47,523 research outputs found
Optimal Estimates for the Electric Field in Two-Dimensions
The purpose of this paper is to set out optimal gradient estimates for
solutions to the isotropic conductivity problem in the presence of adjacent
conductivity inclusions as the distance between the inclusions goes to zero and
their conductivities degenerate. This difficult question arises in the study of
composite media. Frequently in composites, the inclusions are very closely
spaced and may even touch. It is quite important from a practical point of view
to know whether the electric field (the gradient of the potential) can be
arbitrarily large as the inclusions get closer to each other or to the boundary
of the background medium.
In this paper, we establish both upper and lower bounds on the electric field
in the case where two circular conductivity inclusions are very close but not
touching. We also obtain such bounds when a circular inclusion is very close to
the boundary of a circular domain which contains the inclusion. The novelty of
these estimates, which improve and make complete our earlier results published
in Math. Ann., is that they give an optimal information about the blow-up of
the electric field as the conductivities of the inclusions degenerate.Comment: 26 page
Enhancement of plasticity in Ti-based metallic glass matrix composites by controlling characteristic and volume fraction of primary phase
In this study, Ti-based metallic glass matrix composites with high plasticity have been developed by controlling characteristic and volume fraction of primary phase embedded in the glass matrix. By careful alloy design procedure, the compositions of ß/glass phases, which are in metastable equilibrium have been properly selected, therefore the mechanical properties can be tailored by selecting the alloy compositions between the composition of ß and glass phases. The relation between the compressive yield strength and volume fraction of ß phase is well described using the rule of mixtures
Properties of kinematic singularities
The locally rotationally symmetric tilted perfect fluid Bianchi type V
cosmological model provides examples of future geodesically complete spacetimes
that admit a `kinematic singularity' at which the fluid congruence is
inextendible but all frame components of the Weyl and Ricci tensors remain
bounded. We show that for any positive integer n there are examples of Bianchi
type V spacetimes admitting a kinematic singularity such that the covariant
derivatives of the Weyl and Ricci tensors up to the n-th order also stay
bounded. We briefly discuss singularities in classical spacetimes.Comment: 13 pages. Published version. One sentence from version 2 correcte
Observation of the single-electron regime in a highly tunable silicon quantum dot
We report on low-temperature electronic transport measurements of a silicon
metal-oxide-semiconductor quantum dot, with independent gate control of
electron densities in the leads and the quantum dot island. This architecture
allows the dot energy levels to be probed without affecting the electron
density in the leads, and vice versa. Appropriate gate biasing enables the dot
occupancy to be reduced to the single-electron level, as evidenced by
magnetospectroscopy measurements of the ground state of the first two charge
transitions. Independent gate control of the electron reservoirs also enables
discrimination between excited states of the dot and density of states
modulations in the leads.Comment: 4 pages, 3 figures, accepted for Applied Physics Letter
Reactive-site mutants of N-TIMP-3 that selectively inhibit ADAMTS-4 and ADAMTS-5: biological and structural implications.
Published versio
Automated knowledge capture in 2D and 3D design environments
In Life Cycle Engineering, it is vital that the engineering knowledge for the product is captured throughout its life cycle in a formal and structured manner. This will allow the information to be referred to in the future by engineers who did not work on the original design but are wanting to understand the reasons that certain design decisions were made. In the past, attempts were made to try to capture this knowledge by having the engineer record the knowledge manually during a design session. However, this is not only time-consuming but is also disruptive to the creative process. Therefore, the research presented in this paper is concerned with capturing design knowledge automatically using a traditional 2D design environment and also an immersive 3D design environment. The design knowledge is captured by continuously and non-intrusively logging the user during a design session and then storing this output in a structured eXtensible Markup Language (XML) format. Next, the XML data is analysed and the design processes that are involved can be visualised by the automatic generation of IDEF0 diagrams. Using this captured knowledge, it forms the basis of an interactive online assistance system to aid future users who are carrying out a similar design task
Resonant tunneling magnetoresistance in epitaxial metal-semiconductor heterostructures
We report on resonant tunneling magnetoresistance via localized states
through a ZnSe semiconducting barrier which can reverse the sign of the
effective spin polarization of tunneling electrons. Experiments performed on
Fe/ZnSe/Fe planar junctions have shown that positive, negative or even its
sign-reversible magnetoresistance can be obtained, depending on the bias
voltage, the energy of localized states in the ZnSe barrier and spatial
symmetry. The averaging of conduction over all localized states in a junction
under resonant condition is strongly detrimental to the magnetoresistance
Defect Motion and Lattice Pinning Barrier in Josephson-Junction Ladders
We study motion of domain wall defects in a fully frustrated
Josephson-unction ladder system, driven by small applied currents. For small
system sizes, the energy barrier E_B to the defect motion is computed
analytically via symmetry and topological considerations. More generally, we
perform numerical simulations directly on the equations of motion, based on the
resistively-shunted junction model, to study the dynamics of defects, varying
the system size. Coherent motion of domain walls is observed for large system
sizes. In the thermodynamical limit, we find E_B=0.1827 in units of the
Josephson coupling energy.Comment: 7 pages, and to apear in Phys. Rev.
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