285,718 research outputs found
From buildings to cities: techniques for the multi-scale analysis of urban form and function
The built environment is a significant factor in many urban processes, yet direct measures of built form are
seldom used in geographical studies. Representation and analysis of urban form and function could provide
new insights and improve the evidence base for research. So far progress has been slow due to limited data
availability, computational demands, and a lack of methods to integrate built environment data with
aggregate geographical analysis. Spatial data and computational improvements are overcoming some of
these problems, but there remains a need for techniques to process and aggregate urban form data. Here we
develop a Built Environment Model of urban function and dwelling type classifications for Greater
London, based on detailed topographic and address-based data (sourced from Ordnance Survey
MasterMap). The multi-scale approach allows the Built Environment Model to be viewed at fine-scales for
local planning contexts, and at city-wide scales for aggregate geographical analysis, allowing an improved
understanding of urban processes. This flexibility is illustrated in the two examples, that of urban function
and residential type analysis, where both local-scale urban clustering and city-wide trends in density and
agglomeration are shown. While we demonstrate the multi-scale Built Environment Model to be a viable
approach, a number of accuracy issues are identified, including the limitations of 2D data, inaccuracies in
commercial function data and problems with temporal attribution. These limitations currently restrict the
more advanced applications of the Built Environment Model
Optical observation of "bandātoāband" scattering by timeāresolved phosphorescence line narrowing: Exciton dephasing in a quasiāoneādimensional solid
Abstract Unavailable
Characterization of vibrational overtones and "local" modes by emission spectroscopy
Abstract unavailable
Schleiermacher and Otto on religion : a reappraisal
An interpretation of the work of Schleiermacher and Otto recently offered by Andrew Dole, according to which these two thinkers differed over the extent to which religion can be explained naturalistically, and over the sense in which the supernatural can be admitted, is examined and refuted. It is argued that there is no difference between the two thinkers on this issue. It is shown that Schleiermacher's claim that a supernatural event is at the same time a natural event does not invite, but rather forecloses the possibility of, a naturalistic explanation of the event. It is further demonstrated that Otto, like Schleiermacher, denied the existence of supernatural events interpreted as events that infringe the laws of nature
Combustion instability sustained by unsteady vortex combustion
The determination of an internal feedback mechanism which leads to combustion instability inside a small scale
laboratory combustor is presented in this paper. During combustion instability, the experimental findings show that a large vortical structure is formed at an acoustic resonant mode of the system. The subsequent unsteady burning, within the vortex as it is convected downstream,
feeds energy into the acoustic field and sustains the large resonant oscillations. These vortices are formed when the
acoustic velocity fluctuation at the flameholder is a large fraction of the mean flow velocity. The propagation of
these vortices is not a strong function of the mean flow speed and appears to be dependent upon the frequency of the
instability. Continued existence of large vortical structures which characterize unstable operation depends upon the fuel-air ratio, system acoustics, and fuel type
Evidence of a saturated gravity-wave spectrum throughout the atmosphere
The view adapted here is that the dominant mesoscale motions are due to internal gravity waves and show that previous and new vertical wave number spectra of horizontal winds are consistent with the notion of a saturation limit on wave amplitudes. It is also proposed that, at any height, only those vertical wave numbers m less than m sub asterisk are at saturation amplitudes, where m sub asterisk is the vertical wave number of the dominant energy-containing scale. Wave numbers m less than m sub asterisk are unsaturated, but experience growth with height due to the decrease of atmospheric density. The result is a saturated spectrum of gravity waves with both m sub asterisk decreasing and wave energy increasing with height. This saturation theory is consistent with a variety of atmospheric spectral observations and provides a basis for the notion of a universal spectrum of atmospheric gravity waves
Discrete Logarithms in Generalized Jacobians
D\'ech\`ene has proposed generalized Jacobians as a source of groups for
public-key cryptosystems based on the hardness of the Discrete Logarithm
Problem (DLP). Her specific proposal gives rise to a group isomorphic to the
semidirect product of an elliptic curve and a multiplicative group of a finite
field. We explain why her proposal has no advantages over simply taking the
direct product of groups. We then argue that generalized Jacobians offer poorer
security and efficiency than standard Jacobians
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