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This article systematically reconstructs the main genealogy of the merchant's handbooks during the early Spanish Enlightenment. It shows that Spain made a frequently forgotten but not insignificant contribution to this international print culture movement. The article analyses the main merchants' handbooks of the day as well as reviewing the legacy handed down to the eighteenth century by sixteenth and seventeenth century Spanish commercial arithmetic –especially that rooted in Castile and the Crown of Aragon–. It also studies the different formats taken by these handbooks (accounting books, treatises on metal assaying, etc.). In general terms it can be said that these books were collections of rudimentary and barely original knowledge about mathematics and economics. However, beyond the intellectual history context, they had considerable social and cultural significance and proliferated because in a Monarchy like Spain there was no clear alternative to them that was capable of fulfilling several cultural, social and professional functions, beyond the strictly educational. Este trabajo reconstruye las líneas genealógicas principales de los manuales de comercio de la Ilustración española temprana. En él se muestra que España realizó una notable contribución, frecuentemente olvidada, a este movimiento internacional de la cultura impresa. El trabajo analiza los principales manuales de comerciantes de la época y revisa el legado depositado en el siglo XVIII por los tratados de aritmética comercial de las dos centurias previas –en particular, de los concebidos en el Reino de Castilla y la Corona de Aragón–. También estudia la pluralidad de formatos que se dieron cita bajo el título de «manuales de comerciantes» (libros de cuentas, tratados de sobre el arte de metales, etc.). En términos generales, puede afirmarse que este tipo de libros reunió una colección de conocimientos en matemáticas y en economía poco original y muy rudimentaria. Sin embargo, más allá de la historia intelectual, tuvieron una significación social y cultural muy notable y proliferaron debido a que en una Monarquía como la española no existían alternativas claras a ellos capaces de cubrir diferentes funciones culturales, sociales y profesionales, más allá de las estrictamente educativas.

Recensione

The present paper aims to study a robust-entropic optimal control problem arising in the management of financial institutions. More precisely, we consider an economic agent who manages the portfolio of a financial firm. The manager has the possibility to invest part of the firm's wealth in a classical Black-Scholes type financial market, and also, as the firm is exposed to a stochastic cash flow of liabilities, to proportionally transfer part of its liabilities to a third party as a means of reducing risk. However, model uncertainty aspects are introduced as the manager does not fully trust the model she faces, hence she decides to make her decision robust. By employing robust control and dynamic programming techniques, we provide closed form solutions for the cases of the (i) logarithmic; (ii) exponential and (iii) power utility functions. Moreover, we provide a detailed study of the limiting behavior, of the associated stochastic differential game at hand, which, in a special case, leads to break down of the solution of the resulting Hamilton-Jacobi-Bellman-Isaacs equation. Finally, we present a detailed numerical study that elucidates the effect of robustness on the optimal decisions of both players.

This letter deals with second-order statistics (SOS) of continuous-phase modulated (CPM) signals. To overcome some mathematical inconsistencies emerging from the idealized assumption that the CPM signal evolves from $t=-\infty$ , we consider a one-sided model for the signal, which starts from $t=0$ , noting also that such a model emerges naturally when building practical SOS estimators. On the basis of such a model, we first evaluate the SOS of the pseudosymbols, which arise when expressing a CPM signal in terms of its Laurent representation, as well as closed-form expressions of the cyclic autocorrelation and conjugate correlation functions of one-sided CPM signals.

This letter provides tight upper bounds on the weak restricted isometry constant for compressed sensing with finite Gaussian measurement matrices. The bounds are used to develop a unified framework for the guaranteed recovery assessment of jointly sparse matrices from multiple measurement vectors. The analysis is based on the exact distribution of the extreme singular values of Gaussian matrices. Several joint sparse reconstruction algorithms are analytically compared in terms of the maximum support cardinality ensuring signal recovery, i.e., mixed norm minimization, MUSIC, and OSMP based algorithms.

not present; this is a Technical Note, only requiring an Introduction section

In this paper we use the theoretical framework of General Linear Methods (GLMs) to analyze and generalize the class of Cash's Modified Extended Backward Differentiation Formulae (MEBDF). Keeping the structure of MEBDF and their computational cost we propose a more general class of methods that can be viewed as a composition of modified linear multistep methods. These new methods are characterized by smaller error constants and possibly larger angles of A ( α ) -stability. Numerical experiments which confirm the good performance of these methods on a set of stiff problems are also reported.

We perform one and two-parameter numerical bifurcation analysis of a mechanotransduction model approximating the dynamics of mesenchymal stem cell differentiation into neurons, adipocytes, myocytes and osteoblasts. For our analysis, we use as bifurcation parameters the stiffness of the extracellular matrix and parameters linked with the positive feedback mechanisms that up-regulate the production of the YAP/TAZ transcriptional regulators (TRs) and the cell-substrate adhesion area. Our analysis reveals regimes of hysteresis and multistability, stable oscillations of the effective adhesion area, the YAP/TAZ TRs and the PPAR γ receptors associated with the adipogenic fate, as well as homoclinic bifurcations that interrupt high-amplitude oscillations abruptly. The two-parameter bifurcation analysis of the Andronov–Hopf points that give birth to the oscillating patterns predicts their existence for soft extracellular substrates ( 1 k P a ), a regime that favours the neurogenic and the adipogenic cell fate. Furthermore, in these regimes, the analysis reveals the presence of homoclinic bifurcations that result in the sudden loss of stable oscillations of the cell-substrate adhesion towards weaker adhesions and high expression levels of the gene encoding Tubulin beta-3 chain, thus favouring the phase transition from the adipogenic to the neurogenic fate.

The class of majorization---minimization algorithms is based on the principle of successively minimizing upper bounds of the objective function. Each upper bound, or surrogate function, is locally tight at the current estimate, and each minimization step decreases the value of the objective function. We present a majorization---minimization approach based on a novel convex---nonconvex upper bounding strategy for the solution of a certain class of nonconvex nonsmooth optimization problems. We propose an efficient algorithm for minimizing the (convex) surrogate function based on the alternating direction method of multipliers. A preliminary convergence analysis for the proposed approach is provided. Numerical experiments show the effectiveness of the proposed method for the solution of nonconvex nonsmooth minimization problems.

We present a short survey of the literature on indexing and retrieval of mathematical knowledge, with pointers to 72 papers and tentative taxonomies of both retrieval problems and recurring techniques.

The main limitation of digital image correlation is the remarkable noise affecting the digital image correlation–computed strain distributions. Neither manufacturers of digital image correlation systems nor the literature provide guidelines for optimal filtering of digital image correlation strain distributions. However, filtering is also associated with loss of information (smoothing of the strain gradients). We systematically explored different filtering strategies to reduce noise while minimizing the loss of information in the digital image correlation–computed strain distributions. The first filtering strategy was directly applied to the acquired images that were then fed to the digital image correlation software. Median adaptive low-pass filters and notch filters were used to eliminate noise: both strategies increased (rather than reducing) the noise in the digital image correlation–computed strain distributions. The second strategy explored was a Gaussian low-pass filtering of the strain distributions. When the optimal cutoff frequency was selected, the noise was remarkably reduced (by 70%) without excessive loss of information. At the same time, when non-optimal cutoff frequencies were used, the residual noise and/or loss of information seriously compromised the results. Finally, image combination techniques were applied both to the input images and to the strain distributions. This strategy was extremely time-consuming but not very effective (noise reduction

The aim of this paper is the analysis of simultaneous attitude control and momentum-wheel management of a spacecraft by means of magnetic actuators only. A proof of almost global asymptotic stability is derived for control laws that drive a rigid satellite toward attitude stabilization in the orbit frame when the momentum wheel is aligned with one of the principal axes of inertia. Performance of the proposed control laws is demonstrated by numerical simulations under actuator saturation. Robustness to external disturbances and model uncertainties is also evaluated.

We investigate the dynamics of a cobweb type model with nonlinear demand and supply curves in which producers make forecasts on future prices with a backward looking expectation formation mechanism: the expected price for the next period is obtained by a weighted average of the prices observed in the last two periods. The study herewith presents aims at confirming the existence of a locally stabilising effect due to the presence of memory, but an increase of memory in price expectations can be globally qualitatively destabilising, in the sense that it leads to coexistence of different attractors with their respective basins of attraction.

The homogenization of two liquids of different densities and viscosities in a pipeline equipped with a corrugated plate SMV static mixer is investigated by RANS-based CFD simulations. The blending effectiveness of the mixer is compared at different Richardson numbers and viscosity ratios for equal Reynolds numbers. The mixedness level is found to be a function of the Richardson number. As a result, depending on the pipeline scale, equal density differences require a different number of pipe diameters for the achievement of the same level of homogenization. The dynamic viscosity differences give rise to less marked effects, unless back-mixing becomes significant. Besides the coefficient of variation of the scalar concentration, which is often adopted as a measure of the intensity of segregation in turbulent static mixers, novel definitions of the scale and of the rate of change of segregation are proposed, in order to add deeper insight into the evaluation of the mixing features.

In this paper we reconsider the sub-Riemannian cortical model of image completion introduced in [G. Citti and A. Sarti, J. Math. Imaging Vision, 24 (2006), pp. 307–326]. This model combines two mechanisms, the sub-Riemannian diffusion and the concentration, giving rise to a diffusion driven motion by curvature. In this paper we give a formal proof of the existence of viscosity solutions of the sub-Riemannian motion by curvature. Furthermore we illustrate the sub-Riemannian finite difference scheme used to implement the model and we discuss some properties of the algorithm. Finally results of completion and enhancement on a number of natural images are shown and compared with other models.

Monitoring of foetal heart rate and its variability (FHRV) covers an important role in assessing health of foetus. Many analysis methods have been used to get quantitative measures of FHRV. FHRV has been studied in time and in frequency domain and interesting clinical results have been obtained. Nevertheless, a standardized definition of FHRV and a precise methodology to be used for its evaluation are lacking. We carried out a literature overview about both frequency domain analysis (FDA) and time domain analysis (TDA). Then, by using simulated FHR signals, we defined the methodology for FDA. Further, employing more than 400 real FHR signals, we analysed some of the most common indexes, Short Term Variability for TDA and power content of the spectrum bands and sympathovagal balance for FDA, and evaluated their ranges of values, which in many cases are a novelty. Finally, we verified the relationship between these indexes and two important parameters: week of gestation, indicator of foetal growth, and foetal state, classified as active or at rest. Our results indicate that, according to literature, it is necessary to standardize the procedure for FHRV evaluation and to consider week of gestation and foetal state before FHR analysis.

We evaluate the non-equilibrium spin polarization induced by an applied electric field for a tight-binding model of electron states at oxides interfaces in LAO/STO heterostructures. By a combination of analytic and numerical approaches we investigate how the spin texture of the electron eigenstates due to the interplay of spin-orbit coupling and inversion asymmetry determines the sign of the induced spin polarization as a function of the chemical potential or band filling, both in the absence and presence of local disorder. With the latter, we find that the induced spin polarization evolves from a non monotonous behavior at zero temperature to a monotonous one at higher temperature. Our results may provide a sound framework for the interpretation of recent experiments., Submitted to Proceedings of SPIE Nanoscience + Engineering 2018, Spintronics XI, 23 pages, 9 figures

Single sensors or small arrays of manually assembled neutron transmutation doped germanium (NTD-Ge) based microcalorimeters have been widely used as high energy-resolution detectors from infrared to hard X-rays. Several planar technological processes were developed in the last years aimed at the fabrication of NTD-Ge arrays, specifically designed to produce soft X-ray detectors. One of these processes consists in the fabrication of the absorbers. In order to absorb efficiently hard X-ray photons, the absorber has to be properly designed and a suitable material has to be employed. Bismuth offers interesting properties in terms of absorbing capability, of low heat capacity (needed to obtain high energy resolution) and deposition technical feasibility, moreover, it has already been used as absorber for other types of microcalorimeters. Here we present the electroplating process we adopted to grow bismuth absorbers for fabricating planar microcalorimeter arrays for hard X-rays detection. The process was specifically tuned to grow uniform Bi films with thickness up to ~ 70 μm. This work is part of a feasibility study for a stratospheric balloon borne experiment that would observe hard X-rays (20-100 keV) from solar corona.

Copyright 2018 Society of Photo-Optical Instrumentation Engineers (SPIE). One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. The X-IFU instrument of the ATHENA mission requires a set of thermal filters to reduce the photon shot noise onto its cryogenic detector and to protect it from molecular contamination. A set of five filters, operating at different nominal temperatures corresponding to the cryostat shield temperatures, is currently baselined. The knowledge of the actual filter temperature profiles is crucial to have a good estimation of the radiative load on the detector. Furthermore, a few filters may need to be warmed-up to remove contaminants and it is necessary to ensure that a threshold temperature is reached throughout the filters surface. For these reasons, it is fundamental to develop a thermal modeling of the full set of filters in a representative configuration. The baseline filter is a polyimide membrane 45 nm thick coated with 30 nm of highpurity aluminum, mechanically supported by a metallic honeycomb mesh. In this paper, we describe the implemented thermal modeling and report the results obtained in different studies: (i) a trade-off analysis on how to reach a minimum target temperature throughout the outer filter, (ii) a thermal analysis when varying the emissivity of the filter surfaces, and (iii) the effect of removing one of the filters.

Copyright 2018 Society of Photo-Optical Instrumentation Engineers (SPIE). One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. ATHENA is a Large high energy astrophysics space mission selected by ESA in the Cosmic Vision 2015-2025 Science Program. It will be equipped with two interchangeable focal plane detectors: the X-Ray Integral Field Unit (X-IFU) and the Wide Field Imager (WFI). Both detectors require x-ray transparent filters to fully exploit their sensitivity. In order to maximize the X-ray transparency, filters must be very thin, from a few tens to few hundreds of nm, on the other hand, they must be strong enough to survive the severe launch stresses. In particular, the WFI OBF, being launched in atmospheric pressure, shall also survive acoustic loads. In this paper, we present a review of the structural modeling performed to assist the ATHENA filters design, the preliminary results from vibration and acoustic tests, and we discuss future activities necessary to consolidate the filters design, before the preliminary requirement review of the ATHENA instruments, scheduled before the end of 2018.

Copyright 2018 Society of Photo-Optical Instrumentation Engineers (SPIE). One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. The X-ray Integral Field Unit (X-IFU) is one of the two instruments of the Athena astrophysics space mission approved by ESA in the Cosmic Vision 2015-2025 Science Programme. The X-IFU consists of a large array of transition edge sensor micro-calorimeters that will operate at 100 mK inside a sophisticated cryostat. A set of thin filters, highly transparent to X-rays, will be mounted on the opening windows of the cryostat thermal shields in order to attenuate the IR radiative load, to attenuate radio frequency electromagnetic interferences, and to protect the detector from contamination. Thermal filters are critical items in the proper operation of the X-IFU detector in space. They need to be strong enough to survive the launch stresses but very thin to be highly transparent to X-rays. They essentially define the detector quantum efficiency at low energies and are fundamental to make the photon shot noise a negligible contribution to the energy resolution budget. In this paper, we review the main results of modeling and characterization tests of the thermal filters performed during the phase A study to identify the suitable materials, optimize the design, and demonstrate that the chosen technology can reach the proper readiness before mission adoption.

The angular differential imaging (ADI) is used to improve contrast in high resolution astronomical imaging. An example is the direct imaging of exoplanet in camera fed by Extreme Adaptive Optics. The subtraction of the main dazzling object to observe the faint companion was improved using Principal Component Analysis (PCA). It factorizes the positive astronomical frames into positive and negative components. On the contrary, the Nonnegative Matrix Factorization (NMF) uses only positive components, mimicking the actual composition of the long exposure images., 9 pages, 7 Figures, Proceeding of the SPIE Conference Adaptive Optics Systems VI, SPIE Astronomical Telescopes + Instrumentation, Austin Convention Center Austin, Texas, United States 10 - 15 June 2018

With its array of 3840 Transition Edge Sensors (TESs) operated at 90 mK, the X-Ray Integral Field Unit (X-IFU) on board the ESA L2 mission Athena will provide spatially resolved high-resolution spectroscopy (2.5 eV FWHM up to 7 keV) over the 0.2 to 12 keV bandpass. The in-flight performance of the X-IFU will be strongly affected by the calibration of the instrument. Uncertainties in the knowledge of the overall system, from the filter transmission to the energy scale, may introduce systematic errors in the data, which could potentially compromise science objectives - notably those involving line characterisation e.g. turbulence velocity measurements - if not properly accounted for. Defining and validating calibration requirements is therefore of paramount importance. In this paper, we put forward a simulation tool based on the most up-to-date configurations of the various subsystems (e.g. filters, detector absorbers) which allows us to estimate systematic errors related to uncertainties in the instrumental response. Notably, the effect of uncertainties in the energy resolution and of the instrumental quantum efficiency on X-IFU observations is assessed, by taking as a test case the measurements of the iron K complex in the hot gas surrounding clusters of galaxies. In-flight and ground calibration of the energy resolution and the quantum efficiency is also addressed. We demonstrate that provided an accurate calibration of the instrument, such effects should be low in both cases with respect to statistics during observations., Comment: 9 pages, 4 figures, SPIE proceeding Austin 2018

Structural Health Monitoring deals mainly with structures instrumented by secondary bonded or embedded sensors. Sensors, acting passively or actively as both signal generators and receivers, are able to “listen” to any event happening in the structure (passive SHM) and to “interrogate” the structure to check its “health status” (active SHM). Structures embedded with sensors appear promising for reducing the maintenance costs and the weight of aerospace composite structures, without any reduction of the safety level required. Among many actuators/sensors technologies under investigation for active SHM systems, the combination of piezoelectric patches employed as guided wave exciters or impact sensors and optical fiber Bragg gratings (FBG) as stress wave detectors look promising for their distributed sensing capability as well as weight reduction compromise in a so-called “hybrid structural component”. FBGs have been employed only recently as stress ultrasonic wave sensors due to the reduced number of high-frequency optical interrogators available. One such device, a multi-channel fiber optic acoustic emission (FAESense™) system developed by Redondo Optics, has been employed by the authors for this purpose. Hybrid SHM systems employing FBGs as sensor arrays could provide more distributed data about the local integrity of the structure with less weight addition compared to other sensor types. Typical diameter of fiber optics could allow the embedding of sensor arrays within the composite laminate. Finally, FBGS can provide simultaneously high frequency data characterizing guided wave propagation as well as low frequency local deformations permitting an SHM approach combining global and local impact and damage detection. Intent of this paper is to summarize the first experience gained by the authors in developing SHM systems for composite plate-like hybrid structures for impact detection.

In this paper, we investigate the impact of agent personality on the complex dynamics taking place in financial markets. Leveraging recent findings, we model the artificial financial market as a complex evolving network: we consider discrete dynamics for the node state variables, which are updated at each trading session, while the edge state variables, which define a network of mutual influence, evolve continuously with time. This evolution depends on the way the agents rank their trading abilities in the network. By means of extensive numerical simulations in selected scenarios, we shed light on the role of overconfident agents in shaping the emerging network topology, thus impacting on the overall market dynamics.

Variation of trailing edge camber proved to be one of the easiest and most effective ways to modify aerofoil shape to match different aircraft operational weights, with benefits approaching 3% of fuel savings or, equivalently, range extension. This is particularly the case of commercial planes, where both initial take-off conditions (because of the unpredictable payload or the specific required mission – transfer flight, for instance) and in-flight states (for the kerosene consumption) can undergo significant differences. Several studies (like the European Research Programs SARISTU or JTI-GRA) demonstrated that the most sensible region for installing an adaptive trailing edge system for those aims is towards the wing tip. This is unfortunately a very delicate area where usually ailerons are deployed and where significant mass insertions could affect the aeroelastic response with some risks of instabilities. Furthermore, the volume available are really limited so that the installation of a fully embedded system is challenging. Moving from the experience taken in many former projects as the cited ones, the authors faced the problem of installing a fully integrated adaptive trailing edge system within the existing structural skeleton of a reference aileron and defined a design strategy to take into account the aeroelastic modifications due to the installation of such a device. Besides, the architecture preserved the original function of that control surface so that it could work as a standard aileron (classical rigid tab movement) with the augmented function of a deformable, quasi-static shape. In this sense, the proposed system exhibited a double functionality: a conventional rigid aileron with augmented shape modification capability plus a continuous, slow change of the trailing edge, occurring during flight for compensating aircraft weight variation. The research was carried out within the Italian-Canadian program MDO-505 and led to the realisation of a multifunctional aileron with two operational motor systems (one for the classical aileron working and the other for the morphing enforcement), completely integrated so that no external element was visible or affected the aerodynamics of the wing. The manufacture of this device was possible thanks to the development of a suitable design process that allowed taking into account both the structural and the aeroelastic response of the integrated architecture. This system was part of an adaptive wing section that was completed with the realisations made by the ETS of Montreal, the Quebecoise Consortium for Aerospace Research and Innovation (CRIAQ) and the IAR-NRC, supported by Bombardier and Thales Canada. The joint demonstrator was tested in the wind tunnel at the NRC facilities in Ottawa and gave confirmation of the aerodynamic, aeroelastic and structural predictions. The paper that is herein presented deals therefore with the design process and the manufacture of an adaptive trailing edge, installed within the existing aileron system of a wing segment, to undergo wind tunnel tests. The resulting device considers the definition of the kinematic structural system, the development of the integrated actuator system, their integration and the assessment of their static and dynamic structural response, and the verification of a safe aeroelastic behavior. Numerical and experimental results are presented, achieved in lab and wind tunnel environments.

The paper presents a preliminary study about a de-icing system using ultrasonic waves. The activity has been developed within the project “SMart On-Board Systems” (SMOS), which is part of Italian Aerospace National Research Program, funded by the Italian Ministry of Education and Research and coordinated by CIRA. Conceived for an aircraft wing leading edge, the system shall be extended to other aircraft components, once its efficiency and reliability will be demonstrated. Herein, the results of a preliminary numerical work on a NACA 0012 profile are presented. Guided waves are generated by a piezoelectric transducer bonded on the structure and they cause shear stresses that induce ice delamination and fracture. The investigation is focused on the selection of most suitable excitation frequency for the actuator. Finite element analyses are performed to demonstrate the effectiveness of this approach.

This work deals with the problem of noninteraction (and the dual problem of fault detection) for discrete-time linear time-invariant finite-dimensional state space systems. In particular, the standard, infinite horizon, noninteracting control requirement is replaced by a less demanding one, where noninteracting control is only sought on finite time horizons, suitably defined in connection with some structural properties of the system subblocks. A necessary and sufficient condition for solvability of the finite horizon problem thus stated is derived in terms of the almost controllability subspaces associated with the block structure of the system. The proof of the condition is constructive in the sense that it leads to a design procedure for the feedforward compensators that guarantee noninteracting control over the given time horizons. The underlying idea of the proof, i.e. the exploitation of the almost controllability subspace algorithm in the case of finite horizon noninteraction, is also compatible with a modified procedure for designing the compensators achieving infinite horizon noninteraction, which may be admissible for some specific subblocks of the system. In fact, in this latter case, it is the effective use of the controllability subspace algorithm which plays a key role. The dual counterpart in the context of fault detection introduces a structural means to identify and treat the cases where, due to the structural properties of the monitored system, some of the residuals which can be generated are only significant in a limited time. These concepts are also illustrated with a detailed numerical example.

In this work is exploited the possibility to use Electronic Speckle Pattern Interferometry (ESPI) for the characterization of different tyres with particular attention to the tyres shoulder section. Tyres characterization is of fundamental importance for vehicle dynamics modelling, since they are the main responsible of vehicles dynamical behaviour and thanks to their ability to deform, they allow to drive a vehicle generating the appropriate interaction forces at the interface with the road. Their behaviour is a consequence to their very complex structure. Two different racing tyres, one for car and other for motorcycle, have been considered. The investigation has been focused at the aim to evaluate and measure the section's components in order to get accurate information about the different layers along through the tyres shoulder section. Here we demonstrate that the different layers (rubber, nylon, steel) can be easily highlighted and identified by mean of the ESPI that, thanks to its high sensitivity, is capable to estimate the different out of plane displacement of the different layers that respond in a different way (i.e. with a different deformation) to a thermal stimulus highlighting the layers themselves. Moreover, we introduce a de-noising step in the reconstruction process: In particular we enhance the wrapped phase information by using a suitable algorithm called SPADEDH. It is important to note that the assessment about the different layers along the section is a very difficult task to obtain by visual inspection or classical microscopy. In fact, the condition of the cutted surface, or rather the strong inhomogeneity and the roughness make impossible to obtain good images especially in the shoulder area.

We show that complex representations of Clifford algebra can always be reduced either to a real or to a quaternionic algebra depending on signature of complex space thus showing that complex spinors are unavoidably either real Majorana spinors or quaternionic spinors. We use this result to support (1,3) signature for Minkowski space., Comment: 16 pages, 1 figure

The authors study the use of the virtual element method (VEM for short) of order k for general second order elliptic problems with variable coefficients in three space dimensions. Moreover, they investigate numerically also the serendipity version of the VEM and the associated computational gain in terms of degrees of freedom.

Beamsteering massive arrays have been recently proposed for indoor environment mapping in next 5G scenarios, thanks to their capability to better penetrate materials with respect to current laser or vision-based systems. From the perspective of integrating radars in small portable devices, architectures based on non-coherent processing of raw measurements represent a viable solution to overcome the limitations of current indoor radio mapping techniques, which entail a too high processing or receiver complexity. In this correspondence, we investigate the capability of low-complexity mobile radars, equipped with mm-wave massive arrays, to adapt to the environment in order to reconstruct it, by adjusting a threshold with respect to the collected data and the radiation pattern. Results, corroborated by means of a measurement campaign, show the effectiveness of the proposed approach.

In this paper, we address the problem of scheduling and routing design in a multi-hop heterogeneous radio network. The scenario consists of two types of nodes: scheduled nodes, which depend upon a centralised resource scheduling scheme, and uncoordinated nodes, which employ an asynchronous Carrier Sense Multiple Access (CSMA) based medium access control protocol. Both types of nodes co-exist on the same spectrum and may interfere each other. In fact, scheduled nodes are synchronized to the Base Station (BS) and communicate to it in a multi-hop fashion, while uncoordinated users are asynchronous with respect to the BS and the other nodes. Our work focuses on the problem of routing and scheduling for the scheduled set of nodes, with the aim of avoiding interference caused by CSMA nodes. In particular, we propose a Coexistence-Aware (CA) routing scheme, based on the definition of a novel link cost metric accounting for the number of potential uncoordinated nodes interfering. The output of the CA routing scheme serves an input to a Multi-Link Proportional Fair (MLPF) scheme, where a new scheduling metric, accounting for the number of hops needed to reach the BS, is designed. The proposed algorithm is compared with a benchmark solution, where routing is based on the level of received power over the links and where the MLPF algorithm presented in the literature is applied. Results show the improvement achieved with the proposed solution.

Event: SPIE Astronomical Telescopes + Instrumentation, 2018, Austin, Texas, United States., The X-IFU will be provided by an international consortium led by France, The Netherlands and Italy, with further ESA member state contributions from Belgium, Finland, Germany, Poland, Spain, Switzerland and two international partners from the United States and Japan: et al., The X-ray Integral Field Unit (X-IFU) is the high resolution X-ray spectrometer of the ESA Athena X-ray observatory. Over a field of view of 5’ equivalent diameter, it will deliver X-ray spectra from 0.2 to 12 keV with a spectral resolution of 2.5 eV up to 7 keV on ∼ 5” pixels. The X-IFU is based on a large format array of super-conducting molybdenum-gold Transition Edge Sensors cooled at ∼ 90 mK, each coupled with an absorber made of gold and bismuth with a pitch of 249 μm. A cryogenic anti-coincidence detector located underneath the prime TES array enables the non X-ray background to be reduced. A bath temperature of ∼ 50 mK is obtained by a series of mechanical coolers combining 15K Pulse Tubes, 4K and 2K Joule-Thomson coolers which pre-cool a sub Kelvin cooler made of a 3He sorption cooler coupled with an Adiabatic Demagnetization Refrigerator. Frequency domain multiplexing enables to read out 40 pixels in one single channel. A photon interacting with an absorber leads to a current pulse, amplified by the readout electronics and whose shape is reconstructed on board to recover its energy with high accuracy. The defocusing capability offered by the Athena movable mirror assembly enables the X-IFU to observe the brightest X-ray sources of the sky (up to Crab-like intensities) by spreading the telescope point spread function over hundreds of pixels. Thus the X-IFU delivers low pile-up, high throughput (< 50%), and typically 10 eV spectral resolution at 1 Crab intensities, i.e. a factor of 10 or more better than Silicon based X-ray detectors. In this paper, the current X-IFU baseline is presented, together with an assessment of its anticipated performance in terms of spectral resolution, background, and count rate capability. The X-IFU baseline configuration will be subject to a preliminary requirement review that is scheduled at the end of 2018., We acknowledge support from the Athena Science Study Team, the Athena Working Group Chairs, the Athena Topical Panel Chairs and the Topical Panel members in strengthening the X-IFU top level performance requirements. Particular thanks go to: E. Rasia, V. Biffi, S. Borgani and K. Dolag for providing cosmological hydrodynamic simulations of a cluster used to produce simulation of X-IFU observation presented in Fig. 2; P.T. O'Brien for assistance with Sect. 2.2.1, A.C. Fabian and C. Pinto for providing inputs for Figure 1. We also thank the ESA project team, and in particular Mark Ayre and Ivo Ferreira, for their work on the assessment of the ToO efficiency requirement. The Italian contribution to X-IFU is supported through the ASI contractn. 2015-046-R.0. XB, MTC and BC acknowledge nancial support by MINECO through grant ESP2014-53672-C3-1-P. A.R., P.O, and A.J. were supported by Polish NSC grants: 2015/17/B/ST9/03422 and 2015/18/M/ST9/00541. GR, ER, YN, and PJ acknowledges support by FNRS and Prodex (Belspo). This work was supported by the French Space Agency (CNES).

This paper introduces a model-based control strategy for a wave energy converter (WEC) based on dielectric elastomer generators (DEGs), i.e. a device that can convert the energy of ocean waves into electricity by employing deformable elastomeric transducers with variable capacitance. The analysed system combines the concept of oscillating water column WEC with an inflated circular diaphragm DEG (ICD-DEG). The device features strongly nonlinear dynamics due to the ICD-DEG electro-hyperelastic response and the compressibility of the air volume comprised between the water column and the ICD-DEG, while the hydrodynamic loads can be approximated as linear. The optimal control solution that maximises the power extraction of the device is numerically investigated in the case of monochromatic waves over the typical frequency and amplitude ranges of sea waves. The more realistic case of panchromatic waves is also analysed through the implementation, in simulation environment, of a real-time controller. This regulator is based on a simple sub-optimal control logic that is deduced from the monochromatic case. The performance of the proposed control strategy is illustrated in comparison with unoptimised algorithms.

Dielectric fluid transducers (DFTs) are electrostatic devices which alternate solid compliant dielectric layers/electrodes with dielectric fluid layers, and they enable the conversion of electrical energy into mechanical work (and vice versa) through capacitance variations associated with a modification of their shape. Compared to other capacitive transducers, e.g., dielectric elastomer transducers, DFTs feature better tolerance to electrical break-down and larger ratio between converted energy and stored elastic energy. To date, practical DFT topologies have been proposed and demonstrated for both actuation and generation purposes, showing promising performance in terms of converted energy density and efficiency. This paper presents an overview on operating principles/layouts, introduces a simplified analytical modelling approach and proposes some figure of merit to evaluate the performances of this new class of transducers.

The knowledge of spatial distributions of physical quantities, such as radio-frequency (RF) interference, pollution, geomagnetic field magnitude, temperature, humidity, audio, and light intensity, will foster the development of new context-aware applications. For example, knowing the distribution of RF interference might significantly improve cognitive radio systems [1], [2]. Similarly, knowing the spatial variations of the geomagnetic field could support autonomous navigation of robots (including drones) in factories and/or hazardous scenarios [3]. Other examples are related to the estimation of temperature gradients, detection of sources of RF signals, or percentages of certain chemical components. As a result, people could get personalized health-related information based on their exposure to sources of risks (e.g., chemical or pollution). We refer to these spatial distributions of physical quantities as spatial fields. All of the aforementioned examples have in common that learning the spatial fields requires a large number of sensors (agents) surveying the area [4], [5].

Copyright 2018 Society of Photo-Optical Instrumentation Engineers (SPIE). One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. The Wide Field Imager (WFI) is one of the two instruments of the ATHENA astrophysics space mission approved by ESA as the second large mission in the Cosmic Vision 2015-2025 Science Programme. The WFI, based on a large array of depleted field effect transistors (DEPFET), will provide imaging in the 0.2-15 keV band over a 40'x40' field of view, simultaneously with spectrally and time resolved photon counting. The WFI detector is also sensitive to UV/Vis photons, with an electron-hole pair production efficiency in the UV/VIS larger than that for X-ray photons. Optically generated photo-electrons may degrade the spectral resolution as well as change the energy scale by introducing a signal offset. For this reason, the use of X-ray transparent optical blocking filters (OBFs) are needed to allow the observation of X-ray sources that present a UV/Vis bright counterpart. The OBFs design is challenging since one of the two required filters is quite large ( 160 mm × 160 mm), very thin (< 200 nm), and shall survive the mechanical load during the launch. In this paper, we review the main results of modeling and characterization tests of OBF partially representative samples, performed during the phase A study, to identify the suitable materials, optimize the design, prove that the filters can be launched in atmospheric pressure, and thus demonstrate that the chosen technology can reach the proper technical readiness before mission adoption.

Maintenance tasks and safety aspects represent a strategic role in the managing of the modern aircraft fleets. The demand for reliable techniques for structural health monitoring represent so a key aspect looking forward to new generation aircraft. In particular, the use of more technologically complex materials and manufacturing methods requires anyway more efficient as well as rapid application processes to improve the design strength and service life. Actually, it is necessary to rely on survey instruments, which allow for safeguarding the structural integrity of the aircraft, especially after the wide use of composite structures highly susceptible to non-detected damages as delamination of the ply. In this paper, the authors have investigated the feasibility to implement a neural network-based algorithm to predict the impact event at low frequency, typically due to the bird collision. Relying upon a numerical model, representative of a composite flat panel, the approach has been also experimentally validated. The purpose of the work is therefore the presentation of an innovative application within the Non Destructive Testing field based upon vibration measurements. The aim of the research has been the development of a Non Destructive Test which meets most of the mandatory requirements for effective health monitoring systems while, at the same time, reducing as much as possible the complexity of the data analysis algorithm and the experimental acquisition instrumentation. Future activities will be addressed to test such technique on a more complex aeronautical system.

Copyright 2018 Society of Photo-Optical Instrumentation Engineers (SPIE). One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. The X-ray Integral Field Unit (X-IFU) is one of the two detectors of the ATHENA astrophysics space mission approved by ESA in the Cosmic Vision 2015-2025 Science Programme. The X-IFU consists of a large array of transition edge sensors (TES) micro-calorimeters covering a field of view of 5' diameter, sensitive in the energy range 0.2-12 keV, and providing a spectral resolution of 2.5 eV at 7 keV. Both the TES and superconducting quantum interference devices (SQUID) based read-out electronics are very sensitive to electromagnetic interferences (EMI), and a proper shielding of the focal plane assembly (FPA) is required to prevent a deterioration of the energy resolution. A set of thin filters, highly transparent to X-rays, will be mounted on the FPA and on the cryostat thermal shields in order to attenuate the infrared radiative load, and to protect the detector from contamination. Some of these filters are also aimed at providing proper radio frequency (RF) shielding in the frequency range of the satellite telemetry downlink antenna. In addition, filters should also be effective in shielding any RF interference generated by other on-board electronics. In this paper, we present results from RF measurements performed on thin plastic foils coated with an aluminum layer, with and without metal meshes, and identify the filter characteristics matching the RF shielding requirements.

During the last years, the research interest in assessing noise and vibration optimization has been addressed on different control typologies, based both on active and passive architectures. Within the paper, some preliminary activities aimed at the realization of a structurally simple, cheap and easily replaceable active control systems is discussed. Under these premises, the paper deals with the assessment of an Enhanced Synchronized Shunted Switch Architecture (SSSA) control architecture, based upon the use of piezoelectric devices, specifically optimized for a cantilver beam structure. Main activities regarded the control system set up and optimization, both under the electronic than the piezo location points of view, and control results under deterministic and stochastic forcing actions. Experimental results have been compared with the numerical one as well as a comparison between the SSSA approach and other active control architectures has been also presented and discussed. Results have shown a good performances of the proposed approach that present also a relative easy implementation if compared with already assessed control technologies.

The reduction of the environmental impact imposed by Kyoto Protocol and the growth of competitiveness imposed by the shipping market have urged shipping companies to pay increasing attention to ship energy efficiency improvement and CO2 emission reduction. According to the Ship Energy Efficiency Management Plan (SEEMP) recommended by the International Maritime Organization (IMO), the main scope of this article is in fact to overcome the deterministic limits of the monitoring systems installed in modern ships and support technical management in decision making based on large navigation databases. The proposed statistical approach is founded on a multiple linear regression and allows for both pointwise and interval predictions of the fuel consumption. At the end of each voyage, the model can be used to alert management for a possible change in ship performance in all those situations where the actual fuel consumption lies outside the prediction interval. Moreover, the model can also be utilized to quantify the contribution to the fuel consumption due to the hull and propeller fouling, which is particularly profitable for shipping companies and operators to claim for carbon credits after a specific improvement operation.