27 research outputs found
A Rapid Classification of Cross-Contaminations in Aviation Oil Using Impedance-Driven Supervised Machine Learning
No full textReal-time monitoring of lube oil plays a crucial role in ensuring optimal machinery performance, preventing failures, and facilitating timely maintenance strategies. The approach proposed in this work, based on impedance spectroscopy and supervised machine learning (ML), addresses this need by a novel solution to a multiclass classification problem of cross-contaminations in aviation lubricant. Impedance measurements were performed at room temperature by immersing a microfabricated sensor in 16 aged oil samples containing increasing concentrations of water and aviation fuel. Two datasets were constructed: the first based on impedance components spectra and the second based on dissipation factor spectra. A data pre-processing and augmentation method was proposed for generating synthetic examples from the measured data. Both datasets were independently used to train three supervised classifiers, whose performance was evaluated based on three different approaches of dataset split ratio and k-fold cross-validation. The 1-nearest neighbors (NN) classifier proved to be the most effective in reducing false positives (FPs), false negatives (FNs), and computational running time. The best results were obtained by employing a split ratio of 60:40 and threefold cross-validation scheme on the impedance components-based dataset, yielding an accuracy of 99.8%
Synthesis and Piezoelectric Characterization of UV-Curable Nanocellulose/ZnO/AlN Polymeric Flexible Films for Green Energy Generation Applications
No full textIn this work, the fabrication of composites consisting of piezoelectric ZnO ceramic nanostructures and nanocellulose fillers in a UV-cured acrylic matrix has been exploited for the design of new functional coatings for green energy generation. The piezoelectric behavior was investigated at different accelerations applied to cantilever beams. The piezoelectric signal generated by the different ZnO nanostructures was improved by aluminum nitride film integration on the beam and proof mass insertion at the tip
A 18-ms Measurement-Time MLS-Based System for Moisture Assessment in Lubricant Oil
No full textIn this article, a system and a measurement approach to reduce the measurement time in the assessment of moisture contamination in lubricant oils is presented. The system's sensing principle leverages the permittivity change of a miniaturized interdigital capacitor (IDC) while immersed in oil. The time-domain impedance concept, that is, the impulse response (IR), is exploited by using maximum length sequences (MLSs) as efficient broadband signals for the sensor's excitation in a wide range of frequencies. Different from conventional impedance spectroscopy (IS), MLS-based measurements are performed with simpler hardware, higher computational efficiency, lower power consumption, and lower measurement time. As a novelty with respect to the state-of-the-art, this article introduces a linear model to relate a single measured quantity from the IR to water concentration in oil. This permits to reduce the digital processing operations, leading to low measurement time and, thus, to low energy-per-measurement parameters with respect to other works which rely on laboratory instrumentation. The validity of the linear model, for the detection of small concentrations of water in lubricant oil, has been verified through experimental measurements. Water-oil samples have been prepared with 0.2 vol%, 0.5 vol%, 1 vol%, 2 vol%, and 3 vol% water concentrations at room temperature, obtaining an estimated limit of detection (LOD) of 6.3 ppm. A low measurement time of 18 ms has been achieved which advances the state-of-the-art
Micromachined Vaporizing Liquid Microthruster With Pulsed Dual Heating: Sensors & Efficiency
No full textStructural, morphological and chemical properties of Cu/TiN versus Cu thin layers for HEMT backside metallization
No full textA Combined Measurement System for Fast Classification of Water Contamination in Lubricant Oil
No full textIn this paper, a measurement system aimed to the fast classification of water contamination in oil samples will be presented. The transduction principle is based on the permittivity change of an interdigital capacitor which changes its capacitance value while immersed in oil samples with different water concentrations. Differently from other works, the presented system proposes a circuit and a measurement approach. It combines the broadband excitation property of MLS-based impulse response (IR) measurements with the support vector machine (SVM) machine-learning (ML) model. This approach allows
to speed up the measurements, thus reducing the energy-per measurement parameter in order to make the system suitable for battery-powered portable devices. The theoretical foundations, the circuit-level description of the analog front-end, and the used ML model will be presented in detail. The classification capability of the system will be proved by evaluating 40 IRs from 6 prepared oil samples at water concentrations of 0 vol%, 0.2 vol%, 0.5 vol%, 1 vol%, 2 vol%, and 3 vol%. The proposed system is able to measure a 1023-point IR in 700 ms, which is better than the state-of-the-art. Finally, an overall classification accuracy of 90% is obtained after the SVM training process with a 10 fold cross-validation
Preparation and characterization of UV-cured composite films containing ZnO nanostructures: effect of filler geometric features on piezoelectric response
No full textZnO nanofillers, with different morphologies, were synthesized by a facile aqueous sol-gel approach and embedded, at low concentration (i.e. 4 wt.%), into a UV-curable acrylic system. SEM observations showed a homogeneous distribution of the fillers within the cured network. The different morphologies of ZnO nanostructures were found to significantly affect the thermo-oxidative stability and the glass transition temperature of the obtained UV-cured films. Microcantilevers, made of the prepared films with sputtered aluminum contact, were fabricated by using standard microfabrication technology and their piezoelectric response was investigated both at the resonance frequency and at lower frequency values. Despite the low ZnO content, all the UV-cured nanocomposite films showed interesting piezoelectric properties: in particular, the devices containing flower-like nano-structures exhibited the highest root mean square voltage both at 150 Hz and at the resonance frequency (about 0.176±0.001 and 0.914±0.001 mV, respectively). In addition, these devices also showed maximum peak-peak voltage values at both the selected frequencies
Heat Transfer Assessment in a Vaporizing Liquid Microthruster undergoing Dual Heating Control
No full textIn the present work, a new VLM design is proposed to ensure a safer and more efficient heat transfer
of high-energy from solid walls to fluid. In this regard, an innovative approach is introduced to separate the boiling and overheating processes by implementing two distinct heating chambers. A quasi-1D
steady-state numerical model has been developed to solve the flow into the VLM at constant heat flux
boundary conditions, allowing for a preliminary performance assessment of dual heating control. Thus,
in-depth insights derived from both the experimental assessment and numerical analysis are comprehensively discussed and presented, highlighting their relevance and significance in understanding the heat
transfer process.the most relevant insights are discussed together with the numerical analysis
Ricordi di religiosi Passionisti
No full textNella Sala da pranzo in primo piano Suora Passionista Vincenzina Corvinelli, P. Tarcisio Turrisi, P. Ignazio Del Vecchio, P. Ireneo Materdomini , P. Giovanni Continisio; in secondo piano P. Raffaele Riccitelli, Fra’ Vincenzo Putignano, due signore, due Suore Passioniste: Maria Rosa Lombardo, Superiora e Assunta Balducci.NOTE: data precisa sconosciut
Active Sensors/Actuators-Based Flow and Noise Control for Aerospace Applications
No full textThe present work introduces a method for flow and noise control using plasma actuation. The Single Dielectric Barrier Discharge Plasma Actuator (SDBDPA) device is object of study. A discussion of potential applications in flow and noise control in aerospace field is initially done. Then experimental results on separation control applications are presented. The investigated, SDBDPA was manufactured by means of photolithographic technique. Particular attention was paid in materials selection because of possible degradation in plasma environment. The device separation control authority was investigated locating it on a curved plate with a shape designed to reproduce the suction surface of a low pressure turbine (LPT) rotor blade. The changes in the device performances with aging were quantified by monitoring in time the actuator power consumption. Scanning electron microscope (SEM) images on the new and used device were also used to complement the investigation
