30,330 research outputs found
Barriers to Investment Abroad as Tools of Payments Policy
The thesis examines the fatigue life of weld ends, where very little usable research previously has been conducted, and often the weld ends are the critical parts of the weld. It is essential knowing the fatigue life of welds to be able to use them most efficiently.The report is divided into two parts; in the first the different calculation methods used today at Toyota Material Handling are examined and compared. Based on the results from the analysis and what is used mostly today, the effective notch approach is the method used in part two.To validate the calculation methods and models used, fatigue testing of the welded test specimens was conducted together with a stress test. New modelling methods of the weld ends that coincide with the test results were made in the finite element software Abaqus. A new way of modelling the weld ends for the effective notch method is also proposed. By using a notch radius of 0.2 mm and rounded weld ends the calculated fatigue life better matches the life of the real weld ends
HOST turbine heat transfer subproject overview
The experimental part of the turbine heat transfer subproject consists of six large experiments, which are highlighted in this overview, and three of somewhat more modest scope. One of the initial efforts was the stator airfoil heat transfer program. The non-film cooled and the showerhead film cooled data have already been reported. The gill region film cooling effort is currently underway. The investigation of secondary flows in a 90 deg curved duct, was completed. The first phase examined flows with a relatively thin inlet boundary layer and low free stream turbulence. The second phase studied a thicker inlet boundary layer and higher free stream turbulence. A comparison of analytical and experimental cross flow velocity vectors is shown for the 60 deg plane. Two experiments were also conducted in the high pressure facility. One examined full coverage film cooled vanes, and the other, advanced instrumentation. The other three large experimental efforts were conducted in a rotation reference frame. An experiment to obtain gas path airfoil heat transfer coefficients in the large, low speed turbine was completed. Single-stage data with both high and low-inlet turbulence were taken. The second phase examined a one and one-half stage turbine and focused on the second vane row. Under phase 3 aerodynamic quantities such as interrow time-averaged and rms values of velocity, flow angle, inlet turbulence, and surface pressure distribution were measured
Review and assessment of the HOST turbine heat transfer program
The objectives of the HOST Turbine Heat Transfer subproject were to obtain a better understanding of the physics of the aerothermodynamic phenomena occurring in high-performance gas turbine engines and to assess and improve the analytical methods used to predict the fluid dynamics and heat transfer phenomena. At the time the HOST project was initiated, an across-the-board improvement in turbine design technology was needed. Therefore, a building-block approach was utilized, with research ranging from the study of fundamental phenomena and analytical modeling to experiments in simulated real-engine environments. Experimental research accounted for 75 percent of the project, and analytical efforts accounted for approximately 25 percent. Extensive experimental datasets were created depicting the three-dimensional flow field, high free-stream turbulence, boundary-layer transition, blade tip region heat transfer, film cooling effects in a simulated engine environment, rough-wall cooling enhancement in a rotating passage, and rotor-stator interaction effects. In addition, analytical modeling of these phenomena was initiated using boundary-layer assumptions as well as Navier-Stokes solutions
Dissipative quantum mechanics beyond Bloch-Redfield: A consistent weak-coupling expansion of the ohmic spin boson model at arbitrary bias
We study the time dynamics of the ohmic spin boson model at arbitrary bias
and small coupling to the bosonic bath. Using perturbation
theory and the real-time renormalization group (RG) method we present a
consistent zero-temperature weak-coupling expansion for the time evolution of
the reduced density matrix one order beyond the Bloch-Redfield solution. We
develop a renormalized perturbation theory and present an analytical solution
covering the whole range from small to large times, including further results
for exponentially small or large times. Resumming all secular terms in all
orders of perturbation theory we find exponential decay for all terms of the
time evolution. We determine the preexponential functions and find slowly
varying logarithmic terms with the renormalized Rabi frequency as
energy scale together with strongly varying parts falling off asymptocially as
in leading order, in contrast to the unbiased case. Resumming all
logarithmic terms in all orders of perturbation theory via real-time RG we find
the correct renormalized tunneling and a power-law behaviour for the
oscillating modes with exponent crossing over from for exponentially
small times to a bias-dependent value for
exponentially large times. Furthermore, we present a degenerate perturbation
theory to calculate consistently the purely decaying mode one order beyond
Bloch-Redfield.Comment: 27 pages, 2 figure
Endomorphisms of Banach algebras of infinitely differentiable functions on compact plane sets
In this note we study the endomorphisms of certain Banach algebras of
infinitely differentiable functions on compact plane sets, associated with
weight sequences M. These algebras were originally studied by Dales, Davie and
McClure.
In a previous paper this problem was solved in the case of the unit interval
for many weights M. Here we investigate the extent to which the methods used
previously apply to general compact plane sets, and introduce some new methods.
In particular, we obtain many results for the case of the closed unit disc.
This research was supported by EPSRC grant GR/M31132Comment: 15 pages LaTe
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