193,319 research outputs found
Thin FRP/GFRC structural elements
This paper presents background work leading to the development of thin structural elements made of GFRC (Glass Fibre Reinforced Concrete) reinforced with FRP (Fiber Reinforced Polymer) bars. Such thin structural elements are suitable for a variety of applications such as cladding, security screens, etc, but this paper focuses on their use as permanent formwork. The first part of the paper deals with optimising a uniform thickness GFRC section to achieve maximum flexural capacity at minimum weight. The second part deals with the interaction between FRP and GFRC, in particular with the issues of bond. The third part presents the performance of a 3 m span thin GFRC permanent formwork panel system reinforced with FRP. Both experimental and analytical studies are presented and it is concluded that FRP/GFRC thin structural elements can be designed using conventional techniques requiring only the use of appropriate material characteristics
Quantum Description for the Decay of NSNS Brane-Antibrane Systems
The stringy description for the instabilities in the charged
pairs is now well understood in terms of the open string
tachyon condensation. The quantum interpretation presumably via the stringy
description for the instabilities in the -charged and
pairs in IIA/IIB theories, however, has not been established
yet. This would be partly because of the absence (for the case)
or our relatively poor understanding (for the case) of their
worldvolume (gauge theory) dynamics. In the present work, using the well-known
quantum description for instabilities in the -charged
systems and in the M-theory brane-antibrane systems and invoking appropriate
string dualities, the stringy nature of the instabilities in the -charged
and systems has been uncovered. For the
annihilations to string vacua, the quantum, stringy interpretations are simple
extensions of Sen's conjecture for those in -charged brane-antibrane
systems.Comment: 22 pages, 4 eps figures, Latex, comments and references adde
Density Fluctuations in the Oscillatory Phase of Nonclassical Inflaton in FRW Universe
Using coherent and squeezed state formalisms of quantum optics for a
minimally coupled non-classical inflaton in the FRW mertic is studied, in
semiclassical theory of gravity. The leading order solution for the
semiclassical Einstein equations in the coherent, squeezed and squeezed vacuum
states are obtained perturbatively and are exhibit powerlaw expansion
behaviour. The validity of the semiclassical theory is examined in the squeezed
vacuum state in the oscillatory phase of the inflaton. The semiclassical theory
in the oscillatory phase of the non-classical inflaton holds only if the
associated squeezing parameter is much less compared to unity. Quantum
fluctuations of the inflaton is also examined in coherent and squeezed state
formalisms.Comment: 14 pages, 2 figures, To appear in Int.J.Mod.Phys.
Norm Estimates for the Difference Between Bochner's Integral and the Convex Combination of Function's Values
Norm estimates are developed between the Bochner integral of a vector-valued
function in Banach spaces having the Radon-Nikodym property and the convex
combination of function values taken on a division of the interval [a,b]
Studies of acoustic emission from point and extended sources
The use of simulated and controlled acoustic emission signals forms the basis of a powerful tool for the detailed study of various deformation and wave interaction processes in materials. The results of experiments and signal analyses of acoustic emission resulting from point sources such as various types of indentation-produced cracks in brittle materials and the growth of fatigue cracks in 7075-T6 aluminum panels are discussed. Recent work dealing with the modeling and subsequent signal processing of an extended source of emission in a material is reviewed. Results of the forward problem and the inverse problem are presented with the example of a source distributed through the interior of a specimen
A box-covering algorithm for fractal scaling in scale-free networks
A random sequential box-covering algorithm recently introduced to measure the
fractal dimension in scale-free networks is investigated. The algorithm
contains Monte Carlo sequential steps of choosing the position of the center of
each box, and thereby, vertices in preassigned boxes can divide subsequent
boxes into more than one pieces, but divided boxes are counted once. We find
that such box-split allowance in the algorithm is a crucial ingredient
necessary to obtain the fractal scaling for fractal networks; however, it is
inessential for regular lattice and conventional fractal objects embedded in
the Euclidean space. Next the algorithm is viewed from the cluster-growing
perspective that boxes are allowed to overlap and thereby, vertices can belong
to more than one box. Then, the number of distinct boxes a vertex belongs to is
distributed in a heterogeneous manner for SF fractal networks, while it is of
Poisson-type for the conventional fractal objects.Comment: 12 pages, 11 figures, a proceedings of the conference, "Optimization
in complex networks." held in Los Alamo
NiO Exchange Bias Layers Grown by Direct Ion Beam Sputtering of a Nickel Oxide Target
A new process for fabricating NiO exchange bias layers has been developed.
The process involves the direct ion beam sputtering (IBS) of a NiO target. The
process is simpler than other deposition techniques for producing NiO buffer
layers, and facilitates the deposition of an entire spin-valve layered
structure using IBS without breaking vacuum. The layer thickness and
temperature dependence of the exchange field for NiO/NiFe films produced using
IBS are presented and are similar to those reported for similar films deposited
using reactive magnetron sputtering. The magnetic properties of highly textured
exchange couples deposited on single crystal substrates are compared to those
of simultaneously deposited polycrystalline films, and both show comparable
exchange fields. These results are compared to current theories describing the
exchange coupling at the NiO/NiFe interface.Comment: 9 pages, Latex 2.09, 3 postscript figures. You can also this
manuscript at http://www.wsrcc.com/alison/fixed-nio/manuscript.html To be
published in _IEEE Trans. Magn._, Nov. 199
Feynman's Decoherence
Gell-Mann's quarks are coherent particles confined within a hadron at rest,
but Feynman's partons are incoherent particles which constitute a hadron moving
with a velocity close to that of light. It is widely believed that the quark
model and the parton model are two different manifestations of the same
covariant entity. If this is the case, the question arises whether the Lorentz
boost destroys coherence. It is pointed out that this is not the case, and it
is possible to resolve this puzzle without inventing new physics. It is shown
that this decoherence is due to the measurement processes which are less than
complete.Comment: RevTex 15 pages including 6 figs, presented at the 9th Int'l
Conference on Quantum Optics (Raubichi, Belarus, May 2002), to be published
in the proceeding
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