Non-Equilibrium Modeling of the Fe XVII 3C/3D ratio for an Intense X-ray Free Electron Laser

We present a review of two methods used to model recent LCLS experimental results for the 3C/3D line intensity ratio of Fe XVII (Bernitt et al. 2012), the time-dependent collisional-radiative method and the density-matrix approach. These are described and applied to a two-level atomic system excited by an X-ray free electron laser. A range of pulse parameters is explored and the effects on the predicted Fe XVII 3C and 3D line intensity ratio are calculated. In order to investigate the behavior of the predicted line intensity ratio, a particular pair of A-values for the 3C and 3D transitions was chosen (2.22 $\times$ 10$^{13}$ s$^{-1}$ and 6.02 $\times$ 10$^{12}$ s$^{-1}$ for the 3C and 3D, respectively), but our conclusions are independent of the precise values. We also reaffirm the conclusions from Oreshkina et al.(2014, 2015): the non-linear effects in the density matrix are important and the reduction in the Fe XVII 3C/3D line intensity ratio is sensitive to the laser pulse parameters, namely pulse duration, pulse intensity, and laser bandwidth. It is also shown that for both models the lowering of the 3C/3D line intensity ratio below the expected time-independent oscillator strength ratio has a significant contribution due to the emission from the plasma after the laser pulse has left the plasma volume. Laser intensities above $\sim 1\times 10^{12}$ W/cm$^{2}$ are required for a reduction in the 3C/3D line intensity ratio below the expected time independent oscillator strength ratio

Product selling vs. pay-per-use service: a strategic analysis of competing business models

We present a model that suggests possible explanations for the observed proliferation of “pay-per-use" (PPU) business models over the last two decades. Delivering “fractions" of a product as a service offers a cost advantage to customers with lower usage but requires extra delivery costs. Previous research focused on information goods (with negligible production costs) and predicted that PPU, when arising as a differentiation to selling in equilibrium, fundamentally achieves lower profits than selling. We extend the theory by covering goods with any production cost, in duopolistic competition. We show that PPU business models can be more profitable than selling (especially at mid-range production costs), as long as their delivery costs are not too high, a requirement that is more easily fulfilled as new technologies reduce these costs. Moreover, if firms are imperfectly informed about their customers' usage profiles, PPU's effective pricing of customers' varying usage offers an additional advantage over selling. This requires companies to employ accounting methods that do not inappropriately allocate production costs over stochastic usage levels. If PPU service provision suffers from queueing inefficiencies, this does not fundamentally change the relative profitability of the PPU and selling models, provided that PPU providers can attract sufficiently high demand to benefit from pooling economies

Dirac R-matrix calculations for the electron-impact excitation of neutral tungsten providing noninvasive diagnostics for magnetic confinement fusion

Neutral tungsten is the primary candidate as a wall material in the divertor region of the International Thermonuclear Experimental Reactor (ITER). The efficient operation of ITER depends heavily on precise atomic physics calculations for the determination of reliable erosion diagnostics, helping to characterise the influx of tungsten impurities into the core plasma. The following paper presents detailed calculations of the atomic structure of neutral tungsten using the multiconfigurational Dirac-Fock method, drawing comparisons with experimental measurements where available, and includes a critical assessment of existing atomic structure data. We investigate the electron-impact excitation of neutral tungsten using the Dirac R-matrix method and, by employing collisional-radiative models, we benchmark our results with recent Compact Toroidal Hybrid measurements. The resulting comparisons highlight alternative diagnostic lines to the widely used 400.88nm line.Comment: 10 pages, 6 figure

Lower entropy bounds and particle number fluctuations in a Fermi sea

We demonstrate, in an elementary manner, that given a partition of the single particle Hilbert space into orthogonal subspaces, a Fermi sea may be factored into pairs of entangled modes, similar to a BCS state. We derive expressions for the entropy and for the particle number fluctuations of a subspace of a fermi sea, at zero and finite temperatures, and relate these by a lower bound on the entropy. As an application we investigate analytically and numerically these quantities for electrons in the lowest Landau level of a quantum Hall sample.Comment: shorter version, typos fixe

A large-scale R-matrix calculation for electron-impact excitation of the Ne2+^{2+} O-like ion

The five J$\Pi$ levels within a $np^2$ or $np^4$ ground state complex provide an excellent testing ground for the comparison of theoretical line ratios with astrophysically observed values, in addition to providing valuable electron temperature and density diagnostics. The low temperature nature of the line ratios ensure that the theoretically derived values are sensitive to the underlying atomic structure and electron-impact excitation rates. Previous R-matrix calculations for the Ne$^{2+}$ O-like ion exhibit large spurious structure in the cross sections at higher electron energies, which may affect Maxwellian averaged rates even at low temperatures. Furthermore, there is an absence of comprehensive excitation data between the excited states that may provide newer diagnostics to compliment the more established lines discussed in this paper. To resolve these issues, we present both a small scale 56-level Breit-Pauli (BP) calculation and a large-scale 554 levels R-matrix Intermediate Coupling Frame Transformation (ICFT) calculation that extends the scope and validity of earlier JAJOM calculations both in terms of the atomic structure and scattering cross sections. Our results provide a comprehensive electron-impact excitation data set for all transitions to higher $n$ shells. The fundamental atomic data for this O-like ion is subsequently used within a collisional radiative framework to provide the line ratios across a range of electron temperatures and densities of interest in astrophysical observations.Comment: 17 pages, 8 figure

Electron-Impact Ionization of Be-like C III, N IV, and O V

We present recent measurements of absolute electron-impact ionization cross sections for Be-like C III, N IV, and O V forming Li-like C IV, N V, and O VI. The measurements were taken using the crossed-beams apparatus at Oak Ridge National Laboratory. A gas cell beam attenuation method was used to independently measure the metastable fractions present in the ion beams. The measured ionization cross sections were compared with calculations using the R-matrix with pseudostates and distorted-wave theoretical methods. Best agreement is found with the R-matrix with pseudostates cross sections results that account for the metastable fractions inferred from the gas attenuation measurements. We present a set of recommended rate coefficients for electron-impact single ionization from the ground state and metastable term of each ion

TESTING PROCEDURES TO CHARACTERISE TUNNELLING RISK ON SPOIL MATERIALS

Abstract Many factors affect the success or failure of attempts to stabilise and rehabilitate waste rock dumps on mines. Major erosion causing waste rock dump "failure" is often associated with unstable materials prone to tunnelling, including dispersive spoils. The presence of these materials commonly results in the failure of berms at points where tunnels develop, creation of relatively unsafe landforms with widespread tunnels immediately below the soil surface, development of large gullies when tunnels collapse, and instability of rock drains. Although tunnel erosion is commonly considered to be associated with dispersion, some non-dispersive mine spoil materials have been shown to be highly susceptible to tunnelling. Similarly, materials that are initially stable often undergo chemical and physical changes over time that lead to subsequent tunnel formation. Hence, there is a need for the development of more comprehensive testing procedures to identify materials at risk of tunnel erosion. This paper reports on the development of a laboratory based testing procedure to characterise the risk of tunnelling failure on the basis of soil properties and failure mechanisms. The test procedure also provides information on the impact of leaching on the potential for tunnel formation over time

THE TOOLS AND MONTE CARLO WORKING GROUP Summary Report from the Les Houches 2009 Workshop on TeV Colliders

This is the summary and introduction to the proceedings contributions for the Les Houches 2009 "Tools and Monte Carlo" working group.Comment: 144 Pages. Workshop site http://wwwlapp.in2p3.fr/conferences/LesHouches/Houches2009/ . Conveners were Butterworth, Maltoni, Moortgat, Richardson, Schumann and Skand

TESTING DJI PHANTOM 4 PRO FOR URBAN GEOREFERENCING

The urban environment is dynamic and is constantly changing. In Brazil, it has been recently published a decree for urban land regulation for the cadastre – Decree No 9.310 of 2018 15 of March which fixes 8,0 centimeters as the maximum spherical positional error for vertex of an urban property stock being georeferenced by Global Navigation Satellite System – GNSS equipment or aerial orthophotograph. Nowadays it has been noticed a growing use of Unmanned Aircraft Vehicle System – UAVS for remote sensing. This work aims to test if the accuracy of orthophoto-mosaic from a small UAVS mapping data of an urban area for a parcel scale georeferencing is answering the new decree of urban land regulation for the cadastre. It is intended to check the number of Ground Control Points (GCPs) to reach the best quality in terms of geometric resolution according to the necessity of positional quality for the urban parcel georeferenced for the cadastre. As a final consideration, the results implied that mapping a small surveying area with small UAVS is worth, being a potential tool for georeferencing city blocks, and using 20 pairs of GCPs is enough to reach the quality of positional geometry adequate to the Brazilian legislation