11,219 research outputs found
The Viability and Potential Consequences of IoT-Based Ransomware
With the increased threat of ransomware and the substantial growth of the Internet of Things (IoT) market, there is significant motivation for attackers to carry out IoT-based ransomware campaigns. In this thesis, the viability of such malware is tested.
As part of this work, various techniques that could be used by ransomware developers to attack commercial IoT devices were explored. First, methods that attackers could use to communicate with the victim were examined, such that a ransom note was able to be reliably sent to a victim. Next, the viability of using "bricking" as a method of ransom was evaluated, such that devices could be remotely disabled unless the victim makes a payment to the attacker. Research was then performed to ascertain whether it was possible to remotely gain persistence on IoT devices, which would improve the efficacy of existing ransomware methods, and provide opportunities for more advanced ransomware to be created. Finally, after successfully identifying a number of persistence techniques, the viability of privacy-invasion based ransomware was analysed.
For each assessed technique, proofs of concept were developed. A range of devices -- with various intended purposes, such as routers, cameras and phones -- were used to test the viability of these proofs of concept. To test communication hijacking, devices' "channels of communication" -- such as web services and embedded screens -- were identified, then hijacked to display custom ransom notes. During the analysis of bricking-based ransomware, a working proof of concept was created, which was then able to remotely brick five IoT devices. After analysing the storage design of an assortment of IoT devices, six different persistence techniques were identified, which were then successfully tested on four devices, such that malicious filesystem modifications would be retained after the device was rebooted. When researching privacy-invasion based ransomware, several methods were created to extract information from data sources that can be commonly found on IoT devices, such as nearby WiFi signals, images from cameras, or audio from microphones. These were successfully implemented in a test environment such that ransomable data could be extracted, processed, and stored for later use to blackmail the victim.
Overall, IoT-based ransomware has not only been shown to be viable but also highly damaging to both IoT devices and their users. While the use of IoT-ransomware is still very uncommon "in the wild", the techniques demonstrated within this work highlight an urgent need to improve the security of IoT devices to avoid the risk of IoT-based ransomware causing havoc in our society. Finally, during the development of these proofs of concept, a number of potential countermeasures were identified, which can be used to limit the effectiveness of the attacking techniques discovered in this PhD research
The impact of innovative technologies in construction activities on concrete debris recycling in China : a system dynamics-based analysis
As construction activities become more intensive in developing countries, increasing improperly managed construction and demolition waste (CDW) brings serious environmental impacts. Recycling is a beneficial way to dispose of CDW that reduces environmental impact and brings economic benefits, especially for concrete. China is the country that generates the most CDW in the world, but its domestic recycling rate is much lower than that of developed countries. While the efficient technologies in developed regions have helped them to achieve a well-established recycling industry, whether these innovative technologies can be used to improve the concrete debris recycling targets in developing regions is unclear. This study examines whether innovations currently widely used in construction activities and materials can have a positive effect on the recycling of End-of-Life concrete materials in China. Results from modeling system dynamics imply that the introduction of innovative technologies in the recycling system of concrete debris can probably contribute to CO2 reduction (3.6% reduction) and economic benefits (2.6 times increase, but mainly from landfill charges and fines) from 2022 to 2030. Prefabrication and 3D printing significantly impact recycled concrete production and CDW recycling, and they are recommended as a priority for promotion. In contrast, carbonation is not suggested for application due to its minor role. Nevertheless, since the market share of innovative technologies and the basic CDW recycling rates are currently low in China, fluctuations in their usage are hardly to have a substantial positive impact. We suggest that financial support from the government is needed for upcycling by recyclers and technology providers to improve the base recycling rate in order for innovative technologies to make an effective contribution to the sustainable construction industry, creating a win–win situation for both the economy and the environment of the recycling system
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
Towards Reuse and Recycling of Lithium-ion Batteries: Tele-robotics for Disassembly of Electric Vehicle Batteries
Disassembly of electric vehicle batteries is a critical stage in recovery,
recycling and re-use of high-value battery materials, but is complicated by
limited standardisation, design complexity, compounded by uncertainty and
safety issues from varying end-of-life condition. Telerobotics presents an
avenue for semi-autonomous robotic disassembly that addresses these challenges.
However, it is suggested that quality and realism of the user's haptic
interactions with the environment is important for precise, contact-rich and
safety-critical tasks. To investigate this proposition, we demonstrate the
disassembly of a Nissan Leaf 2011 module stack as a basis for a comparative
study between a traditional asymmetric haptic-'cobot' master-slave framework
and identical master and slave cobots based on task completion time and success
rate metrics. We demonstrate across a range of disassembly tasks a time
reduction of 22%-57% is achieved using identical cobots, yet this improvement
arises chiefly from an expanded workspace and 1:1 positional mapping, and
suffers a 10-30% reduction in first attempt success rate. For unbolting and
grasping, the realism of force feedback was comparatively less important than
directional information encoded in the interaction, however, 1:1 force mapping
strengthened environmental tactile cues for vacuum pick-and-place and contact
cutting tasks.Comment: 21 pages, 12 figures, Submitted to Frontiers in Robotics and AI;
Human-Robot Interactio
Long term clinical results following Salto Talaris total ankle arthroplasty
INTRODUCTION: Total ankle arthroplasty is a surgery that is being performed at an increasing rate. As this is a fairly new procedure in the realm of orthopedics, there is limited data on the survival ship of modern fixed-bearing total ankle replacements. With increased prevalence around the country, more long-term data is required to determine the expected survival of the implant, as well as common complications over the long-term. This study seeks to follow-up on our previous mean 5.2-year study to determine implant survival of a modern fixed-bearing total ankle arthroplasty performed by a single surgeon. The specific model in question is the Salto Talaris TAA system. It is hypothesized that the survival of the metallic component of the implant will decrease dramatically compared to the previous follow-up, as the implant reaches its lifespan.
METHODS: We reviewed the charts of 78 consecutive patients (81 ankles) that were involved in a previous mean 5.2-year study. Of these 78 patients, 63 were still living of which we were able to follow-up with 45 (87.2%) of them (47 ankles). From the 45 patients we followed up with 31 of these patients (33 ankles) completed self-reported questionnaires, including the visual analog scale (VAS) for pain, the Short Form (SF)-36v2, and the Foot and Ankle Disability Index (FADI). At each follow-up visit patients underwent range-of-motion examination and radiographic evaluation of the implant. Updated radiographs were obtained on 34 of the patients.
RESULTS: Implant survival of the metallic components of the cohort was 87.5% at a mean follow-up time of 10.1 years. There were a total of six revisions, one of which was complicated by a deep infection and explant after revision surgery. 17 ankles required subsequent surgery after the index total ankle replacement, with gutter debridement being the most common (n = 10). Outcome scores at a mean of 10.1 years revealed promising and stable scores from the 5.2-year study with a mean VAS pain of 18.5 and FADI of 77.7. Mean total range of motion was 35.7º.
CONCLUSION: Salto Talaris fixed-bearing total ankle arthroplasty had excellent implant survival, maintained range of motion, and good functional outcomes at a mean follow-up of 10.1 years. This study provided evidence that total ankle arthroplasty is a viable long-term alternative to ankle arthrodesis for the treatment of end-stage arthritis, but more prospective research is needed to justify this claim
EVALUACIÓN ANALGÉSICA PERIOPERATORIA DEL ACETAMINOFÉN EN PERRAS SOMETIDAS A OVARIOHISTERECTOMÍA ELECTIVA
Tesis de doctorado que evalúa el efecto analgésico del acetaminofén en perras ovarihisterectomizadas.La administración de analgésicos antiinflamatorios no esteroidales (AINES) para el control del
dolor post-quirúrgico en perros es una práctica común, debido a sus efectos analgésicos,
antiinflamatorios y antipiréticos. En el presente trabajo se realizaron dos estudios. En el
experimento 1, el objetivo fue evaluar la analgesia post-operatoria del acetaminofén
(paracetamol) a través de la utilización de las escalas de reconocimiento clínico del dolor
DIVAS (Escala Dinámica e Interactiva Analógica Visual) y UMPS (Escala de la Universidad
de Melbourne), en perras sometidas a ovariohisterectomía electiva. Además de valorar la
seguridad y eficacia clínica del uso del acetaminofén en perros mediante pruebas de
funcionamiento hepático y renal en el post-operatorio inmediato. Para ello, se utilizaron 30
perras de diferentes razas que fueron asignadas aleatoriamente a uno de los tres grupos de
tratamiento: acetaminofén [GACET; n=10, 15 mg kg-1 intravenoso (IV)], carprofeno (GCARP;
n=10, 4 mg kg-1 IV) y meloxicam (GMELOX; n=10, 0.2 mg kg-1 IV). Todos los tratamientos se
administraron 30 minutos antes de la cirugía y posterior a esta durante 48 horas. En este período
el acetaminofén se administró por vía oral cada 8 horas (15 mg kg-1); el carprofeno (4 mg kg-1)
y el meloxicam (0.1 mg kg-1) se administraron por vía IV cada 24 horas. Durante el
postoperatorio, los sistemas de puntuación del dolor DIVAS y UMPS fueron medidos a las 1,
2, 4, 6, 8, 12, 16, 20, 24, 36 y 48 horas post-cirugía. Para evaluar la seguridad clínica de los
tratamientos, se recolectaron muestras de sangre de la vena yugular para realizar la medición de
enzimas ALT, AST, ALP, y los metabolitos bilirrubina directa, bilirrubina indirecta, bilirrubina
total, creatinina, urea, albúmina y glucosa. Esto fue realizado en T0 (pre-anestesia; TBASAL), 48
y 96 horas después de la cirugía (T48, T96). Los resultados indican que en la evaluación clínica
del dolor de todos los grupos de estudio, hubo una reducción gradual en la percepción del mismo
durante el postoperatorio en ambos sistemas de puntuación; no obstante, también fue observado
que ninguna escala difirió significativamente entre los tres grupos de tratamiento (P>0.05) en
cada momento de evaluación durante las 48 horas post-cirugía. En cuanto a los parámetros
bioquímico séricos, sólo la ALT aumentó significativamente en T96 en el GACET y GCARP con
respecto a los valores basales (P<0.01). El resto de los analitos séricos evaluados se mantuvo
en rangos normales. En el experimento 2 bajo el mismo diseño experimental de tratamientos
administrados, el objetivo fue evaluar el efecto analgésico perioperatorio del acetaminofén
2
administrado pre y post-quirúrgicamente en perras sometidas a ovariohisterectomía electiva a
través de la medición del índice de la actividad del tono parasimpático (PTA). Este parámetro
hemodinámico fue medido 60 minutos antes de la cirugía (TBASAL) y durante el transquirúrgico
en la aplicación de estímulos nociceptivos: colocación de las pinzas de campo backhouse
(TPINZ), incisión de piel y abordaje quirúrgico primario (TINC), ligadura y extracción de pedículo
ovárico izquierdo (TOVI) y derecho (TOVD), ligadura y transfixión del cuello uterino (TLIGUT),
sección quirúrgica del cuello uterino (TCUT), reconstrucción de peritoneo y planos anatómicos
musculares (TMUSC) y sutura de piel (TSUT). Durante el postoperatorio, el índice PTA fue
valorado a las 1, 2, 4, 6, 8, 12, 16, 20, 24, 36 y 48 horas, en los mismos tiempos en que fueron
evaluadas las escalas de reconocimiento de dolor DIVAS y UMPS. Los resultados obtenidos en
la medición del índice PTA basal para GACET fue 65 ± 8, para GCARP 65 ± 7 y para GMELOX 62 ±
5. Durante los diferentes tiempos transquirúrgicos, los valores promedio de índice PTA indican
que GACET (76 ± 14) y GMELOX (72 ± 18) muestran tendencia a manifestar mayores niveles en
comparación con GCARP (62 ± 13) desde el inicio del procedimiento quirúrgico sin que esto
pudiera comprobarse estadísticamente, ya que no hubo diferencias significativas entre grupos
de tratamiento ni entre los tiempos quirúrgicos evaluados (P>0.05). En el postoperatorio, el
índice PTA fue de 65 ± 9 en el GACET, 63 ± 8 en el GCARP y 65 ± 8 en el GMELOX. Los resultados
tampoco mostraron diferencias estadísticamente significativas con los valores basales o entre
los tratamientos (P>0.05). El índice PTA postoperatorio mostró una sensibilidad del 40%,
especificidad del 98.46% y valor predictivo negativo del 99.07% con respecto a la escala
validada de UMPS. En conclusión, el acetaminofén puede considerarse una herramienta para el
tratamiento efectivo del dolor perioperatorio agudo en perros, ya que mostró la misma eficacia
clínica que el meloxicam y el carprofeno para la analgesia postquirúrgica en perras sometidas a
ovariohisterectomía electiva. Además, la evidencia del uso de este medicamento no condujo a
reacciones adversas o cambios en los parámetros evaluados, lo que indica su seguridad clínica.
Finalmente, destacar que el índice PTA representa una medición objetiva del comfort y
analgesia postoperatoria, por lo que es una herramienta que podría ayudar a predecir las
respuestas hemodinámicas asociadas con el dolor
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
Proof of Concept of Therapeutic Gene Modulation of MBNL1/2 in Myotonic Dystrophy
La distrofia miotónica tipo 1 es una enfermedad genética rara multisistémica que afecta a 1 de cada 3000-8000 personas. La causa molecular de la enfermedad proviene de repeticiones tóxicas “CTG” en el gen DMPK (DM Protein Kinase). Tras la transcripción, estas repeticiones forman una estructura de horquilla que se une con alta afinidad a la familia de proteínas MBNL (Muscleblind-like) que agota su función de regulación de la poliadenilación y el splicing alternativo postranscripcional en numerosos transcritos. La pérdida de función de MBNL provoca una cascada de efectos posteriores, que eventualmente conducen a síntomas clínicos que incluyen miotonía, debilidad y atrofia muscular, cataratas, disfunción cardíaca y trastorno cognitivo. La restauración de la función de la proteína MBNL es clave para aliviar los síntomas debilitantes de esta enfermedad. Se han utilizado oligonucleótidos antisentido (AON) para apuntar a las repeticiones de DMPK y liberar MBNL del secuestro, lo que da como resultado resultados terapéuticos prometedores en modelos celulares y animales de la enfermedad. Otro factor que interviene en la pérdida de función de las proteínas MBNL son los miRNAs que regulan su traducción. Aquí se muestra el uso de AON dirigidos a la actividad de miR-23b y miR-218, que se ha demostrado previamente que regulan directamente MBNL1 y MBNL2. Estos antimiRs recibieron modificaciones FANA para aumentar su entrega en las células y reducir la toxicidad. También se probaron los AON, denominados blockmiRs, que se unen de manera complementaria a los sitios de unión confirmados de miR-23b y miR-218 en los 3'-UTR de las transcripciones de MBNL1 y MBNL2. De esta manera, los miRNAs no pueden unirse y regular la traducción de MBNL, lo que aumenta la cantidad de proteína MBNL producida en una célula deficiente. Aquí se propone el uso de AON de nuevo diseño dirigidos a la actividad de miR-23b y miR-218 para regular MBNL1 y MBNL2 a través de (1) exploración del bloqueo de miRNA a través de FANA-antimiR AON in vitro, (2) exploración del bloqueo del sitio de unión de miRNA a través de la estrategia blockmiR in vitro e in vivo con el uso de modificaciones químicas de LNA, y (3) mejora de la química de la estrategia blockmiR mediante el uso de tecnología de péptidos de penetración celular in vitro e in vivo.Myotonic Dystrophy Type 1 is a multi-systemic rare genetic disease affecting 1 in 3000-8000 people. The molecular cause of the disease stems from toxic “CTG” repetitions in the DMPK (DM Protein Kinase) gene. Upon transcription, these repetitions form a hairpin structure that binds with high affinity to the MBNL (Muscleblind-like) family of proteins depleting their function of post-transcriptional alternative splicing and polyadenylation regulation on numerous transcripts. MBNL loss-of-function causes a cascade of downstream effects, which eventually lead to clinical symptoms including myotonia, muscle weakness and atrophy, cataracts, cardiac dysfunction, and cognitive disorder. The restoration of MBNL protein function is key to relieving the debilitating symptoms of this disease. Antisense oligonucleotides (AONs) have been used to target the DMPK repeats and release MBNL from sequestration resulting in promising therapeutic results in cellular and animal models of the disease. Another factor playing a role in the loss-of-function of MBNL proteins are the miRNAs that regulate their translation. Here is shown the use of AONs targeting miR-23b and miR-218 activity, which have been previously shown to directly regulate MBNL1 and MBNL2. These antimiRs were given FANA modifications to increase their delivery in cells and lower toxicity. Also tested are AONs, termed blockmiRs, that complementary bind to the confirmed binding sites of miR-23b and miR-218 in the 3’-UTRs of MBNL1 and MBNL2 transcripts. In this way, the miRNAs are unable to bind and regulate the translation of MBNL thereby augmenting the amount of MBNL protein made in an otherwise deficient cell. Proposed here is the use of newly designed AONs targeting miR-23b and miR-218 activity in order to regulate MBNL1 and MBNL2 through (1) exploration of miRNA blocking through FANA-antimiR AONs in vitro, (2) exploration of miRNA binding site blocking through blockmiR strategy in vitro and in vivo with the use of LNA chemical modifications, and (3) improvement of the chemistry of the blockmiR strategy through the use of cell penetrating peptide technology in vitro and in vivo
Predictive Maintenance of Critical Equipment for Floating Liquefied Natural Gas Liquefaction Process
Predictive Maintenance of Critical Equipment for Liquefied Natural Gas Liquefaction Process
Meeting global energy demand is a massive challenge, especially with the quest of more affinity towards sustainable and cleaner energy. Natural gas is viewed as a bridge fuel to a renewable energy. LNG as a processed form of natural gas is the fastest growing and cleanest form of fossil fuel. Recently, the unprecedented increased in LNG demand, pushes its exploration and processing into offshore as Floating LNG (FLNG). The offshore topsides gas processes and liquefaction has been identified as one of the great challenges of FLNG. Maintaining topside liquefaction process asset such as gas turbine is critical to profitability and reliability, availability of the process facilities. With the setbacks of widely used reactive and preventive time-based maintenances approaches, to meet the optimal reliability and availability requirements of oil and gas operators, this thesis presents a framework driven by AI-based learning approaches for predictive maintenance. The framework is aimed at leveraging the value of condition-based maintenance to minimises the failures and downtimes of critical FLNG equipment (Aeroderivative gas turbine).
In this study, gas turbine thermodynamics were introduced, as well as some factors affecting gas turbine modelling. Some important considerations whilst modelling gas turbine system such as modelling objectives, modelling methods, as well as approaches in modelling gas turbines were investigated. These give basis and mathematical background to develop a gas turbine simulated model. The behaviour of simple cycle HDGT was simulated using thermodynamic laws and operational data based on Rowen model. Simulink model is created using experimental data based on Rowen’s model, which is aimed at exploring transient behaviour of an industrial gas turbine. The results show the capability of Simulink model in capture nonlinear dynamics of the gas turbine system, although constraint to be applied for further condition monitoring studies, due to lack of some suitable relevant correlated features required by the model.
AI-based models were found to perform well in predicting gas turbines failures. These capabilities were investigated by this thesis and validated using an experimental data obtained from gas turbine engine facility. The dynamic behaviours gas turbines changes when exposed to different varieties of fuel. A diagnostics-based AI models were developed to diagnose different gas turbine engine’s failures associated with exposure to various types of fuels. The capabilities of Principal Component Analysis (PCA) technique have been harnessed to reduce the dimensionality of the dataset and extract good features for the diagnostics model development.
Signal processing-based (time-domain, frequency domain, time-frequency domain) techniques have also been used as feature extraction tools, and significantly added more correlations to the dataset and influences the prediction results obtained. Signal processing played a vital role in extracting good features for the diagnostic models when compared PCA. The overall results obtained from both PCA, and signal processing-based models demonstrated the capabilities of neural network-based models in predicting gas turbine’s failures. Further, deep learning-based LSTM model have been developed, which extract features from the time series dataset directly, and hence does not require any feature extraction tool. The LSTM model achieved the highest performance and prediction accuracy, compared to both PCA-based and signal processing-based the models.
In summary, it is concluded from this thesis that despite some challenges related to gas turbines Simulink Model for not being integrated fully for gas turbine condition monitoring studies, yet data-driven models have proven strong potentials and excellent performances on gas turbine’s CBM diagnostics. The models developed in this thesis can be used for design and manufacturing purposes on gas turbines applied to FLNG, especially on condition monitoring and fault detection of gas turbines. The result obtained would provide valuable understanding and helpful guidance for researchers and practitioners to implement robust predictive maintenance models that will enhance the reliability and availability of FLNG critical equipment.Petroleum Technology Development Funds (PTDF) Nigeri
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