9,132 research outputs found
Improving the applicability of radar rainfall estimates for urban pluvial flood modelling and forecasting
This work explores the possibility of improving the applicability of radar rainfall estimates (whose accuracy is generally insufficient) to the verification and operation of urban storm-water drainage models by employing a number of local gauge-based radar rainfall adjustment techniques. The adjustment techniques tested in this work include a simple mean-field bias (MFB) adjustment, as well as a more complex Bayesian radar-raingauge data merging method which aims at better preserving the spatial structure of rainfall fields. In addition, a novel technique (namely, local singularity analysis) is introduced and shown to improve the Bayesian method by better capturing and reproducing storm patterns and peaks. Two urban catchments were used as case studies in this work: the Cranbrook catchment (9 km2) in North-East London, and the Portobello catchment (53 km2) in the East of Edinburgh. In the former, the potential benefits of gauge-based adjusted radar rainfall estimates in an operational context were analysed, whereas in the latter the potential benefits of adjusted estimates for model verification purposes were explored. Different rainfall inputs, including raingauge, original radar and the aforementioned merged estimates were fed into the urban drainage models of the two catchments. The hydraulic outputs were compared against available flow and depth records. On the whole, the tested adjustment techniques proved to improve the applicability of radar rainfall estimates to urban hydrological applications, with the Bayesian-based methods, in particular the singularity sensitive one, providing more realistic and accurate rainfall fields which result in better reproduction of the urban drainage systemâs dynamics. Further testing is still necessary in order to better assess the benefits of these adjustment methods, identify their shortcomings and improve them accordingly
A3 thinking approach to support knowledge-driven design
Problem solving is a crucial skill in product development. Any lack of effective decision making at an early design stage will affect productivity and increase costs and the lead time for the other stages of the product development life cycle. This could be improved by the use of a simple and informative approach which allows the designers and engineers to make decisions in product design by providing useful knowledge. This paper presents a novel A3 thinking approach to problem solving in product design, and provides a new A3 template which is structured from a combination of customised elements (e.g. the 8 Disciplines approach) and reflection practice. This approach was validated using a case study in the Electromagnetic Compatibility (EMC) design issue for an automotive electrical sub-assembly product. The main advantage of the developed approach is to create and capture the useful knowledge in a simple manner. Moreover, the approach provides a reflection section allowing the designers to turn their experience of design problem solving into proper learning and to represent their understanding of the design solution. These will be systematically structured (e.g. as a design checklist) to be circulated and shared as a reference for future design projects. Thus, the recurrence of similar design problems will be prevented and will aid the designers in adopting the expected EMC test results
Dust-acoustic instability driven by drifting ions and electrons in the dust plasma with Lorentzian kappa distribution
The instability of the dust-acoustic waves driven by drifting electrons and
ions in a dusty plasma is investigated by the kinetic theory. All the plasma
components (electrons, ions and dust particles) are assumed to be the
Lorentzian kappa-distributions. The spectral indexes kappa of the
kappa-distributions for the three plasma components are different from each
other. The obtained instability growth rate depends on the physical quantities
of the plasma not only, but on the spectral indexes. The numerical results for
the kappa-effect on the instability growth rate show that, if the normalized
wave number is small, the index of electrons has a stabilized effect on the
dust acoustic waves and the index of ions has an instability effect on the
waves, but if the normalized wave number is large, they both nearly have no any
effect on the waves. In reverse, the index of dust grains has nearly no any
effect on the instability growth rate if the normalized wave number is small,
but it has a stabilized effect on the dust waves if the normalized wave number
is large.Comment: 14 pages, 4 figures,25 reference
A zone of preferential ion heating extends tens of solar radii from Sun
The extreme temperatures and non-thermal nature of the solar corona and solar
wind arise from an unidentified physical mechanism that preferentially heats
certain ion species relative to others. Spectroscopic indicators of unequal
temperatures commence within a fraction of a solar radius above the surface of
the Sun, but the outer reach of this mechanism has yet to be determined. Here
we present an empirical procedure for combining interplanetary solar wind
measurements and a modeled energy equation including Coulomb relaxation to
solve for the typical outer boundary of this zone of preferential heating.
Applied to two decades of observations by the Wind spacecraft, our results are
consistent with preferential heating being active in a zone extending from the
transition region in the lower corona to an outer boundary 20-40 solar radii
from the Sun, producing a steady state super-mass-proportional
-to-proton temperature ratio of . Preferential ion heating
continues far beyond the transition region and is important for the evolution
of both the outer corona and the solar wind. The outer boundary of this zone is
well below the orbits of spacecraft at 1 AU and even closer missions such as
Helios and MESSENGER, meaning it is likely that no existing mission has
directly observed intense preferential heating, just residual signatures. We
predict that {Parker Solar Probe} will be the first spacecraft with a perihelia
sufficiently close to the Sun to pass through the outer boundary, enter the
zone of preferential heating, and directly observe the physical mechanism in
action.Comment: 11 pages, 7 figures, accepted for publication in the Astrophysical
Journal on 1 August 201
An Open Logical Framework
The LFP Framework is an extension of the Harper-Honsell-Plotkin's Edinburgh Logical Framework LF with external predicates, hence the name Open Logical Framework. This is accomplished by defining lock type constructors, which are a sort of \u25a1-modality constructors, releasing their argument under the condition that a possibly external predicate is satisfied on an appropriate typed judgement. Lock types are defined using the standard pattern of constructive type theory, i.e. via introduction, elimination and equality rules. Using LFP, one can factor out the complexity of encoding specific features of logical systems, which would otherwise be awkwardly encoded in LF, e.g. side-conditions in the application of rules in Modal Logics, and sub-structural rules, as in non-commutative Linear Logic. The idea of LFP is that these conditions need only to be specified, while their verification can be delegated to an external proof engine, in the style of the Poincar Principle or Deduction Modulo. Indeed such paradigms can be adequately formalized in LFP. We investigate and characterize the meta-theoretical properties of the calculus underpinning LFP: strong normalization, confluence and subject reduction. This latter property holds under the assumption that the predicates are well-behaved, i.e. closed under weakening, permutation, substitution and reduction in the arguments. Moreover, we provide a canonical presentation of LFP, based on a suitable extension of the notion of \u3b2\u3b7-long normal form, allowing for smooth formulations of adequacy statements. \ua9 The Author, 2013
The oblique firehose instability in a bi-kappa magnetized plasma
In this work, we derive a dispersion equation that describes the excitation
of the oblique (or Alfv\'en) firehose instability in a plasma that contains
both electron and ion species modelled by bi-kappa velocity distribution
functions. The equation is obtained with the assumptions of low-frequency waves
and moderate to large values of the parallel (respective to the ambient
magnetic field) plasma beta parameter, but it is valid for any direction of
propagation and for any value of the particle gyroradius (or Larmor radius).
Considering values for the physical parameters typical to those found in the
solar wind, some solutions of the dispersion equation, corresponding to the
unstable mode, are presented. In order to implement the dispersion solver,
several new mathematical properties of the special functions occurring in a
kappa plasma are derived and included. The results presented here suggest that
the superthermal characteristic of the distribution functions leads to
reductions to both the maximum growth rate of the instability and of the
spectral range of its occurrence
Dispersion of Waves in Relativistic Plasmas with Isotropic Particle Distributions
The dispersion laws of Langmuir and transverse waves are calculated in the
relativistic non-magnetized formalism for several isotropic particle
distributions: thermal, power-law, relativistic Lorentzian and hybrid
. For Langmuir waves the parameters of superluminal undamped, subluminal
damped principal and higher modes are determined for a range of distribution
parameters. The undamped and principal damped modes are found to match
smoothly. Principal damped and second damped modes are found not to match
smoothly. The presence of maximum wavenumber is discovered above that no
longitudinal modes formally exist. The higher damped modes are discovered to be
qualitatively different for thermal and certain non-thermal distributions.
Consistently with the known results, the Landau damping is calculated to be
stronger for non-thermal power-law-like distributions. The dispersion law is
obtained for the single undamped transverse mode. The analytic results for the
simplest distributions are provided.Comment: 8 pages, 12 figures, accepted by Physics of Plasma
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