5,549 research outputs found
Broadband Coherent Anti-Stokes Raman Spectroscopy: A Comprehensive Approach to Analyzing Crystalline Materials
Broadband Coherent Anti-Stokes Raman scattering (B-CARS) is an advanced Raman spectroscopy technique used to investigate the vibrational properties of materials. B-CARS combines the spectral sensitivity of spontaneous Raman scattering with the enhanced signal intensity of coherent Raman techniques. While B-CARS has been successfully applied in biomedicine for ultra-fast imaging of biological tissue, its potential in solid-state physics remains largely unexplored. This work delves into the challenges and adaptations necessary to apply B-CARS to crystalline materials and shows its potential as a powerful tool for high-speed, hyperspectral investigations.
The theoretical part of this work covers inelastic light-matter scattering fundamentals and the signal generation process of B-CARS, with special attention given to the so-called Non-Resonant Background (NRB). This sample-unspecific signal amplifies the B-CARS intensity but also distorts the shape and position of the measured spectral peaks.
A reliable NRB correction becomes crucial to retrieve precise spectral parameters containing information on the investigated material's crystallographic structure, defect density, and stress distribution.
The first results chapter presents a practical guideline for an optimized workflow of sample preparation, measurement procedure, and data analysis. The influences of sample surfaces, focus positioning, and polarization sensitivity are discussed. The successful NRB removal is achieved by adapting an algorithm initially designed for biomedical purposes.
The second chapter involves a transnational Round Robin investigating the same set of materials using different experimental setups. The influences of laser source, detection range, and transmission vs. epi detection are explored to optimize the experimental parameters.
This work showcases applications such as high-speed, hyperspectral imaging of ferroelectric domain walls in LiNbO3, demonstrating the potential of B-CARS in the cutting-edge field of domain wall engineering.
Additionally, imaging and polarization-sensitive measurements are shown for MoO3 flakes, paving the way for B-CARS investigations of 2D materials.
The final chapter presents advanced techniques, such as Three-Color CARS and Time-Delay CARS, applied to crystalline materials. Three-Color CARS is especially promising, as it enhances the signal intensity for low-frequency Raman modes, which are particularly interesting for solid-state physics compared to the usual large-shift modes investigated in biomedical research. Meanwhile, Time-Delay CARS is sensitive to relaxation processes of vibrational and NRB states, enabling experimental NRB removal and lifetime measurements. Additionally, a neural network-based NRB removal method is presented, eliminating the need for a prior NRB spectrum and offering rapid computation.
In summary, this work demonstrates the successful implementation of B-CARS for crystalline materials and provides a comprehensive guideline for the optimal experimental setup, workflow, and data processing. The application of B-CARS for imaging bulk crystalline materials, ferroelectric domain walls, and 2D structures shows promising possibilities for future research
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A comprehensive review of renewables and electric vehicles hosting capacity in active distribution networks
© Copyright 2023 The Author(s). The excessive integration of renewable distributed generation (RDG) and electric vehicles (EVs) could be considered the two most problematic elements representing the greatest threat to the distribution network (DN) technical operation. In order to avoid going beyond technical limitations, the term hosting capacity (HC) was proposed to define the highest permitted amount of distributed generation (DG) or EVs that can be integrated safely into the DN. The connection of RDGs was first brought to the attention of researchers and DN operators since it accounts for the most notable portion of these technical issues. Hence, the phrase ‘DG-HC’ was initially proposed and evolved significantly over the last few years. Currently, EV integration in most DNs worldwide is still low, but given the worldwide support for clean transportation options, expectations are raised for a significant increase. As a result, it is anticipated that over the next years, the effect of EV integration on the DN will be highly noticeable, requiring greater attention from researchers and DN operators to define the accepted limits of EV penetration levels, ‘EV-HC,’ which is expected to pass along the same line of DG-HC. This article provides an in-depth review of both DG-HC and EV-HC. It first analyses how the DG-HC research has grown over the years and then studies the published EV-HC papers, illustrating to what extent there is a similarity between them and, finally, employs these analyses to expect future development in the EV-HC research area. This article includes the different uses of the term HC, the most common performance indices of DG-HC, the various methods for assessing DG-HC, the different techniques for DG-HC enhancement, the effects of integrating EVs on the DG-HC, and finally, calculating and enhancing methods for EV-HC
Development of a SQUID magnetometry system for cryogenic neutron electric dipole moment experiment
A measurement of the neutron electric dipole moment (nEDM) could hold the key to understanding why the visible universe is the way it is: why matter should predominate over antimatter. As a charge-parity violating (CPV) quantity, an nEDM could provide an insight into new mechanisms that address this baryon asymmetry. The motivation for an improved sensitivity to an nEDM is to find it to be non-zero at a level consistent with certain beyond the Standard Model theories that predict new sources of CPV, or to establish a new limit that constrains them.
CryoEDM is an experiment that sought to better the current limit of cm by an order of magnitude. It is designed to measure the nEDM via the Ramsey Method of Separated Oscillatory Fields, in which it is critical that the magnetic field remains stable throughout. A way of accurately tracking the magnetic fields, moreover at a temperature K, is crucial for CryoEDM, and for future cryogenic projects.
This thesis presents work focussing on the development of a 12-SQUID magnetometry system for CryoEDM, that enables the magnetic field to be monitored to a precision of pT. A major component of its infrastructure is the superconducting capillary shields, which screen the input lines of the SQUIDs from the pick up of spurious magnetic fields that will perturb a SQUID's measurement. These are shown to have a transverse shielding factor of , which is a few orders of magnitude greater than the calculated requirement.
Efforts to characterise the shielding of the SQUID chips themselves are also discussed. The use of Cryoperm for shields reveals a tension between improved SQUID noise and worse neutron statistics. Investigations show that without it, SQUIDs have an elevated noise when cooled in a substantial magnetic field; with it, magnetostatic simulations suggest that it is detrimental to the polarisation of neutrons in transport. The findings suggest that with proper consideration, it is possible to reach a compromise between the two behaviours.
Computational work to develop a simulation of SQUID data is detailed, which is based on the Laplace equation for the magnetic scalar potential. These data are ultimately used in the development of a linear regression technique to determine the volume-averaged magnetic field in the neutron cells. This proves highly effective in determining the fields within the pT requirement under certain conditions
Understanding Agreement and Disagreement in Listeners’ Perceived Emotion in Live Music Performance
Emotion perception of music is subjective and time dependent. Most computational music emotion recognition (MER) systems overlook time- and listener-dependent factors by averaging emotion judgments across listeners. In this work, we investigate the influence of music, setting (live vs lab vs online), and individual factors on music emotion perception over time. In an initial study, we explore changes in perceived music emotions among audience members during live classical music performances. Fifteen audience members used a mobile application to annotate time-varying emotion judgments based on the valence-arousal model. Inter-rater reliability analyses indicate that consistency in emotion judgments varies significantly across rehearsal segments, with systematic disagreements in certain segments. In a follow-up study, we examine listeners' reasons for their ratings in segments with high and low agreement. We relate these reasons to acoustic features and individual differences. Twenty-one listeners annotated perceived emotions while watching a recorded video of the live performance. They then reflected on their judgments and provided explanations retrospectively. Disagreements were attributed to listeners attending to different musical features or being uncertain about the expressed emotions. Emotion judgments were significantly associated with personality traits, gender, cultural background, and music preference. Thematic analysis of explanations revealed cognitive processes underlying music emotion perception, highlighting attributes less frequently discussed in MER studies, such as instrumentation, arrangement, musical structure, and multimodal factors related to performer expression. Exploratory models incorporating these semantic features and individual factors were developed to predict perceived music emotion over time. Regression analyses confirmed the significance of listener-informed semantic features as independent variables, with individual factors acting as moderators between loudness, pitch range, and arousal. In our final study, we analyzed the effects of individual differences on music emotion perception among 128 participants with diverse backgrounds. Participants annotated perceived emotions for 51 piano performances of different compositions from the Western canon, spanning various era. Linear mixed effects models revealed significant variations in valence and arousal ratings, as well as the frequency of emotion ratings, with regard to several individual factors: music sophistication, music preferences, personality traits, and mood states. Additionally, participants' ratings of arousal, valence, and emotional agreement were significantly associated to the historical time periods of the examined clips. This research highlights the complexity of music emotion perception, revealing it to be a dynamic, individual and context-dependent process. It paves the way for the development of more individually nuanced, time-based models in music psychology, opening up new avenues for personalised music emotion recognition and recommendation, music emotion-driven generation and therapeutic applications
Fundamental Valuation of NOV
The purpose of this thesis is to conduct a fundamental valuation of NOV to provide an equity
value and share price as of 17 January 2023. To support the fundamental valuation of the
company, I have also performed a relative valuation, using the EV/EBITDA and P/S multiples.
I conduct a comprehensive examination of macroeconomic, industry-, and company-specific
factors that drive value in the oilfield services and equipment industry. These analyses are
utilized to make necessary assumptions, forecast NOV’s future performance, and ultimately
estimate the company’s equity value and final price target.
Acknowledging the accelerating global energy transition and growing public concern about
climate change, companies that offer equipment and technologies supportive of cleaner energy
sources have experienced considerable demand growth in recent years. Driven by regulatory
changes, subsidies, volatile oil and gas prices, and the ongoing shift towards sustainable
energy sources, the industry is continuously nudged to adapt and innovate. With its long
history as a market leader in the global oilfield services and equipment industry, an extensive
product portfolio, and a global customer base comprising several large upstream oil and gas
companies, NOV is solidly positioned within the global energy markets. Amid a moderately
competitive situation, NOV is poised to continue to grow the upcoming years, particularly as
it ventures into the booming renewable energy market.
Considering these factors, the fundamental valuation yields an estimated share price of 12,5, derived from a weighted average of the estimations
from both fundamental and relative valuation methods, allocated with a 70/30 weight,
respectively. While the estimates are characterized by a high degree of uncertainty, as
investigated through a sensitivity analysis, the conclusion suggests a potential overvaluation
of NOV. Hence, as of January 17, 2023, I would propose a sell recommendation.nhhma
Towards a muon collider
A muon collider would enable the big jump ahead in energy reach that is needed for a fruitful exploration of fundamental interactions. The challenges of producing muon collisions at high luminosity and 10 TeV centre of mass energy are being investigated by the recently-formed International Muon Collider Collaboration. This Review summarises the status and the recent advances on muon colliders design, physics and detector studies. The aim is to provide a global perspective of the field and to outline directions for future work
Physical sketching tools and techniques for customized sensate surfaces
Sensate surfaces are a promising avenue for enhancing human interaction with digital systems due to their inherent intuitiveness and natural user interface. Recent technological advancements have enabled sensate surfaces to surpass the constraints of conventional touchscreens by integrating them into everyday objects, creating interactive interfaces that can detect various inputs such as touch, pressure, and gestures. This allows for more natural and intuitive control of digital systems. However, prototyping interactive surfaces that are customized to users' requirements using conventional techniques remains technically challenging due to limitations in accommodating complex geometric shapes and varying sizes. Furthermore, it is crucial to consider the context in which customized surfaces are utilized, as relocating them to fabrication labs may lead to the loss of their original design context. Additionally, prototyping high-resolution sensate surfaces presents challenges due to the complex signal processing requirements involved. This thesis investigates the design and fabrication of customized sensate surfaces that meet the diverse requirements of different users and contexts. The research aims to develop novel tools and techniques that overcome the technical limitations of current methods and enable the creation of sensate surfaces that enhance human interaction with digital systems.Sensorische Oberflächen sind aufgrund ihrer inhärenten Intuitivität und natürlichen Benutzeroberfläche ein vielversprechender Ansatz, um die menschliche Interaktionmit digitalen Systemen zu verbessern. Die jüngsten technologischen Fortschritte haben es ermöglicht, dass sensorische Oberflächen die Beschränkungen herkömmlicher Touchscreens überwinden, indem sie in Alltagsgegenstände integriert werden und interaktive Schnittstellen schaffen, die diverse Eingaben wie Berührung, Druck, oder Gesten erkennen können. Dies ermöglicht eine natürlichere und intuitivere Steuerung von digitalen Systemen. Das Prototyping interaktiver Oberflächen, die mit herkömmlichen Techniken an die Bedürfnisse der Nutzer angepasst werden, bleibt jedoch eine technische Herausforderung, da komplexe geometrische Formen und variierende Größen nur begrenzt berücksichtigt werden können. Darüber hinaus ist es von entscheidender Bedeutung, den Kontext, in dem diese individuell angepassten Oberflächen verwendet werden, zu berücksichtigen, da eine Verlagerung in Fabrikations-Laboratorien zum Verlust ihres ursprünglichen Designkontextes führen kann. Zudem stellt das Prototyping hochauflösender sensorischer Oberflächen aufgrund der komplexen Anforderungen an die Signalverarbeitung eine Herausforderung dar. Diese Arbeit erforscht dasDesign und die Fabrikation individuell angepasster sensorischer Oberflächen, die den diversen Anforderungen unterschiedlicher Nutzer und Kontexte gerecht werden. Die Forschung zielt darauf ab, neuartigeWerkzeuge und Techniken zu entwickeln, die die technischen Beschränkungen derzeitigerMethoden überwinden und die Erstellung von sensorischen Oberflächen ermöglichen, die die menschliche Interaktion mit digitalen Systemen verbessern
Resumen de tesis. Development of ultra-stable characterization techniques for ultrashort laser beams
[EN]The dramatic evolution that the laser Science has undergone in the last six decades, and particularly in the field of ultrashort pulses, has been accompanied by breakthrough advances in the development of techniques for their characterization. Despite the large number of characterization techniques developed in the last two decades, it is still necessary to Implement simpler and more robust techniques that can also operate in multiple spectral ranges.
This Thesis is devoted to the study and development of temporal and spatiotemporal characterization techniques with compact and stable configurations, which are versatile, e.g., to analyze ultrashort laser beams with
different temporal durations and in various spectral regions. The structure of this Thesis is made up of four main blocks. Firstly, a brief introduction to ultrafast optical metrology and the state of the art of spatial, temporal and spatiotemporal characterization techniques is presented in Part I. Then, Part II is focused on the review and extension of the capabilities of the amplitude swing temporal characterization technique, demonstrating three key advances: operation in different spectral regions from visible to near-infrared, with a tunability range spanning of more than one octave; Characterization of ultrashort pulses in the few-cycle regime; or study of the implementation with different amplitude modulation schemes.
In addition, a new retrieval algorithm is developed to analyze the amplitude swing traces based on differential evolution strategies. Thirdly, the fundamentals, operation range and experimental demonstration of a spatiotemporal
characterization technique based on bulk lateral shearing interferometry are depicted in Part III. Furthermore, the technique is applied to characterize complex spatiotemporal couplings, like constant and time-varying optical vortices or the aberrations when focusing with astigmatic lenses. Finally, the main conclusions of the work and future perspectives are discussed in Part IV[ES]La drástica evolución que ha experimentado la ciencia láser en las últimas seis décadas, y en particular en el campo de los pulsos ultracortos, ha ido acompañada de grandes avances en el desarrollo de técnicas para su caracterización. A pesar de la gran cantidad de métodos de caracterización desarrollados en las últimas dos décadas, aún es necesario implementar sistemas más simples y robustos que también puedan operar en múltiples rangos espectrales. Esta Tesis está dedicada al estudio y desarrollo de técnicas de caracterización temporal y espaciotemporal con configuraciones compactas y estables, que sean versátiles para, por ejemplo, analizar haces láser ultracortos con
diferentes duraciones temporales y en diversas regiones espectrales. La estructura de la Tesis está dividida en cuatro bloques principales. En primer lugar, en la Parte I se presenta una breve introducción a la metrología
óptica ultrarrápida y los avances de las técnicas de caracterización espacial, temporal y espaciotemporal a lo largo de los últimos años. Después, la Parte II se enfoca en la revisión y extensión de las capacidades de la técnica de caracterización temporal amplitude swing, demostrando tres avances clave: operación en diferentes regiones espectrales desde visible hasta infrarrojo cercano, con un rango de sintonizabilidad que abarca más de una octava;
caracterización de pulsos ultracortos en régimen de pocos ciclos; o estudio de diferentes esquemas de modulación de amplitud. Además, se implementa un nuevo algoritmo de reconstrucción para analizar las trazas del sistema amplitude swing basado en las estrategias Differential Evolution. En tercer lugar, en la Parte III se describen los fundamentos, el rango de operación y la demostración experimental de una técnica de caracterización espaciotemporal basada en la interferometría lateral compacta (bulk lateral shearing interferometry). Además, la técnica se emplea para caracterizar acoplamientos
espaciotemporales complejos, como son los vórtices ópticos constantes y variables en el tiempo o las aberraciones introducidas al focalizar haces láser con
lentes astigmáticas. Finalmente, en la Parte IV se resumen las principales conclusiones y futuras líneas de trabajo.Thesis memory and supplementary material folder: Vídeo 1 ("VideoThesis_GeneralizingAswing_Noise.avi"), Noise analysis amplitude swing configurations video. Vídeo 2 ("VideoThesis_Vortices_ProofOfConcept.avi"), Proof of concept spatiotemporal technique video. Vídeo 3 ("VideoThesis_Vortex_NIR_Lneg1.avi"), Near-infrared vortex video: orbital angular momentum of −1. Vídeo 4 ("VideoThesis_Vortex_NIR_L1.avi"), Near-infrared vortex video: orbital angular momentum of +1. Vídeo 5 ("VideoThesis_Vortex_NIR_L3.avi"), Near-infrared vortex video: orbital angular momentum of +3. Vídeo 6 ("VideoThesis_Vortex_VIS_Lneg2.avi"), Visible vortex video: orbital angular momentum of -2. Vídeo 7 ("VideoThesis_Vortex_VIS_L2.avi"), Visible vortex video: orbital angular momentum of +2. Vídeo 8 ("VideoThesis_Vortex_VIS_L4.avi"), Visible vortex video: orbital angular momentum of +4. Vídeo 9 ("VideoThesis_TimeVaryingVortex_Exp.avi"), Time varying vortex video: Experiment. Vídeo 10 ("VideoThesis_TimeVaryingVortex_Sim.avi"), Time varying vortex video: Simulation. Vídeo 11 ("VideoThesis_Astigmatic_Biconvergent.avi"), Astigmatic beam video: z = da = 49 cm. Vídeo 12 ("VideoThesis_Astigmatic_ConvDiv.avi"), Astigmatic beam video: z = db = 137 cm
Cardiovascular health: from cardiomyocyte electrostimulation to miRNA detection
Current methods of cell culture where electrical stimulation is applied during culture require a wired connection to a power supply to generate an electric field with which to stimulate the cells. This method is intrusive in a lab setting and does not conveniently allow for traditional cell culture techniques during stimulation, hence it is frequently omitted from cell culture protocols. The aim of this work is to demonstrate a novel method of electrical stimulation of cardiomyocytes using wireless bipolar electrochemical techniques. The work describes the design and characterisation of a wireless bipolar electrode and wireless bipolar electrochemical cell to facilitate wireless bipolar electrostimulation. By using a wireless connection more versatile experiments can be conducted on cells in culture while mitigating the contamination risk of a traditional wired stimulation platform.
Using a polypyrrole based conducting film doped with fibronectin molecules to facilitate the adherence and growth of cardiomyocytes on the bipolar electrode surface. Cell culture on a conductive film opens the possibility of future applications in electroceuticals by providing a wireless platform to deliver and electric field to cells in culture.
Demonstrating cell culture on conductive polymer with the application of electric fields allows for the study of healthy and disease cell populations in the presence of electrical stimuli. Biomarker monitoring during this work is important to characterise and understand the impact of stimuli on the cells in culture. As such, an electrochemical miRNA biosensor was also explored in this work. The assay was based on the detection of miRNA through hydrogen peroxide degradation. The assay was built of screen-printed electrodes as a method to characterise cell cultures. The ability to monitor biomarkers both in vitro and in vivo is important in generating an understanding of disease models and in the development of point-of-care testing capabilities
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