5,986 research outputs found
Overall buckling of lightweight stiffened panels using an adapted orthotropic plate method
The ultimate longitudinal bending strength of thin plated steel structures such as box girder bridges and ship hulls can be determined using an incremental–iterative procedure known as the Smith progressive collapse method. The Smith method first calculates the response of stiffened panel sub-structures in the girder and then integrates over the cross section of interest to calculate a moment–curvature response curve. A suitable technique to determine the strength behaviour of stiffened panels within the Smith method is therefore of critical importance. A fundamental assumption of the established progressive collapse method is that the buckling and collapse behaviour of the compressed panels within the girder occurs between adjacent transverse frames. However, interframe buckling may not always be the dominant collapse mode, especially for lightweight stiffened panels such as are found in naval ships and aluminium high speed craft. In these cases overall failure modes, where the buckling mode extends over several frame spaces, may dominate the buckling and collapse response. To account for this possibility, an adaptation to large deflection orthotropic plate theory is presented. The adapted orthotropic method is able to calculate panel stress–strain response curves accounting for both interframe and overall collapse. The method is validated with equivalent nonlinear finite element analyses for a range of regular stiffened panel geometries. It is shown how the adapted orthotropic method is implemented into an extended progressive collapse method, which enhances the capability for determining the ultimate strength of a lightweight stiffened box girder
From continuum mechanics to general relativity
Using ideas from continuum mechanics we construct a theory of gravity. We
show that this theory is equivalent to Einstein's theory of general relativity;
it is also a much faster way of reaching general relativity than the
conventional route. Our approach is simple and natural: we form a very general
model and then apply two physical assumptions supported by experimental
evidence. This easily reduces our construction to a model equivalent to general
relativity. Finally, we suggest a simple way of modifying our theory to
investigate non-standard space-time symmetries.Comment: 7 pages, this essay received a honorable mention in the 2014 essay
competition of the Gravity Research Foundatio
Acceptance checkout equipment - Spacecraft Monthly progress report, 15 Jan. - 15 Feb. 1966
Acceptance checkout equipment and spacecraft testin
Rotational elasticity
We consider an infinite 3-dimensional elastic continuum whose material points
experience no displacements, only rotations. This framework is a special case
of the Cosserat theory of elasticity. Rotations of material points are
described mathematically by attaching to each geometric point an orthonormal
basis which gives a field of orthonormal bases called the coframe. As the
dynamical variables (unknowns) of our theory we choose the coframe and a
density. We write down the general dynamic variational functional for our
rotational theory of elasticity, assuming our material to be physically linear
but the kinematic model geometrically nonlinear. Allowing geometric
nonlinearity is natural when dealing with rotations because rotations in
dimension 3 are inherently nonlinear (rotations about different axes do not
commute) and because there is no reason to exclude from our study large
rotations such as full turns. The main result of the paper is an explicit
construction of a class of time-dependent solutions which we call plane wave
solutions; these are travelling waves of rotations. The existence of such
explicit closed form solutions is a nontrivial fact given that our system of
Euler-Lagrange equations is highly nonlinear. In the last section we consider a
special case of our rotational theory of elasticity which in the stationary
setting (harmonic time dependence and arbitrary dependence on spatial
coordinates) turns out to be equivalent to a pair of massless Dirac equations
CVcat: an interactive database on cataclysmic variables
CVcat is a database that contains published data on cataclysmic variables and
related objects. Unlike in the existing online sources, the users are allowed
to add data to the catalogue. The concept of an ``open catalogue'' approach is
reviewed together with the experience from one year of public usage of CVcat.
New concepts to be included in the upcoming AstroCat framework and the next
CVcat implementation are presented. CVcat can be found at http://www.cvcat.org.Comment: 5 pages A&A Latex, 4 figures, accepted for publication in A&
The Legendary Visit of Emerson to Tallahassee
Among the pioneers in the perennial migration of winter visitors to Florida was Ralph Waldo Emerson, the beloved philosopher of American ideals. In 1827, ten years before the flowering of the stirring essays on “The American Scholar” and ”Self-Reliance,” the unknown tubercular youth sailed into castle-shadowed St. Augustine harbor seeking the healing climate of the newly-acquired Florida Territory
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