16,395 research outputs found
Application of 2D hydroelasticity theory to investigate the failure of a containership
This paper focuses on the investigation carried out on the failure of the MSC Napoli using two-dimensional (2D) symmetric (i.e. vertical bending) hydroelasticity analysis. The aim of the investigation was to assess the influence of whipping-induced loads on the structural strength of this containership. Relevant structural, hydrostatic and operational data were provided. The calculations were carried out in head regular and long-crested irregular waves. Both cases included the effect of bottom slamming only. Global wave-induced loads were evaluated along the hull, focusing in particular in the vicinity of the engine room. The investigation showed that whipping, due to bottom slamming, is only important for severe seas. The investigation also showed that the keel stresses, in way of the engine room, can be as large as the keel stresses at amidships
On The Capacity of Surfaces in Manifolds with Nonnegative Scalar Curvature
Given a surface in an asymptotically flat 3-manifold with nonnegative scalar
curvature, we derive an upper bound for the capacity of the surface in terms of
the area of the surface and the Willmore functional of the surface. The
capacity of a surface is defined to be the energy of the harmonic function
which equals 0 on the surface and goes to 1 at infinity. Even in the special
case of Euclidean space, this is a new estimate. More generally, equality holds
precisely for a spherically symmetric sphere in a spatial Schwarzschild
3-manifold. As applications, we obtain inequalities relating the capacity of
the surface to the Hawking mass of the surface and the total mass of the
asymptotically flat manifold.Comment: 18 page
Deducing Cosmological Observables from the S-matrix
We study one loop quantum gravitational corrections to the long range force
induced by the exchange of a massless scalar between two massive scalars. The
various diagrams contributing to the flat space S-matrix are evaluated in a
general covariant gauge and we show that dependence on the gauge parameters
cancels at a point considerably {\it before} forming the full S-matrix, which
is unobservable in cosmology. It is possible to interpret our computation as a
solution to the effective field equations --- which could be done even in
cosmology --- but taking account of quantum gravitational corrections from the
source and from the observer.Comment: 28 pages, 5 figures, uses LaTeX2
The perils of credit booms
We present a dynamic general equilibrium model of production economies with adverse selection in the financial market to study the interaction between funding liquidity and market liquidity and its impact on business cycles. Entrepreneurs can take on short-term collateralized debt and trade long-term assets to finance investment. Funding liquidity can erode market liquidity. High funding liquidity discourages firms from selling their good long-term assets since these good assets have to subsidize lemons when there is information asymmetry. This can cause a liquidity dry-up in the market for long-term assets and even a market breakdown, resulting in a financial crisis. Multiple equilibria can coexist. Credit booms combined with changes in beliefs can cause equilibrium regime shifts, leading to an economic crisis or expansion.Published versio
The Graviton Tail almost Completely Wags the Dog
One graviton loop corrections to the vacuum polarization on de Sitter show
two interesting infrared effects: a secular enhancement of the photon electric
field strength and a long range running of the Coulomb potential. We show that
the first effect derives solely from the "tail" term of the graviton
propagator, but that the second effect does not. Our result agrees with the
earlier observation that the secular enhancement of massless fermion mode
functions derives from solely from the tail term. We discuss the implications
this has for the important project of generalizing to quantum gravity the
Starobinsky technique for summing the series of leading infrared effects from
inflationary quantum field theory.Comment: 17 pages, 1 figure, uses LaTeX2
The effect of structural discontinuity on antisymmetric response of a container ship
Recent trends in capacity, hence size, growth in container ships have increased the importance of torsion, particularly how it is influenced by the large deck openings and structural discontinuities present in such ships. This paper investigates the consequences of these effects on the ‘dry’ antisymmetric modal characteristics and consequent wave-induced loads. A beam model with more accurate representation of warping and structural discontinuities is applied to a box beam to assess these influences and compare predictions of natural frequencies and mode shapes with previous calculations and finite element (FE) predictions. The analysis is subsequently applied to a feeder containership travelling in regular oblique waves and resultant loads are compared with predictions obtained from previous two (2D) - and three-dimensional (3D) hydroelasticity analyses
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