25,763 research outputs found
Anisotropic fluids in the case of stationary and axisymmetric spaces of General Relativity
We present a stationary axisymmetric solution belonging to Carter's family
[A] of spaces and representing an anisotropic fluid configuration.Comment: 14 pages,submitted to Int J Mod Phys
Morphology investigation on direct current pulsed gas tungsten arc welded additive layer manufactured Ti6Al4V alloy
The effects of pulsed gas tungsten arc weldingparameters on the morphology of
additive layer manufacturedTi6Al4V has been investigated in this study. Thepeak/
base current ratio and pulse frequency are found tohave no significant effect on
the refinement of prior betagrain size. However, it is found that the wire feed
ratehas a considerable effect on the prior beta grainrefinement at a given heat
input. This is due to the extrawire input being able to supply many
heterogeneousnucleation sites and also results in a negative temperaturegradient
in the front of the liquidus which blocks thecolumnar growth and changes the
columnar growth toequiaixal growth
Spin tests of a single-engine, high-wing light airplane
The airplane has a relatively steep spin mode (low angle of attack) with a high load factor and high velocity. The airplane recovers almost immediately after any deviation from the prospin control positions, except for one maneuver with reduced flexibility in the elevator control system
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Strength of the DTM RapidSteel 1.0 Material
This paper reports the results of a study into the strength of the DTM RapidSteel 1.0 material.
Elastic modulus and strength of the metal/copper composite material was investigated as a
function of the distance from the point of copper infiltration, the furnace cycle duration, and the
furnace type. The microstructure of the RapidSteel material was also examined in an attempt to
understand the science behind the infiltration process. The results have implications for the
design of tools to be made using the RapidTool process in situations where the tool will be used
as a production tool, rather than a prototype tool.Mechanical Engineerin
A Renormalization Group Improved Calculation of Top Quark Production near Threshold
The top quark cross section close to threshold in annihilation is
computed including the summation of logarithms of the velocity at
next-to-next-to-leading-logarithmic order in QCD. The remaining theoretical
uncertainty in the normalization of the total cross section is at the few
percent level, an order of magnitude smaller than in previous
next-to-next-to-leading order calculations. This uncertainty is smaller than
the effects of a light standard model Higgs boson.Comment: changed figures, added reference
The Marysville, Montana Geothermal Project
Drilling the first geothermal well in Montana presented many challenges, not only in securing materials and planning strategies for drilling the wildcat well but also in addressing the environmental, legal, and institutional issues raised by the request for permission to explore a resource which lacked legal definition. The Marysville Geothermal Project was to investigate a dry hot rock heat anomaly. The well was drilled to a total depth of 6790 feet and many fractured water bearing zones were encountered below 1800 feet
A simplex-like search method for bi-objective optimization
We describe a new algorithm for bi-objective optimization, similar to the Nelder Mead simplex
algorithm, widely used for single objective optimization. For diferentiable bi-objective functions on
a continuous search space, internal Pareto optima occur where the two gradient vectors point in
opposite directions. So such optima may be located by minimizing the cosine of the angle between
these vectors. This requires a complex rather than a simplex, so we term the technique the \cosine
seeking complex". An extra beneft of this approach is that a successful search identifes the direction
of the effcient curve of Pareto points, expediting further searches. Results are presented for some
standard test functions. The method presented is quite complicated and space considerations here
preclude complete details. We hope to publish a fuller description in another place
Jet Regions from Event Shapes and the N-Jet Soft Function at Hadron Colliders
The N-jettiness event shape divides phase space into N+2 regions, each
containing one jet or beam. These jet regions are insensitive to the
distribution of soft radiation and, with a geometric measure for N-jettiness,
have circular boundaries. We give a factorization theorem for the cross section
which is fully differential in the mass of each jet, and compute the
corresponding soft function at next-to-leading order (NLO). For N-jettiness,
all ingredients are now available to extend NLO cross sections to resummed
predictions at next-to-next-to-leading logarithmic order.Comment: 3 pages, 2 figures, part of PANIC 2011 proceeding
Physical Purification of Quantum States
We introduce the concept of a physical process that purifies a mixed quantum
state, taken from a set of states, and investigate the conditions under which
such a purification map exists. Here, a purification of a mixed quantum state
is a pure state in a higher-dimensional Hilbert space, the reduced density
matrix of which is identical to the original state. We characterize all sets of
mixed quantum states, for which perfect purification is possible. Surprisingly,
some sets of two non-commuting states are among them. Furthermore, we
investigate the possibility of performing an imperfect purification.Comment: 5 pages, 1 figure; published versio
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