10,893 research outputs found
Durability of zirconia thermal-barrier ceramic coatings on air-cooled turbine blades in cyclic jet engine operation
Thermal barrier ceramic coatings of stabilized zirconia over a bond coat of Ni Cr Al Y were tested for durability on air cooled turbine rotor blades in a research turbojet engine. Zirconia stabilized with either yttria, magnesia, or calcia was investigated. On the basis of durability and processing cost, the yttria stabilized zirconia was considered the best of the three coatings investigated
Semi-classical scattering in two dimensions
The semi-classical limit of quantum-mechanical scattering in two dimensions
(2D) is developed. We derive the Wentzel-Kramers-Brillouin and Eikonal results
for 2D scattering. No backward or forward glory scattering is present in 2D.
Other phenomena, such as rainbow or orbiting do show up.Comment: 6 page
Quantum Aspects of the Noncommutative Sine-Gordon Model
In this paper, we first use semi-classical methods to study quantum field
theoretical aspects of the integrable noncommutative sine-Gordon model proposed
in [hep-th/0406065]. In particular, we examine the fluctuations at quadratic
order around the static kink solution using the background field method. We
derive equations of motion for the fluctuations and argue that at O(theta^2)
the spectrum of fluctuations remains essentially the same as that of the
corresponding commutative theory. We compute the one-loop two-point functions
of the sine-Gordon field and the additional scalar field present in the model
and exhibit logarithmic divergences, only some of which lead to UV/IR mixing.
We briefly discuss the one-loop renormalization in Euclidean signature and
comment on the obstacles in determining the noncommutativity corrections to the
quantum mass of the kink.Comment: 1+14 pages, 8 eps figures, Added references, Version to appear in
JHE
Two-dimensional shear modulus of a Langmuir foam
We deform a two-dimensional (2D) foam, created in a Langmuir monolayer, by
applying a mechanical perturbation, and simultaneously image it by Brewster
angle microscopy. We determine the foam stress tensor (through a determination
of the 2D gas-liquid line tension, 2.35 0.4 pJm) and the
statistical strain tensor, by analyzing the images of the deformed structure.
We deduce the 2D shear modulus of the foam, .
The foam effective rigidity is predicted to be , which agrees with the value obtained in an independent mechanical measurement.Comment: submitted May 12, 2003 ; resubmitted Sept 9, 200
Colloid-colloid and colloid-wall interactions in driven suspensions
We investigate the non-equilibrium fluid structure mediated forces between
two colloids driven through a suspension of mutually non-interacting Brownian
particles as well as between a colloid and a wall in stationary situations. We
solve the Smoluchowski equation in bispherical coordinates as well as with a
method of reflections, both in linear approximation for small velocities and
numerically for intermediate velocities, and we compare the results to a
superposition approximation considered previously. In particular we find an
enhancement of the friction (compared to the friction on an isolated particle)
for two colloids driven side by side as well as for a colloid traveling along a
wall. The friction on tailgating colloids is reduced. Colloids traveling side
by side experience a solute induced repulsion while tailgating colloids are
attracted to each other.Comment: 8 Pages, 8 figure
Managing sleep and wakefulness in a 24 hour world
This article contributes to literature on the sociology of sleep by exploring the sleeping practices and subjective sleep experiences of two social groups: shift workers and students. It draws on data, collected in the UK from 25 semi-structured interviews, to discuss the complex ways in which working patterns and social activities impact upon experiences and expectations of sleep in our wired awake world. The data show that, typically, sleep is valued and considered to be important for health, general wellbeing, appearance and physical and cognitive functioning. However, sleep time is often cut back on in favour of work demands and social activities. While shift workers described their efforts to fit in an adequate amount of sleep per 24-hour period, for students, the adoption of a flexible sleep routine was thought to be favourable for maintaining a work–social life balance. Collectively, respondents reported using a wide range of strategies, techniques, technologies and practices to encourage, overcome or delay sleep(iness) and boost, promote or enhance wakefulness/alertness at socially desirable times. The analysis demonstrates how social context impacts not only on how we come to think about sleep and understand it, but also how we manage or self-regulate our sleeping patterns
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