33,904 research outputs found
Infrared emissivities and absorptivities of gases
Approximate analytic expressions are obtained for the "effective band widths" and emissivities of diatomic molecules at elevated pressures. The absorptivities of molecular vibrationârotation bands are evaluated for radiation emitted by similar molecular vibrationârotation bands and for radiation emitted by blackbodies. The results obtained for the absorptivity calculations compare favorably with available empirical correlations for H_2O. The postulated model does not apply to CO_2 and, therefore, no satisfactory theoretical formula has been derived for the absorptivities of this molecule. The appendix (by A. Thomson) is devoted to a critical examination of the limits of validity of the effective bandâwidth concept for different molecules
Advances in understanding autogyro flight dynamics
A comprehensive flight dynamics study of the
autogyro is presented in this paper. A state of the art generic
simulation of the vehicle type was developed and validated
against flight data. This validation is presented in the paper
and it is shown that the model can be applied to the autogyro
with some confidence within well defined limitations
bounds. It is also shown that the general stability
characteristics of the autogyro can be considered as a mix of
helicopter and fixed wing aircraft modes of flight. Most
significantly the autogyro has a lightly damped, high
frequency phugoid mode. Further, it is demonstrated that
the only significant configurational effect is related to the
relative vertical position of the centre of gravity with respect
to the propeller thrustline, a centre of gravity which lies
above the thrustline being more desirable. Results from
preliminary handling qualities trials applying the techniques
of ADS33 to an autogyro are also presented. Results from
flight trials to investigate the teetering motion of the rotor
are described, and the influence of the research on air
accident investigation is also discussed
Bose and Mott Glass Phases in Dimerized Quantum Antiferromagnets
We examine the effects of disorder on dimerized quantum antiferromagnets in a
magnetic field, using the mapping to a lattice gas of hard-core bosons with
finite-range interactions. Combining a strong-coupling expansion, the replica
method, and a one-loop renormalization group analysis, we investigate the
nature of the glass phases formed. We find that away from the tips of the Mott
lobes, the transition is from a Mott insulator to a compressible Bose glass,
however the compressibility at the tips is strongly suppressed. We identify
this finding with the presence of a rare Mott glass phase not previously
described by any analytic theory for this model and demonstrate that the
inclusion of replica symmetry breaking is vital to correctly describe the
glassy phases. This result suggests that the formation of Bose and Mott glass
phases is not simply a weak localization phenomenon but is indicative of much
richer physics. We discuss our results in the context of both ultracold atomic
gases and spin-dimer materials.Comment: 10 pages (including supplementary material), 3 figure
Towards dynamic context discovery and composition
Context-awareness has been identified as a key characteristic for pervasive computing systems. As a variety of context-aware environments begin to flourish, pervasive applications shall have to interact different environments well. In this paper we propose extensions to the Strathclyde Context Infrastructure that gives context-aware applications the potential to adapt to unfamiliar environments transparently. We present a vision of a context discovery technique based on automated semantic reasoning about context information and services. The technique will offer higher levels of scalability and of interoperability with new context environments that cannot be achieved with current methods
Situation determination with distributed context histories
Determining the situation within an environment is a key goal of smart environment research. A significant challenge in situation determination is reasoning about openended groups of people and devices that a smart environment may contain. Contemporary solutions are often tailored to the specific environment. In this position paper, we present a novel general situation determination framework, that by viewing people and tools as playing roles in a situation, can easily adapt recognition to incorporate the dynamic structure of a situation over time
- âŠ