965 resultados para accumulative roll bonding
Resumo:
A literatura tem referido que a prematuridade do bebé gera nas mães níveis mais elevados de ansiedade, sentimentos depressivos, assim como níveis mais baixos de autoestima, comparativamente com mães de bebés de termo, o que poderá conduzir a um envolvimento emocional mais negativo com o recémnascido. Essa vivência parece variar em função da paridade das mães (i.e., mãe pela primeira vez vs. multípara) não obstante não serem muito claras as particularidades desta variável. Este estudo teve como objetivo analisar num grupo de mães primíparas e multíparas com bebés prematuros, as associações entre o estado Psicoemocional, a Autoestima e o Bonding maternos. Participaram 50 mães (27 primíparas e 23 multíparas), com bebés pré-termo recrutados numa maternidade pública de Lisboa. Os resultados indicam que as mães multíparas apresentam níveis mais elevados de Sentimentos Depressivos expressando, também, uma maior Capacidade e Preparação Geral para a função materna. A Capacidade Geral para tratar do bebé surge associada de forma negativa com o seu estado Psicoemocional e de forma positiva com o Bonding. As associações negativas encontradas entre Ansiedade e Aceitação do bebé, e entre Estado Psicoemocional e Bonding não parecem variar em função da paridade, mostrando que os desafios se colocam a ambos os grupos de mães.
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Studiens syfte är att, genom observationer, undersöka djurens roll i förskolans verksamhet. Syftet är således att skildra de pedagogiska lärprocesser som förekommer i förskolor som involverar djur i sin dagliga verksamhet, bidra med kunskaper om hur djur kan påverka förskolans verksamhet och hur djurhållning kan tillämpas i den traditionella förskolan. Vårt teoretiska ramverk utgår ifrån sociokulturellt perspektiv med inriktning mot Vygotskijs och Leontyevs ”Aktivitetstrianglar” som Engeström sedan utformade grafiskt. Ramverket möjliggör användningen av begrepp som till exempel artefakter, mediering, objekt och subjekt vilket skapar en röd tråd genom hela studien. Metoden som valts är en kvalitativ fallstudie och genom denna metod kan fördjupning göras av hur två specifika förskolor med djur i verksamheten fungerar. Studiens frågeställningar bygger på ett kunskaps intresse och har fungerat som en vägledning genom studien. Frågeställningarna är: hur är djur involverade i lärandeaktiviteterna på lantbruksförskolan och hur är djur involverade i lärandeaktiviteterna på djurparksförskolan. Observationerna skedde på två olika förskolor och för att komplettera data genomfördes också samtal med förskollärarna i verksamheten. Observationerna och samtalen analyserades utifrån en tematisk analysmetod som kompletterades med en narrativ analysmetod för att ge ett djupare resultat. Resultatet visade på att det fanns både skillnader och likheter mellan förskolorna som observerades. Baserat på resultatet fördes en diskussion kring hur skillnaderna och likheterna på förskolorna med djurinriktning kunde appliceras på en traditionell förskola. Slutsatsen visar att det är möjligt att använda djur i en traditionell förskola men att tillämpningen beror på den enskilda förskolans förutsättningar.
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A three-dimensional finite element model of cold pilgering of stainless steel tubes is developed in this paper. The objective is to use the model to increase the understanding of forces and deformations in the process. The focus is on the influence of vertical displacements of the roll stand and axial displacements of the mandrel and tube. Therefore, the rigid tools and the tube are supported with elastic springs. Additionally, the influences of friction coefficients in the tube/mandrel and tube/roll interfaces are examined. A sensitivity study is performed to investigate the influences of these parameters on the strain path and the roll separation force. The results show the importance of accounting for the displacements of the tube and rigid tools on the roll separation force and the accumulative plastic strain.
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This work addresses the development of new ultra-fine grained/ nano-structured high strength aluminium alloys designed for automotive applications and explores the frontiers of the roll forming process.
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The formation of social bonds outside the mated pair is not frequently reported in monogamous birds, although it may be expected in some species like rooks, living in groups all year round. Here we explore the social structure of captive adult rooks over three breeding seasons. We recorded proximities and affiliations (i.e., allofeeding, allopreening, contact-sit) to classify relationships according to their strength. Three categories of relationships emerged: primary (i.e., pairs), secondary and weak relationships. Affiliations and sexual behaviours were not restricted to pairs, and secondary relationships were clearly recognizable. Mixed-sex secondary relationships were qualitatively equivalent to pairs (i.e., same behaviours in the same proportions), although they were quantitatively less intense. Same sex pairs occurred, and were qualitatively equivalent to mixedsex pairs. Overall we found that rooks social structure is more than just an aggregation of pairs, which highlights the importance of considering extra-pair relationships in socially monogamous birds.
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Fleck and Johnson (Int. J. Mech. Sci. 29 (1987) 507) and Fleck et al. (Proc. Inst. Mech. Eng. 206 (1992) 119) have developed foil rolling models which allow for large deformations in the roll profile, including the possibility that the rolls flatten completely. However, these models require computationally expensive iterative solution techniques. A new approach to the approximate solution of the Fleck et al. (1992) Influence Function Model has been developed using both analytic and approximation techniques. The numerical difficulties arising from solving an integral equation in the flattened region have been reduced by applying an Inverse Hilbert Transform to get an analytic expression for the pressure. The method described in this paper is applicable to cases where there is or there is not a flat region.
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Purpose: In the present study, we consider mechanical properties of phosphate glasses under high temperatureinduced and under friction-induced cross-linking, which enhance the modulus of elasticity. Design/methodology/approach: Two nanomechanical properties are evaluated, the first parameter is the modulus of elasticity (E) (or Young's modulus) and the second parameter is the hardness (H). Zinc meta-, pyro - and orthophosphates were recognized as amorphous-colloidal nanoparticles were synthesized under laboratory conditions and showed antiwear properties in engine oil. Findings: Young's modulus of the phosphate glasses formed under high temperature was in the 60-89 GPa range. For phosphate tribofilm formed under friction hardness and the Young's modulus were in the range of 2-10 GPa and 40-215 GPa, respectively. The degree of cross-linking during friction is provided by internal pressure of about 600 MPa and temperature close to 1000°C enhancing mechanical properties by factor of 3 (see Fig 1). Research limitations/implications: The addition of iron or aluminum ions to phosphate glasses under high temperature - and friction-induced amorphization of zinc metaphosphate and pyrophosphate tends to provide more cross-linking and mechanically stronger structures. Iron and aluminum (FeO4 or AlO4 units), incorporated into phosphate structure as network formers, contribute to the anion network bonding by converting the P=O bonds into bridging oxygen. Future work should consider on development of new of materials prepared by solgel processes, eg., zinc (II)-silicic acid. Originality/value: This paper analyses the friction pressure-induced and temperature–induced the two factors lead phosphate tribofilm glasses to chemically advanced glass structures, which may enhance the wear inhibition. Adding the coordinating ions alters the pressure at which cross-linking occurs and increases the antiwear properties of the surface material significantly.
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This paper explores a new interpretation of experiments on foil rolling. The assumption that the roll remains convex is relaxed so that the strip profile may become concave, or thicken in the roll gap. However, we conjecture that the concave profile is associated with phenomena which occur after the rolls have stopped. We argue that the yield criterion must be satisfied in a nonconventional manner if such a phenomenon is caused plastically. Finite element analysis on an extrusion problem appears to confirm this conjecture.
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It is known that boehmite (AlOOH) nanofibers formed in the presence of nonionic poly(ethylene oxide) (PEO) surfactant at 373 K. A novel approach is proposed in this study for the growth of the boehmite nanofibers: when fresh aluminum hydrate precipitate was added at regular interval to initial mixture of boehmite and PEO surfactant at 373 K, the nanofibers grow from 40 to 50 nm long to over 100 nm. It is believed that the surfactant micelles play an important role in the nanofiber growth: directing the assembly of aluminum hydrate particles through hydrogen bonding with the hydroxyls on the surface of aluminum hydrate particles. Meanwhile a gradual improvement in the crystallinity of the fibers during growth is observed and attributed to the Ostwald ripening process. This approach allows us to precisely control the size and morphology of boehmite nanofibers using soft chemical methods and could be useful for low temperature, aqueous syntheses of other oxide nanomaterials with tailorable structural specificity such as size, dimension and morphology.
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Practitioners and academics have developed numerous maturity models for many domains in order to measure competency. These initiatives have often been influenced by the Capability Maturity Model. However, an accumulative effort has not been made to generalize the phases of developing a maturity model in any domain. This paper proposes such a methodology and outlines the main phases of generic model development. The proposed methodology is illustrated with the help of examples from two advanced maturity models in the domains of Business Process Management and Knowledge Management.
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Inclusions of sp-hybridised, trans-polyacetylene [trans-(CH)x] and poly(p-phenylene vinylene) (PPV) chains are revealed using resonant Raman scattering (RRS) investigation of amorphous hydrogenated carbon (a-C:H) films in the near IR – UV range. The RRS spectra of trans-(CH)x core Ag modes and the PPV CC-H phenylene mode are found to transform and disperse as the laser excitation energy ћωL is increased from near IR through visible to UV, whereas sp-bonded inclusions only become evident in UV. This is attributed to ћωL probing of trans-(CH)x chain inhomogeneity and the distribution of chains with varying conjugation length; for PPV to the resonant probing of phelynene ring disorder; and for sp segments, to ћωL probing of a local band gap of end-terminated polyynes. The IR spectra analysis confirmed the presence of sp, trans-(CH)x and PPV inclusions. The obtained RRS results for a-C:H denote differentiation between the core Ag trans-(CH)x modes and the PPV phenylene mode. Furthermore, it was found that at various laser excitation energies the changes in Raman spectra features for trans-(CH)x segments included in an amorphous carbon matrix are the same as in bulk trans-polyacetylene. The latter finding can be used to facilitate identification of trans-(CH)x in the spectra of complex carbonaceous materials.
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This document provides the findings of a national review of investment decision-making practices in road asset management. Efforts were concentrated on identifying the strategic objectives of agencies in road asset management, establishing and understanding criteria different organisations adopted and ascertaining the exact methodologies used by different sate road authorities. The investment objectives of Australian road authorities are based on triple-bottom line considerations (social, environmental, economic and political). In some cases, comparing with some social considerations, such as regional economic development, equity, and access to pubic service etc., Benefit-Cost Ratio has limited influence on the decision-making. Australian road authorities have developed various decision support tools. Although Multi-Criteria Analysis has been preliminarily used in case by case study, pavement management systems, which are primarily based on Benefit Cost Analysis, are still the main decision support tool. This situation is not compatible with the triple-bottom line objectives. There is need to fill the gap between decision support tools and decision-making itself. Different decision criteria should be adopted based on the contents of the work. Additional decision criteria, which are able to address social, environmental and political impacts, are needed to develop or identify. Environmental issue plays a more and more important role in decision-making. However, the criteria and respective weights in decision-making process are yet to be clearly identified. Social and political impacts resulted from road infrastructure investment can be identified through Community Perceptions Survey. With accumulative data, prediction models, which are similar as pavement performance models, can be established. Using these models, the decision-makers are able to foresee the social and political consequences of investment alternatives.
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This paper compares and reviews the recommendations and contents of the guide for the design and construction of externally bonded FRP systems for strengthening concrete structures reported by ACI committee 440 and technical report of Externally bonded FRP reinforcement for RC structures (FIB 14) in application of carbon fiber reinforced polymer (CFRP) composites in strengthening of an aging reinforced concrete headstock. The paper also discusses the background, limitations, strengthening for flexure and shear, and other related issues in use of FRP for strengthening of a typical reinforced concrete headstock structure such as durability, de-bonding, strengthening limits, fire and environmental conditions. A case study of strengthening of a bridge headstock using FRP composites is presented as a worked example in order to illustrate and compare the differences between these two design guidelines when used in conjunction with the philosophy of the Austroads (1992) bridge design code.