1,277 research outputs found

    Synthesis and Characterization of Inorganic Perovskites for Nanophotonics

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    In questa tesi di dottorato vengono affrontati diversi aspetti riguardanti la fisica delle perovskiti inorganiche alogenate. In particolare mi focalizzerò su: • Proprietà intrinseche del materiale come il disordine strutturale e dinamico, approfondito da uno studio della fotoluminescenza in un grande insieme di campioni CsPbBr3 che si differenziano per morfologia e protocollo di sintesi. Siccome il disordine pregiudica la forma spettrale della linea della fotoluminescenza e gioca un ruolo importante nelle proprietà di trasporto del supporto al bordo della banda, l’indagine presentata in questa tesi è di interesse per l’ampio insieme delle applicazioni optoelettroniche delle perovskiti alogenate. I risultati ottenuti durante l’attività di dottorato contribuiscono a chiarire le principali caratteristiche del disordine in questa classe di semiconduttori. • L’interazione tra i microcristalli di CsPbBr3 e il substrato/metasuperficie su cui sono depositati. Infatti, l’integrazione di perovskiti alogenate su metasuperfici e strutture fotoniche è una ricerca in fase iniziale e un’indagine approfondita è necessaria prima dell’implementazione di dispositivi fotonici innovativi. In particolare presenterò una serie di risultati sperimentali riguardanti effetti non lineari (comportamento superlineare e sublineare) nell’emissione radiativa di film CsPbBr3 depositati da spin-coating su un particolare tipo di metasuperficie realizzata da microrisonatori core-shell (T-Rex) assemblati in pattern esagonali su un substrato di silicio. I risultati sperimentali evidenziano la presenza di Amplified Spontaneous Emission (ASE) che, a seconda della struttura del campione, si presenta e non si presenta con un aumento superlineare dell’emissione. In particolare si distinguono due processi: l’amplificazione della luce da emettitori disposti in modo casuale e l’amplificazione da una distribuzione abbastanza ordinata di nanocristalli intorno a un risonatore. • CsPbBr3 ha caratteristiche ottimali come adsorbitore e catalizzatore nei pro- cessi di assorbimento degli inquinanti dalle acque reflue industriali. Nella parte finale del mio lavoro mostrerò i risultati preliminari riguardanti il rapido assorbimento del Blu di Metilene (MB), una sostanza tipicamente utilizzata nell’industria tessile, disciolta in soluzione acquosa quando le nanopolveri di CsPbBr3 (NPs) sono incapsulate all’interno di sferette di chitosano (CH-BB). Un aumento significativo della percentuale di adsorbimento di MB si ottiene in presenza delle nanopolveri di perovskite rispetto all’uso delle sferette di chitosano vuote.In this PhD thesis several aspects of the physics of halide inorganic perovskites are addressed. In particular I will focus on: • Intrinsic properties of the material such as the structural and dynamical disorder by a deep study of the photoluminescence in a large set of CsPbBr3 samples differing for morphology and synthesis protocol. Being the disorder affecting the spectral line shape of the photoluminescence, and playing a major role in the carrier transport properties at the band edge, the investigation here presented is of interest for the large set of optoelectronic applications of halide perovskites. The results obtained during the PhD activity contribute to clarify the main characteristics of disorder in this class of semiconductors. • The interaction between CsPbBr3 microcrystals and the substrate/metasurface where they are deposited. In fact, the integration of halide perovskites in metasurfaces and photonic structures is a research at the early stage and deep investigation is required before the implementation of innovative photonic devices. In particular I will present a set of experimental results concerning non-linear effects (superlinear and sublinear behavior) in the radiative emission of CsPbBr3 films deposited by spin-coating on a particular type of metasurface realized by core-shell microresonators (T-Rex) assembled in an esagonal pattern on a silicon substrate. The experimental results evidence the presence of Amplified Spontaneous Emission (ASE) which, depending on the sample structure, does or does not show up with a superlinear increase of the emission. In particular we distinguish between two processes: light amplification by randomly arranged emitters and amplification by a quite ordered distribution of nanocrystals around a resonator. • CsPbBr3 has optimal characteristics as adsorber and catalyst in the processes of absorption of pollutants from industrial waste water. In the final part of my work I will show preliminary results concerning the fast adsorption of Methylene Blue (MB), a substance typically used in the textile industry, dissolved in aqueous solution when CsPbBr3 nanopowders (NPs) are encapsulated inside chitosan bubbles (CH-BB). A significant increase of the adsorption percentage of MB is obtained in presence of the perovskite nanopowders respect to the use of empty chitosan bubbles

    Introduction to Facial Micro Expressions Analysis Using Color and Depth Images: A Matlab Coding Approach (Second Edition, 2023)

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    The book attempts to introduce a gentle introduction to the field of Facial Micro Expressions Recognition (FMER) using Color and Depth images, with the aid of MATLAB programming environment. FMER is a subset of image processing and it is a multidisciplinary topic to analysis. So, it requires familiarity with other topics of Artifactual Intelligence (AI) such as machine learning, digital image processing, psychology and more. So, it is a great opportunity to write a book which covers all of these topics for beginner to professional readers in the field of AI and even without having background of AI. Our goal is to provide a standalone introduction in the field of MFER analysis in the form of theorical descriptions for readers with no background in image processing with reproducible Matlab practical examples. Also, we describe any basic definitions for FMER analysis and MATLAB library which is used in the text, that helps final reader to apply the experiments in the real-world applications. We believe that this book is suitable for students, researchers, and professionals alike, who need to develop practical skills, along with a basic understanding of the field. We expect that, after reading this book, the reader feels comfortable with different key stages such as color and depth image processing, color and depth image representation, classification, machine learning, facial micro-expressions recognition, feature extraction and dimensionality reduction. The book attempts to introduce a gentle introduction to the field of Facial Micro Expressions Recognition (FMER) using Color and Depth images, with the aid of MATLAB programming environment.Comment: This is the second edition of the boo

    Nonlinear Spectroscopy for Characterizing Cells, Proteins, and the Origins of the Photobiomodulation Effect

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    The introduction of the laser in the 1960s brough forth the discovery of many nonlinear phenomena and marked the beginning of the field of nonlinear optics. Nonlinear spectroscopy offers many additional features over conventional linear spectroscopy which can be useful towards biomedical applications. In this work, we employ nonlinear spectroscopy and phenomena towards solving problems in biomedical fields. In the first study, the visible light generation following filamentation is studied to address knowledge gaps within the American National Standard for the Safe Use of Lasers (ANSI Z136.1-2014). The ANSI standards provide maximum permissible exposure (MPE) values for skin and retinal tissue; however, nonlinear optical effects that cause visible light generation are currently not addressed. In this study, we measure the visible light following filamentation of ultrafast near- to mid- infrared (IR) light. Near-IR light, which normally attenuates before reaching the retina in the eye, was found to generate sufficient visible light following filamentation to exceed the MPE values set by ANSI. In the next two studies, ultrafast transient absorption spectroscopy is used to study the mechanisms underlying the photobiomodulation (PBM) effect. PBM is the use of low irradiance light in the red to near-IR range to stimulate beneficial effects in tissues and cells. However, the electronic or molecular mechanisms which initiate that effect are not well understood. In our first study, we introduce a novel methodology which couples a continuous wave (CW) laser with ultrafast transient absorption spectroscopy (TAS), coined as CW-TAS, and test the proof-of-principle with the mitochondrial protein, cytochrome c (Cyt c). The TAS data for Cyt c remained intact and unperturbed with the addition of the CW light compared to standard TAS. This indicated that CW-TAS can be used on the more complex mitochondrial proteins suspected to be involved in PBM, and it provided further evidence that Cyt c was not an initiator of the PBM effect. In our second study, we apply the CW-TAS technique to the more complex mitochondrial protein, Complex III (C-III), from a mammalian source. This study provided the first TAS characterization for C-III from specifically a mammalian source. In addition, the photodissociation and recombination of the axial ligand that was tested with TAS was found to not exhibit changes when measured with CW-TAS. Therefore, we conclude that this electronic process of C-III is eliminated from being a potential initiator of the PBM effect. In the final study, beam shaping techniques were applied to improve the spectral resolution of impulsive stimulated Brillouin scattering (ISBS) spectroscopy towards cellular studies. Brillouin spectroscopy, which studies the elastic properties of materials, has been demonstrated to be useful for biomedical imaging and sensing. In particular, ISBS microscopy has recently been introduced towards biomedical applications; however, improvements to the spectral resolution have not been currently addressed. In this study, we expand the initial pump beam diameter with a 4f configuration and employ the use of a cylindrical lens to focus it into the system. The ISBS linewidth in the Fourier domain was found to be dependent on the pump beam’s spatial geometry. By increasing the spectral resolution, close elastic signals can be resolved which is important in biological and cellular studies where samples contain a high water content

    Proceedings of the 8th Workshop on Detection and Classification of Acoustic Scenes and Events (DCASE 2023)

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    This volume gathers the papers presented at the Detection and Classification of Acoustic Scenes and Events 2023 Workshop (DCASE2023), Tampere, Finland, during 21–22 September 2023

    Relative Navigation Strategy About Unknown and Uncooperative Targets

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    In recent years, space debris has become a threat for satellites operating in low Earth orbit. Even by applying mitigation guidelines, their number will still increase over the course of the century. As a consequence, active debris removal missions and on-orbit servicing missions have gained momentum at both academic and industrial level. The crucial step in both scenarios is the capability of navigating in the neighborhood of a target resident space object. This problem has been tackled many times in literature with varying level of cooperativeness of the target required. While several techniques are available when the target is cooperative or its shape is known, no approach is mature enough to deal with uncooperative and unknown targets. This paper proposes a hybrid method to tackle this issue called Coarse Model-Based Relative Navigation (CoMBiNa). The main idea of this algorithm is to split the mission into two phases. During the first phase, the algorithm constructs a coarse model of the target. In the second phase, this coarse model is used as a reference for a relative navigation technique, effectively shifting the focus toward state and inertia estimation. In addition, this paper proposes a strategy to leverage the structure of the selected navigation method to detect and reject outliers. To conclude, CoMBiNa is tested on a simulated environment to highlight its benefits and its shortcomings, while also assessing its applicability on a limited-resource single-board computer

    A survey, review, and future trends of skin lesion segmentation and classification

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    The Computer-aided Diagnosis or Detection (CAD) approach for skin lesion analysis is an emerging field of research that has the potential to alleviate the burden and cost of skin cancer screening. Researchers have recently indicated increasing interest in developing such CAD systems, with the intention of providing a user-friendly tool to dermatologists to reduce the challenges encountered or associated with manual inspection. This article aims to provide a comprehensive literature survey and review of a total of 594 publications (356 for skin lesion segmentation and 238 for skin lesion classification) published between 2011 and 2022. These articles are analyzed and summarized in a number of different ways to contribute vital information regarding the methods for the development of CAD systems. These ways include: relevant and essential definitions and theories, input data (dataset utilization, preprocessing, augmentations, and fixing imbalance problems), method configuration (techniques, architectures, module frameworks, and losses), training tactics (hyperparameter settings), and evaluation criteria. We intend to investigate a variety of performance-enhancing approaches, including ensemble and post-processing. We also discuss these dimensions to reveal their current trends based on utilization frequencies. In addition, we highlight the primary difficulties associated with evaluating skin lesion segmentation and classification systems using minimal datasets, as well as the potential solutions to these difficulties. Findings, recommendations, and trends are disclosed to inform future research on developing an automated and robust CAD system for skin lesion analysis

    Decision Making Under Scarcity: An Inquiry into The Effects of Cognitive Load

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    Scarcity, or the feeling of having less than you need, alters the decision-making process. This poverty-triggered mechanism makes economic decisions more difficult by curtailing cognitive control. This involuntary load redirects the deliberative part of the cognitive system towards making rational choices for scarcity alleviation. At the same time, other preferences get overwhelmingly guided by the affective system. Such recalibration results in the rational-bias split or tunnelling in preferences. Pressed for resources, people become judicious about relevant commitments as other beneficial but irrelevant choices suffer. This sensitivity to ‘what matters’ changes preferences. My work investigates this dichotomy of preferences. I look at financial scarcity and intimate partner violence as sources of cognitive load and examine split and changes in probability weighting function and risk preferences through the attentional mechanism. I undertook two lab-in-field experiments in Uganda and the Dominican Republic to investigate this framework. To understand the within-subject differences, each participant takes two decisions- one relevant to resolve the scarcity at hand and the other that is not. I use the common consequence ladders to track probability weighting, Eckel Grossman and Holt-Laury price lists for risk preferences. I confirm the pervasive characteristics of scarcity. Finances are a constant worry for those facing shortages. The level of scarcity affects cognitive load: inhibitory control and attention are taxed by expected scarcity. Working memory scores are affected by unexpected scarcity and the interaction of expected and shock. Additionally, previous experience of economic abuse, higher inhibitory control, and attention risk seeking. Finally, the scarcity-irrelevant probability weighting function is more likely to be non-linear than that for the scarcity-relevant attribute. I show that split or tunnelling depends on the strength of the top-down force of scarcity, the bottom-up force from the choice and their congruence. I find a by-scarcity-relevance split in probability weighting and risk preferences
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