2,645 research outputs found
Measurement of residual stress by using focused ion beam and digital image correlation method in thin-sized wires used for steel cords
Residual stress in the axial direction of the steel wires has been measured by using a method based on the combination of the focused ion beam (FIB) milling and digital image correlation software. That is, the residual stress was calculated from the measured displacement field before and after the introduction of a slot along the steel wires. The displacement was obtained by the digital correlation analysis of high-resolution scanning electron micrographs, while the slot was introduced by FIB milling with low energy beam. The fitting of the experimental results to an analytical model with the independent Young's modulus determined allows us to find the residual stress. The complete experimental procedures are described and its feasibilities are also evaluated for the thin-sized steel wires.open112sciescopu
Quantum and Classical divide: the gravitational case
We study the transition between quantum and classical behavior of particles
in a gravitational quantum well. We analyze how an increase in the particles
mass turns the energy spectrum into a continuous one, from an experimental
point of view. We also discuss the way these effects could be tested by
conducting experiments with atoms and fullerene-type molecules.Comment: Revtex4, 5 pages, 2 figures; version to appear in Physics Letters
One-loop four-graviton amplitude in eleven-dimensional supergravity
We find explicit expression for the one-loop four-graviton amplitude in
eleven-dimensional supergravity compactified on a circle. Represented in terms
of the string coupling (related to the compactification radius) it takes the
form of an infinite sum of perturbative string loop corrections. We also
compute the amplitude in the case of compactification on a 2-torus which is
given by an SL(2,Z) invariant expansion in powers of the torus area. We discuss
the structure of quantum corrections in eleven-dimensional theory and their
relation to string theory.Comment: 14 pages, harvmac. Remarks on the amplitude in uncompactified D=11
space and on explicit structure of R^4 terms adde
Constructing 3D crystal templates for photonic band gap materials using holographic optical tweezers
A simple and robust method is presented for the construction of 3-dimensional crystals from silica and polystyrene microspheres. The crystals are suitable for use as templates in the production of three-dimensional photonic band gap (PBG) materials. Manipulation of the microspheres was achieved using a dynamic holographic assembler (DHA) consisting of computer controlled holographic optical tweezers. Attachment of the microspheres was achieved by adjusting their colloidal interactions during assembly. The method is demonstrated by constructing a variety of 3-dimensional crystals using spheres ranging in size from 3 µm down to 800 nm. A major advantage of the technique is that it may be used to build structures that cannot be made using self-assembly. This is illustrated through the construction of crystals in which line defects have been deliberately included, and by building simple cubic structures
Toroidal mode number estimation of the edge-localized modes using the KSTAR 3-D electron cyclotron emission imaging system
A new and more accurate technique is presented for determining the toroidal mode number n of edge-localized modes (ELMs) using two independent electron cyclotron emission imaging (ECEI) systems in the Korea Superconducting Tokamak Advanced Research (KSTAR) device. The technique involves the measurement of the poloidal spacing between adjacent ELM filaments, and of the pitch angle ?? O of filaments at the plasma outboard midplane. Equilibrium reconstruction verifies that ?? O is nearly constant and thus well-defined at the midplane edge. Estimates of n obtained using two ECEI systems agree well with n measured by the conventional technique employing an array of Mirnov coils.open3
Lognormal Properties of SGR 1806-20 and Implications for Other SGR Sources
The time interval between successive bursts from SGR 1806-20 and the
intensity of these bursts are both consistent with lognormal distributions.
Monte Carlo simulations of lognormal burst models with a range of distribution
parameters have been investigated. The main conclusions are that while most
sources like SGR 1806-20 should be detected in a time interval of 25 years,
sources with means about 100 times longer have a probability of about 5\% of
being detected in the same interval. A new breed of experiments that operate
for long periods are required to search for sources with mean recurrence
intervals much longer than SGR 1806-20.Comment: 4 pages, latex with seperate file containing 2 uuencoded, gzip'ed,
tarred, .eps figures. Replaced with file that does not use kluwer.sty to
allow automatic postscript generation. To appear in proceedings of ESLAB 2
Trace anomaly induced effective action and 2d black holes for dilaton coupled supersymmetric theories
The action for 2d dilatonic supergravity with dilaton coupled matter and
dilaton multiplets is constructed. Trace anomaly and anomaly induced effective
action (in components as well as in supersymmetric form) for matter
supermultiplet on bosonic background are found. The one-loop effective action
and large- effective action for quantum dilatonic supergravity are also
calculated. Using induced effective action one can estimate the back-reaction
of dilaton coupled matter to the classical black hole solutions of dilatonic
supergravity. That is done on the example of supersymmetric CGHS model with
dilaton coupled quantum matter where Hawking radiation which turns out to be
zero is calculated. Similar 2d analysis maybe used to study spherically
symmetric collapse for other models of 4d supergravity.Comment: 21 pages, LaTeX, NDA-FP-3
Open Strings in PP-Wave Background from Defect Conformal Field Theory
We consider open strings ending on a D5-brane in the pp-wave background,
which is realized in the Penrose limit of with an
brane. A complete list of gauge invariant operators in the
defect conformal field theory is constructed which is dual to the open string
states.Comment: 14+1 pages, no figures, LaTex (v2: references added, typos corrected,
discussion expanded in section 4
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On the distribution of bids for construction contract auctions
The statistical distribution representing bid values constitutes an essential part of many auction models and has involved a wide range of assumptions, including the Uniform, Normal, Lognormal and Weibull densities. From a modelling point of view, its goodness is defined by how well it enables the probability of a particular bid value to be estimated – a past bid for ex-post analysis and a future bid for ex-ante (forecasting) analysis. However, there is no agreement to date of what is the most appropriate form and empirical work is sparse.
Twelve extant construction datasets from four continents over different time periods are analysed in this paper for their fit to a variety of candidate statistical distributions assuming homogeneity of bidders (ID not known). The results show there is no one single fit-all distribution, but that the 3p Log-Normal, Fréchet/2p Log-Normal, Normal, Gamma and Gumbel generally rank the best ex-post, and the 2p Log-Normal, Normal, Gamma and Gumbel the best ex-ante – with ex-ante having around three to four times worse fit than ex-post. Final comments focus on the results relating to the third and fourth standardised moments of the bids and a post-hoc rationalisation of the empirical outcome of the analysis
Angle-resolved photoemission in doped charge-transfer Mott insulators
A theory of angle-resolved photoemission (ARPES) in doped cuprates and other
charge-transfer Mott insulators is developed taking into account the realistic
(LDA+U) band structure, (bi)polaron formation due to the strong electron-phonon
interaction, and a random field potential. In most of these materials the first
band to be doped is the oxygen band inside the Mott-Hubbard gap. We derive the
coherent part of the ARPES spectra with the oxygen hole spectral function
calculated in the non-crossing (ladder) approximation and with the exact
spectral function of a one-dimensional hole in a random potential. Some unusual
features of ARPES including the polarisation dependence and spectral shape in
YBa2Cu3O7 and YBa2Cu4O8 are described without any Fermi-surface, large or
small. The theory is compatible with the doping dependence of kinetic and
thermodynamic properties of cuprates as well as with the d-wave symmetry of the
superconducting order parameter.Comment: 8 pages (RevTeX), 10 figures, submitted to Phys. Rev.
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