Bibliografias temáticas / Extension de cycles

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Literatura científica selecionada sobre o tema "Extension de cycles"

Autor: Grafiati

Publicado: 22 de fevereiro de 2025

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Artigos de revistas sobre o assunto "Extension de cycles"

Reed, Richard. "Fashion Life Cycles and Extension Theory". European Journal of Marketing 21, n.º 3 (março de 1987): 52–62. http://dx.doi.org/10.1108/eum0000000004686.

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Coupechoux, Pierre. "Extension of universal cycles for globally identifying colorings of cycles". Discrete Mathematics 340, n.º 7 (julho de 2017): 1456–66. http://dx.doi.org/10.1016/j.disc.2017.02.002.

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Boumasmoud, Réda, Ernest Hunter Brooks e Dimitar P. Jetchev. "Vertical Distribution Relations for Special Cycles on Unitary Shimura Varieties". International Mathematics Research Notices 2020, n.º 13 (14 de junho de 2018): 3902–26. http://dx.doi.org/10.1093/imrn/rny119.

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Abstract We consider cycles on three-dimensional Shimura varieties attached to unitary groups, defined over extensions of a complex multiplication (CM) field $E$, which appear in the context of the conjectures of Gan et al. [6]. We establish a vertical distribution relation for these cycles over an anticyclotomic extension of $E$, complementing the horizontal distribution relation of [8], and use this to define a family of norm-compatible cycles over these fields, thus obtaining a universal norm construction similar to the Heegner $\Lambda $-module constructed from Heegner points.

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Katona, Gyula Y. "Extension of paths and cycles for hypergraphs". Electronic Notes in Discrete Mathematics 45 (janeiro de 2014): 3–7. http://dx.doi.org/10.1016/j.endm.2013.11.002.

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Gehrlein, William V., e Peter C. Fishburn. "Linear extension majority cycles on partial orders". Annals of Operations Research 23, n.º 1 (dezembro de 1990): 311–22. http://dx.doi.org/10.1007/bf02204855.

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Bernhardt, Chris. "Time-symmetric cycles". International Journal of Mathematics and Mathematical Sciences 2003, n.º 26 (2003): 1683–92. http://dx.doi.org/10.1155/s0161171203208097.

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The main result of this note is that given any two time-symmetric cycles, one can find a time-symmetric extension of one by the other. This means that given a time-symmetric cycle, both time-symmetric doubles and square roots can be found.

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COLACCHIO, GIORGIO, MARCO SPARRO e CLAUDIO TEBALDI. "SEQUENCES OF CYCLES AND TRANSITIONS TO CHAOS IN A MODIFIED GOODWIN'S GROWTH CYCLE MODEL". International Journal of Bifurcation and Chaos 17, n.º 06 (junho de 2007): 1911–32. http://dx.doi.org/10.1142/s0218127407018117.

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The model introduced by Goodwin [1967] in "A Growth Cycle" represents a milestone in the nonlinear modeling of economic dynamics. On the basis of a few simple assumptions, the Goodwin Model (GM) is formulated exactly as the well-known Lotka–Volterra system, in terms of the two variables "wage share" and "employment rate". A number of extensions have been proposed with the aim to make the model more robust, in particular, to obtain structural stability, lacking in GM original formulation. We propose a new extension that: (a) removes the limiting hypothesis of "Harrod-neutral" technical progress: (b) on the line of Lotka–Volterra models with adaptation, introduces the concept of "memory", which plays a relevant role in the dynamics of economic systems. As a consequence, an additional equation appears, the validity of the model is substantially extended and a rich phenomenology is obtained, in particular, transition to chaotic behavior via period-doubling bifurcations.

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Ewacha, Kevin, Peter C. Fishburn e W. V. Gehrlein. "Linear extension majority cycles in height-1 orders". Order 6, n.º 4 (1990): 313–18. http://dx.doi.org/10.1007/bf00346127.

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Wang, Kailong, Yuxi Ling, Yanjun Zhang, Zhou Yu, Haoyu Wang, Guangdong Bai, Beng Chin Ooi e Jin Song Dong. "Characterizing Cryptocurrency-themed Malicious Browser Extensions". Proceedings of the ACM on Measurement and Analysis of Computing Systems 6, n.º 3 (dezembro de 2022): 1–31. http://dx.doi.org/10.1145/3570603.

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Due to the surging popularity of various cryptocurrencies in recent years, a large number of browser extensions have been developed as portals to access relevant services, such as cryptocurrency exchanges and wallets. This has stimulated a wild growth of cryptocurrency themed malicious extensions that cause heavy financial losses to the users and legitimate service providers. They have shown their capability of evading the stringent vetting processes of the extension stores, highlighting a lack of understanding of this emerging type of malware in our community. In this work, we conduct the first systematic study to identify and characterize cryptocurrency-themed malicious extensions. We monitor seven official and third-party extension distribution venues for 18 months (December 2020 to June 2022) and have collected around 3600 unique cryptocurrency-themed extensions. Leveraging a hybrid analysis, we have identified 186 malicious extensions that belong to five categories. We then characterize those extensions from various perspectives including their distribution channels, life cycles, developers, illicit behaviors, and illegal gains. Our work unveils the status quo of the cryptocurrency-themed malicious extensions and reveals their disguises and programmatic features on which detection techniques can be based. Our work serves as a warning to extension users, and an appeal to extension store operators to enact dedicated countermeasures. To facilitate future research in this area, we release our dataset of the identified malicious extensions and open-source our analyzer.

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Wang, Kailong, Yuxi Ling, Yanjun Zhang, Zhou Yu, Haoyu Wang, Guangdong Bai, Beng Chin Ooi e Jin Song Dong. "Characterizing Cryptocurrency-themed Malicious Browser Extensions". ACM SIGMETRICS Performance Evaluation Review 51, n.º 1 (26 de junho de 2023): 91–92. http://dx.doi.org/10.1145/3606376.3593529.

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Due to the surging popularity of various cryptocurrencies in recent years, a large number of browser extensions have been developed as portals to access relevant services, such as cryptocurrency exchanges and wallets. This has stimulated a wild growth of cryptocurrency-themed malicious extensions that cause heavy financial losses to the users and legitimate service providers. They have shown their capability of evading the stringent vetting processes of the extension stores, highlighting a lack of understanding of this emerging type of malware in our community. In this work, we conduct the first systematic study to identify and characterize cryptocurrency-themed malicious extensions. We monitor seven official and third-party extension distribution venues for 18 months (December 2020 to June 2022) and have collected around 3600 unique cryptocurrency-themed extensions. Leveraging a hybrid analysis, we have identified 186 malicious extensions that belong to five categories. We then characterize those extensions from various perspectives including their distribution channels, life cycles, developers, illicit behaviors, and illegal gains. Our work unveils the status quo of the cryptocurrency-themed malicious extensions and reveals their disguises and programmatic features on which detection techniques can be based. Our work serves as a warning to extension users, and an appeal to extension store operators to enact dedicated countermeasures. To facilitate future research in this area, we release our dataset of the identified malicious extensions and open-source our analyzer.

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Teses / dissertações sobre o assunto "Extension de cycles"

Branch, Judy. "Cultivating Extension Communities of Practice". ScholarWorks @ UVM, 2008. http://scholarworks.uvm.edu/graddis/28.

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This study empirically describes and analyzes the characteristics and functionality of the ―Communities of Practice (CoPs)‖ used within eXtension, a new initiative of the Cooperative Extension (CE) system. It also endeavors to lay the foundation for empirical analysis of CoP processes, which to date have been explained almost exclusively using qualitative case study methods. Land-grant universities were founded on the ideals that higher education should be accessible to all, that the university should teach liberal and practical subjects and should share the college's knowledge with people throughout their states. eXtension is an educational partnership of more than 70 land-grant universities. Its reported purpose is to help Americans improve their lives with access to timely, objective, research-based information and educational opportunities accessed through http://www.extension.org . This Web resource is customized with links to state land-grant university CE Web sites. This mixed-method, action research project applied to the virtual environment describes the extent to which people who became part of an eXtension Communities of Practice (XCoPs) reported that they engaged in purposeful cycles of continuous inquiry in dialog, decision, action, and evaluation (DDAE) and the attainment of eXtension‘s goals. An Internet survey obtained descriptive data of members‘ participation within the eight pioneer XCoPs to assess the extent to which each XCoP engaged in the DDAE cycles of inquiry. Analysis of the survey data resulted in the categorization of low-, medium-, and high-level functioning XCoPs. Members of three pioneer XCoPs representing each category (low, medium, high collaboration) participated in online interviews that revealed how CE‘s reward structure, XCoP membership composition, and leader/member skill sets impact XCoP performance in meeting eXtension goals. Two sets of ―best practices‖ for eXtension initiative staff and XCoPs emerge from the discussion of triangulated data.

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Simon, Cedric. "Réactivité des cycles tendus du silicium vis-à-vis des métaux de transitions : un accès rapide à des drogues silylées polycycliques". Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066465/document.

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Ces travaux de thèse portent sur le développement de la première synthèse du squelette des 10-silastéroïdes, et cela grâce à une cascade cycloaddition [2+2+2]/extension de cycle. Après quelques rappels sur la chimie du silicium et sur son utilisation comme bioisostère du carbone en chimie médicinale, une vue d’ensemble de la littérature concernant les extensions de cycles tendus sera réalisée. Celle-ci nous amènera à détailler notre stratégie et ses trois défis importants qui seront abordés dans les chapitres suivants. Le premier est la préparation de silanes polyinsaturés susceptibles de réaliser notre cascade réactionnelle. Pour cela, le silicium doit porter quatre groupements différents. Dans ce but, trois synthèses ont été mises au point afin d’améliorer sans cesse la préparation de ces silanes. Le second défi de ce projet est l’accès au benzosilacyclobutène par cycloaddition [2+2+2], ceci étant la première étape de notre cascade. Cela est réalisé à l’aide d’une catalyse au NbCl3.DME, permettant ainsi la synthèse de benzosilacyclobutènes hautement fonctionnalisés avec de très bons rendements. Cette nouvelle synthèse est plus performante que la seule voie de synthèse existante dans la littérature, que se soit au niveau des rendements, de la fonctionnalisation des substrats, mais aussi grâce à des conditions plus douces. Le troisième défi est le contrôle de la régiosélectivité de la réaction d’extension de cycle des benzosilacyclobutènes. Cette régiosélectivité est grandement influencé par le métal utilisé. Ainsi, l’utilisation du catalyseur de cobalt CpCo(CO)2 pour notre cascade conduit au silapolycycle linéaire. La catalyse avec RhCl(PPh3)3 permet quant à elle d’accéder au silapolycycle angulaire désiré, possédant un atome de silicium en jonction de cycle, et donc au premier squelette de 10-silastéroïde
This PhD work deals with the development of the first synthesis of the 10-silasteroids scaffold, using a cascade [2+2+2] cycloaddition/ring expansion. An overview of silicon chemistry and its use as a carbon bioisoster in medicinal chemistry is covered, followed by a description of the literature on ring expansion. Then, we will explain our strategy and its three main challenges will be discussed in the following chapters. The first one is the preparation of polyunsaturated silanes wich is capable of performing our cascade reaction. For this purpose, the silicon atom must have four different substituents. To reach this goal, three synthesis were developed in order to gradually increase the preparation of the silanes. The second challenge is the access to benzosilacyclobutenes by a [2+2+2] cycloaddition reaction, this reaction being the first step of our cascade reaction. It was done using NbCl3.DME catalysis, allowing the formation of highly functionalized benzosilacyclobutenes in high yields. This new synthesis is more efficient than the previously described literature synthesis, in means of yields, substrat functionnalizations, and mild reaction condition. The third challenge is the control of the regioselectivity of the ring expansion of the benzosilacyclobutenes. This regioselectivity mainly depends on the metal used. For exemple, the use of CpCo(CO)2 catalyst gives to the linear silapolycycle. Whereas, RhCl(PPh3)3 catalysis yields to the desired angular silapolycycle, containing the silicon atom at the ring junction, leading to the first synthesis of the 10-silasteroids scaffolds

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Hur, Seok. "Extension de la théorie de Bautin à des dimensions supérieures : notion de centre et structure de composition". Paris 6, 2003. http://www.theses.fr/2003PA066162.

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Saylor, Joel Edward. "The Late Miocene through Modern Evolution of the Zhada Basin, South-Western Tibet". Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/194652.

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The uplift history of the Tibetan Plateau is poorly constrained in part due to its complex and extended tectonic history. This study uses basin analysis, stable isotope analysis, magnetostratigraphy, detrital zircon U-Pb dating, and paleoaltimetry, and frequency analysis to reconstruct the tectonic, spatial, and environmental evolution of the Zhada basin in southwestern Tibet since the late Miocene. The Zhada Formation, which occupies the Zhada basin and consists of ~ 850 m of fluvial, alluvial fan, eolian, and lacustrine sediments, is undeformed and lies in angular unconformity above Tethyan sedimentary sequence strata. The most negative Miocene δ¹⁸Opsw (paleo-surface water) values reconstructed from aquatic gastropods are significantly more negative than the most negative modern δ¹⁸O(sw) (surface water) values. In the absence of any known climate change which would have produced this difference, we interpret it as indicating a decrease in elevation in the catchment between the late Miocene and the present. Basin analysis indicates that the decrease in elevation was accomplished by two low-angle detachment faults which root beneath the Zhada basin and exhume mid-crustal rocks. This exhumation results from ongoing arc-parallel extension and provides accommodation for Zhada basin fill. Sequence stratigraphy shows that the basin evolved from an overfilled to an underfilled basin but that further evolution was truncated by an abrupt return to overfilled, incising conditions. This evolution is linked to progressive damming of the paleo-Sutlej River. During the underfilled portion of basin evolution, depositional environments were strongly influenced by Milancovitch cyclicity: particularly at the precession and eccentricity frequencies.

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Cormier, Gabriel. "Réaction domino photochimique pour la synthèse d'hétérocycles soufrés". Electronic Thesis or Diss., université Paris-Saclay, 2025. http://www.theses.fr/2025UPASF003.

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Les réactions photochimiques constituent un outil puissant pour créer de la diversité moléculaire en chimie organique. A partir de substrats simples et d'un photon, elles permettent de donner accès à des structures moléculaires complexes qu'il serait difficile d'obtenir avec des méthodologies plus classiques. Ces transformations induites par l'absorption de la lumière sont particulièrement intéressantes dans le contexte du développement durable et peuvent participer à relever ce défi plus efficacement lorsqu'elles sont incorporées dans des processus domino. En effet, combinée avec des réactions thermiques ou mieux encore avec d'autres transformations photochimiques, cette stratégie est économe en temps, en énergie et en déchets et peut éviter d'isoler des intermédiaires intrinsèquement instables. Ces cascades photochimiques permettent en outre d'accroitre de façon notable la complexité moléculaire des composés obtenus.Parmi les chromophores possédant un état excité hautement réactif, générés par l'absorption d'un seul photon, les composés thiocarbonylés précurseurs des thiétanes via la réaction de thia-Paternò_Büchi avec un partenaire alcène ont été sous-exploités et la plupart des études impliquant ces dérivés datent de plusieurs décennies. La raison majeure de ce faible développement réside dans la grande instabilité des thiocétones et des thioaldéhydes. Durant cette thèse, il a été décidé de réinvestir la photochimie des thiocarbonyles stables et instables, dans le cadre de réactions domino pour la synthèse de nouveaux squelettes thiétaniques ainsi que pour leurs post-fonctionnalisations photochimiques. Afin de contrer l'instabilité intrinsèque des thiocarbonyles et de permettre leur utilisation dans leurs états excités, singulet ou triplet, nous avons tiré profit de la réaction de fragmentation de Norrish-II de sulfures de phénacyles et de pyrénacyles pour les générer in-situ et ainsi les engager dans d'autres transformations induites par la lumière au sein de cascades photochimiques.Dans ce cadre, nous avons tout d'abord combiné la fragmentation de Norrish-II des sulfures de phénacyles et la réaction de thia-Paternò_Büchi en présence de partenaires alcènes appauvris en électrons et ainsi obtenu une grande bibliothèque de thiétanes (37 exemples) sous irradiation UV. Puis, grâce aux nouvelles propriétés photosensibilisatrices du 1-acétylpyrène, un sous-produit formé par la fragmentation des sulfures de pyrènacyles sous lumière visible, cette même cascade photochimique a pu être développée en présence d'alcènes enrichis en électrons et a permis d'accroitre la liste de nouveaux thiétanes (26 exemples). Un troisième projet décrit la post-fonctionnalisation photochimique des thiétanes dans une réaction inédite d'agrandissement de cycle et la synthèse régiosélective de motifs dithianes par l'incorporation d'un motif thiocarbonyle généré in-situ (17 exemples). Enfin, une quatrième cascade photochimique a été mise en place impliquant une fragmentation de Norrish-II, une réaction de thia-Paternò_Büchi, un agrandissement de cycles thiétanes par un intermédiaire thiocarbonyle, puis enfin une contraction du dithiane pour conduire à la synthèse de tétrahydrothiophènes (7 exemples). Dans ce dernier cas, la réaction domino met en jeu quatre transformations photochimiques successives.Ces cascades photochimiques impliquant les motifs thiocarbonyles ont ainsi permis, à partir de sulfures de phénacyles ou de pyrénacyles et par irradiation à la lumière UV ou visible, de synthétiser les hétérocycles soufrés à quatre, cinq et six chaînons que sont les thiétanes, les tétrahydrothiophènes et les dithianes
Photochemical reactions constitute a powerful tool for the creation of molecular diversity in organic chemistry. From a simple starting material and a photon, they provide access to complex molecular structures that would be difficult to obtain with classical methodologies. These transformations induced by light absorption are particularly attractive in the context of sustainable development and they can address this challenge more effectively when they are incorporated into domino processes. Indeed, combined with thermal reactions or even better with other photochemical transformations, this strategy is economical in terms of time, energy, waste and can avoid the isolation of intrinsically unstable intermediates. These photochemical cascades also allow to significantly increase the molecular complexity of the obtained compounds.Among the chromophores possessing a highly reactive excited state generated by the absorption of a single photon, thiocarbonyl compounds, precursors of thietanes via the thia-Paternò_Büchi reaction with an alkene partner, have been underexploited and most studies involving these derivatives date from several decades ago. The main reason for this weak development is due to the huge instability of thioketones and thioaldehydes. During this PhD thesis, it has been decided to reinvest the photochemistry of stable and unstable thiocabonyls in the frame of domino sequences for the synthesis of new thietane scaffolds and their photochemical post-functionalization. To tackle the intrinsic instability of thiocarbonyls and to allow their use in excited state, singlet or triplet, we took advantage of the Norrish-II fragmentation of phenacyl or pyrenacyl sulfides to generate them in-situ and to engage then into other light-induced transformations within photochemical cascades.In this purpose, we first combined the Norrish-II fragmentation of phenacyl sulfides and the thia-Paternò_Büchi reaction in the presence of electron-withdrawing alkene partners to obtain a large library of thietanes (37 examples) under UV irradiation. Then, thanks to the new photosensitizing properties of the 1-acetylpyrene, a by-product formed during the fragmentation of pyrenacyl sulfides under visible light, the same photochemical cascade has been developed in the presence of electron-realizing alkene partners to enlarge the collection of unprecedented thietanes (26 examples). A third project describes the photochemical post-functionalization of thietanes in a new regioselective ring enlargement for the synthesis of dithiane scaffolds by the incorporation of in-situ generated thiocarbonyls (17 examples). Finally, a fourth photochemical cascade procedure has been described involving a Norrish-II fragmentation, a thia-Paternò_Büchi reaction, a ring enlargement of the thietane core by a thiocarbonyl intermediate and then a contraction of dithiane to allow the synthesis of tetrahydrothiophenes (7 examples). In the latter case, the domino reaction involves four successive photochemical transformations.From phenacyl or pyrenacyl sulfides and by UV or visible light irradiation, these photochemical cascades involving thiocarbonyl units provided access to four, five and six-membered ring sulfur heterocycles: thietanes, tetrahydrothiophene and dithianes, respectively

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Wagner, Katharina. "An Extension to Endoreversible Thermodynamics for Multi-Extensity Fluxes and Chemical Reaction Processes". Doctoral thesis, Universitätsbibliothek Chemnitz, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-146781.

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In this thesis extensions to the formalism of endoreversible thermodynamics for multi-extensity fluxes and chemical reactions are introduced. These extensions make it possible to model a great variety of systems which could not be investigated with standard endoreversible thermodynamics. Multi-extensity fluxes are important when studying processes with matter fluxes or processes in which volume and entropy are exchanged between subsystems. For including reversible as well as irreversible chemical reaction processes a new type of subsystems is introduced - the so called reactor. It is similar to endoreversible engines, because the fluxes connected to it are balanced. The difference appears in the balance equations for particle numbers, which contain production or destruction terms, and in the possible entropy production in the reactor. Both extensions are then applied to an endoreversible fuel cell model. The chemical reactions in the anode and cathode of the fuel cell are included with the newly introduced subsystem -- the reactor. For the transport of the reactants and products as well as the proton transport through the electrolyte membrane, the multi-extensity fluxes are used. This fuel cell model is then used to calculate power output, efficiency and cell voltage of a fuel cell with irreversibilities in the proton and electron transport. It directly connects the pressure and temperature dependencies of the cell voltage with the dissipation due to membrane resistance. Additionally, beside the listed performance measures it is possible to quantify and localize the entropy production and dissipated heat with only this one model
In dieser Arbeit erweitere ich den Formalismus der endoreversiblen Thermodynamik, um Flüsse mit mehr als einer extensiven Größe sowie chemische Reaktionsprozesse modellieren zu können. Mit Hilfe dieser Erweiterungen eröffnen sich zahlreiche neue Anwendungsmöglichkeiten für endoreversible Modelle. Flüsse mit mehreren extensiven Größen sind für die Betrachtung von Masseströmen ebenso nötig wie für Prozesse, bei denen sowohl Volumen als auch Entropie zwischen zwei Teilsystem ausgetauscht werden. Für sowohl reversibel wie auch irreversibel geführte chemische Reaktionsprozesse wird ein neues Teilsystem - der "Reaktor" - vorgestellt, welches sich ähnlich wie endoreversible Maschinen durch Bilanzgleichungen auszeichnet. Der Unterschied zu den Maschinen besteht in den Produktions- bzw. Vernichtungstermen in den Teilchenzahlbilanzen sowie der möglichen Entropieproduktion innerhalb des Reaktors. Beide Erweiterungen finden dann in einem endoreversiblen Modell einer Brennstoffzelle Anwendung. Dabei werden Flüsse mehrerer gekoppelter Extensitäten für den Zustrom von Wasserstoff und Sauerstoff sowie für den Protonentransport durch die Elektrolytmembran benötigt. Chemische Reaktionen treten in der Anode und Kathode der Brennstoffzelle auf. Diese werden mit dem neu eingeführten Teilsystem, dem Reaktor, eingebunden. Mit Hilfe des Modells werden dann Wirkungsgrad, Zellspannung und Leistung einer Brennstoffzelle unter Berücksichtigung der Partialdrücke der Substanzen, der Temperatur sowie der Dissipation beim Protonentransport berechnet. Dabei zeigt sich, dass experimentelle Daten für die Zellspannung sowohl qualitativ als auch näherungsweise quantitativ durch das Modell abgebildet werden können. Der Vorteil des endoreversiblen Modells liegt dabei in der Möglichkeit, mit nur einem Modell neben den genannten Kenngrößen auch die abgegebene Wärme sowie die Entropieproduktion zu quantifizieren und den einzelnen Teilprozessen zuzuordnen

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Galvin, Mark Robert. "Maintenance cycle extension in advanced light water reactor plant design". Thesis, Springfield, Va. : Available from National Technical Information Service, 2001. http://handle.dtic.mil/100.2/ADA393174.

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Galvin, Mark Robert 1967. "Maintenance cycle extension in advanced light water reactor plant design". Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/91336.

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Thesis (Nav.E.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2001.
"June 2001."
Includes bibliographical references.
by Mark Robert Galvin.
Nav.E.
S.M.

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Spielmann, Kim. "Synthèse asymétrique de petits cycles et leur réarrangement via des extensions cycliques". Thesis, Montpellier, Ecole nationale supérieure de chimie, 2018. http://www.theses.fr/2018ENCM0015.

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Ce manuscrit de thèse est consacré à l’élaboration asymétrique de petits cycles et à leur fonctionnalisation. En premier lieu, la synthèse énantiosélective de δ-lactones α,β-insaturées par une réaction de Mukaiyama vinylogue catalytique asymétrique a été examinée. Une étude pluridisciplinaire a permis de déterminer le cycle catalytique de cette transformation dans son ensemble. Par ailleurs, grâce à une hydrogénolyse stéréospécifique de ces lactones, la synthèse totale de deux produits naturels, (R)-curcumène et (R)-ar-himachalène, a pu être réalisée. Dans un second temps, une réaction de cycloaddition (3+2) palladocatalysée sur des vinyl-aziridines et cyclopropanes a été développée. Ainsi, des imidazolidines et des pyrrolidines hautement fonctionnalisées ont pu être isolées avec de bons rendements. En fonction du substrat utilisé, des comportements réactionnels différents ont pu être mis en évidence. Ces petits cycles peuvent être considérés comme des « briques moléculaires » polyvalentes pour accéder à des molécules plus complexes
This manuscript deals with the asymmetrical synthesis of small cyclic compounds and their functionalization. In a first part, the enantioselective synthesis of α,β-unsaturated δ-lactones by a catalytic asymmetric vinylogous Mukaiyama reaction was examined. A multidisciplinary study made possible the elucidation of the whole catalytic cycle. Moreover, thanks to a stereospecific hydrogenolysis of these lactones, the total synthesis of two natural products, (R)-ar-Himachalene and (R)-curcumene, could be achieved.In a second part, a palladocatalyzed (3+2) cycloaddition reaction of vinyl aziridines and cyclopropanes was developed. Thus, highly functionalized imidazolidines and pyrrolidines could be isolated with good yields. Depending on the substrate used, different reaction behaviors could be highlighted. These small cycles can be considered as versatile "building blocks" to access more complex molecules

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Law, Hiu-fai. "On quadratic extensions of cyclic projective planes". Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B36837490.

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Mais fontes

Livros sobre o assunto "Extension de cycles"

Aulin, Arvid. Causal and stochastic elements in business cycles: An essential extension of macroeconomics leading to improved predictions of data. New York: Springer-Verlag, 1996.

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Alpern, Steve. Cycles in extensive form perfect information games. London: Suntory-Toyota International Centre for Economics and Related Disciplines, 1989.

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Mayeske, George W. Life cycle program management: An heuristic approach. Washington, D.C: [Planning, Development and Evaluation Staff], Extension Service, U.S. Dept. of Agriculture, 1993.

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Greither, Cornelius. Cyclic Galois Extensions of Commutative Rings. Berlin, Heidelberg: Springer Berlin Heidelberg, 1992. http://dx.doi.org/10.1007/bfb0089165.

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Greither, Cornelius. Cyclic Galois extensions of commutative rings. Berlin: Springer-Verlag, 1992.

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Mayeske, George W. Life cycle program management & evaluation: An heuristic approach. 2^a ed. Washington, D.C: Extension Service, U.S. Dept. of Agriculture, 1994.

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Mayeske, George W. Life cycle program management & evaluation: An heuristic approach. 2^a ed. Washington, D.C: Extension Service, U.S. Dept. of Agriculture, 1994.

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Spokes, Leicester. Knighton Way & Knighton Grange extension [and] Braunstone cycle route: Spokes proposals and costings as submitted toLeicester Environmental City, 1991. Leicester: Leicester Spokes, 1991.

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Voet, Martin A. The generic challenge: Understanding patents, FDA & pharmaceutical life-cycle management. 2^a ed. Boca Raton: BrownWalker Press, 2008.

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VORONCOV, Andrey. Modern methods of training elite swimmers. ru: INFRA-M Academic Publishing LLC., 2023. http://dx.doi.org/10.12737/1865999.

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The textbook is based on the personal experience of a well—known specialist in the field of swimming A.R. Vorontsov. Technologies of preparation of swimmers of the highest international level for the largest competitions — the European championships, the world and the Olympic Games are considered. The analysis of the modern system of training in swimming is given. The development of a system of views on the training of swimmers is shown. The modern directions and content of the training process of swimmers of various specializations are highlighted, the features of classes in water and on land are revealed. The modern periodization of the training process is presented and examples of the construction of highly effective training programs by the world's leading trainers in the annual cycle of swimmer training are given. The manual contains an extensive collection of training sessions and training series with a detailed description and methodological explanations of their implementation. For professional swimming coaches, teachers and students of universities of physical culture, as well as for anyone interested in swimming.

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Mais fontes

Capítulos de livros sobre o assunto "Extension de cycles"

Jannsen, Uwe. "Algebraic cycles, K-theory, and extension classes". In Lecture Notes in Mathematics, 57–188. Berlin, Heidelberg: Springer Berlin Heidelberg, 1990. http://dx.doi.org/10.1007/bfb0085082.

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Schrefl, Michael, e Markus Stumptner. "Behavior consistent extension of object life cycles". In OOER '95: Object-Oriented and Entity-Relationship Modeling, 133–45. Berlin, Heidelberg: Springer Berlin Heidelberg, 1995. http://dx.doi.org/10.1007/bfb0020527.

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Fohr, Sherry E. "Karma, Austerity, and Time Cycles: Jainism and Radical Life Extension". In Religion and the Implications of Radical Life Extension, 75–84. New York: Palgrave Macmillan US, 2009. http://dx.doi.org/10.1057/9780230100725_7.

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Kappel, Gerti, e Michael Schrefl. "Inheritance of Object Behavior — Consistent Extension of Object Life Cycles". In Workshops in Computing, 289–300. London: Springer London, 1995. http://dx.doi.org/10.1007/978-1-4471-3577-7_21.

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Schwahn, Marie, Lukas Block, Thomas Potinecke e Maximilian Werner. "Modelling Usage-Specific Circularity Measueres for Individual Life Cycle Paths in Life Cycle Engineering". In Zukunftstechnologien für den multifunktionalen Leichtbau, 267–78. Wiesbaden: Springer Fachmedien Wiesbaden, 2024. https://doi.org/10.1007/978-3-658-45889-8_21.

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AbstractCircularity measures like repair, remanufacture and refurbish provide options to enhance the life cycle and thus the sustainability of a product besides measures, which primarily concentrate on the end-of-life of a product. To integrate the concept of circular value creation engendered by such measures in the development process of a product, we extended the idea of modelling standard life cycles as introduced by Block et al. [3]. This extension introduces the novel notion of undesired states within a product’s life cycle. Undesired states can be dissolved with the help of circularity measures. A Model Based Systems Engineering (MBSE) approach was developed to implement this strategy. The resultant modelling approach is implemented in form of a software tool. The system is evaluated within an automotive development project revealing a significant advantage in contrast to previous methods.

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Cullinane, Kevin, e Gordon Wilmsmeier. "The Contribution of the Dry Port Concept to the Extension of Port Life Cycles". In Operations Research/Computer Science Interfaces Series, 359–79. New York, NY: Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4419-8408-1_18.

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Andò, E., E. Salvatore, J. Desrues, P. Charrier, J. B. Toni, G. Modoni e G. Viggiani. "Strain Localisation in Sand in Cycles of Triaxial Compression and Extension: Continuum and Grain-Scale Analysis". In Springer Series in Geomechanics and Geoengineering, 489–97. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-56397-8_62.

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Müller, Rainer, e Martin Karkowski. "Generic Modeling Technique for Flexible and Highly Available Assembly Systems". In Annals of Scientific Society for Assembly, Handling and Industrial Robotics 2021, 3–14. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-74032-0_1.

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AbstractTo face the major challenges posed by the increasing product variants with shortening life cycles and fluctuating market conditions, modular and adaptable assembly systems are used. Their strong dependency on software creates a new void in the planning and implementation processes of these assembly systems. Usually, the programmer fills this void based on his knowledge, which leads to frequent and large adaptations of the code base. This is rather counter-productive. To address this challenge, we developed a generic user-friendly graphical API (Application Programming Interface) for a process owner in our previous work (Müller et al, Proc CIRP 81:730–735, 2019, [1]). This API can describe any assembly system and the associated task and is used to get the boilerplate code needed to execute the process on a programmable logic controller (PLC)—the standard hardware used in the industry. In this paper, the virtual description of an assembly system used by the API is extended to include a goal-oriented task description by defining the process and the structure. We believe that this extension provides the proper abstraction needed by the process owner. In addition, this extension significantly reduces the modeling effort.

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Escofier, Jean-Pierre. "Cyclic Extensions". In Graduate Texts in Mathematics, 179–93. New York, NY: Springer New York, 2001. http://dx.doi.org/10.1007/978-1-4613-0191-2_10.

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Roman, Steven. "Cyclic Extensions". In Field Theory, 209–14. New York, NY: Springer New York, 1995. http://dx.doi.org/10.1007/978-1-4612-2516-4_12.

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Trabalhos de conferências sobre o assunto "Extension de cycles"

Rakoczy, Anna M., Lukasz Porzyc e Diogo Ribeiro. "Predicting long-term service performance of a prestressed concrete bridge using a probabilistic method and remote bridge inspection technologies". In IABSE Congress, San José 2024: Beyond Structural Engineering in a Changing World, 987–94. Zurich, Switzerland: International Association for Bridge and Structural Engineering (IABSE), 2024. https://doi.org/10.2749/sanjose.2024.0987.

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<p>The bridge structures are exposed to numerous live loads and environmental cycles during their service, which can cause degradation, defects, and reduction of the bridge capacity. As the capacity of the bridge reduces over time, the reliability index also reduces, which indicates the safety of bridge operation is compromised. Fitness for Service (FFS) assessment, which uses probabilistic methods and is supplemented by and consistent with detailed technical inspections of the structures, provides most accurate assessment of the expected bridge service. This article presents a probabilistic method used for the forecasting FFS of existing railway bridges and viaducts. The methodology is presented on a prestressed concrete viaduct that serves as a crucial link to the Pirâmides bridge and forms a railway extension to the coastal maritime port of Aveiro, Portugal. The FFS assessment accounted for the finding from remote bridge inspection.</p>

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Moreira, Margarida, Eliseu Pereira e Gil Gonçalves. "Data-Driven Predictive Maintenance for Component Life-Cycle Extension". In 21st International Conference on Informatics in Control, Automation and Robotics, 126–36. SCITEPRESS - Science and Technology Publications, 2024. http://dx.doi.org/10.5220/0013014200003822.

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Boswell, Richard S., e Bobby Wright. "State-of-the-Art Improvements in Coke Drum Design and Life Extension Practices". In ASME 2007 Pressure Vessels and Piping Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/creep2007-26254.

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Coke drums are vessels critical to the operation and profitability of today’s oil refinery and tar sands facilities. These vessels operate in batch cycles at relatively high temperatures, ∼800F+, and about once a day they are filled with vapor and hot oil and finally quenched with water. They have historically been designed according as ASME Section VIII Division 1 pressure vessels with little or no account for the cyclic operation or fatigue service in which they operate. In the past ten years, the frequency and severity of these cycles dramatically increased while cycle times steadily decreased from 24 to 12 hour cycles and, more recently, to as low as 10 hour cycles. As a result, coke drums with few or no previous problems began to crack through wall in the shell and/or skirt region. In addition, many new coke drums are cracking through wall in as few as four to five years because they were not designed for the more severe fatigue service in which they currently operate. These observations have been learned by extensive monitoring and evaluation: • drums experienced lower switch temperatures (inadequate pre-warm for the skirt), • drums were heated and cooled much faster than anticipated, • contraction of the drum walls compacted the coke, • feed stocks were now different and produced harder coke, • reducing cycle times by as little as two hours caused average fatigue damage per cycle to increase by more than 30%. All of these occurrences can increase cyclic stress on drums and significantly accelerate cracking.

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Ronevich, Joseph A., Chris San Marchi, Dusty Brooks, John M. Emery, Peter Grimmer, Eileen Chant, J. Robert Sims, Alex Belokobylka, Dave Farese e John Felbaum. "Exploring Life Extension Opportunities of High-Pressure Hydrogen Pressure Vessels at Refueling Stations". In ASME 2021 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/pvp2021-61815.

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Abstract High pressure Type 2 hoop-wrapped, thick-walled vessels are commonly used at hydrogen refueling stations. Vessels installed at stations circa 2010 are now reaching their design cycle limit and are being retired, which is the motivation for exploring life extension opportunities. The number of design cycles is based on a fatigue life calculation using a fracture mechanics assessment according to ASME Section VIII, Division 3, which assumes each cycle is the full pressure range identified in the User’s Design Specification for a given pressure vessel design; however, assessment of service data reveals that the actual pressure cycles are more conservative than the design specification. A case study was performed in which in-service pressure cycles were used to re-calculate the design cycles. It was found that less than 1% of the allowable crack extension was consumed when crack growth was assessed using in-service design pressures compared to the original design fatigue life from 2010. Additionally, design cycles were assessed on the 2010 era vessels based on design curves from the recently approved ASME Code Case 2938, which were based on fatigue crack growth rate relationships over a broader range of ΔK. Using the Code Case 2938 design curves yielded nearly 2.7 times greater design cycles compared to the 2010 vessel original design basis. The benefits of using in-service pressure cycles to assess the design life and the implications of using the design curves in Code Case 2938 are discussed in detail in this paper.

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Shen, Jun, Mingwan Lu, Zhenyu Wang, Heng Peng e Yinghua Liu. "Modification and Extension of Screening Criteria for Fatigue Analysis". In ASME 2019 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/pvp2019-93341.

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Abstract ASME Code VIII-2-2017 and previous versions provided three screening criteria for fatigue analysis. From Edition 2004 to 2017, the design factor for material allowable stress decreased and the considered range of permissible cyclic number for design fatigue curve extended. However, screening criterion are almost unchanged except one restriction: If the specified number of cycles is greater than 106, then the screening criteria are not applicable and a fatigue analysis is required. In this paper, percentage limit of the design pressure in Method A is modified and the specified number of cycles is extended. Some revision suggestions are also proposed to broaden the applicable range of the screening criterion.

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Muthu, S. Esakki, A. Selwyn, Hardik Roy e Girish K. Degaonkar. "Life Extension of Axial Compressor Disc of a Turbo-Shaft Engine". In ASME 2013 Gas Turbine India Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/gtindia2013-3645.

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The cost of aero engine and its maintenance is going higher day by day, the life of the critical parts and its availability play a major role to keep the fleet in operation. Engine components works under extremely high stress levels so the life of the components is limited. Most of the critical components are retired by the operator before they reach their theoretical life. The uncertainty in accurate life prediction induces the risk which is the cause for premature retirement. Metallurgical study of the life expired components and fatigue/fracture methodologies are used to estimate the residual useful life of the components. This paper describes the life extension methodology used for an axial compressor disc of turbo-shaft engine. The disc has completed its safe life in the aircraft. The studies are carried out to determine the residual life of the disc to extend the life. Two life completed disc are identified. Specimens are cut from the disc for tensile test and LCF tests. Probable mission cycles for the aircraft are collected and fatigue cycle data are prepared. Finite element based stress analysis is carried out using Ansys software with multi axial loads. Based on the stress analysis, disc bore and pin hole are identified as critical area. The computed stress–strain response is used to predict the fatigue crack initiation life using effective strain range parameters on the critical areas. Fatigue damage for different mission cycles are also calculated using critical plane approach. The plane where crack initiate is called critical plane and it is calculated iteratively based on the nodal stress result. Life for different mission cycle is calculated and minimum life of all the cycle is determined. This calculated life gives the amount of residual life available and the scope for life extension. The disc is tested in cyclic spin test rig to confirm the remaining potential life. The test results are compared with the numerical estimation. It is found that the residual life of the life completed component has got potential life of one more overhaul.

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Wheeler, Robert W., Joseph Ronevich, Chris San Marchi, Peter Grimmer e John M. Emery. "Development of C-Ring Geometry to Explore Fatigue Crack Extension and Verification in High-Pressure Vessels". In ASME 2022 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/pvp2022-84635.

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Abstract High pressure hydrogen storage vessels are frequently retired upon reaching their designed number of pressure cycles, even in cases where the in-use pressure cycles are significantly less severe than the design pressure cycle. One method for extending the life of hydrogen vessels is recertification through non-destructive evaluation (NDE); however, NDE techniques are frequently evaluated with machined defects in test samples rather than fatigue cracks which occur during pressure cycling and may be more difficult to detect. In this paper, 50 mm wide ring sections (called C-rings, since they represent slightly more than half the circumference) were extracted from pressure vessels and mechanically cycled to establish fatigue cracks. Sub-millimeter starter notches were machined, via plunge electrical discharge machining (EDM), to control the location of crack initiation. Crack growth was monitored via direct current potential difference (DCPD) and backface strain gauges, both of which were shown to be good indicators for crack propagation. The C-ring geometry and fatigue crack growth were modeled to demonstrate the ability to monitor/control the crack length and area, which can be used to develop calibration samples of varying crack depth for NDE techniques. Additionally, this sample is intended to evaluate the influence of residual stresses on the sensitivity of NDE techniques, such as the design stresses in autofrettaged vessels.

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Sakamoto, Haruo, Hiromichi Ishiduka, Makoto Akama e Kenichi Tanaka. "Possibility of Fatigue Crack Extension Under Cyclic Large Compressive Stress by Medium Frequency Induction Hardening". In ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-66185.

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Induction hardened axles have been used since the start of the Shinkansen (Japanese Bullet train) service in 1964. Axles are subjected to cyclic loading, and induction hardened axles are used under cyclic compressive stress conditions because of the large compressive stress state caused by induction hardening along the axle surface. Japanese Railways regularly inspect its axles, and if any crack larger than 0.15 mm in depth is found, the axle is taken out of service. The compressive stress is around −500 MPa, and magnetic particle inspection is conducted at intervals of 2.2×108 and 4.4×108 rotation. The issue of whether or not a crack more than 0.15 mm in depth will propagate under cyclic large compressive stress conditions is of great importance from the viewpoint of railroad safety. From the above mentioned background, a literature survey and experiment of fatigue crack extension under a cyclic large compressive stress condition were conducted. The results show that the crack did extend in the range of around 3.6–5.0×108 cycles under the condition of −500∼0 MPa cycle. Elastic-perfectly plastic stress analysis was also conducted to understand the possibility of tensile residual stress origination, which is considered to be a cause of extension. The analysis of −500∼0 MPa cycle showed that a large tensile stress of about 89.5 MPa originated at the crack tip when unloading. Whereas, the analysis of −560∼−440 MPa cycle for actual maximum stress in the field showed compressive when unloading.

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Kinoshita, Keisuke, Yoshitaka Suzuki, Takuya Kumagai, Osamu Watanabe e Akihiro Matsuda. "Multiple Crack Extension and Temperature Effect of Perforated Plate in Elevated Temperature Fatigue Test". In ASME 2013 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/pvp2013-97871.

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The present paper presents the experimental results for fatigue crack propagation of SUS304 steel perforated plate at an elevated temperature of 550°C. (1) The specimens have two holes placed at an angle of 30°, 60° and 90°. Crack initiation cycle is determined from the pictures showing crack propagation process, which are measured with a CCD camera at a regular interval cycle. The stress concentration is larger in the order of 60°, 90° and 30°, the number of cycles to failure Nf follows this order. By using the inelastic strain amplitude, cycles to crack initiation for each specimen can be predicted. Hereafter, multiple cracks at different sites propagate according to the strain concentration contours. (2) The effect of high temperature on fatigue strength is also investigated for temperature from 500°C to 700°C. Cracks occurring at hole sides are measured by a CCD camera and the crack growth is calculated from photographs. Some specimens show the multiple small cracks at hole-side. (3) This paper also discusses fatigue evaluation of the circular notched plate under the inter-laminar shear loading at elevated temperature. FEM analysis of a specimen shows the distribution of stress under inter-laminar shear loading. Fatigue tests were conducted, and compared with results of analysis. The stress distribution under the inter-laminar shear loading shows unique distributions compared with those under the tensile loading, which is consistent with experimental results.

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Zhang, Hongbin, Cole Blakely e Jianguo Yu. "Demonstration of Multi-Physics Evaluation of Fuel Rod Burst Probability With Burnup Extension Under LBLOCA Conditions". In 2020 International Conference on Nuclear Engineering collocated with the ASME 2020 Power Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/icone2020-16098.

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Abstract Extending the fuel discharge burnup level, e.g., from the current limit of rod averaged discharge burnup limit of 62 GWD/MT to a proposed new limit of 75 GWD/MT, can provide significant economic benefits to the current fleet of operating light water reactors (LWRs). It allows for longer operating cycles and improved resource utilization. The major economic gain of longer operating cycles is attributable to the increased capacity factor resulting from decreased refueling time as a fraction of total operating time, as well as fewer assemblies to be discharged for a given amount of energy produced. The main licensing challenges for higher burnup fuel are to ensure fuel rod safety under design basis accident conditions, especially under large-break loss-of-coolant accident (LBLOCA) and reactivity insertion accident (RIA). In this work, two-year cycle core design for a typical 4-loop pressurized water reactor (PWR) is performed with enrichment increased up to 6% and burnup extended to 75 GWD/MT. The fuel rod burst potential evaluations under large-break loss-of-coolant accident (LBLOCA) conditions are subsequently performed using the multi-physics best estimate plus uncertainty analysis framework LOTUS (LOCA Toolkit for the U.S. LWRs) and the preliminary results are presented.

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Relatórios de organizações sobre o assunto "Extension de cycles"

Mahmoud, Hussam, Guillermo Riveros, Lauren Hudak e Emad Hassan. Experimental fatigue evaluation of underwater steel panels retrofitted with fiber polymers. Engineer Research and Development Center (U.S.), março de 2023. http://dx.doi.org/10.21079/11681/46647.

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Many steel structures are susceptible to fatigue loading and damage that potentially threaten their integrity. Steel hydraulic structures (SHS) experience fatigue loading during operation and exposure to harsh environmental conditions that can further reduce fatigue life through stress corrosion cracking and corrosion fatigue, for example. Dewatering to complete inspections or repairs to SHS is time consuming and leads to economic losses, and current repair methods, such as rewelding, often cause new cracks to form after relatively few cycles, requiring repeated inspection and repair. The use of bonded carbon fiber–reinforced polymer (CFRP) to repair fatigue cracks in metallic structures has been successful in other industries; recent work suggests that this method offers a more reliable repair method for SHS. Studies regarding CFRP retrofits of SHS indicate that early bond failure often controls the degree of fatigue life extension provided by the repair. This study aims to extend previous studies and increase the fatigue life of repaired steel components by employing methods to improve CFRP bonding. Additionally, using basalt reinforced polymer (BFRP) instead of CFRP is proposed. BFRP is attractive for SHS because it does not react galvanically and has excellent resistance to chemically active environments.

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Devereux, Michael, e Viktoria Hnatkovska. The Extensive Margin, Sectoral Shares and International Business Cycles. Cambridge, MA: National Bureau of Economic Research, agosto de 2011. http://dx.doi.org/10.3386/w17289.

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Jovanovic, Boyan, e Peter Rousseau. Extensive and Intensive Investment over the Business Cycle. Cambridge, MA: National Bureau of Economic Research, maio de 2009. http://dx.doi.org/10.3386/w14960.

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Professor Neill Todreas. Nuclear Systems Enhanced Performance Program, Maintenance Cycle Extension in Advanced Light Water Reactor Design. Office of Scientific and Technical Information (OSTI), outubro de 2001. http://dx.doi.org/10.2172/839057.

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Williams. L51671 Criteria for Dent Acceptability of Offshore Pipelines. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), julho de 1992. http://dx.doi.org/10.55274/r0010217.

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Extensive research has provided an understanding in the behavior of pipelines subjected to mechanical damage. The presence of a gouge or the combination of a gouge and a dent has been proven detrimental to the burst strength of pipelines. The research has also revealed that plain smooth dents, in the absence of a defect, do not significantly reduce the burst strength of pipelines. On the other hand, plain dents locally increase the pipe stress due to pressure. Thus, fatigue failures from dents can occur from normal operating pressure fluctuations in the lines over a period of time This report documents the testing and analysis work done to establish the effects of pipeline dents (without gouges) under cyclic internal pressure loading. The work consisted of several sub-tasks. First, operators were surveyed regarding the expected dent shapes and failures from dents that had been experienced. Secondly, a full scale test program utilizing 12-3/4" pipe was carried out. In this program eight pipes, each 20" long with diameter/thickness ratios of 18-50, were subjected to three dents each of various sizes and pressure cycled until failure or until 50,000 to 70,000 equivalent cycles of 0 - 1200 psi pressure was achieved. Next, elastic finite element analysis was utilized to determine the significance of dent shapes and lengths. Finally plastic finite element analysis was utilized to determine analytically the stress to pressure ratios so that a fatigue analysis could be done.

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Gálvez, Julio. Household portfolio choices under (non-)linear income risk: an empirical framework. Madrid: Banco de España, setembro de 2023. http://dx.doi.org/10.53479/33792.

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This paper develops a flexible, semi-structural framework to empirically quantify the non-linear transmission of income shocks to household portfolio choice decisions both at the extensive and intensive margins. I model stock market participation and portfolio allocation rules as age-dependent functions of persistent and transitory earnings components, wealth and unobserved taste shifters. I establish non-parametric identification and propose a tractable, simulation-based estimation algorithm, building on recent developments in the sample selection literature. Using recent waves of PSID data, I find heterogeneous income and wealth effects on both extensive and intensive margins, over the wealth and life-cycle dimensions. These results suggest that preferences are heterogeneous across the wealth distribution and over the life cycle. Moreover, in impulse response exercises, I find sizeable extensive margin responses to persistent income shocks. Finally, I find heterogeneity in participation costs across households in the wealth distribution.

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Moisseytsev, A. Extension of Argonne’s Plant Dynamics Code (PDC) Capabilities to TerraPower Direct-Cycle Supercritical CO2 (“Pascal”) Nuclear Reactor Concept. Office of Scientific and Technical Information (OSTI), maio de 2023. http://dx.doi.org/10.2172/1988244.

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Buchanan, Randy, Christina Rinaudo, George Gallarno e M. Lagarde. Early life-cycle prediction of reliability. Engineer Research and Development Center (U.S.), abril de 2023. http://dx.doi.org/10.21079/11681/46919.

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The intent of this project is to investigate a variety of approaches for the development of a basic model for the early life-cycle prediction of reliability (pre-Milestone A). The United States Department of Defense (DoD) currently utilizes an acquisition framework in which system development advances through a series of checkpoints known as milestones. Each milestone represents a decision point, with Milestone A being the earliest in the life cycle. At Milestone A, also known as the risk-reduction decision, the DoD evaluates design concepts while also committing funds to the maturation of technologies in an effort to mitigate future risks. Typically, little is known about the particular system to be developed at this point in the acquisition life cycle, but DoD regulations require program man-agers to submit system reliability information (OUSD[A&S] 2015). Traditional reliability predictions, however, require extensive knowledge of the system of interest to produce accurate results. This level of knowledge is unavailable at or before Milestone A, there-fore, there is a need to create models and methodologies for the prediction of system reliability. This report provides an overview of a variety of methods investigated to improve the prediction of early life cycle reliability.

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Pu, Zhaoxia, Carolyn Reynolds e Allen Zhao. The Properties of Convective Clouds over the Western Pacific and Their Relationship to the Environment of Tropical Cyclones (No-Cost Extension). Fort Belvoir, VA: Defense Technical Information Center, setembro de 2013. http://dx.doi.org/10.21236/ada597928.

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Olsen e Fletcher. L52071 Literature Review Fuel-Air Mixing in Large Bore Natural Gas Engines. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), março de 1999. http://dx.doi.org/10.55274/r0010949.

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Mixing is viewed as being problematic in many internal combustion engines, particularly large bore natural gas engines. In reviewing the literature an attempt is made to distinguish between the influences of mixing and turbulence, although for much of the published research the distinction is not made. Mixing is determined to have a major impact on engine efficiency, overall emissions, flame propagation, and cycle-to-cycle variations. The improvement of engine efficiency and overall emissions is concluded to be primarily due to the extension of the lean limit, a direct consequence of improved mixing. Test results from a study on propane combustion in a constant volume combustion chamber indicate that there is an optimum level of mixing for maximizing the flame propagation speed. In other words, the fastest flame speed occurs when there is some level of mixture heterogeneity, as opposed to a completely uniform mixture. A detailed literature review is carried out on air-fuel mixing in internal combustion engines, emphasizing application to direct injection large bore natural gas engines. The literature is separated into three broad categories, (1) the effects of mixing on engine performance, emissions, and combustion characteristics, (2) factors affecting mixing, and (3) mixing characterization.

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