51 research outputs found
Experimental investigation on the detection of fatigue failures in hydraulic turbines
Hydroelectric power stations are nowadays one of the most important ways to obtain a clean and sustainable electricity supply. Actually, hydroelectric energy is the most renewable energy used in the world. Even so, there still exists a very important potential of development in many areas in these kinds of stations. These plants use mainly 3 types of turbines, called Francis, Kaplan, and Pelton, to obtain electricity due to the flow of water through its blades. We will focus our project on the Kaplan turbines. For doing so, the core of this project was the use of a flat disk of six blades linked with a shaft, which is a simplification of a Kaplan turbine. After installing it in a test rig of reduced scale in a laboratory, some experimental analysis were carried out. The project intention was to investigate the feasibility of detecting fatigue cracks in submerged structures such as Kaplan turbine blades by means of adequate sensors, measurement techniques and signal processing tools. For that, a series of experiments have been carried out in a laboratory with a simplified structure where a fatigue failure has been artificially provoked, which keeps similarity with the cracks observed in actual hydraulic turbines. Various detection techniques have been tested and evaluated to determine their capability to achieve the expected objective. To define a representative crack, before the experiments in the laboratory, some numerical simulations have been carried out to better understand the fracture mechanisms involved, and those simulations have been used to select the best experimental set up in the laboratory machines. Software like SolidWorks or Ansys have been used to simulate the appearance and spread of a crack in the disk until the failure of the structure. To analyze the effect of fatigue in the simplified structure used, a modal analysis has been carried out using instrumentation like accelerometers, software like Labview and theory about vibrations in machines. During this project, thus, the concepts of vibrational behavior and fatigue phenomena have gone hand in hand. Results obtained were really similar between the experiments and the numerical simulations. For the most destructive frequencies, the way that our structure vibrated with a crack practically matched between the numerical simulation and the experiments. Regarding some other frequencies of higher value, results were even closer. Moreover, the variation of frequency as the crack spreads presents a characteristic shape, similar to other machines. Due to the results obtained, I can confirm that it is possible to detect fatigue cracks that appear in the blades of a turbine and identify, by the vibration of the structure, the length of that crack. Linking the brands of studies mentioned (both numerical and experimental), the results obtained, the path we have followed to obtain these results, and with further studies, the future work will try to develop predictive maintenance techniques in actual hydraulic machines in order to avoid failures in the hydroelectric power stations due to the effect of fatigueObjectius de Desenvolupament Sostenible::7 - Energia Assequible i No ContaminantObjectius de Desenvolupament Sostenible::9 - Indústria, Innovació i Infraestructur
A PHILOSOPHICAL RECAP OF THE NOTION OF SEMANTIC VALUE: AN ARGUMENT FOR SEMANTIC FOUNDATIONALISM AND A REVIEW OF THE PRAGMATIC FOUNDATION OF CONSENSUS PRODUCTION
This paper is an assessment of the scientific role of the study of semantics to represent the technical types of consensus produced in human practice. We propose that "meaning" should not be understood as a projection of success, canonized as an absolute rational method; but rather as a series of strategies of meaning, which develop circularly in the historical sphere of communication. With this we intend to bring up the problem of meaning outside the comfortable sphere of a simple, synchronic and a-historical line between meaning and pseudo-meaning. In the conclusion we will reach a reflective take on the philosophical spaces where the problem of meaning is conciliated to the problem of consensus and its formation, and then we will suggest a philosophical reflection on “failure” to mean. Among these philosophical spaces of reflection, we will discuss transcendentalism and dogmatism, and suggest the question on whether semantics can escape these so to speak atavistic patterns of philosophical expression
Collected Papers (on Physics, Artificial Intelligence, Health Issues, Decision Making, Economics, Statistics), Volume XI
This eleventh volume of Collected Papers includes 90 papers comprising 988 pages on Physics, Artificial Intelligence, Health Issues, Decision Making, Economics, Statistics, written between 2001-2022 by the author alone or in collaboration with the following 84 co-authors (alphabetically ordered) from 19 countries: Abhijit Saha, Abu Sufian, Jack Allen, Shahbaz Ali, Ali Safaa Sadiq, Aliya Fahmi, Atiqa Fakhar, Atiqa Firdous, Sukanto Bhattacharya, Robert N. Boyd, Victor Chang, Victor Christianto, V. Christy, Dao The Son, Debjit Dutta, Azeddine Elhassouny, Fazal Ghani, Fazli Amin, Anirudha Ghosha, Nasruddin Hassan, Hoang Viet Long, Jhulaneswar Baidya, Jin Kim, Jun Ye, Darjan Karabašević, Vasilios N. Katsikis, Ieva Meidutė-Kavaliauskienė, F. Kaymarm, Nour Eldeen M. Khalifa, Madad Khan, Qaisar Khan, M. Khoshnevisan, Kifayat Ullah,, Volodymyr Krasnoholovets, Mukesh Kumar, Le Hoang Son, Luong Thi Hong Lan, Tahir Mahmood, Mahmoud Ismail, Mohamed Abdel-Basset, Siti Nurul Fitriah Mohamad, Mohamed Loey, Mai Mohamed, K. Mohana, Kalyan Mondal, Muhammad Gulfam, Muhammad Khalid Mahmood, Muhammad Jamil, Muhammad Yaqub Khan, Muhammad Riaz, Nguyen Dinh Hoa, Cu Nguyen Giap, Nguyen Tho Thong, Peide Liu, Pham Huy Thong, Gabrijela Popović, Surapati Pramanik, Dmitri Rabounski, Roslan Hasni, Rumi Roy, Tapan Kumar Roy, Said Broumi, Saleem Abdullah, Muzafer Saračević, Ganeshsree Selvachandran, Shariful Alam, Shyamal Dalapati, Housila P. Singh, R. Singh, Rajesh Singh, Predrag S. Stanimirović, Kasan Susilo, Dragiša Stanujkić, Alexandra Şandru, Ovidiu Ilie Şandru, Zenonas Turskis, Yunita Umniyati, Alptekin Ulutaș, Maikel Yelandi Leyva Vázquez, Binyamin Yusoff, Edmundas Kazimieras Zavadskas, Zhao Loon Wang.
Sums, numbers and infinity:Collections in Bolzano's mathematics and philosophy
This dissertation is a collection of essays almost exclusively focussing on Bernard Bolzano's theory of collections, and its connections to his conception of mathematics. The first significant contribution of this work is that it develops a novel approach for comparing and appraising Bolzano’s collections against the alternatives offered by set theory and mereology. This approach consists in focusing not on the metaphysical comparison but on the role Bolzano's collections play in his mathematics vis à vis the role the sets of set theory (ZFC) play for modern-day mathematics. The second important contribution of this dissertation is a novel interpretation of the interaction between Bolzano's theory of concepts on the one hand, and his way of comparing the size of infinite collections of natural numbers on the other. This culminates in a completely new interpretation of Bolzano's famous Paradoxes of the Infinite as a work that is not an anticipation of Cantorian set theory, but an attempt at deploying philosophical insights on the infinite to develop a sound treatment of infinite series, both converging and diverging ones
An unbridled search for logic: four studies of Husserl's logical investigations (1900-01)
The early Husserl wants to know what logic is, or what we should call ‘logic.’ He poses the question in a way that knowingly encompasses both what the 19th century (after Kant but before Frege) and the 20th century (since Frege) call ‘logic.’ But that he asks the question, and with such scope, has yet to be widely recognized. In particular, Husserl scholars still lack an overview of how Husserl’s early, explicitly logical inquiries, driven more by this single question than any worry about doctrinal consistency, does at least two things at once: probe what will later be called ‘pure phenomenology’ or ‘transcendental logic,’ and delimit logic as a positive yet mathematical discipline. With the aim of providing the neglected overview of this project, this dissertation takes the measure of Husserl’s two-volume Logical Investigations (1900-01) in four studies.
Chapter I argues that the first volume, the Prolegomena to Pure Logic (1900), intends at once to resolve a 19th-century conflict and to establish logic’s possibility as its own discipline, all by means of demonstrating the confusion of psychologism (the view that empirical psychology could set the terms for logic as a discipline). Chapter II then contends that most of the Prolegomena’s first chapter falls outside this intention, departing from the book’s Bolzano-inspired argumentative framework yet thereby anticipating Husserl’s later ‘transcendental logic.’ Chapter III presents Frege and Husserl as two images of indecision as to how it falls to logic to know truth’s laws. Chapter IV concludes by expounding Husserl’s conception of logic as noetics, the self-clarification of knowing, thus completing the picture of Husserl’s indecision, while also laying groundwork to track the development of his thinking after the Logical Investigations
Grounding, Quantifiers, and Paradoxes
International audienceThe notion of grounding is usually conceived as an objective and explanatory relation. It connects two relata if one-the ground-determines or explains the other-the consequence. In the contemporary literature on grounding, much effort has been devoted to logically characterize the formal aspects of grounding, but a major hard problem remains: defining suitable grounding principles for universal and existential formulae. Indeed, several grounding principles for quantified formulae have been proposed, but all of them are exposed to reflexivity and symmetry paradoxes in some very natural contexts of application. We introduce in this paper a first-order formal system that captures the notion of grounding and avoids, in a novel and non-trivial way, both reflexivity and symmetry paradoxes. The presented system formally develops Bolzano's ideas on grounding by employing Hilbert's ε-terms and an adapted version of Fine's theory of arbitrary objects
Follow the Flow: sets, relations, and categories as special cases of functions with no domain
We introduce, develop, and apply a new approach for dealing with the intuitive notion of function, called Flow Theory. Within our framework all functions are monadic and none of them has any domain. Sets, proper classes, categories, functors, and even relations are special cases of functions. In this sense, functions in Flow are not equivalent to functions in ZFC. Nevertheless, we prove both ZFC and Category Theory are naturally immersed within Flow. Besides, our framework provides major advantages as a language for axiomatization of standard mathematical and physical theories. Russell's paradox is avoided without any equivalent to the Separation Scheme. Hierarchies of sets are obtained without any equivalent to the Power Set Axiom. And a clear principle of duality emerges from Flow, in a way which was not anticipated neither by Category Theory nor by standard set theories. Besides, there seems to be within Flow an identification not only with the common practice of doing mathematics (which is usually quite different from the ways proposed by logicians), but even with the common practice of teaching this formal science
Neighbours at Puhoi River: A cross-cultural dual biography of Te Hemara Tauhia(1815-1891) and Martin Krippner(1817-1894)
This thesis seeks to re-construct the biographies of two relatively obscure, yet fascinating and controversial players in the history of Aotearoa New Zealand. Both historical figures were initiators and leaders of neighbouring settlements: the rangatira, Te Hemara Tauhia (1815 – 1891), in his role as chief of the Te Kawerau/Ngāti Rongo hapū of the Ngāti Whātua iwi, re-occupying ancestral lands after living in captivity with Ngāpuhi, and the former Austrian captain, Martin Krippner (1817 – 1894), organiser of an Austrian-Bohemian settlement made possible under the Auckland Provincial Government land grant scheme. Despite their efforts for each community, both men were accused by their own people of misusing their positions for personal gains. Te Hemara Tauhia was blamed for selling off tribal lands to cover personal debts. Martin Krippner was never forgiven for promising his Bohemian compatriots a ‘land of milk and honey’ while leading them to near starvation and struggle within dense New Zealand bush, and subsequently into war in the Waikato where Krippner was commissioned captain in the Waikato Militia.
Focussing on three main objectives, this cross-cultural dual biography provides an original contribution to historical scholarship: Firstly, it looks behind the myths that have been created around Te Hemara Tauhia and Martin Krippner; it thoroughly examines what both men did and how social, economic and political circumstances influenced their motivations and choices at that particular time. Secondly, placing Tauhia’s and Krippner’s biographies side-by-side provides a novel view of a range of historical phenomena from both Tangata Whenua (indigenous peoples) and European settlers (Pākehā) perspectives. Looking at the same events from different angles and perspectives, a cross-cultural, dual biography can act like a prismatic tool, revealing the complexity of a shared history. The third aim of this research encompasses my intention to contribute to and to participate in a dialogue between ethnic groups in Aotearoa New Zealand, especially between Māori and Pākehā, in order to challenge stereotypes and generalisations based on lack of knowledge of historical and cultural contexts
Acts of Time: Cohen and Benjamin on Mathematics and History
This paper argues that the principle of continuity that underlies Benjamin’s understanding of what makes the reality of a thing thinkable, which in the Kantian context implies a process of “filling time” with an anticipatory structure oriented to the subject, is of a different order than that of infinitesimal calculus—and that a “discontinuity” constitutive of the continuity of experience and (merely) counterposed to the image of actuality as an infinite gradation of ultimately thetic acts cannot be the principle on which Benjamin bases the structure of becoming. Tracking the transformation of the process of “filling time” from its logical to its historical iteration, or from what Cohen called the “fundamental acts of time” in Logik der reinen Erkenntnis to Benjamin’s image of a language of language (qua language touching itself), the paper will suggest that for Benjamin, moving from 0 to 1 is anything but paradoxical, and instead relies on the possibility for a mathematical function to capture the nature of historical occurrence beyond paradoxes of language or phenomenality
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