554 research outputs found
Equilibrium distributions in thermodynamical traffic gas
We derive the exact formula for thermal-equilibrium spacing distribution of
one-dimensional particle gas with repulsive potential V(r)=r^(-a) (a>0)
depending on the distance r between the neighboring particles. The calculated
distribution (for a=1) is successfully compared with the highway-traffic
clearance distributions, which provides a detailed view of changes in
microscopical structure of traffic sample depending on traffic density. In
addition to that, the observed correspondence is a strong support of studies
applying the equilibrium statistical physics to traffic modelling.Comment: 5 pages, 6 figures, changed content, added reference
Ray-based calculations of backscatter in laser fusion targets
A 1D, steady-state model for Brillouin and Raman backscatter from an
inhomogeneous plasma is presented. The daughter plasma waves are treated in the
strong damping limit, and have amplitudes given by the (linear) kinetic
response to the ponderomotive drive. Pump depletion, inverse-bremsstrahlung
damping, bremsstrahlung emission, Thomson scattering off density fluctuations,
and whole-beam focusing are included. The numerical code DEPLETE, which
implements this model, is described. The model is compared with traditional
linear gain calculations, as well as "plane-wave" simulations with the paraxial
propagation code pF3D. Comparisons with Brillouin-scattering experiments at the
OMEGA Laser Facility [T. R. Boehly et al., Opt. Commun. 133, p. 495 (1997)]
show that laser speckles greatly enhance the reflectivity over the DEPLETE
results. An approximate upper bound on this enhancement, motivated by phase
conjugation, is given by doubling the DEPLETE coupling coefficient. Analysis
with DEPLETE of an ignition design for the National Ignition Facility (NIF) [J.
A. Paisner, E. M. Campbell, and W. J. Hogan, Fusion Technol. 26, p. 755
(1994)], with a peak radiation temperature of 285 eV, shows encouragingly low
reflectivity. Re-absorption of Raman light is seen to be significant in this
design.Comment: 16 pages, 19 figure
Host Star Properties And Transit Exclusion For The HD 38529 Planetary System
The transit signature of exoplanets provides an avenue through which characterization of exoplanetary properties may be undertaken, such as studies of mean density, structure, and atmospheric composition. The Transit Ephemeris Refinement and Monitoring Survey is a program to expand the catalog of transiting planets around bright host stars by refining the orbits of known planets discovered with the radial velocity technique. Here we present results for the HD 38529 system. We determine fundamental properties of the host star through direct interferometric measurements of the radius and through spectroscopic analysis. We provide new radial velocity measurements that are used to improve the Keplerian solution for the two known planets, and we find no evidence for a previously postulated third planet. We also present 12 years of precision robotic photometry of HD 38529 that demonstrate the inner planet does not transit and the host star exhibits cyclic variations in seasonal mean brightness with a timescale of approximately six years
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Scenarios as the basis for assessment of mitigation and adaptation
The possibilities and need for adaptation and mitigation depends on uncertain future developments with respect to socio-economic factors and the climate system. Scenarios are used to explore the impacts of different strategies under uncertainty. In this chapter, some scenarios are presented that are used in the ADAM project for this purpose. One scenario explores developments with no mitigation, and thus with high temperature increase and high reliance on adaptation (leading to 4oC increase by 2100 compared to pre-industrial levels). A second scenario explores an ambitious mitigation strategy (leading to 2oC increase by 2100 compared to pre-industrial levels). In the latter scenario, stringent mitigation strategies effectively reduces the risks of climate change, but based on uncertainties in the climate system a temperature increase of 3oC or more cannot be excluded. The analysis shows that, in many cases, adaptation and mitigation are not trade-offs but supplements. For example, the number of people exposed to increased water resource stress due to climate change can be substantially reduced in the mitigation scenario, but even then adaptation will be required for the remaining large numbers of people exposed to increased stress. Another example is sea level rise, for which adaptation is more cost-effective than mitigation, but mitigation can help reduce damages and the cost of adaptation. For agriculture, finally, only the scenario based on a combination of adaptation and mitigation is able to avoid serious climate change impacts
Threshold for Electron Trapping Nonlinearity in Langmuir Waves
We assess when electron trapping nonlinearity is expected to be important in
Langmuir waves. The basic criterion is that the inverse of the detrapping rate
nu_d of electrons in the trapping region of velocity space must exceed the
bounce period of deeply-trapped electrons, tau_B = (n_e/delta n)^{1/2}
2pi/omega_pe. A unitless figure of merit, the "bounce number" N_B = 1/(nu_d
tau_B), encapsulates this condition and defines a trapping threshold amplitude
for which N_B=1. The detrapping rate is found for convective loss (transverse
and longitudinal) out of a spatially finite Langmuir wave. Simulations of
driven waves with a finite transverse profile, using the 2D-2V Vlasov code
Loki, show trapping nonlinearity increases continuously with N_B for transverse
loss, and is significant for N_B ~ 1. The detrapping rate due to Coulomb
collisions (both electron-electron and electron-ion) is also found, with
pitch-angle scattering and parallel drag and diffusion treated in a unified
manner. A simple way to combine convective and collisional detrapping is given.
Application to underdense plasma conditions in inertial confinement fusion
targets is presented. The results show that convective transverse loss is
usually the most potent detrapping process in a single f/8 laser speckle. For
typical plasma and laser conditions on the inner laser cones of the National
Ignition Facility, local reflectivities ~3% are estimated to produce
significant trapping effects.Comment: 16 pages, 15 figures, accepted for publication in Phys. Plasma
The band structure of BeTe - a combined experimental and theoretical study
Using angle-resolved synchrotron-radiation photoemission spectroscopy we have
determined the dispersion of the valence bands of BeTe(100) along ,
i.e. the [100] direction. The measurements are analyzed with the aid of a
first-principles calculation of the BeTe bulk band structure as well as of the
photoemission peaks as given by the momentum conserving bulk transitions.
Taking the calculated unoccupied bands as final states of the photoemission
process, we obtain an excellent agreement between experimental and calculated
spectra and a clear interpretation of almost all measured bands. In contrast,
the free electron approximation for the final states fails to describe the BeTe
bulk band structure along properly.Comment: 21 pages plus 4 figure
Systematic sensitivity analysis of the full economic impacts of sea level rise
The potential impacts of sea level rise (SLR) due to climate change have been widely studied in the literature. However, the uncertainty and robustness of these estimates has seldom been explored. Here we assess the model input uncertainty regarding the wide effects of SLR on marine navigation from a global economic perspective. We systematically assess the robustness of computable general equilibrium (CGE) estimates to model’s inputs uncertainty. Monte Carlo (MC) and Gaussian quadrature (GQ) methods are used for conducting a Systematic sensitivity analysis (SSA). This design allows to both explore the sensitivity of the CGE model and to compare the MC and GQ methods. Results show that, regardless whether triangular or piecewise linear Probability distributions are used, the welfare losses are higher in the MC SSA than in the original deterministic simulation. This indicates that the CGE economic literature has potentially underestimated the total economic effects of SLR, thus stressing the necessity of SSA when simulating the general equilibrium effects of SLR. The uncertainty decomposition shows that land losses have a smaller effect compared to capital and seaport productivity losses. Capital losses seem to affect the developed regions GDP more than the productivity losses do. Moreover, we show the uncertainty decomposition of the MC results and discuss the convergence of the MC results for a decomposed version of the CGE model. This paper aims to provide standardised guidelines for stochastic simulation in the context of CGE modelling that could be useful for researchers in similar settings
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