6,440 research outputs found
Enhancing strength without compromising ductility in copper by combining extrusion machining and heat treatment
No full textIt is a challenge to produce metallic materials with high strength and good ductility. Improving the strength of metallic materials usually sacrifices the ductility or work-hardening capacity. Here combining extrusion machining and heat treatment, we improve the strength of copper without losing strain hardening capacity and therefore the ductility remains. Copper was first deformed by extrusion machining at shear strain 3.1 and then annealed at 523 K for 5 min. Compared with the initial workpiece, the processed copper possesses five times higher yield strength and alike work hardening behavior. Microstructural characterizations illustrate that high strength and high strain hardening are attributed to the hierarchical microstructure that the recrystallized grains are surrounded by elongated subgrains. Finally, an analytical modeling was employed to rationalize the mechanical properties of copper processed by the proposed strategy. The theoretical results are in agreement with the experimental measurements
In-cylinder flow and combustion studies in an air-assisted direct injection gasoline engine
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.In-cylinder flows and CAI combustion were investigated in a single cylinder, air-assisted gasoline direct injection engine. CAI was promoted and controlled by internal exhaust gas recirculation, achieved by employing short duration camshafts and early exhaust valve closure. The effects of valve and injection timing and engine speed on exhaust emissions, fuel consumption, combustion phasing and operating region were investigated. The results show that valve timing mainly affects engine load and CAI combustion phasing through changes in trapped residual levels and stratification of fresh and residual gases respectively. Injection of fuel into residual gases during the recompression process was found to increase the operating region and reduce uHC emissions though charge cooling effects and increased fuel ignitability via internal fuel reformation. The increased ignitability of the mixture also advanced ignition timing, resulting in increased in-cylinder temperatures and NOx concentrations. It was found that, compared to SI combustion in the same engine, CAI operation reduced NOx emissions by between 98% and 80% while fuel consumption was reduced by between 9% and 17%. The in-cylinder flows of intake air and fuel droplets from the air-assisted injection system and cylinder head were investigated using the PIV technique. No significant large-scale flow structures were found in the in-cylinder airflow and the fuel spray appeared unaffected by the in-cylinder air motion. In addition, the in-cylinder fuel distribution from the air-assisted injection system was measured using laser induced exiplex fluorescence. A combination of naphthalene and DMA in isooctane was used to form an exiplex and simultaneous qualitative images of the liquid and vapour fuel phases were obtained. When using a late injection strategy, a well stratified mixture was formed at the end of the compression stroke, while injection during the intake stroke left a well mixed homogenous charge
Generalized Verma modules over sl(n+2) induced from U(h)-free sl(n+1)-modules
No full textA class of generalized Verma modules over sl(n+2) is constructed fromsl(n+1)-modules which are U(h)-free modules of rank 1. The necessary and sufficient conditions for these sl(n+2)-modules to be simple are determined. This leads to a class of new simple sl(n+2)-modules.</p
Hierarchical-microstructure based modeling for plastic deformation of partial recrystallized copper
No full textHierarchical microstructure in partial recrystallized materials can simultaneously improve the strength and ductility of metallic materials. Modeling the mechanical behavior of partial recrystallized materials helps to process materials with superior combination of ductility and strength. Here, using experimental characterization, cellular automation (CA) and finite element method, hierarchical-microstructure based modeling was proposed to simulate the tensile deformation of partial recrystallized copper. Firstly, partial recrystallized coppers with different volume fractions of recrystallization were produced by means of extrusion machining and subsequent heat treatment (HT). Uniaxial tensile tests and microstructural observations show that the hierarchical-microstructure of recrystallized grains (RGs) surrounded by elongated subgrains has a significant effect on the mechanical properties. Then, based on the experimental results, a hierarchical-microstructure based plasticity model was developed to describe the yield surface of partial recrystallized materials. CA was further employed to simulate the hierarchical microstructure. By embedding the plasticity model and simulated hierarchical-microstructure in finite element method, a finite element model (FEM) for mechanical behavior of partial recrystallized copper was proposed, where the elongated subgrain with forest dislocation and low angle grain boundary, the RG with few dislocations and twin boundary, and volume fraction of recrystallization were taken into consideration. Finally, the experimental data and the comparison with the conventional plasticity model validate the rationality of the proposed model
A modification of the Suinn-Lew Asian self-identity acculturation scale (SL-ASIA)
No full textAcculturative stress has a significant impact on the mental health of Asian Americans, leading to common challenges such as depression, anxiety, and post-traumatic stress disorder (Hsueh et al., 2015). However, measuring acculturation can be challenging because the widely used Suinn-Lew Asian Self-Identity Acculturation Scale (SL-ASIA) is limited in capturing the complexities of acculturation (Dao et al., 2011). Despite this challenge, healthcare providers and researchers need to recognize this limitation and explore additional ways or improvements for measuring self-identity acculturation better to understand its impact on Asian Americans' health. This project modified the SL-ASIA to address this limitation by adding two questions on decision-making topics based on Triandis' (1995) cultural orientation concept. These questions aimed to assess an individual's level of self-identity acculturation by examining their beliefs and values regarding the selection of a life partner and decision-making in family conflict. This modification was evaluated by three expert evaluators for the appropriateness of these added questions. With the potential to offer a more comprehensive instrument, the modified SL-ASIA will provide valuable insights into the relationship between acculturation, self-identity acculturation, and health outcomes for researchers and healthcare providers
CR1 Knops blood group alleles are not associated with severe malaria in the Gambia
No full textThe Knops blood group antigen erythrocyte polymorphisms have been associated with reduced falciparum malaria-based in vitro rosette formation (putative malaria virulence factor). Having previously identified single-nucleotide polymorphisms (SNPs) in the human complement receptor 1 (CR1/CD35) gene underlying the Knops antithetical antigens Sl1/Sl2 and McC(a)/McC(b), we have now performed genotype comparisons to test associations between these two molecular variants and severe malaria in West African children living in the Gambia. While SNPs associated with Sl:2 and McC(b+) were equally distributed among malaria-infected children with severe malaria and control children not infected with malaria parasites, high allele frequencies for Sl 2 (0.800, 1,365/1,706) and McC(b) (0.385, 658/1706) were observed. Further, when compared to the Sl 1/McC(a) allele observed in all populations, the African Sl 2/McC(b) allele appears to have evolved as a result of positive selection (modified Nei-Gojobori test Ka-Ks/s.e.=1.77, P-valu
Avatares no second life: corpo e movimento na constituição da noção de pessoa on-line
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Desportos. Programa de Pós-graduação em Educação FísicaEsta dissertação configura-se como uma busca interpretativa da constituição do "ser" on-line. Pretende-se revelar de que forma corpo e movimento, consolidados objetos de intervenção pedagógica da Educação Física, são problematizados no ciberespaço, em especial no jogo de computador Second Life. Trata-se de um percurso que busca colaborar para uma "Antropologia no ciberespaço", compreendendo, com ênfase no aspecto vivencial dos sujeitos, o ciberespaço como um campo antropológico onde se fazem etnografias. Assume-se o corpo como uma construção simbólica e o ciberespaço como uma das dimensões constituintes das sociedades complexas. Da reunião de ações e diálogos que se desenrolaram em um espaço social compartilhado a partir de avatares, pode-se destacar as inúmeras estratégias, recursos, dimensões, regras, interações que contribuem para a construção da noção de pessoa on-line. A partir das observações, percebeu-se que os conceitos de imaginação e imaginário são essenciais para compreender como os participantes tecem caminhos em suas brincadeiras narrativas para construir no ciberespaço uma corporalidade que é central em suas interações. O sentido do avatar e dos demais objetos do Second Life só pode ser dado a partir das ações dos participantes no jogo. Estes, sujeitos dotados de intencionalidade, fazem parte de uma rede de relações ao mesmo tempo em que suas ações são condição para a que a relação exista. É no momento em que as brincadeiras narrativas acontecem no Second Life que cada participante tenta traçar para a sua identidade on-line uma estabilidade que o faça tanto reconhecido quanto aceito nas situações interativas do grupo. A brincadeira de construir-se corporalmente no ciberespaço pode ser um momento privilegiado para refletir e questionar a visão dualística cartesiana que entende o corpo como entidade que contém somente aquilo que é abrangido pelo invólucro externo, a pele humana. Para justificar o objeto e o campo de estudo, o trabalho também discorre sobre as possíveis aproximações das tecnologias digitais - em especial dos jogos eletrônicos - com a Educação Física e traz reflexões sobre o conceito do que é virtual em busca do rompimento da oposição dualística com o real
Quantum and its irreducible representations
No full textWe define for real a unital -algebra
quantizing the universal enveloping
-algebra of . The -algebra
is realized as a -subalgebra of the
Drinfeld double of and its dual Hopf -algebra
, generated by the equatorial Podle\'s sphere coideal
-subalgebra of and
its associated orthogonal coideal -subalgebra . We then classify all the irreducible
-representations of .Comment: 22 pages; author accepted manuscrip
On the sheaf-theoretic SL(2, C) Casson–Lin invariant
No full textWe prove that the (τ-weighted, sheaf-theoretic) SL(2, C) Casson–Lin invariant introduced by Manolescu and the first author is generically independent of the parameter τ and additive under connected sums of knots in integral homology 3-spheres. This addresses two questions asked by Manolescu and the first author. Our arguments involve a mix of topology and algebraic geometry, and rely crucially on the fact that the SL(2, C) Casson–Lin invariant admits an alternative interpretation via the theory of Behrend functions.</p
Candidatus Rhetoricae (or Novus Candidatus).
No full textThis little book is a find whatever it finally turns out to be! For now it seems to be a Jesuit collegium text in rhetoric following the Progymnasmata of Aphthonius. If one works from the back of the book, there is an apparently independent 48-page work, Angelus Pacis by Nicolas Caussini (Latinized name), S.J. The rest of the book seems to be a commentary on or presentation of Aphthonius' Progymnasmata in 3 parts covering 435 pages, followed by a T of C and an AI, which is often one page off. Pars II is titled Rhetoricae Praecepta, Pars III De Panegyrico seu Laudatione. Pars I seems to be Apparatus ad Fabulam et Narrationem. Fable is handled on 15-31. After the famous Greek definition of Theion done into Latin ( sermo falsus veritatem effingens ), the author distinguishes rational (human) and moral (animal) fables, with mixed fables including both. He holds (19) that the sense of the fable generally needs to be expressed; otherwise people often miss the point of a fable. His Latin for promythium is praefabulatio, for epimythium affabulatio. Apologus and parabola are identical for him with fabula. After describing the qualities and uses of fables, the author presents some nine fables that exemplify various levels of style, twice telling the same stories on two levels (WL and FC). The last example is of the florid style: The Silkworm and the Spider takes four pages to tell! I found this book sitting in a box of disparate, unmarked, old books. It pays to look!This is a hardbound book (hard cover)Language note: Bilingual: Greek/LatinElzevers
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