Showing papers by "Milena Martarelli published in 2022"
TL;DR: In this paper , 2D digital image correlation and thermo-elastic stress analysis are combined to map the stress and the strain performance of an airless wheel prototype, which is 3D-printed by fused deposition modeling and stereolithography in poly-lactic acid and photopolymer resin, respectively.
Abstract: Additive Manufacturing (AM) is becoming a widely employed technique also in mass production. In this field, compliances with geometry and mechanical performance standards represent a crucial constrain. Since 3D printed products exhibit a mechanical behaviour that is difficult to predict and investigate due to the complex shape and the inaccuracy in reproducing nominal sizes, optical non-contact techniques are an appropriate candidate to solve these issues. In this paper, 2D digital image correlation and thermoelastic stress analysis are combined to map the stress and the strain performance of an airless wheel prototype. The innovative airless wheel samples are 3D-printed by fused deposition modelling and stereolithography in poly-lactic acid and photopolymer resin, respectively. The static mechanical behaviour for different wheel-ground contact configurations is analysed using the aforementioned non-contact techniques. Moreover, the wheel-ground contact pressure is mapped, and a parametric finite element model is developed. The results presented in the paper demonstrate that several factors have great influence on 3D printed airless wheels: a) the type of material used for manufacturing the specimen; b) the correct transfer of the force line (i.e., the loading system); c) the geometric complexity of the lattice structure of the airless wheel. The work confirms the effectiveness of the proposed non-contact measurement procedures for characterizing complex shaped prototypes manufactured using AM.
3 citations
TL;DR: In this article , a neural network-based approach was proposed to detect whether a stain is blood or not and then obtain the spectra that the same stain would have on a reference white substrate with a mean absolute percentage error of 1.11%.
Abstract: In the recent past, hyper-spectral imaging has found widespread application in forensic science, performing both geometric characterization of biological traces and trace classification by exploiting their spectral emission. Methods proposed in the literature for blood stain analysis have been shown to be effectively limited to collaborative surfaces. This proves to be restrictive in real-case scenarios. The problem of the substrate material and color is then still an open issue for blood stain analysis. This paper presents a novel method for blood spectra correction when contaminated by the influence of the substrate, exploiting a neural network-based approach. Blood stains hyper-spectral images deposited on 12 different substrates for 12 days at regular intervals were acquired via a hyper-spectral camera. The data collected were used to train and test the developed neural network model. Starting from the spectra of a blood stain deposited in a generic substrate, the algorithm at first recognizes whether it is blood or not, then allows to obtain the spectra that the same blood stain, at the same time, would have on a reference white substrate with a mean absolute percentage error of 1.11%. Uncertainty analysis has also been performed by comparing the ground truth reflectance spectra with the predicted ones by the neural model.
3 citations
TL;DR: In this paper , a specific method for the evaluation of the water level was developed using photogrammetry that is derived from images that were recorded by UAVs, and the plane that better fits the river water surface was found by the use of the random sample consensus (RANSAC) method.
Abstract: Water-level monitoring systems are fundamental for flood warnings, disaster risk assessment and the periodical analysis of the state of reservoirs. Many advantages can be obtained by performing such investigations without the need for field measurements. In this paper, a specific method for the evaluation of the water level was developed using photogrammetry that is derived from images that were recorded by unmanned aerial vehicles (UAVs). A dense point cloud was retrieved and the plane that better fits the river water surface was found by the use of the random sample consensus (RANSAC) method. A reference point of a known altitude within the image was then exploited in order to compute the distance between it and the fitted plane, in order to monitor the altitude of the free surface of the river. This paper further aims to perform a critical analysis of the sensitivity of these photogrammetric techniques for river water level determination, starting from the effects that are highlighted by the state of the art, such as random noise that is related to the image data quality, reflections and process parameters. In this work, the influences of the plane depth and number of iterations have been investigated, showing that in correspondence to the optimal plane depth (0.5 m) the error is not affected by the number of iterations.
2 citations
TL;DR: It emerges that porosity and breathability are strongly correlated to acoustic attenuation, while bacterial filtration efficiency is not.
Abstract: This paper presents an experimental study on acoustic attenuation of different types of face masks in use by the general population during the COVID-19 pandemic. In particular, measurements are performed on ten samples of masks, of which four are medical masks, three are respirators, and three are community masks. Breathability and Bacterial Filtration Efficiency (BFE) tests, in compliance to the standard characterization process of medical masks, are also carried out. The porosity on each layer composing the masks is measured by processing their scanning electron microscopy (SEM) images. The analysis of the results aims to establish if acoustic attenuation is correlated to any of these parameters. It emerges that porosity and breathability are strongly correlated to acoustic attenuation, while bacterial filtration efficiency is not.
1 citations
05 Jul 2022
TL;DR: In this paper , an Internet of Things (IoT) infrared sensor is used to acquire continuously thermographic images and to perform a long-term monitoring in buildings to identify the main sources of inefficiencies in building's envelope and to provide real information about the thermal behaviour of the facades.
Abstract: Continuous measurement of building's thermal performance is relevant to guarantee a comfortable and healthy living environment with minimum energy consumption. The Comfort Eye, an Internet of Things (IoT) infrared sensor, allows to acquire continuously thermographic images and to perform a long-term monitoring in buildings. A mathematical model is applied to the thermographic images to identify the main sources of inefficiencies in building's envelope and to provide real information about the thermal behaviour of the facades. The innovative methodology, the Comfort Eye, can be used for relatively fast and inexpensive U-value estimation of façade walls without the use of additional measurement equipment (e.g., heat flux sensors). The Comfort Eye, scanning the entire walls facing the exterior, allows to identify potential thermal bridges and therefore it can be considered an effective tool to support buildings renovation for performance improvement. This paper presents the application of the methodology in real demonstration cases. The analysis allows to scan all the walls, measure the U-value, with discrepancies between the U-values estimated using Comfort Eye, and U-values estimated using the HFM of 0%-10%, in any point of an entire wall and to delimit thermal bridge as well as its area of greater influence.
1 citations
TL;DR: In this paper , the formulation of Lagrange Multiplier State-Space Substructuring (LM-SSS) is presented and extended to directly compute coupled displacement and velocity state-space models.
1 citations
TL;DR: In this article , the authors present an application of the Experimental Acoustic Modal Analysis (AMA) on a vintage 10 M Conn tenor saxophone, which is based on the measurement of Frequency Response Functions (FRFs) as a ratio of the acoustic pressure, measured by means of a set of microphones positioned along the saxophone body, and the volume velocity produced by an acoustic source and measured at the instrument input.
Abstract: This paper presents an application of the Experimental Acoustic Modal Analysis (AMA) on a vintage 10 M Conn tenor saxophone. This technique originates from the traditional Modal Analysis which is commonly adopted to determine the dynamic behaviour of solid structures. The methodology is based on the measurement of Frequency Response Functions (FRFs) as a ratio of the acoustic pressure, measured by means of a set of microphones positioned along the saxophone body, and the volume velocity produced by an acoustic source and measured at the instrument input. The microphones are housed on the stripped saxophone keys by means of tailored three-dimensional printed adapters. The AMA makes use of the FRFs to extract modal parameters, such as resonance frequencies, loss factors, and mode shapes. These parameters pertain to the cavity modes of the saxophone passive resonator. The analysis has been performed for three different notes (B ♭, B, and C) and for two registers of the instrument in order to show the potential of the technique. Moreover, the influence of the mouthpiece volume on the cavity modes has been shown. The information obtained by AMA can find useful application in the validation of analytical or numerical models of this kind of musical instruments.
25 May 2022
TL;DR: In this article , the authors present the application of a non-intrusive and scalable IoT sensing solution for continuous indoor environmental quality measurement in occupied buildings during the renovation process, which can be used to support the renovation project, thus helping to improve the indoor air quality.
Abstract: The importance of Indoor Environmental Quality (IEQ) - Thermal Comfort, Acoustic Comfort, and Indoor Air Quality (IAQ) - is relevant since the first function of a building is to provide a comfortable and healthy living environment. However, most of the existing buildings were built before the introduction of regulations and certification schemes that include the IEQ. For this reason, a practical framework to assess the IEQ by means of measurements has been developed. The outcome can be used to support the renovation project, thus helping to improve the IEQ. This paper presents the application of a non-intrusive and scalable IoT sensing solution for continuous IEQ measurement in occupied buildings during the renovation process. Results show the IEQ assessment in a residential building in Warmond, the Netherlands.
DOI•
03 Nov 2022
TL;DR: In this paper , an exploration of non-contact measurements (RGB video, thermal, Hyperspectral imaging) and of the analysis methodologies was carried out in order to identify the ones which are most significant for the different phases of the BSF life cycle, and which can be automated within the production lines.
Abstract: Black Soldier flies (BSFs) are very effective for the treatment of organic waste and their transformation into insect proteins and oils that can be used to produce feed and biofuels. An increasing number of startups and companies are breeding BSFs to take advantage of the numerous potential applications due to the larval diets. Although the breeding of BSF larvae requires artificially controlled conditions, methods for the characterization of the life cycle in production plan are lacking. Most of the analyses and procedures available in the literature cannot be used within the production lines of breeders. In the present study, an exploration of non-contact measurements (RGB video, thermal, Hyperspectral imaging) and of the analysis methodologies was carried out in order to identify the ones which are most significant for the different phases of the BSF life cycle, and which can be automated within the production lines. The result of the study was the definition of the criteria for the characterization, through non-contact measurements of the life cycle of the BSFs: computer vision algorithms based on image and data acquisitions were developed using 1) RGB camera for size / weight estimation and movement / vitality for the phases where the nutritional substrate is not present (pupae); 2) IR camera for the evaluation of movement / vitality for the phases where the nutrient substrate (larvae) is present and for the identification of temperature anomalies (metabolism too slow or too fast); 3) hyperspectral chamber to evaluate the growth of the larvae in relation to the chosen diet.
16 Aug 2022
TL;DR: In this article , an efficient crack detection system for Aluminum based in-service structures has been increasing becoming critical with revolutionary concepts of Industry 4.0, where EMATs can be used to detect cracks in such structures using less time and more reliability.
Abstract: Efficient Crack detection system for Aluminum based in-service structures has been increasing becoming critical with revolutionary concepts of Industry 4.0. EMATs (Electromagnetic Acoustic Transducers) can be used to detect cracks in such structures using less time and more reliability having added advantage of being non-contact. Ultrasonic signal because of Lorentz Force in these sensors pass through the structure is disturbed in the presence of any flaw. This research uses artificial small holes machined on Al Alloy plate. The response shows delay in signal reception as well as decreased signal amplitude of Rayleigh Wave in the presence of defect. The inspection system being non-contact in nature can efficiently detect defects with minimal setup time making this system an effective solution for health monitoring of structures in Aerospace, Maritime and industries having large in-service Aluminum parts.
TL;DR: In this paper , the authors proposed a new design concept for compact metamaterials exhibiting extraordinary properties in terms of wide and low frequency bandgap and structural characteristics, such as a 4'cm side length unit cell, its bandgap opening frequency of 1478'Hz, and its band-stop filter behavior in the range 1.48'-15.24'kHz.
Abstract: Engineering the architecture of materials is a new and very promising approach to obtain vibration isolation properties. The biggest challenge for lattice structures exhibiting vibration isolation properties is the trade-off between compactness and wide and low-frequency bandgaps, i.e., frequency ranges where the propagation of elastic or acoustic waves is prohibited. Here, we, both numerically and experimentally, propose and demonstrate a new design concept for compact metamaterials exhibiting extraordinary properties in terms of wide and low frequency bandgap and structural characteristics. With its 4 cm side length unit cell, its bandgap opening frequency of 1478 Hz, its band-stop filter behavior in the range 1.48–15.24 kHz, and its structural characteristics, the proposed [Formula: see text] metastructure represents great progress in the field of vibration isolation and a very promising solution for hand-held vibration probes applications that were unattainable so far through conventional materials.
26 Oct 2022
TL;DR: In this article , the authors present the design and development of a procedure that allows the detection and identification of biological traces, in particular blood stains, using hyperspectral technology, using a commercial Hyper-Spectral Imaging (HSI) system, operating in the Visible and Near Infra-Red (VNIR) range between 500 nm and 900 nm.
Abstract: This paper presents the design and development of a procedure that allows the detection and identification of biological traces, in particular blood stains, using hyperspectral technology. A commercial Hyper-Spectral Imaging (HSI) system, operating in the Visible and Near Infra-Red (VNIR) range between 500 nm and 900 nm has been used to collect the reflectance spectra of different liquid stains, including blood traces. Since the analysis of the spectral signatures of the various stains did not allow to identify the blood ones, an image processing method have been developed able to classify and accurately separate the regions where the blood was deposited from the background and the other liquids.