Archivio Istituzionale della Ricerca - Università degli Studi di Pavia
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Electro-Mechanical Frequency Response of a Piezo-MEMS Speaker Measured by Laser Diode Feedback Interferometry
No full textPiezo-MEMS speakers based on the inverse piezoelectric effect are becoming increasingly attractive thanks to their low power consumption and are good candidates for miniaturized devices for in-ear audio systems. In this work, we report the use of laser diode feedback interferometry, or self-mixing interferometry, for analyzing the out-of-plane vibration performance of a commercial piezo-MEMS speaker. The photodetected signal provided by the monitor photodiode contained in the laser package was acquired in the frequency domain in the band 0 – 25.6 kHz to analyze the electro-mechanical spectral response of the piezo-MEMS, under conditions of small displacements, by driving it with electrical white noise. Two resonances were detected, one at ≈ 2.8 kHz, with low quality factor Q and consistent with device specifications, and one at ≈ 21.4 kHz, slightly above the audible frequency range for humans, with higher Q. To obtain the displacement sensitivity, the MEMS was actuated with sinusoidal signals at different frequencies and amplitudes. The photodetected signal, acquired in the time domain, was used to recover the diaphragm displacement amplitude and phase delay. In particular, we were able to highlight the non-linear spectral response of the high-Q resonance, under conditions of high stress and large displacement, and to reconstruct the hysteretic cycle for upward and downward frequency sweeps. The electro-mechanical frequency response detected with our extremely compact and low-cost interferometric configuration provides a complete overview of the vibration performance of the speaker, useful as a significantly easier preliminary investigation before the electro-acoustic characterization. [2024-0204
A SAR-assisted Incremental ΣΔ ADC with Accumulation based S/H Circuit for Shunt Current Measurements
No full textAbstract: This thesis presents a SAR-assisted first-order incremental ΣΔ analog-to-digital converter (ADC) that features an accumulation-based sample- and-hold (S/H) circuit. The purpose of this circuit is to effectively mitigate the (kT/C) noise contribution, which can be a potential bottleneck for the resolution performance of the converter. The system has been designed for shunt current measurements in brushless DC motor (BLDCM) speed control. Accurate sensing and digitization of current information play a crucial role in effectively monitoring and regulating the behavior of the motors. The sensor digitizes the voltage drop across an external shunt resistor when current flows through it. Specifically, the sensor consists of an accumulation-based S/H circuit to handle a high common-mode voltage range of 0–60 V, followed by a successive approximation register (SAR)-assisted incremental delta-sigma ADC. The sensor was fabricated using a standard 0.13 μm CMOS process. It occupies an area of 0.4 mm2 and draws 6.7 mA from a 1.5 V supply. Over the temperature range of -20°C to 100°C and a ±4 A current range, it achieves a gain error of ±0.8%. With this shunt configuration, it achieves a dynamic range of 78 dB in a
2.75 μs conversion time.Abstract: This thesis presents a SAR-assisted first-order incremental ΣΔ analog-to-digital converter (ADC) that features an accumulation-based sample- and-hold (S/H) circuit. The purpose of this circuit is to effectively mitigate the (kT/C) noise contribution, which can be a potential bottleneck for the resolution performance of the converter. The system has been designed for shunt current measurements in brushless DC motor (BLDCM) speed control. Accurate sensing and digitization of current information play a crucial role in effectively monitoring and regulating the behavior of the motors. The sensor digitizes the voltage drop across an external shunt resistor when current flows through it. Specifically, the sensor consists of an accumulation-based S/H circuit to handle a high common-mode voltage range of 0–60 V, followed by a successive approximation register (SAR)-assisted incremental delta-sigma ADC. The sensor was fabricated using a standard 0.13 μm CMOS process. It occupies an area of 0.4 mm2 and draws 6.7 mA from a 1.5 V supply. Over the temperature range of -20°C to 100°C and a ±4 A current range, it achieves a gain error of ±0.8%. With this shunt configuration, it achieves a dynamic range of 78 dB in a
2.75 μs conversion time
A Rare Case of Exophiala Dermatitidis Isolation in a Patient with Non-Cystic Fibrosis Bronchiectasis: Colonization or True Infection?
No full textBackground: Exophiala dermatitidis is a dematiaceous, thermotolerant, yeast-like fungus increasingly recognized as an opportunistic pathogen in chronic airway diseases. While commonly associated with cystic fibrosis, its clinical significance in non-cystic fibrosis bronchiectasis (NCFB) remains unclear. Case Presentation: We report the case of a 66-year-old immunocompetent woman with a history of breast cancer in remission and NCFB, who presented with chronic cough and dyspnea. Chest CT revealed bilateral bronchiectasis with new pseudonodular opacities. Bronchoalveolar lavage cultures identified E. dermatitidis, along with Pseudomonas aeruginosa and methicillin-sensitive Staphylococcus aureus. Given clinical stability and the absence of systemic signs, initial therapy included oral voriconazole, levofloxacin, doxycycline, and inhaled amikacin. Despite persistent fungal isolation on repeat bronchoscopy, the patient remained asymptomatic with stable radiologic and functional findings. Antifungal therapy was discontinued, and the patient continued under close monitoring. The patient exhibited clinical and radiological stability despite repeated fungal isolation, reinforcing the hypothesis of persistent colonization rather than active infection. Discussion: This case underscores the diagnostic challenges in distinguishing fungal colonization from true infection in structurally abnormal lungs. In NCFB, disrupted mucociliary clearance and microbial dysbiosis may facilitate fungal persistence, even in the absence of overt immunosuppression. The detection of E. dermatitidis should prompt a comprehensive evaluation, integrating clinical, radiologic, and microbiologic data to guide management. Voriconazole is currently the antifungal agent of choice, though therapeutic thresholds and duration remain undefined. Conclusions: This report highlights the potential role of E. dermatitidis as an under-recognized respiratory pathogen in NCFB and the importance of a multidisciplinary, individualized approach to diagnosis and treatment. This case underscores the need for further research on fungal colonization in NCFB and the development of evidence-based treatment guidelines. Further studies are needed to clarify the pathogenic significance, optimal management, and long-term outcomes of E. dermatitidis in non-CF chronic lung diseases
A kinetic approach to consensus-based segmentation of biomedical images
No full textIn this work, we apply a kinetic version of a bounded confidence consensus model to biomedical segmentation problems. In the presented approach, time-dependent information on the microscopic state of each particle/pixel includes its space position and a feature representing a static characteristic of the system, i.e. the gray level of each pixel. From the introduced microscopic model we derive a kinetic formulation of the model. The large time behavior of the system is then computed with the aid of a surrogate Fokker-Planck approach that can be obtained in the quasi-invariant scaling. We exploit the computational efficiency of direct simulation Monte Carlo methods for the obtained Boltzmann-type description of the problem for parameter identification tasks. Based on a suitable loss function measuring the distance between the ground truth segmentation mask and the evaluated mask, we minimize the introduced segmentation metric for a relevant set of 2D gray-scale images. Applications to biomedical segmentation concentrate on different imaging research contexts
Rethinking food policy framework to tackle childhood obesity in the Italian context.
No full textPediatric obesity has been described by the World Health Organization as 1 of the most serious public health challenges of the 21st century. Projections of increasing burdens of pediatric obesity and its related diseases on society highlight the need for urgent and substantial action. Many scientific and public debates about the prevention of childhood obesity are centered around simple dichotomies presenting a single-level solution. In contrast, efficient prevention programs should overcome these overly simplistic dichotomies and proceed in the early years of life within the family environment and the whole society, throughout one's lifetime. Food policies have the potential to counteract pediatric obesity by creating healthy food environments. However, the current food policies approach lacks monitoring indicators to assess short- and long-term impact, and is not well integrated into regional, national, and cross-cutting initiatives. Therefore, redesigning and rethinking food policy strategies and goals is an important opportunity to address childhood obesity, safeguard the planet, and contribute to economic and social prosperity
Responsabilità dell'Attestatore
No full textIl contributo è dedicato alla Responsabilità dell'attestatore ed esamina i doveri e gli obblighi del professionista incaricato di attestare la fattibilità del piano di risanamento o il miglior soddisfacimento dei creditori.
L'attestatore è tenuto a svolgere un’analisi approfondita e indipendente, garantendo trasparenza, diligenza e imparzialità nel valutare le proiezioni economico-finanziarie e la coerenza delle soluzioni proposte.
La sua responsabilità si estende anche alle conseguenze di eventuali attestazioni errate o negligenti, che possono comportare profili di responsabilità sia civile che penale, in caso di danni arrecati a creditori o terzi
Il contrasto alla violenza domestica: appunti per una politica criminale evidence-based
No full textL’art. 11 della Convenzione di Istanbul impone agli Stati di adottare scelte di politica criminale “evidence-based”, verificando alla luce delle scienze empiriche l’efficacia delle misure messe in campo per contrastare le forme di violenza oggetto della Convenzione. Il contributo muove da tale presupposto per interrogarsi sull’adeguatezza delle norme di contrasto alla violenza domestica: a questo scopo, premesse alcune considerazioni relative alla diffusione del fenomeno nel nostro Paese, l’Autrice svolge una panoramica dei principali studi che sono stati realizzati per individuare le caratteristiche della violenza domestica e indagarne le cause. I risultati del lavoro costituiscono la base per alcune riflessioni finali volte a orientare le future scelte di politica criminale
Recycle of Critical Raw Materials from WEEE as Catalysts in Chemical Transformations
No full textLe materie prime critiche (CRM) sono essenziali per lo sviluppo tecnologico ma soffrono di una fornitura scarsa e di alti costi. Le proposte di economia circolare, come il riciclo, l’upcycling e il riutilizzo di rifiuti elettronici, sono importanti per un progresso sostenibile. Gli stessi metalli di transizione e terre rare hanno un ruolo ben noto nei processi catalitici in sintesi organica.
Recenti sviluppi nel recupero di magneti Sm-Co hanno aperto a nuove opportunità per l’upcycling per processi chimici. Pertanto, questa tesi descrive l’uso di una miscela metallica Sm/Co e degli scarti recuperati Sm(III)-Co(II) come catalizzatori. Una miscela simulata di metalli ha mediato con successo riduzioni da SmI2 e reazioni MPV asimmetriche, mentre la miscela di cloruri recuperata è stata impiegata come catalizzatore di Sm(III) o Co(II), oppure in elettrosintesi. Intermedi di prodotti naturali, API e fragranze aromatiche sono state preparate con questo materiale riciclato.Critical raw materials (CRMs) are essential for technological development but suffer from limited supply and high costs. Circular economy initiatives, such as recycling, upcycling, and reusing electronic waste, are important for sustainable progress. The same transition metals and rare earth elements have a commonly known role in catalytic processes for organic synthesis.
Recent advancements in recovering Sm-Co magnets opened new opportunities for upcycling for chemical processes. Therefore, this thesis describes the use of a Sm/Co metal mixture and of the Sm(III)-Co(II) recovered waste as catalysts. A simulated waste mixture of metals has successfully mediated SmI2 reductions and asymmetric MPV reactions, while the recovered chloride mixture was employed as a Sm(III) or Co(II) catalyst, or in electrosynthesis. Natural product intermediates, APIs and aromatic fragrances have been prepared with this upcycled material