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Thermal and energy analysis of DMTA tests
No full textThis paper investigates the suitability of the isothermal linear viscoelastic framework to describe the behavior of polymers observed during DMTA tests. A good interpretation of these tests is important because, in practice, they are used to construct master curves using the time-temperature superposition principle at small strain. These curves are then considered to predict the material behavior under experimentally unreachable thermal and/or loading frequency conditions. Currently, the DMTA protocol neglects the temperature variations induced by the deformation of polymers. We wonder if these temperature variations can have an influence on the measurement of dynamic moduli. To answer this question, quantitative infrared techniques were developed and used to assess small temperature variations of samples undergoing cyclic loadings during mechanical spectrometry tests. Thermal and mechanical data were used to quantify the viscous dissipated and the thermoelastic coupling energies that can be both associated with the hysteretic stress-strain response of polymers. Energy balances were then performed to quantify the relative importance of dissipative and thermoelastic coupling heat sources. From the energy standpoint, it is found that the thermoelastic energy rate was dozens of times higher than the dissipation. Especially at low frequencies, thermoelastic effects can have a greater influence on the loss modulus value than viscosity
Plasticity and ductility of an anisotropic recrystallized AA2198 Al-Cu-Li alloy in T3 and T8 conditions during proportional and non-proportional loading paths: simulations and experiments
No full textThe anisotropic material behaviour of a recrystallized AA2198 Al-Cu-Li alloy in T3 and T8 conditions was assessed by proportional loading of uniaxial-tension specimens in rolling (L), transverse (T) and diagonal (D) orientations. The width and longitudinal strains were measured to quantify plastic anisotropy. Notched-tension samples were tested in L and T directions. The material showed weak anisotropy in terms of stress strain curves and a moderate plastic anisotropy, consistent with its texture obtained by EBSD. An anisotropic Bron-Besson type material model was identified using this data base and a micro shear-only (SO) test. The model succeeded in predicting the behaviour of micro specimens for proportional tension-only (TO) loading and non-proportional load path changes including 'shear to tension' (ST) as well as 'tension to shear' (TS) tests. The non-proportional loading was achieved using a newly designed cross shaped sample. It was loaded in one direction, unloaded and subsequently loaded in the orthogonal direction till fracture. The average stretch to fracture of both alloys measured by a four point frame optical extensometer decreased by 29 % and 16 % for T3 and T8 respectively for the 'shear to tension' experiment compared to the proportional TO experiment. The average stretch to fracture of 'tension to shear' tests was reduced by 10 % for 2198T3 and hardly reduced for 2198T8 compared to the stretch to fracture of the SO tests, but subject to strong scatter. FE simulations showed local accumulated strain to fracture values that were similar for all loading histories for the T8 condition (0.73 − 0.84). Lower strain to fracture values were found in T3 condition (0.45 − 0.73), despite the enhanced macroscopic ductility in tension. This was attributed to larger less localized plastic zones, especially for the ST test. The ductility scatter was attributed to necking and damage development in tension that can affect strain localization, associated fracture path and ductility, as observed by DIC and fractography
Multi-recipient and threshold encryption based on hidden multipliers
No full textLet be a pool of parties and Alice be the dealer. In this paper, wepropose a scheme that allows the dealer to encrypt messages in such a way thatonly one authorized coalition of parties (which the dealer chooses depending onthe message) can decrypt. At the setup stage, each of the parties involved inthe process receives an individual key from the dealer. To decrypt information,an authorized coalition of parties must work together to use their keys. Basedon this scheme, we propose a threshold encryption scheme. For a given message the dealer can choose any threshold More precisely, any set ofparties of size at least can evaluate ; any set of size less than cannot do this. Similarly, the distribution of keys among the included partiescan be done in such a way that authorized coalitions of parties will be giventhe opportunity to put a collective digital signature on any documents. Thisprimitive can be generalized to the dynamic setting, where any user candynamically join the pool . In this case the new user receives a key fromthe dealer. Also any user can leave the pool . In both cases, alreadydistributed keys of other users do not change. The main feature of the proposedschemes is that for a given the keys are distributed once and can be usedmultiple times. The proposed scheme is based on the idea of hidden multipliers in encryption.As a platform, one can use both multiplicative groups of finite fields andgroups of invertible elements of commutative rings, in particular,multiplicative groups of residue rings. We propose two versions of this scheme.Comment: 12 pages. Published in journal of Groups, Complexity, Cryptology. arXiv admin note: substantial text overlap with arXiv:2108.0696
On the minimal model program for projective varieties with pseudo-effective tangent sheaf
No full textIn this paper, we develop a theory of pseudo-effective sheaves on normalprojective varieties. As an application, by running the minimal model program,we show that projective klt varieties with pseudo-effective tangent sheaf canbe decomposed into Fano varieties and Q-abelian varieties.Comment: completely revised version, 13 page
Minimal toughness in special graph classes
No full textLet be a positive real number. A graph is called -tough if the removalof any vertex set that disconnects the graph leaves at most components, and all graphs are considered 0-tough. The toughness of a graph isthe largest for which the graph is -tough, whereby the toughness ofcomplete graphs is defined as infinity. A graph is minimally -tough if thetoughness of the graph is , and the deletion of any edge from the graphdecreases the toughness. In this paper, we investigate the minimum degree andthe recognizability of minimally -tough graphs in the classes of chordalgraphs, split graphs, claw-free graphs, and -free graphs
A Formal Model for Polarization under Confirmation Bias in Social Networks
No full textWe describe a model for polarization in multi-agent systems based on Estebanand Ray's standard family of polarization measures from economics. Agentsevolve by updating their beliefs (opinions) based on an underlying influencegraph, as in the standard DeGroot model for social learning, but under aconfirmation bias; i.e., a discounting of opinions of agents with dissimilarviews. We show that even under this bias polarization eventually vanishes(converges to zero) if the influence graph is strongly-connected. If theinfluence graph is a regular symmetric circulation, we determine the uniquebelief value to which all agents converge. Our more insightful resultestablishes that, under some natural assumptions, if polarization does noteventually vanish then either there is a disconnected subgroup of agents, orsome agent influences others more than she is influenced. We also prove thatpolarization does not necessarily vanish in weakly-connected graphs underconfirmation bias. Furthermore, we show how our model relates to the classicDeGroot model for social learning. We illustrate our model with severalsimulations of a running example about polarization over vaccines and of othercase studies. The theoretical results and simulations will provide insight intothe phenomenon of polarization.Comment: arXiv admin note: substantial text overlap with arXiv:2104.1153
Adaptive Merging on Phase Change Memory
No full textIndexing is a well-known database technique used to facilitate data accessand speed up query processing. Nevertheless, the construction and modificationof indexes are very expensive. In traditional approaches, all records in thedatabase table are equally covered by the index. It is not effective, sincesome records may be queried very often and some never. To avoid this problem,adaptive merging has been introduced. The key idea is to create indexadaptively and incrementally as a side-product of query processing. As aresult, the database table is indexed partially depending on the queryworkload. This paper faces a problem of adaptive merging for phase changememory (PCM). The most important features of this memory type are: limitedwrite endurance and high write latency. As a consequence, adaptive mergingshould be investigated from the scratch. We solve this problem in two steps.First, we apply several PCM optimization techniques to the traditional adaptivemerging approach. We prove that the proposed method (eAM) outperforms atraditional approach by 60%. After that, we invent the framework for adaptivemerging (PAM) and a new PCM-optimized index. It further improves the systemperformance by 20% for databases where search queries interleave with datamodifications
A Finite Axiomatisation of Finite-State Automata Using String Diagrams
No full textWe develop a fully diagrammatic approach to finite-state automata, based onreinterpreting their usual state-transition graphical representation as atwo-dimensional syntax of string diagrams. In this setting, we are able toprovide a complete equational theory for language equivalence, with two notablefeatures. First, the proposed axiomatisation is finite. Second, the Kleene staris a derived concept, as it can be decomposed into more primitive algebraicblocks.Comment: arXiv admin note: text overlap with arXiv:2009.1457
Can a Catholic be Liberal? Roman Catholicism and Liberalism in a Political Economy Perspective (1800–1970)
No full textThe philosophy of the Enlightenment and political thought of modernity found tough opposition in the Roman Catholic Church. Liberalism was associated with Free Masons and revolutionary intent. Nonetheless, liberalism and political economy stimulated some theoretical analysis and specific theoretical positions in terms of social philosophy and social economics by the Church. This paper presents an analysis of encyclical letters and other papal documents, as well as the writings of other Catholic scholars, to elaborate on the theoretical points used to contrast liberalism. Compromises, as well as turning points in the evolution of the Catholic position, are investigated. Lastly, the epistemological and historical reasons for the affinity of Roman Catholicism with ethical liberalism and the limits of this similarity are discussed. 1. Liberal and Catholic, an Italian dram
