453 research outputs found

    High pressure mechanical seal

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    A relatively impervious mechanical seal is formed between the outer surface of a tube and the inside surface of a mechanical fitting of a high pressure fluid or hydraulic system by applying a very thin soft metal layer onto the outer surface of the hard metal tube and/or inner surface of the hard metal fitting, prior to swaging the fitting onto the tube. The thickness of such thin metal layer is independent of the size of the tube and/or fittings. Many metals and alloys of those metals exhibit the requisite softness, including silver, gold, nickel, tin, platinum, indium, rhodium and cadmium. Suitably, the coating is about 0.0025 millimeters (0.10 mils) in thickness. After swaging, the tube and fitting combination exhibits very low leak rates on the order or 10.sup.-8 cubic centimeters per second or less as meaured using the Helium leak test

    Preparing academic libraries to negotiate a sustainable future

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    Learn about a multi-institutional project developing curriculum and open educational resources (OER) to equip academic library workers with negotiation skills within the context of academic libraries work with third party vendors. The project team is intentionally working to center the experiences of BIPOC library workers through each stage of the project including curriculum design, OER creation, and pilot testing. This presentation will walk through the key learnings around negotiations and the curriculum, before opening the session for discussion and feedback. A core ethos of the project is that something created to serve the community cannot be made without the community. Learning Outcomes: Participants will be able to articulate why negotiation skills are a necessary skill set for work and life. Participants will understand key issues facing academic library workers when negotiating with third-party vendors so that they may begin to proactively plan how to address at their own institutions. Participants will gain resources to get started in developing negotiation skills so that they may be more prepared for their next negotiation at work.IMLS Laura Bush 21st Century Librarian Grant Progra

    S'more skills for everyone: Addressing scale and access in negotiation education by developing an OER

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    Learn about a multi-institutional project developing open educational resources (OER) to equip academic library workers with negotiation skills within the context of academic libraries work with third party vendors. Presenters will share project learnings thus far providing insights regarding e-resource negotiations and resources to aid participants in their own negotiations.IMLS Laura Bush 21st Century Librarian Grant Progra

    Representing addition and subtraction : learning the formal conventions

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    The study was designed to test the effects of a structured intervention in teaching children to represent addition and subtraction. In a post-test only control group design, 90 five-year-olds experienced the intervention entitled Bi-directional Translation whilst 90 control subjects experienced typical teaching. Post-intervention testing showed some significant differences between the two groups both in terms of being able to effect the addition and subtraction operations and in being able to determine which operation was appropriate. The results suggest that, contrary to historical practices, children's exploration of real world situations should precede practice in arithmetical symbol manipulation

    Galaxy Properties at the Faint End of the H I Mass Function

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    The Survey of H I in Extremely Low-mass Dwarfs (SHIELD) includes a volumetrically complete sample of 82 gas-rich dwarfs with MHI107.2{M}_{{\rm{H}}\,{\rm\small{I}}}\lesssim {10}^{7.2} M{M}_{\odot } selected from the ALFALFA survey. We are obtaining extensive follow-up observations of the SHIELD galaxies to study their gas, stellar, and chemical content, and to better understand galaxy evolution at the faint end of the H I mass function. Here, we investigate the properties of 30 SHIELD galaxies using Hubble Space Telescope imaging of their resolved stars and Westerbork Synthesis Radio Telescope observations of their neutral hydrogen. We measure tip of the red giant branch (TRGB) distances, star formation activity, and gas properties. The TRGB distances are up to 4× greater than estimates from flow models, highlighting the importance of velocity-independent distance indicators in the nearby universe. The SHIELD galaxies are in underdense regions, with 23% located in voids; one galaxy appears paired with a more massive dwarf. We quantify galaxy properties at low masses including stellar and H I masses, star formation rate (SFRs), specific SFRs, star formation efficiencies, birth-rate parameters, and gas fractions. The lowest-mass systems lie below the mass thresholds where stellar mass assembly is predicted to be impacted by reionization. Even so, we find the star formation properties follow the same trends as higher-mass gas-rich systems, albeit with a different normalization. The H I disks are small ( r0.7kpc \langle r \rangle 0.7\,{\rm{kpc}} ), making it difficult to measure the H I rotation using standard techniques; we develop a new methodology and report the velocity extent, and its associated spatial extent, with robust uncertainties

    Pesquisas atuais sobre a construção do conceito de número: para além de Piaget?

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    As atuais pesquisas acerca da construção do número vêm resgatando o papel desempenhado pelas atividades numéricas (em particular, a contagem) na construção do número. Para a maioria dos autores dessas pesquisas e outros estudiosos do tema, os resultados mais recentes, quando não contrariam, ultrapassam, do ponto de vista teórico, o estágio alcançado pelas pesquisas do Centro Internacional de Epistemologia Genética. Neste trabalho discutimos o papel da contagem no desenvolvimento do número segundo a Epistemologia Genética. Buscando destacar a atualidade da teoria piagetiana, comentamos algumas das recentes pesquisas e propostas metodológicas sobre a construção do conceito de número que se fundamentam quase que exclusivamente na contagem, procurando verificar se os resultados encontrados ou as sugestões apresentadas pelos pesquisadores estariam, do ponto de vista teórico, "além de Piaget"

    Whole number thinking, learning and development: neuro-cognitive, cognitive and developmental approaches

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    The participants of working group 2 presented a broad range of studies, 11 papers in total, related to whole number learning representing research groups from 11 countries as follows. Two large cross-sectional studies focused on developmental aspects of young children’s number learning provide a lens for re-examining ‘traditional’ features of number acquisition. van den Heuvel-Panhuizen (the Netherlands) presented a co-authored paper with Elia (Cyprus; Elia and van den Heuvel-Panhuizen 2015) on a cross-cultural study of kindergartners’ number competence focused on counting, additive and multiplicative thinking. Second, Milinković (2015) examined the development of young Serbian children’s initial understanding of representations of whole numbers and counting strategies in a large study of 3- to 7-year-olds. Children’s invented (formal) representations such as set representation and the number line were found to be limited in their recordings. In a South African study focused on early counting and addition, Roberts (2015) directs attention to the role of teachers by providing a framework to support teachers’ interpretation of young disadvantaged learners’ representations of number when engaging with whole number additive tasks. Some papers reflected the increasing role of neuroscientific concepts and methodologies utilised in research on WNA learning and development. Sinclair and Coles (2015) drew upon neuroscientific research to highlight the significant role of symbol-to-symbol connections and the use of fingers and touch counting exempli- fied by the TouchCounts iPad app. Gould (2015) reported aspects of a large Australian large study of children in the first years of schooling aimed at improving numeracy and literacy in disadvantaged communities. A case study exemplified how numerals were identified by relying on a mental number line by using location to retrieve number names. This raised the question addressed in the neuroscientific work of Dehaene and other papers focused on individual differences in how the brain processes numbers. The Italian PerContare1 project (Baccaglini-Frank 2015) built upon the collaboration between cognitive psychologists and mathematics educators, aimed at developing teaching strategies for preventing and addressing early low achievement in arithmetic. It takes an innovative approach to the development of number sense that is grounded upon a kinaesthetic and visual-spatial approach to part-whole relationships. Mulligan and Woolcott (2015) provided a discussion paper on the underlying nature of number. They presented a broader view of mathematics learning (including WNA) as linked to spatial interaction with the environment; the concept of connectivity across concepts and the development of underlying pattern and structural relationships are central to their approach

    Functional Imaging of Numerical Processing in Adults and 4-y-Old Children

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    Adult humans, infants, pre-school children, and non-human animals appear to share a system of approximate numerical processing for non-symbolic stimuli such as arrays of dots or sequences of tones. Behavioral studies of adult humans implicate a link between these non-symbolic numerical abilities and symbolic numerical processing (e.g., similar distance effects in accuracy and reaction-time for arrays of dots and Arabic numerals). However, neuroimaging studies have remained inconclusive on the neural basis of this link. The intraparietal sulcus (IPS) is known to respond selectively to symbolic numerical stimuli such as Arabic numerals. Recent studies, however, have arrived at conflicting conclusions regarding the role of the IPS in processing non-symbolic, numerosity arrays in adulthood, and very little is known about the brain basis of numerical processing early in development. Addressing the question of whether there is an early-developing neural basis for abstract numerical processing is essential for understanding the cognitive origins of our uniquely human capacity for math and science. Using functional magnetic resonance imaging (fMRI) at 4-Tesla and an event-related fMRI adaptation paradigm, we found that adults showed a greater IPS response to visual arrays that deviated from standard stimuli in their number of elements, than to stimuli that deviated in local element shape. These results support previous claims that there is a neurophysiological link between non-symbolic and symbolic numerical processing in adulthood. In parallel, we tested 4-y-old children with the same fMRI adaptation paradigm as adults to determine whether the neural locus of non-symbolic numerical activity in adults shows continuity in function over development. We found that the IPS responded to numerical deviants similarly in 4-y-old children and adults. To our knowledge, this is the first evidence that the neural locus of adult numerical cognition takes form early in development, prior to sophisticated symbolic numerical experience. More broadly, this is also, to our knowledge, the first cognitive fMRI study to test healthy children as young as 4 y, providing new insights into the neurophysiology of human cognitive development

    Kindergarten Children Solving Additive Problems: Which Strategies?

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    Os estudos desenvolvidos em diferentes contextos ressaltam a capacidade que as crianças têm de resolver corretamente problemas de adição e subtração, antes ainda destas operações lhes serem formalmente ensinadas. O estudo aqui descrito procura perceber como as crianças dos 4 aos 6 anos (N=90) entendem os problemas de estrutura aditiva. Para tal, tenta responder às seguintes questões: 1) Que desempenhos apresentam as crianças quando resolvem problemas de estrutura aditiva? 2) Que estratégias usam para resolver os problemas de estrutura aditiva? Adotou-se uma metodologia quantitativa que analisa os desempenhos e as estratégias das crianças quando resolvem 28 problemas de estrutura aditiva, apresentados a partir de entrevistas estruturadas individuais. Os resultados sugerem que as crianças resolvem com facilidade os problemas propostos e utilizam estratégias adequadas para responderem corretamente, chegando mesmo a recorrer a estratégias abstratas como a contagem e os fatos numéricos.Several studies report young children's ability to solve addition and subtraction problems before receiving any formal instruction. This study focuses on how 4-6-year-old children (N=90) understand additive structure problems. It addresses two questions: 1) How do children perform when solving additive structure problems? 2) What strategies do children use when solving additive structure problems? Quantitative methods were used to analyse children's performance and strategies when solving 28 additive structure problems presented to them using individual interviews. Results suggest that children easily solved the given problems using adequate strategies, some could even count and rely on numerical factsApoio financeiro do CIEC (Centro de Investigação em Estudos da Criança, IE, UMinho; UI 317 da FCT, Portugal) através do Projeto Estratégico UID/CED/00317/2013, financiado através dos Fundos Nacionais da FCT (Fundação para a Ciência e a Tecnologia), cofinanciado pelo Fundo Europeu de Desenvolvimento Regional (FEDER) através do COMPETE 2020 – Programa Operacional Competitividade e Internacionalização (POCI) com a referência POCI-01-0145-FEDER-007562info:eu-repo/semantics/publishedVersio
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