14,175 research outputs found

    Intelligent Control Schemes for Maximum Power Extraction from Photovoltaic Arrays under Faults

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    Investigation of power output from PV arrays under different fault conditions is an essential task to enhance performance of a photovoltaic system under all operating conditions. Significant reduction in power output can occur during various PV faults such as module disconnection, bypass diode failure, bridge fault, and short circuit fault under non-uniform shading conditions. These PV faults may cause several peaks in the characteristics curve of PV arrays, which can lead to failure of the MPPT control strategy. In fact, impact of a fault can differ depending on the type of PV array, and it can make the control of the system more complex. Therefore, consideration of suitable PV arrays with an effective control design is necessary for maximum power output from a PV system. For this purpose, the proposed study presents a comparative study of two intelligent control schemes, i.e., fuzzy logic (FL) and particle swarm optimization (PSO), with a conventional control scheme known as perturb and observe (P&O) for power extraction from a PV system. The comparative analysis is based on the performance of the control strategies under several faults and the types of PV modules, i.e., monocrystalline and thin-film PV arrays. In this study, numerical analysis for complex fault scenarios like multiple faults under partial shading have also been performed. Different from the previous literature, this study will reveal the performance of FL-, PSO-, and P&O-based MPPT strategies to track maximum peak power during multiple severe fault conditions while considering the accuracy and fast-tracking efficiencies of the control techniques. A thorough analysis along with in-depth quantitative data are presented, confirming the superiority of intelligent control techniques under multiple faults and different PV types

    Эксгумация пород верхней мантии и нижней коры в Центральной Атлантике

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    В статье приведены примеры эксгумации пород верхней мантии и нижней коры в различных областях Атлантического океана и механизмов вывода этих глубинных образований в верхние горизонты коры в области перехода от континента к океану, в областях океанических поднятий и трогов, в гребневой части медленно-спредингового Срединно-Атлантического хребта (САХ). Последняя рассматривается, в том числе, на основе оригинальных данных, полученных во время многолетних геолого-геофизических исследований в Центральной Атлантике на научно-исследовательском судне «Академик Николай Страхов». Основное внимание уделено внутренним океаническим комплексам (ВОК), являющимися потенциальными объектами для добычи полиметаллических сульфидных руд и природными лабораториями для изучения процессов рудогенеза океанической литосферы и образования абиогенных углеводородов. Показано, что вывод глубинных пород на дно Центральной Атлантики имел место на всем протяжении истории ее раскрытия, начиная с рифтогенеза континентальной литосферы в раннем мелу и заканчивая становлением ВОК в осевой части САХ на современном этапе. Сделаны выводы о том, что эксгумация пород верхней мантии и нижней коры является ярким проявлением тектонической расслоенности литосферы Центральной Атлантики

    Elite perceptions of the Victorian and Edwardian past in inter-war England

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    It is often argued by historians that members of the cultivated Elite after 1918 rejected the pre-war past. or at least subjected it to severe denigration. This thesis sets out to challenge such a view. Above all, it argues that inter-war critics of the Victorian and Edwardian past were unable to reject it even if that was what they felt inclined to do. This was because they were tied to those periods by the affective links of memory, family, and the continually unfolding consequences of the past in the present. Even the severest critics of the pre-war world, such as Lytton Strachey, were less frequently dismissive of history than ambivalent towards it. This ambivalence, it is argued, helped to keep the past alive and often to humanise it. The thesis also explores more positive estimation of Victorian and Edwardian history between the wars. It examines nostalgia for the past, as well as instances of continuity of practice and attitude. It explores the way in which inter-war society drew upon aspects of Victorian and Edwardian history both as illuminating parallels to contemporary affairs and to understand directly why the present was shaped as it was. Again, this testifies to the enduring power of the past after 1918. There are three parts to this thesis. Part One outlines the cultural context in which writers contemplated the Victorian and Edwardian past. Part Two explores some of the ways in which history was written about and used by inter-war society. Part Three examines the ways in which biographical depictions of eminent Victorians after 1918 encouraged emotional negotiation with the pas

    Plato’s Later Moral Epistemology

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    This Ph.D. thesis aims to provide a comprehensive account of the relationship between ethics and epistemology in Plato’s late dialogues (specifically, Sophist, Statesman, Philebus, and Laws). While scholars have been concerned with understanding the extent to which Plato’s middle dialogues resonate with his early theory of ethical intellectualism (according to which knowledge is a necessary and sufficient condition for virtue), Plato’s later moral epistemology has received much less attention. The few scholars who have worked on the subject have argued that Plato’s late dialogues present a radical transformation of the epistemological and ethical ideas displayed in Plato’s earlier works. The scholarly debate has almost unanimously concluded that Plato’s late dialogues heavily revise the theory of ethical intellectualism that, arguably, features in the earlier works. Through an in-depth analysis of the late dialogues’ textual evidence, this thesis will show that the so-called Socratic theory of ethical intellectualism has not been abandoned by Plato in his late works. To this end, I will contend that the Sophist, the Statesman, the Philebus, and the Laws suggest that (philosophical) knowledge is the ultimate condition that a moral agent has to meet to be fully virtuous. In addition, taking for granted that philosophers alone can achieve a full and philosophical virtue, I will also show that Plato’s later moral epistemology extends beyond philosophers. For, while achieving philosophical knowledge is presented as a necessary and sufficient condition for being virtuous, I will argue that Plato’s late dialogues establish that opinion, if true, is sufficient for acting virtuously

    Metaphors of London fog, smoke and mist in Victorian and Edwardian Art and Literature

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    Julian Wolfreys has argued that after 1850 writers employed stock images of the city without allowing them to transform their texts. This thesis argues, on the contrary, that metaphorical uses of London fog were complex and subtle during the Victorian and Edwardian periods, at least until 1914. Fog represented, in particular, formlessness and the dissolution of boundaries. Examining the idea of fog in literature, verse, newspaper accounts and journal articles, as well as in the visual arts, as part of a common discourse about London and the state of its inhabitants, this thesis charts how the metaphorical appropriation of this idea changed over time. Four of Dickens's novels are used to track his use of fog as part of a discourse of the natural and unnatural in individual and society, identifying it with London in progressively more negative terms. Visual representations of fog by Constable, Turner, Whistler, Monet, Markino, O'Connor, Roberts and Wyllie and Coburn showed an increasing readiness to engage with this discourse. Social tensions in the city in the 1880s were articulated in art as well as in fiction. Authors like Hay and Barr showed the destruction of London by its fog because of its inhabitants' supposed degeneracy. As the social threat receded, apocalyptic scenarios gave way to a more optimistic view in the work of Owen and others. Henry James used fog as a metaphorical representation of the boundaries of gendered behaviour in public, and the problems faced by women who crossed them. The dissertation also examines fog and individual transgression, in novels and short stories by Lowndes, Stevenson, Conan Doyle and Joseph Conrad. After 1914, fog was no more than a crude signifier of Victorian London in literature, film and, later, television, deployed as a cliche instead of the subtle metaphorical idea discussed in this thesis

    Coloniality and the Courtroom: Understanding Pre-trial Judicial Decision Making in Brazil

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    This thesis focuses on judicial decision making during custody hearings in Rio de Janeiro, Brazil. The impetus for the study is that while national and international protocols mandate the use of pre-trial detention only as a last resort, judges continue to detain people pre-trial in large numbers. Custody hearings were introduced in 2015, but the initiative has not produced the reduction in pre-trial detention that was hoped. This study aims to understand what informs judicial decision making at this stage. The research is approached through a decolonial lens to foreground legacies of colonialism, overlooked in mainstream criminological scholarship. This is an interview-based study, where key court actors (judges, prosecutors, and public defenders) and subject matter specialists were asked about influences on judicial decision making. Interview data is complemented by non-participatory observation of custody hearings. The research responds directly to Aliverti et al.'s (2021) call to ‘decolonize the criminal question’ by exposing and explaining how colonialism informs criminal justice practices. Answering the call in relation to judicial decision making, findings provide evidence that colonial-era assumptions, dynamics, and hierarchies were evident in the practice of custody hearings and continue to inform judges’ decisions, thus demonstrating the coloniality of justice. This study is significant for the new empirical data presented and theoretical innovation is also offered via the introduction of the ‘anticitizen’. The concept builds on Souza’s (2007) ‘subcitizen’ to account for the active pursuit of dangerous Others by judges casting themselves as crime fighters in a modern moral crusade. The findings point to the limited utility of human rights discourse – the normative approach to influencing judicial decision making around pre-trial detention – as a plurality of conceptualisations compete for dominance. This study has important implications for all actors aiming to reduce pre-trial detention in Brazil because unless underpinning colonial logics are addressed, every innovation risks becoming the next lei para inglês ver (law [just] for the English to see)

    Towards a more just refuge regime: quotas, markets and a fair share

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    The international refugee regime is beset by two problems: Responsibility for refuge falls disproportionately on a few states and many owed refuge do not get it. In this work, I explore remedies to these problems. One is a quota distribution wherein states are distributed responsibilities via allotment. Another is a marketized quota system wherein states are free to buy and sell their allotments with others. I explore these in three parts. In Part 1, I develop the prime principles upon which a just regime is built and with which alternatives can be adjudicated. The first and most important principle – ‘Justice for Refugees’ – stipulates that a just regime provides refuge for all who have a basic interest in it. The second principle – ‘Justice for States’ – stipulates that a just distribution of refuge responsibilities among states is one that is capacity considerate. In Part 2, I take up several vexing questions regarding the distribution of refuge responsibilities among states in a collective effort. First, what is a state’s ‘fair share’? The answer requires the determination of some logic – some metric – with which a distribution is determined. I argue that one popular method in the political theory literature – a GDP-based distribution – is normatively unsatisfactory. In its place, I posit several alternative metrics that are more attuned with the principles of justice but absent in the political theory literature: GDP adjusted for Purchasing Power Parity and the Human Development Index. I offer an exploration of both these. Second, are states required to ‘take up the slack’ left by defaulting peers? Here, I argue that duties of help remain intact in cases of partial compliance among states in the refuge regime, but that political concerns may require that such duties be applied with caution. I submit that a market instrument offers one practical solution to this problem, as well as other advantages. In Part 3, I take aim at marketization and grapple with its many pitfalls: That marketization is commodifying, that it is corrupting, and that it offers little advantage in providing quality protection for refugees. In addition to these, I apply a framework of moral markets developed by Debra Satz. I argue that a refuge market may satisfy Justice Among States, but that it is violative of the refugees’ welfare interest in remaining free of degrading and discriminatory treatment

    Supernatural crossing in Republican Chinese fiction, 1920s–1940s

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    This dissertation studies supernatural narratives in Chinese fiction from the mid-1920s to the 1940s. The literary works present phenomena or elements that are or appear to be supernatural, many of which remain marginal or overlooked in Sinophone and Anglophone academia. These sources are situated in the May Fourth/New Culture ideological context, where supernatural narratives had to make way for the progressive intellectuals’ literary realism and their allegorical application of supernatural motifs. In the face of realism, supernatural narratives paled, dismissed as impractical fantasies that distract one from facing and tackling real life. Nevertheless, I argue that the supernatural narratives do not probe into another mystical dimension that might co-exist alongside the empirical world. Rather, they imagine various cases of the characters’ crossing to voice their discontent with contemporary society or to reflect on the notion of reality. “Crossing” relates to characters’ acts or processes of trespassing the boundary that separates the supernatural from the conventional natural world, thus entailing encounters and interaction between the natural and the supernatural. The dissertation examines how crossing, as a narrative device, disturbs accustomed and mundane situations, releases hidden tensions, and discloses repressed truths in Republican fiction. There are five types of crossing in the supernatural narratives. Type 1 is the crossing into “haunted” houses. This includes (intangible) human agency crossing into domestic spaces and revealing secrets and truths concealed by the scary, feigned ‘haunting’, thus exposing the hidden evil and the other house occupiers’ silenced, suffocated state. Type 2 is men crossing into female ghosts’ apparitional residences. The female ghosts allude to heart-breaking, traumatic experiences in socio-historical reality, evoking sympathetic concern for suffering individuals who are caught in social upheavals. Type 3 is the crossing from reality into the characters’ delusional/hallucinatory realities. While they physically remain in the empirical world, the characters’ abnormal perceptions lead them to exclusive, delirious, and quasi-supernatural experiences of reality. Their crossings blur the concrete boundaries between the real and the unreal on the mental level: their abnormal perceptions construct a significant, meaningful reality for them, which may be as real as the commonly regarded objective reality. Type 4 is the crossing into the netherworld modelled on the real world in the authors’ observation and bears a spectrum of satirised objects of the Republican society. The last type is immortal visitors crossing into the human world. This type satirises humanity’s vices and destructive potential. The primary sources demonstrate their writers’ witty passion to play with super--natural notions and imagery (such as ghosts, demons, and immortals) and stitch them into vivid, engaging scenes using techniques such as the gothic, the grotesque, and the satirical, in order to evoke sentiments such as terror, horror, disgust, dis--orientation, or awe, all in service of their insights into realist issues. The works also creatively tailor traditional Chinese modes and motifs, which exemplifies the revival of Republican interest in traditional cultural heritage. The supernatural narratives may amaze or disturb the reader at first, but what is more shocking, unpleasantly nudging, or thought-provoking is the problematic society and people’s lives that the supernatural (misunderstandings) eventually reveals. They present a more compre--hensive treatment of reality than Republican literature with its revolutionary consciousness surrounding class struggle. The critical perspectives of the supernatural narratives include domestic space, unacknowledged history and marginal individuals, abnormal mentality, and pervasive weaknesses in humanity. The crossing and supernatural narratives function as a means of better understanding the lived reality. This study gathers diverse primary sources written by Republican writers from various educational and political backgrounds and interprets them from a rare perspective, thus filling a research gap. It promotes a fuller view of supernatural narratives in twentieth-century Chinese literature. In terms of reflecting the social and personal reality of the Republican era, the supernatural narratives supplement the realist fiction of the time

    An investigation of the geothermal potential of the Upper Devonian sandstones beneath eastern Glasgow

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    The urban development of the city of Glasgow is a consequence of its economic development, in part fuelled by local coalfields which exploited rocks in the same sedimentary basin within which geothermal resources in flooded abandoned mine workings, and deeper hot sedimentary aquifers (HSA), are present. This creates an opportunity to provide geothermal heating to areas of dense urban population with high heat demand. The depth of the target HSA geothermal resource, in Upper Devonian aged sandstones of the Stratheden Group, beneath eastern Glasgow was determined by gravity surveying and structural geological modelling. The estimated depth of the geothermal resource ranged from c.1500-2000 m, in the eastward deepening sedimentary basin. To reliably estimate the temperature of the geothermal resource, rigorous corrections to account for the effects of palaeoclimate and topography on heat flow were applied to boreholes in the Greater Glasgow area. The mean regional corrected heat flow was calculated as 75.7 mW m-2, an increase of 13.8 mW m-2 from the uncorrected value of 61.9 mW m-2, emphasising the extent to which heat flow was previously underestimated. Extrapolation of the geothermal gradient, calculated from the mean regional corrected heat flow, results in aquifer temperatures of c. 64-79 °C at depths of c.1500-2000 m beneath eastern Glasgow. The geothermal resource may, therefore, be capable of supporting a wide variety of direct heat use applications if sufficient matrix permeability or fracture networks are present. However, diagenetic effects such as quartz and carbonate cementation were found to restrict the porosity in Upper Devonian sandstones in a borehole and outcrop analogue study. These effects may likewise reduce porosity and intergranular permeability in the target aquifer, although this crucial aspect cannot be fully understood without deep exploratory drilling. To quantify the magnitude of the deep geothermal resource, the indicative thermal power outputs of geothermal doublet wells located in Glasgow’s East End were calculated for the first time, with outputs ranging from 1.3-2.1 MW dependent upon the aquifer depth. This, however, is predicated upon an aquifer permeability of c. 40 mD, which if reduced to 10 mD or less due to the effects of diagenesis, significantly reduces the thermal power outputs to 230-390 kW. The lack of assured project-success, given uncertainties related to the aquifer properties at depth, coupled with high capital costs of drilling, pose barriers to the development of deep geothermal energy in Glasgow. Further investigation of the economic viability of geothermal exploration, and alternative technological solutions is therefore required to mitigate the technical and economic risks. However, if sufficient matrix permeability or fracture networks are present at depth in the Upper Devonian sandstone sequence, then the potential contribution that geothermal energy could make to meeting local heat demand, reducing greenhouse gas emissions, and addressing the ‘energy trilemma’ in Glasgow is significant

    Predictive Maintenance of Critical Equipment for Floating Liquefied Natural Gas Liquefaction Process

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    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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