1,010 research outputs found
Some aspects of tensile and shear fatigue in carbon fibre reinforced plastics, including hoop-wound tubes.
Results of zero-tension fatigue tests are presented for flat sheet unidirectional 0° and angle-plied +/-45° carbon fibre reinforced plastics. Torsional-shear and transverse fatigue tests were made on hoop-wound tubes. These have shown that surface finish has a significant role in determining the fatigue performance of CFRP.A method is presented for assessing the fatigue stress bandwidth in zero-tension fatigue at 0° CFRP. A mechanism of fatigue failure in 0° CFRP is also postulated. Fatigue induced creep effects were observed during shear loadings and these are shown to relate to cracking and crack growth in +/-45° material. A shell theory analysis of tubular CFRP test-pieces was made which demonstrates the suitability of this specimen for 0° longitudinal and 90° hoop-windings. Hoop-wound tubes were used to show that the mutual interactions between shear and transverse elastic properties are not significantly affected by transverse fatigue stresses
Symplectic algorithm for constant-pressure molecular dynamics using a Nose-Poincare thermostat
We present a new algorithm for isothermal-isobaric molecular-dynamics
simulation. The method uses an extended Hamiltonian with an Andersen piston
combined with the Nos'e-Poincar'e thermostat, recently developed by Bond,
Leimkuhler and Laird [J. Comp. Phys., 151, (1999)]. This
Nos'e-Poincar'e-Andersen (NPA) formulation has advantages over the
Nos'e-Hoover-Andersen approach in that the NPA is Hamiltonian and can take
advantage of symplectic integration schemes, which lead to enhanced stability
for long-time simulations. The equations of motion are integrated using a
Generalized Leapfrog Algorithm and the method is easy to implement, symplectic,
explicit and time reversible. To demonstrate the stability of the method we
show results for test simulations using a model for aluminum.Comment: 7 page
Adjusting the melting point of a model system via Gibbs-Duhem integration: application to a model of Aluminum
Model interaction potentials for real materials are generally optimized with
respect to only those experimental properties that are easily evaluated as
mechanical averages (e.g., elastic constants (at T=0 K), static lattice
energies and liquid structure). For such potentials, agreement with experiment
for the non-mechanical properties, such as the melting point, is not guaranteed
and such values can deviate significantly from experiment. We present a method
for re-parameterizing any model interaction potential of a real material to
adjust its melting temperature to a value that is closer to its experimental
melting temperature. This is done without significantly affecting the
mechanical properties for which the potential was modeled. This method is an
application of Gibbs-Duhem integration [D. Kofke, Mol. Phys.78, 1331 (1993)].
As a test we apply the method to an embedded atom model of aluminum [J. Mei and
J.W. Davenport, Phys. Rev. B 46, 21 (1992)] for which the melting temperature
for the thermodynamic limit is 826.4 +/- 1.3K - somewhat below the experimental
value of 933K. After re-parameterization, the melting temperature of the
modified potential is found to be 931.5K +/- 1.5K.Comment: 9 pages, 5 figures, 4 table
The Relationship Between Belief and Credence
Sometimes epistemologists theorize about belief, a tripartite attitude on which one can believe, withhold belief, or disbelieve a proposition. In other cases, epistemologists theorize about credence, a fine-grained attitude that represents oneâs subjective probability or confidence level toward a proposition. How do these two attitudes relate to each other? This article explores the relationship between belief and credence in two categories: descriptive and normative. It then explains the broader significance of the belief-credence connection and concludes with general lessons from the debate thus far
Exploring segregation and sharing in a divided city: A PGIS approach
This article presents a novel exploratory investigation into the location and characteristics of spaces that are segregated and shared between Protestant and Catholic communities in Belfast, Northern Ireland (UK). Focusing on a particularly segregated part of the city, this study uses state-of-the-art participatory geographic information systems (PGIS) and visualization techniques to create qualitative, bottom-up maps of segregation and sharing within the city, as experienced by the people who live there. In doing so, it identifies important and previously unreported patterns in segregation and sharing between sectarian communities, challenging normative approaches to PGIS, illustrating how alternative methods might provide deeper insights into complex social geographies such as those of segregation. Finally, the findings of this work are formulated into a set of hypotheses that can contribute to a future research agenda into segregation and sharing, both in Belfast and in other divided cities
Rethinking globalised resistance : feminist activism and critical theorising in international relations
This article argues that a feminist approach to the 'politics of resistance' offers a number of important empirical insights which, in turn, open up lines of theoretical inquiry which critical theorists in IR would do well to explore. Concretely, we draw on our ongoing research into feminist 'anti-globalisation' activism to rethink the nature of the subject of the politics of resistance, the conditions under which resistance emerges and how resistance is enacted and expressed. We begin by discussing the relationship of feminism to critical IR theory as a way of situating and explaining the focus and approach of our research project. We then summarise our key empirical arguments regarding the emergence, structure, beliefs, identities and practices of feminist 'anti-globalisation' activism before exploring the implications of these for a renewed critical theoretical agenda in IR
Can Modal Skepticism Defeat Humean Skepticism?
My topic is moderate modal skepticism in the spirit of Peter van Inwagen. Here understood, this is a conservative version of modal empiricism that severely limits the extent to which an ordinary agent can reasonably believe âexoticâ possibility claims. I offer a novel argument in support of this brand of skepticism: modal skepticism grounds an attractive (and novel) reply to Humean skepticism. Thus, I propose that modal skepticism be accepted on the basis of its theoretical utility as a tool for dissolving philosophical paradox
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Density changes in Ga-stabilized delta-Pu, and what they mean
Ga-stabilized {delta}-Pu undergoes small changes in density with time. These have been associated with four different causes: an initial reversible expansion that saturates after a short time; a continuous change that can be attributed to the in-growth of helium and actinide daughter products from the radioactive decay of plutonium; possible void swelling; and phase instability. We review our present understanding of these processes and evaluate their contributions to density changes. It is shown that the initial transient expansion is intimately connected with the metastability of the {delta}-phase at ambient temperature
Revisiting the technical validation of tumour biomarker assays: how to open a Pandora's box
A tumour biomarker is a characteristic that is objectively measured and evaluated in tumour samples as an indicator of normal biological processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention. The development of a biomarker contemplates distinct phases, including discovery by hypothesis-generating preclinical or exploratory studies, development and qualification of the assay for the identification of the biomarker in clinical samples, and validation of its clinical significance. Although guidelines for the development and validation of biomarkers are available, their implementation is challenging, owing to the diversity of biomarkers being developed. The term 'validation' undoubtedly has several meanings; however, in the context of biomarker research, a test may be considered valid if it is 'fit for purpose'. In the process of validation of a biomarker assay, a key point is the validation of the methodology. Here we discuss the challenges for the technical validation of immunohistochemical and gene expression assays to detect tumour biomarkers and provide suggestions of pragmatic solutions to address these challenges
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