Multi-Sensor Data Fusion Approach for Kinematic Quantities

A theoretical framework to implement multi-sensor data fusion methods for kinematic quantities is proposed. All methods defined through the framework allow the combination of signals obtained from position, velocity and acceleration sensors addressing the same target, and improvement in the observation of the kinematics of the target. Differently from several alternative methods, the considered ones need no dynamic and/or error models to operate and can be implemented with low computational burden. In fact, they gain measurements by summing filtered versions of the heterogeneous kinematic quantities. In particular, in the case of position measurement, the use of filters with finite impulse responses, all characterized by finite gain throughout the bandwidth, in place of straightforward time-integrative operators, prevents the drift that is typically produced by the offset and low-frequency noise affecting velocity and acceleration data. A simulated scenario shows that the adopted method keeps the error in a position measurement, obtained indirectly from an accelerometer affected by an offset equal to 1 ppm on the full scale, within a few ppm of the full-scale position. If the digital output of the accelerometer undergoes a second-order time integration, instead, the measurement error would theoretically rise up to 1 n(n + 1) ppm in the full scale at the n-th 2 discrete time instant. The class of methods offered by the proposed framework is therefore interesting in those applications in which the direct position measurements are characterized by poor accuracy and one has also to look at the velocity and acceleration data to improve the tracking of a target

Broadband Power Line Communication in Railway Traction Lines: A Survey

Power line communication (PLC) is a technology that exploits existing electrical transmission and distribution networks as guiding structures for electromagnetic signal propagation. This facilitates low-rate data transmission for signaling and control operations. As the demand in terms of data rate has greatly increased in the last years, the attention paid to broadband PLC (BPLC) has also greatly increased. This concept also extended to railways as broadband traction power line communication (BTPLC), aiming to offer railway operators an alternative data network in areas where other technologies are lacking. However, BTPLC implementation faces challenges due to varying operating scenarios like urban, rural, and galleries. Hence, ensuring coverage and service continuity demands the suitable characterization of the communication channel. In this regard, the scientific literature, which is an indicator of the body of knowledge related to BTPLC systems, is definitely poor if compared to that addressed to BPLC systems installed on the electrical transmission and distribution network. The relative papers dealing with BTPLC systems and focusing on the characterization of the communication channel show some theoretical approaches and, rarely, measurements guidelines and experimental results. In addition, to the best of the author's knowledge, there are no surveys that comprehensively address these aspects. To compensate for this lack of information, a survey of the state of the art concerning BTPLC systems and the measurement methods that assist their installation, assessment, and maintenance is presented. The primary goal is to provide the interested readers with a thorough understanding of the matter and identify the current research gaps, in order to drive future research towards the most significant issues

Enabling Fine Sample Rate Settings in DSOs with Time-Interleaved ADCs

The time-base used by digital storage oscilloscopes allows limited selections of the sample rate, namely constrained to a few integer submultiples of the maximum sample rate. This limitation offers the advantage of simplifying the data transfer from the analog-to-digital converter to the acquisition memory, and of assuring stability performances, expressed in terms of absolute jitter, that are independent of the chosen sample rate. On the counterpart, it prevents an optimal usage of the memory resources of the oscilloscope and compels to post processing operations in several applications. A time-base that allows selecting the sample rate with very fine frequency resolution, in particular as a rational submultiple of the maximum rate, is proposed. The proposal addresses the oscilloscopes with time-interleaved converters, that require a dedicated and multifaceted approach with respect to architectures where a single monolithic converter is in charge of signal digitization. The proposed time-base allows selecting with fine frequency resolution sample rate values up to 200 GHz and beyond, still assuring jitter performances independent of the sample rate selection

SVILUPPO DI UN SENSORE INNOVATIVO PER LA MISURA DEL CONTENUTO D’ACQUA DI TERRENI PARZIALMENTE SATURI

La nota presenta lo sviluppo e la calibrazione di un sistema innovativo per la misura del contenuto d’acqua in terreni parzialmente saturi, basato sulla spettroscopia d’impedenza. Tale tecnica, relativamente recente e poco comune in applicazioni geotecniche, permette di caratterizzare un campione di terreno a partire dalle sue proprietà elettriche, determinate applicando una tensione alternata e misurando l’intensità di corrente nel campione per valori di frequenza compresi nell’intervallo [500 Hz - 50 kHz]. L’impedenza del mezzo, dovuta sia alla resistenza opposta al passaggio di corrente sia alla reattanza, ovvero alla capacità di immagazzinare e cedere energia, dipende dal contenuto d’acqua del campione di terreno. La sperimentazione di laboratorio discussa in questa nota è volta a costruire una funzione di calibrazione del sistema di misura. I risultati preliminari mostrano un adeguato grado di ripetibilità delle misure e suggeriscono l’esistenza di una correlazione monotona tra il modulo dell’impedenza e il contenuto d’acqua gravimetrico

Digital Circuit for the Arbitrary Selection of Sample Rate in Digital Storage Oscilloscopes

Fine resolution selection of the sample rate is not available in digital storage oscilloscopes. They rely on offline processing to cope with such need. The paper presents an algorithm that, exploiting online processing with a digital filter characterized by dynamically generated coefficients and a memory management strategy, allows almost arbitrary selection of the sample rate from an incoming stream of samples. The paper also proposes a digital circuit implemented on FPGA to devise the possible performance of the method

Digital Circuit for the Arbitrary Selection of Sample Rate in Digital Storage Oscilloscopes.

Fine resolution selection of the sample rate is not available in digital storage oscilloscopes. They rely on offline processing to cope with such need. The paper presents an algorithm that, exploiting online processing with a digital filter characterized by dynamically generated coefficients and a memory management strategy, allows almost arbitrary selection of the sample rate from an incoming stream of samples. The paper also proposes a digital circuit implemented on FPGA to devise the possible performance of the method

Testing high resolution DACs: A contribution to draft standard IEEE P1658

The dynamic characterization of digital to analog converters (DACs) is still an open issue, on whose criticality both the scientific and industrial community agree. At present, only a draft standard (IEEE P1658) has been proposed, which is currently being discussed. In the last years, in fact, several works have been presented in the literature, but at the moment none of them seems to be robust enough to be easily included in the standard. Most of the proposed method, which are well structured from a theoretical point of view, and yield very encouraging simulative results, seem to suffer from some problems in the practical implementation. Such problems basically depend on the accuracy of the instrumentation they need to be implemented. The paper presents a contribution in this direction, consisting in a method for the dynamic characterization of DAC that is capable of reconstructing and analyzing DAC output with an equivalent resolution much greater than that of DAC itself even though a low resolution data acquisition system is used. The method consists of four phases each of which is carefully described and discussed in the following: (i) generation of DAC output signal, (ii) signal conditioning by means of an analog filter and a differential amplifier, (iii) acquisition and reconstruction of signal generated by the DAC, and (iv) recognition of the codes associated with the generic acquired voltage value. The method is also implemented in a suitable measurement station through which several tests have been performed on actual DACs. The experimental results show the good performance of the proposed method, which can thus be considered as a useful contribution to the draft standard IEEE P1658

A prototype for water content measurement in partially saturated soils

The paper presents the technological set-up and calibration of a system based on impedance spectroscopy for measuring water content in partially saturated soils. The technique adopted is relatively recent in geotechnical practice; it is used herein to characterize the electrical response of a soil specimen among two conducting electrodes upon application of an alternate voltage and the measurement of the current intensity resulting across the specimen, for frequency values in the range [500 Hz – 50 kHz]. The complex impedance of the soil specimen is due to both resistance, i.e. opposition to current, and reactance, i.e. tendency of the system to yield and retrieve energy, and it depends on the specimen water content. An on-purpose experimental plan has been conceived and is presented herein, aimed at building a calibration function for deriving the water content in pyroclastic soils from the impedance measurements. Preliminary results reveal an adequate level of repeatability of the measurements and suggest the existence of a monotonic correlation between the impedance modulus and the gravimetric water content

Hydrogen, boron and nitrogen atoms in diamond: a quantum mechanical vibrational analysis

International audienceThe structural, electronic and vibrational properties of two common defects in diamond, CHN and CHB, describing the case in which a carbon C1 atom is substituted by a nitrogen atom, or by a boron atom, breaking a C1–C2 bond, followed by the saturation of the dangling bond of C2 by a hydrogen atom, are investigated at the quantum mechanical level, by using a periodic supercell approach, hybrid DFT functionals and a local Gaussian-type basis set as implemented in the CRYSTAL code. The effect of concentration of the defects has been explored, by considering two supercells containing 64 and 216 atoms (S64 and S216). Formation and hydrogenation energies, geometries, Mulliken charges and the band structure of both defects are reported. The vibrational features of the defects have been investigated, by generating the IR and Raman spectra, and by analyzing graphically and through the isotopic substitution (H → D, 11B → 10B and 14N → 15N) the nature of the most relevant modes related to the defects. The computed C–H stretching mode of CHN, once corrected for anharmonicity (3408 cm−1), falls to wavenumbers very close to the experimental peak observed at 3394 cm−1, which can then be reasonably attributed to this specific defect. The present manuscript is included in a special volume in honor and memory of János Ángyán. Although he did not study in particular the kind of defects discussed in the present manuscript, the many methodological contributions he introduced in computational science have inspired many of the tools we have been using here. One of the present authors, RD, in particular, is grateful to János for the illuminating discussions they had in Paris, Nancy and Torino

Crystal14

CRYSTAL is a general-purpose program for the study of crystalline solids, and the first which has been distributed publicly. The first version was released in 1988 and then six next versions have followed: CRYSTAL92, CRYSTAL95, CRYSTAL98, CRYSTAL03, CRYSTAL06 and CRYSTAL09. The CRYSTAL program computes the electronic structure of periodic systems within Hartree Fock, density functional or various hybrid approximations (global, range-separated and double-hybrids). The Bloch functions of the periodic systems are expanded as linear combinations of atom centred Gaussian functions. Powerful screening techniques are used to exploit real space locality. Restricted (Closed Shell) and Unrestricted (Spin-polarized) calculations can be performed with all-electron and valence-only basis sets with effective core pseudo-potentials. The program can automatically handle space symmetry (230 space groups, 80 two-sided plane groups, 99 rod groups, 45 point groups are available ). Point symmetries compatible with translation symmetry are provided for molecules. Helical symmetry is now available (up to order 48). Input tools allow the generation of a slab (2D system), or a cluster (0D system), from a 3D crystalline structure, or the creation of a supercell with a defect, or nanotubes (1D system) from a single-layer slab model (2D system). The code may be used to perform consistent studies of the physical and chemical properties of molecules, polymers, nanotubes, surfaces and crystalline solids: Structural features Vibrational properties More information can be found at the following link Examples of graphical animations of vibrational modes are shown here Electronic structure Magnetic properties Dielectric properties (linear and non-linear electric susceptibilities up to forth-order) Elastic, piezoelectric and photoelastic properties A list of applications in solid state chemistry and physics gives an overview of the program capabilities