11,653 research outputs found

    Convergence Analysis of the Straightforward Expansion Perturbation Method for Weakly Nonlinear Vibrations

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    There are typically several perturbation methods for approaching the solution of weakly nonlinear vibrations (where the nonlinear terms are "small" compared to the linear ones): the Method of Strained Parameters, the Naive Singular Perturbation Method, the Method of Multiple Scales, the Method of Harmonic Balance and the Method of Averaging. The Straightforward Expansion Perturbation Method (SEPM) applied to weakly nonlinear vibrations does not usually yield to correct solutions. In this manuscript, we provide mathematical proof of the inaccuracy of the SEPM in general cases. Nevertheless, we also provide a sufficient condition for the SEPM to be successfully applied to weakly nonlinear vibrations. This mathematical formalism is written in the syntax of the first-order formal language of Set Theory under the methodology framework provided by the Category Theory

    “Enriching Lives within Sedimentary Geology”: Actionable Recommendations for Making SEPM a Diverse, Equitable and Inclusive Society for All Sedimentary Geologists

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    Innovative science benefits from diversity of thought and influence at all waypoints along the scientific journey, from early education to career-length contributions in research and mentorship. Scientific societies, like the Society for Sedimentary Geology (SEPM), steward their innovators and the direction of the science, thereby defining the societal impact and evolution of a discipline. They are uniquely positioned to promote the representation and success of all scientists, including those from minoritized populations, through proactive advocacy, and inclusive mentorship, awards, and leadership. We introspectively review available records of SEPM membership, leadership, awardees, and editorial boards to identify areas for growth and begin a dialogue about how the society and its members can work together to better reflect our community. In the last decade, SEPM has seen a decline in membership, while representation and recognition of scientists from minoritized groups has remained low. Awards and honors have overwhelmingly gone to men, even in the last ten years, and very few women or people of color are in leadership roles. SEPM has recently taken positive steps towards becoming more inclusive (e.g., the Code of Professional Conduct); however, much more work is needed. We provide recommendations for swift actions that SEPM and its members should undertake for the society to become a diverse, inclusive, and equitable environment where all scientists thrive. The systemic changes needed will take continuous effort, which must be shared by all of us, to build an enduring legacy that we can be proud of

    Determinacy of games with Stochastic Eventual Perfect Monitoring

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    We consider an infinite two-player stochastic zero-sum game with a Borel winning set, in which the opponent's actions are monitored via stochastic private signals. We introduce two conditions of the signalling structure: Stochastic Eventual Perfect Monitoring (SEPM) and Weak Stochastic Eventual Perfect Monitoring (WSEPM). When signals are deterministic these two conditions coincide and by a recent result due to Shmaya (2011) entail determinacy of the game. We generalize Shmaya's (2011) result and show that in the stochastic learning environment SEPM implies determinacy while WSEPM does not

    Multilingualism and Formulations of Scholarship: The Rosen Vocabulary

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    The Rosen Vocabulary is an Old Babylonian bilingual text. Through an edition of this text, I argue that the ad-hoc mixed vocabularies known from the Old Babylonian period feature citations or allusions to literary compositions as well as subsequent analogous expressions, both in Sumerian and in Akkadian

    Atmospheric particulate matter from an industrial area as a source of metal nanoparticle contamination in aquatic ecosystems

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    Air pollution legislation and control worldwide is based on the size of particulate matter (PM) to evaluate the effects on environmental and human health, in which the small diameter particles are considered more dangerous than larger sizes. This study investigates the composition, stability, size and dispersion of atmospheric settleable particulate matter (SePM) in an aqueous system. We aimed to interrogate the changes in the physical properties and characteristics that can contribute to increased metal uptake by aquatic biota. Samples collected in an area influenced by the steel and iron industry were separated into 8 fractions (425 to ≤10 μm) and analysed physically and chemically. Results from ICP-MS and X-ray showed that the PM composition was mainly hematite with 80% of Fe, followed by Al, Mn and Ti. Among 27 elements analysed we found 19 metals, showing emerging metallic contaminants such as Y, Zr, Sn, La, Ba and Bi. Scanning electron microscopy (SEM) showed that SePM fractions are formed by an agglomeration of nanoparticles. Furthermore, dynamic light scattering (DLS), zeta potential and nanoparticle tracking analysis (NTA) demonstrated that SPM were dissociated in water, forming nanoparticles smaller than 200 nm, which can also contribute to water pollution. This study highlights that SePM contamination may be substantially higher than expected under that allowed in atmospheric regulatory frameworks, thereby extending their negative effect to water bodies upon settling, which is an underexplored area of our knowledge. We therefore provide important insights for future investigations on safety regulations involving SePM in the environment, indicating the need to revise the role of SePM, not solely associated with air pollution but also considering their deleterious effects on water resources
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