6,637 research outputs found
Satellite Image Based Cross-view Localization for Autonomous Vehicle
Existing spatial localization techniques for autonomous vehicles mostly use a
pre-built 3D-HD map, often constructed using a survey-grade 3D mapping vehicle,
which is not only expensive but also laborious. This paper shows that by using
an off-the-shelf high-definition satellite image as a ready-to-use map, we are
able to achieve cross-view vehicle localization up to a satisfactory accuracy,
providing a cheaper and more practical way for localization. While the
utilization of satellite imagery for cross-view localization is an established
concept, the conventional methodology focuses primarily on image retrieval.
This paper introduces a novel approach to cross-view localization that departs
from the conventional image retrieval method. Specifically, our method develops
(1) a Geometric-align Feature Extractor (GaFE) that leverages measured 3D
points to bridge the geometric gap between ground and overhead views, (2) a
Pose Aware Branch (PAB) adopting a triplet loss to encourage pose-aware feature
extraction, and (3) a Recursive Pose Refine Branch (RPRB) using the
Levenberg-Marquardt (LM) algorithm to align the initial pose towards the true
vehicle pose iteratively. Our method is validated on KITTI and Ford Multi-AV
Seasonal datasets as ground view and Google Maps as the satellite view. The
results demonstrate the superiority of our method in cross-view localization
with median spatial and angular errors within meter and ,
respectively.Comment: Accepted by ICRA202
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Ensuring Access to Safe and Nutritious Food for All Through the Transformation of Food Systems
Complement mediated synapse elimination in schizophrenia
Schizophrenia (SCZ) is a devastating psychiatric disorder with a typically age of onset in late adolescence. The heritability is estimated to be in between 60-80% and large-scale genome-wide studies have revealed a prominent polygenic component to SCZ risk and identified more than three-hundred common risk variants. Despite a better understanding of which genetic risk variants that increases SCZ risk, it has been challenging to map out the pathophysiology of the disorder. This has stalled the development of target drugs and current treatment options display moderate efficacy and are prone to produce side-effects. SCZ is generally considered a neurodevelopmental disorder and it was proposed more than forty years ago that physiological removal of less active synapses in adolescence, i.e., synaptic pruning, is increased in SCZ and hereby causes the core symptoms of the disorder.
This theory has then been supported by post-mortem brain tissue and imaging studies displaying decreased synapse density in SCZ. More recently, it was then shown that the most strongly associated risk loci can largely be explained by copy numbers of a gene coding for the complement factor 4A (C4A). As microglia prune synapses with the help of complement signalling, we therefore decided to use a recently developed human 2D in vitro assay to assess microglial uptake of synaptic structures in models based on cells from individuals with SCZ and healthy controls (study I). We observed excessive uptake of synaptic structures in SCZ models and by mixing synapses from healthy controls with microglia from SCZ patients, and vice versa, we showed the contribution of microglial and neuronal factors contributing to this excessive uptake of synaptic structures.
We then developed an in vitro assay to study neuronal complement deposition dependent on copy numbers of C4A in the neuronal lines. Complement 3 (C3) deposition increased by C4A copy numbers but was independent of C4B copy numbers (also unrelated to SCZ risk). Similar C4A copy numbers correlated with the extent of microglial uptake of synapses. Microglial uptake of synaptic structures could also be inhibited by the tetracycline minocycline that also decreased risk of developing SCZ in an electronic health record cohort.
In study II, we cerebrospinal fluid (CSF) from first-episode psychosis patients to measure protein levels of C4A. In two independent cohorts, we observed elevated C4A levels (although not C4B levels) in first-episode patients that later were to develop SCZ and could show correlations with markers of synapse density. However, elevated C4A levels could not fully be explained by more copy numbers of C4A in individuals with SCZ and in vitro experiments revealed that SCZ-associated cytokines can induce C4A mRNA expression while also correlating with C4A in patient-derived CSF.
In study III, we set-up a 3D brain organoid models to more fully comprehensively capture processes in the developing human brain and then also included innately developing microglia. We display synaptic pruning within these models and use single cell RNA sequencing to validate them.
In conclusion, this thesis uses patient-derived cellular modelling to uncover a disease mechanism in SCZ that link genetic risk variants with bona fide protein changes in living patients
Norsk rå kumelk, en kilde til zoonotiske patogener?
The worldwide emerging trend of eating “natural” foods, that has not been
processed, also applies for beverages. According to Norwegian legislation, all
milk must be pasteurized before commercial sale but drinking milk that has
not been heat-treated, is gaining increasing popularity. Scientist are warning
against this trend and highlights the risk of contracting disease from milkborne
microorganisms. To examine potential risks associated with drinking
unpasteurized milk in Norway, milk- and environmental samples were
collected from dairy farms located in south-east of Norway. The samples
were analyzed for the presence of specific zoonotic pathogens; Listeria
monocytogenes, Campylobacter spp., and Shiga toxin-producing Escherichia
coli (STEC). Cattle are known to be healthy carriers of these pathogens, and
Campylobacter spp. and STEC have a low infectious dose, meaning that
infection can be established by ingesting a low number of bacterial cells. L.
monocytogenes causes one of the most severe foodborne zoonotic diseases,
listeriosis, that has a high fatality rate. All three pathogens have caused milk
borne disease outbreaks all over the world, also in Norway.
During this work, we observed that the prevalence of the three examined
bacteria were high in the environment at the examined farms. In addition, 7%
of the milk filters were contaminated by STEC, 13% by L. monocytogenes and
4% by Campylobacter spp. Four of the STEC isolates detected were eaepositive,
which is associated with the capability to cause severe human
disease. One of the eae-positive STEC isolates were collected from a milk
filter, which strongly indicate that Norwegian raw milk may contain potential
pathogenic STEC.
To further assess the possibilities of getting ill by STEC after consuming raw
milk, we examined the growth of the four eae-positive STEC isolates in raw milk at different temperatures. All four isolates seemed to have ability to multiply in raw milk at 8°C, and one isolate had significant growth after 72 hours. Incubation at 6°C seemed to reduce the number of bacteria during the
first 24 hours before cell death stopped. These findings highlight the
importance of stable refrigerator temperatures, preferable < 4°C, for storage
of raw milk.
The L. monocytogenes isolates collected during this study show genetic
similarities to isolates collected from urban and rural environmental
locations, but different clones were predominant in agricultural
environments compared to clinical and food environments. However, the
results indicate that the same clone can persist in a farm over time, and that
milk can be contaminated by L. monocytogenes clones present in farm
environment.
Despite testing small volumes (25 mL) of milk, we were able to isolate both
STEC and Campylobacter spp. directly from raw milk. A proportion of 3% of
the bulk tank milk and teat milk samples were contaminated by
Campylobacter spp. and one STEC was isolated from bulk tank milk. L
monocytogenes was not detected in bulk tank milk, nor in teat milk samples.
The agricultural evolvement during the past decades have led to larger
production units and new food safety challenges. Dairy cattle production in
Norway is in a current transition from tie-stall housing with conventional
pipeline milking systems, to modern loose housing systems with robotic
milking. The occurrence of the three pathogens in this project were higher in
samples collected from farms with loose housing compared to those with tiestall
housing.
Pasteurization of cow’s milk is a risk reducing procedure to protect
consumers from microbial pathogens and in most EU countries, commercial
distribution of unpasteurized milk is legally restricted. Together, the results
presented in this thesis show that the animal housing may influence the level
of pathogenic bacteria in the raw milk and that ingestion of Norwegian raw
cow’s milk may expose consumers to pathogenic bacteria which can cause
severe disease, especially in children, elderly and in persons with underlying
diseases. The results also highlight the importance of storing raw milk at low
temperatures between milking and consumption.Å spise mat som er mindre prosessert og mer «naturlig» er en pågående
trend i Norge og i andre deler av verden. Interessen for å drikke melk som
ikke er varmebehandlet, såkalt rå melk, er også økende. I Norge er det påbudt
å pasteurisere melk før kommersielt salg for å beskytte forbrukeren mot
sykdomsfremkallende mikroorganismer. Fagfolk advarer mot å drikke rå
melk, og påpeker risikoen for å bli syk av patogene bakterier som kan finnes i
melken.
I denne avhandlingen undersøker vi den potensielle risikoen det medfører å
drikke upasteurisert melk fra Norge. I tillegg til å samle inn tankmelk- og
speneprøver fra melkegårder i sørøst Norge, samlet vi også miljøprøver fra
de samme gårdene for å kartlegge forekomst og for å identifisere potensielle
mattrygghetsrisikoer i melkeproduksjonen. Alle prøvene ble analysert for de
zoonotiske sykdomsfremkallende bakteriene Listeria monocytogenes,
Campylobacter spp., og Shiga toksin-produserende Escherichia coli (STEC).
Kyr kan være friske smittebærere av disse bakteriene, som dermed kan
etablere et reservoar på gårdene. Bakteriene kan overføres fra gårdsmiljøet
til melkekjeden og dermed utfordre mattryggheten. Disse bakteriene har
forårsaket melkebårne sykdomsutbrudd over hele verden, også i Norge.
Campylobacter spp. og STEC har lav infeksiøs dose, som vil si at man kan bli
syk selv om man bare inntar et lavt antall bakterieceller. L. monocytogenes
kan gi sykdommen listeriose, en av de mest alvorlige matbårne zoonotiske
sykdommene vi har i den vestlige verden.
Resultater fra denne oppgaven viser en høy forekomst av de tre patogenene i
gårdsmiljøet. I tillegg var 7% av melkefiltrene vi testet positive for STEC, 13%
positive for L. monocytogenes og 4% positive for Campylobacter spp.. Fire av
STEC isolatene bar genet for Intimin, eae, som er ansett som en viktig
virulensfaktor som øker sjansen for alvorlig sykdom. Ett av de eae-positive
isolatene ble funnet i et melkefilter, noe som indikerer at norsk rå melk kan
inneholde patogene STEC. For å videre vurdere risikoen for å bli syk av STEC
fra rå melk undersøkte vi hvordan de fire eae-positive isolatene vokste i rå
melk lagret ved forskjellige temperaturer. For alle isolatene økte antall
bakterier etter lagring ved 8°C, og for et isolat var veksten signifikant. Etter
lagring ved 6°C ble antallet bakterier redusert de første 24 timene, deretter
stoppet reduksjonen i antall bakterier. Disse resultatene viser hvor viktig det
er å ha stabil lav lagringstemperatur for rå melk, helst < 4°C.
L. monocytogenes isolatene som ble samlet inn fra melkegårdene viste
genetiske likheter med isolater samlet inn fra urbane og rurale miljøer rundt
omkring i Norge. Derimot var kloner som dominerte i landbruksmiljøet
forskjellige fra kliniske isolater og isolater fra matproduksjonslokaler. Videre
så man at en klone kan persistere på en gård over tid og at melk kan
kontamineres av L. monocytogenes kloner som er til stede i gårdsmiljøet.
Til tross for små testvolum av tankmelken (25 mL) fant vi både STEC og
Campylobacter spp. i melkeprøvene. 3% av tankmelkprøvene og
speneprøvene var positive for Campylobacter spp. og ett STEC isolat ble
funnet i tankmelk. L. monocytogenes ble ikke funnet direkte i melkeprøvene.
Landbruket i Norge er i stadig utvikling der besetningene blir større, men
færre. Melkebesetningene er midt i en overgang der tradisjonell oppstalling
med melking på bås byttes ut med løsdriftssystemer og melkeroboter.
Forekomsten av de tre patogenene funnet i denne studien var høyere i
besetningene med løsdrift sammenliknet med besetningene som hadde
melkekyrne oppstallet på bås.
Pasteurisering er et viktig forebyggende tiltak for å beskytte konsumenter fra
mikrobielle patogener, og i de fleste EU-land er kommersielt salg av rå melk
juridisk begrenset. Denne studien viser at oppstallingstype kan påvirke
nivåene av patogene bakterier i gårdsmiljøet og i rå melk. Inntak av rå melk
kan eksponere forbruker for patogene bakterier som kan gi alvorlig sykdom,
spesielt hos barn, eldre og personer med underliggende sykdommer.
Resultatene underbygger viktigheten av å pasteurisere melk for å sikre
mattryggheten, og at det er avgjørende å lagre rå melk ved kontinuerlig lave
temperaturer for å forebygge vekst av zoonotiske patogener
Anuário científico da Escola Superior de Tecnologia da Saúde de Lisboa - 2021
É com grande prazer que apresentamos a mais recente edição (a 11.ª) do Anuário Científico da Escola Superior de Tecnologia da Saúde de Lisboa. Como instituição de ensino superior, temos o compromisso de promover e incentivar a pesquisa científica em todas as áreas do conhecimento que contemplam a nossa missão. Esta publicação tem como objetivo divulgar toda a produção científica desenvolvida pelos Professores, Investigadores, Estudantes e Pessoal não Docente da ESTeSL durante 2021. Este Anuário é, assim, o reflexo do trabalho árduo e dedicado da nossa comunidade, que se empenhou na produção de conteúdo científico de elevada qualidade e partilhada com a Sociedade na forma de livros, capítulos de livros, artigos publicados em revistas nacionais e internacionais, resumos de comunicações orais e pósteres, bem como resultado dos trabalhos de 1º e 2º ciclo. Com isto, o conteúdo desta publicação abrange uma ampla variedade de tópicos, desde temas mais fundamentais até estudos de aplicação prática em contextos específicos de Saúde, refletindo desta forma a pluralidade e diversidade de áreas que definem, e tornam única, a ESTeSL. Acreditamos que a investigação e pesquisa científica é um eixo fundamental para o desenvolvimento da sociedade e é por isso que incentivamos os nossos estudantes a envolverem-se em atividades de pesquisa e prática baseada na evidência desde o início dos seus estudos na ESTeSL. Esta publicação é um exemplo do sucesso desses esforços, sendo a maior de sempre, o que faz com que estejamos muito orgulhosos em partilhar os resultados e descobertas dos nossos investigadores com a comunidade científica e o público em geral. Esperamos que este Anuário inspire e motive outros estudantes, profissionais de saúde, professores e outros colaboradores a continuarem a explorar novas ideias e contribuir para o avanço da ciência e da tecnologia no corpo de conhecimento próprio das áreas que compõe a ESTeSL. Agradecemos a todos os envolvidos na produção deste anuário e desejamos uma leitura inspiradora e agradável.info:eu-repo/semantics/publishedVersio
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The Epidemiology and Genetic Architecture of Vitamin D Deficiency in African Children
Vitamin D deficiency is a common public health problem worldwide. However, little is known about the epidemiology of vitamin D deficiency in Africa. In this thesis, I aimed to determine: 1) the prevalence of and risk factors associated with vitamin D deficiency in studies conducted in Africa; 2) the prevalence and predictors of vitamin D deficiency in African children; 3) the association between vitamin D and iron deficiency in African children; and 4) genetic variants that influence vitamin D status in Africans.
In a systematic review and meta-analyses of previous vitamin D studies in Africa, the average prevalence of low vitamin D status was 18.5%, 34.2% and 59.5% using cut-offs of 25-hydroxyvitamin D (25(OH)D) levels of <30 nmol/L, <50 nmol/L and <75 nmol/L, respectively. Populations at risk of vitamin D deficiency included newborns, women, and people living in high latitudes or urban areas.
In an epidemiological study of young children living in Africa, the prevalence of low vitamin D status was 0.6%, 7.8% and 44.5% using cut-offs of 25(OH)D levels of GC2 variant of the group-specific component (GC) gene, which encodes vitamin D binding protein.
Vitamin D deficiency was also associated with 80% higher odds of iron deficiency in these children. Adjusted regression models revealed that vitamin D deficiency was associated with higher ferritin and hepcidin levels suggesting lower iron status, and reduced sTfR and transferrin levels and increased TSAT and serum iron levels suggesting improved iron status.
Genome-wide association study (GWAS) in Africans revealed genetic variants that influence vitamin D status in vitamin D metabolism genes: DHCR7/NADSYN1, CYP2R1 and GC. However, the majority of SNPs from previous European GWASs did not replicate in the current GWAS.
Findings from this thesis indicate that vitamin D deficiency is prevalent in many African populations and should be considered in public health strategies in Africa
Learning disentangled speech representations
A variety of informational factors are contained within the speech signal and a single short recording of speech reveals much more than the spoken words. The best method to extract and represent informational factors from the speech signal ultimately depends on which informational factors are desired and how they will be used. In addition, sometimes methods will capture more than one informational factor at the same time such as speaker identity, spoken content, and speaker prosody.
The goal of this dissertation is to explore different ways to deconstruct the speech signal into abstract representations that can be learned and later reused in various speech technology tasks. This task of deconstructing, also known as disentanglement, is a form of distributed representation learning. As a general approach to disentanglement, there are some guiding principles that elaborate what a learned representation should contain as well as how it should function. In particular, learned representations should contain all of the requisite information in a more compact manner, be interpretable, remove nuisance factors of irrelevant information, be useful in downstream tasks, and independent of the task at hand. The learned representations should also be able to answer counter-factual questions.
In some cases, learned speech representations can be re-assembled in different ways according to the requirements of downstream applications. For example, in a voice conversion task, the speech content is retained while the speaker identity is changed. And in a content-privacy task, some targeted content may be concealed without affecting how surrounding words sound. While there is no single-best method to disentangle all types of factors, some end-to-end approaches demonstrate a promising degree of generalization to diverse speech tasks.
This thesis explores a variety of use-cases for disentangled representations including phone recognition, speaker diarization, linguistic code-switching, voice conversion, and content-based privacy masking. Speech representations can also be utilised for automatically assessing the quality and authenticity of speech, such as automatic MOS ratings or detecting deep fakes. The meaning of the term "disentanglement" is not well defined in previous work, and it has acquired several meanings depending on the domain (e.g. image vs. speech). Sometimes the term "disentanglement" is used interchangeably with the term "factorization". This thesis proposes that disentanglement of speech is distinct, and offers a viewpoint of disentanglement that can be considered both theoretically and practically
Estudo da remodelagem reversa miocárdica através da análise proteómica do miocárdio e do líquido pericárdico
Valve replacement remains as the standard therapeutic option for aortic
stenosis patients, aiming at abolishing pressure overload and triggering
myocardial reverse remodeling. However, despite the instant hemodynamic
benefit, not all patients show complete regression of myocardial hypertrophy,
being at higher risk for adverse outcomes, such as heart failure. The current
comprehension of the biological mechanisms underlying an incomplete reverse
remodeling is far from complete. Furthermore, definitive prognostic tools and
ancillary therapies to improve the outcome of the patients undergoing valve
replacement are missing. To help abridge these gaps, a combined myocardial
(phospho)proteomics and pericardial fluid proteomics approach was followed,
taking advantage of human biopsies and pericardial fluid collected during
surgery and whose origin anticipated a wealth of molecular information
contained therein.
From over 1800 and 750 proteins identified, respectively, in the myocardium
and in the pericardial fluid of aortic stenosis patients, a total of 90 dysregulated
proteins were detected. Gene annotation and pathway enrichment analyses,
together with discriminant analysis, are compatible with a scenario of increased
pro-hypertrophic gene expression and protein synthesis, defective ubiquitinproteasome system activity, proclivity to cell death (potentially fed by
complement activity and other extrinsic factors, such as death receptor
activators), acute-phase response, immune system activation and fibrosis.
Specific validation of some targets through immunoblot techniques and
correlation with clinical data pointed to complement C3 β chain, Muscle Ring
Finger protein 1 (MuRF1) and the dual-specificity Tyr-phosphorylation
regulated kinase 1A (DYRK1A) as potential markers of an incomplete
response. In addition, kinase prediction from phosphoproteome data suggests
that the modulation of casein kinase 2, the family of IκB kinases, glycogen
synthase kinase 3 and DYRK1A may help improve the outcome of patients
undergoing valve replacement. Particularly, functional studies with DYRK1A+/-
cardiomyocytes show that this kinase may be an important target to treat
cardiac dysfunction, provided that mutant cells presented a different response
to stretch and reduced ability to develop force (active tension).
This study opens many avenues in post-aortic valve replacement reverse
remodeling research. In the future, gain-of-function and/or loss-of-function
studies with isolated cardiomyocytes or with animal models of aortic bandingdebanding will help disclose the efficacy of targeting the surrogate therapeutic
targets. Besides, clinical studies in larger cohorts will bring definitive proof of
complement C3, MuRF1 and DYRK1A prognostic value.A substituição da válvula aórtica continua a ser a opção terapêutica de
referência para doentes com estenose aórtica e visa a eliminação da
sobrecarga de pressão, desencadeando a remodelagem reversa miocárdica.
Contudo, apesar do benefício hemodinâmico imediato, nem todos os pacientes
apresentam regressão completa da hipertrofia do miocárdio, ficando com maior
risco de eventos adversos, como a insuficiência cardíaca. Atualmente, os
mecanismos biológicos subjacentes a uma remodelagem reversa incompleta
ainda não são claros. Além disso, não dispomos de ferramentas de
prognóstico definitivos nem de terapias auxiliares para melhorar a condição
dos pacientes indicados para substituição da válvula. Para ajudar a resolver
estas lacunas, uma abordagem combinada de (fosfo)proteómica e proteómica
para a caracterização, respetivamente, do miocárdio e do líquido pericárdico
foi seguida, tomando partido de biópsias e líquidos pericárdicos recolhidos em
ambiente cirúrgico.
Das mais de 1800 e 750 proteínas identificadas, respetivamente, no miocárdio
e no líquido pericárdico dos pacientes com estenose aórtica, um total de 90
proteínas desreguladas foram detetadas. As análises de anotação de genes,
de enriquecimento de vias celulares e discriminativa corroboram um cenário de
aumento da expressão de genes pro-hipertróficos e de síntese proteica, um
sistema ubiquitina-proteassoma ineficiente, uma tendência para morte celular
(potencialmente acelerada pela atividade do complemento e por outros fatores
extrínsecos que ativam death receptors), com ativação da resposta de fase
aguda e do sistema imune, assim como da fibrose.
A validação de alguns alvos específicos através de immunoblot e correlação
com dados clínicos apontou para a cadeia β do complemento C3, a Muscle
Ring Finger protein 1 (MuRF1) e a dual-specificity Tyr-phosphoylation
regulated kinase 1A (DYRK1A) como potenciais marcadores de uma resposta
incompleta. Por outro lado, a predição de cinases a partir do fosfoproteoma,
sugere que a modulação da caseína cinase 2, a família de cinases do IκB, a
glicogénio sintase cinase 3 e da DYRK1A pode ajudar a melhorar a condição
dos pacientes indicados para intervenção. Em particular, a avaliação funcional
de cardiomiócitos DYRK1A+/- mostraram que esta cinase pode ser um alvo
importante para tratar a disfunção cardíaca, uma vez que os miócitos mutantes
responderam de forma diferente ao estiramento e mostraram uma menor
capacidade para desenvolver força (tensão ativa).
Este estudo levanta várias hipóteses na investigação da remodelagem reversa.
No futuro, estudos de ganho e/ou perda de função realizados em
cardiomiócitos isolados ou em modelos animais de banding-debanding da
aorta ajudarão a testar a eficácia de modular os potenciais alvos terapêuticos
encontrados. Além disso, estudos clínicos em coortes de maior dimensão
trarão conclusões definitivas quanto ao valor de prognóstico do complemento
C3, MuRF1 e DYRK1A.Programa Doutoral em Biomedicin
Gasificação direta de biomassa para produção de gás combustível
The excessive consumption of fossil fuels to satisfy the world necessities of
energy and commodities led to the emission of large amounts of greenhouse
gases in the last decades, contributing significantly to the greatest
environmental threat of the 21st century: Climate Change. The answer to this
man-made disaster is not simple and can only be made if distinct stakeholders
and governments are brought to cooperate and work together. This is
mandatory if we want to change our economy to one more sustainable and
based in renewable materials, and whose energy is provided by the eternal
nature energies (e.g., wind, solar). In this regard, biomass can have a main role
as an adjustable and renewable feedstock that allows the replacement of fossil
fuels in various applications, and the conversion by gasification allows the
necessary flexibility for that purpose. In fact, fossil fuels are just biomass that
underwent extreme pressures and heat for millions of years. Furthermore,
biomass is a resource that, if not used or managed, increases wildfire risks.
Consequently, we also have the obligation of valorizing and using this
resource.
In this work, it was obtained new scientific knowledge to support the
development of direct (air) gasification of biomass in bubbling fluidized bed
reactors to obtain a fuel gas with suitable properties to replace natural gas in
industrial gas burners. This is the first step for the integration and development
of gasification-based biorefineries, which will produce a diverse number of
value-added products from biomass and compete with current petrochemical
refineries in the future. In this regard, solutions for the improvement of the raw
producer gas quality and process efficiency parameters were defined and
analyzed. First, addition of superheated steam as primary measure allowed the
increase of H2 concentration and H2/CO molar ratio in the producer gas without
compromising the stability of the process. However, the measure mainly
showed potential for the direct (air) gasification of high-density biomass (e.g.,
pellets), due to the necessity of having char accumulation in the reactor bottom
bed for char-steam reforming reactions. Secondly, addition of refused derived
fuel to the biomass feedstock led to enhanced gasification products, revealing
itself as a highly promising strategy in terms of economic viability and
environmental benefits of future gasification-based biorefineries, due to the
high availability and low costs of wastes. Nevertheless, integrated techno economic and life cycle analyses must be performed to fully characterize the
process. Thirdly, application of low-cost catalyst as primary measure revealed
potential by allowing the improvement of the producer gas quality (e.g., H2 and
CO concentration, lower heating value) and process efficiency parameters with
distinct solid materials; particularly, the application of concrete, synthetic
fayalite and wood pellets chars, showed promising results. Finally, the
economic viability of the integration of direct (air) biomass gasification
processes in the pulp and paper industry was also shown, despite still lacking
interest to potential investors. In this context, the role of government policies
and appropriate economic instruments are of major relevance to increase the
implementation of these projects.O consumo excessivo de combustíveis fósseis para garantir as necessidades e
interesses da sociedade conduziu à emissão de elevadas quantidades de
gases com efeito de estufa nas últimas décadas, contribuindo
significativamente para a maior ameaça ambiental do século XXI: Alterações
Climáticas. A solução para este desastre de origem humana é de caráter
complexo e só pode ser atingida através da cooperação de todos os governos
e partes interessadas. Para isto, é obrigatória a criação de uma bioeconomia
como base de um futuro mais sustentável, cujas necessidades energéticas e
materiais sejam garantidas pelas eternas energias da natureza (e.g., vento,
sol). Neste sentido, a biomassa pode ter um papel principal como uma matéria prima ajustável e renovável que permite a substituição de combustíveis fósseis
num variado número de aplicações, e a sua conversão através da gasificação
pode ser a chave para este propósito. Afinal, na prática, os combustíveis
fósseis são apenas biomassa sujeita a elevada temperatura e pressão durante
milhões de anos. Além do mais, a gestão eficaz da biomassa é fundamental
para a redução dos riscos de incêndio florestal e, como tal, temos o dever de
utilizar e valorizar este recurso.
Neste trabalho, foi obtido novo conhecimento científico para suporte do
desenvolvimento das tecnologias de gasificação direta (ar) de biomassa em
leitos fluidizados borbulhantes para produção de gás combustível, com o
objetivo da substituição de gás natural em queimadores industriais. Este é o
primeiro passo para o desenvolvimento de biorrefinarias de gasificação, uma
potencial futura indústria que irá providenciar um variado número de produtos
de valor acrescentado através da biomassa e competir com a atual indústria
petroquímica. Neste sentido, foram analisadas várias medidas para a melhoria
da qualidade do gás produto bruto e dos parâmetros de eficiência do processo.
Em primeiro, a adição de vapor sobreaquecido como medida primária permitiu
o aumento da concentração de H2 e da razão molar H2/CO no gás produto sem
comprometer a estabilidade do processo. No entanto, esta medida somente
revelou potencial para a gasificação direta (ar) de biomassa de alta densidade
(e.g., pellets) devido à necessidade da acumulação de carbonizados no leito
do reator para a ocorrência de reações de reforma com vapor. Em segundo, a
mistura de combustíveis derivados de resíduos e biomassa residual florestal
permitiu a melhoria dos produtos de gasificação, constituindo desta forma uma
estratégia bastante promissora a nível económico e ambiental, devido à
elevada abundância e baixo custo dos resíduos urbanos. Contudo, devem ser
efetuadas análises técnico-económicas e de ciclo de vida para a completa
caraterização do processo. Em terceiro, a aplicação de catalisadores de baixo
custo como medida primária demonstrou elevado potencial para a melhoria do
gás produto (e.g., concentração de H2 e CO, poder calorífico inferior) e para o
incremento dos parâmetros de eficiência do processo; em particular, a
aplicação de betão, faialite sintética e carbonizados de pellets de madeira,
demonstrou resultados promissores. Finalmente, foi demonstrada a viabilidade
económica da integração do processo de gasificação direta (ar) de biomassa
na indústria da pasta e papel, apesar dos parâmetros determinados não serem
atrativos para potenciais investidores. Neste contexto, a intervenção dos
governos e o desenvolvimento de instrumentos de apoio económico é de
grande relevância para a implementação destes projetos.Este trabalho foi financiado pela The Navigator Company e por Fundos Nacionais através da Fundação para a Ciência e a Tecnologia (FCT).Programa Doutoral em Engenharia da Refinação, Petroquímica e Químic
Image classification over unknown and anomalous domains
A longstanding goal in computer vision research is to develop methods that are simultaneously applicable to a broad range of prediction problems. In contrast to this, models often perform best when they are specialized to some task or data type. This thesis investigates the challenges of learning models that generalize well over multiple unknown or anomalous modes and domains in data, and presents new solutions for learning robustly in this setting.
Initial investigations focus on normalization for distributions that contain multiple sources (e.g. images in different styles like cartoons or photos). Experiments demonstrate the extent to which existing modules, batch normalization in particular, struggle with such heterogeneous data, and a new solution is proposed that can better handle data from multiple visual modes, using differing sample statistics for each.
While ideas to counter the overspecialization of models have been formulated in sub-disciplines of transfer learning, e.g. multi-domain and multi-task learning, these usually rely on the existence of meta information, such as task or domain labels. Relaxing this assumption gives rise to a new transfer learning setting, called latent domain learning in this thesis, in which training and inference are carried out over data from multiple visual domains, without domain-level annotations. Customized solutions are required for this, as the performance of standard models degrades: a new data augmentation technique that interpolates between latent domains in an unsupervised way is presented, alongside a dedicated module that sparsely accounts for hidden domains in data, without requiring domain labels to do so.
In addition, the thesis studies the problem of classifying previously unseen or anomalous modes in data, a fundamental problem in one-class learning, and anomaly detection in particular. While recent ideas have been focused on developing self-supervised solutions for the one-class setting, in this thesis new methods based on transfer learning are formulated. Extensive experimental evidence demonstrates that a transfer-based perspective benefits new problems that have recently been proposed in anomaly detection literature, in particular challenging semantic detection tasks
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