5,191 research outputs found
Innovative Hybrid Approaches for Vehicle Routing Problems
This thesis deals with the efficient resolution of Vehicle Routing Problems (VRPs).
The first chapter faces the archetype of all VRPs: the Capacitated Vehicle Routing Problem (CVRP). Despite having being introduced more than 60 years ago, it still remains an extremely challenging problem. In this chapter I design a Fast Iterated-Local-Search Localized Optimization algorithm for the CVRP, shortened to FILO. The simplicity of the CVRP definition allowed me to experiment with advanced local search acceleration and pruning techniques that have eventually became the core optimization engine of FILO. FILO experimentally shown to be extremely scalable and able to solve very large scale instances of the CVRP in a fraction of the computing time compared to existing state-of-the-art methods, still obtaining competitive solutions in terms of their quality.
The second chapter deals with an extension of the CVRP called the Extended Single Truck and Trailer Vehicle Routing Problem, or simply XSTTRP. The XSTTRP models a broad class of VRPs in which a single vehicle, composed of a truck and a detachable trailer, has to serve a set of customers with accessibility constraints making some of them not reachable by using the entire vehicle. This problem moves towards VRPs including more realistic constraints and it models scenarios such as parcel deliveries in crowded city centers or rural areas, where maneuvering a large vehicle is forbidden or dangerous. The XSTTRP generalizes several well known VRPs such as the Multiple Depot VRP and the Location Routing Problem. For its solution I developed an hybrid metaheuristic which combines a fast heuristic optimization with a polishing phase based on the resolution of a limited set partitioning problem. Finally, the thesis includes a final chapter aimed at guiding the computational evaluation of new approaches to VRPs proposed by the machine learning community
Full stack development toward a trapped ion logical qubit
Quantum error correction is a key step toward the construction of a large-scale quantum computer, by preventing small infidelities in quantum gates from accumulating over the course of an algorithm. Detecting and correcting errors is achieved by using multiple physical qubits to form a smaller number of robust logical
qubits. The physical implementation of a logical qubit requires multiple qubits, on which high fidelity gates
can be performed.
The project aims to realize a logical qubit based on ions confined on a microfabricated surface trap. Each
physical qubit will be a microwave dressed state qubit based on 171Yb+ ions. Gates are intended to be realized through RF and microwave radiation in combination with magnetic field gradients. The project vertically integrates software down to hardware compilation layers in order to deliver, in the near future, a fully functional small device demonstrator.
This thesis presents novel results on multiple layers of a full stack quantum computer model. On the hardware level a robust quantum gate is studied and ion displacement over the X-junction geometry is demonstrated.
The experimental organization is optimized through automation and compressed waveform data transmission. A new quantum assembly language purely dedicated to trapped ion quantum computers is introduced. The demonstrator is aimed at testing implementation of quantum error correction codes while preparing for larger
scale iterations.Open Acces
Scalable software and models for large-scale extracellular recordings
The brain represents information about the world through the electrical activity of
populations of neurons. By placing an electrode near a neuron that is firing (spiking), it
is possible to detect the resulting extracellular action potential (EAP) that is transmitted
down an axon to other neurons. In this way, it is possible to monitor the communication
of a group of neurons to uncover how they encode and transmit information. As the
number of recorded neurons continues to increase, however, so do the data processing
and analysis challenges. It is crucial that scalable software and analysis tools are developed
and made available to the neuroscience community to keep up with the large
amounts of data that are already being gathered.
This thesis is composed of three pieces of work which I develop in order to better
process and analyze large-scale extracellular recordings. My work spans all stages of extracellular
analysis from the processing of raw electrical recordings to the development
of statistical models to reveal underlying structure in neural population activity.
In the first work, I focus on developing software to improve the comparison and adoption
of different computational approaches for spike sorting. When analyzing neural
recordings, most researchers are interested in the spiking activity of individual neurons,
which must be extracted from the raw electrical traces through a process called
spike sorting. Much development has been directed towards improving the performance
and automation of spike sorting. This continuous development, while essential,
has contributed to an over-saturation of new, incompatible tools that hinders rigorous
benchmarking and complicates reproducible analysis. To address these limitations, I
develop SpikeInterface, an open-source, Python framework designed to unify preexisting
spike sorting technologies into a single toolkit and to facilitate straightforward
benchmarking of different approaches. With this framework, I demonstrate that modern,
automated spike sorters have low agreement when analyzing the same dataset, i.e.
they find different numbers of neurons with different activity profiles; This result holds
true for a variety of simulated and real datasets. Also, I demonstrate that utilizing a
consensus-based approach to spike sorting, where the outputs of multiple spike sorters
are combined, can dramatically reduce the number of falsely detected neurons.
In the second work, I focus on developing an unsupervised machine learning approach
for determining the source location of individually detected spikes that are
recorded by high-density, microelectrode arrays. By localizing the source of individual
spikes, my method is able to determine the approximate position of the recorded neuriii
ons in relation to the microelectrode array. To allow my model to work with large-scale
datasets, I utilize deep neural networks, a family of machine learning algorithms that
can be trained to approximate complicated functions in a scalable fashion. I evaluate
my method on both simulated and real extracellular datasets, demonstrating that it is
more accurate than other commonly used methods. Also, I show that location estimates
for individual spikes can be utilized to improve the efficiency and accuracy of spike
sorting. After training, my method allows for localization of one million spikes in approximately
37 seconds on a TITAN X GPU, enabling real-time analysis of massive
extracellular datasets.
In my third and final presented work, I focus on developing an unsupervised machine
learning model that can uncover patterns of activity from neural populations
associated with a behaviour being performed. Specifically, I introduce Targeted Neural
Dynamical Modelling (TNDM), a statistical model that jointly models the neural activity
and any external behavioural variables. TNDM decomposes neural dynamics (i.e.
temporal activity patterns) into behaviourally relevant and behaviourally irrelevant dynamics;
the behaviourally relevant dynamics constitute all activity patterns required
to generate the behaviour of interest while behaviourally irrelevant dynamics may be
completely unrelated (e.g. other behavioural or brain states), or even related to behaviour
execution (e.g. dynamics that are associated with behaviour generally but are not
task specific). Again, I implement TNDM using a deep neural network to improve its
scalability and expressivity. On synthetic data and on real recordings from the premotor
(PMd) and primary motor cortex (M1) of a monkey performing a center-out reaching
task, I show that TNDM is able to extract low-dimensional neural dynamics that are
highly predictive of behaviour without sacrificing its fit to the neural data
Playing no solo imagination: synthesising the rhythmic emergence of sound and sign through embodied drum kit performance and writing
This practice-based PhD explores musical imagination by examining the relationships of embodied musical performance and writing. The submission comprises audio recordings of original musical material and accompanying literary output, which are contextualised through a written commentary. Through creative practice-led research based on the author’s experience as a performing musician, the thesis explores and details the generative relationship between imagination and intersubjectivity. In demonstrating musical performance as an ecologically-grounded activity animated by polyvalent real and imaginary elements, the thesis ultimately challenges the notion of an autonomous, solo subject in musical performance practice.
The research context draws on music, creative writing and a range of artistic and theoretical scholarship on the subjective experience: of emotion and feeling; intersubjectivity and embodiment; semiotics and the musical imagination; histories of time and rhythm. By engaging performance and writing as situated, ecological activities, creative practice is used productively as a research methodology through the following devices: (1) The drum kit—the author’s primary performance vehicle—is treated to a broadly historical and theoretical examination of material practice. A ‘hybrid drum kit’—combining acoustic drums, cymbals, and synthetic sounds—is proposed, and used by the author as the basis for this project’s practical explorations; (2) Rhythm is conceptualised and deployed as a systematic and recursive method for musical play, in order to investigate the interrelationship of sonic, semantic and physical elements; (3) Creative writing, based on theories of embodied cognition, is used to explore and inscribe the imagination of musical play.
This creative practice methodology is used to articulate and respond to the following questions: (a) What is the felt relationship between listening and inscription? (b) How do particular words, diagrams, real and imagined materials effect the sound of drum performance? (c) How do movements of the body relate to semantic and timbral conventions? The methodology is productive generating emergent structures which express embodied cognition, demonstrating the function of musical imagination. The approach serves simultaneously to expose the bias of perceptual filtering, and to challenge conventions of movement and quantification that condition musical subjectivity.
The research is formally presented in a way that reflects the synthesis of real, imagined, poetic and analytic elements under scrutiny in this thesis, through a series of interconnected units: thesis, audio recordings, and attendant written outputs. Exercises generate scores, in turn performed and recorded live. Sonic and written outcomes are combined, resulting in two publications, and a speculative performance. Narrated by a number of fictional characters, through various imaginary spaces, these outputs constitute three ‘Rhythmic Figure’ studies—‘Ductus,’ ‘Nsular’ and ‘Gyri’—produced as independent documents, and presented in the central ‘Garden’ section of the thesis. ‘Anteroom’ and ‘Exits’ sections, framing the ‘Garden,’ introduce, and conclude the thesis, respectively.
In its original, creative demonstration of the interconnected contribution of non-verbal, sensory, and intersubjective imagination to musical play, this creative practice research project contributes argument and evidence for the manifold ways of knowing music—listen, feel, move, write—which sit beyond discursive norms.This practice-based PhD explores musical imagination by examining the relationships of embodied musical performance and writing. The submission comprises audio recordings of original musical material and accompanying literary output, which are contextualised through a written commentary. Through creative practice-led research based on the author’s experience as a performing musician, the thesis explores and details the generative relationship between imagination and intersubjectivity. In demonstrating musical performance as an ecologically-grounded activity animated by polyvalent real and imaginary elements, the thesis ultimately challenges the notion of an autonomous, solo subject in musical performance practice.
The research context draws on music, creative writing and a range of artistic and theoretical scholarship on the subjective experience: of emotion and feeling; intersubjectivity and embodiment; semiotics and the musical imagination; histories of time and rhythm. By engaging performance and writing as situated, ecological activities, creative practice is used productively as a research methodology through the following devices: (1) The drum kit—the author’s primary performance vehicle—is treated to a broadly historical and theoretical examination of material practice. A ‘hybrid drum kit’—combining acoustic drums, cymbals, and synthetic sounds—is proposed, and used by the author as the basis for this project’s practical explorations; (2) Rhythm is conceptualised and deployed as a systematic and recursive method for musical play, in order to investigate the interrelationship of sonic, semantic and physical elements; (3) Creative writing, based on theories of embodied cognition, is used to explore and inscribe the imagination of musical play.
This creative practice methodology is used to articulate and respond to the following questions: (a) What is the felt relationship between listening and inscription? (b) How do particular words, diagrams, real and imagined materials effect the sound of drum performance? (c) How do movements of the body relate to semantic and timbral conventions? The methodology is productive generating emergent structures which express embodied cognition, demonstrating the function of musical imagination. The approach serves simultaneously to expose the bias of perceptual filtering, and to challenge conventions of movement and quantification that condition musical subjectivity.
The research is formally presented in a way that reflects the synthesis of real, imagined, poetic and analytic elements under scrutiny in this thesis, through a series of interconnected units: thesis, audio recordings, and attendant written outputs. Exercises generate scores, in turn performed and recorded live. Sonic and written outcomes are combined, resulting in two publications, and a speculative performance. Narrated by a number of fictional characters, through various imaginary spaces, these outputs constitute three ‘Rhythmic Figure’ studies—‘Ductus,’ ‘Nsular’ and ‘Gyri’—produced as independent documents, and presented in the central ‘Garden’ section of the thesis. ‘Anteroom’ and ‘Exits’ sections, framing the ‘Garden,’ introduce, and conclude the thesis, respectively.
In its original, creative demonstration of the interconnected contribution of non-verbal, sensory, and intersubjective imagination to musical play, this creative practice research project contributes argument and evidence for the manifold ways of knowing music—listen, feel, move, write—which sit beyond discursive norms
Study of the Degradation of New Lubricant Oil Formulations with the Design and Demands of Current and Future Engines
[ES] El análisis de los aceites lubricantes de motor, englobado dentro de las tareas realizadas en el Oil Condition Monitoring (OCM), resulta ser una herramienta poderosa con la cual se es capaz de extraer información de utilidad. Por este motivo, en esta Tesis se decidió explotar este campo realizando un estudio en profundidad centrado en tres aspectos: mejorar las técnicas y protocolos ya existentes, desarrollar procedimientos propios acorde con las necesidades y requisitos del momento y, para terminar, poner en valor la información obtenida del análisis de los lubricantes mediante el uso de tratamientos estadísticos y quimiométricos. Bajo estas tres premisas, se ha desarrollado toda la tarea de investigación de esta Tesis.
En primer lugar, en relación con el análisis de los aceites lubricantes, se realizó un estudio acerca de la degradación de cuatro formulaciones de aceites lubricantes. En este estudio se analizaron aspectos propios de los aceites como: su viscosidad cinemática, oxidación, nitración, caída de los aditivos antioxidantes, etc. así como parámetros de desgaste de motor (monitorizando la presencia de metales). Como resultado de este estudio fue posible encontrar limitaciones en las técnicas actuales, lo cual condujo a realizar mejoras y/o adaptaciones de estas técnicas para conseguir obtener la información deseada.
El siguiente aspecto tratado en esta Tesis es una consecuencia de la necesidad de, en ciertas situaciones, disponer de información acerca de uno o varios parámetros de una determinada forma y con un grado de precisión elevado. El caso en cuestión analizado en la Tesis está relacionado con la cuantificación de hollín en el aceite lubricante. Respecto a la cuantificación del hollín se requirió encontrar una técnica que fuera capaz de aportar información de una forma rápida y, además, poder detectar pequeños cambios. Esta técnica fue la espectroscopia Ultravioleta-Visible, con la cual se diseñó un protocolo analítico que permitiera trabajar con muestras de aceites lubricante con muy poco uso y, por ende, poca cantidad de hollín disuelta, consiguiendo resultados muy satisfactorios en periodos de tiempo cortos.
Por último, debido a la disponibilidad de una cantidad de datos considerable fruto del trabajo realizado durante todo el tiempo de duración de la Tesis, se decidió emplear toda ella para conseguir extraer la máxima información posible gracias al uso de tratamientos estadísticos y quimiométricos. Este trabajo, nuevo en la línea, se dividió en dos vertientes: la primera focalizada en el conjunto de datos de los aceites ya caracterizados (procedentes del estudio de la degradación de los aceites) y la otra parte en encontrar sinergias entre las técnicas espectroscópicas (FT-IR y NIR) y los ensayos de caracterización de los lubricantes. Como resultado de ello, se obtuvieron relaciones entre parámetros que anteriormente no se tenían presentes, así como modelos predictivos de propiedades de los lubricantes a partir del análisis de sus espectros.
El presente documento de Tesis se encuentra redactado en dos idiomas: en español y en inglés. Principalmente el documento se encuentra redactado en inglés para hacer especial énfasis en aquellas labores de investigación desarrolladas en esta etapa, así como los resultados derivados de los diferentes estudios realzados. Mientras que, la parte confeccionada en español hace referencia a aquellos aspectos más descriptivos del documento de Tesis.[CA] L'anàlisi dels olis lubrificants de motor, englobat dins de les tasques realitzades en el Oil Condition Monitoring (OCM), resulta ser una eina poderosa amb la qual s'és capaç d'extraure informació d'utilitat. Per aquest motiu, en aquesta Tesi es va decidir explotar aquest camp realitzant un estudi en profunditat centrat en tres aspectes: millorar les tècniques i protocols ja existents, desenvolupar procediments propis d'acord amb les necessitats i requisits del moment i, per a acabar, posar en valor la informació obtinguda de l'anàlisi dels lubrificants mitjançant l'ús de tractaments estadístics i quimiomètrics. Sota aquestes tres premisses, s'ha desenvolupat tota la tasca d'investigació d'aquesta Tesi.
En primer lloc, en relació a l'anàlisi dels olis lubrificants, es va realitzar un estudi sobre la degradació de quatre formulacions d'olis lubrificants. En aquest estudi es van analitzar aspectes propis dels olis com: la seua viscositat cinemàtica, oxidació, nitració, caiguda dels additius antioxidants, etc. així com paràmetres de desgast de motor (monitorant la presència de metalls). Com a resultat d'aquest estudi va ser possible trobar limitacions en les tècniques actuals, la qual cosa va conduir a realitzar millores i/o adaptacions d'aquestes tècniques per a aconseguir obtindre la informació desitjada.
El següent aspecte tractat en aquesta Tesi és una conseqüència de la necessitat de, en unes certes situacions, disposar d'informació sobre un o diversos paràmetres d'una determinada forma i amb un grau de precisió elevat. El cas en qüestió analitzat en la Tesi està relacionat amb la quantificació de sutge (soot en anglès). Respecte a la quantificació del soot es va requerir trobar una tècnica que fora capaç d'aportar informació d'una forma ràpida i, a més, poder detectar xicotets canvis. Aquesta tècnica va ser l'espectroscòpia Ultravioleta-Visible, amb la qual es va dissenyar un protocol analític que permetera treballar amb mostres d'oli lubrificant amb molt poc ús i, per tant, poca quantitat de soot dissolta, aconseguint resultats molt satisfactoris en períodes de temps curts.
Finalment, a causa de la disponibilitat d'una quantitat de dades considerable fruit del treball realitzat durant tot el temps de duració de la Tesi, es va decidir emprar tota ella per a aconseguir extraure la màxima informació possible gràcies a l'ús de tractaments estadístics i quimiomètrics. Aquest treball, nou en la línia, es va dividir en dos vessants: la primera focalitzada en el conjunt de dades dels olis ja caracteritzats (procedents de l'estudi de la degradació dels olis) i l'altra part a trobar sinergies entre les tècniques espectroscòpiques (FT-IR i NIR) i els assajos de caracterització dels lubrificants. Com a resultat d'això, es van obtindre relacions entre paràmetres que anteriorment no es tenien presents així com models predictius de propietats dels lubrificants a partir de l'anàlisi dels seus espectres.
El present document de Tesi es troba redactat en dos idiomes: en espanyol i en anglès. Principalment el document es troba redactat en anglès per a fer especial èmfasi en aquelles labors d'investigació desenvolupades en aquesta etapa així com els resultats derivats dels diferents estudis realitzats. Mentre que, la part confeccionada en espanyol,
fa referència a aquells aspectes més descriptius del document de Tesi.[EN] The analysis of engine lubricating oils, encompassed within the tasks carried out in Oil Condition Monitoring (OCM), is a powerful tool with which it is possible to extract useful information. For this reason, in this Thesis it has been decided to exploit this field by carrying out an in-depth study focusing on three aspects: improving existing techniques and protocols, developing our own procedures in accordance with current needs and requirements and finally, adding value to the information obtained from the analysis of lubricants through the use of statistical and chemometric treatments. All the research work in this Thesis has been carried out under these three premises.
Firstly, in relation to the analysis of lubricating oils, a study was carried out on the degradation of four lubricating oil formulations. This study analysed aspects of the oils, such as their kinematic viscosity, oxidation, nitration, antioxidant additives depletion, etc. as well as engine wear parameters (monitoring the presence of metals). Using this study, it was possible to find limitations in the current techniques, which led to improvements and/or adaptations of these techniques in order to obtain the desired information.
The next aspect dealt with in this Thesis is a consequence of the need, in certain situations, to have information about one or more parameters in a certain form and with a high degree of accuracy. The case in question analysed in the Thesis is related to the quantification of soot. With regard to soot quantification, it was necessary to find a technique that was capable of providing information quickly and, in addition, being able to detect small changes. This technique was Ultraviolet-Visible spectroscopy, with which an analytical protocol was designed to work with samples of lubricating oils with very little use and therefore, with a small amount of dissolved soot, achieving very satisfactory results in short periods of time.
Finally, due to the availability of a considerable amount of information resulting from the work carried out throughout the duration of the Thesis, it was decided to use all of these data to extract as much information as possible, thanks to the use of statistical and chemometric treatments. This work, new in the research line, was divided into two parts: the first focused on the dataset of oils already characterised (from the study of oil degradation) and the other on finding synergies between spectroscopic techniques (FT-IR and NIR) and lubricant characterisation tests. As a result, relationships between previously unknown parameters were obtained, as well as predictive models of lubricant properties based on the analysis of their spectra.
This Thesis document is written in two languages: Spanish and English. The document is mainly written in English in order to place special emphasis on the research work carried out at this stage, as well as the results derived from the different studies carried out. The part written in Spanish refers to the more descriptive aspects of the Thesis document.García Barberá, A. (2022). Study of the Degradation of New Lubricant Oil Formulations with the Design and Demands of Current and Future Engines [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/181668TESI
Hegemony, marginalisation, and hierarchies: Masculinities in contemporary Pakistani anglophone fiction
By being empowered as subjects, authors of Pakistani anglophone fiction present a more nuanced, layered, and complex picture of Pakistan than the Western hegemonic discursive construction of the country as a hub of terror. Contemporary Pakistani anglophone fiction provides an insight into the collisions of culture, modernity, and religion in Pakistan. This literature also offers a way of understanding gender dynamics in contemporary Pakistani society. Scholarship on the representation of men and masculinities in South Asian anglophone literature, especially Pakistani anglophone fiction, is sparse. My study seeks to fill this lacuna and focuses on fiction by four male authors, namely, Nadeem Aslam, Mohsin Hamid, Muhammad Hanif, and Daniyal Mueenuddin. My research highlights the potentially powerful existence of male narratives exposing, critiquing, and resisting misogyny, male violence, and gendered oppression. This research explores how these authors fashion the narrative of Pakistani masculinity and how these representations are shaped by wider societal, cultural, political, economic, and religious contexts. I draw on theories of performativity, intersectionality, and a range of scholarship about masculinities for my analysis.
Examining texts which bear the imprint of socio-cultural practices offers a tool to understand the social, cultural, and religious pressures that shape patriarchy, dictate men’s actions, and control masculine perceptions of identity and self-worth. Each chapter explores a different aspect of Pakistani masculinity, ranging from the depiction of the feudal and capitalist masculinities in rural Pakistan in In Other Rooms, Other Wonders to representations of toxic and hostile masculinities among working-class and lower-class men in Our Lady of Alice Bhatti and the clash between urban middle-class and elite Pakistani masculinities in Moth Smoke. The final two chapters reach beyond the geographic borders of the nation to focus on the depiction of the impact of honour culture, male entitlement, and racial marginalisation on diasporic Pakistani masculinities in Maps for Lost Lovers and the impact of global and political shifts on hegemonic masculine ideals and transnational business masculinity in The Reluctant Fundamentalist. This research maps a range of representations of the diversity, complexity, and unequal power dynamics of Pakistani masculinities. This study also explores the formation and representations of female identity and femininities in negotiations with masculinities in the selected fiction, for example, emphasized femininity in Maps for Lost Lovers, rural femininity in In Other Rooms, Other Wonders, and enlightened femininity in Moth Smoke. Through this study, I hope to widen the critical discourse about gender in relation to Pakistani anglophone fiction and contribute towards an expansion of scholarship seeking to interrogate and interpret Pakistani masculinities
Participation in the Pentecostal liturgy: an ecclesiology of the prophethood of all believers
This thesis develops an ecclesiology of participation in Pentecostalism by utilizing the concept of the prophethood of all believers as a theological and hermeneutical device to articulate how the laity can fully take part in the ritual life of the church. Pentecostalism as a liturgically diverse tradition composed of hierarchical and democratic types of churches that reflect both episcopal and non-episcopal ecclesiological models has created ambiguity in how the doctrine of the prophethood of all believers and the egalitarian nature of the church should be understood. Based on a perspective informed by pneumatology and Pentecost, this project provides a means to theologically convey how greater participation can take place in Pentecostal communities of worship through every believer’s empowerment with the Holy Spirit. The idea of the prophethood of all believers is projected onto the dominant rituals of the Pentecostal liturgy through an altar hermeneutic that allows for all members of the worshipping community to have a transformative encounter with God in dynamic fellowship with others. What results is a truly egalitarian view of church that directs entire communities of faith towards participation in Pentecost through the Spirit. Through critical analysis of and constructive theological engagement with the Pentecostal liturgy, the chapters of this thesis contribute to a better understanding of what is meant by “the altar” in the rites of Pentecostal worship
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