine which port modes are associated with the quasi-resonant and backward modes. Finally, it is shown that glide symmetry can advantageously be used to reduce the dispersion and broadens the operating band of the modes. [ABSTRACT FROM AUTHOR]