12,348 research outputs found
Socio-hydrological modelling: a review asking “why, what and how?”
Interactions between humans and the environment are occurring on a scale that
has never previously been seen; the scale of human interaction with the water
cycle, along with the coupling present between social and hydrological
systems, means that decisions that impact water also impact people. Models
are often used to assist in decision-making regarding hydrological systems,
and so in order for effective decisions to be made regarding water resource
management, these interactions and feedbacks should be accounted for in
models used to analyse systems in which water and humans interact. This paper
reviews literature surrounding aspects of socio-hydrological modelling. It
begins with background information regarding the current state of
socio-hydrology as a discipline, before covering reasons for modelling and
potential applications. Some important concepts that underlie
socio-hydrological modelling efforts are then discussed, including ways of
viewing socio-hydrological systems, space and time in modelling, complexity,
data and model conceptualisation. Several modelling approaches are described,
the stages in their development detailed and their applicability to
socio-hydrological cases discussed. Gaps in research are then highlighted to
guide directions for future research. The review of literature suggests that
the nature of socio-hydrological study, being interdisciplinary, focusing on
complex interactions between human and natural systems, and dealing with long
horizons, is such that modelling will always present a challenge; it is,
however, the task of the modeller to use the wide range of tools afforded to
them to overcome these challenges as much as possible. The focus in
socio-hydrology is on understanding the human–water system in a holistic
sense, which differs from the problem solving focus of other water management
fields, and as such models in socio-hydrology should be developed with a view
to gaining new insight into these dynamics. There is an essential choice that
socio-hydrological modellers face in deciding between representing individual
system processes or viewing the system from a more abstracted level and
modelling it as such; using these different approaches has implications for
model development, applicability and the insight that they are capable of
giving, and so the decision regarding how to model the system requires
thorough consideration of, among other things, the nature of understanding
that is sought
The Reconstruction of Supersymmetric Theories at High Energy Scales
The reconstruction of fundamental parameters in supersymmetric theories
requires the evolution to high scales, where the characteristic regularities in
mechanisms of supersymmetry breaking become manifest. We have studied a set of
representative examples in this context: minimal supergravity and a left--right
symmetric extension; gauge mediated supersymmetry breaking; and superstring
effective field theories. Through the evolution of the parameters from the
electroweak scale the regularities in different scenarios at the high scales
can be unravelled if precision analyses of the supersymmetric particle sector
at e+ e- linear colliders are combined with analyses at the LHC.Comment: 36 pages, latex, 6 figure
Numerical method for evolving the Projected Gross-Pitaevskii equation
In this paper we describe a method for evolving the projected
Gross-Pitaevskii equation (PGPE) for a Bose gas in a harmonic oscillator
potential. The central difficulty in solving this equation is the requirement
that the classical field is restricted to a small set of prescribed modes that
constitute the low energy classical region of the system. We present a scheme,
using a Hermite-polynomial based spectral representation, that precisely
implements this mode restriction and allows an efficient and accurate solution
of the PGPE. We show equilibrium and non-equilibrium results from the
application of the PGPE to an anisotropic trapped three-dimensional Bose gas.Comment: 12 pages, 5 figures. To appear in Phys. Rev. E. Convergence results
added, a few minor changes made and typos fixe
IUE observations of oxygen-rich supernova remnants
The IUE observations were used to determine the composition of the ejecta (especially C and Si abundances) and to test models for the ionization and excitation of the ejecta of two oxygen-rich supernova remnants (N132D in the Large Magellanic Cloud and 1E 0102-7219 in the Small Magellanic Cloud). Time-dependent photoionization by the EUV and X-ray radiation from 1E 0102-7219 can qualitatively explain its UV and optical line emission, but the density and ionization structures are complex and prevent a unique model from being specified. Many model parameters are poorly constrained, including the time dependence and shape of the ionizing spectrum. Moreover, the models presented are not self-consistent in that the volumes and densities of the optically emitting gas imply optical depths of order unity in the EUV, but absorption of the ionizing radiation was ignored. It is possible that these shortcomings reflect a more fundamental limitation of the model assumptions. It is assumed that the electron velocity distribution is Maxwellian and that the energy deposited by photoionization heats the electrons directly. The 500 eV electrons produced by the Auger process may excite or ionize other ions before they slow down enough to share their energy with other electrons. Many of the excitations would produce photons that could ionize lower ionization stages
Observation of enhanced optical spring damping in a macroscopic mechanical resonator and application for parametric instability control in advanced gravitational-wave detectors
We show that optical spring damping in an optomechanical resonator can be enhanced by injecting a phase delay in the laser frequency-locking servo to rotate the real and imaginary components of the optical spring constant. This enhances damping at the expense of optical rigidity. We demonstrate enhanced parametric damping which reduces the Q factor of a 0.1-kg-scale resonator from 1.3Ă—10^5 to 6.5Ă—10^3. By using this technique adequate optical spring damping can be obtained to damp parametric instability predicted for advanced laser interferometer gravitational-wave detectors
- …