64,691 research outputs found
Anisotropic Compacts Stars on Paraboloidal Spacetime with Linear Equation of State
New exact solutions of Einstein's field equations (EFEs) by assuming linear
equation of state, where is the radial
pressure and is the surface density, are obtained on the background
of a paraboloidal spacetime. By assuming estimated mass and radius of strange
star candidate 4U 1820-30, various physical and energy conditions are used for
estimating the range of parameter . The suitability of the model for
describing pulsars like PSR J1903+327, Vela X-1, Her X-1 and SAX J1804.3658 has
been explored and respective ranges of , for which all physical and
energy conditions are satisfied throughout the distribution, are obtained.Comment: 10 pages, 12 figures, 1 tabl
Surface Plasmon Driven Electric and Magnetic Resonators for Metamaterials
Using interplay between surface plasmons and metamaterials, we propose a new
technique for novel metamaterial designs. We show that surface plasmons
existing on thin metal surfaces can be used to "drive" non-resonant structures
in their vicinity to provide new types of electric and magnetic resonators.
These resonators strictly adhere to surface plasmon dispersion of the host
metal film. The operating frequency of the resultant metamaterials can be
scaled to extremely high frequencies, otherwise not possible with conventional
split-ring-resonator-based designs. Our approach opens new possibilities for
theory and experiment in the interface of plasmonics and metamaterials to
harvest many potential applications of both fields combined.Comment: Less than 5 Journal Pages, 5 Figure
Wear and Friction Modeling on Lifeboat Launch Systems
The RNLI provides search and rescue cover along the UK and RoI coast using a variety of lifeboats
and launch techniques. In locations where there is no natural harbour it is necessary to use a slipway
to launch the lifeboat into the sea. Lifeboat slipway stations consist of an initial section where the
boat is held on rollers followed by an inclined keelway lined with low friction composite materials,
the lifeboat is released from the top of the slipway and proceeds under its own weight into the water.
The lifeboat is later recovered using a winch line. It is common to manually apply grease to the
composite slipway lining before each launch and recovery in order to ensure sufficiently low friction
for successful operation. With the introduction of the Tamar class lifeboat it is necessary to upgrade
existing boathouses and standardise slipway operational procedures to ensure consistent operation.
The higher contact pressures associated with the new lifeboat have led to issues of high friction and
wear on the composite slipway linings and the manual application of grease to reduce friction is to be
restricted due to environmental impact and cost factors. This paper presents a multidisciplinary
approach to modelling slipway panel wear and friction using tribometer testing in conjunction with
finite element analysis and slipway condition surveys to incorporate common real-world effects such
as panel misalignments. Finally, it is shown that a freshwater lubrication system is effective,
reducing cost and environmental impacts while maintaining good friction and wear performance
A review of fracture mechanics life technology
Current lifetime prediction technology for structural components subjected to cyclic loads was reviewed. The central objectives of the project were to report the current state of and recommend future development of fracture mechanics-based analytical tools for modeling and forecasting subcritical fatigue crack growth in structures. Of special interest to NASA was the ability to apply these tools to practical engineering problems and the developmental steps necessary to bring vital technologies to this stage. A survey of published literature and numerous discussions with experts in the field of fracture mechanics life technology were conducted. One of the key points made is that fracture mechanics analyses of crack growth often involve consideration of fatigue and fracture under extreme conditions. Therefore, inaccuracies in predicting component lifetime will be dominated by inaccuracies in environment and fatigue crack growth relations, stress intensity factor solutions, and methods used to model given loads and stresses. Suggestions made for reducing these inaccuracies include: development of improved models of subcritical crack growth, research efforts aimed at better characterizing residual and assembly stresses that can be introduced during fabrication, and more widespread and uniform use of the best existing methods
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