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Tape casting technique was used to develop hybrid laminates constituting by SiC and ZrB2–SiC layers; the main aim is obtaining a structure which integrate the unique properties of these materials and potentially extent their application temperature range. Multilayer with ZrB2–SiC layers stacked in between SiC ones were successfully processed. Thin cracks propagated in the composite layers without affecting SiC ones; their formation was due to residual stresses developed in the two materials because of the differences in their shrinkage and coefficients of thermal expansion. However, these cracks did not significantly affect the material properties: relative density, elastic modulus and flexural strength of hybrid laminates was indeed only slightly lower than those of laminates made up of layers with the same composition. [ABSTRACT FROM AUTHOR]

We characterize the optimal prize allocation, namely the allocation that maximizes a group's effectiveness, in a model of contests. The model has the following features: (i) it allows for heterogeneity between and within groups; (ii) it classifies contests as "easy" and "hard" depending on whether the marginal costs are concave or convex. Thus, we show that in an "easy" contest the optimal prize allocation assigns the entire prize to one group member, the most skilled one. Conversely, all group members receive a positive share of the prize when the contest is "hard" and players have unbounded above marginal productivities. If the contest is "hard" and the marginal productivities are bounded above, then only the most skilled group members are certain of receiving a positive share of the prize for any distribution of abilities. Finally, we study the effects of a change in the distribution of abilities within a group. Our analysis shows that if the contest is either "easy" or a particular subset of "hard", then the more the heterogeneity within a group, the higher its probability of winning the prize. [ABSTRACT FROM AUTHOR]

The mechanical properties and biocompatibility of titanium alloy medical devices and implants produced by additive manufacturing (AM) technologies – in particular, selective laser melting (SLM), electron beam melting (EBM) and laser metal deposition (LMD) – have been investigated by several researchers demonstrating how these innovative processes are able to fulfil medical requirements for clinical applications. This work reviews the advantages given by these technologies, which include the possibility to create porous complex structures to improve osseointegration and mechanical properties (best match with the modulus of elasticity of local bone), to lower processing costs, to produce custom-made implants according to the data for the patient acquired via computed tomography and to reduce waste. [ABSTRACT FROM AUTHOR]

The aim of this review is to analyze and to summarize the state of the art of the processing of aluminum alloys, and in particular of the AlSi10Mg alloy, obtained by means of the Additive Manufacturing (AM) technique known as Selective Laser Melting (SLM). This process is gaining interest worldwide, thanks to the possibility of obtaining a freeform fabrication coupled with high mechanical properties related to a very fine microstructure. However, SLM is very complex, from a physical point of view, due to the interaction between a concentrated laser source and metallic powders, and to the extremely rapid melting and the subsequent fast solidification. The effects of the main process variables on the properties of the final parts are analyzed in this review: from the starting powder properties, such as shape and powder size distribution, to the main process parameters, such as laser power and speed, layer thickness, and scanning strategy. Furthermore, a detailed overview on the microstructure of the AlSi10Mg material, with the related tensile and fatigue properties of the final SLM parts, in some cases after different heat treatments, is presented. [ABSTRACT FROM AUTHOR]

The numerical modeling of nanoscale electron devices needs the development of accurate and efficient numerical methods, in particular, for the numerical solution of the Schrödinger problem. If FEMs allow an accurate geometric representation of the device, they lead to a discrete counterpart of Schrödinger problem in terms of a computationally heavy generalized eigenvalue problem. Exploiting the geometric structure behind the Schrödinger problem, we will construct a numerically efficient discrete counterpart of it, yielding to a standard eigenvalue problem. We will also show how the two approaches are only partially akin to each other even when lumping is applied. [ABSTRACT FROM AUTHOR]

Abstract: The time independent Schrödinger equation stems from quantum theory axioms as a partial differential equation. This work aims at providing a novel discrete geometric formulation of this equation in terms of integral variables associated with precise geometric elements of a pair of three-dimensional interlocked grids, one of them based on tetrahedra. We will deduce, in a purely geometric way, a computationally efficient discrete counterpart of the time independent Schrödinger equation in terms of a standard symmetric eigenvalue problem. Moreover boundary and interface conditions together with non homogeneity and anisotropy of the media involved are accounted for in a straightforward manner. This approach yields to a sensible computational advantage with respect to the finite element method, where a generalized eigenvalue problem has to be solved instead. Such a modeling tool can be used for analyzing a number of quantum phenomena in modern nano-structured devices, where the accounting of the real 3D geometry is a crucial issue. [ABSTRACT FROM AUTHOR]

The aim of the paper is to highlight some of the innovative methodologies, techniques and systems for nondestructive electromagnetic testing, which have been developed in the framework of the applications of methods of a diagnostics electromagnetic project partially funded by the Italian Ministry of University and Research. In particular, we will present the feasibility design of a suitable exciting-receiving coils configuration able to detect long defects by means of eddy-currents. To solve the forward eddy-currents problem, advanced analysis tools have been developed and validated. [ABSTRACT FROM AUTHOR]

We propose a discrete geometric formulation based on a magnetic scalar potential and on the circulation of an electric vector potential to solve eddy-current problems for nondestructive evaluation of steel bars with longitudinal defects. [ABSTRACT FROM AUTHOR]

Abstract: In this paper a novel approach is proposed for constructing discrete counterparts of constitutive equations over polyhedral grids which ensure both consistency and stability of the algebraic equations discretizing an electromagnetic field problem. The idea is to construct discrete constitutive equations preserving the thermodynamic relations for constitutive equations. In this way, consistency and stability of the discrete equations are ensured. At the base, a purely geometric condition between the primal and the dual grids has to be satisfied for a given primal polyhedral grid, by properly choosing the dual grid. Numerical experiments demonstrate that the proposed discrete constitutive equations lead to accurate approximations of the electromagnetic field. [Copyright &y& Elsevier]

Using a geometric formulation for eddy currents, we present a geometric approach to constructing approximations of the discrete magnetic and Ohm's constitutive matrices. In the case of Ohm's matrix, we also show how to make it symmetric. We compared the impact on the solution of the proposed Ohm's matrices, and an iterative technique to obtain a consistent right-hand-side term in the final system is described. [ABSTRACT FROM AUTHOR]

Deals with a study which presented the solution of a three-dimensional magnetostatic problem using the finite formulation of an electromagnetic field. Background on finite formulation and space discretization; Constitutive equation; Magnetostatic formulations; Numerical experiments and discussion; Conclusion.

Deals with a study which applied the finite formulation method to the solution of plane electrostatic problems on triangular and quadrilateral primal mesh elements. Information on global variables in finite formulation; Electric constitutive equation; Numerical results and discussion; Conclusion.

Focuses on a study which described an approach to plasma magnetic boundary identification in tokamak reactors. Discussion on the reconstruction of the plasma magnetic contour as a discrete identification problem; Description of magnetic measurements; Integration of the linear algebraic and differential equations; Analysis of results.

Deals with the application of the Genetic Algorithms (GA) to solve the inverse problem of the synthesis of the magnetic configuration for Magnetic Resonance Imaging. Description of the Genetic Algorithms; Details on the synthesis problem; Results of the application of the GA; Sensitivity analysis; Conclusions.

Provides information on a study which examined a method for the identification of plasma magnetic contour in machines for fusion research using magnetic measurements. Description of the identification problem; Application and results; Conclusions.

The geometric reinterpretation of the Finite Element Method (FEM) shows that Raviart–Thomas and Nédélec mass matrices map from degrees of freedoms (DoFs) attached to geometric elements of a tetrahedral grid to DoFs attached to the barycentric dual grid. The algebraic inverses of the mass matrices map DoFs attached to the barycentric dual grid back to DoFs attached to the corresponding primal tetrahedral grid, but they are of limited practical use since they are dense. In this paper we present a new geometric construction of sparse inverse mass matrices for arbitrary tetrahedral grids and possibly inhomogeneous and anisotropic materials, debunking the conventional wisdom that the barycentric dual grid prohibits a sparse representation for inverse mass matrices. In particular, we provide a unified framework for the construction of both edge and face mass matrices and their sparse inverses. Such a unifying principle relies on novel geometric reconstruction formulas, from which, according to a well-established design strategy, local mass matrices are constructed as the sum of a consistent and a stabilization part. A major difference with the approaches proposed so far is that the consistent part is defined geometrically and explicitly, that is, without the necessity of computing the inverses of local matrices. This provides a sensible speedup and an easier implementation. We use these new sparse inverse mass matrices to discretize a three-dimensional Poisson problem, providing the comparison between the results obtained by various formulations on a benchmark problem with analytical solution. • First construction of sparse inverses of edge and face Finite Elements mass matrices for arbitrary tetrahedral grids. • We provide a unified framework for the design of both edges and face mass matrices and their sparse inverses. • Our construction handles inhomogeneous and anisotropic materials. • The entries of the sparse inverse mass matrices are geometrically defined with closed form expressions. [ABSTRACT FROM AUTHOR]

The aim of this study is to define the process parameters to build components for industrial applications in A357 alloy by Laser Powder Bed Fusion (LPBF) and to evaluate the effects of post-processing heat treatments on the microstructure and mechanical properties in order to obtain the highest hardness and strength. First, process parameters values were defined to obtain full dense components with highest productivity. Then samples were built for microstructural, hardness, and tensile strength investigation in different conditions: as-built, after a stress-relieving treatment, and after a T6 precipitation hardening treatment. For this latest treatment, different time and temperatures for solution and ageing were investigated to find the best in terms of final hardness achievable. It is demonstrated that samples in A357 alloy can be successfully fabricated by LPBF with a density of 99.9% and a mean hardness value achievable of 116 HV0.1, in as-built condition. However, for production purposes, it is fundamental to reduce the residual stresses typical of LPBF. It was shown that a similar hardness value could be obtained after a stress-relieving treatment followed by a proper T6 treatment, together with a coarser but more isotropic microstructure. [ABSTRACT FROM AUTHOR]

This paper focuses on the characterization of radio propagation, and data communication in a marine environment. More specifically, we consider signal propagation when three different sub-gigahertz industrial, scientific, and medical (ISM) bands, i.e., 169 MHz, 434 MHz, and 868 MHz, are used. The main focus of the paper is to evaluate the path loss (PL), i.e., the power loss that a propagation radio wave would experience when communication occurs between a sail boat and a buoy. We describe the measurement results obtained performing three different radio power measurement campaigns, at the three different aforementioned ISM sub-gigahertz bands. We also want to correlate the radio propagation quality with the weather conditions present in the measurement areas. The obtained results show that higher distances are achieved by transmitting at lower frequencies, i.e., 169 MHz, and, on average, the propagation is directly dependent from the dew point index. [ABSTRACT FROM AUTHOR]

This contribution introduces a novel method for constructing mass matrices for general tetrahedral elements. By considering the construction of the reluctivity mass matrix as an example, a new derivation of a recipe to geometrically construct a symmetric positive semi-definite and consistent mass matrix is provided. It is shown why such a matrix can be used inside formulations where the mass matrix is right multiplied by the appropriate incidence matrix. Then, a second recipe is introduced to produce a consistent and symmetric positive definite matrix. The proposed method is based on an original algebraic technique that differs fundamentally from what is available in the literature. The proposed recipe opens also the possibility to improve the conditioning of the resulting elementary mass matrices. [ABSTRACT FROM AUTHOR]

In this paper, we apply for the first time the nonlinear-embedding technique to the design of power amplifiers (PAs) based on laterally-diffused metal-oxide-semiconductor (LDMOS) field-effect transistors. Such a design technique is based on setting the transistor load line at the intrinsic current-generator plane, according to well-known theoretical guidelines. Then, the selected operating condition can be transposed at any design frequency at the extrinsic transistor terminals, by means of a model of the device nonidealities, such as the nonlinear intrinsic capacitances and the linear parasitic effects. A harmonically-tuned high-efficiency class-F and a wideband class-AB PAs operating within the FM broadcasting band 88 ÷ 108 MHz based on a 10-W LDMOS are then designed and realized. To definitely assess the validity of the proposed approach for the LDMOS technology, we compare the measured performance on the fabricated PAs with the expected predictions. [ABSTRACT FROM AUTHOR]

This paper first introduces a simplified construction of the constitutive matrices for general polyhedral meshes. These constitutive matrices are geometrically defined by means of simple closed-form expressions involving the geometric elements of the primal and dual meshes. Then, we solve for the first time the Maxwell’s eigenvalue problem on general polyhedral meshes. In particular, we analyze the convergence of the eigenvalues when the mesh is adaptively refined by using the subgridding technique together with the constitutive inconsistency as error indicator. [ABSTRACT FROM AUTHOR]

In the recent years, reformulating the mathematical description of physical laws in an algebraic form using tools from algebraic topology gained popularity in computational physics. Physical variables are defined as fluxes or circulations on oriented geometric elements of a pair of dual interlocked cell complexes, while physical laws are expressed in a metric-free fashion with incidence matrices. The metric and the material information are encoded in the discrete counterpart of the constitutive laws of materials, also referred to as constitutive or material matrices. The stability and consistency of the method is guaranteed by precise properties (symmetry, positive definiteness, consistency) that material matrices have to fulfill. The main advantage of this approach is that material matrices, even for arbitrary star-shaped polyhedral elements, can be geometrically defined, by simple closed-form expressions, in terms of the geometric elements of the primal and dual grids. That is why this original technique may be considered as a "Discrete Geometric Approach" (DGA) to computational physics. This paper first details the set of vector basis functions associated with the edges and faces of a polyhedral primal grid or of a dual grid. Then, it extends the construction of constitutive matrices for bianisotropic media. [ABSTRACT FROM AUTHOR]

This paper presents a novel discrete model for cell membranes and electrodes contact impedances alternative to the widely used finite elements. The finite element approach can be considered as a tool for constructing finite dimensional systems of equations that approximate the specific electroquasistatic biological problem on the discrete level. Although the finite element technique is explained typically in terms of variational or weighted-residual approaches, another, less familiar way is available to reformulate geometrically the same physical problem. This approach, referred to as discrete geometric approach, allows a direct link between geometry and the degrees of freedom describing the specific biological problem. It is straightforward to implement in any finite element open software and it assures a correct modeling of voltages and currents playing a fundamental role in a biological problem. The validation has been performed, as a first step, against analytical solutions; then, we considered impedance measurements regarding erythrocytes in whole blood flowing in microchannels at high shear rates. [ABSTRACT FROM PUBLISHER]

Abstract: By exploiting the geometric structure behind Maxwell’s equations, the so called discrete geometric approach allows to translate the physical laws of electromagnetism into discrete relations, involving circulations and fluxes associated with the geometric elements of a pair of interlocked grids: the primal grid and the dual grid. To form a finite dimensional system of equations, discrete counterparts of the constitutive relations must be introduced in addition. They are referred to as constitutive matrices which must comply with precise properties (symmetry, positive definiteness, consistency) in order to guarantee the stability and consistency of the overall finite dimensional system of equations. The aim of this work is to introduce a general and efficient set of vector functions associated with the edges and faces of a polyhedral primal grids or of a dual grid obtained from the barycentric subdivision of the boundary of the primal grid; these vector functions comply with precise specifications which allow to construct stable and consistent discrete constitutive equations for the discrete geometric approach in the framework of an energetic method. [ABSTRACT FROM AUTHOR]

The aim of the paper is to present an automatic and general technique, suitable with the A-X geometric eddy-current formulation, to impose sources over massive conductors of any shape. For this purpose, the localized source approach is used, which does not require the solutions of steady-state conduction problems in the preprocessing stage. Nevertheless, this approach needs a thick cut in each active conductor, which is usually found "by hand." In this paper, an automatic and general algorithm to compute such thick cuts is introduced. Some benchmark problems are presented to demonstrate the generality and the robustness of the algorithm. [ABSTRACT FROM AUTHOR]

As a first step, we will investigate the extent of the consistency error for a hexahedral primal grid due to the use mass matrices of finite elements within the discrete geometric approach (DGA) as discrete counterparts of the constitutive relations. Such matrices are constructed by resorting to mixed elements edge and face vector functions. Then, we will propose a novel set of geometric vector basis functions for hexahedra that guarantee consistency and stability of the constitutive matrices for the DGA constructed according to the so-called energetic approach. [ABSTRACT FROM AUTHOR]

The aim of this paper is to introduce a Discrete Geometric Approach to solving 2-D non-linear magnetostatic problems. In particular, an efficient algorithm will be presented to solve magnetostatics in isotropic non-linear media by means of a Newton-Raphson scheme, in which the Jacobian is calculated analytically. Results on a reference configuration (TEAM Workshop Problem 25) are reported and discussed. [ABSTRACT FROM AUTHOR]

Abstract: In this paper a Geometric T–Ω formulation to solve eddy-current problems on a tetrahedral mesh is presented. When non-simply-connected conducting regions are considered, the formulation requires the so-called thick cuts, while, in the literature, more attention is usually given to the so-called thin cuts. While the automatic construction of thin cuts has been theoretically solved many years ago, no implementation of an algorithm to compute the thick cuts which can be used in practice exists so far. In this paper, we propose how to fill this gap by introducing an algorithm to automatically compute the thick cuts on real-sized meshes, based on a belted tree and a tree–cotree decomposition. The belted tree is constructed by means of a homology computation by exploiting efficient reduction methods. A number of benchmarks are presented to demonstrate the generality and the robustness of the algorithm. A rigorous definition of thick cuts, which necessarily has to rely on cohomology, is presented in addition. [Copyright &y& Elsevier]

Abstract: An electromagnetic problem can be discretized on a pair of interlocked primal–dual grids according to discrete geometric approaches like the Finite Integration Technique (FIT) or the Cell Method (CM). The critical aspect is however the construction of the discrete counterparts of the constitutive relations assuring stability and consistency of the overall discrete system of algebraic equations. Initially only orthogonal Cartesian grids where considered; more recently primal grids of tetrahedra and oblique prisms with triangular base can be handled. With this paper a novel set of edge and face vector functions for general polyhedral primal grids is presented, complying with precise specifications which allow to construct stable and consistent discrete constitutive equations in the framework of an energetic approach. [Copyright &y& Elsevier]

We propose a geometric reinterpretation of the Nodal Force Method in the framework of a pair of discrete formulations for magneto- statics on complementary meshes. [ABSTRACT FROM AUTHOR]

We examine the construction of reluctivity and Ohm's constitutive matrices for discrete geometric approaches using nonregular hexa-hedra as primal volumes. The effect of element deformation on the representation of uniform fields have been investigated for static fields. Then convergence and accuracy of the proposed matrices has been carried out using an eddy-current problem as working example. [ABSTRACT FROM AUTHOR]

We examine the construction of a symmetric positive definite conductance matrix for eddy-current problems, using a discrete approach. We construct a new set of piecewise uniform basis vector functions on both the primal and the dual complex. We define these vector functions for both tetrahedra and prisms. [ABSTRACT FROM AUTHOR]

The paper deals with the electromagnetic analysis of the superconducting multistrand cables used to manufacture magnets for fusion research. An analysis method is described, in which the cable is represented as an equivalent lumped network, whose parameters are automatically computed starting from the cable geometrical data. The network is then solved in transient regime. [ABSTRACT FROM AUTHOR]

• We uncover hidden geometric aspects of low-order compatible numerical schemes. • Proof of the equivalence between mimetic numerical schemes and geometric approaches. • Novel geometric definition of polynomial consistency for reconstruction operators. • Proof of the existence of other dual grids besides the barycentric dual grid. • Optimization of reconstruction operators to minimize the reconstruction error. In this work, we uncover hidden geometric aspect of low-order compatible numerical schemes. First, we rewrite standard mimetic reconstruction operators defined by Stokes theorem using geometric elements of the barycentric dual grid, providing the equivalence between mimetic numerical schemes and discrete geometric approaches. Second, we introduce a novel global property of the reconstruction operators, called P 0 -consistency, which extends the standard consistency requirement of the mimetic framework. This concept characterizes the whole class of reconstruction operators that can be used to construct a global mass matrix in such a way that a global patch test is passed. Given the geometric description of the scheme, we can set up a correspondence between entries of reconstruction operators and geometric elements of a secondary grid, which is built by duality from the primary grid used in the scheme formulation. Finally, we show the that the geometric interpretation is necessary for the correct evaluation of certain physical variables in the post-processing stage. A discussion on how the geometric viewpoint allows to optimize reconstruction operators completes the exposition. [ABSTRACT FROM AUTHOR]

Oceanus is a hardware and software platform designed and developed to provide useful information to the crew of a racing yacht. The key features of the proposed solution are its reliability, the possibility to extend and customise it, and its context-awareness, which simplifies its usage in an intelligent way. The target users of the system are both beginners who want a navigation aid, but cannot afford the expensive and often overly complicated commercial systems available on the market, and more experienced sailors who can benefit from an open and customisable instrument to study and fine-tune the setup and performance of their sailing boats. Furthermore, Oceanus strives to be as much as possible a low-cost architecture, both in software and hardware requirements. [ABSTRACT FROM AUTHOR]

We present a new mimetic finite difference method for diffusion problems that converges on grids with curved (i.e., non-planar) faces. Crucially, it gives a symmetric discrete problem that uses only one discrete unknown per curved face. The principle at the core of our construction is to abandon the standard definition of local consistency of mimetic finite difference methods. Instead, we exploit the novel and global concept of P 0 -consistency. Numerical examples confirm the consistency and the optimal convergence rate of the proposed mimetic method for cubic grids with randomly perturbed nodes as well as grids with curved boundaries. • Novel mimetic finite difference method able to deal with highly curved faces. • It achieves a convergent discrete problem which is symmetric and uses one degree of freedom for each curved face. • It can deal with geometries having curved boundaries. • It introduces a novel concept of consistency applicable to mimetic finite difference methods. [ABSTRACT FROM AUTHOR]

We propose a novel technique to estimate the total volume of unknown insulating inclusions in an electrically conducting body from voltage measurements. Unlike conventional Electrical Impedance Tomography (EIT) systems that usually exhibit low spatial resolution and accuracy, the proposed device is composed of a pair of driving electrodes which, supplied with a known sinusoidal voltage, create a current density field inside a region of interest. The electrodes are designed to generate a current density field in the region of interest that is uniform, to a good approximation, when the inclusions are not present. A set of electrodes with a polygonal geometry is used for four-wires resistance measurements. The proposed technique has been tested designing a low cost prototype, where all electrodes are on the bottom of the conducting body, showing good performances. Such a device may be used to monitor the volume of biological cells inside cell culture dishes or the volume of blood clots in micro-channels in lab-on-a-chip biosensors. [ABSTRACT FROM AUTHOR]

A fundamental extension for a recently introduced numerical scheme for the time-domain solution of Maxwell’s equations on tetrahedral meshes is introduced: the algorithm is here shown to be able to handle materials with finite electric resistivity, without losing any of its amenable properties. A theoretic stability analysis, valid for the extended algorithm, is presented for the first time, and a Courant–Friedrich–Lewy sufficient condition on the maximum time step allowed for the scheme to be stable is derived analytically. This result is completely novel for finite-difference time-domain (FDTD)-like approaches on tetrahedral grids. Finally, the accuracy of the extended algorithm is tested with respect to the well-known implicit finite-element method scheme on tetrahedral grids, to the canonical FDTD scheme on Cartesian orthogonal grids, and to a commercial code implementing FDTD with staircasing mitigation techniques. [ABSTRACT FROM AUTHOR]

A recently introduced time-domain method for the numerical solution of Maxwell’s equations on unstructured grids is reformulated in a novel way, with the aim of implementation on graphical processing units (GPUs). Numerical tests show that the GPU implementation of the resulting scheme yields correct results, while also offering an order of magnitude in speedup and still preserving all of the main properties of the original finite-difference time-domain algorithm. [ABSTRACT FROM AUTHOR]

A new biosensor for the real-time analysis of thrombus formation is reported. The fast and accurate monitoring of the individual thrombotic risk represents a challenge in cardiovascular diagnostics and in treatment of hemostatic diseases. Thrombus volume, as representative index of the related thrombotic status, is usually estimated with confocal microscope at the end of each in vitro experiment, without providing a useful behavioral information of the biological sample such as platelets adhesion and aggregation in flowing blood. Our device has been developed to work either independently or integrated with the microscopy system; thus, images of the fluorescently labeled platelets are acquired in real-time during the whole blood perfusion, while the global electrical impedance of the blood sample is simultaneously monitored between a pair of specifically designed gold microelectrodes. Fusing optical and electrical data with a novel technique, the dynamic of thrombus formation events in flowing blood can be reconstructed in real-time, allowing an accurate extrapolation of the three-dimensional shape and the spatial distribution of platelet thrombi forming and growing within artificial capillaries. This biosensor is accurate and it has been used to discriminate different hemostatic conditions and to identify weakening and detaching platelet aggregates. The results obtained appear compatible with those quantified with the traditional optical method. With advantages in terms of small size, user-friendliness and promptness of response, it is a promising device for the fast and automatic individual health monitoring at the Point of Care (POC). [ABSTRACT FROM AUTHOR]

The frequency-domain wave propagation problem is notoriously difficult to solve through iterative methods because it leads to a symmetric but indefinite linear system. For this reason, direct methods are usually employed at the expense of great memory usage. Convergence of iterative methods, however, could be obtained by regularizing the wave equation. We introduce such regularization in discrete geometric approach framework on polyhedral grids. Moreover, we extend the regularization to the impedance boundary condition. [ABSTRACT FROM AUTHOR]

We present a numerical method named mixed high order (MHO) to obtain high order of convergence for electrostatic problems solved on general polyhedral meshes. The method, based on high-order local reconstructions of differential operators from face and cell degrees of freedom, exhibits a moderate computational cost thanks to hybridization and static condensation that eliminate cell unknowns. After surveying the method, we assess its effectiveness for 3-D problems by comparing, for the first time in literature, its performances with classical conforming finite elements. Moreover, we emphasize the algebraic equivalence of MHO in the lowest order with the analog formulation obtained with the discrete geometric approach or the finite-integration technique. [ABSTRACT FROM AUTHOR]

The term waveform engineering denotes all those circuit design techniques that are based on shaping the transistor voltage and current waveforms. From a general perspective, these design techniques can be grouped in two main categories according to the adopted design tool: measurement- and model-based. In the last two decades, thanks to the proliferation of setups enabling calibrated waveform acquisition at microwave frequencies, waveform engineering has attracted continuously increasing interest in the microwave engineering community. In this article, a comprehensive analysis of the waveform-engineering based design techniques is reported, paying particular attention to the advantages and drawbacks associated to each approach. [ABSTRACT FROM AUTHOR]

Numerical simulation of anechoic chambers is an important topic nowadays, since it can provide useful data about the performance of an electromagnetic compatibility site. However, the mathematical nature of the problem, the physical dimensions of the simulated sites, and the frequency ranges pose nontrivial challenges to the numerical simulation. Computational requirements, in particular, will quickly become unmanageable if adequate techniques are not employed. In this paper, we describe a novel approach, based on equivalent elements, that enables the simulation of large chambers with modest computational resources. The method is then validated against 558 real measurement results. [ABSTRACT FROM AUTHOR]

This paper presents a general technique to apply excitations in the framework of discrete geometric numerical methods using dual grids, such as discrete geometric approach and finite integration technique. The technique overcomes some limitations of the impedance boundary condition we proposed in a previous work, especially when dealing with waveguides, where specific excitation modes must be applied. The proposed approach is based on a scattering/total field decomposition, which, if needed, allows to study scatterings due to objects. [ABSTRACT FROM AUTHOR]

An electromagnetic wave propagation problem can be formulated according to a pair of complementary formulations, called the e -formulation and the h -formulation. The two formulations are linked to each other by Maxwell’s curl equations, and, in the continuous setting, they are perfectly equivalent in describing the wave propagation phenomenon. However, this is not true in the discrete setting, where the two formulations, in general, give different solutions. In the past decades, complementary formulations were widely studied for static problems and eddy-current problems, where they were exploited as error estimators for adaptive refinement schemes. Moreover, the so-called bilateral energy bounds arise for some problems whether theoretically or at least numerically. However, to the best of our knowledge, little attention has been given to complementarity in the wave propagation problems. In this paper, we propose an adaptive refinement scheme using the constitutive error as an estimator, and then, we investigate the behavior in terms of bilateral energy bounds. [ABSTRACT FROM AUTHOR]

This paper presents how a plane wave excitation could be modeled in the context of the discrete geometric approach (DGA) by means of an impedance boundary condition, a capability that DGA was lacking. A methodology for the construction of an equivalent model of an anechoic wall is then presented as an application of the developed theory. The advantages of the resulting model are twofold: considering all the geometric details of the anechoic material requires more computational resources; in addition when an entire anechoic chamber is to be modeled, it is easier to deal with a flat wall rather than one covered with cones and ferrite tiles. The proposed equivalent model allows for a great simplification, while maintaining a good degree of accuracy. [ABSTRACT FROM PUBLISHER]

The aim of this paper is to present a novel inversion technique to measure the volume of thrombus induced under blood flow conditions in a lab-on-a-chip device. The device is composed by a microscope slide where gold electrodes are sputtered and by a polydimethylsiloxane microchannel placed on the top of the slide. A thrombogenic substance is placed on the slide in such a way that hemostasis is induced when whole blood flows in the microchannel. The novel idea behind the inversion technique is to fuse optical and electrical impedance data to obtain a quasi-real-time reconstruction of thrombus volume. This is not possible with present state-of-the-art optical imaging based on confocal microscopy, which provides the thrombus volume estimation only at the end of the thrombus formation. [ABSTRACT FROM AUTHOR]

This paper aims at comparing the pseudospectral method and discrete geometric approach for modeling quantization effects in nanoscale devices. To this purpose, we implemented a simulation tool, based on both methods, to solve a self-consistent Schrödinger–Poisson coupled problem for a 2-D electron carrier confinement according to the effective mass approximation model (suitable for FinFETs and nanowire FETs). [ABSTRACT FROM PUBLISHER]

A numerical model of the cathode of a proton-exchange membrane fuel cell (PEMFC) based on the discrete geometric approach is presented. The current density distribution inside a PEMFC cathode is simulated. The discrete formulation of a steady-state conduction problem in nonisotropic media is coupled to nonlinear boundary conditions representing the charge transfer at catalyst layers. The cathode performance is assessed under different load conditions by assuming a constant voltage operation mode. Results are in good agreement with those presented in the literature. [ABSTRACT FROM PUBLISHER]